基于知识图谱的遥感图像检索定位方法

为了快速、准确地在海量遥感图像库中检索出所需的遥感图像资源，提出了一种基于知识图谱的遥感图像检索定位方法。为了充分利用遥感图像中所蕴含的地理语义信息，方法中使用知识图谱节点代表遥感图像，根据图像间的相似程度和地理位置在节点间建立关系。通过知识图谱缩小图像检索空间，加快检索速度，准确地定位遥感图像所示区域的地理信息，并返回最相似的图像。将此方法应用于卫星自主导航领域中，与传统的线性检索相比，图像检索的时间缩短了50%，准确率也得到提高。     

无人战斗机缩比训练机气动特性计算分析

针对无人战斗机系统维护和飞行训练耗费巨大的问题,借鉴缩比模型验证机飞行试验的思路,研制具有相同飞行性能和操纵特性的缩比训练机。应用相似性原理,通过相似参数分析获得了缩比机与全尺寸原型机的飞行范围。在缩比机几何外形的基础上,应用Gridgen软件创建机体周围流场的非结构网格。通过Fluent软件,计算了缩比机纵向气动特性。根据俯仰力矩系数估算出全机气动中心位置,为缩比机的操纵性稳定性研究和控制率设计奠定了基础。     

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.     

超视距空战仿真中的策略识别

针对超视距空战仿真中敌机策略的识别问题,研究了一种基于案例的策略识别方法。该方法通过构建包含假定的对手任务目标、观测数据、策略等内容的案例库,采用相似度计算选择与新的观测相似的案例库子集,并计算策略概率分布来识别对手策略。实验证明,相比与常规的基于案例推理方法,在案例中增加敌机任务目标提高了策略识别准确率,并且在假定敌机目标不正确时,能修复错误假定并进行策略识别,改善了基于案例策略识别方法的性能。