https://www.um.edu.mt/library/oar/handle/123456789/23632 2026-04-04T19:38:09Z https://www.um.edu.mt/library/oar/handle/123456789/24493 Title: The Collection IV Editors: Sciriha, Irene Abstract: Fourth issue of The Collection, a journal by the Department of Mathematics at the University of Malta. 2001-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/24456 Title: The use of choice Abstract: The aim of this note is to present two examples, one shown use of the Axiom of Choice and the other that of Zorn's Lemma in Mathematics. We begin by stating the mentioned two equivalent axioms. 2001-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/24455 Title: Quaternion roots Abstract: We define a quaternion to be an expression a + bi + c.1 + dk, where CL, b, c, el E R, and define addition and multiplication in the natural way with: i2=j2 = k2 = -1 ij= -ji = k jk= -kj= i ki= -ik= j (1) The set of real quaternions forms a skew field or a division ring which fails to be a field because commutativity under multiplication does not hold. 2001-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/24454 Title: Petri nets Abstract: Petri Nets (PN) provide a graphical approach to the modelling of communicating systems. PN have been introduced by Carl A. Petri in his dissertation presented in 1962. The purpose was to analyse communication systems. Further study on this subject has led to a vast applicability of PN in many sectors like in I.T. and manufacturing. The reason for such a vast applicability of PN is clue to the fact that PN hold a considerable modelling power as well as efficient methods for proper performance analysis of the system under study. In fact, PN may be shown to be effective in the modelling of concurrency, conflict and synchronisation. 2001-01-01T00:00:00Z