# All Questions

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### 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 ...
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 ...
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. ...
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 ...
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: ...
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 ...
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: ...
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 ...
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 ...
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 ...
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 ...
30 views

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 ...
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 ...
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. ...
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 ...
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 ...
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 ...
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 ...
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-...
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 ...
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 ...
307 views