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Sensors, Volume 9, Issue 4 (April 2009), Pages 2222-3160

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Open AccessArticle The Micro-Pillar Shear-Stress Sensor MPS3 for Turbulent Flow
Sensors 2009, 9(4), 2222-2251; doi:10.3390/s90402222
Received: 9 January 2009 / Revised: 25 March 2009 / Accepted: 26 March 2009 / Published: 30 March 2009
Cited by 14 | PDF Full-text (2700 KB) | HTML Full-text | XML Full-text
Abstract
Wall-shear stress results from the relative motion of a fluid over a body surface as a consequence of the no-slip condition of the fluid in the vicinity of the wall. To determine the two-dimensional wall-shear stress distribution is of utter importance in [...] Read more.
Wall-shear stress results from the relative motion of a fluid over a body surface as a consequence of the no-slip condition of the fluid in the vicinity of the wall. To determine the two-dimensional wall-shear stress distribution is of utter importance in theoretical and applied turbulence research. In this article, characteristics of the Micro-Pillar Shear-Stress Sensor MPS3, which has been shown to offer the potential to measure the two-directional dynamic wall-shear stress distribution in turbulent flows, will be summarized. After a brief general description of the sensor concept, material characteristics, possible sensor-structure related error sources, various sensitivity and distinct sensor performance aspects will be addressed. Especially, pressure-sensitivity related aspects will be discussed. This discussion will serve as ‘design rules’ for possible new fields of applications of the sensor technology. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany)
Open AccessArticle An Integrated Photogrammetric and Spatial Database Management System for Producing Fully Structured Data Using Aerial and Remote Sensing Images
Sensors 2009, 9(4), 2320-2333; doi:10.3390/s90402320
Received: 18 December 2008 / Revised: 19 February 2009 / Accepted: 11 March 2009 / Published: 30 March 2009
Cited by 2 | PDF Full-text (209 KB) | HTML Full-text | XML Full-text
Abstract
3D spatial data acquired from aerial and remote sensing images by photogrammetric techniques is one of the most accurate and economic data sources for GIS, map production, and spatial data updating. However, there are still many problems concerning storage, structuring and appropriate [...] Read more.
3D spatial data acquired from aerial and remote sensing images by photogrammetric techniques is one of the most accurate and economic data sources for GIS, map production, and spatial data updating. However, there are still many problems concerning storage, structuring and appropriate management of spatial data obtained using these techniques. According to the capabilities of spatial database management systems (SDBMSs); direct integration of photogrammetric and spatial database management systems can save time and cost of producing and updating digital maps. This integration is accomplished by replacing digital maps with a single spatial database. Applying spatial databases overcomes the problem of managing spatial and attributes data in a coupled approach. This management approach is one of the main problems in GISs for using map products of photogrammetric workstations. Also by the means of these integrated systems, providing structured spatial data, based on OGC (Open GIS Consortium) standards and topological relations between different feature classes, is possible at the time of feature digitizing process. In this paper, the integration of photogrammetric systems and SDBMSs is evaluated. Then, different levels of integration are described. Finally design, implementation and test of a software package called Integrated Photogrammetric and Oracle Spatial Systems (IPOSS) is presented. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Detection of Biomolecular Binding Through Enhancement of Localized Surface Plasmon Resonance (LSPR) by Gold Nanoparticles
Sensors 2009, 9(4), 2334-2344; doi:10.3390/s90402334
Received: 13 March 2009 / Revised: 23 March 2009 / Accepted: 30 March 2009 / Published: 30 March 2009
Cited by 22 | PDF Full-text (702 KB) | HTML Full-text | XML Full-text
Abstract
To amplify the difference in localized surface plasmon resonance (LSPR) spectra of gold nano-islands due to intermolecular binding events, gold nanoparticles were used. LSPR-based optical biosensors consisting of gold nano-islands were readily made on glass substrates using evaporation and heat treatment. Streptavidin [...] Read more.
To amplify the difference in localized surface plasmon resonance (LSPR) spectra of gold nano-islands due to intermolecular binding events, gold nanoparticles were used. LSPR-based optical biosensors consisting of gold nano-islands were readily made on glass substrates using evaporation and heat treatment. Streptavidin (STA) and biotinylated bovine serum albumin (Bio-BSA) were chosen as the model receptor and the model analyte, respectively, to demonstrate the effectiveness of this detection method. Using this model system, we were able to enhance the sensitivity in monitoring the binding of Bio-BSA to gold nano-island surfaces functionalized with STA through the addition of gold nanoparticle-STA conjugates. In addition, SU-8 well chips with gold nano-island surfaces were fabricated through a conventional UV patterning method and were then utilized for image detection using the attenuated total reflection mode. These results suggest that the gold nano-island well chip may have the potential to be used for multiple and simultaneous detection of various bio-substances. Full article
(This article belongs to the Special Issue Nanotechnological Advances in Biosensors)
Open AccessArticle Digital Mirror Device Application in Reduction of Wave-front Phase Errors
Sensors 2009, 9(4), 2345-2351; doi:10.3390/s90402345
Received: 21 January 2009 / Revised: 17 March 2009 / Accepted: 24 March 2009 / Published: 30 March 2009
PDF Full-text (274 KB) | HTML Full-text | XML Full-text
Abstract
In order to correct the image distortion created by the mixing/shear layer, creative and effectual correction methods are necessary. First, a method combining adaptive optics (AO) correction with a digital micro-mirror device (DMD) is presented. Second, performance of an AO system using [...] Read more.
In order to correct the image distortion created by the mixing/shear layer, creative and effectual correction methods are necessary. First, a method combining adaptive optics (AO) correction with a digital micro-mirror device (DMD) is presented. Second, performance of an AO system using the Phase Diverse Speckle (PDS) principle is characterized in detail. Through combining the DMD method with PDS, a significant reduction in wavefront phase error is achieved in simulations and experiments. This kind of complex correction principle can be used to recovery the degraded images caused by unforeseen error sources. Full article
Open AccessArticle Preparation and Properties of Various Magnetic Nanoparticles
Sensors 2009, 9(4), 2352-2362; doi:10.3390/s90402352
Received: 13 February 2009 / Revised: 23 March 2009 / Accepted: 30 March 2009 / Published: 30 March 2009
Cited by 48 | PDF Full-text (445 KB) | HTML Full-text | XML Full-text
Abstract
The fabrications of iron oxides nanoparticles using co-precipitation and gadolinium nanoparticles using water in oil microemulsion method are reported in this paper. Results of detailed phase analysis by XRD and Mössbauer spectroscopy are discussed. XRD analysis revealed that the crystallite size (mean [...] Read more.
The fabrications of iron oxides nanoparticles using co-precipitation and gadolinium nanoparticles using water in oil microemulsion method are reported in this paper. Results of detailed phase analysis by XRD and Mössbauer spectroscopy are discussed. XRD analysis revealed that the crystallite size (mean coherence length) of iron oxides (mainly γ-Fe2O3) in the Fe2O3 sample was 30 nm, while in Fe2O3/SiO2 where the ε-Fe2O3 phase dominated it was only 14 nm. Gd/SiO2 nanoparticles were found to be completely amorphous, according to XRD. The samples showed various shapes of hysteresis loops and different coercivities. Differences in the saturation magnetization (MS) correspond to the chemical and phase composition of the sample materials. However, we observed that MS was not reached in the case of Fe2O3/SiO2, while for Gd/SiO2 sample the MS value was extremely low. Therefore we conclude that only unmodified Fe2O3 nanoparticles are suitable for intended biosensing application in vitro (e.g. detection of viral nucleic acids) and the phase purification of this sample for this purpose is not necessary. Full article
Open AccessArticle Fieldservers and Sensor Service Grid as Real-time Monitoring Infrastructure for Ubiquitous Sensor Networks
Sensors 2009, 9(4), 2363-2370; doi:10.3390/s90402363
Received: 11 March 2009 / Revised: 24 March 2009 / Accepted: 30 March 2009 / Published: 31 March 2009
Cited by 16 | PDF Full-text (1328 KB) | HTML Full-text | XML Full-text
Abstract
The fieldserver is an Internet based observation robot that can provide an outdoor solution for monitoring environmental parameters in real-time. The data from its sensors can be collected to a central server infrastructure and published on the Internet. The information from the [...] Read more.
The fieldserver is an Internet based observation robot that can provide an outdoor solution for monitoring environmental parameters in real-time. The data from its sensors can be collected to a central server infrastructure and published on the Internet. The information from the sensor network will contribute to monitoring and modeling on various environmental issues in Asia, including agriculture, food, pollution, disaster, climate change etc. An initiative called Sensor Asia is developing an infrastructure called Sensor Service Grid (SSG), which integrates fieldservers and Web GIS to realize easy and low cost installation and operation of ubiquitous field sensor networks. Full article
(This article belongs to the Special Issue Workshop Sensing A Changing World)
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Open AccessArticle Development of a Dynamic Web Mapping Service for Vegetation Productivity Using Earth Observation and in situ Sensors in a Sensor Web Based Approach
Sensors 2009, 9(4), 2371-2388; doi:10.3390/s90402371
Received: 11 March 2009 / Revised: 27 March 2009 / Accepted: 31 March 2009 / Published: 31 March 2009
Cited by 13 | PDF Full-text (735 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes the development of a sensor web based approach which combines earth observation and in situ sensor data to derive typical information offered by a dynamic web mapping service (WMS). A prototype has been developed which provides daily maps of [...] Read more.
This paper describes the development of a sensor web based approach which combines earth observation and in situ sensor data to derive typical information offered by a dynamic web mapping service (WMS). A prototype has been developed which provides daily maps of vegetation productivity for the Netherlands with a spatial resolution of 250 m. Daily available MODIS surface reflectance products and meteorological parameters obtained through a Sensor Observation Service (SOS) were used as input for a vegetation productivity model. This paper presents the vegetation productivity model, the sensor data sources and the implementation of the automated processing facility. Finally, an evaluation is made of the opportunities and limitations of sensor web based approaches for the development of web services which combine both satellite and in situ sensor sources. Full article
(This article belongs to the Special Issue Workshop Sensing A Changing World)
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Open AccessArticle Thermal Actuation Based 3-DoF Non-Resonant Microgyroscope Using MetalMUMPs
Sensors 2009, 9(4), 2389-2414; doi:10.3390/s90402389
Received: 21 February 2009 / Revised: 18 March 2009 / Accepted: 30 March 2009 / Published: 1 April 2009
Cited by 3 | PDF Full-text (1783 KB) | HTML Full-text | XML Full-text
Abstract
High force, large displacement and low voltage consumption are a primary concern for microgyroscopes. The chevron-shaped thermal actuators are unique in terms of high force generation combined with the large displacements at a low operating voltage in comparison with traditional electrostatic actuators. [...] Read more.
High force, large displacement and low voltage consumption are a primary concern for microgyroscopes. The chevron-shaped thermal actuators are unique in terms of high force generation combined with the large displacements at a low operating voltage in comparison with traditional electrostatic actuators. A Nickel based 3-DoF micromachined gyroscope comprising 2-DoF drive mode and 1-DoF sense mode oscillator utilizing the chevron-shaped thermal actuators is presented here. Analytical derivations and finite element simulations are carried out to predict the performance of the proposed device using the thermo-physical properties of electroplated nickel. The device sensitivity is improved by utilizing the dynamical amplification of the oscillation in 2-DoF drive mode using an active-passive mass configuration. A comprehensive theoretical description, dynamics and mechanical design considerations of the proposed gyroscopes model are discussed in detail. Parametric optimization of gyroscope, its prototype modeling and fabrication using MetalMUMPs has also been investigated. Dynamic transient simulation results predicted that the sense mass of the proposed device achieved a drive displacement of 4.1µm when a sinusoidal voltage of 0.5V is applied at 1.77 kHz exhibiting a mechanical sensitivity of 1.7μm /o/s in vacuum. The wide bandwidth frequency response of the 2-DoF drive mode oscillator consists of two resonant peaks and a flat region of 2.11 kHz between the peaks defining the operational frequency region. The sense mode resonant frequency can lie anywhere within this region and therefore the amplitude of the response is insensitive to structural parameter variations, enhancing device robustness against such variations. The proposed device has a size of 2.2 x 2.6 mm2, almost one third in comparison with existing M-DoF vibratory gyroscope with an estimated power consumption of 0.26 Watts. These predicted results illustrate that the chevron-shaped thermal actuator has a large voltage-stroke ratio shifting the paradigm in MEMS gyroscope design from the traditional interdigitated comb drive electrostatic actuator. These actuators have low damping compared to electrostatic comb drive actuators which may result in high quality factor microgyroscopes operating at atmospheric pressure. Full article
Open AccessArticle A Feature Extraction Method Based on Information Theory for Fault Diagnosis of Reciprocating Machinery
Sensors 2009, 9(4), 2415-2436; doi:10.3390/s90402415
Received: 27 February 2009 / Revised: 7 March 2009 / Accepted: 25 March 2009 / Published: 1 April 2009
Cited by 19 | PDF Full-text (375 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a feature extraction method based on information theory for fault diagnosis of reciprocating machinery. A method to obtain symptom parameter waves is defined in the time domain using the vibration signals, and an information wave is presented based on [...] Read more.
This paper proposes a feature extraction method based on information theory for fault diagnosis of reciprocating machinery. A method to obtain symptom parameter waves is defined in the time domain using the vibration signals, and an information wave is presented based on information theory, using the symptom parameter waves. A new way to determine the difference spectrum of envelope information waves is also derived, by which the feature spectrum can be extracted clearly and machine faults can be effectively differentiated. This paper also compares the proposed method with the conventional Hilbert-transform-based envelope detection and with a wavelet analysis technique. Practical examples of diagnosis for a rolling element bearing used in a diesel engine are provided to verify the effectiveness of the proposed method. The verification results show that the bearing faults that typically occur in rolling element bearings, such as outer-race, inner-race, and roller defects, can be effectively identified by the proposed method, while these bearing faults are difficult to detect using either of the other techniques it was compared to. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan)
Open AccessArticle Electrochemical Direct Determination of Catecholamines for the Early Detection of Neurodegenerative Diseases
Sensors 2009, 9(4), 2437-2445; doi:10.3390/s90402437
Received: 26 February 2009 / Revised: 1 April 2009 / Accepted: 7 April 2009 / Published: 7 April 2009
Cited by 6 | PDF Full-text (129 KB) | HTML Full-text | XML Full-text
Abstract
Smart (Nano) materials with biosensing functions posses enormous potential in development of new generation of stable biosensors, chemical sensors, and actuators. Recently, there is a considerable interest in using TiO2 nanostructured materials as a film-forming material since they have high surface [...] Read more.
Smart (Nano) materials with biosensing functions posses enormous potential in development of new generation of stable biosensors, chemical sensors, and actuators. Recently, there is a considerable interest in using TiO2 nanostructured materials as a film-forming material since they have high surface area, optical transparency, high bio-compatibility, and relatively good conductivity. In this work, TiO2 nanostructured films were used as nanoporous electrodes to study the electron transfer mechanisms of dopamine. epinephrine and norepinephrine, in order to develop a new generation of chemical sensors. The interesting results obtained are described herein and the analytical characterization of these neurotransmitter sensors is reported. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)
Open AccessArticle Energy-efficient Area Coverage by Sensors with Adjustable Ranges
Sensors 2009, 9(4), 2446-2460; doi:10.3390/s90402446
Received: 19 January 2009 / Revised: 30 March 2009 / Accepted: 6 April 2009 / Published: 8 April 2009
Cited by 25 | PDF Full-text (356 KB) | HTML Full-text | XML Full-text
Abstract
In wireless sensor networks, density control is an important technique for prolonging a network's lifetime. To reduce the overall energy consumption, it is desirable to minimize the overlapping sensing area of the sensor nodes. In this paper, we study the problem of [...] Read more.
In wireless sensor networks, density control is an important technique for prolonging a network's lifetime. To reduce the overall energy consumption, it is desirable to minimize the overlapping sensing area of the sensor nodes. In this paper, we study the problem of energy-efficient area coverage by the regular placement of sensors with adjustable sensing and communication ranges. We suggest a more accurate method to estimate efficiency than those currently used for coverage by sensors with adjustable ranges, and propose new density control models that considerably improve coverage using sensors with two sensing ranges. Calculations and extensive simulation show that the new models outperform existing ones in terms of various performance metrics. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessCommunication Data Compression by Shape Compensation for Mobile Video Sensors
Sensors 2009, 9(4), 2461-2469; doi:10.3390/s90402461
Received: 26 February 2009 / Revised: 17 March 2009 / Accepted: 8 April 2009 / Published: 9 April 2009
PDF Full-text (237 KB) | HTML Full-text | XML Full-text
Abstract
Most security systems, with their transmission bandwidth and computing power both being sufficient, emphasize their automatic recognition techniques. However, in some situations such as baby monitors and intruder avoidance by mobile sensors, the decision function sometimes can be shifted to the concerned [...] Read more.
Most security systems, with their transmission bandwidth and computing power both being sufficient, emphasize their automatic recognition techniques. However, in some situations such as baby monitors and intruder avoidance by mobile sensors, the decision function sometimes can be shifted to the concerned human to reduce the transmission and computation cost. We therefore propose a binary video compression method in low resolution to achieve a low cost mobile video communication for inexpensive camera sensors. Shape compensation as proposed in this communication successfully replaces the standard Discrete Cosine Transformation (DCT) after motion compensation. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Fabrication of Submicron Beams with Galvanic Etch Stop for Si in TMAH
Sensors 2009, 9(4), 2470-2477; doi:10.3390/s90402470
Received: 17 February 2009 / Revised: 15 March 2009 / Accepted: 2 April 2009 / Published: 9 April 2009
Cited by 3 | PDF Full-text (270 KB) | HTML Full-text | XML Full-text
Abstract
A novel method has been developed to fabricate submicron beams with galvanic etch stop for Si in TMAH. The different Au:Si area ratios before and after the release of the beams are used to trigger the galvanic etch stop to fabricate submicron [...] Read more.
A novel method has been developed to fabricate submicron beams with galvanic etch stop for Si in TMAH. The different Au:Si area ratios before and after the release of the beams are used to trigger the galvanic etch stop to fabricate submicron single crystal Si beams in standard Si wafers. Before the beams are released from the substrate, the Au electrodes are connected to the substrate electrically. The Au:Si area ratios are much smaller than the threshold value. TMAH etches the Si wafers. After the beams are fully released, they are mechanically supported by the Au wires, which also serve as the galvanic etch stop cathodes. The Au:Si area ratios are much larger than the threshold value. The beams are protected by galvanic etch stop. The thicknesses of the beams are determined by shallow dry etching before TMAH etching. A 530 nm thick beam was fabricated in standard (111) wafers. Experiments showed that the beam thicknesses did not change with over etching, even if the SiO2 layers on the surface of the beams were stripped. Full article
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Open AccessArticle Fabrication and Characterization of a Ruthenium Nitride Membrane for Electrochemical pH Sensors
Sensors 2009, 9(4), 2478-2490; doi:10.3390/s90402478
Received: 12 February 2009 / Revised: 27 March 2009 / Accepted: 31 March 2009 / Published: 9 April 2009
Cited by 9 | PDF Full-text (450 KB) | HTML Full-text | XML Full-text
Abstract
ThepH sensing and nonideal characteristics of a ruthenium nitride (RuN) sensing membrane pH sensor were investigated. RuN thin films were deposited from a 99.9% ruthenium target on p-type silicon substrates using radio frequency (r.f.) sputtering with N2 gas. Subsequently, the nanometric [...] Read more.
ThepH sensing and nonideal characteristics of a ruthenium nitride (RuN) sensing membrane pH sensor were investigated. RuN thin films were deposited from a 99.9% ruthenium target on p-type silicon substrates using radio frequency (r.f.) sputtering with N2 gas. Subsequently, the nanometric structure and surface morphology of RuN thin films were determined. The sensitivity of the RuN sensing membrane pH sensor was 58.03 mV/pH, obtained from ID-VG curves with a current-voltage (I-V) measurement system in standard buffer solutions from pH 1 to pH 13 at room temperature (25 °C). Moreover, the nonideal characteristics of the RuN sensing membrane, such as temperature coefficient, drift with light influence, drift rate and hysteresis width, etc. were also investigated. Finally, the sensing characteristics of the RuN membrane were compared with titanium nitride (TiN), aluminum nitride (AlN) and silicon nitride (Si3N4) membranes. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Chopper Stabilized Low Resistance Comparator
Sensors 2009, 9(4), 2491-2497; doi:10.3390/s90402491
Received: 18 March 2009 / Revised: 6 April 2009 / Accepted: 7 April 2009 / Published: 9 April 2009
Cited by 3 | PDF Full-text (434 KB) | HTML Full-text | XML Full-text
Abstract
The paper describes an improvement of the chopper method for elimination of parasitic voltages in a low resistance comparison and measurement procedure. The basic circuit diagram along with a short description of the working principle are presented and the appropriate low resistance [...] Read more.
The paper describes an improvement of the chopper method for elimination of parasitic voltages in a low resistance comparison and measurement procedure. The basic circuit diagram along with a short description of the working principle are presented and the appropriate low resistance comparator prototype was designed and realized. Preliminary examinations confirm the possibility of measuring extremely low voltages. Very high accuracy in resistance comparison and measurement is achieved (0.08 ppm for 1,000 attempts). Some special critical features in the design are discussed and solutions for overcoming the problems are described. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Small-Displacement Sensor Using Total Internal Reflection Theory and Surface Plasmon Resonance Technology for Heterodyne Interferometry
Sensors 2009, 9(4), 2498-2510; doi:10.3390/s90402498
Received: 20 March 2009 / Revised: 9 April 2009 / Accepted: 10 April 2009 / Published: 14 April 2009
Cited by 10 | PDF Full-text (319 KB) | HTML Full-text | XML Full-text
Abstract
A small-displacement sensor based on total-internal reflection theory and surface plasmon resonance technology is proposed for use in heterodyne interferometry. A small displacement can be obtained simply by measuring the variation in phase difference between s- and p-polarization states with the small-displacement [...] Read more.
A small-displacement sensor based on total-internal reflection theory and surface plasmon resonance technology is proposed for use in heterodyne interferometry. A small displacement can be obtained simply by measuring the variation in phase difference between s- and p-polarization states with the small-displacement sensor. The theoretical displacement resolution of the small-displacement sensor can reach 0.45 nm. The sensor has some additional advantages, e.g., a simple optical setup, high resolution, high sensitivity and rapid measurement. Its feasibility is also demonstrated. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Biotelemetric Monitoring of Brain Neurochemistry in Conscious Rats Using Microsensors and Biosensors
Sensors 2009, 9(4), 2511-2523; doi:10.3390/s90402511
Received: 3 March 2009 / Revised: 8 April 2009 / Accepted: 14 April 2009 / Published: 14 April 2009
Cited by 21 | PDF Full-text (353 KB) | HTML Full-text | XML Full-text
Abstract
In this study we present the real-time monitoring of three key brain neurochemical species in conscious rats using implantable amperometric electrodes interfaced to a biotelemetric device. The new system, derived from a previous design, was coupled with carbon-based microsensors and a platinum-based [...] Read more.
In this study we present the real-time monitoring of three key brain neurochemical species in conscious rats using implantable amperometric electrodes interfaced to a biotelemetric device. The new system, derived from a previous design, was coupled with carbon-based microsensors and a platinum-based biosensor for the detection of ascorbic acid (AA), O2 and glucose in the striatum of untethered, freely-moving rats. The miniaturized device consisted of a single-supply sensor driver, a current-to-voltage converter, a microcontroller and a miniaturized data transmitter. The redox currents were digitized to digital values by means of an analog-to-digital converter integrated in a peripheral interface controller (PIC), and sent to a personal computer by means of a miniaturized AM transmitter. The electronics were calibrated and tested in vitro under different experimental conditions and exhibited high stability, low power consumption and good linear response in the nanoampere current range. The in-vivo results confirmed previously published observations on striatal AA, oxygen and glucose dynamics recorded in tethered rats. This approach, based on simple and inexpensive components, could be used as a rapid and reliable model for studying the effects of different drugs on brain neurochemical systems Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)
Open AccessArticle An Adaptable, Portable Microarray Reader for Biodetection
Sensors 2009, 9(4), 2524-2537; doi:10.3390/s90402524
Received: 25 February 2009 / Revised: 7 April 2009 / Accepted: 14 April 2009 / Published: 14 April 2009
Cited by 7 | PDF Full-text (815 KB) | HTML Full-text | XML Full-text
Abstract
We have developed an inexpensive portable microarray reader that can be applied to standard microscope slide-based arrays and other array formats printed on chemically modified surfaces. Measuring only 19 cm in length, the imaging device is portable and may be applicable to [...] Read more.
We have developed an inexpensive portable microarray reader that can be applied to standard microscope slide-based arrays and other array formats printed on chemically modified surfaces. Measuring only 19 cm in length, the imaging device is portable and may be applicable to both triage and clinical settings. For multiplexing and adaptability purposes, it can be modified to work with multiple excitation/emission wavelengths. Our device is shown to be comparable to a commercial laser scanner when detecting both streptavidin-biotin and antibody interactions. This paper presents the development and characterization of a handheld microarray imager and directly compares it with a commercial scanner. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Parallel Processing Method for Airborne Laser Scanning Data Using a PC Cluster and a Virtual Grid
Sensors 2009, 9(4), 2555-2573; doi:10.3390/s90402555
Received: 2 April 2009 / Revised: 9 April 2009 / Accepted: 10 April 2009 / Published: 14 April 2009
Cited by 17 | PDF Full-text (1519 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a parallel processing method using a PC cluster and a virtual grid is proposed for the fast processing of enormous amounts of airborne laser scanning (ALS) data. The method creates a raster digital surface model (DSM) by interpolating point [...] Read more.
In this study, a parallel processing method using a PC cluster and a virtual grid is proposed for the fast processing of enormous amounts of airborne laser scanning (ALS) data. The method creates a raster digital surface model (DSM) by interpolating point data with inverse distance weighting (IDW), and produces a digital terrain model (DTM) by local minimum filtering of the DSM. To make a consistent comparison of performance between sequential and parallel processing approaches, the means of dealing with boundary data and of selecting interpolation centers were controlled for each processing node in parallel approach. To test the speedup, efficiency and linearity of the proposed algorithm, actual ALS data up to 134 million points were processed with a PC cluster consisting of one master node and eight slave nodes. The results showed that parallel processing provides better performance when the computational overhead, the number of processors, and the data size become large. It was verified that the proposed algorithm is a linear time operation and that the products obtained by parallel processing are identical to those produced by sequential processing. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Non-Contact Detection of Breathing Using a Microwave Sensor
Sensors 2009, 9(4), 2574-2585; doi:10.3390/s90402574
Received: 13 March 2009 / Revised: 7 April 2009 / Accepted: 14 April 2009 / Published: 14 April 2009
Cited by 20 | PDF Full-text (305 KB) | HTML Full-text | XML Full-text
Abstract
In this paper the use of a continuous-wave microwave sensor as a non-contact tool for quantitative measurement of respiratory tidal volume has been evaluated by experimentation in seventeen healthy volunteers. The sensor working principle is reported and several causes that can affect [...] Read more.
In this paper the use of a continuous-wave microwave sensor as a non-contact tool for quantitative measurement of respiratory tidal volume has been evaluated by experimentation in seventeen healthy volunteers. The sensor working principle is reported and several causes that can affect its response are analyzed. A suitable data processing has been devised able to reject the majority of breath measurements taken under non suitable conditions. Furthermore, a relationship between microwave sensor measurements and volume inspired and expired at quiet breathing (tidal volume) has been found. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)
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Open AccessArticle An Artificial Neural Network Embedded Position and Orientation Determination Algorithm for Low Cost MEMS INS/GPS Integrated Sensors
Sensors 2009, 9(4), 2586-2610; doi:10.3390/s90402586
Received: 17 February 2009 / Revised: 5 April 2009 / Accepted: 10 April 2009 / Published: 15 April 2009
Cited by 15 | PDF Full-text (2290 KB) | HTML Full-text | XML Full-text
Abstract
Digital mobile mapping, which integrates digital imaging with direct geo-referencing, has developed rapidly over the past fifteen years. Direct geo-referencing is the determination of the time-variable position and orientation parameters for a mobile digital imager. The most common technologies used for this [...] Read more.
Digital mobile mapping, which integrates digital imaging with direct geo-referencing, has developed rapidly over the past fifteen years. Direct geo-referencing is the determination of the time-variable position and orientation parameters for a mobile digital imager. The most common technologies used for this purpose today are satellite positioning using Global Positioning System (GPS) and Inertial Navigation System (INS) using an Inertial Measurement Unit (IMU). They are usually integrated in such a way that the GPS receiver is the main position sensor, while the IMU is the main orientation sensor. The Kalman Filter (KF) is considered as the optimal estimation tool for real-time INS/GPS integrated kinematic position and orientation determination. An intelligent hybrid scheme consisting of an Artificial Neural Network (ANN) and KF has been proposed to overcome the limitations of KF and to improve the performance of the INS/GPS integrated system in previous studies. However, the accuracy requirements of general mobile mapping applications can’t be achieved easily, even by the use of the ANN-KF scheme. Therefore, this study proposes an intelligent position and orientation determination scheme that embeds ANN with conventional Rauch-Tung-Striebel (RTS) smoother to improve the overall accuracy of a MEMS INS/GPS integrated system in post-mission mode. By combining the Micro Electro Mechanical Systems (MEMS) INS/GPS integrated system and the intelligent ANN-RTS smoother scheme proposed in this study, a cheaper but still reasonably accurate position and orientation determination scheme can be anticipated. Full article
(This article belongs to the Special Issue Neural Networks and Sensors)
Open AccessArticle A Peristaltic Micro Pump Driven by a Rotating Motor with Magnetically Attracted Steel Balls
Sensors 2009, 9(4), 2611-2620; doi:10.3390/s90402611
Received: 19 February 2009 / Revised: 30 March 2009 / Accepted: 1 April 2009 / Published: 15 April 2009
Cited by 16 | PDF Full-text (237 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we present a membrane peristaltic micro pump driven by a rotating motor with magnetically attracted steel balls for lab-on-a-chip applications. The fabrication process is based on standard soft lithography technology and bonding of a PDMS layer with a PMMA [...] Read more.
In this paper, we present a membrane peristaltic micro pump driven by a rotating motor with magnetically attracted steel balls for lab-on-a-chip applications. The fabrication process is based on standard soft lithography technology and bonding of a PDMS layer with a PMMA substrate. A linear flow rate range ~490 μL/min was obtained by simply varying the rotation speed of a DC motor, and a maximum back pressure of 592 Pa was achieved at a rotation speed of 43 rpm. The flow rate of the pump can also be adjusted by using steel balls with different diameters or changing the number of balls. Nevertheless, the micro pump can also work in high speed mode. A high back pressure up to 10 kPa was achieved at 500 rpm using a high speed DC motor, and an utmost flow rate up to 5 mL/min was reached. Full article
Open AccessArticle Automatic Registration of Terrestrial Laser Scanning Point Clouds using Panoramic Reflectance Images
Sensors 2009, 9(4), 2621-2646; doi:10.3390/s90402621
Received: 11 March 2009 / Revised: 10 April 2009 / Accepted: 13 April 2009 / Published: 15 April 2009
Cited by 35 | PDF Full-text (1983 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a new approach to the automatic registration of terrestrial laser scanning (TLS) point clouds using panoramic reflectance images. The approach follows a two-step procedure that includes both pair-wise registration and global registration. The pair-wise registration consists of image matching [...] Read more.
This paper presents a new approach to the automatic registration of terrestrial laser scanning (TLS) point clouds using panoramic reflectance images. The approach follows a two-step procedure that includes both pair-wise registration and global registration. The pair-wise registration consists of image matching (pixel-to-pixel correspondence) and point cloud registration (point-to-point correspondence), as the correspondence between the image and the point cloud (pixel-to-point) is inherent to the reflectance images. False correspondences are removed by a geometric invariance check. The pixel-to-point correspondence and the computation of the rigid transformation parameters (RTPs) are integrated into an iterative process that allows for the pair-wise registration to be optimised. The global registration of all point clouds is obtained by a bundle adjustment using a circular self-closure constraint. Our approach is tested with both indoor and outdoor scenes acquired by a FARO LS 880 laser scanner with an angular resolution of 0.036° and 0.045°, respectively. The results show that the pair-wise and global registration accuracies are of millimetre and centimetre orders, respectively, and that the process is fully automatic and converges quickly. Full article
(This article belongs to the Special Issue LiDAR for 3D City Modeling)
Open AccessCommunication Development of a Green Roof Environmental Monitoring and Meteorological Network in New York City
Sensors 2009, 9(4), 2647-2660; doi:10.3390/s90402647
Received: 18 March 2009 / Revised: 4 April 2009 / Accepted: 10 April 2009 / Published: 15 April 2009
Cited by 18 | PDF Full-text (2898 KB) | HTML Full-text | XML Full-text
Abstract
Green roofs (with plant cover) are gaining attention in the United States as a versatile new environmental mitigation technology. Interest in data on the environmental performance of these systems is growing, particularly with respect to urban heat island mitigation and stormwater runoff [...] Read more.
Green roofs (with plant cover) are gaining attention in the United States as a versatile new environmental mitigation technology. Interest in data on the environmental performance of these systems is growing, particularly with respect to urban heat island mitigation and stormwater runoff control. We are deploying research stations on a diverse array of green roofs within the New York City area, affording a new opportunity to monitor urban environmental conditions at small scales. We show some green roof systems being monitored, describe the sensor selection employed to study energy balance, and show samples of selected data. These roofs should be superior to other urban rooftops as sites for meteorological stations. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Discovery Mechanisms for the Sensor Web
Sensors 2009, 9(4), 2661-2681; doi:10.3390/s90402661
Received: 5 March 2009 / Revised: 7 April 2009 / Accepted: 15 April 2009 / Published: 16 April 2009
Cited by 37 | PDF Full-text (119 KB) | HTML Full-text | XML Full-text
Abstract
This paper addresses the discovery of sensors within the OGC Sensor Web Enablement framework. Whereas services like the OGC Web Map Service or Web Coverage Service are already well supported through catalogue services, the field of sensor networks and the according discovery [...] Read more.
This paper addresses the discovery of sensors within the OGC Sensor Web Enablement framework. Whereas services like the OGC Web Map Service or Web Coverage Service are already well supported through catalogue services, the field of sensor networks and the according discovery mechanisms is still a challenge. The focus within this article will be on the use of existing OGC Sensor Web components for realizing a discovery solution. After discussing the requirements for a Sensor Web discovery mechanism, an approach will be presented that was developed within the EU funded project “OSIRIS”. This solution offers mechanisms to search for sensors, exploit basic semantic relationships, harvest sensor metadata and integrate sensor discovery into already existing catalogues. Full article
(This article belongs to the Special Issue Workshop Sensing A Changing World)
Open AccessArticle Quantum Cascade Laser-Based Photoacoustic Sensor for Trace Detection of Formaldehyde Gas
Sensors 2009, 9(4), 2697-2705; doi:10.3390/s90402697
Received: 6 February 2009 / Revised: 2 April 2009 / Accepted: 16 April 2009 / Published: 16 April 2009
Cited by 20 | PDF Full-text (297 KB) | HTML Full-text | XML Full-text
Abstract
We report on the development of a photoacoustic sensor for the detection of formaldehyde (CH2O) using a thermoelectrically cooled distributed-feedback quantum cascade laser operating in pulsed mode at 5.6 mm. A resonant photoacoustic cell, equipped with four electret microphones, is [...] Read more.
We report on the development of a photoacoustic sensor for the detection of formaldehyde (CH2O) using a thermoelectrically cooled distributed-feedback quantum cascade laser operating in pulsed mode at 5.6 mm. A resonant photoacoustic cell, equipped with four electret microphones, is excited in its first longitudinal mode at 1,380 Hz. The absorption line at 1,778.9 cm-1 is selected for CH2O detection. A detection limit of 150 parts per billion in volume in nitrogen is achieved using a 10 seconds time constant and 4 mW laser power. Measurements in ambient air will require water vapour filters. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)
Open AccessArticle Comparison between Deflection and Vibration Characteristics of Rectangular and Trapezoidal profile Microcantilevers
Sensors 2009, 9(4), 2706-2718; doi:10.3390/s90402706
Received: 2 April 2009 / Revised: 10 April 2009 / Accepted: 15 April 2009 / Published: 16 April 2009
Cited by 13 | PDF Full-text (481 KB) | HTML Full-text | XML Full-text
Abstract
Arrays of microcantilevers are increasingly being used as physical, biological, and chemical sensors in various applications. To improve the sensitivity of microcantilever sensors, this study analyses and compares the deflection and vibration characteristics of rectangular and trapezoidal profile microcantilevers. Three models of [...] Read more.
Arrays of microcantilevers are increasingly being used as physical, biological, and chemical sensors in various applications. To improve the sensitivity of microcantilever sensors, this study analyses and compares the deflection and vibration characteristics of rectangular and trapezoidal profile microcantilevers. Three models of each profile are investigated. The cantilevers are analyzed for maximum deflection, fundamental resonant frequency and maximum stress. The surface stress is modelled as in-plane tensile force applied on the top edge of the microcantilevers. A commercial finite element analysis software ANSYS is used to analyze the designs. Results show paddled trapezoidal profile microcantilevers have better sensitivity. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Orientation Effects in Ballistic High-Strained P-type Si Nanowire FETs
Sensors 2009, 9(4), 2746-2759; doi:10.3390/s90402746
Received: 22 March 2009 / Revised: 15 April 2009 / Accepted: 16 April 2009 / Published: 17 April 2009
Cited by 5 | PDF Full-text (671 KB) | HTML Full-text | XML Full-text
Abstract
In order to design and optimize high-sensitivity silicon nanowire-field-effect transistor (SiNW FET) pressure sensors, this paper investigates the effects of channel orientations and the uniaxial stress on the ballistic hole transport properties of a strongly quantized SiNW FET placed near the high [...] Read more.
In order to design and optimize high-sensitivity silicon nanowire-field-effect transistor (SiNW FET) pressure sensors, this paper investigates the effects of channel orientations and the uniaxial stress on the ballistic hole transport properties of a strongly quantized SiNW FET placed near the high stress regions of the pressure sensors. A discrete stress-dependent six-band k.p method is used for subband structure calculation, coupled to a two-dimensional Poisson solver for electrostatics. A semi-classical ballistic FET model is then used to evaluate the ballistic current-voltage characteristics of SiNW FETs with and without strain. Our results presented here indicate that [110] is the optimum orientation for the p-type SiNW FETs and sensors. For the ultra-scaled 2.2 nm square SiNW, due to the limit of strong quantum confinement, the effect of the uniaxial stress on the magnitude of ballistic drive current is too small to be considered, except for the [100] orientation. However, for larger 5 nm square SiNW transistors with various transport orientations, the uniaxial tensile stress obviously alters the ballistic performance, while the uniaxial compressive stress slightly changes the ballistic hole current. Furthermore, the competition of injection velocity and carrier density related to the effective hole masses is found to play a critical role in determining the performance of the nanotransistors. Full article
Open AccessArticle Adapting Mobile Beacon-Assisted Localization in Wireless Sensor Networks
Sensors 2009, 9(4), 2760-2779; doi:10.3390/s90402760
Received: 26 March 2009 / Revised: 14 April 2009 / Accepted: 16 April 2009 / Published: 20 April 2009
Cited by 20 | PDF Full-text (284 KB) | HTML Full-text | XML Full-text
Abstract
The ability to automatically locate sensor nodes is essential in many Wireless Sensor Network (WSN) applications. To reduce the number of beacons, many mobile-assisted approaches have been proposed. Current mobile-assisted approaches for localization require special hardware or belong to centralized localization algorithms [...] Read more.
The ability to automatically locate sensor nodes is essential in many Wireless Sensor Network (WSN) applications. To reduce the number of beacons, many mobile-assisted approaches have been proposed. Current mobile-assisted approaches for localization require special hardware or belong to centralized localization algorithms involving some deterministic approaches due to the fact that they explicitly consider the impreciseness of location estimates. In this paper, we first propose a range-free, distributed and probabilistic Mobile Beacon-assisted Localization (MBL) approach for static WSNs. Then, we propose another approach based on MBL, called Adapting MBL (A-MBL), to increase the efficiency and accuracy of MBL by adapting the size of sample sets and the parameter of the dynamic model during the estimation process. Evaluation results show that the accuracy of MBL and A-MBL outperform both Mobile and Static sensor network Localization (MSL) and Arrival and Departure Overlap (ADO) when both of them use only a single mobile beacon for localization in static WSNs. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
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Open AccessArticle Use of Naturally Available Reference Targets to Calibrate Airborne Laser Scanning Intensity Data
Sensors 2009, 9(4), 2780-2796; doi:10.3390/s90402780
Received: 9 March 2009 / Revised: 31 March 2009 / Accepted: 20 April 2009 / Published: 20 April 2009
Cited by 25 | PDF Full-text (902 KB) | HTML Full-text | XML Full-text
Abstract
We have studied the possibility of calibrating airborne laser scanning (ALS) intensity data, using land targets typically available in urban areas. For this purpose, a test area around Espoonlahti Harbor, Espoo, Finland, for which a long time series of ALS campaigns is [...] Read more.
We have studied the possibility of calibrating airborne laser scanning (ALS) intensity data, using land targets typically available in urban areas. For this purpose, a test area around Espoonlahti Harbor, Espoo, Finland, for which a long time series of ALS campaigns is available, was selected. Different target samples (beach sand, concrete, asphalt, different types of gravel) were collected and measured in the laboratory. Using tarps, which have certain backscattering properties, the natural samples were calibrated and studied, taking into account the atmospheric effect, incidence angle and flying height. Using data from different flights and altitudes, a time series for the natural samples was generated. Studying the stability of the samples, we could obtain information on the most ideal types of natural targets for ALS radiometric calibration. Using the selected natural samples as reference, the ALS points of typical land targets were calibrated again and examined. Results showed the need for more accurate ground reference data, before using natural samples in ALS intensity data calibration. Also, the NIR camera-based field system was used for collecting ground reference data. This system proved to be a good means for collecting in situ reference data, especially for targets with inhomogeneous surface reflection properties. Full article
(This article belongs to the Special Issue LiDAR for 3D City Modeling)
Open AccessArticle A Novel Intra-body Sensor for Vaginal Temperature Monitoring
Sensors 2009, 9(4), 2797-2808; doi:10.3390/s90402797
Received: 1 April 2009 / Revised: 15 April 2009 / Accepted: 20 April 2009 / Published: 21 April 2009
Cited by 8 | PDF Full-text (1255 KB) | HTML Full-text | XML Full-text
Abstract
Over the years some medical studies have tried to better understand the internal behavior of human beings. Many researchers in this domain have been striving to find relationships between intra-vaginal temperature and certain female health conditions, such as ovulation and fertile period [...] Read more.
Over the years some medical studies have tried to better understand the internal behavior of human beings. Many researchers in this domain have been striving to find relationships between intra-vaginal temperature and certain female health conditions, such as ovulation and fertile period since woman’s intra-vaginal temperature is one of the body parameters most preferred in such studies. However, due to lack of a appropriate technology, medical research devoted to studying correlations of such body parameters with certain womans’ body phenomena could not obtain better results. This article presents the design and implementation of a novel intra-body sensor for acquisition and monitoring of intra-vaginal temperatures. This novel intra-body sensor provides data collection that is used for studying the relation between temperature variations and female health conditions, such as anticipation and monitoring of the ovulation period, detection of pregnancy contractions, preterm labor prevention, etc.. The motivation for this work focuses on the development of this new intra-body sensor that will represent a major step in medical technology. The novel sensor was tested and validated on hospitalized women as well as normal healthy women. Finally our medical team has attested to the accuracy, usability and performance of this novel intra-body sensor. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Open AccessArticle Anchor-Free Localization Method for Mobile Targets in Coal Mine Wireless Sensor Networks
Sensors 2009, 9(4), 2836-2850; doi:10.3390/s90402836
Received: 13 March 2009 / Revised: 15 April 2009 / Accepted: 20 April 2009 / Published: 21 April 2009
Cited by 16 | PDF Full-text (803 KB) | HTML Full-text | XML Full-text
Abstract
Severe natural conditions and complex terrain make it difficult to apply precise localization in underground mines. In this paper, an anchor-free localization method for mobile targets is proposed based on non-metric multi-dimensional scaling (Multi-dimensional Scaling: MDS) and rank sequence. Firstly, a coal [...] Read more.
Severe natural conditions and complex terrain make it difficult to apply precise localization in underground mines. In this paper, an anchor-free localization method for mobile targets is proposed based on non-metric multi-dimensional scaling (Multi-dimensional Scaling: MDS) and rank sequence. Firstly, a coal mine wireless sensor network is constructed in underground mines based on the ZigBee technology. Then a non-metric MDS algorithm is imported to estimate the reference nodes’ location. Finally, an improved sequence-based localization algorithm is presented to complete precise localization for mobile targets. The proposed method is tested through simulations with 100 nodes, outdoor experiments with 15 ZigBee physical nodes, and the experiments in the mine gas explosion laboratory with 12 ZigBee nodes. Experimental results show that our method has better localization accuracy and is more robust in underground mines. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
Open AccessArticle A Weld Defects Detection System Based on a Spectrometer
Sensors 2009, 9(4), 2851-2861; doi:10.3390/s90402851
Received: 17 March 2009 / Revised: 7 April 2009 / Accepted: 20 April 2009 / Published: 21 April 2009
Cited by 6 | PDF Full-text (1153 KB) | HTML Full-text | XML Full-text
Abstract
Improved product quality and production methods, and decreased production costs are important objectives of industries. Welding processes are part of this goal. There are many studies about monitoring and controlling welding process. This work presents a non-intrusive on-line monitoriment system and some [...] Read more.
Improved product quality and production methods, and decreased production costs are important objectives of industries. Welding processes are part of this goal. There are many studies about monitoring and controlling welding process. This work presents a non-intrusive on-line monitoriment system and some algorithms capable of detecting GTAW weld defects. Some experiments were made to simulate weld defects by disturbing the electric arc. The data comes from a spectrometer which captures perturbations on the electric arc by the radiation emission of chosen lines. Algorithms based on change detection methods are used to indicate the presence and localization of those defects. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Wireless in-situ Sensor Network for Agriculture and Water Monitoring on a River Basin Scale in Southern Finland: Evaluation from a Data User’s Perspective
Sensors 2009, 9(4), 2862-2883; doi:10.3390/s90402862
Received: 4 March 2009 / Revised: 20 April 2009 / Accepted: 21 April 2009 / Published: 21 April 2009
Cited by 22 | PDF Full-text (369 KB) | HTML Full-text | XML Full-text
Abstract
Sensor networks are increasingly being implemented for environmental monitoring and agriculture to provide spatially accurate and continuous environmental information and (near) real-time applications. These networks provide a large amount of data which poses challenges for ensuring data quality and extracting relevant information. [...] Read more.
Sensor networks are increasingly being implemented for environmental monitoring and agriculture to provide spatially accurate and continuous environmental information and (near) real-time applications. These networks provide a large amount of data which poses challenges for ensuring data quality and extracting relevant information. In the present paper we describe a river basin scale wireless sensor network for agriculture and water monitoring. The network, called SoilWeather, is unique and the first of this type in Finland. The performance of the network is assessed from the user and maintainer perspectives, concentrating on data quality, network maintenance and applications. The results showed that the SoilWeather network has been functioning in a relatively reliable way, but also that the maintenance and data quality assurance by automatic algorithms and calibration samples requires a lot of effort, especially in continuous water monitoring over large areas. We see great benefits on sensor networks enabling continuous, real-time monitoring, while data quality control and maintenance efforts highlight the need for tight collaboration between sensor and sensor network owners to decrease costs and increase the quality of the sensor data in large scale applications. Full article
(This article belongs to the Special Issue Workshop Sensing A Changing World)
Open AccessArticle On the Capability of Artificial Neural Networks to Compensate Nonlinearities in Wavelength Sensing
Sensors 2009, 9(4), 2884-2894; doi:10.3390/s90402884
Received: 6 April 2009 / Revised: 6 April 2009 / Accepted: 21 April 2009 / Published: 21 April 2009
Cited by 8 | PDF Full-text (258 KB) | HTML Full-text | XML Full-text
Abstract
An intelligent sensor for light wavelength readout, suitable for visible range optical applications, has been developed. Using buried triple photo-junction as basic pixel sensing element in combination with artificial neural network (ANN), the wavelength readout with a full-scale error of less than [...] Read more.
An intelligent sensor for light wavelength readout, suitable for visible range optical applications, has been developed. Using buried triple photo-junction as basic pixel sensing element in combination with artificial neural network (ANN), the wavelength readout with a full-scale error of less than 1.5% over the range of 400 to 780 nm can be achieved. Through this work, the applicability of the ANN approach in optical sensing is investigated and compared with conventional methods, and a good compromise between accuracy and the possibility for on-chip implementation was thus found. Indeed, this technique can serve different purposes and may replace conventional methods. Full article
(This article belongs to the Special Issue Neural Networks and Sensors)
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Open AccessArticle A MEMS-based Benzene Gas Sensor with a Self-heating WO3 Sensing Layer
Sensors 2009, 9(4), 2895-2906; doi:10.3390/s90402895
Received: 31 March 2009 / Revised: 17 April 2009 / Accepted: 21 April 2009 / Published: 21 April 2009
Cited by 27 | PDF Full-text (489 KB) | HTML Full-text | XML Full-text
Abstract
In the study, a MEMS-based benzene gas sensor is presented, consisting of a quartz substrate, a thin-film WO3 sensing layer, an integrated Pt micro-heater, and Pt interdigitated electrodes (IDEs). When benzene is present in the atmosphere, oxidation occurs on the heated [...] Read more.
In the study, a MEMS-based benzene gas sensor is presented, consisting of a quartz substrate, a thin-film WO3 sensing layer, an integrated Pt micro-heater, and Pt interdigitated electrodes (IDEs). When benzene is present in the atmosphere, oxidation occurs on the heated WO3 sensing layer. This causes a change in the electrical conductivity of the WO3 film, and hence changes the resistance between the IDEs. The benzene concentration is then computed from the change in the measured resistance. A specific orientation of the WO3 layer is obtained by optimizing the sputtering process parameters. It is found that the sensitivity of the gas sensor is optimized at a working temperature of 300 °C. At the optimal working temperature, the experimental results show that the sensor has a high degree of sensitivity (1.0 KΩ ppm-1), a low detection limit (0.2 ppm) and a rapid response time (35 s). Full article
(This article belongs to the Special Issue Gas Sensors 2009)
Open AccessArticle Interpretation of Absorption Bands in Airborne Hyperspectral Radiance Data
Sensors 2009, 9(4), 2907-2925; doi:10.3390/s90402907
Received: 16 March 2009 / Revised: 17 April 2009 / Accepted: 22 April 2009 / Published: 22 April 2009
Cited by 3 | PDF Full-text (851 KB) | HTML Full-text | XML Full-text
Abstract
It is demonstrated that hyperspectral imagery can be used, without atmospheric correction, to determine the presence of accessory phytoplankton pigments in coastal waters using derivative techniques. However, care must be taken not to confuse other absorptions for those caused by the presence [...] Read more.
It is demonstrated that hyperspectral imagery can be used, without atmospheric correction, to determine the presence of accessory phytoplankton pigments in coastal waters using derivative techniques. However, care must be taken not to confuse other absorptions for those caused by the presence of pigments. Atmospheric correction, usually the first step to making products from hyperspectral data, may not completely remove Fraunhofer lines and atmospheric absorption bands and these absorptions may interfere with identification of phytoplankton accessory pigments. Furthermore, the ability to resolve absorption bands depends on the spectral resolution of the spectrometer, which for a fixed spectral range also determines the number of observed bands. Based on this information, a study was undertaken to determine under what circumstances a hyperspectral sensor may determine the presence of pigments. As part of the study a hyperspectral imager was used to take high spectral resolution data over two different water masses. In order to avoid the problems associated with atmospheric correction this data was analyzed as radiance data without atmospheric correction. Here, the purpose was to identify spectral regions that might be diagnostic for photosynthetic pigments. Two well proven techniques were used to aid in absorption band recognition, the continuum removal of the spectra and the fourth derivative. The findings in this study suggest that interpretation of absorption bands in remote sensing data, whether atmospherically corrected or not, have to be carefully reviewed when they are interpreted in terms of photosynthetic pigments. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Language-Based Access to Large Sensor Repositories
Sensors 2009, 9(4), 2926-2943; doi:10.3390/s90402926
Received: 25 February 2009 / Revised: 20 April 2009 / Accepted: 21 April 2009 / Published: 22 April 2009
Cited by 1 | PDF Full-text (257 KB) | HTML Full-text | XML Full-text
Abstract
Sensor data have broadened their scope recently, ranging now from the simple time series measurements to, e.g., hyperspectral satellite image maps timeseries. In addition to observed data, simulation data increasingly have to be merged, for example 4-D ocean and atmospheric data. The [...] Read more.
Sensor data have broadened their scope recently, ranging now from the simple time series measurements to, e.g., hyperspectral satellite image maps timeseries. In addition to observed data, simulation data increasingly have to be merged, for example 4-D ocean and atmospheric data. The majority of these data fall into the category of multi-dimensional rasters. However, when it comes to flexible retrieval, including sensor data search, aggregation, analysis, fusion, etc., standard query language support in the past has not kept up with the service level of, e.g., metadata retrieval. To close this gap, the Open GeoSpatial Consortium (OGC) has issued the Web Coverage Processing Service (WCPS) Standard in December 2008. WCPS defines a request language for multi-dimensional raster data, suitable for specifying navigation, download, and analysis of sensor, image, and statistics data. This contribution emphasises sensor data modeling and the perspectives for an integrated, cross-dimensional sensor data retrieval. Further, the WCPS reference implementation is briefly discussed. Full article
(This article belongs to the Special Issue Workshop Sensing A Changing World)
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Open AccessArticle Compact Integration of a GSM-19 Magnetic Sensor with High-Precision Positioning using VRS GNSS Technology
Sensors 2009, 9(4), 2944-2950; doi:10.3390/s90402944
Received: 24 March 2009 / Revised: 8 April 2009 / Accepted: 20 April 2009 / Published: 22 April 2009
Cited by 7 | PDF Full-text (378 KB) | HTML Full-text | XML Full-text
Abstract
Magnetic data consists of a sequence of collected points with spatial coordinates and magnetic information. The spatial location of these points needs to be as exact as possible in order to develop a precise interpretation of magnetic anomalies. GPS is a valuable [...] Read more.
Magnetic data consists of a sequence of collected points with spatial coordinates and magnetic information. The spatial location of these points needs to be as exact as possible in order to develop a precise interpretation of magnetic anomalies. GPS is a valuable tool for accomplishing this objective, especially if the RTK approach is used. In this paper the VRS (Virtual Reference Station) technique is introduced as a new approach for real-time positioning of magnetic sensors. The main advantages of the VRS approach are, firstly, that only a single GPS receiver is needed (no base station is necessary), reducing field work and equipment costs. Secondly, VRS can operate at distances separated 50-70 km from the reference stations without degrading accuracy. A compact integration of a GSM-19 magnetometer sensor with a geodetic GPS antenna is presented; this integration does not diminish the operational flexibility of the original magnetometer and can work with the VRS approach. The coupled devices were tested in marshlands around Gandia, a city located approximately 100 km South of Valencia (Spain), thought to be the site of a Roman cemetery. The results obtained show adequate geometry and high-precision positioning for the structures to be studied (a comparison with the original low precision GPS of the magnetometer is presented). Finally, the results of the magnetic survey are of great interest for archaeological purposes. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle New Dielectric Sensors and Sensing Techniques for Soil and Snow Moisture Measurements
Sensors 2009, 9(4), 2951-2967; doi:10.3390/s90402951
Received: 8 April 2009 / Revised: 17 April 2009 / Accepted: 22 April 2009 / Published: 22 April 2009
Cited by 13 | PDF Full-text (970 KB) | HTML Full-text | XML Full-text
Abstract
Measurements of material moisture are essential in fields such as agriculture or civil engineering. Electromagnetic techniques, more precisely dielectric methods, have gained wide acceptance in the last decades. Frequency or Time Domain methods take advantage of the high dielectric permittivity of water [...] Read more.
Measurements of material moisture are essential in fields such as agriculture or civil engineering. Electromagnetic techniques, more precisely dielectric methods, have gained wide acceptance in the last decades. Frequency or Time Domain methods take advantage of the high dielectric permittivity of water compared to dry materials. This paper presents four new dielectric sensors for the determination of soil or snow water content. After a short introduction into the principles, both the hardware and operating mode of each sensor are described. Field test results show the advantages and potentials such as automatic measurement and profiling, state-of-ground detection or large-scale determination. From the results it follows that the presented sensors offer promising new tools for modern environmental research. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany)
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Open AccessArticle Use of Vegetation Health Data for Estimation of Aus Rice Yield in Bangladesh
Sensors 2009, 9(4), 2968-2975; doi:10.3390/s90402968
Received: 18 March 2009 / Revised: 19 April 2009 / Accepted: 22 April 2009 / Published: 23 April 2009
Cited by 7 | PDF Full-text (112 KB) | HTML Full-text | XML Full-text
Abstract
Rice is a vital staple crop for Bangladesh and surrounding countries, with interannual variation in yields depending on climatic conditions. We compared Bangladesh yield of aus rice, one of the main varieties grown, from official agricultural statistics with Vegetation Health (VH) Indices [...] Read more.
Rice is a vital staple crop for Bangladesh and surrounding countries, with interannual variation in yields depending on climatic conditions. We compared Bangladesh yield of aus rice, one of the main varieties grown, from official agricultural statistics with Vegetation Health (VH) Indices [Vegetation Condition Index (VCI), Temperature Condition Index (TCI) and Vegetation Health Index (VHI)] computed from Advanced Very High Resolution Radiometer (AVHRR) data covering a period of 15 years (1991–2005). A strong correlation was found between aus rice yield and VCI and VHI during the critical period of aus rice development that occurs during March-April (weeks 8–13 of the year), several months in advance of the rice harvest. Stepwise principal component regression (PCR) was used to construct a model to predict yield as a function of critical-period VHI. The model reduced the yield prediction error variance by 62% compared with a prediction of average yield for each year. Remote sensing is a valuable tool for estimating rice yields well in advance of harvest and at a low cost. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Matrix Effects on the Microcystin-LR Fluorescent Immunoassay Based on Optical Biosensor
Sensors 2009, 9(4), 3000-3010; doi:10.3390/s90403000
Received: 12 March 2009 / Revised: 25 March 2009 / Accepted: 15 April 2009 / Published: 23 April 2009
Cited by 8 | PDF Full-text (211 KB) | HTML Full-text | XML Full-text
Abstract
Matrix effects on the microcystin-LR fluorescent immunoassay based on the evanescent wave all-fiber immunosensor (EWAI) and their elimination methods were studied. The results indicated that PBS and humic acid did not affect the monitoring of samples under the investigated conditions. When the [...] Read more.
Matrix effects on the microcystin-LR fluorescent immunoassay based on the evanescent wave all-fiber immunosensor (EWAI) and their elimination methods were studied. The results indicated that PBS and humic acid did not affect the monitoring of samples under the investigated conditions. When the pH was less than 6 or higher than 8, the fluorescence signals detected by immunosensor systems were obviously reduced with the decrease or increase of pH. When the pH ranged from 6 to 8, IC50 and the linear working range of MC-LR calculated from the detection curves were 1.01~1.04 μg/L and 0.12~10.5 μg/L, respectively, which was favourable for an MC-LR immunoassay. Low concentrations of Cu2+ rarely affected the detection performance of MC-LR. When the concentration of CuSO4 was higher than 5 mg/L, the fluorescence signal detected by EWAI clearly decreased, and when the concentration of CuSO4 was 10 mg/L, the fluorescence signal detected was reduced by 70%. The influence of Cu2+ on the immunoassay could effectively be compromised when chelating reagent EDTA was added to the pre-reaction mixture. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Heat Transfer Measurements with Surface Mounted Foil-Sensors in an Active Mode: A Comprehensive Review and a New Design
Sensors 2009, 9(4), 3011-3032; doi:10.3390/s90403011
Received: 23 March 2009 / Revised: 7 April 2009 / Accepted: 22 April 2009 / Published: 23 April 2009
Cited by 6 | PDF Full-text (443 KB) | HTML Full-text | XML Full-text
Abstract
A comprehensive review of film-sensors shows that they are primarily operated in a passive mode, i.e. without being actively heated to an extent, whereby they create a heat transfer situation on their own. Only when these sensors are used for wall shear [...] Read more.
A comprehensive review of film-sensors shows that they are primarily operated in a passive mode, i.e. without being actively heated to an extent, whereby they create a heat transfer situation on their own. Only when these sensors are used for wall shear stress measurements, the detection of laminar/turbulent transition, or the measurement of certain flow velocities, they are operated in an active mode, i.e. heated by an electrical current (after an appropriate calibration). In our study we demonstrate how these R(T)-based sensors (temperature dependence of the electrical resistance R) can also be applied in an active mode for heat transfer measurements. These measurements can be made on cold, unheated bodies, provided certain requirements with respect to the flow field are fulfilled. Our new sensors are laminated nickel- and polyimide-foils manufactured with a special technology, which is also described in detail. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany)
Open AccessArticle Sensing Human Activity: GPS Tracking
Sensors 2009, 9(4), 3033-3055; doi:10.3390/s90403033
Received: 6 February 2009 / Revised: 26 March 2009 / Accepted: 22 April 2009 / Published: 24 April 2009
Cited by 21 | PDF Full-text (968 KB) | HTML Full-text | XML Full-text
Abstract
The enhancement of GPS technology enables the use of GPS devices not only as navigation and orientation tools, but also as instruments used to capture travelled routes: as sensors that measure activity on a city scale or the regional scale. TU Delft [...] Read more.
The enhancement of GPS technology enables the use of GPS devices not only as navigation and orientation tools, but also as instruments used to capture travelled routes: as sensors that measure activity on a city scale or the regional scale. TU Delft developed a process and database architecture for collecting data on pedestrian movement in three European city centres, Norwich, Rouen and Koblenz, and in another experiment for collecting activity data of 13 families in Almere (The Netherlands) for one week. The question posed in this paper is: what is the value of GPS as ‘sensor technology’ measuring activities of people? The conclusion is that GPS offers a widely useable instrument to collect invaluable spatial-temporal data on different scales and in different settings adding new layers of knowledge to urban studies, but the use of GPS-technology and deployment of GPS-devices still offers significant challenges for future research. Full article
(This article belongs to the Special Issue Workshop Sensing A Changing World)
Open AccessArticle Application of Neurocomputing for Data Approximation and Classification in Wireless Sensor Networks
Sensors 2009, 9(4), 3056-3077; doi:10.3390/s90403056
Received: 3 April 2009 / Revised: 21 April 2009 / Accepted: 24 April 2009 / Published: 24 April 2009
Cited by 8 | PDF Full-text (738 KB) | HTML Full-text | XML Full-text
Abstract
A new application of neurocomputing for data approximation and classification is introduced to process data in a wireless sensor network. For this purpose, a simplified dynamic sliding backpropagation algorithm is implemented on a wireless sensor network for transportation applications. It is able [...] Read more.
A new application of neurocomputing for data approximation and classification is introduced to process data in a wireless sensor network. For this purpose, a simplified dynamic sliding backpropagation algorithm is implemented on a wireless sensor network for transportation applications. It is able to approximate temperature and humidity in sensor nodes. In addition, two architectures of “radial basis function” (RBF) classifiers are introduced with probabilistic features for data classification in sensor nodes. The applied approximation and classification algorithms could be used in similar applications for data processing in embedded systems. Full article
(This article belongs to the Special Issue Neural Networks and Sensors)
Open AccessArticle Networked Estimation for Event-Based Sampling Systems with Packet Dropouts
Sensors 2009, 9(4), 3078-3089; doi:10.3390/s90403078
Received: 23 March 2009 / Revised: 21 April 2009 / Accepted: 24 April 2009 / Published: 24 April 2009
Cited by 14 | PDF Full-text (477 KB) | HTML Full-text | XML Full-text
Abstract
This paper is concerned with a networked estimation problem in which sensor data are transmitted over the network. In the event-based sampling scheme known as level-crossing or send-on-delta (SOD), sensor data are transmitted to the estimator node if the difference between the [...] Read more.
This paper is concerned with a networked estimation problem in which sensor data are transmitted over the network. In the event-based sampling scheme known as level-crossing or send-on-delta (SOD), sensor data are transmitted to the estimator node if the difference between the current sensor value and the last transmitted one is greater than a given threshold. Event-based sampling has been shown to be more efficient than the time-triggered one in some situations, especially in network bandwidth improvement. However, it cannot detect packet dropout situations because data transmission and reception do not use a periodical time-stamp mechanism as found in time-triggered sampling systems. Motivated by this issue, we propose a modified event-based sampling scheme called modified SOD in which sensor data are sent when either the change of sensor output exceeds a given threshold or the time elapses more than a given interval. Through simulation results, we show that the proposed modified SOD sampling significantly improves estimation performance when packet dropouts happen. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Simulation of EO-1 Hyperion Data from ALI Multispectral Data Based on the Spectral Reconstruction Approach
Sensors 2009, 9(4), 3090-3108; doi:10.3390/s90403090
Received: 11 March 2009 / Revised: 16 April 2009 / Accepted: 20 April 2009 / Published: 24 April 2009
Cited by 13 | PDF Full-text (827 KB) | HTML Full-text | XML Full-text
Abstract
Data simulation is widely used in remote sensing to produce imagery for a new sensor in the design stage, for scale issues of some special applications, or for testing of novel algorithms. Hyperspectral data could provide more abundant information than traditional multispectral [...] Read more.
Data simulation is widely used in remote sensing to produce imagery for a new sensor in the design stage, for scale issues of some special applications, or for testing of novel algorithms. Hyperspectral data could provide more abundant information than traditional multispectral data and thus greatly extend the range of remote sensing applications. Unfortunately, hyperspectral data are much more difficult and expensive to acquire and were not available prior to the development of operational hyperspectral instruments, while large amounts of accumulated multispectral data have been collected around the world over the past several decades. Therefore, it is reasonable to examine means of using these multispectral data to simulate or construct hyperspectral data, especially in situations where hyperspectral data are necessary but hard to acquire. Here, a method based on spectral reconstruction is proposed to simulate hyperspectral data (Hyperion data) from multispectral Advanced Land Imager data (ALI data). This method involves extraction of the inherent information of source data and reassignment to newly simulated data. A total of 106 bands of Hyperion data were simulated from ALI data covering the same area. To evaluate this method, we compare the simulated and original Hyperion data by visual interpretation, statistical comparison, and classification. The results generally showed good performance of this method and indicated that most bands were well simulated, and the information both preserved and presented well. This makes it possible to simulate hyperspectral data from multispectral data for testing the performance of algorithms, extend the use of multispectral data and help the design of a virtual sensor. Full article
(This article belongs to the Special Issue Sensor Algorithms)
Open AccessArticle A Near-Infrared Spectrometer Based on Novel Grating Light Modulators
Sensors 2009, 9(4), 3109-3121; doi:10.3390/s90403109
Received: 24 February 2009 / Revised: 9 April 2009 / Accepted: 20 April 2009 / Published: 24 April 2009
PDF Full-text (1209 KB) | HTML Full-text | XML Full-text
Abstract
A near-infrared spectrometer based on novel MOEMS grating light modulators is proposed. The spectrum detection method that combines a grating light modulator array with a single near-infrared detector has been applied. Firstly, optics theory has been used to analyze the essential principles [...] Read more.
A near-infrared spectrometer based on novel MOEMS grating light modulators is proposed. The spectrum detection method that combines a grating light modulator array with a single near-infrared detector has been applied. Firstly, optics theory has been used to analyze the essential principles of the proposed spectroscopic sensor. Secondly, the grating light modulators have been designed and fabricated by micro-machining technology. Finally, the principles of this spectroscopic sensor have been validated and its key parameters have been tested by experiments. The result shows that the spectral resolution is better than 10 nm, the wavelength deviation is less than 1 nm, the deviation of the intensity of peak wavelength is no more than 0.5%, the driving voltage of grating light modulators array device is below 25 V and the response frequency of it is about 5 kHz. With low cost, satisfactory precision, portability and other advantages, the spectrometer should find potential applications in food safety and quality monitoring, pharmaceutical identification and agriculture product quality classification. Full article
Open AccessArticle Measurement Uncertainty Estimation of a Robust Photometer Circuit
Sensors 2009, 9(4), 3149-3160; doi:10.3390/s90403149
Received: 28 March 2009 / Revised: 22 April 2009 / Accepted: 24 April 2009 / Published: 24 April 2009
Cited by 4 | PDF Full-text (262 KB) | HTML Full-text | XML Full-text
Abstract
In this paper the uncertainty of a robust photometer circuit (RPC) was estimated. Here, the RPC was considered as a measurement system, having input quantities that were inexactly known, and output quantities that consequently were also inexactly known. Input quantities represent information [...] Read more.
In this paper the uncertainty of a robust photometer circuit (RPC) was estimated. Here, the RPC was considered as a measurement system, having input quantities that were inexactly known, and output quantities that consequently were also inexactly known. Input quantities represent information obtained from calibration certificates, specifications of manufacturers, and tabulated data. Output quantities describe the transfer function of the electrical part of the photodiode. Input quantities were the electronic components of the RPC, the parameters of the model of the photodiode and its sensitivity at 670 nm. The output quantities were the coefficients of both numerator and denominator of the closed-loop transfer function of the RPC. As an example, the gain and phase shift of the RPC versus frequency was evaluated from the transfer function, with their uncertainties and correlation coefficient. Results confirm the robustness of photodiode design. Full article
(This article belongs to the Section Chemical Sensors)

Review

Jump to: Research

Open AccessReview Visual Sensor Technology for Advanced Surveillance Systems: Historical View, Technological Aspects and Research Activities in Italy
Sensors 2009, 9(4), 2252-2270; doi:10.3390/s90402252
Received: 9 January 2009 / Revised: 25 March 2009 / Accepted: 26 March 2009 / Published: 30 March 2009
Cited by 9 | PDF Full-text (2055 KB) | HTML Full-text | XML Full-text
Abstract
The paper is a survey of the main technological aspects of advanced visual-based surveillance systems. A brief historical view of such systems from the origins to nowadays is given together with a short description of the main research projects in Italy on [...] Read more.
The paper is a survey of the main technological aspects of advanced visual-based surveillance systems. A brief historical view of such systems from the origins to nowadays is given together with a short description of the main research projects in Italy on surveillance applications in the last twenty years. The paper then describes the main characteristics of an advanced visual sensor network that (a) directly processes locally acquired digital data, (b) automatically modifies intrinsic (focus, iris) and extrinsic (pan, tilt, zoom) parameters to increase the quality of acquired data and (c) automatically selects the best subset of sensors in order to monitor a given moving object in the observed environment. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)
Open AccessReview Small Magnetic Sensors for Space Applications
Sensors 2009, 9(4), 2271-2288; doi:10.3390/s90402271
Received: 23 December 2008 / Revised: 7 March 2009 / Accepted: 26 March 2009 / Published: 30 March 2009
Cited by 50 | PDF Full-text (418 KB) | HTML Full-text | XML Full-text
Abstract
Small magnetic sensors are widely used integrated in vehicles, mobile phones, medical devices, etc for navigation, speed, position and angular sensing. These magnetic sensors are potential candidates for space sector applications in which mass, volume and power savings are important issues. This [...] Read more.
Small magnetic sensors are widely used integrated in vehicles, mobile phones, medical devices, etc for navigation, speed, position and angular sensing. These magnetic sensors are potential candidates for space sector applications in which mass, volume and power savings are important issues. This work covers the magnetic technologies available in the marketplace and the steps towards their implementation in space applications, the actual trend of miniaturization the front-end technologies, and the convergence of the mature and miniaturized magnetic sensor to the space sector through the small satellite concept. Full article
(This article belongs to the Special Issue Aerospace Sensor Systems)
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Open AccessReview Electrochemical Sensors Based on Carbon Nanotubes
Sensors 2009, 9(4), 2289-2319; doi:10.3390/s90402289
Received: 8 January 2009 / Revised: 17 March 2009 / Accepted: 30 March 2009 / Published: 30 March 2009
Cited by 119 | PDF Full-text (397 KB) | HTML Full-text | XML Full-text
Abstract
This review focuses on recent contributions in the development of the electrochemical sensors based on carbon nanotubes (CNTs). CNTs have unique mechanical and electronic properties, combined with chemical stability, and behave electrically as a metal or semiconductor, depending on their structure. For [...] Read more.
This review focuses on recent contributions in the development of the electrochemical sensors based on carbon nanotubes (CNTs). CNTs have unique mechanical and electronic properties, combined with chemical stability, and behave electrically as a metal or semiconductor, depending on their structure. For sensing applications, CNTs have many advantages such as small size with larger surface area, excellent electron transfer promoting ability when used as electrodes modifier in electrochemical reactions, and easy protein immobilization with retention of its activity for potential biosensors. CNTs play an important role in the performance of electrochemical biosensors, immunosensors, and DNA biosensors. Various methods have been developed for the design of sensors using CNTs in recent years. Herein we summarize the applications of CNTs in the construction of electrochemical sensors and biosensors along with other nanomaterials and conducting polymers. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessReview Advances in Microbial Biofilm Prevention on Indwelling Medical Devices with Emphasis on Usage of Acoustic Energy
Sensors 2009, 9(4), 2538-2554; doi:10.3390/s90402538
Received: 20 January 2009 / Revised: 27 March 2009 / Accepted: 14 April 2009 / Published: 14 April 2009
Cited by 18 | PDF Full-text (223 KB) | HTML Full-text | XML Full-text
Abstract
Microbial biofilms are a major impediment to the use of indwelling medical devices, generating device-related infections with high morbidity and mortality. Major efforts directed towards preventing and eradicating the biofilm problem face difficulties because biofilms protect themselves very effectively by producing a [...] Read more.
Microbial biofilms are a major impediment to the use of indwelling medical devices, generating device-related infections with high morbidity and mortality. Major efforts directed towards preventing and eradicating the biofilm problem face difficulties because biofilms protect themselves very effectively by producing a polysaccharide coating, reducing biofilm sensitivity to antimicrobial agents. Techniques applied to combating biofilms have been primarily chemical. These have met with partial and limited success rates, leading to current trends of eradicating biofilms through physico-mechanical strategies. Here we review the different approaches that have been developed to control biofilm formation and removal, focusing on the utilization of acoustic energy to achieve these objectives. Full article
(This article belongs to the Special Issue Pathogen Sensors)
Open AccessReview Nanoparticle Thin Films for Gas Sensors Prepared by Matrix Assisted Pulsed Laser Evaporation
Sensors 2009, 9(4), 2682-2696; doi:10.3390/s90402682
Received: 27 February 2009 / Revised: 7 April 2009 / Accepted: 10 April 2009 / Published: 16 April 2009
Cited by 38 | PDF Full-text (802 KB) | HTML Full-text | XML Full-text
Abstract
The matrix assisted pulsed laser evaporation (MAPLE) technique has been used for the deposition of metal dioxide (TiO2, SnO2) nanoparticle thin films for gas sensor applications. For this purpose, colloidal metal dioxide nanoparticles were diluted in volatile solvents, [...] Read more.
The matrix assisted pulsed laser evaporation (MAPLE) technique has been used for the deposition of metal dioxide (TiO2, SnO2) nanoparticle thin films for gas sensor applications. For this purpose, colloidal metal dioxide nanoparticles were diluted in volatile solvents, the solution was frozen at the liquid nitrogen temperature and irradiated with a pulsed excimer laser. The dioxide nanoparticles were deposited on Si and Al2O3 substrates. A rather uniform distribution of TiO2 nanoparticles with an average size of about 10 nm and of SnO2 nanoparticles with an average size of about 3 nm was obtained, as demonstrated by high resolution scanning electron microscopy (SEM-FEG) inspections. Gas-sensing devices based on the resistive transduction mechanism were fabricated by depositing the nanoparticle thin films onto suitable rough alumina substrates equipped with interdigitated electrical contacts and heating elements. Electrical characterization measurements were carried out in controlled environment. The results of the gas-sensing tests towards low concentrations of ethanol and acetone vapors are reported. Typical gas sensor parameters (gas responses, response/recovery time, sensitivity, and low detection limit) towards ethanol and acetone are presented. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)
Open AccessReview Retrieving Leaf Area Index (LAI) Using Remote Sensing: Theories, Methods and Sensors
Sensors 2009, 9(4), 2719-2745; doi:10.3390/s90402719
Received: 25 November 2008 / Revised: 3 April 2009 / Accepted: 17 April 2009 / Published: 17 April 2009
Cited by 92 | PDF Full-text (468 KB) | HTML Full-text | XML Full-text
Abstract
The ability to accurately and rapidly acquire leaf area index (LAI) is an indispensable component of process-based ecological research facilitating the understanding of gas-vegetation exchange phenomenon at an array of spatial scales from the leaf to the landscape. However, LAI is difficult [...] Read more.
The ability to accurately and rapidly acquire leaf area index (LAI) is an indispensable component of process-based ecological research facilitating the understanding of gas-vegetation exchange phenomenon at an array of spatial scales from the leaf to the landscape. However, LAI is difficult to directly acquire for large spatial extents due to its time consuming and work intensive nature. Such efforts have been significantly improved by the emergence of optical and active remote sensing techniques. This paper reviews the definitions and theories of LAI measurement with respect to direct and indirect methods. Then, the methodologies for LAI retrieval with regard to the characteristics of a range of remotely sensed datasets are discussed. Remote sensing indirect methods are subdivided into two categories of passive and active remote sensing, which are further categorized as terrestrial, aerial and satellite-born platforms. Due to a wide variety in spatial resolution of remotely sensed data and the requirements of ecological modeling, the scaling issue of LAI is discussed and special consideration is given to extrapolation of measurement to landscape and regional levels. Full article
(This article belongs to the Section Remote Sensors)
Open AccessReview Root Zone Sensors for Irrigation Management in Intensive Agriculture
Sensors 2009, 9(4), 2809-2835; doi:10.3390/s90402809
Received: 4 March 2009 / Revised: 15 April 2009 / Accepted: 20 April 2009 / Published: 21 April 2009
Cited by 23 | PDF Full-text (188 KB) | HTML Full-text | XML Full-text
Abstract
Crop irrigation uses more than 70% of the world’s water, and thus, improving irrigation efficiency is decisive to sustain the food demand from a fast-growing world population. This objective may be accomplished by cultivating more water-efficient crop species and/or through the application [...] Read more.
Crop irrigation uses more than 70% of the world’s water, and thus, improving irrigation efficiency is decisive to sustain the food demand from a fast-growing world population. This objective may be accomplished by cultivating more water-efficient crop species and/or through the application of efficient irrigation systems, which includes the implementation of a suitable method for precise scheduling. At the farm level, irrigation is generally scheduled based on the grower’s experience or on the determination of soil water balance (weather-based method). An alternative approach entails the measurement of soil water status. Expensive and sophisticated root zone sensors (RZS), such as neutron probes, are available for the use of soil and plant scientists, while cheap and practical devices are needed for irrigation management in commercial crops. The paper illustrates the main features of RZS’ (for both soil moisture and salinity) marketed for the irrigation industry and discusses how such sensors may be integrated in a wireless network for computer-controlled irrigation and used for innovative irrigation strategies, such as deficit or dual-water irrigation. The paper also consider the main results of recent or current research works conducted by the authors in Tuscany (Italy) on the irrigation management of container-grown ornamental plants, which is an important agricultural sector in Italy. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)
Open AccessReview Magnetic Particle-Based Hybrid Platforms for Bioanalytical Sensors
Sensors 2009, 9(4), 2976-2999; doi:10.3390/s90402976
Received: 19 February 2009 / Revised: 13 April 2009 / Accepted: 23 April 2009 / Published: 23 April 2009
Cited by 28 | PDF Full-text (468 KB) | HTML Full-text | XML Full-text
Abstract
Biomagnetic nano and microparticles platforms have attracted considerable interest in the field of biological sensors due to their interesting physico-chemical properties, high specific surface area, good mechanical stability and opportunities for generating magneto-switchable devices. This review discusses recent advances in the development [...] Read more.
Biomagnetic nano and microparticles platforms have attracted considerable interest in the field of biological sensors due to their interesting physico-chemical properties, high specific surface area, good mechanical stability and opportunities for generating magneto-switchable devices. This review discusses recent advances in the development and characterization of active biomagnetic nanoassemblies, their interaction with biological molecules and their use in bioanalytical sensors. Full article
(This article belongs to the Special Issue Toxin Sensors)
Open AccessReview Overview of Electrochemical DNA Biosensors: New Approaches to Detect the Expression of Life
Sensors 2009, 9(4), 3122-3148; doi:10.3390/s90403122
Received: 18 March 2009 / Revised: 20 April 2009 / Accepted: 23 April 2009 / Published: 24 April 2009
Cited by 52 | PDF Full-text (3014 KB) | HTML Full-text | XML Full-text
Abstract
DNA microarrays are an important tool with a variety of applications in gene expression studies, genotyping, pharmacogenomics, pathogen classification, drug discovery, sequencing and molecular diagnostics. They are having a strong impact in medical diagnostics for cancer, toxicology and infectious disease applications. A [...] Read more.
DNA microarrays are an important tool with a variety of applications in gene expression studies, genotyping, pharmacogenomics, pathogen classification, drug discovery, sequencing and molecular diagnostics. They are having a strong impact in medical diagnostics for cancer, toxicology and infectious disease applications. A series of papers have been published describing DNA biochips as alternative to conventional microarray platforms to facilitate and ameliorate the signal readout. In this review, we will consider the different methods proposed for biochip construction, focusing on electrochemical detection of DNA. We also introduce a novel single-stranded DNA platform performing high-throughput SNP detection and gene expression profiling. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy)
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