10,531 research outputs found
Transition time asymptotics of queue-based activation protocols in random-access networks
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The asymptotic workload behavior of two coupled queues
Full text linkThe asymptotic workload behavior of two coupled queues S.C. Borst, O.J. Boxma, M.J.G. van Uiter
Stochastische modellen voor random-access-netwerken
No full textDraadloze communicatienetwerken spelen een cruciale rol in het verbinden van laptops, smartphones, sensoren en talloze fysieke apparaten, en zijn van vitaal belang voor het uitwisselen van data tussen personen, computerbreinen en andere elementen in onze informatiemaatschappij. Wegens de immense schaalgrootte en fijnmazige infrastructuur, is het onmogelijk centraal de regie te voeren over het dataverkeer in deze netwerken. Doorgaans worden dan ook zogenaamde random-access-algoritmen gebruikt, waar individuele gebruikers de datastromen op autonome wijze aansturen. Sem Borst, Johan van Leeuwaarden en Peter van de Ven beschrijven in dit artikel stochastische deeltjesmodellen om het macroscopische gedrag van deze netwerken te begrijpen en de prestaties te verbeteren
Heavy loads and heavy tails
Full text linkThe present paper is concerned with the stationary workload of queues with heavy-tailed (regularly varying) characteristics. We adopt a transform perspective to illuminate a close connection between the tail asymptotics and heavy-traffic limit in infinite-variance scenarios. This serves as a tribute to some of the pioneering results of J.W. Cohen in this domain. We specifically demonstrate that reduced-load equivalence properties established for the tail asymptotics of the workload naturally extend to the heavy-traffic limit.</p
A method for in situ SEM fracture studies of brittle materials using the double torsion technique : application to nuclear graphite
No full textThis work concerned the design and development of a miniature double torsion (DT) testing rig, for use inside the chamber of a scanning electron microscope, to perform in situ loading studies of brittle materials using the DT fracture mechanics specimen. The in situ performance of the system inside the SEM was highly satisfactory, while still providing free rotation of the attached stepper motor. Crack growth rates of down to 19nm/s were directly observed in PMMA specimens. It was concluded that the technique displayed merit in its ability to contribute to the knowledge base of slow cracking and damage development in brittle materials, with the advantage being that the gearing ratios of the current device resulted in slower specimen loading rates, which were more controlled, than reported previously
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