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改进半透镜半姆欧型继电器特性的研究

河北电力技术 1986年第3期 49-56页

作者： M.S.Li t.c.cheng c.Y.Wu 赵自刚

多年来,姆欧型方向阻抗继电器已广泛应用于高压和特高压系统.但其在某些故障条件下的误动一直是一个需要解决的主要问题.一种情况是发生出口带接地电阻短路时,安装在非故障相的姆欧继电器将误动作.另一种情况是发生带接地电阻的反方向... 详细信息

多年来,姆欧型方向阻抗继电器已广泛应用于高压和特高压系统.但其在某些故障条件下的误动一直是一个需要解决的主要问题.一种情况是发生出口带接地电阻短路时,安装在非故障相的姆欧继电器将误动作.另一种情况是发生带接地电阻的反方向故障时姆欧继电器的误动.理论分析和数字计算表明,在这些偶然情况下,由距离继电器所看到的阻抗在第二象限进入继电器动作区.为改善保护的特性,有必要限制或缩小其在第二象限的动作区.在R-X平面上具有半透镜半姆欧特性的方向阻抗继电器能满足上述要求.本文详细分析了具有透镜或透镜一姆欧特性的各种方向阻抗继电器的原理.提出了一种构成成透镜一姆欧继电器的实用方法.为评价透镜一姆欧继电器的特性,在不同条件下进行了一系列试验研究.还进行了计算机模拟和电力系统模型试验.结果表明,透镜一姆欧继电器的特性与理论分析相当吻合,证明该继电器更适用于大容量、重负荷、长距离特高压的输电线路.在用于500KV电力系统中的JGBJ—500距离保护上采用了这种透镜一姆欧继电器.

关键词：继电器动作特性故障相特高压系统第二象限电子元件电器特性透镜电压矢量

基于人工神经网络的变压器绝缘模型放电模式识别的研究

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中国电机工程学报 2001年第1期21卷 21-24页

作者：姜磊朱德恒李福祺谈克雄覃刚力金显贺王昌长 t.c.cheng 清华大学电机工程系北京100084 南加州大学洛杉矶ca900089

分析了变压器绝缘的主要放电形式 ,设计了模拟变压器放电的 7种试验模型和 3种模拟空气中放电干扰的模型 ,进行了不同情况下模型的放电试验。使用数字化测量装置 ,取得了各种模型放电的放电量相位信息。采用三维谱图提取放电指纹特征 ... 详细信息

分析了变压器绝缘的主要放电形式 ,设计了模拟变压器放电的 7种试验模型和 3种模拟空气中放电干扰的模型 ,进行了不同情况下模型的放电试验。使用数字化测量装置 ,取得了各种模型放电的放电量相位信息。采用三维谱图提取放电指纹特征 ,并用人工神经网络ANN来识别不同的放电类型。研究结果表明 ,人工神经网络对油纸变压器绝缘放电有足够的识别能力。

关键词：变压器绝缘局部放电人工神经网络模式识别

Decision and coordination of an E-commerce Supply chain considering Returns and Network Externalities

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Journal of Systems Science and Systems Engineering 2024年第5期33卷 552-575页

作者： Liang Shen Fei Lin Yuyan Wang Luping Ding t.c.E.cheng Dexia Wang School of Public Finance and taxation Shandong University of Finance and Economicsjinan 250014China bschool of Management Science and Engineering Shandong University of Finance and EconomicsJinan 250014China PolyU Business School The Hong Kong Polytechnic UniversityHung HomKowloonHong Kong 999077China

considering the large number of returns in online sales and the network externalities of e-platforms,we develop a decentralized model and a centralized model to explore the impacts of returns and network externalities on e-commerce supply chain(EcSc)*** show that in the decentralized model,the service level,price,market demand,and EcSc members’profits increase with the network externality ***,the service level and price increase,while the market demand and EcSc members’profits decrease with the product return *** centralized model is the optimal operating mode when it is properly *** design the“commission and return cost-sharing”contract to optimize EcSc,in which the proportion of the e-platform’s sharing of the return handling cost is exactly equal to the proportion of the system profit after *** on the decentralized model,we develop two extended models in which we endogenize the impacts of the service level and return rate on the network externality *** comparisons between the extended and decentralized models,we show that high-quality service can improve EcSc’s profitability,while a high return rate hurts its economic performance.

关键词： E-commerce supply chain coordination mechanism network externalities return products

Dissipationless layertronics in axion insulator MnBi2te4

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National Science Review 2024年第6期11卷 189-196页

作者： Shuai Li Ming Gong Shuguang cheng Hua Jiang X.c.Xie School of Physical Science and technology Soochow University Institute for Advanced Study Soochow University International center for Quantum Materials School of Physics Peking University Department of Physics Northwest University Interdisciplinary center for theoretical Physics and Information Sciences Fudan University Hefei National Laboratory

Surface electrons in axion insulators are endowed with a topological layer degree of freedom followed by exotic transport phenomena, e.g., the layer Hall effect. Here, we propose that such a layer degree of freedom can be manipulated in a dissipationless way based on the antiferromagnetic MnBi2te4with tailored domain structure. this makes MnBi2te4a versatile platform to exploit the ‘layertronics’ to encode, process and store information. Importantly, the layer filter, layer valve and layer reverser devices can be achieved using the layer-locked chiral domain wall modes. the dissipationless nature of the domain wall modes makes the performance of the layertronic devices superior to those in spintronics and valleytronics. Specifically, the layer reverser, a layer version of the Datta–Das transistor, also fills up the blank in designing the valley reverser in valleytronics. Our work sheds light on constructing new generation electronic devices with high performance and low-energy consumption in the framework of layertronics.

关键词： axion insulator MnBi2te4 layertronics antiferromagnetic domain wall dissipationless transport

Féeton(B-L gauge boson)dark matter for the 511-keV gamma-ray excess and the prediction of low-energy neutrino flux

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chinese Physics c 2024年第8期48卷 76-82页

作者： Jie Sheng Yu cheng Weikang Lin tsutomu t.Yanagida tsung-Dao Lee Institute&School of Physics and Astronomy Shanghai Jiao Tong UniversityChina Key Laboratory for Particle Astrophysics and cosmology(MOE)&Shanghai Key Laboratory for Particle Physics and cosmology Shanghai Jiao Tong UniversityShanghai 200240China South-Western Institute For Astronomy Research Yunnan UniversityKunming 650500China Kavli IPMU(WPI) UTIASUniversity of TokyoKashiwa277-8583Japan

the féeton is the gauge boson of the U(1)_(B−L) gauge *** the gauge coupling constant is extremely small,the féeton becomes a candidate for dark *** show that its decay to a pair of an electron and a positron explains the observed Galactic 511-keV gamma-ray excess in a consistent *** féeton dark matter decays mainly into pairs neutrino and *** low-energy experiments with improved directional capability will enable capturing these neutrino *** seesaw-motivated parameter space predicts a relatively short féeton lifetime that is comparable to the current cosmological constraint.

关键词： feeton 511-keV gamma-ray excess low-energy neutrino

An improved initial rotor position estimation method using high-frequency pulsating voltage injection for PMSM

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Defence technology（防务技术） 2024年第3期33卷 19-29页

作者： Yang Jiang Ming cheng School of Electrical Engineering Southeast UniversityNanjing 210096China

High frequency pulsating voltage injection method is a good candidate for detecting the initial rotor position of permanent magnet synchronous ***,traditional methods require a large number of filters,which leads to the deterioration of system stability and dynamic *** order to solve these problems,a new signal demodulation method is proposed in this *** proposed new method can directly obtain the amplitude of high-frequency current,thus eliminating the use of filters,improving system stability and dynamic performance and saving the work of adjusting filter *** addition,a new magnetic polarity detection method is proposed,which is robust to current measurement ***,experiments verify the effectiveness of the method.

关键词： Initial position detection Signal demodulation algorithm Magnetic polarity detection Filter elimination

Reliability of a Multicomponent Stress-strength Model Based on a Bivariate Kumaraswamy Distribution with censored Data

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Acta Mathematicae Applicatae Sinica 2024年第2期40卷 478-507页

作者： cong-hua cheng School of Mathematics and Statistics Zhaoqing UniversityZhaoqing 526061China

In this paper,we consider a system which has k statistically independent and identically distributed strength components and each component is constructed by a pair of statistically dependent elements with doubly type-II censored *** elements(X1,Y1),(X2,Y2),…,(Xk,Yk)follow a bivariate Kumaraswamy distribution and each element is exposed to a common random stress t which follows a Kumaraswamy *** system is regarded as operating only if at least s out of k(1≤s≤k)strength variables exceed the random *** multicomponent reliability of the system is given by Rs,k=P(at least s of the(Z1,…,Zk)exceed t)where Zi=min(Xi,Yi),i=1,…,*** Bayes estimates of Rs,k have been developed by using the Markov chain Monte carlo methods due to the lack of explicit *** uniformly minimum variance unbiased and exact Bayes estimates of Rs,k are obtained analytically when the common second shape parameter is *** asymptotic confidence interval and the highest probability density credible interval are constructed for Rs,*** reliability estimators are compared by using the estimated risks through Monte carlo simulations.

关键词： stress-strength model bivariate Kumaraswamy distribution multicomponent reliability doubly type-II censored scheme interval estimation

Effects of layer interactions on instantaneous stability of finite Stokes flows

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Applied Mathematics and Mechanics(English Edition) 2024年第1期45卷 69-84页

作者： chen ZHAO Zhenli cHEN c.t.MUtASA Dong LI School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China

the stability analysis of a finite Stokes layer is of practical importance in flow control. In the present work, the instantaneous stability of a finite Stokes layer with layer interactions is studied via a linear stability analysis of the frozen phases of the base flow. the oscillations of two plates can have different velocity amplitudes, initial phases, and frequencies. the effects of the Stokes-layer interactions on the stability when two plates oscillate synchronously are analyzed. the growth rates of two most unstable modes when δ t equal, and δ = δ*/h*, where δ*and h*are the Stokes-layer thickness and the half height of the channel, respectively. However, their vorticities are different. the vorticity of the most unstable mode is symmetric, while the other is asymmetric. the Stokes-layer interactions have a destabilizing effect on the most unstable mode when δ tabilizing effect when δ > 0.68. However, the interactions always have a stabilizing effect on the other unstable mode. It is explained that one of the two unstable modes has much higher dissipation than the other one when the Stokes-layer interactions are strong. We also find that the stability of the Stokes layer is closely related to the inflectional points of the base-flow velocity profile. the effects of inconsistent velocity-amplitude, initial phase, and frequency of the oscillations on the stability are analyzed. the energy of the most unstable eigenvector is mainly distributed near the plate of higher velocity amplitude or higher oscillation frequency. the effects of the initial phase difference are complicated because the base-flow velocity is extremely sensitive to the initial phase.

关键词： finite Stokes layer instantaneous stability Stokes-layer interaction asynchronous oscillation

SARS-coV-2 and innate immunity:the good,the bad,and the"goldilocks"

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cellular & Molecular Immunology 2024年第2期21卷 171-183页

作者： Benjamin L.Sievers Mark t.K.cheng Kata csiba Bo Meng Ravindra K.Gupta Department of Medicine University of CambridgeCambridgeUK cambridge Institute of therapeutic Immunology&Infectious Disease(cItID) Department of MedicineUniversity of CambridgeCambridgeUk

An ancient conflict between hosts and pathogens has driven the innate and adaptive arms of *** about this interplay can not only help us identify biological mechanisms but also reveal pathogen vulnerabilities that can be leveraged *** humoral response to SARS-coV-2 infection has been the focus of intense research,and the role of the innate immune system has received significantly less ***,we review current knowledge of the innate immune response to SARS-coV-2 infection and the various means SARS-coV-2 employs to evade innate defense *** also consider the role of innate immunity in SARS-coV-2 vaccines and in the phenomenon of long cOVID.

关键词： SARS-coV-2 Innate immune response Interferon cytokines Inflammation Antiviral targets