薄片分离过程流场特性的数值仿真研究

利用弹簧近似法和局部网格重构相结合的非结构动网格方法,耦合求解Navier-Stokes方程和六自由度刚体动力学方程,数值模拟了三维薄片非定常分离过程。数值仿真结果有效反映出薄片分离过程中运动速度、轨迹、受力变化规律及流场特性的发展与变化。根据数值仿真结果对薄片分离机理、多体气动干扰作用进行了分析。分离过程中单个薄片与主体段周围形成复杂流动,并伴随着尾迹涡的运动、发展等非定常过程。气动载荷的非线性变化是薄片分离的主要原因。     

Observations of Vertical Reflections from the Topside Martian Ionosphere

The Martian ionosphere has for the first time been probed by a low frequency topside radio wave sounder experiment (MARSIS) (Gurnett et al., 2005). The density profiles in the Martian ionosphere have for the first time been observed for solar zenith angles less than 48 degrees. The sounder spectrograms typically have a single trace of echoes, which are controlled by reflections from the ionosphere in the direction of nadir. With the local density at the spacecraft derived from the sounder measurements and using the lamination technique the spectrograms are inverted to electron density profiles. The measurements yield electron density profiles from the sub-solar region to past the terminator. The maximum density varies in time with the solar rotation period, indicating control of the densities by solar ionizing radiation. Electron density increases associated with solar flares were observed. The maximum electron density varies with solar zenith angle as predicted by theory. The altitude profile of electron densities between the maximum density and about 170m altitude is well approximated by a classic Chapman layer. The neutral scale height is close to 10 to 13 km. At altitudes above 180 km the densities deviate from and are larger than inferred by the Chapman layer. At altitudes above the exobase the density decrease was approximated by an exponential function with scale heights between 24 and 65 km. The densities in the top side ionosphere above the exobase tends to be larger than the densities extrapolated from the Chapman layer fitted to the measurements at lower altitudes, implying more efficient upward diffusion above the collision dominated photo equilibrium region.     

浅析促进高等职业教育发展的对策

当今世界范围的竞争日趋激烈，经济的竞争，科学技术的竞争，归根到底是教育的竞争和人才的竞争。因此，提高劳动者的全面素质，对于一个国家的社会经济发展可以说具有决定性的意义。高等职业教育承担着培养一线劳动者的任务，办好高等职业教育，对于全面提高劳动者素质，发展生产力，提高产品质量，促进经济发展具有巨大的作用。本文详细分析并论述了推动高等职业教育发展的措施。     

The 1972 Liability Convention: time for revision?

The 1972 Liability Convention is an example of the interaction of international policy, international relations and economy. It helps define liability for damage caused by space objects. However, with more and more space activities taking place on a daily basis, along with the trend towards commercialization, the continued application of the Convention faces severe challenges. Consequently, a serious review of the Convention is needed after more than 30 years of its existence. With possible revision the Convention would offer clear guidelines for decision makers to decide cases in a rational way best suited to the development of space operations.     

电液比例阀的设计与实验研究

在电液比例阀的设计与计算中,弹簧的设计与计算一直是设计人员头痛的问题,在设计电液比例阀的过程中,本文作者通过大量实验和研究,总结出了电液比例阀中弹簧的设计与检验方法。     

论微电子机械系统MEMS

简介了微电子机械系统MEMS的基本概念、构成及显著特点 ,并对微电子机械系统的典型器件如传感器 ,执行器等作了介绍与分析 ,提出了微系统之间要研究的问题 ;探讨了微电子机械系统的发展应用前景     

里泼丝竹:迤沙拉彝村的谈经古乐

从攀枝花市仁和区平地镇乘车去迤沙拉,远远望去。依山而建的彝村像一只展翅飞翔的大鸟。这只不知其名不知来历的大鸟,不知何时以这种飞翔的姿势定格在这片土地上是一个谜。对许多人来说,迤沙拉村更是一个谜。     

串联TBCC可调喷管气膜冷却数值模拟

针对在宽飞行马赫数范围内工作的某串联TBCC可调喷管较高的进口总温易引起壁面材料烧蚀的问题,提出一种适用于飞行包线内不同飞行马赫数且对喷管热防护有明显作用的气膜冷却方案,并基于CFD的方法模拟了不同飞行马赫数的冷却效果.研究表明开设二元缝槽将比开设环形缝槽对附近流场状况产生更明显的影响.采用气膜冷却方案后,喷管壁面平均温度较未经气膜冷却时有超过1000K的明显下降.壁面二元缝槽下游中心线上的气膜冷却绝热效率在多数飞行马赫数下可达0.9以上.缝槽下游温度在展向上多呈对称分布,向下游发展时温度均匀性逐渐降低.      

HDJT企业年金初探

介绍了企业年金的起源与发展以及建立企业年金的意义和作用，对建立企业年金的原则和具体程序进行了阐述，并对HDJT公司建立企业年金的可行性和必要性进行了分析。     

某型直升机发电机控制盒故障原因分析

本文研究了通过试验手段对某型直升机发电机控制盒故障进行复现,确定了故障件,并分析了故障原因,制订了改进措施。