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    I Preconditioning for linear equations

    I understand that for many iterative methods, convergence rates can be shown to depend on the condition number of the coefficient matrix A in the linear equation $$Ax=y.$$ Therefore, if a preconditioner satisfies $$P \approx A,$$ then by solving the transformed linear equation $$(AP^{-1})...
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    Brake design for a small RC car

    Hi! For a university project I have to design a braking mechanism for a remote controlled car. I have very little experience in designing constructions, so I thought I'd ask here for any advice on the matter. I'm mostly curious about the design pattern, the thought process I should be going...
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    Physical realization of a system

    @stephen: I guess that's the same conclusion I'm arriving at, that the naming is for historical reasons, or is very strict to avoid any confusion. Perhaps a better way of saying would be that the system is realizable "in a given frequency domain", and the formal definition requires it to be...
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    Physical realization of a system

    OK, so I understand how the idea is that you shouldn't get an infinite response from an infinite frequency input, because a physical system wouldn't have enough energy to produce that. 1) However, why is an infinite frequency input considered physically realizable? Is it possible to generate...
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    Physical realization of a system

    I'm sorry, I don't understand how that helps... That's the same link I posted, and it doesn't provide an explanation as to why the statements it makes are true. What am I missing? Why wouldn't my capacitor example be considered a realization?
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    Physical realization of a system

    Hi! I have a simple question regarding the realization of systems. In my university course books, it's mentioned multiple times that a system with a transfer function G(s) is realizable, if the denominator's degree is at least that of the numerator's degree. I found the same statement on the...
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    Fortran Help using FortranCL

    Yes, you are perfectly right that I don't really know how to use MinGW. (I am able to use it to compile fortran code in windows though). I didn't know about MSYS, and I didn't include it when installing MinGW. But now I installed it as well, and the ./configure command is working! My next step...
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    Fortran Help using FortranCL

    Hi! Thanks for the quick reply. Yes, I am in the proper directory, and there is a file named 'configure', no extension. I'm using Windows 7, but I read that fortranCL should work there too. I hope that's not the problem.
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    Fortran Help using FortranCL

    Hi! I wanted to ask if anybody here has any experience with FortranCL, the Fortran implementation of OpenCL. If so, I would be really thankful if you could help me in setting up the programming environment to use it. So far, I downloaded the MinGW compilers for fortran and c, and the latest...
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    Simulink help solving numerical oscillation

    Hi! Yes, I realized that the behavior is caused by the nature of the differential equations I'm working with. It seems the only solution is to modify the system in exchange for stability. The difficulty now arises in finding the least amount of modification needed to stabilize the system...
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    Help solving Simulink numerical oscillation

    Hi! I think I found a solution to my problem in the case of two chambers connected by a valve. I can calculate the amplitude of the oscillation that occurres, and have given a condition that leads to the oscillation damping, and my results agree with what I see in Simulink. If anyone would go...
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    Help solving Simulink numerical oscillation

    Hi! I posted a new thread about a week ago, but so far no one was able to help me: https://www.physicsforums.com/showthread.php?t=761892 I wasn't sure if I posted in the right forum, so I'm posting it here hoping to reach a wider audience :) Any help is greatly appreciated! -Tusike
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    Simulink help solving numerical oscillation

    Hi! I'm trying to compute air flow between chambers for a project. I'm having a numerical oscillation problem, and I've created an example Simulink program that highlights the cause. Please see the attached Simulink model for a clear understanding; in the following I will do my best to give...
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    How to remember static IP address

    Hi! I have Windows 7 installed on my laptop. At home we have a wireless router, which in order to work, requires me to put in static IP addresses and DNS servers in the network connection's TCP/IP settings. In my university, in order for the internet to work, I have to tell the computer to...
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    Proving i=sqr(-1)

    Oh, I see it now. Thanks!
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    Proving i=sqr(-1)

    @ArcanaNoir: in that multiplication rule you already used that i^2=-1. Okay so then how do you prove whether i is + or -sqr(-1)?
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    Proving i=sqr(-1)

    Homework Statement Our teacher said we can try to prove that the complex numbers will only work so that they are an extension to real numbers if i=sqr(-1). Homework Equations We know that |i|=1, and that for any complex numbers |a||b|=|ab|, and of course that the complex numbers are...
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    Water leaking through floor below balcony

    Hi! Sorry for the late reply, I got a bit sidetracked. Anyway, it seems I was a bit unclear. What I meant was, imagine the roof (upside down V shaped, not flat) above a house, then suddenly it stops but the first level still continues, having a balcony or terrace or whatever you call it go...
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    Water leaking through floor below balcony

    Hi! We have a balcony above our kitchen, and the tiles have been replaced about 7-8 years ago, with some sort of sealant added. However, due to the rain and more probably snow, water has somehow leaked through all that, and now the ceiling above the kitchen is starting to come down and is...
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    Thoroid circuit problem

    Whenever I said "have two coils", I meant that the fact it's a toroid and the coil is in a circle doesn't make a difference, but we can have two straight coils connected with an iron ring inside them. Anyway it doesn't matter, sorry for the misunderstanding. From you're 5 steps, one of my...
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    Thoroid circuit problem

    It is toroid isn't it? I wrote that in the first place, then saw something on the internet and changed everything to thoroid:) oh well... Anyway, I realize the iron core is just for concentrating the flux, and that we can break it down into two pieces, but there isn't much I could to from...
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    Thoroid circuit problem

    Homework Statement Hi! This problem was posted last month, and the due date was on the 10th so I can ask now. Here is the problem: http://www.komal.hu/verseny/feladat.cgi?a=honap&h=201102&t=fiz&l=en" problem # P.4325 Homework Equations Kirchoff's laws The Attempt at a Solution...
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    Collision with wall

    Here's what I think sums this all up: If the point of contact doesn't slide, F cannot be kinetic friction. Also, if the "point" of contact doesn't slide, we must still think of the collision as one without deformation, otherwise the problem would say "point". If so, there isn't any rolling...
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    Collision with wall

    Hi! I was perfectly content with the explanation to my problem in the OP, until today when I came across the 1994 IPhO, Theoretical Problem 3 (http://www.jyu.fi/ipho/). The problem assumes an elastic collision, but doesn't assume that the point of contact does not slide during the entire...
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    Forces when pulling a cylinder

    Thanks, it's clear now. By the way, I bumped it because it was going "down" in the list of posts, and was afraid that people wouldn't see it:) but I'll make sure to bump only in case of having no replies after a few days.
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    Forces when pulling a cylinder

    Homework Statement I have a book with the following problem: What force is needed to pull a cylinder so that it wouldn't tumble over? The frictional constant, and the height and radius of the cylinder are given, and the height of our vertical force exerted on the cylinder. Now, the problem...
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    Collision with wall

    I see now; that explanation was exactly what I was looking for. Thanks again!
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    Collision with wall

    I still don't see how that is possible. Looking at only the x components: Any time during the collision, if any dF force acts on the disk, it acts on the outer edge, so it's R away from the center. So it's torque would be dF*R... So the angular momentum can only be changed by the sum of these...
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