Sensors

304 KiB

Open AccessArticle

A Compact Optical Instrument with Artificial Neural Network for pH Determination

by Sonia Capel-Cuevas, Nuria López-Ruiz, Antonio Martinez-Olmos, Manuel P. Cuéllar, Maria Del Carmen Pegalajar, Alberto José Palma, Ignacio De Orbe-Payá and Luis Fermin Capitán-Vallvey

Sensors 2012, 12(5), 6746-6763; https://doi.org/10.3390/s120506746 - 22 May 2012

Cited by 11 | Viewed by 7733

Abstract

The aim of this work was the determination of pH with a sensor array-based optical portable instrument. This sensor array consists of eleven membranes with selective colour changes at different pH intervals. The method for the pH calculation is based on the implementation [...] Read more.

The aim of this work was the determination of pH with a sensor array-based optical portable instrument. This sensor array consists of eleven membranes with selective colour changes at different pH intervals. The method for the pH calculation is based on the implementation of artificial neural networks that use the responses of the membranes to generate a final pH value. A multi-objective algorithm was used to select the minimum number of sensing elements required to achieve an accurate pH determination from the neural network, and also to minimise the network size. This helps to minimise instrument and array development costs and save on microprocessor energy consumption. A set of artificial neural networks that fulfils these requirements is proposed using different combinations of the membranes in the sensor array, and is evaluated in terms of accuracy and reliability. In the end, the network including the response of the eleven membranes in the sensor was selected for validation in the instrument prototype because of its high accuracy. The performance of the instrument was evaluated by measuring the pH of a large set of real samples, showing that high precision can be obtained in the full range. Full article

(This article belongs to the Section Chemical Sensors)

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384 KiB

Open AccessArticle

Development of a Voice Activity Controlled Noise Canceller

by Ali O. Abid Noor, Salina Abdul Samad and Aini Hussain

Sensors 2012, 12(5), 6727-6745; https://doi.org/10.3390/s120506727 - 22 May 2012

Cited by 4 | Viewed by 7870

Abstract

In this paper, a variable threshold voice activity detector (VAD) is developed to control the operation of a two-sensor adaptive noise canceller (ANC). The VAD prohibits the reference input of the ANC from containing some strength of actual speech signal during adaptation periods. [...] Read more.

In this paper, a variable threshold voice activity detector (VAD) is developed to control the operation of a two-sensor adaptive noise canceller (ANC). The VAD prohibits the reference input of the ANC from containing some strength of actual speech signal during adaptation periods. The novelty of this approach resides in using the residual output from the noise canceller to control the decisions made by the VAD. Thresholds of full-band energy and zero-crossing features are adjusted according to the residual output of the adaptive filter. Performance evaluation of the proposed approach is quoted in terms of signal to noise ratio improvements as well mean square error (MSE) convergence of the ANC. The new approach showed an improved noise cancellation performance when tested under several types of environmental noise. Furthermore, the computational power of the adaptive process is reduced since the output of the adaptive filter is efficiently calculated only during non-speech periods. Full article

(This article belongs to the Section Physical Sensors)

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852 KiB

Open AccessArticle

Blurred Star Image Processing for Star Sensors under Dynamic Conditions

by Weina Zhang, Wei Quan and Lei Guo

Sensors 2012, 12(5), 6712-6726; https://doi.org/10.3390/s120506712 - 22 May 2012

Cited by 72 | Viewed by 8762

Abstract

The precision of star point location is significant to identify the star map and to acquire the aircraft attitude for star sensors. Under dynamic conditions, star images are not only corrupted by various noises, but also blurred due to the angular rate of [...] Read more.

The precision of star point location is significant to identify the star map and to acquire the aircraft attitude for star sensors. Under dynamic conditions, star images are not only corrupted by various noises, but also blurred due to the angular rate of the star sensor. According to different angular rates under dynamic conditions, a novel method is proposed in this article, which includes a denoising method based on adaptive wavelet threshold and a restoration method based on the large angular rate. The adaptive threshold is adopted for denoising the star image when the angular rate is in the dynamic range. Then, the mathematical model of motion blur is deduced so as to restore the blurred star map due to large angular rate. Simulation results validate the effectiveness of the proposed method, which is suitable for blurred star image processing and practical for attitude determination of satellites under dynamic conditions. Full article

(This article belongs to the Section Physical Sensors)

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1262 KiB

Open AccessArticle

Categorization of Indoor Places Using the Kinect Sensor

by Oscar Martinez Mozos, Hitoshi Mizutani, Ryo Kurazume and Tsutomu Hasegawa

Sensors 2012, 12(5), 6695-6711; https://doi.org/10.3390/s120506695 - 22 May 2012

Cited by 48 | Viewed by 9034

Abstract

The categorization of places in indoor environments is an important capability for service robots working and interacting with humans. In this paper we present a method to categorize different areas in indoor environments using a mobile robot equipped with a Kinect camera. Our [...] Read more.

The categorization of places in indoor environments is an important capability for service robots working and interacting with humans. In this paper we present a method to categorize different areas in indoor environments using a mobile robot equipped with a Kinect camera. Our approach transforms depth and grey scale images taken at each place into histograms of local binary patterns (LBPs) whose dimensionality is further reduced following a uniform criterion. The histograms are then combined into a single feature vector which is categorized using a supervised method. In this work we compare the performance of support vector machines and random forests as supervised classifiers. Finally, we apply our technique to distinguish five different place categories: corridors, laboratories, offices, kitchens, and study rooms. Experimental results show that we can categorize these places with high accuracy using our approach. Full article

(This article belongs to the Section Physical Sensors)

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Graphical abstract

1738 KiB

Open AccessArticle

Flexible Graphite-on-Paper Piezoresistive Sensors

by Tian-Ling Ren, He Tian, Dan Xie and Yi Yang

Sensors 2012, 12(5), 6685-6694; https://doi.org/10.3390/s120506685 - 22 May 2012

Cited by 89 | Viewed by 16057

Abstract

We demonstrate novel graphite-on-paper piezoresistive devices. The graphite was used as sensing component. The fabrication process can be finished in a short time with simple tools (e.g., a scissor and a pencil). A small array of six paper-based piezoresistive devices is made. The [...] Read more.

We demonstrate novel graphite-on-paper piezoresistive devices. The graphite was used as sensing component. The fabrication process can be finished in a short time with simple tools (e.g., a scissor and a pencil). A small array of six paper-based piezoresistive devices is made. The whole device is flexible. The test results showed that the change of resistance was proportional to the applied force. A paper-based weighing balance was also made as an example of applications. This novel array of paper-based piezoresistive devices will open wide applications in force and acceleration sensing areas. Full article

(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)

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Graphical abstract

992 KiB

Open AccessArticle

Tip-Jump Response of an Amplitude-Modulated Atomic Force Microscope

by Po-Jen Shih

Sensors 2012, 12(5), 6666-6684; https://doi.org/10.3390/s120506666 - 22 May 2012

Cited by 6 | Viewed by 5998

Abstract

The dynamic behaviors of an Atomic Force Microscope are of interest, and variously unpredictable phenomena are experimentally measured. In practical measurements, researchers have proposed many methods for avoiding these uncertainties. However, causes of these phenomena are still hard to demonstrate in simulation. To [...] Read more.

The dynamic behaviors of an Atomic Force Microscope are of interest, and variously unpredictable phenomena are experimentally measured. In practical measurements, researchers have proposed many methods for avoiding these uncertainties. However, causes of these phenomena are still hard to demonstrate in simulation. To demonstrate these phenomena, this paper claims the tip-jump motion is a predictable process, and the jumping kinetic energy results in different nonlinear phenomena. It emphasizes the variation in the eigenvalues of an AFM with tip-sample distance. This requirement ensures the phase transformations from one associated with the oscillation mode to one associated with the tip-jump/sample-contact mode. Also, multi-modal analysis was utilized to ensure the modal transformation in varying tip-sample distances. In the presented model, oscillations with various tip-sample distances and with various excitation frequencies and amplitudes were compared. The results reveal that the tip-jump motion separates the oscillation orbit into two regions, and the jumping kinetic energy, comparing with the superficial potential energy, leads the oscillation to be bistable or intermittent. The sample-contact condition associates to bifurcation and chaos. Additionally, the jumping is a strong motion that occurrs before the tip-sample contacts, and this motion signal can replace the sample-contact-signal to avoid destroying the sample. Full article

(This article belongs to the Section Physical Sensors)

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339 KiB

Open AccessReview

Detection of AI-2 Receptors in Genomes of Enterobacteriaceae Suggests a Role of Type-2 Quorum Sensing in Closed Ecosystems

by Fabio Rezzonico, Theo H. M. Smits and Brion Duffy

Sensors 2012, 12(5), 6645-6665; https://doi.org/10.3390/s120506645 - 21 May 2012

Cited by 48 | Viewed by 11601

Abstract

The LuxS enzyme, an S-ribosyl-homocysteine lyase, catalyzes the production of the signal precursor for autoinducer-2 mediated quorum sensing (QS-2) in Vibrio. Its widespread occurrence among bacteria is often considered the evidence for a universal language for interspecies communication. Presence of the luxS [...] Read more.

The LuxS enzyme, an S-ribosyl-homocysteine lyase, catalyzes the production of the signal precursor for autoinducer-2 mediated quorum sensing (QS-2) in Vibrio. Its widespread occurrence among bacteria is often considered the evidence for a universal language for interspecies communication. Presence of the luxS gene and production of the autoinducer-2 (AI-2) signal have repeatedly been the only evidences presented to assign a functional QS-2 to the most diverse species. In fact, LuxS has a primary metabolic role as part of the activated methyl cycle. In this review we have analyzed the distribution of QS-2 related genes in Enterobacteriaceae by moving the focus of the investigation from AI-2 production to the detection of potential AI-2 receptors. The latter are common in pathogens or endosymbionts of animals, but were also found in a limited number of Enterobacteriaceae of the genera Enterobacter, Klebsiella, and Pantoea that live in close association with plants or fungi. Although a precise function of QS-2 in these species has not been identified, they all show an endophytic or endosymbiontic lifestyle that suggests a role of type-2 quorum sensing in the adaptation to closed ecosystems. Full article

(This article belongs to the Special Issue Microbial Quorum Sensing: Linking the Outside World to Microbial Behaviour)

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525 KiB

Open AccessArticle

Dynamic Structural Health Monitoring of Slender Structures Using Optical Sensors

by Paulo Antunes, Rui Travanca, Hugo Rodrigues, José Melo, José Jara, Humberto Varum and Paulo André

Sensors 2012, 12(5), 6629-6644; https://doi.org/10.3390/s120506629 - 18 May 2012

Cited by 24 | Viewed by 9530

Abstract

In this paper we summarize the research activities at the Instituto de Telecomunicações—Pólo de Aveiro and University of Aveiro, in the field of fiber Bragg grating based sensors and their applications in dynamic measurements for Structural Health Monitoring of slender structures such as [...] Read more.

In this paper we summarize the research activities at the Instituto de Telecomunicações—Pólo de Aveiro and University of Aveiro, in the field of fiber Bragg grating based sensors and their applications in dynamic measurements for Structural Health Monitoring of slender structures such as towers. In this work we describe the implementation of an optical biaxial accelerometer based on fiber Bragg gratings inscribed on optical fibers. The proof-of-concept was done with the dynamic monitoring of a reinforced concrete structure and a slender metallic telecommunication tower. Those structures were found to be suitable to demonstrate the feasibility of FBG accelerometers to obtain the structures’ natural frequencies, which are the key parameters in Structural Health Monitoring and in the calibration of numerical models used to simulate the structure behavior. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Portugal)

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754 KiB

Open AccessArticle

Energy Performance Assessment of Virtualization Technologies Using Small Environmental Monitoring Sensors

by Lu Liu, Osama Masfary and Nick Antonopoulos

Sensors 2012, 12(5), 6610-6628; https://doi.org/10.3390/s120506610 - 18 May 2012

Cited by 20 | Viewed by 9565

Abstract

The increasing trends of electrical consumption within data centres are a growing concern for business owners as they are quickly becoming a large fraction of the total cost of ownership. Ultra small sensors could be deployed within a data centre to monitor environmental [...] Read more.

The increasing trends of electrical consumption within data centres are a growing concern for business owners as they are quickly becoming a large fraction of the total cost of ownership. Ultra small sensors could be deployed within a data centre to monitor environmental factors to lower the electrical costs and improve the energy efficiency. Since servers and air conditioners represent the top users of electrical power in the data centre, this research sets out to explore methods from each subsystem of the data centre as part of an overall energy efficient solution. In this paper, we investigate the current trends of Green IT awareness and how the deployment of small environmental sensors and Site Infrastructure equipment optimization techniques which can offer a solution to a global issue by reducing carbon emissions. Full article

(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)

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1340 KiB

Open AccessArticle

IVAN: Intelligent Van for the Distribution of Pharmaceutical Drugs

by Asier Moreno, Ignacio Angulo, Asier Perallos, Hugo Landaluce, Ignacio Julio García Zuazola, Leire Azpilicueta, José Javier Astrain, Francisco Falcone and Jesús Villadangos

Sensors 2012, 12(5), 6587-6609; https://doi.org/10.3390/s120506587 - 18 May 2012

Cited by 25 | Viewed by 9074

Abstract

This paper describes a telematic system based on an intelligent van which is capable of tracing pharmaceutical drugs over delivery routes from a warehouse to pharmacies, without altering carriers’ daily conventional tasks. The intelligent van understands its environment, taking into account its location, [...] Read more.

This paper describes a telematic system based on an intelligent van which is capable of tracing pharmaceutical drugs over delivery routes from a warehouse to pharmacies, without altering carriers’ daily conventional tasks. The intelligent van understands its environment, taking into account its location, the assets and the predefined delivery route; with the capability of reporting incidences to carriers in case of failure according to the established distribution plan. It is a non-intrusive solution which represents a successful experience of using smart environments and an optimized Radio Frequency Identification (RFID) embedded system in a viable way to resolve a real industrial need in the pharmaceutical industry. The combination of deterministic modeling of the indoor vehicle, the implementation of an ad-hoc radiating element and an agile software platform within an overall system architecture leads to a competitive, flexible and scalable solution. Full article

(This article belongs to the Special Issue Select papers from UCAmI 2011 - the 5th International Symposium on Ubiquitous Computing and Ambient Intelligence (UCAmI'11))

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322 KiB

Open AccessReview

A Critical Review of Published Data on the Gas Temperature and the Electron Density in the Electrolyte Cathode Atmospheric Glow Discharges

by Pál Mezei and Tamás Cserfalvi

Sensors 2012, 12(5), 6576-6586; https://doi.org/10.3390/s120506576 - 18 May 2012

Cited by 38 | Viewed by 6848

Abstract

Electrolyte Cathode Discharge (ELCAD) spectrometry, a novel sensitive multielement direct analytical method for metal traces in aqueous solutions, was introduced in 1993 as a new sensing principle. Since then several works have tried to develop an operational mechanism for this exotic atmospheric glow [...] Read more.

Electrolyte Cathode Discharge (ELCAD) spectrometry, a novel sensitive multielement direct analytical method for metal traces in aqueous solutions, was introduced in 1993 as a new sensing principle. Since then several works have tried to develop an operational mechanism for this exotic atmospheric glow plasma technique, however these attempts cannot be combined into a valid model description. In this review we summarize the conceptual and technical problems we found in this upcoming research field of direct sensors. The T_G gas temperature and the n_e electron density values published up to now for ELCAD are very confusing. These data were evaluated by three conditions. The first is the gas composition of the ELCAD plasma, since T_G was determined from the emitted intensity of the N₂ and OH bands. Secondly, since the ELCAD is an atmospheric glow discharge, thus, the obtained T_G has to be close to the T_e electron temperature. This can be used for the mutual validation of the received temperature data. Thirdly, as a consequence of the second condition, the values of T_G and n_e have to agree with the Engel-Brown approximation of the Saha-equation related to weakly ionized glow discharge plasmas. Application of non-adequate experimental methods and theoretical treatment leads to unreliable descriptions which cannot be used to optimize the detector performance. Full article

(This article belongs to the Section Chemical Sensors)

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2331 KiB

Open AccessArticle

Architecture for Improving Terrestrial Logistics Based on the Web of Things

by Miguel Castro, Antonio J. Jara and Antonio Skarmeta

Sensors 2012, 12(5), 6538-6575; https://doi.org/10.3390/s120506538 - 18 May 2012

Cited by 16 | Viewed by 9139

Abstract

Technological advances for improving supply chain efficiency present three key challenges for managing goods: tracking, tracing and monitoring (TTM), in order to satisfy the requirements for products such as perishable goods where the European Legislations requires them to ship within a prescribed temperature [...] Read more.

Technological advances for improving supply chain efficiency present three key challenges for managing goods: tracking, tracing and monitoring (TTM), in order to satisfy the requirements for products such as perishable goods where the European Legislations requires them to ship within a prescribed temperature range to ensure freshness and suitability for consumption. The proposed system integrates RFID for tracking and tracing through a distributed architecture developed for heavy goods vehicles, and the sensors embedded in the SunSPOT platform for monitoring the goods transported based on the concept of the Internet of Things. This paper presents how the Internet of Things is integrated for improving terrestrial logistics offering a comprehensive and flexible architecture, with high scalability, according to the specific needs for reaching an item-level continuous monitoring solution. The major contribution from this work is the optimization of the Embedded Web Services based on RESTful (Web of Things) for the access to TTM services at any time during the transportation of goods. Specifically, it has been extended the monitoring patterns such as observe and blockwise transfer for the requirements from the continuous conditional monitoring, and for the transfer of full inventories and partial ones based on conditional queries. In definitive, this work presents an evolution of the previous TTM solutions, which were limited to trailer identification and environment monitoring, to a solution which is able to provide an exhaustive item-level monitoring, required for several use cases. This exhaustive monitoring has required new communication capabilities through the Web of Things, which has been optimized with the use and improvement of a set of communications patterns. Full article

(This article belongs to the Special Issue Select papers from UCAmI 2011 - the 5th International Symposium on Ubiquitous Computing and Ambient Intelligence (UCAmI'11))

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660 KiB

Open AccessArticle

Electrochemical Detection of Anti-Breast-Cancer Agents in Human Serum by Cytochrome P450-Coated Carbon Nanotubes

by Camilla Baj-Rossi, Giovanni De Micheli and Sandro Carrara

Sensors 2012, 12(5), 6520-6537; https://doi.org/10.3390/s120506520 - 18 May 2012

Cited by 85 | Viewed by 9564

Abstract

We report on the electrochemical detection of anti-cancer drugs in human serum with sensitivity values in the range of 8–925 nA/µM. Multi-walled carbon nanotubes were functionalized with three different cytochrome P450 isoforms (CYP1A2, CYP2B6, and CYP3A4). A model used to effectively describe the [...] Read more.

We report on the electrochemical detection of anti-cancer drugs in human serum with sensitivity values in the range of 8–925 nA/µM. Multi-walled carbon nanotubes were functionalized with three different cytochrome P450 isoforms (CYP1A2, CYP2B6, and CYP3A4). A model used to effectively describe the cytochrome P450 deposition onto carbon nanotubes was confirmed by Monte Carlo simulations. Voltammetric measurements were performed in phosphate buffer saline (PBS) as well as in human serum, giving well-defined current responses upon addition of increasing concentrations of anti-cancer drugs. The results assert the capability to measure concentration of drugs in the pharmacological ranges in human serum. Another important result is the possibility to detect pairs of drugs present in the same sample, which is highly required in case of therapies with high side-effects risk and in anti-cancer pharmacological treatments based on mixtures of different drugs. Our technology holds potentials for inexpensive multi-panel drug-monitoring in personalized therapy. Full article

(This article belongs to the Section Biosensors)

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Graphical abstract

3262 KiB

Open AccessArticle

Structure and Process of Infrared Hot Electron Transistor Arrays

by Richard Fu

Sensors 2012, 12(5), 6508-6519; https://doi.org/10.3390/s120506508 - 16 May 2012

Viewed by 6959

Abstract

An infrared hot-electron transistor (IHET) 5 × 8 array with a common base configuration that allows two-terminal readout integration was investigated and fabricated for the first time. The IHET structure provides a maximum factor of six in improvement in the photocurrent to dark [...] Read more.

An infrared hot-electron transistor (IHET) 5 × 8 array with a common base configuration that allows two-terminal readout integration was investigated and fabricated for the first time. The IHET structure provides a maximum factor of six in improvement in the photocurrent to dark current ratio compared to the basic quantum well infrared photodetector (QWIP), and hence it improved the array S/N ratio by the same factor. The study also showed for the first time that there is no electrical cross-talk among individual detectors, even though they share the same emitter and base contacts. Thus, the IHET structure is compatible with existing electronic readout circuits for photoconductors in producing sensitive focal plane arrays. Full article

(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)

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343 KiB

Open AccessArticle

Using Micromechanical Resonators to Measure Rheological Properties and Alcohol Content of Model Solutions and Commercial Beverages

by Rosemary Paxman, Jake Stinson, Anna Dejardin, Rachel A. McKendry and Bart W. Hoogenboom

Sensors 2012, 12(5), 6497-6507; https://doi.org/10.3390/s120506497 - 16 May 2012

Cited by 13 | Viewed by 8014

Abstract

Micromechanic resonators provide a small-volume and potentially high-throughput method to determine rheological properties of fluids. Here we explore the accuracy in measuring mass density and viscosity of ethanol-water and glycerol-water model solutions, using a simple and easily implemented model to deduce the hydrodynamic [...] Read more.

Micromechanic resonators provide a small-volume and potentially high-throughput method to determine rheological properties of fluids. Here we explore the accuracy in measuring mass density and viscosity of ethanol-water and glycerol-water model solutions, using a simple and easily implemented model to deduce the hydrodynamic effects on resonating cantilevers of various length-to-width aspect ratios. We next show that these measurements can be extended to determine the alcohol percentage of both model solutions and commercial beverages such as beer, wine and liquor. This demonstrates how micromechanical resonators can be used for quality control of every-day drinks. Full article

(This article belongs to the Section Chemical Sensors)

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1494 KiB

Open AccessArticle

Evaluation of the Impact of Furniture on Communications Performance for Ubiquitous Deployment of Wireless Sensor Networks in Smart Homes

by Andrés L. Bleda, Antonio J. Jara, Rafael Maestre, Guadalupe Santa and Antonio F. Gómez Skarmeta

Sensors 2012, 12(5), 6463-6496; https://doi.org/10.3390/s120506463 - 16 May 2012

Cited by 18 | Viewed by 10739

Abstract

The extensions of the environment with the integration of sensing systems in any space, in conjunction with ubiquitous computing are enabling the so-called Smart Space Sensor Networks. This new generation of networks are offering full connectivity with any object, through the Internet of [...] Read more.

The extensions of the environment with the integration of sensing systems in any space, in conjunction with ubiquitous computing are enabling the so-called Smart Space Sensor Networks. This new generation of networks are offering full connectivity with any object, through the Internet of Things (IoT) and/or the Web, i.e., the Web of Things. These connectivity capabilities are making it feasible to sense the behaviours of people at home and act accordingly. These sensing systems must be integrated within typical elements found at home such as furniture. For that reason, this work considers furniture as an interesting element for the transparent location of sensors. Furniture is a ubiquitous object, i.e., it can be found everywhere at home or the office, and it can integrate and hide the sensors of a network. This work addresses the lack of an exhaustive study of the effect of furniture on signal losses. In addition an easy-to-use tool for estimating the robustness of the communication channel among the sensor nodes and gateways is proposed. Specifically, the losses in a sensor network signal due to the materials found within the communication link are evaluated. Then, this work proposes a software tool that gathers the obtained results and is capable of evaluating the impact of a given set of materials on the communications. This tool also provides a mechanism to optimize the sensor network deployments during the definition of smart spaces. Specifically, it provides information such as: maximum distances between sensor nodes, most suitable type of furniture to integrate sensors, or battery life of sensor nodes. This tool has been validated empirically in the lab, and it is currently being used by several enterprise partners of the Technological Centre of Furniture and Wood in the southeast of Spain. Full article

(This article belongs to the Special Issue Ubiquitous Sensing)

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Graphical abstract

548 KiB

Open AccessArticle

Electromagnetic Field Analysis and Modeling of a Relative Position Detection Sensor for High Speed Maglev Trains

by Song Xue, Ning He and Zhiqiang Long

Sensors 2012, 12(5), 6447-6462; https://doi.org/10.3390/s120506447 - 15 May 2012

Cited by 11 | Viewed by 7913

Abstract

The long stator track for high speed maglev trains has a tooth-slot structure. The sensor obtains precise relative position information for the traction system by detecting the long stator tooth-slot structure based on nondestructive detection technology. The magnetic field modeling of the sensor [...] Read more.

The long stator track for high speed maglev trains has a tooth-slot structure. The sensor obtains precise relative position information for the traction system by detecting the long stator tooth-slot structure based on nondestructive detection technology. The magnetic field modeling of the sensor is a typical three-dimensional (3-D) electromagnetic problem with complex boundary conditions, and is studied semi-analytically in this paper. A second-order vector potential (SOVP) is introduced to simplify the vector field problem to a scalar field one, the solution of which can be expressed in terms of series expansions according to Multipole Theory (MT) and the New Equivalent Source (NES) method. The coefficients of the expansions are determined by the least squares method based on the boundary conditions. Then, the solution is compared to the simulation result through Finite Element Analysis (FEA). The comparison results show that the semi-analytical solution agrees approximately with the numerical solution. Finally, based on electromagnetic modeling, a difference coil structure is designed to improve the sensitivity and accuracy of the sensor. Full article

(This article belongs to the Section Physical Sensors)

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274 KiB

Open AccessArticle

Temperature Drift Compensation for Hemispherical Resonator Gyro Based on Natural Frequency

by Xu Wang, Wenqi Wu, Zhen Fang, Bing Luo, Yun Li and Qingan Jiang

Sensors 2012, 12(5), 6434-6446; https://doi.org/10.3390/s120506434 - 15 May 2012

Cited by 53 | Viewed by 9253

Abstract

Temperature changes have a strong effect on Hemispherical Resonator Gyro (HRG) output; therefore, it is of vital importance to observe their influence and then make necessary compensations. In this paper, a temperature compensation model for HRG based on the natural frequency of the [...] Read more.

Temperature changes have a strong effect on Hemispherical Resonator Gyro (HRG) output; therefore, it is of vital importance to observe their influence and then make necessary compensations. In this paper, a temperature compensation model for HRG based on the natural frequency of the resonator is established and then temperature drift compensations are accomplished. To begin with, a math model of the relationship between the temperature and the natural frequency of HRG is set up. Then, the math model is written into a Taylor expansion expression and the expansion coefficients are calibrated through temperature experiments. The experimental results show that the frequency changes correspond to temperature changes and each temperature only corresponds to one natural frequency, so the output of HRG can be compensated through the natural frequency of the resonator instead of the temperature itself. As a result, compensations are made for the output drift of HRG based on natural frequency through a stepwise linear regression method. The compensation results show that temperature-frequency method is valid and suitable for the gyroscope drift compensation, which would ensure HRG’s application in a larger temperature range in the future. Full article

(This article belongs to the Section Physical Sensors)

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854 KiB

Open AccessArticle

Road Sign Recognition with Fuzzy Adaptive Pre-Processing Models

by Chien-Chuan Lin and Ming-Shi Wang

Sensors 2012, 12(5), 6415-6433; https://doi.org/10.3390/s120506415 - 15 May 2012

Cited by 12 | Viewed by 6684

Abstract

A road sign recognition system based on adaptive image pre-processing models using two fuzzy inference schemes has been proposed. The first fuzzy inference scheme is to check the changes of the light illumination and rich red color of a frame image by the [...] Read more.

A road sign recognition system based on adaptive image pre-processing models using two fuzzy inference schemes has been proposed. The first fuzzy inference scheme is to check the changes of the light illumination and rich red color of a frame image by the checking areas. The other is to check the variance of vehicle’s speed and angle of steering wheel to select an adaptive size and position of the detection area. The Adaboost classifier was employed to detect the road sign candidates from an image and the support vector machine technique was employed to recognize the content of the road sign candidates. The prohibitory and warning road traffic signs are the processing targets in this research. The detection rate in the detection phase is 97.42%. In the recognition phase, the recognition rate is 93.04%. The total accuracy rate of the system is 92.47%. For video sequences, the best accuracy rate is 90.54%, and the average accuracy rate is 80.17%. The average computing time is 51.86 milliseconds per frame. The proposed system can not only overcome low illumination and rich red color around the road sign problems but also offer high detection rates and high computing performance. Full article

(This article belongs to the Section Physical Sensors)

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654 KiB

Open AccessArticle

Integral T-Shaped Phantom-Dosimeter System to Measure Transverse and Longitudinal Dose Distributions Simultaneously for Stereotactic Radiosurgery Dosimetry

by Wook Jae Yoo, Jinsoo Moon, Kyoung Won Jang, Ki-Tek Han, Sang Hun Shin, Dayeong Jeon, Jang-Yeon Park, Byung Gi Park and Bongsoo Lee

Sensors 2012, 12(5), 6404-6414; https://doi.org/10.3390/s120506404 - 14 May 2012

Cited by 10 | Viewed by 6896

Abstract

A T-shaped fiber-optic phantom-dosimeter system was developed using square scintillating optical fibers, a lens system, and a CMOS image camera. Images of scintillating light were used to simultaneously measure the transverse and longitudinal distributions of absorbed dose of a 6 MV photon beam [...] Read more.

A T-shaped fiber-optic phantom-dosimeter system was developed using square scintillating optical fibers, a lens system, and a CMOS image camera. Images of scintillating light were used to simultaneously measure the transverse and longitudinal distributions of absorbed dose of a 6 MV photon beam with field sizes of 1 × 1 and 3 × 3 cm². Each optical fiber has a very small sensitive volume and the sensitive material is water equivalent. This allows the measurements of cross-beam profile as well as the percentage depth dose of small field sizes. In the case of transverse dose distribution, the measured beam profiles were gradually become uneven and the beam edge had a gentle slope with increasing depth of the PMMA phantom. In addition, the maximum dose values of longitudinal dose distribution for 6 MV photon beam with field sizes of 1 × 1 and 3 × 3 cm² were found to be at a depth of approximately 15 mm and the percentage depth dose of both field sizes were nearly in agreement at the skin dose level. Based on the results of this study, it is anticipated that an all-in-one phantom-dosimeter can be developed to accurately measure beam profiles and dose distribution in a small irradiation fields prior to carrying out stereotactic radiosurgery. Full article

(This article belongs to the Section Physical Sensors)

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432 KiB

Open AccessArticle

Design of Compensation Coils for EMI Suppression in Magnetostrictive Linear Position Sensors

by Yongjie Zhang, Weiwen Liu, Jinfeng Yang, Chunfeng Lv and Hui Zhao

Sensors 2012, 12(5), 6395-6403; https://doi.org/10.3390/s120506395 - 14 May 2012

Cited by 14 | Viewed by 8247

Abstract

This paper presents recent development on magnetostrictive linear position sensors (MLPS). A new compensation coil structure improves the EMI suppression and accuracy considerably. Furthermore, experimental results indicate that the new structure can improve the accuracy to ±0.13 mm nearly double the ±0.2 mm [...] Read more.

This paper presents recent development on magnetostrictive linear position sensors (MLPS). A new compensation coil structure improves the EMI suppression and accuracy considerably. Furthermore, experimental results indicate that the new structure can improve the accuracy to ±0.13 mm nearly double the ±0.2 mm obtained with traditional structures. As another design continuation after the differential waveguide structure, this new structure is a practical and reliable implementation technique for the commercialization of MLPS. Full article

(This article belongs to the Section Physical Sensors)

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721 KiB

Open AccessArticle

Enabling Communication in Emergency Response Environments

by Roberto G. Aldunate, Klaus Nicholas Schmidt and Oriel Herrera

Sensors 2012, 12(5), 6380-6394; https://doi.org/10.3390/s120506380 - 14 May 2012

Cited by 3 | Viewed by 7805

Abstract

Effective communication among first responders during response to natural and human-made large-scale catastrophes has increased tremendously during the last decade. However, most efforts to achieve a higher degree of effectiveness in communication lack synergy between the environment and the technology involved to support [...] Read more.

Effective communication among first responders during response to natural and human-made large-scale catastrophes has increased tremendously during the last decade. However, most efforts to achieve a higher degree of effectiveness in communication lack synergy between the environment and the technology involved to support first responders operations. This article presents a natural and intuitive interface to support Stigmergy; or communication through the environment, based on intuitively marking and retrieving information from the environment with a pointer. A prototype of the system was built and tested in the field, however the pointing activity revealed challenges regarding accuracy due to limitations of the sensors used. The results obtained from these field tests were the basis for this research effort and will have the potential to enable communication through the environment for first responders operating in highly dynamical and inhospitable disaster relief environments. Full article

(This article belongs to the Special Issue Select papers from UCAmI 2011 - the 5th International Symposium on Ubiquitous Computing and Ambient Intelligence (UCAmI'11))

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941 KiB

Open AccessArticle

Fabrication and Characteristics of an nc-Si/c-Si Heterojunction MOSFETs Pressure Sensor

by Xiaofeng Zhao, Dianzhong Wen and Gang Li

Sensors 2012, 12(5), 6369-6379; https://doi.org/10.3390/s120506369 - 14 May 2012

Cited by 22 | Viewed by 8098

Abstract

A novel nc-Si/c-Si heterojunction MOSFETs pressure sensor is proposed in this paper, with four p-MOSFETs with nc-Si/c-Si heterojunction as source and drain. The four p-MOSFETs are designed and fabricated on a square silicon membrane by CMOS process and MEMS technology where channel resistances [...] Read more.

A novel nc-Si/c-Si heterojunction MOSFETs pressure sensor is proposed in this paper, with four p-MOSFETs with nc-Si/c-Si heterojunction as source and drain. The four p-MOSFETs are designed and fabricated on a square silicon membrane by CMOS process and MEMS technology where channel resistances of the four nc-Si/c-Si heterojunction MOSFETs form a Wheatstone bridge. When the additional pressure is P, the nc-Si/c-Si heterojunction MOSFETs pressure sensor can measure this additional pressure P. The experimental results show that when the supply voltage is 3 V, length-width (L:W) ratio is 2:1, and the silicon membrane thickness is 75 μm, the full scale output voltage of the pressure sensor is 15.50 mV at room temperature, and pressure sensitivity is 0.097 mV/kPa. When the supply voltage and L:W ratio are the same as the above, and the silicon membrane thickness is 45 μm, the full scale output voltage is 43.05 mV, and pressure sensitivity is 2.153 mV/kPa. Therefore, the sensor has higher sensitivity and good temperature characteristics compared to the traditional piezoresistive pressure sensor. Full article

(This article belongs to the Section Physical Sensors)

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3889 KiB

Open AccessArticle

Accuracy Assessment of Digital Surface Models Based on WorldView-2 and ADS80 Stereo Remote Sensing Data

by Martina L. Hobi and Christian Ginzler

Sensors 2012, 12(5), 6347-6368; https://doi.org/10.3390/s120506347 - 11 May 2012

Cited by 96 | Viewed by 11508

Abstract

Digital surface models (DSMs) are widely used in forest science to model the forest canopy. Stereo pairs of very high resolution satellite and digital aerial images are relatively new and their absolute accuracy for DSM generation is largely unknown. For an assessment of [...] Read more.

Digital surface models (DSMs) are widely used in forest science to model the forest canopy. Stereo pairs of very high resolution satellite and digital aerial images are relatively new and their absolute accuracy for DSM generation is largely unknown. For an assessment of these input data two DSMs based on a WorldView-2 stereo pair and a ADS80 DSM were generated with photogrammetric instruments. Rational polynomial coefficients (RPCs) are defining the orientation of the WorldView-2 satellite images, which can be enhanced with ground control points (GCPs). Thus two WorldView-2 DSMs were distinguished: a WorldView-2 RPCs-only DSM and a WorldView-2 GCP-enhanced RPCs DSM. The accuracy of the three DSMs was estimated with GPS measurements, manual stereo-measurements, and airborne laser scanning data (ALS). With GCP-enhanced RPCs the WorldView-2 image orientation could be optimised to a root mean square error (RMSE) of 0.56 m in planimetry and 0.32 m in height. This improvement in orientation allowed for a vertical median error of −0.24 m for the WorldView-2 GCP-enhanced RPCs DSM in flat terrain. Overall, the DSM based on ADS80 images showed the highest accuracy of the three models with a median error of 0.08 m over bare ground. As the accuracy of a DSM varies with land cover three classes were distinguished: herb and grass, forests, and artificial areas. The study suggested the ADS80 DSM to best model actual surface height in all three land cover classes, with median errors < 1.1 m. The WorldView-2 GCP-enhanced RPCs model achieved good accuracy, too, with median errors of −0.43 m for the herb and grass vegetation and −0.26 m for artificial areas. Forested areas emerged as the most difficult land cover type for height modelling; still, with median errors of −1.85 m for the WorldView-2 GCP-enhanced RPCs model and −1.12 m for the ADS80 model, the input data sets evaluated here are quite promising for forest canopy modelling. Full article

(This article belongs to the Section Remote Sensors)

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479 KiB

Open AccessReview

Advances in Atomic Gyroscopes: A View from Inertial Navigation Applications

by JianCheng Fang and Jie Qin

Sensors 2012, 12(5), 6331-6346; https://doi.org/10.3390/s120506331 - 11 May 2012

Cited by 152 | Viewed by 15528

Abstract

With the rapid development of modern physics, atomic gyroscopes have been demonstrated in recent years. There are two types of atomic gyroscope. The Atomic Interferometer Gyroscope (AIG), which utilizes the atomic interferometer to sense rotation, is an ultra-high precision gyroscope; and the Atomic [...] Read more.

With the rapid development of modern physics, atomic gyroscopes have been demonstrated in recent years. There are two types of atomic gyroscope. The Atomic Interferometer Gyroscope (AIG), which utilizes the atomic interferometer to sense rotation, is an ultra-high precision gyroscope; and the Atomic Spin Gyroscope (ASG), which utilizes atomic spin to sense rotation, features high precision, compact size and the possibility to make a chip-scale one. Recent developments in the atomic gyroscope field have created new ways to obtain high precision gyroscopes which were previously unavailable with mechanical or optical gyroscopes, but there are still lots of problems that need to be overcome to meet the requirements of inertial navigation systems. This paper reviews the basic principles of AIG and ASG, introduces the recent progress in this area, focusing on discussing their technical difficulties for inertial navigation applications, and suggests methods for developing high performance atomic gyroscopes in the near future. Full article

(This article belongs to the Section Physical Sensors)

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1555 KiB

Open AccessArticle

Sharing Human-Generated Observations by Integrating HMI and the Semantic Sensor Web

by Álvaro Sigüenza, David Díaz-Pardo, Jesús Bernat, Vasile Vancea, José Luis Blanco, David Conejero and Luis Hernández Gómez

Sensors 2012, 12(5), 6307-6330; https://doi.org/10.3390/s120506307 - 11 May 2012

Cited by 2 | Viewed by 9699

Abstract

Current “Internet of Things” concepts point to a future where connected objects gather meaningful information about their environment and share it with other objects and people. In particular, objects embedding Human Machine Interaction (HMI), such as mobile devices and, increasingly, connected vehicles, home [...] Read more.

Current “Internet of Things” concepts point to a future where connected objects gather meaningful information about their environment and share it with other objects and people. In particular, objects embedding Human Machine Interaction (HMI), such as mobile devices and, increasingly, connected vehicles, home appliances, urban interactive infrastructures, etc., may not only be conceived as sources of sensor information, but, through interaction with their users, they can also produce highly valuable context-aware human-generated observations. We believe that the great promise offered by combining and sharing all of the different sources of information available can be realized through the integration of HMI and Semantic Sensor Web technologies. This paper presents a technological framework that harmonizes two of the most influential HMI and Sensor Web initiatives: the W3C’s Multimodal Architecture and Interfaces (MMI) and the Open Geospatial Consortium (OGC) Sensor Web Enablement (SWE) with its semantic extension, respectively. Although the proposed framework is general enough to be applied in a variety of connected objects integrating HMI, a particular development is presented for a connected car scenario where drivers’ observations about the traffic or their environment are shared across the Semantic Sensor Web. For implementation and evaluation purposes an on-board OSGi (Open Services Gateway Initiative) architecture was built, integrating several available HMI, Sensor Web and Semantic Web technologies. A technical performance test and a conceptual validation of the scenario with potential users are reported, with results suggesting the approach is sound. Full article

(This article belongs to the Special Issue Select papers from UCAmI 2011 - the 5th International Symposium on Ubiquitous Computing and Ambient Intelligence (UCAmI'11))

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1442 KiB

Open AccessArticle

An Approach for Representing Sensor Data to Validate Alerts in Ambient Assisted Living

by Andrés Muñoz, Emilio Serrano, Ana Villa, Mercedes Valdés and Juan A. Botía

Sensors 2012, 12(5), 6282-6306; https://doi.org/10.3390/s120506282 - 11 May 2012

Cited by 21 | Viewed by 9855

Abstract

The mainstream of research in Ambient Assisted Living (AAL) is devoted to developing intelligent systems for processing the data collected through artificial sensing. Besides, there are other elements that must be considered to foster the adoption of AAL solutions in real environments. In [...] Read more.

The mainstream of research in Ambient Assisted Living (AAL) is devoted to developing intelligent systems for processing the data collected through artificial sensing. Besides, there are other elements that must be considered to foster the adoption of AAL solutions in real environments. In this paper we focus on the problem of designing interfaces among caregivers and AAL systems. We present an alert management tool that supports carers in their task of validating alarms raised by the system. It generates text-based explanations—obtained through an argumentation process—of the causes leading to alarm activation along with graphical sensor information and 3D models, thus offering complementary types of information. Moreover, a guideline to use the tool when validating alerts is also provided. Finally, the functionality of the proposed tool is demonstrated through two real cases of alert. Full article

(This article belongs to the Special Issue Select papers from UCAmI 2011 - the 5th International Symposium on Ubiquitous Computing and Ambient Intelligence (UCAmI'11))

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318 KiB

Open AccessArticle

Wireless Biosensor System for Real-Time L-Lactic Acid Monitoring in Fish

by Kyoko Hibi, Kengo Hatanaka, Mai Takase, Huifeng Ren and Hideaki Endo

Sensors 2012, 12(5), 6269-6281; https://doi.org/10.3390/s120506269 - 11 May 2012

Cited by 22 | Viewed by 8721

Abstract

We have developed a wireless biosensor system to continuously monitor L-lactic acid concentrations in fish. The blood L-lactic acid level of fish is a barometer of stress. The biosensor comprised Pt-Ir wire (φ0.178 mm) as the working electrode and Ag/AgCl paste as the [...] Read more.

We have developed a wireless biosensor system to continuously monitor L-lactic acid concentrations in fish. The blood L-lactic acid level of fish is a barometer of stress. The biosensor comprised Pt-Ir wire (φ0.178 mm) as the working electrode and Ag/AgCl paste as the reference electrode. Lactate oxidase was immobilized on the working electrode using glutaraldehyde. The sensor calibration was linear and good correlated with L-lactic acid levels (R = 0.9959) in the range of 0.04 to 6.0 mg·dL⁻¹. We used the eyeball interstitial sclera fluid (EISF) as the site of sensor implantation. The blood L-lactic acid levels correlated closely with the EISF L-lactic acid levels in the range of 3 to 13 mg·dL⁻¹ (R = 0.8173, n = 26). Wireless monitoring of L-lactic acid was performed using the sensor system in free-swimming fish in an aquarium. The sensor response was stable for over 60 h. Thus, our biosensor provided a rapid and convenient method for real-time monitoring of L-lactic acid levels in fish. Full article

(This article belongs to the Section Biosensors)

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8302 KiB

Open AccessArticle

FPGA Implementation of Generalized Hebbian Algorithm for Texture Classification

by Shiow-Jyu Lin, Wen-Jyi Hwang and Wei-Hao Lee

Sensors 2012, 12(5), 6244-6268; https://doi.org/10.3390/s120506244 - 10 May 2012

Cited by 6 | Viewed by 6971

Abstract

This paper presents a novel hardware architecture for principal component analysis. The architecture is based on the Generalized Hebbian Algorithm (GHA) because of its simplicity and effectiveness. The architecture is separated into three portions: the weight vector updating unit, the principal computation unit [...] Read more.

This paper presents a novel hardware architecture for principal component analysis. The architecture is based on the Generalized Hebbian Algorithm (GHA) because of its simplicity and effectiveness. The architecture is separated into three portions: the weight vector updating unit, the principal computation unit and the memory unit. In the weight vector updating unit, the computation of different synaptic weight vectors shares the same circuit for reducing the area costs. To show the effectiveness of the circuit, a texture classification system based on the proposed architecture is physically implemented by Field Programmable Gate Array (FPGA). It is embedded in a System-On-Programmable-Chip (SOPC) platform for performance measurement. Experimental results show that the proposed architecture is an efficient design for attaining both high speed performance andlow area costs. Full article

(This article belongs to the Section Physical Sensors)

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789 KiB

Open AccessArticle

Mobile, Collaborative Situated Knowledge Creation for Urban Planning

by Gustavo Zurita and Nelson Baloian

Sensors 2012, 12(5), 6218-6243; https://doi.org/10.3390/s120506218 - 10 May 2012

Cited by 14 | Viewed by 8023

Abstract

Geo-collaboration is an emerging research area in computer sciences studying the way spatial, geographically referenced information and communication technologies can support collaborative activities. Scenarios in which information associated to its physical location are of paramount importance are often referred as Situated Knowledge Creation [...] Read more.

Geo-collaboration is an emerging research area in computer sciences studying the way spatial, geographically referenced information and communication technologies can support collaborative activities. Scenarios in which information associated to its physical location are of paramount importance are often referred as Situated Knowledge Creation scenarios. To date there are few computer systems supporting knowledge creation that explicitly incorporate physical context as part of the knowledge being managed in mobile face-to-face scenarios. This work presents a collaborative software application supporting visually-geo-referenced knowledge creation in mobile working scenarios while the users are interacting face-to-face. The system allows to manage data information associated to specific physical locations for knowledge creation processes in the field, such as urban planning, identifying specific physical locations, territorial management, etc.; using Tablet-PCs and GPS in order to geo-reference data and information. It presents a model for developing mobile applications supporting situated knowledge creation in the field, introducing the requirements for such an application and the functionalities it should have in order to fulfill them. The paper also presents the results of utility and usability evaluations. Full article

(This article belongs to the Special Issue Select papers from UCAmI 2011 - the 5th International Symposium on Ubiquitous Computing and Ambient Intelligence (UCAmI'11))

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Sensors, Volume 12, Issue 5 (May 2012) – 89 articles , Pages 5195-6763

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