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Sensors, Volume 14, Issue 8 (August 2014), Pages 13308-15640

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Editorial

Jump to: Research, Review, Other

Open AccessEditorial Polymeric Micro Sensors and Actuators
Sensors 2014, 14(8), 15065-15066; doi:10.3390/s140815065
Received: 13 August 2014 / Accepted: 15 August 2014 / Published: 15 August 2014
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Abstract Sensors and actuators using polymeric systems, constitute one of the most promising fields of “smart polymers”, and it is becoming ever more important to associate artificial sensing and actuating systems with living organisms. [...] Full article
(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)
Open AccessEditorial Sensors and Technologies in Spain: State-of-the-Art
Sensors 2014, 14(8), 15282-15303; doi:10.3390/s140815282
Received: 14 August 2014 / Accepted: 19 August 2014 / Published: 19 August 2014
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Abstract
The aim of this special issue was to provide a comprehensive view on the state-of-the-art sensor technology in Spain. Different problems cause the appearance and development of new sensor technologies and vice versa, the emergence of new sensors facilitates the solution of
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The aim of this special issue was to provide a comprehensive view on the state-of-the-art sensor technology in Spain. Different problems cause the appearance and development of new sensor technologies and vice versa, the emergence of new sensors facilitates the solution of existing real problems. [...] Full article

Research

Jump to: Editorial, Review, Other

Open AccessArticle Temperature Measurement in PV Facilities on a Per-Panel Scale
Sensors 2014, 14(8), 13308-13323; doi:10.3390/s140813308
Received: 18 April 2014 / Revised: 14 July 2014 / Accepted: 14 July 2014 / Published: 24 July 2014
Cited by 2 | PDF Full-text (1448 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the design, construction and testing of an instrumentation system for temperature measurement in PV facilities on a per-panel scale (i.e., one or more temperature measurements per panel). Its main characteristics are: precision, ease of connection, immunity to noise,
[...] Read more.
This paper presents the design, construction and testing of an instrumentation system for temperature measurement in PV facilities on a per-panel scale (i.e., one or more temperature measurements per panel). Its main characteristics are: precision, ease of connection, immunity to noise, remote operation, easy scaling; and all of this at a very low cost. The paper discusses the advantages of temperature measurements in PV facilities on a per-panel scale. The paper presents the whole development to implementation of a real system that is being tested in an actual facility. This has enabled the authors to provide the readers with practical guidelines, which would be very difficult to achieve if the developments were implemented by just simulation or in a theoretical way. The instrumentation system is fully developed, from the temperature sensing to its presentation in a virtual instrument. The developed instrumentation system is able to work both locally and remotely connected to both wired and wireless network. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A Sensor Fusion Method for Tracking Vertical Velocity and Height Based on Inertial and Barometric Altimeter Measurements
Sensors 2014, 14(8), 13324-13347; doi:10.3390/s140813324
Received: 26 January 2014 / Revised: 8 July 2014 / Accepted: 21 July 2014 / Published: 24 July 2014
Cited by 8 | PDF Full-text (3901 KB) | HTML Full-text | XML Full-text
Abstract
A sensor fusion method was developed for vertical channel stabilization by fusing inertial measurements from an Inertial Measurement Unit (IMU) and pressure altitude measurements from a barometric altimeter integrated in the same device (baro-IMU). An Extended Kalman Filter (EKF) estimated the quaternion from
[...] Read more.
A sensor fusion method was developed for vertical channel stabilization by fusing inertial measurements from an Inertial Measurement Unit (IMU) and pressure altitude measurements from a barometric altimeter integrated in the same device (baro-IMU). An Extended Kalman Filter (EKF) estimated the quaternion from the sensor frame to the navigation frame; the sensed specific force was rotated into the navigation frame and compensated for gravity, yielding the vertical linear acceleration; finally, a complementary filter driven by the vertical linear acceleration and the measured pressure altitude produced estimates of height and vertical velocity. A method was also developed to condition the measured pressure altitude using a whitening filter, which helped to remove the short-term correlation due to environment-dependent pressure changes from raw pressure altitude. The sensor fusion method was implemented to work on-line using data from a wireless baro-IMU and tested for the capability of tracking low-frequency small-amplitude vertical human-like motions that can be critical for stand-alone inertial sensor measurements. Validation tests were performed in different experimental conditions, namely no motion, free-fall motion, forced circular motion and squatting. Accurate on-line tracking of height and vertical velocity was achieved, giving confidence to the use of the sensor fusion method for tracking typical vertical human motions: velocity Root Mean Square Error (RMSE) was in the range 0.04–0.24 m/s; height RMSE was in the range 5–68 cm, with statistically significant performance gains when the whitening filter was used by the sensor fusion method to track relatively high-frequency vertical motions. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Digital Multigate Doppler Method for High Frequency Ultrasound
Sensors 2014, 14(8), 13348-13360; doi:10.3390/s140813348
Received: 15 June 2014 / Revised: 7 July 2014 / Accepted: 7 July 2014 / Published: 24 July 2014
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Abstract
Noninvasive visualization of blood flow with high frequency Doppler ultrasound has been extensively used to assess the morphology and hemodynamics of the microcirculation. A completely digital implementation of multigate pulsed-wave (PW) Doppler method was proposed in this paper for high frequency ultrasound applications.
[...] Read more.
Noninvasive visualization of blood flow with high frequency Doppler ultrasound has been extensively used to assess the morphology and hemodynamics of the microcirculation. A completely digital implementation of multigate pulsed-wave (PW) Doppler method was proposed in this paper for high frequency ultrasound applications. Analog mixer was eliminated by a digital demodulator and the same data acquisition path was shared with traditional B-mode imaging which made the design compact and flexible. Hilbert transform based quadrature demodulation scheme was employed to achieve the multigate Doppler acquisition. A programmable high frequency ultrasound platform was also proposed to facilitate the multigate flow visualization. Experimental results showed good performance of the proposed method. Parabolic velocity gradient inside the vessel and velocity profile with different time slots were acquired to demonstrate the functionality of the multigate Doppler. Slow wall motion was also recorded by the proposed method. Full article
Open AccessArticle Emotion Recognition from Single-Trial EEG Based on Kernel Fisher’s Emotion Pattern and Imbalanced Quasiconformal Kernel Support Vector Machine
Sensors 2014, 14(8), 13361-13388; doi:10.3390/s140813361
Received: 29 April 2014 / Revised: 11 July 2014 / Accepted: 18 July 2014 / Published: 24 July 2014
Cited by 4 | PDF Full-text (4788 KB) | HTML Full-text | XML Full-text
Abstract
Electroencephalogram-based emotion recognition (EEG-ER) has received increasing attention in the fields of health care, affective computing, and brain-computer interface (BCI). However, satisfactory ER performance within a bi-dimensional and non-discrete emotional space using single-trial EEG data remains a challenging task. To address this issue,
[...] Read more.
Electroencephalogram-based emotion recognition (EEG-ER) has received increasing attention in the fields of health care, affective computing, and brain-computer interface (BCI). However, satisfactory ER performance within a bi-dimensional and non-discrete emotional space using single-trial EEG data remains a challenging task. To address this issue, we propose a three-layer scheme for single-trial EEG-ER. In the first layer, a set of spectral powers of different EEG frequency bands are extracted from multi-channel single-trial EEG signals. In the second layer, the kernel Fisher’s discriminant analysis method is applied to further extract features with better discrimination ability from the EEG spectral powers. The feature vector produced by layer 2 is called a kernel Fisher’s emotion pattern (KFEP), and is sent into layer 3 for further classification where the proposed imbalanced quasiconformal kernel support vector machine (IQK-SVM) serves as the emotion classifier. The outputs of the three layer EEG-ER system include labels of emotional valence and arousal. Furthermore, to collect effective training and testing datasets for the current EEG-ER system, we also use an emotion-induction paradigm in which a set of pictures selected from the International Affective Picture System (IAPS) are employed as emotion induction stimuli. The performance of the proposed three-layer solution is compared with that of other EEG spectral power-based features and emotion classifiers. Results on 10 healthy participants indicate that the proposed KFEP feature performs better than other spectral power features, and IQK-SVM outperforms traditional SVM in terms of the EEG-ER accuracy. Our findings also show that the proposed EEG-ER scheme achieves the highest classification accuracies of valence (82.68%) and arousal (84.79%) among all testing methods. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
Open AccessArticle MobiPag: Integrated Mobile Payment, Ticketing and Couponing Solution Based on NFC
Sensors 2014, 14(8), 13389-13415; doi:10.3390/s140813389
Received: 15 March 2014 / Revised: 13 July 2014 / Accepted: 16 July 2014 / Published: 24 July 2014
Cited by 5 | PDF Full-text (1124 KB) | HTML Full-text | XML Full-text
Abstract
Mobile payments still remain essentially an emerging technology, seeking to fill the gap between the envisioned potential and widespread usage. In this paper, we present an integrated mobile service solution based on the near field communication (NFC) protocol that was developed under a
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Mobile payments still remain essentially an emerging technology, seeking to fill the gap between the envisioned potential and widespread usage. In this paper, we present an integrated mobile service solution based on the near field communication (NFC) protocol that was developed under a research project called MobiPag. The most distinctive characteristic of Mobipag is its open architectural model that allows multiple partners to become part of the payment value-chain and create solutions that complement payments in many unexpected ways. We describe the Mobipag architecture and how it has been used to support a mobile payment trial. We identify a set of design lessons resulting from usage experiences associated with real-world payment situations with NFC-enabled mobile phones. Based on results from this trial, we identify a number of challenges and guidelines that may help to shape future versions of NFC-based payment systems. In particular, we highlight key challenges for the initial phases of payment deployments, where it is essential to focus on scenarios that can be identified as more feasible for early adoption. We also have identified a fundamental trade-off between the flexibility supported by the Mobipag solution and the respective implications for the payment process, particularly on the users’ mental model. Full article
Open AccessArticle Experimental Energy Consumption of Frame Slotted ALOHA and Distributed Queuing for Data Collection Scenarios
Sensors 2014, 14(8), 13416-13436; doi:10.3390/s140813416
Received: 21 June 2014 / Revised: 16 July 2014 / Accepted: 17 July 2014 / Published: 24 July 2014
Cited by 1 | PDF Full-text (1470 KB) | HTML Full-text | XML Full-text
Abstract
Data collection is a key scenario for the Internet of Things because it enables gathering sensor data from distributed nodes that use low-power and long-range wireless technologies to communicate in a single-hop approach. In this kind of scenario, the network is composed of
[...] Read more.
Data collection is a key scenario for the Internet of Things because it enables gathering sensor data from distributed nodes that use low-power and long-range wireless technologies to communicate in a single-hop approach. In this kind of scenario, the network is composed of one coordinator that covers a particular area and a large number of nodes, typically hundreds or thousands, that transmit data to the coordinator upon request. Considering this scenario, in this paper we experimentally validate the energy consumption of two Medium Access Control (MAC) protocols, Frame Slotted ALOHA (FSA) and Distributed Queuing (DQ). We model both protocols as a state machine and conduct experiments to measure the average energy consumption in each state and the average number of times that a node has to be in each state in order to transmit a data packet to the coordinator. The results show that FSA is more energy efficient than DQ if the number of nodes is known a priori because the number of slots per frame can be adjusted accordingly. However, in such scenarios the number of nodes cannot be easily anticipated, leading to additional packet collisions and a higher energy consumption due to retransmissions. Contrarily, DQ does not require to know the number of nodes in advance because it is able to efficiently construct an ad hoc network schedule for each collection round. This kind of a schedule ensures that there are no packet collisions during data transmission, thus leading to an energy consumption reduction above 10% compared to FSA. Full article
(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)
Open AccessArticle From the Solution Processing of Hydrophilic Molecules to Polymer-Phthalocyanine Hybrid Materials for Ammonia Sensing in High Humidity Atmospheres
Sensors 2014, 14(8), 13476-13495; doi:10.3390/s140813476
Received: 20 May 2014 / Revised: 28 June 2014 / Accepted: 21 July 2014 / Published: 24 July 2014
Cited by 3 | PDF Full-text (10470 KB) | HTML Full-text | XML Full-text
Abstract
We have prepared different hybrid polymer-phthalocyanine materials by solution processing, starting from two sulfonated phthalocyanines, s-CoPc and CuTsPc, and polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), poly(acrylic acid-co-acrylamide) (PAA-AM), poly(diallyldimethylammonium chloride) (PDDA) and polyaniline (PANI) as polymers. We also studied the response to ammonia (NH
[...] Read more.
We have prepared different hybrid polymer-phthalocyanine materials by solution processing, starting from two sulfonated phthalocyanines, s-CoPc and CuTsPc, and polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), poly(acrylic acid-co-acrylamide) (PAA-AM), poly(diallyldimethylammonium chloride) (PDDA) and polyaniline (PANI) as polymers. We also studied the response to ammonia (NH3) of resistors prepared from these sensing materials. The solvent casted films, prepared from s-CoPc and PVP, PEG and PAA-AM, were highly insulating and very sensitive to the relative humidity (RH) variation. The incorporation of s-CoPc in PDDA by means of layer-by-layer (LBL) technique allowed to stabilize the film, but was too insulating to be interesting. We also prepared PANI-CuTsPc hybrid films by LBL technique. It allowed a regular deposition as evidenced by the linear increase of the absorbance at 688 nm as a function of the number of bilayers. The sensitivity to ammonia (NH3) of PANi-CuTsPc resistors was very high compared to that of individual materials, giving up to 80% of current decrease when exposed to 30 ppm NH3. Contrarily to what happens with neutral polymers, in PANI, CuTsPc was stabilized by strong electrostatic interactions, leading to a stable response to NH3, whatever the relative humidity in the range 10%–70%. Thus, the synergy of PANI with ionic macrocycles used as counteranions combined with their simple aqueous solution processing opens the way to the development of new gas sensors capable of operating in real world conditions. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in France)
Open AccessArticle Disseminating Ambient Assisted Living in Rural Areas
Sensors 2014, 14(8), 13496-13531; doi:10.3390/s140813496
Received: 9 March 2014 / Revised: 24 June 2014 / Accepted: 14 July 2014 / Published: 25 July 2014
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Abstract
The smart home, ambient intelligence and ambient assisted living have been intensively researched for decades. Although rural areas are an important potential market, because they represent about 80% of the territory of the EU countries and around 125 million inhabitants, there is currently
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The smart home, ambient intelligence and ambient assisted living have been intensively researched for decades. Although rural areas are an important potential market, because they represent about 80% of the territory of the EU countries and around 125 million inhabitants, there is currently a lack of applicable AAL solutions. This paper discusses the theoretical foundations of AAL in rural areas. This discussion is underlined by the achievements of the empirical field study, Casa Vecchia, which has been carried out over a four-year period in a rural area in Austria. The major goal of Casa Vecchia was to evaluate the feasibility of a specific form of AAL for rural areas: bringing AAL technology to the homes of the elderly, rather than moving seniors to special-equipped care facilities. The Casa Vecchia project thoroughly investigated the possibilities, challenges and drawbacks of AAL related to this specific approach. The findings are promising and somewhat surprising and indicate that further technical, interactional and socio-psychological research is required to make AAL in rural areas reasonable in the future. Full article
Open AccessArticle Near Infrared Spectroscopy Calibration for Wood Chemistry: Which Chemometric Technique Is Best for Prediction and Interpretation?
Sensors 2014, 14(8), 13532-13547; doi:10.3390/s140813532
Received: 29 May 2014 / Revised: 12 July 2014 / Accepted: 21 July 2014 / Published: 25 July 2014
Cited by 4 | PDF Full-text (1032 KB) | HTML Full-text | XML Full-text
Abstract
This paper addresses the precision in factor loadings during partial least squares (PLS) and principal components regression (PCR) of wood chemistry content from near infrared reflectance (NIR) spectra. The precision of the loadings is considered important because these estimates are often utilized to
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This paper addresses the precision in factor loadings during partial least squares (PLS) and principal components regression (PCR) of wood chemistry content from near infrared reflectance (NIR) spectra. The precision of the loadings is considered important because these estimates are often utilized to interpret chemometric models or selection of meaningful wavenumbers. Standard laboratory chemistry methods were employed on a mixed genus/species hardwood sample set. PLS and PCR, before and after 1st derivative pretreatment, was utilized for model building and loadings investigation. As demonstrated by others, PLS was found to provide better predictive diagnostics. However, PCR exhibited a more precise estimate of loading peaks which makes PCR better for interpretation. Application of the 1st derivative appeared to assist in improving both PCR and PLS loading precision, but due to the small sample size, the two chemometric methods could not be compared statistically. This work is important because to date most research works have committed to PLS because it yields better predictive performance. But this research suggests there is a tradeoff between better prediction and model interpretation. Future work is needed to compare PLS and PCR for a suite of spectral pretreatment techniques. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Two-Level Optical Coherence Tomography Scheme for Suppressing Spectral Saturation Artifacts
Sensors 2014, 14(8), 13548-13555; doi:10.3390/s140813548
Received: 12 June 2014 / Revised: 15 July 2014 / Accepted: 23 July 2014 / Published: 25 July 2014
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Abstract
We demonstrate a novel method for reducing saturation artifacts in spectral-domain optical coherence tomography (SD-OCT) systems. This method is based on a two-level SD-OCT system with a dual-line charge-coupled device (CCD) camera. We compensate the saturated signal detected by the first line using
[...] Read more.
We demonstrate a novel method for reducing saturation artifacts in spectral-domain optical coherence tomography (SD-OCT) systems. This method is based on a two-level SD-OCT system with a dual-line charge-coupled device (CCD) camera. We compensate the saturated signal detected by the first line using the unsaturated signal detected by the second line. The Fourier transform of the compensated spectrum shows effective suppression of saturation artifacts. This method was also successfully performed on phantom material and skin on a human finger. Our method causes neither back-scattering power loss nor signal-to-noise ratio (SNR) degradation. The only difference between the traditional system and our two-level system is our utilization of the dual-line CCD camera; no additional devices or complex designs are needed. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Comprehensive Review of Sensors and Instrumentation Methods in Devices for Musical Expression
Sensors 2014, 14(8), 13556-13591; doi:10.3390/s140813556
Received: 17 May 2014 / Revised: 4 July 2014 / Accepted: 16 July 2014 / Published: 25 July 2014
Cited by 3 | PDF Full-text (1161 KB) | HTML Full-text | XML Full-text
Abstract
Digital Musical Instruments (DMIs) are musical instruments typically composed of a control surface where user interaction is measured by sensors whose values are mapped to sound synthesis algorithms. These instruments have gained interest among skilled musicians and performers in the last decades leading
[...] Read more.
Digital Musical Instruments (DMIs) are musical instruments typically composed of a control surface where user interaction is measured by sensors whose values are mapped to sound synthesis algorithms. These instruments have gained interest among skilled musicians and performers in the last decades leading to artistic practices including musical performance, interactive installations and dance. The creation of DMIs typically involves several areas, among them: arts, design and engineering. The balance between these areas is an essential task in DMI design so that the resulting instruments are aesthetically appealing, robust, and allow responsive, accurate and repeatable sensing. In this paper, we review the use of sensors in the DMI community as manifested in the proceedings of the International Conference on New Interfaces for Musical Expression (NIME 2009–2013). Focusing on the sensor technologies and signal conditioning techniques used by the NIME community. Although it has been claimed that specifications for artistic tools are harder than those for military applications, this study raises a paradox showing that in most of the cases, DMIs are based on a few basic sensors types and unsophisticated engineering solutions, not taking advantage of more advanced sensing, instrumentation and signal processing techniques that could dramatically improve their response. We aim to raise awareness of limitations of any engineering solution and to assert the benefits of advanced electronics instrumentation design in DMIs. For this, we propose the use of specialized sensors such as strain gages, advanced conditioning circuits and signal processing tools such as sensor fusion. We believe that careful electronic instrumentation design may lead to more responsive instruments. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors in Canada 2014)
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Open AccessArticle A Selective Ultrahigh Responding High Temperature Ethanol Sensor Using TiO2 Nanoparticles
Sensors 2014, 14(8), 13613-13627; doi:10.3390/s140813613
Received: 9 June 2014 / Revised: 17 July 2014 / Accepted: 17 July 2014 / Published: 28 July 2014
Cited by 4 | PDF Full-text (13723 KB) | HTML Full-text | XML Full-text
Abstract
In this research work, the sensitivity of TiO2 nanoparticles towards C2H5OH, H2 and CH4 gases was investigated. The morphology and phase content of the particles was preserved during sensing tests by prior heat treatment of the
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In this research work, the sensitivity of TiO2 nanoparticles towards C2H5OH, H2 and CH4 gases was investigated. The morphology and phase content of the particles was preserved during sensing tests by prior heat treatment of the samples at temperatures as high as 750 °C and 1000 °C. Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis were employed to characterize the size, morphology and phase content of the particles. For sensor fabrication, a film of TiO2 was printed on a Au interdigitated alumina substrate. The sensing temperature was varied from 450 °C to 650 °C with varying concentrations of target gases. Results show that the sensor has ultrahigh response towards ethanol (C2H5OH) compared to hydrogen (H2) and methane (CH4). The optimum sensing temperature was found to be 600 °C. The response and recovery times of the sensor are 3 min and 15 min, respectively, for 20 ppm C2H5OH at the optimum operating temperature of 600 °C. It is proposed that the catalytic action of TiO2 with C2H5OH is the reason for the ultrahigh response of the sensor. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Humidity Sensors Printed on Recycled Paper and Cardboard
Sensors 2014, 14(8), 13628-13643; doi:10.3390/s140813628
Received: 31 May 2014 / Revised: 13 July 2014 / Accepted: 21 July 2014 / Published: 28 July 2014
Cited by 4 | PDF Full-text (1085 KB) | HTML Full-text | XML Full-text
Abstract
Research, design, fabrication and results of various screen printed capacitive humidity sensors is presented in this paper. Two types of capacitive humidity sensors have been designed and fabricated via screen printing on recycled paper and cardboard, obtained from the regional paper and cardboard
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Research, design, fabrication and results of various screen printed capacitive humidity sensors is presented in this paper. Two types of capacitive humidity sensors have been designed and fabricated via screen printing on recycled paper and cardboard, obtained from the regional paper and cardboard industry. As printing ink, commercially available silver nanoparticle-based conductive ink was used. A considerable amount of work has been devoted to the humidity measurement methods using paper as a dielectric material. Performances of different structures have been tested in a humidity chamber. Relative humidity in the chamber was varied in the range of 35%–80% relative humidity (RH) at a constant temperature of 23 °C. Parameters of interest were capacitance and conductance of each sensor material, as well as long term behaviour. Process reversibility has also been considered. The results obtained show a mainly logarithmic response of the paper sensors, with the only exception being cardboard-based sensors. Recycled paper-based sensors exhibit a change in value of three orders of magnitude, whereas cardboard-based sensors have a change in value of few 10s over the entire scope of relative humidity range (RH 35%–90%). Two different types of capacitor sensors have been investigated: lateral (comb) type sensors and modified, perforated flat plate type sensors. The objective of the present work was to identify the most important factors affecting the material performances with humidity, and to contribute to the development of a sensor system supported with a Radio Frequency Identification (RFID) chip directly on the material, for use in smart packaging applications. Therefore, the authors built a passive and a battery-supported wireless module based on SL900A smart sensory tag’s IC to achieve UHF-RFID functionality with data logging capability. Full article
(This article belongs to the Special Issue Printed Sensors)
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Open AccessArticle Smart Elasto-Magneto-Electric (EME) Sensors for Stress Monitoring of Steel Cables: Design Theory and Experimental Validation
Sensors 2014, 14(8), 13644-13660; doi:10.3390/s140813644
Received: 4 April 2014 / Revised: 2 July 2014 / Accepted: 16 July 2014 / Published: 28 July 2014
Cited by 6 | PDF Full-text (2837 KB) | HTML Full-text | XML Full-text
Abstract
An elasto-magnetic (EM) and magneto-electric (ME) effect based elasto-magneto-electric (EME) sensor has been proposed recently by the authors for stress monitoring of steel cables with obvious superiorities over traditional elasto-magnetic sensors. For design optimization and engineering application of the EME sensor, the design
[...] Read more.
An elasto-magnetic (EM) and magneto-electric (ME) effect based elasto-magneto-electric (EME) sensor has been proposed recently by the authors for stress monitoring of steel cables with obvious superiorities over traditional elasto-magnetic sensors. For design optimization and engineering application of the EME sensor, the design theory is interpreted with a developed model taking into account the EM coupling effect and ME coupling effect. This model is able to approximate the magnetization changes that a steel structural component undergoes when subjected to excitation magnetic field and external stress, and to simulate the induced ME voltages of the ME sensing unit located in the magnetization area. A full-scale experiment is then carried out to verify the model and to calibrate the EME sensor as a non-destructive evaluation (NDE) tool to monitor the cable stress. The experimental results agree well with the simulation results using the developed model. The proposed EME sensor proves to be feasible for stress monitoring of steel cables with high sensitivity, fast response, and ease of installation. Full article
Open AccessArticle A Novel Optimal Configuration form Redundant MEMS Inertial Sensors Based on the Orthogonal Rotation Method
Sensors 2014, 14(8), 13661-13678; doi:10.3390/s140813661
Received: 22 May 2014 / Revised: 20 July 2014 / Accepted: 22 July 2014 / Published: 29 July 2014
Cited by 7 | PDF Full-text (1352 KB) | HTML Full-text | XML Full-text
Abstract
In order to improve the accuracy and reliability of micro-electro mechanical systems (MEMS) navigation systems, an orthogonal rotation method-based nine-gyro redundant MEMS configuration is presented. By analyzing the accuracy and reliability characteristics of an inertial navigation system (INS), criteria for redundant configuration design
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In order to improve the accuracy and reliability of micro-electro mechanical systems (MEMS) navigation systems, an orthogonal rotation method-based nine-gyro redundant MEMS configuration is presented. By analyzing the accuracy and reliability characteristics of an inertial navigation system (INS), criteria for redundant configuration design are introduced. Then the orthogonal rotation configuration is formed through a two-rotation of a set of orthogonal inertial sensors around a space vector. A feasible installation method is given for the real engineering realization of this proposed configuration. The performances of the novel configuration and another six configurations are comprehensively compared and analyzed. Simulation and experimentation are also conducted, and the results show that the orthogonal rotation configuration has the best reliability, accuracy and fault detection and isolation (FDI) performance when the number of gyros is nine. Full article
Open AccessArticle Thermal Tracking of Sports Players
Sensors 2014, 14(8), 13679-13691; doi:10.3390/s140813679
Received: 15 May 2014 / Revised: 18 July 2014 / Accepted: 21 July 2014 / Published: 29 July 2014
Cited by 6 | PDF Full-text (910 KB) | HTML Full-text | XML Full-text
Abstract
We present here a real-time tracking algorithm for thermal video from a sports game. Robust detection of people includes routines for handling occlusions and noise before tracking each detected person with a Kalman filter. This online tracking algorithm is compared with a state-of-the-art
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We present here a real-time tracking algorithm for thermal video from a sports game. Robust detection of people includes routines for handling occlusions and noise before tracking each detected person with a Kalman filter. This online tracking algorithm is compared with a state-of-the-art offline multi-target tracking algorithm. Experiments are performed on a manually annotated 2-minutes video sequence of a real soccer game. The Kalman filter shows a very promising result on this rather challenging sequence with a tracking accuracy above 70% and is superior compared with the offline tracking approach. Furthermore, the combined detection and tracking algorithm runs in real time at 33 fps, even with large image sizes of 1920 × 480 pixels. Full article
Open AccessArticle The Recovery of Weak Impulsive Signals Based on Stochastic Resonance and Moving Least Squares Fitting
Sensors 2014, 14(8), 13692-13707; doi:10.3390/s140813692
Received: 15 May 2014 / Revised: 1 July 2014 / Accepted: 18 July 2014 / Published: 29 July 2014
Cited by 3 | PDF Full-text (8973 KB) | HTML Full-text | XML Full-text
Abstract
In this paper a stochastic resonance (SR)-based method for recovering weak impulsive signals is developed for quantitative diagnosis of faults in rotating machinery. It was shown in theory that weak impulsive signals follow the mechanism of SR, but the SR produces a nonlinear
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In this paper a stochastic resonance (SR)-based method for recovering weak impulsive signals is developed for quantitative diagnosis of faults in rotating machinery. It was shown in theory that weak impulsive signals follow the mechanism of SR, but the SR produces a nonlinear distortion of the shape of the impulsive signal. To eliminate the distortion a moving least squares fitting method is introduced to reconstruct the signal from the output of the SR process. This proposed method is verified by comparing its detection results with that of a morphological filter based on both simulated and experimental signals. The experimental results show that the background noise is suppressed effectively and the key features of impulsive signals are reconstructed with a good degree of accuracy, which leads to an accurate diagnosis of faults in roller bearings in a run-to failure test. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Calibration of an Outdoor Distributed Camera Network with a 3D Point Cloud
Sensors 2014, 14(8), 13708-13729; doi:10.3390/s140813708
Received: 5 March 2014 / Revised: 17 July 2014 / Accepted: 17 July 2014 / Published: 29 July 2014
Cited by 2 | PDF Full-text (15097 KB) | HTML Full-text | XML Full-text
Abstract
Outdoor camera networks are becoming ubiquitous in critical urban areas of the largest cities around the world. Although current applications of camera networks are mostly tailored to video surveillance, recent research projects are exploiting their use to aid robotic systems in people-assisting tasks.
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Outdoor camera networks are becoming ubiquitous in critical urban areas of the largest cities around the world. Although current applications of camera networks are mostly tailored to video surveillance, recent research projects are exploiting their use to aid robotic systems in people-assisting tasks. Such systems require precise calibration of the internal and external parameters of the distributed camera network. Despite the fact that camera calibration has been an extensively studied topic, the development of practical methods for user-assisted calibration that minimize user intervention time and maximize precision still pose significant challenges. These camera systems have non-overlapping fields of view, are subject to environmental stress, and are likely to suffer frequent recalibration. In this paper, we propose the use of a 3D map covering the area to support the calibration process and develop an automated method that allows quick and precise calibration of a large camera network. We present two cases of study of the proposed calibration method: one is the calibration of the Barcelona Robot Lab camera network, which also includes direct mappings (homographies) between image coordinates and world points in the ground plane (walking areas) to support person and robot detection and localization algorithms. The second case consist of improving the GPS positioning of geo-tagged images taken with a mobile device in the Facultat de Matemàtiques i Estadística (FME) patio at the Universitat Politècnica de Catalunya (UPC). Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Automated Detection and Recognition of Wildlife Using Thermal Cameras
Sensors 2014, 14(8), 13778-13793; doi:10.3390/s140813778
Received: 15 May 2014 / Revised: 1 July 2014 / Accepted: 17 July 2014 / Published: 30 July 2014
Cited by 11 | PDF Full-text (9574 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In agricultural mowing operations, thousands of animals are injured or killed each year, due to the increased working widths and speeds of agricultural machinery. Detection and recognition of wildlife within the agricultural fields is important to reduce wildlife mortality and, thereby, promote wildlife-friendly
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In agricultural mowing operations, thousands of animals are injured or killed each year, due to the increased working widths and speeds of agricultural machinery. Detection and recognition of wildlife within the agricultural fields is important to reduce wildlife mortality and, thereby, promote wildlife-friendly farming. The work presented in this paper contributes to the automated detection and classification of animals in thermal imaging. The methods and results are based on top-view images taken manually from a lift to motivate work towards unmanned aerial vehicle-based detection and recognition. Hot objects are detected based on a threshold dynamically adjusted to each frame. For the classification of animals, we propose a novel thermal feature extraction algorithm. For each detected object, a thermal signature is calculated using morphological operations. The thermal signature describes heat characteristics of objects and is partly invariant to translation, rotation, scale and posture. The discrete cosine transform (DCT) is used to parameterize the thermal signature and, thereby, calculate a feature vector, which is used for subsequent classification. Using a k-nearest-neighbor (kNN) classifier, animals are discriminated from non-animals with a balanced classification accuracy of 84.7% in an altitude range of 3–10 m and an accuracy of 75.2% for an altitude range of 10–20 m. To incorporate temporal information in the classification, a tracking algorithm is proposed. Using temporal information improves the balanced classification accuracy to 93.3% in an altitude range 3–10 of meters and 77.7% in an altitude range of 10–20 m Full article
Open AccessArticle A Practical Application Combining Wireless Sensor Networks and Internet of Things: Safety Management System for Tower Crane Groups
Sensors 2014, 14(8), 13794-13814; doi:10.3390/s140813794
Received: 21 March 2014 / Revised: 11 July 2014 / Accepted: 17 July 2014 / Published: 30 July 2014
Cited by 4 | PDF Full-text (3536 KB) | HTML Full-text | XML Full-text
Abstract
The so-called Internet of Things (IoT) has attracted increasing attention in the field of computer and information science. In this paper, a specific application of IoT, named Safety Management System for Tower Crane Groups (SMS-TC), is proposed for use in the construction industry
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The so-called Internet of Things (IoT) has attracted increasing attention in the field of computer and information science. In this paper, a specific application of IoT, named Safety Management System for Tower Crane Groups (SMS-TC), is proposed for use in the construction industry field. The operating status of each tower crane was detected by a set of customized sensors, including horizontal and vertical position sensors for the trolley, angle sensors for the jib and load, tilt and wind speed sensors for the tower body. The sensor data is collected and processed by the Tower Crane Safety Terminal Equipment (TC-STE) installed in the driver’s operating room. Wireless communication between each TC-STE and the Local Monitoring Terminal (LMT) at the ground worksite were fulfilled through a Zigbee wireless network. LMT can share the status information of the whole group with each TC-STE, while the LMT records the real-time data and reports it to the Remote Supervision Platform (RSP) through General Packet Radio Service (GPRS). Based on the global status data of the whole group, an anti-collision algorithm was executed in each TC-STE to ensure the safety of each tower crane during construction. Remote supervision can be fulfilled using our client software installed on a personal computer (PC) or smartphone. SMS-TC could be considered as a promising practical application that combines a Wireless Sensor Network with the Internet of Things. Full article
(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)
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Open AccessArticle High-Sensitivity Low-Noise Miniature Fluxgate Magnetometers Using a Flip Chip Conceptual Design
Sensors 2014, 14(8), 13815-13829; doi:10.3390/s140813815
Received: 9 June 2014 / Revised: 18 July 2014 / Accepted: 21 July 2014 / Published: 30 July 2014
Cited by 9 | PDF Full-text (8201 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel class of miniature fluxgate magnetometers fabricated on a print circuit board (PCB) substrate and electrically connected to each other similar to the current “flip chip” concept in semiconductor package. This sensor is soldered together by reversely flipping a
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This paper presents a novel class of miniature fluxgate magnetometers fabricated on a print circuit board (PCB) substrate and electrically connected to each other similar to the current “flip chip” concept in semiconductor package. This sensor is soldered together by reversely flipping a 5 cm × 3 cm PCB substrate to the other identical one which includes dual magnetic cores, planar pick-up coils, and 3-D excitation coils constructed by planar Cu interconnections patterned on PCB substrates. Principles and analysis of the fluxgate sensor are introduced first, and followed by FEA electromagnetic modeling and simulation for the proposed sensor. Comprehensive characteristic experiments of the miniature fluxgate device exhibit favorable results in terms of sensitivity (or “responsivity” for magnetometers) and field noise spectrum. The sensor is driven and characterized by employing the improved second-harmonic detection technique that enables linear V-B correlation and responsivity verification. In addition, the double magnitude of responsivity measured under very low frequency (1 Hz) magnetic fields is experimentally demonstrated. As a result, the maximum responsivity of 593 V/T occurs at 50 kHz of excitation frequency with the second harmonic wave of excitation; however, the minimum magnetic field noise is found to be 0.05 nT/Hz1/2 at 1 Hz under the same excitation. In comparison with other miniature planar fluxgates published to date, the fluxgate magnetic sensor with flip chip configuration offers advances in both device functionality and fabrication simplicity. More importantly, the novel design can be further extended to a silicon-based micro-fluxgate chip manufactured by emerging CMOS-MEMS technologies, thus enriching its potential range of applications in modern engineering and the consumer electronics market. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Tracheal Sounds Acquisition Using Smartphones
Sensors 2014, 14(8), 13830-13850; doi:10.3390/s140813830
Received: 12 June 2014 / Revised: 22 July 2014 / Accepted: 25 July 2014 / Published: 30 July 2014
Cited by 5 | PDF Full-text (2802 KB) | HTML Full-text | XML Full-text
Abstract
Tracheal sounds have received a lot of attention for estimating ventilation parameters in a non-invasive way. The aim of this work was to examine the feasibility of extracting accurate airflow, and automating the detection of breath-phase onset and respiratory rates all directly from
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Tracheal sounds have received a lot of attention for estimating ventilation parameters in a non-invasive way. The aim of this work was to examine the feasibility of extracting accurate airflow, and automating the detection of breath-phase onset and respiratory rates all directly from tracheal sounds acquired from an acoustic microphone connected to a smartphone. We employed the Samsung Galaxy S4 and iPhone 4s smartphones to acquire tracheal sounds from N = 9 healthy volunteers at airflows ranging from 0.5 to 2.5 L/s. We found that the amplitude of the smartphone-acquired sounds was highly correlated with the airflow from a spirometer, and similar to previously-published studies, we found that the increasing tracheal sounds’ amplitude as flow increases follows a power law relationship. Acquired tracheal sounds were used for breath-phase onset detection and their onsets differed by only 52 ± 51 ms (mean ± SD) for Galaxy S4, and 51 ± 48 ms for iPhone 4s, when compared to those detected from the reference signal via the spirometer. Moreover, it was found that accurate respiratory rates (RR) can be obtained from tracheal sounds. The correlation index, bias and limits of agreement were r2 = 0.9693, 0.11 (−1.41 to 1.63) breaths-per-minute (bpm) for Galaxy S4, and r2 = 0.9672, 0.097 (–1.38 to 1.57) bpm for iPhone 4s, when compared to RR estimated from spirometry. Both smartphone devices performed similarly, as no statistically-significant differences were found. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
Open AccessArticle A Capacitive Touch Screen Sensor for Detection of Urinary Tract Infections in Portable Biomedical Devices
Sensors 2014, 14(8), 13851-13862; doi:10.3390/s140813851
Received: 1 June 2014 / Revised: 2 July 2014 / Accepted: 18 July 2014 / Published: 30 July 2014
Cited by 6 | PDF Full-text (2375 KB) | HTML Full-text | XML Full-text
Abstract
Incidence of urinary tract infections (UTIs) is the second highest among all infections; thus, there is a high demand for bacteriuria detection. Escherichia coli are the main cause of UTIs, with microscopy methods and urine culture being the detection standard of these bacteria.
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Incidence of urinary tract infections (UTIs) is the second highest among all infections; thus, there is a high demand for bacteriuria detection. Escherichia coli are the main cause of UTIs, with microscopy methods and urine culture being the detection standard of these bacteria. However, the urine sampling and analysis required for these methods can be both time-consuming and complex. This work proposes a capacitive touch screen sensor (CTSS) concept as feasible alternative for a portable UTI detection device. Finite element method (FEM) simulations were conducted with a CTSS model. An exponential response of the model to increasing amounts of E. coli and liquid samples was observed. A measurable capacitance change due to E. coli presence and a tangible difference in the response given to urine and water samples were also detected. Preliminary experimental studies were also conducted on a commercial CTSS using liquid solutions with increasing amounts of dissolved ions. The CTSS was capable of distinguishing different volumes of liquids, also giving an exponential response. Furthermore, the CTSS gave higher responses to solutions with a superior amount of ions. Urine samples gave the top response among tested liquids. Thus, the CTSS showed the capability to differentiate solutions by their ionic content. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Enterobacter asburiae Strain L1: Complete Genome and Whole Genome Optical Mapping Analysis of a Quorum Sensing Bacterium
Sensors 2014, 14(8), 13913-13924; doi:10.3390/s140813913
Received: 26 May 2014 / Revised: 7 July 2014 / Accepted: 23 July 2014 / Published: 30 July 2014
Cited by 5 | PDF Full-text (1729 KB) | HTML Full-text | XML Full-text
Abstract
Enterobacter asburiae L1 is a quorum sensing bacterium isolated from lettuce leaves. In this study, for the first time, the complete genome of E. asburiae L1 was sequenced using the single molecule real time sequencer (PacBio RSII) and the whole genome sequence was
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Enterobacter asburiae L1 is a quorum sensing bacterium isolated from lettuce leaves. In this study, for the first time, the complete genome of E. asburiae L1 was sequenced using the single molecule real time sequencer (PacBio RSII) and the whole genome sequence was verified by using optical genome mapping (OpGen) technology. In our previous study, E. asburiae L1 has been reported to produce AHLs, suggesting the possibility of virulence factor regulation which is quorum sensing dependent. This evoked our interest to study the genome of this bacterium and here we present the complete genome of E. asburiae L1, which carries the virulence factor gene virK, the N-acyl homoserine lactone-based QS transcriptional regulator gene luxR and the N-acyl homoserine lactone synthase gene which we firstly named easI. The availability of the whole genome sequence of E. asburiae L1 will pave the way for the study of the QS-mediated gene expression in this bacterium. Hence, the importance and functions of these signaling molecules can be further studied in the hope of elucidating the mechanisms of QS-regulation in E. asburiae. To the best of our knowledge, this is the first documentation of both a complete genome sequence and the establishment of the molecular basis of QS properties of E. asburiae. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Dependence of the Contact Resistance on the Design of Stranded Conductors
Sensors 2014, 14(8), 13925-13942; doi:10.3390/s140813925
Received: 21 March 2014 / Revised: 14 July 2014 / Accepted: 15 July 2014 / Published: 30 July 2014
Cited by 2 | PDF Full-text (6161 KB) | HTML Full-text | XML Full-text
Abstract
During the manufacturing process multi-strand conductors are subject to compressive force and rotation moments. The current distribution in the multi-strand conductors is not uniform and is controlled by the transverse resistivity. This is mainly determined by the contact resistance at the strand crossovers
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During the manufacturing process multi-strand conductors are subject to compressive force and rotation moments. The current distribution in the multi-strand conductors is not uniform and is controlled by the transverse resistivity. This is mainly determined by the contact resistance at the strand crossovers and inter-strand contact resistance. The surface layer properties, and in particular the crystalline structure and degree of oxidation, are key parameters in determining the transverse resistivity. The experimental set-ups made it possible to find the dependence of contact resistivity as a function of continuous working stresses and cable design. A study based on measurements and numerical simulation is made to identify the contact resistivity functions. Full article
Open AccessCommunication eL-Chem Viewer: A Freeware Package for the Analysis of Electroanalytical Data and Their Post-Acquisition Processing
Sensors 2014, 14(8), 13943-13954; doi:10.3390/s140813943
Received: 27 June 2014 / Revised: 19 July 2014 / Accepted: 22 July 2014 / Published: 31 July 2014
Cited by 6 | PDF Full-text (1843 KB) | HTML Full-text | XML Full-text
Abstract
In electrochemical sensing, a number of voltammetric or amperometric curves are obtained which are subsequently processed, typically by evaluating peak currents and peak potentials or wave heights and half-wave potentials, frequently after background correction. Transformations of voltammetric data can help to extract specific
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In electrochemical sensing, a number of voltammetric or amperometric curves are obtained which are subsequently processed, typically by evaluating peak currents and peak potentials or wave heights and half-wave potentials, frequently after background correction. Transformations of voltammetric data can help to extract specific information, e.g., the number of transferred electrons, and can reveal aspects of the studied electrochemical system, e.g., the contribution of adsorption phenomena. In this communication, we introduce a LabView-based software package, ‘eL-Chem Viewer’, which is for the analysis of voltammetric and amperometric data, and enables their post-acquisition processing using semiderivative, semiintegral, derivative, integral and elimination procedures. The software supports the single-click transfer of peak/wave current and potential data to spreadsheet software, a feature that greatly improves productivity when constructing calibration curves, trumpet plots and performing similar tasks. eL-Chem Viewer is freeware and can be downloaded from www.lchem.cz/elchemviewer.htm. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Ambient Agents: Embedded Agents for Remote Control and Monitoring Using the PANGEA Platform
Sensors 2014, 14(8), 13955-13979; doi:10.3390/s140813955
Received: 8 April 2014 / Revised: 15 July 2014 / Accepted: 21 July 2014 / Published: 31 July 2014
Cited by 3 | PDF Full-text (759 KB) | HTML Full-text | XML Full-text
Abstract
Ambient intelligence has advanced significantly during the last few years. The incorporation of image processing and artificial intelligence techniques have opened the possibility for such aspects as pattern recognition, thus allowing for a better adaptation of these systems. This study presents a new
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Ambient intelligence has advanced significantly during the last few years. The incorporation of image processing and artificial intelligence techniques have opened the possibility for such aspects as pattern recognition, thus allowing for a better adaptation of these systems. This study presents a new model of an embedded agent especially designed to be implemented in sensing devices with resource constraints. This new model of an agent is integrated within the PANGEA (Platform for the Automatic Construction of Organiztions of Intelligent Agents) platform, an organizational-based platform, defining a new sensor role in the system and aimed at providing contextual information and interacting with the environment. A case study was developed over the PANGEA platform and designed using different agents and sensors responsible for providing user support at home in the event of incidents or emergencies. The system presented in the case study incorporates agents in Arduino hardware devices with recognition modules and illuminated bands; it also incorporates IP cameras programmed for automatic tracking, which can connect remotely in the event of emergencies. The user wears a bracelet, which contains a simple vibration sensor that can receive notifications about the emergency situation. Full article
(This article belongs to the Special Issue Sensors Data Fusion for Healthcare)
Open AccessArticle A Novel Diagnosis Method for a Hall Plates-Based Rotary Encoder with a Magnetic Concentrator
Sensors 2014, 14(8), 13980-13998; doi:10.3390/s140813980
Received: 31 May 2014 / Revised: 7 July 2014 / Accepted: 8 July 2014 / Published: 31 July 2014
Cited by 1 | PDF Full-text (1523 KB) | HTML Full-text | XML Full-text
Abstract
In the last few years, rotary encoders based on two-dimensional complementary metal oxide semiconductors (CMOS) Hall plates with a magnetic concentrator have been developed to measure contactless absolute angle. There are various error factors influencing the measuring accuracy, which are difficult to locate
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In the last few years, rotary encoders based on two-dimensional complementary metal oxide semiconductors (CMOS) Hall plates with a magnetic concentrator have been developed to measure contactless absolute angle. There are various error factors influencing the measuring accuracy, which are difficult to locate after the assembly of encoder. In this paper, a model-based rapid diagnosis method is presented. Based on an analysis of the error mechanism, an error model is built to compare minimum residual angle error and to quantify the error factors. Additionally, a modified particle swarm optimization (PSO) algorithm is used to reduce the calculated amount. The simulation and experimental results show that this diagnosis method is feasible to quantify the causes of the error and to reduce iteration significantly. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Analytical and Numerical Investigations into Hemisphere-Shaped Electrostatic Sensors
Sensors 2014, 14(8), 14021-14037; doi:10.3390/s140814021
Received: 21 March 2014 / Revised: 27 June 2014 / Accepted: 27 June 2014 / Published: 31 July 2014
Cited by 2 | PDF Full-text (922 KB) | HTML Full-text | XML Full-text
Abstract
Electrostatic sensors have been widely used in many applications due to their advantages of low cost and robustness. Their spatial sensitivity and time-frequency characteristics are two important performance parameters. In this paper, an analytical model of the induced charge on a novel hemisphere-shaped
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Electrostatic sensors have been widely used in many applications due to their advantages of low cost and robustness. Their spatial sensitivity and time-frequency characteristics are two important performance parameters. In this paper, an analytical model of the induced charge on a novel hemisphere-shaped electrostatic sensor was presented to investigate its accurate sensing characteristics. Firstly a Poisson model was built for electric fields produced by charged particles. Then the spatial sensitivity and time-frequency response functions were directly derived by the Green function. Finally, numerical calculations were done to validate the theoretical results. The results demonstrate that the hemisphere-shaped sensors have highly 3D-symmetrical spatial sensitivity expressed in terms of elementary function, and the spatial sensitivity is higher and less homogeneous near the hemispherical surface and vice versa. Additionally, the whole monitoring system, consisting of an electrostatic probe and a signal conditioner circuit, acts as a band-pass filter. The time-frequency characteristics depend strongly on the spatial position and velocity of the charged particle, the radius of the probe as well as the equivalent resistance and capacitance of the circuit. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Anion Binding Studies on Receptors Derived from the Indolo[2,3-a]carbazole Scaffold Having Different Binding Cavity Sizes
Sensors 2014, 14(8), 14038-14049; doi:10.3390/s140814038
Received: 4 July 2014 / Revised: 25 July 2014 / Accepted: 28 July 2014 / Published: 31 July 2014
PDF Full-text (1042 KB) | HTML Full-text | XML Full-text
Abstract
The indolo[2,3-a]carbazole scaffold is a fused polyheteroaromatic system bearing two NH groups which suitably converge as hydrogen bond donor sites for the recognition of anions. A simple derivatisation of the indolocarbazole system at positions 1 and 10 with different functional groups,
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The indolo[2,3-a]carbazole scaffold is a fused polyheteroaromatic system bearing two NH groups which suitably converge as hydrogen bond donor sites for the recognition of anions. A simple derivatisation of the indolocarbazole system at positions 1 and 10 with different functional groups, namely alcohols and amides, has contributed to modulate the anion binding selectivity and sensibility. A particularly good response has been obtained for the benzoate anion. Full article
(This article belongs to the Special Issue Molecular Sensing and Molecular Electronics)
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Open AccessArticle Analysis of Vehicle Detection with WSN-Based Ultrasonic Sensors
Sensors 2014, 14(8), 14050-14069; doi:10.3390/s140814050
Received: 11 June 2014 / Revised: 22 July 2014 / Accepted: 24 July 2014 / Published: 4 August 2014
Cited by 9 | PDF Full-text (3687 KB) | HTML Full-text | XML Full-text
Abstract
Existing traffic information acquisition systems suffer from high cost and low scalability. To address these problems, the application of wireless sensor networks (WSNs) has been studied, as WSN-based systems are highly scalable and have a low cost of installing and replacing the systems.
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Existing traffic information acquisition systems suffer from high cost and low scalability. To address these problems, the application of wireless sensor networks (WSNs) has been studied, as WSN-based systems are highly scalable and have a low cost of installing and replacing the systems. Magnetic, acoustic and accelerometer sensors have been considered for WSN-based traffic surveillance, but the use of ultrasonic sensors has not been studied. The limitations of WSN-based systems make it necessary to employ power saving methods and vehicle detection algorithms with low computational complexity. In this paper, we model and analyze optimal power saving methodologies for an ultrasonic sensor and present a computationally-efficient vehicle detection algorithm using ultrasonic data. The proposed methodologies are implemented and evaluated with a tiny microprocessor on real roads. The evaluation results show that the low computational complexity of our algorithm does not compromise the accuracy of vehicle detection. Full article
(This article belongs to the Special Issue Positioning and Tracking Sensors and Technologies in Road Transport)
Open AccessArticle A Cloud-Based Internet of Things Platform for Ambient Assisted Living
Sensors 2014, 14(8), 14070-14105; doi:10.3390/s140814070
Received: 13 April 2014 / Revised: 12 July 2014 / Accepted: 25 July 2014 / Published: 4 August 2014
Cited by 13 | PDF Full-text (2308 KB) | HTML Full-text | XML Full-text
Abstract
A common feature of ambient intelligence is that many objects are inter-connected and act in unison, which is also a challenge in the Internet of Things. There has been a shift in research towards integrating both concepts, considering the Internet of Things as
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A common feature of ambient intelligence is that many objects are inter-connected and act in unison, which is also a challenge in the Internet of Things. There has been a shift in research towards integrating both concepts, considering the Internet of Things as representing the future of computing and communications. However, the efficient combination and management of heterogeneous things or devices in the ambient intelligence domain is still a tedious task, and it presents crucial challenges. Therefore, to appropriately manage the inter-connection of diverse devices in these systems requires: (1) specifying and efficiently implementing the devices (e.g., as services); (2) handling and verifying their heterogeneity and composition; and (3) standardizing and managing their data, so as to tackle large numbers of systems together, avoiding standalone applications on local servers. To overcome these challenges, this paper proposes a platform to manage the integration and behavior-aware orchestration of heterogeneous devices as services, stored and accessed via the cloud, with the following contributions: (i) we describe a lightweight model to specify the behavior of devices, to determine the order of the sequence of exchanged messages during the composition of devices; (ii) we define a common architecture using a service-oriented standard environment, to integrate heterogeneous devices by means of their interfaces, via a gateway, and to orchestrate them according to their behavior; (iii) we design a framework based on cloud computing technology, connecting the gateway in charge of acquiring the data from the devices with a cloud platform, to remotely access and monitor the data at run-time and react to emergency situations; and (iv) we implement and generate a novel cloud-based IoT platform of behavior-aware devices as services for ambient intelligence systems, validating the whole approach in real scenarios related to a specific ambient assisted living application. Full article
Open AccessArticle Relevance-Based Template Matching for Tracking Targets in FLIR Imagery
Sensors 2014, 14(8), 14106-14130; doi:10.3390/s140814106
Received: 16 May 2014 / Revised: 17 July 2014 / Accepted: 17 July 2014 / Published: 4 August 2014
Cited by 5 | PDF Full-text (3035 KB) | HTML Full-text | XML Full-text
Abstract
One of the main challenges in automatic target tracking applications is represented by the need to maintain a low computational footprint, especially when dealing with real-time scenarios and the limited resources of embedded environments. In this context, significant results can be obtained by
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One of the main challenges in automatic target tracking applications is represented by the need to maintain a low computational footprint, especially when dealing with real-time scenarios and the limited resources of embedded environments. In this context, significant results can be obtained by using forward-looking infrared sensors capable of providing distinctive features for targets of interest. In fact, due to their nature, forward-looking infrared (FLIR) images lend themselves to being used with extremely small footprint techniques based on the extraction of target intensity profiles. This work proposes a method for increasing the computational efficiency of template-based target tracking algorithms. In particular, the speed of the algorithm is improved by using a dynamic threshold that narrows the number of computations, thus reducing both execution time and resources usage. The proposed approach has been tested on several datasets, and it has been compared to several target tracking techniques. Gathered results, both in terms of theoretical analysis and experimental data, showed that the proposed approach is able to achieve the same robustness of reference algorithms by reducing the number of operations needed and the processing time. Full article
Open AccessArticle Minimum Time Search in Uncertain Dynamic Domains with Complex Sensorial Platforms
Sensors 2014, 14(8), 14131-14179; doi:10.3390/s140814131
Received: 3 February 2014 / Revised: 21 July 2014 / Accepted: 25 July 2014 / Published: 4 August 2014
Cited by 3 | PDF Full-text (6485 KB) | HTML Full-text | XML Full-text
Abstract
The minimum time search in uncertain domains is a searching task, which appears in real world problems such as natural disasters and sea rescue operations, where a target has to be found, as soon as possible, by a set of sensor-equipped searchers. The
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The minimum time search in uncertain domains is a searching task, which appears in real world problems such as natural disasters and sea rescue operations, where a target has to be found, as soon as possible, by a set of sensor-equipped searchers. The automation of this task, where the time to detect the target is critical, can be achieved by new probabilistic techniques that directly minimize the Expected Time (ET) to detect a dynamic target using the observation probability models and actual observations collected by the sensors on board the searchers. The selected technique, described in algorithmic form in this paper for completeness, has only been previously partially tested with an ideal binary detection model, in spite of being designed to deal with complex non-linear/non-differential sensorial models. This paper covers the gap, testing its performance and applicability over different searching tasks with searchers equipped with different complex sensors. The sensorial models under test vary from stepped detection probabilities to continuous/discontinuous differentiable/non-differentiable detection probabilities dependent on distance, orientation, and structured maps. The analysis of the simulated results of several static and dynamic scenarios performed in this paper validates the applicability of the technique with different types of sensor models. Full article
Open AccessArticle Optimal Service Distribution in WSN Service System Subject to Data Security Constraints
Sensors 2014, 14(8), 14180-14209; doi:10.3390/s140814180
Received: 28 May 2014 / Revised: 15 July 2014 / Accepted: 16 July 2014 / Published: 4 August 2014
Cited by 2 | PDF Full-text (12653 KB) | HTML Full-text | XML Full-text
Abstract
Services composition technology provides a flexible approach to building Wireless Sensor Network (WSN) Service Applications (WSA) in a service oriented tasking system for WSN. Maintaining the data security of WSA is one of the most important goals in sensor network research. In this
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Services composition technology provides a flexible approach to building Wireless Sensor Network (WSN) Service Applications (WSA) in a service oriented tasking system for WSN. Maintaining the data security of WSA is one of the most important goals in sensor network research. In this paper, we consider a WSN service oriented tasking system in which the WSN Services Broker (WSB), as the resource management center, can map the service request from user into a set of atom-services (AS) and send them to some independent sensor nodes (SN) for parallel execution. The distribution of ASs among these SNs affects the data security as well as the reliability and performance of WSA because these SNs can be of different and independent specifications. By the optimal service partition into the ASs and their distribution among SNs, the WSB can provide the maximum possible service reliability and/or expected performance subject to data security constraints. This paper proposes an algorithm of optimal service partition and distribution based on the universal generating function (UGF) and the genetic algorithm (GA) approach. The experimental analysis is presented to demonstrate the feasibility of the suggested algorithm. Full article
(This article belongs to the Special Issue Sensor Computing for Mobile Security and Big Data Analytics)
Open AccessArticle A Thermally Annealed Mach-Zehnder Interferometer for High Temperature Measurement
Sensors 2014, 14(8), 14210-14221; doi:10.3390/s140814210
Received: 23 May 2014 / Revised: 21 July 2014 / Accepted: 25 July 2014 / Published: 4 August 2014
Cited by 1 | PDF Full-text (990 KB) | HTML Full-text | XML Full-text
Abstract
An in-fiber Mach-Zehnder interferometer (MZI) for high temperature measurement is proposed and experimentally demonstrated. The device is constructed of a piece of thin-core fiber (TCF) sandwiched between two short sections of multimode fiber (MMF), i.e., a MMF-TCF-MMF structure. A well-defined interference spectrum
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An in-fiber Mach-Zehnder interferometer (MZI) for high temperature measurement is proposed and experimentally demonstrated. The device is constructed of a piece of thin-core fiber (TCF) sandwiched between two short sections of multimode fiber (MMF), i.e., a MMF-TCF-MMF structure. A well-defined interference spectrum is obtained owing to the core-mismatch, and the interference dips are sensitive to the ambient temperature. The experimental results show that the proposed interferometer is capable of high temperature measurement up to 875 °C with a sensitivity of 92 pm/°C over repeated measurements. The explored wavelength drop point may limit the measurement range, which can be improved by repeated thermal annealing. Full article
Open AccessArticle Development of a Hydrogen Peroxide Sensor Based on Screen-Printed Electrodes Modified with Inkjet-Printed Prussian Blue Nanoparticles
Sensors 2014, 14(8), 14222-14234; doi:10.3390/s140814222
Received: 13 June 2014 / Revised: 16 July 2014 / Accepted: 23 July 2014 / Published: 4 August 2014
Cited by 9 | PDF Full-text (2422 KB) | HTML Full-text | XML Full-text
Abstract
A sensor for the simple and sensitive measurement of hydrogen peroxide has been developed which is based on screen printed electrodes (SPEs) modified with Prussian blue nanoparticles (PBNPs) deposited using piezoelectric inkjet printing. PBNP-modified SPEs were characterized using physical and electrochemical techniques to
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A sensor for the simple and sensitive measurement of hydrogen peroxide has been developed which is based on screen printed electrodes (SPEs) modified with Prussian blue nanoparticles (PBNPs) deposited using piezoelectric inkjet printing. PBNP-modified SPEs were characterized using physical and electrochemical techniques to optimize the PBNP layer thickness and electroanalytical conditions for optimum measurement of hydrogen peroxide. Sensor optimization resulted in a limit of detection of 2 × 10−7 M, a linear range from 0 to 4.5 mM and a sensitivity of 762 μA∙mM–1∙cm–2 which was achieved using 20 layers of printed PBNPs. Sensors also demonstrated excellent reproducibility (<5% rsd). Full article
(This article belongs to the Special Issue Printed Sensors)
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Open AccessArticle Development of a Modularized Seating System to Actively Manage Interface Pressure
Sensors 2014, 14(8), 14235-14252; doi:10.3390/s140814235
Received: 14 May 2014 / Revised: 6 July 2014 / Accepted: 28 July 2014 / Published: 5 August 2014
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Abstract
Pressure ulcers can be a fatal complication. Many immobile wheelchair users face this threat. Current passive and active cushions do reduce the incidence of pressure ulcers and they have different merits. We proposed an active approach to combine their advantages which is based
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Pressure ulcers can be a fatal complication. Many immobile wheelchair users face this threat. Current passive and active cushions do reduce the incidence of pressure ulcers and they have different merits. We proposed an active approach to combine their advantages which is based on the concept that the interface pressure can be changed with different supporting shapes. The purpose of this paper is to verify the proposed approach. With practical applications in mind, we have developed a modular system whose support surface is composed by height-adjustable support elements. Each four-element module was self-contained and composed of force sensors, position sensors, linear actuators, signal conditioners, driving circuits, and signal processors. The modules could be chained and assembled together easily to form different-sized support surfaces. Each support element took up a 3 cm × 3 cm supporting area. The displacement resolution was less than 0.1 mm and the force sensor error was less than 1% in the 2000 g range. Each support element of the system could provide 49 N pushing force (408 mmHg over the 3 cm × 3 cm area) at a speed of 2.36 mm/s. Several verification tests were performed to assess the whole system’s feasibility. Further improvements and clinical applications were discussed. In conclusion, this modularized system is capable of actively managing interface pressure in real time. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
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Open AccessArticle Appearance-Based Multimodal Human Tracking and Identification for Healthcare in the Digital Home
Sensors 2014, 14(8), 14253-14277; doi:10.3390/s140814253
Received: 2 April 2014 / Revised: 3 July 2014 / Accepted: 8 July 2014 / Published: 5 August 2014
Cited by 4 | PDF Full-text (1725 KB) | HTML Full-text | XML Full-text
Abstract
There is an urgent need for intelligent home surveillance systems to provide home security, monitor health conditions, and detect emergencies of family members. One of the fundamental problems to realize the power of these intelligent services is how to detect, track, and identify
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There is an urgent need for intelligent home surveillance systems to provide home security, monitor health conditions, and detect emergencies of family members. One of the fundamental problems to realize the power of these intelligent services is how to detect, track, and identify people at home. Compared to RFID tags that need to be worn all the time, vision-based sensors provide a natural and nonintrusive solution. Observing that body appearance and body build, as well as face, provide valuable cues for human identification, we model and record multi-view faces, full-body colors and shapes of family members in an appearance database by using two Kinects located at a home’s entrance. Then the Kinects and another set of color cameras installed in other parts of the house are used to detect, track, and identify people by matching the captured color images with the registered templates in the appearance database. People are detected and tracked by multisensor fusion (Kinects and color cameras) using a Kalman filter that can handle duplicate or partial measurements. People are identified by multimodal fusion (face, body appearance, and silhouette) using a track-based majority voting. Moreover, the appearance-based human detection, tracking, and identification modules can cooperate seamlessly and benefit from each other. Experimental results show the effectiveness of the human tracking across multiple sensors and human identification considering the information of multi-view faces, full-body clothes, and silhouettes. The proposed home surveillance system can be applied to domestic applications in digital home security and intelligent healthcare. Full article
(This article belongs to the Special Issue Sensors Data Fusion for Healthcare)
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Open AccessArticle Dual-Element Transducer with Phase-Inversion for Wide Depth of Field in High-Frequency Ultrasound Imaging
Sensors 2014, 14(8), 14278-14288; doi:10.3390/s140814278
Received: 4 June 2014 / Revised: 14 July 2014 / Accepted: 28 July 2014 / Published: 5 August 2014
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Abstract
In high frequency ultrasound imaging (HFUI), the quality of focusing is deeply related to the length of the depth of field (DOF). In this paper, a phase-inversion technique implemented by a dual-element transducer is proposed to enlarge the DOF. The performance of the
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In high frequency ultrasound imaging (HFUI), the quality of focusing is deeply related to the length of the depth of field (DOF). In this paper, a phase-inversion technique implemented by a dual-element transducer is proposed to enlarge the DOF. The performance of the proposed method was numerically demonstrated by using the ultrasound simulation program called Field-II. A simulated dual-element transducer was composed of a disc- and an annular-type elements, and its aperture was concavely shaped to have a confocal point at 6 mm. The area of each element was identical in order to provide same intensity at the focal point. The outer diameters of the inner and the outer elements were 2.1 mm and 3 mm, respectively. The center frequency of each element was 40 MHz and the f-number (focal depth/aperture size) was two. When two input signals with 0° and 180° phases were applied to inner and outer elements simultaneously, a multi-focal zone was generated in the axial direction. The total −6 dB DOF, i.e., sum of two −6 dB DOFs in the near and far field lobes, was 40% longer than that of the conventional single element transducer. The signal to noise ratio (SNR) was increased by about two times, especially in the far field. The point and cyst phantom simulation were conducted and their results were identical to that of the beam pattern simulation. Thus, the proposed scheme may be a potential method to improve the DOF and SNR in HFUI. Full article
Open AccessArticle A Class of Coning Algorithms Based on a Half-Compressed Structure
Sensors 2014, 14(8), 14289-14301; doi:10.3390/s140814289
Received: 7 May 2014 / Revised: 7 July 2014 / Accepted: 23 July 2014 / Published: 6 August 2014
Cited by 4 | PDF Full-text (732 KB) | HTML Full-text | XML Full-text | Correction
Abstract
Aiming to advance the coning algorithm performance of strapdown inertial navigation systems, a new half-compressed coning correction structure is presented. The half-compressed algorithm structure is analytically proven to be equivalent to the traditional compressed structure under coning environments. The half-compressed algorithm coefficients allow
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Aiming to advance the coning algorithm performance of strapdown inertial navigation systems, a new half-compressed coning correction structure is presented. The half-compressed algorithm structure is analytically proven to be equivalent to the traditional compressed structure under coning environments. The half-compressed algorithm coefficients allow direct configuration from traditional compressed algorithm coefficients. A type of algorithm error model is defined for coning algorithm performance evaluation under maneuver environment conditions. Like previous uncompressed algorithms, the half-compressed algorithm has improved maneuver accuracy and retained coning accuracy compared with its corresponding compressed algorithm. Compared with prior uncompressed algorithms, the formula for the new algorithm coefficients is simpler. Full article
(This article belongs to the Special Issue Optical Gyroscopes and Navigation Systems)
Open AccessArticle A Mobile Virtual Butler to Bridge the Gap between Users and Ambient Assisted Living: A Smart Home Case Study
Sensors 2014, 14(8), 14302-14329; doi:10.3390/s140814302
Received: 1 May 2014 / Revised: 2 July 2014 / Accepted: 30 July 2014 / Published: 6 August 2014
Cited by 3 | PDF Full-text (6095 KB) | HTML Full-text | XML Full-text
Abstract
Ambient Intelligence promises to transform current spaces into electronic environments that are responsive, assistive and sensitive to human presence. Those electronic environments will be fully populated with dozens, hundreds or even thousands of connected devices that share information and thus become intelligent. That
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Ambient Intelligence promises to transform current spaces into electronic environments that are responsive, assistive and sensitive to human presence. Those electronic environments will be fully populated with dozens, hundreds or even thousands of connected devices that share information and thus become intelligent. That massive wave of electronic devices will also invade everyday objects, turning them into smart entities, keeping their native features and characteristics while seamlessly promoting them to a new class of thinking and reasoning everyday objects. Although there are strong expectations that most of the users’ needs can be fulfilled without their intervention, there are still situations where interaction is required. This paper presents work being done in the field of human-computer interaction, focusing on smart home environments, while being a part of a larger project called Aging Inside a Smart Home. This initiative arose as a way to deal with a large scourge of our country, where lots of elderly persons live alone in their homes, often with limited or no physical mobility. The project relies on the mobile agent computing paradigm in order to create a Virtual Butler that provides the interface between the elderly and the smart home infrastructure. The Virtual Butler is receptive to user questions, answering them according to the context and knowledge of the AISH. It is also capable of interacting with the user whenever it senses that something has gone wrong, notifying next of kin and/or medical services, etc. The Virtual Butler is aware of the user location and moves to the computing device which is closest to the user, in order to be always present. Its avatar can also run in handheld devices keeping its main functionality in order to track user when s/he goes out. According to the evaluation carried out, the Virtual Butler is assessed as a very interesting and loved digital friend, filling the gap between the user and the smart home. The evaluation also showed that the Virtual Butler concept can be easily ported to other types of possible smart and assistive environments like airports, hospitals, shopping malls, offices, etc. Full article
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Open AccessArticle Laser-Machined Microcavities for Simultaneous Measurement of High-Temperature and High-Pressure
Sensors 2014, 14(8), 14330-14338; doi:10.3390/s140814330
Received: 10 March 2014 / Revised: 24 May 2014 / Accepted: 22 July 2014 / Published: 7 August 2014
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Abstract
Laser-machined microcavities for simultaneous measurement of high-temperature and high-pressure are demonstrated. These two cascaded microcavities are an air cavity and a composite cavity including a section of fiber and an air cavity. They are both placed into a pressure chamber inside a furnace
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Laser-machined microcavities for simultaneous measurement of high-temperature and high-pressure are demonstrated. These two cascaded microcavities are an air cavity and a composite cavity including a section of fiber and an air cavity. They are both placed into a pressure chamber inside a furnace to perform simultaneous pressure and high-temperature tests. The thermal and pressure coefficients of the short air cavity are ~0.0779 nm/°C and ~1.14 nm/MPa, respectively. The thermal and pressure coefficients of the composite cavity are ~32.3 nm/°C and ~24.4 nm/MPa, respectively. The sensor could be used to separate temperature and pressure due to their different thermal and pressure coefficients. The excellent feature of such a sensor head is that it can withstand high temperatures of up to 400 °C and achieve precise measurement of high-pressure under high temperature conditions. Full article
(This article belongs to the Special Issue Micro-Optical Sensors)
Open AccessArticle Nitrogen-Rich Multinuclear Ferrocenophanes as Multichannel Chemosensor Molecules for Transition and Heavy-Metal Cations
Sensors 2014, 14(8), 14339-14355; doi:10.3390/s140814339
Received: 1 July 2014 / Revised: 23 July 2014 / Accepted: 27 July 2014 / Published: 7 August 2014
Cited by 4 | PDF Full-text (4768 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
[m.n] Multinuclear ferrocenophanes prepared by aza-Wittig reaction of bisiminophosphoranes derived from 1,1'-diazidoferrocene and isophthaladelhyde or 2,5-diformylthiophene, behave as efficient electrochemical and chromogenic chemosensor molecules for Zn2+, Pb2+, and Hg2+ metal cations. Whereas the OSWV of receptor 3,
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[m.n] Multinuclear ferrocenophanes prepared by aza-Wittig reaction of bisiminophosphoranes derived from 1,1'-diazidoferrocene and isophthaladelhyde or 2,5-diformylthiophene, behave as efficient electrochemical and chromogenic chemosensor molecules for Zn2+, Pb2+, and Hg2+ metal cations. Whereas the OSWV of receptor 3, bearing two m-phenylene units in the bridges, display one oxidation peak, receptor 4 incorporating two thiophene rings in the bridges, exhibits two well-separated oxidation peaks. In both receptors only the addition of Zn2+, Pb2+, and Hg2+ metal cations induced a remarkable anodic shift of ferrocene/ferrocenium redox couple. Likewise, in the absorption spectra of these receptors the low energy band is red-shifted by Δλ = 165 − 209 nm, and these changes promoted a significant color changes which could be used for the naked eye detection of these metal cations. The coordination modes for two representative cases were unveiled by DFT calculations that show an unsual coordination in the [42Pb]2+ complex with the Pb2+ cation in a distorted cubic N4S4 donor cage. Full article
(This article belongs to the Special Issue Molecular Sensing and Molecular Electronics)
Open AccessArticle Examination of a Mechanical Amplifier in the Incudostapedial Joint Gap: FEM Simulation and Physical Model
Sensors 2014, 14(8), 14356-14374; doi:10.3390/s140814356
Received: 15 June 2014 / Revised: 22 July 2014 / Accepted: 31 July 2014 / Published: 7 August 2014
Cited by 3 | PDF Full-text (2090 KB) | HTML Full-text | XML Full-text
Abstract
Implantable assembly components that are biocompatible and highly miniaturized are an important objective for hearing aid development. We introduce a mechanical transducer, which could be suitable as part of a prospective fully-implantable hearing aid. The transducer comprises a sensor and an actuator unit
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Implantable assembly components that are biocompatible and highly miniaturized are an important objective for hearing aid development. We introduce a mechanical transducer, which could be suitable as part of a prospective fully-implantable hearing aid. The transducer comprises a sensor and an actuator unit in one housing, located in the joint gap between the middle ear ossicles, the incus and stapes. The setup offers the advantage of a minimally invasive and reversible surgical solution. However, feedback between actuator and sensor due to mechanical coupling limits the available stable gain. We show that the system can be stabilized by digital control algorithms. The transducer is tested both in a finite elements method simulation of the middle ear and a physical model of a human middle ear. First, we characterize the sensor and actuator elements separately. Then, the maximum stable gain (MSG) of the whole transducer is experimentally determined in the middle ear model. With digital feedback control (using a least mean squares algorithm) in place, the total signal gain is greater than 30 dB for frequencies of 1 kHz and above. This shows the potential of the transducer as a high frequency hearing aid. Full article
(This article belongs to the Special Issue Implantable Sensors)
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Open AccessArticle Indoor Magnetic Signature Based Localization Algorithm without Person-Dependent Parameter Calibration
Sensors 2014, 14(8), 14375-14398; doi:10.3390/s140814375
Received: 24 February 2014 / Revised: 25 July 2014 / Accepted: 31 July 2014 / Published: 7 August 2014
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Abstract
Location-dependent differences of ambient magnetic fields inside a building can be used to estimate location. In this paper, an inertial/magnetic sensor is attached to a belt position and its location is estimated using the ambient magnetic field. The walking distance is estimated using
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Location-dependent differences of ambient magnetic fields inside a building can be used to estimate location. In this paper, an inertial/magnetic sensor is attached to a belt position and its location is estimated using the ambient magnetic field. The walking distance is estimated using the linear relationship between the walking step length and the maximum acceleration during the step. The magnetic field data during walking is compared with a pre-collected magnetic signature. In this process, calibration steps are required for two person-dependent parameters : the walking step length estimation parameter and the hard iron parameter. An adaptive algorithm is proposed, in which these person-dependent parameters are estimated in addition to the location. Thus no person-dependent parameter calibration process is required. Through experiments, it is shown that the location and parameters are estimated accurately. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle A Study on N2O Measurement Characteristics Using Photoacoustic Spectroscopy (PAS)
Sensors 2014, 14(8), 14399-14410; doi:10.3390/s140814399
Received: 14 May 2014 / Revised: 18 July 2014 / Accepted: 23 July 2014 / Published: 7 August 2014
Cited by 3 | PDF Full-text (375 KB) | HTML Full-text | XML Full-text
Abstract
N2O, which is emitted mainly from nitrogen decomposition via bacteria, livestock manure, agricultural fertilizer use, fossil fuel combustion and waste incineration, is classified as a substance that causes significant destruction of the ozone layer. The N2O measurement methods for
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N2O, which is emitted mainly from nitrogen decomposition via bacteria, livestock manure, agricultural fertilizer use, fossil fuel combustion and waste incineration, is classified as a substance that causes significant destruction of the ozone layer. The N2O measurement methods for these emission sources may be divided into chromatography, optical, and electrical current measurements. Chromatography has been widely utilized for analyzing N2O. However, up until now, few studies have been conducted on N2O using photoacoustic spectroscopy. Therefore, this study aimed to evaluate performance of photoacoustic spectroscopy in this regard based on laboratory and field test results. The repeatability of photoacoustic spectroscopy was measured at 1.12%, which is lower than the repeatability of 3.0% suggested by the ISO 1564 standard, so, it has shown an excellent repeatability. The detection limit was determined to be 0.025 ppm, and the response time was confirmed to be 3 min and 26 s. The results of comparison between these measurements and GC show that the latter has superior accuracy, but mobility and convenience are superior for PAS. On the contrary, GC has a continuous measurement limitation, but PAS makes it possible to conduct continuous measurements. Therefore, PAS can be extremely useful to confirm the characteristics of N2O emissions and to quantify their amount. Full article
(This article belongs to the Special Issue Modern Technologies for Sensing Pollution in Air, Water, and Soil)
Open AccessArticle A Unitary ESPRIT Scheme of Joint Angle Estimation for MOTS MIMO Radar
Sensors 2014, 14(8), 14411-14422; doi:10.3390/s140814411
Received: 22 May 2014 / Revised: 24 June 2014 / Accepted: 24 June 2014 / Published: 7 August 2014
Cited by 2 | PDF Full-text (172 KB) | HTML Full-text | XML Full-text
Abstract
The transmit array of multi-overlapped-transmit-subarray configured bistatic multiple-input multiple-output (MOTS MIMO) radar is partitioned into a number of overlapped subarrays, which is different from the traditional bistatic MIMO radar. In this paper, a new unitary ESPRIT scheme for joint estimation of the direction
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The transmit array of multi-overlapped-transmit-subarray configured bistatic multiple-input multiple-output (MOTS MIMO) radar is partitioned into a number of overlapped subarrays, which is different from the traditional bistatic MIMO radar. In this paper, a new unitary ESPRIT scheme for joint estimation of the direction of departure (DOD) and the direction of arrival (DOA) for MOTS MIMO radar is proposed. In our method, each overlapped-transmit-subarray (OTS) with the identical effective aperture is regarded as a transmit element and the characteristics that the phase delays between the two OTSs is utilized. First, the measurements corresponding to all the OTSs are partitioned into two groups which have a rotational invariance relationship with each other. Then, the properties of centro-Hermitian matrices and real-valued rotational invariance factors are exploited to double the measurement samples and reduce computational complexity. Finally, the close-formed solution of automatically paired DOAs and DODs of targets is derived in a new manner. The proposed scheme provides increased estimation accuracy with the combination of inherent advantages of MOTS MIMO radar with unitary ESPRIT. Simulation results are presented to demonstrate the effectiveness and advantage of the proposed scheme. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Electrochemical Quantification of the Antioxidant Capacity of Medicinal Plants Using Biosensors
Sensors 2014, 14(8), 14423-14439; doi:10.3390/s140814423
Received: 30 June 2014 / Revised: 28 July 2014 / Accepted: 30 July 2014 / Published: 8 August 2014
Cited by 8 | PDF Full-text (767 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The working area of a screen-printed electrode, SPE, was modified with the enzyme tyrosinase (Tyr) using different immobilization methods, namely entrapment with water-soluble polyvinyl alcohol (PVA), cross-linking using glutaraldehyde (GA), and cross-linking using GA and human serum albumin (HSA); the resulting electrodes were
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The working area of a screen-printed electrode, SPE, was modified with the enzyme tyrosinase (Tyr) using different immobilization methods, namely entrapment with water-soluble polyvinyl alcohol (PVA), cross-linking using glutaraldehyde (GA), and cross-linking using GA and human serum albumin (HSA); the resulting electrodes were termed SPE/Tyr/PVA, SPE/Tyr/GA and SPE/Tyr/HSA/GA, respectively. These biosensors were characterized by means of amperometry and EIS techniques. From amperometric evaluations, the apparent Michaelis-Menten constant, Km′, of each biosensor was evaluated while the respective charge transfer resistance, Rct, was assessed from impedance measurements. It was found that the SPE/Tyr/GA had the smallest Km′ (57 ± 7) µM and Rct values. This electrode also displayed both the lowest detection and quantification limits for catechol quantification. Using the SPE/Tyr/GA, the Trolox Equivalent Antioxidant Capacity (TEAC) was determined from infusions prepared with “mirto” (Salvia microphylla), “hHierba dulce” (Lippia dulcis) and “salve real” (Lippia alba), medicinal plants commonly used in Mexico. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle An Adaptive Jitter Mechanism for Reactive Route Discovery in Sensor Networks
Sensors 2014, 14(8), 14440-14471; doi:10.3390/s140814440
Received: 21 April 2014 / Revised: 16 July 2014 / Accepted: 21 July 2014 / Published: 8 August 2014
Cited by 3 | PDF Full-text (430 KB) | HTML Full-text | XML Full-text
Abstract
This paper analyses the impact of jitter when applied to route discovery in reactive (on-demand) routing protocols. In multi-hop non-synchronized wireless networks, jitter—a small, random variation in the timing of message emission—is commonly employed, as a means to avoid collisions of simultaneous transmissions
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This paper analyses the impact of jitter when applied to route discovery in reactive (on-demand) routing protocols. In multi-hop non-synchronized wireless networks, jitter—a small, random variation in the timing of message emission—is commonly employed, as a means to avoid collisions of simultaneous transmissions by adjacent routers over the same channel. In a reactive routing protocol for sensor and ad hoc networks, jitter is recommended during the route discovery process, specifically, during the network-wide flooding of route request messages, in order to avoid collisions. Commonly, a simple uniform jitter is recommended. Alas, this is not without drawbacks: when applying uniform jitter to the route discovery process, an effect called delay inversion is observed. This paper, first, studies and quantifies this delay inversion effect. Second, this paper proposes an adaptive jitter mechanism, designed to alleviate the delay inversion effect and thereby to reduce the route discovery overhead and (ultimately) allow the routing protocol to find more optimal paths, as compared to uniform jitter. This paper presents both analytical and simulation studies, showing that the proposed adaptive jitter can effectively decrease the cost of route discovery and increase the path quality. Full article
(This article belongs to the Section Sensor Networks)
Open AccessCommunication Colorimetric Detection of Ehrlichia Canis via Nucleic Acid Hybridization in Gold Nano-Colloids
Sensors 2014, 14(8), 14472-14487; doi:10.3390/s140814472
Received: 10 April 2014 / Revised: 30 June 2014 / Accepted: 14 July 2014 / Published: 8 August 2014
Cited by 3 | PDF Full-text (928 KB) | HTML Full-text | XML Full-text
Abstract
Canine monocytic ehrlichiosis (CME) is a major thick-bone disease of dog caused by Ehrlichia canis. Detection of this causal agent outside the laboratory using conventional methods is not effective enough. Thus an assay for E. canis detection based on the p30 outer
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Canine monocytic ehrlichiosis (CME) is a major thick-bone disease of dog caused by Ehrlichia canis. Detection of this causal agent outside the laboratory using conventional methods is not effective enough. Thus an assay for E. canis detection based on the p30 outer membrane protein gene was developed. It was based on the p30 gene amplification using loop-mediated isothermal DNA amplification (LAMP). The primer set specific to six areas within the target gene were designed and tested for their sensitivity and specificity. Detection of DNA signals was based on modulation of gold nanoparticles’ surface properties and performing DNA/DNA hybridization using an oligonucleotide probe. Presence of target DNA affected the gold colloid nanoparticles in terms of particle aggregation with a plasmonic color change of the gold colloids from ruby red to purple, visible by the naked eye. All the assay steps were completed within 90 min including DNA extraction without relying on standard laboratory facilities. This method was very specific to target bacteria. Its sensitivity with probe hybridization was sufficient to detect 50 copies of target DNA. This method should provide an alternative choice for point of care control and management of the disease. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Genotyping Single Nucleotide Polymorphisms Using Different Molecular Beacon Multiplexed within a Suspended Core Optical Fiber
Sensors 2014, 14(8), 14488-14499; doi:10.3390/s140814488
Received: 25 June 2014 / Revised: 1 August 2014 / Accepted: 5 August 2014 / Published: 8 August 2014
Cited by 3 | PDF Full-text (1373 KB) | HTML Full-text | XML Full-text
Abstract
We report a novel approach to genotyping single nucleotide polymorphisms (SNPs) using molecular beacons in conjunction with a suspended core optical fiber (SCF). Target DNA sequences corresponding to the wild- or mutant-type have been accurately recognized by immobilizing two different molecular beacons on
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We report a novel approach to genotyping single nucleotide polymorphisms (SNPs) using molecular beacons in conjunction with a suspended core optical fiber (SCF). Target DNA sequences corresponding to the wild- or mutant-type have been accurately recognized by immobilizing two different molecular beacons on the core of a SCF. The two molecular beacons differ by one base in the loop-probe and utilize different fluorescent indicators. Single-color fluorescence enhancement was obtained when the immobilized SCFs were filled with a solution containing either wild-type or mutant-type sequence (homozygous sample), while filling the immobilized SCF with solution containing both wild- and mutant-type sequences resulted in dual-color fluorescence enhancement, indicating a heterozygous sample. The genotyping was realized amplification-free and with ultra low-volume for the required DNA solution (nano-liter). This is, to our knowledge, the first genotyping device based on the combination of optical fiber and molecular beacons. Full article
(This article belongs to the Special Issue FRET Biosensors)
Open AccessArticle Resource Optimization Scheme for Multimedia-Enabled Wireless Mesh Networks
Sensors 2014, 14(8), 14500-14525; doi:10.3390/s140814500
Received: 8 April 2014 / Revised: 24 July 2014 / Accepted: 28 July 2014 / Published: 8 August 2014
Cited by 5 | PDF Full-text (1752 KB) | HTML Full-text | XML Full-text
Abstract
Wireless mesh networking is a promising technology that can support numerous multimedia applications. Multimedia applications have stringent quality of service (QoS) requirements, i.e., bandwidth, delay, jitter, and packet loss ratio. Enabling such QoS-demanding applications over wireless mesh networks (WMNs) require
[...] Read more.
Wireless mesh networking is a promising technology that can support numerous multimedia applications. Multimedia applications have stringent quality of service (QoS) requirements, i.e., bandwidth, delay, jitter, and packet loss ratio. Enabling such QoS-demanding applications over wireless mesh networks (WMNs) require QoS provisioning routing protocols that lead to the network resource underutilization problem. Moreover, random topology deployment leads to have some unused network resources. Therefore, resource optimization is one of the most critical design issues in multi-hop, multi-radio WMNs enabled with multimedia applications. Resource optimization has been studied extensively in the literature for wireless Ad Hoc and sensor networks, but existing studies have not considered resource underutilization issues caused by QoS provisioning routing and random topology deployment. Finding a QoS-provisioned path in wireless mesh networks is an NP complete problem. In this paper, we propose a novel Integer Linear Programming (ILP) optimization model to reconstruct the optimal connected mesh backbone topology with a minimum number of links and relay nodes which satisfies the given end-to-end QoS demands for multimedia traffic and identification of extra resources, while maintaining redundancy. We further propose a polynomial time heuristic algorithm called Link and Node Removal Considering Residual Capacity and Traffic Demands (LNR-RCTD). Simulation studies prove that our heuristic algorithm provides near-optimal results and saves about 20% of resources from being wasted by QoS provisioning routing and random topology deployment. Full article
(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)
Open AccessArticle An Ionizing Radiation Sensor Using a Pre-Programmed MAHAOS Device
Sensors 2014, 14(8), 14553-14566; doi:10.3390/s140814553
Received: 7 May 2014 / Revised: 14 July 2014 / Accepted: 23 July 2014 / Published: 11 August 2014
Cited by 3 | PDF Full-text (1194 KB) | HTML Full-text | XML Full-text
Abstract
Metal-aluminum oxide–hafnium aluminum oxide‒silicon oxide–silicon (hereafter MAHAOS) devices can be candidates for ionizing radiation sensor applications. In this work, MAHAOS devices (SONOS-like structures with high k stack gate dielectric) were studied regarding the first known characterization of the ionization radiation sensing response. The
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Metal-aluminum oxide–hafnium aluminum oxide‒silicon oxide–silicon (hereafter MAHAOS) devices can be candidates for ionizing radiation sensor applications. In this work, MAHAOS devices (SONOS-like structures with high k stack gate dielectric) were studied regarding the first known characterization of the ionization radiation sensing response. The change of threshold voltage VT for a MAHAOS device after gamma ray exposure had a strong correlation to the total ionization dose (TID) of gamma radiation up to at least 5 Mrad TID. In this paper, the gamma radiation response performances of the pre-programmed and virgin (non-pre-programmed) MAHAOS devices are presented. The experimental data show that the change of VT for the pre-programmed MAHAOS device with gamma irradiation is very significant. The data of pre-programmed MAHAOS devices written by 5 Mrad TID of gamma radiation was also stable for a long time with data storage. The sensing of gamma radiation by pre-programmed MAHAOS devices with high k stack gate dielectric reported in this study has demonstrated their potential application for non-volatile ionizing radiation sensing technology in the future. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle LiftingWiSe: A Lifting-Based Efficient Data Processing Technique in Wireless Sensor Networks
Sensors 2014, 14(8), 14567-14585; doi:10.3390/s140814567
Received: 28 April 2014 / Revised: 30 July 2014 / Accepted: 31 July 2014 / Published: 11 August 2014
Cited by 1 | PDF Full-text (3176 KB) | HTML Full-text | XML Full-text
Abstract
Monitoring thousands of objects which are deployed over large-hard-to-reach areas, is an important application of the wireless sensor networks (WSNs). Such an application requires disseminating a large amount of data within the WSN. This data includes, but is not limited to, the object’s
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Monitoring thousands of objects which are deployed over large-hard-to-reach areas, is an important application of the wireless sensor networks (WSNs). Such an application requires disseminating a large amount of data within the WSN. This data includes, but is not limited to, the object’s location and the environment conditions at that location. WSNs require efficient data processing and dissemination processes due to the limited storage, processing power, and energy available in the WSN nodes. The aim of this paper is to propose a data processing technique that can work under constrained storage, processing, and energy resource conditions. The proposed technique utilizes the lifting procedure in processing the disseminated data. Lifting is usually used in discrete wavelet transform (DWT) operations. The proposed technique is referred to as LiftingWiSe, which stands for Lifting-based efficient data processing technique for Wireless Sensor Networks. LiftingWiSe has been tested and compared to other relevant techniques from the literature. The test has been conducted via a simulation of the monitored field and the deployed wireless sensor network nodes. The simulation results have been analyzed and discussed. Full article
(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)
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Open AccessArticle Enhanced Ethanol Gas Sensing Properties of SnO2-Core/ZnO-Shell Nanostructures
Sensors 2014, 14(8), 14586-14600; doi:10.3390/s140814586
Received: 21 July 2014 / Revised: 4 August 2014 / Accepted: 5 August 2014 / Published: 11 August 2014
Cited by 14 | PDF Full-text (6227 KB) | HTML Full-text | XML Full-text
Abstract
An inexpensive single-step carbon-assisted thermal evaporation method for the growth of SnO2-core/ZnO-shell nanostructures is described, and the ethanol sensing properties are presented. The structure and phases of the grown nanostructures are investigated by field-emission scanning electron microscopy (FESEM), transmission electron microscopy
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An inexpensive single-step carbon-assisted thermal evaporation method for the growth of SnO2-core/ZnO-shell nanostructures is described, and the ethanol sensing properties are presented. The structure and phases of the grown nanostructures are investigated by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. XRD analysis indicates that the core-shell nanostructures have good crystallinity. At a lower growth duration of 15 min, only SnO2 nanowires with a rectangular cross-section are observed, while the ZnO shell is observed when the growth time is increased to 30 min. Core-shell hierarchical nanostructures are present for a growth time exceeding 60 min. The growth mechanism for SnO2-core/ZnO-shell nanowires and hierarchical nanostructures are also discussed. The sensitivity of the synthesized SnO2-core/ZnO-shell nanostructures towards ethanol sensing is investigated. Results show that the SnO2-core/ZnO-shell nanostructures deposited at 90 min exhibit enhanced sensitivity to ethanol. The sensitivity of SnO2-core/ZnO-shell nanostructures towards 20 ppm ethanol gas at 400 °C is about ~5-times that of SnO2 nanowires. This improvement in ethanol gas response is attributed to high active sensing sites and the synergistic effect of the encapsulation of SnO2 by ZnO nanostructures. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle An Energy-Efficient and Compact Clustering Scheme with Temporary Support Nodes for Cognitive Radio Sensor Networks
Sensors 2014, 14(8), 14634-14653; doi:10.3390/s140814634
Received: 28 April 2014 / Revised: 24 June 2014 / Accepted: 6 August 2014 / Published: 11 August 2014
Cited by 2 | PDF Full-text (1743 KB) | HTML Full-text | XML Full-text
Abstract
A cognitive radio sensor network (CRSN) is a wireless sensor network whose sensor nodes are equipped with cognitive radio capability. Clustering is one of the most challenging issues in CRSNs, as all sensor nodes, including the cluster head, have to use the same
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A cognitive radio sensor network (CRSN) is a wireless sensor network whose sensor nodes are equipped with cognitive radio capability. Clustering is one of the most challenging issues in CRSNs, as all sensor nodes, including the cluster head, have to use the same frequency band in order to form a cluster. However, due to the nature of heterogeneous channels in cognitive radio, it is difficult for sensor nodes to find a cluster head. This paper proposes a novel energy-efficient and compact clustering scheme named clustering with temporary support nodes (CENTRE). CENTRE efficiently achieves a compact cluster formation by adopting two-phase cluster formation with fixed duration. By introducing a novel concept of temporary support nodes to improve the cluster formation, the proposed scheme enables sensor nodes in a network to find a cluster head efficiently. The performance study shows that not only is the clustering process efficient and compact but it also results in remarkable energy savings that prolong the overall network lifetime. In addition, the proposed scheme decreases both the clustering overhead and the average distance between cluster heads and their members. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle Development of a PET Scanner for Simultaneously Imaging Small Animals with MRI and PET
Sensors 2014, 14(8), 14654-14671; doi:10.3390/s140814654
Received: 4 April 2014 / Revised: 4 July 2014 / Accepted: 28 July 2014 / Published: 12 August 2014
Cited by 8 | PDF Full-text (3890 KB) | HTML Full-text | XML Full-text
Abstract
Recently, positron emission tomography (PET) is playing an increasingly important role in the diagnosis and staging of cancer. Combined PET and X-ray computed tomography (PET-CT) scanners are now the modality of choice in cancer treatment planning. More recently, the combination of PET and
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Recently, positron emission tomography (PET) is playing an increasingly important role in the diagnosis and staging of cancer. Combined PET and X-ray computed tomography (PET-CT) scanners are now the modality of choice in cancer treatment planning. More recently, the combination of PET and magnetic resonance imaging (MRI) is being explored in many sites. Combining PET and MRI has presented many challenges since the photo-multiplier tubes (PMT) in PET do not function in high magnetic fields, and conventional PET detectors distort MRI images. Solid state light sensors like avalanche photo-diodes (APDs) and more recently silicon photo-multipliers (SiPMs) are much less sensitive to magnetic fields thus easing the compatibility issues. This paper presents the results of a group of Canadian scientists who are developing a PET detector ring which fits inside a high field small animal MRI scanner with the goal of providing simultaneous PET and MRI images of small rodents used in pre-clinical medical research. We discuss the evolution of both the crystal blocks (which detect annihilation photons from positron decay) and the SiPM array performance in the last four years which together combine to deliver significant system performance in terms of speed, energy and timing resolution. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors in Canada 2014)
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Open AccessArticle Development of an ELISA and Immunochromatographic Strip for Highly Sensitive Detection of Microcystin-LR
Sensors 2014, 14(8), 14672-14685; doi:10.3390/s140814672
Received: 25 June 2014 / Revised: 3 August 2014 / Accepted: 6 August 2014 / Published: 12 August 2014
Cited by 20 | PDF Full-text (2624 KB) | HTML Full-text | XML Full-text
Abstract
A monoclonal antibody for microcystin–leucine–arginine (MC-LR) was produced by cell fusion. The immunogen was synthesized in two steps. First, ovalbumin/ bovine serum albumin was conjugated with 6-acetylthiohexanoic acid using a carbodiimide EDC (1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride)/ NHS (N-hydroxysulfosuccinimide) reaction. After dialysis, the protein was reacted
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A monoclonal antibody for microcystin–leucine–arginine (MC-LR) was produced by cell fusion. The immunogen was synthesized in two steps. First, ovalbumin/ bovine serum albumin was conjugated with 6-acetylthiohexanoic acid using a carbodiimide EDC (1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride)/ NHS (N-hydroxysulfosuccinimide) reaction. After dialysis, the protein was reacted with MC-LR based on a free radical reaction under basic solution conditions. The protein conjugate was used for immunization based on low volume. The antibodies were identified by indirect competitive (ic)ELISA and were subjected to tap water and lake water analysis. The concentration causing 50% inhibition of binding of MC-LR (IC50) by the competitive indirect ELISA was 0.27 ng/mL. Cross-reactivity to the MC-RR, MC-YR and MC-WR was good. The tap water and lake water matrices had no effect on the detection limit. The analytical recovery of MC-LR in the water samples in the icELISA was 94%–110%. Based on this antibody, an immunochromatographic biosensor was developed with a cut-off value of 1 ng/mL, which could satisfy the requirement of the World Health Organization for MC-LR detection in drinking water. This biosensor could be therefore be used as a fast screening tool in the field detection of MC-LR. Full article
(This article belongs to the Special Issue Nanoparticle-Based Biosensors)
Open AccessArticle A Novel Carbon Nanofibers Grown on Glass Microballoons Immunosensor: A Tool for Early Diagnosis of Malaria
Sensors 2014, 14(8), 14686-14699; doi:10.3390/s140814686
Received: 8 June 2014 / Revised: 31 July 2014 / Accepted: 4 August 2014 / Published: 12 August 2014
Cited by 3 | PDF Full-text (1496 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel method for direct detection of Plasmodium falciparum histidine rich protein-2 (PfHRP-2) antigen using carbon nanofiber (CNF) forests grown on glass microballoons (NMBs). Secondary antibodies specific to PfHRP-2 densely attached to the CNFs exhibit extraordinary ability
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This paper presents a novel method for direct detection of Plasmodium falciparum histidine rich protein-2 (PfHRP-2) antigen using carbon nanofiber (CNF) forests grown on glass microballoons (NMBs). Secondary antibodies specific to PfHRP-2 densely attached to the CNFs exhibit extraordinary ability for the detection of minute concentrations of Plasmodium species. A sandwich immunoassay protocol was employed, where a glass substrate was used to immobilize primary antibodies at designated capture zones. High signal amplification was obtained in both colorimetric and electrical measurements due to the CNFs through specific binding. As a result, it was possible to detect PfHRP-2 levels as low as 0.025 ng/mL concentration in phosphate buffered saline (PBS) using a visual signal within only 1 min of test duration. Lower limits of 0.01 ng/mL was obtained by measuring the electrical resistivity of the capture zone. This method is also highly selective and specific in identifying PfHRP-2 and other Plasmodium species from the same solution. In addition, the stability of the labeling mechanism eliminates the false signals generated by the use of dyes in current malaria rapid diagnostic test kits (MRDTs). Thus, the rapid, sensitive and high signal amplification capabilities of NMBs is a promising tool for early diagnosis of malaria and other infectious diseases. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle A Catheter-Based Acoustic Interrogation Device for Monitoring Motility Dynamics of the Lower Esophageal Sphincter
Sensors 2014, 14(8), 14700-14711; doi:10.3390/s140814700
Received: 13 June 2014 / Revised: 2 August 2014 / Accepted: 5 August 2014 / Published: 12 August 2014
Cited by 1 | PDF Full-text (607 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents novel minimally-invasive, catheter-based acoustic interrogation device for monitoring motility dynamics of the lower esophageal sphincter (LES). A micro-oscillator actively emitting sound wave at 16 kHz is located at one side of the LES, and a miniature microphone is located at
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This paper presents novel minimally-invasive, catheter-based acoustic interrogation device for monitoring motility dynamics of the lower esophageal sphincter (LES). A micro-oscillator actively emitting sound wave at 16 kHz is located at one side of the LES, and a miniature microphone is located at the other side of the sphincter to capture the sound generated from the oscillator. Thus, the dynamics of the opening and closing of the LES can be quantitatively assessed. In this paper, experiments are conducted utilizing an LES motility dynamics simulator. The sound strength is captured by the microphone and is correlated to the level of LES opening and closing controlled by the simulator. Measurements from the simulator model show statistically significant (p < 0.05) Pearson correlation coefficients (0.905 on the average in quiet environment and 0.736 on the average in noisy environment, D.O.F. = 9). Measuring the level of LES opening and closing has the potential to become a valuable diagnostic technique for understanding LES dysfunction and the disorders associated with it. Full article
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Open AccessArticle A Wireless Portable High Temperature Data Monitor for Tunnel Ovens
Sensors 2014, 14(8), 14712-14731; doi:10.3390/s140814712
Received: 11 June 2014 / Revised: 25 July 2014 / Accepted: 25 July 2014 / Published: 12 August 2014
Cited by 1 | PDF Full-text (5717 KB) | HTML Full-text | XML Full-text
Abstract
Tunnel ovens are widely used in the food industry to produce biscuits and pastries. In order to obtain a high quality product, it is very important to control the heat transferred to each piece of dough during baking. This paper proposes an innovative,
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Tunnel ovens are widely used in the food industry to produce biscuits and pastries. In order to obtain a high quality product, it is very important to control the heat transferred to each piece of dough during baking. This paper proposes an innovative, non-distorting, low cost wireless temperature measurement system, called “eBiscuit”, which, due to its size, format and location in the metal rack conveyor belt in the oven, is able to measure the temperature a real biscuit experience while baking. The temperature conditions inside the oven are over 200 °C for several minutes, which could damage the “eBiscuit” electronics. This paper compares several thermal insulating materials that can be used in order to avoid exceeding the maximum operational conditions (80 °C) in the interior of the “eBiscuit. The data registered is then transmitted to a base station where information can be processed to obtain an oven model. The experimental results with real tunnel ovens confirm its good performance, which allows detecting production anomalies early on. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Flexible Capacitive Electrodes for Minimizing Motion Artifacts in Ambulatory Electrocardiograms
Sensors 2014, 14(8), 14732-14743; doi:10.3390/s140814732
Received: 24 June 2014 / Revised: 5 August 2014 / Accepted: 7 August 2014 / Published: 12 August 2014
Cited by 14 | PDF Full-text (1183 KB) | HTML Full-text | XML Full-text
Abstract
This study proposes the use of flexible capacitive electrodes for reducing motion artifacts in a wearable electrocardiogram (ECG) device. The capacitive electrodes have conductive foam on their surface, a shield, an optimal input bias resistor, and guarding feedback. The electrodes are integrated in
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This study proposes the use of flexible capacitive electrodes for reducing motion artifacts in a wearable electrocardiogram (ECG) device. The capacitive electrodes have conductive foam on their surface, a shield, an optimal input bias resistor, and guarding feedback. The electrodes are integrated in a chest belt, and the acquired signals are transmitted wirelessly for ambulatory heart rate monitoring. We experimentally validated the electrode performance with subjects standing and walking on a treadmill at speeds of up to 7 km/h. The results confirmed the highly accurate heart rate detection capacity of the developed system and its feasibility for daily-life ECG monitoring. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
Open AccessArticle A Group Neighborhood Average Clock Synchronization Protocol for Wireless Sensor Networks
Sensors 2014, 14(8), 14744-14764; doi:10.3390/s140814744
Received: 12 May 2014 / Revised: 21 July 2014 / Accepted: 4 August 2014 / Published: 12 August 2014
Cited by 3 | PDF Full-text (2722 KB) | HTML Full-text | XML Full-text
Abstract
Clock synchronization is a very important issue for the applications of wireless sensor networks. The sensors need to keep a strict clock so that users can know exactly what happens in the monitoring area at the same time. This paper proposes a novel
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Clock synchronization is a very important issue for the applications of wireless sensor networks. The sensors need to keep a strict clock so that users can know exactly what happens in the monitoring area at the same time. This paper proposes a novel internal distributed clock synchronization solution using group neighborhood average. Each sensor node collects the offset and skew rate of the neighbors. Group averaging of offset and skew rate value are calculated instead of conventional point-to-point averaging method. The sensor node then returns compensated value back to the neighbors. The propagation delay is considered and compensated. The analytical analysis of offset and skew compensation is presented. Simulation results validate the effectiveness of the protocol and reveal that the protocol allows sensor networks to quickly establish a consensus clock and maintain a small deviation from the consensus clock. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle Active In-Database Processing to Support Ambient Assisted Living Systems
Sensors 2014, 14(8), 14765-14785; doi:10.3390/s140814765
Received: 26 March 2014 / Revised: 28 July 2014 / Accepted: 1 August 2014 / Published: 12 August 2014
Cited by 2 | PDF Full-text (533 KB) | HTML Full-text | XML Full-text
Abstract
As an alternative to the existing software architectures that underpin the development of smart homes and ambient assisted living (AAL) systems, this work presents a database-centric architecture that takes advantage of active databases and in-database processing. Current platforms supporting AAL systems use database
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As an alternative to the existing software architectures that underpin the development of smart homes and ambient assisted living (AAL) systems, this work presents a database-centric architecture that takes advantage of active databases and in-database processing. Current platforms supporting AAL systems use database management systems (DBMSs) exclusively for data storage. Active databases employ database triggers to detect and react to events taking place inside or outside of the database. DBMSs can be extended with stored procedures and functions that enable in-database processing. This means that the data processing is integrated and performed within the DBMS. The feasibility and flexibility of the proposed approach were demonstrated with the implementation of three distinct AAL services. The active database was used to detect bed-exits and to discover common room transitions and deviations during the night. In-database machine learning methods were used to model early night behaviors. Consequently, active in-database processing avoids transferring sensitive data outside the database, and this improves performance, security and privacy. Furthermore, centralizing the computation into the DBMS facilitates code reuse, adaptation and maintenance. These are important system properties that take into account the evolving heterogeneity of users, their needs and the devices that are characteristic of smart homes and AAL systems. Therefore, DBMSs can provide capabilities to address requirements for scalability, security, privacy, dependability and personalization in applications of smart environments in healthcare. Full article
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Open AccessArticle Security Analysis and Improvements of Authentication and Access Control in the Internet of Things
Sensors 2014, 14(8), 14786-14805; doi:10.3390/s140814786
Received: 14 May 2014 / Revised: 19 July 2014 / Accepted: 30 July 2014 / Published: 13 August 2014
Cited by 4 | PDF Full-text (766 KB) | HTML Full-text | XML Full-text
Abstract
Internet of Things is a ubiquitous concept where physical objects are connected over the internet and are provided with unique identifiers to enable their self-identification to other devices and the ability to continuously generate data and transmit it over a network. Hence, the
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Internet of Things is a ubiquitous concept where physical objects are connected over the internet and are provided with unique identifiers to enable their self-identification to other devices and the ability to continuously generate data and transmit it over a network. Hence, the security of the network, data and sensor devices is a paramount concern in the IoT network as it grows very fast in terms of exchanged data and interconnected sensor nodes. This paper analyses the authentication and access control method using in the Internet of Things presented by Jing et al. According to our analysis, Jing et al.’s protocol is costly in the message exchange and the security assessment is not strong enough for such a protocol. Therefore, we propose improvements to the protocol to fill the discovered weakness gaps. The protocol enhancements facilitate many services to the users such as user anonymity, mutual authentication, and secure session key establishment. Finally, the performance and security analysis show that the improved protocol possesses many advantages against popular attacks, and achieves better efficiency at low communication cost. Full article
(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)
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Open AccessArticle Acoustic Devices for Particle and Cell Manipulation and Sensing
Sensors 2014, 14(8), 14806-14838; doi:10.3390/s140814806
Received: 15 June 2014 / Revised: 2 August 2014 / Accepted: 7 August 2014 / Published: 13 August 2014
Cited by 11 | PDF Full-text (32761 KB) | HTML Full-text | XML Full-text
Abstract
An emerging demand for the precise manipulation of cells and particles for applications in cell biology and analytical chemistry has driven rapid development of ultrasonic manipulation technology. Compared to the other manipulation technologies, such as magnetic tweezing, dielectrophoresis and optical tweezing, ultrasonic manipulation
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An emerging demand for the precise manipulation of cells and particles for applications in cell biology and analytical chemistry has driven rapid development of ultrasonic manipulation technology. Compared to the other manipulation technologies, such as magnetic tweezing, dielectrophoresis and optical tweezing, ultrasonic manipulation has shown potential in a variety of applications, with its advantages of versatile, inexpensive and easy integration into microfluidic systems, maintenance of cell viability, and generation of sufficient forces to handle particles, cells and their agglomerates. This article briefly reviews current practice and reports our development of various ultrasonic standing wave manipulation devices, including simple devices integrated with high frequency (>20 MHz) ultrasonic transducers for the investigation of biological cells and complex ultrasonic transducer array systems to explore the feasibility of electronically controlled 2-D and 3-D manipulation. Piezoelectric and passive materials, fabrication techniques, characterization methods and possible applications are discussed. The behavior and performance of the devices have been investigated and predicted with computer simulations, and verified experimentally. Issues met during development are highlighted and discussed. To assist long term practical adoption, approaches to low-cost, wafer level batch-production and commercialization potential are also addressed. Full article
Open AccessArticle Design and Implementation of a RF Powering Circuit for RFID Tags or Other Batteryless Embedded Devices
Sensors 2014, 14(8), 14839-14857; doi:10.3390/s140814839
Received: 20 January 2014 / Revised: 5 August 2014 / Accepted: 6 August 2014 / Published: 13 August 2014
Cited by 3 | PDF Full-text (6928 KB) | HTML Full-text | XML Full-text
Abstract
A RF powering circuit used in radio-frequency identification (RFID) tags and other batteryless embedded devices is presented in this paper. The RF powering circuit harvests energy from electromagnetic waves and converts the RF energy to a stable voltage source. Analysis of a NMOS
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A RF powering circuit used in radio-frequency identification (RFID) tags and other batteryless embedded devices is presented in this paper. The RF powering circuit harvests energy from electromagnetic waves and converts the RF energy to a stable voltage source. Analysis of a NMOS gate-cross connected bridge rectifier is conducted to demonstrate relationship between device sizes and power conversion efficiency (PCE) of the rectifier. A rectifier with 38.54% PCE under normal working conditions is designed. Moreover, a stable voltage regulator with a temperature and voltage optimizing strategy including adoption of a combination resistor is developed, which is able to accommodate a large input range of 4 V to 12 V and be immune to temperature variations. Latch-up prevention and noise isolation methods in layout design are also presented. Designed with the HJTC 0.25 μm process, this regulator achieves 0.04 mV/°C temperature rejection ratio (TRR) and 2.5 mV/V voltage rejection ratio (VRR). The RF powering circuit is also fabricated in the HJTC 0.25 μm process. The area of the RF powering circuit is 0.23 × 0.24 mm2. The RF powering circuit is successfully integrated with ISO/IEC 15693-compatible and ISO/IEC 14443-compatible RFID tag chips. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Implantable Impedance Plethysmography
Sensors 2014, 14(8), 14858-14872; doi:10.3390/s140814858
Received: 10 June 2014 / Revised: 21 July 2014 / Accepted: 1 August 2014 / Published: 13 August 2014
PDF Full-text (9606 KB) | HTML Full-text | XML Full-text
Abstract
We demonstrate by theory, as well as by ex vivo and in vivo measurements that impedance plethysmography, applied extravascularly directly on large arteries, is a viable method for monitoring various cardiovascular parameters, such as blood pressure, with high accuracy. The sensor is designed
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We demonstrate by theory, as well as by ex vivo and in vivo measurements that impedance plethysmography, applied extravascularly directly on large arteries, is a viable method for monitoring various cardiovascular parameters, such as blood pressure, with high accuracy. The sensor is designed as an implant to monitor cardiac events and arteriosclerotic progression over the long term. Full article
(This article belongs to the Special Issue Implantable Sensors)
Open AccessArticle Liquid Seal for Temperature Sensing with Fiber-Optic Refractometers
Sensors 2014, 14(8), 14873-14884; doi:10.3390/s140814873
Received: 14 June 2014 / Revised: 4 August 2014 / Accepted: 5 August 2014 / Published: 13 August 2014
Cited by 4 | PDF Full-text (1694 KB) | HTML Full-text | XML Full-text
Abstract
Liquid sealing is an effective method to convert a fiber-optic refractometer into a simple and highly sensitive temperature sensor. A refractometer based on the thin-core fiber modal interferometer is sealed in a capillary tube filled with Cargille oil. Due to the thermo-optic effect
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Liquid sealing is an effective method to convert a fiber-optic refractometer into a simple and highly sensitive temperature sensor. A refractometer based on the thin-core fiber modal interferometer is sealed in a capillary tube filled with Cargille oil. Due to the thermo-optic effect of the sealing liquid, the high refractive-index sensitivity refractometer is subsequently sensitive to the ambient temperature. It is found that the liquid-sealed sensor produces a highest sensitivity of −2.30 nm/°C, which is over 250 times higher than its intrinsic sensitivity before sealing and significantly higher than that of a grating-based fiber sensors. The sensing mechanisms, including the incidental temperature-induced strain effect, are analyzed in detail both theoretically and experimentally. The liquid sealing technique is easy and low cost, and makes the sensor robust and insensitive to the surrounding refractive index. It can be applied to other fiber-optic refractometers for temperature sensing. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Time- and Computation-Efficient Calibration of MEMS 3D Accelerometers and Gyroscopes
Sensors 2014, 14(8), 14885-14915; doi:10.3390/s140814885
Received: 18 June 2014 / Revised: 30 July 2014 / Accepted: 11 August 2014 / Published: 13 August 2014
Cited by 5 | PDF Full-text (1210 KB) | HTML Full-text | XML Full-text
Abstract
We propose calibration methods for microelectromechanical system (MEMS) 3D accelerometers and gyroscopes that are efficient in terms of time and computational complexity. The calibration process for both sensors is simple, does not require additional expensive equipment, and can be performed in the field
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We propose calibration methods for microelectromechanical system (MEMS) 3D accelerometers and gyroscopes that are efficient in terms of time and computational complexity. The calibration process for both sensors is simple, does not require additional expensive equipment, and can be performed in the field before or between motion measurements. The methods rely on a small number of defined calibration measurements that are used to obtain the values of 12 calibration parameters. This process enables the static compensation of sensor inaccuracies. The values detected by the 3D sensor are interpreted using a generalized 3D sensor model. The model assumes that the values detected by the sensor are equal to the projections of the measured value on the sensor sensitivity axes. Although this finding is trivial for 3D accelerometers, its validity for 3D gyroscopes is not immediately apparent; thus, this paper elaborates on this latter topic. For an example sensor device, calibration parameters were established using calibration measurements of approximately 1.5 min in duration for the 3D accelerometer and 2.5 min in duration for the 3D gyroscope. Correction of each detected 3D value using the established calibration parameters in further measurements requires only nine addition and nine multiplication operations. Full article
(This article belongs to the Special Issue Optical Gyroscopes and Navigation Systems)
Open AccessArticle Design of a Device for Sky Light Polarization Measurements
Sensors 2014, 14(8), 14916-14931; doi:10.3390/s140814916
Received: 10 June 2014 / Revised: 20 July 2014 / Accepted: 6 August 2014 / Published: 14 August 2014
Cited by 10 | PDF Full-text (1856 KB) | HTML Full-text | XML Full-text
Abstract
ky polarization patterns can be used both as indicators of atmospheric turbidity and as a sun compass for navigation. The objective of this study is to improve the precision of sky light polarization measurements by optimal design of the device used. The central
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ky polarization patterns can be used both as indicators of atmospheric turbidity and as a sun compass for navigation. The objective of this study is to improve the precision of sky light polarization measurements by optimal design of the device used. The central part of the system is composed of a Charge Coupled Device (CCD) camera; a fish-eye lens and a linear polarizer. Algorithms for estimating parameters of the polarized light based on three images are derived and the optimal alignments of the polarizer are analyzed. The least-squares estimation is introduced for sky light polarization pattern measurement. The polarization patterns of sky light are obtained using the designed system and they follow almost the same patterns of the single-scattering Rayleigh model. Deviations of polarization angles between observation and the theory are analyzed. The largest deviations occur near the sun and anti-sun directions. Ninety percent of the deviations are less than 5° and 40% percent of them are less than 1°. The deviations decrease evidently as the degree of polarization increases. It also shows that the polarization pattern of the cloudy sky is almost identical as in the blue sky. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Holistic Approach to ZigBee Performance Enhancement for Home Automation Networks
Sensors 2014, 14(8), 14932-14970; doi:10.3390/s140814932
Received: 9 June 2014 / Revised: 18 July 2014 / Accepted: 29 July 2014 / Published: 14 August 2014
Cited by 2 | PDF Full-text (1597 KB) | HTML Full-text | XML Full-text
Abstract
Wireless home automation networks are gaining importance for smart homes. In this ambit, ZigBee networks play an important role. The ZigBee specification defines a default set of protocol stack parameters and mechanisms that is further refined by the ZigBee Home Automation application profile.
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Wireless home automation networks are gaining importance for smart homes. In this ambit, ZigBee networks play an important role. The ZigBee specification defines a default set of protocol stack parameters and mechanisms that is further refined by the ZigBee Home Automation application profile. In a holistic approach, we analyze how the network performance is affected with the tuning of parameters and mechanisms across multiple layers of the ZigBee protocol stack and investigate possible performance gains by implementing and testing alternative settings. The evaluations are carried out in a testbed of 57 TelosB motes. The results show that considerable performance improvements can be achieved by using alternative protocol stack configurations. From these results, we derive two improved protocol stack configurations for ZigBee wireless home automation networks that are validated in various network scenarios. In our experiments, these improved configurations yield a relative packet delivery ratio increase of up to 33.6%, a delay decrease of up to 66.6% and an improvement of the energy efficiency for battery powered devices of up to 48.7%, obtainable without incurring any overhead to the network. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle A Comprehensive Method for GNSS Data Quality Determination to Improve Ionospheric Data Analysis
Sensors 2014, 14(8), 14971-14993; doi:10.3390/s140814971
Received: 5 October 2013 / Revised: 18 July 2014 / Accepted: 6 August 2014 / Published: 14 August 2014
Cited by 1 | PDF Full-text (3234 KB) | HTML Full-text | XML Full-text
Abstract
Global Navigation Satellite Systems (GNSS) are now recognized as cost-effective tools for ionospheric studies by providing the global coverage through worldwide networks of GNSS stations. While GNSS networks continue to expand to improve the observability of the ionosphere, the amount of poor quality
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Global Navigation Satellite Systems (GNSS) are now recognized as cost-effective tools for ionospheric studies by providing the global coverage through worldwide networks of GNSS stations. While GNSS networks continue to expand to improve the observability of the ionosphere, the amount of poor quality GNSS observation data is also increasing and the use of poor-quality GNSS data degrades the accuracy of ionospheric measurements. This paper develops a comprehensive method to determine the quality of GNSS observations for the purpose of ionospheric studies. The algorithms are designed especially to compute key GNSS data quality parameters which affect the quality of ionospheric product. The quality of data collected from the Continuously Operating Reference Stations (CORS) network in the conterminous United States (CONUS) is analyzed. The resulting quality varies widely, depending on each station and the data quality of individual stations persists for an extended time period. When compared to conventional methods, the quality parameters obtained from the proposed method have a stronger correlation with the quality of ionospheric data. The results suggest that a set of data quality parameters when used in combination can effectively select stations with high-quality GNSS data and improve the performance of ionospheric data analysis. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Automated In-Situ Laser Scanner for Monitoring Forest Leaf Area Index
Sensors 2014, 14(8), 14994-15008; doi:10.3390/s140814994
Received: 9 June 2014 / Revised: 7 August 2014 / Accepted: 7 August 2014 / Published: 14 August 2014
Cited by 9 | PDF Full-text (1734 KB) | HTML Full-text | XML Full-text
Abstract
An automated laser rangefinding instrument was developed to characterize overstorey and understorey vegetation dynamics over time. Design criteria were based on information needs within the statewide forest monitoring program in Victoria, Australia. The ground-based monitoring instrument captures the key vegetation structural information needed
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An automated laser rangefinding instrument was developed to characterize overstorey and understorey vegetation dynamics over time. Design criteria were based on information needs within the statewide forest monitoring program in Victoria, Australia. The ground-based monitoring instrument captures the key vegetation structural information needed to overcome ambiguity in the estimation of forest Leaf Area Index (LAI) from satellite sensors. The scanning lidar instrument was developed primarily from low cost, commercially accessible components. While the 635 nm wavelength lidar is not ideally suited to vegetation studies, there was an acceptable trade-off between cost and performance. Tests demonstrated reliable range estimates to live foliage up to a distance of 60 m during night-time operation. Given the instrument’s scan angle of 57.5 degrees zenith, the instrument is an effective tool for monitoring LAI in forest canopies up to a height of 30 m. An 18 month field trial of three co-located instruments showed consistent seasonal trends and mean LAI of between 1.32 to 1.56 and a temporal LAI variation of 8 to 17% relative to the mean. Full article
(This article belongs to the Special Issue Agriculture and Forestry: Sensors, Technologies and Procedures)
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Open AccessArticle Enclosed Electronic System for Force Measurements in Knee Implants
Sensors 2014, 14(8), 15009-15021; doi:10.3390/s140815009
Received: 19 June 2014 / Revised: 5 August 2014 / Accepted: 12 August 2014 / Published: 14 August 2014
Cited by 3 | PDF Full-text (3675 KB) | HTML Full-text | XML Full-text
Abstract
Total knee arthroplasty is a widely performed surgical technique. Soft tissue force balancing during the operation relies strongly on the experience of the surgeon in equilibrating tension in the collateral ligaments. Little information on the forces in the implanted prosthesis is available during
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Total knee arthroplasty is a widely performed surgical technique. Soft tissue force balancing during the operation relies strongly on the experience of the surgeon in equilibrating tension in the collateral ligaments. Little information on the forces in the implanted prosthesis is available during surgery and post-operative treatment. This paper presents the design, fabrication and testing of an instrumented insert performing force measurements in a knee prosthesis. The insert contains a closed structure composed of printed circuit boards and incorporates a microfabricated polyimide thin-film piezoresistive strain sensor for each condylar compartment. The sensor is tested in a mechanical knee simulator that mimics in-vivo conditions. For characterization purposes, static and dynamic load patterns are applied to the instrumented insert. Results show that the sensors are able to measure forces up to 1.5 times body weight with a sensitivity fitting the requirements for the proposed use. Dynamic testing of the insert shows a good tracking of slow and fast changing forces in the knee prosthesis by the sensors. Full article
(This article belongs to the Special Issue Implantable Sensors)
Open AccessArticle Fault Detection of a Roller-Bearing System through the EMD of a Wavelet Denoised Signal
Sensors 2014, 14(8), 15022-15038; doi:10.3390/s140815022
Received: 26 May 2014 / Revised: 2 August 2014 / Accepted: 5 August 2014 / Published: 14 August 2014
Cited by 10 | PDF Full-text (2951 KB) | HTML Full-text | XML Full-text
Abstract
This paper investigates fault detection of a roller bearing system using a wavelet denoising scheme and proper orthogonal value (POV) of an intrinsic mode function (IMF) covariance matrix. The IMF of the bearing vibration signal is obtained through empirical mode decomposition (EMD). The
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This paper investigates fault detection of a roller bearing system using a wavelet denoising scheme and proper orthogonal value (POV) of an intrinsic mode function (IMF) covariance matrix. The IMF of the bearing vibration signal is obtained through empirical mode decomposition (EMD). The signal screening process in the wavelet domain eliminates noise-corrupted portions that may lead to inaccurate prognosis of bearing conditions. We segmented the denoised bearing signal into several intervals, and decomposed each of them into IMFs. The first IMF of each segment is collected to become a covariance matrix for calculating the POV. We show that covariance matrices from healthy and damaged bearings exhibit different POV profiles, which can be a damage-sensitive feature. We also illustrate the conventional approach of feature extraction, of observing the kurtosis value of the measured signal, to compare the functionality of the proposed technique. The study demonstrates the feasibility of wavelet-based de-noising, and shows through laboratory experiments that tracking the proper orthogonal values of the covariance matrix of the IMF can be an effective and reliable measure for monitoring bearing fault. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle An Intelligent Space for Mobile Robot Localization Using a Multi-Camera System
Sensors 2014, 14(8), 15039-15064; doi:10.3390/s140815039
Received: 9 July 2014 / Revised: 1 August 2014 / Accepted: 7 August 2014 / Published: 15 August 2014
Cited by 5 | PDF Full-text (17065 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes an intelligent space, whose objective is to localize and control robots or robotic wheelchairs to help people. Such an intelligent space has 11 cameras distributed in two laboratories and a corridor. The cameras are fixed in the environment, and image
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This paper describes an intelligent space, whose objective is to localize and control robots or robotic wheelchairs to help people. Such an intelligent space has 11 cameras distributed in two laboratories and a corridor. The cameras are fixed in the environment, and image capturing is done synchronously. The system was programmed as a client/server with TCP/IP connections, and a communication protocol was defined. The client coordinates the activities inside the intelligent space, and the servers provide the information needed for that. Once the cameras are used for localization, they have to be properly calibrated. Therefore, a calibration method for a multi-camera network is also proposed in this paper. A robot is used to move a calibration pattern throughout the field of view of the cameras. Then, the captured images and the robot odometry are used for calibration. As a result, the proposed algorithm provides a solution for multi-camera calibration and robot localization at the same time. The intelligent space and the calibration method were evaluated under different scenarios using computer simulations and real experiments. The results demonstrate the proper functioning of the intelligent space and validate the multi-camera calibration method, which also improves robot localization. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle Wave Dispersion and Attenuation on Human Femur Tissue
Sensors 2014, 14(8), 15067-15083; doi:10.3390/s140815067
Received: 30 May 2014 / Revised: 27 July 2014 / Accepted: 6 August 2014 / Published: 15 August 2014
Cited by 4 | PDF Full-text (1529 KB) | HTML Full-text | XML Full-text
Abstract
Cortical bone is a highly heterogeneous material at the microscale and has one of the most complex structures among materials. Application of elastic wave techniques to this material is thus very challenging. In such media the initial excitation energy goes into the formation
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Cortical bone is a highly heterogeneous material at the microscale and has one of the most complex structures among materials. Application of elastic wave techniques to this material is thus very challenging. In such media the initial excitation energy goes into the formation of elastic waves of different modes. Due to “dispersion”, these modes tend to separate according to the velocities of the frequency components. This work demonstrates elastic wave measurements on human femur specimens. The aim of the study is to measure parameters like wave velocity, dispersion and attenuation by using broadband acoustic emission sensors. First, four sensors were placed at small intervals on the surface of the bone to record the response after pencil lead break excitations. Next, the results were compared to measurements on a bulk steel block which does not exhibit heterogeneity at the same wave lengths. It can be concluded that the microstructure of the tissue imposes a dispersive behavior for frequencies below 1 MHz and care should be taken for interpretation of the signals. Of particular interest are waveform parameters like the duration, rise time and average frequency, since in the next stage of research the bone specimens will be fractured with concurrent monitoring of acoustic emission. Full article
Open AccessArticle Stability Analysis for a Multi-Camera Photogrammetric System
Sensors 2014, 14(8), 15084-15112; doi:10.3390/s140815084
Received: 6 June 2014 / Revised: 7 August 2014 / Accepted: 11 August 2014 / Published: 18 August 2014
Cited by 7 | PDF Full-text (1262 KB) | HTML Full-text | XML Full-text
Abstract
Consumer-grade digital cameras suffer from geometrical instability that may cause problems when used in photogrammetric applications. This paper provides a comprehensive review of this issue of interior orientation parameter variation over time, it explains the common ways used for coping with the issue,
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Consumer-grade digital cameras suffer from geometrical instability that may cause problems when used in photogrammetric applications. This paper provides a comprehensive review of this issue of interior orientation parameter variation over time, it explains the common ways used for coping with the issue, and describes the existing methods for performing stability analysis for a single camera. The paper then points out the lack of coverage of stability analysis for multi-camera systems, suggests a modification of the collinearity model to be used for the calibration of an entire photogrammetric system, and proposes three methods for system stability analysis. The proposed methods explore the impact of the changes in interior orientation and relative orientation/mounting parameters on the reconstruction process. Rather than relying on ground truth in real datasets to check the system calibration stability, the proposed methods are simulation-based. Experiment results are shown, where a multi-camera photogrammetric system was calibrated three times, and stability analysis was performed on the system calibration parameters from the three sessions. The proposed simulation-based methods provided results that were compatible with a real-data based approach for evaluating the impact of changes in the system calibration parameters on the three-dimensional reconstruction. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors in Canada 2014)
Open AccessArticle Genetic Algorithm with Maximum-Minimum Crossover (GA-MMC) Applied in Optimization of Radiation Pattern Control of Phased-Array Radars for Rocket Tracking Systems
Sensors 2014, 14(8), 15113-15141; doi:10.3390/s140815113
Received: 23 January 2014 / Revised: 20 June 2014 / Accepted: 9 July 2014 / Published: 18 August 2014
Cited by 1 | PDF Full-text (902 KB) | HTML Full-text | XML Full-text
Abstract
In launching operations, Rocket Tracking Systems (RTS) process the trajectory data obtained by radar sensors. In order to improve functionality and maintenance, radars can be upgraded by replacing antennas with parabolic reflectors (PRs) with phased arrays (PAs). These arrays enable the electronic control
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In launching operations, Rocket Tracking Systems (RTS) process the trajectory data obtained by radar sensors. In order to improve functionality and maintenance, radars can be upgraded by replacing antennas with parabolic reflectors (PRs) with phased arrays (PAs). These arrays enable the electronic control of the radiation pattern by adjusting the signal supplied to each radiating element. However, in projects of phased array radars (PARs), the modeling of the problem is subject to various combinations of excitation signals producing a complex optimization problem. In this case, it is possible to calculate the problem solutions with optimization methods such as genetic algorithms (GAs). For this, the Genetic Algorithm with Maximum-Minimum Crossover (GA-MMC) method was developed to control the radiation pattern of PAs. The GA-MMC uses a reconfigurable algorithm with multiple objectives, differentiated coding and a new crossover genetic operator. This operator has a different approach from the conventional one, because it performs the crossover of the fittest individuals with the least fit individuals in order to enhance the genetic diversity. Thus, GA-MMC was successful in more than 90% of the tests for each application, increased the fitness of the final population by more than 20% and reduced the premature convergence. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Emergency Navigation without an Infrastructure
Sensors 2014, 14(8), 15142-15162; doi:10.3390/s140815142
Received: 6 May 2014 / Revised: 3 July 2014 / Accepted: 8 August 2014 / Published: 18 August 2014
Cited by 7 | PDF Full-text (289 KB) | HTML Full-text | XML Full-text
Abstract
Emergency navigation systems for buildings and other built environments, such as sport arenas or shopping centres, typically rely on simple sensor networks to detect emergencies and, then, provide automatic signs to direct the evacuees. The major drawbacks of such static wireless sensor network
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Emergency navigation systems for buildings and other built environments, such as sport arenas or shopping centres, typically rely on simple sensor networks to detect emergencies and, then, provide automatic signs to direct the evacuees. The major drawbacks of such static wireless sensor network (WSN)-based emergency navigation systems are the very limited computing capacity, which makes adaptivity very difficult, and the restricted battery power, due to the low cost of sensor nodes for unattended operation. If static wireless sensor networks and cloud-computing can be integrated, then intensive computations that are needed to determine optimal evacuation routes in the presence of time-varying hazards can be offloaded to the cloud, but the disadvantages of limited battery life-time at the client side, as well as the high likelihood of system malfunction during an emergency still remain. By making use of the powerful sensing ability of smart phones, which are increasingly ubiquitous, this paper presents a cloud-enabled indoor emergency navigation framework to direct evacuees in a coordinated fashion and to improve the reliability and resilience for both communication and localization. By combining social potential fields (SPF) and a cognitive packet network (CPN)-based algorithm, evacuees are guided to exits in dynamic loose clusters. Rather than relying on a conventional telecommunications infrastructure, we suggest an ad hoc cognitive packet network (AHCPN)-based protocol to adaptively search optimal communication routes between portable devices and the network egress nodes that provide access to cloud servers, in a manner that spares the remaining battery power of smart phones and minimizes the time latency. Experimental results through detailed simulations indicate that smart human motion and smart network management can increase the survival rate of evacuees and reduce the number of drained smart phones in an evacuation process. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle An Energy Efficient Distance-Aware Routing Algorithm with Multiple Mobile Sinks for Wireless Sensor Networks
Sensors 2014, 14(8), 15163-15181; doi:10.3390/s140815163
Received: 20 June 2014 / Revised: 7 August 2014 / Accepted: 13 August 2014 / Published: 18 August 2014
Cited by 5 | PDF Full-text (479 KB) | HTML Full-text | XML Full-text
Abstract
Traffic patterns in wireless sensor networks (WSNs) usually follow a many-to-one model. Sensor nodes close to static sinks will deplete their limited energy more rapidly than other sensors, since they will have more data to forward during multihop transmission. This will cause network
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Traffic patterns in wireless sensor networks (WSNs) usually follow a many-to-one model. Sensor nodes close to static sinks will deplete their limited energy more rapidly than other sensors, since they will have more data to forward during multihop transmission. This will cause network partition, isolated nodes and much shortened network lifetime. Thus, how to balance energy consumption for sensor nodes is an important research issue. In recent years, exploiting sink mobility technology in WSNs has attracted much research attention because it can not only improve energy efficiency, but prolong network lifetime. In this paper, we propose an energy efficient distance-aware routing algorithm with multiple mobile sink for WSNs, where sink nodes will move with a certain speed along the network boundary to collect monitored data. We study the influence of multiple mobile sink nodes on energy consumption and network lifetime, and we mainly focus on the selection of mobile sink node number and the selection of parking positions, as well as their impact on performance metrics above. We can see that both mobile sink node number and the selection of parking position have important influence on network performance. Simulation results show that our proposed routing algorithm has better performance than traditional routing ones in terms of energy consumption. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle The Open Service Signal in Space Navigation Data Comparison of the Global Positioning System and the BeiDou Navigation Satellite System
Sensors 2014, 14(8), 15182-15202; doi:10.3390/s140815182
Received: 17 June 2014 / Revised: 24 July 2014 / Accepted: 15 August 2014 / Published: 19 August 2014
Cited by 4 | PDF Full-text (974 KB) | HTML Full-text | XML Full-text
Abstract
More and more Global Navigation Satellite Systems (GNSSs) have been developed and are in operation. Before integrating information on various GNSSs, the differences between the various systems must be studied first. This research focuses on analyzing the navigation data differences between the Chinese
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More and more Global Navigation Satellite Systems (GNSSs) have been developed and are in operation. Before integrating information on various GNSSs, the differences between the various systems must be studied first. This research focuses on analyzing the navigation data differences between the Chinese BeiDou Navigation Satellite System (BDS) and the United States’ Global Positioning System (GPS). In addition to explaining the impact caused by these two different coordinate and time systems, this research uses an actual open service signal in space (SIS) for both GPS and BDS to analyze their current system performance. Five data quality analysis (DQA) mechanisms are proposed in this research to validate both systems’ SIS navigation data. These five DQAs evaluate the differences in ephemeris and almanac messages from both systems for stability and accuracy. After all of the DQAs, the different issues related to GPS and BDS satellite information are presented. Finally, based on these DQA results, this research provides suggested resolutions for the combined use of GPS and BDS for navigation and guidance. Full article
(This article belongs to the Special Issue Sensor Innovations for Spacecraft Guidance, Navigation, and Control)
Open AccessArticle Focal-Plane Sensing-Processing: A Power-Efficient Approach for the Implementation of Privacy-Aware Networked Visual Sensors
Sensors 2014, 14(8), 15203-15226; doi:10.3390/s140815203
Received: 10 July 2014 / Revised: 12 August 2014 / Accepted: 14 August 2014 / Published: 19 August 2014
Cited by 7 | PDF Full-text (3636 KB) | HTML Full-text | XML Full-text
Abstract
The capture, processing and distribution of visual information is one of the major challenges for the paradigm of the Internet of Things. Privacy emerges as a fundamental barrier to overcome. The idea of networked image sensors pervasively collecting data generates social rejection in
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The capture, processing and distribution of visual information is one of the major challenges for the paradigm of the Internet of Things. Privacy emerges as a fundamental barrier to overcome. The idea of networked image sensors pervasively collecting data generates social rejection in the face of sensitive information being tampered by hackers or misused by legitimate users. Power consumption also constitutes a crucial aspect. Images contain a massive amount of data to be processed under strict timing requirements, demanding high-performance vision systems. In this paper, we describe a hardware-based strategy to concurrently address these two key issues. By conveying processing capabilities to the focal plane in addition to sensing, we can implement privacy protection measures just at the point where sensitive data are generated. Furthermore, such measures can be tailored for efficiently reducing the computational load of subsequent processing stages. As a proof of concept, a full-custom QVGA vision sensor chip is presented. It incorporates a mixed-signal focal-plane sensing-processing array providing programmable pixelation of multiple image regions in parallel. In addition to this functionality, the sensor exploits reconfigurability to implement other processing primitives, namely block-wise dynamic range adaptation, integral image computation and multi-resolution filtering. The proposed circuitry is also suitable to build a granular space, becoming the raw material for subsequent feature extraction and recognition of categorized objects. Full article
(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)
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Open AccessArticle Simultaneous Electrochemical Detection of Dopamine and Ascorbic Acid Using an Iron Oxide/Reduced Graphene Oxide Modified Glassy Carbon Electrode
Sensors 2014, 14(8), 15227-15243; doi:10.3390/s140815227
Received: 28 April 2014 / Revised: 2 July 2014 / Accepted: 11 July 2014 / Published: 19 August 2014
Cited by 21 | PDF Full-text (1268 KB) | HTML Full-text | XML Full-text
Abstract
The fabrication of an electrochemical sensor based on an iron oxide/graphene modified glassy carbon electrode (Fe3O4/rGO/GCE) and its simultaneous detection of dopamine (DA) and ascorbic acid (AA) is described here. The Fe3O4/rGO nanocomposite was synthesized
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The fabrication of an electrochemical sensor based on an iron oxide/graphene modified glassy carbon electrode (Fe3O4/rGO/GCE) and its simultaneous detection of dopamine (DA) and ascorbic acid (AA) is described here. The Fe3O4/rGO nanocomposite was synthesized via a simple, one step in-situ wet chemical method and characterized by different techniques. The presence of Fe3O4 nanoparticles on the surface of rGO sheets was confirmed by FESEM and TEM images. The electrochemical behavior of Fe3O4/rGO/GCE towards electrocatalytic oxidation of DA was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) analysis. The electrochemical studies revealed that the Fe3O4/rGO/GCE dramatically increased the current response against the DA, due to the synergistic effect emerged between Fe3O4 and rGO. This implies that Fe3O4/rGO/GCE could exhibit excellent electrocatalytic activity and remarkable electron transfer kinetics towards the oxidation of DA. Moreover, the modified sensor electrode portrayed sensitivity and selectivity for simultaneous determination of AA and DA. The observed DPVs response linearly depends on AA and DA concentration in the range of 1–9 mM and 0.5–100 µM, with correlation coefficients of 0.995 and 0.996, respectively. The detection limit of (S/N = 3) was found to be 0.42 and 0.12 µM for AA and DA, respectively. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Optimization of a Cell Counting Algorithm for Mobile Point-of-Care Testing Platforms
Sensors 2014, 14(8), 15244-15261; doi:10.3390/s140815244
Received: 26 May 2014 / Revised: 4 August 2014 / Accepted: 8 August 2014 / Published: 19 August 2014
Cited by 1 | PDF Full-text (2735 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In a point-of-care (POC) setting, it is critically important to reliably count the number of specific cells in a blood sample. Software-based cell counting, which is far faster than manual counting, while much cheaper than hardware-based counting, has emerged as an attractive solution
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In a point-of-care (POC) setting, it is critically important to reliably count the number of specific cells in a blood sample. Software-based cell counting, which is far faster than manual counting, while much cheaper than hardware-based counting, has emerged as an attractive solution potentially applicable to mobile POC testing. However, the existing software-based algorithm based on the normalized cross-correlation (NCC) method is too time- and, thus, energy-consuming to be deployed for battery-powered mobile POC testing platforms. In this paper, we identify inefficiencies in the NCC-based algorithm and propose two synergistic optimization techniques that can considerably reduce the runtime and, thus, energy consumption of the original algorithm with negligible impact on counting accuracy. We demonstrate that an AndroidTM smart phone running the optimized algorithm consumes 11.5× less runtime than the original algorithm. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Particle Swarm Inspired Underwater Sensor Self-Deployment
Sensors 2014, 14(8), 15262-15281; doi:10.3390/s140815262
Received: 9 June 2014 / Revised: 27 July 2014 / Accepted: 8 August 2014 / Published: 19 August 2014
Cited by 7 | PDF Full-text (1341 KB) | HTML Full-text | XML Full-text
Abstract
Underwater sensor networks (UWSNs) can be applied in sea resource reconnaissance, pollution monitoring and assistant navigation, etc., and have become a hot research field in wireless sensor networks. In open and complicated underwater environments, targets (events) tend to be highly dynamic and
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Underwater sensor networks (UWSNs) can be applied in sea resource reconnaissance, pollution monitoring and assistant navigation, etc., and have become a hot research field in wireless sensor networks. In open and complicated underwater environments, targets (events) tend to be highly dynamic and uncertain. It is important to deploy sensors to cover potential events in an optimal manner. In this paper, the underwater sensor deployment problem and its performance evaluation metrics are introduced. Furthermore, a particle swarm inspired sensor self-deployment algorithm is presented. By simulating the flying behavior of particles and introducing crowd control, the proposed algorithm can drive sensors to cover almost all the events, and make the distribution of sensors match that of events. Through extensive simulations, we demonstrate that it can solve the underwater sensor deployment problem effectively, with fast convergence rate, and amiable to distributed implementation. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle A Novel Approach for Weed Type Classification Based on Shape Descriptors and a Fuzzy Decision-Making Method
Sensors 2014, 14(8), 15304-15324; doi:10.3390/s140815304
Received: 5 March 2014 / Revised: 7 July 2014 / Accepted: 8 August 2014 / Published: 19 August 2014
Cited by 2 | PDF Full-text (1403 KB) | HTML Full-text | XML Full-text
Abstract
An important objective in weed management is the discrimination between grasses (monocots) and broad-leaved weeds (dicots), because these two weed groups can be appropriately controlled by specific herbicides. In fact, efficiency is higher if selective treatment is performed for each type of infestation
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An important objective in weed management is the discrimination between grasses (monocots) and broad-leaved weeds (dicots), because these two weed groups can be appropriately controlled by specific herbicides. In fact, efficiency is higher if selective treatment is performed for each type of infestation instead of using a broadcast herbicide on the whole surface. This work proposes a strategy where weeds are characterised by a set of shape descriptors (the seven Hu moments and six geometric shape descriptors). Weeds appear in outdoor field images which display real situations obtained from a RGB camera. Thus, images present a mixture of both weed species under varying conditions of lighting. In the presented approach, four decision-making methods were adapted to use the best shape descriptors as attributes and a choice was taken. This proposal establishes a novel methodology with a high success rate in weed species discrimination. Full article
(This article belongs to the Special Issue Agriculture and Forestry: Sensors, Technologies and Procedures)
Open AccessArticle Preceding Vehicle Detection and Tracking Adaptive to Illumination Variation in Night Traffic Scenes Based on Relevance Analysis
Sensors 2014, 14(8), 15325-15347; doi:10.3390/s140815325
Received: 29 May 2014 / Revised: 14 July 2014 / Accepted: 12 August 2014 / Published: 19 August 2014
Cited by 5 | PDF Full-text (765 KB) | HTML Full-text | XML Full-text
Abstract
Preceding vehicle detection and tracking at nighttime are challenging problems due to the disturbance of other extraneous illuminant sources coexisting with the vehicle lights. To improve the detection accuracy and robustness of vehicle detection, a novel method for vehicle detection and tracking at
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Preceding vehicle detection and tracking at nighttime are challenging problems due to the disturbance of other extraneous illuminant sources coexisting with the vehicle lights. To improve the detection accuracy and robustness of vehicle detection, a novel method for vehicle detection and tracking at nighttime is proposed in this paper. The characteristics of taillights in the gray level are applied to determine the lower boundary of the threshold for taillights segmentation, and the optimal threshold for taillight segmentation is calculated using the OTSU algorithm between the lower boundary and the highest grayscale of the region of interest. The candidate taillight pairs are extracted based on the similarity between left and right taillights, and the non-vehicle taillight pairs are removed based on the relevance analysis of vehicle location between frames. To reduce the false negative rate of vehicle detection, a vehicle tracking method based on taillights estimation is applied. The taillight spot candidate is sought in the region predicted by Kalman filtering, and the disturbed taillight is estimated based on the symmetry and location of the other taillight of the same vehicle. Vehicle tracking is completed after estimating its location according to the two taillight spots. The results of experiments on a vehicle platform indicate that the proposed method could detect vehicles quickly, correctly and robustly in the actual traffic environments with illumination variation. Full article
(This article belongs to the Special Issue Positioning and Tracking Sensors and Technologies in Road Transport)
Open AccessArticle Intra-and-Inter Species Biomass Prediction in a Plantation Forest: Testing the Utility of High Spatial Resolution Spaceborne Multispectral RapidEye Sensor and Advanced Machine Learning Algorithms
Sensors 2014, 14(8), 15348-15370; doi:10.3390/s140815348
Received: 26 April 2014 / Revised: 14 June 2014 / Accepted: 6 August 2014 / Published: 20 August 2014
Cited by 23 | PDF Full-text (827 KB) | HTML Full-text | XML Full-text
Abstract
The quantification of aboveground biomass using remote sensing is critical for better understanding the role of forests in carbon sequestration and for informed sustainable management. Although remote sensing techniques have been proven useful in assessing forest biomass in general, more is required to
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The quantification of aboveground biomass using remote sensing is critical for better understanding the role of forests in carbon sequestration and for informed sustainable management. Although remote sensing techniques have been proven useful in assessing forest biomass in general, more is required to investigate their capabilities in predicting intra-and-inter species biomass which are mainly characterised by non-linear relationships. In this study, we tested two machine learning algorithms, Stochastic Gradient Boosting (SGB) and Random Forest (RF) regression trees to predict intra-and-inter species biomass using high resolution RapidEye reflectance bands as well as the derived vegetation indices in a commercial plantation. The results showed that the SGB algorithm yielded the best performance for intra-and-inter species biomass prediction; using all the predictor variables as well as based on the most important selected variables. For example using the most important variables the algorithm produced an R2 of 0.80 and RMSE of 16.93 t·ha−1 for E. grandis; R2 of 0.79, RMSE of 17.27 t·ha−1 for P. taeda and R2 of 0.61, RMSE of 43.39 t·ha−1 for the combined species data sets. Comparatively, RF yielded plausible results only for E. dunii (R2 of 0.79; RMSE of 7.18 t·ha−1). We demonstrated that although the two statistical methods were able to predict biomass accurately, RF produced weaker results as compared to SGB when applied to combined species dataset. The result underscores the relevance of stochastic models in predicting biomass drawn from different species and genera using the new generation high resolution RapidEye sensor with strategically positioned bands. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle An Ultrasonic Contactless Sensor for Breathing Monitoring
Sensors 2014, 14(8), 15371-15386; doi:10.3390/s140815371
Received: 10 June 2014 / Revised: 2 August 2014 / Accepted: 5 August 2014 / Published: 20 August 2014
Cited by 7 | PDF Full-text (1587 KB) | HTML Full-text | XML Full-text
Abstract
The monitoring of human breathing activity during a long period has multiple fundamental applications in medicine. In breathing sleep disorders such as apnea, the diagnosis is based on events during which the person stops breathing for several periods during sleep. In polysomnography, the
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The monitoring of human breathing activity during a long period has multiple fundamental applications in medicine. In breathing sleep disorders such as apnea, the diagnosis is based on events during which the person stops breathing for several periods during sleep. In polysomnography, the standard for sleep disordered breathing analysis, chest movement and airflow are used to monitor the respiratory activity. However, this method has serious drawbacks. Indeed, as the subject should sleep overnight in a laboratory and because of sensors being in direct contact with him, artifacts modifying sleep quality are often observed. This work investigates an analysis of the viability of an ultrasonic device to quantify the breathing activity, without contact and without any perception by the subject. Based on a low power ultrasonic active source and transducer, the device measures the frequency shift produced by the velocity difference between the exhaled air flow and the ambient environment, i.e., the Doppler effect. After acquisition and digitization, a specific signal processing is applied to separate the effects of breath from those due to subject movements from the Doppler signal. The distance between the source and the sensor, about 50 cm, and the use of ultrasound frequency well above audible frequencies, 40 kHz, allow monitoring the breathing activity without any perception by the subject, and therefore without any modification of the sleep quality which is very important for sleep disorders diagnostic applications. This work is patented (patent pending 2013-7-31 number FR.13/57569). Full article
Open AccessArticle Directional Navigation Improves Opportunistic Communication for Emergencies
Sensors 2014, 14(8), 15387-15399; doi:10.3390/s140815387
Received: 2 May 2014 / Revised: 1 June 2014 / Accepted: 14 August 2014 / Published: 20 August 2014
Cited by 3 | PDF Full-text (494 KB) | HTML Full-text | XML Full-text
Abstract
We present a novel direction based shortest path search algorithm to guide evacuees during an emergency. It uses opportunistic communications (oppcomms) with low-cost wearable mobile nodes that can exchange packets at close range of a few to some tens of meters without help
[...] Read more.
We present a novel direction based shortest path search algorithm to guide evacuees during an emergency. It uses opportunistic communications (oppcomms) with low-cost wearable mobile nodes that can exchange packets at close range of a few to some tens of meters without help of an infrastructure. The algorithm seeks the shortest path to exits which are safest with regard to a hazard, and is integrated into an autonomous Emergency Support System (ESS) to guide evacuees in a built environment. The algorithm proposed that ESSs are evaluated with the DBES (Distributed Building Evacuation Simulator) by simulating a shopping centre where fire is spreading. The results show that the directional path finding algorithm can offer significant improvements for the evacuees. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Rapid, Single-Molecule Assays in Nano/Micro-Fluidic Chips with Arrays of Closely Spaced Parallel Channels Fabricated by Femtosecond Laser Machining
Sensors 2014, 14(8), 15400-15414; doi:10.3390/s140815400
Received: 16 July 2014 / Revised: 8 August 2014 / Accepted: 18 August 2014 / Published: 20 August 2014
PDF Full-text (523 KB) | HTML Full-text | XML Full-text
Abstract
Cost-effective pharmaceutical drug discovery depends on increasing assay throughput while reducing reagent needs. To this end, we are developing an ultrasensitive, fluorescence-based platform that incorporates a nano/micro-fluidic chip with an array of closely spaced channels for parallelized optical readout of single-molecule assays. Here
[...] Read more.
Cost-effective pharmaceutical drug discovery depends on increasing assay throughput while reducing reagent needs. To this end, we are developing an ultrasensitive, fluorescence-based platform that incorporates a nano/micro-fluidic chip with an array of closely spaced channels for parallelized optical readout of single-molecule assays. Here we describe the use of direct femtosecond laser machining to fabricate several hundred closely spaced channels on the surfaces of fused silica substrates. The channels are sealed by bonding to a microscope cover slip spin-coated with a thin film of poly(dimethylsiloxane). Single-molecule detection experiments are conducted using a custom-built, wide-field microscope. The array of channels is epi-illuminated by a line-generating red diode laser, resulting in a line focus just a few microns thick across a 500 micron field of view. A dilute aqueous solution of fluorescently labeled biomolecules is loaded into the device and fluorescence is detected with an electron-multiplying CCD camera, allowing acquisition rates up to 7 kHz for each microchannel. Matched digital filtering based on experimental parameters is used to perform an initial, rapid assessment of detected fluorescence. More detailed analysis is obtained through fluorescence correlation spectroscopy. Simulated fluorescence data is shown to agree well with experimental values. Full article
(This article belongs to the Special Issue Opto-Microfluidics for Bio Applications)
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Open AccessArticle A Kalman Filter-Based Short Baseline RTK Algorithm for Single-Frequency Combination of GPS and BDS
Sensors 2014, 14(8), 15415-15433; doi:10.3390/s140815415
Received: 25 June 2014 / Revised: 11 August 2014 / Accepted: 13 August 2014 / Published: 20 August 2014
Cited by 4 | PDF Full-text (1445 KB) | HTML Full-text | XML Full-text
Abstract
The emerging Global Navigation Satellite Systems (GNSS) including the BeiDou Navigation Satellite System (BDS) offer more visible satellites for positioning users. To employ those new satellites in a real-time kinematic (RTK) algorithm to enhance positioning precision and availability, a data processing model for
[...] Read more.
The emerging Global Navigation Satellite Systems (GNSS) including the BeiDou Navigation Satellite System (BDS) offer more visible satellites for positioning users. To employ those new satellites in a real-time kinematic (RTK) algorithm to enhance positioning precision and availability, a data processing model for the dual constellation of GPS and BDS is proposed and analyzed. A Kalman filter-based algorithm is developed to estimate the float ambiguities for short baseline scenarios. The entire work process of the high-precision algorithm based on the proposed model is deeply investigated in detail. The model is validated with real GPS and BDS data recorded from one zero and two short baseline experiments. Results show that the proposed algorithm can generate fixed baseline output with the same precision level as that of either a single GPS or BDS RTK algorithm. The significantly improved fixed rate and time to first fix of the proposed method demonstrates a better availability and effectiveness on processing multi-GNSSs. Full article
(This article belongs to the Special Issue Positioning and Tracking Sensors and Technologies in Road Transport)
Open AccessArticle Estimation of Spatial-Temporal Gait Parameters Using a Low-Cost Ultrasonic Motion Analysis System
Sensors 2014, 14(8), 15434-15457; doi:10.3390/s140815434
Received: 28 May 2014 / Revised: 14 August 2014 / Accepted: 15 August 2014 / Published: 20 August 2014
Cited by 3 | PDF Full-text (1191 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a low-cost motion analysis system using a wireless ultrasonic sensor network is proposed and investigated. A methodology has been developed to extract spatial-temporal gait parameters including stride length, stride duration, stride velocity, stride cadence, and stride symmetry from 3D foot
[...] Read more.
In this paper, a low-cost motion analysis system using a wireless ultrasonic sensor network is proposed and investigated. A methodology has been developed to extract spatial-temporal gait parameters including stride length, stride duration, stride velocity, stride cadence, and stride symmetry from 3D foot displacements estimated by the combination of spherical positioning technique and unscented Kalman filter. The performance of this system is validated against a camera-based system in the laboratory with 10 healthy volunteers. Numerical results show the feasibility of the proposed system with average error of 2.7% for all the estimated gait parameters. The influence of walking speed on the measurement accuracy of proposed system is also evaluated. Statistical analysis demonstrates its capability of being used as a gait assessment tool for some medical applications. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A High-Pressure Bi-Directional Cycloid Rotor Flowmeter
Sensors 2014, 14(8), 15480-15495; doi:10.3390/s140815480
Received: 27 June 2014 / Revised: 5 August 2014 / Accepted: 6 August 2014 / Published: 21 August 2014
Cited by 1 | PDF Full-text (2496 KB) | HTML Full-text | XML Full-text
Abstract
The measurement of the flow rate of various liquids and gases is critical in industrial automation. Rotary positive displacement meters (rotary PD meters) are highly accurate flowmeters that are widely employed in engineering applications, especially in custody transfer operations and hydraulic control systems.
[...] Read more.
The measurement of the flow rate of various liquids and gases is critical in industrial automation. Rotary positive displacement meters (rotary PD meters) are highly accurate flowmeters that are widely employed in engineering applications, especially in custody transfer operations and hydraulic control systems. This paper presents a high pressure rotary PD meter containing a pair of internal cycloid rotors. It has the advantages of concise structure, low pressure loss, high accuracy and low noise. The curve of the internal rotor is designed as an equidistant curtate epicycloid curve with the external rotor curve as its conjugate. The calculation method used to determine the displacement of the cycloid rotor flowmeter is discussed. A prototype was fabricated, and experiments were performed to confirm measurements over a flow range of 1–100 L/min with relative errors of less than ±0.5%. The pressure loss through the flowmeter was about 3 bar at a flow rate of 100 L/min. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Lab-on-Chip Cytometry Based on Magnetoresistive Sensors for Bacteria Detection in Milk
Sensors 2014, 14(8), 15496-15524; doi:10.3390/s140815496
Received: 23 May 2014 / Revised: 14 July 2014 / Accepted: 1 August 2014 / Published: 21 August 2014
Cited by 12 | PDF Full-text (4767 KB) | HTML Full-text | XML Full-text
Abstract
Flow cytometers have been optimized for use in portable platforms, where cell separation, identification and counting can be achieved in a compact and modular format. This feature can be combined with magnetic detection, where magnetoresistive sensors can be integrated within microfluidic channels to
[...] Read more.
Flow cytometers have been optimized for use in portable platforms, where cell separation, identification and counting can be achieved in a compact and modular format. This feature can be combined with magnetic detection, where magnetoresistive sensors can be integrated within microfluidic channels to detect magnetically labelled cells. This work describes a platform for in-flow detection of magnetically labelled cells with a magneto-resistive based cell cytometer. In particular, we present an example for the validation of the platform as a magnetic counter that identifies and quantifies Streptococcus agalactiae in milk. Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)
Open AccessArticle Efficient Sensor Placement Optimization Using Gradient Descent and Probabilistic Coverage
Sensors 2014, 14(8), 15525-15552; doi:10.3390/s140815525
Received: 20 June 2014 / Revised: 8 August 2014 / Accepted: 14 August 2014 / Published: 21 August 2014
Cited by 1 | PDF Full-text (3886 KB) | HTML Full-text | XML Full-text
Abstract
We are proposing an adaptation of the gradient descent method to optimize the position and orientation of sensors for the sensor placement problem. The novelty of the proposed method lies in the combination of gradient descent optimization with a realistic model, which considers
[...] Read more.
We are proposing an adaptation of the gradient descent method to optimize the position and orientation of sensors for the sensor placement problem. The novelty of the proposed method lies in the combination of gradient descent optimization with a realistic model, which considers both the topography of the environment and a set of sensors with directional probabilistic sensing. The performance of this approach is compared with two other black box optimization methods over area coverage and processing time. Results show that our proposed method produces competitive results on smaller maps and superior results on larger maps, while requiring much less computation than the other optimization methods to which it has been compared. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors in Canada 2014)
Open AccessArticle Application of Service Oriented Architecture for Sensors and Actuators in District Heating Substations
Sensors 2014, 14(8), 15553-15572; doi:10.3390/s140815553
Received: 7 March 2014 / Revised: 12 August 2014 / Accepted: 13 August 2014 / Published: 21 August 2014
Cited by 2 | PDF Full-text (503 KB) | HTML Full-text | XML Full-text
Abstract
Hardwired sensor installations using proprietary protocols found in today’s district heating substations limit the potential usability of the sensors in and around the substations. If sensor resources can be shared and re-used in a variety of applications, the cost of sensors and installation
[...] Read more.
Hardwired sensor installations using proprietary protocols found in today’s district heating substations limit the potential usability of the sensors in and around the substations. If sensor resources can be shared and re-used in a variety of applications, the cost of sensors and installation can be reduced, and their functionality and operability can be increased. In this paper, we present a new concept of district heating substation control and monitoring, where a service oriented architecture (SOA) is deployed in a wireless sensor network (WSN), which is integrated with the substation. IP-networking is exclusively used from sensor to server; hence, no middleware is needed for Internet integration. Further, by enabling thousands of sensors with SOA capabilities, a System of Systems approach can be applied. The results of this paper show that it is possible to utilize SOA solutions with heavily resource-constrained embedded devices in contexts where the real-time constrains are limited, such as in a district heating substation. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Energy-Efficient ZigBee-Based Wireless Sensor Network for Track Bicycle Performance Monitoring
Sensors 2014, 14(8), 15573-15592; doi:10.3390/s140815573
Received: 12 July 2014 / Revised: 11 August 2014 / Accepted: 13 August 2014 / Published: 22 August 2014
Cited by 6 | PDF Full-text (880 KB) | HTML Full-text | XML Full-text
Abstract
In a wireless sensor network (WSN), saving power is a vital requirement. In this paper, a simple point-to-point bike WSN was considered. The data of bike parameters, speed and cadence, were monitored and transmitted via a wireless communication based on the ZigBee protocol.
[...] Read more.
In a wireless sensor network (WSN), saving power is a vital requirement. In this paper, a simple point-to-point bike WSN was considered. The data of bike parameters, speed and cadence, were monitored and transmitted via a wireless communication based on the ZigBee protocol. Since the bike parameters are monitored and transmitted on every bike wheel rotation, this means the sensor node does not sleep for a long time, causing power consumption to rise. Therefore, a newly proposed algorithm, known as the Redundancy and Converged Data (RCD) algorithm, was implemented for this application to put the sensor node into sleep mode while maintaining the performance measurements. This is achieved by minimizing the data packets transmitted as much as possible and fusing the data of speed and cadence by utilizing the correlation measurements between them to minimize the number of sensor nodes in the network to one node, which results in reduced power consumption, cost, and size, in addition to simpler hardware implementation. Execution of the proposed RCD algorithm shows that this approach can reduce the current consumption to 1.69 mA, and save 95% of the sensor node energy. Also, the comparison results with different wireless standard technologies demonstrate minimal current consumption in the sensor node. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Use of Temperature and Humidity Sensors to Determine Moisture Content of Oolong Tea
Sensors 2014, 14(8), 15593-15609; doi:10.3390/s140815593
Received: 22 June 2014 / Revised: 19 August 2014 / Accepted: 20 August 2014 / Published: 22 August 2014
Cited by 3 | PDF Full-text (755 KB) | HTML Full-text | XML Full-text
Abstract
The measurement of tea moisture content is important for processing and storing tea. The moisture content of tea affects the quality and durability of the product. Some electrical devices have been proposed to measure the moisture content of tea leaves but are not
[...] Read more.
The measurement of tea moisture content is important for processing and storing tea. The moisture content of tea affects the quality and durability of the product. Some electrical devices have been proposed to measure the moisture content of tea leaves but are not practical. Their performance is influenced by material density and packing. The official oven method is time-consuming. In this study, the moisture content of Oolong tea was measured by the equilibrium relative humidity technique. The equilibrium relative humidity, and temperature, of tea materials were measured by using temperature and relative humidity sensors. Sensors were calibrated, and calibration equations were established to improve accuracy. The moisture content was calculated by using an equilibrium moisture content model. The error of the moisture content determined with this method was within 0.5% w.b. at moisture <15% w.b. Uncertainty analysis revealed that the performance of the humidity sensor had a significant effect on the accuracy of moisture determination. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Analytical Model of Large Data Transactions in CoAP Networks
Sensors 2014, 14(8), 15610-15638; doi:10.3390/s140815610
Received: 26 June 2014 / Revised: 7 August 2014 / Accepted: 13 August 2014 / Published: 22 August 2014
PDF Full-text (5298 KB) | HTML Full-text | XML Full-text
Abstract
We propose a novel analytical model to study fragmentation methods in wireless sensor networks adopting the Constrained Application Protocol (CoAP) and the IEEE 802.15.4 standard for medium access control (MAC). The blockwise transfer technique proposed in CoAP and the 6LoWPAN fragmentation are included
[...] Read more.
We propose a novel analytical model to study fragmentation methods in wireless sensor networks adopting the Constrained Application Protocol (CoAP) and the IEEE 802.15.4 standard for medium access control (MAC). The blockwise transfer technique proposed in CoAP and the 6LoWPAN fragmentation are included in the analysis. The two techniques are compared in terms of reliability and delay, depending on the traffic, the number of nodes and the parameters of the IEEE 802.15.4 MAC. The results are validated trough Monte Carlo simulations. To the best of our knowledge this is the first study that evaluates and compares analytically the performance of CoAP blockwise transfer and 6LoWPAN fragmentation. A major contribution is the possibility to understand the behavior of both techniques with different network conditions. Our results show that 6LoWPAN fragmentation is preferable for delay-constrained applications. For highly congested networks, the blockwise transfer slightly outperforms 6LoWPAN fragmentation in terms of reliability. Full article
(This article belongs to the Special Issue Wireless Sensor Networks and the Internet of Things)
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Review

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Open AccessReview Trends in Correlation-Based Pattern Recognition and Tracking in Forward-Looking Infrared Imagery
Sensors 2014, 14(8), 13437-13475; doi:10.3390/s140813437
Received: 18 June 2014 / Revised: 16 July 2014 / Accepted: 16 July 2014 / Published: 24 July 2014
Cited by 3 | PDF Full-text (1819 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we review the recent trends and advancements on correlation-based pattern recognition and tracking in forward-looking infrared (FLIR) imagery. In particular, we discuss matched filter-based correlation techniques for target detection and tracking which are widely used for various real time applications.
[...] Read more.
In this paper, we review the recent trends and advancements on correlation-based pattern recognition and tracking in forward-looking infrared (FLIR) imagery. In particular, we discuss matched filter-based correlation techniques for target detection and tracking which are widely used for various real time applications. We analyze and present test results involving recently reported matched filters such as the maximum average correlation height (MACH) filter and its variants, and distance classifier correlation filter (DCCF) and its variants. Test results are presented for both single/multiple target detection and tracking using various real-life FLIR image sequences. Full article
Open AccessReview Virus Outbreaks in Chemical and Biological Sensors
Sensors 2014, 14(8), 13592-13612; doi:10.3390/s140813592
Received: 18 April 2014 / Revised: 8 July 2014 / Accepted: 8 July 2014 / Published: 25 July 2014
Cited by 4 | PDF Full-text (6811 KB) | HTML Full-text | XML Full-text
Abstract
Filamentous bacteriophages have successfully been used to detect chemical and biological analytes with increased selectivity and sensitivity. The enhancement largely originates not only from the ability of viruses to provide a platform for the surface display of a wide range of biological ligands,
[...] Read more.
Filamentous bacteriophages have successfully been used to detect chemical and biological analytes with increased selectivity and sensitivity. The enhancement largely originates not only from the ability of viruses to provide a platform for the surface display of a wide range of biological ligands, but also from the geometric morphologies of the viruses that constitute biomimetic structures with larger surface area-to-volume ratio. This review will appraise the mechanism of multivalent display of the viruses that enables surface modification of virions either by chemical or biological methods. The accommodation of functionalized virions to various materials, including polymers, proteins, metals, nanoparticles, and electrodes for sensor applications will also be discussed. Full article
(This article belongs to the Section Biosensors)
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Open AccessReview High Performance Relaxor-Based Ferroelectric Single Crystals for Ultrasonic Transducer Applications
Sensors 2014, 14(8), 13730-13758; doi:10.3390/s140813730
Received: 11 June 2014 / Revised: 18 July 2014 / Accepted: 18 July 2014 / Published: 29 July 2014
Cited by 8 | PDF Full-text (1351 KB) | HTML Full-text | XML Full-text
Abstract
Relaxor-based ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) have drawn much attention in the ferroelectric field because of their excellent piezoelectric properties and high electromechanical coupling coefficients (d33~2000 pC/N, kt~60%) near the morphotropic phase
[...] Read more.
Relaxor-based ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) have drawn much attention in the ferroelectric field because of their excellent piezoelectric properties and high electromechanical coupling coefficients (d33~2000 pC/N, kt~60%) near the morphotropic phase boundary (MPB). Ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals also possess outstanding performance comparable with PMN-PT single crystals, but have higher phase transition temperatures (rhombohedral to tetragonal Trt, and tetragonal to cubic Tc) and larger coercive field Ec. Therefore, these relaxor-based single crystals have been extensively employed for ultrasonic transducer applications. In this paper, an overview of our work and perspectives on using PMN-PT and PIN-PMN-PT single crystals for ultrasonic transducer applications is presented. Various types of single-element ultrasonic transducers, including endoscopic transducers, intravascular transducers, high-frequency and high-temperature transducers fabricated using the PMN-PT and PIN-PMN-PT crystals and their 2-2 and 1-3 composites are reported. Besides, the fabrication and characterization of the array transducers, such as phased array, cylindrical shaped linear array, high-temperature linear array, radial endoscopic array, and annular array, are also addressed. Full article
Open AccessReview Bio-Mimetic Sensors Based on Molecularly Imprinted Membranes
Sensors 2014, 14(8), 13863-13912; doi:10.3390/s140813863
Received: 18 April 2014 / Revised: 16 July 2014 / Accepted: 21 July 2014 / Published: 30 July 2014
Cited by 24 | PDF Full-text (1053 KB) | HTML Full-text | XML Full-text
Abstract
An important challenge for scientific research is the production of artificial systems able to mimic the recognition mechanisms occurring at the molecular level in living systems. A valid contribution in this direction resulted from the development of molecular imprinting. By means of this
[...] Read more.
An important challenge for scientific research is the production of artificial systems able to mimic the recognition mechanisms occurring at the molecular level in living systems. A valid contribution in this direction resulted from the development of molecular imprinting. By means of this technology, selective molecular recognition sites are introduced in a polymer, thus conferring it bio-mimetic properties. The potential applications of these systems include affinity separations, medical diagnostics, drug delivery, catalysis, etc. Recently, bio-sensing systems using molecularly imprinted membranes, a special form of imprinted polymers, have received the attention of scientists in various fields. In these systems imprinted membranes are used as bio-mimetic recognition elements which are integrated with a transducer component. The direct and rapid determination of an interaction between the recognition element and the target analyte (template) was an encouraging factor for the development of such systems as alternatives to traditional bio-assay methods. Due to their high stability, sensitivity and specificity, bio-mimetic sensors-based membranes are used for environmental, food, and clinical uses. This review deals with the development of molecularly imprinted polymers and their different preparation methods. Referring to the last decades, the application of these membranes as bio-mimetic sensor devices will be also reported. Full article
(This article belongs to the Special Issue Biomimetic Receptors and Sensors)
Open AccessReview One-Dimensional Nanostructure Field-Effect Sensors for Gas Detection
Sensors 2014, 14(8), 13999-14020; doi:10.3390/s140813999
Received: 18 June 2014 / Revised: 29 June 2014 / Accepted: 15 July 2014 / Published: 31 July 2014
Cited by 9 | PDF Full-text (4866 KB) | HTML Full-text | XML Full-text
Abstract
Recently; one-dimensional (1D) nanostructure field-effect transistors (FETs) have attracted much attention because of their potential application in gas sensing. Micro/nanoscaled field-effect sensors combine the advantages of 1D nanostructures and the characteristic of field modulation. 1D nanostructures provide a large surface area-volume ratio; which
[...] Read more.
Recently; one-dimensional (1D) nanostructure field-effect transistors (FETs) have attracted much attention because of their potential application in gas sensing. Micro/nanoscaled field-effect sensors combine the advantages of 1D nanostructures and the characteristic of field modulation. 1D nanostructures provide a large surface area-volume ratio; which is an outstanding advantage for gas sensors with high sensitivity and fast response. In addition; the nature of the single crystals is favorable for the studies of the response mechanism. On the other hand; one main merit of the field-effect sensors is to provide an extra gate electrode to realize the current modulation; so that the sensitivity can be dramatically enhanced by changing the conductivity when operating the sensors in the subthreshold regime. This article reviews the recent developments in the field of 1D nanostructure FET for gas detection. The sensor configuration; the performance as well as their sensing mechanism are evaluated. Full article
(This article belongs to the Special Issue Gas Sensors Based on the Field Effect)
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Open AccessReview High Temperature, High Power Piezoelectric Composite Transducers
Sensors 2014, 14(8), 14526-14552; doi:10.3390/s140814526
Received: 18 June 2014 / Revised: 30 July 2014 / Accepted: 30 July 2014 / Published: 8 August 2014
Cited by 7 | PDF Full-text (5848 KB) | HTML Full-text | XML Full-text
Abstract
Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and
[...] Read more.
Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined. Full article
Open AccessReview A Review of Brain-Computer Interface Games and an Opinion Survey from Researchers, Developers and Users
Sensors 2014, 14(8), 14601-14633; doi:10.3390/s140814601
Received: 12 February 2014 / Revised: 25 July 2014 / Accepted: 28 July 2014 / Published: 11 August 2014
Cited by 11 | PDF Full-text (1560 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In recent years, research on Brain-Computer Interface (BCI) technology for healthy users has attracted considerable interest, and BCI games are especially popular. This study reviews the current status of, and describes future directions, in the field of BCI games. To this end, we
[...] Read more.
In recent years, research on Brain-Computer Interface (BCI) technology for healthy users has attracted considerable interest, and BCI games are especially popular. This study reviews the current status of, and describes future directions, in the field of BCI games. To this end, we conducted a literature search and found that BCI control paradigms using electroencephalographic signals (motor imagery, P300, steady state visual evoked potential and passive approach reading mental state) have been the primary focus of research. We also conducted a survey of nearly three hundred participants that included researchers, game developers and users around the world. From this survey, we found that all three groups (researchers, developers and users) agreed on the significant influence and applicability of BCI and BCI games, and they all selected prostheses, rehabilitation and games as the most promising BCI applications. User and developer groups tended to give low priority to passive BCI and the whole head sensor array. Developers gave higher priorities to “the easiness of playing” and the “development platform” as important elements for BCI games and the market. Based on our assessment, we discuss the critical point at which BCI games will be able to progress from their current stage to widespread marketing to consumers. In conclusion, we propose three critical elements important for expansion of the BCI game market: standards, gameplay and appropriate integration. Full article
(This article belongs to the Section Physical Sensors)
Open AccessReview Recent Developments in Optical Detection Technologies in Lab-on-a-Chip Devices for Biosensing Applications
Sensors 2014, 14(8), 15458-15479; doi:10.3390/s140815458
Received: 15 July 2014 / Revised: 14 August 2014 / Accepted: 15 August 2014 / Published: 21 August 2014
Cited by 29 | PDF Full-text (1092 KB) | HTML Full-text | XML Full-text
Abstract
The field of microfluidics has yet to develop practical devices that provide real clinical value. One of the main reasons for this is the difficulty in realizing low-cost, sensitive, reproducible, and portable analyte detection microfluidic systems. Previous research has addressed two main approaches
[...] Read more.
The field of microfluidics has yet to develop practical devices that provide real clinical value. One of the main reasons for this is the difficulty in realizing low-cost, sensitive, reproducible, and portable analyte detection microfluidic systems. Previous research has addressed two main approaches for the detection technologies in lab-on-a-chip devices: (a) study of the compatibility of conventional instrumentation with microfluidic structures, and (b) integration of innovative sensors contained within the microfluidic system. Despite the recent advances in electrochemical and mechanical based sensors, their drawbacks pose important challenges to their application in disposable microfluidic devices. Instead, optical detection remains an attractive solution for lab-on-a-chip devices, because of the ubiquity of the optical methods in the laboratory. Besides, robust and cost-effective devices for use in the field can be realized by integrating proper optical detection technologies on chips. This review examines the recent developments in detection technologies applied to microfluidic biosensors, especially addressing several optical methods, including fluorescence, chemiluminescence, absorbance and surface plasmon resonance. Full article
(This article belongs to the Special Issue Opto-Microfluidics for Bio Applications)

Other

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Open AccessCase Report Confronting Passive and Active Sensors with Non-Gaussian Statistics
Sensors 2014, 14(8), 13759-13777; doi:10.3390/s140813759
Received: 21 May 2014 / Revised: 22 July 2014 / Accepted: 28 July 2014 / Published: 30 July 2014
Cited by 2 | PDF Full-text (5920 KB) | HTML Full-text | XML Full-text
Abstract
This paper has two motivations: firstly, to compare the Digital Surface Models (DSM) derived by passive (digital camera) and by active (terrestrial laser scanner) remote sensing systems when applied to specific architectural objects, and secondly, to test how well the Gaussian classic statistics,
[...] Read more.
This paper has two motivations: firstly, to compare the Digital Surface Models (DSM) derived by passive (digital camera) and by active (terrestrial laser scanner) remote sensing systems when applied to specific architectural objects, and secondly, to test how well the Gaussian classic statistics, with its Least Squares principle, adapts to data sets where asymmetrical gross errors may appear and whether this approach should be changed for a non-parametric one. The field of geomatic technology automation is immersed in a high demanding competition in which any innovation by one of the contenders immediately challenges the opponents to propose a better improvement. Nowadays, we seem to be witnessing an improvement of terrestrial photogrammetry and its integration with computer vision to overcome the performance limitations of laser scanning methods. Through this contribution some of the issues of this “technological race” are examined from the point of view of photogrammetry. A new software is introduced and an experimental test is designed, performed and assessed to try to cast some light on this thrilling match. For the case considered in this study, the results show good agreement between both sensors, despite considerable asymmetry. This asymmetry suggests that the standard Normal parameters are not adequate to assess this type of data, especially when accuracy is of importance. In this case, standard deviation fails to provide a good estimation of the results, whereas the results obtained for the Median Absolute Deviation and for the Biweight Midvariance are more appropriate measures. Full article
(This article belongs to the Section Physical Sensors)
Open AccessCorrection Correction: Supuk, T.G., et al. Design, Development and Testing of a Low-Cost sEMG System and Its Use in Recording Muscle Activity in Human Gait. Sensors 2014, 14, 8235–8258
Sensors 2014, 14(8), 15639-15640; doi:10.3390/s140815639
Received: 25 July 2014 / Accepted: 4 August 2014 / Published: 22 August 2014
PDF Full-text (620 KB) | HTML Full-text | XML Full-text
Abstract
The authors wish to make the following correction to this paper [1]. Due to an error Figure 15 was a duplicate of Figure 13, the former Figure 15 (labelled here as Previous Figure 15) should be replaced by the new version shown below
[...] Read more.
The authors wish to make the following correction to this paper [1]. Due to an error Figure 15 was a duplicate of Figure 13, the former Figure 15 (labelled here as Previous Figure 15) should be replaced by the new version shown below (labeled here as New Figure 15):[...] Full article
(This article belongs to the Special Issue Biomedical Sensors and Systems)

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