Computational Science Weekly Newsletter - Tuesday, September 30, 2014

Computational Science newsletter

Top new questions this week: Numerical methods for boundary-value ODEs with a jump condition I want to solve a non linear system of equations of a particular kind. I find it hard to formulate clearly so I directly give a simple example. $ f''=A(f,g)\\ g''=B(f,g) $ with the boundary … ode nonlinear-equations   asked by David 5 votes answered by Geoff Oxberry 4 votes Mesh generator that can do 2D & 3D elements combined? I'm trying to analyze a circuit card assembly (CCA). The biggest problem is always trying to mesh the thin copper layers along with the thicker epoxy layers between. I'm making the approximation that … finite-element mesh-generation   asked by drewd423 4 votes answered by Geoff Oxberry 3 votes Behavior of integration method I was playing with N-body simulations of a game called Kerbal Space Program, which itself uses the patched conics approximation. I have read that for long term stability it is best to use symplectic … time-integration   asked by fibonatic 4 votes answered by Kirill 1 vote Least-squares for a diagonal matrix This is a follow-up to a different question I asked with more detail. For $v\in\mathbb{R}^n$, denote $D_v\in\mathbb{R}^n$ as the diagonal matrix with elements in $v$. Given a "tall" matrix … linear-algebra linear-solver matrix matrix-equations linear-system   asked by Justin Solomon 4 votes Solving "Hadamard systems" Suppose we have two matrices $A$ and $B$ (we can assume they're symmetric; if absolutely necessary I think they may be positive definite). Then, is there any technique for solving $$(A\circ B)x=b,$$ … linear-algebra linear-solver linear-system   asked by Justin Solomon 4 votes answered by Paul 2 votes Method with low memory requirement for large-scale eigenvalue problem I am working on the flow stability problem. In this work the main complication is solving generalized eigenvalue problem for a large scale Non-Hermitian matrix. I need only one eigenvalue (most left … petsc eigenvalues   asked by Kirill Belyaev 3 votes How to solve this optimization problem with abs object function? Helo, every one. May I ask for help about how to solve this problem. $\begin{align} & \text{max}_{x_i} \quad |\sum_{i=1}^{4} a_i x_i | \\ & s.t. \quad \sum_{i=1}^4 x_i^2=1 \end{align} $ … optimization nonlinear-programming   asked by user3909401 3 votes answered by IainDunning 5 votes Greatest hits from previous weeks: Libraries for solving sparse linear systems There are a number of different libraries out there that solve a sparse linear system of equations, however I'm finding it difficult to figure out what the differences are. As far as I can tell there … linear-algebra linear-solver libraries   asked by Andrew Spott 15 votes answered by aterrel 24 votes Matlab element within ranges and distance between two points I have a 53534x3 matrix with x, y and z coordinates. I want to find the element of matrix within ranges as follows: % coordinate range; x1(x<-25|x>0); x2(x<0|x>25); y1(y<-40|y>0); … matlab matrix elements   asked by user3991 2 votes answered by Michael Grant 3 votes Can you answer these? Deriving entropy function and entropy flux for a system of equations I've been reading up on the concept of entropy as a useful way of developing a natural residual for a system of equations. For example, the entropy function for compressible Navier-Stokes is … fluid-dynamics   asked by Truman Ellis 2 votes 2D Neumann Conditions on Irregular Domain I would like to model the 2D diffusion equation with Neumann BC's inside the following domain: I would like to use the finite difference method with the discretization implied by the image above, … finite-difference   asked by tom 1 vote

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