bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-dimensional gallium and indium oxides from global structure searching: Ferromagnetism and half metallicity via hole doping
Authors: Meng Ruishen , Houssa Michel , Iordanidou Konstantina , Pourtois Geoffrey , Afanasiev Valeri , Stesmans André
Published: July 2020

There has been tremendous research effort in hunting for novel two-dimensional (2D) materials with exotic properties, showing great promise for various potential applications. Here, we report the findings about a new hexagonal phase of 2D Ga2O3 and In2O3, with high energetic stability, using a global searching method based on an evolutionary algorithm, combined with density functional theory calculations. Their structural and thermal stabilities are investigated by the calculations of their phonon spectra and by ab initio molecular dynamics simulations. They are predicted to be intrinsically non-magnetic stable semiconductors, with a flatband edge around the valence band top, leading to itinerant ferromagnetism and half-metallicity upon hole doping. Bilayer Ga2O3 is also studied and found to exhibit ferromagnetism without extra hole doping. The Curie temperature of these materials, estimated using Monte Carlo simulations based on the Heisenberg model, is around 40–60 K upon a moderate hole doping density.
Iodine orbital moment and chromium anisotropy contributions to CrI3 magnetism
Authors: Choi Y. , Ryan P. J. , Haskel D. , McChesney J. L. , Fabbris G. , McGuire M. A. , Kim J.-W.
Published: July 2020

The recent discovery of two-dimensional (2D) magnets, with a number of interesting magnetic properties, has drawn much interest due to their potential for future 2D spintronic device applications. CrI3, a van der Waals magnet, exhibits two-dimensional ferromagnetism even in monolayer form, stabilized by strong magnetic anisotropy. Its interlayer magnetic ordering is coupled to structural layer stacking, implying that the charge density distribution mediating van der Waals interactions plays a key role in the magnetic interaction between the layers. Using polarization-dependent x-ray spectroscopy, we investigated the response of the electronic environment around Cr and I sites to structural changes of layer stacking order. The highly anisotropic nature of the Cr local environment is significantly enhanced and is accompanied by changes in the valence band, in the rhombohedral phase. Magnetic spectroscopy measurements reveal a sizable iodine orbital moment, indicating the iodine contribution to magnetic anisotropy. Our results uncover an important role for the extended nature of anisotropic Cr orbital states in dictating interlayer magnetic interactions and the iodine contribution to magnetic anisotropy.
A mechanism-aware and multiomic machine-learning pipeline characterizes yeast cell growth
Authors: Culley Christopher , Vijayakumar Supreeta , Zampieri Guido , Angione Claudio
Published: July 2020

Significance

Linking genotype and phenotype is a fundamental problem in biology, key to several biomedical and biotechnological applications. Cell growth is a central phenotypic trait, resulting from interactions between environment, gene regulation, and metabolism, yet its functional bases are still not completely understood. We propose and test a machine-learning approach that integrates large-scale gene expression profiles and mechanistic metabolic models, for characterizing cell growth and understanding its driving mechanisms in
Saccharomyces cerevisiae
. At its core, a custom-built multimodal learning method merges experimentally generated and model-generated data. We show that our approach can leverage the advantages of both machine learning and metabolic modeling, revealing unknown interactions between biological domains, incorporating mechanistic knowledge, and therefore overcoming black-box limitations of conventional data-driven approaches.
What ATP binding does to the Ca
2+
pump and how nonproductive phosphoryl transfer is prevented in the absence of Ca
2+
Authors: Kabashima Yoshiki , Ogawa Haruo , Nakajima Rie , Toyoshima Chikashi
Published: July 2020

Significance

During phosphoryl transfer from ATP in P-type ion translocating ATPases, very large-scale and complex structural changes take place, resulting in occlusion of ions to be translocated. In the present report, we describe a new crystal structure of a calcium pump in the absence of Ca
2+
but with a bound ATP analogue. We show that the ATP analogue is delivered to the phosphorylation site with a correct geometry despite the absence of Ca
2+
. Yet phosphoryl transfer from ATP never occurs in the absence of Ca
2+
, although phosphorylation by P
i
is possible as a backward reaction. We describe the structural changes that ATP binding alone elicits in the calcium pump and why Ca
2+
binding is absolutely necessary for phosphoryl transfer.
Trading Options and the Unattainable Dream: Some Reflections on Semiotic Ideologies
Authors: Souleles Daniel
Published: July 2020

Over the last few decades there has been a miniature industrial revolution in the buying and selling of securities on capital and derivatives markets. Whereas most trading once happened in open outcry pits or over the phone, trading now occurs primarly via electronic limit order books. Whereas once traders could have little education and find work as a consequence of membership in a local insular network, new financial hires are now the most talented graduates of PhD and master’s programs in the hard sciences and mathematics. Even though these circumstances are well attested, knowing is not enough for some to become this new kind of trader. I suggest that the theory of semiotic ideologies—that is, what grounding assumptions people bring to the process of interpreting signs—can be used to illustrate boundary cases of social change in which people are simply unable to learn enough to adapt to new circumstances in their lives. I will show that even though traders can adopt the appropriate semiotic ideology of markets that their times demand, some of them will never be skilled enough to fully participate. This, in turn, has to do with the nature of change in a capitalist economic system.
The Epistemic and Performative Dynamics of Machine Learning Praxis
Authors: Kockelman Paul
Published: July 2020

This article is about machine learning as it relates to classic concerns in anthropology and the social sciences, regarding meaning, value, and culture, as well as agency, power and performativity. It focuses on the role of machine learning, with its peculiar manner of modeling phenomena, in mediating: (i) the sensibilities and assumptions agents have (qua interpretive grounds and algorithmic models) insofar as these mediate their actions, inferences, and affects; and (ii) the actions, inferences, and affects of agents (qua computational processes and interpretive practices) insofar as these drive their sensibilities and assumptions. More generally, it offers a model of the process of modeling per se, so far as this process unfolds in contexts of machine learning and beyond. In this respect, the metamodel offered is meant to capture some of the key dynamics of the tense and mutually transformative relations linking objects (of analysis), data (drawn from those objects), models (of such objects, as informed by such data), and actions (grounded in such models, and often transformative of such objects). It foregrounds the wily, epistemic, performative, and often violent dynamics of such processes when the objects being modeled are themselves agents capable of modeling.
Polarization control in a crossed undulator without a monochromator
Authors: Kaneyasu Tatsuo , Hikosaka Yasumasa , Fujimoto Masaki , Iwayama Hiroshi , Katoh Masahiro
Published: July 2020

In this study, it was demonstrated that the polarization control of light from a crossed undulator can be achieved using material response, without any prior monochromatization. Nonmonochromatized horizontally and vertically polarized radiation emitted from two undulators is irradiated to He atoms, and Rydberg states in the extreme ultraviolet region are excited resonantly. The polarization of the photoexcitation is adjustable in a controlled manner by tuning the electron beam orbit between the two undulators, which is verified by observing Zeeman quantum beats in the fluorescence decays of the He Rydberg states.
ECCD-induced sawtooth crashes at W7-X
Authors: Zanini M. , Laqua H.P. , Thomsen H. , Stange T. , Brandt C. , Braune H. , Brunner K.J. , Fuchert G. , Hirsch M. , Knauer J. , Höfel U. , Marsen S. , Pasch E. , Rahbarnia K. , Schilling J. , Turkin Y. , Wolf R.C. , Zocco A.
Published: July 2020

The optimised superconducting stellarator W7-X generates its rotational transform by means of external coils, therefore no toroidal current is necessary for plasma confinement. Electron cyclotron current drive experiments were conducted for strikeline control and safe divertor operation. During current drive experiments periodic and repetitive crashes of the central electron temperature, similar to sawtooth crashes in tokamaks, were detected. Measurements from soft x-ray tomography and electron cyclotron emission show that the crashes are preceded by weak oscillating precursors and a displacement of the plasma core, consistent with a (m, n) = (1, 1) mode. The displacement occurs within

100

μ

s

, followed by expulsion and redistribution of the core into the external part of the plasma. Two types of crashes, with different frequencies and amplitudes are detected in the experimental program. For these non-stationary parameters a strong dependence on the toroidal current is found. A 1-D heuristic model for current diffusion is proposed as a first step to explain the characteristic crash time. Initial results show that the modelled current diffusion timescale is consistent with the initial crash frequency and that the toroidal current rise shifts the position where the instability is triggered, resulting in larger crash amplitudes.
Stabilization of energetic-ion driven toroidal Alfvén eigenmode by energetic electrons in tokamak plasmas
Authors: Wang Jialei , Todo Yasushi , Wang Hao , Wang Zheng-Xiong , Idouakass Malik
Published: July 2020

Energetic electron effects on an energetic-ion driven toroidal Alfvén eigenmode (TAE) are investigated via hybrid simulations of an MHD fluid interacting with energetic particles. Both energetic electrons and energetic ions described by drift-kinetic equations are included in the present work. It is found that the TAE can be effectively stabilized by off-axis peaked energetic electrons which are located near the mode center, while the centrally peaked energetic electrons fail to stabilize the mode. It is confirmed that the spatially localized pressure profile of energetic electrons causes the stabilization of TAE. The stabilized TAE has a more localized mode structure accompanied by a significant reduction in the energetic ion driving rate. The small change of mode frequency and dissipation rate indicate the stabilization mechanism is different from the so-called pressure gradient stabilization that drives the TAE into continuum. The results suggest that the strong plasma non-uniformity induced by the energetic electron beta profile may be responsible for the change of mode structure. It is also found that this stabilizing effect is more effective for a high-n TAE. Moreover, it is numerically verified that the positive (negative) pressure gradient at the TAE center will increase (decrease) the mode frequency. The wave-particle interactions are also analysed for a case with energetic electrons peaked at the inner side of the TAE center. It is found that the power transfer to a resonant barely trapped energetic electron, which taps energy from the wave, can be comparable to the power transfer from a resonant energetic ion. This suggests that if a sufficient number of resonant barely trapped electrons are present, they might stabilize energetic-ion driven TAE through the wave-particle interaction.
Research on Android Ransomware Protection Technology
Authors: Hu Jian Wei , Zhang Yu , Cui Yan Peng
Published: July 2020

With the popularity of smart devices such as smartphones and pads, the attack of Android ransomware is becoming increasingly serious. Compared with other malicious software, ransomware is widely favoured by hackers because of hard restoration and the directness of obtaining benefits, which also brings serious spiritual and property damage to users. To protect our smart devices from ransomware and reduce threats and losses, researchers conduct a lot of research on Android ransomware and propose many practical detection schemes. This paper first summarizes the characteristics of Android ransomware, and then summarizes the existing research work on detecting and safeguarding against ransomware on the Android platform and makes a comprehensive analysis and comparison on them. Finally, it points out that the remaining problems of these solutions, puts forward corresponding suggestions and proposes future research directions.
Research on Effectiveness Evaluation Method of Product Quality Improvement Plan Based on Actor Analysis Method
Authors: Qian Wu , Chaowei Wang , Fei Pei , Yingcheng Xu , Xiaowei Lu
Published: July 2020

This paper divides the effectiveness evaluation index of product quality improvement programs into objective and quantifiable cost-based index such as equipment modification cost, personnel training cost, process upgrading cost, and other costs which is subjective unquantifiable index such as production level, quality and safety level, sales volume, and customer satisfaction. By introducing actor analysis method, the effectiveness evaluation model of product quality improvement plan based on actor analysis method is established. A toy manufacturer is used as an example in applying and analyzing the model and comprehensively evaluating the effectiveness of each proposed plan to verify the operability of the model. The method is scientific and reasonable, simple and easy to operate, can be widely spread in relevant enterprises, and can provide effective method guidance for enterprises in selecting the optimal plan and avoiding unnecessary losses.
RETRACTED: Studies on Data Quality Evaluation Index System for Internet Plus Government Services in Big Data Era
Authors: Ya Li , Heliang Song , Yingcheng Xu
Published: July 2020

This paper studies and analyzes the related theories of data quality and data quality of Internet plus Government Services in big data era, summarizes and references the data quality evaluation indexes at home and abroad, puts forward the primary and secondary indexes suitable for evaluating the data quality of Internet plus Government Service in big data era in China, and constructs a scientific, systematic, developmental and operable data quality evaluation index system. The index system determines, according to the characteristics of big data, 5 primary data quality evaluation indexes (inherent quality of data, quality of data expression, situation quality related to the system, utility quality of data, and user experience quality of data) and 10 secondary data quality evaluation indexes. The construction of the system provides an effective data quality evaluation tool for government departments. Through data quality evaluation, relevant data quality problems can be found, analyzed and improved, which is conducive to improving the level of data quality.
Optimal Calculation of Solid Propellant Burning Equilibrium Ingredients Based on Genetic Algorithm
Authors: Kuan Hu , Lin Zhang , Xinlong Chang , Chunwen Wang
Published: July 2020

To aim at defects caused by using Lagrange multiplier to solve equilibrium ingredients in engineering, genetic algorithm based on reduction of dimensionality and mixture rank are adopted in this paper. In genetic algorithm, design dimension is decreased through independence analysis of design variables, and individuals are ranked with violation degree and violation times simultaneously. The method in this paper can solve the problems brought by Lagrange multiplier method, which were unable to effectively deal with quantity equal constraints in equilibrium ingredients optimization and increased the number of unknown variables and calculation difficulties for complex propellant. Moreover, the method can also avoid the problem of computing termination on account of minus value during ingredients calculation, and can be easier to get global optimal solution. Furthermore, an integrated calculation frame of equilibrium ingredients is established by combining equilibrium ingredients optimization model with burning temperature model. Finally, an example is used to verify the method’s validity and feasibility.
Dynamic Interest Retransmission Interval Method for Congestion Control in NLSR
Authors: Hao Yuanchen , Xue Yanming , Li Tong , Ji Junwei , Ma Miaomiao
Published: July 2020

Named data link state routing (NLSR) protocol is widely used in current NDN architecture. Due to the limited bandwidth resources of NDN, in the large-scale network running NLSR, when routing information is frequently updated, resulting in a sudden increase in interactive information and the Interest storm is formed. It will cause congestion of protocol information flow and affect network quality and performance index. NLSR does not take corresponding control measures for its Interest traffic and transmission frequency. Therefore, we propose a method to solve this Interest storm: the exponential regression algorithm is used to dynamically adjust the retransmission interval of Sync Interest and the timeout retransmission Interest quantity detection method is provided to add the flow control. The simulation results show that the congestion control method can adjust the sending quantity and retransmission interval of Interest well according to the network traffic.
Design of Wireless Monitoring System for Power Terminal Equipment based on NB-IoT
Authors: Sun Lei , Hu Xianhua , Li Jinxuan , Xie Tairong
Published: July 2020

The application of Low-Power Wide-Area Network (LPWAN) technology in wireless monitoring of power terminal equipment is studied in this paper. From the aspects of hardware and software design of monitoring terminal, communication protocol, remote data management cloud platform, the wireless monitoring system of power terminal based on Narrow Band Internet of Things (NB-IoT) is designed in detail. STM32L151 is chosen as the main controller of the monitoring terminal owing to its low power consumption. After simple edge calculation and data packaging, the terminal equipment status information is reported to the remote data management platform via NB-IoT network based on system setting. The platform supports various functions such as a variety of terminal access methods, terminal identity authentication, parameter configuration, data forwarding, and terminal abnormal data information reporting and so on. In order to improve the User Datagram Protocol (UDP) transmission reliability, the terminal drop detection mechanism is designed on UDP communication protocol. Eventually, the system is applied in monitoring power terminal equipment status such as transmission and distribution pole tower, power well cover, cable trench cover, knife brake of distribution line, etc. The experimental results show that the power terminal monitoring system based on NB-IoT can achieve unified access and centralized management of power equipment status information in different power scenarios, and this system greatly enhances the reliability and efficiency of power system terminal equipment operation and maintenance, and has value in engineering.
Nodes Non-uniform Deployment with Energy Harvesting in Linear WSN
Authors: Li Cuiran , Jin Meijuan , Lv Anqi
Published: July 2020

Aiming at the problem that the network lifetime declines in linear WSN powered by battery, node energy model with energy harvesting (EH) and prediction is constructed. Based on the model, the multi-sink WSN network is deployed in an optimal non-uniform way. The mathematical expressions of the average packet delivery ratio and throughput density of the optimal deployment strategy are deduced theoretically. The performances of the average packet delivery ratio, throughput density, network lifetime, and residual energy ratio are simulated in EH-WSN and WSN, as well as the ratio q and the signal-to-interference noise ratio (SINR) threshold θ. The results show that the lifetime of EH-WSN is prolonged by adjusting the ratio q and the SINR threshold θ, compared with WSN powered by battery. The proposed strategy has good scalability, suitable for the non-uniform deployment in linear EH-WSN, especially with a large number of nodes and a long distance.
Design of Wide Interval Frequency Hopping Pattern for Frequency Hopping Mobile Ad-hoc Networks
Authors: Zhao Yadong , Zhang Yu , Song Jian
Published: July 2020

The frequency hopping mobile ad-hoc network (FH MANET) is a communication network that combines frequency hopping (FH) technology and mobile ad-hoc network (MANET) technology. FH technology can improve the anti-interference performance of the network, and MANET technology improves the mobility and anti-destructiveness of the network. It can be networked autonomously without manual intervention and other network facilities. It has strong application value in complex battlefield environment and occasions with harsh environment and high confidentiality requirements. The frequency hopping pattern (FHP) design is a key technology in the FH MANET, which is directly related to the network’s anti-interference and multipath fading capabilities. In this paper, a wide interval expansion method (WIEBM) based on m-sequence and non-continuous tap L-G model is proposed. The experimental results demonstrate that proposed scheme can effectively improve the anti-interference ability of the system. It has the ability to resist more than 30% of broadband interference.
Application Analysis of 5G Communication in Power System
Authors: Zhao Yang , Zhao Xiaohong , Ren Tiancheng , Liu Xin , Wang Wenting
Published: July 2020

In 2019, State Grid Corporation of China (SGCC) proposed the strategic goal of building and developing a strong smart power grid and ubiquitous power Internet of things. Smart power grid and ubiquitous power Internet of things involve massive information interaction in power system, which cannot be separated from the support of advanced communication technology. 5G communication system integrates advanced network technology, and has the advantages of high resource utilization, fast transmission rate and high spectrum utilization. Compared with existing 4G communication systems, it has a great improvement in user experience, transmission delay and coverage. In this paper, we take the application of 5G communication system in power system as the main research content, discuss various wireless communication application scenarios in power system, and analyze the feasibility of 5G communication to support the ubiquitous power Internet of things construction in terms of key technologies and application costs of 5G communication. However, the energy consumption and security of 5G communication system are still major factors that limit its application in the ubiquitous power Internet of things, and these problems need to be fully paid attention to by researchers.
Intelligent Identification and Classification of Product Quality Incidents Based on Rules and Statistics
Authors: Xu Yingcheng , Wang Haiyan , Feng Wei , Zheng Xiaojun
Published: July 2020

Product quality and safety incidents are closely related to the lives of ordinary people, and have always been the focus of all countriesgovernments. Using related technologies and methods, how to intelligently identify and classify product quality and safety incidents, and find out the evolution and spread of events at the first time, and deal with them quickly, has always been a difficult problem for product quality and safety supervision departments to solve. Based on rules and statistics, a multi-layer text classifier is built to identify and classify product quality incidents. The first layer implements rough segmentation of the news concerning product quality incidents based on rule classifier. The second layer matches the news in a level-wise manner from the top down by calculating the text similarity until the corresponding subclass is found. The experiments show that the proposed classifier can effectively identify the product quality incidents in Web news.
Research on the Protection Mechanism of Cisco IOS Exploit
Authors: Wang Jinzhu , Cai Ruijie , Liu Shengli
Published: July 2020

Cisco IOS is an operating system that runs on Cisco routing and switching equipment. Its security is important to the entire network. Since vulnerability attacks have become one of the main sources of threat to Cisco IOS security, it is necessary to analyze the defense mechanism of IOS against vulnerability attacks. The purpose of this paper is to find out the deficiencies of IOS vulnerability defense mechanism in time and put forward improvement methods and preventive measures. Firstly, this paper introduces the protection mechanism of Cisco IOS vulnerability, including CheckHeaps, DEP, ASLR. The principle of these mechanisms and the idea of vulnerability protection are analyzed. And then, after analyzing the shortcomings of these protection mechanisms, the basic idea of bypassing these protection mechanisms is proposed. Finally, in view of the shortcomings of Cisco IOS vulnerability defense mechanism and the proposed bypass methods, some advices about how to better protect Cisco IOS from vulnerability exploitation are given.
Study of the Local Oxidation of Silicon Waveguide for Realizing the Intra-Guided Mode Conversions
Authors: Yu Ting , Wang Bin , Sun Degui
Published: July 2020

The impressive achievements in research and developments of silicon-on-insulator (SOI) based silicon photonic integrated (PIC) devices have been made, but the coupling loss between the fibre and SOI waveguide is still a fatal problem. As well known, the butt coupling between a fibre and a low index-contrast silica-on-silicon (SOS) waveguide only causes a much lower optical loss, however, such a process between a fibre and a high index-contrast SOI waveguide creates a much higher optical loss. In this work, a 2-step intra-guide mode conversion of fibre-SOS-SOI structure is modelled and studied, in which a mitigating structure of SOS waveguide is created via a local oxidation of silicon (LOCOS) technique. The LOCOS method is an in-situ chemical process during the waveguides are fabricated without causing any extra fabrication, but it can control the physical parameters of the SOS waveguide through a chemical process. In such a 2-step intra-guide mode conversion, the total optical efficiency of the fibre-SOS-SOI structure is modelled, and the optical efficiencies of both the fibre-SOS mode conversion and the SOS-SOI mode conversion are systematically studied, and the broad dependences of guided mode profile on the chemical parameters of the LOCOS process are discussed. As a result, a total optical loss of <0.5dB for a butt coupling process between fibre and single-mode SOI-waveguide is achieved. So far, no similar practical butt-coupling method has been reported yet.
Analysis of Financial Crisis Early Warning Model of Listed Enterprises in China
Authors: Chong Zhang , Zhengyu Duan , Meikang Luo
Published: July 2020

In recent years, many studies show that corporate financial crisis usually has a long hidden period. If this hypothesis can predict the financial crisis of enterprises, it is expected to control the destructive power brought about by the financial crisis to a minimum. Therefore, this paper takes 108 listed financial crisis companies (ST companies) and 435 non-ST listed companies in China’s A-share annual report in 2019 as reference samples. Then, on the basis of these indicators, the corresponding models are established. The results show that through the analysis of various indicators, we can find the potential financial crisis prediction information and predict the company’s financial distress. From the results of the model analysis, we can see that in the year before the financial crisis, the variables of the financial model are the most. This shows that the closer the year of ST occurs, the higher the accuracy of the model.
Service Migration in Mobile Edge Computing Based on Reinforcement Learning
Authors: Fan Chen , Li Li
Published: July 2020

Mobile edge computing (MEC) provides users with cloud computing capabilities at the edge of the mobile network, which effectively reduces network latency and improves the experience of end-users. User mobility in MEC is a factor that cannot be ignored, and mobility management is an urgent problem to be solved. Service migration is an effective way to manage user mobility. However, it is not appropriate to perform migration too frequently due to expensive migration overhead. In this paper, we propose a service migration decision algorithm to decide whether to migrate or not when the user moves out of the coverage of the offloaded MEC server. Markov decision process (MDP) is used to model the service migration decision problem. We comprehensively consider the distance between users and services, resource requirements of the services, and resource availability of the MEC servers. On the premise of considering both migration costs and resource conditions, aiming at maximizing quality of service (QoS), the reward function of MDP is defined, and the migration decision strategy is solved by Q-learning algorithm. Finally, our proposed migration decision algorithm is validated by simulation.
A Study on Risk Assessment of Non-economic Factors of an Accident Based on Monte Carlo Simulation
Authors: Xiaowei Lu , Wu Qian , Ya Li , Li Yulong
Published: July 2020

This paper makes a systematic analysis of the losses caused by accidents and disasters and models the non-economic factors of an accident. Based on a brief introduction to traditional analysis methods, we introduced Monte Carlo simulation. This paper further analyses the application of the model by taking a concrete case as an example, verifying the practicability and scientificity of the model. This paper introduce and analyse the principle and superiority of Monte Carlo method, and combine the three links of risk analysis to analyse the implementation process of this method for non-economic factors risk analysis simulation. The analysis framework includes the basic ideas of each step of risk analysis under Monte Carlo simulation, the applicable methods of each step, and the selection of evaluation indicators. This method is scientific, reasonable and easy to operate, and could be applied in similar cases to provide a more scientific risk assessment for non-economic factors.
A Fast Calculation and Rendering Method for Infrared Characteristics of Hypersonic Vehicle
Authors: Bao Chenying , Li Ni , Gong Guanghong , Tian Chao , Lu Yuanjie
Published: July 2020

In this paper, a fast calculation and rendering method for infrared characteristics of hypersonic vehicle is proposed, which covers the overall infrared simulation process. The key point of this method is the heterogeneous interpolation algorithm, which can map the data from dense grid to sparse grid, thus greatly reducing the volume of data and improving rendering efficiency on the premise of guaranteeing the simulation reliability. Taking the hypersonic vehicle X-43A as an example, we realize the calculation and rendering of its infrared characteristics. Experimental results show that the infrared radiation characteristics of hypersonic vehicle are primely reproduced in the rendering process.
Research on Modal Analysis of Qin Structure Based on Finite Element Technology
Authors: Hu Bing , Li Haoran
Published: July 2020

Qin is one of the traditional plucked musical instruments in China and has a history of more than 3,000 years. Qin has deep historical heritage and rich cultural connotation. It is often used for solo, but also for accompaniment. The timbre of Qin is quiet and the aftertaste is long. It is often used to express a person’s interest and purity. It is a traditional musical instrument which puts emotions on it. Qin is loved by the public. Based on the finite element analysis method, this paper makes use of the Hypermesh finite element calculation and analysis software to obtain the finite element model of the Qin and analyze the modal of the Qin. [1] Through modal analysis, the effectiveness of the computer simulation method using in the production of Qin has been verified, which supplies data sustain and theoretical sustain for the study of the structure of the Qin and the other traditional Chinese national musical instruments.
A Novel Grid-Connected Current Control Method Based on Frequency Adaptive Proportional Resonance
Authors: He Laipei , Zheng Shousen , Qi Xinmei , Huang Yuhe
Published: July 2020

In this paper, a novel quasi-proportional resonance (quasi-PR) controller for grid-connected current control is proposed. For the traditional quasi-PR controller, the performance decreases in cases when a large gird frequency deviation is going through. To solve the problem, a frequency adaptive structure is applied in the current control method to achieve online correction on the resonance frequency, so that a high control accuracy is maintained and the robustness of the control system is enhanced. The feasibility of the proposed method has been verified by experimental results.
Optimization of impulse resistance reduction for tower grounding device of transmission line
Authors: Chen Sixiang , Wu Lihui , Li Hengzhen , Chen Daopin , Liu Yijun , Wu Tongshuai
Published: July 2020

When the lightning strikes the tower, the lightning current is discharged into the ground through the tower grounding device. The magnitude of the impulse earthed resistance of the tower grounding device determines the lightning discharge capacity of the tower. Therefore, the tower grounding device directly affects the lightning protection level of the tower. This paper first introduces three commonly used shock resistance reduction methods: long vertical ground electrode, acupuncture ground electrode, and externally induced rays. Then, the CDEGS software is used to simulate and analyze the long vertical grounding electrode, and a method of insulation short shield is proposed to determine the optimal length of the vertical grounding conductor of the grounding device. Finally, the different resistance reduction effects under the change of length and number of roots are explored, and the optimal resistance reduction arrangement under the same economic conditions is realized.
Production and Suppression of Resonance Overvoltage for a Type of DC De-icer Installation
Authors: Zhaoxia HE , Chuanqi WU , Jun Chen , Tao Wan , Tian Xia , Jingbin LI
Published: July 2020

The DC de-icer installation has been widely used in the ice protection of power system. Because of the difference between the design and the actual operation of the installation, the resonance overvoltage has been threatening the device body from the distribution parameters of the de-icer transmissions. In this paper, based on the analysis on the mechanism of the resonance overvoltage, the estimate expression of the resonant length of the transmission has been derived. Through the simulation modeling by PSCAD/EMTDC, the effectiveness of the estimate expression has been verified. The suppression measures of the resonance overvoltage have been proposed.
Research on IGBT junction temperature overload algorithm of servo driver
Authors: Guo Rui , Xie Baochang
Published: July 2020

As the core of industrial control, servo drives have become evident in small volume, multi-spindle integration, acclimatization and energy conservation in recent years. The main domestic and foreign servo drives adopt module temperature detection, thermal accumulation - heat dissipation model or inverse time overload algorithm. The overload multiple and time are relatively fixed, and cannot further improve overload capacity according to the environment temperature or load condition. Due to the low utilization rate of the radiator, the servo drive selection usually amplifies the first gear and increases the cost of the electrical system. Without adding energy feedback cells or capacitors, it’s not efficient to recycle the energy produced by braking. This paper mainly studies the overload algorithm which based on junction temperature prediction. The overloading algorithm can increase the overload capacity by 40%. Fanless design can be realized to meet the application of negative conditions such as conductive dust, cutting fluid and cotton. In general, the overload algorithm which based on junction temperature prediction is suit for the application of printing, packaging, semiconductor silicon, forging, laser cutting machines.
Research on Key Technology Development and Application of Grid Asset Management
Authors: Chen Yinghua , Dong Litong , Liu Wenxia , Guo Haoming , Huang Yuchen , Ge Yanqin
Published: July 2020

With the improvement of grid reliability requirements in social development, grid asset management must develop in the direction of digitization and informatization. Based on the latest research results of asset management and risk assessment, the article first discusses the current development status of grid asset management technology, then introduces the theoretical methods of three key technologies and their application status in asset management, i.e. state assessment, reliability and risk assessment, and Life Cycle Cost (LCC) analysis. Secondly, this paper summarizes the application of information technology in power grid asset management, and analyzes the supporting role of digital technology in asset management and its key technologies. On this basis, it puts forward suggestions for China’s power grid asset management, in order to provide a useful reference for the improvement of China’s power grid asset management from the technical level.
Research on Method of Improving Voltage Stability of Distribution Network with Distributed Generation
Authors: Li Dashuang
Published: July 2020

With the increase of distributed generation capacity, grid-connected distributed generation (DG) has an impact on the stability of distribution network. This paper studies the influence of the access of DG on the stability of distribution network. In view of the impact of the access of DG on the distribution network, a method is proposed to improve the voltage stability of the distribution network through the configuration of energy storage equipment in the distribution network. The effectiveness of adding energy storage equipment to improve the voltage stability of distribution network is verified by the simulation results through the MATLAB / Simulink simulation model of DG.
Research and application of a real-time operation risk assessment method for power grid based on random forest algorithm
Authors: Chen Junquan , Wu Shihong , Ye Hangchao , Yang Fu , Song Xian
Published: July 2020

Real-time operation risk assessment of power grid is not only an important content of power grid dispatching and operation control, but also an important reference factor in power grid accident disposal. It is difficult for the traditional evaluation methods to meet power system online operation control requirements, because of their complex process and long calculation time. To this end, a real-time power grid operation risk assessment method based on random forest intelligent algorithm is proposed in this paper, The basic concepts and implementation points of random forest algorithm is introduced. The implementation framework of real-time operation risk assessment based on random forest is proposed taking the need of power grid operation risk assessment into consideration. Compared with the traditional evaluation method, this method can calculate the power grid operation risk level directly according to some key operation indexes without complex power grid analysis, such as N-1 security check. Finally, the two-years practical application in a certain provincial power grid in China shows that the method has high evaluation accuracy and computational efficiency, which can match the traditional evaluation method and improve the calculation efficiency and accuracy of risk assessment.
Two-stage Control Strategy for UHVDC Voltage based on Bifurcation Trajectory Sensitivity
Authors: Yang C , Tang W , Shi L Q , Wu D , Bao W , Zhang J
Published: July 2020

In order to solve the voltage bifurcation phenomenon caused by the continuous change of the load on the UHV grid receiving end system, this paper proposes a two-stage control strategy based on the bifurcation trajectory sensitivity. Firstly, the mechanism of bifurcation of UHV receiving part’s voltage is analyzed. Then the coordination correction model of voltage auxiliary decision and prediction control using bifurcation sensitivity is described. In order to verify the effect proposed, a typical accident of an ultra-high voltage receiving end is used for simulation. The simulation results show that the control effect can meet the stability requirements of the power grid, Two-stage Control Strategy could apply to solve the bifurcation problem.
Reliability Evaluation of Distribution System Considering Distributed Generation Correlation
Authors: Xuan Juqin , Zheng Jieyun , Shi Pengjia , Chen Jinpeng , Lin Mingrong , Hu Zhijian
Published: July 2020

The correlation between distributed generation (DG) can affect the reliability of distribution networks. To analyze the influence of this factor, first use Latin Hypercube Sampling, combine Spearman rank correlation coefficient and Cholesky decomposition to obtain the DG output power sample of the specified correlation coefficient. The bidirectional hierarchical structure reliability evaluation algorithm considering switch failure is used to evaluate the system. Considering the island operation mode of the distribution network after DG access, an improved heuristic load reduction strategy is proposed, and the reliability index of the load in the island is revised. The experimental results show that the reliability index of the system is closely related to the rated capacity of DG, the correlation between DG, and different load reduction strategies.
The Reliability Evaluation of Power Supply Distribution System Based on Distribution Automation
Authors: Xuan Guoli , Wang Wei , Liu Yu , Lang Bin
Published: July 2020

This paper presents an improved failure mode and effect analysis for reliability evaluation of distribution network. By introducing the state factor of switch automation, the calculation formula of power supply reliability index of load point is modified, and the traditional consequence analysis method of fault mode is improved. Taking the test model of overhead lines as an example, the effectiveness of the improved method is verified, and the importance of distribution automation in the reliability improvement of distribution network power supply is affirmed, and the practical principle of terminal configuration is given in conjunction with the situation of distribution network in Anhui Province.
Research Progress of Electromagnetic Interference Suppression in Power Converters
Authors: Shichao Guo , Dandan Guo , Qiongyu Zhang , Nankai Wu , Jiaxin Deng
Published: July 2020

In this paper, the related concepts of Electromagnetic Interference (EMI) and Electromagnetic Compatibility (EMC) were expounded, the research progress of EMI suppression methods for power converters was summarized, and the future development trend of EMI suppression for power converters was pointed out, for example, EMI suppression method of changing circuit topology, EMI suppression method for improving control strategy, EMI suppression method of optimized driving circuit.
Dimension Reduction Method for Probabilistic Power Flow Computation Considering Wind Farms
Authors: Fu Haoyan , Wu Lianghong , Zhang Hongqiang , Liu Zhenzhu , Li Jingzhe
Published: July 2020

With the large-scale integration of renewable energy sources into the power system, a new source of uncertainty is added to the operation planning problem. In this paper, the rank correlation coefficient is introduced to characterize the dependency among random variables in power flow equations, and Nataf transformation is used to map the probabilistic power flow (PPF) problem to the independent standard normal space. Dimension reduction model is introduced to approximation the function relationship between PPF inputs and outputs. Gauss-Hermite quadrature is used to obtain the statistical moments of the univariate function, whereby the statistical moments of outputs of power flow equations are obtained. Testing on an IEEE-118 system, the dimension reduction method is compared with Hong’s point estimate method, it is found the dimension reduction method can improve the accuracy without extra computational burden.
Scheduling optimization model for integrated energy systems considering conditional value-at-risk
Authors: Peng Q , Wang X L , Qi S X , Wang Z D , Yan S , Chen Y T
Published: July 2020

The integrated energy system (IES) promotes the integration of renewable energy and improves energy efficiency, but it also brings uncertainty to the system. The uncertainty of the output of renewable energy may lead to imbalance of supply and demand, which brings the risk of cost increase to the economic dispatch. This paper mainly studies IES with energy hub as the research object, and studies the IES modeling and the optimal scheduling problem considering Conditional Value-at-Risk (CVaR). Firstly, the mathematical model of energy hub is established. Next, the network model of power system and natural gas system is established and the energy hub is reasonably connected to them. Then, for analyzing the uncertainty of wind power output, this paper develops scenarios using Latin hypercube sampling method and uses K-medoids clustering algorithm to reduce the scenarios. After defining the risk cost under uncertainty, CVaR is introduced into the objective function of IES optimal dispatch to describe the risk which operating personnel faces. Based on CVaR, the IES scheduling model is established and linearized into a mixed integer linear programming problem to be solved. Finally, numerical case studies verify that the IES scheduling model can reduce the risks with least costs and determine whether the system needs to avoid risks.
Real-world insights on public charging demand and infrastructure use from electric vehicles
Authors: Hardinghaus Michael , Löcher Markus , Anderson John E
Published: July 2020

The city of Berlin has significantly expanded public charging infrastructure for electric vehicles. As a result of this investment, real-world charging data for the city of Berlin are available for the first time. In addition to other metrics, this dataset contains specific information about carsharing vehicles. This research letter offers numerous insights into public charging demand and infrastructure. The results are only now available due to a sufficient fleet size of electric vehicles.

The analysis shows that the distribution of charging stations is very unequal in Berlin. The data also show that the infrastructure network is much denser in the city center. While there is an unequal distribution of infrastructure, we see that the utilization of infrastructure is relatively equal. This reflects unequal charging demand, as can be expected based on the location of the infrastructure. We also determine that the majority of public charging events come from free-floating carsharing vehicles. The analysis of infrastructure use shows that the edge of the city center has the highest rates of stations occupied by vehicles after completing charging. Carsharing users occupy infrastructure after charging significantly more than individual private and commercial users. However, if the pricing scheme allows, individual users also occupy infrastructure after completing charging.

The research letter provides several policy recommendations for the build-up and operation of charging infrastructure. These focus on charging demand from individual users, infrastructure efficiency, and carsharing operators and their business models. The results are timely as decisions on public charging infrastructure must be made now to meet electric vehicle demand.