系统群进化环境的模型设计

由于系统群复杂性的增加和有关实践的非成熟性，开发了一个系统化的方法来进行进化活动显得十分必要。本提出了一个系统群进化的综合环境的设计模型，介绍了该环境的设计思想，操作的流程，主要的模块以及如何运用系统构架知识来支持系统的进化，最后给出了该环境设计的高层结构。     

GEO/IGSO混合区域导航星座的设计与优化算法

区域导航星座能够以较低成本和较短时间获得目标区域导航能力,且地球同步轨道是构建非极区区域导航星座的重要轨道类型.提出一种基于GEO(地球静止轨道)和IGSO(倾斜地球同步轨道)的区域导航星座设计方法.基于星下点轨迹特性构造对称星座设计参数和优化参数集,并考虑地球扁率长期摄动影响,计算星座轨道参数.以导航服务区的统计GD...     

正交铺设陶瓷基复合材料基体裂纹演化研究(英文)

采用能量平衡法对正交铺设陶瓷基复合材料在单轴拉伸载荷作用下的基体裂纹演化进行了研究。在拉伸载荷的作用下,正交铺设陶瓷基复合材料有5种开裂模式。开裂模式3包括横向开裂、基体开裂和纤维/基体界面脱粘;开裂模式5只包括基体开裂和纤维/基体界面脱粘。本文得到了两条横向裂纹之间出现开裂模式3和5的初始基体开裂应力;并得到了开裂模式3多裂纹演化的初始基体开裂应力。讨论了铺层厚度、纤维体积含量、纤维/基体界面剪应力和界面脱粘能对基体开裂应力和基体裂纹演化的影响。结果表明,对于SiC/CAS材料而言,两条横向裂纹之间首先出现开裂模式3。     

信息系统群演化的综合环境SEE的研究

旨在通过对系统构架各视角的研究，开发一个信息系统综合演化环境，从而提供针对各类系统演化特征的通用的解决方案，并利用方法论的手段规范、指导和维护系统(群)的演化活动。本文首先论述了大型系统中各个系统和组件变化及改进活动中存在的问题，分析相关的研究及面临的挑战，从而提出系统群演化的概念。然后文章概括了系统群演化的特征，提出解决以上问题的思想方法，即开发“信息系统群演化的综合环境(Synthetic environment of evolution，SEE)”，将各种演化活动纳入规范，指导系统群的演化活动；在此基础上，进一步就实现SEE的关键技术给出了描述及运用的范例。     

跨介质航行器波浪环境入水流场演变和运动特性研究

跨介质航行器是一种既可以在空中飞行又可以在水下潜航的新概念航行器,基于仿生学原理,提出一种通过改变外形实现水空介质跨越的航行器模型,通过入水试验装置和计算流体动力学方法,对航行器带攻角从空气到水的介质跨越过程进行了试验和数值仿真研究,得到了跨介质入水过程航行器的运动姿态和入水空泡形态,并通过数值仿真得到了航行器的升力、阻力、速度和加速度演化规律。同时基于数值模拟方法对有波浪情况和静水情况下航行器入水过程空泡演变以及运动特性进行对比。结果表明:提出的航行器构型在水中具有较好的姿态调整能力,波浪的有无和波高的不同都会对航行体入水运动特性造成影响。     

编队卫星姿态的自适应协同控制

研究了无向信息交互条件下的多卫星姿态同步和跟踪问题,分别在模型参数精确已知和存在模型参数不确定性的情形下设计分散式协同控制算法。当模型参数精确已知时,基于滑动模态变量设计的协同控制力矩,实现了编队卫星姿态的同步机动,即保证编队卫星姿态的同步,并同时跟踪期望的时变参考姿态轨迹。当在轨卫星存在模型参数不确定性和常值未知扰动力矩时,提出了一种自适应协同控制律,仍能实现多卫星姿态的同步机动。基于Lyapunov-Krasovskii的分析表明,当星间链路存在任意未知的定常通讯时延时,本文设计的控制器有效。数值仿真算例验证了本文提出的控制算法。     

用于痕量气体检测的宽调谐外腔量子级联激光器研究

研究基于闪耀光栅的Littrow外腔量子级联激光器,设计一种改进型Littrow外腔腔型,实现了小型化样机研制。测试结果表明,输出激光波长调谐范围1317cm^–1(7.593μm)至983cm^–1(10.173μm),最大平均功率17.7m W,激光线宽小于1cm^–1,功率稳定性优于0.5%(4h),波长稳定性优于0.12cm^–1(5.4h)。样机激光头尺寸76mm×54mm×50mm,部分技术指标优于国外商业产品。     

Halo White Dwarfs and Baryonic Dark Matter

We describe the formation of hot intergalactic gas along with baryonic remnants in galaxy halos. In this scenario, the mass and metallicity of the hot intracluster and intragroup gas relates directly to the production of baryonic remnants during the collapse of galactic halos. We construct a schematic but self-consistent model in which early bursts of star formation lead to a large remnant population in the halo, and to the outflow of stellar ejecta into the halo and ultimately the Local Group. We consider local as well as high redshift constraints on this scenario. This study suggests that the microlensing objects in the Galactic halo may predominantly be 0.5M white dwarfs, assuming that the initial mass function for early star formation favored the formation of intermediate mass stars with m 1M. However, the bulk of the baryonic dark matter in this scenario is associated with the ejecta of the white dwarf progenitors, and resides in the hot intergalactic medium.     

The Primordial Helium-4 Abundance from Observations of a Large Sample of Blue Compact Dwarf Galaxies

We use a sample of 45 low-metallicity H II regions in blue compact dwarf (BCD) galaxies to determine the primordial helium abundance YP with a precision better than 5%. We have carefully investigated the physical effects which may make the He I line intensities deviate from their recombination values such as collisional and fluorescent enhancements, underlying He I stellar absorption and absorption by Galactic interstellar Na I. By extrapolating the Y vs. O/H and Y vs. N/H linear regressions to O/H = N/H = 0, we obtain YP = 0.244±0.002 and 0.245±0.001, respectively, higher than previous determinations (YP = 0.230 - 0.234). Part of the difference comes from the fact that previous investigators have not taken into account underlying He I stellar absorption, especially in the NW component of the BCD I Zw 18 which, because of its extremely low metallicity plays a key role in the determination of YP. We derive a slope dY/dZ = 2.3±1.0, considerably smaller than those derived before. With this smaller slope and taking into account the errors, chemical evolution models with an outflow of well-mixed material can be built for star-forming dwarf galaxies which satisfy all the observational constraints. Our YP gives _bh ₅₀ ² = 0.058±0.007,f consistent with the lower limit set by dynamical measurements and X-ray observations of clusters of galaxies. It is also consistent, within the framework of standard big bang nucleosynthesis theory, with measurements of primordial 7Li in galactic halo stars and with the D/H abundance measured in absorption systems toward quasars by Burles and Tytler (1997).     

XMM-Newton study of soft excess X-ray emission in clusters of galaxies

We discuss the detection of soft excess X-ray emission in a sample of 19 clusters of galaxies observed by XMM-Newton. In 6/19 clusters evidence for a soft X-ray excess is found. Four of these clusters show soft X-ray and O VII line emission from gas with a temperature of 0.2 keV. The centroid of this oxygen line is consistent with the redshift of the cluster. The intensity and spatial extend of the soft excess agrees with previous PSPC measurements. These observations are interpreted as emission from warm-hot intergalactic medium filaments, with density enhancements near the cluster centers, consistent with theoretical predictions. In the other two soft excess clusters a non-thermal origin is consistent with the data.