Sensors

1373 KiB

Open AccessArticle

BlueDetect: An iBeacon-Enabled Scheme for Accurate and Energy-Efficient Indoor-Outdoor Detection and Seamless Location-Based Service

by Han Zou, Hao Jiang, Yiwen Luo, Jianjie Zhu, Xiaoxuan Lu and Lihua Xie

Sensors 2016, 16(2), 268; https://doi.org/10.3390/s16020268 - 22 Feb 2016

Cited by 100 | Viewed by 10283

Abstract

The location and contextual status (indoor or outdoor) is fundamental and critical information for upper-layer applications, such as activity recognition and location-based services (LBS) for individuals. In addition, optimizations of building management systems (BMS), such as the pre-cooling or heating process of the [...] Read more.

The location and contextual status (indoor or outdoor) is fundamental and critical information for upper-layer applications, such as activity recognition and location-based services (LBS) for individuals. In addition, optimizations of building management systems (BMS), such as the pre-cooling or heating process of the air-conditioning system according to the human traffic entering or exiting a building, can utilize the information, as well. The emerging mobile devices, which are equipped with various sensors, become a feasible and flexible platform to perform indoor-outdoor (IO) detection. However, power-hungry sensors, such as GPS and WiFi, should be used with caution due to the constrained battery storage on mobile device. We propose BlueDetect: an accurate, fast response and energy-efficient scheme for IO detection and seamless LBS running on the mobile device based on the emerging low-power iBeacon technology. By leveraging the on-broad Bluetooth module and our proposed algorithms, BlueDetect provides a precise IO detection service that can turn on/off on-board power-hungry sensors smartly and automatically, optimize their performances and reduce the power consumption of mobile devices simultaneously. Moreover, seamless positioning and navigation services can be realized by it, especially in a semi-outdoor environment, which cannot be achieved by GPS or an indoor positioning system (IPS) easily. We prototype BlueDetect on Android mobile devices and evaluate its performance comprehensively. The experimental results have validated the superiority of BlueDetect in terms of IO detection accuracy, localization accuracy and energy consumption. Full article

(This article belongs to the Section Physical Sensors)

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7884 KiB

Open AccessArticle

Parametric Cognitive Modeling of Information and Computer Technology Usage by People with Aging- and Disability-Derived Functional Impairments

by Rebeca I. García-Betances, María Fernanda Cabrera-Umpiérrez, Manuel Ottaviano, Matteo Pastorino and María T. Arredondo

Sensors 2016, 16(2), 266; https://doi.org/10.3390/s16020266 - 22 Feb 2016

Cited by 17 | Viewed by 7279

Abstract

Despite the speedy evolution of Information and Computer Technology (ICT), and the growing recognition of the importance of the concept of universal design in all domains of daily living, mainstream ICT-based product designers and developers still work without any truly structured tools, guidance [...] Read more.

Despite the speedy evolution of Information and Computer Technology (ICT), and the growing recognition of the importance of the concept of universal design in all domains of daily living, mainstream ICT-based product designers and developers still work without any truly structured tools, guidance or support to effectively adapt their products and services to users’ real needs. This paper presents the approach used to define and evaluate parametric cognitive models that describe interaction and usage of ICT by people with aging- and disability-derived functional impairments. A multisensorial training platform was used to train, based on real user measurements in real conditions, the virtual parameterized user models that act as subjects of the test-bed during all stages of simulated disabilities-friendly ICT-based products design. An analytical study was carried out to identify the relevant cognitive functions involved, together with their corresponding parameters as related to aging- and disability-derived functional impairments. Evaluation of the final cognitive virtual user models in a real application has confirmed that the use of these models produce concrete valuable benefits to the design and testing process of accessible ICT-based applications and services. Parameterization of cognitive virtual user models allows incorporating cognitive and perceptual aspects during the design process. Full article

(This article belongs to the Special Issue Data in the IoT: from Sensing to Meaning)

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3287 KiB

Open AccessArticle

Thin Film Differential Photosensor for Reduction of Temperature Effects in Lab-on-Chip Applications

by Giampiero De Cesare, Matteo Carpentiero, Augusto Nascetti and Domenico Caputo

Sensors 2016, 16(2), 267; https://doi.org/10.3390/s16020267 - 20 Feb 2016

Cited by 3 | Viewed by 5059

Abstract

This paper presents a thin film structure suitable for low-level radiation measurements in lab-on-chip systems that are subject to thermal treatments of the analyte and/or to large temperature variations. The device is the series connection of two amorphous silicon/amorphous silicon carbide heterojunctions designed [...] Read more.

This paper presents a thin film structure suitable for low-level radiation measurements in lab-on-chip systems that are subject to thermal treatments of the analyte and/or to large temperature variations. The device is the series connection of two amorphous silicon/amorphous silicon carbide heterojunctions designed to perform differential current measurements. The two diodes experience the same temperature, while only one is exposed to the incident radiation. Under these conditions, temperature and light are the common and differential mode signals, respectively. A proper electrical connection reads the differential current of the two diodes (ideally the photocurrent) as the output signal. The experimental characterization shows the benefits of the differential structure in minimizing the temperature effects with respect to a single diode operation. In particular, when the temperature varies from 23 to 50 °C, the proposed device shows a common mode rejection ratio up to 24 dB and reduces of a factor of three the error in detecting very low-intensity light signals. Full article

(This article belongs to the Section Physical Sensors)

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5543 KiB

Open AccessArticle

Fast, Highly-Sensitive, and Wide-Dynamic-Range Interdigitated Capacitor Glucose Biosensor Using Solvatochromic Dye-Containing Sensing Membrane

by Md. Rajibur Rahaman Khan, Alireza Khalilian and Shin-Won Kang

Sensors 2016, 16(2), 265; https://doi.org/10.3390/s16020265 - 20 Feb 2016

Cited by 21 | Viewed by 9760

Abstract

In this paper, we proposed an interdigitated capacitor (IDC)-based glucose biosensor to measure different concentrations of glucose from 1 μM to 1 M. We studied four different types of solvatochromic dyes: Auramine O, Nile red, Rhodamine B, and Reichardt’s dye (R-dye). These dyes [...] Read more.

In this paper, we proposed an interdigitated capacitor (IDC)-based glucose biosensor to measure different concentrations of glucose from 1 μM to 1 M. We studied four different types of solvatochromic dyes: Auramine O, Nile red, Rhodamine B, and Reichardt’s dye (R-dye). These dyes were individually incorporated into a polymer [polyvinyl chloride (PVC)] and N,N-Dimethylacetamide (DMAC) solution to make the respective dielectric/sensing materials. To the best of our knowledge, we report for the first time an IDC glucose biosensing system utilizing a solvatochromic-dye-containing sensing membrane. These four dielectric or sensing materials were individually placed into the interdigitated electrode (IDE) by spin coating to make four IDC glucose biosensing elements. The proposed IDC glucose biosensor has a high sensing ability over a wide dynamic range and its sensitivity was about 23.32 mV/decade. It also has fast response and recovery times of approximately 7 s and 5 s, respectively, excellent reproducibility with a standard deviation of approximately 0.023, highly stable sensing performance, and real-time monitoring capabilities. The proposed IDC glucose biosensor was compared with an IDC, potentiometric, FET, and fiber-optic glucose sensor with respect to response time, dynamic range width, sensitivity, and linearity. We observed that the designed IDC glucose biosensor offered excellent performance. Full article

(This article belongs to the Section Biosensors)

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6592 KiB

Open AccessArticle

A Dual-Linear Kalman Filter for Real-Time Orientation Determination System Using Low-Cost MEMS Sensors

by Shengzhi Zhang, Shuai Yu, Chaojun Liu, Xuebing Yuan and Sheng Liu

Sensors 2016, 16(2), 264; https://doi.org/10.3390/s16020264 - 20 Feb 2016

Cited by 41 | Viewed by 8734

Abstract

To provide a long-time reliable orientation, sensor fusion technologies are widely used to integrate available inertial sensors for the low-cost orientation estimation. In this paper, a novel dual-linear Kalman filter was designed for a multi-sensor system integrating MEMS gyros, an accelerometer, and a [...] Read more.

To provide a long-time reliable orientation, sensor fusion technologies are widely used to integrate available inertial sensors for the low-cost orientation estimation. In this paper, a novel dual-linear Kalman filter was designed for a multi-sensor system integrating MEMS gyros, an accelerometer, and a magnetometer. The proposed filter precludes the impacts of magnetic disturbances on the pitch and roll which the heading is subjected to. The filter can achieve robust orientation estimation for different statistical models of the sensors. The root mean square errors (RMSE) of the estimated attitude angles are reduced by 30.6% under magnetic disturbances. Owing to the reduction of system complexity achieved by smaller matrix operations, the mean total time consumption is reduced by 23.8%. Meanwhile, the separated filter offers greater flexibility for the system configuration, as it is possible to switch on or off the second stage filter to include or exclude the magnetometer compensation for the heading. Online experiments were performed on the homemade miniature orientation determination system (MODS) with the turntable. The average RMSE of estimated orientation are less than 0.4° and 1° during the static and low-dynamic tests, respectively. More realistic tests on two-wheel self-balancing vehicle driving and indoor pedestrian walking were carried out to evaluate the performance of the designed MODS when high accelerations and angular rates were introduced. Test results demonstrate that the MODS is applicable for the orientation estimation under various dynamic conditions. This paper provides a feasible alternative for low-cost orientation determination. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems)

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1356 KiB

Open AccessArticle

A Layered Approach for Robust Spatial Virtual Human Pose Reconstruction Using a Still Image

by Chengyu Guo, Songsong Ruan, Xiaohui Liang and Qinping Zhao

Sensors 2016, 16(2), 263; https://doi.org/10.3390/s16020263 - 20 Feb 2016

Cited by 1 | Viewed by 5192

Abstract

Pedestrian detection and human pose estimation are instructive for reconstructing a three-dimensional scenario and for robot navigation, particularly when large amounts of vision data are captured using various data-recording techniques. Using an unrestricted capture scheme, which produces occlusions or breezing, the information describing [...] Read more.

Pedestrian detection and human pose estimation are instructive for reconstructing a three-dimensional scenario and for robot navigation, particularly when large amounts of vision data are captured using various data-recording techniques. Using an unrestricted capture scheme, which produces occlusions or breezing, the information describing each part of a human body and the relationship between each part or even different pedestrians must be present in a still image. Using this framework, a multi-layered, spatial, virtual, human pose reconstruction framework is presented in this study to recover any deficient information in planar images. In this framework, a hierarchical parts-based deep model is used to detect body parts by using the available restricted information in a still image and is then combined with spatial Markov random fields to re-estimate the accurate joint positions in the deep network. Then, the planar estimation results are mapped onto a virtual three-dimensional space using multiple constraints to recover any deficient spatial information. The proposed approach can be viewed as a general pre-processing method to guide the generation of continuous, three-dimensional motion data. The experiment results of this study are used to describe the effectiveness and usability of the proposed approach. Full article

(This article belongs to the Special Issue Sensors for Robots)

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Figure 1
Overview of the framework. With the normalized input, three levels of processing are conducted for part detection, planar pose estimation and spatial pose reconstruction. Full article ">Figure 2
The structure schematic of the deep model at the low level. With two convolution and pooling layers, the scores are mapped to the heat map, which indicates the possible joint distribution of the input image. Full article ">Figure 3
The hierarchical body part templates are used. <math display="inline"> <msubsup> <mi>h</mi> <mi>i</mi> <mi>j</mi> </msubsup> </math> indicates the visibility state parameters of the i-th template in the j-th layer. <math display="inline"> <mrow> <mi>S</mi> <mi>c</mi> <mi>o</mi> <mi>r</mi> <msub> <mi>e</mi> <mi>i</mi> </msub> </mrow> </math> is the detection results from the second pooling layer of the deep model, which indicates the possibility of each visible body part. Full article ">Figure 4
The body structure used in our experiment. (a) The fundamental body part structure; (b) the joints of the model that need to be estimated and reconstructed in planar and spatial space; (c) a division for body parts, which guides the layering of the occlusion templates. Full article ">Figure 5
The performance of body joint estimation in planar space on the FLICtest-set. (a) Elbow estimation result; (b) wrist estimation result; (c) foot estimation result. Full article ">Figure 6
Typical examples for successful and failed three-dimensional pose reconstruction. (a,b) Two positive results on reconstruction; (c,d) two typical negative results on reconstruction. Full article ">

1095 KiB

Open AccessArticle

Sensitivity Enhancement in Magnetic Sensors Based on Ferroelectric-Bimorphs and Multiferroic Composites

by Gollapudi Sreenivasulu, Peng Qu, Vladimir Petrov, Hongwei Qu and Gopalan Srinivasan

Sensors 2016, 16(2), 262; https://doi.org/10.3390/s16020262 - 20 Feb 2016

Cited by 25 | Viewed by 6322

Abstract

Multiferroic composites with ferromagnetic and ferroelectric phases have been studied in recent years for use as sensors of AC and DC magnetic fields. Their operation is based on magneto-electric (ME) coupling between the electric and magnetic subsystems and is mediated by mechanical strain. [...] Read more.

Multiferroic composites with ferromagnetic and ferroelectric phases have been studied in recent years for use as sensors of AC and DC magnetic fields. Their operation is based on magneto-electric (ME) coupling between the electric and magnetic subsystems and is mediated by mechanical strain. Such sensors for AC magnetic fields require a bias magnetic field to achieve pT-sensitivity. Novel magnetic sensors with a permanent magnet proof mass, either on a ferroelectric bimorph or a ferromagnetic-ferroelectric composite, are discussed. In both types, the interaction between the applied AC magnetic field and remnant magnetization of the magnet results in a mechanical strain and a voltage response in the ferroelectric. Our studies have been performed on sensors with a Nd-Fe-B permanent magnet proof mass on (i) a bimorph of oppositely-poled lead zirconate titanate (PZT) platelets and (ii) a layered multiferroic composite of PZT-Metglas-Ni. The sensors have been characterized in terms of sensitivity and equivalent magnetic noise N. Noise N in both type of sensors is on the order of 200 pT/√Hz at 1 Hz, a factor of 10 improvement compared to multiferroic sensors without a proof mass. When the AC magnetic field is applied at the bending resonance for the bimorph, the measured N ≈ 700 pT/√Hz. We discuss models based on magneto-electro-mechanical coupling at low frequency and bending resonance in the sensors and theoretical estimates of ME voltage coefficients are in very good agreement with the data. Full article

(This article belongs to the Special Issue Magnetic Sensor Device-Part 1)

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Figure 1
Diagram showing a cantilever of PZT-bimorph with NdFeB permanent magnet proof mass. Full article ">Figure 2
(a) ME sensitivity S vs. frequency f profile showing the sensor response for H at 1 Hz; (b) MEVC vs. f data showing resonance enhancement in MEVC at the bending mode for the bimorph-proof mass system. Full article ">Figure 3
(a) Equivalent magnetic noise N as a function of frequency for the PZT-bimorph sensor; and (b) Results as in (a), but for frequencies centered around the bending resonance in the sensor. The minimum in N occurs close to bending mode frequency for the cantilever sensor. Full article ">Figure 4
(a) ME voltage coefficient as a function for bias magnetic field Hb for the multiferroic composite without the proof mass; and (b) Equivalent magnetic noise versus frequency under Hb = 0. Full article ">Figure 5
(a) Variation of the ME voltage coefficient at 1 Hz with the mass m of the proof mass for the multiferroic composite; and (b) N vs. f data for the composite with a proof mass m = 10 g. Full article ">Figure 6
The bending resonance frequency fr and the MEVC at resonance frequency as a function of the mass m of the proof mass for the multiferroic composite. Full article ">Figure 7
(a) Theoretical MEVC as a function of frequency for the PZT bimorph with permanent magnet tip mass. Measured values are also shown for comparison; and (b) Calculated bending mode frequency as a function of the mass of permanent magnet. Full article ">

2700 KiB

Open AccessArticle

CSRQ: Communication-Efficient Secure Range Queries in Two-Tiered Sensor Networks

by Hua Dai, Qingqun Ye, Geng Yang, Jia Xu and Ruiliang He

Sensors 2016, 16(2), 259; https://doi.org/10.3390/s16020259 - 20 Feb 2016

Cited by 11 | Viewed by 6473

Abstract

In recent years, we have seen many applications of secure query in two-tiered wireless sensor networks. Storage nodes are responsible for storing data from nearby sensor nodes and answering queries from Sink. It is critical to protect data security from a compromised storage [...] Read more.

In recent years, we have seen many applications of secure query in two-tiered wireless sensor networks. Storage nodes are responsible for storing data from nearby sensor nodes and answering queries from Sink. It is critical to protect data security from a compromised storage node. In this paper, the Communication-efficient Secure Range Query (CSRQ)—a privacy and integrity preserving range query protocol—is proposed to prevent attackers from gaining information of both data collected by sensor nodes and queries issued by Sink. To preserve privacy and integrity, in addition to employing the encoding mechanisms, a novel data structure called encrypted constraint chain is proposed, which embeds the information of integrity verification. Sink can use this encrypted constraint chain to verify the query result. The performance evaluation shows that CSRQ has lower communication cost than the current range query protocols. Full article

(This article belongs to the Special Issue Security and Privacy in Sensor Networks)

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2189 KiB

Open AccessArticle

An Effective Collaborative Mobile Weighted Clustering Schemes for Energy Balancing in Wireless Sensor Networks

by Chengpei Tang, Sanesy Kumcr Shokla, George Modhawar and Qiang Wang

Sensors 2016, 16(2), 261; https://doi.org/10.3390/s16020261 - 19 Feb 2016

Cited by 5 | Viewed by 5114

Abstract

Collaborative strategies for mobile sensor nodes ensure the efficiency and the robustness of data processing, while limiting the required communication bandwidth. In order to solve the problem of pipeline inspection and oil leakage monitoring, a collaborative weighted mobile sensing scheme is proposed. By [...] Read more.

Collaborative strategies for mobile sensor nodes ensure the efficiency and the robustness of data processing, while limiting the required communication bandwidth. In order to solve the problem of pipeline inspection and oil leakage monitoring, a collaborative weighted mobile sensing scheme is proposed. By adopting a weighted mobile sensing scheme, the adaptive collaborative clustering protocol can realize an even distribution of energy load among the mobile sensor nodes in each round, and make the best use of battery energy. A detailed theoretical analysis and experimental results revealed that the proposed protocol is an energy efficient collaborative strategy such that the sensor nodes can communicate with a fusion center and produce high power gain. Full article

(This article belongs to the Special Issue Mobile Sensor Computing: Theory and Applications)

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3252 KiB

Open AccessArticle

Characterization of Degradation Progressive in Composite Laminates Subjected to Thermal Fatigue and Moisture Diffusion by Lamb Waves

by Weibin Li, Chunguang Xu and Younho Cho

Sensors 2016, 16(2), 260; https://doi.org/10.3390/s16020260 - 19 Feb 2016

Cited by 17 | Viewed by 5981

Abstract

Laminate composites which are widely used in the aeronautical industry, are usually subjected to frequency variation of environmental temperature and excessive humidity in the in-service environment. The thermal fatigue and moisture absorption in composites may induce material degradation. There is a demand to [...] Read more.

Laminate composites which are widely used in the aeronautical industry, are usually subjected to frequency variation of environmental temperature and excessive humidity in the in-service environment. The thermal fatigue and moisture absorption in composites may induce material degradation. There is a demand to investigate the coupling damages mechanism and characterize the degradation evolution of composite laminates for the particular application. In this paper, the degradation evolution in unidirectional carbon/epoxy composite laminates subjected to thermal fatigue and moisture absorption is characterized by Lamb waves. The decrease rate of Lamb wave velocity is used to track the degradation evolution in the specimens. The results show that there are two stages for the progressive degradation of composites under the coupling effect of thermal cyclic loading and moisture diffusion. The present work provides an alternative to monitoring the degradation evolution of in-service aircraft composite Laminates. Full article

(This article belongs to the Special Issue Integrated Structural Health Monitoring in Polymeric Composites)

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1264 KiB

Open AccessArticle

Detection of Gold Nanoparticles Aggregation Growth Induced by Nucleic Acid through Laser Scanning Confocal Microscopy

by Ramla Gary, Giovani Carbone, Gia Petriashvili, Maria Penelope De Santo and Riccardo Barberi

Sensors 2016, 16(2), 258; https://doi.org/10.3390/s16020258 - 19 Feb 2016

Cited by 7 | Viewed by 6247

Abstract

The gold nanoparticle (GNP) aggregation growth induced by deoxyribonucleic acid (DNA) is studied by laser scanning confocal and environmental scanning electron microscopies. As in the investigated case the direct light scattering analysis is not suitable, we observe the behavior of the fluorescence produced [...] Read more.

The gold nanoparticle (GNP) aggregation growth induced by deoxyribonucleic acid (DNA) is studied by laser scanning confocal and environmental scanning electron microscopies. As in the investigated case the direct light scattering analysis is not suitable, we observe the behavior of the fluorescence produced by a dye and we detect the aggregation by the shift and the broadening of the fluorescence peak. Results of laser scanning confocal microscopy images and the fluorescence emission spectra from lambda scan mode suggest, in fact, that the intruding of the hydrophobic moiety of the probe within the cationic surfactants bilayer film coating GNPs results in a Förster resonance energy transfer. The environmental scanning electron microscopy images show that DNA molecules act as template to assemble GNPs into three-dimensional structures which are reminiscent of the DNA helix. This study is useful to design better nanobiotechnological devices using GNPs and DNA. Full article

(This article belongs to the Special Issue FRET Biosensors)

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19128 KiB

Open AccessArticle

Technique for Determining Bridge Displacement Response Using MEMS Accelerometers

by Hidehiko Sekiya, Kentaro Kimura and Chitoshi Miki

Sensors 2016, 16(2), 257; https://doi.org/10.3390/s16020257 - 19 Feb 2016

Cited by 50 | Viewed by 9161

Abstract

In bridge maintenance, particularly with regard to fatigue damage in steel bridges, it is important to determine the displacement response of the entire bridge under a live load as well as that of each member. Knowing the displacement response enables the identification of [...] Read more.

In bridge maintenance, particularly with regard to fatigue damage in steel bridges, it is important to determine the displacement response of the entire bridge under a live load as well as that of each member. Knowing the displacement response enables the identification of dynamic deformations that can cause stresses and ultimately lead to damage and thus also allows the undertaking of appropriate countermeasures. In theory, the displacement response can be calculated from the double integration of the measured acceleration. However, data measured by an accelerometer include measurement errors caused by the limitations of the analog-to-digital conversion process and sensor noise. These errors distort the double integration results. Furthermore, as bridges in service are constantly vibrating because of passing vehicles, estimating the boundary conditions for the numerical integration is difficult. To address these problems, this paper proposes a method for determining the displacement of a bridge in service from its acceleration based on its free vibration. To verify the effectiveness of the proposed method, field measurements were conducted using nine different accelerometers. Based on the results of these measurements, the proposed method was found to be highly accurate in comparison with the reference displacement obtained using a contact displacement gauge. Full article

(This article belongs to the Section Physical Sensors)

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927 KiB

Open AccessArticle

Measurement and Modeling of Narrowband Channels for Ultrasonic Underwater Communications

by Francisco J. Cañete, Jesús López-Fernández, Celia García-Corrales, Antonio Sánchez, Encarnación Robles, Francisco J. Rodrigo and José F. Paris

Sensors 2016, 16(2), 256; https://doi.org/10.3390/s16020256 - 19 Feb 2016

Cited by 33 | Viewed by 8760

Abstract

Underwater acoustic sensor networks are a promising technology that allow real-time data collection in seas and oceans for a wide variety of applications. Smaller size and weight sensors can be achieved with working frequencies shifted from audio to the ultrasonic band. At these [...] Read more.

Underwater acoustic sensor networks are a promising technology that allow real-time data collection in seas and oceans for a wide variety of applications. Smaller size and weight sensors can be achieved with working frequencies shifted from audio to the ultrasonic band. At these frequencies, the fading phenomena has a significant presence in the channel behavior, and the design of a reliable communication link between the network sensors will require a precise characterization of it. Fading in underwater channels has been previously measured and modeled in the audio band. However, there have been few attempts to study it at ultrasonic frequencies. In this paper, a campaign of measurements of ultrasonic underwater acoustic channels in Mediterranean shallow waters conducted by the authors is presented. These measurements are used to determine the parameters of the so-called κ-μ shadowed distribution, a fading model with a direct connection to the underlying physical mechanisms. The model is then used to evaluate the capacity of the measured channels with a closed-form expression. Full article

(This article belongs to the Special Issue Underwater Sensor Nodes and Underwater Sensor Networks 2016)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
Channel modeling diagrams: (a) example of underwater acoustic communications system; (b) classification of fading models. Full article ">Figure 2
Measurements setup: (a) block diagram of the measurement equipment; (b) picture of the receiver part at the laboratory. Full article ">Figure 3
Segment of the received signal in Channel A6-128. Full article ">Figure 4
Normalized Doppler spectrum in Channels A6-32, A6-64 and A6-128. Full article ">Figure 5
Cumulative distribution function (CDF) of the power gain estimated from measurements: (a) for two different transducers’ depth and the same link distance (200 m) and sounding frequency (64 kHz); (b) for two different link distances and the same transducers’ depth (6 m) and sounding frequency (64 kHz). Full article ">Figure 6
Example of the <math display="inline"> <mrow> <mi>κ</mi> <mo>-</mo> <mi>μ</mi> </mrow> </math> model fit and the Rice model fit for one of the measured channels: C9-32. Full article ">Figure 7
Evaluation of the ergodic capacity (by means of the model) for the measured channels with TS = 200 m and ASD = 25 m. Full article ">

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Open AccessArticle

UAV-Based Estimation of Carbon Exports from Heterogeneous Soil Landscapes—A Case Study from the CarboZALF Experimental Area

by Marc Wehrhan, Philipp Rauneker and Michael Sommer

Sensors 2016, 16(2), 255; https://doi.org/10.3390/s16020255 - 19 Feb 2016

Cited by 24 | Viewed by 8260

Abstract

The advantages of remote sensing using Unmanned Aerial Vehicles (UAVs) are a high spatial resolution of images, temporal flexibility and narrow-band spectral data from different wavelengths domains. This enables the detection of spatio-temporal dynamics of environmental variables, like plant-related carbon dynamics in agricultural [...] Read more.

The advantages of remote sensing using Unmanned Aerial Vehicles (UAVs) are a high spatial resolution of images, temporal flexibility and narrow-band spectral data from different wavelengths domains. This enables the detection of spatio-temporal dynamics of environmental variables, like plant-related carbon dynamics in agricultural landscapes. In this paper, we quantify spatial patterns of fresh phytomass and related carbon (C) export using imagery captured by a 12-band multispectral camera mounted on the fixed wing UAV Carolo P360. The study was performed in 2014 at the experimental area CarboZALF-D in NE Germany. From radiometrically corrected and calibrated images of lucerne (Medicago sativa), the performance of four commonly used vegetation indices (VIs) was tested using band combinations of six near-infrared bands. The highest correlation between ground-based measurements of fresh phytomass of lucerne and VIs was obtained for the Enhanced Vegetation Index (EVI) using near-infrared band b₈₉₉. The resulting map was transformed into dry phytomass and finally upscaled to total C export by harvest. The observed spatial variability at field- and plot-scale could be attributed to small-scale soil heterogeneity in part. Full article

(This article belongs to the Special Issue UAV Sensors for Environmental Monitoring)

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3901 KiB

Open AccessArticle

A Robust Camera-Based Interface for Mobile Entertainment

by Maria Francesca Roig-Maimó, Cristina Manresa-Yee and Javier Varona

Sensors 2016, 16(2), 254; https://doi.org/10.3390/s16020254 - 19 Feb 2016

Cited by 20 | Viewed by 5851

Abstract

Camera-based interfaces in mobile devices are starting to be used in games and apps, but few works have evaluated them in terms of usability or user perception. Due to the changing nature of mobile contexts, this evaluation requires extensive studies to consider the [...] Read more.

Camera-based interfaces in mobile devices are starting to be used in games and apps, but few works have evaluated them in terms of usability or user perception. Due to the changing nature of mobile contexts, this evaluation requires extensive studies to consider the full spectrum of potential users and contexts. However, previous works usually evaluate these interfaces in controlled environments such as laboratory conditions, therefore, the findings cannot be generalized to real users and real contexts. In this work, we present a robust camera-based interface for mobile entertainment. The interface detects and tracks the user’s head by processing the frames provided by the mobile device’s front camera, and its position is then used to interact with the mobile apps. First, we evaluate the interface as a pointing device to study its accuracy, and different factors to configure such as the gain or the device’s orientation, as well as the optimal target size for the interface. Second, we present an in the wild study to evaluate the usage and the user’s perception when playing a game controlled by head motion. Finally, the game is published in an application store to make it available to a large number of potential users and contexts and we register usage data. Results show the feasibility of using this robust camera-based interface for mobile entertainment in different contexts and by different people. Full article

(This article belongs to the Special Issue Sensors for Entertainment)

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3653 KiB

Open AccessArticle

Cable Crosstalk Suppression with Two-Wire Voltage Feedback Method for Resistive Sensor Array

by Jianfeng Wu, Shangshang He, Jianqing Li and Aiguo Song

Sensors 2016, 16(2), 253; https://doi.org/10.3390/s16020253 - 19 Feb 2016

Cited by 22 | Viewed by 5594

Abstract

Using a long, flexible test cable connected with a one-wire voltage feedback circuit, a resistive tactile sensor in a shared row-column fashion exhibited flexibility in robotic operations but suffered from crosstalk caused by the connected cable due to its wire resistances and its [...] Read more.

Using a long, flexible test cable connected with a one-wire voltage feedback circuit, a resistive tactile sensor in a shared row-column fashion exhibited flexibility in robotic operations but suffered from crosstalk caused by the connected cable due to its wire resistances and its contacted resistances. Firstly, we designed a new non-scanned driving-electrode (VF-NSDE) circuit using two wires for every row line and every column line to reduce the crosstalk caused by the connected cables in the circuit. Then, an equivalent resistance expression of the element being tested (EBT) for the two-wire VF-NSDE circuit was analytically derived. Following this, the one-wire VF-NSDE circuit and the two-wire VF-NSDE circuit were evaluated by simulation experiments. Finally, positive features of the proposed method were verified with the experiments of a two-wire VF-NSDE prototype circuit. The experiment results show that the two-wire VF-NSDE circuit can greatly reduce the crosstalk error caused by the cables in the 2-D networked resistive sensor array. Full article

(This article belongs to the Section Physical Sensors)

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479 KiB

Open AccessArticle

A Secure Scheme for Distributed Consensus Estimation against Data Falsification in Heterogeneous Wireless Sensor Networks

by Shichao Mi, Hui Han, Cailian Chen, Jian Yan and Xinping Guan

Sensors 2016, 16(2), 252; https://doi.org/10.3390/s16020252 - 19 Feb 2016

Cited by 8 | Viewed by 5275

Abstract

Heterogeneous wireless sensor networks (HWSNs) can achieve more tasks and prolong the network lifetime. However, they are vulnerable to attacks from the environment or malicious nodes. This paper is concerned with the issues of a consensus secure scheme in HWSNs consisting of two [...] Read more.

Heterogeneous wireless sensor networks (HWSNs) can achieve more tasks and prolong the network lifetime. However, they are vulnerable to attacks from the environment or malicious nodes. This paper is concerned with the issues of a consensus secure scheme in HWSNs consisting of two types of sensor nodes. Sensor nodes (SNs) have more computation power, while relay nodes (RNs) with low power can only transmit information for sensor nodes. To address the security issues of distributed estimation in HWSNs, we apply the heterogeneity of responsibilities between the two types of sensors and then propose a parameter adjusted-based consensus scheme (PACS) to mitigate the effect of the malicious node. Finally, the convergence property is proven to be guaranteed, and the simulation results validate the effectiveness and efficiency of PACS. Full article

(This article belongs to the Special Issue Security and Privacy in Sensor Networks)

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A network with eight honest sensor nodes, three relay nodes and one attacker. Full article ">Figure 2
Convergence of parameter adjusted-based consensus (PACS): (a) without attackers; (b) with one Perception Data Falsification (PDF) attacker; (c) with one Iteration Data Falsification (IDF) attacker; (d) with one Random Data Falsification (RDF) attacker. Full article ">Figure 2 Cont.
Convergence of parameter adjusted-based consensus (PACS): (a) without attackers; (b) with one Perception Data Falsification (PDF) attacker; (c) with one Iteration Data Falsification (IDF) attacker; (d) with one Random Data Falsification (RDF) attacker. Full article ">Figure 3
Convergence of the Olfati algorithm: (a) without attackers; (b) with one SDF attacker; (c) with one IDF attacker; (d) with one RDF attacker. Full article ">Figure 3 Cont.
Convergence of the Olfati algorithm: (a) without attackers; (b) with one SDF attacker; (c) with one IDF attacker; (d) with one RDF attacker. Full article ">Figure 4
A network with 27 honest sensor nodes, 13 relay nodes and three attackers. Full article ">Figure 5
Convergence of PACS in numerical Example 2: (a) without attackers; (b) with three attackers. Full article ">Figure 5 Cont.
Convergence of PACS in numerical Example 2: (a) without attackers; (b) with three attackers. Full article ">Figure 6
Convergence of Olfati in numerical example 2: (a) without attackers; (b) with three attackers. Full article ">Figure 6 Cont.
Convergence of Olfati in numerical example 2: (a) without attackers; (b) with three attackers. Full article ">

1297 KiB

Open AccessArticle

Improved Sensitivity MEMS Cantilever Sensor for Terahertz Photoacoustic Spectroscopy

by Ronald A. Coutu, Ivan R. Medvedev and Douglas T. Petkie

Sensors 2016, 16(2), 251; https://doi.org/10.3390/s16020251 - 19 Feb 2016

Cited by 19 | Viewed by 8146

Abstract

In this paper, a microelectromechanical system (MEMS) cantilever sensor was designed, modeled and fabricated to measure the terahertz (THz) radiation induced photoacoustic (PA) response of gases under low vacuum conditions. This work vastly improves cantilever sensitivity over previous efforts, by reducing internal beam [...] Read more.

In this paper, a microelectromechanical system (MEMS) cantilever sensor was designed, modeled and fabricated to measure the terahertz (THz) radiation induced photoacoustic (PA) response of gases under low vacuum conditions. This work vastly improves cantilever sensitivity over previous efforts, by reducing internal beam stresses, minimizing out of plane beam curvature and optimizing beam damping. In addition, fabrication yield was improved by approximately 50% by filleting the cantilever’s anchor and free end to help reduce high stress areas that occurred during device fabrication and processing. All of the cantilever sensors were fabricated using silicon-on-insulator (SOI) wafers and tested in a custom built, low-volume, vacuum chamber. The resulting cantilever sensors exhibited improved signal to noise ratios, sensitivities and normalized noise equivalent absorption (NNEA) coefficients of approximately 4.28 × 10⁻¹⁰ cm⁻¹·WHz^−1/2. This reported NNEA represents approximately a 70% improvement over previously fabricated and tested SOI cantilever sensors for THz PA spectroscopy. Full article

(This article belongs to the Special Issue Infrared and THz Sensing and Imaging)

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3236 KiB

Open AccessArticle

Inspection Robot Based Mobile Sensing and Power Line Tracking for Smart Grid

by Bat-erdene Byambasuren, Donghan Kim, Mandakh Oyun-Erdene, Chinguun Bold and Jargalbaatar Yura

Sensors 2016, 16(2), 250; https://doi.org/10.3390/s16020250 - 19 Feb 2016

Cited by 16 | Viewed by 8662

Abstract

Smart sensing and power line tracking is very important in a smart grid system. Illegal electricity usage can be detected by remote current measurement on overhead power lines using an inspection robot. There is a need for accurate detection methods of illegal electricity [...] Read more.

Smart sensing and power line tracking is very important in a smart grid system. Illegal electricity usage can be detected by remote current measurement on overhead power lines using an inspection robot. There is a need for accurate detection methods of illegal electricity usage. Stable and correct power line tracking is a very prominent issue. In order to correctly track and make accurate measurements, the swing path of a power line should be previously fitted and predicted by a mathematical function using an inspection robot. After this, the remote inspection robot can follow the power line and measure the current. This paper presents a new power line tracking method using parabolic and circle fitting algorithms for illegal electricity detection. We demonstrate the effectiveness of the proposed tracking method by simulation and experimental results. Full article

(This article belongs to the Special Issue Integration of Sensors in Complex, Intelligent Systems—Selected Papers from the CHARMS 2015 Workshop)

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1597 KiB

Open AccessArticle

Joint Transmit Antenna Selection and Power Allocation for ISDF Relaying Mobile-to-Mobile Sensor Networks

by Lingwei Xu, Hao Zhang and T. Aaron Gulliver

Sensors 2016, 16(2), 249; https://doi.org/10.3390/s16020249 - 19 Feb 2016

Cited by 5 | Viewed by 4954

Abstract

The outage probability (OP) performance of multiple-relay incremental-selective decode-and-forward (ISDF) relaying mobile-to-mobile (M2M) sensor networks with transmit antenna selection (TAS) over N-Nakagami fading channels is investigated. Exact closed-form OP expressions for both optimal and suboptimal TAS schemes are derived. The power allocation [...] Read more.

The outage probability (OP) performance of multiple-relay incremental-selective decode-and-forward (ISDF) relaying mobile-to-mobile (M2M) sensor networks with transmit antenna selection (TAS) over N-Nakagami fading channels is investigated. Exact closed-form OP expressions for both optimal and suboptimal TAS schemes are derived. The power allocation problem is formulated to determine the optimal division of transmit power between the broadcast and relay phases. The OP performance under different conditions is evaluated via numerical simulation to verify the analysis. These results show that the optimal TAS scheme has better OP performance than the suboptimal scheme. Further, the power allocation parameter has a significant influence on the OP performance. Full article

(This article belongs to the Special Issue Mobile Sensor Computing: Theory and Applications)

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The system model. Full article ">Figure 2
The effect of the power allocation parameter K on the OP performance. Full article ">Figure 3
The effect of the relative geometrical gain μ on the OP performance. Full article ">Figure 4
The OP performance of the optimal TAS scheme when γth < γP. Full article ">Figure 5
The OP performance of the optimal TAS scheme when γth > γP. Full article ">Figure 6
The OP performance of the suboptimal TAS scheme when γth < γP. Full article ">Figure 7
The OP performance of the suboptimal TAS scheme when γth > γP. Full article ">Figure 8
The OP performance of the optimal and suboptimal TAS schemes for different numbers of antennas Nt. Full article ">

310 KiB

Open AccessArticle

Angle-Polarization Estimation for Coherent Sources with Linear Tripole Sensor Arrays

by Kun Wang, Jin He, Ting Shu and Zhong Liu

Sensors 2016, 16(2), 248; https://doi.org/10.3390/s16020248 - 19 Feb 2016

Cited by 8 | Viewed by 4203

Abstract

We propose a parallel factor (PARAFAC) analysis-based angle and polarization estimation algorithm for multiple coherent sources using a uniformly-spaced linear tripole sensor array. By forming a PARAFAC model using the spatial signature of the tripole array, the new algorithm requires neither spatial smoothing [...] Read more.

We propose a parallel factor (PARAFAC) analysis-based angle and polarization estimation algorithm for multiple coherent sources using a uniformly-spaced linear tripole sensor array. By forming a PARAFAC model using the spatial signature of the tripole array, the new algorithm requires neither spatial smoothing nor vector-field smoothing to decorrelate the signal coherency. We also establish that the angle-polarization parameters of K coherent signals can be uniquely determined by PARAFAC analysis, as long as the number of tripoles L ≥ 2K − 1 . In addition, the proposed algorithm can offer enhanced angle and polarization estimation accuracy by extending the interspacing of the tripoles beyond a half wavelength. Full article

(This article belongs to the Section Physical Sensors)

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1764 KiB

Open AccessArticle

Social Milieu Oriented Routing: A New Dimension to Enhance Network Security in WSNs

by Lianggui Liu, Li Chen and Huiling Jia

Sensors 2016, 16(2), 247; https://doi.org/10.3390/s16020247 - 19 Feb 2016

Cited by 7 | Viewed by 5233

Abstract

In large-scale wireless sensor networks (WSNs), in order to enhance network security, it is crucial for a trustor node to perform social milieu oriented routing to a target a trustee node to carry out trust evaluation. This challenging social milieu oriented routing with [...] Read more.

In large-scale wireless sensor networks (WSNs), in order to enhance network security, it is crucial for a trustor node to perform social milieu oriented routing to a target a trustee node to carry out trust evaluation. This challenging social milieu oriented routing with more than one end-to-end Quality of Trust (QoT) constraint has proved to be NP-complete. Heuristic algorithms with polynomial and pseudo-polynomial-time complexities are often used to deal with this challenging problem. However, existing solutions cannot guarantee the efficiency of searching; that is, they can hardly avoid obtaining partial optimal solutions during a searching process. Quantum annealing (QA) uses delocalization and tunneling to avoid falling into local minima without sacrificing execution time. This has been proven a promising way to many optimization problems in recently published literatures. In this paper, for the first time, with the help of a novel approach, that is, configuration path-integral Monte Carlo (CPIMC) simulations, a QA-based optimal social trust path (QA_OSTP) selection algorithm is applied to the extraction of the optimal social trust path in large-scale WSNs. Extensive experiments have been conducted, and the experiment results demonstrate that QA_OSTP outperforms its heuristic opponents. Full article

(This article belongs to the Special Issue Security and Privacy in Sensor Networks)

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2064 KiB

Open AccessArticle

A Game Theory Algorithm for Intra-Cluster Data Aggregation in a Vehicular Ad Hoc Network

by Yuzhong Chen, Shining Weng, Wenzhong Guo and Naixue Xiong

Sensors 2016, 16(2), 245; https://doi.org/10.3390/s16020245 - 19 Feb 2016

Cited by 24 | Viewed by 7116

Abstract

Vehicular ad hoc networks (VANETs) have an important role in urban management and planning. The effective integration of vehicle information in VANETs is critical to traffic analysis, large-scale vehicle route planning and intelligent transportation scheduling. However, given the limitations in the precision of [...] Read more.

Vehicular ad hoc networks (VANETs) have an important role in urban management and planning. The effective integration of vehicle information in VANETs is critical to traffic analysis, large-scale vehicle route planning and intelligent transportation scheduling. However, given the limitations in the precision of the output information of a single sensor and the difficulty of information sharing among various sensors in a highly dynamic VANET, effectively performing data aggregation in VANETs remains a challenge. Moreover, current studies have mainly focused on data aggregation in large-scale environments but have rarely discussed the issue of intra-cluster data aggregation in VANETs. In this study, we propose a multi-player game theory algorithm for intra-cluster data aggregation in VANETs by analyzing the competitive and cooperative relationships among sensor nodes. Several sensor-centric metrics are proposed to measure the data redundancy and stability of a cluster. We then study the utility function to achieve efficient intra-cluster data aggregation by considering both data redundancy and cluster stability. In particular, we prove the existence of a unique Nash equilibrium in the game model, and conduct extensive experiments to validate the proposed algorithm. Results demonstrate that the proposed algorithm has advantages over typical data aggregation algorithms in both accuracy and efficiency. Full article

(This article belongs to the Special Issue Mobile Sensor Computing: Theory and Applications)

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9587 KiB

Open AccessArticle

A Vehicle Active Safety Model: Vehicle Speed Control Based on Driver Vigilance Detection Using Wearable EEG and Sparse Representation

by Zutao Zhang, Dianyuan Luo, Yagubov Rasim, Yanjun Li, Guanjun Meng, Jian Xu and Chunbai Wang

Sensors 2016, 16(2), 242; https://doi.org/10.3390/s16020242 - 19 Feb 2016

Cited by 68 | Viewed by 13196

Abstract

In this paper, we present a vehicle active safety model for vehicle speed control based on driver vigilance detection using low-cost, comfortable, wearable electroencephalographic (EEG) sensors and sparse representation. The proposed system consists of three main steps, namely wireless wearable EEG collection, driver [...] Read more.

In this paper, we present a vehicle active safety model for vehicle speed control based on driver vigilance detection using low-cost, comfortable, wearable electroencephalographic (EEG) sensors and sparse representation. The proposed system consists of three main steps, namely wireless wearable EEG collection, driver vigilance detection, and vehicle speed control strategy. First of all, a homemade low-cost comfortable wearable brain-computer interface (BCI) system with eight channels is designed for collecting the driver’s EEG signal. Second, wavelet de-noising and down-sample algorithms are utilized to enhance the quality of EEG data, and Fast Fourier Transformation (FFT) is adopted to extract the EEG power spectrum density (PSD). In this step, sparse representation classification combined with k-singular value decomposition (KSVD) is firstly introduced in PSD to estimate the driver’s vigilance level. Finally, a novel safety strategy of vehicle speed control, which controls the electronic throttle opening and automatic braking after driver fatigue detection using the above method, is presented to avoid serious collisions and traffic accidents. The simulation and practical testing results demonstrate the feasibility of the vehicle active safety model. Full article

(This article belongs to the Special Issue Sensors in New Road Vehicles)

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6650 KiB

Open AccessArticle

Hybrid EEG—Eye Tracker: Automatic Identification and Removal of Eye Movement and Blink Artifacts from Electroencephalographic Signal

by Malik M. Naeem Mannan, Shinjung Kim, Myung Yung Jeong and M. Ahmad Kamran

Sensors 2016, 16(2), 241; https://doi.org/10.3390/s16020241 - 19 Feb 2016

Cited by 33 | Viewed by 9442

Abstract

Contamination of eye movement and blink artifacts in Electroencephalogram (EEG) recording makes the analysis of EEG data more difficult and could result in mislead findings. Efficient removal of these artifacts from EEG data is an essential step in improving classification accuracy to develop [...] Read more.

Contamination of eye movement and blink artifacts in Electroencephalogram (EEG) recording makes the analysis of EEG data more difficult and could result in mislead findings. Efficient removal of these artifacts from EEG data is an essential step in improving classification accuracy to develop the brain-computer interface (BCI). In this paper, we proposed an automatic framework based on independent component analysis (ICA) and system identification to identify and remove ocular artifacts from EEG data by using hybrid EEG and eye tracker system. The performance of the proposed algorithm is illustrated using experimental and standard EEG datasets. The proposed algorithm not only removes the ocular artifacts from artifactual zone but also preserves the neuronal activity related EEG signals in non-artifactual zone. The comparison with the two state-of-the-art techniques namely ADJUST based ICA and REGICA reveals the significant improved performance of the proposed algorithm for removing eye movement and blink artifacts from EEG data. Additionally, results demonstrate that the proposed algorithm can achieve lower relative error and higher mutual information values between corrected EEG and artifact-free EEG data. Full article

(This article belongs to the Section Physical Sensors)

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3147 KiB

Open AccessArticle

An Efficient Virtual Machine Consolidation Scheme for Multimedia Cloud Computing

by Guangjie Han, Wenhui Que, Gangyong Jia and Lei Shu

Sensors 2016, 16(2), 246; https://doi.org/10.3390/s16020246 - 18 Feb 2016

Cited by 92 | Viewed by 10566

Abstract

Cloud computing has innovated the IT industry in recent years, as it can delivery subscription-based services to users in the pay-as-you-go model. Meanwhile, multimedia cloud computing is emerging based on cloud computing to provide a variety of media services on the Internet. However, [...] Read more.

Cloud computing has innovated the IT industry in recent years, as it can delivery subscription-based services to users in the pay-as-you-go model. Meanwhile, multimedia cloud computing is emerging based on cloud computing to provide a variety of media services on the Internet. However, with the growing popularity of multimedia cloud computing, its large energy consumption cannot only contribute to greenhouse gas emissions, but also result in the rising of cloud users’ costs. Therefore, the multimedia cloud providers should try to minimize its energy consumption as much as possible while satisfying the consumers’ resource requirements and guaranteeing quality of service (QoS). In this paper, we have proposed a remaining utilization-aware (RUA) algorithm for virtual machine (VM) placement, and a power-aware algorithm (PA) is proposed to find proper hosts to shut down for energy saving. These two algorithms have been combined and applied to cloud data centers for completing the process of VM consolidation. Simulation results have shown that there exists a trade-off between the cloud data center’s energy consumption and service-level agreement (SLA) violations. Besides, the RUA algorithm is able to deal with variable workload to prevent hosts from overloading after VM placement and to reduce the SLA violations dramatically. Full article

(This article belongs to the Special Issue Identification, Information & Knowledge in the Internet of Things)

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1269 KiB

Open AccessArticle

Determination and Visualization of pH Values in Anaerobic Digestion of Water Hyacinth and Rice Straw Mixtures Using Hyperspectral Imaging with Wavelet Transform Denoising and Variable Selection

by Chu Zhang, Hui Ye, Fei Liu, Yong He, Wenwen Kong and Kuichuan Sheng

Sensors 2016, 16(2), 244; https://doi.org/10.3390/s16020244 - 18 Feb 2016

Cited by 27 | Viewed by 5798

Abstract

Biomass energy represents a huge supplement for meeting current energy demands. A hyperspectral imaging system covering the spectral range of 874–1734 nm was used to determine the pH value of anaerobic digestion liquid produced by water hyacinth and rice straw mixtures used for [...] Read more.

Biomass energy represents a huge supplement for meeting current energy demands. A hyperspectral imaging system covering the spectral range of 874–1734 nm was used to determine the pH value of anaerobic digestion liquid produced by water hyacinth and rice straw mixtures used for methane production. Wavelet transform (WT) was used to reduce noises of the spectral data. Successive projections algorithm (SPA), random frog (RF) and variable importance in projection (VIP) were used to select 8, 15 and 20 optimal wavelengths for the pH value prediction, respectively. Partial least squares (PLS) and a back propagation neural network (BPNN) were used to build the calibration models on the full spectra and the optimal wavelengths. As a result, BPNN models performed better than the corresponding PLS models, and SPA-BPNN model gave the best performance with a correlation coefficient of prediction (r_p) of 0.911 and root mean square error of prediction (RMSEP) of 0.0516. The results indicated the feasibility of using hyperspectral imaging to determine pH values during anaerobic digestion. Furthermore, a distribution map of the pH values was achieved by applying the SPA-BPNN model. The results in this study would help to develop an on-line monitoring system for biomass energy producing process by hyperspectral imaging. Full article

(This article belongs to the Special Issue The Use of New and/or Improved Materials for Sensing Applications)

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2360 KiB

Open AccessArticle

One-Pot Hydrothermal Synthesis of Magnetite Prussian Blue Nano-Composites and Their Application to Fabricate Glucose Biosensor

by Ezzaldeen Younes Jomma and Shou-Nian Ding

Sensors 2016, 16(2), 243; https://doi.org/10.3390/s16020243 - 18 Feb 2016

Cited by 35 | Viewed by 9866

Abstract

In this work, we presented a simple method to synthesize magnetite Prussian blue nano-composites (Fe₃O₄-PB) through one-pot hydrothermal process. Subsequently, the obtained nano-composites were used to fabricate a facile and effective glucose biosensor. The obtained nanoparticles were characterized using [...] Read more.

In this work, we presented a simple method to synthesize magnetite Prussian blue nano-composites (Fe₃O₄-PB) through one-pot hydrothermal process. Subsequently, the obtained nano-composites were used to fabricate a facile and effective glucose biosensor. The obtained nanoparticles were characterized using transmission electron microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, UV-vis absorbance spectroscopy, cyclic voltammetry and chronoamperometry. The resultant Fe₃O₄-PB nanocomposites have magnetic properties which could easily controlled by an external magnetic field and the electro-catalysis of hydrogen peroxide. Thus, a glucose biosensor based on Fe₃O₄-PB was successfully fabricated. The biosensor showed super-electrochemical properties toward glucose detection exhibiting fast response time within 3 to 4 s, low detection limit of 0.5 µM and wide linear range from 5 µM to 1.2 mM with sensitivity of 32 µA∙mM⁻¹∙cm⁻² and good long-term stability. Full article

(This article belongs to the Special Issue Microbial and Enzymatic Biosensors)

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1096 KiB

Open AccessArticle

Classification between Failed Nodes and Left Nodes in Mobile Asset Tracking Systems †

by Kwangsoo Kim, Jae-Yeon Jin and Seong-il Jin

Sensors 2016, 16(2), 240; https://doi.org/10.3390/s16020240 - 18 Feb 2016

Cited by 3 | Viewed by 5115

Abstract

Medical asset tracking systems track a medical device with a mobile node and determine its status as either in or out, because it can leave a monitoring area. Due to a failed node, this system may decide that a mobile asset is outside [...] Read more.

Medical asset tracking systems track a medical device with a mobile node and determine its status as either in or out, because it can leave a monitoring area. Due to a failed node, this system may decide that a mobile asset is outside the area, even though it is within the area. In this paper, an efficient classification method is proposed to separate mobile nodes disconnected from a wireless sensor network between nodes with faults and a node that actually has left the monitoring region. The proposed scheme uses two trends extracted from the neighboring nodes of a disconnected mobile node. First is the trend in a series of the neighbor counts; the second is that of the ratios of the boundary nodes included in the neighbors. Based on such trends, the proposed method separates failed nodes from mobile nodes that are disconnected from a wireless sensor network without failures. The proposed method is evaluated using both real data generated from a medical asset tracking system and also using simulations with the network simulator (ns-2). The experimental results show that the proposed method correctly differentiates between failed nodes and nodes that are no longer in the monitoring region, including the cases that the conventional methods fail to detect. Full article

(This article belongs to the Special Issue Mobile Sensor Computing: Theory and Applications)

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3766 KiB

Open AccessArticle

A Rapid Coordinate Transformation Method Applied in Industrial Robot Calibration Based on Characteristic Line Coincidence

by Bailing Liu, Fumin Zhang, Xinghua Qu and Xiaojia Shi

Sensors 2016, 16(2), 239; https://doi.org/10.3390/s16020239 - 18 Feb 2016

Cited by 24 | Viewed by 7739

Abstract

Coordinate transformation plays an indispensable role in industrial measurements, including photogrammetry, geodesy, laser 3-D measurement and robotics. The widely applied methods of coordinate transformation are generally based on solving the equations of point clouds. Despite the high accuracy, this might result in no [...] Read more.

Coordinate transformation plays an indispensable role in industrial measurements, including photogrammetry, geodesy, laser 3-D measurement and robotics. The widely applied methods of coordinate transformation are generally based on solving the equations of point clouds. Despite the high accuracy, this might result in no solution due to the use of ill conditioned matrices. In this paper, a novel coordinate transformation method is proposed, not based on the equation solution but based on the geometric transformation. We construct characteristic lines to represent the coordinate systems. According to the space geometry relation, the characteristic line scan is made to coincide by a series of rotations and translations. The transformation matrix can be obtained using matrix transformation theory. Experiments are designed to compare the proposed method with other methods. The results show that the proposed method has the same high accuracy, but the operation is more convenient and flexible. A multi-sensor combined measurement system is also presented to improve the position accuracy of a robot with the calibration of the robot kinematic parameters. Experimental verification shows that the position accuracy of robot manipulator is improved by 45.8% with the proposed method and robot calibration. Full article

(This article belongs to the Special Issue Sensors for Robots)

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