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Brownian ratchets driven by flashing noise strength

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chinese Science Bulletin 1999年第21期44卷 1956-1961页

作者： ZHAO Tongjun, ZHAN Yong, ZHUO Yizhong and WU XizhenDepartment of Applied Mathematics and physics , Hebei University of Technology , Tianjin 300130, china china institute of Atomic Energy, beijing 102413, china institute of theoretical physics, chinese academy of sciences , beijing 100080, china Corresponding author Dept. of Appl. Math. and physics Hebei University of Technology Tianjin 300130 China china institute of Atomic Energy Beijing 102413 China institute of theoretical physics Chinese Academy of Sciences Beijing 100080 China

The stochastic transport driven by flashing multi-noise sources in a ratchet is studied. The stationary current versus the noise strength and the colored noise correlated time T is obtained . At a fixed flip rate and strength of the colored noises, the novel phenomenon of the current reversal occurs as T reaches a certain value. More than one reversal point exists when

关键词： flashing force ratchet current reversal Langevian equation.

An efficient chiral synthesis of (R)-N-[3-acetyl-4-(2-hydroxy-3-isopropylamino-propoxy)phenyl]-butanamide with high enantioselectivity

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Science china Chemistry 2009年第8期52卷 1216-1219页

作者： WANG NaiXing1,2 & TANG XinLiang1,3 1 Technical institute of physics and Chemistry,chinese academy of sciences,beijing 100080,china 2 College of Chemistry and Chemical Engineering,Graduate University of chinese academy of sciences,beijing 100049,china 3 School of Chemical Engineering and Environment,beijing institute of Technology,beijing 100081,china Technical institute of physics and Chemistry Chinese Academy of Sciences Beijing China College of Chemistry and Chemical Engineering Graduate University of Chinese Academy of Sciences Beijing China School of Chemical Engineering and Environment Beijing Institute of Technology Beijing China

R-Enantiomer of the β-receptor antagonist N-[3-acetyl-4-(2-hydroxy-3-isopropylamino-propoxy)phenyl] butanamide with high enantioselectivity was synthesized from cheap starting materials and enantiopure chiral reagent through an efficient,convenient and practical synthetic *** product was detected by 1H NMR,13C NMR,and MS,and the enatiomeric excess was determined by chiral HPLC analysis using a chiracel AD-H column.

关键词： chiral synthesis enantioselectivity enatiomeric excess chiral HPLC analysis

Anomalous dielectric behavior in nanocrystalline γ-Fe_2O_3

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chinese Science Bulletin 1999年第2期44卷 186-189页

作者： YE Xisheng , SHA Jian , CHEN Bin , JIAO Zhengkuan ZHANG LideDepartment of physics, Zhejiang University, Hangzhou 310027, china Northwest institute of Nuclear Technology, Xi’ an 710024, china institute of theoretical physics, chinese academy of sciences, beijing 100080, china institute of Solid State physics, chinese academy of sciences, Hefei 230031, china Department of physics Zhejiang University Hangzhou China Northwst institute of Nuclear Technology Xi’an China institute of theoretical physics Chinese Academy of Sciences Beijing China institute of Solid State physics Chinese Academy of Sciences Hefie China

The measurements of electric capacities and dielectric loss angles for nanocrystalline yFe2O3 under air and vacuum atmospheres have been conducted by using ac LRC method, and the conductivity and the polarization relaxation time have also been calculated from the frequency spectra of real and imaginary parts of the dielectric constants. The anomalous dielectric behavior implies the existence of two kinds of polarization mechanisms with different relaxation times, which are caused by the defects and the dangling bonds in the interfaces, respectively. The experimental and calculated results indicated that the polarization loss and the conductance loss are dominant in air atmosphere and vacuum, respectively.

关键词： nanocrystalline γ-Fe2O3 dielectric behavior polarization mechanism.

Effect of Li and Ti Additions on Lα(Al)+Mg_2Si Pseudobinary Eutectic Reaction

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Journal of Materials Science & Technology 1997年第6期13卷 487-490页

作者： Shengxu ZHAO Shunpu LI Deqian ZHAO Mingxiang PAN and Xichen CHEN(institute of physics, chinese academy of sciences, beijing 100080, china) institute of physics Chinese Academy of Sciences Beijing 100080 China

Effect of Li and Ti additions on Lα(AI)+Mg2Si pseudobinary eutectic reaction in ternary Al-Mg-Si system has been investigated by thermoanalysis, directional solidification and metallographic techniques in this study. It has been found that Li addition causes decreasing of the volume fraction of Mg2Si, while a little amount of Ti causes to increasing, which is of a great importance to the adjustment of phase constitution and alloy properties. Doping components have little influence on the eutectic temperature.

关键词： Si Al Mg2Si Pseudobinary Eutectic Reaction Effect of Li and Ti Additions on L Li Ti

An optimization approach to the similarity criteria of flows and its application

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Progress in Natural Science:Materials International 2006年第3期16卷 241-247页

作者： ZHOU Jifu and LI Jiachun (institute of Mechanics, chinese academy of sciences, beijing 100080, china) institute of Mechanics Chinese Academy of Sciences Beijing 100080 China

In the present paper, we propose an optimization approach to investigate the similarity criteria of complex flows. With this approach, we may identify the dominant dimensionless variables governing complex flows by numerical sensitivity analysis. Firstly, we define the sensitivity factor and examine its dependence on the dimensionless variables. Then, we apply this approach to study the similarity criteria of porous media flow in a presumed oil reservoir. The similarity principle obtained from the numerical sensitivity analysis is in agreement with the theoretical law, thus demonstrating the feasibility of the proposed optimization approach. Further explanation is given by analyzing the deviation of pressure distribution in a model from its prototype. In addition, we examine the effects of flow parameter variation on the sensitivity factors and find that the dominant dimensionless variables may change from different sets of parameters.

关键词： similarity optimization sensitivity analysis complex flows model.

Current distribution and stability of LTS/HTS hybrid superconducting conductors

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Science china(Technological sciences) 2010年第7期53卷 2000-2007页

作者： GUAN XiaoJin1,2, WANG YinShun1 & ZHOU WeiWei3 1 Key Laboratory of HV and EMC beijing, North china Electric Power University, beijing 102206, china 2 Department of physics, Baoding University, Baoding 071000, china 3 institute of Electrical Engineering, chinese academy of sciences, beijing 100190, china Key Laboratory of HV and EMC beijing North China Electric Power University Beijing China Department of physics Baoding University Baoding China institute of Electrical Engineering Chinese Academy of Sciences Beijing China

Current distribution and stability of a hybrid LTS/HTS superconductor, consisting of multifilamentary NbTi/Cu and Bi2223/Ag tapes, were numerically analyzed according to power-law models. The results showed that most of current passed through the LTS and the current increased in the HTS with temperature rise when the transport current was below the critical current of the hybrid conductor. The quench propagation velocity of the hybrid conductor was smaller but its minimum quench energy was larger than those of LTS conductors, indicating that the stability of the hybrid superconducting conductor was effectively improved and a high engineering current density was simultaneously achieved. Finally, a hybrid sample, made by soldering Bi2223/Ag tape onto NbTi/Cu conductor, was prepared and tested successfully at helium temperature. The experimental results qualitatively agreed with the simulated ones.

关键词： distribution hybrid conductor minimum quench energy quench propagation velocity n value stability

Narrow line Seyfert 1 galaxies: where are the broad line regions?

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Science china(physics,Mechanics & Astronomy) 2010年第12期53卷 2307-2311,2339-2343页

作者： MAO WeiMing 1,2,3 , HU Chen 2 , WANG JianMin 2 , BIAN WeiHao 4 , ZHANG Shu 2 & ZHAO Gang 1 1 Key Laboratory of Optical Astronomy, National Astronomical Observatories, chinese academy of sciences, beijing 100012, china 2 Key Laboratory for Particle Astrophysics, institute of High Energy physics, chinese academy of sciences, beijing 100049, china 3 Graduate University of the chinese academy of sciences, beijing 100049, china 4 Department of physics, Nanjing Normal University, Nanjing 210011, china chinese academy of sciences Key Laboratory of Optical Astronomy National Astronomical Observatories Beijing China (GRID:grid.9227.e) (ISNI:***) chinese academy of sciences Key Laboratory for Particle Astrophysics Institute of High Energy Physics Beijing China (GRID:grid.9227.e) (ISNI:***) Graduate University of the chinese academy of sciences Beijing China (GRID:grid.458514.9) chinese academy of sciences Key Laboratory for Particle Astrophysics Institute of High Energy Physics Beijing China (GRID:grid.9227.e) (ISNI:***) Nanjing Normal University Department of Physics Nanjing China (GRID:grid.260474.3) (ISNI:***) chinese academy of sciences Key Laboratory of Optical Astronomy National Astronomical Observatories Beijing China (GRID:grid.9227.e) (ISNI:***)

A sample consisting of 211 narrow line Seyfert 1 galaxies (NLS1s) with high quality spectra from the Sloan Digital Sky Survey (SDSS) is selected to explore where broad line regions are in these objects. We find that the Hβ profile can be fitted well by three (narrow, intermediate and broad) Gaussian components, and the FWHM ratios of the broad to the intermediate components hold a constant of 3.0 roughly for the entire sample. If the broad components originate from the region scaled by the well-determined Hβ reverberation mapping relation, we find that the intermediate components originate from the inner edge of the torus, which is scaled by dust K-band reverberation. We find that the IC and the BC are strongly linked dynamically, but the relation of their covering factors is much more relaxed, implying that both regions are clumpy.

关键词： black hole physics galaxies: evolution quasars: general

Some characteristics of the atmosphere during an adiabatic process

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Progress in Natural Science:Materials International 2006年第6期16卷 644-648页

作者： GAO Li, LI Jianping and REN Hongli (LASG, institute of Atmospheric physics, chinese academy of sciences, beijing 100029, china Graduate School of chinese academy of sciences, beijing 100049, china National Climate Center, Laboratory of Climate Studies, china Meteorological Administration, beijing 100081, china) LASG Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China Graduate School of chinese academy of sciences Beijing 100049 China National Climate Center Laboratory of Climate Studies China Meteorological Administration Beijing 100081 China

Some important characteristics of the atmosphere during an adiabatic process are investigated, which include the invariability of atmospheric entropy range and local surface potential temperature, the conservation of the atmospheric mass intervened between any isentropic surface and the ground, and the isentropic surface intersecting with the ground. The analysis shows that the atmospheric reference state (ARS) for investigation on available potential energy (APE) should be defined objectively as the state which could be approached from the existing atmosphere by adiabatic adjustment, and be related to initial atmospheric state before adjustment. For the initial atmosphere state at any time, its corresponding ARS is different from the one at another time. Based on the above-mentioned conclusions, the reference state proposed by Lorenz cannot be obtained physically, so a new conception, the conditional minimum total potential energy, is put forward in order to objectively investigate atmospheric APE.

关键词： available potential energy adiabatic isentropic surface atmospheric reference state conditional minimum total potential energy.

The effects of shock wave and quasi-traveling wave in the mechanical impact test

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Science china(Technological sciences) 2010年第9期53卷 2535-2541页

作者： WU Mei1,5,SUN ZhongFeng2,ZHANG LuMei3,CHEN Yong1 & JI LinHong4 1 institute of High Energy physics,chinese academy of sciences,beijing 100049,china 2 School of Mathematical sciences,Peking University,beijing 100871,china 3 High School of Central University for Nationalities,beijing 100081,china 4 institute of Mechanical Design,Department of Precision Instruments and Mechanology,Tsinghua University,beijing 100084,china 5 academy of Opto-electronics,chinese academy of sciences,beijing 100190,china institute of High Energy physics Chinese Academy of Sciences School of Mathematical sciences Peking University High School of Central University for Nationalities

It is well-known that the numerical value is always larger than the measured value,amounting to many times,if we calculate the stress of the specimen in the impulse test using the NASTRAN and ANSYS (N-A) *** believe that the impact induces shock wave or quasi-traveling wave in the specimen,which can qualitatively explain the discrepancy of the two *** order to verify it,the Lax-Friedrichs (L-F) scheme is taken to simulate the transmission of shock wave and quasi-traveling wave in *** results show that the action area of the stress wave is small and the action time is very short,so the resulting stress and actual work are not *** addition,the distribution of the impact values obtained by the numerical simulation is in accordance with the trend of the measured impact values.

关键词： aerospace environment test shock wave quasi-traveling wave