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Sensors, Volume 13, Issue 2 (February 2013), Pages 1385-2699

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Editorial

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Open AccessEditorial Sensors Best Paper Award 2013
Sensors 2013, 13(2), 2113-2116; doi:10.3390/s130202113
Received: 30 January 2013 / Accepted: 31 January 2013 / Published: 5 February 2013
Cited by 2 | PDF Full-text (141 KB) | HTML Full-text | XML Full-text
Abstract Since 2011, Sensors has instituted an annual award to recognize outstanding papers that are related to sensing technologies and applications and meet the aims, scope and high standards of this journal [1,2]. [...] Full article
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Research

Jump to: Editorial, Review

Open AccessArticle Complete Low-Cost Implementation of a Teleoperated Control System for a Humanoid Robot
Sensors 2013, 13(2), 1385-1401; doi:10.3390/s130201385
Received: 30 November 2012 / Revised: 24 December 2012 / Accepted: 17 January 2013 / Published: 24 January 2013
Cited by 8 | PDF Full-text (2174 KB) | HTML Full-text | XML Full-text
Abstract
Humanoid robotics is a field of a great research interest nowadays. This work implements a low-cost teleoperated system to control a humanoid robot, as a first step for further development and study of human motion and walking. A human suit is built, consisting
[...] Read more.
Humanoid robotics is a field of a great research interest nowadays. This work implements a low-cost teleoperated system to control a humanoid robot, as a first step for further development and study of human motion and walking. A human suit is built, consisting of 8 sensors, 6 resistive linear potentiometers on the lower extremities and 2 digital accelerometers for the arms. The goal is to replicate the suit movements in a small humanoid robot. The data from the sensors is wirelessly transmitted via two ZigBee RF configurable modules installed on each device: the robot and the suit. Replicating the suit movements requires a robot stability control module to prevent falling down while executing different actions involving knees flexion. This is carried out via a feedback control system with an accelerometer placed on the robot’s back. The measurement from this sensor is filtered using Kalman. In addition, a two input fuzzy algorithm controlling five servo motors regulates the robot balance. The humanoid robot is controlled by a medium capacity processor and a low computational cost is achieved for executing the different algorithms. Both hardware and software of the system are based on open platforms. The successful experiments carried out validate the implementation of the proposed teleoperated system. Full article
(This article belongs to the Special Issue New Trends towards Automatic Vehicle Control and Perception Systems)
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Open AccessArticle Human Behavior Cognition Using Smartphone Sensors
Sensors 2013, 13(2), 1402-1424; doi:10.3390/s130201402
Received: 28 November 2012 / Revised: 26 December 2012 / Accepted: 15 January 2013 / Published: 24 January 2013
Cited by 39 | PDF Full-text (1030 KB) | HTML Full-text | XML Full-text
Abstract
This research focuses on sensing context, modeling human behavior and developing a new architecture for a cognitive phone platform. We combine the latest positioning technologies and phone sensors to capture human movements in natural environments and use the movements to study human behavior.
[...] Read more.
This research focuses on sensing context, modeling human behavior and developing a new architecture for a cognitive phone platform. We combine the latest positioning technologies and phone sensors to capture human movements in natural environments and use the movements to study human behavior. Contexts in this research are abstracted as a Context Pyramid which includes six levels: Raw Sensor Data, Physical Parameter, Features/Patterns, Simple Contextual Descriptors, Activity-Level Descriptors, and Rich Context. To achieve implementation of the Context Pyramid on a cognitive phone, three key technologies are utilized: ubiquitous positioning, motion recognition, and human behavior modeling. Preliminary tests indicate that we have successfully achieved the Activity-Level Descriptors level with our LoMoCo (Location-Motion-Context) model. Location accuracy of the proposed solution is up to 1.9 meters in corridor environments and 3.5 meters in open spaces. Test results also indicate that the motion states are recognized with an accuracy rate up to 92.9% using a Least Square-Support Vector Machine (LS-SVM) classifier. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Fiber Optic pH Sensor with Self-Assembled Polymer Multilayer Nanocoatings
Sensors 2013, 13(2), 1425-1434; doi:10.3390/s130201425
Received: 7 December 2012 / Revised: 16 January 2013 / Accepted: 21 January 2013 / Published: 24 January 2013
Cited by 8 | PDF Full-text (962 KB) | HTML Full-text | XML Full-text
Abstract
A fiber-optic pH sensor based on a tilted fiber Bragg grating (TFBG) with electrostatic self-assembly multilayer sensing film is presented. The pH sensitive polymeric film, poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) was deposited on the circumference of the TFBG with the layer-by-layer
[...] Read more.
A fiber-optic pH sensor based on a tilted fiber Bragg grating (TFBG) with electrostatic self-assembly multilayer sensing film is presented. The pH sensitive polymeric film, poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) was deposited on the circumference of the TFBG with the layer-by-layer (LbL) electrostatic self-assembly technique. The PDDA/PAA film exhibits a reduction in refractive index by swelling in different pH solutions. This effect results in wavelength shifts and transmission changes in the spectrum of the TFBG. The peak amplitude of the dominant spectral fringes over a certain window of the transmission spectrum, obtained by FFT analysis, has a near-linear pH sensitivity of 117 arbitrary unit (a.u.)/pH unit and an accuracy of ±1 a.u. (in the range of pH 4.66 to pH 6.02). The thickness and surface morphology of the sensing multilayer film were characterized to investigate their effects on the sensor’s performance. The dynamic response of the sensor also has been studied (10 s rise time and 18 s fall time for a sensor with six bilayers of PDDA/PAA). Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Virtual Induction Loops Based on Cooperative Vehicular Communications
Sensors 2013, 13(2), 1467-1476; doi:10.3390/s130201467
Received: 19 November 2012 / Revised: 19 December 2012 / Accepted: 14 January 2013 / Published: 24 January 2013
Cited by 10 | PDF Full-text (992 KB) | HTML Full-text | XML Full-text
Abstract
Induction loop detectors have become the most utilized sensors in traffic management systems. The gathered traffic data is used to improve traffic efficiency (i.e., warning users about congested areas or planning new infrastructures). Despite their usefulness, their deployment and maintenance costs are expensive.
[...] Read more.
Induction loop detectors have become the most utilized sensors in traffic management systems. The gathered traffic data is used to improve traffic efficiency (i.e., warning users about congested areas or planning new infrastructures). Despite their usefulness, their deployment and maintenance costs are expensive. Vehicular networks are an emerging technology that can support novel strategies for ubiquitous and more cost-effective traffic data gathering. In this article, we propose and evaluate VIL (Virtual Induction Loop), a simple and lightweight traffic monitoring system based on cooperative vehicular communications. The proposed solution has been experimentally evaluated through simulation using real vehicular traces. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Nanobiosensors Based on Chemically Modified AFM Probes: A Useful Tool for Metsulfuron-Methyl Detection
Sensors 2013, 13(2), 1477-1489; doi:10.3390/s130201477
Received: 20 November 2012 / Revised: 6 January 2013 / Accepted: 6 January 2013 / Published: 24 January 2013
Cited by 9 | PDF Full-text (931 KB) | HTML Full-text | XML Full-text
Abstract
The use of agrochemicals has increased considerably in recent years, and consequently, there has been increased exposure of ecosystems and human populations to these highly toxic compounds. The study and development of methodologies to detect these substances with greater sensitivity has become extremely
[...] Read more.
The use of agrochemicals has increased considerably in recent years, and consequently, there has been increased exposure of ecosystems and human populations to these highly toxic compounds. The study and development of methodologies to detect these substances with greater sensitivity has become extremely relevant. This article describes, for the first time, the use of atomic force spectroscopy (AFS) in the detection of enzyme-inhibiting herbicides. A nanobiosensor based on an atomic force microscopy (AFM) tip functionalised with the acetolactate synthase (ALS) enzyme was developed and characterised. The herbicide metsulfuron-methyl, an ALS inhibitor, was successfully detected through the acquisition of force curves using this biosensor. The adhesion force values were considerably higher when the biosensor was used. An increase of ~250% was achieved relative to the adhesion force using an unfunctionalised AFM tip. This considerable increase was the result of a specific interaction between the enzyme and the herbicide, which was primarily responsible for the efficiency of the nanobiosensor. These results indicate that this methodology is promising for the detection of herbicides, pesticides, and other environmental contaminants. Full article
(This article belongs to the Special Issue Enzymatic Biosensors)
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Open AccessArticle Scour Monitoring System for Subsea Pipeline Based on Active Thermometry: Numerical and Experimental Studies
Sensors 2013, 13(2), 1490-1509; doi:10.3390/s130201490
Received: 1 December 2012 / Revised: 29 December 2012 / Accepted: 14 January 2013 / Published: 24 January 2013
Cited by 5 | PDF Full-text (984 KB) | HTML Full-text | XML Full-text
Abstract
A scour monitoring system for subsea pipeline based on active thermometry is proposed in this paper. The temperature reading of the proposed system is based on a distributed Brillouin optical fiber sensing technique. A thermal cable acts as the main component of the
[...] Read more.
A scour monitoring system for subsea pipeline based on active thermometry is proposed in this paper. The temperature reading of the proposed system is based on a distributed Brillouin optical fiber sensing technique. A thermal cable acts as the main component of the system, which consists of a heating belt, armored optical fibers and heat-shrinkable tubes which run parallel to the pipeline. The scour-induced free span can be monitored through different heat transfer behaviors of in-water and in-sediment scenarios during heating and cooling processes. Two sets of experiments, including exposing different lengths of the upper surface of the pipeline to water and creating free spans of various lengths, were carried out in laboratory. In both cases, the scour condition was immediately detected by the proposed monitoring system, which confirmed the system is robust and very sensitive. Numerical study of the method was also investigated by using the finite element method (FEM) with ANSYS, resulting in reasonable agreement with the test data. This brand new system provides a promising, low cost, highly precise and flexible approach for scour monitoring of subsea pipelines. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Low-Cost MEMS Sensors and Vision System for Motion and Position Estimation of a Scooter
Sensors 2013, 13(2), 1510-1522; doi:10.3390/s130201510
Received: 7 December 2012 / Revised: 18 January 2013 / Accepted: 21 January 2013 / Published: 24 January 2013
Cited by 11 | PDF Full-text (717 KB) | HTML Full-text | XML Full-text
Abstract
The possibility to identify with significant accuracy the position of a vehicle in a mapping reference frame for driving directions and best-route analysis is a topic which is attracting a lot of interest from the research and development sector. To reach the objective
[...] Read more.
The possibility to identify with significant accuracy the position of a vehicle in a mapping reference frame for driving directions and best-route analysis is a topic which is attracting a lot of interest from the research and development sector. To reach the objective of accurate vehicle positioning and integrate response events, it is necessary to estimate position, orientation and velocity of the system with high measurement rates. In this work we test a system which uses low-cost sensors, based on Micro Electro-Mechanical Systems (MEMS) technology, coupled with information derived from a video camera placed on a two-wheel motor vehicle (scooter). In comparison to a four-wheel vehicle; the dynamics of a two-wheel vehicle feature a higher level of complexity given that more degrees of freedom must be taken into account. For example a motorcycle can twist sideways; thus generating a roll angle. A slight pitch angle has to be considered as well; since wheel suspensions have a higher degree of motion compared to four-wheel motor vehicles. In this paper we present a method for the accurate reconstruction of the trajectory of a “Vespa” scooter; which can be used as alternative to the “classical” approach based on GPS/INS sensor integration. Position and orientation of the scooter are obtained by integrating MEMS-based orientation sensor data with digital images through a cascade of a Kalman filter and a Bayesian particle filter. Full article
(This article belongs to the Special Issue New Trends towards Automatic Vehicle Control and Perception Systems)
Open AccessArticle Strategy for the Development of a Smart NDVI Camera System for Outdoor Plant Detection and Agricultural Embedded Systems
Sensors 2013, 13(2), 1523-1538; doi:10.3390/s130201523
Received: 27 November 2012 / Revised: 15 January 2013 / Accepted: 16 January 2013 / Published: 24 January 2013
Cited by 12 | PDF Full-text (1633 KB) | HTML Full-text | XML Full-text
Abstract
The application of (smart) cameras for process control, mapping, and advanced imaging in agriculture has become an element of precision farming that facilitates the conservation of fertilizer, pesticides, and machine time. This technique additionally reduces the amount of energy required in terms of
[...] Read more.
The application of (smart) cameras for process control, mapping, and advanced imaging in agriculture has become an element of precision farming that facilitates the conservation of fertilizer, pesticides, and machine time. This technique additionally reduces the amount of energy required in terms of fuel. Although research activities have increased in this field, high camera prices reflect low adaptation to applications in all fields of agriculture. Smart, low-cost cameras adapted for agricultural applications can overcome this drawback. The normalized difference vegetation index (NDVI) for each image pixel is an applicable algorithm to discriminate plant information from the soil background enabled by a large difference in the reflectance between the near infrared (NIR) and the red channel optical frequency band. Two aligned charge coupled device (CCD) chips for the red and NIR channel are typically used, but they are expensive because of the precise optical alignment required. Therefore, much attention has been given to the development of alternative camera designs. In this study, the advantage of a smart one-chip camera design with NDVI image performance is demonstrated in terms of low cost and simplified design. The required assembly and pixel modifications are described, and new algorithms for establishing an enhanced NDVI image quality for data processing are discussed. Full article
(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)
Open AccessArticle Motion Mode Recognition and Step Detection Algorithms for Mobile Phone Users
Sensors 2013, 13(2), 1539-1562; doi:10.3390/s130201539
Received: 1 December 2012 / Revised: 18 January 2013 / Accepted: 22 January 2013 / Published: 24 January 2013
Cited by 66 | PDF Full-text (1508 KB) | HTML Full-text | XML Full-text
Abstract
Microelectromechanical Systems (MEMS) technology is playing a key role in the design of the new generation of smartphones. Thanks to their reduced size, reduced power consumption, MEMS sensors can be embedded in above mobile devices for increasing their functionalities. However, MEMS cannot allow
[...] Read more.
Microelectromechanical Systems (MEMS) technology is playing a key role in the design of the new generation of smartphones. Thanks to their reduced size, reduced power consumption, MEMS sensors can be embedded in above mobile devices for increasing their functionalities. However, MEMS cannot allow accurate autonomous location without external updates, e.g., from GPS signals, since their signals are degraded by various errors. When these sensors are fixed on the user’s foot, the stance phases of the foot can easily be determined and periodic Zero velocity UPdaTes (ZUPTs) are performed to bound the position error. When the sensor is in the hand, the situation becomes much more complex. First of all, the hand motion can be decoupled from the general motion of the user. Second, the characteristics of the inertial signals can differ depending on the carrying modes. Therefore, algorithms for characterizing the gait cycle of a pedestrian using a handheld device have been developed. A classifier able to detect motion modes typical for mobile phone users has been designed and implemented. According to the detected motion mode, adaptive step detection algorithms are applied. Success of the step detection process is found to be higher than 97% in all motion modes. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A New Method for Flow Rate Measurement in Millimeter-Scale Pipes
Sensors 2013, 13(2), 1563-1577; doi:10.3390/s130201563
Received: 19 November 2012 / Revised: 10 January 2013 / Accepted: 14 January 2013 / Published: 25 January 2013
Cited by 4 | PDF Full-text (409 KB) | HTML Full-text | XML Full-text
Abstract
Combining the Capacitively Coupled Contactless Conductivity Detection (C4D) technique and the principle of cross correlation flow measurement, a new method for flow rate measurement in millimeter-scale pipes was proposed. The research work included two parts. First, a new five-electrode C4
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Combining the Capacitively Coupled Contactless Conductivity Detection (C4D) technique and the principle of cross correlation flow measurement, a new method for flow rate measurement in millimeter-scale pipes was proposed. The research work included two parts. First, a new five-electrode C4D sensor was developed. Second, with two conductivity signals obtained by the developed sensor, the flow rate measurement was implemented by using the principle of cross correlation flow measurement. The experimental results showed that the proposed flow rate measurement method was effective, the developed five-electrode C4D sensor was successful, and the measurement accuracy was satisfactory. In five millimeter-scale pipes with different inner diameters of 0.5, 0.8, 1.8, 3.0 and 3.9 mm respectively, the maximum relative difference of the flow rate measurement between the reference flow rate and the measured flow rate was less than 5%. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Fast Classification of Meat Spoilage Markers Using Nanostructured ZnO Thin Films and Unsupervised Feature Learning
Sensors 2013, 13(2), 1578-1592; doi:10.3390/s130201578
Received: 31 October 2012 / Revised: 9 January 2013 / Accepted: 16 January 2013 / Published: 25 January 2013
Cited by 8 | PDF Full-text (345 KB) | HTML Full-text | XML Full-text
Abstract
This paper investigates a rapid and accurate detection system for spoilage in meat. We use unsupervised feature learning techniques (stacked restricted Boltzmann machines and auto-encoders) that consider only the transient response from undoped zinc oxide, manganese-doped zinc oxide, and fluorine-doped zinc oxide in
[...] Read more.
This paper investigates a rapid and accurate detection system for spoilage in meat. We use unsupervised feature learning techniques (stacked restricted Boltzmann machines and auto-encoders) that consider only the transient response from undoped zinc oxide, manganese-doped zinc oxide, and fluorine-doped zinc oxide in order to classify three categories: the type of thin film that is used, the type of gas, and the approximate ppm-level of the gas. These models mainly offer the advantage that features are learned from data instead of being hand-designed. We compare our results to a feature-based approach using samples with various ppm level of ethanol and trimethylamine (TMA) that are good markers for meat spoilage. The result is that deep networks give a better and faster classification than the feature-based approach, and we thus conclude that the fine-tuning of our deep models are more efficient for this kind of multi-label classification task. Full article
Open AccessArticle Temperature Grid Sensor for the Measurement of Spatial Temperature Distributions at Object Surfaces
Sensors 2013, 13(2), 1593-1602; doi:10.3390/s130201593
Received: 9 November 2012 / Revised: 4 January 2013 / Accepted: 6 January 2013 / Published: 25 January 2013
Cited by 4 | PDF Full-text (923 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents results of the development and application of a new temperature grid sensor based on the wire-mesh sensor principle. The grid sensor consists of a matrix of 256 Pt1000 platinum chip resistors and an associated electronics that measures the grid resistances
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This paper presents results of the development and application of a new temperature grid sensor based on the wire-mesh sensor principle. The grid sensor consists of a matrix of 256 Pt1000 platinum chip resistors and an associated electronics that measures the grid resistances with a multiplexing scheme at high speed. The individual sensor elements can be spatially distributed on an object surface and measure transient temperature distributions in real time. The advantage compared with other temperature field measurement approaches such as infrared cameras is that the object under investigation can be thermally insulated and the radiation properties of the surface do not affect the measurement accuracy. The sensor principle is therefore suited for various industrial monitoring applications. Its applicability for surface temperature monitoring has been demonstrated through heating and mixing experiments in a vessel. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany 2012)
Open AccessArticle Critical Evaluation of Acetylthiocholine Iodide and Acetylthiocholine Chloride as Substrates for Amperometric Biosensors Based on Acetylcholinesterase
Sensors 2013, 13(2), 1603-1613; doi:10.3390/s130201603
Received: 30 November 2012 / Revised: 15 January 2013 / Accepted: 22 January 2013 / Published: 25 January 2013
Cited by 6 | PDF Full-text (247 KB) | HTML Full-text | XML Full-text
Abstract
Numerous amperometric biosensors have been developed for the fast analysis of neurotoxic insecticides based on inhibition of cholinesterase (AChE). The analytical signal is quantified by the oxidation of the thiocholine that is produced enzymatically by the hydrolysis of the acetylthiocholine pseudosubstrate. The pseudosubstrate
[...] Read more.
Numerous amperometric biosensors have been developed for the fast analysis of neurotoxic insecticides based on inhibition of cholinesterase (AChE). The analytical signal is quantified by the oxidation of the thiocholine that is produced enzymatically by the hydrolysis of the acetylthiocholine pseudosubstrate. The pseudosubstrate is a cation and it is associated with chloride or iodide as corresponding anion to form a salt. The iodide salt is cheaper, but it is electrochemically active and consequently more difficult to use in electrochemical analytical devices. We investigate the possibility of using acetylthiocholine iodide as pseudosubstrate for amperometric detection. Our investigation demonstrates that operational conditions for any amperometric biosensor that use acetylthiocholine iodide must be thoroughly optimized to avoid false analytical signals or a reduced sensitivity. The working overpotential determined for different screen-printed electrodes was: carbon-nanotubes (360 mV), platinum (560 mV), gold (370 mV, based on a catalytic effect of iodide) or cobalt phthalocyanine (110 mV, but with a significant reduced sensitivity in the presence of iodide anions). Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Automatic Stem Mapping by Merging Several Terrestrial Laser Scans at the Feature and Decision Levels
Sensors 2013, 13(2), 1614-1634; doi:10.3390/s130201614
Received: 29 November 2012 / Revised: 23 January 2013 / Accepted: 23 January 2013 / Published: 25 January 2013
Cited by 24 | PDF Full-text (838 KB) | HTML Full-text | XML Full-text
Abstract
Detailed up-to-date ground reference data have become increasingly important in quantitative forest inventories. Field reference data are conventionally collected at the sample plot level by means of manual measurements, which are both labor-intensive and time-consuming. In addition, the number of attributes collected from
[...] Read more.
Detailed up-to-date ground reference data have become increasingly important in quantitative forest inventories. Field reference data are conventionally collected at the sample plot level by means of manual measurements, which are both labor-intensive and time-consuming. In addition, the number of attributes collected from the tree stem is limited. More recently, terrestrial laser scanning (TLS), using both single-scan and multi-scan techniques, has proven to be a promising solution for efficient stem mapping at the plot level. In the single-scan method, the laser scanner is placed at the center of the plot, creating only one scan, and all trees are mapped from the single-scan point cloud. Consequently, the occlusion of stems increases as the range of the scanner increases, depending on the forest’s attributes. In the conventional multi-scan method, several scans are made simultaneously inside and outside of the plot to collect point clouds representing all trees within the plot, and these scans are accurately co-registered by using artificial reference targets manually placed throughout the plot. The additional difficulty of applying the multi-scan method is due to the point-cloud registration of several scans not being fully automated yet. This paper proposes a multi-single-scan (MSS) method to map the sample plot. The method does not require artificial reference targets placed on the plot or point-level registration. The MSS method is based on the fully automated processing of each scan independently and on the merging of the stem positions automatically detected from multiple scans to accurately map the sample plot. The proposed MSS method was tested on five dense forest plots. The results show that the MSS method significantly improves the stem-detection accuracy compared with the single-scan approach and achieves a mapping accuracy similar to that achieved with the multi-scan method, without the need for the point-level registration. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Design of a Novel MEMS Gyroscope Array
Sensors 2013, 13(2), 1651-1663; doi:10.3390/s130201651
Received: 23 November 2012 / Revised: 18 January 2013 / Accepted: 21 January 2013 / Published: 28 January 2013
Cited by 15 | PDF Full-text (204 KB) | HTML Full-text | XML Full-text
Abstract
This paper reports a novel four degree-of-freedom (DOF) MEMS vibratory gyroscope. A MEMS gyroscope array is then presented using the novel gyroscope unit. In the design of the proposed 4-DOF MEMS vibratory gyroscope, the elements of the drive-mode are set inside the whole
[...] Read more.
This paper reports a novel four degree-of-freedom (DOF) MEMS vibratory gyroscope. A MEMS gyroscope array is then presented using the novel gyroscope unit. In the design of the proposed 4-DOF MEMS vibratory gyroscope, the elements of the drive-mode are set inside the whole gyroscope architecture, and the elements of sense-mode are set around the drive-mode, which thus makes it possible to combine several gyroscope units into a gyroscope array through sense-modes of all the units. The complete 2-DOF vibratory structure is utilized in both the drive-mode and sense-mode of the gyroscope unit, thereby providing the desired bandwidth and inherent robustness. The gyroscope array combines several gyroscope units by using the unique detection mass, which will increase the gain of sense-mode and improve the sensitivity of the system. The simulation results demonstrate that, compared to a single gyroscope unit, the gain of gyroscope array (n = 6) is increased by about 8 dB; a 3 dB bandwidth of 100 Hz in sense-mode and 190 Hz in drive-mode are also provided. The bandwidths of both modes are highly matched with each other, providing a bandwidth of 100 Hz for the entire system, thus illustrating that it could satisfy the requirements in practical applications. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Magnetic Field Analysis of Lorentz Motors Using a Novel Segmented Magnetic Equivalent Circuit Method
Sensors 2013, 13(2), 1664-1678; doi:10.3390/s130201664
Received: 14 December 2012 / Revised: 17 January 2013 / Accepted: 21 January 2013 / Published: 28 January 2013
Cited by 1 | PDF Full-text (554 KB) | HTML Full-text | XML Full-text
Abstract
A simple and accurate method based on the magnetic equivalent circuit (MEC) model is proposed in this paper to predict magnetic flux density (MFD) distribution of the air-gap in a Lorentz motor (LM). In conventional MEC methods, the permanent magnet (PM) is treated
[...] Read more.
A simple and accurate method based on the magnetic equivalent circuit (MEC) model is proposed in this paper to predict magnetic flux density (MFD) distribution of the air-gap in a Lorentz motor (LM). In conventional MEC methods, the permanent magnet (PM) is treated as one common source and all branches of MEC are coupled together to become a MEC network. In our proposed method, every PM flux source is divided into three sub-sections (the outer, the middle and the inner). Thus, the MEC of LM is divided correspondingly into three independent sub-loops. As the size of the middle sub-MEC is small enough, it can be treated as an ideal MEC and solved accurately. Combining with decoupled analysis of outer and inner MECs, MFD distribution in the air-gap can be approximated by a quadratic curve, and the complex calculation of reluctances in MECs can be avoided. The segmented magnetic equivalent circuit (SMEC) method is used to analyze a LM, and its effectiveness is demonstrated by comparison with FEA, conventional MEC and experimental results. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Time-Domain CMOS Oscillator-Based Thermostat with Digital Set-Point Programming
Sensors 2013, 13(2), 1679-1691; doi:10.3390/s130201679
Received: 19 November 2012 / Revised: 21 January 2013 / Accepted: 21 January 2013 / Published: 29 January 2013
Cited by 2 | PDF Full-text (448 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a time-domain CMOS oscillator-based thermostat with digital set-point programming [without a digital-to-analog converter (DAC) or external resistor] to achieve on-chip thermal management of modern VLSI systems. A time-domain delay-line-based thermostat with multiplexers (MUXs) was used to substantially reduce the power
[...] Read more.
This paper presents a time-domain CMOS oscillator-based thermostat with digital set-point programming [without a digital-to-analog converter (DAC) or external resistor] to achieve on-chip thermal management of modern VLSI systems. A time-domain delay-line-based thermostat with multiplexers (MUXs) was used to substantially reduce the power consumption and chip size, and can benefit from the performance enhancement due to the scaling down of fabrication processes. For further cost reduction and accuracy enhancement, this paper proposes a thermostat using two oscillators that are suitable for time-domain curvature compensation instead of longer linear delay lines. The final time comparison was achieved using a time comparator with a built-in custom hysteresis to generate the corresponding temperature alarm and control. The chip size of the circuit was reduced to 0.12 mm2 in a 0.35-mm TSMC CMOS process. The thermostat operates from 0 to 90 °C, and achieved a fine resolution better than 0.05 °C and an improved inaccuracy of ± 0.6 °C after two-point calibration for eight packaged chips. The power consumption was 30 µW at a sample rate of 10 samples/s. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Sensor for the Measurement of the Moisture of Undisturbed Soil Samples
Sensors 2013, 13(2), 1692-1705; doi:10.3390/s130201692
Received: 25 November 2012 / Revised: 10 January 2013 / Accepted: 15 January 2013 / Published: 29 January 2013
Cited by 5 | PDF Full-text (339 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a very accurate sensor for the measurement of the moisture of undisturbed soil samples. The sensor relies on accurate estimation of the permittivity which is performed independently of the soil type, and a subsequent calibration. The sensor is designed as
[...] Read more.
This paper presents a very accurate sensor for the measurement of the moisture of undisturbed soil samples. The sensor relies on accurate estimation of the permittivity which is performed independently of the soil type, and a subsequent calibration. The sensor is designed as an upgrade of the conventional soil sampling equipment used in agriculture—the Kopecky cylinder. The detailed description of the device is given, and the method for determining soil moisture is explained in detail. Soil moisture of unknown test samples was measured with an absolute error below 0.0057 g/g, which is only 2.24% of the full scale output, illustrating the high accuracy of the sensor. Full article
(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)
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Open AccessArticle On the Design of a Bioacoustic Sensor for the Early Detection of the Red Palm Weevil
Sensors 2013, 13(2), 1706-1729; doi:10.3390/s130201706
Received: 21 December 2012 / Revised: 25 January 2013 / Accepted: 25 January 2013 / Published: 30 January 2013
Cited by 7 | PDF Full-text (882 KB) | HTML Full-text | XML Full-text
Abstract
During the last two decades Red Palm Weevil (RPW, Rynchophorus Ferrugineus) has become one of the most dangerous threats to palm trees in many parts of the World. Its early detection is difficult, since palm trees do not show visual evidence of
[...] Read more.
During the last two decades Red Palm Weevil (RPW, Rynchophorus Ferrugineus) has become one of the most dangerous threats to palm trees in many parts of the World. Its early detection is difficult, since palm trees do not show visual evidence of infection until it is too late for them to recover. For this reason the development of efficient early detection mechanisms is a critical element of RPW pest management systems. One of the early detection mechanisms proposed in the literature is based on acoustic monitoring, as the activity of RPW larvae inside the palm trunk is audible for human operators under acceptable environmental noise levels (rural areas, night periods, etc.). In this work we propose the design of an autonomous bioacoustic sensor that can be installed in every palm tree under study and is able to analyze the captured audio signal during large periods of time. The results of the audio analysis would be reported wirelessly to a control station, to be subsequently processed and conveniently stored. That control station is to be accessible via the Internet. It is programmed to send warning messages when predefined alarm thresholds are reached, thereby allowing supervisors to check on-line the status and evolution of the palm tree orchards. We have developed a bioacoustic sensor prototype and performed an extensive set of experiments to measure its detection capability, achieving average detection rates over 90%. Full article
(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)
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Open AccessArticle Hybrid Modeling Method for a DEP Based Particle Manipulation
Sensors 2013, 13(2), 1730-1753; doi:10.3390/s130201730
Received: 11 November 2012 / Revised: 20 December 2012 / Accepted: 9 January 2013 / Published: 30 January 2013
Cited by 4 | PDF Full-text (8686 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a new modeling approach for Dielectrophoresis (DEP) based particle manipulation is presented. The proposed method fulfills missing links in finite element modeling between the multiphysic simulation and the biological behavior. This technique is amongst the first steps to develop a
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In this paper, a new modeling approach for Dielectrophoresis (DEP) based particle manipulation is presented. The proposed method fulfills missing links in finite element modeling between the multiphysic simulation and the biological behavior. This technique is amongst the first steps to develop a more complex platform covering several types of manipulations such as magnetophoresis and optics. The modeling approach is based on a hybrid interface using both ANSYS and MATLAB to link the propagation of the electrical field in the micro-channel to the particle motion. ANSYS is used to simulate the electrical propagation while MATLAB interprets the results to calculate cell displacement and send the new information to ANSYS for another turn. The beta version of the proposed technique takes into account particle shape, weight and its electrical properties. First obtained results are coherent with experimental results. Full article
(This article belongs to the Special Issue BioMEMS and Advanced Analytical Sensors for Biological Applications)
Open AccessArticle Enhancement of NH3 Gas Sensitivity at Room Temperature by Carbon Nanotube-Based Sensor Coated with Co Nanoparticles
Sensors 2013, 13(2), 1754-1762; doi:10.3390/s130201754
Received: 27 November 2012 / Revised: 25 January 2013 / Accepted: 29 January 2013 / Published: 30 January 2013
Cited by 31 | PDF Full-text (466 KB) | HTML Full-text | XML Full-text
Abstract
Multi-walled carbon nanotube (MWCNT) film has been fabricated onto Pt-patterned alumina substrates using the chemical vapor deposition method for NH3 gas sensing applications. The MWCNT-based sensor is sensitive to NH3 gas at room temperature. Nanoclusters of Co catalysts have been sputtered
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Multi-walled carbon nanotube (MWCNT) film has been fabricated onto Pt-patterned alumina substrates using the chemical vapor deposition method for NH3 gas sensing applications. The MWCNT-based sensor is sensitive to NH3 gas at room temperature. Nanoclusters of Co catalysts have been sputtered on the surface of the MWCNT film to enhance gas sensitivity with respect to unfunctionalized CNT films. The gas sensitivity of Co-functionalized MWCNT-based gas sensors is thus significantly improved. The sensor exhibits good repeatability and high selectivity towards NH3, compared with alcohol and LPG. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Combining Wireless Sensor Networks and Semantic Middleware for an Internet of Things-Based Sportsman/Woman Monitoring Application
Sensors 2013, 13(2), 1787-1835; doi:10.3390/s130201787
Received: 21 December 2012 / Revised: 24 January 2013 / Accepted: 24 January 2013 / Published: 31 January 2013
Cited by 14 | PDF Full-text (1257 KB) | HTML Full-text | XML Full-text
Abstract
Wireless Sensor Networks (WSNs) are spearheading the efforts taken to build and deploy systems aiming to accomplish the ultimate objectives of the Internet of Things. Due to the sensors WSNs nodes are provided with, and to their ubiquity and pervasive capabilities, these networks
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Wireless Sensor Networks (WSNs) are spearheading the efforts taken to build and deploy systems aiming to accomplish the ultimate objectives of the Internet of Things. Due to the sensors WSNs nodes are provided with, and to their ubiquity and pervasive capabilities, these networks become extremely suitable for many applications that so-called conventional cabled or wireless networks are unable to handle. One of these still underdeveloped applications is monitoring physical parameters on a person. This is an especially interesting application regarding their age or activity, for any detected hazardous parameter can be notified not only to the monitored person as a warning, but also to any third party that may be helpful under critical circumstances, such as relatives or healthcare centers. We propose a system built to monitor a sportsman/woman during a workout session or performing a sport-related indoor activity. Sensors have been deployed by means of several nodes acting as the nodes of a WSN, along with a semantic middleware development used for hardware complexity abstraction purposes. The data extracted from the environment, combined with the information obtained from the user, will compose the basis of the services that can be obtained. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle Distributed Temperature and Strain Discrimination with Stimulated Brillouin Scattering and Rayleigh Backscatter in an Optical Fiber
Sensors 2013, 13(2), 1836-1845; doi:10.3390/s130201836
Received: 3 December 2012 / Revised: 21 January 2013 / Accepted: 28 January 2013 / Published: 31 January 2013
Cited by 10 | PDF Full-text (502 KB) | HTML Full-text | XML Full-text
Abstract
A distributed optical fiber sensor with the capability of simultaneously measuring temperature and strain is proposed using a large effective area non-zero dispersion shifted fiber (LEAF) with sub-meter spatial resolution. The Brillouin frequency shift is measured using Brillouin optical time-domain analysis (BOTDA) with
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A distributed optical fiber sensor with the capability of simultaneously measuring temperature and strain is proposed using a large effective area non-zero dispersion shifted fiber (LEAF) with sub-meter spatial resolution. The Brillouin frequency shift is measured using Brillouin optical time-domain analysis (BOTDA) with differential pulse-width pair technique, while the spectrum shift of the Rayleigh backscatter is measured using optical frequency-domain reflectometry (OFDR). These shifts are the functions of both temperature and strain, and can be used as two independent parameters for the discrimination of temperature and strain. A 92 m measurable range with the spatial resolution of 50 cm is demonstrated experimentally, and accuracies of ±1.2 °C in temperature and ±15 με in strain could be achieved. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Thermal Strain Analysis of Optic Fiber Sensors
Sensors 2013, 13(2), 1846-1855; doi:10.3390/s130201846
Received: 16 January 2013 / Revised: 24 January 2013 / Accepted: 28 January 2013 / Published: 31 January 2013
Cited by 8 | PDF Full-text (469 KB) | HTML Full-text | XML Full-text
Abstract
An optical fiber sensor surface bonded onto a host structure and subjected to a temperature change is analytically studied in this work. The analysis is developed in order to assess the thermal behavior of an optical fiber sensor designed for measuring the strain
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An optical fiber sensor surface bonded onto a host structure and subjected to a temperature change is analytically studied in this work. The analysis is developed in order to assess the thermal behavior of an optical fiber sensor designed for measuring the strain in the host structure. For a surface bonded optical fiber sensor, the measuring sensitivity is strongly dependent on the bonding characteristics which include the protective coating, adhesive layer and the bonding length. Thermal stresses can be generated due to a mismatch of thermal expansion coefficients between the optical fiber and host structure. The optical fiber thermal strain induced by the host structure is transferred via the adhesive layer and protective coating. In this investigation, an analytical expression of the thermal strain and stress in the optical fiber is presented. The theoretical predictions are validated using the finite element method. Numerical results show that the thermal strain and stress are linearly dependent on the difference in thermal expansion coefficients between the optical fiber and host structure and independent of the thermal expansion coefficients of the adhesive and coating. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A New Mirroring Circuit for Power MOS Current Sensing Highly Immune to EMI
Sensors 2013, 13(2), 1856-1871; doi:10.3390/s130201856
Received: 8 November 2012 / Revised: 27 December 2012 / Accepted: 8 January 2013 / Published: 31 January 2013
Cited by 3 | PDF Full-text (300 KB) | HTML Full-text | XML Full-text
Abstract
This paper deals with the monitoring of power transistor current subjected to radio-frequency interference. In particular, a new current sensor with no connection to the power transistor drain and with improved performance with respect to the existing current-sensing schemes is presented. The operation
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This paper deals with the monitoring of power transistor current subjected to radio-frequency interference. In particular, a new current sensor with no connection to the power transistor drain and with improved performance with respect to the existing current-sensing schemes is presented. The operation of the above mentioned current sensor is discussed referring to time-domain computer simulations. The susceptibility of the proposed circuit to radio-frequency interference is evaluated through time-domain computer simulations and the results are compared with those obtained for a conventional integrated current sensor. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Italy 2012)
Open AccessArticle Visible/Near Infrared Spectroscopy and Chemometrics for the Prediction of Trace Element (Fe and Zn) Levels in Rice Leaf
Sensors 2013, 13(2), 1872-1883; doi:10.3390/s130201872
Received: 8 January 2013 / Revised: 24 January 2013 / Accepted: 28 January 2013 / Published: 1 February 2013
Cited by 6 | PDF Full-text (225 KB) | HTML Full-text | XML Full-text
Abstract
Two sensitive wavelength (SW) selection methods combined with visible/near infrared (Vis/NIR) spectroscopy were investigated to determine the levels of some trace elements (Fe, Zn) in rice leaf. A total of 90 samples were prepared for the calibration (n = 70) and validation (n
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Two sensitive wavelength (SW) selection methods combined with visible/near infrared (Vis/NIR) spectroscopy were investigated to determine the levels of some trace elements (Fe, Zn) in rice leaf. A total of 90 samples were prepared for the calibration (n = 70) and validation (n = 20) sets. Calibration models using SWs selected by LVA and ICA were developed and nonlinear regression of a least squares-support vector machine (LS-SVM) was built. In the nonlinear models, six SWs selected by ICA can provide the optimal ICA-LS-SVM model when compared with LV-LS-SVM. The coefficients of determination (R2), root mean square error of prediction (RMSEP) and bias by ICA-LS-SVM were 0.6189, 20.6510 ppm and −12.1549 ppm, respectively, for Fe, and 0.6731, 5.5919 ppm and 1.5232 ppm, respectively, for Zn. The overall results indicated that ICA was a powerful way for the selection of SWs, and Vis/NIR spectroscopy combined with ICA-LS-SVM was very efficient in terms of accurate determination of trace elements in rice leaf. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A Silicon Carbide Wireless Temperature Sensing System for High Temperature Applications
Sensors 2013, 13(2), 1884-1901; doi:10.3390/s130201884
Received: 5 December 2012 / Revised: 6 January 2013 / Accepted: 11 January 2013 / Published: 1 February 2013
Cited by 17 | PDF Full-text (1027 KB) | HTML Full-text | XML Full-text
Abstract
In this article, an extreme environment-capable temperature sensing system based on state-of-art silicon carbide (SiC) wireless electronics is presented. In conjunction with a Pt-Pb thermocouple, the SiC wireless sensor suite is operable at 450 °C while under centrifugal load greater than 1,000 g.
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In this article, an extreme environment-capable temperature sensing system based on state-of-art silicon carbide (SiC) wireless electronics is presented. In conjunction with a Pt-Pb thermocouple, the SiC wireless sensor suite is operable at 450 °C while under centrifugal load greater than 1,000 g. This SiC wireless temperature sensing system is designed to be non-intrusively embedded inside the gas turbine generators, acquiring the temperature information of critical components such as turbine blades, and wirelessly transmitting the information to the receiver located outside the turbine engine. A prototype system was developed and verified up to 450 °C through high temperature lab testing. The combination of the extreme temperature SiC wireless telemetry technology and integrated harsh environment sensors will allow for condition-based in-situ maintenance of power generators and aircraft turbines in field operation, and can be applied in many other industries requiring extreme environment monitoring and maintenance. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle 3D LIDAR-Camera Extrinsic Calibration Using an Arbitrary Trihedron
Sensors 2013, 13(2), 1902-1918; doi:10.3390/s130201902
Received: 14 November 2012 / Revised: 8 January 2013 / Accepted: 24 January 2013 / Published: 1 February 2013
Cited by 12 | PDF Full-text (3521 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel way to address the extrinsic calibration problem for a system composed of a 3D LIDAR and a camera. The relative transformation between the two sensors is calibrated via a nonlinear least squares (NLS) problem, which is formulated in
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This paper presents a novel way to address the extrinsic calibration problem for a system composed of a 3D LIDAR and a camera. The relative transformation between the two sensors is calibrated via a nonlinear least squares (NLS) problem, which is formulated in terms of the geometric constraints associated with a trihedral object. Precise initial estimates of NLS are obtained by dividing it into two sub-problems that are solved individually. With the precise initializations, the calibration parameters are further refined by iteratively optimizing the NLS problem. The algorithm is validated on both simulated and real data, as well as a 3D reconstruction application. Moreover, since the trihedral target used for calibration can be either orthogonal or not, it is very often present in structured environments, making the calibration convenient. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Extended Kalman Filter-Based Methods for Pose Estimation Using Visual, Inertial and Magnetic Sensors: Comparative Analysis and Performance Evaluation
Sensors 2013, 13(2), 1919-1941; doi:10.3390/s130201919
Received: 12 December 2012 / Revised: 24 January 2013 / Accepted: 26 January 2013 / Published: 4 February 2013
Cited by 25 | PDF Full-text (427 KB) | HTML Full-text | XML Full-text
Abstract
In this paper measurements from a monocular vision system are fused with inertial/magnetic measurements from an Inertial Measurement Unit (IMU) rigidly connected to the camera. Two Extended Kalman filters (EKFs) were developed to estimate the pose of the IMU/camera sensor moving relative to
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In this paper measurements from a monocular vision system are fused with inertial/magnetic measurements from an Inertial Measurement Unit (IMU) rigidly connected to the camera. Two Extended Kalman filters (EKFs) were developed to estimate the pose of the IMU/camera sensor moving relative to a rigid scene (ego-motion), based on a set of fiducials. The two filters were identical as for the state equation and the measurement equations of the inertial/magnetic sensors. The DLT-based EKF exploited visual estimates of the ego-motion using a variant of the Direct Linear Transformation (DLT) method; the error-driven EKF exploited pseudo-measurements based on the projection errors from measured two-dimensional point features to the corresponding three-dimensional fiducials. The two filters were off-line analyzed in different experimental conditions and compared to a purely IMU-based EKF used for estimating the orientation of the IMU/camera sensor. The DLT-based EKF was more accurate than the error-driven EKF, less robust against loss of visual features, and equivalent in terms of computational complexity. Orientation root mean square errors (RMSEs) of 1° (1.5°), and position RMSEs of 3.5 mm (10 mm) were achieved in our experiments by the DLT-based EKF (error-driven EKF); by contrast, orientation RMSEs of 1.6° were achieved by the purely IMU-based EKF. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Routing Protocol Based on Energy and Link Quality for Internet of Things Applications
Sensors 2013, 13(2), 1942-1964; doi:10.3390/s130201942
Received: 15 December 2012 / Revised: 20 January 2013 / Accepted: 25 January 2013 / Published: 4 February 2013
Cited by 18 | PDF Full-text (1646 KB) | HTML Full-text | XML Full-text
Abstract
The Internet of Things (IoT) is attracting considerable attention from the universities, industries, citizens and governments for applications, such as healthcare, environmental monitoring and smart buildings. IoT enables network connectivity between smart devices at all times, everywhere, and about everything. In this context,
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The Internet of Things (IoT) is attracting considerable attention from the universities, industries, citizens and governments for applications, such as healthcare, environmental monitoring and smart buildings. IoT enables network connectivity between smart devices at all times, everywhere, and about everything. In this context, Wireless Sensor Networks (WSNs) play an important role in increasing the ubiquity of networks with smart devices that are low-cost and easy to deploy. However, sensor nodes are restricted in terms of energy, processing and memory. Additionally, low-power radios are very sensitive to noise, interference and multipath distortions. In this context, this article proposes a routing protocol based on Routing by Energy and Link quality (REL) for IoT applications. To increase reliability and energy-efficiency, REL selects routes on the basis of a proposed end-to-end link quality estimator mechanism, residual energy and hop count. Furthermore, REL proposes an event-driven mechanism to provide load balancing and avoid the premature energy depletion of nodes/networks. Performance evaluations were carried out using simulation and testbed experiments to show the impact and benefits of REL in small and large-scale networks. The results show that REL increases the network lifetime and services availability, as well as the quality of service of IoT applications. It also provides an even distribution of scarce network resources and reduces the packet loss rate, compared with the performance of well-known protocols. Full article
(This article belongs to the Special Issue Ubiquitous Sensing)
Open AccessArticle Numerical Simulation of Optically-Induced Dielectrophoresis Using a Voltage-Transformation-Ratio Model
Sensors 2013, 13(2), 1965-1983; doi:10.3390/s130201965
Received: 13 December 2012 / Revised: 16 January 2013 / Accepted: 29 January 2013 / Published: 4 February 2013
Cited by 5 | PDF Full-text (788 KB) | HTML Full-text | XML Full-text
Abstract
Optically-induced dielectrophoresis (ODEP) has been extensively used for the manipulation and separation of cells, beads and micro-droplets in microfluidic devices. With this approach, non-uniform electric fields induced by light projected on a photoconductive layer can be used to generate attractive or repulsive forces
[...] Read more.
Optically-induced dielectrophoresis (ODEP) has been extensively used for the manipulation and separation of cells, beads and micro-droplets in microfluidic devices. With this approach, non-uniform electric fields induced by light projected on a photoconductive layer can be used to generate attractive or repulsive forces on dielectric materials. Then, moving these light patterns can be used for the manipulation of particles in the microfluidic devices. This study reports on the results from numerical simulation of the ODEP platform using a new model based on a voltage transformation ratio, which takes the effective electrical voltage into consideration. Results showed that the numerical simulation was in reasonably agreement with experimental data for the manipulation of polystyrene beads and emulsion droplets, with a coefficient of variation less than 6.2% (n = 3). The proposed model can be applied to simulations of the ODEP force and may provide a reliable tool for estimating induced dielectrophoretic forces and electric fields, which is crucial for microfluidic applications. Full article
(This article belongs to the Special Issue Microfluidic Devices)
Open AccessArticle A Selective Iodide Ion Sensor Electrode Based on Functionalized ZnO Nanotubes
Sensors 2013, 13(2), 1984-1997; doi:10.3390/s130201984
Received: 3 December 2012 / Revised: 29 January 2013 / Accepted: 29 January 2013 / Published: 4 February 2013
Cited by 13 | PDF Full-text (408 KB) | HTML Full-text | XML Full-text
Abstract
In this research work, ZnO nanotubes were fabricated on a gold coated glass substrate through chemical etching by the aqueous chemical growth method. For the first time a nanostructure-based iodide ion selective electrode was developed. The ZnO nanotubes were functionalized with miconazole ion
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In this research work, ZnO nanotubes were fabricated on a gold coated glass substrate through chemical etching by the aqueous chemical growth method. For the first time a nanostructure-based iodide ion selective electrode was developed. The ZnO nanotubes were functionalized with miconazole ion exchanger and the electromotive force (EMF) was measured by the potentiometric method. The iodide ion sensor exhibited a linear response over a wide range of concentrations (1 × 10−6 to 1 × 10−1 M) and excellent sensitivity of –62 ± 1 mV/decade. The detection limit of the proposed sensor was found to be 5 × 10−7 M. The effects of pH, temperature, additive, plasticizer and stabilizer on the potential response of iodide ion selective electrode were also studied. The proposed iodide ion sensor demonstrated a fast response time of less than 5 s and high selectivity against common organic and the inorganic anions. All the obtained results revealed that the iodide ion sensor based on functionalized ZnO nanotubes may be used for the detection of iodide ion in environmental water samples, pharmaceutical products and other real samples. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle A MEMS Device Capable of Measuring Near-Field Thermal Radiation between Membranes
Sensors 2013, 13(2), 1998-2010; doi:10.3390/s130201998
Received: 9 December 2012 / Revised: 14 January 2013 / Accepted: 15 January 2013 / Published: 4 February 2013
Cited by 10 | PDF Full-text (5616 KB) | HTML Full-text | XML Full-text
Abstract
For sensors constructed by freestanding membranes, when the gap between a freestanding membrane and the substrate or between membranes is at micron scale, the effects of near-field radiative heat transfer on the sensors’ thermal performance should be considered during sensor design. The radiative
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For sensors constructed by freestanding membranes, when the gap between a freestanding membrane and the substrate or between membranes is at micron scale, the effects of near-field radiative heat transfer on the sensors’ thermal performance should be considered during sensor design. The radiative heat flux is transferred from a membrane to a plane or from a membrane to a membrane. In the current study of the near-field thermal radiation, the scanning probe technology has difficulty in making a membrane separated at micron scale parallel to a plane or another membrane. A novel MEMS (micro electromechanical system) device was developed by sacrificial layer technique in this work to realize a double parallel freestanding membrane structure. Each freestanding membrane has a platinum thin-film resistor and the distance between the two membranes is 1 m. After evaluating the electrical and thermal characteristics of the lower freestanding membrane, experimental measurements of near-field radiative heat transfer between the lower membrane and the upper membrane were carried out by setting the lower membrane as a heat emitter and the upper membrane as a heat receiver. The near-field radiative heat transfer between the two membranes was validated by finding a larger-than-blackbody radiative heat transfer based on the experimental data. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Fluorescent One-Dimensional Photonic Crystal for Label-Free Biosensing Based on Bloch Surface Waves
Sensors 2013, 13(2), 2011-2022; doi:10.3390/s130202011
Received: 31 December 2012 / Revised: 29 January 2013 / Accepted: 4 February 2013 / Published: 5 February 2013
Cited by 20 | PDF Full-text (441 KB) | HTML Full-text | XML Full-text
Abstract
A one-dimensional photonic crystal (1DPC) based on a planar stack of dielectric layers is used as an optical transducer for biosensing, upon the coupling of TE-polarized Bloch Surface Waves (BSW). The structure is tailored with a polymeric layer providing a chemical functionality facilitating
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A one-dimensional photonic crystal (1DPC) based on a planar stack of dielectric layers is used as an optical transducer for biosensing, upon the coupling of TE-polarized Bloch Surface Waves (BSW). The structure is tailored with a polymeric layer providing a chemical functionality facilitating the covalent binding of orienting proteins needed for a subsequent grafting of antibodies in an immunoassay detection scheme. The polymeric layer is impregnated with Cy3 dye, in such a way that the photonic structure can exhibit an emissive behavior. The BSW-coupled fluorescence shift is used as a means for detecting refractive index variations occurring at the 1DPC surface, according to a label-free concept. The proposed working principle is successfully demonstrated in real-time tracking of protein G covalent binding on the 1DPC surface within a fluidic cell. Full article
(This article belongs to the Special Issue Photonic Crystal Sensors)
Open AccessArticle Characterization of a Sulfonated Polycarbonate Resistive Humidity Sensor
Sensors 2013, 13(2), 2023-2032; doi:10.3390/s130202023
Received: 30 November 2012 / Revised: 12 January 2013 / Accepted: 15 January 2013 / Published: 5 February 2013
Cited by 5 | PDF Full-text (527 KB) | HTML Full-text | XML Full-text
Abstract
In this work; resistive moisture sensors were obtained by dip coating sulfonated polycarbonate (SPC) onto silver interdigitated electrodes. Commercial polycarbonate was sulfonated with acetyl sulphate at two different sulfonation degrees corresponding to 9.0 and 18.0 mole %. Impedance spectroscopy was used to investigate
[...] Read more.
In this work; resistive moisture sensors were obtained by dip coating sulfonated polycarbonate (SPC) onto silver interdigitated electrodes. Commercial polycarbonate was sulfonated with acetyl sulphate at two different sulfonation degrees corresponding to 9.0 and 18.0 mole %. Impedance spectroscopy was used to investigate the humidity sensing properties at controlled relative humidity (RH%) environments generated from standard saline solutions in the range of 11–90 RH%. For the highest sulfonated sample; in the RH% range investigated (11 to 90%); the sensor impedance changed from 4.7 MΩ to 18 kΩ. Humidity sensors made from sulfonated polycarbonate showed exponential decay behavior of the impedance at constant frequency with the environmental relative humidity. Sample 9SPC presented dielectric relaxation response for environmental humidity between 58 and 90 RH% while sample 18SPC presented dielectric relaxation response for the entire measured range between 11 and 90 RH%. Sulfonated polycarbonate could be a promising material for the fabrication of simple and cheap humidity-sensing sensors for the assessment of relative humidity of the surrounding environment, as suggested by experimental results. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Creation of 3D Multi-Body Orthodontic Models by Using Independent Imaging Sensors
Sensors 2013, 13(2), 2033-2050; doi:10.3390/s130202033
Received: 24 December 2012 / Revised: 22 January 2013 / Accepted: 1 February 2013 / Published: 5 February 2013
Cited by 21 | PDF Full-text (1049 KB) | HTML Full-text | XML Full-text
Abstract
In the field of dental health care, plaster models combined with 2D radiographs are widely used in clinical practice for orthodontic diagnoses. However, complex malocclusions can be better analyzed by exploiting 3D digital dental models, which allow virtual simulations and treatment planning processes.
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In the field of dental health care, plaster models combined with 2D radiographs are widely used in clinical practice for orthodontic diagnoses. However, complex malocclusions can be better analyzed by exploiting 3D digital dental models, which allow virtual simulations and treatment planning processes. In this paper, dental data captured by independent imaging sensors are fused to create multi-body orthodontic models composed of teeth, oral soft tissues and alveolar bone structures. The methodology is based on integrating Cone-Beam Computed Tomography (CBCT) and surface structured light scanning. The optical scanner is used to reconstruct tooth crowns and soft tissues (visible surfaces) through the digitalization of both patients’ mouth impressions and plaster casts. These data are also used to guide the segmentation of internal dental tissues by processing CBCT data sets. The 3D individual dental tissues obtained by the optical scanner and the CBCT sensor are fused within multi-body orthodontic models without human supervisions to identify target anatomical structures. The final multi-body models represent valuable virtual platforms to clinical diagnostic and treatment planning. Full article
(This article belongs to the Special Issue Medical & Biological Imaging)
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Open AccessArticle A Cognitive Mobile BTS Solution with Software-Defined Radioelectric Sensing
Sensors 2013, 13(2), 2051-2075; doi:10.3390/s130202051
Received: 7 November 2012 / Revised: 23 January 2013 / Accepted: 30 January 2013 / Published: 5 February 2013
PDF Full-text (3000 KB) | HTML Full-text | XML Full-text
Abstract
Private communications inside large vehicles such as ships may be effectively provided using standard cellular systems. In this paper we propose a new solution based on software-defined radio with electromagnetic sensing support. Software-defined radio allows low-cost developments and, potentially, added-value services not available
[...] Read more.
Private communications inside large vehicles such as ships may be effectively provided using standard cellular systems. In this paper we propose a new solution based on software-defined radio with electromagnetic sensing support. Software-defined radio allows low-cost developments and, potentially, added-value services not available in commercial cellular networks. The platform of reference, OpenBTS, only supports single-channel cells. Our proposal, however, has the ability of changing BTS channel frequency without disrupting ongoing communications. This ability should be mandatory in vehicular environments, where neighbouring cell configurations may change rapidly, so a moving cell must be reconfigured in real-time to avoid interferences. Full details about frequency occupancy sensing and the channel reselection procedure are provided in this paper. Moreover, a procedure for fast terminal detection is proposed. This may be decisive in emergency situations, e.g., if someone falls overboard. Different tests confirm the feasibility of our proposal and its compatibility with commercial GSM terminals. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle An Image Reconstruction Algorithm for Electrical Capacitance Tomography Based on Robust Principle Component Analysis
Sensors 2013, 13(2), 2076-2092; doi:10.3390/s130202076
Received: 6 December 2012 / Revised: 23 January 2013 / Accepted: 1 February 2013 / Published: 5 February 2013
Cited by 7 | PDF Full-text (361 KB) | HTML Full-text | XML Full-text
Abstract
Electrical capacitance tomography (ECT) attempts to reconstruct the permittivity distribution of the cross-section of measurement objects from the capacitance measurement data, in which reconstruction algorithms play a crucial role in real applications. Based on the robust principal component analysis (RPCA) method, a dynamic
[...] Read more.
Electrical capacitance tomography (ECT) attempts to reconstruct the permittivity distribution of the cross-section of measurement objects from the capacitance measurement data, in which reconstruction algorithms play a crucial role in real applications. Based on the robust principal component analysis (RPCA) method, a dynamic reconstruction model that utilizes the multiple measurement vectors is presented in this paper, in which the evolution process of a dynamic object is considered as a sequence of images with different temporal sparse deviations from a common background. An objective functional that simultaneously considers the temporal constraint and the spatial constraint is proposed, where the images are reconstructed by a batching pattern. An iteration scheme that integrates the advantages of the alternating direction iteration optimization (ADIO) method and the forward-backward splitting (FBS) technique is developed for solving the proposed objective functional. Numerical simulations are implemented to validate the feasibility of the proposed algorithm. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Comparative Study on the Performance of Five Different Hall Effect Devices
Sensors 2013, 13(2), 2093-2112; doi:10.3390/s130202093
Received: 12 December 2012 / Revised: 25 January 2013 / Accepted: 4 February 2013 / Published: 5 February 2013
Cited by 15 | PDF Full-text (524 KB) | HTML Full-text | XML Full-text
Abstract
Five different Hall Effect sensors were modeled and their performance evaluated using a three dimensional simulator. The physical structure of the implemented sensors reproduces a certain technological fabrication process. Hall voltage, absolute, current-related, voltage-related and power-related sensitivities were obtained for each sensor. The
[...] Read more.
Five different Hall Effect sensors were modeled and their performance evaluated using a three dimensional simulator. The physical structure of the implemented sensors reproduces a certain technological fabrication process. Hall voltage, absolute, current-related, voltage-related and power-related sensitivities were obtained for each sensor. The effect of artificial offset was also investigated for cross-like structures. The simulation procedure guides the designer in choosing the Hall cell optimum shape, dimensions and device polarization conditions that would allow the highest performance. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Huanglongbing (Citrus Greening) Detection Using Visible, Near Infrared and Thermal Imaging Techniques
Sensors 2013, 13(2), 2117-2130; doi:10.3390/s130202117
Received: 5 December 2012 / Revised: 26 January 2013 / Accepted: 30 January 2013 / Published: 6 February 2013
Cited by 17 | PDF Full-text (861 KB) | HTML Full-text | XML Full-text
Abstract
This study demonstrates the applicability of visible-near infrared and thermal imaging for detection of Huanglongbing (HLB) disease in citrus trees. Visible-near infrared (440–900 nm) and thermal infrared spectral reflectance data were collected from individual healthy and HLB-infected trees. Data analysis revealed that the
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This study demonstrates the applicability of visible-near infrared and thermal imaging for detection of Huanglongbing (HLB) disease in citrus trees. Visible-near infrared (440–900 nm) and thermal infrared spectral reflectance data were collected from individual healthy and HLB-infected trees. Data analysis revealed that the average reflectance values of the healthy trees in the visible region were lower than those in the near infrared region, while the opposite was the case for HLB-infected trees. Moreover, 560 nm, 710 nm, and thermal band showed maximum class separability between healthy and HLB-infected groups among the evaluated visible-infrared bands. Similarly, analysis of several vegetation indices indicated that the normalized difference vegetation index (NDVI), Vogelmann red-edge index (VOG) and modified red-edge simple ratio (mSR) demonstrated good class separability between the two groups. Classification studies using average spectral reflectance values from the visible, near infrared, and thermal bands (13 spectral features) as input features indicated that an average overall classification accuracy of about 87%, with 89% specificity and 85% sensitivity could be achieved with classification models such as support vector machine for trees with symptomatic leaves. Full article
(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)
Open AccessArticle Reduction of the Radiating Sound of a Submerged Finite Cylindrical Shell Structure by Active Vibration Control
Sensors 2013, 13(2), 2131-2147; doi:10.3390/s130202131
Received: 22 January 2013 / Revised: 30 January 2013 / Accepted: 30 January 2013 / Published: 6 February 2013
Cited by 13 | PDF Full-text (1351 KB) | HTML Full-text | XML Full-text
Abstract
In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain
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In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs) were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water. Full article
(This article belongs to the Section Physical Sensors)
Open AccessCommunication Investigation into Mass Loading Sensitivity of Sezawa Wave Mode-Based Surface Acoustic Wave Sensors
Sensors 2013, 13(2), 2164-2175; doi:10.3390/s130202164
Received: 15 November 2012 / Revised: 5 January 2013 / Accepted: 21 January 2013 / Published: 6 February 2013
Cited by 7 | PDF Full-text (1049 KB) | HTML Full-text | XML Full-text
Abstract
In this work mass loading sensitivity of a Sezawa wave mode based surface acoustic wave (SAW) device is investigated through finite element method (FEM) simulation and the prospects of these devices to function as highly sensitive SAW sensors is reported. A ZnO/Si layered
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In this work mass loading sensitivity of a Sezawa wave mode based surface acoustic wave (SAW) device is investigated through finite element method (FEM) simulation and the prospects of these devices to function as highly sensitive SAW sensors is reported. A ZnO/Si layered SAW resonator is considered for the simulation study. Initially the occurrence of Sezawa wave mode and displacement amplitude of the Rayleigh and Sezawa wave mode is studied for lower ZnO film thickness. Further, a thin film made of an arbitrary material is coated over the ZnO surface and the resonance frequency shift caused by mass loading of the film is estimated. It was observed that Sezawa wave mode shows significant sensitivity to change in mass loading and has higher sensitivity (eight times higher) than Rayleigh wave mode for the same device configuration. Further, the mass loading sensitivity was observed to be greater for a low ZnO film thickness to wavelength ratio. Accordingly, highly sensitive SAW sensors can be developed by coating a sensing medium over a layered SAW device and operating at Sezawa mode resonance frequency. The sensitivity can be increased by tuning the ZnO film thickness to wavelength ratio. Full article
(This article belongs to the Special Issue Piezoelectric Sensors and Actuators)
Open AccessArticle A Micro Dynamically Tuned Gyroscope with Adjustable Static Capacitance
Sensors 2013, 13(2), 2176-2195; doi:10.3390/s130202176
Received: 8 January 2013 / Revised: 28 January 2013 / Accepted: 29 January 2013 / Published: 6 February 2013
Cited by 9 | PDF Full-text (1999 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel micro dynamically tuned gyroscope (MDTG) with adjustable static capacitance. First, the principle of MDTG is theoretically analyzed. Next, some simulations under the optimized structure parameters are given as a reference for the mask design of the rotor wafer
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This paper presents a novel micro dynamically tuned gyroscope (MDTG) with adjustable static capacitance. First, the principle of MDTG is theoretically analyzed. Next, some simulations under the optimized structure parameters are given as a reference for the mask design of the rotor wafer and electrode plates. As two key components, the process flows of the rotor wafer and electrode plates are described in detail. All the scanning electron microscopy (SEM) photos show that the fabrication process is effective and optimized. Then, an assembly model is designed for the static capacitance adjustable MDTG, whose static capacitance can be changed by rotating the lower electrode plate support and substituting gasket rings of different thicknesses. Thus, the scale factor is easily changeable. Afterwards, the digitalized closed-loop measurement circuit is simulated. The discrete correction and decoupling modules are designed to make the closed-loop stable and cross-coupling effect small. The dual axis closed-loop system bandwidths can reach more than 60 Hz and the dual axis scale factors are completely symmetrical. All the simulation results demonstrate the proposed fabrication of the MDTG can meet the application requirements. Finally, the paper presents the test results of static and dynamic capacitance values which are consistent with the simulation values. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Monolithically Integrated Mid-Infrared Quantum Cascade Laser and Detector
Sensors 2013, 13(2), 2196-2205; doi:10.3390/s130202196
Received: 4 January 2013 / Revised: 30 January 2013 / Accepted: 1 February 2013 / Published: 6 February 2013
Cited by 16 | PDF Full-text (356 KB) | HTML Full-text | XML Full-text
Abstract
We demonstrate the monolithic integration of a mid-infrared laser and detector utilizing a bi-functional quantum cascade active region. When biased, this active region provides optical gain, while it can be used as a detector at zero bias. With our novel approach we can
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We demonstrate the monolithic integration of a mid-infrared laser and detector utilizing a bi-functional quantum cascade active region. When biased, this active region provides optical gain, while it can be used as a detector at zero bias. With our novel approach we can measure the light intensity of the laser on the same chip without the need of external lenses or detectors. Based on a bound-to-continuum design, the bi-functional active region has an inherent broad electro-luminescence spectrum of 200 cm-1, which indicates its use for single mode laser arrays. We have measured a peak signal of 191.5 mV at the on-chip detector, without any amplification. The room-temperature pulsed emission with an averaged power consumption of 4 mW and the high-speed detection makes these devices ideal for low-power sensors. The combination of the on-chip detection functionality, the broad emission spectrum and the low average power consumption indicates the potential of our bi-functional quantum cascade structures to build a mid-infrared lab-on-a-chip based on quantum cascade laser technology. Full article
(This article belongs to the Special Issue Laser Sensing and Imaging)
Open AccessArticle Frequency Noise Properties of Lasers for Interferometry in Nanometrology
Sensors 2013, 13(2), 2206-2219; doi:10.3390/s130202206
Received: 26 November 2012 / Revised: 31 January 2013 / Accepted: 4 February 2013 / Published: 7 February 2013
Cited by 21 | PDF Full-text (886 KB) | HTML Full-text | XML Full-text
Abstract
In this contribution we focus on laser frequency noise properties and their influence on the interferometric displacement measurements. A setup for measurement of laser frequency noise is proposed and tested together with simultaneous measurement of fluctuations in displacement in the Michelson interferometer. Several
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In this contribution we focus on laser frequency noise properties and their influence on the interferometric displacement measurements. A setup for measurement of laser frequency noise is proposed and tested together with simultaneous measurement of fluctuations in displacement in the Michelson interferometer. Several laser sources, including traditional He-Ne and solid-state lasers, and their noise properties are evaluated and compared. The contribution of the laser frequency noise to the displacement measurement is discussed in the context of other sources of uncertainty associated with the interferometric setup, such as, mechanics, resolution of analog-to-digital conversion, frequency bandwidth of the detection chain, and variations of the refractive index of air. Full article
(This article belongs to the Special Issue Laser Sensing and Imaging)
Open AccessArticle Architecture for Multi-Technology Real-Time Location Systems
Sensors 2013, 13(2), 2220-2253; doi:10.3390/s130202220
Received: 28 December 2012 / Revised: 22 January 2013 / Accepted: 5 February 2013 / Published: 7 February 2013
Cited by 4 | PDF Full-text (1306 KB) | HTML Full-text | XML Full-text
Abstract
The rising popularity of location-based services has prompted considerable research in the field of indoor location systems. Since there is no single technology to support these systems, it is necessary to consider the fusion of the information coming from heterogeneous sensors. This paper
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The rising popularity of location-based services has prompted considerable research in the field of indoor location systems. Since there is no single technology to support these systems, it is necessary to consider the fusion of the information coming from heterogeneous sensors. This paper presents a software architecture designed for a hybrid location system where we can merge information from multiple sensor technologies. The architecture was designed to be used by different kinds of actors independently and with mutual transparency: hardware administrators, algorithm developers and user applications. The paper presents the architecture design, work-flow, case study examples and some results to show how different technologies can be exploited to obtain a good estimation of a target position. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle Investigations on a Novel Inductive Concept Frequency Technique for the Grading of Oil Palm Fresh Fruit Bunches
Sensors 2013, 13(2), 2254-2266; doi:10.3390/s130202254
Received: 18 December 2012 / Revised: 30 January 2013 / Accepted: 4 February 2013 / Published: 7 February 2013
Cited by 6 | PDF Full-text (783 KB) | HTML Full-text | XML Full-text
Abstract
From the Malaysian harvester’s perspective, the determination of the ripeness of the oil palm (FFB) is a critical factor to maximize palm oil production. A preliminary study of a novel oil palm fruit sensor to detect the maturity of oil palm fruit bunches
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From the Malaysian harvester’s perspective, the determination of the ripeness of the oil palm (FFB) is a critical factor to maximize palm oil production. A preliminary study of a novel oil palm fruit sensor to detect the maturity of oil palm fruit bunches is presented. To optimize the functionality of the sensor, the frequency characteristics of air coils of various diameters are investigated to determine their inductance and resonant characteristics. Sixteen samples from two categories, namely ripe oil palm fruitlets and unripe oil palm fruitlets, are tested from 100 Hz up to 100 MHz frequency. The results showed the inductance and resonant characteristics of the air coil sensors display significant changes among the samples of each category. The investigations on the frequency characteristics of the sensor air coils are studied to observe the effect of variations in the coil diameter. The effect of coil diameter yields a significant 0.02643 MHz difference between unripe samples to air and 0.01084 MHz for ripe samples to air. The designed sensor exhibits significant potential in determining the maturity of oil palm fruits. Full article
(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)
Open AccessArticle Label-Free Potentiometry for Detecting DNA Hybridization Using Peptide Nucleic Acid and DNA Probes
Sensors 2013, 13(2), 2267-2278; doi:10.3390/s130202267
Received: 25 October 2012 / Revised: 15 January 2013 / Accepted: 4 February 2013 / Published: 7 February 2013
Cited by 14 | PDF Full-text (479 KB) | HTML Full-text | XML Full-text
Abstract
Peptide nucleic acid (PNA) has outstanding affinity over DNA for complementary nucleic acid sequences by forming a PNA-DNA heterodimer upon hybridization via Watson-Crick base-pairing. To verify whether PNA probes on an electrode surface enhance sensitivity for potentiometric DNA detection or not, we conducted
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Peptide nucleic acid (PNA) has outstanding affinity over DNA for complementary nucleic acid sequences by forming a PNA-DNA heterodimer upon hybridization via Watson-Crick base-pairing. To verify whether PNA probes on an electrode surface enhance sensitivity for potentiometric DNA detection or not, we conducted a comparative study on the hybridization of PNA and DNA probes on the surface of a 10-channel gold electrodes microarray. Changes in the charge density as a result of hybridization at the solution/electrode interface on the self-assembled monolayer (SAM)-formed microelectrodes were directly transformed into potentiometric signals using a high input impedance electrometer. The charge readout allows label-free, reagent-less, and multi-parallel detection of target oligonucleotides without any optical assistance. The differences in the probe lengths between 15- to 22-mer dramatically influenced on the sensitivity of the PNA and DNA sensors. Molecular type of the capturing probe did not affect the degree of potential shift. Theoretical model for charged rod-like duplex using the Gouy-Chapman equation indicates the dominant effect of electrostatic attractive forces between anionic DNA and underlying electrode at the electrolyte/electrode interface in the potentiometry. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan 2012)
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Open AccessArticle Statistical Modeling of Large-Scale Signal Path Loss in Underwater Acoustic Networks
Sensors 2013, 13(2), 2279-2294; doi:10.3390/s130202279
Received: 28 December 2012 / Revised: 6 February 2013 / Accepted: 7 February 2013 / Published: 8 February 2013
Cited by 4 | PDF Full-text (761 KB) | HTML Full-text | XML Full-text
Abstract
In an underwater acoustic channel, the propagation conditions are known to vary in time, causing the deviation of the received signal strength from the nominal value predicted by a deterministic propagation model. To facilitate a large-scale system design in such conditions (e.g., power
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In an underwater acoustic channel, the propagation conditions are known to vary in time, causing the deviation of the received signal strength from the nominal value predicted by a deterministic propagation model. To facilitate a large-scale system design in such conditions (e.g., power allocation), we have developed a statistical propagation model in which the transmission loss is treated as a random variable. By applying repetitive computation to the acoustic field, using ray tracing for a set of varying environmental conditions (surface height, wave activity, small node displacements around nominal locations, etc.), an ensemble of transmission losses is compiled and later used to infer the statistical model parameters. A reasonable agreement is found with log-normal distribution, whose mean obeys a log-distance increases, and whose variance appears to be constant for a certain range of inter-node distances in a given deployment location. The statistical model is deemed useful for higher-level system planning, where simulation is needed to assess the performance of candidate network protocols under various resource allocation policies, i.e., to determine the transmit power and bandwidth allocation necessary to achieve a desired level of performance (connectivity, throughput, reliability, etc.). Full article
(This article belongs to the Special Issue Last Trends in Acoustic Sensing)
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Open AccessArticle High-Visibility Photonic Crystal Fiber Interferometer as Multifunctional Sensor
Sensors 2013, 13(2), 2349-2358; doi:10.3390/s130202349
Received: 31 December 2012 / Accepted: 4 February 2013 / Published: 8 February 2013
Cited by 16 | PDF Full-text (762 KB) | HTML Full-text | XML Full-text
Abstract
A photonic crystal fiber (PCF) interferometer that exhibits record fringe contrast (~40 dB) is demonstrated along with its sensing applications. The device operates in reflection mode and consists of a centimeter-long segment of properly selected PCF fusion spliced to single mode optical fibers.
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A photonic crystal fiber (PCF) interferometer that exhibits record fringe contrast (~40 dB) is demonstrated along with its sensing applications. The device operates in reflection mode and consists of a centimeter-long segment of properly selected PCF fusion spliced to single mode optical fibers. Two identical collapsed zones in the PCF combined with its modal properties allow high-visibility interference patterns. The interferometer is suitable for refractometric and liquid level sensing. The measuring refractive index range goes from 1.33 to 1.43 and the maximum resolution is ~1.6 × 10−5. Full article
(This article belongs to the Special Issue Photonic Crystal Sensors)
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Open AccessArticle Energy Harvesting Thermoelectric Generators Manufactured Using the Complementary Metal Oxide Semiconductor Process
Sensors 2013, 13(2), 2359-2367; doi:10.3390/s130202359
Received: 31 December 2012 / Revised: 6 February 2013 / Accepted: 7 February 2013 / Published: 8 February 2013
Cited by 6 | PDF Full-text (527 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the fabrication and characterization of energy harvesting thermoelectric micro generators using the commercial complementary metal oxide semiconductor (CMOS) process. The micro generator consists of 33 thermocouples in series. Thermocouple materials are p-type and n-type polysilicon since they have a large
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This paper presents the fabrication and characterization of energy harvesting thermoelectric micro generators using the commercial complementary metal oxide semiconductor (CMOS) process. The micro generator consists of 33 thermocouples in series. Thermocouple materials are p-type and n-type polysilicon since they have a large Seebeck coefficient difference. The output power of the micro generator depends on the temperature difference in the hot and cold parts of the thermocouples. In order to increase this temperature difference, the hot part of the thermocouples is suspended to reduce heat-sinking. The micro generator needs a post-CMOS process to release the suspended structures of hot part, which the post-process includes an anisotropic dry etching to etch the sacrificial oxide layer and an isotropic dry etching to remove the silicon substrate. Experiments show that the output power of the micro generator is 9.4 mW at a temperature difference of 15 K. Full article
(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering 2013)
Open AccessArticle Development of a Compact Wireless Laplacian Electrode Module for Electromyograms and Its Human Interface Applications
Sensors 2013, 13(2), 2368-2383; doi:10.3390/s130202368
Received: 7 December 2012 / Revised: 24 January 2013 / Accepted: 2 February 2013 / Published: 8 February 2013
Cited by 2 | PDF Full-text (875 KB) | HTML Full-text | XML Full-text
Abstract
In this study, we developed a compact wireless Laplacian electrode module for electromyograms (EMGs). One of the advantages of the Laplacian electrode configuration is that EMGs obtained with it are expected to be sensitive to the firing of the muscle directly beneath the
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In this study, we developed a compact wireless Laplacian electrode module for electromyograms (EMGs). One of the advantages of the Laplacian electrode configuration is that EMGs obtained with it are expected to be sensitive to the firing of the muscle directly beneath the measurement site. The performance of the developed electrode module was investigated in two human interface applications: character-input interface and detection of finger movement during finger Braille typing. In the former application, the electrode module was combined with an EMG-mouse click converter circuit. In the latter, four electrode modules were used for detection of finger movements during finger Braille typing. Investigation on the character-input interface indicated that characters could be input stably by contraction of (a) the masseter, (b) trapezius, (c) anterior tibialis and (d) flexor carpi ulnaris muscles. This wide applicability is desirable when the interface is applied to persons with physical disabilities because the disability differs one to another. The investigation also demonstrated that the electrode module can work properly without any skin preparation. Finger movement detection experiments showed that each finger movement was more clearly detectable when comparing to EMGs recorded with conventional electrodes, suggesting that the Laplacian electrode module is more suitable for detecting the timing of finger movement during typing. This could be because the Laplacian configuration enables us to record EMGs just beneath the electrode. These results demonstrate the advantages of the Laplacian electrode module. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan 2012)
Open AccessArticle Rapid Characterization of Vegetation Structure with a Microsoft Kinect Sensor
Sensors 2013, 13(2), 2384-2398; doi:10.3390/s130202384
Received: 14 November 2012 / Revised: 26 December 2012 / Accepted: 31 January 2013 / Published: 11 February 2013
Cited by 27 | PDF Full-text (6753 KB) | HTML Full-text | XML Full-text
Abstract
The importance of vegetation structure and biomass in controlling land-atmosphere exchange is widely recognized, but measurements of canopy structure are challenging, time consuming, and often rely on destructive methods. The Microsoft Kinect is an infrared sensor designed for video gaming that outputs synchronized
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The importance of vegetation structure and biomass in controlling land-atmosphere exchange is widely recognized, but measurements of canopy structure are challenging, time consuming, and often rely on destructive methods. The Microsoft Kinect is an infrared sensor designed for video gaming that outputs synchronized color and depth images and that has the potential to allow rapid characterization of vegetation structure. We compared depth images from a Kinect sensor with manual measurements of plant structure and size for two species growing in a California grassland. The depth images agreed well with the horizontal and vertical measurements of plant size made manually. Similarly, the plant volumes calculated with a three-dimensional convex hulls approach was well related to plant biomass. The Kinect showed some limitations for ecological observation associated with a short measurement range and daytime light contamination. Nonetheless, the Kinect’s light weight, fast acquisition time, low power requirement, and cost make it a promising tool for rapid field surveys of canopy structure, especially in small-statured vegetation. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle An Infrastructureless Approach to Estimate Vehicular Density in Urban Environments
Sensors 2013, 13(2), 2399-2418; doi:10.3390/s130202399
Received: 8 January 2013 / Revised: 25 January 2013 / Accepted: 30 January 2013 / Published: 11 February 2013
Cited by 17 | PDF Full-text (1238 KB) | HTML Full-text | XML Full-text
Abstract
In Vehicular Networks, communication success usually depends on the density of vehicles, since a higher density allows having shorter and more reliable wireless links. Thus, knowing the density of vehicles in a vehicular communications environment is important, as better opportunities for wireless communication
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In Vehicular Networks, communication success usually depends on the density of vehicles, since a higher density allows having shorter and more reliable wireless links. Thus, knowing the density of vehicles in a vehicular communications environment is important, as better opportunities for wireless communication can show up. However, vehicle density is highly variable in time and space. This paper deals with the importance of predicting the density of vehicles in vehicular environments to take decisions for enhancing the dissemination of warning messages between vehicles. We propose a novel mechanism to estimate the vehicular density in urban environments. Our mechanism uses as input parameters the number of beacons received per vehicle, and the topological characteristics of the environment where the vehicles are located. Simulation results indicate that, unlike previous proposals solely based on the number of beacons received, our approach is able to accurately estimate the vehicular density, and therefore it could support more efficient dissemination protocols for vehicular environments, as well as improve previously proposed schemes. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Light-Intensity-Induced Characterization of Elastic Constants and d33 Piezoelectric Coefficient of PLZT Single Fiber Based Transducers
Sensors 2013, 13(2), 2419-2429; doi:10.3390/s130202419
Received: 20 December 2012 / Revised: 28 January 2013 / Accepted: 2 February 2013 / Published: 12 February 2013
Cited by 3 | PDF Full-text (840 KB) | HTML Full-text | XML Full-text
Abstract
Enhanced functionality of electro-optic devices by implementing piezoelectric micro fibers into their construction is proposed. Lanthanum-modified lead zirconate titanate (PLZT) ceramics are known to exhibit high light transparency, desirable electro-optic properties and fast response. In this study PLZT fibers with a diameter of
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Enhanced functionality of electro-optic devices by implementing piezoelectric micro fibers into their construction is proposed. Lanthanum-modified lead zirconate titanate (PLZT) ceramics are known to exhibit high light transparency, desirable electro-optic properties and fast response. In this study PLZT fibers with a diameter of around 300 microns were produced by a thermoplastic processing method and their light-induced impedance and piezoelectric coefficient were investigated at relatively low light intensity (below 50 mW/cm2). The authors experimentally proved higher performance of light controlled microfiber transducers in comparison to their bulk form. The advantage of the high surface area to volume ratio is shown to be an excellent technique to design high quality light sensors by using fibrous materials. The UV absorption induced change in elastic constants of 3% and 4% for the piezoelectric coefficient d33. Full article
(This article belongs to the Special Issue Piezoelectric Sensors and Actuators)
Open AccessArticle Fusion of Building Information and Range Imaging for Autonomous Location Estimation in Indoor Environments
Sensors 2013, 13(2), 2430-2446; doi:10.3390/s130202430
Received: 15 October 2012 / Revised: 4 February 2013 / Accepted: 4 February 2013 / Published: 14 February 2013
Cited by 2 | PDF Full-text (1241 KB) | HTML Full-text | XML Full-text
Abstract
We present a novel approach for autonomous location estimation and navigation in indoor environments using range images and prior scene knowledge from a GIS database (CityGML). What makes this task challenging is the arbitrary relative spatial relation between GIS and Time-of-Flight (ToF) range
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We present a novel approach for autonomous location estimation and navigation in indoor environments using range images and prior scene knowledge from a GIS database (CityGML). What makes this task challenging is the arbitrary relative spatial relation between GIS and Time-of-Flight (ToF) range camera further complicated by a markerless configuration. We propose to estimate the camera’s pose solely based on matching of GIS objects and their detected location in image sequences. We develop a coarse-to-fine matching strategy that is able to match point clouds without any initial parameters. Experiments with a state-of-the-art ToF point cloud show that our proposed method delivers an absolute camera position with decimeter accuracy, which is sufficient for many real-world applications (e.g., collision avoidance). Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Performance Enhancement of a GaAs Detector with a Vertical Field and an Embedded Thin Low-Temperature Grown Layer
Sensors 2013, 13(2), 2475-2483; doi:10.3390/s130202475
Received: 17 December 2012 / Revised: 6 February 2013 / Accepted: 8 February 2013 / Published: 18 February 2013
Cited by 3 | PDF Full-text (432 KB) | HTML Full-text | XML Full-text
Abstract
Low temperature growth of GaAs (LT-GaAs) near 200 °C results in a recombination lifetime of nearly 1 ps, compared with approximately 1 ns for regular temperature ~600 °C grown GaAs (RT-GaAs), making it suitable for ultra high speed detection applications. However, LT-GaAs detectors
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Low temperature growth of GaAs (LT-GaAs) near 200 °C results in a recombination lifetime of nearly 1 ps, compared with approximately 1 ns for regular temperature ~600 °C grown GaAs (RT-GaAs), making it suitable for ultra high speed detection applications. However, LT-GaAs detectors usually suffer from low responsivity due to low carrier mobility. Here we report electro-optic sampling time response measurements of a detector that employs an AlGaAs heterojunction, a thin layer of LT-GaAs, a channel of RT-GaAs, and a vertical electric field that together facilitate collection of optically generated electrons while suppressing collection of lower mobility holes. Consequently, these devices have detection efficiency near that of RT-GaAs yet provide pulse widths nearly an order of magnitude faster—~6 ps for a cathode-anode separation of 1.3 μm and ~12 ps for distances more than 3 μm. Full article
(This article belongs to the Special Issue Photodetectors)
Open AccessArticle Detection of Micrococcus Luteus Biofilm Formation in Microfluidic Environments by pH Measurement Using an Ion-Sensitive Field-Effect Transistor
Sensors 2013, 13(2), 2484-2493; doi:10.3390/s130202484
Received: 26 December 2012 / Revised: 8 February 2013 / Accepted: 10 February 2013 / Published: 18 February 2013
Cited by 5 | PDF Full-text (653 KB) | HTML Full-text | XML Full-text
Abstract
Biofilm formation in microfluidic channels is difficult to detect because sampling volumes are too small for conventional turbidity measurements. To detect biofilm formation, we used an ion-sensitive field-effect transistor (ISFET) measurement system to measure pH changes in small volumes of bacterial suspension. Cells
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Biofilm formation in microfluidic channels is difficult to detect because sampling volumes are too small for conventional turbidity measurements. To detect biofilm formation, we used an ion-sensitive field-effect transistor (ISFET) measurement system to measure pH changes in small volumes of bacterial suspension. Cells of Micrococcus luteus (M. luteus) were cultured in polystyrene (PS) microtubes and polymethylmethacrylate (PMMA)-based microfluidic channels laminated with polyvinylidene chloride. In microtubes, concentrations of bacteria and pH in the suspension were analyzed by measuring turbidity and using an ISFET sensor, respectively. In microfluidic channels containing 20 μL of bacterial suspension, we measured pH changes using the ISFET sensor and monitored biofilm formation using a microscope. We detected acidification and alkalinization phases of M. luteus from the ISFET sensor signals in both microtubes and microfluidic channels. In the alkalinization phase, after 2 day culture, dense biofilm formation was observed at the bottom of the microfluidic channels. In this study, we used an ISFET sensor to detect biofilm formation in clinical and industrial microfluidic environments by detecting alkalinization of the culture medium. Full article
(This article belongs to the Special Issue Microfluidic Devices)
Open AccessArticle Hardware Implementation of Lorenz Circuit Systems for Secure Chaotic Communication Applications
Sensors 2013, 13(2), 2494-2505; doi:10.3390/s130202494
Received: 4 January 2013 / Revised: 7 February 2013 / Accepted: 8 February 2013 / Published: 18 February 2013
Cited by 5 | PDF Full-text (508 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the synchronization between the master and slave Lorenz chaotic systems by slide mode controller (SMC)-based technique. A proportional-integral (PI) switching surface is proposed to simplify the task of assigning the performance of the closed-loop error system in sliding mode. Then,
[...] Read more.
This paper presents the synchronization between the master and slave Lorenz chaotic systems by slide mode controller (SMC)-based technique. A proportional-integral (PI) switching surface is proposed to simplify the task of assigning the performance of the closed-loop error system in sliding mode. Then, extending the concept of equivalent control and using some basic electronic components, a secure communication system is constructed. Experimental results show the feasibility of synchronizing two Lorenz circuits via the proposed SMC. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle High Throughput Molecular Confirmation of β-Thalassemia Mutations Using Novel TaqMan Probes
Sensors 2013, 13(2), 2506-2514; doi:10.3390/s130202506
Received: 22 November 2012 / Revised: 25 January 2013 / Accepted: 6 February 2013 / Published: 18 February 2013
Cited by 5 | PDF Full-text (906 KB) | HTML Full-text | XML Full-text
Abstract
β-Thalassemia is a public health problem where 4.5% of Malaysians are β-thalassemia carriers. The genetic disorder is caused by defects in the β-globin gene complex which lead to reduced or complete absence of β-globin chain synthesis. Five TaqMan genotyping assays were designed and
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β-Thalassemia is a public health problem where 4.5% of Malaysians are β-thalassemia carriers. The genetic disorder is caused by defects in the β-globin gene complex which lead to reduced or complete absence of β-globin chain synthesis. Five TaqMan genotyping assays were designed and developed to detect the common β-thalassemia mutations in Malaysian Malays. The assays were evaluated with 219 "blinded" DNA samples and the results showed 100% sensitivity and specificity. The in-house designed TaqMan genotyping assays were found to be cost- and time-effective for characterization of β-thalassemia mutations in the Malaysian population. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle Forgery Detection and Value Identification of Euro Banknotes
Sensors 2013, 13(2), 2515-2529; doi:10.3390/s130202515
Received: 18 December 2012 / Revised: 29 January 2013 / Accepted: 4 February 2013 / Published: 18 February 2013
Cited by 10 | PDF Full-text (1532 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes both hardware and software components to detect counterfeits of Euro banknotes. The proposed system is also able to recognize the banknote values. Differently than other state-of-the-art methods, the proposed approach makes use of banknote images acquired with a near infrared
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This paper describes both hardware and software components to detect counterfeits of Euro banknotes. The proposed system is also able to recognize the banknote values. Differently than other state-of-the-art methods, the proposed approach makes use of banknote images acquired with a near infrared camera to perform recognition and authentication. This allows one to build a system that can effectively deal with real forgeries, which are usually not detectable with visible light. The hardware does not use any mechanical parts, so the overall system is low-cost. The proposed solution is reliable for ambient light and banknote positioning. Users should simply lean the banknote to be analyzed on a flat glass, and the system detects forgery, as well as recognizes the banknote value. The effectiveness of the proposed solution has been properly tested on a dataset composed by genuine and fake Euro banknotes provided by Italy's central bank. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Heart Sound Biometric System Based on Marginal Spectrum Analysis
Sensors 2013, 13(2), 2530-2551; doi:10.3390/s130202530
Received: 14 November 2012 / Revised: 28 January 2013 / Accepted: 4 February 2013 / Published: 18 February 2013
Cited by 9 | PDF Full-text (673 KB) | HTML Full-text | XML Full-text
Abstract
This work presents a heart sound biometric system based on marginal spectrum analysis, which is a new feature extraction technique for identification purposes. This heart sound identification system is comprised of signal acquisition, pre-processing, feature extraction, training, and identification. Experiments on the selection
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This work presents a heart sound biometric system based on marginal spectrum analysis, which is a new feature extraction technique for identification purposes. This heart sound identification system is comprised of signal acquisition, pre-processing, feature extraction, training, and identification. Experiments on the selection of the optimal values for the system parameters are conducted. The results indicate that the new spectrum coefficients result in a significant increase in the recognition rate of 94.40% compared with that of the traditional Fourier spectrum (84.32%) based on a database of 280 heart sounds from 40 participants. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A Novel Two-Axis Load Sensor Designed for in Situ Scratch Testing inside Scanning Electron Microscopes
Sensors 2013, 13(2), 2552-2565; doi:10.3390/s130202552
Received: 16 December 2012 / Revised: 29 January 2013 / Accepted: 29 January 2013 / Published: 18 February 2013
Cited by 1 | PDF Full-text (799 KB) | HTML Full-text | XML Full-text
Abstract
Because of a lack of available miniaturized multiaxial load sensors to measure the normal load and the lateral load simultaneously, quantitative in situ scratch devices inside scanning electron microscopes and the transmission electron microscopes have barely been developed up to now. A novel
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Because of a lack of available miniaturized multiaxial load sensors to measure the normal load and the lateral load simultaneously, quantitative in situ scratch devices inside scanning electron microscopes and the transmission electron microscopes have barely been developed up to now. A novel two-axis load sensor was designed in this paper. With an I-shaped structure, the sensor has the function of measuring the lateral load and the normal load simultaneously, and at the same time it has compact dimensions. Finite element simulations were carried out to evaluate stiffness and modal characteristics. A decoupling algorithm was proposed to resolve the cross-coupling between the two-axis loads. Natural frequency of the sensor was tested. Linearity and decoupling parameters were obtained from the calibration experiments, which indicate that the sensor has good linearity and the cross-coupling between the two axes is not strong. Via the decoupling algorithm and the corresponding decoupling parameters, simultaneous measurement of the lateral load and the normal load can be realized via the developed two-axis load sensor. Preliminary applications of the load sensor for scratch testing indicate that the load sensor can work well during the scratch testing. Taking advantage of the compact structure, it has the potential ability for applications in quantitative in situ scratch testing inside SEMs. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Photonic Crystal Biosensor Based on Optical Surface Waves
Sensors 2013, 13(2), 2566-2578; doi:10.3390/s130202566
Received: 11 January 2013 / Revised: 7 February 2013 / Accepted: 8 February 2013 / Published: 19 February 2013
Cited by 22 | PDF Full-text (2703 KB) | HTML Full-text | XML Full-text
Abstract
A label-free biosensor device based on registration of photonic crystal surface waves is described. Angular interrogation of the optical surface wave resonance is used to detect changes in the thickness of an adsorbed layer, while an additional simultaneous detection of the critical angle
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A label-free biosensor device based on registration of photonic crystal surface waves is described. Angular interrogation of the optical surface wave resonance is used to detect changes in the thickness of an adsorbed layer, while an additional simultaneous detection of the critical angle of total internal reflection provides independent data of the liquid refractive index. The abilities of the device are demonstrated by measuring of biotin molecule binding to a streptavidin monolayer, and by measuring association and dissociation kinetics of immunoglobulin G proteins. Additionally, deposition of PSS / PAH polyelectrolytes is recorded in situ resulting calculation of PSS and PAH monolayer thicknesses separately. Full article
(This article belongs to the Special Issue Photonic Crystal Sensors)
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Open AccessArticle Wedge-Filtering of Geomorphologic Terrestrial Laser Scan Data
Sensors 2013, 13(2), 2579-2594; doi:10.3390/s130202579
Received: 4 January 2013 / Revised: 4 February 2013 / Accepted: 8 February 2013 / Published: 20 February 2013
Cited by 3 | PDF Full-text (1559 KB) | HTML Full-text | XML Full-text
Abstract
Terrestrial laser scanning is of increasing importance for surveying and hazard assessments. Digital terrain models are generated using the resultant data to analyze surface processes. In order to determine the terrain surface as precisely as possible, it is often necessary to filter out
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Terrestrial laser scanning is of increasing importance for surveying and hazard assessments. Digital terrain models are generated using the resultant data to analyze surface processes. In order to determine the terrain surface as precisely as possible, it is often necessary to filter out points that do not represent the terrain surface. Examples are vegetation, vehicles, and animals. Filtering in mountainous terrain is more difficult than in other topography types. Here, existing automatic filtering solutions are not acceptable, because they are usually designed for airborne scan data. The present article describes a method specifically suitable for filtering terrestrial laser scanning data. This method is based on the direct line of sight between the scanner and the measured point and the assumption that no other surface point can be located in the area above this connection line. This assumption is only true for terrestrial laser data, but not for airborne data. We present a comparison of the wedge filtering to a modified inverse distance filtering method (IDWMO) filtered point cloud data. Both methods use manually filtered surfaces as reference. The comparison shows that the mean error and root–mean-square-error (RSME) between the results and the manually filtered surface of the two methods are similar. A significantly higher number of points of the terrain surface could be preserved, however, using the wedge-filtering approach. Therefore, we suggest that wedge-filtering should be integrated as a further parameter into already existing filtering processes, but is not suited as a standalone solution so far. Full article
(This article belongs to the Special Issue Laser Sensing and Imaging)
Open AccessArticle Virtual and Remote Robotic Laboratory Using EJS, MATLAB and LabVIEW
Sensors 2013, 13(2), 2595-2612; doi:10.3390/s130202595
Received: 28 December 2012 / Revised: 1 February 2013 / Accepted: 16 February 2013 / Published: 21 February 2013
Cited by 18 | PDF Full-text (1289 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes the design and implementation of a virtual and remote laboratory based on Easy Java Simulations (EJS) and LabVIEW. The main application of this laboratory is to improve the study of sensors in Mobile Robotics, dealing with the problems that arise
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This paper describes the design and implementation of a virtual and remote laboratory based on Easy Java Simulations (EJS) and LabVIEW. The main application of this laboratory is to improve the study of sensors in Mobile Robotics, dealing with the problems that arise on the real world experiments. This laboratory allows the user to work from their homes, tele-operating a real robot that takes measurements from its sensors in order to obtain a map of its environment. In addition, the application allows interacting with a robot simulation (virtual laboratory) or with a real robot (remote laboratory), with the same simple and intuitive graphical user interface in EJS. Thus, students can develop signal processing and control algorithms for the robot in simulation and then deploy them on the real robot for testing purposes. Practical examples of application of the laboratory on the inter-University Master of Systems Engineering and Automatic Control are presented. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle A Neuro-Fuzzy System for Characterization of Arm Movements
Sensors 2013, 13(2), 2613-2630; doi:10.3390/s130202613
Received: 13 December 2012 / Revised: 15 February 2013 / Accepted: 16 February 2013 / Published: 21 February 2013
Cited by 10 | PDF Full-text (705 KB) | HTML Full-text | XML Full-text
Abstract
The myoelectric signal reflects the electrical activity of skeletal muscles and contains information about the structure and function of the muscles which make different parts of the body move. Advances in engineering have extended electromyography beyond the traditional diagnostic applications to also include
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The myoelectric signal reflects the electrical activity of skeletal muscles and contains information about the structure and function of the muscles which make different parts of the body move. Advances in engineering have extended electromyography beyond the traditional diagnostic applications to also include applications in diverse areas such as rehabilitation, movement analysis and myoelectric control of prosthesis. This paper aims to study and develop a system that uses myoelectric signals, acquired by surface electrodes, to characterize certain movements of the human arm. To recognize certain hand-arm segment movements, was developed an algorithm for pattern recognition technique based on neuro-fuzzy, representing the core of this research. This algorithm has as input the preprocessed myoelectric signal, to disclosed specific characteristics of the signal, and as output the performed movement. The average accuracy obtained was 86% to 7 distinct movements in tests of long duration (about three hours). Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle On the Effects of the Lateral Strains on the Fiber Bragg Grating Response
Sensors 2013, 13(2), 2631-2644; doi:10.3390/s130202631
Received: 6 December 2012 / Revised: 6 February 2013 / Accepted: 13 February 2013 / Published: 21 February 2013
Cited by 13 | PDF Full-text (822 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a combined experimental-numerical based work was undertaken to investigate the Bragg wavelength shift response of an embedded FBG sensor when subjected to different conditions of multi-axial loading (deformation). The following cases are examined: (a) when an isotropic host material with
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In this paper, a combined experimental-numerical based work was undertaken to investigate the Bragg wavelength shift response of an embedded FBG sensor when subjected to different conditions of multi-axial loading (deformation). The following cases are examined: (a) when an isotropic host material with no constrains on planes normal to the embedded sensor’s axis is biaxially loaded, (b) when the same isotropic host material is subjected to hydrostatic pressure and (c) when the hydrostatically loaded host material is an anisotropic one, as in the case of a composite material, where the optical fiber is embedded along the reinforcing fibers. The comparison of the experimental results and the finite element simulations shows that, when the axial strain on the FBG sensor is the dominant component, the standard wavelength-shift strain relation can be used even if large lateral strains apply on the sensor. However when this is not the case, large errors may be introduced in the conversion of the wavelength to axial strains on the fiber. This situation arises when the FBG is placed parallel to high modulus reinforcing fibers of a polymer composite. Full article
(This article belongs to the Special Issue Laser Sensing and Imaging)
Open AccessArticle Autonomous Docking Based on Infrared System for Electric Vehicle Charging in Urban Areas
Sensors 2013, 13(2), 2645-2663; doi:10.3390/s130202645
Received: 11 December 2012 / Revised: 24 January 2013 / Accepted: 5 February 2013 / Published: 21 February 2013
Cited by 7 | PDF Full-text (1283 KB) | HTML Full-text | XML Full-text
Abstract
Electric vehicles are progressively introduced in urban areas, because of their ability to reduce air pollution, fuel consumption and noise nuisance. Nowadays, some big cities are launching the first electric car-sharing projects to clear traffic jams and enhance urban mobility, as an alternative
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Electric vehicles are progressively introduced in urban areas, because of their ability to reduce air pollution, fuel consumption and noise nuisance. Nowadays, some big cities are launching the first electric car-sharing projects to clear traffic jams and enhance urban mobility, as an alternative to the classic public transportation systems. However, there are still some problems to be solved related to energy storage, electric charging and autonomy. In this paper, we present an autonomous docking system for electric vehicles recharging based on an embarked infrared camera performing infrared beacons detection installed in the infrastructure. A visual servoing system coupled with an automatic controller allows the vehicle to dock accurately to the recharging booth in a street parking area. The results show good behavior of the implemented system, which is currently deployed as a real prototype system in the city of Paris. Full article
(This article belongs to the Special Issue New Trends towards Automatic Vehicle Control and Perception Systems)
Open AccessArticle An Incremental Target-Adapted Strategy for Active Geometric Calibration of Projector-Camera Systems
Sensors 2013, 13(2), 2664-2681; doi:10.3390/s130202664
Received: 11 January 2013 / Revised: 11 February 2013 / Accepted: 15 February 2013 / Published: 22 February 2013
Cited by 8 | PDF Full-text (2169 KB) | HTML Full-text | XML Full-text
Abstract
The calibration of a projector-camera system is an essential step toward accurate 3-D measurement and environment-aware data projection applications, such as augmented reality. In this paper we present a two-stage easy-to-deploy strategy for robust calibration of both intrinsic and extrinsic parameters of a
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The calibration of a projector-camera system is an essential step toward accurate 3-D measurement and environment-aware data projection applications, such as augmented reality. In this paper we present a two-stage easy-to-deploy strategy for robust calibration of both intrinsic and extrinsic parameters of a projector. Two key components of the system are the automatic generation of projected light patterns and the incremental calibration process. Based on the incremental strategy, the calibration process first establishes a set of initial parameters, and then it upgrades these parameters incrementally using the projection and captured images of dynamically-generated calibration patterns. The scene-driven light patterns allow the system to adapt itself to the pose of the calibration target, such that the difficulty in feature detection is greatly lowered. The strategy forms a closed-loop system that performs self-correction as more and more observations become available. Compared to the conventional method, which requires a time-consuming process for the acquisition of dense pixel correspondences, the proposed method deploys a homography-based coordinate computation, allowing the calibration time to be dramatically reduced. The experimental results indicate that an improvement of 70% in reprojection errors is achievable and 95% of the calibration time can be saved. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Unified Framework for Activity Recognition-Based Behavior Analysis and Action Prediction in Smart Homes
Sensors 2013, 13(2), 2682-2699; doi:10.3390/s130202682
Received: 16 December 2012 / Revised: 12 February 2013 / Accepted: 15 February 2013 / Published: 22 February 2013
Cited by 17 | PDF Full-text (615 KB) | HTML Full-text | XML Full-text
Abstract
In recent years, activity recognition in smart homes is an active research area due to its applicability in many applications, such as assistive living and healthcare. Besides activity recognition, the information collected from smart homes has great potential for other application domains like
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In recent years, activity recognition in smart homes is an active research area due to its applicability in many applications, such as assistive living and healthcare. Besides activity recognition, the information collected from smart homes has great potential for other application domains like lifestyle analysis, security and surveillance, and interaction monitoring. Therefore, discovery of users common behaviors and prediction of future actions from past behaviors become an important step towards allowing an environment to provide personalized service. In this paper, we develop a unified framework for activity recognition-based behavior analysis and action prediction. For this purpose, first we propose kernel fusion method for accurate activity recognition and then identify the significant sequential behaviors of inhabitants from recognized activities of their daily routines. Moreover, behaviors patterns are further utilized to predict the future actions from past activities. To evaluate the proposed framework, we performed experiments on two real datasets. The results show a remarkable improvement of 13.82% in the accuracy on average of recognized activities along with the extraction of significant behavioral patterns and precise activity predictions with 6.76% increase in F-measure. All this collectively help in understanding the users” actions to gain knowledge about their habits and preferences. Full article
(This article belongs to the Section Physical Sensors)

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Open AccessReview Synthetic and Bio-Artificial Tactile Sensing: A Review
Sensors 2013, 13(2), 1435-1466; doi:10.3390/s130201435
Received: 1 November 2012 / Revised: 31 December 2012 / Accepted: 11 January 2013 / Published: 24 January 2013
Cited by 37 | PDF Full-text (439 KB) | HTML Full-text | XML Full-text
Abstract
This paper reviews the state of the art of artificial tactile sensing, with a particular focus on bio-hybrid and fully-biological approaches. To this aim, the study of physiology of the human sense of touch and of the coding mechanisms of tactile information is
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This paper reviews the state of the art of artificial tactile sensing, with a particular focus on bio-hybrid and fully-biological approaches. To this aim, the study of physiology of the human sense of touch and of the coding mechanisms of tactile information is a significant starting point, which is briefly explored in this review. Then, the progress towards the development of an artificial sense of touch are investigated. Artificial tactile sensing is analysed with respect to the possible approaches to fabricate the outer interface layer: synthetic skin versus bio-artificial skin. With particular respect to the synthetic skin approach, a brief overview is provided on various technologies and transduction principles that can be integrated beneath the skin layer. Then, the main focus moves to approaches characterized by the use of bio-artificial skin as an outer layer of the artificial sensory system. Within this design solution for the skin, bio-hybrid and fully-biological tactile sensing systems are thoroughly presented: while significant results have been reported for the development of tissue engineered skins, the development of mechanotransduction units and their integration is a recent trend that is still lagging behind, therefore requiring research efforts and investments. In the last part of the paper, application domains and perspectives of the reviewed tactile sensing technologies are discussed. Full article
(This article belongs to the Special Issue Live Cell-Based Sensors)
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Open AccessReview Exploring Techniques for Vision Based Human Activity Recognition: Methods, Systems, and Evaluation
Sensors 2013, 13(2), 1635-1650; doi:10.3390/s130201635
Received: 29 October 2012 / Revised: 20 January 2013 / Accepted: 22 January 2013 / Published: 25 January 2013
Cited by 22 | PDF Full-text (302 KB) | HTML Full-text | XML Full-text
Abstract
With the wide applications of vision based intelligent systems, image and video analysis technologies have attracted the attention of researchers in the computer vision field. In image and video analysis, human activity recognition is an important research direction. By interpreting and understanding human
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With the wide applications of vision based intelligent systems, image and video analysis technologies have attracted the attention of researchers in the computer vision field. In image and video analysis, human activity recognition is an important research direction. By interpreting and understanding human activity, we can recognize and predict the occurrence of crimes and help the police or other agencies react immediately. In the past, a large number of papers have been published on human activity recognition in video and image sequences. In this paper, we provide a comprehensive survey of the recent development of the techniques, including methods, systems, and quantitative evaluation towards the performance of human activity recognition. Full article
(This article belongs to the Section Physical Sensors)
Open AccessReview Recent Advances in Bacteriophage Based Biosensors for Food-Borne Pathogen Detection
Sensors 2013, 13(2), 1763-1786; doi:10.3390/s130201763
Received: 17 November 2012 / Revised: 16 January 2013 / Accepted: 29 January 2013 / Published: 30 January 2013
Cited by 72 | PDF Full-text (604 KB) | HTML Full-text | XML Full-text
Abstract
Foodborne diseases are a major health concern that can have severe impact on society and can add tremendous financial burden to our health care systems. Rapid early detection of food contamination is therefore relevant for the containment of food-borne pathogens. Conventional pathogen detection
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Foodborne diseases are a major health concern that can have severe impact on society and can add tremendous financial burden to our health care systems. Rapid early detection of food contamination is therefore relevant for the containment of food-borne pathogens. Conventional pathogen detection methods, such as microbiological and biochemical identification are time-consuming and laborious, while immunological or nucleic acid-based techniques require extensive sample preparation and are not amenable to miniaturization for on-site detection. Biosensors have shown tremendous promise to overcome these limitations and are being aggressively studied to provide rapid, reliable and sensitive detection platforms for such applications. Novel biological recognition elements are studied to improve the selectivity and facilitate integration on the transduction platform for sensitive detection. Bacteriophages are one such unique biological entity that show excellent host selectivity and have been actively used as recognition probes for pathogen detection. This review summarizes the extensive literature search on the application of bacteriophages (and recently their receptor binding proteins) as probes for sensitive and selective detection of foodborne pathogens, and critically outlines their advantages and disadvantages over other recognition elements. Full article
Open AccessReview In Vitro Androgen Bioassays as a Detection Method for Designer Androgens
Sensors 2013, 13(2), 2148-2163; doi:10.3390/s130202148
Received: 6 December 2012 / Revised: 22 January 2013 / Accepted: 30 January 2013 / Published: 6 February 2013
Cited by 11 | PDF Full-text (317 KB) | HTML Full-text | XML Full-text
Abstract
Androgens are the class of sex steroids responsible for male sexual characteristics, including increased muscle mass and decreased fat mass. Illicit use of androgen doping can be an attractive option for those looking to enhance sporting performance and/or physical appearance. The use of
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Androgens are the class of sex steroids responsible for male sexual characteristics, including increased muscle mass and decreased fat mass. Illicit use of androgen doping can be an attractive option for those looking to enhance sporting performance and/or physical appearance. The use of in vitro bioassays to detect androgens, especially designer or proandrogens, is becoming increasingly important in combating androgen doping associated with nutritional supplements. The nutritional sports supplement market has grown rapidly throughout the past decade. Many of these supplements contain androgens, designer androgens or proandrogens. Many designer or proandrogens cannot be detected by the standard highly-sensitive screening methods such as gas chromatography-mass spectrometry because their chemical structure is unknown. However, in vitro androgen bioassays can detect designer and proandrogens as these assays are not reliant on knowing the chemical structure but instead are based on androgen receptor activation. For these reasons, it may be advantageous to use routine androgen bioassay screening of nutraceutical samples to help curb the increasing problem of androgen doping. Full article
(This article belongs to the Section Biosensors)
Open AccessReview Diverse Applications of Electronic-Nose Technologies in Agriculture and Forestry
Sensors 2013, 13(2), 2295-2348; doi:10.3390/s130202295
Received: 1 December 2012 / Revised: 30 January 2013 / Accepted: 30 January 2013 / Published: 8 February 2013
Cited by 50 | PDF Full-text (561 KB) | HTML Full-text | XML Full-text
Abstract
Electronic-nose (e-nose) instruments, derived from numerous types of aroma-sensor technologies, have been developed for a diversity of applications in the broad fields of agriculture and forestry. Recent advances in e-nose technologies within the plant sciences, including improvements in gas-sensor designs, innovations in data
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Electronic-nose (e-nose) instruments, derived from numerous types of aroma-sensor technologies, have been developed for a diversity of applications in the broad fields of agriculture and forestry. Recent advances in e-nose technologies within the plant sciences, including improvements in gas-sensor designs, innovations in data analysis and pattern-recognition algorithms, and progress in material science and systems integration methods, have led to significant benefits to both industries. Electronic noses have been used in a variety of commercial agricultural-related industries, including the agricultural sectors of agronomy, biochemical processing, botany, cell culture, plant cultivar selections, environmental monitoring, horticulture, pesticide detection, plant physiology and pathology. Applications in forestry include uses in chemotaxonomy, log tracking, wood and paper processing, forest management, forest health protection, and waste management. These aroma-detection applications have improved plant-based product attributes, quality, uniformity, and consistency in ways that have increased the efficiency and effectiveness of production and manufacturing processes. This paper provides a comprehensive review and summary of a broad range of electronic-nose technologies and applications, developed specifically for the agriculture and forestry industries over the past thirty years, which have offered solutions that have greatly improved worldwide agricultural and agroforestry production systems. Full article
(This article belongs to the Special Issue Sensor-Based Technologies and Processes in Agriculture and Forestry)
Open AccessReview Progress in the Development of CdZnTe Unipolar Detectors for Different Anode Geometries and Data Corrections
Sensors 2013, 13(2), 2447-2474; doi:10.3390/s130202447
Received: 14 November 2012 / Revised: 25 January 2013 / Accepted: 5 February 2013 / Published: 18 February 2013
Cited by 14 | PDF Full-text (2281 KB) | HTML Full-text | XML Full-text
Abstract
CdZnTe detectors have been under development for the past two decades, providing good stopping power for gamma rays, lightweight camera heads and improved energy resolution. However, the performance of this type of detector is limited primarily by incomplete charge collection problems resulting from
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CdZnTe detectors have been under development for the past two decades, providing good stopping power for gamma rays, lightweight camera heads and improved energy resolution. However, the performance of this type of detector is limited primarily by incomplete charge collection problems resulting from charge carriers trapping. This paper is a review of the progress in the development of CdZnTe unipolar detectors with some data correction techniques for improving performance of the detectors. We will first briefly review the relevant theories. Thereafter, two aspects of the techniques for overcoming the hole trapping issue are summarized, including irradiation direction configuration and pulse shape correction methods. CdZnTe detectors of different geometries are discussed in detail, covering the principal of the electrode geometry design, the design and performance characteristics, some detector prototypes development and special correction techniques to improve the energy resolution. Finally, the state of art development of 3-D position sensing and Compton imaging technique are also discussed. Spectroscopic performance of CdZnTe semiconductor detector will be greatly improved even to approach the statistical limit on energy resolution with the combination of some of these techniques. Full article
(This article belongs to the Section Physical Sensors)

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