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2011 International Conference on Chemical Engineering and advanced materials, CEAM 2011

作者： Wang, Tianguo Qin, Qun Zhang, Wenjun Department of Material Science and Engineering Hubei University of Automotive Technology Shiyan 442002 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology 122 Luoshi Road Wuhan 430070 China

ISBN: (纸本)9783037851197

WO3-based varistors doped with Y2O3 were prepared and the microstructure, nonlinear electrical properties, and dielectric properties were investigated. Breakdown voltages Eb of WO 3 doped with Y2O3 are lower than that of undoped WO3, indicating that the dopant can reduce the breakdown voltage. The dielectric constant of doped samples is higher than that of undoped samples, and the high dielectric constant makes them suitable as capacitor-varistor materials. It was found that the sample of WO3-0.5 mol% Y2O3 sintered at 1150 °C has an optimal nonlinear coefficient of 3.4 and a breakdown voltage of 17.1 V/mm. WO3 ceramic doped with Y2O3 is a new kind of low voltage capacitor-varistor material. © (2011) Trans Tech Publications, Switzerland.

关键词： Microstructure

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Wire extension with dual freedom PID control in pulsed MIG welding process of aluminum alloy

Wire extension with dual freedom PID control in pulsed MIG w...

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2011 2nd International Conference on Mechanic Automation and Control Engineering, MACE 2011

作者： Huang, Jiankang Fan, Jiawei Shi, Yu Lu, Lihui Shao, Ling Fan, Ding Key Lab. of Non-ferrous Metal Alloys and Processing under the Management for Ministry of Education Lanzhou University of Technology Lanzhou China State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials Lanzhou University of Technology Lanzhou China

ISBN: (纸本)9781424494392

Research work of wire extension control with Dual freedom PID controller in pulsed MIG welding process of aluminum alloy. In the condition of optimum parameters, the simulations were firstly completed by separately using Routine PID control and Dual freedom PID control, based on designing the wire speed of wire extension step response and gaining identification model. Based on the results of simulation using Matlab.Simulink, the experimental research on aluminum alloy pulsed MIG welding by using Dual freedom PID control was carried out in the real-time target environment with XPC Target. In the pulsed MIG welding process of aluminum alloy, the results prove that the Dual freedom PID control can bring higher precision and quicker response speed, efficiently control the stability of wire extension, and satisfy the stability of welding process. © 2011 IEEE.

关键词： Three term control systems

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Fabrication of translucent boron nitride dispersed polycrystalline silicon nitride ceramics

Fabrication of translucent boron nitride dispersed polycryst...

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International Symposium on Multifunctional Ceramic materials Based on Nanotechnology, ISMCN 2010

作者： Joshi, B. Fu, Z. Niihara, K. Lee, S.W. Department of Metallurgy and Material Engineering Sunmoon University Korea Republic of State Key Lab. of Advanced Technology for Material Synthesis and Processing Wuhan University of Technology China Nagaoka University of Technology Nagaoka Japan Department of Environment Engineering Sunmoon University Asan Korea Republic of

Optical transparency was achieved at infrared region and overall translucent silicon nitride was fabricated using hot press sintering (HPS). The increase in h-BN content decreased the optical transparency. Microstructral observations shows that the optical, mechanical and tribological properties of BN dispersed polycrystalline Si3N4 ceramics were affected by the density, α:β-phase ratio and content of h-BN in sintered ceramics. The hot pressed samples were prepared from the mixture of α-Si3N4, AlN, MgO and h-BN at 1850°C. The composite contained from 0.25 to 2 mass % BN powder with sintering aids (9% AlN + 3% MgO). Maximum transmittance of 57% was achieved for 0.25 mass % BN doped Si3N4 ceramics. Fracture toughness was increased and wear volume and friction coefficient were decreased with increase in BN content.

关键词： III-V semiconductors

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Operation characteristic of proton exchange membrane fuel cell under medium-pressure

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Huagong Xuebao/CIESC Journal 2012年第SUPPL.1期63卷 204-207页

作者： Liu, Jing Wan, Zhongmin Wan, Junhua Ding, Gangqiang Tu, Zhengkai Liu, Wei School of Information Engineering Hunan Institute of Science and Technology Yueyang 414006 Hunan China College of Chemistry and Chemical Engineering Huazhong University of Science and Technology Wuhan 430074 Hubei China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 Hubei China College of Energy and Power Engineering Huazhong University of Science and Technology Wuhan 430074 Hubei China

The operation characteristics of proton exchange membrane fuel cells with the channel width of 1mm and 2 mm under a medium-pressure are addressed, and the effect of temperature on the operation characteristic is investigated in detail. The results show that fuel cell with a 2 mm channel width can realize the long time operation in a closed-ended situation. The voltage of the 1mm width cell can drop from 0.7 V to 0.5 V in 3 min, while the 2 mm width cell can last for more than 53 min. Moreover, the temperature has a significant effect on the performance, the voltage of the 1 mm width cell can drop from 0.69 V to 0.5 V in less than 1.7 min. The resistance of the cell is increasing with the temperature, but the amplitude is smaller in high temperature.

关键词： Oxygen

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Preparation and Properties of Li-Mn-O-F Compounds as Cathode in Li-Ion Batteries

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MRS Online Proceedings Library (OPL) 2011年第1期755卷 DD6.25-DD6.25页

作者： Hanxing Liu Chen Hu Junlei Xia Shixi Zhao Shixi Ouyang State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 P.R. China

In present study LiMn2O4-xFx were prepared by the sol-gel method. X-ray diffraction (XRD) and scanning electron microscope (SEM ) were employed to detect the microstructure of the reaction products. It were found perfect crystal particles were obtained, and its' size were uniform in 1∼2 μ m. The specific capacity and cycleability were measured basing on battery program control test system. The results shown the substitution of F for O increased the specific capacity of the material at the cost of the cycleability due to more Mn3+ and less Mn4+ existed in the material. The exist of Mn3+ would reduce cycleability of cathode material due to the Jahn-Teller effect which were caused by the deformation of the crystal structure.

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synthesis of Single-Crystalline Silicon Nitride (α-Si 3 N 4 ) Nanowires with Controlled Diameters by Nitriding Cryomilled Nanocrystalline Silicon Powder

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MRS Online Proceedings Library 2011年第1期1279卷 1-9页

作者： Fei Chen Zhihao Wang Qiang Shen Zhixiong Huang Lianmeng Zhang Key Laboratory of Advanced Technology for Specially Functional Materials Ministry of Education Wuhan University of Technology Wuhan China State Key Lab of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan P. R. China

In the present work, silicon nitride nanowires (SNNWs) have been synthesized via nitriding cryomilled nanocrystalline silicon powder. The silicon powder exhibits a fine polycrystalline structure after the cryomilling process, with an average grain size of 25 to 125 nm at various cryomilling times. The SNNWs that form after the nitridation of the cryomilled silicon powder exhibit single crystal structure and are 20 to 100 nm in diameter and ∼10 µm in length. The diameter of the nanowires is in agreement with the grain size of the cryomilled Si powder. Microstructural characterization reveals that the as-synthesized nanowires have a hexagonal structure and their primary growth direction is along the [0001] direction. The formation of the Si–N–Si bond during the cryomilling process, as investigated theoretically with density functional theory, promotes the subsequent synthesis of the α-Si3N4 nanowires. The mechanism for nanowire formation appears to be a vapor-solid (VS) reaction.

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The Interactions between SBT and Transition Metal Studied by DV-Xa Method

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MRS Online Proceedings Library (OPL) 2011年第1期747卷 V3.10-V3.10页

作者： Hanxing Liu Xinmin Min Xiaoqin Sun Jing Xiao Shixi Ouyang State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Luoshi Road 122 Wuhan 430070 PR. China

In the present study electronic structures of the interface between SBT and transition metal including Au, Ag, Cu, Ni, Pt were studied by employing DV-Xα method. The calculations were performed on cluster models of the interface which were SrTa8O36-M2 (M=Au, Ag, Cu, Ni, Pt, and Bi). The calculations results including Fermi level, bond order, atomic charge distribution shown that there existed significant hybridization between metal d states and the O2p–Ta3d states. The Fermi levels of the metals located in the gap of SBT and metal-induced states, and the position of the Fermi levels did not change greatly due to the different transition metals. The charge of Sr and the transition metal atom transferred to oxygen atom, so that the bonding between Sr (or metal atom) and O was almost ionic bonding. The interactions between transition metal and SBT mainly came from the Coulomb interaction.

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Experimental and numerical investigations into extrusion to produce thin-walled seamless tubes for vascular stents

Experimental and numerical investigations into extrusion to ...

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10th International Conference on technology of Plasticity, ICTP 2011

作者： Fang, G. Ai, W.-J. Leeflang, M.A. Zhou, J. Duszczyk, J. Department of Mechanical Engineering Tsinghua University Beijing China Key Lab. of Advanced Materials Processing Ministry of Education Beijing China Department of Biomechanical Engineering Delft University of Technology Delft Netherlands

ISBN: (纸本)9783514007840

The present research aimed to develop the indirect extrusion technology for thin-walled seamless tubing made of a magnesium alloy with an outside diameter of 3.0 mm and a wall thickness of 0.2 mm so that the tubing would meet geometrical and structural requirements for further processing into biodegradable coronary stents. Numerical simulations of the indirect extrusion process were performed using DEFORM 2D to investigate the material flow, extrusion force, temperature distribution and velocity distribution during extrusion with a set of tooling and the influence of stem speed on the billet temperature variation and extrusion force during the process. The billet material was subjected for compression tests to obtain rigid-viscoplastic constitutive parameters. The extrusion die and the other tooling were assumed to fit in a rigid material model with thermal effects incorporated. Experiments were carried out using a special extrusion press to verify the results obtained from the simulations in terms of the peak extrusion force and tube dimensions. The microstructure of the extruded tube on the cross section was examined. Recrystallized grains were found to be uniformly distributed from the inner part to the outer part of the tube, as required for subsequent processing. © 2011 IBF (RWTH Aachen) & IUL (TU Dortmund).

关键词： Extrusion

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The research on RSS filter for indoor positioning system based on wireless LANs

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Advances in Information Sciences and Service Sciences 2011年第4期3卷 1-9页

作者： Ren, Gao Yongxiang, Zhao Long, Tang School of Electronic Information of Wuhan University Hubei University of Economics State Key Lab of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan University

Recently, indoor positioning technology based on received signal strength in wireless networks are becoming more and more attractive. In this paper, we firstly introduced the experimental testbed in a typical office building. Then, we proposed the mechanism to improve the positioning accuracy by using five different filtering methods because of harsh multi-path environment and all kinds of disturbance in indoor areas. Thirdly, the experimental parameters of five filtering methods, called Limit Filter, Threshold Filter, Max Filter, MA Filter and Kalman Filter, were optimized and analyzed. Finally, we summarized the five filtering methods, and compared the performance of Limit Filter, Threshold Filter and Max Filter in detail. Experimental results demonstrated that the proposed Limit Filter andThreshold Filter can increase the accuracy in 3 meters of 91% to 98%.

关键词： Kalman filters

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Electron transportation and recombination in TiO2film for flexible dye-sensitized solar cell

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key Engineering materials 2011年 451卷 123-133页

作者： Lin, Hong Zhao, Xiaochong Liu, Yizhu Li, Xin Li, Jianbao State Key Lab. of New Ceramics and Fine Processing Department of Material Science and Engineering Tsinghua University Beijing 100084 China Pen-Tung Sah Micro-Nano Technology Research Center Xiamen University Xiamen 361005 Fujian China Key Lab. for Si-Zr-Ti Resource of Hainan Province School of Materials and Chemical Engineering Haidan University Haikou 570228 China

ISBN: (纸本)9780878492473

Research on the flexible dye-sensitized solar cells (DSCs) has been more and more extensively conducted during the recent years both academically and comercially for the sake of its further reduced expense and even broader application. However, significant promotion of electron transport properties and consequently the photovoltaic performances of such devices are perpetually hindered by the key problem that the poor heat tolerance of the plastic substrates employed in flexible DSCs makes high-temperature sintering of the photoanode films impossible. Based on a brief overview of the current state of research on flexible DSCs, including new materials and delicate processing techniques, and the research results from the author's own group, this chapter specially treats the profound mechanistic issue of electron transport and recombination in flexible DSCs, which is rarely discussed and relatively less well understood up to now. It is pointed out that the electron transport and recombination dominate photovoltaic performance of the flexible DSCs and suppressing the recombination of injected electrons with electrolyte redox species is of crucial sense for performance promotion. Besides, the methods for restraining electron recombination are proposed and the developing trend and prospects of flexible DSCs are also presented© 2011 Trans Tech Publications, Switzerland.

关键词： Electron transport properties

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