Key Technology in Physical Layer of WiMAX System

随着无线通信中语音业务、数据业务和多媒体业务日益增加，在传输速率、服务质量和系统业务容量等方面的要求与日俱增，因而需要先进的无线通信技术以提高频谱利用效率和链路可靠性。宽带化、无线化已成为接入网的发展方向。 宽带接入方式可分为无线接入和有线接入两种，近年来摆脱了有线束缚，满足人们自由接入的宽带无线接入（BWA）技术越来越引人注目，已成为新技术的热点，有着广阔的发展前景。由IEEE802.16工作组制定的WiMAX无线宽带接入技术更是为众多运营商、设备厂商所青睐。WiMAX物理层采用的是正交频分复用（0FDM）技术。 OFDM是一种多载波数字通信调制技术，它具有频谱利用率高和可对抗多径时延扩...With the growing requirement of voice services, data services and multimedia services in the wireless communication, high data rate, QoS and channel capacity are increasingly necessary, which promote people to improve the spectrum efficiency and stability of the link. So the development of broadband access network focuses on two trends as broadband and wireless. Broadband access technology is divi...学位：理学硕士院系专业：信息科学与技术学院电子工程系_无线电物理学号：20043000

The abundance and diversity of nanoplankton in Arcitic Ocean

近年来随着全球气候变化对北冰洋生态环境的影响日益显现,北极微型浮游生物生态学研究得到了广泛的重视和实质性的进展。对北冰洋微型浮游生物的主要类群:异养细菌、古菌、光合异养原核生物和微型真核生物的分布及其多样性研究进展做了概述,并在此基础上展望了未来北冰洋微型浮游生物学研究。Asthe most abundant and the most taxonomically and genetically diverse organisms in the marine ceosystem,nanoplankton predominate in the marine system concerning their bioactivity,biomass,and production.They play an important role in the carbon fixation process in the Arctic Ocean,and are an important component to regulate the biosphere.Furtherly,nanoplankton can be an important indicator of the changing environment,since the changes in the community,structure and biomass of nanoplankton reflect the changes in the pathways of nutrient and energy transferring in the food web and the changes in the biogeochemical cycle.Recently,ecology study of the Arctic nanoplankton has been paid more attention due to the increasing impacts of climate change on the Arctic marine ecosystems.Substantial progress has been achieved.The Arctic heterotrophic bacteria were reported to resemble those in the seas of lower altitudes in their high abundance and biomass with seasonal successions.Particle-associated bacteria often show a higher specific metabolic activity than the free-living communities.So far,there are few reports on the proteorhodopsin(PR)-containing bacteria.High diversity has been reported for this group in the Chukchi Sea,which can be attribute to yariable bacteria communities.A large number of aerobic anoxygenic phototrophic(AAP) bacteria have been found in the Chukchi Sea with a distinctly seasonal succession.The photosynthetic group in the Arctic Ocean was found to be mostly composed with the nanoplankton(≤20μm),described as a polar ecotype of the small prasinophyte Micromonas.The high correlation between the abundance of coccoid cynaobacteria and temperature results their low abundance at the high latitudes There are only a few studies of Synechococcus in the coastal Arctic Ocean.The Micromonas is proved to be ubiquitous throughout the Arctic Ocean,especially at the chlorophyll-maximum layer,and may be a major contributor to the primary production in the Arctic Ocean.Until now little is known about the distribution of heterotrophic nanoflagellates in the Arctic Ocean,compared with phytoplankton and prokaryotes.Many scientific questions,which deserve special attention,remain unsolved due to lack of continuous sampling and the complexity of the nanoplankton characteristics.Some of them have been highlighted here in the Arctic nanoplankton ecology.(1) More attention should be paid to the effect of the climate change on the nanoplankton community in the Arctic Ocean,considering its major and often dominant contribution to the total ecosystem.(2)Most of the investigations of nanoplankton community are focused on the Atlantic Arctic Ocean of the Arctic Ocean.It is necessary to investigate the community structure of the nanoplankton in the entire Arctic Ocean.(3) As a photoheterotrophic microbe,AAP bacteria may play a special role in the ecology in the Arctic Ocean.However,little is known about the distribution,abundance,and diversity of the AAP bacteria in Arctic Ocean.(4)Archaea seems to be of special significance in the Arctic waters with large population existing in the surface water.More work need to be done on their diversity and their functions in the energy flow.国家自然科学基金(40576002;41076130);国家海洋局青年基金项目(2010116

毕赤酵母分泌表达嵌合HEV表位的HBcAg颗粒

在毕赤酵母分泌表达嵌合有HEV受体相关表位12A10的HBcAg蛋白,经甲醇诱导后的培养液上清通过切向流浓缩、更换缓冲液后,进行疏水层析纯化.CsCl等密度梯度离心测得分泌的重组颗粒的密度为1.32 g/mL.透射电镜观察显示,纯化的重组颗粒为均一的直径30 nm左右的空心颗粒.小鼠免疫实验表明,纯化颗粒免疫8周后鼠血清中的特异性12A10抗体滴度可达到1.6×105,并且重组颗粒较好地呈递了HEV受体相关的非免疫优势表位.本文的结果为毕赤酵母胞外分泌表达其它大尺度的重组蛋白颗粒提供了参考,为研究携带表位多肽的疫苗载体提供了范例

Research and Analysis on Energy-Efficient MAC Protocols for Ad Hoc Networks

为了解决自组织网节点供电不足的问题,在MAC接入方式的算法上进行改进是有必要的。从功率控制和能量管理两个方面,讨论自组织网几种典型的MAC层节能协议,分析这些算法减少功耗的能力以及在这些协议下自组织网络的吞吐量、时延等网络性能,并指出他们的优势和局限性,最后给出了结论。To solve the problem of inadequate power supply of ad-hoc network nodes,it is necessary to improve the algorithm in the MAC layer.In this paper,several typical MAC layer protocols for Ad Hoc networks are discussed from energy management to power control.We analyze the ability of reducing consumption of these algorithms and also the network performance such as network throughput,transmission delay,and note their advantages as well as the limitations.The conclusions are given in the end

Modeling and Analysis of MANET

简要介绍了自组织网络相比于传统蜂窝网络的优点和研究难点,阐述了基于IEEE 802.11的移动Ad Hoc网络的MAC层的工作原理并从数学理论上分析了吞吐量,接着介绍了软件建模的流程,并给出了理论与仿真的比较分析,同时获得基于IEEE 802.11的MANET吞吐量的最大值以及达到该最大值时网络所承受的业务量的理论值和实际值。The advantages and challenge of Ad Hoc network would be introduced first.Then the principle of MAC of MANET based on IEEE 802.11 will be presented.Meanwhile the theoretic throughput of the network is analyzed.Finally,the process of modeling and analyzing data will be put forward.The situation and value of maximal throughput of the MANET will be acquired.美国高通公司无线通信研究基金资

卒中后失眠的研究进展 Research Progress of Insomnia after Stroke

卒中后失眠是在卒中后首次出现并达到失眠诊断标准的一组临床综合征，与临床常见失眠相类似，主要表现为睡眠深度异常和平均每晚睡眠时间少于6 h。meta分析显示，卒中急性期、亚急性期及恢复期患者符合失眠障碍诊断标准的比例分别为32.5%、34.8%和37.1%。卒中后失眠不仅增加了卒中死亡及复发风险，而且对卒中康复与预后造成不利影响。本文对卒中后失眠的发病情况、发病机制及治疗等进行综述，以便为临床实践提供信息，并为卒中后失眠提供针对性干预治疗措施。 Abstract: Post stroke insomnia (PSI) is a group of clinical syndromes that first appear after a stroke and meet the diagnostic criteria for insomnia. Similar to common clinical insomnia, the main manifestations are abnormal sleep depth and average sleep time less than 6 hours per night. Meta-analysis showed that 32.5%, 34.8% and 37.1% of patients in acute, subacute and convalescent stages of stroke met the diagnostic criteria for insomnia disorders, respectively. PSI not only increases the risk of stroke death and recurrence, but also has adverse effects on stroke rehabilitation and prognosis. This paper reviews the incidence, pathogenesis, and treatment of insomnia after stroke, in order to provide information for clinical practice and provide targeted intervention and treatment measures for insomnia after stroke

具有可见光活性的TiO_2薄膜的制备及光催化性能

运用磁控溅射技术在浸渍－提拉法制得的TiO2薄膜上溅射三氧化钨层得到光催化薄膜。采用SEM、XRD、AES、UV－vis漫反射光谱等方法表征催化剂薄膜的厚度、晶相结构、化学元素组成及光吸收性能。以甲基橙的光催化降解为反应模型，高压汞灯为光源，溅射有三氧化钨薄膜的光催化活性低于纯TiO2薄膜；滤过紫外光后，溅射有三化钨的薄膜光催化活性明显高于纯TiO2薄膜。本实验提供了一种制备高可见光活性的TiO2薄膜的方法

基于二进制编码多导频搜索的导频设计

针对正交频分复用(OFDM)系统中的稀疏信道估计问题，文章提出了一种基于二进制编码的多导频并行搜索导频设计算法。文章所提算法在最小互不相干性(MIP)规则下，通过最小化字典矩阵的相干性来考虑确定性导频设计问题，并要求将导频分配放在有效子载波范围内以实现更实际的目的。导频集在文章所提算法中是二进制编码的。在每次迭代中，将二进制编码段的序列重新组合，以更新近似最优导频位置。某些编码段的更新可以同时改变多个导频位置，既增加了导频的多样性，又降低了计算的复杂度。实验结果表明，与现有导频优化方法相比，文章所提算法可以找到更小的MIP测量矩阵，相应的导频模式可以显著提高信道估计的性能