Surface composition and electronic structure of Ni2+xMn1−xGa studied by X-ray photoelectron spectroscopy

The surface of Ni_2+xMn_1−xGa have been studied using X-ray photoelectron spectroscopy under different conditions of surface preparation. We find that the surface becomes Ni rich by argon ion sputtering. However, the change in surface composition due to sputtering can be reverted by annealing at appropriate temperature so that the bulk composition is restored at the surface. The origin of a satellite feature observed both in the valence band and the Ni 2p core-level spectra is discussed. The magnetic microstructures at the surface have been observed by using magnetic force microscopy.     

工作在卫星链路上的STU—Ⅲ

本文描述语音处理技术在STU—Ⅲ保密电话机中的应用以及STU—Ⅲ应用到卫星链路上的接口和试验。     

多馈源卫星接收天线的设计和应用

阐述了设计多馈源卫星地面接收天线的必要性、可行性和基本原理，以及对推导出的确定焦点的基本公式及工程实用化公式的正确性进行了验证，对应用中安装调试方面的问题也进行了探讨。     

战斗互联网通信体系的研究

根据现代战争的要求和特点,提出了战斗互联网的通信体系,从网络结构、协议结构和通信手段等方面进行了分析和性能评估。     

Variation of Satellite Intensity Factors with n in the 1s~2s∈lc→1s~23dnl→1s~2pnl Dielectronic Recombination of Lithiumlike Ions

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Efficient modulation techniques for satellite telemetry—receiver design and performance evaluation

In this paper we address the design of the data demodulator for high-efficiency satellite communications suited for telemetry applications. We choose Gaussian minimum shift keying as the modulation format and analyse its relative merits with respect to the more traditional filtered offset quadrature phase-shift keying scheme, when applied to medium-to-high data rate telemetry. Our study encompasses both geostationary orbits and the more challenging low earth orbit scenarios, and investigates the acquisition and tracking performance of the receiver with the aid of computer simulations. In particular, we present design criteria leading to the development of efficient, low-complexity schemes for symbol timing and carrier phase/frequency recovery and we analyse the impact of these synchronization algorithms on the system performance. Next, we discuss the demodulator performance degradation when the transmitted signal is passed through on-board solid-state or travelling-wave-tube power amplifiers. The paper is concluded by a comparative analysis of the above modulation schemes, with special emphasis on their power and spectral efficiency.     

UHF机载卫星通信系统设计

本文以ＳＡＴＣＯＭ系统机载通信为例，介绍发机载卫星通信系统的设计思想，以及提高通信链路容限所采用的技术。     

Massive-scale visual information retrieval towards city residential environment surveillance

Urban residential environment surveillance plays an important role in modern intelligent city. Satellite images have been applied in various fields, and the analysis and processing of satellite images has become an important means to obtain the information perceived by satellites. This paper focuses on city residential environment surveillance based on massive-scale visual information retrieval. Since the shortcomings of low contrast, blurred boundary, large amount of information and susceptibility to noise, the performance of satellite image segmentation is not satisfactory, which will affect residential environment surveillance. We design an improved rough set fuzzy C-means clustering algorithm combined with ant colony algorithm. More specifically, satellite images are classified based on the gradient of pixels according to the indistinguishable relation of the image combined with rough set theory. Then, the traditional fuzzy set-based fuzzy C-means clustering algorithm is applied to the satellite image segmentation technology. Subsequently, the improved algorithm-quantum ant colony algorithm and rough set fuzzy clustering C-means algorithm are combined to achieve accurate segmentation of satellite images. Afterwards, we propose a satellite image retrieval algorithm, which can assist city residential environment surveillance. Comprehensive experiment show that our proposed method is effective and robust in residential environment surveillance.     

卫星导航授时信号的抗干扰和欺骗检测技术综述

随着全球卫星导航系统在经济、军事、国防、民生等领域的广泛发展,提高卫星导航系统的可靠性、安全性和鲁棒性成为当今研究的热点。本文介绍了卫星干扰信号的类型以及相对应的抗干扰和欺骗检测技术,在此基础上分析比较了各个技术的优缺点、实现难度和抗干扰效果,最后对未来研究的重点和方向进行了展望。