尾数细分计数逻辑对捷联惯导系统姿态误差的影响

为了提高激光陀螺的检测分辨率,采用了尾数细分计数逻辑新方法,并分析了此方法对捷联惯导系统姿态误差的影响.首先分析了常规四倍频细分计数逻辑的原理与特点,得出其分辨率约为1/4周期的结论;然后对比分析了基于常规四倍频的尾数细分计数逻辑的原理、实现方法及其特点,分析与试验表明,此方法能够进一步大幅度提高检测分辨率.基于以上结...     

FTLAN系统故障检测技术

FTLAN(Fanlt Tolerant Local Area Network）系统是在Novell网环境下开发的一个基于消息驱动与同步的容错局域网系统,故障检测是该系统中需解决的关键技术之一。本文介绍了FTLAN系统中的各个节点机发生故障时,系统是如何检测的,并对其进行了简要的分析。     

离散随机系统的一类综合控制

研究离散线性随机系统在方差约束下的综合控制设计问题,即设计期望的静态输出反馈控制器,使闭环极点位于单位圆内的一个环形区域内。同时,每个稳态状态方差都满足给定的上界约束,从而使闭环系统具有良好的稳定特性和动态性能。本文利用修正的代数Ｌｙａｐｕｎｏｖ方程,推导出控制器存在的充分条件和解集刻划,并提供了说明性的数值算例。文中所得结果具有形式简洁、易于工程实现的特点     

三种局部环的同调刻划

给出了C-M环、Gorenstein环和正则环上C-M模的同调性质,并用这种性质描述了这三种环的联系与区别     

Quantifying optimal mesh and ring design costs

During the last decade telecommunication operators have been deploying WDM (Wavelength Division Multiplexing) technology to satisfy the exponential growth in global communication. While facilitating the advanced information society of today, this has also led to a higher dependency on the networks, and furthermore the high capacity utilization of optical fibers means that a single link failure will influence many users and enterprises. For these reasons, protection of network connections has become a major competitive parameter for the operators. Currently, the most popular protection method is ring protection, due to its simplicity, requiring only basic management functionality and operating with local restoration control. While many optical rings have been deployed, little work has been published on exactly what the cost of ring networks are, compared to general mesh networks. In this article we perform a quantitative comparison between ring protection and mesh protection, using real world network data and realistic prices for network components. Extending classic LP flow models to take rings and node costs into account, and using a link‐path based mesh network LP model, we are able to perform a total cost comparison of the two architectures, and of manual ring network design. The results suggest that the price of mesh network components must be reduced significantly to be competitive with ring based networks, and also that manual network design does not necessarily lead to the most cost‐efficient designs. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2005     

War’s Horizon: Soldier-Led Adaptation in Iraq and Vietnam

Wartime adaptation is a process of adjustment from the war you planned for to the one you have. This process of adjustment is done, in part, by the practitioners of war in the theater of conflict–soldier-led adaptation. Drawing upon two case studies of gun truck development in Iraq and Vietnam I argue that soldiers created networks in order to adapt to battlefield challenges and that the pattern of those networks carries implications for the likelihood of formal adoption by the organization. Simply put, the pattern of the flow of ideas, resources, and skills across the battlefield may affect the likelihood of bottom-up adaptation.     

基于Kriging模型的环形桁架可展天线结构参数优化方法

针对传统结构动力学优化过程中求解效率较低的问题,以环形桁架可展天线结构参数优化为研究背景,在环形桁架可展天线结构的参数变量空间中,以试验设计方法选取样本点,通过有限元方法得到各个样本点的第一阶固有频率、固定载荷最大变形等响应值,利用样本点和响应值的关系建立Kriging近似模型进行优化算法的寻优,得到满足所有约束条件的最优解。结果表明,所得到的环形桁架可展天线第一阶固有频率、固定载荷最大变形的响应面呈现比较明显的非线性关系,基于Kriging模型的结构优化方法能比较准确地对环形桁架可展天线进行寻优设计。     

Development of multi-physics numerical simulation model to investigate thermo-mechanical fatigue crack propagation in an autofrettaged gun barrel

In this research, a detailed multi-physics study has been carried out by numerically simulating a solid fractured gun barrel for 20 thermo-mechanical cycles. The numerical model is based on thermal effects, mechanical stress fields and fatigue crack mechanics. Elastic-plastic material data of modified AISI 4340 at temperatures ranging from 25 to 1200 °C and at strain rates of 4, 16, 32 and 48 s⁻¹ was acquired from high-temperature compression tests. This was used as material property data in the simulation model. The boundary conditions applied are kept similar to the working gun barrel during continuous firing. A methodology has been provided to define thermo-mechanically active surface-to-surface type interface between the crack faces for a better approximation of stresses at the crack tip. Comparison of results from non-autofrettaged and autofrettaged simulation models provide useful information about the evolution of strains and stresses in the barrel at different points under combined thermo-mechanical loading cycles in both cases. The effect of thermal fatigue under already induced compressive yield due to autofrettage and the progressive degradation of the accumulated stresses due to thermo-mechanical cyclic loads on the internal surface of the gun barrel (mimicking the continuous firing scenario) has been analyzed. Comparison between energy release rate at tips of varying crack lengths due to cyclic thermo-mechanical loading in the non-autofrettaged and autofrettaged gun has been carried out.