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Sensors, Volume 9, Issue 2 (February 2009), Pages 696-1294

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Open AccessArticle Energy Efficient Sensor Scheduling with a Mobile Sink Node for the Target Tracking Application
Sensors 2009, 9(2), 696-716; doi:10.3390/s90100696
Received: 14 November 2008 / Revised: 16 January 2009 / Accepted: 16 January 2009 / Published: 23 January 2009
Cited by 7 | PDF Full-text (341 KB) | HTML Full-text | XML Full-text
Abstract
Measurement losses adversely affect the performance of target tracking. The sensor network’s life span depends on how efficiently the sensor nodes consume energy. In this paper, we focus on minimizing the total energy consumed by the sensor nodes whilst avoiding measurement losses. Since
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Measurement losses adversely affect the performance of target tracking. The sensor network’s life span depends on how efficiently the sensor nodes consume energy. In this paper, we focus on minimizing the total energy consumed by the sensor nodes whilst avoiding measurement losses. Since transmitting data over a long distance consumes a significant amount of energy, a mobile sink node collects the measurements and transmits them to the base station. We assume that the default transmission range of the activated sensor node is limited and it can be increased to maximum range only if the mobile sink node is out-side the default transmission range. Moreover, the active sensor node can be changed after a certain time period. The problem is to select an optimal sensor sequence which minimizes the total energy consumed by the sensor nodes. In this paper, we consider two different problems depend on the mobile sink node’s path. First, we assume that the mobile sink node’s position is known for the entire time horizon and use the dynamic programming technique to solve the problem. Second, the position of the sink node is varied over time according to a known Markov chain, and the problem is solved by stochastic dynamic programming. We also present sub-optimal methods to solve our problem. A numerical example is presented in order to discuss the proposed methods’ performance. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Open AccessArticle Capture of Escherichia coli O157:H7 Using Immunomagnetic Beads of Different Size and Antibody Conjugating Chemistry
Sensors 2009, 9(2), 717-730; doi:10.3390/s90200717
Received: 17 October 2008 / Revised: 29 December 2008 / Accepted: 19 January 2009 / Published: 29 January 2009
Cited by 24 | PDF Full-text (86 KB) | HTML Full-text | XML Full-text
Abstract
Immunomagnetic beads (IMB) were synthesized using anti-Escherichia coli O157 antibodies and magnetic beads of two different sizes (1 mm and 2.6 to 2.8 mm) that contained a streptavidin coating, activated carboxyl groups or tosylated surfaces. The synthesized IMB, together with a commercially
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Immunomagnetic beads (IMB) were synthesized using anti-Escherichia coli O157 antibodies and magnetic beads of two different sizes (1 mm and 2.6 to 2.8 mm) that contained a streptavidin coating, activated carboxyl groups or tosylated surfaces. The synthesized IMB, together with a commercially available IMB, were used to capture different strains of E. coli O157:H7 and E. coli O157:NM. The E. coli capture was measured by the time resolved fluorescence (TRF) intensity using a sandwich assay which we have previously demonstrated of having a sensitivity of 1 CFU/g after 4.5 hour enrichment [1]. The analyses of measured TRF intensity and determined antibody surface concentration indicated that larger beads provided higher response signals than smaller beads and were more effective in capturing the target of interest in pure culture and ground beef. In addition, while each type of IMB showed different favorable capture of E. coli O157:H7, streptavidin-coated IMB elicited the highest response, on average. Streptavidin-coated IMB also provided an economic benefit, costing less than $0.50 per assay. The results could be used to guide the proper choice of IMB for applications in developing detection processes for E. coli O157:H7. Full article
(This article belongs to the Special Issue Pathogen Sensors)
Open AccessArticle Bayesian Algorithm Implementation in a Real Time Exposure Assessment Model on Benzene with Calculation of Associated Cancer Risks
Sensors 2009, 9(2), 731-755; doi:10.3390/s90200731
Received: 7 November 2008 / Revised: 5 January 2009 / Accepted: 12 January 2009 / Published: 2 February 2009
Cited by 12 | PDF Full-text (806 KB) | HTML Full-text | XML Full-text
Abstract
The objective of the current study was the development of a reliable modeling platform to calculate in real time the personal exposure and the associated health risk for filling station employees evaluating current environmental parameters (traffic, meteorological and amount of fuel traded) determined
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The objective of the current study was the development of a reliable modeling platform to calculate in real time the personal exposure and the associated health risk for filling station employees evaluating current environmental parameters (traffic, meteorological and amount of fuel traded) determined by the appropriate sensor network. A set of Artificial Neural Networks (ANNs) was developed to predict benzene exposure pattern for the filling station employees. Furthermore, a Physiology Based Pharmaco-Kinetic (PBPK) risk assessment model was developed in order to calculate the lifetime probability distribution of leukemia to the employees, fed by data obtained by the ANN model. Bayesian algorithm was involved in crucial points of both model sub compartments. The application was evaluated in two filling stations (one urban and one rural). Among several algorithms available for the development of the ANN exposure model, Bayesian regularization provided the best results and seemed to be a promising technique for prediction of the exposure pattern of that occupational population group. On assessing the estimated leukemia risk under the scope of providing a distribution curve based on the exposure levels and the different susceptibility of the population, the Bayesian algorithm was a prerequisite of the Monte Carlo approach, which is integrated in the PBPK-based risk model. In conclusion, the modeling system described herein is capable of exploiting the information collected by the environmental sensors in order to estimate in real time the personal exposure and the resulting health risk for employees of gasoline filling stations. Full article
(This article belongs to the Special Issue Sensor Algorithms)
Open AccessArticle Membrane Based Measurement Technology for in situ Monitoring of Gases in Soil
Sensors 2009, 9(2), 756-767; doi:10.3390/s90200756
Received: 23 September 2008 / Revised: 19 January 2009 / Accepted: 21 January 2009 / Published: 2 February 2009
Cited by 12 | PDF Full-text (594 KB) | HTML Full-text | XML Full-text
Abstract
The representative measurement of gas concentration and fluxes in heterogeneous soils is one of the current challenges when analyzing the interactions of biogeochemical processes in soils and global change. Furthermore, recent research projects on CO2-sequestration have an urgent need of CO
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The representative measurement of gas concentration and fluxes in heterogeneous soils is one of the current challenges when analyzing the interactions of biogeochemical processes in soils and global change. Furthermore, recent research projects on CO2-sequestration have an urgent need of CO2-monitoring networks. Therefore, a measurement method based on selective permeation of gases through tubular membranes has been developed. Combining the specific permeation rates of gas components for a membrane and Dalton’s principle, the gas concentration (or partial pressure) can be determined by the measurement of physical quantities (pressure or volume) only. Due to the comparatively small permeation constants of membranes, the influence of the sensor on its surrounding area can be neglected. The design of the sensor membranes can be adapted to the spatial scale from the bench scale to the field scale. The sensitive area for the measurement can be optimized to obtain representative results. Furthermore, a continuous time-averaged measurement is possible where the time for averaging is simply controlled by the wall-thickness of the membrane used. The measuring method is demonstrated for continuous monitoring of O2 and CO2 inside of a sand filled Lysimeter. Using three sensor planes inside the sand pack, which were installed normal to the gas flow direction and a reference measurement system, we demonstrate the accuracy of the gas-detection for different flux-based boundary conditions. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany)
Open AccessArticle Comparison Between Fractional Vegetation Cover Retrievals from Vegetation Indices and Spectral Mixture Analysis: Case Study of PROBA/CHRIS Data Over an Agricultural Area
Sensors 2009, 9(2), 768-793; doi:10.3390/s90200768
Received: 4 December 2008 / Revised: 23 January 2009 / Accepted: 27 January 2009 / Published: 2 February 2009
Cited by 45 | PDF Full-text (1350 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we compare two different methodologies for Fractional Vegetation Cover (FVC) retrieval from Compact High Resolution Imaging Spectrometer (CHRIS) data onboard the European Space Agency (ESA) Project for On-Board Autonomy (PROBA) platform. The first methodology is based on empirical approaches using
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In this paper we compare two different methodologies for Fractional Vegetation Cover (FVC) retrieval from Compact High Resolution Imaging Spectrometer (CHRIS) data onboard the European Space Agency (ESA) Project for On-Board Autonomy (PROBA) platform. The first methodology is based on empirical approaches using Vegetation Indices (VIs), in particular the Normalized Difference Vegetation Index (NDVI) and the Variable Atmospherically Resistant Index (VARI). The second methodology is based on the Spectral Mixture Analysis (SMA) technique, in which a Linear Spectral Unmixing model has been considered in order to retrieve the abundance of the different constituent materials within pixel elements, called Endmembers (EMs). These EMs were extracted from the image using three different methods: i) manual extraction using a land cover map, ii) Pixel Purity Index (PPI) and iii) Automated Morphological Endmember Extraction (AMEE). The different methodologies for FVC retrieval were applied to one PROBA/CHRIS image acquired over an agricultural area in Spain, and they were calibrated and tested against in situ measurements of FVC estimated with hemispherical photographs. The results obtained from VIs show that VARI correlates better with FVC than NDVI does, with standard errors of estimation of less than 8% in the case of VARI and less than 13% in the case of NDVI when calibrated using the in situ measurements. The results obtained from the SMA-LSU technique show Root Mean Square Errors (RMSE) below 12% when EMs are extracted from the AMEE method and around 9% when extracted from the PPI method. A RMSE value below 9% was obtained for manual extraction of EMs using a land cover use map. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Performance of Three Reflectance Calibration Methods for Airborne Hyperspectral Spectrometer Data
Sensors 2009, 9(2), 794-813; doi:10.3390/s90200794
Received: 30 December 2008 / Revised: 29 January 2009 / Accepted: 3 February 2009 / Published: 3 February 2009
Cited by 5 | PDF Full-text (3784 KB) | HTML Full-text | XML Full-text
Abstract
In this study, the performances and accuracies of three methods for converting airborne hyperspectral spectrometer data to reflectance factors were characterized and compared. The “reflectance mode (RM)” method, which calibrates a spectrometer against a white reference panel prior to mounting on an aircraft,
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In this study, the performances and accuracies of three methods for converting airborne hyperspectral spectrometer data to reflectance factors were characterized and compared. The “reflectance mode (RM)” method, which calibrates a spectrometer against a white reference panel prior to mounting on an aircraft, resulted in spectral reflectance retrievals that were biased and distorted. The magnitudes of these bias errors and distortions varied significantly, depending on time of day and length of the flight campaign. The “linear-interpolation (LI)” method, which converts airborne spectrometer data by taking a ratio of linearly-interpolated reference values from the preflight and postflight reference panel readings, resulted in precise, but inaccurate reflectance retrievals. These reflectance spectra were not distorted, but were subject to bias errors of varying magnitudes dependent on the flight duration length. The “continuous panel (CP)” method uses a multi-band radiometer to obtain continuous measurements over a reference panel throughout the flight campaign, in order to adjust the magnitudes of the linear-interpolated reference values from the preflight and post-flight reference panel readings. Airborne hyperspectral reflectance retrievals obtained using this method were found to be the most accurate and reliable reflectance calibration method. The performances of the CP method in retrieving accurate reflectance factors were consistent throughout time of day and for various flight durations. Based on the dataset analyzed in this study, the uncertainty of the CP method has been estimated to be 0.0025 ± 0.0005 reflectance units for the wavelength regions not affected by atmospheric absorptions. The RM method can produce reasonable results only for a very short-term flight (e.g., < 15 minutes) conducted around a local solar noon. The flight duration should be kept shorter than 30 minutes for the LI method to produce results with reasonable accuracies. An important advantage of the CP method is that the method can be used for long-duration flight campaigns (e.g., 1-2 hours). Although this study focused on reflectance calibration of airborne spectrometer data, the methods evaluated in this study and the results obtained are directly applicable to ground spectrometer measurements. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle A Fast Level Set Method for Synthetic Aperture Radar Ocean Image Segmentation
Sensors 2009, 9(2), 814-829; doi:10.3390/s90200814
Received: 14 December 2008 / Revised: 30 January 2009 / Accepted: 2 February 2009 / Published: 3 February 2009
Cited by 7 | PDF Full-text (1932 KB) | HTML Full-text | XML Full-text
Abstract
Segmentation of high noise imagery like Synthetic Aperture Radar (SAR) images is still one of the most challenging tasks in image processing. While level set, a novel approach based on the analysis of the motion of an interface, can be used to address
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Segmentation of high noise imagery like Synthetic Aperture Radar (SAR) images is still one of the most challenging tasks in image processing. While level set, a novel approach based on the analysis of the motion of an interface, can be used to address this challenge, the cell-based iterations may make the process of image segmentation remarkably slow, especially for large-size images. For this reason fast level set algorithms such as narrow band and fast marching have been attempted. Built upon these, this paper presents an improved fast level set method for SAR ocean image segmentation. This competent method is dependent on both the intensity driven speed and curvature flow that result in a stable and smooth boundary. Notably, it is optimized to track moving interfaces for keeping up with the point-wise boundary propagation using a single list and a method of fast up-wind scheme iteration. The list facilitates efficient insertion and deletion of pixels on the propagation front. Meanwhile, the local up-wind scheme is used to update the motion of the curvature front instead of solving partial differential equations. Experiments have been carried out on extraction of surface slick features from ERS-2 SAR images to substantiate the efficacy of the proposed fast level set method. Full article
(This article belongs to the Special Issue Synthetic Aperture Radar (SAR))
Open AccessArticle Detection of Seagrass Distribution Changes from 1991 to 2006 in Xincun Bay, Hainan, with Satellite Remote Sensing
Sensors 2009, 9(2), 830-844; doi:10.3390/s90200830
Received: 29 October 2008 / Revised: 12 January 2009 / Accepted: 23 January 2009 / Published: 5 February 2009
Cited by 23 | PDF Full-text (1044 KB) | HTML Full-text | XML Full-text
Abstract
Seagrass distribution is a very important index for costal management and protection. Seagrass distribution changes can be used as indexes to analyze the reasons for the changes. In this paper, in situ hyperspectral observation and satellite images of QuickBird, CBERS (China Brazil Earth
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Seagrass distribution is a very important index for costal management and protection. Seagrass distribution changes can be used as indexes to analyze the reasons for the changes. In this paper, in situ hyperspectral observation and satellite images of QuickBird, CBERS (China Brazil Earth Resources Satellite data) and Landsat data were used to retrieve bio-optical models and seagrass (Enhalus acoroides,Thalassia hemperichii) distribution in Xincun Bay, Hainan province, and seagrass distribution changes from 1991 to 2006 were analyzed. Hyperspectral results showed that the spectral bands at 555, 635, 650 and 675 nm are sensitive to leaf area index (LAI). Seagrass detection with QuickBird was more accurate than that with Landsat TM and CBERS; five classes could be classified clearly and used as correction for seagrass remote sensing data from Landsat TM and CBERS. In order to better describe seagrass distribution changes, the seagrass distribution area was divided as three regions: region A connected with region B in 1991, however it separated in 1999 and was wholly separated in 2001; seagrass in region C shrank gradually and could not be detected in 2006. Analysis of the reasons for seagrass reduction indicated it was mainly affected by aquaculture and typhoons and in recent years, by land use changes. Full article
(This article belongs to the Special Issue Sensor Algorithms)
Open AccessArticle Enhanced TDMA Based Anti-Collision Algorithm with a Dynamic Frame Size Adjustment Strategy for Mobile RFID Readers
Sensors 2009, 9(2), 845-858; doi:10.3390/s90200845
Received: 14 October 2008 / Revised: 29 December 2008 / Accepted: 5 February 2009 / Published: 6 February 2009
Cited by 23 | PDF Full-text (341 KB) | HTML Full-text | XML Full-text
Abstract
In the fields of production, manufacturing and supply chain management, Radio Frequency Identification (RFID) is regarded as one of the most important technologies. Nowadays, Mobile RFID, which is often installed in carts or forklift trucks, is increasingly being applied to the search for
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In the fields of production, manufacturing and supply chain management, Radio Frequency Identification (RFID) is regarded as one of the most important technologies. Nowadays, Mobile RFID, which is often installed in carts or forklift trucks, is increasingly being applied to the search for and checkout of items in warehouses, supermarkets, libraries and other industrial fields. In using Mobile RFID, since the readers are continuously moving, they can interfere with each other when they attempt to read the tags. In this study, we suggest a Time Division Multiple Access (TDMA) based anti-collision algorithm for Mobile RFID readers. Our algorithm automatically adjusts the frame size of each reader without using manual parameters by adopting the dynamic frame size adjustment strategy when collisions occur at a reader. Through experiments on a simulated environment for Mobile RFID readers, we show that the proposed method improves the number of successful transmissions by about 228% on average, compared with Colorwave, a representative TDMA based anti-collision algorithm. Full article
Open AccessArticle Performance of a Diaphragmed Microlens for a Packaged Microspectrometer
Sensors 2009, 9(2), 859-868; doi:10.3390/s90200859
Received: 4 November 2008 / Revised: 9 January 2009 / Accepted: 4 February 2009 / Published: 6 February 2009
PDF Full-text (861 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes the design, fabrication, packaging and testing of a microlens integrated in a multi-layered MEMS microspectrometer. The microlens was fabricated using modified PDMS molding to form a suspended lens diaphragm. Gaussian beam propagation model was used to measure the focal length
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This paper describes the design, fabrication, packaging and testing of a microlens integrated in a multi-layered MEMS microspectrometer. The microlens was fabricated using modified PDMS molding to form a suspended lens diaphragm. Gaussian beam propagation model was used to measure the focal length and quantify M2 value of the microlens. A tunable calibration source was set up to measure the response of the packaged device. Dual wavelength separation by the packaged device was demonstrated by CCD imaging and beam profiling of the spectroscopic output. We demonstrated specific techniques to measure critical parameters of microoptics systems for future optimization of spectroscopic devices Full article
(This article belongs to the Special Issue BioMEMS)
Open AccessArticle Manufacture of a Polyaniline Nanofiber Ammonia Sensor Integrated with a Readout Circuit Using the CMOS-MEMS Technique
Sensors 2009, 9(2), 869-880; doi:10.3390/s90200869
Received: 13 December 2008 / Revised: 15 January 2009 / Accepted: 9 February 2009 / Published: 10 February 2009
Cited by 41 | PDF Full-text (534 KB) | HTML Full-text | XML Full-text
Abstract
This study presents the fabrication of a polyaniline nanofiber ammonia sensor integrated with a readout circuit on a chip using the commercial 0.35 mm complementary metal oxide semiconductor (CMOS) process and a post-process. The micro ammonia sensor consists of a sensing resistor and
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This study presents the fabrication of a polyaniline nanofiber ammonia sensor integrated with a readout circuit on a chip using the commercial 0.35 mm complementary metal oxide semiconductor (CMOS) process and a post-process. The micro ammonia sensor consists of a sensing resistor and an ammonia sensing film. Polyaniline prepared by a chemical polymerization method was adopted as the ammonia sensing film. The fabrication of the ammonia sensor needs a post-process to etch the sacrificial layers and to expose the sensing resistor, and then the ammonia sensing film is coated on the sensing resistor. The ammonia sensor, which is of resistive type, changes its resistance when the sensing film adsorbs or desorbs ammonia gas. A readout circuit is employed to convert the resistance of the ammonia sensor into the voltage output. Experimental results show that the sensitivity of the ammonia sensor is about 0.88 mV/ppm at room temperature Full article
(This article belongs to the Special Issue Gas Sensors 2009)
Open AccessArticle Direct Electrochemistry of Horseradish Peroxidase-Gold Nanoparticles Conjugate
Sensors 2009, 9(2), 881-894; doi:10.3390/s90200881
Received: 27 November 2008 / Revised: 6 January 2009 / Accepted: 6 January 2009 / Published: 10 February 2009
Cited by 28 | PDF Full-text (309 KB) | HTML Full-text | XML Full-text
Abstract
We have studied the direct electrochemistry of horseradish peroxidase (HRP) coupled to gold nanoparticles (AuNP) using electrochemical techniques, which provide some insight in the application of biosensors as tools for diagnostics because HRP is widely used in clinical diagnostics kits. AuNP capped with
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We have studied the direct electrochemistry of horseradish peroxidase (HRP) coupled to gold nanoparticles (AuNP) using electrochemical techniques, which provide some insight in the application of biosensors as tools for diagnostics because HRP is widely used in clinical diagnostics kits. AuNP capped with (i) glutathione and (ii) lipoic acid was covalently linked to HRP. The immobilized HRP/AuNP conjugate showed characteristic redox peaks at a gold electrode. It displayed good electrocatalytic response to the reduction of H2O2, with good sensitivity and without any electron mediator. The covalent linking of HRP and AuNP did not affect the activity of the enzyme significantly. The response of the electrode towards the different concentrations of H2O2 showed the characteristics of Michaelis Menten enzyme kinetics with an optimum pH between 7.0 to 8.0. The preparation of the sensor involves single layer of enzyme, which can be carried out efficiently and is also highly reproducible when compared to other systems involving the layer-by-layer assembly, adsorption or encapsulation of the enzyme. The immobilized AuNP-HRP can be used for immunosensor applications Full article
(This article belongs to the Section Chemical Sensors)
Figures

Open AccessArticle A Real-Time De-Noising Algorithm for E-Noses in a Wireless Sensor Network
Sensors 2009, 9(2), 895-908; doi:10.3390/s90200895
Received: 3 December 2008 / Revised: 15 January 2009 / Accepted: 9 February 2009 / Published: 11 February 2009
Cited by 11 | PDF Full-text (260 KB) | HTML Full-text | XML Full-text
Abstract
A wireless e-nose network system is developed for the special purpose of monitoring odorant gases and accurately estimating odor strength in and around livestock farms. This system is to simultaneously acquire accurate odor strength values remotely at various locations, where each node is
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A wireless e-nose network system is developed for the special purpose of monitoring odorant gases and accurately estimating odor strength in and around livestock farms. This system is to simultaneously acquire accurate odor strength values remotely at various locations, where each node is an e-nose that includes four metal-oxide semiconductor (MOS) gas sensors. A modified Kalman filtering technique is proposed for collecting raw data and de-noising based on the output noise characteristics of those gas sensors. The measurement noise variance is obtained in real time by data analysis using the proposed slip windows average method. The optimal system noise variance of the filter is obtained by using the experiments data. The Kalman filter theory on how to acquire MOS gas sensors data is discussed. Simulation results demonstrate that the proposed method can adjust the Kalman filter parameters and significantly reduce the noise from the gas sensors. Full article
(This article belongs to the Special Issue Gas Sensors 2009)
Open AccessArticle Routing in Wireless Sensor Networks Using an Ant Colony Optimization (ACO) Router Chip
Sensors 2009, 9(2), 909-921; doi:10.3390/s90200909
Received: 25 November 2008 / Revised: 27 January 2009 / Accepted: 11 February 2009 / Published: 13 February 2009
Cited by 73 | PDF Full-text (100 KB) | HTML Full-text | XML Full-text
Abstract
Wireless Sensor Networks consisting of nodes with limited power are deployed to gather useful information from the field. In WSNs it is critical to collect the information in an energy efficient manner. Ant Colony Optimization, a swarm intelligence based optimization technique, is widely
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Wireless Sensor Networks consisting of nodes with limited power are deployed to gather useful information from the field. In WSNs it is critical to collect the information in an energy efficient manner. Ant Colony Optimization, a swarm intelligence based optimization technique, is widely used in network routing. A novel routing approach using an Ant Colony Optimization algorithm is proposed for Wireless Sensor Networks consisting of stable nodes. Illustrative examples, detailed descriptions and comparative performance test results of the proposed approach are included. The approach is also implemented to a small sized hardware component as a router chip. Simulation results show that proposed algorithm provides promising solutions allowing node designers to efficiently operate routing tasks. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Modeling Gross Primary Production of Agro-Forestry Ecosystems by Assimilation of Satellite-Derived Information in a Process-Based Model
Sensors 2009, 9(2), 922-942; doi:10.3390/s90200922
Received: 6 October 2008 / Revised: 10 February 2009 / Accepted: 12 February 2009 / Published: 13 February 2009
Cited by 17 | PDF Full-text (475 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we present results obtained in the framework of a regional-scale analysis of the carbon budget of poplar plantations in Northern Italy. We explored the ability of the process-based model BIOME-BGC to estimate the gross primary production (GPP) using an inverse
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In this paper we present results obtained in the framework of a regional-scale analysis of the carbon budget of poplar plantations in Northern Italy. We explored the ability of the process-based model BIOME-BGC to estimate the gross primary production (GPP) using an inverse modeling approach exploiting eddy covariance and satellite data. We firstly present a version of BIOME-BGC coupled with the radiative transfer models PROSPECT and SAILH (named PROSAILH-BGC) with the aims of i) improving the BIOME-BGC description of the radiative transfer regime within the canopy and ii) allowing the assimilation of remotely-sensed vegetation index time series, such as MODIS NDVI, into the model. Secondly, we present a two-step model inversion for optimization of model parameters. In the first step, some key ecophysiological parameters were optimized against data collected by an eddy covariance flux tower. In the second step, important information about phenological dates and about standing biomass were optimized against MODIS NDVI. Results obtained showed that the PROSAILH-BGC allowed simulation of MODIS NDVI with good accuracy and that we described better the canopy radiation regime. The inverse modeling approach was demonstrated to be useful for the optimization of ecophysiological model parameters, phenological dates and parameters related to the standing biomass, allowing good accuracy of daily and annual GPP predictions. In summary, this study showed that assimilation of eddy covariance and remote sensing data in a process model may provide important information for modeling gross primary production at regional scale. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle A Contextual Fire Detection Algorithm for Simulated HJ-1B Imagery
Sensors 2009, 9(2), 961-979; doi:10.3390/s90200961
Received: 20 November 2008 / Revised: 29 December 2008 / Accepted: 6 January 2009 / Published: 13 February 2009
Cited by 6 | PDF Full-text (412 KB) | HTML Full-text | XML Full-text
Abstract
The HJ-1B satellite, which was launched on September 6, 2008, is one of the small ones placed in the constellation for disaster prediction and monitoring. HJ-1B imagery was simulated in this paper, which contains fires of various sizes and temperatures in a wide
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The HJ-1B satellite, which was launched on September 6, 2008, is one of the small ones placed in the constellation for disaster prediction and monitoring. HJ-1B imagery was simulated in this paper, which contains fires of various sizes and temperatures in a wide range of terrestrial biomes and climates, including RED, NIR, MIR and TIR channels. Based on the MODIS version 4 contextual algorithm and the characteristics of HJ-1B sensor, a contextual fire detection algorithm was proposed and tested using simulated HJ-1B data. It was evaluated by the probability of fire detection and false alarm as functions of fire temperature and fire area. Results indicate that when the simulated fire area is larger than 45 m2 and the simulated fire temperature is larger than 800 K, the algorithm has a higher probability of detection. But if the simulated fire area is smaller than 10 m2, only when the simulated fire temperature is larger than 900 K, may the fire be detected. For fire areas about 100 m2, the proposed algorithm has a higher detection probability than that of the MODIS product. Finally, the omission and commission error were evaluated which are important factors to affect the performance of this algorithm. It has been demonstrated that HJ-1B satellite data are much sensitive to smaller and cooler fires than MODIS or AVHRR data and the improved capabilities of HJ-1B data will offer a fine opportunity for the fire detection. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Surface Acoustic WaveAmmonia Sensors Based on ST-cut Quartz under Periodic Al Structure
Sensors 2009, 9(2), 980-994; doi:10.3390/s90200980
Received: 16 January 2009 / Accepted: 13 February 2009 / Published: 16 February 2009
Cited by 14 | PDF Full-text (585 KB) | HTML Full-text | XML Full-text
Abstract
Surface acoustic wave (SAW) devices are key components for sensing applications. SAW propagation under a periodic grating was investigated in this work. The theoretical method used here is the space harmonic method. We also applied the results of SAW propagation studied in this
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Surface acoustic wave (SAW) devices are key components for sensing applications. SAW propagation under a periodic grating was investigated in this work. The theoretical method used here is the space harmonic method. We also applied the results of SAW propagation studied in this work to design a two-port resonator with an Al grating on ST-cut quartz. The measured frequency responses of the resonator were similar to the simulation ones. Then, the chemical interface of polyaniline/WO3 composites was coated on the SAW sensor for ammonia detection. The SAW sensor responded to ammonia gas and could be regenerated using dry nitrogen. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Apparent Thixotropic Properties of Saline/Glycerol Drops with Biotinylated Antibodies on Streptavidin-Coated Glass Slides: Implications for Bacterial Capture on Antibody Microarrays
Sensors 2009, 9(2), 995-1011; doi:10.3390/s90200995
Received: 28 November 2008 / Accepted: 11 February 2009 / Published: 16 February 2009
Cited by 2 | PDF Full-text (505 KB) | HTML Full-text | XML Full-text
Abstract
The thixotropic-like properties of saline/glycerol drops, containing biotinylated capture antibodies, on streptavidin-coated glass slides have been investigated, along with their implications for bacterial detection in a fluorescent microarray immunoassay. The thixotropic-like nature of 60:40 saline-glycerol semisolid droplets (with differing amounts of antibodies) was
[...] Read more.
The thixotropic-like properties of saline/glycerol drops, containing biotinylated capture antibodies, on streptavidin-coated glass slides have been investigated, along with their implications for bacterial detection in a fluorescent microarray immunoassay. The thixotropic-like nature of 60:40 saline-glycerol semisolid droplets (with differing amounts of antibodies) was observed when bacteria were captured, and their presence detected using a fluorescently-labeled antibody. Semisolid, gel-like drops of biotinylated capture antibody became liquefied and moved, and then returned to semisolid state, during the normal immunoassay procedures for bacterial capture and detection. Streaking patterns were observed that indicated thixotropic-like characteristics, and this appeared to have allowed excess biotinylated capture antibody to participate in bacterial capture and detection. When developing a microarray for bacterial detection, this must be considered for optimization. For example, with the appropriate concentration of antibody (in this study, 0.125 ng/nL), spots with increased diameter at the point of contact printing (and almost no streaking) were produced, resulting in a maximal signal. With capture antibody concentrations greater than 0.125 ng/nL, the excess biotinylated capture antibody (i.e., that which was residing in the three-dimensional, semisolid droplet space above the surface) was utilized to capture more bacteria. Similarly, when the immunoassay was performed within a hydrophobic barrier (i.e., without a coverslip), brighter spots with increased signal were observed. In addition, when higher concentrations of cells (~108 cells/mL) were available for capture, the importance of unbound capture antibody in the semisolid droplets became apparent because washing off the excess, unbound biotinylated capture antibody before the immunoassay was performed reduced the signal intensity by nearly 50%. This reduction in signal was not observed with lower concentrations of cells (~106 cells/mL). With increased volumes of capture antibody, abnormal spots were visualized, along with decreased signal intensity, after bacterial detection, indicating that the increased droplet volume detrimentally affected the immunoassay. Full article
(This article belongs to the Special Issue Pathogen Sensors)
Open AccessArticle Efficient Chemical Sensing by Coupled Slot SOI Waveguides
Sensors 2009, 9(2), 1012-1032; doi:10.3390/s90201012
Received: 29 January 2009 / Revised: 11 February 2009 / Accepted: 13 February 2009 / Published: 16 February 2009
Cited by 42 | PDF Full-text (972 KB) | HTML Full-text | XML Full-text
Abstract
A guided-wave chemical sensor for the detection of environmental pollutants or biochemical substances has been designed. The sensor is based on an asymmetric directional coupler employing slot optical waveguides. The use of a nanometer guiding structure where optical mode is confined in a
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A guided-wave chemical sensor for the detection of environmental pollutants or biochemical substances has been designed. The sensor is based on an asymmetric directional coupler employing slot optical waveguides. The use of a nanometer guiding structure where optical mode is confined in a low-index region permits a very compact sensor (device area about 1200 μm2) to be realized, having the minimum detectable refractive index change as low as 10-5. Silicon-on-Insulator technology has been assumed in sensor design and a very accurate modelling procedure based on Finite Element Method and Coupled Mode Theory has been pointed out. Sensor design and optimization have allowed a very good trade-off between device length and sensitivity. Expected device sensitivity to glucose concentration change in an aqueous solution is of the order of 0.1 g/L. Full article
(This article belongs to the Special Issue Nanotechnological Advances in Biosensors)
Open AccessArticle Discrepancy Between ASTER- and MODIS- Derived Land Surface Temperatures: Terrain Effects
Sensors 2009, 9(2), 1054-1066; doi:10.3390/s90201054
Received: 11 December 2008 / Revised: 10 February 2009 / Accepted: 11 February 2009 / Published: 17 February 2009
Cited by 8 | PDF Full-text (977 KB) | HTML Full-text | XML Full-text
Abstract
The MODerate resolution Imaging Spectroradiometer (MODIS) and the Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER) are onboard the same satellite platform NASA TERRA. Both MODIS and ASTER offer routine retrieval of land surface temperatures (LSTs), and the ASTER- and MODIS-retrieved LST products have
[...] Read more.
The MODerate resolution Imaging Spectroradiometer (MODIS) and the Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER) are onboard the same satellite platform NASA TERRA. Both MODIS and ASTER offer routine retrieval of land surface temperatures (LSTs), and the ASTER- and MODIS-retrieved LST products have been used worldwide. Because a large fraction of the earth surface consists of mountainous areas, variations in elevation, terrain slope and aspect angles can cause biases in the retrieved LSTs. However, terrain-induced effects are generally neglected in most satellite retrievals, which may generate discrepancy between ASTER and MODIS LSTs. In this paper, we reported the terrain effects on the LST discrepancy with a case examination over a relief area at the Loess Plateau of China. Results showed that the terrain-induced effects were not major, but nevertheless important for the total LST discrepancy. A large local slope did not necessarily lead to a large LST discrepancy. The angle of emitted radiance was more important than the angle of local slope in generating the LST discrepancy. Specifically, the conventional terrain correction may be unsuitable for densely vegetated areas. The distribution of ASTER-to-MODIS emissivity suggested that the terrain correction was included in the generalized split window (GSW) based approach used to rectify MODIS LSTs. Further study should include the classification-induced uncertainty in emissivity for reliable use of satellite-retrieved LSTs over relief areas. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan)
Open AccessArticle Error in Radar-Derived Soil Moisture due to Roughness Parameterization: An Analysis Based on Synthetical Surface Profiles
Sensors 2009, 9(2), 1067-1093; doi:10.3390/s90201067
Received: 15 December 2008 / Accepted: 14 January 2009 / Published: 17 February 2009
Cited by 36 | PDF Full-text (5246 KB) | HTML Full-text | XML Full-text
Abstract
In the past decades, many studies on soil moisture retrieval from SAR demonstrated a poor correlation between the top layer soil moisture content and observed backscatter coefficients, which mainly has been attributed to difficulties involved in the parameterization of surface roughness. The present
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In the past decades, many studies on soil moisture retrieval from SAR demonstrated a poor correlation between the top layer soil moisture content and observed backscatter coefficients, which mainly has been attributed to difficulties involved in the parameterization of surface roughness. The present paper describes a theoretical study, performed on synthetical surface profiles, which investigates how errors on roughness parameters are introduced by standard measurement techniques, and how they will propagate through the commonly used Integral Equation Model (IEM) into a corresponding soil moisture retrieval error for some of the currently most used SAR configurations. Key aspects influencing the error on the roughness parameterization and consequently on soil moisture retrieval are: the length of the surface profile, the number of profile measurements, the horizontal and vertical accuracy of profile measurements and the removal of trends along profiles. Moreover, it is found that soil moisture retrieval with C-band configuration generally is less sensitive to inaccuracies in roughness parameterization than retrieval with L-band configuration. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Enhanced Photoelectrochemical Detection of Bioaffinity Reactions by Vertically Oriented Au Nanobranches Complexed with a Biotinylated Polythiophene Derivative
Sensors 2009, 9(2), 1094-1107; doi:10.3390/s90201094
Received: 31 December 2008 / Revised: 10 February 2009 / Accepted: 11 February 2009 / Published: 19 February 2009
Cited by 10 | PDF Full-text (764 KB) | HTML Full-text | XML Full-text
Abstract
Four nanostructured Au electrodes were prepared by a simple and templateless electrochemical deposition technique. After complexing with a biotinylated polythiophene derivative (PTBL), photocurrent generation and performance of PTBL/Au-nanostructured electrodes as photoelectrochemical biosensors were investigated. Among these four nanostructured Au electrodes, vertically oriented nanobranches
[...] Read more.
Four nanostructured Au electrodes were prepared by a simple and templateless electrochemical deposition technique. After complexing with a biotinylated polythiophene derivative (PTBL), photocurrent generation and performance of PTBL/Au-nanostructured electrodes as photoelectrochemical biosensors were investigated. Among these four nanostructured Au electrodes, vertically oriented nanobranches on the electrode significantly improved the photoelectric conversion, because the vertically oriented nanostructures not only benefit light harvesting but also the transfer of the photogenerated charge carriers. Owing to this advantaged nanostructure, the PTBL/Au-nanobranch electrode showed higher sensitivity and faster response times in the photoelectrochemical detection of a streptavidin-biotin affinity reaction compared to a PTBL/Au-nanoparticle electrode. Full article
(This article belongs to the Section Biosensors)
Figures

Open AccessArticle 3D Digital Surveying and Modelling of Cave Geometry: Application to Paleolithic Rock Art
Sensors 2009, 9(2), 1108-1127; doi:10.3390/s90201108
Received: 5 December 2008 / Revised: 18 February 2009 / Accepted: 20 February 2009 / Published: 20 February 2009
Cited by 28 | PDF Full-text (1125 KB) | HTML Full-text | XML Full-text
Abstract
3D digital surveying and modelling of cave geometry represents a relevant approach for research, management and preservation of our cultural and geological legacy. In this paper, a multi-sensor approach based on a terrestrial laser scanner, a high-resolution digital camera and a total station
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3D digital surveying and modelling of cave geometry represents a relevant approach for research, management and preservation of our cultural and geological legacy. In this paper, a multi-sensor approach based on a terrestrial laser scanner, a high-resolution digital camera and a total station is presented. Two emblematic caves of Paleolithic human occupation and situated in northern Spain, “Las Caldas” and “Peña de Candamo”, have been chosen to put in practise this approach. As a result, an integral and multi-scalable 3D model is generated which may allow other scientists, pre-historians, geologists…, to work on two different levels, integrating different Paleolithic Art datasets: (1) a basic level based on the accurate and metric support provided by the laser scanner; and (2) a advanced level using the range and image-based modelling. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle An Updating System for the Gridded Population Database of China Based on Remote Sensing, GIS and Spatial Database Technologies
Sensors 2009, 9(2), 1128-1140; doi:10.3390/s90201128
Received: 18 December 2008 / Revised: 13 February 2009 / Accepted: 17 February 2009 / Published: 20 February 2009
Cited by 12 | PDF Full-text (271 KB) | HTML Full-text | XML Full-text
Abstract
The spatial distribution of population is closely related to land use and land cover (LULC) patterns on both regional and global scales. Population can be redistributed onto geo-referenced square grids according to this relation. In the past decades, various approaches to monitoring LULC
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The spatial distribution of population is closely related to land use and land cover (LULC) patterns on both regional and global scales. Population can be redistributed onto geo-referenced square grids according to this relation. In the past decades, various approaches to monitoring LULC using remote sensing and Geographic Information Systems (GIS) have been developed, which makes it possible for efficient updating of geo-referenced population data. A Spatial Population Updating System (SPUS) is developed for updating the gridded population database of China based on remote sensing, GIS and spatial database technologies, with a spatial resolution of 1 km by 1 km. The SPUS can process standard Moderate Resolution Imaging Spectroradiometer (MODIS L1B) data integrated with a Pattern Decomposition Method (PDM) and an LULC-Conversion Model to obtain patterns of land use and land cover, and provide input parameters for a Population Spatialization Model (PSM). The PSM embedded in SPUS is used for generating 1 km by 1 km gridded population data in each population distribution region based on natural and socio-economic variables. Validation results from finer township-level census data of Yishui County suggest that the gridded population database produced by the SPUS is reliable. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Piezoresistive Sensitivity, Linearity and Resistance Time Drift of Polysilicon Nanofilms with Different Deposition Temperatures
Sensors 2009, 9(2), 1141-1166; doi:10.3390/s90201141
Received: 23 January 2009 / Revised: 12 February 2009 / Accepted: 18 February 2009 / Published: 23 February 2009
Cited by 15 | PDF Full-text (4476 KB) | HTML Full-text | XML Full-text
Abstract
Our previous research work indicated that highly boron doped polysilicon nanofilms (≤100 nm in thickness) have higher gauge factor (the maximum is ~34 for 80 nm-thick films) and better temperature stability than common polysilicon films (≥ 200nm in thickness) at the same doping
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Our previous research work indicated that highly boron doped polysilicon nanofilms (≤100 nm in thickness) have higher gauge factor (the maximum is ~34 for 80 nm-thick films) and better temperature stability than common polysilicon films (≥ 200nm in thickness) at the same doping levels. Therefore, in order to further analyze the influence of deposition temperature on the film structure and piezoresistance performance, the piezoresistive sensitivity, piezoresistive linearity (PRL) and resistance time drift (RTD) of 80 nm-thick highly boron doped polysilicon nanofilms (PSNFs) with different deposition temperatures were studied here. The tunneling piezoresistive model was established to explain the relationship between the measured gauge factors (GFs) and deposition temperature. It was seen that the piezoresistance coefficient (PRC) of composite grain boundaries is higher than that of grains and the magnitude of GF is dependent on the resistivity of grain boundary (GB) barriers and the weight of the resistivity of composite GBs in the film resistivity. In the investigations on PRL and RTD, the interstitial-vacancy (IV) model was established to model GBs as the accumulation of IV pairs. And the recrystallization of metastable IV pairs caused by material deformation or current excitation is considered as the prime reason for piezoresistive nonlinearity (PRNL) and RTD. Finally, the optimal deposition temperature for the improvement of film performance and reliability is about 620 °C and the high temperature annealing is not very effective in improving the piezoresistive performance of PSNFs deposited at lower temperatures. Full article
Open AccessArticle Detection of Neolithic Settlements in Thessaly (Greece) Through Multispectral and Hyperspectral Satellite Imagery
Sensors 2009, 9(2), 1167-1187; doi:10.3390/s90201167
Received: 14 November 2008 / Revised: 16 February 2009 / Accepted: 20 February 2009 / Published: 23 February 2009
Cited by 32 | PDF Full-text (1871 KB) | HTML Full-text | XML Full-text
Abstract
Thessaly is a low relief region in Greece where hundreds of Neolithic settlements/tells called magoules were established from the Early Neolithic period until the Bronze Age (6,000 – 3,000 BC). Multi-sensor remote sensing was applied to the study area in order to evaluate
[...] Read more.
Thessaly is a low relief region in Greece where hundreds of Neolithic settlements/tells called magoules were established from the Early Neolithic period until the Bronze Age (6,000 – 3,000 BC). Multi-sensor remote sensing was applied to the study area in order to evaluate its potential to detect Neolithic settlements. Hundreds of sites were geo-referenced through systematic GPS surveying throughout the region. Data from four primary sensors were used, namely Landsat ETM, ASTER, EO1 - HYPERION and IKONOS. A range of image processing techniques were originally applied to the hyperspectral imagery in order to detect the settlements and validate the results of GPS surveying. Although specific difficulties were encountered in the automatic classification of archaeological features composed by a similar parent material with the surrounding landscape, the results of the research suggested a different response of each sensor to the detection of the Neolithic settlements, according to their spectral and spatial resolution. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Flexible Electronics Sensors for Tactile Multi-Touching
Sensors 2009, 9(2), 1188-1203; doi:10.3390/s9021188
Received: 12 February 2009 / Revised: 20 February 2009 / Accepted: 23 February 2009 / Published: 24 February 2009
Cited by 20 | PDF Full-text (406 KB) | HTML Full-text | XML Full-text
Abstract
Flexible electronics sensors for tactile applications in multi-touch sensing and large scale manufacturing were designed and fabricated. The sensors are based on polyimide substrates, with thixotropy materials used to print organic resistances and a bump on the top polyimide layer. The gap between
[...] Read more.
Flexible electronics sensors for tactile applications in multi-touch sensing and large scale manufacturing were designed and fabricated. The sensors are based on polyimide substrates, with thixotropy materials used to print organic resistances and a bump on the top polyimide layer. The gap between the bottom electrode layer and the resistance layer provides a buffer distance to reduce erroneous contact during large bending. Experimental results show that the top membrane with a bump protrusion and a resistance layer had a large deflection and a quick sensitive response. The bump and resistance layer provided a concentrated von Mises stress force and inertial force on the top membrane center. When the top membrane had no bump, it had a transient response delay time and took longer to reach steady-state. For printing thick structures of flexible electronics sensors, diffusion effects and dimensional shrinkages can be improved by using a paste material with a high viscosity. Linear algorithm matrixes with Gaussian elimination and control system scanning were used for multi-touch detection. Flexible electronics sensors were printed with a resistance thickness of about 32 µm and a bump thickness of about 0.2 mm. Feasibility studies show that printing technology is appropriate for large scale manufacturing, producing sensors at a low cost. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle SITHON: An Airborne Fire Detection System Compliant with Operational Tactical Requirements
Sensors 2009, 9(2), 1204-1220; doi:10.3390/s90201204
Received: 29 January 2009 / Revised: 19 February 2009 / Accepted: 19 February 2009 / Published: 24 February 2009
Cited by 6 | PDF Full-text (595 KB) | HTML Full-text | XML Full-text
Abstract
In response to the urging need of fire managers for timely information on fire location and extent, the SITHON system was developed. SITHON is a fully digital thermal imaging system, integrating INS/GPS and a digital camera, designed to provide timely positioned and projected
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In response to the urging need of fire managers for timely information on fire location and extent, the SITHON system was developed. SITHON is a fully digital thermal imaging system, integrating INS/GPS and a digital camera, designed to provide timely positioned and projected thermal images and video data streams rapidly integrated in the GIS operated by Crisis Control Centres. This article presents in detail the hardware and software components of SITHON, and demonstrates the first encouraging results of test flights over the Sithonia Peninsula in Northern Greece. It is envisaged that the SITHON system will be soon operated onboard various airborne platforms including fire brigade airplanes and helicopters as well as on UAV platforms owned and operated by the Greek Air Forces. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Improving Ship Detection with Polarimetric SAR based on Convolution between Co-polarization Channels
Sensors 2009, 9(2), 1221-1236; doi:10.3390/s90201221
Received: 31 December 2008 / Revised: 20 February 2009 / Accepted: 21 February 2009 / Published: 24 February 2009
Cited by 13 | PDF Full-text (1100 KB) | HTML Full-text | XML Full-text
Abstract
The convolution between co-polarization amplitude only data is studied to improve ship detection performance. The different statistical behaviors of ships and surrounding ocean are characterized a by two-dimensional convolution function (2D-CF) between different polarization channels. The convolution value of the ocean decreases relative
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The convolution between co-polarization amplitude only data is studied to improve ship detection performance. The different statistical behaviors of ships and surrounding ocean are characterized a by two-dimensional convolution function (2D-CF) between different polarization channels. The convolution value of the ocean decreases relative to initial data, while that of ships increases. Therefore the contrast of ships to ocean is increased. The opposite variation trend of ocean and ships can distinguish the high intensity ocean clutter from ships’ signatures. The new criterion can generally avoid mistaken detection by a constant false alarm rate detector. Our new ship detector is compared with other polarimetric approaches, and the results confirm the robustness of the proposed method. Full article
(This article belongs to the Special Issue Ocean Remote Sensing)
Open AccessArticle Combining Multiple Algorithms for Road Network Tracking from Multiple Source Remotely Sensed Imagery: a Practical System and Performance Evaluation
Sensors 2009, 9(2), 1237-1258; doi:10.3390/s90201237
Received: 31 October 2008 / Revised: 20 February 2009 / Accepted: 24 February 2009 / Published: 24 February 2009
Cited by 19 | PDF Full-text (843 KB) | HTML Full-text | XML Full-text
Abstract
In light of the increasing availability of commercial high-resolution imaging sensors, automatic interpretation tools are needed to extractroad features. Currently, many approaches for road extraction are available, but it is acknowledged that there is no single method that would be successful in extracting
[...] Read more.
In light of the increasing availability of commercial high-resolution imaging sensors, automatic interpretation tools are needed to extractroad features. Currently, many approaches for road extraction are available, but it is acknowledged that there is no single method that would be successful in extracting all types of roads from any remotely sensed imagery. In this paper, a novel classification of roads is proposed, based on both the roads’ geometrical, radiometric properties and the characteristics of the sensors. Subsequently, a general road tracking framework is proposed, and one or more suitable road trackers are designed or combined for each type of roads. Extensive experiments are performed to extract roads from aerial/satellite imagery, and the results show that a combination strategy can automatically extract more than 60% of the total roads from very high resolution imagery such as QuickBird and DMC images, with a time-saving of approximately 20%, and acceptable spatial accuracy. It is proven that a combination of multiple algorithms is more reliable, more efficient and more robust for extracting road networks from multiple-source remotely sensed imagery than the individual algorithms. Full article
(This article belongs to the Special Issue Sensor Algorithms)
Open AccessArticle A New Method for Node Fault Detection in Wireless Sensor Networks
Sensors 2009, 9(2), 1282-1294; doi:10.3390/s90201282
Received: 12 September 2008 / Revised: 16 February 2009 / Accepted: 17 February 2009 / Published: 24 February 2009
Cited by 82 | PDF Full-text (201 KB) | HTML Full-text | XML Full-text
Abstract
Wireless sensor networks (WSNs) are an important tool for monitoring distributed remote environments. As one of the key technologies involved in WSNs, node fault detection is indispensable in most WSN applications. It is well known that the distributed fault detection (DFD) scheme checks
[...] Read more.
Wireless sensor networks (WSNs) are an important tool for monitoring distributed remote environments. As one of the key technologies involved in WSNs, node fault detection is indispensable in most WSN applications. It is well known that the distributed fault detection (DFD) scheme checks out the failed nodes by exchanging data and mutually testing among neighbor nodes in this network., but the fault detection accuracy of a DFD scheme would decrease rapidly when the number of neighbor nodes to be diagnosed is small and the node’s failure ratio is high. In this paper, an improved DFD scheme is proposed by defining new detection criteria. Simulation results demonstrate that the improved DFD scheme performs well in the above situation and can increase the fault detection accuracy greatly. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)

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Open AccessReview Passive and Self-Powered Autonomous Sensors for Remote Measurements
Sensors 2009, 9(2), 943-960; doi:10.3390/s90200943
Received: 28 January 2009 / Revised: 11 February 2009 / Accepted: 11 February 2009 / Published: 13 February 2009
Cited by 25 | PDF Full-text (900 KB) | HTML Full-text | XML Full-text
Abstract
Autonomous sensors play a very important role in the environmental, structural, and medical fields. The use of this kind of systems can be expanded for several applications, for example in implantable devices inside the human body where it is impossible to use wires.
[...] Read more.
Autonomous sensors play a very important role in the environmental, structural, and medical fields. The use of this kind of systems can be expanded for several applications, for example in implantable devices inside the human body where it is impossible to use wires. Furthermore, they enable measurements in harsh or hermetic environments, such as under extreme heat, cold, humidity or corrosive conditions. The use of batteries as a power supply for these devices represents one solution, but the size, and sometimes the cost and unwanted maintenance burdens of replacement are important drawbacks. In this paper passive and self-powered autonomous sensors for harsh or hermetical environments without batteries are discussed. Their general architectures are presented. Sensing strategies, communication techniques and power management are analyzed. Then, general building blocks of an autonomous sensor are presented and the design guidelines that such a system must follow are given. Furthermore, this paper reports different proposed applications of autonomous sensors applied in harsh or hermetic environments: two examples of passive autonomous sensors that use telemetric communication are proposed, the first one for humidity measurements and the second for high temperatures. Other examples of self-powered autonomous sensors that use a power harvesting system from electromagnetic fields are proposed for temperature measurements and for airflow speeds. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)
Open AccessReview Recent Advances in Nanotechnology Applied to Biosensors
Sensors 2009, 9(2), 1033-1053; doi:10.3390/s90201033
Received: 8 December 2008 / Revised: 15 February 2009 / Accepted: 16 February 2009 / Published: 17 February 2009
Cited by 122 | PDF Full-text (651 KB) | HTML Full-text | XML Full-text
Abstract
In recent years there has been great progress the application of nanomaterials in biosensors. The importance of these to the fundamental development of biosensors has been recognized. In particular, nanomaterials such as gold nanoparticles, carbon nanotubes, magnetic nanoparticles and quantum dots have been
[...] Read more.
In recent years there has been great progress the application of nanomaterials in biosensors. The importance of these to the fundamental development of biosensors has been recognized. In particular, nanomaterials such as gold nanoparticles, carbon nanotubes, magnetic nanoparticles and quantum dots have been being actively investigated for their applications in biosensors, which have become a new interdisciplinary frontier between biological detection and material science. Here we review some of the main advances in this field over the past few years, explore the application prospects, and discuss the issues, approaches, and challenges, with the aim of stimulating a broader interest in developing nanomaterial-based biosensors and improving their applications in disease diagnosis and food safety examination. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessReview Improvement of the Accuracy of InSAR Image Co-Registration Based On Tie Points – A Review
Sensors 2009, 9(2), 1259-1281; doi:10.3390/s90201259
Received: 12 January 2009 / Revised: 11 February 2009 / Accepted: 17 February 2009 / Published: 24 February 2009
Cited by 7 | PDF Full-text (2970 KB) | HTML Full-text | XML Full-text
Abstract
Interferometric Synthetic Aperture Radar (InSAR) is a new measurement technology, making use of the phase information contained in the Synthetic Aperture Radar (SAR) images. InSAR has been recognized as a potential tool for the generation of digital elevation models (DEMs) and the measurement
[...] Read more.
Interferometric Synthetic Aperture Radar (InSAR) is a new measurement technology, making use of the phase information contained in the Synthetic Aperture Radar (SAR) images. InSAR has been recognized as a potential tool for the generation of digital elevation models (DEMs) and the measurement of ground surface deformations. However, many critical factors affect the quality of InSAR data and limit its applications. One of the factors is InSAR data processing, which consists of image co-registration, interferogram generation, phase unwrapping and geocoding. The co-registration of InSAR images is the first step and dramatically influences the accuracy of InSAR products. In this paper, the principle and processing procedures of InSAR techniques are reviewed. One of important factors, tie points, to be considered in the improvement of the accuracy of InSAR image co-registration are emphatically reviewed, such as interval of tie points, extraction of feature points, window size for tie point matching and the measurement for the quality of an interferogram. Full article
(This article belongs to the Special Issue Synthetic Aperture Radar (SAR))

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