A spatial publish subscribe overlay for massively multiuser virtual environments

Proceedings of the International Conference on Electronics and Information Engineering, 2010, v. 2, p. 314-318Peer-to-peer (P2P) architectures have become popular for designing scalable virtual environments (VEs) in recent years. However, one question that remains is whether a single overlay can be flexible enough to support different types of VEs. We present S-VON, a P2P overlay that attempts this goal by providing spatial publish / subscribe (SPS) services. Besides flexibility, S-VON also aims to be practical and efficient by utilizing super-peers and considering the physical topology (i.e., network distance) to reduce latencies. Our simulations show that super-peers provide a unique design space where both bandwidth usage and latencies can be effectively reduced, such that even a crowded Second Life region can be hosted with residential ADSL. © 2010 IEEE.published_or_final_versio

Optimization of the Injectors Position for an Electric Arc Furnace by using CFD Simulation

In this study, complex processes in a typical Electric Arc Furnace (EAF) such as combustion, radiation, heat, and mass transfer were solved and the optimum injector location was found using computational fluid dynamics (CFD). The main aim of the injection optimization was to improve the thermal performance and the metallurgical process by changing the injection angle, the central angle of the injector (CAI), and injector length. Fifteen parametric cases were predicted and analyzed for optimization study. To decrease each simulation solution time of each cases, a polyhedral mesh structure was used instead of tetrahedral mesh for the EAF geometry. Thus, the total element number of the model was decreased by 1/5 while providing faster and unchanging results compared to the case with a tetrahedral mesh structure. The response surface optimization method was used for the optimization study. As a result, the optimum injector positioning was obtained as injection angle: -45°, injector length 614 mm, and CAI: 60°

Effects of EGR rate on performance and emissions of a diesel power generator fueled by B7

This paper analyses the impacts of the application of an exhaust gas recirculation (EGR) system on the performance and emissions of a stationary, direct-injection diesel engine operating with diesel oil containing 7% biodiesel (B7). Experiments were carried out in a 49-kW diesel power generator with the adapted EGR system, and engine performance and emissions were evaluated for different load and EGR settings. The results were compared with the engine operating with its original configuration without the EGR system, and revealed a reduction of peak cylinder pressure and fuel conversion efficiency, mainly at high engine loads. The use of EGR caused opposite effects on carbon dioxide (CO2), carbon monoxide (CO) and total hydrocarbons (THC) emissions, depending on load and EGR rate, showing an increase in most situations. The application of EGR consistently reduced oxides of nitrogen (NOX) emissions, reaching a maximum reduction close to 30%. In general, the use of EGR increased CO2, CO and THC emissions at high loads. The use of 7.5% EGR was found to be at an adequate rate to simultaneously reduce CO, THC and NOX emissions at low and moderate loads, without major penalties on CO2 emissions and engine performance

Resource allocation in underpro-visioned multioverlay peer-to-peer live video sharing services.

International audienceMultioverlay peer-to-peer live video streaming systems face the problem of finding a suitable peer upload bandwidth allocation among concurrent overlays. So far, no efficient solution has been proposed for the important case where the overall system is underprovisioned, that is, when peers do not have enough upload bandwidth to ensure video distribution at full quality. We design various objective functions for this upload bandwidth allocation problem and show how optimal solutions can be computed using a bipartite flow network. Simulation results show that our solutions improve on existing algorithms in terms of video quality