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Sensors, Volume 8, Issue 3 (March 2008) – 40 articles , Pages 1351-2042

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3208 KiB  
Article
Monitoring the Effects of Forest Restoration Treatments on Post-Fire Vegetation Recovery with MODIS Multitemporal Data
by Willem J. D. Van Leeuwen
Sensors 2008, 8(3), 2017-2042; https://doi.org/10.3390/s8032017 - 25 Mar 2008
Cited by 125 | Viewed by 19329
Abstract
This study examines how satellite based time-series vegetation greenness data and phenological measurements can be used to monitor and quantify vegetation recovery after wildfire disturbances and examine how pre-fire fuel reduction restoration treatments impact fire severity and impact vegetation recovery trajectories. Pairs of [...] Read more.
This study examines how satellite based time-series vegetation greenness data and phenological measurements can be used to monitor and quantify vegetation recovery after wildfire disturbances and examine how pre-fire fuel reduction restoration treatments impact fire severity and impact vegetation recovery trajectories. Pairs of wildfire affected sites and a nearby unburned reference site were chosen to measure the post-disturbance recovery in relation to climate variation. All site pairs were chosen in forested uplands in Arizona and were restricted to the area of the Rodeo-Chediski fire that occurred in 2002. Fuel reduction treatments were performed in 1999 and 2001. The inter-annual and seasonal vegetation dynamics before, during, and after wildfire events can be monitored using a time series of biweekly composited MODIS NDVI (Moderate Resolution Imaging Spectroradiometer - Normalized Difference Vegetation Index) data. Time series analysis methods included difference metrics, smoothing filters, and fitting functions that were applied to extract seasonal and inter-annual change and phenological metrics from the NDVI time series data from 2000 to 2007. Pre- and post-fire Landsat data were used to compute the Normalized Burn Ratio (NBR) and examine burn severity at the selected sites. The phenological metrics (pheno-metrics) included the timing and greenness (i.e. NDVI) for the start, peak and end of the growing season as well as proxy measures for the rate of green-up and senescence and the annual vegetation productivity. Pre-fire fuel reduction treatments resulted in lower fire severity, which reduced annual productivity much less than untreated areas within the Rodeo-Chediski fire perimeter. The seasonal metrics were shown to be useful for estimating the rate of post-fire disturbance recovery and the timing of phenological greenness phases. The use of satellite time series NDVI data and derived pheno-metrics show potential for tracking vegetation cover dynamics and successional changes in response to drought, wildfire disturbances, and forest restoration treatments in fire-suppressed forests. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
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<p>General location of the study area in Arizona and the position of the Rodeo-Chediski burn perimeter</p> Full article ">
<p>Annual mean cumulative spring (Jan.-June) and monsoon (July-Dec.) precipitation data showing the drop in precipitation in 2002.</p> Full article ">
<p>Study sites and land cover classification map based on SWReGAP [<a href="#b35-sensors-08-02017" class="html-bibr">35</a>].The study sites are dominated by Ponderosa pine and some Madrean pine oak.</p> Full article ">
<p>MODIS NDVI time series imagery for the selected study sites are shown for August (2001) and June (2002) before the Rodeo-Chediski fire showing relatively high NDVI values for the study sites. Low NDVI values are observed for the August (2002) right after the fire, with the NDVI gradually increasing in the August images for 2003, 2005 and 2007.</p> Full article ">
<p>An example of the phenological metrics that are retrieved based on time series (blue curve) of 16-day composites of MODIS NDVI data for <span class="html-italic">Ponderosa pine</span> land cover and TIMESAT software [<a href="#b33-sensors-08-02017" class="html-bibr">33</a>]. The brown line is the fitted curve with the brown circles indicating the start and end of the growing seasons.</p> Full article ">
<p>Pre- and post-fire RGB (ETM bands 7, 4, and 3) color composites for June 5, 2002 and July 7, 2002, respectively. The Rodeo-Chediski fire was on June 18, 2002. The selected sites and fire perimeter are indicated as well. Some clouds and their shadows are visible in the Northeast side of the burn perimeter in the post-fire scene.</p> Full article ">
<p>Examples of the effect of low severity (left) and high severity (right) fires on sites inside Apache-Sitgreaves National Forest. Fuel reduction treatments (thinning) were applied at the site displayed in the picture to the left. Pictures taken in May, 2004.</p> Full article ">
<p>Locations of the 1999 and 2001 prescribed fire treatments on Apache-Sitgreaves National Forest lands reveal that the fire mostly avoided the two treatment areas. Burn severity for the entire study area, including the reference site and Rodeo–Chediski fire area, was classified based on the ΔNBR that was derived from the pre-fire image acquired on 5 June 2002, and the post-fire image acquired on 7 July 2002. Values of ΔNBR were classified into five fire severity categories (adapted from [<a href="#b37-sensors-08-02017" class="html-bibr">37</a>]) based on ΔNBR ranges that correspond with visible indications of fire damage to understory and tree foliage and crowns: Regrowth (ΔNBR &lt;-100, Unburned (-100≤ΔNBR &lt;100), Low severity (100≤ΔNBR &lt;270, ground fire; foliage still green), Moderate severity (270≤ΔNBR &lt;550, green and brown foliage with significant foliage consumed by fire), and High severity (ΔNBR &gt;550, crown fire; complete consumption of foliage). Fire severity was reduced greatly within treatment units (outlined with light green and blue polygons;.</p> Full article ">
<p>MODIS NDVI times series data for all composite periods of 2000-2007. Seasonality and an abrupt decrease in the NDVI are seen for all sites except the unburned reference site. The NDVI for the complete Rodeo-Chediski (RC) area drops the most. The results of the post-fire linear regression vegetation recovery model are shown for years 2003 through 2007.</p> Full article ">
2415 KiB  
Article
Role of Satellite Sensors in Groundwater Exploration
by Saumitra Mukherjee
Sensors 2008, 8(3), 2006-2016; https://doi.org/10.3390/s8032006 - 24 Mar 2008
Cited by 20 | Viewed by 13205
Abstract
Spatial as well as spectral resolution has a very important role to play in water resource management. It was a challenge to explore the groundwater and rainwater harvesting sites in the Aravalli Quartzite-Granite-Pegmatite Precambrian terrain of Delhi, India. Use of only panchromatic sensor [...] Read more.
Spatial as well as spectral resolution has a very important role to play in water resource management. It was a challenge to explore the groundwater and rainwater harvesting sites in the Aravalli Quartzite-Granite-Pegmatite Precambrian terrain of Delhi, India. Use of only panchromatic sensor data of IRS-1D satellite with 5.8-meter spatial resolution has the potential to infer lineaments and faults in this hard rock area. It is essential to identify the location of interconnected lineaments below buried pediment plains in the hard rock area for targeting sub-surface water resources. Linear Image Self Scanning sensor data of the same satellite with 23.5-meter resolution when merged with the panchromatic data has produced very good results in delineation of interconnected lineaments over buried pediment plains as vegetation anomaly. These specific locations of vegetation anomaly were detected as dark red patches in various hard rock areas of Delhi. Field investigation was carried out on these patches by resistivity and magnetic survey in parts of Jawaharlal Nehru University (JNU), Indira Gandhi national Open University, Research and Referral Hospital and Humayuns Tomb areas. Drilling was carried out in four locations of JNU that proved to be the most potential site with ground water discharge ranging from 20,000 to 30,000 liters per hour with 2 to 4 meters draw down. Further the impact of urbanization on groundwater recharging in the terrain was studied by generating Normalized difference Vegetation Index (NDVI) map which was possible to generate by using the LISS-III sensor of IRS-1D satellite. Selection of suitable sensors has definitely a cutting edge on natural resource exploration and management including groundwater. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
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<p>AWIFS sensor showing lineaments (L) in south Delhi but detailed information of hydrogeology is not possible to infer for water resource management.</p> Full article ">
<p>IRS-1D LISS-III sensor data using ERDAS software showing details of lineaments (L) and detailed hydrogeological information of whole Delhi for ground water management.</p> Full article ">
<p>IRS-1D Panchromatic sensor data using ERDAS software showing detailed landuse useful in pinpoint location of groundwater recharge points.</p> Full article ">
<p>Change in NDVI study by IRS-1D LISS-III and PAN sensor data showing more vegetation as black patch in JNU, a part of Aravalli Quartzite ridge in New Delhi, India. This data was used for selection and monitoring of groundwater recharge (check dam).</p> Full article ">
<p>Merged data (PAN+ LISS-III sensor) of RR Hospital area, part of Aravalli ridge showing higher value of Normalized Difference Vegetation Index (NDVI) in increasing suitability for groundwater exploration with increasing red colour of satellite image.</p> Full article ">
<p>Merged sensor data shows high accuracy groundwater recharge site map of whole Delhi using digital image processing and GIS techniques.</p> Full article ">
368 KiB  
Review
Innovative Sensors for Environmental Monitoring in Museums
by Mauro Bacci, Costanza Cucci, Andrea Azelio Mencaglia and Anna Grazia Mignani
Sensors 2008, 8(3), 1984-2005; https://doi.org/10.3390/s8031984 - 22 Mar 2008
Cited by 44 | Viewed by 17896
Abstract
Different physical and chemical factors, such as light, temperature, relative humidity, pollutants and so on, can affect works of art on display. Each factor does not act individually, but its effect can be enhanced or accelerated by the presence of other factors. Accordingly, [...] Read more.
Different physical and chemical factors, such as light, temperature, relative humidity, pollutants and so on, can affect works of art on display. Each factor does not act individually, but its effect can be enhanced or accelerated by the presence of other factors. Accordingly, an evaluation of the impact of the whole environment on art objects is recognized as an essential requirement for conservation purposes. To meet the most up-todate guidelines on preventive conservation, in recent years several scientific projects supported by the EC were aimed at developing innovative tools that could complement the standard methods for environmental monitoring in museums. These research projects produced a new generation of passive sensors that are capable of taking into account the overall environmental effects by mimicking in some way the behaviour of real works of art. The main goal of the present paper is to provide a survey of these sensors, which represent a new frontier in the environmental control in museums. Furthermore, the use of optical fibres, as both intrinsic sensors and devices for interrogating sensors, will also be illustrated, and examples of their use in the cultural heritage field will be reported. Full article
(This article belongs to the Special Issue Active and Passive Sensors for Art Diagnostic, Analysis and Investigation)
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<p>a) The mock paintings panel exposed in the Pollaiolo Room at the Uffizi Gallery Florence. b) The panel exposed together with conventional instruments for monitoring environmental parameters (temperature, RH%, visible and UV light). c) Detail of the panel.</p> Full article ">
<p>a) The mock paintings panel exposed in the Pollaiolo Room at the Uffizi Gallery Florence. b) The panel exposed together with conventional instruments for monitoring environmental parameters (temperature, RH%, visible and UV light). c) Detail of the panel.</p> Full article ">
<p>An example of the use of a colour reference scale for the LightCheck® system (LCU). After exposure close to the artefact, the colour of the dosimeter is visually compared with a colour reference scale that contains five labelled colour steps and indications of the corresponding light-doses. (Image reproduced with permission of the Trustees of the V&amp;A Museum, London. Photo by Maja Kardum).</p> Full article ">
<p>The CORRLOG sensor for monitoring corrosion in metallic artefacts. (Photo: courtesy of Tomas Prosek).</p> Full article ">
<p>Scheme of the varnished optical fibre used as a probe-head in the sensor for monitoring painted surfaces.</p> Full article ">
<p>(a) The optical-fiber device for monitoring lighting conditions in museums: the spectral features of exposed samples are visualized in real time on the PC. (b) View of the optical fiber probe connected to the miniaturized spectrophotometer within the case.</p> Full article ">
<p>(a) The optical-fiber device for monitoring lighting conditions in museums: the spectral features of exposed samples are visualized in real time on the PC. (b) View of the optical fiber probe connected to the miniaturized spectrophotometer within the case.</p> Full article ">
438 KiB  
Article
Hardware and Software of a Bipolar Current Source Controlled by PC
by Dragan Milivojević, Zoran Stević and Mirjana Rajčić-Vujasinović
Sensors 2008, 8(3), 1977-1983; https://doi.org/10.3390/s8031977 - 22 Mar 2008
Cited by 1 | Viewed by 8284
Abstract
This paper describes a realization of a bipolar current source developed by the paper's authors. The source is intended for use in galvanic and other industrial plants, where a pulse-reverse current supply (with the desired shape in time) is required. A prototype of [...] Read more.
This paper describes a realization of a bipolar current source developed by the paper's authors. The source is intended for use in galvanic and other industrial plants, where a pulse-reverse current supply (with the desired shape in time) is required. A prototype of the device, which provides the outcome current intensity up to ± 50 A, has been constructed. The hardware of the source consists of a Pentium IV PC, a commercial ADDA converter, an interface of authors’ original construction as well as a current regulator. The application software is developed using a commercial packet LabView as the basis. Full article
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<p>Block scheme of interface.</p> Full article ">
<p>The scheme of the main supply ± 12 V.</p> Full article ">
<p>The scheme of the additional supply.</p> Full article ">
<p>The scheme of current regulator.</p> Full article ">
<p>Control panel.</p> Full article ">
<p>Scheme of the application.</p> Full article ">
178 KiB  
Article
A Novel Optical Fiber Sensor for Steel Corrosion in Concrete Structures
by Christopher K.Y. Leung, Kai Tai Wan and Liquan Chen
Sensors 2008, 8(3), 1960-1976; https://doi.org/10.3390/s8031960 - 20 Mar 2008
Cited by 112 | Viewed by 14293
Abstract
Steel corrosion resulting from the penetration of chloride ions or carbon dioxide is a major cause of degradation for reinforced concrete structures,. The objective of the present investigation was to develop a low-cost sensor for steel corrosion, which is based on a very [...] Read more.
Steel corrosion resulting from the penetration of chloride ions or carbon dioxide is a major cause of degradation for reinforced concrete structures,. The objective of the present investigation was to develop a low-cost sensor for steel corrosion, which is based on a very simple physical principle. The flat end of a cut optical fiber is coated with an iron thin film using the ion sputtering technique. Light is then sent into a fiber embedded in concrete and the reflected signal is monitored. Initially, most of the light is reflected by the iron layer. When corrosion occurs to remove the iron layer, a significant portion of the light power will leave the fiber at its exposed end, and the reflected power is greatly reduced. Monitoring of the reflected signal is hence an effective way to assess if the concrete environment at the location of the fiber tip may induce steel corrosion or not. In this paper, first the principle of the corrosion sensor and its fabrication are described. The sensing principle is then verified by experimental results. Sensor packaging for practical installation will be presented and the performance of the packaged sensors is assessed by additional experiments. Full article
(This article belongs to the Special Issue Photonic Sensors for Chemical, Biological, and Nuclear Agent Detection)
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<p>Illustration of the corrosion sensing principle.</p> Full article ">
<p>Plausible ways for retrofitting the sensor on an existing structure with (a) boxed section, (b) solid section.</p> Full article ">
<p>Relationship between the reflectivity at the coated fiber end and the film thickness.</p> Full article ">
<p>Effect of chloride concentration on corrosion sensor output.</p> Full article ">
<p>Output from sensor embedded in concrete under different environments.</p> Full article ">
<p>Schematic diagram of sensor packaging.</p> Full article ">
<p>Fiber sensor packaged inside a mortar block.</p> Full article ">
<p>Experimental set-up of the test of sensors in drilled hole of a hardened cement mortar block.</p> Full article ">
<p>Set-up to compare optical sensor output with corrosion current of steel.</p> Full article ">
113 KiB  
Article
Electrooxidation and Determination of Dopamine Using a Nafion®-Cobalt Hexacyanoferrate Film Modified Electrode
by Suely S. L. Castro, Roger J. Mortimer, Marcelo F. De Oliveira and Nelson R. Stradiotto
Sensors 2008, 8(3), 1950-1959; https://doi.org/10.3390/s8031950 - 19 Mar 2008
Cited by 52 | Viewed by 9816
Abstract
The electrocatalysis of dopamine has been studied using a cobalt hexacyanoferrate film (CoHCFe)-modified glassy carbon electrode. Using a rotating disk CoHCFe-modified electrode, the reaction rate constant for dopamine was found to be 3.5 × 105 cm3 mol-1 s-1 at a [...] Read more.
The electrocatalysis of dopamine has been studied using a cobalt hexacyanoferrate film (CoHCFe)-modified glassy carbon electrode. Using a rotating disk CoHCFe-modified electrode, the reaction rate constant for dopamine was found to be 3.5 × 105 cm3 mol-1 s-1 at a concentration of 5.0 × 10-5 mol L-1. When a Nafion® film is applied to the CoHCFe-modified electrode surface a high selectivity for the determination of dopamine over ascorbic acid was obtained. The analytical curve for dopamine presented linear dependence over the concentration range from 1.2 × 10-5 to 5.0 × 10-4 mol L-1 with a slope of 23.5 mA mol-1 L and a linear correlation coefficient of 0.999. The detection limit of this method was 8.9 × 10-6 mol L-1 and the relative standard deviation for five measurements of 2.5 × 10-4 mol L-1 dopamine was 0.58%. Full article
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<p>Cyclic voltammetric responses of CoHCFe films in 1.0 mol L<sup>-1</sup> KCl (curve a) and in 1.0 mol L<sup>-1</sup> NaCl (curve b). v = 50 mV s<sup>-1</sup>.</p> Full article ">
<p>Cyclic voltammogram of 2.8 × 10<sup>-4</sup> mol L<sup>-1</sup> dopamine in 1.0 mol L<sup>-1</sup> NaCl at glassy carbon electrode. ν = 50 mV s<sup>-1</sup>.</p> Full article ">
<p>Cyclic voltammograms of the CoHCFe film-modified electrode in (a) 1.0 mol L<sup>-1</sup> NaCl solution and (b) 2.8 × 10<sup>-4</sup> mol L<sup>-1</sup> dopamine in 1.0 mol L<sup>-1</sup> NaCl. ν = 50 mV s<sup>-1</sup>.</p> Full article ">
<p>A) Levich plot for dopamine oxidation at CoHCFe film modified electrode in 1.0 mol L<sup>-1</sup> NaCl solution. The curve (a) is the expected mass transport limited current and the curve (b) was obtained experimentally for concentration of 5.0 × 10<sup>-5</sup> mol L<sup>-1</sup> dopamine. B) Koutecky-Levich plot for equal experimental condition as in <a href="#f4-sensors-08-01950" class="html-fig">Figure 4A</a>.</p> Full article ">
<p>Effect of selectivity of Nafion<sup>®</sup> film for dopamine using cyclic voltammetry (<span class="html-italic">ν</span> = 50 mV s<sup>-1</sup>.): a) CoHCFe-Nafion<sup>®</sup> film; b) addition of dopamine at final concentration of 1.4 × 10<sup>-4</sup> mol L<sup>-1</sup>; c) addition of ascorbic acid at final concentration of 1.8 × 10<sup>-3</sup> mol L<sup>-1</sup>.</p> Full article ">
3054 KiB  
Article
Assessment and Analysis of QuikSCAT Vector Wind Products for the Gulf of Mexico: A Long-Term and Hurricane Analysis
by Neha Sharma and Eurico D’Sa
Sensors 2008, 8(3), 1927-1949; https://doi.org/10.3390/s8031927 - 18 Mar 2008
Cited by 26 | Viewed by 15149
Abstract
The northern Gulf of Mexico is a region that has been frequently impacted in recent years by natural disasters such as hurricanes. The use of remote sensing data such as winds from NASA’s QuikSCAT satellite sensor would be useful for emergency preparedness during [...] Read more.
The northern Gulf of Mexico is a region that has been frequently impacted in recent years by natural disasters such as hurricanes. The use of remote sensing data such as winds from NASA’s QuikSCAT satellite sensor would be useful for emergency preparedness during such events. In this study, the performance of QuikSCAT products, including JPL’s latest Level 2B (L2B) 12.5 km swath winds, were evaluated with respect to buoy-measured winds in the Gulf of Mexico for the period January 2005 to February 2007. Regression analyses indicated better accuracy of QuikSCAT’s L2B DIRTH, 12.5 km than the Level 3 (L3), 25 km wind product. QuikSCAT wind data were compared directly with buoy data keeping a maximum time interval of 20 min and spatial interval of 0.1° (?10 km). R2 values for moderate wind speeds were 0.88 and 0.93 for L2B, and 0.75 and 0.89 for L3 for speed and direction, respectively. QuikSCAT wind comparisons for buoys located offshore were better than those located near the coast. Hurricanes that took place during 2002-06 were studied individually to obtain regressions of QuikSCAT versus buoys for those events. Results show QuikSCAT’s L2B DIRTH wind product compared well with buoys during hurricanes up to the limit of buoy measurements. Comparisons with the National Hurricane Center (NHC) best track analyses indicated QuikSCAT winds to be lower than those obtained by NHC, possibly due to rain contamination, while buoy measurements appeared to be constrained at high wind speeds. This study has confirmed good agreement of the new QuikSCAT L2B product with buoy measurements and further suggests its potential use during extreme weather conditions in the Gulf of Mexico. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
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<p>Location of the buoys in the Gulf of Mexico along with tracks of all the hurricanes considered in this study.</p> Full article ">
<p>Time Series of monthly averaged QuikSCAT wind speed for buoys 42001, 42002, 42019 and 42020 (blue line) is shown along with the difference in speed between QuikSCAT and buoy measurements (green line).</p> Full article ">
<p>Level 2B regressions for all wind speeds in the Gulf of Mexico (a, b) and the Pacific Ocean (c, d). Left panels depict wind speed measurements. Right panels depict wind direction measurements. ‘R<sup>2</sup>′ is the coefficient of determination and ‘n’ is the number of data points.</p> Full article ">
<p>Level 2B DIRTH regressions for moderate winds (light/strong winds in gray) in the Gulf of Mexico (a, b, e, f) and the Pacific Ocean (c, d, g, h). Left panels depict wind speed measurements. Right panels depict wind direction measurements. ‘R<sup>2</sup>′ is the coefficient of determination and ‘n’ is the number of data points for moderate winds only.</p> Full article ">
<p>Level 2B measurements shown as difference in QuikSCAT and buoy measurements in the Gulf of Mexico (a, b) and the Pacific Ocean (c, d). Left panels depict wind speed measurements. Right panels depict wind direction measurements.</p> Full article ">
<p>Box plots depicting variations at individual buoys for speed (left panels) and direction (right panel) difference between QuikSCAT and buoys (x-axis). Top panels (a, b) show variations for all wind speeds. Bottom (c, d) panels show variations for moderate winds. The central lines of the boxes denote the median and the edges depict the 25<sup>th</sup> and 75<sup>th</sup> percentile. The error bars beyond the boxes depict the 10<sup>th</sup> and 90<sup>th</sup> percentile and the points depict the 5<sup>th</sup> and 95<sup>th</sup> percentile.</p> Full article ">
<p>Level 3 regressions in the Gulf of Mexico (a, b, e, f) and the Pacific Ocean (c, d, g, h). Left panels depict wind speed measurements and right panels depict wind direction measurements. ‘R<sup>2</sup>′ is the coefficient of determination and ‘n’ is the number of data points. Moderate winds are shown by dark symbols and light/strong winds are shown by gray symbols.</p> Full article ">
<p>Level 3 measurements shown as difference between QuikSCAT and buoy measurements for the Gulf of Mexico (a, c) and the Pacific Ocean (b, d) with dark symbols denoting moderate winds. Left panels depict wind speed measurements and right panels depict wind direction measurements. Line indicates the regression line.</p> Full article ">
<p>Box plots depicting variations at individual buoys for speed (left panels) and direction (right panel) difference between QuikSCAT and buoys. Top panels (a, b) show variations for all wind speeds. Bottom (c, d) panels show variations for moderate winds. The central lines of the boxes denote the median and the edges depict the 25<sup>th</sup> and 75<sup>th</sup> percentile. The error bars beyond the boxes depict the 10<sup>th</sup> and 90<sup>th</sup> percentile and the points depict the 5<sup>th</sup> and 95<sup>th</sup> percentile.</p> Full article ">
346 KiB  
Article
A Dynamic Range Expansion Technique for CMOS Image Sensors with Dual Charge Storage in a Pixel and Multiple Sampling
by Suhaidi Shafie, Shoji Kawahito and Shinya Itoh
Sensors 2008, 8(3), 1915-1926; https://doi.org/10.3390/s8031915 - 18 Mar 2008
Cited by 13 | Viewed by 11033
Abstract
A dynamic range expansion technique for CMOS image sensors with dual charge storage in a pixel and multiple sampling technique is presented. Each pixel contains a photodiode and a storage diode which is connected to the photodiode via a separation gate. The sensitivity [...] Read more.
A dynamic range expansion technique for CMOS image sensors with dual charge storage in a pixel and multiple sampling technique is presented. Each pixel contains a photodiode and a storage diode which is connected to the photodiode via a separation gate. The sensitivity of the signal charge in the storage diode can be controlled either by a separation gate which limits the charge to flow into the storage diode or by controlling the accumulation time in the storage diode. The operation of the sensitivity control with separation gate techniques is simulated and it is found that a blocking layer to the storage diode plays an important role for high controllability of sensitivity of the storage diode. A prototype chip for testing multiple short time accumulations is fabricated and measured. Full article
(This article belongs to the Special Issue Integrated High-performance Imagers)
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<p>(a) Simplified structure and (b) Cross section at line aa' of the proposed pixel.</p> Full article ">
<p>Direction of charge flows when the SP gate is opened and closed.</p> Full article ">
<p>Accumulation and readout timing of proposed sensitivity control with SP gate.</p> Full article ">
<p>Accumulation and readout timing of proposed multiples short accumulation and gated charge</p> Full article ">
<p>Moving light pattern captured by a line sensor.</p> Full article ">
<p>The movement of photo-electron diffused from deep inside the pixel to the surface.</p> Full article ">
<p>Sensitivity when the SP gate is closed.</p> Full article ">
<p>Sensitivity when the SP gate is opened and closed.</p> Full article ">
<p>Equivalent pixel structure implemented.</p> Full article ">
2378 KiB  
Article
Sensor Performance Requirements for the Retrieval of Atmospheric Aerosols by Airborne Optical Remote Sensing
by Felix Seidel, Daniel Schläpfer, Jens Nieke and Klaus I. Itten
Sensors 2008, 8(3), 1901-1914; https://doi.org/10.3390/s8031901 - 18 Mar 2008
Cited by 16 | Viewed by 13295
Abstract
This study explores performance requirements for the retrieval of the atmospheric aerosol optical depth (AOD) by airborne optical remote sensing instruments. Independent of any retrieval techniques, the calculated AOD retrieval requirements are compared with the expected performance parameters of the upcoming hyperspectral sensor [...] Read more.
This study explores performance requirements for the retrieval of the atmospheric aerosol optical depth (AOD) by airborne optical remote sensing instruments. Independent of any retrieval techniques, the calculated AOD retrieval requirements are compared with the expected performance parameters of the upcoming hyperspectral sensor APEX at the reference wavelength of 550nm. The AOD accuracy requirements are defined to be capable of resolving transmittance differences of 0.01 to 0.04 according to the demands of atmospheric corrections for remote sensing applications. For the purposes of this analysis, the signal at the sensor level is simulated by radiation transfer equations. The resulting radiances are translated into the AOD retrieval sensitivity (???aer ) and compared to the available measuring sensitivity of the sensor (NE ?L?sensor). This is done for multiple signal-to-noise ratios (SNR) and surface reflectance values. It is shown that an SNR of 100 is adequate for AOD retrieval at 550nm under typical remote sensing conditions and a surface reflectance of 10% or less. Such dark surfaces require the lowest SNR values and therefore offer the best sensitivity for measuring AOD. Brighter surfaces with up to 30% reflectance require an SNR of around 300. It is shown that AOD retrieval for targets above 50% surface reflectance is more problematic with the current sensor performance as it may require an SNR larger than 1000. In general, feasibility is proven for the analyzed cases under simulated conditions. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
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<p>Black lines show the radiance simulations, while the MODTRAN4 reference calculations are given by colored lines with circles. (a) Influence of AOD <math display="inline"> <semantics id="sm130"> <mrow> <msubsup> <mi>τ</mi> <mrow> <mn>550</mn> <mtext mathvariant="italic">nm</mtext></mrow> <mtext mathvariant="italic">aer</mtext></msubsup></mrow></semantics></math> on the observed path-radiance <math display="inline"> <semantics id="sm131"> <mrow> <mrow> <mo stretchy="false">(</mo> <mrow> <msubsup> <mi>ρ</mi> <mi>λ</mi> <mtext mathvariant="italic">sfc</mtext></msubsup> <mo>=</mo> <mn>0</mn></mrow> <mo stretchy="false">)</mo></mrow></mrow></semantics></math> with the single scattering approximation <math display="inline"> <semantics id="sm132"> <mrow> <mrow> <mo stretchy="false">(</mo> <mrow> <msubsup> <mi>L</mi> <mrow> <mn>550</mn> <mi>n</mi> <mi>m</mi> <mo>,</mo> <mtext mathvariant="italic">SSA</mtext></mrow> <mtext mathvariant="italic">atm</mtext></msubsup></mrow> <mo stretchy="false">)</mo></mrow></mrow></semantics></math> from <a href="#FD3" class="html-disp-formula">Equation 3</a> and with multiple scattering <math display="inline"> <semantics id="sm133"> <mrow> <mrow> <mo stretchy="false">(</mo> <mrow> <msubsup> <mi>L</mi> <mrow> <mn>550</mn> <mtext mathvariant="italic">nm</mtext></mrow> <mtext mathvariant="italic">atm</mtext></msubsup></mrow> <mo stretchy="false">)</mo></mrow></mrow></semantics></math> from <a href="#FD5" class="html-disp-formula">Equation 5</a>. (b) Influence of <math display="inline"> <semantics id="sm134"> <mrow> <mrow> <mrow> <msubsup> <mi>τ</mi> <mrow> <mn>550</mn> <mtext mathvariant="italic">nm</mtext></mrow> <mtext mathvariant="italic">aer</mtext></msubsup></mrow></mrow></mrow></semantics></math> on the observed radiance <math display="inline"> <semantics id="sm135"> <mo stretchy="false">(</mo> <mrow> <msubsup> <mi>L</mi> <mrow> <mn>550</mn> <mtext mathvariant="italic">nm</mtext></mrow> <mtext mathvariant="italic">sensor</mtext></msubsup></mrow> <mo stretchy="false">)</mo></semantics></math> including the surface contribution from <a href="#FD8" class="html-disp-formula">Equation (8)</a>. <span class="html-italic">ρ</span> = ‥% denotes the corresponding surface reflectance <math display="inline"> <semantics id="sm136"> <mrow> <msubsup> <mi>ρ</mi> <mi>λ</mi> <mtext mathvariant="italic">sfc</mtext></msubsup></mrow></semantics></math>.</p> Full article ">
<p>Influence of <math display="inline"> <semantics id="sm137"> <mrow> <msubsup> <mi>τ</mi> <mrow> <mn>550</mn> <mtext mathvariant="italic">nm</mtext></mrow> <mtext mathvariant="italic">aer</mtext></msubsup></mrow></semantics></math> on the AOD retrieval sensitivity <math display="inline"> <semantics id="sm138"> <mrow> <mi>N</mi> <mi>E</mi> <mi mathvariant="normal">Δ</mi> <msubsup> <mi>τ</mi> <mrow> <mn>550</mn> <mtext mathvariant="italic">nm</mtext></mrow> <mtext mathvariant="italic">aer</mtext></msubsup></mrow></semantics></math> for different SNR values. AOD retrieval is feasible outside the red area, while the transmittance accuracy requirement complies with 0.01 &lt; <span class="html-italic">ε</span> &lt; 0.04 within the light orange area and with <span class="html-italic">ε</span> &lt; 0.01 within the white area.</p> Full article ">
<p>Influence of <math display="inline"> <semantics id="sm139"> <mrow> <msubsup> <mi>τ</mi> <mrow> <mn>550</mn> <mtext mathvariant="italic">nm</mtext></mrow> <mtext mathvariant="italic">aer</mtext></msubsup></mrow></semantics></math> on the AOD retrieval sensitivity <math display="inline"> <semantics id="sm140"> <mrow> <mi>N</mi> <mi>E</mi> <mi mathvariant="normal">Δ</mi> <msubsup> <mi>τ</mi> <mrow> <mn>550</mn> <mtext mathvariant="italic">nm</mtext></mrow> <mtext mathvariant="italic">aer</mtext></msubsup></mrow></semantics></math> for different surface reflectances <math display="inline"> <semantics id="sm141"> <mrow> <msubsup> <mi>ρ</mi> <mrow> <mn>550</mn> <mtext mathvariant="italic">nm</mtext></mrow> <mtext mathvariant="italic">sfc</mtext></msubsup></mrow></semantics></math>. AOD retrieval is feasible outside the red area, while the transmittance accuracy requirement complies with 0.01 &lt; <span class="html-italic">ε</span> &lt; 0.04 within the light orange area and with <span class="html-italic">ε</span> &lt; 0.01 within the white area.</p> Full article ">
370 KiB  
Article
Electrochemical Determination of Trace Sudan I Contamination in Chili Powder at Carbon Nanotube Modified Electrodes
by Liang Ming, Xia Xi, Tingting Chen and Jie Liu
Sensors 2008, 8(3), 1890-1900; https://doi.org/10.3390/s8031890 - 17 Mar 2008
Cited by 26 | Viewed by 11550
Abstract
We have developed a simple, convenient and inexpensive voltammetric method for determining trace Sudan I contamination in chili powder, based on the catalyzed electrochemical reduction of Sudan I at the carbon nanotube modified electrode. Under optimized conditions, the method exhibited acceptable analytical performance [...] Read more.
We have developed a simple, convenient and inexpensive voltammetric method for determining trace Sudan I contamination in chili powder, based on the catalyzed electrochemical reduction of Sudan I at the carbon nanotube modified electrode. Under optimized conditions, the method exhibited acceptable analytical performance in terms of linearity (over the concentration range 6.0×10–7 to 7.5×10–5 M, r = 0.9967), detection limit (2.0×10–7 M) and reproducibility (RSD = 4.6%, n=10, for 2.0×10–5 M Sudan I). Full article
(This article belongs to the Special Issue Utilization of Electrochemical Sensors and Biosensors in Biochemistry and Molecular Biology)
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<p>Chemical structure of Sudan I.</p> Full article ">
<p>TEM image of the MWCNTs (a) and SEM image of the MWCNTs modified GCE (b).</p> Full article ">
<p>Cyclic voltammograms of the MWCNTs modified GCE (a, b) or the bare GCE (c, d) when placed in 0.1 M PBS (pH 7.0) in the presence (a, c) and absence (b, d) of 2.0×10<sup>−5</sup> M Sudan I. Scan rate: 100 mV/s.</p> Full article ">
<p>Linear sweep voltammograms of Sudan I at the MWCNTs modified GCE in 0.1 M PBS (pH 7.0) containing 5.0×10<sup>−5</sup> (a), 4.0×10<sup>−5</sup> (b), 3.0×10<sup>−5</sup> (c), 2.0×10<sup>−5</sup> (d), 5.0×10<sup>−6</sup> (e), 0 (f) M of Sudan I, respectively. Accumulation time = 3 min. Scan rate: 100 mV/s.</p> Full article ">
88 KiB  
Review
Sensitive Detection of Haloperidol and Hydroxyzine at Multi-Walled Carbon Nanotubes-Modified Glassy Carbon Electrodes
by Fei Huang, Youyuan Peng, Guiying Jin, Song Zhang and Jilie Kong
Sensors 2008, 8(3), 1879-1889; https://doi.org/10.3390/s8031879 - 17 Mar 2008
Cited by 39 | Viewed by 11548
Abstract
Haloperidol (i.e. HPD) and hydroxyzine (i.e. HXY), two effective and important tranquilizers with low redox activity, were found to generate an irreversible anodic peak at about +0.86 V (vs. SCE) or two anodic peaks at about +0.83 and +0.91 V in 0.05 M [...] Read more.
Haloperidol (i.e. HPD) and hydroxyzine (i.e. HXY), two effective and important tranquilizers with low redox activity, were found to generate an irreversible anodic peak at about +0.86 V (vs. SCE) or two anodic peaks at about +0.83 and +0.91 V in 0.05 M NaH2PO4-Na2HPO4 (pH=7.0) buffer solution with a multi-walled carbon nanotubes-modified glassy carbon electrode (i.e. MWNTs/GC), respectively. Their sensitive and quantitative measurement based on the first two anodic peaks was established under the optimum conditions. The anodic peak current was linear to HPD and HXY concentration from 1×10-7 to 2.5 ×10-5 M and 5×10-8 to 2.5 ×10-5 M, the detection limits obtained were 8×10-9 and 5×10-9 M, separately. The modified electrode exhibited some excellent characteristics including easy regeneration, high stability, good reproducibility and selectivity. The method proposed was successfully applied to the detection of HPD and HXY in drug tablets and proved to be reliable compared with ultraviolet spectrophotometry. The modified electrode was characterized by electrochemical methods. Full article
(This article belongs to the Special Issue Utilization of Electrochemical Sensors and Biosensors in Biochemistry and Molecular Biology)
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<p>CVs of 2 mM K<sub>3</sub>Fe(CN)<sub>6</sub> at bare GC electrode (A) and MWNTs/GC modified electrode (B). Scan rate: 100 mV s<sup>-1</sup>; supporting electrolyte: 0.05 M KNO<sub>3</sub>.</p> Full article ">
<p>EIS spectra of bare GC electrode (A) and MWNTs/GC modified electrode (B). Frequency used: 0.1 Hz to 100 KHz; solution: 2 mM K<sub>3</sub>Fe(CN)<sub>6</sub>/K<sub>4</sub>Fe(CN)<sub>6</sub> containing 0.1 M KNO<sub>3</sub>. The insert is the amplification of (B).</p> Full article ">
<p>CVs of 5×10<sup>-6</sup> M HPD or HXY at the bare GC electrode (A) and the MWNTs/GC modified electrode (C). CVs of MWNTs/GC modified electrode in blank solution (B). Scan rate: 100 mV s<sup>-1</sup>; supporting electrolyte: 0.05 M NaH<sub>2</sub>PO<sub>4</sub>-Na<sub>2</sub>HPO<sub>4</sub> (pH=7.0); accumulation time: 180 s (at open circuit).</p> Full article ">
<p>Influence of pH on the anodic peak current (A) and peak potential (B) of HPD or HXY. Supporting electrolyte: 0.05 M phosphate. Other conditions as in <a href="#f3-sensors-08-01879" class="html-fig">Figure 3</a>.</p> Full article ">
<p>Influence of amount of MWNTs suspension on the anodic peak current of HPD or HXY. Other conditions as in <a href="#f3-sensors-08-01879" class="html-fig">Figure 3</a>.</p> Full article ">
<p>Molecular structure of haloperidol (HPD) or hydroxyzine (HXY).</p> Full article ">
136 KiB  
Article
High Sensitive Temperature Sensor Using a Liquid-core Optical Fiber with Small Refractive Index Difference Between Core and Cladding Materials
by Yonghao Xu, Xianfeng Chen and Yu Zhu
Sensors 2008, 8(3), 1872-1878; https://doi.org/10.3390/s8031872 - 17 Mar 2008
Cited by 41 | Viewed by 10951
Abstract
An intensive temperature sensor based on a liquid-core optical fiber has been demonstrated for the measuring the temperature of the environment. The core of fiber is filled with a mixture of toluene and chloroform in order to make the refractive index of the [...] Read more.
An intensive temperature sensor based on a liquid-core optical fiber has been demonstrated for the measuring the temperature of the environment. The core of fiber is filled with a mixture of toluene and chloroform in order to make the refractive index of the liquid-core and the cladding of the fiber close. The experiment shows that a temperature sensitivity of about 5 dB/K and a tunable temperature range (from 20 oC to 60 oC) can be achieved. Based on the dielectric-clad liquid core fiber model, a simulation was carried out and the calculated results were in good accord with the experimental measurement. Full article
(This article belongs to the Special Issue Optical Biosensors)
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<p>Experiment setup for the liquid-core fiber temperature sensor.</p> Full article ">
<p>Variation of normalized transmitted intensity as a function of the temperature for liquid mixture with three kinds of concentrations of the toluene.</p> Full article ">
<p>Comparison of theoretical and experimental results (the concentration of the toluene is 30%).</p> Full article ">
92 KiB  
Article
Amperometric Determination of Sulfite by Gas Diffusion- Sequential Injection with Boron-Doped Diamond Electrode
by Chakorn Chinvongamorn, Kulwadee Pinwattana, Narong Praphairaksit, Toshihiko Imato and Orawon Chailapakul
Sensors 2008, 8(3), 1846-1857; https://doi.org/10.3390/s8031846 - 17 Mar 2008
Cited by 49 | Viewed by 14830
Abstract
A gas diffusion sequential injection system with amperometric detection using aboron-doped diamond electrode was developed for the determination of sulfite. A gasdiffusion unit (GDU) was used to prevent interference from sample matrices for theelectrochemical measurement. The sample was mixed with an acid solution [...] Read more.
A gas diffusion sequential injection system with amperometric detection using aboron-doped diamond electrode was developed for the determination of sulfite. A gasdiffusion unit (GDU) was used to prevent interference from sample matrices for theelectrochemical measurement. The sample was mixed with an acid solution to generategaseous sulfur dioxide prior to its passage through the donor channel of the GDU. Thesulfur dioxide diffused through the PTFE hydrophobic membrane into a carrier solution of 0.1 M phosphate buffer (pH 8)/0.1% sodium dodecyl sulfate in the acceptor channel of theGDU and turned to sulfite. Then the sulfite was carried to the electrochemical flow cell anddetected directly by amperometry using the boron-doped diamond electrode at 0.95 V(versus Ag/AgCl). Sodium dodecyl sulfate was added to the carrier solution to preventelectrode fouling. This method was applicable in the concentration range of 0.2-20 mgSO32?/L and a detection limit (S/N = 3) of 0.05 mg SO32?/L was achieved. This method wassuccessfully applied to the determination of sulfite in wines and the analytical resultsagreed well with those obtained by iodimetric titration. The relative standard deviations forthe analysis of sulfite in wines were in the range of 1.0-4.1 %. The sampling frequency was65 h?1. Full article
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<p>SIA manifold for the determination of sulfite: EC, electrochemical flow cell.</p> Full article ">
<p>Cyclic voltammograms of 1mM Na<sub>2</sub>SO<sub>3</sub> in 0.1 M phosphate buffer (a) pH 4-7 and (b) pH 7-10 at the BDD electrode. The sweep rate was 50 mV/s. The area of the electrode was 0.07 cm<sup>2</sup>.</p> Full article ">
<p>(a) Hydrodynamic voltammetric results for 10 mg SO<sub>3</sub><sup>2−</sup>/L (Signal) and 0.1 M phosphate buffer pH 8/0.1% SDS (Background) at 0.70-1.05 V (vs. Ag/AgCl). The SIA operating sequence is listed in <a href="#t1-sensors-08-01846" class="html-table">Table 1</a>. (b) Hydrodynamic voltammogram of signal-to-background ratios.</p> Full article ">
<p>SIA with amperometric detection results for 15 consecutive injections of 10 mg SO<sub>3</sub><sup>2−</sup>/L. Carrier was 0.1 M phosphate buffer pH 8 (-□-) and 0.1 M phosphate buffer pH 8/0.1% SDS (-●-). The SIA operating sequence is listed in <a href="#t1-sensors-08-01846" class="html-table">Table 1</a>.</p> Full article ">
<p>Relationship between the average peak current and the volume of the second plug of 2 M H<sub>2</sub>SO<sub>4</sub>. The concentration of sulfite was 10 mg/L.</p> Full article ">
<p>SIA with amperometric detection results at various flow rate of carrier for 10 mg SO<sub>3</sub><sup>2−</sup>/L. Carrier was 0.1 M phosphate buffer pH 8/0.1% SDS. The SIA operating sequence is listed in <a href="#t1-sensors-08-01846" class="html-table">Table 1</a>.</p> Full article ">
<p>Relationship between the average peak current and the sample volume of 10 mg/L sulfite.</p> Full article ">
<p>SIA with amperometric detection results for various concentrations of SO<sub>3</sub><sup>2−</sup>. The SIA operating sequence is listed in <a href="#t1-sensors-08-01846" class="html-table">Table 1</a>. The calibration curve is shown in the inset.</p> Full article ">
354 KiB  
Article
Estimation of the Total Atmospheric Water Vapor Content and Land Surface Temperature Based on AATSR Thermal Data
by Tangtang Zhang, Jun Wen, Rogier Van der Velde, Xianhong Meng, Zhenchao Li, Yuanyong Liu and Rong Liu
Sensors 2008, 8(3), 1832-1845; https://doi.org/10.3390/s8031832 - 16 Mar 2008
Cited by 9 | Viewed by 12503
Abstract
The total atmospheric water vapor content (TAWV) and land surfacetemperature (LST) play important roles in meteorology, hydrology, ecology and some otherdisciplines. In this paper, the ENVISAT/AATSR (The Advanced Along-Track ScanningRadiometer) thermal data are used to estimate the TAWV and LST over the Loess [...] Read more.
The total atmospheric water vapor content (TAWV) and land surfacetemperature (LST) play important roles in meteorology, hydrology, ecology and some otherdisciplines. In this paper, the ENVISAT/AATSR (The Advanced Along-Track ScanningRadiometer) thermal data are used to estimate the TAWV and LST over the Loess Plateauin China by using a practical split window algorithm. The distribution of the TAWV isaccord with that of the MODIS TAWV products, which indicates that the estimation of thetotal atmospheric water vapor content is reliable. Validations of the LST by comparingwith the ground measurements indicate that the maximum absolute derivation, themaximum relative error and the average relative error is 4.0K, 11.8% and 5.0%respectively, which shows that the retrievals are believable; this algorithm can provide anew way to estimate the LST from AATSR data. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
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<p>Location and land-use classification of the Loess Plateau in the Eastern Gansu Province.</p> Full article ">
<p>MODTRAN simulated radiance at the AATSR thermal bands.</p> Full article ">
<p>Atmospheric transmittance of the AATSR thermal bands with total atmospheric water vapor content simulated by MODTRAN.</p> Full article ">
<p>Flow chart for retrieving land surface temperature from AATSR data.</p> Full article ">
<p>Distribution of the total atmospheric water vapor content over the eastern Gansu province of the Loess Plateau (a: 27<sup>th</sup> Jun, 2005; b: 13<sup>th</sup> Jul, 2005).</p> Full article ">
<p>Distribution of land surface temperature over the eastern Gansu of the Loess Plateau (a: 27<sup>th</sup> Jun, 2005; b: 13<sup>th</sup> Jul, 2005).</p> Full article ">
<p>Histograms of the TAWV and the LST of the two days.</p> Full article ">
1111 KiB  
Article
A New PC and LabVIEW Package Based System for Electrochemical Investigations
by Zoran Stević, Zoran Andjelković and Dejan Antić
Sensors 2008, 8(3), 1819-1831; https://doi.org/10.3390/s8031819 - 15 Mar 2008
Cited by 32 | Viewed by 11586
Abstract
The paper describes a new PC and LabVIEW software package based system forelectrochemical research. An overview of well known electrochemical methods, such aspotential measurements, galvanostatic and potentiostatic method, cyclic voltammetry andEIS is given. Electrochemical impedance spectroscopy has been adapted for systemscontaining large capacitances. [...] Read more.
The paper describes a new PC and LabVIEW software package based system forelectrochemical research. An overview of well known electrochemical methods, such aspotential measurements, galvanostatic and potentiostatic method, cyclic voltammetry andEIS is given. Electrochemical impedance spectroscopy has been adapted for systemscontaining large capacitances. For signal generation and recording of the response ofinvestigated electrochemical cell, a measurement and control system was developed, basedon a PC P4. The rest of the hardware consists of a commercially available AD-DA converterand an external interface for analog signal processing. The interface is a result of authorsown research. The software platform for desired measurement methods is LabVIEW 8.2package, which is regarded as a high standard in the area of modern virtual instruments. Thedeveloped system was adjusted, tested and compared with commercially available systemand ORCAD simulation. Full article
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<p>The block diagram of the interface.</p> Full article ">
<p>Front Panel of instrument for measuring the open circuit potential.</p> Full article ">
<p>Block diagram of instrument for measuring the open circuit potential.</p> Full article ">
<p>Front panel of the instrument for galvanostatic method.</p> Full article ">
<p>Block diagram of the instrument for galvanostatic method.</p> Full article ">
<p>Front panel of the instruments for potentiostatic method.</p> Full article ">
<p>Block diagram of the instruments for potentiostatic method.</p> Full article ">
<p>Algorithmic scheme of VI for cyclic voltammetry.</p> Full article ">
<p>Front panel of the instrument for cyclic voltammetry.</p> Full article ">
384 KiB  
Article
Localization Algorithm Based on a Spring Model (LASM) for Large Scale Wireless Sensor Networks
by Wanming Chen, Tao Mei, Max Q.-H. Meng, Huawei Liang, Yumei Liu, Yangming Li and Shuai Li
Sensors 2008, 8(3), 1797-1818; https://doi.org/10.3390/s8031797 - 15 Mar 2008
Cited by 17 | Viewed by 14272
Abstract
A navigation method for a lunar rover based on large scale wireless sensornetworks is proposed. To obtain high navigation accuracy and large exploration area, highnode localization accuracy and large network scale are required. However, thecomputational and communication complexity and time consumption are greatly [...] Read more.
A navigation method for a lunar rover based on large scale wireless sensornetworks is proposed. To obtain high navigation accuracy and large exploration area, highnode localization accuracy and large network scale are required. However, thecomputational and communication complexity and time consumption are greatly increasedwith the increase of the network scales. A localization algorithm based on a spring model(LASM) method is proposed to reduce the computational complexity, while maintainingthe localization accuracy in large scale sensor networks. The algorithm simulates thedynamics of physical spring system to estimate the positions of nodes. The sensor nodesare set as particles with masses and connected with neighbor nodes by virtual springs. Thevirtual springs will force the particles move to the original positions, the node positionscorrespondingly, from the randomly set positions. Therefore, a blind node position can bedetermined from the LASM algorithm by calculating the related forces with the neighbornodes. The computational and communication complexity are O(1) for each node, since thenumber of the neighbor nodes does not increase proportionally with the network scale size.Three patches are proposed to avoid local optimization, kick out bad nodes and deal withnode variation. Simulation results show that the computational and communicationcomplexity are almost constant despite of the increase of the network scale size. The time consumption has also been proven to remain almost constant since the calculation steps arealmost unrelated with the network scale size. Full article
(This article belongs to the Special Issue Energy Efficiency and Intelligent Signal Processing for Wireless Sensing)
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<p>Spring model for wireless sensor networks.</p> Full article ">
<p>Explanation of the proposed localization algorithm based on spring model. <ul class="html-roman-upper"><li><div class="html-p">wireless sensor network</p> Full article ">
<p>An specific example where node a can also be localized.</p> Full article ">
<p>The simulation process and results of LASM. (a) the position estimation error changes in simulation process, <span class="html-italic">Tforce</span>=1. (b) <span class="html-italic">Tforce</span>=0.1. (c) The result of position estimation in LASM(B), <span class="html-italic">Tforce</span>=1. (d) LASM(P), <span class="html-italic">Tforce</span>=1. (e) LASM(B), <span class="html-italic">Tforce</span>=0.1. (e) LASM(P), <span class="html-italic">Tforce</span>=0.1.</p> Full article ">
<p>The robustness of the LASM algorithm in 100 randomly generated examples. (a) general calculation steps in LASM(B). (b) general calculation steps in LASM(P). (c) position error in LASM(B). (d) position error in LASM(P).</p> Full article ">
<p>The communication cost and position error versus the number of nodes. (a) average calculation steps versus the number of nodes in LASM(B). (b) average calculation steps in LASM(P). (c) the position error versus the number of nodes in LASM(B). (d) position error in LASM(P).</p> Full article ">
<p>Comparisons with MDS-MAP. (a) a random example in uniform networks. (b) a random example in C-shaped networks. (c) the position error versus connectivity in uniform networks. (d) the position error versus connectivity in C-shaped networks.</p> Full article ">
<p>Experiment design. (a) The proposed sensor node architecture (b) the sensor node designed by us (c) experiment field to test the localization algorithm (d) the result of experiment.</p> Full article ">
225 KiB  
Article
Development and Demonstration of Measurement-Time Efficient Methods for Impedance Spectroscopy of Electrode and Sensor Arrays
by Kevin R. Cooper, Matthew Smith and Derek Johnson
Sensors 2008, 8(3), 1774-1796; https://doi.org/10.3390/s8031774 - 14 Mar 2008
Cited by 9 | Viewed by 9083
Abstract
The development of impedance-based array devices is hindered by a lack ofrobust platforms and methods upon which to evaluate and interrogate sensors. One aspectto be addressed is the development of measurement-time efficient techniques forbroadband impedance spectroscopy of large electrode arrays. The objective of [...] Read more.
The development of impedance-based array devices is hindered by a lack ofrobust platforms and methods upon which to evaluate and interrogate sensors. One aspectto be addressed is the development of measurement-time efficient techniques forbroadband impedance spectroscopy of large electrode arrays. The objective of this workwas to substantially increase the low frequency impedance measurement throughputcapability of a large channel count array analyzer by developing true parallel measurementmethods. The goal was achieved by Fourier transform-based analysis of simultaneouslyacquiredmulti-channel time-based current and voltage data. Efficacy and quantitativeanalysis of the parallel approach at frequencies less than ca. 10 Hz as well as a combinedsequential parallel approach for efficient broadband impedance spectroscopy over 5-orders of magnitude in frequency is demonstrated through complex impedancemeasurement of arrays consisting of up to 100 elements. Full article
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<p>Typical experimental set-up for electrical or electrochemical testing of a microelectrode or sensor array. The set-up is similar to a traditional 3-electrode configuration consisting of a working electrode (WE), counter electrode (CE) and reference electrode (RE) with the exception that the single WE is replaced with <span class="html-italic">N</span> working electrodes resulting in an <span class="html-italic">N</span> + 2 electrode configuration. Both inter-electrode and polarized cell currents can exist within the cell depending on the relative potentials imposed on the array elements.</p> Full article ">
<p>Key to placement of twenty equivalent circuit dummy cells across array analyzer segments and groups (10 groups of 10 segments/group).</p> Full article ">
<p>(a) Raw current I(x,y) and voltage data acquired at ∼ 22 frames/second with the MMA instrument imposing a 10 Hz, 0.25 V AC signal. The frequency-dependence of the data is not apparent in the raw data. (b) Post-FFT data processing, the time-dependent AC response is reproduced with the expected 0.1 second period. Time skew between the individual current channel data and the voltage channel data is apparent in the reconstructed data set.</p> Full article ">
<p>Low frequency impedance of an array of one hundred 100 kΩ resistors determined from DC time-based I<sub>k</sub>(ω),V(ω) data. (a) Without time skew correction factor the phase error approached 180° at 10 Hz. (b) With time skew correction factors the phase error is less than 2.5° at 10 Hz. Application of the time skew correction significantly improves the accuracy and decreases the phase angle error at all but the lowest frequencies.</p> Full article ">
<p>Low frequency impedance of an array of one hundred 100 kΩ resistors determined from DC time-based I<sub>k</sub>(ω),V(ω) data. (a) Without time skew correction factor the phase error approached 180° at 10 Hz. (b) With time skew correction factors the phase error is less than 2.5° at 10 Hz. Application of the time skew correction significantly improves the accuracy and decreases the phase angle error at all but the lowest frequencies.</p> Full article ">
<p>Real(Z) by standard <span class="html-italic">vs.</span> parallel method at three frequencies. The box indicates the range of resistances expected based on ±1 % rated accuracy of the resistor.</p> Full article ">
<p>Low frequency impedance of an array of one hundred resistors ranging from 1 MΩ to 50 MΩ. (a) Complex impedance obtained from parallel FFT method in 7 minutes. With time skew correction factors applied the phase error is less than 2.5° at 10 Hz indicating that the parallel measurement method can be used to simultaneously obtain the impedance of large array. (b) Complex impedance determined using standard sequential measurement approach in 120 minutes.</p> Full article ">
<p>Complex plane plots (Z″ <span class="html-italic">vs.</span> Z′) and Bode plots (log |Z| and phase angle <span class="html-italic">vs.</span> log ω) of the equivalent circuit dummy cells. Impedance in ohms and phase angle theta in degree.</p> Full article ">
<p>Complex plane plots (Z″ <span class="html-italic">vs.</span> Z′) and Bode plots (log |Z| and phase angle <span class="html-italic">vs.</span> log ω) of the equivalent circuit dummy cells. Impedance in ohms and phase angle theta in degree.</p> Full article ">
<p>Impedance plots for standard method (○) + parallel (□) measurement method for one of each of 4 types of equivalent circuit dummy cells. This page: Type A and B, next page: Type C and D. Standard Method: 10 kHz to 10 Hz; Parallel Method: 10 Hz to 0.1 Hz. See text for impedance measurement conditions.</p> Full article ">
<p>Impedance plots for standard method (○) + parallel (□) measurement method for one of each of 4 types of equivalent circuit dummy cells. This page: Type A and B, next page: Type C and D. Standard Method: 10 kHz to 10 Hz; Parallel Method: 10 Hz to 0.1 Hz. See text for impedance measurement conditions.</p> Full article ">
187 KiB  
Communication
An Open Distributed Architecture for Sensor Networks for Risk Management
by John Douglas, Thomas Usländer, Gerald Schimak, J. Fernando Esteban and Ralf Denzer
Sensors 2008, 8(3), 1755-1773; https://doi.org/10.3390/s8031755 - 13 Mar 2008
Cited by 29 | Viewed by 17526
Abstract
Sensors provide some of the basic input data for risk management of natural andman-made hazards. Here the word ‘sensors’ covers everything from remote sensingsatellites, providing invaluable images of large regions, through instruments installed on theEarth’s surface to instruments situated in deep boreholes and [...] Read more.
Sensors provide some of the basic input data for risk management of natural andman-made hazards. Here the word ‘sensors’ covers everything from remote sensingsatellites, providing invaluable images of large regions, through instruments installed on theEarth’s surface to instruments situated in deep boreholes and on the sea floor, providinghighly-detailed point-based information from single sites. Data from such sensors is used inall stages of risk management, from hazard, vulnerability and risk assessment in the preeventphase, information to provide on-site help during the crisis phase through to data toaid in recovery following an event. Because data from sensors play such an important part inimproving understanding of the causes of risk and consequently in its mitigation,considerable investment has been made in the construction and maintenance of highlysophisticatedsensor networks. In spite of the ubiquitous need for information from sensornetworks, the use of such data is hampered in many ways. Firstly, information about thepresence and capabilities of sensor networks operating in a region is difficult to obtain dueto a lack of easily available and usable meta-information. Secondly, once sensor networkshave been identified their data it is often difficult to access due to a lack of interoperability between dissemination and acquisition systems. Thirdly, the transfer and processing ofinformation from sensors is limited, again by incompatibilities between systems. Therefore,the current situation leads to a lack of efficiency and limited use of the available data thathas an important role to play in risk mitigation. In view of this situation, the EuropeanCommission (EC) is funding a number of Integrated Projects within the Sixth FrameworkProgramme concerned with improving the accessibility of data and services for riskmanagement. Two of these projects: ‘Open Architecture and Spatial Data Infrastructure forRisk Management’ (ORCHESTRA, http://www.eu-orchestra.org/) and ‘Sensors Anywhere’(SANY, http://sany-ip.eu/) are discussed in this article. These projects have developed anopen distributed information technology architecture and have implemented web servicesfor the accessing and using data emanating, for example, from sensor networks. Thesedevelopments are based on existing data and service standards proposed by internationalorganizations. The projects seek to develop the ideals of the EC directive INSPIRE(http://inspire.jrc.it), which was launched in 2001 and whose implementation began this year(2007), into the risk management domain. Thanks to the open nature of the architecture andservices being developed within these projects, they can be implemented by any interestedparty and can be accessed by all potential users. The architecture is based around a serviceorientedapproach that makes use of Internet-based applications (web services) whose inputsand outputs conform to standards. The benefit of this philosophy is that it is expected tofavor the emergence of an operational market for risk management services in Europe, iteliminates the need to replace or radically alter the hundreds of already operational ITsystems in Europe (drastically lowering costs for users), and it allows users and stakeholdersto achieve interoperability while using the system most adequate to their needs, budgets,culture etc. (i.e. it has flexibility). Full article
(This article belongs to the Special Issue Sensors for Disaster and Emergency Management Decision Making)
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<p>SANY inheritance and relationship diagram. SSE refers to the European Space Agency's Service Support Environment and i-MARQ is a previous project funded by the EC under their Information Society Technology Programme (1998-2002).</p> Full article ">
<p>Abstract and Concrete Service Platforms.</p> Full article ">
<p>Functional Domains of SANY Services.</p> Full article ">
246 KiB  
Article
Assessing Steady-state Fluorescence and PRI from Hyperspectral Proximal Sensing as Early Indicators of Plant Stress: The Case of Ozone Exposure
by Michele Meroni, Micol Rossini, Valentina Picchi, Cinzia Panigada, Sergio Cogliati, Cristina Nali and Roberto Colombo
Sensors 2008, 8(3), 1740-1754; https://doi.org/10.3390/s8031740 - 13 Mar 2008
Cited by 114 | Viewed by 16821
Abstract
High spectral resolution spectrometers were used to detect optical signals ofongoing plant stress in potted white clover canopies subjected to ozone fumigation. Thecase of ozone stress is used in this manuscript as a paradigm of oxidative stress. Steadystatefluorescence (Fs) and the Photochemical Reflectance [...] Read more.
High spectral resolution spectrometers were used to detect optical signals ofongoing plant stress in potted white clover canopies subjected to ozone fumigation. Thecase of ozone stress is used in this manuscript as a paradigm of oxidative stress. Steadystatefluorescence (Fs) and the Photochemical Reflectance Index (PRI) were investigatedas advanced hyperspectral remote sensing techniques able to sense variations in the excessenergy dissipation pathways occurring when photosynthesis declines in plants exposed to astress agent. Fs and PRI were monitored in control and ozone fumigated canopies during a21-day experiment together with the traditional Normalized Difference Vegetation Index(NDVI) and physiological measurements commonly employed by physiologists to describestress development (i.e. net CO2 assimilation, active fluorimetry, chlorophyll concentrationand visible injuries). It is shown that remote detection of an ongoing stress through Fs andPRI can be achieved in an early phase, characterized by the decline of photosynthesis. Onthe contrary, NDVI was able to detect the stress only when damage occurred. These resultsopen up new possibilities for assessment of plant stress by means of hyperspectral remotesensing. Full article
(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)
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<p>Fluorescence emission spectrum of a white clover leaf excited with a tungsten halogen light source filtered with a short-pass filter blocking the light in the emission region 650-800 nm (continuous curve). Reflectance spectrum of the same leaf (dashed curve). Position of the hydrogen absorption Hα (656 nm) and oxygen absorption A (760 nm) and B (687 nm) bands (grey vertical lines).</p> Full article ">
<p>Incident solar radiance (<span class="html-italic">L<sup>i</sup></span>, black continuous curve) and radiance upwelling from a vegetated target (<span class="html-italic">L<sup>s</sup></span>, black dashed curve) around the A band. The grey curve is the resulting apparent reflectance. Measurements were collected over a white clover canopy with a HR4000 (OceanOptics, USA) characterized by a full width at half maximum (FWHM) of 0.13 nm.</p> Full article ">
<p>Time series of physiological variables measured at 10:30 a.m. (solar time): (a) A, net CO<sub>2</sub> assimilation rate (μmol CO<sub>2</sub> m<sup>−2</sup> s<sup>−1</sup>); (b) AF/F<sub>m</sub>′, fluorescence quantum yield; (c) F<sub>v</sub>/F<sub>m</sub>, maximum photochemical efficiency of dark-adapted samples; (d) SPAD, relative leaf chlorophyll concentration. Full and empty dots refer to control and treatment samples respectively. Values represent means ± SE (n = 6). Comparison between means was performed according to Student's t-test (ns : P &gt; 0.05; * : P &lt; 0.05; ** : P &lt; 0.01; *** : P &lt; 0.001).</p> Full article ">
<p>Time series of spectral variables measured at 10:30 a.m. (solar time): (a) solar-induced steady-state fluorescence at 760 nm (Fs<sub>760</sub>); (b) normalized fluorescence at 760 nm (NFs<sub>760</sub>); (c) Photochemical Reflectance Index (PRI); (d) Normalized Difference Vegetation Index (NDVI). Full and empty dots refer to control and treatment samples respectively. Values represent means ± SE (n = 3). Comparison between means was performed according to Student's t-test (ns : P &gt; 0.05; * : P ≤ 0.05; ** : P ≤ 0.01; *** : P ≤ 0.001).</p> Full article ">
448 KiB  
Article
Applications of the Integrated High-Performance CMOS Image Sensor to Range Finders — from Optical Triangulation to the Automotive Field
by Jih-Huah Wu, Cheng-Chung Pen and Joe-Air Jiang
Sensors 2008, 8(3), 1719-1739; https://doi.org/10.3390/s8031719 - 13 Mar 2008
Cited by 12 | Viewed by 14059
Abstract
With their significant features, the applications of complementary metal-oxidesemiconductor (CMOS) image sensors covers a very extensive range, from industrialautomation to traffic applications such as aiming systems, blind guidance, active/passiverange finders, etc. In this paper CMOS image sensor-based active and passive rangefinders are presented. [...] Read more.
With their significant features, the applications of complementary metal-oxidesemiconductor (CMOS) image sensors covers a very extensive range, from industrialautomation to traffic applications such as aiming systems, blind guidance, active/passiverange finders, etc. In this paper CMOS image sensor-based active and passive rangefinders are presented. The measurement scheme of the proposed active/passive rangefinders is based on a simple triangulation method. The designed range finders chieflyconsist of a CMOS image sensor and some light sources such as lasers or LEDs. Theimplementation cost of our range finders is quite low. Image processing software to adjustthe exposure time (ET) of the CMOS image sensor to enhance the performance oftriangulation-based range finders was also developed. An extensive series of experimentswere conducted to evaluate the performance of the designed range finders. From theexperimental results, the distance measurement resolutions achieved by the active rangefinder and the passive range finder can be better than 0.6% and 0.25% within themeasurement ranges of 1 to 8 m and 5 to 45 m, respectively. Feasibility tests onapplications of the developed CMOS image sensor-based range finders to the automotivefield were also conducted. The experimental results demonstrated that our range finders arewell-suited for distance measurements in this field. Full article
(This article belongs to the Special Issue Integrated High-performance Imagers)
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<p>General experimental layout of the designed active range finder.</p> Full article ">
<p>System layout of the designed passive range finder.</p> Full article ">
<p>Simplified experimental layout of the active range finder.</p> Full article ">
<p>Measured distance versus the distance between the optic axis and spot.</p> Full article ">
<p>The signal processing flowchart of the passive range finder used in door.</p> Full article ">
<p>Real image captured by the CMOS image sensor of the designed passive range finder under the case of two LEDs located at a distance of 45 m.</p> Full article ">
<p>Intensity contours of LD and LED measured by CMOS image sensor at different times: (a) at time T1 and (b) at time T2.</p> Full article ">
<p>Experimental results for optical aberration effect: (a) spot on optic axis and (b) spot off optic axis.</p> Full article ">
<p>Test results for the effects of gain control on CMOS image sensor: the real captured images with (a) ET = 20 and (b) ET = 2.</p> Full article ">
66 KiB  
Communication
Carbon Nanotubes Based Glucose Needle-type Biosensor
by Jinyan Jia, Wenjun Guan, Minghao Sim, Yongquan Li and Hong Li
Sensors 2008, 8(3), 1712-1718; https://doi.org/10.3390/s8031712 - 12 Mar 2008
Cited by 27 | Viewed by 9419
Abstract
A novel needle-type biosensor based on carbon nanotubes is reported. Thebiosensor was prepared by packing a mixture of multi-wall carbon nanotubes (MWCNTs),graphite powder and glucose oxidase (Gox) freeze-dried powder into a glass capillary of 0.5mm inner diameter. The resulting amperometric biosensor [...] Read more.
A novel needle-type biosensor based on carbon nanotubes is reported. Thebiosensor was prepared by packing a mixture of multi-wall carbon nanotubes (MWCNTs),graphite powder and glucose oxidase (Gox) freeze-dried powder into a glass capillary of 0.5mm inner diameter. The resulting amperometric biosensor was characterizedelectrochemically using amperometry in the presence of hydrogen peroxide and in thepresence of glucose. The glucose biosensor sensitivity was influenced by the glucoseoxidase concentration within the MWCNTs mixture. The optimized glucose needle-typebiosensor displayed better sensitivity and stability, and a detected range of up to 20 mM.Based on its favorable stability, the needle biosensor was first time used in real-timemonitoring system as a kind of online glucose detector. The decay of current response isless than 10% after 24-hour continuous observation. Full article
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<p>Influence of G<sub>ox</sub> contents upon the amperometric glucose response. ▲-MWCNTs mixture/G<sub>ox</sub> needle biosensor at 5:1 composition ratio, ●- MWCNTs mixture/G<sub>ox</sub> needle biosensor at 5:3 composition ratio, ■- MWCNTs mixture/G<sub>ox</sub> needle biosensor at 5:5 composition ratio.</p> Full article ">
<p>Storage stability of needle-type biosensor. ▲- MWCNTs mixture/G<sub>ox</sub> needle-type biosensor (5:1 composition ratio), ●-MWCNTs mixture/G<sub>ox</sub> needle-type biosensor (5:3 composition ratio), ■- MWCNTs mixture/G<sub>ox</sub> needle-type biosensor (5:5 composition ratio). The data points represent biosensor's current response to 20 mM glucose, pH 7.0 PBS, measured for 100 second at 0.60 V on a given day. The response was normalized with respect to that on day 1.</p> Full article ">
<p>24-hour current response of the needle-type biosensor. The needle-type MWCNTs mixtue/G<sub>ox</sub> biosensor used in this experiment has 5:3 composition ratio of MWCNTs mixtue and G<sub>ox</sub>.</p> Full article ">
171 KiB  
Article
Multiscale Unsupervised Segmentation of SAR Imagery Using the Genetic Algorithm
by Xian-Bin Wen, Hua Zhang and Ze-Tao Jiang
Sensors 2008, 8(3), 1704-1711; https://doi.org/10.3390/s8031704 - 12 Mar 2008
Cited by 20 | Viewed by 11594
Abstract
A valid unsupervised and multiscale segmentation of synthetic aperture radar(SAR) imagery is proposed by a combination GA-EM of the Expectation Maximization(EM) algorith with the genetic algorithm (GA). The mixture multiscale autoregressive(MMAR) model is introduced to characterize and exploit the scale-to-scale statisticalvariations and statistical [...] Read more.
A valid unsupervised and multiscale segmentation of synthetic aperture radar(SAR) imagery is proposed by a combination GA-EM of the Expectation Maximization(EM) algorith with the genetic algorithm (GA). The mixture multiscale autoregressive(MMAR) model is introduced to characterize and exploit the scale-to-scale statisticalvariations and statistical variations in the same scale in SAR imagery due to radar speckle,and a segmentation method is given by combining the GA algorithm with the EMalgorithm. This algorithm is capable of selecting the number of components of the modelusing the minimum description length (MDL) criterion. Our approach benefits from theproperties of the Genetic and the EM algorithm by combination of both into a singleprocedure. The population-based stochastic search of the genetic algorithm (GA) exploresthe search space more thoroughly than the EM method. Therefore, our algorithm enablesescaping from local optimal solutions since the algorithm becomes less sensitive to itsinitialization. Some experiment results are given based on our proposed approach, andcompared to that of the EM algorithms. The experiments on the SAR images show that theGA-EM outperforms the EM method. Full article
(This article belongs to the Special Issue Synthetic Aperture Radar (SAR))
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<p>Sequence of three multiresolution SAR images mapped onto a quadtree.</p> Full article ">
<p>(a) Original SAR image. (b) Segmented image from EM algorithm. (c) Segmented image from GA-EM algorithm.</p> Full article ">
337 KiB  
Article
Schiff's Bases and Crown Ethers as Supramolecular Sensing Materials in the Construction of Potentiometric Membrane Sensors
by Farnoush Faridbod, Mohammad Reza Ganjali, Rassoul Dinarvand, Parviz Norouzi and Siavash Riahi
Sensors 2008, 8(3), 1645-1703; https://doi.org/10.3390/s8031645 - 11 Mar 2008
Cited by 217 | Viewed by 22626
Abstract
Ionophore incorporated PVC membrane sensors are well-established analyticaltools routinely used for the selective and direct measurement of a wide variety of differentions in complex biological and environmental samples. Potentiometric sensors have someoutstanding advantages including simple design and operation, wide linear dynamic range,relatively fast [...] Read more.
Ionophore incorporated PVC membrane sensors are well-established analyticaltools routinely used for the selective and direct measurement of a wide variety of differentions in complex biological and environmental samples. Potentiometric sensors have someoutstanding advantages including simple design and operation, wide linear dynamic range,relatively fast response and rational selectivity. The vital component of such plasticizedPVC members is the ionophore involved, defining the selectivity of the electrodes' complexformation. Molecular recognition causes the formation of many different supramolecules.Different types of supramolecules, like calixarenes, cyclodextrins and podands, have beenused as a sensing material in the construction of ion selective sensors. Schiff's bases andcrown ethers, which feature prominently in supramolecular chemistry, can be used assensing materials in the construction of potentiometric ion selective electrodes. Up to now,more than 200 potentiometric membrane sensors for cations and anions based on Schiff's bases and crown ethers have been reported. In this review cation binding and anioncomplexes will be described. Liquid membrane sensors based on Schiff's bases and crownethers will then be discussed. Full article
(This article belongs to the Special Issue Supramolecular Sensors)
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<p>An example of an UV-Vis. spectrum for complexation study. A: ligand spectrum; B: the complex spectrum; C: metal ion spectrum.</p> Full article ">
<p>An example of fluorescence spectrum for complexation study. The ligand fluorescence intensity is quenched in the presence of increseing concentration of metal ion.</p> Full article ">
<p>An example of polarographic study for complexation. Differential pulse polarogram of a metal ion in the absence (1) and in the presensce of the increasing ligand concentration (from 2 to 5).</p> Full article ">
<p>Some examples of theoretical calculation for complexation study. Optimal conformation of the ionophore complexation with ions is shown in these figures.</p> Full article ">
<p>Structure of a podand.</p> Full article ">
<p>A symmetric tripod ligand.</p> Full article ">
<p>Structure of a porphyrin.</p> Full article ">
<p>Structure of a calix[<a href="#b4-sensors-08-01645" class="html-bibr">4</a>]arene.</p> Full article ">
<p>Structure of bis(5-phenyl azo salicylaldehyde) 2,3-naphthalene diimine (5PHAZOSALNPHN) (Al<sup>3+</sup>-1).</p> Full article ">
127 KiB  
Communication
A Fluorescent Sensor for Dinitrobenzoic Acid Based on a Cyanuric Acid and Xanthene Skeleton
by Francisco M. Muñiz, Luis Simón, Silvia Sáez, César Raposo, Victoria Alcázar and Joaquín R. Morán
Sensors 2008, 8(3), 1637-1644; https://doi.org/10.3390/s8031637 - 11 Mar 2008
Cited by 7 | Viewed by 10441
Abstract
A new fluorescent sensor based on a dimethylxanthene skeleton has beensynthesized. Because of its oxyanion hole structure, this receptor includes a suitablecavity for the association of carboxylic acids. The receptor’s fluorescence is quenchedupon addition of dinitrobenzoic acid. Full article
(This article belongs to the Special Issue Molecular Recognition and Sensors, Including Molecular Imprinting)
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<p>Oxyanion hole of the enoyl-CoA hydratase with a superimposed 4,5-diacetamidoxanthene, showing the similarity of the H-bonds (level of theory: HF/6-31G).</p> Full article ">
<p>Conformation of the dansyl group for daxacyan, where the interaction between H-3 and the dansyl group can be observed.</p> Full article ">
<p>Synthesis of daxacyan.Proposed dimeric structure for daxacyan.</p> Full article ">
<p>Synthesis of daxacyan.Proposed dimeric structure for daxacyan.</p> Full article ">
<p>Weak complex between daxacyan and glutarimide and its non-bonding electron repulsion.</p> Full article ">
<p>Proposed geometry for the associate between daxacyan and decanoic acid and the chemical shifts of its protons.</p> Full article ">
<p>Changes in the fluorescence of the daxacyan receptor.</p> Full article ">
<p>Proposed structure for the complex between daxacyan and the phthaloylalanine.</p> Full article ">
<p>Preparation of the <span class="html-italic">N</span>-Boc-protected xanthenediamine.</p> Full article ">
801 KiB  
Article
Object-based Land Cover Classification and Change Analysis in the Baltimore Metropolitan Area Using Multitemporal High Resolution Remote Sensing Data
by Weiqi Zhou, Austin Troy and Morgan Grove
Sensors 2008, 8(3), 1613-1636; https://doi.org/10.3390/s8031613 - 10 Mar 2008
Cited by 240 | Viewed by 19226
Abstract
Accurate and timely information about land cover pattern and change in urbanareas is crucial for urban land management decision-making, ecosystem monitoring andurban planning. This paper presents the methods and results of an object-basedclassification and post-classification change detection of multitemporal high-spatialresolution Emerge aerial imagery [...] Read more.
Accurate and timely information about land cover pattern and change in urbanareas is crucial for urban land management decision-making, ecosystem monitoring andurban planning. This paper presents the methods and results of an object-basedclassification and post-classification change detection of multitemporal high-spatialresolution Emerge aerial imagery in the Gwynns Falls watershed from 1999 to 2004. TheGwynns Falls watershed includes portions of Baltimore City and Baltimore County,Maryland, USA. An object-based approach was first applied to implement the land coverclassification separately for each of the two years. The overall accuracies of theclassification maps of 1999 and 2004 were 92.3% and 93.7%, respectively. Following theclassification, we conducted a comparison of two different land cover change detectionmethods: traditional (i.e., pixel-based) post-classification comparison and object-basedpost-classification comparison. The results from our analyses indicated that an objectbasedapproach provides a better means for change detection than a pixel based methodbecause it provides an effective way to incorporate spatial information and expertknowledge into the change detection process. The overall accuracy of the change mapproduced by the object-based method was 90.0%, with Kappa statistic of 0.854, whereasthe overall accuracy and Kappa statistic of that by the pixel-based method were 81.3% and0.712, respectively. Full article
(This article belongs to the Special Issue Sensors for Urban Environmental Monitoring)
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<p>The Gwynns Falls watershed includes portions of Baltimore City and Baltimore County, MD, USA, and drains into the Chesapeake Bay.</p> Full article ">
<p>Image objects for change detection (Panel C) represent the intersections between the two classification maps (Panel A: 1999; Panel B: 2004). Paned D shows the change detection results obtained from the object-based approach.</p> Full article ">
<p>The class hierarchy for object-based post-classification comparison change detection.</p> Full article ">
<p>The classification result of the 5 land cover classes for the Gwynns Falls watershed in 1999.</p> Full article ">
<p>The classification result of the 5 land cover classes for the Gwynns Falls watershed in 2004.</p> Full article ">
<p>The land cover change map for the Gwynns Falls watershed from 1999 to 2004, which was derived from an object-based change detection approach.</p> Full article ">
<p>Examples that change map shows different patterns of land cover changes. Panel A shows an example that a big chunk of forestland was converted to development, whereas pane B shows that the gain of tree canopy mainly came from the growth or expansion of existing trees and forest stands, with the form of numerous small pieces. Please refer to <a href="#f6-sensors-08-01613" class="html-fig">Figure 6</a> for legend information.</p> Full article ">
<p>A comparison of the change detection results of the same landscape using the two different approaches: the pixel-based post-classification comparison (Panel C) and the object-based post-classification comparison (Panel D). Panel A shows the 1999 Emerge image for the landscape, while Panel B shows the one for 2004.</p> Full article ">
659 KiB  
Review
SU-8 Cantilevers for Bio/chemical Sensing; Fabrication, Characterisation and Development of Novel Read-out Methods
by Maria Nordström, Stephan Keller, Michael Lillemose, Alicia Johansson, Søren Dohn, Daniel Haefliger, Gabriela Blagoi, Mogens Havsteen-Jakobsen and Anja Boisen
Sensors 2008, 8(3), 1595-1612; https://doi.org/10.3390/s8031595 - 10 Mar 2008
Cited by 120 | Viewed by 18797
Abstract
Here, we present the activities within our research group over the last five yearswith cantilevers fabricated in the polymer SU-8. We believe that SU-8 is an interestingpolymer for fabrication of cantilevers for bio/chemical sensing due to its simple processingand low Young’s modulus. We [...] Read more.
Here, we present the activities within our research group over the last five yearswith cantilevers fabricated in the polymer SU-8. We believe that SU-8 is an interestingpolymer for fabrication of cantilevers for bio/chemical sensing due to its simple processingand low Young’s modulus. We show examples of different integrated read-out methodsand their characterisation. We also show that SU-8 cantilevers have a reduced sensitivity tochanges in the environmental temperature and pH of the buffer solution. Moreover, weshow that the SU-8 cantilever surface can be functionalised directly with receptormolecules for analyte detection, thereby avoiding gold-thiol chemistry. Full article
(This article belongs to the Special Issue Cantilever, Microcantilevers and Nanocantilever Sensors and Biosensors)
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<p>As molecules selectively bind to one surface of the cantilever, the structure is deflected due to the generated surface stress. Image courtesy Rodolphe Marie.</p> Full article ">
<p>Schematic drawing of the different steps involved in the fabrication of the SU-8 cantilevers.</p> Full article ">
<p>SEM image showing a 2-μm-thin and perfectly straight cantilever. The width and length of the cantilever is 75 μm and 200 μm respectively.</p> Full article ">
<p>The introduction of 2 μM ssDNA results in a six times larger deflection of the SU-8 cantilever (2500 nm deflection) compared to the Si<sub>3</sub>N<sub>4</sub> cantilever (400 nm deflection seen in inset) due to the lower Young's modulus of the polymer cantilever [<a href="#b31-sensors-08-01595" class="html-bibr">31</a>]. Both cantilevers are coated with a 20 nm thin layer of Au and the deflections are read out by the optical lever principle.</p> Full article ">
<p><b>(a).</b> As the temperature is cycled between 22 and 24 °C the deflections of the Si3N4 cantilever (dashed line) is 14 times greater than the deflections of the SU-8 cantilever (solid line). The reason for the difference is that the Si3N4 cantilever needs to be coated with an Au layer for the immobilisation of molecules, something which can be done directly on the SU-8 surface [<a href="#b31-sensors-08-01595" class="html-bibr">31</a>].<b>(b).</b> Compared to the Au coated Si3N4 cantilever the fluorocarbon-coated SU-8 cantilever is less sensitive to pH changes [<a href="#b31-sensors-08-01595" class="html-bibr">31</a>].</p> Full article ">
<p>SEM image of two free-hanging cantilevers in the microfluidic channel. The cantilevers are 75 μm wide, 100 μm long and 4.5 μm thick.</p> Full article ">
<p>The light travels through the system, via the cantilever that also acts as a waveguide and is collected on the opposite side.</p> Full article ">
<p>Comparison between calculated and measured values of the sensitivity. When operated in the most sensitive region, at an initial cantilever deflection of 4 μm, a deflection resolution of 45 nm can be obtained.</p> Full article ">
<p><b>(a).</b> Schematic drawing of the four cantilevers with the integrated piezoresistors, situated in the micro channel.<b>(b).</b> Optical image of the complete SU-8 chip. The cantilevers are situated in the micro channel. The Au contact pads are visible.</p> Full article ">
135 KiB  
Article
An Artificial Neural Network Approach for the Prediction of Absorption Measurements of an Evanescent Field Fiber Sensor
by Ö. Galip Saracoglu
Sensors 2008, 8(3), 1585-1594; https://doi.org/10.3390/s8031585 - 10 Mar 2008
Cited by 44 | Viewed by 11010
Abstract
This paper describes artificial neural network (ANN) based prediction of theresponse of a fiber optic sensor using evanescent field absorption (EFA). The sensingprobe of the sensor is made up a bundle of five PCS fibers to maximize the interaction ofevanescent field with the [...] Read more.
This paper describes artificial neural network (ANN) based prediction of theresponse of a fiber optic sensor using evanescent field absorption (EFA). The sensingprobe of the sensor is made up a bundle of five PCS fibers to maximize the interaction ofevanescent field with the absorbing medium. Different backpropagation algorithms areused to train the multilayer perceptron ANN. The Levenberg-Marquardt algorithm, aswell as the other algorithms used in this work successfully predicts the sensor responses. Full article
(This article belongs to the Special Issue Intelligent Sensors)
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<p>The arrangement for evanescent field absorption sensor [<a href="#b23-sensors-08-01585" class="html-bibr">23</a>].</p> Full article ">
<p>The PCS fiber in the bundle (PCS200A, Quartz&amp;Silice, France).</p> Full article ">
<p>The geometry of the sensing region.</p> Full article ">
<p>The sensor response (<span class="html-italic">P<sub>out</sub></span>/<span class="html-italic">P<sub>in</sub></span>) in terms of γ [<a href="#b23-sensors-08-01585" class="html-bibr">23</a>].</p> Full article ">
<p>General structure of an MLPNN.</p> Full article ">
<p>An example of the networks proposed in this work.</p> Full article ">
<p>Comparisons of the best and the worst ANN outputs with the sensor responses.</p> Full article ">
490 KiB  
Article
Low-cost Sensors Based on the GMI Effect in Recycled Transformer Cores
by Pongsakorn Jantaratana and Chitnarong Sirisathitkul
Sensors 2008, 8(3), 1575-1584; https://doi.org/10.3390/s8031575 - 10 Mar 2008
Cited by 11 | Viewed by 9017
Abstract
Sensors based on the giant magnetoimpedance (GMI) effect in silicon steelswere constructed. Strips of silicon steels (0.500 mm-thick, 35.0 mm-long) with widthsranging from 0.122 to 1.064 mm were cut from recycled transformer cores. Since amaximum GMI ratio of 300% and a maximum field [...] Read more.
Sensors based on the giant magnetoimpedance (GMI) effect in silicon steelswere constructed. Strips of silicon steels (0.500 mm-thick, 35.0 mm-long) with widthsranging from 0.122 to 1.064 mm were cut from recycled transformer cores. Since amaximum GMI ratio of 300% and a maximum field sensitivity of 1.5%/Oe were observedin a 1.064 mm-wide sample at 200 kHz, the 1.064 mm-wide strips were chosen as sensingelements in a slot key switch, angular velocity sensor, current sensor and force sensor. Thesensing elements were integrated into electronic circuits and the changes in impedancewere monitored. Variations in voltage due to these changes were typically small and musttherefore be amplified by the electronic circuits. For the current sensor and force sensor,the variation in the voltage drop across the GMI sensing element had non-linear variationswith either current or force and a conversion formula from a computer program wastherefore needed. The performance of the systems was tested. These sensing systems werestable, highly sensitive, hysteresis-free and could be produced on a mass scale. Based ontheir GMI effect, the silicon steels are versatile alternative low-cost sensors. Full article
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<p>Longitudinal hysteresis loop of a silicon steel strip obtained by fluxmetric induction method at room temperature.</p> Full article ">
<p>Dependence of GMI ratio (for samples of varying widths at their characteristic frequencies) on the longitudinal magnetic field obtained by the auto balancing bridge method at room temperature.</p> Full article ">
<p>(a) Configuration and (b) photograph of a GMI slot key switch (a file showing the operation of this switch is available as <a href="#SD1" class="html-supplementary-material">supplementary material</a>: <a href="http://www.mdpi.org/sensors/papers/s8031575-1.mpg" target="_blank">http://www.mdpi.org/sensors/papers/s8031575-1.mpg</a>, 5369 KB).</p> Full article ">
<p>Circuit diagram of a slot key switch with U-shape silicon steel as a GMI element.</p> Full article ">
<p>(a) Configuration and (b) photograph of an angular velocity sensor (a file showing the operation of this sensor is available as <a href="#SD1" class="html-supplementary-material">supplementary material</a>: <a href="http://www.mdpi.org/sensors/papers/s8031575-2.mpg" target="_blank">http://www.mdpi.org/sensors/papers/s8031575-2.mpg</a>, 5349 KB).</p> Full article ">
<p>Schematic diagram of an angular velocity sensor system.</p> Full article ">
<p>(a) Configuration and (b) photograph of a current sensor.</p> Full article ">
<p>Schematic connection of a GMI based current sensor system.</p> Full article ">
<p>Variation of voltage drop across a GMI element in a current sensor as a function of the current.</p> Full article ">
805 KiB  
Review
Ground Based Ultraviolet Remote Sensing of Volcanic Gas Plumes
by Euripides P. Kantzas and Andrew J. S. McGonigle
Sensors 2008, 8(3), 1559-1574; https://doi.org/10.3390/s8031559 - 10 Mar 2008
Cited by 14 | Viewed by 14506
Abstract
Ultraviolet spectroscopy has been implemented for over thirty years to monitorvolcanic SO2 emissions. These data have provided valuable information concerningunderground magmatic conditions, which have been of utility in eruption forecastingefforts. During the last decade the traditionally used correlation spectrometers have beenupgraded with [...] Read more.
Ultraviolet spectroscopy has been implemented for over thirty years to monitorvolcanic SO2 emissions. These data have provided valuable information concerningunderground magmatic conditions, which have been of utility in eruption forecastingefforts. During the last decade the traditionally used correlation spectrometers have beenupgraded with miniature USB coupled UV spectrometers, opening a series of exciting newempirical possibilities for understanding volcanoes and their impacts upon the atmosphere.Here we review these technological developments, in addition to the scientific insightsthey have precipitated, covering the strengths and current limitations of this approach. Full article
(This article belongs to the Special Issue Sensors for Disaster and Emergency Management Decision Making)
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<p>Mt. Etna's gas plume.</p> Full article ">
<p>Principle of spectroscopic remote sensing. Spectra are collected both with and without the volcanic gas plume in the optical path. Identification of the wavelengths at which absorption occurs, and the depths of these features, provides information on which plume gases are present, and in what abundances, respectively.</p> Full article ">
<p><b>a)</b> Under plume traverse configuration for UV spectroscopic volcanic SO<sub>2</sub> flux measurements; <b>b)</b> the instrumental payload: zenith skylight is captured to the spectrometer via an optical fibre and telescope; spectra are saved to the computer and georeferenced using contemporaneous data from a hand held GPS receiver.</p> Full article ">
<p>volcanoSO2.exe software for capturing and analysing GPS and USB2000 spectral data in order to compute SO<sub>2</sub> fluxes. Here the code is looping through spectra from a previous traverse (e.g., that shown in the spectra window). The corresponding differential absorption spectrum, showing the fine spectral resolution SO<sub>2</sub> absorption structure is shown in the fitting window, and the resulting plume SO<sub>2</sub> cross sectional profile in the concentrations field.</p> Full article ">
<p><b>a)</b> Configuration for using three vertically pointing USB2000s to measure overhead SO<sub>2</sub> concentration time series; <b>b)</b> sample data, where the traces (above) from spectrometers a, b and c are temporally offset relative to one another owing to the units' different distances from the source. The series are then cross-correlated to determine the time shift at which they best overlap (e.g., lag time), as applied in the lower plot, from which plume speed can be calculated.</p> Full article ">
<p>Configuration of a two UV scanning spectrometer network.</p> Full article ">
<p>Under plume UAV traverse at La Fossa crater, Vulcano Island, Italy, with the 1.5 kg SO<sub>2</sub> flux measurement UV spectroscopic payload. The USB2000 and miniature laptop computer are in the vibrationally damped instrument tray, the GPS is mounted to the fore, and the fibre and vertical telescope to the reverse of the base. The helicopter fuselage is 141 cm long.</p> Full article ">
353 KiB  
Review
Transgenic Plants as Sensors of Environmental Pollution Genotoxicity
by Igor Kovalchuk and Olga Kovalchuk
Sensors 2008, 8(3), 1539-1558; https://doi.org/10.3390/s8031539 - 10 Mar 2008
Cited by 32 | Viewed by 13517
Abstract
Rapid technological development is inevitably associated with manyenvironmental problems which primarily include pollution of soil, water and air. In manycases, the presence of contamination is difficult to assess. It is even more difficult toevaluate its potential danger to the environment and humans. Despite [...] Read more.
Rapid technological development is inevitably associated with manyenvironmental problems which primarily include pollution of soil, water and air. In manycases, the presence of contamination is difficult to assess. It is even more difficult toevaluate its potential danger to the environment and humans. Despite the existence ofseveral whole organism-based and cell-based models of sensing pollution and evaluationof toxicity and mutagenicity, there is no ideal system that allows one to make a quick andcheap assessment. In this respect, transgenic organisms that can be intentionally altered tobe more sensitive to particular pollutants are especially promising. Transgenic plantsrepresent an ideal system, since they can be grown at the site of pollution or potentiallydangerous sites. Plants are ethically more acceptable and esthetically more appealing thananimals as sensors of environmental pollution. In this review, we will discuss varioustransgenic plant-based models that have been successfully used for biomonitoringgenotoxic pollutants. We will also discuss the benefits and potential drawbacks of thesesystems and describe some novel ideas for the future generation of efficient transgenicphytosensors. Full article
(This article belongs to the Special Issue Phytosensors: Environmental Sensing with Plants and Plant Cells)
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<p>Non-transgenic tobacco-based system for detecting the genotoxicity. The system is based on naturally occurring mutation at the <span class="html-italic">Sulfur</span> (<span class="html-italic">Su</span>) gene. Plants heterozygous for the gene, <span class="html-italic">Su</span>/+ are pale green. Mutations that inactivate the only <span class="html-italic">Su</span> allele are visualized as dark green spots (A). Rearrangements that occur between <span class="html-italic">Su</span> and + allele result in the formation of a “twin” spot visualized as a dual sector of dark green (+/+) and albino (<span class="html-italic">Su</span>/<span class="html-italic">Su</span>) (B).</p> Full article ">
<p>Transgenic “recombination” system for the detection of environmental mutagens. Transgenic plants carry in the genome two non-functional truncated copies of the GUS gene, depicted as “UG” and “US”. The two parts of the truncated, overlapping GUS gene can be in either orientation with respect to each other. Activation of the β-glucuronidase (GUS) gene via homologous recombination (HR) restores the gene activity and is visualized as blue spots after histochemical staining.</p> Full article ">
<p>Transgenic plants carrying the luciferase recombination marker allow continuous visualization of recombination events. A). Recombination events in plants before the application of the mutagene. B). Recombination events in the same plants 3 days after the UVC treatment.</p> Full article ">
<p>Schematic diagram of microsatellite-containing phytosensor. Active copy of the β-glucuronidase (GUS) gene was disrupted by integration of microsatellite containing sixteen G nucleotides (shown in green). This resulted in a complete inactivation of the gene (pale blue). Mutations leading to gain of 2 guanines or loss of 1 guanine restore the frame and result in activation of the transgene (dark blue).</p> Full article ">
<p>Possible tetracycline repressor-based system. A) Marker gene placed under the tetracycline repressor/promoter element is not active since the repressor blocks the promoter. B) Any mutation (point, deletion, insertion etc.) in the repressor region leading to production of inactive repressor or no repressor at all will result in activation of the marker gene. This should result in the appearance of discrete spots representing cells and their progeny where the mutation has occurred.</p> Full article ">
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