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781.
随着相控阵天线的不断发展,有限扫描反射面天线已经成为当前的研究热点,为了符合新时代天线多功能的需求,提出一种基于抛物面形变的纵向偏焦特性。设计一个标准正馈反射面天线,使其馈源固定不动,而利用调节反射面焦距来达成天线的偏焦,其偏焦特性类似于抛物面天线的纵向偏焦特性;设计一个双焦点反射面,由XOZ平面抛物线和YOZ平面抛物线正交互异设计双焦点反射面天线,令YOZ平面抛物线焦点外推、XOZ平面抛物线焦点不变构成一个双焦点反射面。验证了该方法在一维阵列作为馈源的有效性,双焦点反射面相较于标准抛物面,在EL方向上该天线增益上升了1429dB,且波束宽度基本不变;此外,该方法还能容纳所有馈源同时工作,降低了单个馈源喇叭的功率且增益相较于点波束天线只下降了485dB。该方法将为后续有限扫描反射面天线在设计一维扫描或二维不等范围扫描提供理论支撑。  相似文献   
782.
三维编织机锭子,轨道及锭槽结构尺寸的选择   总被引:3,自引:1,他引:2  
分析了三维四步法编织机锭子运动的特点,提出了锭子与锭槽尺寸公差的选择原则;讨论了各种误差存在时,锭子可能窜入相邻轨道锭槽的情况,提出了防止锭子卡死或发生其它不良情况的结构措施,并举例进行了结构尺寸的选择。  相似文献   
783.
基于TestStand及LabVIEW软件平台,以航电通用故障监控软件为例,从测试架构、测试逻辑等角度,为航空电子软件自动化测试提供思路和方法.  相似文献   
784.
Space law education has an essential role in the space capacity building of a country because of its importance for human resources development in space law. Comparisons between Canada and China, the European Union and China and the United States of America (USA) and China in space law degree education, course, teaching methodology, institute and practice and communication platform are provided in an attempt to review some issues which exist within the Chinese space law educational system and to seek a better choice for China’s space law education reform. Chinese space law education has achieved noticeable progress over the past two decades. However, it is still limited in comparison to its counterparts in Europe and Northern America. The range of the space law degree education programmes and space-law-related courses is comparatively limited. A gap remains between space law education and practice in China. Chinese space law classes are still dominated by the teacher-centred teaching methodology, although several universities have some new teaching practices. The establishment of seven space law-related research institutes plays an increasingly important role in Chinese space law education, space law and policy research and legal advisory services for the Chinese government and non-governmental sectors. However, these institutes still have a long way to go in comparison with their counterparts in Europe and Northern America. While China has established domestic research platforms for space law communication through international cooperation, it does not provide space law practice platforms for space law education. While international space law does not provide a direct legal foundation for space law education in China, Chinese educational laws can lay a profound legal foundation for Chinese space law education. To promote its national expertise and capacity in space law, based on the three-pillar model and the experiences of its counterparts in North America and Europe, China should adopt a systematic and sustainable regime for its space law education.  相似文献   
785.
星载激光雷达是高精度测量全球温室气体和气溶胶垂直廓线的重要手段,大气环境监测卫星大气探测激光雷达(ACDL)在国际首次采用激光积分路径差分吸收技术测量全球CO2柱浓度,采用532 nm高光谱探测技术测量气溶胶和云的廓线。星载激光雷达载荷研制期间,同步研制一套主要功能一致的机载大气探测激光雷达校飞样机,并开展机载飞行试验,获取了大量飞行试验及其对比数据,提供了机载平台真实的数据源,对于优化ACDL激光雷达系统参数和研究星载数据反演算法至关重要。最后在机载飞行平台下,验证了优于1 ppm的CO2柱浓度测量精度和优于15%的气溶胶测量精度。未来利用该机载样机可以进一步开展星地对比验证。  相似文献   
786.
787.
The European Stratospheric Balloon Observatory (ESBO) initiative aims at simplifying the access to stratospheric balloon missions. We plan to provide platforms and support with instrument design in order to support scientists. During the design process, the inevitable question of qualification for the harsh flight conditions arises. Unfortunately, there is no existing standard for qualification of stratospheric ballooning hardware. Thus, we developed a qualification procedure for use within ESBO and similar projects.In this paper, we present our analysis of the environmental conditions in the stratosphere. While conditions at typical balloon float altitudes are similar to the space environment, there are also some relevant differences. For example, the thermal environment is dominated by radiation and thermal conduction, but the remaining atmosphere still supports a certain amount of convection. The remaining atmospheric pressure in the stratosphere also leads to reduced arcing distances. Vibrational loads are far less than for space missions, but quasi-static or shock loads may occur. The criticality of radiation increases with mission duration.Based on the environmental conditions, we present the qualification procedures for ESBO, which are based on the European Cooperation for Space Standardization (ECSS) standards for space systems. Overtesting against too high requirements leads to overengineering, driving mission cost and mitigating the advantages of balloons over space missions. Therefore, we modified the ECSS standards to fit typical scientific ballooning missions over several days at altitudes up to 40 km. Furthermore, we analyzed design rules for space systems with regard to their relevance for scientific ballooning, including material and component selection. We present the experience from the hardware qualification process for the ESBO prototype STUDIO (Stratospheric UV Demonstrator of an Imaging Observatory). Even though boundary conditions are different for each individual mission, we aimed for a broader approach: We investigated more general requirements for scientific ballooning missions to support future flights.  相似文献   
788.
We report dusty photo-ionization models for two Planetary Nebulae NGC 2452 and IC 2003, which have [WR] type central stars, using 1D photo-ionization code Cloudy17.02. We used the medium resolution optical spectra and archival IRAS photometry to constrain our models. The physical size of the ionized nebula derived using accurate distance measurements and absolute Hβ flux available in the literature were used as additional constrains. We examine the importance of photo-electric heating and found that models with and without considering photo-electric heating do not make significant difference for both PNe for the MRN grain size distribution considered in this study. We derive the nebular elemental abundances of these PNe by the empirical method as well as by making dusty photo-ionization models. The values of N/O ratios for both PNe obtained from our models are lower than their respective values arrived using empirical methods. The central stars are assumed to be black bodies and the photospheric temperatures derived respectively for NGC 2452 and IC 2003 from their best fit models are 182 kK and 155 kK and their respective luminosities are 630L and 1015L. We propose that both the PNe were resulted from low-mass progenitors of mass ?2.8 M.  相似文献   
789.
航空电子产品中为了满足高安全等级应用的驻留需求,通用处理模块的数据完整性指标需要达到 Level A(10-9)级。基于当前元器件的可靠性和产品设计的复杂度,产品的数据完整性一般在10-3 到10-5 的水平, 无法满足产品的设计需求。本文提出了一种基于数据锁步的设计方法,该方法可用当前的软硬件资源在工程项 目中设计出满足高完整性要求的产品。  相似文献   
790.
失速/尾旋一直是通航飞机面临的最严重的左边界飞行安全问题,失速/尾旋事故统计结果表明,具备尾旋改出能力,不能避免失速/尾旋造成灾难性后果。为了避免飞机出现无意偏离可控飞行的趋势,通过对“多重防御”理念和基于此理念修订的失速/尾旋条款及其符合性验证方法的解析,提出通过提升飞行员的状态感知、增强飞机抗偏离特性和降低失控危害程度等层面的通航飞机左边界飞行的多重防御体系构建方法。本文提出的方法有助于通航飞机更好的符合新规章中失速尾旋适航条款的要求,达到提升左边界飞行安全的目的。  相似文献   
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