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Effect of forced-air cooling on the microstructure and age-hardening response of extruded Mg-Gd-Y-zn-zr alloy full with LPsO lamella

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Journal of Materials science & Technology 2021年第14期73卷 66-75页

作者： s.z.wu T.Nakata G.z.Tang C.Xu X.J.Wang X.W.Li X.G.Qiao M.Y.zheng L.Geng s.Kamado G.H.Fan school of Materials science and Engineering Harbin Institute of TechnologyHarbin 150001China Research Center for Advanced Magnesium Technology Nagaoka University of TechnologyNagaoka 940-2188Japan school of Material science and Engineering Harbin University of Science and TechnologyHarbin 150040China Key Laboratory for Light-weight Materials Nanjing Tech UniversityNanjing 211816China

The homogenized Mg-8.2 Gd-3.8 Y-1.0 zn-0.4 zr(wt.%)alloy full of plate-shaped long period stacking ordered(LPsO)phases was hot extruded in the atmosphere and cooled by the forced-air,then the effect of forced-air cooling on the microstructure and age-hardening response of the alloy was investigated in this *** results show that in comparison with the extruded sample cooling in the atmosphere,the forced-air cooling restricts dynamic recrystallization(DRX)and brings about finer dynamic recrystallized(DRXed)grain size,stronger basal texture and higher dislocation ***,the forced-air cooling promotes the dynamic precipitation in the DRXed regions and facilitates formation of plate-shaped LPsO phases andγ’phases with smaller interspacing in the unrecrystallized(un DRXed)regions,then slightly restricts the precipitation ofβphases during *** peak-ageing treatment,the extruded sample with forced-air cooling shows superior tensile properties with a tensile yield strength of 439 MPa,an ultimate tensile strength of 493 MPa,and elongation to failure of 18.6%.

关键词： Mg-RE alloy LPsO phase Dynamic recrystallization Precipitation Mechanical properties

Nonlinear branched flow of intense laser light in randomly uneven media

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Matter and Radiation at Extremes 2023年第2期8卷 25-32页

作者： K.Jiang T.W.Huang C.N.wu M.Y.Yu H.zhang s.z.wu H.B.zhuo A.Pukhov C.T.zhou s.C.Ruan College of Applied sciences Shenzhen UniversityShenzhen 518060People’s Republic of China shenzhen Key Laboratory of Ultraintense Laser and Advanced Material Technology Center for Advanced Material Diagnostic Technologyand College of Engineering PhysicsShenzhen Technology UniversityShenzhen 518118People’s Republic of China Institut für Theoretische Physik I Heinrich-Heine-Universität Düsseldorf40225 DüsseldorfGermany

Branched flow is an interesting phenomenon that can occur in diverse *** is usually linear in the sense that the flow does not alter the properties of the *** flow of light on thin films has recently been *** is therefore of interest to know whether nonlinear light branching can also ***,using particle-in-cell simulations,we find that in the case of an intense laser propagating through a randomly uneven medium,cascading local photoionization by the incident laser,together with the response of freed electrons in the strong laser fields,triggers space–time-dependent optical *** resulting branching pattern depends dramatically on the laser *** is,the branching here is distinct from the existing linear *** observed branching properties agree well with theoretical analyses based on the Helmholtz *** branched propagation of intense lasers potentially opens up a new area for laser–matter interaction and may be relevant to other branching phenomena of a nonlinear nature.

关键词： laser intense flow

Probing the Bardeen-Kiselev black hole with the cosmological constant caused by Einstein equations coupled with nonlinear electrodynamics using quasinormal modes and greybody bounds

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Communications in Theoretical Physics 2024年第6期76卷 102-119页

作者： s R wu B Q Wang z W Long College of Physics Guizhou UniversityGuiyang 550025China College Pharmacy Guizhou University of Traditional Chinese MedicineGuiyang 550025China

In this work,we investigate a static and spherically symmetric Bardeen-Kiselev black hole(BH)with the cosmological constant,which is a solution of the Einstein-non-linear Maxwell field *** compute the quasinormal frequencies for the Bardeen-Kiselev BH with the cosmological constant due to electromagnetic and gravitational *** varying the BH parameters,we discuss the behavior of both real and imaginary parts of the BH quasinormal frequencies and compare these frequencies with the Reissner-Nordström-de sitter BH surrounded by quintessence(RN-dsQ).Interestingly,it is shown that the responses of the Bardeen-Kiselev BH with the cosmological constant and the RN-dsQ under electromagnetic perturbations are different when the charge parameter q,the state parameter w and the normalization factor c are varied;however,for the gravitational perturbations,the responses of the Bardeen-Kiselev BH with the cosmological constant and the RN-dsQ are different only when the charge parameter q is ***,compared with the gravitational perturbations,the electromagnetic perturbations can be used to understand nonlinear and linear electromagnetic fields in curved spacetime *** interesting observation is that,due to the presence of Kiselev quintessence,the electromagnetic perturbations around the Bardeen-Kiselev BH with the cosmological constant damps faster and oscillates slowly;for the gravitational perturbations,the quasinormal mode decays slowly and oscillates *** also study the reflection and transmission coefficients along with the absorption cross section in the Bardeen-Kiselev BH with the cosmological constant;it is shown that the transmission coefficients will increase due to the presence of Kiselev quintessence.

关键词： quasinormal modes greybody factors Bardeen-Kiselev black hole with cosmological constant

Asymmetrical Fault Current Calculation Method and Influencing Factors Analysis of Droop-Controlled Inverters

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CsEE Journal of Power and Energy systems 2024年第2期10卷 562-573页

作者： Huimin zhao zhikang shuai Jun Ge An Luo Weimin wu z.John shen College of Electrical and Information Engineering Hunan UniversityChangsha 410006China Electrical Engineering Department Shanghai Maritime UniversityShanghai 201306China Department of Electrical and Computer Engineering Ilinois Institute of TechnologyChicagoIL 60616 USA

since the fault dynamic of droop-controlled inverter is different from synchronous generators (sGs), protection devices may become invalid, and the fault overcurrent may damage power electronic devices and threaten the safety of the microgrid. Therefore, it is imperative to conduct a comprehensive fault analysis of the inverter to guide the design of protection schemes. However, due to the complexity of droop control strategy, existing literatures have simplified asymmetric fault analysis of droop-controlled inverters to varying degrees. Therefore, accurate fault analysis of a droop-controlled inverter is needed. In this paper, by analyzing the control system, an accurate fault model is established. Based on this, a calculation method for instantaneous asymmetrical fault current is proposed. In addition, the current components and current characteristics are analyzed. It was determined that fault currents are affected by control loops, fault types, fault distance and nonlinear limiters. In particular, the influences of limiters on the fault model, fault current calculation and fault current characteristics were analyzed. Through detailed analysis, it was found that dynamics of the control loop cannot be ignored, the fault type and fault distance determine fault current level, and part of the limiters will totally change the fault current trend. Finally, calculation and experimental results verify the correctness of the proposed method.

关键词： Asymmetrical fault analysis droop control fault current calculation method limiter transient fault characteristics

Granger causal representation learning for groups of time series

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science China(Information sciences) 2024年第5期67卷 56-68页

作者： Ruichu CAI Yunjin wu Xiaokai HUANG Wei CHEN Tom z.J.FU zhifeng HAO school of Computer science Guangdong University of Technology Peng Cheng Laboratory College of science Shantou University

Discovering causality from multivariate time series is an important but challenging *** existing methods focus on estimating the Granger causal structures among multivariate time series,while ignoring the prior knowledge of these time series, e.g., the group of the time series. Focusing on discovering the Granger causal structures among groups of time series, we propose a Granger causal representation learning method to solve this problem. First, we use the multiset canonical correlation analysis method to learn the Granger causal representation of each group of time series. Then, we model the Granger causal relationships among the learned Granger causal representations using a recurrent neural network with temporal information. Finally, we formulate the above two stages into one unified optimization problem, which is efficiently solved using the augmented Lagrangian method. We conduct extensive experiments on synthetic and real-world datasets to validate the correctness and effectiveness of the proposed method.

关键词： Granger causal discovery Granger causal representation learning time series data recurrent neural network multiset canonical correlation analysis

Effects of dopants on magnetic properties of Cu-doped znO thin films

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Effects of dopants on magnetic properties of Cu-doped ZnO th...

Change in ferromagnetic properties with the growth of oxygen pressure in Boron-doped znO thin films

2011中国材料研讨会

作者： H.L.Yang,X.G.Xu,s.z.wu,K.wu,C.Ai,J.Miao,Y.Jiang state Key Laboratory for Advanced Metals and Materials,school of Materials science and Engineering,University of science and Technology Beijing,Beijing 100083,China.

＜正＞Because neither metallic Cu nor Cu oxide is ferromagnetic and Cu2+is a potential magnetic ion with a total spin of1/2according to Hund’s rule,Cu is an ideal doping element

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Change in ferromagnetic properties with the growth of oxygen...

Dynamics of a rotating ring-stiffened sandwich conical shell with an auxetic honeycomb core

2011中国材料研讨会

作者： H.L.Yang,X.G.Xu,s.z.wu,J.Miao,Y.Jiang state Key Laboratory for Advanced Metals and Materials,school of Materials science and Engineering,University of science and Technology Beijing,Beijing 100083,China.

＜正＞Recently,unexpected high-temperature"d0Ferromagnetism"was reported in Carbon-doped znO.[1]However,the mechanism of the ferromagnetic properties isunclear in znO"d0ferromagnetism"system

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Applied Mathematics and Mechanics(English Edition) 2024年第6期45卷 963-982页

作者： s.JAHANGIRI A.GHORBANPOUR ARANI z.KHODDAMI MARAGHI Department of solid Mechanics Faculty of Mechanical EngineeringUniversity of KashanKashan ***Iran Faculty of Engineering Mahallat Institute of Higher EducationMahallat ***Iran

The free vibration analysis of a rotating sandwich conical shell with a reentrant auxetic honeycomb core and homogenous isotropic face layers reinforced with a ring support is *** shell is modeled utilizing the first-order shear deformation theory(FsDT)incorporating the relative,centripetal,and Coriolis accelerations alongside the initial hoop tension created by the *** governing equations,compatibility conditions,and boundary conditions are attained using Hamilton’s *** trigonometric functions,an analytical solution is derived in the circumferential direction,and a numerical one is presented in the meridional direction via the differential quadrature method(DQM).The effects of various factors on the critical rotational speeds and forward and backward frequencies of the shell are *** present work is the first theoretical work regarding the dynamic analysis of a rotating sandwich conical shell with an auxetic honeycomb core strengthened with a ring support.

关键词： free vibration conical shell rotating shell ring support auxetic honeycomb

stability Investigation and Improvement for DC Cascade systems with simplified Impedance-based stability Criterion

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CsEE Journal of Power and Energy systems 2024年第3期10卷 1044-1052页

作者： Junbin Fang zhikang shuai Yang Li zhibing Wang Xiangyang wu Xia shen z.John shen College of Electrical and Information Engineering Hunan UniversityChangsha 410082China Renewable Energy Department of China Electric Power Research Institute Beijing 100192China Department of Electrical and Computer Engineering Illinois Institute of TechnologyChicagoIL 60616USA IEEE

In DC distributed power systems(DPss),the complex impedance interactions possibly lead to DC bus voltage oscillation or *** previous research,the stability analysis of DPss is implemented based on mathematical analysis in control *** specific mechanisms of the instability of the cascade system have not been intuitively *** this paper,the stability analysis of DPss based on the traditional Nyquist criterion is simplified to the resonance analysis of the seriesconnected port impedance(z=R+jX)of source and load *** reveals that the essential reason for impedance instability of a DC cascade system is that the negative damping characteristic(Rs the internal resonance source at reactance zero-crossing *** simplified stability criterion for DC cascade systems can be concluded as:in the negative damping frequency ranges(Rsts no zero-crossing point of the reactance component(i.e.,X=0).According to the proposed stability criterion,the oscillation modes of cascade systems are classified.A typical one is the internal impedance instability excited by the negative damping,and the other one is that the external disturbance amplified by negativity in a low stability ***,the impedance reshaping method for stability improvement of the system can be further *** validity of the simplified criterion is verified theoretically and experimentally by a positive damping reshaping method.

关键词： DC cascaded system,impedance model impedance reconstruction stability criterion