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Sensors, Volume 10, Issue 11 (November 2010) , Pages 9541-10505

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Open AccessReview Photo-Detectors for Time of Flight Positron Emission Tomography (ToF-PET)
Sensors 2010, 10(11), 10484-10505; https://doi.org/10.3390/s101110484
Received: 25 September 2010 / Revised: 27 October 2010 / Accepted: 30 October 2010 / Published: 18 November 2010
Cited by 37 | Viewed by 8238 | PDF Full-text (1603 KB) | HTML Full-text | XML Full-text
Abstract
We present the most recent advances in photo-detector design employed in time of flight positron emission tomography (ToF-PET). PET is a molecular imaging modality that collects pairs of coincident (temporally correlated) annihilation photons emitted from the patient body. The annihilation photon detector typically
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We present the most recent advances in photo-detector design employed in time of flight positron emission tomography (ToF-PET). PET is a molecular imaging modality that collects pairs of coincident (temporally correlated) annihilation photons emitted from the patient body. The annihilation photon detector typically comprises a scintillation crystal coupled to a fast photo-detector. ToF information provides better localization of the annihilation event along the line formed by each detector pair, resulting in an overall improvement in signal to noise ratio (SNR) of the reconstructed image. Apart from the demand for high luminosity and fast decay time of the scintillation crystal, proper design and selection of the photo-detector and methods for arrival time pick-off are a prerequisite for achieving excellent time resolution required for ToF-PET. We review the two types of photo-detectors used in ToF-PET: photomultiplier tubes (PMTs) and silicon photo-multipliers (SiPMs) with a special focus on SiPMs. Full article
(This article belongs to the Special Issue Photodetectors and Imaging Technologies)
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Open AccessArticle A Local Weighted Nearest Neighbor Algorithm and a Weighted and Constrained Least-Squared Method for Mixed Odor Analysis by Electronic Nose Systems
Sensors 2010, 10(11), 10467-10483; https://doi.org/10.3390/s101110467
Received: 1 November 2010 / Revised: 11 November 2010 / Accepted: 15 November 2010 / Published: 18 November 2010
Cited by 5 | Viewed by 4856 | PDF Full-text (480 KB) | HTML Full-text | XML Full-text
Abstract
A great deal of work has been done to develop techniques for odor analysis by electronic nose systems. These analyses mostly focus on identifying a particular odor by comparing with a known odor dataset. However, in many situations, it would be more practical
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A great deal of work has been done to develop techniques for odor analysis by electronic nose systems. These analyses mostly focus on identifying a particular odor by comparing with a known odor dataset. However, in many situations, it would be more practical if each individual odorant could be determined directly. This paper proposes two methods for such odor components analysis for electronic nose systems. First, a K-nearest neighbor (KNN)-based local weighted nearest neighbor (LWNN) algorithm is proposed to determine the components of an odor. According to the component analysis, the odor training data is firstly categorized into several groups, each of which is represented by its centroid. The examined odor is then classified as the class of the nearest centroid. The distance between the examined odor and the centroid is calculated based on a weighting scheme, which captures the local structure of each predefined group. To further determine the concentration of each component, odor models are built by regressions. Then, a weighted and constrained least-squares (WCLS) method is proposed to estimate the component concentrations. Experiments were carried out to assess the effectiveness of the proposed methods. The LWNN algorithm is able to classify mixed odors with different mixing ratios, while the WCLS method can provide good estimates on component concentrations. Full article
(This article belongs to the Special Issue Direct and Indirect Sensing of Odor and VOCs and Their Control)
Open AccessArticle An Online Universal Diagnosis Procedure Using Two External Flux Sensors Applied to the AC Electrical Rotating Machines
Sensors 2010, 10(11), 10448-10466; https://doi.org/10.3390/s101110448
Received: 28 September 2010 / Revised: 27 October 2010 / Accepted: 10 November 2010 / Published: 18 November 2010
Cited by 13 | Viewed by 4192 | PDF Full-text (401 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an original non-invasive procedure for the diagnosis of electromagnetic devices, as well as AC electrical rotating machines using two external flux coil sensors that measure the external magnetic field in the machines’ vicinity. The diagnosis exploits the signal delivered by
[...] Read more.
This paper presents an original non-invasive procedure for the diagnosis of electromagnetic devices, as well as AC electrical rotating machines using two external flux coil sensors that measure the external magnetic field in the machines’ vicinity. The diagnosis exploits the signal delivered by the two sensors placed in particular positions. Contrary to classical methods using only one sensor, the presented method does not require any knowledge of a presumed machine’s healthy former state. On the other hand, the loading operating is not a disturbing factor but it is used to the fault discrimination. In order to present this procedure, an internal stator inter-turn short-circuit fault is considered as well. Full article
Open AccessArticle Design and Implementation of a GPS Guidance System for Agricultural Tractors Using Augmented Reality Technology
Sensors 2010, 10(11), 10435-10447; https://doi.org/10.3390/s101110435
Received: 28 October 2010 / Revised: 10 November 2010 / Accepted: 11 November 2010 / Published: 18 November 2010
Cited by 11 | Viewed by 9056 | PDF Full-text (1192 KB) | HTML Full-text | XML Full-text
Abstract
Current commercial tractor guidance systems present to the driver information to perform agricultural tasks in the best way. This information generally includes a treated zones map referenced to the tractor’s position. Unlike actual guidance systems where the tractor driver must mentally associate treated
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Current commercial tractor guidance systems present to the driver information to perform agricultural tasks in the best way. This information generally includes a treated zones map referenced to the tractor’s position. Unlike actual guidance systems where the tractor driver must mentally associate treated zone maps and the plot layout, this paper presents a guidance system that using Augmented Reality (AR) technology, allows the tractor driver to see the real plot though eye monitor glasses with the treated zones in a different color. The paper includes a description of the system hardware and software, a real test done with image captures seen by the tractor driver, and a discussion predicting that the historical evolution of guidance systems could involve the use of AR technology in the agricultural guidance and monitoring systems. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
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Open AccessArticle Using a Floating-Gate MOS Transistor as a Transducer in a MEMS Gas Sensing System
Sensors 2010, 10(11), 10413-10434; https://doi.org/10.3390/s101110413
Received: 30 September 2010 / Revised: 28 October 2010 / Accepted: 10 November 2010 / Published: 18 November 2010
Cited by 8 | Viewed by 7986 | PDF Full-text (1572 KB) | HTML Full-text | XML Full-text
Abstract
Floating-gate MOS transistors have been widely used in diverse analog and digital applications. One of these is as a charge sensitive device in sensors for pH measurement in solutions or using gates with metals like Pd or Pt for hydrogen sensing. Efforts are
[...] Read more.
Floating-gate MOS transistors have been widely used in diverse analog and digital applications. One of these is as a charge sensitive device in sensors for pH measurement in solutions or using gates with metals like Pd or Pt for hydrogen sensing. Efforts are being made to monolithically integrate sensors together with controlling and signal processing electronics using standard technologies. This can be achieved with the demonstrated compatibility between available CMOS technology and MEMS technology. In this paper an in-depth analysis is done regarding the reliability of floating-gate MOS transistors when charge produced by a chemical reaction between metallic oxide thin films with either reducing or oxidizing gases is present. These chemical reactions need temperatures around 200 °C or higher to take place, so thermal insulation of the sensing area must be assured for appropriate operation of the electronics at room temperature. The operation principle of the proposal here presented is confirmed by connecting the gate of a conventional MOS transistor in series with a Fe2O3 layer. It is shown that an electrochemical potential is present on the ferrite layer when reacting with propane. Full article
(This article belongs to the Special Issue Gas Sensors - 2010)
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Open AccessArticle Process Monitoring Evaluation and Implementation for the Wood Abrasive Machining Process
Sensors 2010, 10(11), 10401-10412; https://doi.org/10.3390/s101110401
Received: 29 July 2010 / Revised: 10 November 2010 / Accepted: 11 November 2010 / Published: 18 November 2010
Cited by 6 | Viewed by 5623 | PDF Full-text (751 KB) | HTML Full-text | XML Full-text
Abstract
Wood processing industries have continuously developed and improved technologies and processes to transform wood to obtain better final product quality and thus increase profits. Abrasive machining is one of the most important of these processes and therefore merits special attention and study. The
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Wood processing industries have continuously developed and improved technologies and processes to transform wood to obtain better final product quality and thus increase profits. Abrasive machining is one of the most important of these processes and therefore merits special attention and study. The objective of this work was to evaluate and demonstrate a process monitoring system for use in the abrasive machining of wood and wood based products. The system developed increases the life of the belt by detecting (using process monitoring sensors) and removing (by cleaning) the abrasive loading during the machining process. This study focused on abrasive belt machining processes and included substantial background work, which provided a solid base for understanding the behavior of the abrasive, and the different ways that the abrasive machining process can be monitored. In addition, the background research showed that abrasive belts can effectively be cleaned by the appropriate cleaning technique. The process monitoring system developed included acoustic emission sensors which tended to be sensitive to belt wear, as well as platen vibration, but not loading, and optical sensors which were sensitive to abrasive loading. Full article
Open AccessArticle Data Refinement and Channel Selection for a Portable E-Nose System by the Use of Feature Feedback
Sensors 2010, 10(11), 10387-10400; https://doi.org/10.3390/s101110387
Received: 17 September 2010 / Revised: 25 October 2010 / Accepted: 1 November 2010 / Published: 17 November 2010
Cited by 12 | Viewed by 5266 | PDF Full-text (533 KB) | HTML Full-text | XML Full-text
Abstract
We propose a data refinement and channel selection method for vapor classification in a portable e-nose system. For the robust e-nose system in a real environment, we propose to reduce the noise in the data measured by sensor arrays and distinguish the important
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We propose a data refinement and channel selection method for vapor classification in a portable e-nose system. For the robust e-nose system in a real environment, we propose to reduce the noise in the data measured by sensor arrays and distinguish the important part in the data by the use of feature feedback. Experimental results on different volatile organic compounds data show that the proposed data refinement method gives good clustering for different classes and improves the classification performance. Also, we design a new sensor array that consists only of the useful channels. For this purpose, each channel is evaluated by measuring its discriminative power based on the feature mask used in the data refinement. Through the experimental results, we show that the new sensor array improves both the classification rates and the efficiency in computation and data storage. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Research on a Denial of Service (DoS) Detection System Based on Global Interdependent Behaviors in a Sensor Network Environment
Sensors 2010, 10(11), 10376-10386; https://doi.org/10.3390/s101110376
Received: 30 September 2010 / Revised: 25 October 2010 / Accepted: 8 November 2010 / Published: 17 November 2010
Cited by 5 | Viewed by 5081 | PDF Full-text (394 KB) | HTML Full-text | XML Full-text
Abstract
This research suggests a Denial of Service (DoS) detection method based on the collection of interdependent behavior data in a sensor network environment. In order to collect the interdependent behavior data, we use a base station to analyze traffic and behaviors among nodes
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This research suggests a Denial of Service (DoS) detection method based on the collection of interdependent behavior data in a sensor network environment. In order to collect the interdependent behavior data, we use a base station to analyze traffic and behaviors among nodes and introduce methods of detecting changes in the environment with precursor symptoms. The study presents a DoS Detection System based on Global Interdependent Behaviors and shows the result of detecting a sensor carrying out DoS attacks through the test-bed. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A General Purpose Feature Extractor for Light Detection and Ranging Data
Sensors 2010, 10(11), 10356-10375; https://doi.org/10.3390/s101110356
Received: 17 September 2010 / Revised: 7 October 2010 / Accepted: 30 October 2010 / Published: 17 November 2010
Cited by 18 | Viewed by 4992 | PDF Full-text (1096 KB) | HTML Full-text | XML Full-text
Abstract
Feature extraction is a central step of processing Light Detection and Ranging (LIDAR) data. Existing detectors tend to exploit characteristics of specific environments: corners and lines from indoor (rectilinear) environments, and trees from outdoor environments. While these detectors work well in their intended
[...] Read more.
Feature extraction is a central step of processing Light Detection and Ranging (LIDAR) data. Existing detectors tend to exploit characteristics of specific environments: corners and lines from indoor (rectilinear) environments, and trees from outdoor environments. While these detectors work well in their intended environments, their performance in different environments can be poor. We describe a general purpose feature detector for both 2D and 3D LIDAR data that is applicable to virtually any environment. Our method adapts classic feature detection methods from the image processing literature, specifically the multi-scale Kanade-Tomasi corner detector. The resulting method is capable of identifying highly stable and repeatable features at a variety of spatial scales without knowledge of environment, and produces principled uncertainty estimates and corner descriptors at same time. We present results on both software simulation and standard datasets, including the 2D Victoria Park and Intel Research Center datasets, and the 3D MIT DARPA Urban Challenge dataset. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
Open AccessArticle Fabrication and Characterization of 3D Micro- and Nanoelectrodes for Neuron Recordings
Sensors 2010, 10(11), 10339-10355; https://doi.org/10.3390/s101110339
Received: 18 October 2010 / Revised: 28 October 2010 / Accepted: 15 November 2010 / Published: 17 November 2010
Cited by 16 | Viewed by 5148 | PDF Full-text (917 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we discuss the fabrication and characterization of three dimensional (3D) micro- and nanoelectrodes with the goal of using them for extra- and intracellular studies. Two different types of electrodes will be described: high aspect ratio microelectrodes for studying the communication
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In this paper we discuss the fabrication and characterization of three dimensional (3D) micro- and nanoelectrodes with the goal of using them for extra- and intracellular studies. Two different types of electrodes will be described: high aspect ratio microelectrodes for studying the communication between cells and ultimately for brain slice recordings and small nanoelectrodes for highly localized measurements and ultimately for intracellular studies. Electrical and electrochemical characterization of these electrodes as well as the results of PC12 cell differentiation on chip will be presented and discussed. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Denmark)
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Open AccessArticle Dynamic Load Balancing Data Centric Storage for Wireless Sensor Networks
Sensors 2010, 10(11), 10328-10338; https://doi.org/10.3390/s101110328
Received: 12 October 2010 / Revised: 3 November 2010 / Accepted: 10 October 2010 / Published: 17 November 2010
Cited by 3 | Viewed by 3717 | PDF Full-text (237 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a new data centric storage that is dynamically adapted to the work load changes is proposed. The proposed data centric storage distributes the load of hot spot areas to neighboring sensor nodes by using a multilevel grid technique. The proposed
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In this paper, a new data centric storage that is dynamically adapted to the work load changes is proposed. The proposed data centric storage distributes the load of hot spot areas to neighboring sensor nodes by using a multilevel grid technique. The proposed method is also able to use existing routing protocols such as GPSR (Greedy Perimeter Stateless Routing) with small changes. Through simulation, the proposed method enhances the lifetime of sensor networks over one of the state-of-the-art data centric storages. We implement the proposed method based on an operating system for sensor networks, and evaluate the performance through running based on a simulation tool. Full article
Open AccessArticle A New Wireless Biosensor for Intra-Vaginal Temperature Monitoring
Sensors 2010, 10(11), 10314-10327; https://doi.org/10.3390/s101110314
Received: 28 September 2010 / Revised: 3 November 2010 / Accepted: 9 November 2010 / Published: 17 November 2010
Cited by 8 | Viewed by 7172 | PDF Full-text (354 KB) | HTML Full-text | XML Full-text
Abstract
Wireless Body Sensors for medical purposes offer valuable contributions to improve patients’ healthcare, including diagnosis and/or therapeutics monitoring. Body temperature is a crucial parameter in healthcare diagnosis. In gynecology and obstetrics it is measured at the skin’s surface, which is very influenced by
[...] Read more.
Wireless Body Sensors for medical purposes offer valuable contributions to improve patients’ healthcare, including diagnosis and/or therapeutics monitoring. Body temperature is a crucial parameter in healthcare diagnosis. In gynecology and obstetrics it is measured at the skin’s surface, which is very influenced by the environment. This paper proposes a new intra-body sensor for long-term intra-vaginal temperature collection. The embedded IEEE 802.15.4 communication module allows the integration of this sensor in a Wireless Sensor Network (WSN) for remote data access and monitoring. We present the sensor architecture, the construction of the corresponding testbed, and its performance evaluation. This sensor may be used in different medical applications, including preterm labor prevention and fertility and ovulation period detection. The features of the constructed testbed were validated in laboratory tests verifying its accuracy and performance. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Biocatalysts Immobilized in Ultrathin Ordered Films
Sensors 2010, 10(11), 10298-10313; https://doi.org/10.3390/s101110298
Received: 29 September 2010 / Revised: 2 November 2010 / Accepted: 10 November 2010 / Published: 16 November 2010
Cited by 2 | Viewed by 4145 | PDF Full-text (738 KB) | HTML Full-text | XML Full-text
Abstract
The immobilization of enzymes and other proteins into ordered thin materials has attracted considerable attention over the past few years. This research has demonstrated that biomolecules immobilized in different [Langmuir-Blodgett (LB)/Langmuir-Schaefer (LS)] matrixes retain their functional characteristics to a large extent. These new
[...] Read more.
The immobilization of enzymes and other proteins into ordered thin materials has attracted considerable attention over the past few years. This research has demonstrated that biomolecules immobilized in different [Langmuir-Blodgett (LB)/Langmuir-Schaefer (LS)] matrixes retain their functional characteristics to a large extent. These new materials are of interest for applications as biosensors and biocatalysts. We review the growing field of oxidases immobilized onto ordered Langmiur-Blodgett and Langmuir-Schaefer films. Strategies for the preparation of solid supports and the essential properties of the resulting materials with respect to the envisaged applications are presented. Basic effects of the nature of the adsorption and various aspects of the application of these materials as biosensors, biocatalysts are discussed. Outlook of potential applications and further challenges are also provided. Full article
(This article belongs to the Special Issue Bio-devices and Materials)
Open AccessReview An Overview of Kinematic and Calibration Models Using Internal/External Sensors or Constraints to Improve the Behavior of Spatial Parallel Mechanisms
Sensors 2010, 10(11), 10256-10297; https://doi.org/10.3390/s101110256
Received: 27 September 2010 / Revised: 25 October 2010 / Accepted: 5 November 2010 / Published: 16 November 2010
Cited by 44 | Viewed by 7624 | PDF Full-text (1439 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an overview of the literature on kinematic and calibration models of parallel mechanisms, the influence of sensors in the mechanism accuracy and parallel mechanisms used as sensors. The most relevant classifications to obtain and solve kinematic models and to identify
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This paper presents an overview of the literature on kinematic and calibration models of parallel mechanisms, the influence of sensors in the mechanism accuracy and parallel mechanisms used as sensors. The most relevant classifications to obtain and solve kinematic models and to identify geometric and non-geometric parameters in the calibration of parallel robots are discussed, examining the advantages and disadvantages of each method, presenting new trends and identifying unsolved problems. This overview tries to answer and show the solutions developed by the most up-to-date research to some of the most frequent questions that appear in the modelling of a parallel mechanism, such as how to measure, the number of sensors and necessary configurations, the type and influence of errors or the number of necessary parameters. Full article
(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)
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Open AccessArticle A Wearable Ground Reaction Force Sensor System and Its Application to the Measurement of Extrinsic Gait Variability
Sensors 2010, 10(11), 10240-10255; https://doi.org/10.3390/s101110240
Received: 12 October 2010 / Revised: 10 November 2010 / Accepted: 15 November 2010 / Published: 16 November 2010
Cited by 53 | Viewed by 6320 | PDF Full-text (286 KB) | HTML Full-text | XML Full-text
Abstract
Wearable sensors for gait analysis are attracting wide interest. In this paper, a wearable ground reaction force (GRF) sensor system and its application to measure extrinsic gait variability are presented. To validate the GRF and centre of pressure (CoP) measurements of the sensor
[...] Read more.
Wearable sensors for gait analysis are attracting wide interest. In this paper, a wearable ground reaction force (GRF) sensor system and its application to measure extrinsic gait variability are presented. To validate the GRF and centre of pressure (CoP) measurements of the sensor system and examine the effectiveness of the proposed method for gait analysis, we conducted an experimental study on seven volunteer subjects. Based on the assessment of the influence of the sensor system on natural gait, we found that no significant differences were found for almost all measured gait parameters (p-values < 0.05). As for measurement accuracy, the root mean square (RMS) differences for the two transverse components and the vertical component of the GRF were 7.2% ± 0.8% and 9.0% ± 1% of the maximum of each transverse component and 1.5% ± 0.9% of the maximum vertical component of GRF, respectively. The RMS distance between both CoP measurements was 1.4% ± 0.2% of the length of the shoe. The area of CoP distribution on the foot-plate and the average coefficient of variation of the triaxial GRF, are the introduced parameters for analysing extrinsic gait variability. Based on a statistical analysis of the results of the tests with subjects wearing the sensor system, we found that the proposed parameters changed according to walking speed and turning (p-values < 0.05). Full article
(This article belongs to the Special Issue Sensors in Biomechanics and Biomedicine)
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Open AccessArticle Fabrication and Performance of All-Solid-State Chloride Sensors in Synthetic Concrete Pore Solutions
Sensors 2010, 10(11), 10226-10239; https://doi.org/10.3390/s10111022
Received: 13 October 2010 / Revised: 4 November 2010 / Accepted: 8 November 2010 / Published: 16 November 2010
Cited by 4 | Viewed by 4649 | PDF Full-text (207 KB) | HTML Full-text | XML Full-text
Abstract
One type of all-solid-state chloride sensor was fabricated using a MnO2 electrode and a Ag/AgCl electrode. The potentiometric response of the sensor to chloride in synthetic concrete pore solutions was systematically studied, and the polarization performance was also evaluated. The results show
[...] Read more.
One type of all-solid-state chloride sensor was fabricated using a MnO2 electrode and a Ag/AgCl electrode. The potentiometric response of the sensor to chloride in synthetic concrete pore solutions was systematically studied, and the polarization performance was also evaluated. The results show a good linear relationship between the potential reading of the sensor and the logarithm of chloride activity (concentration ranges from 0.05 to 5.0 M), and the potential value remains stable with increasing immersion time. The existence of K+, Ca2+, Na+ and SO42− ions have little influence on the potentiometric response of the sensor to chloride, but the pH has a significant influence on the potential value of the sensor at low chloride concentration. The potential reading of the sensor increases linearly with the solution temperature over the range from 5 to 45 °C. Meanwhile, an excellent polarization behavior is proven by galvanostatic and potentiodynamic tests. All of the results reveal that the developed sensor has a great potential for monitoring chloride ions in concrete environments. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Polymer-Based Capacitive Sensing Array for Normal and Shear Force Measurement
Sensors 2010, 10(11), 10211-10225; https://doi.org/10.3390/s101110211
Received: 18 October 2010 / Revised: 5 November 2010 / Accepted: 8 November 2010 / Published: 15 November 2010
Cited by 58 | Viewed by 5868 | PDF Full-text (744 KB) | HTML Full-text | XML Full-text
Abstract
In this work, we present the development of a polymer-based capacitive sensing array. The proposed device is capable of measuring normal and shear forces, and can be easily realized by using micromachining techniques and flexible printed circuit board (FPCB) technologies. The sensing array
[...] Read more.
In this work, we present the development of a polymer-based capacitive sensing array. The proposed device is capable of measuring normal and shear forces, and can be easily realized by using micromachining techniques and flexible printed circuit board (FPCB) technologies. The sensing array consists of a polydimethlysiloxane (PDMS) structure and a FPCB. Each shear sensing element comprises four capacitive sensing cells arranged in a 2 × 2 array, and each capacitive sensing cell has two sensing electrodes and a common floating electrode. The sensing electrodes as well as the metal interconnect for signal scanning are implemented on the FPCB, while the floating electrodes are patterned on the PDMS structure. This design can effectively reduce the complexity of the capacitive structures, and thus makes the device highly manufacturable. The characteristics of the devices with different dimensions were measured and discussed. A scanning circuit was also designed and implemented. The measured maximum sensitivity is 1.67%/mN. The minimum resolvable force is 26 mN measured by the scanning circuit. The capacitance distributions induced by normal and shear forces were also successfully captured by the sensing array. Full article
(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)
Open AccessArticle Plastic Optical Fiber Displacement Sensor Based on Dual Cycling Bending
Sensors 2010, 10(11), 10198-10210; https://doi.org/10.3390/s101110198
Received: 28 September 2010 / Revised: 9 November 2010 / Accepted: 10 November 2010 / Published: 15 November 2010
Cited by 18 | Viewed by 6505 | PDF Full-text (528 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a high sensitivity and easy fabricated plastic optical fiber (POF) displacement sensor is proposed. A POF specimen subjected to dual cyclic bending is used to improve the sensitivity of the POF displacement sensor. The effects of interval between rollers, relative
[...] Read more.
In this study, a high sensitivity and easy fabricated plastic optical fiber (POF) displacement sensor is proposed. A POF specimen subjected to dual cyclic bending is used to improve the sensitivity of the POF displacement sensor. The effects of interval between rollers, relative displacement and number of rollers on the sensitivity of the displacement sensor are analyzed both experimentally and numerically. A good agreement between the experimental measurements and numerical calculations is obtained. The results show that the interval between rollers affects sensitivity most significantly than the other design parameters. Based on the experimental data, a linear equation is derived to estimate the relationship between the power loss and the relative displacement. The difference between the estimated results and the experimental results is found to be less than 8%. The results also show that the proposed POF displacement sensor based on dual cyclic bending can be used to detect displacement accurately. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Extended Target Recognition in Cognitive Radar Networks
Sensors 2010, 10(11), 10181-10197; https://doi.org/10.3390/s101110181
Received: 25 September 2010 / Revised: 30 October 2010 / Accepted: 1 November 2010 / Published: 11 November 2010
Cited by 12 | Viewed by 6918 | PDF Full-text (327 KB) | HTML Full-text | XML Full-text
Abstract
We address the problem of adaptive waveform design for extended target recognition in cognitive radar networks. A closed-loop active target recognition radar system is extended to the case of a centralized cognitive radar network, in which a generalized likelihood ratio (GLR) based sequential
[...] Read more.
We address the problem of adaptive waveform design for extended target recognition in cognitive radar networks. A closed-loop active target recognition radar system is extended to the case of a centralized cognitive radar network, in which a generalized likelihood ratio (GLR) based sequential hypothesis testing (SHT) framework is employed. Using Doppler velocities measured by multiple radars, the target aspect angle for each radar is calculated. The joint probability of each target hypothesis is then updated using observations from different radar line of sights (LOS). Based on these probabilities, a minimum correlation algorithm is proposed to adaptively design the transmit waveform for each radar in an amplitude fluctuation situation. Simulation results demonstrate performance improvements due to the cognitive radar network and adaptive waveform design. Our minimum correlation algorithm outperforms the eigen-waveform solution and other non-cognitive waveform design approaches. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessReview Large Lateral Photovoltaic Effect in Metal-(Oxide-)Semiconductor Structures
Sensors 2010, 10(11), 10155-10180; https://doi.org/10.3390/s101110155
Received: 26 September 2010 / Revised: 14 October 2010 / Accepted: 25 October 2010 / Published: 11 November 2010
Cited by 32 | Viewed by 8184 | PDF Full-text (2800 KB) | HTML Full-text | XML Full-text
Abstract
The lateral photovoltaic effect (LPE) can be used in position-sensitive detectors to detect very small displacements due to its output of lateral photovoltage changing linearly with light spot position. In this review, we will summarize some of our recent works regarding LPE in
[...] Read more.
The lateral photovoltaic effect (LPE) can be used in position-sensitive detectors to detect very small displacements due to its output of lateral photovoltage changing linearly with light spot position. In this review, we will summarize some of our recent works regarding LPE in metal-semiconductor and metal-oxide-semiconductor structures, and give a theoretical model of LPE in these two structures. Full article
(This article belongs to the Special Issue Photodetectors and Imaging Technologies)
Open AccessArticle Sensor Based Framework for Secure Multimedia Communication in VANET
Sensors 2010, 10(11), 10146-10154; https://doi.org/10.3390/s101110146
Received: 29 September 2010 / Revised: 9 November 2010 / Accepted: 10 November 2010 / Published: 11 November 2010
Cited by 11 | Viewed by 4704 | PDF Full-text (221 KB) | HTML Full-text | XML Full-text
Abstract
Secure multimedia communication enhances the safety of passengers by providing visual pictures of accidents and danger situations. In this paper we proposed a framework for secure multimedia communication in Vehicular Ad-Hoc Networks (VANETs). Our proposed framework is mainly divided into four components: redundant
[...] Read more.
Secure multimedia communication enhances the safety of passengers by providing visual pictures of accidents and danger situations. In this paper we proposed a framework for secure multimedia communication in Vehicular Ad-Hoc Networks (VANETs). Our proposed framework is mainly divided into four components: redundant information, priority assignment, malicious data verification and malicious node verification. The proposed scheme jhas been validated with the help of the NS-2 network simulator and the Evalvid tool. Full article
Open AccessArticle Error Analysis of Terrestrial Laser Scanning Data by Means of Spherical Statistics and 3D Graphs
Sensors 2010, 10(11), 10128-10145; https://doi.org/10.3390/s101110128
Received: 26 August 2010 / Revised: 18 October 2010 / Accepted: 5 November 2010 / Published: 10 November 2010
Cited by 16 | Viewed by 7672 | PDF Full-text (552 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a complete analysis of the positional errors of terrestrial laser scanning (TLS) data based on spherical statistics and 3D graphs. Spherical statistics are preferred because of the 3D vectorial nature of the spatial error. Error vectors have three metric elements
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This paper presents a complete analysis of the positional errors of terrestrial laser scanning (TLS) data based on spherical statistics and 3D graphs. Spherical statistics are preferred because of the 3D vectorial nature of the spatial error. Error vectors have three metric elements (one module and two angles) that were analyzed by spherical statistics. A study case has been presented and discussed in detail. Errors were calculating using 53 check points (CP) and CP coordinates were measured by a digitizer with submillimetre accuracy. The positional accuracy was analyzed by both the conventional method (modular errors analysis) and the proposed method (angular errors analysis) by 3D graphics and numerical spherical statistics. Two packages in R programming language were performed to obtain graphics automatically. The results indicated that the proposed method is advantageous as it offers a more complete analysis of the positional accuracy, such as angular error component, uniformity of the vector distribution, error isotropy, and error, in addition the modular error component by linear statistics. Full article
(This article belongs to the Special Issue Photodetectors and Imaging Technologies)
Open AccessArticle Feasibility of Fiber Bragg Grating and Long-Period Fiber Grating Sensors under Different Environmental Conditions
Sensors 2010, 10(11), 10105-10127; https://doi.org/10.3390/s101110105
Received: 22 October 2010 / Revised: 3 November 2010 / Accepted: 8 November 2010 / Published: 10 November 2010
Cited by 24 | Viewed by 8338 | PDF Full-text (1622 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the feasibility of utilizing fiber Bragg grating (FBG) and long-period fiber grating (LPFG) sensors for nondestructive evaluation (NDE) of infrastructures using Portland cement concretes and asphalt mixtures for temperature, strain, and liquid-level monitoring. The use of hybrid FBG and LPFG
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This paper presents the feasibility of utilizing fiber Bragg grating (FBG) and long-period fiber grating (LPFG) sensors for nondestructive evaluation (NDE) of infrastructures using Portland cement concretes and asphalt mixtures for temperature, strain, and liquid-level monitoring. The use of hybrid FBG and LPFG sensors is aimed at utilizing the advantages of two kinds of fiber grating to implement NDE for monitoring strains or displacements, temperatures, and water-levels of infrastructures such as bridges, pavements, or reservoirs for under different environmental conditions. Temperature fluctuation and stability tests were examined using FBG and LPFG sensors bonded on the surface of asphalt and concrete specimens. Random walk coefficient (RWC) and bias stability (BS) were used for the first time to indicate the stability performance of fiber grating sensors. The random walk coefficients of temperature variations between FBG (or LPFG) sensor and a thermocouple were found in the range of −0.7499 °C/ to −1.3548 °C/. In addition, the bias stability for temperature variations, during the fluctuation and stability tests with FBG (or LPFG) sensors were within the range of 0.01 °C/h with a 15–18 h time cluster to 0.09 °C/h with a 3–4 h time cluster. This shows that the performance of FBG or LPFG sensors is comparable with that of conventional high-resolution thermocouple sensors under rugged conditions. The strain measurement for infrastructure materials was conducted using a packaged FBG sensor bonded on the surface of an asphalt specimen under indirect tensile loading conditions. A finite element modeling (FEM) was applied to compare experimental results of indirect tensile FBG strain measurements. For a comparative analysis between experiment and simulation, the FEM numerical results agreed with those from FBG strain measurements. The results of the liquid-level sensing tests show the LPFG-based sensor could discriminate five stationary liquid-levels and exhibits at least 1,050-mm liquid-level measurement capacity. Thus, the hybrid FBG and LPFG sensors reported here could benefit the NDE development and applications for infrastructure health monitoring such as strain, temperature and liquid-level measurements. Full article
(This article belongs to the Special Issue Advanced Sensing Technology for Nondestructive Evaluation)
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Open AccessArticle Polypyrrole Porous Micro Humidity Sensor Integrated with a Ring Oscillator Circuit on Chip
Sensors 2010, 10(11), 10095-10104; https://doi.org/10.3390/s101110095
Received: 25 September 2010 / Revised: 28 October 2010 / Accepted: 28 October 2010 / Published: 10 November 2010
Cited by 32 | Viewed by 5652 | PDF Full-text (622 KB) | HTML Full-text | XML Full-text
Abstract
This study presents the design and fabrication of a capacitive micro humidity sensor integrated with a five-stage ring oscillator circuit on chip using the complimentary metal oxide semiconductor (CMOS) process. The area of the humidity sensor chip is about 1 mm2.
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This study presents the design and fabrication of a capacitive micro humidity sensor integrated with a five-stage ring oscillator circuit on chip using the complimentary metal oxide semiconductor (CMOS) process. The area of the humidity sensor chip is about 1 mm2. The humidity sensor consists of a sensing capacitor and a sensing film. The sensing capacitor is constructed from spiral interdigital electrodes that can enhance the sensitivity of the sensor. The sensing film of the sensor is polypyrrole, which is prepared by the chemical polymerization method, and the film has a porous structure. The sensor needs a post-CMOS process to coat the sensing film. The post-CMOS process uses a wet etching to etch the sacrificial layers, and then the polypyrrole is coated on the sensing capacitor. The sensor generates a change in capacitance when the sensing film absorbs or desorbs vapor. The ring oscillator circuit converts the capacitance variation of the sensor into the oscillation frequency output. Experimental results show that the sensitivity of the humidity sensor is about 99 kHz/%RH at 25 °C. Full article
(This article belongs to the Special Issue Gas Sensors - 2010)
Open AccessArticle Performance Evaluation of an Infrared Thermocouple
Sensors 2010, 10(11), 10081-10094; https://doi.org/10.3390/s101110081
Received: 28 October 2010 / Revised: 2 November 2010 / Accepted: 8 November 2010 / Published: 10 November 2010
Cited by 3 | Viewed by 4883 | PDF Full-text (209 KB) | HTML Full-text | XML Full-text
Abstract
The measurement of the leaf temperature of forests or agricultural plants is an important technique for the monitoring of the physiological state of crops. The infrared thermometer is a convenient device due to its fast response and nondestructive measurement technique. Nowadays, a novel
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The measurement of the leaf temperature of forests or agricultural plants is an important technique for the monitoring of the physiological state of crops. The infrared thermometer is a convenient device due to its fast response and nondestructive measurement technique. Nowadays, a novel infrared thermocouple, developed with the same measurement principle of the infrared thermometer but using a different detector, has been commercialized for non-contact temperature measurement. The performances of two-kinds of infrared thermocouples were evaluated in this study. The standard temperature was maintained by a temperature calibrator and a special black cavity device. The results indicated that both types of infrared thermocouples had good precision. The error distribution ranged from −1.8 °C to 18 °C as the reading values served as the true values. Within the range from 13 °C to 37 °C, the adequate calibration equations were the high-order polynomial equations. Within the narrower range from 20 °C to 35 °C, the adequate equation was a linear equation for one sensor and a two-order polynomial equation for the other sensor. The accuracy of the two kinds of infrared thermocouple was improved by nearly 0.4 °C with the calibration equations. These devices could serve as mobile monitoring tools for in situ and real time routine estimation of leaf temperatures. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
Open AccessArticle A Method for Evaluating Dynamical Friction in Linear Ball Bearings
Sensors 2010, 10(11), 10069-10080; https://doi.org/10.3390/s101110069
Received: 16 September 2010 / Revised: 10 October 2010 / Accepted: 15 October 2010 / Published: 9 November 2010
Cited by 5 | Viewed by 5363 | PDF Full-text (806 KB) | HTML Full-text | XML Full-text
Abstract
A method is proposed for evaluating the dynamical friction of linear bearings, whose motion is not perfectly linear due to some play in its internal mechanism. In this method, the moving part of a linear bearing is made to move freely, and the
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A method is proposed for evaluating the dynamical friction of linear bearings, whose motion is not perfectly linear due to some play in its internal mechanism. In this method, the moving part of a linear bearing is made to move freely, and the force acting on the moving part is measured as the inertial force given by the product of its mass and the acceleration of its centre of gravity. To evaluate the acceleration of its centre of gravity, the acceleration of two different points on it is measured using a dual-axis optical interferometer. Full article
Open AccessArticle Non-Destructive Optical Monitoring of Grape Maturation by Proximal Sensing
Sensors 2010, 10(11), 10040-10068; https://doi.org/10.3390/s101110040
Received: 13 September 2010 / Revised: 19 October 2010 / Accepted: 26 October 2010 / Published: 9 November 2010
Cited by 94 | Viewed by 8494 | PDF Full-text (670 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A new, commercial, fluorescence-based optical sensor for plant constituent assessment was recently introduced. This sensor, called the Multiplex® (FORCE-A, Orsay, France), was used to monitor grape maturation by specifically monitoring anthocyanin accumulation. We derived the empirical anthocyanin content calibration curves for Champagne
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A new, commercial, fluorescence-based optical sensor for plant constituent assessment was recently introduced. This sensor, called the Multiplex® (FORCE-A, Orsay, France), was used to monitor grape maturation by specifically monitoring anthocyanin accumulation. We derived the empirical anthocyanin content calibration curves for Champagne red grape cultivars, and we also propose a general model for the influence of the proportion of red berries, skin anthocyanin content and berry size on Multiplex® indices. The Multiplex® was used on both berry samples in the laboratory and on intact clusters in the vineyard. We found that the inverted and log-transformed far-red fluorescence signal called the FERARI index, although sensitive to sample size and distance, is potentially the most widely applicable. The more robust indices, based on chlorophyll fluorescence excitation ratios, showed three ranges of dependence on anthocyanin content. We found that up to 0.16 mg cm−2, equivalent to approximately 0.6 mg g−1, all indices increase with accumulation of skin anthocyanin content. Excitation ratio-based indices decrease with anthocyanin accumulation beyond 0.27 mg cm−2. We showed that the Multiplex® can be advantageously used in vineyards on intact clusters for the non-destructive assessment of anthocyanin content of vine blocks and can now be tested on other fruits and vegetables based on the same model. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
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Open AccessArticle A Novel Acoustic Sensor Approach to Classify Seeds Based on Sound Absorption Spectra
Sensors 2010, 10(11), 10027-10039; https://doi.org/10.3390/s101110027
Received: 14 September 2010 / Revised: 1 November 2010 / Accepted: 5 November 2010 / Published: 9 November 2010
Cited by 3 | Viewed by 5475 | PDF Full-text (1539 KB) | HTML Full-text | XML Full-text
Abstract
A non-destructive and novel in situ acoustic sensor approach based on the sound absorption spectra was developed for identifying and classifying different seed types. The absorption coefficient spectra were determined by using the impedance tube measurement method. Subsequently, a multivariate statistical analysis, i.e
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A non-destructive and novel in situ acoustic sensor approach based on the sound absorption spectra was developed for identifying and classifying different seed types. The absorption coefficient spectra were determined by using the impedance tube measurement method. Subsequently, a multivariate statistical analysis, i.e., principal component analysis (PCA), was performed as a way to generate a classification of the seeds based on the soft independent modelling of class analogy (SIMCA) method. The results show that the sound absorption coefficient spectra of different seed types present characteristic patterns which are highly dependent on seed size and shape. In general, seed particle size and sphericity were inversely related with the absorption coefficient. PCA presented reliable grouping capabilities within the diverse seed types, since the 95% of the total spectral variance was described by the first two principal components. Furthermore, the SIMCA classification model based on the absorption spectra achieved optimal results as 100% of the evaluation samples were correctly classified. This study contains the initial structuring of an innovative method that will present new possibilities in agriculture and industry for classifying and determining physical properties of seeds and other materials. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
Open AccessArticle Effects of the Intermittent Pneumatic Circulator on Blood Pressure during Hemodialysis
Sensors 2010, 10(11), 10014-10026; https://doi.org/10.3390/s101110014
Received: 12 July 2010 / Revised: 10 September 2010 / Accepted: 23 October 2010 / Published: 9 November 2010
Cited by 1 | Viewed by 6220 | PDF Full-text (241 KB) | HTML Full-text | XML Full-text
Abstract
Hypotension is frequently reported during hemodialysis. This study aimed to examine the effect of the intermittent pneumatic circulator on blood pressure during hemodialysis. Sixteen subjects with chronic hemodialysis were recruited. Each subject randomly received two test conditions on separate days, hemodialysis with and
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Hypotension is frequently reported during hemodialysis. This study aimed to examine the effect of the intermittent pneumatic circulator on blood pressure during hemodialysis. Sixteen subjects with chronic hemodialysis were recruited. Each subject randomly received two test conditions on separate days, hemodialysis with and without the circulator. The circulator was applied to the subject on lower extremities during 0.5–1 hr, 1.5–2 hr, 2.5–3 hr, and 3.5–4 hr of hemodialysis. Systolic and diastolic blood pressures (SBP and DBP) and heart rate (HR) were analyzed at pre-dialysis, 1 hr, 2 hr, and 3 hr of hemodialysis. Stroke volume (SV) and cardiac output (CO) were evaluated between 2.5 and 3.0 hr of hemodialysis. Blood chemicals (sodium, calcium, potassium, and phosphorous) and Kt/V before and after each hemodialysis session were analyzed. The number of episodes of hypotension was also recorded. The circulator intervention significantly improved SBP and DBP across all time points (P = 0.002 for SBP; P = 0.002 for DBP). The frequency of hypotension was significantly decreased (P = 0.028). SV and CO were significantly improved with the circulator intervention (P = 0.017 for SV; P = 0.026 for CO) and no statistical significances were found on blood chemicals or Kt/V analyses. The results suggested that the circulator intervention helps stabilize blood pressure and appears to be a practical treatment. Future studies are suggested to develop new circulator innovations with sensor feedback systems to enhance safety and maximize treatment efficiency. Full article
(This article belongs to the Special Issue Sensors in Biomechanics and Biomedicine)
Open AccessArticle A QoS Scheme for a Congestion Core Network Based on Dissimilar QoS Structures in Smart-Phone Environments
Sensors 2010, 10(11), 10006-10013; https://doi.org/10.3390/s101110006
Received: 25 September 2010 / Revised: 20 October 2010 / Accepted: 25 October 2010 / Published: 9 November 2010
Cited by 3 | Viewed by 5724 | PDF Full-text (363 KB) | HTML Full-text | XML Full-text
Abstract
This study suggests an approach to effective transmission of multimedia content in a rapidly changing Internet environment including smart-phones. Guaranteeing QoS in networks is currently an important research topic. When transmitting Assured Forwarding (AF) packets in a Multi-DiffServ network environment, network A may
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This study suggests an approach to effective transmission of multimedia content in a rapidly changing Internet environment including smart-phones. Guaranteeing QoS in networks is currently an important research topic. When transmitting Assured Forwarding (AF) packets in a Multi-DiffServ network environment, network A may assign priority in an order AF1, AF2, AF3 and AF4; on the other hand, network B may reverse the order to a priority AF4, AF3, AF2 and AF1. In this case, the AF1 packets that received the best quality of service in network A will receive the lowest in network B, which may result in dropping of packets in network B and vice versa. This study suggests a way to guarantee QoS between hosts by minimizing the loss of AF packet class when one network transmits AF class packets to another network with differing principles. It is expected that QoS guarantees and their experimental value may be utilized as principles which can be applied to various mobile-web environments based on smart-phones. Full article
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