Sharif Digital Repository

Nowadays evolutionary algorithms help developers to solve many problems in applied science and engineering aspects. So the main goal of this thesis is to apply and verify the ability of evolutionary algorithms and artificial neural networks in optimization of Ethane recovery unit. Algorithms applied in this study are Ant Colony Algorithm, Artificial Immune Systems Algorithm, Incremental Evolutionary Algorithm, Chaotic Based Algorithm, Variable Population Size Genetic Algorithm, Frog Leaping Algorithm, Frog Leaping with Bacterial Optimization Approach and Different types of Particle Swarm Optimization Algorithm. Optimization methods based on local search are also applied in order to compare... 

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... 

Heterogeneity is one of the challenges in the current NoC (Network-on-Chip) domain which oblige designers to consider less regular topologies to provide the best cost-performance trade-off while minimizing resource and power consumption and providing the maximum flexibility. Irregular mesh is a topology which combines the benefits of regularity and advantage of irregularity. Another important issue in any NoC is the selection of routing algorithm which provides the best performance. Routing algorithms especially those coupled with wormhole switching should deal with deadlock occurrences. Deadlock detection and recovery-based routing schemes for this type of switching gained attraction since... 

The ever increasing usage of modified binders in road construction requires that the effect of different modifiers on the performance characteristics of the asphalt binder be determined through laboratory testing. The current Superpave protocol for performance grading asphalt binders has proven to be insufficient to properly characterize modified binders, thus researchers have searched for other testing methods to complement or possibly replace some of the Superpave tests. Most notable are the time sweep test for fatigue resistance, the multiple stress creep and recovery test (MSCR) for rutting resistance and the direct tension test (DTT) for low temperature cracking characteristics. In the... 

Relative permeability is an important factor that controls the two phase fluid flow in porous media. The use of carbon dioxide in enhanced oil recovery methods is common. But the question is, how does the carbon dioxide affect the relative permeability curves? In this thesis, the CO2-oil relative permeability is measured in CO2 flooding process with unsteady state method. For this purpose, the core flooding apparatus is used and the results are compared with N2-oil relative permeability in N2 flooding. The results of comparison show that oil relative permeability in CO2 flooding is higher than N2 flooding. Reduction of Interfacial tension and oil viscosity, solubility of CO2 in oil and oil... 

Hard real-time embedded systems often operate in harsh environmental conditions that necessitate fault tolerant computing techniques. These embedded systems are also energy-constrained, since energy consumption is one of the key objectives. Examples include satellites, surveillance systems, autonomous seaborne and airborne systems. Generally, fault tolerance is obtained by hardware or time redundancy in these systems. Checkpointing with rollback recovery which employs time redundancy is one of the common techniques for tolerating transient faults in real-time embedded systems. Using checkpointing in energy constrained hard real-time systems should be carefully employed. In this thesis, we... 

During the various stages of uranium processing in Uranium Conversion Facility (UCF) in Isfahan, significant amounts of liquid waste stream is produced which is sent to evaporation ponds. In addition to environmental considerations, uranium recovery from existing pools is also economically feasible due to high concentration uranium in liquid waste. Several methods have been evolved over the years to remove dissolved uranium from uranium bearing solution. These methods are: chemical precipitation, liquid-liquid extraction, ion exchange and membrane processes. The purpose of this study is recovery of uranium from liquid waste of Isfahan UCF plant by using ion exchange method. Although this... 

Streaming video over the Internet has become popular in recent years. There are also popular solutions for data delivery, but these approaches are very inflexible and unpleasant because no appropriate error recovery technique isprovided in the application level of these systems for multimedia contents. In the past few years numerous error resilience Peer-to-Peer (P2P) systems have been introduced but still there is no fully dynamic error recovery technique. In this thesisthe researcher proposed a frame-based hybrid FEC-ARQ (Forward Error Correction – Automatic Repeat request) error recovery in Variable Bit Rate (VBR) video streams based on the network situation in a way that before... 

The effects of biosurfactants on sandstone rocks are known in the literature. However, there are few examples of experimental works in Iranian carbonate reservoirs dealing with the effects of biosurfactants under reservoir conditions. This thesis discusses the effect of an efficient biosurfactant produced from Pseudomonas aeroginosa MRo1, a bacterial strain isolated from oil excavation areas in southern Iran, on the recovery of residual oil trapped within carbonate rocks was investigated. The MRO1 could reduce surface tension from 72 to 28 dyne/cm. It also could reduce Interfacial tension from 18.382 to 5.646 dyne/cm.
In a core holder set-up bearing four limestone- and... 

Error concealment is one of the effective ways to alleviate the effect of packet loss in video communication over error-prone environments. In order to estimate lost macro-blocks, we have employed Bayesian estimation as an efficient and robust framework. Gaussian process regression has been used as the modeling approach through this framework. Considering luminance component as Gaussian process,a minimum mean squared error estimation of the lost macro-block is obtained. This estimator, as a function of the existing data, is only determined by the covariance matrix defined over them. Therefore,the main step in Gaussian process regression, is construction of the convenient covariance matrix... 

This thesis studies the economic feasibility of replacing a throttling valve with an expansion turbine in a city gate station for the purpose of distributed electricity generation through exergy recovery from pressurized natural gas. Conventionally, high pressure natural gas stream enters a pressure reduction station with its physical exergy completely destroyed in an irreversible Joule-Thompson effect of a throttling valve. To avoid hydrate formation at the outlet of the turboexpander, the inlet stream should be preheated. Although pressure reduction stations are inherently subject to seasonal fluctuations of inlet natural gas pressure and flow rate, the preheating temperature should be... 

Compressor stations with gas turbine drive have become common in transport of natural gas. However, the thermal efficiency of the gas turbines used in these stations is low. One reason for this is that 70% of the heat of combustion of the fuel gas used by the gas turbine is lost with its exhaust gases. Hence, heat recovery from gas turbine exhaust gas would increase the cycle efficiency by decreasing the fuel gas consumed. On the other hand, gas turbine efficiency highly depends on the climatic conditions of operation. Among several well known methods of performance improvement, the use of an absorption chiller for inlet air cooling has been studied from both process and economic points of... 

There are a lot of Fractured reservoirs around the world that have large portion of oil production. These reservoirs have complex structure and fractures have important role in production but the remaining oil in matrix causes that the oil recovery decreases. One of the most important factors in these reservois are wettability. Because most of the fractured reservoirs are oil wet and water injection process in these reservoirs are not effective and chemical EOR methods such as surfactant flooding method is used. Surfactant improve oil recovery by two reasons: 1- reduction of interfacial tension between oil and water . 2-Wettability alteration of matrix. The porpose of this project is... 

During various stages of processing uranium in Uranium conversion facility (UCF) in Isfahan, significant amounts of liquid waste is produced which leads to evaporation ponds. Since the concentration of uranium in evaporation ponds is relatively high, it seems to addition to environmental issues with recycled uranium from existing pools is also economically. Various physical and chemical methods for removal of uranium waste is used such as solvent extraction, ion exchange, chemical precipitation, membrane processes, etc. Each method has advantages and disadvantages. The ion exchange method, The due to lower cost, less acid pollution with organic copmpounds, convenience and high selectivity... 

After primary and secondary recovery processes more than 50 percent of oil remains in reservoirs. Therefore for more recovery from these reservoirs, methods of enhanced oil recovery should be applied.In this paper the effect of nanoparticles of SiO2 in size of 14 nm, on wettability is investigated. Using this nanoparticle, the wettability of carbonate rock in reservoirs could be changed and alter from oil-wet or mix-wet to water-wet. To assess this, hydrophilic changes of sandstone core and carbonate core are studied using the contact angle test. The same test is done on the carbonate core saturated with brine and oil that had received injection with brine and nanoparticles of SiO2 with two... 

Binder modification, to improve the rheological properties and meet the standard requirements, is a common practice. The modification is usually done by adding polymers like Ethylene Vinyl Acetate (EVA) and Styrene Butadiene Styrene (SBS), waste materials like crumb rubber, or acids like Poly phosphoric acid (PPA) or by air blowing techniques. High temperature rheological properties of modified binders are usually improved by using polymers while the low temperature rheological properties mostly depend on the original binder. Therefore, the rheological properties at low temperatures do not show clear improvements in the modified binder compared to the original binder. This indicates that a... 

Today, due to limited number of light oil reservoirs, enhanced recovery from heavy oil reservoirs is taken into consideration. During the early production from heavy oil reservoirs, due to high viscosity, only a small amount (about 5%) of the oil can be produced; also after water injection operation due to unfavorable mobility ratio of water and oil, sorely more than about 10% of the original oil can be produced. On the other hand, fractured reservoirs represent about 20% of the world's oil reserves, while over 60% of the world's remaining oil reserves are in fractured reservoirs. Water flooding process leaves very high amounts of oil as remaining oil in these reservoirs too. One of the... 

Uranium is the most important element in the nuclear fuel cycle. Recovery of uranium from waste produced at every stage of the fuel cycle is not only economically important, but also environmentally important. In the production phase of uranium hexafluoride, certain amount of solid waste is produced in the bottom of the fluorination reactor. In order to extract the uranium from this waste, we have to eliminate the fluorine contained in the waste. This is because the fluorine forms strong complex with uranyl ions during the extraction process, and prevents from efficient extraction of uranium. In the current thesis؛ first, we examined the characteristics of the waste ... 

The aim of this project is Industrial Solvents (White Spirit) producing in Tehran Refinery. For this manner “Wild Naphtha” from Gasoil Hydrotreater and Kerosene Hydrotreater Units was chosen as feed stock for solvents preparation. In addition, Pentane Recovery Column is selected for Simulation and Optimization based on Wild Naphtha. As a Result, Abadan White Spirit 402 and 410 has been produced and a side stream which is full of Aromatic is obtained. Simultaneously, Tray Hydraulics and Solvents production in different cases (Various Pressure and different Split Ratio of Feed Stock) are evaluated, so optimum Tower process conditions such as pressure, Temperature and Split Ratio of Feed Stock... 

In this thesis, scheduling of surgery rooms is investigated and the objective is minimizing total patient’s departure time from the ward room in a flexible flow shop manner. Here, some constraints like the capacity of recovery rooms, no-wait motion between the rooms and machine eligibility restrictions ( , Σ ) are considered.For solving this problem,we proposed two mixed integer linear programming models for the research problem. Since the research problem is shown to be NP-complete, we developed several algorithm based on Tabu Search (TS) to heuristically solve it. In TS algorithm two different methods and one neighborhood structures are applied to generate initial solution and...