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Robust Design for Generalized Minimum Variance Controllers

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International Journal of Minerals,metallurgy and Materials 1999年第2期13卷 144-148页

作者： Heping liu Xin Shim (Information Engineering school, university of science and technology beijing, beijing 100083, china) (Shenyang Aircraft Corporation, Shenyang 110034, china) Information Engineering school University of Science and Technology Beijing Beijing 100083 China Shenyang Aircraft Corporation Shenyang 110034 China

In order to improve the robustness and noise resistance of generalized minimum valance cothrol systems, several generalizedminimum variance control schemes are synthetically analyzed. The output variance caused by stochastic noise is decomposed to two parts. One part accords with the output variance of minboum vedance control and the other is the additional term of output variance causedby the control weighting factors. At the same time, the sensitivity function of modeling error is also deduced. A new robast design method that can minimize the sensitivity and the additional part of output variance is Presented by regulating variable parameters of contollers. The simulation results of self-tuning control show the effect of this method.

关键词： generalized minimum variance control variance robustness sensitivity

Three-Dimensional and Cross-sectional Characteristics of Normal Grain Growth Based on Monte Carlo Simulation

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International Journal of Minerals,metallurgy and Materials 1998年第3期12卷 129-133,139页

作者： Xiaoyan Song Guoquan liu(Material science and Engineering school, university of science and technology beijing, beijing 100083, china)(Department of Materials science and Engineering, Hebei university of technology, Tianjin 300130, china) Material science and Engineering school University of Science and Technology Beijing Beijing 100083 China Departments of Materials science and Engineering Hebei University of Technology Tianjin 300130 China

An appropriate Monte Carlo method was developed to simulate the three-dimensional normal grain growth more completely. Comparative investigation on the three-dimensional and the cross-sectional characteristics of normal grain growth was done. It was found that the time exponent of grain growth determined from cross-section exhibits the same rule of increasing slowly with time and approaching the theoretical value n = 0.5 of steadygrain growth as the three-dimensional (3-D) system. From change of the number of grains per unit area with timemeasured in cross-section, the state of 3-D normal grain growth may be predicted. The gtain size distribution incross-section is different from that in 3-D system and can not express the evolution characteristic of the 3-D distribution. Furthermore, there exists statistical connection between the topological parameters in cross-section and thosein three-dimensions.

关键词： Monte Carlo simulation normal grain growth three-dimension cross-section characteristics

Molar heat capacities of La2Mo2O9 and La1.9Sr0.1Mo2O9-δ

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International Journal of Minerals,metallurgy and Materials 2007年第5期14卷 395-398页

作者： Baijun Yan, Jianhua liu, Yunduo Dai, Qifeng Shu, and Zhihua Ren Metallurgical and Ecological Engineering school, university of science and technology beijing, beijing 100083, china [a]Metallurgical Ecological Engineering school university of science technology beijing beijing 100083 china

The molar heat capacities of La2Mo2O9 and La1.9Sr0.1Mo2O9-δ were obtained using the differential scanning calorimetry (DSC) technique in a temperature range from 298 to 1473 K. The DSC curve of La2Mo2O9 showed an endothermal peak around 834 K corresponding to a first-order monoclinic-cubic phase transition, and the enthalpy change accompanying this phase transition is 5.99 kJ/mol. No evident endothermal peak existed in the DSC curve of La1.9Sr0.1Mo2O9-δ, but a broad thermal anomaly existed in its heat capacity curve at around 832 K. In addition, the heat capacity values of La2Mo2O9 and La1.9Sr0.1Mo2O9-δ began to decrease at 1196 and 1330 K, respectively. The non-transitional heat capacity values of La2Mo2O9 and La1.9Sr0.1Mo2O9-δ were formulated using multiple regression analysis in two temperature ranges.

关键词： heat capacity phase transition La2Mo2O9 La1.9Sr0.1Mo2O9-δ DSC

Effect of Austenitizing Treatment on Structure and Hardness of Bainite DuctileCast Iron

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International Journal of Minerals,metallurgy and Materials 1999年第4期13卷 250-252页

作者： Qijie Zhai Guojun liu Yulong Zhu Dilin Chen(Foundry Institute, university’ of science and technology’ beijing, beijing 100083, china) Foundy Institute University of Science and Technology Beijing Beijing 100083 China

By continuous quenching process, the effect of austenitizing temperature and time on the structure and hardness of bainiteductile cast iron was studied. It was found that (l) low austenitizing temperature would result in scrap ferrite existing in matrix, whichreduces the macro-hardness of bainite ductile cast iron; (2) high austenitizing temperature would make carbide decomposed, which alsoinduces the macro-hardness of bainite cast iron, and (3) austenitizing time has little effect on the structure of bainite ductile cast iron, butas it increases, the macro-hardness ofbainite ductile cast iron and micro-hardness of bainite increases. To the ductile cast iron, as a result,the suitable austenitizing temperature and time are recommended as 880 and 120 min respectively.

关键词： austenitizing treatment bainite ductile cast iron structure hardness

Fretting corrosion of surgical 316L stainless steel in saline solutions

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International Journal of Minerals,metallurgy and Materials 1997年第3期11卷 18-21页

作者： BAI Zhijun WU Yinshun ZHANG Tiancheng liu Qiang (Material science and Engineering school, university of science and technology beijing, beijing 100083, china)

A new simulation system for the laboratory investigation of fretting wear is developed. It consist of a mechanism device, a electrochemical cell and a datum acqulsition and process software. Fretting of surgical 316L stainlesssteel in saline is studied. The results show that electrochemical corrosion is enhanced by fretting and anodic currentdensity under fretting is 100 times than static condition. Fretting corrosion is a mechanic -elec trochemical al Process.

关键词： fretting system 316L sninless steel saline solution

Pb(Mg_(1/3)Nb_(2/3))O_3-PbTiO_3-BaTiO_3 Complex Perovskite Ferroelectric Ceramics with High Dielectric Constant and Low Firing Temperature

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International Journal of Minerals,metallurgy and Materials 2000年第2期14卷 115-117页

作者： Zhen Ji Zhhong Xiao Xuqing liu Zhaozeng Ma Zongsen Yu(Material science and Engineering school, university of science and technology Bejing, beijing 100083, china) Material science and Engineering school University of Science and Technology Beijing Beijing 100083 China

The effects of different firing temperatures on the stability of perovskite phase, grain size, and dielectric properties were investigated by XRD, TEM, SEM and dielectric measurements. The dielectric ceramics of Pb(Mg1/3Nb2/3)O3-PbTiO3-BaTiO3 system were obtained by chemical coprecipitation in water. The ceramics have higher dielectric constant (7003-9714), lower firing temperature(950-1150℃), quite uniform microstructure with grain size less than 2.5 mp, and lower temperature coefficients of capacitance. As a re-sult, it was confirmed that the simple and low cost chemical route used namely coprecipitation in water is a desired method for preparinghigh property dielectfic materials applicable to multilayer capacitors.

关键词： PMN-PT-BT coprecipitation dielectric property

Fabrication of W/Cu and Mo/Cu FGM as Plasma-facing Materials

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International Journal of Minerals,metallurgy and Materials 2000年第2期14卷 122-125页

作者： Changchun Ge Zhangjian Zhou Jiangtao Li Xiang liu Zhengyu Xu(Laboratory of Special Ceramics and Powder metallurgy, university of science and technology beijing, beijing 100083, china)(Southwest Institute of Nuclear Physics, Chengdu 610041, china) Laboratory of Special Ceramics and Powder metallurgy University of Science and Technology Beijing Beijing 100083 China Southwest Institute of Nuclear Physics Chengdu 610041 China

W/Cu Functionally Graded Materials (FGM) was designed not only for reducing the thermal stress caused by the mismatch of thermal expansion coefficients, but also for combining the features of W, Mo - high plasma-erosion resistance and the advantages of Cu - high heat conductivity and ductility. Four different fabrication processes for W/Cu or Mo/Cu, including hot-pressing, Cu infiltration of sintered porosity-graded W skeleton, spark plasma sintering and plasma spraying, were investigated and compared. It was foundthat the hot-pressing process is difficult to keep the designed composition gradient, while the other three processes are successful in making W/Cu or Mo/Cu FGM. Meanwhile, microstructures and composition gradients are analyzed with SEM and EDAX.

关键词： FGM plasma-facing material W/Cu and Mo/Cu alloy

High Purity Mullite-Corundum Thermal Insulating Firebricks

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International Journal of Minerals,metallurgy and Materials 1999年第4期13卷 237-241页

作者： Wen Ni Fengmei liu(Resource Engineering school, university’ of Sctence and technology beijing beijing. 100083, china) Resource Engineering school University of Science and Technology Beijing Beijing 100083 China

Laboratory and industrial experiments were carried out to study the possibility of producing high purity purity mullite-corundumthermal insulating firebricks. The results show that by using industrial alumina. natuual powder power, coal gangues and a small amountof additives. high purity mullite-corundum thermal insulating firebrieks can be produced The service. temperature of these brick can beup to 1780 with low. thermal conductivity' and good thermal shock resistance

关键词： mullite corundum thermal insulating firebricks

Oxide and Sulfide Dispersive Precipitation in Ultra-low Carbon Steels

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Journal of university of science and technology beijing 2001年第4期8卷 314-315页

作者： Delu liu, Xangdong Huo, Yuanli Wang, Jie Fu, Yongin Kang, Nanjing Chen 1 ) Materials science and Engineering school, university of science and technology beijing, Bejing 100083, china 2) metallurgy school, university of science and technology beijing, Bei Univ Sci & Technol beijing Sch Mat Sci & Engn Beijing 100083 Peoples R China Univ Sci & Technol beijing Met Sch Beijing 100083 Peoples R China