Sharif Digital Repository

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... 

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... 

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... 

In this research sequence-dependent flowshop and flexible flowshop group scheduling problems are investigated. Several upper and lower bounding methods are proposed for the research problems. Permutation flowshop sequence-dependent group scheduling problem with minimization of total completion time is considered. Since the problem is shown to be strongly NP-hard, a Memetic algorithm (MA) is proposed. A lower bounding method base on the Branch-and-Price algrithm is also proposed. A statistical comparison shows that both the proposed MA and the proposed lower bounding method have better performance than the other methods from the literature with an average 5.96% percentage gap. Flexible... 

Due to the use of rotor dynamics, in the rotating systems such as pumps, turbines and machine tool spindle gained special significance in recent decades and a growing need for rotating machines with high speed, leading to extensive research in this area. Due to instability in the dynamics of these systems, check the stability of the rotor system has been given special emphasis, so that studies and research in terms of models and methods allocated to this topic. The project analyzed the stability of a rotor that includes an elastic shaft is placed on the bearings as it is objective. From point of modeling, the rotor is modeled using Timoshenko beam theory and the rotor mounted on bearing with... 

This research intends to analysis the determinants of child work and schooling in Iran. To do this we use the Household’s Income and Expenditure survey of Iran in 2009. There are two competing theoretical base of household’s time allocation, the unitary and collective bargaining decision approaches. We use the later to consider the differences in preferences of parents toward the child’s time allocation. Making use of Bivariate Probit and Tobit, we examined the effects of parents’ bargaining power and child’s birth order on his/her schooling and work decision. Our finding, confirm that, mother’s bargaining power has negative association with the work participation of her son and daughter but...