How much can large-scale Video-On-Demand benefit from users’ cooperation?

We propose an analytical framework to tightly characterize the scaling laws for the additional bandwidth that servers must supply to guarantee perfect service in peer-assisted Video-on-Demand systems, taking into account essential aspects such as peer churn, bandwidth heterogeneity, and Zipf-like video popularity. Our results reveal that the catalog size and the content popularity distribution have a huge effect on the system performance. We show that users' cooperation can effectively reduce the servers' burden for a wide range of system parameters, confirming to be an attractive solution to limit the costs incurred by content providers as the system scales to large populations of users

How much can large-scale video-on-demand benefit from users' cooperation?

We propose an analytical framework to tightly characterize the scaling laws for the additional bandwidth that servers must supply to guarantee perfect service in peer-assisted Video-on-Demand systems, taking into account essential aspects such as peer churn, bandwidth heterogeneity, and Zipf-like video popularity. Our results reveal that the catalog size and the content popularity distribution have a huge effect on the system performance. We show that users' cooperation can effectively reduce the servers' burden for a wide range of system parameters, confirming to be an attractive solution to limit the costs incurred by content providers as the system scales to large populations of user

Archivio russo-italiano VI. Olga Signorelli e la cultura del suo tempo. Vol. I.

Il libro è dedicato alla vita e all'opera di Olga Resnevic Signorelli (1883-1973), traduttrice, studiosa di Eleonora Duse, mecenate, testimone di sett'antanni di cultura italiana e russa. L'edizione contiene saggi e pubblicazioni di inediti (carteggi commentati, memorie)

Experiment K-6-03. Gravity and skeletal growth, part 1. Part 2: Morphology and histochemistry of bone cells and vasculature of the tibia; Part 3: Nuclear volume analysis of osteoblast histogenesis in periodontal ligament cells; Part 4: Intervertebral disc swelling pressure associated with microgravity

Bone area, bone electrophysiology, bone vascularity, osteoblast morphology, and osteoblast histogenesis were studied in rats associated with Cosmos 1887. The results suggest that the synchronous animals were the only group with a significantly larger bone area than the basal group, that the bone electrical potential was more negative in flight than in the synchronous rats, that the endosteal osteoblasts from flight rats had greater numbers of transitional Golgi vesicles but no difference in the large Golgi saccules or the alkaline phosphatase activity, that the perioteal vasculature in the shaft of flight rats often showed very dense intraluminal deposits with adjacent degenerating osteocytes as well as lipid accumulations within the lumen of the vessels and sometimes degeneration of the vascular wall (this change was not present in the metaphyseal region of flight animals), and that the progenitor cells decreased in flight rats while the preosteoblasts increased compared to controls. Many of the results suggest that the animals were beginning to recover from the effects of spaceflight during the two day interval between landing and euthanasia; flight effects, such as the vascular changes, did not appear to recover

Refinement of Mg alloys crystal structure via Nb-based heterogeneous substrates for improved performances

Copyright © 2018 The Author(s). Lightness and high specific strength make magnesium alloys ideal materials for the transportation industry, especially the automotive sector that is struggling to cope with the everyday more stringent regulations on emission of carbon dioxide. Wrought magnesium alloys are difficult to deform because of the few active slip systems characteristic of their hexagonal close-packed lattice. Consequently, most of the commercially available magnesium alloys are alloys based on the Mg-Al binary system used in casting processes. The improvement of the mechanical properties of these alloys cannot be achieved by means of grain refinement using Zr due to the formation of Zr aluminides. In this study we propose a novel chemical composition that can refine all types of Mg alloys as proved in the Al-containing AM50 Mg alloy. We demonstrate that Nb-B inoculation of Mg alloys promotes the formation of heterogeneously nucleated primary α-Mg grains leading to the reduction of the grain size and this is obtained over a wide range of cooling rates. We also show that the grain refinement achieved leads to the improvement of the properties of high pressure die cast Mg automotive components and has the potential to enhance the mechanical properties of cast Mg alloys.Engineering and Physical Sciences Research Counci

Analysis of defect capture cross sections using non-radiative multiphonon-assisted trapping model

A multiphonon-assisted model included in a Poisson-Schroedinger solver has been applied to the calculation of the capture/emission trapping rates of CMOS oxide interface defects. The dependencies of trap capture cross-sections with trap energy, depth, applied bias and temperature have been extracted, with the purpose of evaluating the accuracy of constant cross-section models adopted in compact and empirical approaches. The model has been applied to the extraction of interface trap concentrations and to the accurate AC analysis of the trap frequency response