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Stationary solution converge but time dependent doesn't

I've coupled a COMSOL model for fluid dynamics with a very simple pde that model the transport of humidity in air. When I solve it for the stationary case, the solution converge easily, but when I ...
0
votes
1answer
32 views

Polynomial solvability [duplicate]

Consider the following optimization problem: Min$_{x}$ $\qquad \sum_{(i,j,t,s)\in I_r}||x_ix_j-x_tx_s||^2$ S.t.: $\qquad x\in \mathcal{C} ;$ where $x=(x_1,x_2,...x_n)$ and $\quad x_j\geq 0\;\; j=...
0
votes
0answers
151 views

FFT - function only in sine series? Can be done with MKL / Lapack? [duplicate]

please can I ask, how one can make from function sine series (Fourier transform) with MKL? I can do "normal" exponential FFT with MKL (Lapack of course), how can I say that I want only sine series? ...
0
votes
0answers
206 views

computation complexity of OLS in estimating a VAR model

Could someone tell me the computation cost of using Ordinary least squares in estimating a Vector autoregression model? I am thinking the cost is O(n) where n is the number of the training instance. ...
0
votes
0answers
51 views

Lagrangian Duality [duplicate]

Possible Duplicate: Linear programming boundedness Consider the following LP: $\max$ $\sum_{i=1}^N b_i \pi_i$ s.t. $\;\;$ $\pi_i-\pi_j\leq 1 $ $\quad$ for each $(i,j) \in \tilde{A}$ $\...
0
votes
0answers
374 views

How to move particles in a variational Monte Carlo simulation?

I'm attempting to implement some code that moves particles and then calculated the acceptance/rejection of the move, but I'm stuck in a rut. Here is my Python code: ...
0
votes
0answers
87 views

Produce equation of curve, given some coordinates [duplicate]

Possible Duplicate: Get equation for a curve which intersects x at seemingly randomly distributed points? I tried asking something similar to this before, but I guess I didn't explain very well. ...
0
votes
0answers
164 views

Permissive Math Library for Parameter Statistics in C++

I am looking for recommendations for a C++ math library, with a permissive licence, well suited to calculating a wide variety of statistics on segmentations of timebased parameter data. I would be ...
0
votes
1answer
36 views

Shooting Method- Boundary value problem starting from -1 to 1

The equation is $\rho \frac{d \bar{u}}{dy} = -\frac{d\bar{p}}{dx} + \mu\frac{d^2\bar{u}}{dy^2} $ with boundary condition $u(-1)=0$ and $u(1)=1$ I am to solve it using fifth order runge-kutta ...
0
votes
1answer
90 views

Newbie help on FEM contact problem

I am modelling the time-evolution of a soft material with a tetrahedral mesh. I use an FEM method to compute the forces on each node, and then numerically integrate the positions and velocity of the ...
0
votes
1answer
1k views

Faster code for double integration using Gauss-Legendre quadrature

I came with a the following code to evaluate a double integral using Gauss Legendre quadrature in MatLab ...
0
votes
1answer
33 views

Generating pseudorandom sequences based on measured sequences

I'm looking for an algorithm to generate discrete-time pseudorandom sequences based on other sequences I already have that would be used to train the algorithm. More specifically, I have some time-...
0
votes
1answer
229 views

Applying Runge-Kutta to nonlinear system of PDEs

I am applying a 4th order Runge-Kutta code, using the method of lines, to solve the following: \begin{equation} \frac {\partial y_1}{\partial t} = y_2 y_3 - C_1 y_1 \end{equation} \begin{equation} \...
0
votes
1answer
233 views

Robust Counterpart of an uncertain LP

Consider the following robust optimization problem: min c'x s.t.: $Ax\geq b \;\;\forall (A,b)\in \mathcal{U}$. Why can the robust counterpart of the problem be written in this form? $min_x{\{ ...
-1
votes
4answers
161 views

System Speed - Refactoring [closed]

Could the runtime of methods within a system potentially be reduced via refactoring during development (pre-public release)? i.e. Let's assume that methodX() takes ...
-1
votes
1answer
91 views

Why is this method for simulating a system of springs and masses unstable?

I have a computer simulation system of bodies connected by springs, so their movement is governed by: $x_{n+1} = x_n-\Delta tk(x_n-r)$ Where $r$ is the idea distance between every two bodies, and $\...
-1
votes
3answers
2k views

optimization non linear problem with java code

Is there some packages in java that can be included to eclipse in order to solve a non linear problem? I have used ipopt but when running, there is a notification which say "NOTE: You are using Ipopt ...
-1
votes
2answers
111 views

RK4 for stiff IVP

I need a solver of stiff Inital-Value Problems (IVP) in python exploiting RK4 preferably explicit. I have been searching for past few days but could not find it. Following are my queries: Does the ...
-1
votes
1answer
535 views

Pde problem with robin boundary condition

I have my pde 2D problem with robin condition (form: du/dn +ku=g) to solve with matlab. i have the exact function u and I want to find the function g in robin condition. How can i do it? thanks for ...
-1
votes
1answer
76 views

Is it possible to simulate life? [closed]

Has anybody ever managed to simulate even the simplest form of life by merely simulating the interactions of the molecules of the organisms body? What would be the theoretical minimum number of ...
-1
votes
1answer
1k views

Using scipy.odeint to solve coupled equations [closed]

I have a set of three coupled autonomous equations: ${y_{1}}\prime = y_{1}(\frac{\Omega_{m}}{y_{1}^3} + \frac{y_{3}^2}{6.0} + \frac{V(y_{2})}{2.H_{0}^2})$ $y_{2}\prime = y_{3}$ $y_{3}\prime = -3\frac{...
-1
votes
2answers
359 views

Stability of matrix equations in MATLAB

Is there a method to check for unconditional stability or positive-definiteness of large matrices in MATLAB? For example, I know that matrices with property M (positive main diagonal elements and ...
-1
votes
1answer
318 views

Which ODE solver in Matlab allows me to advance in just one timestep only

[t,y] = odeXX(odefun,tspan,y0) I have a solver odeXX, and the tspan = [0 0.0001]. It seems that for any ode solver in MATLAB, they integrate by breaking ...
-1
votes
1answer
380 views

Finite Difference for Fourth-Order PDE

How to discretize the following 4th order PDE using finite difference method? $$\frac{\partial^{2} y}{\partial t^{2}}+\frac{\partial^{4} y}{\partial x^{4}}=0$$ thanks
-1
votes
1answer
59 views

Is it possible to find a formula for a set of number from the result? [closed]

I have these two sets of number, I also have a result. Is it possible to compute the relation between them so that I can figure out how the result is generated ? for example I have : Set A=4 6 12 25 ...
-1
votes
3answers
159 views

How to solve numerically such system of equations

I have a system of equations $$ S_{m}(\xi) +P_{m}(\xi)=f(\xi) $$ where $\xi$ can be choosen arbitrary in some domain in $\mathbb{C}$, $f$ is known, $P_m$ is a polynomial of degree at most $m$. ...
-1
votes
1answer
222 views

Scipy Two-point Boundary value Problem

Nonlinear ODE Statement I would like to use scipy to solve the following: u'' + (u')^2 = sin(x) u(0)=0, u(1)=1 where u = u(x). Approach I am looking at the ...
-1
votes
1answer
73 views

Relation of Condition of a Matrix and Convergency

Can anybody explain me the relation between the condition of a Matrix and the convergency of a problem. For example how is the relation between the condition of the stiffness Matrix occuring in FEM ...
-1
votes
1answer
71 views

Anyone knows where I can find a simple FEniCS code where I can understand basic implantation? [closed]

I found this one, but does not work: http://www.karlin.mff.cuni.cz/~hron/warsaw_2014/pl2014_lecture5.pdf
-1
votes
1answer
520 views

Stability analysis for coupled nonlinear system of partial differential equations

I'm trying to solve a nonlinear partial differential equation \begin{equation} L(u_{xxtt},u_{xx}u_{tt},u_{xt}^2,u_{xt},u_{tt})=0 \end{equation} using finite difference methods. In order to remove the ...
-1
votes
1answer
63 views

I have a problem in finding the exact area and estimating the error [closed]

The program should first read from the keyboard the values of a and b then estimate the area under f(x) in the interval [a, b] using Simpson’s 1/3rd rule and display the estimated area and the error ...
-1
votes
1answer
141 views

Problem using MATLAB `fminunc` [closed]

I am trying to find the minimum of this function. But I receive the following error when I run the script. What am I doing wrong: ...
-1
votes
1answer
378 views

How to initiate spirals in this model?

I am trying to reproduce Tang & Othmer paper which is related to excitations and oscillations in G-protein model in Dictyostelium discoideum, an amoeba species. The mathematical model in the paper ...
-1
votes
1answer
82 views

Is iteration an efficient algorithm in this case? [closed]

My task in numerical analysis is We are interested in finding values of β0 for which z(x) = 2500. Use an efficient algorithm to determine the rays which pass through the receiver. Now I'm just ...
-1
votes
1answer
183 views

Solving large system of equations, is linear programming best option? [closed]

I have a problem where I am trying to solve many systems of equations, that have very few variables per equation, but a lot of equations. For example potentially 10 variables max in a single equation,...
-1
votes
1answer
176 views

How do I stop negative numbers and error message: " Failure at t=3.562559e+03. Unable to meet integration tolerances

I am using 8 ODEs in Matlab to simulate the effect of asymptomatic infections in the epidemiology of a vector borne disease. Searching the parameter space under certain settings produces negative ...
-1
votes
1answer
107 views

Can you give some information for rothe method [closed]

I want to learn a numerical method for PDEs other than finite difference method. After some research on internet i have found Rothe method and it looks interesting to me. Unfortunately, i couldn't ...
-1
votes
1answer
102 views

Libraries with the method of lines for parabolic PDEs [closed]

Could you please advise some programs or libraries for solving parabolic PDEs (or its systems) in 1D, 2D and 3D, for example, with the method of lines? The system of parabolic PDEs can be nonlinear in ...
-1
votes
1answer
4k views

Runge-Kutta 4th order for 4 coupled first order differential equation [closed]

I have to solve 4 coupled first order differential equations for $f(t)$ ,$g(t)$, $h(t)$ and $w(t)$ witch are only functions of $t$ , but for every reference link a function of 3 variables is assumed (...
-1
votes
1answer
949 views

Explicit scheme for heat equation with Neumann boundary conditions in Maple

$\displaystyle \frac{\partial u}{\partial t}=\alpha(x,t)\cdot \frac{\partial^2 u}{\partial x^2}+b(x,t)$ $u(x,0)=f(x)$ Initial condition $u_x(0,t)=0$ 2nd type Boundary condition $u_x(1,t)=0$ 2nd ...
-1
votes
2answers
4k views

Confusion Over Navier-Stokes, RANS and URANS in a Flow With Laminar-Turbulent Transition [closed]

I have been working on a transient simulation, using the SST k-w turbulence model in Fluent(TM). An unsteady boundary condition is used: at the beginning of the simulation the flow is laminar and ...
-1
votes
1answer
214 views

A question on CHOLMOD: long int vs int, still failing after change to long int [closed]

Changing cholmod_* to cholmod_l_* results in the following error: sparse:error: integer and real must match the routines ...
-1
votes
1answer
748 views

Open Foam User Guide Tutorial [closed]

I am trying to follow the Openfoam user guide but I'm stuck at the first tutorial 1. In fact, when I try to run the blockMesh command (using the administrator account), the following appears: ...
-1
votes
1answer
55 views

Simulating magnetic particles in a field free point generated by two opposing magnets

This is probably a long shot with such a short time, but I've been trying to get theoretical data for a project I'm working on. The project involves using a very simplified version of magnetic ...
-1
votes
1answer
68 views

Finite element convergence rate and possion's ratio

I am running simulations of a cantilever beam where it is fixed on one end and negative force applied to the other end. The first simulation is with 4-node linear quadrilateral elements and the other ...
-1
votes
1answer
62 views

Writing parallel code for molecular computation [duplicate]

I recently moved towards computational biophysics from an experimental science background. As of now, I am learning the fundamentals and doing some basic monte carlo simulations of LJ fluid on my ...
-1
votes
1answer
23 views

Semi-Definite relaxation of non-linear constraint?

I am implementing an optimization problem using semi-definite approach. One of my constraints is of following form $ trace(A∗X)−(k∗trace(A∗X))+(k∗\sqrt {(trace(B∗X)} )==0$ where k is a constant, A ...
-1
votes
1answer
231 views

Gauss-Seidel method convergence

I am currently programming a code to find the equilibrium function that satisfies the poisson equation in 2D. In order to do this I use finite difference methods and the discrete equation I want to ...
-1
votes
1answer
596 views

Eulerian vs Lagrangian vs Mesh-based vs Meshfree/Meshless methods

Hailing from the scicomp community recently getting into computer-graphics, I have noticed that the scicomp communities talk about mesh-based methods like FDM, FVM, FEM, etc, vs meshfree or meshless ...
-1
votes
1answer
141 views

ODE15s: unable to meet integration tolerances

I have to solve $$\left\{\begin{matrix} \ddot{R}=-\frac{3}{2}\frac{\dot{R}^{2}}{R}+\frac{1}{R\rho}\left [P_{v}(T_{\infty})-P_{0}-a_{1}t^{2}-a_{2}t+\frac{(L\rho_{g})^{2}}{hT_{\infty}}\dot{R}-4\mu \frac{...

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