Effects of wall temperature on boundary layer stability over a blunt cone at Mach 7.99

Effects of wall temperature on stabilities of hypersonic boundary layer over a 7-degree half-cone-angle blunt cone are studied by using both direct numerical simulation (DNS) and linear stability theory (LST) analysis. Four isothermal wall cases with Tw/T0= 0.5, 0.7, 0.8 and 0.9, as well as an adiabatic wall case are considered. Results of both DNS and LST indicate that wall temperature has significant effects on the growth of disturbance waves. Cooling the surface accelerates unstable Mack II mode waves and decelerates the first mode (Tollmien–Schlichting mode) waves. LST results show that growth rate of the most unstable Mack II mode waves for the cases of cold wall Tw/T0=0.5 and 0.7 are about 45% and 25% larger than that for the adiabatic wall, respectively. Numerical results show that surface cooling modifies the profiles of rdut/dyn and temperature in the boundary layers, and thus changes the stability haracteristic of the boundary layers, and then effects on the growth of unstable waves. The results of DNS indicate that the disturbances with the frequency range from about 119.4 to 179.1 kHz, including the most unstable Mack modes, produce strong mode competition in the downstream region from about 11 to 100 nose radii. And adiabatic wall enhances the amplitudes of disturbance according to the results of DNS, although the LST indicates that the growth rate of the disturbance of cold wall is larger. That because the growth of the disturbance does not only depend on the development of the second unstable mode

长期保存起源信息封装技术的比较研究

文章详细介绍了四种国际主流起源信息的封装格式和应用方案，对其封装方法、元数据支持、工具支 持和易用性等进行了对比分析，进一步探讨了四种方法在实际应用中的问题及其应对策略，并建议在实际运用 中，应结合具体场景选择合适的封装格式和封装策略，以达到最佳效果。</p

基于OAIS信息模型的起源信息封装策略研究与应用

［目的/意义］探索设计并实施长期保存系统起源信息封装策略。［方法/过程］首先分析 OAIS 信息 模型的详细组成，然后分析长期保存系统起源封装的特定服务需求，总结国际主流起源封装策略的基本特点， 提出基于 OAIS 信息模型的起源信息封装策略，并利用 Fedora 仓储系统的内容模型 FOXML 进行封装实现。 ［结果/结论］该策略遵循 OAIS 及 PＲEMIS 标准，全面记录起源信息，具有灵活可扩展的特点，但同时管理和使 用相对比较复杂。</p

构建以事件为核心的长期保存系统起源管理框架

［目的/意义］研究建立长期保存系统起源管理框架，通过有效管理起源信息，确保长期保存系统所 存档数据的真实可靠可用。［方法/过程］基于数字对象保存周期进行起源事件定义，基于 OAIS 保存流程进行 起源管理框架设计，以事件为核心进行起源管理功能模型和起源信息模型设计。［结果/结论］初步完成基于事 件的保存系统起源管理框架的设计，既遵循保存领域的相关标准，同时兼顾实践需求，对长期保存系统具有很 好的普适性和可行性，但其在有效性和实用性方面还有待进一步验证。</p

构建以事件为核心的长期保存系统起源管理框架

［目的/意义］研究建立长期保存系统起源管理框架，通过有效管理起源信息，确保长期保存系统所 存档数据的真实可靠可用。［方法/过程］基于数字对象保存周期进行起源事件定义，基于 OAIS 保存流程进行 起源管理框架设计，以事件为核心进行起源管理功能模型和起源信息模型设计。［结果/结论］初步完成基于事 件的保存系统起源管理框架的设计，既遵循保存领域的相关标准，同时兼顾实践需求，对长期保存系统具有很 好的普适性和可行性，但其在有效性和实用性方面还有待进一步验证。</p

Direct numerical simulation of hypersonic boundary layer transition over a blunt cone with a small angle of attack

The direct numerical simulation of boundary layer transition over a 5&deg; half-cone-angle blunt cone is performed. The free-stream Mach number is 6 and the angle of attack is 1&deg;. Random wall blow-and-suction perturbations are used to trigger the transition. Different from the authors&rsquo; previous work [Li et al., AIAA J. 46, 2899(2008)], the whole boundary layer flow over the cone is simulated (while in the author&rsquo;s previous work, only two 45&deg; regions around the leeward and the windward sections are simulated). The transition location on the cone surface is determined through the rapid increase in skin fraction coefficient (Cf). The transition line on the cone surface shows a nonmonotonic curve and the transition is delayed in the range of 0&deg; &le; &theta; &le; 30&deg; (&theta; = 0&deg; is the leeward section). The mechanism of the delayed transition is studied by using joint frequency spectrum analysis and linear stability theory (LST). It is shown that the growth rates of unstable waves of the second mode are suppressed in the range of 20&deg; &le; &theta; &le; 30&deg;, which leads to the delayed transition location. Very low frequency waves VLFWs� are found in the time series recorded just before the transition location, and the periodic times of VLFWs are about one order larger than those of ordinary Mack second mode waves. Band-pass filter is used to analyze the low frequency waves, and they are deemed as the effect of large scale nonlinear perturbations triggered by LST waves when they are strong enough.The direct numerical simulation of boundary layer transition over a 5&deg; half-cone-angle blunt cone is performed. The free-stream Mach number is 6 and the angle of attack is 1&deg;. Random wall blow-and-suction perturbations are used to trigger the transition. Different from the authors&rsquo; previous work [ Li et al., AIAA J. 46, 2899 (2008) ], the whole boundary layer flow over the cone is simulated (while in the author&rsquo;s previous work, only two 45&deg; regions around the leeward and the windward sections are simulated). The transition location on the cone surface is determined through the rapid increase in skin fraction coefficient (Cf). The transition line on the cone surface shows a nonmonotonic curve and the transition is delayed in the range of 20&deg; &le; &theta; &le; 30&deg; (&theta; = 0&deg; is the leeward section). The mechanism of the delayed transition is studied by using joint frequency spectrum analysis and linear stability theory (LST). It is shown that the growth rates of unstable waves of the second mode are suppressed in the range of 20&deg; &le; &theta; &le; 30&deg;, which leads to the delayed transition location. Very low frequency waves (VLFWs) are found in the time series recorded just before the transition location, and the periodic times of VLFWs are about one order larger than those of ordinary Mack second mode waves. Band-pass filter is used to analyze the low frequency waves, and they are deemed as the effect of large scale nonlinear perturbations triggered by LST waves when they are strong enough

以事件为核心的长期保存数字起源管理框架研究

首先分析了长期保存领域相关标准OAIS,PREMIS和TRAC对起源信息的解释和要求,然后对比分析了已有的长期保存系统对起源的应用情况。在此基础上,提出了以事件为核心记录起源的应用框架,并对关键问题加以分析,包括起源的内容,组织方案,存储封装和技术实施方案,为长期保存系统组织管理起源信息提供参考。&nbsp;</p

A New High Order Accurate Shock Capture Method with Wave Booster

A new kind of shock capturing method is developed. Before applying the high order accurate traditional scheme which is called as base scheme in this paper the fluid parameters are preconditioned in order to control the group velocity. The newly constructed scheme is high order accurate, simple, has high resolution of the shock, and less computer time consumed

American Faculty Development in the Age of Networker: Multiple Interpretations and Practical Strategies

美国高校教师专业发展培训经历了从无到有的阶段,如今已经进入了“协统时代“。这个时代有着不同以往的鲜明特色,对高校教师培训工作提出了全新的挑战。“协统时代“的美国高校教师培训工作需要致力于满足教师职业的多种角色定位、应对学生群体的新变化,并适应高等教育教学、学习与学术的新范式。“协统时代“的培训工作在实践层面主要采取三种策略:扩大培训范围、丰富培训项目和加强项目评估。在这个时代,美国的高校教师培训工作已从早期“被边缘化“的状态一跃成为大学保持创造力的动力来源。After the development of more than fifty years,the faculty development practice in American universities and colleges has stepped into the Age of Networker.The new age has some distinctive features and challenging requirements.The faculty developers need to help balance the multiple roles required by the meta-profession,to help meet the needs of increasingly diversified college students groups,and to adapt to the new paradigm of teaching,learning and scholarship.In practice,three key strategies are undertaken,which are to enlarge the scope of trainees,to enrich the development programs and to implement program evaluations.全国教育科学“十二五”规划2011年度国家重点课题(AFA110008)研究成果之一; 中国博士后科学基金第51批资助项目(2012M511443)研究成果之