最速下降法在半盲信道估计中的应用

 信道估计是无线通信中的基本问题.介绍了一种适用于静态多径信道的参数建模的半盲信道估计方法.该方法根据SRM准则推导出代价函数,而后又分两步求解:首先通过线性搜索定位粗略的估计值,再用最速下降法改善估计精度.计算机仿真表明,建议的最速下降法所需迭代次数少于高斯牛顿法,且显著减少计算量,缩短运行时间.     

基于导频辅助的单载波空时分组编码传输技术

研究了频率选择性衰落信道中采用2个发送天线1个接收天线的单载波Alamouti空时分组编码数据块传输技术．在传输系统发射端利用导频符号辅助的思想设计出伪噪声PN导频序列和信息数据的排布结构;接收端一方面利用导频PN序列循环相关的信道估计算法获得信道冲激响应估值,另一方面采用干扰抵消技术消除导频序列对接收信息数据的影响,之后引入单载波频域均衡技术对接收数据进行处理以克服信道的频率选择性衰落．仿真结果表明,这种基于导频辅助的单载波空时分组编码传输系统相对于单天线传输系统获得了空时结构所带来的全速率下的最大分集增益,具有比Alamouti空时分组编码与OFDM相结合的传输系统更高的数据传输效率和更好的系统性能．     

3．5GHz频段城市环境下的宽带无线信道测量分析

研究了在典型城市室外环境下的3·5GHz无线信道的小尺度传播特性,构建了一个用于信道测量的测量系统,完成了固定与移动场景下的信道测量,得出了功率延迟分布(PDP)、抽头延迟线模型、多径分布和莱斯K因子等参数,测量结果证明该环境提供了多天线无线通信所需要的富散射环境.     

基于几何模型的MIMO衰落信道相关性分析

针对非频率选择性Rice衰落MIMO移动信道的特点,提出一个MIMO衰落信道的几何模型,并据此推导出空时联合相关函数.理论分析和仿真结果表明,新的空时相关函数能准确地反映天线间距等因素对MIMO信道各链路间存在的相关性的影响,且形式更简洁.     

无线通信系统中基于线性变换的多用户发送分集

研究了蜂窝通信系统中基站同时与N个移动用户通信时一种新的发送分集方法。该方法将N个用户的信源信号在发送端采用线性变换进行联合编码后送入N个独立信道进行传送。分集发送信号经衰落信道传送后,对每一个信号接收者,其收到的信号可以表示成格型码的形式,可以使用球型译码算法进行信号解调     

Synthesis and fading of eighteenth‐century Prussian blue pigments: a combined study by spectroscopic and diffractive techniques using laboratory and synchrotron radiation sources

Prussian blue, a hydrated iron(III) hexacyanoferrate(II) complex, is a synthetic pigment discovered in Berlin in 1704. Because of both its highly intense color and its low cost, Prussian blue was widely used as a pigment in paintings until the 1970s. The early preparative methods were rapidly recognized as a contributory factor in the fading of the pigment, a fading already known by the mid‐eighteenth century. Herein two typical eighteenth‐century empirical recipes have been reproduced and the resulting pigment analyzed to better understand the reasons for this fading. X‐ray absorption and Mössbauer spectroscopy indicated that the early syntheses lead to Prussian blue together with variable amounts of an undesirable iron(III) product. Pair distribution functional analysis confirmed the presence of nanocrystalline ferrihydrite, Fe₁₀O₁₄(OH)₂, and also identified the presence of alumina hydrate, Al₁₀O₁₄(OH)₂, with a particle size of ～15 Å. Paint layers prepared from these pigments subjected to accelerated light exposure showed a tendency to turn green, a tendency that was often reported in eighteenth‐ and nineteenth‐century books. The presence of particles of hydrous iron(III) oxides was also observed in a genuine eighteenth‐century Prussian blue sample obtained from a polychrome sculpture.     

蓝黑墨水字迹褪变机理探讨

通过对蓝黑墨水字迹色素成分鞣酸铁和没食子酸铁的形成、结构、性质进行分析与研究,揭示引起蓝黑墨水字迹褪变的内因和外因.同时,对传统档案文献保护技术理论中蓝黑墨水字迹耐久性的归属提出不同看法,并提出不宜使用蓝黑墨水书写文件的建议及如何保护蓝黑墨水字迹档案文献的方法.     

Fading Spectrophotometric Method for the Determination of Polyvinylpyrrolidone with Eosin Y

在弱酸性HC1-NaAc缓冲介质中,曙红Y（EY）在可见光区有强烈的光吸收,其最大吸收波长(lmax)位于517 nm处,而聚乙烯吡咯烷酮(PVP)在250-700 nm之间无光吸收,当EY与PVP反应形成结合产物时,EY发生明显的褪色作用,最大褪色波长仍位于517 nm,并在545 nm处出现一个较小的吸收峰。其褪色程度（DA）与PVP浓度在0.40~3.20 µg mL-1范围成线性关系,此褪色反应的灵敏度高,摩尔吸光系数(ε)是6.4 × 106 L mol-1 cm-1,对PVP的检出限为0.12 µg mL-1。并研究了反应的影响因素,结果表明方法具有较好的选择性,据此发展了一种曙红Y褪色分光光度法测定PVP的新方法。方法简便快速,可用于啤酒中PVP的定量测定。     

基于合成导向矢量广义MUSIC算法的水平极化米波雷达测高方法

米波雷达具有抗击隐身目标和反辐射导弹的天然优势,但其俯仰维波束较宽,探测低空目标时波束打地,多径效应的存在严重影响米波雷达测高精度。针对这一问题,采用均匀线阵米波雷达经典镜像多径传播信号模型,总结归纳了以广义多重信号分类算法为基础的3种测高方法,并在此基础上提出了一种适用于水平极化米波雷达基于合成导向矢量广义MUSIC算法的精确测高方法,仿真实验与性能最优的第三种测高方法进行对比,在重点分析目标仰角、信噪比、快拍数、幅相误差和地面反射系数等因素对低空目标测高性能影响的基础上得出一般性结论,证明了新方法的优越性。     

Pseudo almost automorphic solutions for some partial functional differential equations with infinite delay

In this work, we study the existence of pseudo almost automorphic solution for some partial functional differential equations with infinite delay. We assume that the undelayed part is not necessarily densely defined and satisfies the Hille–Yosida condition. We use the variation of constant formula developed recently in 1 Hino, Y, Murakami, S and Naito, T. 1991. “Functional Differential Equations with Infinite Delay”. In Lecture Notes in Mathematics, Vol. 1473, New York: Springer-Verlag.  [Google Scholar] to get the existence and uniqueness of pseudo almost automorphic solution when the linear equation has an exponential dichotomy. We also give an application of the abstract results to a Lotka–Volterra model with diffusion.