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Volume 17
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Sensors, Volume 17, Issue 8 (August 2017) – 233 articles

Cover Story (view full-size image): The Biomedical REAl-Time Health Evaluation (BREATHE) platform for real-time secure data communication mobile Health (mHealth) systems for pediatric asthma. Wireless physiological and environmental wireless sensors send data to a smartwatch and smartphone, where it is combined with available sensor data in real time. This data is then sent to a cloud through Health Insurance Portability and Accountability Act (HIPAA) compliant cryptography and combined with online sources to provide an enriched dataset for real-time individualized assessments of the risk of an asthma attack. The risk level (high, medium, or low risk) is then determined using a random forest classifier and sent to the smartwatch to be visualized as an animated dragon graphic for easy interpretation by children. View Paper here
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8735 KiB  
Article
Experimental Study on Stress Monitoring of Sand-Filled Steel Tube during Impact Using Piezoceramic Smart Aggregates
by Guofeng Du, Juan Zhang, Jicheng Zhang and Gangbing Song
Sensors 2017, 17(8), 1930; https://doi.org/10.3390/s17081930 - 22 Aug 2017
Cited by 37 | Viewed by 5344
Abstract
The filling of thin-walled steel tubes with quartz sand can help to prevent the premature buckling of the steel tube at a low cost. During an impact, the internal stress of the quartz sand-filled steel tube column is subjected to not only axial [...] Read more.
The filling of thin-walled steel tubes with quartz sand can help to prevent the premature buckling of the steel tube at a low cost. During an impact, the internal stress of the quartz sand-filled steel tube column is subjected to not only axial force but also lateral confining force, resulting in complicated internal stress. A suitable sensor for monitoring the internal stress of such a structure under an impact is important for structural health monitoring. In this paper, piezoceramic Smart Aggregates (SAs) are embedded into a quartz Sand-Filled Steel Tube Column (SFSTC) to monitor the internal structural stress during impacts. The piezoceramic smart aggregates are first calibrated by an impact hammer. Tests are conducted to study the feasibility of monitoring the internal stress of a structure. The results reflect that the calibration value of the piezoceramic smart aggregate sensitivity test is in good agreement with the theoretical value, and the output voltage value of the piezoceramic smart aggregate has a good linear relationship with external forces. Impact tests are conducted on the sand-filled steel tube with embedded piezoceramic smart aggregates. By analyzing the output signal of the piezoceramic smart aggregates, the internal stress state of the structure can be obtained. Experimental results demonstrated that, under the action of impact loads, the piezoceramic smart aggregates monitor the compressive stress at different locations in the steel tube, which verifies the feasibility of using piezoceramic smart aggregate to monitor the internal stress of a structure. Full article
(This article belongs to the Section Physical Sensors)
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6342 KiB  
Article
A Fast Room Temperature NH3 Sensor Based on an Al/p-Si/Al Structure with Schottky Electrodes
by Suwan Zhu, Xiaolong Liu, Jun Zhuang and Li Zhao
Sensors 2017, 17(8), 1929; https://doi.org/10.3390/s17081929 - 22 Aug 2017
Cited by 13 | Viewed by 5243
Abstract
In this paper, an electrical-based NH3 sensor with an Al/p-Si/Al structure is reported. The p-Si substrate is microstructured by fs-laser irradiation and then etched by 30% alkaline solution. This sensor works well at room temperature with fast response/recovery for NH3 gas [...] Read more.
In this paper, an electrical-based NH3 sensor with an Al/p-Si/Al structure is reported. The p-Si substrate is microstructured by fs-laser irradiation and then etched by 30% alkaline solution. This sensor works well at room temperature with fast response/recovery for NH3 gas at 5–100 ppm concentration. However, when the sensor is annealed in N2/H2 forming gas or short-circuited for Al/Si electrodes, its sensitivity decreases drastically and almost vanishes. Further I-V and FT-IR results show that the two back-to-back Schottky diodes on the device play a key role in its sensing performance. Full article
(This article belongs to the Collection Gas Sensors)
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2237 KiB  
Article
Landmark-Based Homing Navigation Using Omnidirectional Depth Information
by Changmin Lee, Seung-Eun Yu and DaeEun Kim
Sensors 2017, 17(8), 1928; https://doi.org/10.3390/s17081928 - 22 Aug 2017
Cited by 17 | Viewed by 6005
Abstract
A number of landmark-based navigation algorithms have been studied using feature extraction over the visual information. In this paper, we apply the distance information of the surrounding environment in a landmark navigation model. We mount a depth sensor on a mobile robot, in [...] Read more.
A number of landmark-based navigation algorithms have been studied using feature extraction over the visual information. In this paper, we apply the distance information of the surrounding environment in a landmark navigation model. We mount a depth sensor on a mobile robot, in order to obtain omnidirectional distance information. The surrounding environment is represented as a circular form of landmark vectors, which forms a snapshot. The depth snapshots at the current position and the target position are compared to determine the homing direction, inspired by the snapshot model. Here, we suggest a holistic view of panoramic depth information for homing navigation where each sample point is taken as a landmark. The results are shown in a vector map of homing vectors. The performance of the suggested method is evaluated based on the angular errors and the homing success rate. Omnidirectional depth information about the surrounding environment can be a promising source of landmark homing navigation. We demonstrate the results that a holistic approach with omnidirectional depth information shows effective homing navigation. Full article
(This article belongs to the Special Issue Sensors and Sensing in Indoor Localization, Tracking, Navigation and Activity Monitoring)
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684 KiB  
Review
A Review of Pedestrian Indoor Positioning Systems for Mass Market Applications
by Alejandro Correa, Marc Barcelo, Antoni Morell and Jose Lopez Vicario
Sensors 2017, 17(8), 1927; https://doi.org/10.3390/s17081927 - 22 Aug 2017
Cited by 97 | Viewed by 9322
Abstract
In the last decade, the interest in Indoor Location Based Services (ILBS) has increased stimulating the development of Indoor Positioning Systems (IPS). In particular, ILBS look for positioning systems that can be applied anywhere in the world for millions of users, that is, [...] Read more.
In the last decade, the interest in Indoor Location Based Services (ILBS) has increased stimulating the development of Indoor Positioning Systems (IPS). In particular, ILBS look for positioning systems that can be applied anywhere in the world for millions of users, that is, there is a need for developing IPS for mass market applications. Those systems must provide accurate position estimations with minimum infrastructure cost and easy scalability to different environments. This survey overviews the current state of the art of IPSs and classifies them in terms of the infrastructure and methodology employed. Finally, each group is reviewed analysing its advantages and disadvantages and its applicability to mass market applications. Full article
(This article belongs to the Section Physical Sensors)
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2550 KiB  
Article
RUDO: A Home Ambient Intelligence System for Blind People
by Milan Hudec and Zdenek Smutny
Sensors 2017, 17(8), 1926; https://doi.org/10.3390/s17081926 - 22 Aug 2017
Cited by 32 | Viewed by 9548
Abstract
The article introduces an ambient intelligence system for blind people which besides providing assistance in home environment also helps with various situations and roles in which blind people may find themselves involved. RUDO, the designed system, comprises several modules that mainly support or [...] Read more.
The article introduces an ambient intelligence system for blind people which besides providing assistance in home environment also helps with various situations and roles in which blind people may find themselves involved. RUDO, the designed system, comprises several modules that mainly support or ensure recognition of approaching people, alerting to other household members’ movement in the flat, work on a computer, supervision of (sighted) children, cooperation of a sighted and a blind person (e.g., when studying), control of heating and zonal regulation by a blind person. It has a unified user interface that gives the blind person access to individual functions. The interface for blind people offers assistance with work on a computer, including writing in Braille on a regular keyboard and specialized work in informatics and electronics (e.g., programming). RUDO can complement the standard aids used by blind people at home, it increases their independence and creates conditions that allow them to become fully involved. RUDO also supports blind people sharing a home with sighted people, which contributes to their feeling of security and greater inclusion in society. RUDO has been implemented in a household for two years, which allows an evaluation of its use in practice. Full article
(This article belongs to the Special Issue Advances in Sensors for Sustainable Smart Cities and Smart Buildings)
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8275 KiB  
Article
Crack Monitoring of Operational Wind Turbine Foundations
by Marcus Perry, Jack McAlorum, Grzegorz Fusiek, Pawel Niewczas, Iain McKeeman and Tim Rubert
Sensors 2017, 17(8), 1925; https://doi.org/10.3390/s17081925 - 21 Aug 2017
Cited by 25 | Viewed by 9131
Abstract
The degradation of onshore, reinforced-concrete wind turbine foundations is usually assessed via above-ground inspections, or through lengthy excavation campaigns that suspend wind power generation. Foundation cracks can and do occur below ground level, and while sustained measurements of crack behaviour could be used [...] Read more.
The degradation of onshore, reinforced-concrete wind turbine foundations is usually assessed via above-ground inspections, or through lengthy excavation campaigns that suspend wind power generation. Foundation cracks can and do occur below ground level, and while sustained measurements of crack behaviour could be used to quantify the risk of water ingress and reinforcement corrosion, these cracks have not yet been monitored during turbine operation. Here, we outline the design, fabrication and field installation of subterranean fibre-optic sensors for monitoring the opening and lateral displacements of foundation cracks during wind turbine operation. We detail methods for in situ sensor characterisation, verify sensor responses against theoretical tower strains derived from wind speed data, and then show that measured crack displacements correlate with monitored tower strains. Our results show that foundation crack opening displacements respond linearly to tower strain and do not change by more than ±5 μ m. Lateral crack displacements were found to be negligible. We anticipate that the work outlined here will provide a starting point for real-time, long-term and dynamic analyses of crack displacements in future. Our findings could furthermore inform the development of cost-effective monitoring systems for ageing wind turbine foundations. Full article
(This article belongs to the Special Issue Fiber Bragg Grating Based Sensors)
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2833 KiB  
Article
Ultrasensitive Terahertz Biosensors Based on Fano Resonance of a Graphene/Waveguide Hybrid Structure
by Banxian Ruan, Jun Guo, Leiming Wu, Jiaqi Zhu, Qi You, Xiaoyu Dai and Yuanjiang Xiang
Sensors 2017, 17(8), 1924; https://doi.org/10.3390/s17081924 - 21 Aug 2017
Cited by 55 | Viewed by 7036
Abstract
Graphene terahertz (THz) surface plasmons provide hope for developing functional devices in the THz frequency. By coupling graphene surface plasmon polaritons (SPPs) and a planar waveguide (PWG) mode, Fano resonances are demonstrated to realize an ultrasensitive terahertz biosensor. By analyzing the dispersion relation [...] Read more.
Graphene terahertz (THz) surface plasmons provide hope for developing functional devices in the THz frequency. By coupling graphene surface plasmon polaritons (SPPs) and a planar waveguide (PWG) mode, Fano resonances are demonstrated to realize an ultrasensitive terahertz biosensor. By analyzing the dispersion relation of graphene SPPs and PWG, the tunable Fano resonances in the terahertz frequency are discussed. It is found that the asymmetric lineshape of Fano resonances can be manipulated by changing the Fermi level of graphene, and the influence of the thickness of coupling layer and air layer in sandwich structure on the Fano resonances is also discussed in detail. We then apply the proposed Fano resonance to realize the ultrasensitive terahertz biosensors, it is shown that the highest sensitivities of 3260 RIU−1 are realized. Our result is two orders of a conventional surface plasmon resonance sensor. Furthermore, we find that when sensing medium is in the vicinity of water in THz, the sensitivity increases with increasing refractive index of the sensing medium. Full article
(This article belongs to the Special Issue Surface Plasmon Resonance Sensing)
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5820 KiB  
Article
Evaluation of Flexible Force Sensors for Pressure Monitoring in Treatment of Chronic Venous Disorders
by Suresh Parmar, Iryna Khodasevych and Olga Troynikov
Sensors 2017, 17(8), 1923; https://doi.org/10.3390/s17081923 - 21 Aug 2017
Cited by 58 | Viewed by 9401
Abstract
The recent use of graduated compression therapy for treatment of chronic venous disorders such as leg ulcers and oedema has led to considerable research interest in flexible and low-cost force sensors. Properly applied low pressure during compression therapy can substantially improve the treatment [...] Read more.
The recent use of graduated compression therapy for treatment of chronic venous disorders such as leg ulcers and oedema has led to considerable research interest in flexible and low-cost force sensors. Properly applied low pressure during compression therapy can substantially improve the treatment of chronic venous disorders. However, achievement of the recommended low pressure levels and its accurate determination in real-life conditions is still a challenge. Several thin and flexible force sensors, which can also function as pressure sensors, are commercially available, but their real-life sensing performance has not been evaluated. Moreover, no researchers have reported information on sensor performance during static and dynamic loading within the realistic test conditions required for compression therapy. This research investigated the sensing performance of five low-cost commercial pressure sensors on a human-leg-like test apparatus and presents quantitative results on the accuracy and drift behaviour of these sensors in both static and dynamic conditions required for compression therapy. Extensive experimental work on this new human-leg-like test setup demonstrated its utility for evaluating the sensors. Results showed variation in static and dynamic sensing performance, including accuracy and drift characteristics. Only one commercially available pressure sensor was found to reliably deliver accuracy of 95% and above for all three test pressure points of 30, 50 and 70 mmHg. Full article
(This article belongs to the Special Issue Force and Pressure Based Sensing Medical Application)
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9561 KiB  
Article
Estimating Hourly Concentrations of PM2.5 across a Metropolitan Area Using Low-Cost Particle Monitors
by Nadezda Zikova, Mauro Masiol, David C. Chalupa, David Q. Rich, Andrea R. Ferro and Philip K. Hopke
Sensors 2017, 17(8), 1922; https://doi.org/10.3390/s17081922 - 21 Aug 2017
Cited by 83 | Viewed by 9554
Abstract
There is concern regarding the heterogeneity of exposure to airborne particulate matter (PM) across urban areas leading to negatively biased health effects models. New, low-cost sensors now permit continuous and simultaneous measurements to be made in multiple locations. Measurements of ambient PM were [...] Read more.
There is concern regarding the heterogeneity of exposure to airborne particulate matter (PM) across urban areas leading to negatively biased health effects models. New, low-cost sensors now permit continuous and simultaneous measurements to be made in multiple locations. Measurements of ambient PM were made from October to April 2015–2016 and 2016–2017 to assess the spatial and temporal variability in PM and the relative importance of traffic and wood smoke to outdoor PM concentrations in Rochester, NY, USA. In general, there was moderate spatial inhomogeneity, as indicated by multiple pairwise measures including coefficient of divergence and signed rank tests of the value distributions. Pearson correlation coefficients were often moderate (~50% of units showed correlations >0.5 during the first season), indicating that there was some coherent variation across the area, likely driven by a combination of meteorological conditions (wind speed, direction, and mixed layer heights) and the concentration of PM2.5 being transported into the region. Although the accuracy of these PM sensors is limited, they are sufficiently precise relative to one another and to research grade instruments that they can be useful is assessing the spatial and temporal variations across an area and provide concentration estimates based on higher-quality central site monitoring data. Full article
(This article belongs to the Special Issue Air Pollution Sensors: A New Class of Tools to Measure Air Quality)
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11553 KiB  
Article
An Extended Kalman Filter-Based Attitude Tracking Algorithm for Star Sensors
by Jian Li, Xinguo Wei and Guangjun Zhang
Sensors 2017, 17(8), 1921; https://doi.org/10.3390/s17081921 - 21 Aug 2017
Cited by 27 | Viewed by 7593
Abstract
Efficiency and reliability are key issues when a star sensor operates in tracking mode. In the case of high attitude dynamics, the performance of existing attitude tracking algorithms degenerates rapidly. In this paper an extended Kalman filtering-based attitude tracking algorithm is presented. The [...] Read more.
Efficiency and reliability are key issues when a star sensor operates in tracking mode. In the case of high attitude dynamics, the performance of existing attitude tracking algorithms degenerates rapidly. In this paper an extended Kalman filtering-based attitude tracking algorithm is presented. The star sensor is modeled as a nonlinear stochastic system with the state estimate providing the three degree-of-freedom attitude quaternion and angular velocity. The star positions in the star image are predicted and measured to estimate the optimal attitude. Furthermore, all the cataloged stars observed in the sensor field-of-view according the predicted image motion are accessed using a catalog partition table to speed up the tracking, called star mapping. Software simulation and night-sky experiment are performed to validate the efficiency and reliability of the proposed method. Full article
(This article belongs to the Special Issue Inertial Sensors for Positioning and Navigation)
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3412 KiB  
Article
Genome-Wide SNP Signal Intensity Scanning Revealed Genes Differentiating Cows with Ovarian Pathologies from Healthy Cows
by Ricardo Salomón-Torres, Martin F. Montaño-Gómez, Rafael Villa-Angulo, Víctor M. González-Vizcarra, Carlos Villa-Angulo, Gerardo E. Medina-Basulto, Noé Ortiz-Uribe, Padmanabhan Mahadevan and Víctor H. Yaurima-Basaldúa
Sensors 2017, 17(8), 1920; https://doi.org/10.3390/s17081920 - 21 Aug 2017
Cited by 2 | Viewed by 4269
Abstract
Hypoplasia and ovarian cysts are the most common ovarian pathologies in cattle. In this genome-wide study we analyzed the signal intensity of 648,315 Single Nucleotide Polymorphisms (SNPs) and identified 1338 genes differentiating cows with ovarian pathologies from healthy cows. The sample consisted of [...] Read more.
Hypoplasia and ovarian cysts are the most common ovarian pathologies in cattle. In this genome-wide study we analyzed the signal intensity of 648,315 Single Nucleotide Polymorphisms (SNPs) and identified 1338 genes differentiating cows with ovarian pathologies from healthy cows. The sample consisted of six cows presenting an ovarian pathology and six healthy cows. SNP signal intensities were measured with a genotyping process using the Axiom Genome-Wide BOS 1 SNPchip. Statistical tests for equality of variance and mean were applied to SNP intensities, and significance p-values were obtained. A Benjamini-Hochberg multiple testing correction reveled significant SNPs. Corresponding genes were identified using the Bovine Genome UMD 3.1 annotation. Principal Components Analysis (PCA) confirmed differentiation. An analysis of Copy Number Variations (CNVs), obtained from signal intensities, revealed no evidence of association between ovarian pathologies and CNVs. In addition, a haplotype frequency analysis showed no association with ovarian pathologies. Results show that SNP signal intensity, which captures not only information for base-pair genotypes elucidation, but the amount of fluorescence nucleotide synthetization produced in an enzymatic reaction, is a rich source of information that, by itself or in combination with base-pair genotypes, might be used to implement differentiation, prediction and diagnostic procedures, increasing the scope of applications for Genotyping Microarrays. Full article
(This article belongs to the Section Biosensors)
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1383 KiB  
Review
Carbon Nanomaterial Based Biosensors for Non-Invasive Detection of Cancer and Disease Biomarkers for Clinical Diagnosis
by Tibor Pasinszki, Melinda Krebsz, Thanh Tran Tung and Dusan Losic
Sensors 2017, 17(8), 1919; https://doi.org/10.3390/s17081919 - 20 Aug 2017
Cited by 136 | Viewed by 14503
Abstract
The early diagnosis of diseases, e.g., Parkinson’s and Alzheimer’s disease, diabetes, and various types of cancer, and monitoring the response of patients to the therapy plays a critical role in clinical treatment; therefore, there is an intensive research for the determination of many [...] Read more.
The early diagnosis of diseases, e.g., Parkinson’s and Alzheimer’s disease, diabetes, and various types of cancer, and monitoring the response of patients to the therapy plays a critical role in clinical treatment; therefore, there is an intensive research for the determination of many clinical analytes. In order to achieve point-of-care sensing in clinical practice, sensitive, selective, cost-effective, simple, reliable, and rapid analytical methods are required. Biosensors have become essential tools in biomarker sensing, in which electrode material and architecture play critical roles in achieving sensitive and stable detection. Carbon nanomaterials in the form of particle/dots, tube/wires, and sheets have recently become indispensable elements of biosensor platforms due to their excellent mechanical, electronic, and optical properties. This review summarizes developments in this lucrative field by presenting major biosensor types and variability of sensor platforms in biomedical applications. Full article
(This article belongs to the Section Biosensors)
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5540 KiB  
Article
Evolutionary Beamforming Optimization for Radio Frequency Charging in Wireless Rechargeable Sensor Networks
by Ke-Han Yao, Jehn-Ruey Jiang, Chung-Hsien Tsai and Zong-Syun Wu
Sensors 2017, 17(8), 1918; https://doi.org/10.3390/s17081918 - 20 Aug 2017
Cited by 4 | Viewed by 5935
Abstract
This paper investigates how to efficiently charge sensor nodes in a wireless rechargeable sensor network (WRSN) with radio frequency (RF) chargers to make the network sustainable. An RF charger is assumed to be equipped with a uniform circular array (UCA) of 12 antennas [...] Read more.
This paper investigates how to efficiently charge sensor nodes in a wireless rechargeable sensor network (WRSN) with radio frequency (RF) chargers to make the network sustainable. An RF charger is assumed to be equipped with a uniform circular array (UCA) of 12 antennas with the radius λ, where λ is the RF wavelength. The UCA can steer most RF energy in a target direction to charge a specific WRSN node by the beamforming technology. Two evolutionary algorithms (EAs) using the evolution strategy (ES), namely the Evolutionary Beamforming Optimization (EBO) algorithm and the Evolutionary Beamforming Optimization Reseeding (EBO-R) algorithm, are proposed to nearly optimize the power ratio of the UCA beamforming peak side lobe (PSL) and the main lobe (ML) aimed at the given target direction. The proposed algorithms are simulated for performance evaluation and are compared with a related algorithm, called Particle Swarm Optimization Gravitational Search Algorithm-Explore (PSOGSA-Explore), to show their superiority. Full article
(This article belongs to the Special Issue Wireless Rechargeable Sensor Networks)
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1900 KiB  
Article
Development of the MOOSY4 eNose IoT for Sulphur-Based VOC Water Pollution Detection
by Enric Climent, Jose Pelegri-Sebastia, Tomas Sogorb, J. B. Talens and Jose Chilo
Sensors 2017, 17(8), 1917; https://doi.org/10.3390/s17081917 - 20 Aug 2017
Cited by 16 | Viewed by 5988
Abstract
In this paper, we describe a new low-cost and portable electronic nose instrument, the Multisensory Odor Olfactory System MOOSY4. This prototype is based on only four metal oxide semiconductor (MOS) gas sensors suitable for IoT technology. The system architecture consists of four stages: [...] Read more.
In this paper, we describe a new low-cost and portable electronic nose instrument, the Multisensory Odor Olfactory System MOOSY4. This prototype is based on only four metal oxide semiconductor (MOS) gas sensors suitable for IoT technology. The system architecture consists of four stages: data acquisition, data storage, data processing, and user interfacing. The designed eNose was tested with experiment for detection of volatile components in water pollution, as a dimethyl disulphide or dimethyl diselenide or sulphur. Therefore, the results provide evidence that odor information can be recognized with around 86% efficiency, detecting smells unwanted in the water and improving the quality control in bottled water factories. Full article
(This article belongs to the Special Issue Electronic Tongues and Electronic Noses)
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3609 KiB  
Article
Development and Evaluation of A Novel and Cost-Effective Approach for Low-Cost NO2 Sensor Drift Correction
by Li Sun, Dane Westerdahl and Zhi Ning
Sensors 2017, 17(8), 1916; https://doi.org/10.3390/s17081916 - 19 Aug 2017
Cited by 45 | Viewed by 8721
Abstract
Emerging low-cost gas sensor technologies have received increasing attention in recent years for air quality measurements due to their small size and convenient deployment. However, in the diverse applications these sensors face many technological challenges, including sensor drift over long-term deployment that cannot [...] Read more.
Emerging low-cost gas sensor technologies have received increasing attention in recent years for air quality measurements due to their small size and convenient deployment. However, in the diverse applications these sensors face many technological challenges, including sensor drift over long-term deployment that cannot be easily addressed using mathematical correction algorithms or machine learning methods. This study aims to develop a novel approach to auto-correct the drift of commonly used electrochemical nitrogen dioxide (NO2) sensor with comprehensive evaluation of its application. The impact of environmental factors on the NO2 electrochemical sensor in low-ppb concentration level measurement was evaluated in laboratory and the temperature and relative humidity correction algorithm was evaluated. An automated zeroing protocol was developed and assessed using a chemical absorbent to remove NO2 as a means to perform zero correction in varying ambient conditions. The sensor system was operated in three different environments in which data were compared to a reference NO2 analyzer. The results showed that the zero-calibration protocol effectively corrected the observed drift of the sensor output. This technique offers the ability to enhance the performance of low-cost sensor based systems and these findings suggest extension of the approach to improve data quality from sensors measuring other gaseous pollutants in urban air. Full article
(This article belongs to the Special Issue Air Pollution Sensors: A New Class of Tools to Measure Air Quality)
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3252 KiB  
Article
Performance Analysis of ToA-Based Positioning Algorithms for Static and Dynamic Targets with Low Ranging Measurements
by André G. Ferreira, Duarte Fernandes, André P. Catarino and João L. Monteiro
Sensors 2017, 17(8), 1915; https://doi.org/10.3390/s17081915 - 19 Aug 2017
Cited by 46 | Viewed by 6160
Abstract
Indoor Positioning Systems (IPSs) for emergency responders is a challenging field attracting researchers worldwide. When compared with traditional indoor positioning solutions, the IPSs for emergency responders stand out as they have to operate in harsh and unstructured environments. From the various technologies available [...] Read more.
Indoor Positioning Systems (IPSs) for emergency responders is a challenging field attracting researchers worldwide. When compared with traditional indoor positioning solutions, the IPSs for emergency responders stand out as they have to operate in harsh and unstructured environments. From the various technologies available for the localization process, ultra-wide band (UWB) is a promising technology for such systems due to its robust signaling in harsh environments, through-wall propagation and high-resolution ranging. However, during emergency responders’ missions, the availability of UWB signals is generally low (the nodes have to be deployed as the emergency responders enter a building) and can be affected by the non-line-of-sight (NLOS) conditions. In this paper, the performance of four typical distance-based positioning algorithms (Analytical, Least Squares, Taylor Series, and Extended Kalman Filter methods) with only three ranging measurements is assessed based on a COTS UWB transceiver. These algorithms are compared based on accuracy, precision and root mean square error (RMSE). The algorithms were evaluated under two environments with different propagation conditions (an atrium and a lab), for static and mobile devices, and under the human body’s influence. A NLOS identification and error mitigation algorithm was also used to improve the ranging measurements. The results show that the Extended Kalman Filter outperforms the other algorithms in almost every scenario, but it is affected by the low measurement rate of the UWB system. Full article
(This article belongs to the Special Issue Sensors and Sensing in Indoor Localization, Tracking, Navigation and Activity Monitoring)
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4124 KiB  
Article
Development and Testing of an LED-Based Near-Infrared Sensor for Human Kidney Tumor Diagnostics
by Andrey Bogomolov, Urszula Zabarylo, Dmitry Kirsanov, Valeria Belikova, Vladimir Ageev, Iskander Usenov, Vladislav Galyanin, Olaf Minet, Tatiana Sakharova, Georgy Danielyan, Elena Feliksberger and Viacheslav Artyushenko
Sensors 2017, 17(8), 1914; https://doi.org/10.3390/s17081914 - 19 Aug 2017
Cited by 22 | Viewed by 7196
Abstract
Optical spectroscopy is increasingly used for cancer diagnostics. Tumor detection feasibility in human kidney samples using mid- and near-infrared (NIR) spectroscopy, fluorescence spectroscopy, and Raman spectroscopy has been reported (Artyushenko et al., Spectral fiber sensors for cancer diagnostics in vitro. In Proceedings of [...] Read more.
Optical spectroscopy is increasingly used for cancer diagnostics. Tumor detection feasibility in human kidney samples using mid- and near-infrared (NIR) spectroscopy, fluorescence spectroscopy, and Raman spectroscopy has been reported (Artyushenko et al., Spectral fiber sensors for cancer diagnostics in vitro. In Proceedings of the European Conference on Biomedical Optics, Munich, Germany, 21–25 June 2015). In the present work, a simplification of the NIR spectroscopic analysis for cancer diagnostics was studied. The conventional high-resolution NIR spectroscopic method of kidney tumor diagnostics was replaced by a compact optical sensing device constructively represented by a set of four light-emitting diodes (LEDs) at selected wavelengths and one detecting photodiode. Two sensor prototypes were tested using 14 in vitro clinical samples of 7 different patients. Statistical data evaluation using principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) confirmed the general applicability of the LED-based sensing approach to kidney tumor detection. An additional validation of the results was performed by means of sample permutation. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany)
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7197 KiB  
Article
Dual Quaternions as Constraints in 4D-DPM Models for Pose Estimation
by Enrique Martinez-Berti, Antonio-José Sánchez-Salmerón and Carlos Ricolfe-Viala
Sensors 2017, 17(8), 1913; https://doi.org/10.3390/s17081913 - 19 Aug 2017
Cited by 2 | Viewed by 5116
Abstract
The goal of this research work is to improve the accuracy of human pose estimation using the Deformation Part Model (DPM) without increasing computational complexity. First, the proposed method seeks to improve pose estimation accuracy by adding the depth channel to DPM, which [...] Read more.
The goal of this research work is to improve the accuracy of human pose estimation using the Deformation Part Model (DPM) without increasing computational complexity. First, the proposed method seeks to improve pose estimation accuracy by adding the depth channel to DPM, which was formerly defined based only on red–green–blue (RGB) channels, in order to obtain a four-dimensional DPM (4D-DPM). In addition, computational complexity can be controlled by reducing the number of joints by taking it into account in a reduced 4D-DPM. Finally, complete solutions are obtained by solving the omitted joints by using inverse kinematics models. In this context, the main goal of this paper is to analyze the effect on pose estimation timing cost when using dual quaternions to solve the inverse kinematics. Full article
(This article belongs to the Special Issue Imaging Depth Sensors—Sensors, Algorithms and Applications)
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6610 KiB  
Article
A Third Generation Glucose Biosensor Based on Cellobiose Dehydrogenase Immobilized on a Glassy Carbon Electrode Decorated with Electrodeposited Gold Nanoparticles: Characterization and Application in Human Saliva
by Paolo Bollella, Lo Gorton, Roland Ludwig and Riccarda Antiochia
Sensors 2017, 17(8), 1912; https://doi.org/10.3390/s17081912 - 18 Aug 2017
Cited by 80 | Viewed by 14323
Abstract
Efficient direct electron transfer (DET) between a cellobiose dehydrogenase mutant from Corynascus thermophilus (CtCDH C291Y) and a novel glassy carbon (GC)-modified electrode, obtained by direct electrodeposition of gold nanoparticles (AuNPs) was realized. The electrode was further modified with a mixed self-assembled monolayer of [...] Read more.
Efficient direct electron transfer (DET) between a cellobiose dehydrogenase mutant from Corynascus thermophilus (CtCDH C291Y) and a novel glassy carbon (GC)-modified electrode, obtained by direct electrodeposition of gold nanoparticles (AuNPs) was realized. The electrode was further modified with a mixed self-assembled monolayer of 4-aminothiophenol (4-APh) and 4-mercaptobenzoic acid (4-MBA), by using glutaraldehyde (GA) as cross-linking agent. The CtCDH C291Y/GA/4-APh,4-MBA/AuNPs/GC platform showed an apparent heterogeneous electron transfer rate constant (ks) of 19.4 ± 0.6 s−1, with an enhanced theoretical and real enzyme surface coverage (Γtheor and Γreal) of 5287 ± 152 pmol cm−2 and 27 ± 2 pmol cm−2, respectively. The modified electrode was successively used as glucose biosensor exhibiting a detection limit of 6.2 μM, an extended linear range from 0.02 to 30 mM, a sensitivity of 3.1 ± 0.1 μA mM−1 cm−2 (R2 = 0.995), excellent stability and good selectivity. These performances compared favourably with other glucose biosensors reported in the literature. Finally, the biosensor was tested to quantify the glucose content in human saliva samples with successful results in terms of both recovery and correlation with glucose blood levels, allowing further considerations on the development of non-invasive glucose monitoring devices. Full article
(This article belongs to the Special Issue Advanced Sensors Based on Carbon Electrodes)
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1295 KiB  
Article
Vertical-Strip-Fed Broadband Circularly Polarized Dielectric Resonator Antenna
by Amir Altaf, Jin-Woo Jung, Youngoo Yang, Kang-Yoon Lee and Keum Cheol Hwang
Sensors 2017, 17(8), 1911; https://doi.org/10.3390/s17081911 - 18 Aug 2017
Cited by 11 | Viewed by 6383
Abstract
A vertical-strip-fed dielectric resonator antenna exhibiting broadband circular polarization characteristics is presented. A broad 3 dB axial ratio bandwidth (ARBW) is achieved by combining multiple orthogonal modes due to the use of a special-shaped dielectric resonator. The proposed antenna is fabricated to evaluate [...] Read more.
A vertical-strip-fed dielectric resonator antenna exhibiting broadband circular polarization characteristics is presented. A broad 3 dB axial ratio bandwidth (ARBW) is achieved by combining multiple orthogonal modes due to the use of a special-shaped dielectric resonator. The proposed antenna is fabricated to evaluate its actual performance capabilities. The antenna exhibits a measured 3 dB ARBW of 44.2% (3.35–5.25 GHz), lying within a −10 dB reflection bandwidth of 82.7% (2.44–5.88 GHz). The measured peak gain within 3 dB ARBW is found to be 5.66 dBic at 4.8 GHz. The measured results are in good agreement with the simulated results. Full article
(This article belongs to the Section Physical Sensors)
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3363 KiB  
Review
Electrochemical Biosensors for Rapid Detection of Foodborne Salmonella: A Critical Overview
by Stefano Cinti, Giulia Volpe, Silvia Piermarini, Elisabetta Delibato and Giuseppe Palleschi
Sensors 2017, 17(8), 1910; https://doi.org/10.3390/s17081910 - 18 Aug 2017
Cited by 65 | Viewed by 10637
Abstract
Abstract: Salmonella has represented the most common and primary cause of food poisoning in many countries for at least over 100 years. Its detection is still primarily based on traditional microbiological culture methods which are labor-intensive, extremely time consuming, and not suitable [...] Read more.
Abstract: Salmonella has represented the most common and primary cause of food poisoning in many countries for at least over 100 years. Its detection is still primarily based on traditional microbiological culture methods which are labor-intensive, extremely time consuming, and not suitable for testing a large number of samples. Accordingly, great efforts to develop rapid, sensitive and specific methods, easy to use, and suitable for multi-sample analysis, have been made and continue. Biosensor-based technology has all the potentialities to meet these requirements. In this paper, we review the features of the electrochemical immunosensors, genosensors, aptasensors and phagosensors developed in the last five years for Salmonella detection, focusing on the critical aspects of their application in food analysis. Full article
(This article belongs to the Special Issue Sensors for Toxic and Pathogen Detection)
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12613 KiB  
Article
A Novel Partial Discharge Localization Method in Substation Based on a Wireless UHF Sensor Array
by Zhen Li, Lingen Luo, Nan Zhou, Gehao Sheng and Xiuchen Jiang
Sensors 2017, 17(8), 1909; https://doi.org/10.3390/s17081909 - 18 Aug 2017
Cited by 21 | Viewed by 6333
Abstract
Effective Partial Discharge (PD) localization can detect the insulation problems of the power equipment in a substation and improve the reliability of power systems. Typical Ultra-High Frequency (UHF) PD localization methods are mainly based on time difference information, which need a high sampling [...] Read more.
Effective Partial Discharge (PD) localization can detect the insulation problems of the power equipment in a substation and improve the reliability of power systems. Typical Ultra-High Frequency (UHF) PD localization methods are mainly based on time difference information, which need a high sampling rate system. This paper proposes a novel PD localization method based on a received signal strength indicator (RSSI) fingerprint to quickly locate the power equipment with potential insulation defects. The proposed method consists of two stages. In the offline stage, the RSSI fingerprint data of the detection area is measured by a wireless UHF sensor array and processed by a clustering algorithm to reduce the PD interference and abnormal RSSI values. In the online stage, when PD happens, the RSSI fingerprint of PD is measured via the input of pattern recognition for PD localization. To achieve an accurate localization, the pattern recognition process is divided into two steps: a preliminary localization is implemented by cluster recognition to reduce the localization region, and the compressed sensing algorithm is used for accurate PD localization. A field test in a substation indicates that the mean localization error of the proposed method is 1.25 m, and 89.6% localization errors are less than 3 m. Full article
(This article belongs to the Section Physical Sensors)
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2512 KiB  
Article
The Potentiodynamic Bottom-up Growth of the Tin Oxide Nanostructured Layer for Gas-Analytical Multisensor Array Chips
by Fedor S. Fedorov, Dmitry Podgainov, Alexey Varezhnikov, Andrey Lashkov, Michail Gorshenkov, Igor Burmistrov, Martin Sommer and Victor Sysoev
Sensors 2017, 17(8), 1908; https://doi.org/10.3390/s17081908 - 18 Aug 2017
Cited by 12 | Viewed by 6736
Abstract
We report a deposition of the tin oxide/hydroxide nanostructured layer by the potentiodynamic method from acidic nitrate solutions directly over the substrate, equipped with multiple strip electrodes which is employed as a gas-analytical multisensor array chip. The electrochemical synthesis is set to favor [...] Read more.
We report a deposition of the tin oxide/hydroxide nanostructured layer by the potentiodynamic method from acidic nitrate solutions directly over the substrate, equipped with multiple strip electrodes which is employed as a gas-analytical multisensor array chip. The electrochemical synthesis is set to favor the growth of the tin oxide/hydroxide phase, while the appearance of metallic Sn is suppressed by cycling. The as-synthesized tin oxide/hydroxide layer is characterized by mesoporous morphology with grains, 250–300 nm diameter, which are further crystallized into fine SnO2 poly-nanocrystals following heating to 300 °C for 24 h just on the chip. The fabricated layer exhibits chemiresistive properties under exposure to organic vapors, which allows the generation of a multisensor vector signal capable of selectively distinguishing various vapors. Full article
(This article belongs to the Special Issue Gas Sensors based on Semiconducting Metal Oxides)
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5598 KiB  
Article
A DFT Calculation of Fluoride-Doped TiO2 Nanotubes for Detecting SF6 Decomposition Components
by Xiaoxing Zhang, Jun Zhang, Xingchen Dong and Hao Cui
Sensors 2017, 17(8), 1907; https://doi.org/10.3390/s17081907 - 18 Aug 2017
Cited by 14 | Viewed by 5861
Abstract
Gas insulated switchgear (GIS) plays an important role in the transmission and distribution of electric energy. Detecting and analyzing the decomposed components of SF6 is one of the important methods to realize the on-line monitoring of GIS equipment. In this paper, considering [...] Read more.
Gas insulated switchgear (GIS) plays an important role in the transmission and distribution of electric energy. Detecting and analyzing the decomposed components of SF6 is one of the important methods to realize the on-line monitoring of GIS equipment. In this paper, considering the performance limits of intrinsic TiO2 nanotube gas sensor, the adsorption process of H2S, SO2, SOF2 and SO2F2 on fluoride-doped TiO2 crystal plane was simulated by the first-principle method. The adsorption mechanism of these SF6 decomposition components on fluorine-doped TiO2 crystal plane was analyzed from a micro perspective. Calculation results indicate that the order of adsorption effect of four SF6 decomposition components on fluoride-doped TiO2 crystal plane is H2S > SO2 > SOF2 > SO2F2. Compared with the adsorption results of intrinsic anatase TiO2 (101) perfect crystal plane, fluorine doping can obviously enhance the adsorption ability of TiO2 (101) crystal plane. Fluorine-doped TiO2 can effectively distinguish and detect the SF6 decomposition components based on theoretical analysis. Full article
(This article belongs to the Section Physical Sensors)
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503 KiB  
Article
Energy Efficiency Maximization for WSNs with Simultaneous Wireless Information and Power Transfer
by Hongyan Yu, Yongqiang Zhang, Songtao Guo, Yuanyuan Yang and Luyue Ji
Sensors 2017, 17(8), 1906; https://doi.org/10.3390/s17081906 - 18 Aug 2017
Cited by 28 | Viewed by 6295
Abstract
Recently, the simultaneous wireless information and power transfer (SWIPT) technique has been regarded as a promising approach to enhance performance of wireless sensor networks with limited energy supply. However, from a green communication perspective, energy efficiency optimization for SWIPT system design has not [...] Read more.
Recently, the simultaneous wireless information and power transfer (SWIPT) technique has been regarded as a promising approach to enhance performance of wireless sensor networks with limited energy supply. However, from a green communication perspective, energy efficiency optimization for SWIPT system design has not been investigated in Wireless Rechargeable Sensor Networks (WRSNs). In this paper, we consider the tradeoffs between energy efficiency and three factors including spectral efficiency, the transmit power and outage target rate for two different modes, i.e., power splitting (PS) and time switching modes (TS), at the receiver. Moreover, we formulate the energy efficiency maximization problem subject to the constraints of minimum Quality of Service (QoS), minimum harvested energy and maximum transmission power as non-convex optimization problem. In particular, we focus on optimizing power control and power allocation policy in PS and TS modes to maximize energy efficiency of data transmission. For PS and TS modes, we propose the corresponding algorithm to characterize a non-convex optimization problem that takes into account the circuit power consumption and the harvested energy. By exploiting nonlinear fractional programming and Lagrangian dual decomposition, we propose suboptimal iterative algorithms to obtain the solutions of non-convex optimization problems. Furthermore, we derive the outage probability and effective throughput from the scenarios that the transmitter does not or partially know the channel state information (CSI) of the receiver. Simulation results illustrate that the proposed optimal iterative algorithm can achieve optimal solutions within a small number of iterations and various tradeoffs between energy efficiency and spectral efficiency, transmit power and outage target rate, respectively. Full article
(This article belongs to the Special Issue Wireless Rechargeable Sensor Networks)
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7176 KiB  
Article
Towards Scalable Strain Gauge-Based Joint Torque Sensors
by Hamza Khan, Mariapaola D’Imperio, Ferdinando Cannella, Darwin G. Caldwell, Alfred Cuschieri and Claudio Semini
Sensors 2017, 17(8), 1905; https://doi.org/10.3390/s17081905 - 18 Aug 2017
Cited by 24 | Viewed by 10781
Abstract
During recent decades, strain gauge-based joint torque sensors have been commonly used to provide high-fidelity torque measurements in robotics. Although measurement of joint torque/force is often required in engineering research and development, the gluing and wiring of strain gauges used as torque sensors [...] Read more.
During recent decades, strain gauge-based joint torque sensors have been commonly used to provide high-fidelity torque measurements in robotics. Although measurement of joint torque/force is often required in engineering research and development, the gluing and wiring of strain gauges used as torque sensors pose difficulties during integration within the restricted space available in small joints. The problem is compounded by the need for a scalable geometric design to measure joint torque. In this communication, we describe a novel design of a strain gauge-based mono-axial torque sensor referred to as square-cut torque sensor (SCTS), the significant features of which are high degree of linearity, symmetry, and high scalability in terms of both size and measuring range. Most importantly, SCTS provides easy access for gluing and wiring of the strain gauges on sensor surface despite the limited available space. We demonstrated that the SCTS was better in terms of symmetry (clockwise and counterclockwise rotation) and more linear. These capabilities have been shown through finite element modeling (ANSYS) confirmed by observed data obtained by load testing experiments. The high performance of SCTS was confirmed by studies involving changes in size, material and/or wings width and thickness. Finally, we demonstrated that the SCTS can be successfully implementation inside the hip joints of miniaturized hydraulically actuated quadruped robot-MiniHyQ. This communication is based on work presented at the 18th International Conference on Climbing and Walking Robots (CLAWAR). Full article
(This article belongs to the Section Physical Sensors)
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507 KiB  
Article
Dynamic Fuzzy-Logic Based Path Planning for Mobility-Assisted Localization in Wireless Sensor Networks
by Abdullah Alomari, William Phillips, Nauman Aslam and Frank Comeau
Sensors 2017, 17(8), 1904; https://doi.org/10.3390/s17081904 - 18 Aug 2017
Cited by 48 | Viewed by 6993
Abstract
Mobile anchor path planning techniques have provided as an alternative option for node localization in wireless sensor networks (WSNs). In such context, path planning is a movement pattern where a mobile anchor node’s movement is designed in order to achieve a maximum localization [...] Read more.
Mobile anchor path planning techniques have provided as an alternative option for node localization in wireless sensor networks (WSNs). In such context, path planning is a movement pattern where a mobile anchor node’s movement is designed in order to achieve a maximum localization ratio possible with a minimum error rate. Typically, the mobility path planning is designed in advance, which is applicable when the mobile anchor has sufficient sources of energy and time. However, when the mobility movement is restricted or limited, a dynamic path planning design is needed. This paper proposes a novel distributed range-free movement mechanism for mobility-assisted localization in WSNs when the mobile anchor’s movement is limited. The designed movement is formed in real-time pattern using a fuzzy-logic approach based on the information received from the network and the nodes’ deployment. Our proposed model, Fuzzy-Logic based Path Planning for mobile anchor-assisted Localization in WSNs (FLPPL), offers superior results in several metrics including both localization accuracy and localization ratio in comparison to other similar works. Full article
(This article belongs to the Section Sensor Networks)
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3733 KiB  
Article
LoRa Mobile-To-Base-Station Channel Characterization in the Antarctic
by Johnny Gaelens, Patrick Van Torre, Jo Verhaevert and Hendrik Rogier
Sensors 2017, 17(8), 1903; https://doi.org/10.3390/s17081903 - 18 Aug 2017
Cited by 43 | Viewed by 7139
Abstract
Antarctic conditions demand that wireless sensor nodes are operational all year round and that they provide a large communication range of several tens of kilometers. LoRa technology operating in sub-GHz frequency bands implements these wireless links with minimal power consumption. The employed chirp [...] Read more.
Antarctic conditions demand that wireless sensor nodes are operational all year round and that they provide a large communication range of several tens of kilometers. LoRa technology operating in sub-GHz frequency bands implements these wireless links with minimal power consumption. The employed chirp spread spectrum modulation provides a large link budget, combined with the excellent radio-wave propagation characteristics in these bands. In this paper, an experimental wireless link from a mobile vehicle which transmits sensor data to a base station is measured and analyzed in terms of signal-to-noise ratio and packet loss. These measurements confirm the usefulness of LoRa technology for wireless sensor systems in polar regions. By deploying directional antennas at the base station, a range of up to 30 km is covered in case of Line-of-Sight radio propagation in both the 434 and 868 MHz bands. Varying terrain elevation is shown to be the dominating factor influencing the propagation, sometimes causing the Line-of-Sight path to be obstructed. Tropospheric radio propagation effects were not apparent in the measurements. Full article
(This article belongs to the Section Sensor Networks)
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339 KiB  
Article
Tree Alignment Based on Needleman-Wunsch Algorithm for Sensor Selection in Smart Homes
by Sook-Ling Chua and Lee Kien Foo
Sensors 2017, 17(8), 1902; https://doi.org/10.3390/s17081902 - 18 Aug 2017
Cited by 5 | Viewed by 6110
Abstract
Activity recognition in smart homes aims to infer the particular activities of the inhabitant, the aim being to monitor their activities and identify any abnormalities, especially for those living alone. In order for a smart home to support its inhabitant, the recognition system [...] Read more.
Activity recognition in smart homes aims to infer the particular activities of the inhabitant, the aim being to monitor their activities and identify any abnormalities, especially for those living alone. In order for a smart home to support its inhabitant, the recognition system needs to learn from observations acquired through sensors. One question that often arises is which sensors are useful and how many sensors are required to accurately recognise the inhabitant’s activities? Many wrapper methods have been proposed and remain one of the popular evaluators for sensor selection due to its superior accuracy performance. However, they are prohibitively slow during the evaluation process and may run into the risk of overfitting due to the extent of the search. Motivated by this characteristic, this paper attempts to reduce the cost of the evaluation process and overfitting through tree alignment. The performance of our method is evaluated on two public datasets obtained in two distinct smart home environments. Full article
(This article belongs to the Special Issue Advances in Sensors for Sustainable Smart Cities and Smart Buildings)
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4193 KiB  
Review
Surface-Enhanced Raman Scattering in Molecular Junctions
by Madoka Iwane, Shintaro Fujii and Manabu Kiguchi
Sensors 2017, 17(8), 1901; https://doi.org/10.3390/s17081901 - 18 Aug 2017
Cited by 11 | Viewed by 8300
Abstract
Surface-enhanced Raman scattering (SERS) is a surface-sensitive vibrational spectroscopy that allows Raman spectroscopy on a single molecular scale. Here, we present a review of SERS from molecular junctions, in which a single molecule or molecules are made to have contact from the top [...] Read more.
Surface-enhanced Raman scattering (SERS) is a surface-sensitive vibrational spectroscopy that allows Raman spectroscopy on a single molecular scale. Here, we present a review of SERS from molecular junctions, in which a single molecule or molecules are made to have contact from the top to the bottom of metal surfaces. The molecular junctions are nice platforms for SERS as well as transport measurement. Electronic characterization based on the transport measurements of molecular junctions has been extensively studied for the development of miniaturized electronic devices. Simultaneous SERS and transport measurement of the molecular junctions allow both structural (geometrical) and electronic information on the single molecule scale. The improvement of SERS measurement on molecular junctions open the door toward new nanoscience and nanotechnology in molecular electronics. Full article
(This article belongs to the Special Issue Surface Plasmon Resonance Sensing)
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