层状介质模型的散射波场

运用逆散射序列方法能去除自由表面和内部多次波 .通过研究正散射序列的性质 ,讨论了散射序列与一次波和多次波的关系 ,指出了用散射理论描述多次波和一次波的步骤和方法 ;此外 ,讨论了Born近似与逆散射序列成像之间的差异 .研究结果表明 :Born近似成像法仅对于小扰动量适用 ,对于大扰动量 ,Born近似值会产生较大的误差 。

层状介质结构的超声回波信号特征提取方法研究

本文分析研究了层状介质结构与超声回波信号特征的关系，着重研究并比较了离散傅里叶交换与离散余弦变换对提取层状介质回波信号特征的效果。理论分析和实验验证得出离散余弦变换是一种提取反映层状介质结构的超声回波信号特征的较理想方法。

层状饱和土Biot固结问题状态空间法

针对饱和多孔介质空间非轴对称Biot固结问题,引入状态变量,构造了两组相互独立的状态变量方程.利用Fourier级数和Laplace-Hankel变换,将状态变量方程转换为两组一阶常微分方程组,提出了均质饱和多孔介质空间非轴对称Biot固结问题的传递矩阵,得到以状态变量和传递矩阵乘积的形式表示的均质饱和多孔介质空间非轴对称Biot固结问题的解.利用层间完全接触的条件,可得到N层饱和多孔介质空间非轴对称Biot固结问题的一般解析表达式.文中考虑几种不同的边界条件,分析了两个算例.数值结果表明该方法具有较高的计算精度和良好的计算稳定性.

信息与知识概念的再思考

本文针对当前信息和知识两个概念的多种不同定义给相关研究带来混乱的问题,认为有关信息和知识方面的研究应该基于一个较为规范、统一的定义.对信息和知识的定义阐述了自己的观点并讨论了数据、信息和知识之间的关系,以期引起信息与知识研究的争鸣.

Visualization of Understanding of Media Characteristics Using Analytic Hierarchy Process

The purpose of this study is to design a tool, adapted to students＇ individual contexts and to enable students to reflect on their understanding of media characteristics. AHP （analytic hierarchy process） is a structured technique for organizing and analyzing complex decisions. Using AHP, students have to define appropriate criteria and priorities for using media. It is expected that students＂ understanding of the characteristics of different types of media will emerge through reflection. Seventy two university students took part in this research. They were asked to prioritize their ways.of obtaining information about current affairs using sets of media such as TV, books, newspapers and web pages, Twitter and Facebook. AHP enables us to visualize a ＂real＂ understanding of media characteristics and students can reflect on that basis. As far as ＂information sources and media＂ is concerned, a few students indicated that it was the information source itself that was important rather than the type of media. Our tool fulfils the role of encouraging this type of reflection.