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Sensors, Volume 7, Issue 11 (November 2007) – 36 articles , Pages 2492-3011

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Article
Effect of Electrical Contact on the Contact Residual Stress of a Microrelay Switch
Sensors 2007, 7(11), 2997-3011; https://doi.org/10.3390/s7112997 - 26 Nov 2007
Cited by 2 | Viewed by 7707
Abstract
This paper investigates the effect of electrical contact on the thermal contactstress of a microrelay switch. A three-dimensional elastic-plastic finite element model withcontact elements is used to simulate the contact behavior between the microcantilever beamand the electrode. A model with thermal-electrical coupling and [...] Read more.
This paper investigates the effect of electrical contact on the thermal contactstress of a microrelay switch. A three-dimensional elastic-plastic finite element model withcontact elements is used to simulate the contact behavior between the microcantilever beamand the electrode. A model with thermal-electrical coupling and thermal-stress coupling isused in the finite element analysis. The effects of contact gap, plating film thickness andnumber of switching cycles on the contact residual stress, contact force, plastic deformation,and temperature rise of the microrelay switch are explored. The numerical results indicatethat the residual stress increases with increasing contact gap or decreasing plating filmthickness. The results also show that the residual stress increases as the number of switchingcycles increases. A large residual stress inside the microcantilever beam can decrease thelifecycle of the microrelay. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)
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Article
A Novel Gas Sensor Transducer Based on Phthalocyanine Heterojunction Devices
Sensors 2007, 7(11), 2984-2996; https://doi.org/10.3390/s7112984 - 26 Nov 2007
Cited by 85 | Viewed by 7588
Abstract
Experimental data concerning the changes in the current-voltage (I-V) perfor-mances of a molecular material-based heterojunction consisting of hexadecafluorinatednickel phthalocyanine (Ni(F16Pc)) and nickel phthalocyanine (NiPc),(Au|Ni(F16Pc)|NiPc|Al) are introduced as an unprecedented principle of transduction for gassensing performances. The respective n- and [...] Read more.
Experimental data concerning the changes in the current-voltage (I-V) perfor-mances of a molecular material-based heterojunction consisting of hexadecafluorinatednickel phthalocyanine (Ni(F16Pc)) and nickel phthalocyanine (NiPc),(Au|Ni(F16Pc)|NiPc|Al) are introduced as an unprecedented principle of transduction for gassensing performances. The respective n- and p-type doped-insulator behaviors of therespective materials are supported, owing to the observed changes in surface potential(using the Kelvin probe method) after submission to electron donor (ammonia) and electronacceptor gases (ozone). On the other hand, the bilayer device exhibits strong variations inthe built-in potential of the junction and in its rectification ratio. Moreover, large increasesoccur in forward and reverse currents in presence of ammonia vapors. These make possiblea multimodal principle of detection controlled by a combined effect between theheterojunction and the NiPc|Al contact. Indeed, this metal/organic junction plays a criticalrole regarding the steady asymmetry of the I-V profiles during the device’s doping evenusing high ammonia concentrations. This approach offers a more sophisticated alternative tothe classically studied, but at times rather operation-limited, resistive gas sensors. Full article
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Article
Recent Advances in High-Birefringence Fiber Loop Mirror Sensors
Sensors 2007, 7(11), 2970-2983; https://doi.org/10.3390/s7112970 - 26 Nov 2007
Cited by 124 | Viewed by 9222
Abstract
Recent advances in devices and applications of high-birefringence fiber loopmirror sensors are addressed. In optical sensing, these devices may be used as strain andtemperature sensors, in a separate or in a simultaneous measurement. Other describedapplications include: refractive index measurement, optical filters for interrogate [...] Read more.
Recent advances in devices and applications of high-birefringence fiber loopmirror sensors are addressed. In optical sensing, these devices may be used as strain andtemperature sensors, in a separate or in a simultaneous measurement. Other describedapplications include: refractive index measurement, optical filters for interrogate gratingsstructures and chemical etching control. The paper analyses and compares different types ofhigh-birefringence fiber loop mirror sensors using conventional and microstructured opticalfibers. Some configurations are presented for simultaneous measurement of physicalparameters when combined with others optical devices, for example with a long periodgrating. Full article
(This article belongs to the Special Issue Optical Biosensors)
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Article
Tactile Fabric Panel in an Eight Zones Structure
Sensors 2007, 7(11), 2953-2969; https://doi.org/10.3390/s7112953 - 23 Nov 2007
Viewed by 8244
Abstract
By introducing a percentage of conductive material during the manufacture ofsewing thread, it is possible to obtain a fabric which is able to detect variations in pressurein certain areas. In previous experiments the existence of resistance variations has beendemonstrated, although some constrains of [...] Read more.
By introducing a percentage of conductive material during the manufacture ofsewing thread, it is possible to obtain a fabric which is able to detect variations in pressurein certain areas. In previous experiments the existence of resistance variations has beendemonstrated, although some constrains of cause and effect were found in the fabric. Theresearch has been concentrated in obtaining a fabric that allows electronic detection of itsshape changes. Additionally, and because a causal behavior is needed, it is necessary thatthe fabric recovers its original shape when the external forces cease. The structure of thefabric varies with the type of deformation applied. Two kinds of deformation aredescribed: those caused by stretching and those caused by pressure. This last type ofdeformation gives different responses depending on the conductivity of the object used tocause the pressure. This effect is related to the type of thread used to manufacture thefabric. So, if the pressure is caused by a finger the response is different compared to theresponse caused by a conductive object. Another fact that has to be mentioned is that apressure in a specific point of the fabric can affect other detection points depending on theforce applied. This effect is related to the fabric structure. The goals of this article arevalidating the structure of the fabric used, as well as the study of the two types ofdeformation mentioned before. Full article
(This article belongs to the Special Issue Intelligent Sensors)
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Article
Monitoring Transport Across Modified Nanoporous Alumina Membranes
Sensors 2007, 7(11), 2942-2952; https://doi.org/10.3390/s7112942 - 23 Nov 2007
Cited by 21 | Viewed by 7150
Abstract
This paper describes the use of several characterization methods to examinealumina nanotubule membranes that have been modified with specific silanes. The functionof these silanes is to alter the transport properties through the membrane by changing thelocal environment inside the alumina nanotube. The presence [...] Read more.
This paper describes the use of several characterization methods to examinealumina nanotubule membranes that have been modified with specific silanes. The functionof these silanes is to alter the transport properties through the membrane by changing thelocal environment inside the alumina nanotube. The presence of alkyl groups, either long(C18) or short and branched (isopropyl) hydrocarbon chains, on these silanes significantlydecreases the rate of transport of permeant molecules through membranes containingalumina nanotubes as monitored via absorbance spectroscopy. The presence of an ionicsurfactant can alter the polarity of these modified nanotubes, which correlates to anincreased transport of ions. Fluorescent spectroscopy is also utilized to enhance thesensitivity of detecting these permeant molecules. Confirmation of the alkylsilaneattachment to the alumina membrane is achieved with traditional infrared spectroscopy,which can also examine the lifetime of the modified membrane. The physical parameters ofthese silane-modified porous alumina membranes are studied via scanning electronmicroscopy. The alumina nanotubes are not physically closed off or capped by the silanesthat are attached to the alumina surfaces. Full article
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Article
Enhanced Sensory Properties of a Multichannel Quartz Crystal Microbalance Coated with Polymeric Nanobeads
Sensors 2007, 7(11), 2920-2928; https://doi.org/10.3390/S7112920 - 23 Nov 2007
Cited by 29 | Viewed by 7275
Abstract
In this study the sensorial performances of a four-channel quartz crystalmicrobalance implemented on a single quartz plate are reported and compared with those offour independent quartz crystal microbalances. Particular attention has been devoted to bothcross talk in responses and sensor sensitivity. A recently [...] Read more.
In this study the sensorial performances of a four-channel quartz crystalmicrobalance implemented on a single quartz plate are reported and compared with those offour independent quartz crystal microbalances. Particular attention has been devoted to bothcross talk in responses and sensor sensitivity. A recently synthesized nanostructuredpolymer, poly[phenylacetylene-(co-2-hydroxyethyl methacrylate)], has been used aschemical interactive material. The interactions of our sensor system with relative humidityare also reported. The multichannel device shows a better homogeneity of the masssensitivity with a spread of the values less then 4% compared to a 50% spread observed inthe set of four microbalances. Full article
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Article
Magnetostrictive Microcantilever as an Advanced Transducer for Biosensors
Sensors 2007, 7(11), 2929-2941; https://doi.org/10.3390/S7112929 - 22 Nov 2007
Cited by 32 | Viewed by 9199
Abstract
The magnetostrictive microcantilever (MSMC) as a high-performance transducer was introduced for the development of biosensors. The principle and characterization of MSMC are presented. The MSMC is wireless and can be easily actuated and sensed using magnetic field/signal. More importantly, the MSMC exhibits a [...] Read more.
The magnetostrictive microcantilever (MSMC) as a high-performance transducer was introduced for the development of biosensors. The principle and characterization of MSMC are presented. The MSMC is wireless and can be easily actuated and sensed using magnetic field/signal. More importantly, the MSMC exhibits a high Q value and works well in liquid. The resonance behavior of MSMC is characterized in air at different pressures and in different liquids, respectively. It is found that the Q value of the MSMC in water reaches about 40. Although the density and viscosity of the surrounding media affect the resonance frequency and the Q value of MSMC, the density has a stronger influence on the resonance frequency and the viscosity has a stronger influence on the Q value, which result in that, for MSMC in air at pressure of less than 100 Pa, the resonance frequency of MSMC is almost independent of the pressure, while the Q value increases with decreasing pressure. MSMC array was developed and characterized. It is experimentally demonstrated that the characterization of an MSMC array is as simple as the characterization of a single MSMC. A filamentous phage against Salmonella typhimurium was utilized as bio-recognition unit to develop an MSMC based biosensor. The detection of S. typhimurium in water demonstrated that the MSMC works well in liquid. Full article
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Article
Novel Deployment Schemes for Mobile Sensor Networks
Sensors 2007, 7(11), 2907-2919; https://doi.org/10.3390/S7112907 - 21 Nov 2007
Cited by 97 | Viewed by 6899
Abstract
Virtual Force Algorithm (VFA) is becoming a main solution to area coverage forhomogeneous wireless sensor networks with random distribution of mobile sensor nodes.Consider the factors of the convergence, the boundary in Region Of Interest (ROI), effec-tive distance of acting force and useless moving, [...] Read more.
Virtual Force Algorithm (VFA) is becoming a main solution to area coverage forhomogeneous wireless sensor networks with random distribution of mobile sensor nodes.Consider the factors of the convergence, the boundary in Region Of Interest (ROI), effec-tive distance of acting force and useless moving, etc, VFA is improved to overcome the aboveproblems. Furthermore, an expression of exponential function for the relationship of vir-tual force is proposed to converge rapidly. Extensive simulation results indicate that theseimproved VFA get better performance in coverage rate, moving energy consumption, conver-gence etc. than original VFA. Full article
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Article
Tempo-Spatial Patterns of Land Use Changes and Urban Development in Globalizing China: A Study of Beijing
Sensors 2007, 7(11), 2881-2906; https://doi.org/10.3390/S7112881 - 20 Nov 2007
Cited by 60 | Viewed by 10049
Abstract
This study examines the temporal and spatial changes in land use as aconsequence of rapid urban development in the city of Beijing. Using a combination oftechniques of remote sensing and GIS, the study identifies a substantial loss of plaindryland and a phenomenal expansion [...] Read more.
This study examines the temporal and spatial changes in land use as aconsequence of rapid urban development in the city of Beijing. Using a combination oftechniques of remote sensing and GIS, the study identifies a substantial loss of plaindryland and a phenomenal expansion of urban construction land over the recent decade.Geographically, there is a clear shifting of urban construction land from the inner city tothe outskirts as a consequence of suburbanization. The outward expansion of the ring-roadsystem is found to be one of the most important driving forces explaining the temporal andspatial pattern of land use change. The uneven distribution of population stands as anotherfactor with significant correlation with land use change. The application of the techniquesof remote sensing and GIS can enhance the precision and comparability of research onland use change and urban transformation in China. Full article
(This article belongs to the Special Issue Sensors for Urban Environmental Monitoring)
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Article
Object-Based Classification of Ikonos Imagery for Mapping Large-Scale Vegetation Communities in Urban Areas
Sensors 2007, 7(11), 2860-2880; https://doi.org/10.3390/s7112860 - 20 Nov 2007
Cited by 116 | Viewed by 12532
Abstract
Effective assessment of biodiversity in cities requires detailed vegetation maps.To date, most remote sensing of urban vegetation has focused on thematically coarse landcover products. Detailed habitat maps are created by manual interpretation of aerialphotographs, but this is time consuming and costly at large [...] Read more.
Effective assessment of biodiversity in cities requires detailed vegetation maps.To date, most remote sensing of urban vegetation has focused on thematically coarse landcover products. Detailed habitat maps are created by manual interpretation of aerialphotographs, but this is time consuming and costly at large scale. To address this issue, wetested the effectiveness of object-based classifications that use automated imagesegmentation to extract meaningful ground features from imagery. We applied thesetechniques to very high resolution multispectral Ikonos images to produce vegetationcommunity maps in Dunedin City, New Zealand. An Ikonos image was orthorectified and amulti-scale segmentation algorithm used to produce a hierarchical network of image objects.The upper level included four coarse strata: industrial/commercial (commercial buildings),residential (houses and backyard private gardens), vegetation (vegetation patches larger than0.8/1ha), and water. We focused on the vegetation stratum that was segmented at moredetailed level to extract and classify fifteen classes of vegetation communities. The firstclassification yielded a moderate overall classification accuracy (64%, κ = 0.52), which ledus to consider a simplified classification with ten vegetation classes. The overallclassification accuracy from the simplified classification was 77% with a κ value close tothe excellent range (κ = 0.74). These results compared favourably with similar studies inother environments. We conclude that this approach does not provide maps as detailed as those produced by manually interpreting aerial photographs, but it can still extract ecologically significant classes. It is an efficient way to generate accurate and detailed maps in significantly shorter time. The final map accuracy could be improved by integrating segmentation, automated and manual classification in the mapping process, especially when considering important vegetation classes with limited spectral contrast. Full article
(This article belongs to the Special Issue Sensors for Urban Environmental Monitoring)
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Article
Quantitative Accelerated Life Testing of MEMS Accelerometers
Sensors 2007, 7(11), 2846-2859; https://doi.org/10.3390/s7112846 - 20 Nov 2007
Cited by 20 | Viewed by 9224
Abstract
Quantitative Accelerated Life Testing (QALT) is a solution for assessing thereliability of Micro Electro Mechanical Systems (MEMS). A procedure for QALT is shownin this paper and an attempt to assess the reliability level for a batch of MEMSaccelerometers is reported. The testing plan [...] Read more.
Quantitative Accelerated Life Testing (QALT) is a solution for assessing thereliability of Micro Electro Mechanical Systems (MEMS). A procedure for QALT is shownin this paper and an attempt to assess the reliability level for a batch of MEMSaccelerometers is reported. The testing plan is application-driven and contains combinedtests: thermal (high temperature) and mechanical stress. Two variants of mechanical stressare used: vibration (at a fixed frequency) and tilting. Original equipment for testing at tiltingand high temperature is used. Tilting is appropriate as application-driven stress, because thetilt movement is a natural environment for devices used for automotive and aerospaceapplications. Also, tilting is used by MEMS accelerometers for anti-theft systems. The testresults demonstrated the excellent reliability of the studied devices, the failure rate in the“worst case” being smaller than 10-7h-1. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)
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Article
Study on a Concentric Tube Bulb Manometer and its Performance Compared to U-shaped Manometer
Sensors 2007, 7(11), 2835-2845; https://doi.org/10.3390/s7112835 - 20 Nov 2007
Cited by 3 | Viewed by 5946
Abstract
This paper presents comparative study of a new type of manometer calledconcentric tube bulb (C.T.B) manometer. Its performance of measuring differential heightis studied against conventional U-shaped manometer. Pressure drops and mass flow ratesare calculated by taking various systems comprising of different flow measuring [...] Read more.
This paper presents comparative study of a new type of manometer calledconcentric tube bulb (C.T.B) manometer. Its performance of measuring differential heightis studied against conventional U-shaped manometer. Pressure drops and mass flow ratesare calculated by taking various systems comprising of different flow measuring devicessuch as orifice and venturimeters using both U- shaped and C.T.B manometers.Comparison between the physically measured values of differential pressure drops andmass flow rates with the calculated values based on theoretical equations is also made.Experiments are carried out using mercury and CCl4 in these manometers as sensing fluids.Water is used as flowing fluid for mass flow rate and pressure drop measurements, whereasin gauge pressure measurements air is used. Full article
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Article
Piezoelectric Biosensor for a Simple Serological Diagnosis of Tularemia in Infected European Brown Hares (Lepus europaeus)
Sensors 2007, 7(11), 2825-2834; https://doi.org/10.3390/s7112825 - 19 Nov 2007
Cited by 18 | Viewed by 6581
Abstract
Piezoelectric biosensor was used for diagnosis of infection by Francisellatularensis subsp. holarctica in European brown hares. Two kinds of experiments wereperformed in this study. First, sera from experimentally infected European brown hares(Lepus europaeus) were assayed by piezoelectric biosensor and the seventh day postinfection [...] Read more.
Piezoelectric biosensor was used for diagnosis of infection by Francisellatularensis subsp. holarctica in European brown hares. Two kinds of experiments wereperformed in this study. First, sera from experimentally infected European brown hares(Lepus europaeus) were assayed by piezoelectric biosensor and the seventh day postinfection was found as the first one when statistically significant diagnosis of tularemia waspossible; all other sera collected from hares later than on day 7 following the infection werefound tularemia positive. Typing to classify the field strain of F. tularensis used for theexperimental infection was confirmed by proteome study. Second, sera from 35 Europeanbrown hare specimens sampled at hunting grounds and tested as tularemia positive by slowagglutination allowed diagnosis of tularemia by the piezoelectric biosensor. All these sera ofnaturally infected hares were found as tularemia positive, too. Efficacy of the piezoelectricbiosensor for the serological diagnosis of tularemia is discussed. Full article
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Article
Antimicrobial Peptides: New Recognition Molecules for Detecting Botulinum Toxins
Sensors 2007, 7(11), 2808-2824; https://doi.org/10.3390/s7112808 - 16 Nov 2007
Cited by 26 | Viewed by 7297
Abstract
Many organisms secrete antimicrobial peptides (AMPs) for protection againstharmful microbes. The present study describes detection of botulinum neurotoxoids A, Band E using AMPs as recognition elements in an array biosensor. While AMP affinitieswere similar to those for anti-botulinum antibodies, differences in binding patterns [...] Read more.
Many organisms secrete antimicrobial peptides (AMPs) for protection againstharmful microbes. The present study describes detection of botulinum neurotoxoids A, Band E using AMPs as recognition elements in an array biosensor. While AMP affinitieswere similar to those for anti-botulinum antibodies, differences in binding patterns wereobserved and can potentially be used for identification of toxoid serotype. Furthermore,some AMPs also demonstrated superior detection sensitivity compared to antibodies: toxoidA could be detected at 3.5 LD50 of the active toxin in a 75-min assay, whereas toxoids B andE were detected at 14 and 80 LD50 for their respective toxins. Full article
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Article
Robust Forecasting for Energy Efficiency of Wireless Multimedia Sensor Networks
Sensors 2007, 7(11), 2779-2807; https://doi.org/10.3390/s7112779 - 15 Nov 2007
Cited by 19 | Viewed by 7320
Abstract
An important criterion of wireless sensor network is the energy efficiency inspecified applications. In this wireless multimedia sensor network, the observations arederived from acoustic sensors. Focused on the energy problem of target tracking, this paperproposes a robust forecasting method to enhance the energy [...] Read more.
An important criterion of wireless sensor network is the energy efficiency inspecified applications. In this wireless multimedia sensor network, the observations arederived from acoustic sensors. Focused on the energy problem of target tracking, this paperproposes a robust forecasting method to enhance the energy efficiency of wirelessmultimedia sensor networks. Target motion information is acquired by acoustic sensornodes while a distributed network with honeycomb configuration is constructed. Thereby,target localization is performed by multiple sensor nodes collaboratively through acousticsignal processing. A novel method, combining autoregressive moving average (ARMA)model and radial basis function networks (RBFNs), is exploited to perform robust targetposition forecasting during target tracking. Then sensor nodes around the target areawakened according to the forecasted target position. With committee decision of sensornodes, target localization is performed in a distributed manner and the uncertainty ofdetection is reduced. Moreover, a sensor-to-observer routing approach of the honeycombmesh network is investigated to solve the data reporting considering the residual energy ofsensor nodes. Target localization and forecasting are implemented in experiments.Meanwhile, sensor node awakening and dynamic routing are evaluated. Experimentalresults verify that energy efficiency of wireless multimedia sensor network is enhanced bythe proposed target tracking method. Full article
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Article
Statistical Modeling of Spatio-Temporal Variability in Monthly Average Daily Solar Radiation over Turkey
Sensors 2007, 7(11), 2763-2778; https://doi.org/10.3390/s7112763 - 15 Nov 2007
Cited by 14 | Viewed by 6030
Abstract
Though one of the most significant driving forces behind ecological processessuch as biogeochemical cycles and energy flows, solar radiation data are limited or non-existent by conventional ground-based measurements, and thus, often estimated from othermeteorological data through (geo)statistical models. In this study, spatial and [...] Read more.
Though one of the most significant driving forces behind ecological processessuch as biogeochemical cycles and energy flows, solar radiation data are limited or non-existent by conventional ground-based measurements, and thus, often estimated from othermeteorological data through (geo)statistical models. In this study, spatial and temporalpatterns of monthly average daily solar radiation on a horizontal surface at the ground levelwere quantified using 130 climate stations for the entire Turkey and its conventionally-accepted seven geographical regions through multiple linear regression (MLR) models as afunction of latitude, longitude, altitude, aspect, distance to sea; minimum, maximum andmean air temperature and relative humidity, soil temperature, cloudiness, precipitation, panevapotranspiration, day length, maximum possible sunshine duration, monthly average dailyextraterrestrial solar radiation, and time (month), and universal kriging method. Theresulting 20 regional best-fit MLR models (three MLR models for each region) based onparameterization datasets had R2adj values of 91.5% for the Central Anatolia region to 98.0%for the Southeast Anatolia region. Validation of the best-fit MLR models for each region led to R2 values of 87.7% for the Mediterranean region to 98.5% for the Southeast Anatoliaregion. The best-fit anisotropic semi-variogram models for universal kriging as a result ofone-leave-out cross-validation gave rise to R2 values of 10.9% in July to 52.4% inNovember. Surface maps of monthly average daily solar radiation were generated overTurkey, with a grid resolution of 500 m x 500 m. Full article
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Article
Metalloporphyrin - based Electronic Tongue: an Application for the Analysis of Italian White wines
Sensors 2007, 7(11), 2750-2762; https://doi.org/10.3390/s7112750 - 15 Nov 2007
Cited by 40 | Viewed by 8422
Abstract
An Electronic Tongue system (ET) composed of “all-solid-state” potentiometricsensors was developed and applied for the identification of white wines. The sensingproperties were due to the PVC based membranes doped with several metallo-porphyrinsdeposited on the surface of glassy carbon working electrodes; potentiometric responsetowards several [...] Read more.
An Electronic Tongue system (ET) composed of “all-solid-state” potentiometricsensors was developed and applied for the identification of white wines. The sensingproperties were due to the PVC based membranes doped with several metallo-porphyrinsdeposited on the surface of glassy carbon working electrodes; potentiometric responsetowards several ions in a concentration range from 10-5 M to 10-1 M were studied and cross-sensitivity of sensors was estimated. The sensor array was applied both for the classificationand quantitative analysis of “Verdicchio D.O.C.” Italian dry white wines produced by ninecantinas. Peculiar parameters of white wines (namely alcoholic degree, volatile acidity, SO2,L-Malic Acid, L-Lactic Acid and Total Polyphenols) individuated by standard analyticalmethods were compared with the values evaluated by metalloporphyrin-based ET. Thesystem satisfactory discriminates between an artificial wine control and analyzed winescoming from different cantinas and produced in different years. A satisfactory correlationbetween results of wine analysis performed by certified methods and ET response has beenobtained for SO2, L-Malic Acid, and Total Phenols content. The developed procedureallows the monitoring of the acetic acid amount in wines and hence to control wine volatileacidity, so indicating the initial steps of wine spoilage process. Full article
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Article
Ammonia Optical Sensing by Microring Resonators
Sensors 2007, 7(11), 2741-2749; https://doi.org/10.3390/s7112741 - 15 Nov 2007
Cited by 84 | Viewed by 8269
Abstract
A very compact (device area around 40 μm2) optical ammonia sensor based on amicroring resonator is presented in this work. Silicon-on-insulator technology is used insensor design and a dye doped polymer is adopted as sensing material. The sensor exhibitsa very good [...] Read more.
A very compact (device area around 40 μm2) optical ammonia sensor based on amicroring resonator is presented in this work. Silicon-on-insulator technology is used insensor design and a dye doped polymer is adopted as sensing material. The sensor exhibitsa very good linearity and a minimum detectable refractive index shift of sensing materialas low as 8x10-5, with a detection limit around 4 ‰. Full article
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Article
Modelling a Peroxidase-based Optical Biosensor
Sensors 2007, 7(11), 2723-2740; https://doi.org/10.3390/s7112723 - 14 Nov 2007
Cited by 6 | Viewed by 5979
Abstract
The response of a peroxidase-based optical biosensor was modelled digitally.A mathematical model of the optical biosensor is based on a system of non-linear reaction-diffusion equations. The modelling biosensor comprises two compartments, an enzyme layerand an outer diffusion layer. The digital simulation was carried [...] Read more.
The response of a peroxidase-based optical biosensor was modelled digitally.A mathematical model of the optical biosensor is based on a system of non-linear reaction-diffusion equations. The modelling biosensor comprises two compartments, an enzyme layerand an outer diffusion layer. The digital simulation was carried out using finite differencetechnique. The influence of the substrate concentration as well as of the thickness of both theenzyme and diffusion layers on the biosensor response was investigated. Calculations showedcomplex kinetics of the biosensor response, especially at low concentrations of the peroxidaseand of the hydrogen peroxide. Full article
(This article belongs to the Special Issue Optical Biosensors)
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Article
Hierarchical Wireless Multimedia Sensor Networks for Collaborative Hybrid Semi-Supervised Classifier Learning
Sensors 2007, 7(11), 2693-2722; https://doi.org/10.3390/s7112693 - 13 Nov 2007
Cited by 7 | Viewed by 7374
Abstract
Wireless multimedia sensor networks (WMSN) have recently emerged as one ofthe most important technologies, driven by the powerful multimedia signal acquisition andprocessing abilities. Target classification is an important research issue addressed in WMSN,which has strict requirement in robustness, quickness and accuracy. This paper [...] Read more.
Wireless multimedia sensor networks (WMSN) have recently emerged as one ofthe most important technologies, driven by the powerful multimedia signal acquisition andprocessing abilities. Target classification is an important research issue addressed in WMSN,which has strict requirement in robustness, quickness and accuracy. This paper proposes acollaborative semi-supervised classifier learning algorithm to achieve durative onlinelearning for support vector machine (SVM) based robust target classification. The proposedalgorithm incrementally carries out the semi-supervised classifier learning process inhierarchical WMSN, with the collaboration of multiple sensor nodes in a hybrid computingparadigm. For decreasing the energy consumption and improving the performance, somemetrics are introduced to evaluate the effectiveness of the samples in specific sensor nodes,and a sensor node selection strategy is also proposed to reduce the impact of inevitablemissing detection and false detection. With the ant optimization routing, the learningprocess is implemented with the selected sensor nodes, which can decrease the energyconsumption. Experimental results demonstrate that the collaborative hybrid semi-supervised classifier learning algorithm can effectively implement target classification inhierarchical WMSN. It has outstanding performance in terms of energy efficiency and timecost, which verifies the effectiveness of the sensor nodes selection and ant optimizationrouting. Full article
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Article
Four-Wire Impedance Spectroscopy on Planar Zeolite/Chromium Oxide Based Hydrocarbon Gas Sensors
Sensors 2007, 7(11), 2681-2692; https://doi.org/10.3390/s7112681 - 13 Nov 2007
Cited by 18 | Viewed by 6727
Abstract
Impedometric zeolite hydrocarbon sensors with a chromium oxide intermediatelayer show a very promising behavior with respect to sensitivity and selectivity. Theunderlying physico-chemical mechanism is under investigation at the moment. In order toverify that the effect occurs at the electrode and that zeolite bulk [...] Read more.
Impedometric zeolite hydrocarbon sensors with a chromium oxide intermediatelayer show a very promising behavior with respect to sensitivity and selectivity. Theunderlying physico-chemical mechanism is under investigation at the moment. In order toverify that the effect occurs at the electrode and that zeolite bulk properties remain almostunaffected by hydrocarbons, a special planar setup was designed, which is very close to realsensor devices. It allows for conducting four-wire impedance spectroscopy as well as two-wire impedance spectroscopy. Using this setup, it could be clearly demonstrated that thesensing effect can be ascribed to an electrode impedance. Furthermore, by combining two-and four-wire impedance measurements at only one single frequency, the interference of thevolume impedance can be suppressed and an easy signal evaluation is possible, withouttaking impedance data at different frequencies. Full article
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Article
Electrochemical Interrogation of Interactions between Surface-Confined DNA and Methylene Blue
Sensors 2007, 7(11), 2671-2680; https://doi.org/10.3390/s7112671 - 12 Nov 2007
Cited by 64 | Viewed by 6645
Abstract
In this work, we reported a systematic investigation on the interactions betweenmethylene blue (MB) and surface-confined DNA by using electrochemical methods. Wedemonstrated that the redox potential of MB and binding and dissociation kinetics of MB toDNA differed significantly for single-stranded DNA (ss-DNA) and [...] Read more.
In this work, we reported a systematic investigation on the interactions betweenmethylene blue (MB) and surface-confined DNA by using electrochemical methods. Wedemonstrated that the redox potential of MB and binding and dissociation kinetics of MB toDNA differed significantly for single-stranded DNA (ss-DNA) and double-stranded DNA(ds-DNA) immobilized on gold electrodes. This was possibly due to the different bindingmechanism between MB and ss- or ds-DNA. This work might provide useful informationfor developing MB-based sequence-specific electrochemical DNA sensors. Full article
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Article
Modeling and Manufacturing of Micromechanical RF Switch with Inductors
Sensors 2007, 7(11), 2660-2670; https://doi.org/10.3390/s7112670 - 09 Nov 2007
Cited by 27 | Viewed by 7587
Abstract
This study presents the simulation, fabrication and characterization ofmicromechanical radio frequency (RF) switch with micro inductors. The inductors areemployed to enhance the characteristic of the RF switch. An equivalent circuit model isdeveloped to simulate the performance of the RF switch. The behaviors of [...] Read more.
This study presents the simulation, fabrication and characterization ofmicromechanical radio frequency (RF) switch with micro inductors. The inductors areemployed to enhance the characteristic of the RF switch. An equivalent circuit model isdeveloped to simulate the performance of the RF switch. The behaviors of themicromechanical RF switch are simulated by the finite element method software,CoventorWare. The micromechanical RF switch is fabricated using the complementarymetal oxide semiconductor (CMOS) and a post-process. The post-process employs a wetetching to etch the sacrificial layer, and to release the suspended structures of the RF switch.The structure of the RF switch contains a coplanar waveguide (CPW), a suspendedmembrane, eight springs and two inductors in series. Experimental results reveal that theinsertion loss and isolation of the switch are 1.7 dB at 21 GHz and 19 dB at 21 GHz,respectively. The driving voltage of the switch is about 13 V. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)
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Article
Application to Temperature Sensor Based on Green Up-conversion of Er3+ Doped Silicate Glass
Sensors 2007, 7(11), 2652-2659; https://doi.org/10.3390/s7112652 - 07 Nov 2007
Cited by 90 | Viewed by 6781
Abstract
The green up-conversion emissions centered at the wavelengths of about 534nmand 549nm of the Er3+ doped silicate glass were recorded, using a 978 nm semiconductorlaser diode (LD) as an excitation source. The fluorescence intensity ratio (FIR) of the greenup-conversion emissions at about [...] Read more.
The green up-conversion emissions centered at the wavelengths of about 534nmand 549nm of the Er3+ doped silicate glass were recorded, using a 978 nm semiconductorlaser diode (LD) as an excitation source. The fluorescence intensity ratio (FIR) of the greenup-conversion emissions at about 534nm and 549nm in the Er3+ doped silicate glass wasstudied as a function of temperature over the temperature range of 296K-673K. Themaximum sensitivity and the temperature resolution derived from the FIR of the green up-conversion emissions are approximately 0.0023K-1 and 0.8K, respectively. It isdemonstrated that the prototype optical temperature sensor based on the FIR technique fromthe green up-conversion emissions in the Er3+ doped silicate glass could play a major role intemperature measurement. Full article
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Article
Sensitivity of the Enhanced Vegetation Index (EVI) and Normalized Difference Vegetation Index (NDVI) to Topographic Effects: A Case Study in High-density Cypress Forest
Sensors 2007, 7(11), 2636-2651; https://doi.org/10.3390/s7112636 - 05 Nov 2007
Cited by 302 | Viewed by 19596
Abstract
Vegetation indices play an important role in monitoring variations in vegetation.The Enhanced Vegetation Index (EVI) proposed by the MODIS Land Discipline Groupand the Normalized Difference Vegetation Index (NDVI) are both global-based vegetationindices aimed at providing consistent spatial and temporal information regarding globalvegetation. However, [...] Read more.
Vegetation indices play an important role in monitoring variations in vegetation.The Enhanced Vegetation Index (EVI) proposed by the MODIS Land Discipline Groupand the Normalized Difference Vegetation Index (NDVI) are both global-based vegetationindices aimed at providing consistent spatial and temporal information regarding globalvegetation. However, many environmental factors such as atmospheric conditions and soilbackground may produce errors in these indices. The topographic effect is another veryimportant factor, especially when the indices are used in areas of rough terrain. In thispaper, we theoretically analyzed differences in the topographic effect on the EVI and theNDVI based on a non-Lambertian model and two airborne-based images acquired from amountainous area covered by high-density Japanese cypress plantation were used as a casestudy. The results indicate that the soil adjustment factor “L” in the EVI makes it moresensitive to topographic conditions than is the NDVI. Based on these results, we stronglyrecommend that the topographic effect should be removed in the reflectance data beforethe EVI was calculated—as well as from other vegetation indices that similarly include a term without a band ratio format (e.g., the PVI and SAVI)—when these indices are used in the area of rough terrain, where the topographic effect on the vegetation indices having only a band ratio format (e.g., the NDVI) can usually be ignored. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
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Article
Carbon-based Composite Electrodes: Preparation, Characterization and Application in Electroanalysis
Sensors 2007, 7(11), 2626-2635; https://doi.org/10.3390/s7112626 - 05 Nov 2007
Cited by 21 | Viewed by 6538
Abstract
Electrodes based on carbon, i.e., expanded graphite (20%, wt.)-epoxy composite(20EG-Epoxy) and expanded graphite (20%, wt.)-polystyrene composite (20EG-PS) havebeen prepared, characterized using scanning electron microscopy (SEM) and cyclicvoltammetry (CV), and tested as anodic sensors. The electrodes exhibited good mechanicalresistance and low electrical resistances. Scan [...] Read more.
Electrodes based on carbon, i.e., expanded graphite (20%, wt.)-epoxy composite(20EG-Epoxy) and expanded graphite (20%, wt.)-polystyrene composite (20EG-PS) havebeen prepared, characterized using scanning electron microscopy (SEM) and cyclicvoltammetry (CV), and tested as anodic sensors. The electrodes exhibited good mechanicalresistance and low electrical resistances. Scan rate dependent cyclic voltammetry responsesat 20EG-Epoxy and 20EG-PS composite electrodes, which were exemplified for thiourea(TU), a toxic sulphur organic compound selected as testing target analyte in 0.1 M Na2SO4 supporting electrolyte, were investigated. The obtained voltammetric data were inaccordance with those for a random array of microelectrodes. The voltammetric andchronoamperometric detection results of TU in tap water samples, without a supplementaryaddition of supporting electrolyte, at 20EG-Epoxy electrode proved its use for directanalysis of environmental samples. Full article
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Article
Glucose Determination by Means of Steady-state and Time-course UV Fluorescence in Free or Immobilized Glucose Oxidase
Sensors 2007, 7(11), 2612-2625; https://doi.org/10.3390/s7112612 - 05 Nov 2007
Cited by 16 | Viewed by 9957
Abstract
Changes in steady-state UV fluorescence emission from free or immobilizedglucose oxidase have been investigated as a function of glucose concentration.Immobilized GOD has been obtained by entrapment into a gelatine membrane. Changes insteady-state UV fluorescence have been quantitatively characterized by means ofoptokinetic parameters and [...] Read more.
Changes in steady-state UV fluorescence emission from free or immobilizedglucose oxidase have been investigated as a function of glucose concentration.Immobilized GOD has been obtained by entrapment into a gelatine membrane. Changes insteady-state UV fluorescence have been quantitatively characterized by means ofoptokinetic parameters and their values have been compared with those previouslyobtained for FAD fluorescence in the visible range. The results confirmed that greatercalibration ranges are obtained from UV signals both for free and immobilized GOD inrespect to those obtained under visible fluorescence excitation. An alternative method tothe use UV fluorescence for glucose determination has been investigated by using timecourse measurements for monitoring the differential fluorescence of the redox forms of theFAD in GOD. Also in this case quantitative analysis have been carried out and acomparison with different experimental configurations has been performed. Time coarsemeasurements could be particularly useful for glucose monitoring in complex biologicalfluids in which the intrinsic UV fluorescence of GOD could be not specific by consideringthe presence of numerous proteins. Full article
(This article belongs to the Special Issue Optical Biosensors)
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Article
Biochemical Markers for Assessing Aquatic Contamination
Sensors 2007, 7(11), 2599-2611; https://doi.org/10.3390/s7112599 - 02 Nov 2007
Cited by 29 | Viewed by 7643
Abstract
Biochemical markers, specifically enzymes of the first phase of xenobiotic transformation - cytochrome P450 and ethoxyresorufin-O-deethylase (EROD) - were used to determine the quantities of persistent organic pollutants (POPs) in fish muscle (PCB, HCB, HCH, OCS, DDT). Eight rivers were monitored (Orlice, Chrudimka, [...] Read more.
Biochemical markers, specifically enzymes of the first phase of xenobiotic transformation - cytochrome P450 and ethoxyresorufin-O-deethylase (EROD) - were used to determine the quantities of persistent organic pollutants (POPs) in fish muscle (PCB, HCB, HCH, OCS, DDT). Eight rivers were monitored (Orlice, Chrudimka, Cidlina, Jizera, Vltava, Ohře and Bílina; and the River Blanice was used as a control). The indicator species selected was the chub (Leuciscus cephalus L.). There were no significant differences in cytochrome P450 content between the locations monitored. The highest concentration of cytochrome P450 in fish liver was in the Vltava (0.241 nmol mg-1 protein), and the lowest was in the Orlice (0.120 nmol mg-1 protein). Analysis of EROD activity showed a significant difference between the Blanice and the Vltava (P< 0.05), and also between the Orlice and the Vltava (P< 0.01), the Orlice and the Bílina (P< 0.01), and the Orlice and the Ohře (P< 0.05). The highest EROD activity in fish liver was in the Vltava (576.4 pmol min-1 mg-1 protein), and the lowest was in the Orlice (63.05 pmol min-1 mg-1 protein). In individual locations, results of chemical monitoring and values of biochemical markers were compared. A significant correlation (P< 0.05) was found between biochemical markers and OCS, and PCB. Among the tributaries studied those that contaminated the Elbe most were the Vltava and the Bílina. These tributaries should not be considered the main sources of industrial contamination of the River Elbe, because the most important contamination sources were along the river Elbe itself. Full article
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Article
Determining Position Inside Non-industrial Buildings Using Ultrasound Transducers
Sensors 2007, 7(11), 2579-2598; https://doi.org/10.3390/s7112579 - 02 Nov 2007
Cited by 1 | Viewed by 9535
Abstract
The position determination inside a building where no GPS signal is beingreceived can be ascertained using laser transmitters in industrial situations where there areno people or using triangulation of the signal strength, normally electro-magnetic signals,if the required accuracy is more than a metre. [...] Read more.
The position determination inside a building where no GPS signal is beingreceived can be ascertained using laser transmitters in industrial situations where there areno people or using triangulation of the signal strength, normally electro-magnetic signals,if the required accuracy is more than a metre. Our solution is aimed at situations wherepeople are present and where the required accuracy is less than 30 cm, such as in shoppingprecincts or supermarkets. To achieve this, a network of ultrasonic transmitters is fittedinto the ceiling which receives a synchronised time signal. Each transmitter has a uniqueidentifier code and emits its code with a delay with respect to the common time signalwhich is proportional to its code number with an ASK modulation over the ultrasonic bandcentred on 40 KHz. The receivers circulating beneath the transmitters receive the codes ofthose within their detection range, translate the time delays into distances and then obtaintheir position by triangulation since the receivers know the position of every transmitter.Since the receivers are not synchronised with the common time signal or the actual speedof the sound, whose value varies appreciably with temperature, relative humidity andatmospheric pressure, a consecutive approximation algorithm has been introduced. This isbased on the fact that the Z coordinator of the receiver is known and constant and thus it is possible, with only three different identifiers received, to deduce the phase of the common time signal and estimate the speed of the sound with a fourth identifier. Full article
(This article belongs to the Special Issue Intelligent Sensors)
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Article
SU-8 Guiding Layer for Love Wave Devices
Sensors 2007, 7(11), 2539-2547; https://doi.org/10.3390/s71102539 - 01 Nov 2007
Cited by 8 | Viewed by 7557
Abstract
SU-8 is a technologically important photoresist used extensively for thefabrication of microfluidics and MEMS, allowing high aspect ratio structures to beproduced. In this work we report the use of SU-8 as a Love wave sensor guiding layerwhich allows the possibility of integrating a [...] Read more.
SU-8 is a technologically important photoresist used extensively for thefabrication of microfluidics and MEMS, allowing high aspect ratio structures to beproduced. In this work we report the use of SU-8 as a Love wave sensor guiding layerwhich allows the possibility of integrating a guiding layer with flow cell during fabrication.Devices were fabricated on ST-cut quartz substrates with a single-single finger design suchthat a surface skimming bulk wave (SSBW) at 97.4 MHz was excited. SU-8 polymer layerswere successively built up by spin coating and spectra recorded at each stage; showing afrequency decrease with increasing guiding layer thickness. The insertion loss andfrequency dependence as a function of guiding layer thickness was investigated over thefirst Love wave mode. Mass loading sensitivity of the resultant Love wave devices wasinvestigated by deposition of multiple gold layers. Liquid sensing using these devices wasalso demonstrated; water-glycerol mixtures were used to demonstrate sensing of density-viscosity and the physical adsorption and removal of protein was also assessed usingalbumin and fibrinogen as model proteins. Full article
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