共查询到17条相似文献,搜索用时 125 毫秒
1.
有限区间上正交小波基 总被引:3,自引:2,他引:1
Chui C K 等于 1992 年构造出尺度因子 a = 3 时紧支集正交对称的尺度函数和两个相对应的正交小波。其中一个为对称的,另一个为反对称的。在此基础上,这里对尺度函数和两个小波进行了折叠,得到了尺度因子 a = 3 时有限区间上的正交小波基。 相似文献
2.
3.
4.
5.
由一个函数的分数次伸缩得到由N个函数组成的函数族{φ(2^(j-1)/Nx),j=1,…,N,N是某个固定的自然数},这N个函数的平移构成L^2(R)上的多分辨分析(Vm)m∈Z中V0的Riesz基。给出{φ(2^(j-1)/Nx-n),φ(2^(j-1)/Nx-n),j=1,…,N}生成V1的Riesz基及V1的分解 与重构的充分必要条件。最后给出由以上N个函数构成的尺度函数和小波函数的对偶。 相似文献
6.
7.
基于正交单尺度函数,给出一种构造2重正交多尺度函数的方法。也给出对应正交多小波的显式构造公式。由于构造的2重正交多尺度函数中的个是所给的正交单尺度函数,另一个是新构造出的函数,因此这种多小波比相关的单小波具有更好的频率局部性。 相似文献
8.
9.
10.
分析了以小波基取代传统无单元法中多项式基的原因,阐述了小波基无单元法的基本原理,并将其与有限元法在基本思路、形函数、位移边界条件、计算精度和适用范围等方面的区别进行了比较研究,最后通过算例验证了B-样条小波基在无单元法中应用的可行性以及小波基无单元法相对于有限元法的优势. 相似文献
11.
本文引入一种矩阵滤波器的特殊变换。任一紧支撑正交多尺度函数都可由一个简单的矩阵滤波器通过这种变换得到。由此给出一种由多尺度函数构造相应紧支撑正交多小波的算法。与传统方法相比,这种方法既不需要对罗朗多项式矩阵逐行降次,也不需要将多项矩阵分解成特殊的形式,并且不受滤波器长度的限制。可以利用该方法构造出GHM正交多小波。 相似文献
12.
给出α尺度正交多尺度函数一种新的构造方法。α尺度正交的多尺度函数可由任意α尺度正交的单尺度函数及滤波器组构造出来的。由于α尺度单正交尺度函数选取的任意性和用于构造的滤波器组具有相当大的自由度,从而使得有可能构造出大量的具有很好性质的α尺度的多尺度函数,进而得到良好性质的多小波。 相似文献
13.
14.
Mesh-based numerical implementation of the localized boundary-domain integral-equation method to a variable-coefficient Neumann problem 总被引:1,自引:0,他引:1
An implementation of the localized boundary-domain integral-equation (LBDIE) method for the numerical solution of the Neumann boundary-value problem for a second-order linear elliptic PDE with variable coefficient is discussed. The LBDIE method uses a specially constructed localized parametrix (Levi function) to reduce the BVP to a LBDIE. After employing a mesh-based discretization, the integral equation is reduced to a sparse system of linear algebraic equations that is solved numerically. Since the Neumann BVP is not unconditionally and uniquely solvable, neither is the LBDIE. Numerical implementation of the finite-dimensional perturbation approach that reduces the integral equation to an unconditionally and uniquely solvable equation, is also discussed. 相似文献
15.
16.
The propagation of Love waves on an elastic homogeneous half-space with a piezoelectric gradient covering layer is studied by the geometric integration method in this article. First, the state transfer equation of a Love wave is derived from the governing equations and constitutive relations. Then, the transfer matrix of the state vector is obtained by solving the state transfer equation of a Love wave and then the stiffness matrix is obtained. By combining transfer matrices and the stiffness matrices of the gradient covering layer and the homogeneous half-space, the total surface stiffness matrix of a Love wave is obtained. Lastly, the application of the electrically open circuit and short circuit conditions and mechanically traction-free conditions gives the frequency dispersive relation of a Love wave. For the gradient covering layer, the material constants at the bottom of the covering layer may be greater or smaller than that at the top of the covering layer. The two situations and three kinds of gradient profiles for each of these two situations are investigated. The numerical results show that the Love wave speed is sensitive to not only the material constants at the bottom and the top of the covering layer, but also the gradient profiles of the covering layer. 相似文献
17.
K. Sukumaran K.K. Ravikumar S.G.K. Pillai T.P.D. Rajan M. Ravi R.M. Pillai B.C. Pai 《Materials Science and Engineering: A》2008,490(1-2):235-241
Aluminium 2124 alloy and its composite with 10% SiC particles of average particle size of 23 μm were squeeze cast at different pressures. The effect of squeeze pressure during solidification was evaluated with respect to microstructural characteristics using optical microscopy and image analysis and mechanical properties by tensile testing. The microstructural refinement, elimination of casting defects such as shrinkage and gas porosities and improved distribution of SiC particles in the case of the composite were resulted when pressure is applied during solidification. A pressure level of 100 MPa was found to be sufficient to get the microstructural refinement and very low porosity level in both the alloy and the composite. The improved mechanical properties observed in the squeeze cast alloy and the composite could be attributed to the refinement of microstructure within the material. 相似文献