特征无反射边界条件应用于二维圆柱绕流模拟

采用特征无反射边界条件和吸收层技术相结合的边界处理方法,研究了二维圆柱绕流模拟的边界反射问题。近年来在计算气动声学中提出了将大涡模拟和声学传播方程结合的混合方法求解声场,基于计算量的考虑,须在较小的计算区域内进行大涡模拟,这就需要在计算区域较小时,边界的反射尽可能小。作为大涡模拟研究的技术储备,将该方法应用于二维圆柱绕流的模拟中。数值结果表明这种方法在计算区域较小时,能起到很好的无反射效果,计算结果与前人在计算区域取得很大时的结果比较吻合。     

我国航空情报服务向航空信息管理方向发展探索

AIM是近年来国际民航界提出的一个新的航空信息管理的概念,它包含一系列航空信息服务的理论、目标和方法。本文通过对AIM的核心内容、目标和技术实现进行分析,提出了我国航空情报的发展方向。     

除冰液对道面混凝土的影响及保护剂防护效果

通过冻融和化学侵蚀试验，研究了NW-056A机场道面除冰液对道面水混混凝土耐久性的影响以及在道面除冰液环境下两种新型混凝土保护剂的防护效果。结果表明：①混凝土在道面除冰液中冻融后表面无明显剥落现象，相对动弹模损失率比在水中小很多，道面除冰液延缓了混凝土的冻融破坏：②混凝土在道面除冰液常温浸泡下表面无剥蚀现象，但强度比在水中降低很多，因此存在化学腐蚀．且主要表现为对混凝土内部结构的缓慢损伤；（④两种新型混凝土保护剂均对预防混凝土的冻融破坏以及除冰液环境下的腐蚀破坏起到一定作用，涂刷混凝土保护剂是提高混凝土道面耐久性的有效方法。     

反导预警雷达部署方案的评价与优选

合理部署反导预警雷达对提高反导作战效能起着重要作用。反导预警雷达部署要考虑的因素较多,部分因素存在冲突。本文分析了反导预警雷达部署评价应考虑的因素,提出了相关评价指标,主要有不同配置距离下雷达对目标的发现概率、提供的预警时间、落点预报精度、全程跟踪目标时长等,建立了不同评价指标的计算方法,给出了反导预警雷达部署方案的综合评价与优选方法。本文方法对反导预警雷达部署方案的建立优选具有指导意义。     

A Test Method for the Static/Moving State of Targets Applied to Airport Surface Surveillance MLAT System

Due to the particularity of its location algorithm,there are some unique difficulties and features regarding the test of target motion states of multilateration(MLAT)system for airport surface surveillance.This paper proposed a test method applicable for the airport surface surveillance MLAT system,which can effectively determine whether the target is static or moving at a certain speed.Via a normalized test statistic designed in the sliding data window,the proposed method not only eliminates the impact of geometry Dilution of precision(GDOP)effectively,but also transforms the test of different motion states into the test of different probability density functions.Meanwhile,by adjusting the size of the sliding window,it can fulfill different test performance requirements.The method was developed through strict theoretical extrapolation and performance analysis,and simulations results verified its correctness and effectiveness.     

A novel signal processing approach for LEO space debris based on a fence-type space surveillance radar system

The increase in space debris can seriously threaten regular activities in the Low Earth Orbit (LEO) environment. Therefore, it is necessary to develop robust, efficient and reliable techniques to understand the potential motions of the LEO debris. In this paper, we propose a novel signal processing approach to detect and estimate the motions of LEO space debris that is based on a fence-type space surveillance radar system. Because of the sparse distribution of the orbiting debris through the fence in our observations, we formulate the signal detection and the motion parameter estimation as a sparse signal reconstruction problem with respect to an over-complete dictionary. Moreover, we propose a new scheme to reduce the size of the original over-complete dictionary without the loss of the important information. This new scheme is based on a careful analysis of the relations between the acceleration and the directions of arrival for the corresponding LEO space debris. Our simulation results show that the proposed approach can achieve extremely good performance in terms of the accuracy for detection and estimation. Furthermore, our simulation results demonstrate the robustness of the approach in scenarios with a low Signal-to-Noise Ratio (SNR) and the super-resolution properties. We hope our signal processing approach can stimulate further work on monitoring LEO space debris.     

基于复杂性图的到场航班调配方法研究

为了在保障到场交通安全运行的基础上更加充分地利用五边航段的空闲空域,基于对复杂性图的客观分析,总结了复杂性图的直观特点,并利用相关特点建立了搜索五边可用空域的方法,提出了一套对到场航班进行调配的方法,为管制工作的决策提供了简洁直观的新思路.     

基于Poisson圆盘分布的河流仿真技术

针对目前河流仿真所存在的计算效率低,渲染效果不够真实的问题, 介绍了一种基于物理规律的河流实时仿真的方法.提出了一种Poisson圆盘分布的算法,可实现屏幕空间的优秀的分布样式,该算法产生的分布粒子用于表达河流的速度场,进而重构河流表面; 采用一种纹理精灵的技术,通过纹理的动态访问和纹理混合,有效地实现河流表面的渲染.仿真实验证明:该方法可以产生渲染效果非常逼真的河流视景,并能够满足实时仿真的要求.     

A new inversion method of plasma density distribution of plasmasphere in the geomagnetic equatorial plane from IMAGE data

The plasma density distribution of plasmasphere in the geomagnetic equatorial plane can help us study the magnetosphere like plasmasphere, ionosphere and their kinetics. In this paper, we introduce a new inversion method, GE-ART, to calculate the plasma density distribution in the geomagnetic equatorial plane from the Extreme Ultraviolet (EUV) data of IMAGE satellite under the assumption that the plasma density is constant along each geomagnetic field line. The new GE-ART algorithm was derived from the traditional Algebraic Reconstruction Techniques (ART) in Computed Tomography (CT) which was different from the several existing methods. In this new method, each value of the EUV image data was back-projected evenly to the geomagnetic field lines intersected by this EUV sight. A 3-D inversion matrix was produced by the contributions of all the voxels contained in the plasmasphere covered by the EUV sensor. That is, we considered that each value of the EUV image data was relative to the plasma densities of all the voxels passed through by the corresponding EUV radiation, which is the biggest difference to all the existing inversion methods. Finally, the GE-ART algorithm was evaluated by the real EUV data from the IMAGE satellite.     

用模糊集方法实现管理系统仿真输入非参数化的研究

以模糊信息优化处理的观点，研究了信息扩散方式实现非参数输入的途径、方法和效果、本文用正态扩散方式处理知识样本，形成参数概率颁上模式，通过ＳＩＭＡＮ仿真语言，对某一高速公路的一部分收费系统进行了仿真研究，结果表明：当人们对系统掌握的资料不多时，新方法有较大的优越性；如有较多的资料，新方法的结果与传统方法一致。