基于高轨导航接收机的自动化地面测试系统

高轨卫星导航接收机是实现高轨航天器自主定轨的核心设备。为在地面测试阶段对高轨卫星导航接收机进行充分高效的验证，亟需设计基于高轨卫星导航接收机的地面测试系统。设计了一种基于高轨卫星导航接收机的自动化地面测试系统，主要创新点如下：第一，本系统可对高轨卫星导航接收机实际在轨状态下接收到的导航星座信号进行仿真；第二，具有模拟包含北斗三号等多导航卫星星座信号的功能；第三，本系统充分考虑自动化、通用化与一体化设计。提出的基于高轨卫星导航接收机的自动化地面测试系统能够在地面测试阶段对高轨卫星导航接收机进行充分验证，并充分考虑测试实施，从自动化、通用化、一体化方面提升测试效率，减少人为操作失误导致的质量问题，解决人工判读带来的误判漏判问题。     

离心式压气机出口动态压力的关联维数特征分析

基于相空间重构理论,以800kW离心式压气机在不同工况下的出口动态压力为研究对象,分析了其时域、频域和关联维数特征,目的是实现喘振识别.结果表明:系统稳态时,动态压力幅值小且随机特性强,系统的混沌特征较为明显.此状态下的关联维数曲线波动很大,饱和关联维数也较大(8～20),并且部分时段不存在饱和关联维数.而随着系统经过...     

基于多层次特征的高分影像海岸带地物分类

针对高分辨率影像地物光谱丰富复杂的问题，文章提出了一种结合像元-对象-空间格局特征的水域、盐田等海岸带精细地物分类方法。首先基于像元和空间格局特征分别利用遗传算法优化随机森林参数进行分类；其次将两种分类结果采用D-S证据理论融合；然后基于不同地物斑块的空间上下文信息，采用粒子群算法优化支持向量机（Support Vector Machine，SVM）参数实现面向对象的二次分类。为验证方法的有效性，收集山东省莱州湾海岸带附近区域的“高分二号”卫星影像，开展了水域及水利设施用地、盐田、工矿用地、交通运输用地、住宅用地、沿海滩涂、海域与耕地8类地物的分类实验，总体精度达到97.21%，Kappa系数为0.964 2。实验结果表明，文章提出的高分影像海岸带地物分类方法兼顾像元、对象及空间格局特征优点，能够实现多层次细致分类，并同时兼具较短的训练时长与较高的分类精度。该研究成果可为中国海岸带生态环境监测与土地利用规划提供一定技术支撑。     

Study of aerodynamic and inertial forces of a experimental and numerical methods

The force-generation mechanism of a dovelike flapping-wing micro air vehicle was studied by numerical simulation and experiment. To obtain the real deformation pattern of the flapping wing, the digital image correlation technology was used to measure the dynamic deformation of the wing. The dynamic deformation data were subsequently interpolated and embedded into the CFD solver to account for the aeroelastic effects. The dynamic deformation data were further used to calculate the inertial forces...     

一种互相关法测量相位噪声理论及仿真分析

相位噪声测量是无线电计测领域的重要研究内容，随着信号源等各种信号仪器设备的不断发展，相位噪声测量技术方面也产生了更高的要求。介绍了互相关法测量相位噪声的理论与仿真分析方法，通过理论推导阐释了互相关法抑制干扰噪声的原理，在推论的基础上建立了基于MATLAB的仿真分析模型，仿真验证了不同互相关次数下，系统噪声底部的改善程度，并进一步分析了双通道相关性对互相关运算结果的影响，得到了对应的仿真验证结果，为相关的工程设计提供参考。     

On the time lag between solar wind dynamic parameters and solar activity UV proxies

The solar activity displays variability and periodic behaviours over a wide range of timescales, with the presence of a most prominent cycle with a mean length of 11 years. Such variability is transported within the heliosphere by solar wind, radiation and other processes, affecting the properties of the interplanetary medium. The presence of solar activity–related periodicities is well visible in different solar wind and geomagnetic indices, although their time lags with respect to the solar cycle lead to hysteresis cycles. Here, we investigate the time lag behaviour between a physical proxy of the solar activity, the Ca II K index, and two solar wind parameters (speed and dynamic pressure), studying how their pairwise relative lags vary over almost five solar cycles. We find that the lag between Ca II K index and solar wind speed is not constant over the whole time interval investigated, with values ranging from 6 years to $～$1 year (average 3.2 years). A similar behaviour is found also for the solar wind dynamic pressure. Then, by using a Lomb-Scargle periodogram analysis we obtain a 10.21-year mean periodicity for the speed and 10.30-year for the dynamic pressure. We speculate that the different periodicities of the solar wind parameters with respect to the solar 11-year cycle may be related to the overall observed temporal evolution of the time lags. Finally, by accounting for them, we obtain empirical relations that link the amplitude of the Ca II K index to the two solar wind parameters.     

POBI interpolation algorithm for CYGNSS near real time flood detection research: A case study of extreme precipitation events in Henan,China in 2021

In late 2016, NASA launched the first constellation of the global navigation satellite system reflectometry (GNSS-R) small satellites called the Cyclone Global Navigation Satellite System (CYGNSS). The stable data quality and continuous free availability of CYGNSS scientific data provided a new method for flood monitoring. However, owing to the pseudorandom distribution of CYGNSS data, researchers must always choose between high temporal resolution and high spatial resolution during the performance of flood monitoring based on CYGNSS data. For floods caused by extreme precipitation with sudden and short durations, the current flood mapping based on CYGNSS data cannot be updated in near real time. However, the near real time update of the flood distribution range is meaningful for postdisaster emergency response and rapid rescue. This study aimed to address this problem using a newly proposed spatial interpolation method based on previously observed behaviour (POBI). First, a method for calculating the surface reflectivity of the CYGNSS was introduced, followed by the principle of the POBI spatial interpolation method. The applicability of the POBI method in Henan Province, China, was then analysed, and by using the flood in Henan Province, China, in July 2021 as an example, the feasibility of CYGNSS near real time flood mapping based on the POBI method was evaluated. Based on the results, near real time and 3 km flood distribution monitoring results can be obtained using the proposed new method. The results were evaluated using MODIS (Moderate Resolution Imaging Spectroradiometer) images and compared with the observations of SMAP (Soil Moisture Active Passive) and GPM (Global Precipitation Measurement) in the same period. The results show that the flooded areas obtained by CYGNSS correspond to the inundated areas in MODIS images and are also in high agreement with the SMAP. In addition, CYGNSS allows for finer mapping and quantification of inundation areas and flood duration. Moreover, we also discussed the potential of CYGNSS to detect floods in shorter periods of time (a few hours) and did a preliminary evaluation using precipitation data from meteorological stations. The results are also highly consistent.     

地面放射性测量模型γ剂量率值空间分布规律研究

地面模型是根据IAEA174号报告研建的用于校准便携式γ能谱仪、γ辐射仪的计量标准装置，最初主要用于地质勘查。2016年至2018年，新研建了钾含量30 %（YK3）和铀含量1 %（YU4）的两个模型，并确定了模型量值。远离模型表面中心位置的剂量率较低，随着中心点的接近，剂量率逐渐上升，YK3和YU4的剂量率坪区分别为模型中心点及周围半径约40 cm和50 cm范围内，在坪区内剂量率变化均不大于0.6 %；在参考点3.0 cm上的剂量率分别为320.8 nGy·h^-1和4.3×10⁴ nGy·h^-1；超过3.0 cm时，剂量率随高度呈非线性变化；根据不同高度上的理论计算和实测结果比对，在40 cm高度实测范围以内，YK3实测结果与理论计算结果相对偏差在3 %范围以内，120 cm高度实测范围内，YU4实测结果与理论计算结果相对偏差在2 %范围以内。     

未知纬度条件下基于空间圆拟合的SINS初始对准方法

传统的捷联惯导系统(SINS)晃动基座初始对准算法,如积分双矢量方法和多矢量Wahba方法等均需要精确的纬度信息,粗对准偏航角误差较大.针对此特点,提出了一种未知纬度条件下基于空间圆拟合的SINS初始对准方法.根据重力矢量在惯性系中绕地轴旋转包含北向信息的特征,以初始时刻凝固载体坐标系作为惯性系,首先对重力矢量在凝固载体系内进行投影并滤波,对其矢量端点进行空间圆拟合,然后通过三角几何关系得到导航坐标系,从而完成对准过程.通过仿真验证,证实了该对准方法不需要已知对准点的精确位置信息,相比于积分双矢量方法与多矢量Wahba方法,偏航角对准精度分别提高了12.37'与5.10'.