A Hitch-hiker’s Guide to Stochastic Differential Equations

In this review, an overview of the recent history of stochastic differential equations (SDEs) in application to particle transport problems in space physics and astrophysics is given. The aim is to present a helpful working guide to the literature and at the same time introduce key principles of the SDE approach via “toy models”. Using these examples, we hope to provide an easy way for newcomers to the field to use such methods in their own research. Aspects covered are the solar modulation of cosmic rays, diffusive shock acceleration, galactic cosmic ray propagation and solar energetic particle transport. We believe that the SDE method, due to its simplicity and computational efficiency on modern computer architectures, will be of significant relevance in energetic particle studies in the years to come.     

A study on optimal control of the aero-propulsion system acceleration process under the supersonic state

In order to solve the aero-propulsion system acceleration optimal problem, the necessity of inlet control is discussed, and a fully new aero-propulsion system acceleration process control design including the inlet, engine, and nozzle is proposed in this paper. In the proposed propulsion system control scheme, the inlet, engine, and nozzle are simultaneously adjusted through the FSQP method. In order to implement the control scheme design, an aero-propulsion system component-level model is built to simulate the inlet working performance and the matching problems between the inlet and engine. Meanwhile, a stabilizing inlet control scheme is designed to solve the inlet con-trol problems. In optimal control of the aero-propulsion system acceleration process, the inlet is an emphasized control unit in the optimal acceleration control system. Two inlet control patterns are discussed in the simulation. The simulation results prove that by taking the inlet ramp angle as an active control variable instead of being modulated passively, acceleration performance could be obviously enhanced. Acceleration objectives could be obtained with a faster acceleration time by 5%.     

Rapid deployment and continuous shape maintenance of tethered-space net robot based on single-pulse action

The tethered-space net robot is one of new technologies for capturing space debris. Rapid deployment and continuous shape maintenance of the tethered-space net robot system are essential in capturing space debris. A single-pulse rotation deployment strategy of the tethered-net robot system is proposed in this paper. The rapid deployment and continuous shape maintenance of the tethered-net are investigated through dimensional analysis, numerical simulation, and regression analysis. Results reveal that the single-pulse rotation deployment strategy can fully deploy the net and maintain the net-shape without any closed-loop controller, and it dramatically increases the effective deployment distance of the net. The parameter sensitivity analyses provide a reference for the rapid deployment and continuous shape maintenance of the tethered-space net robot system.     

IVIG无反应川崎病的预测研究进展

川崎病多发病于 5岁以下的儿童，静脉免疫球蛋白 (Intravenous Immunoglobulin，IVIG) 无反应的川崎病患儿罹患心血管并发症风险明显增高，而早期识别IVIG无反应的川崎病患儿并予以积极治疗可有效改善其预后。本综述结合文献，对IVIG无反应川崎病的预测单项指标及预测模型进行总结，为川崎病患儿诊疗提供依据。     

表面粗糙度对航空液压作动器密封性能的影响

航空液压作动器普遍应用在飞机机翼、舱门、起落架等部位,往复密封为其典型密封形式,密封失效会 严重影响飞机任务的执行和飞行安全。密封副表面粗糙度是重要的工程可控参数且对于密封性能的影响很 大,因此分析表面粗糙度对作动器密封性能的影响具有重要的理论和实际意义。建立适用于往复组合密封的 确定性混合润滑数值仿真模型,并与有限元分析方法结合计算膜厚值,分析密封圈表面粗糙的幅值和波长变化 以及运动速度和液压油黏度变化对密封圈润滑性能和密封性能的影响。结果表明:正弦粗糙表面的幅值和波 长增大,会引起油膜压力和油膜厚度波动的幅值增大,但会减小摩擦系数;正弦粗糙表面的幅值增大,有利于减 小密封间隙的最小膜厚和泄漏量,但是波长变化的影响作用不大;液压油黏度和活塞运动速度增大,有利于增 大密封间隙油膜厚度,但会增大泄漏量和摩擦系数。     

天翼1无人机电动化改造可行性分析

电动飞机正在国内外通用航空领域蓬勃发展,并影响着未来航空的发展方向。利用电推进技术对无人机进行电动化改造,能大大提高无人机的安全性、可靠性和维修性,降低使用成本。以天翼1无人机为电动化改造对象,提出了电动化改造方案,详细计算分析了电推进系统中电动机和锂电池组的主要参数,并从无人机的重量重心、性能以及电推进系统的安装方式等方面分析了改造的可行性。分析结果表明,天翼1无人机电动化改造基本可行;并提出了后续改造实施中需注意的问题。     

喷流噪声声源识别与声源机理分析方法进展

喷流噪声是航空气动噪声的主要来源,会造成严重的环境污染和健康威胁。缺乏对湍流涡如何产生 噪声辐射这一物理过程的深刻理解,是难以设计出高精度噪声预测方法和高效降噪装置的根本原因。本文总结公开发表文献中喷流噪声的声源识别与声源机理分析的研究进展和局限。从噪声由湍流脉动产生这一因果 律出发,指出未来研究仍需要对噪声和湍流脉动建立合理的物理模型和控制方程,进行合理的分离,并将噪声 脉动表示为背景湍流的广义函数,从动力学角度揭示非定常湍流涡演化产生噪声辐射的物理机理。     

自动飞行控制计算机通用自动测试平台设计

自动飞行控制计算机故障时飞机自带系统级自检测模块只能将故障定位在自动飞控计算机,地勤人 员需要将整个自动飞行控制计算机返回给供应商进行检测维修,这一过程耗时较长会降低飞机的完好出勤率, 为解决该问题设计通用自动测试平台。通过分析自动飞行控制计算机的外部交联关系确定通用自动测试平台 需要进行仿真的接口及功能模块;通用自动测试技术平台的硬件平台基于通用标准仪器总线架构,软件平台基 于标准自动测试标记语言描述,实现硬件仪器资源的自由扩展和各软件模块的相互独立以及不依赖于硬件和 操作系统的可移植性;根据自动飞行控制计算机的接口、功能及组成架构设计检测自动飞行控制计算机各个功 能模块的测试方法和测试流程,使用自动测试标记语言将其编译成计算机可运行的测试程序集。该平台在试 用中测试效果较好,可以实现故障模块的快速定位,缩短维修时间。     

计算域大小对大涡模拟计算结果的影响

为了节省计算资源,提升计算效率,在保证计算结果准确的前提下,尽可能选取较小的计算域显得尤为重要。针对该问题,分别沿槽道的展向和流向选取不同的计算尺度(053πδ×2δ×0177πδ、πδ×2δ×05πδ、2πδ×2δ×πδ、3πδ×2δ×15πδ,δ为槽高的一半),在相同的计算条件且设置均满足大涡模拟计算要求的前提下,对摩擦雷诺数为540和930两种摩擦雷诺数下计算域大小对大涡模拟数值计算结果的影响进行了研究。结果发现:计算尺度不小于2πδ×2δ×πδ的计算域能很好的呈现湍流计算结果。此外,在摩擦雷诺数为930时,相同计算域下所能检测的范围均有所提升,得到的计算结果更加准确。