FractalDim

arithemetic code on visual c++

自己写了一个二维Euler方程的间断有限元程序 上次发了一个三角形单元的程序 因为不是曲边单元 所以在圆柱后面容易形成涡 现在把程序改为曲边四边形单元了 没有涡出现 单元是8节点四边形单元 节点编号顺序是 1 5 2 6 3 7 4 8 也就是四个角点依次 是1 2 3 4 然后是边的中点编号 5 6 7 8. 时间推进采用 Runge-Kutta 方法 数值通量采用全局Lax-Friedrichs通量 仍然不能捕捉激波 因为没有做重构或者加人工粘性 等这个做出来了 再发一次。 程序没有进行优化 比如说内存的消耗没有优化 比如直边单元的边界积分仍然采 用了曲边的积分方法 增加了计算量 比如面积分、线积分都是采用的是Gauss- Legendre-Lobatto积分 积分精度会比一般的Gauss-Legendre积分精度低一阶 等 等问题。 二维的 纯属交流性质 就没有考虑这些问题 ^_^ 如果物面全部是直边 那么只要改变一个参数N 就可以获得不同的计算精度 且具 有谱精度 因为单元的节点是Gauss-Legendre-Lobatto积分点。 其实就是谱元法 （物面是曲边的情况我不清楚是不是也可以通过提高基函数的阶数 也就是增加N 来提高计算精度）(Wrote a two-dimensional Euler equations with discontinuous finite element program Last made ​ ​ a triangular element of the program, not curved edge unit is so easy to form a vortex in the cylinder behind the Program to curved edge quadrilateral element vortices appear Unit is the order of 8-node quadrilateral element node number is 15,263,748 which is the four corners of the points in turn Is 1234 and then the side of the midpoint of the number 5678. Time promote the use of Runge-Kutta method Numerical flux of the overall situation of Lax-Friedrichs, flux Still can not capture the shock wave did not do the reconstruction or artificial viscosity do it Zaifayici. The program is not optimized for example, memory consumption is not optimized such as straight-edge boundary integral of the unit is still mining Integral method to increase the amount of computation such as surface integral with a curved edge, the line integral using the Gauss- The Legendr)

C++实现的FFT，详细，简单，内含多个测试类(using C++ implements fft，including serials class)

埃特金加速法 中国矿业大学理学院 计算方法实验5,还可以的(Aitken acceleration method China mining university faculty of science calculation method for the experiment 5, you can also)

可进行最小二乘法线性拟合输出，包含源代码及生成后的程序(Least-squares linear fit can be output)

多项式的加减法运算，输入的多项式带有未知数x和数字(Polynomial addition and subtraction calculations)

同时辨识模型阶次及参数算法。用阶次递推算法，结合AIC法——利用赤池信息准则辨识上例的模型阶次和参数。(At the same time identify model order and parameters algorithm. By order recursive algorithm, combined with AIC method- the use of Akaike information criterion to identify the cases of the model order and parameters.)

C++实现的FFT，详细，简单，内含多个测试类(using C++ implements fft，including serials class)

比Windows自带的高级一点的计算器，能将整个表达式输入，然后求值。 这个程序要求读者具备编译原理的一些知识。 (Advanced calculator than Windows built, the whole expression input can be then evaluated. This program requires the reader to have some knowledge of compiler theory.)

说明：  曲线的三次样条插值，在非首尾节点处具有三次光滑性质(Curve cubic spline interpolation, in both nodes with non-smooth nature of the three)