Sharif Digital Repository

To investigate boiling heat transfer characteristics of nanofluids, transient quenching¬ experiments of a high temperature silver sphere in water-based nanofluids with Ag and TiO2 nanoparticles were performed. A silver sphere of 10 mm in diameter at the initial temperature of 700o C was quenched in the nanofluids at the temperature of 90o C. The results showed considerable reduction in the quenching ability of nanofluids compared to that of pure water. The presence of nanoparticles in water caused film boiling mode to vanish at lower temperatures depending on the mixture concentration. Computed heat transfer rates in nanofluids were lower than those in pure water. In the quenching... 

Although the differences between retail and institutional investors in the stock market can have important effects on key processes such as liquidity and price formation in this market, there are significant differences of opinion about how these differences would affect mentioned processes. An interesting question for financial researchers is how the effects of different groups affect the liquidity of the stock market. Liquidity is defined as the ability to carry out transactions with high speed, low cost and without being heavily influenced by the price. In this research, using 10-year stock information (2012-2022) such as order book, price and volume of transactions, we showed that the... 

One of the major issues raised in the numerical models is the effects of various input parameters on the model output. Identifying the most important parameters in the output is very important in petroleum engineering, especially in tuning equation of states and history matching. Screening the most important parameters from unimportant parameters is assessable by sensitivity analysis.In this study local and global sensitivity analysis methods are used to identify the most important parameters in tuning EOS for seven different fluid samples. Global sensitivity analysis methods are more successful in correct ranking of tuning parameters. Morris method as a global method can screen the... 

Due to popularity of mobile wireless devices, security of mobile ad hoc networks (MANETs) being more important than before. Traditional key management schemes based on symmetric key cryptography are became ineffective because of dynamic and infrastructureless nature of these networks.Recent studies are mainly based on traditional public key cryptography schemes and ID-based cryptography schemes. On the other hand, Contributory schemes seem suitable for MANETs because of their inherent self-organize property. Key update and Key revocation are the fundamental issues of key management schemes in mobile ad hoc networks. Certificateless public key cryptography, in addition to solve those issues,... 

One of the most important issues in modeling and simulation of reservoirs is determination of different rock types or Rock Typing. In this study, after a brief review of some conventional methods for rock typing, their capabilities have been investigated. In this way, for the first time, pore network modeling is used as a tool for validating the rock typing methods. By using flow simulation in porous medium with pore network modeling approach, similar rock types data have been generated and these artificially data have been used for validating of rock typing methods. To form more realistic pore networks, both regular and irregular pore network have been modeled and analyzed. Pore size... 

Alavand Oil field is located 50 Km away from west of Siri Island and includes DPG and DPH platforms. The production from Alavand field started in 1998 and till now 11 wells have been totally drilled .Since a production peak in 2001, the oil production in Alvand field has decreased. Water cut is increasing and reservoir pressure is decreasing gradually. Considering poor reservoir characteristic of this reservoir, productivity indexes of wells are relatively low. In addition; natural depletion of reservoir caused the wells to be unable to flow naturally and either closed or produce periodically consequently. To increase production and extend the lifetime of Alvand field, it is decided to start... 

Matrix acidizing aims at bypassing near wellbore damages in typical carbonate reservoirs or enhancing permeability and hydraulic conductivity in naturally fracture ones. The simulation of acidizing process at pore scale and complex geometries by LBM will lead to gain more knowledge about molecular mechanisms that govern rock dissolution, diffusion and advection of reactive fluid and help the evaluation of acidizing efficiency.In this thesis, simulation of acidizing includes the following steps:
• Multicomponent fluid convection
• Fluid diffusion into the solid
• Fluid-rock reaction
• Boundary conditions including periodic, bounceback, non-equilibrium bounceback, Dirichlet,... 

In particle physics, spontaneous chiral symmetry breaking generates new phases of quark matter, and leads to significant changes od quark masses. The Nambu-Jona–Lasinio (NJL) model is a useful fermionic model which describes the spontaneous chiral symmetry breaking through the creation of a condensate. This model can be for instance used to determine various phases of Quantum Chromodynamics (QCD) in finite electromagnetic fields. This work consists of several parts. First, we describe the spontaneous chiral symmetry breaking in detail. Second, we extract the NJL model from the Lagrangian density of QCD. Third, we derive a covariant form of the partition function of a fermionic system.... 

Drilling Operations constitute more than fifty percent of total costs of well construction operations. Due to this fact, optimization of drilling operations could have significant effect on decrease in total costs of well construction. It is mentioning worthy that there are a variety of parameters which affect drilling operations from the view point of optimization. In many cases several of those aforementioned parameters are contrary in nature. Thus obtaining an integrated approach to optimize the operation by considering these effects is necessity. The goal of this thesis is to investigate different influential parameters of drilling operation optimization and to develop computer-based... 

Large amounts of relief resources such as water, tents, medical equipment and fuel after a major disaster need to reach the affected people. Satisfying the needs of victims is crucial to the success of crisis relief operations, as a lack of relief resources can lead to the suffering and loss of lives of victims. According to studies, large-scale catastrophes have occurred frequently in recent years. Therefore, it is necessary to pay more attention to the management of post-crisis resources. Since the distribution of emergency resources depends largely on the efficiency and effectiveness of logistics operations, the primary objectives include minimizing logistics time and cost, minimizing... 

Scale formation is an unpleasant phenomenon that occurs when the mixed fluids are incompatible. The scales damage the reservoir, wellbore and the surface facilities. They reduce the effective fluid path and increase the pressure drop of the system; so it is necessary to study the precipitation thermodynamics of scale formation, and present a trustable method for banning the scales from precipitation. In this project, it has been tried to study the value of precipitated scale due to the mixing of two incompatible waters (Civand and Sea Water). The results of which are compared with the results of a geochemical software named PHREEQC. Then, the performance of hydro chloridric acid as a scale... 

The main responsibility of a primary cement job is to provide hydraulic isolation between various zones. Cement-sheath evaluation is concerned with the question of whether zonal isolation exists. Cement Evaluation Logs are used to evaluate the quality of cement sheath behind the casing or liner after cement job. these logs are a part of well integrity logs. Cement Evaluation Log results are complex and can be misunderstood, and it can lead to bad decisions that could have severe consequences. Cement evaluation logs must therefore be interpreted by experienced professionals. To help these interpreters, we propose a system for automatically interpreting cement evaluation logs, which they can... 

In today's era, metal nanoparticles play an important role in technologies emerging from different sciences, such as chemistry, physics, optics, material science, due to their unique characteristics. In the development of nanooptics science, it can be said that metal nanoparticles play an important role. The ability of conductive electrons collective oscillation causes surface charge density fluctuations in nanoparticles, this phenomenon is known as surface plasmons. Surface plasmons are surprisingly coupled with light and cause the significant increase in the intensity of optical fields induced in nanoparticles. Therefore, with the presence of localized surface plasmons or plasmon... 

Underbalanced drilling is a type of drilling operation in which the pressure of the drilling fluid is less than the pressure of the formation. This pressure difference has created advantages for this method. Less formation damage, reduction of pipe stuck, increasing rate of penetration and production during drilling are the advantages of this method compared to traditional methods. To reduce the pressure of the drilling fluid, very low density fluids should be used. One way to reduce density is to mix a compressible fluid such as gas into water. Due to the difference in density and surface tensile strength of water and gas, these two phases do not combine, so a stable combination of these...