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Sensors, Volume 11, Issue 3 (March 2011), Pages 2282-3400

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Open AccessArticle Efficient Smart CMOS Camera Based on FPGAs Oriented to Embedded Image Processing
Sensors 2011, 11(3), 2282-2303; doi:10.3390/s110302282
Received: 10 December 2010 / Revised: 2 February 2011 / Accepted: 12 February 2011 / Published: 24 February 2011
Cited by 9 | PDF Full-text (633 KB) | HTML Full-text | XML Full-text
Abstract
This article describes an image processing system based on an intelligent ad-hoc camera, whose two principle elements are a high speed 1.2 megapixel Complementary Metal Oxide Semiconductor (CMOS) sensor and a Field Programmable Gate Array (FPGA). The latter is used to control [...] Read more.
This article describes an image processing system based on an intelligent ad-hoc camera, whose two principle elements are a high speed 1.2 megapixel Complementary Metal Oxide Semiconductor (CMOS) sensor and a Field Programmable Gate Array (FPGA). The latter is used to control the various sensor parameter configurations and, where desired, to receive and process the images captured by the CMOS sensor. The flexibility and versatility offered by the new FPGA families makes it possible to incorporate microprocessors into these reconfigurable devices, and these are normally used for highly sequential tasks unsuitable for parallelization in hardware. For the present study, we used a Xilinx XC4VFX12 FPGA, which contains an internal Power PC (PPC) microprocessor. In turn, this contains a standalone system which manages the FPGA image processing hardware and endows the system with multiple software options for processing the images captured by the CMOS sensor. The system also incorporates an Ethernet channel for sending processed and unprocessed images from the FPGA to a remote node. Consequently, it is possible to visualize and configure system operation and captured and/or processed images remotely. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Accuracy and Feasibility of Optoelectronic Sensors for Weed Mapping in Wide Row Crops
Sensors 2011, 11(3), 2304-2318; doi:10.3390/s110302304
Received: 20 December 2010 / Revised: 28 January 2011 / Accepted: 10 February 2011 / Published: 24 February 2011
Cited by 16 | PDF Full-text (309 KB) | HTML Full-text | XML Full-text
Abstract
The main objectives of this study were to assess the accuracy of a ground-based weed mapping system that included optoelectronic sensors for weed detection, and to determine the sampling resolution required for accurate weed maps in maize crops. The optoelectronic sensors were [...] Read more.
The main objectives of this study were to assess the accuracy of a ground-based weed mapping system that included optoelectronic sensors for weed detection, and to determine the sampling resolution required for accurate weed maps in maize crops. The optoelectronic sensors were located in the inter-row area of maize to distinguish weeds against soil background. The system was evaluated in three maize fields in the early spring. System verification was performed with highly reliable data from digital images obtained in a regular 12 m × 12 m grid throughout the three fields. The comparison in all these sample points showed a good relationship (83% agreement on average) between the data of weed presence/absence obtained from the optoelectronic mapping system and the values derived from image processing software (“ground truth”). Regarding the optimization of sampling resolution, the comparison between the detailed maps (all crop rows with sensors separated 0.75 m) with maps obtained with various simulated distances between sensors (from 1.5 m to 6.0 m) indicated that a 4.5 m distance (equivalent to one in six crop rows) would be acceptable to construct accurate weed maps. This spatial resolution makes the system cheap and robust enough to generate maps of inter-row weeds. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
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Open AccessArticle New Finger Biometric Method Using Near Infrared Imaging
Sensors 2011, 11(3), 2319-2333; doi:10.3390/s110302319
Received: 7 January 2011 / Revised: 21 January 2011 / Accepted: 10 February 2011 / Published: 24 February 2011
Cited by 52 | PDF Full-text (851 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we propose a new finger biometric method. Infrared finger images are first captured, and then feature extraction is performed using a modified Gaussian high-pass filter through binarization, local binary pattern (LBP), and local derivative pattern (LDP) methods. Infrared finger [...] Read more.
In this paper, we propose a new finger biometric method. Infrared finger images are first captured, and then feature extraction is performed using a modified Gaussian high-pass filter through binarization, local binary pattern (LBP), and local derivative pattern (LDP) methods. Infrared finger images include the multimodal features of finger veins and finger geometries. Instead of extracting each feature using different methods, the modified Gaussian high-pass filter is fully convolved. Therefore, the extracted binary patterns of finger images include the multimodal features of veins and finger geometries. Experimental results show that the proposed method has an error rate of 0.13%. Full article
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Open AccessArticle Non Destructive Defect Detection by Spectral Density Analysis
Sensors 2011, 11(3), 2334-2346; doi:10.3390/s110302334
Received: 3 January 2011 / Revised: 28 January 2011 / Accepted: 2 February 2011 / Published: 24 February 2011
Cited by 23 | PDF Full-text (779 KB) | HTML Full-text | XML Full-text
Abstract
The potential nondestructive diagnostics of solid objects is discussed in this article. The whole process is accomplished by consecutive steps involving software analysis of the vibration power spectrum (eventually acoustic emissions) created during the normal operation of the diagnosed device or under [...] Read more.
The potential nondestructive diagnostics of solid objects is discussed in this article. The whole process is accomplished by consecutive steps involving software analysis of the vibration power spectrum (eventually acoustic emissions) created during the normal operation of the diagnosed device or under unexpected situations. Another option is to create an artificial pulse, which can help us to determine the actual state of the diagnosed device. The main idea of this method is based on the analysis of the current power spectrum density of the received signal and its postprocessing in the Matlab environment with a following sample comparison in the Statistica software environment. The last step, which is comparison of samples, is the most important, because it is possible to determine the status of the examined object at a given time. Nowadays samples are compared only visually, but this method can’t produce good results. Further the presented filter can choose relevant data from a huge group of data, which originate from applying FFT (Fast Fourier Transform). On the other hand, using this approach they can be subjected to analysis with the assistance of a neural network. If correct and high-quality starting data are provided to the initial network, we are able to analyze other samples and state in which condition a certain object is. The success rate of this approximation, based on our testing of the solution, is now 85.7%. With further improvement of the filter, it could be even greater. Finally it is possible to detect defective conditions or upcoming limiting states of examined objects/materials by using only one device which contains HW and SW parts. This kind of detection can provide significant financial savings in certain cases (such as continuous casting of iron where it could save hundreds of thousands of USD). Full article
(This article belongs to the Special Issue Advanced Sensing Technology for Nondestructive Evaluation)
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Open AccessArticle An MILP-Based Cross-Layer Optimization for a Multi-Reader Arbitration in the UHF RFID System
Sensors 2011, 11(3), 2347-2368; doi:10.3390/s110302347
Received: 30 January 2011 / Accepted: 22 February 2011 / Published: 24 February 2011
Cited by 7 | PDF Full-text (193 KB) | HTML Full-text | XML Full-text
Abstract
In RFID systems, the performance of each reader such as interrogation range and tag recognition rate may suffer from interferences from other readers. Since the reader interference can be mitigated by output signal power control, spectral and/or temporal separation among readers, the [...] Read more.
In RFID systems, the performance of each reader such as interrogation range and tag recognition rate may suffer from interferences from other readers. Since the reader interference can be mitigated by output signal power control, spectral and/or temporal separation among readers, the system performance depends on how to adapt the various reader arbitration metrics such as time, frequency, and output power to the system environment. However, complexity and difficulty of the optimization problem increase with respect to the variety of the arbitration metrics. Thus, most proposals in previous study have been suggested to primarily prevent the reader collision with consideration of one or two arbitration metrics. In this paper, we propose a novel cross-layer optimization design based on the concept of combining time division, frequency division, and power control not only to solve the reader interference problem, but also to achieve the multiple objectives such as minimum interrogation delay, maximum reader utilization, and energy efficiency. Based on the priority of the multiple objectives, our cross-layer design optimizes the system sequentially by means of the mixed-integer linear programming. In spite of the multi-stage optimization, the optimization design is formulated as a concise single mathematical form by properly assigning a weight to each objective. Numerical results demonstrate the effectiveness of the proposed optimization design. Full article
(This article belongs to the Special Issue Adaptive Sensing)
Open AccessArticle Classification and Quality Evaluation of Tobacco Leaves Based on Image Processing and Fuzzy Comprehensive Evaluation
Sensors 2011, 11(3), 2369-2384; doi:10.3390/s110302369
Received: 6 January 2011 / Revised: 17 February 2011 / Accepted: 21 February 2011 / Published: 25 February 2011
Cited by 10 | PDF Full-text (427 KB) | HTML Full-text | XML Full-text
Abstract
Most of classification, quality evaluation or grading of the flue-cured tobacco leaves are manually operated, which relies on the judgmental experience of experts, and inevitably limited by personal, physical and environmental factors. The classification and the quality evaluation are therefore subjective and [...] Read more.
Most of classification, quality evaluation or grading of the flue-cured tobacco leaves are manually operated, which relies on the judgmental experience of experts, and inevitably limited by personal, physical and environmental factors. The classification and the quality evaluation are therefore subjective and experientially based. In this paper, an automatic classification method of tobacco leaves based on the digital image processing and the fuzzy sets theory is presented. A grading system based on image processing techniques was developed for automatically inspecting and grading flue-cured tobacco leaves. This system uses machine vision for the extraction and analysis of color, size, shape and surface texture. Fuzzy comprehensive evaluation provides a high level of confidence in decision making based on the fuzzy logic. The neural network is used to estimate and forecast the membership function of the features of tobacco leaves in the fuzzy sets. The experimental results of the two-level fuzzy comprehensive evaluation (FCE) show that the accuracy rate of classification is about 94% for the trained tobacco leaves, and the accuracy rate of the non-trained tobacco leaves is about 72%. We believe that the fuzzy comprehensive evaluation is a viable way for the automatic classification and quality evaluation of the tobacco leaves. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Sparsity-Based Spatial Interpolation in Wireless Sensor Networks
Sensors 2011, 11(3), 2385-2407; doi:10.3390/s110302385
Received: 8 November 2010 / Revised: 26 December 2010 / Accepted: 9 February 2011 / Published: 25 February 2011
Cited by 16 | PDF Full-text (1171 KB) | HTML Full-text | XML Full-text
Abstract
In wireless sensor networks, due to environmental limitations or bad wireless channel conditions, not all sensor samples can be successfully gathered at the sink.  In this paper, we try to recover these missing samples without retransmission. The missing samples estimation problem is [...] Read more.
In wireless sensor networks, due to environmental limitations or bad wireless channel conditions, not all sensor samples can be successfully gathered at the sink.  In this paper, we try to recover these missing samples without retransmission. The missing samples estimation problem is mathematically formulated as a 2-D spatial interpolation. Assuming the 2-D sensor data can be sparsely represented by a dictionary, a sparsity-based recovery approach by solving for l1 norm minimization is proposed. It is shown that these missing samples can be reasonably recovered based on the null space property of the dictionary. This property also points out the way to choose an appropriate sparsifying dictionary to further reduce the recovery errors. The simulation results on synthetic and real data demonstrate that the proposed approach can recover the missing data reasonably well and that it outperforms the weighted average interpolation methods when the data change relatively fast or blocks of samples are lost. Besides, there exists a range of missing rates where the proposed approach is robust to missing block sizes. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Laboratory Calibration of a Field Imaging Spectrometer System
Sensors 2011, 11(3), 2408-2425; doi:10.3390/s110302408
Received: 9 December 2010 / Revised: 19 January 2011 / Accepted: 15 February 2011 / Published: 25 February 2011
Cited by 17 | PDF Full-text (734 KB) | HTML Full-text | XML Full-text
Abstract
A new Field Imaging Spectrometer System (FISS) based on a cooling area CCD was developed. This paper describes the imaging principle, structural design, and main parameters of the FISS sensor. The FISS was spectrally calibrated with a double grating monochromator to determine [...] Read more.
A new Field Imaging Spectrometer System (FISS) based on a cooling area CCD was developed. This paper describes the imaging principle, structural design, and main parameters of the FISS sensor. The FISS was spectrally calibrated with a double grating monochromator to determine the center wavelength and FWHM of each band. Calibration results showed that the spectral range of the FISS system is 437–902 nm, the number of channels is 344 and the spectral resolution of each channel is better than 5 nm. An integrating sphere was used to achieve absolute radiometric calibration of the FISS with less than 5% calibration error for each band. There are 215 channels with signal to noise ratios (SNRs) greater than 500 (62.5% of the bands). The results demonstrated that the FISS has achieved high performance that assures the feasibility of its practical use in various fields. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Modeling of Nonlinear Aggregation for Information Fusion Systems with Outliers Based on the Choquet Integral
Sensors 2011, 11(3), 2426-2446; doi:10.3390/s110302426
Received: 25 December 2010 / Revised: 25 January 2011 / Accepted: 15 February 2011 / Published: 25 February 2011
Cited by 4 | PDF Full-text (556 KB) | HTML Full-text | XML Full-text
Abstract
Modern information fusion systems essentially associate decision-making processes with multi-sensor systems. Precise decision-making processes depend upon aggregating useful information extracted from large numbers of messages or large datasets; meanwhile, the distributed multi-sensor systems which employ several geographically separated local sensors are required [...] Read more.
Modern information fusion systems essentially associate decision-making processes with multi-sensor systems. Precise decision-making processes depend upon aggregating useful information extracted from large numbers of messages or large datasets; meanwhile, the distributed multi-sensor systems which employ several geographically separated local sensors are required to provide sufficient messages or data with similar and/or dissimilar characteristics. These kinds of information fusion techniques have been widely investigated and used for implementing several information retrieval systems. However, the results obtained from the information fusion systems vary in different situations and performing intelligent aggregation and fusion of information from a distributed multi-source, multi-sensor network is essentially an optimization problem. A flexible and versatile framework which is able to solve complex global optimization problems is a valuable alternative to traditional information fusion. Furthermore, because of the highly dynamic and volatile nature of the information flow, a swift soft computing technique is imperative to satisfy the demands and challenges. In this paper, a nonlinear aggregation based on the Choquet integral (NACI) model is considered for information fusion systems that include outliers under inherent interaction among feature attributes. The estimation of interaction coefficients for the proposed model is also performed via a modified algorithm based on particle swarm optimization with quantum-behavior (QPSO) and the high breakdown value estimator, least trimmed squares (LTS). From simulation results, the proposed MQPSO algorithm with LTS (named LTS-MQPSO) readily corrects the deviations caused by outliers and swiftly achieves convergence in estimating the parameters of the proposed NACI model for the information fusion systems with outliers. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A Non-Invasive Thermal Drift Compensation Technique Applied to a Spin-Valve Magnetoresistive Current Sensor
Sensors 2011, 11(3), 2447-2458; doi:10.3390/s110302447
Received: 10 January 2011 / Revised: 10 February 2011 / Accepted: 11 February 2011 / Published: 25 February 2011
Cited by 12 | PDF Full-text (516 KB) | HTML Full-text | XML Full-text
Abstract
A compensation method for the sensitivity drift of a magnetoresistive (MR) Wheatstone bridge current sensor is proposed. The technique was carried out by placing a ruthenium temperature sensor and the MR sensor to be compensated inside a generalized impedance converter circuit (GIC). [...] Read more.
A compensation method for the sensitivity drift of a magnetoresistive (MR) Wheatstone bridge current sensor is proposed. The technique was carried out by placing a ruthenium temperature sensor and the MR sensor to be compensated inside a generalized impedance converter circuit (GIC). No internal modification of the sensor bridge arms is required so that the circuit is capable of compensating practical industrial sensors. The method is based on the temperature modulation of the current supplied to the bridge, which improves previous solutions based on constant current compensation. Experimental results are shown using a microfabricated spin-valve MR current sensor. The temperature compensation has been solved in the interval from 0 °C to 70 °C measuring currents from −10 A to +10 A. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Performance of an Ultrasonic Ranging Sensor in Apple Tree Canopies
Sensors 2011, 11(3), 2459-2477; doi:10.3390/s110302459
Received: 13 December 2010 / Revised: 19 January 2011 / Accepted: 14 February 2011 / Published: 28 February 2011
Cited by 19 | PDF Full-text (1537 KB) | HTML Full-text | XML Full-text
Abstract
Electronic canopy characterization is an important issue in tree crop management. Ultrasonic and optical sensors are the most used for this purpose. The objective of this work was to assess the performance of an ultrasonic sensor under laboratory and field conditions in [...] Read more.
Electronic canopy characterization is an important issue in tree crop management. Ultrasonic and optical sensors are the most used for this purpose. The objective of this work was to assess the performance of an ultrasonic sensor under laboratory and field conditions in order to provide reliable estimations of distance measurements to apple tree canopies. To this purpose, a methodology has been designed to analyze sensor performance in relation to foliage ranging and to interferences with adjacent sensors when working simultaneously. Results show that the average error in distance measurement using the ultrasonic sensor in laboratory conditions is ±0.53 cm. However, the increase of variability in field conditions reduces the accuracy of this kind of sensors when estimating distances to canopies. The average error in such situations is ±5.11 cm. When analyzing interferences of adjacent sensors 30 cm apart, the average error is ±17.46 cm. When sensors are separated 60 cm, the average error is ±9.29 cm. The ultrasonic sensor tested has been proven to be suitable to estimate distances to the canopy in field conditions when sensors are 60 cm apart or more and could, therefore, be used in a system to estimate structural canopy parameters in precision horticulture. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
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Open AccessArticle Laser Chemosensor with Rapid Responsivity and Inherent Memory Based on a Polymer of Intrinsic Microporosity
Sensors 2011, 11(3), 2478-2487; doi:10.3390/s110302478
Received: 2 December 2010 / Revised: 1 February 2011 / Accepted: 10 February 2011 / Published: 28 February 2011
Cited by 28 | PDF Full-text (492 KB) | HTML Full-text | XML Full-text
Abstract
This work explores the use of a polymer of intrinsic microporosity (PIM-1) as the active layer within a laser sensor to detect nitroaromatic-based explosive vapors. We show successful detection of dinitrobenzene (DNB) by monitoring the real-time photoluminescence. We also show that PIM-1 [...] Read more.
This work explores the use of a polymer of intrinsic microporosity (PIM-1) as the active layer within a laser sensor to detect nitroaromatic-based explosive vapors. We show successful detection of dinitrobenzene (DNB) by monitoring the real-time photoluminescence. We also show that PIM-1 has an inherent memory, so that it accumulates the analyte during exposure. In addition, the optical gain and refractive index of the polymer were studied by amplified spontaneous emission and variable-angle ellipsometry, respectively. A second-order distributed feedback PIM-1 laser sensor was fabricated and found to show an increase in laser threshold of 2.5 times and a reduction of the laser slope efficiency by 4.4 times after a 5-min exposure to the DNB vapor. For pumping at 2 times threshold, the lasing action was stopped within 30 s indicating that PIM-1 has a very fast responsivity and as such has a potential sensing ability for ultra-low-concentration explosives. Full article
(This article belongs to the Special Issue Optical Resonant Microsensors)
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Open AccessArticle A Transflective Nano-Wire Grid Polarizer Based Fiber-Optic Sensor
Sensors 2011, 11(3), 2488-2495; doi:10.3390/s110302488
Received: 9 January 2011 / Revised: 27 January 2011 / Accepted: 17 February 2011 / Published: 28 February 2011
Cited by 9 | PDF Full-text (322 KB) | HTML Full-text | XML Full-text
Abstract
A transflective nano-wire grid polarizer is fabricated on a single mode fiber tip by focused ion beam machining. In contrast to conventional absorptive in-line polarizers, the wire grids reflect TE-mode, while transmitting TM-mode light so that no light power is discarded. A [...] Read more.
A transflective nano-wire grid polarizer is fabricated on a single mode fiber tip by focused ion beam machining. In contrast to conventional absorptive in-line polarizers, the wire grids reflect TE-mode, while transmitting TM-mode light so that no light power is discarded. A reflection contrast of 13.7 dB and a transmission contrast of 4.9 dB are achieved in the 1,550 nm telecom band using a 200-nm wire grid fiber polarizer. With the help of an optic circulator, the polarization states of both the transmissive and reflective lights in the fiber may be monitored simultaneously. A kind of robust fiber optic sensor is thus proposed that could withstand light power variations. To verify the idea, a fiber pressure sensor with the sensitivity of 0.24 rad/N is demonstrated. The corresponding stress-optic coefficient of the fiber is measured. In addition to pressure sensing, this technology could be applied in detecting any polarization state change induced by magnetic fields, electric currents and so on. Full article
(This article belongs to the Special Issue Metamaterials for Sensing)
Open AccessCommunication Patrol Detection for Replica Attacks on Wireless Sensor Networks
Sensors 2011, 11(3), 2496-2504; doi:10.3390/s110302496
Received: 31 December 2010 / Revised: 10 February 2011 / Accepted: 14 February 2011 / Published: 28 February 2011
Cited by 11 | PDF Full-text (226 KB) | HTML Full-text | XML Full-text
Abstract
Replica attack is a critical concern in the security of wireless sensor networks. We employ mobile nodes as patrollers to detect replicas distributed in different zones in a network, in which a basic patrol detection protocol and two detection algorithms for stationary [...] Read more.
Replica attack is a critical concern in the security of wireless sensor networks. We employ mobile nodes as patrollers to detect replicas distributed in different zones in a network, in which a basic patrol detection protocol and two detection algorithms for stationary and mobile modes are presented. Then we perform security analysis to discuss the defense strategies against the possible attacks on the proposed detection protocol. Moreover, we show the advantages of the proposed protocol by discussing and comparing the communication cost and detection probability with some existing methods. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle W-MAC: A Workload-Aware MAC Protocol for Heterogeneous Convergecast in Wireless Sensor Networks
Sensors 2011, 11(3), 2505-2524; doi:10.3390/s110302505
Received: 30 November 2010 / Revised: 19 January 2011 / Accepted: 14 February 2011 / Published: 28 February 2011
Cited by 3 | PDF Full-text (260 KB) | HTML Full-text | XML Full-text
Abstract
The power consumption and latency of existing MAC protocols for wireless sensor networks (WSNs) are high in heterogeneous convergecast, where each sensor node generates different amounts of data in one convergecast operation. To solve this problem, we present W-MAC, a workload-aware MAC [...] Read more.
The power consumption and latency of existing MAC protocols for wireless sensor networks (WSNs) are high in heterogeneous convergecast, where each sensor node generates different amounts of data in one convergecast operation. To solve this problem, we present W-MAC, a workload-aware MAC protocol for heterogeneous convergecast in WSNs. A subtree-based iterative cascading scheduling mechanism and a workload-aware time slice allocation mechanism are proposed to minimize the power consumption of nodes, while offering a low data latency. In addition, an efficient schedule adjustment mechanism is provided for adapting to data traffic variation and network topology change. Analytical and simulation results show that the proposed protocol provides a significant energy saving and latency reduction in heterogeneous convergecast, and can effectively support data aggregation to further improve the performance. Full article
Open AccessArticle Microstructured Optical Fiber Sensors Embedded in a Laminate Composite for Smart Material Applications
Sensors 2011, 11(3), 2566-2579; doi:10.3390/s110302566
Received: 24 November 2010 / Revised: 3 February 2011 / Accepted: 12 February 2011 / Published: 28 February 2011
Cited by 45 | PDF Full-text (1321 KB) | HTML Full-text | XML Full-text
Abstract
Fiber Bragg gratings written in highly birefringent microstructured optical fiber with a dedicated design are embedded in a composite fiber-reinforced polymer. The Bragg peak wavelength shifts are measured under controlled axial and transversal strain and during thermal cycling of the composite sample. [...] Read more.
Fiber Bragg gratings written in highly birefringent microstructured optical fiber with a dedicated design are embedded in a composite fiber-reinforced polymer. The Bragg peak wavelength shifts are measured under controlled axial and transversal strain and during thermal cycling of the composite sample. We obtain a sensitivity to transversal strain that exceeds values reported earlier in literature by one order of magnitude. Our results evidence the relevance of using microstructured optical fibers for structural integrity monitoring of composite material structures. Full article
(This article belongs to the Special Issue Advanced Embedded Sensors)
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Open AccessArticle Development of Micro-Heaters with Optimized Temperature Compensation Design for Gas Sensors
Sensors 2011, 11(3), 2580-2591; doi:10.3390/s110302580
Received: 11 January 2011 / Revised: 15 February 2011 / Accepted: 15 February 2011 / Published: 1 March 2011
Cited by 28 | PDF Full-text (476 KB) | HTML Full-text | XML Full-text
Abstract
One of the key components of a chemical gas sensor is a MEMS micro-heater. Micro-heaters are used in both semiconductor gas sensors and NDIR gas sensors; however they each require different heat dissipation characteristics. For the semiconductor gas sensors, a uniform temperature [...] Read more.
One of the key components of a chemical gas sensor is a MEMS micro-heater. Micro-heaters are used in both semiconductor gas sensors and NDIR gas sensors; however they each require different heat dissipation characteristics. For the semiconductor gas sensors, a uniform temperature is required over a wide area of the heater. On the other hand, for the NDIR gas sensor, the micro-heater needs high levels of infrared radiation in order to increase sensitivity. In this study, a novel design of a poly-Si micro-heater is proposed to improve the uniformity of heat dissipation on the heating plate. Temperature uniformity of the micro-heater is achieved by compensating for the variation in power consumption around the perimeter of the heater. With the power compensated design, the uniform heating area is increased by 2.5 times and the average temperature goes up by 40 °C. Therefore, this power compensated micro-heater design is suitable for a semiconductor gas sensor. Meanwhile, the poly-Si micro-heater without compensation shows a higher level of infrared radiation under equal power consumption conditions. This indicates that the micro-heater without compensation is more suitable for a NDIR gas sensor. Furthermore, the micro-heater shows a short response time of less than 20ms, indicating a very high efficiency of pulse driving. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Analysis of Coaxial Soil Cell in Reflection and Transmission
Sensors 2011, 11(3), 2592-2610; doi:10.3390/s110302592
Received: 20 January 2011 / Revised: 20 February 2011 / Accepted: 23 February 2011 / Published: 1 March 2011
Cited by 3 | PDF Full-text (497 KB) | HTML Full-text | XML Full-text
Abstract
Accurate measurement of moisture content is a prime requirement in hydrological, geophysical and biogeochemical research as well as for material characterization and process control. Within these areas, accurate measurements of the surface area and bound water content is becoming increasingly important for [...] Read more.
Accurate measurement of moisture content is a prime requirement in hydrological, geophysical and biogeochemical research as well as for material characterization and process control. Within these areas, accurate measurements of the surface area and bound water content is becoming increasingly important for providing answers to many fundamental questions ranging from characterization of cotton fiber maturity, to accurate characterization of soil water content in soil water conservation research to bio-plant water utilization to chemical reactions and diffusions of ionic species across membranes in cells as well as in the dense suspensions that occur in surface films. In these bound water materials, the errors in the traditional time-domain-reflectometer, “TDR”, exceed the range of the full span of the material’s permittivity that is being measured. Thus, there is a critical need to re-examine the TDR system and identify where the errors are to direct future research. One promising technique to address the increasing demands for higher accuracy water content measurements is utilization of electrical permittivity characterization of materials. This technique has enjoyed a strong following in the soil-science and geological community through measurements of apparent permittivity via time-domain-reflectometery as well in many process control applications. Recent research however, is indicating a need to increase the accuracy beyond that available from traditional TDR. The most logical pathway then becomes a transition from TDR based measurements to network analyzer measurements of absolute permittivity that will remove the adverse effects that high surface area soils and conductivity impart onto the measurements of apparent permittivity in traditional TDR applications. This research examines the theoretical basis behind the coaxial probe, from which the modern TDR probe originated from, to provide a basis on which to perform absolute permittivity measurements. The research reveals currently utilized formulations in accepted techniques for permittivity measurements which violate the underlying assumptions inherent in the basic models due to the TDR acting as an antenna by radiating energy off the end of the probe, rather than returning it back to the source as is the current assumption. To remove the effects of radiation from the experimental results obtain herein, this research utilized custom designed coaxial probes of various diameters and probe lengths by which to test the coaxial cell measurement technique for accuracy in determination of absolute permittivity. In doing so, the research reveals that the basic models available in the literature all omitted a key correction factor that is hypothesized by this research as being most likely due to fringe capacitance. To test this theory, a Poisson model of a coaxial cell was formulated to calculate the effective extra length provided by the fringe capacitance which is then used to correct the experimental results such that experimental measurements utilizing differing coaxial cell diameters and probe lengths, upon correction with the Poisson model derived correction factor, all produce the same results thereby lending support for the use of an augmented measurement technique, described herein, for measurement of absolute permittivity, as opposed to the traditional TDR measurement of apparent permittivity. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle User Identification Using Gait Patterns on UbiFloorII
Sensors 2011, 11(3), 2611-2639; doi:10.3390/s110302611
Received: 10 January 2011 / Revised: 7 February 2011 / Accepted: 22 February 2011 / Published: 1 March 2011
Cited by 15 | PDF Full-text (2145 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a system of identifying individuals by their gait patterns. We take into account various distinguishable features that can be extracted from a user’s gait and then divide them into two classes: walking pattern and stepping pattern. The conditions we [...] Read more.
This paper presents a system of identifying individuals by their gait patterns. We take into account various distinguishable features that can be extracted from a user’s gait and then divide them into two classes: walking pattern and stepping pattern. The conditions we assume are that our target environments are domestic areas, the number of users is smaller than 10, and all users ambulate with bare feet considering the everyday lifestyle of the Korean home. Under these conditions, we have developed a system that identifies individuals’ gait patterns using our biometric sensor, UbiFloorII. We have created UbiFloorII to collect walking samples and created software modules to extract the user’s gait pattern. To identify the users based on the gait patterns extracted from walking samples over UbiFloorII, we have deployed multilayer perceptron network, a feedforward artificial neural network model. The results show that both walking pattern and stepping pattern extracted from users’ gait over the UbiFloorII are distinguishable enough to identify the users and that fusing two classifiers at the matching score level improves the recognition accuracy. Therefore, our proposed system may provide unobtrusive and automatic user identification methods in ubiquitous computing environments, particularly in domestic areas. Full article
(This article belongs to the Special Issue Advanced Embedded Sensors)
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Open AccessArticle Study of Temperature Characteristics of Micromachined Suspended Coplanar Waveguides for Biosensing Applications
Sensors 2011, 11(3), 2640-2651; doi:10.3390/s110302640
Received: 15 November 2010 / Revised: 11 January 2011 / Accepted: 22 February 2011 / Published: 1 March 2011
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Abstract
In the recent development on biosensors, coplanar waveguide based microwave dielectric sensors have been attracting more and more attentions. In this paper, microwave performance of a suspended coplanar waveguide subject to temperature variations, particularly in a small range, is studied. The prototype [...] Read more.
In the recent development on biosensors, coplanar waveguide based microwave dielectric sensors have been attracting more and more attentions. In this paper, microwave performance of a suspended coplanar waveguide subject to temperature variations, particularly in a small range, is studied. The prototype is realized through a MEMS fabrication foundry. The thermal transfer analysis of the device is conducted using finite element method, and the microwave properties of the device are characterized. One of the results shows that at 20 GHz, the S11 has decreased by 7.4%, and S21 has increased by 3.5% when the voltage applied to the heaters varies from 9 V to 29 V. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Nanosensor for TNT Detection Based on Molecularly Imprinted Polymers and Surface Enhanced Raman Scattering
Sensors 2011, 11(3), 2700-2714; doi:10.3390/s110302700
Received: 11 January 2011 / Revised: 8 February 2011 / Accepted: 22 February 2011 / Published: 1 March 2011
Cited by 65 | PDF Full-text (481 KB) | HTML Full-text | XML Full-text
Abstract
We report on a new sensor strategy that integrates molecularly imprinted polymers (MIPs) with surface enhanced Raman scattering (SERS). The sensor was developed to detect the explosive, 2,4,6-trinitrotoluene (TNT). Micron thick films of sol gel-derived xerogels were deposited on a SERS-active surface [...] Read more.
We report on a new sensor strategy that integrates molecularly imprinted polymers (MIPs) with surface enhanced Raman scattering (SERS). The sensor was developed to detect the explosive, 2,4,6-trinitrotoluene (TNT). Micron thick films of sol gel-derived xerogels were deposited on a SERS-active surface as the sensing layer. Xerogels were molecularly imprinted for TNT using non-covalent interactions with the polymer matrix. Binding of the TNT within the polymer matrix results in unique SERS bands, which allow for detection and identification of the molecule in the MIP. This MIP-SERS sensor exhibits an apparent dissociation constant of (2.3 ± 0.3) × 10−5 M for TNT and a 3 µM detection limit. The response to TNT is reversible and the sensor is stable for at least 6 months. Key challenges, including developing a MIP formulation that is stable and integrated with the SERS substrate, and ensuring the MIP does not mask the spectral features of the target analyte through SERS polymer background, were successfully met. The results also suggest the MIP-SERS protocol can be extended to other target analytes of interest. Full article
(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)
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Open AccessArticle Wireless Remote Weather Monitoring System Based on MEMS Technologies
Sensors 2011, 11(3), 2715-2727; doi:10.3390/s110302715
Received: 31 December 2010 / Revised: 12 February 2011 / Accepted: 14 February 2011 / Published: 1 March 2011
Cited by 7 | PDF Full-text (382 KB) | HTML Full-text | XML Full-text
Abstract
This study proposes a wireless remote weather monitoring system based on Micro-Electro-Mechanical Systems (MEMS) and wireless sensor network (WSN) technologies comprising sensors for the measurement of temperature, humidity, pressure, wind speed and direction, integrated on a single chip. The sensing signals are [...] Read more.
This study proposes a wireless remote weather monitoring system based on Micro-Electro-Mechanical Systems (MEMS) and wireless sensor network (WSN) technologies comprising sensors for the measurement of temperature, humidity, pressure, wind speed and direction, integrated on a single chip. The sensing signals are transmitted between the Octopus II-A sensor nodes using WSN technology, following amplification and analog/digital conversion (ADC). Experimental results show that the resistance of the micro temperature sensor increases linearly with input temperature, with an average TCR (temperature coefficient of resistance) value of 8.2 × 10−4 (°C−1). The resistance of the pressure sensor also increases linearly with air pressure, with an average sensitivity value of 3.5 × 10−2 (Ω/kPa). The sensitivity to humidity increases with ambient temperature due to the effect of temperature on the dielectric constant, which was determined to be 16.9, 21.4, 27.0, and 38.2 (pF/%RH) at 27 °C, 30 °C, 40 °C, and 50 °C, respectively. The velocity of airflow is obtained by summing the variations in resistor response as airflow passed over the sensors providing sensitivity of 4.2 × 10−2, 9.2 × 10−2, 9.7 × 10−2 (Ω/ms−1) with power consumption by the heating resistor of 0.2, 0.3, and 0.5 W, respectively. The passage of air across the surface of the flow sensors prompts variations in temperature among each of the sensing resistors. Evaluating these variations in resistance caused by the temperature change enables the measurement of wind direction. Full article
(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)
Open AccessArticle Subtractive Inhibition Assay for the Detection of E. coli O157:H7 Using Surface Plasmon Resonance
Sensors 2011, 11(3), 2728-2739; doi:10.3390/s110302728
Received: 8 January 2011 / Revised: 29 January 2011 / Accepted: 21 February 2011 / Published: 1 March 2011
Cited by 25 | PDF Full-text (286 KB) | HTML Full-text | XML Full-text
Abstract
A surface plasmon resonance (SPR) immunosensor was developed for the detection of E. coli O157:H7 by means of a new subtractive inhibition assay. In the subtractive inhibition assay, E. coli O157:H7 cells and goat polyclonal antibodies for E. coli O157:H7 were incubated [...] Read more.
A surface plasmon resonance (SPR) immunosensor was developed for the detection of E. coli O157:H7 by means of a new subtractive inhibition assay. In the subtractive inhibition assay, E. coli O157:H7 cells and goat polyclonal antibodies for E. coli O157:H7 were incubated for a short of time, and then the E. coli O157:H7 cells which bound antibodies were removed by a stepwise centrifugation process. The remaining free unbound antibodies were detected through interaction with rabbit anti-goat IgG polyclonal antibodies immobilized on the sensor chip using a BIAcore 3000 biosensor. The results showed that the signal was inversely correlated with the concentration of E. coli O157:H7 cells in a range from 3.0 × 104 to 3.0 × 108 cfu/mL with a detection limit of 3.0 × 104 cfu/mL. Compared with direct SPR by immobilizing antibodies on the chip surface to capture the bacterial cells and ELISA for E. coli O157:H7 (detection limit: both 3.0 × 105 cfu/mL in this paper), the detection limit of subtractive inhibition assay method was reduced by one order of magnitude. The method simplifies bacterial cell detection to protein-protein interaction, which has the potential for providing a practical alternative for the monitoring of E. coli O157:H7 and other pathogens. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Sub-Micron Particle Based Structures as Reconfigurable Photonic Devices Controllable by External Photonic and Magnetic Fields
Sensors 2011, 11(3), 2740-2750; doi:10.3390/s110302740
Received: 28 January 2011 / Revised: 10 February 2011 / Accepted: 14 February 2011 / Published: 2 March 2011
Cited by 4 | PDF Full-text (555 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we present the configurations of two nanometer scale structures—one of them optically controllable and the second one magnetically controllable. The first involves an array of nanoparticles that are made up of two layers (i.e., Au on top [...] Read more.
In this paper we present the configurations of two nanometer scale structures—one of them optically controllable and the second one magnetically controllable. The first involves an array of nanoparticles that are made up of two layers (i.e., Au on top of a Si layer). The device may exhibits a wide range of plasmonic resonance according to external photonic radiation. The second type of device involves the usage of sub micron superparamagnetic particles located on a suitable structuring grid, that according to the angle of the external magnetic field allows control of the length of the structuring grid and therefore control the diffraction order of each wavelength. Full article
(This article belongs to the Special Issue Optical Resonant Microsensors)
Open AccessArticle Characterisation of the LMS200 Laser Beam under the Influence of Blockage Surfaces. Influence on 3D Scanning of Tree Orchards
Sensors 2011, 11(3), 2751-2772; doi:10.3390/s110302751
Received: 27 December 2010 / Revised: 20 January 2011 / Accepted: 30 January 2011 / Published: 2 March 2011
Cited by 17 | PDF Full-text (5076 KB) | HTML Full-text | XML Full-text
Abstract
The geometric characterisation of tree orchards is a high-precision activity comprising the accurate measurement and knowledge of the geometry and structure of the trees. Different types of sensors can be used to perform this characterisation. In this work a terrestrial LIDAR sensor [...] Read more.
The geometric characterisation of tree orchards is a high-precision activity comprising the accurate measurement and knowledge of the geometry and structure of the trees. Different types of sensors can be used to perform this characterisation. In this work a terrestrial LIDAR sensor (SICK LMS200) whose emission source was a 905-nm pulsed laser diode was used. Given the known dimensions of the laser beam cross-section (with diameters ranging from 12 mm at the point of emission to 47.2 mm at a distance of 8 m), and the known dimensions of the elements that make up the crops under study (flowers, leaves, fruits, branches, trunks), it was anticipated that, for much of the time, the laser beam would only partially hit a foreground target/object, with the consequent problem of mixed pixels or edge effects. Understanding what happens in such situations was the principal objective of this work. With this in mind, a series of tests were set up to determine the geometry of the emitted beam and to determine the response of the sensor to different beam blockage scenarios. The main conclusions that were drawn from the results obtained were: (i) in a partial beam blockage scenario, the distance value given by the sensor depends more on the blocked radiant power than on the blocked surface area; (ii) there is an area that influences the measurements obtained that is dependent on the percentage of blockage and which ranges from 1.5 to 2.5 m with respect to the foreground target/object. If the laser beam impacts on a second target/object located within this range, this will affect the measurement given by the sensor. To interpret the information obtained from the point clouds provided by the LIDAR sensors, such as the volume occupied and the enclosing area, it is necessary to know the resolution and the process for obtaining this mesh of points and also to be aware of the problem associated with mixed pixels. Full article
(This article belongs to the Special Issue Advanced Sensing Technology for Nondestructive Evaluation)
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Open AccessArticle A Virtual Sensor for Online Fault Detection of Multitooth-Tools
Sensors 2011, 11(3), 2773-2795; doi:10.3390/s110302773
Received: 7 January 2011 / Revised: 12 February 2011 / Accepted: 14 February 2011 / Published: 2 March 2011
Cited by 7 | PDF Full-text (523 KB) | HTML Full-text | XML Full-text
Abstract
The installation of suitable sensors close to the tool tip on milling centres is not possible in industrial environments. It is therefore necessary to design virtual sensors for these machines to perform online fault detection in many industrial tasks. This paper presents [...] Read more.
The installation of suitable sensors close to the tool tip on milling centres is not possible in industrial environments. It is therefore necessary to design virtual sensors for these machines to perform online fault detection in many industrial tasks. This paper presents a virtual sensor for online fault detection of multitooth tools based on a Bayesian classifier. The device that performs this task applies mathematical models that function in conjunction with physical sensors. Only two experimental variables are collected from the milling centre that performs the machining operations: the electrical power consumption of the feed drive and the time required for machining each workpiece. The task of achieving reliable signals from a milling process is especially complex when multitooth tools are used, because each kind of cutting insert in the milling centre only works on each workpiece during a certain time window. Great effort has gone into designing a robust virtual sensor that can avoid re-calibration due to, e.g., maintenance operations. The virtual sensor developed as a result of this research is successfully validated under real conditions on a milling centre used for the mass production of automobile engine crankshafts. Recognition accuracy, calculated with a k-fold cross validation, had on average 0.957 of true positives and 0.986 of true negatives. Moreover, measured accuracy was 98%, which suggests that the virtual sensor correctly identifies new cases. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Characteristics of Polysilicon Wire Glucose Sensors with a Surface Modified by Silica Nanoparticles/γ-APTES Nanocomposite
Sensors 2011, 11(3), 2796-2808; doi:10.3390/s110302796
Received: 28 January 2011 / Revised: 14 February 2011 / Accepted: 28 February 2011 / Published: 2 March 2011
Cited by 4 | PDF Full-text (1238 KB) | HTML Full-text | XML Full-text
Abstract
This report investigates the sensing characteristics of polysilicon wire (PSW) glucose biosensors, including thickness characteristics and line-width effects on detection limits, linear range and interference immunity with membranes coated by micropipette/spin-coating and focus-ion-beam (FIB) processed capillary atomic-force-microscopy (C-AFM) tip scan/coating methods. The [...] Read more.
This report investigates the sensing characteristics of polysilicon wire (PSW) glucose biosensors, including thickness characteristics and line-width effects on detection limits, linear range and interference immunity with membranes coated by micropipette/spin-coating and focus-ion-beam (FIB) processed capillary atomic-force-microscopy (C-AFM) tip scan/coating methods. The PSW surface was modified with a mixture of 3-aminopropyl-triethoxysilane (γ-APTES) and polydimethylsiloxane (PDMS)-treated hydrophobic fumed silica nanoparticles (NPs). We found that the thickness of the γ-APTES+NPs nonocomposite could be controlled well at about 22 nm with small relative standard deviation (RSD) with repeated C-AFM tip scan/coatings. The detection limit increased and linear range decreased with the line width of the PSW through the tip-coating process. Interestingly, the interference immunity ability improves as the line width increases. For a 500 nm-wide PSW, the percentage changes of the channel current density changes (ΔJ) caused by acetaminophen (AP) can be kept below 3.5% at an ultra-high AP-to-glucose concentration ratio of 600:1. Simulation results showed that the line width dependence of interference immunity was strongly correlated with the channel electrical field of the PSW biosensor. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Virtual Surface Characteristics of a Tactile Display Using Magneto-Rheological Fluids
Sensors 2011, 11(3), 2845-2856; doi:10.3390/s110302845
Received: 19 January 2011 / Revised: 10 February 2011 / Accepted: 20 February 2011 / Published: 2 March 2011
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Abstract
Virtual surface characteristics of tactile displays are investigated to characterize the feeling of human touch for a haptic interface application. In order to represent the tactile feeling, a prototype tactile display incorporating Magneto-Rheological (MR) fluid has been developed. Tactile display devices simulate [...] Read more.
Virtual surface characteristics of tactile displays are investigated to characterize the feeling of human touch for a haptic interface application. In order to represent the tactile feeling, a prototype tactile display incorporating Magneto-Rheological (MR) fluid has been developed. Tactile display devices simulate the finger’s skin to feel the sensations of contact such as compliance, friction, and topography of the surface. Thus, the tactile display can provide information on the surface of an organic tissue to the surgeon in virtual reality. In order to investigate the compliance feeling of a human finger’s touch, normal force responses of a tactile display under various magnetic fields have been assessed. Also, shearing friction force responses of the tactile display are investigated to simulate the action of finger dragging on the surface. Moreover, different matrix arrays of magnetic poles are applied to form the virtual surface topography. From the results, different tactile feelings are observed according to the applied magnetic field strength as well as the arrays of magnetic poles combinations. This research presents a smart tactile display technology for virtual surfaces. Full article
(This article belongs to the Special Issue Advanced Sensing Technology for Nondestructive Evaluation)
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Open AccessArticle A Novel Multi-Aperture Based Sun Sensor Based on a Fast Multi-Point MEANSHIFT (FMMS) Algorithm
Sensors 2011, 11(3), 2857-2874; doi:10.3390/s110302857
Received: 23 January 2011 / Revised: 20 February 2011 / Accepted: 28 February 2011 / Published: 3 March 2011
Cited by 5 | PDF Full-text (534 KB) | HTML Full-text | XML Full-text
Abstract
With the current increased widespread interest in the development and applications of micro/nanosatellites, it was found that we needed to design a small high accuracy satellite attitude determination system, because the star trackers widely used in large satellites are large and heavy, [...] Read more.
With the current increased widespread interest in the development and applications of micro/nanosatellites, it was found that we needed to design a small high accuracy satellite attitude determination system, because the star trackers widely used in large satellites are large and heavy, and therefore not suitable for installation on micro/nanosatellites. A Sun sensor + magnetometer is proven to be a better alternative, but the conventional sun sensor has low accuracy, and cannot meet the requirements of the attitude determination systems of micro/nanosatellites, so the development of a small high accuracy sun sensor with high reliability is very significant. This paper presents a multi-aperture based sun sensor, which is composed of a micro-electro-mechanical system (MEMS) mask with 36 apertures and an active pixels sensor (APS) CMOS placed below the mask at a certain distance. A novel fast multi-point MEANSHIFT (FMMS) algorithm is proposed to improve the accuracy and reliability, the two key performance features, of an APS sun sensor. When the sunlight illuminates the sensor, a sun spot array image is formed on the APS detector. Then the sun angles can be derived by analyzing the aperture image location on the detector via the FMMS algorithm. With this system, the centroid accuracy of the sun image can reach 0.01 pixels, without increasing the weight and power consumption, even when some missing apertures and bad pixels appear on the detector due to aging of the devices and operation in a harsh space environment, while the pointing accuracy of the single-aperture sun sensor using the conventional correlation algorithm is only 0.05 pixels. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Multi-Hop Routing-Based Optimization of the Number of Cluster-Heads in Wireless Sensor Networks
Sensors 2011, 11(3), 2875-2884; doi:10.3390/s110302875
Received: 21 January 2011 / Revised: 16 February 2011 / Accepted: 28 February 2011 / Published: 3 March 2011
Cited by 7 | PDF Full-text (355 KB) | HTML Full-text | XML Full-text
Abstract
Wireless sensor networks require energy-efficient data transmission because the sensor nodes have limited power. A cluster-based routing method is more energy-efficient than a flat routing method as it can only send specific data for user requirements and aggregate similar data by dividing [...] Read more.
Wireless sensor networks require energy-efficient data transmission because the sensor nodes have limited power. A cluster-based routing method is more energy-efficient than a flat routing method as it can only send specific data for user requirements and aggregate similar data by dividing a network into a local cluster. However, previous clustering algorithms have some problems in that the transmission radius of sensor nodes is not realistic and multi-hop based communication is not used both inside and outside local clusters. As energy consumption based on clustering is dependent on the number of clusters, we need to know how many clusters are best. Thus, we propose an optimal number of cluster-heads based on multi-hop routing in wireless sensor networks. We observe that a local cluster made by a cluster-head influences the energy consumption of sensor nodes. We determined an equation for the number of packets to send and relay, and calculated the energy consumption of sensor networks using it. Through the process of calculating the energy consumption, we can obtain the optimal number of cluster-heads in wireless sensor networks. Full article
(This article belongs to the Special Issue Selected Papers from FGIT 2010)
Open AccessCommunication Smart Query Answering for Marine Sensor Data
Sensors 2011, 11(3), 2885-2897; doi:10.3390/s110302885
Received: 17 December 2010 / Revised: 17 February 2011 / Accepted: 28 February 2011 / Published: 3 March 2011
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Abstract
We review existing query answering systems for sensor data. We then propose an extended query answering approach termed smart query, specifically for marine sensor data. The smart query answering system integrates pattern queries and continuous queries. The proposed smart query system [...] Read more.
We review existing query answering systems for sensor data. We then propose an extended query answering approach termed smart query, specifically for marine sensor data. The smart query answering system integrates pattern queries and continuous queries. The proposed smart query system considers both streaming data and historical data from marine sensor networks. The smart query also uses query relaxation technique and semantics from domain knowledge as a recommender system. The proposed smart query benefits in building data and information systems for marine sensor networks. Full article
(This article belongs to the Special Issue Semantic Sensor Network Technologies and Applications)
Open AccessArticle An Emergency-Adaptive Routing Scheme for Wireless Sensor Networks for Building Fire Hazard Monitoring
Sensors 2011, 11(3), 2899-2919; doi:10.3390/s110302899
Received: 16 February 2011 / Accepted: 4 March 2011 / Published: 4 March 2011
Cited by 19 | PDF Full-text (319 KB) | HTML Full-text | XML Full-text
Abstract
Fire hazard monitoring and evacuation for building environments is a novel application area for the deployment of wireless sensor networks. In this context, adaptive routing is essential in order to ensure safe and timely data delivery in building evacuation and fire fighting [...] Read more.
Fire hazard monitoring and evacuation for building environments is a novel application area for the deployment of wireless sensor networks. In this context, adaptive routing is essential in order to ensure safe and timely data delivery in building evacuation and fire fighting resource applications. Existing routing mechanisms for wireless sensor networks are not well suited for building fires, especially as they do not consider critical and dynamic network scenarios. In this paper, an emergency-adaptive, real-time and robust routing protocol is presented for emergency situations such as building fire hazard applications. The protocol adapts to handle dynamic emergency scenarios and works well with the routing hole problem. Theoretical analysis and simulation results indicate that our protocol provides a real-time routing mechanism that is well suited for dynamic emergency scenarios in building fires when compared with other related work. Full article
Open AccessArticle ECS: Efficient Communication Scheduling for Underwater Sensor Networks
Sensors 2011, 11(3), 2920-2938; doi:10.3390/s110302920
Received: 23 January 2011 / Revised: 23 February 2011 / Accepted: 28 February 2011 / Published: 4 March 2011
Cited by 9 | PDF Full-text (276 KB) | HTML Full-text | XML Full-text
Abstract
TDMA protocols have attracted a lot of attention for underwater acoustic sensor networks (UWSNs), because of the unique characteristics of acoustic signal propagation such as great energy consumption in transmission, long propagation delay and long communication range. Previous TDMA protocols all allocated [...] Read more.
TDMA protocols have attracted a lot of attention for underwater acoustic sensor networks (UWSNs), because of the unique characteristics of acoustic signal propagation such as great energy consumption in transmission, long propagation delay and long communication range. Previous TDMA protocols all allocated transmission time to nodes based on discrete time slots. This paper proposes an efficient continuous time scheduling TDMA protocol (ECS) for UWSNs, including the continuous time based and sender oriented conflict analysis model, the transmission moment allocation algorithm and the distributed topology maintenance algorithm. Simulation results confirm that ECS improves network throughput by 20% on average, compared to existing MAC protocols. Full article
(This article belongs to the Special Issue Adaptive Sensing)
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Open AccessArticle Nanofluidic Refractive-Index Sensors Formed by Nanocavity Resonators in Metals without Plasmons
Sensors 2011, 11(3), 2939-2945; doi:10.3390/s110302939
Received: 28 January 2011 / Revised: 28 February 2011 / Accepted: 3 March 2011 / Published: 4 March 2011
Cited by 2 | PDF Full-text (618 KB) | HTML Full-text | XML Full-text
Abstract
Nanocavity resonators in metals acting as nanofluidic refractive-index sensors were analyzed theoretically. With the illumination of transverse electric polarized light, the proposed refractive index sensor structure acts as a pure electromagnetic resonator without the excitation of surface plasmons. The reflected signal from [...] Read more.
Nanocavity resonators in metals acting as nanofluidic refractive-index sensors were analyzed theoretically. With the illumination of transverse electric polarized light, the proposed refractive index sensor structure acts as a pure electromagnetic resonator without the excitation of surface plasmons. The reflected signal from the nanocavity resonators can be very sensitive to the refractive index of the fluids inside the nanocavities due to the enhancement of the electric field of the resonant mode inside the cavities. Such a sensor configuration can be a useful tool for probing the refractive index change of the fluid inside the nanocavities using the spectral, angular or intensity interrogation schemes. The wavelength sensitivity of 430 nm/RIU, angular sensitivity of 200–1,000 deg/RIU and intensity sensitivity of 25.5 RIU−1 can be achieved in the proposed sensor configuration. Full article
(This article belongs to the Special Issue Optical Resonant Microsensors)
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Open AccessArticle On the Optimal Identification of Tag Sets in Time-Constrained RFID Configurations
Sensors 2011, 11(3), 2946-2960; doi:10.3390/s110302946
Received: 25 January 2011 / Revised: 1 March 2011 / Accepted: 2 March 2011 / Published: 4 March 2011
Cited by 11 | PDF Full-text (250 KB) | HTML Full-text | XML Full-text
Abstract
In Radio Frequency Identification facilities the identification delay of a set of tags is mainly caused by the random access nature of the reading protocol, yielding a random identification time of the set of tags. In this paper, the cumulative distribution function [...] Read more.
In Radio Frequency Identification facilities the identification delay of a set of tags is mainly caused by the random access nature of the reading protocol, yielding a random identification time of the set of tags. In this paper, the cumulative distribution function of the identification time is evaluated using a discrete time Markov chain for single-set time-constrained passive RFID systems, namely those ones where a single group of tags is assumed to be in the reading area and only for a bounded time (sojourn time) before leaving. In these scenarios some tags in a set may leave the reader coverage area unidentified. The probability of this event is obtained from the cumulative distribution function of the identification time as a function of the sojourn time. This result provides a suitable criterion to minimize the probability of losing tags. Besides, an identification strategy based on splitting the set of tags in smaller subsets is also considered. Results demonstrate that there are optimal splitting configurations that reduce the overall identification time while keeping the same probability of losing tags. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Driving down the Detection Limit in Microstructured Fiber‑Based Chemical Dip Sensors
Sensors 2011, 11(3), 2961-2971; doi:10.3390/s110302961
Received: 25 November 2010 / Revised: 17 January 2011 / Accepted: 21 February 2011 / Published: 4 March 2011
Cited by 26 | PDF Full-text (937 KB) | HTML Full-text | XML Full-text
Abstract
We present improvements to fluorescence sensing in soft-glass microstructured optical fibers that result in significantly improved sensitivity relative to previously published results. Concentrations of CdSe quantum dots down to 10 pM levels have been demonstrated. We show that the primary limitation to [...] Read more.
We present improvements to fluorescence sensing in soft-glass microstructured optical fibers that result in significantly improved sensitivity relative to previously published results. Concentrations of CdSe quantum dots down to 10 pM levels have been demonstrated. We show that the primary limitation to the sensitivity of these systems is the intrinsic fluorescence of the glass itself. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Mapping the Philippines’ Mangrove Forests Using Landsat Imagery
Sensors 2011, 11(3), 2972-2981; doi:10.3390/s110302972
Received: 6 February 2011 / Accepted: 25 February 2011 / Published: 7 March 2011
Cited by 24 | PDF Full-text (629 KB) | HTML Full-text | XML Full-text
Abstract
Current, accurate, and reliable information on the areal extent and spatial distribution of mangrove forests in the Philippines is limited. Previous estimates of mangrove extent do not illustrate the spatial distribution for the entire country. This study, part of a global assessment [...] Read more.
Current, accurate, and reliable information on the areal extent and spatial distribution of mangrove forests in the Philippines is limited. Previous estimates of mangrove extent do not illustrate the spatial distribution for the entire country. This study, part of a global assessment of mangrove dynamics, mapped the spatial distribution and areal extent of the Philippines’ mangroves circa 2000. We used publicly available Landsat data acquired primarily from the Global Land Survey to map the total extent and spatial distribution. ISODATA clustering, an unsupervised classification technique, was applied to 61 Landsat images. Statistical analysis indicates the total area of mangrove forest cover was approximately 256,185 hectares circa 2000 with overall classification accuracy of 96.6% and a kappa coefficient of 0.926. These results differ substantially from most recent estimates of mangrove area in the Philippines. The results of this study may assist the decision making processes for rehabilitation and conservation efforts that are currently needed to protect and restore the Philippines’ degraded mangrove forests. Full article
(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)
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Open AccessArticle Application of V2O5/WO3/TiO2 for Resistive-Type SO2 Sensors
Sensors 2011, 11(3), 2982-2991; doi:10.3390/s110302982
Received: 11 February 2011 / Revised: 1 March 2011 / Accepted: 3 March 2011 / Published: 7 March 2011
Cited by 17 | PDF Full-text (615 KB) | HTML Full-text | XML Full-text
Abstract
A study on the application of V2O5/WO3/TiO2 (VWT) as the sensitive material for resistive-type SO2 sensor was conducted, based on the fact that VWT is a well-known catalyst material for good selective catalytic nitrogen [...] Read more.
A study on the application of V2O5/WO3/TiO2 (VWT) as the sensitive material for resistive-type SO2 sensor was conducted, based on the fact that VWT is a well-known catalyst material for good selective catalytic nitrogen oxide reduction with a proven excellent durability in exhaust gases. The sensors fabricated in this study are planar ones with interdigitated electrodes of Au or Pt. The vanadium content of the utilized VWT is 1.5 or 3.0 wt%. The resistance of VWT decreases with an increasing SO2 concentration in the range from 20 ppm to 5,000 ppm. The best sensor response to SO2 occurs at 400 °C using Au electrodes. The sensor response value is independent on the amount of added vanadium but dependent on the electrode materials at 400 °C. These results are discussed and a sensing mechanism is discussed. Full article
(This article belongs to the Special Issue Gas Sensors - 2010)
Open AccessArticle Gas-to-Particle Conversion in Surface Discharge Nonthermal Plasmas and Its Implications for Atmospheric Chemistry
Sensors 2011, 11(3), 2992-3003; doi:10.3390/s110302992
Received: 6 January 2011 / Revised: 21 February 2011 / Accepted: 4 March 2011 / Published: 7 March 2011
Cited by 4 | PDF Full-text (266 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents some experimental data on gas-to-particle conversion of benzene using nonthermal plasma (NTP) technology and discusses the possibility of its technical application in atmospheric chemistry. Aerosol measurement using a differential mobility analyzer (DMA) revealed that the parts of benzene molecules [...] Read more.
This paper presents some experimental data on gas-to-particle conversion of benzene using nonthermal plasma (NTP) technology and discusses the possibility of its technical application in atmospheric chemistry. Aerosol measurement using a differential mobility analyzer (DMA) revealed that the parts of benzene molecules were converted into a nanometer-sized aerosol. Aerosol formation was found to be highly related with the missing part in carbon balance. Scanning electron microscopy analysis showed that the aerosols formed in synthetic humid air are the collection of nanoparticles. The carbonyl band (C=O) was found to be an important chemical constituent in the aerosol. The potential of the NTP as an accelerated test tool in studying secondary organic aerosol (SOA) formation from VOCs will be also addressed. Full article
(This article belongs to the Special Issue Direct and Indirect Sensing of Odor and VOCs and Their Control)
Open AccessCommunication Photonic Biosensor Assays to Detect and Distinguish Subspecies of Francisella tularensis
Sensors 2011, 11(3), 3004-3019; doi:10.3390/s110303004
Received: 15 January 2011 / Revised: 15 February 2011 / Accepted: 2 March 2011 / Published: 7 March 2011
Cited by 3 | PDF Full-text (491 KB) | HTML Full-text | XML Full-text
Abstract
The application of photonic biosensor assays to diagnose the category-A select agent Francisella tularensis was investigated. Both interferometric and long period fiber grating sensing structures were successfully demonstrated; both these sensors are capable of detecting the optical changes induced by either [...] Read more.
The application of photonic biosensor assays to diagnose the category-A select agent Francisella tularensis was investigated. Both interferometric and long period fiber grating sensing structures were successfully demonstrated; both these sensors are capable of detecting the optical changes induced by either immunological binding or DNA hybridization. Detection was made possible by the attachment of DNA probes or immunoglobulins (IgG) directly to the fiber surface via layer-by-layer electrostatic self-assembly. An optical fiber biosensor was tested using a standard transmission mode long period fiber grating of length 15 mm and period 260 µm, and coated with the IgG fraction of antiserum to F. tularensis. The IgG was deposited onto the optical fiber surface in a nanostructured film, and the resulting refractive index change was measured using spectroscopic ellipsometry. The presence of F. tularensis was detected from the decrease of peak wavelength caused by binding of specific antigen. Detection and differentiation of F. tularensis subspecies tularensis (type A strain TI0902) and subspecies holarctica (type B strain LVS) was further accomplished using a single-mode multi-cavity fiber Fabry-Perot interferometric sensor. These sensors were prepared by depositing seven polymer bilayers onto the fiber tip followed by attaching one of two DNA probes: (a) a 101-bp probe from the yhhW gene unique to type-A strains, or (b) a 117-bp probe of the lpnA gene, common to both type-A and type-B strains. The yhhW probe was reactive with the type-A, but not the type-B strain. Probe lpnA was reactive with both type-A and type-B strains. Nanogram quantities of the target DNA could be detected, highlighting the sensitivity of this method for DNA detection without the use of PCR. The DNA probe reacted with 100% homologous target DNA, but did not react with sequences containing 2-bp mismatches, indicating the high specificity of the assay. These assays will fill an important void that exists for rapid, culture-free, and field-compatible diagnosis of F. tularensis. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Estimation of Physiological Tremor from Accelerometers for Real-Time Applications
Sensors 2011, 11(3), 3020-3036; doi:10.3390/s110303020
Received: 10 January 2011 / Revised: 28 February 2011 / Accepted: 4 March 2011 / Published: 7 March 2011
Cited by 35 | PDF Full-text (654 KB) | HTML Full-text | XML Full-text
Abstract
Accurate filtering of physiological tremor is extremely important in robotics assisted surgical instruments and procedures. This paper focuses on developing single stage robust algorithms for accurate tremor filtering with accelerometers for real-time applications. Existing methods rely on estimating the tremor under the [...] Read more.
Accurate filtering of physiological tremor is extremely important in robotics assisted surgical instruments and procedures. This paper focuses on developing single stage robust algorithms for accurate tremor filtering with accelerometers for real-time applications. Existing methods rely on estimating the tremor under the assumption that it has a single dominant frequency. Our time-frequency analysis on physiological tremor data revealed that tremor contains multiple dominant frequencies over the entire duration rather than a single dominant frequency. In this paper, the existing methods for tremor filtering are reviewed and two improved algorithms are presented. A comparative study is conducted on all the estimation methods with tremor data from microsurgeons and novice subjects under different conditions. Our results showed that the new improved algorithms performed better than the existing algorithms for tremor estimation. A procedure to separate the intended motion/drift from the tremor component is formulated. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Analysis of RFI Identification and Mitigation in CAROLS Radiometer Data Using a Hardware Spectrum Analyser
Sensors 2011, 11(3), 3037-3050; doi:10.3390/s110303037
Received: 30 January 2011 / Revised: 26 February 2011 / Accepted: 28 February 2011 / Published: 7 March 2011
Cited by 7 | PDF Full-text (1558 KB) | HTML Full-text | XML Full-text
Abstract
A method to identify and mitigate radio frequency interference (RFI) in microwave radiometry based on the use of a spectrum analyzer has been developed. This method has been tested with CAROLS L-band airborne radiometer data that are strongly corrupted by RFI. RFI [...] Read more.
A method to identify and mitigate radio frequency interference (RFI) in microwave radiometry based on the use of a spectrum analyzer has been developed. This method has been tested with CAROLS L-band airborne radiometer data that are strongly corrupted by RFI. RFI is a major limiting factor in passive microwave remote sensing interpretation. Although the 1.400–1.427 GHz bandwidth is protected, RFI sources close to these frequencies are still capable of corrupting radiometric measurements. In order to reduce the detrimental effects of RFI on brightness temperature measurements, a new spectrum analyzer has been added to the CAROLS radiometer system. A post processing algorithm is proposed, based on selective filters within the useful bandwidth divided into sub-bands. Two discriminant analyses based on the computation of kurtosis and Euclidian distances have been compared evaluated and validated in order to accurately separate the RF interference from natural signals. Full article
(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)
Open AccessArticle Adaptive Sampling for Learning Gaussian Processes Using Mobile Sensor Networks
Sensors 2011, 11(3), 3051-3066; doi:10.3390/s110303051
Received: 4 January 2011 / Revised: 25 February 2011 / Accepted: 27 February 2011 / Published: 9 March 2011
Cited by 23 | PDF Full-text (1519 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel class of self-organizing sensing agents that adaptively learn an anisotropic, spatio-temporal Gaussian process using noisy measurements and move in order to improve the quality of the estimated covariance function. This approach is based on a class of [...] Read more.
This paper presents a novel class of self-organizing sensing agents that adaptively learn an anisotropic, spatio-temporal Gaussian process using noisy measurements and move in order to improve the quality of the estimated covariance function. This approach is based on a class of anisotropic covariance functions of Gaussian processes introduced to model a broad range of spatio-temporal physical phenomena. The covariance function is assumed to be unknown a priori. Hence, it is estimated by the maximum a posteriori probability (MAP) estimator. The prediction of the field of interest is then obtained based on the MAP estimate of the covariance function. An optimal sampling strategy is proposed to minimize the information-theoretic cost function of the Fisher Information Matrix. Simulation results demonstrate the effectiveness and the adaptability of the proposed scheme. Full article
(This article belongs to the Special Issue Adaptive Sensing)
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Open AccessArticle Open-Gated pH Sensor Fabricated on an Undoped-AlGaN/GaN HEMT Structure
Sensors 2011, 11(3), 3067-3077; doi:10.3390/s110303067
Received: 10 January 2011 / Revised: 28 February 2011 / Accepted: 7 March 2011 / Published: 9 March 2011
Cited by 8 | PDF Full-text (605 KB) | HTML Full-text | XML Full-text
Abstract
The sensing responses in aqueous solution of an open-gated pH sensor fabricated on an AlGaN/GaN high-electron-mobility-transistor (HEMT) structure are investigated. Under air-exposed ambient conditions, the open-gated undoped AlGaN/GaN HEMT only shows the presence of a linear current region. This seems to show [...] Read more.
The sensing responses in aqueous solution of an open-gated pH sensor fabricated on an AlGaN/GaN high-electron-mobility-transistor (HEMT) structure are investigated. Under air-exposed ambient conditions, the open-gated undoped AlGaN/GaN HEMT only shows the presence of a linear current region. This seems to show that very low Fermi level pinning by surface states exists in the undoped AlGaN/GaN sample. In aqueous solution, typical current-voltage (I-V) characteristics with reasonably good gate controllability are observed, showing that the potential of the AlGaN surface at the open-gated area is effectively controlled via aqueous solution by the Ag/AgCl gate electrode. The open-gated undoped AlGaN/GaN HEMT structure is capable of distinguishing pH level in aqueous electrolytes and exhibits linear sensitivity, where high sensitivity of 1.9 mA/pH or 3.88 mA/mm/pH at drain-source voltage, VDS = 5 V is obtained. Due to the large leakage current where it increases with the negative gate voltage, Nernstian like sensitivity cannot be determined as commonly reported in the literature. This large leakage current may be caused by the technical factors rather than any characteristics of the devices. Surprisingly, although there are some imperfections in the device preparation and measurement, the fabricated devices work very well in distinguishing the pH levels. Suppression of current leakage by improving the device preparation is likely needed to improve the device performance. The fabricated device is expected to be suitable for pH sensing applications. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle An Efficient Transmission Power Control Scheme for Temperature Variation in Wireless Sensor Networks
Sensors 2011, 11(3), 3078-3093; doi:10.3390/s110303078
Received: 14 February 2011 / Revised: 6 March 2011 / Accepted: 7 March 2011 / Published: 10 March 2011
Cited by 9 | PDF Full-text (909 KB) | HTML Full-text | XML Full-text
Abstract
Wireless sensor networks collect data from several nodes dispersed at remote sites. Sensor nodes can be installed in harsh environments such as deserts, cities, and indoors, where the link quality changes considerably over time. Particularly, changes in transmission power may be caused [...] Read more.
Wireless sensor networks collect data from several nodes dispersed at remote sites. Sensor nodes can be installed in harsh environments such as deserts, cities, and indoors, where the link quality changes considerably over time. Particularly, changes in transmission power may be caused by temperature, humidity, and other factors. In order to compensate for link quality changes, existing schemes detect the link quality changes between nodes and control transmission power through a series of feedback processes, but these approaches can cause heavy overhead with the additional control packets needed. In this paper, the change of the link quality according to temperature is examined through empirical experimentation. A new power control scheme combining both temperature-aware link quality compensation and a closed-loop feedback process to adapt to link quality changes is proposed. We prove that the proposed scheme effectively adapts the transmission power to the changing link quality with less control overhead and energy consumption. Full article
(This article belongs to the Special Issue Semantic Sensor Network Technologies and Applications)
Open AccessArticle Optimization of Sensing and Feedback Control for Vibration/Flutter of Rotating Disk by PZT Actuators via Air Coupled Pressure
Sensors 2011, 11(3), 3094-3116; doi:10.3390/s110303094
Received: 11 February 2011 / Revised: 1 March 2011 / Accepted: 3 March 2011 / Published: 10 March 2011
Cited by 3 | PDF Full-text (3334 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a feedback control mechanism and its optimization for rotating disk vibration/flutter via changes of air-coupled pressure generated using piezoelectric patch actuators are studied. A thin disk rotates in an enclosure, which is equipped with a feedback control loop consisting [...] Read more.
In this paper, a feedback control mechanism and its optimization for rotating disk vibration/flutter via changes of air-coupled pressure generated using piezoelectric patch actuators are studied. A thin disk rotates in an enclosure, which is equipped with a feedback control loop consisting of a micro-sensor, a signal processor, a power amplifier, and several piezoelectric (PZT) actuator patches distributed on the cover of the enclosure. The actuator patches are mounted on the inner or the outer surfaces of the enclosure to produce necessary control force required through the airflow around the disk. The control mechanism for rotating disk flutter using enclosure surfaces bonded with sensors and piezoelectric actuators is thoroughly studied through analytical simulations. The sensor output is used to determine the amount of input to the actuator for controlling the response of the disk in a closed loop configuration. The dynamic stability of the disk-enclosure system, together with the feedback control loop, is analyzed as a complex eigenvalue problem, which is solved using Galerkin’s discretization procedure. The results show that the disk flutter can be reduced effectively with proper configurations of the control gain and the phase shift through the actuations of PZT patches. The effectiveness of different feedback control methods in altering system characteristics and system response has been investigated. The control capability, in terms of control gain, phase shift, and especially the physical configuration of actuator patches, are also evaluated by calculating the complex eigenvalues and the maximum displacement produced by the actuators. To achieve a optimal control performance, sizes, positions and shapes of PZT patches used need to be optimized and such optimization has been achieved through numerical simulations. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Simple Random Sampling-Based Probe Station Selection for Fault Detection in Wireless Sensor Networks
Sensors 2011, 11(3), 3117-3134; doi:10.3390/s110303117
Received: 10 January 2011 / Revised: 28 February 2011 / Accepted: 1 March 2011 / Published: 14 March 2011
Cited by 3 | PDF Full-text (1205 KB) | HTML Full-text | XML Full-text
Abstract
Fault detection for wireless sensor networks (WSNs) has been studied intensively in recent years. Most existing works statically choose the manager nodes as probe stations and probe the network at a fixed frequency. This straightforward solution leads however to several deficiencies. Firstly, [...] Read more.
Fault detection for wireless sensor networks (WSNs) has been studied intensively in recent years. Most existing works statically choose the manager nodes as probe stations and probe the network at a fixed frequency. This straightforward solution leads however to several deficiencies. Firstly, by only assigning the fault detection task to the manager node the whole network is out of balance, and this quickly overloads the already heavily burdened manager node, which in turn ultimately shortens the lifetime of the whole network. Secondly, probing with a fixed frequency often generates too much useless network traffic, which results in a waste of the limited network energy. Thirdly, the traditional algorithm for choosing a probing node is too complicated to be used in energy-critical wireless sensor networks. In this paper, we study the distribution characters of the fault nodes in wireless sensor networks, validate the Pareto principle that a small number of clusters contain most of the faults. We then present a Simple Random Sampling-based algorithm to dynamic choose sensor nodes as probe stations. A dynamic adjusting rule for probing frequency is also proposed to reduce the number of useless probing packets. The simulation experiments demonstrate that the algorithm and adjusting rule we present can effectively prolong the lifetime of a wireless sensor network without decreasing the fault detected rate. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A High Temperature Capacitive Humidity Sensor Based on Mesoporous Silica
Sensors 2011, 11(3), 3135-3144; doi:10.3390/s110303135
Received: 30 January 2011 / Revised: 20 February 2011 / Accepted: 25 February 2011 / Published: 14 March 2011
Cited by 17 | PDF Full-text (604 KB) | HTML Full-text | XML Full-text
Abstract
Capacitive sensors are the most commonly used devices for the detection of humidity because they are inexpensive and the detection mechanism is very specific for humidity. However, especially for industrial processes, there is a lack of dielectrics that are stable at high [...] Read more.
Capacitive sensors are the most commonly used devices for the detection of humidity because they are inexpensive and the detection mechanism is very specific for humidity. However, especially for industrial processes, there is a lack of dielectrics that are stable at high temperature (>200 °C) and under harsh conditions. We present a capacitive sensor based on mesoporous silica as the dielectric in a simple sensor design based on pressed silica pellets. Investigation of the structural stability of the porous silica under simulated operating conditions as well as the influence of the pellet production will be shown. Impedance measurements demonstrate the utility of the sensor at both low (90 °C) and high (up to 210 °C) operating temperatures. Full article
(This article belongs to the Special Issue Gas Sensors - 2010)
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Open AccessArticle State Derivation of a 12-Axis Gyroscope-Free Inertial Measurement Unit
Sensors 2011, 11(3), 3145-3162; doi:10.3390/s110303145
Received: 28 December 2010 / Revised: 6 February 2011 / Accepted: 22 February 2011 / Published: 14 March 2011
Cited by 5 | PDF Full-text (445 KB) | HTML Full-text | XML Full-text
Abstract
The derivation of linear acceleration, angular acceleration, and angular velocity states from a 12-axis gyroscope-free inertial measurement unit that utilizes four 3-axis accelerometer measurements at four distinct locations is reported. Particularly, a new algorithm which derives the angular velocity from its quadratic [...] Read more.
The derivation of linear acceleration, angular acceleration, and angular velocity states from a 12-axis gyroscope-free inertial measurement unit that utilizes four 3-axis accelerometer measurements at four distinct locations is reported. Particularly, a new algorithm which derives the angular velocity from its quadratic form and derivative form based on the context-based interacting multiple model is demonstrated. The performance of the system was evaluated under arbitrary 3-dimensional motion. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Delaunay Triangulation as a New Coverage Measurement Method in Wireless Sensor Network
Sensors 2011, 11(3), 3163-3176; doi:10.3390/s110303163
Received: 15 January 2011 / Revised: 25 February 2011 / Accepted: 28 February 2011 / Published: 15 March 2011
Cited by 10 | PDF Full-text (985 KB) | HTML Full-text | XML Full-text
Abstract
Sensing and communication coverage are among the most important trade-offs in Wireless Sensor Network (WSN) design. A minimum bound of sensing coverage is vital in scheduling, target tracking and redeployment phases, as well as providing communication coverage. Some methods measure the coverage [...] Read more.
Sensing and communication coverage are among the most important trade-offs in Wireless Sensor Network (WSN) design. A minimum bound of sensing coverage is vital in scheduling, target tracking and redeployment phases, as well as providing communication coverage. Some methods measure the coverage as a percentage value, but detailed information has been missing. Two scenarios with equal coverage percentage may not have the same Quality of Coverage (QoC). In this paper, we propose a new coverage measurement method using Delaunay Triangulation (DT). This can provide the value for all coverage measurement tools. Moreover, it categorizes sensors as ‘fat’, ‘healthy’ or ‘thin’ to show the dense, optimal and scattered areas. It can also yield the largest empty area of sensors in the field. Simulation results show that the proposed DT method can achieve accurate coverage information, and provides many tools to compare QoC between different scenarios. Full article
(This article belongs to the Special Issue Advanced Sensing Technology for Nondestructive Evaluation)
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Open AccessArticle Ontological Problem-Solving Framework for Dynamically Configuring Sensor Systems and Algorithms
Sensors 2011, 11(3), 3177-3204; doi:10.3390/s110303177
Received: 7 January 2011 / Revised: 4 February 2011 / Accepted: 11 March 2011 / Published: 15 March 2011
Cited by 3 | PDF Full-text (297 KB) | HTML Full-text | XML Full-text
Abstract
The deployment of ubiquitous sensor systems and algorithms has led to many challenges, such as matching sensor systems to compatible algorithms which are capable of satisfying a task. Compounding the challenges is the lack of the requisite knowledge models needed to discover [...] Read more.
The deployment of ubiquitous sensor systems and algorithms has led to many challenges, such as matching sensor systems to compatible algorithms which are capable of satisfying a task. Compounding the challenges is the lack of the requisite knowledge models needed to discover sensors and algorithms and to subsequently integrate their capabilities to satisfy a specific task. A novel ontological problem-solving framework has been designed to match sensors to compatible algorithms to form synthesized systems, which are capable of satisfying a task and then assigning the synthesized systems to high-level missions. The approach designed for the ontological problem-solving framework has been instantiated in the context of a persistence surveillance prototype environment, which includes profiling sensor systems and algorithms to demonstrate proof-of-concept principles. Even though the problem-solving approach was instantiated with profiling sensor systems and algorithms, the ontological framework may be useful with other heterogeneous sensing-system environments. Full article
(This article belongs to the Special Issue Semantic Sensor Network Technologies and Applications)
Open AccessArticle Adaptive Marginal Median Filter for Colour Images
Sensors 2011, 11(3), 3205-3213; doi:10.3390/s110303205
Received: 5 January 2011 / Revised: 3 February 2011 / Accepted: 10 March 2011 / Published: 15 March 2011
Cited by 13 | PDF Full-text (1421 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes a new filter for impulse noise reduction in colour images which is aimed at improving the noise reduction capability of the classical vector median filter. The filter is inspired by the application of a vector marginal median filtering process [...] Read more.
This paper describes a new filter for impulse noise reduction in colour images which is aimed at improving the noise reduction capability of the classical vector median filter. The filter is inspired by the application of a vector marginal median filtering process over a selected group of pixels in each filtering window. This selection, which is based on the vector median, along with the application of the marginal median operation constitutes an adaptive process that leads to a more robust filter design. Also, the proposed method is able to process colour images without introducing colour artifacts. Experimental results show that the images filtered with the proposed method contain less noisy pixels than those obtained through the vector median filter. Full article
(This article belongs to the Special Issue Adaptive Sensing)
Open AccessArticle Potentiometric Electronic Tongue to Resolve Mixtures of Sulfide and Perchlorate Anions
Sensors 2011, 11(3), 3214-3226; doi:10.3390/s110303214
Received: 11 January 2011 / Revised: 24 February 2011 / Accepted: 10 March 2011 / Published: 16 March 2011
Cited by 12 | PDF Full-text (449 KB) | HTML Full-text | XML Full-text
Abstract
This work describes the use of an array of potentiometric sensors and an artificial neural network response model to determine perchlorate and sulfide ions in polluted waters, by what is known as an electronic tongue. Sensors used have been all-solid-state PVC membrane [...] Read more.
This work describes the use of an array of potentiometric sensors and an artificial neural network response model to determine perchlorate and sulfide ions in polluted waters, by what is known as an electronic tongue. Sensors used have been all-solid-state PVC membrane selective electrodes, where their ionophores were different metal-phtalocyanine complexes with specific and anion generic responses. The study case illustrates the potential use of electronic tongues in the quantification of mixtures when interfering effects need to be counterbalanced: relative errors in determination of individual ions can be decreased typically from 25% to less than 5%, if compared to the use of a single proposed ion-selective electrode. Full article
(This article belongs to the Special Issue Bioinspired Sensor Systems)
Open AccessArticle Gyroscope Pivot Bearing Dimension and Surface Defect Detection
Sensors 2011, 11(3), 3227-3248; doi:10.3390/s110303227
Received: 31 January 2011 / Revised: 1 March 2011 / Accepted: 4 March 2011 / Published: 16 March 2011
Cited by 2 | PDF Full-text (725 KB) | HTML Full-text | XML Full-text
Abstract
Because of the perceived lack of systematic analysis in illumination system design processes and a lack of criteria for design methods in vision detection a method for the design of a task-oriented illumination system is proposed. After detecting the micro-defects of a [...] Read more.
Because of the perceived lack of systematic analysis in illumination system design processes and a lack of criteria for design methods in vision detection a method for the design of a task-oriented illumination system is proposed. After detecting the micro-defects of a gyroscope pivot bearing with a high curvature glabrous surface and analyzing the characteristics of the surface detection and reflection model, a complex illumination system with coaxial and ring lights is proposed. The illumination system is then optimized based on the analysis of illuminance uniformity of target regions by simulation and grey scale uniformity and articulation that are calculated from grey imagery. Currently, in order to apply the Pulse Coupled Neural Network (PCNN) method, structural parameters must be tested and adjusted repeatedly. Therefore, this paper proposes the use of a particle swarm optimization (PSO) algorithm, in which the maximum between cluster variance rules is used as fitness function with a linearily reduced inertia factor. This algorithm is used to adaptively set PCNN connection coefficients and dynamic threshold, which avoids algorithmic precocity and local oscillations. The proposed method is used for pivot bearing defect image processing. The segmentation results of the maximum entropy and minimum error method and the one described in this paper are compared using buffer region matching, and the experimental results show that the method of this paper is effective. Full article
(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)
Open AccessArticle Three Realizations and Comparison of Hardware for Piezoresistive Tactile Sensors
Sensors 2011, 11(3), 3249-3266; doi:10.3390/s110303249
Received: 17 January 2011 / Revised: 10 March 2011 / Accepted: 14 March 2011 / Published: 17 March 2011
Cited by 21 | PDF Full-text (862 KB) | HTML Full-text | XML Full-text
Abstract
Tactile sensors are basically arrays of force sensors that are intended to emulate the skin in applications such as assistive robotics. Local electronics are usually implemented to reduce errors and interference caused by long wires. Realizations based on standard microcontrollers, Programmable Systems [...] Read more.
Tactile sensors are basically arrays of force sensors that are intended to emulate the skin in applications such as assistive robotics. Local electronics are usually implemented to reduce errors and interference caused by long wires. Realizations based on standard microcontrollers, Programmable Systems on Chip (PSoCs) and Field Programmable Gate Arrays (FPGAs) have been proposed by the authors for the case of piezoresistive tactile sensors. The solution employing FPGAs is especially relevant since their performance is closer to that of Application Specific Integrated Circuits (ASICs) than that of the other devices. This paper presents an implementation of such an idea for a specific sensor. For the purpose of comparison, the circuitry based on the other devices is also made for the same sensor. This paper discusses the implementation issues, provides details regarding the design of the hardware based on the three devices and compares them. Full article
(This article belongs to the Special Issue Bioinspired Sensor Systems)
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Open AccessArticle Optical Sensor for Diverse Organic Vapors at ppm Concentration Ranges
Sensors 2011, 11(3), 3267-3280; doi:10.3390/s110303267
Received: 17 February 2011 / Revised: 12 March 2011 / Accepted: 15 March 2011 / Published: 17 March 2011
Cited by 9 | PDF Full-text (291 KB) | HTML Full-text | XML Full-text
Abstract
A broadly responsive optical organic vapor sensor is described that responds to low concentrations of organic vapors without significant interference from water vapor. Responses to several classes of organic vapors are highlighted, and trends within classes are presented. The relationship between molecular [...] Read more.
A broadly responsive optical organic vapor sensor is described that responds to low concentrations of organic vapors without significant interference from water vapor. Responses to several classes of organic vapors are highlighted, and trends within classes are presented. The relationship between molecular properties (vapor pressure, boiling point, polarizability, and refractive index) and sensor response are discussed. Full article
(This article belongs to the Special Issue Direct and Indirect Sensing of Odor and VOCs and Their Control)
Open AccessArticle A Compatible Control Algorithm for Greenhouse Environment Control Based on MOCC Strategy
Sensors 2011, 11(3), 3281-3302; doi:10.3390/s110303281
Received: 21 February 2011 / Accepted: 10 March 2011 / Published: 18 March 2011
Cited by 9 | PDF Full-text (596 KB) | HTML Full-text | XML Full-text
Abstract
Conventional methods used for solving greenhouse environment multi-objective conflict control problems lay excessive emphasis on control performance and have inadequate consideration for both energy consumption and special requirements for plant growth. The resulting solution will cause higher energy cost. However, during the [...] Read more.
Conventional methods used for solving greenhouse environment multi-objective conflict control problems lay excessive emphasis on control performance and have inadequate consideration for both energy consumption and special requirements for plant growth. The resulting solution will cause higher energy cost. However, during the long period of work and practice, we find that it may be more reasonable to adopt interval or region control objectives instead of point control objectives. In this paper, we propose a modified compatible control algorithm, and employ Multi-Objective Compatible Control (MOCC) strategy and an extant greenhouse model to achieve greenhouse climate control based on feedback control architecture. A series of simulation experiments through various comparative studies are presented to validate the feasibility of the proposed algorithm. The results are encouraging and suggest the energy-saving application to real-world engineering problems in greenhouse production. It may be valuable and helpful to formulate environmental control strategies, and to achieve high control precision and low energy cost for real-world engineering application in greenhouse production. Moreover, the proposed approach has also potential to be useful for other practical control optimization problems with the features like the greenhouse environment control system. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Contrast-Independent Biologically Inspired Motion Detection
Sensors 2011, 11(3), 3303-3326; doi:10.3390/s110303303
Received: 28 January 2011 / Revised: 15 March 2011 / Accepted: 17 March 2011 / Published: 18 March 2011
Cited by 7 | PDF Full-text (5324 KB) | HTML Full-text | XML Full-text
Abstract
Optic flow, i.e., retinal image movement resulting from ego-motion, is a crucial source of information used for obstacle avoidance and course control in flying insects. Optic flow analysis may prove promising for mobile robotics although it is currently not among the [...] Read more.
Optic flow, i.e., retinal image movement resulting from ego-motion, is a crucial source of information used for obstacle avoidance and course control in flying insects. Optic flow analysis may prove promising for mobile robotics although it is currently not among the standard techniques. Insects have developed a computationally cheap analysis mechanism for image motion. Detailed computational models, the so-called elementary motion detectors (EMDs), describe motion detection in insects. However, the technical application of EMDs is complicated by the strong effect of local pattern contrast on their motion response. Here we present augmented versions of an EMD, the (s)cc-EMDs, which normalise their responses for contrast and thereby reduce the sensitivity to contrast changes. Thus, velocity changes of moving natural images are reflected more reliably in the detector response. The (s)cc-EMDs can easily be implemented in hardware and software and can be a valuable novel visual motion sensor for mobile robots. Full article
Open AccessArticle Signal Injection as a Fault Detection Technique
Sensors 2011, 11(3), 3356-3380; doi:10.3390/s110303356
Received: 25 January 2011 / Revised: 28 February 2011 / Accepted: 10 March 2011 / Published: 21 March 2011
Cited by 8 | PDF Full-text (2188 KB) | HTML Full-text | XML Full-text
Abstract
Double frequency tests are used for evaluating stator windings and analyzing the temperature. Likewise, signal injection on induction machines is used on sensorless motor control fields to find out the rotor position. Motor Current Signature Analysis (MCSA), which focuses on the spectral [...] Read more.
Double frequency tests are used for evaluating stator windings and analyzing the temperature. Likewise, signal injection on induction machines is used on sensorless motor control fields to find out the rotor position. Motor Current Signature Analysis (MCSA), which focuses on the spectral analysis of stator current, is the most widely used method for identifying faults in induction motors. Motor faults such as broken rotor bars, bearing damage and eccentricity of the rotor axis can be detected. However, the method presents some problems at low speed and low torque, mainly due to the proximity between the frequencies to be detected and the small amplitude of the resulting harmonics. This paper proposes the injection of an additional voltage into the machine being tested at a frequency different from the fundamental one, and then studying the resulting harmonics around the new frequencies appearing due to the composition between injected and main frequencies. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Reliable Energy-Efficient Multi-Level Routing Algorithm for Wireless Sensor Networks Using Fuzzy Petri Nets
Sensors 2011, 11(3), 3381-3400; doi:10.3390/s110303381
Received: 25 January 2011 / Revised: 16 February 2011 / Accepted: 4 March 2011 / Published: 22 March 2011
Cited by 16 | PDF Full-text (311 KB) | HTML Full-text | XML Full-text
Abstract
A reliable energy-efficient multi-level routing algorithm in wireless sensor networks is proposed. The proposed algorithm considers the residual energy, number of the neighbors and centrality of each node for cluster formation, which is critical for well-balanced energy dissipation of the network. In [...] Read more.
A reliable energy-efficient multi-level routing algorithm in wireless sensor networks is proposed. The proposed algorithm considers the residual energy, number of the neighbors and centrality of each node for cluster formation, which is critical for well-balanced energy dissipation of the network. In the algorithm, a knowledge-based inference approach using fuzzy Petri nets is employed to select cluster heads, and then the fuzzy reasoning mechanism is used to compute the degree of reliability in the route sprouting tree from cluster heads to the base station. Finally, the most reliable route among the cluster heads can be constructed. The algorithm not only balances the energy load of each node but also provides global reliability for the whole network. Simulation results demonstrate that the proposed algorithm effectively prolongs the network lifetime and reduces the energy consumption. Full article
(This article belongs to the Section Physical Sensors)

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Open AccessReview Non-Destructive Techniques Based on Eddy Current Testing
Sensors 2011, 11(3), 2525-2565; doi:10.3390/s110302525
Received: 5 January 2011 / Revised: 19 January 2011 / Accepted: 9 February 2011 / Published: 28 February 2011
Cited by 97 | PDF Full-text (3772 KB) | HTML Full-text | XML Full-text
Abstract
Non-destructive techniques are used widely in the metal industry in order to control the quality of materials. Eddy current testing is one of the most extensively used non-destructive techniques for inspecting electrically conductive materials at very high speeds that does not require [...] Read more.
Non-destructive techniques are used widely in the metal industry in order to control the quality of materials. Eddy current testing is one of the most extensively used non-destructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor. This paper includes an overview of the fundamentals and main variables of eddy current testing. It also describes the state-of-the-art sensors and modern techniques such as multi-frequency and pulsed systems. Recent advances in complex models towards solving crack-sensor interaction, developments in instrumentation due to advances in electronic devices, and the evolution of data processing suggest that eddy current testing systems will be increasingly used in the future. Full article
(This article belongs to the Special Issue Advanced Sensing Technology for Nondestructive Evaluation)
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Open AccessReview New Generation Sensor Web Enablement
Sensors 2011, 11(3), 2652-2699; doi:10.3390/s110302652
Received: 17 January 2011 / Revised: 15 February 2011 / Accepted: 25 February 2011 / Published: 1 March 2011
Cited by 179 | PDF Full-text (809 KB) | HTML Full-text | XML Full-text
Abstract
Many sensor networks have been deployed to monitor Earth’s environment, and more will follow in the future. Environmental sensors have improved continuously by becoming smaller, cheaper, and more intelligent. Due to the large number of sensor manufacturers and differing accompanying protocols, integrating [...] Read more.
Many sensor networks have been deployed to monitor Earth’s environment, and more will follow in the future. Environmental sensors have improved continuously by becoming smaller, cheaper, and more intelligent. Due to the large number of sensor manufacturers and differing accompanying protocols, integrating diverse sensors into observation systems is not straightforward. A coherent infrastructure is needed to treat sensors in an interoperable, platform-independent and uniform way. The concept of the Sensor Web reflects such a kind of infrastructure for sharing, finding, and accessing sensors and their data across different applications. It hides the heterogeneous sensor hardware and communication protocols from the applications built on top of it. The Sensor Web Enablement initiative of the Open Geospatial Consortium standardizes web service interfaces and data encodings which can be used as building blocks for a Sensor Web. This article illustrates and analyzes the recent developments of the new generation of the Sensor Web Enablement specification framework. Further, we relate the Sensor Web to other emerging concepts such as the Web of Things and point out challenges and resulting future work topics for research on Sensor Web Enablement. Full article
(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)
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Open AccessReview Theory, Instrumentation and Applications of Magnetoelastic Resonance Sensors: A Review
Sensors 2011, 11(3), 2809-2844; doi:10.3390/s110302809
Received: 10 January 2011 / Revised: 10 February 2011 / Accepted: 14 February 2011 / Published: 2 March 2011
Cited by 51 | PDF Full-text (5167 KB) | HTML Full-text | XML Full-text
Abstract
Thick-film magnetoelastic sensors vibrate mechanically in response to a time varying magnetic excitation field. The mechanical vibrations of the magnetostrictive magnetoelastic material launch, in turn, a magnetic field by which the sensor can be monitored. Magnetic field telemetry enables contact-less, remote-query operation [...] Read more.
Thick-film magnetoelastic sensors vibrate mechanically in response to a time varying magnetic excitation field. The mechanical vibrations of the magnetostrictive magnetoelastic material launch, in turn, a magnetic field by which the sensor can be monitored. Magnetic field telemetry enables contact-less, remote-query operation that has enabled many practical uses of the sensor platform. This paper builds upon a review paper we published in Sensors in 2002 (Grimes, C.A.; et al. Sensors 2002, 2, 294-313), presenting a comprehensive review on the theory, operating principles, instrumentation and key applications of magnetoelastic sensing technology. Full article
(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)
Open AccessReview Functional Polymers in Protein Detection Platforms: Optical, Electrochemical, Electrical, Mass-Sensitive, and Magnetic Biosensors
Sensors 2011, 11(3), 3327-3355; doi:10.3390/s110303327
Received: 26 January 2011 / Revised: 26 February 2011 / Accepted: 15 March 2011 / Published: 21 March 2011
Cited by 17 | PDF Full-text (1399 KB) | HTML Full-text | XML Full-text
Abstract
The rapidly growing field of proteomics and related applied sectors in the life sciences demands convenient methodologies for detecting and measuring the levels of specific proteins as well as for screening and analyzing for interacting protein systems. Materials utilized for such protein [...] Read more.
The rapidly growing field of proteomics and related applied sectors in the life sciences demands convenient methodologies for detecting and measuring the levels of specific proteins as well as for screening and analyzing for interacting protein systems. Materials utilized for such protein detection and measurement platforms should meet particular specifications which include ease-of-mass manufacture, biological stability, chemical functionality, cost effectiveness, and portability. Polymers can satisfy many of these requirements and are often considered as choice materials in various biological detection platforms. Therefore, tremendous research efforts have been made for developing new polymers both in macroscopic and nanoscopic length scales as well as applying existing polymeric materials for protein measurements. In this review article, both conventional and alternative techniques for protein detection are overviewed while focusing on the use of various polymeric materials in different protein sensing technologies. Among many available detection mechanisms, most common approaches such as optical, electrochemical, electrical, mass-sensitive, and magnetic methods are comprehensively discussed in this article. Desired properties of polymers exploited for each type of protein detection approach are summarized. Current challenges associated with the application of polymeric materials are examined in each protein detection category. Difficulties facing both quantitative and qualitative protein measurements are also identified. The latest efforts on the development and evaluation of nanoscale polymeric systems for improved protein detection are also discussed from the standpoint of quantitative and qualitative measurements. Finally, future research directions towards further advancements in the field are considered. Full article
(This article belongs to the Section Biosensors)

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Open AccessRetraction Retraction: Zeng, Y.; Xiong, N.; Park, J.H.; Zheng, G. An Emergency-Adaptive Routing Scheme for Wireless Sensor Networks for Building Fire Hazard Monitoring. Sensors 2010, 10, 6128-6148.
Sensors 2011, 11(3), 2898; doi:10.3390/s110302898
Received: 2 March 2011 / Published: 4 March 2011
PDF Full-text (115 KB) | HTML Full-text | XML Full-text
Abstract
It has been brought to our attention by a reader of Sensors that there existed arguments on both authorship and financial support for this article [1]. After confirming with all authors, we have determined that indeed this manuscript violates the generally accepted [...] Read more.
It has been brought to our attention by a reader of Sensors that there existed arguments on both authorship and financial support for this article [1]. After confirming with all authors, we have determined that indeed this manuscript violates the generally accepted policies and ethics of scientific publishing. Consequently, the Editorial Team and the Publisher have determined that the original paper should be retracted and republished with the authorship and financial support fully disclosed. The paper has been republished as [2]. We apologize for any inconvenience this may cause to our readers. Full article

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