检索结果-南通市图书馆

THE LARGE TIME CONVERGENCE OF SPECTRAL METHOD FOR GENERALIZED KURAMOTO-SIVASHINSKY EQUATIONS

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 1997年第1期15卷 1-13页

作者： guo, b Xiang, XM SHANGHAI NORMAL UNIV SHANGHAIPEOPLES R CHINA INST APPL PHYS & COMPUTAT MATH BEIJINGPEOPLES R CHINA

In this paper we use the spectral method to analyse the generalized Kuramoto-Sivashinsky equations. We prove the existence and uniqueness of global smooth solution of the equations. Finally, we obtain the error estima... 详细信息

关键词： UN EH THE LARGE TIME CONVERGENCE OF SPECTRAL METHOD FOR GENERALIZED KURAMOTO-SIVASHINSKY EQUATIONS

Crystallization behaviour and high coercivity of (Nd,Pr)_(13)Fe_(80)Nb_1b_6 melt-spun ribbons

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2009年第3期28卷 253-256页

作者： guo Pengju LIU Xincai PAN Jing XU Feng LI Yong CUI Ping Faculty of Materials Science and Chemical Engineering Ningbo University Ningbo 315211 China Institute of Solid State Physics Chinese Academy of Sciences Hefei 230031 China Ningbo Institute of Materials of Technology and Engineering Chinese Academy of Sciences Ningbo 315040 China

Amorphous （Nd,Pr）13Fe80Nb1b6 ribbons were crystallized at 670-730°C for 5-25 min to study the effects of isothermal crystallization on their behavior and magnetic properties. XRD results indicate that the isothermal incubation time is 12, 5, and less than 5 min at 670, 700, and 730°C, respectively. High coercivities, with the maximum value of iHc = 1616 kA/m at 700°C for 19 min, measured by a physical property measurement system, are obtained in the crystallized ribbons. This is mainly attributed to the addition of Pr and Nb, because Pr2Fe14b has a higher anisotropic field than Nd2Fe14b, and Nb enriched in the grain boundary regions can not only reduce the exchange-coupling effects among hard grains, but also impede grain growth during the crystallization process. In addition, it should also be related to the characteristics of the furnace that the authors designed.

关键词： Nd-Fe-b isothermal crystallization coercivity melt-spun ribbons Pr substitution

A quantitative microplasticity-based approach to rationalize the poor strengthening response of polycrystalline Mg alloys

在线全文

学校读者我要写书评

暂无评论

Journal of Magnesium and Alloys 2023年第5期11卷 1656-1671页

作者： X.Z.Jin W.C.Xu D.b.Shan b.guo b.Jin M.T.Pérez-Prado National Key Laboratory for Precision Hot Processing of Metals&School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001PR China IMDEA Materials Institute C/Eric Kandel2GetafeMadrid 28906Spain Advanced Composites Simulation Lab University of Southern CaliforniaLos AngelesCA 90089U.S.A M.C.Gill Composites Center University of Southern CaliforniaLos AngelesCA 90089U.S.A

This work aims to understand the inefficiency of nanoprecipitates to strengthen a weakly textured,polycrystalline Mg-Gd-Y-Zr *** experimental micromechanical approach consisting on micropillar compression combined with analytical electron microscopy is put in place to analyze the effect of nanoprecipitation on soft and hard basal slip and twinning in individual grains with different *** study shows that,in grains that are favorably oriented for basal slip(“soft”basal slip),aging leads to extreme localization due to the ability of basal dislocations to shear the nanoparticles,resulting overall in the softening of basal ***,in grains in which the c-axis is almost perpendicular to the compression axis,prismatic slip dominates deformation in the solid solution state and nanoprecipitation favors twinning due to the concomitant lattice solute ***,in grains oriented with their c-axis making an angle of about 5-7°with respect to the compression axis,which deform mainly by“hard”basal slip,precipitation leads to the strengthening of basal systems in the absence of obvious *** work reveals that the poor hardening response of the polycrystalline alloy is related to the capability of basal dislocations to shear the nanoparticles,in the absence of Orowan looping events,and to the associated basal slip localization.

关键词： Magnesium Precipitation basal slip Particle shearing Slip localization

Effects of Nd^(3+)on the microstructure and magnetic properties of Ni-Zn ferrites

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2008年第3期27卷 287-291页

作者： FAN Xiufeng REN Huiping ZHANG Yanghuan guo Shihai WANG Xinlin Department of Functional Material Research Central Iron and Steel Research Institute Beijing 100081 China School of Material and Metallurgy lnnerMongolia University of Science and Technology Baotou 014010 China

Ni0.4Zn0.6Fe2-xNdxO4（x = 0-0.07） ferrites doped with different amounts of Nd2O3 were prepared using standard ceramic technique. The samples were uniaxially pressed and sintered at 1250℃ for 4 h in air. The phase structure and microstructure of the samples were investigated using X-ray diffraction and scanning electron microscope, respectively. The complex permeability was measured using the impedance analyzer in the range of 1-100 MHz. The results indicate that with increasing Nd^3＋ content, the relative density and lattice parameter a of the sintered samples increase, whereas the real part of permeability （μ′） and the magnetic loss tangent （tan δ） decrease. The substitution of Nd^3＋ for Fe^3＋ forms a secondary phase on the grain boundary of the matrix, which strongly restrains the grain growth of the matrix.

关键词： Ni-Zn ferrite microstructure complex permeability relative density

STUDY ON THE SiC_p./Al-ALLOY COMPOSITE AUTOMOTIVE bRAKE ROTORS

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2000年第4期13卷 974-980页

作者： Ding, Z.L. Fan, Y.C. Qi, H.b. Ren, D.L. guo, J.b. Jiang, Z.Q. Shijiazhuang Railway Inst Shijiazhuang China

The SiCp/Al-alloy composite front brake rotors designed for Shanghai Santana cars were prepared by semi-solid stirring+liquid forging process. The composite brake rotors were subjected to dynamometer tests on a SCHENCK brake testing system, referring to TL110 standard of VOLKSWAGEN Co. The friction coefficient and thermal response during fade testing and the wear performance of the composite rotors were studied as the functions of various parameters such as braking pressures, initial speeds, initial temperatures, torque and decelerations, and were compared with those of conventional cast iron rotors. The results show that the properties of the composite rotors can achieve the requirements of commercial cast iron rotors. The results also show that the friction coefficients of the composite rotors under different braking conditions are within the deviation band specified by the TL110 standard, and the temperature rise of composite rotors is lower than that of cast iron rotors at the end of each fade stop. The wear resistance of composite rotors is higher than that of cast iron rotors. The friction mechanism and wear mechanism were analyzed.

关键词： brakes Friction Metallic matrix composites Rotors Silicon carbide Wear resistance

FEM ANALYSIS OF THERMAL STRESSES IN GRADIENT THERMAL bARRIER COATINGS PRODUCED bY Eb-PVD

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2001年第6期14卷 493-496页

作者： H.b. guo, H.b. Xu and S.K. Gong (Department of Materials Science & Engineering, beijing University of Aeronautics and Astronautics, beijing 100083, China) Department of Materials Science & Engineering Beijing University of Aeronautics and Astronautics

Gradient thermal barrier coatings (GTbCs) produced by co-deposition of mixtures ofAl-Al2 O3-YSZ onto metallic bond coat exhibited longer lifetimes than the two-layeredTbCs. The finite element method (FEM) numerical models were used to investigatestress and strain states in the GTbCs and traditional two-layered TbCs as they cooledto 750℃ from a stress-free state at 850℃.

关键词： Eb-PVD gradient thermal barrier coating finite element method

Powder injection molding of pure titanium

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2009年第3期28卷 261-265页

作者： guo Shibo DUAN bohua HE Xinb QU Xuanhui Advanced Materials Synthesis and Applied Technology Laboratory College of Electromechanical Engineering Hunan University of Science and Engineering Xiangtan 411201 China School of Materials Science and Engineering University of Science and Technology of Beijing Beijing 100083 China

An improved wax-based binder was developed for powder injection molding of pure titanium. A critical powder loading of 69 vol.% and a pseudo-plastic flow behavior were obtained by the feedstock based on the binder. The injection molding, debinding, and sintering process were studied. An ideal control of carbon and oxygen contents was achieved by thermal debinding in vacuum atmosphere （10^-3 Pa）. The mechanical properties of as-sintered specimens were less than those of titanium made by the conventional press-sintering process. Good shape retention and ±0.04 mm dimension deviation were achieved.

关键词： powder injection molding titanium debinding sintering mechanical properties

Constraints on the late Mesozoic regional angular unconformity in West Liaoning-North Hebei by LA-ICP-MS dating

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2008年第11期18卷 1395-1402页

作者： Hong Zhang~(a,b,*) Wenmin guo~a Xiaoming Liu~b a College of Mechanical and Energy Engineering,Jiangsu Polytechnic University,Changzhou 213016,China b Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi’an 710069,China College of Mechanical and Energy Engineering Jiangsu Polytechnic University Changzhou 213016 China Key Laboratory of Continental Dynamics Department of Geology Northwest University Xi’an 710069 China

The angular unconformity between the Tuchengzi Formation and the Zhangjiakou Formation in the Chengde area is commonly regarded as the direct evidence of boundary between Jurassic and Cretaceous systems,and as the evidence of tectonic transformation interfaces in Mesozoic Era in the West Liaoning-North ***,the lower boundary age of the Zhangjiakou Formation in the Chengde was to be thought about 135 Myr in the *** on the detailed study and systematic sampling in Yixian-beipiao,Lingy- uan,Chengde and Luanping areas in the field,the authors obtained the following isotopic ages by means of LA-ICP-MS dating:In the Lingyuan area,the Zhangjiakou Formation and the Yixian Formation are in angular unconformable contact;the age range of the Zhangjiakou Formation volcanic rock is from 133 to 130 Myr(seven samples),and that of the Yixian Formation volcanic rock is from 126 to 121 Myr(eleven samples).In the Luotuoshan of Chengde,the Tuchengzi Formation and the Zhangjiakou Formation are in angu- lar unconformable contact;the age at the lower Zhangjiakou Formation is about 124 Myr(one sample),which reflects that the age range of the lower Zhangjiakou Formation is from 129 to 124 Myr combined with the previous *** the Luanping basin,there is the larg- est sediment gap in upper Mesozoic,whose lower boundary age is confined in 131 to 130 *** the Yixian-beipiao area,the second Member of the Yixian Formation,making up more than 3/4 thickness of the Yixian Formation,was formed in 126 to 119 Myr,and the age of the Yixian Formation at the bottom is about 132 ***,the upper boundary age of the Tuchengzi Formation is about 136 Myr in the West Liaoning-North Hebei *** on the above isotopic data combined with the geological characteristics in the field in the West Liaoning-North Hebei region,it reflects that there was a widespread tectonic event in the period of 136 to 126 Myr (mainly in 130-126 Myr)in the West Liaoning-North Hebei,and it formed the

关键词： Dating LA-ICP-MS Angular unconformity Interface of tectonic transformation West Liaoning-North Hebei

Promoting remyelination for the treatment of multiple sclerosis:opportunities and challenges

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Neuroscience bulletin 2013年第2期29卷 144-154页

作者： Yueting Zhang Taylor b.guo Hongtao Lu Neuroimmunology Discovery Performance Unit GlaxoSmithKline Research and Development Center

Multiple sclerosis （MS） is a chronic and devastating autoimmune demyelinating disease of the central nervous system. With the increased understanding of the pathophysiology of this disease in the past two decades, many disease-modifying therapies that primarily target adaptive immunity have been shown to prevent exacerbations and new lesions in patients with relapsing-remitting MS. However, these therapies only have limited efficacy on the progression of disability. Increasing evidence has pointed to innate immunity, axonal damage and neuronal loss as important contributors to disease progression. Remyelination of denuded axons is considered an effective way to protect neurons from damage and to restore neuronal function. The identification of several key molecules and pathways controlling the differentiation of oligodendrocyte progenitor cells and myelination has yielded clues for the development of drug candidates that directly target remyelination and neuroprotection. The long-term efficacy of this strategy remains to be evaluated in clinical trials. Here, we provide an overview of current and emerging therapeutic concepts, with a focus on the opportunities and challenges for the remyelination approach to the treatment of MS.

关键词： multiple sclerosis myelination neurodegeneration oligodendrocytes disease progression disease modifying therapy drug target animal models