最短路径的编程实现

本文介绍了求最短路径的Floyd算法的设计思路及C语言编程实现.     

循环冗余码的软件实现方法及应注意的问题

】介绍了ＣＲＣ码并行算法的软件实现和串行算法的硬件实现方法，同时比较它们的差异，并指出了实践中应注意的问题     

多序列激光阴影成像技术研究及应用

为获取超高速碰撞过程中弹丸的飞行姿态及碰撞所产生的碎片云特性,开展了多序列激光阴影成像技术研究。利用多光源空间分离、偏振分光、光束角放大和补偿滤光等技术解决了单色光带来的衍射和干涉噪声以及碰撞瞬间强烈的自发光干扰问题,并先后在碰撞靶上建立了2序列、4序列和8序列激光阴影成像系统。该系统可以获得最小间隔1μs、曝光时间10ns、像素1000万的多个不同时刻的超高速瞬态变化过程图像,并在超高速碰撞靶试验中得到应用,获得了2～7km/s 撞击速度时碎片云的多序列阴影图像,该序列图像清晰地描述了碎片云的轮廓发展变化过程。该技术以低成本的方式实现了超高速摄影机的功能,满足目前碰撞试验粒子的飞行姿态及碎片云显示需要,并可以应用于其它超高速瞬态过程测量及流场结构显示。     

星箭耦合力学分析中的卫星混合模型研究

为准确预示卫星所承受的载荷和动力学环境,需要卫星研制单位提供卫星动力学模型,进行星箭耦合动力学响应分析。随着“细长型”构型卫星逐步增多,仅以星箭界面载荷进行卫星强度校核会带来较严重的过设计,需要形成一种适应内部界面载荷提取的卫星分析模型生成方法。基于子结构缩聚及装配的基本原理,将卫星合理划分为多个子结构,推导了各子结构缩聚后质量和刚度矩阵的生成方式,介绍了子结构间物理连接单元与各子结构缩聚模型装配的原理以及卫星混合数学模型生成过程。以某典型卫星结构为例进行分析验证,结果表明:卫星混合模型在保留了缩聚模型各项优点基础上,实现了卫星内部界面物理单元的载荷输出。     

Prediction of forming limit curve （FLC） for AI-Li alloy 2198-T3 sheet using different yield functions

The Forming Limit Curve （FLC） of the third generation aluminum-lithium （Al-Li） alloy 2198-T3 is measured by conducting a hemispherical dome test with specimens of different widths. The theoretical prediction of the FLC of 2198-T3 is based on the M-K theory utilizing respectively the von Mises, Hill＇48, Hosford and Barlat 89 yield functions, and the different predicted curves due to different yield functions are compared with the experimentally measured FLC of 2198-T3. The results show that though there are differences among the four predicted curves, yet they all agree well with the experimentally measured curve. In the area near the planar strain state, the predicted curves and experimentally measured curve are very close. The predicted curve based on the Hosford yield function is more accurate under the tension-compression strain states described in the left part of the FLC, while the accuracy is better for the predicted curve based on Hill＇48 yield function under the tension-tension strain states shown in the right part.     

Prediction of forming limit curve (FLC) for Al-Li alloy 2198-T3 sheet using different yield functions

The Forming Limit Curve (FLC) of the third generation aluminum-lithium (Al-Li) alloy 2198-T3 is measured by conducting a hemispherical dome test with specimens of different widths. The theoretical pred...     

NMOHEMS探头模型的制作及实验方法研究

NMOHEMS探头设计的有效性及其运动的CFD仿真计算方法都需要实验进行检验,利用计算机辅助设计结合三维快速成型技术制作了探头模型,在实验室水箱和水库两种环境下设计并完成了模型实验。其中,水箱实验利用有限实验水深,精确调整探头质量,利用高速摄像和图像处理技术,对多个较小质量探头的下沉运动进行了精密测量,详细的误差分析和修正后,获得不同质量探头运动的下落曲线和极限速度,以调整CFD仿真计算方法;水库实验利用自主研制的实验装置,对较大质量探头的下沉运动进行测量,误差修正后的极限速度为1．923m／s,验证了探头设计的有效性。     

数控机床轻量化技术研究进展

随着工业技术的快速发展,对数控机床和生产系统的要求越来越多地聚焦在节能与绿色发展等问题上,这给数控机床开发人员带来了新的挑战。轻量化技术不仅能够节省大量材料,而且还能优化机床结构的性能,为高性能数控机床的研制创造了有利条件。阐述了轻量化技术在数控机床中的应用,讨论了轻量化设计方法对机床绿色循环制造及其可持续发展的影响;着重分析了实现数控机床轻量化设计目标的有效方法及技术手段,并且对轻量化技术在数控机床设计中的发展前景进行了展望,提出一些建议。     

Detached-eddy simulation of supersonic flow past a spike-tipped blunt nose

Space vehicle in atmosphere travels mostly at supersonic speed and generates a very strong bow shockwave around its blunt nose. Oblique shock and conical separated flow zone generated by a forward disk-tip spike significantly reduce the drag by reducing the high pressure area on the blunt nose. This study employs improved delayed detached eddy simulation to investigate the characteristic flow structures around a spike-tipped blunt nose at Mach number of 3 and Reynolds number(based on the blunt-body diameter) of 2.72x10~8. The calculated time-averaged quantities agree well with experimental data. Characteristic frequencies in different flow regions are extracted using fast Fourier transform. It is found that two distinct instability modes exist: oscillation mode and pulsation mode. The former is related to the foreshock/turbulence interaction with nondimensional frequency at around 0.004. The latter corresponds to the interaction between turbulence and shock structures around the blunt nose, with a typical coherent structure shedding frequency at 0.092.