卫星导航有源接收天线噪声温度测量

卫星导航有源接收天线的噪声温度是导航接收系统的关键技术指标之一。针对卫星导航有源天线总体噪声温度无法测量的问题，研制了两台口面型噪声源，口面噪声源主要由辐射体、辐射体物理温度控制和温度测量仪等组成。两个口面噪声源在L和S波段分别提供高低温标准噪声温度，采用Y系数测量方法测量有源接收天线的总体天线噪声温度。测量了某卫星导航有源天线的总噪声温度，在(1.19～1.29) GHz的频率范围内，中心频率1.24 GHz上噪声温度测量结果为206 K，但是在1.266 GHz频率点上噪声温度测量大于4 000 K，说明天线与滤波器之间、滤波器与放大器之间存在设计问题或其它问题，体现出测量有源天线噪声温度的必要性。     

太极二号卫星精密热控关键技术及试验验证

针对引力波探测太极二号卫星提出的高稳定度温控需求，开展了高分辨率测温系统和高稳定度热控技术的研究，提出了多级阻尼的热控设计方法，建立了多级阻尼状态空间数学模型，揭示了系统中热量传递特性。该方法在太极二号核心载荷上进行了地面试验验证，试验结果表明核心舱关键仪器的温度满足指标要求。试验结果的噪声分析，不仅验证了精密热控关键技术，而且提出了关于热噪声分析与抑制的新方法，为后续航天器精密热控技术提供了理论分析方法和工程参考依据。     

基于模态缩聚的限位状态驱动机构非线性动力学分析

含限位的驱动机构具有刚度非线性特征，在正弦振动力学试验中，不同试验量级加速度激励下其主频位置、响应放大倍数等动力学特性均会发生变化，需要开展动力学响应分析提前预示非线性影响，指导产品抗力学环境设计。基于模态缩聚理论，发展了一套针对限位非线性问题的正弦振动响应快速分析方法，可适用于各类复杂驱动机构类产品，避免了大规模有限元模型的非线性计算。算例分析表明:该方法可有效预示不同振动输入量级下限位非线性对产品响应特性的影响，反映出典型的非线性频响突变现象，且计算效率高，可为产品力学特性仿真和力学试验的开展提供有力支持。     

Deployment of SMP Miura-ori sheet and its application: Aerodynamic drag and RCS reduction

Origami, such as Miura-ori, is the art of folding two-dimensional materials into complex, elaborate, and multifunctional three-dimensional objects. In this paper, SMP MO sheet are prepared, and the accuracy of deployable process is verified by experiments. The folding and deployable process of SMP MO sheet is divided into 4 stages, and each stage is described in detail. The stiffness of smart deployable stage is characterized by an exponential decline at the beginning and a gradual decrease to 0, and this is similar to the theoretical shear equivalent modulus in the Y direction. The effects of various parameters on strain and stress are also explored. The purpose of studying these mechanical characteristics is to provide driving force reference in application; In terms of application, the flow field and electromagnetic characteristics of MO sheet in different directions are studied. The aerodynamic drag and RCS reduction of MO unit cell and graded MO sheet during the deployable process are evaluated. When the dihedral fold angle is about 45°, the RCS reduction and drag reduction characteristics of MO sheet are relatively optimal, which is most beneficial to morphing aircraft.     

基于边界层燃烧方法的宽速域飞行器内流道减阻研究

为了降低宽速域飞行器的内流阻力，基于边界层燃烧方法，分析了系列进口马赫数条件下二维扩散段总阻力中摩阻和压阻的特性，研究了不同进口马赫数下摩阻和压阻分量对总减阻的贡献、燃烧影响区域和壁面热流密度，探讨了喷射参数对减阻效果的影响，探索了边界层燃烧方法在典型混压式进气道中的减阻应用。结果表明，随着进口马赫数的增加，总阻力中摩阻分量随之增加；边界层燃烧对摩阻和压阻减阻的机理有所不同，壁面附近流场特性变化使得摩擦系数减小，燃烧局部增压对壁面产生的增推效果使得压力系数减小；从总内阻减阻百分比看，在相同燃料/空气当量比下，低马赫数工况下边界层燃烧减阻效果不如高马赫数工况，且在低马赫数工况下，喷嘴附近壁面热流密度会显著增加；在本文所研究的参数范围内，摩阻和压阻对当量油气比更为敏感，而对喷射方向和喷射速度不敏感。     

Compact wideband FSS-absorber-based low-RCS reflectarray antenna

This paper presents a method to realize compact broadband low-RCS Reflect Array(RA) antenna based on a Frequency Selective Surface(FSS) absorber and a reflective metasurface.Such an FSS absorber consists of a resistance-loaded lossy layer and an FSS layer, which is utilized to reach an absorption-transmission response. The bottom reflective metasurface works as a phase array, reshaping the quasi-sphere wave from the feeding antenna into the quasi-plane wave. As a demonstration, the low-RCS RA an...     

Experimental and numerical investigation on opposing plasma synthetic jet for drag reduction

Experimental and numerical studies are carried out to validate the potential of opposing Plasma Synthetic Jet (PSJ) for drag reduction for a hemisphere. Firstly, flow field changes of opposing PSJ are analyzed by comparing the experimental schlieren images and simulation results in a supersonic free stream of Mach number 3. As PSJ is a kind of unsteady pulsed jet, the shock standoff distance increases initially and then decreases under the control of PSJ, which corresponds to the change of the strength of PSJ. Accordingly, the amount of drag reduction of the hemisphere increases initially and then decreases. It is found that there is a short period of “drag rise” during the formation of PSJ before the drag reduction, which is induced by the generation of normal shock waves and the area difference of the cavity wall of PSJ Actuator (PSJA). Secondly, the effects of five parameters, including exit diameter, discharge energy of PSJA, Mach number, static pressure of incoming flow and angle of attack, on drag reduction of opposing PSJ were studied in detail by using numerical method. It is found that the Maximum Pressure Ratio (MPR) has a significant impact on the average drag reduction for a configuration-determined PSJA. For the configuration selected in this study, the flow field of opposing PSJ shows typical Short Penetration Mode (SPM) in a control cycle of PSJ when the MPR is less than 0.89. However, the flow field shows typical Long Penetration Mode (LPM) at some time when the MPR is bigger than 0.89. Relatively better drag reduction is achieved in this case.