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Jun 19, 2018
02:21 PM

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Jun 19, 2018
02:21 PM

matrix finite difference method

Hi,

please try to find solusion of the problem in attachament. Please solve it for coefficients A B C f v = 1. I tried write the matrix but i've could not. Please help write correct matrix for my problem and then solve linear it. The matrix i the importantiest

Solved! Go to Solution.

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Jun 23, 2018
05:28 AM

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Jun 23, 2018
05:28 AM

Thanks for help.It was wery helpfull for me. But this is only 1 problem. We need it resume with the neuton-rapson method. I need only sample for it.

24 REPLIES 24

Jun 19, 2018
03:25 PM

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Jun 19, 2018
03:25 PM

Couple things:

Mathcad considers that array and matrix indexes start at 0 by default. You change this with the system variable ORIGIN.

The order you do things makes a difference. I've put in a small example (3 by 3 instead of 440 by 440) to demonstrate:

Jun 19, 2018
04:44 PM

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Jun 19, 2018
04:44 PM

Hi,

I think for matrix K you intend to assemble as one large matrix, but you have made a nested matrix.

This shows how you assemble a larger matrix from four smaller ones.

Cheers

Terry

Jun 20, 2018
10:24 AM

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Jun 20, 2018
10:24 AM

Hi,

By chance, is the K11 matrix tridiagonal? that is:

Jun 23, 2018
05:28 AM

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Jun 23, 2018
05:28 AM

Jun 23, 2018
07:17 AM

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Jun 23, 2018
07:17 AM

Are you looking for Newton-Raphson in several variables algorithm? see attached.

Jun 24, 2018
02:05 AM

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Jun 24, 2018
02:05 AM

Thanks for this informaction we will back to this nxt time.I ve done it but i am not sure if i did it correctly, would you like looking it in attachment?

Jun 24, 2018
04:32 AM

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Jun 24, 2018
07:58 AM

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Jun 24, 2018
07:58 AM

Great job. Thanks. How we can write separately u and v? then see a graph in 2d for i and j parameters?

Jun 24, 2018
08:21 AM

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Jun 24, 2018
08:21 AM

I do not know the various steps you did to get the matrix that I renamed MK, so I do not know how to proceed. u and v?

Jun 24, 2018
11:48 AM

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Jun 24, 2018
11:48 AM

Look at the equation. we have u and v dimensions. Results is for both dimensions. We need to divide it on down matrix u and v. Then we need to show results on graphs.

Jun 25, 2018
01:51 AM

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Jun 25, 2018
01:51 AM

I could hazard this solution ..... but it is completely heuristic ....

Jun 25, 2018
03:25 AM

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Jun 25, 2018
03:25 AM

Hello, wow, great job. Would you compare solution in two case. For me is not the same. Is possibility draw a graph u,v in 3d?

Jun 25, 2018
04:36 AM

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Jun 26, 2018
04:43 AM

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Jun 26, 2018
04:43 AM

Hej. Thanks for solusions. Would you like preparining a situaction when we have orgin=1. This will be the best situaction. I going to prepare real seample and then I will show you it.

Jun 26, 2018
08:46 AM

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Jun 26, 2018
02:06 PM

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Jun 26, 2018
02:06 PM

Hi, I am from Poland, I've been writing PhD and I have some problems with the finite.... I need to take your solisions and think how it write with real coefficients. I going to write it and we will think about it.ok?

Jun 27, 2018
02:57 AM

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Jun 27, 2018
02:57 AM

Ok!

Jul 09, 2018
08:27 AM

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Jul 09, 2018
08:27 AM

Hi. I could not have solved my problem. In attachment you will find a sample of shield. I discretizationed it and for it we have model of finite difference method the same like last time. for point 3 - u,v=0 for point 28 - u,v=0. For point 5,10,15,20,25 - right site of equation is 10. Please help.

Jul 09, 2018
09:34 AM

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Jul 09, 2018
09:34 AM

Please be clearer. You should consider the fact that I am not aware of the physical system related to the differential equations that you have published, so I do not know how to help you.

Jul 09, 2018
12:24 PM

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Jul 09, 2018
12:24 PM

ok. i will write some. I need only help in mathcad I can write what we need to do in Word.

Jul 15, 2018
09:46 AM

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Jul 15, 2018
09:46 AM

I ve done some. I do not know why i have 74 x74=K we need 72x72 and order are the same like in sample. positions 36 of v are ok. this means 36 u and 36 v from beginning 1,i and i,1

Jul 15, 2018
11:18 AM

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Jul 15, 2018
11:18 AM

You've set N:=72, and you let j run from Origin to N+Origin (that's up to N+Origin=72+1=73).

Then you index MK up to j+1. That makes 73+1 =74 maximum.

Success!

Luc

Jul 16, 2018
05:43 AM

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Jul 16, 2018
05:43 AM

Hi,

Jul 19, 2018
03:58 AM

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Jul 19, 2018
03:58 AM

Hi. I ve done some but I need to do stresses and I do not know how to take into account boundary conditions. Solution is without it.