Sharif Digital Repository

Nanostructured materials are a new kind of engineering materials which attracted researchers’ interest because of their interesting mechanical /physical properties, as well as controllable microstructural design ability for desired applications. These new materials are homogeneous at the macroscale but at the microstructural level, may have heterogeneities including common nanostructures. Because of multiscale nature of these materials, new multiscale methods should be developed and used for better understanding the behavior of them. Multiscale methods could be categorized into concurrent and hierarchical methods. In concurrent methods, the domain under study is explicitly divided into... 

Using Peer-to-Peer (P2P) overlay networks have become a progressively popular approach for streaming live media over the Internet due to their scalability and deployment simplicity. In this project, we have proposed a hybrid push-pull live P2P video streaming protocol called PPM that combines the benefits of pull and push-based mechanisms for video delivery. The main goal of this research is to minimize the network end-to-end delay in comparison to pure mesh networks. The low end-to-end delay is achieved through two phases: the first phase is to select a parent node based on peers’ overlay hop count in a mesh topology and the second is to construct a dynamic tree in order to push the most... 

Covalent organic frameworks are one of the attractive and important research fields that deals with the huge and predesigned polymeric structures. It is a developing field which focuses on the synthesis of different architectures with specific applications. In recent years, fluorinated materials have gained a high interest due to their unique physicochemical properties. The fluorinated microporous structures, due to their potential applications in gas, energy and materials storage as well as catalyst, are of high interest. In this work, fluorinated two-dimensional nanomaterials were synthesized based on hexafluorobenzene and decafluorobiphenyl. Catalyst free [2+2+2] cyclotrimerization of... 

There are many linear and nonlinear programming problems with uncertain parameters and variables. These types of linear and nonlinear models are called fuzzy linear and nonlinear programming problems. Solving such problems is important, due to applications and variety of these models. Here, we first review various types of fuzzy linear programming problems based on the models or the solution methods. Next, we revise a method due to Kerre to compare two unipolar LR fuzzy numbers and present some new results on the comparison of LR fuzzy numbers. Then, we solve linear programming problems with unipolar fuzzy numbers by our proposed time varient particle swarm optimization (TV-PSO) algorithm.... 

The main focus of this project is the fabrication of surface engineering scaffolds based on polyurethane and titanium dioxide. The research's aim is the creation of the synergistic properties of TiO2 and PU as a new strategy for engineering artificial autologous blood vessels. In the first section, PU-TiO2 nanocomposites were synthesized by co-insitu synthesis of nanoparticles and polymer. The nanocomposite films were prepared by solvent casting and thermally induced phase separation methods. Mechanical and biological properties of films were compared with pure PU film. In solvent casting method, the outcomes revealed that the rate of endothelialization of the nanocomposite scaffold after 7... 

In this project, in continuation of a PhD resreach undertaken in this research group in 2017, the synthesis and study of two new tweezer and linker molecule bearing azobenzene moiety were carried out, characterized by applying IR spectroscopy, ¹H and ¹³C {¹H} NMR, fluorescence spectroscopy, UV-visible spectroscopy, elemental analysis and X-ray crystallography. Firstly, interaction of T2 with meso-tetraphenylporphyrinato zinc(II) and aluminium tetraphenylporphyrinato were studied using the fluorescence spectroscopy. The formation constant of T2 in cis and trans isomer with ZnTPP was measured as 5.1(±0.4) ×108 and 2.0×108(±1074) dm6mol-2, respectively. The formation constant of T2 in with...