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ELIMIMATION OF RANDOM DEFACTS IN AEROSPACE MATERIALS

Acta Metallurgica Sinica(English Letters) 1999年第4期12卷 283-296页

作者： A. Mitchell Advanced Materials Research Laboratory, university of British Columbia, Vancouver BC,canada

In the pastfew years,severalnew melting processeshavebeenindustrialised forthe produc tion ofsuperalloys,titanium alloysand high qualitysteelsfor useintheaero *** beam , plasma,inductionskull,andthe”triple melt”process( VIM + ESR+ VAR) . These developments have allbeen instituted in responsetothe major per ceived problem oftheindustry ;that oftheincidence of random defectsin the alloys whichcause problemsinregardto predictablelifing ofthefinished partinservice. Thedirectconse quenceofthe uncertaintyislossof revenue due to premature retirement of parts which mayhavecompleted on a fraction oftheir actualservicelife; a conservatism on the partof design parameters whichleadsto uneccesary weightin thepart;and ariskofeitherservicefailuresor partrecalls whichinterruptengine performance. Thebenefitsoftheprocesschangesinrespectoftheproducts’absolute propertiesand alsoonthereproducibility and inspectability ofthose properties have been substantial. Itisclearthattheprocesses offer the industry a solution to the present dilem ma of how to treatthe ”rare”defectsfrom the pointof view of fracture mechanicslifing methodology. The use ofprocesscontrols which guarantee”zero defect”productisdevelopingintoacriticaltoolfortheextension oftherangeof a given alloy’s use. Itislikelyto permit very substantial gainsinboth componentlife and intheallowablestressin rotating parts withoutthe needtointroduce new materials carrying new problems of user confidence, production reliability and data base. Weconcludethatthenew processesareatastageof development wherethey arereadyforwideindustry usein production. They will not add significantly tothecomponentcost andthey willgive a renwed lifespan to the more familiar materials and methodsof aero engineconstruction.

关键词： AIME USA PA ELIMIMATION OF RANDOM DEFACTS IN AEROSPACE MATERIALS TMS

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Transient Free Convection and Thermal Stratification in Uniformly-Heated Partially-Filled Horizontal Cylindrical and Spherical Vessels

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Journal of Thermal Science 1992年第2期1卷 114-122页

作者： C.M.Yu Professor,Department of Thermal Engineering,university of Science and Technology Beijing,Beijing 100083,ChinaN.U.Aydemir Atomic Energy of canada Limited,Whiteshell Nuclear Research Establishment,Pinawa,Manitoba,ROE 1LO,canadaJ.E.S.Venart Fire Science Centre,university of New Brunswick,P.O.Box 4400,Fredericton,NB E3B 5A3,canada Department of Thermal Engineering University of Science and Technology Beijing Beijing China Atomic Energy of canada Limited Whiteshell Nuclear Research Establishment Pinawa Canada Fire Science Centre University of New Brunswick Fredericton Canada

An integral approach has been used to analyze the development of the free convection boundary layer on heated concave surfaces,such as those in horizontal cylinders or a *** on the non-dimensional laminar and turbulent velocity and temperature profiles closed form expressions for the boundary layer thickness,velocity scale as well as the boundary layer commencement after the point of instability are *** addition,the mass flowrate to the thermal stratified region is given.

关键词： free convection boundary layer concave surfaces horizontal cylinder sphere

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A Remark on Finite Horizon Markov Decision processes

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经济数学 1989年第5期7卷 76-80页

作者： XikUi Wang (university of Saskatchewan, canada)

本文是利用压缩算子求解的折扣有限水平Markov决策过程逼近非折扣情形的一点注记。这里涉及的状态集与活动集均为可数集。

关键词：压缩算子可数集 Horizon 决策过程 monotone 状态集 horizon uniformly erion duality

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Hamiltonian Cycles in 2-Connected Claw-Free Graphs

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新疆大学学报(自然科学版)(中英文) 1999年第1期 2-14页

作者： Li Mingchu (Department of Mathematics,university of Toronto,Toronto,Ontario,canada M5S 3G3)

１ＩｎｔｒｏｄｕｃｉｔｉｏｎＩｎｔｈｉｓｐａｐｅｒｗｅｄｅａｌｗｉｔｈｆｉｎｉｔｅｓｉｍｐｌｅｇｒａｐｈｓ．ＬｅｔＧｂｅａｇｒａｐｈ．Ｗｅｄｅｎｏｔｅｂｙδ（Ｇ）（ｏｒδ）ａｎｄｋ（Ｇ）ｔｈｅｍｉｎｉｍｕｍｄｅｇｒｅ... 详细信息

１ＩｎｔｒｏｄｕｃｉｔｉｏｎＩｎｔｈｉｓｐａｐｅｒｗｅｄｅａｌｗｉｔｈｆｉｎｉｔｅｓｉｍｐｌｅｇｒａｐｈｓ．ＬｅｔＧｂｅａｇｒａｐｈ．Ｗｅｄｅｎｏｔｅｂｙδ（Ｇ）（ｏｒδ）ａｎｄｋ（Ｇ）ｔｈｅｍｉｎｉｍｕｍｄｅｇｒｅｅａｎｄｔｈｅｃｏｎｎｅｃｔｉｖｉ...

关键词： Claw-Free Connected Cycles Graphs

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OSCILLATION CRITERIA FOR NONLINEAR SECOND ORDER ELLIPTIC DIFFERENTIAL EQUATIONS

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Chinese Annals of Mathematics,Series B 1996年第1期17卷 89-102页

作者： ZHANG BINGGEN ZHAO TAO B. S. LALLI (Department of Mathematics, Ocean university of Qingdao, Qingdao 266003, China.)(Department of Mathematics, Arizona State university, U.S.A.)(Departmemt of Mathematics, university of Saskatchewan, canada.) 青岛海洋大学数学系山东青岛 Arizona State university 美国 university of Saskatchewan 加拿大

The second order elliptic differential equations are considered in an exterior domain Ω Rn, n≥2, where p can chang sign. Some new sufficient conditions for the oscillation of solutions of (1.1) and (1.2) are establi... 详细信息

关键词： Oscillation Nonlinear elliptic equation Riccati inequality

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The great Ordovician radiation of marine life: Examples from South China

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Progress in Natural Science:Materials International 2008年第1期18卷 1-12页

作者： Renbin Zhan a,*, Jisuo Jin b, Yuandong Zhang a, Wenwei Yuan a a State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China b Department of Earth Sciences, university of Western Ontario, London Ont., canada N6A 5B7 State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences Nanjing 210008 China Department of Earth Sciences University of Western Ontario London Ont. Canada N6A 5B7

The Ordovician radiation is the earliest and most important biodiversification event in the evolution of the Paleozoic Evolutionary Fauna (PEF), when the basic framework of PEF was established. The radiation underwent a gradual, protracted process spanning more than 40 million years and was marked by several diversity maxima of the PEF. Case studies conducted on the Upper Yangtze Platform (South China Palaeoplate) showed that the Ordovician radiation was characterized by drastic increases in a- and b-diversity in various groups of organisms. During the radiation, brachiopods, trilobites, and graptolites of the PEF became more diverse to dominate over the Cambrian Evolutionary Fauna (CEF) in all marine environments. At either global or regional scales, however, the Ordovician radiation was highly heterogeneous in time and space, and the rate and pattern of radiation exhibited by difierent major fossil groups were also variable.

关键词： Ordovician radiation Paleozoic Evolutionary Fauna a-diversity b-diversity Upper Yangtze Platform

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Calculus 5th ed.

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丛书名：海外优秀数学类教材系列丛书

2004年

作者： James Stewart，mcmaster university[]

来源：畅想之星图书光盘版（南... 评论

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Traditional herbal medicine research with special reference to tetrandrine and related bis-benzylisoquinoline alkaloids: a preface to this special issue on herbal drugs

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Acta Pharmacologica Sinica 2002年第12期 2-2页

作者： Chiu-Yin KWANGuest Editor of this issue, Professor of Department of Medicine, Faculty of Health Sciences, mcmaster university, Hamilton, Ontario L8N 3Z5, canada

Since the inaugural publication of the special issue on Traditional Herbal Medicine Research in December2000 and a subsequent follow-up issue in December 2001, the Editorial Office of Acta Pharmacologica Sinica hasreceived a number of encouraging positive feedback from the general readers and academic authorities. I washonored to have been encouraged by the Editor-in-Chief, Professor DING Guang-Sheng to take up the guesteditorship for the 3rd special December issue on Traditional Herbal Medicine Research in 2002.

关键词： this Traditional herbal medicine research with special reference to tetrandrine and related bis-benzylisoquinoline alkaloids a preface to this special issue on herbal drugs

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Approximation of dense-n/2-subgraph and table compression problems

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Science China Mathematics 2005年第9期48卷 1223-1233页

作者： XU Dachuan~1 HAN Jiye~2 & DU Dongle~3 1. College of Applied Sciences,Beijing university of Technology,Beijing 100022,China 2. Institute of Applied Mathematics,Academy of Mathematics and Systems Science,Chinese Academy of Sciences,Beijing 100080,China 3. Faculty of Administration,university of New Brunswick,P.O.Box 4400,Fredericton,NB E3B 5A3,canada College of Applied Sciences Beijing University of Technology Beijing 100022 China Institute of Applied Mathematics Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100080 China Faculty of Administration University of New Brunswick P.O. Box 4400 Fredericton NB E3B 5A3 Canada

We develop improved approximation algorithms for two NP-hard problems: the dense-n/2-subgraph and table *** on SDP relaxation and advanced rounding techniques,we first propose 0. 5982 and 0. 5970-approximation algorithms respec- tively for the dense-n/2-subgraph problem (DSP) and the table compression problem (TCP). Then we improve these bounds to 0. 6243 and 0. 6708 respectively for DSP and TCP by adding triangle inequalities to strengthen the SDP *** results for TCP beat the 0. 5 bound of a simple greedy algorithm on this problem,and hence answer an open question of Anderson in an affirmative way.

关键词： dense-n/2-subgraph problem(DSP) table compression problem(TCP) SDP approximation ratio

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INDUCTION PLASMA REACTIVE DEPOSITION OF TUNGSTEN CARBIDE FROM TUNGSTEN METAL POWDER

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Acta Metallurgica Sinica(English Letters) 2001年第5期14卷 352-358页

作者： X.L. Jiang Institute of Surface and Coatings Technology, Central South university, Changsha 410083, China M.I. Boulos Department of Chemical Engineering, university of Sherbrooke, Sherbrooke, J1K 2R1, canada Central South Univ. Changsha 410083 China

Experimental results on the primary carburization reaction between the tungsten powder and methane in the induction plasma, and the secondary carburization of the deposit on substrate at high temperature are reported. Optical microscopy and scanning electron microscopy were used to examine the microstructures of starting tungsten powder, carburized powder, and deposit. X-ray diffraction analysis, thermal gravimetric analysis and microhardness measurement were used to characterize the structures and properties of the powder and the deposit. It is found that the primary carburization reaction in the induction plasma starts from the surface of tungsten particles when the particles are melted. Tungsten particles are partially carburized inside the reactive plasma. Complete carburization is achieved through the secondary carburization reaction of the deposit on substrate at high temperature.

关键词： Carburizing Deposition Methane Powder metals Tungsten Tungsten carbide

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