Sharif Digital Repository

The purpose of this project is investigating the effect of cross flow and electric field on a liquid simple-jet experimentally. In this research the effect of parameters such as liquid to air momentum ratio, electric field on jet trajectory, penetration and the lenght of breakup point with respect to the jet outlet were studied. The air was produced by a blower in a duct with square test section of 8 cm sides. The air velocity varied from 1 m/s to 11 m/s. Liquid ethanol was injected into the duct with a needle with outer diameter of 0/62 mm and inner diameter of 0.4 mm and 28 mm length. The velocity of jet was 0/62 m/s while the change of liquid to air momentum ratio was from 3 to 260 The... 

Water flooding is known as a common method to maintain reservoir pressure/enhance oil recovery. The major problem in this process induced from inorganic deposits that caused formation damage around wellbore region. It is due to incompatible nature of injected and formation water which results in permeability reduction and well productivity decrease. Solving this problem is an important issue in the petroleum industry. BaSO4, CaSO4 and SrSO4 are inorganic sediments formed in this process. The physical model of water transport in reservoir and scaling damage due to sediments contains at least two dominant parameters; the kinetics coefficient that specifies the velocity of chemical reaction,... 

Concrete gravity dams are structures of much importance which their failure due to earthquakes results in a catastrophe. Therefore, precise stability analysis of these types of dams against sliding and overturning is essential. The common method of safety assessment of gravity dams is based on limit equilibrium method assuming that dam slides and overturns as a rigid structure. Although providing high safety factors is somehow acceptable to meet the safety requirements of dams, it should be considered that the whole system of dam body and foundation is flexible in reality and its performance should be studied in this case for stability analysis. In this investigation, first, stability... 

The aim ofthis work is constructing a dye laser pumped in visible spectrum by a second harmonic of aNd:YAG laser.For this purpose, 12mJ of its energy focused by a cylendrical lens into a dye cell. Instead of usual telescope, making aberration in two dimensions, we have used multi prism beam expander to eliminate aberration and also expand beam beyond 10 times. The more magnification resulted in narrowing laser linewidth and it was about 2 nm for two prism beam expander and 0.5 nm for four prism beam expander.
Beam expander configurations were designed in zero dispersioncondition.Therefore,scanning laser spectrum becomes possible. The wavelength was scanned between 565 nm to595 nm, and... 

Today in many industrial sectors, technology has made significant progress. Investing in advanced manufacturing technologies, especially computer integrated manufacturing systems is essential in order to survive in a competitive environment, improve performance, response to demand fluctuations and increase customer satisfaction. With available technologies and systems in computer integrated manufacturing (CIM) and its related technologies, the application of CIM in manufacturing enterprises is a reality and can meet the need of complicated manufacturing environment. Implementation of these systems brings many tangible and intangible benefits. But, according to several factors that must be... 

This paper examines the effects of institutional price pressure caused by severe inflows and outflows of capital by studying mutual funds transactions in the Iranian stock market between 2010 and 2017. According to the findings, mutual funds that experience severe outflows tend to reduce or eliminate existing positions in their portfolios, which creates a severe price pressure in the securities held by distressed funds. This price pressure caused by a severe outflow of capital leads to decrease stock prices below their intrinsic value. So investors who buy shares that sold by mutual funds earn abnormal returns for providing liquidity. On the other hand, funds with severe capital inflows tend... 

In just a decade, perovskite solar cells have emerged as the next generation of photovoltaic technologies due to their high efficiency, low manufacturing cost, and easy fabrication methods compared to silicon solar cells. To date, highly efficient perovskite cells (with an efficiency of approximately 25.5%) have been fabricated on small substrates by a spin-coating process. In the spin coating process, perovskite precursor is spread on the substrate through shear force. However, the reproducibility of the cells coated with this method varies between research laboratories. Furthermore, since the solution is wasted during the deposition of the perovskite precursor on large substrates, a... 

The primary purpose of acidizing operations in the oil and gas industry is to enhance hydrocarbon production. Acidizing has been a common and conventional method for years, especially when production engineers face issues like declining reservoir pressure leading to reduced production rates. Initially, the treatment solution is referred to as matrix acidizing. In acidizing operations, different additives are combined with the acid to control its behavior in the reservoir. These additives may include iron control agents, corrosion inhibitors, friction reducers, and more. Incompatibility among these additives, the acid, and reservoir fluids can lead to severe damage to the reservoir.... 

The goal of this research is the simulation of the annular combustion chamber of the turbine engine utilized by liquid fuel. The achievement to this goal will lead to create numerical tools for parametric study, analysis and combustion chamber designing.For this reason simple geometry has been considered. This simplicity of geometry causes to facilitate in parametric study and decrease in saving time for modeling and meshing. This combustion chamber is a simplified model of engine CF6. In recent study, the k – ε realizable model has been used for turbulence modeling. For non-adiabatic condition, chemical reaction is dissolved by utilizing probability density function along with laminar... 

During the last few years, the study of urban environment structures is considered as a research field of interest in remote sensing. In satellite observations of the earth's surface, continuous imaging in terms of time and space has caused the remote sensing technique to be proposed as a useful and efficient tool for the analysis of urban areas. Obtaining quantitative spatial information from the urban environment in fields such as determining the height of buildings plays an essential role in urban planning, monitoring damage to buildings, establishing communication bases and digital cities. During the last two decades, the use of Tomosar approach in order to reconstruct the structures of... 

In this work, the dynamic competition between firms providing internet services is studied. The framework is Markov equilibrium whereby structural parameters are obtained using two-step estimations, allowing for analyzing the situation in case of subsidies for service upgrade. The results show that such subsidy has little effect on the number of firms while increasing the number of fast firms  

Estimating the price elasticity of gas demand involves complexities depending on the gas market structure and pricing mechanisms in different countries. Distinguishing between supply and demand shocks and block pricing are among the main challenges that can cause endogeneity in elasticity estimates. Iran's domestic gas network, one of the largest and most extensive household gas markets, is divided into five climatic zones based on weather conditions. The pricing steps for these five climates during the five cold months are such that a customer in a warmer climate pays higher prices. Conversely, the pricing steps for the seven warm months are the same for all climates. This policy creates a... 

The correlation between religious adherence and voter turnout is widely studied. However, whether the relation is causal is an open question. We use Household Expenditures and Income Survey (HEIS) data in Iran, which encompasses nine distinct religious expenditures. These expenditures have low correlation with each other and represent different aspects of religious adherence. We use Imamzadeh (some historical holy shrines) as Instruments to estimate the causal effect of religious expenditures on voter turnout. The results reveal that religious expenditures influence both presidential and parliamentary voter turnout, with a notably stronger impact on presidential elections