Computational Science Weekly Newsletter - Tuesday, April 28, 2015

Computational Science newsletter

Top new questions this week: Need a good reference for numerical transport phenomena I'm a chemical engineering undergraduate and I'm currently starting to work in a theoretical transport phenomena/colloid science group. While my group has a nice code base for larger scale ... finite-difference reference-request   asked by ColloidSci 4 votes answered by Geoff Oxberry 2 votes Numerical solution of IVP for linear ODE with variable coefficient blows up Cross posted in Mathematica.SE, I'll try to rephrase it in a more general way here. A friend of mine showed me this initial value problem (IVP) for a linear ordinary differential equation (ODE) with ... ode stability time-integration   asked by xzczd 3 votes answered by Bill Greene 2 votes optimization subject to disjunction of inequality constraints I want to solve $$\min_x f(x)\qquad \textrm{s.t.}\qquad g_i(x) \geq 0\ \ \textrm{or}\ \ h_i(x) \geq 0$$ for $i=1,\ldots,m$. Clearly if the inequality constraints split the feasible set into $2^m$ ... constrained-optimization   asked by user168715 3 votes answered by Geoff Oxberry 0 votes 2D Poisson Solver for Taylor Green Vortex Problem I am trying to write a 2D Navier Stokes solver using an RK3 for time advancement in python. For debugging, I have converted the RK3 to an Euler step for simplicity. Checking my divergence for my ... fluid-dynamics python poisson navier-stokes   asked by cbell14 3 votes Shell vs frame element model stiffness differences I have a model of a tall, slender structure that I am investigating using both shell and 3D frame elements. The shell elements are type MITC4, 4-node membrane elements. The frame elements are the ... finite-element   asked by Madeleine P. Vincent 3 votes answered by Bill Greene 0 votes 2D wave equation with Mur boundary condition - setting up the RHS and solving (time-steps) I am trying to solve a 2D wave equation implicitly using FD with central approximations with the following boundary conditions $$\begin{align} &u=2\sin\left(\frac{2\pi}{5}t\right)\quad \text{at ... matlab finite-difference boundary-conditions wave-propagation   asked by user2579288 3 votes Natural spline conditions for 2D cubic splines I am currently working on 2D interpolation and I am using cubic splines. In 1D given N points one would use N+2 splines and would have to apply additional constraints in order to achieve a square ... image-processing   asked by user2785954 2 votes answered by Thomas Klimpel 1 vote Greatest hits from previous weeks: Basic explanation of shape function well this is my first time posting here. I just started studying FEM in a more structured basis compared to what I used to do during my undergraduate courses. I'm doing this because, despite the fact ... finite-element   asked by Alfonso Santiago 8 votes answered by Christian Clason 14 votes C++ vs Fortran for HPC In my computational science PhD program, we are working almost exclusively in C++ and Fortran. It seems like some professors prefer one over the other. I am wondering which one is 'better' or if one ... hpc fortran c++ languages   asked by Laurbert515 32 votes answered by khinsen 38 votes Can you answer these? Aliasing question for a spectrally derived Lagrangian Consider two functions $$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. ... spectral-method   asked by Nick P 1 vote 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 ... algorithms parallel-computing eigenvalues   asked by Ramón 1 vote Efficient Implementation of the Log Sum Exp Log trick for Preventing Underflow erros So I'm constructing a Gibbs sampler for a moderately sized graphical model, and I started encountering underflow errors (the computed relative frequencies were all very small). To get around this, ... efficiency numerical-limitations   asked by Dan 1 vote

Subscribe to more Stack Exchange newsletters Unsubscribe from this newsletter or change your email preferences by visiting your subscriptions page on stackexchange.com. Questions? Comments? Let us know on our feedback site. If you no longer want to receive mail from Stack Exchange, unsubscribe from all stackexchange.com emails. Stack Exchange, Inc. 110 William St, 28th Floor, NY NY 10038 <3