数值算法

In this paper we discuss the optimal approximation of matrices and its numerical algorithm on some closed convex cone .

讨论矩阵在闭凸锥上的最佳逼近及其数值算法，在对称半正定矩阵集上，给出了最佳逼近数值算法的MATLAB程序和数值例子。

Through adopting frequency-response functions and railway track irregularity PSD, methods and models are optimized. The speed of simulation is enhanced with fast Fourier transformation.

通过引入频响函数及轨道不平顺谱优化了列车荷载数值算法及计算模型，并在数值计算中采用傅里叶快速数值算法，提高列车荷载的模拟的效率和可靠性。

When the solution for the linear equation is not unique, this thesis discusses the solution space of homogeneous equation and gives an orthonormal system, which yields all solutions of linear equation.

同时在再生核空间W_2~1中给出了一种求解该问题的稳定数值算法。对实际数据用该算法进行数值模拟，并与以前的工作相比较，得到了较好的结果。

Firstly, Wavelet-Galerkin algorithm for solving the first kind of singular integral equation with the Hilbert kernel is proposed, we use the characteristic of periodic wavelet on L~2([0,1]) and Hilbert kernel to solve and make stiff matrix lower dimensions and become sparser through thresholding,thus the cost of computation is reduced. Because of the singularity of Hilbert kernel we use Tikhonov regularization method to solve the system of stiff equation. At last the convergence and numerical result of approximate solution are given. Secondly, an approach of regularization based on Fourier is presented for sideways heat equation; we give the theory proof and error estimate.

首先，提出了含Hilbert核的第一类奇异积分方程的小波伽辽金(Wavelet-Galerkin)数值算法，该算法中利用了L~2([0，1])上的周期小波和Hilbert核的特点进行处理，使得刚性矩阵维数降低并且通过阈值使得它更加稀疏，减少了计算量；由于Hilbert核的奇异性，通过Tikhonov正则化方法求解所得到的刚性方程组，给出了收敛性和数值结果；其次，对标准的一维逆热传导方程给出了一种基于Fourier正则化方法，给出了理论证明及其误差估计，解决了文献中算法与理论误差估计的不相匹配的现象，该正则化方法不仅保留了测量数据的部分高频成份，且与文献中的算法具有同样的计算量和误差估计。

The discrete velocity ordinate method in the kinetic theory of gases is developed and applied to discretize the correspo

借助非定常时间分裂法和无波动无自由参数的NND耗散格式，建立直接求解微观分子速度分布函数的有限差分数值格式；研究并发展可用于离散速度坐标点选取和离散速度空间宏观取矩的高斯─埃尔米特无穷积分方法、等均间隔的牛顿─柯斯复合积分法、以勒让德多项式的根为积分结点的高斯─勒让德数值积分法，并应用于不同马赫数绕流模拟；通过对不同流域一维激波管问题、二维圆柱绕流问题和三维球体绕流的计算研究，并将计算结果与其他途径得到的研究结果诸如DSMC模拟值、N-S解及有关实验数据进行比较分析，创建了一套能有效模拟稀薄流到连续流不同流域气体流动问题简化的统一数值算法研究框架

Mathieu function is the base of field theory analysis in elliptical cylinder coordinate system. So, firstly, detail investigation has been given about the problem of numerical analysis of Matheiu functions, based on the predecessor's contribution, an improved faster algorithm of numerical analysis and confirmation algorithm of Matheiu functions has been presented.

Mathieu函数是椭圆柱坐标系统下场论分析的基础，因此本文首先对Mathieu函数的数值计算问题进行了详细研究，并在前人基础上完善并进一步改进了目前被认为较为可行的数值算法，并提出了验证算法。

Therefore, numerical analysis has been duly noted and come up with a variety of numerical integration, numerical differentiation, as well as the numerical solution of differential equations, the calculation of the volume comes down to basic computing, which laid the foundation of modern computer based on the numerical algorithm.

于是，数值分析受到了重视，研究出各种数值积分，数值微分，以及微分方程数值解法，把计算过程归结为巨量的基本运算，从而奠定了现代计算机的数值算法基础。

Our results improve the former results. For periodic Jacobi matrix, some new spectral properties of periodic Jacobi matrix are given by studying the relationship of the eigenvalues of periodic Jacobi matrix and its n—1 principal submatrix. Applying these spectral properties, we present a necessary and sufficient condition for the solvability of an inverse problem of periodic Jacobi matrices and discuss the number and the relationship of its solutions. Furthermore, we propose a new algorithm to construct its solution and compare it with the former algorithms. As this inverse problem of periodic Jacobi matrix usually has multiple solutions as many other eigenvalue inverse problems, we study the uniqueness of this problem. And a necessary and sufficient condition is given to ensure its uniqueness, under which an algorithm is presented and the stability analysis is also given. Finally, we put forward a new inverse problem for periodic Jacobi matrix which has not been solved.

对周期Jacobi矩阵特征值反问题，通过研究周期Jacobi矩阵与其n-1阶主子阵特征值的关系，给出了周期Jacobi矩阵的一些新的谱性质；利用这些谱性质，研究了一类周期Jacobi矩阵特征值反问题，用新的方法推导出了该类特征值反问题有解的充分必要条件，并讨论了解的个数以及解与解之间的关系；此外，提出了一种新的构造周期Jacobi矩阵反问题解的数值算法，并与前人的算法做了一定比较；由于周期Jacobi矩阵特征值反问题和其他很多特征值反问题一样往往存在多个解，本论文给出了周期Jacobi矩阵反问题解唯一的充要条件，并发现周期Jacobi矩阵特征值反问题的解唯一当且仅当构造的矩阵满足一定的条件；在解唯一的情况下，给出了构造唯一解的数值算法，并做了相应的稳定性分析；最后，提出了一类新的有待于解决的周期Jacobi矩阵特征值反问题。

This thesis will be expanded from two aspects: first, delta-sequence obtained by cubic spline interpolation cardinal function showed the properties of symmetry, Riesz basis and interpolation. Non linear convection diffusion equation (Burgers′equation) was used as an example. Then we modified this delta-sequence to improve the attenuation, the same example was used in numerical application.

在小波方法与PDE算法相结合方面，本文主要从两方面入手：首先是以样条插值基函数为基础构造δ-序列核，以非线性对流扩散方程为例给出了一种数值算法；进而对三次样条插值基函数进行改进，构造新的具有更快衰减性质的δ-序列核，同样以非线性对流扩散方程为例验证了新函数在数值求解中的有效性。

It is apparent that using mechanism for handling the discontinuities is better than ordinary method for saving computational time.

数值算例结果表明，采用间断处理后的数值算法较原算法相比可以较大程度地节省计算时间。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。