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Sensors, Volume 12, Issue 8 (August 2012), Pages 9951-11434

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Editorial

Jump to: Research, Review, Other

Open AccessEditorial Sensorial Systems Applied to Intelligent Spaces
Sensors 2012, 12(8), 10707-10712; doi:10.3390/s120810707
Received: 31 July 2012 / Accepted: 1 August 2012 / Published: 6 August 2012
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Abstract
The definition of “Intelligent Space” (IS) was formerly proposed for an environmental system capable of offering humans informative and physical support. Currently an IS denotes a space containing human and artificial systems, the space itself being considered an intelligent system. Human and [...] Read more.
The definition of “Intelligent Space” (IS) was formerly proposed for an environmental system capable of offering humans informative and physical support. Currently an IS denotes a space containing human and artificial systems, the space itself being considered an intelligent system. Human and artificial systems become clients of the IS and simultaneously the artificial systems become agents of the IS. Since the whole space is an intelligent system, it is able to monitor and provide services to many different clients with ease. For example, an IS uses electronic displays to provide information to humans, then robots are used to offer physical services to them as physical agents. [...] Full article
(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)

Research

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Open AccessArticle Vehicle Unpaved Road Response Spectrum Acquisition Based on Accelerometer and GPS Data
Sensors 2012, 12(8), 9951-9964; doi:10.3390/s120809951
Received: 10 April 2012 / Revised: 6 July 2012 / Accepted: 16 July 2012 / Published: 25 July 2012
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Abstract
This paper describes a response acquisition system composed of some spindle accelerometers and a time synchronized on-board GPS receiver developed in order to collect the dynamic response of vehicle riding on an unpaved road. A method of time-space conversion for calculating the [...] Read more.
This paper describes a response acquisition system composed of some spindle accelerometers and a time synchronized on-board GPS receiver developed in order to collect the dynamic response of vehicle riding on an unpaved road. A method of time-space conversion for calculating the response spectrum is proposed to eliminate the adverse effect of time-varying speed, based on the transform from the equitime sampled spindle acceleration responses to equidistance sampling. By using two groups of independent distance histories acquired from GPS, a method called long-range error correction is proposed to improve the accuracy of the vehicle’s distance information, which is critical for the time-space conversion. The accuracy and limitations of the system have been analyzed, and its validity has been verified by implementing the system on a wheel loader for road response spectrum measuring. This paper offers a practical approach to obtaining unpaved road response spectra for durability road simulation. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Validation of SMOS Soil Moisture Products over the Maqu and Twente Regions
Sensors 2012, 12(8), 9965-9986; doi:10.3390/s120809965
Received: 4 June 2012 / Revised: 4 July 2012 / Accepted: 18 July 2012 / Published: 25 July 2012
Cited by 22 | PDF Full-text (4492 KB) | HTML Full-text | XML Full-text
Abstract
The validation of Soil Moisture and Ocean Salinity (SMOS) soil moisture products is a crucial step in the investigation of their inaccuracies and limitations, before planning further refinements of the retrieval algorithm. Therefore, this study intended to contribute to the validation of [...] Read more.
The validation of Soil Moisture and Ocean Salinity (SMOS) soil moisture products is a crucial step in the investigation of their inaccuracies and limitations, before planning further refinements of the retrieval algorithm. Therefore, this study intended to contribute to the validation of the SMOS soil moisture products, by comparing them with the data collected in situ in the Maqu (China) and Twente (The Netherlands) regions in 2010. The seasonal behavior of the SMOS soil moisture products is generally in agreement with the in situ measurements for both regions. However, the validation analysis resulted in determination coefficients of 0.55 and 0.51 over the Maqu and Twente region, respectively, for the ascending pass data, and of 0.24 and 0.41, respectively, for the descending pass data. Moreover, a systematic dry bias of the SMOS soil moisture was found of approximately 0.13 m3/m3 for the Maqu region and 0.17 m3/m3 for the Twente region for ascending pass data. Several factors might have affected the retrieval accuracy, such as the presence of Radio Frequency Interference (RFI), the use of inaccurate land cover information and the presence of frozen soils not correctly detected in winter. Improving the RFI filtering method and the quality of the retrieval algorithm inputs, such as land surface temperature and land cover, would certainly improve the accuracy of the retrieved soil moisture. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Experimental Estimating Deflection of a Simple Beam Bridge Model Using Grating Eddy Current Sensors
Sensors 2012, 12(8), 9987-10000; doi:10.3390/s120809987
Received: 10 June 2012 / Revised: 1 July 2012 / Accepted: 9 July 2012 / Published: 25 July 2012
Cited by 5 | PDF Full-text (615 KB) | HTML Full-text | XML Full-text
Abstract
A novel three-point method using a grating eddy current absolute position sensor (GECS) for bridge deflection estimation is proposed in this paper. Real spatial positions of the measuring points along the span axis are directly used as relative reference points of each [...] Read more.
A novel three-point method using a grating eddy current absolute position sensor (GECS) for bridge deflection estimation is proposed in this paper. Real spatial positions of the measuring points along the span axis are directly used as relative reference points of each other rather than using any other auxiliary static reference points for measuring devices in a conventional method. Every three adjacent measuring points are defined as a measuring unit and a straight connecting bar with a GECS fixed on the center section of it links the two endpoints. In each measuring unit, the displacement of the mid-measuring point relative to the connecting bar measured by the GECS is defined as the relative deflection. Absolute deflections of each measuring point can be calculated from the relative deflections of all the measuring units directly without any correcting approaches. Principles of the three-point method and displacement measurement of the GECS are introduced in detail. Both static and dynamic experiments have been carried out on a simple beam bridge model, which demonstrate that the three-point deflection estimation method using the GECS is effective and offers a reliable way for bridge deflection estimation, especially for long-term monitoring. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Research on a Novel Low Modulus OFBG Strain Sensor for Pavement Monitoring
Sensors 2012, 12(8), 10001-10013; doi:10.3390/s120810001
Received: 25 June 2012 / Revised: 16 July 2012 / Accepted: 17 July 2012 / Published: 25 July 2012
Cited by 3 | PDF Full-text (671 KB) | HTML Full-text | XML Full-text
Abstract
Because of the fatigue and deflection damage of asphalt pavement, it is very important for researchers to monitor the strain response of asphalt layers in service under vehicle loads, so in this paper a novel polypropylene based OFBG (Optical Fiber Bragg Gratings) [...] Read more.
Because of the fatigue and deflection damage of asphalt pavement, it is very important for researchers to monitor the strain response of asphalt layers in service under vehicle loads, so in this paper a novel polypropylene based OFBG (Optical Fiber Bragg Gratings) strain sensor with low modulus and large strain sensing scale was designed and fabricated. PP with MA-G-PP is used to package OFBG. The fabrication techniques, the physical properties and the sensing properties were tested. The experimental results show that this kind of new OFBG strain sensor is a wonderful sensor with low modulus (about 1 GPa) and good sensitivity, which would meet the needs for monitoring some low modulus materials or structures. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Wireless Interface for Replacing the Cables in Bridge-Sensor Applications
Sensors 2012, 12(8), 10014-10033; doi:10.3390/s120810014
Received: 18 June 2012 / Revised: 13 July 2012 / Accepted: 16 July 2012 / Published: 25 July 2012
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Abstract
This paper presents a solution in which a wireless interface is employed to replace the cables in bridge-sensor measurement applications. The most noticeable feature of the presented approach is the fact that the wireless interface simply replaces the cables without any additional [...] Read more.
This paper presents a solution in which a wireless interface is employed to replace the cables in bridge-sensor measurement applications. The most noticeable feature of the presented approach is the fact that the wireless interface simply replaces the cables without any additional hardware modification to the existing system. In this approach, the concept of reciprocal topology is employed, where the transmitter side acquires signals with its own transfer function and the receiver side reconstructs them with the transfer function reciprocal to the transmitter transfer function. In this paper the principle of data acquisition and reconstruction is described together with the implementation details of the signal transfer from the sensor to the signal-monitoring equipment. The wireless data communication was investigated and proprietary data-reduction methods were developed. The proposed methods and algorithms were implemented using two different wireless technologies. The performance was evaluated with a dedicated data-acquisition system and finally, the test results were analyzed. The two different sets of results indicated the high level of amplitude and the temporal accuracy of the wirelessly transferred sensor signals. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Fabrication of High Sensitivity Carbon Microcoil Pressure Sensors
Sensors 2012, 12(8), 10034-10041; doi:10.3390/s120810034
Received: 1 July 2012 / Revised: 17 July 2012 / Accepted: 17 July 2012 / Published: 25 July 2012
Cited by 6 | PDF Full-text (628 KB) | HTML Full-text | XML Full-text
Abstract
This work demonstrates a highly sensitive pressure sensor that was fabricated using carbon microcoils (CMCs) and polydimethylsiloxane (PDMS). CMCs were grown by chemical vapor deposition using various ratios of Fe-Sn catalytic solution. The pressure sensor has a sandwiched structure, in which the [...] Read more.
This work demonstrates a highly sensitive pressure sensor that was fabricated using carbon microcoils (CMCs) and polydimethylsiloxane (PDMS). CMCs were grown by chemical vapor deposition using various ratios of Fe-Sn catalytic solution. The pressure sensor has a sandwiched structure, in which the as-grown CMCs were inserted between two PDMS layers. The pressure sensor exhibits piezo-resistivity changes in response to mechanical loading using a load cell system. The yields of the growth of CMCs at a catalyst proportion of Fe:Sn = 95:5 reach 95%. Experimental results show that the sensor achieves a high sensitivity of 0.93%/kPa from the CMC yield of 95%. The sensitivity of the pressure sensor increases with increasing yield of CMCs. The demonstrated pressure sensor shows the advantage of high sensitivity and is suitable for mass production. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Low-Voltage 96 dB Snapshot CMOS Image Sensor with 4.5 nW Power Dissipation per Pixel
Sensors 2012, 12(8), 10067-10085; doi:10.3390/s120810067
Received: 21 May 2012 / Revised: 12 July 2012 / Accepted: 13 July 2012 / Published: 25 July 2012
Cited by 3 | PDF Full-text (803 KB) | HTML Full-text | XML Full-text
Abstract
Modern “smart” CMOS sensors have penetrated into various applications, such as surveillance systems, bio-medical applications, digital cameras, cellular phones and many others. Reducing the power of these sensors continuously challenges designers. In this paper, a low power global shutter CMOS image sensor [...] Read more.
Modern “smart” CMOS sensors have penetrated into various applications, such as surveillance systems, bio-medical applications, digital cameras, cellular phones and many others. Reducing the power of these sensors continuously challenges designers. In this paper, a low power global shutter CMOS image sensor with Wide Dynamic Range (WDR) ability is presented. This sensor features several power reduction techniques, including a dual voltage supply, a selective power down, transistors with different threshold voltages, a non-rationed logic, and a low voltage static memory. A combination of all these approaches has enabled the design of the low voltage “smart” image sensor, which is capable of reaching a remarkable dynamic range, while consuming very low power. The proposed power-saving solutions have allowed the maintenance of the standard architecture of the sensor, reducing both the time and the cost of the design. In order to maintain the image quality, a relation between the sensor performance and power has been analyzed and a mathematical model, describing the sensor Signal to Noise Ratio (SNR) and Dynamic Range (DR) as a function of the power supplies, is proposed. The described sensor was implemented in a 0.18 um CMOS process and successfully tested in the laboratory. An SNR of 48 dB and DR of 96 dB were achieved with a power dissipation of 4.5 nW per pixel. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Magnetic Properties of Liquid-Phase Sintered CoFe2O4 for Application in Magnetoelastic and Magnetoelectric Transducers
Sensors 2012, 12(8), 10086-10096; doi:10.3390/s120810086
Received: 31 May 2012 / Revised: 9 July 2012 / Accepted: 10 July 2012 / Published: 25 July 2012
Cited by 3 | PDF Full-text (495 KB) | HTML Full-text | XML Full-text
Abstract
Cobalt ferrite is a ferrimagnetic magnetostrictive ceramic that has potential application in magnetoelastic and magnetoelectric transducers. In this work, CoFe2O4 was obtained using a conventional ceramic method and Bi2O3 was used as additive in order to [...] Read more.
Cobalt ferrite is a ferrimagnetic magnetostrictive ceramic that has potential application in magnetoelastic and magnetoelectric transducers. In this work, CoFe2O4 was obtained using a conventional ceramic method and Bi2O3 was used as additive in order to obtain liquid-phase sintered samples. Bi2O3 was added to the ferrite in amounts ranging from 0.25 mol% to 0.45 mol% and samples were sintered at 900 °C and 950 °C. It was observed the presence of Bi-containing particles in the microstructure of the sintered samples and the magnetostriction results indicated microstructural anisotropy. It was verified that it is possible to get dense cobalt ferrites, liquid-phase sintered, with relative densities higher than 90% and with magnetostriction values very close to samples sintered without additives. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Label-Free Electrochemical Diagnosis of Viral Antigens with Genetically Engineered Fusion Protein
Sensors 2012, 12(8), 10097-10108; doi:10.3390/s120810097
Received: 10 May 2012 / Revised: 12 July 2012 / Accepted: 15 July 2012 / Published: 26 July 2012
Cited by 4 | PDF Full-text (429 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We have developed a simple electrochemical biosensing strategy for the label-free diagnosis of hepatitis B virus (HBV) on a gold electrode surface. Gold-binding polypeptide (GBP) fused with single-chain antibody (ScFv) against HBV surface antigen (HBsAg), in forms of genetically engineered protein, was [...] Read more.
We have developed a simple electrochemical biosensing strategy for the label-free diagnosis of hepatitis B virus (HBV) on a gold electrode surface. Gold-binding polypeptide (GBP) fused with single-chain antibody (ScFv) against HBV surface antigen (HBsAg), in forms of genetically engineered protein, was utilized. This GBP-ScFv fusion protein can directly bind onto the gold substrate with the strong binding affinity between the GBP and the gold surface, while the recognition site orients toward the sample for target binding at the same time. Furthermore, this one-step immobilization strategy greatly simplifies a fabrication process without any chemical modification as well as maintaining activity of biological recognition elements. This system allows specific immobilization of proteins and sensitive detection of targets, which were verified by surface plasmon resonance analysis and successfully applied to electrochemical cyclic voltammetry and impedance spectroscopy upto 0.14 ng/mL HBsAg. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle A Monotonic Degradation Assessment Index of Rolling Bearings Using Fuzzy Support Vector Data Description and Running Time
Sensors 2012, 12(8), 10109-10135; doi:10.3390/s120810109
Received: 6 June 2012 / Revised: 4 July 2012 / Accepted: 9 July 2012 / Published: 26 July 2012
Cited by 20 | PDF Full-text (937 KB) | HTML Full-text | XML Full-text
Abstract
Performance degradation assessment based on condition monitoring plays an important role in ensuring reliable operation of equipment, reducing production downtime and saving maintenance costs, yet performance degradation has strong fuzziness, and the dynamic information is random and fuzzy, making it a challenge [...] Read more.
Performance degradation assessment based on condition monitoring plays an important role in ensuring reliable operation of equipment, reducing production downtime and saving maintenance costs, yet performance degradation has strong fuzziness, and the dynamic information is random and fuzzy, making it a challenge how to assess the fuzzy bearing performance degradation. This study proposes a monotonic degradation assessment index of rolling bearings using fuzzy support vector data description (FSVDD) and running time. FSVDD constructs the fuzzy-monitoring coefficient which is sensitive to the initial defect and stably increases as faults develop. Moreover, the parameter describes the accelerating relationships between the damage development and running time. However, the index with an oscillating trend disagrees with the irreversible damage development. The running time is introduced to form a monotonic index, namely damage severity index (DSI). DSI inherits all advantages of and overcomes its disadvantage. A run-to-failure test is carried out to validate the performance of the proposed method. The results show that DSI reflects the growth of the damages with running time perfectly. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Synthesis of Bioactive Microcapsules Using a Microfluidic Device
Sensors 2012, 12(8), 10136-10147; doi:10.3390/s120810136
Received: 8 June 2012 / Revised: 4 July 2012 / Accepted: 18 July 2012 / Published: 26 July 2012
Cited by 7 | PDF Full-text (972 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Bioactive microcapsules containing Bacillus thuringiensis (BT) spores were generated by a combination of a hydro gel, microfluidic device and chemical polymerization method. As a proof-of-principle, we used BT spores displaying enhanced green fluorescent protein (EGFP) on the spore surface to [...] Read more.
Bioactive microcapsules containing Bacillus thuringiensis (BT) spores were generated by a combination of a hydro gel, microfluidic device and chemical polymerization method. As a proof-of-principle, we used BT spores displaying enhanced green fluorescent protein (EGFP) on the spore surface to spatially direct the EGFP-presenting spores within microcapsules. BT spore-encapsulated microdroplets of uniform size and shape are prepared through a flow-focusing method in a microfluidic device and converted into microcapsules through hydrogel polymerization. The size of microdroplets can be controlled by changing both the dispersion and continuous flow rate. Poly(N-isoproplyacrylamide) (PNIPAM), known as a hydrogel material, was employed as a biocompatible material for the encapsulation of BT spores and long-term storage and outstanding stability. Due to these unique properties of PNIPAM, the nutrients from Luria-Bertani complex medium diffused into the microcapsules and the microencapsulated spores germinated into vegetative cells under adequate environmental conditions. These results suggest that there is no limitation of transferring low-molecular-weight-substrates through the PNIPAM structures, and the viability of microencapsulated spores was confirmed by the culture of vegetative cells after the germinations. This microfluidic-based microencapsulation methodology provides a unique way of synthesizing bioactive microcapsules in a one-step process. This microfluidic-based strategy would be potentially suitable to produce microcapsules of various microbial spores for on-site biosensor analysis. Full article
(This article belongs to the Special Issue Live Cell-Based Sensors)
Open AccessArticle On-Line Estimation of Laser-Drilled Hole Depth Using a Machine Vision Method
Sensors 2012, 12(8), 10148-10162; doi:10.3390/s120810148
Received: 7 June 2012 / Revised: 23 July 2012 / Accepted: 23 July 2012 / Published: 27 July 2012
Cited by 6 | PDF Full-text (1867 KB) | HTML Full-text | XML Full-text
Abstract
The paper presents a novel method for monitoring and estimating the depth of a laser-drilled hole using machine vision. Through on-line image acquisition and analysis in laser machining processes, we could simultaneously obtain correlations between the machining processes and analyzed images. Based [...] Read more.
The paper presents a novel method for monitoring and estimating the depth of a laser-drilled hole using machine vision. Through on-line image acquisition and analysis in laser machining processes, we could simultaneously obtain correlations between the machining processes and analyzed images. Based on the machine vision method, the depths of laser-machined holes could be estimated in real time. Therefore, a low cost on-line inspection system is developed to increase productivity. All of the processing work was performed in air under standard atmospheric conditions and gas assist was used. A correlation between the cumulative size of the laser-induced plasma region and the depth of the hole is presented. The result indicates that the estimated depths of the laser-drilled holes were a linear function of the cumulative plasma size, with a high degree of confidence. This research provides a novel machine vision-based method for estimating the depths of laser-drilled holes in real time. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Search Strategy of Level-Based Flooding for the Internet of Things
Sensors 2012, 12(8), 10163-10195; doi:10.3390/s120810163
Received: 18 May 2012 / Revised: 18 July 2012 / Accepted: 20 July 2012 / Published: 27 July 2012
Cited by 4 | PDF Full-text (612 KB) | HTML Full-text | XML Full-text
Abstract
This paper deals with the query problem in the Internet of Things (IoT). Flooding is an important query strategy. However, original flooding is prone to cause heavy network loads. To address this problem, we propose a variant of flooding, called Level-Based Flooding [...] Read more.
This paper deals with the query problem in the Internet of Things (IoT). Flooding is an important query strategy. However, original flooding is prone to cause heavy network loads. To address this problem, we propose a variant of flooding, called Level-Based Flooding (LBF). With LBF, the whole network is divided into several levels according to the distances (i.e., hops) between the sensor nodes and the sink node. The sink node knows the level information of each node. Query packets are broadcast in the network according to the levels of nodes. Upon receiving a query packet, sensor nodes decide how to process it according to the percentage of neighbors that have processed it. When the target node receives the query packet, it sends its data back to the sink node via random walk. We show by extensive simulations that the performance of LBF in terms of cost and latency is much better than that of original flooding, and LBF can be used in IoT of different scales. Full article
(This article belongs to the Special Issue Ubiquitous Sensing)
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Open AccessArticle Behavior-Based Cleaning for Unreliable RFID Data Sets
Sensors 2012, 12(8), 10196-10207; doi:10.3390/s120810196
Received: 11 June 2012 / Revised: 11 July 2012 / Accepted: 21 July 2012 / Published: 30 July 2012
Cited by 7 | PDF Full-text (969 KB) | HTML Full-text | XML Full-text
Abstract
Radio Frequency IDentification (RFID) technology promises to revolutionize the way we track items and assets, but in RFID systems, missreading is a common phenomenon and it poses an enormous challenge to RFID data management, so accurate data cleaning becomes an essential task [...] Read more.
Radio Frequency IDentification (RFID) technology promises to revolutionize the way we track items and assets, but in RFID systems, missreading is a common phenomenon and it poses an enormous challenge to RFID data management, so accurate data cleaning becomes an essential task for the successful deployment of systems. In this paper, we present the design and development of a RFID data cleaning system, the first declarative, behavior-based unreliable RFID data smoothing system. We take advantage of kinematic characteristics of tags to assist in RFID data cleaning. In order to establish the conversion relationship between RFID data and kinematic parameters of the tags, we propose a movement behavior detection model. Moreover, a Reverse Order Filling Mechanism is proposed to ensure a more complete access to get the movement behavior characteristics of tag. Finally, we validate our solution with a common RFID application and demonstrate the advantages of our approach through extensive simulations. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Distributed Reasoning Engine Ecosystem for Semantic Context-Management in Smart Environments
Sensors 2012, 12(8), 10208-10227; doi:10.3390/s120810208
Received: 9 June 2012 / Revised: 12 July 2012 / Accepted: 26 July 2012 / Published: 30 July 2012
Cited by 4 | PDF Full-text (755 KB) | HTML Full-text | XML Full-text
Abstract
To be able to react adequately a smart environment must be aware of the context and its changes. Modeling the context allows applications to better understand it and to adapt to its changes. In order to do this an appropriate formal representation [...] Read more.
To be able to react adequately a smart environment must be aware of the context and its changes. Modeling the context allows applications to better understand it and to adapt to its changes. In order to do this an appropriate formal representation method is needed. Ontologies have proven themselves to be one of the best tools to do it. Semantic inference provides a powerful framework to reason over the context data. But there are some problems with this approach. The inference over semantic context information can be cumbersome when working with a large amount of data. This situation has become more common in modern smart environments where there are a lot sensors and devices available. In order to tackle this problem we have developed a mechanism to distribute the context reasoning problem into smaller parts in order to reduce the inference time. In this paper we describe a distributed peer-to-peer agent architecture of context consumers and context providers. We explain how this inference sharing process works, partitioning the context information according to the interests of the agents, location and a certainty factor. We also discuss the system architecture, analyzing the negotiation process between the agents. Finally we compare the distributed reasoning with the centralized one, analyzing in which situations is more suitable each approach. Full article
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Open AccessArticle Mosaicing of Hyperspectral Images: The Application of a Spectrograph Imaging Device
Sensors 2012, 12(8), 10228-10247; doi:10.3390/s120810228
Received: 15 June 2012 / Revised: 19 July 2012 / Accepted: 23 July 2012 / Published: 30 July 2012
Cited by 5 | PDF Full-text (2572 KB) | HTML Full-text | XML Full-text
Abstract
Hyperspectral monitoring of large areas (more than 10 km2) can be achieved via the use of a system employing spectrometers and CMOS cameras. A robust and efficient algorithm for automatically combining multiple, overlapping images of a scene to form a [...] Read more.
Hyperspectral monitoring of large areas (more than 10 km2) can be achieved via the use of a system employing spectrometers and CMOS cameras. A robust and efficient algorithm for automatically combining multiple, overlapping images of a scene to form a single composition (i.e., for the estimation of the point-to-point mapping between views), which uses only the information contained within the images themselves is described here. The algorithm, together with the 2D fast Fourier transform, provides an estimate of the displacement between pairs of images by accounting for rotations and changes of scale. The resulting mosaic was successively georeferenced within the WGS-84 geographic coordinate system. This paper also addresses how this information can be transferred to a push broom type spectral imaging device to build the hyperspectral cube of the area prior to land classification. The performances of the algorithm were evaluated using sample images and image sequences acquired during a proximal sensing field campaign conducted in San Teodoro (Olbia-Tempio—Sardinia). The hyperspectral cube closely corresponds to the mosaic. Mapping allows for the identification of objects within the image and agrees well with ground-truth measurements. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Harvesting Energy from the Counterbalancing (Weaving) Movement in Bicycle Riding
Sensors 2012, 12(8), 10248-10258; doi:10.3390/s120810248
Received: 25 May 2012 / Revised: 12 July 2012 / Accepted: 17 July 2012 / Published: 30 July 2012
Cited by 6 | PDF Full-text (1676 KB) | HTML Full-text | XML Full-text
Abstract
Bicycles are known to be rich source of kinetic energy, some of which is available for harvesting during speedy and balanced maneuvers by the user. A conventional dynamo attached to the rim can generate a large amount of output power at an [...] Read more.
Bicycles are known to be rich source of kinetic energy, some of which is available for harvesting during speedy and balanced maneuvers by the user. A conventional dynamo attached to the rim can generate a large amount of output power at an expense of extra energy input from the user. However, when applying energy conversion technology to human powered equipments, it is important to minimize the increase in extra muscular activity and to maximize the efficiency of human movements. This study proposes a novel energy harvesting methodology that utilizes lateral oscillation of bicycle frame (weaving) caused by user weight shifting movements in order to increase the pedaling force in uphill riding or during quick speed-up. Based on the 3D motion analysis, we designed and implemented the prototype of an electro-dynamic energy harvester that can be mounted on the bicycle’s handlebar to collect energy from the side-to-side movement. The harvester was found to generate substantial electric output power of 6.6 mW from normal road riding. It was able to generate power even during uphill riding which has never been shown with other approaches. Moreover, harvesting of energy from weaving motion seems to increase the economy of cycling by helping efficient usage of human power. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle FunBlocks. A Modular Framework for AmI System Development
Sensors 2012, 12(8), 10259-10291; doi:10.3390/s120810259
Received: 6 June 2012 / Revised: 12 July 2012 / Accepted: 27 July 2012 / Published: 30 July 2012
Cited by 2 | PDF Full-text (377 KB) | HTML Full-text | XML Full-text
Abstract
The last decade has seen explosive growth in the technologies required to implement Ambient Intelligence (AmI) systems. Technologies such as facial and speech recognition, home networks, household cleaning robots, to name a few, have become commonplace. However, due to the multidisciplinary nature [...] Read more.
The last decade has seen explosive growth in the technologies required to implement Ambient Intelligence (AmI) systems. Technologies such as facial and speech recognition, home networks, household cleaning robots, to name a few, have become commonplace. However, due to the multidisciplinary nature of AmI systems and the distinct requirements of different user groups, integrating these developments into full-scale systems is not an easy task. In this paper we propose FunBlocks, a minimalist modular framework for the development of AmI systems based on the function module abstraction used in the IEC 61499 standard for distributed control systems. FunBlocks provides a framework for the development of AmI systems through the integration of modules loosely joined by means of an event-driven middleware and a module and sensor/actuator catalog. The modular design of the FunBlocks framework allows the development of AmI systems which can be customized to a wide variety of usage scenarios. Full article
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Open AccessArticle A Wireless Magnetic Resonance Energy Transfer System for Micro Implantable Medical Sensors
Sensors 2012, 12(8), 10292-10308; doi:10.3390/s120810292
Received: 16 May 2012 / Revised: 11 July 2012 / Accepted: 16 July 2012 / Published: 30 July 2012
Cited by 17 | PDF Full-text (1091 KB) | HTML Full-text | XML Full-text
Abstract
Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit [...] Read more.
Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and resonant transmitter coils, and in vivo part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm3. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Detection of Formaldehyde in Water: A Shape-Effect on the Plasmonic Sensing Properties of the Gold Nanoparticles
Sensors 2012, 12(8), 10309-10325; doi:10.3390/s120810309
Received: 7 May 2012 / Revised: 13 July 2012 / Accepted: 18 July 2012 / Published: 30 July 2012
Cited by 12 | PDF Full-text (1270 KB) | HTML Full-text | XML Full-text
Abstract
The effect of morphology on the plasmonic sensing of the presence of formaldehyde in water by gold nanostructures has been investigated. The gold nanostructures with two different morphologies, namely spherical and rod, were prepared using a seed-mediated method. In typical results, it [...] Read more.
The effect of morphology on the plasmonic sensing of the presence of formaldehyde in water by gold nanostructures has been investigated. The gold nanostructures with two different morphologies, namely spherical and rod, were prepared using a seed-mediated method. In typical results, it was found that the plasmonic properties of gold nanostructures were very sensitive to the presence of formaldehyde in their surrounding medium by showing the change in both the plasmonic peaks position and the intensity. Spherical nanoparticles (GNS), for example, indicated an increase in the sensitivity when the size was increased from 25 to 35 nm and dramatically decreased when the size was further increased. An m value, the ratio between plasmonic peak shift and refractive index change, as high as 36.5 nm/RIU (refractive index unit) was obtained so far. An expanded sensing mode to FD was obtained when gold nanostructures with nanorods morphology (GNR) were used because of the presence of two plasmonic modes for response probing. However, in the present study, effective plasmonic peak shift was not observed due to the intense plasmonic coupling of closely packed nanorod structures on the surface. Nevertheless, the present results at least provide a potential strategy for response enhancement via shape-effects. High performance plasmonic sensors could be obtained if controlled arrays of nanorods can be prepared on the surface. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Multi-Sensor Fusion of Infrared and Electro-Optic Signals for High Resolution Night Images
Sensors 2012, 12(8), 10326-10338; doi:10.3390/s120810326
Received: 4 June 2012 / Revised: 8 July 2012 / Accepted: 12 July 2012 / Published: 30 July 2012
Cited by 3 | PDF Full-text (1857 KB) | HTML Full-text | XML Full-text
Abstract
Electro-optic (EO) image sensors exhibit the properties of high resolution and low noise level at daytime, but they do not work in dark environments. Infrared (IR) image sensors exhibit poor resolution and cannot separate objects with similar temperature. Therefore, we propose a [...] Read more.
Electro-optic (EO) image sensors exhibit the properties of high resolution and low noise level at daytime, but they do not work in dark environments. Infrared (IR) image sensors exhibit poor resolution and cannot separate objects with similar temperature. Therefore, we propose a novel framework of IR image enhancement based on the information (e.g., edge) from EO images, which improves the resolution of IR images and helps us distinguish objects at night. Our framework superimposing/blending the edges of the EO image onto the corresponding transformed IR image improves their resolution. In this framework, we adopt the theoretical point spread function (PSF) proposed by Hardie et al. for the IR image, which has the modulation transfer function (MTF) of a uniform detector array and the incoherent optical transfer function (OTF) of diffraction-limited optics. In addition, we design an inverse filter for the proposed PSF and use it for the IR image transformation. The framework requires four main steps: (1) inverse filter-based IR image transformation; (2) EO image edge detection; (3) registration; and (4) blending/superimposing of the obtained image pair. Simulation results show both blended and superimposed IR images, and demonstrate that blended IR images have better quality over the superimposed images. Additionally, based on the same steps, simulation result shows a blended IR image of better quality when only the original IR image is available. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Grey Level and Noise Evaluation of a Foveon X3 Image Sensor: A Statistical and Experimental Approach
Sensors 2012, 12(8), 10339-10368; doi:10.3390/s120810339
Received: 29 June 2012 / Revised: 24 July 2012 / Accepted: 30 July 2012 / Published: 31 July 2012
Cited by 3 | PDF Full-text (5294 KB) | HTML Full-text | XML Full-text
Abstract
Radiometric values on digital imagery are affected by several sources of uncertainty. A practical, comprehensive and flexible procedure to analyze the radiometric values and the uncertainty effects due to the camera sensor system is described in this paper. The procedure is performed [...] Read more.
Radiometric values on digital imagery are affected by several sources of uncertainty. A practical, comprehensive and flexible procedure to analyze the radiometric values and the uncertainty effects due to the camera sensor system is described in this paper. The procedure is performed on the grey level output signal using image raw units with digital numbers ranging from 0 to 212-1. The procedure is entirely based on statistical and experimental techniques. Design of Experiments (DoE) for Linear Models (LM) are derived to analyze the radiometric values and estimate the uncertainty. The presented linear model integrates all the individual sensor noise sources in one global component and characterizes the radiometric values and the uncertainty effects according to the influential factors such as the scene reflectance, wavelength range and time. The experiments are carried out under laboratory conditions to minimize the rest of uncertainty sources that might affect the radiometric values. It is confirmed the flexibility of the procedure to model and characterize the radiometric values, as well as to determine the behaviour of two phenomena when dealing with image sensors: the noise of a single image and the stability (trend and noise) of a sequence of images. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A Multi-Parameter Decoupling Method with a Lamb Wave Sensor for Improving the Selectivity of Label-Free Liquid Detection
Sensors 2012, 12(8), 10369-10380; doi:10.3390/s120810369
Received: 17 June 2012 / Revised: 17 July 2012 / Accepted: 24 July 2012 / Published: 31 July 2012
Cited by 2 | PDF Full-text (798 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a liquid multi-parameter decoupling method with only one Lamb wave sensor is presented. In a Lamb wave sensor, antisymmetric modes (A01 mode for low frequency, A03 mode for high frequency) and symmetric modes (S0 mode) are [...] Read more.
In this paper, a liquid multi-parameter decoupling method with only one Lamb wave sensor is presented. In a Lamb wave sensor, antisymmetric modes (A01 mode for low frequency, A03 mode for high frequency) and symmetric modes (S0 mode) are used to detect multiple parameters of a liquid, such as its density, sound velocity, and viscosity. We found they can play very different roles in the detections. For example, the A01 mode is very sensitive to the liquid’s density but the A03 mode is sensitive to the sound velocity. Here, the A0 mode is used to identify the density of the detected liquid and with this density value we obtained the viscosity by the amplitude shifts of the S0 mode. This could be a way to distinguish an unknown liquid with high sensitivity or to solve the problem of selectivity of label-free detection on biosensors. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Non-Destructive Inspection Methods for LEDs Using Real-Time Displaying Optical Coherence Tomography
Sensors 2012, 12(8), 10395-10406; doi:10.3390/s120810395
Received: 25 June 2012 / Revised: 24 July 2012 / Accepted: 24 July 2012 / Published: 31 July 2012
Cited by 7 | PDF Full-text (1912 KB) | HTML Full-text | XML Full-text
Abstract
In this study, we report the applicability of two different Optical Coherence Tomography (OCT) technologies for inspecting Light Emitting Diode (LED) structures. Sectional images of a LED were captured using a Spectral Domain OCT (SD-OCT) system and a Swept Source OCT (SS-OCT) [...] Read more.
In this study, we report the applicability of two different Optical Coherence Tomography (OCT) technologies for inspecting Light Emitting Diode (LED) structures. Sectional images of a LED were captured using a Spectral Domain OCT (SD-OCT) system and a Swept Source OCT (SS-OCT) system. Their center wavelengths are 850 and 1,310 nm, respectively. We acquired cross-sectional two dimensional (2D) images of a normal LED and extracted sectional profiles to inspect possible wire disconnection that may be present in the LED manufacturing process. The SD-OCT and SS-OCT images were compared with each other in the same sample to study their advantages. The distribution of fluorescence material was observed more clearly with the SD-OCT of 850 nm wavelength, whereas the status of wire connection was clearer in the SS-OCT images with 1,310 nm wavelength. In addition, the volume of the fluorophore space was calculated from the OCT images. This is the first report that a nondestructive optical imaging modality such as OCT can be applied to finding screen defects in LED. We expect this method can improve the inspection efficacy over traditional inspection methods such as Charged Coupled Device (CCD) camera or X-ray instruments. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Semantic Autonomous Video Surveillance System for Dense Camera Networks in Smart Cities
Sensors 2012, 12(8), 10407-10429; doi:10.3390/s120810407
Received: 2 May 2012 / Revised: 21 July 2012 / Accepted: 26 July 2012 / Published: 2 August 2012
Cited by 7 | PDF Full-text (1030 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a proposal of an intelligent video surveillance system able to detect and identify abnormal and alarming situations by analyzing object movement. The system is designed to minimize video processing and transmission, thus allowing a large number of cameras to [...] Read more.
This paper presents a proposal of an intelligent video surveillance system able to detect and identify abnormal and alarming situations by analyzing object movement. The system is designed to minimize video processing and transmission, thus allowing a large number of cameras to be deployed on the system, and therefore making it suitable for its usage as an integrated safety and security solution in Smart Cities. Alarm detection is performed on the basis of parameters of the moving objects and their trajectories, and is performed using semantic reasoning and ontologies. This means that the system employs a high-level conceptual language easy to understand for human operators, capable of raising enriched alarms with descriptions of what is happening on the image, and to automate reactions to them such as alerting the appropriate emergency services using the Smart City safety network. Full article
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Open AccessArticle Mechanisms for the Direct Electron Transfer of Cytochrome c Induced by Multi-Walled Carbon Nanotubes
Sensors 2012, 12(8), 10450-10462; doi:10.3390/s120810450
Received: 18 June 2012 / Revised: 17 July 2012 / Accepted: 17 July 2012 / Published: 2 August 2012
Cited by 11 | PDF Full-text (336 KB) | HTML Full-text | XML Full-text
Abstract
Multi-walled carbon nanotube (MWCNT)-modified electrodes can promote the direct electron transfer (DET) of cytochrome c (Cyt c). There are several possible mechanisms that explain the DET of Cyt c. In this study, several experimental methods, including Fourier transform infrared spectroscopy, circular dichroism, [...] Read more.
Multi-walled carbon nanotube (MWCNT)-modified electrodes can promote the direct electron transfer (DET) of cytochrome c (Cyt c). There are several possible mechanisms that explain the DET of Cyt c. In this study, several experimental methods, including Fourier transform infrared spectroscopy, circular dichroism, ultraviolet-visible absorption spectroscopy, and electron paramagnetic resonance spectroscopy were utilized to investigate the conformational changes of Cyt c induced by MWCNTs. The DET mechanism was demonstrated at various nano-levels: secondary structure, spatial orientation, and spin state. In the presence of MWCNTs, the secondary structure of Cyt c changes, which exposes the active site, then, the orientation of the heme is optimized, revolving the exposed active center to the optimum spatial orientation for DET; and finally, a transition of spin states is induced, providing relatively high energy and a more open microenvironment for electron transfer. These changes at different nano-levels are closely connected and form a complex process that promotes the electron transfer of Cyt c. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Cognitive LF-Ant: A Novel Protocol for Healthcare Wireless Sensor Networks
Sensors 2012, 12(8), 10463-10486; doi:10.3390/s120810463
Received: 15 June 2012 / Revised: 11 July 2012 / Accepted: 18 July 2012 / Published: 2 August 2012
Cited by 11 | PDF Full-text (400 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the authors present the Cognitive LF-Ant protocol for emergency reporting in healthcare wireless sensor networks. The protocol is inspired by the natural behaviour of ants and a cognitive component provides the capabilities to dynamically allocate resources, in accordance with [...] Read more.
In this paper, the authors present the Cognitive LF-Ant protocol for emergency reporting in healthcare wireless sensor networks. The protocol is inspired by the natural behaviour of ants and a cognitive component provides the capabilities to dynamically allocate resources, in accordance with the emergency degree of each patient. The intra-cluster emergency reporting is inspired by the different capabilities of leg-manipulated ants. The inter-cluster reporting is aided by the cooperative modulation diversity with spectrum sensing, which can detect new emergency reporting requests and forward them. Simulations results show the decrease of average delay time as the probability of opportunistic access increases, which privileges the emergency reporting related to the patients with higher priority of resources’ usage. Furthermore, the packet loss rate is decreased by the use of cooperative modulation diversity with spectrum sensing. Full article
(This article belongs to the Special Issue Ubiquitous Sensing)
Open AccessArticle Detection of Non-PCR Amplified S. enteritidis Genomic DNA from Food Matrices Using a Gold-Nanoparticle DNA Biosensor: A Proof-of-Concept Study
Sensors 2012, 12(8), 10487-10499; doi:10.3390/s120810487
Received: 4 June 2012 / Revised: 27 July 2012 / Accepted: 31 July 2012 / Published: 2 August 2012
Cited by 8 | PDF Full-text (311 KB) | HTML Full-text | XML Full-text
Abstract
Bacterial pathogens pose an increasing food safety and bioterrorism concern. Current DNA detection methods utilizing sensitive nanotechnology and biosensors have shown excellent detection, but require expensive and time-consuming polymerase chain reaction (PCR) to amplify DNA targets; thus, a faster, more economical method [...] Read more.
Bacterial pathogens pose an increasing food safety and bioterrorism concern. Current DNA detection methods utilizing sensitive nanotechnology and biosensors have shown excellent detection, but require expensive and time-consuming polymerase chain reaction (PCR) to amplify DNA targets; thus, a faster, more economical method is still essential. In this proof-of-concept study, we investigated the ability of a gold nanoparticle-DNA (AuNP-DNA) biosensor to detect non-PCR amplified genomic Salmonella enterica serovar Enteritidis (S. enteritidis) DNA, from pure or mixed bacterial culture and spiked liquid matrices. Non-PCR amplified DNA was hybridized into sandwich-like structures (magnetic nanoparticles/DNA/AuNPs) and analyzed through detection of gold voltammetric peaks using differential pulse voltammetry. Our preliminary data indicate that non-PCR amplified genomic DNA can be detected at a concentration as low as 100 ng/mL from bacterial cultures and spiked liquid matrices, similar to reported PCR amplified detection levels. These findings also suggest that AuNP-DNA biosensors are a first step towards a viable detection method of bacterial pathogens, in particular, for resource-limited settings, such as field-based or economically limited conditions. Future efforts will focus on further optimization of the DNA extraction method and AuNP-biosensors, to increase sensitivity at lower DNA target concentrations from food matrices comparable to PCR amplified DNA detection strategies. Full article
Open AccessArticle A Four-Quadrant PVDF Transducer for Surface Acoustic Wave Detection
Sensors 2012, 12(8), 10500-10510; doi:10.3390/s120810500
Received: 1 July 2012 / Revised: 17 July 2012 / Accepted: 25 July 2012 / Published: 2 August 2012
Cited by 4 | PDF Full-text (1147 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a polyvinylidene fluoride (PVDF) piezoelectric transducer was developed to detect laser-induced surface acoustic waves in a SiO2-thin film–Si-substrate structure. In order to solve the problems related to, firstly, the position of the probe, and secondly, the fact [...] Read more.
In this paper, a polyvinylidene fluoride (PVDF) piezoelectric transducer was developed to detect laser-induced surface acoustic waves in a SiO2-thin film–Si-substrate structure. In order to solve the problems related to, firstly, the position of the probe, and secondly, the fact that signals at different points cannot be detected simultaneously during the detection process, a four-quadrant surface acoustic wave PVDF transducer was designed and constructed for the purpose of detecting surface acoustic waves excited by a pulse laser line source. The experimental results of the four-quadrant piezoelectric detection in comparison with the commercial nanoindentation technology were consistent, the relative error is 0.56%, and the system eliminates the piezoelectric surface wave detection direction deviation errors, improves the accuracy of the testing system by 1.30%, achieving the acquisition at the same time at different testing positions of the sample. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Pedestrian Navigation Based on a Waist-Worn Inertial Sensor
Sensors 2012, 12(8), 10536-10549; doi:10.3390/s120810536
Received: 1 July 2012 / Revised: 17 July 2012 / Accepted: 25 July 2012 / Published: 3 August 2012
Cited by 19 | PDF Full-text (656 KB) | HTML Full-text | XML Full-text
Abstract
We present a waist-worn personal navigation system based on inertial measurement units. The device makes use of the human bipedal pattern to reduce position errors. We describe improved algorithms, based on detailed description of the heel strike biomechanics and its translation to [...] Read more.
We present a waist-worn personal navigation system based on inertial measurement units. The device makes use of the human bipedal pattern to reduce position errors. We describe improved algorithms, based on detailed description of the heel strike biomechanics and its translation to accelerations of the body waist to estimate the periods of zero velocity, the step length, and the heading estimation. The experimental results show that we are able to support pedestrian navigation with the high-resolution positioning required for most applications. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Numerical Investigations on Electric Field Characteristics with Respect to Capacitive Detection of Free-Flying Droplets
Sensors 2012, 12(8), 10550-10565; doi:10.3390/s120810550
Received: 11 June 2012 / Revised: 17 July 2012 / Accepted: 25 July 2012 / Published: 3 August 2012
PDF Full-text (773 KB) | HTML Full-text | XML Full-text
Abstract
In this paper a multi-disciplinary simulation of a capacitive droplet sensor based on an open plate capacitor as transducing element is presented. The numerical simulations are based on the finite volume method (FVM), including calculations of an electric field which changes according to the presence of a liquid droplet. The volume of fluid (VOF) method is applied for the simulation of the ejection process of a liquid droplet out of a dispenser nozzle. The simulations were realised using the computational fluid dynamic (CFD) software CFD ACE+. The investigated capacitive sensing principle enables to determine the volume of a micro droplet passing the sensor capacitor due to the induced change in capacity. It could be found that single droplets in the considered volume range of 5 nL < Vdrop < 100 nL lead to a linear change of the capacity up to ΔQ < 30 fC. The sensitivity of the focused capacitor geometry was evaluated to be Si = 0.3 fC/nL. The simulation results are validated by experiments which exhibit good agreement. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany 2012)
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Open AccessArticle Numerical and Experimental Study on the Development of Electric Sensor as for Measurement of Red Blood Cell Deformability in Microchannels
Sensors 2012, 12(8), 10566-10583; doi:10.3390/s120810566
Received: 10 May 2012 / Revised: 18 July 2012 / Accepted: 25 July 2012 / Published: 3 August 2012
PDF Full-text (748 KB) | HTML Full-text | XML Full-text
Abstract
A microsensor that can continuously measure the deformability of a single red blood cell (RBC) in its microchannels using microelectrodes is described in this paper. The time series of the electric resistance is measured using an AC current vs. voltage method as [...] Read more.
A microsensor that can continuously measure the deformability of a single red blood cell (RBC) in its microchannels using microelectrodes is described in this paper. The time series of the electric resistance is measured using an AC current vs. voltage method as the RBC passes between counter-electrode-type micro-membrane sensors attached to the bottom wall of the microchannel. The RBC is deformed by the shear flow created in the microchannel; the degree of deformation depends on the elastic modulus of the RBC. The resistance distribution, which is unique to the shape of the RBC, is analyzed to obtain the deformability of each cell. First, a numerical simulation of the electric field around the electrodes and RBC is carried out to evaluate the influences of the RBC height position, channel height, distance between the electrodes, electrode width, and RBC shape on the sensor sensitivity. Then, a microsensor was designed and fabricated on the basis of the numerical results. Resistance measurement was carried out using samples of normal RBCs and rigidified (Ca2+-A23186 treated) RBCs. Visualization measurement of the cells’ behavior was carried out using a high-speed camera, and the results were compared with those obtained above to evaluate the performance of the sensor. Full article
(This article belongs to the Special Issue Micro and Nano Technologies for Point-of-Care Diagnosis)
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Open AccessArticle Binaural Sound Localizer for Azimuthal Movement Detection Based on Diffraction
Sensors 2012, 12(8), 10584-10603; doi:10.3390/s120810584
Received: 30 May 2012 / Revised: 10 July 2012 / Accepted: 25 July 2012 / Published: 3 August 2012
Cited by 3 | PDF Full-text (908 KB) | HTML Full-text | XML Full-text
Abstract
Sound localization can be realized by utilizing the physics of acoustics in various methods. This paper investigates a novel detection architecture for the azimuthal movement of sound source based on the interaural level difference (ILD) between two receivers. One of the microphones [...] Read more.
Sound localization can be realized by utilizing the physics of acoustics in various methods. This paper investigates a novel detection architecture for the azimuthal movement of sound source based on the interaural level difference (ILD) between two receivers. One of the microphones in the system is surrounded by barriers of various heights in order to cast the direction dependent diffraction of the incoming signal. The gradient analysis of the ILD between the structured and unstructured microphone demonstrates the rotation directions as clockwise, counter clockwise, and no rotation of the sound source. Acoustic experiments with different types of sound source over a wide range of target movements show that the average true positive and false positive rates are 67% and 16%, respectively. Spectral analysis demonstrates that the low frequency delivers decreased true and false positive rates and the high frequency presents increases of both rates, overall. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Resolution in QCM Sensors for the Viscosity and Density of Liquids: Application to Lead Acid Batteries
Sensors 2012, 12(8), 10604-10620; doi:10.3390/s120810604
Received: 27 June 2012 / Revised: 25 July 2012 / Accepted: 31 July 2012 / Published: 3 August 2012
Cited by 6 | PDF Full-text (3544 KB) | HTML Full-text | XML Full-text
Abstract
In battery applications, particularly in automobiles, submarines and remote communications, the state of charge (SoC) is needed in order to manage batteries efficiently. The most widely used physical parameter for this is electrolyte density. However, there is greater dependency between electrolyte viscosity [...] Read more.
In battery applications, particularly in automobiles, submarines and remote communications, the state of charge (SoC) is needed in order to manage batteries efficiently. The most widely used physical parameter for this is electrolyte density. However, there is greater dependency between electrolyte viscosity and SoC than that seen for density and SoC. This paper presents a Quartz Crystal Microbalance (QCM) sensor for electrolyte density-viscosity product measurements in lead acid batteries. The sensor is calibrated in H2SO4 solutions in the battery electrolyte range to obtain sensitivity, noise and resolution. Also, real-time tests of charge and discharge are conducted placing the quartz crystal inside the battery. At the same time, the present theoretical “resolution limit” to measure the square root of the density-viscosity product ( ) of a liquid medium or best resolution achievable with a QCM oscillator is determined. Findings show that the resolution limit only depends on the characteristics of the liquid to be studied and not on frequency. The QCM resolution limit for measurements worsens when the density-viscosity product of the liquid is increased, but it cannot be improved by elevating the work frequency. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Optimal Design of the Absolute Positioning Sensor for a High-Speed Maglev Train and Research on Its Fault Diagnosis
Sensors 2012, 12(8), 10621-10638; doi:10.3390/s120810621
Received: 5 July 2012 / Revised: 25 July 2012 / Accepted: 25 July 2012 / Published: 3 August 2012
Cited by 2 | PDF Full-text (648 KB) | HTML Full-text | XML Full-text
Abstract
This paper studies an absolute positioning sensor for a high-speed maglev train and its fault diagnosis method. The absolute positioning sensor is an important sensor for the high-speed maglev train to accomplish its synchronous traction. It is used to calibrate the error [...] Read more.
This paper studies an absolute positioning sensor for a high-speed maglev train and its fault diagnosis method. The absolute positioning sensor is an important sensor for the high-speed maglev train to accomplish its synchronous traction. It is used to calibrate the error of the relative positioning sensor which is used to provide the magnetic phase signal. On the basis of the analysis for the principle of the absolute positioning sensor, the paper describes the design of the sending and receiving coils and realizes the hardware and the software for the sensor. In order to enhance the reliability of the sensor, a support vector machine is used to recognize the fault characters, and the signal flow method is used to locate the faulty parts. The diagnosis information not only can be sent to an upper center control computer to evaluate the reliability of the sensors, but also can realize on-line diagnosis for debugging and the quick detection when the maglev train is off-line. The absolute positioning sensor we study has been used in the actual project. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Hyperspectral Analysis of Soil Nitrogen, Carbon, Carbonate, and Organic Matter Using Regression Trees
Sensors 2012, 12(8), 10639-10658; doi:10.3390/s120810639
Received: 1 July 2012 / Revised: 27 July 2012 / Accepted: 1 August 2012 / Published: 3 August 2012
Cited by 10 | PDF Full-text (1793 KB) | HTML Full-text | XML Full-text
Abstract
The characterization of soil attributes using hyperspectral sensors has revealed patterns in soil spectra that are known to respond to mineral composition, organic matter, soil moisture and particle size distribution. Soil samples from different soil horizons of replicated soil series from sites located within Washington and Oregon were analyzed with the FieldSpec Spectroradiometer to measure their spectral signatures across the electromagnetic range of 400 to 1,000 nm. Similarity rankings of individual soil samples reveal differences between replicate series as well as samples within the same replicate series. Using classification and regression tree statistical methods, regression trees were fitted to each spectral response using concentrations of nitrogen, carbon, carbonate and organic matter as the response variables. Statistics resulting from fitted trees were: nitrogen R2 0.91 (p < 0.01) at 403, 470, 687, and 846 nm spectral band widths, carbonate R2 0.95 (p < 0.01) at 531 and 898 nm band widths, total carbon R2 0.93 (p < 0.01) at 400, 409, 441 and 907 nm band widths, and organic matter R2 0.98 (p < 0.01) at 300, 400, 441, 832 and 907 nm band widths. Use of the 400 to 1,000 nm electromagnetic range utilizing regression trees provided a powerful, rapid and inexpensive method for assessing nitrogen, carbon, carbonate and organic matter for upper soil horizons in a nondestructive method. Full article
(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)
Open AccessArticle Ubiquitous Green Computing Techniques for High Demand Applications in Smart Environments
Sensors 2012, 12(8), 10659-10677; doi:10.3390/s120810659
Received: 19 March 2012 / Revised: 23 July 2012 / Accepted: 27 July 2012 / Published: 3 August 2012
Cited by 2 | PDF Full-text (587 KB) | HTML Full-text | XML Full-text
Abstract
Ubiquitous sensor network deployments, such as the ones found in Smart cities and Ambient intelligence applications, require constantly increasing high computational demands in order to process data and offer services to users. The nature of these applications imply the usage of data [...] Read more.
Ubiquitous sensor network deployments, such as the ones found in Smart cities and Ambient intelligence applications, require constantly increasing high computational demands in order to process data and offer services to users. The nature of these applications imply the usage of data centers. Research has paid much attention to the energy consumption of the sensor nodes in WSNs infrastructures. However, supercomputing facilities are the ones presenting a higher economic and environmental impact due to their very high power consumption. The latter problem, however, has been disregarded in the field of smart environment services. This paper proposes an energy-minimization workload assignment technique, based on heterogeneity and application-awareness, that redistributes low-demand computational tasks from high-performance facilities to idle nodes with low and medium resources in the WSN infrastructure. These non-optimal allocation policies reduce the energy consumed by the whole infrastructure and the total execution time. Full article
Open AccessArticle Intelligent Urban Public Transportation for Accessibility Dedicated to People with Disabilities
Sensors 2012, 12(8), 10678-10692; doi:10.3390/s120810678
Received: 19 June 2012 / Revised: 23 July 2012 / Accepted: 31 July 2012 / Published: 6 August 2012
Cited by 9 | PDF Full-text (607 KB) | HTML Full-text | XML Full-text
Abstract
The traditional urban public transport system generally cannot provide an effective access service for people with disabilities, especially for disabled, wheelchair and blind (DWB) passengers. In this paper, based on advanced information & communication technologies (ICT) and green technologies (GT) concepts, a dedicated public urban transportation service access system named Mobi+ has been introduced, which facilitates the mobility of DWB passengers. The Mobi+ project consists of three subsystems: a wireless communication subsystem, which provides the data exchange and network connection services between buses and stations in the complex urban environments; the bus subsystem, which provides the DWB class detection & bus arrival notification services; and the station subsystem, which implements the urban environmental surveillance & bus auxiliary access services. The Mobi+ card that supports multi-microcontroller multi-transceiver adopts the fault-tolerant component-based hardware architecture, in which the dedicated embedded system software, i.e., operating system micro-kernel and wireless protocol, has been integrated. The dedicated Mobi+ embedded system provides the fault-tolerant resource awareness communication and scheduling mechanism to ensure the reliability in data exchange and service provision. At present, the Mobi+ system has been implemented on the buses and stations of line ‘2’ in the city of Clermont-Ferrand (France). The experiential results show that, on one hand the Mobi+ prototype system reaches the design expectations and provides an effective urban bus access service for people with disabilities; on the other hand the Mobi+ system is easily to deploy in the buses and at bus stations thanks to its low energy consumption and small form factor. Full article
(This article belongs to the Special Issue New Trends towards Automatic Vehicle Control and Perception Systems)
Open AccessArticle A Wide Linear Range Eddy Current Displacement Sensor Equipped with Dual-Coil Probe Applied in the Magnetic Suspension Flywheel
Sensors 2012, 12(8), 10693-10706; doi:10.3390/s120810693
Received: 10 June 2012 / Revised: 27 June 2012 / Accepted: 12 July 2012 / Published: 6 August 2012
Cited by 1 | PDF Full-text (2131 KB) | HTML Full-text | XML Full-text
Abstract
The Eddy Current Displacement Sensor (ECDS) is widely used in the Magnetic Suspension Flywheel (MSFW) to measure the tiny clearance between the rotor and the magnetic bearings. The linear range of the ECDS is determined by the diameter of its probe coil. [...] Read more.
The Eddy Current Displacement Sensor (ECDS) is widely used in the Magnetic Suspension Flywheel (MSFW) to measure the tiny clearance between the rotor and the magnetic bearings. The linear range of the ECDS is determined by the diameter of its probe coil. Wide clearances must be measured in some new MSFWs recently designed for the different space missions, but the coil diameter is limited by some restrictions. In this paper, a multi-channel ECDS equipped with dual-coil probes is proposed to extend the linear range to satisfy the demands of such MSFWs. In order to determine the best configuration of the dual-coil probe, the quality factors of the potential types of the dual-coil probes, the induced eddy current and the magnetic intensity on the surface of the measuring object are compared with those of the conventional single-coil probe. The linear range of the ECDS equipped with the selected dual-coil probe is extended from 1.1 mm to 2.4 mm under the restrictions without adding any cost for additional compensation circuits or expensive coil materials. The effectiveness of the linear range extension ability and the dynamic response of the designed ECDS are confirmed by the testing and the applications in the MSFW. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Automatic Carbon Dioxide-Methane Gas Sensor Based on the Solubility of Gases in Water
Sensors 2012, 12(8), 10742-10758; doi:10.3390/s120810742
Received: 1 July 2012 / Revised: 31 July 2012 / Accepted: 2 August 2012 / Published: 6 August 2012
Cited by 5 | PDF Full-text (821 KB) | HTML Full-text | XML Full-text
Abstract
Biogas methane content is a relevant variable in anaerobic digestion processing where knowledge of process kinetics or an early indicator of digester failure is needed. The contribution of this work is the development of a novel, simple and low cost automatic carbon [...] Read more.
Biogas methane content is a relevant variable in anaerobic digestion processing where knowledge of process kinetics or an early indicator of digester failure is needed. The contribution of this work is the development of a novel, simple and low cost automatic carbon dioxide-methane gas sensor based on the solubility of gases in water as the precursor of a sensor for biogas quality monitoring. The device described in this work was used for determining the composition of binary mixtures, such as carbon dioxide-methane, in the range of 0–100%. The design and implementation of a digital signal processor and control system into a low-cost Field Programmable Gate Array (FPGA) platform has permitted the successful application of data acquisition, data distribution and digital data processing, making the construction of a standalone carbon dioxide-methane gas sensor possible. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Sensing Free Sulfur Dioxide in Wine
Sensors 2012, 12(8), 10759-10773; doi:10.3390/s120810759
Received: 26 June 2012 / Revised: 24 July 2012 / Accepted: 25 July 2012 / Published: 6 August 2012
Cited by 4 | PDF Full-text (641 KB) | HTML Full-text | XML Full-text
Abstract
Sulfur dioxide (SO2) is important in the winemaking process as it aids in preventing microbial growth and the oxidation of wine. These processes and others consume the SO2 over time, resulting in wines with little SO2 protection. Furthermore, [...] Read more.
Sulfur dioxide (SO2) is important in the winemaking process as it aids in preventing microbial growth and the oxidation of wine. These processes and others consume the SO2 over time, resulting in wines with little SO2 protection. Furthermore, SO2 and sulfiting agents are known to be allergens to many individuals and for that reason their levels need to be monitored and regulated in final wine products. Many of the current techniques for monitoring SO2 in wine require the SO2 to be separated from the wine prior to analysis. This investigation demonstrates a technique capable of measuring free sulfite concentrations in low volume liquid samples in white wine. This approach adapts a known colorimetric reaction to a suspended core optical fiber sensing platform, and exploits the interaction between guided light located within the fiber voids and a mixture of the wine sample and a colorimetric analyte. We have shown that this technique enables measurements to be made without dilution of the wine samples, thus paving the way towards real time in situ wine monitoring. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle An Integrative Architecture for a Sensor-Supported Trust Management System
Sensors 2012, 12(8), 10774-10787; doi:10.3390/s120810774
Received: 11 June 2012 / Revised: 17 July 2012 / Accepted: 25 July 2012 / Published: 6 August 2012
Cited by 4 | PDF Full-text (405 KB) | HTML Full-text | XML Full-text
Abstract
Trust plays a key role not only in e-worlds and emerging pervasive computing environments, but also already for millennia in human societies. Trust management solutions that have being around now for some fifteen years were primarily developed for the above mentioned cyber [...] Read more.
Trust plays a key role not only in e-worlds and emerging pervasive computing environments, but also already for millennia in human societies. Trust management solutions that have being around now for some fifteen years were primarily developed for the above mentioned cyber environments and they are typically focused on artificial agents, sensors, etc. However, this paper presents extensions of a new methodology together with architecture for trust management support that is focused on humans and human-like agents. With this methodology and architecture sensors play a crucial role. The architecture presents an already deployable tool for multi and interdisciplinary research in various areas where humans are involved. It provides new ways to obtain an insight into dynamics and evolution of such structures, not only in pervasive computing environments, but also in other important areas like management and decision making support. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Vision-Based Sensor for Early Detection of Periodical Defects in Web Materials
Sensors 2012, 12(8), 10788-10809; doi:10.3390/s120810788
Received: 21 May 2012 / Revised: 25 July 2012 / Accepted: 25 July 2012 / Published: 6 August 2012
Cited by 7 | PDF Full-text (1240 KB) | HTML Full-text | XML Full-text
Abstract
During the production of web materials such as plastic, textiles or metal, where there are rolls involved in the production process, periodically generated defects may occur. If one of these rolls has some kind of flaw, it can generate a defect on [...] Read more.
During the production of web materials such as plastic, textiles or metal, where there are rolls involved in the production process, periodically generated defects may occur. If one of these rolls has some kind of flaw, it can generate a defect on the material surface each time it completes a full turn. This can cause the generation of a large number of surface defects, greatly degrading the product quality. For this reason, it is necessary to have a system that can detect these situations as soon as possible. This paper presents a vision-based sensor for the early detection of this kind of defects. It can be adapted to be used in the inspection of any web material, even when the input data are very noisy. To assess its performance, the sensor system was used to detect periodical defects in hot steel strips. A total of 36 strips produced in ArcelorMittal Avilés factory were used for this purpose, 18 to determine the optimal configuration of the proposed sensor using a full-factorial experimental design and the other 18 to verify the validity of the results. Next, they were compared with those provided by a commercial system used worldwide, showing a clear improvement. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessCommunication Development of a Plastic-Based Microfluidic Immunosensor Chip for Detection of H1N1 Influenza
Sensors 2012, 12(8), 10810-10819; doi:10.3390/s120810810
Received: 4 July 2012 / Revised: 26 July 2012 / Accepted: 31 July 2012 / Published: 6 August 2012
Cited by 6 | PDF Full-text (824 KB) | HTML Full-text | XML Full-text
Abstract
Lab-on-a-chip can provide convenient and accurate diagnosis tools. In this paper, a plastic-based microfluidic immunosensor chip for the diagnosis of swine flu (H1N1) was developed by immobilizing hemagglutinin antigen on a gold surface using a genetically engineered polypeptide. A fluorescent dye-labeled antibody [...] Read more.
Lab-on-a-chip can provide convenient and accurate diagnosis tools. In this paper, a plastic-based microfluidic immunosensor chip for the diagnosis of swine flu (H1N1) was developed by immobilizing hemagglutinin antigen on a gold surface using a genetically engineered polypeptide. A fluorescent dye-labeled antibody (Ab) was used for quantifying the concentration of Ab in the immunosensor chip using a fluorescent technique. For increasing the detection efficiency and reducing the errors, three chambers and three microchannels were designed in one microfluidic chip. This protocol could be applied to the diagnosis of other infectious diseases in a microfluidic device. Full article
(This article belongs to the Special Issue Bioassays)
Open AccessArticle A Linear, Millimetre Displacement-to-Frequency Transducer
Sensors 2012, 12(8), 10820-10833; doi:10.3390/s120810820
Received: 1 July 2012 / Revised: 21 July 2012 / Accepted: 26 July 2012 / Published: 6 August 2012
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Abstract
The paper presents a novel linear, high-fidelity millimetre displacement-to-frequency transducer, based on the resistive conversion of displacement into a proportional voltage, and then frequency. The derivation of the nonlinearity, fidelity and sensitivity of the transducer is presented. Experimental results confirm that a [...] Read more.
The paper presents a novel linear, high-fidelity millimetre displacement-to-frequency transducer, based on the resistive conversion of displacement into a proportional voltage, and then frequency. The derivation of the nonlinearity, fidelity and sensitivity of the transducer is presented. Experimental results confirm that a displacement of 0–100 mm is converted into a frequency range of 0–100 kHz, with a normalised fidelity factor of 99.91%, and a worst-case nonlinearity of less than 0.08%. Tests using laboratory standards show that a displacement of 10 mm is transduced with an accuracy of ±0.6%, and a standard deviation of 530 Hz. Estimates included in the paper show that the transducer could cost less than 1% of existing systems for millimeter displacement measurement. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Detecting Unknown Attacks in Wireless Sensor Networks That Contain Mobile Nodes
Sensors 2012, 12(8), 10834-10850; doi:10.3390/s120810834
Received: 10 June 2012 / Revised: 28 July 2012 / Accepted: 31 July 2012 / Published: 7 August 2012
Cited by 1 | PDF Full-text (886 KB) | HTML Full-text | XML Full-text
Abstract
As wireless sensor networks are usually deployed in unattended areas, security policies cannot be updated in a timely fashion upon identification of new attacks. This gives enough time for attackers to cause significant damage. Thus, it is of great importance to provide [...] Read more.
As wireless sensor networks are usually deployed in unattended areas, security policies cannot be updated in a timely fashion upon identification of new attacks. This gives enough time for attackers to cause significant damage. Thus, it is of great importance to provide protection from unknown attacks. However, existing solutions are mostly concentrated on known attacks. On the other hand, mobility can make the sensor network more resilient to failures, reactive to events, and able to support disparate missions with a common set of sensors, yet the problem of security becomes more complicated. In order to address the issue of security in networks with mobile nodes, we propose a machine learning solution for anomaly detection along with the feature extraction process that tries to detect temporal and spatial inconsistencies in the sequences of sensed values and the routing paths used to forward these values to the base station. We also propose a special way to treat mobile nodes, which is the main novelty of this work. The data produced in the presence of an attacker are treated as outliers, and detected using clustering techniques. These techniques are further coupled with a reputation system, in this way isolating compromised nodes in timely fashion. The proposal exhibits good performances at detecting and confining previously unseen attacks, including the cases when mobile nodes are compromised. Full article
Open AccessArticle A Low-Cost, Portable, High-Throughput Wireless Sensor System for Phonocardiography Applications
Sensors 2012, 12(8), 10851-10870; doi:10.3390/s120810851
Received: 2 July 2012 / Revised: 27 July 2012 / Accepted: 30 July 2012 / Published: 7 August 2012
Cited by 4 | PDF Full-text (1006 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the design and testing of a wireless sensor system developed using a Microchip PICDEM developer kit to acquire and monitor human heart sounds for phonocardiography applications. This system can serve as a cost-effective option to the recent developments in [...] Read more.
This paper presents the design and testing of a wireless sensor system developed using a Microchip PICDEM developer kit to acquire and monitor human heart sounds for phonocardiography applications. This system can serve as a cost-effective option to the recent developments in wireless phonocardiography sensors that have primarily focused on Bluetooth technology. This wireless sensor system has been designed and developed in-house using off-the-shelf components and open source software for remote and mobile applications. The small form factor (3.75 cm ´ 5 cm ´ 1 cm), high throughput (6,000 Hz data streaming rate), and low cost ($13 per unit for a 1,000 unit batch) of this wireless sensor system make it particularly attractive for phonocardiography and other sensing applications. The experimental results of sensor signal analysis using several signal characterization techniques suggest that this wireless sensor system can capture both fundamental heart sounds (S1 and S2), and is also capable of capturing abnormal heart sounds (S3 and S4) and heart murmurs without aliasing. The results of a denoising application using Wavelet Transform show that the undesirable noises of sensor signals in the surrounding environment can be reduced dramatically. The exercising experiment results also show that this proposed wireless PCG system can capture heart sounds over different heart conditions simulated by varying heart rates of six subjects over a range of 60–180 Hz through exercise testing. Full article
(This article belongs to the Special Issue BioMEMS and Advanced Analytical Sensors for Biological Applications)
Open AccessArticle Fast Analysis of Superoxide Dismutase (SOD) Activity in Barley Leaves Using Visible and Near Infrared Spectroscopy
Sensors 2012, 12(8), 10871-10880; doi:10.3390/s120810871
Received: 14 May 2012 / Revised: 20 June 2012 / Accepted: 31 July 2012 / Published: 7 August 2012
Cited by 5 | PDF Full-text (673 KB) | HTML Full-text | XML Full-text
Abstract
Visible and near infrared (Vis/NIR) spectroscopy was investigated for the fast analysis of superoxide dismutase (SOD) activity in barley (Hordeum vulgare L.) leaves. Seven different spectra preprocessing methods were compared. Four regression methods were used for comparison of prediction performance, including [...] Read more.
Visible and near infrared (Vis/NIR) spectroscopy was investigated for the fast analysis of superoxide dismutase (SOD) activity in barley (Hordeum vulgare L.) leaves. Seven different spectra preprocessing methods were compared. Four regression methods were used for comparison of prediction performance, including partial least squares (PLS), multiple linear regression (MLR), least squares-support vector machine (LS-SVM) and Gaussian process regress (GPR). Successive projections algorithm (SPA) and regression coefficients (RC) were applied to select effective wavelengths (EWs) to develop more parsimonious models. The results indicated that Savitzky-Golay smoothing (SG) and multiplicative scatter correction (MSC) should be selected as the optimum preprocessing methods. The best prediction performance was achieved by the LV-LS-SVM model on SG spectra, and the correlation coefficients (r) and root mean square error of prediction (RMSEP) were 0.9064 and 0.5336, respectively. The conclusion was that Vis/NIR spectroscopy combined with multivariate analysis could be successfully applied for the fast estimation of SOD activity in barley leaves. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Comb-Drive Actuator Driven by Capacitively-Coupled-Power
Sensors 2012, 12(8), 10881-10889; doi:10.3390/s120810881
Received: 20 June 2012 / Revised: 17 July 2012 / Accepted: 27 July 2012 / Published: 7 August 2012
Cited by 2 | PDF Full-text (373 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a new actuation mechanism to drive comb-drive actuators. An asymmetric configuration of the finger overlap was used to generate capacitive coupling for the actuation mechanism. When the driving voltages were applied on the stators, a voltage would be induced [...] Read more.
This paper presents a new actuation mechanism to drive comb-drive actuators. An asymmetric configuration of the finger overlap was used to generate capacitive coupling for the actuation mechanism. When the driving voltages were applied on the stators, a voltage would be induced at the rotor due to the capacitive coupling. Then, an electrostatic force would be exerted onto the rotor due to the voltage differences between the stators and the rotor. The actuator’s static displacement and resonant frequency were theoretically analyzed. To verify the design, a comb-drive actuator with different initial finger overlaps, i.e., 159.3 μm and 48.9 μm on each side, was fabricated and tested. The results show that the actuator worked well using the proposed actuation mechanism. A static displacement of 41.7 μm and a resonant frequency of 577 Hz were achieved. Using the actuation mechanism, no electrical connection is required between the rotor and the outside power supply. This makes some comb-drive actuators containing heterogeneous structures easy to design and actuate. Full article
(This article belongs to the Special Issue Transducer Systems)
Open AccessArticle Determination of Soil Pore Water Salinity Using an FDR Sensor Working at Various Frequencies up to 500 MHz
Sensors 2012, 12(8), 10890-10905; doi:10.3390/s120810890
Received: 18 June 2012 / Revised: 27 July 2012 / Accepted: 1 August 2012 / Published: 7 August 2012
Cited by 11 | PDF Full-text (1298 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the application of a frequency-domain reflectometry (FDR) sensor designed for soil salinity assessment of sandy mineral soils in a wide range of soil moisture and bulk electrical conductivity, through the determination of soil complex dielectric permittivity spectra in the [...] Read more.
This paper presents the application of a frequency-domain reflectometry (FDR) sensor designed for soil salinity assessment of sandy mineral soils in a wide range of soil moisture and bulk electrical conductivity, through the determination of soil complex dielectric permittivity spectra in the frequency range 10–500 MHz. The real part of dielectric permittivity was assessed from the 380–440 MHz, while the bulk electrical conductivity was calculated from the 165–325 MHz range. The FDR technique allows determination of bulk electrical conductivity from the imaginary part of the complex dielectric permittivity, without disregarding the dielectric losses. The soil salinity status was determined using the salinity index, defined as a partial derivative of the soil bulk electrical conductivity with respect to the real part of the soil complex dielectric permittivity. The salinity index method enables determining the soil water electrical conductivity value. For the five sandy mineral soils that have been tested, the relationship between bulk electrical conductivity and the real part of dielectric permittivity is essentially linear. As a result, the salinity index method applied for FDR measurements may be adapted to field use after examination of loam and clayey soils. Full article
(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)
Open AccessArticle Novel Fiber Optic Sensor Probe with a Pair of Highly Reflected Connectors and a Vessel of Water Absorption Material for Water Leak Detection
Sensors 2012, 12(8), 10906-10919; doi:10.3390/s120810906
Received: 23 July 2012 / Revised: 3 August 2012 / Accepted: 3 August 2012 / Published: 7 August 2012
Cited by 5 | PDF Full-text (679 KB) | HTML Full-text | XML Full-text
Abstract
The use of a fiber optic quasi-distributed sensing technique for detecting the location and severity of water leakage is suggested. A novel fiber optic sensor probe is devised with a vessel of water absorption material called as water combination soil (WCS) located [...] Read more.
The use of a fiber optic quasi-distributed sensing technique for detecting the location and severity of water leakage is suggested. A novel fiber optic sensor probe is devised with a vessel of water absorption material called as water combination soil (WCS) located between two highly reflected connectors: one is a reference connector and the other is a sensing connector. In this study, the sensing output is calculated from the reflected light signals of the two connectors. The first reflected light signal is a reference and the second is a sensing signal which is attenuated by the optical fiber bending loss due to the WCS expansion absorbing water. Also, the bending loss of each sensor probe is determined by referring to the total number of sensor probes and the total power budget of an entire system. We have investigated several probe characteristics to show the design feasibility of the novel fiber sensor probe. The effects of vessel sizes of the probes on the water detection sensitivity are studied. The largest vessel probe provides the highest sensitivity of 0.267 dB/mL, while the smallest shows relatively low sensitivity of 0.067 dB/mL, and unstable response. The sensor probe with a high output value provides a high sensitivity with various detection levels while the number of total installable sensor probes decreases. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2012)
Open AccessArticle Aircraft Aerodynamic Parameter Detection Using Micro Hot-Film Flow Sensor Array and BP Neural Network Identification
Sensors 2012, 12(8), 10920-10929; doi:10.3390/s120810920
Received: 25 April 2012 / Revised: 29 June 2012 / Accepted: 1 August 2012 / Published: 7 August 2012
Cited by 11 | PDF Full-text (477 KB) | HTML Full-text | XML Full-text
Abstract
Air speed, angle of sideslip and angle of attack are fundamental aerodynamic parameters for controlling most aircraft. For small aircraft for which conventional detecting devices are too bulky and heavy to be utilized, a novel and practical methodology by which the aerodynamic [...] Read more.
Air speed, angle of sideslip and angle of attack are fundamental aerodynamic parameters for controlling most aircraft. For small aircraft for which conventional detecting devices are too bulky and heavy to be utilized, a novel and practical methodology by which the aerodynamic parameters are inferred using a micro hot-film flow sensor array mounted on the surface of the wing is proposed. A back-propagation neural network is used to model the coupling relationship between readings of the sensor array and aerodynamic parameters. Two different sensor arrangements are tested in wind tunnel experiments and dependence of the system performance on the sensor arrangement is analyzed. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle A Beacon Interval Shifting Scheme for Interference Mitigation in Body Area Networks
Sensors 2012, 12(8), 10930-10946; doi:10.3390/s120810930
Received: 10 April 2012 / Revised: 22 May 2012 / Accepted: 3 August 2012 / Published: 7 August 2012
Cited by 3 | PDF Full-text (372 KB) | HTML Full-text | XML Full-text
Abstract
This paper investigates the issue of interference avoidance in body area networks (BANs). IEEE 802.15 Task Group 6 presented several schemes to reduce such interference, but these schemes are still not proper solutions for BANs. We present a novel distributed TDMA-based beacon [...] Read more.
This paper investigates the issue of interference avoidance in body area networks (BANs). IEEE 802.15 Task Group 6 presented several schemes to reduce such interference, but these schemes are still not proper solutions for BANs. We present a novel distributed TDMA-based beacon interval shifting scheme that reduces interference in the BANs. A design goal of the scheme is to avoid the wakeup period of each BAN coinciding with other networks by employing carrier sensing before a beacon transmission. We analyze the beacon interval shifting scheme and investigate the proper back-off length when the channel is busy. We compare the performance of the proposed scheme with the schemes presented in IEEE 802.15 Task Group 6 using an OMNeT++ simulation. The simulation results show that the proposed scheme has a lower packet loss, energy consumption, and delivery-latency than the schemes of IEEE 802.15 Task Group 6. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Adaptive Color Calibration Based One-Shot Structured Light System
Sensors 2012, 12(8), 10947-10963; doi:10.3390/s120810947
Received: 15 June 2012 / Revised: 23 July 2012 / Accepted: 23 July 2012 / Published: 8 August 2012
Cited by 5 | PDF Full-text (2439 KB) | HTML Full-text | XML Full-text
Abstract
In one-shot color structured light systems, the color of stripe patterns are typically distorted with respect to color crosstalk, ambient light and the albedo of the scanned objects, leading to mismatch in the correspondence of color stripes between the projected and captured [...] Read more.
In one-shot color structured light systems, the color of stripe patterns are typically distorted with respect to color crosstalk, ambient light and the albedo of the scanned objects, leading to mismatch in the correspondence of color stripes between the projected and captured images. In this paper, an adaptive color calibration and Discrete Trend Transform algorithm are presented to achieve high-resolution 3D reconstructions. The adaptive color calibration, according to the relative albedo in RGB channels, can improve the accuracy of labeling stripe by alleviating the effect of albedo and ambient light while decoding the color. Furthermore, the Discrete Trend Transform in the M channel makes the color calibration an effective method for detecting weak stripes due to the uneven surfaces or reflectance characteristics of the scanned objects. With this approach, the presented system is suitable for scanning moving objects and generating high-resolution 3D reconstructions without the need of dark laboratory environments. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle The Combined Application of Impinger System and Permeation Tube for the Generation of Volatile Organic Compound Standard Gas Mixtures at Varying Diluent Flow Rates
Sensors 2012, 12(8), 10964-10979; doi:10.3390/s120810964
Received: 21 May 2012 / Revised: 13 July 2012 / Accepted: 2 August 2012 / Published: 8 August 2012
Cited by 1 | PDF Full-text (583 KB) | HTML Full-text | XML Full-text
Abstract
Commercial standard gas generators are often complex and expensive devices. The objective of this research was to assess the performance of a simplified glass impinger system for standard gas generation from a permeation tube (PT) device. The performance of the impinger standard [...] Read more.
Commercial standard gas generators are often complex and expensive devices. The objective of this research was to assess the performance of a simplified glass impinger system for standard gas generation from a permeation tube (PT) device. The performance of the impinger standard gas generation system was assessed for four aromatic VOCs (benzene, toluene, ethylbenzene, and m-xylene; BTEX) at varying flow rates (FR) of 50 to 800 mL·min−1. Because actual permeation rate (APR) values deviated from those computed by the manufacturer’s formula (MPR), new empirical relationships were developed to derive the predicted PR (PPR) of the target components. Experimental results corrected by such a formula indicate that the compatibility between the APR and MPR generally increased with low FR, while the reproducibility was generally reduced with decreasing flow rate. Although compatibility between different PRs is at a relatively small and narrow FR range, the use of correction formula is recommendable for the accurate use of PT. Full article
Open AccessArticle Use of a Combined SpO2/PtcCO2 Sensor in the Delivery Room
Sensors 2012, 12(8), 10980-10989; doi:10.3390/s120810980
Received: 12 June 2012 / Revised: 16 July 2012 / Accepted: 31 July 2012 / Published: 8 August 2012
Cited by 3 | PDF Full-text (321 KB) | HTML Full-text | XML Full-text
Abstract
Arterial oxygen saturation (SaO2) and partial arterial pressure of carbon dioxide (PaCO2) are important respiratory parameters in critically ill neonates. A sensor combining a pulse oximeter with the Stow-Severinghaus electrode, required for the measurement of peripheral oxygen saturation [...] Read more.
Arterial oxygen saturation (SaO2) and partial arterial pressure of carbon dioxide (PaCO2) are important respiratory parameters in critically ill neonates. A sensor combining a pulse oximeter with the Stow-Severinghaus electrode, required for the measurement of peripheral oxygen saturation (SpO2) and transcutaneous partial pressure of carbon dioxide (PtcCO2), respectively, has been recently used in neonatal clinical practice (TOSCA500ÒRadiometer). We evaluated TOSCA usability and reliability in the delivery room (DR), throughout three different periods, on term, late-preterm, and preterm neonates. During the first period (period A), 30 healthy term neonates were simultaneously monitored with both TOSCA and a MASIMO pulse oximeter. During the second period (period B), 10 healthy late-preterm neonates were monitored with both TOSCA and a transcutaneous device measuring PtcCO2 (TINAÒ TCM3, Radiometer). During the third period (period C), 15 preterm neonates were monitored with TOSCA and MASIMO after birth, during stabilization, and during transport to the neonatal intensive care unit (NICU). Blood gas analyses were performed to compare transcutaneous and blood gas values. TOSCA resulted easily and safely usable in the DR, allowing reliable noninvasive SaO2 estimation. Since PtcCO2 measurements with TOSCA required at least 10 min to be stable and reliable, this parameter was not useful during the early resuscitation immediately after birth. Moreover, PtcCO2 levels were less precise if compared to the conventional transcutaneous monitoring. However, PtcCO2 measurement by TOSCA was useful as trend-monitoring after stabilization and during transport to NICU. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2012)
Open AccessArticle A Comparison between Metaheuristics as Strategies for Minimizing Cyclic Instability in Ambient Intelligence
Sensors 2012, 12(8), 10990-11012; doi:10.3390/s120810990
Received: 3 June 2012 / Revised: 3 July 2012 / Accepted: 10 July 2012 / Published: 8 August 2012
Cited by 1 | PDF Full-text (1296 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we present a comparison between six novel approaches to the fundamental problem of cyclic instability in Ambient Intelligence. These approaches are based on different optimization algorithms, Particle Swarm Optimization (PSO), Bee Swarm Optimization (BSO), micro Particle Swarm Optimization (μ-PSO), [...] Read more.
In this paper we present a comparison between six novel approaches to the fundamental problem of cyclic instability in Ambient Intelligence. These approaches are based on different optimization algorithms, Particle Swarm Optimization (PSO), Bee Swarm Optimization (BSO), micro Particle Swarm Optimization (μ-PSO), Artificial Immune System (AIS), Genetic Algorithm (GA) and Mutual Information Maximization for Input Clustering (MIMIC). In order to be able to use these algorithms, we introduced the concept of Average Cumulative Oscillation (ACO), which enabled us to measure the average behavior of the system. This approach has the advantage that it does not need to analyze the topological properties of the system, in particular the loops, which can be computationally expensive. In order to test these algorithms we used the well-known discrete system called the Game of Life for 9, 25, 49 and 289 agents. It was found that PSO and μ-PSO have the best performance in terms of the number of agents locked. These results were confirmed using the Wilcoxon Signed Rank Test. This novel and successful approach is very promising and can be used to remove instabilities in real scenarios with a large number of agents (including nomadic agents) and complex interactions and dependencies among them. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Fault Diagnostics for Turbo-Shaft Engine Sensors Based on a Simplified On-Board Model
Sensors 2012, 12(8), 11061-11076; doi:10.3390/s120811061
Received: 12 June 2012 / Revised: 30 July 2012 / Accepted: 30 July 2012 / Published: 9 August 2012
Cited by 7 | PDF Full-text (553 KB) | HTML Full-text | XML Full-text
Abstract
Combining a simplified on-board turbo-shaft model with sensor fault diagnostic logic, a model-based sensor fault diagnosis method is proposed. The existing fault diagnosis method for turbo-shaft engine key sensors is mainly based on a double redundancies technique, and this can’t be satisfied [...] Read more.
Combining a simplified on-board turbo-shaft model with sensor fault diagnostic logic, a model-based sensor fault diagnosis method is proposed. The existing fault diagnosis method for turbo-shaft engine key sensors is mainly based on a double redundancies technique, and this can’t be satisfied in some occasions as lack of judgment. The simplified on-board model provides the analytical third channel against which the dual channel measurements are compared, while the hardware redundancy will increase the structure complexity and weight. The simplified turbo-shaft model contains the gas generator model and the power turbine model with loads, this is built up via dynamic parameters method. Sensor fault detection, diagnosis (FDD) logic is designed, and two types of sensor failures, such as the step faults and the drift faults, are simulated. When the discrepancy among the triplex channels exceeds a tolerance level, the fault diagnosis logic determines the cause of the difference. Through this approach, the sensor fault diagnosis system achieves the objectives of anomaly detection, sensor fault diagnosis and redundancy recovery. Finally, experiments on this method are carried out on a turbo-shaft engine, and two types of faults under different channel combinations are presented. The experimental results show that the proposed method for sensor fault diagnostics is efficient. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Closed Loop Control of Penetration Depth during CO2 Laser Lap Welding Processes
Sensors 2012, 12(8), 11077-11090; doi:10.3390/s120811077
Received: 25 June 2012 / Revised: 2 August 2012 / Accepted: 6 August 2012 / Published: 9 August 2012
Cited by 5 | PDF Full-text (297 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we describe a novel spectroscopic closed loop control system capable of stabilizing the penetration depth during laser welding processes by controlling the laser power. Our novel approach is to analyze the optical emission from the laser generated plasma plume [...] Read more.
In this paper we describe a novel spectroscopic closed loop control system capable of stabilizing the penetration depth during laser welding processes by controlling the laser power. Our novel approach is to analyze the optical emission from the laser generated plasma plume above the keyhole, to calculate its electron temperature as a process-monitoring signal. Laser power has been controlled by using a quantitative relationship between the penetration depth and the plasma electron temperature. The sensor is able to correlate in real time the difference between the measured electron temperature and its reference value for the requested penetration depth. Accordingly the closed loop system adjusts the power, thus maintaining the penetration depth. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Design and Fabrication of a Large-Stroke Deformable Mirror Using a Gear-Shape Ionic-Conductive Polymer Metal Composite
Sensors 2012, 12(8), 11100-11112; doi:10.3390/s120811100
Received: 10 June 2012 / Revised: 24 July 2012 / Accepted: 31 July 2012 / Published: 9 August 2012
Cited by 3 | PDF Full-text (1006 KB) | HTML Full-text | XML Full-text
Abstract
Conventional camera modules with image sensors manipulate the focus or zoom by moving lenses. Although motors, such as voice-coil motors, can move the lens sets precisely, large volume, high power consumption, and long moving time are critical issues for motor-type camera modules. [...] Read more.
Conventional camera modules with image sensors manipulate the focus or zoom by moving lenses. Although motors, such as voice-coil motors, can move the lens sets precisely, large volume, high power consumption, and long moving time are critical issues for motor-type camera modules. A deformable mirror (DM) provides a good opportunity to improve these issues. The DM is a reflective type optical component which can alter the optical power to focus the lights on the two dimensional optical image sensors. It can make the camera system operate rapidly. Ionic polymer metal composite (IPMC) is a promising electro-actuated polymer material that can be used in micromachining devices because of its large deformation with low actuation voltage. We developed a convenient simulation model based on Young’s modulus and Poisson’s ratio. We divided an ion exchange polymer, also known as Nafion®, into two virtual layers in the simulation model: one was expansive and the other was contractive, caused by opposite constant surface forces on each surface of the elements. Therefore, the deformation for different IPMC shapes can be described more easily. A standard experiment of voltage vs. tip displacement was used to verify the proposed modeling. Finally, a gear shaped IPMC actuator was designed and tested. Optical power of the IPMC deformable mirror is experimentally demonstrated to be 17 diopters with two volts. The needed voltage was about two orders lower than conventional silicon deformable mirrors and about one order lower than the liquid lens. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle An Intelligent Knowledge-Based and Customizable Home Care System Framework with Ubiquitous Patient Monitoring and Alerting Techniques
Sensors 2012, 12(8), 11154-11186; doi:10.3390/s120811154
Received: 9 July 2012 / Revised: 5 August 2012 / Accepted: 8 August 2012 / Published: 10 August 2012
Cited by 7 | PDF Full-text (2442 KB) | HTML Full-text | XML Full-text
Abstract
This study develops and integrates an efficient knowledge-based system and a component-based framework to design an intelligent and flexible home health care system. The proposed knowledge-based system integrates an efficient rule-based reasoning model and flexible knowledge rules for determining efficiently and rapidly [...] Read more.
This study develops and integrates an efficient knowledge-based system and a component-based framework to design an intelligent and flexible home health care system. The proposed knowledge-based system integrates an efficient rule-based reasoning model and flexible knowledge rules for determining efficiently and rapidly the necessary physiological and medication treatment procedures based on software modules, video camera sensors, communication devices, and physiological sensor information. This knowledge-based system offers high flexibility for improving and extending the system further to meet the monitoring demands of new patient and caregiver health care by updating the knowledge rules in the inference mechanism. All of the proposed functional components in this study are reusable, configurable, and extensible for system developers. Based on the experimental results, the proposed intelligent homecare system demonstrates that it can accomplish the extensible, customizable, and configurable demands of the ubiquitous healthcare systems to meet the different demands of patients and caregivers under various rehabilitation and nursing conditions. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A Hybrid TOA-Fingerprinting Based Localization of Mobile Nodes Using UWB Signaling for Non Line-Of-Sight Conditions
Sensors 2012, 12(8), 11187-11204; doi:10.3390/s120811187
Received: 2 July 2012 / Revised: 3 August 2012 / Accepted: 7 August 2012 / Published: 10 August 2012
Cited by 9 | PDF Full-text (2022 KB) | HTML Full-text | XML Full-text
Abstract
Recently, Impulse Radio Ultra Wideband (IR-UWB) signaling has become popular for providing precise location accuracy for mobile and wireless sensor node localization in the indoor environment due to its large bandwidth and high time resolution while providing ultra-high transmission capacity. However, the [...] Read more.
Recently, Impulse Radio Ultra Wideband (IR-UWB) signaling has become popular for providing precise location accuracy for mobile and wireless sensor node localization in the indoor environment due to its large bandwidth and high time resolution while providing ultra-high transmission capacity. However, the Non-line-of-sight (NLOS) error mitigation has considerable importance in localization of wireless nodes. In order to mitigate NLOS errors in indoor localization this paper proposes and investigates a novel approach which creates a hybrid combination of channel impulse response (CIR)-based fingerprinting (FP) positioning and an iterative Time of Arrival (TOA) real time positioning method using Ultra Wideband (UWB) signaling. Besides, to reduce the calculation complexities in FP method, this paper also introduces a unique idea for the arrangement of reference nodes (or tags) to create a fingerprinting database. The simulation results confirm that the proposed hybrid method yields better positioning accuracies and is much more robust in NLOS error mitigation than TOA only and FP only and a conventional iterative positioning method. Full article
(This article belongs to the Special Issue Ubiquitous Sensing)
Open AccessArticle Noise Smoothing for Structural Vibration Test Signals Using an Improved Wavelet Thresholding Technique
Sensors 2012, 12(8), 11205-11220; doi:10.3390/s120811205
Received: 11 June 2012 / Revised: 6 August 2012 / Accepted: 6 August 2012 / Published: 10 August 2012
Cited by 38 | PDF Full-text (822 KB) | HTML Full-text | XML Full-text
Abstract
In structural vibration tests, one of the main factors which disturb the reliability and accuracy of the results are the noise signals encountered. To overcome this deficiency, this paper presents a discrete wavelet transform (DWT) approach to denoise the measured signals. The [...] Read more.
In structural vibration tests, one of the main factors which disturb the reliability and accuracy of the results are the noise signals encountered. To overcome this deficiency, this paper presents a discrete wavelet transform (DWT) approach to denoise the measured signals. The denoising performance of DWT is discussed by several processing parameters, including the type of wavelet, decomposition level, thresholding method, and threshold selection rules. To overcome the disadvantages of the traditional hard- and soft-thresholding methods, an improved thresholding technique called the sigmoid function-based thresholding scheme is presented. The procedure is validated by using four benchmarks signals with three degrees of degradation as well as a real measured signal obtained from a three-story reinforced concrete scale model shaking table experiment. The performance of the proposed method is evaluated by computing the signal-to-noise ratio (SNR) and the root-mean-square error (RMSE) after denoising. Results reveal that the proposed method offers superior performance than the traditional methods no matter whether the signals have heavy or light noises embedded. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Complete Scene Recovery and Terrain Classification in Textured Terrain Meshes
Sensors 2012, 12(8), 11221-11237; doi:10.3390/s120811221
Received: 16 July 2012 / Revised: 7 August 2012 / Accepted: 7 August 2012 / Published: 13 August 2012
Cited by 2 | PDF Full-text (1232 KB) | HTML Full-text | XML Full-text
Abstract
Terrain classification allows a mobile robot to create an annotated map of its local environment from the three-dimensional (3D) and two-dimensional (2D) datasets collected by its array of sensors, including a GPS receiver, gyroscope, video camera, and range sensor. However, parts of [...] Read more.
Terrain classification allows a mobile robot to create an annotated map of its local environment from the three-dimensional (3D) and two-dimensional (2D) datasets collected by its array of sensors, including a GPS receiver, gyroscope, video camera, and range sensor. However, parts of objects that are outside the measurement range of the range sensor will not be detected. To overcome this problem, this paper describes an edge estimation method for complete scene recovery and complete terrain reconstruction. Here, the Gibbs-Markov random field is used to segment the ground from 2D videos and 3D point clouds. Further, a masking method is proposed to classify buildings and trees in a terrain mesh. Full article
(This article belongs to the Special Issue Ubiquitous Sensing)
Open AccessArticle Biotin-Functionalized Semiconducting Polymer in an Organic Field Effect Transistor and Application as a Biosensor
Sensors 2012, 12(8), 11238-11248; doi:10.3390/s120811238
Received: 24 July 2012 / Revised: 8 August 2012 / Accepted: 9 August 2012 / Published: 13 August 2012
Cited by 3 | PDF Full-text (533 KB) | HTML Full-text | XML Full-text
Abstract
This report presents biotin-functionalized semiconducting polymers that are based on fluorene and bithiophene co-polymers (F8T2). Also presented is the application of these polymers to an organic thin film transistor used as a biosensor. The side chains of fluorene were partially biotinylated after [...] Read more.
This report presents biotin-functionalized semiconducting polymers that are based on fluorene and bithiophene co-polymers (F8T2). Also presented is the application of these polymers to an organic thin film transistor used as a biosensor. The side chains of fluorene were partially biotinylated after the esterification of the biotin with corresponding alcohol-groups at the side chain in F8T2. Their properties as an organic semiconductor were tested using an organic thin film transistor (OTFT) and were found to show typical p-type semiconductor curves. The functionality of this biosensor in the sensing of biologically active molecules such as avidin in comparison with bovine serum albumin (BSA) was established through a selective decrease in the conductivity of the transistor, as measured with a device that was developed by the authors. Changes to the optical properties of this polymer were also measured through the change in the color of the UV-fluorescence before and after a reaction with avidin or BSA. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Three-Dimensional Laser Scanning for Geometry Documentation and Construction Management of Highway Tunnels during Excavation
Sensors 2012, 12(8), 11249-11270; doi:10.3390/s120811249
Received: 19 June 2012 / Revised: 20 July 2012 / Accepted: 30 July 2012 / Published: 14 August 2012
Cited by 16 | PDF Full-text (891 KB) | HTML Full-text | XML Full-text
Abstract
Driven by progress in sensor technology, computer software and data processing capabilities, terrestrial laser scanning has recently proved a revolutionary technique for high accuracy, 3D mapping and documentation of physical scenarios and man-made structures. Particularly, this is of great importance in the [...] Read more.
Driven by progress in sensor technology, computer software and data processing capabilities, terrestrial laser scanning has recently proved a revolutionary technique for high accuracy, 3D mapping and documentation of physical scenarios and man-made structures. Particularly, this is of great importance in the underground space and tunnel construction environment as surveying engineering operations have a great impact on both technical and economic aspects of a project. This paper discusses the use and explores the potential of laser scanning technology to accurately track excavation and construction activities of highway tunnels. It provides a detailed overview of the static laser scanning method, its principles of operation and applications for tunnel construction operations. Also, it discusses the planning, execution, data processing and analysis phases of laser scanning activities, with emphasis given on geo-referencing, mesh model generation and cross-section extraction. Specific case studies are considered based on two construction sites in Greece. Particularly, the potential of the method is examined for checking the tunnel profile, producing volume computations and validating the smoothness/thickness of shotcrete layers at an excavation stage and during the completion of excavation support and primary lining. An additional example of the use of the method in the geometric documentation of the concrete lining formwork is examined and comparisons against dimensional tolerances are examined. Experimental comparisons and analyses of the laser scanning method against conventional surveying techniques are also considered. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Semi-Automatic Image-Based Close Range 3D Modeling Pipeline Using a Multi-Camera Configuration
Sensors 2012, 12(8), 11271-11293; doi:10.3390/s120811271
Received: 30 June 2012 / Revised: 1 August 2012 / Accepted: 6 August 2012 / Published: 14 August 2012
Cited by 6 | PDF Full-text (2364 KB) | HTML Full-text | XML Full-text
Abstract
The generation of photo-realistic 3D models is an important task for digital recording of cultural heritage objects. This study proposes an image-based 3D modeling pipeline which takes advantage of a multi-camera configuration and multi-image matching technique that does not require any markers [...] Read more.
The generation of photo-realistic 3D models is an important task for digital recording of cultural heritage objects. This study proposes an image-based 3D modeling pipeline which takes advantage of a multi-camera configuration and multi-image matching technique that does not require any markers on or around the object. Multiple digital single lens reflex (DSLR) cameras are adopted and fixed with invariant relative orientations. Instead of photo-triangulation after image acquisition, calibration is performed to estimate the exterior orientation parameters of the multi-camera configuration which can be processed fully automatically using coded targets. The calibrated orientation parameters of all cameras are applied to images taken using the same camera configuration. This means that when performing multi-image matching for surface point cloud generation, the orientation parameters will remain the same as the calibrated results, even when the target has changed. Base on this invariant character, the whole 3D modeling pipeline can be performed completely automatically, once the whole system has been calibrated and the software was seamlessly integrated. Several experiments were conducted to prove the feasibility of the proposed system. Images observed include that of a human being, eight Buddhist statues, and a stone sculpture. The results for the stone sculpture, obtained with several multi-camera configurations were compared with a reference model acquired by an ATOS-I 2M active scanner. The best result has an absolute accuracy of 0.26 mm and a relative accuracy of 1:17,333. It demonstrates the feasibility of the proposed low-cost image-based 3D modeling pipeline and its applicability to a large quantity of antiques stored in a museum. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Switching Algorithm for Maglev Train Double-Modular Redundant Positioning Sensors
Sensors 2012, 12(8), 11294-11306; doi:10.3390/s120811294
Received: 28 June 2012 / Revised: 30 July 2012 / Accepted: 1 August 2012 / Published: 15 August 2012
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Abstract
High-resolution positioning for maglev trains is implemented by detecting the tooth-slot structure of the long stator installed along the rail, but there are large joint gaps between long stator sections. When a positioning sensor is below a large joint gap, its positioning [...] Read more.
High-resolution positioning for maglev trains is implemented by detecting the tooth-slot structure of the long stator installed along the rail, but there are large joint gaps between long stator sections. When a positioning sensor is below a large joint gap, its positioning signal is invalidated, thus double-modular redundant positioning sensors are introduced into the system. This paper studies switching algorithms for these redundant positioning sensors. At first, adaptive prediction is applied to the sensor signals. The prediction errors are used to trigger sensor switching. In order to enhance the reliability of the switching algorithm, wavelet analysis is introduced to suppress measuring disturbances without weakening the signal characteristics reflecting the stator joint gap based on the correlation between the wavelet coefficients of adjacent scales. The time delay characteristics of the method are analyzed to guide the algorithm simplification. Finally, the effectiveness of the simplified switching algorithm is verified through experiments. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Self-Optimizing Scheme for Energy Balanced Routing in Wireless Sensor Networks Using SensorAnt
Sensors 2012, 12(8), 11307-11333; doi:10.3390/s120811307
Received: 7 June 2012 / Revised: 23 July 2012 / Accepted: 3 August 2012 / Published: 15 August 2012
Cited by 9 | PDF Full-text (1118 KB) | HTML Full-text | XML Full-text
Abstract
Planning of energy-efficient protocols is critical for Wireless Sensor Networks (WSNs) because of the constraints on the sensor nodes’ energy. The routing protocol should be able to provide uniform power dissipation during transmission to the sink node. In this paper, we present [...] Read more.
Planning of energy-efficient protocols is critical for Wireless Sensor Networks (WSNs) because of the constraints on the sensor nodes’ energy. The routing protocol should be able to provide uniform power dissipation during transmission to the sink node. In this paper, we present a self-optimization scheme for WSNs which is able to utilize and optimize the sensor nodes’ resources, especially the batteries, to achieve balanced energy consumption across all sensor nodes. This method is based on the Ant Colony Optimization (ACO) metaheuristic which is adopted to enhance the paths with the best quality function. The assessment of this function depends on multi-criteria metrics such as the minimum residual battery power, hop count and average energy of both route and network. This method also distributes the traffic load of sensor nodes throughout the WSN leading to reduced energy usage, extended network life time and reduced packet loss. Simulation results show that our scheme performs much better than the Energy Efficient Ant-Based Routing (EEABR) in terms of energy consumption, balancing and efficiency. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Energy-Efficient Scheduling for Hybrid Tasks in Control Devices for the Internet of Things
Sensors 2012, 12(8), 11334-11359; doi:10.3390/s120811334
Received: 19 June 2012 / Revised: 1 August 2012 / Accepted: 6 August 2012 / Published: 17 August 2012
PDF Full-text (342 KB) | HTML Full-text | XML Full-text
Abstract
In control devices for the Internet of Things (IoT), energy is one of the critical restriction factors. Dynamic voltage scaling (DVS) has been proved to be an effective method for reducing the energy consumption of processors. This paper proposes an energy-efficient scheduling [...] Read more.
In control devices for the Internet of Things (IoT), energy is one of the critical restriction factors. Dynamic voltage scaling (DVS) has been proved to be an effective method for reducing the energy consumption of processors. This paper proposes an energy-efficient scheduling algorithm for IoT control devices with hard real-time control tasks (HRCTs) and soft real-time tasks (SRTs). The main contribution of this paper includes two parts. First, it builds the Hybrid tasks with multi-subtasks of different function Weight (HoW) task model for IoT control devices. HoW describes the structure of HRCTs and SRTs, and their properties, e.g., deadlines, execution time, preemption properties, and energy-saving goals, etc. Second, it presents the Hybrid Tasks’ Dynamic Voltage Scaling (HTDVS) algorithm. HTDVS first sets the slowdown factors of subtasks while meeting the different real-time requirements of HRCTs and SRTs, and then dynamically reclaims, reserves, and reuses the slack time of the subtasks to meet their ideal energy-saving goals. Experimental results show HTDVS can reduce energy consumption about 10%–80% while meeting the real-time requirements of HRCTs, HRCTs help to reduce the deadline miss ratio (DMR) of systems, and HTDVS has comparable performance with the greedy algorithm and is more favorable to keep the subtasks’ ideal speeds. Full article
(This article belongs to the Special Issue Ubiquitous Sensing)
Open AccessArticle An Improved Force Feedback Control Algorithm for Active Tendons
Sensors 2012, 12(8), 11360-11371; doi:10.3390/s120811360
Received: 20 July 2012 / Revised: 9 August 2012 / Accepted: 10 August 2012 / Published: 20 August 2012
Cited by 4 | PDF Full-text (342 KB) | HTML Full-text | XML Full-text
Abstract
An active tendon, consisting of a displacement actuator and a co-located force sensor, has been adopted by many studies to suppress the vibration of large space flexible structures. The damping, provided by the force feedback control algorithm in these studies, is small [...] Read more.
An active tendon, consisting of a displacement actuator and a co-located force sensor, has been adopted by many studies to suppress the vibration of large space flexible structures. The damping, provided by the force feedback control algorithm in these studies, is small and can increase, especially for tendons with low axial stiffness. This study introduces an improved force feedback algorithm, which is based on the idea of velocity feedback. The algorithm provides a large damping ratio for space flexible structures and does not require a structure model. The effectiveness of the algorithm is demonstrated on a structure similar to JPL-MPI. The results show that large damping can be achieved for the vibration control of large space structures. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Miniaturized Integrated Platform for Electrical and Optical Monitoring of Cell Cultures
Sensors 2012, 12(8), 11372-11390; doi:10.3390/s120811372
Received: 16 May 2012 / Revised: 2 August 2012 / Accepted: 2 August 2012 / Published: 21 August 2012
PDF Full-text (2928 KB) | HTML Full-text | XML Full-text
Abstract
The following paper describes the design and functions of a miniaturized integrated platform for optical and electrical monitoring of cell cultures and the necessary steps in the fabrication and testing of a silicon microchip Micro ElectroMechanical Systems (MEMS)-based technology for cell data [...] Read more.
The following paper describes the design and functions of a miniaturized integrated platform for optical and electrical monitoring of cell cultures and the necessary steps in the fabrication and testing of a silicon microchip Micro ElectroMechanical Systems (MEMS)-based technology for cell data recording, monitoring and stimulation. The silicon microchip consists of a MEMS machined device containing a shank of 240 μm width, 3 mm long and 50 μm thick and an enlarged area of 5 mm × 5 mm hosting the pads for electrical connections. Ten platinum electrodes and five sensors are placed on the shank and are connected with the external electronics through the pads. The sensors aim to monitor the pH, the temperature and the impedance of the cell culture. The electrodes are bidirectional and can be used both for electrical potential recording and stimulation of cells. The fabrication steps are presented, along with the electrical and optical characterization of the system. The target of the research is to develop a new and reconfigurable platform according to the particular applications needs, as a tool for the biologist, chemists and medical doctors working is the field of cell culture monitoring in terms of growth, maintenance conditions, reaction to electrical or chemical stimulation (drugs, toxicants, etc.). HaCaT (Immortalised Human Keratinocyte) cell culture has been used for demonstration purposes in order to provide information on the platform electrical and optical functions. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Real Time Voltage and Current Phase Shift Analyzer for Power Saving Applications
Sensors 2012, 12(8), 11391-11405; doi:10.3390/s120811391
Received: 26 June 2012 / Revised: 13 August 2012 / Accepted: 14 August 2012 / Published: 21 August 2012
Cited by 10 | PDF Full-text (1439 KB) | HTML Full-text | XML Full-text
Abstract
Nowadays, high importance is given to low energy devices (such as refrigerators, deep-freezers, washing machines, pumps, etc.) that are able to produce reactive power in power lines which can be optimized (reduced). Reactive power is the main component which overloads power [...] Read more.
Nowadays, high importance is given to low energy devices (such as refrigerators, deep-freezers, washing machines, pumps, etc.) that are able to produce reactive power in power lines which can be optimized (reduced). Reactive power is the main component which overloads power lines and brings excessive thermal stress to conductors. If the reactive power is optimized, it can significantly lower the electricity consumption (from 10 to 30%—varies between countries). This paper will examine and discuss the development of a measuring device for analyzing reactive power. However, the main problem is the precise real time measurement of the input and output voltage and current. Such quality measurement is needed to allow adequate action intervention (feedback which reduces or fully compensates reactive power). Several other issues, such as the accuracy and measurement speed, must be examined while designing this device. The price and the size of the final product need to remain low as they are the two important parameters of this solution. Full article
(This article belongs to the Section Physical Sensors)

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Open AccessReview CMOS Cell Sensors for Point-of-Care Diagnostics
Sensors 2012, 12(8), 10042-10066; doi:10.3390/s120810042
Received: 15 May 2012 / Revised: 6 July 2012 / Accepted: 21 July 2012 / Published: 25 July 2012
Cited by 9 | PDF Full-text (2336 KB) | HTML Full-text | XML Full-text
Abstract
The burden of health-care related services in a global era with continuously increasing population and inefficient dissipation of the resources requires effective solutions. From this perspective, point-of-care diagnostics is a demanded field in clinics. It is also necessary both for prompt diagnosis [...] Read more.
The burden of health-care related services in a global era with continuously increasing population and inefficient dissipation of the resources requires effective solutions. From this perspective, point-of-care diagnostics is a demanded field in clinics. It is also necessary both for prompt diagnosis and for providing health services evenly throughout the population, including the rural districts. The requirements can only be fulfilled by technologies whose productivity has already been proven, such as complementary metal-oxide-semiconductors (CMOS). CMOS-based products can enable clinical tests in a fast, simple, safe, and reliable manner, with improved sensitivities. Portability due to diminished sensor dimensions and compactness of the test set-ups, along with low sample and power consumption, is another vital feature. CMOS-based sensors for cell studies have the potential to become essential counterparts of point-of-care diagnostics technologies. Hence, this review attempts to inform on the sensors fabricated with CMOS technology for point-of-care diagnostic studies, with a focus on CMOS image sensors and capacitance sensors for cell studies. Full article
(This article belongs to the Special Issue Micro and Nano Technologies for Point-of-Care Diagnosis)
Open AccessReview In-Line Fiber Optic Interferometric Sensors in Single-Mode Fibers
Sensors 2012, 12(8), 10430-10449; doi:10.3390/s120810430
Received: 14 May 2012 / Revised: 5 June 2012 / Accepted: 30 July 2012 / Published: 2 August 2012
Cited by 40 | PDF Full-text (1126 KB) | HTML Full-text | XML Full-text
Abstract
In-line fiber optic interferometers have attracted intensive attention for their potential sensing applications in refractive index, temperature, pressure and strain measurement, etc. Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers. It’s known that the in-line fiber [...] Read more.
In-line fiber optic interferometers have attracted intensive attention for their potential sensing applications in refractive index, temperature, pressure and strain measurement, etc. Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers. It’s known that the in-line fiber optic interferometers based on single-mode fibers can exhibit compact structures, easy fabrication and low cost. In this paper, we review two kinds of typical in-line fiber optic interferometers formed in single-mode fibers fabricated with different post-processing techniques. Also, some recently reported specific technologies for fabricating such fiber optic interferometers are presented. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessReview Cross Layer Adaptation of Check Intervals in Low Power Listening MAC Protocols for Lifetime Improvement in Wireless Sensor Networks
Sensors 2012, 12(8), 10511-10535; doi:10.3390/s120810511
Received: 16 July 2012 / Revised: 16 July 2012 / Accepted: 27 July 2012 / Published: 2 August 2012
Cited by 3 | PDF Full-text (546 KB) | HTML Full-text | XML Full-text
Abstract
Preamble sampling-based MAC protocols designed forWireless Sensor Networks (WSN) are aimed at prolonging the lifetime of the nodes by scheduling their times of activity. This scheduling exploits node synchronization to find the right trade-off between energy consumption and delay. In this paper [...] Read more.
Preamble sampling-based MAC protocols designed forWireless Sensor Networks (WSN) are aimed at prolonging the lifetime of the nodes by scheduling their times of activity. This scheduling exploits node synchronization to find the right trade-off between energy consumption and delay. In this paper we consider the problem of node synchronization in preamble sampling protocols. We propose Cross Layer Adaptation of Check intervals (CLAC), a novel protocol intended to reduce the energy consumption of the nodes without significantly increasing the delay. Our protocol modifies the scheduling of the nodes based on estimating the delay experienced by a packet that travels along a multi-hop path. CLAC uses routing and MAC layer information to compute a delay that matches the packet arrival time. We have implemented CLAC on top of well-known routing and MAC protocols for WSN, and we have evaluated our implementation using the Avrora simulator. The simulation results confirm that CLAC improves the network lifetime at no additional packet loss and without affecting the end-to-end delay. Full article
(This article belongs to the Section Sensor Networks)
Open AccessReview Lab-on-a-Chip Pathogen Sensors for Food Safety
Sensors 2012, 12(8), 10713-10741; doi:10.3390/s120810713
Received: 9 May 2012 / Revised: 28 June 2012 / Accepted: 4 July 2012 / Published: 6 August 2012
Cited by 39 | PDF Full-text (1224 KB) | HTML Full-text | XML Full-text
Abstract
There have been a number of cases of foodborne illness among humans that are caused by pathogens such as Escherichia coli O157:H7, Salmonella typhimurium, etc. The current practices to detect such pathogenic agents are cell culturing, immunoassays, or polymerase chain [...] Read more.
There have been a number of cases of foodborne illness among humans that are caused by pathogens such as Escherichia coli O157:H7, Salmonella typhimurium, etc. The current practices to detect such pathogenic agents are cell culturing, immunoassays, or polymerase chain reactions (PCRs). These methods are essentially laboratory-based methods that are not at all real-time and thus unavailable for early-monitoring of such pathogens. They are also very difficult to implement in the field. Lab-on-a-chip biosensors, however, have a strong potential to be used in the field since they can be miniaturized and automated; they are also potentially fast and very sensitive. These lab-on-a-chip biosensors can detect pathogens in farms, packaging/processing facilities, delivery/distribution systems, and at the consumer level. There are still several issues to be resolved before applying these lab-on-a-chip sensors to field applications, including the pre-treatment of a sample, proper storage of reagents, full integration into a battery-powered system, and demonstration of very high sensitivity, which are addressed in this review article. Several different types of lab-on-a-chip biosensors, including immunoassay- and PCR-based, have been developed and tested for detecting foodborne pathogens. Their assay performance, including detection limit and assay time, are also summarized. Finally, the use of optical fibers or optical waveguide is discussed as a means to improve the portability and sensitivity of lab-on-a-chip pathogen sensors. Full article
(This article belongs to the Special Issue Micro and Nano Technologies for Point-of-Care Diagnosis)
Open AccessReview Fully Integrated Biochip Platforms for Advanced Healthcare
Sensors 2012, 12(8), 11013-11060; doi:10.3390/s120811013
Received: 19 June 2012 / Revised: 10 July 2012 / Accepted: 17 July 2012 / Published: 8 August 2012
Cited by 24 | PDF Full-text (971 KB) | HTML Full-text | XML Full-text
Abstract
Recent advances in microelectronics and biosensors are enabling developments of innovative biochips for advanced healthcare by providing fully integrated platforms for continuous monitoring of a large set of human disease biomarkers. Continuous monitoring of several human metabolites can be addressed by using [...] Read more.
Recent advances in microelectronics and biosensors are enabling developments of innovative biochips for advanced healthcare by providing fully integrated platforms for continuous monitoring of a large set of human disease biomarkers. Continuous monitoring of several human metabolites can be addressed by using fully integrated and minimally invasive devices located in the sub-cutis, typically in the peritoneal region. This extends the techniques of continuous monitoring of glucose currently being pursued with diabetic patients. However, several issues have to be considered in order to succeed in developing fully integrated and minimally invasive implantable devices. These innovative devices require a high-degree of integration, minimal invasive surgery, long-term biocompatibility, security and privacy in data transmission, high reliability, high reproducibility, high specificity, low detection limit and high sensitivity. Recent advances in the field have already proposed possible solutions for several of these issues. The aim of the present paper is to present a broad spectrum of recent results and to propose future directions of development in order to obtain fully implantable systems for the continuous monitoring of the human metabolism in advanced healthcare applications. Full article
(This article belongs to the Special Issue Biochips)
Open AccessReview A Survey on Clustering Routing Protocols in Wireless Sensor Networks
Sensors 2012, 12(8), 11113-11153; doi:10.3390/s120811113
Received: 2 May 2012 / Revised: 26 July 2012 / Accepted: 6 August 2012 / Published: 9 August 2012
Cited by 109 | PDF Full-text (579 KB) | HTML Full-text | XML Full-text
Abstract
The past few years have witnessed increased interest in the potential use of wireless sensor networks (WSNs) in a wide range of applications and it has become a hot research area. Based on network structure, routing protocols in WSNs can be divided [...] Read more.
The past few years have witnessed increased interest in the potential use of wireless sensor networks (WSNs) in a wide range of applications and it has become a hot research area. Based on network structure, routing protocols in WSNs can be divided into two categories: flat routing and hierarchical or clustering routing. Owing to a variety of advantages, clustering is becoming an active branch of routing technology in WSNs. In this paper, we present a comprehensive and fine grained survey on clustering routing protocols proposed in the literature for WSNs. We outline the advantages and objectives of clustering for WSNs, and develop a novel taxonomy of WSN clustering routing methods based on complete and detailed clustering attributes. In particular, we systematically analyze a few prominent WSN clustering routing protocols and compare these different approaches according to our taxonomy and several significant metrics. Finally, we summarize and conclude the paper with some future directions. Full article
(This article belongs to the Section Sensor Networks)
Open AccessReview Development and Application of Integrated Optical Sensors for Intense E-Field Measurement
Sensors 2012, 12(8), 11406-11434; doi:10.3390/s120811406
Received: 22 June 2012 / Revised: 25 July 2012 / Accepted: 31 July 2012 / Published: 21 August 2012
Cited by 13 | PDF Full-text (819 KB) | HTML Full-text | XML Full-text
Abstract
The measurement of intense E-fields is a fundamental need in various research areas. Integrated optical E-field sensors (IOESs) have important advantages and are potentially suitable for intense E-field detection. This paper comprehensively reviews the development and applications of several types of IOESs [...] Read more.
The measurement of intense E-fields is a fundamental need in various research areas. Integrated optical E-field sensors (IOESs) have important advantages and are potentially suitable for intense E-field detection. This paper comprehensively reviews the development and applications of several types of IOESs over the last 30 years, including the Mach-Zehnder interferometer (MZI), coupler interferometer (CI) and common path interferometer (CPI). The features of the different types of IOESs are compared, showing that the MZI has higher sensitivity, the CI has a controllable optical bias, and the CPI has better temperature stability. More specifically, the improvement work of applying IOESs to intense E-field measurement is illustrated. Finally, typical uses of IOESs in the measurement of intense E-fields are demonstrated, including application areas such as E-fields with different frequency ranges in high-voltage engineering, simulated nuclear electromagnetic pulse in high-power electromagnetic pulses, and ion-accelerating field in high-energy physics. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)

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Open AccessTechnical Note A Synchronous Multi-Body Sensor Platform in a Wireless Body Sensor Network: Design and Implementation
Sensors 2012, 12(8), 10381-10394; doi:10.3390/s120810381
Received: 16 March 2012 / Revised: 24 July 2012 / Accepted: 26 July 2012 / Published: 31 July 2012
Cited by 9 | PDF Full-text (754 KB) | HTML Full-text | XML Full-text
Abstract
Background: Human life can be further improved if diseases and disorders can be predicted before they become dangerous, by correctly recognizing signals from the human body, so in order to make disease detection more precise, various body-signals need to be measured simultaneously [...] Read more.
Background: Human life can be further improved if diseases and disorders can be predicted before they become dangerous, by correctly recognizing signals from the human body, so in order to make disease detection more precise, various body-signals need to be measured simultaneously in a synchronized manner. Object: This research aims at developing an integrated system for measuring four signals (EEG, ECG, respiration, and PPG) and simultaneously producing synchronous signals on a Wireless Body Sensor Network. Design: We designed and implemented a platform for multiple bio-signals using Bluetooth communication. Results: First, we developed a prototype board and verified the signals from the sensor platform using frequency responses and quantities. Next, we designed and implemented a lightweight, ultra-compact, low cost, low power-consumption Printed Circuit Board. Conclusion: A synchronous multi-body sensor platform is expected to be very useful in telemedicine and emergency rescue scenarios. Furthermore, this system is expected to be able to analyze the mutual effects among body signals. Full article
(This article belongs to the Special Issue Body Sensor Networks for Healthcare and Pervasive Applications)
Open AccessLetter Long-Term Stability of the SGA-WZ Strapdown Airborne Gravimeter
Sensors 2012, 12(8), 11091-11099; doi:10.3390/s120811091
Received: 17 June 2012 / Revised: 30 July 2012 / Accepted: 3 August 2012 / Published: 9 August 2012
Cited by 5 | PDF Full-text (281 KB) | HTML Full-text | XML Full-text
Abstract
Accelerometers are one of the most important sensors in a strapdown airborne gravimeter. The accelerometer’s drift determines the long-term accuracy of the strapdown inertial navigation system (SINS), which is the primary and most critical component of the strapdown airborne gravimeter. A long-term [...] Read more.
Accelerometers are one of the most important sensors in a strapdown airborne gravimeter. The accelerometer’s drift determines the long-term accuracy of the strapdown inertial navigation system (SINS), which is the primary and most critical component of the strapdown airborne gravimeter. A long-term stability test lasting 104 days was conducted to determine the characteristics of the strapdown airborne gravimeter’s long-term drift. This stability test was based on the first set of strapdown airborne gravimeters built in China, the SGA-WZ. The test results reveal a quadratic drift in the strapdown airborne gravimeter data. A drift model was developed using the static data in the two end sections, and then this model was used to correct the test data. After compensating for the drift, the drift effect improved from 70 mGal to 3.46 mGal with a standard deviation of 0.63 mGal. The quadratic curve better reflects the drift’s real characteristics. In comparison with other methodologies, modelling the drift as a quadratic curve was shown to be more appropriate. Furthermore, this method allows the drift to be adjusted throughout the course of the entire campaign. Full article
(This article belongs to the Section Physical Sensors)

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