Sensors

19 pages, 2983 KiB

Open AccessArticle

A Handheld Real-Time Photoacoustic Imaging System for Animal Neurological Disease Models: From Simulation to Realization

by Yu-Hang Liu, Yu Xu, Lun-De Liao, Kim Chuan Chan and Nitish V. Thakor

Sensors 2018, 18(11), 4081; https://doi.org/10.3390/s18114081 - 21 Nov 2018

Cited by 13 | Viewed by 5888

Abstract

This article provides a guide to design and build a handheld, real-time photoacoustic (PA) imaging system from simulation to realization for animal neurological disease models. A pulsed laser and array-based ultrasound (US) platform were utilized to develop the system for evaluating vascular functions [...] Read more.

This article provides a guide to design and build a handheld, real-time photoacoustic (PA) imaging system from simulation to realization for animal neurological disease models. A pulsed laser and array-based ultrasound (US) platform were utilized to develop the system for evaluating vascular functions in rats with focal ischemia or subcutaneous tumors. To optimize the laser light delivery, finite element (FE)-based simulation models were developed to provide information regarding light propagation and PA wave generation in soft tissues. Besides, simulations were also conducted to evaluate the ideal imaging resolution of the US system. As a result, a PA C-scan image of a designed phantom in 1% Lipofundin was reconstructed with depth information. Performance of the handheld PA system was tested in an animal ischemia model, which revealed that cerebral blood volume (CBV) changes at the cortical surface could be monitored immediately after ischemia induction. Another experiment on subcutaneous tumors showed the anomalous distribution of the total hemoglobin concentration (HbT) and oxygen saturation (SO₂), while 3D and maximum intensity projection (MIP) PA images of the subcutaneous tumors are also presented in this article. Overall, this system shows promise for monitoring disease progression in vascular functional impairments. Full article

(This article belongs to the Special Issue Advances in Optical Sensing for Biomedical and Biotechnological Applications)

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15 pages, 2060 KiB

Open AccessArticle

Correntropy Based Divided Difference Filtering for the Positioning of Ships

by Xi Liu, Badong Chen, Shiyuan Wang and Shaoyi Du

Sensors 2018, 18(11), 4080; https://doi.org/10.3390/s18114080 - 21 Nov 2018

Cited by 4 | Viewed by 3356

Abstract

In this paper, robust first and second-order divided difference filtering algorithms based on correntropy are proposed, which not only retain the advantages of divided difference filters, but also exhibit robustness in the presence of non-Gaussian noises, especially when the measurements are contaminated by [...] Read more.

In this paper, robust first and second-order divided difference filtering algorithms based on correntropy are proposed, which not only retain the advantages of divided difference filters, but also exhibit robustness in the presence of non-Gaussian noises, especially when the measurements are contaminated by heavy-tailed noises. The proposed filters are then applied to the problem of ship positioning. In order to improve the accuracy and reliability of ship positioning, the positioning method combines the Dead Reckoning (DR) algorithm and the Global Positioning System (GPS). Experimental results of an illustrative example show the superior performance of the new algorithms when applied to ship positioning. Full article

(This article belongs to the Section Remote Sensors)

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12 pages, 4158 KiB

Open AccessArticle

A 40-MHz Ultrasound Transducer with an Angled Aperture for Guiding Percutaneous Revascularization of Chronic Total Occlusion: A Feasibility Study

by Junsu Lee and Jin Ho Chang

Sensors 2018, 18(11), 4079; https://doi.org/10.3390/s18114079 - 21 Nov 2018

Cited by 12 | Viewed by 4778

Abstract

Complete blockage of a coronary artery, called chronic total occlusion (CTO), frequently occurs due to atherosclerosis. To reopen the obstructed blood vessels with a stent, guidewire crossing is performed with the help of angiography that can provide the location of CTO lesions and [...] Read more.

Complete blockage of a coronary artery, called chronic total occlusion (CTO), frequently occurs due to atherosclerosis. To reopen the obstructed blood vessels with a stent, guidewire crossing is performed with the help of angiography that can provide the location of CTO lesions and the image of guidewire tip. Since angiography is incapable of imaging inside a CTO lesion, the surgeons are blind during guidewire crossing. For this reason, the success rate of guidewire crossing relies upon the proficiency of the surgeon, which is considerably reduced from 69.0% to 32.5% if extensive calcification, not penetrated by a guidewire, exists in CTO lesions. In this paper, a recently developed 40-MHz forward-looking intravascular ultrasound (FL–IVUS) transducer to visualize calcification within CTO lesions is reported. This transducer consists of a single element angled aperture and a guidewire passage. The aperture is spherically deformed to have a focal length of 3 mm in order to improve spatial resolution of FL–IVUS images. The angle between the beam direction and the axis of rotation is designed to be 30° to effectively visualize calcification within a CTO lesion as well as the blood vessel wall. The experimental results demonstrated that the developed FL–IVUS transducer facilitates visualization of calcification within CTO lesions and makes it possible to help the surgeon make decisions about whether to push the guidewire in order to cross the lesion or to change the surgical procedure. Full article

(This article belongs to the Special Issue Ultrasound Transducers)

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Conceptual illustration of (a) the proposed forward-looking intravascular ultrasound (FL–IVUS) transducer consisting of a single-element angled aperture and a guidewire passage, (b) the conical imaging plane along the vertical direction of the blood vessel, and (c) the FL–IVUS image expected to be displayed on a monitor. α and θ indicate the slant height and semi-vertical angle of the conical imaging plane. β is the closest distance between the imaging plane and the guidewire position plane. d0 and dW are the distances from the vertex of the cone to the aperture surface and to the center of the guidewire passage, respectively. Full article ">Figure 2
Pulse-echo response (solid line) and its frequency spectrum (dashed line) obtained by simulation using a PiezoCAD program (Sonic Concept, Woodinville, WA, USA). Full article ">Figure 3
Photographs of the finished FL–IVUS transducer and the zoomed-in version of the white solid circle. Full article ">Figure 4
Measured pulse–echo response (solid line) and frequency spectrum (dashed line) of the developed FL–IVUS transducer. Full article ">Figure 5
(a) Ultrasound B-mode image of a 25 μm wire acquired at a focal depth of 3 mm, (b) the axial and (c) lateral beam profiles measured from the wire image indicated by a white dotted circle. Full article ">Figure 6
(a) Photograph of the custom blood-vessel-mimicking phantom and (b–d) FL–IVUS images inside the hole of the phantom (see the white solid circle in (a)). The white solid arrows in (a) indicate hyperechogenic regions (i.e., the calcification-mimicking parts), and the white arrow head is the boundary between the water and the tissue-mimicking phantom. The space between the white bars on the IVUS images indicates 1 mm in the slant height. The hole in (a) is 8 mm in diameter. Full article ">Figure 7
(a,c) Photographs of the custom blood-vessel-mimicking phantoms and (b,d) FL–IVUS images inside the hole of the each phantom. The white solid arrows in (a,b) indicate hyperechogenic regions (i.e., the calcification-mimicking parts), and the white arrow heads in (a,b) are the boundary between the water and the tissue-mimicking phantom. The space between the white bars on the IVUS images indicates 1 mm in the slant height. The holes in (a,c) are 5 mm in diameter. Full article ">

11 pages, 4158 KiB

Open AccessArticle

Improving the Error of Time Differences of Arrival on Partial Discharges Measurement in Gas-Insulated Switchgear

by Jun Jiang, Kai Wang, Chaohai Zhang, Min Chen, Hong Zheng and Ricardo Albarracín

Sensors 2018, 18(11), 4078; https://doi.org/10.3390/s18114078 - 21 Nov 2018

Cited by 11 | Viewed by 5319

Abstract

Partial Discharge (PD) detection based on Ultra-High-Frequency (UHF) measurements in Gas-Insulated Switchgear (GIS) is often used for fault location based on extraction of Time Differences of Arrival (TDoA), and the core technique is to obtain the precise time difference of each UHF signal. [...] Read more.

Partial Discharge (PD) detection based on Ultra-High-Frequency (UHF) measurements in Gas-Insulated Switchgear (GIS) is often used for fault location based on extraction of Time Differences of Arrival (TDoA), and the core technique is to obtain the precise time difference of each UHF signal. Usually, TDoA extraction algorithms can be categorized as cross-correlation function method (CCF), minimum energy method (ME), and threshold value method (TV) are not qualified to analyze the time difference with high accuracy and efficiency, especially the complicated UHF PD signals in the field. In this paper, multiple tests were carried out based on the real GIS UHF signals. Three typical algorithms (CCF, ME, and TV) were used to extract and calculate the TDoA of UHF signals. Afterwards, depending on the disassembly of equipment, the accuracy and effective range of the algorithms are analyzed by means of error and variance. To minimize the error and the variance, an average method with the combination (CA) and portfolio of traditional algorithms is proposed and verified in different situations. The results demonstrate that the improved algorithm could increase the accuracy of time difference extraction, less than 4.0%. Full article

(This article belongs to the Special Issue UHF and RF Sensor Technology for Partial Discharge Detection)

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10 pages, 2535 KiB

Open AccessLetter

Frequency Offset Tolerant Synchronization Signal Design in NB-IoT

by Jun Zou and Chen Xu

Sensors 2018, 18(11), 4077; https://doi.org/10.3390/s18114077 - 21 Nov 2018

Cited by 11 | Viewed by 4439

Abstract

Timing detection is the first step and very important in wireless communication systems. Timing detection performance is usually affected by the frequency offset. Therefore, it is a challenge to design the synchronization signal in massive narrowband Internet of Things (NB-IoT) scenarios where the [...] Read more.

Timing detection is the first step and very important in wireless communication systems. Timing detection performance is usually affected by the frequency offset. Therefore, it is a challenge to design the synchronization signal in massive narrowband Internet of Things (NB-IoT) scenarios where the frequency offset is usually large due to the low cost requirement. In this paper, we firstly proposed a new general synchronization signal structure with a couple of sequences which are conjugated to remove the potential timing error that arises from large frequency offset. Then, we analyze the suitable sequence for our proposed synchronization signal structure and discuss a Zadoff–Chu (ZC) sequence with root 1 as an example. Finally, the simulation results demonstrate that our proposed synchronization signal can work well when the frequency offset is large. It means that our proposed synchronization signal design is very suitable for the massive NB-IoT. Full article

(This article belongs to the Section Internet of Things)

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Illustration of our proposed conjugated-sequences-based primary synchronization signal (PSS) structure. Full article ">Figure 2
Illustration of the maximum correlator output of Zadoff–Chu (ZC) sequences with different roots (<math display="inline"><semantics> <mrow> <mi>N</mi> <mo>=</mo> <mn>131</mn> </mrow> </semantics></math>). Full article ">Figure 3
Illustration of the correlator output of the ZC sequence with root <math display="inline"><semantics> <mrow> <mi>μ</mi> <mo>=</mo> <mn>1</mn> </mrow> </semantics></math> under different timing offsets. Full article ">Figure 4
Illustration of the main lobes of the correlator output around the maximum frequency offset <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>λ</mi> <mrow> <mi>max</mi> </mrow> </msub> </mrow> </semantics></math> (<math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>λ</mi> <mrow> <mi>max</mi> </mrow> </msub> </mrow> </semantics></math> > 0 in this example). The dash line is the copy of the solid one with the same color. Full article ">Figure 5
Timing detection error rate of the M-part correlator and the differential correlator with different frequency offsets. Full article ">Figure 6
Timing detection error rate of our proposed synchronization signal with different frequency offsets. Full article ">

15 pages, 4540 KiB

Open AccessArticle

Sensitive and Reproducible Gold SERS Sensor Based on Interference Lithography and Electrophoretic Deposition

by June Sik Hwang and Minyang Yang

Sensors 2018, 18(11), 4076; https://doi.org/10.3390/s18114076 - 21 Nov 2018

Cited by 25 | Viewed by 7160

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a promising analytical tool due to its label-free detection ability and superior sensitivity, which enable the detection of single molecules. Since its sensitivity is highly dependent on localized surface plasmon resonance, various methods have been applied for electric [...] Read more.

Surface-enhanced Raman spectroscopy (SERS) is a promising analytical tool due to its label-free detection ability and superior sensitivity, which enable the detection of single molecules. Since its sensitivity is highly dependent on localized surface plasmon resonance, various methods have been applied for electric field-enhanced metal nanostructures. Despite the intensive research on practical applications of SERS, fabricating a sensitive and reproducible SERS sensor using a simple and low-cost process remains a challenge. Here, we report a simple strategy to produce a large-scale gold nanoparticle array based on laser interference lithography and the electrophoretic deposition of gold nanoparticles, generated through a pulsed laser ablation in liquid process. The fabricated gold nanoparticle array produced a sensitive, reproducible SERS signal, which allowed Rhodamine 6G to be detected at a concentration as low as 10⁻⁸ M, with an enhancement factor of 1.25 × 10⁵. This advantageous fabrication strategy is expected to enable practical SERS applications. Full article

(This article belongs to the Special Issue Applications of Raman Spectroscopy in Sensors)

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27 pages, 1615 KiB

Open AccessArticle

Wireless Communication Technologies for Safe Cooperative Cyber Physical Systems

by Ali Balador, Anis Kouba, Dajana Cassioli, Fotis Foukalas, Ricardo Severino, Daria Stepanova, Giovanni Agosta, Jing Xie, Luigi Pomante, Maurizio Mongelli, Pierluigi Pierini, Stig Petersen and Timo Sukuvaara

Sensors 2018, 18(11), 4075; https://doi.org/10.3390/s18114075 - 21 Nov 2018

Cited by 16 | Viewed by 7245

Abstract

Cooperative Cyber-Physical Systems (Co-CPSs) can be enabled using wireless communication technologies, which in principle should address reliability and safety challenges. Safety for Co-CPS enabled by wireless communication technologies is a crucial aspect and requires new dedicated design approaches. In this paper, we provide [...] Read more.

Cooperative Cyber-Physical Systems (Co-CPSs) can be enabled using wireless communication technologies, which in principle should address reliability and safety challenges. Safety for Co-CPS enabled by wireless communication technologies is a crucial aspect and requires new dedicated design approaches. In this paper, we provide an overview of five Co-CPS use cases, as introduced in our SafeCOP EU project, and analyze their safety design requirements. Next, we provide a comprehensive analysis of the main existing wireless communication technologies giving details about the protocols developed within particular standardization bodies. We also investigate to what extent they address the non-functional requirements in terms of safety, security and real time, in the different application domains of each use case. Finally, we discuss general recommendations about the use of different wireless communication technologies showing their potentials in the selected real-world use cases. The discussion is provided under consideration in the 5G standardization process within 3GPP, whose current efforts are inline to current gaps in wireless communications protocols for Co-CPSs including many future use cases. Full article

(This article belongs to the Special Issue Advances on Vehicular Networks: From Sensing to Autonomous Driving)

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16 pages, 1953 KiB

Open AccessArticle

Stackelberg Dynamic Game-Based Resource Allocation in Threat Defense for Internet of Things

by Bingjie Liu, Haitao Xu and Xianwei Zhou

Sensors 2018, 18(11), 4074; https://doi.org/10.3390/s18114074 - 21 Nov 2018

Cited by 12 | Viewed by 4372

Abstract

With the rapid development of the Internet of Things, there are a series of security problems faced by the IoT devices. As the IoT devices are generally devices with limited resources, how to effectively allocate the restricted resources facing the security problems is [...] Read more.

With the rapid development of the Internet of Things, there are a series of security problems faced by the IoT devices. As the IoT devices are generally devices with limited resources, how to effectively allocate the restricted resources facing the security problems is the key issue at present. In this paper, we study the resource allocation problem in threat defense for the resource-constrained IoT system, and propose a Stackelberg dynamic game model to get the optimal allocated resources for both the defender and attackers. The proposed Stackelberg dynamic game model is composed by one defender and many attackers. Given the objective functions of the defender and attackers, we analyze both the open-loop Nash equilibrium and feedback Nash equilibrium for the defender and attackers. Then both the defender and attackers can control their available resources based on the Nash equilibrium solutions of the dynamic game. Numerical simulation results show that correctness and effeteness of the proposed model. Full article

(This article belongs to the Special Issue Threat Identification and Defence for Internet-of-Things)

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(a) Optimal strategy of the attackers; (b) optimal strategy of the defender. Full article ">Figure 2
Optimal strategy of the attacker with different <math display="inline"><semantics> <mrow> <msubsup> <mi>u</mi> <mn>0</mn> <mrow/> </msubsup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> </mrow> </semantics></math> over time. Full article ">Figure 3
(a) Risk level variation for a system with one attacker; (b) risk level variation for a system with different numbers of attackers. Full article ">Figure 4
Risk level with a large number of attackers under open-loop control. Full article ">Figure 5
(a) Optimal strategy of the attacker; (b) optimal strategy of the defender. Full article ">Figure 6
(a) Risk level variation for a system with one attacker; (b) risk level variation for a system with different numbers of attackers. Full article ">Figure 7
Risk level with a large number of attackers under feedback control. Full article ">Figure 8
The time complexity of the proposed game model. Full article ">

30 pages, 5749 KiB

Open AccessArticle

Enhancement of Localization Systems in NLOS Urban Scenario with Multipath Ray Tracing Fingerprints and Machine Learning

by Marcelo N. de Sousa and Reiner S. Thomä

Sensors 2018, 18(11), 4073; https://doi.org/10.3390/s18114073 - 21 Nov 2018

Cited by 33 | Viewed by 6832

Abstract

A hybrid technique is proposed to enhance the localization performance of a time difference of arrival (TDOA) deployed in non-line-of-sight (NLOS) suburban scenario. The idea was to use Machine Learning framework on the dataset, produced by the ray tracing simulation, and the Channel [...] Read more.

A hybrid technique is proposed to enhance the localization performance of a time difference of arrival (TDOA) deployed in non-line-of-sight (NLOS) suburban scenario. The idea was to use Machine Learning framework on the dataset, produced by the ray tracing simulation, and the Channel Impulse Response estimation from the real signal received by each sensor. Conventional localization techniques mitigate errors trying to avoid NLOS measurements in processing emitter position, while the proposed method uses the multipath fingerprint information produced by ray tracing (RT) simulation together with calibration emitters to refine a Machine Learning engine, which gives an extra layer of information to improve the emitter position estimation. The ray-tracing fingerprints perform the target localization embedding all the reflection and diffraction in the propagation scenario. A validation campaign was performed and showed the feasibility of the proposed method, provided that the buildings can be appropriately included in the scenario description. Full article

(This article belongs to the Special Issue Selected Papers from 8th International Conference on Localization and GNSS 2018 (ICL-GNSS 2018))

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19 pages, 1725 KiB

Open AccessArticle

Optimal Routing for Time-Driven EH-WSN under Regular Energy Sources

by Sebastià Galmés

Sensors 2018, 18(11), 4072; https://doi.org/10.3390/s18114072 - 21 Nov 2018

Cited by 7 | Viewed by 3277

Abstract

The recent provision of energy-harvesting capabilities to wireless sensor networks (WSN) has entailed the redefinition of design objectives. Specifically, the traditional goal of maximizing network lifetime has been replaced by optimizing network performance, namely delay and throughput. The present paper contributes to this [...] Read more.

The recent provision of energy-harvesting capabilities to wireless sensor networks (WSN) has entailed the redefinition of design objectives. Specifically, the traditional goal of maximizing network lifetime has been replaced by optimizing network performance, namely delay and throughput. The present paper contributes to this reformulation by considering the routing problem for the class of time-driven energy-harvesting WSN (EH-WSN) under regular or quasi-periodic energy sources. In particular, this paper shows that the minimum hop count (MHC) criterion maximizes the average duty cycle that can be sustained by nodes in this type of scenarios. This is a primary objective in EH-WSN, since large duty cycles lead to enhanced performance. Based on a previous result, a general expression is first obtained that gives mathematical form to the relationship between duty cycle and traffic load for any node in a time-driven EH-WSN fed by a regular energy source. This expression reveals that the duty cycle achievable by a node decreases as its traffic load increases. Then, it is shown that MHC minimizes the average traffic load over the network, and thus it maximizes the average duty cycle of nodes. This result is numerically validated via simulation by comparison with other well-known routing strategies. Accordingly, this paper suggests assigning top priority to the MHC criterion in the development of routing protocols for time-driven EH-WSN under regular energy sources. Full article

(This article belongs to the Section Sensor Networks)

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Uncoupled duty cycles between a transmitter node (T) and a receiver node (R) in asynchronous communication. Full article ">Figure 2
Operation of Low Power Listening (LPL) in TinyOS sensor nodes: Node A transmits a packet to node B, which receives and forwards this packet. Full article ">Figure 3
Relative error between exact and approximate energy consumption models for TinyOS sensor nodes. Full article ">Figure 4
Layer decomposition of a connected network. Lines represent feasible links for the given transmission range. Only inter-layer links are drawn. BS denotes the base station. Full article ">Figure 5
Converting an inter-layer connection into an intra-layer (1) or a backward inter-layer (2) connection. Full article ">Figure 6
Evolution of the average traffic load with regard to the network size, for the routing metrics considered in the analysis. The surprisingly small value obtained for MHC is a consequence of the large network densities managed in the simulation. Full article ">Figure 7
Evolution of the average duty cycle in terms of the network size, for different routing criteria. Full article ">

9 pages, 2365 KiB

Open AccessArticle

Ordinary Optical Fiber Sensor for Ultra-High Temperature Measurement Based on Infrared Radiation

by Qijing Lin, Na Zhao, Kun Yao, Zhuangde Jiang, Bian Tian, Peng Shi and Feng Chen

Sensors 2018, 18(11), 4071; https://doi.org/10.3390/s18114071 - 21 Nov 2018

Cited by 9 | Viewed by 4734

Abstract

An ordinary optical fiber ultra-high temperature sensor based on infrared radiation with the advantages of simple structure and compact is presented. The sensing system consists of a detection fiber and a common transmission fiber. The detector fiber is formed by annealing a piece [...] Read more.

An ordinary optical fiber ultra-high temperature sensor based on infrared radiation with the advantages of simple structure and compact is presented. The sensing system consists of a detection fiber and a common transmission fiber. The detector fiber is formed by annealing a piece of ordinary fiber at high temperature twice, which changes the properties of the fiber and breaks the temperature limit of ordinary fiber. The transmission fiber is a bending insensitive optical fiber. A static calibration system was set up to determine the performance of the sensor and three heating experiments were carried out. The temperature response sensitivities were 0.010 dBm/K, 0.009 dBm/K and 0.010 dBm/K, respectively, which indicate that the sensor has good repeatability. The sensor can withstand a high temperature of 1823 K for 58 h with an error of less than 1%. The main reason why the developed ordinary optical fiber sensor can work steadily for a long time at high temperature is the formation of β-cristobalite, which is stable at high-temperature. Full article

(This article belongs to the Section Physical Sensors)

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20 pages, 5196 KiB

Open AccessArticle

An Integrated Machine Learning Algorithm for Separating the Long-Term Deflection Data of Prestressed Concrete Bridges

by Xijun Ye, Xueshuai Chen, Yaxiong Lei, Jiangchao Fan and Liu Mei

Sensors 2018, 18(11), 4070; https://doi.org/10.3390/s18114070 - 21 Nov 2018

Cited by 19 | Viewed by 4838

Abstract

Deflection is one of the key indexes for the safety evaluation of bridge structures. In reality, due to the changing operational and environmental conditions, the deflection signals measured by structural health monitoring systems are greatly affected. These ambient changes in the system often [...] Read more.

Deflection is one of the key indexes for the safety evaluation of bridge structures. In reality, due to the changing operational and environmental conditions, the deflection signals measured by structural health monitoring systems are greatly affected. These ambient changes in the system often cover subtle changes in the vibration signals caused by damage to the system. The deflection signals of prestressed concrete (PC) bridges are regarded as the superposition of different effects, including concrete shrinkage, creep, prestress loss, material deterioration, temperature effects, and live load effects. According to multiscale analysis theory of the long-term deflection signal, in this paper, an integrated machine learning algorithm that combines a Butterworth filter, ensemble empirical mode decomposition (EEMD), principle component analysis (PCA), and fast independent component analysis (FastICA) is proposed for separating the individual deflection components from a measured single channel deflection signal. The proposed algorithm consists of four stages: (1) the live load effect, which is a high-frequency signal, is separated from the raw signal by a Butterworth filter; (2) the EEMD algorithm is used to extract the intrinsic mode function (IMF) components; (3) these IMFs are utilized as input in the PCA model and some uncorrelated and dominant basis components are extracted; and (4) FastICA is applied to derive the independent deflection component. The simulated results show that each individual deflection component can be successfully separated when the noise level is under 10%. Verified by a practical application, the algorithm is feasible for extracting the structural deflection (including concrete shrinkage, creep, and prestress loss) only caused by structural damage or material deterioration. Full article

(This article belongs to the Special Issue Bridge Structural Health Monitoring and Damage Identification)

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12 pages, 13062 KiB

Open AccessArticle

Gaussian Process Based Bayesian Inference System for Intelligent Surface Measurement

by Ming Jun Ren, Chi Fai Cheung and Gao Bo Xiao

Sensors 2018, 18(11), 4069; https://doi.org/10.3390/s18114069 - 21 Nov 2018

Cited by 6 | Viewed by 3907

Abstract

This paper presents a Gaussian process based Bayesian inference system for the realization of intelligent surface measurement on multi-sensor instruments. The system considers the surface measurement as a time series data collection process, and the Gaussian process is used as mathematical foundation to [...] Read more.

This paper presents a Gaussian process based Bayesian inference system for the realization of intelligent surface measurement on multi-sensor instruments. The system considers the surface measurement as a time series data collection process, and the Gaussian process is used as mathematical foundation to establish an inferring plausible model to aid the measurement process via multi-feature classification and multi-dataset regression. Multi-feature classification extracts and classifies the geometric features of the measured surfaces at different scales to design an appropriate composite covariance kernel and corresponding initial sampling strategy. Multi-dataset regression takes the designed covariance kernel as input to fuse the multi-sensor measured datasets with Gaussian process model, which is further used to adaptively refine the initial sampling strategy by taking the credibility of the fused model as the critical sampling criteria. Hence, intelligent sampling can be realized with consecutive learning process with full Bayesian treatment. The statistical nature of the Gaussian process model combined with various powerful covariance kernel functions offer the system great flexibility for different kinds of complex surfaces. Full article

(This article belongs to the Collection Multi-Sensor Information Fusion)

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10 pages, 2543 KiB

Open AccessArticle

Designing a Robust Kelvin Probe Setup Optimized for Long-Term Surface Photovoltage Acquisition

by Elke Beyreuther, Stefan Grafström and Lukas M. Eng

Sensors 2018, 18(11), 4068; https://doi.org/10.3390/s18114068 - 21 Nov 2018

Cited by 3 | Viewed by 4178

Abstract

We introduce a robust low-budget Kelvin probe design that is optimized for the long-term acquisition of surface photovoltage (SPV) data, especially developed for highly resistive systems, which exhibit—in contrast to conventional semiconductors—very slow photoinduced charge relaxation processes in the range of hours and [...] Read more.

We introduce a robust low-budget Kelvin probe design that is optimized for the long-term acquisition of surface photovoltage (SPV) data, especially developed for highly resistive systems, which exhibit—in contrast to conventional semiconductors—very slow photoinduced charge relaxation processes in the range of hours and days. The device provides convenient optical access to the sample, as well as high mechanical and electrical stability due to off-resonance operation, showing a noise band as narrow as 1 mV. Furthermore, the acquisition of temperature-dependent SPV transients necessary for SPV-based deep-level transient spectroscopy becomes easily possible. The performance of the instrument is demonstrated by recording long-term SPV transients of the ultra-slowly relaxing model oxide strontium titanate (SrTiO

_{3}

) over 20 h. Full article

(This article belongs to the Section Physical Sensors)

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23 pages, 8184 KiB

Open AccessArticle

Accuracy Assessment of Semi-Automatic Measuring Techniques Applied to Displacement Control in Self-Balanced Pile Capacity Testing Appliance

by Zbigniew Muszyński, Jarosław Rybak and Paulina Kaczor

Sensors 2018, 18(11), 4067; https://doi.org/10.3390/s18114067 - 21 Nov 2018

Cited by 16 | Viewed by 3926

Abstract

Static load tests of foundation piles are the basic method for the designing or verification of adopted design solutions which concern the foundation of a building structure. Preparation of a typical test station using the so-called inverted beam method is very expensive and [...] Read more.

Static load tests of foundation piles are the basic method for the designing or verification of adopted design solutions which concern the foundation of a building structure. Preparation of a typical test station using the so-called inverted beam method is very expensive and labor-intensive. The settlement values of the loaded pile are usually recorded using accurate dial gauges. These gauges are attached to a reference beam located in close proximity to the pile under test, which may cause systematic errors (difficult to detect) caused by the displacement of the adopted reference beam. The application of geodetic methods makes it possible to maintain an independent, external reference system, and to verify the readouts from dial gauges. The article presents an innovative instrumentation for a self-balanced stand for the static load test made from a closed-end, double steel pipe. Instead of typical, precise geometric leveling, the semi-automatic measuring techniques were used: motorized total station measurement and terrestrial laser scanning controlled by a computer. The processing of the acquired data made it possible to determine the vertical displacements of both parts of the examined pile and compare displacements with the results from the dial gauges. On the basis of the excess of the collected observations, it was possible to assess the accuracy, which confirmed the usefulness of measuring techniques under study. Full article

(This article belongs to the Special Issue Terrestrial Laser Scanning)

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21 pages, 864 KiB

Open AccessArticle

Evaluation of Strategies for the Development of Efficient Code for Raspberry Pi Devices

by Javier Corral-García, José-Luis González-Sánchez and Miguel-Ángel Pérez-Toledano

Sensors 2018, 18(11), 4066; https://doi.org/10.3390/s18114066 - 21 Nov 2018

Cited by 6 | Viewed by 4141

Abstract

The Internet of Things (IoT) is faced with challenges that require green solutions and energy-efficient paradigms. Architectures (such as ARM) have evolved significantly in recent years, with improvements to processor efficiency, essential for always-on devices, as a focal point. However, as far as [...] Read more.

The Internet of Things (IoT) is faced with challenges that require green solutions and energy-efficient paradigms. Architectures (such as ARM) have evolved significantly in recent years, with improvements to processor efficiency, essential for always-on devices, as a focal point. However, as far as software is concerned, few approaches analyse the advantages of writing efficient code when programming IoT devices. Therefore, this proposal aims to improve source code optimization to achieve better execution times. In addition, the importance of various techniques for writing efficient code for Raspberry Pi devices is analysed, with the objective of increasing execution speed. A complete set of tests have been developed exclusively for analysing and measuring the improvements achieved when applying each of these techniques. This will raise awareness of the significant impact the recommended techniques can have. Full article

(This article belongs to the Special Issue Green Communications and Networking for IoT)

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Percentages of improvement in the runtime achieved by writing efficient code (without compiler optimization). Full article ">Figure 2
Percentages of improvement in the runtime achieved by writing efficient code (with compiler optimization level 3). Full article ">Figure 3
Cascaded function calls. Percentage of improvement in the runtime according to the number of calls to the function (number of iterations of the loop) in RPi 3B+. Full article ">Figure 4
Row-major accessing. Percentage of improvement in the runtime according to the matrix size in RPi 3B+. Full article ">Figure 5
Loop count down. Percentages of improvement in the runtime according to the array size (number of elements) in RPi 3B+. Full article ">Figure 6
Loop unrolling in RPi 3B+. Percentages of improvement in the runtime according to the number of iterations. (a) Array size of 50 elements. (b) Array size of 100 elements. (c) Array size of 200 elements. (d) Array size of 300 elements. Full article ">Figure 7
Linear search with for loops. Percentages of improvement in the runtime according to the array size (number of elements) in RPi 3B+. Full article ">

13 pages, 1705 KiB

Open AccessArticle

Characterization of Sicilian Honeys Pollen Profiles Using a Commercial E-Tongue and Melissopalynological Analysis for Rapid Screening: A Pilot Study

by Ambra R. Di Rosa, Anna M. F. Marino, Francesco Leone, Giuseppe G. Corpina, Renato P. Giunta and Vincenzo Chiofalo

Sensors 2018, 18(11), 4065; https://doi.org/10.3390/s18114065 - 21 Nov 2018

Cited by 23 | Viewed by 4066

Abstract

Honey is usually classified as “unifloral” or “multifloral”, depending on whether a dominating pollen grain, originating from only one particular plant, or no dominant pollen type in the sample is found. Unifloral honeys are usually more expensive and appreciated than multifloral honeys, which [...] Read more.

Honey is usually classified as “unifloral” or “multifloral”, depending on whether a dominating pollen grain, originating from only one particular plant, or no dominant pollen type in the sample is found. Unifloral honeys are usually more expensive and appreciated than multifloral honeys, which highlights the importance of honey authenticity. Melissopalynological analysis is used to identify the botanical origin of honey, counting down the number of pollens grains of a honey sample, and calculating the respective percentages of the nectariferous pollens. In addition, sensory properties are also very important for honey characterization, and electronic senses emerged as useful tools for honey authentication. In this work, a comparison of the results obtained from melissopalynological analysis with those provided by a potentiometric electronic tongue is given, resulting in a 100% match between the two techniques. Full article

(This article belongs to the Section Chemical Sensors)

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9 pages, 2158 KiB

Open AccessArticle

Comparison of CO₂ Vertical Profiles in the Lower Troposphere between 1.6 µm Differential Absorption Lidar and Aircraft Measurements Over Tsukuba

by Yasukuni Shibata, Chikao Nagasawa, Makoto Abo, Makoto Inoue, Isamu Morino and Osamu Uchino

Sensors 2018, 18(11), 4064; https://doi.org/10.3390/s18114064 - 21 Nov 2018

Cited by 7 | Viewed by 5865

Abstract

A 1.6 μm differential absorption Lidar (DIAL) system for measurement of vertical CO₂ mixing ratio profiles has been developed. A comparison of CO₂ vertical profiles measured by the DIAL system and an aircraft in situ sensor in January 2014 over the [...] Read more.

A 1.6 μm differential absorption Lidar (DIAL) system for measurement of vertical CO₂ mixing ratio profiles has been developed. A comparison of CO₂ vertical profiles measured by the DIAL system and an aircraft in situ sensor in January 2014 over the National Institute for Environmental Studies (NIES) in Tsukuba, Japan, is presented. The DIAL measurement was obtained at an altitude range of between 1.56 and 3.60 km with a vertical resolution of 236 m (below 3 km) and 590 m (above 3 km) at an average error of 1.93 ppm. An in situ sensor for cavity ring-down spectroscopy of CO₂ was installed in an aircraft. CO₂ mixing ratio measured by DIAL and the aircraft sensor ranged from 398.73 to 401.36 ppm and from 399.08 to 401.83 ppm, respectively, with an average difference of −0.94 ± 1.91 ppm below 3 km and −0.70 ± 1.98 ppm above 3 km between the two measurements. Full article

(This article belongs to the Special Issue Lidar Technologies, Techniques, and Applications for Atmospheric Remote Sensing)

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18 pages, 2552 KiB

Open AccessArticle

A Bayesian Density Model Based Radio Signal Fingerprinting Positioning Method for Enhanced Usability

by Zheng Li, Jingbin Liu, Fan Yang, Xiaoguang Niu, Leilei Li, Zemin Wang and Ruizhi Chen

Sensors 2018, 18(11), 4063; https://doi.org/10.3390/s18114063 - 21 Nov 2018

Cited by 21 | Viewed by 5238

Abstract

Indoor navigation and location-based services increasingly show promising marketing prospects. Indoor positioning based on Wi-Fi radio signal has been studied for more than a decade because Wi-Fi, a signal of opportunity without extra cost, is extensively deployed for internet connections. Bayesian fingerprinting positioning, [...] Read more.

Indoor navigation and location-based services increasingly show promising marketing prospects. Indoor positioning based on Wi-Fi radio signal has been studied for more than a decade because Wi-Fi, a signal of opportunity without extra cost, is extensively deployed for internet connections. Bayesian fingerprinting positioning, a classical Wi-Fi-based indoor positioning method, consists of two phases: radio map learning and position inference. Thus far, the application of Bayesian fingerprinting positioning is limited due to its poor usability; radio map learning requires an adequate number of received signal strength indication (RSSI) observables at each reference point, long-term fieldwork, and high development and maintenance costs. In this paper, based on a statistical analysis of actual RSSI observables, a Weibull–Bayesian density model is proposed to represent the probability density of Wi-Fi RSSI observables. The Weibull model, which is parameterized with three parameters that can be calculated with fewer samples, can calculate the probability density with a higher accuracy than the traditional histogram method. Furthermore, the parameterized Weibull model can simplify the radio map by storing only three parameters that can restore the whole probability density, i.e., it is not necessary to store the probability distribution based on traditionally separated RSSI bins. Bayesian positioning inference is performed in the positioning phase using probability density rather than the traditional probability distribution of predefined RSSI bins. The proposed method was implemented on an Android smartphone, and the performance was evaluated in different indoor environments. Results revealed that the proposed method enhanced the usability of Wi-Fi Bayesian fingerprinting positioning by requiring fewer RSSI observables and improved the positioning accuracy by 19–32% in different building environments compared with the classic histogram-based method, even when more samples were used. Full article

(This article belongs to the Collection Positioning and Navigation)

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14 pages, 4567 KiB

Open AccessArticle

Validation of Finite Element Model by Smart Aggregate-Based Stress Monitoring

by Haibin Zhang, Shuang Hou and Jinping Ou

Sensors 2018, 18(11), 4062; https://doi.org/10.3390/s18114062 - 21 Nov 2018

Cited by 4 | Viewed by 4088

Abstract

Concrete compressive strength is an important parameter of material properties for assessing seismic performance of reinforced concrete (RC) structures, which has a certain level of uncertainty due to its inherent variability. In this paper, the method of concrete strength validation of finite element [...] Read more.

Concrete compressive strength is an important parameter of material properties for assessing seismic performance of reinforced concrete (RC) structures, which has a certain level of uncertainty due to its inherent variability. In this paper, the method of concrete strength validation of finite element model using smart aggregate (SA)-based stress monitoring is proposed. The FE model was established using Open System for Earthquake Engineering Simulation (OpenSEES) platform. The concrete strengths obtained from the material test, peak stress of SA, and estimated concrete strength based on SA stress were employed in FE models. The lateral displacement monitored by Liner variable differential transformer and vertical axial load monitored by load cell in the experiment are applied in the model. By comparing the global response (i.e., lateral reaction force and hysteretic loop), local response (i.e., concrete stress, rebar strain, and cross-section moment) and corresponding root-mean-square error obtained from experiment and numerical analysis, the capabilities of validation of FE model using SA-based stress monitoring method were demonstrated. Full article

(This article belongs to the Special Issue Recent Advances of Piezoelectric Transducers and Applications)

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12 pages, 3820 KiB

Open AccessArticle

A Tellurium Oxide Microcavity Resonator Sensor Integrated On-Chip with a Silicon Waveguide

by Henry C. Frankis, Daniel Su, Dawson B. Bonneville and Jonathan D. B. Bradley

Sensors 2018, 18(11), 4061; https://doi.org/10.3390/s18114061 - 21 Nov 2018

Cited by 6 | Viewed by 5473

Abstract

We report on thermal and evanescent field sensing from a tellurium oxide optical microcavity resonator on a silicon photonics platform. The on-chip resonator structure is fabricated using silicon-photonics-compatible processing steps and consists of a silicon-on-insulator waveguide next to a circular trench that is [...] Read more.

We report on thermal and evanescent field sensing from a tellurium oxide optical microcavity resonator on a silicon photonics platform. The on-chip resonator structure is fabricated using silicon-photonics-compatible processing steps and consists of a silicon-on-insulator waveguide next to a circular trench that is coated in a tellurium oxide film. We characterize the device’s sensitivity by both changing the temperature and coating water over the chip and measuring the corresponding shift in the cavity resonance wavelength for different tellurium oxide film thicknesses. We obtain a thermal sensitivity of up to 47 pm/°C and a limit of detection of 2.2 × 10⁻³ RIU for a device with an evanescent field sensitivity of 10.6 nm/RIU. These results demonstrate a promising approach to integrating tellurium oxide and other novel microcavity materials into silicon microphotonic circuits for new sensing applications. Full article

(This article belongs to the Special Issue Resonator Sensors 2018)

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(a) Top view drawing of the resonator sensor showing the pulley-coupled silicon bus waveguide (red) and the TeO2 microcavity (green). (b) Cross-section schematic of the device through the section indicated by the dashed line in (a), showing the silicon bus waveguide and the TeO2 resonator layer coated into the trench. (c) Calculated fundamental transverse electric (TE) polarized electric field mode profiles for the TeO2 resonator and silicon bus waveguide in the region indicated by the dashed line in (b). (d) Focused ion beam (FIB) scanning electron microscope (SEM) cross-section image of a fabricated device showing the realized structure. Full article ">Figure 2
Diagram of the optical setup used to characterize the devices. Full article ">Figure 3
Resonance spectra measured at temperatures ranging from 20 to 40 °C for the microcavity with a 1100-nm-thick TeO2 film, showing shifting of the resonance wavelength. Full article ">Figure 4
Measured wavelength shift versus temperature for 480-, 900-, and 1100-nm-thick TeO2 cavities, fitted to have thermal sensitivities of 28, 47, and 30 pm/°C, respectively. Full article ">Figure 5
Resonance spectra measured in air (pink) and after covering the chip in water (blue) for (a) 900-nm-thick and (b) 1100-nm-thick TeO2 resonators. Full article ">Figure 6
Measured resonance shift vs. cladding refractive index for a 900-nm-thick TeO2 microcavity coated in solutions with varying concentrations of glycerol and water. Full article ">Figure 7
Cavity resonance modes around 1600 nm measured in air (fit with red line) and after coating the chip in water (fit with blue line) for (a) 900-nm-thick and (b) 1100-nm-thick TeO2 resonators, demonstrating resonance broadening in water. Full article ">Figure 8
Simulated (a) wavelength shift and (b) RIU sensitivity vs. evanescent medium refractive index for cavities with TeO2 coating thicknesses ranging from 0.5 to 1.1 μm. Full article ">

17 pages, 2530 KiB

Open AccessArticle

Evaluation of Object Surface Edge Profiles Detected with a 2-D Laser Scanning Sensor

by Tingting Yan, Xiaochan Wang, Heping Zhu and Peter Ling

Sensors 2018, 18(11), 4060; https://doi.org/10.3390/s18114060 - 21 Nov 2018

Cited by 7 | Viewed by 4650

Abstract

Canopy edge profile detection is a critical component of plant recognition in variable-rate spray control systems. The accuracy of a high-speed 270° radial laser sensor was evaluated in detecting the surface edge profiles of six complex-shaped objects. These objects were toy balls with [...] Read more.

Canopy edge profile detection is a critical component of plant recognition in variable-rate spray control systems. The accuracy of a high-speed 270° radial laser sensor was evaluated in detecting the surface edge profiles of six complex-shaped objects. These objects were toy balls with a pink smooth surface, light brown rectangular cardboard boxes, black and red texture surfaced basketballs, white smooth cylinders, and two different sized artificial plants. Evaluations included reconstructed three-dimensional (3-D) images for the object surfaces with the data acquired from the laser sensor at four different detection heights (0.25, 0.50, 0.75, and 1.00 m) above each object, five sensor travel speeds (1.6, 2.4, 3.2, 4.0, and 4.8 km h⁻¹), and 8 to 15 horizontal distances to the sensor ranging from 0 to 3.5 m. Edge profiles of the six objects detected with the laser sensor were compared with images taken with a digital camera. The edge similarity score (ESS) was significantly affected by the horizontal distances of the objects, and the influence became weaker when the objects were placed closer to each other. The detection heights and travel speeds also influenced the ESS slightly. The overall average ESS ranged from 0.38 to 0.95 for all the objects under all the test conditions, thereby providing baseline information for the integration of the laser sensor into future development of greenhouse variable-rate spray systems to improve pesticide, irrigation, and nutrition application efficiencies through watering booms. Full article

(This article belongs to the Special Issue Terrestrial Laser Scanning)

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The 270° radial range laser sensor mounted on a constant-speed track to detect six rows of different objects (artificial plant 1, artificial plant 2, basketball, rectangular box, toy ball, and cylinder). Full article ">Figure 2
Geometry analysis of the laser beam points transmitted on the object surface on one side of the sensor. Full article ">Figure 3
Calculated detection resolution of the laser sensor along the horizontal direction (DRH) with Equation (1) for different horizontal distances and detection heights. Full article ">Figure 4
Processing edge similarity score (ESS) for paired images of eight 0.5 m evenly spaced objects obtained from the camera (upper) and laser sensor (lower): (a) toy ball, (b) basketball, (c) rectangular box, (d) cylinder, (e) artificial plant 1, and (f) artificial plant 2. The reconstructed images from the laser sensor were taken at 3.2 km h−1 travel speed and 0.5 m detection height. Different colors represent different vertical distances between the object surfaces and the laser sensor. Full article ">Figure 4 Cont.
Processing edge similarity score (ESS) for paired images of eight 0.5 m evenly spaced objects obtained from the camera (upper) and laser sensor (lower): (a) toy ball, (b) basketball, (c) rectangular box, (d) cylinder, (e) artificial plant 1, and (f) artificial plant 2. The reconstructed images from the laser sensor were taken at 3.2 km h−1 travel speed and 0.5 m detection height. Different colors represent different vertical distances between the object surfaces and the laser sensor. Full article ">Figure 5
Processing ESS for paired images of eight 0.25 m evenly spaced objects obtained from the camera (upper) and laser sensor (lower): (a) toy ball, (b) artificial plant 1. The reconstructed images from the laser sensor were taken at 3.2 km h−1 travel speed and 0.5 m detection height. Different colors represent different vertical distances between the object surfaces and the laser sensor. Full article ">

13 pages, 2849 KiB

Open AccessArticle

Employing Ray-Tracing and Least-Squares Support Vector Machines for Localisation

by Benny Chitambira, Simon Armour, Stephen Wales and Mark Beach

Sensors 2018, 18(11), 4059; https://doi.org/10.3390/s18114059 - 20 Nov 2018

Cited by 3 | Viewed by 3344

Abstract

This article evaluates the use of least-squares support vector machines, with ray-traced data, to solve the problem of localisation in multipath environments. The schemes discussed concern 2-D localisation, but could easily be extended to 3-D. It does not require NLOS identification and mitigation, [...] Read more.

This article evaluates the use of least-squares support vector machines, with ray-traced data, to solve the problem of localisation in multipath environments. The schemes discussed concern 2-D localisation, but could easily be extended to 3-D. It does not require NLOS identification and mitigation, hence, it can be applied in any environment. Some background details and a detailed experimental setup is provided. Comparisons with schemes that require NLOS identification and mitigation, from earlier work, are also presented. The results demonstrate that the direct localisation scheme using least-squares support vector machine (the Direct method) achieves superior outage to TDOA and TOA/AOA for NLOS environments. TDOA has better outage in LOS environments. TOA/AOA performs better for an accepted outage probability of 20 percent or greater but as the outage probability lowers, the Direct method becomes better. Full article

(This article belongs to the Special Issue Selected Papers from 8th International Conference on Localization and GNSS 2018 (ICL-GNSS 2018))

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12 pages, 1684 KiB

Open AccessArticle

Scaling Effect of Fused ASTER-MODIS Land Surface Temperature in an Urban Environment

by Hua Liu and Qihao Weng

Sensors 2018, 18(11), 4058; https://doi.org/10.3390/s18114058 - 20 Nov 2018

Cited by 29 | Viewed by 4181

Abstract

There is limited research in land surface temperatures (LST) simulation using image fusion techniques, especially studies addressing the downscaling effect of LST image fusion. LST simulation and associated downscaling effect can potentially benefit the thermal studies requiring both high spatial and temporal resolutions. [...] Read more.

There is limited research in land surface temperatures (LST) simulation using image fusion techniques, especially studies addressing the downscaling effect of LST image fusion. LST simulation and associated downscaling effect can potentially benefit the thermal studies requiring both high spatial and temporal resolutions. This study simulated LSTs based on observed Terra Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Terra Moderate Resolution Imaging Spectroradiometer (MODIS) LST imagery with Spatial and Temporal Adaptive Reflectance Fusion Model, and investigated the downscaling effect of LST image fusion at 15, 30, 60, 90, 120, 250, 500, and 1000 m spatial resolutions. The study area partially covered the City of Los Angeles, California, USA, and surrounding areas. The reference images (observed ASTER and MODIS LST imagery) were acquired on 04/03/2007 and 07/01/2007, with simulated LSTs produced for 4/28/2007. Three image resampling methods (Cubic Convolution, Bilinear Interpolation, and Nearest Neighbor) were used during the downscaling and upscaling processes, and the resulting LST simulations were compared. Results indicated that the observed ASTER LST and simulated ASTER LST images (date 04/28/2007, spatial resolution 90 m) had high agreement in terms of spatial variations and basic statistics based on a comparison between the observed and simulated ASTER LST maps. Urban developed lands possessed higher LSTs with lighter tones and mountainous areas showed dark tones with lower LSTs. The Cubic Convolution and Bilinear Interpolation resampling methods yielded better results over Nearest Neighbor resampling method across the scales from 15 to 1000 m. The simulated LSTs with image fusion can be used as valuable inputs in heat related studies that require frequent LST measurements with fine spatial resolutions, e.g., seasonal movements of urban heat islands, monthly energy budget assessment, and temperature-driven epidemiology. The observation of scale-independency of the proposed image fusion method can facilitate with image selections of LST studies at various locations. Full article

(This article belongs to the Special Issue Advances in Remote Sensing of Land-Cover and Land-Use Changes)

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13 pages, 1118 KiB

Open AccessArticle

NLOS Identification in WLANs Using Deep LSTM with CNN Features

by Viet-Hung Nguyen, Minh-Tuan Nguyen, Jeongsik Choi and Yong-Hwa Kim

Sensors 2018, 18(11), 4057; https://doi.org/10.3390/s18114057 - 20 Nov 2018

Cited by 21 | Viewed by 4778

Abstract

Identifying channel states as line-of-sight or non-line-of-sight helps to optimize location-based services in wireless communications. The received signal strength identification and channel state information are used to estimate channel conditions for orthogonal frequency division multiplexing systems in indoor wireless local area networks. This [...] Read more.

Identifying channel states as line-of-sight or non-line-of-sight helps to optimize location-based services in wireless communications. The received signal strength identification and channel state information are used to estimate channel conditions for orthogonal frequency division multiplexing systems in indoor wireless local area networks. This paper proposes a joint convolutional neural network and recurrent neural network architecture to classify channel conditions. Convolutional neural networks extract the feature from frequency-domain characteristics of channel state information data and recurrent neural networks extract the feature from time-varying characteristics of received signal strength identification and channel state information between packet transmissions. The performance of the proposed methods is verified under indoor propagation environments. Experimental results show that the proposed method has a 2% improvement in classification performance over the conventional recurrent neural network model. Full article

(This article belongs to the Section Sensor Networks)

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14 pages, 464 KiB

Open AccessArticle

Message Integration Authentication in the Internet-of-Things via Lattice-Based Batch Signatures

by Xiuhua Lu, Wei Yin, Qiaoyan Wen, Kaitai Liang, Liqun Chen and Jiageng Chen

Sensors 2018, 18(11), 4056; https://doi.org/10.3390/s18114056 - 20 Nov 2018

Cited by 4 | Viewed by 3344

Abstract

The internet-of-things (also known as IoT) connects a large number of information-sensing devices to the Internet to collect all kinds of information needed in real time. The reliability of the source of a large number of accessed information tests the processing speed of [...] Read more.

The internet-of-things (also known as IoT) connects a large number of information-sensing devices to the Internet to collect all kinds of information needed in real time. The reliability of the source of a large number of accessed information tests the processing speed of signatures. Batch signature allows a signer to sign a group of messages at one time, and signatures’ verification can be completed individually and independently. Therefore, batch signature is suitable for data integration authentication in IoT. An outstanding advantage of batch signature is that a signer is able to sign as many messages as possible at one time without worrying about the size of signed messages. To reduce complexity yielded by multiple message signing, a binary tree is usually leveraged in the construction of batch signature. However, this structure requires a batch residue, making the size of a batch signature (for a group of messages) even longer than the sum of single signatures. In this paper, we make use of the intersection method from lattice to propose a novel generic method for batch signature. We further combine our method with hash-and-sign paradigm and Fiat–Shamir transformation to propose new batch signature schemes. In our constructions, a batch signature does not need a batch residue, so that the size of the signature is relatively smaller. Our schemes are securely proved to be existential unforgeability against adaptive chosen message attacks under the small integer solution problem, which shows great potential resisting quantum computer attacks. Full article

(This article belongs to the Special Issue Threat Identification and Defence for Internet-of-Things)

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41 pages, 12398 KiB

Open AccessArticle

Adding Active Slot Joint Larger Broadcast Radius for Fast Code Dissemination in WSNs

by Wei Yang, Wei Liu, Zhiwen Zeng, Anfeng Liu, Guosheng Huang, Neal N. Xiong and Zhiping Cai

Sensors 2018, 18(11), 4055; https://doi.org/10.3390/s18114055 - 20 Nov 2018

Cited by 13 | Viewed by 4580

Abstract

By using Software Defined Network (SDN) technology, senor nodes can get updated program code which can provide new features, so it has received extensive attention. How to effectively spread code to each node fast is a challenge issue in wireless sensor networks (WSNs). [...] Read more.

By using Software Defined Network (SDN) technology, senor nodes can get updated program code which can provide new features, so it has received extensive attention. How to effectively spread code to each node fast is a challenge issue in wireless sensor networks (WSNs). In this paper, an Adding Active Slot joint Larger Broadcast Radius (AAS-LBR) scheme is proposed for fast code dissemination. The AAS-LBR scheme combines the energy of data collection and code dissemination, making full use of the remaining energy in the far-sink area to increase the active slot and the broadcast radius to speed up the code dissemination. The main contributions of the proposed AAS-LBR scheme are the following: (1) Make full use of the remaining energy of the far sink area to expand the broadcast radius, so that the node broadcasts a longer distance. The wide range of broadcasts makes the number of nodes receiving code more, which speeds up the spread of code dissemination. (2) AAS-LBR uses two improved methods to further reduce the number of broadcasts and speed up the code dissemination: (a) When constructing the broadcast backbone whose nodes dominate all nodes in network and are responsible for broadcasting code, the active slot is added to the next hop node in a pipeline style on the diffusion path, which enables the code dissemination process to continue without pause. Thus, the code can quickly spread to the entire broadcast backbone. (b) For the nodes in the non-broadcast backbone whose nodes are dominated by the broadcast backbone and only for receiving code, an active slot is added coincident with its broadcast backbone’ active slot, which can reduce the time required for code dissemination and reduce the number of broadcasts. A lot of performance analysis and simulation results show that compared to previous schemed, the AAS-LBR scheme can balance energy consumption, the transmission delay can be reduced 43.09–78.69%, the number of broadcasts can be reduced 44.51–86.18% and the energy efficiency is improved by about 24.5%. Full article

(This article belongs to the Special Issue Advances in Sensing, Processing and Transmission for IoT-Oriented Sensors Networks)

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16 pages, 4531 KiB

Open AccessArticle

Intersection Intelligence: Supporting Urban Platooning with Virtual Traffic Lights over Virtualized Intersection-Based Routing

by José Víctor Saiáns-Vázquez, Esteban Fernando Ordóñez-Morales, Martín López-Nores, Yolanda Blanco-Fernández, Jack Fernando Bravo-Torres, José Juan Pazos-Arias, Alberto Gil-Solla and Manuel Ramos-Cabrer

Sensors 2018, 18(11), 4054; https://doi.org/10.3390/s18114054 - 20 Nov 2018

Cited by 13 | Viewed by 4927

Abstract

The advent of the autonomous car is paving the road to the realization of ideas that will help optimize traffic flows, increase safety and reduce fuel consumption, among other advantages. We present one proposal to bring together Virtual Traffics Lights (VTLs) and platooning [...] Read more.

The advent of the autonomous car is paving the road to the realization of ideas that will help optimize traffic flows, increase safety and reduce fuel consumption, among other advantages. We present one proposal to bring together Virtual Traffics Lights (VTLs) and platooning in urban scenarios, leaning on vehicle-to-vehicle (V2V) communication protocols that turn intersections into virtual containers of data. Newly-introduced protocols for the combined management of VTLs and platoons are validated by simulation, comparing a range of routing protocols for the vehicular networks with the baseline given by common deployments of traditional traffic lights ruled by state-of-the-art policies. The simulation results show that the combination of VTLs and platoons can achieve significant reductions in travel times and fuel consumption, provided that proper algorithms are used to handle the V2V communications. Full article

(This article belongs to the Special Issue Advances on Vehicular Networks: From Sensing to Autonomous Driving)

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21 pages, 551 KiB

Open AccessArticle

Adaptive Data Synchronization Algorithm for IoT-Oriented Low-Power Wide-Area Networks

by Andrea Petroni, Francesca Cuomo, Leonisio Schepis, Mauro Biagi, Marco Listanti and Gaetano Scarano

Sensors 2018, 18(11), 4053; https://doi.org/10.3390/s18114053 - 20 Nov 2018

Cited by 12 | Viewed by 4683

Abstract

The Internet of Things (IoT) is by now very close to be realized, leading the world towards a new technological era where people’s lives and habits will be definitively revolutionized. Furthermore, the incoming 5G technology promises significant enhancements concerning the Quality of Service [...] Read more.

The Internet of Things (IoT) is by now very close to be realized, leading the world towards a new technological era where people’s lives and habits will be definitively revolutionized. Furthermore, the incoming 5G technology promises significant enhancements concerning the Quality of Service (QoS) in mobile communications. Having billions of devices simultaneously connected has opened new challenges about network management and data exchange rules that need to be tailored to the characteristics of the considered scenario. A large part of the IoT market is pointing to Low-Power Wide-Area Networks (LPWANs) representing the infrastructure for several applications having energy saving as a mandatory goal besides other aspects of QoS. In this context, we propose a low-power IoT-oriented file synchronization protocol that, by dynamically optimizing the amount of data to be transferred, limits the device level of interaction within the network, therefore extending the battery life. This protocol can be adopted with different Layer 2 technologies and provides energy savings at the IoT device level that can be exploited by different applications. Full article

(This article belongs to the Special Issue Green Communications and Networking for IoT)

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23 pages, 1372 KiB

Open AccessArticle

A Joint Multi-Path and Multi-Channel Protocol for Traffic Routing in Smart Grid Neighborhood Area Networks

by Juan Pablo Astudillo León and Luis J. De la Cruz Llopis

Sensors 2018, 18(11), 4052; https://doi.org/10.3390/s18114052 - 20 Nov 2018

Cited by 11 | Viewed by 4573

Abstract

In order to improve the management mechanisms of the electric energy transport infrastructures, the smart grid networks have associated data networks that are responsible for transporting the necessary information between the different elements of the electricity network and the control center. Besides, they [...] Read more.

In order to improve the management mechanisms of the electric energy transport infrastructures, the smart grid networks have associated data networks that are responsible for transporting the necessary information between the different elements of the electricity network and the control center. Besides, they make possible a more efficient use of this type of energy. Part of these data networks is comprised of the Neighborhood Area Networks (NANs), which are responsible for interconnecting the different smart meters and other possible devices present at the consumers’ premises with the control center. Among the proposed network technologies for NANs, wireless technologies are becoming more relevant due to their flexibility and increasing available bandwidth. In this paper, some general modifications are proposed for the routing protocol of the wireless multi-hop mesh networks standardized by the IEEE. In particular, the possibility of using multiple paths and transmission channels at the same time, depending on the quality of service needs of the different network traffic, is added. The proposed modifications have been implemented in the ns-3 simulator and evaluated in situations of high traffic load. Simulation results show improvements in the network performance in terms of packet delivery ratio, throughput and network transit time. Full article

(This article belongs to the Special Issue Smart Grid Networks and Energy Cyber Physical Systems)

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