Comparison of Achievable Rates of OFDM and Single Carrier Communication Systems

This paper presents a theoretical comparison of a single carrier system and a multi-carrier system through an analysis of the achievable rate under frequency selective fading with channel state information at the receiver. A scheme was designed to compare the achievable rates of a single carrier system and an Or-thogonal Frequency Division Multiplexing (OFDM) system. A thorough theoretical analysis of the two-path channel was conducted, and simulations were also used to analyze practical stochastic channels. Analysis and simulation results show that the achievable rates of the two approaches are comparable when the channel is flat fading. However, when the channel is frequency selective fading, the single carrier system outperforms the OFDM system. The achievable rate of the OFDM system is about 10% lower than that of the single carrier system at higher SNRs.     

从价格的演变历程浅析国内民航运输价格改革

从价格的演变历程入手,对目前民航客运价格存在的问题及成因进行初步分析,提出价格改革的思路,进而促进相关垄断行业的改革与发展.     

基于真假设比例广义推断的多重检验方法

研究了多重假设检验方法的改进问题,基于真假设所占比例的广义推断,利用其广义置信上限对现有的多重假设检验方法进行改进.该方法更好地利用了水平,在功效上有很大提升.采用广义推断方法,即使在假设个数比较小时,也能对真假设所占比例做出较好推断.模拟结果表明,该方法显著提高了传统方法的功效.     

Zircon U-Pb ages of granites at Changba and Huangzhuguan in western Qinling and implications for source nature

Mesozoic granitoids are widespread in the Qinling-Dabie-Sulu orogenic belt. Precise U-Pb dating on these granitoids can reveal the evolution of the continental collision orogen and thus provide information on the nature of magma sources. This study presents zircon LA-ICP-MS U-Pb dating and whole-rock geochemical analyses for two intrusions at Changba and Huangzhuguan in western Qinling. Zircon U-Pb ages for central and marginal phases of the Huangzhuguang intrusion are 214±1 Ma and 213±3 Ma, respectively. Zircons from the Changba intrusion yield a dominant cluster with an U-Pb age of 213±2 Ma. Collectively, these ages are younger than ages of 220 to 240 Ma for ultrahigh-pressure metamorphism due to the continental collision between the South China Block and the North China Block, corresponding to syn-exhumation magmatism. Some inherited zircons occur in the Changba intrusion, yielding a weighted mean of ²⁰⁶Pb/²³⁸U ages at 757±14 Ma. This indicates that the Changba intrusion has the crustal source of mid-Neoproterozoic ages and a tectonic affinity to the South China Block. Geochemically, the two intrusuons are both rich in LILE and LREE but depleted in HFSE and HREE, similar to arc-type igneous rocks. The Huangzhuguang intrusion exhibits linear correlations between SiO₂ and the other major oxides, implying chemical evolution from a cognate magma source. It contains mafic enclaves, suggesting possible mixing of felsic-mafic magmas. The Changba granite is rich in Si and K but poor in Fe and Mg as well as has a high value of Fe*, suggesting strong differentiation of granitic magma. Therefore, the two intrusions were derived from the Late Triassic anatexis of the continental crust of different compositions in the northern margin of South China Block. This process may be coupled with exhumation of the subducted continental crust in the stage of late collision.     

浅谈高速公路涵洞施工工艺

涵洞施工是公路建设的一个重要组成部分,为了使人工和机械得到合理的运用,提高施工效率、保证施工质量,在施工期间应考虑很多因素,才能使涵洞施工技术有一个新的发展。     

黑龙江七星河国家级湿地自然保护区生态旅游开发的SWOT分析

采用SWOT分析法较为详细地分析了七星河国家级湿地自然保护区发展生态旅游业的优势、弱势、机遇和威胁。得出黑龙江七星国家级河湿地自然保护区不仅具备景观资源独特、动植物资源丰富、旅游环境优越等开展湿地生态旅游的先决条件,而且拥有国内外生态旅游发展的有利形势和地方政策大力支持的大好机遇;但同时存在湿地保护和专业人员匮乏、旅游...     

拱桥加固实例

根据仁义桥的基本情况,文章从加固技术标准、加固方法、加固顺序、加固主要材料及注意事项等方面,对拱桥的施工方案进行了介绍。     

大学生自我同一性与亲密感相关研究——以福州市四所高校抽样问卷为例

采用问卷法对福州市四所高校300名大学生进行随机调查。结果表明：1）有恋爱经验的大学生在自我同一性的承诺及探索因子上的得分均高于从未恋爱组,但无显著差异。2）成人依恋中回避和焦虑因子的得分在不同同一性状态之间均不存在显著差异。但进一步比较发现,早闭型在焦虑因子上的得分显著低于延缓型。3）大学生成人依恋中的焦虑及回避因子与自我同一性的承诺因子都存在显著负相关,且承诺因子是焦虑与回避的有效预测变量;而成人依恋与探索因子尚不存在相关,但探索因子对成人依恋的焦虑具有预测作用。     

一种适用于军事MANET的服务查找算法

因为高效、负载均衡及可扩展性强等特点,Chord服务查找算法在Internet中得到了成功的应用。然而研究表明,在带宽受限、信道质量差的移动Ad-hoc网络(MANET)中,Chord算法的性能会明显下降。长期以来,人们主要在民用MANET中对Chord算法进行了改进,而对军事MANET的关注很少。为改善Chord算法在军事MANET中的性能,从优化建环过程,改善Finger表和适当增加冗余查找信息三方面对Chord算法进行了改进,提出了一种新的适用于军事MANET环境的MM-Chord(MILITARYMANET Chord)算法。仿真结果与分析表明,MM-Chord算法不仅在查找成功率和查找时延两个关键性能方面明显优于Chord算法,而且比Chord算法具有更好的可扩展性。     

论信息系统项目人力资源管理

人力资源的最终目的是建设一个团结高效的团队,以达到项目成功.因此,需根据需求层次建立多种激励方式,利用多种方式加强绩效考核；加强人员培训,把培训贯穿于项目的始终,以培养团队为目标；根据个人情况,按性格、能力、经验分配相应的工作.