### Jelle Pelfrene

Shared publicly -Fantastische analogie om de vergrijzingskost te begrijpen.

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Jelle Pelfrene

Worked at Space Applications Services

Attends Katholieke Universiteit Leuven

Lived in belgium

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Fantastische analogie om de vergrijzingskost te begrijpen.

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interessante grafiek toont correlatie interestaflossingen - recessie , terwijl interestaflossingen niet gebruikt worden in gewone macro modellen .

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Very interesting talk on how biases as failures to reason in classical logic can be seen as following from reasoning with defensible logics instead.

Video of my lecture at Munich Center for Mathematical Philosophy (MCMP) last week, 'Reasoning biases and non-monotonic logics'.

https://cast.itunes.uni-muenchen.de/vod/clips/3Qpc7Lsw19/quicktime.mp4

https://cast.itunes.uni-muenchen.de/vod/clips/3Qpc7Lsw19/quicktime.mp4

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Geweldig voorbeeld voor in de les (in de wiskunde richting, jaja), als puzzel.

Buffon asked: if you drop a needle on the floor, how likely is it to cross a floorboard line? Assume that the needle length is the same as the floorboard width (and that the flooboards are long).

I learned Barbier's great solution some time ago at the link below, and I wanted to share it.

First, let's generalize the problem to include needles of any length, but instead of asking for the probability, ask for the expected number of floorboard line crossings. (Which could only be zero or one in the original problem, with probability 1.) Call this e(r), where r = (needle length)/(floorboard spacing).

Second, note that e(a+b) = e(a) + e(b), i.e. if we attach an a-segment to a b-segment, the number of lines you expect them to cross is additive. With that and continuity one can infer that e(a) = a e(1).

Third, that holds even if the two segments aren't aligned. They could each be curved! Say, piecewise differentiable. So e(a) gives the expectation for any reasonable curve of length a, not just a straight line.

Finally, if our curve is a hoop whose diameter is the floorboard spacing, then with probability 1 it crosses the same line twice. So e(pi) = 2.

Hence the answer to Buffon's question is 2/pi ~ 64% probability.

I learned Barbier's great solution some time ago at the link below, and I wanted to share it.

First, let's generalize the problem to include needles of any length, but instead of asking for the probability, ask for the expected number of floorboard line crossings. (Which could only be zero or one in the original problem, with probability 1.) Call this e(r), where r = (needle length)/(floorboard spacing).

Second, note that e(a+b) = e(a) + e(b), i.e. if we attach an a-segment to a b-segment, the number of lines you expect them to cross is additive. With that and continuity one can infer that e(a) = a e(1).

Third, that holds even if the two segments aren't aligned. They could each be curved! Say, piecewise differentiable. So e(a) gives the expectation for any reasonable curve of length a, not just a straight line.

Finally, if our curve is a hoop whose diameter is the floorboard spacing, then with probability 1 it crosses the same line twice. So e(pi) = 2.

Hence the answer to Buffon's question is 2/pi ~ 64% probability.

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Another analysis that seems to make a lot of sense at http://www.eurointelligence.com/eurointelligence-news/macro/singleview/article/the-eurozones-giant-sucking-sound.html . For the Belgian perspective, how does this mesh with the message of Geert Noels +*****?

Besides the logic itself, an argument from authority here is that the author +Miguel Carrion Alvarez did his phd under +John Baez , see also the interesting thread at http://johncarlosbaez.wordpress.com/2011/01/08/mathematical-economics/

Besides the logic itself, an argument from authority here is that the author +Miguel Carrion Alvarez did his phd under +John Baez , see also the interesting thread at http://johncarlosbaez.wordpress.com/2011/01/08/mathematical-economics/

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This seems like a frank assesment of our current situation: austerity starving the economy while saving only the rentier class (for now).

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Wow, Rolf Olson saw the disk of Beta Pictoris with only a 25cm telescope and a little digital help. Amazing work, and a great sky down there ...

John Baez originally shared:

You've probably seen this by now, but I can't resist. It's the first photo of another solar system taken by an amateur astronomer!

http://www.stuff.co.nz/national/6046887/Kiwis-space-photos-stun-astronomers

**Three cheers for Rolf Olsen**, who took this shot of the protoplanetary disc around Beta Pictoris, 63 light years away, using a 25 centimeter telescope at his home.

Here is his website:

http://www.pbase.com/rolfolsen/astro_photography

and here's a nice discussion of what he just did:

http://blogs.discovermagazine.com/badastronomy/2011/11/26/amateur-astronomer-glimpses-an-alien-solar-system/

Thanks to +Mikki Michelle for bringing this to my attention, again... and making me realize it was so cool I had to talk about it.

http://www.stuff.co.nz/national/6046887/Kiwis-space-photos-stun-astronomers

Here is his website:

http://www.pbase.com/rolfolsen/astro_photography

and here's a nice discussion of what he just did:

http://blogs.discovermagazine.com/badastronomy/2011/11/26/amateur-astronomer-glimpses-an-alien-solar-system/

Thanks to +Mikki Michelle for bringing this to my attention, again... and making me realize it was so cool I had to talk about it.

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In his circles

144 people

QB50 satellite SIMBA is going where no one has gone before to pay for a better attitude control system !

Supporting space research by launching the first billboard in space. http://spacebillboard.com #SpaceBillboard #CubeSats +Jelle Pelfrene

Project description. SpaceBillboard is a unique and one-time advertising project. SpaceBillboard will launch the first billboard in space. The billboard contains company logos, visible on our website. Using our unique story, a global media campaign involving traditional and social media will be ...

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I'm looking for a thorough analysis / critique of the Modest Proposal of Yanis Varoufakis .

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How do we teach this to adults as well as kids? And do people at large still respobd to arguments from mathematical authority, or has the scientific class lost too much credibility?

Here’s a public lecture I gave yesterday at the 55th annual meeting of the South African Mathematical Society. The global warming crisis is part of a bigger transformation in which humanity realizes that the Earth is a finite system and that our population, energy usage, and the like cannot continue to grow exponentially. If civilization survives this transformation, it will affect mathematics—and be affected by it—just as dramatically as the agricultural revolution or industrial revolution. We cannot know for sure what the effect will be... but we can already make some guesses, and that's what I did!

You can get the slides of the talk here:

http://math.ucr.edu/home/baez/planet/planet.pdf

To see the source of any piece of information on these slides, just*click on it.*

You can get the slides of the talk here:

http://math.ucr.edu/home/baez/planet/planet.pdf

To see the source of any piece of information on these slides, just

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Steve Keen touches on the importance of heterodox economics in a promo session for his department.

Keen is on Dirk Bezemer's list of economists who called the crisis:

Dean Baker,US

Wynne Godley, UK

Fred Harrison, UK

Michael Hudson, US

Eric Janszen, US

Stephen Keen, Australia

Jakob Brochner Madsen and Jens Kjaer Sorenson, Denmark

Kurt Richebacher, US

Nouriel Roubini, US

Peter Schiff, US

Robert Shiller, US.

Keen is on Dirk Bezemer's list of economists who called the crisis:

Dean Baker,US

Wynne Godley, UK

Fred Harrison, UK

Michael Hudson, US

Eric Janszen, US

Stephen Keen, Australia

Jakob Brochner Madsen and Jens Kjaer Sorenson, Denmark

Kurt Richebacher, US

Nouriel Roubini, US

Peter Schiff, US

Robert Shiller, US.

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Wow. Wow. Wow.

Even if it is fake. http://gizmodo.com/5895235/cgi-experts-say-flying-bird-man-is-fake

Even if it is fake. http://gizmodo.com/5895235/cgi-experts-say-flying-bird-man-is-fake

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In his circles

144 people

Work

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- Space Applications ServicesSoftware Engineer

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belgium

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Introduction

I'm interested in a lot of things, but currently reading up on:

- ecological economics

- basic category theory

Education

- Katholieke Universiteit LeuvenMathematics teacher, 2011 - present
- Katholieke Universiteit LeuvenEngineering : Computer Science, 2008

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Married