Using parallel computing for the display and simulation of the space debris environment

Parallelism is becoming the leading paradigm in today’s computer architectures. In order to take full advantage of this development, new algorithms have to be specifically designed for parallel execution while many old ones have to be upgraded accordingly. One field in which parallel computing has been firmly established for many years is computer graphics. Calculating and displaying three-dimensional computer generated imagery in real time requires complex numerical operations to be performed at high speed on a large number of objects. Since most of these objects can be processed independently, parallel computing is applicable in this field. Modern graphics processing units (GPUs) have become capable of performing millions of matrix and vector operations per second on multiple objects simultaneously.     

Physical properties and long-term evolution of the debris clouds produced by two catastrophic collisions in Earth orbit

The population of cataloged orbital debris increased by approximately 40% in just a couple of years, from January 2007 to February 2009. This was due to two collisions in space, which involved the catastrophic destruction of three intact satellites (Fengyun 1C, Cosmos 2251 and Iridium 33) in high inclination orbits. Both events occurred in the altitude range already most affected by previous launch activity and breakup events, thus boosting the cataloged population in low Earth orbit by more than 60%.     

Semi-analytical investigations of the long term evolution of the eccentricity of Galileo and GPS-like orbits

This paper aims at investigating the stability over 150 years of a very large number of trajectories in the Medium Earth Orbit (MEO) region, near the orbits devoted to radionavigation such as the Global Navigation Satellite Systems (GNSS like GPS, Glonass, Galileo, COMPASS).     

一种个性化标签云中的标签排序算法

社会化标签能够直接反映用户兴趣和商品特征,因而可用于个性化推荐系统中。使用标签进行推荐时,需要将其排序,而现有标签云中的标签排序都是按标签被标记次数或字典顺序进行降序排列的,这些排列方式未考虑用户个性化的需求和标签的时效性。提出了一种个性化标签云中的标签排序算法,通过用户自身的兴趣与挖掘出的用户潜在兴趣进行标签排序,从而构建个性化的标签云,并根据用户兴趣的变化定期对标签云进行更新,可以更好地发现电子商务网站中用户感兴趣的商品。实验对比结果表明,个性化标签云中的标签排序算法能够有效的提高商品推荐质量。     

云存储环境下的负载均衡策略研究

云存储系统具有高容错性、部署在低廉的硬件上、易扩展性、提供高传输率访问数据的优点,但是在云存储环境下的HDFS架构中,原有的数据节点选择策略有可能造成大文件存储负载不均衡,从而影响整个系统的性能。针对这一问题,综合考虑多个因素对其进行改进,提出了设备选择策略算法,用以均衡系统的负载。并设计仿真实验,验证了算法的有效性。     

Asymptotically Optimal Simulation Budget Allocation under Fixed Confidence Level by Ordinal Optimization

Ordinal optimization concentrates on isolating a subset of good designs with high probability and reduces the required simulation time dramatically for discrete event simulation. To obtain the same probability level,we may optimally allocate our computing budget among different designs,instead of equally simulating all different designs. In this paper we present an effective approach to optimally allocate computing budget for discrete-event system simulation. While ordinal optimization can dramatically reduce the computation cost, our approach can further reduce the already-low cost.     

Heliosphereic Physics Research in China:2002-2003

This brief report summarized the latest advances of the heliospheric physics research in China during the period of 2002-2003, made independently by Chinese space physicists and through international collaboration. The report covers all aspects of the heliospheric physics, including theoretical studies, numerical simulation and data analysis.     

风扇叶片脱落机匣包容性仿真并行计算一致性研究

风扇叶片脱落并行计算结果的一致性非常重要。在共享内存并行(SMP)模式下,由于计算随机误差和误差累积现象的存在,计算结果可能不一致。针对该问题,对某型大涵道比涡扇发动机简化的三叶片模型进行并行仿真计算,分析造成计算结果不一致的误差来源,提出四种控制策略,研究表明,通过计算方法的改进和计算平台的选择可以有效避免误差累积现象,提高并行计算精度。     

基于VTK的激光跟踪测量可视化软件设计

测量数据的三维可视化是激光跟踪测量数据处理的关键步骤之一。结合大型激光跟踪测量软件系统的开发实践,对VTK技术特点和体系结构进行深入研究,设计实现了对测量数据进行处理和显示的类和接口。在此基础上,基于Microsoft Visual Studio 2010平台,利用C++和VTK技术开发了一款三维测量数据处理及可视化软件,实现了测量点云拟合、三维图形显示以及交互功能,并通过实例验证了软件的有效性和可用性,证明了VTK在工业测量可视化领域具有很大的应用价值。     

一种应用云计算技术的航天器综合测试方法

首先介绍了目前国内外航天器综合测试系统的现状,指出其资源利用率低、测试成本高的不足;然后针对这些不足,结合未来航天器综合测试业务新需求,提出了一种应用云计算平台的航天器综合测试方法,给出了该方法的综合测试云架构,分析了其在资源利用率、可靠性、可扩展性等方面的技术优势;最后给出航天器综合测试云系统的实施方案,供今后我国航天器测试系统建设参考。