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Effec. of different w.ter supply on morphology, grow.h and physiologic.l c.arac.eristic. of Salix psammophila seedlings in Maow.su sandland, c.ina

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Journal of Environmental Sc.enc.s 2001年第4期13卷 411-417页

作者： Xiao, c.-w. Lab. Quantitative Vegetation Ec.l. Institute of Botany Chinese Academy of Sciences Beijing 100093 China

Response pattern w.s investigated for seedlings of Salix psammophila, a dominant shrub in Maow.su sandland, to the simulated prec.pitation ch.nge by artific.ally c.ntrolling w.ter supply at four levels. The grow.h c.arac.ers, in terms of plant height, stem diameter, total branc. number, total leaf number and area, total bifurc.tion ratio, total branc. lenght and branc. number, branc. lenght, leaf number and leaf area of eac. branc. order, and leaf, branc. and root biomass signific.ntly inc.eased w.en w.ter supply inc.eased. That w.ter supply had signific.nt effec. on biomass alloc.tion show.d different investment pattern of biomass resourc. of the seedlings grow. under different w.ter supply treatments. Stomatal density of abaxial leaf surfac. dec.eased, and stomatal apparatus length and w.dth of adaxial and abaxial leaf surfac. inc.eased w.th the inc.ease of w.ter supply, w.ile Stomatal density of adaxial leaf surfac. w.s not affec.ed by w.ter supply. w.ter supply obviously affec.ed the diumal ch.nges of photosynthetic.rate, and the photosynthetic.rate of the seedlings show.d strongly midday depression grow. under the 157.5 mm w.ter supply, but not grow. under higher w.ter supply. Additionally the assimilation-light response c.rves and flouresc.nc. effic.enc. more show.d that w.ter supply improve photosynthesis c.pac.ty. Finally, S. psammophila seedlings stood out by their slow.grow.h and relatively high investments in root grow.h in order to reduc. tissue losing rate and c.nsumption of w.ter resourc. for keeping w.ter balanc. under w.ter stress. The seedlings that grow. under ric. w.ter supply did by their fast grow.h and relatively high investments in branc. and leaf grow.h in order to improve the pow.r of c.pturing light energy for higher photosynthesis.

关键词： Biomass Fluoresc.nc. Morphology Photosynthesis Physiology Plants (botany) Prec.pitation (c.emic.l) Seed Tissue

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Is a nanorod (or nanotube) w.th a low.r Young’s modulus stiffer? Is not Young’s modulus a stiffness indic.tor?

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Sc.enc. c.ina(Physic.,Mec.anic. & Astronomy) 2010年第4期53卷 712-724页

作者： Lim c. w. Department of Building and c.nstruc.ion City University of Hong Kong

It has been a know. fac. in c.assic.l mec.anic. of materials that Young’s modulus is an indic.tor of material stiffness and materials w.th a higher Young’s modulus are stiffer. At the nanosc.le, w.thin the sc.pe and under spec.fic.c.rc.mstanc.s desc.ibed in this paper, how.ver, a nanorod (or a nanotube) w.th a smaller Young’s modulus (smaller stress-strain rate) is stiffer. In suc. a sc.nario, Young’s modulus is not a stiffness indic.tor for nanostruc.ures. Furthermore, the nonloc.l stress-strain rate is dependent on types of load, boundary c.nditions and loc.tion. This is likely to be one of the many possible reasons w.y numerous experiments in the past obtained signific.ntly varying values of Young’s modulus for a seemingly identic.l nanotube, i.e. bec.use the types of loading and/or boundary c.nditions in the experiments w.re different, as w.ll as at w.ic. point the property w.s measured. Based on the nonloc.l elastic.ty theory and w.thin the sc.pe of material and geometric.linearity, this paper reports the strange and hitherto unrealized effec. that a nanorod (or a nanotube) w.th a low.r Young’s modulus (smaller stress-strain rate) indic.tes smaller extension in tensile analysis. Similarly, it is also predic.ed that a nanorod (or a nanotube) w.th a low.r Young’s modulus results in smaller bending deflec.ion, higher c.itic.l buc.ling load, higher free vibration frequenc. and higher w.ve propagation veloc.ty, w.ic. are at all c.nsequenc.s of a stiffer nanostruc.ure.

关键词： nanorod nanotube nonloc.l stress nonloc.l elastic.ty stiffness tensile Young’s modulus

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On the truth of nanosc.le for nanobeams based on nonloc.l elastic.stress field theory:equilibrium,governing equation and static.deflec.ion

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Applied Mathematic. and Mec.anic.(English Edition) 2010年第1期31卷 37-54页

作者： c. w. LIM Department of Building and c.nstruc.ion City University of Hong Kong

This paper has suc.essfully addressed three c.itic.l but overlooked issues in nonloc.l elastic.stress field theory for nanobeams：（i） w.y does the presenc. of inc.easing nonloc.l effec.s induc. reduc.d nanostruc.ural stiffness in many, but not c.nsistently for all, c.ses of study, i.e., inc.easing static.deflec.ion, dec.easing natural frequenc. and dec.easing buc.ling load, although physic.l intuition ac.ording to the nonloc.l elastic.ty field theory first established by Eringen tells otherw.se？（ii） the intriguing c.nc.usion that nanosc.le effec.s are missing in the solutions in many exemplary c.ses of study, e.g., bending deflec.ion of a c.ntilever nanobeam w.th a point load at its tip; and （iii） the non-existenc. of additional higher-order boundary c.nditions for a higher-order governing differential equation. Applying the nonloc.l elastic.ty field theory in nanomec.anic. and an exac. variational princ.pal approac., w. derive the new.equilibrium c.nditions, do- main governing differential equation and boundary c.nditions for bending of nanobeams. These equations and c.nditions involve essential higher-order differential terms w.ic. are opposite in sign w.th respec. to the previously studies in the static. and dynamic. of nonloc.l nano-struc.ures. The differenc. in higher-order terms results in reverse trends of nanosc.le effec.s w.th respec. to the c.nc.usion of this paper. Effec.ively, this paper reports new.equilibrium c.nditions, governing differential equation and boundary c.ndi- tions and the true basic.static.responses for bending of nanobeams. It is also c.nc.uded that the w.dely ac.epted equilibrium c.nditions of nonloc.l nanostruc.ures are in fac. not in equilibrium, but they c.n be made perfec. should the nonloc.l bending moment be replac.d by an effec.ive nonloc.l bending moment. These c.nc.usions are substantiated, in a general sense, by other approac.es in nanostruc.ural models suc. as strain gradient theory, modified c.uple stress models and experim

关键词： bending effec.ive nonloc.l bending moment nanobeam nanomec.anic.,nanosc.le nonloc.l elastic.stress strain gradient

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Asymptotic.analysis of a vibrating c.ntilever w.th a nonlinear boundary

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Sc.enc. c.ina(Physic.,Mec.anic. & Astronomy) 2009年第9期52卷 1414-1422页

作者： c. w. LIM Department of Building and c.nstruc.ion City University of Hong Kong

Nonlinear vibration of a c.ntilever in a c.ntac. atomic.forc. mic.osc.pe is analyzed via an asymptotic.approac.. The asymptotic.solution is sought for a beam equation w.th a nonlinear boundary c.ndition. The steady-state responses are determined in primary resonanc. and subharmonic.resonanc.. The relations betw.en the response amplitudes and the exc.tation frequenc.es and amplitudes are derived from the solvability c.ndition. Multivaluedness oc.urs in the relations as a c.nsequenc. of the nonlinearity. The stability of steady-state responses is analyzed by use of the Lyapunov linearized stability theory. The stability analysis predic.s the jumping phenomenon for c.rtain parameters. The c.rves of the response amplitudes ch.nging w.th the exc.tation frequenc.es are numeric.lly c.mpared w.th those obtained via the method of multiple sc.les. The c.lc.lation results demonstrate that the tw. methods predic. the same varying tendenc.es w.ile there are small quantitative differenc.s.

关键词： asymptotic analysis vibration nonlinear boundary c.ndition beam c.ntac.

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Nonlinear vibrations of nano-beams ac.ounting for nonloc.l effec. using a multiple sc.le method

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Sc.enc. c.ina(Tec.nologic.l Sc.enc.s) 2009年第3期52卷 617-621页

作者： c. w. LIM Department of Building and c.nstruc.ion City University of Hong Kong

The nonlinear free transverse vibrations of a nano-beam on simple supports are investigated based on nonloc.l elastic.ty theory. The governing equation is proposed by c.nsidering geometric.nonlinearity due to finite stretch.ng of the beam. The method of multiple sc.les is applied to the governing equa- tion to evaluate the nonlinear natural frequenc.es. Numeric.l examples are presented to demonstrate the analytic.l results and highlight the c.ntributions of the nonlinear term and nonloc.l effec..

关键词： nonloc.l elastic.ty theory nanobeam natural frequenc. method of multiple sc.les

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Dynamic.behaviour of axially moving nanobeams based on nonloc.l elastic.ty approac.

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Ac.a Mec.anic. Sinic. 2010年第5期26卷 755-765页

作者： c. w. Lim c. Li Ji-Lin Yu Department of Building and c.nstruc.ion City Universityof Hong Kong Tat Chee Avenue KowloonHong Kong SAR China State Key Laboratory of Struc.ural Analysis for IndustrialEquipment Dalian University of TechnologyDalian 116024 China Department of Modem Mec.anic. University of Scienceand Technology of China Hefei 230026 China

In this artic.e, transverse free vibrations of axially moving nanobeams subjec.ed to axial tension are studied based on nonloc.l stress elastic.ty theory. A new.higher-order differential equation of motion is derived from the variational princ.ple w.th c.rresponding higher-order, non-c.assic.l boundary c.nditions. Tw. supporting c.nditions are investigated, i.e. simple supports and c.amped supports. Effec.s of nonloc.l nanosc.le, dimensionless axial veloc.ty, density and axial tension on natural frequenc.es are presented and disc.ssed through numeric.l examples. It is found that these fac.ors have great influenc. on the dynamic.behaviour of an axially moving nanobeam. In partic.lar, the nonloc.l effec. tends to induc. higher vibration frequenc.es as c.mpared to the results obtained from c.assic.l vibration theory. Analytic.l solutions for c.itic.l veloc.ty of these nanobeams w.en the frequenc. vanishes are also derived and the influenc.s of nonloc.l nanosc.le and axial tension on the c.itic.l veloc.ty are disc.ssed.

关键词： Axially moving nanobeams c.itic.l veloc.ty Free vibration Natural frequenc. Nonloc.l elastic.ty

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Planning and c.ntrol of c.P-Sw.tc.-Based Planar Biped w.lking

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Journal of Bionic.Engineering 2011年第1期8卷 33-48页

作者： X. Luo w. Li c. Zhu Sc.ool of Mec.anic.l Engineering Southeast University Nanjing 210018 P. R. China Department of Systems Life Engineering Maebashi Institute of Technology Gunma Prefecture 371-0816 Japan

Effic.ent w.lking is one of the main goals of researc.es on biped robots. A feasible w.y is to translate the understanding from human w.lking into robot w.lking, for example, an artific.al c.ntrol approac. on a human like w.lking struc.ure. In this paper, a w.lking pattern based on c.nter of Pressure （c.P） sw.tc.ed and modeled after human w.lking is introduc.d firstly. Then, a parameterization method for the proposed w.lking gait is presented. In view.of the c.mplic.tion, a multi-spac. planning method w.ic. divides the w.ole planning task into three sub-spac.s, inc.uding simplified model spac., w.rk spac. and joint spac., is proposed. Furthermore, a finite-state-based c.ntrol method is also developed to implement the proposed w.lking pattern. The state sw.tc.es of this method are driven by sensor events. For c.nvinc.ng verific.tion, a 2D simulation system w.th a 9-1ink planar biped robot is developed. The simulation results exhibit an effic.ent w.lking gait.

关键词： biped w.lking bio-inspired c.P sw.tc. c.ntrol multi-spac. planning simulation

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Energetic. and c.nserved quantity of an axially moving string undergoing three-dimensional nonlinear vibration

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Ac.a Mec.anic. Sinic. 2008年第2期24卷 215-221页

作者： Liqun c.en c. w. Lim Hu Ding Department of Mec.anic. Shanghai University Shanghai 200444 China Department of c.nstruc.ion and Building City University of Hong Kong Hong Kong China Shanghai Institute of Applied Mathematic. and Mec.anic. Shanghai 200072 China

Nonlinear three-dimensional vibration of axially moving strings is investigated in the view.of energetic.. The governing equation is derived from the Eulerian equation of motion of a c.ntinuum for axially ac.elerating strings. The time-rate of the total mec.anic.l energy assoc.ated w.th the vibration is c.lc.lated for the string w.th its ends moving in a presc.ibed w.y. For a string moving in a c.nstant axial speed and c.nstrained by tw. fixed ends, a c.nserved quantity is proved to remain unch.nged during three-dimensional vibration, w.ile the string energy is not c.nserved. An approximate c.nserved quantity is derived from the c.nserved quantity in the neighborhood of the straight equilibrium c.nfiguration. The approximate c.nserved quantity is applied to verify the Lyapunov stability of the straight equilibrium c.nfiguration. Numeric.l simulations are performed for a rubber string and a steel string. The results demonstrate the variation of the total mec.anic.l energy and the invarianc. of the c.nserved quantity.

关键词： Nonlinear free vibration Axial movingstring Energetic. c.nserved quantity Stability

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Ac.ive c.ntrol and experiment study of a flexible hub-beam system

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Ac.a Mec.anic. Sinic. 2010年第2期26卷 289-298页

作者： Guoping c.i Youyou Teng c. w. Lira Department of Engineering Mec.anic. State Key Laboratory of Ocean Engineering Shanghai Jiaotong University 200240 Shanghai China Department of Building and c.nstruc.ion City Universityof Hong Kong Tat Chee Avenue Kowloon Hong Kong China

The first-order approximation c.upling （FOAc. model w.s proposed rec.ntly for dynamic. and c.ntrol of flexible hub-beam systems. This model may deal w.th system dynamic. for both low.and high rotation speed, w.ile the c.assic.l zeroth-order approximation c.upling （ZOAc. model is only available for low.rotation speed. This paper assumes the FOAc.model to present experimental study of ac.ive positioning c.ntrol of a flexible hub-beam system. Linearization and nonlinear c.ntrol strategies are both c.nsidered. An experiment system based on a DSP TMS320F2812 board is introduc.d. The differenc. betw.en linearization and nonlinear c.ntrol strategies are studied both numeric.lly and experimentally. Simulation and experimental results indic.te that, linearized c.ntroller c.n make the system reac. an expec.ed position w.th suppressed vibration of flexible beam, but the time taken to position is longer than expec.ed, w.ereas nonlinear c.ntroller w.rks w.ll w.th prec.se positioning, suppression of vibration and time c.ntrol.

关键词： Flexible hub-beam system First-order approximation c.upling (FOAc. model Linearizationc.ntrol Nonlinear c.ntrol Experiment

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Experimental symmetric.private information retrieval w.th measurement-devic.-independent quantum netw.rk

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Light(Sc.enc. & Applic.tions) 2022年第10期11卷 2399-2405页

作者： c.ao w.ng w.n Yu Kon Hong Jie ng c.arles c.-w.Lim Department of Elec.ric.l&c.mputer Engineering National University of SingaporeSingaporeSingapore c.ntre for Quantum Tec.nologies National University of SingaporeSingaporeSingapore

Sec.re information retrieval is an essential task in today's highly digitised *** some applic.tions,it may be nec.ssary that user query's privac. and database c.ntent's sec.rity are *** these settings,symmetric.private information retrieval(SPIR)c.uld be employed,but its implementation is know. to be demanding,requiring a private key-exch.nge netw.rk as the base ***,w. report for the first time a realisation of provably-sec.re SPIR supported by a quantum-sec.re key-exch.nge *** SPIR sc.eme looks at biometric.sec.rity,offering sec.re retrieval of 582-byte fingerprint files from a database w.th 800 *** experimental results c.early demonstrate the feasibility of SPIR w.th quantum sec.re c.mmunic.tions,thereby opening up new.possibilities in sec.re distributed data storage and c.oud c.mputinq over the future Quantum Internet.

关键词： database netw.rk quantum

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