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non linear partial diferential equation
I don't see a similarity to the heat equation. You will have to discretize the left-hand side of the equation and use ode15s to...

mehr als 2 Jahre vor | 0

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求助：编写程序求解积分方程中的参数k的值
gamma_wc = 0.38; t_ITZ = 40; D_c = 0.488; lambda = 1.08; fun = @(k) 125/(1+3.15*gamma_wc)-(125-t_ITZ)*D_c-integral(@(x)D_c*(...

mehr als 2 Jahre vor | 1

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Algae growing. Concentration curve problem
Here is a code for a simple heat-conduction equation dT/dt = d^2T/dz^2 T(z,0) = 0 T(0,t) = 200 T(1,t) = 340 T(0.5,t) = 90 ...

mehr als 2 Jahre vor | 0

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Usage of ode function
I assume you know r0=r(t=0) and v0=v(t=0). Then r = r0 + cumtrapz(t,(a.*F_yf - b.*F_yr)./I) v = v0 + cumtrapz(t,(F_yf+F_yr-m....

mehr als 2 Jahre vor | 0

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How to solve the error "Error using sqpInterface Nonlinear constraint function is undefined at initial point. Fmincon cannot continue." Error occurred when calling NLP solver
Before calling "fmincon", call the constraint function with your initial vector. My guess is that it returns NaN or Inf for some...

mehr als 2 Jahre vor | 0

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Passing out additions parameters after ODE solver.
sol = adsorptionSolver(t,z,yF,TPF) for i = 1:size(sol.y,2) [~,velocity(:,i)] = adsorptionModel(sol.x(i),sol.y(:,i),z(2)-z(...

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Using bvp4c for coupled second order ODEs. Issue in calling bvp4c.
guess = bvpinit(y, uinit); y must be the spatial mesh, uinit must either be a function handle that returns a 4x1 vector of in...

mehr als 2 Jahre vor | 1

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Saving an extra variable from PDEPE
After the computation with "pdepe" is completed, call "pdeval" to get the spatial derivatives of your solution on the x-mesh and...

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bvp5c:Unable to solve the collocation equations -- a singular Jacobian encountered
I get syms x1 x2 x3 x4 x5 x6 real syms D11 D12 D13 D22 D23 D33 real syms u l1 l2 l3 l4 l5 l6 f1 f2 f3 f4 f5 f6 h1 h2 h3 b1 b2...

mehr als 2 Jahre vor | 0

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Unable to get the following DAE system of equations solved
The time derivative of the first equation is 1e45 at the beginning. Check your parameters and their units. %% DAE of solution ...

mehr als 2 Jahre vor | 0

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How to solve Ax=b with some all knowns except some x values
This gives 2 equations in 1 unknown. You must be lucky if you get a value for # that satisfies both equations. In this case, it ...

mehr als 2 Jahre vor | 1

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difficulty solving simulataneous equations
syms Ra Rb La Lb Va Vb iaD ibD ia ib eqns = [Lb*ibD - La*iaD + Rb*ib - Ra*ia + Vb == Va, iaD == -ibD] S = solve(eqns, [iaD,ib...

mehr als 2 Jahre vor | 0

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Calculus Variational; code for finding the value of two constants for 2 values of the variable
I didn't check whether the Euler equation gives x(t) = 5*t^3/6 + c1*t + c2, but if this is the case, you can get c1 and c2 via ...

mehr als 2 Jahre vor | 0

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fsolve not varying input variable
I included your code and inserted the line norm((fun(x0+[0 0 0 0 0 sqrt(eps)])-fun(x0))) before your call to "fsolve". sqrt(e...

mehr als 2 Jahre vor | 1

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I should get a straight line graph in this equation after substituting initial conditions. I dont know where I am getting wrong. Can anyone help me with this?
For which solution variable do you expect a line as solution ? syms t y(t) Dy = diff(y,t); D2y = diff(y,t,2); m=1; k=1; c=...

mehr als 2 Jahre vor | 0

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below are the codes to solve heat transfer using implicit and explicit method but my implicit method is showing huge error, what is wrong on the implicit method
Implicit scheme means: (ut(i,j+1)-ut(i,j))/dt = (ut(i-1,j+1)-2*ut(i,j+1)+ut(i+1,j+1))/dx^2 or ut(i,j+1)/dt - (ut(i-1,j+1)-2*...

mehr als 2 Jahre vor | 0

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whether meshes affect computational step lengths in pdepe
Adaptive in x: no. Adaptive in t: yes. Thus the x-mesh affects computational accuracy, the t-mesh not. The accuracy in t is infl...

mehr als 2 Jahre vor | 1

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calculate the perimeter of a polygon arranged in space
After reading the x/y data, sum up the lengths of the line segments that constitute the circumference: perimeter = 0; for i = ...

mehr als 2 Jahre vor | 0

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Differential Equation - Integral Equation
syms r z k eqn = int((20-1.19e8*r^2)/(1.19e8*r^2),r,30e-6,40e-6)==int(0.54*8*1e-3/4e3,z,0,k); knum = solve(eqn,k) knum = doub...

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can anyone help me to get rid of the error not enough input arguments in line 7?
x0 = [10; 0]; Time_Span = [0, 40.0]; [t_ex2, x_ex2] = ode45(@ODE_Damped_Spring, Time_Span, x0); figure; plot(t_ex2, x_ex2(:...

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Interpolation schemes that produce positive second derivatives of the interpolant
If you do function approximation (e.g. by splines), there are methods to enforce f''>=0. But for function interpolation, it does...

mehr als 2 Jahre vor | 1

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Why do I get different lognormal parameters using lognfit vs. using the fit function with the lognormal equation?
Does this help ? https://uk.mathworks.com/matlabcentral/answers/2067676-lognormal-fitting-with-the-pore-size-and-its-probabilit...

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How to overcome this error while using lsqnonlin for curvefitting??
clc clear all close all warning off %25wt.% freq = [3.21760012464137 3.47500813461269 3.73241614458399 4.05417615704813 4.3...

mehr als 2 Jahre vor | 0

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How to integrate a function over an implicitly defined domains
I'd define the function to be integrated as f .* (g>0) and integrate over the rectangular domain. Here, g is the function that i...

mehr als 2 Jahre vor | 2

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simulation of program in matlab
M2_eq = 1; D2_ov = 1e-2; m=2; x = linspace(0,1,100); t = linspace(0,2,10); u = pdepe(m,@(x,t,u,DuDx)eqn1(x,t,u,DuDx,D2_ov),...

mehr als 2 Jahre vor | 0

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Error when using lsqnonlin in for loop
As you can see, the dimension of "distances" is only 1x4. But it should be 100x4. And better use objective_function = @(p5) [ ...

mehr als 2 Jahre vor | 1

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simulation of program in matlab
Use MATLAB's "pdepe".

mehr als 2 Jahre vor | 0

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Integral with limit variable
Note that t is at the same time integration variable and upper limit of the integral. That's confusing. You should rename one of...

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i have been trying to solve 50 nonlinear equations simultaneously
epsilon = 0.2; N = 0.5; L = 1; bvpfcn = @(x,y)[y(2);(-epsilon*y(2)^2+N^2*y(1))/(1+epsilon*y(1))]; bcfcn = @(ya,yb)[ya(2);yb(...

mehr als 2 Jahre vor | 0

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i have been trying to solve 50 nonlinear equations simultaneously
Does the approximate solution below look correct ? Note that you don't set F(49) in your code. clc clear all mata=zeros(1,50...

mehr als 2 Jahre vor | 0