Sharif Digital Repository

The traditional backup protection system of transmission lines are self-contained and only use from local measurements and generally, don’t use from wide area measurements. Hence, it can misoperate when the power system is extremely under stress conditions. So, the zone 3 of distance relays have been recognized as one of important participating causes of cascading phenomena that lead to major power system blackouts. In modern societies, power systems have become one of most important critical infrastructures, accordingly, blackouts can have catastrophic effects. Therefore, the novel backup protection schemes are required to improve security and dependability of protection system.
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Microbial fuel cell is one of the new technologies in the field of power generation from the organic energy resource. The fuel cell system in a process similar to chemical fuel cell generate electrical energy through oxidation of organic composition by uses of electrogenic microorganisms as biocatalyst. In this study the main object is providing a comprehensive mathematical model for the fuel cell system in micro-liter size. To achieve this purpose, we start to investigate properties of fuel cell system in this size. And according to the geometry of system we choose chemotactic equation for estimating hydrodynamic behavior of microorganism and using combination of conductive base and... 

The promotion of oil and gas industry of a country or region requires foreign and long-term investments. Ensuring the security of demand is one of the major driving forces for increasing investments in oil and gas sectors.The status of the Caspian markets in terms of energy demand security is the main issue in this study. Just like security of supply, security of energy demand will not be affected by economic logic alone, but the combination of various factors should be considered; So in this study Combined criteria was developed.According to the horizons of policy making for the energy export of Caspian, 2015 year as the recent past, 2020 as the medium-term and 2030 as the long-term have... 

Nonlinear transmission line (NLTL) a guiding structure contains nonlinear elements. For discrete NLTLs, this structure is periodically loaded with nonlinear elements. In the structure of this line nonlinear elements such as ceramic capacitors, nonlinear magnetic elements, vector diodes, Mos transistors, etc can be used. With the rapid development of semiconductor devices and microwave band systems, the demand for implementation of NLTLs has increased. These lines provide wide band-width, cut-off frequencies over the hundreds of GHz and picosecond rise time for various systems.Among the applications of NLTL, the generation of high power RF pulses has attracted the most attention. In this... 

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... 

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  

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... 

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... 

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  

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... 

During the brewing process, beer alternately goes through different chemical and biochemical reactions and solid–liquid separation stages. The clarification at the final step of brewing is a highly critical stage when it comes to producing a clear and bright beer. Recently, membrane technology has been successfully used in beer clarification, wherein Kieselguhr (diatomaceous earth) filtration is replaced by cross-flow microfiltration. The most important disadvantages of using microfiltration in clarification of beer is the fouling and flux decline during the process. The phenomenology of fouling mechanisms is still undefined and selection of an appropriate technique for flux enhancement in... 

Different methods can be used to produce reduction gas. One example is using coal. But today there’s a tendency to use natural gas. One way of transforming natural gas to reduction gas is to burn it with gases produced by combustion, such as or vapor; usually a catalyst is used in this method. Another method is burning natural gas directly with oxygen or air. The recent method is of benefit especially in Iran, because of available natural gas resources and avoiding catalyst problems. Designing a burner for this purpose is an important step in reaching this goal. In this project such a burner is designed and manufactured. The burner manufactured in this project burns natural gas with...