1982年12月30日日浪

介绍了１９８２年１２月３０日太阳视面上Ｓ１０Ｗ２０处伴随耀斑产生的日浪形态，并给出其速度场随时间演变的特征．光谱观测结果表明，日浪上升过程中有旋转运动，速度为２０—３０ｋｍ／ｓ，旋转速度随时间而减小．     

遥感图象几何校正的有限元法

本文介绍了在选好地面控制点后,按最优原则自动构成三角形网。建立三角单元的仿射变换,求出仿射变换系数。为了避免计算仿射系数可能失败,对边框及三角形的长边进行了适当分割。几何校正时,采用了行列式的判断条件及漂浮法的判断技巧,防止了判断失误,提高了运算速度。文中还提出几何校正边界的一种处理方法。     

Control system design of the Korean lunar lander demonstrator

In preparation for the lunar exploration program scheduled to be launched during the early 2020s in Korea, a lunar lander demonstrator, which will be used for developing and demonstrating lunar landing technologies, is being developed. The control configuration of the lunar lander demonstrator is determined with the consideration of available technologies and flight requirements. It is suggested that altitude control be achieved by clustering five 200 N monopropellant thrusters and attitude control with eight 3 N thrusters. A control algorithm designed to follow a predefined trajectory is developed using quaternion feedback. Control system configuration and control logic are verified by using computer simulations. Simulation results show that a soft landing with a touchdown velocity of less than 3 m/s is achieved. Attitude control performance is also verified using computer simulations. The developed control configuration will be further tested by hardware in the loop simulations and ground based firing tests during the next phase of the study.     

多旋翼无人机在某测控设备标校工作中的应用

为了提高综合测控设备标校效率，简化标校流程，克服传统标校的各项缺点，进行了多旋翼无人机在某综合测控设备标校工作中的应用研究。分析了某综合测控设备相位标校工作的现状，对引入多旋翼无人机进行相位标校工作进行了需求分析，建立了无人机相位标校的数学模型。在选定无人机型号、设计实现小型化信标机、飞行电池与信标机固定支架等工作的基础上，实现了无人机在某综合测控设备相位标校工作上的应用。经过实际标校工作检验，多旋翼无人机不但能应用于某综合测控设备相位标校工作中，而且同时能够检验综合测控设备的动态跟踪性能，在同类型设备中具有一定的推广应用价值。     

Using vegetation indices and texture measures to estimate vegetation fractional coverage (VFC) of planted and natural forests in Nanjing city,China

Vegetation fractional coverage (VFC) is an important vegetation parameter affecting exchanges of carbon, water, energy between the atmosphere and surface. In this study, the applicability of tonal and texture measures calculated using an IKONOS_2 image in retrieving VFC of forests was investigated in the urban area of Nanjing city, China. Four spectral vegetation indices (VI) and six texture measures (TEX) were related to VFCs acquired from in situ measurements. Models for estimating VFC based on VIs or/and TEXs were established and validated for planted low broad-leaf forest plots (PLB), planted mature forest plots (PMF), natural broad-leaf forest plots (NBF), and all forest plots (ALLv), respectively. The results show that high spatial resolution remote sensing data is applicable to estimate VFC in urban areas, and TEXs may act as effective supplements of vegetation indices (VIs) for the retrieval of VFC. VIs are suitable for VFC estimation of mature forests (such as NBF and PMF) with high vegetation density, and TEXs can yield a more accurate estimate for planted forests (such as PLB and PMF) with regular spatial distribution if they are calculated with proper parameters, such as window size. The combination of VIs and TEXs improve the estimation of VFC if forest types are not previously differentiated. The results can be used as a reference for determining effective spectral or texture parameters in VFC estimation under similar environmental conditions according to vegetation maturity and regularity.     

A comparative study on acoustic damping induced by half-wave, quarter-wave, and Helmholtz resonators

The damping characteristics of three-type resonators, a half-wave, a quarter-wave, and a Helmholtz resonator are studied experimentally by adopting linear acoustic test. A quantitative acoustic property of sound absorption coefficient in a model enclosure with the resonators is measured and thereby, the acoustic-damping capacity of a resonator is characterized. For a comparative study on acoustic damping, the damping capacity of a half-wave resonator is compared with that of the other resonators. A half-wave and a quarter-wave resonators have the same damping mechanism, but a quarter-wave resonator has much larger damping capacity than a half-wave resonator with the same diameter of a single resonator. It is found that shorter length of a resonator has the advantage of longer one with respect to the damping capacity. The damping capacity of a Helmholtz resonator increases with cavity volume and does as the orifice length decreases. A Helmholtz resonator has the highest damping capacity of three-type resonators and a half-wave resonator has the lowest. Besides, a Helmholtz resonator requires the smallest number of resonators for optimal damping. The design criterion of each resonator on the optimal damping is provided by the normalized parameter of open-area ratio and the similarity behavior for the optimal damping is observed for various enclosure diameters.     

HTPB固化交联体系在降低其推进剂燃速中的重要作用

本文研究了HTPB固化交联体系对其推进剂燃速的影响。实验发现,在固化交联体系中含MAPO的推进剂燃速要比用已三醇交联的推进剂燃速高18.4％。应用热分析、中止燃烧、电子扫描显微镜等实验方法,对其作用机理作了分析说明。     

近空间可变翼飞行器小翼切换滑模反步控制

针对近空间可变翼飞行器在小翼切换过程中存在参数不确定性的问题,设计了滑模控制和反步法相结合的控制方法以保证飞行器的跟踪性能。首先研究了近空间可变翼飞行器的纵向运动模型,在此基础上设计了速度和高度的反步控制器,同时采用动态面控制方法消除微分膨胀问题,然后结合滑模控制以增强控制器的跟踪性能,最后基于Lyapunov稳定性理论证明了系统的稳定性。仿真结果表明,在参数不确定性时滑模反步控制器能保证系统的稳定性和跟踪性能。     

国外EPDM老化性能简介

三元乙丙(EPDM)绝热烧蚀材料是一种新型的柔性绝热烧蚀材料,它在固体火箭发动机上正在获得越来越多的应用.它可用作火箭发动机燃烧室内绝热层,也可用作火箭发动机喷管收敛段及火箭的外绝热层.老化性能是材料的主要性能指标之一.它决定材料使用寿命及使用这种材料的产品寿命.固体推进火箭发动机对绝热烧蚀材料提出了相当高的要求,为使三元乙丙柔性绝热烧蚀材料在固体火箭发动机上获得广泛的应用,有必要对EPDM的老化性能有一个充分的认识.本文基于这个目的,对国外在EPDM胶料的老化、固化体系的影响;卤素有机化合物、抗氧剂的影响;以及火箭发动机用绝热层的老化等方面的研究作简要介绍,以提高我们对EPDM柔性绝热烧蚀材料老化性能的了解.