Analysis of the solar sail deformation based on the point cloud method

The deformation of the solar-sail membrane is an important factor for causing inaccuracies in the solar-sail missions. This paper describes the solar sail under deformation by using a new modelling technique based on point cloud and triangular mesh generation. Two types of deformation, stemming from wrinkling and billowing, are modelled. The changes in the solar radiation pressure force and the moment caused by deformation are calculated and compared to the ideal non-deformed case. The heliocentric spiral trajectory and the orbital angular momentum reversal trajectory are taken as examples to quantify the influence of the deformation from an orbit point of view. Additionally, point cloud simplification, based on the normal vector and bounding box, is utilized to simplify the original deformed-sail model. It involves a reasonable reduction and renewal of the points in the model considering the variation of surface curvature. The simplification and its modelling accuracy are numerically investigated as well as computational efficiency.     

随机数对遗传算法计算效率的影响分析及改进研究

遗传算法要求计算过程产生均匀随机数,针对目前采用的线性同余随机函数发生器长周期与稀疏网格局限,提出以当前时间折合为百分秒初始化结合洗牌技术处理,同时采用以群体规模数为基准的归一化方法来产生[0,1]范围内的均匀随机数用于遗传算法编程计算.实例计算说明,所提出的处理方法可有效提高算法的计算效率.     

Ground-Based Cloud Using Exponential Entropy/Exponential Gray Entropy and UPSO

Objective and accurate classification model or method of cloud image is a prerequisite for accurate weather monitoring and forecast. Thus safety of aircraft taking off and landing and air flight can be guaranteed. Thresholding is a kind of simple and effective method of cloud classification. It can realize automated ground-based cloud detection and cloudage observation. The existing segmentation methods based on fixed threshold and single threshold cannot achieve good segmentation effect. Thus it is difficult to obtain the accurate result of cloud detection and cloudage observation. In view of the above-mentioned problems, multi-thresholding methods of ground-based cloud based on exponential entropy/exponential gray entropy and uniform searching particle swarm optimization （UPSO） are proposed. Exponential entropy and exponential gray entropy make up for the defects of undefined value and zero value in Shannon entropy. In addition, exponential gray entropy reflects the relative uniformity of gray levels within the cloud cluster and background cluster. Cloud regions and background regions of different gray level ranges can be distinguished more precisely using the multi-thresholding strategy. In order to reduce computational complexity of original exhaustive algorithm for multi-threshold selection, the UPSO algorithm is adopted. It can find the optimal thresholds quickly and accurately. As a result, the real-time processing of segmentation of groundbased cloud image can be realized. The experimental results show that, in comparison with the existing groundbased cloud image segmentation methods and multi-thresholding method based on maximum Shannon entropy, the proposed methods can extract the boundary shape, textures and details feature of cloud more clearly. Therefore, the accuracies of cloudage detection and morphology classification for ground-based cloud are both improved.     

云计算综述

论述了云计算的起源、概念、特点,与分布式计算和网格计算的区别;介绍了云计算厂商,及各厂商采用的数据存储、数据管理、编程模式、提供的服务种类云计算存在的问题,特别是云计算安全的风险种类及防护方法。提出了云计算需解决的问题。     

Hamilton圈问题的DNA算法

基于目前可以使用的DNA实验技术并采用试管与表面相结合的方式,设计了解决H am ilton圈问题的DNA算法;详细地介绍了对图的顶点和边的分子编码;描述了算法的生物化学实现过程。由于采用了有控的部分穷举策略,因而既提高了解的可靠性,又抑制了大量伪解的产生。最后,讨论了算法的性能特点并指出进一步的研究方向。     

多序列激光阴影成像技术研究及应用

为获取超高速碰撞过程中弹丸的飞行姿态及碰撞所产生的碎片云特性,开展了多序列激光阴影成像技术研究。利用多光源空间分离、偏振分光、光束角放大和补偿滤光等技术解决了单色光带来的衍射和干涉噪声以及碰撞瞬间强烈的自发光干扰问题,并先后在碰撞靶上建立了2序列、4序列和8序列激光阴影成像系统。该系统可以获得最小间隔1μs、曝光时间10ns、像素1000万的多个不同时刻的超高速瞬态变化过程图像,并在超高速碰撞靶试验中得到应用,获得了2～7km/s 撞击速度时碎片云的多序列阴影图像,该序列图像清晰地描述了碎片云的轮廓发展变化过程。该技术以低成本的方式实现了超高速摄影机的功能,满足目前碰撞试验粒子的飞行姿态及碎片云显示需要,并可以应用于其它超高速瞬态过程测量及流场结构显示。     

基于 C-AHP的舰炮装备保障性指标体系

在指标体系构建过程中,应用一种云模型（CloudModel）与层次分析法（AHP）相结合的云层次分析法（C—AHP）,构建舰炮装备保障性指标体系的层次结构,针对指标体系中定性定量指标的特性,依据指标的相对重要性筛选各层次指标。实例证明,该方法可有效解决舰炮装备保障性指标体系构建中指标分类不明确,以及由于各类定性定量指标繁杂导致的指标筛选困难等问题。     

择优比较法的水面舰艇反导作战通道性能分析

通过对影响水面舰艇反导作战通道性能的因素进行分析,构建了水面舰艇反导作战通道效能评价指标体系,建立了水面舰艇反导作战通道性能云模型,为水面舰艇反导作战通道性能评估提供了定量算法。水面舰艇反导作战效能的定量评估,对提高水面舰艇反导作战能力具有重要作用。     

机载220 GHz云雷达衰减订正模拟试验

针对220 GHz云雷达回波信号的衰减问题，结合典型云滴谱和云参数，对水云和冰云模拟取样2 100次，应用离散偶极子近似法计算了220 GHz云雷达探测云滴粒子的衰减系数kc和雷达反射率因子Z的关系。在考虑大气和云对220 GHz云雷达信号衰减的基础上，对水云和冰云的机载220 GHz雷达回波强度进行了数值模拟，根据得到的kc-Z关系，进行衰减订正的模拟试验。结果表明:水滴云比冰晶云的衰减系数大2~3个数量级;相对于小粒子的水云和冰云，大气吸收是造成机载220 GHz云雷达衰减的主要原因。高频段的雷达信号在传播路径上的衰减非常明显，本研究中给出的kc-Z关系适用于220 GHz频率雷达的云衰减订正计算。     

基于GPU加速的binLBT压缩解压算法

地形数据的压缩/解压是大规模地形实时绘制方法的关键步骤,与绘制效率密切相关.通过对压缩/解压方法核心重叠双正交变换的分析,采用重叠双正交变换的整数提升方法将变换中的浮点数操作转换为整数操作及移位操作.使用支持图形处理单元(GPU,Graphic Processing Unit)通用计算的CUDA(Compute Unified Device Architecture)对变换过程及编码过程进行加速.针对数据超出显存容量的情况,采取数据分块的方法将数据分别载入显存进行变换与编码以完成对整体数据的处理.实验结果表明,基于GPU加速的重叠双正交变换整数提升方法的压缩算法有效提高了地形数据处理的效率,并加快了大规模地形绘制速度.