Sharif Digital Repository

In the second half of the 20th century, the standard cosmology was encountered some problems like flatness problem and horizon problem. The inflation theory proposed by Alan Guth in the 1980s, not only solved these problems but also predicted some primordial fulctuations for the universe that as a source for the fluctuations of cosmic microwave background, could explain our observations.The fluctuations predicted by simple inflationary models, are Gaussain. Although we have not found a valid observational result suggesting Non-Gaussianity in the primordial fluctuations so far, but these simple single scalar field inflationary models, are very specific. So it is very probable that in the... 

According to the standard model of cosmology, around 26% of the universe’s energy content consists of a type of cold matter with minimal non-gravitational interaction, known as ”dark matter.” The standard ”cold dark matter” (CDM) can successfully explain observations across various scales. However, it faces challenges on small (galactic) scales, such as the ”core-cusp problem,” ”the missing satellite problem,” and ”the too-big-to-fail problem.” Fuzzy dark matter is a promising candidate for dark matter. It is characterized by its ultra-light mass, which gives rise to wave effects at astrophysical scales. These effects offer potential solutions to small-scale issues. In this thesis, we... 

Overlay Peer-to-Peer networks opposed to their high scalability and more robustness against network errors, are more considerable rather than other content distribution approaches such as Client/Server and multicast video streaming. At this thesis we investigate the video streaming over these networks, which includes more than half of internet traffic nowadays.Localized video streaming is one of the techniques for improving quality of service (QoS) over peer-to-peer networks. With localization techniques, video chunks distribute among neighbors that have more proximity with each other and traffic is held localized over the network.We proposed a new metric for estimating network proximity of... 

In this study, ananomagnetic polyamidoamine (PAMAM) dendrimer was synthesized as a novel SPME fiber coating and implemented to the determination of traces of chlorophenols in water samples. The synthesized magnetic PAMAM shows to have many polar groups with an enhanced internal porosity which is promising to be used as an efficient extracting medium. With this purpose, a thin stainless steel wire was coated by the network of dendritic PAMAM polymer through electrolysis and chemical reactions. The synthesized fiber is physical stable since it was chemically bonded to the substrate. Extraction efficiency of new coating was investigated by headspace SPME of chlorophenols from aqueous samples... 

Selective molecule design is one of the great challenges in drug design. Recently, with the introduction of diffusion models, good progress has been made in discovering new pharmaceutical compounds. These tools can produce new and diverse compounds with desired biological properties and activities. In this research, we propose a new framework for designing a molecular linker, the goal of which is to connect two or more molecules with a linker that increases their binding affinity and selectivity. We use a graph neural network to encode molecular features and a diffusion model to generate linker candidates. Also, in this research, we apply the structural features of the protein pocket in graph... 

The purpose of this project is to design and build a motorized walker with sit to stand ability, by means of which the user can get up from a chair or the edge of the bed and stand with complete independence; Relying on it, the patient could walk easily and finally sit down on the chair, the edge of the bed, or the toilet seat. For this purpose, the conducted researches and previously built devices were studied and the strengths and weaknesses of each were examined. The stages of conceptual design including the design of the sit to stand mechanism, the design of the structure and finally the control algorithm were completed, then the detailed design of the mentioned topics was carried out....