Search results

1. How to use 3D FDTD code for 1D problem?

Hello, I have a three dimensional FDTD code. The problem I have for simulation is one dimensional. How can I use this 3D FDTD code for the 1D problem. The 1D problem is like this: in one-dimension half of the problem space is filled with a dielectric medium and the other half is free-space. A...
2. How to find Resonance frequency of rectangualr cavity from FDTD data

Hello, I have written 3D FDTD code with Mur ABC which gives correct results for time domain data. Now I want to compute the resonance frequency of a rectangular cavity using this 3D FDTD code. I donot know how I will do that. Would someone please advise me the steps I need to follow now to...
3. Fortran (Fortran) Does order of accessing a matrix affect the performance?

Hello, In Fortran 90, will the performance (in terms of computational efficiency) of the following two be the same. If not, which one will be faster. Please advise with the reasoning: (i) do i = imin,imax do j = jmin,jmax do k = kmin,kmax Several statements (rigorous...
4. Help with awk command please

Hello, I have about 8000 files in a directory all having names like file000001.txt file000002.txt file000003.txt file000004.txt ---------- ---------- file007999.txt file008000.txt Now I need to do 2 things: 1. I found out that I donot actually need the data from the files whose...
5. How can I do this with AWK

Hi, I need to modify a shell script and add the following into it: location: 200 200 1 location: 200 200 2 location: 200 200 3 --------- --------- --------- location: 200 200 449 location: 200 200 500 I thought using some awk command one could produce the series...
6. Mathematica How to do it in Mathematica

If I want to simplify an extremely large algebraic expression which equals zero to a simple neat equation -- how do I do that in Mathematica (or symbolic package of Matlab). Giving you an example of the equation below: (c1 (-1 + E^(I dx kx)) (-1 + v4))...
7. MATLAB Using Matlab functions in Fortran - need help

Hello, My work is on numerical techniques which require to solve sparse matrices etc. All my work is in fortran and I have almost no skill in Matlab.But I have just realized that Matlab can do some computations quite easily with its built-in functions and I want to take advantage of this. I...
8. Mathematica Symbolic computation: Mathematica help

Hi, I need to get a simplified equation by setting the determinant of the following expression to zero: exp(j.omega.dt). [I] - [G] Here, I is an 18x18 identity matrix and G is an 18x18 matrix that I got by doing some symbolic computation in Mathematica (in fact G is huge). Can anyone...
9. MATLAB Matlab: how to extract blocks from a large matrix

Hi, I have a 24000x24000 sparse matrix. I want to extract 4 blocks out of it; (0,0) to (6000,6000) (6001,6001) to (12000,12000) (12001,12001) to (18000,18000) (18001,18001) to (24000,24000) By use of those my aim is to make a block diagonal matrix using matlab command 'blkdiag' . Can...
10. MATLAB Matlab problen with reading from files - need help

Hi, I have a formatted data file (obtained from fortran) which has 1 column and 24000 rows. The values are like -0.8736252526127E-9 -0.1928287267367E-11 0.28373737626278E-12 etc etc. I have tried to read these data in matlab using the following command : fid=fopen('filename')...
11. MATLAB Need help on Matlab code

Hello. Can anyone help me in producing a Matlab code that will read a sparse matrix and then calculate the eigenvalues of it, show the sparsity pattern of it etc. I have the the sparse matrix data in compressed sparse row (CSR), compressed sparse column (CSC) formats and also in Co-ordinate...