Sharif Digital Repository

Acidophilic microorganisms such as Thiobacillus ferrooxidans have the capability to carry out process of biorecovery of heavy metals. Its principle is the microbial production of the sulphuric acid and simultaneous recovery of metals. Acidithiobacillus ferrooxidans derives the energy for their metabolism from ferrous iron oxidation process which can be affected by the presence of heavy metals in the medium. In this study the ability of Acidithiobacillus ferrooxidans, on the biorecovery of heavy metals in shake flask has been investigated The adaptation of the Acidithiobacillus ferrooxidans to a kind of heavy metal such as Nickel, Cobalt, Vanadium, Molybdenum, Tungsten and the mixture of the... 

Foamy oil reservoirs and reservoirs which have water in oil emulsions have some difficulties through production with water based enhanced oil recovery techniques. Study of IFT of these oils may improve production of these reservoirs, especially for water based techniques which are most popular techniques. In this study, IFT of these oils were studied in reservoir condition. Effects of pressure, temperature and water composition were investigated. These effects were studied through Pendant drop technique and VIT apparatus  

In this thesis, A novel approach for ¼-rate clock Phase Detector (PD) structure for Phase Locked Loop (PLL)-based Clock and Data Recovery (CDR) is proposed. In this approach, the retimed data is generated within the circuit and no extra circuit is needed. Another advantage of this topology is that the error and reference signals are independent of delay time through gates and no extra replica circuit is needed to compensate the delay. This topology results in a lower power circuit and smaller area for high speed application compared to conventional topologies  

In the present work, large eddy simulation approach was employed to investigate flows such as backward facing step and internal channel flow, using Smagorinsky and explicit algebraic subgrid-scale models (EASSM) in OpenFOAM software. For this purpose, an explicit algebraic subgrid-scale model was added to OpenFOAM. Coupling pressure and velocity fields were applied to the PISO-SIMPLE (PIMPLE) algorithm. The focus of the present study was to assess various subgrid scale models, in order to predict the behavior of several flows, as well as their extensive numerical study. The results were compared to available experimental data showning that the EASSM results were more accurate than... 

Heavy oil reservoirs include a major part of the world’s oil reservoirs. Therefore consideration to their enhanced oil recovery (EOR) aspects has a great importance. In heavy oil reservoirs secondary and tertiary EOR methods, have an insignificant effect on oil recovery and so we’d better to use chemical methods to improve mobility and oil recovery. One of the appropriate EOR methods which has attracted a lot of attention is alkaline – surfactant – polymer (ASP) flooding which has a considerable impact on EOR from heavy oil reservoirs. In this EOR method, the low concentration of surfactant in the injecting fluid, results in a low or ultra-low interfacial tension (IFT) between residual oil... 

In oil industry, increment of drilling mud viscosity is of great importance. Water based polymers are widely use as drilling fluid to achieve this goal. Formation damages can be occurred by invading polymer solution into the formation in different ways such as scale and precipitation. These damages appear in different shapes such as reduction in relative permeability and productivity index reduction. In this study we have proposed, designed and fabricated a novel device, called sand pack, to measure the damage of the reservoir which enable us to calculate relative permeability and recovery factor by means of pressure difference and flow rate. Using this lab-scaled device we have measured... 

FE simulations have been widely used to investigate the response of the brain tissue in various circumstances. The accuracy of the material models critically affects the results of the numerical simulation. However, despite the numerous studies aiming for the material modeling of the brain, there is still divergence between the results reported in the literature. A part of this discrepancy is due to the inherent difference between samples. Nonetheless, another part of it is resulted from the differences between testing protocols used by researchers. In some protocols multiple mechanical tests are performed on each sample. Enough recovery time should be considered between consecutive test... 

The objective of this MSc. thesis is to study the impact of the reactive method and the enhanced reactive method on enhancing the exploitation efficiency of Iran's offshore oil reservoir. This is achieved by enhancing production and the recovery factor of the reactive methods with respect to the currently used proactive method. Unlike the currently used proactive method that implements a fixed rate injection strategy, in this MSc. thesis water is injected to reservoir with multi-rate for the pressure stabilization of the reservoir. In order to scale up this strategy, the ensemble Kalman filter is used to frequently update the reservoir mathematical model using the available measurements from... 

Recovery of low-rank matrices from compressed linear measurements is an extension for the more well-known topic of recovery of sprse vectors from underdetermined measurements.Since the natural approach (i.e., rank minimization) for recovery of low-rank matrices is generally NP-hard, several alternatives have been proposed. However, there is a large gap between what can be achieved from these alternatives and the natural approach in terms of maximum rank of the unique solutions and the error of recovery. To narrow this gap, two novel algorithms are proposed. The main idea of both algorithms is to closely approximate the rank with a smooth function of singular values and then minimize the... 

The combination of photovoltaic technology and Organic Rankine Cycle reduces the temperature of the solar panel and, on the other hand, generates separate electricity from excess heat. The reason for the use of the Organic Rankine Cycle is the low temperature of the heat source. It is not economical to use other cycles like steam Rankine cycle in low-temperature heat sources. To maximize the plant factor of the Organic Rankine cycle system, especially when there is not enough solar radiation, it is possible to utilize the flue gas heat recovery in office buildings and reduce the cost of electricity generation. In this project, the simulation of this system is carried out for the Energy... 

Evidently, environment contamination by water insoluble chemicals present at the industrial wastes could bring about catastrophic consequences to the biosphere. Biological based cleaning technologies are commonly considered as a practical remedy to remove these contaminations. In fact, these techniques are founded on the ability of certain microorganisms to degrade the contaminants. It is crystal clear that the availability of contaminants to the microorganisms is an essential parameter determining the final efficiency of the biodegradation process. In practice, the limited solubility of the contaminants in the aqueous phase leads to mass transfer constraints which consequently, decrease the... 

Gas injection process is one of the main methods to increase the hydrocarbon reservoirs. Minimum Miscibility pressure is a key parameter that controls the efficiency of the gas injection process. It depends on the temperature, the composition of the injected gas and the composition of the reservoir fluids. In this study, the interfacial tension of the live oil-gas system of one of the reservoirs of southwestern Iran was obtained by analyzing the Pendant drop method at 225 ° F and different pressures, and then by using the Vanishing Interfacial Tension method, the Minimum Miscibility Pressure has been computed .In this study, pure and base gases such as nitrogen, methane and injection gas of... 

In this thesis the resilience of a neural network is examined under structural perturbation.The network consists of Spiking neurons with specific dynamics or they are binary neurons and the network is non-spiking. Neural network is a multi-dimensional and multi-stable system therefore we can map their dynamical equations to effective one-dimensional equation with one parameter which shows the environmental conditions.The resilience of the system is evaluated with respect to changes in weights and edges of the network and the the resilience pattern of the system is obtained.Finally, the recovery and control methods are briefly discussed  

In the contemporary pursuit of sustainable energy solutions to address the escalating demand for electrical power, a crucial focus lies on the exploration of renewable energies and the harnessing of wasted energy in industrial processes. This research contributes to this imperative by investigating active cooling methods, specifically employing jet impingement and spray techniques, for the cooling of thermoelectric generators and the recovery of wasted heat. The study empirically assesses three distinct cooling approaches, encompassing a heat pipe relying on free convective heat transfer with air, a heat pipe cooled by water jet impingement, and a heat pipe incorporating spray application.... 

In this research, a comprehensive examination on hot and cold deformation of Al-Mg6 alloy has been performed. In order to find out hot deformation behavior of Al-Mg6, hot compression tests at 350, 450, and 550 oC and at strain rates of 0.001, 0.1, and 1 s-1 have been carried out. After the correction of the curves due to friction and adiabatic heating effects, constitutive equation of this alloy has been derived. Corrected curves show the occurrence of dynamic recovery. A new method for developing strain dependent constitutive equation has been employed using normalized stress and strain curve. After normalization, the curves at all deformation conditions follow a similar behavior.Rolling of... 

Twin intake is a new version of intakes for supersonic fighters with high performance. Investigations on these types of intakes show that with some modifications in design procedure and modifying the desired parameters, one could result in an intake compatible with the body and nose of the fighter with high efficiency. In this investigation the results of experiments on a supersonic air intake which is designed for 1.7 Mach number at angles of attack ranging from -4 to +6 degrees are presented. The main goal of this investigation is to analyze the effect of angle of attack on the performance of the intake in design and off-design conditions. In order to reduce the boundary layer thickness... 

The consumption of fossil fuels (oil, gas and coal) increased the concentration of greenhouse gases in the atmosphere that cause increase of earth atmosphere temperature and lots of environmental problems. Using appropriate alternative energy sources is one way to control this emission, while considering energy infrastructures shows this is a far solution. An early way for decreasing the emission of greenhouse gases in the atmosphere is injection of CO2 in geological formations. Since approximately 50 years ago some researches in this area have been developing. The most important limit of these projects is its costs so it is wise to combine them with gas injection projects in gas and oil... 

Nowadays, due to limitation of production from conventional oil reservoirs, enhanced recovery from heavy oil reservoirs are of great concern. In heavy oil reservoirs, only 5% of initial oil in place (IOIP) is producible due to high viscosity. Water flooding increases oil recovery just up to 10% which is due to improper mobility ratio. One of popular methods for increasing oil recovery is injection of chemical materials. Chemical methods are used in reservoirs that have high degree of heterogeneity like heterogeneous and layered reservoirs. These heterogeneities cause diversion and loss of injected water which leads to remaining of oil in its place. Using surface active agents, as a popular... 

Heat sources with temperatures less than 100 °C are available in various processes in the form of waste heat and from renewable sources such as solar energy. One of the methods of gaining benefit from these ubiquitous and abundant heat sources is using thermal harvesters that convert low-temperature heat into electrical energy without the need for the power grid. Portable harvesters can be a reliable and low-cost option for providing stable energy for low-power electronic devices such as wireless sensors. Many studies have been conducted at the global level to design and develop efficient low-temperature heat harvesting mechanisms. However, each of them is associated with fundamental... 

Embedded systems are employed as crucial control components in safety-critical and real-time areas such as medical devices, automobile, and aviation. To maintaining the dependability of such applications, several fault tolerance techniques have been proposed in the recent decades.In the recent years, the improvements in the performance of hardware devices lead to excessive attentions to software fault tolerance techniques. The software fault tolerance techniques can be implemented at the application code or operating system of an embedded system. Applying the fault tolerance techniques in operating system allow the designers to develop their application without worrying about the...