Sharif Digital Repository

The commercial breakthrough of micro-tubular solid oxide fuel cells (MT-SOFCs) is still facing so many challenges because of the complexity of their manufacturing process and the high cost associated with them. By deploying electrophoretic deposition as a simple and cost-effective method, the different components of the fuel cells (the anode, electrolyte, and cathode) can deposit on the graphite rod as a sacrificial substrate. The next step is eliminating the sacrificial substrate which will make hollow rods of cell components. The results of this study show that the use of a particular type of pencil lead will have a minimal negative impact on the overall fuel cell performance, leading to a... 

In this research, aluminum matrix composites (AMCs) reinforced by different contents of zirconium dioxide nanoparticles, graphite microparticles, and a mixture of both with various hybrid ratios, into a cold-rolled Aluminum1050 as base metal, fabricated by 4-passes friction stir processing. Observations show that the processing of composites reinforced by Gr particles is significantly hard due to the low friction coefficient of graphite resulting in the decline in the maximum temperature during the process and the type of base metal. The mixtures of graphite and zirconia resulted in more homogenous dispersion of particles in the matrix due to deterring a drastic drop in friction coefficient... 

Data traffic in communication network has increased steadily in recent years. Service requirements have also changed to become more complex. Moreover decrease in relative prices of computation and storage against communication encourages using more caching in these networks . Meanwhile increased use of encryption in internet has forced service providers who were willing to enter content distribution market to cooperate with content providers. But the cooperation is discouraged by willingness of both parties to hide their internal information. There are solutions proposed for interaction and information exchange between ISPs and CPs which are based on game theory. However, these solutions... 

The main purpose of this study is to estimate the natural frequency and damping ratio for soil-structure systems with embedded foundation with sufficient accuracy. The results are then compared to guidelines in current seismic codes. This is done through an extensive parametric study using a set of non-dimensional parameters, which define the soil-structure systems. For this purpose a simplified soil-structure model is used. Although more rigorous models and numerical solutions are available, they are time consuming and not suitable for parametric study. Existing formula for seismic provisions for the equivalent period and damping ratio of soil-structure systems are based on studies on... 

One of the most important variants of classical logic is intuitionistic logic, which has arisen from the contemporary studies in the foundation of mathematics. Suppose we want to investigate the foundation of mathematics from a constructive point of view. For this purpose, we can choose two different ways. The first one is to modify the classical set theory, ZFC, in a way that is valid from a constructive point of view and is enough to formulate constructive mathematics, as well. The second approach, which is somehow different from the first one, is a foundational and dependent codification of the same foundation in a way that completely reflects constructive views.In this work we will... 

After the fisher hypothesis about the relationship between asset returns and inflation, numerous studies tried to examine the accuracy of the hypothesis. Contradicted results continued to the proxy hypothesis by Fama (1981). In this thesis, after a thorough survey of the literature, both theoretically and empirically, in order to find the inflation hedging ability of the land, gold and stock in Iran, we try to find the hedging ability of the assets in Iran. Considering the seasonal characteristic of the data, we employed HEGY (1990) unit root test. Finally, by using vector error correction models we show that in the long run, stock and land hedge the wealth against inflation. In the short... 

In the last 4 years, while the annual investment return on 5 years bank deposits was 25 percent; the total index of Tehran Stock Exchange on average grew by 155 percent. Why the investors are not so willing to invest in the stock market? This research deals with existence of equity premium puzzle in Tehran Stock Exchange. Therefore, the Total Price Index of exchange market is considered as a risky asset and the return on long-term (5 years) deposit is a proxy for risk free asset. Data is monthly and covers the first month of 1380 (Persian Calendar) to the beginning of the second month of 1391 (equivalent to Aug 2010 to Jan 2013); which is converted to real term using monthly inflation rate.... 

Detecting of coherent structures in bidirectional vortex combustion chamber is the original aim of this project. For this aim a numerical simulation is performed by using OpenFOAM, open-source CFD software. Also influence of fuel nozzle places in formation of coherent structures is analyzed. Effects of combustion in these structures and differences in cold and hot flows are analyzed too. There are papers that present influence of coherent structures in vortex burners and other applications, but based on reviews that are performed in this work, it seems that influence of coherent structures have not seen in bidirectional vortex chambers. So it can be one of innovations of this work. Swirl... 

An increasing important issue faced by Iranian labor market at the current decade is the job positions which have been occupying by workers who are not match for them. Over the recent past years the supply of college educated labor has experienced a significant increase, while the demand side of the market has shrunk because of low economic growth. This study intends to examine intensity of the over-education on the individuals’ wage By making two alternative definitions for overeducaion namely; realized match and job analysis. To this end we use households’ income and expenditure survey for 2001, 2005, 2009 and 2012 in rural and urban areas. Theoretical background is based on the Duncan and... 

The use of nanofluids to improve the heat transfer has a special attention in the industry. researches focus on the efficiency of heat transfer nanofluids dates back to 1998. Ferrofluids are a particular type of nanofluids which their nanoparticles have magnetic effect and heat transfer can be increased by applying magnetic field to them. In this work, thermal and hydrodynamic performance of ferromagnetic fluid which flows through a copper tube in thermal entrance region has been studied. The flow in the tube is laminar and is affected by constant heat flux. Part of the tube contains a porous medium with paramagnetic properties and porosity of 0.46. Ferrofluid is composed of F e3O4 and water... 

The Reconfigurable manufacturing system (RMS) was first introduced in 1996 with the ability to respond quickly to market changes and in response to global competition between companies. The effort of this research is to expand the problem presented in the Moghaddam et al. (2019) by introducing the concept of raw materials for the production of parts and related issues such as purchasing and warehousing raw materials, and providing a suitable solution to the problem. In the basic article, the RMS should utilize the best combination of machines and their configurations in proportion to the demand of the products in order to minimize the cost and produce all the demand. In this study, a large... 

In this study, we intend to investigate the effect of pollution levels on the valuation of residential units in Tehran. The method used in this research is Hadanik pricing method. Data required for the project, in relation to the intrinsic characteristics of housing including number of bedrooms, building life, area and… air pollution index by regional stations on a daily basis and housing environmental characteristics including per capita green space, day and night pollution index, density The population of the area and… are collected. According to the results, they have the greatest impact on determining the value of the building area and building life, and after controlling for other... 

Urban mobility platforms introduced as an innovation in matching suppliers and demanders to each other in the transportation market in recent years. In this research, we applying synthetic control method to analyze the impact of this kind of platforms on labor market variables like work hours, income and number of employed persons in affected activity group. We use the ISIC correspondence tables for versions 3.1 and 4 and also Iran labor force survey and household survey to making activity control groups. The results show that work hours for main work in the related group were reduced. As well as the number of employees in the group increased 100 thousand people and the number of earners... 

In general, the output power of the gas turbines decreases as the ambient temperature increases. One of the ways to deal with such a performance loss is to use a wet compression system, which reduces the air temperature rise throughout the compressor. In this system, the water droplets are injected into the compressor inlet and evaporated throughout the stages. As a result, the work of the compressor decreases, and the power and efficiency of the whole engine increase. Most of the researchers in this field have tried to develop mathematical models to investigate the effects of this system on compressor and gas turbine performance in steady-state conditions. However, it is necessary to... 

In economies with high inflation rates, investors are concerned about their purchasing power and assets’ value. Traders are interested to choose optimal portfolios in terms of risk and return. In recent years, the Iranian stock market and real estate experienced a quiet long period of boom with high rates of return. In this study, we estimate and analyze the equi-correlation between the returns in the markets. For this purpose, we use the monthly data of real estate prices in Tehran and the Tehran Stock Exchange Index for a twenty-four-year period, applying the DCC technique. Our results reveal that the long-term correlation between these two markets is not strong, leading us to suggest them... 

Which capital structure theories have the power to explain the determinant of capital structure in capital market companies, assuming the difference between the institutional and fundamental structure of Iran with other countries, which affects the behavior and decision-making style of managers. After the emergence of capital structure theories, studies were performed to assess the explanatory power of theories. The results revealed the fact that the differences in the institutional structure of countries affects the behavior and decision-making style of managers for adopting the optimal capital structure, and the determinants of capital structure followed a limited number of theories. In... 

The objective of this study is to explore the relationship between the stock price volatility and dividend policy (dividend yield and dividend payout ratio) for the Iranian stock market. According to the studies of Baskin (1989) and Allen and Rachim (1996), the fixed effect and random effect regression models are applied in this research. The sample of data is composed of 200 public firms which are listed on the Tehran Stock Exchange (TSE) and paid dividends continuously from 2010 to 2020. The results indicate that the dividend policy has a significantly negative relationship with the stock price volatility. In addition, the Size of the company is negatively related to the stock price... 

The low female labor force participation rate in the Iranian labor market relative to the global average and even to countries that do not differ significantly from the socio-economic characteristics of our country is one of the important questions of the Iranian labor market. In this study, we seek to answer the question of whether the economic participation rate of married women will increase if the gender gaps in wages, job findings and job losses among women and men are eliminated in the Iranian labor market. To answer this question using household expenditure and income data and labor force data, we show that between the two categories of occupations, in terms of the share of women's... 

Fatigue crack growth can have harmful effects on the reliability rotary machine. While an early warning to crack, can be used to extend the life of these expensive machines and increase reliability.Structural Vibration Condition Monitoring as a primary fault detection method, achieved to a lot amazing result and for this reason studies vibration behavior of cracked rotational shaft is a big issue for engineers of dynamic machine.In this research, first check the fault detection methods based on structural vibration condition monitoring, mode shape methods were extracted. Then by modeling rotational shaft in computer and creation of crack on it, fault detection quality of these methods have...