复杂环境下的A/C模式信号处理算法及其实现

本文基于软件无线电的思想,提出一种复杂环境下的A/C模式信号处理算法,该算法从脉冲识别,A/C模式框架判决以及信息代码提取三个方面进行了研究,在识别多目标混叠、拒绝目标幻影,避免异步串扰方面,达到了较好的效果,并在FPGA上实现了该算法.     

空间站物资标签高可靠性编码方案

文章提出了一种用于空间站物资管理的RFID（Radio Frequency Identification）系统电子标签信息编码方案。在该方案中,对电子标签中存储的物资基本信息进行纠错编码,从而增强了信息的可靠性。理论分析表明,与存储更多物资基本信息的原始方案相比,在相同条件下,采用合适的纠错码,新方案的信息可靠性更高。数值仿真结果与理论分析结果相吻合。     

一种软件科斯塔斯环的模型建立与实现

文章通过双线性变换法建立了科斯塔斯环的Z域模型,分析了Z域模型下环路各项性能指标和环路参数之间的关系,系统总结了设计步骤和参数的选择方法。试验仿真结果证明捕获与跟踪性能符合理论分析。最后给出了科斯塔斯环在FPGA中的硬件实现结构。     

浅谈奥米加导航系统的位置误差

奥米加导航系统是一种全球性导航系统.在一般天气条件下,该系统具有良好的导航性能,但是在复杂天气条件下,也暴露出了一些缺点或不足。本文针对使用中出现的问题,根据其工作特性、信号格式、信息处理、定位计算,误差处理方式进行一些理论分析,并对改进系统操作进行一些探索。     

Particle Acceleration by the Sun: Electrons, Hard X-rays/Gamma-rays

Observations of hard X-ray (HXR)/γ-ray continuum and γ-ray lines produced by energetic electrons and ions, respectively, colliding with the solar atmosphere, have shown that large solar flares can accelerate ions up to many GeV and electrons up to hundreds of MeV. Solar energetic particles (SEPs) are observed by spacecraft near 1 AU and by ground-based instrumentation to extend up to similar energies, but it appears that a different acceleration process, one associated with fast Coronal Mass Ejections (CMEs) is responsible. Much weaker SEP events are observed that are generally rich in electrons, ³He, and heavy elements. The energetic particles in these events appear to be similar to those accelerated in flares. The Ramaty High Energy Solar Spectroscopic Imager (RHESSI) mission provides high-resolution spectroscopy and imaging of flare HXRs and γ-rays. The observations of the location, energy spectra, and composition of the flare accelerated energetic particles at the Sun strongly imply that the acceleration is closely related to the magnetic reconnection that releases the energy in solar flares. Here preliminary comparisons of the RHESSI observations with observations of both energetic electrons and ions near 1 AU are reviewed, and the implications for the particle acceleration and escape processes are discussed.     

Global monitoring of tropospheric water vapor with GPS radio occultation aboard CHAMP

The global positioning system radio occultation (GPS RO) technique provides a powerful tool for atmospheric sounding which requires no calibration, is not affected by clouds, aerosols or precipitation, and provides an almost uniform global coverage. The paper deals with application of GPS RO measurements from CHAllenging Minisatellite Payload (CHAMP) for the retrieval of tropospheric water vapor profiles. CHAMP RO data are available since 2001 with up to 200 high resolution atmospheric profiles per day. We introduce a new direct method for water vapor retrieval from GPS RO data. Additionally, a 1Dvar algorithm is used for this purpose. The so derived CHAMP water vapor profiles are validated with radiosonde data on a global scale. Here, both methods come to statistically comparable results revealing a negative bias of less than 0.1 g/kg and a standard deviation of less than 1 g/kg specific humidity in the mid troposphere. Potentials of CHAMP RO retrievals for monitoring the mean tropospheric water vapor distribution on a global scale are presented.     

基于乘波体的高超音速运载器气动布局设计

采用基于无粘锥形流的反设计方法以Ma=6为设计点设计具有高升阻比的乘波体外形;取基准圆锥激波角为12°,并利用上表面的膨胀降压作用,这一外形优化有效提高了乘波体的升阻特性,在考虑粘性影响的情况下Ma=6时的升阻比可从3.356?3提高到4.598?1;将具有高升低阻效能的乘波体作为机身初步设计单级入轨运载器布局,通过数值模拟的方法进行研究,结果表明布局在大速度范围内的升阻比得到了令人满意的结果,同时具备静稳定性.     

大功率无线电波与低电离层的相互作用

地面入射的大功率无线电波能加热电离层等离子体，引起电离层电子温度和密度的扰动，实现电离层的地面人工变态．本文中，着重考虑电波和电离层相互作用过程中的自吸收，构造一个自治的相互作用模型，在一定功率和频率的加热电波作用下，利用该模型计算了白天低电离层电子温度和由温度的变化而引起的电子密度的变化．计算结果表明，在白天低电离层，电波的自吸收在90km以下比较显著，而最大温度变化在70km高度上，大约增加了2倍．在α复合的假设下，电子密度变化幅度随高度的增加而减少，在70km处，大约增加55％、120km处则为4％左右．     

快变分量观测与基本分量特性

本文对太阳２２周峰年期云南天文台日冕射电频谱仪观测到的６０个快速事件作了分析。从中获得了尖峰辐射、增强噪暴、快速起伏、类尖峰、叠加脉冲五种快变型别，对它们的亮温度、叠加特性、特征时间、辐射源尺度、偏振特性以及辐射机制六个方面作了分析研究后，对射电爆发、缓变分量和宁静太阳的辐射特征参量也作了研究，从而得出基本分量特性。     

Measurements of the 12C/13C Ratio in Planetary Nebulae and Implications for Stellar Evolution

We present the results of a study aimed at determining the 12C/13C ratio in two samples of planetary nebulae (PNe) by means of mm-wave observations of 12CO and 13CO. The first group includes six PNe which have been observed in the 3He+ hyperfine transition; the other group consists of 23 nebulae with rich molecular envelopes. We have determined the isotopic ratio in 14 objects and the results indicate a range of values between 9 and 23. In particular, three PNe have ratios well below the value predicted by standard evolutionary models ( 20), indicating that some extra-mixing process has occurred in these stars. We briefly discuss the implications of our results for standard and nonstandard stellar nucleosynthesis.