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POTENTIAL INVERSION PROBLEMS FOR COUPLED SYSTEM OF DOWNGOING AND UPCOMING ONE-WAY WAVE EQUATIONS

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Journal of Computational Mathematics 1998年第6期16卷 551-560页

作者： Zhang, GQ dou, xl Chinese Acad Sci ICMSEC State Key Lab Sci & Engn Comp Beijing 100080 Peoples R China Beijing Res Inst Remote Sensing Informat Beijing 100011 Peoples R China

By using wave splitting method the formulation of the two-dimensional potential inversion problem is set up in terms of the coupled system for downgoing and upcoming wavefields. The boundary counditions on the characteristic surface needed for solving the problem are derived by singularity analysis. Two stability theorems are given for the direct problems of the system treated as Cauchy problems in the direction of depth.

关键词： 2-D potential inversion wave splitting singularity analysis

Nonequilibrium Microstructures and Phase Evolutions of and Iron-based Laser Clad Coating

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Journal of Materials Science & Technology 1999年第6期15卷 541-547页

作者： Wu, xl Chen, GN Chinese Acad Sci Inst Mech Lab Nonlinear Mech Continuous Media Beijing 100080 Peoples R China

The microstructural and compositional features of the laser-solidified microstructures and phase evolutions occurring during high temperature tempering were investigated by using analytical electron microscopy with energy dispersive X-ray analysis. The cladded alloy, a powder mixture of Fe, Cr, W, Ni and C with a weight ratio of 10:5: 1:1:1, was processed with a 3 kW continuous wave CO2 laser. The cladded coating possessed the hypoeutectic microstructure of the primary dendritic γ-austenite and interdendritic eutectic consisting of (γ+M7C3). The γ-austenite is a nonequilibrium phase with extended solid solution of alloying elements. And, a great deal of fine structures, i.e., a high density ofdislocations,twins,andstackingfaultsexistedinaustenite phase. During high temperature aging,the precipitation of M23C6, MC and M2C in austenite and in situ transformation of M7C3(+γ) → M23C6 and M7C3+7→ M6C occurred. The laserclad coating revealed an evident secondary hardening and superior impact wear resistance

关键词： Cladding (coating)

Microstructure and Wear Resistance of In situ TiCp Composite Coating by Laser Cladding

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Journal of Materials Science & Technology 1999年第3期15卷 233-238页

作者： Wu, xl Chen, GN Chinese Acad Sci Inst Mech Ctr Mat Res Beijing 100080 Peoples R China

A new in situ method was realized by one step laser cladding to produce Ni-base alloy composite coating reinforced by in situ reacted and gradiently distributed TiCp particles. The submicron TiCp particles were formed and uniformly distributed because of the in situ reaction and trapping effect under the rapid solidification condition. And, TiCp particles were of gradient distribution on a macro scale and their volume fraction increased from 1.86% at the layer/substrate interface to a maximum 38.4% at the surface of the layer. Furthermore, the in situ generated TiCp/gamma-Ni interfaces were free from deleterious surface reactions. Additionally, the clad coating also revealed a high microhardness of gradient variation with the layer depth and the superior abrasive wear resistance.

关键词： Composite materials

Influence of Deformation and Heat Treatment on Seawater Corrosion of 70Cu-30Ni Alloy

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Journal of Materials Science & Technology 1998年第1期14卷 57-61页

作者： Zhu, xl Lei, TQ Gen Res Inst NonFerrous Met Beijing 100088 Peoples R China Harbin Inst Technol Harbin 150001 Peoples R China

After deformed and annealed, 70Cu-30Ni alloy with irrecrystallization or incomplete recrystallization mainly consisting of deformed grains displayed unstable E-c (corrosion potential) and low R-p (polarization resistance) in 3.5%NaCl, and corrosion product film contained a lot of seawater species in the outer layer and denickelified in the inner layer immersed in seawater for 3 and 6 months, and intergranular corrosion occurred in the matrix. With the increase of deformation and annealing temperature, the anodic oxide film formed by polarization in artificial seawater was increasingly stable. The recrystallized alloy was stable in E-c and high in R-p and its corrosion product film formed in seawater was uniform and rich in Ni.

关键词： Copper alloys

QUADRILATERAL FINITE ELEMENTS FOR PLANAR LINEAR ELASTICITY PROBLEM WITH LARGE LAME CONSTANT

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Journal of Computational Mathematics 1998年第4期16卷 357-366页

作者： Cheng, xl Huang, HC Zou, J Hangzhou Univ Dept Math Hangzhou Peoples R China Hong Kong Baptist Univ Dept Math Hong Kong Hong Kong Chinese Univ Hong Kong Dept Math Hong Kong Hong Kong

In this paper, we discuss the quadrilateral, finite element approximation to the two-dimensional linear elasticity problem associated with a homogeneous isotropic elastic material. The optimal convergence of the finite element method is proved for both the L-2-norm and energy-norm, and in particular, the convergence is uniform with respect to the Lame constant lambda. Also the performance of the scheme does not deteriorate as the material becomes nearly incompressible, Numerical experiments are given which are consistent with our theory.

关键词： planar linear elasticity optimal error estimates large Lame constant locking phenomenon

Protective effects of prostaglandin E1 on hepatocytes

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World Journal of Gastroenterology 2000年第3期6卷 326-329页

作者： Liu xl Fan DM Fourth Mil Med Univ Xijing Hosp Inst Digest Dis Xian 710032 Peoples R China

INTRODUCTION E Numerous studies have demonstrated the protective action of prostaglandin E1(PGE1) on experimental animal models of liver injury and on patients with

关键词： prostaglandin El hepatitis liver injury hepatic cytoprotective effects lipid microspheres

The Friedel-Crafts Acylation of Substituted Benzene with 2 - Phenylfuran-3, 4-dicarboxylic Acid Anhydride

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Chinese Chemical Letters 1998年第2期9卷 125-129页

作者： Nie, XP Ye, xl Peking Univ Dept Chem Beijing 100871 Peoples R China

2-Phenylfuran-3,4-dicarboxylic acid anhydride reacted with seven aromatic compounds, of which five gave keto acids in yields of 94%-63%. The structure of the keto acid was elucidated by reducing it to hydroxy acid and... 详细信息

关键词： Friedel-Crafts acylation 2-phenylfuran-3,4-dicarboxylic acid anhydride structure elucidation

Hepatic angiomyolipoma-misdiagnosis as hepatocellular carcinoma:A report of 14 cases

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World Journal of Gastroenterology 2000年第4期6卷 608-612页

作者： Zhong DR Ji xl Gen Hosp PLA Dept Pathol Beijing 100853 Peoples R China

Angiomyolipoma (AML) is a rare benign mesenchymal tumor of the liver, composed of a varying heterogeneous mixture of three tissue components: blood vessels, smooth muscle, and adipose cells. It has recently been proposed that the perivascular epithelial cell (PEC) is the common progenitor[1，2] Since its first description by Ishak in 1976[3], there have been more than 100 cases reported in the English literature[4-6]. With the advance of radiological techniques, many more tumors are being diagnosed by the means. But radiological findings of AML may only be suggestive of the lesion; its definitive diagnosis requires histological confirmation[9-19]. Some authors regard renal and hepatic AMLs, pulmonary and soft tissue lymphangiomyomatosis[2], pulmonary and pancreatic clear cell “sugar” tumor, and cardiac rhabdomyoma as closely related groups of tumors, based on their morphologic overlap and common immunoreactivity for HMB-45[l]. They show different microscopic appearances, however, according to their organ of origin. The goals of this study were to highlight more subtle morphology and to gain possible insights into the differential diagnosis that could provide important information about this disease.

关键词： angiomyolipoma liver neoplasms/diagnosis immunohistochemistry microscopy electron carcinoma hepatocellular/pathology case-control studies

Treatment of corticosteroid-resistant ulcerative colitis with oral low molecular weight heparin

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World Journal of Gastroenterology 1999年第5期5卷 448-450页

作者： Cui HF Jiang xl Shandong Med Univ Dept Biochem Pharmaceut Jinan 250012 Peoples R China Chinese PLA Gen Hosp Jinan Command Dept Gastroenterol Jinan 250031 Peoples R China

INTRODUCTIONThe etiology and pathogenesis of ulcerative colitis (UC) have remained unclear. Treatment is nonspecific based on the anti-inflammatory agents corticosteroid and sulfasalazine. A significant proportion fail to respond to this therapy[1]. As the relapse, refractory or serious UC patients had a hypercoagulable state and an increased incidence of thromboembolic events[2-4], heparin has been used by some authors[5-7]. Yet, its half-life period is short, needing long-term injection, which restricts its further clinical application. Our previous studies have demonstrated oral LMWH not only overcomes the shortcomings of common heparin[8,9], but also has anti-inflammatory effects[10,11]. The aim of this paper is to study the therapeutic effects and mechanism of oral LMWH in patients with corticosteroid-resistant UC.

关键词： colitis ulcerative/drug therapy heparin/therapertic use corticosteroidresistant