Sharif Digital Repository

New materials as hybrid materials or laminate composites, due to combination of many properties, can be used in many industries. The aim of this research is bonding of three-layered St/AZ31/St composite by roll-bonding process. The roll-bonding process was performed at three preheating temperatures, 340, 400 and 450 ⁰C, with thickness reduction of 30 to 68% and different thicknesses of intermediate layer (AZ31). In order to improve the bonding strength, the as-rolled specimens were annealed at constant temperature of 375 ⁰C. For evaluation of bond strength and investigating the formation of a diffusion layer, the results of peel test and microscopic images were studied. Tensile specimens... 

During software evolution and maintenance, developers deal with various challenges, such as locating features, fixing bugs, and adding new features. One of the first steps to perform most of the software maintenance activities, such as updating features or fixing bugs, is to have a relatively good understanding of the program’s source code which is often written by other developers. A code summary is a description about a program’s entities (e.g., its methods) which helps developers have a better comprehension of the code in a shorter period of time. However, generating code summaries can be a challenging task. To mitigate this problem, in this thesis, we introduce CrowdSummarizer, a code... 

Due to increased mortality from Coronary Heart Disease, it is important to work on ways to treat this disease. An effective method of treatment on this disease is the coronary stent implantation. There are nearly two decades passed since implanting the first heart stent. The main objective of this research is design and manufacturing of the medical stents of stainless steel 316 L. Stent materials should have excellent corrosion resistance and biocompatibility. Various materials such as stainless steel 316 L, platinum alloys, niobium alloys, cobalt alloys are used for manufacturing the stents. In this project, at the first stage seam tube was prodected with laser welding of a tube with... 

The trend of increasing energy intensity in the country, despite awareness of the officials and managers of the need to take action to improve it, is ongoing. Various studies conducted worldwide to improve the productivity of energy. These studies suggest ways for improving energy intensity; suggestions that will never be implemented, because of lack of utility consideration of actors. In this research, in search for energy intensity reduction barriers in the industrial sector of the country, a game theoretical approach has been applied. In this study’s modeling, energy consuming firms as an actor, compete with each other and the government as an important actor in the implementation or... 

Energy efficiency for Iran, which has large reserves of oil and gas but also has a high energy consumption is important because it ensures the country's energy security and saving each energy unit creates energy exports opportunity. Buildings have high energy saving potential; this sector uses about thirty percent of energy consumption (about half the gas and thirty percent of the annual electricity consumption). Households are not motivated in saving energy because government pays energy subsidy. In this research building energy consumption (in Tehran) modeled by bottom up approach. Then the effect of economic incentive tools such as subsidy, loan and tax on motivation in energy saving... 

Client applications are often developed with the help of software frameworks in order to reduce the development costs and to increase the software quality. However, frameworks may evolve to add new features or to fix bugs, and thus, their APIs may change at the same time. Nevertheless, these API changes can cause the client applications to not work properly. New frameworks typically use the deprecation mechanism to reduce this effect, but their documents often do not provide sufficient information. Consequently, deprecated APIs usages remain unresolved in client applications. To tackle this issue, we introduce ARFES (Automated Recommender of Framework Evolution Solutions) that provides... 

Nowadays one of the main challenges facing fluid dynamics simulations is the long duration of numerical calculations. The goal of this research is to use FPGAs (Field Programmable Gate Arrays) to accelerate fluid dynamics solutions. First, the ability of FPGAs in mathematical operations on floating point numbers is studied. Then, various fluid dynamics problems are implemented on the FPGA hardware, and each one is solved separately. Unsteady 1D Couette problem, 2D potential flow (Laplace equation), incompressible viscous fluid flow over a backward facing step, and compressible inviscid flow over a bump are some of the problems in question. FPGA is an integrated circuit containing a number of... 

The ever increasing growth of smart phones and their applications have led to the emergence of various platforms, i.e. online stores, for distributing them among users and providing a way for customers and developers to interact with each other. In recent years, these stores have turned into an important form of software repositories, which brought out new challenges for researchers. One of these challenges is the task of searching for suitable applications and providing simple access to them for users. Pervious work has focused on the relationships between users and applications’ contents. Among the shortcomings of these approaches, is not considering users’ reviews of applications and what... 

Increasing popularity and use of smartphones has led to rapid growth in number of mobile applications. With the increasing number of available apps in app stores, some of them may have many similarities to each other in functional aspects. Detecting similar apps among a large number of different applications is an important and difficult problem which is useful in a variety of applications, such as app recommendation, comparing competitor apps, app search engines, etc. In order to investigate the functional similarities between applications, high-level and low-level characteristics can be used. With using the high-level characteristics, app functionality features can be extracted from... 

Due to financial resources constraints, the country's oil industry, especially the upstream oil sector accounting for most of the country's foreign exchange and budget revenues, has not been developed. Thanks to the international sanctions against our country, the conventional financing methods are difficult to use anymore. According to the the current circumstances, the alternative sources of funding using modern approaches are necessary. Moreover, small capital is one of the alternative sources with the high potential for the high level of the liquidity in the society. This study, investigates the financial tools regarding capital market to attract small capital in order to finance... 

Butadiene is one of the most widely used materials in the Iran polymer industry. In order to use this material in the first step, the inhibitor must be separated. Consequently, at the start of the project, the separation of Tert butylcatechol inhibitors from butadiene was studied by the adsorption process on active alumina. The results of the condensed butadiene gas chromatography–mass spectrometry test indicate that, by using the active alumina as an adsorbent, the tert butylcatechol will be removed completely. In the next step, 1,3 butadiene, acrylonitrile, acrylic acid acid terpolymer, which one of its applications is manufacturing of artificial teeth, was synthesized by emulsion... 

Dental implants should be biocompatible. This ability cause bone growth beside implant and increases stability of implant. Manufactoring method and materials used in implants are main parameters affectig biocompatibility of implants. Fabrication of functionally graded structures is a novel method to increase biocompatibility. Stress shielding is one of the main causes of failures in current dental implants. This phenomenon takes place due to different young modulus of dental implants and host bone. Pouros structures remedial this problem and implant’s young modulus comes closer to host bone. The aim of this project is to study feasibily of fabrication of functionally graded titanium dental... 

Lithium ion battery is one of the innovative and emerging technologies in energy sector that has played a major role in electricity supply security by integration of renewable energy technologies in electrical grid, implementation of electrical transportation system and de-carbonation of the both sectors in recent years. On the other hand, the formation of the potential market of technology as one of the functions of the technological innovation system plays an essential role in creation and advancement of innovation in the energy sector. Therefore, in this thesis, the development of lithium ion battery technology in Iran has been investigated from the perspective of the technology market in... 

The oil refining industry, as the first oil supply chain, is of great importance. By examining the issue of the Iranian Oil Refining Industry, using the game theory, one can find an accurate analysis of the barriers to the development of this industry. For this purpose, the main factors affecting the oil refining industry, the government and the refinery's owner, are modeled and their benefits are considered. By examining the relationship between these actors and their actions, the following strategies are proposed to improve the administration and regulate the Iranian oil refining industry:
1- Refining feed prices, according to the quality of crude oil (sulfur content and API... 

This study will examine the interests of Iran in entering one of the largest and most outreaching LNG markets which is China. In order to examine these interests, understanding China's policy on importing LNG and the competitive environment in this market is necessary. First, the decision theory is used to simulate China's policy on adjusting the import mix during the demand growth period of 2011 to 2017.This provides a simulated picture of its policy on increasing demand for the 2020. Then, the behavior of other LNG exporting countries to China is analyzed using game theory approach. By analyzing the sensitivity of the parameters in which uncertainty exist, it was revealed that Iran's... 

Using flapping motions, birds produce aerodynamic forces required to fly. Flapping wing aerodynamics is one of the most complicated problems in unsteady aerodynamic field. Experimental study on the structure, the way of production and growth and the feasibility of controlling the leading edge vortex are the main goals of this research in order to improve the aerodynamic performance of flapping wings. Since leading edge vortex structure appears in both upstroke and downstroke of a complete storke in flapping motion, controlling the structure in one of the half-storkes can provide the possibility of having a better aerodynamic performance. In this research, the wing is designed and... 

In recent years, with the rise of the smartphones, mobile apps have seen unprecedented growth and their stores have gained popularity among users. The direct connection of users to these stores and the ability to comment on the applications, have made them big repositories of information. In particular, user reviews provide developers with valuable information on strengths and weaknesses of application and users' problems when using it, which can serve as a guide to improve their application.There are a lot of research on exploring user reviews but few have been trying to find a link between reviews and source code of application. In this research, for the first time, all of the code... 

Iran has the second largest gas reserves in the world with huge gas reserves about 32 trillion cubic meters. The expansion of gas exports in recent decades has been accompanied by liquefied natural gas exports, with the LNG industry growing rapidly due to the inability to export gas via pipeline to distant markets. The expansion of the LNG industry around the world, there have been various markets for this product that the Southeast Asian market being the largest market for this product and Japan is the largest importer in this sector.Specific mechanisms of the Japanese market, which have separated it from the rest of the LNG importing countries, are the extension of long-term contracts for... 

The subsidies targeting law was ratified on October 23, 2009. At mentioned law appointed that the government redistributes up to 50% of earned revenues from price reforming of energy carriers to households by cash and non-cash payments and 30% of earned revenues to the production sector. But reports studies indicate that from 2010 to 2016, the government allocated 93.4% of the revenues to households in cash and non-cash and only 0.7% to the production sector. It can, therefore, be concluded that the subsidies targeting law has not been properly implemented. Indeed, the government has not only failed to fully reform energy carriers prices, but also has increased the households’ share of... 

In present research, a new system of energy extraction from water flow has been studied and optimized. This semi-active energy harvesting system consists of an airfoil that is connected to the generator by an arm. The passage of water causes the airfoil to move, so the hydrodynamic forces on the airfoil will cause the arm to move and finally the generator. In this research, complete dynamic modeling of this energy extraction system including generator, airfoil, controller and actuator modeling is presented and the governing dynamic equations are extracted using this modeling for dynamic simulation. Two dimensional fluid simulations have also been performed using fluent software. Finally, in...