Nothing takes place in the world whose meaning is not that of some maximum or minimum - Euler

Mathematics, research and interests

Research interests

At the moment I'm mostly interested in algebraïc techniques in combinatorial optimization, scheduling, design theory, matroids and graph theory and any mathematics related to mechanical puzzles, origami, art or magic.

Education

Vector Calculus (2DM30)

Optimization in Rⁿ (2P610, 2WO11)

I ~~give~~ gave instruction for the course Optimization in Rⁿ. For a description of the course and requirements see Rudi's page. At the end of the lecture notes is a study guide and some pointers to what will be tested at the exam. Looking at several older exams (see Rudi's page or GEWIS) will tell you much of what will be expected of you. The lectures have been recorded in 2010, so watch them (again) in your own time (and speed :) if needed.

Solutions to exercises were available here after (or around) each week's instruction; these have been handed over to the new instructor.

Optimization in networks (2WO10,2WO12)

Lectures by Gerhard Woeginger. Selected answers and hints to the exercises are available here (last updated: July 13 2010).

Seminar graphs and matroids

At the Technische Universiteit Eindhoven there was a (more or less) weekly seminar on graphs and matroid theory for which i toke care of announcements and speakers. It has been merged with the EIDMA Seminar Combinatorial Theory. So if you wish to receive announcements and/or give a talk, please look there.

English

Check pronunciation (ship or sheep), closely related words, and writing.

Publications

Motion planning with pulley, rope, and baskets, (with Gerhard J. Woeginger), In: Proceedings of the 29th Symposium on Theoretical Aspects of Computer Science (STACS 2012), Leibniz International Proceedings in Informatics (2012), pp. 374-383 [DOI]

Reachability and deadlocking problems in multi-stage scheduling, (with Gerhard J. Woeginger), In: Reachability Problems (5th International Workshop, RP 2011, Genoa, Italy, September 28-30, 2011. Proceedings). Lecture Notes in Computer Science, 6945 (2011) pp.153-164 [DOI]

Analysis of multi-stage open shop processing systems, (with Alexander Schrijver, and Gerhard J. Woeginger), In: Proceedings of the 28th Symposium on Theoretical Aspects of Computer Science (STACS 2011), Leibniz International Proceedings in Informatics (2011), pp. 484-494. [DOI]

The hardness of train rearrangements, (with Cor Hurkens, Maciej Modelski, and Gerhard Woeginger), Operations Research Letters, 37 (2009), no. 2, pp. 80-82. [DOI] [Zentralblatt Math]

The Untangler Project, (with Tom Verhoeff) Cubism for Fun, 79 (2009), pp. 32-35.

Multimagic squares, (with Harm Derksen and Arno van den Essen), American Mathematical Monthly 114 (2007), no. 8, pp. 703-713. [MathSciNet] [Zentralblatt Math]

Multimagic squares, (with Harm Derksen and Arno van den Essen), (2005)
A more technically written preprint. The article in the Monthly is less general and much more readable.

A class of triangular derivations having a slice, (with Arno van den Essen), Journal of Pure and Applied Algebra 114 (1997), no. 2, pp. 209-215. [DOI] [MathSciNet] [Zentralblatt Math]

My doctoraalscriptie on multimagic squares and cubes is also available. The related newspaper articles, TV news item and other interviews can be found on puzzled.nl. I also compiled a partial list of references. It includes pointers to several freely available old books and even letters. However many more can nowadays be found at e.g. archive.org.

Talks and Prizes

2012-03-20 Talk Motion planning on graphs at ORStat, KUleuven, Belgium.

2012-02-01 PhD defense, Reachability Problems in Scheduling and Planning (pdf `lekenpraatje')
Promotor: Gerhard Woeginger, co-promotor: Cor Hurkens, Committee: Marc Uetz, Frits Spieksma, Jan Friso Groote, Stan van Hoesel, Ton de Kok

2011-09-28 Talk Reachability and deadlocking problems in multi-stage scheduling (pdf) at 5th Workshop on Reachability Problems (RP'11), DISI, Università di Genova, Italy.

2011-03-11 Talk Analysis of multi-stage open shop processing systems (pdf) at 28th International Symposium on Theoretical Aspects of Computer Science (STACS 2011), TU Dortmund, Germany.

2011-2-19 Invited talk Vouwen en kleuren at the Reünie Vierkant voor Wiskunde Kampen in Lunteren, the Netherlands (most slides, 4x4 magic trick and the challenges). On the revolution in Origami caused by Mathematics the last 50 years: some history, a magic trick, puzzles and mathematical ideas and background for children (10-18yrs) and kampleiding.

2010-10-17 Talk Folding puzzles at the Dutch Cube Day (and Dutch Open 2010) in Emmen, the Netherlands.

2010-05-27 Talk Deadlocks in Open Shop Systems (pdf) at the DIAMANT/EIDMA symposium in Nunspeet, the Netherlands.

2010-04-27 Talk Deadlocks in Open Shop Systems (pdf) at the 12th International Workshop on Project Management and Scheduling in Tours (France). With this i won the Best Student Paper Award - 1st Prize!

2010-03-31 Talk Deadlocks in Open Shop Systems at the EIDMA Seminar Combinatorial Theory.

2010-03-10 Talk Safety in Jobshop (pdf) at the EIDMA Seminar Combinatorial Theory.

2009-06-30 Talk Disruption Managment for Commercial Aviation, Roadef 2009 Challenge (pdf) at Models and Algorithms for Planning and Scheduling Problems 2009, Abbey Rolduc, the Netherlands.

2009-04-16 Workshop Invarianten en kleuringen at Stedelijk Gymnasium Nijmegen in their Project Week. A Math Circle-like adventure through some hands-on puzzles and games with circa 25 children (12-13 yrs). Great fun!

2009-02-11 Talk Fixing a broken Flight Schedule (pdf) at Roadef Conference 2009, Nancy (France)
A very short description of our method for the Roadef Challenge in which we won 1st prize in the junior category! For more see the website of the Roadef Challenge. (results,photos).

2009-01-28 Talk Balancing Carry-Over Effects (pdf) at the Graphs and Matroids seminar.

2009-01-14 Fixing a broken Flight Schedule, Roadef Challenge 2009 (pdf) at 34th Conference on the Mathematics of Operations Research, Lunteren.

Before Several talks on Multimagic Squares: at the Graphs and Matroids Seminar (2008, pdf), at the Colloquium (2007, pdf) of the Mathematics departement from the Radboud University and at the Dutch Cube Day 24 (2004, ppt).