固体火箭发动机滚动球窝喷管弹塑性摩擦接触承载性能分析

固体火箭发动机滚动球窝喷管的弹塑性摩擦接触承载性能,属于复杂结构在复杂载荷作用下的弹塑性摩擦接触问题,它直接决定着系统的结构设计和功能发挥。为保证系统在承受极端工作载荷时,喷管不产生大的轴向位移,阴球、阳球与滚动体间具有一定的接触强度,同时不产生过量的塑性变形,设计阶段,基于计算精度高的三维摩擦接触问题的Lagrange乘子法,解决了与弹塑性耦合的算法问题;在滚动体运动分析及摩擦测试的基础上,模拟系统冷试车冲压试验,充分考虑材料表面强化层,建立了各构件间的弹塑性摩擦接触模型。有限元计算结果及冷试车分解试验、系统作动力矩测试试验结果表明,系统弹塑性摩擦接触承载性能满足结构设计要求,有限元建模及计算结果正确。     

THE UNIT BALL OF C*-ALGEBRA AND DIFFERENTIABILITY OF SUPPORT FUNCTION

In this paper we show that the unit ball of an infinite dimensional commutative C-algebra lacks strongly exposed points, so they have no predual. Also in the second part, we use the concept of strongly exposed points in the Frechet differentiability of support convex functions.     

基于模糊大间隔最小球分类模型的恒星光谱离群数据挖掘方法

由于人类对宇宙的认识有限,因此,如何通过对光谱数据分析发现一些新的、特殊的天体成为天文学家面临的重要课题。目前,常见特殊天体发现方法的基本思想是利用智能分类算法对离群数据进行分析。然而,当前主流分类算法大多对离群数据不敏感,分类性能甚至受离群点影响较大,因而无法完成特殊天体发现任务。鉴于此,提出基于模糊大间隔最小球分类模型的离群数据挖掘方法,该方法利用部分一般样本和离群样本建立最小球模型,并在此基础上引入模糊技术,通过降低噪声的权重,尽量减少噪声的影响。与C-SVM,SVDD,KNN等传统分类方法在SDSS恒星光谱数据集上的比较实验表明所提方法的有效性。     

The mathematical phenomenological mapping in non-linear dynamics of spur gear pair and radial ball bearing due to the variable stiffness

In this paper the philosophy of mathematical phenomenological mapping has been applied to the non-linear dynamics of spur gears and radial ball bearings. The spur gear pair dynamics and rolling element bearing dynamics are analyzed separately, but with a tendency to reduce the both of the systems to the same mathematical model. The different reasonable assumptions are taken in every of these analyzes, but they do not have significant influence to the accuracy of the results. The systems are reduced to the single degree of freedom dynamics model. The total gear stiffness and ball bearing stiffness are recognized as the main influent factor of vibration behavior of these machine elements. Therefore, the special attention was paid to the new approach and procedure for stiffness solving and related problems. A single spur gear pair dynamics is solved and the results for total gear stiffness and vibration are shown. The conclusions emphasize the importance of described parallel analyzes in order to reduce the calculation time in solving different phenomena with usage of the principle of mathematical phenomenology.     

钢球检测用展开轮表面微结构增摩降磨特性分析

针对钢球缺陷检测过程中,镜面钢球打滑引起的滑动摩擦导致展开轮磨损这一问题,以实现展开轮增摩降磨为目标,提出将微结构应用于钢球展开轮表面的方法.首先,应用激光微造型技术在T10A试件表面加工不同特征参数凹坑微结构,采用单因素法在MMW-1立式万能磨擦试验机上进行点接触干滑动摩擦试验;在综合考虑局部激光硬化和几何参数对磨损性能影响的基础上,结合试验数据建立基于Archard理论的微结构磨损模型;最后通过仿真技术及磨损试验验证磨损模型的正确性,进而对微结构特征参数进行优选.结果表明:在点接触干滑动摩擦工况下,提出的三种微结构表面均可以实现增摩降磨;建立的磨损模型能准确地计算磨损系数用以分析实际工况的磨损特性;优选了凹坑面积在S_2~S_4范围内的菱形微结构.提出的方法为钢球表面缺陷检测设备提供了技术支持,所建的磨损模型为干摩擦状态下凹坑微结构表面磨损程度的预测提供了理论参考.     

具有干燥功能的简易微型气体发生器

针对现有气体发生器本身不具备干燥功能等不足,利用医疗和生活中的物品--一次性注射器、输液器、圆珠笔芯等设计制作了一件自带干燥装置的微型气体发生器。     

A general strategy of in-situ warpage characterization for solder attached packages with digital image correlation method

Recently, 3-D Digital Image Correlation (DIC) is widely applied to the reliability analysis of electronic packages, which particularly characterizes the in-situ deformation of ball grid array (BGA) packages. During the image correlation procedure, many parameters influence the accuracy and data integrity of measurement result. Facet (subset) size is the principal parameter and has been studied with much effort. However, the solder balls, which are built on the substrate surface, make the scenario different with the conventional 3-D DIC experiment for the planar samples. The undulant surface generates more obstacles for the successful image correlation. In order to summarize an effective solution of 3-D DIC measurement method for solder balls attached packages, camera angle, facet size and facet step are studied with different BGA packages and different stereoscopic camera systems to achieve the best correlation quality. Also, a novel surface treatment method is introduced to guarantee the surface speckles are generated uniformly on the fluctuant surface.     

A Functional LIL for m-Fold Integrated Brownian Motion

Abstract Let {X _m (t); t ∈ R ₊} be an m-Fold integrated Brownian motion. In this paper, with the help of small ball probability estimate, a functional law of the iterated logarithm (LIL) for X _m (t) is established. This extends the classic Chung type liminf result for this process. Furthermore, a result about the weighted occupation measure for X _m (t) is also obtained. *Project supported by the National Natural Science Foundation of China (No.10131040) and the Specialized Research Fund for the Doctor Program of Higher Education (No.2002335090).     

A Note on the Fractional Integrated Fractional Brownian Motion

We characterize the lower classes of the fractional integrated fractional Brownian motion by an integral test.