广义二阶流体管内轴向流动

在流体的本构关系中引入分数阶导数运算，对于介于粘性与弹性之间的流体的描述更具有合理性。本文将这种关系引入二阶流体，研究其管内轴向流动。我们先求出了１／２阶导数的解析解，用以验证Ｌａｐｌａｃｅ数值反演的ＣＲＵＭＰ方法的有效性。然后用ＣＲＵＭＰ法分析二阶流体管内轴向流动的特征。分析表明粘弹性特征越明显的流体，其速度与应力对分数导数的阶数越具有敏感性。     

Sources of velocity spread in electron beams from magnetron injection guns

Calculated trajectories for the electron beam of a known gyrotron have been analysed to determine the relative importance of some of the contributions to velocity spread. For the geometry analysed, space-charge and thermal velocities at the cathode produced only a small part of the calculated velocity spread; much more was generated by the variation of electric field over the length of the cathode surface. The total range of transverse velocity was substantially reduced by adjustment of the shape of one electrode.     

第二类Stirling数的新表示式

以组合分析方法引入指数型生成函数,利用正交关系通过迭代给出第二类 Stir-ling 数的两个新的解析表示式.     

Lyapunov spectrum determination from the FEM simulation of a chaotic advecting flow

The problem of the determination of the Lyapunov spectrum in chaotic advection using approximated velocity fields resulting from a standard FEM method is investigated. A fourth order Runge–Kutta scheme for trajectory integration is combined with a third order Jacobian matrix method with QR ‐factorization. After checking the algorithm on the standard Lorenz and coupled quartic oscillator systems, the method is applied to a model 3‐D steady flow for which an analytical expression is known. Both linear and quadratic approximated velocity fields succeed in predicting the Lyapunov exponents as well as describing the chaotic or regular regions inside the flow with satisfactory accuracy. A more realistic flow is then studied in order to delineate the possible limitations of the approach. Copyright © 2005 John Wiley & Sons, Ltd.     

Dehydroaromatization of Methane with a Small Amount of Ethane for Higher Yield of Benzene

The dehydroaromatization of methane was investigated with addition of a few ethane. A high benzene yield was achieved at a higher space velocity. The addition of CO2 could improve the stability.     

The cluster-galaxy cross-correlation and the average infall velocity around cluster in the modified CDM models

The cluster-galaxy cross-correlation and the average infall velocity around cluster for the tilted CDM models, the hot-cold mixed dark matter models (MDM) and theA CDM models are calculated. And it is found that the prediction of the cluster-galaxy cross-correlation of theA CDM models with Ω_A=0.9, Ω_C=0.1,h=1,b = 1 or 2 is much higher than that of observation for the radius larger than 10 h⁻¹ Mpc (H₀ = 100 h.kms⁻¹Mpc⁻¹), and the other models are compatible with the observation on the scale of (3–20) h⁻ Mpc. The results can be used to compare with new observations to restrict the nature of the dark matter and the biasing factor. Project supported by the National Natural Science Foundation of China (Grant No. 19733001).     

Measurement of Solid-gas Two-phase Flow using Optical Fiber Sensor

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用1-3及2-2连通复合换能器测量冻土

根据冻土弹性波测试要求，研制了一种测试冻土用的500kHz纵波，横波1-3及2-2连通复合超声换能器，其灵敏度高，频带宽，声阻抗低，波形简单及脉冲波形前沿徒削，亦适用于其它介质力学特性测试。文章介绍了换能结构原理及测量系统特性，实测了不同含水量（7%-25%）及负温（-2℃--20℃）条件下兰州黄土试块的纵，横波声速，获得很高测量精度（10ps级）。     

PROPAGATION OF SURFACE ACOUSTIC WAVES IN PRESTRESSED ANISOTROPIC LAYERED PIEZOELECTRIC STRUCTURES

The propagation of surface acoustic waves in layered piezoelectric structures withinitial stresses is investigated.The phase velocity equations are obtained for electrically free andshorted cases,respectively.Effects of the initial stresses on the phase velocity and the electrome-chanical coupling coefficient for the fundamental mode of the layered piezoelectric structures arediscussed.Numerical results for the c-axis oriented fihn of LiNbO_3 on a sapphire substrate aregiven.It is found that the fractional change in phase velocity is a linear function with the ini-tial stresses,and the electromechanical coupling factor increases with an increase of the absolutevalues of the compressive initial stresses.The results are useful for the design of surface acousticwave devices.