Torsten

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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...

2 Tage vor | 0

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

3 Tage vor | 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...

5 Tage vor | 0

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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 Tage vor | 0

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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 Tage vor | 1

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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...

6 Tage vor | 0

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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...

6 Tage vor | 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...

6 Tage vor | 0

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

7 Tage vor | 0

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

7 Tage vor | 0

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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...

7 Tage vor | 0

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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 Tage vor | 0

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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...

8 Tage vor | 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...

9 Tage vor | 0

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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...

9 Tage vor | 1

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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 Tage vor | 0

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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...

10 Tage vor | 1

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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_...

13 Tage vor | 0

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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...

14 Tage vor | 0

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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 Tage vor | 0

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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 ...

17 Tage vor | 0

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

19 Tage vor | 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...

19 Tage vor | 0

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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;...

19 Tage vor | 0

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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...

21 Tage vor | 0

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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 Tage vor | 1

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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 Tage vor | 0

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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:...

23 Tage vor | 0

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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 Tage vor | 0

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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 Tage vor | 0

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