卷积Turbo码及其在802．16宽带无线接入中的应用

首先对 IEEE 80 2 .1 6标准进行简要介绍 ,接着阐述卷积 Turbo码的编译码原理 ,在此基础上给出了 Turbo码的 log_ MAP算法 ,最后讨论 Turbo码实现过程中影响译码性能的4个关键问题     

基于边界和模糊集理论的三维图像分割

本文提出了一种基于边界和模糊集理论的三维图象分割方法，利用高斯－拉普拉斯算子检测出图象中各结构的边界后，通过区域增长获取感光趣结构的三维二值模板，由高斯－拉普拉斯图象和二值模板出发，利用模糊集理论，确定感兴趣结构的三维模糊模板，从而达到在体积图象中分割出感兴趣结构的目的。     

A novel method of preparation-adsorption desulfurization process for dibenzothiophene over sawdust-derived nickel/activated carbon

In this work we proposed a novel preparation-adsorption desulfurization method for dibenzothiophene over sawdust-derived nickel/activated carbon prepared by 400°C one step carbonization-activation-modified process. The adsorbent was characterized by X-ray Diffraction (XRD), Boehm titration method, Scanning Electron Microscope (SEM) and N₂ adsorption-desorption technology. The result show that 30% HNO₃ aqueous solution and calcination 2 h for the 30%-NiO/AC adsorbent trend to better desulfurization performance with NiO active adsorption sites and surface oxygen-containing functional groups. After high temperature adsorption desulfurization, the sawdust-derived nickel/activated carbon occurred activation and reaming again, both the specific surface and the microspore volume have been great changed.     

气压高度表模拟器的研究

文中介绍了一种气压高度表模拟器，它能够对高度表的气路特性同时进行静态，动脉模拟。检验气压高度表的静，动态特性，其方法简单经济，可靠性高，可重复性高。     

频谱分析仪在射电法测量天线增益和G／T值中的应用

本文给出了频谱分析仪在射电法测量天线增益和Ｇ／Ｔ值中的应用方法以及计算公式，并对测量误差进行了分析，讨论了ＬＮＡ的噪声温度与Ｙ因子大小的关系，给出了对测量精度的影响和常用不同频段可测天线口径的下限。     

Order statistic filter banks

Filter banks play a major role in multirate signal processing where these have been successfully used in a variety of applications. In the past, filter banks have been developed within the framework of linear filters. It is well known, however, that linear filters may have less than satisfactory performance whenever the underlying processes are non-Gaussian. We introduce the nonlinear class of order statistic (OS) filter banks that exploit the spectral characteristics of the input signal as well as its rank-ordering structure. The attained subband signals provide frequency and rank information in a localized time interval. OS filter banks can lead to significant gains over linear filter banks, particularly when the input signals contain abrupt changes and details, as is common with image and video signals. OS filter banks are formed using traditional linear filter banks as fundamental building blocks. It is shown that OS filter banks subsume linear filter banks and that the latter are obtained by simple linear transformations of the former. To illustrate the properties of OS filter banks, we develop simulations showing that the learning characteristics of the LMS algorithm, which are used to optimize the weight taps of OS filters, can be significantly improved by performing the adaptation in the OS subband domain.     

Synthesis and characterization of sulfonated poly(arylene ether ketone ketone sulfone) membranes for application in proton exchange membrane fuel cells

A series of sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS) copolymers were synthesized by nucleophilic polycondensation. The copolymers exhibit good thermal and oxidative stabilities, all the SPAEKKS copolymers can be cast into tough membranes. Ionic exchange capacities (IEC), water uptake properties, thermal stabilities, methanol diffusion coefficients and proton conductivities were thoroughly studied. Also the microstructures of the membranes were investigated by TEM. The proton conductivity of the SPAEKKS-4 membrane is close to that of Nafion-117 at 80 °C. The methanol diffusion coefficient of the membrane is much lower than that of Nafion-117 under the same testing conditions. The SPAEKKS membranes are promising in proton exchange membranes fuel cell (PEMFC) application.     

北京平原地热资源与地热供暖

本文对北京平原地区地热资源条件和供暖现状进行了概述,分析了地热供暖技术的特点、优势以及当前制约其推广发展的“瓶颈”,针对北京平原地热资源的可持续发展提出了两点具体建议。     

KM496GB型柴油机机油压力低的原因分析及对策

通过对KM496GB柴油机机油压力低的试验分析表明,引起故障主要原因有:机油泵故障,限压阀未备紧,机油泵油量偏低,并介绍了所采取的相应措施。