Sharif Digital Repository

People use social networks to share millions of stories every day, but these stories rarely become viral. Can we estimate the probability that a story becomes a viral cascade If so, can we find a set of users that are more likely to trigger viral cascades These estimation and maximization problems are very challenging since both rare-event nature of viral cascades and efficiency requirement should be considered. Unfortunately, this problem still remains largely unexplored to date. In this paper, given temporal dynamics of a network, we first develop an efficient viral cascade probability estimation method, VICE, that leverages an special importance sampling approximation to achieve high... 

People use social networks to share millions of stories every day, but these stories rarely become viral. Can we estimate the probability that a story becomes a viral cascade? If so, can we find a set of users that are more likely to trigger viral cascades? These estimation and maximization problems are very challenging since both rare-event nature of viral cascades and efficiency requirement should be considered. Unfortunately, this problem still remains largely unexplored to date. In this paper, given temporal dynamics of a network, we first develop an efficient viral cascade probability estimation method, ViCE, that leverages an special importance sampling approximation to achieve high... 

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... 

Wireless mesh networks (WMNs) are well-promising future networks especially for ubiquitous connection to Internet. In this paper, we propose an analytical model in order to evaluate the maximum stable throughput of a WMN based on a simplified version of IEEE 802.11s MAC protocol. Our modeling approach is based on a multi-class open queueing network. In this respect, we map some of the important features of IEEE 802.11s MAC protocol, esp., its contention-based and contention-free periods onto different parameters of the proposed queueing network. By solving the related traffic equations and applying the stability condition, we determine the maximum stable throughput, i.e., the maximum packet... 

Key performance indicators (KPIs) are the fundamental building blocks in measuring and monitoring processes of safety management. This chapter describes a classification of safety KPIs and a review of literature leads to a new framework. It aims to develop a logical selection and aggregation methodology for generating a single number that reflects safety performance. Determining a mechanism for performance measurement and monitoring is a key part of any management system, and this has a higher importance for total safety management. Personal safety deals with the prevention of occupational accidents that usually have low severities and high frequencies. The measurement of safety has been... 

Key performance indicators (KPIs) are the fundamental building blocks in measuring and monitoring processes of safety management. This chapter describes a classification of safety KPIs and a review of literature leads to a new framework. It aims to develop a logical selection and aggregation methodology for generating a single number that reflects safety performance. Determining a mechanism for performance measurement and monitoring is a key part of any management system, and this has a higher importance for total safety management. Personal safety deals with the prevention of occupational accidents that usually have low severities and high frequencies. The measurement of safety has been... 

We propose a blind image steganalysis method based on the Singular Value Decomposition (SVD) of the Discrete Cosine Transform (DCT) coefficients that are revisited in this work. We compute geometric mean, mean of log values, and statistical moments (mean, variance and skewness) of the SVDs of the DCT sub-blocks that are averaged over the whole image to construct a 480-element feature vector for steganalysis. These features are fed to a Support Vector Machine (SVM) classifier to discriminate between stego and cover images. Experimental results show that the proposed method outperforms most powerful steganalyzers when applied to some well-known steganography algorithms  

Minimization of the number of cluster heads in a wireless sensor network is a very important problem to reduce channel contention and to improve the efficiency of the algorithm when executed at the level of cluster-heads. In this paper, we propose an efficient method based on genetic algorithms (GAs) to solve a sensor network optimization problem. Long communication distances between sensors and a sink in a sensor network can greatly drain the energy of sensors and reduce the lifetime of a network. By clustering a sensor network into a number of independent clusters using a GA, we can greatly minimize the total communication distance, thus prolonging the network lifetime. Simulation results... 

A great amount of effort has been made in order to reach a more precise understanding of the adhesion phenomenon that happens as a vital component of several biological systems. Therefore, a firm understanding of the important factors that influence this phenomenon is of special importance in triggering the adhesive characteristics of different biological, bio-inspired and synthetic materials in fields such as tissue engineering. In this study the adhesive characteristics of a multi-material system consisting of the frequently used synthetic material, graphene, in the form of armchair-configuration sheets, and an important biological filament which is type 1 Collagen consisting of 3 alpha... 

Wet cooling towers are one of the most water-intensive technologies, which are widely used in air conditioning applications, especially in dry regions. Considering the current water crisis around the world, it is essential to improve the design of these cooling towers to reduce their water consumption, while maintaining their cooling performance. Makeup water of cooling tower is usually a constant-temperature water which is cold enough to condensate the moisture content of the cooling tower exhaust air. Therefore, it has great potential to recycle water evaporation of cooling towers, which is not considered so far. This paper investigates a novel design for cooling towers utilising the...