加速器高频D���路Q值的计算与测量

介绍了回旋加速器高频单D���盒D���路Q值的计算与测量方法。重点对Q值的理论计算进行推导,并对计算原理进行说明。然后对计算结果和测量结果进行比较。得出的计算和测量结果基本吻合。误差产生的主要原因是计算过程中的近似和短路片接触电阻的取值,其中短路片接触电阻是一个重要因素,在设计腔体时应引起足够的重视。

中国及相关海域褐虾总科系统分类学和动物地理学研究

褐虾总科包括褐虾科和镰虾科，是重要的底栖生物类群，而且很多褐虾种为常见的经济种，其中中国北方海域最常见的为日本褐虾Crangon hakodatei Rathbun, 1902，另外黄海褐虾Crangon uritai Kim & Hayashi, 1999在黄渤海也较为常见。在东海和南海，污泥疣褐虾Pontocaris pennata (Bate, 1888)和拉氏爱琴虾Aegaeon lacazei (Gourret, 1887)在底栖生物拖网时常可采到，有很大的经济价值。我国对褐虾总科的研究很少，亟需对我国海域的褐虾进行全面的系统分类学和地理分布研究。 本论文所依据的标本主要为中国科学院海洋研究所海洋生物标本馆馆藏的约1600号褐虾类标本，标本主要采自渤海、黄海、东海、南海四大海域，也有部分标本采自日本海、南极和北极等海域，并得到国外同行专家惠赠的褐虾类标本约100号，同时也检查了其它单位保藏的少量标本。 本论文主要采用传统的形态学方法进行分类学研究，共鉴定出褐虾科14属25种，其中1个新种，6个新记录种，镰虾科1属7种，其中2个新种，3个新记录种。参照历史文献与现在研究结果，中国海域的褐虾类至少有2科11属44种。 本文通过对约1700号标本的详细检查，总结了各个属和种的分类学特征和地理分布特点，对各属的分种均附有详细系统的检索表，对鉴定的32种褐虾均附有详细的背面整体图和侧面整体图以及附肢等的局部形态图，并对各种进行了中文名称的考订。 本研究是我国首次关于褐虾总科的系统分类学和动物地理学研究，研究结果将改变我国在褐虾总科研究报道方面的薄弱现状，并为此动物类群的多样性等研究提供重要的基础资料。研究结果澄清了分类学上存在争议的疑难种，发现了3个新种，报道了9个新记录种，阐明了我国褐虾总科的区系特点。

三峡永久船闸高边坡开挖三维离散元数值模拟:3-D Simulation of the Excavation of High Steep Slope of Three-Gorges Permanent Lock by Distinct Element Method

采用面一面接触的三维离散元刚性块体模型,从实测节理面中取出其中的三组,按照其倾向、倾角和节理间距将三峡永久船闸未开挖的区域划分为10~5个离散单元,通过施加力边界条件,给出了与实测初始地应力场接近的数值模拟结果；然后,分4步模拟了永久船闸的开挖过程。计算结果表明：开挖过程会引起节理面出现张开趋势,个别岩体还会沿着节理面滑移。岩体位移的不对称现象较为自然地说明了由节理引起的岩体各向异性特征。

Perturbational Finite Volume Method For The Solution of 2-D Navier-Stokes Equations on Unstructured and Structured Colocated Meshes

Based on the first-order upwind and second-order central type of finite volume( UFV and CFV) scheme, upwind and central type of perturbation finite volume ( UPFV and CPFV) schemes of the Navier-Stokes equations were developed. In PFV method, the mass fluxes of across the cell faces of the control volume (CV) were expanded into power series of the grid spacing and the coefficients of the power series were determined by means of the conservation equation itself. The UPFV and CPFV scheme respectively uses the same nodes and expressions as those of the normal first-order upwind and second-order central scheme, which is apt to programming. The results of numerical experiments about the flow in a lid-driven cavity and the problem of transport of a scalar quantity in a known velocity field show that compared to the first-order UFV and second-order CFV schemes, upwind PFV scheme is higher accuracy and resolution, especially better robustness. The numerical computation to flow in a lid-driven cavity shows that the under-relaxation factor can be arbitrarily selected ranging from 0.3 to 0. 8 and convergence perform excellent with Reynolds number variation from 102 to 104.

High Aspect Ratio (L/D) Riser Viv Prediction Using Wake Oscillator Model

A two-dimensional (2-D) vortex-induced vibration (VIV) prediction model for high aspect ratio (LID) riser subjected to uniform and sheared flow is studied in this paper. The nonlinear structure equations are considered. The near wake dynamics describing the fluctuating nature of vortex shedding is modeled using classical van der Pol equation. A new approach was applied to calibrate the empirical parameters in the wake oscillator model. Compared the predicted results with the experimental data and computational fluid dynamic (CFD) results. Good agreements are observed. It can be concluded that the present model can be used as simple computational tool in predicting some aspects of VIV of long flexible structures. (C) 2008 Elsevier Ltd. All rights reserved.

Stress intensity factor histories of a steadily propagating crack under 3-D combined mode traction

Elastodynamic stress intensity factor histories of an unbounded solid containing a semi-infinite plane crack that propagates at a constant velocity under 3-D time-independent combined mode loading are considered. The fundamental solution, which is the response of point loading, is obtained. Then, stress intensity factor histories of a general loading system are written out in terms of superposition integrals. The methods used here are the Laplace transform methods in conjunction with the Wiener-Hopf technique.