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# Bill Greene

### MathWorks

100 total contributions since 2012

CAE Consultant

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Deflection of a Square Plate Calculated With PDE Toolbox
Deflection of a Square Plate Calculated With PDE Toolbox

Solving 2 PDEs across one domain.
This documentation page shows how to specify an f-coefficient on a specific domain: <http://www.mathworks.com/help/pde/ug/sca...

5 years ago | 0

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Solved

Times 2 - START HERE
Try out this test problem first. Given the variable x as your input, multiply it by two and put the result in y. Examples:...

5 years ago

Solved

Make the vector [1 2 3 4 5 6 7 8 9 10]
In MATLAB, you create a vector by enclosing the elements in square brackets like so: x = [1 2 3 4] Commas are optional, s...

5 years ago

Simulation of coupled partial differential equation using MATLAB.
I took a look at your attachment and think I understand most, but not all, of the problem you are trying to solve (I don't under...

5 years ago | 0

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Problems with LDL factorization
Have you tried solving the over-determined system directly: x = A\b; Computing using the normal equations, A'*A, is almost...

5 years ago | 0

Can I use Poisson equation or any equation with desired parameters in PDE Toolbox using Rectangular shape?
Take a look at this example: <http://www.mathworks.com/help/pde/ug/electrostatics.html> Bill

5 years ago | 0

Why aren't the essential boundary conditions fulfilled?
I ran this example in R2014a of MATLAB and I do get -1 at the lower left corner (and upper right) I created the example in pd...

5 years ago | 0

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Solve parabolic coupled PDE's using MATLAB's pdepe solver?
Yes, pdepe can definitely solve systems of pde. In general, the u argument to the functions you define has as many rows as ther...

5 years ago | 0

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structured quadrilateral mesh in PDE Toolbox
There is no support for quadrilateral elements in PDE Toolbox-- either in the meshers or the computational modules. However, if...

5 years ago | 0

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How to define a temperature dependent parameters in a PDE Toolbox?
Yes, PDE Toolbox allows the coefficients to be functions of the dependent variables (e.g. temperature). This documentation page ...

5 years ago | 2

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Setting up the initial conditions for BVP4C?
From your call to bvpinit where you have this [0.01; 0.9] for the initial guess, it looks like you have 2 differential equation...

5 years ago | 1

Matlab hyperbolic PDE equation errors
There are several ways to define PDE Toolbox coefficients that vary spatially. But, defining the value of the coefficient at eve...

5 years ago | 1

How to solve system of three nonlinear PDE?
pdenonlin is for solving only PDE that are not a function of time. However, the parabolic function can solve equations that a...

5 years ago | 0

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Solve a non linear differential equation systems with only boundary conditions
You have a system of two first order differential equations so you need just two boundary conditions. I would guess that specify...

5 years ago | 0

Reg. PDEPE 's internal discretization of time
pdepe uses the variable time step ODE solver, ode15s, internally. http://www.mathworks.com/help/matlab/ref/ode15s.html The...

5 years ago | 1

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Insert f coefficient in pdetool
Do you calculate F in fcoeff? If so, you can make it a global variable and it will retain its value between calls to fcoeff. ...

5 years ago | 0

pdepe daeic12 (line 77) eror
I don't see any boundary conditions on c3. I think this may be the cause of your problem. Bill

5 years ago | 0

Error solving simultaneous PDEs.
The first thing I should say is that pdepe is designed to solve systems of parabolic and elliptic PDEs. Practically this means t...

6 years ago | 0

create sparse matrix from diagonal arrays
This doesn't exactly answer your question but still may be useful. This example: http://math.mit.edu/cse/codes/mit18086_poiss...

6 years ago | 0

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How to implement irregular, time-dependent boundary condition in PDEPE function?
I think that pr = interp1(timedata, tempdata, t) - ur; may be what you need. Assuming the lengths of timedata and temp...

6 years ago | 1

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How can I solve a PDE with given coefficients in time?
Take a look at this example: <http://www.mathworks.com/help/pde/ug/nonlinear-heat-transfer-in-a-thin-plate.html Nonlinear Hea...

6 years ago | 0

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Function of boundary conditions PDEPE
To set the temperature at each end to fittedmodel(t), you would define: pl = ul-fittedmodel(t); pr = ur-fittedmodel(t); ...

6 years ago | 0

calculate the capacitance with PDE toolbox
One of the simplest ways to calculate capacitance using PDE Toolbox is from the energy: C = 2*U/V^2 where U is the electrostatic...

6 years ago | 1

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How to control times at which PDE Toolbox solves a parabolic equation?
I'm afraid I wasn't able to run your example. I believe that your fcoeff function has an error in it. I did take a look at th...

6 years ago | 0

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Calculation of Jacobian for ode15s in hyperbolic/parabolic-Solver?
If the Jacobian is a function of the dependent variables (or time), ode15s will typically call pdehypdf many times during a com...

6 years ago | 0

Calculation of Jacobian for ode15s in hyperbolic/parabolic-Solver?
Hi Lena, Yes, you are correct that the Jacobian calculated in parabolic/hyperbolic is only approximate. However, in my experi...

6 years ago | 0

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How to control times at which PDE Toolbox solves a parabolic equation?
>This does not yield correct results at the time values I ask it to plot the results So, why don't you request results at the...

6 years ago | 0

eigs - Error with ARPACK routine znaupd: info = -8
I'm not certain what the problem is but I can suggest something to try. I'll assume you really want around 20 eigenvalues. By...

6 years ago | 0