# All Questions

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### Realistic expression to induce a seismic wave in 2D/ 3D fem mesh?

I have a 2D square mesh and a 3D beam shaped mesh and I want to propagate a seismic wave in them. I am trying to simulate them using Open source FEM codes (fenics). I have left the top surface to be ...
27 views

### A fast I/O file format readable by Fortran, Java, PHP?

I am writing a Fortran program that does fairly light weigt computation on fairly large data files. The output must be readable by some Java-script (that i have no insight in) and preferably also by ...
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### Reaction-diffusion equations

I'm simulating a biological phenomena with reaction diffusion equations. There are multiple diffusing materials and there are some complex relations about consumption and production of such materials. ...
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### Matlab PDE toolbox problems specifying geometry with large size differences

I am trying to solve an elliptic PDE using MATLAB's PDE toolbox. I am trying to solve the problem on an annulus where the inner radius (r_0) is significantly smaller than the outer radius (R.) ...
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### Exact finite difference method for advection equation

I want to solve the advection equation: $u_t+au_x=0, a > 0$. Here is our method: $$U_j^{n+1}=U_{j-1}^n-\left(\frac{ak}{h}-1\right)(U_{j-1}^n - U_{j-2}^n)$$ I am trying to answer the following ...
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### hyperbolic equation and characteristics

I am a little confused about the connection between variables for the plain advection pde: $$u_t+au_x=0$$ So initially I thought $x$ and $t$ are independent and $u$ is a function of those, but then we ...
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### Implicit projection method with inflow boundary conditions

I am trying to use a projection method that deals with the viscous effects implicitly to model flow around a cylinder. I'm having trouble figuring out what the boundary conditions should be, ...
36 views

### Weak form for elastoplastic wave propagation

I am trying to simulate elastoplastic seismic wave propagation using Fenics Solid Mechanics Application. The app. provides some quasi-static demos to show elastoplastic behaviour in a cube/ beam/ ...
23 views

### How to impose boundary conditions for higher order derivatives in eigenvalue problems?

The following boundary value problem $y'''' + r \, y'' = 0$ with the boundary conditions $y'' =y'''=0$ at both ends is a generalised eigenvalue problem of the kind M\,x = \lambda \, ...
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### How to calculate multi-class prediction probabilities using One vs All and One vs One classifiers

To be specific, let's consider Support Vector Machines. In the 1 vs all case, one has $n$ binary classifiers where $n$ is the number of classes. In each classifier one has two labels 0, 1 and for a ...
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### Effects of Lumping Mass Matrix

I've recently finished an introductory course on the finite element method from a more mathematical perspective (following Brenner and Scott) and we were introduced to the finite element mass matrix ...