基于802.11a的OFDM符号起始位置估计算法

OFDM(Orthogonal Frequency Divided Multiplication,正交频分复用)技术具有很高的频谱利用率和较好的抗多径衰落,在WLAN 802.11a/g,Wimax,高清数字电视广播和3Gpp-LTE等通信中都采用OFDM技术。OFDM通过循环前缀来抑制符号间干扰。基于802.11a无线帧结构,提出1种基于相关累加的OFDM符号起始位置估计算法,最大程度抑制OFDM符号间干扰(ISI,Inter Symbol Interfernce)。     

东北亚冷夏的年代际变化

通过对1881～2000年东北亚夏季气温的分析,发现东北亚夏季气温有明显的年代际变化,时间尺度为80年左右和30年左右;120年来东北亚共发生27次冷夏(平均气温距平≤-0.5°C),其中6次为严重冷夏(平均气温距平≤-1.0°C).通过对海平面气压场、对流层中层500 hPa高度场及海温场的分析,研究了东北亚冷夏的环流机制以及与SST异常的关系,指出东北亚夏季气温的年代际变化与大尺度环流特征及海温的变化关系密切.     

近30年江淮地区梅雨期降水的空间多型态特征

该文比较了不同站点分布情况下我国江淮地区梅雨期降水基本空间型态,发现较高分辨率的站点分布能得到更细化的空间型态。1979—2010年我国江淮地区梅雨期降水基本空间型态主要包括南部型、长江型和江淮型。年际变化上,梅雨期降水的南北反位相特征更加明显;而长江型梅雨期降水较其他两个型态而言相对独立。回归分析表明,3种降水型态所对应的东亚夏季风环流子系统的位置、季风经圈环流及梅雨期水汽输送等均存在明显差别,其中东亚太平洋遥相关型 (EAP) 和欧亚遥相关型 (EU) 对南部型降水有显著影响。1979年以来,前期赤道东太平洋海温主要影响我国长江流域和江南地区梅雨期降水,而江淮型梅雨期降水与热带海温没有显著的相关关系。     

An Early Paleozoic Inter‐Platform Shelf in the Southwest of Tarim Basin,NW China and its Significance for Petroleum Exploration

An early Paleozoic inter‐platform, platform, slope and shelf succession comprised of five Cambrian to mid‐Ordovician seismic sequences, has been identified in the southwestern part of the Tarim Basin. A previously unknown, elongate shelf succession that extends from east to west transects the Taxinan area of the southwestern Tarim Basin. It was flanked by carbonate platforms and platform margins, and by peri‐platform margin slopes on its north and south sides. The Markit platform margin and slope, located along the northern side of the shelf, extended nearly linearly west to east with some headlands and embayments towards the east. The Tangnan platform margin and slope, located along the southern side of the shelf, extended southwest to northeast and was more sinuous with pronounced northwest‐directed headlands flanked by embayments. Differentiation of these settings began in earliest Cambrian time during continental breakup. Initially, broad gentle slopes flanked an open shelf seaway in Cambrian time. In Early Ordovician time, the Markit and Tangnan platform margins became more distinct and rimmed, and were flanked by slightly steeper, but still very gentle slopes. During their deposition, these platform margins and their adjoining slopes exhibited some lateral migration, with a slight overall widening of the open shelf seaway between them from Cambrian to Ordovician time. The presence of these platform margin and slope successions in the southwestern area of the Tarim basin provides another focus for petroleum exploration and discovery of additional carbonate reef‐shoal reservoirs in the Markit and Tangnan areas. The adjoining deep‐water shelf shale and mudstone shelf succession itself is an additional prospective petroleum source rock in close proximity to these potential reef‐shoal reservoirs.     

定线水准测量平差软件的开发与应用

本软件主要为满足水利水电定线测量、公路测量及其他管线工程五等及图根水准测量数据在电脑中完成记录及平差计算,具有简单、方便、快捷等特点。     

A fuzzy–random analysis model for seismic performance of framed structures incorporating structural and non‐structural damage

Past earthquake experiences indicate that most buildings designed in accordance with modern seismic design codes could survive moderate‐to‐strong earthquakes; however, the financial loss due to repairing cost and the subsequent business interruption can be unacceptable. Designing building structures to meet desired performance targets has become a clear direction in future seismic design practice. As a matter of fact, the performance of buildings is affected by structural as well as non‐structural components, and involves numerous uncertainties. Therefore, appropriate probabilistic approach taking into account structural and non‐structural damages is required. This paper presents a fuzzy–random model for the performance reliability analysis of RC framed structures considering both structural and non‐structural damages. The limit state for each performance level is defined as an interval of inter‐storey drift ratios concerning, respectively, the non‐structural and structural damage with a membership function, while the relative importance of the two aspects is reflected through the use of an appropriate cost function. To illustrate the methodology, herein the non‐structural damage is represented by infill masonry walls. The probabilistic drift limits for RC components and masonry walls from the associated studies are employed to facilitate the demonstration of the proposed model in an example case study. The results are compared with those obtained using classical reliability model based on single‐threshold performance definition. The proposed model provides a good basis for incorporating different aspects into the performance assessment of a building system. Copyright © 2005 John Wiley & Sons, Ltd.     

夯实地基土的微结构特性及其对工程性质的影响

通过对地基土强夯前后的微观结构进行研究 ,从微结构角度解释了强夯时地基土的变形破坏机理。世纪花园高饱和度地基土由于存在粘粒及集聚体 ,强夯后使土的渗透性变差 ,超孔隙压力难以快速消散 ,致使土发生变形破坏。     

近期中国省际经济社会要素流动的空间特征

本文运用GIS空间分析和图形技术 ,就中国省 (区 )际人口迁移、铁路客流、航空客流、铁路货流、信件流等经济社会要素流动的空间特征进行综合分析。结果表明 :地区经济水平对要素流的形成与分布影响较大 ,京津唐、沪苏浙和广东构成了要素流的三大核心 ;要素流呈现为 4种基本空间型态和两类空间模式 ;各要素流的空间分布很不均衡 ,流量重心大幅偏离我国国土几何重心 ,但与人口和经济分布重心吻合度较高。     

2014年鲁甸6.5级地震震前TEC异常分析

2014年8月3日云南省鲁甸发生了6.5级地震.针对震前电离层异常问题,利用IGS提供的全球电离层数据,采用滑动四分位法对鲁甸地震震中及其周围格网点的TEC进行异常探测,发现震前3d、6d和13 d电离层有明显的异常,其中震前3d、6d的异常最为显著.在进一步分析了太阳地磁活动及这几天的全球TEC异常分布后,认为这3d的电离层异常可能与震前的孕育地震有关.另外,这3d的TEC异常分布区域都满足在经度方向跨度和纬度方向跨度长度比约为3:1,且异常的峰值点并不位于震中的正上方,而是位于震中偏向赤道方向,同时赤道共轭区域也存在异常,但范围和幅度都较小.     

桐柏地区新城-应山韧性剪切带研究

研究了桐柏地区新城—应山韧性剪切带的变形特征、动力学成因机制,并根据横切韧性剪切带的３条剖面的变形特征,认为中生代华北、扬子两大板块陆陆碰撞的动力来自扬子板块。