# Torsten

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**Content Feed**

How to solve below PDE based model using finite difference scheme.

Take a grid (ai,xj) over your rectangular region with 0 = a1 < a2 < ... < an = 60 0 = x1 < x2 < ... < xm = 40 Approximate the...

ungefär 5 timmar ago | 1

Error: Array indices must be positive integers or logical values. implementing fletcher reeves method

[xmin,valormin]=fletcherreeves2([5;5],@(x) x(1)^2-x(1)*x(2)+4*x(2)^2+3*x(1)+2,@(x) [2*x(1)-x(2)+3;-x(1)+8*x(2)],10^-(6)) func...

ungefär 21 timmar ago | 0

Why do I get 'Array indices must be positive or logical values' in symsum function?

h=0.05; U=0.02; delta_t=1; v=1.846*10^-5; d=1.117; t=50; y=0.2; P=pi; n = 1:300; Fn = 1./n.*exp(-(n.^2*P^2*v*t)/(d*h^2)...

ungefär 23 timmar ago | 0

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How to get numerical values of nonlinear implicit function?

k = -1.5; F = @(t,y) log(abs(y)) - y.^2/2 - t - k; fimplicit(F,[0,4],'*') t = 0:0.01:0.99; y0 = 2.0; y = zeros(size(t)); f...

ungefär 23 timmar ago | 0

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How to write the equation in matlab I= A A* T² exp (qob/kT) exp (q(V - Rs I /kT)) (exp (-1/n) ? Why is the curve not shown in the drawing?

Maybe you mean I = A*a*T^2*exp(q*phi_b/(K*T))*exp(q*(V-I1*Rs/(K*T)))*exp(-1/n) ?

ungefär 23 timmar ago | 0

How to solve three coupled partial differential equations using matlab code?

Use MATLAB's "pdepe".

en dag ago | 0

it says it cant plot because my vectors aren't the same size but they are

Check whether size(yvar) equals size(xvar). I think this cannot be true because the following code works: yvec=[6.67 17.33 42...

en dag ago | 0

I'm trying to run a code to plot conversion vs catalyst mass in a packed bed reactor, but something is wrong.

You tell the integrator that you have four additional inputs to your function [W,F]=ode45(@(t,F)ODEfun(t,F,T,P_total,F0_total,R...

2 dagar ago | 0

Bisection function to determine the value of (k) not working.

Please fill in the missing values and try again. If you don't succeed, it usually helps to plot f in the range 1e-12:1-1e-12 fo...

3 dagar ago | 0

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2nd Order ODE Euler method not producing expected results

Not that bad. %Coefficients m1=3; m2=6; k1=1; k2=9; k3=3; c1=0.02; c2=0.09; c3=0.06; % Step sizes h=0.00005; t...

3 dagar ago | 0

Index exceeds the number of array elements (7).

The last two loops also have to run from 1 to length(code), not from 1 to length(t).

3 dagar ago | 0

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Summing over indices using symsum

u=symunit; Q(1)=10E-9*(u.C); Q(2)=15E-9*(u.C); Q(3)=7E-9*(u.C); Qsum = sum(Q)

3 dagar ago | 1

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Fitting method with multiple response variables (y1, y2, y3).

rng("default") X = linspace(0, 10, 100)'; Y1 = 2*X.^2 - 3*X + randn(size(X))*0.5; Y2 = 2.5*X.^2 - 3*X + randn(size(X))*0.5; ...

3 dagar ago | 0

sym/besseli - Too many input arguments.

There is no third argument in the symbolic function "besseli": https://de.mathworks.com/help/symbolic/besseli.html

3 dagar ago | 2

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Symbolic Computations for three non-linear equations solution

fl = [1.883806, 1.883135, 1.882170]*10^9; Qe = [161.43, 10.765, 2.5734]*10^4; syms A fu alpha eq1=fl(1)-(1+(A/(Qe(1)^alpha))...

3 dagar ago | 1

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i am trying nonlinear for nonlinear ode using by finite difference method

You want to solve a nonlinear system of equations using Newton's method, but you didn't supply the Jacobian "df". i.e. df{i}/dx...

3 dagar ago | 0

which of the following sets vectors are independent?

In order to prove that sin(t), cos(t) and cos(2*t) are independent, you have to show that if f(t) = a*sin(t) + b*cos(t) + c*co...

3 dagar ago | 0

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Help in writing a a code for an array based on comdition.

A1 = [-0.0082 -0.0409 -0.0175 -0.0853 0.0217 -0.2556 -0.0302] A = -(A1<0) + (A1>0) s = sum(A) threshold = 12; v...

4 dagar ago | 0

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Keep getting an error with trapz. Please help

baba = trapz(time,ribua) instead of baba = trapz(T,ribua)

4 dagar ago | 1

Fitting a Transcendental Equation with Multiple Solutions

You can try "lsqnonlin" with the functions F_ij defined as F_ij = f(a1,a2,a3,x_i,y_ji) - c Here, the y_ji are the y-values cor...

5 dagar ago | 2

| accepted

ODE45 ERROR en el @odefun

Use dfidt=[dfi1;dfi2]; instead of dfidt=[dfi1(1);dfi2(2)]

5 dagar ago | 1

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Error using plot. Data must be numeric, datetime, duration or an array convertible to double.

Arm = 5; T = 2; t = linspace(0,5*T,1000); t = t.'; hold on for N=0:Arm n = 1:N; A0 = 5/4*ones(size(t)); An= ...

5 dagar ago | 0

Why do fit results and parameter confidence intervals depend on magnitude of units? Why are confidence intervals nonsense on a good fit?

Your model is not adequate because it needs 3 parameters, not 4. Write it as curvem(x) = a.*(x./b).^(-c) + d = a/b^(-c) * x^(-...

5 dagar ago | 0

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How to observe parameter value existing in constraint while solving problem using "ga"

Add the line left_hand_side = E_prop + cumsum(sol.S.*(sum(Energy_Pr,2))) after the solution has been obtained.

6 dagar ago | 0

selecting indices in a matrix and setting the rest to zero

A = rand(5,3); idx = [2 4].'; idx_left = setdiff(1:size(A,1),idx) A(idx_left,:) = zeros(numel(idx_left),size(A,2))

6 dagar ago | 0

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I am trying to solve current equations of a pv cell using fsolve butit keeps showing error, can someone pls see what the error in my code is?

clc; clear all; Pmpp = 50; %Max Power Vmpp = 17.98; %Vol at Pmax Impp = 2.77; %Current at Pmax Isc= 3; ...

6 dagar ago | 0

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Use one function in another

n = 7; a = [3 4 1 2 5 2 1]; A = createMatrix(n, a) period = findPeriod(A) function A = createMatrix(n, a) A = zeros(n);...

6 dagar ago | 0

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Bvp4c 2nd order equation with 2nd and 3rd order boundary conditions

Since you can only impose two boundary conditions for a second-order equation, take the first and the third. They should already...

6 dagar ago | 0

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How can ı solve this difference equation ?

um2 = 0; um1 = 0; u0 = 1.5820; u1 = -0.5820; u2 = 0; xm2 = 0; xm1 = 0; x0 = 1.3679*xm1 - 0.3679*xm2 + 0.3679*um1 + 0.2642...

7 dagar ago | 0

| accepted