超低比转速离心泵内流场计算及分析

运用FLUENT流体计算软件及GAMBIT前处理软件,采用三维k-ε双模型方程计算了一台高速超低比转速离心泵的内部流场。计算区域为从诱导轮进口到蜗壳出口的整个流场,通过计算得到了泵内流场的流动规律,并结合传统的泵水力估算方法,估算了泵的扬程、轴功率及效率,最后对该高速超低比转速离心泵进行了水力验证试验。验证结果表明所采用的计算方法可行。     

两种供操纵系统强度校核用载荷计算方法比较

传统计算和运用有限元计算是操纵系统现有的两种供强度校核用载荷计算方法,本文运用这两种方法对飞机操纵系统的典型段进行了计算,并比较了两种方法的具体计算结果,得出了相应的结论,扩展了计算供操纵系统强度校核用载荷的方法。     

脉冲雷达频率稳定度问题的仿真研究

本文用蒙特卡罗计算机仿真法研究振荡信号频率起伏对脉冲雷达性能的影响。由于现代脉冲雷达存在明显的混叠效应,和由放大链引入附加噪声等情况,使其仿真方法要比连续波时复杂得多。本文提出的五阶ARMA滤波以及间隔取数据的办法可较好地解放混叠效应的仿真问题。文末举脉冲多普勒雷达为例,介绍仿习具体步骤和仿真结果。     

辊弯成形仿真分析与参数优化(英文)

辊弯成形工艺是一种在常温下将平板金属材料通过连续转动的成形辊成形为所需截面的加工方法.本文通过有限元模型建立了一套避免重大产品质量缺陷的设计方法.通过对真实产品的仿真,在设计中考虑了两个辊弯成形主要缺陷,即边波和回弹.设计结果表明,该设计方法能够有效地控制这两大质量问题.     

On the origin of satellite swarms

For a species to develop in nature basically two things are needed: an enabling technology and a “niche”. In spacecraft design the story is the same. Both a suitable technology and a niche application need to be there before a new generation of spacecraft can be developed. In the last century two technologies have emerged which had and still have a huge impact on the development of technical systems: Micro-Electronics (ME) and Micro-Systems Technology (MST). Many different terrestrial systems have changed dramatically since the introduction of ME and MST and many new systems have emerged. In the same period many nano-satellites have been built and launched and shown that they can perform in space. Still it is not clear what the specific role of these small satellites will be. Where will they go? What will they do? In this paper the authors will try to answer these questions and will refer to the OLFAR space born radio telescope as one of the niche applications for a nano-satellite swarm.     

Forest Fire Monitoring Methods and Applications of HJ-1A/B Satellites

Forest fire is a frequent natural disaster and spreads randomly across forestland.It can cause great damage and loss to forest resources,the ecological system and people’s life and property. It is necessary to monitor and detect forest fire at the beginning.     

Design and Experiments of Model-free Compound Controller of Flight Simulator

A model-free compound controller design method is proposed to achieve the wide frequency bandwidth requirement of flight simulators. The method based on quantitative feedback theory, acquires system uncertainty under different working conditions through closed-loop identification with power spectrum estimation. Then in controller designing, it makes a tradeoff between the strict requirements for magnitude-frequency characteristics and those for phase-frequency characteristics of flight simulators, by converting the indices of magnitude-frequency characteristics of flight simulators into quantitative feedback theory-based tracking specification bounds and using feedforward controller to attain the required phase-frequency characteristics. Simulation and experimental results indicate that, when used to design inner frame controller of flight simulator, the proposed method can fulfill the requirements for wide frequency bandwidth indices. Compared with other controller design methods, it has the property of model-free and transparency.     

X-34主推进系统输送管路的流动分析

X-34主推进系统(MPS)管路结构包括液氧(LOX)和火箭推进剂#1(RP-1)的输送管路。这些管路的流动分析已经完成并已编入相关文献中,分析结果表明:在管路入口处,有相对较低的流动畸变,在发动机接口有近乎均匀的流动分离。近来,已建议对主推进系统的管路结构进行新的改进设计。新的结构为:把RP-1管路中弯管的曲率半径变得更小;在常平座间加了一段缩颈结构。相反地,液氧管路的结构和原来的结构非常相似。许多人认为在发动机接口处,新的RP-1管路结构比原结构会产生更大的流动畸变。为了解决这个问题,应用计算流体动力(CFD)分析,确定了新RP-1输送管路的内流场。     

机载电子对抗系统效能评估方法研究

通过干扰方程计算出了最小干扰距离，用检测理论求得了干扰压制九，用排队论导出了突防概率，并对攻防双方武器系统的战术技术性能进行了分析。     

用城市经营理念 构筑“和谐廊坊”

21世纪是城市发展与竞争的世纪,要赢得经济主动权,须按照城市经营理念构筑和谐社会。本文从现象、理论、具体实践,探讨了“和谐廊坊”城市经营的特色。