Sharif Digital Repository

Centrifugal compressors are widely utilized in various industrial systems; however, their performance under uncertain operating conditions is influenced by random variations parameters. This research presents a comprehensive investigation and analysis of uncertainties in the performance of the NASA low-speed centrifugal compressor (LSCC). The primary focus of this study is to analyze the impact of uncertain operating conditions such as total inlet pressure, total inlet temperature, mass flow rate, inlet flow angle, and rotational speed, all of which are modeled using the beta probability distribution. To conduct this analysis, the non-intrusive polynomial chaos expansion method has been... 

Zero-knowledge proofs are one of the most useful constructions of modern cryptography. Their invention has greatly affected both cryptography and complexity theories. The seemingly paradoxical characteristic of zero-knowledge proofs is that they convince the verifier of the validity of the proposition being proved, yet they yield to further knowledge to him. Two primary applications of zero-knowledge proofs are authentication protocols, as well as sub-protocols which prove that parties involved in some main protocol have acted honestly. In this research, we will survey the models and definitions of zero-knowledge, and analyze their relationship. We then pertain to the interplay between... 

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  

Free and Open-Source Software (FOSS) is grown rapidly and many researches are conducted to study FOSS developments. The studies aim to help FOSS development by finding bugs, analyzing developers, modeling evolution of software and categorizing them. Finding proper developers or key developers of each group is essential in developing software, recommend developers and assigning bugs to proper developers. Community detection detects groups of nodes having dense connections. The groups represent developers which cooperate closely on developing FOSS. The thesis proposes a method based on evolutionary algorithms and topological analysis to detect communities in open-source software development... 

In the current study, the dispersion of four major air pollutants, sulphur dioxide, nitrogen oxide, carbon monoxide, and particulate matter from gas flares of an oil field, in Iran, was investigated for year 2011 by application of a conventional steady state Gaussian dispersion model, AERMOD. Two scenarios were applied in modeling, first application of flare parameters based on technologies that exist and the other one using new technologies in flares such as steam assisted with better combustion efficiency. Due to the complexity of meteorological parameters in modeling area, CALPUFF model was used in this study. CALPUFF which is a more advanced model that considers the effect of... 

The Cu2ZnSnS4 (CZTS) quaternary compound, with suitable optical and electrical properties, is one of the most interesting materials for absorber layer of thin film solar cell. Since all constituents of CZTS, are abundant in earth’s crust and non-toxic, it is a proper replacement for the materials like CdTe and CuInSe2. The CZTS pellet was synthesized by the solid-state reaction and deposited on soda lime glass substrates by pulsed laser deposition (PLD) method. PLD technique has the advantages of offering stoichiometric preservation during the materials transformation from target to substrate and good crystallinity due to the highly energetic species. CZTS has was deposited in order to... 

Most of dynamical models in the real world, have various restrictions and complexities in their structures. These constraints make the controller design much more difficult. In this work, it has been tried to design the controller for two kinds of common dynamical systems in the presence of these restriction by using the fuzzy logic systems. Several restrictions are investigated in this project such as unknown dynamic of the model, unmeasured state variables, unknown control directions, existence of time delay in the input and the state variables, input saturation and controller singularity.The backstepping technique and the dynamic surfaces control approach have been used to design the... 

In this thesis, we study the problem of guarding art galleries with sliding cameras and k-transmitter. This problem is a new version of classic art gallery problem, which the goal is covering the entire region with minimum number of guards. In early version of art gallery problem, usually point guards with 360 degree vision were used, but in this thesis we use sliding cameras instead. This new guards specified by an orthogonal segment which entirely settled interior of polygon and can see up to k walls. Based on this two notions (sliding camera and k-transmitter) we say that a guard can see point p, if the intersections number of normal segment through p to corresponding segment of guard...