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final value of x in PDE
i want to solve this equation for r at given time and concentration I assume that the time for which you want to get r is in th...

más de 2 años hace | 0

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How to prevent substrate concentration going below minimum limit in fed batch fermentation model.
You can use the "Events" option of the ode integrators to interrupt and restart integration with different settings if a certain...

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How can I ensure that the initial solution (x0) for fsolve does not result in Inf or NaN values?
You know your "external_fun" best. Try to deduce in advance which inputs will lead to failure. Maybe you can use "lsqnonlin" ins...

más de 2 años hace | 0

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Huge minimum value from expected results
I cannot run this code because it takes too long or maybe the matrix exponential cannot be computed analytically. Does it give ...

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ODE45 solver returning constant value as the input variable.
As you can see when you run the below code, p is in the order of 1e12 which makes dL/dt effectivly 0. Check your units. %Def...

más de 2 años hace | 1

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The code does not converge
I seems your function does not vary much with rho. The evaluation cannot find a value for rho for which the function has a zero....

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How to plot the error of two numerical methods on the same graph?
%% Given data f=@(x) 8-4.5*(x-sin(x)); df=@(x) -4.5*(1-cos(x)); x0=1; tol=0.0001; n=50; [x_newton,i_newton,Error_newton]=n...

más de 2 años hace | 1

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Modifying the objective function in order to meet the optimization variable boundaries
if (A <= 1e-04) & (A >= 4e-04) How can A be <= 1e-4 and >= 4e-4 at the same time ? And if-statements have to be done elementwi...

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Solve a matrix equation
D = eig(A) will give you the values for D for which det(A-DI)=0

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Solving goal programming problem with MATLAB
x0 must be a vector of size 1x5, not 1x4. Further, your function must return a vector of length 4, not 3. Further, the first o...

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plot() and fplot() give different results for the same function
x = linspace(0, 100, 10000); y = 2*sqrt(1+x)+sin(sqrt(pi)*x).*sin(sqrt(1+x)*pi).*(2*x+1)./sqrt(x) - 2*sqrt(1+x).*cos(sqrt(x)*pi...

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Vpasolve can not find a solution that I know it exist
Maybe it must read Eq2 = ((a21*W2)/(c2*(a21+a22))) - x12 == 0; instead of Eq2 = ((a12*W2)/(c2*(a21+a22))) - x12 == 0; ? c...

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How to build a graph of the solution of a second-order differential equation in MATLAB
Since sin(pi) = 0, your differential equation reduces to y'' + y = 0 with general solution a*sin(t) + b*cos(t) Now incorpor...

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"Busy" when running this code with ODE45
Use ode15s instead of ode45 - you have a stiff system of differential equations.

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How to solve complex equations?
Your equation has only complex solutions. Note that you used sind instead of sin in the function definition. Thus assuming the...

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how to output quantities involving time derivatives in pdepe
You don't have access to the spatial discretization of pdepe, thus no access to the exact time derivatives. But if you choose th...

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lsqcurvefit claiming complex-valued function
Although the fiting function fit_function is the log of a real valued part of the function, why is it considering that the funct...

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How to test whether a function has roots within a given range?
F = @(x) sin(x); xmin = 0; xmax = 6*pi; x = linspace(xmin,xmax); Fx = F(x); I = find(diff(sign(Fx))) F(x(I)) F(x(I+1))

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how to output quantities within pdefun, bcfun, icfun in pdepe
After pdepe has finished, call "heatcyl" at the output times. x = linspace(0,1,25); t = linspace(0,1,25); m = 1; sol = pdepe...

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user defined function including a for loop taking vector input giving vector output
p = 10; result = myfunc2(p) function [y2]=myfunc2(p) y2 = zeros(1,p); y2(1) = 1; for t=1:p-1 y2(t+1)=y2(t)+t; ...

más de 2 años hace | 1

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how to input variable with set of value to the PDE
The x-interval of integration was missing, and your boundary condition at x = xl would not work. Further, I changed the T-vector...

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what's the relation between A , B and M,G for this Nonlinear system of equation ?
A^2 + B^2 - 2*A*B*cos(2*Phi) = G^2 + M^2

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Why Dsolve considers my equations' variables constants!?
syms t x1(t) x2(t) p1(t) p2(t) eq = [diff(x1, t) == x2, diff(x2, t) == - p2 - x2, diff(p1, t) == 0, diff(p2, t) == p2 - p1] ds...

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Difference Plot in matlab
You must either interpolate the output values of the first signal to the times of the second signal or the output values of the ...

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I'm suppose to plot the conventional integral , but I'm getting wrong values
syms t x(t) zeta = 0.1; omegan = 3; f1 = 1; f2 = 0; T1 = 7; T2 = 30; T3 = 40; D2x = diff(x,t,2); Dx = diff(x,t); eqn =...

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Unable to perform assignment because the left and right sides have a different number of elements.
r0=0.05; k1=0.5; k2=0.5; mu=0.5; rho=0.5; epsilon=0.25; K=1; alpha=0.1; q=0.1; eta=0.05; sigma=5; zeta=0.05; omega0=...

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How do I solve multiple bvps with coupled boundary values?
Use the facility of bvp4c to solve multipoint boundary value problems as in your case: https://uk.mathworks.com/help/matlab/mat...

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Solving a nonlinear system of equations (360 unknowns) with constraints
There are specialized algorithms for network simulation. Just blindly writing down the equations and applying a general-purpose ...

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Stacked Cuboid for PDE Domain
Usually in such cases the domain is divided into subcubes that share common faces. E.g. the upper cube could be divided into 9 ...

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Solving system of nonlinear equations using Matlab
You equations only have a negative solution for x3 as you can see from the function plot. syms x1 x2 x3 f1 = x1*24.57^2*1.6^2 ...

más de 2 años hace | 0