Semi-analytical investigations of high area-to-mass ratio geosynchronous space debris including Earth’s shadowing effects

This paper investigates the long-term perturbations of the orbits of geosynchronous space debris influenced by direct radiation pressure including the Earth’s shadowing effects. For this purpose, we propose an extension of our homemade semi-analytical theory [Valk, S., Lemaître, A., Deleflie, F. Semi-analytical theory of mean orbital motion for geosynchronous space debris under gravitational influence. Adv. Space Res., submitted for publication], based on the method developed by Aksnes [Aksnes, K. Short-period and long-period perturbations of a spherical satellite due to direct solar radiation. Celest. Mech. Dyn. Astron. 13, 89–104, 1976] and generalized into a more convenient non-singular formalism. The perturbations accounting for the direct radiation pressure with the Earth’s shadow are computed on a revolution-by-revolution basis, retaining the original osculating Hamiltonian disturbing function. In this framework, we compute the non-singular mean longitude at shadow entry and shadow exit at every orbital revolution in opposition to classical approaches where the singular eccentric anomalies at shadow entry and shadow exit are computed. This new algorithm is developed using non-singular variables. Consequently, it is particularly suitable for both near-circular and near-equatorial orbits as well as orbits which transit periodically around null eccentricities and null inclinations.The algorithm is tested by means of numerical integrations of the equations, averaged over the short periods, including radiation pressure, J₂, the combined Moon and Sun third body attraction as well as the long-term effects of the 1:1 resonance occurring for geosynchronous objects. As an extension of [Valk, S., Lemaître, A., Anselmo, L. Analytical and semi-analytical investigations of geosynchronous space debris with high area-to-mass ratios influenced by solar radiation pressure. Adv. Space Res., doi:10.1016/j.asr.2007.10.025, 2007b], we especially apply our analysis to space debris with area-to-mass as high as 20 m²/kg. This paper provides numerical and semi-analytical investigations leading to a deep understanding of the long-term evolution of the semi-major axis. Finally, these semi-analytical investigations are compared with accurate numerical integrations of the osculating equations of motion over time scales as high as 25 years.     

交会对接远距离导引精度分析

为确定交会对接任务地面远距离导引控制可达到的精度,分析了影响精度的误差因素;提出了利用简化动力学模型、采用拟平均根数法和协方差法进行误差传播计算的方法;推导了误差传播和误差分析数学模型;进行了仿真计算.结果表明:远距离导引终点精度主要由传播误差决定,在一定初始条件下,当外推时间小于6 h时,终点位置精度可达到2~5 km,速度精度可达到2~3 m/s;误差传播中,沿迹和径向误差因素占主要成份,且随外推时间增加沿迹误差影响逐渐增大;终点精度的提高应从抑制沿迹、径向误差着手.提出的地面导引控制精度分析方法综合考虑了各种误差因素,计算便捷,适用于工程方案设计阶段的精度分析与估计.      

甲烷-空气的二次爆炸流场实验研究

为了揭示二次爆炸的产生机制及其影响因素,采用带导管的柱形泄爆装置对向空气中泄爆的过程进行了实验。实验获得了在不同泄爆条件下清晰的时序阴影照片和外流场测点的压力历程。根据实验结果分析了二次爆炸的产生条件,并详细讨论了二次爆炸影响因素在不同泄爆条件的变化,从而分析和解释了二次爆炸强度在相应泄爆条件下的变化规律。     

输送线网络监控系统的设计与实现

对可编程控制器控制原理进行分析,提出一种在已有设备的基础上进行改造,从而实现基于网络的监控技术。通过RS-485数据传输技术,运用TCP/IP协议,用MCGS(Mon itor and Control Generated System)组态软件编写程序软件,以图形界面实现对输送线的过程进行监控。     

高空长航时飞行器机翼跨声速气动优化设计

高空长航时飞行器应具有升阻比高和俯仰力矩小的气动特性.基于遗传算法的随机性和隐含并行性,结合适用于多目标处理的Pareto方法,在低雷诺数和跨声速条件下,展开了高空长航时飞行器机翼外形的多目标、多设计点的数值优化设计.仿真计算结果表明,所设计的机翼具有较高的升阻比和较低的俯仰力矩,同时在设计马赫数附近升阻比的变化比较平稳,具有良好的综合气动性能.     

305m长线缆的回波损耗和近端串扰的测试方法研究

数字平衡线缆广泛应用于综合布线系统以连通设备、互传信息,是工程建设中最常用的传输介质,其质量是保证信息顺利传递的关键,目前国际上通行的测试标准和方法均是基于90m长度的基线模型,而数字平衡线缆在工厂制造中通常是以1 000ft(305m)为基本单位进行绕匝装箱。因此为方便对生产线缆进行性能检测和质量控制,针对整箱线缆的测试方法研究尤为必要。文章提出针对305m长线缆的回波损耗和近端串扰的测试方法,利用网络分析仪和阻抗转换器实现对双绞线所有线对的近端性能测试,并与国际标准进行对比,验证了可以通过测试305m长线缆的回波损耗和近端串扰值来初步判断线缆的传输质量是否合格。     

E1784K基因变异与钠离子通道病建模与仿真(英文)

临床报道发现SCN5A上的一个位点突变E1784K基因变异会导致同时出现长QT间期III型综合征和Brugada综合征的特征。E1784K基因变异引起钠离子通道功能改变,但无法确定钠离子通道功能的改变是否能够解释LQT3和BrS交叠现象。为分析该问题,建立了详细的计算模型,从动作电位、有效不应期和伪心电图三方面进行仿真。仿真结果表明E1784K基因突变导致钠离子通道改变不能直接解释LQT3和BrS心电图特征交叠现象,而间接引起的ITo或者ICaL重构可以解释该现象。     

Analysis of the current density characteristics in through-mask electrochemical micromachining (TMEMM) for fabrication of micro-hole arrays on invar alloy film

Invar alloy consisting of 64% iron and 36% nickel has been widely used for the production of shadow masks for organic light emitting diodes(OLEDs) because of its low thermal expansion coefficient(1.86 ? 10à6cm/°C).To fabricate micro-hole arrays on 30 lm invar alloy film,through-mask electrochemical micromachining(TMEMM) was developed and combined with a portion of the photolithography etching process.For precise hole shapes,patterned photoresist(PR) film was applied as an insulating mask.To investigate the relationship between the current density and the material removal rate,the principle of the electrochemical machining was studied with a focus on the equation.The finite element method(FEM) was used to verify the influence of each parameter on the current density on the invar alloy film surface.The parameters considered were the thickness of the PR mask,inter-electrode gap(IEG),and electrolyte concentration.Design of experiments(DOE) was used to figure out the contribution of each parameter.A simulation was conducted with varying parameters to figure out their relationships with the current density.Optimization was conducted to select the suitable conditions.An experiment was carried out to verify the simulation results.It was possible to fabricate micro-hole arrays on invar alloy film using TMEMM,which is a promising method that can be applied to fabrications of OLEDs shadow masks.     

大跨度桥梁抖振响应研究

简要介绍了处于自然大气湍流中的大跨度桥梁易发生的风振形式之一的抖振概念以及分析抖振的频域法和时域法 ,概括地介绍了中国空气动力研究与发展中心低速所在该方向上的一些研究工作以及拟开展的研究工作。     

一种激光长刻机的工作原理

介绍了一种静态激光长刻机的工作原理,并介绍了该光刻方法的关键技术和工艺.