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Electronics, Volume 8, Issue 3 (March 2019)

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Cover Story (view full-size image) The Internet of Things is fostering the integration and interoperation of novel technologies at [...] Read more.
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Open AccessArticle
Multi-Objective Service Restoration of Radial Distribution System in the Presence of Non-Linear Loads
Electronics 2019, 8(3), 369; https://doi.org/10.3390/electronics8030369
Received: 24 January 2019 / Revised: 9 March 2019 / Accepted: 16 March 2019 / Published: 26 March 2019
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Abstract
Most of the power electronic components act as non-linear loads because they draw non- sinusoidal current from the power supply. Due to these non-linear loads, current harmonics are injected in the power network. For normal operation, any power network is equipped with provisions [...] Read more.
Most of the power electronic components act as non-linear loads because they draw non- sinusoidal current from the power supply. Due to these non-linear loads, current harmonics are injected in the power network. For normal operation, any power network is equipped with provisions to keep the harmonics level to a minimum value. Whenever a fault occurs in the distribution system, the primary goal is to re-energize the healthy part of the network which got interrupted. It can be done by changing the topology of the network. This method is called as Service Restoration (SR). In this paper, a service restoration strategy is proposed when non-linear loads are present in the radial distribution system. Service restoration problem is formulated as a multi-objective, constrained optimization problem. Three new objectives are included to address the problem of harmonics injection by non-linear loads. Multi-Objective Particle Swarm Optimization (MOPSO) and Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) are used to find the optimal switching sequence for restoration. To test the effectiveness of the proposed methodology, IEEE 33 bus and IEEE 69 bus test systems are taken. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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Open AccessArticle
Design and Development of a Reduced Form-Factor High Accuracy Three-Axis Teslameter
Electronics 2019, 8(3), 368; https://doi.org/10.3390/electronics8030368
Received: 11 March 2019 / Revised: 20 March 2019 / Accepted: 22 March 2019 / Published: 26 March 2019
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Abstract
A novel three-axis teslameter and other similar machines have been designed and developed for SwissFEL at the Paul Scherrer Institute (PSI). The developed instrument will be used for high fidelity characterisation and optimisation of the undulators for the ATHOS soft X-ray beamline. The [...] Read more.
A novel three-axis teslameter and other similar machines have been designed and developed for SwissFEL at the Paul Scherrer Institute (PSI). The developed instrument will be used for high fidelity characterisation and optimisation of the undulators for the ATHOS soft X-ray beamline. The teslameter incorporates analogue signal conditioning for the three-axes interface to a SENIS Hall probe, an interface to a Heidenhain linear absolute encoder and an on-board high-resolution 24-bit analogue-to-digital conversion. This is in contrast to the old instrumentation setup used, which only comprises the analogue circuitry with digitization being done externally to the instrument. The new instrument fits in a volumetric space of 150 mm × 50 mm × 45 mm, being very compact in size and also compatible with the in-vacuum undulators. This paper describes the design and the development of the different components of the teslameter. Performance results are presented that demonstrate offset fluctuation and drift (0.1–10 Hz) with a standard deviation of 0.78 µT and a broadband noise (10–500 Hz) of 2.05 µT with an acquisition frequency of 2 kHz. Full article
(This article belongs to the Special Issue Filter Design Solutions for RF systems)
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Open AccessArticle
Open-Source Hardware Platforms for Smart Converters with Cloud Connectivity
Electronics 2019, 8(3), 367; https://doi.org/10.3390/electronics8030367
Received: 24 February 2019 / Revised: 18 March 2019 / Accepted: 22 March 2019 / Published: 26 March 2019
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Abstract
This paper presents the design and hardware implementation of open-source hardware dedicated to smart converter systems development. Smart converters are simple or interleaved converters. They are equipped with controllers that are able to online impedance match for the maximum power transfer. These conversion [...] Read more.
This paper presents the design and hardware implementation of open-source hardware dedicated to smart converter systems development. Smart converters are simple or interleaved converters. They are equipped with controllers that are able to online impedance match for the maximum power transfer. These conversion systems are particularly feasible for photovoltaic and all renewable energies systems working in continuous changing operating conditions. Smart converters represent promising solutions in recent energetic scenarios, in fact their application is deepening and widening. In this context, the availability of a hardware platform could represent a useful tool. The platform was conceived and released as an open hardware instrument for academy and industry to benefit from the improvements brought by the researchers’ community. The usage of a novel, open-source platform would allow many developers to design smart converters, focusing on algorithms instead of electronics, which could result in a better overall development ecosystem and rapid growth in the number of smart converter applications. The platform itself is proposed as a benchmark in the development and testing of different maximum power point tracking algorithms. The designed system is capable of accurate code implementations, allowing the testing of different current and voltage-controlled algorithms for different renewable energies systems. The circuit features a bi-directional radio frequency communication channel that enables real-time reading of measurements and parameters, and remote modification of both algorithm types and settings. The proposed system was developed and successfully tested in laboratory with a solar module simulator and with real photovoltaic generators. Experimental results indicate state-of-art performances as a converter, while enhanced smart features pave the way to system-level management, real-time diagnostics, and on-the-flight parameters change. Furthermore, the deployment feasibility allows different combinations and arrangements of several energy sources, converters (both single and multi-converters), and modulation strategies. To our knowledge, this project remains the only open-source hardware smart converter platform used for educational, research, and industrial purposes so far. Full article
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Open AccessArticle
Magnetic Switching of a Stoner-Wohlfarth Particle Subjected to a Perpendicular Bias Field
Electronics 2019, 8(3), 366; https://doi.org/10.3390/electronics8030366
Received: 28 February 2019 / Revised: 21 March 2019 / Accepted: 21 March 2019 / Published: 26 March 2019
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Abstract
Characterized by uniaxial magnetic anisotropy, the Stoner-Wohlfarth particle experiences a change in magnetization leading to a switch in behavior when tuned by an externally applied field, which relates to the perpendicular bias component (hperp) that remains substantially small in comparison [...] Read more.
Characterized by uniaxial magnetic anisotropy, the Stoner-Wohlfarth particle experiences a change in magnetization leading to a switch in behavior when tuned by an externally applied field, which relates to the perpendicular bias component (hperp) that remains substantially small in comparison with the constant switching field (h0). The dynamics of the magnetic moment that governs the magnetic switching is studied numerically by solving the Landau-Lifshitz-Gilbert (LLG) equation using the Mathematica code without any physical approximations; the results are compared with the switching time obtained from the analytic method that intricately treats the non-trivial bias field as a perturbation. A good agreement regarding the magnetic switching time (ts) between the numerical calculation and the analytic results is found over a wide initial angle range (0.01 < θ0 < 0.3), as h0 and hperp are 1.5 × K and 0.02 × K, where K represents the anisotropy constant. However, the quality of the analytic approximation starts to deteriorate slightly in contrast to the numerical approach when computing ts in terms of the field that satisfies hperp > 0.15 × K and h0 = 1.5 × K. Additionally, existence of a comparably small perpendicular bias field (hperp << h0) causes ts to decrease in a roughly exponential manner when hperp increases. Full article
(This article belongs to the Section Microwave and Wireless Communications)
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Open AccessArticle
Analysis and Experimental Test of Electrical Characteristics on Bonding Wire
Electronics 2019, 8(3), 365; https://doi.org/10.3390/electronics8030365
Received: 20 February 2019 / Revised: 22 March 2019 / Accepted: 23 March 2019 / Published: 26 March 2019
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Abstract
In this paper, electrical characteristic analysis and corresponding experimental tests on gold bonding wire are presented. Firstly, according to EIA (Electronic Industries Association)/JEDEC97 standards, this paper establishes the electromagnetic structure model of gold bonding wire. The parameters, including flat length ratio, diameter, span [...] Read more.
In this paper, electrical characteristic analysis and corresponding experimental tests on gold bonding wire are presented. Firstly, according to EIA (Electronic Industries Association)/JEDEC97 standards, this paper establishes the electromagnetic structure model of gold bonding wire. The parameters, including flat length ratio, diameter, span and bonding height, were analyzed. In addition, the influence of three kinds of loops of bonding wire is discussed in relation to the S parameters. An equivalent circuit model of bonding wire is proposed. The effect of bonding wire on signal transmission was analyzed by eye diagram as well. Secondly, gold bonding wire design and measurement experiments were implemented based on radio frequency (RF) circuit theory analysis and test methods. Meanwhile, the original measurement data was compared with the simulation model data and the error was analyzed. At last, the data of five frequency points were processed to eliminate the fixture error as much as possible based on port embedding theory. The measurement results using port extension method were compared with the original measurement data and electromagnetic field simulation data, which proved the correctness of the simulation results and design rules. Full article
(This article belongs to the Special Issue Applications of Electromagnetic Waves)
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Open AccessArticle
A Topology-Based Approach to Improve Vehicle-Level Electromagnetic Radiation
Electronics 2019, 8(3), 364; https://doi.org/10.3390/electronics8030364
Received: 27 January 2019 / Revised: 11 March 2019 / Accepted: 20 March 2019 / Published: 25 March 2019
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Abstract
The popularity of the electric vehicle (EV) brings us many challenges of electromagnetic compatibility (EMC). Automotive manufacturers are obliged to keep their products in compliance with EMC regulations. However, the EV is a complex system composed of various electromagnetic interferences (EMI), sensitive equipment [...] Read more.
The popularity of the electric vehicle (EV) brings us many challenges of electromagnetic compatibility (EMC). Automotive manufacturers are obliged to keep their products in compliance with EMC regulations. However, the EV is a complex system composed of various electromagnetic interferences (EMI), sensitive equipment and complicated coupling paths, which pose great challenges to the efficient troubleshooting of EMC problems. This paper presents an electromagnetic topology (EMT) based model and analysis method for vehicle-level EMI prediction, which decomposes an EV into multi-subsystems and transforms electromagnetic coupling paths into network parameters. This way, each part could be modelled separately with different technologies and vehicle-level EMI was able to be predicted by algebra calculations. The effectiveness of the proposed method was validated by comparing predicted vehicle-radiated emissions at low frequency with experimental results, and application to the troubleshooting of emission problems. Full article
(This article belongs to the Special Issue Industrial Applications of Power Electronics)
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Open AccessArticle
Modeling and Control of the Starter Motor and Start-Up Phase for Gas Turbines
Electronics 2019, 8(3), 363; https://doi.org/10.3390/electronics8030363
Received: 18 February 2019 / Revised: 14 March 2019 / Accepted: 19 March 2019 / Published: 25 March 2019
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Abstract
Improving the performance of industrial gas turbines has always been at the focus of attention of researchers and manufacturers. Nowadays, the operating environment of gas turbines has been transformed significantly respect to the very fast growth of renewable electricity generation where gas turbines [...] Read more.
Improving the performance of industrial gas turbines has always been at the focus of attention of researchers and manufacturers. Nowadays, the operating environment of gas turbines has been transformed significantly respect to the very fast growth of renewable electricity generation where gas turbines should provide a safe, reliable, fast, and flexible transient operation to support their renewable partners. So, having a reliable tools to predict the transient behavior of the gas turbine is becoming more and more important. Regarding the response time and flexibility, improving the turbine performance during the start-up phase is an important issue that should be taken into account by the turbine manufacturers. To analyze the turbine performance during the start-up phase and to implement novel ideas so as to improve its performance, modeling, and simulation of an industrial gas turbine during cold start-up phase is investigated this article using an integrated modular approach. During this phase, a complex mechatronic system comprised of an asynchronous AC motor (electric starter), static frequency converter drive, and gas turbine exists. The start-up phase happens in this manner: first, the clutch transfers the torque generated by the electric starter to the gas turbine so that the turbine reaches a specific speed (cranking stage). Next, the turbine spends some time at this speed (purging stage), after which the turbine speed decreases, sparking stage begins, and the turbine enters the warm start-up phase. It is, however, possible that the start-up process fails at an intermediate stage. Such unsuccessful start-ups can be caused by turbine vibrations, the increase in the gradients of exhaust gases, or issues with fuel spray nozzles. If, for any reason, the turbine cannot reach the self-sustained speed and the speed falls below a certain threshold, the clutch engages once again with the turbine shaft and the start-up process is repeated. Consequently, when modeling the start-up phase, we face discontinuities in performance and a system with variable structure owing to the existence of clutch. Modeling the start-up phase, which happens to exist in many different fields including electric and mechanical application, brings about problems in numerical solutions (such as algebraic loop). Accordingly, this study attempts to benefit from the bond graph approach (as a powerful physical modeling approach) to model such a mechatronic system. The results confirm the effectiveness of the proposed approach in detailed performance prediction of the gas turbine in start-up phase. Full article
(This article belongs to the Section Systems & Control Engineering)
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Open AccessArticle
LLC Resonant Converter for LEV (Light Electric Vehicle) Fast Chargers
Electronics 2019, 8(3), 362; https://doi.org/10.3390/electronics8030362
Received: 22 February 2019 / Revised: 18 March 2019 / Accepted: 22 March 2019 / Published: 25 March 2019
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Abstract
This paper presents a Light Electric Vehicle (LEV) fast charger with a Lithium-Ion Battery (LIB) and Super-Capacitor (SC). The LEV fast charger consists of an AC/DC rectifier and LLC (Inductor-Inductor-Capacitor) resonant Full bridge converter. The LLC resonant converter has high-efficiency and low switching [...] Read more.
This paper presents a Light Electric Vehicle (LEV) fast charger with a Lithium-Ion Battery (LIB) and Super-Capacitor (SC). The LEV fast charger consists of an AC/DC rectifier and LLC (Inductor-Inductor-Capacitor) resonant Full bridge converter. The LLC resonant converter has high-efficiency and low switching loss because of Zero Voltage Switching (ZVS). So, it is used widely in the industry. In general, the fast charger algorithm uses the Constant Current (CC) mode and Constant Voltage (CV). The CC mode starts at first and then the CV mode finishes. However, there is a big control value gap between the CC mode and CV mode. Therefore, when changing from CC to CV, the transient state occurs. To compensate for the transient state, we propose a new control algorithm. By means of this algorithm, we can achieve a higher level of safety and stability. The fast charger with LIB of 800 Wh and SC of 50 Wh is analyzed and verified, and we obtain a maximum efficiency of 96.4%. The discussions are validated using the LLC resonant full bridge converter prototype at the laboratory level. Full article
(This article belongs to the Section Electrical and Autonomous Vehicles)
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Open AccessArticle
The Improved Division-Less MT-Type Velocity Estimation Algorithm for Low-Cost FPGAs
Electronics 2019, 8(3), 361; https://doi.org/10.3390/electronics8030361
Received: 23 February 2019 / Revised: 20 March 2019 / Accepted: 21 March 2019 / Published: 25 March 2019
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Abstract
Advanced motion control applications require smooth and highly accurate high-bandwidth velocity feedback, which is usually provided by an incremental encoder. Furthermore, high sampling rates are also demanded in order to achieve cutting-edge system performance. Such control system performance with high accuracy can be [...] Read more.
Advanced motion control applications require smooth and highly accurate high-bandwidth velocity feedback, which is usually provided by an incremental encoder. Furthermore, high sampling rates are also demanded in order to achieve cutting-edge system performance. Such control system performance with high accuracy can be achieved easily by FPGA-based controllers. On the other hand, the well-known MT method for velocity estimation has been well proven in practice. However, its complexity, which is related to the inherent arithmetic division involved in the calculus part of the method, prevents its holistic implementation as a single-chip solution on small-size low-cost FPGAs that are suitable for practical optimized control systems. In order to overcome this obstacle, we proposed a division-less MT-type algorithm that consumes only minimal FPGA resources, which makes it proper for modern cost-optimized FPGAs. In this paper, we present new results. The recursive discrete algorithm has been further optimized, in order to improve the accuracy of the velocity estimation. The novel algorithm has also been implemented on the experimental FPGA board, and validated by practical experiments. The enhanced algorithm design resulted in improved practical performance. Full article
(This article belongs to the Section Systems & Control Engineering)
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Open AccessArticle
Reducing Unnecessary Alerts in Pedestrian Protection Systems Based on P2V Communications
Electronics 2019, 8(3), 360; https://doi.org/10.3390/electronics8030360
Received: 6 February 2019 / Revised: 13 March 2019 / Accepted: 21 March 2019 / Published: 25 March 2019
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Abstract
There are different proposals in the literature on how to protect pedestrians using warning systems to alert drivers of their presence. They can be based on onboard perception systems or wireless communications. The evaluation of these systems has been focused on testing their [...] Read more.
There are different proposals in the literature on how to protect pedestrians using warning systems to alert drivers of their presence. They can be based on onboard perception systems or wireless communications. The evaluation of these systems has been focused on testing their ability to detect pedestrians. A problem that has received much less attention is the possibility of generating too many alerts in the warning systems. In this paper, we propose and analyze four different algorithms to take the decision on generating alerts in a warning system that is based on direct wireless communications between vehicles and pedestrians. With the algorithms, we explore different strategies to reduce unnecessary alerts. The feasibility of the implementation of the algorithms was evaluated with a deployment using real equipment, and tests were carried out to verify their behavior in real scenarios. The ability of each algorithm to reduce unnecessary alerts was evaluated with realistic simulations in an urban scenario, using a traffic simulator with vehicular and pedestrian flows. The results show the importance of tackling the problem of driver overload in warning systems, and that it is not straightforward to predict the load of alerts generated by an algorithm in a large-scale deployment, in which there are multiple interactions between vehicles and pedestrians. Full article
(This article belongs to the Special Issue Smart, Connected and Efficient Transportation Systems)
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Open AccessFeature PaperArticle
IoToF: A Long-Reach Fully Passive Low-Rate Upstream PHY for IoT over Fiber
Electronics 2019, 8(3), 359; https://doi.org/10.3390/electronics8030359
Received: 13 February 2019 / Revised: 22 March 2019 / Accepted: 22 March 2019 / Published: 25 March 2019
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Abstract
Internet of things (IoT) devices heavily rely on wireless connectivity. There are intrinsic overlooked limitations such as reach, availability, security and safety vulnerabilities closely associated with wireless solutions. Wired connectivity is the alternative to tackle those issues, and optical fibers directly connecting IoT [...] Read more.
Internet of things (IoT) devices heavily rely on wireless connectivity. There are intrinsic overlooked limitations such as reach, availability, security and safety vulnerabilities closely associated with wireless solutions. Wired connectivity is the alternative to tackle those issues, and optical fibers directly connecting IoT devices could provide them unique features such as huge bandwidth, long reach, signal integrity and high security grade for the transmitted information. Nevertheless, it can be prohibitive for IoT devices which are power hungry and have costly electrical-to-optical conversions. In this paper, first, a niche is identified for IoT over fiber (IoToF) based on fully passive optical solutions for long reach upstream of low data rate optical connectivity over dark fibers. Then, we proposed, implemented and characterized a prototype physical connectivity (PHY) based on fiber Bragg grating (FBG) low-cost acousto-optic modulation at IoT devices and respective optical edge-filtering as wavelength discriminator at the receiver. Finally, we performed an experimental demonstration of upstream data communication based on simple M-ary frequency-shift keying (FSK), with baud rate of 300 bps transmitted over 30 km range. In terms of data rate and reach for niche applications, IoToF can outperform traditional wireless technologies, such as Sigfox or LoRa. IoToF will enable monitoring urban areas with scarce and polluted spectrum, industrial areas requiring intrinsic safety, and upstreaming data from IoT devices in remote locations with unfavorable wireless propagation but with dark fibers available. Full article
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Open AccessArticle
Sparse-Based Millimeter Wave Channel Estimation With Mutual Coupling Effect
Electronics 2019, 8(3), 358; https://doi.org/10.3390/electronics8030358
Received: 14 February 2019 / Revised: 14 March 2019 / Accepted: 19 March 2019 / Published: 25 March 2019
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Abstract
The imperfection of antenna array degrades the communication performance in the millimeter wave (mmWave) communication system. In this paper, the problem of channel estimation for the mmWave communication system is investigated, and the unknown mutual coupling (MC) effect between antennas is considered. By [...] Read more.
The imperfection of antenna array degrades the communication performance in the millimeter wave (mmWave) communication system. In this paper, the problem of channel estimation for the mmWave communication system is investigated, and the unknown mutual coupling (MC) effect between antennas is considered. By exploiting the channel sparsity in the spatial domain with mmWave frequency bands, the problem of channel estimation is converted into that of sparse reconstruction. The MC effect is described by a symmetric Toeplitz matrix, and the sparse-based mmWave system model with MC coefficients is formulated. Then, a two-stage method is proposed by estimating the sparse signals and MC coefficients iteratively. Simulation results show that the proposed method can significantly improve the channel estimation performance in the scenario with unknown MC effect and the estimation performance for both direction of arrival (DOA) and direction of departure (DoD) can be improved by about 8 dB by reducing the MC effect about 4 dB. Full article
(This article belongs to the Special Issue Millimeter Wave Technology in 5G)
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Open AccessArticle
Selecting Ultracapacitors for Smoothing Voltage Deviations in Local Grids Fed by Transformer with Tap-Changer and Distributed PV Facilities
Electronics 2019, 8(3), 357; https://doi.org/10.3390/electronics8030357
Received: 11 March 2019 / Revised: 14 March 2019 / Accepted: 21 March 2019 / Published: 24 March 2019
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Abstract
Widespread use of photovoltaic (PV) small and middle-power plants close or inside existing townships and villages may cause significant deviations of the grid voltage. Owing to the oscillation of solar irradiation and corresponding power flows these voltage instabilities can damage equipment and must [...] Read more.
Widespread use of photovoltaic (PV) small and middle-power plants close or inside existing townships and villages may cause significant deviations of the grid voltage. Owing to the oscillation of solar irradiation and corresponding power flows these voltage instabilities can damage equipment and must be prevented. Designated for the voltage regulation tap-changers in distribution transformers located in a significant distance of such settlements have a sluggish response time. As a possible answer for their delay is the smoothing energy of flows in PV power installation by intermittent capacitor low-pass filtering (LPF) located near those PV facilities. The application of ultracapacitors (UC) for LPF is remarkable due to their sustainability and relatively low costs of energy storage. The parameters selection of such appliances is a well-designed procedure for linear circuits. However, DC–AC inverters in PV facilities are represented by a power (instead of a voltage) source. As a result, the total circuit including such LPF becomes a non-linear and its transient process and consequently, its efficiency is difficult to assess requiring each time of development the UC storage an application complex numerical procedure. Engineers are usual to work with linear circuits that are describing fine by a time constant is designated as a multiplication of a capacitance times load equivalent resistance. In the case of PV DC–AC inverters, such an approach can be applied as well but a value of a time constant should be corrected. Considering a significant cost of UC storage, the non-optimal selection of a correcting coefficient may cause considerable loses. Submitted in the presented article is an original approximation procedure giving an efficiently approachable technique to select correcting coefficient for describing non-linear dynamic process by its linear analog. This way the development low-pass UC filtering in electrical systems with PV plants becomes more efficient and simpler task. Full article
(This article belongs to the Section Power Electronics)
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Open AccessArticle
Exponential Synchronization in Inertial Neural Networks with Time Delays
Electronics 2019, 8(3), 356; https://doi.org/10.3390/electronics8030356
Received: 17 February 2019 / Revised: 7 March 2019 / Accepted: 18 March 2019 / Published: 24 March 2019
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Abstract
In this paper, exponential synchronization for inertial neural networks with time delays is investigated. First, by introducing a directive Lyapunov functional, a sufficient condition is derived to ascertain the global exponential synchronization of the drive and response systems based on feedback control. Second, [...] Read more.
In this paper, exponential synchronization for inertial neural networks with time delays is investigated. First, by introducing a directive Lyapunov functional, a sufficient condition is derived to ascertain the global exponential synchronization of the drive and response systems based on feedback control. Second, by introducing a variable substitution, the second-order differential equation is transformed into a first-order differential equation. As such, a new Lyapunov functional is constructed to formulate a novel global exponential synchronization for the systems under study. The two obtained sufficient conditions complement each other and are suitable to be applied in different cases. Finally, two numerical examples are given to illustrated the effectiveness of the proposed theoretical results. Full article
(This article belongs to the Special Issue Recent Developments on Time-Delay Systems and Its Applications)
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Open AccessArticle
Active and Passive Haptic Perception of Shape: Passive Haptics Can Support Navigation
Electronics 2019, 8(3), 355; https://doi.org/10.3390/electronics8030355
Received: 19 February 2019 / Revised: 13 March 2019 / Accepted: 19 March 2019 / Published: 23 March 2019
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Abstract
Real-time haptic interactions occur under two exploration modes: active and passive. In this paper, we present a series of experiments that evaluate the main perceptual characteristics of both exploration modes. In particular, we focus on haptic shape recognition as it represents a fundamental [...] Read more.
Real-time haptic interactions occur under two exploration modes: active and passive. In this paper, we present a series of experiments that evaluate the main perceptual characteristics of both exploration modes. In particular, we focus on haptic shape recognition as it represents a fundamental task in many applications using haptic environments. The results of four experiments conducted with a group of 10 voluntary subjects show that the differences in motor activity between active and passive haptics ease the perception of surfaces for the first case and the perception of pathways for the latter. In addition, the guidance nature of passive haptics makes the pathway direction easy to recognize. This work shows that this last observation could find application in more challenging tasks such as navigation in space. Full article
(This article belongs to the Section Systems & Control Engineering)
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Open AccessArticle
On Spatial Smoothing for DOA Estimation of 2D Coherently Distributed Sources with Double Parallel Linear Arrays
Electronics 2019, 8(3), 354; https://doi.org/10.3390/electronics8030354
Received: 17 February 2019 / Revised: 19 March 2019 / Accepted: 20 March 2019 / Published: 23 March 2019
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Abstract
Considering coherently-distributed (CD) sources are correlated with each other, a two-dimensional (2D) coherent CD source model is proposed according to the characteristics of an underwater acoustic channel. Under the assumption of small angular spreads, rotational invariance relationships within and between subarrays of double [...] Read more.
Considering coherently-distributed (CD) sources are correlated with each other, a two-dimensional (2D) coherent CD source model is proposed according to the characteristics of an underwater acoustic channel. Under the assumption of small angular spreads, rotational invariance relationships within and between subarrays of double parallel linear arrays are derived. As the covariance matrix of spatial smoothing obtained from receive vectors expressed by rotational invariance relationships is proven to be full rank, decoherence of the 2D coherent CD source is proposed by spatial smoothing of the double parallel linear arrays. A propagator method base on spatial smoothing (SS-PM) and estimation of signal parameters via rotational invariance techniques (ESPRIT) base on spatial smoothing (SS-ESPRIT) method established by covariance matrix of spatial smoothing are proposed. The proposed methods do not require peak-searching, angles matching and information of deterministic angular signal distribution function. Simulations are conducted to verify the effectiveness of the proposed methods. Full article
(This article belongs to the Special Issue Recent Advances in Array Antenna and Array Signal Processing)
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Open AccessArticle
Supervised Single Channel Speech Enhancement Based on Dual-Tree Complex Wavelet Transforms and Nonnegative Matrix Factorization Using the Joint Learning Process and Subband Smooth Ratio Mask
Electronics 2019, 8(3), 353; https://doi.org/10.3390/electronics8030353
Received: 15 February 2019 / Revised: 8 March 2019 / Accepted: 21 March 2019 / Published: 22 March 2019
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Abstract
In this paper, we propose a novel speech enhancement method based on dual-tree complex wavelet transforms (DTCWT) and nonnegative matrix factorization (NMF) that exploits the subband smooth ratio mask (ssRM) through a joint learning process. The discrete wavelet packet transform (DWPT) suffers the [...] Read more.
In this paper, we propose a novel speech enhancement method based on dual-tree complex wavelet transforms (DTCWT) and nonnegative matrix factorization (NMF) that exploits the subband smooth ratio mask (ssRM) through a joint learning process. The discrete wavelet packet transform (DWPT) suffers the absence of shift invariance, due to downsampling after the filtering process, resulting in a reconstructed signal with significant noise. The redundant stationary wavelet transform (SWT) can solve this shift invariance problem. In this respect, we use efficient DTCWT with a shift invariance property and limited redundancy and calculate the ratio masks (RMs) between the clean training speech and noisy speech (i.e., training noise mixed with clean speech). We also compute RMs between the noise and noisy speech and then learn both RMs with their corresponding clean training clean speech and noise. The auto-regressive moving average (ARMA) filtering process is applied before NMF in previously generated matrices for smooth decomposition. An ssRM is proposed to exploit the advantage of the joint use of the standard ratio mask (sRM) and square root ratio mask (srRM). In short, the DTCWT produces a set of subband signals employing the time-domain signal. Subsequently, the framing scheme is applied to each subband signal to form matrices and calculates the RMs before concatenation with the previously generated matrices. The ARMA filter is implemented in the nonnegative matrix, which is formed by considering the absolute value. Through ssRM, speech components are detected using NMF in each newly formed matrix. Finally, the enhanced speech signal is obtained via the inverse DTCWT (IDTCWT). The performances are evaluated by considering an IEEE corpus, the GRID audio-visual corpus, and different types of noises. The proposed approach significantly improves objective speech quality and intelligibility and outperforms the conventional STFT-NMF, DWPT-NMF, and DNN-IRM methods. Full article
(This article belongs to the Section Circuit and Signal Processing)
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Open AccessArticle
Power Balance Method using Coupled Shunt Inductor and Multiple-Input Transformer for ISOP LLC Converter
Electronics 2019, 8(3), 352; https://doi.org/10.3390/electronics8030352
Received: 25 February 2019 / Revised: 18 March 2019 / Accepted: 20 March 2019 / Published: 22 March 2019
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Abstract
High-capacity power-supply systems using a large input voltage typically improve efficiency and can be miniaturized by dividing the input voltage into multiple small voltages, thereby minimizing the stress on the switching element and thus materializing a fast switching function. When a large input [...] Read more.
High-capacity power-supply systems using a large input voltage typically improve efficiency and can be miniaturized by dividing the input voltage into multiple small voltages, thereby minimizing the stress on the switching element and thus materializing a fast switching function. When a large input voltage is divided into small voltages in series through a DC link capacitor, power is supplied to each converter and the power of each LLC (Inductor-Inductor-Capacitor) converter can be divided and converted. However, such LLC converters, which are configured by the division of the input voltage, have power imbalance due to the parameter variation between active and passive elements of the power board, which results in an increase in the stress and heat of a particular element. As this problem of power balance necessitates a design for securing a power margin and as the heated element increases its volume, the efficiency and reliability of the LLC converter are degenerated. Accordingly, this study attempted to solve the problem of the power imbalance of LLC converters at each level using a coupled shunt inductor and multiple-input transformers sharing magnetic coupling. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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Open AccessArticle
Heterogeneous Integration of GaN and BCD Technologies
Electronics 2019, 8(3), 351; https://doi.org/10.3390/electronics8030351
Received: 7 January 2019 / Revised: 12 March 2019 / Accepted: 18 March 2019 / Published: 22 March 2019
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Abstract
Light-emitting diodes (LEDs) are solid-state devices that are highly energy efficient, fast switching, have a small form factor, and can emit a specific wavelength of light. The ability to precisely control the wavelength of light emitted with the fabrication process enables LEDs to [...] Read more.
Light-emitting diodes (LEDs) are solid-state devices that are highly energy efficient, fast switching, have a small form factor, and can emit a specific wavelength of light. The ability to precisely control the wavelength of light emitted with the fabrication process enables LEDs to not only provide illumination, but also find applications in biology and life science research. To enable the new generation of LED devices, methods to improve the energy efficiency for possible battery operation and integration level for miniaturized lighting devices should be explored. This paper presents the first case of the heterogeneous integration of gallium nitride (GaN) power devices, both GaN LED and GaN transistor, with bipolar CMOS DMOS (BCD) circuits that can achieve this. To validate this concept, an LED driver was designed, implemented and verified experimentally. It features an output electrical power of 1.36 W and compact size of 2.4 × 4.4 mm2. The designed fully integrated LED lighting device emits visible light at a wavelength of approximately 454 nm and can therefore be adopted for biology research and life science applications. Full article
(This article belongs to the Special Issue Latest Developments in LED Drivers)
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Open AccessArticle
A 2.5 Gbps, 10-Lane, Low-Power, LVDS Transceiver in 28 nm CMOS Technology
Electronics 2019, 8(3), 350; https://doi.org/10.3390/electronics8030350
Received: 16 January 2019 / Revised: 7 March 2019 / Accepted: 16 March 2019 / Published: 22 March 2019
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Abstract
This paper presents a 2.5 Gbps 10-lane low-power low voltage differential signaling (LVDS) transceiver for a high-speed serial interface. In the transmitter, a complementary MOS H-bridge output driver with a common mode feedback (CMFB) circuit was used to achieve a stipulated common mode [...] Read more.
This paper presents a 2.5 Gbps 10-lane low-power low voltage differential signaling (LVDS) transceiver for a high-speed serial interface. In the transmitter, a complementary MOS H-bridge output driver with a common mode feedback (CMFB) circuit was used to achieve a stipulated common mode voltage over process, voltage and temperature (PVT) variations. The receiver was composed of a pre-stage common mode voltage shifter and a rail-to-rail comparator. The common mode voltage shifter with an error amplifier shifted the common mode voltage of the input signal to the required range, thereby the following rail-to-rail comparator obtained the maximum transconductance to recover the signal. The chip was fabricated using SMIC 28 nm CMOS technology, and had an area of 1.46 mm2. The measured results showed that the output swing of the transmitter was around 350 mV, with a root-mean-square (RMS) jitter of 3.65 [email protected] Gbps, and the power consumption of each lane was 16.51 mW under a 1.8 V power supply. Full article
(This article belongs to the Special Issue Signal Processing and Analysis of Electrical Circuit)
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Open AccessFeature PaperArticle
K/Ka-Band Very High Data-Rate Receivers: A Viable Solution for Future Moon Exploration Missions
Electronics 2019, 8(3), 349; https://doi.org/10.3390/electronics8030349
Received: 16 January 2019 / Revised: 5 March 2019 / Accepted: 15 March 2019 / Published: 22 March 2019
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Abstract
This paper presents a feasibility study for a very high data rate receiver operating in the K/Ka-band suitable to future Moon exploration missions. The receiver specifications are outlined starting from the mission scenario and from a careful system analysis. The designed architecture uses [...] Read more.
This paper presents a feasibility study for a very high data rate receiver operating in the K/Ka-band suitable to future Moon exploration missions. The receiver specifications are outlined starting from the mission scenario and from a careful system analysis. The designed architecture uses a low noise front-end to down-convert the incoming K/Ka-band signal into a 3.7 GHz intermediate frequency (IF). For maximum flexibility, a software defined radio (SDR) is adopted for the I/Q demodulation and for the analog to digital conversion (ADC). The decoding operations and the data interface are carried out by a processor based on field programmable gate array (FPGA) circuits. To experimentally verify the above concepts, a preliminary front-end breadboard is implemented, operating between 27.5 and 30 GHz. The breadboard, which uses components off the shelf (COTS) and evaluation boards (EVBs), is characterized by a 46 dB gain, a 3.4 dB noise figure and a 37 dBm input-referred 1 dB compression point. Finally, a 40 Msym / s quadrature phase shift keying (QPSK) signal is demodulated by means of a commercially available SDR, demonstrating the above concept. The importance of these results is that they have been obtained exploiting a class of miniaturized and low cost microwave integrated circuits currently available on the market, opening the way to a dense communication infrastructure on cislunar space. Full article
(This article belongs to the Section Microwave and Wireless Communications)
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Open AccessArticle
A Dual-Band Dual-Antenna System with Common-Metal Rim for Smartphone Applications
Electronics 2019, 8(3), 348; https://doi.org/10.3390/electronics8030348
Received: 25 January 2019 / Revised: 12 March 2019 / Accepted: 13 March 2019 / Published: 22 March 2019
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Abstract
A dual-antenna system operating at WIFI and GPS bands is proposed for common-metal rimmed smartphones applications. This dual-antenna system, which is horizontally placed on a ground plane of 4.5 × 75 mm2, consists of two folded inverted-F antennas (IFAs) sharing the [...] Read more.
A dual-antenna system operating at WIFI and GPS bands is proposed for common-metal rimmed smartphones applications. This dual-antenna system, which is horizontally placed on a ground plane of 4.5 × 75 mm2, consists of two folded inverted-F antennas (IFAs) sharing the same metal rim. Each IFA contains part of the metal radiating arm, and both IFAs own approximately one-quarter free space wavelengths at 2.44 GHz. A matching network is embedded in the feeding line of the left IFA to provide a resonant frequency at 1.575 GHz. By adjusting the positions of the shorting branch and feeding line, good impedance matching is obtained. Two gaps in the metal frame and a center shorting branch between two IFAs are adopted to improve the isolation. The isolations of better than 22 dB and 19 dB in GPS and WIFI bands are attained, respectively. The proposed antenna is fabricated, and the measured results regarding S-parameters, radiation efficiency, gain, as well as diversity performances are presented. Full article
(This article belongs to the Section Microwave and Wireless Communications)
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Open AccessArticle
Wideband Printed Wide-Slot Antenna with Fork-Shaped Stub
Electronics 2019, 8(3), 347; https://doi.org/10.3390/electronics8030347
Received: 1 March 2019 / Revised: 14 March 2019 / Accepted: 18 March 2019 / Published: 21 March 2019
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Abstract
This paper presents a multiple-resonance technique that sought to achieve a wide bandwidth for printed wide-slot antennas with fork-shaped stubs. By properly appending an extra fork-shaped stub onto the main fork-shaped stub, the impedance bandwidth was able to be clearly broadened. To validate [...] Read more.
This paper presents a multiple-resonance technique that sought to achieve a wide bandwidth for printed wide-slot antennas with fork-shaped stubs. By properly appending an extra fork-shaped stub onto the main fork-shaped stub, the impedance bandwidth was able to be clearly broadened. To validate this technique, two designs where the extra stubs were added at different positions of the main stub were constructed. The measured impedance bandwidths of the proposed antennas reached 148.6% (0.9–6.1 GHz) for S11 < −10 dB, indicating a 17.9% wider bandwidth than that of the normal antenna (0.9–4.3 GHz). Moreover, a stable radiation pattern was observed within the operating frequency range. The proposed antennas were confirmed to be much-improved candidates for applications in various wireless communication systems. Full article
(This article belongs to the Section Microwave and Wireless Communications)
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Open AccessArticle
Parametric Design of a Class of Full-Band Waveguide Differential Phase Shifters
Electronics 2019, 8(3), 346; https://doi.org/10.3390/electronics8030346
Received: 5 March 2019 / Revised: 18 March 2019 / Accepted: 19 March 2019 / Published: 21 March 2019
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Abstract
Differential phase shifters are common circuits in communication systems where a fixed phase difference between two points within the circuit is required. Among the available technologies, waveguide phase shifters are preferred for applications such as antenna feed or beam-forming networks. Typical designs in [...] Read more.
Differential phase shifters are common circuits in communication systems where a fixed phase difference between two points within the circuit is required. Among the available technologies, waveguide phase shifters are preferred for applications such as antenna feed or beam-forming networks. Typical designs in the literature are devoted to specific phase delays such as 90° or 180°, but any phase shift might be required, and therefore a design procedure resulting in mechanically-related parameter fitting equations for any arbitrary phase difference would be advantageous. This paper presents a parametric design of full-band (40% relative bandwidth) waveguide differential phase shifters, providing polynomial equations for all design parameters in order to obtain arbitrary phase shifts between standard rectangular waveguides with equal physical lengths. The phase shift is achieved through the use of a multi-step ridge section together with a single width-step in the shift line. The proposed design procedure results in differential phase shifters with 25 dB of return loss and minimal physical length for any phase shift between 0° and 180°. To validate this parametric design process, two exemplary differential phase shifters with 30° and 140° phase shifts were measured, showing very good agreement with the simulated results. Full article
(This article belongs to the Section Microwave and Wireless Communications)
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Open AccessArticle
Semiactive Hybrid Energy Management System: A Solution for Electric Wheelchairs
Electronics 2019, 8(3), 345; https://doi.org/10.3390/electronics8030345
Received: 21 February 2019 / Revised: 15 March 2019 / Accepted: 20 March 2019 / Published: 21 March 2019
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Abstract
Many disabled people use electric wheelchairs (EWs) in their daily lives. EWs take a considerable amount of time to charge and are less efficient in high-power-demand situations. This paper addresses these two problems using a semiactive hybrid energy storage system (SA-HESS) with a [...] Read more.
Many disabled people use electric wheelchairs (EWs) in their daily lives. EWs take a considerable amount of time to charge and are less efficient in high-power-demand situations. This paper addresses these two problems using a semiactive hybrid energy storage system (SA-HESS) with a smart energy management system (SEMS). The SA-HESS contained a lithium-ion battery (LIB) and supercapacitor (SC) connected to a DC bus via a bidirectional DC–DC converter. The first task of the proposed SEMS was to charge the SA-HESS rapidly using a fuzzy-logic-controlled charging system. The second task was to reduce the stress of the LIB. The proposed SEMS divided the discharging operation into starting-, normal-, medium-, and high-power currents. The LIB was used in normal conditions, while the SC was mostly utilized during medium-power conditions, such as starting and uphill climbing of the EW. The conjunction of LIB and SC was employed to meet the high-power demand for smooth and reliable operation. A prototype was designed to validate the proposed methodology, and a comparison of the passive hybrid energy management system (P-HESS) and SA-HESS was performed under different driving tracks and loading conditions. The experimental results showed that the proposed system required less charging time and effectively utilized the power of the SC compared with P-HESS. Full article
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Open AccessArticle
Hybrid Inference Based Scheduling Mechanism for Efficient Real Time Task and Resource Management in Smart Cars for Safe Driving
Electronics 2019, 8(3), 344; https://doi.org/10.3390/electronics8030344
Received: 4 March 2019 / Revised: 16 March 2019 / Accepted: 18 March 2019 / Published: 21 March 2019
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Abstract
In recent years, the focus of the smart transportation industry has been shifting towards the research and development of smart cars with autonomous control. Smart cars are considered to be a smart investment, as they promote safe driving while focusing on an alternate [...] Read more.
In recent years, the focus of the smart transportation industry has been shifting towards the research and development of smart cars with autonomous control. Smart cars are considered to be a smart investment, as they promote safe driving while focusing on an alternate transportation fuel resource, making them eco-friendly too. Safe driving is one of the crucial concerns in autonomous smart cars. The major issue for the better provision of safe driving is real time tasks management and an efficient inference system for autonomous control. Real time task management is of huge significance in smart cars control systems. An optimal control system consists of a knowledge base and a control unit; where the knowledge base contains the data and thresholds for rules and the control unit contains the functionality for smart vehicle autonomous control. In this work, we propose a hybrid of an inference engine and a real time task scheduler for an efficient task management and resource consumption. Our proposed hybrid inference engine and task scheduler mechanism provides an efficient way of controlling smart cars in different scenarios such as heavy rainfall, obstacle detection, driver’s focus diversion etc., while ensuring the practices of safe driving. For the performance analysis of our proposed hybrid inference based scheduling mechanism, we have simulated a non-hybrid version with the same system constraints and a basic implementation of inference engine. For performance evaluation, CPU time utilization, tasks’ missing rate, average response time are used as performance metrics. Full article
(This article belongs to the Special Issue Real Time Dependable Distributed Control Systems)
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Open AccessArticle
Compact UV LED Lamp with Low Heat Emissions for Biological Research Applications
Electronics 2019, 8(3), 343; https://doi.org/10.3390/electronics8030343
Received: 27 February 2019 / Revised: 18 March 2019 / Accepted: 19 March 2019 / Published: 21 March 2019
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Abstract
Much biomedical research focuses on the effects of UV light on human cells. UV light sources are a prerequisite for such research. This paper presents the design and achieved performance of a UVA (Ultraviolet A: 320–400 nm) and a UVB (Ultraviolet B: 290–320 [...] Read more.
Much biomedical research focuses on the effects of UV light on human cells. UV light sources are a prerequisite for such research. This paper presents the design and achieved performance of a UVA (Ultraviolet A: 320–400 nm) and a UVB (Ultraviolet B: 290–320 nm) LED-based lamp suitable for use in bioassays, as well as inside an incubator. Numerical simulations were used to optimise the number, layout and output power of LEDs to achieve good irradiance homogeneity while maintaining low costs. Design was optimised for the efficient transfer of generated heat away from the irradiated samples through the heatsink at the back of the lamps. The average irradiance of the target surface by the UVA lamp was 70.1 W/m2 with a maximum deviation of 4.9%, and the average irradiance by the UVB lamp was 3.1 W/m2 with a maximum deviation of 4.8%. With the UVA and UVB lamps, the temperature of samples undergoing irradiation in the incubator rises from 37 to 42 °C within 40 and 67 min, respectively. This by far exceeds the required UV irradiation time in most cases. Tests on Jurkat and HEK-293 cell cultures confirmed the suitability of our lamps for biomedical research. Full article
(This article belongs to the Section Microelectronics and Optoelectronics)
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Open AccessArticle
Estimation of Optimal Operating Frequency for Wireless EV Charging System under Misalignment
Electronics 2019, 8(3), 342; https://doi.org/10.3390/electronics8030342
Received: 25 December 2018 / Revised: 14 March 2019 / Accepted: 15 March 2019 / Published: 21 March 2019
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Abstract
Wireless charging of electric vehicles is achieved by a resonance-enhanced inductive power transfer technique. In this paper, a new method is proposed for the estimation of the operating frequency under the contingency of misalignment of the pickup coil. Analytically, the mutual inductance between [...] Read more.
Wireless charging of electric vehicles is achieved by a resonance-enhanced inductive power transfer technique. In this paper, a new method is proposed for the estimation of the operating frequency under the contingency of misalignment of the pickup coil. Analytically, the mutual inductance between the primary and secondary coils is represented in terms of their vertical and horizontal displacements, using Neumann’s approximation formula. The operating frequency of the high-frequency inverter corresponds to the resonance condition, a function of the mutual inductance, which is decided by the coil misalignment. The obtained relations are corroborated with studies of simulations. The proposed method is validated by numerical simulation. A 1 kW experimental prototype is designed and tested. Experimental results corroborate the notion about the analytical expression. Full article
(This article belongs to the Section Electrical and Autonomous Vehicles)
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Open AccessArticle
Raspberry Pi-Based Low-Cost Connected Device for Assessing Road Surface Friction
Electronics 2019, 8(3), 341; https://doi.org/10.3390/electronics8030341
Received: 8 January 2019 / Revised: 14 March 2019 / Accepted: 15 March 2019 / Published: 20 March 2019
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Abstract
Measuring friction between the tyres of a vehicle and the road, often and on as many locations on the road network as possible, can be a valuable tool for ensuring traffic safety. Rather than by using specialised equipment for sequential measurements, this can [...] Read more.
Measuring friction between the tyres of a vehicle and the road, often and on as many locations on the road network as possible, can be a valuable tool for ensuring traffic safety. Rather than by using specialised equipment for sequential measurements, this can be achieved by using several low-cost measuring devices on vehicles that travel on the road network as part of their daily assignments. The presented work proves the hypothesis that a low cost measuring device can be built and can provide measurement results comparable to those obtained from expensive specialised measuring devices. As a proof of concept, two copies of a prototype device, based on the Raspberry Pi single-board computer, have been developed, built and tested. They use accelerometers to measure vehicle braking deceleration and include a global positioning receiver for obtaining the geolocation of each test. They run custom-developed data acquisition software on the Linux operating system and provide automatic measurement data transfer to a server. The operation is controlled by an intuitive user interface consisting of two illuminated physical pushbuttons. The results show that for braking tests and friction coefficient measurements the developed prototypes compare favourably to a widely used professional vehicle performance computer. Full article
(This article belongs to the Special Issue Smart, Connected and Efficient Transportation Systems)
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Open AccessArticle
Transmission Capacity Characterization in VANETs with Enhanced Distributed Channel Access
Electronics 2019, 8(3), 340; https://doi.org/10.3390/electronics8030340
Received: 14 January 2019 / Revised: 15 March 2019 / Accepted: 15 March 2019 / Published: 20 March 2019
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Abstract
The traditional research on the capacity of the Vehicular Ad Hoc Networks (VANETs) mainly lacks realistic models mimicking the behaviors of vehicles and the MAC protocol applied by IEEE 802.11p. To overcome these drawbacks, in this paper, the network transmission capacity analysis for [...] Read more.
The traditional research on the capacity of the Vehicular Ad Hoc Networks (VANETs) mainly lacks realistic models mimicking the behaviors of vehicles and the MAC protocol applied by IEEE 802.11p. To overcome these drawbacks, in this paper, the network transmission capacity analysis for VANETs is carried out from the perspective of the spatial geometric relationship among different vehicles. Specifically, the transmission scheme in this system is set to mimic enhanced distributed channel access (EDCA) protocol, in which the division of priorities is taken into account both the data type and the transmission distance requirement. Meanwhile, the moving pattern of vehicles is described as the classic car-following model according to realistic characteristics of VANET, and the propagation channel is modeled as a combination of large-scale path-loss and small-scale Rayleigh fading. Based on this model, the transmission opportunity under EDCA protocol is quantified and compared with that of CSMA/CA, and then the outage probability is calculated under the worst interfered scenario. Finally, the transmission capacity is thereby calculated and verified by the simulation results. Full article
(This article belongs to the Special Issue Vehicular Networks and Communications)
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