Showing posts from October, 2019

A note on Rudi Mathon

From BICA (12) 1994 by John van Rees Rudi Mathon Professor, University of Toronto We are always looking for new methods to tackle our favourite intractable problems. Those of us who know the hill-climbing and simulated annealing techniques realize that these are wonderful algorithms for finding various combinatorial objects. But often these algorithms are not powerful enough to do the job. So it is with great interest that we learn from Rudi Mathon, via his talk at the Vermont Summer Workshop, that there is a new variation to the search algorithms developed by the optimization people that may help us all. Rudi was examining Steiner Systems, S(t,k,v), exact packings of k-sets from a v-set with the property that each t-set occurs exactly once. For t ≥ 5, there are only 9 orders known to S(5,6,168). Rudi assumed the design had PSL2(23) as an automorphism group, obtained the 5-set and 6-set orbit representatives, and found which 6-set orbit representative covered which 5-set orbit r

Carsten Thomassen, Honorary Fellow

On Friday, September 27, 2019, Carsten Thomassen gave the Tutte Distinguished Lecture at University of Waterloo.             Title:  Countable weighted graphs with no unfriendly partitions             Abstract:   The vertex set of every finite graph can be partitioned into two sets such              that each vertex has at least as many vertices in the opposite set as in its own set.                    Such a partition is called unfriendly. It is known that there are infinite graphs with                no unfriendly partition but it is open if every countable graph has an unfriendly                    partition. In this talk we show that the there are edge-weighted countable graphs                  with no unfriendly partition. Following the talk, Dr Stinson presented him with the certificate naming him an Honorary Fellow of the ICA.  Pictures are below the link to his citation:

In Memoriam Frank Yates 1902-1994

From BICA 12(1994) Obituary: Frank Yates May 12, 1902-June 17, 1994 It is impossible to summarise the research achievements of one of the great statisticians of this century in a brief obituary. The Times (Saturday, June 25, 1994) spends half of its space in giving an account of the work Dr Yates did during the War in analysing the strike patterns of V-ls around London so as to identify the sites being targeted, and thus aid in the deployment of interceptor fighter squadrons. A better insight into the enormous impact of the work of Dr Yates is provided by the article F.Y.-A Personal Note, by M.J.R. Healy (Utilitas Mathematica, 21A, 1982, 3-12); this article introduces the two special volumes that were published on the occasion of Dr Yates's 80th birthday. Healy's article shows the enormous contribution that Yates made to experimental design and to the analysis of design, as well as his later major contributions to sampling and to the use of computers in statistical analy

News of Member Jeff Dinitz

From BICA (11) 1994 PERSONALITY OF THE MONTH Jeff Dinitz Professor, University of Vermont The Bulletin has to start this vignette with an apology to Jeff. By a fluke, Jeffs name was left off the list of members of the Council of the ICA. This omission has now been corrected - see page 1 of this issue of the Bulletin.  Jeff is a member of Council for a three-year term from 1993 to 1996. In 1992, Jeff Dinitz and Doug Stinson, published Contemporary Design Theory, A Collection of Surveys (John Wiley and Sons, Inc.). This book was reviewed in Volume 9 of the Bulletin (page 9), and continues to receive a lot of well deserved acclaim; Jeff and Doug seem to have filled a real need with this timely and outstanding work. Last year, graph theorists received electrifying news from Jeff on the famous problem of the number of one factorizations of K_12 . Here is an extract from the email message of Monday, September 20, 1993 at 16:04:28. Theorem. There are 526,915,620 non-isomorphi

Dr Ronald Graham awarded the 1993 Euler Medal of the ICA

EULER MEDALS FOR 1993 In announcing the Euler Medallists for 1993, a reminder about the qualifications for the Medals is in order. Up to two Euler Medals per year may be awarded. A recipient must be a Fellow of the ICA and must have made a particularly distinguished lifetime career contribution to research in Combinatorics; the Euler Medal is not meant to recognize one specific achievement. Furthermore, a recipient should still be active in research. By majority vote of the ICA Council, 1993 Euler Medals have been awarded to Claude Berge, one of the world's most distinguished graph theorists, and Ronald Graham, a research combinatoricist of enormous breadth, depth, and influence. Members of the ICA may be interested in the extremely brief summaries of their research careers that follow. Ronald L. Graham . Ph.D., University of California (Berkeley), NSF Fellow and Woodrow Wilson Fellow. 1962- Adjunct Director, Research, Information Sciences Division AT&T Bell Labs 198