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Electronics, Volume 10, Issue 2 (January-2 2021) – 123 articles

Cover Story (view full-size image): A simple metasurface integrated with horn antenna exhibiting wide bandwidth, covering the full Ku-band, using 3D printing is presented. It consists of a 3D-printed horn and a 3D-printed phase transformation surface placed at the horn aperture. The proposed surface is configured by unit cells and helps to improve the field over the horn aperture, resulting in lower phase variations, lower sidelobe levels in both E- and H-planes, overall increment in directivity with peak measured directivity up to 24.8 dBi, and improvement in aperture efficiency of about 35% to 72% in the frequency range 10–18 GHz. The total weight of the proposed antenna is about 345.37 g; it is a low-cost and rapid manufacturing solution using 3D printing technology. View this paper
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Article
Dead-Time Correction Applied for Extended Flux-Based Sensorless Control of Assisted PMSMs in Electric Vehicles
Electronics 2021, 10(2), 220; https://doi.org/10.3390/electronics10020220 - 19 Jan 2021
Viewed by 500
Abstract
Sensorless control technology of PMSMs is of great importance for safety and reliability in electric vehicles. Among all existing methods, only the extended flux-based method has great performance over all speed range. However, the accuracy and reliability of the extended flux rotor position [...] Read more.
Sensorless control technology of PMSMs is of great importance for safety and reliability in electric vehicles. Among all existing methods, only the extended flux-based method has great performance over all speed range. However, the accuracy and reliability of the extended flux rotor position observer are greatly affected by the dead-time effect. In this paper, the extended flux-based observer is adopted to develop a sensorless control system. The influence of dead-time effect on the observer is analyzed and a dead-time correction method is specially designed to guarantee the reliability of the whole control system. A comparison of estimation precision among the extended flux-based method, the electromotive force (EMF)-based method and the high frequency signal injection method is given by simulations. The performance of the proposed sensorless control system is verified by experiments. The experimental results show that the proposed extended flux-based sensorless control system with dead-time correction has satisfactory performance over full speed range in both loaded and non-loaded situations. The estimation error of rotor speed is within 4% in all working conditions. The dead-time correction method improves the reliability of the control system effectively. Full article
(This article belongs to the Section Electrical and Autonomous Vehicles)
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Review
Sensor System: A Survey of Sensor Type, Ad Hoc Network Topology and Energy Harvesting Techniques
Electronics 2021, 10(2), 219; https://doi.org/10.3390/electronics10020219 - 19 Jan 2021
Viewed by 697
Abstract
People nowadays are entering an era of rapid evolution due to the generation of massive amounts of data. Such information is produced with an enormous contribution from the use of billions of sensing devices equipped with in situ signal processing and communication capabilities [...] Read more.
People nowadays are entering an era of rapid evolution due to the generation of massive amounts of data. Such information is produced with an enormous contribution from the use of billions of sensing devices equipped with in situ signal processing and communication capabilities which form wireless sensor networks (WSNs). As the number of small devices connected to the Internet is higher than 50 billion, the Internet of Things (IoT) devices focus on sensing accuracy, communication efficiency, and low power consumption because IoT device deployment is mainly for correct information acquisition, remote node accessing, and longer-term operation with lower battery changing requirements. Thus, recently, there have been rich activities for original research in these domains. Various sensors used by processing devices can be heterogeneous or homogeneous. Since the devices are primarily expected to operate independently in an autonomous manner, the abilities of connection, communication, and ambient energy scavenging play significant roles, especially in a large-scale deployment. This paper classifies wireless sensor nodes into two major categories based the types of the sensor array (heterogeneous/homogeneous). It also emphasizes on the utilization of ad hoc networking and energy harvesting mechanisms as a fundamental cornerstone to building a self-governing, sustainable, and perpetually-operated sensor system. We review systems representative of each category and depict trends in system development. Full article
(This article belongs to the Special Issue Multidimensional Digital Signal Processing)
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Article
Wireless Sensor Networks for Smart Cities: Network Design, Implementation and Performance Evaluation
Electronics 2021, 10(2), 218; https://doi.org/10.3390/electronics10020218 - 19 Jan 2021
Cited by 4 | Viewed by 1455
Abstract
The advent of various wireless technologies has paved the way for the realization of new infrastructures and applications for smart cities. Wireless Sensor Networks (WSNs) are one of the most important among these technologies. WSNs are widely used in various applications in our [...] Read more.
The advent of various wireless technologies has paved the way for the realization of new infrastructures and applications for smart cities. Wireless Sensor Networks (WSNs) are one of the most important among these technologies. WSNs are widely used in various applications in our daily lives. Due to their cost effectiveness and rapid deployment, WSNs can be used for securing smart cities by providing remote monitoring and sensing for many critical scenarios including hostile environments, battlefields, or areas subject to natural disasters such as earthquakes, volcano eruptions, and floods or to large-scale accidents such as nuclear plants explosions or chemical plumes. The purpose of this paper is to propose a new framework where WSNs are adopted for remote sensing and monitoring in smart city applications. We propose using Unmanned Aerial Vehicles to act as a data mule to offload the sensor nodes and transfer the monitoring data securely to the remote control center for further analysis and decision making. Furthermore, the paper provides insight about implementation challenges in the realization of the proposed framework. In addition, the paper provides an experimental evaluation of the proposed design in outdoor environments, in the presence of different types of obstacles, common to typical outdoor fields. The experimental evaluation revealed several inconsistencies between the performance metrics advertised in the hardware-specific data-sheets. In particular, we found mismatches between the advertised coverage distance and signal strength with our experimental measurements. Therefore, it is crucial that network designers and developers conduct field tests and device performance assessment before designing and implementing the WSN for application in a real field setting. Full article
(This article belongs to the Section Networks)
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Article
A Modified Chaotic Binary Particle Swarm Optimization Scheme and Its Application in Face-Iris Multimodal Biometric Identification
Electronics 2021, 10(2), 217; https://doi.org/10.3390/electronics10020217 - 19 Jan 2021
Cited by 1 | Viewed by 1375
Abstract
In order to improve the recognition rate of the biometric identification system, the features of each unimodal biometric are often combined in a certain way. However, there are some mutually exclusive redundant features in those combined features, which will degrade the identification performance. [...] Read more.
In order to improve the recognition rate of the biometric identification system, the features of each unimodal biometric are often combined in a certain way. However, there are some mutually exclusive redundant features in those combined features, which will degrade the identification performance. To solve this problem, this paper proposes a novel multimodal biometric identification system for face-iris recognition.It is based on binary particle swarm optimization. The face features are extracted by 2D Log-Gabor and Curvelet transform, while iris features are extracted by Curvelet transform. In order to reduce the complexity of the feature-level fusion, we propose a modified chaotic binary particle swarm optimization (MCBPSO) algorithm to select features. It uses kernel extreme learning machine (KELM) as a fitness function and chaotic binary sequences to initialize particle swarms. After the global optimal position (Gbest) is generated in each iteration, the position of Gbest is varied by using chaotic binary sequences, which is useful to realize chaotic local search and avoid falling into the local optimal position. The experiments are conducted on CASIA multimodal iris and face dataset from Chinese Academy of Sciences.The experimental results demonstrate that the proposed system can not only reduce the number of features to one tenth of its original size, but also improve the recognition rate up to 99.78%. Compared with the unimodal iris and face system, the recognition rate of the proposed system are improved by 11.56% and 2% respectively. The experimental results reveal its performance in the verification mode compared with the existing state-of-the-art systems. The proposed system is satisfactory in addressing face-iris multimodal biometric identification. Full article
(This article belongs to the Special Issue Evolutionary Machine Learning for Nature-Inspired Problem Solving)
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Article
Scattering from Spheres: A New Look into an Old Problem
Electronics 2021, 10(2), 216; https://doi.org/10.3390/electronics10020216 - 19 Jan 2021
Viewed by 630
Abstract
In this work, we introduce a theoretical framework to describe the scattering from spheres. In our proposed framework, the total field in the outer medium is decomposed in terms of inward and outward electromagnetic fields, rather than in terms of incident and scattered [...] Read more.
In this work, we introduce a theoretical framework to describe the scattering from spheres. In our proposed framework, the total field in the outer medium is decomposed in terms of inward and outward electromagnetic fields, rather than in terms of incident and scattered fields, as in the classical Lorenz–Mie formulation. The fields are expressed as series of spherical harmonics, whose combination weights can be interpreted as reflection and transmission coefficients, which provides an intuitive understanding of the propagation and scattering phenomena. Our formulation extends the previously proposed theory of non-uniform transmission lines by introducing an expression for impedance transfer, which yields a closed-form solution for the fields inside and outside the sphere. The power transmitted in and scattered by the sphere can be also evaluated with a simple closed-form expression and related with the modulus of the reflection coefficient. We showed that our method is fully consistent with the classical Mie scattering theory. We also showed that our method can provide an intuitive physical interpretation of electromagnetic scattering in terms of impedance matching and resonances, and that it is especially useful for the case of inward traveling spherical waves generated by sources surrounding the scatterer. Full article
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Article
Stateless Re-Association in WPA3 Using Paired Token
Electronics 2021, 10(2), 215; https://doi.org/10.3390/electronics10020215 - 19 Jan 2021
Viewed by 537
Abstract
In Wi-Fi Protected Access 3 (WPA3), a secure connection is established in two sequential stages. Firstly, in the authentication and association stage, a pairwise master key (PMK) is generated. Secondly, in the post-association stage, a pairwise transient key (PTK) is generated from PMK [...] Read more.
In Wi-Fi Protected Access 3 (WPA3), a secure connection is established in two sequential stages. Firstly, in the authentication and association stage, a pairwise master key (PMK) is generated. Secondly, in the post-association stage, a pairwise transient key (PTK) is generated from PMK using the traditional 4-way handshake protocol. To reduce the heavy load of the first stage, PMK caching can be used. If the client and AP are previously authenticated and have a PMK cache, the first heavy stage can be skipped and the cached PMK can be used to directly execute the 4-way handshake. However, PMK caching is a very primitive technology to manage shared key between a client and AP and there are many limitations; AP has to manage a stateful cache for a large number of clients, cache lifetime is limited, etc. Paired token (PT)is a new secondary credential scheme that provides stateless pre-shared key (PSK) in a client-server environment. The server issues a paired token (public token and secret token) to an authenticated client where the public token has the role of signed identity and the secret token is a kind of shared secret. Once a client is equipped with PT, it can be used for many symmetric key-based cryptographic applications such as authentication, authorization, key establishment, etc. In this paper, we apply the PT approach to WPA3 and try to replace the PMK caching with the one-time authenticated key establishment using PT. At the end of a successful full handshake, AP securely issues PT to the client. Then, in subsequent re-association requests, the client and AP can compute the same one-time authenticated PMK using PT in a stateless way. Using this kind of stateless re-association technology, AP can provide a high performance Wi-Fi service to a larger number of clients. Full article
(This article belongs to the Section Microwave and Wireless Communications)
Article
Improving the Prediction Quality in Memory-Based Collaborative Filtering Using Categorical Features
Electronics 2021, 10(2), 214; https://doi.org/10.3390/electronics10020214 - 18 Jan 2021
Cited by 4 | Viewed by 517
Abstract
Despite years of evolution of recommender systems, improving prediction accuracy remains one of the core problems among researchers and industry. It is common to use side information to bolster the accuracy of recommender systems. In this work, we focus on using item categories, [...] Read more.
Despite years of evolution of recommender systems, improving prediction accuracy remains one of the core problems among researchers and industry. It is common to use side information to bolster the accuracy of recommender systems. In this work, we focus on using item categories, specifically movie genres, to improve the prediction accuracy as well as coverage, precision, and recall. We derive the user’s taste for an item using the ratings expressed. Similarly, using the collective ratings given to an item, we identify how much each item belongs to a certain genre. These two vectors are then combined to get a user-item-weight matrix. In contrast to the similarity-based weight matrix in memory-based collaborative filtering, we use user-item-weight to make predictions. The user-item-weights can be used to explain to users why certain items have been recommended. We evaluate our proposed method using three real-world datasets. The proposed model performs significantly better than the baseline methods. In addition, we use the user-item-weight matrix to alleviate the sparsity problem associated with correlation-based similarity. In addition to that, the proposed model has a better computational complexity for making predictions than the k-nearest neighbor (kNN) method. Full article
(This article belongs to the Section Computer Science & Engineering)
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Article
An Optimal Digital Filtering Technique for Incremental Delta-Sigma ADCs Using Passive Integrators
Electronics 2021, 10(2), 213; https://doi.org/10.3390/electronics10020213 - 18 Jan 2021
Viewed by 586
Abstract
This paper presents an optimal digital filtering technique to enhance the resolution of incremental delta-sigma modulators (incremental DSMs, IDSMs) using a low-power passive integrator. We first describe a link between a passive integrator and its impact on the output of the IDSM. We [...] Read more.
This paper presents an optimal digital filtering technique to enhance the resolution of incremental delta-sigma modulators (incremental DSMs, IDSMs) using a low-power passive integrator. We first describe a link between a passive integrator and its impact on the output of the IDSM. We then show that the optimal digital filter design can be cast as a convex optimization problem, which can be efficiently solved. As a test vehicle of the proposed technique, we use a behavioral 2nd-order IDSM model that captures critical non-idealities of the integrator, such as gain compression and output saturation. The effectiveness of the presented technique is verified using extensive simulations. The result shows that the presented filtering technique improves signal-to-noise and distortion ratio (SNDR) by 15 dB–20 dB, achieving SNDR over 90 dB when the oversampling ratio (OSR) = 256, and this corresponds to best-in-class performance when compared to previously published DSM designs using passive integrators. Full article
(This article belongs to the Section Circuit and Signal Processing)
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Article
Adaptive Sliding Mode Neural Network Control and Flexible Vibration Suppression of a Flexible Spatial Parallel Robot
Electronics 2021, 10(2), 212; https://doi.org/10.3390/electronics10020212 - 18 Jan 2021
Cited by 1 | Viewed by 575
Abstract
With the goal of creating a flexible spatial parallel robot system in which the elastic deformation of the flexible link causes a rigid moving platform to produce small vibrations, we proposed an adaptive sliding mode control algorithm based on a neural network. To [...] Read more.
With the goal of creating a flexible spatial parallel robot system in which the elastic deformation of the flexible link causes a rigid moving platform to produce small vibrations, we proposed an adaptive sliding mode control algorithm based on a neural network. To improve the calculation efficiency, the finite element method was used to discretize the flexible spatial link, and then the displacement field of the flexible spatial link was described based on floating frame of reference coordinates, and the dynamic differential equation of the flexible spatial link considering high-frequency vibrations was established through the Lagrange equation. This was combined with the dynamic equation of the rigid link and the dynamic equation considering small displacements of the rigid movable platform due to elastic deformation, and a highly nonlinear and accurate dynamic model with a rigid–flexible coupling effect was obtained. Based on the established accurate multi-body dynamics model, the driving torque with coupling effects was calculated in advance for feedforward compensation, and the adaptive sliding mode controller was used to improve the tracking performance of the system. The nonlinear error was examined to determine the performance of the neural network’s approximation of the nonlinear system. The trajectory errors of the moving platform in the X-, Y-, and Z-directions were reduced by 12.1%, 38.8%, and 50.34%, respectively. The results showed that the designed adaptive sliding mode neural network control met the control accuracy requirements, and suppressed the vibrations generated by the deformation of the flexible spatial link. Full article
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Article
Constant Envelope Multiplexing of Multi-Carrier DSSS Signals Considering Sub-Carrier Frequency Constraint
Electronics 2021, 10(2), 211; https://doi.org/10.3390/electronics10020211 - 18 Jan 2021
Viewed by 395
Abstract
With the development of global navigation satellite systems (GNSS), multiple signals modulated on different sub-carriers are needed to provide various services and to ensure compatibility with previous signals. As an effective method to provide diversified signals without introducing the nonlinear distortion of High [...] Read more.
With the development of global navigation satellite systems (GNSS), multiple signals modulated on different sub-carriers are needed to provide various services and to ensure compatibility with previous signals. As an effective method to provide diversified signals without introducing the nonlinear distortion of High Power Amplifier (HPA), the multi-carrier constant envelope multiplexing is widely used in satellite navigation systems. However, the previous method does not consider the influence of sub-carrier frequency constraint on the multiplexing signal, which may lead to signal power leakage. By determining the signal states probability according to the sub-carrier frequency constraint and solving the orthogonal bases according to the homogeneous equations, this article proposed multi-carrier constant envelope multiplexing methods based on probability and homogeneous equations. The analysis results show that the methods can multiplex multi-carrier signals without power leakage, thereby reducing the impact on signal ranging performance. Meanwhile, the methods could reduce the computation complexity. In the case of three different carriers multiplexing, the number of optimization equations is reduced by nearly 66%. Full article
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Article
Measurements and Computations of Internal Temperatures of the IGBT and the Diode Situated in the Common Case
Electronics 2021, 10(2), 210; https://doi.org/10.3390/electronics10020210 - 18 Jan 2021
Cited by 4 | Viewed by 551
Abstract
This article proposes effective methods of measurements and computations of internal temperature of the dies of the Insulted Gate Bipolar Transistor (IGBT) and the diode mounted in the common case. The nonlinear compact thermal model of the considered device is proposed. This model [...] Read more.
This article proposes effective methods of measurements and computations of internal temperature of the dies of the Insulted Gate Bipolar Transistor (IGBT) and the diode mounted in the common case. The nonlinear compact thermal model of the considered device is proposed. This model takes into account both self-heating phenomena in both dies and mutual thermal couplings between them. In the proposed model, the influence of the device internal temperature on self and transfer thermal resistances is taken into account. Methods of measurements of each self and transfer transient thermal impedances occurring in this model are described and factors influencing the measurement error of these methods are analysed. Some results illustrating thermal properties of the investigated devices including the IGBT and the antiparallel diode in the common case are shown and discussed. Computations illustrating the usefulness of the proposed compact thermal model are presented and compared to the results of measurements. It is proved that differences between internal temperature of both dies included in the TO-247 case can exceed even 15 K. Full article
(This article belongs to the Section Semiconductor Devices)
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Article
Bi-Objective Workflow Scheduling on Heterogeneous Computing Systems Using a Memetic Algorithm
Electronics 2021, 10(2), 209; https://doi.org/10.3390/electronics10020209 - 18 Jan 2021
Viewed by 469
Abstract
Due to the high power bills and the negative environmental impacts, workflow scheduling with energy consciousness has been an emerging need for modern heterogeneous computing systems. A number of approaches have been developed to find suboptimal schedules through heuristics by means of slack [...] Read more.
Due to the high power bills and the negative environmental impacts, workflow scheduling with energy consciousness has been an emerging need for modern heterogeneous computing systems. A number of approaches have been developed to find suboptimal schedules through heuristics by means of slack reclamation or trade-off functions. In this article, a memetic algorithm for energy-efficient workflow scheduling is proposed for a quality-guaranteed solution with high runtime efficiency. The basic idea is to retain the advantages of population-based, heuristic-based, and local search methods while avoiding their drawbacks. Specifically, the proposed algorithm incorporates an improved non-dominated sorting genetic algorithm (NSGA-II) to explore potential task priorities and allocates tasks to processors by an earliest finish time (EFT)-based heuristic to provide a time-efficient candidate. Then, a local search method integrated with a pruning technique is launched with a low possibility, to exploit the feasible region indicated by the candidate schedule. Experimental results on workflows from both randomly-generated and real-world applications suggest that the proposed algorithm achieves bi-objective optimization, improving makespan, and energy saving by 4.9% and 24.3%, respectively. Meanwhile, it has a low time complexity compared to the similar work HECS. Full article
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Article
Latencies in Power Systems: A Database-Based Time-Delay Compensation for Memory Controllers
Electronics 2021, 10(2), 208; https://doi.org/10.3390/electronics10020208 - 18 Jan 2021
Cited by 1 | Viewed by 616
Abstract
Time-delay is inherent to communications schemes in power systems, and in a closed loop strategy the presence of latencies increases inter-area oscillations and security problems in tie-lines. Recently, Wide Area Measurement Systems (WAMS) have been introduced to improve observability and overcome slow-rate communications [...] Read more.
Time-delay is inherent to communications schemes in power systems, and in a closed loop strategy the presence of latencies increases inter-area oscillations and security problems in tie-lines. Recently, Wide Area Measurement Systems (WAMS) have been introduced to improve observability and overcome slow-rate communications from traditional Supervisory Control and Data Acquisition (SCADA). However, there is a need for tackling time-delays in control strategies based in WAMS. For this purpose, this paper proposes an Enhanced Time Delay Compensator (ETDC) approach which manages varying time delays introducing the perspective of network latency instead dead time; also, ETDC takes advantage of real signals and measurements transmission procedure in WAMS building a closed-loop memory control for power systems. The strength of the proposal was tested satisfactorily in a widely studied benchmark model in which inter-area oscillations were excited properly. Full article
(This article belongs to the Special Issue Grid-Connected Renewable Energy Sources)
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Article
Experimental Validation of Metaheuristic and Conventional Modulation, and Hysteresis Control of the Dual Boost Nine-Level Inverter
Electronics 2021, 10(2), 207; https://doi.org/10.3390/electronics10020207 - 18 Jan 2021
Viewed by 762
Abstract
In this article, various modulation strategies and hysteresis-band control of a recently introduced dual-boost nine-level inverter (DB9LI) are implemented. DB9LI is a switched capacitor based inverter capable of generating symmetrical nine output voltage levels by employing a single DC source. The topology generates [...] Read more.
In this article, various modulation strategies and hysteresis-band control of a recently introduced dual-boost nine-level inverter (DB9LI) are implemented. DB9LI is a switched capacitor based inverter capable of generating symmetrical nine output voltage levels by employing a single DC source. The topology generates a boosted bipolar voltage at the output side without applying end-side H-bridge (usually employed to generate negative levels), which contrasts with some of the switched-capacitor topologies. The capacitors employed have an inherent self-balancing feature. Additionally, due to lower individual and total standing voltages, switches of low voltage ratings are required. As a result, the cost of switches and the inverter reduces considerably. Metaheuristic-based selective harmonic elimination and mitigation (SHE and SHM) and various sine-triangular pulse width modulation techniques are implemented and compared on various parameters. Finally, a robust eight-band hysteresis control is designed and implemented, which helps to obtain sinusoidal load current with a unity power factor. The modulation strategies and the hysteresis control are validated on the MATLAB simulation environment and an experimental prototype. Full article
(This article belongs to the Section Industrial Electronics)
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Article
An MPPT Strategy Based on a Surface-Based Polynomial Fitting for Solar Photovoltaic Systems Using Real-Time Hardware
Electronics 2021, 10(2), 206; https://doi.org/10.3390/electronics10020206 - 17 Jan 2021
Cited by 4 | Viewed by 1053
Abstract
This paper presents an optimal design of a surface-based polynomial fitting for tracking the maximum power point (MPPT) of a photovoltaic (PV) system, here named surface-based polynomial fitting (MPPT-SPF). The procedure of the proposed MPPT-SPF strategy is based on a polynomial model to [...] Read more.
This paper presents an optimal design of a surface-based polynomial fitting for tracking the maximum power point (MPPT) of a photovoltaic (PV) system, here named surface-based polynomial fitting (MPPT-SPF). The procedure of the proposed MPPT-SPF strategy is based on a polynomial model to characterize data from the PV module with a global fit. The advantage of using polynomials is that they provide a good fit within a predefined data range even though they can diverge greatly from that range. The MPPT-SPF strategy is integrated with a DC-DC boost converter to verify its performance and its interaction with different control loops. Therefore, the MPPT strategy is applied to the reference outer PI control loop, which in turn provides the current reference to the inner current loop based on a discrete-time sliding current control. A real-time and high-speed simulator (PLECS RT Box 1) and a digital signal controller (DSC) are used to implement the hardware-in-the-loop system to obtain the results. The proposed strategy does not have a high computational cost and can be implemented in a commercial low-cost DSC (TI 28069M). The proposed MPPT strategy is compared with a conventional perturb and observe method to prove its effectiveness under demanding tests. Full article
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Article
Algorithmic-Level Approximate Tensorial SVM Using High-Level Synthesis on FPGA
Electronics 2021, 10(2), 205; https://doi.org/10.3390/electronics10020205 - 17 Jan 2021
Cited by 3 | Viewed by 955
Abstract
Approximate Computing Techniques (ACT) are promising solutions towards the achievement of reduced energy, time latency and hardware size for embedded implementations of machine learning algorithms. In this paper, we present the first FPGA implementation of an approximate tensorial Support Vector Machine (SVM) classifier [...] Read more.
Approximate Computing Techniques (ACT) are promising solutions towards the achievement of reduced energy, time latency and hardware size for embedded implementations of machine learning algorithms. In this paper, we present the first FPGA implementation of an approximate tensorial Support Vector Machine (SVM) classifier with algorithmic level ACTs using High-Level Synthesis (HLS). A touch modality classification framework was adopted to validate the effectiveness of the proposed implementation. When compared to exact implementation presented in the state-of-the-art, the proposed implementation achieves a reduction in power consumption by up to 49% with a speedup of 3.2×. Moreover, the hardware resources are reduced by 40% while consuming 82% less energy in classifying an input touch with an accuracy loss less than 5%. Full article
(This article belongs to the Special Issue Advanced Embedded HW/SW Development)
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Article
Autonomous Operation Control of IoT Blockchain Networks
Electronics 2021, 10(2), 204; https://doi.org/10.3390/electronics10020204 - 17 Jan 2021
Cited by 1 | Viewed by 787
Abstract
Internet of Things (IoT) networks are typically composed of many sensors and actuators. The operation controls for robots in smart factories or drones produce a massive volume of data that requires high reliability. A blockchain architecture can be used to build highly reliable [...] Read more.
Internet of Things (IoT) networks are typically composed of many sensors and actuators. The operation controls for robots in smart factories or drones produce a massive volume of data that requires high reliability. A blockchain architecture can be used to build highly reliable IoT networks. The shared ledger and open data validation among users guarantee extremely high data security. However, current blockchain technology has limitations for its overall application across IoT networks. Because general permission-less blockchain networks typically target high-performance network nodes with sufficient computing power, a blockchain node with low computing power and memory, such as an IoT sensor/actuator, cannot operate in a blockchain as a fully functional node. A lightweight blockchain provides practical blockchain availability over IoT networks. We propose essential operational advances to develop a lightweight blockchain over IoT networks. A dynamic network configuration enforced by deep clustering provides ad-hoc flexibility for IoT network environments. The proposed graph neural network technique enhances the efficiency of dApp (distributed application) spreading across IoT networks. In addition, the proposed blockchain technology is highly implementable in software because it adopts the Hyperledger development environment. Directly embedding the proposed blockchain middleware platform in small computing devices proves the practicability of the proposed methods. Full article
(This article belongs to the Special Issue AI Applications in IoT and Mobile Wireless Networks)
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Article
Full Digital Control of an All-Si On-Board Charger Operating in Discontinuous Conduction Mode
Electronics 2021, 10(2), 203; https://doi.org/10.3390/electronics10020203 - 17 Jan 2021
Cited by 4 | Viewed by 635
Abstract
This paper deals with the design, tuning and implementation of a digital controller for an all-Si electric vehicle (EV) on-board battery charger operated in discontinuous conduction mode (DCM). This charger consists of two cascaded conversion stages: a front-end power factor corrector (PFC) with [...] Read more.
This paper deals with the design, tuning and implementation of a digital controller for an all-Si electric vehicle (EV) on-board battery charger operated in discontinuous conduction mode (DCM). This charger consists of two cascaded conversion stages: a front-end power factor corrector (PFC) with two interleaved legs and an isolated phase-shifted full bridge DC/DC converter. Both stages operate in DCM over the complete battery charging power range, allowing lower inductance values for both the PFC and the DC/DC filtering elements. Moreover, DCM operation ensures a large reduction of the reverse-recovery losses in the power diodes, enabling the adoption of relatively cheap Si devices. The main goal of the work is to address the well-known DCM control challenges, leveraging a novel control strategy for both converter stages. This control scheme counteracts the DCM system non-linearities with a proper feed-forward contribution and an open-loop gain adjustment, ensuring consistent dynamical performance over the complete operating range. The designed controllers are tuned analytically, taking into account the delay components related to the digital implementation. Finally, the proposed control strategy is implemented on a single general purpose microcontroller unit (MCU) and its performance is experimentally validated on a 3.3 kW battery charger prototype. Full article
(This article belongs to the Special Issue Design and Applications of Multiple Output DC-DC Converters)
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Article
NDF of Scattered Fields for Strip Geometries
Electronics 2021, 10(2), 202; https://doi.org/10.3390/electronics10020202 - 17 Jan 2021
Cited by 5 | Viewed by 2044
Abstract
Solving inverse scattering problems by numerical methods requires investigating the number of independent pieces of information that can be reconstructed stably. To this end, we address the evaluation of the Number of Degrees of Freedom (NDF) of far-zone scattered fields for some strip [...] Read more.
Solving inverse scattering problems by numerical methods requires investigating the number of independent pieces of information that can be reconstructed stably. To this end, we address the evaluation of the Number of Degrees of Freedom (NDF) of far-zone scattered fields for some strip geometries under the first-order Born approximation. The analysis is performed by employing the Singular Value Decomposition (SVD) of the scattering operator in the two-dimensional scalar geometry of one or more strips illuminated by a TM polarized plane wave. It is known that investigating the scattering scene at different incident plane waves (multi-view configuration) enhances the NDF. Therefore we mean to examine the minimum number of incident plane waves providing the NDF of the scattered fields both by theoretical estimations and numerical verifications. Full article
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Article
A Non-Linear Convolution Network for Image Processing
Electronics 2021, 10(2), 201; https://doi.org/10.3390/electronics10020201 - 17 Jan 2021
Cited by 2 | Viewed by 618
Abstract
This paper proposes a new neural network structure for image processing whose convolutional layers, instead of using kernels with fixed coefficients, use space-variant coefficients. The adoption of this strategy allows the system to adapt its behavior according to the spatial characteristics of the [...] Read more.
This paper proposes a new neural network structure for image processing whose convolutional layers, instead of using kernels with fixed coefficients, use space-variant coefficients. The adoption of this strategy allows the system to adapt its behavior according to the spatial characteristics of the input data. This type of layers performs, as we demonstrate, a non-linear transfer function. The features generated by these layers, compared to the ones generated by canonical CNN layers, are more complex and more suitable to fit to the local characteristics of the images. Networks composed by these non-linear layers offer performance comparable with or superior to the ones which use canonical Convolutional Networks, using fewer layers and a significantly lower number of features. Several applications of these newly conceived networks to classical image-processing problems are analyzed. In particular, we consider: Single-Image Super-Resolution (SISR), Edge-Preserving Smoothing (EPS), Noise Removal (NR), and JPEG artifacts removal (JAR). Full article
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Article
Influence of Active Channel Layer Thickness on SnO2 Thin-Film Transistor Performance
Electronics 2021, 10(2), 200; https://doi.org/10.3390/electronics10020200 - 17 Jan 2021
Cited by 1 | Viewed by 892
Abstract
Sol-gel processed SnO2 thin-film transistors (TFTs) were fabricated on SiO2/p+ Si substrates. The SnO2 active channel layer was deposited by the sol-gel spin coating method. Precursor concentration influenced the film thickness and surface roughness. As the concentration of [...] Read more.
Sol-gel processed SnO2 thin-film transistors (TFTs) were fabricated on SiO2/p+ Si substrates. The SnO2 active channel layer was deposited by the sol-gel spin coating method. Precursor concentration influenced the film thickness and surface roughness. As the concentration of the precursor was increased, the deposited films were thicker and smoother. The device performance was influenced by the thickness and roughness of the SnO2 active channel layer. Decreased precursor concentration resulted in a fabricated device with lower field-effect mobility, larger subthreshold swing (SS), and increased threshold voltage (Vth), originating from the lower free carrier concentration and increase in trap sites. The fabricated SnO2 TFTs, with an optimized 0.030 M precursor, had a field-effect mobility of 9.38 cm2/Vs, an SS of 1.99, an Ion/Ioff value of ~4.0 × 107, and showed enhancement mode operation and positive Vth, equal to 9.83 V. Full article
(This article belongs to the Special Issue Applications of Thin Films in Microelectronics)
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Article
Sentiment Level Evaluation of 3D Handicraft Products Application for Smartphones Usage
Electronics 2021, 10(2), 199; https://doi.org/10.3390/electronics10020199 - 16 Jan 2021
Viewed by 692
Abstract
Three-dimensional (3D) technology has attracted users’ attention because it creates objects that can interact with a given product in a system. Nowadays, Thailand’s government encourages sustainability projects through advertising, trade shows and information systems for small rural entrepreneurship. However, the government’s systems do [...] Read more.
Three-dimensional (3D) technology has attracted users’ attention because it creates objects that can interact with a given product in a system. Nowadays, Thailand’s government encourages sustainability projects through advertising, trade shows and information systems for small rural entrepreneurship. However, the government’s systems do not include virtual products with a 3D display. The objective of this study was four-fold: (1) develop a prototype of 3D handicraft product application for smartphones; (2) create an online questionnaire to collect user usage assessment data in terms of five sentiment levels—strongly negative, negative, neutral, positive and strongly positive—in response to the usage of the proposed 3D application; (3) evaluate users’ sentiment level in 3D handicraft product application usage; and (4) investigate attracting users’ attention to handicraft products after using the proposed 3D handicraft product application. The results indicate that 78.87% of participants’ sentiment was positive and strongly positive under accept using 3D handicraft product application, and evaluations in terms of assessing attention paid by participants to the handicraft products revealed that positive and strongly positive sentiment was described by 79.61% of participants. The participants’ evaluation results in this study prove that our proposed 3D handicraft product application affected users by attracting their attention towards handicraft products. Full article
(This article belongs to the Special Issue Human Computer Interaction for Intelligent Systems)
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Article
Mobile-Based Sensing Scheme to Minimize Battery Power Consumption for Urban Monitoring Systems
Electronics 2021, 10(2), 198; https://doi.org/10.3390/electronics10020198 - 16 Jan 2021
Cited by 1 | Viewed by 465
Abstract
In urban monitoring systems, mobile sensing is imperative to acquire data from sensors and relay them to a cloud server. Mobile devices can be used anytime and anywhere, enabling communication with pervasive sensing in various conditions to obtain the data. Reliable data acquisition [...] Read more.
In urban monitoring systems, mobile sensing is imperative to acquire data from sensors and relay them to a cloud server. Mobile devices can be used anytime and anywhere, enabling communication with pervasive sensing in various conditions to obtain the data. Reliable data acquisition has been required in urban monitoring systems from the macroscale to the microscale. However, a broadcast method for the data acquisition process may lead to the increased battery power consumption of mobile devices. Managing the battery power consumption of mobile devices is essential for reliable data acquisition. In this paper, we propose an urban monitoring system with an optimization algorithm in which a cloud server broadcasts a communication request that includes battery power consumption and the data acquisition quantity of mobile devices. Game theoretic optimization is formulated with a decision process. We derive a best response and Nash equilibrium for mobile communication with sensors and a cloud server. Evaluation results demonstrate that the proposed system can guarantee a low battery power consumption, as well as acquire the desired data quantity. Full article
(This article belongs to the Special Issue Green Internet-of-Thing Design and Modeling in AI and 5G Ecosystems)
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Article
Examination of Abnormal Behavior Detection Based on Improved YOLOv3
Electronics 2021, 10(2), 197; https://doi.org/10.3390/electronics10020197 - 16 Jan 2021
Cited by 2 | Viewed by 922
Abstract
Examination is a way to select talents, and a perfect invigilation strategy can improve the fairness of the examination. To realize the automatic detection of abnormal behavior in the examination room, the method based on the improved YOLOv3 (The third version of the [...] Read more.
Examination is a way to select talents, and a perfect invigilation strategy can improve the fairness of the examination. To realize the automatic detection of abnormal behavior in the examination room, the method based on the improved YOLOv3 (The third version of the You Only Look Once algorithm) algorithm is proposed. The YOLOv3 algorithm is improved by using the K-Means algorithm, GIoUloss, focal loss, and Darknet32. In addition, the frame-alternate dual-thread method is used to optimize the detection process. The research results show that the improved YOLOv3 algorithm can improve both the detection accuracy and detection speed. The frame-alternate dual-thread method can greatly increase the detection speed. The mean Average Precision (mAP) of the improved YOLOv3 algorithm on the test set reached 88.53%, and the detection speed reached 42 Frames Per Second (FPS) in the frame-alternate dual-thread detection method. The research results provide a certain reference for automated invigilation. Full article
(This article belongs to the Section Computer Science & Engineering)
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Article
Robust Adaptive Filtering Algorithm for Self-Interference Cancellation with Impulsive Noise
Electronics 2021, 10(2), 196; https://doi.org/10.3390/electronics10020196 - 16 Jan 2021
Cited by 1 | Viewed by 533
Abstract
Self-interference (SI) is usually generated by the simultaneous transmission and reception in the same system, and the variable SI channel and impulsive noise make it difficult to eliminate. Therefore, this paper proposes an adaptive digital SI cancellation algorithm, which is an improved normalized [...] Read more.
Self-interference (SI) is usually generated by the simultaneous transmission and reception in the same system, and the variable SI channel and impulsive noise make it difficult to eliminate. Therefore, this paper proposes an adaptive digital SI cancellation algorithm, which is an improved normalized sub-band adaptive filtering (NSAF) algorithm based on the sparsity of the SI channel and the arctangent cost function. The weight vector is hardly updated when the impulsive noise occurs, and the iteration error resulting from impulsive noise is significantly reduced. Another major factor affecting the performance of SI cancellation is the variable SI channel. To solve this problem, the sparsity of the SI channel is estimated with the estimation of the weight vector at each iteration, and it is used to adjust the weight vector. Then, the convergence performance and calculation complexity are analyzed theoretically. Simulation results indicate that the proposed algorithm has better performance than the referenced algorithms. Full article
(This article belongs to the Section Circuit and Signal Processing)
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Article
Novel Dual Beam Cascaded Schemes for 346 GHz Harmonic-Enhanced TWTs
Electronics 2021, 10(2), 195; https://doi.org/10.3390/electronics10020195 - 16 Jan 2021
Viewed by 453
Abstract
The applications of terahertz (THz) devices in communication, imaging, and plasma diagnostic are limited by the lack of high-power, miniature, and low-cost THz sources. To develop high-power THz source, the high-harmonic traveling wave tube (HHTWT) is introduced, which is based on the theory [...] Read more.
The applications of terahertz (THz) devices in communication, imaging, and plasma diagnostic are limited by the lack of high-power, miniature, and low-cost THz sources. To develop high-power THz source, the high-harmonic traveling wave tube (HHTWT) is introduced, which is based on the theory that electron beam modulated by electromagnetic (EM) waves can generate high harmonic signals. The principal analysis and simulation results prove that amplifying high harmonic signal is a promising method to realize high-power THz source. For further improvement of power and bandwidth, two novel dual-beam schemes for high-power 346 GHz TWTs are proposed. The first TWT is comprised of two cascaded slow wave structures (SWSs), among which one SWS can generate a THz signal by importing a millimeter-wave signal and the other one can amplify THz signal of interest. The simulation results show that the output power exceeds 400 mW from 340 GHz to 348 GHz when the input power is 200 mW from 85 GHz to 87 GHz. The peak power of 1100 mW is predicted at 346 GHz. The second TWT is implemented by connecting a pre-amplification section to the input port of the HHTWT. The power of 600 mW is achieved from 338 GHz to 350 GHz. The 3-dB bandwidth is 16.5 GHz. In brief, two novel schemes have advantages in peak power and bandwidth, respectively. These two dual-beam integrated schemes, constituted respectively by two TWTs, also feature rugged structure, reliable performance, and low costs, and can be considered as promising high-power THz sources. Full article
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Article
A Study on the Effect of Bond Wires Lift-Off on IGBT Thermal Resistance Measurement
Electronics 2021, 10(2), 194; https://doi.org/10.3390/electronics10020194 - 15 Jan 2021
Viewed by 503
Abstract
Bond wire lift-off will cause an increase of remaining wires’ power dissipation, which usually is ignored for healthy modules. However, only partial wires’ power dissipation transfers through thermal path from junction to case, which will lead to overestimate the whole power dissipation from [...] Read more.
Bond wire lift-off will cause an increase of remaining wires’ power dissipation, which usually is ignored for healthy modules. However, only partial wires’ power dissipation transfers through thermal path from junction to case, which will lead to overestimate the whole power dissipation from collector to emitter pole and underestimate the calculated thermal resistance using the proportion of temperature difference to power dissipation. A FEM model is established to show the change of heat flow after bond wires were removed, the temperature of bond wires increases, and the measured thermal resistance decrease after bond wires lift-off. It is validated by experimental results using open package Insulated Gate Bipolar Transistor (IGBT) modules under different current conditions. This conclusion might be helpful to indicate the bond wires lift-off and solder fatigue by comparing the change of measured thermal resistance. Using the Kelvin setup to measure thermal resistance will cause misjudgment of failure mode due to the ignoring of wires’ power dissipation. This paper proposed that the lift-off of bond wires will lead to underestimating the thermal resistance measurement, which will overestimate the lifetime of IGBT module and misjudge its state of health. Full article
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Article
RCVC: RSU-Aided Cluster-Based Vehicular Clouds Architecture for Urban Areas
Electronics 2021, 10(2), 193; https://doi.org/10.3390/electronics10020193 - 15 Jan 2021
Cited by 1 | Viewed by 606
Abstract
As a promising topic of research, Vehicular Cloud (VC) incorporates cloud computing and ad-hoc vehicular network (VANET). In VC, supplier vehicles provide their services to consumer vehicles in real-time. These services have a significant impact on the applications of internet access, storage and [...] Read more.
As a promising topic of research, Vehicular Cloud (VC) incorporates cloud computing and ad-hoc vehicular network (VANET). In VC, supplier vehicles provide their services to consumer vehicles in real-time. These services have a significant impact on the applications of internet access, storage and data. Due to the high-speed mobility of vehicles, users in consumer vehicles need a mechanism to discover services in their vicinity. Besides this, quality of service varies from one supplier vehicle to another; thus, consumer vehicles attempt to pick out the most appropriate services. In this paper, we propose a novel protocol named RSU-aided Cluster-based Vehicular Clouds protocol (RCVC), which constructs the VC using the Road Side Unit (RSU) directory and Cluster Head (CH) directory to make the resources of supplier vehicles more visible. While clusters of vehicles that move on the same road form a mobile cloud, the remaining vehicles form a different cloud on the road side unit. Furthermore, the consumption operation is achieved via the service selection method, which is managed by the CHs and RSUs based on a mathematical model to select the best services. Simulation results prove the effectiveness of our protocol in terms of service discovery and end-to-end delay, where we achieved service discovery and end-to-end delay of 3 × 10−3 s and 13 × 10−2 s, respectively. Moreover, we carried out an experimental comparison, revealing that the proposed method outperformed several states of the art protocols. Full article
(This article belongs to the Section Electrical and Autonomous Vehicles)
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Article
Active Contour Model Using Fast Fourier Transformation for Salient Object Detection
Electronics 2021, 10(2), 192; https://doi.org/10.3390/electronics10020192 - 15 Jan 2021
Viewed by 513
Abstract
The active contour model is a comprehensive research technique used for salient object detection. Most active contour models of saliency detection are developed in the context of natural scenes, and their role with synthetic and medical images is not well investigated. Existing active [...] Read more.
The active contour model is a comprehensive research technique used for salient object detection. Most active contour models of saliency detection are developed in the context of natural scenes, and their role with synthetic and medical images is not well investigated. Existing active contour models perform efficiently in many complexities but facing challenges on synthetic and medical images due to the limited time like, precise automatic fitted contour and expensive initialization computational cost. Our intention is detecting automatic boundary of the object without re-initialization which further in evolution drive to extract salient object. For this, we propose a simple novel derivative of a numerical solution scheme, using fast Fourier transformation (FFT) in active contour (Snake) differential equations that has two major enhancements, namely it completely avoids the approximation of expansive spatial derivatives finite differences, and the regularization scheme can be generally extended more. Second, FFT is significantly faster compared to the traditional solution in spatial domain. Finally, this model practiced Fourier-force function to fit curves naturally and extract salient objects from the background. Compared with the state-of-the-art methods, the proposed method achieves at least a 3% increase of accuracy on three diverse set of images. Moreover, it runs very fast, and the average running time of the proposed methods is about one twelfth of the baseline. Full article
(This article belongs to the Special Issue Multidimensional Digital Signal Processing)
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Article
An Efficient Indexing Scheme for Network Traffic Collection and Retrieval System
Electronics 2021, 10(2), 191; https://doi.org/10.3390/electronics10020191 - 15 Jan 2021
Viewed by 442
Abstract
Historical network traffic retrieval, both at the packet and flow level, has been applied in many fields of network security, such as network traffic analysis and network forensics. To retrieve specific packets from a vast number of packet traces, it is an effective [...] Read more.
Historical network traffic retrieval, both at the packet and flow level, has been applied in many fields of network security, such as network traffic analysis and network forensics. To retrieve specific packets from a vast number of packet traces, it is an effective solution to build indexes for the query attributes. However, it brings challenges of storage consumption and construction time overhead for packet indexing. To address these challenges, we propose an efficient indexing scheme called IndexWM based on the wavelet matrix data structure for packet indexing. Moreover, we design a packet storage format based on the PcapNG format for our network traffic collection and retrieval system, which can speed up the extraction of index data from packet traces. Offline experiments on randomly generated network traffic and actual network traffic are performed to evaluate the performance of the proposed indexing scheme. We choose an open-source and widely used bitmap indexing scheme, FastBit, for comparison. Apart from the native bitmap compression method Word-Aligned Hybrid (WAH), we implement an efficient bitmap compression method Scope-Extended COMPAX (SECOMPAX) in FastBit for performance evaluation. The comparison results show that our scheme outperforms the selected bitmap indexing schemes in terms of time consumption, storage consumption and retrieval efficiency. Full article
(This article belongs to the Section Computer Science & Engineering)
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