Sharif Digital Repository

Increasing in social communication via electronic ways has been made social network analysis of these communications more important each day. One of the most important aspects in social network analysis is community detection in such networks. There are many different ways to extract communities from social graph structure which in some of them the content of communication between actors has been noticed in community extraction algorithm. In this thesis after a short survey over advantages and disadvantages of existing methods for community detection, a new method for extracting communities from social networks has been suggested which in addition to streaming property of data it spot the... 

As mobile multimedia services become popular, it is expected that mobile devices provide more multimedia functions such as real-time video playback, TV watching, and video games. However, real-time video applications running on mobile devices are heavily constrained by their limited computing power, compared to high-end consumer devices. In order to playback a high resolution video on mobile devices, a typical approach would be to fully decode video bitstream into the pixel-domain, and then spatially downscale the decoded frames at a desired resolution. However, due to large computation and memory required for decoding followed by downscaling, this approach is unsuitable for real-time video... 

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... 

Motion simulators have been highly sought after by the growth of the aerospace industry. In the meantime, the Stewart mechanism, or the so-called Hexapads, is a robot that, in addition to being used in machining tools, is mainly used to simulate the flight. The Stewart-Gaph mechanism was created and introduced in 1954 and 1965, and since then dynamics and control have been widely addressed in the mechanical engineering literature. The robot is considering the project to test parts and equipment installed in marine vessels under sea movements and waves. Therefore, according to information obtained through relevant organs, the purpose of this project is to design and implement a hexapad... 

In the first section, a novel No-Reference Video Quality Assessment (NR-VQA) method, based on Convolutional Neural Network (CNN) for High Efficiency Video Codec (HEVC) is presented. Deep Compressed-domain Video Quality (DCVQ) measures the video quality, with compressed domain features such as motion vector, bit allocation, partitioning and quantization parameter. For the training of the network, normalized PSNR is used due to the limitation of existing datasets. The evaluation of the proposed method shows that it has”96%” correlation to subjective quality assessment (MOS). The method can work simultaneously with the decoding process and measures the quality each frame in the different... 

Studying the performance of flow meters is of great importance in order to improve their quality. In this study, we are looking for an optimal design for a turbine flow meter in which the measurement accuracy, pressure drop and response speed indices are improved. For this purpose, a turbine flow meter with a diameter of 2 inches has been selected and its performance has been numerically modeled using computational fluid dynamics in a steady and transient state. By modeling the steady state, the measurement accuracy and pressure drop indices are obtained, and by modeling the transient state, the response time of the flow meter is obtained. In order to increase the accuracy of numerical... 

One way to increase the efficiency and improve the performance of a gas turbine is to increase the inlet gas temperature. On the other hand, the inlet temperature has an allowable operating range, and increasing it beyond the tolerance of the alloys used in turbine blades causes structural defects and significantly reduces the blade life. Therefore, to increase the blade life, various cooling methods such as internal and layer cooling are used. Considering the blade geometry and cooling paths, accuracy in the manufacturing process is doubly important in the production of these blades. The importance of this issue is that if the cooling channels produced are inconsistent with the design... 

The standard model of Cosmology (SM), based on Einstein’s theory of general relativity (GR), is the best model in describing the cosmic-scale observations. In galactic scales, however, galactic dynamics show a discrepancy between the observed luminous mass and the predicted value from the theory. Two approaches are suggested to eliminate this inconsistency: assuming the existence of dark matter within the context of GR, or modifying the theory of gravity in galactic scales, like MOND or MOG. In this thesis, we study the spherical collapse and the formation of shell galaxies in MOG, in comparison with SM. We introduce the action and the field equations of MOG and the equation of motion of a... 

Strongly Rayleigh measures are an important class of negatively dependent (repulsive) probability measures. These measures are defined via a geometric condition, called “real stability”, on their generating polynomials, and have interesting probabilistic properties. On one important property of negatively dependent measures is their rigid dependence structure. In other words, the it is impossible for these measures to have strong overall dependencies. In this thesis, we study two manifestations if this phenomenon: (1) paving property and (2) tail triviality. Informally, the paving property states that it is possible to partition the set of the components of every strongly Rayleigh random... 

Corneal diseases are one of the most common causes of blindness worldwide. The most common way to treat these diseases is to replace the damaged cornea with the donor cornea by corneal transplant. But limitations such as donor tissue deficiency, the risk of disease transmission and transplant rejection have made treatment of these diseases very difficult. A cornea made by tissue engineering can be used as a suitable alternative because of the limitations mentioned for corneal transplantation with donated tissue. At the same time, similarity of the scaffold to normal corneal tissue, both in terms of matrial and structural properties, is essential for proper repair of this scaffold by cells... 

It is generally believed that the only utility of tests as a critical instrument is to be at the service of educational institutions. To broadly consider their different usefulness, tests can serve other purposes like focusing on the ethical and moral issues. As it is called Critical Language Testing, tests are not reliable instruments and they have the capacity of being used not only in educational, but also in political contexts. This philosophy has not been brought into perspective, and, as a result, the literature deserves more comprehensive attention. This study, guided by the principles of Grounded Theory and Qualitative research design, pursued three purposes: To investigate the... 

At present, urban aircraft do not exist. An essential question arises: if such aircraft were to be established, what infrastructure would be necessary for landing, takeoff, and service provision? Can the existing airport infrastructure be adapted for urban aircraft, or would a different approach be required? Consequently, the focus of this current research is to address this issue. The research involves the development of a multi-agent model using the Python programming language to study how important parameters such as the operation rule between aircraft and station, capacity and speed of the aircraft, and the distance between stations are related to the operational indicators of the... 

The growing global demographic and the growing rate of osteoporosis provide the definitive rationale for the development of effective methods for the treatment of osteoporotic defects of bone. These methods should not only compensate for ongoing injuries but should also manipulate the inherent disease processes to enhance the effectiveness of treatment. Therefore, the present study attempts to develop bioactive nanocomposite hydrogels through two different modalities—microgels and injectable bulk hydrogels—for the purpose of delivering alendronate (ALN) as a treatment approach for osteoporotic fractures. During the first phase of the research, gelatin-containing nanocomposite microgels... 

Coupling of optical and mechanical degrees of freedom through radiation pressure was, first, observed in the experiments for detection of gravitational waves. Recent experimental advances have granted reality to the long-hankered-after coupling between microscopic and macroscopic systems. In the first step, this thesis will review different aspects of cavity Optomechanics, such as: cooling, side-band formation and dynamics of an Optomechanical cavity. Then we will go further and study the Optomechanical dynamics of a cavity in the presence of an atom. To do so, we will analyze the entanglement, created between the center of mass motion of the atom and the mirror and will probe into its... 

In this thesis, consider three important questions in the Iranian Wholesale Electricity Market (IWEM) and answer its. The first one is whether the bidding behavior of the firms in the IWEM has been ex-post optimal? The results of the research show that, on average, the firm’s bidding behavior didn’t optimal in the IWEM, and therefore the bidding strategy of them could be improved. This issue is importance from the regulatory viewpoint in terms of assessing market efficiency and market power of firms, as well as from the firm’s point of view to improve the bidding strategy and increase its profits. The second issue is the assessment of the firm’s ability to exercise unilateral market power by... 

Office buildings, as one of the largest energy consumers in the building sector, play a significant role in national energy consumption. Given the importance of energy optimization in achieving sustainable development, reducing energy consumption in these buildings not only lowers costs but also helps preserve natural resources and mitigate environmental impacts. In this regard, providing energy optimization solutions, improving efficiency, and revising operational patterns play a key role in reducing energy consumption and ensuring user comfort. On the other hand, attention to indoor air quality is equally critical, as polluted indoor air can negatively affect the health and productivity of... 

This study develops an innovative modeling framework for the integrated assessment of energy systems, environmental impacts of greenhouse gas (GHG) emissions, and human health effects of air pollution. The primary objective is to analyze the co-benefits between GHG emission mitigation and the health benefits resulting from improved air quality for metropolises, moving beyond the conventional economic costs typically evaluated by energy models. For this purpose, a structured linkage is established between downscaling models for temperature, energy demand, energy supply, emissions, air quality, and human health impact assessment. An innovative recurrent ensemble model is designed for... 

In this work, an improved model for simulating carbonate core acidizing, with the ability of correctly modeling fluid diversion in dual-core experiments is created based on an existing two-scale continuum model. The improvements are applied on the momentum transfer equation, continuity equation, pore-scale structure-property relations and fluid rheology model. Also a more realistic injection scenario and geometry configuration are presented for simulating the diversion experiments. The Darcy-Brinkman-Stokes equation is implemented instead of Darcy’s equation and the continuity equation is modified by adding the mass source term. A global rheology model is developed capable of capturing exact... 

Structural changes in the energy sector, including the need to diversify sources of energy supply, security of supply, energy consumption growth in developing countries, rising oil prices and the exhaustibility of fossil fuel reserves, environmental issues, increased consumption of petrochemical products etc., has led to increased share of natural gas in primary energy supply. Iran has a wide range of options to use natural gas endowment. The present research aims to develop a model for optimal allocation of natural gas to various applications.The gas distribution system is modeled in the present study. Technical onstraints together with economic characteristics are considered in the model.... 

This study aimed to investigate the efficiency of machine learning algorithms in capturing the dynamics of water particles' age distribution and in estimating the time series of median travel time (MTT) in river basins. The mechanism of solute transport in a catchment does not follow the hydrograph shape of the catchment and depends on the spatial and temporal distribution of solute resident time. The equations governing the age dynamics of water particles discharged from a catchment have been presented analytically in recent research. These equations showed that the transfer of solutes depends on various factors, including climatic conditions, basin topography, and basin vegetation. Also,...