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Sensors, Volume 10, Issue 8 (August 2010), Pages 7067-7895

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Open AccessArticle A Sensor System for Detection of Hull Surface Defects
Sensors 2010, 10(8), 7067-7081; doi:10.3390/s100807067
Received: 21 May 2010 / Revised: 14 June 2010 / Accepted: 18 June 2010 / Published: 26 July 2010
Cited by 4 | PDF Full-text (759 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a sensor system for detecting defects in ship hull surfaces. The sensor was developed to enable a robotic system to perform grit blasting operations on ship hulls. To achieve this, the proposed sensor system captures images with the help [...] Read more.
This paper presents a sensor system for detecting defects in ship hull surfaces. The sensor was developed to enable a robotic system to perform grit blasting operations on ship hulls. To achieve this, the proposed sensor system captures images with the help of a camera and processes them in real time using a new defect detection method based on thresholding techniques. What makes this method different is its efficiency in the automatic detection of defects from images recorded in variable lighting conditions. The sensor system was tested under real conditions at a Spanish shipyard, with excellent results. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Volume Fraction Determination of Binary Liquid Mixtures by Measurement of the Equalization Wavelength
Sensors 2010, 10(8), 7082-7088; doi:10.3390/s100807082
Received: 18 June 2010 / Revised: 10 July 2010 / Accepted: 15 July 2010 / Published: 27 July 2010
PDF Full-text (209 KB) | HTML Full-text | XML Full-text
Abstract
A method for determination of the volume fraction in binary liquid mixtures by measurement of the equalization wavelength of intermodal interference of modes LP01 and LP11 in a liquid core optical fiber is presented in this paper. This method was [...] Read more.
A method for determination of the volume fraction in binary liquid mixtures by measurement of the equalization wavelength of intermodal interference of modes LP01 and LP11 in a liquid core optical fiber is presented in this paper. This method was studied using a liquid core optical fiber with fused silica cladding and a core made up of a binary silicon oil/chloroform liquid mixture with different volume fractions of chloroform. The interference technique used allows us to determine the chloroform volume fraction in the binary mixture with accuracy better than 0.1%. One of the most attractive advantages of presented method is very small volume of investigated mixture needed, as only a few hundred picoliters are necessary for reliable results. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Development of a Fully Automated Flow Injection Analyzer Implementing Bioluminescent Biosensors for Water Toxicity Assessment
Sensors 2010, 10(8), 7089-7098; doi:10.3390/s100807089
Received: 11 May 2010 / Revised: 2 June 2010 / Accepted: 12 July 2010 / Published: 27 July 2010
Cited by 12 | PDF Full-text (293 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes the development of an automated Flow Injection analyzer for water toxicity assessment. The analyzer is validated by assessing the toxicity of heavy metal (Pb2+, Hg2+ and Cu2+) solutions. One hundred μL of a Vibrio [...] Read more.
This paper describes the development of an automated Flow Injection analyzer for water toxicity assessment. The analyzer is validated by assessing the toxicity of heavy metal (Pb2+, Hg2+ and Cu2+) solutions. One hundred μL of a Vibrio fischeri suspension are injected in a carrier solution containing different heavy metal concentrations. Biosensor cells are mixed with the toxic carrier solution in the mixing coil on the way to the detector. Response registered is % inhibition of biosensor bioluminescence due to heavy metal toxicity in comparison to that resulting by injecting the Vibrio fischeri suspension in deionised water. Carrier solutions of mercury showed higher toxicity than the other heavy metals, whereas all metals show concentration related levels of toxicity. The biosensor’s response to carrier solutions of different pHs was tested. Vibrio fischeri’s bioluminescence is promoted in the pH 5–10 range. Experiments indicate that the whole cell biosensor, as applied in the automated fluidic system, responds to various toxic solutions. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Automated Signal Processing Applied to Volatile-Based Inspection of Greenhouse Crops
Sensors 2010, 10(8), 7122-7133; doi:10.3390/s100807122
Received: 21 June 2010 / Revised: 15 July 2010 / Accepted: 20 July 2010 / Published: 28 July 2010
Cited by 8 | PDF Full-text (308 KB) | HTML Full-text | XML Full-text
Abstract
Gas chromatograph–mass spectrometers (GC-MS) have been used and shown utility for volatile-based inspection of greenhouse crops. However, a widely recognized difficulty associated with GC-MS application is the large and complex data generated by this instrument. As a consequence, experienced analysts are often [...] Read more.
Gas chromatograph–mass spectrometers (GC-MS) have been used and shown utility for volatile-based inspection of greenhouse crops. However, a widely recognized difficulty associated with GC-MS application is the large and complex data generated by this instrument. As a consequence, experienced analysts are often required to process this data in order to determine the concentrations of the volatile organic compounds (VOCs) of interest. Manual processing is time-consuming, labour intensive and may be subject to errors due to fatigue. The objective of this study was to assess whether or not GC-MS data can also be automatically processed in order to determine the concentrations of crop health associated VOCs in a greenhouse. An experimental dataset that consisted of twelve data files was processed both manually and automatically to address this question. Manual processing was based on simple peak integration while the automatic processing relied on the algorithms implemented in the MetAlignTM software package. The results of automatic processing of the experimental dataset resulted in concentrations similar to that after manual processing. These results demonstrate that GC-MS data can be automatically processed in order to accurately determine the concentrations of crop health associated VOCs in a greenhouse. When processing GC-MS data automatically, noise reduction, alignment, baseline correction and normalisation are required. Full article
(This article belongs to the Special Issue Direct and Indirect Sensing of Odor and VOCs and Their Control)
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Open AccessArticle Reaction Force/Torque Sensing in a Master-Slave Robot System without Mechanical Sensors
Sensors 2010, 10(8), 7134-7145; doi:10.3390/s100807134
Received: 20 June 2010 / Revised: 1 July 2010 / Accepted: 15 July 2010 / Published: 29 July 2010
Cited by 5 | PDF Full-text (262 KB) | HTML Full-text | XML Full-text
Abstract
In human-robot cooperative control systems, force feedback is often necessary in order to achieve high precision and high stability. Usually, traditional robot assistant systems implement force feedback using force/torque sensors. However, it is difficult to directly mount a mechanical force sensor on [...] Read more.
In human-robot cooperative control systems, force feedback is often necessary in order to achieve high precision and high stability. Usually, traditional robot assistant systems implement force feedback using force/torque sensors. However, it is difficult to directly mount a mechanical force sensor on some working terminals, such as in applications of minimally invasive robotic surgery, micromanipulation, or in working environments exposed to radiation or high temperature. We propose a novel force sensing mechanism for implementing force feedback in a master-slave robot system with no mechanical sensors. The system consists of two identical electro-motors with the master motor powering the slave motor to interact with the environment. A bimanual coordinated training platform using the new force sensing mechanism was developed and the system was verified in experiments. Results confirm that the proposed mechanism is capable of achieving bilateral force sensing and mirror-image movements of two terminals in two reverse control directions. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle A Piezoelectric Plethysmograph Sensor Based on a Pt Wire Implanted Lead Lanthanum Zirconate Titanate Bulk Ceramic
Sensors 2010, 10(8), 7146-7156; doi:10.3390/s100807146
Received: 15 June 2010 / Revised: 30 June 2010 / Accepted: 15 July 2010 / Published: 29 July 2010
Cited by 7 | PDF Full-text (1116 KB) | HTML Full-text | XML Full-text
Abstract
This work reports on the development of a Lead Lanthanum Zirconate Titanate (PLZT) bulk ferroelectric poled ceramic structure as a Piezoelectric Plethysmograph (PZPG) sensor. The ceramic was implanted during its fabrication with a platinum (Pt) wire which works as an internal electrode. [...] Read more.
This work reports on the development of a Lead Lanthanum Zirconate Titanate (PLZT) bulk ferroelectric poled ceramic structure as a Piezoelectric Plethysmograph (PZPG) sensor. The ceramic was implanted during its fabrication with a platinum (Pt) wire which works as an internal electrode. The ceramic was then submitted to an experimental setup in order to validate and determine the Pt-wire mechanical effects. This PZPG sensor was also mounted on a finger splint in order to measure the blood flow that results from the pulsations of blood occurring with each heartbeat. Fingertip pulses were recorded jointly with an ECG signal from a 25 year old male to compare the time shift; the PZPG sensor guarantees the electrical isolation of the patient. The proposed PZPG has several advantages: it can be adjusted for fingertip measurements, but it can easily be extended by means of spare bands, therefore making possible PZPG measurements from different body locations, e.g., forehead, forearm, knee, neck, etc. Full article
(This article belongs to the Special Issue Sensors in Biomechanics and Biomedicine)
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Open AccessArticle Detecting Solenoid Valve Deterioration in In-Use Electronic Diesel Fuel Injection Control Systems
Sensors 2010, 10(8), 7157-7169; doi:10.3390/s100807157
Received: 17 June 2010 / Revised: 20 July 2010 / Accepted: 26 July 2010 / Published: 29 July 2010
Cited by 4 | PDF Full-text (593 KB) | HTML Full-text | XML Full-text
Abstract
The diesel engine is the main power source for most agricultural vehicles. The control of diesel engine emissions is an important global issue. Fuel injection control systems directly affect fuel efficiency and emissions of diesel engines. Deterioration faults, such as rack deformation, [...] Read more.
The diesel engine is the main power source for most agricultural vehicles. The control of diesel engine emissions is an important global issue. Fuel injection control systems directly affect fuel efficiency and emissions of diesel engines. Deterioration faults, such as rack deformation, solenoid valve failure, and rack-travel sensor malfunction, are possibly in the fuel injection module of electronic diesel control (EDC) systems. Among these faults, solenoid valve failure is most likely to occur for in-use diesel engines. According to the previous studies, this failure is a result of the wear of the plunger and sleeve, based on a long period of usage, lubricant degradation, or engine overheating. Due to the difficulty in identifying solenoid valve deterioration, this study focuses on developing a sensor identification algorithm that can clearly classify the usability of the solenoid valve, without disassembling the fuel pump of an EDC system for in-use agricultural vehicles. A diagnostic algorithm is proposed, including a feedback controller, a parameter identifier, a linear variable differential transformer (LVDT) sensor, and a neural network classifier. Experimental results show that the proposed algorithm can accurately identify the usability of solenoid valves. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Adaptive Compression of Slowly Varying Images Transmitted over Wireless Sensor Networks
Sensors 2010, 10(8), 7170-7191; doi:10.3390/s100807170
Received: 10 May 2010 / Revised: 9 July 2010 / Accepted: 16 July 2010 / Published: 29 July 2010
Cited by 6 | PDF Full-text (2153 KB) | HTML Full-text | XML Full-text
Abstract
In this article a scheme for image transmission over Wireless Sensor Networks (WSN) with an adaptive compression factor is introduced. The proposed control architecture affects the quality of the transmitted images according to: (a) the traffic load within the network and (b) [...] Read more.
In this article a scheme for image transmission over Wireless Sensor Networks (WSN) with an adaptive compression factor is introduced. The proposed control architecture affects the quality of the transmitted images according to: (a) the traffic load within the network and (b) the level of details contained in an image frame. Given an approximate transmission period, the adaptive compression mechanism applies Quad Tree Decomposition (QTD) with a varying decomposition compression factor based on a gradient adaptive approach. For the initialization of the proposed control scheme, the desired a priori maximum bound for the transmission time delay is being set, while a tradeoff among the quality of the decomposed image frame and the time needed for completing the transmission of the frame should be taken under consideration. Based on the proposed control mechanism, the quality of the slowly varying transmitted image frames is adaptively deviated based on the measured time delay in the transmission. The efficacy of the adaptive compression control scheme is validated through extended experimental results. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Performance Evaluation of Triangulation Based Range Sensors
Sensors 2010, 10(8), 7192-7215; doi:10.3390/s100807192
Received: 5 July 2010 / Revised: 23 July 2010 / Accepted: 27 July 2010 / Published: 29 July 2010
Cited by 14 | PDF Full-text (1874 KB) | HTML Full-text | XML Full-text
Abstract
The performance of 2D digital imaging systems depends on several factors related with both optical and electronic processing. These concepts have originated standards, which have been conceived for photographic equipment and bi-dimensional scanning systems, and which have been aimed at estimating different [...] Read more.
The performance of 2D digital imaging systems depends on several factors related with both optical and electronic processing. These concepts have originated standards, which have been conceived for photographic equipment and bi-dimensional scanning systems, and which have been aimed at estimating different parameters such as resolution, noise or dynamic range. Conversely, no standard test protocols currently exist for evaluating the corresponding performances of 3D imaging systems such as laser scanners or pattern projection range cameras. This paper is focused on investigating experimental processes for evaluating some critical parameters of 3D equipment, by extending the concepts defined by the ISO standards to the 3D domain. The experimental part of this work concerns the characterization of different range sensors through the extraction of their resolution, accuracy and uncertainty from sets of 3D data acquisitions of specifically designed test objects whose geometrical characteristics are known in advance. The major objective of this contribution is to suggest an easy characterization process for generating a reliable comparison between the performances of different range sensors and to check if a specific piece of equipment is compliant with the expected characteristics. Full article
Open AccessArticle Correlating Multimodal Physical Sensor Information with Biological Analysis in Ultra Endurance Cycling
Sensors 2010, 10(8), 7216-7235; doi:10.3390/s100807216
Received: 20 June 2010 / Revised: 10 July 2010 / Accepted: 20 July 2010 / Published: 30 July 2010
Cited by 1 | PDF Full-text (3833 KB) | HTML Full-text | XML Full-text
Abstract
The sporting domain has traditionally been used as a testing ground for new technologies which subsequently make their way into the public domain. This includes sensors. In this article a range of physical and biological sensors deployed in a 64 hour ultra-endurance [...] Read more.
The sporting domain has traditionally been used as a testing ground for new technologies which subsequently make their way into the public domain. This includes sensors. In this article a range of physical and biological sensors deployed in a 64 hour ultra-endurance non-stop cycling race are described. A novel algorithm to estimate the energy expenditure while cycling and resting during the event are outlined. Initial analysis in this noisy domain of “sensors in the field” are very encouraging and represent a first with respect to cycling. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Wireless Sensor Network Deployment for Monitoring Wildlife Passages
Sensors 2010, 10(8), 7236-7262; doi:10.3390/s100807236
Received: 1 February 2010 / Revised: 21 May 2010 / Accepted: 23 July 2010 / Published: 3 August 2010
Cited by 26 | PDF Full-text (1203 KB) | HTML Full-text | XML Full-text
Abstract
Wireless Sensor Networks (WSNs) are being deployed in very diverse application scenarios, including rural and forest environments. In these particular contexts, specimen protection and conservation is a challenge, especially in natural reserves, dangerous locations or hot spots of these reserves (i.e., [...] Read more.
Wireless Sensor Networks (WSNs) are being deployed in very diverse application scenarios, including rural and forest environments. In these particular contexts, specimen protection and conservation is a challenge, especially in natural reserves, dangerous locations or hot spots of these reserves (i.e., roads, railways, and other civil infrastructures). This paper proposes and studies a WSN based system for generic target (animal) tracking in the surrounding area of wildlife passages built to establish safe ways for animals to cross transportation infrastructures. In addition, it allows target identification through the use of video sensors connected to strategically deployed nodes. This deployment is designed on the basis of the IEEE 802.15.4 standard, but it increases the lifetime of the nodes through an appropriate scheduling. The system has been evaluated for the particular scenario of wildlife monitoring in passages across roads. For this purpose, different schemes have been simulated in order to find the most appropriate network operational parameters. Moreover, a novel prototype, provided with motion detector sensors, has also been developed and its design feasibility demonstrated. Original software modules providing new functionalities have been implemented and included in this prototype. Finally, main performance evaluation results of the whole system are presented and discussed in depth. Full article
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Open AccessArticle A Field Programmable Gate Array-Based Reconfigurable Smart-Sensor Network for Wireless Monitoring of New Generation Computer Numerically Controlled Machines
Sensors 2010, 10(8), 7263-7286; doi:10.3390/s100807263
Received: 26 May 2010 / Revised: 7 July 2010 / Accepted: 29 July 2010 / Published: 3 August 2010
Cited by 8 | PDF Full-text (2073 KB) | HTML Full-text | XML Full-text
Abstract
Computer numerically controlled (CNC) machines have evolved to adapt to increasing technological and industrial requirements. To cover these needs, new generation machines have to perform monitoring strategies by incorporating multiple sensors. Since in most of applications the online Processing of the variables [...] Read more.
Computer numerically controlled (CNC) machines have evolved to adapt to increasing technological and industrial requirements. To cover these needs, new generation machines have to perform monitoring strategies by incorporating multiple sensors. Since in most of applications the online Processing of the variables is essential, the use of smart sensors is necessary. The contribution of this work is the development of a wireless network platform of reconfigurable smart sensors for CNC machine applications complying with the measurement requirements of new generation CNC machines. Four different smart sensors are put under test in the network and their corresponding signal processing techniques are implemented in a Field Programmable Gate Array (FPGA)-based sensor node. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
Open AccessArticle Experimental Demonstration of Masking Phenomena between Competing Odorants via an Air Dilution Sensory Test
Sensors 2010, 10(8), 7287-7302; doi:10.3390/s100807287
Received: 9 June 2010 / Revised: 8 July 2010 / Accepted: 22 July 2010 / Published: 3 August 2010
Cited by 29 | PDF Full-text (154 KB) | HTML Full-text | XML Full-text
Abstract
To simulate the occurrence of masking phenomena with the aid of an air dilution sensory (ADS) test, two types of odorant mixtures were prepared: (1) M2 with two individual odorants [H2S and acetaldehyde (AA)] and (2) M6 with [...] Read more.
To simulate the occurrence of masking phenomena with the aid of an air dilution sensory (ADS) test, two types of odorant mixtures were prepared: (1) M2 with two individual odorants [H2S and acetaldehyde (AA)] and (2) M6 with six individual odorants (H2S and five aldehydes). The test results derived for samples containing single individual odorants at a wide range of concentrations are initially used to define the empirical relationship between the dilution-to-threshold (D/T) ratio and odor intensity (OI) scaling. Based on these relationships, the D/T ratios were estimated for each odorant with the same intensity as the synthetic mixture. The relative contribution of each odorant to such mixture is then assessed by comparing the estimated and measured D/T values. This stepwise test confirmed the dominance of certain compounds at a given OI rating. In the case of M2, H2S showed sensitive detection at high OI range, while AA did so at low end. The pattern of a competing relationship is also seen consistently from M6 between AA (low) and iso-valeraldehyde (IA: high OI range). The overall results thus suggest that the masking phenomena between strong odorants should proceed under competing relationships, if released at the same time. Full article
(This article belongs to the Special Issue Direct and Indirect Sensing of Odor and VOCs and Their Control)
Open AccessArticle Visual Control of Robots Using Range Images
Sensors 2010, 10(8), 7303-7322; doi:10.3390/s100807303
Received: 20 May 2010 / Revised: 23 July 2010 / Accepted: 28 July 2010 / Published: 4 August 2010
Cited by 8 | PDF Full-text (788 KB) | HTML Full-text | XML Full-text
Abstract
In the last years, 3D-vision systems based on the time-of-flight (ToF) principle have gained more importance in order to obtain 3D information from the workspace. In this paper, an analysis of the use of 3D ToF cameras to guide a robot arm [...] Read more.
In the last years, 3D-vision systems based on the time-of-flight (ToF) principle have gained more importance in order to obtain 3D information from the workspace. In this paper, an analysis of the use of 3D ToF cameras to guide a robot arm is performed. To do so, an adaptive method to simultaneous visual servo control and camera calibration is presented. Using this method a robot arm is guided by using range information obtained from a ToF camera. Furthermore, the self-calibration method obtains the adequate integration time to be used by the range camera in order to precisely determine the depth information. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Location-Aware Dynamic Session-Key Management for Grid-Based Wireless Sensor Networks
Sensors 2010, 10(8), 7347-7370; doi:10.3390/s100807347
Received: 20 June 2010 / Revised: 5 July 2010 / Accepted: 15 July 2010 / Published: 4 August 2010
Cited by 9 | PDF Full-text (435 KB) | HTML Full-text | XML Full-text
Abstract
Security is a critical issue for sensor networks used in hostile environments. When wireless sensor nodes in a wireless sensor network are distributed in an insecure hostile environment, the sensor nodes must be protected: a secret key must be used to protect [...] Read more.
Security is a critical issue for sensor networks used in hostile environments. When wireless sensor nodes in a wireless sensor network are distributed in an insecure hostile environment, the sensor nodes must be protected: a secret key must be used to protect the nodes transmitting messages. If the nodes are not protected and become compromised, many types of attacks against the network may result. Such is the case with existing schemes, which are vulnerable to attacks because they mostly provide a hop-by-hop paradigm, which is insufficient to defend against known attacks. We propose a location-aware dynamic session-key management protocol for grid-based wireless sensor networks. The proposed protocol improves the security of a secret key. The proposed scheme also includes a key that is dynamically updated. This dynamic update can lower the probability of the key being guessed correctly. Thus currently known attacks can be defended. By utilizing the local information, the proposed scheme can also limit the flooding region in order to reduce the energy that is consumed in discovering routing paths. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Use of a Multiplexed CMOS Microarray to Optimize and Compare Oligonucleotide Binding to DNA Probes Synthesized or Immobilized on Individual Electrodes
Sensors 2010, 10(8), 7371-7385; doi:10.3390/s100807371
Received: 20 June 2010 / Revised: 15 July 2010 / Accepted: 30 July 2010 / Published: 5 August 2010
Cited by 15 | PDF Full-text (728 KB) | HTML Full-text | XML Full-text
Abstract
The CombiMatrix microarray with 12,544 electrodes supports in situ electrochemical synthesis of user-defined DNA probes. As an alternative, we immobilized commercially synthesized DNA probes on individual electrodes coated with electropolymerized polypyrrole (Ppy). Hybridization was measured using a biotinylated target oligonucleotide and either [...] Read more.
The CombiMatrix microarray with 12,544 electrodes supports in situ electrochemical synthesis of user-defined DNA probes. As an alternative, we immobilized commercially synthesized DNA probes on individual electrodes coated with electropolymerized polypyrrole (Ppy). Hybridization was measured using a biotinylated target oligonucleotide and either Cy5-streptavidin and fluorescence detection or horseradish peroxidase-streptavidin and enzyme-enhanced electrochemical detection. Detection efficiencies were optimized by varying the deposition of the Ppy, the terminal groups on the DNA probes, and other factors that impacted fluorescence quenching and electrical conductivity. Optimized results were compared against those obtained using a microarray with the same DNA sequences synthesized in situ. Immobilized probes produced higher fluorescence signals, possibly by providing a greater stand off between the Cy5 on the target oligonucleotide and the quenching effects of the Ppy and the platinum electrode. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle Observing the Forest Canopy with a New Ultra-Violet Compact Airborne Lidar
Sensors 2010, 10(8), 7386-7403; doi:10.3390/s100807386
Received: 6 May 2010 / Revised: 1 June 2010 / Accepted: 21 June 2010 / Published: 6 August 2010
Cited by 10 | PDF Full-text (975 KB) | HTML Full-text | XML Full-text
Abstract
We have developed a new airborne UV lidar for the forest canopy and deployed it in the Landes forest (France). It is the first one that: (i) operates at 355 nm for emitting energetic pulses of 16 mJ at 20 Hz while [...] Read more.
We have developed a new airborne UV lidar for the forest canopy and deployed it in the Landes forest (France). It is the first one that: (i) operates at 355 nm for emitting energetic pulses of 16 mJ at 20 Hz while fulfilling eye-safety regulations and (ii) is flown onboard an ultra-light airplane for enhanced flight flexibility. Laser footprints at ground level were 2.4 m wide for a flying altitude of 300 m. Three test areas of ~500 × 500 m2 with Maritime pines of different ages were investigated. We used a threshold method adapted for this lidar to accurately extract from its waveforms detailed forest canopy vertical structure: canopy top, tree crown base and undergrowth heights. Good detection sensitivity enabled the observation of ground returns underneath the trees. Statistical and one-to-one comparisons with ground measurements by field foresters indicated a mean absolute accuracy of ~1 m. Sensitivity tests on detection threshold showed the importance of signal to noise ratio and footprint size for a proper detection of the canopy vertical structure. This UV-lidar is intended for future innovative applications of simultaneous observation of forest canopy, laser-induced vegetation fluorescence and atmospheric aerosols. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle High Accuracy Acoustic Relative Humidity Measurement inDuct Flow with Air
Sensors 2010, 10(8), 7421-7433; doi:10.3390/s100807421
Received: 20 June 2010 / Revised: 15 July 2010 / Accepted: 30 July 2010 / Published: 9 August 2010
Cited by 4 | PDF Full-text (909 KB) | HTML Full-text | XML Full-text
Abstract
An acoustic relative humidity sensor for air-steam mixtures in duct flow is designed and tested. Theory, construction, calibration, considerations on dynamic response and results are presented. The measurement device is capable of measuring line averaged values of gas velocity, temperature and relative [...] Read more.
An acoustic relative humidity sensor for air-steam mixtures in duct flow is designed and tested. Theory, construction, calibration, considerations on dynamic response and results are presented. The measurement device is capable of measuring line averaged values of gas velocity, temperature and relative humidity (RH) instantaneously, by applying two ultrasonic transducers and an array of four temperature sensors. Measurement ranges are: gas velocity of 0–12 m/s with an error of ±0.13 m/s, temperature 0–100 °C with an error of ±0.07 °C and relative humidity 0–100% with accuracy better than 2 % RH above 50 °C. Main advantage over conventional humidity sensors is the high sensitivity at high RH at temperatures exceeding 50 °C, with accuracy increasing with increasing temperature. The sensors are non-intrusive and resist highly humid environments. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in The Netherlands)
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Open AccessArticle Development and Implementation of Image-based Algorithms for Measurement of Deformations in Material Testing
Sensors 2010, 10(8), 7469-7495; doi:10.3390/s100807469
Received: 1 July 2010 / Revised: 15 July 2010 / Accepted: 3 August 2010 / Published: 10 August 2010
Cited by 20 | PDF Full-text (1441 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the development and implementation of three image-based methods used to detect and measure the displacements of a vast number of points in the case of laboratory testing on construction materials. Starting from the needs of structural engineers, three ad [...] Read more.
This paper presents the development and implementation of three image-based methods used to detect and measure the displacements of a vast number of points in the case of laboratory testing on construction materials. Starting from the needs of structural engineers, three ad hoc tools for crack measurement in fibre-reinforced specimens and 2D or 3D deformation analysis through digital images were implemented and tested. These tools make use of advanced image processing algorithms and can integrate or even substitute some traditional sensors employed today in most laboratories. In addition, the automation provided by the implemented software, the limited cost of the instruments and the possibility to operate with an indefinite number of points offer new and more extensive analysis in the field of material testing. Several comparisons with other traditional sensors widely adopted inside most laboratories were carried out in order to demonstrate the accuracy of the implemented software. Implementation details, simulations and real applications are reported and discussed in this paper. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle T-Patterns Revisited: Mining for Temporal Patterns in Sensor Data
Sensors 2010, 10(8), 7496-7513; doi:10.3390/s100807496
Received: 2 December 2009 / Revised: 23 February 2010 / Accepted: 23 July 2010 / Published: 10 August 2010
Cited by 12 | PDF Full-text (282 KB) | HTML Full-text | XML Full-text
Abstract
The trend to use large amounts of simple sensors as opposed to a few complex sensors to monitor places and systems creates a need for temporal pattern mining algorithms to work on such data. The methods that try to discover re-usable and [...] Read more.
The trend to use large amounts of simple sensors as opposed to a few complex sensors to monitor places and systems creates a need for temporal pattern mining algorithms to work on such data. The methods that try to discover re-usable and interpretable patterns in temporal event data have several shortcomings. We contrast several recent approaches to the problem, and extend the T-Pattern algorithm, which was previously applied for detection of sequential patterns in behavioural sciences. The temporal complexity of the T-pattern approach is prohibitive in the scenarios we consider. We remedy this with a statistical model to obtain a fast and robust algorithm to find patterns in temporal data. We test our algorithm on a recent database collected with passive infrared sensors with millions of events. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in The Netherlands)
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Open AccessArticle A Software Architecture for Adaptive Modular Sensing Systems
Sensors 2010, 10(8), 7514-7560; doi:10.3390/s100807514
Received: 8 June 2010 / Revised: 14 July 2010 / Accepted: 5 August 2010 / Published: 10 August 2010
Cited by 3 | PDF Full-text (5202 KB) | HTML Full-text | XML Full-text
Abstract
By combining a number of simple transducer modules, an arbitrarily complex sensing system may be produced to accommodate a wide range of applications. This work outlines a novel software architecture and knowledge representation scheme that has been developed to support this type [...] Read more.
By combining a number of simple transducer modules, an arbitrarily complex sensing system may be produced to accommodate a wide range of applications. This work outlines a novel software architecture and knowledge representation scheme that has been developed to support this type of flexible and reconfigurable modular sensing system. Template algorithms are used to embed intelligence within each module. As modules are added or removed, the composite sensor is able to automatically determine its overall geometry and assume an appropriate collective identity. A virtual machine-based middleware layer runs on top of a real-time operating system with a pre-emptive kernel, enabling platform-independent template algorithms to be written once and run on any module, irrespective of its underlying hardware architecture. Applications that may benefit from easily reconfigurable modular sensing systems include flexible inspection, mobile robotics, surveillance, and space exploration. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
Open AccessArticle Bayesian Model for Matching the Radiometric Measurements of Aerospace and Field Ocean Color Sensors
Sensors 2010, 10(8), 7561-7575; doi:10.3390/s100807561
Received: 11 June 2010 / Revised: 16 July 2010 / Accepted: 10 August 2010 / Published: 11 August 2010
Cited by 8 | PDF Full-text (419 KB) | HTML Full-text | XML Full-text
Abstract
A Bayesian model is developed to match aerospace ocean color observation tofield measurements and derive the spatial variability of match-up sites. The performance of the model is tested against populations of synthesized spectra and full and reduced resolutions of MERIS data. The model derived the scale difference between synthesized satellite pixel and point measurements with R2 > 0.88 and relative error < 21% in the spectral range from 400 nm to 695 nm. The sub-pixel variabilities of reduced resolution MERIS image are derived with less than 12% of relative errors in heterogeneous region. The method is generic and applicable to different sensors. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in The Netherlands)
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Open AccessArticle Detecting Abnormal Vehicular Dynamics at Intersections Based on an Unsupervised Learning Approach and a Stochastic Model
Sensors 2010, 10(8), 7576-7601; doi:10.3390/s100807576
Received: 1 July 2010 / Revised: 4 August 2010 / Accepted: 5 August 2010 / Published: 11 August 2010
Cited by 6 | PDF Full-text (4759 KB) | HTML Full-text | XML Full-text
Abstract
This investigation demonstrates an unsupervised approach for modeling traffic flow and detecting abnormal vehicle behaviors at intersections. In the first stage, the approach reveals and records the different states of the system. These states are the result of coding and grouping the [...] Read more.
This investigation demonstrates an unsupervised approach for modeling traffic flow and detecting abnormal vehicle behaviors at intersections. In the first stage, the approach reveals and records the different states of the system. These states are the result of coding and grouping the historical motion of vehicles as long binary strings. In the second stage, using sequences of the recorded states, a stochastic graph model based on a Markovian approach is built. A behavior is labeled abnormal when current motion pattern cannot be recognized as any state of the system or a particular sequence of states cannot be parsed with the stochastic model. The approach is tested with several sequences of images acquired from a vehicular intersection where the traffic flow and duration used in connection with the traffic lights are continuously changed throughout the day. Finally, the low complexity and the flexibility of the approach make it reliable for use in real time systems. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Efficacy of a Computerized Sensor System for Evaluation and Training of Dizzy Patients
Sensors 2010, 10(8), 7602-7620; doi:10.3390/s100807602
Received: 28 May 2010 / Revised: 2 July 2010 / Accepted: 5 August 2010 / Published: 12 August 2010
PDF Full-text (527 KB) | HTML Full-text | XML Full-text
Abstract
Patients with vestibular hypofunction often experience dizziness and unsteadiness while moving their heads. Appropriate sensors can effectively detect a patient’s dynamic visual acuity and associated body balance control. Forty-one vestibular-deficit patients and 10 normal individuals were invited to participate in this study. [...] Read more.
Patients with vestibular hypofunction often experience dizziness and unsteadiness while moving their heads. Appropriate sensors can effectively detect a patient’s dynamic visual acuity and associated body balance control. Forty-one vestibular-deficit patients and 10 normal individuals were invited to participate in this study. Questionnaires, clinical assessment scales and objective measures were evaluated on participants’ first visits. After 12 sessions of training, all scales were evaluated again on vestibular-deficit patients. The computerized system was composed of sensors, including a gyro and strain gauges, data acquisition accessories and LabVIEW software. Results revealed that the system could effectively distinguish normal subjects from subjects with vestibular deficits. In addition, after a rehabilitation program, subjects’ subjective and objective performances were significantly improved. Based on our results, we concluded that the present system, which uses a gyro and strain gauges, may provide an effective method for assessing and treating vestibular-deficit patients. Full article
(This article belongs to the Special Issue Sensors in Biomechanics and Biomedicine)
Open AccessArticle Dynamic Uncertainty for Compensated Second-Order Systems
Sensors 2010, 10(8), 7621-7631; doi:10.3390/s100807621
Received: 10 June 2010 / Revised: 10 July 2010 / Accepted: 2 August 2010 / Published: 13 August 2010
Cited by 8 | PDF Full-text (450 KB) | HTML Full-text | XML Full-text
Abstract
The compensation of LTI systems and the evaluation of the according uncertainty is of growing interest in metrology. Uncertainty evaluation in metrology ought to follow specific guidelines, and recently two corresponding uncertainty evaluation schemes have been proposed for FIR and IIR filtering. [...] Read more.
The compensation of LTI systems and the evaluation of the according uncertainty is of growing interest in metrology. Uncertainty evaluation in metrology ought to follow specific guidelines, and recently two corresponding uncertainty evaluation schemes have been proposed for FIR and IIR filtering. We employ these schemes to compare an FIR and an IIR approach for compensating a second-order LTI system which has relevance in metrology. Our results suggest that the FIR approach is superior in the sense that it yields significantly smaller uncertainties when real-time evaluation of uncertainties is desired. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Gaussian Mixture Model-Based Continuous Boundary Detection for 3D Sensor Networks
Sensors 2010, 10(8), 7632-7650; doi:10.3390/s100807632
Received: 25 June 2010 / Revised: 18 July 2010 / Accepted: 30 July 2010 / Published: 13 August 2010
Cited by 3 | PDF Full-text (778 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a high precision Gaussian Mixture Model-based novel Boundary Detection 3D (BD3D) scheme with reasonable implementation cost for 3D cases by selecting a minimum number of Boundary sensor Nodes (BNs) in continuous moving objects. It shows apparent advantages in that [...] Read more.
This paper proposes a high precision Gaussian Mixture Model-based novel Boundary Detection 3D (BD3D) scheme with reasonable implementation cost for 3D cases by selecting a minimum number of Boundary sensor Nodes (BNs) in continuous moving objects. It shows apparent advantages in that two classes of boundary and non-boundary sensor nodes can be efficiently classified using the model selection techniques for finite mixture models; furthermore, the set of sensor readings within each sensor node’s spatial neighbors is formulated using a Gaussian Mixture Model; different from DECOMO [1] and COBOM [2], we also formatted a BN Array with an additional own sensor reading to benefit selecting Event BNs (EBNs) and non-EBNs from the observations of BNs. In particular, we propose a Thick Section Model (TSM) to solve the problem of transition between 2D and 3D. It is verified by simulations that the BD3D 2D model outperforms DECOMO and COBOM in terms of average residual energy and the number of BNs selected, while the BD3D 3D model demonstrates sound performance even for sensor networks with low densities especially when the value of the sensor transmission range (r) is larger than the value of Section Thickness (d) in TSM. We have also rigorously proved its correctness for continuous geometric domains and full robustness for sensor networks over 3D terrains. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle A Reaction-Diffusion-Based Coding Rate Control Mechanism for Camera Sensor Networks
Sensors 2010, 10(8), 7651-7673; doi:10.3390/s100807651
Received: 13 April 2010 / Revised: 28 June 2010 / Accepted: 19 July 2010 / Published: 13 August 2010
Cited by 2 | PDF Full-text (2431 KB) | HTML Full-text | XML Full-text
Abstract
A wireless camera sensor network is useful for surveillance and monitoring for its visibility and easy deployment. However, it suffers from the limited capacity of wireless communication and a network is easily overflown with a considerable amount of video traffic. In this [...] Read more.
A wireless camera sensor network is useful for surveillance and monitoring for its visibility and easy deployment. However, it suffers from the limited capacity of wireless communication and a network is easily overflown with a considerable amount of video traffic. In this paper, we propose an autonomous video coding rate control mechanism where each camera sensor node can autonomously determine its coding rate in accordance with the location and velocity of target objects. For this purpose, we adopted a biological model, i.e., reaction-diffusion model, inspired by the similarity of biological spatial patterns and the spatial distribution of video coding rate. Through simulation and practical experiments, we verify the effectiveness of our proposal. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Flat-Cladding Fiber Bragg Grating Sensors for Large Strain Amplitude Fatigue Tests
Sensors 2010, 10(8), 7674-7680; doi:10.3390/s100807674
Received: 16 July 2010 / Revised: 9 August 2010 / Accepted: 10 August 2010 / Published: 16 August 2010
Cited by 2 | PDF Full-text (482 KB) | HTML Full-text | XML Full-text
Abstract
We have successfully developed a flat-cladding fiber Bragg grating sensor for large cyclic strain amplitude tests of up to ±8,000 με. The increased contact area between the flat-cladding fiber and substrate, together with the application of a new bonding process, has significantly [...] Read more.
We have successfully developed a flat-cladding fiber Bragg grating sensor for large cyclic strain amplitude tests of up to ±8,000 με. The increased contact area between the flat-cladding fiber and substrate, together with the application of a new bonding process, has significantly increased the bonding strength. In the push-pull fatigue tests of an aluminum alloy, the plastic strain amplitudes measured by three optical fiber sensors differ only by 0.43% at a cyclic strain amplitude of ±7,000 με and 1.9% at a cyclic strain amplitude of ±8,000 με. We also applied the sensor on an extruded magnesium alloy for evaluating the peculiar asymmetric hysteresis loops. The results obtained were in good agreement with those measured from the extensometer, a further validation of the sensor. Full article
Open AccessArticle Mobile Calibration Based on Laser Metrology and Approximation Networks
Sensors 2010, 10(8), 7681-7704; doi:10.3390/s100807681
Received: 30 June 2010 / Revised: 20 July 2010 / Accepted: 5 August 2010 / Published: 17 August 2010
Cited by 3 | PDF Full-text (640 KB) | HTML Full-text | XML Full-text
Abstract
A mobile calibration technique for three-dimensional vision is presented. In this method, vision parameters are computed automatically by approximation networks built based on the position of a camera and image processing of a laser line. The networks also perform three-dimensional visualization. In [...] Read more.
A mobile calibration technique for three-dimensional vision is presented. In this method, vision parameters are computed automatically by approximation networks built based on the position of a camera and image processing of a laser line. The networks also perform three-dimensional visualization. In the proposed system, the setup geometry can be modified online, whereby an online re-calibration is performed based on data provided by the network and the required modifications of extrinsic and intrinsic parameters are thus determined, overcoming any calibration limitations caused by the modification procedure. The mobile calibration also avoids procedures involving references, which are used in traditional online re-calibration methods. The proposed mobile calibration thus improves the accuracy and performance of the three-dimensional vision because online data of calibrated references are not passed on to the vision system. This work represents a contribution to the field of online re-calibration, as verified by a comparison with the results based on lighting methods, which are calibrated and re-calibrated via perspective projection. Processing time is also studied. Full article
Open AccessArticle Multi-Walled Carbon Nanotube-Doped Tungsten Oxide Thin Films for Hydrogen Gas Sensing
Sensors 2010, 10(8), 7705-7715; doi:10.3390/s100807705
Received: 20 June 2010 / Revised: 15 July 2010 / Accepted: 30 July 2010 / Published: 17 August 2010
Cited by 41 | PDF Full-text (870 KB) | HTML Full-text | XML Full-text
Abstract
In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO3) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of [...] Read more.
In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO3) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO3 thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO3 hydrogen sensor prepared by the E-beam method. Full article
(This article belongs to the Special Issue Gas Sensors - 2010)
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Open AccessArticle A Universal Intelligent System-on-Chip Based Sensor Interface
Sensors 2010, 10(8), 7716-7747; doi:10.3390/s100807716
Received: 11 June 2010 / Revised: 6 August 2010 / Accepted: 12 August 2010 / Published: 17 August 2010
Cited by 16 | PDF Full-text (1647 KB) | HTML Full-text | XML Full-text
Abstract
The need for real-time/reliable/low-maintenance distributed monitoring systems, e.g., wireless sensor networks, has been becoming more and more evident in many applications in the environmental, agro-alimentary, medical, and industrial fields. The growing interest in technologies related to sensors is an important indicator of [...] Read more.
The need for real-time/reliable/low-maintenance distributed monitoring systems, e.g., wireless sensor networks, has been becoming more and more evident in many applications in the environmental, agro-alimentary, medical, and industrial fields. The growing interest in technologies related to sensors is an important indicator of these new needs. The design and the realization of complex and/or distributed monitoring systems is often difficult due to the multitude of different electronic interfaces presented by the sensors available on the market. To address these issues the authors propose the concept of a Universal Intelligent Sensor Interface (UISI), a new low-cost system based on a single commercial chip able to convert a generic transducer into an intelligent sensor with multiple standardized interfaces. The device presented offers a flexible analog and/or digital front-end, able to interface different transducer typologies (such as conditioned, unconditioned, resistive, current output, capacitive and digital transducers). The device also provides enhanced processing and storage capabilities, as well as a configurable multi-standard output interface (including plug-and-play interface based on IEEE 1451.3). In this work the general concept of UISI and the design of reconfigurable hardware are presented, together with experimental test results validating the proposed device. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
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Open AccessArticle Field Evaluation of Polymer Capacitive Humidity Sensors for Bowen Ratio Energy Balance Flux Measurements
Sensors 2010, 10(8), 7748-7771; doi:10.3390/s100807748
Received: 28 June 2010 / Revised: 20 July 2010 / Accepted: 5 August 2010 / Published: 20 August 2010
Cited by 11 | PDF Full-text (1470 KB) | HTML Full-text | XML Full-text
Abstract
The possibility of reliable, reasonably accurate and relatively inexpensive estimates of sensible heat and latent energy fluxes was investigated using a commercial combination thin-film polymer capacitive relative humidity and adjacent temperature sensor instrument. Long-term and unattended water vapour pressure profile difference measurements [...] Read more.
The possibility of reliable, reasonably accurate and relatively inexpensive estimates of sensible heat and latent energy fluxes was investigated using a commercial combination thin-film polymer capacitive relative humidity and adjacent temperature sensor instrument. Long-term and unattended water vapour pressure profile difference measurements using low-power combination instruments were compared with those from a cooled dewpoint mirror hygrometer, the latter often used with Bowen ratio energy balance (BREB) systems. An error analysis, based on instrument relative humidity and temperature errors, was applied for various capacitive humidity instrument models. The main disadvantage of a combination capacitive humidity instrument is that two measurements, relative humidity and temperature, are required for estimation of water vapour pressure as opposed to one for a dewpoint hygrometer. In a laboratory experiment using an automated procedure, water vapour pressure differences generated using a reference dewpoint generator were measured using a commercial model (Dew-10) dewpoint hygrometer and a combination capacitive humidity instrument. The laboratory measurement comparisons showed that, potentially, an inexpensive model combination capacitive humidity instrument (CS500 or HMP50), or for improved results a slightly more expensive model (HMP35C or HMP45C), could substitute for the more expensive dewpoint hygrometer. In a field study, in a mesic grassland, the water vapour pressure measurement noise for the combination capacitive humidity instruments was greater than that for the dewpoint hygrometer. The average water vapour pressure profile difference measured using a HMP45C was highly correlated with that from a dewpoint hygrometer with a slope less than unity. Water vapour pressure measurements using the capacitive humidity instruments were not as accurate, compared to those obtained using a dewpoint hygrometer, but the resolution magnitudes for the profile difference measurements were less than the minimum of 0.01 kPa required for BREB measurements when averaged over 20 min. Furthermore, the longer-term capacitive humidity measurements are more reliable and not dependent on a sensor bias adjustment as is the case for the dewpoint hygrometer. A field comparison of CS500 and HMP45C profile water vapour pressure differences yielded a slope of close to unity. However, the CS500 exhibited more variable water vapour pressure measurements mainly due to its increased variation in temperature measurements compared to the HMP45C. Comparisons between 20-min BREB sensible heat fluxes obtained using a HMP45C and a dewpoint hygrometer yielded a slope of almost unity. BREB sensible heat fluxes measured using a HMP45C were reasonably well correlated with those obtained using a surface-layer scintillometer and eddy covariance (slope of 0.9629 and 0.9198 respectively). This reasonable agreement showed that a combination capacitive humidity instrument, with similar relative humidity (RH) and temperature error magnitudes of at most 2% RH and 0.3 °C respectively, and similar measurement time response, would be an adequate and less expensive substitute for a dewpoint hygrometer. Furthermore, a combination capacitive humidity instrument requires no servicing compared to a dewpoint hygrometer which requires a bias adjustment and mirror cleaning each week. These findings make unattended BREB measurements of sensible heat flux and evaporation cheaper and more reliable with the system easier to assemble and service and with reduced instrument power. Full article
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Open AccessArticle Acute Response in vivo of a Fiber-Optic Sensor for Continuous Glucose Monitoring from Canine Studies on Point Accuracy
Sensors 2010, 10(8), 7789-7802; doi:10.3390/s100807789
Received: 22 June 2010 / Revised: 26 July 2010 / Accepted: 5 August 2010 / Published: 20 August 2010
Cited by 6 | PDF Full-text (1698 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this study was to evaluate the acute response of SencilTM, a fiber-optic sensor, in point accuracy for glucose monitoring in vivo on healthy dogs under anesthesia.  A total of four dogs with clinically normal glycemia were implanted [...] Read more.
The objective of this study was to evaluate the acute response of SencilTM, a fiber-optic sensor, in point accuracy for glucose monitoring in vivo on healthy dogs under anesthesia.  A total of four dogs with clinically normal glycemia were implanted with one sensor each in the chest region to measure the interstitial glucose concentration during the ovariohysterectomy procedure. The data was acquired every 10 seconds after initiation, and was compared to the concentration of venous plasma glucose sampled during the surgery procedures for accuracy of agreement analysis. In the four trials with a range of 71–297 mg/dL plasma glucose, the collected 21 pairs of ISF readings from the SencilTM and the plasma reference showed superior dispersion of residue values than the conventional system, and a linear correlation (the Pearson correlation coefficient is 0.9288 and the y-intercept is 14.22 mg/dL). The MAD (17.6 mg/dL) and RMAD (16.16%) of SencilTM measurements were in the comparable range of the conventional system. The Clarke error grid analysis indicated that 100% of the paired points were in the clinically acceptable zone A (61.9%) and B (38.1%). Full article
(This article belongs to the Special Issue Glucose Sensors)
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Open AccessArticle Class Separation Improvements in Pixel Classification Using Colour Injection
Sensors 2010, 10(8), 7803-7842; doi:10.3390/s100807803
Received: 25 June 2010 / Revised: 20 July 2010 / Accepted: 4 August 2010 / Published: 20 August 2010
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Abstract
This paper presents an improvement in the colour image segmentation in the Hue Saturation (HS) sub-space. The authors propose to inject (add) a colour vector in the Red Green Blue (RGB) space to increase the class separation in [...] Read more.
This paper presents an improvement in the colour image segmentation in the Hue Saturation (HS) sub-space. The authors propose to inject (add) a colour vector in the Red Green Blue (RGB) space to increase the class separation in the HS plane. The goal of the work is the development of an algorithm to obtain the optimal colour vector for injection that maximizes the separation between the classes in the HS plane. The chromatic Chrominace-1 Chrominance-2 sub-space (of the Luminance Chrominace-1 Chrominance-2 (YC1C2) space) is used to obtain the optimal vector to add. The proposal is applied on each frame of a colour image sequence in real-time. It has been tested in applications with reduced contrast between the colours of the background and the object, and particularly when the size of the object is very small in comparison with the size of the captured scene. Numerous tests have confirmed that this proposal improves the segmentation process, considerably reducing the effects of the variation of the light intensity of the scene. Several tests have been made in skin segmentation in applications for sign language recognition via computer vision, where an accurate segmentation of hands and face is required. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
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Open AccessArticle Characteristics of Ambient Volatile Organic Compounds (VOCs) Measured in Shanghai, China
Sensors 2010, 10(8), 7843-7862; doi:10.3390/s100807843
Received: 25 June 2010 / Revised: 3 July 2010 / Accepted: 9 August 2010 / Published: 20 August 2010
Cited by 18 | PDF Full-text (666 KB) | HTML Full-text | XML Full-text
Abstract
To better understand the characteristics of ambient abundance of volatile organic compounds (VOCs) in Shanghai, one of the biggest metropolis of China, VOCs were measured with a gas chromatography system equipped with a mass-selective detector (GC/MSD) from July 2006 to February 2010. [...] Read more.
To better understand the characteristics of ambient abundance of volatile organic compounds (VOCs) in Shanghai, one of the biggest metropolis of China, VOCs were measured with a gas chromatography system equipped with a mass-selective detector (GC/MSD) from July 2006 to February 2010. An intensive measurement campaign was conducted (eight samples per day with a 3 hour interval) during May 2009. The comparison of ambient VOCs collected in different regions of Shanghai shows that the concentrations are slightly higher in the busy commercial area (28.9 ppbv at Xujiaui) than in the urban administrative area (24.3 ppbv at Pudong). However, during the intensive measurement period, the concentrations in the large steel industrial area (28.7 ppbv at Baoshan) were much higher than in the urban administrative area (18 ppbv at Pudong), especially for alkanes, alkenes, and toluene. The seasonal variations of ambient VOC concentrations measured at the Xujiahui sampling site indicate that the VOC concentrations are significantly affected by meteorological conditions (such as wind direction and precipitation). In addition, although alkanes are the most abundant VOCs at the Xujiahui measurement site, the most important VOCs contributing to ozone formation potential (OFP) are aromatics, accounting for 57% of the total OFP. The diurnal variations of VOC concentrations show that VOC concentrations are higher on weekdays than in weekends at the Xujiahui sampling site, suggesting that traffic condition and human activities have important impacts on VOC emissions in Shanghai. The evidence also shows that the major sources of isoprene are mainly resulted from gasoline evaporation at a particular time (06:00–09:00) in the busy commercial area. The results gained from this study provide useful information for better understanding the characteristics of ambient VOCs and the sources of VOCs in Shanghai. Full article
(This article belongs to the Special Issue Direct and Indirect Sensing of Odor and VOCs and Their Control)
Open AccessArticle Flame-Spray-Made Undoped Zinc Oxide Films for Gas Sensing Applications
Sensors 2010, 10(8), 7863-7873; doi:10.3390/s100807863
Received: 7 July 2010 / Revised: 16 August 2010 / Accepted: 20 August 2010 / Published: 23 August 2010
Cited by 19 | PDF Full-text (1296 KB) | HTML Full-text | XML Full-text
Abstract
Using zinc naphthenate dissolved in xylene as a precursor undoped ZnO nanopowders were synthesized by the flame spray pyrolysis technique. The average diameter and length of ZnO spherical and hexagonal particles were in the range of 5 to 20 nm, while ZnO [...] Read more.
Using zinc naphthenate dissolved in xylene as a precursor undoped ZnO nanopowders were synthesized by the flame spray pyrolysis technique. The average diameter and length of ZnO spherical and hexagonal particles were in the range of 5 to 20 nm, while ZnO nanorods were found to be 5–20 nm wide and 20–40 nm long, under 5/5 (precursor/oxygen) flame conditions. The gas sensitivity of the undoped ZnO nanopowders towards 50 ppm of NO2, C2H5OH and SO2 were found to be 33, 7 and 3, respectively. The sensors showed a great selectivity towards NO2 at high working temperature (at 300 °C), while small resistance variations were observed for C2H5OH and SO2, respectively. Full article
(This article belongs to the Special Issue Gas Sensors - 2010)
Open AccessArticle Non Invasive Sensors for Monitoring the Efficiency of AC Electrical Rotating Machines
Sensors 2010, 10(8), 7874-7895; doi:10.3390/s100807874
Received: 6 July 2010 / Revised: 9 August 2010 / Accepted: 12 August 2010 / Published: 23 August 2010
Cited by 7 | PDF Full-text (1457 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a non invasive method for estimating the energy efficiency of induction motors used in industrial applications. This method is innovative because it is only based on the measurement of the external field emitted by the motor. The paper describes [...] Read more.
This paper presents a non invasive method for estimating the energy efficiency of induction motors used in industrial applications. This method is innovative because it is only based on the measurement of the external field emitted by the motor. The paper describes the sensors used, how they should be placed around the machine in order to decouple the external field components generated by both the air gap flux and the winding end-windings. The study emphasizes the influence of the eddy currents flowing in the yoke frame on the sensor position. A method to estimate the torque from the external field use is proposed. The measurements are transmitted by a wireless module (Zig-Bee) and they are centralized and stored on a PC computer. Full article

Review

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Open AccessReview Molecular Biosensing Mechanisms in the Spleen for the Removal of Aged and Damaged Red Cells from the Blood Circulation
Sensors 2010, 10(8), 7099-7121; doi:10.3390/s100807099
Received: 5 June 2010 / Revised: 25 June 2010 / Accepted: 10 July 2010 / Published: 27 July 2010
Cited by 5 | PDF Full-text (1359 KB) | HTML Full-text | XML Full-text
Abstract
Heinz bodies are intraerythrocytic inclusions of hemichrome formed as a result of hemoglobin (Hb) oxidation. They typically develop in aged red cells. Based on the hypothesis that hemichrome formation is an innate characteristic of physiologically normal Hb molecules, we present an overview [...] Read more.
Heinz bodies are intraerythrocytic inclusions of hemichrome formed as a result of hemoglobin (Hb) oxidation. They typically develop in aged red cells. Based on the hypothesis that hemichrome formation is an innate characteristic of physiologically normal Hb molecules, we present an overview of our previous findings regarding the molecular instability of Hb and the formation of hemichrome, as well as recent findings on Heinz body formation within normal human erythrocytes. Human adult Hb (HbO2 A) prepared from healthy donors showed a tendency to produce hemichrome, even at close to physiological temperature and pH. Recent studies found that the number of Heinz bodies formed in red cells increased with increasing temperature when freshly drawn venous blood from healthy donors was subjected to mild heating above 37 °C. These findings suggest that Hb molecules control the removal of non-functional erythrocytes from the circulation via hemichrome formation and subsequent Heinz body clustering. In this review, we discuss the molecular biosensing mechanisms in the spleen, where hemichrome formation and subsequent Heinz body clustering within erythrocytes play a key role in the removal of aged and damaged red cells from the blood circulation. Full article
(This article belongs to the Special Issue Sensors in Biomechanics and Biomedicine)
Open AccessReview Small Molecule Immunosensing Using Surface Plasmon Resonance
Sensors 2010, 10(8), 7323-7346; doi:10.3390/s100807323
Received: 18 June 2010 / Revised: 15 July 2010 / Accepted: 25 July 2010 / Published: 4 August 2010
Cited by 62 | PDF Full-text (544 KB) | HTML Full-text | XML Full-text
Abstract
Surface plasmon resonance (SPR) biosensors utilize refractive index changes to sensitively detect mass changes at noble metal sensor surface interfaces. As such, they have been extensively applied to immunoassays of large molecules, where their high mass and use of sandwich immunoassay formats [...] Read more.
Surface plasmon resonance (SPR) biosensors utilize refractive index changes to sensitively detect mass changes at noble metal sensor surface interfaces. As such, they have been extensively applied to immunoassays of large molecules, where their high mass and use of sandwich immunoassay formats can result in excellent sensitivity. Small molecule immunosensing using SPR is more challenging. It requires antibodies or high-mass or noble metal labels to provide the required signal for ultrasensitive assays. Also, it can suffer from steric hindrance between the small antigen and large antibodies. However, new studies are increasingly meeting these and other challenges to offer highly sensitive small molecule immunosensor technologies through careful consideration of sensor interface design and signal enhancement. This review examines the application of SPR transduction technologies to small molecule immunoassays directed to different classes of small molecule antigens, including the steroid hormones, toxins, drugs and explosives residues. Also considered are the matrix effects resulting from measurement in chemically complex samples, the construction of stable sensor surfaces and the development of multiplexed assays capable of detecting several compounds at once. Assay design approaches are discussed and related to the sensitivities obtained. Full article
(This article belongs to the Special Issue Immunosensors)
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Open AccessReview Use of Sensors in the Treatment and Follow-up of Patients with Diabetes Mellitus
Sensors 2010, 10(8), 7404-7420; doi:10.3390/s100807404
Received: 29 June 2010 / Revised: 28 July 2010 / Accepted: 6 August 2010 / Published: 9 August 2010
Cited by 4 | PDF Full-text (185 KB) | HTML Full-text | XML Full-text
Abstract
Glucose control is the cornerstone of Diabetes Mellitus (DM) treatment. Although self-regulation using capillary glycemia (SRCG) still remains the best procedure in clinical practice, continuous glucose monitoring systems (CGM) offer the possibility of continuous and dynamic assessment of interstitial glucose concentration. CGM [...] Read more.
Glucose control is the cornerstone of Diabetes Mellitus (DM) treatment. Although self-regulation using capillary glycemia (SRCG) still remains the best procedure in clinical practice, continuous glucose monitoring systems (CGM) offer the possibility of continuous and dynamic assessment of interstitial glucose concentration. CGM systems have the potential to improve glycemic control while decreasing the incidence of hypoglycemia but the efficiency, compared with SRCG, is still debated. CGM systems have the greatest potential value in patients with hypoglycemic unawareness and in controlling daily fluctuations in blood glucose. The implementation of continuous monitoring in the standard clinical setting has not yet been established but a new generation of open and close loop subcutaneous insulin infusion devices are emerging making insulin treatment and glycemic control more reliable.Glucose control is the cornerstone of Diabetes Mellitus (DM) treatment. Although self-regulation using capillary glycemia (SRCG) still remains the best procedure in clinical practice, continuous glucose monitoring systems (CGM) offer the possibility of continuous and dynamic assessment of interstitial glucose concentration. CGM systems have the potential to improve glycemic control while decreasing the incidence of hypoglycemia but the efficiency, compared with SRCG, is still debated. CGM systems have the greatest potential value in patients with hypoglycemic unawareness and in controlling daily fluctuations in blood glucose. The implementation of continuous monitoring in the standard clinical setting has not yet been established but a new generation of open and close loop subcutaneous insulin infusion devices are emerging making insulin treatment and glycemic control more reliable. Full article
(This article belongs to the Special Issue Glucose Sensors)
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Open AccessReview Laser Induced Breakdown Spectroscopy for Elemental Analysis in Environmental, Cultural Heritage and Space Applications: A Review of Methods and Results
Sensors 2010, 10(8), 7434-7468; doi:10.3390/s100807434
Received: 7 April 2010 / Revised: 24 May 2010 / Accepted: 22 June 2010 / Published: 9 August 2010
Cited by 81 | PDF Full-text (658 KB) | HTML Full-text | XML Full-text
Abstract
Analytical applications of Laser Induced Breakdown Spectroscopy (LIBS), namely optical emission spectroscopy of laser-induced plasmas, have been constantly growing thanks to its intrinsic conceptual simplicity and versatility. Qualitative and quantitative analysis can be performed by LIBS both by drawing calibration lines and [...] Read more.
Analytical applications of Laser Induced Breakdown Spectroscopy (LIBS), namely optical emission spectroscopy of laser-induced plasmas, have been constantly growing thanks to its intrinsic conceptual simplicity and versatility. Qualitative and quantitative analysis can be performed by LIBS both by drawing calibration lines and by using calibration-free methods and some of its features, so as fast multi-elemental response, micro-destructiveness, instrumentation portability, have rendered it particularly suitable for analytical applications in the field of environmental science, space exploration and cultural heritage. This review reports and discusses LIBS achievements in these areas and results obtained for soils and aqueous samples, meteorites and terrestrial samples simulating extraterrestrial planets, and cultural heritage samples, including buildings and objects of various kinds. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessReview A Review of Accelerometry-Based Wearable Motion Detectors for Physical Activity Monitoring
Sensors 2010, 10(8), 7772-7788; doi:10.3390/s100807772
Received: 15 July 2010 / Revised: 2 August 2010 / Accepted: 16 August 2010 / Published: 20 August 2010
Cited by 169 | PDF Full-text (278 KB) | HTML Full-text | XML Full-text
Abstract
Characteristics of physical activity are indicative of one’s mobility level, latent chronic diseases and aging process. Accelerometers have been widely accepted as useful and practical sensors for wearable devices to measure and assess physical activity. This paper reviews the development of wearable [...] Read more.
Characteristics of physical activity are indicative of one’s mobility level, latent chronic diseases and aging process. Accelerometers have been widely accepted as useful and practical sensors for wearable devices to measure and assess physical activity. This paper reviews the development of wearable accelerometry-based motion detectors. The principle of accelerometry measurement, sensor properties and sensor placements are first introduced. Various research using accelerometry-based wearable motion detectors for physical activity monitoring and assessment, including posture and movement classification, estimation of energy expenditure, fall detection and balance control evaluation, are also reviewed. Finally this paper reviews and compares existing commercial products to provide a comprehensive outlook of current development status and possible emerging technologies. Full article
(This article belongs to the Special Issue Sensors in Biomechanics and Biomedicine)

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