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Jeff Erickson
Works at University of Illinois
Attended Rice University
Lives in Urbana, IL
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Jeff Erickson

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My first "publication" (with +Bob Hearn) is finally properly available online at the Internet Archive, in two different versions,

• Preprint: https://archive.org/details/a2gs_Topdraw_1989_Styleware

• Final: https://archive.org/details/a2gs_Beagle_Draw_1989_Beagle_Brothers_FW

The manual and its errata have already been available at the Internet Archive for a few years:
https://archive.org/details/TopDraw-Manual
https://archive.org/details/TopDraw-Errata
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Jeff Erickson

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Boaz Barak and Madhu Sudan to join Harvard
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Some figures from the presentation of Steinitz's theorem in Vorlesung über die Theorie der Polyeder by Steinitz and Rademacher (1936).

Top row: A portion of the medial graph of a polyhedron, a spindle, and an irreducible spindle.

Middle row: The medial graphs of the square antiprism, the tetrahedron, and the square pyramid.  (Also: The dual graphs of Schneider's pyramid, the cube, and the octagonal spindle.  The first and third of these are well-known bad examples for hexahedral meshing!)

Bottom row: A YΔ-transformation (solid to dashed), and the corresponding change in the medial graph (removing a triangular face from the shaded spindle).
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Cool!  There's a lot of material on 'medial graphs' in this paper, which is open-access:

• E.B. Curtis, D. Ingerman and J.A. Morrow, Circular planar graphs and resistor networks, http://www.sciencedirect.com/science/article/pii/S0024379598100873
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That's cutting up a knot (projection), and looking at it with halves replaced by something i don't remember the name of right now.

Very nice +Jeff Erickson​​!
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If you are like me you will find yourself thinking, "What did I mean by that?" or "How does this follow?" or, all too often, "Who wrote this crap?"

[via MetaFilter]
The 'curse of knowledge' leads writers to assume their readers know everything they know
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There's a decent discussion of this at http://www.metafilter.com/150950/The-Curse-of-Knowledge
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Yo, dawg, I heard you liked mayo.

I remember seeing this cartoon years ago and loving it. I only now just realized it was directed by Rebecca Sugar, of Adventure Time and Steven Universe fame, with assistance from Ian Jones-Quartey, one if the main animators for Steven Universe.
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Yo, dawg, I heard yo dawg likes to jump at dogs. So I showed yo dawg yo dawg so yo dawg can jump while he jumps.
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Needs more infinite zoom.
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An "irreducible spindle" from Ernst Steinitz's 1916 proof that (in modern language) every 3-connected planar graph ("K-polyeder") is the 1-skeleton of a convex 3-polytope.  Steinitz observes that the medial graph ("Θ-Prozeß") of every 3-connected planar graph G contains an irreducible spindle. He then argues that every 3-connected planar graph G fits one of the following cases.

(0) G is the 1-skeleton of the tetrahedron.

(1) The smallest irreducible spindle in the medial graph Θ(G) contains exactly two faces.  In this case, G contains a vertex of degree 3 incident to a triangular face.  In this case, one can simplify G by applying one ΔY-transformation and at most three series-parallel reductions to obtain a 3-connected planar graph G' with fewer edges than G.

(2) Every irreducible spindle in Θ(G) has at least three faces. In this case, one can "simplify" G by applying a ΔY-transformation to obtain a 3-connected planar graph G' with the same number of edges as G, but whose smallest irreducible spindle has one fewer face than in G. Specifically, we can apply "a type-3 Reidemeister move" to remove one triangular face incident to the boundary of the minimum spindle.

In the second and third cases, the inductive hypothesis implies that there is a polytope P' whose 1-skeleton is G'. In both cases, Steinitz describes how to modify P' to obtain a new polytope P whose 1-skeleton is G.

Steinitz's proof technique also immediately yields to two other theorems about planar curves and planar graphs.

(A) Every regular closed curve in the plane can be reduced to a circle using a finite number of "planar Reidemeister" moves. Reidemeister moves for knots were first proposed in 1926 by Reidemeister (and independently by Alexander and Briggs, also in 1926). The version of Steinitz's proof that appear in his posthumous 1934 monograph with Hans Rademacher includes images of a type-3 "Reidemeister" move.

(B) Every connected planar graph can be reduced to a single vertex by a finite number of degree-1 vertex deletions, empty loop deletions, series-parallel reductions, and ΔY- or YΔ-transformations.  This theorem is normally attributed to Epifanov in 1966 (50 years after Steinitz) and Grünbaum in his 1967 monograph Convex Polytopes. But in fact, Grünbaum just repeats Steinitz's proof in more detail. Steinitz did not use the term "ΔY-transformation" (even though that transformation had been used in circuit analysis since Kennelly in 1899), but he describes the transformation in detail, and his 1934 monograph includes a clear illustration.
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Jeff Erickson

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Generate your own Neural Network inspired images with DeepDream

Two weeks ago we blogged about a visualization tool designed to help us understand how neural networks work and what each layer has learned (http://goo.gl/pUfbyH). In addition to gaining some insight on how these networks carry out classification tasks, we found that this process also generated some beautiful art.

Now you can make your own images using an open source IPython notebook, which allows you to choose which layers in the network to enhance, how many iterations to apply and how far to zoom in. Alternatively, different pre-trained networks can be plugged in.

It'll be interesting to see what imagery people are able to generate. If you post images to Google+, Facebook, or Twitter, be sure to tag them with #deepdream so other researchers can check them out too.
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By an overwhelming majority vote at the SOCG 2015 business meeting in Eindhoven, SOCG 2017 will be held in Brisbane, Australia.
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Have him in circles
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Work
Occupation
I am the very model of the tenured professoriat.
Skills
Nunchucks, bow-hunting, computer hacking
Employment
  • University of Illinois
    Professor, 1998 - present
Places
Map of the places this user has livedMap of the places this user has livedMap of the places this user has lived
Currently
Urbana, IL
Previously
Klosterneuburg, Austria - Berlin, Germany - Brooklyn, NY - Nancy, France - Champaign, IL - Chapel Hill, NC - Berkeley, CA - Saarbrücken, Germany - Oakland, CA - Northampton, MA - Irvine, CA - Saratoga, CA - Cupertino, CA - Houston, TX - La Paz, Bolivia -
Story
Tagline
I am an amateur double-dactylicist.
Introduction
Frequently Asked Questions:

Q: What software do you use to draw pictures?
A: Mostly OmniGraffle, but occasionally Adobe Illustrator.

Q: Your algorithms class has been full for weeks. Can you let me in anyway?
A: Yes, but only if you're graduating this semester and it's a degree requirement.

Q: Do you mind if I use your lecture notes in my class?
A: Not at all. That's why they're on the web.  Please send me bug reports!

Q: Would you send me solutions for...
A: No.
Bragging rights
I only listed places where I've lived at least 30 days in a row.
Education
  • Rice University
    Comp Sci & Math Sci, 1983 - 1987
  • University of California, Irvine
    Information and Computer Science, 1990 - 1992
  • University of California, Berkeley
    Computer Science, 1992 - 1996
Basic Information
Gender
Male