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Sensors, Volume 14, Issue 5 (May 2014) , Pages 7580-9368

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Open AccessArticle
Real-Time Algebraic Derivative Estimations Using a Novel Low-Cost Architecture Based on Reconfigurable Logic
Sensors 2014, 14(5), 9349-9368; https://doi.org/10.3390/s140509349
Received: 20 January 2014 / Revised: 12 May 2014 / Accepted: 21 May 2014 / Published: 23 May 2014
Cited by 5 | Viewed by 2513 | PDF Full-text (895 KB) | HTML Full-text | XML Full-text
Abstract
Time derivative estimation of signals plays a very important role in several fields, such as signal processing and control engineering, just to name a few of them. For that purpose, a non-asymptotic algebraic procedure for the approximate estimation of the system states is [...] Read more.
Time derivative estimation of signals plays a very important role in several fields, such as signal processing and control engineering, just to name a few of them. For that purpose, a non-asymptotic algebraic procedure for the approximate estimation of the system states is used in this work. The method is based on results from differential algebra and furnishes some general formulae for the time derivatives of a measurable signal in which two algebraic derivative estimators run simultaneously, but in an overlapping fashion. The algebraic derivative algorithm presented in this paper is computed online and in real-time, offering high robustness properties with regard to corrupting noises, versatility and ease of implementation. Besides, in this work, we introduce a novel architecture to accelerate this algebraic derivative estimator using reconfigurable logic. The core of the algorithm is implemented in an FPGA, improving the speed of the system and achieving real-time performance. Finally, this work proposes a low-cost platform for the integration of hardware in the loop in MATLAB. Full article
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Open AccessArticle
Dynamic Bayesian Networks for Context-Aware Fall Risk Assessment
Sensors 2014, 14(5), 9330-9348; https://doi.org/10.3390/s140509330
Received: 19 March 2014 / Revised: 12 May 2014 / Accepted: 21 May 2014 / Published: 23 May 2014
Cited by 8 | Viewed by 3474 | PDF Full-text (468 KB) | HTML Full-text | XML Full-text
Abstract
Fall incidents among the elderly often occur in the home and can cause serious injuries affecting their independent living. This paper presents an approach where data from wearable sensors integrated in a smart home environment is combined using a dynamic Bayesian network. The [...] Read more.
Fall incidents among the elderly often occur in the home and can cause serious injuries affecting their independent living. This paper presents an approach where data from wearable sensors integrated in a smart home environment is combined using a dynamic Bayesian network. The smart home environment provides contextual data, obtained from environmental sensors, and contributes to assessing a fall risk probability. The evaluation of the developed system is performed through simulation. Each time step is represented by a single user activity and interacts with a fall sensors located on a mobile device. A posterior probability is calculated for each recognized activity or contextual information. The output of the system provides a total risk assessment of falling given a response from the fall sensor. Full article
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Open AccessArticle
ATHENA: A Personalized Platform to Promote an Active Lifestyle and Wellbeing Based on Physical, Mental and Social Health Primitives
Sensors 2014, 14(5), 9313-9329; https://doi.org/10.3390/s140509313
Received: 14 March 2014 / Revised: 2 May 2014 / Accepted: 14 May 2014 / Published: 23 May 2014
Cited by 18 | Viewed by 4042 | PDF Full-text (902 KB) | HTML Full-text | XML Full-text
Abstract
Technology provides ample opportunities for the acquisition and processing of physical, mental and social health primitives. However, several challenges remain for researchers as how to define the relationship between reported physical activities, mood and social interaction to define an active lifestyle. We are [...] Read more.
Technology provides ample opportunities for the acquisition and processing of physical, mental and social health primitives. However, several challenges remain for researchers as how to define the relationship between reported physical activities, mood and social interaction to define an active lifestyle. We are conducting a project, ATHENA(activity-awareness for human-engaged wellness applications) to design and integrate the relationship between these basic health primitives to approximate the human lifestyle and real-time recommendations for wellbeing services. Our goal is to develop a system to promote an active lifestyle for individuals and to recommend to them valuable interventions by making comparisons to their past habits. The proposed system processes sensory data through our developed machine learning algorithms inside smart devices and utilizes cloud infrastructure to reduce the cost. We exploit big data infrastructure for massive sensory data storage and fast retrieval for recommendations. Our contributions include the development of a prototype system to promote an active lifestyle and a visual design capable of engaging users in the goal of increasing self-motivation. We believe that our study will impact the design of future ubiquitous wellness applications. Full article
Open AccessArticle
A New Acquisition and Imaging System for Environmental Measurements: An Experience on the Italian Cultural Heritage
Sensors 2014, 14(5), 9290-9312; https://doi.org/10.3390/s140509290
Received: 15 February 2014 / Revised: 5 May 2014 / Accepted: 19 May 2014 / Published: 23 May 2014
Cited by 35 | Viewed by 2965 | PDF Full-text (772 KB) | HTML Full-text | XML Full-text
Abstract
A new acquisition system for remote control of wall paintings has been realized and tested in the field. The system measures temperature and atmospheric pressure in an archeological site where a fresco has been put under control. The measuring chain has been designed [...] Read more.
A new acquisition system for remote control of wall paintings has been realized and tested in the field. The system measures temperature and atmospheric pressure in an archeological site where a fresco has been put under control. The measuring chain has been designed to be used in unfavorable environments where neither electric power nor telecommunication infrastructures are available. The environmental parameters obtained from the local monitoring are then transferred remotely allowing an easier management by experts in the field of conservation of cultural heritage. The local acquisition system uses an electronic card based on microcontrollers and sends the data to a central unit realized with a Raspberry-Pi. The latter manages a high quality camera to pick up pictures of the fresco. Finally, to realize the remote control at a site not reached by internet signals, a WiMAX connection based on different communication technologies such as WiMAX, Ethernet, GPRS and Satellite, has been set up. Full article
(This article belongs to the Special Issue Sensors for Cultural Heritage Diagnostics)
Open AccessArticle
MLAOS: A Multi-Point Linear Array of Optical Sensors for Coniferous Foliage Clumping Index Measurement
Sensors 2014, 14(5), 9271-9289; https://doi.org/10.3390/s140509271
Received: 6 January 2014 / Revised: 23 April 2014 / Accepted: 16 May 2014 / Published: 23 May 2014
Cited by 7 | Viewed by 2411 | PDF Full-text (1261 KB) | HTML Full-text | XML Full-text
Abstract
The canopy foliage clumping effect is primarily caused by the non-random distribution of canopy foliage. Currently, measurements of clumping index (CI) by handheld instruments is typically time- and labor-intensive. We propose a low-cost and low-power automatic measurement system called Multi-point Linear Array of [...] Read more.
The canopy foliage clumping effect is primarily caused by the non-random distribution of canopy foliage. Currently, measurements of clumping index (CI) by handheld instruments is typically time- and labor-intensive. We propose a low-cost and low-power automatic measurement system called Multi-point Linear Array of Optical Sensors (MLAOS), which consists of three above-canopy and nine below-canopy optical sensors that capture plant transmittance at different times of the day. Data communication between the MLAOS node is facilitated by using a ZigBee network, and the data are transmitted from the field MLAOS to a remote data server using the Internet. The choice of the electronic element and design of the MLAOS software is aimed at reducing costs and power consumption. A power consumption test showed that, when a 4000 mAH Li-ion battery is used, a maximum of 8–10 months of work can be achieved. A field experiment on a coniferous forest revealed that the CI of MLAOS may reveal a clumping effect that occurs within the canopy. In further work, measurement of the multi-scale clumping effect can be achieved by utilizing a greater number of MLAOS devices to capture the heterogeneity of the plant canopy. Full article
(This article belongs to the Section Remote Sensors, Control, and Telemetry)
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Open AccessArticle
A Measuring System for Well Logging Attitude and a Method of Sensor Calibration
Sensors 2014, 14(5), 9256-9270; https://doi.org/10.3390/s140509256
Received: 10 March 2014 / Revised: 12 May 2014 / Accepted: 21 May 2014 / Published: 23 May 2014
Cited by 9 | Viewed by 2634 | PDF Full-text (721 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes an approach for measuring the azimuth angle and tilt angle of underground drilling tools with a MEMS three-axis accelerometer and a three-axis fluxgate sensor. A mathematical model of well logging attitude angle is deduced based on combining space coordinate transformations [...] Read more.
This paper proposes an approach for measuring the azimuth angle and tilt angle of underground drilling tools with a MEMS three-axis accelerometer and a three-axis fluxgate sensor. A mathematical model of well logging attitude angle is deduced based on combining space coordinate transformations and algebraic equations. In addition, a system implementation plan of the inclinometer is given in this paper, which features low cost, small volume and integration. Aiming at the sensor and assembly errors, this paper analyses the sources of errors, and establishes two mathematical models of errors and calculates related parameters to achieve sensor calibration. The results show that this scheme can obtain a stable and high precision azimuth angle and tilt angle of drilling tools, with the deviation of the former less than ±1.4° and the deviation of the latter less than ±0.1°. Full article
(This article belongs to the Special Issue Optical Gyroscopes and Navigation Systems)
Open AccessArticle
A Low-Power Integrated Humidity CMOS Sensor by Printing-on-Chip Technology
Sensors 2014, 14(5), 9247-9255; https://doi.org/10.3390/s140509247
Received: 25 April 2014 / Revised: 19 May 2014 / Accepted: 20 May 2014 / Published: 23 May 2014
Cited by 5 | Viewed by 3132 | PDF Full-text (299 KB) | HTML Full-text | XML Full-text
Abstract
A low-power, wide-dynamic-range integrated humidity sensing chip is implemented using a printable polymer sensing material with an on-chip pulse-width-modulation interface circuit. By using the inkjet printing technique, poly(3,4-ethylene-dioxythiophene)/polystyrene sulfonate that has humidity sensing features can be printed onto the top metal layer of [...] Read more.
A low-power, wide-dynamic-range integrated humidity sensing chip is implemented using a printable polymer sensing material with an on-chip pulse-width-modulation interface circuit. By using the inkjet printing technique, poly(3,4-ethylene-dioxythiophene)/polystyrene sulfonate that has humidity sensing features can be printed onto the top metal layer of a 0.35 μm CMOS IC. The developed printing-on-chip humidity sensor achieves a heterogeneous three dimensional sensor system-on-chip architecture. The humidity sensing of the implemented printing-on-chip sensor system is experimentally tested. The sensor shows a sensitivity of 0.98% to humidity in the atmosphere. The maximum dynamic range of the readout circuit is 9.8 MΩ, which can be further tuned by the frequency of input signal to fit the requirement of the resistance of printed sensor. The power consumption keeps only 154 μW. This printing-on-chip sensor provides a practical solution to fulfill an ultra-small integrated sensor for the applications in miniaturized sensing systems. Full article
(This article belongs to the Special Issue Printed Sensors)
Open AccessArticle
RESTful Discovery and Eventing for Service Provisioning in Assisted Living Environments
Sensors 2014, 14(5), 9227-9246; https://doi.org/10.3390/s140509227
Received: 1 April 2014 / Revised: 18 May 2014 / Accepted: 20 May 2014 / Published: 23 May 2014
Cited by 4 | Viewed by 2850 | PDF Full-text (547 KB) | HTML Full-text | XML Full-text
Abstract
Service provisioning in assisted living environments faces distinct challenges due to the heterogeneity of networks, access technology, and sensing/actuation devices in such an environment. Existing solutions, such as SOAP-based web services, can interconnect heterogeneous devices and services, and can be published, discovered and [...] Read more.
Service provisioning in assisted living environments faces distinct challenges due to the heterogeneity of networks, access technology, and sensing/actuation devices in such an environment. Existing solutions, such as SOAP-based web services, can interconnect heterogeneous devices and services, and can be published, discovered and invoked dynamically. However, it is considered heavier than what is required in the smart environment-like context and hence suffers from performance degradation. Alternatively, REpresentational State Transfer (REST) has gained much attention from the community and is considered as a lighter and cleaner technology compared to the SOAP-based web services. Since it is simple to publish and use a RESTful web service, more and more service providers are moving toward REST-based solutions, which promote a resource-centric conceptualization as opposed to a service-centric conceptualization. Despite such benefits of REST, the dynamic discovery and eventing of RESTful services are yet considered a major hurdle to utilization of the full potential of REST-based approaches. In this paper, we address this issue, by providing a RESTful discovery and eventing specification and demonstrate it in an assisted living healthcare scenario. We envisage that through this approach, the service provisioning in ambient assisted living or other smart environment settings will be more efficient, timely, and less resource-intensive. Full article
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Open AccessArticle
Comparative Study on a Solving Model and Algorithm for a Flush Air Data Sensing System
Sensors 2014, 14(5), 9210-9226; https://doi.org/10.3390/s140509210
Received: 17 March 2014 / Revised: 13 May 2014 / Accepted: 19 May 2014 / Published: 23 May 2014
Cited by 2 | Viewed by 1900 | PDF Full-text (912 KB) | HTML Full-text | XML Full-text
Abstract
With the development of high-performance aircraft, precise air data are necessary to complete challenging tasks such as flight maneuvering with large angles of attack and high speed. As a result, the flush air data sensing system (FADS) was developed to satisfy the stricter [...] Read more.
With the development of high-performance aircraft, precise air data are necessary to complete challenging tasks such as flight maneuvering with large angles of attack and high speed. As a result, the flush air data sensing system (FADS) was developed to satisfy the stricter control demands. In this paper, comparative stuides on the solving model and algorithm for FADS are conducted. First, the basic principles of FADS are given to elucidate the nonlinear relations between the inputs and the outputs. Then, several different solving models and algorithms of FADS are provided to compute the air data, including the angle of attck, sideslip angle, dynamic pressure and static pressure. Afterwards, the evaluation criteria of the resulting models and algorithms are discussed to satisfy the real design demands. Futhermore, a simulation using these algorithms is performed to identify the properites of the distinct models and algorithms such as the measuring precision and real-time features. The advantages of these models and algorithms corresponding to the different flight conditions are also analyzed, furthermore, some suggestions on their engineering applications are proposed to help future research. Full article
(This article belongs to the Section Physical Sensors)
Open AccessReview
Surveying Wearable Human Assistive Technology for Life and Safety Critical Applications: Standards, Challenges and Opportunities
Sensors 2014, 14(5), 9153-9209; https://doi.org/10.3390/s140509153
Received: 18 March 2014 / Revised: 25 April 2014 / Accepted: 14 May 2014 / Published: 23 May 2014
Cited by 88 | Viewed by 6035 | PDF Full-text (1312 KB) | HTML Full-text | XML Full-text
Abstract
In this survey a new application paradigm life and safety for critical operations and missions using wearable Wireless Body Area Networks (WBANs) technology is introduced. This paradigm has a vast scope of applications, including disaster management, worker safety in harsh environments such as [...] Read more.
In this survey a new application paradigm life and safety for critical operations and missions using wearable Wireless Body Area Networks (WBANs) technology is introduced. This paradigm has a vast scope of applications, including disaster management, worker safety in harsh environments such as roadside and building workers, mobile health monitoring, ambient assisted living and many more. It is often the case that during the critical operations and the target conditions, the existing infrastructure is either absent, damaged or overcrowded. In this context, it is envisioned that WBANs will enable the quick deployment of ad-hoc/on-the-fly communication networks to help save many lives and ensuring people’s safety. However, to understand the applications more deeply and their specific characteristics and requirements, this survey presents a comprehensive study on the applications scenarios, their context and specific requirements. It explores details of the key enabling standards, existing state-of-the-art research studies, and projects to understand their limitations before realizing aforementioned applications. Application-specific challenges and issues are discussed comprehensively from various perspectives and future research and development directions are highlighted as an inspiration for new innovative solutions. To conclude, this survey opens up a good opportunity for companies and research centers to investigate old but still new problems, in the realm of wearable technologies, which are increasingly evolving and getting more and more attention recently. Full article
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Open AccessArticle
Discovery of Pantoea rodasii Strain ND03 that Produces N-(3-Oxo-hexanoyl)-L-homoserine Lactone
Sensors 2014, 14(5), 9145-9152; https://doi.org/10.3390/s140509145
Received: 8 April 2014 / Revised: 13 May 2014 / Accepted: 16 May 2014 / Published: 23 May 2014
Cited by 4 | Viewed by 2322 | PDF Full-text (288 KB) | HTML Full-text | XML Full-text
Abstract
Proteobacteria use quorum sensing to regulate target gene expression in response to population density. Quorum sensing (QS) is achieved via so-called signalling molecules and the best-studied QS signalling system uses N-acyl homoserine lactones (AHLs). This study aimed to identify and characterize the [...] Read more.
Proteobacteria use quorum sensing to regulate target gene expression in response to population density. Quorum sensing (QS) is achieved via so-called signalling molecules and the best-studied QS signalling system uses N-acyl homoserine lactones (AHLs). This study aimed to identify and characterize the production of AHLs by a bacterium ND03 isolated from a Malaysian tropical rainforest waterfall. Molecular identification showed that ND03 is a Pantoea sp. closely related to Pantoea rodasii. We used Chromobacterium violaceum CV026, an AHL biosensor for preliminary AHL production screening and then used high resolution triple quadrupole liquid chromatography-mass spectrometry, to confirm that P. rodasii strain ND03 produced N-(3-oxo-hexanoyl)-L-homoserine lactone (3-oxo-C6-HSL). To the best of our knowledge, this is the first report for such a discovery in P. rodasii strain ND03. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle
A Compact Immunoassay Platform Based on a Multicapillary Glass Plate
Sensors 2014, 14(5), 9132-9144; https://doi.org/10.3390/s140509132
Received: 15 April 2014 / Revised: 15 May 2014 / Accepted: 20 May 2014 / Published: 23 May 2014
Cited by 9 | Viewed by 2578 | PDF Full-text (918 KB) | HTML Full-text | XML Full-text
Abstract
A highly sensitive, rapid immunoassay performed in the multi-channels of a micro-well array consisting of a multicapillary glass plate (MCP) and a polydimethylsiloxane (PDMS) slide is described. The micro-dimensions and large surface area of the MCP permitted the diffusion distance to be decreased [...] Read more.
A highly sensitive, rapid immunoassay performed in the multi-channels of a micro-well array consisting of a multicapillary glass plate (MCP) and a polydimethylsiloxane (PDMS) slide is described. The micro-dimensions and large surface area of the MCP permitted the diffusion distance to be decreased and the reaction efficiency to be increased. To confirm the concept of the method, human immunoglobulin A (h-IgA) was measured using both the proposed immunoassay system and the traditional 96-well plate method. The proposed method resulted in a 1/5-fold decrease of immunoassay time, and a 1/56-fold cut in reagent consumption with a 0.05 ng/mL of limit of detection (LOD) for IgA. The method was also applied to saliva samples obtained from healthy volunteers. The results correlated well to those obtained by the 96-well plate method. The method has the potential for use in disease diagnostic or on-site immunoassays. Full article
(This article belongs to the Section Biosensors)
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Open AccessReview
Point-of-care Diagnostic Tools to Detect Circulating MicroRNAS as Biomarkers of Disease
Sensors 2014, 14(5), 9117-9131; https://doi.org/10.3390/s140509117
Received: 26 February 2014 / Revised: 30 April 2014 / Accepted: 4 May 2014 / Published: 22 May 2014
Cited by 13 | Viewed by 2866 | PDF Full-text (356 KB) | HTML Full-text | XML Full-text
Abstract
MicroRNAs or miRNAs are a form of small non-coding RNAs (ncRNAs) of 19–22 nucleotides in length in their mature form. miRNAs are transcribed in the nucleus of all cells from large precursors, many of which have several kilobases in length. Originally identified as [...] Read more.
MicroRNAs or miRNAs are a form of small non-coding RNAs (ncRNAs) of 19–22 nucleotides in length in their mature form. miRNAs are transcribed in the nucleus of all cells from large precursors, many of which have several kilobases in length. Originally identified as intracellular modulators of protein synthesis via posttranscriptional gene silencing, more recently it has been found that miRNAs can travel in extracellular human fluids inside specialized vesicles known as exosomes. We will be referring to this miRNAs as circulating microRNAs. More interestingly, the miRNA content inside exosomes changes during pathological events. In the present review we analyze the literature about circulating miRNAs and their possible use as biomarkers. Furthermore, we explore their future in point-of-care (POC) diagnostics and provide an example of a portable POC apparatus useful in the detection of circulating miRNAs. Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle
A New Method for Ultrasound Detection of Interfacial Position in Gas-Liquid Two-Phase Flow
Sensors 2014, 14(5), 9093-9116; https://doi.org/10.3390/s140509093
Received: 3 December 2013 / Revised: 14 May 2014 / Accepted: 19 May 2014 / Published: 22 May 2014
Cited by 3 | Viewed by 2604 | PDF Full-text (996 KB) | HTML Full-text | XML Full-text
Abstract
Ultrasonic measurement techniques for velocity estimation are currently widely used in fluid flow studies and applications. An accurate determination of interfacial position in gas-liquid two-phase flows is still an open problem. The quality of this information directly reflects on the accuracy of void [...] Read more.
Ultrasonic measurement techniques for velocity estimation are currently widely used in fluid flow studies and applications. An accurate determination of interfacial position in gas-liquid two-phase flows is still an open problem. The quality of this information directly reflects on the accuracy of void fraction measurement, and it provides a means of discriminating velocity information of both phases. The algorithm known as Velocity Matched Spectrum (VM Spectrum) is a velocity estimator that stands out from other methods by returning a spectrum of velocities for each interrogated volume sample. Interface detection of free-rising bubbles in quiescent liquid presents some difficulties for interface detection due to abrupt changes in interface inclination. In this work a method based on velocity spectrum curve shape is used to generate a spatial-temporal mapping, which, after spatial filtering, yields an accurate contour of the air-water interface. It is shown that the proposed technique yields a RMS error between 1.71 and 3.39 and a probability of detection failure and false detection between 0.89% and 11.9% in determining the spatial-temporal gas-liquid interface position in the flow of free rising bubbles in stagnant liquid. This result is valid for both free path and with transducer emitting through a metallic plate or a Plexiglas pipe. Full article
Open AccessArticle
Displacement Parameter Inversion for a Novel Electromagnetic Underground Displacement Sensor
Sensors 2014, 14(5), 9074-9092; https://doi.org/10.3390/s140509074
Received: 7 January 2014 / Revised: 1 May 2014 / Accepted: 9 May 2014 / Published: 22 May 2014
Cited by 1 | Viewed by 2494 | PDF Full-text (486 KB) | HTML Full-text | XML Full-text
Abstract
Underground displacement monitoring is an effective method to explore deep into rock and soil masses for execution of subsurface displacement measurements. It is not only an important means of geological hazards prediction and forecasting, but also a forefront, hot and sophisticated subject in [...] Read more.
Underground displacement monitoring is an effective method to explore deep into rock and soil masses for execution of subsurface displacement measurements. It is not only an important means of geological hazards prediction and forecasting, but also a forefront, hot and sophisticated subject in current geological disaster monitoring. In previous research, the authors had designed a novel electromagnetic underground horizontal displacement sensor (called the H-type sensor) by combining basic electromagnetic induction principles with modern sensing techniques and established a mutual voltage measurement theoretical model called the Equation-based Equivalent Loop Approach (EELA). Based on that work, this paper presents an underground displacement inversion approach named “EELA forward modeling-approximate inversion method”. Combining the EELA forward simulation approach with the approximate optimization inversion theory, it can deduce the underground horizontal displacement through parameter inversion of the H-type sensor. Comprehensive and comparative studies have been conducted between the experimentally measured and theoretically inversed values of horizontal displacement under counterpart conditions. The results show when the measured horizontal displacements are in the 0–100 mm range, the horizontal displacement inversion discrepancy is generally tested to be less than 3 mm under varied tilt angles and initial axial distances conditions, which indicates that our proposed parameter inversion method can predict underground horizontal displacement measurements effectively and robustly for the H-type sensor and the technique is applicable for practical geo-engineering applications. Full article
(This article belongs to the Section Physical Sensors)
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Open AccessArticle
Robust Curb Detection with Fusion of 3D-Lidar and Camera Data
Sensors 2014, 14(5), 9046-9073; https://doi.org/10.3390/s140509046
Received: 12 March 2014 / Revised: 9 May 2014 / Accepted: 16 May 2014 / Published: 21 May 2014
Cited by 14 | Viewed by 3231 | PDF Full-text (14675 KB) | HTML Full-text | XML Full-text
Abstract
Curb detection is an essential component of Autonomous Land Vehicles (ALV), especially important for safe driving in urban environments. In this paper, we propose a fusion-based curb detection method through exploiting 3D-Lidar and camera data. More specifically, we first fuse the sparse 3D-Lidar [...] Read more.
Curb detection is an essential component of Autonomous Land Vehicles (ALV), especially important for safe driving in urban environments. In this paper, we propose a fusion-based curb detection method through exploiting 3D-Lidar and camera data. More specifically, we first fuse the sparse 3D-Lidar points and high-resolution camera images together to recover a dense depth image of the captured scene. Based on the recovered dense depth image, we propose a filter-based method to estimate the normal direction within the image. Then, by using the multi-scale normal patterns based on the curb’s geometric property, curb point features fitting the patterns are detected in the normal image row by row. After that, we construct a Markov Chain to model the consistency of curb points which utilizes the continuous property of the curb, and thus the optimal curb path which links the curb points together can be efficiently estimated by dynamic programming. Finally, we perform post-processing operations to filter the outliers, parameterize the curbs and give the confidence scores on the detected curbs. Extensive evaluations clearly show that our proposed method can detect curbs with strong robustness at real-time speed for both static and dynamic scenes. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Measurement of the D/H, 18O/16O, and 17O/16O Isotope Ratios in Water by Laser Absorption Spectroscopy at 2.73 μm
Sensors 2014, 14(5), 9027-9045; https://doi.org/10.3390/s140509027
Received: 1 March 2014 / Revised: 12 May 2014 / Accepted: 15 May 2014 / Published: 21 May 2014
Cited by 3 | Viewed by 2852 | PDF Full-text (883 KB) | HTML Full-text | XML Full-text
Abstract
A compact isotope ratio laser spectrometry (IRLS) instrument was developed for simultaneous measurements of the D/H, 18O/16O and 17O/16O isotope ratios in water by laser absorption spectroscopy at 2.73 μm. Special attention is paid to the spectral [...] Read more.
A compact isotope ratio laser spectrometry (IRLS) instrument was developed for simultaneous measurements of the D/H, 18O/16O and 17O/16O isotope ratios in water by laser absorption spectroscopy at 2.73 μm. Special attention is paid to the spectral data processing and implementation of a Kalman adaptive filtering to improve the measurement precision. Reduction of up to 3-fold in standard deviation in isotope ratio determination was obtained by the use of a Fourier filtering to remove undulation structure from spectrum baseline. Application of Kalman filtering enables isotope ratio measurement at 1 s time intervals with a precision (<1‰) better than that obtained by conventional 30 s averaging, while maintaining a fast system response. The implementation of the filter is described in detail and its effects on the accuracy and the precision of the isotope ratio measurements are investigated. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Reliable Geographical Forwarding in Cognitive Radio Sensor Networks Using Virtual Clusters
Sensors 2014, 14(5), 8996-9026; https://doi.org/10.3390/s140508996
Received: 14 March 2014 / Revised: 23 April 2014 / Accepted: 7 May 2014 / Published: 21 May 2014
Cited by 10 | Viewed by 2572 | PDF Full-text (2107 KB) | HTML Full-text | XML Full-text
Abstract
The need for implementing reliable data transfer in resource-constrained cognitive radio ad hoc networks is still an open issue in the research community. Although geographical forwarding schemes are characterized by their low overhead and efficiency in reliable data transfer in traditional wireless sensor [...] Read more.
The need for implementing reliable data transfer in resource-constrained cognitive radio ad hoc networks is still an open issue in the research community. Although geographical forwarding schemes are characterized by their low overhead and efficiency in reliable data transfer in traditional wireless sensor network, this potential is still yet to be utilized for viable routing options in resource-constrained cognitive radio ad hoc networks in the presence of lossy links. In this paper, a novel geographical forwarding technique that does not restrict the choice of the next hop to the nodes in the selected route is presented. This is achieved by the creation of virtual clusters based on spectrum correlation from which the next hop choice is made based on link quality. The design maximizes the use of idle listening and receiver contention prioritization for energy efficiency, the avoidance of routing hot spots and stability. The validation result, which closely follows the simulation result, shows that the developed scheme can make more advancement to the sink as against the usual decisions of relevant ad hoc on-demand distance vector route select operations, while ensuring channel quality. Further simulation results have shown the enhanced reliability, lower latency and energy efficiency of the presented scheme. Full article
(This article belongs to the Section Sensor Networks)
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Open AccessReview
Poly (N-isopropylacrylamide) Microgel-Based Optical Devices for Sensing and Biosensing
Sensors 2014, 14(5), 8984-8995; https://doi.org/10.3390/s140508984
Received: 19 March 2014 / Revised: 16 May 2014 / Accepted: 19 May 2014 / Published: 21 May 2014
Cited by 50 | Viewed by 3650 | PDF Full-text (1011 KB) | HTML Full-text | XML Full-text
Abstract
Responsive polymer-based materials have found numerous applications due to their ease of synthesis and the variety of stimuli that they can be made responsive to. In this review, we highlight the group’s efforts utilizing thermoresponsive poly (N-isopropylacrylamide) (pNIPAm) microgel-based optical devices [...] Read more.
Responsive polymer-based materials have found numerous applications due to their ease of synthesis and the variety of stimuli that they can be made responsive to. In this review, we highlight the group’s efforts utilizing thermoresponsive poly (N-isopropylacrylamide) (pNIPAm) microgel-based optical devices for various sensing and biosensing applications. Full article
(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)
Open AccessArticle
A Ubiquitous and Low-Cost Solution for Movement Monitoring and Accident Detection Based on Sensor Fusion
Sensors 2014, 14(5), 8961-8983; https://doi.org/10.3390/s140508961
Received: 7 April 2014 / Revised: 14 May 2014 / Accepted: 15 May 2014 / Published: 21 May 2014
Cited by 21 | Viewed by 2992 | PDF Full-text (678 KB) | HTML Full-text | XML Full-text
Abstract
The low average birth rate in developed countries and the increase in life expectancy have lead society to face for the first time an ageing situation. This situation associated with the World’s economic crisis (which started in 2008) forces the need of equating [...] Read more.
The low average birth rate in developed countries and the increase in life expectancy have lead society to face for the first time an ageing situation. This situation associated with the World’s economic crisis (which started in 2008) forces the need of equating better and more efficient ways of providing more quality of life for the elderly. In this context, the solution presented in this work proposes to tackle the problem of monitoring the elderly in a way that is not restrictive for the life of the monitored, avoiding the need for premature nursing home admissions. To this end, the system uses the fusion of sensory data provided by a network of wireless sensors placed on the periphery of the user. Our approach was also designed with a low-cost deployment in mind, so that the target group may be as wide as possible. Regarding the detection of long-term problems, the tests conducted showed that the precision of the system in identifying and discerning body postures and body movements allows for a valid monitorization and rehabilitation of the user. Moreover, concerning the detection of accidents, while the proposed solution presented a near 100% precision at detecting normal falls, the detection of more complex falls (i.e., hampered falls) will require further study. Full article
(This article belongs to the Special Issue Sensors Data Fusion for Healthcare)
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Open AccessArticle
Nanosized Thin SnO2 Layers Doped with Te and TeO2 as Room Temperature Humidity Sensors
Sensors 2014, 14(5), 8950-8960; https://doi.org/10.3390/s140508950
Received: 2 April 2014 / Revised: 7 May 2014 / Accepted: 14 May 2014 / Published: 21 May 2014
Cited by 5 | Viewed by 2263 | PDF Full-text (425 KB) | HTML Full-text | XML Full-text
Abstract
In this paper the humidity sensing properties of layers prepared by a new method for obtaining doped tin oxide are studied. Different techniques—SEM, EDS in SEM, TEM, SAED, AES and electrical measurements—are used for detailed characterization of the thin layers. The as-deposited layers [...] Read more.
In this paper the humidity sensing properties of layers prepared by a new method for obtaining doped tin oxide are studied. Different techniques—SEM, EDS in SEM, TEM, SAED, AES and electrical measurements—are used for detailed characterization of the thin layers. The as-deposited layers are amorphous with great specific area and low density. They are built up of a fine grained matrix, consisting of Sn- and Te-oxides, and a nanosized dispersed phase of Te, Sn and/or SnTe. The chemical composition of both the matrix and the nanosized particles depends on the ratio RSn/Te and the evaporation conditions. It is shown that as-deposited layers with RSn/Te ranging from 0.4 to 0.9 exhibit excellent characteristics as humidity sensors operating at room temperature—very high sensitivity, good selectivity, fast response and short recovery period. Ageing tests have shown that the layers possess good long-term stability. Results obtained regarding the type of the water adsorption on the layers’ surface help better understand the relation between preparation conditions, structure, composition and humidity sensing properties. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Unusual Multiple Production of N-Acylhomoserine Lactones a by Burkholderia sp. Strain C10B Isolated from Dentine Caries
Sensors 2014, 14(5), 8940-8949; https://doi.org/10.3390/s140508940
Received: 18 April 2014 / Revised: 4 May 2014 / Accepted: 13 May 2014 / Published: 21 May 2014
Cited by 2 | Viewed by 2281 | PDF Full-text (301 KB) | HTML Full-text | XML Full-text
Abstract
Bacteria realize the ability to communicate by production of quorum sensing (QS) molecules called autoinducers, which regulate the physiological activities in their ecological niches. The oral cavity could be a potential area for the presence of QS bacteria. In this study, we report [...] Read more.
Bacteria realize the ability to communicate by production of quorum sensing (QS) molecules called autoinducers, which regulate the physiological activities in their ecological niches. The oral cavity could be a potential area for the presence of QS bacteria. In this study, we report the isolation of a QS bacterial isolate C10B from dentine caries. Preliminary screening using Chromobacterium violaceum CV026 biosensor showed that isolate C10B was able to produce N-acylhomoserine lactones (AHLs). This bacterium was further identified as a member of Burkholderia, an opportunistic pathogen. The isolated Burkholderia sp. was confirmed to produce N-hexanoyl-L-homoserine lactone (C6-HSL), N-octanoyl-L-homoserine lactone (C8-HSL), N-decanoyl-L-homoserine lactone (C10-HSL) and N-dodecanoyl-L-homoserine lactone (C12-HSL). Full article
(This article belongs to the Section Biosensors)
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Open AccessArticle
Electrochemical Detection of p-Aminophenol by Flexible Devices Based on Multi-Wall Carbon Nanotubes Dispersed in Electrochemically Modified Nafion
Sensors 2014, 14(5), 8926-8939; https://doi.org/10.3390/s140508926
Received: 24 February 2014 / Revised: 12 May 2014 / Accepted: 14 May 2014 / Published: 21 May 2014
Cited by 16 | Viewed by 2875 | PDF Full-text (1019 KB) | HTML Full-text | XML Full-text
Abstract
A conducting composite prepared by dispersing multi-walled carbon nanotubes (MWCNTs) into a host matrix consisting of Nafion, electrochemically doped with copper, has been prepared, characterized and used to modify one of the gold electrodes of simply designed electrochemical cells having copier grade transparency [...] Read more.
A conducting composite prepared by dispersing multi-walled carbon nanotubes (MWCNTs) into a host matrix consisting of Nafion, electrochemically doped with copper, has been prepared, characterized and used to modify one of the gold electrodes of simply designed electrochemical cells having copier grade transparency sheets as substrates. Electrical measurements performed in deionized water show that the Au/Nafion/Au-MWCNTs–Nafion:Cu cells can be successfully used in order to detect the presence of p-aminophenol (PAP) in water, without the need for any supporting electrolyte. The intensity of the redox peaks arising when PAP is added to deionized water is found to be linearly related to the analyte in the range from 0.2 to 1.6 µM, with a detection limit of 90 nM and a sensitivity of 7 µA·(µM−1)·cm−2. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle
A Vision-Based System for Intelligent Monitoring: Human Behaviour Analysis and Privacy by Context
Sensors 2014, 14(5), 8895-8925; https://doi.org/10.3390/s140508895
Received: 11 March 2014 / Revised: 23 April 2014 / Accepted: 6 May 2014 / Published: 20 May 2014
Cited by 40 | Viewed by 4599 | PDF Full-text (2836 KB) | HTML Full-text | XML Full-text
Abstract
Due to progress and demographic change, society is facing a crucial challenge related to increased life expectancy and a higher number of people in situations of dependency. As a consequence, there exists a significant demand for support systems for personal autonomy. This article [...] Read more.
Due to progress and demographic change, society is facing a crucial challenge related to increased life expectancy and a higher number of people in situations of dependency. As a consequence, there exists a significant demand for support systems for personal autonomy. This article outlines the [email protected] project, whose goal is to extend independent living at home for elderly and impaired people, providing care and safety services by means of vision-based monitoring. Different kinds of ambient-assisted living services are supported, from the detection of home accidents, to telecare services. In this contribution, the specification of the system is presented, and novel contributions are made regarding human behaviour analysis and privacy protection. By means of a multi-view setup of cameras, people’s behaviour is recognised based on human action recognition. For this purpose, a weighted feature fusion scheme is proposed to learn from multiple views. In order to protect the right to privacy of the inhabitants when a remote connection occurs, a privacy-by-context method is proposed. The experimental results of the behaviour recognition method show an outstanding performance, as well as support for multi-view scenarios and real-time execution, which are required in order to provide the proposed services. Full article
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Open AccessArticle
A Multispectral Photon-Counting Double Random Phase Encoding Scheme for Image Authentication
Sensors 2014, 14(5), 8877-8894; https://doi.org/10.3390/s140508877
Received: 19 February 2014 / Revised: 13 May 2014 / Accepted: 15 May 2014 / Published: 20 May 2014
Cited by 18 | Viewed by 2271 | PDF Full-text (994 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we propose a new method for color image-based authentication that combines multispectral photon-counting imaging (MPCI) and double random phase encoding (DRPE) schemes. The sparsely distributed information from MPCI and the stationary white noise signal from DRPE make intruder attacks difficult. [...] Read more.
In this paper, we propose a new method for color image-based authentication that combines multispectral photon-counting imaging (MPCI) and double random phase encoding (DRPE) schemes. The sparsely distributed information from MPCI and the stationary white noise signal from DRPE make intruder attacks difficult. In this authentication method, the original multispectral RGB color image is down-sampled into a Bayer image. The three types of color samples (red, green and blue color) in the Bayer image are encrypted with DRPE and the amplitude part of the resulting image is photon counted. The corresponding phase information that has nonzero amplitude after photon counting is then kept for decryption. Experimental results show that the retrieved images from the proposed method do not visually resemble their original counterparts. Nevertheless, the original color image can be efficiently verified with statistical nonlinear correlations. Our experimental results also show that different interpolation algorithms applied to Bayer images result in different verification effects for multispectral RGB color images. Full article
(This article belongs to the Section Physical Sensors)
Open AccessArticle
Quantitative Analysis of Staphylococcus Enterotoxin A by Differential Expression of IFN-γ in Splenocyte and CD4+ T-Cells
Sensors 2014, 14(5), 8869-8876; https://doi.org/10.3390/s140508869
Received: 28 March 2014 / Revised: 15 May 2014 / Accepted: 15 May 2014 / Published: 20 May 2014
Cited by 4 | Viewed by 2098 | PDF Full-text (399 KB) | HTML Full-text | XML Full-text
Abstract
Staphylococcus aureus is an important bacterial pathogen that produces a range of Staphylococcal Enterotoxins (SEs) which cause gastroenteritis and superantigen activation of T cells, the mechanism of which is not well understood. The ability to rapidly detect and quantify SEs is very important [...] Read more.
Staphylococcus aureus is an important bacterial pathogen that produces a range of Staphylococcal Enterotoxins (SEs) which cause gastroenteritis and superantigen activation of T cells, the mechanism of which is not well understood. The ability to rapidly detect and quantify SEs is very important in order to learn the causes of staphylococcal outbreaks and to stop similar outbreaks in the future. Enzyme-linked immunosorbent assays (ELISAs) have been developed for detection of several SEs. However, these immunological methods cannot distinguish between active and inactive toxin. It is known that interferon-gamma (IFN-γ) expressed in response to stimulation by SEs contributes significantly to the pathogenesis of S. aureus infection. Nonetheless, the cellular source of IFN-γ is still unclear and the contributions of the specific splenocyte types. In our effort to understand the immunologic response to Staphylococcal Enterotoxin A (SEA) exposure, we studied IFN-γ production in mouse splenocytes. We demonstrated that short term ex vivo exposure of splenocytes or primary naïve CD4+ T-cells to biologically active SEA induces differential expression of IFN-γ mRNA in a time and dose dependent manner and the expression levels reflect the levels of IFN-γ secreted protein. Positive isolated CD4+ T-cells accounted for only 10% of IFN-γ production. We also demonstrate that expression of IFN-γ can be used for rapid quantitative analysis of active SEA with a detection limit of 1 ng/mL. Full article
(This article belongs to the Special Issue Live Cell-Based Sensors with Receptors)
Open AccessArticle
An Optimal Current Observer for Predictive Current Controlled Buck DC-DC Converters
Sensors 2014, 14(5), 8851-8868; https://doi.org/10.3390/s140508851
Received: 16 March 2014 / Revised: 9 May 2014 / Accepted: 12 May 2014 / Published: 19 May 2014
Cited by 3 | Viewed by 2640 | PDF Full-text (1289 KB) | HTML Full-text | XML Full-text
Abstract
In digital current mode controlled DC-DC converters, conventional current sensors might not provide isolation at a minimized price, power loss and size. Therefore, a current observer which can be realized based on the digital circuit itself, is a possible substitute. However, the observed [...] Read more.
In digital current mode controlled DC-DC converters, conventional current sensors might not provide isolation at a minimized price, power loss and size. Therefore, a current observer which can be realized based on the digital circuit itself, is a possible substitute. However, the observed current may diverge due to the parasitic resistors and the forward conduction voltage of the diode. Moreover, the divergence of the observed current will cause steady state errors in the output voltage. In this paper, an optimal current observer is proposed. It achieves the highest observation accuracy by compensating for all the known parasitic parameters. By employing the optimal current observer-based predictive current controller, a buck converter is implemented. The converter has a convergently and accurately observed inductor current, and shows preferable transient response than the conventional voltage mode controlled converter. Besides, costs, power loss and size are minimized since the strategy requires no additional hardware for current sensing. The effectiveness of the proposed optimal current observer is demonstrated experimentally. Full article
Open AccessArticle
Functionality Enhancement of Industrialized Optical Fiber Sensors and System Developed for Full-Scale Pavement Monitoring
Sensors 2014, 14(5), 8829-8850; https://doi.org/10.3390/s140508829
Received: 30 December 2013 / Revised: 1 May 2014 / Accepted: 5 May 2014 / Published: 19 May 2014
Cited by 14 | Viewed by 2760 | PDF Full-text (1131 KB) | HTML Full-text | XML Full-text
Abstract
Pavements always play a predominant role in transportation. Health monitoring of pavements is becoming more and more significant, as frequently suffering from cracks, rutting, and slippage renders them prematurely out of service. Effective and reliable sensing elements are thus in high demand to [...] Read more.
Pavements always play a predominant role in transportation. Health monitoring of pavements is becoming more and more significant, as frequently suffering from cracks, rutting, and slippage renders them prematurely out of service. Effective and reliable sensing elements are thus in high demand to make prognosis on the mechanical properties and occurrence of damage to pavements. Therefore, in this paper, various types of functionality enhancement of industrialized optical fiber sensors for pavement monitoring are developed, with the corresponding operational principles clarified in theory and the performance double checked by basic experiments. Furthermore, a self-healing optical fiber sensing network system is adopted to accomplish full-scale monitoring of pavements. The application of optical fiber sensors assembly and self-healing network system in pavement has been carried out to validate the feasibility. It has been proved that the research in this article provides a valuable method and meaningful guidance for the integrity monitoring of civil structures, especially pavements. Full article
(This article belongs to the Special Issue Photonic Sensors for Industrial, Environmental and Health Monitoring)
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Open AccessLetter
Ultrasonic Lens Based on a Subwavelength Slit Surrounded by Grooves
Sensors 2014, 14(5), 8821-8828; https://doi.org/10.3390/s140508821
Received: 10 April 2014 / Revised: 7 May 2014 / Accepted: 15 May 2014 / Published: 19 May 2014
Cited by 3 | Viewed by 2275 | PDF Full-text (405 KB) | HTML Full-text | XML Full-text
Abstract
The lensing capabilities of a single subwavelength slit surrounded by a finite array of grooves milled into a brass plate is presented. The modulation of the beam intensity of this ultrasonic lens can be adjusted by varying the groove depth. Numerical simulations as [...] Read more.
The lensing capabilities of a single subwavelength slit surrounded by a finite array of grooves milled into a brass plate is presented. The modulation of the beam intensity of this ultrasonic lens can be adjusted by varying the groove depth. Numerical simulations as well as experimental validations at 290 kHz are shown. The experimental results are in good agreement with the numerical simulations. This system is believed to have potential applications for medical ultrasound fields such as tomography and therapy. Full article
Open AccessArticle
A SAW-Based Chemical Sensor for Detecting Sulfur-Containing Organophosphorus Compounds Using a Two-Step Self-Assembly and Molecular Imprinting Technology
Sensors 2014, 14(5), 8810-8820; https://doi.org/10.3390/s140508810
Received: 19 February 2014 / Revised: 28 April 2014 / Accepted: 13 May 2014 / Published: 19 May 2014
Cited by 6 | Viewed by 2715 | PDF Full-text (535 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a new effective approach for the sensitive film deposition of surface acoustic wave (SAW) chemical sensors for detecting organophosphorus compounds such as O-ethyl-S-2-diisopropylaminoethyl methylphosphonothiolate (VX) containing sulfur at extremely low concentrations. To improve the adsorptive efficiency, a two-step technology is [...] Read more.
This paper presents a new effective approach for the sensitive film deposition of surface acoustic wave (SAW) chemical sensors for detecting organophosphorus compounds such as O-ethyl-S-2-diisopropylaminoethyl methylphosphonothiolate (VX) containing sulfur at extremely low concentrations. To improve the adsorptive efficiency, a two-step technology is proposed for the sensitive film preparation on the SAW delay line utilizing gold electrodes. First, mono[6-deoxy-6-[(mercaptodecamethylene)thio]]-β-cyclodextrin is chosen as the sensitive material for VX detection, and a ~2 nm-thick monolayer is formed on the SAW delay line by the binding of Au-S. This material is then analyzed by atomic force microscopy (AFM). Second, the VX molecule is used as the template for molecular imprinting. The template is then removed by washing the delay line with ethanol and distilled water, thereby producing the sensitive and selective material for VX detection. The performance of the developed SAW sensor is evaluated, and results show high sensitivity, low detection limit, and good linearity within the VX concentration of 0.15–5.8 mg/m3. The possible interactions between the film and VX are further discussed. Full article
(This article belongs to the Special Issue Biomimetic Receptors and Sensors)
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