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Partial Differential Equations!

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UnhealthyTruthseeker
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Partial Differential Equations!

Postby UnhealthyTruthseeker » Sat Sep 12, 2009 7:50 pm

Let's discuss Partial Differential Equations! :)

Laplace's equation is nice to work with because it is homogeneous and linear and hence always separable. It's solutions are many, but they are always of a polynomial or exponential nature. Physically, Laplace's equation usually implies some superposition of wave-like behavior in a scalar field.

The equation for a solenoidal vector field (that the vector field has zero divergence) is also very easy to solve and is always separable, but it also doesn't reveal the entire picture. It cannot tell you how the x component of the vector field depends on an additive term containing the y and z variables, for example. In order to figure out the full behavior of the vector field, you must know its curl field as well.

EDIT: I should correct myself. The solutions to Laplace's equation are always of a polynomial or exponential nature for coordinates in a holonomic basis.
Last edited by Katganistan on Sun Sep 13, 2009 8:01 am, edited 2 times in total.
A little homework for you!

What part of L(f(t)) = Int(exp(-s*t)*f(t),t,0,inf) don't you understand?

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Yootopia
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Postby Yootopia » Sat Sep 12, 2009 7:51 pm

What is there to discuss -_-
End the Modigarchy now.

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Wilgrove
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Postby Wilgrove » Sat Sep 12, 2009 7:53 pm

You lost me...

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UnhealthyTruthseeker
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Postby UnhealthyTruthseeker » Sat Sep 12, 2009 7:53 pm

Yootopia wrote:What is there to discuss -_-


Would you rather discuss abortion for the 3.34 x 1028th time?
A little homework for you!

What part of L(f(t)) = Int(exp(-s*t)*f(t),t,0,inf) don't you understand?

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Wilgrove
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Postby Wilgrove » Sat Sep 12, 2009 7:57 pm

UnhealthyTruthseeker wrote:
Yootopia wrote:What is there to discuss -_-


Would you rather discuss abortion for the 3.34 x 1028th time?


Like being a good comedic, in order to make a good thread, your subject has to be universal. This subject is not universal.

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UnhealthyTruthseeker
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Postby UnhealthyTruthseeker » Sat Sep 12, 2009 7:59 pm

Wilgrove wrote:Like being a good comedic, in order to make a good thread, your subject has to be universal. This subject is not universal.


We've pretty much discussed every universal topic hundreds of times. Besides, aren't there comedians that joke about specific topics?
Last edited by UnhealthyTruthseeker on Sat Sep 12, 2009 7:59 pm, edited 1 time in total.
A little homework for you!

What part of L(f(t)) = Int(exp(-s*t)*f(t),t,0,inf) don't you understand?

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Natapoc
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Postby Natapoc » Sat Sep 12, 2009 8:04 pm

UnhealthyTruthseeker wrote:Let's discuss Partial Differential Equations! :)

Laplace's equation is nice to work with because it is homogeneous and linear and hence always separable. It's solutions are many, but they are always of a polynomial or exponential nature. Physically, Laplace's equation usually implies some superposition of wave-like behavior in a scalar field.

The equation for a solenoidal vector field (that the vector field has zero divergence) is also very easy to solve and is always separable, but it also doesn't reveal the entire picture. It cannot tell you how the x component of the vector field depends on an additive term containing the y and z variables, for example. In order to figure out the full behavior of the vector field, you must know its curl field as well.

EDIT: I should correct myself. The solutions to Laplace's equation are always of a polynomial or exponential nature for coordinates in a holonomic basis.


Given the set of solutions to all possible Laplace's equations do you think the number of such solutions that are polynomial are greater then, equal to, or less then the number that are exponential? And why?
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UnhealthyTruthseeker
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Postby UnhealthyTruthseeker » Sat Sep 12, 2009 8:07 pm

Natapoc wrote:Given the set of solutions to all possible Laplace's equations do you think the number of such solutions that are polynomial are greater then, equal to, or less then the number that are exponential? And why?


I would say equal. Both are sets with a cardinality of the continuum.

Also, if you remember, exponentials (and yes, sinusoids are exponential functions) are really just polynomial functions of arbitrarily high degree. (Think about the Taylor series.)
A little homework for you!

What part of L(f(t)) = Int(exp(-s*t)*f(t),t,0,inf) don't you understand?

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Niur
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Postby Niur » Sat Sep 12, 2009 8:08 pm

oh god, what language are you speaking?! were not all mathmaticians here...
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UnhealthyTruthseeker
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Postby UnhealthyTruthseeker » Sat Sep 12, 2009 8:10 pm

Niur wrote:oh god, what language are you speaking?! were not all mathmaticians here...


I'm not speaking any language. However, I am typing in English. ;)
A little homework for you!

What part of L(f(t)) = Int(exp(-s*t)*f(t),t,0,inf) don't you understand?

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Yootopia
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Postby Yootopia » Sat Sep 12, 2009 8:12 pm

UnhealthyTruthseeker wrote:
Yootopia wrote:What is there to discuss -_-


Would you rather discuss abortion for the 3.34 x 1028th time?

Aye aye aye discussing abortion is dull but couldn't you have picked a less utterly pish alternative?
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Postby Natapoc » Sat Sep 12, 2009 8:13 pm

UnhealthyTruthseeker wrote:
Natapoc wrote:Given the set of solutions to all possible Laplace's equations do you think the number of such solutions that are polynomial are greater then, equal to, or less then the number that are exponential? And why?


I would say equal. Both are sets with a cardinality of the continuum.

Also, if you remember, exponentials (and yes, sinusoids are exponential functions) are really just polynomial functions of arbitrarily high degree. (Think about the Taylor series.)


Oh yeah good point. I was not thinking about that. I can see that now. Hmm I'll try to contribute a better question ;)
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UnhealthyTruthseeker
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Postby UnhealthyTruthseeker » Sat Sep 12, 2009 8:14 pm

Yootopia wrote:Aye aye aye discussing abortion is dull but couldn't you have picked a less utterly pish alternative?


Pish as in pissy or as in absurd?
A little homework for you!

What part of L(f(t)) = Int(exp(-s*t)*f(t),t,0,inf) don't you understand?

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Postby Northern Delmarva » Sat Sep 12, 2009 8:17 pm

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UnhealthyTruthseeker
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Postby UnhealthyTruthseeker » Sat Sep 12, 2009 8:20 pm

Natapoc wrote:Oh yeah good point. I was not thinking about that. I can see that now. Hmm I'll try to contribute a better question ;)


And if you look at the kind of exponential products that you get vs. the kind of polynomials you get, you will see that the kinds of polynomial solutions you get really just look like the products of portions of exponential polynomial series.

x3 + 3x2y - 3xy2 - y3

Is one such example. Does that not look like the product of simpler polynomials of a certain kind?
A little homework for you!

What part of L(f(t)) = Int(exp(-s*t)*f(t),t,0,inf) don't you understand?

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Yootopia
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Postby Yootopia » Sat Sep 12, 2009 8:21 pm

UnhealthyTruthseeker wrote:
Yootopia wrote:Aye aye aye discussing abortion is dull but couldn't you have picked a less utterly pish alternative?


Pish as in pissy or as in absurd?

"pish: urine; also denoting that something is bad, e.g. "thats pure pish" - http://www.gla.ac.uk/clubs/ski/weegie.html#pish
Last edited by Yootopia on Sat Sep 12, 2009 8:22 pm, edited 1 time in total.
End the Modigarchy now.

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UnhealthyTruthseeker
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Postby UnhealthyTruthseeker » Sat Sep 12, 2009 8:24 pm

Yootopia wrote:"pish: urine; also denoting that something is bad, e.g. "thats pure pish" - http://www.gla.ac.uk/clubs/ski/weegie.html#pish


You know, you could model a stream of urine using a few partial differential equations. Navier-Stokes and the equation of continuity for mass come to mind.

Also, why is math pure piss?
A little homework for you!

What part of L(f(t)) = Int(exp(-s*t)*f(t),t,0,inf) don't you understand?

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Yootopia
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Postby Yootopia » Sat Sep 12, 2009 8:28 pm

UnhealthyTruthseeker wrote:
Yootopia wrote:"pish: urine; also denoting that something is bad, e.g. "thats pure pish" - http://www.gla.ac.uk/clubs/ski/weegie.html#pish


You know, you could model a stream of urine using a few partial differential equations. Navier-Stokes and the equation of continuity for mass come to mind.

Also, why is math pure piss?

Maths is alright but a poor topic when the OP is made up of declaratives.
End the Modigarchy now.

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UnhealthyTruthseeker
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Postby UnhealthyTruthseeker » Sat Sep 12, 2009 8:29 pm

Yootopia wrote:Maths is alright but a poor topic when the OP is made up of declaratives.


Would you have preferred that I phrase it as questions?
A little homework for you!

What part of L(f(t)) = Int(exp(-s*t)*f(t),t,0,inf) don't you understand?

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Natapoc
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Postby Natapoc » Sat Sep 12, 2009 8:30 pm

UnhealthyTruthseeker wrote:
Yootopia wrote:"pish: urine; also denoting that something is bad, e.g. "thats pure pish" - http://www.gla.ac.uk/clubs/ski/weegie.html#pish


You know, you could model a stream of urine using a few partial differential equations. Navier-Stokes and the equation of continuity for mass come to mind.

Also, why is math pure piss?


Hay that is a great point. Actually this is very important in the development of computer games. If the urine flow is not correctly modeled it could float all over the place and people would not play the game because they think it is to fake.

Want to try to come up with a simplistic model? What variables do you think are important enough to consider for an effective urine flow model?

edit: I need to get some pencil and paper out for this conversation
Last edited by Natapoc on Sat Sep 12, 2009 8:32 pm, edited 1 time in total.
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Postby New Kereptica » Sat Sep 12, 2009 8:32 pm

Natapoc wrote:
UnhealthyTruthseeker wrote:
Yootopia wrote:"pish: urine; also denoting that something is bad, e.g. "thats pure pish" - http://www.gla.ac.uk/clubs/ski/weegie.html#pish


You know, you could model a stream of urine using a few partial differential equations. Navier-Stokes and the equation of continuity for mass come to mind.

Also, why is math pure piss?


Hay that is a great point. Actually this is very important in the development of computer games. If the urine flow is not correctly modeled it could float all over the place and people would not play the game because they think it is to fake.

Want to try to come up with a simplistic model? What variables do you think are important enough to consider for an effective urine flow model?


All of them. No concessions can be made when it comes to realistically modelling urine.
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UnhealthyTruthseeker
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Postby UnhealthyTruthseeker » Sat Sep 12, 2009 8:37 pm

Natapoc wrote:Hay that is a great point. Actually this is very important in the development of computer games. If the urine flow is not correctly modeled it could float all over the place and people would not play the game because they think it is to fake.

Want to try to come up with a simplistic model? What variables do you think are important enough to consider for an effective urine flow model?


Well, it's better than another abortion thread I guess. :lol:

First, urine is very similar to water, so I would say the assumptions of Newtonian fluid and incompressible fluid would hold valid. Next, if you were to put the piss stream into a parabolic cylindrical system (parabolas along the direction of flow and compact [that is to say limited in size] cylinders around the direction of flow), you could model it as irrotational. Also, the parabolic axis would remove the need to take gravitation into account, as the flow solutions would be isoclines of the parabolic axis.
A little homework for you!

What part of L(f(t)) = Int(exp(-s*t)*f(t),t,0,inf) don't you understand?

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Pevisopolis
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Postby Pevisopolis » Sat Sep 12, 2009 8:39 pm

UnhealthyTruthseeker wrote:Let's discuss Partial Differential Equations! :)

Laplace's equation is nice to work with because it is homogeneous and linear and hence always separable. It's solutions are many, but they are always of a polynomial or exponential nature. Physically, Laplace's equation usually implies some superposition of wave-like behavior in a scalar field.

The equation for a solenoidal vector field (that the vector field has zero divergence) is also very easy to solve and is always separable, but it also doesn't reveal the entire picture. It cannot tell you how the x component of the vector field depends on an additive term containing the y and z variables, for example. In order to figure out the full behavior of the vector field, you must know its curl field as well.

EDIT: I should correct myself. The solutions to Laplace's equation are always of a polynomial or exponential nature for coordinates in a holonomic basis.


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UnhealthyTruthseeker
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Postby UnhealthyTruthseeker » Sat Sep 12, 2009 8:42 pm

Pevisopolis wrote:Image


Actually, there are some divide by zero issues when you put the Laplacian into cylindrical or spherical coordinates. Of course, they are removable singularities, because they don't exist in all coordinate systems, and the Laplacian is separable in all coordinates.
A little homework for you!

What part of L(f(t)) = Int(exp(-s*t)*f(t),t,0,inf) don't you understand?

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Vetalia
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Postby Vetalia » Sat Sep 12, 2009 8:43 pm

We should kill all nonwhites. That should spice things up.
Last edited by Vetalia on Sat Sep 12, 2009 8:44 pm, edited 1 time in total.
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