Sharif Digital Repository

The daily growth of cloud computing usage for data based applications and Internet services has caused many challenges in the sense of storage cost, data access performance, QoS provision such as availability, scalability, pay-as-you-go model conformation and etc. Data replication is one of the most important mechanisms for data management in distributed systems. It creates some replicas of data and distributes them to the network. The number of replicas, the time for creating a new replica, the way of their distribution among the nodes and replica replacement strategy in the case of storage unavailability are some important challenges in data replication context. Replication is extensively... 

Extensive growth of the internet has had a profound effect on the business environment and rise to a phenomenon known as electronic commerce.electronic commerce has an important role in improvement of organization performance and likewise,has influence in everyday life.despite its name,e commerce is not fully automated.typically,online transactions require a significant level of human intervention.to achieve high degree of automation,we need a new model of software.this model is based upon the notion of agents.agents can act in different stages of e-commerce.one of the most important of these stages is negotiation.negotiation capabilities are essential for e-commerce systems.the agents... 

Due to unusual response of structures of buildings with irregularity in their architecture to dynamic excitations, to have a comprehensive knowledge of their behavior during earthquakes is of utmost importance. Building irregularities are in general divided into two major categories, namely Irregularity in Plane and Irregularity in Elevation, and one of the forms of the latter is where there is a split in the levels of the building. In this work, through a series of case studies, the effects of P- phenomenon on the behavior of steel split-level building structures were studied. 5, 10 and 15 story buildings with 5 and 6 bays, and level splitting of 30, 60, 90, 120 and 150 cm were studied. All... 

Complex networks have recently become a very noticeable subject because of their remarkable theory on real networks such as rumor spreading. This thesis contributes to a prevention strategy which uses a maximal clique algorithm to find overlapping communities and also uses inverse targeting immunization strategy to immune these communities. By the using maximal clique algorithm combined with inverse targeting strategy we have achieved that the TIK method (targeted immunization using k-clique percolation) obtains 10% of better immunization than HD (highest degree) method which is one of the best methods in targeted immunization strategies. The TIK also demonstrates that rumor spreading is... 

High speed and high accuracy are two of the major trends for many systems in the 21st century, such as machine tools and semiconductor equipment. For the purpose of high speed, it is well known that active magnetic bearing (AMB) is an inevitable substitute for conventional bearings. The noncontact nature of AMB brings up many advantages over the conventional bearing, including energy efficiency, low wearing, long life span, and absence of lubrication. Hence, AMBs are especially essential for high-speed rotating devices nowadays.
While the 3-pole AMB has been proposed for many years, it received little attention due to the magnetic coupling between poles that makes the 3-pole AMB system... 

Vaccination is one of the ways of disease control and prevention, which not only protect individuals against the disease, but also reduce the disease spread rate. Mass vaccination of individuals is not always possible due to the high cost and limitation of immunization resources. Therefore, researchers are always seeking solutions to find the persons that their immunization may have a greater impact in reduction of disease spread rate. The advent of network epidemic models and the possibility of removal the secured nodes in those models, showed that this problem is equivalent to finding a limited set of individuals that their removal will eliminate or minimize the number of people at risk of... 

Researching in the field of optimization of network immunizing and epidemic spreading is an active and important area. According to literature review, influential nodes are detected based on global graph metrics such as centrality measures. On the other hand, when a network infrastructure is not available and a direct or straight path between source and destination may not be accessible, one can use opportunistic networks routing protocols in Delay Tolerant Networks to recognize influential users is an appropriate approach. In this work, we use a real world three layer dataset which consists of digital data (social relations and Bluetooth contact traces) of individuals. We convert the real... 

Open source software development is growing rapidly according to request of market. Different types of analysis have done on open source development networks to extract knowledge and help both developers and users to decide better. In this thesis, we try to extract data from one of the biggest open source development repositories GitHub and then a community detection algorithm will apply on these data for different time stamps. Then we propose an evolution tracking model and implement it to detect evolution of communities from 2013 until 2015. Then communities size evolution and changes in communities such as growth, dissolve, merge, split and formation will be discussed. After that we... 

In this work the response modification factor (RMF), behaviour factor, of two-dimensional regular and split-level steel braced frames was worked out and presented. A total number of 840 frames with various number of stories, spans, braced spans and span lengths were studied. Frames were loaded based on ASCE 7-10 and designed in accordance with AISC 360-10. Static nonlinear analysis and Uang method were used for obtaining the RMFs of the studied frames. The effect of split-level irregularity and parameters such as number of stories on the RMF were worked out and are presented in this thesis. Linear regression was used to develop formulae for RMFs of regular and split-level braced frames.... 

The lateral force & its control has always been a great concern to structural designers. Based on the project’s location, this force can be either earthquake or wind force. In our country, Iran, the earthquake force is usually the dominant one. Of the most important differences between these two kinds of forces, we may point out the cyclic characteristics and nature of earthquake forces. One can choose different strategies to face the earthquake force including the use of dampers. Dampers exist in vast varieties of different categories which we will briefly explain in this thesis. Dampers can be used on their own or in combination with other lateral force resistance systems like bracings or...