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Oxidation-induced strengthening behavior of reaction formed Al_4SiC_4 ceramics

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Rare Metals 2007年第S1期26卷 94-98页

作者： HUANG Xiaoxiao1,2),WEN Guangwu1,3),LIU Ruitang2),and ZHENG Xin1)1) school of materials science and Technology,Harbin Institute of Technology,Harbin 150001,China 2) school of material science and Chemical engineering,Harbin engineering University,Harbin 150001,China 3) school of materials science and Technology,Harbin Institute of Technology at Weihai,Weihai 264209,China Harbin Inst Technol Sch Mat Sci & Technol Harbin 150001 Peoples R China Harbin Inst Technol Sch Mat Sci & Chem Engn Harbin 150001 Peoples R China Harbin Inst Technol Sch Mat Sci & Technol Weihai 264209 Peoples R China

The bending strengths of Al4SiC4 ceramics were investigated from room temperature to 1300 ℃ in air and in vacuum,*** is a novel property that the bending strength increases with increasing test temperatures up to 1300 ℃ in *** strength value of Al4SiC4 ceramics is 449.7 MPa at 1300 ℃ in air,which is about 1.5 times of that at room temperature(300 MPa).The self-healing behavior of the flaws on the specimen surface due to the oxidation of the surface layer of the Al4SiC4 ceramics is considered as the main enhancement mechanism at high temperatures.

关键词： calcination and hot pressing surface strength Al_4SiC_4

UV-Shielding and Catalytic Characteristics of Nanoscale Zinc-Cerium Oxides

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Journal of Wuhan University of Technology(materials science) 2007年第4期22卷 622-625页

作者：柴希娟 school of science and Interior Design Southwest Forestry University

Fine particles of zinc-cerium oxides （ZCO） used as an ultraviolet filter were prepared via combustion synthesis route. The catalytic activity, UV-shielding performance, surface modification and application of ZCO in polyester varnish were discussed in detail. The experimental results indicate that the photo-catalytic activity of ZCO is much smaller than these of ZnO and TiO2; the oxidation catalytic activity of ZCO is far lower than that of CeO2; the ZCO has shown excellent ultraviolet absorption in the range of UV; addition modified ZCO （MZCO） into polyester will enhance the UV-shielding capability of polyester.

关键词： nanoscale zinc-cerium oxides photo-catalysis oxidation catalysis UV-shielding ability surface modification

Influence of polymer on shrinkage and anti-cracking performance of mortar

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Rare Metals 2007年第S1期26卷 120-123页

作者： LI Jiahe1),OU Jinping2),and WANG Zheng1)1) school of material science and engineering,Harbin Institute of Technology,Harbin 150001,China 2) school of Civil engineering,Harbin Institute of Technology,Harbin 150001,China Harbin Inst Technol Sch Mat Sci & Engn Harbin 150001 Peoples R China Harbin Inst Technol Sch Civil Engn Harbin 150001 Peoples R China

A self-designed restrained ring test was applied to investigate cracking of *** cracking total weigh W and cracking control rate K were applied to evaluate anti-cracking performance of *** the above method,the influence of polymer on the shrinkage and anti-cracking performance was *** microstructures of mortar specimens were investigated by means of *** results indicated that the addition of polymer can efficiently reduce the shrinkage of mortar and improve the anti-cracking performance of mortar.

关键词： mortar shrinkage cracking anti-cracking

A priori error analysis of a discontinuous Galerkin approximation for a kind of compressible miscible displacement problems

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science China Mathematics 2010年第10期53卷 2679-2696页

作者： YANG JiMing1,& CHEN YanPing2 1College of science,Hunan Institute of engineering,Xiangtan 411104,China 2school of Mathematical sciences,South China Normal University,Guangzhou 510631,China 1. College of science Hunan Institute of Engineering Xiangtan 411104 China2. School of Mathematical Sciences South China Normal University Guangzhou 510631 China

A kind of compressible miscible displacement problems which include molecular diffusion and dispersion in porous media are investigated.A symmetric interior penalty discontinuous Galerkin (SIPG) method is applied to the coupled system of flow and *** the induction hypotheses instead of the cut-off operator and the interpolation projection properties,a priori hp error estimates are *** error bounds in L2(H1) norm for concentration and in L∞(L2) norm for velocity are optimal in h and suboptimal in p with a loss of power 1/2.

关键词： a priori error discontinuous Galerkin compressible miscible displacement coupled system

Fretting corrosion of surgical 316L stainless steel in saline solutions

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International Journal of Minerals,Metallurgy and materials 1997年第3期11卷 18-21页

作者： BAI Zhijun WU Yinshun ZHANG Tiancheng LIU Qiang (material science and engineering school, University of science and Technology Beijing, Beijing 100083, China)

A new simulation system for the laboratory investigation of fretting wear is developed. It consist of a mechanism device, a electrochemical cell and a datum acqulsition and process software. Fretting of surgical 316L stainlesssteel in saline is studied. The results show that electrochemical corrosion is enhanced by fretting and anodic currentdensity under fretting is 100 times than static condition. Fretting corrosion is a mechanic -elec trochemical al Process.

关键词： fretting system 316L sninless steel saline solution

Restrictive mechanism of flow control among non-cooperative Internet users

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science China(Information sciences) 2011年第1期54卷 12-22页

作者： TAO Jun1,2,ZHONG Xiao1,2 & LU YiFei1,2 1Key Laboratory of Computer Network and Information Integration,Southeast University, Ministry of Education,Nanjing 210096,China 2school of Computer science and engineering,Southeast University,Nanjing 210096,China 1. Key Laboratory of Computer Network and Information Integration Southeast University Ministry of Education Nanjing 210096 China2. School of Computer Science and Engineering Southeast University Nanjing 210096 China

The flow and congestion control methods based on one-shot game model with non-cooperative game theory can explain the non-cooperative behavior of Internet ***,the low effciency of equilibrium solutions affects their *** the behavior of flow and congestion control based on infinitely repeated game models is addressed;the repeated and infinitely repeated flow and congestion control game model is presented; the existence and optimization of the Nash equilibrium point are proved;the discount factor in repeated game is discussed;the punishment and threat strategy to users'misbehavior is studied in N-users infinitely flow control game;the punishment restrictive method of users'behavior is designed in infinitely and finitely games;finally,a flow control algorithm based on repeated game,FCAR,is provided based on the conclusions of repeated game *** results of experiment and simulation show that FCAR algorithm could regularize and restrict users' misbehavior *** algorithm can also make non-cooperative Internet users achieve cooperation in order to optimize the utility of the whole flow and congestion control system.

关键词： Nash equilibrium utility infinitely and finitely repeated game flow and congestion control

Thermochemical Evaluation of Combustion Synthesis of Al_2O_3/B_4C Composite

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International Journal of Minerals,Metallurgy and materials 1998年第2期12卷 90-92页

作者： Yonghe Liu~(1,2)) Sheng Yin~(1)) Weijing Zhang~(1)) Hoyi Lai~(1)) 1) materials science and engineering school, UST Beijing, Beijing 100083, China 2) school of materials science and engineering, Shandong University of Technology, Jinan 250014 materials science and engineering school UST Beijing Beijing 100083 China school of materials science and engineering Shandong University of Technology Jinan 250014 China

The equilibrium phase and adiabatic temperature for combustion synthesis of Al_2O_3/B_4C employing Al, B_2O_3 and C as starting materials is analyzed by both conventional and CALPHAD method. The adiabatic temperature calculed by CALPHAD method is significantly lower than that obtained by conventional method. The CALPHAD calculation also reveals that the equilibrium phases presented at the adiabatic temperature are different to the desired composites. The adiabatic temperature in this system can be lowered by introducing Al_2O_3 as diluents. The maximum amount of Al_2O_3 that can be added to the system while maintain a self-sustaining combusion mode is 1.3 mol.

关键词： thermochemical evaluation SHS Al_2O_3/B_4C composite

Dry Friction Characteristics of Ti-6Al-4V Alloy under High Sliding Velocity

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Journal of Wuhan University of Technology(materials science) 2007年第4期22卷 582-585页

作者：邱明 school of Mechatronic engineering Henan University of Science and Technology Theory of Lubrication and Bearing Institute Xi'an Jiaotong UniversityXi'an 710049China

Tribological behaviours of Ti-6Al-4V alloy pins sliding against GCr15 steel discs over a range of contact pressures （0.33-1.33 MPa） and sliding velocities （30-70 m/s） were investigated using a pin-on-disc tribometer under unlubricated conditions. The wear mechanisms and the wear transition were analyzed based on examinations of worn surfaces using SEM, EDS and XRD. When the velocity increases, the friction coefficient and the wear rate of the Ti-6Al-4V alloy show typical transition features, namely, the critical values of sliding velocities for 0.33 and 0.67 MPa are 60 and 40 m/s, respectively. The experimental results reveal that the tribological behaviours of Ti-6Al-4V alloys are controlled by the thermal-mechanical effects, which connects with the friction heat and hard particles of the pairs. A tribolayer containing mainly Ti oxides and V oxides is formed on the worn surface of Ti-6Al-4V alloy.

关键词： Ti alloy dry sliding friction behavior contact temperature wear mechanism

Effect of bond length and radius on superconducting transition temperature for FeAs-based superconductors

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science China(Physics,Mechanics & Astronomy) 2010年第1期53卷 59-63页

作者： CHEN Ning 1 , LIU Yang 1 , JIA YaKui 1 , QU ShaoPeng 1 , ZHANG WanJie 1 & LI Yang 2 1 school of material science and engineering, University of science and Technology Beijing, Beijing 100083, China 2 Department of engineering science and materials, University of Puerto Rico at Mayaguez, Mayaguez PR 00681-9044, USA 1. school of material science and engineering University of Science and Technology Beijing Beijing 100083 China2. Department of Engineering Science and Materials University of Puerto Rico at Mayaguez Mayaguez PR 00681-9044 USA

By comparing the data of lattice parameters of more than 50 new FeAs-based high temperature superconductors in two syetems, the effect of bondlength on superconducting transition temperature (T C ) was found that, for both FeAs superconductor systems with similar ionic radii of cation A, the bond length L As-A between Arsenic atom and its nearest neighbor cation at the A site is in an inverse proportion to T C , i.e. the larger the bond length L As-A , the lower the T C . In addition, we also found a noticeable effect of ionic radius on T C , in which deviation from the tendency line of bond length vs. T C decreases with the increasing ionic radius. Both bond length-T C and ionic radii-T C relations indicate that the interaction of cation A and As ion have significant effect on superconductivity. The analysis on the electronic structure indicates that there exists the proximity of the secondary-outer p-orbit of the cation A and the 4s orbit of the As ion, both in energy space and in real space. Some high frequency individual vibrating modes would be established through exchange coupling on their inner orbits. It is worth of mention that the superconducting condensation is influenced by the interaction between the cation A and the As atoms.

关键词： lattice constant FeAs-based superconductor superconducting transition temperature