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Modeling Recrystallization of Austenite for C-Mn Steels during Hot Deformation by Cellular Automaton

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Journal of Materials Science & Technology 2002年第2期18卷 163-166页

作者： LinZHANG XianghuaLIU 等 CollegeofScience NortheasternUniversityShengyang110006China TheStateKeyLaboratoryofRollingandAutomation NortheasternUniversityShenyang110016China

By using a cellular automaton method, the microstructure evolution of recrystallization in austenite during hot deformation was simulated for C-Mn steels. A model takes into account the influence of deformation temperature, strain and strain rate on the dynamic recrystallization fraction, and the effect of the keeping time on the static recrystallization fraction based on a hot deformation test on a Gleeble-1500 simulator. In addition, the size changing of γ grains during continuous hot deformation was simulated by use of the model.

关键词： Cellular automaton Recrystallization Grain size Deformation Austenite

Thermal stability of discontinuous precipitation in the Al-Zn-(Cu) system

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Rare Metals 2005年第1期24卷 60-64,104页

作者： LIHongxiao WANGDapeng RENYuping CHENLu ZHAOGang HAOShiming CollegeofMaterialsandMetallurgy NortheasternUniversityShenyang110004China

The coarsening mechanism and kinetics of discontinuous precipitation (DP) in Al-Zn-(Cu) alloys were studied by means of optical microscopy, scanning electron microscopy, and X-ray diffraction analysis. The results show that the coarsening mechanism is different as the aging temperature varies. At a low temperature (150℃), the coarsening occurs through the dissolution and spheroidization of fine laminar structure of DP; at high temperatures (above 200℃), the discontinuous coarsening (DC) of DP microstructure mainly occurs, forming coarsening cells with a larger laminar distance. The growth velocity of coarsening cells rapidly reaches the maximum, and then decreases with the increase of time. The coarsening velocity of DP microstructure decreases due to the addition of Cu element.

关键词： Al-Zn-(Cu) alloy discontinuous coarsening coarsening mechanism coarsening kinetics

Quadratic Stability of Switched Nonlinear Systems in Block-triangular Form

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自动化学报 2005年第4期31卷 631-633页

作者： ZHAOSheng-Zhi： ZHAOJun KeyLaboratoryofProcessIndustryAutomation MinistryofEducationNortheasternUniversityShenyang110004／／DepartmentofMathematicsLiaoningUniversityShenyang110036 KeyLaboratoryofProcessIndustryAutomation MinistryofEducationNortheasternUniversityShenyang110004

The problem of globally quadratic stability of switched nonlinear systems in block-triangular form under arbitrary switching is addressed. Under the assumption that all block-subsystems are zero input-to-state stable, a su?cient condition for the problem to be solvable ispresented. A common Lyapunov function is constructed iteratively by using the Lyapunov functionsof block-subsystems.

关键词：二次方程式非线性转换系统稳定性 Lyapunov函数

Analysis of Chaotic Synchronization Stability and Its Application to a Two-dimensional Advertising Competing Model

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自动化学报 2005年第2期31卷 209-215页

作者：齐洁汪定伟 InstituteofSysternsEngineering SchoolofInformationScienceandEngineeringNortheasternUniversityShenyang110004

A class of map in which chaotic synchronization can occur is defined. The transverse Lyapunov exponents are used to determine the stability of synchronized trajectories. Some complex phenomena closely related to chaotic synchronization, namely riddled basin, riddling bifurcation and blowout bifurcation are theoretically analyzed. Riddling bifurcation and blowout bifurcation may change the synchronization stability of the system. And two types of riddled basins, i.e., global riddled basin and local riddled basin, may come into being after riddling bifurcation. An advertising competing model based on Vidale-Wolfe model is proposed and analyzed by the above theories at the end of the paper.

关键词：混沌同步稳定性分析二维广告竞争模型筛选分歧鼓风分歧

THE OPTIMAL ORDER ERROR ESTIMATES FOR FINITEELEMENT APPROXIMATIONS TO HYPERBOLIC PROBLEMS

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Journal of Computational Mathematics 2005年第3期23卷 275-284页

作者： TieZhang DepartmentofMathematics NortheasternUniversityShenyang110004China

In this paper, the linear finite element approximation to the positive and symmetric,linear hyperbolic systems is analyzed and an O(h^2) order error estimate is established under the conditions of strongly regular triangulation and the H^3-regularity for the exact solutions. The convergence analysis is based on some superclose estimates derived in this paper. Our method and result here are also applicable to general hyperbolic ***, we discuss the linearized shallow water system of equations.

关键词： Hyperbolic problems Finite element approximations Optimal error estimates

Multivariable Intelligent Decoupling Control System and its Application

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自动化学报 2005年第1期31卷 123-131页

作者： Tian-YouCHAI HengYUE NationalEngineeringandTechnologyResearchCenterforMetallurgicIndustryAutomation NortheasternUniversityShenyang110004P.R.China

Many industrial processes have compositive complexities including multivariable, strong coupling, nonlinearity, time-variant and operating condition variations. Combining multivariable adaptive decoupling control with neural networks, this paper presents a multivariable neural networkbased decoupling control algorithm. This control algorithm is integrated with distributed control technique and intelligent control technique, and a three-leveled intelligent decoupling control system consisting of basic control level, coordinating control level, and management and decision level is developed. The configuration and function of the control system are discussed in detail. This system has been successfully applied in ball mill pulverizing systems of 200MW power units, and remarkable benefits have been obtained.

关键词：神经网络去耦合控制智能去耦合控制系统煤粉碎系统多变量系统应用

Modeling Kinetics of Deformation Induced Ferrite Transformation in Fe-C-Mn Alloy

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Journal of Iron and Steel Research(International) 2005年第2期12卷 49-51页

作者： XUYun-bo YUYong-mei LIUXianghua WANGGuo-dong northeasternuniversity Shenyang110004China

The influence of hot deformation on the incubation period of ferrite transformation was calculated to determine the onset of deformation induced transformation. Temperature A r3d depends on deformation condition and alloying composition, and decreases with increasing carbon content. When deformation induced ferrite transformation occurs, the flow curves of dislocation density will show strong softening characteristic. Through temperature heavy deformation, ferrite transformation is enhanced and more volume fraction is obtained. The simulated results are in good agreement with the experiment ones.

关键词： dislocation density Fe-C-Mn alloy ultra-fine steel low temperature heavy deformation

Recrystallization of the cold-deformed discontinuous precipitation microstructure in Al-Zn (-Cu) alloys

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Rare Metals 2004年第4期23卷 358-363页

作者： DINGHua RENYuping HAOShiming WANGDapeng ZHAOGang CollegeofMaterialsandMetallurgy NortheasternUniversityShenyang110004China

Recrystallization of cold-rolled discontinuous, precipitation microstructurewhich has fine laminar structure in an Al-40 percent Zn (atom fraction) binary alloy is investigatedby optical microscopy, SEM and TEM. It is found that there are two kinds of recrystallizationmechanisms: continuous coarsening (CC) and discontinuous coarsening (DC). The latter can be dividedinto coarsening mainly driven by stored deformation energy at colony boundaries and slip bands andthe one mainly driven by boundary energy in the area with little deformation. It is shown that theaddition of Cu can retard the nucleation of coarsening cells and their growth. X-Ray diffractionanalysis indicated the metastable phase CuZn_4 transformed into equilibrium phase A;_4Cu_3Zn duringthe heating process.

关键词： Al-Zn(-Cu) alloy recrystallization discontinuous precipitation discontinuous coarsening cold deformation microstructure

Solidification of Al alloys under electromagnetic field

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中国有色金属学会会刊：英文版 2003年第3期13卷 473-483页

作者：崔建忠：崔建忠不详 KeyLaboratoryofMinistryofEducationforElectromagneticProcessingofMaterials NortheasternUniversity Shenyang110004 China

New theories and technology in the electromagnetic field were put forward about DC casting of Al alloys, including the fundamental research works, i.e, effects of the electromagnetic field on solidus and liquidus, macrosegregation of the main alloying elements, microstructures, content of alloying elements in grains and grain size after solidification under electromagnetic field, and also including a new process DC casting under low frequency electromagnetic field(LFEMC), which can refine microstructure, eliminate macrosegregation, increase the content of alloying elements within grains, decrease the residual stress, avoid cracks and improve surface quality, and another new process DC casting under low frequency electromagnetic vibration(LFEVC), which is a high effective method for grain refining.

关键词：铝合金电磁场电磁铸造凝固显微结构偏析裂纹表面质量 LFEMC LFEVC