A carefully structured practical queue-modelling assignment improves the understanding of queueing theory and teaches modelling and data-analysis skills. The assignment also demonstrates that it may be better to use models to estimate operating characteristics such as mean waiting times, even in circumstances where the system in question and the characteristics can be directly observed.

To each finitely presented module M over a commutative ring R one can associate an R-ideal FitR(M) which is called the (zeroth) Fitting ideal of M over R and which is always contained in the R-annihilator of M . In an earlier article, the second author generalised this notion by replacing R with a (not necessarily commutative) oorder Λ in a finite dimensional separable algebra, where o is an in...

ASTRONOMY AND ASTROPHYSICS The two-component X-ray spectrum of the 6.4 s pulsar 1E 1048.1–5937 Abstract. The 6.4 s X-ray pulsar 1E 1048.1–5937 was observed by BeppoSAX in 1997 May. This source belongs to the class of " anomalous " pulsars which have pulse periods in range 5–11 s, show no evidence of optical or radio counterparts , and exhibit long-term increases in pulse period. The phase-avera...

We show that every finitely generated nilpotent group of class 2 occurs as the quotient of a finitely presented abelian-by-nilpotent group by its largest nilpotent normal subgroup.

Methods for differential psychologists are the methods of all scientists: describe and test models of data. Our field is distinguished by the nature of our data and the specialized tools we use for analysis. For the differential psychologist, data come from self-report, from observations, from physiology, and from behavioral residues. Data are recorded over time and over space. The challenges o...

The growing availability of COTS (Commercial-Off-The-Shelf) components in the software market has concretized the possibility of building whole systems based on components. In this multitude, a recurrent problem is the location and selection of the components that best fit the requirements. Commercial repositories that offer search mechanisms have reduced these difficulties: system integrators ...