试用暗物质理论解释惯性和惯性力的物理机制(上)

基于对暗物质的多年探讨,我们认为宇宙空间是具有质量、相对均匀、连续稳定和有相当弹性暗物质群体(DMG)的空间.自然、宇宙万物终生处于群体引力制约之中,它们因此也获得了相应的惯性.本文立足于上述的宇宙空间,借助宇宙学原理、马赫原理和爱因斯坦等效原理,提出了物质客体的惯性机制和被称为虚力的惯性力机制 同时本文也解读所有惯...     

复飞研究与实践

讨论中断进近复飞决断，有助于提高飞行员的决断能力和处境意识。若很好地完成复飞，飞行员必须明确复飞的前提条件，掌握复飞决断的标准，了解复飞决断的影响因素，理解正确复飞决断的原则，熟练掌握复飞的正确实施方法，这样才能有效地保证飞行安全．顺利完成飞行任务。     

Sensitivity studies of the deployment of a square inflatable solar sail with vanes

This paper summarizes the results of numerical experiments to determine the sensitivity of the final attitude of an inflatable solar sail with vanes after deployment to various parameters affecting the deployment process. These parameters are: in- and out-of-plane asymmetries during deployment, length inflation profile, and vane deployment failures. We show how robust the sail deployment is to geometric asymmetries before a 35° off-Sun angle is reached. Differential delays in the time to inflate the booms and a boom sweep-back angle affect the stability favorably. Adjacent vane failures to deploy affect the stability unfavorably, while the failure of opposing vanes is acceptable. Realistic boom length rate profiles obtained during ground tests are used in the simulation showing that failing adjacent vanes in conjunction with initial inflation delays in adjacent booms represent the worst case. We also demonstrate that by feeding back attitude and attitude rate measurements so that a corrective action is taken during the deployment, the final attitude can be maintained very close to the initial attitude, thus mitigating the attitude changes incurred during deployment.     

Comparative study of productivity of the Rosetta target Comet 67P/Churyumov-Gerasimenko

In an attempt to evaluate correlations between several properties of comets we report the results of a cometary research involving a criterious analysis of gas and dust mass production rates in Comets 67P/Churyumov-Gerasimenko (main target of Rosetta Mission), 1P/Halley, Hyakutake (C/1996 B2), and 46P/Wirtanen and make a comparison between them.     

Height-latitude structure of stationary planetary waves in the stratosphere and lower mesosphere

Daily UK Met Office stratospheric assimilated data for the Northern and Southern Hemispheres, accumulated for the period from 2004 to 2012 and pressure range of 1000–0.1 hPa, are used in this paper. The paper presents and thoroughly discusses spatial–temporal distributions of stationary planetary wave (SPW) amplitudes and phases, calculated on the basis of geopotential height, temperature, zonal and meridional wind data for zonal wave numbers 1 and 2 (SPW1 and SPW2). The climatological planetary wave amplitudes and phases are calculated by extracting waves from three types of data: daily, monthly mean and climatological monthly mean. It has been established that magnitude of amplitudes and height-latitude distribution of amplitudes of SPW1 and SPW2 depend on data processing method for all parameters. It has also been established that height-latitude distribution amplitudes and phases significantly differ for geopotential height, temperature, zonal and meridional wind and depend on wave number and hemisphere. However, height-latitude distributions of phases are little different from each other for the used methods of data processing.     

火星进入气体辐射加热研究进展

针对飞行器进入火星大气时气体辐射加热对防热设计带来不确定性，在简述火星探测和气体辐射研究的发展历程的基础上，对火星进入气体辐射加热研究的进展进行综述。首先，针对火星大气环境描述了气体辐射加热的概念和问题由来。其次，重点综述了近年来火星进入气体辐射加热基础模型的数值和试验研究进展，其中包括：热化学非平衡气体动力学、气体辐射特性和辐射传输的计算模型与方法等数值研究；地面测试设备、试验技术和模拟火星大气环境的气体辐射测量与验证等试验研究。再次，综述了流动辐射耦合和后体气体辐射加热等火星进入器设计方面开展的研究。最后，对未来火星进入气体辐射加热研究进行了展望，提出了研究建议。     

Adaptive neural network control of nonlinear systems with unknown dynamics

In this study, an adaptive neural network control approach is proposed to achieve accurate and robust control of nonlinear systems with unknown dynamics, wherein the neural network is innovatively used to learn the inverse problem of system dynamics with guaranteed convergence. This study focuses on the following three contributions. First, the considered system is transformed into a multi-integrator system using an input–output linearization technique, and an extended state observation technique is used to identify the transformed states. Second, an iterative control learning algorithm is proposed to achieve the neural network training, and stability analysis is given to prove that the network’s predictions converge to ideal control inputs with guaranteed convergence. Third, an adaptive neural network controller is developed by combining the trained network and a proportional-integral controller, and the long-standing challenge of model-based methods for control determination of unknown dynamics is resolved. Simulation results of a virtual control mission and an aerospace altitude tracking mission are provided to substantiate the effectiveness of the proposed techniques and illustrate the adaptability and robustness of the proposed controller.     

Inverted decoupling and LMI-based controller design for a turboprop engine with actuator dynamics

The main objective of the turboprop engine control system is to ensure propeller absorbed power at a constant propeller speed by controlling fuel flow and blade angle. Since each input variable affects the selected output variables, there exist strong interactions between different control loops of a Two-Spool TurboProp Engine (TSTPE). Inverted decoupling is used to decouple the interactions and decompose the TSTPE into two independent single-input single-output systems. The multi-variable PI controller and two single-variable PI controllers are designed for the TSTPE with actuator dynamics based on Linear Matrix Inequality (LMI), respectively, which is derived from static output feedback and pole placement condition. The step responses show that due to the difference in the response times of the selected output variables, it is difficult to design an appropriate multi-variable PI controller. The designed single-variable PI controllers are tested on the TSTPE integrated model to illustrate the effectiveness of the proposed method, that is, the interactions are first decoupled and then the controllers are designed, and the resulting simulated responses show that compared with the controller designed without actuator dynamics, the gas-generator shaft speed and power turbine shaft speed can better track their respective commands under the action of the controller designed with actuator dynamics.     

低空风切变系统建模及其对直升机飞行安全威胁定性分析

系统地建立了含湍流的三维低空风切变模型，并综合分析了其对直升机飞行安全的威胁。建立了微下击暴流风场及大气湍流场组合的风切变模型，在不增加计算量的前提下，选取特征点发展直升机飞行动力学模型，有效捕捉了风切变的切变特性，提高了在风场中的动态响应计算精度。模型配备姿态保持功能的控制增稳系统已符合一般直升机的飞行状态，并改善机体响应。根据风速分布的特点，选取不同飞行速度、不同风场位置进行飞行仿真，定性地对比分析状态量变化与风场对应关系，并且以垂向通道为例，从动力学角度分析验证了响应的理论计算表达式。结果表明：湍流主要导致高频姿态角响应，风切变对飞行状态量变化占主导作用，且垂向风是引起威胁的主要因素，据此提出危险风场规避建议。     

基于三维有限元的火箭模态振型斜率预示方法研究

振型斜率火箭是姿控系统设计的重要参数,对飞行任务的可靠性与安全性有着至关重要的作用。依据全箭动特性的测量原理及参数定义,结合三维有限元建模方法和模型修正技术,全面考虑了速率陀螺、惯组安装位置处的局部刚度对振型和振型斜率的影响,建立了基于局部细节精细化建模的全箭模态振型斜率预示方法,并总结了3种不同的振型斜率提取方法,提高了振型斜率的预示精度。同时提供了三维模型振型一维化的方法,解决了使用三维有限元模型计算弹性运动方程式系数的难题。