Michiel Hazewinkel

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In this paper we study real linear dynamical systems $$\dot x = Fx + Gu,y = Hx,x \in R^n $$ = state space,u ∈ R m = input space,y ∈ R p = output space, under the equivalence relation induced by base change in state space; or in other words we study triples of matrices with real coefficients (F, G, H) of sizesn × n, n × m, p × n respectively, under the(More)
This is partly an introductory survey paper to clustering and classification problems with particular emphasis on the classification of lists of key words and phrases from a given scientific domain such as mathematics. In addition the paper contains a number of new concepts and results; a number of open questions, and some as yet untried embryo clustering(More)
Let A be a reduced incidence relation between n lines and m points. Suppose that (a) Through each two points there pass λ lines (b) Each two lines intersect in µ points. If λ µ = = 1 assume, moreover, that there are four points no three of which are on one line. Then n m = , λ µ = , and there is a number r such that all lines have r points and through each(More)
. This paper is concerned with information retrieval from large scientific data bases of scientific literature. The central idea is to define metrics on the information space of terms (key phrases) and the information space of documents. This leads naturally to the idea of a weak enriched thesaurus and the semiautomatic generation of such tools. Quite a(More)