Fabrication and analysis of TIG welding-brazing butt joints of in-situ TiB2/7050 composite and TA2

Lightweight hybrid structures of Al MMCs and titanium alloy dissimilar materials have great prospect in the defence industry application. So, it is necessary to join Al MMCs with Ti metal to achieve this structural design. In this work, in-situ TiB2/7050 composite and TA2 were firstly attempted to join by TIG welding-brazing technique. The result was that the intact welding-brazing butt joint was successfully fabricated. The joint presents dual characteristics, being a brazing on TA2 side and a welding on TiB2/7050 side. At brazing joint side, ER4043 filler metal effectively wets on TA2 under TIG heating condition, and a continuous interfacial reaction layer with 1—3μm is formed at welded metal/TA2 interface. The whole interfacial reaction layers are composed of Ti(AlSi)3 intermetallic compounds (IMCs), but their morphologies at the different regions present obvious distinguishes. The microhardness of the reaction layers is as much as 141—190 HV. At welding joints side, the fusion zone appears the equixaed crystal structure, and the grain sizes are much smaller than those of welded metal, which is attributed to the effect of TiB2 particulates from the melted TiB2/7050 on acceleration formation and inhibiting growth for the new crystal nucleus. The tensile test results show that average tensile strength of the optimal welding-brazing joint is able to achieve 138 MPa. The failure of the tensile joint occurs by quasi-cleavage pattern, and the cracks initiate from the IMCs layer at the groove surface of TA2 and propagate into the welded metal.     

新指挥控制原理

指挥控制系统是兵力放大器,信息时代的挑战是要突破这种传统理念的束缚。传统的指挥控制赋予兵力系统以自动机功能,而新指挥控制原理则赋予兵力系统具有生命系统特征的进化能力,具有进化特征的兵力系统将更加灵活和更具适应性,采用自组织、自学习、自修复的运作方式,以满足系统与系统对抗、体系与体系对抗的需求为构建目标。文中在分析了指挥控制的基本问题的基础上,从指挥控制的性质的角度,归纳和提出了新指挥控制原理,并尝试解释原理的含义、本质、特点和可能应用。文中的观点对分析设计指挥控制体系、系统、方法具有理论和实践意义。     

电子对抗指挥控制系统的行为功能需求

电子对抗指挥控制系统的军事需求分析是制约电子对抗指挥控制系统建设质量的关键。本文主要介绍了电子对抗指挥控制系统的行为功能需求。     

ITSON：一种基于拓扑演化的P2P智能搜索机制

P2P系统中节点的动态特性对搜索性能的稳定提出了很大挑战。借鉴社会学和组织学相应原理,提出拓扑演化模型捕获节点的运动规律。节点模拟人类在社会网络中的行为,根据自身和他人的兴趣变化,随搜索过程的进行,利用自身局部信息,动态、自适应地调整网络拓扑,及时反映资源分布以及搜索内容的动态变化,维持资源合理组织。在此基础上提出的智能搜索机制ITSON(InTelligent Search based on tOpology evolutioN),利用消息转发的智能性进行路由方向决策,从而迅速定位资源提供节点。仿真结果说明,ITSON能自动优化网络,具有良好的搜索性能和自适应特性。     

基于Maxwell2D和Simplorer的永磁同步电机退磁模型设计

永磁体退磁故障是永磁电机的常见故障,对电机退磁故障进行早期检测和诊断可以有效防止灾难发生,具有重大意义。建立不均匀退磁故障状态下的Maxwell2D电机模型,利用仿真软件Maxwell2D与Simplorer构建永磁同步电机联合仿真系统,分别对电机的正常状态模型与退磁故障模型进行仿真,并对相电流信号进行分析。利用EMD-LSSVM变换建立的故障诊断模型对不同程度的退磁故障进行诊断。仿真结果表明:该模型可以精确地识别出微弱的退磁故障,验证了联合仿真退磁模型的正确性。     

面向作战仿真的指控系统建模技术研究

重点研究指控系统的建模技术,建立了群指挥所、方面作战指挥所和平台指挥所三级指控系统的模型,并确立了三者之间的层次和控制的逻辑关系。从作战方案和战术响应两方面对指控系统进行"静态的"和"动态的"建模,实现了作战双方基于感知态势的闭环仿真。这些模型在海军某作战仿真系统中得到了应用,仿真实验表明该指控系统模型满足作战仿真系统的作战需求,能够提高作战仿真的真实性和合理性。     

SINS/CNS组合导航的导航星表构建方法

构建满足完备性、精简性和查询快速性的导航星表是实现捷联惯性/星光组合导航系统的重要前提和保证。以天文学中的Tycho-2星表作为导航星表的初始星表,对球矩形分区方法进行了改进,包括明确分区及子分区的划分方法,提出了备选导航星的选择策略。实验结果表明,采用改进型球矩形分区方法的备选导航星数量最多只占赤纬带法导航星的19.37%,仅占全天遍历法导航星的3.12%。因此,改进型球矩形分区方法更加精准,查询更快捷,更适用于捷联惯性/星光组合导航系统。     

基于改进LQR的近地轨道编队卫星鲁棒控制*

为了解决编队卫星在近地空间复杂力学环境,特别是地球非球形摄动作用下构型易发散的问题,给出了一种基于改进线性二次型调节器(LQR)的鲁棒的编队卫星构型控制方法。该方法先估计近地空间编队卫星构型设计时由未建模摄动力引起的误差最大有界范围,再利用误差最大有界范围的二范数改进经典的LQR方法,提高经典LQR控制器在控制编队卫星构型时的鲁棒性。为了评价改进方法的有效性,还给出了一种鲁棒性强弱的量化评判标准。仿真结果表明,改进的方法可以大大提高经典LQR方法的鲁棒性,增强编队卫星控制方法对各种不确定项的抵御能力。     

Planning for the next Takur Ghar

The USA is currently facing an increasingly diverse range of threats, including non-state actors, particularly violent extremist organizations attempting to do harm. The national leadership has made it clear that for the near future it will employ Special Operations Forces (SOF) as the tool of choice in short-duration, high-intensity operations that have more in common with the battle of Takur Ghar, than those with a larger footprint. It is critical then that the lessons of the past are learnt now and are applied before employing SOF in the future. This becomes especially important given the short lead-time in concert with the short-duration/high-intensity tempo of their operations. In the Battle of Takur Ghar, during Operation Anaconda, rigid adherence to the joint functions, especially clearer and more robust Command and Control (C2) and Intelligence, Surveillance, and Reconnaissance (ISR) in the planning and execution of Operation Anaconda would have yielded a better operational outcome and saved lives. With the benefit of hindsight, many things could have been done differently, but several key issues stand out. The C2 structure must include all components from the outset to synchronize effects and rapidly re-task ISR. There must be multiple communications redundancies and adequate bandwidth. Finally, all SOF, conventional and interagency capabilities must be synchronized under one task force commander with a sufficiently robust C2 infrastructure to direct the entire effort. As our nation calls on SOF at an ever-increasing rate, we must take those lessons learned and apply them to future operations.     

一种无师训练的模糊极小极大人工神经网络

提出了一种无师训练的fuzzymin max人工神经网络,它兼有一般fuzzymin max网与ART2网的优点,既弥补了fuzzymin max网不能自适应在线学习新类的缺陷,又消除了ART2网警戒门限过高的弊病.经模式识别仿真对比,对同样的输入数据,文中提出的网络用较低的警戒门限值即可达到ART2用很高的警戒门限值才能达到的分类效果,且计算量大大减少.得到的结论是:对模式识别而言,文中提出的网络比fuzzymin max网和ART2网更具有实用价值.