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Sensors, Volume 10, Issue 9 (September 2010) , Pages 7896-8781

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Open AccessArticle Load-Adaptive Practical Multi-Channel Communications in Wireless Sensor Networks
Sensors 2010, 10(9), 8761-8781; https://doi.org/10.3390/s100908761
Received: 19 August 2010 / Revised: 14 September 2010 / Accepted: 15 September 2010 / Published: 21 September 2010
Cited by 2 | Viewed by 5827 | PDF Full-text (523 KB) | HTML Full-text | XML Full-text
Abstract
In recent years, a significant number of sensor node prototypes have been designed that provide communications in multiple channels. This multi-channel feature can be effectively exploited to increase the overall capacity and performance of wireless sensor networks (WSNs). In this paper, we present [...] Read more.
In recent years, a significant number of sensor node prototypes have been designed that provide communications in multiple channels. This multi-channel feature can be effectively exploited to increase the overall capacity and performance of wireless sensor networks (WSNs). In this paper, we present a multi-channel communications system for WSNs that is referred to as load-adaptive practical multi-channel communications (LPMC). LPMC estimates the active load of a channel at the sink since it has a more comprehensive view of the network behavior, and dynamically adds or removes channels based on the estimated load. LPMC updates the routing path to balance the loads of the channels. The nodes in a path use the same channel; therefore, they do not need to switch channels to receive or forward packets. LPMC has been evaluated through extensive simulations, and the results demonstrate that it can effectively increase the delivery ratio, network throughput, and channel utilization, and that it can decrease the end-to-end delay and energy consumption. Full article
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Open AccessArticle Characteristics of Metal Enhanced Evanescent-Wave Microcavities
Sensors 2010, 10(9), 8751-8760; https://doi.org/10.3390/s100908751
Received: 27 July 2010 / Revised: 9 September 2010 / Accepted: 10 September 2010 / Published: 21 September 2010
Cited by 4 | Viewed by 5003 | PDF Full-text (473 KB) | HTML Full-text | XML Full-text
Abstract
This article presents the concept of storing optical energy using a metallic air gap microcavity. Evanescent waves are stored in the air gap of a dielectric/metal/air gap/metal planar microcavity. For an air gap with a micron scale distance between the two metals, incident [...] Read more.
This article presents the concept of storing optical energy using a metallic air gap microcavity. Evanescent waves are stored in the air gap of a dielectric/metal/air gap/metal planar microcavity. For an air gap with a micron scale distance between the two metals, incident light excites the optical interface modes on the two metal-air interfaces simultaneously, being accompanied by enhanced evanescent fields. Numerical simulations show that the reflected light depends remarkably upon distributions of the enhanced electric fields in the air-gap at the optical mode excitations. The metallic microcavities have a Q value on the order of 102, as determined from calculations. Experimentally, a small mechanical variation of the air-gap distance exhibited a change of reflectivity. Full article
(This article belongs to the Special Issue Optical Resonant Microsensors)
Open AccessArticle Design and Analysis of MEMS Based PVDF Ultrasonic Transducers for Vascular Imaging
Sensors 2010, 10(9), 8740-8750; https://doi.org/10.3390/s100908740
Received: 29 July 2010 / Revised: 9 September 2010 / Accepted: 13 September 2010 / Published: 21 September 2010
Cited by 10 | Viewed by 5993 | PDF Full-text (214 KB) | HTML Full-text | XML Full-text
Abstract
Polyvinilidene fluoride (PVDF) single-element transducers for high-frequency (> 30 MHz) ultrasound imaging applications have been developed using MEMS (Micro-electro-Mechanical Systems) compatible techniques. Performance of these transducers has been investigated by analyzing the sources and effects of on-chip parasitic capacitances on the insertion-loss of [...] Read more.
Polyvinilidene fluoride (PVDF) single-element transducers for high-frequency (> 30 MHz) ultrasound imaging applications have been developed using MEMS (Micro-electro-Mechanical Systems) compatible techniques. Performance of these transducers has been investigated by analyzing the sources and effects of on-chip parasitic capacitances on the insertion-loss of the transducers. Modeling and experimental studies showed that on-chip parasitic capacitances degraded the performance of the transducers and an improved method of fabrication was suggested and new devices were built. New devices developed with minimal parasitic effects were shown to improve the performance significantly. A 1-mm aperture PVDF device developed with minimal parasitic effects has resulted in a reduction of insertion loss of 21 dB compared with devices fabricated using a previous method. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Signal Normalization Technique for Illumination-Based Synchronization of 1,000-fps Real-Time Vision Sensors in Dynamic Scenes
Sensors 2010, 10(9), 8719-8739; https://doi.org/10.3390/s100908719
Received: 9 August 2010 / Revised: 9 September 2010 / Accepted: 10 September 2010 / Published: 20 September 2010
Cited by 3 | Viewed by 5084 | PDF Full-text (10768 KB) | HTML Full-text | XML Full-text
Abstract
To acquire images of dynamic scenes from multiple points of view simultaneously, the acquisition time of vision sensors should be synchronized. In this paper, an illumination-based synchronization derived from the phase-locked loop (PLL) mechanism based on the signal normalization method is proposed and evaluated. To eliminate the [...] Read more.
To acquire images of dynamic scenes from multiple points of view simultaneously, the acquisition time of vision sensors should be synchronized. In this paper, an illumination-based synchronization derived from the phase-locked loop (PLL) mechanism based on the signal normalization method is proposed and evaluated. To eliminate the system dependency due to the amplitude fluctuation of the reference illumination, which may be caused by the moving objects or relative positional distance change between the light source and the observed objects, the fluctuant amplitude of the reference signal is normalized framely by the estimated maximum amplitude between the reference signal and its quadrature counterpart to generate a stable synchronization in highly dynamic scenes. Both simulated results and real world experimental results demonstrated successful synchronization result that 1,000-Hz frame rate vision sensors can be successfully synchronized to a LED illumination or its reflected light with satisfactory stability and only 28-μs jitters. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Assessment of Human Ambulatory Speed by Measuring Near-Body Air Flow
Sensors 2010, 10(9), 8705-8718; https://doi.org/10.3390/s100908705
Received: 1 July 2010 / Revised: 2 September 2010 / Accepted: 17 September 2010 / Published: 20 September 2010
Cited by 4 | Viewed by 6173 | PDF Full-text (378 KB) | HTML Full-text | XML Full-text
Abstract
Accurate measurements of physical activity are important for the diagnosis of the exacerbation of chronic diseases. Accelerometers have been widely employed in clinical research for measuring activity intensity and investigating the association between physical activity and adverse health conditions. However, the ability of [...] Read more.
Accurate measurements of physical activity are important for the diagnosis of the exacerbation of chronic diseases. Accelerometers have been widely employed in clinical research for measuring activity intensity and investigating the association between physical activity and adverse health conditions. However, the ability of accelerometers in assessing physical activity intensity such as walking speed has been constrained by the inter-individual variability in sensor output and by the necessity of developing unobtrusive low-power monitoring systems. This paper will present a study aimed at investigating the accuracy of a wearable measuring system of near-body air flow to determine ambulatory speed in the field. Full article
Open AccessArticle Inverse Problem in Nondestructive Testing Using Arrayed Eddy Current Sensors
Sensors 2010, 10(9), 8696-8704; https://doi.org/10.3390/s100908696
Received: 3 August 2010 / Revised: 30 August 2010 / Accepted: 15 September 2010 / Published: 20 September 2010
Cited by 12 | Viewed by 4899 | PDF Full-text (324 KB) | HTML Full-text | XML Full-text
Abstract
A fast crack profile reconstitution model in nondestructive testing is developed using an arrayed eddy current sensor. The inverse problem is based on an iterative solving of the direct problem using genetic algorithms. In the direct problem, assuming a current excitation, the incident [...] Read more.
A fast crack profile reconstitution model in nondestructive testing is developed using an arrayed eddy current sensor. The inverse problem is based on an iterative solving of the direct problem using genetic algorithms. In the direct problem, assuming a current excitation, the incident field produced by all the coils of the arrayed sensor is obtained by the translation and superposition of the 2D axisymmetric finite element results obtained for one coil; the impedance variation of each coil, due to the crack, is obtained by the reciprocity principle involving the dyadic Green’s function. For the inverse problem, the surface of the crack is subdivided into rectangular cells, and the objective function is expressed only in terms of the depth of each cell. The evaluation of the dyadic Green’s function matrix is made independently of the iterative procedure, making the inversion very fast. Full article
Open AccessArticle Broadcast Authentication for Wireless Sensor Networks Using Nested Hashing and the Chinese Remainder Theorem
Sensors 2010, 10(9), 8683-8695; https://doi.org/10.3390/s100908683
Received: 23 July 2010 / Revised: 23 August 2010 / Accepted: 6 September 2010 / Published: 17 September 2010
Cited by 13 | Viewed by 6081 | PDF Full-text (173 KB) | HTML Full-text | XML Full-text
Abstract
Secure broadcasting is an essential feature for critical operations in wireless sensor network (WSNs). However, due to the limited resources of sensor networks, verifying the authenticity for broadcasted messages is a very difficult issue. μTESLA is a broadcast authentication protocol, which uses network-wide [...] Read more.
Secure broadcasting is an essential feature for critical operations in wireless sensor network (WSNs). However, due to the limited resources of sensor networks, verifying the authenticity for broadcasted messages is a very difficult issue. μTESLA is a broadcast authentication protocol, which uses network-wide loose time synchronization with one-way hashed keys to provide the authenticity verification. However, it suffers from several flaws considering the delay tolerance, and the chain length restriction. In this paper, we propose a protocol which provides broadcast authentication for wireless sensor networks. This protocol uses a nested hash chain of two different hash functions and the Chinese Remainder Theorem (CRT). The two different nested hash functions are employed for the seed updating and the key generation. Each sensor node is challenged independently with a common broadcasting message using the CRT. Our algorithm provides forward and non-restricted key generation, and in addition, no time synchronization is required. Furthermore, receivers can instantly authenticate packets in real time. Moreover, the comprehensive analysis shows that this scheme is efficient and practical, and can achieve better performance than the μTESLA system. Full article
Open AccessArticle Automated Construction of Node Software Using Attributes in a Ubiquitous Sensor Network Environment
Sensors 2010, 10(9), 8663-8682; https://doi.org/10.3390/s100908663
Received: 30 July 2010 / Revised: 6 September 2010 / Accepted: 10 September 2010 / Published: 17 September 2010
Cited by 9 | Viewed by 7470 | PDF Full-text (437 KB) | HTML Full-text | XML Full-text
Abstract
In sensor networks, nodes must often operate in a demanding environment facing restrictions such as restricted computing resources, unreliable wireless communication and power shortages. Such factors make the development of ubiquitous sensor network (USN) applications challenging. To help developers construct a large amount [...] Read more.
In sensor networks, nodes must often operate in a demanding environment facing restrictions such as restricted computing resources, unreliable wireless communication and power shortages. Such factors make the development of ubiquitous sensor network (USN) applications challenging. To help developers construct a large amount of node software for sensor network applications easily and rapidly, this paper proposes an approach to the automated construction of node software for USN applications using attributes. In the proposed technique, application construction proceeds by first developing a model for the sensor network and then designing node software by setting the values of the predefined attributes. After that, the sensor network model and the design of node software are verified. The final source codes of the node software are automatically generated from the sensor network model. We illustrate the efficiency of the proposed technique by using a gas/light monitoring application through a case study of a Gas and Light Monitoring System based on the Nano-Qplus operating system. We evaluate the technique using a quantitative metric—the memory size of execution code for node software. Using the proposed approach, developers are able to easily construct sensor network applications and rapidly generate a large number of node softwares at a time in a ubiquitous sensor network environment. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Predicting the Detectability of Thin Gaseous Plumes in Hyperspectral Images Using Basis Vectors
Sensors 2010, 10(9), 8652-8662; https://doi.org/10.3390/s100908652
Received: 17 July 2010 / Revised: 13 August 2010 / Accepted: 19 August 2010 / Published: 17 September 2010
Cited by 1 | Viewed by 5181 | PDF Full-text (558 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes a new method for predicting the detectability of thin gaseous plumes in hyperspectral images. The novelty of this method is the use of basis vectors for each of the spectral channels of a collection instrument to calculate noise-equivalent concentration-pathlengths instead [...] Read more.
This paper describes a new method for predicting the detectability of thin gaseous plumes in hyperspectral images. The novelty of this method is the use of basis vectors for each of the spectral channels of a collection instrument to calculate noise-equivalent concentration-pathlengths instead of matching scene pixels to absorbance spectra of gases in a library. This method provides insight into regions of the spectrum where gas detection will be relatively easier or harder, as influenced by ground emissivity, temperature contrast, and the atmosphere. Our results show that data collection planning could be influenced by information about when potential plumes are likely to be over background segments that are most conducive to detection. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Raman Microspectroscopy of Individual Algal Cells: Sensing Unsaturation of Storage Lipids in vivo
Sensors 2010, 10(9), 8635-8651; https://doi.org/10.3390/s100908635
Received: 30 July 2010 / Revised: 25 August 2010 / Accepted: 14 September 2010 / Published: 17 September 2010
Cited by 94 | Viewed by 8556 | PDF Full-text (1384 KB) | HTML Full-text | XML Full-text
Abstract
Algae are becoming a strategic source of fuels, food, feedstocks, and biologically active compounds. This potential has stimulated the development of innovative analytical methods focused on these microorganisms. Algal lipids are among the most promising potential products for fuels as well as for [...] Read more.
Algae are becoming a strategic source of fuels, food, feedstocks, and biologically active compounds. This potential has stimulated the development of innovative analytical methods focused on these microorganisms. Algal lipids are among the most promising potential products for fuels as well as for nutrition. The crucial parameter characterizing the algal lipids is the degree of unsaturation of the constituent fatty acids quantified by the iodine value. Here we demonstrate the capacity of the spatially resolved Raman microspectroscopy to determine the effective iodine value in lipid storage bodies of individual living algal cells. The Raman spectra were collected from three selected algal species immobilized in an agarose gel. Prior to immobilization, the algae were cultivated in the stationary phase inducing an overproduction of lipids. We employed the characteristic peaks in the Raman scattering spectra at 1,656 cm−1 (cis C=C stretching mode) and 1,445 cm−1 (CH2 scissoring mode) as the markers defining the ratio of unsaturated-to-saturated carbon-carbon bonds of the fatty acids in the algal lipids. These spectral features were first quantified for pure fatty acids of known iodine value. The resultant calibration curve was then used to calculate the effective iodine value of storage lipids in the living algal cells from their Raman spectra. We demonstrated that the iodine value differs significantly for the three studied algal species. Our spectroscopic estimations of the iodine value were validated using GC-MS measurements and an excellent agreement was found for the Trachydiscus minutus species. A good agreement was also found with the earlier published data on Botryococcus braunii. Thus, we propose that Raman microspectroscopy can become technique of choice in the rapidly expanding field of algal biotechnology. Full article
(This article belongs to the Section Biosensors)
Open AccessReview ZnO-Based Ultraviolet Photodetectors
Sensors 2010, 10(9), 8604-8634; https://doi.org/10.3390/s100908604
Received: 30 July 2010 / Revised: 25 August 2010 / Accepted: 10 September 2010 / Published: 17 September 2010
Cited by 294 | Viewed by 13954 | PDF Full-text (5743 KB) | HTML Full-text | XML Full-text
Abstract
Ultraviolet (UV) photodetection has drawn a great deal of attention in recent years due to a wide range of civil and military applications. Because of its wide band gap, low cost, strong radiation hardness and high chemical stability, ZnO are regarded as one [...] Read more.
Ultraviolet (UV) photodetection has drawn a great deal of attention in recent years due to a wide range of civil and military applications. Because of its wide band gap, low cost, strong radiation hardness and high chemical stability, ZnO are regarded as one of the most promising candidates for UV photodetectors. Additionally, doping in ZnO with Mg elements can adjust the bandgap largely and make it feasible to prepare UV photodetectors with different cut-off wavelengths. ZnO-based photoconductors, Schottky photodiodes, metal–semiconductor–metal photodiodes and p–n junction photodetectors have been developed. In this work, it mainly focuses on the ZnO and ZnMgO films photodetectors. We analyze the performance of ZnO-based photodetectors, discussing recent achievements, and comparing the characteristics of the various photodetector structures developed to date. Full article
(This article belongs to the Special Issue Photodetectors and Imaging Technologies)
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Open AccessArticle Java Simulations of Embedded Control Systems
Sensors 2010, 10(9), 8585-8603; https://doi.org/10.3390/s100908585
Received: 1 July 2010 / Revised: 26 August 2010 / Accepted: 26 August 2010 / Published: 15 September 2010
Cited by 3 | Viewed by 8530 | PDF Full-text (318 KB) | HTML Full-text | XML Full-text
Abstract
This paper introduces a new Open Source Java library suited for the simulation of embedded control systems. The library is based on the ideas and architecture of TrueTime, a toolbox of Matlab devoted to this topic, and allows Java programmers to simulate the [...] Read more.
This paper introduces a new Open Source Java library suited for the simulation of embedded control systems. The library is based on the ideas and architecture of TrueTime, a toolbox of Matlab devoted to this topic, and allows Java programmers to simulate the performance of control processes which run in a real time environment. Such simulations can improve considerably the learning and design of multitasking real-time systems. Thechoice of Java increases considerably the usability of our library, because many educators program already in this language. But also because the library can be easily used by Easy Java Simulations (EJS), a popular modeling and authoring tool that is increasingly used in the field of Control Education. EJS allows instructors, students, and researchers with less programming capabilities to create advanced interactive simulations in Java. The paper describes the ideas, implementation, and sample use of the new library both for pure Java programmers and for EJS users. The JTT library and some examples are online available on http://lab.dia.uned.es/jtt. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Identification of Granite Varieties from Colour Spectrum Data
Sensors 2010, 10(9), 8572-8584; https://doi.org/10.3390/s100908572
Received: 30 July 2010 / Revised: 27 August 2010 / Accepted: 8 September 2010 / Published: 14 September 2010
Cited by 8 | Viewed by 7109 | PDF Full-text (345 KB) | HTML Full-text | XML Full-text
Abstract
The granite processing sector of the northwest of Spain handles many varieties of granite with specific technical and aesthetic properties that command different prices in the natural stone market. Hence, correct granite identification and classification from the outset of processing to the end-product [...] Read more.
The granite processing sector of the northwest of Spain handles many varieties of granite with specific technical and aesthetic properties that command different prices in the natural stone market. Hence, correct granite identification and classification from the outset of processing to the end-product stage optimizes the management and control of stocks of granite slabs and tiles and facilitates the operation of traceability systems. We describe a methodology for automatically identifying granite varieties by processing spectral information captured by a spectrophotometer at various stages of processing using functional machine learning techniques. Full article
(This article belongs to the Special Issue Photodetectors and Imaging Technologies)
Open AccessArticle A Rigid Image Registration Based on the Nonsubsampled Contourlet Transform and Genetic Algorithms
Sensors 2010, 10(9), 8553-8571; https://doi.org/10.3390/s100908553
Received: 15 June 2010 / Revised: 5 September 2010 / Accepted: 8 September 2010 / Published: 14 September 2010
Cited by 11 | Viewed by 5446 | PDF Full-text (739 KB) | HTML Full-text | XML Full-text
Abstract
Image registration is a fundamental task used in image processing to match two or more images taken at different times, from different sensors or from different viewpoints. The objective is to find in a huge search space of geometric transformations, an acceptable [...] Read more.
Image registration is a fundamental task used in image processing to match two or more images taken at different times, from different sensors or from different viewpoints. The objective is to find in a huge search space of geometric transformations, an acceptable accurate solution in a reasonable time to provide better registered images. Exhaustive search is computationally expensive and the computational cost increases exponentially with the number of transformation parameters and the size of the data set. In this work, we present an efficient image registration algorithm that uses genetic algorithms within a multi-resolution framework based on the Non-Subsampled Contourlet Transform (NSCT). An adaptable genetic algorithm for registration is adopted in order to minimize the search space. This approach is used within a hybrid scheme applying the two techniques fitness sharing and elitism. Two NSCT based methods are proposed for registration. A comparative study is established between these methods and a wavelet based one. Because the NSCT is a shift-invariant multidirectional transform, the second method is adopted for its search speeding up property. Simulation results clearly show that both proposed techniques are really promising methods for image registration compared to the wavelet approach, while the second technique has led to the best performance results of all. Moreover, to demonstrate the effectiveness of these methods, these registration techniques have been successfully applied to register SPOT, IKONOS and Synthetic Aperture Radar (SAR) images. The algorithm has been shown to work perfectly well for multi-temporal satellite images as well, even in the presence of noise. Full article
(This article belongs to the Special Issue Image Sensors 2009)
Open AccessArticle Recovery of Agricultural Odors and Odorous Compounds from Polyvinyl Fluoride Film Bags
Sensors 2010, 10(9), 8536-8552; https://doi.org/10.3390/s100908536
Received: 7 July 2010 / Revised: 2 August 2010 / Accepted: 20 August 2010 / Published: 13 September 2010
Cited by 43 | Viewed by 7874 | PDF Full-text (320 KB) | HTML Full-text | XML Full-text
Abstract
Accurate sampling methods are necessary when quantifying odor and volatile organic compound emissions at agricultural facilities. The commonly accepted methodology in the U.S. has been to collect odor samples in polyvinyl fluoride bags (PVF, brand name Tedlar®) and, subsequently, analyze with human panelists [...] Read more.
Accurate sampling methods are necessary when quantifying odor and volatile organic compound emissions at agricultural facilities. The commonly accepted methodology in the U.S. has been to collect odor samples in polyvinyl fluoride bags (PVF, brand name Tedlar®) and, subsequently, analyze with human panelists using dynamic triangular forced-choice olfactometry. The purpose of this research was to simultaneously quantify and compare recoveries of odor and odorous compounds from both commercial and homemade PVF sampling bags. A standard gas mixture consisting of p-cresol (40 µg m−3) and seven volatile fatty acids: acetic (2,311 µg m−3), propionic (15,800 µg m−3), isobutyric (1,686 µg m−3), butyric (1,049 µg m−3), isovaleric (1,236 µg m−3), valeric (643 µg m−3), and hexanoic (2,158 µg m−3) was placed in the PVF bags at times of 1 h, 1 d, 2 d, 3 d, and 7 d prior to compound and odor concentration analyses. Compound concentrations were quantified using sorbent tubes and gas chromatography/mass spectrometry. Odor concentration, intensity, and hedonic tone were measured using a panel of trained human subjects. Compound recoveries ranged from 2 to 40% after 1 h and 0 to 14% after 7 d. Between 1 h and 7 d, odor concentrations increased by 45% in commercial bags, and decreased by 39% in homemade bags. Minimal changes were observed in intensity and hedonic tone over the same time period. These results suggest that PVF bags can bias individual compound concentrations and odor as measured by dynamic triangular forced-choice olfactometry. Full article
(This article belongs to the Special Issue Direct and Indirect Sensing of Odor and VOCs and Their Control)
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Open AccessArticle FLP/FRT Recombination from Yeast: Application of a Two Gene Cassette Scheme as an Inducible System in Plants
Sensors 2010, 10(9), 8526-8535; https://doi.org/10.3390/s100908526
Received: 17 July 2010 / Revised: 23 August 2010 / Accepted: 6 September 2010 / Published: 13 September 2010
Cited by 11 | Viewed by 10834 | PDF Full-text (303 KB) | HTML Full-text | XML Full-text
Abstract
Phytosensors are plants that are genetically engineered for sensing and reporting the presence of a specific contaminant, including agriculturally important biological agents. Phytosensors are constructed by transforming plants to contain specific biotic- or abiotic-inducible promoters fused to a reporter gene. When such transgenic [...] Read more.
Phytosensors are plants that are genetically engineered for sensing and reporting the presence of a specific contaminant, including agriculturally important biological agents. Phytosensors are constructed by transforming plants to contain specific biotic- or abiotic-inducible promoters fused to a reporter gene. When such transgenic plants encounter the target biotic or abiotic agent, the specific inducible promoter is triggered and subsequently drives the expression of the reporter gene, which produces a signal for detection. However, several systems lack robustness, rapid induction and promoter strength. Here, we tested the FLP/FRT recombination system in a construct containing a two gene cassette organization and examined its potential in transgenic Arabidopsis and tobacco plants using a b-glucuronidase (GUS) reporter. In this model system, a heat-shock inducible promoter was employed to control the expression of the FLP recombinase gene. Upon heat induction and subsequent active FLP-mediated excision event, the GUS gene was placed in close proximity to the 35S promoter resulting in an active GUS reporter expression. Our results demonstrate that the two gene cassette scheme of inducible FLP/FRT recombination system is functional in tobacco and Arabidopsis, providing additional insights into its possible application in phytosensing such as creating strong readout capabilities. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Sensor Networks in the Low Lands
Sensors 2010, 10(9), 8504-8525; https://doi.org/10.3390/s100908504
Received: 21 July 2010 / Revised: 15 August 2010 / Accepted: 30 August 2010 / Published: 10 September 2010
Cited by 7 | Viewed by 8011 | PDF Full-text (3217 KB) | HTML Full-text | XML Full-text
Abstract
This paper provides an overview of scientific and industrial developments of the last decade in the area of sensor networks in The Netherlands (Low Lands). The goal is to highlight areas in which the Netherlands has made most contributions and is currently a [...] Read more.
This paper provides an overview of scientific and industrial developments of the last decade in the area of sensor networks in The Netherlands (Low Lands). The goal is to highlight areas in which the Netherlands has made most contributions and is currently a dominant player in the field of sensor networks. On the one hand, motivations, addressed topics, and initiatives taken in this period are presented, while on the other hand, special emphasis is given to identifying current and future trends and formulating a vision for the coming five to ten years. The presented overview and trend analysis clearly show that Dutch research and industrial efforts, in line with recent worldwide developments in the field of sensor technology, present a clear shift from sensor node platforms, operating systems, communication, networking, and data management aspects of the sensor networks to reasoning/cognition, control, and actuation. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in The Netherlands)
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Open AccessArticle Accurate Permittivity Measurements for Microwave Imaging via Ultra-Wideband Removal of Spurious Reflectors
Sensors 2010, 10(9), 8491-8503; https://doi.org/10.3390/s100908491
Received: 5 August 2010 / Revised: 31 August 2010 / Accepted: 1 September 2010 / Published: 10 September 2010
Cited by 3 | Viewed by 5859 | PDF Full-text (876 KB) | HTML Full-text | XML Full-text
Abstract
The use of microwave imaging is becoming more prevalent for detection of interior hidden defects in manufactured and packaged materials. In applications for detection of hidden moisture, microwave tomography can be used to image the material and then perform an inverse calculation to [...] Read more.
The use of microwave imaging is becoming more prevalent for detection of interior hidden defects in manufactured and packaged materials. In applications for detection of hidden moisture, microwave tomography can be used to image the material and then perform an inverse calculation to derive an estimate of the variability of the hidden material, such internal moisture, thereby alerting personnel to damaging levels of the hidden moisture before material degradation occurs. One impediment to this type of imaging occurs with nearby objects create strong reflections that create destructive and constructive interference, at the receiver, as the material is conveyed past the imaging antenna array. In an effort to remove the influence of the reflectors, such as metal bale ties, research was conducted to develop an algorithm for removal of the influence of the local proximity reflectors from the microwave images. This research effort produced a technique, based upon the use of ultra-wideband signals, for the removal of spurious reflections created by local proximity reflectors. This improvement enables accurate microwave measurements of moisture in such products as cotton bales, as well as other physical properties such as density or material composition. The proposed algorithm was shown to reduce errors by a 4:1 ratio and is an enabling technology for imaging applications in the presence of metal bale ties. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Adaptive Control of a Vibratory Angle Measuring Gyroscope
Sensors 2010, 10(9), 8478-8490; https://doi.org/10.3390/s100908478
Received: 11 August 2010 / Revised: 20 August 2010 / Accepted: 3 September 2010 / Published: 9 September 2010
Cited by 15 | Viewed by 4140 | PDF Full-text (1088 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an adaptive control algorithm for realizing a vibratory angle measuring gyroscope so that rotation angle can be directly measured without integration of angular rate, thus eliminating the accumulation of numerical integration errors. The proposed control algorithm uses a trajectory following [...] Read more.
This paper presents an adaptive control algorithm for realizing a vibratory angle measuring gyroscope so that rotation angle can be directly measured without integration of angular rate, thus eliminating the accumulation of numerical integration errors. The proposed control algorithm uses a trajectory following approach and the reference trajectory is generated by an ideal angle measuring gyroscope driven by the estimate of angular rate and the auxiliary sinusoidal input so that the persistent excitation condition is satisfied. The developed control algorithm can compensate for all types of fabrication imperfections such as coupled damping and stiffness, and mismatched stiffness and un-equal damping term in an on-line fashion. The simulation results show the feasibility and effectiveness of the developed control algorithm that is capable of directly measuring rotation angle without the integration of angular rate. Full article
(This article belongs to the Special Issue Adaptive Sensing)
Open AccessArticle Detection of Molecular Oxygen at Low Concentrations Using Quartz Enhanced Photoacoustic Spectroscopy
Sensors 2010, 10(9), 8466-8477; https://doi.org/10.3390/s100908466
Received: 10 August 2010 / Revised: 30 August 2010 / Accepted: 8 September 2010 / Published: 9 September 2010
Cited by 17 | Viewed by 5669 | PDF Full-text (474 KB) | HTML Full-text | XML Full-text
Abstract
Molecular oxygen is detected at low concentrations using photoacoustic spectroscopy despite its unfavorable photoacoustic properties. The system consists of a seed laser diode, a tapered amplifier and a quartz tuning fork based spectrophone, thus employing quartz enhanced photoacoustic spectroscopy (QEPAS). With this system [...] Read more.
Molecular oxygen is detected at low concentrations using photoacoustic spectroscopy despite its unfavorable photoacoustic properties. The system consists of a seed laser diode, a tapered amplifier and a quartz tuning fork based spectrophone, thus employing quartz enhanced photoacoustic spectroscopy (QEPAS). With this system a detection limit of 13 ppm is reached with a compact and long term stable setup. Further improvement of the detection limit is possible by adding suitable gases to the sample gas that promote the radiationless de-excitation of the oxygen molecules. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A High-Sensitivity Hydraulic Load Cell for Small Kitchen Appliances
Sensors 2010, 10(9), 8452-8465; https://doi.org/10.3390/s100908452
Received: 13 July 2010 / Revised: 18 August 2010 / Accepted: 6 September 2010 / Published: 9 September 2010
Cited by 2 | Viewed by 5589 | PDF Full-text (949 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we present a hydraulic load cell made from hydroformed metallic bellows. The load cell was designed for a small kitchen appliance with the weighing function integrated into the composite control and protection of the appliance. It is a simple, low-cost [...] Read more.
In this paper we present a hydraulic load cell made from hydroformed metallic bellows. The load cell was designed for a small kitchen appliance with the weighing function integrated into the composite control and protection of the appliance. It is a simple, low-cost solution with small dimensions and represents an alternative to the existing hydraulic load cells in industrial use. A good non-linearity and a small hysteresis were achieved. The influence of temperature leads to an error of 7.5%, which can be compensated for by software to meet the requirements of the target application. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessReview Automated Three-Dimensional Microbial Sensing and Recognition Using Digital Holography and Statistical Sampling
Sensors 2010, 10(9), 8437-8451; https://doi.org/10.3390/s100908437
Received: 18 June 2010 / Revised: 30 August 2010 / Accepted: 3 September 2010 / Published: 9 September 2010
Cited by 10 | Viewed by 7159 | PDF Full-text (852 KB) | HTML Full-text | XML Full-text
Abstract
We overview an approach to providing automated three-dimensional (3D) sensing and recognition of biological micro/nanoorganisms integrating Gabor digital holographic microscopy and statistical sampling methods. For 3D data acquisition of biological specimens, a coherent beam propagates through the specimen and its transversely and longitudinally [...] Read more.
We overview an approach to providing automated three-dimensional (3D) sensing and recognition of biological micro/nanoorganisms integrating Gabor digital holographic microscopy and statistical sampling methods. For 3D data acquisition of biological specimens, a coherent beam propagates through the specimen and its transversely and longitudinally magnified diffraction pattern observed by the microscope objective is optically recorded with an image sensor array interfaced with a computer. 3D visualization of the biological specimen from the magnified diffraction pattern is accomplished by using the computational Fresnel propagation algorithm. For 3D recognition of the biological specimen, a watershed image segmentation algorithm is applied to automatically remove the unnecessary background parts in the reconstructed holographic image. Statistical estimation and inference algorithms are developed to the automatically segmented holographic image. Overviews of preliminary experimental results illustrate how the holographic image reconstructed from the Gabor digital hologram of biological specimen contains important information for microbial recognition. Full article
(This article belongs to the Special Issue Sensors in Biomechanics and Biomedicine)
Open AccessArticle Combined Simulation of a Micro Permanent Magnetic Linear Contactless Displacement Sensor
Sensors 2010, 10(9), 8424-8436; https://doi.org/10.3390/s100908424
Received: 11 June 2010 / Revised: 17 August 2010 / Accepted: 6 September 2010 / Published: 9 September 2010
Cited by 3 | Viewed by 8718 | PDF Full-text (459 KB) | HTML Full-text | XML Full-text
Abstract
The permanent magnetic linear contactless displacement (PLCD) sensor is a new type of displacement sensor operating on the magnetic inductive principle. It has many excellent properties and has already been used for many applications. In this article a Micro-PLCD sensor which can be [...] Read more.
The permanent magnetic linear contactless displacement (PLCD) sensor is a new type of displacement sensor operating on the magnetic inductive principle. It has many excellent properties and has already been used for many applications. In this article a Micro-PLCD sensor which can be used for microelectromechanical system (MEMS) measurements is designed and simulated with the CST EM STUDIO® software, including building a virtual model, magnetostatic calculations, low frequency calculations, steady current calculations and thermal calculations. The influence of some important parameters such as air gap dimension, working frequency, coil current and eddy currents etc. is studied in depth. Full article
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Open AccessReview Novel Ultra-Sensitive Detectors in the 10–50 μm Wavelength Range
Sensors 2010, 10(9), 8411-8423; https://doi.org/10.3390/s100908411
Received: 29 July 2010 / Revised: 13 August 2010 / Accepted: 31 August 2010 / Published: 8 September 2010
Cited by 15 | Viewed by 8412 | PDF Full-text (698 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We have developed novel single-photon detectors in the 10–50 μm wavelength region. The detectors are charge-sensitive infrared phototransistors (CSIPs) fabricated in GaAs/AlGaAs double quantum well (QW) structures, in which a photo-generated hole (+e) in the floating gate (upper QW) modulates the conductance of [...] Read more.
We have developed novel single-photon detectors in the 10–50 μm wavelength region. The detectors are charge-sensitive infrared phototransistors (CSIPs) fabricated in GaAs/AlGaAs double quantum well (QW) structures, in which a photo-generated hole (+e) in the floating gate (upper QW) modulates the conductance of a capacitively-coupled channel located underneath (lower QW). The excellent noise equivalent power (NEP = 8.3 × 10−19 W/Hz1/2) and specific detectivity (D* = 8 × 1014 cm Hz1/2/W) are demonstrated for 15 micron detection up to 23 K, which are by a few orders of magnitude better than those of other state-of-the-art high-sensitivity detectors. The dynamic range exceeds 106 (~aW to pW) by repeatedly resetting the accumulated holes in the upper QW. Simple device structure makes the detectors feasible for array fabrication: Furthermore, monolithic integration with reading circuits will be possible. Full article
(This article belongs to the Special Issue Photodetectors and Imaging Technologies)
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Open AccessArticle A Novel Electrochemical Sensor for Probing Doxepin Created on a Glassy Carbon Electrode Modified with Poly(4-Amino- benzoic Acid)/Multi-Walled Carbon Nanotubes Composite Film
Sensors 2010, 10(9), 8398-8410; https://doi.org/10.3390/s100908398
Received: 7 July 2010 / Revised: 31 July 2010 / Accepted: 7 September 2010 / Published: 8 September 2010
Cited by 8 | Viewed by 5908 | PDF Full-text (622 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A novel electrochemical sensor for sensitive detection of doxepin was prepared, which was based on a glassy carbon electrode modified with poly(4-aminobenzoic acid)/multi-walled carbon nanotubes composite film [poly(4-ABA)/MWNTs/GCE]. The sensor was characterized by scanning electron microscopy and electrochemical methods. It was observed that [...] Read more.
A novel electrochemical sensor for sensitive detection of doxepin was prepared, which was based on a glassy carbon electrode modified with poly(4-aminobenzoic acid)/multi-walled carbon nanotubes composite film [poly(4-ABA)/MWNTs/GCE]. The sensor was characterized by scanning electron microscopy and electrochemical methods. It was observed that poly(4-ABA)/MWNTs/GCE showed excellent preconcentration function and electrocatalytic activities towards doxepin. Under the selected conditions, the anodic peak current was linear to the logarithm of doxepin concentration in the range from 1.0 ´ 10−9 to 1.0 ´ 10−6 M, and the detection limit obtained was 1.0 × 10−10 M. The poly(4-ABA)/MWNTs/GCE was successfully applied in the measurement of doxepin in commercial pharmaceutical formulations, and the analytical accuracy was confirmed by comparison with a conventional ultraviolet spectrophotometry assay. Full article
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Open AccessArticle Data Collection Framework for Energy Efficient Privacy Preservation in Wireless Sensor Networks Having Many-to-Many Structures
Sensors 2010, 10(9), 8375-8397; https://doi.org/10.3390/s100908375
Received: 21 July 2010 / Revised: 3 August 2010 / Accepted: 3 August 2010 / Published: 8 September 2010
Cited by 3 | Viewed by 8030 | PDF Full-text (367 KB) | HTML Full-text | XML Full-text
Abstract
Wireless sensor networks (WSNs) generally have a many-to-one structure so that event information flows from sensors to a unique sink. In recent WSN applications, many-to-many structures evolved due to the need for conveying collected event information to multiple sinks. Privacy preserved data collection [...] Read more.
Wireless sensor networks (WSNs) generally have a many-to-one structure so that event information flows from sensors to a unique sink. In recent WSN applications, many-to-many structures evolved due to the need for conveying collected event information to multiple sinks. Privacy preserved data collection models in the literature do not solve the problems of WSN applications in which network has multiple un-trusted sinks with different level of privacy requirements. This study proposes a data collection framework bases on k-anonymity for preventing record disclosure of collected event information in WSNs. Proposed method takes the anonymity requirements of multiple sinks into consideration by providing different levels of privacy for each destination sink. Attributes, which may identify an event owner, are generalized or encrypted in order to meet the different anonymity requirements of sinks at the same anonymized output. If the same output is formed, it can be multicasted to all sinks. The other trivial solution is to produce different anonymized outputs for each sink and send them to related sinks. Multicasting is an energy efficient data sending alternative for some sensor nodes. Since minimization of energy consumption is an important design criteria for WSNs, multicasting the same event information to multiple sinks reduces the energy consumption of overall network. Full article
Open AccessArticle Color Regeneration from Reflective Color Sensor Using an Artificial Intelligent Technique
Sensors 2010, 10(9), 8363-8374; https://doi.org/10.3390/s100908363
Received: 20 July 2010 / Revised: 10 August 2010 / Accepted: 20 August 2010 / Published: 3 September 2010
Cited by 16 | Viewed by 5253 | PDF Full-text (508 KB) | HTML Full-text | XML Full-text
Abstract
A low-cost optical sensor based on reflective color sensing is presented. Artificial neural network models are used to improve the color regeneration from the sensor signals. Analog voltages of the sensor are successfully converted to RGB colors. The artificial intelligent models presented in [...] Read more.
A low-cost optical sensor based on reflective color sensing is presented. Artificial neural network models are used to improve the color regeneration from the sensor signals. Analog voltages of the sensor are successfully converted to RGB colors. The artificial intelligent models presented in this work enable color regeneration from analog outputs of the color sensor. Besides, inverse modeling supported by an intelligent technique enables the sensor probe for use of a colorimetric sensor that relates color changes to analog voltages. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
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Open AccessArticle Minimum Expected Delay-Based Routing Protocol (MEDR) for Delay Tolerant Mobile Sensor Networks
Sensors 2010, 10(9), 8348-8362; https://doi.org/10.3390/s100908348
Received: 20 July 2010 / Revised: 10 August 2010 / Accepted: 20 August 2010 / Published: 3 September 2010
Cited by 11 | Viewed by 6540 | PDF Full-text (543 KB) | HTML Full-text | XML Full-text
Abstract
It is a challenging work to develop efficient routing protocols for Delay Tolerant Mobile Sensor Networks (DTMSNs), which have several unique characteristics such as sensor mobility, intermittent connectivity, energy limit, and delay tolerability. In this paper, we propose a new routing protocol called [...] Read more.
It is a challenging work to develop efficient routing protocols for Delay Tolerant Mobile Sensor Networks (DTMSNs), which have several unique characteristics such as sensor mobility, intermittent connectivity, energy limit, and delay tolerability. In this paper, we propose a new routing protocol called Minimum Expected Delay-based Routing (MEDR) tailored for DTMSNs. MEDR achieves a good routing performance by finding and using the connected paths formed dynamically by mobile sensors. In MEDR, each sensor maintains two important parameters: Minimum Expected Delay (MED) and its expiration time. According to MED, messages will be delivered to the sensor that has at least a connected path with their hosting nodes, and has the shortest expected delay to communication directly with the sink node. Because of the changing network topology, the path is fragile and volatile, so we use the expiration time of MED to indicate the valid time of the path, and avoid wrong transmissions. Simulation results show that the proposed MEDR achieves a higher message delivery ratio with lower transmission overhead and data delivery delay than other DTMSN routing approaches. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Sturdy Positioning with High Sensitivity GPS Sensors Under Adverse Conditions
Sensors 2010, 10(9), 8332-8347; https://doi.org/10.3390/s100908332
Received: 8 July 2010 / Revised: 20 August 2010 / Accepted: 20 August 2010 / Published: 3 September 2010
Cited by 15 | Viewed by 6914 | PDF Full-text (556 KB) | HTML Full-text | XML Full-text
Abstract
High sensitivity GPS receivers have extended the use of GNSS navigation to environments which were previously deemed unsuitable for satellite signal reception. Under adverse conditions the signals become attenuated and reflected. High sensitivity receivers achieve signal reception by using a large number of [...] Read more.
High sensitivity GPS receivers have extended the use of GNSS navigation to environments which were previously deemed unsuitable for satellite signal reception. Under adverse conditions the signals become attenuated and reflected. High sensitivity receivers achieve signal reception by using a large number of correlators and an extended integration time. Processing the observation data in dynamic and rapidly changing conditions requires a careful and consistent treatment. Code-based autonomous solutions can cause major errors in the estimated position, due primarily to multipath effects. A custom procedure of autonomous GPS positioning has been developed, boosting the positioning performance through appropriate processing of code and Doppler observations. Besides the common positioning procedures, robust estimation methods have been used to minimise the effects of gross observation errors. In normal conditions, differential GNSS yields good results, however, under adverse conditions, it fails to improve significantly the receiver’s position. Therefore, a so-called conditional DGPS has been developed which determines the position differentially by using data from the strong signals only. These custom-developed procedures have been tested in different conditions in static and kinematic cases and the results have been compared to those processed by the receiver. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle FPGA-based Fused Smart Sensor for Real-Time Plant-Transpiration Dynamic Estimation
Sensors 2010, 10(9), 8316-8331; https://doi.org/10.3390/s100908316
Received: 21 July 2010 / Revised: 6 August 2010 / Accepted: 20 August 2010 / Published: 2 September 2010
Cited by 11 | Viewed by 10844 | PDF Full-text (593 KB) | HTML Full-text | XML Full-text
Abstract
Plant transpiration is considered one of the most important physiological functions because it constitutes the plants evolving adaptation to exchange moisture with a dry atmosphere which can dehydrate or eventually kill the plant. Due to the importance of transpiration, accurate measurement methods are [...] Read more.
Plant transpiration is considered one of the most important physiological functions because it constitutes the plants evolving adaptation to exchange moisture with a dry atmosphere which can dehydrate or eventually kill the plant. Due to the importance of transpiration, accurate measurement methods are required; therefore, a smart sensor that fuses five primary sensors is proposed which can measure air temperature, leaf temperature, air relative humidity, plant out relative humidity and ambient light. A field programmable gate array based unit is used to perform signal processing algorithms as average decimation and infinite impulse response filters to the primary sensor readings in order to reduce the signal noise and improve its quality. Once the primary sensor readings are filtered, transpiration dynamics such as: transpiration, stomatal conductance, leaf-air-temperature-difference and vapor pressure deficit are calculated in real time by the smart sensor. This permits the user to observe different primary and calculated measurements at the same time and the relationship between these which is very useful in precision agriculture in the detection of abnormal conditions. Finally, transpiration related stress conditions can be detected in real time because of the use of online processing and embedded communications capabilities. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
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