# All Questions

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142 views

### Clustering with points lying along different 3D planes

I have a bunch of data points in 3D that lie along a few planes. What would be the best approaches to estimate the normals of these planes? Edit: There are roughly equal number of points lying along ...
83 views

### What's a nice simple PDE to play with in Matlab?

I want to learn a very simple PDE to gain physical and mathematical intuition—a PDE with just one spatial dimension $x$ and a time dimension $t$. And, I want to write code for it in Matlab and use a ...
101 views

### Multi-domain 3D Geometries for MATLAB PDE Toolbox

In principle the PDE Toolbox in MATLAB can handle multi-domain 3D geometries as noted here. This feature and the associated function geometryfromMesh were introduced in MATLAB R2018a. The associated ...
67 views

### Defining Current Density in a FEM model (MATLAB)

I'm attempting to solve the Poisson equation in 3D for a magnetic vector potential in the presence of a current source. To validate my code, I'm initially looking to reproduce the model described in ...
35 views

### Find index for submatrix with maximum sum

Given an N-dimensional matrix A, I want to find an M<N dimensional index array I such ...
86 views

### Average value divergence in spectral method for Poisson equation

I'd like to know how to deal with a divergence when trying to solve the Poisson equation for electrostatics with a simple spectral method. I'm not sure how to best state my problem, so I'll explain ...
154 views

### How to optimize sampling for parameter estimation

I have a computer model with a number of parameters that need to be calibrated based on experimental results. It's also important to understand the sensitivity of the results to each parameter ...
23 views

### non premixed Combustion by using oxygen droplets

I am trying to simulate a case in ANSYS FLUENT for combustion of methane and oxygen where oxygen enters the domain in the form of droplets. There is a change in temperature but there is no formation ...
86 views

### Null space for smoothed aggregation algebraic multigrid

I do not really get the point of null space usage for creating the prolongation operator for smoothed aggregation algebraic multigrid. I know what the null space is per definition and I know that the ...
71 views

### Unforeseen behaviour of fix() in Octave and Scilab

I encountered some odd results when using the function fix() in Octave and Scilab. The following is input and output of the Scilab console but the exact same thing happens in Octave. I start with the ...
76 views

### Optimize multivariable function with interdependent variables

I have a cost function with 2 parameters. The variables are dependent on each other. So, if I just take a partial derivative with respect to one variable the slope is in terms of the other variable ...
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### List of Tersoff potentials?

I would like to know some GNU libraries or lists of downloadable Tersoff potentials. I couldn't find that many of them, and I also would like to know if there is a reason as to why this is the case.
88 views

### Solving system equation

Given matrix $K_{n \times n}, H_{n \times n},M_{n \times n}$, I want to solve for $B_{n \times n}$ and $V_{n \times 1}$ from the nonlinear system of equations: \begin{aligned} &H_{i j}=\frac{B_{i ...
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### Change of random variables and check by plot

Question As a test, I transform a uniform distribution over the unit square. But when I check the transformed distribution with Monte Carlo, it is wrong. What went wrong? Thanks. Problem Random ...
96 views

### Numerov method for Schrodinger equation

While learning about numerical methods for solving the Schrödinger equation I came across Numerov's method. I want to get the solution for the harmonic oscillator by alreading giving the eigenvalues. ...
56 views

### Testing a block tridiagonal system of equations

In 1D problems, tridiagonal systems of equations are obtained when we use finite-difference or finite-volumes in a structured mesh. A wide solver is the TDMA algorithm here. In two-dimensional ...