bluuebunny/crossref_metadata_2025 huggingface dataset:
Ergosterol attenuates cigarette smoke extract-induced COPD by modulating inflammation, oxidative stress and apoptosis in vitro and in vivo
Authors: Sun Xiao , Feng Xiuli , Zheng Dandan , Li Ang , Li Chunyan , Li Siying , Zhao Zhongxi
Published: July 2019

Cigarette smoke (CS) is the major cause of chronic obstructive pulmonary disease (COPD). CS heightens inflammation, oxidative stress and apoptosis. Ergosterol is the main bioactive ingredient in Cordyceps sinensis (C. sinensis), a traditional medicinal herb for various diseases. The objective of this work was to investigate the effects of ergosterol on anti-inflammatory and antioxidative stress as well as anti-apoptosis in a cigarette smoke extract (CSE)-induced COPD model both in vitro and in vivo. Our results demonstrate that CSE induced inflammatory and oxidative stress and apoptosis with the involvement of the Bcl-2 family proteins via the nuclear factor kappa B (NF-κB)/p65 pathway in both 16HBE cells and Balb/c mice. CSE induced epithelial cell death and increased the expression of nitric oxide (NO), interleukin-6 (IL-6), tumor necrosis factor α (TNF-α), malondialdehyde (MAD) and the apoptosis-related proteins cleaved caspase 3/7/9 and cleaved-poly-(ADP)-ribose polymerase (PARP) both in vitro and in vivo, whereas decreased the levels of superoxide dismutase (SOD) and catalase (CAT). Treatment of 16HBE cells and Balb/c mice with ergosterol inhibited CSE-induced inflammatory and oxidative stress and apoptosis by inhibiting the activation of NF-κB/p65. Ergosterol suppressed apoptosis by inhibiting the expression of the apoptosis-related proteins both in vitro and in vivo. Moreover, the usage of QNZ (an inhibitor of NF-κB) also partly demonstrated that NF-κB/p65 pathway was involved in the ergosterol protective progress. These results show that ergosterol suppressed COPD inflammatory and oxidative stress and apoptosis through the NF-κB/p65 pathway, suggesting that ergosterol may be partially responsible for the therapeutic effects of cultured C. sinensis on COPD patients.
Interfacial bonding enhancement of the RTV recoating with sandwiched contaminant by plasma jet
Authors: Wang Shanshan , Li Shuang , Li Jianjun , Zhang Ruobing , Liu Hui
Published: July 2019

Room temperature vulcanised (RTV) silicone rubber is widely used in electrical power system, applied to the glass or porcelain insulator surface to enhance insulation. RTV coatings get contaminated after long‐term operation and need to be recoated. Contaminants accumulate and embed into the surface of base RTV coating, forming a hard‐to‐remove inorganic transition layer. Such sandwiched contaminant layer destroys the adhesion between original and reapplied silicone rubber coating greatly. Authors’ study innovatively reports a method to enhance interfacial bond properties of the RTV recoating with sandwiched contaminant layer, by using an atmospheric‐pulsed discharge plasma jet (APPJ) for surface treatment. Water boiling test and 180‐degree peel test were conducted to evaluate interfacial bond properties macroscopically. Scanning electron microscopy (SEM) was applied to observe the cross‐section of recoating interface, while Fourier‐transform infrared spectroscopy (FTIR) to detect chemical changes of contaminant layer, giving out microscopic and theoretical explanation.
Decentralised event‐based synchronisation and control of spacecraft
Authors: Mousavi Seyed Hossein , de Ruiter Anton H. J.
Published: July 2019

In this study a decentralised event‐based scheme is proposed to synchronise the spacecraft's attitudes during their convergence toward the desired attitude, in the presence of disturbance. To achieve this goal, decentralised integral‐based triggering mechanisms are introduced which not only reduce the data transmission among the spacecraft efficiently but also guarantee a minimum inter‐event time for each triggering module. Moreover, a design procedure is given to find the control gains and triggering conditions parameters properly. Finally, simulation results are provided to show the effectiveness of the system.
Distributed optimisation design for solving the Stein equation with constraints
Authors: Chen Guanpu , Zeng Xianlin , Hong Yiguang
Published: July 2019

In this study, the authors consider distributed computation of the Stein equations with set constraints, where each agent or node knows a few rows or columns of coefficient matrices. By formulating an equivalent distributed optimisation problem, they propose a projection‐based algorithm to seek least‐squares solutions to the constrained Stein equation over a multi‐agent system network. Then, they rigorously prove the convergence of the proposed algorithm to a least‐squares solution for any initial condition, and moreover, provide a simplified distributed algorithm with an exponential convergence rate for the case without constraints.
Adaptive MPC for constrained systems with parameter uncertainty and additive disturbance
Authors: Zhang Sixing , Dai Li , Xia Yuanqing
Published: July 2019

In this study, the authors propose an adaptive model predictive control (MPC) algorithm for constrained linear systems in state space subject to uncertain model parameters and disturbances. An iterative set membership identification algorithm is first presented to update the uncertain parameter set at each time step. Based on the shrunken uncertain parameter set, an MPC controller is then designed to robustly stabilise the uncertain systems subject to state and input constraints. The algorithm can efficiently reduce the size of the uncertain parameter set in min–max MPC setting, and therefore improve the control performance. The algorithm is proved to ensure constraint satisfaction, recursive feasibility and input‐to‐state practical stability of the closed‐loop system even in the presence of system uncertainties. A numerical example and a brief comparison with traditional min–max MPC are provided to demonstrate the efficiency of the proposed algorithm.
Through‐the‐wall radar imaging algorithm for moving target under wall parameter uncertainties
Authors: Sun Yanpeng , Chen Li , Qu Lele
Published: July 2019

In order to solve the problems of slow imaging speed and poor reconstruction accuracy of wall parameters under the condition of wall parameter fuzziness, an improved limited Broyden–Fletcher–Goldfarb–Shanno‐particle swarm optimisation (LBFGS‐PSO) algorithm was proposed. The LBFGS‐PSO algorithm model solves the problems of slow calculation speed and large errors of the traditional quasi‐Newton algorithm and particle swarm algorithm. The algorithm combined with block orthogonal matching pursuit algorithm can not only accurately reconstruct the position of the sidewall, but also can use the multi‐path information to accurately reconstruct the moving target and the stationary target. Compared with the traditional BFGS algorithm and PSO algorithm, the proposed algorithm can reduce the calculation time and provide more accurate estimation results. Simulation results and data analysis verify the performance of the proposed algorithm.
Fast and robust ellipse detector based on edge following method
Authors: Liu Yang , Xie Zongwu , Liu Hong
Published: July 2019

This study presents a fast and robust ellipse detector based on edge following method. The detector first extracts segments using an edge predictor based on curvature analysis. Then, line segments are generated based on length condition other than least‐squares approximation. After that, potential ellipses are detected based on edge curvature and convexity. In addition, a re‐find contours detection method is introduced to improve the accuracy by searching edge points in the missing part of the ellipse. The performance of the detector has been tested on different datasets containing both synthetic and real images with three other algorithms based on the edge following method. Experimental results indicate that the proposed method always has the fastest execution time. Besides, it advances the state of the art in accuracy in most cases. Generally speaking, it is a fast, robust and effective ellipse detector for real‐time applications.
Alpha cut for interactive image segmentation of thin and elongated objects
Authors: Tran Nam H. , Seo Dongsun , Woo Dongmin , Won Yongyuk , Tu Hieu T.
Published: July 2019

Shrinking bias problem is a practical limitation of graph‐cut‐based methods for binary image segmentation. The detail parts with thin elongated object are not well preserved in graph cut minimisation as a result. The authors propose to use structure transferring to overcome the problem with an expanded L2 norm of colour difference. They also show that the structure‐transferring output can be integrated into graph cuts as a counter‐balance to shrinking problem. Experimental results show that the proposed alpha‐cutting technique is effective and efficient in improving segmentation of thin elongated objects.
Data embedding in high efficiency video coding (HEVC) videos by modifying the partitioning of coding units
Authors: Shanableh Tamer
Published: July 2019

A data embedding solution in HEVC videos is proposed by modifying the partitioning of coding units (CUs). The partitions of a CU are first represented as a sequence of binary flags. The flags pertaining to 16 × 16 sub CUs are used as a cover for data embedding, where 6 or 4 message bits are embedded per CU. The data embedding algorithm guarantees that a maximum of one partition is modified per message segment, therefore, in a given CU, either 0, 1 or 2 partitions are modified. The proposed solution is assessed in terms of message payload, number of modified partitions, loss in video quality as indicated by the PSNR results, mean objective scores and excessive bitrate. The proposed solution can embed messages with up to an average payload of 32.6 kbit/s with a corresponding average distortion of <0.5 dB. Comparisons with existing solutions reveal that the proposed solution maintains similar message payloads with less modifications of CU partitioning and at the same time resulting in less distortions for the cover video.
Automatic classification of skin burn colour images using texture‐based feature extraction
Authors: Şevik Uğur , Karakullukçu Erdinç , Berber Tolga , Akbaş Yeşim , Türkyılmaz Serdar
Published: July 2019

Current standard of burn wound evaluation is based on digital photography of wounds examined by a burn specialist. Due to subjectivity of this approach, automated burn wound analysis systems are being developed by researchers. Those systems should contain three major components: segmentation of burn images, feature extraction, and classification of segmented regions into healthy skin, burned skin, and background. The first purpose of this study is to examine various methods in each of these steps and to achieve the best combination. Comparing the performance of segmentation‐based classification approach versus deep learning is the second goal of the study. SegNet‐based semantic segmentation was implemented as a deep learning approach. The best combination to successfully classify the images into skin, burn, and background regions was found to be the fuzzy c‐means algorithm for the segmentation part, and a multilayer feed‐forward artificial neural network trained by the back‐propagation algorithm for the classification part. Having an F‐score of 74.28% in the classification of images captured without a protocol, the proposed scheme managed to achieve similar results with deep learning, which had an F‐score of 80.50%.
Multi‐objective genetic algorithm on hexagonal search for fast motion estimation
Authors: Palaniraj Palanivel , Sakthivel Ganesan
Published: July 2019

Motion estimation (ME) is a process of correlating the frames by pointing the blocks in the candidate frame similar to those in the previous frame. Hexagonal Search (HS) reduces 10–15% search points over Diamond Search (DS) with negligible Peak Signal to Noise Ratio (PSNR) loss. Adapting an optimization will achieve a massive improvement on the search process. The proposed HS‐GA method combines the HS with genetic algorithm (GA) to optimize ME. The HS‐GA method reduces 72% on average search points pre block (ASPB) with PSNR loss of 2.5 dB and single generation. If the GA is executed with 10 generations the PSNR loss is reduced to 0.48 dB, but ASPB drastically increase to ∼316%. The proposed work aims at multi objective on selection of better chromosomes and on control of generations to avoid the unnecessary generations to improve the GA. This process is named HSIGA(HS with Intelligent GA). The proposed HSIGA adapts five intelligent techniques like Histogram to decide new generations, Region based chromosome selection, Mutation on inner search gene, second rank valley point stopping criteria and interlaced HS to improve search process with negligible PSNR loss with in affordable search.
Multi‐perspective gait recognition based on classifier fusion
Authors: Wang Xiuhui , Feng Shiling
Published: July 2019

Gait recognition has been well known as a promising biometric, which is non‐offensive and can identify a person from a distance. In this study, a novel ensemble learning framework for gait recognition, namely multi‐perspective gait recognition based on classifier fusion is proposed. Firstly, by utilising bidirectional optical flow, a new algorithm for gait feature extraction is presented, which adaptively extracts the dynamic gait characteristics of walking persons. Secondly, two base classifiers, namely the support vector machine and the hidden Markov model, are trained using the extracted dynamic gait features and traditional gait energy images separately. Thirdly, a novel algorithm is presented for combining two types of base gait classifiers together on the decision level. Finally, the proposed framework by two experiments on the well‐known CASIA and OU‐ISIR gait databases is evaluated, respectively, and demonstrate the advantages of the proposed methods in comparison with others.
Aesthetic assessment of paintings based on visual balance
Authors: Li Mao , Lv Jiancheng , Tang Chenwei
Published: July 2019

All things follow the cosmic equilibrium rule. As one of the important factors in evaluating images of aesthetic effects, the visual balance has not attracted much attention. In this study, a novel method is proposed to quantify the law of visual balance and automatically evaluate the aesthetic value of images. In the proposed method, the authors first analyse the colour composition of images using the K‐means clustering method. Then, based on information aesthetics theory and perspective principles, a calculation method is proposed to find the visual centre of gravity of images. Finally, the aesthetic effect of the image based on visual balance is evaluated according to the positional relationship between the visual centre of gravity and the physical centre of the image. With extensive experimental results, the authors demonstrate qualitatively and quantitatively that the proposed evaluation method is basically consistent with the intuitive experience of most human beings. Moreover, experiments are also conducted on a large and diversified benchmark data set that are competitive with the current state of the art.
Deep supervised hashing network with integrated regularisation
Authors: Liao Jianxin , Li Baoran , Yang Di , Wang Jingyu , Qi Qi , Wang Jing
Published: July 2019

Hashing has been widely deployed to approximate nearest neighbour search for large‐scale multimedia retrieval tasks due to storage and retrieval efficiency. State‐of‐the‐art supervised hashing methods for image retrieval construct deep structures to simultaneously learn image representation and generate good hash codes, and the key step among them is simultaneously learned feature representation and binary hash code. Existing methods use similarity and regularity loss to train deep hashing systems, but these two functions usually work together but not cooperative, which may lead to inadequate performance of the whole system. In this study, a new method for training deep hashing system to learn compact binary codes is presented. The deep supervised hashing network with integrated regularisation (DSHIR) system develop the zero division restriction as a new part of the loss function, which settles the problem of cooperatively guiding the system generate similarity preserving binary codes. DSHIR system also modifies the similarity handling loss to better extract features from image data, which promotes the performance compared to existing end‐to‐end deep hashing systems. Experiments show that DSHIR yields about 10 per cent higher mean average precision on CIFAR‐10 dataset, and also promote on other evaluation indexes compared with state‐of‐the‐art systems.
Mobile terminal trajectory recognition based on improved LSTM model
Authors: Jian Chengfeng , Yang Meiling , Zhang Meiyu
Published: July 2019

Mobile terminal hand trajectory recognition is challenged by spatio‐temporal variations, complex background, light variations as well as the limited computing resources for mobile devices. The authors propose a hand trajectory recognition method based on improved Long‐Short Term Memory network (LSTM) model. First, for the sake of eliminating the effects of complex background and light, the SSD hand detector and multi‐color space are combined to segment gesture. To eliminate the influence of trajectory points' overlap, the sparseness of the trajectory points is used to determine the start and end of the trajectory; then, to maintain the feature difference while decreasing the feature extraction time, they extract the trajectory feature sequence based on the central point direction angle; Finally, a new loss function (M‐Softmax loss) is proposed in LSTM training process to maximise the inter‐class variations and minimise intra‐class variations. At the same time, the adaptive training iteration number is proposed to ensure the convergence of the model and reduce the training time cost. The experimental results illustrate that the improved model learned features are more compact, and the model is easier to deal with external data changes. Authors’ proposed method has great significance in practical applications.
Laser‐based SLAM automatic parallel parking path planning and tracking for passenger vehicle
Authors: Song Jie , Zhang Weiwei , Wu Xuncheng , Cao Haotian , Gao Qiaoming , Luo Suyun
Published: July 2019

Automatic parking system (APS) plays an important role in alleviating drivers' burden and improving vehicle safety. This study proposes a laser‐based simultaneous localisation and mapping (SLAM) automatic parallel parking and tracking control scheme, which include environment perception and reconstruction, parking path planning, and path following. First, the proposed approach selects short‐range lidar to enlarge its perceptron on parking environment and senses available parking space to build neighbourhood mapping with the help of simultaneous localisation. The test evaluation indicates that laser‐SLAM has achieved good performance for recognising free spaces. Then, scene‐dependent B‐spline parallel parking path planning algorithm is proposed to optimise the parking path curve and makes the path meet vehicle kinematics model constrains well, in which vehicle actuator's dynamic performance and parking path smoothness are taken as key attributes. The experiment results indicate that the designed parallel parking path is better smooth. At last, a path following control method based on model predictive control (MPC) algorithm is proposed. The authors built an intelligent vehicle APS platform, and the results indicate that the designed MPC algorithms has excellent robustness and can minimise the tracking error. All the proposed scheme is quantitatively evaluated using different parking scene simulation with satisfactory performance.
Deep learning‐based embedded license plate localisation system
Authors: Yépez Juan , Castro‐Zunti Riel D. , Ko Seok‐Bum
Published: July 2019

In this study the authors propose novel neural network architecture for license plate localisation (LPL) based on an inverted residual structure where the shortcut connections are between the linear bottleneck layers. This residual structure is used for feature extraction in a modified single shot detector for object detection, where standard convolutions are replaced with depthwise separable convolutions in classification layers. The proposed deep learning (DL) solution was tested against three popular international research databases and achieves state‐of‐the‐art results, proving that the proposed model is accurate and robust. Across those databases, the proposed model surpasses other recent LPL works, including DL‐based methods, in terms of accuracy and speed. The authors show the proposed architecture to have significant speedup and computational efficiency gains over other DL models, and to have fast per‐image localisation processing times sufficient for applications deployed on expensive and commodity hardware alike. Using a novel multi‐threading video capture with motion detection then inference algorithm, the authors increase computational efficiency and drop fewer frames overall, allowing for increased performance. Repeated tests show that the proposed method is well‐suited to real‐time and highly accurate LPL, regardless of hardware.
Power charging management strategy for electric vehicles based on a Stackelberg game
Authors: Zhaoan Fei , Baochuan Fu , Xuefeng Xi , Zhengtian Wu , Zhenping Chen , Xinyin Xu
Published: July 2019

Increasing electric vehicles (EV) charging efficiency and reducing charging cost are important issues of EVs power management and key factor that affect the spread of EVs. Researching the competitive relationship between power grids and EV users is the key to solving this problem. Therefore, the authors propose a charging control strategy that is based on a 1‐N‐type Stackelberg game. In the game, power grid, retailers, and users are all able to do power decision making. Thus, the charging strategy here can flexibly meet different demands of power grid, retailers, and users. The equilibrium of the game model is solved by the inverse induction method. The benefits are compared by simulation, by the disordered charging process, and by charging control methods based on static time‐sharing electricity prices. The influence of the parameters on the charging process in the game model is analysed, and the feasibility of the proposed method is verified. Results show that load peak is reduced by 34.9% while users' charging costs are reduced by 25.1%. The approaches they proposed can effectively solve the competition between the two.
Analysis of virtual synchronous generator control and its response based on transfer functions
Authors: Chen Junru , O'Donnell Terence
Published: July 2019

Virtual Synchronous Generator (VSG) control has been proposed as a means to control power electronics converter interfaced generation and storage which retains the dynamics of the conventional synchronous machine. This study provides a comprehensive, transfer function based, analysis of VGS control, which can be used as the basis for the design of VSG transient and steady‐state performance. Based on a hardware validated, large signal model, a small signal model and associated transfer functions which describe the changes in real and reactive powers in response to changes in references and grid frequency disturbances. The derived transfer functions are used to obtain insight into the correct design of VSG controllers. The small signal models, transfer functions and associated analysis are validated by comparison with measured results on a scaled hardware system.
Comprehensive sharing control strategy for input‐series output‐parallel connected modular DC–DC converters
Authors: Abrehdari Meysam , Sarvi Mohammad
Published: July 2019

The systems consisting of multiple DC–DC converters with input‐series output‐parallel (ISOP) connection are widely used in high‐power applications. In the ISOP connection, the total input voltage and output current should be divided equally between the converters. However, in order to achieve this purpose, a proper control scheme should be used. This study proposes two control schemes: (i) output current feedback (OCF) and (ii) input voltage feedback (IVF). Based on the power balance, in the IVF scheme, the total output current, and in the OCF scheme, the total input voltage are divided automatically between the converters, and there is no need to use an extra control loop. The IVF and the OCF control schemes consist of two control loops: a common output voltage regulator (OVR) loop and individual input voltage sharing loops in the IVF scheme or individual output current sharing loops in the OCF scheme. The proposed control scheme can effectively improve the stability and dynamic characteristics of system. Finally, both the results of the simulation and laboratory prototype of an ISOP system consisting two forward converters have verified the performance of the IVF and OCF control schemes.
Single dc‐source‐based seven‐level boost inverter for electric vehicle application
Authors: Pilli Naresh K. , Raghuram M. , Kumar Avneet , Singh Santosh K.
Published: July 2019

This study offers an effective circuit arrangement of a multilevel inverter that can increase the number of output voltage levels with a lesser number of device count. A single dc‐source‐based seven‐level inverter (LI) with boosting capability is proposed in this study. The proposed inverter utilises eight switches, two diodes, two capacitors, one inductor and a single dc source to generate seven‐level boosted output. Usage of single dc source and boosting capability makes the proposed inverter suitable for electric vehicles as less number of series‐connected battery cells are required. Phase‐shifted pulse‐width modulation (PWM), a multi‐carrier‐based PWM technique is utilised to generate switching pulses for the proposed 7LI. Device count‐based comparative analysis of the proposed inverter with recent topologies is done. Viability and impact of the proposed inverter are analysed through simulation and are validated through laboratory prototype.
Survey on magnetic resonant coupling wireless power transfer technology for electric vehicle charging
Authors: Mou Xiaolin , Gladwin Daniel T. , Zhao Rui , Sun Hongjian
Published: July 2019

Wireless power transfer (WPT) technology makes it possible to supply power through an air‐gap, without the need for current‐carrying wires. One important technique of WPT technology is magnetic resonant coupling (MRC) WPT. Based on the advantages of MRC WPT, such as safety and high power transfer efficiency over a long transmit distance, there are many possible applications of MRC WPT. This study provides a comprehensive, state‐of‐the‐art review of the MRC WPT technology and wireless charging for electric vehicle (EV). A comparative overview of MRC WPT system design which includes a detailed description of the prototypes, schematics, compensation circuit topologies (impedance matching), and international charging standards. In addition, this study provides an overview of wireless EV charging including the static wireless EV charging and the dynamic wireless EV charging, which focuses on the coil design, power transfer efficiency, and current research achievement in the literature.
Voltage sensitivity‐based demand‐side management to reduce voltage unbalance in islanded microgrids
Authors: Çimen Halil , Çetinkaya Nurettin
Published: July 2019

Microgrids (MG) provide advantages such as providing energy supply to areas far from the distribution grid, efficient use of resources by supporting demand management and having a more dynamic grid. However, if an advanced control system is not implemented in the islanded MG, problems of power quality may arise. One of these problems is the voltage unbalance. Increasing the number of single‐phase roof‐mounted PV plants and the number of electric vehicle charging stations in recent times may negatively affect voltage unbalance. One of the methods used to mitigate this problem is the demand‐side management (DSM). Here, a solution method based on DSM is presented for the voltage unbalance problem that may occur in an islanded MG. Thermostatically controlled loads, which are often used for DSM, are preferred as controllable loads. A new and novel control algorithm based on voltage sensitivity have been developed. Effects of TCLs on different buses and phases are determined with voltage sensitivity matrix including neutral components. The proposed control algorithm reduces successfully both the voltage unbalance factor and the number of controlled TCLs. The algorithm was tested with the PSCAD/EMTDC analysis software.
Optimal frequency deviations control in microgrid interconnected systems
Authors: Siti Mukwanga W. , Tungadio Diambomba H. , Sun Yanxia , Mbungu Nsilulu T. , Tiako Remy
Published: July 2019

The increase in the price of fossil fuel due to its rarity and emissions means more integration of renewable energy sources (RESs) is required to improve economic management of the grid. This study analyses a combination of the tie‐line power between conventional power sources and the renewable energy system and its frequency deviations which are known as area control error. The minimisation of the tie‐line by optimal control is affected in such a way that the frequency and tie‐line power error can be minimised while maintaining the power balance between generation and load. The tie‐line connected to the microgrid consists of two main parts, namely the conventional source and the renewable energy source, each made up of a synchronous generator. The control application of the active power and frequency to a network is referred to as load frequency control (LFC) with the storage system as an integral part of RES. The simulation results show the performance of the proposed optimal control model in microgrid during the changing loads' condition, where the energy storage system applied to optimal control has shown a quick response to frequency deviation, which is close to 80%.
Coprime beamforming: fast estimation of more sources than sensors
Authors: Baxter William , Nosrati Hamed , Aboutanios Elias
Published: July 2019

In radar, the minimisation of redundancies within the sensing array can lead to significant hardware computational savings. Arrays with a coprime‐pair configuration enjoy increased degrees of freedom and can detect more sources than sensors. To achieve this, a virtual array (VA) consisting of the full complement of lags is usually constructed and subspace‐based algorithms are then employed to obtain the direction‐of‐arrival (DOA) or frequency estimates. However, the application of the subspace techniques to the VA incurs a significant computational cost and requires spatial smoothing. The authors propose and analyse the application of the fast iterative interpolated beamformer (FIIB) to the coprime DOA estimation problem. The FIIB enjoys a computational complexity of the same order as the fast Fourier transform and does not require spatial smoothing. They consider two implementations that construct the VA differently with the first selecting a single estimate for each lag and the other employing averaged values of the lag estimates. They present a comprehensive study of the estimation performance as a function of signal‐to‐noise ratio, number of snapshots and source separation. The results clearly show that the FIIB delivers high‐fidelity frequency estimates that consistently outperform the high‐resolution subspace‐based methods.
Probability of detection and clutter rate estimation in target tracking systems: generalised maximum likelihood approach
Authors: Al‐Hasaeri Asem , Marjanović Aleksandra , Tadić Predrag , Vujnović Sanja , Đurović Željko
Published: July 2019

The efficacy of any moving target tracking technique depends on the understanding the background, or clutter, and the parameters that describe the detection properties of the objects. The nature of these quantities is statistical and not only are they unknown as a rule in practice, but they are also variable over both time and space. The study proposes a method for estimating the time‐varying probability of detection of each tracked object individually, and the density of false alarms in the immediate vicinity of the current position of an object. The method is based on the generalised maximum likelihood approach, assuming tracking of a solitary target. The applicability and constraints of the proposed solution are illustrated by simulations.
Comparison of micro‐Doppler signatures registered using RBM of helicopters and WSM of vehicles
Authors: Gong Jiangkun , Yan Jun , Li Deren
Published: July 2019

Jet engine modulation (JEM) are micro‐Doppler features obtained from the radar data of aircraft, including jet aircraft and helicopters, and generally viewed as unique phenomenon suitable for identifying aerial targets. The authors demonstrate however, that JEM are not unique, and that the rotating wheel spokes on the wheels of ground vehicles produce a modulation similar to the rotating rotor blades of jet engines and helicopter rotor blades. They also develop a mathematical model to analyse the radar signal scattering mechanism of wheel spokes, and also employ a Ku‐band Doppler radar system to collect radar echoes from a wheeled vehicle and a helicopter. Both the theoretical and experimental results verify the existence of rotor blade modulation (RBM) phenomena from helicopters and wheel spoke modulation (WSM) phenomena from vehicles. Both RBM and WSM are similar to JEM features. This fact indicates that JEM is a necessary but insufficient condition for the identification of aerial targets, and additional recognition features inherent in surface surveillance radar are needed to distinguish the JEM spectra arising from aerial targets and ground vehicles.
Developing a spatially and temporally explicit solar resource dataset for Great Britain
Authors: Thomson R. Camilla , Sun Wei , Harrison Gareth P.
Published: July 2019

Existing dispatch and infrastructure investment tools for modelling the Scottish energy system do not currently include solar photovoltaic resource. This study describes the development of three spatially and temporally explicit solar resource datasets for use in these models, for domestic, commercial roof‐mounted and ground‐mounted arrays. They include the whole of Great Britain (GB) and are based on empirical weather data for 2000–2015. They are expected to be a valuable resource for energy system modelling in GB.
Combined source‐effect of photovoltaic generator and bi‐directional dc–dc battery charger on inverter control dynamics
Authors: Sallinen Roosa‐Maria , Messo Tuomas
Published: July 2019

This study presents a method to solve the dynamic model of a grid‐connected photovoltaic (PV) inverter with battery energy storage. A three‐phase grid‐connected solar‐battery system is studied using small‐signal state‐space modelling in the synchronously rotating dq ‐reference frame. The combined effect of a PV generator and a bi‐directional dc–dc battery charger (BC) on the inverter dynamic behaviour is analysed. It is shown that the characteristic right‐half‐plane pole in the PV inverter's dc‐link voltage control dynamics shifts to a lower frequency when the BC is connected, which improves the stability of the system and allows a lower bandwidth for the dc‐link voltage control.
Technical challenges in co‐location of battery storage and generation plants
Authors: Besant A G , Hamidi V
Published: July 2019

This paper has described the technical considerations that are necessary to ensure the cost‐effective and reliable connection of battery energy storage systems co‐located with existing generation plants. The connection requirements of typical battery energy storage systems have been described and the procedures required to meet operational constrictions for connection at an existing plant are explained.
New control paradigm for both islanded and grid‐connected operation of PMSG‐based wind turbine
Authors: Baruwa Muftau O. , Fazeli Meghdad , Egwebe Augustine M.
Published: July 2019

This article proposes a new control paradigm for the seamless operation of a permanent magnet synchronous generator (PMSG) based wind energy conversion system (WECS) in both islanded and grid‐connected modes. Conventionally, grid‐connected WECS are controlled to extract the maximum power from the wind, known as maximum power point tracking (MPPT). However, in islanded operation, the objective is to control the power generated from the WECS to match the load demand, which here is called load following power generation (LFPG). This article proposes a power management system (PMS) which integrates the MPPT and LFPG capabilities of the WECS into a single‐control paradigm. This enables the WECS to seamlessly achieve MPPT in grid operation, LFPG in islanded mode and low‐voltage ride‐through (LVRT) during fault. The proposed scheme is validated using MATLAB/SIMULINK simulations.
Fault‐tolerant matrix‐converter‐controlled IPMSM‐drive system using a predictive controller and sliding‐mode estimator
Authors: Liu Tian‐Hua , Chang Shuo‐Feng
Published: July 2019

This study proposes a fault‐tolerant matrix‐converter‐controlled IPMSM‐drive system, in which a predictive speed‐loop controller and a predictive current‐loop controller are implemented to improve its dynamic responses, including transient responses and load disturbance responses of the IPMSM‐drive system in both normal and faulty conditions. In addition, a sliding‐mode estimator is used to estimate the rotor position, rotor speed, and stator currents of the IPMSM when the encoder or current sensor in the IPMSM‐drive system is faulty. As a result, the IPMSM‐drive system allows for either an encoder fault or a Hall‐effect sensor fault. The detailed fault detection, diagnosis, and control are discussed here. In case of an encoder fault or a Hall‐effect current sensor fault, the IPMSM‐drive system still functions. A digital signal processor, TMS 320LF2407A, is used as a control centre to execute the fault‐tolerant algorithm, state‐estimating algorithm, and control algorithm. Experimental results can validate the correctness and feasibility of the proposed fault‐tolerant and predictive control methods.
In-flight photometry extraction of PLATO targets
Authors: Marchiori V. , Samadi R. , Fialho F. , Paproth C. , Santerne A. , Pertenais M. , Börner A. , Cabrera J. , Monsky A. , Kutrowski N.
Published: July 2019

Context. The ESA PLATO space mission is devoted to unveiling and characterizing new extrasolar planets and their host stars. This mission will encompass a very large (>2100 deg2) field of view, granting it the potential to survey up to one million stars depending on the final observation strategy. The telemetry budget of the spacecraft cannot handle transmitting individual images for such a huge stellar sample at the right cadence, so the development of an appropriate strategy to perform on-board data reduction is mandatory.

Aims. We employ mask-based (aperture) photometry to produce stellar light curves in flight. Our aim is thus to find the mask model that optimizes the scientific performance of the reduced data.

Methods. We considered three distinct aperture models: binary mask, weighted Gaussian mask, and weighted gradient mask giving lowest noise-to-signal ratio, computed through a novel direct method. Each model was tested on synthetic images generated for 50 000 potential PLATO targets. We extracted the stellar population from the Gaia DR2 catalogue. An innovative criterion was adopted for choosing between different mask models. We designated as optimal the model providing the best compromise between sensitivity to detect true and false planet transits. We determined the optimal model based on simulated noise-to-signal ratio and frequency of threshold crossing events.

Results. Our results show that, although the binary mask statistically presents a few percent higher noise-to-signal ratio compared to weighted masks, both strategies have very similar efficiency in detecting legitimate planet transits. When it comes to avoiding spurious signals from contaminant stars however the binary mask statistically collects considerably less contaminant flux than weighted masks, thereby allowing the former to deliver up to ∼30% less false transit signatures at 7.1σ detection threshold.

Conclusions. Our proposed approach for choosing apertures has been proven to be decisive for the determination of a mask model capable to provide near maximum planet yield and substantially reduced occurrence of false positives for the PLATO mission. Overall, this work constitutes an important step in the design of both on-board and on-ground science data processing pipelines.
Disk masses in the Orion Molecular Cloud-2: distinguishing time and environment
Authors: van Terwisga S. E. , Hacar A. , van Dishoeck E. F.
Published: July 2019

Context. The mass evolution of protoplanetary disks is driven by internal processes and by external factors such as photoevaporation. Disentangling these two effects, however, remains difficult.

Aims. We measured the dust masses of a sample of 132 disks in the Orion Molecular Cloud 2 (OMC-2) region, and compared them to externally photoevaporated disks in the Trapezium cluster, and to disks in nearby low-mass star-forming regions (SFRs). This allowed us to test whether initial disk properties are the same in high- and low-mass SFRs, and enabled a direct measurement of the effect of external photoevaporation on disks.

Methods. A ~ 20′ × 4′ mosaic of 3 mm continuum observations from the Atacama Large Millimeter/submillimeter Array (ALMA) was used to measure the fluxes of 132 disks and 35 protostars >0.5 pc away from the Trapezium. We identify and characterize a sample of 34 point sources not included in the Spitzer catalog on which the sample is based.

Results. Of the disks, 37 (28%) are detected, and have masses ranging from 7−270 M⊕. The detection rate for protostars is higher (69%). Disks near the Trapezium are found to be less massive by a factor 0.18−0.11+0.18, implying a mass loss rate of 8 × 10−8 M⊙ yr−1.

Conclusions. Our observations allow us to distinguish the impact of time and environment on disk evolution in a single SFR. The disk mass distribution in OMC-2 is statistically indistinguishable from that in nearby low-mass SFRs like Lupus and Taurus. We conclude that age is the main factor that determines the evolution of these disks. This result is robust with respect to assumptions of dust temperature, sample incompleteness, and biases. The difference between the OMC-2 and Trapezium cluster samples is consistent with mass loss driven by far-ultraviolet radiation near the Trapezium. Taken together, this implies that in isolation disk formation and evolution proceed similarly, regardless of cloud mass.
ALMA view of the12C/13C isotopic ratio in starburst galaxies
Authors: Tang X. D. , Henkel C. , Menten K. M. , Gong Y. , Martín S. , Mühle S. , Aalto S. , Muller S. , García-Burillo S. , Levshakov S. , Aladro R. , Spaans M. , Viti S. , Asiri H. M. , Ao Y. P. , Zhang J. S. , Zheng X. W. , Esimbek J. , Zhou J. J.
Published: July 2019

We derive molecular-gas-phase12C/13C isotope ratios for the central few hundred parsecs of the three nearby starburst galaxies NGC 253, NGC 1068, and NGC 4945 making use of theλ ∼ 3 mm12CN and13CNN= 1–0 lines in the ALMA Band 3. The12C/13C isotopic ratios derived from the ratios of these lines range from 30 to 67 with an average of 41.6 ± 0.2 in NGC 253, from 24 to 62 with an average of 38.3 ± 0.4 in NGC 1068, and from 6 to 44 with an average of 16.9 ± 0.3 in NGC 4945. The highest12C/13C isotopic ratios are determined in some of the outskirts of the nuclear regions of the three starburst galaxies. The lowest ratios are associated with the northeastern and southwestern molecular peaks of NGC 253, the northeastern and southwestern edge of the mapped region in NGC 1068, and the very center of NGC 4945. In the case of NGC 1068, the measured ratios suggest inflow from the outer part of NGC 1068 into the circum-nuclear disk through both the halo and the bar. Low12C/13C isotopic ratios in the central regions of these starburst galaxies indicate the presence of highly processed material.
Opacity distribution functions for stellar spectra synthesis
Authors: Cernetic M. , Shapiro A. I. , Witzke V. , Krivova N. A. , Solanki S. K. , Tagirov R. V.
Published: July 2019

Context. Stellar spectra synthesis is essential for the characterization of potential planetary hosts. In addition, comprehensive stellar variability calculations with fast radiative transfer are needed to disentangle planetary transits from stellar magnetically driven variability. The planet-hunting space telescopes, such as CoRoT, Kepler, and TESS, bring vast quantities of data, rekindling the interest in fast calculations of the radiative transfer.

Aims. We revisit the opacity distribution functions (ODF) approach routinely applied to speed up stellar spectral synthesis. To achieve a considerable speedup relative to the state of the art, we further optimize the approach and search for the best ODF configuration. Furthermore, we generalize the ODF approach for fast calculations of flux in various filters often used in stellar observations.

Methods. In a parameter-sweep fashion, we generated ODF in the spectral range from UV to IR with different setups. The most accurate ODF configuration for each spectral interval was determined. We adapted the wavelength grid based on the transmission curve for calculations of the radiative fluxes through filters before performing the normal ODF procedure.

Results. Our optimum ODF configuration allows for a three-fold speedup, compared to the previously used ODF configurations. The ODF generalization to calculate fluxes through filters results in a speedup of more than two orders of magnitude.
Synthesis, performance and growth mechanism of silver nanoparticle coated SERS fiber probe
Authors: Geng Mengmei , Long Yuting , Liu Tongqing , Du Zijuan , Li Hong , Liu Zirui , Xie Yahong
Published: July 2019

Surface-enhanced Raman Scattering (SERS) fiber probe provides abundant interaction area between light and materials, permits detection within limited space and is especially useful for remote or in situ detection. A silver decorated SERS fiber optic probe was prepared by hydrothermal method. This method manages to accomplish the growth of silver nanoparticles and its adherence on fiber optic tip within one step, simplifying the synthetic procedure. The effects of reaction time on phase composition, surface plasmon resonance property and morphology were investigated by X-ray diffraction analysis (XRD), ultraviolet-visible absorption spectrum (UV-VIS absorption spectrum) and scanning electron microscope (SEM). The results showed that when reaction time is prolonged from 4–8 hours at 180 °C, crystals size and size distribution of silver nanoparticles increase. Furthermore, the morphology, crystal size and distribution density of silver nanoparticles evolve along with reaction time. A growth mechanism based on two factors, equilibrium between nucleation and growth, and the existence of PVP, is hypothesized. The SERS fiber probe can detect rhodamin 6G (R6G) at the concentration of 10−6 M. This SERS fiber probe exhibits promising potential in organic dye and pesticide residue detection.
Evguenii Konstantinovitch Zavoïskii (1907-1976) et la découverte de la résonance paramagnétique électronique
Authors: Semerok Alexandre , Soulié Edgar , Zavoïskaya Natalia E.
Published: July 2019

Evguenii Konstantinovitch Zavoïskii fut un éminent physicien expérimentateur russe. En 1944, à Kazan en URSS, il réalisa l’expérience décisive de la découverte de la résonance paramagnétique électronique (RPE).

La RPE permet d’étudier la structure électronique de molécules paramagnétiques. Elle a un impact significatif en physique, chimie, minéralogie, biologie, médecine et physiologie.

Avec son talent original d’expérimentateur et sa profonde intuition physique, Zavoïskii a aussi mené des recherches brillantes sur la physique nucléaire, la fusion thermonucléaire contrôlée, l’électronique physique et les phénomènes rapides.