bluuebunny/crossref_metadata_2025 huggingface dataset:
Non‐invasive reconstruction of dynamic myocardial transmembrane potential with graph‐based total variation constraints
Authors: Xie Shuting , Wang Linwei , Zhang Heye , Liu Huafeng
Published: October 2019

Non‐invasive reconstruction of electrophysiological activity in the heart is of great significance for clinical disease prevention and surgical treatment. The distribution of transmembrane potential (TMP) in three‐dimensional myocardium can help us diagnose heart diseases such as myocardial ischemia and ectopic pacing. However, the problem of solving TMP is ill‐posed, and appropriate constraints need to be added. The existing state‐of‐art method total variation minimisation only takes advantage of the local similarity in space, which has the problem of over‐smoothing, and fails to take into account the relationship among frames in the dynamic TMP sequence. In this work, the authors introduce a novel regularisation method called graph‐based total variation to make up for the above shortcomings. The graph structure takes the TMP value of a time sequence on each heart node as the criterion to establish the similarity relationship among the heart. Two sets of phantom experiments were set to verify the superiority of the proposed method over the traditional constraints: infarct scar reconstruction and activation wavefront reconstruction. In addition, experiments with ten real premature ventricular contractions patient data were used to demonstrate the accuracy of the authors’ method in clinical applications.
Heat dissipation characteristics of anode saturable reactors with high thermal conductivity epoxy resin used for ultra‐high‐voltage direct current converter valves
Authors: Wei Yang , WeiJiang Chen , Yuan Zhou , Chong Zhang , Zhuo Zhang , Xin Chen , YuShun Zhao , XingMing Bian
Published: October 2019

A saturable reactor is one of the important components of converter valves in high‐voltage direct current transmission systems. With the ever‐increasing capacities of converter valves, the heat losses generated by saturable reactors are also increasing. Thus, a thermal–fluid mechanics coupled heat dissipation model for saturable reactors is proposed. In order to study the factors affecting the thermal dissipation in the saturable reactor, the epoxy resin insulating layers with different thermal conductivity were considered in this work. The simulation results showed that the hot spots in the saturable reactor are on the iron core and close to the pipe inlet that most of the generated heat can be extracted by a cooling pipe and that the effect of heat dissipation can be improved by raising the thermal conductivity of the epoxy resin. The thermal conductivities of the epoxy resin used in the two reactors were 0.8 and 1.2 W/mK, respectively. The time dependence of the iron core temperature was in accordance with the simulation results and the maximum temperatures of the saturable reactor were also consistent with the simulation results. By increasing the thermal conductivity of the epoxy insulation layer, the temperature of the iron core could be significantly reduced.
Ensuring equal outage performance for down‐link secondary users in full/half duplex cognitive NOMA systems
Authors: Aswathi V , Babu A V
Published: October 2019

This study considers an underlay cognitive radio (CR) system, where the secondary network employs cooperative non‐orthogonal multiple access (NOMA) to transfer information for downlink secondary users (SUs). Here the near user is enabled to act as a full duplex/half duplex (FD/HD) decode‐and‐forward (DF) relay for the far user. We derive analytical expressions for the outage probabilities experienced by the SUs in the considered FD/HD – CR‐NOMA network. The maximum transmit power constraint of the secondary nodes and the tolerable interference power constraints at the primary receiver are considered for the analysis. We provide numerical and simulation results to identify the impact of key system parameters on the outage performance of SUs. Further, we provide insights on the selection of key system parameters such as NOMA power allocation coefficient for ensuring that both the SUs experience equal outage performance. Finally, we derive an analytical expression for the system outage probability of the FD‐CR‐NOMA network. We determine the optimal power allocation (OPA) factor at the secondary transmitter that minimises the system outage probability. We establish that OPA can reduce the system outage significantly as compared to the default choice of power allocation factor. The analytical results are validated by extensive simulation studies.
Non‐geometrical stochastic model for non‐stationary wideband vehicular communication channels
Authors: Huang Ziwei , Zhang Xi , Cheng Xiang
Published: October 2019

In this study, the authors propose a new non‐geometrical stochastic model (NGSM) for non‐stationary wideband vehicular communication channels. To include the line‐of‐sight component, the proposed model first generates a non‐uniformly distributed tap phase, which can be obtained from the widely used uniformly distributed tap phase. Moreover, the proposed model can practically experience variable types of Doppler spectra for different delays by modifying the autocorrelation function used in the existing NGSM. In consideration of the non‐stationarity in the frequency domain of vehicular communication channels, the authors further consider that the amplitude and phase of different taps are correlated. To evaluate the performance of the proposed model, they derive some significant statistical properties in terms of the power delay profile, tap correlation coefficient matrix and Doppler power spectral density. It is demonstrated that in comparison with the existing NGSMs, the proposed model possesses the ability to better mimic characteristics of real vehicular channels. Finally, the excellent agreement is achieved between the simulation results and the corresponding measured data, confirming the accuracy of the proposed model.
Design and application of distributed co‐simulation platform for cyber physical power system based on the concepts of software bus and middleware
Authors: Zhao Lili , Ni Ming , Tong Heqin , Li Yuecen
Published: October 2019

Due to the complexity and interdependencies in the cyber‐physical power system, the co‐simulation is a good choice to validate the research and model of the smart grid with existing simulators in different domains. A novel co‐simulation platform, LIghtweight Co‐simulation of Power and Information and communication technology (ICT) systems for performance Evaluation of smart grid (LICPIE), is developed based on the concepts of software bus and middleware in the study. Compared with other co‐simulation platforms, the advantage of LICPIE is that it has a distributed architecture including sub‐simulators; management layer based on software bus and middleware, and defines its own standard interface specialist embedded in middleware. The standard interface specialist relieves the limitation of the interface types supported by sub‐simulators, which makes the LICPIE more extendible and has wide scope of applications. What's more, benefiting from the distributed architecture and the standard interface specialist, sub‐simulators' heterogeneity is avoided and multi‐domain simulators could be combined freely according to simulation requirements. An exemplary application is used to describe how sub‐simulators with different types of interfaces hang themselves on LICPIE. At last, two co‐simulation applications with different combinations of power and ICT systems' simulators show the effectiveness, flexibility and extendibility of the LICPIE.
FreeD∗: a mechanism for finding a short and collision free path
Authors: Al‐darwbi Mohammed , Baroudi Uthman
Published: October 2019

Path planning is extensively used in different fields not only in robotics but also in games, manufacturing, auto‐motive applications, and so on. Robot path planning is one of the major research issues in the area of autonomous mobile robot. The critical step in path planning problem is to find the shortest path from the start position to a defined goal position through a known, unknown, or partially known environment. Hazardous events that may devastate some parts of the intended area convert those areas to untraversable areas. These events introduce topological constraints for the robot motion because of information discrepancy about the environment before and after the damage. In this study, the authors propose a novel method, FreeD∗, to find the shortest path by exploiting the benefits of D∗, Dijkstra, and artificial potential field (APF) algorithms. The generated path using D∗ is optimised using Dijkstra by combining D∗ sub‐paths into a single diagonal path if there is no known obstacle between them. Then, APF is used in unknown obstacle avoidance. The simulation results using Webots simulator demonstrate the effectiveness of FreeD∗ in avoiding unknown obstacles with shortest path.
Differential flatness theory‐based approach to the control of gas‐turbine electric power generation units
Authors: Rigatos Gerasimos , Zervos Nikolaos , Busawon Krishna , Siano Pierluigi , Abbaszadeh Masoud
Published: October 2019

A differential flatness theory‐based control and state estimation method has been developed for electric power units that consist of synchronous generators connected to gas turbines. The dynamic model of the power unit satisfies the properties of differential flatness and this allows for its transformation into an input–output linearized form. Moreover, it is shown that the state‐space description of the power system can be written in the canonical (Brunvsky) form. Using this, a solution for the power unit's control and state estimation problem is given. First, a stabilizing feedback controller is designed. Moreover, with the use of differential flatness theory‐based implementation of the Kalman Filter it becomes possible to solve the state and disturbances estimation problem of the gas‐turbine power unit. The considered filtering method, under the name of Derivative‐free nonlinear Kalman Filter, consists of application of the Kalman Filter's recursion on the linearized equivalent model of the power system, and of an inverse transformation that allows for computing estimates for the state variables of the initial nonlinear system. By redesigning the aforementioned Kalman Filter as a disturbance observer one can also identify and annihilate in real time exogenous perturbations.
Recovering node parameters and topologies of uncertain non‐linearly coupled complex networks
Authors: Wang Xiong , Gu Haibo , Chen Yao , Lü Jinhu
Published: October 2019

Node dynamics and network topologies play vital roles in determining dynamical behaviours and features of complex networks. Thus it is of great theoretical significance and practical value to identify the node parameters and topologies of uncertain complex networks. This study presents adaptive anticipatory synchronisation‐based approaches to identify the unknown node parameters and topologies of uncertain non‐linearly coupled complex networks perturbed by stochastic noise. Moreover, during the identification process, the authors proposed scheme guarantees anticipatory synchronisation between the uncertain drive and constructed response network simultaneously. In particular, their methods can be used to recover node parameters and topologies of complex networks in several special cases, such as cases without node delay or coupling delay. Furthermore, numerical simulations are provided to verify the applicability and effectiveness of their methods for recovering node parameters and topologies of uncertain non‐linearly coupled complex networks.
Online model‐free reinforcement learning for the automatic control of a flexible wing aircraft
Authors: Abouheaf Mohammed , Gueaieb Wail , Lewis Frank
Published: October 2019

The control problem of the flexible wing aircraft is challenging due to the prevailing high non‐linear deformations in the flexible wing system. This urged for new control mechanisms that are robust to the real‐time variations in the wing's aerodynamics. An online control mechanism based on a value iteration reinforcement learning process is developed for flexible wing aerial structures. It employs a model‐free control policy framework and a guaranteed convergent adaptive learning architecture to solve the system's Bellman optimality equation. A Riccati equation is derived and shown to be equivalent to solving the underlying Bellman equation. The online reinforcement learning solution is implemented using means of an adaptive‐critic mechanism. The controller is proven to be asymptotically stable in the Lyapunov sense. It is assessed through computer simulations and its superior performance is demonstrated in two scenarios under different operating conditions.
PDE modelling and vibration control of overhead crane bridge with unknown control directions and parametric uncertainties
Authors: Xing Xueyan , Liu Jinkun
Published: October 2019

In this study, problems of the partial differential equation (PDE) modelling and vibration control design are first resolved for an overhead crane bridge system, which is regarded as a Timoshenko beam with an attached rigid body. With the established infinite‐dimensional PDE model, a Nussbaum function‐based adaptive control approach is developed in order to settle out parametric uncertainties of the system with unknown control directions. Under the proposed control method, states of the overhead crane bridge are globally bounded and finally converge to an adjustable region of zero. The stability of the closed‐loop overhead crane bridge system is analysed by employing Lyapunov's direct method. The effectiveness of the developed control strategy is verified through the simulation results.
Delay‐dependent stability of non‐linear hybrid stochastic functional differential equations
Authors: Song Ruili , Wang Bo , Zhu Quanxin
Published: October 2019

This study investigates delay‐dependent stability of a class of highly non‐linear stochastic functional differential equations with Markovian switching. Some novel boundedness and stability criteria are first established, including stability in , asymptotic stability in and almost surely asymptotic stability, based on Lyapunov functions and generalised Itô formula. Concretely, the authors generalise and improve the existing results to the hybrid stochastic functional differential equations case. An example is presented to illustrate the effectiveness of the obtained results.
Electric drive systems with long feeder cables
Authors: Xie Patrick , Vakil Gaurang , Gerada Chris
Published: October 2019

Electric drive systems with long feeder cables connecting inverter and machine are used for oil exploration, mining, remote operated vehicles, industrial, and aerospace applications. Though this topology has the advantage of providing a better operating environment and easier serviceability for the inverter if the machine is located in an inhospitable and inaccessible environment, it does come with its own drawbacks. Steep‐fronted switched voltages and cable‐machine surge impedance mismatch can lead to high‐amplitude, high‐frequency (HF) voltage oscillations along the feeder cable, at the machine terminals, and throughout the machine's stator windings. These effects can cause high‐electromagnetic interference, corona discharge, insulation failure in the feeder cable and machine's stator windings, common‐mode, differential‐mode, and bearing currents. This study discusses the HF issues relating to electric drive systems with long cable feeders. HF models for feeder cable and machine to analyse these phenomena are presented. The effects on long feeder cable loading on inverter switching characteristics are discussed. Methods to mitigate high‐amplitude and HF oscillations in such systems are shown.
Discrete sliding mode control based on exponential reaching law and time delay estimation for an asymmetrical six‐phase induction machine drive
Authors: Kali Yassine , Saad Maarouf , Doval‐Gandoy Jesus , Rodas Jorge , Benjelloun Khalid
Published: October 2019

This study deals with the problem of controlling rotor speed and stator currents of an asymmetrical six‐phase induction machine with uncertain dynamics, disturbances, and unmeasurable rotor currents and proposes a robust non‐linear variable structure controller. First of all, an outer control loop based on a proportional–integral regulator is performed to control the rotor speed and to construct the desired stator current references. Then, the inner loop is performed based on the proposed method that combines the time delay estimation method and discrete sliding mode control based on exponential reaching law. This structure allows an accurate and simple estimation of uncertainties and rotor currents, a high‐tracking precision, a convergence of the stator currents to their known desired references in finite‐time and chattering reduction. The design procedure is detailed step by step and the stability analysis and the convergence time are established for the current closed‐loop system. Experimental work was carried out on an asymmetrical six‐phase induction motor drive to show the effectiveness and performance of the proposed robust non‐linear discrete method. The results obtained highlighted the good tracking performance of the stator currents.
Design, modelling and optimisation of a slot‐less axial flux permanent magnet generator for direct‐drive wind turbine application
Authors: Ghaheri Aghil , Mohammadi Ajamloo Akbar , Torkaman Hossein , Afjei Ebrahim
Published: October 2019

Axial flux permanent magnet machines (AFPMs) are potential candidates for direct‐drive wind turbines (DDWTs) due to offering high value of torque density. In slotless AFPM topologies, the cogging torque is absent which makes them more suitable for DDWTs, which provides an easier turbine start‐up. In this research, a robust design and optimisation procedure of a slotless double‐sided AFPM is discussed. The non‐linear magnetic equivalent circuit is established and the optimisation is performed by the response surface methodology to achieve a cost‐effective generator with high power density value. The generator is prototyped and the test results are presented comparing them with the numerical study and non‐optimised design results. To minimise the AFPM torque ripple which is necessary for DDWT application, a cost‐effective solution is proposed leading to a dramatic improvement in the AFPM torque ripple without reducing the average torque.
Power quality disturbances classification using rotation forest and multi‐resolution fast S‐transform with data compression in time domain
Authors: Huang Nantian , Wang Da , Lin Lin , Cai Guowei , Huang Guilin , Du Jiping , Zheng Jian
Published: October 2019

Considering the high spatial complexity of signal processing methods and the low diversity between the base classifiers in the ensemble classifier, a new method with optimal multi‐resolution fast S‐transform (OMFST) with low spatial complexity and rotation forest (ROF) was proposed. Firstly, Gini importance of features is evaluated by random forest (RF), and the sequence forward search method was adopted for feature selection. Then, the intermediate matrix was constructed on the optimal feature set. The results of inverse fast Fourier transform in the main frequency points of signals based on OMFST are compressed in time domain. The intermediate matrix was used to extract features for power quality (PQ) disturbances recognition. Finally, the ROF was adopted to encourage simultaneously individual accuracy and diversity within the ensemble. The optimal ROF was applied to identify 17 kinds of PQ disturbance signals. The simulation results show that the new method can effectively compress the time–frequency matrix of the existing S‐transform (ST) method; the space complexity of the ST modular matrix is reduced significantly and has higher accuracy. Besides, the results of the experiment with real PQ data prove that the new method was effective for practical industrial applications.
Reliability evaluation of bulk power systems using the uniform design technique
Authors: Xie Kaigui , Huang Yingcheng , Hu Bo , Tai Heng‐Ming , Wang Leibao , Liao Qinglong
Published: October 2019

Reliability evaluation of bulk power systems (BPSs) has inherent computational complexity due to the numerous system states and the time‐consuming system state analysis, including power flow calculation, load curtailment, recognition of split power systems and network reconfiguration. In this study, a novel uniform‐design based method is proposed to improve the computational efficiency of power system reliability evaluation. The main idea is that the uniform‐design technique is used to generate the system states in reliability evaluation, which makes the sampled states more uniform and representative in the overall state space compared to the enumerated system states in an analytical method or the random‐generated system states in Monte Carlo simulation. As a result, the sample size and the computational time can be significantly reduced. In addition, the confidence intervals of the reliability indices, such as LOLP, FLOL and EENS, are given. And the estimation errors of reliability indices are discussed. The proposed method is tested on several BPSs, including the IEEE‐RTS79, IEEE‐RTS96 and a real BPS in China. All the case studies indicate that the proposed technique can significantly improve the computational efficiency of BPS reliability evaluation.
Dissolved gas analysis differences between natural esters and mineral oils used in power transformers: a review
Authors: Meira Matias , Ruschetti Cristian , Álvarez Raúl , Catalano Leonardo , Verucchi Carlos
Published: October 2019

Typically and historically mineral oil has been used as liquid insulation in power transformers. Its functions are to ensure the isolation between active parts, absorb heat transmitting it to the outer surfaces and protect other insulators (such as paper) from moisture. Moreover, the analysis of insulating oil provides a diagnosis of the state of the transformer. In the last 10 years, there has been resurgence in the use of natural ester (vegetable oil) because of their ‘green’ credentials. Their biodegradability and high fire point compared to mineral oils are some of its advantages. However, its high cost and low evaluation in service (performance) still limit its application. For mineral oils there is a large database and knowledge obtained from numerous transformers studied over many years. For this reason, certain gas patterns can be related to a specific fault. Conversely, the limited field data related to natural ester makes the analysis of dissolved gases unreliable. Some recent studies attempt to determine the differences between each type of oil when a fault takes place. This study presents a review of the difference between the generated gases in mineral oil and natural ester as a result of the most common faults in transformers.
Event‐triggered consensus approach for distributed battery energy storage systems
Authors: Yu Mei , Song Chao , Lv Fangchao , Jin Kaiqi , Tan Wen
Published: October 2019

Owing to the intermittency of the renewable generation and constantly changing load demand, the battery energy storage systems (BESSs) have become a required solution to future power systems. In this study, the BESS is modelled as an agent. The authors propose an event‐trigger finite‐time consensus approach to maintain the supply–demand balance and minimise the total power loss associated with charging/discharging inefficiency. The proposed consensus algorithm can guarantee all BESSs to converge to an optimal operation point in finite‐time. A situation where the charging power of each individual BESS has a constraint is considered. Furthermore, event‐triggered feedback is considered to reduce the frequency of agents’ communicating with their neighbours. The communication bandwidth and energy can be saved corresponding to the goal of economic requirement. Finally, some simulation cases are further presented to illustrate the effectiveness of the scheme.
Integrating storage in planning of LV distribution networks with PV production
Authors: Hadjsaid Ahmed , Alvarez‐Herault Marie‐Cecile , Debusschere Vincent , Caire Raphaël
Published: October 2019

This article studies the issues of storage in the planning of low voltage (LV) networks. An algorithm of advanced automation function is developed to illustrate the maximum economic value of storage, from the distribution system operator (DSO) point of view, in the long‐term planning of LV networks, compared to a conventional reinforcement method. In order to model the randomness that characterises the new actors of the network (distributed production and storage), a stochastic planning study with uncertainties concerning the connection nodes of the batteries and the photovoltaic production in the network is conducted. The results show that compared to reinforcement, storage can present an economic benefit for the DSO, based on a limited but crucial set of elements: cost of remuneration for using storage, topology, and constraints on the network, and characteristics of the equipment presenting the constraints. For the third‐party storage facility owner, the presented benefits constitute the maximal envelop within which a cost benefit analysis should be restricted to be economically viable, as likely to be used to provide services to the DSO. These points are illustrated with two real networks in order to validate the proposed planning tool.
Time decomposition strategy for security‐constrained economic dispatch
Authors: Safdarian Farnaz , Kargarian Amin
Published: October 2019

A horizontal time decomposition strategy to reduce the computation time of security‐constrained economic dispatch (SCED) is presented in this study. The proposed decomposition strategy is fundamentally novel and is developed in this paper for the first time. The considered scheduling horizon is decomposed into multiple smaller sub‐horizons. The concept of overlapping time intervals is introduced to model ramp constraints for the transition from one sub‐horizon to another sub‐horizon. A sub‐horizon includes several internal intervals and one or two overlapping time intervals that interconnect consecutive sub‐horizons. A local SCED is formulated for each sub‐horizon with respect to internal and overlapping intervals’ variables/constraints. The overlapping intervals allow modelling intertemporal constraints between the consecutive sub‐horizons in a distributed fashion. To coordinate the subproblems and find the optimal solution for the whole operation horizon distributedly, accelerated auxiliary problem principle is developed. Furthermore, the authors present an initialisation strategy to enhance the convergence performance of the coordination strategy. The proposed algorithm is applied to three large systems, and promising results are obtained.
Optimal scheduling for urban micro integrated energy system considering decentralised high‐rise buildings heating supply
Authors: Zhang Wentao , Wang Xiuli , Shao Chengcheng , Wu Xiong
Published: October 2019

Different from conventional low‐rise buildings, in high‐rise buildings, the gas pressure can easily exceed the safe limit, and the hot water cannot be easily transported to the higher floors owing to the effect of gravity. Therefore, overcoming these problems to supply heating for high‐rise buildings remains a great challenge. Accordingly, gas‐hanging stoves are introduced in this study as a provision for decentralised heating supply. To analyse the influence of gas hanging stoves on high‐rise buildings and on the entire urban micro integrated energy system (UMIES), two models were developed: a scenario‐based two‐stage stochastic model for optimal scheduling of the UMIES and a gas overpressure model taking both additional overpressures caused by the frictional resistance and gravity into account. Numerical experiments based on two microgrid test systems show the efficiency of gas hanging stoves with regard to reducing operation costs of the UMIES; moreover, the gas pressure in high‐rise buildings becomes more uniform and concentrated. Thus, the supply of gas and heat to high‐rise buildings can be significantly improved.
Optimal utilisation of PMU measurements in power system hybrid state estimators
Authors: Dubey Anamika , Chakrabarti Saikat , Sharma Ankush , Terzija Vladimir
Published: October 2019

A state estimator provides power system states by minimising the difference between the available measurement set and expected measurements. This minimisation problem is solved using the weighted least squares method or conventional optimisation methods. Most of the optimisation‐based conventional methods used for power system state estimation are based on derivative approaches. These traditional methods suffer from problems such as the complication in handling inequality constraints, slow convergence etc. Non‐linear constrained optimisation problems can be efficiently solved by the sequential quadratic programming (SQP) algorithm. SQP can be applied to small as well as large‐scale non‐linear programming problems having a large number of constraints. In the proposed algorithm, hybrid measurement configuration, consisting of measurements from phasor measurement units as well as conventional measurement devices, is used and applied on IEEE 14 bus, IEEE 118 bus test system and Indian northern region power grid‐246 bus system.
Synthesised‐objective collaborative model and its solution algorithm for transmission–distribution coordinated optimisation
Authors: Tang Kunjie , Dong Shufeng , Cui Jianye , Li Youchun , Song Yonghua
Published: October 2019

As the coupling between transmission systems and distribution systems is significantly enhanced, transmission–distribution coordinated optimisation becomes more and more necessary. Considering that the objectives of the transmission system operator (TSO) and the distribution system operator (DSO) are usually significantly different in the type and dimension, a synthesised‐objective collaborative model is proposed in this study, by normalising different objectives, introducing a weight factor to reflect the importance degree difference of multiple objectives and constructing a common objective. Then, a modified heterogeneous decomposition (M‐HGD) algorithm is proposed to solve the model. In the M‐HGD, two modifications on the update of iterative variables and the stop criteria are proposed, which effectively relieves the fluctuation of the iterative variables and restrains the tail effect of the convergence curve. The proposed model and algorithm can avoid privacy issues between the TSO and the DSO, achieve Pareto optimality solutions, and have powerful flexibility. Numerical experiments validate the effectiveness of the proposed model and demonstrate that the M‐HGD has high accuracy and has better convergence and efficiency than traditional distributed optimisation methods.
Image denoising using patch ordering and 3D transformation of patches
Authors: Colak Ozden , Eksioglu Ender M.
Published: October 2019

A novel image denoising algorithm which is based on the ordering of noisy image patches into a 3D array and the application of 3D transformations on this image dependent patch cube is proposed. For a given noisy image, the authors extract all the patches with overlaps. Then, they order these patches according to a predefined similarity measure. After reordering, a possibly separable 3D transformation is applied to the reordered 3D patch cube. The transform domain coefficients are thresholded using a suitably calculated thresholding parameter. Afterwards, the proper 3D inverse transformation is applied to these coefficients. The final denoised image is generated by repositioning the processed patches to their original locations on the image canvas. The developed algorithm presents a novel and efficient combination of patch ordering and 3D transformations. The forward analysis transform as defined by this complex procedure can get restated as the application of a single tight frame. This tight frame depends on the noisy image under consideration. This novel, image dependent forward operator which employs 3D transforms results in improved denoising performance. The experimental results indicate that the proposed algorithm achieves state‐of‐the‐art denoising results with complexity comparable to competing methods.
Area‐efficient parallel adder with faithful approximation for image and signal processing applications
Authors: Palanisamy Gnanambikai , Krishnasamy Natarajan Vijeyakumar , Sundaram Kalaiselvi
Published: October 2019

Design of low‐power and area‐efficient portable complementary metal–oxide–semiconductor processors for image and signal processing applications demand reduction in transistor switching and count. Adder is the fundamental block of all arithmetic operations performed in processing units. In this study, an error‐tolerant parallel adder with faithful approximation is proposed that can optimise area and accuracy. In the proposed parallel adder, for n bit input and m bit adder block, least n/2m blocks are designed with approximate logic using carry by‐pass addition algorithm and most n/2m blocks are designed with exact logic using carry select addition algorithm. Least significant approximate part of the adder is designed with either exact full adder (EFA) or fault‐tolerant full adder (FTFA) cells. This confines the maximum error in the proposed‐EFA and proposed‐FTFA designs to be not more than unit bit value with weights 2[(n/2m)−1]m and 2n/2, respectively. Two different FTFA cells are proposed and implemented in the approximate blocks. The synthesis results of the proposed‐EFA, proposed‐FTFA1 and proposed‐FTFA2 designs using Cadence Encounter with 90 nm ASIC technology for n = 16, m = 4 demonstrated an area saving of 22.3, 28.2 and 35%, respectively, when compared to the conventional counterpart.
Lane‐keeping control based on an improved artificial potential method and coordination of steering/braking systems
Authors: Hongbo Wang , Li Chen , Weihua Zhang
Published: October 2019

Based on the impact of the vehicle velocity on the potential field function, considering the overall lane‐keeping performance and vehicle stability, the yaw angular adjusting factor is introduced to regulate the potential field function. The proportions of vehicle velocity and yaw angle factors in potential field function are distributed by extension decision. The sliding mode controller is designed based on the two‐degree‐of‐freedom vehicle dynamics model to obtain the front wheel steering angle. The fuzzy decision is made for the dynamic thresholds of distance deviation and angle deviation of lane‐keeping system to avoid the control frequently start‐up. Next, the combined control strategy of active steering and differential braking systems is designed based on vehicle driving safety boundary, and the yaw angle rate and mass‐centroid sideslip angle are selected as the characteristic variables for dividing the vehicle driving safety regions. The different weights are determined for the steering and braking systems in different regions. Finally, the simulation by Carsim/Simulink and the hardware‐in‐loop test are carried out to demonstrate that it is effective and superior by adopting the sliding‐mode controller based on the improved artificial potential function and the coordination strategy of steering and braking systems.
Bayesian models with spatial autocorrelation for bike sharing ridership variability based on revealed preference GPS trajectory data
Authors: Christian Kapuku , Cho Shin‐Hyung , Kho Seung‐Young , Kim Dong‐Kyu
Published: October 2019

Increasing bike sharing ridership to reduce traffic congestion and air pollution has become the major goal of policy makers and transportation planners. In this study, aggregated macro‐level models are developed to investigate and quantify correlations of bike sharing ridership variability in the city of Seoul. The bike sharing kilometres travelled (BSKT) is introduced as the ridership measurement, and a revealed preference method for its estimation is proposed using more than five million trip trajectories of global positioning system (GPS) collected from the bike sharing system of Seoul city. Six different models grouped into three categories are estimated, including linear regression, Bayesian model without spatial effect and Bayesian models with spatial autocorrelation. Five categories of variables are used to explain the variability of BSKT in Seoul. The contribution of these variables in intra‐zonal BSKT and inter‐zonal BSKT are also modelled and compared. The findings suggest a strong correlation among BSKT, bike sharing stations and bicycle network variables. The model comparison results indicate that the performances of the models with spatial autocorrelation are considerably improved.
VRDD: vehicular relevance‐based data dissemination in a vehicular ad hoc network
Authors: Chowdhury Debanjan Roy , Jain Vinod Kumar
Published: October 2019

Safety message (SM) dissemination in vehicular ad hoc network needs to be fast as it allows vehicles to become alert and avoid adverse situations. An SM usually gets disseminated within a topology by multi‐hop broadcast technique. Existing protocols have proposed various controlled flooding mechanisms to address the issues of broadcast storm and network partition. However, no work has been done to take care the direction of message dissemination. In a real scenario, all vehicles within an area of interest (AOI) are not equally affected by an emergency incident. The vehicles of the road where the incident happened, or the vehicles of roads which are connected to incident location by nearby junctions, are most affected and hence are more relevant to receive the SM as fast as possible. Hence, this study proposes a novel method to predict the relevance of vehicles using a distributed algorithm and heuristically tries to disseminate SM toward the relevant vehicles. The authors have compared their work with three state of‐the‐art algorithms and found that vehicular relevance‐based data dissemination is compatible with the existing algorithms on the metrics of packet loss and dissemination delay, but clearly leading in the metric of relevant dissemination.
Dual‐band switched‐beam antenna array for MIMO systems
Authors: Vilas Boas Evandro Cesar , Filgueiras Hugo Rodrigues Dias , Feliciano da Costa Igor , Ribeiro Jose Antonio Justion , Sodre Arismar Cerqueira
Published: October 2019

This work reports the development of a dual‐band switched‐beam antenna array for multiple‐input multiple‐output (MIMO) fifth‐generation systems, operating in millimetre waves. The proposed antenna array consists of applying four slotted‐waveguide antenna arrays (SWAAs), rotated by , as the final array element. The SWAA elements were designed to simultaneously operate in the 28 and 38 GHz bands, by using two groups of slots with different electrical lengths on the opposite faces of the waveguide. The measured array fractional bandwidth was ∼25.6 and 10% at 28 and 38 GHz, respectively. Its applicability for MIMO systems was evaluated as a function of mutual coupling, active reflection coefficient, total active reflection coefficient and envelope correlation coefficient. Experimental results demonstrate low mutual coupling as low as −36 dB within the 28 and 38 GHz frequency bands.
SIW planar balun with enlarged bandwidth
Authors: Fu Yunhao , Chan King Yuk , Gong Liang , Ramer Rodica
Published: October 2019

An X‐band substrate integrated waveguide (SIW) balun, based on a Y‐type divider with enlarged bandwidth, is presented in this study. In most SIW Y‐type dividers, the undesired TE30 mode either leads to the deterioration of the in‐band reflection or constrains the bandwidth by a transmission zero. The cause of the transmission zero is analysed and the modes coupling, rather than the step impedance matching, is utilised to reduce its impact. In the traditional Y‐type divider, the frequency band is split by this transmission zero, while in the proposed wideband configuration, the co‐existences of the TE10 and TE30 modes are employed to combine the two non‐contiguous bands. A broadband balun is designed and fabricated, with the improved Y‐type wideband divider serving for the power‐dividing part. The dividing ports are connected to the reversely placed transitions, achieving inherent out‐of‐phase performance and good amplitude property. The measurement of the balun suggests a 43.94% bandwidth from 8.23 to 12.89 GHz, with 15 dB return loss. The measured amplitude and phase imbalance between two output ports are below 0.7 dB and ±3°, respectively. The performance of the fabricated balun is in agreement with the simulation, and it is promising for wideband applications.
Quality factor and absorption bandwidth of electrically small lossy structures
Authors: Markish Ofer , Leviatan Yehuda
Published: October 2019

A new quality factor (Qabs) characterising power absorption by electrically small structures ranging from antennas to lossy objects is defined. In analogy to the radiation quality factor (Qrad), which is evaluated using the antenna radiated fields in transmitting mode, Qabs is evaluated using the fields scattered by the absorbing structure. Similar to the known relationship between the antenna matching bandwidth (Bmatch) and Qrad, it is rigorously shown that for an electrically small lossless receiving antenna Qabs is inversely proportional to the absorption bandwidth (Babs) of the antenna. Based on a circuit model, it is then conjectured that the same Babs–Qabs relation is also valid in the cases of electrically small lossy antennas and objects that do not have terminals. Numerical examples are shown to demonstrate the validity of the presented Babs–Qabs relation.
Review of inductively coupled power transfer for electric vehicle charging
Authors: Aziz Ahmad Fuad Abdul , Romlie Mohd Fakhizan , Baharudin Zuhairi
Published: October 2019

Inductively coupled power transfer (ICPT) is a technology that is implemented to charge electric vehicles (EVs) wirelessly. Some developments from the past years indicate that this promising charging method has the potential to replace wired charging methods. Thus, some aspects of designing ICPT need to be discussed and considered to develop an optimal system. However, most reviews from the previous articles focused on the developments of ICPT systems in the scope of EV charging. This study not only reviews current developments and topical issues and challenges in high‐power ICPT systems, but also presents several techniques for analysing the system as well as further developments for wireless EV charging adapted from the other electromagnetic field applications. This study will assist readers to analyse any proposed ICPT systems using current methods of analysis and to tackle highlighted topical issues presented from the previous technical papers.
Nine‐level voltage‐doubler bi‐polar module for multilevel DC to AC power conversion
Authors: Bhatnagar Pallavee , Agrawal Rekha , Dewangan Niraj Kumar , Jain Sanjay K. , Gupta Krishna Kumar
Published: October 2019

A major disadvantage of two‐stage topologies of switched capacitors based multilevel inverters is the use of H‐bridge switches which endure high peak‐inverse‐voltage (PIV). In such topologies, the H‐bridge stage is preceded by a level‐generation stage which synthesises unipolar voltage levels. In this work, a bi‐polar module is proposed which can synthesise nine levels at the AC terminals with a single DC input. The proposed module uses power switches with PIV equal to that of the input DC source. Use of switched capacitors in each of the proposed module enables a voltage gain of two. Such bi‐polar voltage‐doubler modules can be easily connected in a cascaded fashion to increase the number of levels, without involving H‐bridge switches. Working modes of the module ensure that the capacitors are self‐balanced. A complete analysis of the proposed module is presented. Also, experimental results are presented for validation. In addition, a comparison with other topologies has been presented.
Universal wireless powered terminals for robust overhead transmission line monitoring
Authors: Cai Changsong , Wang Junhua , Jing Hang , Zhang Fan , Zhang Pengcheng , Fang Zhijian , Zhou Ying‐Guo
Published: October 2019

A universal and robust wireless power transfer (WPT) system crossing insulators to feed monitoring terminals on power towers of overhead transmission lines is presented in this study. Analyses of the WPT system crossing high‐voltage insulators string indicate that system characteristics and energy loss vary under different insulation conditions. Transfer characteristics of the WPT system with different relative positions between the coils and insulators are analysed to find an insensitive scheme. To achieve a non‐interacting and relatively efficient operation under the scenarios, magnetic shielding layers are designed to further isolate the WPT system and insulators. Moreover, the resonant frequency point tracking method of this specific WPT system is studied and implemented to achieve robust transfer efficiency. Experimental results prove the feasibility, and the system displays a robust transfer performance with various high‐voltage insulators. Such energy feeding system can be used in disc or composite insulation towers universally with simplified installation methods.
Analysis of cascaded silicon carbide MOSFETs using a single gate driver for medium voltage applications
Authors: Jørgensen Asger Bjørn , Sønderskov Simon Heindorf , Beczkowski Szymon , Bidoggia Benoît , Munk‐Nielsen Stig
Published: October 2019

Medium voltage power supplies for applications such as electrostatic precipitators are used in industrial plants to remove particles from fumes. Current solutions based on silicon devices rely on high‐voltage transformers to reach the required output voltage levels. New wide band gap materials such as silicon carbide have higher electric breakdown voltage, and thus fewer devices are required in series to withstand the output voltage. Owing to the faster switching speed of silicon carbide devices further demands are put on the serialisation method. In this study, a cascaded series‐connection method using only a single external gate signal is analysed in detail, guidelines to size the resistor–capacitor–diode‐snubber are proposed and its applicability is experimentally demonstrated. The circuit is tested with four series‐connected devices in a double pulse test at 2400 V and current levels of 250–800 mA to show the load dependence. The serialisation technique is tested in a boost converter operating in discontinuous conduction mode but is limited to 1200 V due to an oscillating state occurring after zero current crossing. Finally, the technique is tested at 2400 V and 10 kHz in a synchronous boost converter, which demonstrates the proposed design guidelines.