Bridging Different Length and Time Scales in Diffusion Problems Using a Lattice Monte Carlo Method

In this paper, we show how lattice–based random walks of virtual particles directed by Monte Carlo methods (Lattice Monte Carlo) can be used to address a variety of complex phenomenologically mass diffusion problems. Emphasis is put on the practical details of doing the calculations. It is shown how concentration depth profiles can be determined: this is exemplified with diffusion in the presence of isolated dislocation pipes, grain boundary slabs, and oxygen segregation at interfaces in metal-ceramic oxide composites. It is also shown how effective diffusivities can be determined in materials. We also show how temperature profiles and the effective thermal conductivity can be determined for the thermal diffusion analogue of mass diffusion. A detailed comparison is made in one case with the results of the Finite Element method.

Digital Audio Broadcasting in Canada: Technology and Policy in the Transition to Digital Radio

This article presents an overview of digital radio policy in Canada in the period 1995 to 2005 and the attempt to implement the Eureka-147 Digital Audio Broadcasting (DAB) standard as the replacement technology for analog AM and FM broadcasting. Canada was an early adopter of this system, but unfavourable conditions have led it to largely abandon the approach in favour of a multiplatform system. The interaction between industry, government regulation, and broadcasting policy around digital radio reveals a complex situation of competing interests. Despite extensive regulatory intervention to protect Canadian interests, the pace of technological change and the dominant influence of U.S. interests have made the transitional path to digital radio even more uncertain than it was 10 years ago. Résumé : Cet article offre un survol des politiques qui régissent la radio numérique au Canada pour la période de 1995 à 2005 et expose la tentative d'implantation de la norme Eureka-147 Digital Audio Broadcasting (DAB) comme technologie de remplacement pour la diffusion analogue AM et FM. Le Canada fût rapide à adopter ce système, mais des conditions défavorables l'on mené à l'abandonner en très grande partie en faveur d'un système multi plateforme. L'interaction entre l'industrie, la réglementation gouvernementale et la politique de diffusion qui touchent à la radio numérique révèle une réalité complexe composée d'intérêts concurrents. Malgré une vaste intervention en matière de réglementation visant à protéger les intérêts canadiens, le rythme des changements technologiques et l'influence dominante des intérêts américains ont rendu le passage transitoire à la radio numérique encore plus incertain qu'il ne l'était il y a 10 ans.