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A trust region-CG algorithm for deblurring problem in atmospheric image reconstruction

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Science China Mathematics 2002年第6期45卷 731-740页

作者：王彦飞袁亚湘张洪超 stt. key lab. of Sci. and eng. Comp. Inst. Compl. Math. Sci./Eng. Comp. Acad. of Math. and System Sciences Beijing 100080 China

In this paper we solve large scale ill-posed problems, particularly the image restoration problem in atmospheric imaging sciences, by a trust region-CG algorithm. Image restoration involves the removal or minimization of degradation (blur, clutter, noise, etc.) in an image using a priori knowledge about the degradation phenomena. Our basic technique is the so-called trust region method, while the subproblem is solved by the truncated conjugate gradient method, which has been well developed for well-posed *** trust region method, due to its robustness in global convergence, seems to be a promising way to deal with ill-posed problems.

关键词： image reconstruction, ill-posed problems, truncated CG, trust region.

Effects of volume fraction condition on thermodynamic restrictions in mixture theory

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Science China Mathematics 2002年第5期45卷 640-647页

作者：牛永红苗天德 Department of Mechanics Sch. of Phys. Science and Technology Lanzhou University Lanzhou 730000 China stt. key lab. of Frozen Soil eng. Cold Arid Regions Environ. Eng. R. Chinese Academy of Sciences Lanzhou 730000 China

Volume fraction condition is a true constraint that must be taken into consideration in deducing the thermodynamic restrictions of mixture theory applying the axiom of dissipation. For a process to be admissible, the constraints imposed by the volume fraction condition include not only the equation obtained by taking its material derivative with respect to the motion of a given phase, but also those by taking its spatial gradient. The thermodynamic restrictions are deduced under the complete constraints, the results obtained are consistent for the mixtures with or without a compressible phase,and in which the free energy of each phase depends on the densities of all phases.

关键词： mixture theory, volume fraction condition, thermodynamic restrictions.

FORCED WAVE PROPAGATION IN VISCOELASTIC CABLE WITH SMALL SAG

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Acta Mechanica Solida Sinica 2001年第2期14卷 147-154页

作者： Li Yinghui Jian Kailin~1 Gao Qing Yin Xuegang~1 (Department of Applied Mechanics and eng.neering, Southwest Jiaotong University, Cheng.u 610031, China) (1 State key lab.ratory of Mechanical Transmission, Chongqing University, Chongqing 400044, China) Dept. of Appl. Mechanics and eng. Southwest Jiaotong University Chengdu 610031 China stt. key lab. of Mech. Transmission Chongqing University Chongqing 400044 China

Based on the linear viscoelastic differential constitutive law andcable structural model, the coupled longitudinal-transverse wavesthat propagate along a viscoelastic cable with small curvature isinvesti- gated. A mathematical model is presented that describes thethree-dimensional nonlinear response of a vis- coelastic cable. Anasymptotic form of this model is obtained for the linear response ofcables having small equilibrium curvature.

关键词： viscoelastic cable small equilibrium curvature cut-off frequency

Kinetics of Nonisothermal and Isothermal Crystallization of Metallocene Polyethylene

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Chinese Chemical Letters 1999年第2期10卷 175-178页

作者： Yu Ying LI Ji Jun Zeng.Jia Song HE(State key lab.ratory of eng.neering plastics, Institute of Chemistry,The Chinese Academy of Sciences. Beijing 100080) State key lab. of eng. plastics Institute of Chemistry Chinese Academy of Sciences Beijing 100080 China

The kinetics of nonisothermal and isothermal crystallization of metallocene catalyzed and conventional polyethylenes has been studied by differential scanning calorimetry. Using Avrami equation, Ozawa theory and Mo Zhishen method, the experimental data have been analyzed. It is shown that metallocene polyethylene possesses a higher rate of crystallization due to a higher stereoregularity of its molecular chains. Moreover, they have different nonisothermal crystallization mechanisms and identical isothermal crystallization mechanisms.

关键词： metallocene polyethylene nonisothermal crystallization isothermal crystallization

Numerical analysis of ground temperature in Qinghai-Tibet Plateau

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Science China(Technological Sciences) 2002年第4期45卷 433-443页

作者：王铁行胡长顺李宁侯仲杰 College of Civil eng.neering Xi'an Univ. of Arch. and Technology Xi'an 710055 China Res. Inst. of Geotechnical eng. Xi'an University of Technology Xi'an 710048 China College of Highway eng.neering Chang'an University Xi'an 710064 China stt. key lab. of Frozen Soil eng. CAEERI CAS Lanzhou 730000 China

On the basis of the existing theories such as permafrost, thermodynamics and fluid mechanics, as well as the climate features on the Qinghai-Tibet Plateau and the data collected from both lab.ratory and the on-the-spot test, this paper puts forward a set of analytical methods and a numerical module for ground thermal regime with consideration of eng.neering surface features and various natural elements such as wind speed, radiation, evaporation. This paper also probes into the defining method for physical thermal parameter of the silty clay and gravelly sand soil, which widely pervades on the Qinghai-Tibet Plateau. The numerical analysis indicates that the ground thermal regime is a comprehensive reflection of various external elements. It is suggested that the variation of external elements should be fully taken into consideration in eng.neering design. Furthermore, the analysis of the frozen soil subgrade indicates that the transverse thermal difference in subgrade, which affects the subgrade stability, is caused by transverse difference in external elements along the subgrade surface.

关键词： frozen soil, numerical modelling and analysis, the Qinghai-Tibet Plateau, temperature, ground surface, thermal parameter, subgrade.

Ethylene oligomerization by novel iron(Ⅱ) diimine complexes/MAO

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Chinese Science Bulletin 2002年第19期47卷 1616-1618页

作者： WANG Hang, YAN Weidong, JIANG Tao, LIU Binbin, XU Wenqing, MA Jianjiang & HU YouliangState key lab.ratory of eng.neering plastics, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China Graduate Student of State key lab. of eng. plastics Institute of Chemistry Chinese Academy of Sciences Beijing 100080 China Grad. Student Chinese Acad. of Sci. Beijing 100039 China Inst. of Polymer Science/eng.neering School of Chemical Engineering Hebei University of Technology Tianjin 300130 China Dept. of Petrochemical eng.neering Daqing Petroleum Institute Anda 151400 China Res. Inst. Dushanzi Petrochem. Co. PetroChina Xinjiang 833600 China

Two novel Fe(Ⅱ) diimine complexes have been synthesized. In combination with MAO, they generate active catalytic systems that oligomerize ethylene with both high catalytic activity and high selectivity for a-olefins. The effects of substituents on the aryl ring, reaction temperatures and molar ratios of Al/Fe on catalytic activity and product distribution are studied.

关键词： late-transition-metal catalysts ethylene oligomerization α-olefin.