Sharif Digital Repository

Repairing and regeneration of neural tissues have attracted considerable attention due to its direct effect on the quality of patients’ lives. Recent developments in nanotechnology and tissue engineering have facilitated their comprehensive applications in the treatment of neurological diseases, and several effective ways have been proposed to repair defects in neural tissues. The main objective of the researches in this field is to regulate cellular behavior and tissue progression through the design and development of synthetic extracellular matrices, such as novel biomaterials, that enhance cell culture and tissue regeneration. Natural polymers, such as chitosan and gelatin, are suitable... 

Fischer-Tropsch synthesis (FTS) is the main part of a Gas to Liquid (GTL) process. In this reaction which shall be done based upon iron or cobalt catalysts, H2 and CO molecules (namely Syngas) transform to long hydrocarbon chains. Regarding all of the advantages of cobalt catalysts in comparison with iron counterparts, Research Institute of Petroleum Industry (RIPI) began investigations since two decade ago. The present catalyst comprised of cobalt as active metal, ruthenium as activity promiter and lanthanum as support (gamma alumina) modifier. By the way, still some areas such as its lifetime duration and deactivation needs to be improved by complimentary researches. The present... 

Currently, the relatively long time of the turbine life passes and their parts and equipment damage are different, that loss optimum performance and thus reducing their efficiency and may lead to faults and other unexpected stops in their production cycle. Process used to estimate the remaining life of the various components of this turbine is an important tool for improving the efficiency of these units to perform preventive maintenance. In the present thesis, the types of damages in different parts of gas turbines and various methods for detection of critical points, particularly finite element method, high cycle fatigue, modal analysis, methods to estimate the lifetime of a gas turbine... 

Productivity reduction of oil and gas wells due to mud induced permeability impairment is one of challenging problems in drilling and production studies. This phenomenon is of prime importance in fractured reservoirs in which high permeability fracture networks act as conduits for feeding gas or oil from a tight matrix to the wellbore. Up to now, many experimental and modeling investigations have been done in formation damage in conventional reservoirs. But in spite of large contribution of fractured reservoirs in total hydrocarbon reserves, there is very little work reported in the literature investigating formation damage in such reservoirs. In this thesis, the effective parameters in... 

The rheology of oil well cement (OWC) slurries is generally more complicated than that of conventional cement paste. In order to contend with bottom hole conditions, a number of additives are usually used in the OWC slurries. The objective of this research is to develop a fundamental understanding of the important mechanisms that affect the properties of OWC slurry such as rheological properties, free water, compressive strength and thickening time incorporating various chemical and mineral admixtures. The partial replacement of OWC using different nanoparticle weight percent has been proved to be a promising method. The mechanisms underlying the effects of chemical admixtures on the... 

Previous studies indicate that increasing cement compressive strength can’t prevent loss of zonal isolation and casing collapse in worse case during well operations or formation loading. Since standard cements with high compressive strength can’t solve these problems, so application of elastic cements with low Young’s modulus and high Poisson’s ratio becomes important. These cements sustain generated stresses during well operations and prevent creation of point loads when formation creep occurs. For this purpose, a new additive was designed in order to improve the cement elasticity and tensile strength. It is a nanoparticle and named EX-RIPI (by Research Institute of Petroleum Industry,... 

Aqueous phase trapping (APT) in many of the oil and gas reservoirs is a significant mechanism of formation damage during drilling, completion, work over, and stimulation operation. APT can limit the productivity of the well to a high extent, especially in low permeable gas reservoirs. Experimental investigation of factors affecting APT is vital to recognize extends of associated damage and contribution of each factor. Albeit many experimental studies have been conducted as regards factors affecting removal of phase traps in understudy mechanism of formation damage, but up to date no experimental data has been published regarding effect of different factors on reservoir’s potential for APT.... 

One of the most important applications of artificial intelligence, and especially deep learning is image captioning. Given an image, the task is to automatically produce a sentence, describing the image. Image captioning has several real world applications like helping the blind understanding the images, generating automatic captions for the social media, etc. In the past, several different methods for image captioning have been used, but after the emergence of deep learning, like many other areas, image captioning algorithms have been improved significantly. In this thesis, I talk about a specific method for image captioning, called ”Deep Compositional Captioning. In this method, at first... 

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...