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arXiv 2018年

作者： Du, H. Zhao, X. Rybakov, F.N. Borisov, A.B. Wang, S. Tang, J. Jin, C. Wang, C. Wei, W. Kiselev, N.S. Zhang, Y. Che, R. Blügel, S. Tian, M. Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field Laboratory Chinese Academy of Sciences and University of Science and Technology of China Hefei230026 China Department of Physics School of Physics and Materials Science Anhui University Hefei230601 China Laboratory of Advanced Materials Department of Materials Science Collaborative Innovation Center of Chemistry for Energy Materials Fudan University Shanghai200438 China Department of Physics KTH-Royal Institute of Technology StockholmSE-10691 Sweden M.N. Miheev Institute Metal Physics of Ural Branch Russian Academy of Sciences Ekaterinburg620990 Russia Peter Grünberg Institute Institute for Advanced Simulation Forschungszentrum Jülich and JARA Jülich52425 Germany Department of Physics University of Science and Technology of China 230031 China Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing210093 China

We report the direct evidence of field-dependent character of the interaction between individual magnetic skyrmions as well as between skyrmions and edges in B20-type FeGe nanostripes observed by means of high resolution Lorentz transmission electron microscopy. It is shown that above certain critical values of external magnetic field the character of such long-range skyrmion interactions change from attraction to repulsion. Experimentally measured equilibrium inter-skyrmion and skrymion-edge distances as function of applied magnetic field shows quantitative agreement with the results of micromagnetic simulations. Important role of demagnetizing fields and internal symmetry of three-dimensional magnetic skyrmions are discussed in details. Copyright © 2018, The Authors. All rights reserved.

关键词： Magnetic fields

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Topological magneto-optical effect and its quantization in noncoplanar antiferromagnets

arXiv

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arXiv 2018年

作者： Feng, Wanxiang Zhou, Xiaodong Hanke, Jan-Philipp Guo, Guang-Yu Blugel, Stefan Mokrousov, Yuriy Yao, Yugui Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing100081 China Peter Grunberg Institut and Institute for Advanced Simulation Forschungszentrum Julich and Jara Julich52425 Institute of Physics Johannes Gutenberg University Mainz Mainz55099 Germany Department of Physics and Center for Theoretical Physics National Taiwan University Taipei10617 Taiwan Physics Division National Center for Theoretical Sciences Hsinchu30013 Taiwan

Magneto-optical (MO) effects have been known for more than a century as they reflect the basic interactions between light and magnetism. The origin of MO effects is usually ascribed to the simultaneous presence of band exchange splitting and spin-orbit coupling. Using a tight-binding model and first-principles calculations, we show that topological MO effects, in analogy to the topological Hall effect, can arise in noncoplanar antiferromagnets entirely due to the scalar spin chirality instead of spin-orbit coupling. The band exchange splitting is not required for topological MO effects. Moreover, we discover that the Kerr and Faraday rotation angles in two-dimensional insulating noncoplanar antiferromagnets can be quantized in the low-frequency limit, implying the appearance of quantum topological MO effects, accessible by time-domain THz spectroscopy. Copyright © 2018, The Authors. All rights reserved.

关键词： Calculations

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Nonlinear Control Method for Hypersonic Vehicle Based on Double Power Reaching Law of Sliding Mode

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Transactions of Nanjing University of Aeronautics and Astronautics 2018年第5期 849页

作者： Liu Rong Zhang Heng Liang Jin Key Laboratory of UAV’s Advanced Technology (Nanjing University of Aeronautics and Astronautics) Ministry of Industry and Information Technology College of Automation Engineering Nanjing University of Aeronautics and Astronautics Key Laboratory of Aircraft Control Integration Technology Aviation Industry Xi’an Flight Automatic Control Research Institute

The intelligence nonlinear control scheme via double power reaching law based sliding mode control method is proposed to solve the problems of model uncertainties and unknown outside disturbances. Firstly, the aerodynamic parameters of the morphing vehicle are replaced with curve-fitted approximation to build the accurate model for control design in the hypersonic flight. Then the nonlinear vehicle model is transformed into the strict feedback multi-input/multi-output nonlinear system by using the input-output feedback linearization approach. At the same time, the disturbance observer is used to approximate the unknown disturbance, and the sliding mode method is used to solve the problem of non-matching and uncertainty. Finally, according to the buffeting problem in sliding mode control, the double power is improved. simulation results show that the proposed method can ensure the global stability of the closed-loop system, and has good tracking and robust performance.

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Influence of secondary droplet on separation performance of wave-type vane separator

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IOP Conference Series: Earth and Environmental Science 2018年第1期188卷

作者： F L Zhao Q F Liu F Zhang J X Li H L Bo Fundamental Science on Nuclear Safety and Simulation Technology Laboratory Harbin Engineering University Heilongjiang 150001 China Institute of Nuclear and New Energy Technology Tsinghua University Key Laboratory of Advanced Reactor Engineering and Safety of the Ministry of Education Beijing 100084 China

The steam-water separator is a vital device of the steam generator in nuclear power plant. Its separation performance greatly influences the efficiency, safety and reliability of the power station. When the droplet moves in separator, the droplet can collide with the separator wall, and the secondary droplets may generate when the collision velocity of the primary droplet is sufficiently large. To investigate the effect of secondary droplet on separation performance of the separator, the simulation is conducted using droplet motion model and generation model of secondary droplet. The trajectories of both primary droplet and secondary droplet are presented. The effect of the secondary droplet on the separator separation efficiency is analyzed. The results can guide the design of the separator, where both of the droplet motion and the secondary droplets generation need to be considered.

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CHARACTERIZATION, MECHINICAL, THERMAL AND ABLATIVE PROPERTIES OF CERAMIC MODIFIED PHENOLIC RESIN AEROGELS SYNTHSIZED BY AMBIENT PRESSURE DRYING

CHARACTERIZATION, MECHINICAL, THERMAL AND ABLATIVE PROPERTIE...

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第二十一届国际复合材料大会

作者： Jun Zhang Rongying Yin Haiming Cheng Changqing Hong Xinghong Zhang Songhe Meng National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Harbin Institute of Technology China Aerodynamics Research and Development Center Harbin Aircraft industry(Group)Co.Ltd Aviation Industry Corporation of China

During the past few decades, various organic aerogels（AGs） have been synthesized and shown number of exceptional and even unique properties, such as low bulk density, high porosity, grea surface areas, and extremely low thermal conductivity, which enable them being the focus of industr and ***, AGs exhibit substantial performance boosts in numerous applications such a adsorption, separation, catalysis, energy conversion and storage, and so ***, AG generally exhibit high cost, poor thermal and mechanical properties, which seriously restrict the large-scale *** this study, ceramic was introduced into commercial available resin derive aerogel due to the enhancement of silicon to thermal stability and low cost of the *** cerami modified phenolic resin（PR-SiO） aerogel was synthesized by a simple sol-gel polymerization o ceramic precursor, PR, hexamethylenetetramine in an ethylene glycol solution, followed by solven exchange and ambient pressure *** modified effect on the porous structure, textural property and thermal stability was studied by scanning electron microscope（SEM）, nitrogen adsorptio isotherms, and thermogravimetric analysis（TGA）.According to the characterizations of SEM an nitrogen adsorption, the obtained PR-SiO hybrid aerogels have a continuous three dimensiona network that consists of phenolic nano-particles and curved nano-sheets with size from 50 to 90 nm which define numerous mesopores and *** in argon atmosphere indicated that th thermal stability of the PR-SiO aerogels（both maximum decomposition rate and char yield a 1000 ℃） is better than that of the pristine PR *** order to improve the mechanical properties carbon fabric reinforced aerogel composite was prepared by impregnating carbon-bonded carbon fibe（CBCF） composite with the *** the micrographs of the aerogel matrix composite, the aerogel are fully and uniformly occupied the void between carbon fibers, and coated with a t

关键词： Ceramic Phenolic resin Aerogel Mechanical Properties Thermal Properties

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An engineering applicable dynamic equivalent method for large-scale AC system connected to VSC-HVDC

An engineering applicable dynamic equivalent method for larg...

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2016 IEEE PES Asia Pacific Power and Energy Engineering Conference, APPEEC 2016

作者： Lin, Zhu Xueguang, Wu Liu, Dong Global Energy Interconnection Research Institute Beijing China State Key Laboratory of Advanced Power Transmission Technology Beijing China Beijing Key Laboratory of DC Grid Technology and Simulation Beijing China

ISBN: (纸本)9781509054183

To test the software and hardware functions of VSC-HVDC control and protection device, an efficient way is to carry out the hardware-in-loop (HIL) tests and setup a detailed AC/DC transient model in real-time digital simulator. However, taking into account capability of the simulator and details of the simulation, the large scale AC network outside the converters should be simplified and equivalent. In this paper, based on a principle that the short circuit levels should be consistent before and after equivalent, a new equivalent method to calculate the equivalent generator parameters for large scale AC power system is proposed. Firstly, rated capacity and access reactance of equivalent generators are calculated according to equivalent bus's short-current. Secondly, a new criterion is provided based on short-current contribution ratio, according to short-current and short-reactance of the equivalent bus. Finally, this criterion is used to choose dominate controller of the equivalent generators, and calculate controller parameters. At the same time, the Ward method is improved. The negative line resistance and generator active output are corrected. Finally, the proposed method is used for Xiamen equivalent grid which derived from a large scale of 'Sanhua' China power grids and validated by comparison of the bus voltages, power flows, short-circuit levels and the dynamic response characteristics of the equivalent network, the validity of the proposed method is proved. © 2016 IEEE.

关键词： Timing circuits

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Semileptonic B and Bsdecays involving scalar and axial-vector mesons

arXiv

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arXiv 2018年

作者： Kang, Xian-Wei Luo, Tao Zhang, Yi Dai, Ling-Yun Wang, Chao College of Nuclear Science and Technology Beijing Normal University Beijing100875 China Institute of Modern Physics Fudan University Shanghai200443 China School of Physics and Electronics Hunan University Changsha410082 China Institute for Advanced Simulation Institut für Kernphysik Jülich Center for Hadron Physics Forschungszentrum Jülich JülichD-52425 Germany Center for Ecological and Environmental Sciences Key Laboratory for Space Bioscience and Biotechnology Northwestern Polytechnical University Xi'an710072 China

We report our theoretical calculations on the branching fractions for the semileptonic B and Bsdecays based on the form factors in the covariant light-front quark model. That is, B(Bs) → (P, V, S, A)lνl, where P and V denote the pseudoscalar and vector mesons, respectively, while S denotes the scalar meson with mass above 1 GeV and A the axial-vector meson. The branching fractions for the semileptonic B → P and V modes have been measured very well in experiment and our theoretical values are in good agreement with them. The ones for B → S and A modes are our theoretical predictions. There is little experimental information on the semileptonic Bsdecays although much theoretical effort has been done. In addition, we predict the branching fractions of B → D∗0(2400)lνland Bs→ D∗-s0(2317)lνlas (2.31 ± 0.25) × 10-3and (3.07 ± 0.34) × 10-3, in order, assuming them as the conventional mesons with quark-antiquark configuration. The high luminosity e+e--collider SuperKEKB/Belle-II is running, with the data sample enhanced by a factor of 40 compared to Belle, which will provide huge opportunity for the test of the theoretical predictions and further help understand the inner structure of these scalar and axial-vector mesons, e.g., the glueball content of f0(1710) and the mixing angles for the axial-vector mesons. These decay channels can also be accessed by the LHCb experiment. Copyright © 2018, The Authors. All rights reserved.

关键词： Forecasting

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Octet baryon magnetic moments at next-to-next-to-leading order in covariant chiral perturbation theory

arXiv

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arXiv 2018年

作者： Xiao, Yang Ren, Xiu-Lei Lu, Jun-Xu Geng, Li-Sheng Meißner, Ulf-G. School of Physics and Nuclear Energy Engineering Beihang University Beijing100191 China State Key Laboratory of Nuclear Physics and Technology School of Physics Peking University Beijing100871 China Institut fur Theoretische Physik II Ruhr-Universität Bochum BochumD-44780 Germany School of Physics and Nuclear Energy Engineering Beijing Key Laboratory of Advanced Nuclear Materials and Physics Beihang University Beijing100191 China and Beijing Advanced Innovation Center for Big Date-based Precision Medicine Beihang University Beijing 100191 China Helmholtz-Institut fur Strahlen-und Kernphysik and Bethe Center for Theoretical Physics Universität Bonn BonnD-53115 Germany Forschungszentrum Jülich Institute for Advanced Simulation and Jülich Center for Hadron Physics Institut für Kernphysik JülichD-52425 Germany

We calculate the octet baryon magnetic moments in covariant baryon chiral perturbation theory with the extended-on-mass-shell renormalization scheme up to next-to-next-to-leading order. At this order, there are nine low-energy constants, which cannot be uniquely determined by the seven experimental data alone. We propose two strategies to circumvent this problem. First, we assume that chiral perturbation theory has a certain convergence rate and use this as one additional constraint to fix the low-energy constants by fitting to the experimental data. Second, we fit to lattice QCD simulations to determine the low-energy constants. We then compare the resulting predictions of the light and strange quark mass dependence of the octet baryon magnetic moments by the three mostly studied formulations of baryon chiral perturbation theory, namely, the extended-on-mass-shell, the infrared, and the heavy baryon approach. It is shown that once more precise lattice data become available, one will learn more about the convergence pattern of baryon chiral perturbation theory. Copyright © 2018, The Authors. All rights reserved.

关键词： Magnetic moments

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Nonlinear Vibration Response Analysis and Experimental Verification of Thin-walled Structures to Thermal-acoustic Excitations

Nonlinear Vibration Response Analysis and Experimental Verif...

引用

2016 4th International Conference on Machinery,Materials and Information technology Applications(ICMMITA 2016)

作者： SHA Yun-dong Wang Jian Shenyang Aerospace University Liaoning Province Key Laboratory of Advanced Measurement And Test Technology of Aviation Propulsion Systems

ISBN: (纸本)9781510835467

For the nonlinear vibration response problems of aerospace thin-walled structures to thermalacoustic excitation, the theory of structural-acoustic coupling and the coupled FEM/BEM method were used to analyze dynamic response characteristics of super-alloy thin-walled rectangular plates with four edges clamped. Based on different loading ways: diffusion field, progressive wave 0°/ 45°/ 90°, the theories of buckling and snap-through were employed to study the stress/strain response of structures which were subjected to the different thermal-acoustic loading combinations. The majority of the analyses have dealt with the influence of acoustic loading ways and thermal loadings on structure stress/strain responses, the interaction mechanism of phenomenon of buckling and snap-through on stress/strain responses. Meanwhile, the experimental verifications of nature frequencies and strain have been done, respectively. The analysis results will provide a reference to determine a reasonable fatigue life prediction model.

关键词： Acoustic loading ways Vibration response Thin-walled structures Coupled FEM/BEM method Experimental verification

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A step-by-step parameter design method for discrete state space control scheme of dynamic voltage restorer

A step-by-step parameter design method for discrete state sp...

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Annual Conference of Industrial Electronics Society

作者： He Lei Rengcun Fang Dongjun Yang Jingyou Xu Qiushi Xu Zixia Sang Bofeng Gao Yong Kang Lei Wu State Grid Laboratory for Hydro-thermal Power Resources Optimal Allocation & Simulation Technology State Grid HBEPC Economic & Technology Research Institute Wuhan China State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China SG Huangshi Electric Power Supply Company Huangshi China

Dynamic Voltage Restorer (DVR), as a device of voltage sag compensation, demands fast transient response, and the disturbance of source voltage is a main impact on control performance. The DVR control strategy based on discrete state space will enhance control bandwidth and stability. However, for the discrete space control system, the number of parameters is relatively more which will lead to a complicated design process. To solve this problem, this paper proposed a control parameter design method based on the idea of virtual resistor. Firstly, by means of state feedback control, an adjustable virtual resistor can be series in filter inductor. According to the requirements of steady-state error, phase margin and Routh's criterion in w domain, the variation regions of PI parameters and virtual resistance can be solved by a step-by-step method, and then the appropriate control parameters can be selected. Experimental results from a digital signal processor-based system are included to support theoretical analysis.

关键词： Resistors Control systems Voltage control Mathematical model Resistance Aerospace electronics Inductors

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