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Electronics, Volume 8, Issue 10 (October 2019) – 144 articles

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Cover Story (view full-size image) Considering the importance of energy saving in autonomous robot, and knowing that in the industry, [...] Read more.
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Open AccessArticle
Access Latency Reduction in the QUIC Protocol Based on Communication History
Electronics 2019, 8(10), 1204; https://doi.org/10.3390/electronics8101204 - 22 Oct 2019
Cited by 1 | Viewed by 693
Abstract
Internet traffic is experiencing rapid growth, with the majority of traffic generated from video steaming, web data services and Internet of Things. As these services include the transmission of small data, such as web pages, video chunks and sensing data, data latency affects [...] Read more.
Internet traffic is experiencing rapid growth, with the majority of traffic generated from video steaming, web data services and Internet of Things. As these services include the transmission of small data, such as web pages, video chunks and sensing data, data latency affects the quality of experience rather than the throughput. Therefore, this study aims to decrease latency to improve the quality of the user experience. To this end, we measure the web service delay and throughput in mobile networks. The results indicate a low quality experience for mobile users, even though mobile networks support a large throughput. We therefore propose a light-weight latency reduction scheme for the Quick UDP Internet Connections (QUIC) protocol. The proposed scheme calculates the average congestion window, which is utilized as the initial congestion window when a new connection is established. The proposed scheme is evaluated through experiments on a testbed. The results show that our scheme reduces latency significantly. The results of this study can help improve user experiences of video streaming and web data services. Full article
(This article belongs to the Section Networks)
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Open AccessArticle
Nanoseconds Switching Time Monitoring of Insulated Gate Bipolar Transistor Module by Under-Sampling Reconstruction of High-Speed Switching Transitions Signal
Electronics 2019, 8(10), 1203; https://doi.org/10.3390/electronics8101203 - 22 Oct 2019
Cited by 1 | Viewed by 646
Abstract
An insulated gate bipolar transistor (IGBT) is one of the most reliable critical components in power electronics systems (PESs). The switching time during IGBT turn-on/off transitions is a good health status indicator for IGBT. However, online monitoring of IGBT switching time is still [...] Read more.
An insulated gate bipolar transistor (IGBT) is one of the most reliable critical components in power electronics systems (PESs). The switching time during IGBT turn-on/off transitions is a good health status indicator for IGBT. However, online monitoring of IGBT switching time is still difficult in practice due to the requirement of extremely high sampling rate for nanoseconds time resolution. The compressed sensing (CS) method shows a potential to overcome the technical difficult by reducing the sampling rate. To further improve the efficiency and reduce the computational time for IGBT online condition monitoring (CM), an under-sampling reconstruction method of an IGBT high-speed switching signal is presented in this paper. First, the physical mechanism and signal characteristics of IGBT switching transitions are analyzed. Then, by utilizing the sparse characteristics of IGBT switching signal in the wavelet domain, the wavelet basis is used for sparse representation. The stagewise orthogonal matching pursuit (StOMP) algorithm is proposed to enhance the convergence speed for switching signal reconstruction. Experiments are performed on not only a double-pulse test rig but also a real Pulse-Width Modulation (PWM) converter. Results show that the IGBT high-speed switching transitions signal can be accurately recovered with a reduced sampling rate and the nanoseconds switching time change can be monitored for IGBT CM. Full article
(This article belongs to the Section Power Electronics)
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Open AccessArticle
Determination of Liberation Degree of Mechanically Processed Waste Printed Circuit Boards by Using the Digital Microscope and SEM-EDS Analysis
Electronics 2019, 8(10), 1202; https://doi.org/10.3390/electronics8101202 - 22 Oct 2019
Cited by 2 | Viewed by 813
Abstract
Characterization of heterogeneous materials, such as particles from mechanically processed waste printed circuit boards, is a challenging task. The majority of characterization methods either give average information or information that is very limited and in a tiny area of specific interest. That said, [...] Read more.
Characterization of heterogeneous materials, such as particles from mechanically processed waste printed circuit boards, is a challenging task. The majority of characterization methods either give average information or information that is very limited and in a tiny area of specific interest. That said, capturing such heterogeneity is significantly important for any kind of processes. Degree of liberation, indicating how much the target component is liberated from the non-valuable components, is a key property to determine the success of subsequent process for valuable material recovery. This work analyzed the degree of liberation of metals within the products of hammer milling process via the combination of image acquisition and analysis. The digital microscope and a scanning electron microscope (SEM) coupled with the energy dispersive spectroscopy (EDS) were used for image acquisition and elemental mapping, in order to evaluate the selective liberation under different milling conditions (i.e., feed mass, milling time) for different metals (mainly Cu and Al) and particle size fractions. The obtained liberation degree was also modelled and determined the liberation parameters that were compared. The results showed that the degree of liberation significantly depend on the milling conditions and metals we analyzed, and well correlated with the selective metal enrichment behavior. Results between the two methods showed some similarities and discrepancies. The advantages and disadvantages of the above two methods were identified and discussed in the paper, in addition to their methodological developments. Full article
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Open AccessFeature PaperReview
Sodium Batteries: A Review on Sodium-Sulfur and Sodium-Air Batteries
Electronics 2019, 8(10), 1201; https://doi.org/10.3390/electronics8101201 - 22 Oct 2019
Cited by 1 | Viewed by 997
Abstract
Lithium-ion batteries are currently used for various applications since they are lightweight, stable, and flexible. With the increased demand for portable electronics and electric vehicles, it has become necessary to develop newer, smaller, and lighter batteries with increased cycle life, high energy density, [...] Read more.
Lithium-ion batteries are currently used for various applications since they are lightweight, stable, and flexible. With the increased demand for portable electronics and electric vehicles, it has become necessary to develop newer, smaller, and lighter batteries with increased cycle life, high energy density, and overall better battery performance. Since the sources of lithium are limited and also because of the high cost of the metal, it is necessary to find alternatives. Sodium batteries have shown great potential, and hence several researchers are working on improving the battery performance of the various sodium batteries. This paper is a brief review of the current research in sodium-sulfur and sodium-air batteries. Full article
(This article belongs to the Special Issue Advanced Renewable Energy Technologies)
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Open AccessArticle
Modified Technique of Parameter Identification of a Permanent Magnet Synchronous Motor with PWM Inverter in the Presence of Dead-Time Effect and Measurement Noise
Electronics 2019, 8(10), 1200; https://doi.org/10.3390/electronics8101200 - 22 Oct 2019
Cited by 2 | Viewed by 558
Abstract
The paper considers the problem of parameter identification of the surface mounted permanent magnet synchronous motor (SPMSM) with pulse width modulated (PWM) inverter in the presence of dead time of power switches and other nonlinear distortions. Parameter identification of the SPMSM is required [...] Read more.
The paper considers the problem of parameter identification of the surface mounted permanent magnet synchronous motor (SPMSM) with pulse width modulated (PWM) inverter in the presence of dead time of power switches and other nonlinear distortions. Parameter identification of the SPMSM is required for the tuning of the torque control loop, because in some cases, the exact values of phase resistances and inductances are not known. In the absence of nonlinear disturbances, the problem of SPMSM parameters estimation is not difficult. The influence of the dead-time effect, back electromotive force and measurements noise introduces distortions in experimental output data sets, which leads to incorrect parameter estimation. Thus, there is a need to develop new designs of identification experiments and methods of processing of the experimental data. A detailed mathematical model of SPMSM with a PWM inverter in the presence of dead-time effect is considered in the paper. The negative influence of the dead-time effect on the results of parameter estimation is shown. A modified technique of parameter identification of SPMSM based on the estimation of frequency response function is proposed. The applied design of identification experiments, the type of excitation input signal, and methods of data processing allow us to minimize the influence of nonlinear disturbances and to reduce the variance of estimation of frequency response function. These features provide a high performance of SPMSM parameters estimation. Full article
(This article belongs to the Section Systems & Control Engineering)
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Open AccessFeature PaperArticle
Integrated Battery Charger for Electric Vehicles Based on a Dual-Inverter Drive and a Three-Phase Current Rectifier
Electronics 2019, 8(10), 1199; https://doi.org/10.3390/electronics8101199 - 22 Oct 2019
Cited by 1 | Viewed by 866
Abstract
This paper presents a new three-phase battery charger integrated with the propulsion system of an electric vehicle. The propulsion system consists of a dual-inverter topology connected to an induction motor via open windings. The electrical vehicles (EV) batteries are divided by two inverters. [...] Read more.
This paper presents a new three-phase battery charger integrated with the propulsion system of an electric vehicle. The propulsion system consists of a dual-inverter topology connected to an induction motor via open windings. The electrical vehicles (EV) batteries are divided by two inverters. This will result in a drive with multilevel characteristics reducing the total harmonic distortion (THD) of the voltage applied to the motor. The modularity of the multilevel inverter will be maintained since two classical three-phase inverters are used. The charger will be fed by a three-phase high power factor current source rectifier. The motor windings will take the role of the DC-inductor required by the rectifier. In this way, an intermediate storage element between the grid and the batteries of the vehicle exist. For the control system of the battery charger, we propose the use of the instantaneous power theory and a sliding mode controller for the three-phase charger input currents. Finally, to verify the behavior and characteristics of the proposed integrated battery charger and control system, several tests are be presented. Full article
(This article belongs to the Section Electrical and Autonomous Vehicles)
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Open AccessArticle
A Semi-Floating Gate Memory Based on SOI Substrate by TCAD Simulation
Electronics 2019, 8(10), 1198; https://doi.org/10.3390/electronics8101198 - 21 Oct 2019
Viewed by 651
Abstract
Over the past decade, the dimensional scaling of semiconductor electronic devices has been facing fundamental and physical challenges, and there is currently an urgent need to increase the ability of dynamic random-access memory (DRAM). A semi-floating gate (SFG) transistor has been proposed as [...] Read more.
Over the past decade, the dimensional scaling of semiconductor electronic devices has been facing fundamental and physical challenges, and there is currently an urgent need to increase the ability of dynamic random-access memory (DRAM). A semi-floating gate (SFG) transistor has been proposed as a capacitor-less memory with faster speed and higher density as compared with the conventional one-transistor one-capacitor (1T1C) DRAM technology. The integration of SFG-based memory on the silicon-on-insulator (SOI) substrate has been demonstrated in this work by using the Sentaurus Technology Computer-Aided Design (TCAD) simulation. An enhancement in retention characteristics, anti-disturbance ability, and fast writing capability, have been illustrated. The device exhibits a low operation voltage, a large threshold voltage window of ~3 V, and an ultra-fast writing of 4 ns. In addition, the SOI-based memory has shown a much-improved anti-irradiation capability compared to the devices based on bulk silicon, which makes it much more attractive in broader applications. Full article
(This article belongs to the Section Semiconductor Devices)
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Open AccessArticle
Single JFET Front-End Amplifier for Low Frequency Noise Measurements with Cross Correlation-Based Gain Calibration
Electronics 2019, 8(10), 1197; https://doi.org/10.3390/electronics8101197 - 21 Oct 2019
Cited by 1 | Viewed by 591
Abstract
We propose an open loop voltage amplifier topology based on a single JFET front-end for the realization of very low noise voltage amplifiers to be used in the field of low frequency noise measurements. With respect to amplifiers based on differential input stages, [...] Read more.
We propose an open loop voltage amplifier topology based on a single JFET front-end for the realization of very low noise voltage amplifiers to be used in the field of low frequency noise measurements. With respect to amplifiers based on differential input stages, a single transistor stage has, among others, the advantage of a lower background noise. Unfortunately, an open loop approach, while simplifying the realization, has the disadvantage that because of the dispersions in the characteristics of the active device, it cannot ensure that a well-defined gain be obtained by design. To address this issue, we propose to add two simple operational amplifier-based auxiliary amplifiers with known gain as part of the measurement chain and employ cross correlation for the calibration of the gain of the main amplifier. With proper data elaboration, gain calibration and actual measurements can be carried out at the same time. By using the approach we propose, we have been able to design a low noise amplifier relying on a simplified hardware and with background noise as low as 6 nV/√Hz at 200 mHz, 1.7 nV/√Hz at 1 Hz, 0.7 nV/√Hz at 10 Hz, and less than 0.6 nV/√Hz at frequencies above 100 Hz. Full article
(This article belongs to the Special Issue Advances in Low-Frequency Noise Measurements)
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Open AccessArticle
A Deep Learning Method for 3D Object Classification Using the Wave Kernel Signature and A Center Point of the 3D-Triangle Mesh
Electronics 2019, 8(10), 1196; https://doi.org/10.3390/electronics8101196 - 20 Oct 2019
Viewed by 1288
Abstract
Computer vision recently has many applications such as smart cars, robot navigation, and computer-aided manufacturing. Object classification, in particular 3D classification, is a major part of computer vision. In this paper, we propose a novel method, wave kernel signature (WKS) and a center [...] Read more.
Computer vision recently has many applications such as smart cars, robot navigation, and computer-aided manufacturing. Object classification, in particular 3D classification, is a major part of computer vision. In this paper, we propose a novel method, wave kernel signature (WKS) and a center point (CP) method, which extracts color and distance features from a 3D model to tackle 3D object classification. The motivation of this idea is from the nature of human vision, which we tend to classify an object based on its color and size. Firstly, we find a center point of the mesh to define distance feature. Secondly, we calculate eigenvalues from the 3D mesh, and WKS values, respectively, to capture color feature. These features will be an input of a 2D convolution neural network (CNN) architecture. We use two large-scale 3D model datasets: ModelNet10 and ModelNet40 to evaluate the proposed method. Our experimental results show more accuracy and efficiency than other methods. The proposed method could apply for actual-world problems like autonomous driving and augmented/virtual reality. Full article
(This article belongs to the Special Issue Deep Neural Networks and Their Applications)
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Open AccessArticle
An Effective Multiclass Twin Hypersphere Support Vector Machine and Its Practical Engineering Applications
Electronics 2019, 8(10), 1195; https://doi.org/10.3390/electronics8101195 - 20 Oct 2019
Cited by 1 | Viewed by 534
Abstract
Twin-KSVC (Twin Support Vector Classification for K class) is a novel and efficient multiclass twin support vector machine. However, Twin-KSVC has the following disadvantages. (1) Each pair of binary sub-classifiers has to calculate inverse matrices. (2) For nonlinear problems, a pair of additional [...] Read more.
Twin-KSVC (Twin Support Vector Classification for K class) is a novel and efficient multiclass twin support vector machine. However, Twin-KSVC has the following disadvantages. (1) Each pair of binary sub-classifiers has to calculate inverse matrices. (2) For nonlinear problems, a pair of additional primal problems needs to be constructed in each pair of binary sub-classifiers. For these disadvantages, a new multi-class twin hypersphere support vector machine, named Twin Hypersphere-KSVC, is proposed in this paper. Twin Hypersphere-KSVC also evaluates each sample into 1-vs-1-vs-rest structure, as in Twin-KSVC. However, our Twin Hypersphere-KSVC does not seek two nonparallel hyperplanes in each pair of binary sub-classifiers as in Twin-KSVC, but a pair of hyperspheres. Compared with Twin-KSVC, Twin Hypersphere-KSVC avoids computing inverse matrices, and for nonlinear problems, can apply the kernel trick to linear case directly. A large number of comparisons of Twin Hypersphere-KSVC with Twin-KSVC on a set of benchmark datasets from the UCI repository and several real engineering applications, show that the proposed algorithm has higher training speed and better generalization performance. Full article
(This article belongs to the Special Issue Fault Detection and Diagnosis of Intelligent Mechatronic Systems)
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Open AccessArticle
A Smart Overvoltage Monitoring and Hierarchical Pattern Recognizing System for Power Grid with HTS Cables
Electronics 2019, 8(10), 1194; https://doi.org/10.3390/electronics8101194 - 20 Oct 2019
Viewed by 697
Abstract
As one part of the power system, high-temperature superconducting (HTS) cables may be subject to various system faults, such as overvoltage. When overvoltage occurs, HTS cables may quench and the resistance of HTS tapes will increase rapidly, which will result in reduction of [...] Read more.
As one part of the power system, high-temperature superconducting (HTS) cables may be subject to various system faults, such as overvoltage. When overvoltage occurs, HTS cables may quench and the resistance of HTS tapes will increase rapidly, which will result in reduction of transmission capacity, increase of power loss and even electrical insulation breakdown. To protect the operation safety of power system, the level of overvoltage should be investigated in the system. This paper proposes a non-contact variable frequency sampling and hierarchical pattern recognizing system for overvoltage. Lightning and internal overvoltage signals are captured by specially designed non-contact voltage sensors. The sensors are installed at the grounding tap of transformer bushings and the cross arm of transmission towers. A variable sampling technique is employed to solve the conflict between sampling speed and storage capacity. A hierarchical pattern recognizing system is proposed to subdivide each overvoltage into specific types. Seven common overvoltages are discussed and analyzed. Wavelet theory and S-transform singular value decomposition (SVD) theory are adopted to extract the feature parameters of different overvoltages. Particle swarm optimization is employed to maintain a high classification rate and improve the initial set of the support vector machine (SVM) used as recognition algorithm. Field-acquired overvoltage data from an 110 kV substation validate the effectiveness of the proposed recognition system. Full article
(This article belongs to the Special Issue Advanced Energy Systems with Superconductivity)
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Open AccessFeature PaperArticle
LLC Resonant Voltage Multiplier-Based Differential Power Processing Converter Using Voltage Divider with Reduced Voltage Stress for Series-Connected Photovoltaic Panels under Partial Shading
Electronics 2019, 8(10), 1193; https://doi.org/10.3390/electronics8101193 - 20 Oct 2019
Viewed by 927
Abstract
Partial shading on photovoltaic (PV) strings consisting of multiple panels connected in series is known to trigger severe issues, such as reduced energy yield and the occurrence of multiple power point maxima. Various kinds of differential power processing (DPP) converters have been proposed [...] Read more.
Partial shading on photovoltaic (PV) strings consisting of multiple panels connected in series is known to trigger severe issues, such as reduced energy yield and the occurrence of multiple power point maxima. Various kinds of differential power processing (DPP) converters have been proposed and developed to prevent partial shading issues. Voltage stresses of switches and capacitors in conventional DPP converters, however, are prone to soar with the number of panels connected in series, likely resulting in impaired converter performance and increased circuit volume. This paper proposes a DPP converter using an LLC resonant voltage multiplier (VM) with a voltage divider (VD) to reduce voltage stresses of switches and capacitors. The VD can be arbitrarily extended by adding switches and capacitors, and the voltage stresses can be further reduced by extending the VD. Experimental verification tests for four PV panels connected in series were performed emulating partial shading conditions in a laboratory and outdoor. The results demonstrated the proposed DPP converter successfully precluded the negative impacts of partial shading with mitigating the voltage stress issues. Full article
(This article belongs to the Special Issue Emerging Technologies for Photovoltaic Solar Energy)
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Open AccessFeature PaperArticle
Analysis of Energy Consumption and Optimization Techniques for Writing Energy-Efficient Code
Electronics 2019, 8(10), 1192; https://doi.org/10.3390/electronics8101192 - 19 Oct 2019
Cited by 1 | Viewed by 1118
Abstract
The unprecedented growth of connected devices, together with the remarkable convergence of a wide variety of technologies, have led to an exponential increase in the services that the internet of things (IoT) can offer, all aimed at improving quality of life. Consequently, in [...] Read more.
The unprecedented growth of connected devices, together with the remarkable convergence of a wide variety of technologies, have led to an exponential increase in the services that the internet of things (IoT) can offer, all aimed at improving quality of life. Consequently, in order to meet the numerous challenges this produces, the IoT has become a major subject of research. One of these challenges is the reduction of energy consumption given the significant limitations of some devices. In addition, although the search for energy efficiency was initially focused on hardware, it has become a concern for software developers too. In fact, it has become an intense area of research with the principal objective of analyzing and optimizing the energy consumption of software systems. This research analyzes the energy saving that can be achieved when using a broad set of techniques for writing energy-efficient code for Raspberry Pi devices. It also demonstrates that programmers can save more energy if they apply the proposed techniques manually than when relying on other automatic optimization options offered by the GNU compiler collection (GCC). Thus, it is important that programmers are aware of the significant impact these techniques can have on an application’s energy consumption. Full article
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Open AccessFeature PaperArticle
An Ultra-Wideband Sensing Board for Radio Frequency Front-End in IoT Transmitters
Electronics 2019, 8(10), 1191; https://doi.org/10.3390/electronics8101191 - 19 Oct 2019
Viewed by 815
Abstract
The upcoming technologies related to Internet of Things will be characterized by challenging requirements oriented toward the most efficient exploitation of the energy in electronic systems. The use of wireless communications in these devices makes this aspect particularly important, since the performance of [...] Read more.
The upcoming technologies related to Internet of Things will be characterized by challenging requirements oriented toward the most efficient exploitation of the energy in electronic systems. The use of wireless communications in these devices makes this aspect particularly important, since the performance of radio transceivers is strongly dependent on the environmental conditions affecting the antenna electrical characteristics. The use of circuits capable of adapting themselves to the actual state of the environment can be a valuable solution, provided that the implemented sensing features have negligible impact on the overall performance and cost of the system. In this work, we present the design and verification of an innovative ultra-wideband sensing board to detect real-time variations of the antenna impedance in transmitters oriented to Internet of Things applications. The proposed sensing board was widely validated by means of small- and large-signal measurements carried out at microwave frequencies. Full article
(This article belongs to the Special Issue 5G Front-End Transceivers)
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Open AccessReview
Electric Vehicles: A Data Science Perspective Review
Electronics 2019, 8(10), 1190; https://doi.org/10.3390/electronics8101190 - 18 Oct 2019
Cited by 5 | Viewed by 1167
Abstract
Current trends are showing that the popularity of electric vehicles (EVs) has significantly increased over the last few years, causing changes not only in the transportation industry but generally in business and society. This paper covers one possible angle to the (r) evolution [...] Read more.
Current trends are showing that the popularity of electric vehicles (EVs) has significantly increased over the last few years, causing changes not only in the transportation industry but generally in business and society. This paper covers one possible angle to the (r) evolution instigated by EVs, i.e., it provides the data science perspective review of the interdisciplinary area at the intersection of green transportation, energy informatics, and economics. Namely, the review summarizes data-driven research in EVs by identifying two main research streams: (i) socio–economic, and (ii) socio–technical. The socio–economic stream includes research in: (i) acceptance of green transportation in countries and among different populations, (ii) current trends in the EV market, and (iii) forecasting future sales for the green transportation. The socio–technical stream includes research in: (i) electric vehicle battery price and capacity and (ii) charging station management. This kind of study is especially important now when the question is no longer whether the transition from internal-combustion engine vehicles to clean-fuel vehicles is going to happen but how fast it will happen and what are going to be implications for society, governmental policies, and industry. Based on the presented literature review, the paper also outlines the most significant open questions and challenges that are yet to be solved: (i) scarcity of trustworthy (open) data, and (ii) designing a generalized methodology for charging station deployment. Full article
(This article belongs to the Special Issue Electric Vehicles in Smart Grids)
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Open AccessArticle
Low Cross-Polarization Improved-Gain Rectangular Patch Antenna
Electronics 2019, 8(10), 1189; https://doi.org/10.3390/electronics8101189 - 18 Oct 2019
Cited by 1 | Viewed by 1000
Abstract
In this paper, a low cross-polarization improved-gain rectangular patch antenna is presented. A patch-ground shorting pin with defected patch structure (DPS) is introduced to suppress the cross-polarization level. A High Reflective Frequency Selective Surface (HRFSS) superstrate is designed and placed over the proposed [...] Read more.
In this paper, a low cross-polarization improved-gain rectangular patch antenna is presented. A patch-ground shorting pin with defected patch structure (DPS) is introduced to suppress the cross-polarization level. A High Reflective Frequency Selective Surface (HRFSS) superstrate is designed and placed over the proposed antenna at an optimized position to intensify the gain. To characterize the unit-cell of the superstrate, its transmission characteristics are extracted and discussed. Integration of the superstrate achieves a beam contraction resulting in a gain enhancement to 10.65 dBi. The proposed antenna has perfect broadside radiation with a cross-polarization level of below −30 dB in the entire half power beamwidth. The prototype of the antenna exhibits good agreement between experimental and simulated results. Full article
(This article belongs to the Section Microwave and Wireless Communications)
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Open AccessArticle
An Improved UAV-PHD Filter-Based Trajectory Tracking Algorithm for Multi-UAVs in Future 5G IoT Scenarios
Electronics 2019, 8(10), 1188; https://doi.org/10.3390/electronics8101188 - 18 Oct 2019
Cited by 5 | Viewed by 841
Abstract
The 5G cellular network is expected to provide core service platform for the expanded Internet of Things (IoT) by supporting enhanced mobile broadband (eMBB), massive machine-type communication (mMTC), and ultra-reliable low latency communications (URLLC). Unmanned aerial vehicles (UAVs), also known as drones, provide [...] Read more.
The 5G cellular network is expected to provide core service platform for the expanded Internet of Things (IoT) by supporting enhanced mobile broadband (eMBB), massive machine-type communication (mMTC), and ultra-reliable low latency communications (URLLC). Unmanned aerial vehicles (UAVs), also known as drones, provide civil, commercial, and government services in various fields. Particularly in a 5G IoT scenario, UAV-aided network communications will fulfill an increasingly important role and will require the tracking of multiple UAV targets. As UAVs move quickly, maintaining the stability of the communication connection in 5G will be a challenge. Therefore, it is necessary to track the trajectory of UAVs. At present, the GM-PHD filter has a problem that the new target intensity must be known, and it cannot obtain the moving target trajectory and the influence of the clutter is likely to cause false alarm. A UAV-PHD filter is proposed in this work to improve the traditional GM-PHD filter by applying machine learning to the emergency detection and trajectory tracking of UAV targets. An out-of-sight detection algorithm for multiple UAVs is then presented to improve tracking performance. The method is assessed by simulation using MATLAB, and OSPA distance is utilized as an evaluation indicator. The simulation results illustrate that the proposed method can be applied to the tracking of multiple UAV targets in future 5G-IoT scenarios, and the performance is superior to the traditional GM-PHD filter. Full article
(This article belongs to the Special Issue Recent Advances in Mobile Ad Hoc Networks)
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Open AccessFeature PaperArticle
Correlated Blocking in mmWave Cellular Networks: Macrodiversity, Outage, and Interference
Electronics 2019, 8(10), 1187; https://doi.org/10.3390/electronics8101187 - 18 Oct 2019
Cited by 2 | Viewed by 652
Abstract
In this paper, we provide a comprehensive analysis of macrodiversity for millimeter wave (mmWave) cellular networks. The key issue with mmWave networks is that signals are prone to blocking by objects in the environment, which causes paths to go from line-of-sight (LOS) to [...] Read more.
In this paper, we provide a comprehensive analysis of macrodiversity for millimeter wave (mmWave) cellular networks. The key issue with mmWave networks is that signals are prone to blocking by objects in the environment, which causes paths to go from line-of-sight (LOS) to non-LOS (NLOS). We identify macrodiversity as an important strategy for mitigating blocking, as with macrodiversity the user will attempt to connect with two or more base stations. Diversity is achieved because if the closest base station is blocked, then the next base station might still be unblocked. However, since it is possible for a single blockage to simultaneously block the paths to two base stations, the issue of correlated blocking must be taken into account by the analysis. Our analysis characterizes the macrodiverity gain in the presence of correlated random blocking and interference. To do so, we develop a framework to determine distributions for the LOS probability, Signal to Noise Ratio (SNR), and Signal to Interference and Noise Ratio (SINR) by taking into account correlated blocking. We validate our framework by comparing our analysis, which models blockages using a random point process, with an analysis that uses real-world data to account for blockage. We consider a cellular uplink with both diversity combining and selection combining schemes. We also study the impact of blockage size and blockage density along with the effect of co-channel interference arising from other cells. We show that the assumption of independent blocking can lead to an incorrect evaluation of macrodiversity gain, as the correlation tends to decrease macrodiversity gain. Full article
(This article belongs to the Special Issue Millimeter-Wave (mmWave) Communications) Printed Edition available
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Open AccessArticle
Study of Full-Duplex Communication with Excellent Security by 3-Level Communication Method
Electronics 2019, 8(10), 1186; https://doi.org/10.3390/electronics8101186 - 18 Oct 2019
Viewed by 690
Abstract
Currently, the industry is using the MODBUS communication method, utilizing RS485 for the distributed equipment and network construction. This method has a rather good transmission and reception distance but has a disadvantage in that it is a half-duplex communication method that cannot simultaneously [...] Read more.
Currently, the industry is using the MODBUS communication method, utilizing RS485 for the distributed equipment and network construction. This method has a rather good transmission and reception distance but has a disadvantage in that it is a half-duplex communication method that cannot simultaneously transmit and receive. Therefore, there is a great need for a full-duplex communication system that can simultaneously transmit and receive two-wire communications. Therefore, in this paper, we propose new communication hardware equipment that can implement a full-duplex communication method by communication signal level in order to overcome the disadvantage of communication speed when using a full-duplex communication method by time division method. The proposed communication hardware is a structure that can transmit and receive at the same time in such a way that two pieces of equipment communicating by two-wire communication can apply the outgoing signal to the same communication line and detect the received signal at the same time. Therefore, the receiving side can analyze the received signal based on the information on the current transmission signal. This signal can only be analyzed by the two communicating devices, indicating that communication security is very good. Full article
(This article belongs to the Section Circuit and Signal Processing)
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Open AccessFeature PaperReview
Control Strategies for Floating Offshore Wind Turbine: Challenges and Trends
Electronics 2019, 8(10), 1185; https://doi.org/10.3390/electronics8101185 - 18 Oct 2019
Cited by 6 | Viewed by 1314
Abstract
The offshore wind resource has huge energy potential. However, wind turbine floating structures have to withstand harsh conditions. Strong wind and wave effects combine to generate vibrations, fatigue, and heavy loads on the structure and other elements of the wind turbine. These structural [...] Read more.
The offshore wind resource has huge energy potential. However, wind turbine floating structures have to withstand harsh conditions. Strong wind and wave effects combine to generate vibrations, fatigue, and heavy loads on the structure and other elements of the wind turbine. These structural problems increase maintenance requirements and risk of failure, while reducing availability and energy production. Another challenge for wind energy is to reduce production costs in order to be competitive with other alternatives. From the control point of view, the objective of lowering costs can be achieved by operating the turbine close to its optimum point of operation under partial load, guaranteeing reliability by reducing structural loads and regulating the power generated in strong wind regimes. In this typical and challenging context, this paper proposes a critical state-of-the-art review, discussing challenges and trends on floating offshore wind turbines control. Full article
(This article belongs to the Section Systems & Control Engineering)
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Open AccessFeature PaperArticle
Soft Elbow Exoskeleton for Upper Limb Assistance Incorporating Dual Motor-Tendon Actuator
Electronics 2019, 8(10), 1184; https://doi.org/10.3390/electronics8101184 - 18 Oct 2019
Cited by 4 | Viewed by 799
Abstract
Loss of muscle functions, such as the elbow, can affect the quality of life of a person. This research is aimed at developing an affordable two DOF soft elbow exoskeleton incorporating a dual motor-tendon actuator. The soft elbow exoskeleton can be used to [...] Read more.
Loss of muscle functions, such as the elbow, can affect the quality of life of a person. This research is aimed at developing an affordable two DOF soft elbow exoskeleton incorporating a dual motor-tendon actuator. The soft elbow exoskeleton can be used to assist two DOF motions of the upper limb, especially elbow and wrist movements. The exoskeleton is developed using fabric for the convenience purpose of the user. The dual motor-tendon actuator subsystem employs two DC motors coupled with lead-to-screw converting motion from angular into linear motion. The output is connected to the upper arm hook on the soft exoskeleton elbow. With this mechanism, the proposed actuator system is able to assist two DOF movements for flexion/extension and pronation/supination motion. Proportional-Integral (PI) control is implemented for controlling the motion. The optimized value of Kp and Ki are 200 and 20, respectively. Based on the test results, there is a slight steady-state error between the first and the second DC motor. When the exoskeleton is worn by a user, it gives more steady-state errors because of the load from the arm weight. The test results demonstrate that the proposed soft exoskeleton elbow can be worn easily and comfortably by a user to assist two DOF for elbow and wrist motion. The resulted range of motion (ROM) for elbow flexion–extension can be varied from 90° to 157°, whereas the maximum of ROM that can be achieved for pronation and supination movements are 19° and 18°, respectively. Full article
(This article belongs to the Special Issue Design and Application of Biomedical Circuits and Systems)
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Open AccessArticle
Phantom: Towards Vendor-Agnostic Resource Consolidation in Cloud Environments
Electronics 2019, 8(10), 1183; https://doi.org/10.3390/electronics8101183 - 18 Oct 2019
Cited by 1 | Viewed by 767
Abstract
Mobile-oriented internet technologies such as mobile cloud computing are gaining wider popularity in the IT industry. These technologies are aimed at improving the user internet usage experience by employing state-of-the-art technologies or their combination. One of the most important parts of modern mobile-oriented [...] Read more.
Mobile-oriented internet technologies such as mobile cloud computing are gaining wider popularity in the IT industry. These technologies are aimed at improving the user internet usage experience by employing state-of-the-art technologies or their combination. One of the most important parts of modern mobile-oriented future internet is cloud computing. Modern mobile devices use cloud computing technology to host, share and store data on the network. This helps mobile users to avail different internet services in a simple, cost-effective and easy way. In this paper, we shall discuss the issues in mobile cloud resource management followed by a vendor-agnostic resource consolidation approach named Phantom, to improve the resource allocation challenges in mobile cloud environments. The proposed scheme exploits software-defined networks (SDNs) to introduce vendor-agnostic concept and utilizes a graph-theoretic approach to achieve its objectives. Simulation results demonstrate the efficiency of our proposed approach in improving application service response time. Full article
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Open AccessFeature PaperArticle
Data-Dense and Miniature Chipless Moisture Sensor RFID Tag for Internet of Things
Electronics 2019, 8(10), 1182; https://doi.org/10.3390/electronics8101182 - 17 Oct 2019
Cited by 1 | Viewed by 938
Abstract
A novel and miniaturized semi-elliptical 20-bit fully passive chipless RFID sensor tag is proposed in this article. The realized sensor tag is made up of semi-elliptical shaped open-end slots within the compact size of 25 mm × 17 mm. The multi-substrate analysis of [...] Read more.
A novel and miniaturized semi-elliptical 20-bit fully passive chipless RFID sensor tag is proposed in this article. The realized sensor tag is made up of semi-elliptical shaped open-end slots within the compact size of 25 mm × 17 mm. The multi-substrate analysis of the proposed tag is examined using non-flexible and flexible materials. The articulated tag configuration is capable of monitoring moisture levels when the largest resonator is covered by a heat-resistant sheet of Kapton HN (DuPontTM). The proposed tag functions in the operational frequency band of 4.1 GHz–16 GHz and possesses the overall bit density of 4.70 bit/cm2. The structure is composed of a thin passive substrate layer topped with an active layer of conductive path and is considered as a potential candidate for low-cost identification of the tagged objects. In addition to that, its moisture sensing property and flexible nature make it a reliable smart sensor for conformal applications. Full article
(This article belongs to the Special Issue Advanced RFID Technology and Applications)
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Open AccessFeature PaperArticle
A Comprehensive Comparison of EMI Immunity in CMOS Amplifier Topologies
Electronics 2019, 8(10), 1181; https://doi.org/10.3390/electronics8101181 - 17 Oct 2019
Cited by 2 | Viewed by 647
Abstract
This paper provides the results of a comprehensive comparison between complementary metal oxide semiconductor (CMOS) amplifiers with low susceptibility to electromagnetic interference (EMI). They represent the state-of-the-art in low EMI susceptibility design. An exhaustive scenario for EMI pollution has been considered: the injected [...] Read more.
This paper provides the results of a comprehensive comparison between complementary metal oxide semiconductor (CMOS) amplifiers with low susceptibility to electromagnetic interference (EMI). They represent the state-of-the-art in low EMI susceptibility design. An exhaustive scenario for EMI pollution has been considered: the injected interference can indeed directly reach the amplifier pins or can be coupled from the printed circuit board (PCB) ground. This is also a key point for evaluating the susceptibility from EMI coupled to the output pin. All of the amplifiers are re-designed in a United Microelectronics Corporation (UMC) 180 nm CMOS process in order to have a fair comparison. The topologies investigated and compared are basically derived from the Miller and the folded cascode ones, which are well-known and widely used by CMOS analog designers. Full article
(This article belongs to the Special Issue Low-Voltage Integrated Circuits Design and Application)
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Open AccessFeature PaperArticle
A Real-Time Decision Platform for the Management of Structures and Infrastructures
Electronics 2019, 8(10), 1180; https://doi.org/10.3390/electronics8101180 - 17 Oct 2019
Cited by 13 | Viewed by 953
Abstract
Natural disasters and the poor management of civil engineering structures and infrastructures require timely action and new tools such as specially designed structural health monitoring platforms. This paper proposes an innovative platform based on a network of wirelessly connected, low-power, and renewable-energy-fed sensor [...] Read more.
Natural disasters and the poor management of civil engineering structures and infrastructures require timely action and new tools such as specially designed structural health monitoring platforms. This paper proposes an innovative platform based on a network of wirelessly connected, low-power, and renewable-energy-fed sensor units. The platform is a multipurpose tool for diagnostics, maintenance, and supervision, capable of simultaneously carrying out damage detection, localization, identification, and “multiclass” and “multi-material” level quantification of different types of failures. In addition, it works as a decision support tool for emergency management and post-disaster assessment, here tailored for an Italian theme park. The platform uses innovative algorithms based on the concept of the vibro-acoustic signature of the asset monitored. The vibro-acoustic signatures of the monitored assets are gathered by the microphones and accelerometers of the platform’s sensor units. Then, almost simultaneously, they are analyzed using specifically designed wavelet-based and convolutional-neural-network-based algorithms, which are able to extract crucial information about the structural and environmental conditions of both the asset and the areas of the thematic park. In addition, the platform shows escape routes during an emergency, indicating meeting points and helping people to proceed safely along a recognizable escape route to a safe place, as demonstrated by the simulations. Full article
(This article belongs to the Special Issue IoT Technologies for Smart Cities)
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Open AccessArticle
Unsupervised Monocular Depth Estimation Based on Residual Neural Network of Coarse–Refined Feature Extractions for Drone
Electronics 2019, 8(10), 1179; https://doi.org/10.3390/electronics8101179 - 17 Oct 2019
Cited by 1 | Viewed by 673
Abstract
To take full advantage of the information of images captured by drones and given that most existing monocular depth estimation methods based on supervised learning require vast quantities of corresponding ground truth depth data for training, the model of unsupervised monocular depth estimation [...] Read more.
To take full advantage of the information of images captured by drones and given that most existing monocular depth estimation methods based on supervised learning require vast quantities of corresponding ground truth depth data for training, the model of unsupervised monocular depth estimation based on residual neural network of coarse–refined feature extractions for drone is therefore proposed. As a virtual camera is introduced through a deep residual convolution neural network based on coarse–refined feature extractions inspired by the principle of binocular depth estimation, the unsupervised monocular depth estimation has become an image reconstruction problem. To improve the performance of our model for monocular depth estimation, the following innovations are proposed. First, the pyramid processing for input image is proposed to build the topological relationship between the resolution of input image and the depth of input image, which can improve the sensitivity of depth information from a single image and reduce the impact of input image resolution on depth estimation. Second, the residual neural network of coarse–refined feature extractions for corresponding image reconstruction is designed to improve the accuracy of feature extraction and solve the contradiction between the calculation time and the numbers of network layers. In addition, to predict high detail output depth maps, the long skip connections between corresponding layers in the neural network of coarse feature extractions and deconvolution neural network of refined feature extractions are designed. Third, the loss of corresponding image reconstruction based on the structural similarity index (SSIM), the loss of approximate disparity smoothness and the loss of depth map are united as a novel training loss to better train our model. The experimental results show that our model has superior performance on the KITTI dataset composed by corresponding left view and right view and Make3D dataset composed by image and corresponding ground truth depth map compared to the state-of-the-art monocular depth estimation methods and basically meet the requirements for depth information of images captured by drones when our model is trained on KITTI. Full article
(This article belongs to the Special Issue Bioinspired Computer Vision)
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Open AccessFeature PaperArticle
Wearable Augmented Reality Application for Shoulder Rehabilitation
Electronics 2019, 8(10), 1178; https://doi.org/10.3390/electronics8101178 - 17 Oct 2019
Cited by 6 | Viewed by 1043
Abstract
Augmented reality (AR) technology is gaining popularity and scholarly interest in the rehabilitation sector because of the possibility to generate controlled, user-specific environmental and perceptual stimuli which motivate the patient, while still preserving the possibility to interact with the real environment and other [...] Read more.
Augmented reality (AR) technology is gaining popularity and scholarly interest in the rehabilitation sector because of the possibility to generate controlled, user-specific environmental and perceptual stimuli which motivate the patient, while still preserving the possibility to interact with the real environment and other subjects, including the rehabilitation specialist. The paper presents the first wearable AR application for shoulder rehabilitation, based on Microsoft HoloLens, with real-time markerless tracking of the user’s hand. Potentialities and current limits of commercial head-mounted displays (HMDs) are described for the target medical field, and details of the proposed application are reported. A serious game was designed starting from the analysis of a traditional rehabilitation exercise, taking into account HoloLens specifications to maximize user comfort during the AR rehabilitation session. The AR application implemented consistently meets the recommended target frame rate for immersive applications with HoloLens device: 60 fps. Moreover, the ergonomics and the motivational value of the proposed application were positively evaluated by a group of five rehabilitation specialists and 20 healthy subjects. Even if a larger study, including real patients, is necessary for a clinical validation of the proposed application, the results obtained encourage further investigations and the integration of additional technical features for the proposed AR application. Full article
(This article belongs to the Special Issue Recent Advances in Virtual Reality and Augmented Reality)
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Open AccessFeature PaperReview
Survey on Routing Protocols for Vehicular Ad Hoc Networks Based on Multimetrics
Electronics 2019, 8(10), 1177; https://doi.org/10.3390/electronics8101177 - 17 Oct 2019
Cited by 5 | Viewed by 978
Abstract
In the last few years, many routing protocols have been proposed for vehicular ad hoc networks (VANETs) because of their specific characteristics. Protocols that use several metrics have been shown to be the most adequate to VANETs due to their effectiveness in dealing [...] Read more.
In the last few years, many routing protocols have been proposed for vehicular ad hoc networks (VANETs) because of their specific characteristics. Protocols that use several metrics have been shown to be the most adequate to VANETs due to their effectiveness in dealing with dynamic environment changes due to vehicle mobility. Metrics such as distance, density, link stability, speed, and position were selected by the authors for the best proposal. Several surveys of routing proposals have been generated to categorize contributions and their application scenarios, but none of them focused on multimetric approaches. In this paper, we present a review of the routing protocols based on more than one metric to select the best route in a VANET. The main objective of this research was to present the contemporary most frequently used metrics in the different proposals and their application scenarios. This review helps in the selection protocols or the creation of metrics when a new protocol is designed.This survey of multimetric VANET routing protocols employed systematic literature-review (SLR) methodology in four well-knownown databases that allowed to analyze current state-of-the-art proposals. In addition, this paper provides a description of these multimetric routing protocols. Our findings indicate that distance and speed are the most popular and versatile metrics. Finally, we define some possible directions for future research related to the use of this class of protocols. Full article
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Open AccessArticle
Fast Execution of an ASIFT Hardware Accelerator by Prior Data Processing
Electronics 2019, 8(10), 1176; https://doi.org/10.3390/electronics8101176 - 17 Oct 2019
Viewed by 490
Abstract
This paper proposes a new ASIFT hardware architecture that processes a Video Graphics Array (VGA)-sized (640 × 480) video in real time. The previous ASIFT accelerator suffers from low utilization because affine transformed images are computed repeatedly. In order to improve hardware utilization, [...] Read more.
This paper proposes a new ASIFT hardware architecture that processes a Video Graphics Array (VGA)-sized (640 × 480) video in real time. The previous ASIFT accelerator suffers from low utilization because affine transformed images are computed repeatedly. In order to improve hardware utilization, the proposed hardware architecture adopts two schemes to increase the utilization of a bottleneck hardware module. The first is a prior anti-aliasing scheme, and the second is a prior down-scaling scheme. In the proposed method, 1 × 1 and 0.5 × 1 blurred images are generated and they are reused for creating various affine transformed images. Thanks to the proposed schemes, the utilization drop by waiting for the affine transform is significantly decreased, and consequently, the operation speed is increased substantially. Experimental results show that the proposed ASIFT hardware accelerator processes a VGA-sized video at the speed of 28 frames/s, which is 1.36 times faster than that of previous work. Full article
(This article belongs to the Section Circuit and Signal Processing)
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Open AccessArticle
Switching Loss Balancing Technique for Modular Multilevel Converters Operated by Model Predictive Control Method
Electronics 2019, 8(10), 1175; https://doi.org/10.3390/electronics8101175 - 16 Oct 2019
Viewed by 547
Abstract
The sorting algorithm is the most widely accepted capacitor voltage balancing strategy for a modular multilevel converter. This strategy offers to keep the balance among submodule capacitor voltages under all of the modular multilevel converter working conditions. However, this method generates unnecessary switching [...] Read more.
The sorting algorithm is the most widely accepted capacitor voltage balancing strategy for a modular multilevel converter. This strategy offers to keep the balance among submodule capacitor voltages under all of the modular multilevel converter working conditions. However, this method generates unnecessary switching transitions in submodules, which results in high switching frequency and switching loss, and uneven distribution of switching transitions and switching loss among submodules (SMs). In this paper, a simplified switching loss balancing control strategy was proposed in order to handle these issues. The proposed approach adjusted the submodule selection process of the sorting algorithm by taking into consideration the number of switching transitions in addition to the capacitor voltages. Even distribution of switching transitions and switching loss was achieved, and the average switching loss was reduced at the cost of slightly increasing the capacitor voltage fluctuations. The effectiveness of the proposed approach was verified through both simulation and experimental results. Full article
(This article belongs to the Section Power Electronics)
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