Design of an innovative multi-stage forming process for a complex aeronautical thin-walled part with very small radii

In this paper, an aeronautical thin-walled part with a complex geometry which has several sharp bends and curvatures in different directions was investigated. This kind of part is difficult to be manufactured only in one stage. Therefore, an innovative multi-stage active hydroforming process assisted by the rigid forming method was designed. In addition, an optimized blank geometry is obtained. In fact, the main focused point of this paper is to propose a new small radius rounded corner forming technique and analyze the mechanism. Two kinds of forming modes of changing a big rounded corner into a small one, which are related to different tangential positions of the die in the process of calibration, are analyzed theoretically. Meanwhile, the stress and strain states of the deformation region are compared. The relationships between the minimum relative radii of rounded corners I and II in the first stage and the hydraulic pressure are calculated by the bending theory. Finally, the influences of the tensile-bulging effect and the interface condition of the double-layer sheet on the forming quality of the specimen are investigated. The achieved results can make a foundation for utilizing the proposed method in forming of thin-walled parts with very small radii.     

A new weighted mean temperature model in China

The Global Positioning System (GPS) has been applied in meteorology to monitor the change of Precipitable Water Vapor (PWV) in atmosphere, transformed from Zenith Wet Delay (ZWD). A key factor in converting the ZWD into the PWV is the weighted mean temperature ($T_m$), which has a direct impact on the accuracy of the transformation. A number of Bevis-type models, like $T_m-T_s$ and $T_m-T_s\text{,}{P}_s$ type models, have been developed by statistics approaches, and are not able to clearly depict the relationship between $T_m$ and the surface temperature, $T_s$. A new model for $T_m$, called weighted mean temperature norm model (abbreviated as norm model), is derived as a function of $T_s$, the lapse rate of temperature, δ, the tropopause height, $h_{\mathit{trop}}$, and the radiosonde station height, $h_s$. It is found that $T_m$ is better related to $T_s$ through an intermediate temperature. The small effects of lapse rate can be ignored and the tropopause height be obtained from an empirical model. Then the norm model is reduced to a simplified form, which causes fewer loss of accuracy and needs two inputs, $T_s$ and $h_s$. In site-specific fittings, the norm model performs much better, with RMS values reduced averagely by 0.45 K and the Mean of Absolute Differences (MAD) values by 0.2 K. The norm model is also found more appropriate than the linear models to fit $T_m$ in a large area, not only with the RMS value reduced from 4.3 K to 3.80 K, correlation coefficient $R^2$ increased from 0.84 to 0.88, and MAD decreased from 3.24 K to 2.90 K, but also with the distribution of simplified model values to be more reasonable. The RMS and MAD values of the differences between reference and computed PWVs are reduced by on average 16.3% and 14.27%, respectively, when using the new norm models instead of the linear model.     

XML数据到一般关系数据库数据的转换

随着Intemet的不断发展,关系数据库的局限性越来越明显,XML(ExtensibleMarkupLan-glmse—可扩展标记语言)可以有效地存储和管理Web上以指数增长着的数据(文档),使其既能被高效地操作和维护,又能在Web这个平台上方便地表示和交换。本文着重介绍了如何将XML文件数据导入一般关系数据库(本文以oracle关系数据库为例)的具体方法。     

航天器真空热试验测控系统软件结构设计与建模

统一建模语言（Unified Modeling Language,简称UML）是面向对象软件开发方法的重要技术,使用UML对软件系统进行建模研究,有利于提高软件开发的效率和可重用性等。文章给出了真空热试验测控系统软件架构和主要模块的结构设计,并利用Rational Rose结合UML对测控软件进行分析建模和设计。     

红萍湿养栽培供O2装置研制

红萍作为空间站受控生态生命保障系统中的生物部件, 可望为航天员提供O2和新鲜蔬菜并吸收CO2. 研究红萍湿养栽培供O2装置, 旨在建立地面非生物部件, 满足模拟研究的需要. 介绍了所研发装置及关键部件的结构特点和工作原理. 通过红萍湿养板内湿养栽培介质的结构功能设计, 在蓄水保水基质层内部配置具有毛细作用的渗水管路, 介质始终保持整体湿润而表面无明水状态, 为红萍扎根稳固、营养吸收和生长繁殖创造条件. 水压试验确定了渗水管路的主要技术参数和闭合式红萍培养液输配循环系统的间歇循环周期. 整机产出量试验结果表明, 在层间距125 mm, 整机红萍湿养面积6.3 m2, 超高亮度白色LED人工光源能耗152 Wm 2, 红萍表面的光照强度6000~6500 lx, 整机的红萍湿养产量、红萍放O2量和吸收CO2量相应大幅提高, 装置各项性能指标均达到设计要求.      

砂土硬化特征的描述及其试验验证

采用不同路径下砂土的三轴拉伸和三轴压缩试验结果,分别选用塑性体积应变、塑性剪应变、清华模型硬化参数、塑性功和统一硬化参数H作为硬化参数,在以上硬化参数和应力比空间里探讨了砂土的硬化规律和应力路径相关性.基于修正剑桥模型的屈服函数,采用塑性体积应变、塑性功和H作为硬化参数,推导了分别对应的本构模型.通过饱和塔克拉玛干沙漠砂的三轴试验结果,表明了H在描述砂土应力应变特性上的适用性.      

Micro VAX—Ⅱ计算机专用实时接口设备

在实时数字仿真系统中,实时接口设备是仿真机和控制系统实物间的界面,它的性能直接影响着实时数字仿真的精度。本文简要介绍了专为MicroVAX—Ⅱ计算机研制的DSI-4型专用实时接口设备的构成、各功能板的设计,以及DSI-4专用实时接口的工作过程和使用方法。应该指出的是:只要改变连接计算机的总线接口板,DSI-4专用实时接口还可以方便地与其它计算机(例如,CompaQ386机)组成实时数字仿真系统。     

谈正交试验方法的简易化

正交试验法由于其直观、简单、有效,正在获得日益普遍的推广应用。然而各种书刊在正交试验的讲法上很不统一,造成人们理解上的困难,影响着正交试验法的进一步推广。本文指出正交试验法的实质是多因素试验优化法,它能以尽可能少而分布均匀的试验条件通过分批试验逐步地“搜索”到最优解,而且不论实际问题有无交互作用均能适用。文章认为国内数学界倡导的正交试验方法,在安排试验因素时不去专门分析因素间的交互作用、而对试验结果采用直观比较与分析,这是对国外正交试验方法的有效简化。正是这种简化才使正交试验法能在我国获得迅速普及与推广,成为广大群众手中的有效管理工具。     

软件可靠性预计与评估方法探讨

概述了软件可靠性的重要性及预计评估、参数估计方法和数据收集的意义与过程;综述了国外软件可靠性模型的建立情况;最后应用作者开发的软件可靠性预计评估程序(SRPP)对一组数据进行可靠性计算,给出软件可靠度R(t)、MTTF及故障率或故障强度λ(t)等指标;并根据模型有效性的比较准則,对计算结果进行了比较。     

导弹制导与控制一体化三通道解耦设计方法

针对导弹俯冲打击地面目标的问题,基于扩张状态观测器(ESO)和反步滑模设计思想,提出一种导弹制导与控制一体化三通道解耦设计方法。充分考虑制导与控制系统之间以及控制系统三通道间的耦合关系,建立了制导与控制一体化三通道耦合模型。通过ESO对导弹运动六自由度(6DOF)系统内各通道间的动态耦合项和不确定性进行实时观测和动态补偿,实现通道间的主动解耦,从而设计了基于ESO的导弹制导与控制一体化三通道解耦控制律。同时,为了解决在使用ESO对高阶非线性系统进行状态观测时引起的"运算膨胀"问题,通过设计自适应控制律对ESO观测误差进行补偿。基于李雅普诺夫稳定性准则证明了闭环系统所有状态最终一致有界。并与制导与控制一体化三通道独立设计方法和传统的制导与控制系统设计方法进行对比仿真,结果验证了基于ESO的导弹制导与控制一体化三通道解耦设计方法的有效性和优越性。