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Computer simulation of short-circuiting transfer welding under waveform control on inverter power source

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China Welding 2007年第1期16卷 9-13页

作者：杨立军冯胜强董天顺School of Materials Science and technology hebei university of technology Tianjin 李桓 School of Materials Science and technology Tianjin University Tianjin 300072

A simulation model is introduced about the non-linearity process of short-circuiting transfer in CO2 arc welding for displaying the interaction between the inverter power source and welding arc under waveform control. In the simulation model, the feedback signals of current and voltage are taken respectively at the different phase in a short circuit periodic time and applied to the PWM （pulse width modulation） module in a model of inverter power source to control the output of power source. The simulation operation about the dynamic process of CO2 short-circuiting transfer welding is implemented on the founded simulation model with a peak arc current of 400 A and a peak voltage of 35 V, producing the dynamic arc waveforms which can embody the effect of inverter harmonic wave. The simulating waveforms are close to that of welding experiments.

关键词： inverter simulation short-circuiting transfer harmonic wave waveform control

A new contact material—Ag/SnO_2-La_2O_3-Bi_2O_3

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Rare Metals 2002年第4期21卷 289-293页

作者： LU Jianguo, WANG Jingqin, ZHAO Jingying, WEN Ming, WANG Baozhu, and WANG XiaohongInstitute of Electrical Apparatus, hebei university of technology, Tianjin, 300130, China Institute of Electrical Apparatus Hebei University of Technology 天津 300130 Institute of Electrical Apparatus Hebei University of Technology Tiaojin 300130

A super-fine compound powder, Ag/SnO_2+La_2O_3+ Bi_2O_3, has been obtainedusing the chemical coprecipitation method. And a new contact material, Ag/SnO_2+La_2O_3+Bi_2O_3, wasproduced by the powder metallurgy method. Its properties are as follows: the density is 9.75-9.93g/cm^3, the resistivity is 2.31-2.55 μΩ ·cm, the hardness is 880-985 MPa. Its mi-crostructureshows that the fine oxides have a uniform distribution in the silver matrix. The results ofmake-break capacity and temperature rise testing show that the new material has better ability ofanti-arc erosion and lower temperature rise than that of commonly used Ag/CdO.

关键词： contact material silver rare earth oxide powder metallurgy microstructure additive

ON THE CONDITIONAL VERSION OFKOLMOGOROV'S THREE-SERIES THEOREM

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Acta Mathematica Scientia 1999年第3期19卷 300-306页

作者：刘国欣 Department of Mathematics Hebei University of Technology Tianjin 300130 China

This paper studies the conditional version of Kolmogorov’s three-series theorem, and gets a new extention form of the conditional version. The results here present us an answer to the question when (or where) the conditional version also provide necessary conditions for convergence in dependent cases. Furthermore, some new sufficient conditions are obtained.

关键词： Three-series theorem dependent r.v. ’s predictable local absolute continuity martingale

Effect of Titanium,Antimony,Cerium and Carbon Nanotubes on the Morphology and Microhardness of Mg-based Icosahedral Quasicrystal Phase

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Journal of Materials Science & technology 2010年第1期26卷 27-32页

作者： Zhifeng Wang, Weimin Zhao, Haipeng Li, Jian Ding, Yongyan Li and Chunyong Liang School of Materials Science and Engineering, hebei university of technology, Tianjin 300130, China School of Materials Science and Engineering Hebei University of Technology Tianjin 300130 China

For the first time, petal-like and spherical Mg-based icosahedral quasicrystal phase （I-phase） were obtained by introducing Ti, Sb, Ce and C nanotubes into Mg-Zn-Y alloy under normal casting conditions. The formation mechanism and stability criterion of spherical I-phase were discussed. The morphology and microhardness of I-phase and their determinants were studied in this paper. The results show that the different value of microhardness of I-phase could be attributed to the different kinds of the fourth component and its content, and its different innate characters. The final morphology of icosahedral quasicrystalline （IQC） is decided by the size of critical stable radius Rr, the content of the fourth component and degree of undercooling.

关键词： Quasicrystal Magnesium alloy Morphology Microhardness

Effect of As Interstitial Diffusionon on the Properties of Undoped Semi-insulating LECGaAs

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Rare Metals 2001年第3期20卷 187-191页

作者： Ruixia Yang, Fuqiang Zhang, Nuofu Chen 1) hebei university of technology, Tianjin 300130, China 2) Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China 河北工业大学天津 300130 中科院半导体所北京 100083

Annealing was carried out at 950 and 1120 degreesC under various As pressure for undoped (ND) semi-insulating (SI) LECGaAs. The effects of annealing on native defects and electrical properties were investigated. Experimental results indicate that, after an annealing at 950 degreesC for 14 h under low As pressure, the Hall mobility decreases and the resistivity increases dramatically for the samples. These changes in electrical properties are due to the generation of intrinsic acceptor defects, and the generation of the intrinsic acceptor defects originates from the outdiffusion of As interstitial at high temperature. The generation of the intrinsic defects and these changes in electrical properties can be suppressed by increasing the applied As pressure during annealing. The concentration of the main donor defect E12 (AsGaVGa) can be decreased by about one order of magnitude by an evacuated annealing at 1120 degreesC for 2-8 h followed by a fast cooling. The decrease in E12 concentration can also be suppressed by increasing the As pressure during annealing.

关键词： semi-insulating GaAs intrinsic acceptor defects As interstitial indiffusion As pressure annealing

Ferromagnetic barrier-induced negative differential conductance on the surface of a topological insulator

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Chinese Physics B 2014年第10期23卷 464-468页

作者：安兴涛 School of Sciences Hebei University of Science and Technology Department of Physics and Center of Theoretical and Computational Physics University of Hong Kong

The effect of the negative differential conductance of a ferromagnetic barrier on the surface of a topological insulat（ is theoretically investigated. Due to the changes of the shape and position of the Fermi surfaces in the ferromagnetic barrie the transport processes can be divided into three kinds： the total, partial, and blockade transmission mechanisms. The bias voltage can give rise to the transition of the transport processes from partial to blockade transmission mechanisms, which results in a considerable effect of negative differential conductance. With appropriate structural parameters, the currenl voltage characteristics show that the minimum value of the current can reach to zero in a wide range of the bias voltag and then a large peak-to-valley current ratio can be obtained.

关键词： topological insulator negative differential conductance ferromagnetic barrier

Photocatalytic Oxidation Kinetics of Thiophene with Nano-F^-/Fe^(3+)/TiO_2

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China Petroleum Processing & Petrochemical technology 2009年第4期11卷 48-52页

作者： Li Fatang~1 Sun Zhimin~1 Liu Ying~1 Zhao Dishun~2 Liu Ruihong~1 (1.College of Science,hebei university of Science and technology,Shijiazhuang 050018 2.College of Chemical and Pharmaceutical Engineering,hebei university of Science and technology) College of Science Hebei University of Science and Technology Shijiazhuang 050018 China College of Chemical and Pharmaceutical Engineering Hebei University of Science and Technology China

Photocatalytic oxidation kinetics of thiophene in n-octane/water extraction system was studied with fluorine and ferric ion codoped nano-TiO_2(nano-F^-/Fe^(3+)/TiO_2) powders used as the *** of initial concentration of thiophene and additional dosage of F^-/Fe^(3+)/TiO_2 on the reaction rate constant and half-life were *** results showed that the appropriately added dosage of F^-/Fe^(3+)/TiO_2 was 0.1 g in the 100-mL reaction system and the photooxidative kinetics of thiophene in the presence of F^-/Fe^(3+)/TiO_2 catalyst was of first-order with a rate constant of 0.6508 h^(-1) and a half-life of 1.0651 *** desulfurization rate of thiophene was 98.1%in 5 h and the sulfur content could be reduced from 800 ppm to 15 *** reaction rate constant increased with a decreasing initial concentration of thiophene.

关键词： desulfurization thiophene nano-F^-/Fe^(3+)/TiO_2 photocatalytic oxidation kinetics

COMPLEX NONLINEAR MATHEMATICAL MODEL FOR A KIND OF VEHICLE SHOCK ABSORBORS

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Chinese Journal of Mechanical Engineering 1999年第1期12卷 33-40页

作者： Tan Runhua hebei university of technology Chen Ying Zhejiang universityLiu Baoshan Automobile Shock Absorber Factory of Tianjin Lu Yongxiang Chinese Academy of Sciences hebei Univ of technology China

A nonlinear mathematical model for the shock absorber in TJ7100 is developed. The oil compressibility and the entrapped gas in the oil are considered in the model. As a result, the hysteresis in the force velocity diagram is included. The results of computer simulation and the experiment are basically identical. The MATLAB/SIMULINK is used for the development of the simulation software. It is found that the pressure inside the cylinder is high if the inputs of velocity or displacement are big by simulation. This is certainly one of the main reasons for which the leak is appeared between the rod and the seal of the shock absorbers for a relatively short time in China.

关键词： Shock absorber Nonlinear mathematical model Simulation Experiment

A Method on the Item Investment Risk Interval Decision-making of Processing Ranking Style

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Systems Science and Systems Engineering 2002年第3期11卷 333-340页

作者： CHEN Li-wenSchool of management, hebei university of technology, Tianjin 300130, China School of management Hebei University of Technology Tianjin 300130 China

In this paper, on the bases of the defect of riskful type and indefinite type decisions, the concept of the type of item investment probability scheduling decision is given, and a linear programming model and its solution are made out. The feasibility of probability scheduling type item investment plan is studied by applying the quality of interval arithmetic.

关键词： item investment probability scheduling interval sequence relation multi-dimensional decision