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551.
552.
郭方 《中国民航飞行学院学报》2012,(4):30-32
本设计主要基于全相参脉冲多普勒体制,并对气象雷达接收系统的部分组件进行了仿真设计和可靠性分析。难点是涉及的知识面广,专业领域包含雷达、结构、气象和电子等专业,设计难度高,特别是指标的分配与计算复杂。设计方案是在现有技术的基础之上,接收系统尽可能采用成熟的设计,并给出系统主要指标及一些组件的设计方案。设计的目标是得到C波段金相参多普勒天气雷达接收系统设计方案。 相似文献
553.
我国学者关于职教集团的研究综述 总被引:1,自引:0,他引:1
职教集团的发展目前备受关注,不少学者对其概念、性质、优势、理论基础、类型、组织结构、管理、发展策略等进行了研究.对这些研究成果进行综述,更有利于问题研究的进一步深入. 相似文献
554.
采用突发通信模式的低速直升机卫星通信链路同时存在周期性的旋翼遮挡和较大的多普勒动态,且需要工作在低信噪比下,这些特点对解调提出了很大挑战,需要研究高性能、低复杂度的突发解调方法.本文基于分散导频帧结构提出一种译码辅助解调方法.首先进行频偏分区预补偿,然后进行联合频率变化率估计的突发捕获,最后根据译码软输出目标函数,从多... 相似文献
555.
556.
Yaliu Ding Kohei Arai 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
A method for estimation of forest multiple light reflections depending on forest parameters is introduced, based on Monte-Carlo simulations of photon transport with experimental considerations. The model is verified through experiments with two miniature forests, in which two types of small-sized trees with ellipsoid- and cone-shaped crowns are arranged in a grid array. The introduced method was confronted with experimental measurements and showed small deviations from the measured values. It was found that the simulation of three-dimensional photon trajectories allowed a reliable evaluation of multiple light reflections among trees. In addition, the multiple reflections among trees due to the changes of tree inter-distance, crown type and crown shape were clarified with the proposed method. 相似文献
557.
A novel range-Doppler imaging algorithm with OFDM radar 总被引:1,自引:1,他引:0
《中国航空学报》2016,(2):492-501
Traditional pulse Doppler radar estimates the Doppler frequency by taking advantage of Doppler modulation over different pulses and usually it requires a few pulses to estimate the Doppler frequency. In this paper, a novel range-Doppler imaging algorithm based on single pulse with orthogonal frequency division multiplexing(OFDM) radar is proposed, where the OFDM pulse is composed of phase coded symbols. The Doppler frequency is estimated using one single pulse by utilizing Doppler modulation over different symbols, which remarkably increases the data update rate. Besides, it is shown that the range and Doppler estimations are completely independent and the well-known range-Doppler coupling effect does not exist. The effects of target movement on the performances of the proposed algorithm are also discussed and the results show that the algorithm is not sensitive to velocity. Performances of the proposed algorithm as well as comparisons with other range-Doppler algorithms are demonstrated via simulation experiments. 相似文献
558.
L.F. Chernogor K.P. Garmash Q. Guo V.T. Rozumenko Yu Zheng Y. Luo 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(8):2439-2469
The purpose of the present paper is to describe the observations of the variations in the parameters of HF radio waves propagating through the ionosphere when the action of the super typhoon Hagibis on 6–13 October 2019 occurred. The observations have been made with the Harbin Engineering University (the People's Republic of China) multi-frequency multiple path radio system involving the software-defined technology. The action of the super typhoon has been shown to be accompanied by enhanced atmospheric wave activity acting to generate wave processes with periods of 10 to 120 min. Coupling in the atmosphere–upper-atmosphere–ionosphere system has been confirmed to be carried out with atmospheric gravity waves. The ionosphere underwent the greatest impact on those days when the supertyphoon had maximum energy, on 8, 10, and especially 9 October 2019, and when it was found to be in an ~2,500–3,000-km distance range from the propagation path midpoints. Under the action of wave processes, the height of the reflection region was observed to oscillate within the ±(30–90 km) limits. The amplitude of the quasi-periodic variations in the ionospheric F-region electron density was estimated to be 10–12% for periods of ~20 min, and 30–60% for periods of ~60–120 min. The joint action of the dusk terminator and the supertyphoon has been confirmed to enhance wave activity in the ionosphere. Similar effects for the dawn terminator have not been detected. 相似文献
559.
George T.Schmidt 《中国航空学报》2015,28(1):1-10
Position, velocity, and timing(PVT) signals from the Global Positioning System(GPS)are used throughout the world but the availability and reliability of these signals in all environments has become a subject of concern for both civilian and military applications. This presentation summarizes recent advances in navigation sensor technology, including GPS, inertial, and other navigation aids that address these concerns. Also addressed are developments in sensor integration technology with several examples described, including the Bluefin-21 system mechanization. 相似文献
560.
250座级翼身融合无尾布局客机操稳特性设计研究 总被引:5,自引:2,他引:3
翼身融合(BWB)飞翼布局是未来新一代客机的热点方案之一,然而由于没有常规尾翼,面临着稳定性和操纵性方面的困难。为此,在一架250座级BWB客机布局设计研究基础上,根据平衡、增稳和机动等要求,设计了操纵面配置方案;根据适航要求和电传飞机飞行品质要求设定增稳目标,并将其直接纳入特征结构配置要求中,通过前向通道修正响应类型,保证获得与飞行阶段相适应的响应特征和满意的飞行品质参数;为了提高安全性,在增稳控制设计基础上,在指令回路增设了姿态保护和限制模块。研究结果表明, 该设计方案能够提供较合适的稳定性和操纵性,控制增稳后具有满意的飞行品质,保护模块可达到预期效果。 相似文献