Note To The Mixed-Type Splitting Iterative Method For The Positive Real Linear System

In [5] a new iterative method is given for the linear system of equations Au=b , where A is large, sparse and nonsymmetrical and A^{rm T}+A is symmetric and positive definite (SPD) or equivalently A is positive real. The new iterative method is based on a mixed-type splitting of the matrix A and is called the mixed-type splitting iterative method. The iterative method contains an auxiliary matrix D_1 that is restricted to be symmetric. In this note, the auxiliary matrix is allowed to be more general and it is shown that by proper choice of D 1 , the new iterative method is still convergent. It is also shown that by special choice of D_{1} , the new iterative method becomes the well-known (point) accelerated overrelaxation (AOR) [1] method. Hence, it is shown that the (point) AOR method applied to the positive real system is convergent under the proper choice of the overrelaxation parameters y and .     

分块响应面法研究

在对采样点构建插值曲面时,响应面法（Response Surface Method,RSM）通常是对整个曲面进行插值近似,由于计算量的原因,采用的近似曲面阶数通常不超过四阶。但是,对于高度非线性的曲面,使用低阶响应面在较大范围内近似毫无疑问会降低响应面的近似精度。分块响应面法采用一定的策略对近似空间进行合理分块,缩小响应面的近似范围,从而提高了响应面在该空间的近似精度。测试结果表明,在样本数量和样本空间变化时,分块响应面法的近似精度不低于响应面法,尤其是当样本数量较多时,分块响应面法的近似精度要远高于响应面法。这就使得分块响应面法能够有效地应用于多学科设计优化。     

基于改进阈值自适应冗余小波的振动信号去噪

由电主轴动不平衡引起的振动信号在采集的过程中会混人大量强干扰噪声,引起机床主轴系统稳定性差.自适应冗余第二代小波的降噪方法可有效的去除噪声.针对上述方法中存在的传统阈值函数造成小波系数不连续或恒定偏差的问题,引入双变量改进阈值函数,提出了一种改进的自适应冗余第二代小波的振动信号消噪方法.将改进的方法应用于仿真信号及实际采集的电主轴动不平衡振动信号消噪中,结果表明,改进方法融合了自适应冗余第二代小波信号和双变量改进阈值函数的优点,在低信噪比的仿真信号和振动信号消噪中,能很好的保留原信号的特征并且有效的去除噪声,消噪效果更优.