检索结果-南通市图书馆

INFINITELY MANY SOLUTIONS FOR A SINGULAR ELLIPTIC EQUATION INVOLVING CRITICAL SOBOLEV-HARDY EXPONENTS IN R^N

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Scientia 2010年第3期30卷 830-840页

作者：贺小明邹文明 school of Sciences Central University for Nationalities Department of Mathematical Sciences Tsinghua University

In this article, we study the existence of multiple solutions for the singular semilinear elliptic equation involving critical Sobolev-Hardy exponents -△μ-μ｜x｜^2^-μ=α｜x｜^s^-｜μ｜^2＊（s）-2u＋βα（x）｜u｜^r-2u,x∈R^n. By means of the concentration-compactness principle and minimax methods, we obtain infinitely many solutions which tend to zero for suitable positive parameters α,β.

关键词： Singular elliptic equation Multiple solutions Critical Sobolev-Hardy exponent Minimax method

The mathematical model of wetting angle of heterogeneous nucleation

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2004年第4期47卷 391-397页

作者： HUANG Cheng1, SONG Bo1, MAO Jinghong2 & ZHAO Pei3 1. school of Metallurgical and Ecological Engineering, university of Science and Technology beijing, beijing 100083, china 2. school of Material Science, university of Science and Technology beijing, beijing 100083, china 3. central Iron and Steel Research Institute, beijing 100081, china 1. school of Metallurgical and Ecological Engineering University of Science and Technology Beijing 100083 Beijing China 2. school of Material Science University of Science and Technology Beijing 100083 Beijing China 3. central Iron and Steel Research Institute 100081 Beijing China

The heterogeneous nucleation has been analyzed in terms of the thermodynamic theory, and the mathematical model of wetting angle of heterogeneous nucleation has been developed based on the dynamic requirements of hetero- and homogeneous nucleation. With the wetting angel model, the wetting angles of different catalysts in liquid iron have been calculated. The result shows that the wetting angle of most catalysts is smaller than 40, and the value of f() is far less than 1. The wetting angles of TiN, TiC and RE2O3 are smaller, while the wetting angle of MnO is bigger among the ordinary nucleation catalysts. The wetting angles calculated by this model are in agreement with the results of other research work.

关键词： heterogeneous nucleation, mathematical model, wetting angle, undercooling.

Analysis for twinning and slip in face-centered cubic crystals under axisymmetric co-deformation

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2006年第5期49卷 521-536页

作者： CHEN Zhiyong1,2, CAI Hongnian1, ZHANG Xinming2, WANG Fuchi1 & TAN Chengwen1,3 1. school of Material Science and Engineering, beijing Institute of Technology, beijing 100081, china 2. school of Material Science and Engineering, central South university, Changsha 410083, china 3. school of Material Science and Engineering, beijing university of Aeronautics and Astronautics, beijing 100083, china 1. school of Material Science and Engineering Beijing Institute of Technology Beijing 100081 China 2. school of Material Science and Engineering Central South University Changsha 410083 China 3. school of Material Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100083 China

The maximum work principle of Bishop-Hill was developed to analyze the axisymmetric co-deformation in face-centered cubic crystals (f.c.c.) for twinning on {111} 112 and slip on {111} 110 systems. The influence of ξ , the ratio of critical re- solved shear stress for twinning to slip, on the yield stress states and corresponding active slip or/and twinning systems for orientations in the standard stereographic triangle of cubic crystal was investigated systematically. The Taylor factors and the anisotropy of yield strength for three important orientations [100], [110] and [111] in orientation space were analyzed. It is found that the yield strength asymmetry for the case of axisymmetric de- formation of tension and compression can be explained based on the microscopic theory of crystal plasticity. The concept of orientation factor for twinning ability was proposed and the deformation mechanism map in the orientation space was established for the case of axisymmetric deformation. The deformation texture formation and development of f.c.c. crystals with low stacking fault energy for axisymmetric tension can be explained qualita- tively on the basis of analyzed results.

关键词： twinning slip face-centered cubic crystals axisymmetric co-deformation Bishop-Hill maximum work principle yield strength anisotropy

Recommendation Method for Contrastive Enhancement of Neighborhood Information

在线全文

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2024年第1期78卷 453-472页

作者： Hairong Wang beijing Zhou Lisi Zhang He Ma school of Computer Science and Engineering North Minzu UniversityNingxia750021China

Knowledge graph can assist in improving recommendation performance and is widely applied in various person-alized recommendation ***,existing knowledge-aware recommendation methods face challenges such as weak user-item interaction supervisory signals and noise in the knowledge *** tackle these issues,this paper proposes a neighbor information contrast-enhanced recommendation method by adding subtle noise to construct contrast views and employing contrastive learning to strengthen supervisory signals and reduce knowledge ***,first,this paper adopts heterogeneous propagation and knowledge-aware attention networks to obtain multi-order neighbor embedding of users and items,mining the high-order neighbor informa-tion of users and ***,in the neighbor information,this paper introduces weak noise following a uniform distribution to construct neighbor contrast views,effectively reducing the time overhead of view *** paper then performs contrastive learning between neighbor views to promote the uniformity of view information,adjusting the neighbor structure,and achieving the goal of reducing the knowledge noise in the knowledge ***,this paper introduces multi-task learning to mitigate the problem of weak supervisory *** validate the effectiveness of our method,experiments are conducted on theMovieLens-1M,MovieLens-20M,Book-Crossing,and Last-FM *** results showthat compared to the best baselines,our method shows significant improvements in AUC and F1.

关键词： Contrastive learning knowledge graph recommendation method

PDMS prism-glass optical coupling for surface plasmon resonance sensors based on MEMS technology

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science china(Information Sciences) 2010年第10期53卷 2144-2158页

作者： GENG ZhaoXin 1,2 , LI Qing 3 , WANG Wei 1 & LI ZhiHong 1 1 Institute of Microelectronics, Peking university, beijing 100871, china 2 school of Information engineering, Minzu university of china, beijing 100081, china 3 school of Sciences, Changchun university of Science and Technology, Changchun 130000, china 1. Institute of Microelectronics Peking University Beijing 100871 China2. School of Information engineering Minzu University of China Beijing 100081 China3. School of Sciences Changchun University of Science and Technology Changchun 130000 China

A miniaturized surface plasmon resonance (SPR) chip has been developed for biomedical and chem-ical analysis with low cost and high performance. The techniques of bulk silicon micromachining and polymer replication were used to fabricate the Kretschmann SPR sensor composed of a Polydimethylsiloxane (PDMS) prism, a coupling glass and microchannels. The plasmon properties of thin metal films were investigated theoret-ically based on Fresnel analysis, with optical boundary conditions pertaining to the surface plasmon resonance at the gold/water and gold/air interfaces. The theoretical results show that difference in the refractive index (RI) between the PDMS prism and the coupling glass layer affect the precision of the SPR angle and the SPR curve. Meanwhile, the period of the interference fringe attaching on the SPR curve increases with an increase in wavelength and a decrease in the refractive index of the coupling glass layer. The gold thickness of 50 nm is required while employing a fixed incident wavelength of 650 nm, to achieve optimum SPR excitation conditions and the sensor sensitivity. The characteristics of this SPR sensor were evaluated in the angular interrogation mode of employing the incident wavelength of 650 nm in air and water media, respectively. The obtained SPR angles were approximately consistent with the theoretical ones.

关键词： surface plasmon resolance polymer microfluidic PDMS

Finite Element Analysis of Die Geometry and Process Conditions Effects on Equal Channel Angular Extrusion for β-Titanium Alloy

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 Iron and Steel Research International 2012年第10期19卷 54-58页

作者： SI Jia-yong1,2, GAO Fan3, ZHANG Ji3 (1. State Key Laboratory of Powder Metallurgy, central South university, Changsha 410083, Hunan, china 2. College of Mechanical and Electrical Engineering, central South university of Forestry and Technology, Changsha 410004, Hunan, china 3. high Temperature Material Research Division, central Iron and Steel Research Institute, beijing 100081, china) [a] State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 Hunan China [b] College of Mechanical and Electrical Engineering Central South University of Forestry and Technology Changsha 410004 Hunan China [c] high Temperature Material Research Division Central Iron and Steel Research Institute Beijing 100081 China

The finite element analysis was applied to evaluate the respective influences of die geometry and process conditions on plastic strain distribution for β-titanium (Ti-13V11Cr3Al) alloy during the equal channel angular extrusion (ECAE). It was found that optimum equal channel angular extrusion die geometry is strongly material dependent. Optimal strain homogeneity in the Ti-13V11Cr3Al alloy may be achieved at r (inner radius)=5 mm, R (outer radius)=3 mm. The equivalent plastic strain increases with increasing friction coefficient. And the better homogeneity of the equivalent plastic strain distribution can be achieved when friction coefficient value is lower. The faster the ram speed is, the lower the homogeneity of the equivalent plastic strain distribution is and the influence is slight. The back-pressure does not help to improve the plastic strain homogeneity, and the increasing temperature has a slightly favourable effect on the plastic strain homogeneity between 400 and 600 ℃.

关键词： equal channel angular extrusion finite element analysis die geometry β-titanium

Study on Transformation of CaO-Al_2O_3-SiO_2-MgO System Inclusions in ZG06Cr13Ni4Mo Stainless Steel

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2011年第S2期18卷 341-346页

作者： LIU Jian-hui1,3, DONG Han1,3, ZHU Rong2, LI Shi-qi2 (1. Institute for Structural Materials,central Iron and Steel Research Institute, beijing 100081,china 2. school of Metallurgical and Ecological Engineering,university of Science and Technology beijing, beijing 100083,china 3. National Engineering Research Center of Advanced Steel Technology, beijing 100081,china) Cent Iron & Steel Res Inst Inst Struct Mat Beijing 100081 Peoples R China Univ Sci & Technol beijing Sch Met & Ecol Engn Beijing 100083 Peoples R China Natl Engn Res Ctr Adv Steel Technol Beijing 100081 Peoples R China

This paper aims at generally studying on the inclusions of ZGG06Cr13Ni4Mo ultra-low carbon stainless steel used for large scale hydraulic turbine sets. On the basis of analysis the industrial test samples, thermodynamic software FactSage is used to study inclusions transformation process in CaO-SiO2-Al2O3-MgO system while stainless steel is been smelting. The results illustrate the inclusions melting points and plasticity variation law. The reasonable inclusions plasticity controlling area is found out in low melting point. The melting point is up to 1280℃ While MgO weight concentration is 10% in CaO-SiO2-Al2O3-MgO system, SiO2, Al2O3 and CaO in inclusions are in weight concentration range of 50-70%, 10-20% and 10-40%, respectively. For purpose of gaining low melting point inclusions, silicon alumina radio in deoxidant should be controlled between 2-5 for ultra-low carbon stainless steel refining in industry.

关键词： ZG06Cr13Ni4Mo stainless steel low melting point inclusion thermodynamic calculation

An efficient algorithm for finding the largest chain graph according to a given chain graph

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2005年第11期48卷 1517-1530页

作者： LIU Baijun,ZHENG Zhongguo & ZHAO Hui school of Mathematical Sciences, Peking university, beijing 100871, china Department of Statistics, central china Normal university, Wuhan 430079, china 1. school of Mathematical Sciences Peking University 100871 Beijing China 2. Department of Statistics Central China Normal University 430079 Wuhan China

Chain graph (CG) is a general model of graphical Markov models. Some different chain graphs may describe the same conditional independence structure, then we say that these CGs are Markov equivalent. In 1990 Frydenberg showed that every class of Markov equivalent CGs has a CG which is called the largest chain graph with the greatest number of lines. This paper presents an efficient algorithm for finding the largest chain graph of the corresponding Markov equivalent class of a given CG. The computational complexity of the algorithm is O(n3). It is more efficient than the complexity O(n!) of the present algorithms. Also a more intuitive graphical characterization of the largest chain graph is provided based on the algorithm in this paper.

关键词： graphical Markov model,chain graph,largest chain graph,protected arrows,efficient algorithm

Comparative study on CO_2 corrosion behavior of N80,P110,X52 and 13Cr pipe lines in simulated stratum water

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2010年第9期53卷 2342-2349页

作者： CAI YiDong1,GUO PengChao1,LIU DaMeng1,CHEN ShiYu2 & LIU JunLai3 1 school of Energy Resources,china university of Geosciences,beijing 100083,china 2 school of Materials Science and Engineering,university of Science and Technology beijing,beijing 100083,china 3 school of Earth Sciences and Resources,china university of Geosciences,beijing 100083,china 1. school of Energy Resources China University of Geosciences Beijing 100083 China2. School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China3. School of Earth Sciences and Resources China University of Geosciences Beijing 100083 China

To better understand the carbon dioxide (CO2) corrosion behavior of carbon steel and its influence on petroleum development (including drilling,production and transportation) in the Daqing Oilfield,CO2 corrosion behaviors of N80,P110,X52 and 13Cr pipe lines in simulated solution at high temperature and high pressure condition are investigated by dynamic corrosion experiments,scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) *** show that the corrosion rate of all pipe lines increases quickly when CO2 partial pressure increases from 0.5 to 1.5 MPa,but it slows down when CO2 partial pressure further increases from 1.5 to 4.5 MPa,during which localized corrosion is *** the experimental temperature ranges from 60 to 120°C,localized corrosion *** corrosion rate of all pipe lines decreases sharply when the temperature changes from 60 to 100°C,and it becomes stable after the temperature is higher than 100°*** the flow rate is in the range of 0–1.5 m/s,the corrosion rate of sample X52 remains unchanged,but localized corrosion gradually becomes very serious when the flow rate further *** analyzing the corrosion product scales of sample 13Cr,some remarkable phenomena are *** the temperature range of 60–100°C,the corrosion product scales are loose and thick,but become very compact when the temperature increases above 100°*** the later case,localized corrosion is *** main components of the corrosion product scales are FeCO3 and Cr2O3.

关键词： CO2 corrosion pipe lines weight loss SEM EDS