Sharif Digital Repository

Increasing of industrial society's need to refinery's product, high consuming energy in distillation process and pollution product in it cause to researchers investigate about the alternative process for crude oil refinery. At this time, supercritical fluid extraction was regard as a less energy consuming process. The aim of this work was prepare to a computerized model for simulating of crude oil refinery's process. In this work effects of temperature and pressure on the supercritical extraction were investigated. The experiment was done at four temperatures (35, 40, 45, 50°C) and four pressures (100, 120, 140, 160 bar) by supercritical carbon dioxide and obtained samples were analyzed by... 

It is well known that poly(ethylene terephthalate) (PET) is a high melting compound which has exceptional value as a fiber and film-making material, and which currently dominates the whole field of linear polyester substances. However, the high viscosity and limited solubility in liquid solvents restrict its processing to powders and hence the range of applications of such a polymer. Traditionally, crushing, mechanical grinding, ball milling and precipitation from solution are methods for producing powders. The first three ones inevitably change the property of materials. The last one is carried out on the basis of the application of an anti-solvent to decrease the solubility of a... 

The supercritical carbon dioxide is applied in many separation processes as solvent. Due to this applicability of carbon dioxide, in this study, it is applied to oil refinery. In order to find the maximum efficiency, the experiment was conducted in the pressure range of 150-210 bar, and the temperature range 35-65 C of temperature. Based on this study, the changes in pressure show strong effect on the efficiency, and when it increases the efficiency increases, too. Despite of the pressure, when the temperature increases at a constant pressure, the density of supercritical carbon dioxide decreases. As a result, its solubility in decreases and the oil viscosity and mass transfer rate from oil... 

In this study the main goal is to prepare a membrane to perform delayed drug release and absorbtion in the human body. To do so the supercritical method was used. A well-known biodegradable polymer was used. These kinds of polymers are used in drug delivery, wound dressing or scaffolding for cell culture. A membrane produced out of these kin of polymers is expected to have a good accordance with the goals.Ploy Vinyl alcohol, having very good bio degradable characteristics was used as the main polymer and Poly Ethylene Glycol (PEG) was used as an additive to make changes in the membrane structure. Also Dimethyl Sulfoxide, a polar solvent having the capability of solving both polymers is used.... 

Fracture and Matrix permeability systematically change because production time of gas and oil reservoirs is very long and pore pressure, temperature and in-situ stresses continously change in reservoirs.This parameters have an important role in determination and development of wells according to the permeability distribution.The main factors in determination of fracture permeability values is normal and shear stiffness that parameters such as roughness, opening, closure, aperture and asperities influence this factor.In this thesis, we try to investigate the influence of this parameters on fracture permeability according to the normal and shear stresses.Also we want to investigate the... 

In an oil field, there always have been several wells which are produced or injected for several years, parameters such as pore pressure, temperature and stresses have been altered due to these production and injection wells. Having knowledge about the changes in mentioned parameters, new wellbores will confronts instability during drilling in high depth and sensitive layers. This thesis deals with the wellbore instability of sandstone formation with special focus on the effects of stresses and pore pressure changes caused by production and/or injection wells in the vicinity of the area that the new well would be drilled, to begin with the general assumptions and input parameters used in the... 

Instability means that when wellbore is out of circle due to any reasons in which it may be associate with fracture or falling of wellbore wall. Wellbore instability problem in production and exploration wells cause high costs over than 100 million dollars in all over the world in which these costs can be increased to 1 billion dollars so, necessary forecasts for preventing of instability is essential. Up to now, a lot of methods are suggested for investigation of wellbore instability, but in this study, analytical investigation with the help of triaxial tension is considered. Failure criterion and rock behavioral model are two important factors in wellbore stability modeling. In this study,... 

The acidizing operations have significant impact on productivity and production of oil and gas wells, so that wells having shell or regional damage are good candidates for well stimulation operations which could result in significant increase for efficiency or injectivity. Generally, the neural networks are nonlinear learning mathematical systems. In this project consists, At first, wellhead data of acidizing operation are collected in two Gachsaran oil field (38 wells) and Nar and Kangan gas field (35 wells). Generally, the neural networks are nonlinear learning mathematical systems. In the neural Network by using two algorithms, back propagation algorithm and Quick Propagation algorithm... 

In this study we investigated the stress effects on the fractured block in formation and its impact on flow through the matrix. At first the effect of various stresses on reduction of sample's pore volume and thereby reduction the permeability have been studied. The equations used to describe the elasticity relations in saturated matrix block is provided by Bayot theory. In this theory, the system of related equations to stress and strain changes have been developed in matrix. We have used finite element method in COMSOL software to solve the equation system created by elasticity relations in formation. After solving the equations, volume and volumetric strain changes which are caused by the... 

Red grape skin has a lot of antioxidant that called Anthocyanins. In this research this material has been studied and amount of extraction of them have been studied by changing the operational parameter and particle size in taguchi procedure. Pressurized liquid extraction (PLE) was used to extract Anthocyanins from Dried Red Grape Skin (DRGS) with acidified Ethanol solvent (1 %( v/v) of HCl) in 90-120°C, 10-40 bar, and 30 min extraction time. In this study, effect of particle size distribution of DRGS was considered and the results showed that with increasing the temperature (from 90 to 120 °C in 10 °C increments) and decreasing the pressure and particle size the extraction of Anthocyanins... 

In this project after literature survey, an endemic Iranian plant called Dracocephalum kotschyi Boiss. that have various medicinal properties has been selected. The essential oil of this plant has not extracted by supercritical fluid technology up to now and this is first work. In order to achieve the maximum yield and optimization of process five parameter in four level has been selected including: Pressure, Temperature, Carbon dioxide flow rate, particle size and dynamic time. For reduction of the number of experiment, Taguchi design of experiment (DOE) and its L16 orthogonal array has been used. Total yield of extraction in each experiment calculated by dividing the mass of produced... 

Green tea has been receiving significant attention in recent years due to its high content of catechins; Epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC) and especially epigallocatechin gallate (EGCG). As powerful antioxidants, these compounds are believed to have several health benefits. In this study, we used supercritical CO2 with ethanol as co-solvent to extract catechin derivatives from green tea and we investigated the effects of experiment parameters on the extraction. Experiments, designed according to Taguchi algorithm, were conducted with green tea particles of four average diameters of 1500, 855, 605 and 427.5 µm, in an interval of 35- 55 ̊C for temperature and... 

Nowadays, we know that many hydrocarbon reservoirs are fractured regarding this, the investigation of the properties of these reservoirs is necessary to predict the storage, production and the drilling methods. To identify fractured reservoirs, the fracture properties and their geometries under different conditions should be investigated. Besides, the evaluation of the behavior of induced fractures in distinct under ground conditions is very important. The Mechanical properties of the drilling bed like crack propagation, layer and mass rock is impactful in planning of drilling process and hydraulic fracturing operation. In this research, at first we introduce natural and induced fractures... 

Formation damage is defined as any process that reduses the reservoir permeability relative to its normal state. Two major causes of this problem are filtrate and solid invasion into the pore spaces of reservoir rock.Therefore, the drilling fluid used for drilling the reservoir sections should prevent such a problem as much as possible.The goal of this study is to optimize the weighting additive particle size distribution to prevent permeability damage in one of the southern Iranian oil fields. By analizing the capillary pressure data of core samples, it seems that fracture presence in rock matrix leads to poor quality of mudcake, resulting peremabilty reduction in near wellbore region.... 

Wear is the most important cause of surface damage occurs by direct contact of surfaces. Increasing the quality and strength of surface against different kinds of destructive phenomena is significant in manufacturing of mechanical parts. Surface nanocrystallisation can improve the surface protection against wear and can be done by lazer beam and shot peening. In this investigation by sever shot peening process the surface of A356 Aluminium alloy transforms to nanocrystal structure. The dry sliding wear and friction behaviors of A356 Aluminum were evaluated using a pin-on-disk apparatus at ambient conditions. The stationary diameter of 5mm stainless steel pin produced a wear track (scar) on... 

Regarding the increasing trend of network costumers and services, requirement of high-speed and high quality seems to be inevitable. Therefor much effort has been put to issue the problem properly in recent years. Optical fiber networks are attending more attention and optical fiber channels are dominating the world of networking and data. Applying new methods such as CDMA and OFDM raise the issue of maximum achievable rate and quality of these systems.These include the main concentration of this project. First, optical channels are modeled.Then, applying OFDM and CDMA methods, lower and upper bound of channel capacity will be determined  

Critical sets and defining sets in combinatorics have been attended by mathematics fans. These subjects have been debated since 1997 and a lot of researches have been done about them and a lot of articles have been published. But number of unsolved questions might be more than answered questions. In these years critical sets for Latin square and defining sets for vertex coloring have been attended and also enough researches about issues related to defining sets for edge coloring and total coloring have not been done. For these reasons we focus on these issues in this thesis. Issues like defining sets for edge coloring and total coloring in complete graphs, generalized Petersen graphs and also... 

Design of superconducting material based wide band radiation detectors has recently been attractive. Interesting features of detectors, which are based on Josephson Junctions such as high sensitivity in a wide range of frequencies and low power consumption, potentially have many advantages over other semiconductor-based photo-detectors. According to variety of applications of high-Tc superconductors, particularly YBCO, and significant progress in manufacturing of thin films and Josephson junctions, this thesis mainly focuses on investigation of radiation effects on I-V characteristics of high-Tc step-edge Josephson junctions experimentally. The current-voltage characteristics of fabricated... 

In this dissertation, Data analysis and information retrieval from incomplete observations are investigated in different applications. Incomplete observations may be induced by lack of observations or part of data affected by specific noise (quantization noise). Data-driven algorithms are among important hot topics. Our goal is to process the lost information inducing certain assumption on big data structures. Then, the approach is to mathematically model the problem of interest as an optimization problem. Next, the designed algorithms for the optimization problems are proposed trying to cut down on the computational complexity of as well as enhancing recovery accuracy for big data...