A TVD Scheme for Incompressible Flow Coupled With Different Turbulence Modles on A Ground-Mounted Square-RIB Flow

A finite-difference Total Variation Diminishing (TVD) numerical simulation model for coupling the Reynolds Averaged Navier-Stokes (RANS) equations, pressure-relative continuity equation and various k-ε turbulence models was developed to solve the incompressible flow based on the pseudo-compressibility method. The hyperbolicity of all these equations was studied and the discretization of the fully coupling equations with all the primal variables and source terms were made in this article. Numerical simulation for modeling the flow around a ground-mounted square rib was implemented and validated by comparing with the published wind tunnel experimental data. It is shown that such a numerical simulation method with a proper turbulence model has a very good accuracy to simulate the flow around a surface-mounted rib. It is concluded that the Renormalization Group (RNG) and Chen-Kim k-ε turbulence models have much better ability to predict the characteristics of the vortex structure and flow separation than the standard k-ε model.     

水分对高碱值硫化烷基酚钙结构和清净性的影响

采用傅立叶红外光谱仪，分析了水分对清净剂高碱值硫化烷基酚钙结构组成的影响；采用热管氧化试验法和曲轴箱模拟试验法，考察了高碱值硫化烷基酚钙在加水前后清净性能的变化；采用四球试验机和高频往复试验机，分析了水分对高碱值硫化烷基酚钙润滑性能的影响。结果表明，油中的水含量对高碱值硫化烷基酚钙的水解安定性能影响较大，并且随着水含量的增加，油品的清净性能和抗磨性能变差。     

基于自然地理形态的道路测设及其曲线方程的拟合

在山区村镇及风景旅游名胜区的建设中，其道路的曲线测设，往往要基于自然地理形态进行，也就是路径的选择，有时具有不可选择性，且要求与实地具有最大的符合性。因此，其测设的作业方法不同于一般意义的道路测设；其曲线方程的建立，也是极其困难的。本就基于自然地理形态的道路测设工作的曲线类型的选择、曲线的拟合方法、曲线方程的建立及其数据的计算，提出了利用CAD技术进行曲线拟合、曲线方程的建立、曲线计算的实用技术方法。     

Fluctuations of Turbulent Bed Shear Stress

With the assumption that the bed shear stress fluctuates in a lognormal fashion, the probability density function (PDF) of the standardized bed shear stress is derived as a function of the relative shear stress intensity. The PDF is more skewed with larger relative intensities, but approaches a Gaussian function when the relative intensity is small. The computed PDF agrees well with the reported experimental data for flows over a smooth boundary. The higher-order moments of the bed shear stress, skewness, and kurtosis, are shown analytically to be also dependent on the relative intensity. The theoretical dependencies are then compared to a number of measurements available in the literature. The Reynolds number effect on the relative intensity is also discussed.     

大容量数据库如何避免ora-01555错误

本文分析了造成ora-01555错误的原因，并提出解决办法。ora-01555错误一直是DBA与developer争论的焦点，解决其问题应是双方协调的结果。     

Assessing the role of basic control measures, antivirals and vaccine in curtailing pandemic influenza: scenarios for the US, UK and the Netherlands

An increasing number of avian flu cases in humans, arising primarily from direct contact with poultry, in several regions of the world have prompted the urgency to develop pandemic preparedness plans worldwide. Leading recommendations in these plans include basic public health control measures for minimizing transmission in hospitals and communities, the use of antiviral drugs and vaccination. This paper presents a mathematical model for the evaluation of the pandemic flu preparedness plans of the United States (US), the United Kingdom (UK) and the Netherlands. The model is used to assess single and combined interventions. Using data from the US, we show that hospital and community transmission control measures alone can be highly effective in reducing the impact of a potential flu pandemic. We further show that while the use of antivirals alone could lead to very significant reductions in the burden of a pandemic, the combination of transmission control measures, antivirals and vaccine gives the most 'optimal' result. However, implementing such an optimal strategy at the onset of a pandemic may not be realistic. Thus, it is important to consider other plausible alternatives. An optimal preparedness plan is largely dependent on the availability of resources; hence, it is country-specific. We show that countries with limited antiviral stockpiles should emphasize their use therapeutically (rather than prophylactically). However, countries with large antiviral stockpiles can achieve greater reductions in disease burden by implementing them both prophylactically and therapeutically. This study promotes alternative strategies that may be feasible and attainable for the US, UK and the Netherlands. It emphasizes the role of hospital and community transmission control measures in addition to the timely administration of antiviral treatment in reducing the burden of a flu pandemic. The latter is consistent with the preparedness plans of the UK and the Netherlands. Our results indicate that for low efficacy and coverage levels of antivirals and vaccine, the use of a vaccine leads to the greatest reduction in morbidity and mortality compared with the singular use of antivirals. However, as these efficacy and coverage levels are increased, the use of antivirals is more effective.     

一种基于混沌的随机数发生器设计及其IC实现

在密码学、仿真学以及集成电路测试等许多领域 ,随机数起着重要的作用。在密码学中 ,通常要求所使用的随机数具有不可预测性。基于混沌现象 ,使用开关电容技术 ,用集成电路实现了一种硬件随机数发生器。测试结果表明 ,其产生的序列具有不可预测性 ,可以满足密码学的应用要求。     

开发有线电视收费管理系统需注意的问题

分析有线电视业务及用户管理中出现的问题与解决办法，为系统的开发建立数据模型，以确保有线电视网络公司和用户的利益。     

基于环境噪声的真随机数的产生

为了提供一种简便和有效的真随机数生成方法，通过分析环境噪声数据的统计特性，提出同余法和正负法将声音波形数据进行处理。去除声波数据的周期性、连续性、相关性，提取其随机性。同真随机数采集系统设计相关的电路噪声问题以及采集速度问题也作了讨论。用此思路构建的真随机数采集系统原型已经能够用来产生性能较佳的真随机数，证明了设计思路和处理方法的正确有效性。     

环氧大豆油制备工艺研究

介绍了在硫酸、７３２阳离子交换树脂的催化作用下，制备环氧大豆油的工艺，得出了最佳工艺条件。