Numerical Simulation of Two-Dimensional Dendritic Growth Using Phase-Field Model

In this article, we study the phase-field model of solidification for numerical simulation of dendritic crystal growth that occurs during the casting of metals and alloys. Phase-field model of solidification describes the physics of dendritic growth in any material during the process of under cooling. The numerical procedure in this work is based on finite difference scheme for space and the 4th-order Runge-Kutta method for time discretization. The effect of each physical parameter on the shape and growth of dendritic crystal is studied and visualized in detail.

一种时域去走动的四阶模型SAR成像方法

针对大斜视SAR回波耦合性强问题,从提高斜距模型近似精度和距离徙动校正精度两方面对SAR成像进行了研究,推导了一种四阶SAR成像算法模型.首先为了提高模型近似度,将斜距展开到四次项,然后为了将距离向和方位向进行初步解耦,在时域进行走动补偿,通过级数反演法将信号转到二维频域进行距离弯曲校正,方位匹配滤波后得到聚焦后的SAR图像.该方法流程简单,便于实时处理.仿真结果表明,该方法具有较强斜视处理能力,取得了较高的成像分辨率.

双重时序AR-MA模型的高价平稳性(英文)

本文讨论双重时序AR－MA模型的高价（4阶，8阶及一般2m阶）平稳解存在的充分条件，这些结论对建立模型参数的矩估计及讨论估计量的渐近性质都是必不可少的．

双重时序模型的高阶矩结构

为建立双重时序AR-MA模型的矩估计，除了需要模型平稳解序列的二阶矩结构[10]外，还需要建立平稳解序列的高阶矩结构[2]．设｛Xt｝为AR（1）－MA（q）模型的4阶平稳解序列．木文部分地证明了。｛X^2_t｝的相关结构为某一ARMA（3q，3q—1）型，这为．建立模型参数的矩估计创造了条件.