功能分析与失效物理结合的可靠性预计方法

 可靠性预计是产品设计、研发过程中的重要工作,全面准确的可靠性预计可以评价产品的可靠性水平,也可以为设计提供信息,指导设计。全面分析总结当前电子设备可靠性预计相关技术方法,以当前基于失效物理(POF)技术的系统可靠性预计方法中,并未考虑产品功能组成关系的缺陷为突破点,建立了一种以失效物理分析为基础,综合考虑电路功能组成关系的电子设备可靠性预计方法。该方法从电路功能出发,通过灵敏度仿真和主成分分析两种方法,确定对电路性能起主要影响的关键单元,再通过失效物理分析或统计规律明确单元的失效概率分布,通过混合分布获得系统的分布,得到系统可靠性指标。最后以某航空机电产品的电源电路为案例,对本预计方法进行验证。     

宇航用球栅阵列器件装联可靠性评价方法初探

针对球栅阵列（BGA）器件装联可靠性问题多发的现状,对常见宇航用BGA器件的结构及可靠性问题进行分析总结,并提出了一种基于失效物理的宇航用BGA器件装联工艺可靠性评价思路。通过案例分析,结合构成器件的元件和材料的典型特性,获得BGA器件常见失效模式及失效机理;并针对典型失效模式及机理选取疲劳寿命模型进行建模及仿真,依据Coffin-Manson的疲劳失效物理模型及其修正模型,得到工作寿命和试验寿命的预估结果;结合现有检测手段,综合考虑寿命预估结果,提出装联工艺可靠性评价试验项目,建立可靠性考核试验流程;基于国内外现有标准判据确定参考依据,综合考虑不同型号及应用环境的工作应力差别,提出BGA器件的可靠性分级评价量化准则。     

液晶调制技术在太阳磁场探测中的应用及展望

快速偏振调制和超窄带滤光是太阳光学望远镜实现磁场探测的最核心技术途径,而液晶调制是目前唯一可同时满足偏振测量和窄带调谐滤光的电光调制技术。而且,液晶调制器具有口径大、光谱范围宽、调制速度快、无旋转机构以及相位延迟连续可调的优势,使其成为下一代太阳望远镜磁场探测技术的最佳选择。文章简要介绍液晶科学的发展历史及液晶调制器的基本工作原理,详述液晶调制技术在太阳磁场探测中的应用现状和研究进展,探讨液晶调制技术面临的挑战以及未来发展方向。基于我国太阳磁场望远镜的研究和发展态势,相信液晶调制技术将在我国未来空基、地基太阳磁场探测中发挥至关重要的作用。     

平流层臭氧和辐射场的季节分布特征

利用美国NCAR化学气候耦合模式WACCM3对平流层温度场、风场、臭氧及辐射场进行了模拟.结果表明,在适宜飞艇长期驻留的准零风层高度20～22km(对应大气压强范围为50～30hPa,以下均采用气压值表征对应大气高度),7-8月风速小于5m·s^-1的风带可长期稳定在40°N以北.臭氧空间分布显示,在30hPa气压高度处中国地区臭氧浓度出现了带状分布,30hPa高度以下低纬度地区臭氧浓度低于中纬度地区.平流层太阳加热率的时空变化表明,在平流层上层,太阳加热率可达100×10^-6K·s^-1,而在平流层下层,只有10×10^-6K·s^-1.6-8月中国区域的太阳加热率大于9月;在100～30hPa高度内,中纬度地区太阳加热率高于低纬度地区,在30hPa高度以上,低纬度地区太阳加热率高于中纬度地区;8-9月30～40hPa高度处,太阳加热率的空间变化较小.在30hPa高度上,太阳加热率在40°N昼夜变化最大;50hPa高度处,太阳加热率的昼夜变化小于30hPa高度处,而且白天太阳加热率出现极大值的纬度明显靠北.平流层低纬度地区的长波加热率小于中纬度地区.青藏高原由于地形特殊,其6-7月的臭氧浓度、太阳加热率和长波加热率均小于同纬度其他地区.     

PROBA-3 mission and the Shadow Position Sensors: Metrology measurement concept and budget

PROBA-3 is a space mission of the European Space Agency that will test, and validate metrology and control systems for autonomous formation flying of two independent satellites. PROBA-3 will operate in a High Elliptic Orbit and when approaching the apogee at 6·10⁴ Km, the two spacecraft will align to realize a giant externally occulted coronagraph named ASPIICS, with the telescope on one satellite and the external occulter on the other one, at inter-satellite distance of 144.3 m. The formation will be maintained over 6 hrs across the apogee transit and during this time different validation operations will be performed to confirm the effectiveness of the formation flying metrology concept, the metrology control systems and algorithms, and the spacecraft manoeuvring. The observation of the Sun’s Corona in the field of view [1.08;3.0]R_Sun will represent the scientific tool to confirm the formation flying alignment. In this paper, we review the mission concept and we describe the Shadow Position Sensors (SPS), one of the metrological systems designed to provide high accuracy (sub-millimetre level) absolute and relative alignment measurement of the formation flying. The metrology algorithm developed to convert the SPS measurements in lateral and longitudinal movement estimation is also described and the measurement budget summarized.     

高精度时间频率在空间科学技术中的应用探讨CSCD

自上世纪50年代原子频标出现以后,极大促进了科学技术的发展,随着原子频标的发展,高精度时间频率信息在空间科学技术中将发挥重要的作用。本文介绍了空间高精度时间频率在空间科学、基础物理以及卫星导航技术方面应用前景,并对国外正在开展的空间高精度时间频率技术方面的计划、准备开展的相关应用研究,以及对毫秒脉冲星守时技术也进行了初步探讨,最后给出了开展空间高精度时间频率技术研究的一些建议。     

Use of coated silicon field emitters as neutralisers for fundamental physics space missions

Spacecraft neutralisers are required as part of the ion propulsion system for accurate station keeping in fundamental physics missions. This paper describes the use of thin layers of insulating materials as coatings for the gated silicon field emitter array structure used in a spacecraft neutraliser. These thin coatings are postulated to reduce power consumption and reduce overheating. The power consumption and lifetime of aluminium nitride and amorphous hydrogenated diamond-like carbon coatings have been tested by current–voltage and endurance tests. Diamond-like carbon coatings were promising, performing better in endurance tests than uncoated samples, but further work is required to characterise the coating’s physical properties and its effects on field emission. The thermal conductivity of the coating material had little effect on measured sample lifetimes. Aluminium nitride had reduced power consumption compared to diamond-like carbon coated and uncoated samples. A thin (∼5 nm) layer of aluminium nitride was found to be optimal, meeting European Space Agency specifications for the neutraliser engineering model.     

A BRIEF INTRODUCTION TO GEOSPACE DOUBLE STAR PROGRAM

The Geospace Double Star Exploration Project (DSP) contains two small satel lites operating in the near-earth equatorial and polar regions respectively. The tasks of DSP are: (1) to provide high-resolution field, particle and wave mea surements in several important near-earth active regions which have not been covered by existing ISTP missions, such as the near-earth plasma sheet and its boundary layer, the ring current, the radiation belts, the dayside magnetopause boundary layer, and the polar region; (2) to investigate he trigger mechanisms of magnetic storms, magnetospheric substorms, and magnetospheric particle storms, as well as the responses of geospace storms to solar activities and in terplanetary disturbances; (3) to set up the models describing the spatial and temporal variations of the near-earth space environment.To complete the mission, there are eight instruments on board the equatorial satellite and the polar satellite, respectively. The orbit of the equatorial satellite is proposed with a perigee at 550km and an apogee at 60 000km, and the inclination is about 28.5°; while the orbit of the polar satellite with a perigee at 700 km and an apogee at 40 000 km, as well as an inclination about 90°. The equatorial and polar satellites are planed to be launched into orbits in June 2003 and December 2003 respectively to take coordinating measurements with Cluster Ⅱ and other missions.     

考察德国大学物理教学的启示

通过对德国克劳斯塔尔工业大学物理教学的考察，阐述了教学与科研相结合对提高大学物理教学质量的重要性。为寻求教学与科研相结合的途径和改变基础课教师长期脱离科研的现状，在分析我院物理课教学情况的基础上提出了几点建议和想法：首先，我院理学系除了下设物理教研室、物理实验室之外，可以设立研究室或科研课题组；其次，可以结合物理实验教学搞科研；还可以与其他专业合作搞科研。     

Progress of Double Star Program 2006—2008

This paper presents the status of two satellites of Double Star Program,and a part of scientific results based on the data of Double Star Program obtained during the period of 2006-2008.Other scientific results in the magnetospheric physics research can be found in "Multi scale physical process in the magnetosphere" of this issue.