first_order_differ---solve

程序计算在声速梯度下水中声线的传播并计算声线的长度(Program calculates the velocity gradient in the water line of acoustic sound propagation and calculate the length of the line)

数值分析非线性方程求解（五种方法）。分析牛顿法、割线法、对分法、Steffensen法、简易牛顿法解线性方程组的性质(Numerical analysis of nonlinear equations (five methods). Nature of the analysis of Newton, secant, bisection method, Steffensen method, simple Newton method for solving linear equations)

三维的有限时域差分源程序，边界条件为pml(Three-dimensional FDTD source, boundary conditions for the PML)

重力异常正演代码，请好好使用它。帮助学习。。。。(Gravity anomaly forward code, please use it well. Help learn)

说明：  实现快速离散傅里叶变换，即FFT,很有用的程序(Fast discrete Fourier transform, namely, FFT, very useful program)

将txt数据转换为LMS test.lab软件所能接受的格式(Change the txt format file to Unv file which can be read into the famous vibration test software LMS test.lab)

使用lasso方法，对特征矩阵进行优化特征选择（向量选择），使其达到最优。(Use lasso method, optimize the characteristic matrix feature selection (vector selection), to the optimal.)

己知一些离散的点，使用matlab利用最小二乘法拟合(Had a number of discrete points, with linear least squares fitting)

一个简单的网格生成程序，操作方便，易学，类似于easymesh！(A simple grid generation program, easy to operate, easy to learn, like easymesh!)

北京航空航天大学硕士研究生数值分析课的第一次大作业，用幂法反幂法求取矩阵的最大最小特征值(Minimum and maximum eigenvalue of the first graduate of Beijing University of Aeronautics and Astronautics numerical analysis class job, using the power method matrix inverse power law to strike)