全向电场探头及数据采集系统

全向电场探头及数据采集系统是一种近区电场测量装置,主要用于电磁敏感度(EMS)实验,屏蔽室及无回波室内电磁场辐射强度大小的测定。借助于薄膜沉淀与光刻技术,电阻锥形加载的使用,对传统的偶极子单元作了重要改进。拓宽了带宽,得到了平坦的频率响应,宽的动态范围,小的尺寸,减少场的扰动和失真并完全消除了带内谐振。频率范围:100kH～18GHz,频率响应:±2dB(10MHz～18GHz),动态测量范围:1～1600V/m。数据采集系统光纤通讯技术的应用,使电磁场的测量进入了一个新的领域,增强了测试系统的防泄漏、抗干扰能力。微处理器芯片及标准IEEE-488接口的使用,实现了测试设备的可程控、自动化功能。它是一种先进的近区电场测量装置,并且是电磁兼容计量测试实验室中必不可少的测量装置之一。     

原子时自动测量及数据采集系统

介绍了普通的时间实验室的时频测量,实现自动测量和数据收集的基本系统方案,并以上海天文台原子时实验室为例介绍了实际可行的自动测量和数据收集系统,这个系统高性能、低价格,可应用于国内几乎所有的时间实验室。     

A novel system parameters design and performance analysis method for Distributed Satellite-borne SAR system

As a promising new technology emerged in recent years, the Distributed Satellite-borne SAR (DSS) system with Interferometric Synthetic Aperture Radar (InSAR) imaging capability has been recognized by the remote sensing community as an integrated part of the spaceborne earth observation system. However, most researches on DSS were focused on individual aspects of system design/analysis and data processing, while few studies have been dedicated to establishing a standard methodological framework for universal DSS system design. Aiming at this problem, the topics of DSS system error analysis and design method are investigated in this paper. Firstly, a rigorous error propagation model of height measurement is theoretically derived from the DSS InSAR imaging geometry, and the impact of each error sources in this model on the height measurement accuracy is analyzed individually. In particular, the baseline length and its measurement error in the InSAR imaging plane are identified as the dominant factors. Second, a new method for DSS system design is proposed based on our analyses with the error propagation model. This method consists of two important phases, namely collaboration design and monostatic design. The major objective of collaboration design is to determine the configuration and parameters for the coordination between satellites in the DSS system. Afterwards, the key parameters for single satellite and the payload are determined by the monostatic design. Thirdly, a system performance analysis method is developed to comprehensively evaluate the performance of the pre-designed DSS system. In the next section, a typical example of DSS system design is given to demonstrate the effectiveness of the proposed system design and analysis methods. The target DSS system has the same goal and hardware configuration as the TanDEM-X mission. Finally, the conclusion is drawn with our major findings are presented.     

一种面向嵌入式系统的多模型集中存储方法

随着软件安全性的重要性日益增长,使用模型驱动的方法进行软件开发越来越受到重视。针对目前存在跨域模型的集成障碍,提出了一种基于元建模技术提取多视角模型信息进行存储的方法,并详细阐述了针对AADL、SysML、Simulink三种建模语言设计的建模元素解析、集成描述文件生成的方法框架。实验结果表明:按照所提方法实现的模型仓库能够准确提取出不同视角模型间的集成相关信息,在能够正确存储、查询的条件下,实现的元素数量覆盖率均在90%以上。      

机务段设备数据采集通讯系统抗干扰措施探讨

通过对机务段设备工作环境特点分析 ,结合工程设计实验经验 ,提出了机务段设备数据采集系统抗干扰措施。     

基于COM/DCOM的分布式零件参数化 设计系统的研究

为解决基于UG(Unigraphics)的零件分布式设计的问题,分析比较了UG二次开发的两种模式,提出了一种基于零件库的通用参数化设计方法.采用COM(Component Object Model)方式建立了一个基于UG外部开发的通用参数化设计组件,利用DCOM(Distributed Component Object Model)实现了该组件的网络化,并在此基础上选用分布式三层网络模型,构建了一个基于COM/DCOM的分布式零件参数化设计系统,实现了LAN(Local Area Network)下对零件进行参数化设计的功能.      

Feasibility analysis of solar thermal propulsion system with thermal energy storage

Possessing relatively high specific impulse and moderate thrust levels, solar thermal propulsion (STP) is a promising candidate in spacecraft propulsion system. However, the traditional solar thermal propulsion system suffers from thrust failure in the shadow area, which seriously affects its applicability. In this paper, we investigate feasibility of regenerative solar thermal propulsion system (RSTP) incorporating thermal energy storage, which can effectively overcome unmatched synchronous working time and illumination time. A numerical model for RSTP considering the whole energy transfer process from light concentrating, heat storage, to thrust generation is built, which is verified by experiment measurements with relative errors less than 15 %. The result shows that the maximum time to complete heat storage is about 4000 s, which is within the illumination time for low Earth orbit. In the solar eclipse region, the thrust (F_t) and the specific impulse (I_sp) of the system increase with the propellant flow rate, which can reach about 2 N and 690 s, respectively. What’s more, the system can operate for around 100 s continuously at the maximum thrust in the shadow area. This work provides alternative approaches for microsatellite propulsion with high specific impulse, high thrust, and continuous operation despite presence of solar eclipse.     

异构存储系统中基于能量模型的文件迁移策略

异构存储系统的文件迁移策略要求迁移代价小、执行快,有较强的系统适应能力.研究异构存储系统文件迁移策略的特点,提出了一种基于能量的文件迁移策略.通过建立能量模型体现存储单元上文件访问的频繁程度,通过设计基于概率的迁移触发函数减少访问文件倾向性对异构存储单元间负载平衡性能的负面影响,通过文件迁移与用户访问操作的复合减少了系统调整开销.实验证明,基于能量模型的文件迁移策略比传统的磁盘冷却算法在请求平均处理时间、系统吞吐率方面有15%~20% 的提高.      

长期贮存平台惯导系统壳体效应变化行为模型

长期贮存条件下平台惯导系统壳体效应具有与使用状态不同的漂移特性,其漂移规律与各性能参数退化及其相互耦合特性相关,在工程应用中往往难以分析贮存条件下壳体效应稳定性水平和合理配置标定维护资源。本文通过全面分析伺服电路零位和框架轴上干扰力矩引起壳体效应漂移的原理及其漂移表达式,在此基础上深入挖掘了表达式中漂移参数的变化特性,综合给出了伺服电路零位和框架轴上干扰力矩引起壳体效应漂移的变化行为模型,并结合实际贮存环境剖面对其进行了长期漂移特性、加速特性和稳定性分析,分析表明在现有贮存条件下,伺服电路零位和框架轴上干扰力矩引起的壳体效应在X、Y和Z轴的长期漂移特性相近,与实际使用状态的响应特性不同,且无加速特性,具有较好的稳定性水平,从而为合理安排标定维护资源提供了依据。      

基于CFD的水收集系数及防冰表面温度预测

利用计算流体力学(CFD,Computational Fluid Dynamics)软件FLUENT,对二维机翼在结冰气象条件下飞行时的水收集系数,以及防冰系统工作并达到稳定后的防冰表面温度进行了计算.水收集系数计算采用FLUENT中的欧拉两相流模型以及用户自定义函数.特定飞行条件及热气防冰系统结构下的防冰表面平衡温度分布预测采用防冰腔内外热流耦合的方法.所得结果和理论分析一致,表明了利用FLUENT可以有效的进行防冰研究,包括水收集系数及防冰表面温度的预测,为今后进一步研究设计热气或电热防冰系统打下基础.