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Study on Tribological Properties of Irradiated Crosslinking UHMWPE Nano-Composite

Journal of Bionic engineering 2009年第1期6卷 7-13页

作者： Lei Xiong, Dang-sheng Xiong, Jia-bo JinDepartment of materials science and engineering, nanjing university of science and technology, nanjing 210094, P. R. china [a]Department of materials science and engineering Nanjing University of Science and Technology Nanjing 210094 P. R. China

Ultra High Molecular Weight Polyethylene(UHMWPE)has been widely used as a bearing material for artificial joint replacement over forty *** is usually crosslinked by gamma rays irradiation before its implantation into human *** this study,UHMWPE and UHMWPE/nano-hydroxyapatite(n-HA)composite were prepared by vacuum hot-pressing *** prepared materials were irradiated by gamma rays in vacuum and molten heat treated in vacuum just after *** effect of filling n-HA with gamma irradiation on tribological properties of UHMWPE was investigated by using friction and wear experimental machine(model MM-200)under deionized water ***-morphology of worn surface was observed by metallographic *** angle and hardness of the materials were also *** results show that contact angle and hardness are changed by filling n-HA and gamma *** coefficient and wear rate under deionized water lubrication are reduced by filling *** friction coefficient is increased and wear rate is reduced significantly by gamma *** worn surface of unfilled material is mainly characterized as adhesive wear and abrasive wear,and that of n-HA filled material is mainly characterized as abrasive *** gamma irradiation,the degrees of adhesive and abrasive wear for unfilled material and abrasive wear of n-HA filled material are significantly *** and filled materials after irradiation are mainly shown as slight fatigue *** results indicate that UHMWPE and UHMWPE/n-HA irradiated at the dose of 150 kGy can be used as bearing materials in artificial joints for its excellent wear resistance compared to original UHMWPE.

关键词： tribological properties irradiated crosslinking UHMWPE n-HA artificial joints

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The Synthetic Evaluation of Warhead Overall Efficiency

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Journal of Systems engineering and Electronics 2003年第1期14卷 12-17页

作者： Gu Xiaohui & Cao Bing college of Mechanics, nanjing university of science & technology, nanjing 210094, P. R. china college of Mechanics Nanjing University of Science & Technology Nanjmg 210094 P. R. China

The evaluation system of smart ammunition warhead overall efficiency has been established in this paper. Allkinds of evaluation methods have been analyzed. Having led the concept of hierarchical structure into technique for orderpreference by similarity to ideal solution (TOPSIS) method, we put forward the step TOPSIS method which is suitable forevaluating the overall efficiency of smart ammunition warheads. In the calculation of index weight, the graded weight cal-culus is put forward which hardly relies on the subjectivity of decision-makers and can reflect the sensitivity and compatibili-ty of the index. In the graded weight calculation, the proportional-arithmetic weight value calculus and sensitivity-compati-bility weight value calculus are given respectively.

关键词： Step analysis TOPSIS method Warhead Efficiency evaluation.

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Preparation and Properties of Crystallizable Glass/Al_2O_3 Composites for LTCC material

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Journal of Wuhan university of technology(materials science) 2011年第6期26卷 1174-1178页

作者：邵辉周洪庆 college of materials science and engineering Nanjing University of Technology

The investigated low temperature Co fired ceramics（LTCC） composite of 60wt% CaO-Al2O3-B2O3-SiO2 glass and 40wt% α-Al2O3 as a filler is a non-reactive system, which is a critical part of the low temperature Co fired ceramics process. Through a study on densification process, the phase transformation and microstructure can be revealed. Its composites typically consist of CaO-Al2O3-B2O3-SiO2 glass and α-Al2O3 powders of average particle size （D50=3.49 mm）. The sintering behavior, phase evaluation, sintered morphology, and microwave dielectric properties were investigated. In the fire range of 800 to 900 ℃, the composites were crystallized after completion of densification. It is found that the composites start to densify at 825 ℃, simultaneously, the dielectric constant （εr） reaches its maximum. With increasing heat-treatment temperatures, due to the loose microstructure of the material, tanδ increases slightly. The last of the sintered samples were identified as partly Anorthite at 850 ℃. At that temperature it has εr of 7.9 and tanδ less than 1×10-3, and can be used as a promising LTCC material.

关键词： glass-ceramics densification precipitation LTCC materials

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Sufficient and necessary conditions for Lyapunov stability of Lorenz system and their application

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science china(Information sciences) 2010年第8期53卷 1574-1583页

作者： LUO Qi 1 , LIAO XiaoXin 2 & ZENG ZhiGang 2 1 college of Information and Control, nanjing university of Information science and technology, nanjing 210044, china 2 Department of Control science and engineering, Huazhong university of science and technology, Image Processing and Intelligent Control Key Laboratory of Education Ministry of china, Wuhan 430074, china 1. college of Information and Control Nanjing University of Information Science and Technology Nanjing 210044 China2. Department of Control Science and Engineering Huazhong University of Science and Technology Image Processing and Intelligent Control Key Laboratory of Education Ministry of China Wuhan 430074 China

The sufficient and necessary conditions for Lyapunov stability of the zero equilibrium point of Lorenz system are discussed, and some brief criteria are presented for globally exponential stability, globally asymptotical stability and instability. Furthermore, the behavior of the non-zero equilibrium point of Lorenz system is also investigated, and several sufficient and necessary conditions are provided for locally exponential stability and instability. The established theorems in this paper develop and extend the existing achievements on Lyapunov stability of Lorenz system. In conclusion, by applying the obtained results, some less conservative feedback-control laws are derived to guarantee the globally exponential stability of the chaos control of Chen system, Lu¨ system, Yang-Chen system and Yu-Xia Li system.

关键词： Lorenz system Lyapunov stability sufficient and necessary condition bifurcation values globally exponential synchronization

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Alkali-silica Reactivity of Different Aggregates from Mineral and Textural Characteristics

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Journal of Wuhan university of technology(materials science) 2008年第6期23卷 901-906页

作者：莫祥银 Analysis and Testing Center & Jiangsu Key Laboratory of Biofunctional materials Nanjing Normal University

To identify the aggregates causing the alkali-silica reaction, and the reactivity of rocks in different parts of china, the mineral and texture characteristics of some typical coarse ag gregates and the alkali reactivity of these aggregates were systematically investigated. On one hand, petrographic examination of aggregates, combined with X-ray diffraction analysis, chemical analysis, scanning electron microscopy, was conducted for analyzing their mineralogy and texture. It was found that not only mineral characteristics, but also their interior structure would affect their potential alkali-silica reactivity. Furthermore, the alkali-silica reactivity of aggregates is due to their mineral compositions, such as containing different alkali-reactive minerals, while, different stuctures of those aggregates with similar minerals affect their reactivity to some extent. There are some amount of micro-aperture and cracks across the quartz in the aggregate, which may become the natural accesses for Na^＋, K^＋, and OH^- ions to intrude in the mortar or concrete during the process of alkali-silica reaction. Alkali-silica reactivity of the aggregates was detected by the accelerated mortar bars test. It was revealed that all the aggregates tested were alkali-silica reactive and the results were also in accordance with their mineral and structure analysis.

关键词： petrographic examination of aggregates study of thin sections x-ray diffraction analysis chemical analysis scanning electron microscopy

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Mechanical behaviors of alumina ceramics doped with rare-earth oxides

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Rare Metals 2010年第5期29卷 456-459页

作者： YAO Yijun LI Chuncheng WANG Ling JIANG Xiaolong QIU Tai School of Mathematics and Physics Nanjing University of Information Science & Technology Nanjing 210044 China college of materials science and engineering Nanjing University of Technology Nanjing 210009 China

The effects of three types of additives Y2O3, La2O3, and Sm2O3 on the sintering and mechanical behaviors of alumina ceramics were investigated. The bending strengths of alumina ceramics with Sm2O3 and Y2O3 additions were 455 and 439 MPa, respectively, higher than that with La2O3 addition. The fi＇acture toughness of the ceramics with Sm2O3 and Y2O3 were also higher than that with La2O3 addition. The fracture mode of rare earth oxides doped alumina ceramics exhibited obvious transgranular fractures as well as intergranular fracture. The results of research show that the improvement of bending strength and fracture toughness of alumina ceramics with rare earth oxides was achieved by refining the grain size and strengthening the grain boundary.

关键词： rare earths alumina doping mechanical properties microstructure

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Activity and Structure of Calcined Coal Gangue

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Journal of Wuhan university of technology(materials science) 2007年第4期22卷 749-753页

作者：宫晨琛李东旭 college of materials science and engineering Nanjing University of Technology

Coal gangue was activated by means of calcination in seven temperature ranges. Systematic research was made about activation mechanism and structural evolution. Glycerin-ethanol method, SEM, M1P and XRD were used to determine the variation of structure and activation of coal gangue during the calcination. The experimental results show that because of heat treatment in the range of calcination temperature, mineral composition and microstructure of coal gangue are changed. In addition, its activity is improved evidently. The amount of lime absorbed by the sample calcined at 700 ℃ is 2-4 times that by uncalcined coal gangue in the course of hydration. When NaOH is added to coal gangue-lime system, hydration reaction of the system is sped up and the microstructure of hydrating samples of coal gangue is improved.

关键词： coal gangue calcination activation

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Low-complexity distributed differential spacetime coding scheme for amplify-and-forward cooperative networks

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science in china(Series F) 2009年第8期52卷 1418-1427页

作者： YU XiangBin1,2, BI GuangGuo3 & XU WeiYe4 1 college of Information science and technology, nanjing university of Aeronautics and Astronautics, nanjing 210016, china 2 Department of Electronic engineering, City university of Hong Kong, Hong Kong, china 3 National Mobile Communications Research Laboratory, Southeast university, nanjing 210096, china 4 Department of Communication engineering, nanjing Institute of technology, nanjing 211167, china college of Information science and technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Department of Electronic engineering City University of Hong Kong Hong Kong China National Mobile Communications Research Laboratory Southeast University Nanjing 210096 China Department of Communication engineering Nanjing Institute of Technology Nanjing 211167 China

By introducing a space-time coding scheme based on amicable orthogonality, we develop a distributed differential space-time coding scheme with the amplify-and-forward （AF） method for wireless cooperative networks. The scheme requires no knowledge of the channel state information at both transmitters and receivers, and effectively decreases the realization complexity due to no channel estimation. Moreover, it has lower decoding complexity and higher coding advantage than the existing scheme, thus avoiding the shortcoming of exponential decoding complexity of some existing schemes. According to the pairwise error probability （PEP） analysis of the system, the power allocations of source and relay terminals are jointly optimized, and as a result, the PEP is minimized, which will provide a helpful guideline for system design. Numerical calculation and simulation results show that the developed scheme is superior to the existing scheme. Moreover, the scheme with optimal power allocation yields obvious performance improvement over that with equal power allocation.

关键词： differential space-time coding cooperative communication amplify-and-forward method power allocation

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Tribological Properties of Dimpled Surface Alloying Layer on Carbon Steel

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Journal of Wuhan university of technology(materials science) 2009年第2期24卷 218-222页

作者：万轶 Department of materials science & engineering Nanjing University of Science and Technology Department of Mechanical and Electrical engineering Yingtian College

The effect of surface structure and coating on tribological properties of 45^# carbon steel disc was analyzed. A Nd：YAG laser was used to generate rnicrodirnples on steel surfaces. Dimples with diameter of 150 rn and depth of 50 rn were distributed in an orbicular array on disc surface. Then the alloying element Mo was sputtered to 45# carbon steel disc surface by means of double glow plasma technology. Diffusion Mo alloying layer with 30min thickness and high hardness up to 0.025 was formed on the disc surface. Tribological experiments of three types samples （smooth, texturing and texturing＋alloying） were conducted with a pin-on-disc tribometer. It is found that the dimpled-samples are most effective for reducing friction in comparison with smooth steel surthces, improving the lubricating state from boundary to hydrodynamic region.

关键词： laser surface texturing double glow plasma surface alloying technology carbon steel tribological performance lubricating state

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Investigation on the temperature-dependence of absorption properties of solar cells with micro-structured surfaces

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science china(Technological sciences) 2010年第8期53卷 2304-2310页

作者： YANG LiLi,XUAN YiMin ,HAN YuGe&TAN JunJie School of Power engineering,nanjing university of science&technology,nanjing 210094,china 1. School of Power engineering Nanjing University of Science & Technology Nanjing 210094 China

The temperature of a solar cell will increase when it is exposed to the sunlight,which results in variations of optical parameters and thermal expansion coefficient of the cell,thus affecting its spectral absorption *** paper is aimed to investigate the effects of temperature on the absorption property of solar cells with micro-structured *** taking hemispherical, cylindrical and spherical surfaces as models,numerical computation is conducted to obtain spectral distribution of absorptance of such surfaces with different structural parameters by means of the finite difference time domain(FDTD)***,the effects of material properties and structural period on the absorption property are also investigated.

关键词： temperature dielectric function thermal expansion coefficient absorption property

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