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Sensors, Volume 13, Issue 12 (December 2013) , Pages 15863-17533

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Open AccessArticle Fractional Modeling of the AC Large-Signal Frequency Response in Magnetoresistive Current Sensors
Sensors 2013, 13(12), 17516-17533; https://doi.org/10.3390/s131217516
Received: 4 October 2013 / Revised: 5 December 2013 / Accepted: 9 December 2013 / Published: 17 December 2013
Cited by 10 | Viewed by 3237 | PDF Full-text (929 KB) | HTML Full-text | XML Full-text
Abstract
Fractional calculus is considered when derivatives and integrals of non-integer order are applied over a specific function. In the electrical and electronic domain, the transfer function dependence of a fractional filter not only by the filter order n, but additionally, of the [...] Read more.
Fractional calculus is considered when derivatives and integrals of non-integer order are applied over a specific function. In the electrical and electronic domain, the transfer function dependence of a fractional filter not only by the filter order n, but additionally, of the fractional order α is an example of a great number of systems where its input-output behavior could be more exactly modeled by a fractional behavior. Following this aim, the present work shows the experimental ac large-signal frequency response of a family of electrical current sensors based in different spintronic conduction mechanisms. Using an ac characterization set-up the sensor transimpedance function Ζt(jf) is obtained considering it as the relationship between sensor output voltage and input sensing current, Ζt(jf)=Vo,sensor(jf)/Isensor(jf). The study has been extended to various magnetoresistance sensors based in different technologies like anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), spin-valve (GMR-SV) and tunnel magnetoresistance (TMR). The resulting modeling shows two predominant behaviors, the low-pass and the inverse low-pass with fractional index different from the classical integer response. The TMR technology with internal magnetization offers the best dynamic and sensitivity properties opening the way to develop actual industrial applications. Full article
Open AccessArticle Floor Covering and Surface Identification for Assistive Mobile Robotic Real-Time Room Localization Application
Sensors 2013, 13(12), 17501-17515; https://doi.org/10.3390/s131217501
Received: 1 November 2013 / Revised: 9 December 2013 / Accepted: 9 December 2013 / Published: 17 December 2013
Cited by 2 | Viewed by 2498 | PDF Full-text (421 KB) | HTML Full-text | XML Full-text
Abstract
Assistive robotic applications require systems capable of interaction in the human world, a workspace which is highly dynamic and not always predictable. Mobile assistive devices face the additional and complex problem of when and if intervention should occur; therefore before any trajectory assistance [...] Read more.
Assistive robotic applications require systems capable of interaction in the human world, a workspace which is highly dynamic and not always predictable. Mobile assistive devices face the additional and complex problem of when and if intervention should occur; therefore before any trajectory assistance is given, the robotic device must know where it is in real-time, without unnecessary disruption or delay to the user requirements. In this paper, we demonstrate a novel robust method for determining room identification from floor features in a real-time computational frame for autonomous and assistive robotics in the human environment. We utilize two inexpensive sensors: an optical mouse sensor for straightforward and rapid, texture or pattern sampling, and a four color photodiode light sensor for fast color determination. We show how data relating floor texture and color obtained from typical dynamic human environments, using these two sensors, compares favorably with data obtained from a standard webcam. We show that suitable data can be extracted from these two sensors at a rate 16 times faster than a standard webcam, and that these data are in a form which can be rapidly processed using readily available classification techniques, suitable for real-time system application. We achieved a 95% correct classification accuracy identifying 133 rooms’ flooring from 35 classes, suitable for fast coarse global room localization application, boundary crossing detection, and additionally some degree of surface type identification. Full article
(This article belongs to the Section Physical Sensors)
Open AccessReview Data Mining for Wearable Sensors in Health Monitoring Systems: A Review of Recent Trends and Challenges
Sensors 2013, 13(12), 17472-17500; https://doi.org/10.3390/s131217472
Received: 20 September 2013 / Revised: 15 November 2013 / Accepted: 6 December 2013 / Published: 17 December 2013
Cited by 138 | Viewed by 10963 | PDF Full-text (493 KB) | HTML Full-text | XML Full-text
Abstract
The past few years have witnessed an increase in the development of wearable sensors for health monitoring systems. This increase has been due to several factors such as development in sensor technology as well as directed efforts on political and stakeholder levels to [...] Read more.
The past few years have witnessed an increase in the development of wearable sensors for health monitoring systems. This increase has been due to several factors such as development in sensor technology as well as directed efforts on political and stakeholder levels to promote projects which address the need for providing new methods for care given increasing challenges with an aging population. An important aspect of study in such system is how the data is treated and processed. This paper provides a recent review of the latest methods and algorithms used to analyze data from wearable sensors used for physiological monitoring of vital signs in healthcare services. In particular, the paper outlines the more common data mining tasks that have been applied such as anomaly detection, prediction and decision making when considering in particular continuous time series measurements. Moreover, the paper further details the suitability of particular data mining and machine learning methods used to process the physiological data and provides an overview of the properties of the data sets used in experimental validation. Finally, based on this literature review, a number of key challenges have been outlined for data mining methods in health monitoring systems. Full article
(This article belongs to the collection Sensors for Globalized Healthy Living and Wellbeing)
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Open AccessArticle MusA: Using Indoor Positioning and Navigation to Enhance Cultural Experiences in a Museum
Sensors 2013, 13(12), 17445-17471; https://doi.org/10.3390/s131217445
Received: 17 October 2013 / Revised: 29 November 2013 / Accepted: 10 December 2013 / Published: 17 December 2013
Cited by 16 | Viewed by 2947 | PDF Full-text (1005 KB) | HTML Full-text | XML Full-text
Abstract
In recent years there has been a growing interest in the use of multimedia mobile guides in museum environments. Mobile devices have the capabilities to detect the user context and to provide pieces of information suitable to help visitors discover and follow the [...] Read more.
In recent years there has been a growing interest in the use of multimedia mobile guides in museum environments. Mobile devices have the capabilities to detect the user context and to provide pieces of information suitable to help visitors discover and follow the logical and emotional connections that develop during the visit. In this scenario, location based services (LBS) currently represent an asset, and the choice of the technology to determine users’ position, combined with the definition of methods that can effectively convey information, become key issues in the design process. In this work, we present Museum Assistant (MusA), a general framework for the development of multimedia interactive guides for mobile devices. Its main feature is a vision-based indoor positioning system that allows the provision of several LBS, from way-finding to the contextualized communication of cultural contents, aimed at providing a meaningful exploration of exhibits according to visitors’ personal interest and curiosity. Starting from the thorough description of the system architecture, the article presents the implementation of two mobile guides, developed to respectively address adults and children, and discusses the evaluation of the user experience and the visitors’ appreciation of these applications. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Application of Remote Power-by-Light Switching in a Simplified BOTDA Sensor Network
Sensors 2013, 13(12), 17434-17444; https://doi.org/10.3390/s131217434
Received: 7 November 2013 / Revised: 11 December 2013 / Accepted: 12 December 2013 / Published: 17 December 2013
Cited by 2 | Viewed by 2261 | PDF Full-text (687 KB) | HTML Full-text | XML Full-text
Abstract
We propose and demonstrate the use of spatial multiplexing as a means to reduce the costs of distributed sensing networks. We propose a new scheme in which remote power-by-light switching is deployed to scan multiple branches of a distributed sensing network based on [...] Read more.
We propose and demonstrate the use of spatial multiplexing as a means to reduce the costs of distributed sensing networks. We propose a new scheme in which remote power-by-light switching is deployed to scan multiple branches of a distributed sensing network based on Brillouin Optical Time Domain Analysis (BOTDA) sensors. A proof-of-concept system is assembled with two 5-km sensor fiber branches that are alternatively monitored using a fast remotely controlled and optically powered optical switch. The multiplexed distributed sensor fibers were located 10 km away from the interrogation unit and a Raman pump is used to remotely power the switch. Furthermore, the deployed BOTDA unit uses an alternative configuration that can lead to simplified setups. Full article
(This article belongs to the Special Issue Photonic Sensors for Industrial, Environmental and Health Monitoring)
Open AccessArticle Events as Power Source: Wireless Sustainable Corrosion Monitoring
Sensors 2013, 13(12), 17414-17433; https://doi.org/10.3390/s131217414
Received: 30 September 2013 / Revised: 6 November 2013 / Accepted: 19 November 2013 / Published: 17 December 2013
Cited by 2 | Viewed by 2281 | PDF Full-text (8970 KB) | HTML Full-text | XML Full-text
Abstract
This study presents and implements a corrosion-monitoring wireless sensor platform, EPS (Events as Power Source), which monitors the corrosion events in reinforced concrete (RC) structures, while being powered by the micro-energy released from the corrosion process. In EPS, the proposed corrosion-sensing device serves [...] Read more.
This study presents and implements a corrosion-monitoring wireless sensor platform, EPS (Events as Power Source), which monitors the corrosion events in reinforced concrete (RC) structures, while being powered by the micro-energy released from the corrosion process. In EPS, the proposed corrosion-sensing device serves both as the signal source for identifying corrosion and as the power source for driving the sensor mote, because the corrosion process (event) releases electric energy; this is a novel idea proposed by this study. For accumulating the micro-corrosion energy, we integrate EPS with a COTS (Commercial Off-The-Shelf) energy-harvesting chip that recharges a supercapacitor. In particular, this study designs automatic energy management and adaptive transmitted power control polices to efficiently use the constrained accumulated energy. Finally, a set of preliminary experiments based on concrete pore solution are conducted to evaluate the feasibility and the efficacy of EPS. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Mobile Monitoring and Embedded Control System for Factory Environment
Sensors 2013, 13(12), 17379-17413; https://doi.org/10.3390/s131217379
Received: 15 October 2013 / Revised: 26 November 2013 / Accepted: 9 December 2013 / Published: 17 December 2013
Cited by 16 | Viewed by 3655 | PDF Full-text (4201 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a real-time method to carry out the monitoring of factory zone temperatures, humidity and air quality using smart phones. At the same time, the system detects possible flames, and analyzes and monitors electrical load. The monitoring also includes detecting the [...] Read more.
This paper proposes a real-time method to carry out the monitoring of factory zone temperatures, humidity and air quality using smart phones. At the same time, the system detects possible flames, and analyzes and monitors electrical load. The monitoring also includes detecting the vibrations of operating machinery in the factory area. The research proposes using ZigBee and Wi-Fi protocol intelligent monitoring system integration within the entire plant framework. The sensors on the factory site deliver messages and real-time sensing data to an integrated embedded systems via the ZigBee protocol. The integrated embedded system is built by the open-source 32-bit ARM (Advanced RISC Machine) core Arduino Due module, where the network control codes are built in for the ARM chipset integrated controller. The intelligent integrated controller is able to instantly provide numerical analysis results according to the received data from the ZigBee sensors. The Android APP and web-based platform are used to show measurement results. The built-up system will transfer these results to a specified cloud device using the TCP/IP protocol. Finally, the Fast Fourier Transform (FFT) approach is used to analyze the power loads in the factory zones. Moreover, Near Field Communication (NFC) technology is used to carry out the actual electricity load experiments using smart phones. Full article
(This article belongs to the Section Sensor Networks)
Open AccessArticle Study on the Application of an Ultra-High-Frequency Fractal Antenna to Partial Discharge Detection in Switchgears
Sensors 2013, 13(12), 17362-17378; https://doi.org/10.3390/s131217362
Received: 6 October 2013 / Revised: 8 December 2013 / Accepted: 8 December 2013 / Published: 16 December 2013
Cited by 11 | Viewed by 2701 | PDF Full-text (1347 KB) | HTML Full-text | XML Full-text
Abstract
The ultra-high-frequency (UHF) method is used to analyze the insulation condition of electric equipment by detecting the UHF electromagnetic (EM) waves excited by partial discharge (PD). As part of the UHF detection system, the UHF sensor determines the detection system performance in signal [...] Read more.
The ultra-high-frequency (UHF) method is used to analyze the insulation condition of electric equipment by detecting the UHF electromagnetic (EM) waves excited by partial discharge (PD). As part of the UHF detection system, the UHF sensor determines the detection system performance in signal extraction and recognition. In this paper, a UHF antenna sensor with the fractal structure for PD detection in switchgears was designed by means of modeling, simulation and optimization. This sensor, with a flat-plate structure, had two resonance frequencies of 583 MHz and 732 MHz. In the laboratory, four kinds of insulation defect models were positioned in the testing switchgear for typical PD tests. The results show that the sensor could reproduce the electromagnetic waves well. Furthermore, to optimize the installation position of the inner sensor for achieving best detection performance, the precise simulation model of switchgear was developed to study the propagation characteristics of UHF signals in switchgear by finite-difference time-domain (FDTD) method. According to the results of simulation and verification test, the sensor should be positioned at the right side of bottom plate in the front cabinet. This research established the foundation for the further study on the application of UHF technique in switchgear PD online detection. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Practical Monitoring System for the Structural Safety of Mega-Trusses Using Wireless Vibrating Wire Strain Gauges
Sensors 2013, 13(12), 17346-17361; https://doi.org/10.3390/s131217346
Received: 4 October 2013 / Revised: 9 December 2013 / Accepted: 10 December 2013 / Published: 16 December 2013
Cited by 8 | Viewed by 3207 | PDF Full-text (955 KB) | HTML Full-text | XML Full-text
Abstract
Sensor technologies have been actively employed in structural health monitoring (SHM) to evaluate structural safety. To provide stable and real-time monitoring, a practical wireless sensor network system (WSNS) based on vibrating wire strain gauges (VWSGs) is proposed and applied to a building under [...] Read more.
Sensor technologies have been actively employed in structural health monitoring (SHM) to evaluate structural safety. To provide stable and real-time monitoring, a practical wireless sensor network system (WSNS) based on vibrating wire strain gauges (VWSGs) is proposed and applied to a building under construction. In this WSNS, the data measured from each VWSG are transmitted to the sensor node via a signal line and then transmitted to the master node through a short-range wireless communication module (operating on the Industrial, Scientific, and Medical (ISM) band). The master node also employs a long-range wireless communication module (Code Division Multiple Access—CDMA) to transmit the received data from the sensor node to a server located in a remote area, which enables a manager to examine the measured data in real time without any time or location restrictions. In this study, a total of 48 VWSGs, 14 sensor nodes, and seven master nodes were implemented to measure long-term strain variations of mega-trusses in an irregular large-scale building under construction. Based on strain data collected over a 16-month period, a quantitative evaluation of the construction process was performed to determine the aspects that exhibit the greatest influence on member behavior and to conduct a comparison with numerical simulation results. The effect of temperature stress on the structural elements was also analyzed. From these observations, the feasibility of a long-term WSNS based on VWSGs to evaluate the structural safety of an irregular building under construction was confirmed. Full article
(This article belongs to the Section Sensor Networks)
Open AccessReview Applications of Delayed Fluorescence from Photosystem II
Sensors 2013, 13(12), 17332-17345; https://doi.org/10.3390/s131217332
Received: 1 November 2013 / Revised: 9 December 2013 / Accepted: 11 December 2013 / Published: 16 December 2013
Cited by 13 | Viewed by 2109 | PDF Full-text (219 KB) | HTML Full-text | XML Full-text
Abstract
While photosystem II (PSII) of plants utilizes light for photosynthesis, part of the absorbed energy may be reverted back and dissipated as long-term fluorescence (delayed fluorescence or DF). Because the generation of DF is coupled with the processes of forward photosynthetic activities, DF [...] Read more.
While photosystem II (PSII) of plants utilizes light for photosynthesis, part of the absorbed energy may be reverted back and dissipated as long-term fluorescence (delayed fluorescence or DF). Because the generation of DF is coupled with the processes of forward photosynthetic activities, DF contains the information about plant physiological states and plant-environment interactions. This makes DF a potentially powerful biosensing mechanism to measure plant photosynthetic activities and environmental conditions. While DF has attracted the interest of many researchers, some aspects of it are still unknown because of the complexity of photosynthetic system. In order to provide a holistic picture about the usefulness of DF, it is meaningful to summarize the research on DF applications. In this short review, available literature on applications of DF from PSII is summarized. Full article
(This article belongs to the Special Issue Fluorescent Biosensors)
Open AccessArticle Experimental Implementation of a Biometric Laser Synaptic Sensor
Sensors 2013, 13(12), 17322-17331; https://doi.org/10.3390/s131217322
Received: 26 October 2013 / Revised: 27 November 2013 / Accepted: 3 December 2013 / Published: 16 December 2013
Cited by 5 | Viewed by 2372 | PDF Full-text (17751 KB) | HTML Full-text | XML Full-text
Abstract
We fabricate a biometric laser fiber synaptic sensor to transmit information from one neuron cell to the other by an optical way. The optical synapse is constructed on the base of an erbium-doped fiber laser, whose pumped diode current is driven by a [...] Read more.
We fabricate a biometric laser fiber synaptic sensor to transmit information from one neuron cell to the other by an optical way. The optical synapse is constructed on the base of an erbium-doped fiber laser, whose pumped diode current is driven by a pre-synaptic FitzHugh–Nagumo electronic neuron, and the laser output controls a post-synaptic FitzHugh–Nagumo electronic neuron. The implemented laser synapse displays very rich dynamics, including fixed points, periodic orbits with different frequency-locking ratios and chaos. These regimes can be beneficial for efficient biorobotics, where behavioral flexibility subserved by synaptic connectivity is a challenge. Full article
(This article belongs to the Section Physical Sensors)
Open AccessReview Mobile Sensing Systems
Sensors 2013, 13(12), 17292-17321; https://doi.org/10.3390/s131217292
Received: 5 November 2013 / Revised: 2 December 2013 / Accepted: 13 December 2013 / Published: 16 December 2013
Cited by 46 | Viewed by 3693 | PDF Full-text (485 KB) | HTML Full-text | XML Full-text
Abstract
Rich-sensor smart phones have made possible the recent birth of the mobile sensing research area as part of ubiquitous sensing which integrates other areas such as wireless sensor networks and web sensing. There are several types of mobile sensing: individual, participatory, [...] Read more.
Rich-sensor smart phones have made possible the recent birth of the mobile sensing research area as part of ubiquitous sensing which integrates other areas such as wireless sensor networks and web sensing. There are several types of mobile sensing: individual, participatory, opportunistic, crowd, social, etc. The object of sensing can be people-centered or environment-centered. The sensing domain can be home, urban, vehicular… Currently there are barriers that limit the social acceptance of mobile sensing systems. Examples of social barriers are privacy concerns, restrictive laws in some countries and the absence of economic incentives that might encourage people to participate in a sensing campaign. Several technical barriers are phone energy savings and the variety of sensors and software for their management. Some existing surveys partially tackle the topic of mobile sensing systems. Published papers theoretically or partially solve the above barriers. We complete the above surveys with new works, review the barriers of mobile sensing systems and propose some ideas for efficiently implementing sensing, fusion, learning, security, privacy and energy saving for any type of mobile sensing system, and propose several realistic research challenges. The main objective is to reduce the learning curve in mobile sensing systems where the complexity is very high. Full article
Open AccessArticle Reliability of Measured Data for pH Sensor Arrays with Fault Diagnosis and Data Fusion Based on LabVIEW
Sensors 2013, 13(12), 17281-17291; https://doi.org/10.3390/s131217281
Received: 10 October 2013 / Revised: 19 November 2013 / Accepted: 11 December 2013 / Published: 13 December 2013
Cited by 1 | Viewed by 2354 | PDF Full-text (398 KB) | HTML Full-text | XML Full-text
Abstract
Fault diagnosis (FD) and data fusion (DF) technologies implemented in the LabVIEW program were used for a ruthenium dioxide pH sensor array. The purpose of the fault diagnosis and data fusion technologies is to increase the reliability of measured data. Data fusion is [...] Read more.
Fault diagnosis (FD) and data fusion (DF) technologies implemented in the LabVIEW program were used for a ruthenium dioxide pH sensor array. The purpose of the fault diagnosis and data fusion technologies is to increase the reliability of measured data. Data fusion is a very useful statistical method used for sensor arrays in many fields. Fault diagnosis is used to avoid sensor faults and to measure errors in the electrochemical measurement system, therefore, in this study, we use fault diagnosis to remove any faulty sensors in advance, and then proceed with data fusion in the sensor array. The average, self-adaptive and coefficient of variance data fusion methods are used in this study. The pH electrode is fabricated with ruthenium dioxide (RuO2) sensing membrane using a sputtering system to deposit it onto a silicon substrate, and eight RuO2 pH electrodes are fabricated to form a sensor array for this study. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Ultra-Low Power High Temperature and Radiation Hard Complementary Metal-Oxide-Semiconductor (CMOS) Silicon-on-Insulator (SOI) Voltage Reference
Sensors 2013, 13(12), 17265-17280; https://doi.org/10.3390/s131217265
Received: 7 November 2013 / Revised: 5 December 2013 / Accepted: 9 December 2013 / Published: 13 December 2013
Cited by 7 | Viewed by 4176 | PDF Full-text (729 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an ultra-low power CMOS voltage reference circuit which is robust under biomedical extreme conditions, such as high temperature and high total ionized dose (TID) radiation. To achieve such performances, the voltage reference is designed in a suitable 130 nm Silicon-on-Insulator [...] Read more.
This paper presents an ultra-low power CMOS voltage reference circuit which is robust under biomedical extreme conditions, such as high temperature and high total ionized dose (TID) radiation. To achieve such performances, the voltage reference is designed in a suitable 130 nm Silicon-on-Insulator (SOI) industrial technology and is optimized to work in the subthreshold regime of the transistors. The design simulations have been performed over the temperature range of -40–200 °C and for different process corners. Robustness to radiation was simulated using custom model parameters including TID effects, such as mobilities and threshold voltages degradation. The proposed circuit has been tested up to high total radiation dose, i.e., 1 Mrad (Si) performed at three different temperatures (room temperature, 100 °C and 200 °C). The maximum drift of the reference voltage VREF depends on the considered temperature and on radiation dose; however, it remains lower than 10% of the mean value of 1.5 V. The typical power dissipation at 2.5 V supply voltage is about 20 μW at room temperature and only 75 μ W at a high temperature of 200 °C. To understand the effects caused by the combination of high total ionizing dose and temperature on such voltage reference, the threshold voltages of the used SOI MOSFETs were extracted under different conditions. The evolution of VREF and power consumption with temperature and radiation dose can then be explained in terms of the different balance between fixed oxide charge and interface states build-up. The total occupied area including pad-ring is less than 0.09 mm2. Full article
(This article belongs to the Special Issue Sensors for Harsh-Environment Applications)
Open AccessArticle Active Self-Testing Noise Measurement Sensors for Large-Scale Environmental Sensor Networks
Sensors 2013, 13(12), 17241-17264; https://doi.org/10.3390/s131217241
Received: 11 October 2013 / Revised: 26 November 2013 / Accepted: 28 November 2013 / Published: 13 December 2013
Cited by 3 | Viewed by 3721 | PDF Full-text (2843 KB) | HTML Full-text | XML Full-text
Abstract
Large-scale noise pollution sensor networks consist of hundreds of spatially distributed microphones that measure environmental noise. These networks provide historical and real-time environmental data to citizens and decision makers and are therefore a key technology to steer environmental policy. However, the high cost [...] Read more.
Large-scale noise pollution sensor networks consist of hundreds of spatially distributed microphones that measure environmental noise. These networks provide historical and real-time environmental data to citizens and decision makers and are therefore a key technology to steer environmental policy. However, the high cost of certified environmental microphone sensors render large-scale environmental networks prohibitively expensive. Several environmental network projects have started using off-the-shelf low-cost microphone sensors to reduce their costs, but these sensors have higher failure rates and produce lower quality data. To offset this disadvantage, we developed a low-cost noise sensor that actively checks its condition and indirectly the integrity of the data it produces. The main design concept is to embed a 13 mm speaker in the noise sensor casing and, by regularly scheduling a frequency sweep, estimate the evolution of the microphone’s frequency response over time. This paper presents our noise sensor’s hardware and software design together with the results of a test deployment in a large-scale environmental network in Belgium. Our middle-range-value sensor (around €50) effectively detected all experienced malfunctions, in laboratory tests and outdoor deployments, with a few false positives. Future improvements could further lower the cost of our sensor below €10. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle New Methodology of Designing Inexpensive Hybrid Control-Acquisition Systems for Mechatronic Constructions
Sensors 2013, 13(12), 17222-17240; https://doi.org/10.3390/s131217222
Received: 11 October 2013 / Revised: 25 November 2013 / Accepted: 26 November 2013 / Published: 13 December 2013
Cited by 2 | Viewed by 2125 | PDF Full-text (570 KB) | HTML Full-text | XML Full-text
Abstract
This article presents a new methodology for designing a hybrid control and acquisition system consisting of a 32-bit SoC microsystem connected via a direct Universal Serial Bus (USB) with a standard commercial off-the-shelf (COTS) component running the Android operating system. It is proposed [...] Read more.
This article presents a new methodology for designing a hybrid control and acquisition system consisting of a 32-bit SoC microsystem connected via a direct Universal Serial Bus (USB) with a standard commercial off-the-shelf (COTS) component running the Android operating system. It is proposed to utilize it avoiding the use of an additional converter. An Android-based component was chosen to explore the potential for a mobile, compact and energy efficient solution with easy to build user interfaces and easy wireless integration with other computer systems. This paper presents results of practical implementation and analysis of experimental real-time performance. It covers closed control loop time between the sensor/actuator module and the Android operating system as well as the real-time sensor data stream within such a system. Some optimisations are proposed and their influence on real-time performance was investigated. The proposed methodology is intended for acquisition and control of mechatronic systems, especially mobile robots. It can be used in a wide range of control applications as well as embedded acquisition-recording devices, including energy quality measurements, smart-grids and medicine. It is demonstrated that the proposed methodology can be employed without developing specific device drivers. The latency achieved was less than 0.5 ms and the sensor data stream throughput was on the order of 750 KB/s (compared to 3 ms latency and 300 KB/s in traditional solutions). Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Sensor Reliability Evaluation Scheme for Target Classification Using Belief Function Theory
Sensors 2013, 13(12), 17193-17221; https://doi.org/10.3390/s131217193
Received: 28 October 2013 / Revised: 4 December 2013 / Accepted: 8 December 2013 / Published: 13 December 2013
Cited by 2 | Viewed by 2175 | PDF Full-text (1221 KB) | HTML Full-text | XML Full-text
Abstract
In the target classification based on belief function theory, sensor reliability evaluation has two basic issues: reasonable dissimilarity measure among evidences, and adaptive combination of static and dynamic discounting. One solution to the two issues has been proposed here. Firstly, an improved dissimilarity [...] Read more.
In the target classification based on belief function theory, sensor reliability evaluation has two basic issues: reasonable dissimilarity measure among evidences, and adaptive combination of static and dynamic discounting. One solution to the two issues has been proposed here. Firstly, an improved dissimilarity measure based on dualistic exponential function has been designed. We assess the static reliability from a training set by the local decision of each sensor and the dissimilarity measure among evidences. The dynamic reliability factors are obtained from each test target using the dissimilarity measure between the output information of each sensor and the consensus. Secondly, an adaptive combination method of static and dynamic discounting has been introduced. We adopt Parzen-window to estimate the matching degree of current performance and static performance for the sensor. Through fuzzy theory, the fusion system can realize self-learning and self-adapting with the sensor performance changing. Experiments conducted on real databases demonstrate that our proposed scheme performs better in target classification under different target conditions compared with other methods. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessArticle Structural-Acoustic Coupling Effects on the Non-Vacuum Packaging Vibratory Cylinder Gyroscope
Sensors 2013, 13(12), 17176-17192; https://doi.org/10.3390/s131217176
Received: 6 November 2013 / Revised: 21 November 2013 / Accepted: 22 November 2013 / Published: 13 December 2013
Cited by 6 | Viewed by 2433 | PDF Full-text (391 KB) | HTML Full-text | XML Full-text
Abstract
The resonant shells of vibratory cylinder gyroscopes are commonly packaged in metallic caps. In order to lower the production cost, a portion of vibratory cylinder gyroscopes do not employ vacuum packaging. However, under non-vacuum packaging conditions there can be internal acoustic noise leading [...] Read more.
The resonant shells of vibratory cylinder gyroscopes are commonly packaged in metallic caps. In order to lower the production cost, a portion of vibratory cylinder gyroscopes do not employ vacuum packaging. However, under non-vacuum packaging conditions there can be internal acoustic noise leading to considerable acoustic pressure which is exerted on the resonant shell. Based on the theory of the structural-acoustic coupling, the dynamical behavior of the resonant shell under acoustic pressure is presented in this paper. A finite element (FE) model is introduced to quantitatively analyze the effect of the structural-acoustic coupling. Several main factors, such as sealing cap sizes and degree of vacuum which directly affect the vibration of the resonant shell, are studied. The results indicate that the vibration amplitude and the operating frequency of the resonant shell will be changed when the effect of structural-acoustic coupling is taken into account. In addition, an experiment was set up to study the effect of structural-acoustic coupling on the sensitivity of the gyroscope. A 32.4 mV/°/s increase of the scale factor and a 6.2 Hz variation of the operating frequency were observed when the radial gap size between the resonant shell and the sealing cap was changed from 0.5 mm to 20 mm. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Design of a Wireless Sensor Network Platform for Tele-Homecare
Sensors 2013, 13(12), 17156-17175; https://doi.org/10.3390/s131217156
Received: 18 September 2013 / Revised: 21 November 2013 / Accepted: 26 November 2013 / Published: 12 December 2013
Cited by 16 | Viewed by 2724 | PDF Full-text (409 KB) | HTML Full-text | XML Full-text
Abstract
The problem of an ageing population has become serious in the past few years as the degeneration of various physiological functions has resulted in distinct chronic diseases in the elderly. Most elderly are not willing to leave home for healthcare centers, but caring [...] Read more.
The problem of an ageing population has become serious in the past few years as the degeneration of various physiological functions has resulted in distinct chronic diseases in the elderly. Most elderly are not willing to leave home for healthcare centers, but caring for patients at home eats up caregiver resources, and can overwhelm patients’ families. Besides, a lot of chronic disease symptoms cause the elderly to visit hospitals frequently. Repeated examinations not only exhaust medical resources, but also waste patients’ time and effort. To make matters worse, this healthcare system does not actually appear to be effective as expected. In response to these problems, a wireless remote home care system is designed in this study, where ZigBee is used to set up a wireless network for the users to take measurements anytime and anywhere. Using suitable measuring devices, users’ physiological signals are measured, and their daily conditions are monitored by various sensors. Being transferred through ZigBee network, vital signs are analyzed in computers which deliver distinct alerts to remind the users and the family of possible emergencies. The system could be further combined with electric appliances to remotely control the users’ environmental conditions. The environmental monitoring function can be activated to transmit in real time dynamic images of the cared to medical personnel through the video function when emergencies occur. Meanwhile, in consideration of privacy, the video camera would be turned on only when it is necessary. The caregiver could adjust the angle of camera to a proper position and observe the current situation of the cared when a sensor on the cared or the environmental monitoring system detects exceptions. All physiological data are stored in the database for family enquiries or accurate diagnoses by medical personnel. Full article
Open AccessArticle Online Least Squares One-Class Support Vector Machines-Based Abnormal Visual Event Detection
Sensors 2013, 13(12), 17130-17155; https://doi.org/10.3390/s131217130
Received: 30 October 2013 / Revised: 29 November 2013 / Accepted: 29 November 2013 / Published: 12 December 2013
Cited by 14 | Viewed by 3077 | PDF Full-text (1258 KB) | HTML Full-text | XML Full-text
Abstract
The abnormal event detection problem is an important subject in real-time video surveillance. In this paper, we propose a novel online one-class classification algorithm, online least squares one-class support vector machine (online LS-OC-SVM), combined with its sparsified version (sparse online LS-OC-SVM). LS-OC-SVM extracts [...] Read more.
The abnormal event detection problem is an important subject in real-time video surveillance. In this paper, we propose a novel online one-class classification algorithm, online least squares one-class support vector machine (online LS-OC-SVM), combined with its sparsified version (sparse online LS-OC-SVM). LS-OC-SVM extracts a hyperplane as an optimal description of training objects in a regularized least squares sense. The online LS-OC-SVM learns a training set with a limited number of samples to provide a basic normal model, then updates the model through remaining data. In the sparse online scheme, the model complexity is controlled by the coherence criterion. The online LS-OC-SVM is adopted to handle the abnormal event detection problem. Each frame of the video is characterized by the covariance matrix descriptor encoding the moving information, then is classified into a normal or an abnormal frame. Experiments are conducted, on a two-dimensional synthetic distribution dataset and a benchmark video surveillance dataset, to demonstrate the promising results of the proposed online LS-OC-SVM method. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Combined Hand Gesture — Speech Model for Human Action Recognition
Sensors 2013, 13(12), 17098-17129; https://doi.org/10.3390/s131217098
Received: 15 October 2013 / Revised: 2 December 2013 / Accepted: 6 December 2013 / Published: 12 December 2013
Cited by 3 | Viewed by 3580 | PDF Full-text (2111 KB) | HTML Full-text | XML Full-text
Abstract
This study proposes a dynamic hand gesture detection technology to effectively detect dynamic hand gesture areas, and a hand gesture recognition technology to improve the dynamic hand gesture recognition rate. Meanwhile, the corresponding relationship between state sequences in hand gesture and speech models [...] Read more.
This study proposes a dynamic hand gesture detection technology to effectively detect dynamic hand gesture areas, and a hand gesture recognition technology to improve the dynamic hand gesture recognition rate. Meanwhile, the corresponding relationship between state sequences in hand gesture and speech models is considered by integrating speech recognition technology with a multimodal model, thus improving the accuracy of human behavior recognition. The experimental results proved that the proposed method can effectively improve human behavior recognition accuracy and the feasibility of system applications. Experimental results verified that the multimodal gesture-speech model provided superior accuracy when compared to the single modal versions. Full article
(This article belongs to the collection Sensors for Globalized Healthy Living and Wellbeing)
Open AccessArticle Evaluation of Piecewise Polynomial Equations for Two Types of Thermocouples
Sensors 2013, 13(12), 17084-17097; https://doi.org/10.3390/s131217084
Received: 24 November 2013 / Revised: 9 December 2013 / Accepted: 10 December 2013 / Published: 12 December 2013
Cited by 5 | Viewed by 2097 | PDF Full-text (336 KB) | HTML Full-text | XML Full-text
Abstract
Thermocouples are the most frequently used sensors for temperature measurement because of their wide applicability, long-term stability and high reliability. However, one of the major utilization problems is the linearization of the transfer relation between temperature and output voltage of thermocouples. The linear [...] Read more.
Thermocouples are the most frequently used sensors for temperature measurement because of their wide applicability, long-term stability and high reliability. However, one of the major utilization problems is the linearization of the transfer relation between temperature and output voltage of thermocouples. The linear calibration equation and its modules could be improved by using regression analysis to help solve this problem. In this study, two types of thermocouple and five temperature ranges were selected to evaluate the fitting agreement of different-order polynomial equations. Two quantitative criteria, the average of the absolute error values |e|ave and the standard deviation of calibration equation estd, were used to evaluate the accuracy and precision of these calibrations equations. The optimal order of polynomial equations differed with the temperature range. The accuracy and precision of the calibration equation could be improved significantly with an adequate higher degree polynomial equation. The technique could be applied with hardware modules to serve as an intelligent sensor for temperature measurement. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Adaptation of Soil Physical Measurement Techniques for the Delineation of Mud and Lakebed Sediments at Neusiedler See
Sensors 2013, 13(12), 17067-17083; https://doi.org/10.3390/s131217067
Received: 20 October 2013 / Revised: 3 December 2013 / Accepted: 8 December 2013 / Published: 12 December 2013
Cited by 3 | Viewed by 2318 | PDF Full-text (1636 KB) | HTML Full-text | XML Full-text
Abstract
For many water management issues of shallow lakes with non-consolidated sediments hydrographic surveys of the open water area and reed belt areas are required. In the frame of water management strategy for the steppe lake Neusiedler See, located between Austria and Hungary, a [...] Read more.
For many water management issues of shallow lakes with non-consolidated sediments hydrographic surveys of the open water area and reed belt areas are required. In the frame of water management strategy for the steppe lake Neusiedler See, located between Austria and Hungary, a hydrographic survey was conducted. In the open water area (water depth ≥1 m) a sediment echosounder was used. To validate these measurements and to distinguish between water, mud, and sediment layers in the shallow lake and reed belt area additional measurements were needed. As no common standard methods are available yet, we developed a measurement system based on two commonly applied soil physical measurement techniques providing reproducible physical values: a capacitive sensor and a cone penetrometer combined with GNSS-positioning enable dynamic measurements of georeferenced vertical water-mud-bedsediments profiles. The system bases on site-specific calibrated sensors and allows instantaneous, in situ measurements. The measurements manifest a sharp water-mud interface by a sudden decline to smaller water content which is a function of the dielectric permittivity. A second decline indicates the transition to compacted mud. That is concurrently the density where the penetrometer starts registering significant penetration resistance. The penetrometer detects shallow lakebed-sediment layers. Within the lake survey this measurement system was successfully tested. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle Inverse Transient Analysis for Classification of Wall Thickness Variations in Pipelines
Sensors 2013, 13(12), 17057-17066; https://doi.org/10.3390/s131217057
Received: 25 October 2013 / Revised: 2 December 2013 / Accepted: 9 December 2013 / Published: 11 December 2013
Cited by 11 | Viewed by 2607 | PDF Full-text (434 KB) | HTML Full-text | XML Full-text
Abstract
Analysis of transient fluid pressure signals has been investigated as an alternative method of fault detection in pipeline systems and has shown promise in both laboratory and field trials. The advantage of the method is that it can potentially provide a fast and [...] Read more.
Analysis of transient fluid pressure signals has been investigated as an alternative method of fault detection in pipeline systems and has shown promise in both laboratory and field trials. The advantage of the method is that it can potentially provide a fast and cost effective means of locating faults such as leaks, blockages and pipeline wall degradation within a pipeline while the system remains fully operational. The only requirement is that high speed pressure sensors are placed in contact with the fluid. Further development of the method requires detailed numerical models and enhanced understanding of transient flow within a pipeline where variations in pipeline condition and geometry occur. One such variation commonly encountered is the degradation or thinning of pipe walls, which can increase the susceptible of a pipeline to leak development. This paper aims to improve transient-based fault detection methods by investigating how changes in pipe wall thickness will affect the transient behaviour of a system; this is done through the analysis of laboratory experiments. The laboratory experiments are carried out on a stainless steel pipeline of constant outside diameter, into which a pipe section of variable wall thickness is inserted. In order to detect the location and severity of these changes in wall conditions within the laboratory system an inverse transient analysis procedure is employed which considers independent variations in wavespeed and diameter. Inverse transient analyses are carried out using a genetic algorithm optimisation routine to match the response from a one-dimensional method of characteristics transient model to the experimental time domain pressure responses. The accuracy of the detection technique is evaluated and benefits associated with various simplifying assumptions and simulation run times are investigated. It is found that for the case investigated, changes in the wavespeed and nominal diameter of the pipeline are both important to the accuracy of the inverse analysis procedure and can be used to differentiate the observed transient behaviour caused by changes in wall thickness from that caused by other known faults such as leaks. Further application of the method to real pipelines is discussed. Full article
(This article belongs to the Special Issue Sensors for Fluid Leak Detection) Printed Edition available
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Open AccessArticle Sensored Field Oriented Control of a Robust Induction Motor Drive Using a Novel Boundary Layer Fuzzy Controller
Sensors 2013, 13(12), 17025-17056; https://doi.org/10.3390/s131217025
Received: 28 October 2013 / Revised: 2 December 2013 / Accepted: 10 December 2013 / Published: 10 December 2013
Cited by 4 | Viewed by 2767 | PDF Full-text (983 KB) | HTML Full-text | XML Full-text
Abstract
Physical sensors have a key role in implementation of real-time vector control for an induction motor (IM) drive. This paper presents a novel boundary layer fuzzy controller (NBLFC) based on the boundary layer approach for speed control of an indirect field-oriented control (IFOC) [...] Read more.
Physical sensors have a key role in implementation of real-time vector control for an induction motor (IM) drive. This paper presents a novel boundary layer fuzzy controller (NBLFC) based on the boundary layer approach for speed control of an indirect field-oriented control (IFOC) of an induction motor (IM) drive using physical sensors. The boundary layer approach leads to a trade-off between control performances and chattering elimination. For the NBLFC, a fuzzy system is used to adjust the boundary layer thickness to improve the tracking performance and eliminate the chattering problem under small uncertainties. Also, to eliminate the chattering under the possibility of large uncertainties, the integral filter is proposed inside the variable boundary layer. In addition, the stability of the system is analyzed through the Lyapunov stability theorem. The proposed NBLFC based IM drive is implemented in real-time using digital signal processor (DSP) board TI TMS320F28335. The experimental and simulation results show the effectiveness of the proposed NBLFC based IM drive at different operating conditions. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle A Micromachined Pressure Sensor with Integrated Resonator Operating at Atmospheric Pressure
Sensors 2013, 13(12), 17006-17024; https://doi.org/10.3390/s131217006
Received: 20 September 2013 / Revised: 19 November 2013 / Accepted: 28 November 2013 / Published: 10 December 2013
Cited by 16 | Viewed by 3280 | PDF Full-text (1545 KB) | HTML Full-text | XML Full-text
Abstract
A novel resonant pressure sensor with an improved micromechanical double-ended tuning fork resonator packaged in dry air at atmospheric pressure is presented. The resonator is electrostatically driven and capacitively detected, and the sensor is designed to realize a low cost resonant pressure sensor [...] Read more.
A novel resonant pressure sensor with an improved micromechanical double-ended tuning fork resonator packaged in dry air at atmospheric pressure is presented. The resonator is electrostatically driven and capacitively detected, and the sensor is designed to realize a low cost resonant pressure sensor with medium accuracy. Various damping mechanisms in a resonator that is vibrating at atmospheric pressure are analyzed in detail, and a formula is developed to predict the overall quality factor. A trade-off has been reached between the quality factor, stress sensitivity and drive capability of the resonator. Furthermore, differential sense elements and the method of electromechanical amplitude modulation are used for capacitive detection to obtain a large signal-to-noise ratio. The prototype sensor chip is successfully fabricated using a micromachining process based on a commercially available silicon-on-insulator wafer and is hermetically encapsulated in a custom 16-pin Kovar package. Preliminary measurements show that the fundamental frequency of the resonant pressure sensor is approximately 34.55 kHz with a pressure sensitivity of 20.77 Hz/kPa. Over the full scale pressure range of 100–400 kPa and the whole temperature range of −20–60 °C, high quality factors from 1,146 to 1,772 are obtained. The characterization of the prototype sensor reveals the feasibility of a resonant pressure sensor packaged at atmospheric pressure. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle Fall Risk Assessment and Early-Warning for Toddler Behaviors at Home
Sensors 2013, 13(12), 16985-17005; https://doi.org/10.3390/s131216985
Received: 19 September 2013 / Revised: 22 November 2013 / Accepted: 26 November 2013 / Published: 10 December 2013
Cited by 8 | Viewed by 2997 | PDF Full-text (2270 KB) | HTML Full-text | XML Full-text
Abstract
Accidental falls are the major cause of serious injuries in toddlers, with most of these falls happening at home. Instead of providing immediate fall detection based on short-term observations, this paper proposes an early-warning childcare system to monitor fall-prone behaviors of toddlers at [...] Read more.
Accidental falls are the major cause of serious injuries in toddlers, with most of these falls happening at home. Instead of providing immediate fall detection based on short-term observations, this paper proposes an early-warning childcare system to monitor fall-prone behaviors of toddlers at home. Using 3D human skeleton tracking and floor plane detection based on depth images captured by a Kinect system, eight fall-prone behavioral modules of toddlers are developed and organized according to four essential criteria: posture, motion, balance, and altitude. The final fall risk assessment is generated by a multi-modal fusion using either a weighted mean thresholding or a support vector machine (SVM) classification. Optimizations are performed to determine local parameter in each module and global parameters of the multi-modal fusion. Experimental results show that the proposed system can assess fall risks and trigger alarms with an accuracy rate of 92% at a speed of 20 frames per second. Full article
(This article belongs to the collection Sensors for Globalized Healthy Living and Wellbeing)
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Open AccessArticle Automatic and Objective Assessment of Alternating Tapping Performance in Parkinson’s Disease
Sensors 2013, 13(12), 16965-16984; https://doi.org/10.3390/s131216965
Received: 26 September 2013 / Revised: 21 November 2013 / Accepted: 5 December 2013 / Published: 9 December 2013
Cited by 18 | Viewed by 3486 | PDF Full-text (870 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the development and evaluation of a method for enabling quantitative and automatic scoring of alternating tapping performance of patients with Parkinson’s disease (PD). Ten healthy elderly subjects and 95 patients in different clinical stages of PD have utilized a touch-pad [...] Read more.
This paper presents the development and evaluation of a method for enabling quantitative and automatic scoring of alternating tapping performance of patients with Parkinson’s disease (PD). Ten healthy elderly subjects and 95 patients in different clinical stages of PD have utilized a touch-pad handheld computer to perform alternate tapping tests in their home environments. First, a neurologist used a web-based system to visually assess impairments in four tapping dimensions (‘speed’, ‘accuracy’, ‘fatigue’ and ‘arrhythmia’) and a global tapping severity (GTS). Second, tapping signals were processed with time series analysis and statistical methods to derive 24 quantitative parameters. Third, principal component analysis was used to reduce the dimensions of these parameters and to obtain scores for the four dimensions. Finally, a logistic regression classifier was trained using a 10-fold stratified cross-validation to map the reduced parameters to the corresponding visually assessed GTS scores. Results showed that the computed scores correlated well to visually assessed scores and were significantly different across Unified Parkinson’s Disease Rating Scale scores of upper limb motor performance. In addition, they had good internal consistency, had good ability to discriminate between healthy elderly and patients in different disease stages, had good sensitivity to treatment interventions and could reflect the natural disease progression over time. In conclusion, the automatic method can be useful to objectively assess the tapping performance of PD patients and can be included in telemedicine tools for remote monitoring of tapping. Full article
(This article belongs to the collection Sensors for Globalized Healthy Living and Wellbeing)
Open AccessArticle Fault Diagnosis of Rotating Machinery Based on an Adaptive Ensemble Empirical Mode Decomposition
Sensors 2013, 13(12), 16950-16964; https://doi.org/10.3390/s131216950
Received: 8 October 2013 / Revised: 11 November 2013 / Accepted: 22 November 2013 / Published: 9 December 2013
Cited by 43 | Viewed by 3552 | PDF Full-text (443 KB) | HTML Full-text | XML Full-text
Abstract
The vibration based signal processing technique is one of the principal tools for diagnosing faults of rotating machinery. Empirical mode decomposition (EMD), as a time-frequency analysis technique, has been widely used to process vibration signals of rotating machinery. But it has the shortcoming [...] Read more.
The vibration based signal processing technique is one of the principal tools for diagnosing faults of rotating machinery. Empirical mode decomposition (EMD), as a time-frequency analysis technique, has been widely used to process vibration signals of rotating machinery. But it has the shortcoming of mode mixing in decomposing signals. To overcome this shortcoming, ensemble empirical mode decomposition (EEMD) was proposed accordingly. EEMD is able to reduce the mode mixing to some extent. The performance of EEMD, however, depends on the parameters adopted in the EEMD algorithms. In most of the studies on EEMD, the parameters were selected artificially and subjectively. To solve the problem, a new adaptive ensemble empirical mode decomposition method is proposed in this paper. In the method, the sifting number is adaptively selected, and the amplitude of the added noise changes with the signal frequency components during the decomposition process. The simulation, the experimental and the application results demonstrate that the adaptive EEMD provides the improved results compared with the original EEMD in diagnosing rotating machinery. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle InN Based Water Condensation Sensors on Glass and Flexible Plastic Substrates
Sensors 2013, 13(12), 16940-16949; https://doi.org/10.3390/s131216940
Received: 30 September 2013 / Revised: 7 November 2013 / Accepted: 14 November 2013 / Published: 6 December 2013
Cited by 2 | Viewed by 2693 | PDF Full-text (1031 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we report the realization and characterization of a condensation sensor based on indium nitride (InN) layers deposited by magnetron sputtering on glass and flexible plastic substrates, having fast response and using potentially low cost fabrication technology. The InN devices work [...] Read more.
In this paper, we report the realization and characterization of a condensation sensor based on indium nitride (InN) layers deposited by magnetron sputtering on glass and flexible plastic substrates, having fast response and using potentially low cost fabrication technology. The InN devices work as open gate thin film sensitive transistors. Condensed water droplets, formed on the open gate region of the sensors, deplete the electron accumulation layer on the surface of InN film, thus decreasing the current of the sensor. The current increases back to its initial value when water droplets evaporate from the exposed InN film surface. The response time is as low as 2 s. Full article
(This article belongs to the Section Physical Sensors)
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