Thermocapillary simulation of single bubble dynamics in zero gravity

The lack of significant buoyancy effects in zero gravity conditions poses an issue with fluid transfer in a stagnant liquid. In this paper bubble movement in a stagnant liquid is analysed and presented numerically using a computational fluid dynamics (CFD) approach. The governing continuum conservation equations for two phase flow are solved using the commercial software package Ansys-Fluent v.13 and the Volume of Fluid (VOF) method is used to track the liquid/gas interface in 2D and 3D domains. The simulation results are in reasonable agreement with the earlier experimental observations, the VOF algorithm is found to be a valuable tool for studying the phenomena of gas–liquid interaction. The flow is driven via Marangoni influence induced by the temperature difference which in turn drives the bubble from the cold to the hot region. A range of thermal Reynolds (Re_T) and Marangoni numbers (Ma_T) are selected for the numerical simulations, specifically Re_T=13–658 and Ma_T=214–10,721 respectively. The results indicate that the inherent velocity of bubbles decreases with an increase of the Marangoni number, a result that is line with the results of previous space experiments (Kang et al., 2008) [1]. An expression for predicting the scaled velocity of bubble has been derived based on the data obtained in the present numerical study. Some three-dimensional simulations are also performed to compare and examine the results with two-dimensional simulations.     

如何提高飞机表面质量

探讨了提高飞机表面质量的方法。提出提高飞机表面质量是个系统工程，必须从优化设计结构、提高零件和工装的制造准确度及协调准确度，采用合理的铆接装配工艺方法等多方面共同采取措施。     

铝合金材料表面改性研究进展

评述了近年来铝合金表面改性技术取得的研究进展，重点介绍了溶胶-凝胶、稀土转化膜、激光熔覆、阳极氧化和等离子体微弧氧化等方法在铝合金表面制备膜层的原理、特点及研究成果，并对等离子微弧氧化技术提出了展望。     

Interfacial Properties Modification of Carbon Fiber/ Polyarylacetylene Composites

This work was dedicated to performing surface oxidation and coating treatments on carbon fibers (CF) and investigating the changes of fiber surface properties after these treatments, including surface composition, relative volume of functional groups, and sur- face topography with X-ray photoelectron spectroscopy (XPS) and atom force microscopy (AFM) technology. The results show that, after oxidation treatments, interfacial properties between CF and non-polar polyarylacetylene (PAA) resin are remarkably modified by removing weak surface layers and increasing fiber surface roughness. Coating treatment by high char phenolic resin solution after oxida- tion makes interface of CF/PAA composites to be upgraded and the interfacial properties further bettered.     

The X-Ray Spectrometer on the MESSENGER Spacecraft

NASA’s MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission will further the understanding of the formation of the planets by examining the least studied of the terrestrial planets, Mercury. During the one-year orbital phase (beginning in 2011) and three earlier flybys (2008 and 2009), the X-Ray Spectrometer (XRS) onboard the MESSENGER spacecraft will measure the surface elemental composition. XRS will measure the characteristic X-ray emissions induced on the surface of Mercury by the incident solar flux. The Kα lines for the elements Mg, Al, Si, S, Ca, Ti, and Fe will be detected. The 12° field-of-view of the instrument will allow a spatial resolution that ranges from 42 km at periapsis to 3200 km at apoapsis due to the spacecraft’s highly elliptical orbit. XRS will provide elemental composition measurements covering the majority of Mercury’s surface, as well as potential high-spatial-resolution measurements of features of interest. This paper summarizes XRS’s science objectives, technical design, calibration, and mission observation strategy.     

工程陶瓷型面的超声磨削装置设计

以工程陶瓷三维型面的加工为例 ,介绍了超声磨削装置的结构、变幅杆及其系统设计 ,推导了用于数控加工的超声磨削装置变幅杆设计的数学模型。最后 ,在此基础上结合实际范例进行了验证 ,两者结果基本吻合 ,并在相关研究项目的设计中收到了良好的效果。     

金属基复合材料的切削加工

选用四种切削性能优良的刀具材料：细晶粒硬质合金、陶瓷、立方氮化硼和聚晶金刚石，对两种典型的金属基复合材料即氧化铝纤维增强与碳化硅颗粒和氧化铝纤维混杂增强铝基复合材料的切削加工性进行了全面深入地研究。结果表明：加工混杂增强铝基复合材料时，聚晶金刚石刀具的磨损阻力最大。而加工纤维增强复合材料时，细晶粒硬质合金刀具的磨损率低、工件表面完整性好且加工成本最低。本文对刀具的磨损机理也进行了深入探讨。最后，从刀具磨损和表面完整性观点出发，给出了加工不同金属基复合材料的最佳刀具材料。     

关于风洞中用尖劈和粗糙元模拟大气边界层的讨论

尖劈和粗糙元广泛地应用于风洞试验中的大气边界层模拟,该技术成功模拟了不同地貌特征的平均风速和湍流度剖面。随着风工程研究的深入,了解尖劈和粗糙元模拟过程中的作用机理有助于准确地模拟各种大气边界层湍流功率谱和尺度特性。试验表明:尖劈利用其迎风平板的分离流产生湍流涡旋,迎风板的宽度决定了涡旋的大小和湍流脉动强度,同时迎风板阻塞比沿高度递减产生近似线性的风速剖面;粗糙元用于模拟实际地面的摩擦效应,调整平均风速和湍流度的剖面分布。遗憾的是,尖劈下宽上窄的结构特点决定了该技术模拟的湍流功率谱和积分尺度的高度变化律与实际大气边界层相反。基于对模拟机理的认识,异型尖劈上部形状有助于模拟大比例模型试验要求的湍流风场。     

表面粗糙度对铍青铜微电阻点焊接头性能的影响

通过改变铍青铜表面粗糙度,研究了表面粗糙度对微电阻点焊接头强度和焊点组织形貌的影响。结果表面:当表面粗糙度小于0.5μm时,接头拉剪载荷随着表面粗糙度的增大而增大;当表面粗糙度大于0.5μm时,焊接电流不同,表面粗糙度对接头拉剪载荷的影响不同。表面粗糙度的变化基本不对接头组织形貌产生影响。铍青铜微电阻点焊接头由焊核、焊核周围的热影响区以及由焊核向热影响区过渡的熔合区组成。     

玻璃型二次表面镜的卫星飞行试验

文章介绍了兰州物理研究所研制的石英玻璃型二次表面镜（ＯＳＲ）的卫星搭载试验结果，并对ＯＳＲ的长期空间稳定性作了初步预测。试验和计算结果表明，其ＯＳＲ的太阳吸收率的１０年增值△αｓ预计不超过０．０５５，与国外同类产品的空间稳定性水平相当，已能满足卫星应用的要求。