Subspace array processing for the suppression of FM jamming in GPS receivers

The mitigation of FM interference in GPS receivers is considered. In difference to commonly assumed wideband and narrowband interferers, the FM interferers are wideband, but instantaneously narrowband, and as such, have clear time-frequency (TF) signatures that are distinct from the GPS coarse acquisition (C/A) spread spectrum code. In the proposed technique, the estimate of the FM interference instantaneous frequency (IF) and the interference spatial signature are used to construct the spatiotemporal interference subspace. The IF estimates can be provided using existing effective linear or bilinear TF methods. The undesired signal arrival is suppressed by projecting the input data on the interference orthogonal subspace. With a multisensor receiver, the distinctions in both the spatial and TF signatures of signal arrivals allow effective interference suppressions. The deterministic nature of the signal model is considered and the known underlying structure of the GPS C/A code is utilized. We derive the receiver signal-to-interference-plus-noise ratio (SINR) under exact and perturbed IF values. The effect of IF estimation errors on both pseudorange measurements and navigation data recovery is analyzed. Simulation results comparing the receiver performances under IF errors in single and multiantenna GPS receivers are provided.     

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with primary goat embryonic fibroblast showed no difference from traditional feederlayer-based culture method used in mouse and human. The putative primary EG colonies were multilayer clumps ofcompact cel     

略论海峡两岸科技术语的对照和统一

为减少和消除海峡两岸科技文化交流上的词汇障碍，各学科广泛开展着科技术语的调查研究、交流和讨论。当前做法为两步走，首先是分析两岸用词上相同和差异的词目，共同编订对照本，共建对照和约定；然后逐步地通过对存在差异的个例进行选优汰劣和具体的商榷，过渡到更多的协调和一致。     

电子商务及其基本法律问题

本文简单阐述了电子商务的概念、模式、基本流程及其基本法律问题和目前的立法现状，弄清这些问题，无论是对于从事电子商务还是IT产业的经营、管理以及进行相关的科研开发，都具有十分重要的意义。     

计算机帧时间对半实物仿真的影响

半实物仿真试验中,要求计算机帧时间与计算积分步长相一致,但在实际试验中不容易精确地做到。本文分析了这种不一致给半实物仿真试验带来的影响,给出了解决的办法,文章中还给出了一实例来说明。     

Field formation around negatively biased solar arrays in the LEO-plasma

Heavy emission caused by impacting plasma ions results in a fast discharging effect of the initially large surface potentials on the dielectric solar cells. This eventually counteracts the energization process of the plasma ions to the cover glasses and leaves no significant electric fields. Thus, with an existing thermal plasma, electrons are again able to reach dielectric surfaces. Strong localized electric fields of the order of several 10 kV/cm form near the interconnector-cover glass interface.     

EUV emission from normal galaxies

Using data from the Wide Field Camera EUV all-sky survey, we have established upper limits to the EUV flux from a sample of 30 bright, nearby, non-active spiral galaxies. These galaxies were chosen to be those most likely to be detected in the EUV on the basis of (i) low interstellar absorption within our own galaxy, (ii) brightness in other wavebands, (iii) high star formation activity, and (iv) proximity. The derived EUV upper limits are restrictive, and establish for the first time that the EUV flux escaping from galaxies does not constitute a major component of their bolometric luminosity, and in particular that it cannot be the sink for the energy injected into the interstellar medium by supernova explosions, as had been suggested following the failure to detect this power in the X-ray band.     

A bistatic SAR mission for earth observation based on a small satellite

The authors present a new scientific space mission consisting of a satellite carrying a receiving- only SAR which receives the signal transmitted by the ENVISAT-1 SAR. The integration of ENVISAT-1 SAR and bistatic radar data offers an improved potentiality of surface classification, three-dimensional observation, and the opportunity of advanced scientific experiments in the field of bistatic scattering. The small satellite nominal orbit and the attitude manoeuvres are designed in order to maintain an adequate overlap between the two radar swaths along the whole orbit, taking into account the ENVISAT-1 attitude and pointing. A preliminary satellite design (2-year lifetime) is then performed to evaluate the orbit decay and to determine the appropriate orbit manoeuvres (every 4 days) to control the satellites relative phase. The numerical simulation shows that a spacecraft of about 584kg is able to meet the mission requirements.     

一类非线性边值问题的激波解

研究了一类非线性奇摄动方程。首先得到了外层解，利用特异极限阶定了激波层的几种可能位置，对激波层的几种不同位置利用伸长变量构造出内层解。最后利用匹配原则求出了原方程在整个区间上的渐进解。     

金融工程对我国国有银行信用风险管理的启示

多年来信用风险都是各国银行所面临的主要风险,由于历史的原因我国国有银行的信用风险管理问题显得更为突出.针对国有银行信用风险管理现状,引入最新的金融工程的方法和理念,从技术创新和制度创新的角度对国有银行的信用风险管理提出建议.