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Evolution of grain structure in AA2195 Al-Li alloy plate during recrystallization

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中国有色金属学会会刊：英文版 2006年第2期16卷 321-326页

作者：杜予晅张新明叶凌英刘胜胆 School of Materials Science and Engineering Central South University Changsha 410083 China

The evolution of the grain structures in AA2195 Al-Li alloy plate warm-rolled by 80% reduction during recrystallization annealing at 500 ℃ was investigated by electron backscatter diffraction, scanning electron microscopy and transmission electron microscopy. It is found that the elongated grain structures are caused by the lamellar distribution of recrystallization nucleation sites, being lack of large second phase particles (>1 μm), and dispersive coherent particles (such as δ′ and β′) concentrated in planar bands. The recrystallization process may be separated into three stages: firstly, recrystallization nucleation occurs heterogeneously, and the nuclei are concentrated in some planar zones parallel to rolling plane. Secondly, the grain boundaries interacted with small particles concentrate in planar bands, which is able to result in the elongated grain structures. The rate of the grain growth is controlled by the dissolution of these small particles. Thirdly, after most of small particles are dissolved, their hindrance to migration of the grain boundaries fades away, and the unrecrystallized zones are consumed by adjacent recrystallized grains. The migration of high angle grain boundaries along normal direction leads a gradual transformation from the elongated grains to the nearly equiaxed, which is driven by the tension of the grain boundaries.

关键词： Al-Li合金铝合金晶体结构再结晶等轴晶

Effect of extrusion ratio on microstructure and mechanical properties of AZ91D magnesium alloy recycled from scraps by hot extrusion

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Transactions of Nonferrous Metals Society of china 2010年第6期20卷 987-991页

作者：胡茂良吉泽升陈晓瑜 College of Materials Science and Engineering Harbin University of Science and Technology

A method for recycling AZ91D magnesium alloy scraps directly by hot extrusion was *** microstructural analyses were performed using the techniques of optical microscopy,scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).Microstructural observations revealed that all the recycled specimens consisted of fine grains due to the dynamic *** main strengthening mechanism of the recycled specimen was grain refinement strengthening and homogeneous distribution of oxide *** interfaces of individual scraps of extruded materials were not identified when the scraps were extruded with the extrusion ratio of *** layers of the scraps were broken into pieces by high compressive and shear forces under the extrusion ratio of *** ultimate tensile strength and elongation to failure increased with increasing the extrusion *** specimens with the extrusion ratio of 40:1 showed higher ultimate tensile strength of 342.61 MPa and higher elongation to failure of 11.32%,compared with those of the cast specimen.

关键词： extrusion ratio AZ91D magnesium alloy scraps mechanical property microstructure

Structure of Coexistence States for a Class of Quasilinear Elliptic Systems

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Acta Mathematica Sinica,English Series 2007年第9期23卷 1649-1662页

作者： Guo Ying YANG Ming Xin WANG Department of Mathematics He'nan Polytechnic University Jiaozuo 454003 P. R. China Department of Mathematics Xuzhou Normal University Xuzhou 221116 P. R. China and Department of Mathematics Southeast University Nanjing 210018 P. R. China

The structure of positive solutions of the p-Laplacian systems is discussed via bifurcation theory and monotone techniques.

关键词： coexistence states quasilinear elliptic systems bifurcation

Activities of laccase produced by a strains Penicillium simplicissimum induced by chemical agentia and UV radiation

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Journal of Central South University 2017年第9期24卷 1953-1958页

作者：李雪李飞赖萃黄瑾辉庞娅罗琨廖兴盛 Department of Biological and Environmental Engineering Changsha University School of Information and Safety Engineering Zhongnan University of Economics and Law College of Environmental Science and Engineering Hunan University

Penicillium simplicissimum was cultured and preserved on the potato dextrose agar(PDA)***-RBBR(Remazal Brilliant Blue R)medium was used for the screening of the strains,which is able to produce *** the mutation process in Penicillium simplicissimum induced by chemical reagent and ultraviolet radiation,a high laccase-producing strains Penicillium simplicissimum was *** 5 m L diethyl sulfate(2%)was mixed along with 5 m L spore suspension for 30 min,chemical mutagenesis reached its best *** the optimum conditions of UV mutagenesis were that spore suspension was irradiated for 4 min under 15 W UV lamp at a distance of 30 *** highest activity of C_5E_4 strains was 4.80 U/g over 18%higher than the maximum laccase activity of original *** generations of the mutant strains were cultured,and the laccase activity of the strains was *** result showed that C_5E_4 strains can product laccase of the five subcultures stably.

关键词： Penicillium simplicissimum laccase chemical mutation UV mutation

The fabrication and characterization of 4H-SiC power UMOSFETs

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Chinese Physics B 2013年第2期22卷 426-428页

作者：宋庆文张玉明韩吉胜 Philip Tanner Sima Dimitrijev 张义门汤晓燕郭辉 School of Technical Physics Xidian University Key Laboratory of Wide Band Gap Semiconductor Materials and Devices Xidian University Queensland Micro and Nanotechnology Center Griffith University Griffith School of Engineering Griffith University

The fabrication of 4H-SiC vertical trench-gate metal-oxide-semiconductor field-effect transistors（UMOSFETs） is reported in this *** device has a 15-μm thick drift layer with 3×10^15 cm^-3 N-type doping concentration and a 3.1μm channel *** measured on-state source-drain current density is 65.4 A/cm^2 at Vg = 40 V and VDS = 15 *** measured threshold voltage（Vth） is 5.5 V by linear extrapolation from the transfer characteristics.A specific on-resistance（Rsp-on） is 181 mΩ·cm^2 at Vg = 40 V and a blocking voltage（BV） is 880 V（IDS = 100 μA@880V） at Vg = 0 V.

关键词： UMOSFETs 4H-SiC specific on-resistance blocking voltage

Diverse Traversability Mapping Using Hybrid Vision System for Lunar Rover

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Journal of Shanghai Jiaotong university(Science) 2010年第6期15卷 749-755页

作者：顾嘉俊曹其新庄惠敏 Robotics Institute Shanghai Jiaotong University

Autonomous functions including mapping and path planning are very important to ensure effcient exploration and safe navigation of unmanned rover. Conventional navigation schemes based on equipments such as GPS and magnetic sensors have been proven to be ineffective on lunar surface,while sophisticated dead reckoning approach lacks accuracy in loose soil due to slippage. In this paper,we propose a hybrid vision system(HVS) which consists of one stereo and one omnidirectional vision sensor,attempting to integrate the advantages of diverse vision systems. The hierarchical mapping reconstructs environment through HVS in different resolutions and structures,named qualitative,rough and detailed map. These maps are employed for path planning which navigates the rover towards specified destinations autonomously,avoiding obstacles in its way. The HVS aims at providing more effcient and safe navigation. Simulations and experiments demonstrate the functionality and advantage of our approach.

关键词： autonomous navigation machine vision mapping traversability assessment

An access control scheme for distributed Internet of Things based on adaptive trust evaluation and blockchain

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高置信计算(英文) 2023年第1期3卷 75-83页

作者： Wenxian Jiang Zerui Lin Jun Tao School of Cyber Science and Engineering Southeast UniversityNanjing 211189China College of Computer Science and Technology Huaqiao UniversityXiamen 361000China Key Lab of CNII MOESoutheast UniversityNanjing 211189China

The Internet of Things(IoT)has the characteristics of limited resources and wide range of *** at the problems of policy centralization and single point of failure in traditional access control schemes,a distributed access control method based on adaptive trust evaluation and smart contract is proposed to provide fine-grained,flexible and scalable authorization for IoT devices with limited ***,a modular access control architecture with integrated blockchain is proposed to achieve hierarchical management of IoT ***,an IoT trust evaluation model called AITTE based on adaptive fusion weights is designed to effectively improve the identification of illegal access requests from malicious ***,an attribute-based access control model using smart contract called AACSC which is built,which consists of attribute set contract(ASC),registration contract(RC),state judgment contract(SJC),authority permission management contract(AMC),and access control contract(ACC).As experimental results show,the scheme can effectively solve the problem of access security in resource-constrained IoT ***,it also ensures the reliability and efficiency of the access control implementation process.

关键词： Internet of Things Access control Blockchain Smart contract Trust level Evaluation model

Sphingosine-1-phosphate (S1P) mediates darkness-induced stomatal closure through raising cytosol pH and hydrogen peroxide (H_2O_2) levels in guard cells in Vicia faba

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Science china(Life Sciences) 2012年第11期55卷 974-983页

作者： MA YinLi SHE XiaoPing YANG ShuShen School of Life Sciences Shaanxi Normal University Xi'an 710062 China School of Life Sciences Shanxi Normal University Linfen 041004 China School of Life Sciences Northwest A & F University Yangling 712100 China

The role and signaling of sphingosine-l-phosphate （SIP） during darkness-induced stomatal closure were examined in Vicia faba. Darkness substantially raised S 1P and hydrogen peroxide （H202） levels and closed stomata. These darkness effects were significantly suppressed by DL-threo-dihydrosphingosine （DL-threo-DHS） and N,N-dimethylsphingosine （DMS）, two inhibi- tors of long-chain base kinases. Exogenous SIP led to stomatal closure and H202 production, and the effects of SIP were largely prevented by the H202 modulators ascorbic acid, catalase, and diphenyleneiodonium. These results indicated that SIP mediated darkness-induced stomatal closure by triggering H202 production. In addition, DL-threo-DHS and DMS significantly suppressed both darkness-induced cytosolic alkalization in guard cells and stomatal closure. Exogenous SIP caused cytosolic alkalization and stomatal closure, which could be largely abolished by butyric acid. These results demonstrated that SIP syn-thesis was necessary for cytosolic alkalization during stomatal closure caused by darkness. Furthermore, together with the data described above, inhibition of darkness-induced H202 production by butyric acid revealed that S 1P synthesis-induced cytosolic alkalization was a prerequisite for H202 production during stomatal closure caused by darkness, a conclusion supported by the facts that the pH increase caused by exogenous SIP had a shorter lag and peaked faster than H202 levels and that butyric acid prevented exogenous SIP-induced H202 production. Altogether, our data suggested that darkness induced SIP synthesis, causing cytosolic alkalization and subsequent H202 production, finally leading to stomatal closure.

关键词： sphingosine-l-phosphate cytosol pH hydrogen peroxide darkness stomatal closure

Influence of Copper Vapor on Low-Voltage Circuit Breaker Arcs During Stationary and Moving States

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Plasma Science and Technology 2008年第3期10卷 313-318页

作者：马强荣命哲吴翊徐铁军孙志强 State Key Laboratory of Electrical Insulation and Power Equipment Xi'an Jiaotong University Xi'an 710049 China

The influence of copper vapor on the low-voltage circuit breaker arcs is studied. A three-dimensional （3-D） magnetohydrodynamics（MHD） model of arc motion under the effect of external magnetic field is built up. By adopting the commercial computational fluid dynamics （CFD） package FLUENT based on control-volume method, the above MHD model is solved. For the mediums of air-1% Cu and air-10% Cu, the distributions of stationary temperature, pressure, electrical potential and the arc motion processes are compared with those of a pure air arc. The copper vapor diffusion process in the arc chamber and the distribution of copper vapor mass concentration are also simulated. The results shows that the copper vapor has a cooling effect on the arc plasma and can decrease the stationary voltage as well. Moreover, the presence of copper vapor can decelerate the arc motion in the quenching chambers. The maximal copper vapor concentration locates behind the arc root because of the existence of a ＂double vortex＂ near the electrodes.

关键词： arc plasma magnetic hydro-dynamics (MHD) copper vapor arc simulation