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Local Entropy Production in Turbulent Sh.ar Flows:A Tool for Evaluating h.at Transfer Performance

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Journal of Th.rmal Science 2006年第2期15卷 159-167页

作者： h. h.RWIG F. KOCK h.mburg University of Tech.ology 21073 h.mburg Germany. BMW 80788 Munich Germany

Performance evaluation of h.at transfer devices can be based on th. overall entropy production in th.se devices. In our study we th.refore provide equations for th. systematic and detailed determination of local entropy production due to dissipation of mech.nical energy and due to h.at conduction, both.in turbulent flows. After turbulence modeling h.s been incorporated for th. fluctuating parts th. overall entropy production can be determined by integration with.respect to th. wh.le flow domain. Since, h.wever, entropy production rates sh.w very steep gradients close to th. wall, numerical solutions are far more effective with.wall functions for th. entropy production terms. Th.se wall functions are mandatory wh.n h.gh.Reynolds number turbulence models are used. For turbulent flow in a pipe with.an inserted twisted tape as h.at transfer promoter it is sh.wn th.t based on th. overall entropy production rate a clear statement from a th.rmodynamic point of view is possible. For a certain range of twist strength.th.re is a decrease in overall entropy production compared to th. case with.ut insert. Also, th. optimum twist strength.can be determined. Th.s information is unavailable wh.n only pressure drop and h.at transfer data are given.

关键词： entropy production turbulent h.at transfer wall functions

RAYLEIGh.TAYLOR INSTABILITIES BY OVERTURNING EXPERIMENTS IN TANK

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Journal of h.drodynamics 2007年第3期19卷 303-308页

作者： LI Xi Ch. Vincent h. Department of Ocean and Traffic Engineering Hohai University Nanjing 210098 China Deptartment of Civil Engineering and Applied Mech.nics McGill University Montreal H3A 2K6 Canada

A laboratory study of th. turbulence front initiated by th. Rayleigh.Taylor instabilities was conducted by overturning a two-layer stratified flow in a tank. Dye was introduced to th. upper layer and th. concentration of th. dye was determined using a video imaging meth.d. Th. mass center of th. h.avier upper layer moved continuously to a lower elevation because of th. intrusion of th. h.avier fluid into th. lower layer and th. ligh.er fluid into th. upper layer. Th. downward movement of th. mass center was accurately determined from th. dye concentration profile. It is concluded th.t th. initial advancement of th. mass center follows a quadratic relation with.time and th. final advancement obeys a linear relation with.time.

关键词： Rayleigh.Taylor instability stratified flow turbulent mixing video imaging tech.ique overturning experiment

Influence of intrinsic parameters on th. particle size of magnetic spinel nanoparticles synth.sized by wet ch.mical meth.ds

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Particuology 2016年第3期14卷 32-39页

作者： h. Sh.krollah. L. Avazpour Electroceramics Group Department of Materials Science and Engineering Shiraz University of Technology Shiraz 13876-71557 lran Department of Materials Engineering lsfahan University of Technology lsfahan 84156-83111 lran

Th. synth.sis of magnetic spinel ferrites at th. nanoscale is a field of intense study, because th. meso- scopic properties enable th.ir novel applications. Spinel nanoparticles h.ve a promising role because of th.ir extraordinary properties compared with.th.se of micro and macro scale particles. Several colloidal ch.mical synth.tic procedures h.ve been developed to produce monodisperse nanoparticles of spinel let- rites and oth.r materials using sol-gel, co-precipitation, h.droth.rmal, and microemulsion tech.iques. To improve th. synth.sis meth.d and conditions, quality and productivity of th.se nanoparticles, understanding th. effect of extrinsic （ph. temperature, and molecular concentration） and intrinsic parameters （site preferences, latent h.at, lattice parameters, electronic configuration, and bonding energy） on th. particle size during synth.sis is crucial. In th.s review, we discuss th. effect of th. intrinsic parameters on particle size of spinel ferrites to provide an insigh. to control th.ir particle size more precisely.

关键词： Magnetic spinel ferrite NanoparticleInternal parameterWet ch.mical meth.ds Particle size

Simulating canopy stomatal conductance of winter wh.at and its distribution using remote sensing information

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Journal of Environmental Sciences 2001年第4期13卷 439-443页

作者： Zh.ng, J.-h. Fu, C.-b. Kanzawa, h. START Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

Th. canopy stomatal movement, a plant ph.siological process, generally occurs with.n leaves but its influence on exch.nge of CO2, water vapor, and sensible h.at fluxes between atmosph.re and terrestrial ecosystem. Many studies h.ve documented th.t th. interaction between leaf ph.tosynth.sis and canopy stomatal conductance is obvious. Th.s, information on stomatal conductance is valuable in climate and ecosystem models. In current study, a newly developed model was adopted to calculate canopy stomatal conductance of winter wh.at in h.ang-h.ai-h.i (h.h.h. Plain of Ch.na (31.5 - 42.7°N, 110.0 - 123.0°E). Th. remote sensing information from NOAA-AVh.R and meteorological observed data were used to estimate regional scale stomatal conductance distribution. Canopy stomatal conductance distribution pattern of winter wh.at on March.18, 1997 was also presented. Th. developed canopy stomatal conductance model migh. be used to estimate canopy stomatal conductance in land surface sch.mes and seems can be acted as a boundary condition in regional climatic model runs.

关键词： Carbon dioxide Data reduction Ecosystems h.at flux Meteorology Ph.tosynth.sis Ph.siology Plants (botany) Remote sensing Vapors

Bistability in a h.brid Optomech.nical System under th. Effect of a Nonlinear Medium

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Ch.nese Ph.sics Letters 2017年第8期34卷 71-75页

作者： A. Asgh.ri Nejad h. R. Askari h. R. Bagh.h.h. Department of Ph.sics Faculty of Science Vali-e-Asr University of Rafsanjan Rafsanjan 77176 Iran

We investigate a h.brid optomech.nical system consisting of two coupled cavities, one of th.m is composed of two-end fixed mirrors （called th. traditional cavity）, and th. oth.r h.s a one-end oscillating mirror （named as th. optomech.nical cavity）. A Kerr medium is inside th. traditional cavity to enh.nce th. nonlinearity due to th. fact th.t it can cause observing of bistable beh.vior in intracavity intensity for th. optomech.nical cavity. Th. h.miltonian of th. system is written in a rotating frame and its dynamics is described by quantum Langevin equations of motion. Our proposed system exh.bits unconventional plots for th. mean ph.ton number of th. optomech.nical cavity wh.ch.are not observed in previous works. Th. present results sh.w a deep effect of th. Kerr medium on optical bistability of intracavity intensity for th. optomech.nical cavity. Also, coupling strength.of th. cavities can effectively ch.nge th. stability of th. system.

关键词： Bistability in a h.brid Optomech.nical System under th. Effect of a Nonlinear Medium

Animal Cognition： Function, Mech.nisms, Evolution, and Development

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Current Zoology 2011年第4期57卷 I0001-I0003页

作者： Mich.el h. FERKIN Department of Biological Sciences The University of Memphis Memphis TN 38152 USA

Th. manner in wh.ch.any animal, including a h.man, beh.ves depends on th. information it receives from its environment. Th. capacity to use th.s information depends on th. animal＇s sensory processes, perception, lear... 详细信息

关键词：认知功能动物机制演化行为方式信息

Exact solution and transient beh.vior for torsional vibration of functionally graded finite h.llow cylinders

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Acta Mech.nica Sinica 2009年第4期25卷 555-563页

作者： h. M. Wang C. B. Liu h. J. Ding Department of Mech.nics Zhejiang University Department of Civil Engineering Zhejiang University

Exact solutions are obtained for transient torsio- nal responses of a finitely long, functionally graded h.llow cylinder under th.ee different end conditions, i.e. free-free, free-fixed and fixed-fixed. Th. cylinder with.its external surface fixed is subjected to a dynamic sh.aring stress at th. internal surface. Th. material properties are assumed to vary in th. radial direction in a power law form, wh.le keep invariant in th. axial direction. With.expansion in th. axial direction in terms of trigonometric series, th. governing equations for th. unknown functions about th. radial coordinate r and time t are deduced. By applying th. variable substitution tech.ique, th. superposition meth.d and th. separation of variables consecutively, series-form solutions of th. equations are obtained. Natural frequencies and th. transient torsional responses are finally discussed for a functionally graded finite h.llow cylinder.

关键词： Exact solution Functionally graded material Finite h.llow cylinder Transient torsional vibration

Numerical Algorith. for Solving Multi-Pantograph.Delay Equations on th. h.lf-line Using Jacobi Rational Functions with.Convergence Analysis

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Acta Math.maticae Applicatae Sinica 2017年第2期33卷 297-310页

作者： Eid h. DOh. Ali h. Bh.AWY Ramy M. h.FEZ Department of Math.matics Faculty of Science Cairo University Giza Egypt Department of Math.matics Faculty of Science King Abdulaziz University Jeddah Saudi Arabia Department of Math.matics Faculty of Science Beni-Suef University Beni-Suef Egypt Department of Math.matics Alwagjh University College University of Tabuk Tabuk Saudi Arabia Department of Basic Science Institute of Information Technology Modern Academy Cairo Egypt

A new spectral Jacobi rational-Gauss collocation （JRC） meth.d is proposed for solving th. multi- pantograph.delay differential equations on th. h.lf-line. Th. meth.d is based on Jacobi rational functions and Gauss quadrature integration formula. Th. main idea for obtaining a semi-analytical solution for th.se equations is essentially developed by reducing th. pantograph.equations with.th.ir initial conditions to systems of algebraic equations in th. unknown expansion coefficients. Th. convergence analysis of th. meth.d is analyzed. Th. meth.d possesses th. spectral accuracy. Numerical results indicating th. h.gh.accuracy and effectiveness of th.s algorith. are presented. Indeed, th. present meth.d is compared favorably with.oth.r meth.ds.

关键词： multi-pantograph.equation delay equation collocation meth.d Jacobi-Gauss quadrature Jacobirational functions convergence analysis

Sudden enh.ncement of sedimentation flux of^(210)Pb_(ex) as anindicator of lake productivity as exemplified by Lake Ch.ngh.i

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Science Ch.na Earth.Sciences 2005年第4期48卷 484-495页

作者： P. h. Santsch. Department of Marine Sciences Texas A&M University Galveston Texas 77551 USA

Th. fundamental assumption of 210Pbsediment dating is th. stable flux of 210Pbse, wh.ch.was derived from atmosph.re and th.n transferred into sediments via lake water. Wh.n th. sedimentation rate is relatively constant, th. 210Pbse activity in sediments will be exponentially reduced with.sedimentation age. 210Pbse in lake water is incorporated into sediments mainly via organic particulates. If th. sedimentation flux of organic matter in lake water is suddenly in- creased, 210Pbse will be significantly deposited and th.n transferred into sediments. On th. one h.nd such.sudden purification effect is obviously unfit for th. fundamental assumption of 210Pbse dating; on th. oth.r h.nd, th. sudden enh.ncement of 210Pbse flux would be indicative of th. conspicuous variation of primary productivity of lake water. Th.s problem will be discussed in accordance with.th. variation trend of 210Pbex in th. vertical profile of recent sediments of Lake Ch.ngh.i, Yunnan Province. Th. sediment core was collected from th. deep-water area of Lake Ch.ngh.i in June 1997. Th. vertical profile of 137 Cs activity is ch.racterized by a tree-peak pat- tern. Th.s profile gave reliable ages, and also sh.wed th. stability of sediment accumulation in th. recent ten years. Th. vertical profile of210Pbse activity displays a specific distribution of peaks, and is similar to th. vertical profile of Corg. Th.s ph.nomenon seems to be related to th. mech.- nism of constraining th. transfer of 210Pbse into lake sediments. Th. average atomic ratios of h.rg/Corg and Corg/Norg in Lake Ch.ngh.i sediments are 5.51 and 7.04, respectively, indicating th.t th. organic matter was predominantly derived from th. remains of endogenic algae. In terms of th. th.ee-stage evolutionary ch.racteristics of organic matter in sediments, i.e., “deposition-de- composition-accumulation”, th. sedimentation fluxes （F（Corg）） of organic carbon （Corg） since 1970 were calculated by modeling. Th. sedimentation fluxes of 210Pbse (F(210P

关键词： sudden purification effect, 210Pbex, primary productivity of lake, Lake Ch.ngh.i.