检索结果-南通市图书馆

Corrosion Performance of Zinc and Zinc-cobalt Alloy Compositionally Modulated Multilayer (CMM) Coatings

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan university of Technology(Materials Science) 2006年第4期21卷 40-44页

作者：费敬银 department of Applied chemistry Science CollegeNorthwestern Polytechnical University Xi'an 710072China

Varieties of zinc and Zn-Co alloy compositionally modulated multilayer （CMM） coatings were electrodeposited onto steel substrates using dual bath technique. The surface and cross-sectional morphologies of coated samples were examined using scanning electron microscopy （ SEM ）. The existence of iuternal stress in ZnCo alloy deposits was confirmed by the cross-sectional morphalogies for the occurrence of micro-cracks in the thick Zn-Co alloy deposit alone. The corrosion performance was evaluated using neutral salt spray testing, corrosion potential measurement and anodic polarization methods. The experimental results slum, that the zinc and Zn- Co alloy CMM coatings were more corrosion-resistant than the monolithic coatings of zinc or Zn-Co alloy alone with a similar thickness. The analysis on the micrographic features of zinc and Zn-Co alloy CMM coatings, using field emission gun scanning electron microscopy （FEGSEM） after corrosion testing, explains the probable reusons why the Zn-Co/ Zn CMM coating system has a better protective performance.

关键词： corrosion resistance Zn-Co alloy composhionally modulated multilayer coating

On solving equations of algebraic sum of equal powers

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2006年第9期49卷 1153-1157页

作者： WANG Xinghua & YANG Shijun department of Mathematics, Zhejiang university, Hangzhou 31002.,{2. department of Mathematics, Hangzhou Normal College, Hangzhou 310036,{2. department of Mathematics Zhejiang University Hangzhou 310028 China department of Mathematics Hangzhou Normal College Hangzhou 310036 China

It is well known that a system of equations of sum of equal powers can be converted to an algebraic equation of higher degree via Newton's identities. This is the Viete-Newton theorem. This work reports the generalizations of the Viete-Newton theorem to a system of equations of algebraic sum of equal powers. By exploiting some facts from algebra and combinatorics,it is shown that a system of equations of algebraic sum of equal powers can be converted in a closed form to two algebraic equations, whose degree sum equals the number of unknowns of the system of equations of algebraic sum of equal powers.

关键词： algebraic sum of equal powers, Newton's identities, system of equations,roots of a polynomial.

Synthesis of New β-Cyclodextrin Dimers Bridged by Schiff Base

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 1998年第7期9卷 609-610页

作者： Yong LIU Guo Ping XUE Cheng Tai WU (department of chemistry Wuhan {2., Wuhan 430072. Wuhan Univ Dept Chem Wuhan 430072 Peoples R China

Four β-cyclodextrin dimers bearing the Schiff base bridge on their primary faces have been synthesized.

关键词： cyclodextrin dimer Schiff base

PATIENT-SPECIFIC BLOOD DYNAMIC SIMULATIONS IN ASSESSING ENDOVASCULAR OCCLUSION OF INTRACRANIAL ANEURYSMS

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2009年第2期21卷 271-276页

作者： CHEN Jia-liang WANG Sheng-zhang DING Guang-hong YANG Xin-jian LI Hai-yun department of Mechanics and Engineering Science Fudan University Shanghai 200433 China beijing Institute of Neurosurgery Beijing 100050 China department of Biomedical Engineering Capital Medical University Beijing 100050 China

According to recent studies, there are various potential predictors for surgical outcome for cerebral aneurysms. An accurate surgical outcome assessment would help make better-informed decisions and avoid the risk of rebleeding. It is well known that hemodynamic factors play an important role in the pathogenesis and treatment of intracranial aneurysms. In this article, a computational fluid dynamic analysis is applied to one patient-specific model of the cerebral aneurysm located at the tip of basilar artery, by which the differences of hemodynamic parameters before and after endovascular treatment may be evaluated. Based on the model, we show that the flow behavior near the neck of the aneurysm sees great differences after endovascular treatment as compared with that before treatment, which also affects the wall shear stress and the displacement distribution. In addition, our whole simulation process is based on a series of CFD commercial software packages, which are easily available for doctors to implement such a method in their daily practice. These results would be used to assess the outcome of endovascular treatment for the aneurysm occlusion.

关键词： hemodynamics numerical simulation intracranial aneurysm

Reactive Diffusion Bonding of SiCp/Al Composites by Insert Powder Layers with Eutectic Composition

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2005年第5期21卷 779-781页

作者： Jihua HUANG Yueling DONG, Jiangang ZHANG, Yun WAN and Guoan ZHOUSchool of Materials Science and Engineering, university of Science and Technology beijing, beijing 100083, china School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

Mixed Al-Si and Al-Cu powders were investigated as insert layers to reactive diffusion bond SiCp/6063 metal matrix composite （MMC）. The results show that SiCp/6063 MMC joints bonded by the insert layers of the mixed Al-Si and Al-Cu powders have a dense joining layer of high quality. The mass transfer between the bonded materials and insert layers during bonding leads to the hypoeutectic microstructure of the joining layers bonded by both the mixed Al-Si and Al-Cu powders with eutectic composition. At fixed bonding time （temperature）, the shear strength of the joints by both insert layers of the mixed Al-Si and Al-Cu powders increases with increasing the bonding temperature （time）, but get maxima at bonding temperature 600℃ （time 90 min）.

关键词： Reactive diffusion bonding Insert powder layer SiCp/Al metal matrix composites

REMOTE SENSING RESEARCH ON NORTH PART OF THE YULONG COPPER DEPOSITS ZONE IN XIZANG (TIBET)

在线全文

学校读者我要写书评

暂无评论

地学前缘 2000年第S1期7卷 421-422页

作者： Chen Jianping 1,Tang Juxing\+2. Gu Xuexiang\+2.WT5,5”BX](1.china university of Geosciences,{2. 100083,china 2.Chengdu university of Technology,Chengdu 610059,china)

The zone of Yulong copper deposit is considered superlarge in scale all over the world, which is a part of Tethys to Himalaya Ore\|forming zone. The geological background of the Jinshajiang and Lancangjiang Faults provided utility for accumulated of copper, molybdenum and so on. The Yulong copper zone is the most important characteristic in the east Qinghai—Xizang Plateau (Tibet), which isabout 400km in length from north to south, and 30～70km in width from east to west. The structural channel for ores accumulation was constructed in Yanshan orogeny and the process of ore forming of the zone was mainly in Himalaya orogeny. The Yulong copper zone can be divided into three subzones, each named as north, south and east subzone which the north subzone is 50km in length of about NNW direction. Based on the geological interpretation (Fig.1), we understood that NW structures are distributed mainly in this area, then EW and NNW, and the sigmoid structures extended reflect their extrusion character. The EW and NNW structures are distributed in small scale and extended stable, which are cut to each other. The NNW structure was interpreted as undercover fracture, which may occurred earlier than NW one. Beside, of the structure, there are some differences in image tone, linear, relief, strata combination, structure pattern and so on. Therefore, the undercover fault played key efforts to Yulong copper formation.

关键词： remote sensing copper deposit Yulong Tibet

Fabrication and Microstructure of W/Cu Functionally Graded Material

在线全文

学校读者我要写书评

暂无评论

Journal of university of Science and Technology beijing 2001年第3期8卷 198-202页

作者： Yunhan Ling, Jiangtao Li, Zhangjian Zhou, Changchun Ge Laboratory of Special Ceramics & Powder Metallurgy, university of Science and Technology beijing, beijing 100083, china Univ Sci & Technol beijing Lab Special Ceram & Powder Met Beijing 100083 Peoples R China

W/Cu functionally gradient material (FGM) has excellent mechanical properties since it can effectively relax interlayer thermal stresses caused by the mismatch between their thermal expansion coefficients. W/Cu FGM combines the advantages of tungsten such as high melting point and service strength, with heat conductivity and plasticity of copper at room temperature. Thus it demonstrates satisfactory heat corrosion and thermal shock resistance and will be a promising candidate as divertor component in thermonuclear device. Owing to the dramatic difference of melting point between tungsten and copper, conventional processes meet great difficulties in fabricating this kind of FGMs. A new approach termed graded sintering under ultra-high pressure (GSUHP) is proposed, with which a near 96% relative density of W/Cu FGM that contains a full distribution spectrum (0-100%W) has been successfully fabricated. Suitable amount of transition metals (such as nickel, zirconium, vanadium) is employed as additives to activate tungsten's sintering, enhance phase wettability and bonding strength between W and Cu. Densification effects of different layer of FGM were investigated. Microstructure morphology and interface elements distribution were observed and analyzed. The thermal shock performance of W/Cu FGM was also preliminarily tested.

关键词： tungsten copper sintering functionally graded material composite

Numerical simulation of mechanisms of deformation,failure and energy dissipation in porous rock media subjected to wave stresses

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2010年第4期53卷 1098-1113页

作者： JU Yang1,2.WANG HuiJie1,YANG YongMing1,HU QinAng3 & PENG RuiDong1 1 State Key Laboratory of Coal Resources and Safe Mining,beijing Key Laboratory of Fracture and Damage Mechanics of Rock and Concrete,china {2. of Mining and Technology,beijing 100083,china 2.department of Mechanical and Manufacturing Engineering,{2. of Calgary,Calgary,Alberta,T2. 1N4,Canada 3 School of Environment and Civil Engineering,College of Engineering,Oklahoma State {2.,Stillwater,OK 74078,USA 1. State Key Laboratory of Coal Resources and Safe Mining Beijing Key Laboratory of Fracture and Damage Mechanics of Rock and Concrete China University of Mining and Technology Beijing 100083 China2. Department of Mechanical and Manufacturing Engineering University of Calgary Calgary Alberta T2N 1N4 Canada3. School of Environment and Civil Engineering College of Engineering Oklahoma State University Stillwater OK 74078 USA

The pore characteristics,mineral compositions,physical and mechanical properties of the subarkose sandstones were acquired by means of CT scan,X-ray diffraction and physical tests.A few physical models possessing the same pore characteristics and matrix properties but different porosities compared to the natural sandstones were *** 3D finite element models of the rock media with varied porosities were established based on the CT image processing of the physical models and the MIMICS software *** failure processes of the porous rock media loaded by the split Hopkinson pressure bar(SHPB) were simulated by satisfying the elastic wave propagation *** dynamic responses,stress transition,deformation and failure mechanisms of the porous rock media subjected to the wave stresses were *** is shown that an explicit and quantitative analysis of the stress,strain and deformation and failure mechanisms of porous rocks under the wave stresses can be achieved by using the developed 3D finite element *** applied wave stresses of certain amplitude and velocity,no evident pore deformation was observed for the rock media with a porosity less than 15%.The deformation is dominantly the combination of microplasticity(shear strain),cracking(tensile strain) of matrix and coalescence of the cracked regions around *** stresses lead to microplasticity,while tensile stresses result in cracking of the *** and coalescence of the matrix elements in the neighborhood of pores resulted from the high transverse tensile stress or tensile strain which exceeded the threshold *** simulation results of stress wave propagation,deformation and failure mechanisms and energy dissipation in porous rock media were in good agreement with the physical *** present study provides a reference for analyzing the intrinsic mechanisms of the complex dynamic response,stress transit mode,deformation and failure mechanisms and the disaster mechanism

关键词： porous media three-dimensional finite element model rock media stress wave failure mechanism energy dissipation

ON THE CONVERGENCE OF KING-WERNER ITERATIONMETHOD IN BANACH SPACEON THE CONVERGENCE OF KING-WERNER ITERATIONMETHOD IN BANACH SPACE

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2000年第5期18卷 457-466页

作者： Zheng-da Huang (department of Mathematics, XiXi Campus, Zhejiang university, Hangzhou 31002.,{2.) department of Mathematics XiXi Campus Zhejiang University Hangzhou 310028 China

In this paper. a Kantorovitch- Ostrowski type convergence theorem and an error estimate of using the information of higher derivatives at the center between initial points for King-Werner iteration method in Banach ... 详细信息

关键词： Information at the center between initial points King-Werner iteration method Convergence Error estimate.