Sharif Digital Repository

The accessibility of broadband Internet to home users has pushed video broadcasting applications up, in the list of most favorite applications in todays Internet. Such applications involve delivering the data which generated in a single sender to a set of users which are scattered around the world. While it was formerly believed that the IP-Multicasting is the mean to provide this kind of services, the trend has altered to the use of Application Layer Multicasting techniques due to their deployment simplicty. Since their advent, Peer to Peer applications has mitigated many problems previously unsolved in the field of communication. File sharing, distributed file systems, distributed data... 

In this dissertation, initial conditions that cause chaotic movement in the relativistic restricted three body problem was obtained by the fast Lyapunov indicator and the time-frequency analysis. With general relativistic model, we can proceed with more accuracy in the design of stable orbit and this chaotic amplification effect could be used as a novel test of general relativity  

Conveying a successful message within a language profoundly stems from not only a linguistically appropriate utterance, but also a pragmatically appropriate discourse too. Broadly considering various facets of pragmatics, pragmatic assessment has not been potentially brought into perspective, and, as a result, the literature deserves more comprehensive attention. This study, guided by the principles of mixed methods design, pursued three purposes: to inspect the matches and mismatches, to explore rating variations, and to assess the rater consistency between the holistic and analytic rating methods of agreement and disagreement speech acts in L2 by non-native English teachers. To address... 

Today, catalysts have shown the growing applications in chemical industries especially for drug synthesis. Using immobilized heterogeneous catalysts is a sensible way to benefit from advantages of both heterogeneous and homogeneous catalysts. In this regards, homogeneous catalysts are immobilized on to a solid support through various methods. However, low loading amount of homogenous part and subsequently insufficient catalytic activity are main limitations of immobilized heterogeneous catalysts. For this reason, polymeric supports have been introduced to immobilize metal ions or nanoparticles. These polymeric supports not only possess advantages such as anti-corrosive properties, simple... 

Outsourcing is currently a challenging issue in the auto industry. On one hand, outsourcing has be-come a competitive imperative for automakers due to its significant benefits. On the other hand, it involves many aspects of risks that could potentially hurt core competencies of a firm. As such, in the auto industry, it is highly critical to make optimal outsourcing decisions for which an integrated framework offering a holistic view seems quite necessary. In this thesis, based on four fundamental research questions of “Who?”, “What?”, “Whom?” and “How?”, an integrated framework for outsourcing in the auto industry is developed in order to identify effective outsourcing factors and associated... 

Sustainable management of water resources is an important issue today, because it can play a role in achieving environmental protection and economic prosperity. Lake Urmia is a remarkable ecological system, because it includes a unique habitat with native and migratory species, maintains the temperature balance of the region, prevents the formation of dust in the region and is one of the largest Tourism and recreational destinations and a source of income for many people in the Area. However, over the past two decades, the intensification of agricultural activities, the indiscriminate use of water, and climate fluctuations have put significant pressure on it and have led to a gradual... 

Diffractive optical elements with binary surface profile are of great importance in integrated optical applications. Being easy to fabricate and having high degree of freedom in design, such devices play an outstanding role in optical applications. Specifically, binary (multilevel) lenses are investigated in this dissertation. These lenses are fabricated through conventional IC fabrication methods (lithography, etching, …) and have an acceptable performance and small aberration with proper design. Different scalar and vectorial methods for the analysis of finite aperture diffractive optical elements have been investigated and advantages and disadvantages of each one have been discussed.... 

In this paper, a novel control approach for one-dimensional bilateral teleoperated nanomanipulation system is proposed. While manipulating objects with a nanomanipulator, real time visual feedback is not available. So, force feedback is used to compensate for the lack of visual information. Since nanometer scale forces are dominated by surface forces instead of inertial forces as in macro world, scaling of nanoforces is one of the major issues of teleoperation system. The Hertz elastic contact model is used to model the interactions between the slave robot and the environment. The proposed framework uses the simple proportional derivative control, i.e., the master and slave robots are...