深远空连续推进动力与施图林格解的解析

针对太阳系远深距离的探测将是人类下一阶段深空探测活动的主要目标。这一目标的实现依赖于探测器连续推进动力技术的突破。从描述连续常值推力下太空飞行的施图林格解出发,对其中反映的深远空飞行任务有效载荷比、任务时间、飞行距离等关键参数与发动机性能之间的关系进行了深入分析。给出了在特定任务时长、特定飞行距离要求下发动机比冲、功率需要满足的条件及其对有效载荷比、最终飞行速度等指标的影响。此外,基于二体轨道动力学对太阳系行星探测的大椭圆转移轨道和转移能量进行了推导,并对连续推力的太阳帆任务方案涉及的关键技术指标做了理论性的计算。这些结论是对深空探测连续推力方案基础理论的归纳,可以为我国未来开展深远空探测活动提供重要的启发和指导。     

Three dimensional temperature field in a conducting sphere due to an arbitrarily located split ring heating source

Thermal control of spacecrafts plays an important role in space missions. In the design stage the preliminary thermal analysis of the spacecraft requires an estimate of the conductive thermal resistance between the various spacecraft components. With this in mind, the fully three dimensional problem of determining the thermal field in a conducting sphere with an asymmetric split ring current carrying heating source is resolved in an analytical or almost analytical form, implying either a closed form solution or utmost expressions involving a simple numerical integration. This has immediate application for evaluation of thermal resistance in spacecrafts. Green's function integral techniques are used. Comparisons are made with series solutions and also with purely numerical solutions to contrast the simplicity and highlight the elegance of the present method. Parametric studies reveal expected behavior.     

飞机着陆进近穿越风切变的轨迹响应

大气紊流和风切变对飞行活动影响较大,尤以低空风切变危害最大,严重威胁着民航飞行的安全。鉴于飞行器对抗大气扰动的实际能力有限,正确的飞行对策是回避或改出危险的大气扰动区。本文对某训练飞机着陆进近遭遇风切变时飞机轨迹的变化进行了模拟仿真计算。结果表明,采用恒定迎角策略,即采用最大允许迎角（抖动迎角）和最大油门时,改出效果最佳。同时计算出了某训练飞机在水平风为0时,所能抵抗的最大垂直阵风强度;以及在垂直阵风为0时,所能抵抗的最大水平风强度。     

空间真空环境下密封电磁继电器的触点失效研究

密封电磁继电器有其固有的漏率,在应用于空间真空环境下由于气体泄漏使得其内部气体压力逐渐降低,导致继电器的触点在低气压环境下工作失效（负载切换时）。文章选择国产继电器样品对上述机理进行了试验验证,并对继电器内部气体压力与触点电弧失效的规律进行了研究。     

Ion-acoustic waves in unmagnetized collisionless weakly relativistic plasma of warm-ion and isothermal-electron using time-fractional KdV equation

Collisionless unmagnetized plasma consisting of a mixture of warm ion-fluid and isothermal-electron is considered, assuming that the ion flow velocity has a weak relativistic effect. The reductive perturbation method has been employed to derive the Korteweg–de Vries (KdV) equation for small – but finite-amplitude electrostatic ion-acoustic waves in this plasma. The semi-inverse method and Agrawal’s method lead to the Euler–Lagrange equation that leads to the time fractional KdV equation. The variational-iteration method given by He is used to solve the derived time fractional KdV equation. The calculations show that the fractional order may play the same rule of higher order dissipation in KdV equation to modulate the soliton wave amplitude in the plasma system. The results of the present investigation may be applicable to some plasma environments, such as space-plasmas, laser-plasma interaction, plasma sheet boundary layer of the earth’s magnetosphere, solar atmosphere and interplanetary space.     

旋转状态柔性附件航天器振动及其变结构控制

基于Hamilton变分原理,采用Mindlin厚板理论,研究了旋转状态中心刚体—悬臂厚板振动及其变结构控制问题。采用Hamilton状态空间法,应用弹性波与振动模态理论,确定了Mindlin厚板中的振动模态。针对该模型系统设计了控制器,采用滑模变结构控制理论,实现了对系统实施渐近稳定控制的设计。采用的变结构控制能使系统达到所期望的振动状态,有效地抑制了平板振动。最后,给出了数值模拟结果,讨论了中心刚体—悬臂厚板位移的动力学控制规律。该方法和计算结果可望能在带有柔性附件航天器的动力学控制中得到应用。     

无人机用燃料电池阴极供气系统建模与控制

燃料电池因其高效、无污染、噪声小等特点,被认为是未来最具有潜力的无人机（UAV）用动力源,燃料电池阴极供气系统的控制技术是决定燃料电池系统性能和可靠性的关键。针对无人机用质子交换膜燃料电池（PEMFC）阴极供气系统,首先,考虑外界温度、压力、空气密度以及雷诺数等随高度变化的参数,建立了跨高度离心空压机模型并分析了其在不同高度下的工作特性,基于无刷直流电机反电势特征构建了高速空压机驱动电机模型。其次,通过计算燃料电池阴极氧气和氮气的动态分压获取了PEMFC电堆输出电压。设计了基于分数阶PI^λD^μ的过氧比和阴极气压控制方法,驱动电机采用有限集模型预测控制（MPC）实现快速的转矩响应,仿真结果表明设计的控制器可在无人机跨高度运行条件下实现过氧比的快速调节,同时维持阴极气压稳定,满足燃料电池阴极供气需求。     

航空发动机导流叶片角度调节参数变化故障分析

某型发动机低压压气机进口导流叶片角度α1,其电子调节部分执行机构电磁活门的占空比(Sα),在整个调节过程中是起关键作用的重要参数,但在台架试车过程中曾多台次出现在不同次检查时Sα数值变化的故障。通过对α1主调节系统工作原理的深入分析,确定试车中Sα变化故障是由于燃油调节机构掺混入空气所致,并得到试车验证。本研究对发动机试车中类似故障的排除具有重要的参考意义。     

人的全面发展与现代教育改革探索

人的全面发展理论是马克思主义理论的重要组成部分。人的全面发展的内涵包括人的能力的全面发展、人的社会关系的全面发展、人的需要的全面发展和人的个性的全面发展等内容。人的全面发展理论要求现代教育改革必须树立以人为本的教育理念,重视对学生的全面教育、尊重学生的个性、充分挖掘学生潜能、满足学生需要、营造宽松和谐的教学氛围、构建终身教育体系等。以促进学生的全面发展。     

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.