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| bio | website | tudelft.nl |
|---|---|---|
| location | Delft, Netherlands | |
| age | 25 | |
| visits | member for | 5 months |
| seen | 1 hour ago | |
| stats | profile views | 15 |
I am a PhD student in the field of fluid dynamics and soft matter.
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Existence and uniqueness of Stokes flow @Qmechanic Ok! I have corrected the referencing. |
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2d |
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Existence and uniqueness of Stokes flow Don't pin me down on it, but I believe the situation is only unsolvable if the far-field is unbounded |
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May 3 |
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Inaccuracy in numerical calculation of arclength of part of an ellipse ok, this is pretty embarrassing. The mistake was in a function call where I had swapped the parameters of 2 ellipses. So I got the shape-plot for 1 ellipse (with b=2.5) while I got the integral for a different one (with b=0.52). Anyway, it's solved. Thanks for the effort and sorry about the dumb mistake |
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May 3 |
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Inaccuracy in numerical calculation of arclength of part of an ellipse Ah ok, so I am at least getting the same number. So maybe the error is already somewhere earlier: in the value of $\phi_s$. I will look into it and come back here when I sorted things out. Thanks for the help!! It's much appreciated |
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May 3 |
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Inaccuracy in numerical calculation of arclength of part of an ellipse You're right, they both are the same (I was missing a bracket), but still I get a much higher value. What I noticed by the way is that you use b=2.5 while I have b=0.52. What do you get with that smaller b? |
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May 3 |
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Inaccuracy in numerical calculation of arclength of part of an ellipse mmm that's odd. I found this for the integrand: $$a b \sqrt{\frac{b^4 \cos^2\phi+a^4 \sin^2\phi}{(b^2\cos^2\phi+a^2\sin^2\phi)^3}}$$ which is supposed to be the same according to ($\cos^2\phi+\sin^2\phi=1$) but apparently it is not???? |
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May 3 |
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Inaccuracy in numerical calculation of arclength of part of an ellipse By the way: I agree that a different parametrization would be better. The thing is that I also need the polar angle so I will have to do a bit of work connecting the parametrization you suggest with the polar angle |
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May 3 |
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Inaccuracy in numerical calculation of arclength of part of an ellipse yeah, I see that now. Do you have a symbolic answer to the integrand? Then at least I can start looking for my mistake from there! Anyways, Thanks for the quick help!! |
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May 3 |
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Inaccuracy in numerical calculation of arclength of part of an ellipse @your first comment: sorry I wrote down the value in degrees instead of radian, I fixed it in the post. The relative distance comes from the fact that I know where the tip of the ellipse and the point $\phi_s$ are ---- your second comment: So you are saying that the problem is most likely caused by the parametrization in combination with round-off errors? |
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Apr 29 |
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Wisdom of the crowd in estimative calculation @joriki yes, I think it is safe to assume that the estimates for the individual quantities are normally distributed |
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Apr 18 |
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Incomplete elliptic integral of the second kind and the arc length of an ellipse - does a `simple` relation exist? Awesome, thanks!! Could you add this into your answer so I can except it?! (comments tend to be less permanent) |
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Apr 18 |
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Incomplete elliptic integral of the second kind and the arc length of an ellipse - does a `simple` relation exist? Thanks! I corrected the equations in my post. Unfortunately, I was more sloppy in typing up the post then I was in my derivation, in which I did have the correct expressions. So my question still holds |
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Apr 4 |
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Approximations of the incomplete elliptic integral of the second kind Great, I will give that a try! Thanks! |
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Apr 4 |
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Approximations of the incomplete elliptic integral of the second kind @J.M. I need the approximation to determine $l=f(\phi)$ such that I can rewrite it in a form $\phi=f(l)$. With the exact elliptic integral that doesn't seem possible. |
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Apr 4 |
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Approximations of the incomplete elliptic integral of the second kind @J.M. the use of pade approximants seems to me to be a fairly involved approach in which I have to determine all the prefactors, which I would probably need a computer for so then I don't see the point in using the approximation over the 'real' incomplete elliptic integral |
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Apr 3 |
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Approximations of the incomplete elliptic integral of the second kind I hadn't seen it yet, but after taking a look it doesn't get much clearer for me. I can see that Eq 21 in the link is an approximation, but I am not sure how I would go about applying it? |
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Apr 3 |
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Detect values in array that are statistically inconsistent That's a good point. I guess you have to know quite a bit about the physics/chemistry of what you're measuring to be able to set a sensible absolute or relative threshold. |
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Mar 31 |
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Problems with votes Pretty sure that there should be, but that is a bit too tough a nut to crack for me. |
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Mar 31 |
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Determine if the Series Converges and Explain approach Ok, I agree, formally I cannot write $2^\frac{1}{\infty+1}=1$ but I figured that it is obvious that this is correct in the limit of infinity |
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Mar 31 |
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Geometric calculation: two kneading discs Do you know the exact geometry of 1 of the discs? or only the area? If you know the function describing the long edge of the discs then it shouldn't be too hard to come up with an answer |
