Papers by Parvez Mohammed
In recent years, peer-to-peer (P2P) and peer-assisted streaming have emerged as promising models ... more In recent years, peer-to-peer (P2P) and peer-assisted streaming have emerged as promising models for low-cost multimedia distribution to large scale user communities. In this paper, we study streaming of scalable video streams over these systems. Scalable video streams are composed of multiple layers and can easily be adapted according to the characteristics and needs of receivers. Thus, they can efficiently support a wide spectrum of heterogeneous peers participating in a P2P streaming system. We present an analytical model for forecasting the long-term behavior of a P2P streaming system with scalable video streams. Our analysis takes as inputs the characteristics of a dynamic P2P streaming system and the video streams. It then analytically computes the expected throughput of the streaming system and the expected video quality delivered to peers. The analysis also provides an upper bound on the maximum number of peers that can be admitted to the system at once (i.e., in flash crowd scenarios), while ensuring a certain video quality. We present a general analysis framework that can be customized to various practical P2P streaming systems with different characteristics. Then, we show the detailed analysis of a typical P2P streaming system and we explain how other systems can be analyzed using our model. We validate our analysis by comparing its results to those obtained from simulations, which confirm the accuracy of our analysis. Our analysis and simulations enable administrators of P2P streaming systems to predict the throughput and the video quality that can be delivered to users.
Physica A-statistical Mechanics and Its Applications, 2006
The formation of water from hydrogen-oxygen reaction on a metal surface is of immense importance ... more The formation of water from hydrogen-oxygen reaction on a metal surface is of immense importance due to the technological reasons. This reaction has been studied via a thermal mechanism on a Pt single crystal surface where the two molecules, H 2 and O 2 , have been adsorbed dissociatively in atomic form. The reaction takes place between the adsorbed atoms through an intermediate OH radical. We have studied this reaction via a thermal (Langmuir-Hinshelwood mechanism) as well as a non-thermal mechanism (precursor mechanism) by the Monte Carlo computer simulations. In this study, we have applied a novel approach based upon the experimental observations that the dissociated oxygen atoms do not sit next to one another on a catalytic surface. Some interesting results like the shifting of the phase transition points, the broadening of the reaction window width and the elimination of the second-order phase transition in the non-thermal reaction mechanism are obtained by considering various possibilities of the reaction scheme. The phase diagrams as well as the snapshots of the surface covered with the reacting species are presented. r (W. Ahmad). reactors may utilize catalyzed exchange between hydrogen and water . So the interaction of hydrogen, oxygen and water with a catalytic surface is of great interest.
Folia Microbiologica, 1998
Citric acid production from sugar cane molasses byAspergillus niger NIAB 280 was studied in a bat... more Citric acid production from sugar cane molasses byAspergillus niger NIAB 280 was studied in a batch cultivation process. A maximum of 90 g/L total sugar was utilized in citric acid production medium. From the parental strainA. niger, mutant strains showing resistance to 2-deoxyglucose in Vogal's medium containing molasses as a carbon source were induced by γ-irradiation. Among the new series of mutant strains, strain RP7 produced 120 g/L while the parental strain produced 80 g/L citric acid (1.5-fold improvement) from 150 g/L of molasses sugars. The period of citric acid production was shortened from 10 d for the wild-type strain to 6–7 d for the mutant strain. The efficiency of substrate uptake rate with respect to total volume substrate consumption rate,Q s (g per L per h) and specific substrate consumption rate,q s (g substrate per g cells per h) revealed that the mutant grew faster than its parent. This indicated that the selected mutant is insensitive to catabolite repression by higher concentrations of sugars for citric acid production. With respect to the product yield coefficient (Y p/x), volume productivity (Q p) and specific product yields (q p), the mutant strain is significantly (p≤0.05) improved over the parental strain.
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Papers by Parvez Mohammed