微遗传算法优化多层ZnOw雷达吸波涂层

采用微遗传算法对以四针状ZnOw为主要成分的多层雷达吸波材料(RAM)进行优化设计.在给定最大厚度的情况下,在2～18GHz频率范围内,采用对不同频段给定不同吸收率的方案,对多层吸波涂层建立了快速优化设计方法.讨论了吸波涂层的厚度、层数对吸收效果的影响.此外,对于不同频段改变给定的吸收率,分析对于优化结果的影响.     

三层雷达吸波涂层的吸波性能研究

依据阻抗匹配原理制备出一种三层雷达吸波涂层,并研究了其吸波性能.结果表明:多层结构设计对提高涂层的吸波性能起着重要作用.所制备的吸波涂层在8～18GHz频段范围内反射率小于-10dB的带宽达6.0GHz,涂层厚度为1.20mm,面密度为2.80kg/m2.     

宽频段雷达表面波衰减特征规律研究

目标物体上表面波的衰减吸收对目标的隐身起到很大的作用.研究了雷达吸波涂层对宽频段雷达表面波衰减吸收的规律以及频率选择表面与吸波涂层相结合的复合吸波涂层对宽频段表面波衰减吸收的规律.实验结果表明,低厚度的雷达吸波涂层就可以实现高频表面波的强衰减吸收,而频率选择表面与低厚度雷达吸波涂层相结合的复合涂层与雷达吸波涂层共同交替使用可以实现宽频段表面波的强衰减吸收,有望实现目标物体在宽频段范围内的高性能均衡雷达隐身.     

一种三层雷达吸波涂层的制备和性能

在磁性金属微粉的雷达吸波涂层中引入导电纤维层具有减轻质量和展宽吸收频带作用,本文采用磁性金属微粉和短导电纤维制备了一种三层雷达吸波材料.研究表明,三层的相对顺序对吸波涂层的带宽与峰值具有明显影响,在面密度为2.50 kg/m2的条件下,当导电纤维层位于表层时带宽最大,在8～18 GHz频段范围内反射率小于-10 dB的带宽达7 GHz.     

热喷涂雷达吸波涂层研究现状与展望

随着先进军事探测技术的发展,热喷涂雷达吸波涂层在航空航天和军事装备等领域具有巨大的应用前景。简要介绍了雷达吸波材料的工作机理,然后分别从热喷涂铁氧体、炭系材料、碳化硅、金属微粉和导电陶瓷5个方面综述了热喷涂雷达吸波涂层的研究现状,重点评述了热喷涂雷达吸波涂层的电磁参数及吸波性能调控途径。在此基础上,对热喷涂雷达吸波涂层的研究进展进行了系统的总结。最后,提出了热喷涂吸波涂层当前所亟需解决的问题。     

某复合隐身涂层中雷达吸波涂层的测厚系统设计

针对“雷达+红外”复合隐身体系的结构特点和雷达吸波涂层的磁化特性,建立了某复合隐身涂层中雷达吸波涂层的磁力测厚模型,分析了测厚算法。结果表明,当复合隐身体系中红外涂层厚度+某底漆厚度远小于空气涂层厚度时,磁力测厚法可忽略红外涂层和某底漆厚度的影响,直接利用磁力大小与雷达吸波涂层厚度成正比的电磁学特性关系,测出雷达吸波涂层的厚度。本文作者还设计了磁力测厚传感器,开展了磁力测量试验。结果表明,该磁力测厚系统结构简单、测量结果精确。      

雷达吸波涂层制备技术的研究进展

随着雷达技术的迅猛发展,雷达吸波涂层RAC(Radar absorbing coating)在军事装备隐身防御系统中的作用日趋重要.介绍了吸波材料的吸波机理,综述了雷达吸波涂层的3种结构设计.重点评述了物理涂覆、化学镀、热喷涂和溶胶一凝胶法制备工艺的研究进展,最后展望了强、宽、轻、薄吸波涂层的研究方向.     

雷达吸波涂层制备技术的研究进展

随着雷达技术的迅猛发展,雷达吸波涂层RAC(Radar absorbing coating)在军事装备隐身防御系统中的作用日趋重要.介绍了吸波材料的吸波机理,综述了雷达吸波涂层的3种结构设计,重点评述了物理涂覆、化学镀、热喷涂和溶胶-凝胶法制备工艺的研究进展,最后展望了强、宽、轻、薄吸波涂层的研究方向.     

Research Development of Preparation Technology of Radar Absorbing Coating

随着雷达技术的迅猛发展,雷达吸波涂层RAC( Radar absorbing coating)在军事装备隐身防御系统中的作用日趋重要.介绍了吸波材料的吸波机理,综述了雷达吸波涂层的3种结构设计,重点评述了物理涂覆、化学镀、热喷涂和溶胶-凝胶法制备工艺的研究进展,最后展望了强、宽、轻、薄吸波涂层的研究方向.     

雷达隐身技术的研究现状及其展望

叙述了雷达隐身技术的工作原理、类型及研究现状,综述了雷达吸波涂层中使用的吸收剂、胶粘剂和助剂,并介绍了以聚氨酯为胶粘剂的涂层基体,对聚氨酯复合材料进行了展望.回顾了雷达吸波材料的研究和发展,介绍了雷达吸波材料若干新的发现、性能及应用,同时展望了雷达吸波材料的发展趋势和研究发展的重点.     

Optical filling algorithm

The technique of optical symbolic substitution is applied to development of a new filling algorithm that reconstructs an image from its boundary in constant time, whereas known filling algorithms have at least O(n log N) time complexity, where n is the number of boundary pixels of a polygon and N is the diameter of the image expressed in terms of pixels.     

一种改进的亚像素算法

传统的灰度重心法是一种用于对称目标的亚像素定位技术,但其抗噪声性能较差。针对这一问题,本文提出一种改进算法,通过将目标区域划分成内部像素区域和边缘像素区域两部分,并对内部像素灰度进行均值化,从而有效抑制内部像素噪声。同时,利用误差理论对改进算法的不确定性进行分析。最后,通过仿真实验验证了改进算法的正确性,并表明改进算法有更好的噪声抑制性能。     

Hybrid constrained genetic algorithm/particle swarm optimisation load flow algorithm

A hybrid constrained genetic algorithm and particle swarm optimisation (PSO) method for the evaluation of the load flow in heavy-loaded power systems is developed. The new algorithm is applied to find the maximum loading points of three IEEE test systems. The experimental determination of the best values of the parameters for use in the PSO part of the hybrid algorithm is also reported.     

A simplified SPIHT algorithm

Abstract

Based on the SPIHT algorithms, we define two modifications to develop a simpler image coding method. The first concept is obtained from the relationship between the bit‐planes and the target bit‐rate. The second concept is obtained from the relationship between the initial threshold and the target bit‐rate. Based on the abovementioned concepts, we can discard the refinement pass and improve the image quality at different target bit‐rates. The simulation results show that in comparison with the original SPIHT algorithm, the proposed algorithm can reduce memory usage by approximately 50% and computation time by approximately 30% with an acceptable PSNR loss.     

The subcycled Newmark algorithm

The popular Newmark algorithm, used for implicit direct integration of structural dynamics, is extended by means of a nodal partition to permit use of different timesteps in different regions of a structural model. The algorithm developed has as a special case an explicit-explicit subcycling algorithm previously reported by Belytschko, Yen and Mullen. That algorithm has been shown, in the absence of damping or other energy dissipation, to exhibit instability over narrow timestep ranges that become narrower as the number of degrees of freedom increases, making them unlikely to be encountered in practice. The present algorithm avoids such instabilities in the case of a one to two timestep ratio (two subcycles), achieving unconditional stability in an exponential sense for a linear problem. However, with three or more subcycles, the trapezoidal rule exhibits stability that becomes conditional, falling towards that of the central difference method as the number of subcycles increases. Instabilities over narrow timestep ranges, that become narrower as the model size increases, also appear with three or more subcycles. However by moving the partition between timesteps one row of elements into the region suitable for integration with the larger timestep these the unstable timestep ranges become extremely narrow, even in simple systems with a few degrees of freedom. As well, accuracy is improved. Use of a version of the Newmark algorithm that dissipates high frequencies minimises or eliminates these narrow bands of instability. Viscous damping is also shown to remove these instabilities, at the expense of having more effect on the low frequency response.     

Fast three-step phase-shifting algorithm

We propose a new three-step phase-shifting algorithm, which is much faster than the traditional three-step algorithm. We achieve the speed advantage by using a simple intensity ratio function to replace the arctangent function in the traditional algorithm. The phase error caused by this new algorithm is compensated for by use of a lookup table. Our experimental results show that both the new algorithm and the traditional algorithm generate similar results, but the new algorithm is 3.4 times faster. By implementing this new algorithm in a high-resolution, real-time three-dimensional shape measurement system, we were able to achieve a measurement speed of 40 frames per second at a resolution of 532 x 500 pixels, all with an ordinary personal computer.     

Improved noise-immune phase-unwrapping algorithm

An algorithm for unwrapping noisy phase maps has recently been proposed, based on the identification of discontinuity sources that mark the start or end of a 2π phase discontinuity. Branch cuts between sources act as barriers to unwrapping, resulting in a unique phase map that is independent of the unwrapping route. We investigate four methods for optimizing the placement of the cuts. A modified nearest neighbor approach is found to be the most successful and can reliably unwrap unfiltered speckle-interferometry phase maps with discontinuity source densities of 0.05 sources pixel(-1).     

基于遗传算法的LQR算法中权矩阵的优化分析

LQR控制算法是目前结构主动控制设计分析时最广泛采用的方法。在LQR算法中,权矩阵Q和R的选取直接影响着结构的动力反应和控制力。目前如何确定最优形式和大小的Q和R以获得全局最优控制力仍然是个难题。采用遗传算法,在一定的目标函数下对LQR算法中权矩阵Q和R进行优化,使其控制效果能够满足结构性能要求,并对优化结果下的动力反应进行了分析比较和结果的验证。     

基于迷宫算法和遗传算法的船舶管路路径规划

船舶管路的多样性和布局环境中约束的复杂性导致管路设计效率低下.为辅助设计人员提高管路设计效率并减少人为错误,提出了一种新的管路设计方法.首先,基于轴平行包围盒简化管路布局空间,利用栅格法对其进行离散化,并赋予空间网格特定的能量值,构建管路布局优化问题的数学模型.其次,基于遗传算法的框架,引入改进迷宫算法,提出管路路径规划方法,其中:迷宫搜索中引入辅助点的概念,增加了遗传算法中初始种群的多样性,有利于提高遗传算法的全局搜索能力;提出了定长度的编码方法,简化了管路染色体处理难度,提高了算法性能;基于引入方向优先搜索策略的迷宫算法,设计定长度编码遗传算子,保证了子代个体的质量,提高算法的收敛速度.最后,基于仿真试验,验证算法的性能.试验结果表明了该方法的可行性和高效率,以及其对实际管路布局工作具有指导意义.     

An automatic focusing algorithm

A simple and effective automatic focusing algorithm is proposed in this article. The principle of the proposed automatic focusing algorithm is based on that, for the radial test pattern, a best‐focused image should have the smallest blurred region in the middle of the acquired image, and hence, should have the smallest equivalent radius. The circular Hough transform has became a common method in numerous image‐processing applications for circle detection. Various modifications to the basic circular Hough transform have been suggested, such as: the inclusion of edge orientation, simultaneous consideration of a range of circle radii, the use of a complex accumulator array with the phase proportional to the log of the radius, or for filter operations. The purpose of this work is to show that a radius of a circular region extracted by a normalized circular Hough transform is a possible solution for determining the sharpness of images. To acquire high quality images with a given CCD camera, it is crucial that the camera be located exactly at the back length of the lens, i.e., the focus position of the lens. In the best conditions, the contours of the acquired images are of the sharpest, with none of the blurring effects associated with unfocused images. Acquiring such high quality images by these means is the main goal of the automatic focusing algorithm proposed in this article. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 12, 235–238, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10029