# All Questions

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### Why don't I get the expected answer?

In my assignment (page 16) it says You should find that the depth at xf = 25 nautical miles is close to 2500 feet When I try to solve the assignment I can't get that answer. I start with ...
13 views

### Is it possible to locate an image in a video using MATLab?

I'm not a huge programmer, but if it'll save me lots of time, that's when I code (given that it's possible). I know MATLab has a Computer Vision Toolbox, so my question is: is it possible to program ...
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### Am I using the incorrect implementation of the fast Chebyshev transform?

I was told that the fast Chebyshev transform has superior spectral convergence, but I am unable to verify its rumored convergence. I was given plots of its spectral convergence, where the signal's ...
16 views

### Is there an ideal height to inheritance tree? [on hold]

I don't think so but still it would be complicating to handle a lot of levels of inheritance. Any help?
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### Help about Fluid-Fluid coupling techniques

I need a little help and advice with a project I want to do: the idea is to "couple" (I don't know whether I can call it like this) a conservative Navier-Stokes Solver (Fractional-step, 2nd order FDM) ...
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### An algorithm to produce, not necessarily efficiently, another algorithm that efficiently solves the Rubik cube

How complex is the task to formulate an algorithm that produces, not necessarily efficiently, another algorithm to efficiently solves the Rubik cube? Has it been attempted before? What is the latest ...
45 views

### Matlab Large Numbers and Small Numbers

I recently have been assigned a project to calculate the roots of a cubic polynomial. However, the issue is that the roots could be very big, but also extremely small. I've been trying to use ...
178 views

### Applying the Runge-Kutta method to second order ODEs

How can I replace the Euler method by Runge-Kutta 4th order to determine the free fall motion in not constant gravitional magnitude (eg. free fall from 10 000 km above ground)? So far I wrote simple ...
32 views

### The “standard map” and Jupiter's red spot [on hold]

Has there been an attempt to "explain" Jupiter's Red Spot via what is known as the standard map in chaos theory? I cannot be the first to notice the visual similarities...       ...
31 views

### Gonzalez algorithm

I'm getting confused about implementing the Gonzalez algorithm/k-center clustering. The algorithm is : "" let S be a data set Choose z1 ∈ S arbitrarily. # z is center (In general let zi = {z1, ...
93 views

### Doubt regarding stopping criterion for Newton method

I am solving an unconstrained convex optimization problem, which can easily have a million variables. I am trying to get a working system with a toy problem of around 200 variables. I am noticing that ...
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### MCNPX for nuclear simulation [on hold]

is it legal here to ask this problem? I need someone help. I run mcnpx. I try to calculate f4:n using nps:1000. But, it stop directly before culculate f4. There is comment: stack trace terminated ...
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### Finding the time complexity of fibonacci function using recursion tree method [on hold]

I tried it in the following way and I want to know if I am right or wrong
118 views

### Finite elements on manifold

I'd like to solve some PDEs on manifolds, say for example an elliptic equation on a sphere. Where do I start? I'd like to find something that use preexisting code/libraries in 2d , nothing so fancy ...
76 views

### Why are functional representations of systems important in numerical applications?

I tried asking a similar question in SE.Physics, and I got some information regarding the abstract side of this, but I figured I should post here to get more complete information about the numerical ...
55 views

### FFT convolution vs direct convolution

Recently I tried to compare results for 1D direct convolution and convolution via FFT. I expected to get absolutely the same result, however I faced with a problem that results are different, ...
34 views

### Visualization of solution for a MAC grid

So I implemented the projection method as in Chorin (1969) for the solution of the Navier-Stokes Equations with the Boussinesq Approximation, using a 2nd Order accurate FD scheme. The primitive ...
77 views

### Simulating a Simple Pendulum - Increasing amplitude on each swing?

I am trying to animate a dampened pendulum using RK4 for a highschool project. The equations that describe the dampened system are as follows: (from ...
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### Creating FEM mesh for image region — what is the most suitable shape function?

I wish to create a FEM mesh to solve an inverse elasticity problem, for an irregular domain. This domain is given by a medical image, so it is discretised and each square on the grid has one scalar ...
28 views

### Extrapolating a function with increasing slope

I want to extrapolate data for a set of function values on a regular grid. To test different extrapolation routines, I decided sample data from a function, which I believe is the closest known ...
26 views

### Riemann hypothesis and the link to quantum mechanics [closed]

Hello my name is Richard Cespedes and I just put together an idea about just how close the Riemann zeros are to quantum energies. I've put it together on Google Docs and I want to share my link of my ...
25 views

### Piecewise linear fitting of a curve in loglog plot

Iam basically trying to fit a curve similar to that shown in fig (a) with 7 straight line segments (ie. 6 knots) as shown in fig (b) and I need to get the optimum knot positions. This is a tripartite ...
106 views

### Alternative to (costly) matrix multiplication

Consider the integral $$2\pi T = -\frac{1}{2} \int_0^{2\pi} A\frac{\partial B}{\partial \xi} \ d\xi$$ where A= \sum_{-N}^N i \ sign(n) \ B_n e^{-in\xi}; \quad \quad B= \sum_{-N}^N \ B_n ...
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### Adding PAPI into CMakeLists.txt for FEniCS [closed]

I plan on using PAPI to profile my FEniCS applications, and it seems I would have to use the C++ variant of FEniCS to achieve this (but correctly me if I am wrong) On my HPC cluster, I have the ...
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### Algorithm for high quality 1/f noise?

How can I generate arbitrarily high quality $1/f$ noise, for use in a model? My model involves a lot of feedback, over a large number of iterations, with a very high bandwidth, so I'd like the $1/f$ ...
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### Mathematica NIntegrate function in C++

I am working on computing a challenging integral. I am working with someone else who wrote some code in Mathematica to compute it. I do not have mathematica so I am trying to do the same thing in C++. ...
50 views

### Block preconditioners and condition number

I am working with block Jacobi like preconditioners which are very cheap for my problem. But I could not find much about the dynamics of basic preconditioners (block Jacobi, Gauss-Seidel, ILU etc). ...
358 views

### literature on scientific computing

Maybe, this is a dump question. But anyway. I developed a finite difference code for a class of problems in dynamo theory. I used GNU Octave (MATLAB) which is good for testing. The problem size ...
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### Concatenating small windows of EEG signals over trial

My question is regarding the mathematical implications of concatenating very small windows from different trials, of the same size and for the same period in time after a stimuli. In other words, ...
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### What is the difference between SSPRK3 and RK3 time discretization methods?

Here, SSPRK3 refers to third order strong stability preserving Runge-Kutta and RK3 refres to regular third order Runge-Kutta method. The meaning of the method is obvious from the name. However there ...
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### Computational time in fluent using PBM+REACTION

I am having a problem of huge computation time. My system is a reaction, nucleation and growth. Time step i have taken is 10^-6 sec. it takes 10 minutes to reach 10^-2 sec. It will nearly take 70 ...