Sharif Digital Repository

Many pieces of evidence of climate change show that humanity should be concerned about the future of its life and the planet. The concentration of carbon dioxide in the atmosphere has reached its highest level. Therefore, in recent years, the reduction of publications and climate issues has been on the agenda of governments. For this reason, governments and various international organizations are looking for a way to change and reform the global energy system. Forecasts indicate a decrease in the share of fossil fuels and an increase in the percentage of renewable energies and hydrogen. Hydrogen has been introduced as the future fuel carrier due to its many advantages such as the... 

The use of natural gas as a thermal fuel is only a part of the various efficiency cases of this precious material. The increasing need for gas to provide energy and fuel, as well as the currency obtained from its sale and export, and the existence of common natural gas resources with neighboring countries, doubles the need to pay attention to this category. The increasing expansion of the quantitative use and diversity of natural gas consumption as an abundant and cheap energy carrier, as well as the imbalance between the supply and demand of natural gas in cold seasons, require planning to create strategic reserves in the country. These reserves play an important strategic role in... 

A Jupyter Notebook is composed of richly formatted cells containing both markdown and code, making it a primary coding environment for data scientists. While the advantage of seamlessly integrating code, text, and output in these notebooks is evident, criticisms have arisen due to unexpected output and the promotion of poor coding patterns, raising concerns about maintainability and reusability of these notebooks. The unique characteristics of Jupyter Notebooks, combining code and text, pose challenges for traditional methods that rely solely on source code analysis to evaluate comprehension. Notebook-related metrics such as number of markdown cells and developer-related such as performance... 

Magnesium and its alloys have gained significant attention in medical applications due to their good biocompatibility. However, their widespread use has been limited by some inherent drawbacks, such as poor mechanical properties. The ZX00 magnesium alloy has been used in medical applications, including implants, due to its slow degradation rate and good ossification. However, this alloy lacks sufficient strength and ductility. The severe plastic deformation method can create an ultrafine grain structure and improve mechanical properties. In this study, to improve the mechanical properties and create an ultrafine grain structure, the multi-directional forging process was performed on... 

Prioritizing bug issue report is a critical task in the software maintenance cycle of repositories that have a large number of users and contributors. In such software, late fixing of bugs can cause the loss of users’ trust and market loss. At present, a majority of bug report prioritization is manual, in that the bug issue reports are triaged by human experts. However, new automated technologies are becoming feasible. These automated techniques have been shown to be effective in general situations, though a key weakness is that they do not use the criteria for prioritizing. Most of the state-of-the-art approaches are using machine learning algorithms to learn the different features of... 

In the last decade, harvesting energy from renewable phenomena in nature has attracted the attention of many researchers and turned it into a hot research focus. Wind flow around the world is an endless, repeatable and available source of energy. Therefore, harvesting wind energy disrupts the damaging cycle of fossil fuels to nature and fades over time. Therefore, in order to convert the mechanical green energy in the wind into electricity, mechanisms based on aeroelastic instabilities have attracted the attention of researchers. In this research, it is intended to design and build a test platform that is a suitable platform for research and testing on the aeroelastic instability of... 

Energy subsidies are one of the most challenging issues for many countries in the world, specially oil and gas exporting countries. Iran is one of the countries that has lost more than ten percent of its GDP due to energy subsidies in recent years. In this thesis, we are going to analyze experiences of different countries and try to provide policy makers with generalizations about this problem so they can implement reform policies more successfully. We have used Qualitative Comparative Analysis (QCA) methodology. This method can provide modest generalizations by using systematic cross-case comparison between a small number of cases. Details of this method and reasons behind choosing it are... 

Understanding the physics of unsteady flow is very important due to various applications. Axial compressors, turbines, helicopter blades, and energy harvesters are the essential applications of this problem. An airfoil under pitching oscillation is one of the common cases in unsteady aerodynamics, and several characteristics of the flow around it have been investigated up to now. The frequency analysis of the wake flow for pitching airfoils has received less attention. In this research, experimental tests have been carried out for symmetric airfoil NACA 0012 under pitching oscillation in low Reynolds flow (6×104) and before the airfoil stall condition. The experiments were carried out in the... 

Diffusion Weighted Imaging (DWI) is a non-invasive method for investigating the brain white matter. Assuming the Gaussian model for diffusion process, diffusion tensor is constructed and Diffusion Tensor Images (DTI) are obtained. White matter is constructed from fiber bundles which have crossing in most of the regions. In the crossing regions, the Gaussian model cannot work. In this situation, DTI cannot reconstruct the fiber structures correctly. Therefore, High Angular Resolution Diffusion Imaging (HARDI) was proposed to solve this problem. Q-ball imaging is a new technique for HARDI reconstruction which is useful for estimating diffusion Orientation Distribution Function (ODF). ODF is a... 

Hard disk drives are the main component of computers for permanent data storage. The security of the stored data is related closely to the air gap between the read-write head and the surface of disk. This gap which is created by the aerodynamic force between head and the disk is altered continually by lateral oscillations of disk. In the extreme condition of zero gap and contact between the protective coating layer and subsequently the magnetic material of the disk with the head, the disk will be scratched and damaged. Therefore, the active or passive control of these vibrations has a particular importance in the technology of manufacturing of hard disks. The first step in active control... 

Accumulative Roll Bonding (ARB) process has been developed during last decade to produce the Ultra Fine Grained (UFG) structures with high strength. In the present study, a Ti-IF steel was deformed up to equivalent strain of 4.8 at 500 ˚C using ARB process. For comparing the ARB with conventional forming processes, some samples were deformed with similar equivalent strain to ARB conditions at 500 ˚C and 300 ˚C as warm rolling. Moreover, the thermo-mechanical warm rolling was simulated by warm torsion. The ARB and warm rolled samples with largest strains were annealed at 750 ˚C. The microstructure and texture were studied using Electron Back Scattered Diffraction (EBSD) method. The... 

Phospholipid vesicles are able to carry drugs or DNA to infected or cancerous cells. The blood flow can carry them to their target positions but their performance will be enhanced if they complete their attack by swimming in final stages of their journey. Vesicles built only by lipid molecules have rotational symmetry and undergo a random motion in their solvents without having a preferred direction. In this project, we break the symmetrical shape of phospholipid vesicles by a cluster of transmembrane proteins. We use a triangulated model of the membrane, apply the method of multi-particle collision dynamics to the motion of solvent particles, and simulate the motility of vesicles for... 

TRIP steel with good plasticity properties, has ferrite, bainite and retained austenite phases at ambient temperature. According to austenite to martensite phase transformation during plastic deformation, this grade of steel has high elongation and ultimate tensile strength, simultaneously. There are some parameters which affect the stability of retained austenite, such as: imposed strain, strain rate, temperature of deformation, grain size, weight percentage of different alloy elements and crystallographic orientation of existing phases. Mechanical properties of TRIP steels are improved by increasing stability of retained austenite. TRIP steels have been... 

An object-oriented application framework, like Eclipse, not only provides a framework for designing and implementing new applications, but also decreases the time and the cost of developing new software applications. Moreover, theseframeworks increase the maintainability of software systems. Therefore, their popularity is on the rise. The main problem of using object-oriented application frameworks is the lack of proper documentations and guides. Thus, developers often try to learn how to implement their desired concepts (e.g., Context Menu) from available sample applications. This leads the programmers to another problem which is finding the sample applications. Finding a proper sample... 

In this project Iran and Iraq energy relation is investigate. Considering the Importance and the capacity of Iran and Iraq in world and Middle East energy and the geopolitics of these two countries, a good economic relationship between them, especially in energy domain, can highly improve their sustainable relations. In this research the Agent Based Modeling is used for studying Iran and Iraq relationship. In Agent Based Modeling the overall system behavior is made up of individual agents’ behavior. In this modeling, the agents decide based on their own behavioral rules and also their status. In this study Iran and Iraq are modelled as two agents. The state of the two countries in energy,... 

Exceptions are an indispensable part of a software development process. Developers usually rely on imprecise results from a web search to resolve the exceptions. More specifically, they manually design a query based on the information indicated by the exception message and the stack trace of that exception. Afterwards, they choose and adapt a solution from the web search results. In this scenario, there is a gap between the development environment and web browsers. Moreover, manual search is very time consuming and a lot of useful information from the code is lost. In this thesis, we introduce Exception Tracer, an Eclipse plugin that helps developers find solutions of exceptions. Exception... 

In this study, the effect of two inverted piezoelectric flags arrangement on energy harvesting and the kinematics of limited amplitude oscillations which occurs due to flutter instability has been studied experimentally. For this purpose, first a study on piezoelectric materials for application in energy harvesting was carried out. Then, constraints and effective parameters of the inverted flag problem were obtained in terms of structure, fluid and electricity coupling. In the next step, according to these constraints and parameters, a test platform was designed and was built for experimental tests. A circuit with low amount of loss was designed and built to measure the perceptual power.... 

Reverse osmosis membranes are one of the most common methods of desalination of water in the world today. In the meantime, aromatic polyamide thin-film composite reverse osmosis membranes have one of the best performances and can be widely used in industry. This project aims to make surface modifications on the made raw membranes and increase the degree of crosslinking to improve the functional properties of the membrane, such as the percentage of salt rejection and the flux of permeate, and the reduction of fouling. For this purpose, polyvinyl alcohol and l-arginine along with maleic anhydride as the crosslinking agent and hexamethylene diisocyanate were used for surface modification of the...