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Effect of deformation on microstructure and conductivity of hypereutectic aluminum-silicon alloy

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稀有金属材料与工程 2011年第S3期40卷 47-50页

作者： Wang Yuxin 1, 2 , Zhang Yu 1 , yang Ying 1 , Liao Wenjun 1 , Lu Wei 1 , yan Biao 1 , gao Wei 2 , Chen Weiwei 2 1 Tongji University, Shanghai 200092, China 2 The University of Auckland, PB 92019, Auckland, New Zealand Tongji Univ Shanghai Key Lab D&A Met Funct Mat Sch Mat Sci & Engn Shanghai 200092 Peoples R China Univ Auckland Auckland 1 New Zealand

Plastic deformation of sprayed alloy is an effective method to fabricate the hypereutectic aluminum-silicon alloy which combines good conductivity and toughness. In this study, Al-20Si-0.35 RE (wt%) alloy was synthesized by spray atomization and deposition technique. The sprayed deposition and over-spray powder were hot-extruded and plastic deformed respectively. Microstructure and conductivity were systematically performed in order to understand the influence of deformation on microstructure and conductivity of the hypereutectic alloy. The Si particles are refining and uniformly distributed in the Al matrix due to the proper addition of rare earth metal and the rapid solidification preparation method. The microstructure of plastic deformed alloy has invariably indicated that severe plastic deformation lead to the even refinement of microstructure. Both the conductivity of over-spray powder extrusion and sprayed deposition extrusion were obviously improved after plastic deformation. Possible mechanisms of deformation on microstructure and conductivity of hypereutectic aluminum-silicon alloy are discussed.

关键词： hypereutectic Al-Si alloy deformation hot-extrusion conductivity

Zinc oxide nanostructures and porous films produced by oxidation of zinc precursors in wet-oxygen atmosphere

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Progress in Natural Science:Materials International 2011年第2期21卷 81-96页

作者： Rui-qun CHEN~1,Chong-wen ZOU~(1,2),Xiao-dong yan~1,Wei gao~1 1.Department of Chemical and Materials Engineering,University of Auckland, 20 Symonds Street,Private Bag 92019,Auckland 1142,New Zealand 2.National Synchrotron Radiation Laboratory,University of Science and Technology of China,Hefei 230026,China [a] Department of Chemical and Materials Engineering University of Auckland 20 Symonds Street Private Bag 92019 Auckland 1142 New Zealand [b] National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei 230026 China

Wet oxidation can be used to produce high quality zinc oxide（ZnO） nanostructures at moderately high temperatures with low requirements of equipment and experimental *** precursor films were prepared by magnetron sputtering and controlled ZnO nanostructures were produced by oxidation of the Zn precursor films in wet *** growth mechanism of the ZnO nanowires and nanobelts in wet oxidation was discussed based on the experimental *** and nitrogen doping were realized in the wet oxidation process,with different *** structural and optical properties of the ZnO nanostructures were characterized by means of scanning electron microscopy（SEM）,X-ray diffraction（XRD）,transmission electron microscopy（TEM）, and photoluminescence（PL） measurements to understand the growth process of ZnO in wet *** production of ZnO porous films by wet oxidation process is also presented.

关键词： zinc oxide nanostructures wet oxidation

Surfactant-Enhanced Phytoremediation of Soils Contaminated with Hydrophobic Organic Contaminants:Potential and Assessment

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Pedosphere 2007年第4期17卷 409-418页

作者： gao yan-Zheng LING Wan-Ting ZHU Li-Zhong ZHAO Bao-Wei ZHENG Qing-Song College of Resource and Environmental Sciences Nanjing Agricultural University Nanjing 210095 College of Environmental and Resource Sciences Zhejiang University Hangzhou 310028 （China） School of Environmental and Municipal Engineering Lanzhou Jiaotong University Lanzhou 730070 （China）

Phytoremediation is becoming a cost-effective technology for the in-situ clean up of sites polluted with hydrophobic organic contaminants （HOCs）. The major factors limiting phytoremediation are the mass transfer, rate of plant uptake, and microbial biodegradation of HOCs. This article discusses the potential of surfactants to enhance desorption, plant uptake, and biodegradation of HOCs in the contaminated sites. Positive effects of surfactants on phytoremediation have been recently observed in greenhouse studies. The presence of some nonionic surfactants including polyoxyethylene sorbltan monooleate （Tween 80） and polyoxyethylene（23）dodecanol （Brij35） at relatively low concentrations resulted in significant positive effects on phytoremediation for pyrene-contaminated soil. However, the anionic surfactant （sodium dodecyl sulfate, SDS） and the cationic surfactant （cetyltrimethylammonium bromide, CTMAB） were not useful because of their phytotoxicity or low efficiency for surfactant-enhanced phytoremediation （SEPR）. The mechanisms of SEPR for HOC-contaminated sites were evaluated by considering experimental observations. In view of concerns about the cost effectiveness and toxicity of surfactants to plants, more research is needed to enhance the use of SEPR technology.

关键词： hydrophobic organic contaminant remediation SEPR soil surfaztant

Thermal and mechanical behavior of casting copper alloy wheel during wheel and belt continuous casting process

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China Foundry 2024年第1期21卷 82-90页

作者： Kun gao yan Peng School of Mechanical Engineering Yanshan UniversityQinhuangdao 066004HebeiChina

To investigate the thermal and mechanical behavior of casting wheel,a two-dimensional thermoelastic-plastic finite element model was used to predict the temperature,stress and distortion distribution of the casting wheel during the wheel and belt continuous casting *** effects of grinding thickness and casting speed on the thermal and mechanical behaviors of the center of the hot face of the casting wheel were discussed in *** each rotation,the casting wheel passes through four different spray *** results show that the temperature distribution of the casting wheel in different spray zones is similar,the temperature of the hot face is the highest and the temperature reaches the peak in the spray zoneⅢ.The stress and distortion depend on the temperature distribution,and the maximum stress and distortion of the hot face are 358.2 MPa and 1.82 mm,*** temperature at the center of the hot face decreases with increasing grinding thickness and increases with increasing casting speed.

关键词： casting wheel finite element model grinding thickness casting speed hot face spray zones

Numerical simulation of fluid flow and free surface fluctuations during wheel and belt casting process

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Journal of Iron and Steel Research International 2024年第5期31卷 1117-1126页

作者： Kun gao yan Peng National Engineering Research Center for Equipment and Technology of Cold Strip Rolling Yanshan UniversityQinhuangdao066004HebeiChina

The unstable fluid flow and severe free surface fluctuations in the wheel and belt caster can affect the quality of the cast *** lower level height tends to entrap inclusions in the molten *** the other hand,the higher level height makes the production process more dangerous due to the overflow of high temperature fluid from the mold.A computational model of the molten metal pouring process was *** transient fluid flow and free surface fluctuations behavior were calculated using the three-dimensional large eddy simulation model and the volume of fluid *** results show that the flow velocity of the main jet gradually decreases under the influence of the low kinetic energy fluid in the *** is an obvious oscillation in the tail of the jet,while the flow field is asymmetric in *** jet is closer to the inside radius side due to the Coanda effect,and there is a recirculation zone on the inside radius and the outside radius respectively,according to the 10 s time-averaged *** with the industrial observation and simulation results,the shape of the free surface is a wave that varies with *** addition,the free surface height is lowest and the flow velocity is highest in the region near the jet.

关键词： Fluid flow Free surface Wheel and belt caster Large eddy simulation Volume of fluid method

On the core entropy of Newton maps

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Science China Mathematics 2024年第1期67卷 77-128页

作者： yan gao Department of Mathematics Shenzhen UniversityShenzhen 518060China

In this paper,we define the core entropy for postcritically-finite Newton maps and study its continuity within this *** show that the entropy function is not continuous in this family,which is different from the polyn... 详细信息

关键词： core entropy extended Newton graph critical marking polynomial Newton map

Towards Data-Driving Multi-View Evaluation Framework for Scratch

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Tsinghua Science and Technology 2024年第2期29卷 517-528页

作者： Xiaolin Chai yan Sun yan gao Department of Computer Science Beijing University of Posts and TelecommunicationBeijing 100876China Intellectual Property Institute Shandong Polytechnic CollegeJining 272067China

As one of the most popular visual programming languages,Scratch has a lot of evaluation around *** evaluation can help programmers understand their projects *** the same time,it can also provide a reference for them to browse other projects in the online *** of the existing evaluations on Scratch are carried from three perspectives:Computational Thinking(CT)ability,visual presentation aesthetics,and code *** them,the assessment of CT and code quality is mainly carried out from the program script,while the evaluation of visual aesthetics is analyzed from the perspective of image sequences generated by project *** single-view evaluation focuses on the performance of a program in a certain aspect and is *** this paper,we propose a multi-view evaluation framework to integrate various evaluations using different *** quantitatively analyze the assessment of different views driven by *** with overall evaluations that represent human opinions,we analyze their differences and *** experiments,we determine the weights of different integration policies,the proposed multi-view evaluation method can generate evaluation results similar to human opinions.

关键词： Scratch Computational Thinking(CT) visual aesthetic static analysis integration policy machine learning

Electromagnetic characteristic analysis and design of a linear motor used for ultra-high-speed EMS maglev train

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Science China(Technological Sciences) 2024年第6期67卷 1957-1973页

作者： gao Han SHI TingNa gao XinMai LEI yanXiao yan Dong GUO Liyan yan yan College of Electrical Engineering Zhejiang UniversityHangzhou310027China Zhejiang University Advanced Electrical Equipment Innovation Center Hangzhou311107China State Key Laboratory of High-speed Maglev Transportation Technology Qingdao266100China CRRC Qingdao Sifang Co.Ltd. Qingdao266111China

The operating speed of the commercial electromagnetic suspension(EMS)maglev train has been over 430 km/h,making it the fastest means of land *** the increasing demands of people traveling,it is necessary to further improve the operating speed of maglev *** to examine whether the existing EMS system can meet the requirements of ultra-highspeed operation(more than 600 km/h),the electromagnetic characteristics of an EMS linear motor under the operating speed of 600–1000 km/h fed by a square-wave voltage supply is investigated in this ***,an electromagnetic field model of the EMS system under the square-wave voltage supply is established to investigate its electromagnetic performance,e.g.,the characteristics of phase current,the magnetic flux density,and the electromagnetic ***,the relationship between the harmonic components of the air-gap magnetic flux density and electromagnetic force is investigated using the two-dimensional fast Fourier transform(2D-FFT)to reveal the mechanism of electromagnetic force ***,to address the issues of excessive armature current density and significant electromagnetic force ripple,the linear motor is re-designed by enlarging the stator slot area and reshaping the mover's main magnetic ***,the Taguchi method is used to further improve the electromagnetic characteristics of the linear electric ***,the effectiveness of the proposed optimal design is validated by the finite-element analysis(FEA)based co-simulation.

关键词： ultra-high-speed maglev transportation electromagnetic suspension(EMS) linear motor electromagnetic force ripple suppression

Ultra-flexible all-in-one anti-freeze photothermally enhanced supercapacitors

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Nano Research 2024年第8期17卷 7221-7229页

作者： Yongxin Lu Keke Li yan-yan Song Zhida gao Condense matter of physics College of ScienceNortheazistern UniversityShenyang 110004China

Wearable electronics powered by flexible energy storage devices have captured global *** low-temperature conditions,unfortunately,solidification of flexible hydrogel electrolyte and decreased pseudo-capacity of these devices largely hamper their practical *** this study,photothermally-active Prussian blue(PB)was introduced onto poly(3,4-ethylenedioxythiophene)/polyacrylamide(PEDOT/PAM)networks to address the challenges of electrolyte solidification and degraded pseudo-capacitance for flexible all-in-one device at low *** as-constructed PB/PEDOT/PAM hydrogel device delivers stable electrochemical performance and remarkable mechanical property with 1652%***,this hydrogel device well retains its flexibility in cold environment with a freezing point below−30℃.The incorporation of PB extends the voltage range to 1.5 V as a single device,thus significantly enhancing the electrochemical performance as an all-inone integrated *** from the outstanding photo-to-thermal conversion ability of embedded PB nanocubes,the temperature of the assembled all-in-one PB/PEDOT/PAM device increased from^(−2)0 to 17.7℃ after solar-light irradiation for only 5 ***,the degraded pseudo-capacitance was subsequently boosted to 287.1%of its original capacitance at−20℃.This study establishes a connection between flexible all-solid-state hydrogel devices and photothermally enhanced pseudocapacitors in freezing environments,thereby expanding the potential applications of multi-functional pseudo-capacitors.

关键词： all-in-one energy storage devices all-solid-state photothermal flexible low temperatures