一种多码CDMA分层小区模型的呼叫接纳性能分析

为研究第三代移动通信分层小区系统的呼叫接纳策略 ,提出了一种由宏小区层、微小区层和皮小区层构成的多码码分多址 (CDMA)系统分层小区模型。该模型中 ,皮小区层作为“热点”小区层嵌入微小区层 ,采用多码传输方案支持多类型和高速率业务。在分析上行链路干扰的基础上 ,兼顾移动性提出了一种分层小区系统的多业务呼叫接纳控制策略。仿真结果表明 ,多业务呼叫接纳策略优于固定门限呼叫接纳策略。最后得出了多业务呼叫接纳控制策略减少了呼叫业务的切换频度 ,降低了系统信令开销 ,具有良好呼叫接纳性能的结论。     

Isoforms of soluble alpha-tubulin in oocytes and brain of the frog (genus Rana): changes during oocyte maturation

Rana oocytes have previously been shown to contain much more soluble tubulin than does the brain, suggesting different assembly and disassembly dynamics of frog oocyte tubulin compared to that in brain. By using centrifugation, SDS-PAGE, two-dimensional gel electrophoresis and Western blots, probed with anti-α-tubulin monoclonal antibodies, polymorphic α-tubulins (isoforms) were compared in brains and follicle-enclosed oocytes of northern (Rana pipiens) and southern (R. berlandieri) frogs. Oocyte tubulin in both species had isoforms with greater ranges of isoelectric point (pI) than those of brain tubulins; in particular, the oocyte tubulin pIs ranged further into the acidic region of the isoelectric-focusing gels than corresponding brain tubulin. This difference may, in part, be responsible for the previously reported assembly differences between oocyte tubulin (undetectable assembly) and brain tubulin (high assembly). Isoforms of α-tubulin with relat ively acidic pI were more abundant in northern frog brain and oocyte soluble extracts than in analogous extracts from southern frogs. Furthermore, additional acidic α-tubulin isoforms were found in progesterone-treated oocytes (i.e., eggs), indicating increased heterogeneity of acidic a-tubulin isoforms during oocyte meiotic maturation. Among northern frog oocyte soluble components fractionated on Superose-6b columns, tubulin complexes with apparent molecular mass of about 1800 kDa were found to contain acidic α-tubulin isoforms while the putative oligomeric tubulins with an apparent molecular mass of about 250 kDa contained an additional relatively basic α-tubulin isoform. The acidic α-tubulin isoforms, therefore, are proposed to be associated with cold-adaptable cells of brain and oocytes, and may also be involved in stabilization of large soluble tubulin complexes in oocytes of the northern frog. Received 1 October 2002; accepted 9 October 2002 RID="*" ID="*"Corresponding author.     

道路环境中激光雷达互干扰的仿真研究

为解决汽车激光雷达的相互干扰造成目标检测与跟踪性能的严重下降的问题,从空间、时间和调制频率等方面出发,研究脉冲方式和频率调制连续波方式激光雷达在道路环境中可能存在的各种干扰,通过仿真计算干扰发生的概率、分析干扰的特征,以及干扰对测量性能下降的影响.针对可能存在的干扰问题,指出使用伪随机码调制连续波激光器输出幅度的方式可...     

64QAM信号的相位透明LEE氏纠错编码

首先介绍了 L EE氏码对相位透明的多进制线性纠错码的性质 ,然后将它克服解调载波恢复相位模糊的应用从 PSK推广到 6 4QAM系统 ,并给出性能比较分析结果。     

一种新代码优化的方法

介绍了一种新的代码优化的方法-Just In Time Code Layout,它不同于传统的静态链接生成可执行程序映象文件的方法,而是在运行时通过动态链接生成执行程序的映象,对比研究了此方法生成的程序映象和传统方法生成的程序映象及用Pettis方法优化生成程序映象三者之间在运行时Cache性能的差异,证明了这种方法对程序运行的明显效果。     

一种曲率新算法及其在图像处理中的应用

利用曲线所张成的弓形与弦长之间的关系制成查表 ,将曲率求取简化为可以递推的链码和查表运算 .这种算法的精度、速度和稳定性等综合性能均优于以往的曲率算法 ,该法在抗仿射失真的目标识别上取得较满意的效果 .     

Fuzzy信号码

引入了Fuzzy前缀码的一有趣子类——Fuzzy信号码的概念,讨论了它的几个等价关系和一些性质。     

Turbo码在混合自动重复请求通信系统中的应用

探讨了 Turbo码在混合自动重复请求 (ARQ)通信系统中应用 ,并基于 Turbo码提出了一些新的混合 ARQ通信系统方案。     

基于信号空时结构的子空间多用户检测技术

分析了2种线性多用户器（去相关检测器、MMSE检测器）的性能,和在基站使用无线阵列时,2种线性多用户检测器的性能改善,以及相对于没有使用天线时的性能的提高。说明使用天线阵增加了用户的空间特征,从而增加了用户的可辩性,提高了多用户检测器的性能。成为扩展系统容量的有效途径。     

半无限长浅窄航道中船舶变速航行的有限元计算

在流体力学的基础上建立了船舶进入半无限长浅窄航道的数学模型,由于船在狭航道中航行,研究的水的运动是一个变边界问题,采用浅水模型。半连船非惯性坐标系来计算变边界问题,让网格的变化来适应船的移动。开边界处使用辐射边界条件,本文从非守恒型动量方程、二维浅水波动方程、连续性方程出发。采用有限元法计算船舶进入狭航道的水动力学过程;还研究了船和水体的相互作用,描述了自由水面波动、船底部的压力等重要物理量在船行驶过程中的变化规律,给出了船进入狭航道时的水面波高图、压力图。