自适应小波阈值去噪在光谱信号处理中的应用

在光谱数据的多组分定量分析中 ,噪声的存在往往影响分析的准确度。小波变换的多分辨率分析的特性使它成为一种优良的去噪方法。本文基于 Dohono提出的小波阈值去噪和 Mallat,Xu等提出的空域相关去噪法 ,提出了一种新的自适应小波阈值函数滤噪法。与原来方法比较 ,新法能够在有效去除噪声的同时 ,很好地保留了信号的细节。仿真计算和分析表明了此算法的有效性。     

梯形截面硅脊形波导的模式特性及其等离子体色散效应

本文运用有效折射率法和WKB法对具有梯形状截面的硅脊形波导的模式特性作了分析,导出了TE模和TM模的模方程以及截止方程,并运用一阶微扰法对因波导顶部注入载流子而引起的模式调制的大小作了数值估计。其结果可为全硅光波导器件的研制提供指导。     

Multiphase Thermohaline Convection in the Earth’s Crust: II. Benchmarking and Application of a Finite Element – Finite Volume Solution Technique with a NaCl–H2O Equation of State

We present the benchmarking of a new finite element – finite volume (FEFV) solution technique capable of modeling transient multiphase thermohaline convection for geological realistic p-T-X conditions. The algorithm embeds a new and accurate equation of state for the NaCl–H₂O system. Benchmarks are carried out to compare the numerical results for the various component-processes of multiphase thermohaline convection. They include simulations of (i) convection driven by temperature and/or concentration gradients in a single-phase fluid (i.e., the Elder problem, thermal convection at different Rayleigh numbers, and a free thermohaline convection example), (ii) multiphase flow (i.e., the Buckley–Leverett problem), and (iii) energy transport in a pure H₂O fluid at liquid, vapor, supercritical, and two-phase conditions (i.e., comparison to the U.S. Geological Survey Code HYDROTHERM). The results produced with the new FEFV technique are in good agreement with the reference solutions. We further present the application of the FEFV technique to the simulation of thermohaline convection of a 400°C hot and 10 wt.% saline fluid rising from 4 km depth. During the buoyant rise, the fluid boils and separates into a high-density, high-salinity liquid phase and a low-density, low-salinity vapor phase.     

Convolution–backprojection method for the k-plane transform, and Calderón''s identity for ridgelet transforms

We develop a convolution–backprojection method for the k-plane Radon transform , . A slight modification of this method gives an explicit inversion formula for in terms of the corresponding wavelet-like transforms (or the k-plane ridgelet transforms), and a generalization of Calderón's reproducing formula.     

About 3D solution of diffraction problems by MMDS

A new universal 3D scalar and vector modification to the method of discrete sources (MMDS) for the numerical calculation of the scattering pattern of the body of revolution is described. To illustrate the use of the developed technique, the scattered field of the spheroid and multifoil of revolution are calculated. It is shown that analytical transformation of the scatterer's surface and wavelet technique allows creating an efficiency algorithm with rather small time of computation.     

Confinement of the infrared divergence for the Mumford process

The Mumford process X is a stochastic distribution modulo constant and cannot be defined as a stochastic distribution invariant in law by dilations. We present two expansions of X—using wavelet bases—in X=X₀+X₁ which allow us to confine the divergence on the “small term” X₁ and which respect the invariance in law by dyadic dilations of the process.     

用小波变换确定电位滴定终点

将小波变换在信号和图象处理过程中边缘检取的思想方法引入到化学中，以确定电位滴定的终点，能直接对测量的数据进行处理，不会引入人为的误差因素。计算精度可达实验精度的下限，且处理结果的判断非常简便，用本方法对实验数据进行处理，获得满意的结果。     

灰色系统模型的优化岭回归算法

文献[1]指出了目前用普通最小二乘法估计灰微分方程参数的方法由于方程组的病态问题很难求解得合理的参数;文献[2]指出了根据初值求解灰色系统模型的时间响应式的方法由于初值的误差使所求得时间响应式产生系统误差.为了克服灰色模型的上述两个缺点,本文设计了一种求解灰色系统模型的优化岭回归算法,计算一个广泛引用的算例演示了这种算法的优越性.     

基于自适应小波变换和矢量量化的图像压缩编码

运用小波变换进行图像压缩的算法其核心都是小波变换的多分辨率分析以及对不同尺度的小波系数的量化和编码 .本文提出了一种基于能量的自适应小波变换和矢量量化相结合的压缩算法 .即在一定的能量准则下 ,根据子图像的能量大小决定是否进行小波分解 ,然后给出恰当的小波系数量化 .在量化过程中 ,采用一种改进的LBG算法进行码书的训练 .实验表明 ,本算法广泛适用于不同特征的数字图像 ,在取得较高峰值信噪比的同时可以获得较高的重建图像质量 .     

基于多带复数小波与最大后验概率估计法的图像去噪方法

提出一种基于多带复数小波与最大后验概率估计方法的图像去噪方法，与二带小波以及相应的去噪方法相比，性能具有明显改善。