可变随机域宽度的多用户机会频谱接入方案

在分布式多用户频谱接入(OSA)环境下,从用户间信道选择同步问题成为干扰系统全网吞吐量的重要因素. 为解决该问题,提出一种基于可变随机域宽度的多用户频谱接入方案,在充分利用随机化接入方式避免用户间同步的同时,通过改变可供随机接入选择的信道数(即随机域宽度),达到最优信道选择与同步避免的折中. 仿真结果表明,相对于传统的全频段随机化接入同步避免方式,本方案可有效提升多用户机会频谱接入系统的全网吞吐量.     

二项式函数f(x)=(1+x)~α(α≠0)的幂级数展开式及其应用

详细介绍了二项式函数f(x)=(1+x)~a(a≠0)的幂级数展开式、收敛域的确定及其二项式级数在数学中的应用。     

基于用户偏好的垂直搜索算法

提出并研究、实现了基于用户偏好的垂直搜索算法(PVSA)。以领域特征为基本出发点,PVSA借助领域主题偏好向量、领域元数据权重因子、检索名词差异化、行业词典库更新等4项策略,有效地挖掘、表征用户的领域个性化偏好,以此为基础构建基于用户偏好的垂直搜索算法。实验结果表明了PVSA算法的有效性和可行性。     

域名信息主动获取及备份系统的设计和实现*

为解决因国外根/顶级域名系统无法提供域名解析服务而影响我国互联网正常运行的问题,设计并实现了一种高效的DNS信息获取及备份恢复系统。通过被动获取DNS数据包与主动发送DNS请求相结合的方式,可获取网络中活跃的域名信息。利用基于可变长请求队列的发送速度自适应方法来有效控制请求效率,以适应网络带宽和DNS服务器负载。详细介绍了整个系统的设计和实现,并进行了性能测试与分析。该系统对建设国家根/顶级域名备份恢复系统具有重要参考价值。     

基于压缩域水印的AVS视频认证*

为了提高压缩域视频水印的安全性,提出一种基于压缩域的AVS视频认证水印新算法。它从视频空间的三维特性出发,利用I帧分块能量关系、GOP结构信息、帧结构信息等构造特征码。在嵌入算法上,将特征码同时嵌入到中频DCT系数和运动矢量中,在认证端将重建特征值和提取的双水印进行比较。仿真实验结果表明,该算法具有较好的窜改认证能力。     

高端路由器CIDR表非关键字索引的B-Tree机制

不分类的互联网协议(IP)地址方式无类别域间路由(CIDR)可以解决高端路由器中路由匹配延
迟问题. 通过对CIDR表深入分析,在参考数据库的非关键字索引方法和分割索引算法的基础
上,提出了一种满足CIDR表要求的非关键字索引的B Tree算法. 该算法首先对CIDR表的全
部前缀地址集合进行分割索引,分割后,CIDR表被改变成一种B Tree索引结构;然后按照I
P地址的非关键字对CIDR表进行快速查找. 仿真结果表明,本文算法更好地满足了快速查找I
P地址的需求.     

Logistic视频字幕增强模型

目的：为提高复杂背景下的视频字幕在OCR中的识别率,需要对提取的视频字幕进行有效地字幕增强。该文首次将Logistic模型应用到视频字幕增强中,提出了基于Logistic模型的融合多帧信息的视频字幕增强方法。方法：对字幕进行检测与跟踪,将出现在连续多帧中的同一字幕片段进行对齐;通过分析字幕片段在多帧中信息,提出字幕背景在时域上的变化特征、背景和字幕文本的固有特征,并将三个特征进行量化与融合,构建适用于字幕增强的Logistic模型,实现对视频字幕的增强。结果：对含阴影或描边效果的特殊复杂背景字幕、普通复杂背景字幕、单一背景字幕分别进行实验,增强后的字幕在OCR软件中的识别正确率分别为81.76%、97.13%、98.19%,与对比方法比较均有一定的提高。结论：实验结果表明,该文方法既可以降低字幕背景的复杂度,又可以提高字幕背景与文本的对比度,从而可以对复杂背景和单一背景下的视频字幕进行有效地增强。     

PEAK-INSENSITIVE NON-PARAMETRIC SPECTRUM ESTIMATION

Abstract. We study the problem of non-parametric spectrum estimation of a stationary time series that might contain periodic components. In this case the periodogram ordinates have a significant amplitude at frequencies near the frequencies of the periodic components. These can be regarded as outliers in an asymptotically exponential sample. We develop a non-parametric estimator for the spectral density that is insensitive to these outliers in the frequency domain. This is done by robustifying the usual kernel estimator (smoothed periodogram) by means of M-estimation in the frequency domain. We propose to use data-tapered periodograms, which yield a drastic improvement of the procedure, typically for the contaminated situation. This is both shown theoretically and supported by means of simulation. We show consistency of the resulting estimator in the general case, and asymptotic normality in the special case of a Gaussian time series, whether contamination is present or not. Finally we illustrate the finite sample performance of the estimating procedure by some simulation results and by application to the Canadian lynx trappings data.     

改进的细菌觅食优化算法求解0-1背包问题

细菌觅食优化算法作为一种新兴的智能优化算法,一般用来解决连续域的问题。为了解决离散域问题,提出了一种改进的细菌觅食优化算法。采用线性递减的思想和随机的游动长度代替固定步长和随机游动方向,改进了趋向性操作方案,并将其应用于解决0-1背包问题。将改进的细菌觅食优化算法与遗传算法、离散粒子群优化算法及基本的离散化细菌觅食优化算法分别在小规模和大规模的0-1背包问题上进行了仿真比较,表明了改进的细菌觅食优化算法能取得较好的效果,寻优能力强。     

A free space frequency‐time‐domain technique for electromagnetic characterization of materials using reflection‐based measurement

In this report, a free space frequency‐time‐domain technique is presented for characterizing the electrical properties and thickness of the sample using multiple reflections and fabry‐perot resonance phenomenon. The retrieval of constitutive electromagnetic parameters of the sample has been carried out by comparing the measured reflection coefficient data from the sample at two different incident angles. The relative permittivity as well as relative permeability along with the thickness of different samples viz., beryllia, silicon, and plexiglass have been evaluated with high accuracy in the frequency range 1 to 15 GHz. The method is also experimentally validated by successfully reconstructing the unknown material properties of two different samples. The unique advantage of this method lies in non‐requirement of any prior knowledge of the sample's thickness for measuring the complex relative dielectric constant as well as relative permeability of the sample. To determine the electromagnetic properties of the sample, the sole knowledge of reflection coefficient data are needed. Moreover, the method does not involve any additional measurement for the reference calibration. The simple, cost‐effective proposed scheme is quite useful in many applications like accurate determination of signal strength in indoor wireless communication, through wall imaging, food industry, and so on.