Study of Subsonic Flow Over a TOW 2B Missile

The objective of this investigation is to study the subsonic flow over a missile. In this paper, a model of TOW 2B missile is studied. Two computational approaches are being explored, namely solutions based on the Reynolds-averaged compressible Navier-Stokes equations and solutions based on the inviscid flow (small disturbance theory). The simulations are performed at the Mach number of 0.6, 0.7, 0.8, 0.9 and 1.0 at four angles of attack of 2, 4, 6 and 8 degree. Results obtained from analytical simulation are compared with numerical data. It is found that lift and drag coefficients would go up by increasing of the angle of attack and the Mach number. Trend of changes of the results that obtained from the small disturbance theory is roughly as same as the numeric solution.     

用于过程数据压缩的自控精度SDT算法

针对过程数据的压缩,提出一种自控精度SDT算法,通过在压缩过程中对参数的动态调整,使误差控制在给定范围内,保证了压缩精度并且获得了更高的压缩比。相比于SDT算法,压缩比提高了60%~75%,实际误差与期望误差的绝对差在10-3数量级。该算法在UWnTek控制工程软件中测试完成并正式使用,具有重要的工程意义。     

Knowledge-sharing in virtual communities: familiarity,anonymity and self-determination theory

Although the role of motivation has been emphasised in knowledge-sharing literature, traditional motivation theories, such as self-determination theory (SDT), have not been actively used as a research framework in knowledge-sharing research. The purposes of this study are twofold. The first objective is to propose a model, based on SDT, to test the effect of the three basic psychological needs – perceived competence, perceived autonomy and perceived relatedness – on knowledge-sharing behaviours in virtual communities. The second objective is to explore the effects of familiarity and anonymity on the basic psychological needs to better understand individuals’ knowledge-sharing behaviours in virtual communities. The results show that perceived competence and perceived relatedness influence knowledge-sharing behaviours in virtual communities; however, perceived autonomy does not influence knowledge-sharing behaviours; familiarity influences positively perceived competence and perceived relatedness, and anonymity influences negatively perceived autonomy and perceived relatedness.     

Shock Desensitization Effect in the Confined Explosive Component Water Gap Test Defined by the NATO Standardization Agreement (STANAG) 4363

In an effort to extend the modified explosive component water gap test [1–3] defined by the NATO standardization agreement (STANAG) 4363, several countries have investigated the shock sensitiveness of confined lead and booster components having a diameter less than 5 mm [4–8]. A pentaerythritol tetranitrate (PETN) based acceptor pellet is chosen as a reference with a height and diameter of 3 mm. The height of the steel confinement is equal to the one of the HE pellet and the wall thickness varies. A 1‐mm thick wall makes the component more sensitive (larger water gap). As the wall thickness is increased to 2‐mm, the gap increases a lesser amount. A decrease in sensitivity is observed with a 3.5 mm thick wall (smaller water gap). This decrease of the water gap has been reproduced experimentally. This unusual behavior remains puzzling and does not allow the test to be extended for small components. This work presents the numerical simulations performed with LS‐Dyna in 2D axi‐symmetrical and 3D wedge configurations, using an ignition and growth model [9] for LX‐16 (96% PETN, 4% FPC 461) in order to evaluate the shock sensitiveness for a confined HE acceptor.     

Modeling of Geometric Variations Within Three-Dimensional Tolerance Zones

三维公差域内几何特征变动的建模方法

彭和平¹,卢文龙²

（1.江汉大学 机电与建筑工程学院,武汉 430056;

2.华中科技大学 机械科学与工程学院,武汉 430074）

创新点说明：

提出一种复杂特征几何变化的三维公差建模方法。根据新一代产品几何技术规范（GPS）中几何特征的定义和特征变动的分类法,所提出的建模方法基于小位移旋量（SDT）的概念,SDT参数用于建模拟合特征相对于名义特征的几何偏差变动。进一步构造了几种复杂或不规则几何特征的变动区域,讨论了相应的三维公差建模方法。最后,通过数值实例验证了该方法对三维尺寸公差和几何公差建模的有效性。完全基于数学基础提出的建模方法符合现行的GPS标准体系的思想。

研究目的：

本文提出并建立各种复杂非规则几何特征变动的定量化数学模型,开发了集成几何公差在内三维公差建模方法,为进一步研究三维公差分析和设计奠定理论基础,是新一代GPS与现有公差设计理论相结合的学术研究前沿。

研究方法和结论：

基于理论上的探讨,采用实例分析验证方法的有效性。

关键词：产品几何技术规范(GPS);公差建模;特征;几何变动;小位移旋量（SDT）

     

基于雅可比旋量模型的装配体公差统计分析

以SDT(Small Displacement Torsor)理论为基础,研究了平面特征在两种不同类型公差作用下的SDTI(Small Displacement Torsor with Interval)模型及旋量参数间的约束关系。针对装配体公差统计分析中传统随机取值方法存在的不足之处,提出了一种考虑旋量参数间约束关系的装配体公差分析方法,并以顶针为实例进行了分析对比,结果表明考虑参数约束关系的公差分析方法相对于传统方法提高了公差分析的精度。     

SDT算法及其在过程数据压缩中的应用

首先阐述了过程数据压缩的重要性及特点，然后介绍了SDT（Swinging Door Trending)算法的基本原理，给出了离线压缩、在线压缩及信号重建的软件框图，最后介绍了SDT算法的应用，并得出了一些结论。希望对过程数据压缩的研究和应用提供一定的帮助。     

过程数据压缩算法SDT的改进研究与应用

对传统的SDT（Swinging Door Trend）过程数据压缩算法进行算法分析与改进研究,并在此基础上提出了综合去异常值、简单滤波、自适应压缩偏移量与还原曲线平滑化的改进型SDT压缩算法。算法结构简单、计算速度快,以MATLAB为研究仿真工具,通过算法的移植已经成功地应用于工业实时数据库产品FD-RDB中,获得了良好的过程数据压缩质量与还原效果。对工业实时数据库的过程数据压缩算法的设计开发具有很好的参考意义。     

Understanding e-learning continuance intention in the workplace: A self-determination theory perspective

Based on self-determination theory (SDT), this study proposed an extended Technology Acceptance Model (TAM) in the context of e-learning service. In the proposed model perceived usefulness, perceived playfulness and perceived ease of use are predicted to be influenced by perceived autonomy support, perceived competence and perceived relatedness. Although TAM has received fairly extensive attention in prior research, this study is one of the first to examine the effects of motivational factors affecting TAM constructs. The results show that applying SDT to e-learning in a work setting can be useful for predicting continuance intention.     

基于公差原则的直线对称度公差数学模型

在公差数学定义的基础上引入SDT（small displacement torsor），以孔中心轴线为对象，研究了基于公差原则的直线对称度公差数学模型。根据独立原则和最大实体要求应用于中心要素和表面要素的不同情况，详细研究了直线对称度公差的不同约束模式，系统地推导了直线对称度公差的数学模型。由此所建立的数学模型完整、准确地表示出了直线对称度公差的语义，便于公差的计算机处理。最后用实例验证了该公差数学模型的有效性。