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Sensors, Volume 13, Issue 7 (July 2013), Pages 8060-9548

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Open AccessArticle Context Management Platform for Tourism Applications
Sensors 2013, 13(7), 8060-8078; doi:10.3390/s130708060
Received: 3 May 2013 / Revised: 14 June 2013 / Accepted: 17 June 2013 / Published: 24 June 2013
Cited by 7 | PDF Full-text (623 KB) | HTML Full-text | XML Full-text
Abstract
The notion of context has been widely studied and there are several authors that have proposed different definitions of context. However, context has not been widely studied in the framework of human mobility and the notion of context has been imported directly [...] Read more.
The notion of context has been widely studied and there are several authors that have proposed different definitions of context. However, context has not been widely studied in the framework of human mobility and the notion of context has been imported directly from other computing fields without specifically addressing the tourism domain requirements. In order to store and manage context information a context data model and a context management platform are needed. Ontologies have been widely used in context modelling, but many of them are designed to be applied in general ubiquitous computing environments, do not contain specific concepts related to the tourism domain or some approaches do not contain enough concepts to represent context information related to the visitor on the move. That is why we propose a new approach to provide a better solution to model context data in tourism environments, adding more value to our solution reusing data about tourist resources from an Open Data repository and publishing it as Linked Data. We also propose the architecture for a context information management platform based on this context data model. Full article
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Open AccessArticle Fabrication of a Polyaniline Ultramicroelectrode via a Self Assembled Monolayer Modified Gold Electrode
Sensors 2013, 13(7), 8079-8094; doi:10.3390/s130708079
Received: 16 April 2013 / Revised: 14 June 2013 / Accepted: 18 June 2013 / Published: 24 June 2013
Cited by 1 | PDF Full-text (926 KB) | HTML Full-text | XML Full-text
Abstract
Herein, we report a simple and inexpensive way for the fabrication of an ultramicroelectrode and present its characterization by electrochemical techniques. The fabrication of polyaniline UME involves only two steps: modification of a gold (Au) electrode by self assembled monolayers (SAM) and [...] Read more.
Herein, we report a simple and inexpensive way for the fabrication of an ultramicroelectrode and present its characterization by electrochemical techniques. The fabrication of polyaniline UME involves only two steps: modification of a gold (Au) electrode by self assembled monolayers (SAM) and then electrodeposition of polyaniline film on this thiol-coated Au electrode by using cyclic voltammetry and constant potential electrolysis methods. Two types of self-assembled monolayers (4-mercapto-1-butanol, MB, and 11-mercaptoundecanoic acid, MUA) were used, respectively, to see the effect of chain length on microelectrode formation. Microelectrode fabrication and utility of the surface was investigated by cyclic voltammetric measurements in a redox probe. The thus prepared polyaniline microelectrode was then used for DNA immobilization. Discrimination between double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) was obtained with enhanced electrochemical signals compared to a polyaniline-coated Au electrode. Different modifications on the electrode surfaces were examined using scanning electron microscopy (SEM). Full article
(This article belongs to the Special Issue Ultramicroelectrode Electrochemistry - Theory and Applications)
Open AccessArticle An In-Reflection Strain Sensing Head Based on a Hi-Bi Photonic Crystal Fiber
Sensors 2013, 13(7), 8095-8102; doi:10.3390/s130708095
Received: 13 May 2013 / Revised: 13 June 2013 / Accepted: 17 June 2013 / Published: 25 June 2013
Cited by 6 | PDF Full-text (548 KB) | HTML Full-text | XML Full-text
Abstract
A photonic crystal fiber-based sensing head is proposed for strain measurements. The sensor comprises a Hi-Bi PCF sensing head to measure interferometric signals in-reflection. An experimental background study of the sensing head is conducted through an optical backscatter reflectometer confirming the theoretical [...] Read more.
A photonic crystal fiber-based sensing head is proposed for strain measurements. The sensor comprises a Hi-Bi PCF sensing head to measure interferometric signals in-reflection. An experimental background study of the sensing head is conducted through an optical backscatter reflectometer confirming the theoretical predictions, also included. A cost effective setup is proposed where a laser is used as illumination source, which allows accurate high precision strain measurements. Thus, a sensitivity of ~7.96 dB/me was achieved in a linear region of 1,200 μe. Full article
(This article belongs to the Special Issue Optomechatronics) Print Edition available
Open AccessArticle A Robust Self-Alignment Method for Ship’s Strapdown INS Under Mooring Conditions
Sensors 2013, 13(7), 8103-8139; doi:10.3390/s130708103
Received: 22 April 2013 / Revised: 17 June 2013 / Accepted: 19 June 2013 / Published: 25 June 2013
Cited by 10 | PDF Full-text (1082 KB) | HTML Full-text | XML Full-text
Abstract
Strapdown inertial navigation systems (INS) need an alignment process to determine the initial attitude matrix between the body frame and the navigation frame. The conventional alignment process is to compute the initial attitude matrix using the gravity and Earth rotational rate measurements. [...] Read more.
Strapdown inertial navigation systems (INS) need an alignment process to determine the initial attitude matrix between the body frame and the navigation frame. The conventional alignment process is to compute the initial attitude matrix using the gravity and Earth rotational rate measurements. However, under mooring conditions, the inertial measurement unit (IMU) employed in a ship’s strapdown INS often suffers from both the intrinsic sensor noise components and the external disturbance components caused by the motions of the sea waves and wind waves, so a rapid and precise alignment of a ship’s strapdown INS without any auxiliary information is hard to achieve. A robust solution is given in this paper to solve this problem. The inertial frame based alignment method is utilized to adapt the mooring condition, most of the periodical low-frequency external disturbance components could be removed by the mathematical integration and averaging characteristic of this method. A novel prefilter named hidden Markov model based Kalman filter (HMM-KF) is proposed to remove the relatively high-frequency error components. Different from the digital filters, the HMM-KF barely cause time-delay problem. The turntable, mooring and sea experiments favorably validate the rapidness and accuracy of the proposed self-alignment method and the good de-noising performance of HMM-KF. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Development of an Ultrasensitive Immunoassay for Detecting Tartrazine
Sensors 2013, 13(7), 8155-8169; doi:10.3390/s130708155
Received: 29 May 2013 / Revised: 21 June 2013 / Accepted: 21 June 2013 / Published: 25 June 2013
Cited by 3 | PDF Full-text (625 KB) | HTML Full-text | XML Full-text
Abstract
We have developed an ultrasensitive indirect competitive enzyme-linked immunosorbent assay for the determination of tartrazine. Two carboxylated analogues of tartrazine with different spacer lengths, and one derivative from commercial tartrazine after a little chemical modification, were synthesized as haptens in order to [...] Read more.
We have developed an ultrasensitive indirect competitive enzyme-linked immunosorbent assay for the determination of tartrazine. Two carboxylated analogues of tartrazine with different spacer lengths, and one derivative from commercial tartrazine after a little chemical modification, were synthesized as haptens in order to produce antibodies specific to tartrazine. The effect of sulfonic acid groups on the hapten structure of tartrazine was also studied carefully for the first time. A most specific monoclonal antibody against tartrazine was created and exhibited an IC50 value of 0.105 ng/mL and a limit of detection of 0.014 ng/mL, with no cross-reactivity to other structurally-related pigments. The established immunoassay was applied to the determination of tartrazine in fortified samples of orange juice and in real positive samples of carbonated beverages. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Measurements of the Weak UV Absorptions of Isoprene and Acetone at 261–275 nm Using Cavity Ringdown Spectroscopy for Evaluation of a Potential Portable Ringdown Breath Analyzer
Sensors 2013, 13(7), 8170-8187; doi:10.3390/s130708170
Received: 29 April 2013 / Revised: 17 June 2013 / Accepted: 21 June 2013 / Published: 26 June 2013
Cited by 7 | PDF Full-text (481 KB) | HTML Full-text | XML Full-text
Abstract
The weak absorption spectra of isoprene and acetone have been measured in the wavelength range of 261–275 nm using cavity ringdown spectroscopy. The measured absorption cross-sections of isoprene in the wavelength region of 261–266 nm range from 3.65 × 10−21 cm [...] Read more.
The weak absorption spectra of isoprene and acetone have been measured in the wavelength range of 261–275 nm using cavity ringdown spectroscopy. The measured absorption cross-sections of isoprene in the wavelength region of 261–266 nm range from 3.65 × 10−21 cm2·molecule−1 at 261 nm to 1.42 × 10−21 cm2·molecule−1 at 266 nm; these numbers are in good agreement with the values reported in the literature. In the longer wavelength range of 270–275 nm, however, where attractive applications using a single wavelength compact diode laser operating at 274 nm is located, isoprene has been reported in the literature to have no absorption (too weak to be detected). Small absorption cross-sections of isoprene in this longer wavelength region are measured using cavity ringdown spectroscopy for the first time in this work, i.e., 6.20 × 10−23 cm2·molecule−1 at 275 nm. With the same experimental system, wavelength-dependent absorption cross-sections of acetone have also been measured. Theoretical detection limits of isoprene and comparisons of absorbance of isoprene, acetone, and healthy breath gas in this wavelength region are also discussed. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Rapid Detection of Viable Microorganisms Based on a Plate Count Technique Using Arrayed Microelectrodes
Sensors 2013, 13(7), 8188-8198; doi:10.3390/s130708188
Received: 17 April 2013 / Revised: 22 May 2013 / Accepted: 6 June 2013 / Published: 26 June 2013
Cited by 2 | PDF Full-text (424 KB) | HTML Full-text | XML Full-text
Abstract
Development of a miniaturized biosensor system that can be used for rapid detection and counting of microorganisms in food or water samples is described. The developed microsystem employs a highly sensitive impedimetric array of biosensors to monitor the growth of bacterial colonies [...] Read more.
Development of a miniaturized biosensor system that can be used for rapid detection and counting of microorganisms in food or water samples is described. The developed microsystem employs a highly sensitive impedimetric array of biosensors to monitor the growth of bacterial colonies that are dispersed across an agar growth medium. To use the system, a sample containing the bacteria is cultured above the agar layer. Using a multiplexing network, the electrical properties of the medium at different locations are continuously measured, recorded, and compared against a baseline signal. Variations of signals from different biosensors are used to reveal the presence of bacteria in the sample, as well as the locations of bacterial colonies across the biochip. This technique forms the basis for a label-free bacterial detection for rapid analysis of food samples, reducing the detection time by at least a factor of four compared to the current required incubation times of 24 to 72 hours for plate count techniques. The developed microsystem has the potential for miniaturization to a stage where it could be deployed for rapid analysis of food samples at commercial scale at laboratories, food processing facilities, and retailers. Full article
(This article belongs to the Special Issue Ultramicroelectrode Electrochemistry - Theory and Applications)
Open AccessArticle Improving Driver Alertness through Music Selection Using a Mobile EEG to Detect Brainwaves
Sensors 2013, 13(7), 8199-8221; doi:10.3390/s130708199
Received: 19 April 2013 / Revised: 14 June 2013 / Accepted: 21 June 2013 / Published: 26 June 2013
Cited by 6 | PDF Full-text (596 KB) | HTML Full-text | XML Full-text
Abstract
Driving safety has become a global topic of discussion with the recent development of the Smart Car concept. Many of the current car safety monitoring systems are based on image discrimination techniques, such as sensing the vehicle drifting from the main road, [...] Read more.
Driving safety has become a global topic of discussion with the recent development of the Smart Car concept. Many of the current car safety monitoring systems are based on image discrimination techniques, such as sensing the vehicle drifting from the main road, or changes in the driver’s facial expressions. However, these techniques are either too simplistic or have a low success rate as image processing is easily affected by external factors, such as weather and illumination. We developed a drowsiness detection mechanism based on an electroencephalogram (EEG) reading collected from the driver with an off-the-shelf mobile sensor. This sensor employs wireless transmission technology and is suitable for wear by the driver of a vehicle. The following classification techniques were incorporated: Artificial Neural Networks, Support Vector Machine, and k Nearest Neighbor. These classifiers were integrated with integration functions after a genetic algorithm was first used to adjust the weighting for each classifier in the integration function. In addition, since past studies have shown effects of music on a person’s state-of-mind, we propose a personalized music recommendation mechanism as a part of our system. Through the in-car stereo system, this music recommendation mechanism can help prevent a driver from becoming drowsy due to monotonous road conditions. Experimental results demonstrate the effectiveness of our proposed drowsiness detection method to determine a driver’s state of mind, and the music recommendation system is therefore able to reduce drowsiness. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle On the Use of Simple Geometric Descriptors Provided by RGB-D Sensors for Re-Identification
Sensors 2013, 13(7), 8222-8238; doi:10.3390/s130708222
Received: 25 March 2013 / Revised: 7 June 2013 / Accepted: 20 June 2013 / Published: 27 June 2013
Cited by 6 | PDF Full-text (3494 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The re-identification problem has been commonly accomplished using appearance features based on salient points and color information. In this paper, we focus on the possibilities that simple geometric features obtained from depth images captured with RGB-D cameras may offer for the task, [...] Read more.
The re-identification problem has been commonly accomplished using appearance features based on salient points and color information. In this paper, we focus on the possibilities that simple geometric features obtained from depth images captured with RGB-D cameras may offer for the task, particularly working under severe illumination conditions. The results achieved for different sets of simple geometric features extracted in a top-view setup seem to provide useful descriptors for the re-identification task, which can be integrated in an ambient intelligent environment as part of a sensor network. Full article
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Open AccessArticle D-MSR: A Distributed Network Management Scheme for Real-Time Monitoring and Process Control Applications in Wireless Industrial Automation
Sensors 2013, 13(7), 8239-8284; doi:10.3390/s130708239
Received: 8 April 2013 / Revised: 7 May 2013 / Accepted: 12 June 2013 / Published: 27 June 2013
Cited by 9 | PDF Full-text (1717 KB) | HTML Full-text | XML Full-text
Abstract
Current wireless technologies for industrial applications, such as WirelessHART and ISA100.11a, use a centralized management approach where a central network manager handles the requirements of the static network. However, such a centralized approach has several drawbacks. For example, it cannot cope with [...] Read more.
Current wireless technologies for industrial applications, such as WirelessHART and ISA100.11a, use a centralized management approach where a central network manager handles the requirements of the static network. However, such a centralized approach has several drawbacks. For example, it cannot cope with dynamicity/disturbance in large-scale networks in a real-time manner and it incurs a high communication overhead and latency for exchanging management traffic. In this paper, we therefore propose a distributed network management scheme, D-MSR. It enables the network devices to join the network, schedule their communications, establish end-to-end connections by reserving the communication resources for addressing real-time requirements, and cope with network dynamicity (e.g., node/edge failures) in a distributed manner. According to our knowledge, this is the first distributed management scheme based on IEEE 802.15.4e standard, which guides the nodes in different phases from joining until publishing their sensor data in the network. We demonstrate via simulation that D-MSR can address real-time and reliable communication as well as the high throughput requirements of industrial automation wireless networks, while also achieving higher efficiency in network management than WirelessHART, in terms of delay and overhead. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle ADVICE: A New Approach for Near-Real-Time Monitoring of Surface Displacements in Landslide Hazard Scenarios
Sensors 2013, 13(7), 8285-8302; doi:10.3390/s130708285
Received: 8 June 2013 / Revised: 18 June 2013 / Accepted: 24 June 2013 / Published: 27 June 2013
Cited by 8 | PDF Full-text (1055 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We present a new method for near-real-time monitoring of surface displacements due to landslide phenomena, namely ADVanced dIsplaCement monitoring system for Early warning (ADVICE). The procedure includes: (i) data acquisition and transfer protocols; (ii) data collection, filtering, and validation; (iii) [...] Read more.
We present a new method for near-real-time monitoring of surface displacements due to landslide phenomena, namely ADVanced dIsplaCement monitoring system for Early warning (ADVICE). The procedure includes: (i) data acquisition and transfer protocols; (ii) data collection, filtering, and validation; (iii) data analysis and restitution through a set of dedicated software; (iv) recognition of displacement/velocity threshold, early warning messages via SMS and/or emails; (v) automatic publication of the results on a dedicated webpage. We show how the system evolved and the results obtained by applying ADVICE over three years into a real early warning scenario relevant to a large earthflow located in southern Italy. ADVICE has speed-up and facilitated the understanding of the landslide phenomenon, the communication of the monitoring results to the partners, and consequently the decision-making process in a critical scenario. Our work might have potential applications not only for landslide monitoring but also in other contexts, as monitoring of other geohazards and of complex infrastructures, as open-pit mines, buildings, dams, etc. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle Energy Consumption and Control Response Evaluations of AODV Routing in WSANs for Building-Temperature Control
Sensors 2013, 13(7), 8303-8330; doi:10.3390/s130708303
Received: 23 May 2013 / Revised: 12 June 2013 / Accepted: 18 June 2013 / Published: 27 June 2013
Cited by 3 | PDF Full-text (803 KB) | HTML Full-text | XML Full-text
Abstract
The main objective of this paper is to investigate the effects of routing protocols on wireless sensor and actuator networks (WSANs), focusing on the control system response and the energy consumption of nodes in a network. We demonstrate that routing algorithms designed [...] Read more.
The main objective of this paper is to investigate the effects of routing protocols on wireless sensor and actuator networks (WSANs), focusing on the control system response and the energy consumption of nodes in a network. We demonstrate that routing algorithms designed without considering the relationship between communication and control cannot be appropriately used in wireless networked control applications. For this purpose, an ad-hoc on-demand distance vector (AODV) routing, an IEEE 802.15.4, and a building-temperature control system are employed for this exploration. The findings from our scenarios show that the AODV routing can select a path with a high traffic load for data transmission. It takes a long time before deciding to change a new route although it experiences the unsuccessful transmission of packets. As a result, the desirable control target cannot be achieved in time, and nodes consume more energy due to frequent packet collisions and retransmissions. Consequently, we propose a simple routing solution to alleviate these research problems by modifying the original AODV routing protocol. The delay-threshold is considered to avoid any congested connection during routing procedures. The simulation results demonstrate that our solution can be appropriately applied in WSANs. Both the energy consumption and the control system response are improved. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Development of an Enzyme-Linked Immunosorbent Assay for Dibutyl Phthalate in Liquor
Sensors 2013, 13(7), 8331-8339; doi:10.3390/s130708331
Received: 24 April 2013 / Revised: 8 June 2013 / Accepted: 20 June 2013 / Published: 27 June 2013
Cited by 10 | PDF Full-text (167 KB) | HTML Full-text | XML Full-text
Abstract
A monoclonal antibody specifically recognizing dibutyl phthalate (DBP) was prepared based on a hapten (di-n-butyl-4-aminophthalate). After optimizing various parameters such as concentrations of antibody, coating antigen and composition of the assay buffer, an inhibition curve was plotted with the 50% [...] Read more.
A monoclonal antibody specifically recognizing dibutyl phthalate (DBP) was prepared based on a hapten (di-n-butyl-4-aminophthalate). After optimizing various parameters such as concentrations of antibody, coating antigen and composition of the assay buffer, an inhibition curve was plotted with the 50% inhibition concentration value (IC50) 33.6 ± 2.5 ng/mL. A low level of cross-reactivity (<5%) was found for other phthalate esters. Recovery tests were conducted using liquor simulant (a mixture of water and ethanol) at two fortification levels (100 ng/mL and 300 ng/mL). The recovery rates ranged from 84.7% to 94.5% with a coefficient of variation between 7.1% and 12.8%. Nine liquor samples of different alcoholic strengths were detected using the proposed measure and confirmatory analysis was performed using liquid chromatography-mass spectroscopy (LC-MS). The detection results showed good consistency between the two measures and all the data above indicated that the proposed ELISA could be applied in DBP screening. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Organic Plasmon-Emitting Diodes for Detecting Refractive Index Variation
Sensors 2013, 13(7), 8340-8351; doi:10.3390/s130708340
Received: 8 April 2013 / Revised: 17 June 2013 / Accepted: 24 June 2013 / Published: 28 June 2013
Cited by 2 | PDF Full-text (746 KB) | HTML Full-text | XML Full-text
Abstract
A photo-excited organic layer on a metal thin film with a corrugated substrate was used to generate surface plasmon grating coupled emissions (SPGCEs). Directional emissions corresponded to the resonant condition of surface plasmon modes on the Au/air interface. In experimental comparisons of [...] Read more.
A photo-excited organic layer on a metal thin film with a corrugated substrate was used to generate surface plasmon grating coupled emissions (SPGCEs). Directional emissions corresponded to the resonant condition of surface plasmon modes on the Au/air interface. In experimental comparisons of the effects of different pitch sizes on the plasmonic band-gap, the obtained SPGCEs were highly directional, with intensity increases as large as 10.38-fold. The FWHM emission spectrum was less than 70 nm. This method is easily applicable to detecting refractive index changes by using SP-coupled fluorophores in which wavelength emissions vary by viewing angle. The measurements and calculations in this study confirmed that the color wavelength of the SPGCE changed from 545.3 nm to 615.4 nm at certain viewing angles, while the concentration of contacting glucose increased from 10 to 40 wt%, which corresponded to a refractive index increase from 1.3484 to 1.3968. The organic plasmon-emitting diode exhibits a wider linearity range and a resolution of the experimental is 1.056 × 103 RIU. The sensitivity of the detection limit for naked eye of the experimental is 0.6 wt%. At a certain viewing angle, a large spectral shift is clearly distinguishable by the naked eye unaided by optoelectronic devices. These experimental results confirm the potential applications of the organic plasmon-emitting diodes in a low-cost, integrated, and disposable refractive-index sensor. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Data Communications Using Guided Elastic Waves by Time Reversal Pulse Position Modulation: Experimental Study
Sensors 2013, 13(7), 8352-8376; doi:10.3390/s130708352
Received: 19 March 2013 / Revised: 21 June 2013 / Accepted: 26 June 2013 / Published: 1 July 2013
Cited by 3 | PDF Full-text (1039 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we present and demonstrate a low complexity elastic wave signaling and reception method to achieve high data rate communication on dispersive solid elastic media, such as metal pipes, using piezoelectric transducers of PZT (lead zirconate titanate). Data communication is [...] Read more.
In this paper, we present and demonstrate a low complexity elastic wave signaling and reception method to achieve high data rate communication on dispersive solid elastic media, such as metal pipes, using piezoelectric transducers of PZT (lead zirconate titanate). Data communication is realized using pulse position modulation (PPM) as the signaling method and the elastic medium as the communication channel. The communication system first transmits a small number of training pulses to probe the dispersive medium. The time-reversed probe signals are then utilized as the information carrying waveforms. Rapid timing acquisition of transmitted waveforms for demodulation over elastic medium is made possible by exploring the reciprocity property of guided elastic waves. The experimental tests were conducted using a National Instrument PXI system for waveform excitation and data acquisition. Data telemetry bit rates of 10 kbps, 20 kbps, 50 kbps and 100 kbps with the average bit error rates of 0, 5.75 × 10−4, 1.09 × 10−2 and 5.01 × 10−2, respectively, out of a total of 40, 000 transmitted bits were obtained when transmitting at the center frequency of 250 kHz and a 500 kHz bandwidth on steel pipe specimens. To emphasize the influence of time reversal, no complex processing techniques, such as adaptive channel equalization or error correction coding, were employed. Full article
(This article belongs to the Special Issue Piezoelectric Sensors and Actuators)
Open AccessArticle Development of a Wireless Displacement Measurement System Using Acceleration Responses
Sensors 2013, 13(7), 8377-8392; doi:10.3390/s130708377
Received: 14 May 2013 / Revised: 31 May 2013 / Accepted: 13 June 2013 / Published: 1 July 2013
Cited by 8 | PDF Full-text (608 KB) | HTML Full-text | XML Full-text
Abstract
Displacement measurements are useful information for various engineering applications such as structural health monitoring (SHM), earthquake engineering and system identification. Most existing displacement measurement methods are costly, labor-intensive, and have difficulties particularly when applying to full-scale civil structures because the methods require [...] Read more.
Displacement measurements are useful information for various engineering applications such as structural health monitoring (SHM), earthquake engineering and system identification. Most existing displacement measurement methods are costly, labor-intensive, and have difficulties particularly when applying to full-scale civil structures because the methods require stationary reference points. Indirect estimation methods converting acceleration to displacement can be a good alternative as acceleration transducers are generally cost-effective, easy to install, and have low noise. However, the application of acceleration-based methods to full-scale civil structures such as long span bridges is challenging due to the need to install cables to connect the sensors to a base station. This article proposes a low-cost wireless displacement measurement system using acceleration. Developed with smart sensors that are low-cost, wireless, and capable of on-board computation, the wireless displacement measurement system has significant potential to impact many applications that need displacement information at multiple locations of a structure. The system implements an FIR-filter type displacement estimation algorithm that can remove low frequency drifts typically caused by numerical integration of discrete acceleration signals. To verify the accuracy and feasibility of the proposed system, laboratory tests are carried out using a shaking table and on a three storey shear building model, experimentally confirming the effectiveness of the proposed system. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Hydrogen Sensing with Ni-Doped TiO2 Nanotubes
Sensors 2013, 13(7), 8393-8402; doi:10.3390/s130708393
Received: 2 May 2013 / Revised: 19 June 2013 / Accepted: 24 June 2013 / Published: 1 July 2013
Cited by 17 | PDF Full-text (611 KB) | HTML Full-text | XML Full-text
Abstract
Doping with other elements is one of the efficient ways to modify the physical and chemical properties of TiO2 nanomaterials. In the present work, Ni-doped TiO2 nanotubes were fabricated through anodic oxidation of NiTi alloy and further annealing treatment. The [...] Read more.
Doping with other elements is one of the efficient ways to modify the physical and chemical properties of TiO2 nanomaterials. In the present work, Ni-doped TiO2 nanotubes were fabricated through anodic oxidation of NiTi alloy and further annealing treatment. The hydrogen sensing properties of the nanotube sensor were investigated. It was found that the Ni-doped TiO2 nanotubes were sensitive to an atmosphere of 1,000 ppm hydrogen, showing a good response at both room temperature and elevated temperatures. A First-Principle simulation revealed that, in comparison with pure anatase TiO2 oxide, Ni doping in the TiO2 oxide could result in a decreased bandgap. When the oxide sensor adsorbed a certain amount of hydrogen the bandgap increased and the acceptor impurity levels was generated, which resulted in a change of the sensor resistance. Full article
(This article belongs to the Special Issue Gas Sensors - 2013)
Open AccessArticle Novel RF Interrogation of a Fiber Bragg Grating Sensor Using Bidirectional Modulation of a Mach-Zehnder Electro-Optical Modulator
Sensors 2013, 13(7), 8403-8411; doi:10.3390/s130708403
Received: 10 April 2013 / Revised: 20 June 2013 / Accepted: 28 June 2013 / Published: 2 July 2013
Cited by 7 | PDF Full-text (540 KB) | HTML Full-text | XML Full-text
Abstract
We propose and experimentally demonstrate the novel radio-frequency (RF) interrogation of a fiber Bragg grating (FBG) sensor using bidirectional modulation of a Mach-Zehnder electro-optical modulator (MZ-EOM). Based on the microwave photonic technique and active detection, the transfer function of the proposed system [...] Read more.
We propose and experimentally demonstrate the novel radio-frequency (RF) interrogation of a fiber Bragg grating (FBG) sensor using bidirectional modulation of a Mach-Zehnder electro-optical modulator (MZ-EOM). Based on the microwave photonic technique and active detection, the transfer function of the proposed system was obtained, and the time delay was calculated from the change in the free spectral range (FSR) at different wavelengths over the optimal measuring range. The results show that the time delay and the wavelength variation have a good linear relationship, with a gradient of 9.31 ps/nm. An actual measurement taken with a sensing FBG for temperature variation shows the relationship with a gradient of 0.93 ps/10 °C. The developed system could be used for FBG temperature or strain sensing and other multiplexed sensor applications. Full article
(This article belongs to the Special Issue Laser Sensing and Imaging)
Open AccessArticle Measurement of the Robot Motor Capability of a Robot Motor System: A Fitts’s-Law-Inspired Approach
Sensors 2013, 13(7), 8412-8430; doi:10.3390/s130708412
Received: 3 April 2013 / Revised: 26 June 2013 / Accepted: 28 June 2013 / Published: 2 July 2013
Cited by 1 | PDF Full-text (3181 KB) | HTML Full-text | XML Full-text
Abstract
Robot motor capability is a crucial factor for a robot, because it affects how accurately and rapidly a robot can perform a motion to accomplish a task constrained by spatial and temporal conditions. In this paper, we propose and derive a pseudo-index [...] Read more.
Robot motor capability is a crucial factor for a robot, because it affects how accurately and rapidly a robot can perform a motion to accomplish a task constrained by spatial and temporal conditions. In this paper, we propose and derive a pseudo-index of motor performance (pIp) to characterize robot motor capability with robot kinematics, dynamics and control taken into consideration. The proposed pIp provides a quantitative measure for a robot with revolute joints, which is inspired from an index of performance in Fitts’s law of human skills. Computer simulations and experiments on a PUMA 560 industrial robot were conducted to validate the proposed pIp for performing a motion accurately and rapidly. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Active Pneumatic Vibration Control by Using Pressure and Velocity Measurements and Adaptive Fuzzy Sliding-Mode Controller
Sensors 2013, 13(7), 8431-8444; doi:10.3390/s130708431
Received: 14 May 2013 / Revised: 24 June 2013 / Accepted: 28 June 2013 / Published: 2 July 2013
Cited by 1 | PDF Full-text (503 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an intelligent control strategy to overcome nonlinear and time-varying characteristics of a diaphragm-type pneumatic vibration isolator (PVI) system. By combining an adaptive rule with fuzzy and sliding-mode control, the method has online learning ability when it faces the system’s [...] Read more.
This paper presents an intelligent control strategy to overcome nonlinear and time-varying characteristics of a diaphragm-type pneumatic vibration isolator (PVI) system. By combining an adaptive rule with fuzzy and sliding-mode control, the method has online learning ability when it faces the system’s nonlinear and time-varying behaviors during an active vibration control process. Since the proposed scheme has a simple structure, it is easy to implement. To validate the proposed scheme, a composite control which adopts both chamber pressure and payload velocity as feedback signal is implemented. During experimental investigations, sinusoidal excitation at resonance and random-like signal are input on a floor base to simulate ground vibration. Performances obtained from the proposed scheme are compared with those obtained from passive system and PID scheme to illustrate the effectiveness of the proposed intelligent control. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Self-Assembled 3D ZnO Porous Structures with Exposed Reactive {0001} Facets and Their Enhanced Gas Sensitivity
Sensors 2013, 13(7), 8445-8460; doi:10.3390/s130708445
Received: 10 April 2013 / Revised: 21 May 2013 / Accepted: 19 June 2013 / Published: 2 July 2013
Cited by 18 | PDF Full-text (1315 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Complex three-dimensional structures comprised of porous ZnO plates were synthesized in a controlled fashion by hydrothermal methods. Through subtle changes to reaction conditions, the ZnO structures could be self-assembled from 20 nm thick nanosheets into grass-like and flower-like structures which led to [...] Read more.
Complex three-dimensional structures comprised of porous ZnO plates were synthesized in a controlled fashion by hydrothermal methods. Through subtle changes to reaction conditions, the ZnO structures could be self-assembled from 20 nm thick nanosheets into grass-like and flower-like structures which led to the exposure of high proportions of ZnO {0001} crystal facets for both these materials. The measured surface area of the flower-like and the grass, or platelet-like ZnO samples were 72.8 and 52.4 m2∙g−1, respectively. Gas sensing results demonstrated that the porous, flower-like ZnO structures exhibited enhanced sensing performance towards NO2 gas compared with either grass-like ZnO or commercially sourced ZnO nanoparticle samples. The porous, flower-like ZnO structures provided a high surface area which enhanced the ZnO gas sensor response. X-ray photoelectron spectroscopy characterization revealed that flower-like ZnO samples possessed a higher percentage of oxygen vacancies than the other ZnO sample-types, which also contributed to their excellent gas sensing performance. Full article
(This article belongs to the Special Issue Gas Sensors - 2013)
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Open AccessArticle Simulation of a Geiger-Mode Imaging LADAR System for Performance Assessment
Sensors 2013, 13(7), 8461-8489; doi:10.3390/s130708461
Received: 6 May 2013 / Revised: 28 June 2013 / Accepted: 28 June 2013 / Published: 3 July 2013
Cited by 2 | PDF Full-text (1830 KB) | HTML Full-text | XML Full-text
Abstract
As LADAR systems applications gradually become more diverse, new types of systems are being developed. When developing new systems, simulation studies are an essential prerequisite. A simulator enables performance predictions and optimal system parameters at the design level, as well as providing [...] Read more.
As LADAR systems applications gradually become more diverse, new types of systems are being developed. When developing new systems, simulation studies are an essential prerequisite. A simulator enables performance predictions and optimal system parameters at the design level, as well as providing sample data for developing and validating application algorithms. The purpose of the study is to propose a method for simulating a Geiger-mode imaging LADAR system. We develop simulation software to assess system performance and generate sample data for the applications. The simulation is based on three aspects of modeling—the geometry, radiometry and detection. The geometric model computes the ranges to the reflection points of the laser pulses. The radiometric model generates the return signals, including the noises. The detection model determines the flight times of the laser pulses based on the nature of the Geiger-mode detector. We generated sample data using the simulator with the system parameters and analyzed the detection performance by comparing the simulated points to the reference points. The proportion of the outliers in the simulated points reached 25.53%, indicating the need for efficient outlier elimination algorithms. In addition, the false alarm rate and dropout rate of the designed system were computed as 1.76% and 1.06%, respectively. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Transverse Susceptibility as a Biosensor for Detection of Au-Fe3O4 Nanoparticle-Embedded Human Embryonic Kidney Cells
Sensors 2013, 13(7), 8490-8500; doi:10.3390/s130708490
Received: 19 April 2013 / Revised: 24 June 2013 / Accepted: 25 June 2013 / Published: 3 July 2013
Cited by 2 | PDF Full-text (652 KB) | HTML Full-text | XML Full-text
Abstract
We demonstrate the possibility of using a radio-frequency transverse susceptibility (TS) technique based on a sensitive self-resonant tunnel-diode oscillator as a biosensor for detection of cancer cells that have taken up magnetic nanoparticles. This technique can detect changes in frequency on the [...] Read more.
We demonstrate the possibility of using a radio-frequency transverse susceptibility (TS) technique based on a sensitive self-resonant tunnel-diode oscillator as a biosensor for detection of cancer cells that have taken up magnetic nanoparticles. This technique can detect changes in frequency on the order of 10 Hz in 10 MHz. Therefore, a small sample of cells that have taken up nanoparticles when placed inside the sample space of the TS probe can yield a signal characteristic of the magnetic nanoparticles. As a proof of the concept, Fe3O4 nanoparticles coated with Au (mean size ~60 nm) were synthesized using a micellar method and these nanoparticles were introduced to the medium at different concentrations of 0.05, 0.1, 0.5, and 1 mg/mL buffer, where they were taken up by human embryonic kidney (HEK) cells via phagocytosis. While the highest concentration of Au-Fe3O4 nanoparticles (1 mg/mL) was found to give the strongest TS signal, it is notable that the TS signal of the nanoparticles could still be detected at concentrations as low as 0.1 mg/mL. Full article
Open AccessArticle A Robust Approach for a Filter-Based Monocular Simultaneous Localization and Mapping (SLAM) System
Sensors 2013, 13(7), 8501-8522; doi:10.3390/s130708501
Received: 27 April 2013 / Revised: 27 May 2013 / Accepted: 19 June 2013 / Published: 3 July 2013
Cited by 3 | PDF Full-text (1527 KB) | HTML Full-text | XML Full-text
Abstract
Simultaneous localization and mapping (SLAM) is an important problem to solve in robotics theory in order to build truly autonomous mobile robots. This work presents a novel method for implementing a SLAM system based on a single camera sensor. The SLAM with [...] Read more.
Simultaneous localization and mapping (SLAM) is an important problem to solve in robotics theory in order to build truly autonomous mobile robots. This work presents a novel method for implementing a SLAM system based on a single camera sensor. The SLAM with a single camera, or monocular SLAM, is probably one of the most complex SLAM variants. In this case, a single camera, which is freely moving through its environment, represents the sole sensor input to the system. The sensors have a large impact on the algorithm used for SLAM. Cameras are used more frequently, because they provide a lot of information and are well adapted for embedded systems: they are light, cheap and power-saving. Nevertheless, and unlike range sensors, which provide range and angular information, a camera is a projective sensor providing only angular measurements of image features. Therefore, depth information (range) cannot be obtained in a single step. In this case, special techniques for feature system-initialization are needed in order to enable the use of angular sensors (as cameras) in SLAM systems. The main contribution of this work is to present a novel and robust scheme for incorporating and measuring visual features in filtering-based monocular SLAM systems. The proposed method is based in a two-step technique, which is intended to exploit all the information available in angular measurements. Unlike previous schemes, the values of parameters used by the initialization technique are derived directly from the sensor characteristics, thus simplifying the tuning of the system. The experimental results show that the proposed method surpasses the performance of previous schemes. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Major Odorants Released as Urinary Volatiles by Urinary Incontinent Patients
Sensors 2013, 13(7), 8523-8533; doi:10.3390/s130708523
Received: 23 May 2013 / Revised: 27 June 2013 / Accepted: 1 July 2013 / Published: 3 July 2013
Cited by 1 | PDF Full-text (217 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this study, volatile urinary components were collected using three different types of samples from patients suffering from urinary incontinence (UI): (1) urine (A); (2) urine + non-used pad (B); and (3) urine + used pad (C). In addition, urine + non-used [...] Read more.
In this study, volatile urinary components were collected using three different types of samples from patients suffering from urinary incontinence (UI): (1) urine (A); (2) urine + non-used pad (B); and (3) urine + used pad (C). In addition, urine + non-used pad (D) samples from non-patients were also collected as a reference. The collection of urinary volatiles was conducted with the aid of a glass impinger-based mini-chamber method. Each of the four sample types (A through D) was placed in a glass impinger and incubated for 4 hours at 37 °C. Ultra pure air was then passed through the chamber, and volatile urine gas components were collected into Tedlar bags at the other end. These bag samples were then analyzed for a wide range of VOCs and major offensive odorants (e.g., reduced sulfur compounds (RSCs), carbonyls, trimethylamine (TMA), ammonia, etc.). Among the various odorants, sulfur compounds (methanethiol and hydrogen sulfide) and aldehydes (acetaldehyde, butylaldehyde, and isovaleraldehyde) were detected above odor threshold and predicted to contribute most effectively to odor intensity of urine incontinence. Full article
Open AccessArticle Seismic Target Classification Using a Wavelet Packet Manifold in Unattended Ground Sensors Systems
Sensors 2013, 13(7), 8534-8550; doi:10.3390/s130708534
Received: 3 June 2013 / Revised: 23 June 2013 / Accepted: 27 June 2013 / Published: 4 July 2013
Cited by 9 | PDF Full-text (450 KB) | HTML Full-text | XML Full-text
Abstract
One of the most challenging problems in target classification is the extraction of a robust feature, which can effectively represent a specific type of targets. The use of seismic signals in unattended ground sensor (UGS) systems makes this problem more complicated, because [...] Read more.
One of the most challenging problems in target classification is the extraction of a robust feature, which can effectively represent a specific type of targets. The use of seismic signals in unattended ground sensor (UGS) systems makes this problem more complicated, because the seismic target signal is non-stationary, geology-dependent and with high-dimensional feature space. This paper proposes a new feature extraction algorithm, called wavelet packet manifold (WPM), by addressing the neighborhood preserving embedding (NPE) algorithm of manifold learning on the wavelet packet node energy (WPNE) of seismic signals. By combining non-stationary information and low-dimensional manifold information, WPM provides a more robust representation for seismic target classification. By using a K nearest neighbors classifier on the WPM signature, the algorithm of wavelet packet manifold classification (WPMC) is proposed. Experimental results show that the proposed WPMC can not only reduce feature dimensionality, but also improve the classification accuracy up to 95.03%. Moreover, compared with state-of-the-art methods, WPMC is more suitable for UGS in terms of recognition ratio and computational complexity. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Rapid Quantitative Detection of Brucella melitensis by a Label-Free Impedance Immunosensor Based on a Gold Nanoparticle-Modified Screen-Printed Carbon Electrode
Sensors 2013, 13(7), 8551-8563; doi:10.3390/s130708551
Received: 20 May 2013 / Revised: 21 June 2013 / Accepted: 21 June 2013 / Published: 4 July 2013
Cited by 4 | PDF Full-text (596 KB) | HTML Full-text | XML Full-text
Abstract
A rapid and simple method for quantitative monitoring of Brucella melitensis using electrochemical impedance spectroscopy (EIS) is reported for the first time. The label-free immunosensors were fabricated by immobilizing Brucella melitensis antibody on the surface of gold nanoparticle-modified screen-printed carbon electrodes (GNP-SPCEs). [...] Read more.
A rapid and simple method for quantitative monitoring of Brucella melitensis using electrochemical impedance spectroscopy (EIS) is reported for the first time. The label-free immunosensors were fabricated by immobilizing Brucella melitensis antibody on the surface of gold nanoparticle-modified screen-printed carbon electrodes (GNP-SPCEs). Cyclic voltammetry (CV) and EIS were used to characterize the Brucella melitensis antigen interaction on the surface of GNP-SPCEs with antibody. A general electronic equivalent model of an electrochemical cell was introduced for interpretation of the impedance components of the system. The results showed that the change in electron-transfer resistance (Rct) was significantly different due to the binding of Brucella melitensis cells. A linear relationship between the Rct variation and logarithmic value of the cell concentration was found from 4 × 104 to 4 × 106 CFU/mL in pure culture. The label-free impedance biosensor was able to detect as low as 1 × 104 and 4 × 105 CFU/mL of Brucella melitensis in pure culture and milk samples, respectively, in less than 1.5 h. Moreover, a good selectivity versus Escherichia coli O157:H7 and Staphylococcus aureus cells was obtained for our developed immunosensor demonstrating its specificity towards only Brucella melitensis. Full article
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Open AccessArticle Radioactive Quality Evaluation and Cross Validation of Data from the HJ-1A/B Satellites’ CCD Sensors
Sensors 2013, 13(7), 8564-8576; doi:10.3390/s130708564
Received: 20 May 2013 / Revised: 5 June 2013 / Accepted: 24 June 2013 / Published: 5 July 2013
Cited by 7 | PDF Full-text (784 KB) | HTML Full-text | XML Full-text
Abstract
Data from multiple sensors are frequently used in Earth science to gain a more complete understanding of spatial information changes. Higher quality and mutual consistency are prerequisites when multiple sensors are jointly used. The HJ-1A/B satellites successfully launched on 6 September 2008. [...] Read more.
Data from multiple sensors are frequently used in Earth science to gain a more complete understanding of spatial information changes. Higher quality and mutual consistency are prerequisites when multiple sensors are jointly used. The HJ-1A/B satellites successfully launched on 6 September 2008. There are four charge-coupled device (CCD) sensors with uniform spatial resolutions and spectral range onboard the HJ-A/B satellites. Whether these data are keeping consistency is a major issue before they are used. This research aims to evaluate the data consistency and radioactive quality from the four CCDs. First, images of urban, desert, lake and ocean are chosen as the objects of evaluation. Second, objective evaluation variables, such as mean, variance and angular second moment, are used to identify image performance. Finally, a cross validation method are used to ensure the correlation of the data from the four HJ-1A/B CCDs and that which is gathered from the moderate resolution imaging spectro-radiometer (MODIS). The results show that the image quality of HJ-1A/B CCDs is stable, and the digital number distribution of CCD data is relatively low. In cross validation with MODIS, the root mean square errors of bands 1, 2 and 3 range from 0.055 to 0.065, and for band 4 it is 0.101. The data from HJ-1A/B CCD have better consistency. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Gauge Factor and Stretchability of Silicon-on-Polymer Strain Gauges
Sensors 2013, 13(7), 8577-8594; doi:10.3390/s130708577
Received: 3 June 2013 / Revised: 1 July 2013 / Accepted: 2 July 2013 / Published: 5 July 2013
Cited by 17 | PDF Full-text (510 KB) | HTML Full-text | XML Full-text
Abstract
Strain gauges are widely applied to measure mechanical deformation of structures and specimens. While metallic foil gauges usually have a gauge factor slightly over 2, single crystalline silicon demonstrates intrinsic gauge factors as high as 200. Although silicon is an intrinsically stiff [...] Read more.
Strain gauges are widely applied to measure mechanical deformation of structures and specimens. While metallic foil gauges usually have a gauge factor slightly over 2, single crystalline silicon demonstrates intrinsic gauge factors as high as 200. Although silicon is an intrinsically stiff and brittle material, flexible and even stretchable strain gauges have been achieved by integrating thin silicon strips on soft and deformable polymer substrates. To achieve a fundamental understanding of the large variance in gauge factor and stretchability of reported flexible/stretchable silicon-on-polymer strain gauges, finite element and analytically models are established to reveal the effects of the length of the silicon strip, and the thickness and modulus of the polymer substrate. Analytical results for two limiting cases, i.e., infinitely thick substrate and infinitely long strip, have found good agreement with FEM results. We have discovered that strains in silicon resistor can vary by orders of magnitude with different substrate materials whereas strip length or substrate thickness only affects the strain level mildly. While the average strain in silicon reflects the gauge factor, the maximum strain in silicon governs the stretchability of the system. The tradeoff between gauge factor and stretchability of silicon-on-polymer strain gauges has been proposed and discussed. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Direct Electrochemistry of Hemoglobin Immobilized on a Functionalized Multi-Walled Carbon Nanotubes and Gold Nanoparticles Nanocomplex-Modified Glassy Carbon Electrode
Sensors 2013, 13(7), 8595-8611; doi:10.3390/s130708595
Received: 13 May 2013 / Revised: 17 June 2013 / Accepted: 30 June 2013 / Published: 5 July 2013
Cited by 14 | PDF Full-text (800 KB) | HTML Full-text | XML Full-text
Abstract
Direct electron transfer of hemoglobin (Hb) was realized by immobilizing Hb on a carboxyl functionalized multi-walled carbon nanotubes (FMWCNTs) and gold nanoparticles (AuNPs) nanocomplex-modified glassy carbon electrode. The ultraviolet-visible absorption spectrometry (UV-Vis), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) methods [...] Read more.
Direct electron transfer of hemoglobin (Hb) was realized by immobilizing Hb on a carboxyl functionalized multi-walled carbon nanotubes (FMWCNTs) and gold nanoparticles (AuNPs) nanocomplex-modified glassy carbon electrode. The ultraviolet-visible absorption spectrometry (UV-Vis), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) methods were utilized for additional characterization of the AuNPs and FMWCNTs. The cyclic voltammogram of the modified electrode has a pair of well-defined quasi-reversible redox peaks with a formal potential of −0.270 ± 0.002 V (vs. Ag/AgCl) at a scan rate of 0.05 V/s. The heterogeneous electron transfer constant (ks) was evaluated to be 4.0 ± 0.2 s−1. The average surface concentration of electro-active Hb on the surface of the modified glassy carbon electrode was calculated to be 6.8 ± 0.3 × 10−10 mol cm−2. The cathodic peak current of the modified electrode increased linearly with increasing concentration of hydrogen peroxide (from 0.05 nM to 1 nM) with a detection limit of 0.05 ± 0.01 nM. The apparent Michaelis-Menten constant (Kmapp) was calculated to be 0.85 ± 0.1 nM. Thus, the modified electrode could be applied as a third generation biosensor with high sensitivity, long-term stability and low detection limit. Full article
(This article belongs to the Special Issue Nanotube and Nanowire Sensors)
Open AccessArticle A Bandwidth-Efficient Service for Local Information Dissemination in Sparse to Dense Roadways
Sensors 2013, 13(7), 8612-8639; doi:10.3390/s130708612
Received: 29 April 2013 / Revised: 19 June 2013 / Accepted: 27 June 2013 / Published: 5 July 2013
Cited by 5 | PDF Full-text (554 KB) | HTML Full-text | XML Full-text
Abstract
Thanks to the research on Vehicular Ad Hoc Networks (VANETs), we will be able to deploy applications on roadways that will contribute to energy efficiency through a better planning of long trips. With this goal in mind, we have designed a gas/charging [...] Read more.
Thanks to the research on Vehicular Ad Hoc Networks (VANETs), we will be able to deploy applications on roadways that will contribute to energy efficiency through a better planning of long trips. With this goal in mind, we have designed a gas/charging station advertising system, which takes advantage of the broadcast nature of the network. We have found that reducing the number of total sent packets is important, as it allows for a better use of the available bandwidth. We have designed improvements for a distance-based flooding scheme, so that it can support the advertising application with good results in sparse to dense roadway scenarios. Full article
Open AccessArticle Dependence of the Impact Response of Polyvinylidene Fluoride Sensors on Their Supporting Materials’ Elasticity
Sensors 2013, 13(7), 8669-8678; doi:10.3390/s130708669
Received: 13 April 2013 / Revised: 8 May 2013 / Accepted: 23 June 2013 / Published: 5 July 2013
Cited by 8 | PDF Full-text (927 KB) | HTML Full-text | XML Full-text
Abstract
Polyvinylidene fluoride (PVDF) is popular sensing material because of its unique piezoelectric characteristics. In this work an impact sensor was prepared from a sandwiched structure PVDF film, and the related detection circuits were presented. The dependence of the PVDF sensors’ response on [...] Read more.
Polyvinylidene fluoride (PVDF) is popular sensing material because of its unique piezoelectric characteristics. In this work an impact sensor was prepared from a sandwiched structure PVDF film, and the related detection circuits were presented. The dependence of the PVDF sensors’ response on the elasticity of the supporting materials was examined and discussed. Here two response indexes were discussed, which were the peak-to-peak voltage (Vpp) and the recovery time. Firstly, falling impact experiments were executed on desk-supported PVDF sensors (100 mm PVDF film) using free falls of different weights from different heights. Then the same shock experiments were repeated on the same sensor, but changing the backstops to a sponge and rubber, respectively. On the desk, the values of Vpp were bigger than when the other two backstops were used; but the changes of the impact energy could not be reflected by the PVDF sensor when it was supported by a hard material. It was found that the biggest sensitivity of the voltage response (about 96.62 V/J) was obtained by the sponge-supported sensor; for the same sensor, when it was supported by rubber, the slope was 82.26 V/J. Moreover, the recovery time for the desk-supported sensor was almost constant, varying from 0.15 to 0.18 s, while for the same sensor supported by sponge or rubber, its recovery time changed with the shifting of the impact energy in the range of 0.02~0.36 s, but no pattern could be found in the recovery-time characteristics. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle LMD Method and Multi-Class RWSVM of Fault Diagnosis for Rotating Machinery Using Condition Monitoring Information
Sensors 2013, 13(7), 8679-8694; doi:10.3390/s130708679
Received: 25 March 2013 / Revised: 14 June 2013 / Accepted: 25 June 2013 / Published: 5 July 2013
Cited by 6 | PDF Full-text (657 KB) | HTML Full-text | XML Full-text
Abstract
Timely and accurate condition monitoring and fault diagnosis of rotating machinery are very important to maintain a high degree of availability, reliability and operational safety. This paper presents a novel intelligent method based on local mean decomposition (LMD) and multi-class reproducing wavelet [...] Read more.
Timely and accurate condition monitoring and fault diagnosis of rotating machinery are very important to maintain a high degree of availability, reliability and operational safety. This paper presents a novel intelligent method based on local mean decomposition (LMD) and multi-class reproducing wavelet support vector machines (RWSVM), which is applied to diagnose rotating machinery faults. First, the sensor-based vibration signals measured from the rotating machinery are preprocessed by the LMD method and product functions (PFs) are produced. Second, statistic features are extracted to acquire more fault characteristic information from the sensitive PF. Finally, these features are fed into a multi-class RWSVM to identify the rotating machinery health conditions. The experimental results validate the effectiveness of the proposed RWSVM method in identifying rotating machinery fault patterns accurately and effectively and its superiority over that based on the general SVM. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle RoCoMAR: Robots’ Controllable Mobility Aided Routing and Relay Architecture for Mobile Sensor Networks
Sensors 2013, 13(7), 8695-8721; doi:10.3390/s130708695
Received: 28 May 2013 / Revised: 26 June 2013 / Accepted: 1 July 2013 / Published: 5 July 2013
Cited by 9 | PDF Full-text (519 KB) | HTML Full-text | XML Full-text
Abstract
In a practical deployment, mobile sensor network (MSN) suffers from a low performance due to high node mobility, time-varying wireless channel properties, and obstacles between communicating nodes. In order to tackle the problem of low network performance and provide a desired end-to-end [...] Read more.
In a practical deployment, mobile sensor network (MSN) suffers from a low performance due to high node mobility, time-varying wireless channel properties, and obstacles between communicating nodes. In order to tackle the problem of low network performance and provide a desired end-to-end data transfer quality, in this paper we propose a novel ad hoc routing and relaying architecture, namely RoCoMAR (Robots’ Controllable Mobility Aided Routing) that uses robotic nodes’ controllable mobility. RoCoMAR repeatedly performs link reinforcement process with the objective of maximizing the network throughput, in which the link with the lowest quality on the path is identified and replaced with high quality links by placing a robotic node as a relay at an optimal position. The robotic node resigns as a relay if the objective is achieved or no more gain can be obtained with a new relay. Once placed as a relay, the robotic node performs adaptive link maintenance by adjusting its position according to the movements of regular nodes. The simulation results show that RoCoMAR outperforms existing ad hoc routing protocols for MSN in terms of network throughput and end-to-end delay. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle Multi-View Human Activity Recognition in Distributed Camera Sensor Networks
Sensors 2013, 13(7), 8750-8770; doi:10.3390/s130708750
Received: 24 April 2013 / Revised: 10 June 2013 / Accepted: 1 July 2013 / Published: 8 July 2013
Cited by 8 | PDF Full-text (1272 KB) | HTML Full-text | XML Full-text
Abstract
With the increasing demand on the usage of smart and networked cameras in intelligent and ambient technology environments, development of algorithms for such resource-distributed networks are of great interest. Multi-view action recognition addresses many challenges dealing with view-invariance and occlusion, and due [...] Read more.
With the increasing demand on the usage of smart and networked cameras in intelligent and ambient technology environments, development of algorithms for such resource-distributed networks are of great interest. Multi-view action recognition addresses many challenges dealing with view-invariance and occlusion, and due to the huge amount of processing and communicating data in real life applications, it is not easy to adapt these methods for use in smart camera networks. In this paper, we propose a distributed activity classification framework, in which we assume that several camera sensors are observing the scene. Each camera processes its own observations, and while communicating with other cameras, they come to an agreement about the activity class. Our method is based on recovering a low-rank matrix over consensus to perform a distributed matrix completion via convex optimization. Then, it is applied to the problem of human activity classification. We test our approach on IXMAS and MuHAVi datasets to show the performance and the feasibility of the method. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle The Design of High Performance, Low Power Triple-Track Magnetic Sensor Chip
Sensors 2013, 13(7), 8771-8785; doi:10.3390/s130708771
Received: 25 May 2013 / Revised: 1 July 2013 / Accepted: 1 July 2013 / Published: 9 July 2013
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Abstract
This paper presents a design of a high performance and low power consumption triple-track magnetic sensor chip which was fabricated in TSMC 0.35 μm CMOS process. This chip is able to simultaneously sense, decode and read out the information stored in triple-track [...] Read more.
This paper presents a design of a high performance and low power consumption triple-track magnetic sensor chip which was fabricated in TSMC 0.35 μm CMOS process. This chip is able to simultaneously sense, decode and read out the information stored in triple-track magnetic cards. A reference voltage generating circuit, a low-cost filter circuit, a power-on reset circuit, an RC oscillator, and a pre-decoding circuit are utilized as the basic modules. The triple-track magnetic sensor chip has four states, i.e., reset, sleep, swiping card and data read-out. In sleep state, the internal RC oscillator is closed, which means that the digital part does not operate to optimize energy consumption. In order to improve decoding accuracy and expand the sensing range of the signal, two kinds of circuit are put forward, naming offset correction circuit, and tracking circuit. With these two circuits, the sensing function of this chip can be more efficiently and accurately. We simulated these circuit modules with TSMC technology library. The results showed that these modules worked well within wide range input signal. Based on these results, the layout and tape-out were carried out. The measurement results showed that the chip do function well within a wide swipe speed range, which achieved the design target. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Breadth-First Search-Based Single-Phase Algorithms for Bridge Detection in Wireless Sensor Networks
Sensors 2013, 13(7), 8786-8813; doi:10.3390/s130708786
Received: 2 May 2013 / Revised: 28 June 2013 / Accepted: 3 July 2013 / Published: 10 July 2013
PDF Full-text (1060 KB) | HTML Full-text | XML Full-text
Abstract
Wireless sensor networks (WSNs) are promising technologies for exploring harsh environments, such as oceans, wild forests, volcanic regions and outer space. Since sensor nodes may have limited transmission range, application packets may be transmitted by multi-hop communication. Thus, connectivity is a very [...] Read more.
Wireless sensor networks (WSNs) are promising technologies for exploring harsh environments, such as oceans, wild forests, volcanic regions and outer space. Since sensor nodes may have limited transmission range, application packets may be transmitted by multi-hop communication. Thus, connectivity is a very important issue. A bridge is a critical edge whose removal breaks the connectivity of the network. Hence, it is crucial to detect bridges and take preventions. Since sensor nodes are battery-powered, services running on nodes should consume low energy. In this paper, we propose energy-efficient and distributed bridge detection algorithms for WSNs. Our algorithms run single phase and they are integrated with the Breadth-First Search (BFS) algorithm, which is a popular routing algorithm. Our first algorithm is an extended version of Milic’s algorithm, which is designed to reduce the message length. Our second algorithm is novel and uses ancestral knowledge to detect bridges. We explain the operation of the algorithms, analyze their proof of correctness, message, time, space and computational complexities. To evaluate practical importance, we provide testbed experiments and extensive simulations. We show that our proposed algorithms provide less resource consumption, and the energy savings of our algorithms are up by 5.5-times. Full article
(This article belongs to the Special Issue Sensors for Harsh-Environment Applications)
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Open AccessArticle A Remote Sensor for Detecting Methane Based on Palladium-Decorated Single Walled Carbon Nanotubes
Sensors 2013, 13(7), 8814-8826; doi:10.3390/s130708814
Received: 27 May 2013 / Revised: 24 June 2013 / Accepted: 27 June 2013 / Published: 10 July 2013
Cited by 4 | PDF Full-text (523 KB) | HTML Full-text | XML Full-text
Abstract
The remote detection of the concentration of methane at room temperature is performed by a sensor that is configured by the combination of radio frequency identification (RFID), and functionalized carbon nanotubes (CNTs). The proposed sensor is schemed as a thin film RFID [...] Read more.
The remote detection of the concentration of methane at room temperature is performed by a sensor that is configured by the combination of radio frequency identification (RFID), and functionalized carbon nanotubes (CNTs). The proposed sensor is schemed as a thin film RFID tag in a polyethylene substrate, on which a metal trace dipole, a metal trace T impedance matching networks, a 0.5 µm-CMOS RF/DC rectifier chipset and a sensor head of palladium-decorated single walled carbon nanotubes (Pd-SWCNTs) are surface mounted in cascade. The performances of the sensor are examined and described by the defined parameters of the received signal strength index (RSSI) and the comparative analog identifier (∆AID). Results validate the sensor’s ability to detect molecules of methane at room temperature, showing that the RSSI can increase 4 dB and the ∆AID can increase 3% in response to methane concentrations ranging from zero to 100 ppm. Full article
(This article belongs to the Special Issue Gas Sensors - 2013)
Open AccessArticle Fiber-Optic Refractometer Based on an Etched High-Q π-Phase-Shifted Fiber-Bragg-Grating
Sensors 2013, 13(7), 8827-8834; doi:10.3390/s130708827
Received: 28 March 2013 / Revised: 20 May 2013 / Accepted: 2 July 2013 / Published: 10 July 2013
Cited by 2 | PDF Full-text (619 KB) | HTML Full-text | XML Full-text
Abstract
We present a compact and highly-sensitive fiber-optic refractometer based on a high-Q p-phase-shifted fiber-Bragg-grating (pFBG) that is chemically etched to the core of the fiber. Due to the p phase-shift, a strong pFBG forms a high-Q optical resonator and the [...] Read more.
We present a compact and highly-sensitive fiber-optic refractometer based on a high-Q p-phase-shifted fiber-Bragg-grating (pFBG) that is chemically etched to the core of the fiber. Due to the p phase-shift, a strong pFBG forms a high-Q optical resonator and the reflection spectrum features an extremely narrow notch that can be used for highly sensitivity refractive index measurement. The etched pFBG demonstrated here has a diameter of ~9.3 μm and a length of only 7 mm, leading to a refractive index responsivity of 2.9 nm/RIU (RIU: refractive index unit) at an ambient refractive index of 1.318. The reflection spectrum of the etched pFBG features an extremely narrow notch with a linewidth of only 2.1 pm in water centered at ~1,550 nm, corresponding to a Q-factor of 7.4 ´ 105, which allows for potentially significantly improved sensitivity over refractometers based on regular fiber Bragg gratings. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Model-Based Reinforcement of Kinect Depth Data for Human Motion Capture Applications
Sensors 2013, 13(7), 8835-8855; doi:10.3390/s130708835
Received: 15 May 2013 / Revised: 2 July 2013 / Accepted: 8 July 2013 / Published: 10 July 2013
Cited by 9 | PDF Full-text (2152 KB) | HTML Full-text | XML Full-text
Abstract
Motion capture systems have recently experienced a strong evolution. New cheap depth sensors and open source frameworks, such as OpenNI, allow for perceiving human motion on-line without using invasive systems. However, these proposals do not evaluate the validity of the obtained poses. [...] Read more.
Motion capture systems have recently experienced a strong evolution. New cheap depth sensors and open source frameworks, such as OpenNI, allow for perceiving human motion on-line without using invasive systems. However, these proposals do not evaluate the validity of the obtained poses. This paper addresses this issue using a model-based pose generator to complement the OpenNI human tracker. The proposed system enforces kinematics constraints, eliminates odd poses and filters sensor noise, while learning the real dimensions of the performer’s body. The system is composed by a PrimeSense sensor, an OpenNI tracker and a kinematics-based filter and has been extensively tested. Experiments show that the proposed system improves pure OpenNI results at a very low computational cost. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Experimental Results of Underwater Cooperative Source Localization Using a Single Acoustic Vector Sensor
Sensors 2013, 13(7), 8856-8878; doi:10.3390/s130708856
Received: 7 May 2013 / Revised: 29 June 2013 / Accepted: 1 July 2013 / Published: 12 July 2013
Cited by 5 | PDF Full-text (1586 KB) | HTML Full-text | XML Full-text
Abstract
This paper aims at estimating the azimuth, range and depth of a cooperative broadband acoustic source with a single vector sensor in a multipath underwater environment, where the received signal is assumed to be a linear combination of echoes of the source [...] Read more.
This paper aims at estimating the azimuth, range and depth of a cooperative broadband acoustic source with a single vector sensor in a multipath underwater environment, where the received signal is assumed to be a linear combination of echoes of the source emitted waveform. A vector sensor is a device that measures the scalar acoustic pressure field and the vectorial acoustic particle velocity field at a single location in space. The amplitudes of the echoes in the vector sensor components allow one to determine their azimuth and elevation. Assuming that the environmental conditions of the channel are known, source range and depth are obtained from the estimates of elevation and relative time delays of the different echoes using a ray-based backpropagation algorithm. The proposed method is tested using simulated data and is further applied to experimental data from the Makai’05 experiment, where 8–14 kHz chirp signals were acquired by a vector sensor array. It is shown that for short ranges, the position of the source is estimated in agreement with the geometry of the experiment. The method is low computational demanding, thus well-suited to be used in mobile and light platforms, where space and power requirements are limited. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Development of a Network RTK Positioning and Gravity-Surveying Application with Gravity Correction Using a Smartphone
Sensors 2013, 13(7), 8879-8894; doi:10.3390/s130708879
Received: 9 May 2013 / Revised: 3 July 2013 / Accepted: 4 July 2013 / Published: 12 July 2013
PDF Full-text (988 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a smartphone-based network real-time kinematic (RTK) positioning and gravity-surveying application (app) that allows semi-real-time measurements using the built-in Bluetooth features of the smartphone and a third-generation or long-term evolution wireless device. The app was implemented on a single smartphone [...] Read more.
This paper proposes a smartphone-based network real-time kinematic (RTK) positioning and gravity-surveying application (app) that allows semi-real-time measurements using the built-in Bluetooth features of the smartphone and a third-generation or long-term evolution wireless device. The app was implemented on a single smartphone by integrating a global navigation satellite system (GNSS) controller, a laptop, and a field-note writing tool. The observation devices (i.e., a GNSS receiver and relative gravimeter) functioned independently of this system. The app included a gravity module, which converted the measured relative gravity reading into an absolute gravity value according to tides; meter height; instrument drift correction; and network adjustments. The semi-real-time features of this app allowed data to be shared easily with other researchers. Moreover, the proposed smartphone-based gravity-survey app was easily adaptable to various locations and rough terrain due to its compact size. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Background Subtraction Based on Color and Depth Using Active Sensors
Sensors 2013, 13(7), 8895-8915; doi:10.3390/s130708895
Received: 7 May 2013 / Revised: 3 July 2013 / Accepted: 4 July 2013 / Published: 12 July 2013
Cited by 16 | PDF Full-text (2482 KB) | HTML Full-text | XML Full-text
Abstract
Depth information has been used in computer vision for a wide variety of tasks. Since active range sensors are currently available at low cost, high-quality depth maps can be used as relevant input for many applications. Background subtraction and video segmentation algorithms [...] Read more.
Depth information has been used in computer vision for a wide variety of tasks. Since active range sensors are currently available at low cost, high-quality depth maps can be used as relevant input for many applications. Background subtraction and video segmentation algorithms can be improved by fusing depth and color inputs, which are complementary and allow one to solve many classic color segmentation issues. In this paper, we describe one fusion method to combine color and depth based on an advanced color-based algorithm. This technique has been evaluated by means of a complete dataset recorded with Microsoft Kinect, which enables comparison with the original method. The proposed method outperforms the others in almost every test, showing more robustness to illumination changes, shadows, reflections and camouflage. Full article
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Open AccessArticle Rice Seed Cultivar Identification Using Near-Infrared Hyperspectral Imaging and Multivariate Data Analysis
Sensors 2013, 13(7), 8916-8927; doi:10.3390/s130708916
Received: 21 May 2013 / Revised: 26 June 2013 / Accepted: 4 July 2013 / Published: 12 July 2013
Cited by 20 | PDF Full-text (530 KB) | HTML Full-text | XML Full-text
Abstract
A near-infrared (NIR) hyperspectral imaging system was developed in this study. NIR hyperspectral imaging combined with multivariate data analysis was applied to identify rice seed cultivars. Spectral data was exacted from hyperspectral images. Along with Partial Least Squares Discriminant Analysis (PLS-DA), Soft [...] Read more.
A near-infrared (NIR) hyperspectral imaging system was developed in this study. NIR hyperspectral imaging combined with multivariate data analysis was applied to identify rice seed cultivars. Spectral data was exacted from hyperspectral images. Along with Partial Least Squares Discriminant Analysis (PLS-DA), Soft Independent Modeling of Class Analogy (SIMCA), K-Nearest Neighbor Algorithm (KNN) and Support Vector Machine (SVM), a novel machine learning algorithm called Random Forest (RF) was applied in this study. Spectra from 1,039 nm to 1,612 nm were used as full spectra to build classification models. PLS-DA and KNN models obtained over 80% classification accuracy, and SIMCA, SVM and RF models obtained 100% classification accuracy in both the calibration and prediction set. Twelve optimal wavelengths were selected by weighted regression coefficients of the PLS-DA model. Based on optimal wavelengths, PLS-DA, KNN, SVM and RF models were built. All optimal wavelengths-based models (except PLS-DA) produced classification rates over 80%. The performances of full spectra-based models were better than optimal wavelengths-based models. The overall results indicated that hyperspectral imaging could be used for rice seed cultivar identification, and RF is an effective classification technique. Full article
(This article belongs to the Special Issue Spectral Imaging at the Microscale and Beyond)
Open AccessArticle AmI and Deployment Considerations in AAL Services Provision for Elderly Independent Living: The MonAMI Project
Sensors 2013, 13(7), 8950-8976; doi:10.3390/s130708950
Received: 25 March 2013 / Revised: 8 July 2013 / Accepted: 10 July 2013 / Published: 12 July 2013
Cited by 4 | PDF Full-text (2468 KB) | HTML Full-text | XML Full-text
Abstract
The MonAMI project aims to investigate the feasibility of the deployment of open platforms for Ambient Assisted Living (AAL) services provision based on Ambient Intelligence (AmI) and to test user acceptance and the usability of the services. Services were designed to provide [...] Read more.
The MonAMI project aims to investigate the feasibility of the deployment of open platforms for Ambient Assisted Living (AAL) services provision based on Ambient Intelligence (AmI) and to test user acceptance and the usability of the services. Services were designed to provide support in the areas of environmental control, security, well-being and leisure. These services were installed and evaluated in a Spanish geriatric residence. The participants included elderly persons with disabilities, nursing home care givers and informal carers. The concept of the open platform proved to be satisfactory for the provision of the services in a context aware framework. Furthermore, the usability of the technology was viewed positively and the overall results indicate that this system has the potential to prolong independent living at home for elderly people with disabilities. Deployment was proven successful and awareness of open-platform AAL service delivery was raised in local communities throughout Europe. Full article
Open AccessArticle A Radiosonde Using a Humidity Sensor Array with a Platinum Resistance Heater and Multi-Sensor Data Fusion
Sensors 2013, 13(7), 8977-8996; doi:10.3390/s130708977
Received: 21 May 2013 / Revised: 2 July 2013 / Accepted: 8 July 2013 / Published: 12 July 2013
Cited by 5 | PDF Full-text (945 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes the design and implementation of a radiosonde which can measure the meteorological temperature, humidity, pressure, and other atmospheric data. The system is composed of a CPU, microwave module, temperature sensor, pressure sensor and humidity sensor array. In order to [...] Read more.
This paper describes the design and implementation of a radiosonde which can measure the meteorological temperature, humidity, pressure, and other atmospheric data. The system is composed of a CPU, microwave module, temperature sensor, pressure sensor and humidity sensor array. In order to effectively solve the humidity sensor condensation problem due to the low temperatures in the high altitude environment, a capacitive humidity sensor including four humidity sensors to collect meteorological humidity and a platinum resistance heater was developed using micro-electro-mechanical-system (MEMS) technology. A platinum resistance wire with 99.999% purity and 0.023 mm in diameter was used to obtain the meteorological temperature. A multi-sensor data fusion technique was applied to process the atmospheric data. Static and dynamic experimental results show that the designed humidity sensor with platinum resistance heater can effectively tackle the sensor condensation problem, shorten response times and enhance sensitivity. The humidity sensor array can improve measurement accuracy and obtain a reliable initial meteorological humidity data, while the multi-sensor data fusion technique eliminates the uncertainty in the measurement. The radiosonde can accurately reflect the meteorological changes. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering 2013)
Open AccessArticle Sensorized Garments and Textrode-Enabled Measurement Instrumentation for Ambulatory Assessment of the Autonomic Nervous System Response in the ATREC Project
Sensors 2013, 13(7), 8997-9015; doi:10.3390/s130708997
Received: 14 June 2013 / Revised: 3 July 2013 / Accepted: 4 July 2013 / Published: 12 July 2013
Cited by 7 | PDF Full-text (1466 KB) | HTML Full-text | XML Full-text
Abstract
Advances in textile materials, technology and miniaturization of electronics for measurement instrumentation has boosted the development of wearable measurement systems. In several projects sensorized garments and non-invasive instrumentation have been integrated to assess on emotional, cognitive responses as well as physical arousal [...] Read more.
Advances in textile materials, technology and miniaturization of electronics for measurement instrumentation has boosted the development of wearable measurement systems. In several projects sensorized garments and non-invasive instrumentation have been integrated to assess on emotional, cognitive responses as well as physical arousal and status of mental stress through the study of the autonomous nervous system. Assessing the mental state of workers under stressful conditions is critical to identify which workers are in the proper state of mind and which are not ready to undertake a mission, which might consequently risk their own life and the lives of others. The project Assessment in Real Time of the Stress in Combatants (ATREC) aims to enable real time assessment of mental stress of the Spanish Armed Forces during military activities using a wearable measurement system containing sensorized garments and textile-enabled non-invasive instrumentation. This work describes the multiparametric sensorized garments and measurement instrumentation implemented in the first phase of the project required to evaluate physiological indicators and recording candidates that can be useful for detection of mental stress. For such purpose different sensorized garments have been constructed: a textrode chest-strap system with six repositionable textrodes, a sensorized glove and an upper-arm strap. The implemented textile-enabled instrumentation contains one skin galvanometer, two temperature sensors for skin and environmental temperature and an impedance pneumographer containing a 1-channel ECG amplifier to record cardiogenic biopotentials. With such combinations of garments and non-invasive measurement devices, a multiparametric wearable measurement system has been implemented able to record the following physiological parameters: heart and respiration rate, skin galvanic response, environmental and peripheral temperature. To ensure the proper functioning of the implemented garments and devices the full series of 12 sets have been functionally tested recording cardiogenic biopotential, thoracic impedance, galvanic skin response and temperature values. The experimental results indicate that the implemented wearable measurement systems operate according to the specifications and are ready to be used for mental stress experiments, which will be executed in the coming phases of the project with dozens of healthy volunteers. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Vapor Trace Recognition Using a Single Nonspecific Chemiresistor
Sensors 2013, 13(7), 9016-9028; doi:10.3390/s130709016
Received: 29 May 2013 / Revised: 27 June 2013 / Accepted: 8 July 2013 / Published: 12 July 2013
Cited by 3 | PDF Full-text (1411 KB) | HTML Full-text | XML Full-text
Abstract
An application of spectral analysis to the transient response signals of ALD-fabricated conductometric sensors (chemiresistors) upon exposure to short vapor pulses is discussed. It is based on the representation of a response curve in the frequency domain, followed by the multi-dimensional Quadratic [...] Read more.
An application of spectral analysis to the transient response signals of ALD-fabricated conductometric sensors (chemiresistors) upon exposure to short vapor pulses is discussed. It is based on the representation of a response curve in the frequency domain, followed by the multi-dimensional Quadratic Discriminant Analysis (QDA) for analyte identification. Compared to the standard steady-state amplitude analysis, this technique does not depend on a short-term sensor drift, does not have limitations for the number of extracted features and has a strict physical validation. Effective recognition of some relatively simple combustible analytes (acetone, toluene, ethanol) was demonstrated using a single nonspecific chemiresistor. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Seamless Positioning and Navigation by Using Geo-Referenced Images and Multi-Sensor Data
Sensors 2013, 13(7), 9047-9069; doi:10.3390/s130709047
Received: 3 May 2013 / Revised: 13 June 2013 / Accepted: 7 July 2013 / Published: 12 July 2013
Cited by 6 | PDF Full-text (1038 KB) | HTML Full-text | XML Full-text
Abstract
Ubiquitous positioning is considered to be a highly demanding application for today’s Location-Based Services (LBS). While satellite-based navigation has achieved great advances in the past few decades, positioning and navigation in indoor scenarios and deep urban areas has remained a challenging topic [...] Read more.
Ubiquitous positioning is considered to be a highly demanding application for today’s Location-Based Services (LBS). While satellite-based navigation has achieved great advances in the past few decades, positioning and navigation in indoor scenarios and deep urban areas has remained a challenging topic of substantial research interest. Various strategies have been adopted to fill this gap, within which vision-based methods have attracted growing attention due to the widespread use of cameras on mobile devices. However, current vision-based methods using image processing have yet to revealed their full potential for navigation applications and are insufficient in many aspects. Therefore in this paper, we present a hybrid image-based positioning system that is intended to provide seamless position solution in six degrees of freedom (6DoF) for location-based services in both outdoor and indoor environments. It mainly uses visual sensor input to match with geo-referenced images for image-based positioning resolution, and also takes advantage of multiple onboard sensors, including the built-in GPS receiver and digital compass to assist visual methods. Experiments demonstrate that such a system can greatly improve the position accuracy for areas where the GPS signal is negatively affected (such as in urban canyons), and it also provides excellent position accuracy for indoor environments. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Ultra-Precision Measurement and Control of Angle Motion in Piezo-Based Platforms Using Strain Gauge Sensors and a Robust Composite Controller
Sensors 2013, 13(7), 9070-9084; doi:10.3390/s130709070
Received: 8 June 2013 / Revised: 4 July 2013 / Accepted: 5 July 2013 / Published: 15 July 2013
Cited by 5 | PDF Full-text (891 KB) | HTML Full-text | XML Full-text
Abstract
The measurement and control strategy of a piezo-based platform by using strain gauge sensors (SGS) and a robust composite controller is investigated in this paper. First, the experimental setup is constructed by using a piezo-based platform, SGS sensors, an AD5435 platform and [...] Read more.
The measurement and control strategy of a piezo-based platform by using strain gauge sensors (SGS) and a robust composite controller is investigated in this paper. First, the experimental setup is constructed by using a piezo-based platform, SGS sensors, an AD5435 platform and two voltage amplifiers. Then, the measurement strategy to measure the tip/tilt angles accurately in the order of sub-μrad is presented. A comprehensive composite control strategy design to enhance the tracking accuracy with a novel driving principle is also proposed. Finally, an experiment is presented to validate the measurement and control strategy. The experimental results demonstrate that the proposed measurement and control strategy provides accurate angle motion with a root mean square (RMS) error of 0.21 μrad, which is approximately equal to the noise level. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle An Integrative Structural Health Monitoring System for the Local/Global Responses of a Large-Scale Irregular Building under Construction
Sensors 2013, 13(7), 9085-9103; doi:10.3390/s130709085
Received: 10 May 2013 / Revised: 10 July 2013 / Accepted: 11 July 2013 / Published: 15 July 2013
Cited by 18 | PDF Full-text (1562 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a practical and integrative SHM system was developed and applied to a large-scale irregular building under construction, where many challenging issues exist. In the proposed sensor network, customized energy-efficient wireless sensing units (sensor nodes, repeater nodes, and master nodes) [...] Read more.
In this study, a practical and integrative SHM system was developed and applied to a large-scale irregular building under construction, where many challenging issues exist. In the proposed sensor network, customized energy-efficient wireless sensing units (sensor nodes, repeater nodes, and master nodes) were employed and comprehensive communications from the sensor node to the remote monitoring server were conducted through wireless communications. The long-term (13-month) monitoring results recorded from a large number of sensors (75 vibrating wire strain gauges, 10 inclinometers, and three laser displacement sensors) indicated that the construction event exhibiting the largest influence on structural behavior was the removal of bents that were temporarily installed to support the free end of the cantilevered members during their construction. The safety of each member could be confirmed based on the quantitative evaluation of each response. Furthermore, it was also confirmed that the relation between these responses (i.e., deflection, strain, and inclination) can provide information about the global behavior of structures induced from specific events. Analysis of the measurement results demonstrates the proposed sensor network system is capable of automatic and real-time monitoring and can be applied and utilized for both the safety evaluation and precise implementation of buildings under construction. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle An Early Underwater Artificial Vision Model in Ocean Investigations via Independent Component Analysis
Sensors 2013, 13(7), 9104-9131; doi:10.3390/s130709104
Received: 8 June 2013 / Revised: 6 July 2013 / Accepted: 8 July 2013 / Published: 16 July 2013
Cited by 3 | PDF Full-text (4525 KB) | HTML Full-text | XML Full-text
Abstract
Underwater vision is one of the dominant senses and has shown great prospects in ocean investigations. In this paper, a hierarchical Independent Component Analysis (ICA) framework has been established to explore and understand the functional roles of the higher order statistical structures [...] Read more.
Underwater vision is one of the dominant senses and has shown great prospects in ocean investigations. In this paper, a hierarchical Independent Component Analysis (ICA) framework has been established to explore and understand the functional roles of the higher order statistical structures towards the visual stimulus in the underwater artificial vision system. The model is inspired by characteristics such as the modality, the redundancy reduction, the sparseness and the independence in the early human vision system, which seems to respectively capture the Gabor-like basis functions, the shape contours or the complicated textures in the multiple layer implementations. The simulation results have shown good performance in the effectiveness and the consistence of the approach proposed for the underwater images collected by autonomous underwater vehicles (AUVs). Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessArticle A New Full Pose Measurement Method for Robot Calibration
Sensors 2013, 13(7), 9132-9147; doi:10.3390/s130709132
Received: 1 April 2013 / Revised: 6 May 2013 / Accepted: 15 July 2013 / Published: 16 July 2013
Cited by 2 | PDF Full-text (679 KB) | HTML Full-text | XML Full-text
Abstract
Identification of robot kinematic errors during the calibration process often requires accurate full pose measurements (position and orientation) of robot end-effectors in Cartesian space. This paper proposes a new method of full pose measurement of robot end-effectors for calibration. This method is [...] Read more.
Identification of robot kinematic errors during the calibration process often requires accurate full pose measurements (position and orientation) of robot end-effectors in Cartesian space. This paper proposes a new method of full pose measurement of robot end-effectors for calibration. This method is based on an analysis of the features of a set of target points (placed on a rotating end-effector) on a circular trajectory. The accurate measurement is validated by computational simulation results from the Puma robot. Moreover, experimental calibration and validation results for the Hyundai HA-06 robot prove the effectiveness, correctness, and reliability of the proposed method. This method can be applied to robots that have entirely revolute joints or to robots for which only the last joint is revolute. Full article
(This article belongs to the Section Physical Sensors)
Open AccessCommunication Optimizing the Thermal Read-Out Technique for MIP-Based Biomimetic Sensors: Towards Nanomolar Detection Limits
Sensors 2013, 13(7), 9148-9159; doi:10.3390/s130709148
Received: 25 May 2013 / Revised: 27 June 2013 / Accepted: 10 July 2013 / Published: 16 July 2013
Cited by 9 | PDF Full-text (806 KB) | HTML Full-text | XML Full-text
Abstract
In previous work, the novel heat-transfer method (HTM) for the detection of small molecules with Molecularly Imprinted Polymers (MIP)-type receptors was presented. In this study we focus on optimization of this sensor performance, with as final aim to lower the detection limit [...] Read more.
In previous work, the novel heat-transfer method (HTM) for the detection of small molecules with Molecularly Imprinted Polymers (MIP)-type receptors was presented. In this study we focus on optimization of this sensor performance, with as final aim to lower the detection limit by reducing the noise level. It was determined that the noise originates foremost from the power supply, which can be controlled by varying the PID parameters. Therefore, the effect of the individual parameters was evaluated by tuning P, I and D separately at a temperature of 37 °C, giving a first indication of the optimal configuration. Next, a temperature profile was programmed and the standard deviation of the heat-transfer resistance over the entire regime was studied for a set of parameters. The optimal configuration, P1-I6-D0, reduced the noise level with nearly a factor of three compared to the original parameters of P10-I5-D0. With the optimized settings, the detection of L-nicotine in buffer solutions was studied and the detection limit improved significantly from 100 nM to 35 nM. Summarizing, optimization of the PID parameters and thereby improving the detection limit is a key parameter for first applications of the HTM-method for MIP receptors in analytical research. Full article
(This article belongs to the Special Issue Biomimetic Receptors and Sensors)
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Open AccessArticle Metal Oxide Gas Sensor Drift Compensation Using a Dynamic Classifier Ensemble Based on Fitting
Sensors 2013, 13(7), 9160-9173; doi:10.3390/s130709160
Received: 18 April 2013 / Revised: 11 July 2013 / Accepted: 15 July 2013 / Published: 17 July 2013
Cited by 2 | PDF Full-text (242 KB) | HTML Full-text | XML Full-text
Abstract
Sensor drift is currently the most challenging problem in gas sensing. We propose a novel ensemble method with dynamic weights based on fitting (DWF) to solve the gas discrimination problem, regardless of the gas concentration, with high accuracy over extended periods of [...] Read more.
Sensor drift is currently the most challenging problem in gas sensing. We propose a novel ensemble method with dynamic weights based on fitting (DWF) to solve the gas discrimination problem, regardless of the gas concentration, with high accuracy over extended periods of time. The DWF method uses a dynamic weighted combination of support vector machine (SVM) classifiers trained by the datasets that are collected at different time periods. In the testing of future datasets, the classifier weights are predicted by fitting functions, which are obtained by the proper fitting of the optimal weights during training. We compare the performance of the DWF method with that of competing methods in an experiment based on a public dataset that was compiled over a period of three years. The experimental results demonstrate that the DWF method outperforms the other methods considered. Furthermore, the DWF method can be further optimized by applying a fitting function that more closely matches the variation of the optimal weight over time. Full article
(This article belongs to the Special Issue Gas Sensors - 2013)
Open AccessArticle Piezoelectric Driving of Vibration Conveyors: An Experimental Assessment
Sensors 2013, 13(7), 9174-9182; doi:10.3390/s130709174
Received: 3 June 2013 / Revised: 4 July 2013 / Accepted: 7 July 2013 / Published: 17 July 2013
PDF Full-text (625 KB) | HTML Full-text | XML Full-text
Abstract
Vibratory feeders or vibratory conveyors have been widely used for the transport and orientation of individual parts and bulk materials in many branches of industrial activity. From the designer’s standpoint, the current endeavor is to conceive efficient vibratory feeders, satisfying constraints of [...] Read more.
Vibratory feeders or vibratory conveyors have been widely used for the transport and orientation of individual parts and bulk materials in many branches of industrial activity. From the designer’s standpoint, the current endeavor is to conceive efficient vibratory feeders, satisfying constraints of power consumption, vibration transmission and noise emission. Moreover, the interest in the reduction of maintenance cost is always present. In this context, this paper investigates experimentally the concept of vibratory conveying based on the use of piezoelectric materials for motion generation. A small-size prototype of a linear conveyor, in which lead-zirconate-titanate (PZT) patches are bonded to the resilient elements, is described. One of the main design goals is that the prototype is intended to be fed directly from the electric network, aiming at avoiding the use of electronic equipment for driving. To comply with this feature and, at the same time, enable to adjust the transport velocity, a mechanical device has been conceived in such a way that the first natural frequency of the conveyor can be changed. It is shown that the transport velocity is determined by the proximity between the excitation frequency and the first natural frequency of the conveyor. The experimental tests performed to characterize the dynamic behavior of the prototype are described and the range of transport velocities is determined. Full article
(This article belongs to the Special Issue Piezoelectric Sensors and Actuators)
Open AccessArticle Optimal Placement of Accelerometers for the Detection of Everyday Activities
Sensors 2013, 13(7), 9183-9200; doi:10.3390/s130709183
Received: 27 April 2013 / Revised: 28 June 2013 / Accepted: 9 July 2013 / Published: 17 July 2013
Cited by 39 | PDF Full-text (492 KB) | HTML Full-text | XML Full-text
Abstract
This article describes an investigation to determine the optimal placement of accelerometers for the purpose of detecting a range of everyday activities. The paper investigates the effect of combining data from accelerometers placed at various bodily locations on the accuracy of activity [...] Read more.
This article describes an investigation to determine the optimal placement of accelerometers for the purpose of detecting a range of everyday activities. The paper investigates the effect of combining data from accelerometers placed at various bodily locations on the accuracy of activity detection. Eight healthy males participated within the study. Data were collected from six wireless tri-axial accelerometers placed at the chest, wrist, lower back, hip, thigh and foot. Activities included walking, running on a motorized treadmill, sitting, lying, standing and walking up and down stairs. The Support Vector Machine provided the most accurate detection of activities of all the machine learning algorithms investigated. Although data from all locations provided similar levels of accuracy, the hip was the best single location to record data for activity detection using a Support Vector Machine, providing small but significantly better accuracy than the other investigated locations. Increasing the number of sensing locations from one to two or more statistically increased the accuracy of classification. There was no significant difference in accuracy when using two or more sensors. It was noted, however, that the difference in activity detection using single or multiple accelerometers may be more pronounced when trying to detect finer grain activities. Future work shall therefore investigate the effects of accelerometer placement on a larger range of these activities. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in the UK 2013)
Open AccessArticle Investigation on Dynamic Calibration for an Optical-Fiber Solids Concentration Probe in Gas-Solid Two-Phase Flows
Sensors 2013, 13(7), 9201-9222; doi:10.3390/s130709201
Received: 3 April 2013 / Revised: 4 July 2013 / Accepted: 15 July 2013 / Published: 17 July 2013
Cited by 6 | PDF Full-text (442 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a review and analysis of the research that has been carried out on dynamic calibration for optical-fiber solids concentration probes. An introduction to the optical-fiber solids concentration probe was given. Different calibration methods of optical-fiber solids concentration probes reported [...] Read more.
This paper presents a review and analysis of the research that has been carried out on dynamic calibration for optical-fiber solids concentration probes. An introduction to the optical-fiber solids concentration probe was given. Different calibration methods of optical-fiber solids concentration probes reported in the literature were reviewed. In addition, a reflection-type optical-fiber solids concentration probe was uniquely calibrated at nearly full range of the solids concentration from 0 to packed bed concentration. The effects of particle properties (particle size, sphericity and color) on the calibration results were comprehensively investigated. The results show that the output voltage has a tendency to increase with the decreasing particle size, and the effect of particle color on calibration result is more predominant than that of sphericity. Full article
(This article belongs to the Special Issue Optomechatronics) Print Edition available
Open AccessArticle Parallel Hough Transform-Based Straight Line Detection and Its FPGA Implementation in Embedded Vision
Sensors 2013, 13(7), 9223-9247; doi:10.3390/s130709223
Received: 22 May 2013 / Revised: 1 July 2013 / Accepted: 8 July 2013 / Published: 17 July 2013
Cited by 4 | PDF Full-text (614 KB) | HTML Full-text | XML Full-text
Abstract
Hough Transform has been widely used for straight line detection in low-definition and still images, but it suffers from execution time and resource requirements. Field Programmable Gate Arrays (FPGA) provide a competitive alternative for hardware acceleration to reap tremendous computing performance. In [...] Read more.
Hough Transform has been widely used for straight line detection in low-definition and still images, but it suffers from execution time and resource requirements. Field Programmable Gate Arrays (FPGA) provide a competitive alternative for hardware acceleration to reap tremendous computing performance. In this paper, we propose a novel parallel Hough Transform (PHT) and FPGA architecture-associated framework for real-time straight line detection in high-definition videos. A resource-optimized Canny edge detection method with enhanced non-maximum suppression conditions is presented to suppress most possible false edges and obtain more accurate candidate edge pixels for subsequent accelerated computation. Then, a novel PHT algorithm exploiting spatial angle-level parallelism is proposed to upgrade computational accuracy by improving the minimum computational step. Moreover, the FPGA based multi-level pipelined PHT architecture optimized by spatial parallelism ensures real-time computation for 1,024 × 768 resolution videos without any off-chip memory consumption. This framework is evaluated on ALTERA DE2-115 FPGA evaluation platform at a maximum frequency of 200 MHz, and it can calculate straight line parameters in 15.59 ms on the average for one frame. Qualitative and quantitative evaluation results have validated the system performance regarding data throughput, memory bandwidth, resource, speed and robustness. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Retinal Identification Based on an Improved Circular Gabor Filter and Scale Invariant Feature Transform
Sensors 2013, 13(7), 9248-9266; doi:10.3390/s130709248
Received: 3 June 2013 / Revised: 10 July 2013 / Accepted: 12 July 2013 / Published: 18 July 2013
Cited by 6 | PDF Full-text (1625 KB) | HTML Full-text | XML Full-text
Abstract
Retinal identification based on retinal vasculatures in the retina provides the most secure and accurate means of authentication among biometrics and has primarily been used in combination with access control systems at high security facilities. Recently, there has been much interest in [...] Read more.
Retinal identification based on retinal vasculatures in the retina provides the most secure and accurate means of authentication among biometrics and has primarily been used in combination with access control systems at high security facilities. Recently, there has been much interest in retina identification. As digital retina images always suffer from deformations, the Scale Invariant Feature Transform (SIFT), which is known for its distinctiveness and invariance for scale and rotation, has been introduced to retinal based identification. However, some shortcomings like the difficulty of feature extraction and mismatching exist in SIFT-based identification. To solve these problems, a novel preprocessing method based on the Improved Circular Gabor Transform (ICGF) is proposed. After further processing by the iterated spatial anisotropic smooth method, the number of uninformative SIFT keypoints is decreased dramatically. Tested on the VARIA and eight simulated retina databases combining rotation and scaling, the developed method presents promising results and shows robustness to rotations and scale changes. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle An Approach for Characterizing and Comparing Hyperspectral Microscopy Systems
Sensors 2013, 13(7), 9267-9293; doi:10.3390/s130709267
Received: 27 May 2013 / Revised: 8 July 2013 / Accepted: 15 July 2013 / Published: 19 July 2013
Cited by 4 | PDF Full-text (869 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Hyperspectral imaging and analysis approaches offer accurate detection and quantification of fluorescently-labeled proteins and cells in highly autofluorescent tissues. However, selecting optimum acquisition settings for hyperspectral imaging is often a daunting task. In this study, we compared two hyperspectral systems—a widefield system [...] Read more.
Hyperspectral imaging and analysis approaches offer accurate detection and quantification of fluorescently-labeled proteins and cells in highly autofluorescent tissues. However, selecting optimum acquisition settings for hyperspectral imaging is often a daunting task. In this study, we compared two hyperspectral systems—a widefield system with acoustic optical tunable filter (AOTF) and charge coupled device (CCD) camera, and a confocal system with diffraction gratings and photomultiplier tube (PMT) array. We measured the effects of system parameters on hyperspectral image quality and linear unmixing results. Parameters that were assessed for the confocal system included pinhole diameter, laser power, PMT gain and for the widefield system included arc lamp intensity, and camera gain. The signal-to-noise ratio (SNR) and the root-mean-square error (RMS error) were measured to assess system performance. Photobleaching dynamics were studied. Finally, theoretical sensitivity studies were performed to estimate the incremental response (sensitivity) and false-positive detection rates (specificity). Results indicate that hyperspectral imaging assays are highly dependent on system parameters and experimental conditions. For detection of green fluorescent protein (GFP)-expressing cells in fixed lung tissues, a confocal pinhole of five airy disk units, high excitation intensity and low detector gain were optimal. The theoretical sensitivity studies revealed that widefield hyperspectral microscopy was able to detect GFP with fewer false positive occurrences than confocal microscopy, even though confocal microscopy offered improved signal and noise characteristics. These studies provide a framework for optimization that can be applied to a variety of hyperspectral imaging systems. Full article
(This article belongs to the Special Issue Spectral Imaging at the Microscale and Beyond)
Open AccessArticle Fabrication of an SPR Sensor Surface with Antifouling Properties for Highly Sensitive Detection of 2,4,6-Trinitrotoluene Using Surface-Initiated Atom Transfer Polymerization
Sensors 2013, 13(7), 9294-9304; doi:10.3390/s130709294
Received: 9 May 2013 / Revised: 2 July 2013 / Accepted: 15 July 2013 / Published: 19 July 2013
Cited by 6 | PDF Full-text (725 KB) | HTML Full-text | XML Full-text
Abstract
In this study, we modified a surface plasmon resonance immunosensor chip with a polymer using surface-initiated atom transfer polymerization (SI-ATRP) for the highly sensitive detection of 2,4,6-trinitrotoluene (TNT). To immobilize a TNT analogue on the polymer, mono-2-(methacryloyloxy)ethylsuccinate (MES), which has a carboxyl [...] Read more.
In this study, we modified a surface plasmon resonance immunosensor chip with a polymer using surface-initiated atom transfer polymerization (SI-ATRP) for the highly sensitive detection of 2,4,6-trinitrotoluene (TNT). To immobilize a TNT analogue on the polymer, mono-2-(methacryloyloxy)ethylsuccinate (MES), which has a carboxyl group, was used in this study. However, the anti-TNT antibody may adsorb non-specifically on the polymer surface by an electrostatic interaction because MES is negatively charged. Therefore, a mixed monomer with MES and diethylaminoethylmethacrylate (DEAEM), which has a tertiary amino group and is positively charged, was prepared to obtain electroneutrality for suppressing the nonspecific adsorption. The detection of TNT was performed by inhibition assay using the polymer surface. To ensure high sensitivity to TNT, the affinity between the surface and the antibody was optimized by controlling the density of the initiator for ATRP by mixing two types of self-assembled monolayer reagents. As a result, a limit of detection of 5.7 pg/mL (ppt) for TNT was achieved using the optimized surface. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Investigation of Tree Spectral Reflectance Characteristics Using a Mobile Terrestrial Line Spectrometer and Laser Scanner
Sensors 2013, 13(7), 9305-9320; doi:10.3390/s130709305
Received: 3 June 2013 / Revised: 10 July 2013 / Accepted: 16 July 2013 / Published: 19 July 2013
Cited by 5 | PDF Full-text (1015 KB) | HTML Full-text | XML Full-text
Abstract
In mobile terrestrial hyperspectral imaging, individual trees often present large variations in spectral reflectance that may impact the relevant applications, but the related studies have been seldom reported. To fill this gap, this study was dedicated to investigating the spectral reflectance characteristics [...] Read more.
In mobile terrestrial hyperspectral imaging, individual trees often present large variations in spectral reflectance that may impact the relevant applications, but the related studies have been seldom reported. To fill this gap, this study was dedicated to investigating the spectral reflectance characteristics of individual trees with a Sensei mobile mapping system, which comprises a Specim line spectrometer and an Ibeo Lux laser scanner. The addition of the latter unit facilitates recording the structural characteristics of the target trees synchronously, and this is beneficial for revealing the characteristics of the spatial distributions of tree spectral reflectance with variations at different levels. Then, the parts of trees with relatively low-level variations can be extracted. At the same time, since it is difficult to manipulate the whole spectrum, the traditional concept of vegetation indices (VI) based on some particular spectral bands was taken into account here. Whether the assumed VIs capable of behaving consistently for the whole crown of each tree was also checked. The specific analyses were deployed based on four deciduous tree species and six kinds of VIs. The test showed that with the help of the laser scanner data, the parts of individual trees with relatively low-level variations can be located. Based on these parts, the relatively stable spectral reflectance characteristics for different tree species can be learnt. Full article
(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)
Open AccessArticle Three Dimensional Gait Analysis Using Wearable Acceleration and Gyro Sensors Based on Quaternion Calculations
Sensors 2013, 13(7), 9321-9343; doi:10.3390/s130709321
Received: 3 June 2013 / Revised: 11 July 2013 / Accepted: 17 July 2013 / Published: 19 July 2013
Cited by 22 | PDF Full-text (2422 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a method for three dimensional gait analysis using wearable sensors and quaternion calculations. Seven sensor units consisting of a tri-axial acceleration and gyro sensors, were fixed to the lower limbs. The acceleration and angular velocity data of each sensor [...] Read more.
This paper proposes a method for three dimensional gait analysis using wearable sensors and quaternion calculations. Seven sensor units consisting of a tri-axial acceleration and gyro sensors, were fixed to the lower limbs. The acceleration and angular velocity data of each sensor unit were measured during level walking. The initial orientations of the sensor units were estimated using acceleration data during upright standing position and the angular displacements were estimated afterwards using angular velocity data during gait. Here, an algorithm based on quaternion calculation was implemented for orientation estimation of the sensor units. The orientations of the sensor units were converted to the orientations of the body segments by a rotation matrix obtained from a calibration trial. Body segment orientations were then used for constructing a three dimensional wire frame animation of the volunteers during the gait. Gait analysis was conducted on five volunteers, and results were compared with those from a camera-based motion analysis system. Comparisons were made for the joint trajectory in the horizontal and sagittal plane. The average RMSE and correlation coefficient (CC) were 10.14 deg and 0.98, 7.88 deg and 0.97, 9.75 deg and 0.78 for the hip, knee and ankle flexion angles, respectively. Full article
(This article belongs to the Special Issue Wearable Gait Sensors)
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Open AccessArticle Effect of Tensile Strain on Thermal Conductivity in Monolayer Graphene Nanoribbons: A Molecular Dynamics Study
Sensors 2013, 13(7), 9388-9395; doi:10.3390/s130709388
Received: 14 May 2013 / Revised: 12 July 2013 / Accepted: 15 July 2013 / Published: 22 July 2013
Cited by 5 | PDF Full-text (459 KB) | HTML Full-text | XML Full-text
Abstract
The thermal conductivity of monolayer graphene nanoribbons (GNRs) with different tensile strain is investigated by using a nonequilibrium molecular dynamics method. Significant increasing amplitude of the molecular thermal vibration, molecular potential energy vibration and thermal conductivity vibration of stretching GNRs were detected. [...] Read more.
The thermal conductivity of monolayer graphene nanoribbons (GNRs) with different tensile strain is investigated by using a nonequilibrium molecular dynamics method. Significant increasing amplitude of the molecular thermal vibration, molecular potential energy vibration and thermal conductivity vibration of stretching GNRs were detected. Some 20%~30% thermal conductivity decay is found in 9%~15% tensile strain of GNR cases. It is explained by the fact that GNR structural ridges scatter some low-frequency phonons which pass in the direction perpendicular to the direction of GNR stretching which was indicated by a phonon density of state investigation. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Mobile Robots Experimental Environment with Event-Based Wireless Communication
Sensors 2013, 13(7), 9396-9413; doi:10.3390/s130709396
Received: 15 May 2013 / Revised: 12 July 2013 / Accepted: 18 July 2013 / Published: 22 July 2013
Cited by 7 | PDF Full-text (489 KB) | HTML Full-text | XML Full-text
Abstract
An experimental platform to communicate between a set of mobile robots through a wireless network has been developed. The mobile robots get their position through a camera which performs as sensor. The video images are processed in a PC and a Waspmote [...] Read more.
An experimental platform to communicate between a set of mobile robots through a wireless network has been developed. The mobile robots get their position through a camera which performs as sensor. The video images are processed in a PC and a Waspmote card sends the corresponding position to each robot using the ZigBee standard. A distributed control algorithm based on event-triggered communications has been designed and implemented to bring the robots into the desired formation. Each robot communicates to its neighbors only at event times. Furthermore, a simulation tool has been developed to design and perform experiments with the system. An example of usage is presented. Full article
Open AccessArticle Electric Field and Current Transport Mechanisms in Schottky CdTe X-ray Detectors under Perturbing Optical Radiation
Sensors 2013, 13(7), 9414-9434; doi:10.3390/s130709414
Received: 28 May 2013 / Revised: 12 July 2013 / Accepted: 19 July 2013 / Published: 22 July 2013
Cited by 3 | PDF Full-text (872 KB) | HTML Full-text | XML Full-text
Abstract
Schottky CdTe X-ray detectors exhibit excellent spectroscopic performance but suffer from instabilities. Hence it is of extreme relevance to investigate their electrical properties. A systematic study of the electric field distribution and the current flowing in such detectors under optical perturbations is [...] Read more.
Schottky CdTe X-ray detectors exhibit excellent spectroscopic performance but suffer from instabilities. Hence it is of extreme relevance to investigate their electrical properties. A systematic study of the electric field distribution and the current flowing in such detectors under optical perturbations is presented here. The detector response is explored by varying experimental parameters, such as voltage, temperature, and radiation wavelength. The strongest perturbation is observed under 850 nm irradiation, bulk carrier recombination becoming effective there. Cathode and anode irradiations evidence the crucial role of the contacts, the cathode being Ohmic and the anode blocking. In particular, under irradiation of the cathode, charge injection occurs and peculiar kinks, typical of trap filling, are observed both in the current-voltage characteristic and during transients. The simultaneous access to the electric field and the current highlights the correlation between free and fixed charges, and unveils carrier transport/collection mechanisms otherwise hidden. Full article
(This article belongs to the Special Issue Photodetectors)
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Open AccessArticle BeiDou Inter-Satellite-Type Bias Evaluation and Calibration for Mixed Receiver Attitude Determination
Sensors 2013, 13(7), 9435-9463; doi:10.3390/s130709435
Received: 12 June 2013 / Revised: 12 July 2013 / Accepted: 16 July 2013 / Published: 22 July 2013
Cited by 18 | PDF Full-text (2084 KB) | HTML Full-text | XML Full-text
Abstract
The Chinese BeiDou system (BDS), having different types of satellites, is an important addition to the ever growing system of Global Navigation Satellite Systems (GNSS). It consists of Geostationary Earth Orbit (GEO) satellites, Inclined Geosynchronous Satellite Orbit (IGSO) satellites and Medium Earth [...] Read more.
The Chinese BeiDou system (BDS), having different types of satellites, is an important addition to the ever growing system of Global Navigation Satellite Systems (GNSS). It consists of Geostationary Earth Orbit (GEO) satellites, Inclined Geosynchronous Satellite Orbit (IGSO) satellites and Medium Earth Orbit (MEO) satellites. This paper investigates the receiver-dependent bias between these satellite types, for which we coined the name “inter-satellite-type bias” (ISTB), and its impact on mixed receiver attitude determination. Assuming different receiver types may have different delays/biases for different satellite types, we model the differential ISTBs among three BeiDou satellite types and investigate their existence and their impact on mixed receiver attitude determination. Our analyses using the real data sets from Curtin’s GNSS array consisting of different types of BeiDou enabled receivers and series of zero-baseline experiments with BeiDou-enabled receivers reveal the existence of non-zero ISTBs between different BeiDou satellite types. We then analyse the impact of these biases on BeiDou-only attitude determination using the constrained (C-)LAMBDA method, which exploits the knowledge of baseline length. Results demonstrate that these biases could seriously affect the integer ambiguity resolution for attitude determination using mixed receiver types and that a priori correction of these biases will dramatically improve the success rate. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Photo-Detectors Integrated with Resonant Tunneling Diodes
Sensors 2013, 13(7), 9464-9482; doi:10.3390/s130709464
Received: 14 June 2013 / Revised: 9 July 2013 / Accepted: 16 July 2013 / Published: 22 July 2013
Cited by 6 | PDF Full-text (1873 KB) | HTML Full-text | XML Full-text
Abstract
We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 μm in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the [...] Read more.
We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 μm in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR) region. The resonant tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD’s NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems. Full article
(This article belongs to the Special Issue Photodetectors)
Open AccessArticle Fixed-Base Comb with Window-Non-Adjacent Form (NAF) Method for Scalar Multiplication
Sensors 2013, 13(7), 9483-9512; doi:10.3390/s130709483
Received: 23 May 2013 / Revised: 12 July 2013 / Accepted: 16 July 2013 / Published: 23 July 2013
PDF Full-text (7148 KB) | HTML Full-text | XML Full-text
Abstract
Elliptic curve cryptography (ECC) is one of the most promising public-key techniques in terms of short key size and various crypto protocols. For this reason, many studies on the implementation of ECC on resource-constrained devices within a practical execution time have been [...] Read more.
Elliptic curve cryptography (ECC) is one of the most promising public-key techniques in terms of short key size and various crypto protocols. For this reason, many studies on the implementation of ECC on resource-constrained devices within a practical execution time have been conducted. To this end, we must focus on scalar multiplication, which is the most expensive operation in ECC. A number of studies have proposed pre-computation and advanced scalar multiplication using a non-adjacent form (NAF) representation, and more sophisticated approaches have employed a width-w NAF representation and a modified pre-computation table. In this paper, we propose a new pre-computation method in which zero occurrences are much more frequent than in previous methods. This method can be applied to ordinary group scalar multiplication, but it requires large pre-computation table, so we combined the previous method with ours for practical purposes. This novel structure establishes a new feature that adjusts speed performance and table size finely, so we can customize the pre-computation table for our own purposes. Finally, we can establish a customized look-up table for embedded microprocessors. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Further In-vitro Characterization of an Implantable Biosensor for Ethanol Monitoring in the Brain
Sensors 2013, 13(7), 9522-9535; doi:10.3390/s130709522
Received: 5 June 2013 / Revised: 4 July 2013 / Accepted: 17 July 2013 / Published: 23 July 2013
Cited by 2 | PDF Full-text (526 KB) | HTML Full-text | XML Full-text
Abstract
Ethyl alcohol may be considered one of the most widespread central nervous system (CNS) depressants in Western countries. Because of its toxicological and neurobiological implications, the detection of ethanol in brain extracellular fluid (ECF) is of great importance. In a previous study, [...] Read more.
Ethyl alcohol may be considered one of the most widespread central nervous system (CNS) depressants in Western countries. Because of its toxicological and neurobiological implications, the detection of ethanol in brain extracellular fluid (ECF) is of great importance. In a previous study, we described the development and characterization of an implantable biosensor successfully used for the real-time detection of ethanol in the brain of freely-moving rats. The implanted biosensor, integrated in a low-cost telemetry system, was demonstrated to be a reliable device for the short-time monitoring of exogenous ethanol in brain ECF. In this paper we describe a further in-vitro characterization of the above-mentioned biosensor in terms of oxygen, pH and temperature dependence in order to complete its validation. With the aim of enhancing ethanol biosensor performance, different enzyme loadings were investigated in terms of apparent ethanol Michaelis-Menten kinetic parameters, viz. IMAX, KM and linear region slope, as well as ascorbic acid interference shielding. The responses of biosensors were studied over a period of 28 days. The overall findings of the present study confirm the original biosensor configuration to be the best of those investigated for in-vivo applications up to one week after implantation. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Temperature-Insensitive Bend Sensor Using Entirely Centered Erbium Doping in the Fiber Core
Sensors 2013, 13(7), 9536-9546; doi:10.3390/s130709536
Received: 3 June 2013 / Revised: 15 July 2013 / Accepted: 17 July 2013 / Published: 23 July 2013
Cited by 4 | PDF Full-text (785 KB) | HTML Full-text | XML Full-text
Abstract
A fiber based bend sensor using a uniquely designed Bend-Sensitive Erbium Doped Fiber (BSEDF) is proposed and demonstrated. The BSEDF has two core regions, namely an undoped outer region with a diameter of about 9.38 μm encompassing a doped, inner core region [...] Read more.
A fiber based bend sensor using a uniquely designed Bend-Sensitive Erbium Doped Fiber (BSEDF) is proposed and demonstrated. The BSEDF has two core regions, namely an undoped outer region with a diameter of about 9.38 μm encompassing a doped, inner core region with a diameter of 4.00 μm. The doped core region has about 400 ppm of an Er2O3 dopant. Pumping the BSEDF with a conventional 980 nm laser diode gives an Amplified Spontaneous Emission (ASE) spectrum spanning from 1,510 nm to over 1,560 nm at the output power level of about −58 dBm. The ASE spectrum has a peak power of −52 dBm at a central wavelength of 1,533 nm when not spooled. Spooling the BSEDF with diameters of 10 cm to 2 cm yields decreasing peak powers from −57.0 dBm to −61.8 dBm, while the central wavelength remains unchanged. The output is highly stable over time, with a low temperature sensitivity of around ~0.005 dBm/°C, thus allowing for the development of a highly stable sensor system based in the change of the peak power alone. Full article
(This article belongs to the Special Issue Optomechatronics) Print Edition available

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Open AccessReview Stop-and-Go Mode: Sensor Manipulation as Essential as Sensor Development in Terrestrial Laser Scanning
Sensors 2013, 13(7), 8140-8154; doi:10.3390/s130708140
Received: 8 May 2013 / Revised: 15 June 2013 / Accepted: 17 June 2013 / Published: 25 June 2013
Cited by 4 | PDF Full-text (288 KB) | HTML Full-text | XML Full-text
Abstract
This study was dedicated to illustrating the significance of sensor manipulation in the case of terrestrial laser scanning, which is a field now in quick development. In fact, this quickness was mainly rooted in the emergence of new sensors with better performance, [...] Read more.
This study was dedicated to illustrating the significance of sensor manipulation in the case of terrestrial laser scanning, which is a field now in quick development. In fact, this quickness was mainly rooted in the emergence of new sensors with better performance, while the implications of sensor manipulation have not been fully recognized by the whole community. For this technical gap, the stop-and-go mapping mode can be reckoned as one of the potential solution plans. Stop-and-go was first proposed to handle the low efficiency of traditional static terrestrial laser scanning, and then, it was re-emphasized to improve the stability of sample collections for the state-of-the-art technology of mobile laser scanning. This work reviewed the previous efforts of trying the stop-and-go mode for improving the performance of static and mobile terrestrial laser scanning and generalized their principles respectively. This work also analyzed its advantages compared to the fully-static and fully-kinematic terrestrial laser scanning, and suggested the plans with more automatic measures for raising the efficacy of terrestrial laser scanning. Overall, this literature review indicated that the stop-and-go mapping mode as a case with generic sense can verify the presumption of sensor manipulation as essential as sensor development. Full article
(This article belongs to the Section Physical Sensors)
Open AccessReview Fibre Optic Sensors for Selected Wastewater Characteristics
Sensors 2013, 13(7), 8640-8668; doi:10.3390/s130708640
Received: 16 May 2013 / Revised: 20 June 2013 / Accepted: 21 June 2013 / Published: 5 July 2013
Cited by 12 | PDF Full-text (1099 KB) | HTML Full-text | XML Full-text
Abstract
Demand for online and real-time measurements techniques to meet environmental regulation and treatment compliance are increasing. However the conventional techniques, which involve scheduled sampling and chemical analysis can be expensive and time consuming. Therefore cheaper and faster alternatives to monitor wastewater characteristics [...] Read more.
Demand for online and real-time measurements techniques to meet environmental regulation and treatment compliance are increasing. However the conventional techniques, which involve scheduled sampling and chemical analysis can be expensive and time consuming. Therefore cheaper and faster alternatives to monitor wastewater characteristics are required as alternatives to conventional methods. This paper reviews existing conventional techniques and optical and fibre optic sensors to determine selected wastewater characteristics which are colour, Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD). The review confirms that with appropriate configuration, calibration and fibre features the parameters can be determined with accuracy comparable to conventional method. With more research in this area, the potential for using FOS for online and real-time measurement of more wastewater parameters for various types of industrial effluent are promising. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessReview Fluorosomes: Fluorescent Virus-Like Nanoparticles that Represent a Convenient Tool to Visualize Receptor-Ligand Interactions
Sensors 2013, 13(7), 8722-8749; doi:10.3390/s130708722
Received: 7 June 2013 / Revised: 28 June 2013 / Accepted: 5 July 2013 / Published: 8 July 2013
Cited by 4 | PDF Full-text (703 KB) | HTML Full-text | XML Full-text
Abstract
Viruses are the smallest life forms and parasitize on many eukaryotic organisms, including humans. Consequently, the study of viruses and viral diseases has had an enormous impact on diverse fields of biology and medicine. Due to their often pathogenic properties, viruses have [...] Read more.
Viruses are the smallest life forms and parasitize on many eukaryotic organisms, including humans. Consequently, the study of viruses and viral diseases has had an enormous impact on diverse fields of biology and medicine. Due to their often pathogenic properties, viruses have not only had a strong impact on the development of immune cells but also on shaping entire immune mechanisms in their hosts. In order to better characterize virus-specific surface receptors, pathways of virus entry and the mechanisms of virus assembly, diverse methods to visualize virus particles themselves have been developed in the past decades. Apart from characterization of virus-specific mechanisms, fluorescent virus particles also serve as valuable platforms to study receptor-ligand interactions. Along those lines the authors have developed non-infectious virus-like nanoparticles (VNP), which can be decorated with immune receptors of choice and used for probing receptor-ligand interactions, an especially interesting application in the field of basic but also applied immunology research. To be able to better trace receptor-decorated VNP the authors have developed technology to introduce fluorescent proteins into such particles and henceforth termed them fluorosomes (FS). Since VNP are assembled in a simple expression system relying on HEK-293 cells, gene-products of interest can be assembled in a simple and straightforward fashion—one of the reasons why the authors like to call fluorosomes ‘the poor-man’s staining tool’. Within this review article an overview on virus particle assembly, chemical and recombinant methods of virus particle labeling and examples on how FS can be applied as sensors to monitor receptor-ligand interactions on leukocytes are given. Full article
Open AccessReview Dental Optical Coherence Tomography
Sensors 2013, 13(7), 8928-8949; doi:10.3390/s130708928
Received: 28 May 2013 / Revised: 20 June 2013 / Accepted: 20 June 2013 / Published: 12 July 2013
Cited by 14 | PDF Full-text (1481 KB) | HTML Full-text | XML Full-text
Abstract
This review paper describes the applications of dental optical coherence tomography (OCT) in oral tissue images, caries, periodontal disease and oral cancer. The background of OCT, including basic theory, system setup, light sources, spatial resolution and system limitations, is provided. The comparisons [...] Read more.
This review paper describes the applications of dental optical coherence tomography (OCT) in oral tissue images, caries, periodontal disease and oral cancer. The background of OCT, including basic theory, system setup, light sources, spatial resolution and system limitations, is provided. The comparisons between OCT and other clinical oral diagnostic methods are also discussed. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
Open AccessReview Microarray Dot Electrodes Utilizing Dielectrophoresis for Cell Characterization
Sensors 2013, 13(7), 9029-9046; doi:10.3390/s130709029
Received: 7 May 2013 / Revised: 30 May 2013 / Accepted: 14 June 2013 / Published: 12 July 2013
Cited by 5 | PDF Full-text (785 KB) | HTML Full-text | XML Full-text
Abstract
During the last three decades; dielectrophoresis (DEP) has become a vital tool for cell manipulation and characterization due to its non-invasiveness. It is very useful in the trend towards point-of-care systems. Currently, most efforts are focused on using DEP in biomedical applications, [...] Read more.
During the last three decades; dielectrophoresis (DEP) has become a vital tool for cell manipulation and characterization due to its non-invasiveness. It is very useful in the trend towards point-of-care systems. Currently, most efforts are focused on using DEP in biomedical applications, such as the spatial manipulation of cells, the selective separation or enrichment of target cells, high-throughput molecular screening, biosensors and immunoassays. A significant amount of research on DEP has produced a wide range of microelectrode configurations. In this paper; we describe the microarray dot electrode, a promising electrode geometry to characterize and manipulate cells via DEP. The advantages offered by this type of microelectrode are also reviewed. The protocol for fabricating planar microelectrodes using photolithography is documented to demonstrate the fast and cost-effective fabrication process. Additionally; different state-of-the-art Lab-on-a-Chip (LOC) devices that have been proposed for DEP applications in the literature are reviewed. We also present our recently designed LOC device, which uses an improved microarray dot electrode configuration to address the challenges facing other devices. This type of LOC system has the capability to boost the implementation of DEP technology in practical settings such as clinical cell sorting, infection diagnosis, and enrichment of particle populations for drug development. Full article
(This article belongs to the Special Issue Ultramicroelectrode Electrochemistry - Theory and Applications)
Open AccessReview Sensors and Sensory Processing for Airborne Vibrations in Silk Moths and Honeybees
Sensors 2013, 13(7), 9344-9363; doi:10.3390/s130709344
Received: 9 May 2013 / Revised: 2 July 2013 / Accepted: 13 July 2013 / Published: 19 July 2013
Cited by 1 | PDF Full-text (1026 KB) | HTML Full-text | XML Full-text
Abstract
Insects use airborne vibrations caused by their own movements to control their behaviors and produce airborne vibrations to communicate with conspecific mates. In this review, I use two examples to introduce how insects use airborne vibrations to accurately control behavior or for [...] Read more.
Insects use airborne vibrations caused by their own movements to control their behaviors and produce airborne vibrations to communicate with conspecific mates. In this review, I use two examples to introduce how insects use airborne vibrations to accurately control behavior or for communication. The first example is vibration-sensitive sensilla along the wing margin that stabilize wingbeat frequency. There are two specialized sensors along the wing margin for detecting the airborne vibration caused by wingbeats. The response properties of these sensors suggest that each sensor plays a different role in the control of wingbeats. The second example is Johnston’s organ that contributes to regulating flying speed and perceiving vector information about food sources to hive-mates. There are parallel vibration processing pathways in the central nervous system related with these behaviors, flight and communication. Both examples indicate that the frequency of airborne vibration are filtered on the sensory level and that on the central nervous system level, the extracted vibration signals are integrated with other sensory signals for executing quick adaptive motor response. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan 2012)
Open AccessReview In-Plane Resonant Nano-Electro-Mechanical Sensors: A Comprehensive Study on Design, Fabrication and Characterization Challenges
Sensors 2013, 13(7), 9364-9387; doi:10.3390/s130709364
Received: 9 June 2013 / Revised: 12 July 2013 / Accepted: 18 July 2013 / Published: 22 July 2013
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Abstract
The newly proposed in-plane resonant nano-electro-mechanical (IP R-NEM) sensor, that includes a doubly clamped suspended beam and two side electrodes, achieved a mass sensitivity of less than zepto g/Hz based on analytical and numerical analyses. The high frequency characterization and numerical/analytical studies [...] Read more.
The newly proposed in-plane resonant nano-electro-mechanical (IP R-NEM) sensor, that includes a doubly clamped suspended beam and two side electrodes, achieved a mass sensitivity of less than zepto g/Hz based on analytical and numerical analyses. The high frequency characterization and numerical/analytical studies of the fabricated sensor show that the high vacuum measurement environment will ease the resonance detection using the capacitance detection technique if only the thermoelsatic damping plays a dominant role for the total quality factor of the sensor. The usage of the intrinsic junction-less field-effect-transistor (JL FET) for the resonance detection of the sensor provides a more practical detection method for this sensor. As the second proposed sensor, the introduction of the monolithically integrated in-plane MOSFET with the suspended beam provides another solution for the ease of resonance frequency detection with similar operation to the junction-less transistor in the IP R-NEM sensor. The challenging fabrication technology for the in-plane resonant suspended gate field-effect-transistor (IP RSG-FET) sensor results in some post processing and simulation steps to fully explore and improve the direct current (DC) characteristics of the sensor for the consequent high frequency measurement. The results of modeling and characterization in this research provide a realistic guideline for these potential ultra-sensitive NEM sensors. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in the UK 2013)
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Open AccessLetter An In-situ Real-Time Optical Fiber Sensor Based on Surface Plasmon Resonance for Monitoring the Growth of TiO2 Thin Films
Sensors 2013, 13(7), 9513-9521; doi:10.3390/s130709513
Received: 19 June 2013 / Revised: 12 July 2013 / Accepted: 18 July 2013 / Published: 23 July 2013
Cited by 4 | PDF Full-text (511 KB) | HTML Full-text | XML Full-text
Abstract
An optical fiber sensor based on surface plasmon resonance (SPR) is proposed for monitoring the thickness of deposited nano-thin films. A side-polished multimode SPR optical fiber sensor with an 850 nm-LD is used as the transducing element for real-time monitoring of the [...] Read more.
An optical fiber sensor based on surface plasmon resonance (SPR) is proposed for monitoring the thickness of deposited nano-thin films. A side-polished multimode SPR optical fiber sensor with an 850 nm-LD is used as the transducing element for real-time monitoring of the deposited TiO2 thin films. The SPR optical fiber sensor was installed in the TiO2 sputtering system in order to measure the thickness of the deposited sample during TiO2 deposition. The SPR response declined in real-time in relation to the growth of the thickness of the TiO2 thin film. Our results show the same trend of the SPR response in real-time and in spectra taken before and after deposition. The SPR transmitted intensity changes by approximately 18.76% corresponding to 50 nm of deposited TiO2 thin film. We have shown that optical fiber sensors utilizing SPR have the potential for real-time monitoring of the SPR technology of nanometer film thickness. The compact size of the SPR fiber sensor enables it to be positioned inside the deposition chamber, and it could thus measure the film thickness directly in real-time. This technology also has potential application for monitoring the deposition of other materials. Moreover, in-situ real-time SPR optical fiber sensor technology is in inexpensive, disposable technique that has anti-interference properties, and the potential to enable on-line monitoring and monitoring of organic coatings. Full article
(This article belongs to the Special Issue Optomechatronics) Print Edition available
Open AccessCorrection Correction: Ferreira, P.M., et al. A Neural Network Based Intelligent Predictive Sensor for Cloudiness, Solar Radiation and Air Temperature. Sensors 2012, 12, 15750–15777
Sensors 2013, 13(7), 9547-9548; doi:10.3390/s130709547
Received: 17 June 2013 / Revised: 18 June 2013 / Accepted: 18 June 2013 / Published: 23 July 2013
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Abstract The authors would like to correct the acknowledgements of this article [1] as follows: [...] Full article
(This article belongs to the Section Chemical Sensors)

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