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Sensors, Volume 7, Issue 9 (September 2007), Pages 1667-2027

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Research

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Open AccessArticle Mechanosensor Channels in Mammalian Somatosensory Neurons
Sensors 2007, 7(9), 1667-1682; doi:10.3390/s7091667
Received: 10 August 2007 / Accepted: 31 August 2007 / Published: 3 September 2007
Cited by 8 | PDF Full-text (285 KB) | HTML Full-text | XML Full-text
Abstract
Mechanoreceptive sensory neurons innervating the skin, skeletal muscles andviscera signal both innocuous and noxious information necessary for proprioception, touchand pain. These neurons are responsible for the transduction of mechanical stimuli intoaction potentials that propagate to the central nervous system. The ability of these
[...] Read more.
Mechanoreceptive sensory neurons innervating the skin, skeletal muscles andviscera signal both innocuous and noxious information necessary for proprioception, touchand pain. These neurons are responsible for the transduction of mechanical stimuli intoaction potentials that propagate to the central nervous system. The ability of these cells todetect mechanical stimuli impinging on them relies on the presence of mechanosensitivechannels that transduce the external mechanical forces into electrical and chemical signals.Although a great deal of information regarding the molecular and biophysical properties ofmechanosensitive channels in prokaryotes has been accumulated over the past two decades,less is known about the mechanosensitive channels necessary for proprioception and thesenses of touch and pain. This review summarizes the most pertinent data onmechanosensitive channels of mammalian somatosensory neurons, focusing on theirproperties, pharmacology and putative identity. Full article
(This article belongs to the Special Issue Physiological Sensing)
Open AccessArticle The Relative Performance of NDIR-based Sensors in the Near Real-time Analysis of CO2 in Air
Sensors 2007, 7(9), 1683-1696; doi:10.3390/s7091683
Received: 10 July 2007 / Accepted: 27 August 2007 / Published: 3 September 2007
Cited by 19 | PDF Full-text (1231 KB) | HTML Full-text | XML Full-text
Abstract
In this study, the reliability of NDIR-based sensors was explored by evaluatingthe comparability between measurement systems in the near real-time analysis of CO2. Forthis purpose, replicate analyses were performed using sensors of two different model types(H-550 and B-530, ELT Company, Korea).
[...] Read more.
In this study, the reliability of NDIR-based sensors was explored by evaluatingthe comparability between measurement systems in the near real-time analysis of CO2. Forthis purpose, replicate analyses were performed using sensors of two different model types(H-550 and B-530, ELT Company, Korea). Three replicate data of each sensor typecollected continuously by side-by-side analysis in three second intervals (a duration of 304hour) were evaluated for the relative performance of NDIR sensors. The reproducibility ofsensors, when assessed by relative standard error (RSE %) values of all sensor units,showed moderate changes with time with the overall mean of 2.33%. When CO2measurements from all NDIR sensor units were evaluated by correlation analysis, theresults showed strong comparability, regardless of the model type. The overall results ofthis study suggest that NDIR sensors are reliable enough to produce highly comparabledata at least in a relative sense. Full article
Open AccessArticle High Resolution Marine Magnetic Survey of Shallow Water Littoral Area
Sensors 2007, 7(9), 1697-1712; doi:10.3390/s7091697
Received: 29 August 2007 / Accepted: 3 September 2007 / Published: 3 September 2007
Cited by 8 | PDF Full-text (1346 KB) | HTML Full-text | XML Full-text
Abstract
The purpose of this paper is to present a system developed for detection andaccurate mapping of ferro-metallic objects buried below the seabed in shallow waters. Thesystem comprises a precise magnetic gradiometer and navigation subsystem, both installedon a non-magnetic catamaran towed by a low-magnetic
[...] Read more.
The purpose of this paper is to present a system developed for detection andaccurate mapping of ferro-metallic objects buried below the seabed in shallow waters. Thesystem comprises a precise magnetic gradiometer and navigation subsystem, both installedon a non-magnetic catamaran towed by a low-magnetic interfering boat. In addition wepresent the results of a marine survey of a near-shore area in the vicinity of Atlit, a townsituated on the Mediterranean coast of Israel, about 15 km south of Haifa. The primarypurpose of the survey was to search for a Harvard airplane that crashed into the sea in 1960.A magnetic map of the survey area (3.5 km2 on a 0.5 m grid) was created revealing theanomalies at sub-meter accuracy. For each investigated target location a correspondingferro-metallic item was dug out, one of which turned to be very similar to a part of thecrashed airplane. The accuracy of location was confirmed by matching the position of theactual dug artifacts with the magnetic map within a range of ± 1 m, in a water depth of 9 m. Full article
Open AccessArticle Modeling of Photoinduced Deformation in Silicon Microcantilever
Sensors 2007, 7(9), 1713-1719; doi:10.3390/s7091713
Received: 24 July 2007 / Accepted: 27 August 2007 / Published: 3 September 2007
Cited by 9 | PDF Full-text (308 KB) | HTML Full-text | XML Full-text
Abstract
A model for prediction the photostriction effect in silicon microcantilevers is built up based on the fundamentals of mechanics and semiconductor physics. By considering the spatial distribution and surface recombination of photoinduced carriers in silicon, the model interprets the cause of the photoinduced
[...] Read more.
A model for prediction the photostriction effect in silicon microcantilevers is built up based on the fundamentals of mechanics and semiconductor physics. By considering the spatial distribution and surface recombination of photoinduced carriers in silicon, the model interprets the cause of the photoinduced bending. The results from our model much more closely approximate the experimental values than the former model built up by Datskos, Rajic and Datskou [1](APL, Vol.73 (1998) No.16, pp 3219-2321), represented by the reduction of the error between calculation and measurement from 25 times to 0.85 times. Full article
Open AccessArticle Reliability of a MEMS Actuator Improved by Spring Corner Designs and Reshaped Driving Waveforms
Sensors 2007, 7(9), 1720-1730; doi:10.3390/s7091720
Received: 19 July 2007 / Accepted: 31 August 2007 / Published: 3 September 2007
Cited by 9 | PDF Full-text (758 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we report spring corner designs and driving waveforms to improve the reliability for a MEMS (Micro-Electro-Mechanical System) actuator. In order to prevent the stiction problems, no stopper or damping absorber is adopted. Therefore, an actuator could travel long distance by
[...] Read more.
In this paper, we report spring corner designs and driving waveforms to improve the reliability for a MEMS (Micro-Electro-Mechanical System) actuator. In order to prevent the stiction problems, no stopper or damping absorber is adopted. Therefore, an actuator could travel long distance by electromagnetic force without any object in moving path to absorb excess momentum. Due to long displacement and large mass, springs of MEMS actuators tend to crack from weak points with high stress concentration and this situation degrades reliability performance. Stress distribution over different spring designs were simulated and a serpentine spring with circular and wide corner design was chosen due to its low stress concentration. This design has smaller stress concentration versus displacement. Furthermore, the resonant frequencies are removed from the driving waveform based on the analysis of discrete Fourier transfer function. The reshaped waveform not only shortens actuator switching time, but also ensures that the spring is in a small displacement region without overshooting so that the maximum stress is kept below 200 MPa. The experimental results show that the MEMS device designed by theses principles can survive 500 g (gravity acceleration) shock test and pass 150 million switching cycles without failure. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)
Open AccessArticle Cross-Reactive Sensor Array for Metal Ion Sensing Based on Fluorescent SAMs
Sensors 2007, 7(9), 1731-1746; doi:10.3390/s7091731
Received: 20 August 2007 / Accepted: 4 September 2007 / Published: 5 September 2007
Cited by 24 | PDF Full-text (1300 KB) | HTML Full-text | XML Full-text
Abstract
Fluorescent self assembled monolayers (SAMs) on glass were previouslydeveloped in our group as new sensing materials for metal ions. These fluorescent SAMs arecomprised by fluorophores and small molecules sequentially deposited on a monolayer onglass. The preorganization provided by the surface avoids the need
[...] Read more.
Fluorescent self assembled monolayers (SAMs) on glass were previouslydeveloped in our group as new sensing materials for metal ions. These fluorescent SAMs arecomprised by fluorophores and small molecules sequentially deposited on a monolayer onglass. The preorganization provided by the surface avoids the need for complex receptordesign, allowing for a combinatorial approach to sensing systems based on small molecules.Now we show the fabrication of an effective microarray for the screening of metal ions andthe properties of the sensing SAMs. A collection of fluorescent sensing SAMs wasgenerated by combinatorial methods and immobilized on the glass surfaces of a custom-made 140 well microtiter-plate. The resulting libraries are easily measured and show variedresponses to a series cations such as Cu2+ , Co2+ , Pb2+ , Ca2+ and Zn2+ . These surfaces are notdesigned to complex selectively a unique analyte but rather they are intended to producefingerprint type responses to a range of analytes by less specific interactions. The unselectiveresponses of the library to the presence of different cations generate a characteristic patternfor each analyte, a “finger print” response. Full article
(This article belongs to the Special Issue Supramolecular Sensors)
Open AccessArticle A Wireless, Passive Sensor for Quantifying Packaged Food Quality
Sensors 2007, 7(9), 1747-1756; doi:10.3390/s7091747
Received: 23 August 2007 / Accepted: 28 August 2007 / Published: 5 September 2007
Cited by 60 | PDF Full-text (662 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes the fabrication of a wireless, passive sensor based on aninductive-capacitive resonant circuit, and its application for in situ monitoring of thequality of dry, packaged food such as cereals, and fried and baked snacks. The sensor ismade of a planar inductor
[...] Read more.
This paper describes the fabrication of a wireless, passive sensor based on aninductive-capacitive resonant circuit, and its application for in situ monitoring of thequality of dry, packaged food such as cereals, and fried and baked snacks. The sensor ismade of a planar inductor and capacitor printed on a paper substrate. To monitor foodquality, the sensor is embedded inside the food package by adhering it to the package’sinner wall; its response is remotely detected through a coil connected to a sensor reader. Asfood quality degrades due to increasing humidity inside the package, the paper substrateabsorbs water vapor, changing the capacitor’s capacitance and the sensor’s resonantfrequency. Therefore, the taste quality of the packaged food can be indirectly determined bymeasuring the change in the sensor’s resonant frequency. The novelty of this sensortechnology is its wireless and passive nature, which allows in situ determination of foodquality. In addition, the simple fabrication process and inexpensive sensor material ensure alow sensor cost, thus making this technology economically viable. Full article
Open AccessCommunication Study of the origin of bending induced by bimetallic effect on microcantilever
Sensors 2007, 7(9), 1757-1765; doi:10.3390/s7091757
Received: 30 July 2007 / Accepted: 4 September 2007 / Published: 5 September 2007
Cited by 29 | PDF Full-text (173 KB) | HTML Full-text | XML Full-text
Abstract
An analytical model for predicting the deflection and force of a bimaterialcantilever is presented. We introduce the clamping effect characterised by an axial loadupon temperature changes. This new approach predicts a non linear thermal dependence ofcantilever strain. A profilometry technique was used to
[...] Read more.
An analytical model for predicting the deflection and force of a bimaterialcantilever is presented. We introduce the clamping effect characterised by an axial loadupon temperature changes. This new approach predicts a non linear thermal dependence ofcantilever strain. A profilometry technique was used to measure the thermal strain.Comparison with experimental results is used to verify the model. The concordance of theanalytical model presented with experimental measurements is better than 10% Full article
Open AccessArticle Time Series Forecasting Energy-efficient Organization of Wireless Sensor Networks
Sensors 2007, 7(9), 1766-1792; doi:10.3390/s7091766
Received: 9 August 2007 / Accepted: 4 September 2007 / Published: 5 September 2007
Cited by 12 | PDF Full-text (699 KB) | HTML Full-text | XML Full-text
Abstract
Due to their wide potential applications, wireless sensor networks have recentlyreceived tremendous attention. The strict energy constraints of sensor nodes result in thegreat challenges for energy efficiency. This paper investigates the energy efficiency problemand proposes an energy-efficient organization method with time series forecasting.
[...] Read more.
Due to their wide potential applications, wireless sensor networks have recentlyreceived tremendous attention. The strict energy constraints of sensor nodes result in thegreat challenges for energy efficiency. This paper investigates the energy efficiency problemand proposes an energy-efficient organization method with time series forecasting. Theorganization of wireless sensor networks is formulated for target tracking. Target model,multi-sensor model and energy model are defined accordingly. For the target trackingapplication, target localization is achieved by collaborative sensing with multi-sensor fusion.The historical localization results are utilized for adaptive target trajectory forecasting.Empirical mode decomposition is implemented to extract the inherent variation modes in thetime series of a target trajectory. Future target position is derived from autoregressivemoving average (ARMA) models, which forecast the decomposition components,respectively. Moreover, the energy-efficient organization method is presented to enhance theenergy efficiency of wireless sensor networks. The sensor nodes implement sensing tasksaccording to the probability awakening in a distributed manner. When the sensor nodestransfer their observations to achieve data fusion, the routing scheme is obtained by antcolony optimization. Thus, both the operation and communication energy consumption canbe minimized. Experimental results verify that the combination of the ARMA model andempirical mode decomposition can estimate the target position efficiently and energy savingis achieved by the proposed organization method in wireless sensor networks. Full article
Open AccessArticle Energy-efficient Optimization of Reorganization-Enabled Wireless Sensor Networks
Sensors 2007, 7(9), 1793-1816; doi:10.3390/s7091793
Received: 9 August 2007 / Accepted: 4 September 2007 / Published: 5 September 2007
Cited by 8 | PDF Full-text (826 KB) | HTML Full-text | XML Full-text
Abstract
This paper studies the target tracking problem in wireless sensor networkswhere sensor nodes are deployed randomly. To achieve tracking accuracy constrained byenergy consumption, an energy-efficient optimization approach that enablesreorganization of wireless sensor networks is proposed. The approach includes threephases which are related to
[...] Read more.
This paper studies the target tracking problem in wireless sensor networkswhere sensor nodes are deployed randomly. To achieve tracking accuracy constrained byenergy consumption, an energy-efficient optimization approach that enablesreorganization of wireless sensor networks is proposed. The approach includes threephases which are related to prediction, localization and recovery, respectively. A particlefilter algorithm is implemented on the sink node to forecast the future movement of thetarget in the first prediction phase. Upon the completion of this phase, the most energyefficient sensor nodes are awakened to collaboratively locate the target. Energy efficiencyis evaluated by the ratio of mutual information to energy consumption. The recoveryphase is needed to improve the robustness of the approach. It is performed when thetarget is missed because of the incorrect predicted target location. In order to recapture thetarget by awakening additional sensor nodes as few as possible, a genetic-algorithm-basedmechanism is introduced to cover the recovery area. We show that the proposed approachhas excellent tracking performance. Moreover, it can efficiently reduce energyconsumption, prolong network lifetime and reduce network overheads. Full article
Open AccessArticle Multi-scale Analysis of MEMS Sensors Subject to Drop Impacts
Sensors 2007, 7(9), 1817-1833; doi:10.3390/s7081817
Received: 30 August 2007 / Accepted: 6 September 2007 / Published: 7 September 2007
Cited by 35 | PDF Full-text (1199 KB) | HTML Full-text | XML Full-text
Abstract
The effect of accidental drops on MEMS sensors are examined within the frame-work of a multi-scale finite element approach. With specific reference to a polysilicon MEMSaccelerometer supported by a naked die, the analysis is decoupled into macro-scale (at dielength-scale) and meso-scale (at MEMS
[...] Read more.
The effect of accidental drops on MEMS sensors are examined within the frame-work of a multi-scale finite element approach. With specific reference to a polysilicon MEMSaccelerometer supported by a naked die, the analysis is decoupled into macro-scale (at dielength-scale) and meso-scale (at MEMS length-scale) simulations, accounting for the verysmall inertial contribution of the sensor to the overall dynamics of the device. Macro-scaleanalyses are adopted to get insights into the link between shock waves caused by the impactagainst a target surface and propagating inside the die, and the displacement/acceleration his-tories at the MEMS anchor points. Meso-scale analyses are adopted to detect the most stresseddetails of the sensor and to assess whether the impact can lead to possible localized failures.Numerical results show that the acceleration at sensor anchors cannot be considered an ob-jective indicator for drop severity. Instead, accurate analyses at sensor level are necessary toestablish how MEMS can fail because of drops. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)
Open AccessArticle Measurement of the Mass and Rigidity of Adsorbates on a Microcantilever Sensor
Sensors 2007, 7(9), 1834-1845; doi:10.3390/s7091834
Received: 27 July 2007 / Accepted: 6 September 2007 / Published: 7 September 2007
Cited by 15 | PDF Full-text (362 KB) | HTML Full-text | XML Full-text
Abstract
When microcantilevers are used in the dynamic mode, the resonance shift uponmaterial adsorption depends on the position of the adsorbate along the microcantilever. Wehave previously described that the adsorbate stiffness needs to be considered in addition toits mass in order to correctly interpret
[...] Read more.
When microcantilevers are used in the dynamic mode, the resonance shift uponmaterial adsorption depends on the position of the adsorbate along the microcantilever. Wehave previously described that the adsorbate stiffness needs to be considered in addition toits mass in order to correctly interpret the resonance shift. Here we describe a method thatallows obtaining the Young’s modulus of the adsorbed bacteria derived from themeasurement of the frequency shift when adsorbates are placed close to the clampingregion. As a model system we have used E. Coli bacteria deposited on the cantileversurface by the ink-jet technique. We demonstrate that the correct information aboutadsorbed mass can be extracted by recording the cantilever profile and its resonanceresponse. Also, the position and extent of adsorbates is determined by recording themicrocantilever profile. We use a theoretical model based on the Euler – Bernouilliequation for a beam with both mass and flexural rigidity local increase due to the depositedmaterial. Full article
Open AccessArticle Electrodeposited and Sol-gel Precipitated p-type SrTi1-xFexO3-δ Semiconductors for Gas Sensing
Sensors 2007, 7(9), 1871-1886; doi:10.3390/s7091871
Received: 9 August 2007 / Accepted: 8 September 2007 / Published: 7 September 2007
Cited by 17 | PDF Full-text (445 KB) | HTML Full-text | XML Full-text
Abstract
In the present contribution, three methods for the preparation of nanoscaledSrTi1-xFexO3-δ sensor films for hydrocarbon sensing were investigated. Besides screen-printed thick films based on sol-precipitated nanopowders, two novel synthesis methods,electrospinning and electrospraying, were tested successfully. All of these
[...] Read more.
In the present contribution, three methods for the preparation of nanoscaledSrTi1-xFexO3-δ sensor films for hydrocarbon sensing were investigated. Besides screen-printed thick films based on sol-precipitated nanopowders, two novel synthesis methods,electrospinning and electrospraying, were tested successfully. All of these sensor devicesshowed improved sensor functionality in comparison to conventional microscaled thickfilms. In order to explain the impact of the enhanced surface-to-volume ratio on sensorproperties in a quantitative way, a mechanistic model was applied to micro- and nanoscaleddevices. In contrast to the conventional diffusion-reaction model that has been proposed forn-type semiconducting sensors, it contained novel approaches with respect to themicroscopic mechanism. With very few fit variables, the present model was found torepresent well sensor functionality of p-type conducting SrTi0.8Fe0.2O3-δ films. In additionto the temperature dependency of the sensor response, the effect of the specific surface areaon the sensor response was predicted. Full article
Open AccessArticle The Investigation of a Shape Memory Alloy Micro-Damper for MEMS Applications
Sensors 2007, 7(9), 1887-1900; doi:10.3390/s7091887
Received: 6 August 2007 / Accepted: 10 September 2007 / Published: 11 September 2007
Cited by 22 | PDF Full-text (365 KB) | HTML Full-text | XML Full-text
Abstract
Some shape memory alloys like NiTi show noticeable high damping property inpseudoelastic range. Due to its unique characteristics, a NiTi alloy is commonly used forpassive damping applications, in which the energy may be dissipated by the conversion frommechanical to thermal energy. This study
[...] Read more.
Some shape memory alloys like NiTi show noticeable high damping property inpseudoelastic range. Due to its unique characteristics, a NiTi alloy is commonly used forpassive damping applications, in which the energy may be dissipated by the conversion frommechanical to thermal energy. This study presents a shape memory alloy based micro-damper, which exploits the pseudoelasticity of NiTi wires for energy dissipation. Themechanical model and functional principle of the micro-damper are explained in detail.Moreover, the mechanical behavior of NiTi wires subjected to various temperatures, strainrates and strain amplitudes is observed. Resulting from those experimental results, thedamping properties of the micro-damper involving secant stiffness, energy dissipation andloss factor are analyzed. The result indicates the proposed NiTi based micro-damper exhibitsgood energy dissipation ability, compared with conventional materials damper. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)
Open AccessArticle Hybrid Integrated Silicon Microfluidic Platform for Fluorescence Based Biodetection
Sensors 2007, 7(9), 1901-1915; doi:10.3390/s7091901
Received: 24 August 2007 / Accepted: 10 September 2007 / Published: 11 September 2007
Cited by 11 | PDF Full-text (1040 KB) | HTML Full-text | XML Full-text
Abstract
The desideratum to develop a fully integrated Lab-on-a-chip device capable ofrapid specimen detection for high throughput in-situ biomedical diagnoses and Point-of-Care testing applications has called for the integration of some of the novel technologiessuch as the microfluidics, microphotonics, immunoproteomics and Micro ElectroMechanical Systems
[...] Read more.
The desideratum to develop a fully integrated Lab-on-a-chip device capable ofrapid specimen detection for high throughput in-situ biomedical diagnoses and Point-of-Care testing applications has called for the integration of some of the novel technologiessuch as the microfluidics, microphotonics, immunoproteomics and Micro ElectroMechanical Systems (MEMS). In the present work, a silicon based microfluidic device hasbeen developed for carrying out fluorescence based immunoassay. By hybrid attachment ofthe microfluidic device with a Spectrometer-on-chip, the feasibility of synthesizing anintegrated Lab-on-a-chip type device for fluorescence based biosensing has beendemonstrated. Biodetection using the microfluidic device has been carried out usingantigen sheep IgG and Alexafluor-647 tagged antibody particles and the experimentalresults prove that silicon is a compatible material for the present application given thevarious advantages it offers such as cost-effectiveness, ease of bulk microfabrication,superior surface affinity to biomolecules, ease of disposability of the device etc., and is thussuitable for fabricating Lab-on-a-chip type devices. Full article
(This article belongs to the Special Issue Optical Biosensors)
Open AccessArticle The Airborne Visible / Infrared Imaging Spectrometer AVIS: Design, Characterization and Calibration
Sensors 2007, 7(9), 1934-1953; doi:10.3390/s7091934
Received: 31 July 2007 / Accepted: 13 September 2007 / Published: 14 September 2007
Cited by 18 | PDF Full-text (5925 KB) | HTML Full-text | XML Full-text
Abstract
The Airborne Visible / Infrared imaging Spectrometer AVIS is a hyperspectralimager designed for environmental monitoring purposes. The sensor, which wasconstructed entirely from commercially available components, has been successfullydeployed during several experiments between 1999 and 2007. We describe the instrumentdesign and present the results
[...] Read more.
The Airborne Visible / Infrared imaging Spectrometer AVIS is a hyperspectralimager designed for environmental monitoring purposes. The sensor, which wasconstructed entirely from commercially available components, has been successfullydeployed during several experiments between 1999 and 2007. We describe the instrumentdesign and present the results of laboratory characterization and calibration of the system’ssecond generation, AVIS-2, which is currently being operated. The processing of the datais described and examples of remote sensing reflectance data are presented. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
Open AccessArticle Development of a Surface Plasmon Resonance n-dodecane Vapor Sensor
Sensors 2007, 7(9), 1954-1961; doi:10.3390/s7091954
Received: 7 June 2007 / Accepted: 17 September 2007 / Published: 21 September 2007
Cited by 4 | PDF Full-text (265 KB) | HTML Full-text | XML Full-text
Abstract
Using a high density polyethylene thin film over gold layer, a Surface PlasmonResonance sensor for detecting n-dodecane vapor is developed. Preliminary results will bepresented, showing that samples in the range of a few hundred ppm(V) of n-dodecanevapor in butane gas can be sensed.
[...] Read more.
Using a high density polyethylene thin film over gold layer, a Surface PlasmonResonance sensor for detecting n-dodecane vapor is developed. Preliminary results will bepresented, showing that samples in the range of a few hundred ppm(V) of n-dodecanevapor in butane gas can be sensed. Also, studying the response as a function of time, it isdemonstrated that the sensing process is quickly reversible. Full article
(This article belongs to the Special Issue Optical Biosensors)
Open AccessArticle Global Distribution and Density of Constructed Impervious Surfaces
Sensors 2007, 7(9), 1962-1979; doi:10.3390/s7091962
Received: 30 August 2007 / Accepted: 13 September 2007 / Published: 21 September 2007
Cited by 135 | PDF Full-text (4904 KB) | HTML Full-text | XML Full-text
Abstract
We present the first global inventory of the spatial distribution and density ofconstructed impervious surface area (ISA). Examples of ISA include roads, parking lots,buildings, driveways, sidewalks and other manmade surfaces. While high spatialresolution is required to observe these features, the new product reports
[...] Read more.
We present the first global inventory of the spatial distribution and density ofconstructed impervious surface area (ISA). Examples of ISA include roads, parking lots,buildings, driveways, sidewalks and other manmade surfaces. While high spatialresolution is required to observe these features, the new product reports the estimateddensity of ISA on a one-km2 grid based on two coarse resolution indicators of ISA – thebrightness of satellite observed nighttime lights and population count. The model wascalibrated using 30-meter resolution ISA of the USA from the U.S. Geological Survey.Nominally the product is for the years 2000-01 since both the nighttime lights andreference data are from those two years. We found that 1.05% of the United States landarea is impervious surface (83,337 km2) and 0.43 % of the world’s land surface (579,703km2) is constructed impervious surface. China has more ISA than any other country(87,182 km2), but has only 67 m2 of ISA per person, compared to 297 m2 per person in theUSA. The distribution of ISA in the world’s primary drainage basins indicates that watersheds damaged by ISA are primarily concentrated in the USA, Europe, Japan, China and India. The authors believe the next step for improving the product is to include reference ISA data from many more areas around the world. Full article
(This article belongs to the Special Issue Remote Sensing of Land Surface Properties, Patterns and Processes)
Open AccessArticle Models of Hydrogel Swelling with Applications to Hydration Sensing
Sensors 2007, 7(9), 1980-1991; doi:10.3390/s7091980
Received: 7 September 2007 / Accepted: 21 September 2007 / Published: 25 September 2007
Cited by 14 | PDF Full-text (227 KB) | HTML Full-text | XML Full-text
Abstract
Hydrogels, polymers and various other composite materials may be used insensing applications in which the swelling or de-swelling of the material in response tosome analyte is converted via a transducer to a measurable signal. In this paper, we analyzemodels used to predict the
[...] Read more.
Hydrogels, polymers and various other composite materials may be used insensing applications in which the swelling or de-swelling of the material in response tosome analyte is converted via a transducer to a measurable signal. In this paper, we analyzemodels used to predict the swelling behavior of hydrogels that may be used in applicationsrelated to hydration monitoring in humans. Preliminary experimental data related toosmolality changes in fluids is presented to compare to the theoretical models. Overall,good experimental agreement with the models is achieved. Full article
Open AccessArticle Integrated Love Wave Device Dedicated to Biomolecular Interactions Measurements in Aqueous Media
Sensors 2007, 7(9), 1992-2003; doi:10.3390/s7091992
Received: 13 July 2007 / Accepted: 11 September 2007 / Published: 25 September 2007
Cited by 5 | PDF Full-text (902 KB) | HTML Full-text | XML Full-text
Abstract
Mass-sensitive electro-acoustic devices such as surface acoustic wave (SAW)micro-balances, capable to operate with aqueous media are particularly favorable for thedevelopment of biosensors. Their dimensions and physical properties offer a large potentialin biological fluid investigations, especially for measuring physical phenomenon (massdeposition, adsorption, pressure...). In
[...] Read more.
Mass-sensitive electro-acoustic devices such as surface acoustic wave (SAW)micro-balances, capable to operate with aqueous media are particularly favorable for thedevelopment of biosensors. Their dimensions and physical properties offer a large potentialin biological fluid investigations, especially for measuring physical phenomenon (massdeposition, adsorption, pressure...). In this work, we propose a specific gratingconfiguration to lower the influence of viscosity of fluids which reduces the signal dynamicsof the surface wave transducers. A dedicated liquid cell also has been developed to isolatethe electro-active part of the device. The fabrication of the cell is achieved using theSU-8TMphoto-resist, allowing for manufacturing thick structures preventing any contact between thetested liquids and the transducers. Furthermore, the sensing area has been optimized tooptimize the sensor gravimetric sensitivity. The operation of the sensor is illustrated bydetecting bovine serum albumin (BSA) adsorption in the sensing area. Full article
Open AccessArticle Development of Standardization and Management System for the Severity of Unpaved Test Courses
Sensors 2007, 7(9), 2004-2027; doi:10.3390/s7092004
Received: 24 August 2007 / Accepted: 24 September 2007 / Published: 26 September 2007
Cited by 5 | PDF Full-text (1585 KB) | HTML Full-text | XML Full-text
Abstract
The vibration environment essentially accompanied by vehicle operation on theground is determined by the shape of road surface, which is called as profile. This paperfocuses on the development of profile measurement and severity analysis system forunpaved test courses. In general, the profile and
[...] Read more.
The vibration environment essentially accompanied by vehicle operation on theground is determined by the shape of road surface, which is called as profile. This paperfocuses on the development of profile measurement and severity analysis system forunpaved test courses. In general, the profile and severity of unpaved road is an importantissue in the reliability of endurance test. In order to measure and maintain unpaved roadprofile and severity, it is necessary to develop a profilometer system. The developedprofilometer system is composed of data processing computer, power unit, air compressorand sensors(encoder, vertical gyro and laser displacement). This study presents themeasuring system configuration, measurement principle of road profile and analysismethod of road characteristics used at CPG (Chang-won Proving Ground) for this purpose.In order to standardize and manage the severity of unpaved test courses, neural network isapplied Full article

Review

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Open AccessReview A Compact Laboratory Spectro-Goniometer (CLabSpeG) to Assess the BRDF of Materials. Presentation, Calibration and Implementation on Fagus sylvatica L. Leaves
Sensors 2007, 7(9), 1846-1870; doi:10.3390/s7091846
Received: 2 August 2007 / Accepted: 6 September 2007 / Published: 7 September 2007
Cited by 15 | PDF Full-text (706 KB) | HTML Full-text | XML Full-text
Abstract
The design and calibration of a new hyperspectral Compact Laboratory Spectro-Goniometer (CLabSpeG) is presented. CLabSpeG effectively measures the bidirectionalreflectance Factor (BRF) of a sample, using a halogen light source and an AnalyticalSpectral Devices (ASD) spectroradiometer. The apparatus collects 4356 reflectance datareadings covering the
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The design and calibration of a new hyperspectral Compact Laboratory Spectro-Goniometer (CLabSpeG) is presented. CLabSpeG effectively measures the bidirectionalreflectance Factor (BRF) of a sample, using a halogen light source and an AnalyticalSpectral Devices (ASD) spectroradiometer. The apparatus collects 4356 reflectance datareadings covering the spectrum from 350 nm to 2500 nm by independent positioning of thesensor, sample holder, and light source. It has an azimuth and zenith resolution of 30 and15 degrees, respectively. CLabSpeG is used to collect BRF data and extract BidirectionalReflectance Distribution Function (BRDF) data of non-isotropic vegetation elements suchas bark, soil, and leaves. Accurate calibration has ensured robust geometric accuracy of theapparatus, correction for the conicality of the light source, while sufficient radiometricstability and repeatability between measurements are obtained. The bidirectionalreflectance data collection is automated and remotely controlled and takes approximatelytwo and half hours for a BRF measurement cycle over a full hemisphere with 125 cmradius and 2.4 minutes for a single BRF acquisition. A specific protocol for vegetative leafcollection and measurement was established in order to investigate the possibility to extractBRDF values from Fagus sylvatica L. leaves under laboratory conditions. Drying leafeffects induce a reflectance change during the BRF measurements due to the laboratorySensors 2007, 7 1847 illumination source. Therefore, the full hemisphere could not be covered with one leaf. Instead 12 BRF measurements per leaf were acquired covering all azimuth positions for a single light source zenith position. Data are collected in radiance format and reflectance is calculated by dividing the leaf cycle measurement with a radiance cycle of a Spectralon reference panel, multiplied by a Spectralon reflectance correction factor and a factor to correct for the conical effect of the light source. BRF results of measured leaves are presented. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
Open AccessReview Wetland Restoration Response Analysis using MODIS and Groundwater Data
Sensors 2007, 7(9), 1916-1933; doi:10.3390/s7091916
Received: 31 August 2007 / Accepted: 7 September 2007 / Published: 14 September 2007
Cited by 13 | PDF Full-text (2692 KB) | HTML Full-text | XML Full-text
Abstract
Vegetation cover and groundwater level changes over the period of restorationare the two most important indicators of the level of success in wetland ecohydrologicalrestoration. As a result of the regular presence of water and dense vegetation, the highestevapotranspiration (latent heat) rates usually occur
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Vegetation cover and groundwater level changes over the period of restorationare the two most important indicators of the level of success in wetland ecohydrologicalrestoration. As a result of the regular presence of water and dense vegetation, the highestevapotranspiration (latent heat) rates usually occur within wetlands. Vegetation cover andevapotranspiration of large areas of restoration like that of Kissimmee River basin, SouthFlorida will be best estimated using remote sensing technique than point measurements.Kissimmee River basin has been the area of ecological restoration for some years. Thecurrent ecohydrological restoration activities were evaluated through fractional vegetationcover (FVC) changes and latent heat flux using Moderate Resolution ImagingSpectroradiometer (MODIS) data. Groundwater level data were also analyzed for selectedeight groundwater monitoring wells in the basin. Results have shown that the averagefractional vegetation cover and latent heat along 10 km buffer of Kissimmee River betweenLake Kissimmee and Lake Okeechobee was higher in 2004 than in 2000. It is evident thatover the 5-year period of time, vegetated and areas covered with wetlands have increasedsignificantly especially along the restoration corridor. Analysis of groundwater level data(2000-2004) from eight monitoring wells showed that, the average monthly level ofgroundwater was increased by 20 cm and 34 cm between 2000 and 2004, and 2000 and2003, respectively. This change was more evident for wells along the river. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)

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