Sharif Digital Repository

In the current study, shape-memory alloys are analysed analytically under mechanical loading. Due to the special properties of these materials, their usage in various applications is rapidly increasing. However, mostly, the numerical methods such as finite-elements methods are employed to model the thermo-mechanical behavior of these materials. Also, due to the complexity of their behavior, there are few analytical solutions for them in the literature. In this research, an analytical approach is proposed to investigate the response of these materials under mechanical loading using a fundamental model which is suitable for modelling their crystalline structure. Given the impact of multiple... 

In this research a copper- diamond nanocomposite coating prepared by electrodeposition from a sulfate bath in order to increase the hardness and erosion resistance of cooper without disturbing cooper's specific physical properties as like as electrical and thermal conductivity. The mechanism of electrodeposition was analyzed with the technique of Cyclic Voltammetry, Chronopotentiometry and Chronoamperometry. The morphology, hardness, scratch resistance, elastic modulus and friction factor of coating were investigated by using a scanning electron microscope (SEM) and atomic force microscope(AFM) also the mechanism of co- deposition of diamond particles with copper was corresponded with... 

Peer-to-peer streaming has developed as a popular application in today’s Internetinfrastructure. In a typical peer-to-peer live streaming system, publishers provide the streaming content and the interested peers receive and deliver data in a distributed manner and also apeer structure is created by forming an overlay inside the network. In reality, peers are strategic and there is no motivation to contribute any of their upload bandwidth toward other peers. To address this issue, we proposed a simple arcade algorithm that makes an arcade based mechanism for peers to facilitate adjacent peers with more bandwidth to achieve a higher bandwidth themselves.Commensurate with our algorithm, if... 

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... 

In healthcare field to reduce costs, high availability, increasing reliability, access to data from multiple locations and manage distributed information between centers, doctors and patients; there is a certain need to a distributed system and cloud services are a good option to meet that need. In this thesis different models of service delivery in the healthcare were studied which included traditional and cloud models. Also from the survey, the metrics which we used to compare these models were extracted. These metrics include quantitative metrics such as cost, setup time, availability, multi-regional, elasticity, efficiency and qualitative metrics including integrity, privacy,... 

In this study, the behavior of a new innovative bracing system under cyclic loading and according to AISC code is investigated. An Ideal bracing system, in addition to having sufficient stiffness, should have a suitable ductility. Also, in order to prevent inelastic behavior of other structural members, braces, in addition to possessing high architectural adaptivity, must be able to contain the damage within itself and behave like a fuse. Three specimens with different sections, IPE100, HEA100 and 2UNP100, were designed and tested. The results of these tests represent an elastic- (approximately) perfectly plastic behavior of the brace if an appropriate section is used. Moreover, this bracing... 

Urmia Lake is a strong electrolyte containing various salts, with a thermodynamic identity. Changes in the temperature and volume of lake water cause a change in the concentration of ions in this brine as well as the composition and precipitation of salts in the lake. As a result of these changes, the thermodynamic properties of brine are also changed. The purpose of this study was to investigate the effect of mixing the rivers entering the lake and calculate and analyze the changes in the quality and hydrogeochemical characteristics of Urmia Lake and the amount of precipitation and dissolution of the main minerals in Urmia Lake during the period of 2007-2013 per month. For this purpose,...