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Sensors, Volume 11, Issue 2 (February 2011), Pages 1246-2281

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Open AccessArticle A Refrigerated Web Camera for Photogrammetric Video Measurement inside Biomass Boilers and Combustion Analysis
Sensors 2011, 11(2), 1246-1260; doi:10.3390/s110201246
Received: 21 October 2010 / Revised: 24 November 2010 / Accepted: 18 January 2011 / Published: 25 January 2011
Cited by 3 | PDF Full-text (818 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes a prototype instrumentation system for photogrammetric measuring of bed and ash layers, as well as for flying particle detection and pursuit using a single device (CCD) web camera. The system was designed to obtain images of the combustion process [...] Read more.
This paper describes a prototype instrumentation system for photogrammetric measuring of bed and ash layers, as well as for flying particle detection and pursuit using a single device (CCD) web camera. The system was designed to obtain images of the combustion process in the interior of a domestic boiler. It includes a cooling system, needed because of the high temperatures in the combustion chamber of the boiler. The cooling system was designed using CFD simulations to ensure effectiveness. This method allows more complete and real-time monitoring of the combustion process taking place inside a boiler. The information gained from this system may facilitate the optimisation of boiler processes. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Preparation of Mesoporous and/or Macroporous SnO2-Based Powders and Their Gas-Sensing Properties as Thick Film Sensors
Sensors 2011, 11(2), 1261-1276; doi:10.3390/s110201261
Received: 13 December 2010 / Revised: 10 January 2011 / Accepted: 19 January 2011 / Published: 25 January 2011
Cited by 9 | PDF Full-text (812 KB) | HTML Full-text | XML Full-text
Abstract
Mesoporous and/or macroporous SnO2-based powders have been prepared and their gas-sensing properties as thick film sensors towards H2 and NO2 have been investigated. The mesopores and macropores of various SnO2-based powders were controlled by self-assembly of [...] Read more.
Mesoporous and/or macroporous SnO2-based powders have been prepared and their gas-sensing properties as thick film sensors towards H2 and NO2 have been investigated. The mesopores and macropores of various SnO2-based powders were controlled by self-assembly of sodium bis(2-ethylhexyl)sulfosuccinate and polymethyl-methacrylate (PMMA) microspheres (ca. 800 nm in diameter), respectively. The introduction of mesopores and macropores into SnO2-based sensors increased their sensor resistance in air significantly. The additions of SiO2 and Sb2O5 into mesoporous and/or macroporous SnO2 were found to improve the sensing properties of the sensors. The addition of SiO2 into mesoporous and/or macroporous SnO2 was found to increase the sensor resistance in air, whereas doping of Sb2O5 into mesoporous and/or macroporous SnO2 was found to markedly reduce the sensor resistance in air, and to increase the response to 1,000 ppm H2 as well as 1 ppm NO2 in air. Among all the sensors tested, meso-macroporous SnO2 added with 1 wt% SiO2 and 5 wt% Sb2O5, which were prepared with the above two templates simultaneously, exhibited the largest H2 and NO2 responses. Full article
(This article belongs to the Special Issue Gas Sensors - 2010)
Open AccessArticle Energy-Efficiency Analysis of a Distributed Queuing Medium Access Control Protocol for Biomedical Wireless Sensor Networks in Saturation Conditions
Sensors 2011, 11(2), 1277-1296; doi:10.3390/s110201277
Received: 15 December 2010 / Revised: 4 January 2011 / Accepted: 19 January 2011 / Published: 25 January 2011
Cited by 7 | PDF Full-text (289 KB) | HTML Full-text | XML Full-text
Abstract
The aging population and the high quality of life expectations in our society lead to the need of more efficient and affordable healthcare solutions. For this reason, this paper aims for the optimization of Medium Access Control (MAC) protocols for biomedical wireless [...] Read more.
The aging population and the high quality of life expectations in our society lead to the need of more efficient and affordable healthcare solutions. For this reason, this paper aims for the optimization of Medium Access Control (MAC) protocols for biomedical wireless sensor networks or wireless Body Sensor Networks (BSNs). The hereby presented schemes always have in mind the efficient management of channel resources and the overall minimization of sensors’ energy consumption in order to prolong sensors’ battery life. The fact that the IEEE 802.15.4 MAC does not fully satisfy BSN requirements highlights the need for the design of new scalable MAC solutions, which guarantee low-power consumption to the maximum number of body sensors in high density areas (i.e., in saturation conditions). In order to emphasize IEEE 802.15.4 MAC limitations, this article presents a detailed overview of this de facto standard for Wireless Sensor Networks (WSNs), which serves as a link for the introduction and initial description of our here proposed Distributed Queuing (DQ) MAC protocol for BSN scenarios. Within this framework, an extensive DQ MAC energy-consumption analysis in saturation conditions is presented to be able to evaluate its performance in relation to IEEE 802.5.4 MAC in highly dense BSNs. The obtained results show that the proposed scheme outperforms IEEE 802.15.4 MAC in average energy consumption per information bit, thus providing a better overall performance that scales appropriately to BSNs under high traffic conditions. These benefits are obtained by eliminating back-off periods and collisions in data packet transmissions, while minimizing the control overhead. Full article
(This article belongs to the Special Issue Sensors in Biomechanics and Biomedicine)
Open AccessArticle Active Integrated Filters for RF-Photonic Channelizers
Sensors 2011, 11(2), 1297-1320; doi:10.3390/s110201297
Received: 15 December 2010 / Revised: 17 January 2011 / Accepted: 17 January 2011 / Published: 25 January 2011
Cited by 6 | PDF Full-text (1511 KB) | HTML Full-text | XML Full-text
Abstract
A theoretical study of RF-photonic channelizers using four architectures formed by active integrated filters with tunable gains is presented. The integrated filters are enabled by two- and four-port nano-photonic couplers (NPCs). Lossless and three individual manufacturing cases with high transmission, high reflection, [...] Read more.
A theoretical study of RF-photonic channelizers using four architectures formed by active integrated filters with tunable gains is presented. The integrated filters are enabled by two- and four-port nano-photonic couplers (NPCs). Lossless and three individual manufacturing cases with high transmission, high reflection, and symmetric couplers are assumed in the work. NPCs behavior is dependent upon the phenomenon of frustrated total internal reflection. Experimentally, photonic channelizers are fabricated in one single semiconductor chip on multi-quantum well epitaxial InP wafers using conventional microelectronics processing techniques. A state space modeling approach is used to derive the transfer functions and analyze the stability of these filters. The ability of adapting using the gains is demonstrated. Our simulation results indicate that the characteristic bandpass and notch filter responses of each structure are the basis of channelizer architectures, and optical gain may be used to adjust filter parameters to obtain a desired frequency magnitude response, especially in the range of 1–5 GHz for the chip with a coupler separation of ~9 mm. Preliminarily, the measurement of spectral response shows enhancement of quality factor by using higher optical gains. The present compact active filters on an InP-based integrated photonic circuit hold the potential for a variety of channelizer applications. Compared to a pure RF channelizer, photonic channelizers may perform both channelization and down-conversion in an optical domain. Full article
(This article belongs to the Special Issue Optical Resonant Microsensors)
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Open AccessArticle Photo-EMF Sensitivity of Porous Silicon Thin Layer–Crystalline Silicon Heterojunction to Ammonia Adsorption
Sensors 2011, 11(2), 1321-1327; doi:10.3390/s110201321
Received: 20 December 2010 / Revised: 13 January 2011 / Accepted: 21 January 2011 / Published: 25 January 2011
Cited by 3 | PDF Full-text (630 KB) | HTML Full-text | XML Full-text
Abstract
A new method of using photo-electromotive force in detecting gas and controlling sensitivity is proposed. Photo-electromotive force on the heterojunction between porous silicon thin layer and crystalline silicon wafer depends on the concentration of ammonia in the measurement chamber. A porous silicon [...] Read more.
A new method of using photo-electromotive force in detecting gas and controlling sensitivity is proposed. Photo-electromotive force on the heterojunction between porous silicon thin layer and crystalline silicon wafer depends on the concentration of ammonia in the measurement chamber. A porous silicon thin layer was formed by electrochemical etching on p-type silicon wafer. A gas and light transparent electrical contact was manufactured to this porous layer. Photo-EMF sensitivity corresponding to ammonia concentration in the range from 10 ppm to 1,000 ppm can be maximized by controlling the intensity of illumination light. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Carbon Paste Electrodes Made from Different Carbonaceous Materials: Application in the Study of Antioxidants
Sensors 2011, 11(2), 1328-1344; doi:10.3390/s110201328
Received: 23 December 2010 / Accepted: 20 January 2011 / Published: 25 January 2011
Cited by 32 | PDF Full-text (1003 KB) | HTML Full-text | XML Full-text
Abstract
This work describes the sensing properties of carbon paste electrodes (CPEs) prepared from three different types of carbonaceous materials: graphite, carbon microspheres and carbon nanotubes. The electrochemical responses towards antioxidants including vanillic acid, catechol, gallic acid, L-ascorbic acid and L-glutathione have been [...] Read more.
This work describes the sensing properties of carbon paste electrodes (CPEs) prepared from three different types of carbonaceous materials: graphite, carbon microspheres and carbon nanotubes. The electrochemical responses towards antioxidants including vanillic acid, catechol, gallic acid, L-ascorbic acid and L-glutathione have been analyzed and compared. It has been demonstrated that the electrodes based on carbon microspheres show the best performances in terms of kinetics and stability, whereas G-CPEs presented the smallest detection limit for all the antioxidants analyzed. An array of electrodes has been constructed using the three types of electrodes. As demonstrated by means of Principal Component Analysis, the system is able to discriminate among antioxidants as a function of their chemical structure and reactivity. Full article
(This article belongs to the Special Issue Bioinspired Sensor Systems)
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Open AccessArticle A Trust Evaluation Algorithm for Wireless Sensor Networks Based on Node Behaviors and D-S Evidence Theory
Sensors 2011, 11(2), 1345-1360; doi:10.3390/s110201345
Received: 9 December 2010 / Revised: 27 December 2010 / Accepted: 18 January 2011 / Published: 25 January 2011
Cited by 30 | PDF Full-text (359 KB) | HTML Full-text | XML Full-text
Abstract
For wireless sensor networks (WSNs), many factors, such as mutual interference of wireless links, battlefield applications and nodes exposed to the environment without good physical protection, result in the sensor nodes being more vulnerable to be attacked and compromised. In order to [...] Read more.
For wireless sensor networks (WSNs), many factors, such as mutual interference of wireless links, battlefield applications and nodes exposed to the environment without good physical protection, result in the sensor nodes being more vulnerable to be attacked and compromised. In order to address this network security problem, a novel trust evaluation algorithm defined as NBBTE (Node Behavioral Strategies Banding Belief Theory of the Trust Evaluation Algorithm) is proposed, which integrates the approach of nodes behavioral strategies and modified evidence theory. According to the behaviors of sensor nodes, a variety of trust factors and coefficients related to the network application are established to obtain direct and indirect trust values through calculating weighted average of trust factors. Meanwhile, the fuzzy set method is applied to form the basic input vector of evidence. On this basis, the evidence difference is calculated between the indirect and direct trust values, which link the revised D-S evidence combination rule to finally synthesize integrated trust value of nodes. The simulation results show that NBBTE can effectively identify malicious nodes and reflects the characteristic of trust value that ‘hard to acquire and easy to lose’. Furthermore, it is obvious that the proposed scheme has an outstanding advantage in terms of illustrating the real contribution of different nodes to trust evaluation. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Preparation and Electrochemical Characterization of a Carbon Ceramic Electrode Modified with Ferrocenecarboxylic Acid
Sensors 2011, 11(2), 1361-1374; doi:10.3390/s110201361
Received: 3 December 2010 / Revised: 4 January 2011 / Accepted: 17 January 2011 / Published: 25 January 2011
Cited by 13 | PDF Full-text (823 KB) | HTML Full-text | XML Full-text
Abstract
The present paper describes the characterization of a carbon ceramic electrode modified with ferrocenecarboxylic acid (designated as CCE/Fc) by electrochemical techniques and its detection ability for dopamine. From cyclic voltammetric experiments, it was observed that the CCE/Fc presented a redox pair at [...] Read more.
The present paper describes the characterization of a carbon ceramic electrode modified with ferrocenecarboxylic acid (designated as CCE/Fc) by electrochemical techniques and its detection ability for dopamine. From cyclic voltammetric experiments, it was observed that the CCE/Fc presented a redox pair at Epa = 405 mV and Epc = 335 mV (DE = 70 mV), related to the ferrocene/ferrocenium process. Studies showed a considerably increase in the redox currents at the same oxidation potential of ferrocene (Epa = 414 mV vs. Ag/AgCl) in the presence of dopamine (DA), differently from those observed when using only the unmodified CCE, in which the anodic peak increase was considerably lower. From SWV experiments, it was observed that the AA (ascorbic acid) oxidation at CCE/Fc occurred in a different potential than the DA oxidation (with a peak separation of approximately 200 mV). Moreover, CCE/Fc did not respond to different AA concentrations, indicating that it is possible to determine DA without the AA interference with this electrode. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle A Simple Fiber Bragg Grating-Based Sensor Network Architecture with Self-Protecting and Monitoring Functions
Sensors 2011, 11(2), 1375-1382; doi:10.3390/s110201375
Received: 22 November 2010 / Revised: 6 January 2011 / Accepted: 14 January 2011 / Published: 26 January 2011
Cited by 16 | PDF Full-text (365 KB) | HTML Full-text | XML Full-text
Abstract
A novel fiber Bragg grating (FBG)-based passive sensor architecture, which can be used to protect the fiber cut and monitor the multiple sensors simultaneously, is proposed and experimentally demonstrated. Here, we employ a wavelength-tunable erbium-doped fiber (EDF) laser scheme with 25 km [...] Read more.
A novel fiber Bragg grating (FBG)-based passive sensor architecture, which can be used to protect the fiber cut and monitor the multiple sensors simultaneously, is proposed and experimentally demonstrated. Here, we employ a wavelength-tunable erbium-doped fiber (EDF) laser scheme with 25 km cavity length acting as the detecting light source in central office (CO). Each FBG sensor, serving as a feedback element, is used in proposed sensor architecture. By tuning the tunable bandpass filter (TBF) placing inside cavity to match the corresponding Bragg wavelength of FBG over the amplification bandwidth, we can retrieve the related wavelength lasing for the FBG sensing and monitoring simultaneously. Moreover, the survivability and capacity of the passive FBG sensor architecture can be also enhanced. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Study of IEEE 802.15.4 Security Framework for Wireless Body Area Networks
Sensors 2011, 11(2), 1383-1395; doi:10.3390/s110201383
Received: 14 December 2010 / Revised: 5 January 2011 / Accepted: 18 January 2011 / Published: 26 January 2011
Cited by 23 | PDF Full-text (498 KB) | HTML Full-text | XML Full-text
Abstract
A Wireless Body Area Network (WBAN) is a collection of low-power and lightweight wireless sensor nodes that are used to monitor the human body functions and the surrounding environment. It supports a number of innovative and interesting applications, including ubiquitous healthcare and [...] Read more.
A Wireless Body Area Network (WBAN) is a collection of low-power and lightweight wireless sensor nodes that are used to monitor the human body functions and the surrounding environment. It supports a number of innovative and interesting applications, including ubiquitous healthcare and Consumer Electronics (CE) applications. Since WBAN nodes are used to collect sensitive (life-critical) information and may operate in hostile environments, they require strict security mechanisms to prevent malicious interaction with the system. In this paper, we first highlight major security requirements and Denial of Service (DoS) attacks in WBAN at Physical, Medium Access Control (MAC), Network, and Transport layers. Then we discuss the IEEE 802.15.4 security framework and identify the security vulnerabilities and major attacks in the context of WBAN. Different types of attacks on the Contention Access Period (CAP) and Contention Free Period (CFP) parts of the superframe are analyzed and discussed. It is observed that a smart attacker can successfully corrupt an increasing number of GTS slots in the CFP period and can considerably affect the Quality of Service (QoS) in WBAN (since most of the data is carried in CFP period). As we increase the number of smart attackers the corrupted GTS slots are eventually increased, which prevents the legitimate nodes to utilize the bandwidth efficiently. This means that the direct adaptation of IEEE 802.15.4 security framework for WBAN is not totally secure for certain WBAN applications. New solutions are required to integrate high level security in WBAN. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Path Renewal Method in Filtering Based Wireless Sensor Networks
Sensors 2011, 11(2), 1396-1404; doi:10.3390/s110201396
Received: 25 November 2010 / Revised: 4 January 2011 / Accepted: 21 January 2011 / Published: 26 January 2011
Cited by 5 | PDF Full-text (265 KB) | HTML Full-text | XML Full-text
Abstract
In applications of wireless sensor networks, there are many security issues. Attackers can create false reports and transmit the reports to the networks. These false reports can lead not only false alarms, but also the depletion of limited energy resources. In order [...] Read more.
In applications of wireless sensor networks, there are many security issues. Attackers can create false reports and transmit the reports to the networks. These false reports can lead not only false alarms, but also the depletion of limited energy resources. In order to filter out such false reports during the forwarding process, Ye et al. proposed the statistical en-route filtering (SEF). Several research efforts to enhance the efficiency of SEF have been made. Especially, the path selection method proposed by Sun et al. can improve the detection power of SEF by considering the information on the filtering keys of and distances of upstream paths. However, such selection mechanism could lead to favored paths in heavy traffic, which would result in unbalanced energy consumption. In this paper, we propose a path renewal method to provide load balancing for sensor networks in terms of energy consumption. In our method, a node renews its upstream path to save energy resources if the remaining energy of and the communication traffic of the node exceed some threshold values. We show the effectiveness of the proposed method in terms of balanced energy consumption and filtering power by providing simulation results. Full article
Open AccessArticle The Averaging Effect of Odorant Mixing as Determined by Air Dilution Sensory Tests: A Case Study on Reduced Sulfur Compounds
Sensors 2011, 11(2), 1405-1417; doi:10.3390/s110201405
Received: 14 December 2010 / Revised: 5 January 2011 / Accepted: 20 January 2011 / Published: 26 January 2011
Cited by 30 | PDF Full-text (335 KB) | HTML Full-text | XML Full-text
Abstract
To learn more about the effects of mixing different odorants, a series of air dilution sensory (ADS) tests were conducted using four reduced sulfur compounds [RSC: hydrogen sulfide (H2S), methanethiol (CH3SH), dimethylsulfide (DMS), and dimethyldisulfide (DMDS)] at varying [...] Read more.
To learn more about the effects of mixing different odorants, a series of air dilution sensory (ADS) tests were conducted using four reduced sulfur compounds [RSC: hydrogen sulfide (H2S), methanethiol (CH3SH), dimethylsulfide (DMS), and dimethyldisulfide (DMDS)] at varying concentration levels. The tests were initially conducted by analyzing samples containing single individual RSCs at a wide range of concentrations. The resulting data were then evaluated to define the empirical relationship for each RSC between the dilution-to-threshold (D/T) ratio and odor intensity (OI) scaling. Based on the relationships defined for each individual RSC, the D/T ratios were estimated for a synthetic mixture of four RSCs. The effect of mixing was then examined by assessing the relative contribution of each RSC to those estimates with the aid of the actually measured D/T values. This stepwise test confirmed that the odor intensity of the synthetic mixture is not governed by the common theoretical basis (e.g., rule of additivity, synergism, or a stronger component model) but is best represented by the averaged contribution of all RSC components. The overall results of this study thus suggest that the mixing phenomenon between odorants with similar chemical properties (like RSC family) can be characterized by the averaging effect of all participants. Full article
(This article belongs to the Special Issue Direct and Indirect Sensing of Odor and VOCs and Their Control)
Open AccessArticle A Novel Method for In-Situ Monitoring of Local Voltage, Temperature and Humidity Distributions in Fuel Cells Using Flexible Multi-Functional Micro Sensors
Sensors 2011, 11(2), 1418-1432; doi:10.3390/s110201418
Received: 10 December 2010 / Revised: 11 January 2011 / Accepted: 24 January 2011 / Published: 26 January 2011
Cited by 12 | PDF Full-text (1057 KB) | HTML Full-text | XML Full-text
Abstract
In this investigation, micro voltage, temperature and humidity sensors were fabricated and integrated for the first time on a stainless steel foil using micro-electro-mechanical systems (MEMS). These flexible multi-functional micro sensors have the advantages of high temperature resistance, flexibility, smallness, high sensitivity [...] Read more.
In this investigation, micro voltage, temperature and humidity sensors were fabricated and integrated for the first time on a stainless steel foil using micro-electro-mechanical systems (MEMS). These flexible multi-functional micro sensors have the advantages of high temperature resistance, flexibility, smallness, high sensitivity and precision of location. They were embedded in a proton exchange membrane fuel cell (PEMFC) and used to simultaneously measure variations in the inner voltage, temperature and humidity. The accuracy and reproducibility of the calibrated results obtained using the proposed micro sensors is excellent. The experimental results indicate that, at high current density and 100%RH or 75%RH, the relative humidity midstream and downstream saturates due to severe flooding. The performance of the PEM fuel cell can be stabilized using home-made flexible multi-functional micro sensors by the in-situ monitoring of local voltage, temperature and humidity distributions within it. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle MEMS-Based Power Generation Techniques for Implantable Biosensing Applications
Sensors 2011, 11(2), 1433-1460; doi:10.3390/s110201433
Received: 29 October 2010 / Revised: 21 January 2011 / Accepted: 23 January 2011 / Published: 26 January 2011
Cited by 27 | PDF Full-text (493 KB) | HTML Full-text | XML Full-text
Abstract
Implantable biosensing is attractive for both medical monitoring and diagnostic applications. It is possible to monitor phenomena such as physical loads on joints or implants, vital signs, or osseointegration in vivo and in real time. Microelectromechanical (MEMS)-based generation techniques can allow for [...] Read more.
Implantable biosensing is attractive for both medical monitoring and diagnostic applications. It is possible to monitor phenomena such as physical loads on joints or implants, vital signs, or osseointegration in vivo and in real time. Microelectromechanical (MEMS)-based generation techniques can allow for the autonomous operation of implantable biosensors by generating electrical power to replace or supplement existing battery-based power systems. By supplementing existing battery-based power systems for implantable biosensors, the operational lifetime of the sensor is increased. In addition, the potential for a greater amount of available power allows additional components to be added to the biosensing module, such as computational and wireless and components, improving functionality and performance of the biosensor. Photovoltaic, thermovoltaic, micro fuel cell, electrostatic, electromagnetic, and piezoelectric based generation schemes are evaluated in this paper for applicability for implantable biosensing. MEMS-based generation techniques that harvest ambient energy, such as vibration, are much better suited for implantable biosensing applications than fuel-based approaches, producing up to milliwatts of electrical power. High power density MEMS-based approaches, such as piezoelectric and electromagnetic schemes, allow for supplemental and replacement power schemes for biosensing applications to improve device capabilities and performance. In addition, this may allow for the biosensor to be further miniaturized, reducing the need for relatively large batteries with respect to device size. This would cause the implanted biosensor to be less invasive, increasing the quality of care received by the patient. Full article
(This article belongs to the Special Issue Advanced Embedded Sensors)
Open AccessArticle A Parkinson’s Disease Measurement System Using Laser Lines and a CMOS Image Sensor
Sensors 2011, 11(2), 1461-1475; doi:10.3390/s110201461
Received: 8 December 2010 / Revised: 13 January 2011 / Accepted: 17 January 2011 / Published: 26 January 2011
Cited by 9 | PDF Full-text (503 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a non-invasive, non-contact system for the measurement of the arterial dorsum manus vibration waveforms of Parkinson disease patients. The laser line method is applied to detect the dorsum manus vibration in rest and postural situations. The proposed measurement system [...] Read more.
This paper presents a non-invasive, non-contact system for the measurement of the arterial dorsum manus vibration waveforms of Parkinson disease patients. The laser line method is applied to detect the dorsum manus vibration in rest and postural situations. The proposed measurement system mainly consists of a laser diode and a low cost complementary metal-oxide semiconductor (CMOS) image sensor. Laser line and centroid methods are combined with the Fast Fourier Transform (FFT) in this study. The shape and frequency and relative frequency of the dorsum manus vibration waveforms can be detected rapidly using our Parkinson’s disease measurement system. A laser line near the wrist joint is used as the testing line. The experimental results show an obvious increase in the amplitude and frequency of dorsum manus variation in the measured region in patients suffering from Parkinson’s disease, indicating the obvious effects of the disease. Both in postural and rest state measurements, as the patient disease age increases the vibration frequency increases. The measurement system is well suited for evaluating and pre-diagnosing early stage Parkinson’s disease. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Resonant Photonic Biosensors with Polarization-Based Multiparametric Discrimination in Each Channel
Sensors 2011, 11(2), 1476-1488; doi:10.3390/s110201476
Received: 10 December 2010 / Revised: 4 January 2011 / Accepted: 18 January 2011 / Published: 26 January 2011
Cited by 37 | PDF Full-text (456 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we describe guided-mode resonance biochemical sensor technology. We briefly discuss sensor fabrication and show measured binding dynamics for example biomaterials in use in our laboratories. We then turn our attention to a particularly powerful attribute of this technology not [...] Read more.
In this paper, we describe guided-mode resonance biochemical sensor technology. We briefly discuss sensor fabrication and show measured binding dynamics for example biomaterials in use in our laboratories. We then turn our attention to a particularly powerful attribute of this technology not possessed by competing methods. This attribute is the facile generation of multiple resonance peaks at an identical physical location on the sensor surface. These peaks respond uniquely to the biomolecular event, thereby enriching the data set available for event quantification. The peaks result from individual, polarization-dependent resonant leaky modes that are the foundation of this technology. Thus, by modeling the binding event and fitting to a rigorous electromagnetic formalism, we can determine individual attributes of the biolayer and its surroundings and avoid a separate reference site for background monitoring. Examples provide dual-polarization quantification of biotin binding to a silane-coated sensor as well as binding of the cancer biomarker protein calreticulin to its monoclonal IgG capture antibody. Finally, we present dual-polarization resonance response for poly (allylamine hydrochloride) binding to the sensor with corresponding results of backfitting to a simple model; this differentiates the contributions from biolayer adhesion and background changes. Full article
(This article belongs to the Special Issue Optical Resonant Microsensors)
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Open AccessArticle Advances in SXFA-Coated SAW Chemical Sensors for Organophosphorous Compound Detection
Sensors 2011, 11(2), 1526-1541; doi:10.3390/s110201526
Received: 5 December 2010 / Revised: 20 January 2011 / Accepted: 22 January 2011 / Published: 27 January 2011
Cited by 21 | PDF Full-text (1151 KB) | HTML Full-text | XML Full-text
Abstract
A polymer-coated surface acoustic wave (SAW)-based chemical sensor for organophosphorous compound sensing at extremely low concentrations was developed, in which a dual-delay-line oscillator coated with fluoroalcoholpolysiloxane (SXFA) acted as the sensor element. Response mechanism analysis was performed on the SXFA-coated chemical sensor, [...] Read more.
A polymer-coated surface acoustic wave (SAW)-based chemical sensor for organophosphorous compound sensing at extremely low concentrations was developed, in which a dual-delay-line oscillator coated with fluoroalcoholpolysiloxane (SXFA) acted as the sensor element. Response mechanism analysis was performed on the SXFA-coated chemical sensor, resulting in the optimal design parameters. The shear modulus of the SXFA, which is the key parameter for theoretical simulation, was extracted experimentally. New designs were done on the SAW devices to decrease the insertion loss. Referring to the new phase modulation approach, superior short-term frequency stability (±2 Hz in seconds) was achieved from the SAW oscillator using the fabricated 300 MHz delay line as the feedback element. In the sensor experiment on dimethylmethylphosphonate (DMMP) detection, the fabricated SXFA-coated chemical sensor exhibited an excellent threshold detection limit up to 0.004 mg/m3 (0.7 ppb) and good sensitivity (~485 Hz/mg/m3 for a DMMP concentration of 2~14 mg/m3). Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle An Autonomous Wearable System for Predicting and Detecting Localised Muscle Fatigue
Sensors 2011, 11(2), 1542-1557; doi:10.3390/s110201542
Received: 15 December 2010 / Revised: 12 January 2011 / Accepted: 19 January 2011 / Published: 27 January 2011
Cited by 11 | PDF Full-text (2878 KB) | HTML Full-text | XML Full-text
Abstract
Muscle fatigue is an established area of research and various types of muscle fatigue have been clinically investigated in order to fully understand the condition. This paper demonstrates a non-invasive technique used to automate the fatigue detection and prediction process. The system [...] Read more.
Muscle fatigue is an established area of research and various types of muscle fatigue have been clinically investigated in order to fully understand the condition. This paper demonstrates a non-invasive technique used to automate the fatigue detection and prediction process. The system utilises the clinical aspects such as kinematics and surface electromyography (sEMG) of an athlete during isometric contractions. Various signal analysis methods are used illustrating their applicability in real-time settings. This demonstrated system can be used in sports scenarios to promote muscle growth/performance or prevent injury. To date, research on localised muscle fatigue focuses on the clinical side and lacks the implementation for detecting/predicting localised muscle fatigue using an autonomous system. Results show that automating the process of localised muscle fatigue detection/prediction is promising. The autonomous fatigue system was tested on five individuals showing 90.37% accuracy on average of correct classification and an error of 4.35% in predicting the time to when fatigue will onset. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Long Period Gratings in Random Hole Optical Fibers for Refractive Index Sensing
Sensors 2011, 11(2), 1558-1564; doi:10.3390/s110201558
Received: 4 January 2011 / Revised: 18 January 2011 / Accepted: 19 January 2011 / Published: 27 January 2011
Cited by 3 | PDF Full-text (289 KB) | HTML Full-text | XML Full-text
Abstract
We have demonstrated the fabrication of long period gratings in random hole optical fibers. The long period gratings are fabricated by a point-by-point technique using a CO2 laser. The gratings with a periodicity of 450 µm are fabricated and a maximum [...] Read more.
We have demonstrated the fabrication of long period gratings in random hole optical fibers. The long period gratings are fabricated by a point-by-point technique using a CO2 laser. The gratings with a periodicity of 450 µm are fabricated and a maximum coupling efficiency of −9.81 dB has been achieved. Sensing of different refractive indices in the surrounding mediums is demonstrated by applying standard liquids with refractive indices from 1.400 to 1.440 to the long period grating. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Secure Chaotic Map Based Block Cryptosystem with Application to Camera Sensor Networks
Sensors 2011, 11(2), 1607-1619; doi:10.3390/s110201607
Received: 10 December 2010 / Revised: 10 January 2011 / Accepted: 15 January 2011 / Published: 27 January 2011
Cited by 5 | PDF Full-text (465 KB) | HTML Full-text | XML Full-text
Abstract
Recently, Wang et al. presented an efficient logistic map based block encryption system. The encryption system employs feedback ciphertext to achieve plaintext dependence of sub-keys. Unfortunately, we discovered that their scheme is unable to withstand key stream attack. To improve its security, [...] Read more.
Recently, Wang et al. presented an efficient logistic map based block encryption system. The encryption system employs feedback ciphertext to achieve plaintext dependence of sub-keys. Unfortunately, we discovered that their scheme is unable to withstand key stream attack. To improve its security, this paper proposes a novel chaotic map based block cryptosystem. At the same time, a secure architecture for camera sensor network is constructed. The network comprises a set of inexpensive camera sensors to capture the images, a sink node equipped with sufficient computation and storage capabilities and a data processing server. The transmission security between the sink node and the server is gained by utilizing the improved cipher. Both theoretical analysis and simulation results indicate that the improved algorithm can overcome the flaws and maintain all the merits of the original cryptosystem. In addition, computational costs and efficiency of the proposed scheme are encouraging for the practical implementation in the real environment as well as camera sensor network. Full article
Open AccessArticle Mobile Location with NLOS Identification and Mitigation Based on Modified Kalman Filtering
Sensors 2011, 11(2), 1641-1656; doi:10.3390/s110201641
Received: 25 December 2010 / Revised: 20 January 2011 / Accepted: 21 January 2011 / Published: 27 January 2011
Cited by 12 | PDF Full-text (266 KB) | HTML Full-text | XML Full-text
Abstract
In order to enhance accuracy and reliability of wireless location in the mixed line-of-sight (LOS) and non-line-of-sight (NLOS) environments, a robust mobile location algorithm is presented to track the position of a mobile node (MN). An extended Kalman filter (EKF) modified in [...] Read more.
In order to enhance accuracy and reliability of wireless location in the mixed line-of-sight (LOS) and non-line-of-sight (NLOS) environments, a robust mobile location algorithm is presented to track the position of a mobile node (MN). An extended Kalman filter (EKF) modified in the updating phase is utilized to reduce the NLOS error in rough wireless environments, in which the NLOS bias contained in each measurement range is estimated directly by the constrained optimization method. To identify the change of channel situation between NLOS and LOS, a low complexity identification method based on innovation vectors is proposed. Numerical results illustrate that the location errors of the proposed algorithm are all significantly smaller than those of the iterated NLOS EKF algorithm and the conventional EKF algorithm in different LOS/NLOS conditions. Moreover, this location method does not require any statistical distribution knowledge of the NLOS error. In addition, complexity experiments suggest that this algorithm supports real-time applications. Full article
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Open AccessArticle The Properties of Terrestrial Laser System Intensity for Measuring Leaf Geometries: A Case Study with Conference Pear Trees (Pyrus Communis)
Sensors 2011, 11(2), 1657-1681; doi:10.3390/s110201657
Received: 29 December 2010 / Revised: 14 January 2011 / Accepted: 25 January 2011 / Published: 28 January 2011
Cited by 14 | PDF Full-text (1041 KB) | HTML Full-text | XML Full-text
Abstract
Light Detection and Ranging (LiDAR) technology can be a valuable tool for describing and quantifying vegetation structure. However, because of their size, extraction of leaf geometries remains complicated. In this study, the intensity data produced by the Terrestrial Laser System (TLS) FARO [...] Read more.
Light Detection and Ranging (LiDAR) technology can be a valuable tool for describing and quantifying vegetation structure. However, because of their size, extraction of leaf geometries remains complicated. In this study, the intensity data produced by the Terrestrial Laser System (TLS) FARO LS880 is corrected for the distance effect and its relationship with the angle of incidence between the laser beam and the surface of the leaf of a Conference Pear tree (Pyrus Commmunis) is established. The results demonstrate that with only intensity, this relationship has a potential for determining the angle of incidence with the leaves surface with a precision of ±5° for an angle of incidence smaller than 60°, whereas it is more variable for an angle of incidence larger than 60°. It appears that TLS beam footprint, leaf curvatures and leaf wrinkles have an impact on the relationship between intensity and angle of incidence, though, this analysis shows that the intensity of scanned leaves has a potential to eliminate ghost points and to improve their meshing. Full article
(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)
Open AccessArticle IJA: An Efficient Algorithm for Query Processing in Sensor Networks
Sensors 2011, 11(2), 1682-1692; doi:10.3390/s110201682
Received: 29 November 2010 / Revised: 10 January 2011 / Accepted: 12 January 2011 / Published: 28 January 2011
Cited by 2 | PDF Full-text (364 KB) | HTML Full-text | XML Full-text
Abstract
One of main features in sensor networks is the function that processes real time state information after gathering needed data from many domains. The component technologies consisting of each node called a sensor node that are including physical sensors, processors, actuators and [...] Read more.
One of main features in sensor networks is the function that processes real time state information after gathering needed data from many domains. The component technologies consisting of each node called a sensor node that are including physical sensors, processors, actuators and power have advanced significantly over the last decade. Thanks to the advanced technology, over time sensor networks have been adopted in an all-round industry sensing physical phenomenon. However, sensor nodes in sensor networks are considerably constrained because with their energy and memory resources they have a very limited ability to process any information compared to conventional computer systems. Thus query processing over the nodes should be constrained because of their limitations. Due to the problems, the join operations in sensor networks are typically processed in a distributed manner over a set of nodes and have been studied. By way of example while simple queries, such as select and aggregate queries, in sensor networks have been addressed in the literature, the processing of join queries in sensor networks remains to be investigated. Therefore, in this paper, we propose and describe an Incremental Join Algorithm (IJA) in Sensor Networks to reduce the overhead caused by moving a join pair to the final join node or to minimize the communication cost that is the main consumer of the battery when processing the distributed queries in sensor networks environments. At the same time, the simulation result shows that the proposed IJA algorithm significantly reduces the number of bytes to be moved to join nodes compared to the popular synopsis join algorithm. Full article
Open AccessArticle The Effect of Tensile Hysteresis and Contact Resistance on the Performance of Strain-Resistant Elastic-Conductive Webbing
Sensors 2011, 11(2), 1693-1705; doi:10.3390/s110201693
Received: 1 December 2010 / Revised: 20 January 2011 / Accepted: 24 January 2011 / Published: 28 January 2011
Cited by 8 | PDF Full-text (1242 KB) | HTML Full-text | XML Full-text
Abstract
To use e-textiles as a strain-resistance sensor they need to be both elastic and conductive. Three kinds of elastic-conductive webbings, including flat, tubular, and belt webbings, made of Lycra fiber and carbon coated polyamide fiber, were used in this study. The strain-resistance [...] Read more.
To use e-textiles as a strain-resistance sensor they need to be both elastic and conductive. Three kinds of elastic-conductive webbings, including flat, tubular, and belt webbings, made of Lycra fiber and carbon coated polyamide fiber, were used in this study. The strain-resistance properties of the webbings were evaluated in stretch-recovery tests and measured within 30% strain. It was found that tensile hysteresis and contact resistance significantly influence the tensile elasticity and the resistance sensitivity of the webbings. The results showed that the webbing structure definitely contributes to the tensile hysteresis and contact resistance. The smaller the friction is among the yarns in the belt webbing, the smaller the tensile hysteresis loss. However the close proximity of the conductive yarns in flat and tubular webbings results in a lower contact resistance. Full article
(This article belongs to the Special Issue Advanced Sensing Technology for Nondestructive Evaluation)
Open AccessArticle Design and Implementation of a Wireless Sensor Network-Based Remote Water-Level Monitoring System
Sensors 2011, 11(2), 1706-1720; doi:10.3390/s110201706
Received: 3 December 2010 / Revised: 20 January 2011 / Accepted: 22 January 2011 / Published: 28 January 2011
Cited by 9 | PDF Full-text (690 KB) | HTML Full-text | XML Full-text
Abstract
The proposed remote water-level monitoring system (RWMS) consists of a field sensor module, a base station module, adata center module and aWEB releasing module. It has advantages in real time and synchronized remote control, expandability, and anti-jamming capabilities. The RWMS can realize [...] Read more.
The proposed remote water-level monitoring system (RWMS) consists of a field sensor module, a base station module, adata center module and aWEB releasing module. It has advantages in real time and synchronized remote control, expandability, and anti-jamming capabilities. The RWMS can realize real-time remote monitoring, providing early warning of events and protection of the safety of monitoring personnel under certain dangerous circumstances. This system has been successfully applied in Poyanghu Lake. The cost of the whole system is approximately 1,500 yuan (RMB). Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Leg Motion Classification with Artificial Neural Networks Using Wavelet-Based Features of Gyroscope Signals
Sensors 2011, 11(2), 1721-1743; doi:10.3390/s110201721
Received: 14 December 2010 / Revised: 10 January 2011 / Accepted: 13 January 2011 / Published: 28 January 2011
Cited by 22 | PDF Full-text (1558 KB) | HTML Full-text | XML Full-text
Abstract
We extract the informative features of gyroscope signals using the discrete wavelet transform (DWT) decomposition and provide them as input to multi-layer feed-forward artificial neural networks (ANNs) for leg motion classification. Since the DWT is based on correlating the analyzed signal with [...] Read more.
We extract the informative features of gyroscope signals using the discrete wavelet transform (DWT) decomposition and provide them as input to multi-layer feed-forward artificial neural networks (ANNs) for leg motion classification. Since the DWT is based on correlating the analyzed signal with a prototype wavelet function, selection of the wavelet type can influence the performance of wavelet-based applications significantly. We also investigate the effect of selecting different wavelet families on classification accuracy and ANN complexity and provide a comparison between them. The maximum classification accuracy of 97.7% is achieved with the Daubechies wavelet of order 16 and the reverse bi-orthogonal (RBO) wavelet of order 3.1, both with similar ANN complexity. However, the RBO 3.1 wavelet is preferable because of its lower computational complexity in the DWTdecomposition and reconstruction. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Stereovision Matching Strategy for Images Captured with Fish-Eye Lenses in Forest Environments
Sensors 2011, 11(2), 1756-1783; doi:10.3390/s110201756
Received: 21 December 2010 / Revised: 12 January 2011 / Accepted: 27 January 2011 / Published: 31 January 2011
Cited by 6 | PDF Full-text (673 KB) | HTML Full-text | XML Full-text
Abstract
We present a novel strategy for computing disparity maps from hemispherical stereo images obtained with fish-eye lenses in forest environments. At a first segmentation stage, the method identifies textures of interest to be either matched or discarded. This is achieved by applying [...] Read more.
We present a novel strategy for computing disparity maps from hemispherical stereo images obtained with fish-eye lenses in forest environments. At a first segmentation stage, the method identifies textures of interest to be either matched or discarded. This is achieved by applying a pattern recognition strategy based on the combination of two classifiers: Fuzzy Clustering and Bayesian. At a second stage, a stereovision matching process is performed based on the application of four stereovision matching constraints: epipolar, similarity, uniqueness and smoothness. The epipolar constraint guides the process. The similarity and uniqueness are mapped through a decision making strategy based on a weighted fuzzy similarity approach, obtaining a disparity map. This map is later filtered through the Hopfield Neural Network framework by considering the smoothness constraint. The combination of the segmentation and stereovision matching approaches makes the main contribution. The method is compared against the usage of simple features and combined similarity matching strategies. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
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Open AccessArticle Measurement of Blood Pressure Using an Arterial Pulsimeter Equipped with a Hall Device
Sensors 2011, 11(2), 1784-1793; doi:10.3390/s110201784
Received: 1 December 2010 / Revised: 27 January 2011 / Accepted: 29 January 2011 / Published: 31 January 2011
Cited by 25 | PDF Full-text (403 KB) | HTML Full-text | XML Full-text
Abstract
To measure precise blood pressure (BP) and pulse rate without using a cuff, we have developed an arterial pulsimeter consisting of a small, portable apparatus incorporating a Hall device. Regression analysis of the pulse wave measured during testing of the arterial pulsimeter [...] Read more.
To measure precise blood pressure (BP) and pulse rate without using a cuff, we have developed an arterial pulsimeter consisting of a small, portable apparatus incorporating a Hall device. Regression analysis of the pulse wave measured during testing of the arterial pulsimeter was conducted using two equations of the BP algorithm. The estimated values of BP obtained by the cuffless arterial pulsimeter over 5 s were compared with values obtained using electronic or liquid mercury BP meters. The standard deviation between the estimated values and the measured values for systolic and diastolic BP were 8.3 and 4.9, respectively, which are close to the range of values of the BP International Standard. Detailed analysis of the pulse wave measured by the cuffless radial artery pulsimeter by detecting changes in the magnetic field can be used to develop a new diagnostic algorithm for BP, which can be applied to new medical apparatus such as the radial artery pulsimeter. Full article
(This article belongs to the Special Issue Advanced Sensing Technology for Nondestructive Evaluation)
Open AccessArticle Land Use Dynamics of the Fast-Growing Shanghai Metropolis, China (1979–2008) and its Implications for Land Use and Urban Planning Policy
Sensors 2011, 11(2), 1794-1809; doi:10.3390/s110201794
Received: 17 December 2010 / Revised: 17 January 2011 / Accepted: 19 January 2011 / Published: 31 January 2011
Cited by 13 | PDF Full-text (494 KB) | HTML Full-text | XML Full-text
Abstract
Through the integrated approach of remote sensing and geographic information system (GIS) techniques, four Landsat TM/ETM+ imagery acquired during 1979 and 2008 were used to quantitatively characterize the patterns of land use and land cover change (LULC) and urban sprawl in the [...] Read more.
Through the integrated approach of remote sensing and geographic information system (GIS) techniques, four Landsat TM/ETM+ imagery acquired during 1979 and 2008 were used to quantitatively characterize the patterns of land use and land cover change (LULC) and urban sprawl in the fast-growing Shanghai Metropolis, China. Results showed that, the urban/built-up area grew on average by 4,242.06 ha yr−1. Bare land grew by 1,594.66 ha yr−1 on average. In contrast, cropland decreased by 3,286.26 ha yr−1 on average, followed by forest and shrub, water, and tidal land, which decreased by 1,331.33 ha yr−1, 903.43 ha yr−1, and 315.72 ha yr−1 on average, respectively. As a result, during 1979 and 2008 approximately 83.83% of the newly urban/built-up land was converted from cropland (67.35%), forest and shrub (9.12%), water (4.80%), and tidal land (2.19%). Another significant change was the continuous increase in regular residents, which played a very important role in contributing to local population growth and increase in urban/built-up land. This can be explained with this city’s huge demand for investment and qualified labor since the latest industrial transformation. Moreover, with a decrease in cropland, the proportion of population engaged in farming decreased 13.84%. Therefore, significant socio-economic transformation occurred, and this would lead to new demand for land resources. However, due to very scarce land resources and overload of population in Shanghai, the drive to achieve economic goals at the loss of cropland, water, and the other lands is not sustainable. Future urban planning policy aiming at ensuring a win-win balance between sustainable land use and economic growth is urgently needed. Full article
(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)
Open AccessCommunication Optically Defined Modal Sensors Incorporating Spiropyran-Doped Liquid Crystals with Piezoelectric Sensors
Sensors 2011, 11(2), 1810-1818; doi:10.3390/s110201810
Received: 8 December 2010 / Revised: 25 January 2011 / Accepted: 26 January 2011 / Published: 31 January 2011
Cited by 4 | PDF Full-text (422 KB) | HTML Full-text | XML Full-text
Abstract
We integrated a piezoelectric sensing layer lamina containing liquid crystals (LC) and spiropyran (SP) in a LC/SP mixture to create an optically reconfigurable modal sensor for a cantilever beam. The impedance of this LC/SP lamina was decreased by UV irradiation which constituted [...] Read more.
We integrated a piezoelectric sensing layer lamina containing liquid crystals (LC) and spiropyran (SP) in a LC/SP mixture to create an optically reconfigurable modal sensor for a cantilever beam. The impedance of this LC/SP lamina was decreased by UV irradiation which constituted the underlying mechanism to modulate the voltage externally applied to the piezoelectric actuating layer. Illuminating a specific pattern onto the LC/SP lamina provided us with a way to spatially modulate the piezoelectric vibration signal. We showed that if an UV illuminated pattern matches the strain distribution of a specific mode, a piezoelectric modal sensor can be created. Since UV illumination can be changed in situ in real-time, our results confirm for the first time since the inception of smart sensors, that an optically tailored modal sensor can be created. Some potential applications of this type of sensor include energy harvesting devices, bio-chips, vibration sensing and actuating devices. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle High-Performance Piezoresistive MEMS Strain Sensor with Low Thermal Sensitivity
Sensors 2011, 11(2), 1819-1846; doi:10.3390/s110201819
Received: 9 December 2010 / Revised: 18 January 2011 / Accepted: 20 January 2011 / Published: 31 January 2011
Cited by 7 | PDF Full-text (593 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the experimental evaluation of a new piezoresistive MEMS strain sensor. Geometric characteristics of the sensor silicon carrier have been employed to improve the sensor sensitivity. Surface features or trenches have been introduced in the vicinity of the sensing elements. [...] Read more.
This paper presents the experimental evaluation of a new piezoresistive MEMS strain sensor. Geometric characteristics of the sensor silicon carrier have been employed to improve the sensor sensitivity. Surface features or trenches have been introduced in the vicinity of the sensing elements. These features create stress concentration regions (SCRs) and as a result, the strain/stress field was altered. The improved sensing sensitivity compensated for the signal loss. The feasibility of this methodology was proved in a previous work using Finite Element Analysis (FEA). This paper provides the experimental part of the previous study. The experiments covered a temperature range from −50 °C to +50 °C. The MEMS sensors are fabricated using five different doping concentrations. FEA is also utilized to investigate the effect of material properties and layer thickness of the bonding adhesive on the sensor response. The experimental findings are compared to the simulation results to guide selection of bonding adhesive and installation procedure. Finally, FEA was used to analyze the effect of rotational/alignment errors. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle An Energy-Efficient MAC Protocol Using Dynamic Queue Management for Delay-Tolerant Mobile Sensor Networks
Sensors 2011, 11(2), 1847-1864; doi:10.3390/s110201847
Received: 15 November 2010 / Revised: 9 December 2010 / Accepted: 5 January 2011 / Published: 1 February 2011
Cited by 3 | PDF Full-text (472 KB) | HTML Full-text | XML Full-text
Abstract
Conventional MAC protocols for wireless sensor network perform poorly when faced with a delay-tolerant mobile network environment. Characterized by a highly dynamic and sparse topology, poor network connectivity as well as data delay-tolerance, delay-tolerant mobile sensor networks exacerbate the severe power constraints [...] Read more.
Conventional MAC protocols for wireless sensor network perform poorly when faced with a delay-tolerant mobile network environment. Characterized by a highly dynamic and sparse topology, poor network connectivity as well as data delay-tolerance, delay-tolerant mobile sensor networks exacerbate the severe power constraints and memory limitations of nodes. This paper proposes an energy-efficient MAC protocol using dynamic queue management (EQ-MAC) for power saving and data queue management. Via data transfers initiated by the target sink and the use of a dynamic queue management strategy based on priority, EQ-MAC effectively avoids untargeted transfers, increases the chance of successful data transmission, and makes useful data reach the target terminal in a timely manner. Experimental results show that EQ-MAC has high energy efficiency in comparison with a conventional MAC protocol. It also achieves a 46% decrease in packet drop probability, 79% increase in system throughput, and 25% decrease in mean packet delay. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Sensor Proxy Mobile IPv6 (SPMIPv6)—A Novel Scheme for Mobility Supported IP-WSNs
Sensors 2011, 11(2), 1865-1887; doi:10.3390/s110201865
Received: 18 December 2010 / Revised: 20 January 2011 / Accepted: 23 January 2011 / Published: 1 February 2011
Cited by 30 | PDF Full-text (773 KB) | HTML Full-text | XML Full-text
Abstract
IP based Wireless Sensor Networks (IP-WSNs) are gaining importance for their broad range of applications in health-care, home automation, environmental monitoring, industrial control, vehicle telematics and agricultural monitoring. In all these applications, mobility in the sensor network with special attention to energy [...] Read more.
IP based Wireless Sensor Networks (IP-WSNs) are gaining importance for their broad range of applications in health-care, home automation, environmental monitoring, industrial control, vehicle telematics and agricultural monitoring. In all these applications, mobility in the sensor network with special attention to energy efficiency is a major issue to be addressed. Host-based mobility management protocols are not suitable for IP-WSNs because of their energy inefficiency, so network based mobility management protocols can be an alternative for the mobility supported IP-WSNs. In this paper we propose a network based mobility supported IP-WSN protocol called Sensor Proxy Mobile IPv6 (SPMIPv6). We present its architecture, message formats and also evaluate its performance considering signaling cost, mobility cost and energy consumption. Our analysis shows that with respect to the number of IP-WSN nodes, the proposed scheme reduces the signaling cost by 60% and 56%, as well as the mobility cost by 62% and 57%, compared to MIPv6 and PMIPv6, respectively. The simulation results also show that in terms of the number of hops, SPMIPv6 decreases the signaling cost by 56% and 53% as well as mobility cost by 60% and 67% as compared to MIPv6 and PMIPv6 respectively. It also indicates that proposed scheme reduces the level of energy consumption significantly. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Target Coverage Scheduling Scheme Based on Genetic Algorithms in Directional Sensor Networks
Sensors 2011, 11(2), 1888-1906; doi:10.3390/s110201888
Received: 7 December 2010 / Revised: 21 January 2011 / Accepted: 28 January 2011 / Published: 1 February 2011
Cited by 25 | PDF Full-text (607 KB) | HTML Full-text | XML Full-text
Abstract
As a promising tool for monitoring the physical world, directional sensor networks (DSNs) consisting of a large number of directional sensors are attracting increasing attention. As directional sensors in DSNs have limited battery power and restricted angles of sensing range, maximizing the [...] Read more.
As a promising tool for monitoring the physical world, directional sensor networks (DSNs) consisting of a large number of directional sensors are attracting increasing attention. As directional sensors in DSNs have limited battery power and restricted angles of sensing range, maximizing the network lifetime while monitoring all the targets in a given area remains a challenge. A major technique to conserve the energy of directional sensors is to use a node wake-up scheduling protocol by which some sensors remain active to provide sensing services, while the others are inactive to conserve their energy. In this paper, we first address a Maximum Set Covers for DSNs (MSCD) problem, which is known to be NP-complete, and present a greedy algorithm-based target coverage scheduling scheme that can solve this problem by heuristics. This scheme is used as a baseline for comparison. We then propose a target coverage scheduling scheme based on a genetic algorithm that can find the optimal cover sets to extend the network lifetime while monitoring all targets by the evolutionary global search technique. To verify and evaluate these schemes, we conducted simulations and showed that the schemes can contribute to extending the network lifetime. Simulation results indicated that the genetic algorithm-based scheduling scheme had better performance than the greedy algorithm-based scheme in terms of maximizing network lifetime. Full article
Open AccessArticle Detection of Hydrofluoric Acid by a SiO2 Sol-Gel Coating Fiber-Optic Probe Based on Reflection-Based Localized Surface Plasmon Resonance
Sensors 2011, 11(2), 1907-1923; doi:10.3390/s110201907
Received: 7 January 2011 / Revised: 18 January 2011 / Accepted: 26 January 2011 / Published: 1 February 2011
Cited by 5 | PDF Full-text (616 KB) | HTML Full-text | XML Full-text
Abstract
A novel fiber-optic probe based on reflection-based localized surface plasmon resonance (LSPR) was developed to quantify the concentration of hydrofluoric acid (HF) in aqueous solutions. The LSPR sensor was constructed with a gold nanoparticle-modified PMMA fiber, integrated with a SiO2 sol-gel [...] Read more.
A novel fiber-optic probe based on reflection-based localized surface plasmon resonance (LSPR) was developed to quantify the concentration of hydrofluoric acid (HF) in aqueous solutions. The LSPR sensor was constructed with a gold nanoparticle-modified PMMA fiber, integrated with a SiO2 sol-gel coating. This fiber-sensor was utilized to assess the relationship between HF concentration and SiO2 sol-gel layer etching reduction. The results demonstrated the LSPR sensor was capable of detecting HF-related erosion of hydrofluoric acid solutions of concentrations ranging from 1% to 5% using Relative RI Change Rates. The development of the LSPR sensor constitutes the basis of a detector with significant sensitivity for practical use in monitoring HF solution concentrations. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Effect of TiO2 on the Gas Sensing Features of TiO2/PANi Nanocomposites
Sensors 2011, 11(2), 1924-1931; doi:10.3390/s110201924
Received: 11 January 2011 / Revised: 25 January 2011 / Accepted: 28 January 2011 / Published: 1 February 2011
Cited by 39 | PDF Full-text (538 KB) | HTML Full-text | XML Full-text
Abstract
A nanocomposite of titanium dioxide (TiO2) and polyaniline (PANi) was synthesized by in-situ chemical polymerization using aniline (ANi) monomer and TiCl4 as precursors. SEM pictures show that the nanocomposite was created in the form of long PANi chains decorated [...] Read more.
A nanocomposite of titanium dioxide (TiO2) and polyaniline (PANi) was synthesized by in-situ chemical polymerization using aniline (ANi) monomer and TiCl4 as precursors. SEM pictures show that the nanocomposite was created in the form of long PANi chains decorated with TiO2 nanoparticles. FTIR, Raman and UV-Vis spectra reveal that the PANi component undergoes an electronic structure modification as a result of the TiO2 and PANi interaction. The electrical resistor of the nanocomposite is highly sensitive to oxygen and NH3 gas, accounting for the physical adsorption of these gases. A nanocomposite with around 55% TiO2 shows an oxygen sensitivity of 600–700%, 20–25 times higher than that of neat PANi. The n-p contacts between TiO2 nanoparticles and PANi matrix give rise to variety of shallow donors and acceptor levels in the PANi band gap which enhance the physical adsorption of gas molecules. Full article
(This article belongs to the Special Issue Gas Sensors - 2010)
Open AccessArticle Effect of Neuromuscular Electrical Muscle Stimulation on Energy Expenditure in Healthy Adults
Sensors 2011, 11(2), 1932-1942; doi:10.3390/s110201932
Received: 10 January 2011 / Revised: 25 January 2011 / Accepted: 30 January 2011 / Published: 1 February 2011
Cited by 3 | PDF Full-text (174 KB) | HTML Full-text | XML Full-text
Abstract
Weight loss/weight control is a major concern in prevention of cardiovascular disease and the realm of health promotion. The primary aim of this study was to investigate the effect of neuromuscular electrical stimulation (NMES) at different intensities on energy expenditure (oxygen and [...] Read more.
Weight loss/weight control is a major concern in prevention of cardiovascular disease and the realm of health promotion. The primary aim of this study was to investigate the effect of neuromuscular electrical stimulation (NMES) at different intensities on energy expenditure (oxygen and calories) in healthy adults. The secondary aim was to develop a generalized linear regression (GEE) model to predict the increase of energy expenditure facilitated by NMES and identify factors (NMES stimulation intensity level, age, body mass index, weight, body fat percentage, waist/hip ratio, and gender) associated with this NMES-induced increase of energy expenditure. Forty sedentary healthy adults (18 males and 22 females) participated. NMES was given at the following stimulation intensities for 10 minutes each: sensory level (E1), motor threshold (E2), and maximal intensity comfortably tolerated (E3). Cardiopulmonary gas exchange was evaluated during rest, NMES, and recovery stage. The results revealed that NMES at E2 and E3 significantly increased energy expenditure and the energy expenditure at recovery stage was still significantly higher than baseline. The GEE model demonstrated that a linear dose-response relationship existed between the stimulation intensity and the increase of energy expenditure. No subject’s demographic or anthropometric characteristics tested were significantly associated with the increase of energy expenditure. This study suggested NMES may be used to serve as an additional intervention for weight loss programs. Future studies to develop electrical stimulators or stimulation electrodes to maximize the comfort of NMES are recommended. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Forest Cover Classification by Optimal Segmentation of High Resolution Satellite Imagery
Sensors 2011, 11(2), 1943-1958; doi:10.3390/s110201943
Received: 20 December 2010 / Revised: 28 January 2011 / Accepted: 30 January 2011 / Published: 1 February 2011
Cited by 14 | PDF Full-text (783 KB) | HTML Full-text | XML Full-text
Abstract
This study investigated whether high-resolution satellite imagery is suitable for preparing a detailed digital forest cover map that discriminates forest cover at the tree species level. First, we tried to find an optimal process for segmenting the high-resolution images using a region-growing [...] Read more.
This study investigated whether high-resolution satellite imagery is suitable for preparing a detailed digital forest cover map that discriminates forest cover at the tree species level. First, we tried to find an optimal process for segmenting the high-resolution images using a region-growing method with the scale, color and shape factors in Definiens® Professional 5.0. The image was classified by a traditional, pixel-based, maximum likelihood classification approach using the spectral information of the pixels. The pixels in each segment were reclassified using a segment-based classification (SBC) with a majority rule. Segmentation with strongly weighted color was less sensitive to the scale parameter and led to optimal forest cover segmentation and classification. The pixel-based classification (PBC) suffered from the “salt-and-pepper effect” and performed poorly in the classification of forest cover types, whereas the SBC helped to attenuate the effect and notably improved the classification accuracy. As a whole, SBC proved to be more suitable for classifying and delineating forest cover using high-resolution satellite images. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle One-to-One Embedding between Honeycomb Mesh and Petersen-Torus Networks
Sensors 2011, 11(2), 1959-1971; doi:10.3390/s110201959
Received: 23 November 2010 / Revised: 22 December 2010 / Accepted: 11 January 2011 / Published: 1 February 2011
Cited by 3 | PDF Full-text (437 KB) | HTML Full-text | XML Full-text
Abstract
As wireless mobile telecommunication bases organize their structure using a honeycomb-mesh algorithm, there are many studies about parallel processing algorithms like the honeycomb mesh in Wireless Sensor Networks. This paper aims to study the Peterson-Torus graph algorithm in regard to the continuity [...] Read more.
As wireless mobile telecommunication bases organize their structure using a honeycomb-mesh algorithm, there are many studies about parallel processing algorithms like the honeycomb mesh in Wireless Sensor Networks. This paper aims to study the Peterson-Torus graph algorithm in regard to the continuity with honeycomb-mesh algorithm in order to apply the algorithm to sensor networks. Once a new interconnection network is designed, parallel algorithms are developed with huge research costs to use such networks. If the old network is embedded in a newly designed network, a developed algorithm in the old network is reusable in a newly designed network. Petersen-Torus has been designed recently, and the honeycomb mesh has already been designed as a well-known interconnection network. In this paper, we propose a one-to-one embedding algorithm for the honeycomb mesh (HMn) in the Petersen-Torus PT(n,n), and prove that dilation of the algorithm is 5, congestion is 2, and expansion is 5/3. The proposed one-to-one embedding is applied so that processor throughput can be minimized when the honeycomb mesh algorithm runs in the Petersen-Torus. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Compact on-Chip Temperature Sensors Based on Dielectric-Loaded Plasmonic Waveguide-Ring Resonators
Sensors 2011, 11(2), 1992-2000; doi:10.3390/s110201992
Received: 10 December 2010 / Revised: 14 January 2011 / Accepted: 30 January 2011 / Published: 7 February 2011
Cited by 7 | PDF Full-text (286 KB) | HTML Full-text | XML Full-text
Abstract
The application of a waveguide-ring resonator based on dielectric-loaded surface plasmon-polariton waveguides as a temperature sensor is demonstrated in this paper and the influence of temperature change to the transmission through the waveguide-ring resonator system is comprehensively analyzed. The results show that [...] Read more.
The application of a waveguide-ring resonator based on dielectric-loaded surface plasmon-polariton waveguides as a temperature sensor is demonstrated in this paper and the influence of temperature change to the transmission through the waveguide-ring resonator system is comprehensively analyzed. The results show that the roundtrip phase change in the ring resonator due to the temperature change is the major reason for the transmission variation. The performance of the temperature sensor is also discussed and it is shown that for a waveguide-ring resonator with the resonator radius around 5 mm and waveguide-ring gap of 500 nm which gives a footprint around 140 µm2, the temperature sensitivity at the order of 10−2 K can be achieved with the input power of 100 mW within the measurement sensitivity limit of a practical optical detector. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Fabrication of a Microbial Biosensor Based on QD-MWNT Supports by a One-Step Radiation Reaction and Detection of Phenolic Compounds in Red Wines
Sensors 2011, 11(2), 2001-2012; doi:10.3390/s110202001
Received: 8 December 2010 / Revised: 4 January 2011 / Accepted: 6 February 2011 / Published: 8 February 2011
Cited by 6 | PDF Full-text (440 KB) | HTML Full-text | XML Full-text
Abstract
An Acaligense sp.-immobilized biosensor was fabricated based on QD-MWNT composites as an electron transfer mediator and a microbe immobilization support by a one-step radiation reaction and used for sensing phenolic compounds in commercial red wines. First, a quantum dot-modified multi-wall carbon [...] Read more.
An Acaligense sp.-immobilized biosensor was fabricated based on QD-MWNT composites as an electron transfer mediator and a microbe immobilization support by a one-step radiation reaction and used for sensing phenolic compounds in commercial red wines. First, a quantum dot-modified multi-wall carbon nanotube (QD-MWNT) composite was prepared in the presence of MWNT by a one-step radiation reaction in an aqueous solution at room temperature. The successful preparation of the QD-MWNT composite was confirmed by XPS, TEM, and elemental analysis. Second, the microbial biosensor was fabricated by immobilization of Acaligense sp. on the surface of the composite thin film of a glassy carbon (GC) electrode, which was prepared by a hand casting method with a mixture of the previously obtained composite and Nafion solution. The sensing ranges of the microbial biosensor based on CdS-MWNT and Cu2S-MWNT supports were 0.5–5.0 mM and 0.7–10 mM for phenol in a phosphate buffer solution, respectively. Total concentration of phenolic compounds contained in commercial red wines was also determined using the prepared microbial immobilized biosensor. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Energy Saving Effects of Wireless Sensor Networks: A Case Study of Convenience Stores in Taiwan
Sensors 2011, 11(2), 2013-2034; doi:10.3390/s110202013
Received: 15 December 2010 / Revised: 4 January 2011 / Accepted: 8 February 2011 / Published: 10 February 2011
Cited by 8 | PDF Full-text (2686 KB) | HTML Full-text | XML Full-text
Abstract
Wireless sensor network (WSN) technology has been successfully applied to energy saving applications in many places, and plays a significant role in achieving power conservation. However, previous studies do not discuss WSN costs and cost-recovery. The application of WSNs is currently limited [...] Read more.
Wireless sensor network (WSN) technology has been successfully applied to energy saving applications in many places, and plays a significant role in achieving power conservation. However, previous studies do not discuss WSN costs and cost-recovery. The application of WSNs is currently limited to research and laboratory experiments, and not mass industrial production, largely because business owners are unfamiliar with the possible favorable return and cost-recovery on WSN investments. Therefore, this paper focuses on the cost-recovery of WSNs and how to reduce air conditioning energy consumption in convenience stores. The WSN used in this study provides feedback to the gateway and adopts the predicted mean vote (PMV) and computational fluid dynamics (CFD) methods to allow customers to shop in a comfortable yet energy-saving environment. Four convenience stores in Taipei have used the proposed WSN since 2008. In 2008, the experiment was initially designed to optimize air-conditioning for energy saving, but additions to the set-up continued beyond 2008, adding the thermal comfort and crowds peak, off-peak features in 2009 to achieve human-friendly energy savings. Comparison with 2007 data, under the same comfort conditions, shows that the power savings increased by 40% (2008) and 53% (2009), respectively. The cost of the WSN equipment was 500 US dollars. Experimental results, including three years of analysis and calculations, show that the marginal energy conservation benefit of the four convenience stores achieved energy savings of up to 53%, recovering all costs in approximately 5 months. The convenience store group participating in this study was satisfied with the efficiency of energy conservation because of the short cost-recovery period. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Ultra Wide-Band Localization and SLAM: A Comparative Study for Mobile Robot Navigation
Sensors 2011, 11(2), 2035-2055; doi:10.3390/s110202035
Received: 10 December 2010 / Revised: 26 January 2011 / Accepted: 28 January 2011 / Published: 10 February 2011
Cited by 8 | PDF Full-text (7291 KB) | HTML Full-text | XML Full-text
Abstract
In this work, a comparative study between an Ultra Wide-Band (UWB) localization system and a Simultaneous Localization and Mapping (SLAM) algorithm is presented. Due to its high bandwidth and short pulses length, UWB potentially allows great accuracy in range measurements based on [...] Read more.
In this work, a comparative study between an Ultra Wide-Band (UWB) localization system and a Simultaneous Localization and Mapping (SLAM) algorithm is presented. Due to its high bandwidth and short pulses length, UWB potentially allows great accuracy in range measurements based on Time of Arrival (TOA) estimation. SLAM algorithms recursively estimates the map of an environment and the pose (position and orientation) of a mobile robot within that environment. The comparative study presented here involves the performance analysis of implementing in parallel an UWB localization based system and a SLAM algorithm on a mobile robot navigating within an environment. Real time results as well as error analysis are also shown in this work. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Design and Implementation of A CMOS Light Pulse Receiver Cell Array for Spatial Optical Communications
Sensors 2011, 11(2), 2056-2076; doi:10.3390/s110202056
Received: 4 January 2011 / Accepted: 6 February 2011 / Published: 10 February 2011
Cited by 4 | PDF Full-text (1512 KB) | HTML Full-text | XML Full-text
Abstract
A CMOS light pulse receiver (LPR) cell for spatial optical communications is designed and evaluated by device simulations and a prototype chip implementation. The LPR cell consists of a pinned photodiode and four transistors. It works under sub-threshold region of a MOS [...] Read more.
A CMOS light pulse receiver (LPR) cell for spatial optical communications is designed and evaluated by device simulations and a prototype chip implementation. The LPR cell consists of a pinned photodiode and four transistors. It works under sub-threshold region of a MOS transistor and the source terminal voltage which responds to the logarithm of the photo current are read out with a source follower circuit. For finding the position of the light spot on the focal plane, an image pixel array is embedded on the same plane of the LPR cell array. A prototype chip with 640 × 240 image pixels and 640 × 240 LPR cells is implemented with 0.18 μm CMOS technology. A proposed model of the transient response of the LPR cell agrees with the result of the device simulations and measurements. Both imaging at 60 fps and optical communication at the carrier frequency of 1 MHz are successfully performed. The measured signal amplitude and the calculation results of photocurrents show that the spatial optical communication up to 100 m is feasible using a 10 × 10 LED array. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Observing GLUT4 Translocation in Live L6 Cells Using Quantum Dots
Sensors 2011, 11(2), 2077-2089; doi:10.3390/s110202077
Received: 30 November 2010 / Revised: 29 December 2010 / Accepted: 6 February 2011 / Published: 10 February 2011
Cited by 1 | PDF Full-text (725 KB) | HTML Full-text | XML Full-text
Abstract
The glucose transporter 4 (GLUT4) plays a key role in maintaining whole body glucose homeostasis. Tracking GLUT4 in space and time can provide new insights for understanding the mechanisms of insulin-regulated GLUT4 translocation. Organic dyes and fluorescent proteins were used in previous [...] Read more.
The glucose transporter 4 (GLUT4) plays a key role in maintaining whole body glucose homeostasis. Tracking GLUT4 in space and time can provide new insights for understanding the mechanisms of insulin-regulated GLUT4 translocation. Organic dyes and fluorescent proteins were used in previous studies for investigating the traffic of GLUT4 in skeletal muscle cells and adipocytes. Because of their relative weak fluorescent signal against strong cellular autofluorescence background and their fast photobleaching rate, most studies only focused on particular segments of GLUT4 traffic. In this study, we have developed a new method for observing the translocation of GLUT4 targeted with photostable and bright quantum dots (QDs) in live L6 cells. QDs were targeted to GLUT4myc specifically and internalized with GLUT4myc through receptor-mediated endocytosis. Compared with traditional fluorescence dyes and fluorescent proteins, QDs with high brightness and extremely photostability are suitable for long-term single particle tracking, so individual GLUT4-QD complex can be easily detected and tracked for long periods of time. This newly described method will be a powerful tool for observing the translocation of GLUT4 in live L6 cells. Full article
(This article belongs to the Special Issue Sensing with Quantum Dots)
Open AccessArticle Fuzzy Adaptive Interacting Multiple Model Nonlinear Filter for Integrated Navigation Sensor Fusion
Sensors 2011, 11(2), 2090-2111; doi:10.3390/s110202090
Received: 27 December 2010 / Revised: 22 January 2011 / Accepted: 10 February 2011 / Published: 11 February 2011
Cited by 6 | PDF Full-text (620 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the application of the fuzzy interacting multiple model unscented Kalman filter (FUZZY-IMMUKF) approach to integrated navigation processing for the maneuvering vehicle is presented. The unscented Kalman filter (UKF) employs a set of sigma points through deterministic sampling, such that [...] Read more.
In this paper, the application of the fuzzy interacting multiple model unscented Kalman filter (FUZZY-IMMUKF) approach to integrated navigation processing for the maneuvering vehicle is presented. The unscented Kalman filter (UKF) employs a set of sigma points through deterministic sampling, such that a linearization process is not necessary, and therefore the errors caused by linearization as in the traditional extended Kalman filter (EKF) can be avoided. The nonlinear filters naturally suffer, to some extent, the same problem as the EKF for which the uncertainty of the process noise and measurement noise will degrade the performance. As a structural adaptation (model switching) mechanism, the interacting multiple model (IMM), which describes a set of switching models, can be utilized for determining the adequate value of process noise covariance. The fuzzy logic adaptive system (FLAS) is employed to determine the lower and upper bounds of the system noise through the fuzzy inference system (FIS). The resulting sensor fusion strategy can efficiently deal with the nonlinear problem for the vehicle navigation. The proposed FUZZY-IMMUKF algorithm shows remarkable improvement in the navigation estimation accuracy as compared to the relatively conventional approaches such as the UKF and IMMUKF. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Olfaction and Hearing Based Mobile Robot Navigation for Odor/Sound Source Search
Sensors 2011, 11(2), 2129-2154; doi:10.3390/s110202129
Received: 17 December 2010 / Revised: 11 January 2011 / Accepted: 10 February 2011 / Published: 11 February 2011
Cited by 10 | PDF Full-text (757 KB) | HTML Full-text | XML Full-text
Abstract
Bionic technology provides a new elicitation for mobile robot navigation since it explores the way to imitate biological senses. In the present study, the challenging problem was how to fuse different biological senses and guide distributed robots to cooperate with each other [...] Read more.
Bionic technology provides a new elicitation for mobile robot navigation since it explores the way to imitate biological senses. In the present study, the challenging problem was how to fuse different biological senses and guide distributed robots to cooperate with each other for target searching. This paper integrates smell, hearing and touch to design an odor/sound tracking multi-robot system. The olfactory robot tracks the chemical odor plume step by step through information fusion from gas sensors and airflow sensors, while two hearing robots localize the sound source by time delay estimation (TDE) and the geometrical position of microphone array. Furthermore, this paper presents a heading direction based mobile robot navigation algorithm, by which the robot can automatically and stably adjust its velocity and direction according to the deviation between the current heading direction measured by magnetoresistive sensor and the expected heading direction acquired through the odor/sound localization strategies. Simultaneously, one robot can communicate with the other robots via a wireless sensor network (WSN). Experimental results show that the olfactory robot can pinpoint the odor source within the distance of 2 m, while two hearing robots can quickly localize and track the olfactory robot in 2 min. The devised multi-robot system can achieve target search with a considerable success ratio and high stability. 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 Effects of Calcination Temperature and Acid-Base Properties on Mixed Potential Ammonia Sensors Modified by Metal Oxides
Sensors 2011, 11(2), 2155-2165; doi:10.3390/s110202155
Received: 24 December 2010 / Revised: 20 January 2011 / Accepted: 10 February 2011 / Published: 11 February 2011
Cited by 7 | PDF Full-text (284 KB) | HTML Full-text | XML Full-text
Abstract
Mixed potential sensors were fabriated using yttria-stabilized zirconia (YSZ) as a solid electrolyte and a mixture of Au and various metal oxides as a sensing electrode. The effects of calcination temperature ranging from 600 to 1,000 °C and acid-base properties of the [...] Read more.
Mixed potential sensors were fabriated using yttria-stabilized zirconia (YSZ) as a solid electrolyte and a mixture of Au and various metal oxides as a sensing electrode. The effects of calcination temperature ranging from 600 to 1,000 °C and acid-base properties of the metal oxides on the sensing properties were examined. The selective sensing of ammonia was achieved by modification of the sensing electrode using MoO3, Bi2O3 and V2O5, while the use of WO3, Nb2O5 and MgO was not effective. The melting points of the former group were below 820 °C, while those of the latter group were higher than 1,000 °C. Among the former group, the selective sensing of ammonia was strongly dependent on the calcination temperature, which was optimum around melting point of the corresponding metal oxides. The good spreading of the metal oxides on the electrode is suggested to be one of the important factors. In the former group, the relative response of ammonia to propene was in the order of MoO3 > Bi2O3 > V2O5, which agreed well with the acidity of the metal oxides. The importance of the acidic properties of metal oxides for ammonia sensing was clarified. Full article
(This article belongs to the Special Issue Gas Sensors - 2010)
Open AccessArticle 3-D Modeling of Tomato Canopies Using a High-Resolution Portable Scanning Lidar for Extracting Structural Information
Sensors 2011, 11(2), 2166-2174; doi:10.3390/s110202166
Received: 31 December 2010 / Revised: 31 January 2011 / Accepted: 2 February 2011 / Published: 15 February 2011
Cited by 23 | PDF Full-text (535 KB) | HTML Full-text | XML Full-text
Abstract
In the present study, an attempt was made to produce a precise 3D image of a tomato canopy using a portable high-resolution scanning lidar. The tomato canopy was scanned by the lidar from three positions surrounding it. Through the scanning, the point [...] Read more.
In the present study, an attempt was made to produce a precise 3D image of a tomato canopy using a portable high-resolution scanning lidar. The tomato canopy was scanned by the lidar from three positions surrounding it. Through the scanning, the point cloud data of the canopy were obtained and they were co-registered. Then, points corresponding to leaves were extracted and converted into polygon images. From the polygon images, leaf areas were accurately estimated with a mean absolute percent error of 4.6%. Vertical profile of leaf area density (LAD) and leaf area index (LAI) could be also estimated by summing up each leaf area derived from the polygon images. Leaf inclination angle could be also estimated from the 3-D polygon image. It was shown that leaf inclination angles had different values at each part of a leaf. Full article
(This article belongs to the Special Issue Sensors in Agriculture and Forestry)
Open AccessArticle Ultrasonic and LIDAR Sensors for Electronic Canopy Characterization in Vineyards: Advances to Improve Pesticide Application Methods
Sensors 2011, 11(2), 2177-2194; doi:10.3390/s110202177
Received: 10 December 2010 / Revised: 25 January 2011 / Accepted: 28 January 2011 / Published: 15 February 2011
Cited by 41 | PDF Full-text (1604 KB) | HTML Full-text | XML Full-text
Abstract
Canopy characterization is a key factor to improve pesticide application methods in tree crops and vineyards. Development of quick, easy and efficient methods to determine the fundamental parameters used to characterize canopy structure is thus an important need. In this research the [...] Read more.
Canopy characterization is a key factor to improve pesticide application methods in tree crops and vineyards. Development of quick, easy and efficient methods to determine the fundamental parameters used to characterize canopy structure is thus an important need. In this research the use of ultrasonic and LIDAR sensors have been compared with the traditional manual and destructive canopy measurement procedure. For both methods the values of key parameters such as crop height, crop width, crop volume or leaf area have been compared. Obtained results indicate that an ultrasonic sensor is an appropriate tool to determine the average canopy characteristics, while a LIDAR sensor provides more accuracy and detailed information about the canopy. Good correlations have been obtained between crop volume (CVU) values measured with ultrasonic sensors and leaf area index, LAI (R2 = 0.51). A good correlation has also been obtained between the canopy volume measured with ultrasonic and LIDAR sensors (R2 = 0.52). Laser measurements of crop height (CHL) allow one to accurately predict the canopy volume. The proposed new technologies seems very appropriate as complementary tools to improve the efficiency of pesticide applications, although further improvements are still needed. Full article
(This article belongs to the Special Issue Advanced Sensing Technology for Nondestructive Evaluation)
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Open AccessArticle Application of Flexible Micro Temperature Sensor in Oxidative Steam Reforming by a Methanol Micro Reformer
Sensors 2011, 11(2), 2246-2256; doi:10.3390/s110202246
Received: 4 January 2011 / Revised: 14 February 2011 / Accepted: 16 February 2011 / Published: 16 February 2011
PDF Full-text (729 KB) | HTML Full-text | XML Full-text
Abstract
Advances in fuel cell applications reflect the ability of reformers to produce hydrogen. This work presents a flexible micro temperature sensor that is fabricated based on micro-electro-mechanical systems (MEMS) technology and integrated into a flat micro methanol reformer to observe the conditions [...] Read more.
Advances in fuel cell applications reflect the ability of reformers to produce hydrogen. This work presents a flexible micro temperature sensor that is fabricated based on micro-electro-mechanical systems (MEMS) technology and integrated into a flat micro methanol reformer to observe the conditions inside that reformer. The micro temperature sensor has higher accuracy and sensitivity than a conventionally adopted thermocouple. Despite various micro temperature sensor applications, integrated micro reformers are still relatively new. This work proposes a novel method for integrating micro methanol reformers and micro temperature sensors, subsequently increasing the methanol conversion rate and the hydrogen production rate by varying the fuel supply rate and the water/methanol ratio. Importantly, the proposed micro temperature sensor adequately controls the interior temperature during oxidative steam reforming of methanol (OSRM), with the relevant parameters optimized as well. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Development of a Stereo Vision Measurement System for a 3D Three-Axial Pneumatic Parallel Mechanism Robot Arm
Sensors 2011, 11(2), 2257-2281; doi:10.3390/s110202257
Received: 22 November 2010 / Revised: 7 January 2011 / Accepted: 12 January 2011 / Published: 21 February 2011
Cited by 16 | PDF Full-text (1324 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a stereo vision 3D position measurement system for a three-axial pneumatic parallel mechanism robot arm is presented. The stereo vision 3D position measurement system aims to measure the 3D trajectories of the end-effector of the robot arm. To track [...] Read more.
In this paper, a stereo vision 3D position measurement system for a three-axial pneumatic parallel mechanism robot arm is presented. The stereo vision 3D position measurement system aims to measure the 3D trajectories of the end-effector of the robot arm. To track the end-effector of the robot arm, the circle detection algorithm is used to detect the desired target and the SAD algorithm is used to track the moving target and to search the corresponding target location along the conjugate epipolar line in the stereo pair. After camera calibration, both intrinsic and extrinsic parameters of the stereo rig can be obtained, so images can be rectified according to the camera parameters. Thus, through the epipolar rectification, the stereo matching process is reduced to a horizontal search along the conjugate epipolar line. Finally, 3D trajectories of the end-effector are computed by stereo triangulation. The experimental results show that the stereo vision 3D position measurement system proposed in this paper can successfully track and measure the fifth-order polynomial trajectory and sinusoidal trajectory of the end-effector of the three- axial pneumatic parallel mechanism robot arm. Full article
(This article belongs to the Section Physical Sensors)

Review

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Open AccessReview Estimating Three-Dimensional Orientation of Human Body Parts by Inertial/Magnetic Sensing
Sensors 2011, 11(2), 1489-1525; doi:10.3390/s110201489
Received: 15 December 2010 / Revised: 13 January 2011 / Accepted: 15 January 2011 / Published: 26 January 2011
Cited by 57 | PDF Full-text (409 KB) | HTML Full-text | XML Full-text
Abstract
User-worn sensing units composed of inertial and magnetic sensors are becoming increasingly popular in various domains, including biomedical engineering, robotics, virtual reality, where they can also be applied for real-time tracking of the orientation of human body parts in the three-dimensional (3D) [...] Read more.
User-worn sensing units composed of inertial and magnetic sensors are becoming increasingly popular in various domains, including biomedical engineering, robotics, virtual reality, where they can also be applied for real-time tracking of the orientation of human body parts in the three-dimensional (3D) space. Although they are a promising choice as wearable sensors under many respects, the inertial and magnetic sensors currently in use offer measuring performance that are critical in order to achieve and maintain accurate 3D-orientation estimates, anytime and anywhere. This paper reviews the main sensor fusion and filtering techniques proposed for accurate inertial/magnetic orientation tracking of human body parts; it also gives useful recipes for their actual implementation. Full article
(This article belongs to the Special Issue Sensors in Biomechanics and Biomedicine)
Open AccessReview Overview of the Characteristics of Micro- and Nano-Structured Surface Plasmon Resonance Sensors
Sensors 2011, 11(2), 1565-1588; doi:10.3390/s110201565
Received: 1 December 2010 / Revised: 11 January 2011 / Accepted: 24 January 2011 / Published: 27 January 2011
Cited by 154 | PDF Full-text (1992 KB) | HTML Full-text | XML Full-text
Abstract
The performance of bio-chemical sensing devices has been greatly improved by the development of surface plasmon resonance (SPR) based sensors. Advancements in micro- and nano-fabrication technologies have led to a variety of structures in SPR sensing systems being proposed. In this review, [...] Read more.
The performance of bio-chemical sensing devices has been greatly improved by the development of surface plasmon resonance (SPR) based sensors. Advancements in micro- and nano-fabrication technologies have led to a variety of structures in SPR sensing systems being proposed. In this review, SPR sensors (from typical Kretschmann prism configurations to fiber sensor schemes) with micro- or nano-structures for local light field enhancement, extraordinary optical transmission, interference of surface plasmon waves, plasmonic cavities, etc. are discussed. We summarize and compare their performances and present guidelines for the design of SPR sensors. Full article
(This article belongs to the Special Issue Optical Resonant Microsensors)
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Open AccessReview Sensor and Display Human Factors Based Design Constraints for Head Mounted and Tele-Operation Systems
Sensors 2011, 11(2), 1589-1606; doi:10.3390/s110201589
Received: 2 December 2010 / Revised: 5 January 2011 / Accepted: 11 January 2011 / Published: 27 January 2011
PDF Full-text (634 KB) | HTML Full-text | XML Full-text
Abstract
For mobile imaging systems in head mounted displays and tele-operation systems it is important to maximize the amount of visual information transmitted to the human visual system without exceeding its input capacity. This paper aims to describe the design constraints on the [...] Read more.
For mobile imaging systems in head mounted displays and tele-operation systems it is important to maximize the amount of visual information transmitted to the human visual system without exceeding its input capacity. This paper aims to describe the design constraints on the imager and display systems of head mounted devices and tele-operated systems based upon the capabilities of the human visual system. We also present the experimental results of methods to improve the amount of visual information conveyed to a user when trying to display a high dynamic range image on a low dynamic range display. Full article
(This article belongs to the Special Issue Photodetectors and Imaging Technologies)
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Open AccessReview PCF-Based Cavity Enhanced Spectroscopic Sensors for Simultaneous Multicomponent Trace Gas Analysis
Sensors 2011, 11(2), 1620-1640; doi:10.3390/s110201620
Received: 20 October 2010 / Revised: 16 November 2010 / Accepted: 4 January 2011 / Published: 27 January 2011
Cited by 9 | PDF Full-text (414 KB) | HTML Full-text | XML Full-text
Abstract
A multiwavelength, multicomponent CRDS gas sensor operating on the basis of a compact photonic crystal fibre supercontinuum light source has been constructed. It features a simple design encompassing one radiation source, one cavity and one detection unit (a spectrograph with a fitted [...] Read more.
A multiwavelength, multicomponent CRDS gas sensor operating on the basis of a compact photonic crystal fibre supercontinuum light source has been constructed. It features a simple design encompassing one radiation source, one cavity and one detection unit (a spectrograph with a fitted ICCD camera) that are common for all wavelengths. Multicomponent detection capability of the device is demonstrated by simultaneous measurements of the absorption spectra of molecular oxygen (spin-forbidden b-X branch) and water vapor (polyads 4v, 4v + d) in ambient atmospheric air. Issues related to multimodal cavity excitation, as well as to obtaining the best signal-to-noise ratio are discussed together with methods for their practical resolution based on operating the cavity in a “quasi continuum” mode and setting long camera gate widths, respectively. A comprehensive review of multiwavelength CRDS techniques is also given. Full article
(This article belongs to the Special Issue 10 Years Sensors - A Decade of Publishing)
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Open AccessReview Sensing Phosphatidylserine in Cellular Membranes
Sensors 2011, 11(2), 1744-1755; doi:10.3390/s110201744
Received: 7 December 2010 / Revised: 20 January 2011 / Accepted: 26 January 2011 / Published: 28 January 2011
Cited by 18 | PDF Full-text (393 KB) | HTML Full-text | XML Full-text
Abstract
Phosphatidylserine, a phospholipid with a negatively charged head-group, is an important constituent of eukaryotic cellular membranes. On the plasma membrane, rather than being evenly distributed, phosphatidylserine is found preferentially in the inner leaflet. Disruption of this asymmetry, leading to the appearance of [...] Read more.
Phosphatidylserine, a phospholipid with a negatively charged head-group, is an important constituent of eukaryotic cellular membranes. On the plasma membrane, rather than being evenly distributed, phosphatidylserine is found preferentially in the inner leaflet. Disruption of this asymmetry, leading to the appearance of phosphatidylserine on the surface of the cell, is known to play a central role in both apoptosis and blood clotting. Despite its importance, comparatively little is known about phosphatidylserine in cells: its precise subcellular localization, transmembrane topology and intracellular dynamics are poorly characterized. The recent development of new, genetically-encoded probes able to detect phosphatidylserine within live cells, however, is leading to a more in-depth understanding of the biology of this phospholipid. This review aims to give an overview of the current methods for phosphatidylserine detection within cells, and some of the recent realizations derived from their use. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors in Canada)
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Open AccessReview Optical Microcavity: Sensing down to Single Molecules and Atoms
Sensors 2011, 11(2), 1972-1991; doi:10.3390/s110201972
Received: 16 December 2010 / Revised: 13 January 2011 / Accepted: 27 January 2011 / Published: 7 February 2011
Cited by 44 | PDF Full-text (868 KB) | HTML Full-text | XML Full-text | Correction | Supplementary Files
Abstract
This review article discusses fundamentals of dielectric, low-loss, optical micro-resonator sensing, including figures of merit and a variety of microcavity designs, and future perspectives in microcavity-based optical sensing. Resonance frequency and quality (Q) factor are altered as a means of detecting a [...] Read more.
This review article discusses fundamentals of dielectric, low-loss, optical micro-resonator sensing, including figures of merit and a variety of microcavity designs, and future perspectives in microcavity-based optical sensing. Resonance frequency and quality (Q) factor are altered as a means of detecting a small system perturbation, resulting in realization of optical sensing of a small amount of sample materials, down to even single molecules. Sensitivity, Q factor, minimum detectable index change, noises (in sensor system components and microcavity system including environments), microcavity size, and mode volume are essential parameters to be considered for optical sensing applications. Whispering gallery mode, photonic crystal, and slot-type microcavities typically provide compact, high-quality optical resonance modes for optical sensing applications. Surface Bloch modes induced on photonic crystals are shown to be a promising candidate thanks to large field overlap with a sample and ultra-high-Q resonances. Quantum optics effects based on microcavity quantum electrodynamics (QED) would provide novel single-photo-level detection of even single atoms and molecules via detection of doublet vacuum Rabi splitting peaks in strong coupling. Full article
(This article belongs to the Special Issue Optical Resonant Microsensors)
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Open AccessReview Physiological Sensing of Carbon Dioxide/Bicarbonate/pH via Cyclic Nucleotide Signaling
Sensors 2011, 11(2), 2112-2128; doi:10.3390/s110202112
Received: 3 January 2011 / Revised: 28 January 2011 / Accepted: 10 February 2011 / Published: 11 February 2011
Cited by 21 | PDF Full-text (277 KB) | HTML Full-text | XML Full-text
Abstract
Carbon dioxide (CO2) is produced by living organisms as a byproduct of metabolism. In physiological systems, CO2 is unequivocally linked with bicarbonate (HCO3) and pH via a ubiquitous family of carbonic anhydrases, and numerous biological processes [...] Read more.
Carbon dioxide (CO2) is produced by living organisms as a byproduct of metabolism. In physiological systems, CO2 is unequivocally linked with bicarbonate (HCO3) and pH via a ubiquitous family of carbonic anhydrases, and numerous biological processes are dependent upon a mechanism for sensing the level of CO2, HCO3, and/or pH. The discovery that soluble adenylyl cyclase (sAC) is directly regulated by bicarbonate provided a link between CO2/HCO3/pH chemosensing and signaling via the widely used second messenger cyclic AMP. This review summarizes the evidence that bicarbonate-regulated sAC, and additional, subsequently identified bicarbonate-regulate nucleotidyl cyclases, function as evolutionarily conserved CO2/HCO3/pH chemosensors in a wide variety of physiological systems. Full article
(This article belongs to the Special Issue Gas Sensors - 2010)
Open AccessReview Self-Mixing Thin-Slice Solid-State Laser Metrology
Sensors 2011, 11(2), 2195-2245; doi:10.3390/s110202195
Received: 21 January 2011 / Revised: 31 January 2011 / Accepted: 9 February 2011 / Published: 15 February 2011
Cited by 26 | PDF Full-text (2355 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract This paper reviews the dynamic effect of thin-slice solid-state lasers subjected to frequency-shifted optical feedback, which led to the discovery of the self-mixing modulation effect, and its applications to quantum-noise-limited versatile laser metrology systems with extreme optical sensitivity. Full article
(This article belongs to the Special Issue Optical Resonant Microsensors)
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Other

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Open AccessCorrection Correction: Baker, P. et al. Electrochemical Aptasensor for Endocrine Disrupting 17β-Estradiol Based on a Poly(3,4-ethylenedioxylthiopene)-Gold Nanocomposite Platform. Sensors 2010, 10, 9872-9890
Sensors 2011, 11(2), 2175-2176; doi:10.3390/s110202175
Received: 1 February 2011 / Published: 15 February 2011
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Abstract Herewith please find corrected structures for Figure 8 in our paper published in Sensors in 2010. [...] Full article

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