bluuebunny/crossref_metadata_2025 huggingface dataset:
Coupling hierarchical iron cobalt selenide arrays with N-doped carbon as advanced anodes for sodium ion storage
Authors: Wang Peijia , Huang Jiajie , Zhang Jing , Wang Liang , Sun Peiheng , Yang Yefeng , Yao Zhujun
Published: February 2021

Hierarchically core–branched iron cobalt selenide arrays coated with N-doped carbon shell were designed and synthesized on carbon cloth, showing prominent electrochemical performance both in half-cell and full cell sodium ion batteries.
A hierarchical heterojunction polymer aerogel for accelerating charge transfer and separation
Authors: Yin Yue , Wu Chongbei , Yu Guanhang , Wang Haozhen , Han Qing , Qu Liangti
Published: February 2021

A hierarchical heterojunction polymer aerogel based on oxygen- and nitrogen-linked heptazine with a donor–acceptor structure was designed for accelerating charge transfer and separation, which showed advanced photocatalytic H2-production activities.
Combinations of histone post-translational modifications
Authors: Taylor Bethany C. , Young Nicolas L.
Published: February 2021

Histones are essential proteins that package the eukaryotic genome into its physiological state of nucleosomes, chromatin, and chromosomes. Post-translational modifications (PTMs) of histones are crucial to both the dynamic and persistent regulation of the genome. Histone PTMs store and convey complex signals about the state of the genome. This is often achieved by multiple variable PTM sites, occupied or unoccupied, on the same histone molecule or nucleosome functioning in concert. These mechanisms are supported by the structures of ‘readers’ that transduce the signal from the presence or absence of PTMs in specific cellular contexts. We provide background on PTMs and their complexes, review the known combinatorial function of PTMs, and assess the value and limitations of common approaches to measure combinatorial PTMs. This review serves as both a reference and a path forward to investigate combinatorial PTM functions, discover new synergies, and gather additional evidence supporting that combinations of histone PTMs are the central currency of chromatin-mediated regulation of the genome.
Joint caching and computing resource allocation for task offloading in vehicular networks
Authors: Wang Zhi , Hou Ronghui
Published: February 2021

To meet the requirement of constrained delay and computation resource of the future vehicular networks, it is imperative to develop efficient content caching strategy and computation resource allocation strategy in mobile edge computing (MEC) servers. In the proposed network framework, since the caching capacity and computing resource of each MEC are limited, and the coverage areas of MECs are overlapped, the vehicular networks have to decide what contents to cache, how to offload tasks and how much computing resource needs to be allocated for each task. In this study, in order to jointly tackle these issues, we formulate caching strategy, offloading decision and computing resource allocation coordinately as a mixed integer non‐linear programming (MINLP) problem. To solve the MINLP problem, we divide it into two subproblems. Firstly, we investigate a balanced and efficient caching strategy based on similarity in vehicular networks. Secondly, we apply McCormick Envelopes to convert MINLP problem into LP problem, and then adopt improved branch and bound algorithm to obtain the optimal offloading decision and computing resource allocation strategy. Simulation results indicate that the proposed schemes have a good performance in reducing economic cost under the deadline of each task.
Matched‐pole–zero discrete‐time model in the state‐space representation
Authors: Yagi Keisuke
Published: February 2021

In this paper, the matched‐pole–zero model which has been widely used for discretisation of a single‐input–single‐output control system described in transfer‐function forms is extended to be applicable to the system in state‐space forms. The matched‐pole–zero model is classified as the discrete‐time model, where poles and transmission zeros are mapped into the discrete‐time domain according to the same discretisation law defined by a certain algebraic relationship. In order to obtain the matched‐pole–zero model, the paper presents an equivalent reconfiguration, which transforms a system into an internal feedback structure around a subsystem based on the principle of control zeros. Discretisation of the subsystem produces a discrete‐time model, where transmission zeros are mapped according to the desired law. The proposed matched‐pole–zero model is obtained by modifying the pole placements of this discrete‐time model. As long as the direct‐term matrix of the underlying system is nonsingular, the proposed model can be obtained algorithmically and is applicable to a multi‐input‐multi–output system without any modification. The paper provides numerical examples verifying that the proposed matched‐pole‐zero model preserves the unique characteristics of the underlying system due to the zeros, such as the blocking and the decoupling properties, and causes smaller discretisation errors than the comparable matched‐pole–zero model.
Upper body estimation of muscle forces, muscle states, and joint motion using an extended Kalman filter
Authors: Mohammadi Hanieh , Khademi Gholamreza , Simon Dan , van den Bogert Antonie J. , Richter Hanz
Published: February 2021

This study synthesises modelling techniques and dynamic state estimation techniques for the simultaneous estimation of the muscle states, muscle forces, and joint motion states of a dynamic human arm model. The estimator considers both muscle dynamics and motion dynamics. The arm model has two joints and six muscles and contains dynamics both of the muscles and of the motion. We develop an optimally tuned extended Kalman filter using noisy measurements of joint angles with standard deviation 2.87, of joint velocities with standard deviation 6.9/s, and of muscle activations with standard deviation 10% of their peak values, and then simultaneously estimate joint angles, joint velocities, muscle forces, joint moments, and muscle states. The standard deviations of estimation errors (SDEE) are no more than 0.07° for joint angles, 1/s for joint velocities, 0.6 mm for muscle–tendon lengths, and 0.1 Nm for joint torques. The results are compared with a previously developed static optimisation method, and verify the effectiveness of the proposed estimator in providing lower SDEE for both muscle and motion dynamics of the human arm model compared to the static optimisation method.
Adaptive fuzzy output regulation of uncertain pure‐feedback non‐linear systems with prescribed performance
Authors: Jia Fujin , Lu Junwei , Li Yongmin , Liu Yang
Published: February 2021

The output regulation problem for pure‐feedback non‐linear systems with prescribed performance (PP) driven by an external linear system with unknown parameter are investigated. First, an observer with a disturbance signal is designed to observe unmeasured system states. Secondly, fuzzy logic systems (FLS) are used to approximate unknown non‐linear non‐affine functions. Thirdly, a fuzzy internal model is obtained to reject disturbance, and an adaptive fuzzy output feedback algorithm is proposed based on dynamic surface control (DSC) technique and backstepping method. Simultaneously, an L function is constructed so that the overall property (steady‐state property and dynamic property) of the tracking error are constrained by PP functions. The results explain that the proposed control algorithm can make sure that all signals of the closed‐loop system are semi‐globally uniformly ultimately bounded (SUUB), and the tracking error is semi‐globally PP uniformly ultimately bounded (SPPUUB). Finally, two examples are given to show the validity of the results.
Fault estimation for continuous‐time non‐linear switched systems with time‐varying delay based on intermediate estimator
Authors: Wang Yuenan , Zhu Yanzheng , Ji Wenchengyu , Jiang Yulian , Wang Shenquan
Published: February 2021

In this work, the fault estimation (FE) problem is studied for continuous‐time non‐linear switched systems with time‐varying delay over fading channel under average dwell time switching. A novel FE method based on the intermediate estimator is used to eliminate the observer matching constraint condition, where an intermediate variable is introduced to estimate the state and fault simultaneously. Meanwhile, the fading channel of data transmission is modelled as Bernoulli distributed white sequences. Furthermore, because the observer matching conditions are eliminated by the intermediate estimator, both the wirtinger integral inequality and an advanced reciprocal convex combination method are utilised to provide a tighter estimation on continuous derivative of certain Lyapunov–Krasovskii function over fading channel, leading to a less conservative result. Moreover, the solution of the parameters for intermediate estimator is characterised in the feasibility of linear matrix inequality problem. Finally, two numerical examples indicate the proposed technique is valid and superior.
Modified fuzzy neural network control using sliding mode technique for power quality improvement system with experimental verification
Authors: Hou Shixi , Chu Yundi , Fei Juntao
Published: February 2021

This study mainly focuses on the development of a second‐order sliding mode‐based meta‐cognitive fuzzy neural network (MCFNN) control for power quality improvement, whereby an MCFNN is employed to learn modelling uncertainties. First, a second‐order sliding mode control (SOSMC) is designed to track reference current for active power filter. Then, an MCFNN system with accurate approximation capability is further investigated to learn the unknown parts in SOSMC. Different from the existing predefined structure approaches, only necessary data can be extracted to adjust the structure and parameters of the networks in MCFNN. Subsequently, the Lyapunov stability analysis is presented to guarantee tracking performance and stability of the closed‐loop system. Moreover, the excellent performance of the proposed MCFNN scheme is verified by simulation and experimental studies, and its remarkable characteristics are exhibited in comparison with other intelligent control schemes.
Static output feedback sliding mode control under rice fading channel: an interval type‐2 fuzzy modelling method
Authors: Zhang Zhina , Niu Yugang , Chen Bei
Published: February 2021

This work investigates the static output feedback sliding mode control (SMC) design problem of uncertain non‐linear systems with Rice fading channels. The interval type‐2 Takagi‐Sugeno fuzzy modelling approach is exploited to express non‐linear dynamics with uncertain parameters. As the wireless network between the sensor and the controller may be subject to channel fading, the premise variables are probably altered during their propagations. In such cases, a key issue is to synthesise a desired SMC law for stabilising the controlled non‐linear systems. To this end, new membership functions are constructed via employing the fading measurements and the desired SMC law are subsequently synthesised. To deal with the disturbances in communication channels, the notion of input‐to‐state stable in probability (ISSiP) is utilised and sufficient criteria are deduced to guarantee the ISSiP of the resultant closed‐loop systems and the reachability of the prescribed sliding surface. Finally, a simulation example illustrates the designed control strategy.
Stator and rotor turn‐to‐turn fault detection in wound rotor induction machines based on the air‐gap magnetic field distortion
Authors: Nazemi Mohammad Hosein , Haghjoo Farhad , Cruz Sergio Manuel A. , Gallehdar Davar
Published: February 2021

An efficient online flux‐based diagnostic approach is proposed to detect turn‐to‐turn faults in the stator and rotor windings of wound rotor induction machines, at an early stage of development, which can be applied in the online mode. Some flux sensors are installed in the stator slots to detect the rotational magnetic field at various positions along the air‐gap circumference. These sensors measure the flux linked to all winding coil groups, in the three phases. Any fault occurring either in the stator or rotor windings will disturb the air‐gap flux and create an asymmetry in the rotational magnetic field, which is detectable through the difference of the induced voltages in the corresponding flux sensors. The proposed diagnostic technique is evaluated by finite element analysis as well as by multiple experimental tests. The obtained results show that such invasive technique is able to detect and discriminate various faults in the stator and rotor windings with high accuracy, low calculation burden, proper sensitivity and appropriate robustness in the face of machine load level variations.
Stability and bifurcations in low inertia PV rich power networks
Authors: Vinaya Mohanan Vishnu A. , Mareels Iven M. Y. , Evans Robin J. , Morton Anthony B. , Kolluri Ramachandra Rao
Published: February 2021

The present trend of inserting increasingly more solar photovoltaic (PV) sources into the electricity grid leads to a significant reduction in mechanical inertia. Inertia represents energy reserve in the grid, that inherently and instantaneously supports frequency stability. Therefore, recent studies have re‐examined the frequency stability of the grid. Most of these consider scenarios where the participation from grid‐following inverters remains relatively low. More importantly, these studies include an infinite bus in their analyses. The infinite bus acts as a very stiff voltage source which has a significantly stabilising influence, the more so as all control refers back to the infinite bus. Here, the frequency stability of a grid with significant generation from grid‐tied PV inverters is considered without reference to an infinite bus. In the proposed simplified grid model, all the synchronous generators (SGs) are lumped as one large SG complete with classically operating controls. Similarly, all the PV generators are lumped as one large, quasi‐instantaneous, non‐linear power source. In this simplified network, the feasible operating region is identified using bifurcation techniques. It transpires that the stable operating region is bounded by a locus of Hopf bifurcations linked (inter‐alia) to the fraction of power generated by grid‐tied PV inverters.
Effect of ambient temperature variations on estimation of proximity of the voltage collapse point
Authors: Burle Trinadha , Chintapalli V V S Bhaskara Reddy
Published: February 2021

Due to deforestation, greenhouse gases and increasing air conditioner systems, the temperatures are changing drastically and the effects are prominent in summer and winter seasons. These ambient temperature variations are affecting the transmission system parameters and also the voltages at various buses. Changes in the transmission line parameters have non‐negligible impact on system performance and present Energy Management applications are not considering these temperature variations in the power system state estimation. In this paper, impact of temperature variations on the power system Voltage Stability assessment is considered. Voltage stability assessment methods make use of the load flow results. Load flow results without considering the temperature variations are inaccurate in the real‐time and leading to the erroneous results in the voltage stability assessment. In view of this, studies have been carried out on IEEE 30‐bus, 118‐bus and 300‐bus systems, incorporating the seasonal temperature variations on various types of conductors, and also demonstrated the impact with conventional and ZIP type load models. In this paper, four voltage stability indices NLVSI, , FVSI and VCPI(power) are used for identifying the proximity of voltage collapse point, critical line, critical bus voltage, critical bus angle, total system active power loss, total system reactive power loss etc.
Digital image processing for physical basis analysis of electrical failure forecasting in XLPE power cables based on field simulation using finite‐element method
Authors: Talaat M. , Tayseer M. , El‐Zein A.
Published: February 2021

In this research, digital image processing method (DIPM) is used as an innovative approach to predict precisely the shape of electrical tree (ET) in cross‐linked polyethylene (XLPE) power cables in the presence of air voids based on the field calculation using finite‐element method (FEM). With the help of DIPM, two case studies are held to detect the accurate parameters of either the first initiated major branch or the tips of the major branches of ET. A hyperbolic needle‐to‐plane simulation model is proposed to illustrate the ET inception and propagation stages. The non‐uniform electric fields thatare accompanied with the electrical treeing phenomenon are calculated using FEM as one of the most effective numerical methods to deal with non‐uniform shapes. The predicted shapes of ET initiation and growth are provided in an innovative manner with the implemented hybrid connection between FEM and DIPM for the two proposed case studies. Direction branching approach and deviation angle branching approach are provided in this work to predict the shape and the direction of ET branched voids. The validity of the proposed model is assessed with the help of available previous experimental and simulation data.
PMU‐based decentralised mixed algebraic and dynamic state observation in multi‐machine power systems
Authors: Lorenz‐Meyer Nicolai , Bobtsov Alexey , Ortega Romeo , Nikolaev Nikolay , Schiffer Johannes
Published: February 2021

The authors propose a novel decentralised mixed algebraic and dynamic state observation method for multi‐machine power systems with unknown inputs and equipped with phasor measurement units (PMUs). More specifically, they prove that for the third‐order flux‐decay model of a synchronous generator, the local PMU measurements provide enough information to reconstruct algebraically the load angle and quadrature‐axis internal voltage. Due to the algebraic structure, a high numerical efficiency is achieved, which makes the method applicable to large‐scale power systems. Also, they prove that the relative shaft speed can be globally estimated combining a classical immersion and invariance observer with – the recently introduced – dynamic regressor extension and mixing parameter estimator. This adaptive observer ensures global convergence under weak excitation assumptions that are verified in applications. The proposed method neither requires the measurement of exogenous input signals such as the field voltage and the mechanical torque nor the knowledge of mechanical subsystem parameters.
Controller area network reliability: overview of design challenges and safety related perspectives of future transportation systems
Authors: Ben Lakhal Nadhir Mansour , Nasri Othman , Adouane Lounis , Hadj Slama Jaleleddine Ben
Published: February 2021

The in‐vehicular networked control system is among the most critical embedded processes. The controller area network (CAN) has prevailed intra‐vehicle communication for decades. Meanwhile, requirements of future transportation systems are expected to emphasise the in‐vehicle communication complexity, which endangers the reliability/safety of the intelligent navigation. At first, this study reviews the recent solutions proposed to overcome the CAN expanding complexity. Challenges that tomorrow's intelligent vehicles may raise for CAN reliability are investigated. The comprehensive coverage of current research efforts to remove the impact of these challenges is presented. Further, the in‐vehicle system reliability of future automated vehicles is also related to the fault diagnosis performances. Hence, different classes of system‐level diagnosis strategies are compared relatively to the requirements of automotive embedded networks. Furthermore, to thoroughly cover CAN reliability engineering issues, focus is given to the automotive validation techniques. The hardware in the loop, real‐time analysis and computer‐aided‐design tools intervene in various phases along the in‐vehicular network life cycle. Parameters that stand behind the efficiency and accuracy of these techniques in validating the new generation of vehicles are analysed. The authors finally draw some deductive predictions about the future directions related to the reliability of the intelligent transportation system in‐vehicular communication.
Safety assessment of local cooperative warnings and speed limit information
Authors: Rämä Pirkko , Innamaa Satu
Published: February 2021

The study was designed to assess the impacts of cooperative intelligent transport systems (C‐ITS) on traffic safety. The aim was also to review assumptions made in some previous studies and verify or update the earlier safety estimates. Seven informative C‐ITS services warning about various situations and hazards were selected in the study. The expert estimates provided were grounded on new evidence about driver behaviour, the crash categories created in the European Risk Calculation tool (ERiC), and literature. The C‐ITS services were assessed to reduce the number of fatalities and injury crashes. The clearly biggest drop in fatalities was assessed for ‘In‐vehicle signage, speed limit’, ‘Weather warning’ being the second most effective. The next effective were assessed to be ‘Warning of emergency braking ahead’ and ‘Road works warning’. The smallest but still positive impacts were assessed for ‘Traffic jam ahead warning’, ‘Car breakdown warning’ and ‘In‐vehicle signage, child and pedestrian crossing ahead’. Generally, the effectiveness was assessed to be somewhat smaller for injury crashes than fatalities. The authors conclude that the results are positive both for implementing C‐ITS services as such and as supporting measure for the deployment of more intervening ITS and automated driving.
High‐accuracy vehicle lamp detection for real‐time night‐time traffic surveillance
Authors: Tsai Wen‐Kai , Chen Hung‐Ju
Published: February 2021

Vehicle lamps are an important image feature of the night‐time vehicle detection algorithm. This study proposes a real‐time night‐time vehicle detection algorithm based on light attenuation characteristic analysis, which consists of vehicle lamp detection and pairing. For the detection phase, this study proposes an automatic dual‐threshold method to quickly extract the attenuation regions around bright objects. This method is highly adaptable and can accurately extract attenuation regions to identify vehicle lamps and strong reflections. For the pairing phase, this study uses the moving trajectories of vehicle lamps to complete preliminary pairing. Then, the vehicle lamp pairing is optimised using the relative vertical and horizontal lamp positions in continuous images. Pixel‐ and object‐based methods were used to verify the experimental vehicle lamp detection results. The results of both verification methods indicate that the proposed algorithm without morphological operation is superior to other algorithms. The accuracy of the pairing phase was >94.6% in scenes with multiple lamps, high‐driving speed, high traffic flow, and rain. Finally, the proposed night‐time vehicle detection algorithm can achieve a real‐time execution speed for images 960 × 720 pixels in size.
Finite‐time active shimmy control based on uncertain disturbance observer for electric vehicle with independent suspension
Authors: Meng Qinghua , Qian Chunjiang , Hu Chuan , Sun Zong‐Yao , Wang Pan
Published: February 2021

For attenuating the shimmy phenomenon appeared in an electric vehicle (EV) with independent suspension, this study proposes a finite‐time active shimmy stability control method based on an uncertainty estimation observer. Firstly, a four‐degree‐of‐freedoms shimmy model of an EV with independent suspension is constructed. Secondly, in order to deal with the uncertainties in the shimmy model, a finite‐time control method via a non‐linear uncertain disturbance observer is proposed. The direct Lyapunov function method is used to analyse the global stability of the closed‐loop system, and the results show that the system outputs globally converge to zero. Simulation and hardware‐in‐the‐loop simulation test results verify the built shimmy model and show the effectiveness of the designed control method compared with the sliding mode control method.
Novel dual‐layer‐oriented strategy for fully automated vehicles’ lane‐keeping system
Authors: An Quan , Cheng Shuo , Li Liang , Peng Haonan
Published: February 2021

A novel concept of a dual‐layer‐oriented control strategy for fully automated vehicles’ lane‐keeping system is proposed which consists of an inner controller with a modified preview driver model and an outer cooperative copilot controller. With designed weighting function of displacement error based on a hyperbolic tangent and adjustable preview horizon according to road geometry, the inner controller is supposed to track the lane centreline precisely and efficiently through optimal control framework. The outer controller is specially designed for situations where the vehicle may run out of the lane and cause a collision. Only when the vehicle is at high risk of lane‐crossing, the outer controller is activated to guide the vehicle back to lane centreline by exerting proper steering command, which is calculated by solving a model predictive control‐based constrained optimisation problem with a designed quadratic cost function. Finally, simulation tests based on CarSim‐Matlab joint platform are carried out to verify the proposed strategy. Results demonstrate that the modified preview driver model is able to improve path following performance and the dual‐layer‐oriented control strategy with less computational burden can effectively prevent the vehicle from crossing lane boundaries.
Filter‐based control of a buck converter for uncertain non‐linear loads
Authors: Bhagwat Bhagyashri A. , Alqatamin Moath , Hawkins Nicholas , McIntyre Michael L.
Published: February 2021

In this study, a filter‐based control scheme is proposed for dc–dc buck‐type converters. Primarily, this control scheme reduces costs by requiring only a single output voltage measurement, removing the need for potentially noisy current measurements. The proposed controller is compared with a Type III error amplifier, which is a linear controller commonly used for buck‐type converters. The performance of these controllers is compared when applied to linear and non‐linear loads. A Lyapunov stability analysis is utilised to demonstrate the system stability of the proposed control scheme. Experimental results demonstrate excellent voltage regulation and insensitivity to the load variations for the proposed controller as compared to Type III controller.
IZAQ‐LMS‐based control of PV‐battery interfaced microgrid in grid‐connected and autonomous modes
Authors: Gupta Shikha , Verma Anjeet , Singh Bhim , Garg Rachana , Singh Alka
Published: February 2021

This study presents a voltage source converter (VSC) control of solar photovoltaic (PV)‐battery‐based three‐phase grid interfaced microgrid. This microgrid is controlled to operate in an autonomous mode and the grid‐connected mode. In grid integrated mode, the control aims to improve the power quality of the grid current and to ensure the unity power factor operation at the grid. Therefore, in the grid‐connected mode, the improved zero attracting quaternion‐valued least mean square (IZAQLMS) control approach with high DC offset rejection capability is used. Owing to this, the reference grid currents become immune to harmonics and DC‐offset. The control strategy takes power management into account and additionally assists several vital functions such as compensation of reactive power, power factor correction, and harmonics mitigation. This control scheme also ensures the stable system operation in autonomous mode following an unexpected incident deprived of collapse owing to the grid failure and discrepancy in the generation and load demand. In off‐grid mode, the microgrid control generates a good quality of voltages and feeds the power to the load using the PV array and the battery. Simulated and test results on a laboratory prototype validates the effectiveness of the system.
New interleaved high step‐up converter based on a voltage multiplier cell mixed with magnetic devices
Authors: Nouri Tohid , Shaneh Mahdi
Published: February 2021

A high step voltage ratio converter is introduced in this study. In order to improve the voltage gain and the voltage stress of semiconductors, coupled‐inductor (CI) combined with built‐in transformer (BIT) and voltage multiplier cell are employed. Therefore, comparing with previously presented converters in which only CI or BIT structure was used, a greater degree of freedom is obtained. Consequently, the low voltage rated semiconductors can be utilised which in turn decrease the conduction losses. To deal with the ringing phenomenon and reverse recovery problem, zero‐current switching turn‐on/turn‐off are well achieved for switches/diodes via leakage inductances of magnetic means. Moreover, by employing passive clamps, leakage energy is recycled. Furthermore, due to the interleaved structure, the input current ripple is considerably diminished. In addition, the share of input current between different phases is equitable as a result of the charge balance of capacitors. With all these in mind, the proposed structure is a good candidate for high current and high power applications. Finally, in order to validate the effectiveness of the proposed topology, a 600 W 24 V/480 V laboratory prototype is fabricated.
New auxiliary circuit for boost converter to achieve soft‐switching operation and zero input current ripple
Authors: Alavi Peyman , Khoshkbar‐Sadigh Arash , Babaei Ebrahim , Mohseni Parham , Marzang Vafa , Talebian Iman
Published: February 2021

In this study, a simple auxiliary circuit is proposed and investigated to provide soft‐switching operation in the boost converter. The proposed auxiliary circuit includes only a small auxiliary inductor and two auxiliary capacitors. In this structure, by implementing the auxiliary inductor, a negative current flows through the power switch before its turn‐on moment. Therefore, the power switch turns on under zero voltage switching condition. In addition, by properly designing the parallel capacitor of the power switch, a soft‐switching condition can be achieved for its turn‐off. Furthermore, implementing this simple auxiliary circuit can be helpful to decrease the reverse recovery losses of the diode since the diode turns off under zero current switching condition. Another advantage of the proposed structure is its zero input current ripple. In this study, the performance of the proposed auxiliary circuit with conventional boost converter has been analysed, and designing the methodology of the auxiliary components is presented. Voltage stress and power loss of components, converter voltage gain, and closed‐loop model of the converter have been investigated. Moreover, the performance of the proposed auxiliary circuit is compared with previous works and its operation is investigated in a 200 W laboratory prototype.
Wind turbines anomaly detection based on power curves and ensemble learning
Authors: Moreno Sinvaldo R. , Coelho Leandro dos Santos , Ayala Helon V.H. , Mariani Viviana Cocco
Published: February 2021

Wind farms are increasingly important nowadays since in some countries can surpass conventional power sources. However, in countries where the exploration of this renewable source started recently, the lack of knowledge related to maintenance routines and efficient operation has led to fast performance degradation. In this context, wind turbine condition monitoring can detect anomalies in its performance as an unexpected failure, avoiding financial loss. In this study, machine learning approaches are applied as an online tool to detect abnormal wind turbine operation modes, evaluating the wind turbine operation in all regions of the power curve. The methodology has been validated with an original and real dataset collected from a large‐scale onshore wind turbine in Northeast Brazil. The results exhibit an expressive reduction of energy loss and indicate the ability of the proposed approach to assessing the abnormal modes even when a small number of recorded data are available. The standard classifiers reached on average 98.64% accuracy in the holdout data set. Additionally, an ensemble of classifiers is proposed which helped to improve in 12% the accuracy of the best classifier alone, increasing the confidence of alarms raised by the predictive maintenance tool.
Line fault location for multi‐terminal MMC‐HVDC system based on SWT and SVD
Authors: Huai Qing , Liu Kaipei , Hooshyar Ali , Ding Hua , Qin Liang , Chen Kun
Published: February 2021

This study presents a travelling wave (TW)‐based method for locating DC line faults in a modular multilevel converter (MMC)‐based high‐voltage direct current (HVDC) system by using local information. Pole voltage signals are adopted and denoised via stationary wavelet transform (SWT) with improved threshold functions. Hankel matrix‐based singular value decomposition (SVD) is utilised to detect TW arrivals. The arrival times of incidental and reflected wave heads are observed in SVD result. The reflected wave heads from the fault point and the opposite end can be discriminated by comparing surge polarities in SVD result. The proposed method relies on the TW principle but is independent of TW propagation velocity. The feasibility of the proposed algorithm is evaluated considering potential factors, such as fault resistance, close‐in fault, remote fault, sampling rate and noise. The superiority of this method is validated by comparing it with other signal‐processing techniques and TW‐based fault location principles. Electromagnetic transient simulation of the multi‐terminal HVDC system on Power Systems Computer Aided Design / Electromagnetic Transients including DC (PSCAD/EMTDC) is conducted to provide fault TW signals, which are analysed in MATLAB. A corresponding equivalent test model developed in a real‐time digital simulator is also provided for conducting a supplementary study to verify and further research this fault location method.
In‐situ seeding synthesis of walnut kernel‐like Ag nanostructures with highly efficient SERS performance
Authors: Dong Lihong
Published: February 2021

By an in‐situ seeding synthetic route, with biocompatible reagents being used, walnut kernel‐like Ag nanostructures (Ag nanowalnuts) composed of nanoplates were fabricated. The in‐situ formation of seeds and introduction of complex [Ag3(C6H5O7)n+1]3n−were indispensable steps for this kind of self‐assembled nanostructure. The size of Ag nanowalnuts was in the range of 200–400 nm and the thickness of a single nanoplate was about 30 nm. The morphology of nanoplates was of variety, and their surface was bumpy. Such Ag nanostructures with rough surface and high curvature provided plenty of ‘hot spots’ on a single particle for surface‐enhanced Raman scattering (SERS) enhancement. Experimental results indicated that the Ag nanowalnuts offered great surface enhancement for 4‐mercaptobenzoic acid and malachite green molecules. The limit of detection was low to 10−10 and 10−8 M, respectively.
Fabrication and photocatalytic performance of C, Pt‐comodified TiO2 nanotubes
Authors: Huo Guona , Zhou Kehan , Zhang Shasha , Liu Xiaotong , Suo Zhaochen , Zhu Baolin , Zhang Shoumin , Huang Weiping
Published: February 2021

Compared with common TiO2 powder, TiO2 nanotubes can exhibit better catalytic performance for their high specific surface area. By using hydrogen TiO2 nanotubes synthesised via the hydrothermal process as carriers, carbon and platinum co‐modified TiO2 nanotubes (C‐Pt/TiO2NTs) were prepared via impregnation–photoreduction method in this study. X‐ray diffraction, transmission electron microscopy, X‐ray photoelectron spectroscopy, and infrared spectrum were used to characterise the structure and composition of the prepared samples. Their catalytic activities for degrading methyl orange under ultraviolet (UV) illumination and simulated sunlight were evaluated. The influences and mechanism of dopants and their contents on the catalysts’ activity were investigated. Obtained results indicated that the modification can improve the photocatalytic activity of TiO2 nanotubes under both UV light and simulated sunlight. Among them, C‐Pt/TiO2NTs with 0.5 wt% Pt exhibited the best performance.
Effects of anisotropy on absorption cross-section spectra of medium-sized spheroidal corundum particles
Authors: Höfer S. , Mutschke H. , Mayerhöfer Th. G.
Published: February 2021

Context. It has been widely accepted that corundum particles condense in the atmospheres of oxygen-rich asymptotic giant branch stars and effectively produce an infrared emission feature at 13 μm. Laboratory experiments have predicted that these particles have the shape of oblate spheroids.

Aims. We investigate the influence of the material anisotropy of uniaxial corundum on absorption cross section spectra of medium sized spheroidal particles in the infrared spectral region.

Methods. We compared absorption cross-section spectra of the anisotropic corundum particles gained by finite-difference time-domain simulations to spectra calculated by a weighted sum approximation of the according fictive isotropic materials, with one material having the dielectric function of the a–b-plane and the other having the dielectric function of the c-axis of corundum. We carried out investigations for different axes ratios of the spheroids, particles volumes, and different geometries of the dielectric axes to the particle axes as well as to the polarization and propagation direction of the incident light.

Results. We observed several effects attributed to anisotropy that are non-additive, so that they cannot be reproduced with the combined spectra of the isotropic materials.

Conclusions. Care should be taken when calculating the corundum infrared spectrum with simpler approaches. When particle sizes above 1 μm are to be considered, the T-matrix formalism delivers correct band shifts and bulk modes for many, but not all bands. This remains true in orientation-averaged spectra and for particles in the 0.1 μm size range.
Seasonal reappearance of HCl in the atmosphere of Mars during the Mars year 35 dusty season
Authors: Olsen K. S. , Trokhimovskiy A. , Montabone L. , Fedorova A. A. , Luginin M. , Lefèvre F. , Korablev O. I. , Montmessin F. , Forget F. , Millour E. , Bierjon A. , Baggio L. , Alday J. , Wilson C. F. , Irwin P. G. J. , Belyaev D. A. , Patrakeev A. , Shakun A.
Published: February 2021

Hydrogen chloride was discovered in the atmosphere of Mars for the first time during the global dust storm in Mars year (MY) 34 (July 2018) using the Atmospheric Chemistry Suite mid-infrared channel (ACS MIR) on the ExoMars Trace Gas Orbiter. The simultaneity of variations in dust and HCl, and a correlation between water vapour and HCl, led to the proposal of a novel surface-atmosphere coupling analogous to terrestrial HCl production in the troposphere from salt aerosols. After seasonal dust activity restarted in MY 35 (August 2020), we have been monitoring HCl activity to determine whether such a coupling was validated. Here we present a new technique for analysing the absorption features of trace gases close to the ACS MIR noise level and report that HCl mixing ratios are observed to rapidly increase in both hemispheres coincidentally with the onset of the MY 35 perihelion dust season. We present the temporal evolution of the vertical distribution of HCl (0.1–6 ppbv) and of dust activity in both hemispheres. We also report two observations of >2 ppbv HCl below 10 km in the northern hemisphere during the aphelion period.
Analyse von Muskelverletzungen und „Return-to-Training“ im Elite-Taekwondo – Ergebnisse einer prospektiven Kohortenstudie über einen Zeitraum von 5 Jahren
Authors: Rüther Johannes , Willauschus Maximilian , Hammer Alexander , Schröder Jörg , Bail Hermann Josef , Geßlein Markus
Published: February 2021

Hintergrund Muskelverletzungen finden sich häufig in Sprint- und Kontaktsportarten mit explosiven Bewegungsmustern. Bisher liegen keine detaillierten Daten zu Muskelverletzungen im olympischen Taekwondo vor, obwohl in dieser Sportart die Muskulatur der unteren Extremitäten physiologisch extrem stark beansprucht wird.

Methoden Alle im Training und Wettkampf erlittenen Verletzungen von 76 Athleten eines nationalen olympischen Trainingszentrums wurden über einen Zeitraum von 5 Jahren prospektiv erfasst. Die Daten zur Lokalisation der Muskelverletzungen und dem Zeitraum bis zum „Return-to-Training“ wurden retrospektiv ausgewertet. Die Klassifikation der Verletzungen erfolgte mittels British Athletes Muscle Injury Classification System im MRT. Der Zusammenhang zwischen den Untergruppen der MRT-Klassifikation und dem Zeitraum bis zum „Return-to-Training“ wurde untersucht.

Ergebnisse Das Durchschnittsalter der Athleten betrug 22,5 ± 3,2 (16–27) Jahre mit einer mittleren Taekwondo-Praxis von 12,1 ± 4,0 (7–20) Jahren. Am häufigsten betroffen war die ischiocrurale Muskelgruppe (48,4 %), gefolgt vom M. quadriceps femoris (32,3 %) und der Wadenmuskulatur (9,6 %). Die Auswertung der MRT-Klassifikation ergab am häufigsten leichtgrade Muskelverletzungen Grad 1 (3,3 %) und 2 (41,9 %). Es zeigte sich eine positive Korrelation (r = 0,56) zwischen den Subgruppen der MRT-Klassifikation und den Ausfallzeiten der Athleten. Der Vergleich der Ausfallzeiten zwischen den Subgruppen war ebenfalls signifikant unterschiedlich (p < 0,0001).

Zusammenfassung Die ischiocrurale Muskelgruppe ist neben dem M. quadriceps im Taekwondo am häufigsten von Muskelverletzungen betroffen. Am häufigsten wurden indirekte, leichtgradige Muskelverletzungen gefunden (Grad 1–2). Die Ausfallzeit nimmt mit zunehmendem Schweregrad der Verletzung im MRT signifikant zu.
When the ship comes in – COVID-19-Ausbrüche an Bord von Frachtschiffen im Hamburger Hafen
Authors: von Münster Thomas , Kleine-Kampmann Scarlett , Hewelt Elisabeth , Boldt Matthias , Schlaich Clara , Strölin Petra , Oldenburg Marcus , Dirksen-Fischer Martin , Harth Volker
Published: February 2021

Seit Dezember 2019 hält das SARS-CoV-2-Virus die Welt in Atem. Die maritime Welt wird von der Pandemie vielfältig getroffen. Reiserestriktionen schränken den Nachschub von z. B. Ersatzteilen ein und behindern den Crewwechsel massiv. Reguläre und irreguläre Kontakte zur Bevölkerung der jeweiligen Häfen ermöglichen einen Eintrag des Virus in das Schiff. Beengte Lebensverhältnisse an Bord tragen zu einer Ausbreitung des Virus bei. Wir berichten über 2 Ausbruchsgeschehen an Bord von Frachtschiffen, die in ihrer Komplexität die infektionsepidemiologischen Herausforderungen schlaglichtartig beleuchten.
Annahmen und Mythen des Dehnens – Beweglichkeitstraining unter der Lupe
Authors: Kadlec Daniel , Matzka Manuel
Published: February 2021

Dehnen ist oft ein fester Bestandteil von Training und Therapie. Doch notwendig, um gesund und leistungsfähig zu bleiben, scheint diese Intervention gar nicht immer zu sein. Die Trainings- beziehungsweise Therapiezeit könnte demnach bei manchen Athleten und Patienten sinnvoller genutzt werden.
Langzeiteffekte von MT versus OP bei Karpaltunnelsyndrom
Authors: Vielitz Arne
Published: February 2021

Fernández-de-Las-Peñas C, Arias-Burai JL, Cleland JA et al. Manual Therapy Versus Surgery for Carpal Tunnel Syndrome: 4-Year Follow-Up from a Randomized Controlled Trial. Phys Ther 2020; 100: 1987–1996. doi:10.1093/ptj/pzaa150
Es ist noch ein weiter Weg
Authors: Vielitz Arne
Published: February 2021

Buchbinder R, Underwood M, Hartvigsen J et al. The Lancet Series Call to Action to Reduce Low Value Care for Low Back Pain: an Update. Pain 2020; 161: 57–64. doi:10.1097/j.pain.0000000000001869
Sulfation of Quercitrin, Epicatechin and Rutin by Human Cytosolic Sulfotransferases (SULTs): Differential Effects of SULT Genetic Polymorphisms
Authors: Mei Xue , Gohal Saud A. , Alatwi Eid S. , Hui Ying , Yang Chunyan , Song Yongyan , Zhou Chunyang , Liu Ming-Cheh
Published: February 2021

Radix Bupleuri is one of the most widely used herbal medicines in China for the treatment of fever, pain, and/or chronic inflammation. Quercitrin, epicatechin, and rutin, the flavonoids present in Radix Bupleuri, have been reported to display anti-inflammatory, antitumor, and antioxidant biological activities among others. Sulfation has been reported to play an important role in the metabolism of flavonoids. In this study, we aimed to systematically identify the human cytosolic sulfotransferase enzymes that are capable of catalyzing the sulfation of quercitrin, epicatechin, and rutin. Of the thirteen known human cytosolic sulfotransferases, three (cytosolic sulfotransferase 1A1, cytosolic sulfotransferase 1C2, and cytosolic sulfotransferase 1C4) displayed sulfating activity toward quercitrin, three (cytosolic sulfotransferase 1A1, cytosolic sulfotransferase 1A3, and cytosolic sulfotransferase 1C4) displayed sulfating activity toward epicatechin, and six (cytosolic sulfotransferase 1A1, cytosolic sulfotransferase 1A2, cytosolic sulfotransferase 1A3, cytosolic sulfotransferase 1B1, cytosolic sulfotransferase 1C4, and cytosolic sulfotransferase 1E1) displayed sulfating activity toward rutin. The kinetic parameters of the cytosolic sulfotransferases that showed the strongest sulfating activities were determined. To investigate the effects of genetic polymorphisms on the sulfation of quercitrin, epicatechin, and rutin, individual panels of cytosolic sulfotransferase allozymes previously prepared were analyzed and shown to display differential sulfating activities toward each of the three flavonoids. Taken together, these results provided a biochemical basis underlying the metabolism of quercitrin, epicatechin, and rutin through sulfation in humans.
Simultane Implantation von Epithesenankern und Bonebridge zur Versorgung großer Ohrmissbildungen
Authors: Wickert Eva , Kurz Anja , Voelker Johannes , Hagen Rudolf , Kaulitz Stefan , Rak Kristen
Published: February 2021

Hintergrund Die chirurgische Versorgung mit einem Hörimplantat und Epithesen bei Ohrmissbildungen bietet eine gute Kombination aus Hörrehabilitation und kosmetischer Rekonstruktion. Oft wird die Versorgung in 2-zeitigen Operationsschritten durchgeführt. Ziel der Arbeit war es, Erfahrungswerte mit einem Vorgehen zu gewinnen, bei dem das Hörimplantat und die Epithesenanker simultan eingesetzt werden.

Material und Methoden Vier Ohren von 3 Patienten (nw = 1, nm = 2) mit großen Ohrmissbildungen (Typ III nach Weerda) erhielten jeweils in einer Operation eine MedEL Bonebridge und einen Epithesenanker mit 3 Basispfosten. Zuvor war die Indikation mithilfe des Active Middle Ear Implant (aMEI)-Scores nach Frenzel (2013) gestellt worden.

Ergebnisse Alle Patienten erzielten jeweils 4 Punkte im aMEI-Score, was auf eine ungünstige Prognose für eine erfolgreiche Implantation eines aktiven Mittelohrimplantats hinwies. Die Versorgung mit der Bonebridge und einem Epithesenanker konnte daraufhin komplikationslos durchgeführt werden. Postoperativ erfolgten nach 4 Wochen die audiologische Erstanpassung und die Bestückung mit Magneten. In der Audiometrie bestand ein funktioneller Gewinn von bis zu 30 dB sowie ein verbessertes Sprachverständnis. Die Epithese wurde dem gesunden Ohr nachgebildet. Nach der Versorgung waren die Patienten mit dem audiologischen und kosmetischen Ergebnis zufrieden.

Schlussfolgerungen Das simultane chirurgische Vorgehen mit einem Hörimplantat und Epithesenankern stellt eine gute Option in der Versorgung von Ohrmissbildungen dar. Der aMEI-Score war ein hilfreiches Instrument zur Indikationsstellung. Durch das Vorgehen konnten das Operationsrisiko und der Aufwand der Versorgung reduziert werden.