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Sensors, Volume 12, Issue 4 (April 2012), Pages 3789-5194

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Editorial

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Open AccessEditorial Advances in Sensors-Centric Microprocessors and System-on-Chip
Sensors 2012, 12(4), 4820-4823; doi:10.3390/s120404820
Received: 11 April 2012 / Accepted: 12 April 2012 / Published: 12 April 2012
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Abstract
Sensors-based systems are nowadays an extended technology for many markets due to their great potential in the collection of data from the environment and the processing of such data for different purposes. A typical example is the wireless sensor devices, where the [...] Read more.
Sensors-based systems are nowadays an extended technology for many markets due to their great potential in the collection of data from the environment and the processing of such data for different purposes. A typical example is the wireless sensor devices, where the outer temperature, humidity, luminosity and many other parameters can be acquired, measured and processed in order to build useful and fascinating applications that contribute to human welfare. In this scenario, the processing architectures of the sensors-based systems play a very important role. The requirements that are necessary for many such applications (real-time processing, low-power consumption, reduced size, reliability, security and many others) means that research on advanced architectures of Microprocessors and System-on-Chips (SoC) is needed to design and implement a successful product. In this sense, there are many challenges and open questions in this area that need to be addressed. [...] Full article
(This article belongs to the Special Issue Microprocessors and System-on-Chip)
Open AccessEditorial Sensors in Collaboration Increase Individual Potentialities
Sensors 2012, 12(4), 4892-4896; doi:10.3390/s120404892
Received: 6 April 2012 / Accepted: 12 April 2012 / Published: 13 April 2012
Cited by 3 | PDF Full-text (138 KB) | HTML Full-text | XML Full-text
Abstract
Different applications require different sensor technologies and methods to achieve specific goals. Particular sensor designs are focused on solving problems. It is well-known that individual sensors can be limited when complex problems or applications are involved or the application requires sensing in [...] Read more.
Different applications require different sensor technologies and methods to achieve specific goals. Particular sensor designs are focused on solving problems. It is well-known that individual sensors can be limited when complex problems or applications are involved or the application requires sensing in different locations or even different geographical areas. [...] Full article
(This article belongs to the Special Issue Collaborative Sensors)

Research

Jump to: Editorial, Review, Other

Open AccessCommunication Resonant Frequency Characteristics of a SAW Device Attached to Resonating Micropillars
Sensors 2012, 12(4), 3789-3797; doi:10.3390/s120403789
Received: 19 January 2012 / Revised: 29 February 2012 / Accepted: 1 March 2012 / Published: 23 March 2012
Cited by 8 | PDF Full-text (698 KB) | HTML Full-text | XML Full-text
Abstract
Recently we reported experimental and simulation results on an increase in resonance frequency of a SAW resonator caused by mass loading of micropillars made of SU-8, attached normal to the surface of the resonator. We concluded that SAW resonator and the SU-8 [...] Read more.
Recently we reported experimental and simulation results on an increase in resonance frequency of a SAW resonator caused by mass loading of micropillars made of SU-8, attached normal to the surface of the resonator. We concluded that SAW resonator and the SU-8 micropillars in unison form a system of coupled resonators. We have now extended this work and performed a finite element method simulation to study the resonance frequency characteristics of the SAW-based coupled resonator. In this paper we report the effect of the resonance frequency of the micropillars on the resonance frequency of the system of coupled resonators, and observe the coupling of micropillar resonance and the propagating SAW as described in the well known Dybwad system of coupled resonators. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Submersible UV-Vis Spectroscopy for Quantifying Streamwater Organic Carbon Dynamics: Implementation and Challenges before and after Forest Harvest in a Headwater Stream
Sensors 2012, 12(4), 3798-3813; doi:10.3390/s120403798
Received: 3 March 2012 / Revised: 14 March 2012 / Accepted: 21 March 2012 / Published: 23 March 2012
Cited by 7 | PDF Full-text (677 KB) | HTML Full-text | XML Full-text
Abstract
Organic material, including total and dissolved organic carbon (DOC), is ubiquitous within aquatic ecosystems, playing a variety of important and diverse biogeochemical and ecological roles. Determining how land-use changes affect DOC concentrations and bioavailability within aquatic ecosystems is an important means of [...] Read more.
Organic material, including total and dissolved organic carbon (DOC), is ubiquitous within aquatic ecosystems, playing a variety of important and diverse biogeochemical and ecological roles. Determining how land-use changes affect DOC concentrations and bioavailability within aquatic ecosystems is an important means of evaluating the effects on ecological productivity and biogeochemical cycling. This paper presents a methodology case study looking at the deployment of a submersible UV-Vis absorbance spectrophotometer (UV-Vis spectro::lyzer model, s::can, Vienna, Austria) to determine stream organic carbon dynamics within a headwater catchment located near Campbell River (British Columbia, Canada). Field-based absorbance measurements of DOC were made before and after forest harvest, highlighting the advantages of high temporal resolution compared to traditional grab sampling and laboratory measurements. Details of remote deployment are described. High-frequency DOC data is explored by resampling the 30 min time series with a range of resampling time intervals (from daily to weekly time steps). DOC export was calculated for three months from the post-harvest data and resampled time series, showing that sampling frequency has a profound effect on total DOC export. DOC exports derived from weekly measurements were found to underestimate export by as much as 30% compared to DOC export calculated from high-frequency data. Additionally, the importance of the ability to remotely monitor the system through a recently deployed wireless connection is emphasized by examining causes of prior data losses, and how such losses may be prevented through the ability to react when environmental or power disturbances cause system interruption and data loss. Full article
(This article belongs to the Special Issue Underwater Sensor Nodes and Underwater Sensor Networks)
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Open AccessArticle A Variant Quorum Sensing System in Aeromonas veronii MTCC 3249
Sensors 2012, 12(4), 3814-3830; doi:10.3390/s120403814
Received: 21 February 2012 / Revised: 17 March 2012 / Accepted: 20 March 2012 / Published: 26 March 2012
Cited by 4 | PDF Full-text (658 KB) | HTML Full-text | XML Full-text
Abstract
We have investigated the quorum sensing control in Aeromonas veronii MTCC 3249, originally isolated as A. culicicola from the midgut of Culex quinquefasciatus. Based on biosensor assays, the bacterium showed constant production of multiple acyl-homoserine lactones (AHLs) with increasing cell-density. The [...] Read more.
We have investigated the quorum sensing control in Aeromonas veronii MTCC 3249, originally isolated as A. culicicola from the midgut of Culex quinquefasciatus. Based on biosensor assays, the bacterium showed constant production of multiple acyl-homoserine lactones (AHLs) with increasing cell-density. The luxRI gene homologs, acuR (A. culicicola transcriptional Regulator) and acuI (A. culicicola autoInducer) were successfully amplified by inverse-PCR. Sequence analysis indicated acuRI were divergent from all known quorum sensing gene homologs in Aeromonas. Two localized regions in the C-terminal autoinducer binding domain of acuR showed indels suggesting variations in autoinducer specificity. Further, only a single copy of the quorum sensing genes was detected, suggesting a tight regulation of mechanisms under its control. Chromatography and further chemical analysis identified two AHLs in the culture supernatant: 6-carboxy-HHL (homoadipyl homoserine lactone), a novel AHL, and N-tetradecanoylhomoserine lactone. The existence of a potentially variant quorum sensing system might therefore, reflect in some way the ecological strategies adopted by this bacterium in the mosquito midgut. Full article
Open AccessArticle A Neuro-Inspired Spike-Based PID Motor Controller for Multi-Motor Robots with Low Cost FPGAs
Sensors 2012, 12(4), 3831-3856; doi:10.3390/s120403831
Received: 5 February 2012 / Revised: 12 March 2012 / Accepted: 21 March 2012 / Published: 26 March 2012
Cited by 15 | PDF Full-text (811 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we present a neuro-inspired spike-based close-loop controller written in VHDL and implemented for FPGAs. This controller has been focused on controlling a DC motor speed, but only using spikes for information representation, processing and DC motor driving. It could [...] Read more.
In this paper we present a neuro-inspired spike-based close-loop controller written in VHDL and implemented for FPGAs. This controller has been focused on controlling a DC motor speed, but only using spikes for information representation, processing and DC motor driving. It could be applied to other motors with proper driver adaptation. This controller architecture represents one of the latest layers in a Spiking Neural Network (SNN), which implements a bridge between robotics actuators and spike-based processing layers and sensors. The presented control system fuses actuation and sensors information as spikes streams, processing these spikes in hard real-time, implementing a massively parallel information processing system, through specialized spike-based circuits. This spike-based close-loop controller has been implemented into an AER platform, designed in our labs, that allows direct control of DC motors: the AER-Robot. Experimental results evidence the viability of the implementation of spike-based controllers, and hardware synthesis denotes low hardware requirements that allow replicating this controller in a high number of parallel controllers working together to allow a real-time robot control. Full article
(This article belongs to the Special Issue Biomimetic Sensors, Actuators and Integrated Systems)
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Open AccessArticle A Fiber Optic Catalytic Sensor for Neutral Atom Measurements in Oxygen Plasma
Sensors 2012, 12(4), 3857-3867; doi:10.3390/s120403857
Received: 13 February 2012 / Revised: 14 March 2012 / Accepted: 14 March 2012 / Published: 26 March 2012
Cited by 6 | PDF Full-text (361 KB) | HTML Full-text | XML Full-text
Abstract
The presented sensor for neutral oxygen atom measurement in oxygen plasma is a catalytic probe which uses fiber optics and infrared detection system to measure the gray body radiation of the catalyst. The density of neutral atoms can be determined from the [...] Read more.
The presented sensor for neutral oxygen atom measurement in oxygen plasma is a catalytic probe which uses fiber optics and infrared detection system to measure the gray body radiation of the catalyst. The density of neutral atoms can be determined from the temperature curve of the probe, because the catalyst is heated predominantly by the dissipation of energy caused by the heterogeneous surface recombination of neutral atoms. The advantages of this sensor are that it is simple, reliable, easy to use, noninvasive, quantitative and can be used in plasma discharge regions. By using different catalyst materials the sensor can also be applied for detection of neutral atoms in other plasmas. Sensor design, operation, example measurements and new measurement procedure for systematic characterization are presented. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2012)
Open AccessArticle Improvement of KinectTM Sensor Capabilities by Fusion with Laser Sensing Data Using Octree
Sensors 2012, 12(4), 3868-3878; doi:10.3390/s120403868
Received: 21 January 2012 / Revised: 20 February 2012 / Accepted: 21 February 2012 / Published: 26 March 2012
Cited by 4 | PDF Full-text (5802 KB) | HTML Full-text | XML Full-text
Abstract
To enhance sensor capabilities, sensor data readings from different modalities must be fused. The main contribution of this paper is to present a sensor data fusion approach that can reduce KinectTM sensor limitations. This approach involves combining laser with KinectTM [...] Read more.
To enhance sensor capabilities, sensor data readings from different modalities must be fused. The main contribution of this paper is to present a sensor data fusion approach that can reduce KinectTM sensor limitations. This approach involves combining laser with KinectTM sensors. Sensor data is modelled in a 3D environment based on octrees using a probabilistic occupancy estimation. The Bayesian method, which takes into account the uncertainty inherent in the sensor measurements, is used to fuse the sensor information and update the 3D octree map. The sensor fusion yields a significant increase of the field of view of the KinectTM sensor that can be used for robot tasks. Full article
(This article belongs to the Special Issue Collaborative Sensors)
Open AccessArticle Clinical Application of Surface Plasmon Resonance-Based Biosensors for Fetal Fibronectin Detection
Sensors 2012, 12(4), 3879-3890; doi:10.3390/s120403879
Received: 21 February 2012 / Revised: 16 March 2012 / Accepted: 20 March 2012 / Published: 26 March 2012
Cited by 10 | PDF Full-text (511 KB) | HTML Full-text | XML Full-text
Abstract
Preterm birth is the leading cause of perinatal morbidity and mortality. Fetal fibronectin (fFN), a glycoprotein in the extracellular matrix of the amniotic membranes, is the most powerful biomarker for predicting the risk of preterm birth. Biosensors using the surface plasmon resonance [...] Read more.
Preterm birth is the leading cause of perinatal morbidity and mortality. Fetal fibronectin (fFN), a glycoprotein in the extracellular matrix of the amniotic membranes, is the most powerful biomarker for predicting the risk of preterm birth. Biosensors using the surface plasmon resonance (SPR) response are potentially useful in quantitatively measuring molecules. We established a standard calibration curve of SPR intensity against fFN concentration and used the SPR-based biosensor to detect fFN concentrations in the cervicovaginal secretions of pregnant women between 22 and 34 weeks of gestation. The calibration curve extends from 0.5 ng/mL to 100 ng/mL with an excellent correlation (R2 = 0.985) based on standard fFN samples. A cutoff value of 50 ng/mL fFN concentration in commercial ELISA kits corresponds to a relative intensity of 17 arbitrary units (a.u.) in SPR. Thirty-two pregnant women were analyzed in our study. In 11 women, the SPR relative intensity was greater than or equal to 17 a.u., and in 21 women, the SPR relative intensity was less than 17 a.u. There were significant differences between the two groups in regular uterine contractions (p = 0.040), hospitalization for tocolysis (p = 0.049), and delivery weeks (p = 0.043). Our prospective study concluded that SPR-based biosensors can quantitatively measure fFN concentrations. These results reveal the potential utility of SPR-based biosensors in predicting the risk of preterm birth. Full article
(This article belongs to the Special Issue Biomarkers and Nanosensors: New Approaches for Biology and Medicine)
Open AccessArticle Sensitivity Enhancement of Strain Sensing Utilizing a Differential Pair of Fiber Bragg Gratings
Sensors 2012, 12(4), 3891-3900; doi:10.3390/s120403891
Received: 16 February 2012 / Revised: 28 February 2012 / Accepted: 5 March 2012 / Published: 26 March 2012
Cited by 6 | PDF Full-text (596 KB) | HTML Full-text | XML Full-text
Abstract
In strain measurement applications, the matched fiber Bragg gratings (FBG) method is generally used to reduce temperature dependence effects. The FBG parameters have to be designed to meet the requirements by the particular application. The bandwidth and slope of the FBG has [...] Read more.
In strain measurement applications, the matched fiber Bragg gratings (FBG) method is generally used to reduce temperature dependence effects. The FBG parameters have to be designed to meet the requirements by the particular application. The bandwidth and slope of the FBG has to be balanced well, according to the measurement range, accuracy and sensitivity. A sensitivity enhanced strain demodulation method without sacrificing the measurement range for FBG sensing systems is proposed and demonstrated utilizing a pair of reference FBGs. One of the reference FBGs and the sensing FBG have almost the same Bragg wavelength, while the other reference FBGs has a Bragg wavelength offset relative to the sensing FBG. Reflected optical signals from the sensing FBG pass through two reference FBGs, and subtract from each other after the detection. Doubled strain measurement sensitivity is obtained by static rail load experiments compared to the general matched grating approach, and further verified in dynamic load experiments. Experimental results indicate that such a method could be used for real-time rail strain monitoring applications. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2012)
Open AccessArticle Monitoring and Failure Analysis of Corroded Bridge Cables under Fatigue Loading Using Acoustic Emission Sensors
Sensors 2012, 12(4), 3901-3915; doi:10.3390/s120403901
Received: 21 February 2012 / Revised: 19 March 2012 / Accepted: 20 March 2012 / Published: 26 March 2012
Cited by 8 | PDF Full-text (1096 KB) | HTML Full-text | XML Full-text
Abstract
Cables play an important role in cable-stayed systems, but are vulnerable to corrosion and fatigue damage. There is a dearth of studies on the fatigue damage evolution of corroded cable. In the present study, the acoustic emission (AE) technology is adopted to [...] Read more.
Cables play an important role in cable-stayed systems, but are vulnerable to corrosion and fatigue damage. There is a dearth of studies on the fatigue damage evolution of corroded cable. In the present study, the acoustic emission (AE) technology is adopted to monitor the fatigue damage evolution process. First, the relationship between stress and strain is determined through a tensile test for corroded and non-corroded steel wires. Results show that the mechanical performance of corroded cables is changed considerably. The AE characteristic parameters for fatigue damage are then established. AE energy cumulative parameters can accurately describe the fatigue damage evolution of corroded cables. The failure modes in each phase as well as the type of acoustic emission source are determined based on the results of scanning electron microscopy. The waveform characteristics, damage types, and frequency distribution of the corroded cable at different damage phases are collected. Finally, the number of broken wires and breakage time of the cables are determined according to the variation in the margin index. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Dithiooxamide Modified Glassy Carbon Electrode for the Studies of Non-Aqueous Media: Electrochemical Behaviors of Quercetin on the Electrode Surface
Sensors 2012, 12(4), 3916-3928; doi:10.3390/s120403916
Received: 13 February 2012 / Revised: 13 March 2012 / Accepted: 14 March 2012 / Published: 26 March 2012
Cited by 4 | PDF Full-text (1127 KB) | HTML Full-text | XML Full-text
Abstract
Electrochemical oxidation of quercetin, as an important biological molecule, has been studied in non-aqueous media using cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. To investigate the electrochemical properties of quercetin, an important flavonoid derivative, on a different surface, a new [...] Read more.
Electrochemical oxidation of quercetin, as an important biological molecule, has been studied in non-aqueous media using cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. To investigate the electrochemical properties of quercetin, an important flavonoid derivative, on a different surface, a new glassy carbon electrode has been developed using dithiooxamide as modifier in non-aqueous media. The surface modification of glassy carbon electrode has been performed within the 0.0 mV and +800 mV potential range with 20 cycles using 1 mM dithioxamide solution in acetonitrile. However, the modification of quercetin to both bare glassy carbon and dithiooxamide modified glassy carbon electrode surface was carried out in a wide +300 mV and +2,800 mV potential range with 10 cycles. Following the modification process, cyclic voltammetry has been used for the surface characterization in aqueous and non-aqueous media whereas electrochemical impedance spectroscopy has been used in aqueous media. Scanning electron microscopy has also been used to support the surface analysis. The obtained data from the characterization and modification studies of dithioxamide modified and quercetin grafted glassy carbon electrode showed that the developed electrode can be used for the quantitative determination of quercetin and antioxidant capacity determination as a chemical sensor electrode. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A CMOS-Compatible Poly-Si Nanowire Device with Hybrid Sensor/Memory Characteristics for System-on-Chip Applications
Sensors 2012, 12(4), 3952-3963; doi:10.3390/s120403952
Received: 13 January 2012 / Revised: 20 February 2012 / Accepted: 22 March 2012 / Published: 26 March 2012
Cited by 10 | PDF Full-text (374 KB) | HTML Full-text | XML Full-text
Abstract
This paper reports a versatile nano-sensor technology using “top-down” poly-silicon nanowire field-effect transistors (FETs) in the conventional Complementary Metal-Oxide Semiconductor (CMOS)-compatible semiconductor process. The nanowire manufacturing technique reduced nanowire width scaling to 50 nm without use of extra lithography equipment, and exhibited [...] Read more.
This paper reports a versatile nano-sensor technology using “top-down” poly-silicon nanowire field-effect transistors (FETs) in the conventional Complementary Metal-Oxide Semiconductor (CMOS)-compatible semiconductor process. The nanowire manufacturing technique reduced nanowire width scaling to 50 nm without use of extra lithography equipment, and exhibited superior device uniformity. These n type polysilicon nanowire FETs have positive pH sensitivity (100 mV/pH) and sensitive deoxyribonucleic acid (DNA) detection ability (100 pM) at normal system operation voltages. Specially designed oxide-nitride-oxide buried oxide nanowire realizes an electrically Vth-adjustable sensor to compensate device variation. These nanowire FETs also enable non-volatile memory application for a large and steady Vth adjustment window (>2 V Programming/Erasing window). The CMOS-compatible manufacturing technique of polysilicon nanowire FETs offers a possible solution for commercial System-on-Chip biosensor application, which enables portable physiology monitoring and in situ recording. Full article
(This article belongs to the Special Issue Sensing at the Nano-Scale: Chemical and Bio-Sensing)
Open AccessArticle An Environmental Monitoring System for Managing Spatiotemporal Sensor Data over Sensor Networks
Sensors 2012, 12(4), 3997-4015; doi:10.3390/s120403997
Received: 25 February 2012 / Revised: 13 March 2012 / Accepted: 21 March 2012 / Published: 27 March 2012
Cited by 2 | PDF Full-text (1349 KB) | HTML Full-text | XML Full-text
Abstract
In a wireless sensor network, sensors collect data about natural phenomena and transmit them to a server in real-time. Many studies have been conducted focusing on the processing of continuous queries in an approximate form. However, this approach is difficult to apply [...] Read more.
In a wireless sensor network, sensors collect data about natural phenomena and transmit them to a server in real-time. Many studies have been conducted focusing on the processing of continuous queries in an approximate form. However, this approach is difficult to apply to environmental applications which require the correct data to be stored. In this paper, we propose a weather monitoring system for handling and storing the sensor data stream in real-time in order to support continuous spatial and/or temporal queries. In our system, we exploit two time-based insertion methods to store the sensor data stream and reduce the number of managed tuples, without losing any of the raw data which are useful for queries, by using the sensors’ temporal attributes. In addition, we offer a method for reducing the cost of the join operations used in processing spatiotemporal queries by filtering out a list of irrelevant sensors from query range before making a join operation. In the results of the performance evaluation, the number of tuples obtained from the data stream is reduced by about 30% in comparison to a naïve approach, thereby decreasing the query execution time. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Inhibition of Quorum Sensing-Controlled Virulence Factor Production in Pseudomonas aeruginosa PAO1 by Ayurveda Spice Clove (Syzygium Aromaticum) Bud Extract
Sensors 2012, 12(4), 4016-4030; doi:10.3390/s120404016
Received: 16 January 2012 / Revised: 17 March 2012 / Accepted: 21 March 2012 / Published: 27 March 2012
Cited by 50 | PDF Full-text (940 KB) | HTML Full-text | XML Full-text
Abstract
Quorum sensing controls the virulence determinants in most proteobacteria. In this work, the hexane, chloroform and methanol extracts of an Ayurveda spice, namely clove (Syzygium aromaticum), shown anti-quorum sensing activity. Hexane and methanol extracts of clove inhibited the response of [...] Read more.
Quorum sensing controls the virulence determinants in most proteobacteria. In this work, the hexane, chloroform and methanol extracts of an Ayurveda spice, namely clove (Syzygium aromaticum), shown anti-quorum sensing activity. Hexane and methanol extracts of clove inhibited the response of C. violaceum CV026 to exogenously supplied N‑hexanoylhomoserine lactone, in turn preventing violacein production. Chloroform and methanol extracts of clove significantly reduced bioluminescence production by E. coli [pSB1075] grown in the presence of N-(3-oxododecanoyl)-L-homoserine lactone. We demonstrated that clove extract inhibited quorum sensing-regulated phenotypes in Pseudomonas aeruginosa PA01, including expression of lecA::lux (by hexane extract), swarming (maximum inhibition by methanol extract), pyocyanin (maximum inhibition by hexane extract). This study shows that the presence of natural compounds that exhibit anti-quorum sensing activity in the clove extracts may be useful as the lead of anti-infective drugs. Full article
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Open AccessArticle Sensor and Sensorless Fault Tolerant Control for Induction Motors Using a Wavelet Index
Sensors 2012, 12(4), 4031-4050; doi:10.3390/s120404031
Received: 21 February 2012 / Revised: 15 March 2012 / Accepted: 22 March 2012 / Published: 27 March 2012
Cited by 9 | PDF Full-text (748 KB) | HTML Full-text | XML Full-text
Abstract
Fault Tolerant Control (FTC) systems are crucial in industry to ensure safe and reliable operation, especially of motor drives. This paper proposes the use of multiple controllers for a FTC system of an induction motor drive, selected based on a switching mechanism. [...] Read more.
Fault Tolerant Control (FTC) systems are crucial in industry to ensure safe and reliable operation, especially of motor drives. This paper proposes the use of multiple controllers for a FTC system of an induction motor drive, selected based on a switching mechanism. The system switches between sensor vector control, sensorless vector control, closed-loop voltage by frequency (V/f) control and open loop V/f control. Vector control offers high performance, while V/f is a simple, low cost strategy with high speed and satisfactory performance. The faults dealt with are speed sensor failures, stator winding open circuits, shorts and minimum voltage faults. In the event of compound faults, a protection unit halts motor operation. The faults are detected using a wavelet index. For the sensorless vector control, a novel Boosted Model Reference Adaptive System (BMRAS) to estimate the motor speed is presented, which reduces tuning time. Both simulation results and experimental results with an induction motor drive show the scheme to be a fast and effective one for fault detection, while the control methods transition smoothly and ensure the effectiveness of the FTC system. The system is also shown to be flexible, reverting rapidly back to the dominant controller if the motor returns to a healthy state. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Novel Integrated Multifunction Micro-Sensor for Three-Dimensional Micro-Force Measurements
Sensors 2012, 12(4), 4051-4064; doi:10.3390/s120404051
Received: 9 February 2012 / Revised: 22 February 2012 / Accepted: 22 February 2012 / Published: 27 March 2012
Cited by 2 | PDF Full-text (1112 KB) | HTML Full-text | XML Full-text
Abstract
An integrated multifunction micro-sensor for three-dimensional micro-force precision measurement under different pressure and temperature conditions is introduced in this paper. The integrated sensor consists of three kinds of sensors: a three-dimensional micro-force sensor, an absolute pressure sensor and a temperature sensor. The [...] Read more.
An integrated multifunction micro-sensor for three-dimensional micro-force precision measurement under different pressure and temperature conditions is introduced in this paper. The integrated sensor consists of three kinds of sensors: a three-dimensional micro-force sensor, an absolute pressure sensor and a temperature sensor. The integrated multifunction micro-sensor is fabricated on silicon wafers by micromachining technology. Different doping doses of boron ion, placement and structure of resistors are tested for the force sensor, pressure sensor and temperature sensor to minimize the cross interference and optimize the properties. A glass optical fiber, with a ladder structure and sharp tip etched by buffer oxide etch solution, is glued on the micro-force sensor chip as the tactile probe. Experimental results show that the minimum force that can be detected by the force sensor is 300 nN; the lateral sensitivity of the force sensor is 0.4582 mV/μN; the probe length is linearly proportional to sensitivity of the micro-force sensor in lateral; the sensitivity of the pressure sensor is 0.11 mv/KPa; the sensitivity of the temperature sensor is 5.836 × 10−3 KΩ/°C. Thus it is a cost-effective method to fabricate integrated multifunction micro-sensors with different measurement ranges that could be used in many fields. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Quorum Quenching Bacillus sonorensis Isolated from Soya Sauce Fermentation Brine
Sensors 2012, 12(4), 4065-4073; doi:10.3390/s120404065
Received: 16 January 2012 / Revised: 6 March 2012 / Accepted: 22 March 2012 / Published: 27 March 2012
Cited by 15 | PDF Full-text (675 KB) | HTML Full-text | XML Full-text
Abstract
An N-acylhomoserine lactone (AHL)-degrading bacterial strain, L62, was isolated from a sample of fermentation brine of Chinese soya sauce by using rich medium agar supplemented with soya sauce (10% v/v). L62, a rod-shaped Gram positive bacterium with amylolytic activity, was phylogentically [...] Read more.
An N-acylhomoserine lactone (AHL)-degrading bacterial strain, L62, was isolated from a sample of fermentation brine of Chinese soya sauce by using rich medium agar supplemented with soya sauce (10% v/v). L62, a rod-shaped Gram positive bacterium with amylolytic activity, was phylogentically related to Bacillus sonorensis by 16S ribosomal DNA and rpoB sequence analyses. B. sonorensis L62 efficiently degraded N-3-oxohexanoyl homoserine lactone and N-octanoylhomoserine lactone. However, the aiiA homologue, encoding an autoinducer inactivation enzyme catalyzing the degradation of AHLs, was not detected in L62, suggesting the presence of a different AHL-degrading gene in L62. To the best of our knowledge, this is the first report of AHL-degrading B. sonorensis from soya sauce liquid state fermentation. Full article
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Open AccessArticle Equations for Solar Tracking
Sensors 2012, 12(4), 4074-4090; doi:10.3390/s120404074
Received: 9 February 2012 / Revised: 16 March 2012 / Accepted: 16 March 2012 / Published: 27 March 2012
Cited by 2 | PDF Full-text (2757 KB) | HTML Full-text | XML Full-text
Abstract
Direct sunlight absorption by trace gases can be used to quantify them and investigate atmospheric chemistry. In such experiments, the main optical apparatus is often a grating or a Fourier transform spectrometer. A solar tracker based on motorized rotating mirrors is commonly [...] Read more.
Direct sunlight absorption by trace gases can be used to quantify them and investigate atmospheric chemistry. In such experiments, the main optical apparatus is often a grating or a Fourier transform spectrometer. A solar tracker based on motorized rotating mirrors is commonly used to direct the light along the spectrometer axis, correcting for the apparent rotation of the Sun. Calculating the Sun azimuth and altitude for a given time and location can be achieved with high accuracy but different sources of angular offsets appear in practice when positioning the mirrors. A feedback on the motors, using a light position sensor close to the spectrometer, is almost always needed. This paper aims to gather the main geometrical formulas necessary for the use of a widely used kind of solar tracker, based on two 45° mirrors in altazimuthal set-up with a light sensor on the spectrometer, and to illustrate them with a tracker developed by our group for atmospheric research. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Fast Direct Injection Mass-Spectrometric Characterization of Stimuli for Insect Electrophysiology by Proton Transfer Reaction-Time of Flight Mass-Spectrometry (PTR-ToF-MS)
Sensors 2012, 12(4), 4091-4104; doi:10.3390/s120404091
Received: 21 January 2012 / Revised: 14 March 2012 / Accepted: 22 March 2012 / Published: 27 March 2012
Cited by 5 | PDF Full-text (340 KB) | HTML Full-text | XML Full-text
Abstract
Electrophysiological techniques are used in insect neuroscience to measure the response of olfactory neurons to volatile odour stimuli. Widely used systems to deliver an olfactory stimulus to a test insect include airstream guided flow through glass cartridges loaded with a given volatile [...] Read more.
Electrophysiological techniques are used in insect neuroscience to measure the response of olfactory neurons to volatile odour stimuli. Widely used systems to deliver an olfactory stimulus to a test insect include airstream guided flow through glass cartridges loaded with a given volatile compound on a sorbent support. Precise measurement of the quantity of compound reaching the sensory organ of the test organism is an urgent task in insect electrophysiology. In this study we evaluated the performances of the recent realised proton transfer reaction-time of flight mass-spectrometry (PTR-ToF-MS) as a fast and selective gas sensor. In particular, we characterised the gas emission from cartridges loaded with a set of volatile compounds belonging to different chemical classes and commonly used in electrophysiological experiments. PTR-ToF-MS allowed a fast monitoring of all investigated compounds with sufficient sensitivity and time resolution. The detection and the quantification of air contaminants and solvent or synthetic standards impurities allowed a precise quantification of the stimulus exiting the cartridge. The outcome of this study was twofold: on one hand we showed that PTR-ToF-MS allows monitoring fast processes with high sensitivity by real time detection of a broad number of compounds; on the other hand we provided a tool to solve an important issue in insect electrophysiology. Full article
Open AccessCommunication Effect of Functional Group and Carbon Chain Length on the Odor Detection Threshold of Aliphatic Compounds
Sensors 2012, 12(4), 4105-4112; doi:10.3390/s120404105
Received: 30 January 2012 / Revised: 20 March 2012 / Accepted: 22 March 2012 / Published: 27 March 2012
Cited by 6 | PDF Full-text (214 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Odor detection thresholds (ODTs) are used for assessing outdoor and indoor air quality. They are obtained experimentally by olfactometry and psychophysical methods, and large compilations are available in the literature. A non-linear regression equation was fitted to describe the ODT variability of [...] Read more.
Odor detection thresholds (ODTs) are used for assessing outdoor and indoor air quality. They are obtained experimentally by olfactometry and psychophysical methods, and large compilations are available in the literature. A non-linear regression equation was fitted to describe the ODT variability of 114 aliphatic compounds based on the alkyl chain length for different homologous series (carboxylic acids, aldehydes, 2-ketones, esters, 1-alcohols, amines, thiols, thioethers and hydrocarbons). The resulting equation reveals an effect of the functional group, molecular size and also an interaction between both factors. Although the mechanistic interpretation of results is uncertain, the relatively high goodness-of-fit (R2 = 0.90) suggests that ODT values of aliphatic compounds can be predicted rather accurately, which is not the case for rigid molecules. This equation may serve as a basis for the development of more complex ODT models taking into account diverse structural features of odorants. The variability of power-law exponents was also investigated for the homologous series. Full article
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Open AccessArticle Acoustic Transmitters for Underwater Neutrino Telescopes
Sensors 2012, 12(4), 4113-4132; doi:10.3390/s120404113
Received: 29 February 2012 / Revised: 20 March 2012 / Accepted: 22 March 2012 / Published: 27 March 2012
Cited by 7 | PDF Full-text (1319 KB) | HTML Full-text | XML Full-text
Abstract
In this paper acoustic transmitters that were developed for use in underwater neutrino telescopes are presented. Firstly, an acoustic transceiver has been developed as part of the acoustic positioning system of neutrino telescopes. These infrastructures are not completely rigid and require a [...] Read more.
In this paper acoustic transmitters that were developed for use in underwater neutrino telescopes are presented. Firstly, an acoustic transceiver has been developed as part of the acoustic positioning system of neutrino telescopes. These infrastructures are not completely rigid and require a positioning system in order to monitor the position of the optical sensors which move due to sea currents. To guarantee a reliable and versatile system, the transceiver has the requirements of reduced cost, low power consumption, high pressure withstanding (up to 500 bars), high intensity for emission, low intrinsic noise, arbitrary signals for emission and the capacity of acquiring and processing received signals. Secondly, a compact acoustic transmitter array has been developed for the calibration of acoustic neutrino detection systems. The array is able to mimic the signature of ultra-high-energy neutrino interaction in emission directivity and signal shape. The technique of parametric acoustic sources has been used to achieve the proposed aim. The developed compact array has practical features such as easy manageability and operation. The prototype designs and the results of different tests are described. The techniques applied for these two acoustic systems are so powerful and versatile that may be of interest in other marine applications using acoustic transmitters. Full article
(This article belongs to the Special Issue Underwater Sensor Nodes and Underwater Sensor Networks)
Open AccessArticle Differential Binary Encoding Method for Calibrating Image Sensors Based on IOFBs
Sensors 2012, 12(4), 4133-4155; doi:10.3390/s120404133
Received: 3 February 2012 / Revised: 20 March 2012 / Accepted: 22 March 2012 / Published: 27 March 2012
Cited by 3 | PDF Full-text (2282 KB) | HTML Full-text | XML Full-text
Abstract
Image transmission using incoherent optical fiber bundles (IOFBs) requires prior calibration to obtain the spatial in-out fiber correspondence necessary to reconstruct the image captured by the pseudo-sensor. This information is recorded in a Look-Up Table called the Reconstruction Table (RT), used later [...] Read more.
Image transmission using incoherent optical fiber bundles (IOFBs) requires prior calibration to obtain the spatial in-out fiber correspondence necessary to reconstruct the image captured by the pseudo-sensor. This information is recorded in a Look-Up Table called the Reconstruction Table (RT), used later for reordering the fiber positions and reconstructing the original image. This paper presents a very fast method based on image-scanning using spaces encoded by a weighted binary code to obtain the in-out correspondence. The results demonstrate that this technique yields a remarkable reduction in processing time and the image reconstruction quality is very good compared to previous techniques based on spot or line scanning, for example. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Spatial Heterogeneity of Autoinducer Regulation Systems
Sensors 2012, 12(4), 4156-4171; doi:10.3390/s120404156
Received: 21 February 2012 / Revised: 15 March 2012 / Accepted: 21 March 2012 / Published: 28 March 2012
Cited by 8 | PDF Full-text (326 KB) | HTML Full-text | XML Full-text
Abstract
Autoinducer signals enable coordinated behaviour of bacterial populations, a phenomenon originally described as quorum sensing. Autoinducer systems are often controlled by environmental substances as nutrients or secondary metabolites (signals) from neighbouring organisms. In cell aggregates and biofilms gradients of signals and environmental [...] Read more.
Autoinducer signals enable coordinated behaviour of bacterial populations, a phenomenon originally described as quorum sensing. Autoinducer systems are often controlled by environmental substances as nutrients or secondary metabolites (signals) from neighbouring organisms. In cell aggregates and biofilms gradients of signals and environmental substances emerge. Mathematical modelling is used to analyse the functioning of the system. We find that the autoinducer regulation network generates spatially heterogeneous behaviour, up to a kind of multicellularity-like division of work, especially under nutrient-controlled conditions. A hybrid push/pull concept is proposed to explain the ecological function. The analysis allows to explain hitherto seemingly contradicting experimental findings. Full article
Open AccessArticle A High Sensitivity Three-Dimensional-Shape Sensing Patch Prepared by Lithography and Inkjet Printing
Sensors 2012, 12(4), 4172-4186; doi:10.3390/s120404172
Received: 28 February 2012 / Revised: 16 March 2012 / Accepted: 16 March 2012 / Published: 28 March 2012
Cited by 6 | PDF Full-text (1425 KB) | HTML Full-text | XML Full-text
Abstract
A process combining conventional photolithography and a novel inkjet printing method for the manufacture of high sensitivity three-dimensional-shape (3DS) sensing patches was proposed and demonstrated. The supporting curvature ranges from 1.41 to 6.24 ´ 10−2 mm−1 and the sensing patch [...] Read more.
A process combining conventional photolithography and a novel inkjet printing method for the manufacture of high sensitivity three-dimensional-shape (3DS) sensing patches was proposed and demonstrated. The supporting curvature ranges from 1.41 to 6.24 ´ 10−2 mm−1 and the sensing patch has a thickness of less than 130 μm and 20 ´ 20 mm2 dimensions. A complete finite element method (FEM) model with simulation results was calculated and performed based on the buckling of columns and the deflection equation. The results show high compatibility of the drop-on-demand (DOD) inkjet printing with photolithography and the interferometer design also supports bi-directional detection of deformation. The 3DS sensing patch can be operated remotely without any power consumption. It provides a novel and alternative option compared with other optical curvature sensors. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering 2011)
Open AccessArticle Reducing False Negative Reads in RFID Data Streams Using an Adaptive Sliding-Window Approach
Sensors 2012, 12(4), 4187-4212; doi:10.3390/s120404187
Received: 18 February 2012 / Revised: 16 March 2012 / Accepted: 21 March 2012 / Published: 28 March 2012
Cited by 5 | PDF Full-text (404 KB) | HTML Full-text | XML Full-text
Abstract
Unreliability of the data streams generated by RFID readers is among the primary factors which limit the widespread adoption of the RFID technology. RFID data cleaning is, therefore, an essential task in the RFID middleware systems in order to reduce reading errors, [...] Read more.
Unreliability of the data streams generated by RFID readers is among the primary factors which limit the widespread adoption of the RFID technology. RFID data cleaning is, therefore, an essential task in the RFID middleware systems in order to reduce reading errors, and to allow these data streams to be used to make a correct interpretation and analysis of the physical world they are representing. In this paper we propose an adaptive sliding-window based approach called WSTD which is capable of efficiently coping with both environmental variation and tag dynamics. Our experimental results demonstrate the efficacy of the proposed approach. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle A Real-Time Measurement System for Long-Life Flood Monitoring and Warning Applications
Sensors 2012, 12(4), 4213-4236; doi:10.3390/s120404213
Received: 7 February 2012 / Revised: 14 March 2012 / Accepted: 22 March 2012 / Published: 28 March 2012
Cited by 10 | PDF Full-text (9046 KB) | HTML Full-text | XML Full-text
Abstract
A flood warning system incorporates telemetered rainfall and flow/water level data measured at various locations in the catchment area. Real-time accurate data collection is required for this use, and sensor networks improve the system capabilities. However, existing sensor nodes struggle to satisfy [...] Read more.
A flood warning system incorporates telemetered rainfall and flow/water level data measured at various locations in the catchment area. Real-time accurate data collection is required for this use, and sensor networks improve the system capabilities. However, existing sensor nodes struggle to satisfy the hydrological requirements in terms of autonomy, sensor hardware compatibility, reliability and long-range communication. We describe the design and development of a real-time measurement system for flood monitoring, and its deployment in a flash-flood prone 650 km2 semiarid watershed in Southern Spain. A developed low-power and long-range communication device, so-called DatalogV1, provides automatic data gathering and reliable transmission. DatalogV1 incorporates self-monitoring for adapting measurement schedules for consumption management and to capture events of interest. Two tests are used to assess the success of the development. The results show an autonomous and robust monitoring system for long-term collection of water level data inmany sparse locations during flood events. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle Underwater Wireless Sensor Communications in the 2.4 GHz ISM Frequency Band
Sensors 2012, 12(4), 4237-4264; doi:10.3390/s120404237
Received: 20 February 2012 / Revised: 19 March 2012 / Accepted: 26 March 2012 / Published: 28 March 2012
Cited by 19 | PDF Full-text (865 KB) | HTML Full-text | XML Full-text
Abstract
One of the main problems in underwater communications is the low data rate available due to the use of low frequencies. Moreover, there are many problems inherent to the medium such as reflections, refraction, energy dispersion, etc., that greatly degrade communication [...] Read more.
One of the main problems in underwater communications is the low data rate available due to the use of low frequencies. Moreover, there are many problems inherent to the medium such as reflections, refraction, energy dispersion, etc., that greatly degrade communication between devices. In some cases, wireless sensors must be placed quite close to each other in order to take more accurate measurements from the water while having high communication bandwidth. In these cases, while most researchers focus their efforts on increasing the data rate for low frequencies, we propose the use of the 2.4 GHz ISM frequency band in these special cases. In this paper, we show our wireless sensor node deployment and its performance obtained from a real scenario and measures taken for different frequencies, modulations and data transfer rates. The performed tests show the maximum distance between sensors, the number of lost packets and the average round trip time. Based on our measurements, we provide some experimental models of underwater communication in fresh water using EM waves in the 2.4 GHz ISM frequency band. Finally, we compare our communication system proposal with the existing systems. Although our proposal provides short communication distances, it provides high data transfer rates. It can be used for precision monitoring in applications such as contaminated ecosystems or for device communicate at high depth. Full article
(This article belongs to the Special Issue Underwater Sensor Nodes and Underwater Sensor Networks)
Open AccessArticle Parametric Study of the Reflective Periodic Grating for In-Plane Displacement Measurement Using Optical Fibers
Sensors 2012, 12(4), 4265-4280; doi:10.3390/s120404265
Received: 18 January 2012 / Revised: 7 March 2012 / Accepted: 26 March 2012 / Published: 28 March 2012
Cited by 2 | PDF Full-text (1358 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a technique for a simple sensing principle that can be used for the measurement of displacement. The proposed sensor head is composed of a reflective grating panel and an optical fiber as a transceiver. The simplified layout contributes to [...] Read more.
This paper presents a technique for a simple sensing principle that can be used for the measurement of displacement. The proposed sensor head is composed of a reflective grating panel and an optical fiber as a transceiver. The simplified layout contributes to resolving the issues of space restraints during installation and complex cabling problems in transmission fiber optic sensors. In order to verify the effectiveness of the proposed technique, it is important to obtain the sinusoidal signal reflected from the grating for reasonable phase tracking. In the numerical analysis, a real wave based optical beam model is proposed for the extraction of predicted signal according to the grating width and ratio of reflection bar width to spacing. The grating pattern design to obtain a sine wave reflected sensor signal was determined within an R-square value of 0.98 after sine curve fitting analysis. Consequently, the proposed sensor principle achieved the in-plane displacement measurement with a maximum accuracy error of 5.34 µm. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2012)
Open AccessArticle Measurements and Modelling of Base Station Power Consumption under Real Traffic Loads
Sensors 2012, 12(4), 4281-4310; doi:10.3390/s120404281
Received: 1 February 2012 / Revised: 12 March 2012 / Accepted: 26 March 2012 / Published: 28 March 2012
Cited by 43 | PDF Full-text (1940 KB) | HTML Full-text | XML Full-text
Abstract
Base stations represent the main contributor to the energy consumption of a mobile cellular network. Since traffic load in mobile networks significantly varies during a working or weekend day, it is important to quantify the influence of these variations on the base [...] Read more.
Base stations represent the main contributor to the energy consumption of a mobile cellular network. Since traffic load in mobile networks significantly varies during a working or weekend day, it is important to quantify the influence of these variations on the base station power consumption. Therefore, this paper investigates changes in the instantaneous power consumption of GSM (Global System for Mobile Communications) and UMTS (Universal Mobile Telecommunications System) base stations according to their respective traffic load. The real data in terms of the power consumption and traffic load have been obtained from continuous measurements performed on a fully operated base station site. Measurements show the existence of a direct relationship between base station traffic load and power consumption. According to this relationship, we develop a linear power consumption model for base stations of both technologies. This paper also gives an overview of the most important concepts which are being proposed to make cellular networks more energy-efficient. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Integrating Iris and Signature Traits for Personal Authentication Using User-SpecificWeighting
Sensors 2012, 12(4), 4324-4338; doi:10.3390/s120404324
Received: 7 March 2012 / Revised: 22 March 2012 / Accepted: 22 March 2012 / Published: 29 March 2012
Cited by 2 | PDF Full-text (182 KB) | HTML Full-text | XML Full-text
Abstract
Biometric systems based on uni-modal traits are characterized by noisy sensor data, restricted degrees of freedom, non-universality and are susceptible to spoof attacks. Multi-modal biometric systems seek to alleviate some of these drawbacks by providing multiple evidences of the same identity. In [...] Read more.
Biometric systems based on uni-modal traits are characterized by noisy sensor data, restricted degrees of freedom, non-universality and are susceptible to spoof attacks. Multi-modal biometric systems seek to alleviate some of these drawbacks by providing multiple evidences of the same identity. In this paper, a user-score-based weighting technique for integrating the iris and signature traits is presented. This user-specific weighting technique has proved to be an efficient and effective fusion scheme which increases the authentication accuracy rate of multi-modal biometric systems. The weights are used to indicate the importance of matching scores output by each biometrics trait. The experimental results show that our biometric system based on the integration of iris and signature traits achieve a false rejection rate (FRR) of 0.08% and a false acceptance rate (FAR) of 0.01%. Full article
(This article belongs to the Special Issue Biomimetic Sensors, Actuators and Integrated Systems)
Open AccessArticle Silencing Quorum Sensing through Extracts of Melicope lunu-ankenda
Sensors 2012, 12(4), 4339-4351; doi:10.3390/s120404339
Received: 18 January 2012 / Revised: 14 March 2012 / Accepted: 22 March 2012 / Published: 29 March 2012
Cited by 29 | PDF Full-text (741 KB) | HTML Full-text | XML Full-text
Abstract
Quorum sensing regulates bacterial virulence determinants, therefore making it an interesting target to attenuate pathogens. In this work, we screened edible, endemic plants in Malaysia for anti-quorum sensing properties. Extracts from Melicope lunu-ankenda (Gaertn.) T. G. Hartley, a Malay garden salad, inhibited [...] Read more.
Quorum sensing regulates bacterial virulence determinants, therefore making it an interesting target to attenuate pathogens. In this work, we screened edible, endemic plants in Malaysia for anti-quorum sensing properties. Extracts from Melicope lunu-ankenda (Gaertn.) T. G. Hartley, a Malay garden salad, inhibited response of Chromobacterium violaceum CV026 to N-hexanoylhomoserine lactone, thus interfering with violacein production; reduced bioluminescence expression of E. coli [pSB401], disrupted pyocyanin synthesis, swarming motility and expression of lecA::lux of Pseudomonas aeruginosa PAO1. Although the chemical nature of the anti-QS compounds from M. lunu-ankenda is currently unknown, this study proves that endemic Malaysian plants could serve as leads in the search for anti-quorum sensing compounds. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle A Reverse Localization Scheme for Underwater Acoustic Sensor Networks
Sensors 2012, 12(4), 4352-4380; doi:10.3390/s120404352
Received: 16 February 2012 / Revised: 18 March 2012 / Accepted: 19 March 2012 / Published: 29 March 2012
Cited by 11 | PDF Full-text (574 KB) | HTML Full-text | XML Full-text
Abstract
Underwater Wireless Sensor Networks (UWSNs) provide new opportunities to observe and predict the behavior of aquatic environments. In some applications like target tracking or disaster prevention, sensed data is meaningless without location information. In this paper, we propose a novel 3D centralized, [...] Read more.
Underwater Wireless Sensor Networks (UWSNs) provide new opportunities to observe and predict the behavior of aquatic environments. In some applications like target tracking or disaster prevention, sensed data is meaningless without location information. In this paper, we propose a novel 3D centralized, localization scheme for mobile underwater wireless sensor network, named Reverse Localization Scheme or RLS in short. RLS is an event-driven localization method triggered by detector sensors for launching localization process. RLS is suitable for surveillance applications that require very fast reactions to events and could report the location of the occurrence. In this method, mobile sensor nodes report the event toward the surface anchors as soon as they detect it. They do not require waiting to receive location information from anchors. Simulation results confirm that the proposed scheme improves the energy efficiency and reduces significantly localization response time with a proper level of accuracy in terms of mobility model of water currents. Major contributions of this method lie on reducing the numbers of message exchange for localization, saving the energy and decreasing the average localization response time. Full article
(This article belongs to the Special Issue Underwater Sensor Nodes and Underwater Sensor Networks)
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Open AccessArticle Adaptive Redundant Lifting Wavelet Transform Based on Fitting for Fault Feature Extraction of Roller Bearings
Sensors 2012, 12(4), 4381-4398; doi:10.3390/s120404381
Received: 13 February 2012 / Revised: 20 March 2012 / Accepted: 21 March 2012 / Published: 29 March 2012
Cited by 11 | PDF Full-text (411 KB) | HTML Full-text | XML Full-text
Abstract
A least square method based on data fitting is proposed to construct a new lifting wavelet, together with the nonlinear idea and redundant algorithm, the adaptive redundant lifting transform based on fitting is firstly stated in this paper. By variable combination selections [...] Read more.
A least square method based on data fitting is proposed to construct a new lifting wavelet, together with the nonlinear idea and redundant algorithm, the adaptive redundant lifting transform based on fitting is firstly stated in this paper. By variable combination selections of basis function, sample number and dimension of basis function, a total of nine wavelets with different characteristics are constructed, which are respectively adopted to perform redundant lifting wavelet transforms on low-frequency approximate signals at each layer. Then the normalized lP norms of the new node-signal obtained through decomposition are calculated to adaptively determine the optimal wavelet for the decomposed approximate signal. Next, the original signal is taken for subsection power spectrum analysis to choose the node-signal for single branch reconstruction and demodulation. Experiment signals and engineering signals are respectively used to verify the above method and the results show that bearing faults can be diagnosed more effectively by the method presented here than by both spectrum analysis and demodulation analysis. Meanwhile, compared with the symmetrical wavelets constructed with Lagrange interpolation algorithm, the asymmetrical wavelets constructed based on data fitting are more suitable in feature extraction of fault signal of roller bearings. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle 2:1 Multiplexing Function in a Simple Molecular System
Sensors 2012, 12(4), 4421-4430; doi:10.3390/s120404421
Received: 31 December 2011 / Revised: 18 February 2012 / Accepted: 12 March 2012 / Published: 30 March 2012
Cited by 2 | PDF Full-text (388 KB) | HTML Full-text | XML Full-text
Abstract
1-[(Anthracen-9-yl)methylene] thiosemicarbazide shows weak fluorescence due to a photo-induced electron transfer (PET) process from the thiosemicarbazide moiety to the excited anthracene. The anthracene emission can be recovered via protonation of the amine as the protonated aminomethylene as an electron-withdrawing group that suppresses [...] Read more.
1-[(Anthracen-9-yl)methylene] thiosemicarbazide shows weak fluorescence due to a photo-induced electron transfer (PET) process from the thiosemicarbazide moiety to the excited anthracene. The anthracene emission can be recovered via protonation of the amine as the protonated aminomethylene as an electron-withdrawing group that suppresses the PET process. Similarly, chelation between the ligand and the metal ions can also suppress the PET process and results in a fluorescence enhancement (CHEF). When solvents are introduced as the third control, a molecular 2:1 multiplexer is constructed to report selectively the inputs. Therefore, a molecular 2:1 multiplexer is realized in a simple molecular system. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle A Vision Based Top-View Transformation Model for a Vehicle Parking Assistant
Sensors 2012, 12(4), 4431-4446; doi:10.3390/s120404431
Received: 16 March 2012 / Revised: 29 March 2012 / Accepted: 30 March 2012 / Published: 30 March 2012
Cited by 11 | PDF Full-text (642 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes the Top-View Transformation Model for image coordinate transformation, which involves transforming a perspective projection image into its corresponding bird’s eye vision. A fitting parameters searching algorithm estimates the parameters that are used to transform the coordinates from the source [...] Read more.
This paper proposes the Top-View Transformation Model for image coordinate transformation, which involves transforming a perspective projection image into its corresponding bird’s eye vision. A fitting parameters searching algorithm estimates the parameters that are used to transform the coordinates from the source image. Using this approach, it is not necessary to provide any interior and exterior orientation parameters of the camera. The designed car parking assistant system can be installed at the rear end of the car, providing the driver with a clearer image of the area behind the car. The processing time can be reduced by storing and using the transformation matrix estimated from the first image frame for a sequence of video images. The transformation matrix can be stored as the Matrix Mapping Table, and loaded into the embedded platform to perform the transformation. Experimental results show that the proposed approaches can provide a clearer and more accurate bird’s eye view to the vehicle driver. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Gamma Irradiation of Magnetoresistive Sensors for Planetary Exploration
Sensors 2012, 12(4), 4447-4465; doi:10.3390/s120404447
Received: 28 February 2012 / Revised: 12 March 2012 / Accepted: 19 March 2012 / Published: 2 April 2012
Cited by 5 | PDF Full-text (979 KB) | HTML Full-text | XML Full-text
Abstract
A limited number of Anisotropic Magnetoresistive (AMR) commercial-off-the-shelf (COTS) magnetic sensors of the HMC series by Honeywell, with and without integrated front-end electronics, were irradiated with gamma rays up to a total irradiation dose of 200 krad (Si), following the ESCC Basic [...] Read more.
A limited number of Anisotropic Magnetoresistive (AMR) commercial-off-the-shelf (COTS) magnetic sensors of the HMC series by Honeywell, with and without integrated front-end electronics, were irradiated with gamma rays up to a total irradiation dose of 200 krad (Si), following the ESCC Basic Specification No. 22900. Due to the magnetic cleanliness required for these tests a special set-up was designed and successfully employed. Several parameters of the sensors were monitored during testing and the results are reported in this paper. The authors conclude that AMR sensors without front-end electronics seem to be robust against radiation doses of up to 200 krad (Si) with a dose rate of 5 krad (Si)/hour and up to a resolution of tens of nT, but sensors with an integrated front-end seem to be more vulnerable to radiation. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle An Advanced Compiler Designed for a VLIW DSP for Sensors-Based Systems
Sensors 2012, 12(4), 4466-4478; doi:10.3390/s120404466
Received: 14 March 2012 / Revised: 29 March 2012 / Accepted: 29 March 2012 / Published: 2 April 2012
Cited by 4 | PDF Full-text (327 KB) | HTML Full-text | XML Full-text
Abstract
The VLIW architecture can be exploited to greatly enhance instruction level parallelism, thus it can provide computation power and energy efficiency advantages, which satisfies the requirements of future sensor-based systems. However, as VLIW codes are mainly compiled statically, the performance of a [...] Read more.
The VLIW architecture can be exploited to greatly enhance instruction level parallelism, thus it can provide computation power and energy efficiency advantages, which satisfies the requirements of future sensor-based systems. However, as VLIW codes are mainly compiled statically, the performance of a VLIW processor is dominated by the behavior of its compiler. In this paper, we present an advanced compiler designed for a VLIW DSP named Magnolia, which will be used in sensor-based systems. This compiler is based on the Open64 compiler. We have implemented several advanced optimization techniques in the compiler, and fulfilled the O3 level optimization. Benchmarks from the DSPstone test suite are used to verify the compiler. Results show that the code generated by our compiler can make the performance of Magnolia match that of the current state-of-the-art DSP processors. Full article
(This article belongs to the Special Issue Microprocessors and System-on-Chip)
Open AccessArticle Evaluation of Commercial Probes for On-Line Electrical Conductivity Measurements during Goat Gland Milking Process
Sensors 2012, 12(4), 4493-4513; doi:10.3390/s120404493
Received: 18 January 2012 / Revised: 21 February 2012 / Accepted: 16 March 2012 / Published: 10 April 2012
Cited by 6 | PDF Full-text (6927 KB) | HTML Full-text | XML Full-text
Abstract
The measurement of the milk electrical conductivity (EC) during mechanical milking has been widely studied for mastitis detection on cows because its improving of welfare and animal health, although research about small ruminants is scarce. The aim of this study was to [...] Read more.
The measurement of the milk electrical conductivity (EC) during mechanical milking has been widely studied for mastitis detection on cows because its improving of welfare and animal health, although research about small ruminants is scarce. The aim of this study was to evaluate the performance of three commercial conductimeters to be used during mechanical milking of small ruminant halves, especially Murciano-Granadina goats. The objective of this research was to integrate the probes on the milking unit and to check the suitability of the probe selected. The results presented in this research have guided authors to discard the commercial probes and to establish the requirements of a new probe design that is briefly outlined in the conclusions of this contribution. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle An Instrument for In Situ Measuring the Volume Scattering Function of Water: Design, Calibration and Primary Experiments
Sensors 2012, 12(4), 4514-4533; doi:10.3390/s120404514
Received: 29 February 2012 / Revised: 29 March 2012 / Accepted: 30 March 2012 / Published: 10 April 2012
PDF Full-text (1114 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The optical volume scattering function (VSF) of seawater is a fundamental property used in the calculation of radiative transfer for applications in the study of the upper-ocean heat balance, the photosynthetic productivity of the ocean, and the chemical transformation of photoreactive compounds. [...] Read more.
The optical volume scattering function (VSF) of seawater is a fundamental property used in the calculation of radiative transfer for applications in the study of the upper-ocean heat balance, the photosynthetic productivity of the ocean, and the chemical transformation of photoreactive compounds. A new instrument to simultaneously measure the VSF in seven directions between 20° to 160°, the attenuation coefficient, and the depth of water is presented. The instrument is self-contained and can be automatically controlled by the depth under water. The self-contained data can be easily downloaded by an ultra-short-wave communication system. A calibration test was performed in the laboratory based on precise estimation of the scattering volume and optical radiometric calibration of the detectors. The measurement error of the VSF measurement instrument has been estimated in the laboratory based on the Mie theory, and the average error is less than 12%. The instrument was used to measure and analyze the variation characteristics of the VSF with angle, depth and water quality in Daya Bay for the first time. From these in situ data, we have found that the phase functions proposed by Fournier-Forand, measured by Petzold in San Diego Harbor and Sokolov in Black Sea do not fit with our measurements in Daya. These discrepancies could manly due to high proportion of suspended calcium carbonate mineral-like particles with high refractive index in Daya Bay. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle The Application of LiDAR to Assessment of Rooftop Solar Photovoltaic Deployment Potential in a Municipal District Unit
Sensors 2012, 12(4), 4534-4558; doi:10.3390/s120404534
Received: 9 February 2012 / Revised: 28 March 2012 / Accepted: 29 March 2012 / Published: 10 April 2012
Cited by 17 | PDF Full-text (753 KB) | HTML Full-text | XML Full-text
Abstract
A methodology is provided for the application of Light Detection and Ranging (LiDAR) to automated solar photovoltaic (PV) deployment analysis on the regional scale. Challenges in urban information extraction and management for solar PV deployment assessment are determined and quantitative solutions are [...] Read more.
A methodology is provided for the application of Light Detection and Ranging (LiDAR) to automated solar photovoltaic (PV) deployment analysis on the regional scale. Challenges in urban information extraction and management for solar PV deployment assessment are determined and quantitative solutions are offered. This paper provides the following contributions: (i) a methodology that is consistent with recommendations from existing literature advocating the integration of cross-disciplinary competences in remote sensing (RS), GIS, computer vision and urban environmental studies; (ii) a robust methodology that can work with low-resolution, incomprehensive data and reconstruct vegetation and building separately, but concurrently; (iii) recommendations for future generation of software. A case study is presented as an example of the methodology. Experience from the case study such as the trade-off between time consumption and data quality are discussed to highlight a need for connectivity between demographic information, electrical engineering schemes and GIS and a typical factor of solar useful roofs extracted per method. Finally, conclusions are developed to provide a final methodology to extract the most useful information from the lowest resolution and least comprehensive data to provide solar electric assessments over large areas, which can be adapted anywhere in the world. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle A Network Coding Based Routing Protocol for Underwater Sensor Networks
Sensors 2012, 12(4), 4559-4577; doi:10.3390/s120404559
Received: 15 February 2012 / Revised: 14 March 2012 / Accepted: 22 March 2012 / Published: 10 April 2012
Cited by 5 | PDF Full-text (734 KB) | HTML Full-text | XML Full-text
Abstract
Due to the particularities of the underwater environment, some negative factors will seriously interfere with data transmission rates, reliability of data communication, communication range, and network throughput and energy consumption of underwater sensor networks (UWSNs). Thus, full consideration of node energy savings, [...] Read more.
Due to the particularities of the underwater environment, some negative factors will seriously interfere with data transmission rates, reliability of data communication, communication range, and network throughput and energy consumption of underwater sensor networks (UWSNs). Thus, full consideration of node energy savings, while maintaining a quick, correct and effective data transmission, extending the network life cycle are essential when routing protocols for underwater sensor networks are studied. In this paper, we have proposed a novel routing algorithm for UWSNs. To increase energy consumption efficiency and extend network lifetime, we propose a time-slot based routing algorithm (TSR).We designed a probability balanced mechanism and applied it to TSR. The theory of network coding is introduced to TSBR to meet the requirement of further reducing node energy consumption and extending network lifetime. Hence, time-slot based balanced network coding (TSBNC) comes into being. We evaluated the proposed time-slot based balancing routing algorithm and compared it with other classical underwater routing protocols. The simulation results show that the proposed protocol can reduce the probability of node conflicts, shorten the process of routing construction, balance energy consumption of each node and effectively prolong the network lifetime. Full article
(This article belongs to the Special Issue Underwater Sensor Nodes and Underwater Sensor Networks)
Open AccessArticle Long-Period Fiber Grating Sensors for the Measurement of Liquid Level and Fluid-Flow Velocity
Sensors 2012, 12(4), 4578-4593; doi:10.3390/s120404578
Received: 30 December 2011 / Revised: 2 April 2012 / Accepted: 3 April 2012 / Published: 10 April 2012
Cited by 18 | PDF Full-text (547 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the development and assessment of two types of Long Period Fiber Grating (LPFG)-based sensors including a mobile liquid level sensor and a reflective sensor for the measurement of liquid level and fluid-flow velocity. Shewhart control charts were used to [...] Read more.
This paper presents the development and assessment of two types of Long Period Fiber Grating (LPFG)-based sensors including a mobile liquid level sensor and a reflective sensor for the measurement of liquid level and fluid-flow velocity. Shewhart control charts were used to assess the liquid level sensing capacity and reliability of the mobile CO2-laser engraved LPFG sensor. There were ten groups of different liquid level experiment and each group underwent ten repeated wavelength shift measurements. The results showed that all measurands were within the control limits; thus, this mobile sensor was reliable and exhibited at least 100-cm liquid level measurement capacity. In addition, a reflective sensor consisting of five LPFGs in series with a reflective end has been developed to evaluate the liquid level and fluid-flow velocity. These five LPFGs were fabricated by the electrical arc discharge method and the reflective end was coated with silver by Tollen’s test. After each liquid level experiment was performed five times, the average values of the resonance wavelength shifts for LPFG Nos. 1–5 were in the range of 1.35–9.14 nm. The experimental findings showed that the reflective sensor could be used to automatically monitor five fixed liquid levels. This reflective sensor also exhibited at least 100-cm liquid level measurement capacity. The mechanism of the fluid-flow velocity sensor was based on analyzing the relationship among the optical power, time, and the LPFG’s length. There were two types of fluid-flow velocity measurements: inflow and drainage processes. The differences between the LPFG-based fluid-flow velocities and the measured average fluid-flow velocities were found in the range of 8.7–12.6%. For the first time to our knowledge, we have demonstrated the feasibility of liquid level and fluid-flow velocity sensing with a reflective LPFG-based sensor without modifying LPFGs or coating chemical compounds. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Template Free Synthesis of Hollow Ball-Like Nano-Fe2O3 and Its Application to the Detection of Dimethyl Methylphosphonate at Room Temperature
Sensors 2012, 12(4), 4594-4604; doi:10.3390/s120404594
Received: 8 March 2012 / Revised: 29 March 2012 / Accepted: 30 March 2012 / Published: 10 April 2012
Cited by 7 | PDF Full-text (631 KB) | HTML Full-text | XML Full-text
Abstract
This paper is focused on the template-free synthesis of nanosized ferric oxide (nano-Fe2O3) and its application in quartz crystal microbalance (QCM) resonators to detect dimethyl methylphosphonate (DMMP), a simulant of Sarin. The X-ray diffraction (XRD) patterns confirm that [...] Read more.
This paper is focused on the template-free synthesis of nanosized ferric oxide (nano-Fe2O3) and its application in quartz crystal microbalance (QCM) resonators to detect dimethyl methylphosphonate (DMMP), a simulant of Sarin. The X-ray diffraction (XRD) patterns confirm that the synthesized samples are made of Fe2O3 and the scanning electron microscopy (SEM) pictures show that the samples have ball-like shapes. The DMMP sensors with a sensing film of hollow ball-like and solid ball-like Fe2O3 are fabricated and their sensing characteristics are compared. The sensitivity of the hollow ball-like Fe2O3 sensor is more than 500% higher than the one of the solid ball-like Fe2O3 sensor. The hollow ball-like nano-Fe2O3 can be synthesized by a novel low temperature hydrothermal method. The sensors with the hollow ball-like Fe2O3 film perform well in a range of 1 to 6 ppm, with a sensitivity of 29 Hz/ppm at room temperature, while the appropriate recoverability and selectivity are maintained. In addition, the performance of different thicknesses of the sensing film of the hollow ball-like nano-Fe2O3 is investigated and the optimized relative film thickness of the hollow ball-like nano-Fe2O3 is found to be 20 μg/mm2. Full article
(This article belongs to the Special Issue Sensing at the Nano-Scale: Chemical and Bio-Sensing)
Open AccessArticle A Neural Network Approach to Smarter Sensor Networks for Water Quality Monitoring
Sensors 2012, 12(4), 4605-4632; doi:10.3390/s120404605
Received: 21 February 2012 / Revised: 21 March 2012 / Accepted: 30 March 2012 / Published: 10 April 2012
Cited by 10 | PDF Full-text (6662 KB) | HTML Full-text | XML Full-text
Abstract
Environmental monitoring is evolving towards large-scale and low-cost sensor networks operating reliability and autonomously over extended periods of time. Sophisticated analytical instrumentation such as chemo-bio sensors present inherent limitations because of the number of samples that they can take. In order to [...] Read more.
Environmental monitoring is evolving towards large-scale and low-cost sensor networks operating reliability and autonomously over extended periods of time. Sophisticated analytical instrumentation such as chemo-bio sensors present inherent limitations because of the number of samples that they can take. In order to maximize their deployment lifetime, we propose the coordination of multiple heterogeneous information sources. We use rainfall radar images and information from a water depth sensor as input to a neural network (NN) to dictate the sampling frequency of a phosphate analyzer at the River Lee in Cork, Ireland. This approach shows varied performance for different times of the year but overall produces output that is very satisfactory for the application context in question. Our study demonstrates that even with limited training data, a system for controlling the sampling rate of the nutrient sensor can be set up and can improve the efficiency of the more sophisticated nodes of the sensor network. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle Multispectral Palmprint Recognition Using a Quaternion Matrix
Sensors 2012, 12(4), 4633-4647; doi:10.3390/s120404633
Received: 20 February 2012 / Revised: 21 March 2012 / Accepted: 21 March 2012 / Published: 10 April 2012
Cited by 10 | PDF Full-text (770 KB) | HTML Full-text | XML Full-text
Abstract
Palmprints have been widely studied for biometric recognition for many years. Traditionally, a white light source is used for illumination. Recently, multispectral imaging has drawn attention because of its high recognition accuracy. Multispectral palmprint systems can provide more discriminant information under different [...] Read more.
Palmprints have been widely studied for biometric recognition for many years. Traditionally, a white light source is used for illumination. Recently, multispectral imaging has drawn attention because of its high recognition accuracy. Multispectral palmprint systems can provide more discriminant information under different illuminations in a short time, thus they can achieve better recognition accuracy. Previously, multispectral palmprint images were taken as a kind of multi-modal biometrics, and the fusion scheme on the image level or matching score level was used. However, some spectral information will be lost during image level or matching score level fusion. In this study, we propose a new method for multispectral images based on a quaternion model which could fully utilize the multispectral information. Firstly, multispectral palmprint images captured under red, green, blue and near-infrared (NIR) illuminations were represented by a quaternion matrix, then principal component analysis (PCA) and discrete wavelet transform (DWT) were applied respectively on the matrix to extract palmprint features. After that, Euclidean distance was used to measure the dissimilarity between different features. Finally, the sum of two distances and the nearest neighborhood classifier were employed for recognition decision. Experimental results showed that using the quaternion matrix can achieve a higher recognition rate. Given 3000 test samples from 500 palms, the recognition rate can be as high as 98.83%. Full article
(This article belongs to the Special Issue Hand-Based Biometrics Sensors and Systems)
Open AccessArticle Precise Temperature Mapping of GaN-Based LEDs by Quantitative Infrared Micro-Thermography
Sensors 2012, 12(4), 4648-4660; doi:10.3390/s120404648
Received: 20 February 2012 / Revised: 26 March 2012 / Accepted: 27 March 2012 / Published: 10 April 2012
Cited by 7 | PDF Full-text (1247 KB) | HTML Full-text | XML Full-text
Abstract
A method of measuring the precise temperature distribution of GaN-based light-emitting diodes (LEDs) by quantitative infrared micro-thermography is reported. To reduce the calibration error, the same measuring conditions were used for both calibration and thermal imaging; calibration was conducted on a highly [...] Read more.
A method of measuring the precise temperature distribution of GaN-based light-emitting diodes (LEDs) by quantitative infrared micro-thermography is reported. To reduce the calibration error, the same measuring conditions were used for both calibration and thermal imaging; calibration was conducted on a highly emissive black-painted area on a dummy sapphire wafer loaded near the LED wafer on a thermoelectric cooler mount. We used infrared thermal radiation images of the black-painted area on the dummy wafer and an unbiased LED wafer at two different temperatures to determine the factors that degrade the accuracy of temperature measurement, i.e., the non-uniform response of the instrument, superimposed offset radiation, reflected radiation, and emissivity map of the LED surface. By correcting these factors from the measured infrared thermal radiation images of biased LEDs, we determined a precise absolute temperature image. Consequently, we could observe from where the local self-heat emerges and how it distributes on the emitting area of the LEDs. The experimental results demonstrated that highly localized self-heating and a remarkable temperature gradient, which are detrimental to LED performance and reliability, arise near the p-contact edge of the LED surface at high injection levels owing to the current crowding effect. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Sensitivity-Enhanced Refractive Index Sensor Using a Single-Mode Thin-Core Fiber Incorporating an Abrupt Taper
Sensors 2012, 12(4), 4697-4705; doi:10.3390/s120404697
Received: 5 January 2012 / Revised: 23 February 2012 / Accepted: 26 March 2012 / Published: 11 April 2012
Cited by 15 | PDF Full-text (556 KB) | HTML Full-text | XML Full-text
Abstract
A sensitivity-enhanced fiber-optic refractive index (RI) sensor based on a tapered single-mode thin-core diameter fiber is proposed and experimentally demonstrated. The sensor head is formed by splicing a section of tapered thin-core diameter fiber (TCF) between two sections of single-mode fibers (SMFs). [...] Read more.
A sensitivity-enhanced fiber-optic refractive index (RI) sensor based on a tapered single-mode thin-core diameter fiber is proposed and experimentally demonstrated. The sensor head is formed by splicing a section of tapered thin-core diameter fiber (TCF) between two sections of single-mode fibers (SMFs). The cladding modes are excited at the first SMF-TCF interface, and then interfere with the core mode at the second interface, thus forming an inter-modal interferometer (IMI). An abrupt taper (tens of micrometers long) made by the electric-arc-heating method is utilized, and plays an important role in improving sensing sensitivity. The whole manufacture process only involves fiber splicing and tapering, and all the fabrication process can be achieved by a commercial fiber fusion splicer. Using glycerol and water mixture solution as an example, the experimental results show that the refractive index sensitivity is measured to be 0.591 nm for 1% change of surrounding RI. The proposed sensor structure features simple structure, low cost, easy fabrication, and high sensitivity. Full article
(This article belongs to the Section Physical Sensors)
Open AccessCommunication Improvement of Toluene Selectivity via the Application of an Ethanol Oxidizing Catalytic Cell Upstream of a YSZ-Based Sensor for Air Monitoring Applications
Sensors 2012, 12(4), 4706-4714; doi:10.3390/s120404706
Received: 29 February 2012 / Revised: 16 March 2012 / Accepted: 20 March 2012 / Published: 11 April 2012
Cited by 9 | PDF Full-text (479 KB) | HTML Full-text | XML Full-text
Abstract
The sensing characteristics of a yttria-stabilized zirconia (YSZ)-based sensor utilizing a NiO sensing-electrode (SE) towards toluene (C7H8) and interfering gases (C3H6, H2, CO, NO2 and C2H5OH) were [...] Read more.
The sensing characteristics of a yttria-stabilized zirconia (YSZ)-based sensor utilizing a NiO sensing-electrode (SE) towards toluene (C7H8) and interfering gases (C3H6, H2, CO, NO2 and C2H5OH) were evaluated with a view to selective C7H8 monitoring in indoor atmospheres. The fabricated YSZ-based sensor showed preferential responses toward 480 ppb C2H5OH, rather than the target 50 ppb C7H8 at an operational temperature of 450 °C under humid conditions (RH ⋍ 32%). To overcome this limitation, the catalytic activity of Cr2O3, SnO2, Fe2O3 and NiO powders were evaluated for their selective ethanol oxidation ability. Among these oxides, SnO2 was found to selectively oxidize C2H5OH, thus improving C7H8 selectivity. An inline pre-catalytic cell loaded with SnO2 powder was installed upstream of the YSZ-based sensor utilizing NiO-SE, which enabled the following excellent abilities by selectively catalyzing common interfering gases; sensitive ppb level detection of C7H8 lower than the established Japanese Guideline value; low interferences from 50 ppb C3H6, 500 ppb H2, 100 ppb CO, 40 ppb NO2, as well as 480 ppb C2H5OH. These operational characteristics are all indicative that the developed sensor may be suitable for real-time C7H8 concentration monitoring in indoor environments. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle On the Selection of Transmission Range in Underwater Acoustic Sensor Networks
Sensors 2012, 12(4), 4715-4729; doi:10.3390/s120404715
Received: 2 March 2012 / Revised: 5 April 2012 / Accepted: 5 April 2012 / Published: 11 April 2012
Cited by 9 | PDF Full-text (406 KB) | HTML Full-text | XML Full-text
Abstract
Transmission range plays an important role in the deployment of a practical underwater acoustic sensor network (UWSN), where sensor nodes equipping with only basic functions are deployed at random locations with no particular geometrical arrangements. The selection of the transmission range directly [...] Read more.
Transmission range plays an important role in the deployment of a practical underwater acoustic sensor network (UWSN), where sensor nodes equipping with only basic functions are deployed at random locations with no particular geometrical arrangements. The selection of the transmission range directly influences the energy efficiency and the network connectivity of such a random network. In this paper, we seek analytical modeling to investigate the tradeoff between the energy efficiency and the network connectivity through the selection of the transmission range. Our formulation offers a design guideline for energy-efficient packet transmission operation given a certain network connectivity requirement. Full article
(This article belongs to the Special Issue Underwater Sensor Nodes and Underwater Sensor Networks)
Open AccessArticle Rao and Wald Tests for Nonhomogeneous Scenarios
Sensors 2012, 12(4), 4730-4736; doi:10.3390/s120404730
Received: 12 March 2012 / Revised: 28 March 2012 / Accepted: 29 March 2012 / Published: 12 April 2012
Cited by 1 | PDF Full-text (78 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we focus on the design of adaptive receivers for nonhomogeneous scenarios. More precisely, at the design stage we assume a mismatch between the covariance matrix of the noise in the cell under test and that of secondary data. Under [...] Read more.
In this paper, we focus on the design of adaptive receivers for nonhomogeneous scenarios. More precisely, at the design stage we assume a mismatch between the covariance matrix of the noise in the cell under test and that of secondary data. Under the above assumption, we show that the Wald test is the adaptive matched filter, while the Rao test coincides with the receiver obtained by using the Rao test design criterion in homogeneous environment, hence providing a theoretical explanation of the enhanced selectivity of this receiver. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Adapting an Ant Colony Metaphor for Multi-Robot Chemical Plume Tracing
Sensors 2012, 12(4), 4737-4763; doi:10.3390/s120404737
Received: 17 March 2012 / Revised: 26 March 2012 / Accepted: 31 March 2012 / Published: 12 April 2012
Cited by 10 | PDF Full-text (774 KB) | HTML Full-text | XML Full-text
Abstract
We consider chemical plume tracing (CPT) in time-varying airflow environments using multiple mobile robots. The purpose of CPT is to approach a gas source with a previously unknown location in a given area. Therefore, the CPT could be considered as a dynamic [...] Read more.
We consider chemical plume tracing (CPT) in time-varying airflow environments using multiple mobile robots. The purpose of CPT is to approach a gas source with a previously unknown location in a given area. Therefore, the CPT could be considered as a dynamic optimization problem in continuous domains. The traditional ant colony optimization (ACO) algorithm has been successfully used for combinatorial optimization problems in discrete domains. To adapt the ant colony metaphor to the multi-robot CPT problem, the two-dimension continuous search area is discretized into grids and the virtual pheromone is updated according to both the gas concentration and wind information. To prevent the adapted ACO algorithm from being prematurely trapped in a local optimum, the upwind surge behavior is adopted by the robots with relatively higher gas concentration in order to explore more areas. The spiral surge (SS) algorithm is also examined for comparison. Experimental results using multiple real robots in two indoor natural ventilated airflow environments show that the proposed CPT method performs better than the SS algorithm. The simulation results for large-scale advection-diffusion plume environments show that the proposed method could also work in outdoor meandering plume environments. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Fiber Optic Sensor for Acoustic Detection of Partial Discharges in Oil-Paper Insulated Electrical Systems
Sensors 2012, 12(4), 4793-4802; doi:10.3390/s120404793
Received: 16 January 2012 / Revised: 31 March 2012 / Accepted: 5 April 2012 / Published: 12 April 2012
Cited by 22 | PDF Full-text (1497 KB) | HTML Full-text | XML Full-text
Abstract
A fiber optic interferometric sensor with an intrinsic transducer along a length of the fiber is presented for ultrasound measurements of the acoustic emission from partial discharges inside oil-filled power apparatus. The sensor is designed for high sensitivity measurements in a harsh [...] Read more.
A fiber optic interferometric sensor with an intrinsic transducer along a length of the fiber is presented for ultrasound measurements of the acoustic emission from partial discharges inside oil-filled power apparatus. The sensor is designed for high sensitivity measurements in a harsh electromagnetic field environment, with wide temperature changes and immersion in oil. It allows enough sensitivity for the application, for which the acoustic pressure is in the range of units of Pa at a frequency of 150 kHz. In addition, the accessibility to the sensing region is guaranteed by immune fiber-optic cables and the optical phase sensor output. The sensor design is a compact and rugged coil of fiber. In addition to a complete calibration, the in-situ results show that two types of partial discharges are measured through their acoustic emissions with the sensor immersed in oil. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2012)
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Open AccessArticle Nanocharacterization of Soft Biological Samples in Shear Mode with Quartz Tuning Fork Probes
Sensors 2012, 12(4), 4803-4819; doi:10.3390/s120404803
Received: 16 February 2012 / Revised: 29 March 2012 / Accepted: 30 March 2012 / Published: 12 April 2012
Cited by 11 | PDF Full-text (1839 KB) | HTML Full-text | XML Full-text
Abstract
Quartz tuning forks are extremely good resonators and their use is growing in scanning probe microscopy. Nevertheless, only a few studies on soft biological samples have been reported using these probes. In this work, we present the methodology to develop and use [...] Read more.
Quartz tuning forks are extremely good resonators and their use is growing in scanning probe microscopy. Nevertheless, only a few studies on soft biological samples have been reported using these probes. In this work, we present the methodology to develop and use these nanosensors to properly work with biological samples. The working principles, fabrication and experimental setup are presented. The results in the nanocharacterization of different samples in different ambients are presented by using different working modes: amplitude modulation with and without the use of a Phase-Locked Loop (PLL) and frequency modulation. Pseudomonas aeruginosa bacteria are imaged in nitrogen using amplitude modulation. Microcontact printed antibodies are imaged in buffer using amplitude modulation with a PLL. Finally, metastatic cells are imaged in air using frequency modulation. Full article
(This article belongs to the Special Issue Sensing at the Nano-Scale: Chemical and Bio-Sensing)
Open AccessArticle Reconfigurable Routing Protocol for Free Space Optical Sensor Networks
Sensors 2012, 12(4), 4824-4845; doi:10.3390/s120404824
Received: 21 February 2012 / Revised: 23 March 2012 / Accepted: 31 March 2012 / Published: 13 April 2012
Cited by 1 | PDF Full-text (879 KB) | HTML Full-text | XML Full-text
Abstract
Recently, free space optical sensor networks (FSOSNs), which are based on free space optics (FSO) instead of radio frequency (RF), have gained increasing visibility over traditional wireless sensor networks (WSNs) due to their advantages such as larger capacity, higher security, and lower [...] Read more.
Recently, free space optical sensor networks (FSOSNs), which are based on free space optics (FSO) instead of radio frequency (RF), have gained increasing visibility over traditional wireless sensor networks (WSNs) due to their advantages such as larger capacity, higher security, and lower cost. However, the performance of FSOSNs is restricted to the requirement of a direct line-of-sight (LOS) path between a sender and a receiver pair. Once a node dies of energy depletion, the network would probably suffer from a dramatic decrease of connectivity, resulting in a huge loss of data packets. Thus, this paper proposes a reconfigurable routing protocol (RRP) to overcome this problem by dynamically reconfiguring the network virtual topology. The RRP works in three phases: (1) virtual topology construction, (2) routing establishment, and (3) reconfigurable routing. When data transmission begins, the data packets are first routed through the shortest hop paths. Then a reconfiguration is initiated by the node whose residual energy falls below a threshold. Nodes affected by this dying node are classified into two types, namely maintenance nodes and adjustment nodes, and they are reconfigured according to the types. An energy model is designed to evaluate the performance of RRP through OPNET simulation. Our simulation results indicate that the RRP achieves better performance compared with the simple-link protocol and a direct reconfiguration scheme in terms of connectivity, network lifetime, packet delivery ratio and the number of living nodes. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Characterization of Quorum Sensing and Quorum Quenching Soil Bacteria Isolated from Malaysian Tropical Montane Forest
Sensors 2012, 12(4), 4846-4859; doi:10.3390/s120404846
Received: 15 March 2012 / Revised: 4 April 2012 / Accepted: 6 April 2012 / Published: 13 April 2012
Cited by 34 | PDF Full-text (348 KB) | HTML Full-text | XML Full-text
Abstract
We report the production and degradation of quorum sensing N-acyl-homoserine lactones by bacteria isolated from Malaysian montane forest soil. Phylogenetic analysis indicated that these isolates clustered closely to the genera of Arthrobacter, Bacillus and Pseudomonas. Quorum quenching activity was [...] Read more.
We report the production and degradation of quorum sensing N-acyl-homoserine lactones by bacteria isolated from Malaysian montane forest soil. Phylogenetic analysis indicated that these isolates clustered closely to the genera of Arthrobacter, Bacillus and Pseudomonas. Quorum quenching activity was detected in six isolates of these three genera by using a series of bioassays and rapid resolution liquid chromatography analysis. Biosensor screening and high resolution liquid chromatography-mass spectrometry analysis revealed the production of N-dodecanoyl-L-homoserine lactone (C12-HSL) by Pseudomonas frederiksbergensis (isolate BT9). In addition to degradation of a wide range of N-acyl-homoserine lactones, Arthrobacter and Pseudomonas spp. also degraded p-coumaroyl-homoserine lactone. To the best of our knowledge, this is the first documentation of Arthrobacter and Pseudomonas spp. capable of degrading p-coumaroyl-homoserine lactone and the production of C12-HSL by P. frederiksbergensis. Full article
Open AccessArticle Facile One-Step Microwave-Assisted Route towards Ni Nanospheres/Reduced Graphene Oxide Hybrids for Non-Enzymatic Glucose Sensing
Sensors 2012, 12(4), 4860-4869; doi:10.3390/s120404860
Received: 24 February 2012 / Revised: 14 March 2012 / Accepted: 23 March 2012 / Published: 13 April 2012
Cited by 32 | PDF Full-text (734 KB) | HTML Full-text | XML Full-text
Abstract
In this work, a facile one-step microwave-assisted method for deposition of monodisperse Ni nanospheres on reduced graphene oxide (rGO) sheets to form Ni-rGO nanohybrids is discussed. In the presence of hydrazine monohydrate, Ni nanospheres are grown onto rGO sheets using nickel precursor [...] Read more.
In this work, a facile one-step microwave-assisted method for deposition of monodisperse Ni nanospheres on reduced graphene oxide (rGO) sheets to form Ni-rGO nanohybrids is discussed. In the presence of hydrazine monohydrate, Ni nanospheres are grown onto rGO sheets using nickel precursor and GO as starting materials in ethylene glycol (EG) solution under a low level of microwave irradiation (300 W) for 20 min, during which GO is also reduced to rGO. The as-prepared nanohybrids exhibit well-dispersed Ni nanosphere (about 80 nm in diameter) loadings and effective reduction of graphene oxide. The resulting Ni-rGO nanohybrids-modified glassy carbon electrode (GCE) shows significantly improved electrochemical performance in nonenzymatic amperometric glucose detection. In addition, interference from the oxidation of common interfering species under physiological conditions, such as ascorbic acid (AA) and uric acid (UA), is effectively avoided. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Transformation of Ground Vibration Signal for Debris-Flow Monitoring and Detection in Alarm Systems
Sensors 2012, 12(4), 4870-4891; doi:10.3390/s120404870
Received: 9 February 2012 / Revised: 4 April 2012 / Accepted: 6 April 2012 / Published: 13 April 2012
Cited by 8 | PDF Full-text (1572 KB) | HTML Full-text | XML Full-text
Abstract
Debris flows are fast mass movements formed by a mix of water and solid materials, which occur in steep torrents, and are a source of high risks for human settlements. Geophones are widely used to detect the ground vibration induced by passing [...] Read more.
Debris flows are fast mass movements formed by a mix of water and solid materials, which occur in steep torrents, and are a source of high risks for human settlements. Geophones are widely used to detect the ground vibration induced by passing debris flows. However, the recording of geophone signals usually requires storing a huge amount of data, which leads to problems in storage capacity and power consumption. This paper presents a method to transform and simplify the signals measured by geophones. The key input parameter is the ground velocity threshold, which removes the seismic noise that is not related to debris flows. A signal conditioner was developed to implement the transformation and the ground velocity threshold was set by electrical resistors. The signal conditioner was installed at various European monitoring sites to test the method. Results show that data amount and power consumption can be greatly reduced without losing much information on the main features of the debris flows. However, the outcome stresses the importance of choosing a ground vibration threshold, which must be accurately calibrated. The transformation is also suitable to detect other rapid mass movements and to distinguish among different processes, which points to a possible implementation in alarm systems. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Modelling of Amperometric Biosensor Used for Synergistic Substrates Determination
Sensors 2012, 12(4), 4897-4917; doi:10.3390/s120404897
Received: 6 March 2012 / Revised: 2 April 2012 / Accepted: 4 April 2012 / Published: 16 April 2012
Cited by 3 | PDF Full-text (459 KB) | HTML Full-text | XML Full-text
Abstract
In this paper the operation of an amperometric biosensor producing a chemically amplified signal is modelled numerically. The chemical amplification is achieved by using synergistic substrates. The model is based on non-stationary reaction-diffusion equations. The model involves three layers (compartments): a layer [...] Read more.
In this paper the operation of an amperometric biosensor producing a chemically amplified signal is modelled numerically. The chemical amplification is achieved by using synergistic substrates. The model is based on non-stationary reaction-diffusion equations. The model involves three layers (compartments): a layer of enzyme solution entrapped on the electrode surface, a dialysis membrane covering the enzyme layer and an outer diffusion layer which is modelled by the Nernst approach. The equation system is solved numerically by using the finite difference technique. The biosensor response and sensitivity are investigated by altering the model parameters influencing the enzyme kinetics as well as the mass transport by diffusion. The biosensor action was analyzed with a special emphasis to the effect of the chemical amplification. The simulation results qualitatively explain and confirm the experimentally observed effect of the synergistic substrates conversion on the biosensor response. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle A New Methodology for Vibration Error Compensation of Optical Encoders
Sensors 2012, 12(4), 4918-4933; doi:10.3390/s120404918
Received: 7 February 2012 / Revised: 30 March 2012 / Accepted: 31 March 2012 / Published: 17 April 2012
Cited by 8 | PDF Full-text (885 KB) | HTML Full-text | XML Full-text
Abstract
Optical encoders are sensors based on grating interference patterns. Tolerances inherent to the manufacturing process can induce errors in the position accuracy as the measurement signals stand apart from the ideal conditions. In case the encoder is working under vibrations, the oscillating [...] Read more.
Optical encoders are sensors based on grating interference patterns. Tolerances inherent to the manufacturing process can induce errors in the position accuracy as the measurement signals stand apart from the ideal conditions. In case the encoder is working under vibrations, the oscillating movement of the scanning head is registered by the encoder system as a displacement, introducing an error into the counter to be added up to graduation, system and installation errors. Behavior improvement can be based on different techniques trying to compensate the error from measurement signals processing. In this work a new “ad hoc” methodology is presented to compensate the error of the encoder when is working under the influence of vibration. The methodology is based on fitting techniques to the Lissajous figure of the deteriorated measurement signals and the use of a look up table, giving as a result a compensation procedure in which a higher accuracy of the sensor is obtained. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Assessing Ambiguity of Context Data in Intelligent Environments: Towards a More Reliable Context Managing System
Sensors 2012, 12(4), 4934-4951; doi:10.3390/s120404934
Received: 22 February 2012 / Revised: 3 April 2012 / Accepted: 6 April 2012 / Published: 17 April 2012
Cited by 12 | PDF Full-text (518 KB) | HTML Full-text | XML Full-text
Abstract
Modeling and managing correctly the user context in Smart Environments is important to achieve robust and reliable systems. When modeling reality we must take into account its ambiguous nature. Considering the uncertainty and vagueness in context data information it is possible to [...] Read more.
Modeling and managing correctly the user context in Smart Environments is important to achieve robust and reliable systems. When modeling reality we must take into account its ambiguous nature. Considering the uncertainty and vagueness in context data information it is possible to attain a more precise picture of the environment, thus leading to a more accurate inference process. To achieve these goals we present an ontology that models the ambiguity in intelligent environments and a data fusion and inference process that takes advantage of that extra information to provide better results. Our system can assess the certainty of the captured measurements, discarding the unreliable ones and combining the rest into a unified vision of the current user context. It also models the vagueness of the system, combining it with the uncertainty to obtain a richer inference process. Full article
Open AccessArticle Gold Nanoparticles Functionalized with Peptides for Specific Affinity Aggregation Assays of Estrogen Receptors and Their Agonists
Sensors 2012, 12(4), 4952-4961; doi:10.3390/s120404952
Received: 26 March 2012 / Revised: 9 April 2012 / Accepted: 16 April 2012 / Published: 18 April 2012
Cited by 4 | PDF Full-text (361 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Nuclear receptors regulate the transcription of genes and various functions such as development, differentiation, homeostasis, and behavior by formation of complexes with ligand and co-activator. Recent findings have shown that agonists of a ligand may have a toxic effect on cellular/tissular function [...] Read more.
Nuclear receptors regulate the transcription of genes and various functions such as development, differentiation, homeostasis, and behavior by formation of complexes with ligand and co-activator. Recent findings have shown that agonists of a ligand may have a toxic effect on cellular/tissular function through improper activation of nuclear receptors. In this study, a simple assay system of hetero-complexes of three different molecules (estrogen receptor, ligand, and co-activator peptide) has been developed. This assay system employs functionalized gold nanoparticles (GNPs: 15 nm in diameter). The surfaces of the GNPs were modified by a 12- or 20-amino-acid peptide that contains the sequence of co-activator for activating nuclear receptor by an agonist ligand. Owing to the affinity of the peptide, the functionalized GNPs aggregate faster when the nuclear receptor and the agonist ligand are also present. The aggregation of GNPs can be identified by shifts in adsorption spectrum, which give information about the specificity of agonist ligands. Similarly, this spectrum shift can measure concentration of known agonist ligand. This simple agonist screening will be employed as high through-put analysis (HTA) in the discovery of drugs that act through nuclear receptors. Full article
(This article belongs to the Section Biosensors)
Open AccessCommunication Dynamic Sensing of Localized Corrosion at the Metal/Solution Interface
Sensors 2012, 12(4), 4962-4973; doi:10.3390/s120404962
Received: 15 February 2012 / Revised: 10 April 2012 / Accepted: 11 April 2012 / Published: 18 April 2012
Cited by 2 | PDF Full-text (1668 KB) | HTML Full-text | XML Full-text
Abstract
A Mach-Zehnder interferometer is employed to detect localized corrosion at the metal/solution interface in the potentiodynamic sweep of the iron electrode in solutions. During the electrochemical reactions, local variations of the electrolyte’s refractive index, which correlate with the concentration of dissolved species, [...] Read more.
A Mach-Zehnder interferometer is employed to detect localized corrosion at the metal/solution interface in the potentiodynamic sweep of the iron electrode in solutions. During the electrochemical reactions, local variations of the electrolyte’s refractive index, which correlate with the concentration of dissolved species, change the optical path length (OPL) of the object beam when the beam passes through the electrolyte. The distribution of the OPL difference was obtained to present the concentration change of the metal ions visually, which enable direct evidence of corrosion processes. The OPL difference distribution shows localized and general corrosion during the anodic dissolution of the iron electrode in solutions with and without chloride ions, respectively. This method provides an approach for dynamic detection of localized corrosion at the metal/solution interface. Full article
(This article belongs to the Special Issue Sensing at the Nano-Scale: Chemical and Bio-Sensing)
Open AccessArticle Simulation and Experimental Investigation of Structural Dynamic Frequency Characteristics Control
Sensors 2012, 12(4), 4986-5004; doi:10.3390/s120404986
Received: 21 February 2012 / Revised: 28 March 2012 / Accepted: 16 April 2012 / Published: 18 April 2012
Cited by 3 | PDF Full-text (902 KB) | HTML Full-text | XML Full-text
Abstract
In general, mechanical equipment such as cars, airplanes, and machine tools all operate with constant frequency characteristics. These constant working characteristics should be controlled if the dynamic performance of the equipment demands improvement or the dynamic characteristics is intended to change with [...] Read more.
In general, mechanical equipment such as cars, airplanes, and machine tools all operate with constant frequency characteristics. These constant working characteristics should be controlled if the dynamic performance of the equipment demands improvement or the dynamic characteristics is intended to change with different working conditions. Active control is a stable and beneficial method for this, but current active control methods mainly focus on vibration control for reducing the vibration amplitudes in the time domain or frequency domain. In this paper, a new method of dynamic frequency characteristics active control (DFCAC) is presented for a flat plate, which can not only accomplish vibration control but also arbitrarily change the dynamic characteristics of the equipment. The proposed DFCAC algorithm is based on a neural network including two parts of the identification implement and the controller. The effectiveness of the DFCAC method is verified by several simulation and experiments, which provide desirable results. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Penalty Dynamic Programming Algorithm for Dim Targets Detection in Sensor Systems
Sensors 2012, 12(4), 5028-5046; doi:10.3390/s120405028
Received: 12 March 2012 / Revised: 20 March 2012 / Accepted: 10 April 2012 / Published: 18 April 2012
Cited by 2 | PDF Full-text (851 KB) | HTML Full-text | XML Full-text
Abstract
In order to detect and track multiple maneuvering dim targets in sensor systems, an improved dynamic programming track-before-detect algorithm (DP-TBD) called penalty DP-TBD (PDP-TBD) is proposed. The performances of tracking techniques are used as a feedback to the detection part. The feedback [...] Read more.
In order to detect and track multiple maneuvering dim targets in sensor systems, an improved dynamic programming track-before-detect algorithm (DP-TBD) called penalty DP-TBD (PDP-TBD) is proposed. The performances of tracking techniques are used as a feedback to the detection part. The feedback is constructed by a penalty term in the merit function, and the penalty term is a function of the possible target state estimation, which can be obtained by the tracking methods. With this feedback, the algorithm combines traditional tracking techniques with DP-TBD and it can be applied to simultaneously detect and track maneuvering dim targets. Meanwhile, a reasonable constraint that a sensor measurement can originate from one target or clutter is proposed to minimize track separation. Thus, the algorithm can be used in the multi-target situation with unknown target numbers. The efficiency and advantages of PDP-TBD compared with two existing methods are demonstrated by several simulations. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Identification of Cross-Country Skiing Movement Patterns Using Micro-Sensors
Sensors 2012, 12(4), 5047-5066; doi:10.3390/s120405047
Received: 12 March 2012 / Revised: 5 April 2012 / Accepted: 9 April 2012 / Published: 18 April 2012
Cited by 13 | PDF Full-text (3208 KB) | HTML Full-text | XML Full-text
Abstract
This study investigated the potential of micro-sensors for use in the identification of the main movement patterns used in cross-country skiing. Data were collected from four elite international and four Australian athletes in Europe and in Australia using a MinimaxXTM unit [...] Read more.
This study investigated the potential of micro-sensors for use in the identification of the main movement patterns used in cross-country skiing. Data were collected from four elite international and four Australian athletes in Europe and in Australia using a MinimaxXTM unit containing accelerometer, gyroscope and GPS sensors. Athletes performed four skating techniques and three classical techniques on snow at moderate velocity. Data from a single micro-sensor unit positioned in the centre of the upper back was sufficient to visually identify cyclical movement patterns for each technique. The general patterns for each technique were identified clearly across all athletes while at the same time distinctive characteristics for individual athletes were observed. Differences in speed, snow condition and gradient of terrain were not controlled in this study and these factors could have an effect on the data patterns. Development of algorithms to process the micro-sensor data into kinematic measurements would provide coaches and scientists with a valuable performance analysis tool. Further research is needed to develop such algorithms and to determine whether the patterns are consistent across a range of different speeds, snow conditions and terrain, and for skiers of differing ability. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Performance Analyses and Improvements for the IEEE 802.15.4 CSMA/CA Scheme with Heterogeneous Buffered Conditions
Sensors 2012, 12(4), 5067-5104; doi:10.3390/s120405067
Received: 8 March 2012 / Revised: 26 March 2012 / Accepted: 16 April 2012 / Published: 19 April 2012
PDF Full-text (1165 KB) | HTML Full-text | XML Full-text
Abstract
Studies of the IEEE 802.15.4 Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme have been received considerable attention recently, with most of these studies focusing on homogeneous or saturated traffic. Two novel transmission schemes—OSTS/BSTS (One Service a Time Scheme/Bulk Service a [...] Read more.
Studies of the IEEE 802.15.4 Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme have been received considerable attention recently, with most of these studies focusing on homogeneous or saturated traffic. Two novel transmission schemes—OSTS/BSTS (One Service a Time Scheme/Bulk Service a Time Scheme)—are proposed in this paper to improve the behaviors of time-critical buffered networks with heterogeneous unsaturated traffic. First, we propose a model which contains two modified semi-Markov chains and a macro-Markov chain combined with the theory of M/G/1/K queues to evaluate the characteristics of these two improved CSMA/CA schemes, in which traffic arrivals and accessing packets are bestowed with non-preemptive priority over each other, instead of prioritization. Then, throughput, packet delay and energy consumption of unsaturated, unacknowledged IEEE 802.15.4 beacon-enabled networks are predicted based on the overall point of view which takes the dependent interactions of different types of nodes into account. Moreover, performance comparisons of these two schemes with other non-priority schemes are also proposed. Analysis and simulation results show that delay and fairness of our schemes are superior to those of other schemes, while throughput and energy efficiency are superior to others in more heterogeneous situations. Comprehensive simulations demonstrate that the analysis results of these models match well with the simulation results. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Humidity-Induced Charge Leakage and Field Attenuation in Electric Field Microsensors
Sensors 2012, 12(4), 5105-5115; doi:10.3390/s120405105
Received: 15 March 2012 / Revised: 6 April 2012 / Accepted: 9 April 2012 / Published: 19 April 2012
PDF Full-text (501 KB) | HTML Full-text | XML Full-text
Abstract
The steady-state zero output of static electric field measuring systems often fluctuates, which is caused mainly by the finite leakage resistance of the water film on the surface of the electric field microsensor package. The water adsorption has been calculated using the [...] Read more.
The steady-state zero output of static electric field measuring systems often fluctuates, which is caused mainly by the finite leakage resistance of the water film on the surface of the electric field microsensor package. The water adsorption has been calculated using the Boltzmann distribution equation at various relative humidities for borosilicate glass and polytetrafluoroethylene surfaces. At various humidities, water film thickness has been calculated, and the induced charge leakage and field attenuation have been theoretically investigated. Experiments have been performed with microsensors to verify the theoretical predictions and the results are in good agreement. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Method for Optimal Sensor Deployment on 3D Terrains Utilizing a Steady State Genetic Algorithm with a Guided Walk Mutation Operator Based on the Wavelet Transform
Sensors 2012, 12(4), 5116-5133; doi:10.3390/s120405116
Received: 17 January 2012 / Revised: 19 March 2012 / Accepted: 12 April 2012 / Published: 19 April 2012
Cited by 10 | PDF Full-text (740 KB) | HTML Full-text | XML Full-text
Abstract
One of the most critical issues of Wireless Sensor Networks (WSNs) is the deployment of a limited number of sensors in order to achieve maximum coverage on a terrain. The optimal sensor deployment which enables one to minimize the consumed energy, communication [...] Read more.
One of the most critical issues of Wireless Sensor Networks (WSNs) is the deployment of a limited number of sensors in order to achieve maximum coverage on a terrain. The optimal sensor deployment which enables one to minimize the consumed energy, communication time and manpower for the maintenance of the network has attracted interest with the increased number of studies conducted on the subject in the last decade. Most of the studies in the literature today are proposed for two dimensional (2D) surfaces; however, real world sensor deployments often arise on three dimensional (3D) environments. In this paper, a guided wavelet transform (WT) based deployment strategy (WTDS) for 3D terrains, in which the sensor movements are carried out within the mutation phase of the genetic algorithms (GAs) is proposed. The proposed algorithm aims to maximize the Quality of Coverage (QoC) of a WSN via deploying a limited number of sensors on a 3D surface by utilizing a probabilistic sensing model and the Bresenham’s line of sight (LOS) algorithm. In addition, the method followed in this paper is novel to the literature and the performance of the proposed algorithm is compared with the Delaunay Triangulation (DT) method as well as a standard genetic algorithm based method and the results reveal that the proposed method is a more powerful and more successful method for sensor deployment on 3D terrains. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Benefits of Combined GPS/GLONASS with Low-Cost MEMS IMUs for Vehicular Urban Navigation
Sensors 2012, 12(4), 5134-5158; doi:10.3390/s120405134
Received: 13 February 2012 / Revised: 21 March 2012 / Accepted: 16 April 2012 / Published: 19 April 2012
Cited by 17 | PDF Full-text (1150 KB) | HTML Full-text | XML Full-text
Abstract
The integration of Global Navigation Satellite Systems (GNSS) with Inertial Navigation Systems (INS) has been very actively researched for many years due to the complementary nature of the two systems. In particular, during the last few years the integration with micro-electromechanical system [...] Read more.
The integration of Global Navigation Satellite Systems (GNSS) with Inertial Navigation Systems (INS) has been very actively researched for many years due to the complementary nature of the two systems. In particular, during the last few years the integration with micro-electromechanical system (MEMS) inertial measurement units (IMUs) has been investigated. In fact, recent advances in MEMS technology have made possible the development of a new generation of low cost inertial sensors characterized by small size and light weight, which represents an attractive option for mass-market applications such as vehicular and pedestrian navigation. However, whereas there has been much interest in the integration of GPS with a MEMS-based INS, few research studies have been conducted on expanding this application to the revitalized GLONASS system. This paper looks at the benefits of adding GLONASS to existing GPS/INS(MEMS) systems using loose and tight integration strategies. The relative benefits of various constraints are also assessed. Results show that when satellite visibility is poor (approximately 50% solution availability) the benefits of GLONASS are only seen with tight integration algorithms. For more benign environments, a loosely coupled GPS/GLONASS/INS system offers performance comparable to that of a tightly coupled GPS/INS system, but with reduced complexity and development time. Full article
(This article belongs to the Section Remote Sensors)

Review

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Open AccessReview Optical Fiber Networks for Remote Fiber Optic Sensors
Sensors 2012, 12(4), 3929-3951; doi:10.3390/s120403929
Received: 29 January 2012 / Revised: 1 March 2012 / Accepted: 15 March 2012 / Published: 26 March 2012
Cited by 15 | PDF Full-text (402 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an overview of optical fiber sensor networks for remote sensing. Firstly, the state of the art of remote fiber sensor systems has been considered. We have summarized the great evolution of these systems in recent years; this progress confirms [...] Read more.
This paper presents an overview of optical fiber sensor networks for remote sensing. Firstly, the state of the art of remote fiber sensor systems has been considered. We have summarized the great evolution of these systems in recent years; this progress confirms that fiber-optic remote sensing is a promising technology with a wide field of practical applications. Afterwards, the most representative remote fiber-optic sensor systems are briefly explained, discussing their schemes, challenges, pros and cons. Finally, a synopsis of the main factors to take into consideration in the design of a remote sensor system is gathered. Full article
(This article belongs to the Special Issue Optical Fiber Sensors 2012)
Open AccessReview Overview of Data Routing Approaches for Wireless Sensor Networks
Sensors 2012, 12(4), 3964-3996; doi:10.3390/s120403964
Received: 13 February 2012 / Revised: 12 March 2012 / Accepted: 16 March 2012 / Published: 27 March 2012
Cited by 18 | PDF Full-text (742 KB) | HTML Full-text | XML Full-text
Abstract
Recent years have witnessed a growing interest in deploying large populations of microsensors that collaborate in a distributed manner to gather and process sensory data and deliver them to a sink node through wireless communications systems. Currently, there is a lot of [...] Read more.
Recent years have witnessed a growing interest in deploying large populations of microsensors that collaborate in a distributed manner to gather and process sensory data and deliver them to a sink node through wireless communications systems. Currently, there is a lot of interest in data routing for Wireless Sensor Networks (WSNs) due to their unique challenges compared to conventional routing in wired networks. In WSNs, each data routing approach follows a specific goal (goals) according to the application. Although the general goal of every data routing approach in WSNs is to extend the network lifetime and every approach should be aware of the energy level of the nodes, data routing approaches may focus on one (or some) specific goal(s) depending on the application. Thus, existing approaches can be categorized according to their routing goals. In this paper, the main goals of data routing approaches in sensor networks are described. Then, the best known and most recent data routing approaches in WSNs are classified and studied according to their specific goals. Full article
(This article belongs to the Section Sensor Networks)
Open AccessReview Application of Optical Biosensors in Small-Molecule Screening Activities
Sensors 2012, 12(4), 4311-4323; doi:10.3390/s120404311
Received: 22 February 2012 / Revised: 20 March 2012 / Accepted: 23 March 2012 / Published: 28 March 2012
Cited by 13 | PDF Full-text (305 KB) | HTML Full-text | XML Full-text
Abstract
The last two decades have seen remarkable progress and improvements in optical biosensor systems such that those are currently seen as an important and value-adding component of modern drug screening activities. In particular the introduction of microplate-based biosensor systems holds the promise [...] Read more.
The last two decades have seen remarkable progress and improvements in optical biosensor systems such that those are currently seen as an important and value-adding component of modern drug screening activities. In particular the introduction of microplate-based biosensor systems holds the promise to match the required throughput without compromising on data quality thus representing a sought-after complement to traditional fluidic systems. This article aims to highlight the application of the two most prominent optical biosensor technologies, namely surface plasmon resonance (SPR) and optical waveguide grating (OWG), in small-molecule screening and will present, review and discuss the advantages and disadvantages of different assay formats on these platforms. A particular focus will be on the specific advantages of the inhibition in solution assay (ISA) format in contrast to traditional direct binding assays (DBA). Furthermore we will discuss different application areas for both fluidic as well as plate-based biosensor systems by considering the individual strength of the platforms. Full article
(This article belongs to the Special Issue Sensors and Biosensors Using Label Free Chemistries)
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Open AccessReview Optical Triangulation-Based Microtopographic Inspection of Surfaces
Sensors 2012, 12(4), 4399-4420; doi:10.3390/s120404399
Received: 21 February 2012 / Revised: 22 March 2012 / Accepted: 28 March 2012 / Published: 29 March 2012
Cited by 8 | PDF Full-text (1823 KB) | HTML Full-text | XML Full-text
Abstract
The non-invasive inspection of surfaces is a major issue in a wide variety of industries and research laboratories. The vast and increasing range of surface types, tolerance requirements and measurement constraints demanded during the last decades represents a major research effort in [...] Read more.
The non-invasive inspection of surfaces is a major issue in a wide variety of industries and research laboratories. The vast and increasing range of surface types, tolerance requirements and measurement constraints demanded during the last decades represents a major research effort in the development of new methods, systems and metrological strategies. The discreet dimensional evaluation the rugometric characterization and the profilometric inspection seem to be insufficient in many instances. The full microtopographic inspection has became a common requirement. Among the different systems developed, optical methods have the most important role and among those triangulation-based ones have gained a major status thanks to their flexibility, reliability and robustness. In this communication we will provide a brief historical review on the development of optical triangulation application to the dimensional inspection of objects and surfaces and on the work done at the Microtopography Laboratory of the Physics Department of the University of Minho, Portugal, in the development of methods and systems of optical triangulation-based microtopographic inspection of surfaces. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Portugal)
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Open AccessReview Quorum Quenching Revisited—From Signal Decays to Signalling Confusion
Sensors 2012, 12(4), 4661-4696; doi:10.3390/s120404661
Received: 28 February 2012 / Revised: 23 March 2012 / Accepted: 26 March 2012 / Published: 10 April 2012
Cited by 53 | PDF Full-text (344 KB) | HTML Full-text | XML Full-text
Abstract
In a polymicrobial community, while some bacteria are communicating with neighboring cells (quorum sensing), others are interrupting the communication (quorum quenching), thus creating a constant arms race between intercellular communication. In the past decade, numerous quorum quenching enzymes have been found and [...] Read more.
In a polymicrobial community, while some bacteria are communicating with neighboring cells (quorum sensing), others are interrupting the communication (quorum quenching), thus creating a constant arms race between intercellular communication. In the past decade, numerous quorum quenching enzymes have been found and initially thought to inactivate the signalling molecules. Though this is widely accepted, the actual roles of these quorum quenching enzymes are now being uncovered. Recent evidence extends the role of quorum quenching to detoxification or metabolism of signalling molecules as food and energy source; this includes “signalling confusion”, a term coined in this paper to refer to the phenomenon of non-destructive modification of signalling molecules. While quorum quenching has been explored as a novel anti-infective therapy targeting, quorum sensing evidence begins to show the development of resistance against quorum quenching. Full article
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Open AccessReview Multiple Classifier System for Remote Sensing Image Classification: A Review
Sensors 2012, 12(4), 4764-4792; doi:10.3390/s120404764
Received: 22 February 2012 / Revised: 22 March 2012 / Accepted: 6 April 2012 / Published: 12 April 2012
Cited by 51 | PDF Full-text (22962 KB) | HTML Full-text | XML Full-text
Abstract
Over the last two decades, multiple classifier system (MCS) or classifier ensemble has shown great potential to improve the accuracy and reliability of remote sensing image classification. Although there are lots of literatures covering the MCS approaches, there is a lack of [...] Read more.
Over the last two decades, multiple classifier system (MCS) or classifier ensemble has shown great potential to improve the accuracy and reliability of remote sensing image classification. Although there are lots of literatures covering the MCS approaches, there is a lack of a comprehensive literature review which presents an overall architecture of the basic principles and trends behind the design of remote sensing classifier ensemble. Therefore, in order to give a reference point for MCS approaches, this paper attempts to explicitly review the remote sensing implementations of MCS and proposes some modified approaches. The effectiveness of existing and improved algorithms are analyzed and evaluated by multi-source remotely sensed images, including high spatial resolution image (QuickBird), hyperspectral image (OMISII) and multi-spectral image (Landsat ETM+).Experimental results demonstrate that MCS can effectively improve the accuracy and stability of remote sensing image classification, and diversity measures play an active role for the combination of multiple classifiers. Furthermore, this survey provides a roadmap to guide future research, algorithm enhancement and facilitate knowledge accumulation of MCS in remote sensing community. Full article
(This article belongs to the Section Remote Sensors)
Open AccessReview Endogenous Bioactive Peptides as Potential Biomarkers for Atherosclerotic Coronary Heart Disease
Sensors 2012, 12(4), 4974-4985; doi:10.3390/s120404974
Received: 8 February 2012 / Revised: 22 March 2012 / Accepted: 16 April 2012 / Published: 18 April 2012
Cited by 13 | PDF Full-text (294 KB) | HTML Full-text | XML Full-text
Abstract
Cardiovascular disease is the leading cause of death worldwide, with high medical costs and rates of disability. It is therefore important to evaluate the use of cardiovascular biomarkers in the early diagnosis of coronary artery disease (CAD). We have screened a variety [...] Read more.
Cardiovascular disease is the leading cause of death worldwide, with high medical costs and rates of disability. It is therefore important to evaluate the use of cardiovascular biomarkers in the early diagnosis of coronary artery disease (CAD). We have screened a variety of recently identified bioactive peptides candidates in anticipation that they would allow detection of atherosclerotic CAD. Especially, we have focused on novel anti-atherogenic peptides as indicators and negative risk factors for CAD. In vitro, in vivo and clinical studies indicated that human adiponectin, heregulin-β1, glucagon-like peptide-1 (GLP-1), and salusin-α, peptides of 244, 71, 30, and 28 amino acids, respectively, attenuate the development and progression of atherosclerotic lesions by suppressing macrophage foam cell formation via down-regulation of acyl-coenzyme A: cholesterol acyltransferase-1. Circulating levels of these peptides in the blood are significantly decreased in patients with CAD compared to patients without CAD. Receiver operating characteristic analyses showed that salusin-α is a more useful biomarker, with better sensitivity and specificity, compared with the others for detecting CAD. Therefore, salusin-α, heregulin-β1, adiponectin, and/or GLP-1, alone or in various combinations, may be useful as biomarkers for atherosclerotic CAD. Full article
(This article belongs to the Special Issue Biomarkers and Nanosensors: New Approaches for Biology and Medicine)
Open AccessReview Visualizing Sweetness: Increasingly Diverse Applications for Fluorescent-Tagged Glucose Bioprobes and Their Recent Structural Modifications
Sensors 2012, 12(4), 5005-5027; doi:10.3390/s120405005
Received: 28 February 2012 / Revised: 3 April 2012 / Accepted: 9 April 2012 / Published: 18 April 2012
Cited by 26 | PDF Full-text (581 KB) | HTML Full-text | XML Full-text
Abstract
Glucose homeostasis is a fundamental aspect of life and its dysregulation is associated with important diseases, such as cancer and diabetes. Traditionally, glucose radioisotopes have been used to monitor glucose utilization in biological systems. Fluorescent-tagged glucose analogues were initially developed in the [...] Read more.
Glucose homeostasis is a fundamental aspect of life and its dysregulation is associated with important diseases, such as cancer and diabetes. Traditionally, glucose radioisotopes have been used to monitor glucose utilization in biological systems. Fluorescent-tagged glucose analogues were initially developed in the 1980s, but it is only in the past decade that their use as a glucose sensor has increased significantly. These analogues were developed for monitoring glucose uptake in blood cells, but their recent applications include tracking glucose uptake by tumor cells and imaging brain cell metabolism. This review outlines the development of fluorescent-tagged glucose analogues, describes their recent structural modifications and discusses their increasingly diverse biological applications. Full article
Open AccessReview HPV-Associated Head and Neck Cancer: Molecular and Nano-Scale Markers for Prognosis and Therapeutic Stratification
Sensors 2012, 12(4), 5159-5169; doi:10.3390/s120405159
Received: 1 March 2012 / Revised: 27 March 2012 / Accepted: 18 April 2012 / Published: 20 April 2012
Cited by 7 | PDF Full-text (203 KB) | HTML Full-text | XML Full-text
Abstract
Over the last 10 years, it has become clear that patients with head and neck cancer can be stratified into two distinct subgroups on the basis of the etiology of their disease. Patients with human papillomavirus-related cancers have significantly better survival rates [...] Read more.
Over the last 10 years, it has become clear that patients with head and neck cancer can be stratified into two distinct subgroups on the basis of the etiology of their disease. Patients with human papillomavirus-related cancers have significantly better survival rates and may necessitate different therapeutic approaches than those with tobacco and/or alcohol related cancers. This review discusses the various biomarkers currently in use for identification of patients with HPV-positive cancers with a focus on the advantages and limitations of molecular and nano-scale markers. Full article
(This article belongs to the Special Issue Biomarkers and Nanosensors: New Approaches for Biology and Medicine)
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Open AccessReview Exploitation of Unique Properties of Zeolites in the Development of Gas Sensors
Sensors 2012, 12(4), 5170-5194; doi:10.3390/s120405170
Received: 23 February 2012 / Revised: 19 March 2012 / Accepted: 12 April 2012 / Published: 20 April 2012
Cited by 21 | PDF Full-text (1457 KB) | HTML Full-text | XML Full-text
Abstract
The unique properties of microporous zeolites, including ion-exchange properties, adsorption, molecular sieving, catalysis, conductivity have been exploited in improving the performance of gas sensors. Zeolites have been employed as physical and chemical filters to improve the sensitivity and selectivity of gas sensors. [...] Read more.
The unique properties of microporous zeolites, including ion-exchange properties, adsorption, molecular sieving, catalysis, conductivity have been exploited in improving the performance of gas sensors. Zeolites have been employed as physical and chemical filters to improve the sensitivity and selectivity of gas sensors. In addition, direct interaction of gas molecules with the extraframework cations in the nanoconfined space of zeolites has been explored as a basis for developing new impedance-type gas/vapor sensors. In this review, we summarize how these properties of zeolites have been used to develop new sensing paradigms. There is a considerable breadth of transduction processes that have been used for zeolite incorporated sensors, including frequency measurements, optical and the entire gamut of electrochemical measurements. It is clear from the published literature that zeolites provide a route to enhance sensor performance, and it is expected that commercial manifestation of some of the approaches discussed here will take place. The future of zeolite-based sensors will continue to exploit its unique properties and use of other microporous frameworks, including metal organic frameworks. Zeolite composites with electronic materials, including metals will lead to new paradigms in sensing. Use of nano-sized zeolite crystals and zeolite membranes will enhance sensor properties and make possible new routes of miniaturized sensors. Full article
(This article belongs to the Special Issue Sensing at the Nano-Scale: Chemical and Bio-Sensing)

Other

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Open AccessConcept Paper Pressure and Temperature Spin Crossover Sensors with Optical Detection
Sensors 2012, 12(4), 4479-4492; doi:10.3390/s120404479
Received: 15 February 2012 / Revised: 17 March 2012 / Accepted: 20 March 2012 / Published: 10 April 2012
Cited by 83 | PDF Full-text (297 KB) | HTML Full-text | XML Full-text
Abstract
Iron(II) spin crossover molecular materials are made of coordination centres switchable between two states by temperature, pressure or a visible light irradiation. The relevant macroscopic parameter which monitors the magnetic state of a given solid is the high-spin (HS) fraction denoted n [...] Read more.
Iron(II) spin crossover molecular materials are made of coordination centres switchable between two states by temperature, pressure or a visible light irradiation. The relevant macroscopic parameter which monitors the magnetic state of a given solid is the high-spin (HS) fraction denoted nHS, i.e., the relative population of HS molecules. Each spin crossover material is distinguished by a transition temperature T1/2 where 50% of active molecules have switched to the low-spin (LS) state. In strongly interacting systems, the thermal spin switching occurs abruptly at T1/2. Applying pressure induces a shift from HS to LS states, which is the direct consequence of the lower volume for the LS molecule. Each material has thus a well defined pressure value P1/2. In both cases the spin state change is easily detectable by optical means thanks to a thermo/piezochromic effect that is often encountered in these materials. In this contribution, we discuss potential use of spin crossover molecular materials as temperature and pressure sensors with optical detection. The ones presenting smooth transitions behaviour, which have not been seriously considered for any application, are spotlighted as potential sensors which should stimulate a large interest on this well investigated class of materials. Full article
(This article belongs to the Special Issue Molecular Devices and Machines: Cooperativity and Multifunctionality)
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