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Effects of Nitridation on Properties of SiC Fiber and Interface of Ti Matrix Composite

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Journal of Materials Science & Technology 2002年第6期18卷 563-565页

作者： NanlinSHI Z.x.guo 等 InstituteofMetalResearch ChineseAcademyofSciencesShenyang110016China DepartmentofMaterials QueenMaryUniversityofLondonMileEndRoadLondonE14NSUK

Prenitridation of the TiBx coating surface of the Sigma SM1240 SiC fiber can form more stable compounds at the surface and obstruct the release of boron atoms into the Ti-based alloy matrix. The effect of nitridation on the tensile strength of the fiber was investigated in this work. Nitridation could degrade the tensile strength of the SiC fiber if the treating temperature and time are not optimized. The chemical reaction between the W core and SiC and the modification of fiber microstructure during the nitridation are responsible for the degradation in strength. The strength can be maintained by further optimization of the treating temperature and time. Therefore, stabilizing the surface of TiBx coating and hence the interface of the SiCf/Ti composite by the nitridation of the SiC fiber is a feasible technique for practical applications.

关键词： SiC fiber Surface coating Nitridation Tensile strength Interface

New methods to find solutions and analyze stability of equilibrium of nonholonomic mechanical systems

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Acta Mechanica Sinica 2018年第6期34卷 1136-1144页

作者： J.Chen Y.x.guo F.x.Mei School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China School of Physics Liaoning UniversityShenyang 110000China

A large proportion of constrained mechanical systems result in nonlinear ordinary differential equations,for which it is quite difficult to find analytical *** initial motions method proposed by Whittaker is effective to deal with such problems for various constrained mechanical systems,including the nonholonomic systems discussed in the first part of this paper,where in addition to differential equations of motion,nonholonomic constraints *** final equations of motion for these systems are obtained in the form of corresponding power ***,an alternative,direct method to determine the initial values of higher-order derivatives(q)0,(q)0,…is proposed,being different from that of *** second part of this work analyzes the stability of equilibrium of less complex,nonholonomic mechanical systems represented by gradient *** discuss the stability of equilibrium of such systems based on the properties of the gradient *** advantage of this novel method is its avoidance of the difficulty of directly establishing Lyapunov functions aimed at such unsteady nonlinear ***,these theoretical considerations are illustrated through four examples.

关键词： Nonholonomic system Initial motions Gradient system Lyapunov function Stability

One kind motion of controllable constrained Birkhoffian system:the absence of constraints

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Acta Mechanica Sinica 2020年第3期36卷 735-741页

作者： J.Chen F.x.Mei S.x.Liu Y.x.guo School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China School of Physics Liaoning UniversityShenyang 110000China

This paper is devoted to discuss the motion of controllable constrained Birkhoffian system along with its absence of *** first step is to establish the autonomous and non-autonomous differential equations of motion of the system,based on Pfaff-Birkhoff ***,the existence of constraint multipliers are exhaustively ***,the definition of one kind motion of the system,called free motion,is given,which is described and analyzed by the absence of constraints that are determined by constraint *** 2 illustrates that one system can realize its free motion by selecting proper control *** particular,theorem 2 provides that one system can naturally realize free motion when we consider the integral of the unconstrained Birkhoffian system as the constraints of constrained Birkhoffian ***,the results obtained are illustrated by several examples.

关键词： Constrained Birkhoffian system Kinematic control Absence of constraint Free motion

THE ADAPTIVE FINITE ELEMENT REMESHING IN LARGE DEFORMATION OF METAL FORMING

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Acta Metallurgica Sinica(English Letters) 2004年第3期17卷 323-326页

作者： x.x.guo J.S.Liu Advanced Manufacturing Technology and Engineering Department Shenzhen Polytechnic Shenzhen 518055ChinaSchool of Material Science and Engineering Taiyuan Heavy Machinery Institute Taiyuan 030024 China

The adaptive remeshing technique for quadrilateral elements consists of modules thetrigger of remeshing, the new mesh generation, adaptive refinement and interpolationof field variables. The new adaptive mesh genemtion is the key problem. First, acoarse mesh is created by using 'loop algorithm'. Subsequent local mesh adaptiverefinement is performed based on effective strain. Finally, a typical example of upset-ting is given to test efficient of techniques, from which it is verified that the remeshingalgorithm developed here exhibits good performance and has high accuracy.

关键词： adaptive remeshing quadrilateral elements metal forming

Novel Photoinduced Electron Transfer Reaction of N-methylphenothiazine in Carbon Tetrachloride

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Chinese Chemical Letters 1998年第3期9卷 237-240页

作者： guo, x Yang, L Wu, LM Liu, YC Liu, ZL Lanzhou Univ Natl Lab Appl Organ Chem Lanzhou 730000 Gansu Peoples R China

U.V. irradiation of N-methylphenothiazine 1 in carbon tetrachloride produced 3-(phenothiazin-N-yl-carbonyl)-N-methylphenothiazine 2 together with the radical cation salt 1(+) CCl4- and methyl chloride, presumably via ... 详细信息

关键词： methylphenothiazine photoinduced reaction carbon tetrachloride

STUDY ON PROPERTIES OF PULSE ELECTRODEPOSITED RE-Ni-W-P-SiC COMPOSITE COATINGS

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Acta Metallurgica Sinica(English Letters) 2007年第2期20卷 111-116页

作者： Z.C. guo x.Y. Zhu R.D. xu Faculty of Materials and Metallurgical Engineering Kunming University of Science and Technology Kunming 650093 China

The effects of pulse frequency f and duty cycle r on the deposition rate, composition, morphology, and hardness of pulse electrodeposited RE （rare earth）-Ni-W-P-SiC composite coatings have been studied. The results indicate that pulse current can improve the deposition rate of RE-Ni-W-P-SiC composite coatings; W, P, and SiC contents in the coating decrease with the increase of pulse frequency and reach the lowest value at f = 33Hz, whereas the RE content in the composite coatings increases with the increase of pulse frequency. SiC content decreases with the increase of duty cycle, W content reaches the lowest value, and P content reaches the highest value at r = 0.4; pulse current and RE can lead to smaller size of the crystalline grains; however, the effects of different pulse frequency and duty cycle on the morphologies of RE-Ni-W-P-SiC composite coatings are not obvious. The hardness of RE-Ni-W-P-SiC composite coatings is the highest when the duty cycle is at 0.6 and 0.8 and pulse frequency is at 50Hz. At the same pulse frequency, the hardness of RE-Ni-W-P-SiC composite coatings at r= 0.8 is higher than that at r= 0.6.

关键词： frequency duty cycle electrodeposition RE-Ni-W-P-SiC composite coating

Giant Magneto-impedance Effect in Composite Wires with Different Core Layer

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Nano-Micro Letters 2013年第2期5卷 140-144页

作者： R.L.Wang x.Li x.H.Kong Y.x.guo J.Z.Ruan Z.J.Zhao Department of Physics Engineering Research Center for Nanophotonics & Advanced Instrument Ministry of Education East China Normal University Experimental Teaching Center of Physics Shanghai Ocean University

Composite structure materials were potential sensing elements for magnetic sensors due to Giant magnetoimpedance(GMI) effect. Two kinds of composite wires with different magnetic/non-magnetic structures were fabricated by using electroless deposition methods and the magnetoimpedance properties were investigated. The maximum GMI ratio of 114% was acquired at 60 MHz in the composite wires with a ferromagnetic core, whereas, 116% of maximum GMI ratio was found in the composite wires with a conductive core at low frequency of 600 k Hz. These results exhibit that the GMI ratio reaches the maximum when magnetoresistance ratio ?R/R and magnetoinductance ratio ?x/x make the comparative contributions to the total magnetoimpedance(MI). The obvious GMI effect obtained in the composite wires with conductive core frequency may provide a candidate for applications in magnetic sensors, especially at low frequencies.

关键词： Composite wires Electroless deposition Giant Magnetoimpedance effect Resistivity

Experimental methods for determination of mechanical behaviors of materials at high temperatures via the split Hopkinson bars

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Acta Mechanica Sinica 2020年第6期36卷 1275-1293,I0003页

作者： Q.B.Dou K.R.Wu T.Suo C.Zhang x.guo Y.Z.guo W.G.guo Y.L.Li School of Aeronautics Northwestern Polytechnical UniversityXi’an710072China Joint International Research Laboratory of Impact Dynamics and its Engineering Application Xi’an710072China Shaanxi Key Laboratory of Impact Dynamics and its Engineering Application Xi’an710072China State Key Laboratory for Strength and Vibration of Mechanical Structures School of AerospaceXi’an Jiaotong UniversityXi’an710049China

Full understanding of the thermomechanical behaviors of materials at high strain rates and high temperatures are of great importance from not only scientific meaning but also practical value in engineering structure design and safety *** efforts have been made for abilities of operation the split Hopkinson bars,the most popular technique for experimental determination of mechanical behaviors of materials over the strain rates from 10^2 to 10^4 s^−1 over the past 70 years,at high temperatures since 1960s.A review of experiment work is presented in this paper to give an overview of the development of experimental techniques at high temperatures based on Hopkinson bar *** principles of the split Hopkinson bar requires the loading bars avoiding temperature gradient or keeping relatively low temperature when performing high temperature *** such as performing temperature gradient corrections,rapid heating or using special designed automatically assembled systems were proposed by researchers to enable the operation of the split Hopkinson bars at temperature as high as ***,to the application of high speed photographic technique for capturing the dynamic deformation process of the specimen in high temperature Hopkinson bar testing,some key issues of eliminating the strong thermal radiation induced lights oversaturation and de-blurring of images due to insufficient exposure at high temperature and high strain rate condition,as well as fabrication of high contrast speckle pattern for high temperature digital image correlation measurement were also *** technique can now enable the split Hopkinson bar testing to be performed at high temperature up to 1873 K under the loading conditions of compression or tension with the in situ observation and full field measurement of deformation as *** paper concludes with summaries of the most important achievements and highlighting of the prospects,trends and remaining challenge

关键词： Mechanical behaviors Split Hopkinson bar High strain rate High temperature

Enhanced pitting corrosion resistance of a Zr-based metallic glass by ultraviolet light irradiation

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Journal of Iron and Steel Research International 2023年第8期30卷 1642-1649页

作者： Z.Chen D.P.Wang S.Wang Y.x.Geng Y.x.guo Y.C.Wu Z.G.Liu Y.Y.Zhang Y.x.Wang School of Materials Science and Engineering Jiangsu University of Science and Technology.Zhenjiang 212003JiangsuChina School of Mechanical Engineering Jiangsu University of Science and TechnologyZhenjiang 212003JiangsuChina

The influence of ultraviolet light irradiation on the pitting corrosion performance of a Zr_(2)Ni metallic glass was examined using electrochemical methods and immersion test in 0.05 mol/L NaCl *** the results of potentiostatic polarization,the pitting potential of the ultraviolet light-irradiated sample shifted positively with a value of~300 mV,revealing the enhanced pitting corrosion resistance of the *** corrosion morphology after the immersion test also demonstrated lower degree of corrosion damage and improved pitting resistance of the sample with ultraviolet light irradiation.x-ray photoelectron spectroscopy analysis revealed more zirconium enrichment in the passive film and no chloride ions adsorption for the samples with ultraviolet irradiation,accounting for the suppression of the pit generation and *** findings indicate that ultraviolet light irradiation improves the pitting corrosion resistance of the Zr-based metallic glasses,which are promising structural materials to be used in corrosion environments with high ultraviolet irradiation.

关键词： Metallic glass Pitting-Corrosion Ultraviolet light irradiation Passive film