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Homework Help: MATLAB question

  1. Apr 7, 2010 #1
    1. In the below code, I need to know how to ensure that the peaks end up near the middle. I also want to know how to calculate the end value of "u". Thanks!



    2.
    clear all
    close all
    clc

    u = 1000*ones(1,200);
    dt = 0.01;
    dx = 1/201;
    for i = 2:10/dt
    dudt = diff(u(i-1,:));
    Du = 10*log(10*exp(-0.0001*u(i-1,:)));
    dudt = diff(Du(1:end-1).*dudt);
    u(i,:)= u(i-1,:);
    u(i,2:end-1) = u(i,2:end-1)+dudt*dt;
    u(i,1) = u(i,2)-10*(log(10*exp(-0.0001*u(i,1))))*(1-(log(10*exp(-0.0001*u(i,1))))/100)*dx;
    u(i,end) = u(i,end-1)+10*(log(10*exp(-0.0001*u(i,end))))*(1-(log(10*exp(-0.0001*u(i,end))))/100)*dx;

    hold on
    plot(u(i,:))
    end




    3. I tried using "end/2" in the above expression, but it doesn't give me a suitable solution.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Apr 8, 2010 #2

    Mark44

    Staff: Mentor

    Which "above expression"? Which line is causing you problems, and what exactly are the problems?
     
  4. Apr 8, 2010 #3
    u(i,end) = u(i,end-1)+10*(log(10*exp(-0.0001*u(i,end))))*(1-(log(10*exp(-0.0001*u(i,end))))/100)*dx;

    that is the line that is giving me problems. Basically, when I run this simulation I get peaks occuring at the boundaries - instead, I want peaks to occur in the centre. Can I do this by the following code?

    u(i,end) = u(i,end-1)+10*(log(10*exp(-0.0001*u(i,end/2))))*(1-(log(10*exp(-0.0001*u(i,end/2))))/100)*dx;

    ?

    Also, if I wanted to compute the value of u at a particular place, how would I do that? Thanks a lot.
     
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