滑动导轨等部件的微动态特性

1.简介 这份报告给出了关于传统的滑动导轨系统的一些实验结果,同时论及了机构的精密运动控制。 这些年来,诸如导轨、丝杠和其他驱动机构等机械部件的微动态特性,换句话说,就是在很小位移范围内的非线性传递特性。已成为精密机械工程研究的首要问题。超精密仪器、机床和半导体生产系统都对机械部件的控制精度提出了越来越高的要求。对于精     

杂波中跟踪的自适应探测阈值的优化

为概率数据互联(PDA)滤波器研究了杂波环境下跟踪的探测阈值的自适应优化。这个问题的早期文章(4)涉及状态误差协方差的近似稳态分析并且只适合非时变系统。此外,这种方法需要有关于误差协方差更新方程的若干假设和近似,并使用一种麻烦的图解优化算法。本文我们提出了阈值优化的两种自适应方案,即,使均方状态估计误差在探测阈值范围内极小化的先验和后验优化算法。它们分别取决于以前的和当前的时间-步长数据。这些算法适合于时变系统中的实时实现。本文介绍一些仿真结果。     

社会主义市场经济与国民经济动员

本文从分析社会经济体制与国民经济动员的一般关系着手,剖析了现实矛盾,提出了相关对策。     

电子战研究注重海军虚拟现实技术

美国海军研究实验室正在开展利用虚拟现实技术实现电子战仿真的研究,本文对这一称为“海军电子战系统效能分析(ENEWS)”的项目进行了综合介绍,阐述了它的研制目的、系统功能、技术实现原理与工具、系统构成、软件和人机接口设计,并对该项目的开发现状和发展前景作了评述和展望。     

邓小平国防经济思想初探

1930年左右,邓小平先后与张云逸等同志一起,领导了白色、龙州起义,创立了中国工农红军第七、第八军和左右江革命根据地。他半个多世纪的戎马生涯,经历了广泛的社会实践,积累了丰富的军事斗争经验,为他的国防经济思想的形成,打下了坚实的基础。1975年1月,邓小平同志受命于危难之间,肩负起党政军的全面领导工作。在整顿工业、农业、交通等部门的同时,也整顿了军队和国防科技工业,对国防经济建设提出了许多独到的见解。十一届三中全会以后,他重新分析了国际国内形势,在提出建设具有中国特色社会主义     

控制与监视系统的进展

微处理机的出现,使控制工程发生了深刻的革命。直到最近,控制理论才走到了实践的前面。在多变量控制数学和最优滤波不断发展的时候,现实生活中的控制系统却受到电子设备能力的限制。现在常用的“遥控”这个词的含意只不过是远距离开关设备的能力,没有什么更复杂的意思。工业上的过程控制已对小型计算机进行了一段时间的试用。但是在军舰环境中重量和空间的限制,大大地妨碍了小型机的应用。现在有可能用的高速数字系统,在小的体积中具有相当强的处理能力。这些系统以它们的能力和灵活性为控制工程师们创造了极好的机会。看     

新“三资”推进兵团农业产业化

推进农业产业化经营,是在市场经济条件下,更加适应兵团生产力发展要求的经营方式和产业组织形式。而新“三资”则是实现农业产业化、增加农牧团场职工收入的重要途径之一。     

Evaluation of effectiveness of polymer coatings in reducing blast-induced deformation of steel plates

Incorporating elastomers such as polymers in protective structures to withstand high energetic dynamic loads, has gained significant interest. The main objective of this study is to investigate the influence of a Polyurea coating towards the blast-induced response in steel plates. As such, Polyurea coated steel plates were tested under near-field blast loads, produced by the detonation of 1 kg of spherical nitromethane charges, at a standoff distance of 150 mm. Mild steel (XLERPLATE 350) and high-strength steel (BIS80) plates with thicknesses of 10 mm were Polyurea coated with thicknesses of 6 mm and 12 mm on either the front (facing the charge) or the back face. The deformation profiles were measured using 3D scanning. Numerical simulations were performed using the non-linear finite element code LS-DYNA. The strain-dependent behaviour of the steel and Polyurea were represented by Johnson-cook and Money-Rivlin constitutive models, respectively. The numerical models were validated by comparing the plate deflection results obtained from the experiments and were then used in the subsequent parametric study to investigate the optimum thickness of the Polyurea coating. The results indicate that back face coating contributes towards an approximately 20% reduction in the residual deformation as well as the absence of melting of the Polyurea layer, while the front-face coating can be used a means of providing additional standoff distance to the steel plates.     

Impact of atmospheric turbulence on coherent beam combining for laser weapon systems

The performance of a laser weapon system based on coherent beam combining (CBC) depends on its propagation properties in the atmosphere. In this study, an analytical model based on partial coherent beam combining (PCBC) for assumed coherence coefficients between beams in a CBC lattice was developed. The Kolmogorov model of atmospheric turbulence and the Hufnagel-Valley model of Cn2 dependence on atmospheric parameters were implemented. Novel simplified metrics were proposed to assess the CBC performance. Several beam profiles (super-Gaussian, truncated Gaussian, etc.) and ge-ometries were analyzed in terms of maximal intensity in the far field. An approximate formula for PCBC efficiency dependent on the Fried radius was proposed. The results of CBC modeling were compared to those of the Gaussian beam propagation model in a turbulent atmosphere. The dependence of CBC performance on the Cn2 parameter, range, and elevation angle was analyzed. It could be concluded that the application of CBC for medium and long range propagation is impractical without an effective adaptive optics system.     

关于俄国“死光”的一场风波

关于苏联在尺寸符合武器要求的带电粒子束上取得进展的消息看来在情报上是正确的,在物理学上是合理的,但在战略考虑上却是不高明的。