0
votes
0answers
17 views

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 ...
1
vote
1answer
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 ...
0
votes
0answers
28 views

Step-wise finite element formulations: can this be done?

Given some functional of the form: $$ I\!\left[\mathbf{x}\right]=\int^t_0 \mathcal{L}\,\text{d}\tau $$ Which stationary at: $$ \frac{\text{d}\mathbf{x}}{\text{d}t}=\mathbf{A}\mathbf{x} $$ And $$ ...
0
votes
0answers
11 views

What is a composition of two binary relations geometrically? [migrated]

the composition was defined as follow: (a,b) \in (R;S) <=> there is c | (a,c) \in R and (c,b) \in S . If our two relations R and S are two convex polygon ...
0
votes
0answers
26 views

Shallow Water Equations Boundary Conditions

I am trying to solve shallow water equations using DG methods. Flow over a bump is a common problem that comes up in this context. For example ...
0
votes
2answers
38 views

How can I reduce integration tolerance in matlab?

It was said in a comment that I should recude integration tolerance to eps. What does this Matlab error message mean? I read the manual and I still don't know how to do it. Can you please tell me how ...
0
votes
0answers
33 views

Computational problems needed

I'm developing a new distributed computing solution. I'm looking for problems that need a lot of computational power in order to validate the technology and get the first use case. We're currently ...
0
votes
1answer
24 views

Sparse linear system of certain type

Let $n_1,n_2 \in \mathbb{N}$ and $n=n_1n_2$ and $b\in \mathbb{R}^n$. I have a SPD-matrix $A=(a_{i,j})\in \mathbb{R}^{n \times n}$ with $a_{i,j}=0$ if $|i-j| \notin \{0,1,n_1\}$. Can we solve the ...
0
votes
1answer
31 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 ...
2
votes
0answers
41 views

Libraries for symbolic manipulation of polynomials

I have implemented a prototype/reference ENO/WENO scheme for (nonlinear) hyperbolic PDEs in MATLAB, making heavy use of the matlab-specific routines poly(), ...
0
votes
0answers
43 views

Advantages and Disadvantages of PETSC vs HyPre?

What are some of the differences between using Petsc and using Hypre? Also what are some of the advantages and disadvantages of both? Does Petsc use more memory or run faster? Thank you very much for ...
1
vote
2answers
83 views

FLOPs of iterative vs direct solvers

In general, do iterative solvers require more floating point operations than the direct solver counterparts? I have some scientific code (written in both PETSc and FEniCS) for solving a mixed FE ...
3
votes
1answer
166 views

When and why is `r./sum(r)` not a good way to renormalize a vector in PageRank computation?

I experimented with the PageRank algorithm. When the number of pages is large, I encountered a situation when one formula for re-normalizing a vector (so that sum of its components is equal to 1; ...
0
votes
0answers
35 views

Need a Suggestion regarding to final year Project in Computational Phy [on hold]

I need a suggestion regarding to my final year project. I am in 8th semester of BS(Hons) Computational Physics offered by Center For High Energy Physics Punjab University. I want to design a ...
1
vote
1answer
40 views

optimize vertices using a cost function on triangles

I want to optimize the vertex positions in a mesh, with a given cost function on the associated triangles. The paper gives a cost function, which evaluates to an real number by using a sum over the ...
0
votes
0answers
28 views

DrRacket - How to find out the last figure of a number after a decimal point? [on hold]

I need to find out the last figure of any number split with a decimal point. This needs to be finished in DrRacket. I started to eliminate, first of all, all figures after the second decimal place. So ...
-1
votes
0answers
25 views

Collapse a block matrix in matlab or octave

I have a 3x3x3 block matrix i.e. mat(:,:,2) looks like [ A B; C D] Where A-D are NxNxN matrices. Id like to collapse the matrix into 27xNxN and preserve the ...
3
votes
1answer
48 views

Derivative of a generalized eigenvalue problem

I want to compute the derivative of a generalized eigenvalue $\lambda$ which is solution of $A u = \lambda Bu$ ($A,B,u,\lambda$ all depend on $t$; in my case $A,B$ are known explicitly, and the ...
0
votes
1answer
37 views

Mathematical error when attempting to represent step function using fourier series

I am attempting to work through a very simple problem. Determine the Fourier series expansion for the following heat PDE problem with ICS and BCS: $$ u_{t} = \alpha^2u_{xx}$$ $$ u(0, t) = u(L, t) ...
1
vote
0answers
29 views

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 ...
0
votes
0answers
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?
0
votes
0answers
33 views

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) ...
0
votes
0answers
14 views

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 ...
1
vote
3answers
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 ...
5
votes
1answer
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 ...
0
votes
2answers
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...       ...
0
votes
0answers
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, ...
0
votes
1answer
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 ...
1
vote
0answers
46 views

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 ...
0
votes
0answers
22 views

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
9
votes
3answers
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 ...
3
votes
0answers
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 ...
2
votes
1answer
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, ...
0
votes
0answers
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 ...
1
vote
2answers
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 ...
3
votes
0answers
45 views

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 ...
0
votes
0answers
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 ...
-1
votes
0answers
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 ...
0
votes
0answers
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 ...
4
votes
0answers
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 ...
0
votes
0answers
27 views

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 ...
1
vote
1answer
46 views

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 $1/f$ ...
2
votes
1answer
45 views

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++. ...
1
vote
0answers
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). ...
3
votes
2answers
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 ...
1
vote
0answers
11 views

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, ...
0
votes
0answers
80 views

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 ...
0
votes
0answers
19 views

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 ...
2
votes
2answers
135 views

Do you spend time reading pure math books as a graduate student on computational math

I am going to start my first year of a research-oriented master program on inverse problem. From what I know, unlike pure math students, applied math students usually don't spend the first year ...
1
vote
0answers
27 views

How to detect letters in an image? [migrated]

I have a project that requires detecting and processing letters in a given input image. I am also new to subject of image processing. There are lots of subsubjects in image processing. I believe I ...

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