A new global version of M(3000)F2 prediction model based on artificial neural networks

A new version of global empirical model for the ionospheric propagation factor, M(3000)F2 prediction is presented. Artificial neural network (ANN) technique was employed by considering the relevant geophysical input parameters which are known to influence the M(3000)F2 parameter. This new version is an update to the previous neural network based M(3000)F2 global model developed by Oyeyemi et al. (2007), and aims to address the inadequacy of the International Reference Ionosphere (IRI) M(3000)F2 model (the International Radio Consultative Committee (CCIR) M(3000)F2 model). The M(3000)F2 has been found to be relatively inaccurate in representing the diurnal structure of the low latitude region and the equatorial ionosphere. In particular, the existing hmF2 IRI model is unable to reproduce the sharp post-sunset drop in M(3000)F2 values, which correspond to a sharp post-sunset peak in the peak height of the F2 layer, hmF2. Data from 80 ionospheric stations globally, including a good number of stations in the low latitude region were considered for this work. M(3000)F2 hourly values from 1987 to 2008, spanning all periods of low and high solar activity were used for model development and verification process. The ability of the new model to predict the M(3000)F2 parameter especially in the low latitude and equatorial regions, which is known to be problematic for the existing IRI model is demonstrated.     

Cosmic Ray Energetics And Mass for the International Space Station (ISS-CREAM)

The Cosmic Ray Energetics And Mass (CREAM) instrument is configured with a suite of particle detectors to measure TeV cosmic-ray elemental spectra from protons to iron nuclei over a wide energy range. The goal is to extend direct measurements of cosmic-ray composition to the highest energies practical, and thereby have enough overlap with ground based indirect measurements to answer questions on cosmic-ray origin, acceleration and propagation. The balloon-borne CREAM was flown successfully for about 161 days in six flights over Antarctica to measure elemental spectra of Z = 1–26 nuclei over the energy range 10¹⁰ to >10¹⁴ eV. Transforming the balloon instrument into ISS-CREAM involves identification and replacement of components that would be at risk in the International Space Station (ISS) environment, in addition to assessing safety and mission assurance concerns. The transformation process includes rigorous testing of components to reduce risks and increase survivability on the launch vehicle and operations on the ISS without negatively impacting the heritage of the successful CREAM design. The project status, including results from the ongoing analysis of existing data and, particularly, plans to increase the exposure factor by another order of magnitude utilizing the International Space Station are presented.     

The acceleration of Anomalous Cosmic Rays by stochastic acceleration in the heliosheath

Stochastic acceleration in the heliosheath appears to be a likely mechanism by which Anomalous Cosmic Rays (ACRs) are accelerated. However, most stochastic acceleration mechanisms are not appropriate. The energy density in the ACRs and in the interstellar pickup ions out of which the ACRs are accelerated greatly exceeds the energy density in the turbulence in the heliosheath. Thus, a traditional stochastic acceleration mechanism in which particles are accelerated by damping the turbulence will not work. A stochastic acceleration mechanism has been developed in which the total energy of the pickup ions and the ACRs is conserved. Energy is redistributed from the core pickup ions into a suprathermal tail to create the ACRs. A model for the acceleration of the ACRs in the heliosheath, based on this stochastic acceleration mechanism, is presented. The model provides reasonable fits to the spectra of suprathermal particles and ACRs observed by Voyager.     

虚拟化技术在综合化航电系统中的应用

将虚拟化技术应用于航空电子系统的设计,利用虚拟机系统来实现硬件资源的共享管理和软件子系统的划分,并符合ARINC 653规范的要求——模块化、可靠性、隔离性与开放性.构建由硬件平台、虚拟机监视器(VMM,Virtual Machine Monitor)和分区操作系统、航电应用软件所组成的3层软件架构,可以满足综合模块化航电系统(IMA,Integrated Modular Avionics)的功能要求与接口要求.其中,为实现符合ARINC 653要求的VMM,传统分区操作系统需要进行多项关键性调整,包括处理器特权级和特权指令、中断、内存地址空间分配、设备驱动等方面,从而可以构造基于VMM的综合化航空电子系统.     

The radiation environment in the ISS-USLab measured by ALTEA: Spectra and relative nuclear abundances in the polar,equatorial and SAA regions

We present here the energy spectra relative to different geomagnetic regions as measured by the ALTEA (Anomalous Long Term Effects on Astronauts) detector in the International Space Station – USLab from August 2006 to July 2007.     

基于半实物仿真的地磁导航等值线匹配算法评估

影响地磁导航匹配算法性能的因素很多,而现阶段算法的评估完全依靠计算机仿真,其可信性有待进一步验证.以等值线(ICCP)算法为研究对象,首先从理论上分析影响算法性能的因素;然后搭建了地磁匹配导航半实物仿真系统,通过引入磁场仿真环境和磁传感器,提高了仿真的可信度;最后从测量噪声、匹配长度、匹配区域和惯导误差4个方面对ICCP 匹配算法的性能进行半实物仿真试验分析.仿真结果表明,通过半实物仿真试验可以对算法的抗干扰性、算法匹配长度的确定、匹配区域的选择以及惯导误差的影响做出有效评估,从而推动地磁匹配导航及匹配算法的工程化进程.      

使用“均衡记分卡”改善服务质量(英文)

基于“量度什么,便得到什么”的原则而发展起来的“均衡记分卡”可将公司策略清晰地演绎,为每一雇员工作表现指引。除了沿用一般传统财政目标外,“均衡记分卡”提供了一个全面、灵活、有效及均衡的企业表现量度／管理方法。从“顾客角度”、“程序角度”以及“学习角度”所作的度量可能激励企业的财政工作。制定“均衡记分卡”过程可阐明并传递公司的策略于每一雇员。个别工作单位目标及雇员目标亦可结合在一起以改善整体服务质量。     

含孔边裂纹各向异性有限板的二维问题

应用边界元法,并结合一种特殊的复变函数基本解,研究了含孔边裂纹的各向异性有限板的应力强度因子修正系数的计算。这种特解边界元法避免了在裂纹附近划分单元,可以获得较好的数值计算精度。通过算例分析,结果表明本方法精度高,运算量小,具有一定的工程应用价值。     

飞行器雷达罩设计方法的研究

详细分析了飞行器雷达罩设计过程中的基本问题。基于多目标优化设计方法建立了雷达罩结构参数求解的数学模型,给出了求解方法。考虑到雷达罩的安全使用要求,分析了雷达罩防雷击部件的基本要求,提出了设计方法,给出了防雷击部件布置的经验公式。同时还研究了用于飞行器雷达罩金属部件的吸波材料电磁波吸收机理,以及吸波材料电性能设计原理和基本布置准则     

基于Petri网的空中交通管制辅助决策系统

空中交通管制系统是生产实际中的一种典型的离散事件动态系统（Ｄｉｓｃｒｅｔｅ ｅｖｅｎｔ ｄｙｎａｍｉｃｓｙｓｔｅｍ,ＤＥＤＳ）,而Ｐｅｔｒｉ网理论是研究ＤＥＤＳ的有力工具之一。为了描述空中交通管制系统受到外部控制的交互机制及层次结构,文中引入Ｐｅｔｒｉ网概念的一类扩充－－开放Ｐｅｔｒｉ网的概念,并用开放Ｐｅｔｒｉ网工中交通管制辅助决策系统进行建模与分析,阐述了空中交通管制辅助决策系统的开放Ｐｅｔｒ