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Chinese Chemical Letters 1997年第8期8卷 689-690页

作者： Xiao Ping NIE Zhen Qiang WANG Xiu Lin YE(Department of Chemistry,Peking university, beijing, 100871) Department of Chemistry Peking University Beijing 100871 China

The reaction of phenacyl benzoate derivatives with acetamide at about 14.°in the presence of BF3.catalyst gave 2-aryl-4.phenyloxazoles. This method can be applied to the preparation of 2-alkyl-4.phenyloxazoles as well.

关键词： Studies on the Synthesis of Sesamin-Group Lignans A Simplified Sythesis of 2-Aryl-4.phenyloxazoles and 2-Alkyl-4.phenyloxazoles

Remarks on the bounds for cryptanalysis of low private key RSA

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Progress in Natural Science:Materials International 2009年第10期19卷 1327-1331页

作者： Haijian Zhou a,Ping Luo b,Daoshun Wang a,Yiqi Dai a a Department of Computer Science and Technology,Tsinghua university,beijing 100084.China b School of Software,Tsinghua university,beijing 100084.China Department of Computer Science and Technology Tsinghua University Beijing 100084 China School of Software Tsinghua University Beijing 100084 China

Boneh and Durfee have developed a cryptanalytic algorithm on low private key *** algorithm is based on lattice basis reduction and breaks RSA with private key d < N0:*** on,an improved version by Blmer and May enhan... 详细信息

Boneh and Durfee have developed a cryptanalytic algorithm on low private key *** algorithm is based on lattice basis reduction and breaks RSA with private key d 4.bit public key eN;eT.

关键词： RSA Cryptanalysis Low private key Lattice basis reduction

On the dynamics in a transitional boundary layer

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Communications in Nonlinear Science and Numerical Simulation 2001年第3期6卷 111-171页

作者： C. B. LEE and R. LEE Department of Mechanics and Engineering Science/State Key Laboratory for Studies of Turbulence and Complex Systems, Peking university, beijing 100871, China Department of Engineering Mechanics, Tsinghua university, beijing 100084. Chi Department of Mechanics and Engineering Science / State Key Laboratory for Studies of Turbulence and Complex Systems Peking University Beijing 100871 China Department of Engineering Mechanics Tsinghua University Beijing 100084 China

A model is presented to describe the dynamic physical processes that occur in a transitional boundary layer flow. The CS-solitons, the closed vortex, the secondary closed vortex and the chain of ring-like vortices are postulated to be the basic flow structures of the transitional boundary layer as well as the turbulent boundary layer. It is argued that the central features of transitional and developed turbulent boundary layer flows can be explained in terms of how the series vortices interact with each other, and with the CS-solitons. The physical process that leads to the regeneration of the new closed vortex along the border of the CS-soliton, as well as the processes of evolution of the vortices to high frequency vortices, is described. The model is supported by the important developments in a number of "kernel" experiments, which illustrate both transitional and developed turbulent boundary layer. An important aspect of the model is that it has been formulated to be consistent with accepted rational mechanics concepts that are known to provide a proper physical description of other flows.

关键词： boundary layer transition dynamic processes onset of turbulence

DISTRIBUTION OF SULFUR IN HIGH TEMPERATURE PHASES OF CAST IRON

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Acta Metallurgica Sinica(English Letters) 1989年第10期2卷 230-234页

作者： HAN Qiyong YANG Ping SONG Weixi university of Science and Technolonology beijing,beijing,China Division of Metallography,Dept.of Materials,university of Science and Technology beijing,beijing,China

The distribution of subversive element sulfur in high temperature phases during solidification of cast iron was investigated by means of liquid quenching method and *** results show that in grey cast iron,sulfur is concentrated in the liquid,flake graphite and in the peripherial area of D-type supercooled graphite eutectic cells,but less sulfur is in austenite. Besides,the content of sulfur in A-type graphite is higher than that in D-type graphite,and sulfur content in eutectic austenite is a little higher than that in primary ***,in nodular graphite cast iron less sulfur is in liquid and austenite,but more in nodular graphite. The blackness of the spots on the emulsion film corresponds to the atomic percentage of radioactive substances located on the surface of the specimen.

关键词： cast iron autoradiograph sulfur graphite

Preparation of (Ti, Sn)O_2 Nano-Composite Photocatalyst by Supercritical Fluid Dry Combination Technology

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Journal of Materials Science & Technology 2005年第2期21卷 191-195页

作者： Jingchang ZHANG, Qing LI and Weiliang CAO Institute of Modern Catalysis, The Key Laboratory of Science and Technology of Controllable Chemical Reactions, Ministry of Education, beijing university of Chemical Technology, beijing 100029, China Lab. of Controllable Chem. Reactions Inst. of Modern Catalysis Beijing Univ. of Chem. Technol. Beijing 100029 China

A series of TiO2-SnO2 nano-sized composite photo-catalysts containing Sn (9.3.-3..1%) were prepared from TiCI4.and SnCl4.5H2O by using sol-gel, supercritical fluid dry and solid-phase reaction (SCFD) combination technology. Characterizations with X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FTIR) showed that, in addition to anatase type TiO2, a new active phase (Ti, Sn)O2 (with particle size of 2.0-4.3.nm) formed, and there were no SnO2 crystals observed in the range of the doping concentration studied. Photo-catalytic reaction of phenol was used as a model reaction to evaluate the catalytic activities of the obtained catalysts. Compared with pure TiO2 or Ti-Sn catalyst prepared with general sol-gel method, Ti-Sn nano-composite photo-catalyst thus obtained showed significant improvement in catalytic activity. The photo-catalytic degradation rate of phenol could reach as high as 93.5% after 7 h. The preparation conditions of the new phase (Ti, Sn)O2 were investigated and its catalytic mechanism was proposed. The photo-catalytic particles prepared using SCFD combination technology exhibited small particle size, large surface area and high activity.

关键词： Anatase TiO2 (Ti, Sn)O2 Photo-catalytic Supercritical fluid dry method Solid-phase reaction

Protective effect of liver ischemic preconditioning on rat hepatocytes

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Science China(Life Sciences) 2009年第9期52卷 836-840页

作者： FU JianZhu1,2,WANG Yu1,ZHANG LiJun2 & YU ZeLi2 1 Department of General Surgery,beijing Friendship Hospital,Capital Medical university,beijing 100050,China 2 Department of General Surgery,beijing Tongren Hospital,Capital Medical university,beijing 10073.,China Department of General Surgery Beijing Friendship Hospital Capital Medical University Beijing China Department of General Surgery Beijing Tongren Hospital Capital Medical University Beijing China

Ischemic preconditioning (IPC) protects liver graft function following ischemia in liver transplantation and liver resection. The aim of this study was to assess the advantages and any potential disadvantages of liver IPC prior to isolation for rat hepatocytes during isolation and cryopreservation. After isolating and thawing the cryopreserved hepatocytes after 14.and 28 d,cell viability,efficiency,and lactate dehydrogenase (LDH) levels in preserve solution were examined for every group. Groups treated with IPC had better cell viability determination,assessment of plating efficiency and lactate dehydrogenase (LDH) assay than Group without IPC,suggesting that IPC prior to isolation may have a significant protective effect on hepatocytes subjected to isolation and short period cryopreservation.

关键词： liver ischemic preconditioning hepatocytes cryopreservation

Large eddy simulation of stably stratified turbulence

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Science China(Physics,Mechanics & Astronomy) 2010年第1期53卷 135-146页

作者： SHEN Zhi, LI YuPeng, CUI GuiXiang & ZHANG ZhaoShun Department of Engineering Mechanics, Tsinghua university, beijing 100084. China Department of Engineering Mechanics Tsinghua University Beijing China

Stable stratification turbulence, as a common phenomenon in atmospheric and oceanic flows, is an important mechanism for numerical prediction of such flows. In this paper the large eddy simulation is utilized for investigating stable stratification turbulence numerically. The paper is expected to provide correct statistical results in agreement with those measured in the atmosphere or ocean. The fully developed turbulence is obtained in the stable stratification fluid by large eddy simulation with different initial velocity field and characteristic parameters, i.e. Reynolds number Re and Froude number Fr. The evolution of turbulent kinetic energy, characteristic length scales and parameters is analyzed for investigating the development of turbulence in stable stratification fluid. The three-dimensional energy spectra, horizontal and vertical energy spectrum, are compared between numerical simulation and real observation in the atmosphere and ocean in order to test the reliability of the numerical simulation. The results of numerical cases show that the large eddy simulation is capable of predicting the properties of stable stratification turbulence in consistence with real measurements at less computational cost. It has been found in this paper that the turbulence can be developed under different initial velocity conditions and the internal wave energy is dominant in the developed stable stratification turbulence. It is also found that the characteristic parameters must satisfy certain conditions in order to have correct statistical property of stable stratification turbulence in the atmosphere and ocean. The Reynolds number and Froude number are unnecessarily equal to those in atmosphere or ocean, but the Reynolds number must be large enough, say, greater than 10 2 , and Froude number must be less than 0.1. The most important parameter is ReFr 2 which must be greater than 10.

关键词： stratified turbulence internal wave potential vortex large eddy simulation

Mechanical and field-emission properties of individual ZnO nanowires studied in situ by transmission electron microscopy

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功能材料信息 2007年第5期4卷 14-15页

作者： ZHANG Yue~(1,2) BAI Xue-dong~3.GU You-song~1 QI Jun-jie~1 LIAO Qing-liang~1 HUANG Yun-hua~1 (1.Department of Materials Physics,university of Science and Technology beijing,beijing {3.China 2.State Key Laboratory for Advanced Metals and Materials,university of Science and Technology,beijing,beijing {3.China 3.State Key Laboratory for Surface Physics,Institute of Physics,Chinese Academy of Sciences,beijing 100080,China)

The mechanical and field-emission properties of individual ZnO nanowires,grown by a solid-vapour phase thermal sublimation process,were studied in situ by transmission electron microscopy(TEM)using a home-made TEM specimen *** mechanical resonance is electrically induced by applying an oscillating voltage,and in situ imaging has been achieved *** mechanical results indicate that the elastic bending modulus of individual ZnO nanowires were measured to be～58 GPa.A nanobalance was buil...

关键词： ZnO nanowire in situ mechanical property field-emission property

Calculation of light emission in sonoluminescence

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Science China(Physics,Mechanics & Astronomy) 2009年第4期52卷 593-601页

作者： LI ChaoHui1 & AN Yu1,2 1 Department of Physics,Tsinghua university,beijing 100084.China 2 Institute of Acoustics,Chinese Academy of Sciences,beijing 100190,China Department of Physics Tsinghua University Beijing China Institute of Acoustics Chinese Academy of Sciences Beijing China

We modify a uniform model of single bubble sonoluminescence,in which heat diffusion,water vapor diffusion and chemical reactions are included to describe the bubble dynamics,and the processes of electron-atom bremsstrahlung,electron-ion bremsstrahlung and recombination radiation,radiative attachment of electrons to atoms and molecules,line emissions of OH radicals and Na atoms are taken into account to calculate the light emission. With this model,we compute the light pulse width,the photon number per flash,the continuum and line spectra and the gas species as the products of chemical reactions,and try to compare with all the experimental data available. We obtain good agreement with the observations of Ar and Xe bubbles in many cases,but fail to match the experimental data of the photon number per flash. We also find that for He bubble the computed photon number is always too small to interpret the observations.

关键词： sonoluminescence bremsstrahlung radiative attachment line spectrum collision broadening

Logistics Classification Evolution and Microscopic Logistics Freight Integration

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Logistics Classification Evolution and Microscopic Logistics...