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Redevelopment of liftoff rates of saltating sand grains based on a simple optimization model

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Science china Earth Sciences 2010年第4期53卷 568-574页

作者： CHENG Hong & ZOU XueYong state key laboratory of Earth Surface Processes and Resource Ecology,beijing Normal university,beijing 100875,china MOE engineering Center of Desertification and Blown-sand Control,beijing Normal university,beijing 100875,china key laboratory of Environmental Change and Natural Disaster of the Ministry of Education of china,beijing Normal university,beijing 100875,china state key laboratory of Earth Surface Processes and Resource Ecology Beijing Normal University Beijing China MOE engineering Center of Desertification and Blown-sand Control Beijing Normal University Beijing China key laboratory of Environmental Change and Natural Disaster of the Ministry of Education of china Beijing Normal University Beijing China

This paper is a redevelopment result of liftoff rates of saltating sand grains based on our previous *** sand flow is a complex multi-phase flow because of a special two-phase gas-solid flow near ground *** extensive research on the movement of blowing sand,no model fully characterizes aeolian sand flow,and large differences often exist between simulations of aeolian sand movement and field *** key problem is a few of sufficient research on liftoff rates of saltating sand grains(also called the number of liftoff sand grains per unit time and per unit bed area).It is necessary to re-search in advance liftoff rates of saltating sand *** redeveloped liftoff rates of saltating sand grains by establishing an optimization model based on the flux of aeolian sand flow at different heights of the sampler in wind tunnel and the simulated capture of saltating sand grains by different heights of the sampler that are from different liftoff position(distance from the sampler) in order to revise previous inversion condition of liftoff rates of saltating sand *** rates increased rapidly with increasing wind *** frictional wind velocities of u=0.67,0.77,0.82,0.83,and 0.87 m s-1,liftoff rates were 3840,954502,5235114,5499407,and 7696291 sand grain s-1 m-2,*** rates could be expressed as the square of the instantaneous frictional wind velocity and a constant(0.663) that differs from the critical(threshold) frictional wind velocity at which saltation *** our results require additional experimental validation and the simple optimization model must be improved,they nonetheless provide a strong basis for future research.

关键词： liftoff rates of saltating sand grains optimization model wind tunnel two-phase gas-solid flow

SURFACE-ENHANCED CANTILEVER SENSORS WITH NANO-POROUS FILMS

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Acta Mechanica Solida Sinica 2010年第1期23卷 1-12页

作者： Huiling Duan(state key laboratory for Turbulence and Complex System,CAPT and Department of Mechanics and Aerospace engineering,College of engineering,Peking university,beijing 100871,china) state key laboratory for Turbulence and Complex System CAPT and Department of Mechanics and Aerospace Engineering College of Engineering Peking University Beijing China

Developing surface-enhanced microcantilevers with improved sensitivities is of longstanding interest. In this paper, the design of surface-enhanced cantilever sensors using nano- （micro-） porous films as surface layers is proposed. The static deformation and resonance frequencies of these surface-enhanced sensors with the simultaneous effects of the eigenstrain, the surface stress and the adsorption mass are analyzed. It is shown that the sensitivities of these novel cantilever sensors for the static deformation and resonance frequencies can be tuned by the porosity, the size of the pores and the structure of the porous films. For the three kinds of cantilever consisting of solid films, films with aligned cylindrical micro-scale pores, and those with nano-scale pores, the nano-porous one has the highest static and dynamic sensitivities, whereas the solid one has the lowest.

关键词： cantilever sensors nano- (micro-) porous films surface stress curvature resonance frequency

Preparation and thermal stability of zirconia-doped mullite fibers via sol-gel method

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Progress in Natural Science:Materials International 2011年第2期21卷 117-121页

作者： Wei WANG~(1,2),Duan WENG~1,Xiao-dong WU~1 1.state key laboratory of New Ceramics & Fine Process,Department of Materials Science and engineering, tsinghua university,beijing 100084,china 2.The Second Artillery NCO Academy of PLA,Qingzhou,Shandong 262500,china state key laboratory of New Ceramics & Fine Process Department of Materials Science and Engineering Tsinghua University Beijing 100084 China The Second Artillery NCO Academy of PLA Qingzhou Shandong 262500 China

The zirconia-doped mullite fibers were prepared via a sol-gel method from aluminum isopropoxide-aluminum nitrate-tetraethyl orthosilicate *** effects of zirconia doping on the sol spinnability,mullitization,structure and thermal stability of mullite fibers were investigated by means of Fourier transform infrared（FT-IR） spectroscopy,scanning electron microscopy（SEM） and X-ray diffraction（XRD）.The results showed that Zr—O—C bond was presented with the involvement of zirconium acetate,which accelerated the gelation process of the precursor *** mullitization process of the doped fibers was promoted by the formation of less middle-phase residues such as *** the samples investigated,the 1%ZrO2-doped fibers exhibited the highest thermal stability with a grain growth rate of 11%（from 1 000℃to 1300℃）,which is only a half of that for pure mullite fibers.

关键词： mullite fiber zirconia doping thermal stability

Constructions of Some Exact VortexSuperposition Solutions

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Communications in Nonlinear Science and Numerical Simulation 1999年第4期4卷 3-5页

作者： Xin HU Yonghan HUANG(Department of Mechanics and engineering Science, state key laboratory for TurbulenceResearch, Peking university, beijing 100871, china) Department of Mechanics and engineering Science State Key Laboratory for Turbulence Research Peking University Beijing 100871 China

IntroductionOneofthemostusefulmethodstosolvetheN-Sequationistodecomposethevelocity（l）(z)where.（'）--acNow,***3=w3（t）,wewillthengetco3=coear(jb（t）dt).Ifwetakeg=--M（axl+fixs）+ac,T=--M（Axf+Bx;）+cohere,goandcos... 详细信息

关键词： exact solution Stokes-Helmholtz decomposition vorticity equation

Interface-directed sol-gel:direct fabrication of the covalently attached ultraflat inorganic oxide pattern on functionalized plastics

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Science china Chemistry 2010年第1期53卷 173-182,287-288页

作者： GAN ShengHua,YANG Peng & YANG WanTai state key laboratory of Chemical Resource engineering College of Materials Science and engineering,beijing university of Chemical Technology,beijing 100029,china state key laboratory of Chemical Resource engineering College of Materials Science and engineering Beijing University of Chemical Technology Beijing China

For plastic electronics and optics,the fabrication of smooth,transparent and stable crack-free inorganic oxide films(and patterning) on flexible polymeric substrates with strong bonding strength and controllable thickness from nanometers to micrometers is a key but still remains a *** versatile inorganic oxides,silica oxide film as SiOx is especially important because this semiconductor material could provide crucial properties in devices or serve as a base layer for further multilayer *** this paper,we describe a new interface-directed sol-gel method to fabricate flexible high quality silicon oxide film onto commodity *** resulting crack-free silica film has strong covalent bonding with polymer substrates,homogeneous morphology with ultralow roughness,highly optical transparency,tunable thickness from nm to μm,and easy patterning *** fabrication strategy relies on a novel photocatalytic oxidation reaction by photosensitive ammonium persulfate(APS),which is able to fabricate highly reactive hydroxyl monolayer surface on inert polymeric *** kind of hydroxylated surface could serve as nucleation and growth sites to initiate surface sol-gel *** a result,well-defined SiOx film deposition(gelation) occurs,and patterned hydroxylation regions could be easily utilized to induce the formation of patterned oxide film *** strategy also excludes the requirements of clean room and vacuum devices so as to fulfill low-cost and fast fabrication *** application examples from such high quality SiOx layer onto plastics are given but should not be limited within *** is that oxygen permeation rate of SiOx deposited polymer film decreases 25 times than pristine polymer substrate,which is good for the potential packaging *** other one is that silanization monolayer,for example,3-aminopropyltriethoxysilane(APTES),could be successfully constructed onto silica layer through classical silanization reac

关键词： surface patterning silicon oxide sol-gel polymer surface modification functional coatings

An integrated turbocharger design approach to improve engine performance

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Science china(Technological Sciences) 2010年第1期53卷 69-74页

作者： ZHANG YangJun1,CHEN Tao1,ZHUGE WeiLin1,ZHANG ShuYong2 & XU JianZhong3 1 state key laboratory of Automotive Safety and Energy,tsinghua university,beijing 100084,china 2 National key laboratory of Diesel Engine Turbocharging Technology,P.O.B.22,Datong 037036,china 3 Institute of engineering Thermophysics,Chinese Academy of Sciences,beijing 100190,china state key laboratory of Automotive Safety and Energy Tsinghua University Beijing China National key laboratory of Diesel Engine Turbocharging Technology Datong China Institute of engineering Thermophysics Chinese Academy of Sciences Beijing China

Turbocharging technology is today considered as a promising way for internal combustion engine energy saving and CO2 *** design is a major challenge for turbocharged engine performance *** turbocharger designer must draw upon the information of engine operation conditions,and an appropriate link between the engine requirements and design features must be carefully developed to generate the most suitable design *** objective of this research is to develop a turbocharger design approach for better turbocharger matching to an internal combustion *** development of the approach is based on the concept of turbocharger design and interaction links between engine cycle requirements and design parameter values.A turbocharger through flow model is then used to generate the design *** integrated method has been applied with success to a gasoline engine turbocharger assembly.

关键词： turbocharger design internal combustion engine integrated method through flow model

All-optical NOR gate based on injection-locking effect in a semiconductor laser

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光电子快报：英文版 2008年第1期4卷 33-37页

作者： HAN Liu-yan, ZHANG Han-yi, and GUO Yi-li state key laboratory on Integrated Optoelectronics, National laboratory for Information Science and Technology, De- partment of Electronic engineering, tsinghua university, beijing 100084, china state key laboratory on Integrated Optoelectronics National Laboratory for Information Science and Technology Department of Electronic Engineering Tsinghua University Beijing China

A scheme for all-optical NOR logic gate is proposed based on injection-locking effect in a semiconductor laser. In this scheme, signal light injection into the laser will cause frequency shift of laser modes, as a result, the probe light into the laser can be switched between injection-locked and unlocked status, and its output power will be modulated. Theoretical analysis for this scheme is carried out by using a model to describe the dynamics of the injection-locked laser. By numerical simulation, the influence of laser bias current, laser length, injected signal power and signal frequency on the output performance of NOR logic gate is quantitatively analyzed.

关键词：半导体激光器注入锁相效应全光或非门光纤通信

A constitutive model of frozen soil with damage and numerical simulation for the coupled problem

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Science china(Physics,Mechanics & Astronomy) 2010年第4期53卷 699-711页

作者： ZHU ZhiWu, NING JianGuo& MA Wei 1 School of Mechanics and engineering, Southwest Jiaotong university, Chengdu 610031, china 2 state key laboratory of Explosion Science and Technology, beijing Institute of Technology, beijing 100081, china 3 key laboratory of Frozen Soil engineering, CAREERI, CAS, Lanzhou 730000, china School of Mechanics and engineering Southwest Jiaotong University Chengdu China state key laboratory of Explosion Science and Technology Beijing Institute of Technology Beijing China key laboratory of Frozen Soil engineering CAREERI CAS Lanzhou China

Based on the microcosmic mechanics of composite materials, an elastic constitutive model for frozen soil with damage is presented. For frozen sandy soil with a range of ice contents and under a range of temperature conditions, quantitative results determined by this constitutive model agree with practically measured stress-strain curves. After numerically simulating the coupled water, temperature and stress fields of channel frozen and frozen roadbed using a self-developed finite-element routine, more accurate and practical calculation results for the temperature field coupled with stress, displacement and strain fields are obtained; the results match predictions and tests undertaken by earlier researchers. Our results support the reliability of our routine for calculating interdependent physical quantities of frozen soil and for describing the relationships between them. Our program can offer necessary constraints for engineering design and construction in permafrost regions.

关键词： frozen soil microcosmic mechanics roadbed coupling stress field

On monolithic stability and reinforcement analysis of high arch dams

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Science china Technological Sciences 2007年第S1期 90-97页

作者： YANG Qiang?, CHEN YingRu & LIU YaoRu state key laboratory of hydroscience and engineering, tsinghua university, beijing 100084, china

Monolithic stability safety and reinforcement based on monolithic stability are very important for arch dam design. In this paper, the issue is addressed based on deformation reinforcement theory. In this approach, plastic complementary energy norm can be taken as safety index for monolithic stability. According to deformation reinforcement theory, the areas where unbalanced force exists require reinforcement, and the required reinforcement forces are just the unbalanced forces with opposite direction. Results show that areas with unbalanced force mainly concentrate in dam-toes, dam-heels and faults.

关键词： unbalanced force deformation reinforcement self-bearing force monolithic stability