基于遗传算法的大气层外拦截弹拦截优化

提出了一种同时考虑大气层外拦截弹中段和末段飞行过程的拦截优化方法.首先建立了大气层外拦截弹中段和末段飞行的动力学模型,并设计了速度增益中制导律和鲁棒变结构末制导律;然后确定了影响拦截性能的优化控制参数及其约束条件,以拦截过程的燃料消耗质量和脱靶量最小为组合性能指标;最后采用具有全局最优性的遗传算法对这一拦截优化问题进行了仿真研究,并与复形调优算法的结果进行了比较.仿真结果表明,遗传算法与传统优化方法相比在解决大气层外拦截弹带约束复杂非线性组合优化问题时,能更好地收敛到全局最优值,并能有效降低大气层外拦截的燃料消耗和脱靶量.     

栅极偏压对纳米金刚石薄膜沉积过程的影响

在HFCVD系统中施加栅极偏压和衬底偏压,采用双偏压成核和栅极偏压生长的方法成功制备了高质量的纳米金刚石薄膜.采用显微Raman高分辨率SEM和AFM等现代理化分析手段分析纳米金刚石膜的微结构,结果表明双偏压显著促进了金刚石的成核密度,平均晶粒尺寸在20 nm以内.试验观察和理论分析表明栅极偏压促进了热丝附近的等离子体浓度,提高了衬底附近的碳氢基团和氢原子浓度,提高了金刚石的成核密度、在保持晶粒的纳米尺寸的同时保持了较高的成膜质量和较低的生长缺陷.     

杯形砂轮精密磨削WC-Co涂层的磨削力

使用杯形砂轮进行磨削,可以获得较高的加工效率和表面质量.但由于杯形砂轮的平面磨削方式与普通外圆砂轮平面磨削存在差异,故传统的磨削力建模不适合杯形砂轮的平面磨削.为了从本质上解释杯形砂轮磨削力的各种现象,本文对杯形砂轮的磨粒切削过程进行了分析,提出了杯形砂轮有效磨削宽度的概念,分析了杯形砂轮磨削陶瓷涂层时的磨削力,建立了杯形砂轮精密磨削陶瓷涂层磨削力的理论公式.磨削力工艺试验结果验证了理论公式的有效性和正确性.     

基于北斗三号的多区域实时动态授时服务系统

面向新一代移动通信和物联网等领域对高精度、低成本授时的需求,针对典型的实时动态授时服务只能单区域覆盖的问题,提出了一种基于北斗的多区域实时动态精密授时服务系统.该系统由标准时间、时间基准站、高精度时间频率实时传递链路、数据中心和时间用户等部分组成,可实现标准时间实时动态授时服务的全国多区域覆盖.依托中国科学院国家授时中...     

Impact of one satellite outage on ARAIM depleted constellation configurations

Advanced Receiver Autonomous Integrity Monitoring(ARAIM) is a new technology that will provide worldwide coverage of vertical guidance in aviation navigation. The ARAIM performance and improvement under depleted constellations is a practical problem that needs to be faced and researched further. It is a shortcut that improves the availability in position domain whose key idea is to replace the conventional least squares process with a non-least-squares estimator to lower the integrity risk in exchange for a slight increase in nominal position error. The contributions given in this paper include two parts: First, the impacts of one satellite outage on different constellations are analyzed and compared. The conclusion is that GPS is more sensitive and vulnerable to one satellite outage. Second, a constellation weighted ARAIM(CW-ARAIM)position estimator is proposed. The position solution is replaced by a constellation weighted average solution to eliminate the constellation difference. The new solution will move close to the constellation solutions with respect to the accuracy requirement. The simulation results under baseline GPS and Galileo dual-constellation show that the one GPS satellite outage will knock the availability from 91% to only 50%. The performance remains stable with one Galileo satellite outage. With the assistance of the CW-ARAIM method, the availability can increase from 50% to more than80% under depleted GPS configurations. Even without any satellite outage, the proposed method can effectively improve the availability from 91.29% to 98.75%. The test results under optimistic constellations further verify that a balanced constellation is more important than more satellites on orbit and the superiority of CW-ARAIM method is still effective.     

硅橡胶基防热涂层动态烧蚀行为及机理研究

针对两种典型硅橡胶基防热涂层开展高温燃气流烧蚀实验，通过对烧蚀后涂层的宏观及微观形貌分析，探讨了其防隔热机理及烧蚀模型。研究结果表明：烧蚀后两种涂层均存在液态层、陶瓷层、热解层以及原始层；烧蚀过程中甲基苯基硅橡胶涂层主要发生主链“回咬”成环反应，导致树脂基体交联密度降低，力学性能下降，涂层外表面发生开裂，甲基乙烯基硅橡胶涂层则主要发生侧基交联反应，使树脂基体交联密度上升，促进涂层发生陶瓷化转变；热辐射、热容吸热、热解反应吸热以及热阻塞效应为四种主要的热耗散机制，质量损失产生的原因主要包括反应气体释放以及气动剪切力导致的机械剥蚀。     

Assessing ecohydrological factors variations and their relationships at different spatio-temporal scales in semiarid area,northwestern China

As a typical semiarid farming-pastoral ecotone sensitive to the environmennt, the Plain of West Liaohe Basin (WLBP) is currently experiencing drastic environmental changes. To identify how environmental change affect vegetation in the WLBP, we analysed spatiotemporal variation characteristics of Ecological environment factors based on monthly and annual air temperature (T), precipitation (P) and Normalized Difference Vegetation Index (NDVI) from 1982 to 2015. And the correlations between them were investigated by correlation analysis (Simple correlation, partial correlation and complex correlation) at temporal and spatial scale. The results showed that: (1) the vegetation growth of the WLBP showed ameliorated trend, with a change rate of 0.004/yr.; (2) P was more sensitive to NDVI than T; (3) and the influence of hydrothermal changes on vegetation growth was more significant than that of the change of single climate factors at time scales; (4) the effects of anthropogenic factors on vegetation change were 75.07% (1982–1993) and 98.08% (1994–2015), respectively. At the temp-special scales, P&T and land use type change (LUCC) were the main climatic and anthropogenic factors that affect vegetation changes, respectively.     

对我公司开发民用产品的几点思考

分析了南飞公司民品开发中存在的问题及其产生原因；提出开发民品的对策和措施；探讨了开发民品的几种方法及应做好的几项基础工作。