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471.
472.
Effect of the seed perturbation amplitude on the equatorial spread F initiation during solar minimum
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(1):255-267
The contribution of gravity wave (GW) to the initiation/development of spread F during a solar minimum year was investigated through the comparison of the observed precursory parameters and characteristics of the corresponding equatorial spread F (ESF) events. The ionospheric parameters were recorded at the magnetic equatorial station Sao Luis (2.3°S, 44°W, dip latitude 2°S) during March and October 2010. These data were used to estimate the influence of the relative gravity wave amplitude and the ambient ionospheric condition on the diurnal variation of the spread F initiation. The vertical velocity drift indicated a clear control and defines the threshold for the seasonal variability of the ESF occurrence. However, it was insufficient to solely determine or predict the day to day variation of ESF occurrence. Thus, few days with contrasting ambient ionospheric condition and magnitude of GW amplitude were analysed in order to investigate the role of the different precursory factors in the observed diurnal variation of the plasma irregularity development. The density scale length and gravity wave amplitude were shown to immensely contribute to the linear instability growth rate, especially during the days with a low post-sunset rise. Thus, the experimental observations have demonstrated the strong inter-dependence between the precursory factors and they have also highlighted the probable control of the ESF morphology. 相似文献
473.
474.
This paper intends to provide theoretical basis for matching design of hydraulic load simulator (HLS) with aerocraft actuator in hardware-in-loop test, which is expected to help actuator designers overcome the obstacles in putting forward appropriate requirements of HLS. Traditional research overemphasizes the optimization of parameters and methods for HLS controllers. It lacks deliberation because experimental results and project experiences indicate different ultimate performance of a specific HLS. When the actuator paired with this HLS is replaced, the dynamic response and tracing precision of this HLS also change, and sometimes the whole system goes so far as to lose control. Based on the influence analysis of the preceding phenomena, a theory about matching design of aerocraft actuator with HLS is presented, together with two paired new concepts of "Standard Actuator" and "Standard HLS". Further research leads to seven important conclusions of matching design, which suggest that appropriate stiffness and output torque of HLS should be carefully designed and chosen for an actuator. Simulation results strongly support that the proposed principle of matching design can be anticipated to be one of the design criteria for HLS, and successfully used to explain experimental phenomena and project experiences. 相似文献
475.
476.
TMS320VC5402是由TI公司生产的性价比极高的定点DSP芯片。主要研究了基于TMS320VC5402的最小系统板的软硬件设计。针对电源电路、复位电路、时钟电路、JTAG接口电路、DSP芯片电路提出可行的设计方案。同时,给出了一个点亮LED灯的完整汇编源代码。 相似文献
477.
478.
"生态、智能、休闲、商务"8个字,是廊坊城市发展的核心定位。在廊坊城市蓬勃发展的同时,社会各界对政府在承担公共管理责任中是否进行有效管理,其效率和效果由谁来评价,以及怎么评价政府绩效等问题的关注程度越来越高,也越来越迫切。基于此,本文以政府绩效管理内涵入手,分析廊坊市政府绩效管理的发展现状以及存在的主要问题,进而探讨在打造廊坊生态、智能、休闲、商务之城中如何构建政府绩效管理体系,并提出相关改进措施。 相似文献
479.
是贤珠 《民用飞机设计与研究》2012,(1):61-65
由于反推力系统必须在模拟气动载荷下做试验,以验证反推力系统功能的安全可靠性。因此在液压系统地面模拟试验中需配置一套反推力装置加载系统,以实现对反推力在展开和收起过程中所受气动载荷的模拟。在简要介绍反推力系统及其加载系统的基础上,主要研究如何完成某型飞机反推力装置加载试验,并满足其性能要求。 相似文献
480.
Li Wei Li Chunsheng 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
As a promising new technology emerged in recent years, the Distributed Satellite-borne SAR (DSS) system with Interferometric Synthetic Aperture Radar (InSAR) imaging capability has been recognized by the remote sensing community as an integrated part of the spaceborne earth observation system. However, most researches on DSS were focused on individual aspects of system design/analysis and data processing, while few studies have been dedicated to establishing a standard methodological framework for universal DSS system design. Aiming at this problem, the topics of DSS system error analysis and design method are investigated in this paper. Firstly, a rigorous error propagation model of height measurement is theoretically derived from the DSS InSAR imaging geometry, and the impact of each error sources in this model on the height measurement accuracy is analyzed individually. In particular, the baseline length and its measurement error in the InSAR imaging plane are identified as the dominant factors. Second, a new method for DSS system design is proposed based on our analyses with the error propagation model. This method consists of two important phases, namely collaboration design and monostatic design. The major objective of collaboration design is to determine the configuration and parameters for the coordination between satellites in the DSS system. Afterwards, the key parameters for single satellite and the payload are determined by the monostatic design. Thirdly, a system performance analysis method is developed to comprehensively evaluate the performance of the pre-designed DSS system. In the next section, a typical example of DSS system design is given to demonstrate the effectiveness of the proposed system design and analysis methods. The target DSS system has the same goal and hardware configuration as the TanDEM-X mission. Finally, the conclusion is drawn with our major findings are presented. 相似文献