Sharif Digital Repository

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.... 

Ultrasound waves have been one of the passions of researchers of different fields for many years. In recent decades the potential of ultrasound waves for trapping and manipulating micro-particles has been noted by many researchers. “Acoustic Tweezers” is the name given to this application of ultrasonic devices. The advantages of this device over its optical counterpart, named “Optical Tweezers”, are its low price, ease of use, biocompatibility and its capability of being used in opaque media. In acoustic tweezers, particles can be trapped either by making standing acoustic waves, or by making highly focused narrow beams and trapping the particles in potential wells. In this research... 

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... 

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 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... 

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,... 

Ultralight aircraft (VLA category) are usually piloted by novice pilots under Visual Flight Rules (VFR). In this work, we demonstrate how newly developed techniques in robotics could be used to enhance flight safety in this category of aircraft, especially during landing around sunset. In this research we have investigated the ability of Simultaneous Localization And Mapping (SLAM) algorithms in low level flight just before touch-down. Different case-studies show that SLAM algorithm is efficient in detecting the runway threshold. Comparing five different methods of parameterizations for landmarks detection including: (1) Plucker, (2) Anchored Plucker, (3) Homogeneous, (4) Anchored... 

Three-dimensional biological scaffolds, as an emerging strategy in bone tissue engineering, enable the treatment of bone injuries without the need for grafting and implantation. The selection of suitable materials and fabrication methods for producing bone scaffolds is one of the key challenges in bone tissue engineering. This research focuses on the production of poly-lactic acid-bioactive glass S58 composite scaffolds using 3D printing. A solvent-based method was employed to produce poly-lactic acid composites containing bioactive glass particles (0.5, 1, and 1.5 weight percent). The composites were printed after the extrusion process and filament production for evaluating microstructural,... 

In recent decades, the soil-structure effect has been considered in seismic studies. Most of these researches are based on the premise that the foundation is bonded to the ground. However, several examples of structures that experienced uplift have been reported. Uplift affects the soil-structure contribution and nonlinear behavior of the structure. It seems that a parametric study should be done for the simultaneous effects of the soil-structure interaction, foundation uplift and inelastic behavior of the superstructure. Although the most accurate methods to estimate the behavior of structures is the nonlinear time history analysis, this analysis is very time consuming. The endurance time... 

Burnup calculations based on the Monte Carlo method have been developed in line with the improvements in computing technology. Nowadays, in the field of nuclear reactor physics, it is possible to perform burnup calculation in a detailed 3D geometry and continuous energy description by the Monte Carlo method. COMB is a fully automated code in DELPHI 7 that links the MCNP4C Monte Carlo transport code with the radioactive decay and burnup calculation code system, ORIGEN2.1. The principal function of COMB is first to transfer one-group cross sections and fluxes from MCNP4C to ORIGEN2.1, and then transfer the resulting material compositions (after irradiation and/or decay) from ORIGEN2.1 back to... 

Introduction: Today, backward and forward scattering tomography of dispersive medium is of great interest because of its broad applications, especially in medical imaging, of breast cancer, Distinguishing different tissues of the body from each other is one of the necessities. Increasing the quality of the image by just a few percents has great improvement on the tomography resolution.
Materials and Methods: In this project we made phantom of the tissue and tumor from Intralipid 10% plus Agarose and Indian ink for soft tissue and plastic fibers as tumor having birefringence factor of 0.001.After putting the plastic tumor in soft tissue phantom, the polarized white light and a digital...