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Thermoelastic properties of sandwich materials with pin-reinforced foam cores

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Science china(Technological Sciences) 2008年第12期51卷 2059-2074页

作者： LU TianJian1,LIU Tao2,3 & DENG ZiChen2,4 1 MOE key laboratory of Strength and Vibration,School of Aerospace,xi’an jiaotong university,xi’an 710049,china 2 Department of engineering Mechanics,Northwestern Polytechnical university,xi’an 710072,china 3 Department of engineering,university of Cambridge,Cambridge CB2 1PZ,UK 4 state key laboratory of Structural Analysis of Industrial Equipment,Dalian university of Technology,Dalian 116024,china MOE key laboratory of Strength and Vibration School of Aerospace Xi’an Jiaotong University Xi’an 710049 China Department of engineering Mechanics Northwestern Polytechnical University Xi’an 710072 China Department of engineering University of Cambridge Cambridge CB2 1PZ UK state key laboratory of Structural Analysis of Industrial Equipment Dalian University of Technology Dalian 116024 China

Pin-reinforced foam is a novel type of sandwich core materials formed by inserting pins(trusses) into a foam matrix to create a truss-like network reinforced foam *** loading,the pins deform predominantly by local stretching whilst the deformation of foam is governed by local *** paper presents a theoretical study on the thermoelasticity of pin-reinforced foam sandwich *** calculate the effective thermoelastic properties of pin-reinforced foam cores,the energy-based homogenization approach is employed to develop a micromechanics-based model,calibrated by the existing experimental *** is found that the stiffness of the sandwich core is mainly governed by pin reinforcements:the foam matrix contributes little to sandwich *** with traditional foam cores without pin reinforcements,the changes in inplane thermal expansion coefficients are not vigorous as a result of pin reinforcements,while the through-thickness thermal expansion coefficient changes *** is also demonstrated that it is possible to design materials with zero or negative thermal expansion coefficients under such a context.

关键词： sandwich panel pin reinforcement analytical solutions homogenization thermoelasticity thermal expansion

Liquid mean velocity and turbulence in a horizontal air-water bubbly flow

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Nuclear Science and Techniques 2003年第2期14卷 149-152页

作者： YANG Jian, ZHANG Ming-Yuan, ZHANG Chao-Jie, SU Yu-Liang (The state key Lab of multiphase flow in power engineering, xi ’an jiaotong university, xi ’an 710049) xi'an jiaotong university The State Key Lab of Multiphase Flow in Power Engineering Xi'an 710049

The liquid phase turbulent structure of an air-water bubbly horizontal flow in a circular pipe has been investigated experimentally. Three-dimensional measurements were implemented with two "X" type probes oriented in different planes, and local liquid-phase velocities and turbulent stresses were simultaneously obtained. Systematic measurements were conducted covering a range of local void fraction from 0 to 11.7%. The important experiment results and parametric trends are summarized and discussed.

关键词：湍流气泡流液体速度热膜风速测定法

Preparation and Properties of Macroporous Silicon Nitride Ceramics by Gelcasting and Carbonthermal Reaction

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Journal of Materials Science & Technology 2005年第6期21卷 894-898页

作者： Wen ZHANG, Hongjie WANG+ and Zhihao JIN state key laboratory for Mechanical Behavior of Materials, School of Materials Science and engineering, xi’an jiaotonguniversity, xi’an 710049, china state key laboratory for Mechanical Behavior of Materials School of Materials Science and Engineering Xi'an Jiaotong University Xi'an 710049 China

Macroporous silicon nitride （Si3N4） ceramics with high strength, uniform structure and relatively high porosity were obtained by gelcasting and carbonthermal reaction in a two-step sintering technique. Microstructure and composition were investigated by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD）. Open porosity, pore size distribution and basic mechanical performance were measured by Archimedes method, mercury intrusion porosimetry and three-point bending methods, respectively. SEM and TEM results revealed that pores were formed by elongated β-Si3N4. SADP measurement proved the formation of SiC particles. The SiC granules were beneficial for the formation of high ratio elongated β-Si3N4, and at proper amount, they also acted as reinforcement phase. Thermodynamic analysis indicated that the mechanisms of the reactions were mainly associated with liquid-solid reaction and gas-liquid reaction.

关键词： Ceramics Silicon nitride Silicon carbide X-ray diffraction

Microstructure and Mechanical Properties of Nanocrystalline Tungsten Thin Films

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Journal of Materials Science & Technology 2010年第1期26卷 87-92页

作者： H.L. Sun, Z.X. Song, D.G. Guo, F. Ma and K.W. Xu state key laboratory for Mechanical Behavior of Materials, School of Materials Science and engineering, xi an jiaotong university, xi’an 710049, china [a] state key laboratory for Mechanical Behavior of Materials School of Materials Science and engineering xi'an jiaotong university xi'an 710049 china

Tungsten （W） thin films were prepared by magnetron sputtering onto Si （100） substrates. Their microstructures were characterized by X-ray diffraction （XRD）, field emission scanning electron microscopy （FE-SEM） and transmission electron microscopy （TEM）. The hardness and modulus were evaluated by nanoindentation. It is found that a 30 nm Cr sticking layer induces structure changes of deposited W film from β-W to α-W structure. In addition, remarkable hardness enhancement both for the deposited and annealed W films, were compared with that of bulk coarse-grained W, although their nanoindentation modulus is very close to that of corresponding bulk W. The intrinsic reasons that lead to structure changes and super hardness are discussed.

关键词： Tungsten film Microstructure Nanoindentation Hardness Modulus

Thermodynamic Analysis of the Formation of In-situ Reinforced Phases In Cast Al-4.5Cu Alloy

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Journal of Wuhan university of Technology(Materials Science) 2008年第3期23卷 342-345页

作者：梁艳峰 state key laboratory for Mechanical Behavior of Materials School of Materials EngineeringXi’an Jiaotong University School of Materials&Chemical engineering Xi’an Technological UniversityXi'an 710032China

The thermodynamic analysis of the formation of in-situ reinforced phases in （TiB2＋Al3Ti）/Al-4.5Cu composites prepared by mixed salts reaction was conducted, and heat changes of mixed salts system were analyzed by differential thermal analysis（DTA）.The results show that although TiB2 possesses the strongest formation ability in Al-Ti-B ternary system, [Ti] is relatively excessive in the in-situ reaction and it combines with Al to form AlaTi phase. The reinforced phases are TiB2 and AlaTi in the produced composites due to the reaction taking place to form reinforced phase with the addition of mixed salts into Al-4.5Cu melt between 900 ℃ and 1 032 ℃.

关键词： in-situ composites thermodynamic, TiB2 Al3Ti

可膨胀过热水系统多气核演化过程与临界过热度分析

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物理学报 2009年第11期58卷 7596-7602页

作者：厉思杰白博峰西安交通大学动力工程多相流国家重点实验室西安710049

使用分子动力学方法,研究过热水系统均质沸腾核化过程.采用Langevin动力学方法控制体积可变系统的温度与压力,更好地模拟了沸腾实际物理过程.得到了液相系统体积连续膨胀、分子间距逐渐增大,最终稳定在汽相的现象学规律.当过热温度较高... 详细信息

使用分子动力学方法,研究过热水系统均质沸腾核化过程.采用Langevin动力学方法控制体积可变系统的温度与压力,更好地模拟了沸腾实际物理过程.得到了液相系统体积连续膨胀、分子间距逐渐增大,最终稳定在汽相的现象学规律.当过热温度较高时,亚稳态液相系统可能在局部形成不同大小的近球形区域:气核,这些气核是不稳定的,处于不断演化之中.通过分析分子所受引力与斥力的共同作用,得到了气核形成与消亡以及多个气核融合的机理.比较了模拟结果与经典沸腾理论的差异,提出了气核生长是比气泡生长更为微观过程的认识.通过研究不同过热度系统,得到了模拟条件下水的均质沸腾临界过热温度为535K左右,在已有的实验结果范围内.

关键词：过热水系统分子动力学气核临界过热度

Cyclic-delay time-reversal space-time block codes for single-carrier transmission with frequency-domain decision-feedback equalization

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Science china(Information Sciences) 2011年第9期54卷 1905-1915页

作者： FENG Ang,YIN QinYe & WANG HuiMing MOE key laboratory for Intelligent Networks and Network Security,xi’an jiaotong university,xi’an 710049,china 1. MOE key laboratory for Intelligent Networks and Network Security Xi’an Jiaotong University Xi’an 710049 China

Transmit diversity is an important multiple-input multiple-output (MIMO) approach to improve the transmission reliability;however,it is usually designed with maximum-likelihood *** this paper,we investigate a simple transceiver structure for single-carrier MIMO systems,in which the cyclic-delay time-reversal space-time block code (CDTR-STBC) is employed at the transmitter,and the frequency-domain decision-feedback equalization (FD-DFE) is used at the *** separate the transmit antennas into two groups,and then,encode the groups by STBC and cyclically delay the data streams within each *** processing can mitigate the impact of error-propagation and reduce the signal-to-noise ratio (SNR) loss when FD-DFE is employed,in which SNR is defined as the ratio of the received signal power over the noise power at each receive *** support our proposal,this paper also provides the performance analysis of *** is shown that the proposed scheme can achieve full diversity and full transmission rate for a MIMO system employing arbitrary ***,it has considerable performance improvement over the existing schemes.

关键词： single-carrier frequency-domain equalization cyclic delay space-time block code diversity order

Apical-dominant particle swarm optimization

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Progress in Natural Science:Materials International 2008年第12期18卷 1577-1582页

作者： Zhihua Cui~(a,b) xingjuan Cai~b Jianchao Zeng~b Guoji Sun~a a state key laboratory for Manufacturing Systems engineering,xi’an jiaotong university,xi’an 710049,china b Division of System Simulation and Computer Application,Taiyuan university of Science and Technology,Taiyuan 030024,china [a]state key laboratory for Manufacturing Systems engineering Xi’an Jiaotong University Xi’an 710049 China [b]Division of System Simulation and Computer Application Taiyuan University of Science and Technology Taiyuan 030024 China

Particle swarm optimization (PSO) is a new stochastic population-based search methodology by simulating the animal social behaviors such as birds flocking and fish *** improvements have been proposed within the framework of this biological assumption. However,in this paper,the search pattern of PSO is used to model the branch growth process of natural *** provides a different poten- tial manner from artificial *** illustrate the effectiveness of this new model,apical dominance phenomenon is introduced to construct a ncvel variant by emphasizing the influence of the *** this improvement,the population is divided into three different kinds of buds associated with their ***,a mutation strategy is applied to enhance the ability escaping from a local ***- ulation results demonstrate good performance of the new method when solving high-dimensional multi-modal problems.

关键词： Apical-dominance phenomenon Particle swarm optimization Branch growth model High-dimensional multi-modal benchmarks

A mixed-coordination electron trapping-enabled high-precision touch-sensitive screen for wearable devices

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Bio-Design and Manufacturing 2024年第4期7卷 413-427页

作者： xi Zhang Junchi Ma Hualin Deng Jinming Zhong Kaichen Xu Qiang Wu Bo Wen Dongfeng Diao Guangdong Provincial key laboratory of Micro/Nano Optomechatronics engineering College of Mechatronics and Control EngineeringShenzhen UniversityShenzhen 518060China state key laboratory of Fluid power and Mechatronic Systems School of Mechanical EngineeringZhejiang UniversityHangzhou 310058China Shenzhen university General Hospital Shenzhen 518055China Research Center of Medical Plasma Technology Shenzhen UniversityShenzhen 518060China

Touch-sensitive screens are crucial components of wearable *** such as reduced graphene oxide(rGO),carbon nanotubes(CNTs),and graphene offer promising solutions for flexible touch-sensitive ***,when stacked with flexible substrates to form multilayered capacitive touching sensors,these materials often suffer from substrate delamination in response to deformation;this is due to the materials having different Young’s modulus *** results in failure to offer accurate touch screen *** this work,we demonstrate an induced charge-based mutual capacitive touching sensor capable of high-precision touch *** is enabled by electron trapping and polarization effects related to mixed-coordinated bonding between copper nanoparticles and vertically grown graphene ***,we used an electron cyclotron resonance system to directly fabricate graphene-metal nanofilms(GMNFs)using carbon and copper,which are firmly adhered to flexible *** being subjected to 3000 bending actions,we observed almost no change in touch *** screen interaction system,which has a signal-to-noise ratio of 41.16 dB and resolution of 650 dpi,was tested using a handwritten Chinese character recognition trial and achieved an accuracy of 94.82%.Taken together,these results show the promise of touch-sensitive screens that use directly fabricated GMNFs for wearable devices.

关键词： Flexible touch-sensitive screen Graphene-metal nanofilms Mixed coordination Wearable device