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.... 

Occurrence of natural disasters such as earthquake could seriously damage most buildings especially those with insufficient resistance located in urban worn-out textures. In order to reduce unpleasant consequences of an earthquake, appropriate policies need to be considered to persuade the beneficiaries to follow retrofitting standards in the process of planning, designing, and construction of buildings. These policies shall be implemented through institutions in arbitrary or obligatory forms, by encouragement or penalty mechanisms. In order to consider these policies, first of all we need to identify the beneficiaries and their particulars. By studying and considering subjects discussed in... 

Chemotherapy is a proven and effective systematic approach to treat various types of cancers. Despite its advantages, chemotherapy would kill healthy as well as cancer cells. To overcome this problem, different controlling strategies are implemented. This study aims to provide a medicine drug delivery schedule for chemotherapy (by designing a proper controlling system) based on the verifiable mathematical models. First, the dynamic model is analysed and stability points are reviewed. The selected model has five state variables and two inputs. In this study, the focus is on dynamic model analysis and obtaining an effective and appropriate treatment pattern by designing a proper controller. To... 

Natural disasters can damage the infrastructure of society. Damages to the infrastructure components of society can disrupt their service delivery. Disruption in providing services to society's infrastructure can disrupt social and economic activities and impose various significant costs on society. The cost of repairing the damaged infrastructure and reducing the income of households are among the economic damages of accidents. The decline in the quality of life, as well as the death and injury of people due to the breakdown of the infrastructure or the disruption in their services, are among the social damages caused by accidents. In the same way, natural disasters are considered a... 

Due to the vulnerability of urban fabric and residential buildings to earthquakes and considering its destructive social and economic effects on society, the need to adopt appropriate policies to prevent and reduce vulnerability, has been increasingly considered by policy makers. Despite the laws, regulations, incentives and penalties that policymakers have envisioned to prevent unprincipled and unsafe construction, evidence shows that a significant number of new buildings being built in the country are not earthquake resistant and there are many violations in design, implementation and supervision that is done by the stakeholders. To solve this problem, research has been done on the... 

Soil and water pollution is one of the most common types of pollution in terrestrial and aquatic ecosystems. The development of mines and the oil and petrochemical industry on one hand and the non-compliance with environmental requirements on the other hand have caused large amounts of hydrocarbon pollutants and heavy metals to enter the environment in recent decades. Petroleum materials and heavy metals leak into the surrounding environment during drilling and extraction in oil sites and mines or during land and sea transportation, despite the measures taken to control their pollution. The conducted studies show that human industrial activities are the only cause of environmental pollution... 

The power control of horizontal axis wind turbines can affect significantly the vibration loads and fatigue life of the tower and the blades. In this thesis, we are going to consider both the power control and vibration load mitigation of the tower fore-aft vibration. For this purpose, at first, we developed a fully coupled model of the NREL 5MW turbine. This model considers the full aeroelastic behavior of the blades and tower and is validated by experiment results, comparing the time history data with the FAST (Fatigue, Aerodynamics, Structures, and Turbulence ) code which is developed by NREL (National Renewable Energy Lab in the United States). In the next, to estimate EWV, a novel... 

Laboratory studies to investigate the effects of different saline concentrations (such as sodium chloride or calcium chloride) on the soil water retention behavior of clayey soils and their volumetric changes have received much attention recently. However, many previous studies have investigated these effects in only one path of the SWRC (wetting or drying path) and the effects of saline concentration on hydraulic hysteresis have not been considered. In addition, researchers have frequently studied these effects on SWRC on clay samples, and little research has been done on collapsible soils. Therefore, the most important purpose of this study is to investigate the effects of increasing... 

Nowadays electricity power has a key role in developing various aspects of the world. The great importance of fossil fuel power plants come from their large contribution in electricity power generation. Among the different fossil fuel power generation technologies, supercritical power plants have great advantages. They are an advanced power generation technology with high plant efficiency, high coal utilization and low emission. Their complexity and existing many unavoidable uncertainty sources in their dynamic such as changes of ambient temperature, climate condition and wear of components make their control challenging. To overcome mentioned problems and achieving a good performance, a... 

The instability and contamination leakage through tailings dams is one of the major problems of them. These dams are usually constructed through self-consolidation with minimum compaction effort, so special attention must be given to the stability of these structures. In addition, tailings dams contain considerable amounts of metals and chemically soluble contaminants resulting from mining processes in their reservoirs, making them more likely to leak contamination from the dam's foundation and body, causing pollution downstream. The infiltration of various chemical contaminants into the soil may alter its hydraulic and resistance properties. Laboratory studies have shown that pore solution... 

In this research, the main purpose of the controller design is in the second region of operation of a wind turbine, which involves absorbing the maximum energy from the wind. WindPACT 1.5MW turbine has been investigated and the power coefficient of this turbine has been obtained using WT-PERF and FAST softwares. Simulations show that the results of both methods are well matched. Then, using ANFIS, a method for estimating the wind speed is derived from the data obtained by FAST. Inputs to the ANFIS system are the turbine aerodynamic power, rotor speed and blade pitch angle while the output of ANFIS system is the estimated wind speed. The maximum power coefficient of the wind turbine occurs...