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Torsten


Last seen: Today |  Active since 2013

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Answered
Trouble solving system of pdes with pdepe
"pdepe" is a solver for parabolic-elliptic partial differential equations. The positions with zero elements in the f-vector indi...

3 days ago | 0

Answered
Solving the differential equation gives unexpected results. How to fix that?
Better ? v(t) = v(0) - g*t - v0*log(m0/(m0-k*t))

4 days ago | 0

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Define function for transient transient boundary condition
F1= 3.843e-8; F2= -3.482e-5; F3= 1.179e-2; F4= -1.95; F5= 23.69; Trefrig = @(location,state)F1*state.time^4 + F2*state.time...

6 days ago | 0

Answered
How to write an event function to stop at second or third x axis crossing.
I'd make the solver stop at each x-crossing. After it returns control to the calling program, add 1 to the number of crossings a...

6 days ago | 0

Answered
Why don't I need a comment character after an (...) ellipsis?
Most probably there is the convention that ... is the symbol to connect two subsequent lines and that everything behind the ... ...

6 days ago | 1

Answered
AYUDA EN CODIGO DE MATLAB PARA UN ESTRUCTURA DE PUNETE EN 3D
If you insert the lines % Calcular desplazamientos en los grados de libertad libres rank(K_aa) size(K_aa) before the command...

7 days ago | 0

Answered
Why Is Colon Operator Not Equivalent To linspace Command?
Both arrays seem to be generated differently such that floating point issues come into play: z1 = 0:.08:50000; z2 = linspace(0...

7 days ago | 0

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How to draw the function relationship graph between two or three variables, where these variables are solved by a system of equations.
Here are the three possible solutions for VL given tc. % 定义符号变量 VL=20; syms tc t2 Q_out Vco Vcn VL %参数关系 L=100e-9; C=50e-6...

7 days ago | 0

Answered
Plotting a variable versus space and time
Use "slice": https://uk.mathworks.com/help/matlab/ref/slice.html

7 days ago | 0

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Answered
checkGradients, but the objective function has two inputs: x and xdata?
valid = checkGradients(@(p)semiCircle(p, Q),p0)

7 days ago | 0

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Answered
How can I evaluate the transition matrix using the fourth order Runge-Kutta ODEs
Seems to work. What's your problem ? Don't use the transition matrix to integrate in one pass. If you have to, generate it with...

8 days ago | 0

Answered
problem with vpa and symsum
The numerical bessel functions are not able to compute your sum correctly (for higher values of k, they return NaN) (see below)....

8 days ago | 0

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Answered
getting singular jacobian error while using bvp4c solver
I can't interprete your solution curves, but it seems to be a problem for the solver that the Scaled Mass goes to 0 with increas...

9 days ago | 0

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Empty sym: 0-by-1 : Don't understand why
I multiplied by the denominators and squared to get rid of the square roots. Your system seems to have 4 (complex-valued) solut...

10 days ago | 0

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Answered
Non-linear least squares estimation with linear constraints in Simulink?
I vaguely remember that using "lsqcurvefit" within Simulink requires to use the Levenberg-Marquardt algorithm. I can't answer wh...

10 days ago | 1

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Answered
Do I have a convergence issue?
B0 = 0.5; B = fsolve(@fun,B0) function residual = fun(B) g = 10; %m/s^2 Q = 70*1000; %N/m tau_L1 = 24*1000; %Pa t_w = 30...

10 days ago | 0

Answered
HOw to find displacement integrating velocity?
The equation from above describes the stationary velocity profile over the length L. Thus replacing v by dx/dt does not make sen...

11 days ago | 1

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Answered
Integration symbiolic form in matlab gives error
I think you will have big problems if you try to integrate a function with values in the order of +/- 1e70. syms r theta Part_...

14 days ago | 0

Answered
Why the symbolic method fail when I tried to expand a ellipse
I get the correct result (at least for coe = [1;1;1;1;1;1]) : aex = expandA(ones(6,1)).' function aex = expandA(coe) A = co...

15 days ago | 0

Answered
Why did i receive error with my for loop ode45 function?
I used numerical values for L1, L2, mblade, kt and Jblade right from the beginning and got expressions for dL_dtheta2_numeric an...

16 days ago | 0

Answered
Why do i get the error (Array indices must be positive integers or logical values) when trying to calculate the determinant
I don't get any error. But you shouldn't overwrite the function "det" by using the variable name "det" for the result. Name it ...

18 days ago | 0

Answered
having if/else statement go to previous input
r = rand(); if opt == 1 || (opt == 3 && r < 0.5) abc else xyz end

20 days ago | 0

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6x6 system of multivariate quadratic equations ... non-negative real solutions
I think there is no specialized solver for a system of quadratic equations. Thus a general nonlinear solver ("fsolve","lsqnonlin...

20 days ago | 0

Answered
Color Burr distribution function line
pd = makedist('Burr','alpha',1,'c',2,'k',5); R = random(pd,100,1); pd = fitdist(R,'Burr'); figure(1) plot(pd) x = 0:0.01:2;...

20 days ago | 0

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Answered
Writing ODE equations for ode45 to solve;
The form of the equations that can be solved by ode45 is M*y'(t) = f(t,y). So you can decide whether you choose M to be the iden...

22 days ago | 0

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Answered
How to use a solver to get the terminal velocity of a sphere.
v0 = fsolve(@fun,1) function res = fun(v0) d_p =...; rho_air = ...; nu_air = ...; rho_w = ...; g = ...; Re ...

23 days ago | 1

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Answered
Nusselt number and skin friction for bvp4c
Nu1 = -(1+bk*(1+m))*S1.y(5,1) Nu2 = -(1+bk)*S1.y(5,end) Tau1 = (1-bv*(1+m))*S1.y(4,1) Tau2 = (1-bv)*S1.y(4,end)

23 days ago | 0

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Answered
K Nested For Loops for arbitrary K
I'd generate all possible k-tuples out of the n numbers and throw away those that are not monotonic by using the "diff" command:...

24 days ago | 0

Answered
How to find non-zero solutions to underdetermined systems of equations
The null() function gives you a basis for ker(A): A=[0.719600000000000,0.069400000000000,0.526400000000000,0.110700000000000;1....

27 days ago | 0

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Answered
How to get the exact step size used by ode45?
If the stepsize is part of the ODE equation, you cannot use ODE45 to solve. You have to write your own integrator.

29 days ago | 0

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