Sharif Digital Repository

Social media usage is one of the most popular online activities and people shares millions of message in a short time; however this information rarely goes viral. The diffusion process begins with an initial set of source nodes and continues with other nodes. In addition, the viral cascade is triggered when the number of infected nodes exceeds a specific threshold. Then, we find an initial set of source nodes that maximizes the number of infected nodes given the source nodes. This study aims to answer the following questions: how does a spread like a viral cascade propagate in a network? Do the structural properties of the propagation pattern play an important role in virality? If so, can we... 

In the present paper we investigate the problem of water propagation in 2 dimensional (2D) petroleum reservoir in which each site has the probability p of being occupied. We first analyze this propagation pattern described by Darcy equations by focusing on its geometrical features. We find that the domain-walls of this model at p=pc ≃ 0.59 are Schramm-Loewner evolution (SLE) curves with κ=3.05 ∓ 0.1 consistent with the Ising universality class. We also numerically show that the fractal dimension of these domain-walls at p=pc is Df ≃ 1.38 consistent with SLEκ=3. Along with this analysis, we introduce a self-organized critical (SOC) model in which the water movement is modeled by a chain of... 

Accurate Partial Discharge (PD) measurement requires the expansion of the measurement frequency range to Ultra High Frequency (UHF) band. For this it is needed to implement modern techniques when monitoring an important element of power system, such as power transformer. Different kind of experimental models, such as insulation defect models, and the complete transformer windings models are used to simulate the partial insulation failure situations which occur in a real transformer. However, since in these models, some kind of simplifications are employed which may result in an electromagnetic waves (EM) propagation pattern different from what exists in a real transformer and encounter... 

An experimental investigation on the behavior of RC arches strengthened by glass fiber-reinforced polymer (GFRP) composites is presented. Twelve samples were tested in order to determine influence of arrangement and number of GFRP layers on RC arches having different steel reinforcement ratios. The arches were tested under centrally concentrated point load using displacement control condition. Load-deflection behavior, failure mode, GFRP debonding, angle between hinge formation and supports and crack propagation pattern are studied extensively. Based on test results, extrados strengthening is much more effective than intrados strengthening in increasing ultimate load carrying capacity which...