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Effect of Pressure on Minimum Fluidization Velocity

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Journal of Thermal Science 2007年第3期16卷 264-269页

作者： Zhu Zhiping na Yongjie Lu Qinggang Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100080 Graduate School of the Chinese Academy of Science Beijing 100080

Minimum fluidization velocity of quartz sand and glass bead under different pressures of 0.5, 1.0, 1.5 and 2.0 MPa were investigated. The minimum fluidization velocity decreases with the increasing of pressure. The influence of pressure to the minimum fluidization velocities is stronger for larger particles than for smaller ones. Based on the test results and Ergun equation, an experience equation of minimum fluidization velocity is proposed and the calculation results are comparable to other researchers＇ results.

关键词： minimum fluidization velocity pressure Ergun equation

Microstructural Evolution of 6061 Alloy during Isothermal Heat Treatment

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Journal of Materials Science & Technology 2011年第1期27卷 8-14页

作者： na Wang Zhimin Zhou Guimin Lu School of Sciences Northeastern University Shenyang 110004 China School of Resources and Environmental Engineering East China University of Science and Technology Shanghai 200237 China

The semi-solid billet of 6061 aluminum alloy was prepared by the near-liquidus semi-continuous casting（LSC） with rosette or near-spheroide *** pre-deformation processing was applied before partial remelting to further improve the microstructure and properties of the semi-solid *** effects of different processing parameters,such as holding temperature and holding time,on the semisolid microstructures during partial remelting have been *** was found that the optimal partial remelting parameters should be 630℃ and 10-15 min for 6061 alloy cold rolled with 60% reduction in height of *** coarsening rates were anasysed by Lifshitz-Slyozov-Wagner（LSW） *** pre-deformed 6061 alloy exhibits lower coarsening rate constants than that of the as-cast one,and also lower than other alloys processed by different method found in previous *** is because the coarsening rate is associated with the initial microstructure and composition of the *** secondary phases in the alloy inhibit the migration of the liquid film grain *** microstructure obtained by using the combination of near-liquidus semicontinuous casting and pre-deformation treatment is better than that without pre-deformation processing,which demonstrates that the used method is promising for fabricating high quality semi-solid alloys.

关键词： Semi-solid forming Near-liquidus semi-continuous casting 6061 alloy Pre-deformation Partial remelting Coarsening

QoE-driven resource allocation for mobile IP services in wireless network

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Science China(Information Sciences) 2015年第1期58卷 222-231页

作者： FEI ZeSong XING ChengWen LI na School of Information Science and Engineering Beijing Institute of Technology

In this study, quality of experience(QoE)-driven resource allocation for multi-applications in Internet Protocol(IP)-based wireless networks is studied. Considering that the mean opinion score(MOS) summation maximization problem is not fair to satisfy heterogeneous users' QoE with various mobile applications, we apply multi-objective optimization method to maximize each user's MOS utility. At the beginning of this work, the relationship between MOS utility and user transmission rate for three multimedia applications, that is, File Download, Internet Protocol Television, and Voice over Internet Protocol are discussed. However, the relations under diverse evaluation models are quite different and users in various mobile applications have different requirements, which make the optimization problem difficult to solve. To meet each user's minimum rate requirement,the idea of nash bargaining solution is applied in the Hungarian-based subcarrier assignment problem. Then to simplify the power allocation problem, the concept of equivalent channel is introduced. Further by applying the tolerance membership function, we develop a fuzzy Max-Min decision model for generating an optimal power allocation solution. Simulation results demonstrate the satisfying characteristics of the proposed algorithm in terms of MOS utility and average data rate.

关键词： quality of experience mean opinion score tolerance membership function fuzziness multi-objective optimization

Abrasive Waterjet Machining Simulation by Coupling Smoothed Particle Hydrodynamics /Finite Element Method

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Chinese Journal of Mechanical Engineering 2010年第5期23卷 568-573页

作者： WANG Jianming GAO na GONG Wenjun School of Mechanical Engineering Shandong University Jinan 250061 China Key Laboratory of High Efficiency and Clean Mechanical Manufacture of Ministry of Education Shandong University Jinan 250061 China

In dealing with abrasive waterjet machining（AWJM） simulation,most literatures apply finite element method（FEM） to build pure waterjet models or single abrasive particle erosion *** overcome the mesh distortion caused by large deformation using FEM and to consider the effects of both water and abrasive,the smoothed particle hydrodynamics（SPH） coupled FEM modeling for AWJM simulation is presented,in which the abrasive waterjet is modeled by SPH particles and the target material is modeled by *** two parts interact through contact *** this model,abrasive waterjet with high velocity penetrating the target materials is simulated and the mechanism of erosion is *** relationships between the depth of penetration and jet parameters,including water pressure and traverse speed,etc,are analyzed based on the *** simulation results agree well with the existed experimental *** mixing multi-materials SPH particles,which contain abrasive and water,are adopted by means of the randomized algorithm and material model for the abrasive is *** study will not only provide a new powerful tool for the simulation of abrasive waterjet machining,but also be beneficial to understand its cutting mechanism and optimize the operating parameters.

关键词： abrasive waterjet machining randomized algorithm coupling SPH/FEM abrasive material models

Induction of Apoptosis by Superoxide Anion and the Protective Effects of Selenium and Vitamin E

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Biomedical and Environmental Sciences 2001年第3期14卷 241-247页

作者： GUOLING XUEAN－na 等 InstituteofNutritionandFoodHygiene ChineseAcademyofPreventiveMedicineNanWeiRoad29Beijing100050China InstituteofNutritionandFoodHygiene ChineseAcademyofPreventiveMedicineNan

Objective\ The purpose of this study is to investigate the effect of superoxide anion on the apoptosis of cultured fibroblasts and the protective role of selenium and Vitamin E. Methods\ Cultured fibroblasts (NIH3T3), with or without selenium or vitamin E in the medium, were treated by superoxide anion produced by xanthine/xanthine oxidase reaction system and changes in cell structure and Dna were observed microscopically and electrophoretically. Results\ Apoptosis was observed when superoxide anion at a concentration of 5 nmol/L or 10 nmol/L had acted on the fibroblasts for 5-10 h. Selenium and Vitamin E in the medium inhibited the apoptosis significantly when their concentrations reached 1.15 mol/L and 2.3 mol/L respectively. Conclusion Selenium and vitamin E have protective effect against the apoptosis induced by superoxide anion. The effect of selenium is more remarkable than that of vitamin E.

关键词： Apoptosis Antioxidants Cell Culture Techniques Dose-Response Relationship Drug Fibroblasts Humans Selenium Superoxides Vitamin E

A public database of thermoelectric materials and system-identified material representation for data-driven discovery

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npj Computational Materials 2022年第1期8卷 2064-2074页

作者： Gyoung S.na Hyunju Chang Korea Research Institute of Chemical Technology DaejeonRepublic of Korea

Thermoelectric materials have received much attention as energy harvesting devices and power ***,discovering novel high-performance thermoelectric materials is challenging due to the structural diversity and complexity of the thermoelectric materials containing alloys and *** the efficient data-driven discovery of novel thermoelectric materials,we constructed a public dataset that contains experimentally synthesized thermoelectric materials and their experimental thermoelectric *** the collected dataset,we were able to construct prediction models that achieved R^(2)-scores greater than 0.9 in the regression problems to predict the experimentally measured thermoelectric properties from the chemical compositions of the ***,we devised a material descriptor for the chemical compositions of the materials to improve the extrapolation capabilities of machine learning *** on transfer learning with the proposed material descriptor,we significantly improved the R^(2)-score from 0.13 to 0.71 in predicting experimental ZTs of the materials from completely unexplored material groups.

关键词： properties alloys system

Electronic structure,bonding characteristics,and mechanical behaviors of a new family of Si-containing damage-tolerant MAB phases M_(5)SiB_(2)(M=IVB-VIB transition metals)

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Journal of Advanced Ceramics 2022年第10期11卷 1626-1640页

作者： na NI Hanchao ZHANG Yanchun ZHOU School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China

MAB phases are layered ternary compounds with alternative stacking of transition metal boride layers and group A element *** now,most of the investigated MAB phases are concentrated on compounds with Al as the A element *** this work,the family of M_(5)SiB_(2)(M=IVB-VIB transition metals)compounds with silicon as interlayers were investigated by density functional theory(DFT)methods as potential MAB phases for high-temperature *** from the known Mo5SiB2,the electronic structure,bonding characteristics,and mechanical behaviors were systematically investigated and *** the composition of M_(5)SiB_(2) does not follow the general formula of experimentally reported(MB)_(2z)A_(x)(MB_(2))_(y)(z=1,2;x=1,2;y=0,1,2),their layered structure and anisotropic bonding characteristics are similar to other known MAB phases,which justifies their classification as new members of this material *** a result of the higher bulk modulus and lower shear modulus,Mo_(5)SiB_(2) has a Pugh’s ratio of 0.53,which is much lower than the common MAB *** was found that the stability and mechanical properties of M_(5)SiB_(2) compounds depend on their valence electron concentrations(VECs),and an optimum VEC exists as the criteria for *** hypothesized Zr and Hf containing compounds,i.e.,Zr_(5)SiB_(2) and Hf_(5)SiB_(2),which are more interesting in terms of high-temperature oxidation/ablation resistance,were found to be unfortunately *** cope with this problem,a new stable solid solution(Zr_(0.6)Mo_(0.4))_(5)SiB_(2) was designed based on VEC tuning to demonstrate a promising approach for developing new MAB phases with desirable compositions.

关键词： borides MAB phases density functional theory(DFT) thermodynamic stability electronic structure mechanical properties

Novel optimized routing algorithm for LEO satellite IP networks

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Journal of Systems Engineering and Electronics 2011年第6期22卷 917-925页

作者： Zihe Gao Qing Guo Zhenyu na Communication Research Center Harbin Institute of Technology Harbin 150001 E R. China School of Information Science and Technology Dalian Maritime University Dalian 116026 E R. China

A lot of routing algorithms have been proposed for low earth orbit（LEO） satellite IP networks in recent years,but most of them cannot achieve global *** dynamic characters of LEO satellite networks are reflected in two aspects：topology and traffic *** algorithms mentioned above are ＂hard routing＂ which only realize local optimization.A distributed soft routing algorithm combined with multi-agent system（MASSR） is *** MASSR,mobile agents are used to gather routing information actively,and blackboard is introduced to achieve direct information exchange between *** provides traffic adaptive routing and tracks the change of LEO satellite network *** performance of ant colony optimization（ACO） and MASSR are compared in Iridium constellation,and MASSR presents better end-to-end delay as well as enhanced robustness.

关键词： distributed routing multi-agent system(MAS) satellite IP networks.

Structural dynamic responses of a stripped solar sail subjected to solar radiation pressure

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Chinese Journal of Aeronautics 2020年第8期33卷 2204-2211页

作者： Junhui ZHANG na WU An TONG Yinghua LIU School of Civil Engineering North China University of TechnologyBeijing 100144China School of Aerospace Engineering Tsinghua UniversityBeijing 100144China

The stripped solar sail whose membrane is divided into separate narrow membrane strips is believed to have the best structural *** this paper,the stripped solar sail structure is regarded as an assembly made by connecting a number of boom-strip components in *** the coupling effects between booms and membrane strips,an exact and semianalytical method to calculate structural dynamic responses of the stripped solar sail subjected to solar radiation pressure is *** case study of a 100 m stripped solar sail shows that the stripped architecture helps to reduce the static deflections and amplitudes of the steady-state dynamic *** prestress of the membrane strips will decrease stiffness of the sail and increase amplitudes of the steady-state dynamic *** thickness of the boom will benefit to stability of the sail and reduce the resonant *** proposed semi-analytical method provides an efficient analysis tool for structure design and attitude control of the stripped solar sail.

关键词： Distributed transfer function method Frequency response Solar radiation pressure Solar sail Structural dynamic response