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

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 1. State Key Laboratory of Earth Surface Processes and Resource Ecology Beijing Normal University Beijing 100875 China2. MOE Engineering Center of Desertification and Blown-sand Control Beijing Normal University Beijing 100875 China3. Key Laboratory of Environmental Change and Natural Disaster of the Ministry of Education of China Beijing Normal University Beijing 100875 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

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Implementation of a multiple round quantum dense coding using nuclear magnetic resonance

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Science china(Physics,Mechanics & Astronomy) 2005年第6期48卷 706-715页

作者： ZHANG Jingfu1, XIE Jingyi2, WANG Chuan1, DENG Zhiwei3, LU Zhiheng4, & LONG Guilu1,5 1. Key Laboratory For Quantum Information and Measurements of moe, Department of Physics, Tsinghua university, beijing 100084,china 2. Department of Materials Science and engineering, beijing normal university, beijing 100875, china 3. Testing and Analytical center, beijing normal university, beijing 100875.china 4. Department of Physics, beijing normal university, beijing 100875, china 5. Key Laboratory For atomic and Molecular Nanosciences, Tsinghua university, beijing 100084,china 1. Key Laboratory For Quantum Information and Measurements of moe Department of Physics Tsinghua University 100084 Beijing China 2. Department of Materials science and engineering Beijing Normal University 100875 Beijing China 3. Testing and Analytical center Beijing Normal University 100875 Beijing China 4. Department of Physics Beijing Normal University 100875 Beijing China 5. Key Laboratory For Atomic and Molecular Nanosciences Tsinghua University 100084 Beijing China

A multiple round quantum dense coding scheme based on the quantum phase estimation algorithm is proposed and implemented in a three qubit nuclear magnetic resonance (NMR) quantum computer. Using an m + 1 qubit system, Bob can transmit one of 2m+1 messages to Alice, through manipulating only one qubit and exchanging it between Alice and Bob for m rounds. The information capacity is enhanced to m + 1 bits as compared to m bits in a classical scheme. The scheme has been demonstrated in NMR system, and the experimental results show a good agreement between theory and experiment.

关键词： quantum dense coding, multiple round, nuclear magnetic resorance

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Multiparty quantum secret sharing of classical and quantum messages

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Progress in Natural Science:Materials International 2007年第1期17卷 26-31页

作者： CHEN Pan, DENG Fuguo and LONG Guilu ( Key Laboratory for Quantum Information and Measurements, and Department of Physics, Tsinghua university, beijing 100084, china Key Laboratory of Beam Technology and Material Modification, moe, Institute of Low Energy Nuclear Physics, and Department of Material Science and engineering, beijing normal university, beijing 100875, china beijing Radiation center, beijing 100875, china Key Laboratory for Atomic and Molecular Nano-Sciences, Tsinghua university, beijing 100084, china) [a]Key Laboratory for Quantum Information and Measurements and Department of Physics Tsinghua University Beijing China [b]Key Laboratory of Beam Technology and Material Modification MOE Institute of Low Energy Nuclear Physics and Department of Material Science and Engineering Beijing Normal University Beijing China [c]beijing Radiation center Beijing China [d]Key Laboratory for Atomic and Molecular Nano-Sciences Tsinghua University Beijing China

A scheme for multiparty quantum secret sharing of classical and quantum messages is proposed by using entanglement swapping. This scheme can distribute not only the classical information but also the quantum informati... 详细信息

关键词： quantum secret sharing classical message quantum message EPR pair.

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Global view of Hopf bifurcations of a van der Pol oscillator with delayed state feedback

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Science china(Technological Sciences) 2010年第3期53卷 595-607页

作者： ZHANG Li1,WANG HuaiLei1 & HU HaiYan1,2 1 moe Key Lab of Mechanics and control of Aerospace Structures,Nanjing university of Aeronautics and Astronautics,Nanjing 210016,china 2 School of Aerospace engineering,beijing Institute of Technology,beijing 100081,china 1. moe Key Lab of Mechanics and control of Aerospace Structures Nanjing University of Aeronautics and Astronautics Nanjing 210016 China2. School of Aerospace Engineering Beijing Institute of Technology Beijing 100081 China

This paper presents both analytical and numerical studies on the global view of Hopf bifurcations of a van der Pol oscillator with delayed state *** on a detailed analysis of the stability switches of the trivial equilibrium of the system,the stability charts are given in a parameter space consisting of the time delay and the feedback *** center manifold reduc-tion and the normal form method are used to study Hopf bifurcations with respect to the time *** gain an insight into the persistence of a Hopf bifurcation as the time delay varies farther away from its critical value,the method of multiple scales is used to obtain the global view of Hopf bifurcations with respect to the time *** the analytical results of Hopf bifurca-tions and global view of those bifurcations are validated via a collocation scheme implemented on *** most important discovery in this paper is the well-structured global view of Hopf bifurcations for the system of concern,showing the generality of the persistence of Hopf bifurcations.

关键词： Hopf bifurcation global view center manifold reduction method of multiple scales collocation scheme

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