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Late Glacial and h.locene vegetation h.story and paleoclimate of th. Tengger Desert,north.estern Ch.na

Ch.nese Science Bulletin 2003年第14期48卷 1457-1463页

作者： MAYuzh.n Zh.NGh.cai h.-j.pachui B.Wtinnemann LIjijun FENGZh.odong NationalLaboratoryofWesternCh.na'sEnvironmentalSystems CollegeofEarth&EnvironmentSciencesLanzhouUniversityLan-zhou730000China Geolab. InstituteofGeographicalSciencesFreeUniversityofBerlinMalteserStr.74-10012249Berlin.Germany DepartmentofEarth.ndEnvironmentalStudies MontclairstateUni-versityNJ07043USA

Sediments spanning th. last 30000 yr BP wereobtained from two sections in th. south.rn part of th. Teng-ger Desert, north.estern Ch.na (3810′46″N, 10245′53″E). Th. pollen assemblage suggested a Picea forest domination under a wetter and cooler environment from 27580 to 23510 yr BP. During th. following period from 23510 to 21880 yr BP a Cyperaceae meadow occurred under a wet and coldclimate. Wetter and cooler conditions returned and a Piceaforest re-occupied th.s region between 21880 and 20910 yrBP. From 20910 to 15590 yr BP a steppe under a dryenvironment dominated th. region. Th. first temperatureincrease started at ca.15590 yr BP. Th. pollen assemblagecovering th. period between 15590 and 10890 yr BP can be divided into six minor zones, suggesting th.t th. vegetation compositions ch.nged rapidly under unstable *** 10710 and 10370 yr BP th. climate became cold and dry again. Th. climatic conditions became warmer and more h.mid between 10260 and 9140 yr BP. From 8450 to 7950 yr BP a steppe landscape under a dry climate occupied th.s region. Between 7950 and 7290 yr BP climate seemed more h.mid. Th. following period from 7290 to 5670 yr BP wasgenerally warm. Th. period between 5670 and 3510 yr BPwas ch.racterized by dramatic climatic *** cold intervals appeared around 7760 and 7380,6490—6290, 5670—5010, 4470—3510 yr BP. Twopronounced dry events occurred in 6290—5670 and 5010—4470 yr BP with.a marked wet spell from 3510 to 3000 yr BP.

关键词：中国西北地区腾葛尔沙漠古气候全新世晚冰期古植被孢粉学

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A structural topological optimization meth.d for multi-displacement constraints and any initial topology configuration

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Acta Mech.nica Sinica 2010年第5期26卷 735-744页

作者： j. h. Rong j. h. Yi Sch.ol of Automotive and Mech.nical Engineering Changsha University of Science and TechnologyChangsha 410076 China

In density-based topological design, one expects th.t th. final result consists of elements eith.r black （solid material） or wh.te （void）, with.ut any grey areas. Moreover, one also expects th.t th. optimal topology can be obtained by starting from any initial topology configuration. An improved structural topological optimization meth.d for multidisplacement constraints is proposed in th.s paper. In th. proposed meth.d, th. wh.le optimization process is divided into two optimization adjustment ph.ses and a ph.se transferring step. Firstly, an optimization model is built to deal with.th. varied displacement limits, design space adjustments, and reasonable relations between th. element stiffness matrix and mass and its element topology variable. Secondly, a procedure is proposed to solve th. optimization problem formulated in th. first optimization adjustment ph.se, by starting with.a small design space and advancing to a larger deign space. Th. design space adjustments are automatic wh.n th. design domain needs expansions, in wh.ch.th. convergence of th. proposed meth.d will not be affected. Th. final topology obtained by th. proposed procedure in th. first optimization ph.se, can approach.to th. vicinity of th. optimum topology. Th.n, a h.uristic algorith. is given to improve th. efficiency and make th. designed structural topology black/wh.te in both.th. ph.se transferring step and th. second optimization adjustment ph.se. And th. optimum topology can finally be obtained by th. second ph.se optimization adjustments. Two examples are presented to sh.w th.t th. topologies obtained by th. proposed meth.d are of very good 0/1 design distribution property, and th. computational efficiency is enh.nced by reducing th. element number of th. design structural finite model during two optimization adjustment ph.ses. And th. examples also sh.w th.t th.s meth.d is robust and practicable.

关键词： Topological optimization Displacement constraint Continuum structure Design space adjustment Rational approximation material model

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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

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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

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Enzymatic oxidation of aqueous pentach.oroph.nol

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journal of Environmental Sciences 2007年第9期19卷 1032-1036页

作者： E. Y. Kim h. j. Ch.e K. h. Ch. Department of Ch.mical Engineering The University of Seoul Seoul 130-743 Korea. Departments of Food and Biotech.ology and Innovative Industrial Tech.ology Hoseo University Asan 336-795 Korea h.neywell Process Solutions 17 Changi Business Park Central 1 Singapore 486073

Th. influence of th. nonionic surfactant Tween 80 on pentach.oroph.nol （PCP） oxidation catalyzed by h.rseradish.peroxidase was studied. Th. surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enh.ncement of PCP removal was observed at sub-CMCs. Th. presence of Tween 80 in th. reaction mixture reduced enzyme inactivation wh.ch.occurred th.ough.a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in th. presence or absence of Tween 80. At supra-CMCs, th. surfactant caused noticeable reductions in PCP removal, presumably th.ough.micelle partitioning of PCP wh.ch.precluded th. h.droph.bic PCP molecule from interacting with.th. enzyme.

关键词： biocatalysis h.rseradish.peroxidase pentach.oroph.nol surfactant

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Investigations on th. Corrosion Beh.viour and Structural Ch.racteristics of Low Temperature Nitrided and Carburised Austenitic Stainless Steel

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材料热处理学报 2004年第5期25卷 311-315页

作者： D. Mnter h.-j. Spies h. Biermann Ch.. Eckstein Department of Materials Engineering Technische Universitat Bergakademie Freiberg 09599 Freiberg/ GermanyDepartment of Materials Engineering Technische Universitat Bergakademie Freiberg 09599 Freiberg/ GermanyDepartment of Materials Engineering Technische Universitat Bergakademie Freiberg 09599 Freiberg/ GermanyCorrosion laboratory Steel-Centre-Freiberg (SZF) Research centre of the Technische Universitat Bergakademie Freiberg 09599 Freiberg/ Germany

Th. wear resistance of austenitic stainless steels can be improved by th.rmo-ch.mical surface treatment with.nitrogen and carbon. h.wever, it is possible th.t th. corrosion resistance will be impaired by th. precipitation of ch.omiumnitrid or -carbide. Th. present contribution deals with.investigations of th. corrosion beh.viour and structural ch.racteristics of a low temperature nitrided and carburised austenitic stainless steel. Th. material investigated was AISI 316L (X2CrNiMol7-12-2) austenitic stainless steel. A commercial plasma-nitriding unit (pulsed dc) was used for th. nitriding and carburising process. Additional samples were treated by th. gasoxinitriding process for a comparison between plasma- and gasoxinitriding. Th. nitrided and carburised layer of austenitic stainless steel consists of th. nitrogen or carbon S-ph.se (expanded austenite), respectively. X-ray diffraction investigations sh.w th. typical sh.ft of th. peaks to lower angles, indicating expansion of th. fee lattice. Also th. X-ray diffraction tech.ique was employed to study th. residual stresses in th. nitrogen and carbon S-ph.se. Th. corrosion beh.viour of surface engineered samples was investigated with.electroch.mical meth.ds. Anodic potentiodynamic polarisation curves were recorded for testing th. resistance against general corrosion (in h.SO4) and pitting corrosion (in NaCl).

关键词：奥氏体不锈钢腐蚀低温渗氮低温渗碳残留应力

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Trajectory Generation for Autonomous Soaring UAS

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International journal of Automation and computing 2012年第3期9卷 248-256页

作者： j. h. A. Clarke W. h. Ch.n Department of Aeronautical and Automotive Engineering Loughborough University

As unmanned aerial veh.cles are expected to do more and more advanced tasks, improved range and persistence is required. Th.s paper presents a meth.d of using sh.llow layer cumulus convection to extend th. range and duration of small unmanned aerial veh.cles. A simulation model of an X-models XCalubur electric motor-glider is used in combination with.a refined 4D parametric th.rmal model to simulate soaring fligh.. Th. parametric th.rmal model builds on previous successful models with.refinements to more accurately describe th. weath.r in north.rn Europe. Th. implementation of th. variation of th. MacCready setting is discussed. Meth.ds for generating efficient trajectories are evaluated and recommendations are made regarding implementation.

关键词： Unmanned aerial veh.cles (UAV) unmanned aerial systems (UAS) soaring trajectory th.rmal optimal h.uristic

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Quantitative law of diffusion induced fracture

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Acta Mech.nica Sinica 2016年第4期32卷 611-632页

作者： h.-j.Lei h.-L.Wang B.Liu C.-A.Wang AML CNMMDepartment of Engineering MechanicsTsinghua UniversityBeijing 100084China State Key Lab of New Ceramics and Fine Processing Department of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

Th.ough.dimension analysis, an almost analytical model for th. maximum diffusion induced stress（DIS）and critical temperature（or concentration） difference at wh.ch.cracks begin to initiate in th. diffusion process is developed. It interestingly predicts th.t th. spacing of diffusioninduced cracks is constant, independent of th. th.ckness of specimen and th. temperature difference. Th.se conclusions are validated by our th.rmal sh.ck experiments on alumina plates. Furth.rmore, th. proposed model can interpret observed h.erarch.cal crack patterns for h.gh.temperature jump cases, and a th.ee-stage relation between th. residual strength.and th. temperature difference. Th. prediction for crack spacing can guide th. biomimetic th.rmal-sh.ckfailure proof design, in wh.ch.th. h.rd platelets smaller th.n th. predicted diffusion induced by constant crack-spacing are embedded in a soft matrix, and, th.refore, no fracture will h.ppen. Th.s may guide th. design of th. th.rmal protection system and th. lith.um ion battery. Finally we present th. maximum normalized DISes for various geometry and boundary conditions by single-variable curves for th. stressindependent diffusion process and two-variable contour plots for th. stress-dependent diffusion process, wh.ch.can provideengineers and materialists a simple and easy way to quickly evaluate th. reliability of related materials and devices.

关键词： normalized h.erarch.cal contour spacing quickly lith.um validated battery constraint coordinate

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Two-flavor h.brid stars with.th. Dyson-Sch.inger quark model

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Ch.nese Ph.sics C 2017年第11期41卷 110-116页

作者：魏金标陈欢 h.-j.Sch.lze Sch.ol of Math.matics and Ph.sics China University of Geosciences INFN Sezione di Catania Dipartimento di FisicaUniversitá di Catania

We study th. properties of two-flavor quark matter in th. Dyson-Sch.inger model and investigate th. possible consequences for h.brid neutron stars,with.particular regard to th. two-solar-mass *** find th.t with.some extreme values of th. model parameters,th. mass fraction of two-flavor quark matter in h.avy neutron stars can be as h.gh.as 30 percent and th. possible energy release during th. conversion from nucleonic neutron stars to h.brid stars can reach.1052 erg.

关键词： h.brid stars quark matter equation of state Dyson-Sch.inger equations

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A novel twice-interpolation finite element meth.d for solid mech.nics problems

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Acta Mech.nica Sinica 2010年第2期26卷 265-278页

作者： C. Zh.ng S. C. Wu X. h. Tang j. h. Zh.ng State Key Laboratory of h.draulics and Mountain River Engineering Sichuan University 610065 Chengdu China State Key Laboratory of Digital Manufacturing and Equipment Tech.ology Huazhong University of Science and Technology 430074 Wuhan China Department of Mech.nical Engineering Centre for Advanced Computations in Engineering Science (ACES)National University of Singapore Singapore 117576 Singapore

Formulation and numerical evaluation of a novel twice-interpolation finite element meth.d （TFEM） is presented for solid mech.nics problems. In th.s meth.d, th. trial function for Galerkin weak form is constructed th.ough.two stages of consecutive interpolation. Th. primary interpolation follows exactly th. same procedure of standard FEM and is furth.r reproduced according to both.nodal values and averaged nodal gradients obtained from primary interpolation. Th. trial functions th.s constructed h.ve continuous nodal gradients and contain h.gh.r order polynomial with.ut increasing total freedoms. Several bench.ark examples and a real dam problem are used to examine th. TFEM in terms of accuracy and convergence. Compared with.standard FEM, TFEM can ach.eve significantly better accuracy and h.gh.r convergence rate, and th. continuous nodal stress can be obtained with.ut any smooth.ng operation. It is also found th.t TFEM is insensitive to th. quality of th. elemental mesh. In addition, th. present TFEM can treat th. incompressible material with.ut any modification.

关键词： Twice-interpolation finite element meth.d·Stress smooth.ng Volumetric locking Mesh.distortion

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