Headline: teaching - colloquium CGC logo

Winter 2000/01 former semesters

Time: Mondays, 14:15 - 15:45
Location: IFW B 42
(unless stated otherwise)

The CGC colloquium does not take place during the pre-doc courses. Hence, the dates available this year are the Mondays November 27, and December 4, 11, and 18, 2000.


November 27, 2000

Rachid Guerraoui
(EPF Lausanne)

Implementing e-Transactions
Abstractions for reliable distributed programming

December 4, 2000
Jürgen Richter-Gebert
(ETH Zürich)

Dynamic Geometry: Problems, Gadgets and Solutions

December 11, 2000
Tinne Tuytelaars
(KU Leuven)

Local invariant features for image registration and object recognition

December 18, 2000
Angelika Steger
(TU München)

Simplified Witness Tree Arguments


Monday, November 27, 2000, 14:15 - 15:45, IFW B 42

Implementing e-Transactions
Abstractions for reliable distributed programming

Rachid Guerraoui
(EPF Lausanne)

This talk will argue for the use of two primititives for building reliable distributed services: eventual leader election and regular consensus. The talk will give a hint on how to build various replication algorithms using these abstractions and discuss the optimality of those abstractions in terms of performance and ``complexity''.


Monday, December 4, 2000, 14:15 - 15:45, IFW B 42

Dynamic Geometry: Problems, Gadgets and Solutions

Jürgen Richter-Gebert
(ETH Zürich)

Computational Geometry very often focuses on static problems, like computing the convex hull or the Voronoi complex of a given set of points. Fundamentally new questions arise when the objects under consideration are no longer static but may move around with respect to certain constraints. This scenario is not unusual -- for instance every mechanism can be considered as a dynamic geometric entity.

This talk focuses on the principal problems that arise in the context of Dynamic Geometry. It is shown ...

... that natural requirements lead to a setup that requires the consideration of complex functions.

... that in this context natural algorithmic questions arise, that turn out to be difficult to handle (sometimes even undecidable).

... that these problems relate to other areas like CAD, robotics, polynomial equation solving and provide natural complexity bounds in these setups.

... that many proofs in this area can be carried out "hands on" by constructing certain gadgets that "show something".

The talk will be illustrated by several concrete dynamic constructions within the "Cinderella"-framework (see www.cinderella.de).


Monday, December 11, 2000, 14:15 - 15:45, IFW B 42

Local invariant features for image registration and object recognition

Tinne Tuytelaars
(KU Leuven)

We'll start with a short introduction on invariance in the field of computer vision. Invariants are features that remain unaltered under a specific group of transformations. In computer vision, they were initially introduced to allow arbitrary viewpoints, but soon it was realized that they also allow to work under uncalibrated conditions. Moreover, also changes in illumination conditions can be dealt with using invariants. Typical applications include object recognition and the registration of images (i.e. finding corresponding features between different views). Using invariance, this can be achieved without the use of combinatorics, using indexing- or hashing techniques.

Next, we'll focus on affinely invariant regions. These are small, parallelogram- or ellipse-shaped image patches that adapt their shape (based on the underlying image intensities) as to keep on representing the same physical part of the object in spite of varying viewing conditions (if the surface can locally be approximated by a plane). As will be explained in the talk, these are a necessary tool to obtain higher levels of invariance than pure 2D rotation and translation on a local scale in a robust way. Two different methods to extract such regions will be proposed, as well as a method to describe their content in an invariant way, using a feature vector of moment invariants. Finally, some experimental results will show the success of this approach in several application domains.


Monday, December 18, 2000, 14:15 - 15:45, IFW B 42

Simplified Witness Tree Arguments

Angelika Steger
(TU München)

In recent years it turned out that ideas based on so seemingly simple strategies as considering two choices instead of just one can give rise to a dramatic increase in the performance of algorithms. Prominent examples are algorithms for load distribution on multiprocessor machines or for distributing data on multiple servers. In this talk we discuss some of these examples in detail and present some novel proof techniques.


Former semesters

Summer 2000 , Winter 1999/2000 , Summer 1999 , Winter 1998/99 , Summer 1998 , Winter 1997/98 , Summer 1997


Last modified on 2001-02-01 12:21:57 by Sven Schoenherr <sven@inf.ethz.ch>      Copyright © 2000-2001 CGC
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