Sharif Digital Repository

Supply chain problems consist of a large number of issues. One of the key problem in this area is supplier selection in supply chain. Several criteria must be considered in the supplier selection. So, multi criteria decision making approach, neural network, mathematical programming and etc. are used for solving this problems. In most of these problems, supplier selection is done according to the buyer’s objectives.
So far, several methods are provided for supplier selection problem. In majority of them, supplier selection problem is surveyed from buyer’s viewpoint and in those have only been considered the buyer’s benefit maximization that will not necessarily lead to optimal condition... 

One of the main geotechnical phenomena that causes severe damage during earthquake is liquefaction. This incident occurs due to the undrained behavior of loose sandy soils. In this occurrence, the interaction between the solid and liquid phases in a cyclic motion leads to an increase in pore water pressure and a decrease in interactive forces (effective forces) between grains in the solid grains. Therefore, shear strength decreases. Different aspects of the aforementioned phenomenon is investigated, namely, field, laboratory, and numerical; nevertheless, the study is largely focused on the numerical modelling. Most studies in this field are carried out on a one-layer saturated sand. However,... 

To have a deeper understanding of Hydraulic fracturing operation, in this study four important parts in this field was developed and simulated. In the first part, continuity and momentum equations for a single phase flow in a propagating penny-shaped fracture inside an impermeable matrix was revisited based on a fixed coordinate system. Its correctness was validated against experimental data and its features were compared with the well-known lubrication theory in analytical form. The new derived continuity equation caused the fracture tip to have a positive and finite pressure while, the conventional model predicted negative infinity for that. In the second part, Finite Volume method was... 

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  

Mobile edge computing (MEC) is a promising technology that aims to resolve cloud computing’s issues by deploying computation resources at the edge of mobile network and in the proximity of users. The advantages of MEC include reduced latency, energy consumption, and load on access and mobile core networks, to name but a few. Despite all the aforementioned advantages, the mobility of mobile network users causes the traditional MEC architecture to suffer from several issues, such as decreased efficiency and frequent service interruption. One of the methods to manage users’ mobility is virtual machine (VM) migration, where the VM containing the user’s task is migrated to somewhere closer to... 

In this study TiO2/SiO2 thin films were prepared by sol-gel method from Tetra isopropylortho Titanate(TIPT) as the principle of TiO2 material with Tera ethoxysilane(TEOS) as the principle of SiO2 material to achieve high scratch-resistant , antibacterial and self-cleaning surface area under the effect of various percentage of SiO2 . Film deposition was carried out using a dip-coating technique and heat-treatment was used at 700ºC to achieve crystalline of films with excellent adherence the of substrate.
The surface morphology of the films has been observed by Scanning Electron Microscope (SEM) and the tribological properties of the surface were investigated by Atomic Force Microscope... 

In this study steady state and dynamic simulation of an NFM extractive distillation unit for seperation of aromatics and non-aromatic components has been carried out. Column output composition obtained with experimental binary coefficients is compared with those obtainded by UNIFAC equation. The results indicate that using UNIFAC for all binrary coefficients results in an unacceptable error in concentration of benzene. If the experimental binary coefficents of benzene with NFM are used and the rest are calculated by UNIFAC equation, the simulation results will be very close to those obtained via experimental binary coefficients. Also it is shown that considering a constant efficiency for all...