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CSEE Journal of Power and Energy Systems 2021年第4期7卷 821-831页

作者： Yang Liu Zehui Lin Kaishun Xiahou Yuqing Lin q.h.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China

This paper proposes an equivalent hamiltonian equations model for the modular multilevel converter-based high-voltage direct-current(MMC-hVDC)transmission system,and constructs an energy function for multi-machine power systems with MMC-hVDC transmission *** equivalent hamiltonian equations model is verified to be able to track the power output dynamics of the full model of an MMC-hVDC transmission *** theoretical and numerical studies have been undertaken to validate that the energy function proposed for hybrid AC/DC systems satisfies the conditions of an energy *** work of this paper bridges the gap between the well-developed direct methods of transient stability analysis and power systems with MMC-hVDC transmission lines.

关键词： Energy function equivalent hamiltonian equations model hybrid AC/DC power system MMC-hVDC transient stability

IMPrOVEMENT OF CArBIDE MOrPhOLOGY ANDMEChANICAL PrOPErTIES OF Cr12MoV STEELS

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Acta Metallurgica Sinica(English Letters) 2000年第5期13卷 1053-1058页

作者： Cui, X.h. Jiang, q.C. Wang, S.q. he, Z.M. Sch. of Mat. Sci. and Eng. Jilin Univ. of Technol. Changchun 130025 China

Compared with conventional cast Cr12MoV steel and forged Cr12MoV steels, carbide morphology and properties of modified cast Cr12MoV steels were investigated by performing hardness test, impact test, fracture toughness test, fatigue crack propagation test, metallographic examination and quantitatively metallographic analysis. The results indicate that the carbide morphology in modified cast steel is characterized by uniformly-distributed granular carbide, which is different from that of conventional cast steel, but similar to that of forged steel. the impact toughness of modified cast steel is distinctly increased to 12.75 J/cm2 from 6.8 J/cm2 in the conventional cast steel with networked carbide, because of carbide granulation. Furthermore, The fracture toughness and fatigue-crack-propagation threshold of modified cast steel are not only higher than that of the conventional cast steel, but also higher than that of the forged steels.

关键词： Alloys Carbides Mechanical properties Morphology

Laboratory study of fracture initiation and propagation in Barre granite under fluid pressure at stress state close to failure

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Journal of rock Mechanics and Geotechnical Engineering 2023年第3期15卷 538-550页

作者： Bing q.Li Michela Casanova herbert h.Einstein Department of Civil and Environmental Engineering Massachusetts Institute of TechnologyCambridgeUSA Department of Civil and Environmental Engineering Western UniversityLondonCanada School of Architecture Civil and Environmental EngineeringÉcole Polytechnique Fédérale de LausanneLausanneSwitzerland

hydraulic fracturing is frequently used to increase the permeability of rock formations in energy extraction scenarios such as unconventional oil and gas extraction and enhanced geothermal systems(EGSs).The present study addresses uncertainties in the hydraulic fracturing process pertaining to EGSs in crystalline rock such as ***,there is debate in the literature on the mechanisms(*** and/or shear)by which these fractures initiate,propagate,and *** present experiments on Barre granite with pre-cut flaws where the material is loaded to high far-field stresses close to shear failure,and then the fluid pressure in the flaws is increased to move the Mohr’s circle to the left and observe the initiation and propagation of fractures using high-speed imaging and acoustic emissions(AEs).We find that the hydraulic fractures initiate as tensile microcracks at the flaw tips,and then propagate as a combination of tensile and shear *** focal mechanisms also show elevated levels of tensional microfracturing near the flaw tips during pressurization and final *** then consider a numerical model of the experimental setup,where we find that fractures are indeed likely to initiate at flaw tips in tension even at relatively high far-field stresses of 40 MPa where shear failure is generally expected.

关键词： Acoustic emission(AE) hydraulic fracturing Enhanced geothermal system(EGS) Microseismicity

Three principles for preparing Al wire with high strength and high electrical conductivity

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Journal of Materials Science & Technology 2019年第5期35卷 742-751页

作者： J.P.hou r.Li q.Wang h.Y.Yu Z.J.Zhang q.Y.Chen h.Ma X.M.Wu X.W.Li Z.F.Zhang Materials Fatigue and Fracture Division Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China National quality Supervision & Inspection Center of Electrical Equipment Safety Performance Zhejiang Huadian Equipment Testing Institute Hangzhou 310015 China Electric Power research Institute of Liaoning Electric Power Co. Ltd. Liaoning Electric Power Co. Ltd. Shenyang 110006 China Department of Materials Physics and Chemistry School of Materials Science and Engineering Key Laboratory for Anisotropy and Texture of Materials Ministry of Education Northeastern University Shenyang 110819 China

The trade-off relation between the strength and the electrical conductivity has been a Iong-standing dilemma in metallic materials. In the study, three key principles, *** grains, sharp texture and nano-scale precipitates, were presented for preparing Al wire with high strength and high electrical conductivity based on the specially designed experiments for breaking the mutually exclusive relation between the strength and the electrical conductivity. The results show that the elongated grains could lead to a higher electrical conductivity in Al wire without sacrificing the strength;while, the sharp texture can efficiently strengthen the Al wire without influencing the electrical conductivity. Furthermore, nano-scale precipitates with proper size can simultaneously improve the strength and electrical conductivity of Al alloy wire. Under the guidance of the above three key principles, Al wires with high strength and high conductivity were prepared.

关键词： Al wire Texture Precipitates Strength Electrical conductivity

Vibration characteristics of piezoelectric functionally graded carbon nanotube-reinforced composite doubly-curved shells

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Applied Mathematics and Mechanics(English Edition) 2021年第6期42卷 819-840页

作者： V.V.ThAM h.q.TrANT T.M.TU National Univensity of Ciwil Engineering Giai Phong Road 55Hai Ba Trung DistrictHanoi 100000 Vietnam

This paper presents an analytical solution for the free vibration behavior of functionally graded carbon nanotube-reinforced composite(FG-CNTrC) doubly curved shallow shells with integrated piezoelectric layers. here, the linear distribution of electric potential across the thickness of the piezoelectric layer and five different types of carbon nanotube(CNT) distributions through the thickness direction are considered. Based on the four-variable shear deformation refined shell theory, governing equations are obtained by applying hamilton's principle. Navier's solution for the shell panels with the simply supported boundary condition at all four edges is derived. Several numerical examples validate the accuracy of the presented solution. New parametric studies regarding the effects of different material properties, shell geometric parameters, and electrical boundary conditions on the free vibration responses of the hybrid panels are investigated and discussed in detail.

关键词： free vibration four-variable shear deformation refined theory functionally graded carbon nanotube-reinforced composite(FG-CNTrC) piezoelectric material

EFFECT OF MODIFICATION ON CArBIDE GrANULATION AND ITS MEChANISM

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Acta Metallurgica Sinica(English Letters) 1999年第2期12卷 167-172页

作者： Wang, S.q. Jiang, q.C. Cui, X.h. he, Z.M. Jilin Univ of Technology Changchun China

By the modification, network carbide is disconnected at 1100 degree C through uneven dissolution at higher energy places in carbide, where there is twin or lattice distortion, and is granulated at 1130 degree C through element diffusion. The stability of M//7C//3 carbide is decreased because of the modification reducing the segregation of Cr and Mo, thus the temperature, at which uneven dissolution of carbide commenced, is decreased. Also lattice distortion or defect such as twin in carbide is increased by the modification, which prompts widespread disconnections in carbide. In addition, the modification prompts element diffusion to accelerate the kinetics process of carbide granulation. (Edited author abstract) 6 refs.

关键词： Carbides Chromium alloys Granulation Modification Morphology

In situ TEM investigation of electron irradiation and aging-induced high-density nanoprecipitates in an Mg-10Gd-3Y-1Zn-0.5Zr alloy

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Journal of Magnesium and Alloys 2024年第5期12卷 1841-1853页

作者： M.Lv h.L.Ge q.q.Jin X.h.Shao Y.T.Zhou B.Zhang X.L.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Materials Science and Engineering research Center Guangxi University of Science and TechnologyLiuzhou 545006China

In-situ electron irradiation and aging are applied to introduce high-density precipitates in an Mg-10Gd-3Y-1Zn-0.5Zr(GWZ1031K,wt.%)alloy to improve the *** results show that the hardness of the Mg alloy after irradiation for 10 h and aging for 9 h at 250℃ is 1.64 GPa,which is approximately 64% higher than that of the samples before being *** is mainly attributed to γ'precipitates on the basal plane after irradiation and the high-density nanoscale β'precipitates on the prismatic plane after aging,which should be closely related to the irradiation-induced homogenous *** latter plays a key role in precipitation *** result paves a way to improve the mechanical properties of metallic materials by tailoring the precipitation through irradiation and aging.

关键词： Mg alloy Electron beam irradiation hardening Precipitates In-situ TEM

Sol-gel derived hA/TiO_2 double coatings on Ti scaffolds for orthopaedic applications

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中国有色金属学会会刊：英文版 2006年第B01期16卷 209-216页

作者： XU W hU W Y LI M h MA q q P. D. hODGSON WEN C E Department of Applied Physics Hunan University Changsha 410082 China Centre for Material and Fibre Innovation Deakin University Geelong Vic 3217 Australia

hydroxyapatite/titania (hA/TiO2) double layers were coated onto Ti scaffolds throughout for orthopaedic applications by sol-gel method. Differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and X-ray diffractometry (XrD) were used for the characterisation of the phase transformations of the dried gels and coated surface structures. Scanning electron microscope (SEM) equipped with energy dispersive spectrometry (EDS) was used for the observation and evaluation of the morphology and phases of the surface layers and for the assessment of the in vitro tests. The in vitro assessments were performed by soaking the hA/TiO2 double coated samples into the simulated body fluid (SBF) for various periods. The TiO2 dipping-coating method at a speed of 12 cm/min, followed by a heat treatment at 600 ℃ for 20 min. The hA la lyaeyre wr wasa ssu cbosaetqeude bnytl ya dipping-coated on the outer surface at the same speed and then heat-treated at difference temperatures. The results indicat that the hA phase begins to crystallize after a heat treatment at 560 ℃. The crystallinity increases obviously at 760 ℃. SEM observations find no delamination or crack at the interfaces of hA/TiO2 and TiO2/Ti. The hA/TiO2 coated Ti scaffolds displays excellent bone-like apatite forming ability when it is soaked into SBF. Ti scaffolds after hA/TiO2 double coatings can be anticipated as promising implant materials for orthopaedic

关键词：钛支架溶胶-凝胶法羟基磷灰石/二氧化钛涂层医学整形外科应用

Constructing an Energy Function for Power Systems with DFIGWT Generation Based on a Synchronous-generator-mimicking Model

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CSEE Journal of Power and Energy Systems 2022年第1期8卷 64-75页

作者： Yang Liu Chenying Xu Zehui Lin Kaishun Xiahou q.h.Wu the School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China

In this paper we construct an energy function for multi-machine power systems with doubly-fed induction generator-based wind turbine(DFIGWT)according to a synchronous-generator-mimicking(SGM)model of the *** SGM model is proposed to approximate the dynamics of a *** to the modelling of a synchronous generator(SG),the internal dynamics of a DFIGWT are also described with differential equations of newly constructed virtual rotor angle and internal electromotive force(EMF)in the SGM ***,the power flow of a DFIGWT is expressed by nonlinear functions of its virtual rotor angle and internal *** SGM model bridges the gap between the irregular and complex modelling of DFIGWTs and the well-developed energy function construction techniques for SG *** on the SGM model,a numerical energy function is constructed for power systems with DFIGWT *** theoretical analysis and numerical studies were undertaken to validate that the proposed energy function satisfies the necessary conditions for an energy function of a power system.

关键词： DFIGWT energy function multi-machine power systems synchronous-generator-mimicking model

Estimating Critical Clearing Time of Grid Faults Using DA of State-reduction Model of Power Systems

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 807-820页

作者： Yang Liu Zhongyang Chen huanjin Yao Lin Yi q.h.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China China Southern Power Grid research Institute Guangzhou 510663China

This paper proposes a critical clearing time (CCT) estimation method by the domain of attraction (DA) of a state-reduction model of power systems using sum of squares (SOS) programming. By exploiting the property of the Jacobian matrix and the structure of the boundary of the DA, it is found the DA of the state-reduction model and that of the full model of a power system are topological isomorphism. There are one-to-one correspondence relationships between the number of equilibrium points, the type of equilibrium points, and solutions of the two system models. Based on these findings, an expanding interior algorithm is proposed with SOS programming to estimate the DA of the state-reduction model. State trajectories of the full model can be transformed to those of the state-reduction model by orthogonal or equiradius projection. In this way, CCT of a grid fault is estimated with the DA of the state-reduction model. The calculational burden of SOS programming in the DA estimation using the state-reduction model is rather small compared with using the full model. Simulation results show the proposed expanding interior algorithm is able to provide a tight estimation of DA of power systems with higher accuracy and lower time costs.

关键词： Critical clearing time domain of attraction expanding interior algorithm state-reduction model SOS programming