0
votes
0answers
23 views

large eigenvalues with LAPACK

I have question about LAPACK. I calculate eigenvalues of a $16\times16$ Hermitian complex matrix with small entries by ZHEEV ...
0
votes
0answers
12 views

How to solve a nonlinear diffusion equation-comsol?

Consider a thin film with a perpendicular applied magnetic field ${H_{a}}$ (A/m) in z-axis. In fact, By increasing ${H_{a}}$ the magnetic field penetrates gradually the film. The equation for the time ...
0
votes
1answer
33 views

Numerical integration of sharp peaked function (position of peak known)?

What methods are available to integrate a sharply peaked function (position of peak known) on a finite interval (the interval includes the peak)? Currently I am getting underflows using some of GSL's ...
0
votes
0answers
4 views

Calculating win statistics for tennis teams

A tennis club has four teams in three different divisions (two of the teams play in the same division). Players can play for one or more of the teams in a season. I want to calculate the win % for ...
-1
votes
0answers
31 views

How to improve my code for Newton-Raphson method in C? [on hold]

I need help in order to improve my code. This code finds the roots of equation, but when it does not have any root, nothing appears on screen. I need "output" in this way: for instance, "input" ...
2
votes
0answers
42 views

biharmonic equation weak form finite element method

I am trying to solve simple scalar biharmonic equation using bubnov-galerkin finite element method. I am using $H^2$ conforming basis functions. I was wondering that if anyone can give me some ...
0
votes
1answer
31 views

Is there general algorithms to solve such 3D cutting problems?

Suppose a cuboid $\mathbb{A}$ has $L$,$M$ and $N$ as its length, width and height respectively, where $L\ge{M}\ge{N}>0$; Now we want to cut $\mathbb{A}$ into smaller cuboids with length $x$, width ...
0
votes
0answers
11 views

Generate KDE plot with scipy gaussian_kde

I would like to generate a plot of the density of a set of data, and compare to a scatterplot of individual data points. My first plot is generated with: ...
0
votes
0answers
35 views

How to curve fit an unknown function?

I have data which can be described by $y=f(x,z)$ where $z$ varies from 170 ~ 154. Now values given by $ks$ are known sample values that equals value given in the table header, $uks$ are unknown ...
4
votes
1answer
63 views

Find the direction of the gradient on a finite element mesh

Suppose we have a triangular mesh of a two dimensional shape $\Omega$, and on this mesh we define a P1 finite element structure. I know that given $u,v$ by their values at the vertices of the ...
-1
votes
0answers
16 views

Temporal convergence of 2D transient advection-diffusion problem

I have a simple 2D transient linear Advection-diffusion problem with zero source term. And I assume a very large diffusion term (which is very stiff) If I use a standard Galerkin discretization in ...
0
votes
0answers
30 views

Best way to average surface data or function data in 2d grid

I have a pressure data (N/m^2) on a 2d triangular surface. The histogram plot of surface data (nodal values) looks like: I can do average(data). 1) how to do spatial average? 2) is there any ...
1
vote
2answers
51 views

Solve large dense positive-definite linear system

Which method should I choose to solve a large (~20 000 variables) dense symmetric positive-definite, possibly ill-conditioned, system of linear equations? The system will be solved for two vectors. ...
1
vote
0answers
17 views

Resources for large-scale MILP optimization

With the advent of "big data" applications, different algorithms have to be used to efficiently solve optimization problems, even in the convex case (e.g. the recent success of stochastic gradient ...
2
votes
1answer
50 views

precision loss in non-trigonometric, periodic functions using FFTW and NaNs after marching forward in time (Fortran)

I have developed a pseudospectral solver of the Navier-Stokes equations using FFTW. I tested my formulation of right hand sides (RHS) of the NS equations against standard trigonometric functions ...
2
votes
0answers
80 views

Help implementing 1D (ODE) discontinuous Galerkin method

I think I made a mistake in calculating the system matrix $\bf H$ described below, I need help figuring out what went wrong. I'm trying to apply a discontinuous Galerkin method to approximate the ...
0
votes
0answers
9 views

internet protocol OSI [migrated]

Assume a maximum data field for an ethernet frame of 1500bytes. What is the overhead (in%) for a 4096 byte application message? Hint: the message must be segmented into multiple frames and be careful ...
0
votes
1answer
55 views

Solving a PDE using Matlab (with varying initial conditions)

I want to solve a 1-D heat conduction PDE using Matlab which looks like $$ \rho c_p \dfrac{\partial T}{\partial t} = \dfrac{\partial}{\partial z}\left( \lambda \dfrac{\partial T}{\partial z} \right), ...
3
votes
1answer
71 views

What is the case of trade-off in different Runge Kutta methods

There are so many Runge Kutta methods, including Dormand-Prince 45 Cash-Karp 54 Fehlberge 78 Is there any comparison between them? What is each approach sacrificing? What is the general ...
2
votes
1answer
53 views

Calculate contour line length

I would like to know the algorithm to calculate contour line length. Suppose we have numerical data set of an function $f(x,y)$. How could I calculate the length of the line from $(x_1,y_1)$ to ...
2
votes
0answers
80 views

Help understanding the so-called “spectral method”

This is a follow-up question to an answer I read here. $M$ is some hermitian matrix and $V$ an vector. Since the matrix is hermitian, you could use it as a hamiltonian to propagate it in ...
0
votes
2answers
40 views

Compute the intersection of convex sets in Matlab

I'm aware of a Matlab function which take a set of point as an input and select the points which compose the convex hull. Exemples from Mathworks website : ...
0
votes
0answers
12 views

What is the elastic constants for tetragonal zirconia (GPa)? [migrated]

I have known six constants of TZP, what is the relationship between the known and the unknown? known: c11 = 327, c12 = 100, c13 = 62, c33 =264, c44 = 59, and c66 = 64 (units: GPa) unknown: all the ...
4
votes
1answer
34 views

Estimating the local compression/expansion ratio for a transformation on a point cloud

Let's say we have an unorganized point cloud P1 with N points, each with coordinates {x,y,z}. We apply non-rigid transformation to P1 (translation + rotation + warping), to obtain point cloud P2. ...
2
votes
1answer
70 views

Sparse iterative out-of-core parallel solver

Is there an iterative sparse parallel solver with out of core capabilities? I need to solve a very large system of equations. I have implemented direct sparse parallel solvers in core and out of core ...
1
vote
0answers
21 views

Can F-cycle substitue FMG for update of existent solution?

I have a nicely working multigrid solver, which I use for solving the Poisson equation from an electrostatic problem. I solve this equation first without any charges, and then many times with a slowly ...
0
votes
2answers
79 views

Explain this multivariate differential identity

$$ \frac{\partial|\nabla\phi|^2}{\partial\phi}=-2\nabla\cdot\nabla\phi$$ I would very appreciate that you help me . Please do it in detail, I am quite not good at such problems. There is something ...
0
votes
0answers
29 views

Could anyone help me with dde23 function

I have been trying to graph these equations using dde23 but keep having a error. This is very important for my presentation so I would really appreciate any help ...
4
votes
2answers
100 views

Solving Laplace's equation on a domain with moving boundary

Consider a function $X(\xi,\nu)$, $2\pi$ periodic in $\xi$ satisfying $$\nabla^2 X = 0$$ in a domain $D$ with $\nabla = (\partial_{\xi},\partial_{\nu})$. If I know the values of $X$ on the boundary ...
0
votes
0answers
46 views

How to solve a nonlinear diffusion equation?

Consider a thin film with a perpendicular applied magnetic field Ha in z-axis. The nonlocal relation between Ha, the self-field Hself (generated by the eddy current J) and the local magnetic flux ...
1
vote
0answers
50 views
+50

Jacobian-Free Newton-Krylov vs explicitly forming jacobian in DG

For a given discontinuous galerkin (DG) implementation for Navier-Stokes, targeting 10,000 to 1,000,000 4th order cells in 3D, I'm using PETSc's suite of linear/non-linear solvers on the back-end. It ...
0
votes
0answers
40 views

Modelling a Quantum Cascade Laser (QCL - GaAs atop Copper Heat Sink) with COMSOL

I am trying to model this: GaAs on-top of a heat-sink made of Copper. It's trying to simulate a type of Quantum Cascade Laser, I'm looking at the effect the temperature has by running a 10 V ...
1
vote
1answer
85 views

Simple integration in Matlab is off

This is an incredibly mundane integration, but for some reason I can't spot the error. I am just performing a simple 3d integration in spherical coordinates which should return the value of 1.0: ...
0
votes
1answer
61 views

Choosing hardware to use with PETSc

I would like to know more on choosing hardware to get the maximum price/performance when using the PETSc library (and various third-party preconditionners) I am currently working on a 2 cpu ...
4
votes
1answer
44 views

Eikonal Equation solver with different grid densities

The Fast Marching Method, Fast Iterative Method, and Fast Sweeping Method are three ways of solving the Eikonal Equation on a discrete grid, essentially just a wavefront spreading out from initial ...
0
votes
1answer
54 views

FEM - Shape function of a HEX20 - plot in MATLAB

I have a FE model of a simple plate with hole (tension load) with HEX20 mesh. I need to obtain the Shape Function of one of the elements (the one with highest stress) and plot it (with MATLAB). After ...
0
votes
0answers
12 views

Improvement of Minimum description length (MDL) estimate

I earnestly request apology if this question is inappropriate for the forum. The question has two parts one technical and the other is not technical. I would appreciate any response. Let me consider ...
0
votes
0answers
60 views

Conditions for always positive gradient of heat field in evolutionary thermo-elastic system

I am investigating stability and convergence of series of approximations for coupled thermoelasticity problem yielded by one-step recurrent time-integration scheme. I've managed to show that the ...
2
votes
0answers
37 views

Fast Laplace transform

There are examples for fast numerical inversion of the Laplace transforms. For example here: ...
0
votes
1answer
47 views

Standard Algorithms for Permuting CCS or CRS Sparse Matrices

I need to permute the degrees of freedom of a system and apply this permutation to a few sparse matrices in CCS (or CRS) format. I could construct a permutation matrix and perform sparse matrix-matrix ...
3
votes
1answer
32 views

Choosing how many iterations to use in VEGAS

I'm using VEGAS integration, specifically the GSL implementation, for some QCD calculations, and I've been investigating the behavior of the algorithm for various numbers of iterations in an attempt ...
0
votes
0answers
43 views

Intel Xeon Phi and ANSYS FLUENT [closed]

Somebody turned effectively accelerate calculations in ANSYS FLUENT (into ANSYS Workbench 14-15-16 versions) via Intel Xeon Phi: 5110P or 31S1P model? It is possible? FLUENT support this ...
1
vote
0answers
53 views

Calculate Integral Using Gauss Jacobi Quadrature or otherwise

I need to integrate the following integral: \begin{align} I = \int^z\frac{1-\zeta^2}{(1+\zeta^2)(\zeta-\zeta_l)(1-\zeta_l\zeta)}\prod_{k=2}^{n-1}\left ( \frac{\zeta-z_k}{1-\zeta z_k} \right ...
0
votes
0answers
25 views

finite element magnetic field single coil transformer

I am trying to implement a finite element analysis script which calculates the magnetic vector potential in the nodes of a single coil transformer/inductor using a square grid to keep it simple. The ...
0
votes
1answer
42 views

Best path for estimation

I have a Cartesian grid (100x100) in which some of the points are known (30 out of 10,000) and the rest are unknown. I want to use the known points and estimate the other cells. Is there any ...
2
votes
0answers
25 views

Adaptive plotting of two-variable functions $z=f(x,y)$ algorithm pseudocode?

I am looking for explanations of algorithms to adaptively sample a function of two variables $f(x,y)$, in a given domain $x_0\le x \le x_1$, $y_0\le y \le y_1$. Intuitively, I want to sample more ...
1
vote
2answers
158 views

Python, numpy and complex functions (PDE's)

Update 4 I have almost given up on getting this right. This is the solution to the time-independent Schrodinger's equation, so the analytical solution is: $\psi(x,t) = \psi(x,0)e^{\frac{-iE ...
1
vote
1answer
35 views

Least Square fit with Double Zernike Polynomials

I need to describe the optical aberrations of my set-up with Zernike polynomials. To do this, I want to fit the first 15 polynomials in the following way on my data: $$\chi^2 = \sum_k\left(\beta_k^x ...
0
votes
0answers
51 views

Solving PDE with state and time dependent boundary conditions

I am interested in solving the following PDE (heat equation): $$\frac{\partial u}{\partial t} = \kappa \frac{\partial ^2 u}{\partial x^2}$$ In order to solve it, I discretize space uniformly into $N$ ...
0
votes
2answers
39 views

How to obtain streamslines from velocity field data points

I managed to solved a lid-driven cavity flow using LB code. It gave me the velocity field data points. Now I have to obtain streamlines too, of course from the obtained velocity field. Besides, I ...

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