All Questions

Filter by
Sorted by
Tagged with
1
vote
0answers
34 views

How can i get this number set to be recooperated from a product sum? [closed]

W==a(x)=2*(W* x)/41; I'm attempting to make a new type of compression algorithm. A rubber band ball type. I'm trying to make a software that extracts, from that formula, the secret volumes of number ...
1
vote
0answers
455 views

ANSYS Fluent: Defining External Force on a Cell Zone [closed]

I am using ANSYS Fluent 15 to simulate a case of fluid flow. In my case, I have three cell zones in my simulation, let's call them top, middle and bottom. My requirement is to put a vertical constant ...
1
vote
0answers
91 views

Monotonic convergence of Newton's method for boundary value problems [closed]

I’m interested in solving nonlinear elliptic boundary value problems of the type $$ -a\Delta u + f(u) = 0, $$ $$ u|_\Gamma = u_0 $$ by Newton’s method when its convergence is global and monotonic. ...
1
vote
0answers
70 views

Method of lines: explanation for high precision low resolution flux and vice versa

Could someone please explain what is meant with e.g high precision low resolution flux. Does it mean, that I use some higher order method (still first order) but with a more complex stencil and ...
1
vote
0answers
45 views

Relaxation - spreadsheet solution to recursive algorithm

I am setting up a simple model that uses recursion to iterate between known constraints - relaxation, in other words. I need a spreadsheet that allows: ...
1
vote
0answers
119 views

Implicit time integrator for Chebyshev collocation method for linear hyperbolic system

I want to solve linear hyperbolic system using Chebyshev collocation method. As this method puts severe constraint on the time step for the explicit time integration, I decided to switch to implicit ...
1
vote
0answers
169 views

Simple MCMC Algorithm in Matlab

I would be really glad to get some specific advise on how to implement a simple MCMC algorithm (in Matlab, if possible). I'm not yet too familiar with optimization methods. My problem goes as follows: ...
1
vote
0answers
378 views

How can I efficiently solve $Ax$=$b$ given $A$ is symmetric and contains very small (even negative) eigenvalues using EIGEN

Currently I am using the EIGEN C++ library to try to solve $x$ from the equation $Ax$ = $b$. One problem I encountered is that the matrix $A$ is a correlation matrix with size > 5000 and can ...
1
vote
0answers
65 views

"Damping factor" for a set of non-linear ODEs

I have a set of four non-linear ODEs representing a negative feedback. I have done parameter variation by random sampling to study the sensitivity of steady state and other dynamic properties to ...
1
vote
0answers
610 views

General algorithm to solve systems of symbolic equations

I want to simplify (solve) a system of linear + nonlinear symbolic equations as much as possible. the equations are of random orders, without differentiation. is there a general & well-known ...
1
vote
0answers
53 views

Execute commands when starting ipdb [closed]

I usually debug a python script by putting the following line into the source code: import ipdb; ipdb.set_trace() Then when I run the script, ipdb starts. Very ...
1
vote
0answers
30 views

Eigenvalue problem of the symmetric real operator which corresponds to the symmetric positive definite matrix

I have a real symmetric function $C(x,y)$ defined on $x,y\in[0,\infty)$, i.e. $C(x,y)=C(y,x)$. I want to solve the eigenvalues problem, i.e. find eigen values and eigen functions: $$\lambda \psi(x)=\...
1
vote
0answers
122 views

Conservation at grid interface in adaptive mesh refinement

I am using adaptive mesh refinement to solve one dimensional inviscid Burgers equation. However I am facing some difficulty to handle grid interfaces which are not uniform (coarse-fine grid interface)....
1
vote
1answer
333 views

extract exhaustive mutually exclusive intervals from larger set of intervals [closed]

I have a collection of time intervals with integer valued endpoints , e.g. (1,2), (2, 6) (5,6), and the number of events falling in each time interval, and I would like to determine if from them I ...
1
vote
0answers
492 views

scipy.integrate.ode ignores boundary conditions [closed]

I am trying to solve the 1-dimensional diffusion problem numerically using method of lines: $$ \frac{\partial c}{\partial t} =D \frac{\partial^2 c}{\partial z^2},$$ where the right hand side is ...
1
vote
0answers
140 views

Numerical integration when solving PDE: Simpsons rule and high frequency noise [closed]

I am solving a PDE, and one of the intermediate steps is to numerically integrate a function over a compact interval. The function is represented on a linearly spaced grid. I am using Simpsons rule (...
1
vote
0answers
678 views

radially averaged power spectrum of a binary image does not look like power law

It has been known that Fourier power spectrum somehow obeys power law therefore the slope of the spectrum can be used to calculate the fractal dimension of an image. Many people have used it for ...
1
vote
0answers
102 views

Is this problem statement good for a GPU?

I am used to using GPU hardware for large scale matrix operations and vectorizing mathematical operations on a continuous space which has been discretized for numerical computation, but this is a ...
1
vote
0answers
96 views

Elemental vs DPLASMA

I want to use one of these two libraries into my C++ project to basically invert a dense matrix (with Cholesky). Of course, I am interested in a distributed environment. Both libraries seem nice so ...
1
vote
0answers
50 views

Optimization of nonlocal stencil-like operator on subset of regular grid

I am trying to optimize the execution time for this particular piece of fortran code. Details: i_gc is a (ngpts, 3) array of containing (i,j,k) indices for each grid point. This is a subset of the ...
1
vote
0answers
51 views

Numerical Implementation of "integrates to some values" type constraint in convex solvers?

I am maximizing a linear functional subject to an integrates to one constraint. More explicitly, my problem is $$\begin{align} &\max_{x \in \mathbb{R}^n}\quad c \cdot x\\ &\text{subject to} \...
1
vote
0answers
78 views

Monte Carlo sampling of particle system for velocity dependent potential

When sampling configurations of point particles in statistical mechanics by means of (Markov chain) Monte Carlo, we may work with a potential that only depends on the positions of the particles, and ...
1
vote
0answers
172 views

Tips on improving stability in numerical scheme for non-linear PDE

I am solving a non-linear second order system of PDEs in two variables. The equations are too complicated to write out here, but an essential feature is that there is a propagating wave which then ...
1
vote
0answers
39 views

Aliasing question for a spectrally derived Lagrangian

Consider two functions $$X=\sum_{n=-N}^N i\ sign(n) y_n e^{-in\xi}; \quad \quad Y = \sum_{n=-N}^N y_n e^{-in\xi}.$$ where $y_n$ are the dependent variables of the system, and are functions of time. ...
1
vote
0answers
91 views

Gauss Integration over Zero Order Element

I'm working with the Boundary Element Method and want to integrate an expression over a triangular region. I would like to use Gauss Integration to do this, but I'm having trouble since the triangular ...
1
vote
0answers
40 views

Minimum effort merging of two sets

I have the following problem. I have two sequences of elements $A = [a_1,a_2,\cdots,a_n]$ and $B = [b_1,b_2,\cdots,b_m]$. I can build a matrix $D[n \times m]$ where $d_{ij} = d(a_i,b_j)$ My greedy ...
1
vote
0answers
113 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 ...
1
vote
0answers
343 views

How to solve a nonlinear diffusion equation?

Consider a thin film with a perpendicular applied magnetic field $H_a$ in $z$-axis. The nonlocal relation between $H_a$, the self-field $H_\text{self}$ (generated by the eddy current $J$) and the ...
1
vote
0answers
108 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 one-...
1
vote
0answers
2k views

Determining Youngs Modulus of defined material in FEA (ABAQUS)

I am quite new to FEA but need to determine if I am performing my simulations correctly. I have a cube of material with defined elastic properties (Youngs Modulus and poison ratio). I perform a ...
1
vote
0answers
48 views

Can variational formulations be solved using series solutions?

What I specifically mean is, given some functional $F\left[\mathbf{x}\right]$ which is stationary with respect to $\dot{\mathbf{x}}=f(\mathbf{x})$ and some boundary or initial conditions, can one ...
1
vote
0answers
307 views

Spin-spin correlation functions in the Ising Model Monte Carlo [closed]

I'm using the Metropolis algorithm for 2D up to 5D for the Ising Model and I want to compute the spin-spin correlation function. $$c(r)=<s_is_r>−〈s_i〉〈s_r 〉$$ but I'm not sure how to estimate $...
1
vote
0answers
41 views

What library can you use to detect personalities from comments? [closed]

I have a bunch of comments from my website that I want to use to build a profile of someone's personality based on the topics they chose to write in and the their specific comments. I know that this ...
1
vote
0answers
553 views

How to choose (and many) threshold in Eigenface?

I edited my question trying to make it as short and precise. I am developing a prototype of a facial recognition system for my Graduation Project. I use Eigenface and my main source is the document ...
1
vote
0answers
27 views

Using HMM for speech synthesis [closed]

I am trying to make a speech synthesizer using a Hidden Markov Model. I read the wikipedia page and several whitepapers and presentations (such as this one) but I am still not sure how this algorithm ...
1
vote
0answers
237 views

Am I using the incorrect implementation of the fast Chebyshev transform?

I was told that the fast Chebyshev transform has superior spectral convergence, but I am unable to verify its rumored convergence. I was given plots of its spectral convergence, where the signal's ...
1
vote
0answers
64 views

Help about Fluid-Fluid coupling techniques

I need a little help and advice with a project I want to do: the idea is to "couple" (I don't know whether I can call it like this) a conservative Navier-Stokes Solver (Fractional-step, 2nd order FDM) ...
1
vote
0answers
485 views

MCNPX for nuclear simulation [closed]

is it legal here to ask this problem? I need someone help. I run mcnpx. I try to calculate f4:n using nps:1000. But, it stop directly before culculate f4. There is comment: stack trace terminated ...
1
vote
0answers
185 views

Visualization of solution for a MAC grid

So I implemented the projection method as in Chorin (1969) for the solution of the Navier-Stokes Equations with the Boussinesq Approximation, using a 2nd Order accurate FD scheme. The primitive ...
1
vote
0answers
82 views

Piecewise linear fitting of a curve in loglog plot

Iam basically trying to fit a curve similar to that shown in fig (a) with 7 straight line segments (ie. 6 knots) as shown in fig (b) and I need to get the optimum knot positions. This is a tripartite ...
1
vote
0answers
41 views

Resources for viscous behavior in simple FEM

I am working on a simple explicit-integration lumped-mass elastic FEM code which implements CST+DKT triangles (plate+shell) and constant-strain tetrahedra (http://woodem.eu/doc/theory/membrane-element....
1
vote
0answers
280 views

Calculation of phonon dispersion

I have a couple of conceptual questions regarding the calculation of phonon dispersions. I wish to calculate the phonon dispersion of Nickel with my lattice vectors given by [111], [1-10] and [11-2] (...
1
vote
0answers
124 views

HDF5 Many Writers, One External Reader

I have an application where I want to have 3 different machines writing to their own independent HDF5 files at a high rate, but have a way to read data from them externally and combine it. Is HDF5 a ...
1
vote
0answers
568 views

Equilateral triangle based mesh generation by intersection

In work I am currently working on I need to mesh some structure with equilateral triangles to study it using a kind of discrete element method known as spring networks or Lattice model. To mesh the ...
1
vote
0answers
168 views

Estimating the second largest eigenvalue

I am currently dealing with the following problem. I am given a matrix $A$ of order $n \times n$ where $n \leq 20.$ The principal $(n-1) \times (n-1)$ matrix of $A$ is symmetric and contains only $\{...
1
vote
0answers
50 views

What is the Radius of Convergence for analytic functions? [closed]

The radius of convergence of any power series can be found by simply using the root test, ratio test etc. I am confused as to how to find the radius of convergence for an analytic $f$ such as $f(z)...
1
vote
0answers
181 views

Compute eigenvalues with Arpack

I am using Arpack to compute the eigenvalues of the problem $\lambda Mx = Ax$ with reverse shift method with complex shift. $A$ and $M$ are real, $M$ is symmetric. Then, I use znaupd e zneupd. I use ...
1
vote
0answers
67 views

Mapping to a computationally less expensive basis when employing Newton's method

I'm looking for advice, or references, for a change of basis to my dependent variables that leads to a less computationally expensive scheme when solving a system of coupled polynomial equations. ...
1
vote
0answers
56 views

Library for calculating determinants with Kronecker products

I need to calculate a determinant consisting of vectors, using the Kronecker product as product. As an example I would need to be able to calculate: $\left| \begin{array}{cc} \left(\begin{array}{c}1\\...
1
vote
0answers
145 views

Convergence of a DASPK depending on DAE formulation

I have a system of non-linear DAE and I noticed that the system does not converge if some of the equations are not differentiated. For example, if the control volume equation is represented as this: $...

15 30 50 per page
1
159 160
161
162 163
197