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)
In this lecture I discuss some aspects of MKM, Mathematical Knowledge Management, with particuar emphasis on information storage and information retrieval. 1. Is there a problem? The issue at hand is that of information storage and information retrieval as regards mathematics. Or, concentrating on the latter, if one has a mathematical question, can one find(More)
Let A be a bipartite graph between two sets D and T. Then A defines by Hamming distance, metrics on both T and D. The question is studied which pairs of metric spaces can arise this way. If both spaces are trivial the matrix A comes from a Hadamard matrix or is a BIBD. The second question studied is in what ways A can be used to transfer (classification)(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)
BACKGROUND Admission at a closed acute psychiatric ward is a severe and possibly life changing experience for a patient. Sometimes admission is accompanied by coercive measures. Despite the impact that these measures may have on the patient, very little research has been published concerning this patient population. AIM To obtain insight into the(More)