Sharif Digital Repository

The growing use of nanomaterials leads to causing harm to the aquatic environment resulting in a demand for effective methods to remove these nanomaterials from aquatic environment. On the other hand, the high cost of raw materials used for the production of noble metal nanomaterial limits their use or requires the development of recycling and recovery methods. In this study, we found that citrate capped gold nanoparticles (cit-AuNPs) could be removed effectively from waste water using aluminum chloride (AlCl3) coagulant. The effect of pH, of coagulant concentration, and alkalinity on the performance of this coagulant was investigated. It has... 

One of the most significant problems of oil regions is salinity of the produced water extracted from the well. Penetrating the produced water through the surrounding environments of the oil well in recent years, plenty of environmental problems, especially agricultural ones have been caused in these areas. According to the increasing trend of water salinity during the time, one of the urgent action in the oil industry of the country should be finding a way to reduce the amount of dissolved salt in the produced water. The purpose to this project has been representing a more appropriate configuration for desalination of the produced water. Therefore, the water sample containing less than 70000... 

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... 

Off-gas flows in refineries normally consist of hydrogen, methane and heavy hydrocarbons which are burnt in flare. While the demand for hydrogen in refineries is increased and the required hydrogen is provided by steam reforming or partial oxidation of methane or other hydrocarbons, recovering the hydrogen from off-gasses can reduce the refineries losses and optimize it economically. The four main processes for hydrogen recovery unit are the Pressure Swing Adsorption process, Membrane process, Cryogenic process, and absorption process. In the present project besides, considering the process flexibility, reliability, and refinery off-gas properties such as pressure, temperature and mole... 

One of the issues that today is considered by planners and system operators in power systems, especially the Iranian power grid, is the high variation and the lack of uniformity of load curves in different hours of the day. This has led to the use of all installed capacity of the country's production only in peak hours, and in the low and intermediate times, a large amount of installed capacity is out of the circuit, which means Unused capital. This problem is more or less seen in world power networks with high load variation curves. Also, the production of renewable energies has always been fluctuating, and the production of power control to improve this fluctuation is very important. This... 

This study proposes a probabilistic framework to quantify the seismic resilience of urban natural gas distribution networks. Infrastructure resilience is defined as the ability to maintain performance after a hazard or, in case of a loss of performance, return to the minimum desired level in the optimal time. The framework presented in this research is comprised of multiple interconnected probabilistic models. These models work in harmony to characterize the impact of the earthquake on various infrastructures such as the buildings and urban gas distribution network components, as well as the probable consequences of the earthquake. The post-earthquake recovery of the gas distribution network... 

In this work, annealing procedure of cold-deformed AA5052-SiC composite has been simulated by using cellular automata approach and the effect of SiC second phase on softening kinetics has been studied. To do so, site saturated nucleation has been employed to establish initial microstructure. In addition, topological changing due to deformation has been implemented on the microstructure. During annealing, recovery and recrystallization phenomena occur simultaneously, and it has strong effect on the annealed microstructure. Therefore, during annealing, recrystallization and recovery has been considered simultaneously and decreasing in the stored energy, which has developed during deformation... 

Determining the time of breakthrough of injected water is important when assessing waterflood in an oil reservoir. Breakthrough time distribution for a passive tracer (for example water) in percolation porous media (near the percolation threshold) gives insights into the dynamic behavior of flow in geometrically complex systems. However, the application of such distribution to realistic two-phase displacements can be done based on scaling of all parameters. Here, we propose two new approaches for scaling of breakthrough time (characteristic times) in two-dimensional flow through percolation porous media. The first is based on the flow geometry, and the second uses the flow parameters of a... 

In competitive markets where a product or service is provided by multiple providers, as the telecom market, keeping active users is expected to be less expensive than attracting new users. In this regard, first of all, churning should be predicted for active users, and secondly, proper recommendations should be provided to prevent churning. In this thesis, by modeling customer churn as a response to the recommendations, we study the churn prediction and prevention problem as a recommender system. This model enables us to select the best offer for each user to prevent it from churning.Modeling customer churn in a recommender system introduces new challenges, including delay in observing... 

Once a well has been drilled before it is cased with the steels (open-hole well), some logging must be done to record information’s about layers, geologic formations, geophysical and petrophysical properties of well. All the information’s that gathered from sensors and tools transmitted to the surface by a down-hole modem. This information is corrupted during the transmission by the communication channel. The most notable influence of this channel is noise, attenuation and interference between successive data bits. On the other hand, the characteristic of channel changes with the length of the cable, temperature, connections and so on. So using a set of fixed filters is not effective. The... 

Increasing complexity of modern embedded systems has caused tasks with different criticality levels to run on a shared hardware platform, called mixed-criticality systems. In these systems, it is important to use fault tolerant techniques to achieve reliability targets. Moreover, the limited battery life in many applications and real-time requirements make energy-aware reliability management and guaranteeing deadline constraints a major challenge. Checkpointing with rollback recovery is a good option to ensure reliability of these sys- terns because of its low cost and relatively low time overhead. However, improper use of this technique can impose high energy overhead and cause deadline... 

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 emerging field of compressed sensing has found wide-spread applications in signal processing. Exploiting the sparsity of natural image signals on basis of a set of atoms called dictionary, one can find numerous examples for applications of compressed sensing in the field of image processing. One of these interesting applications is to help recover missing samples of a damaged or lossy image signal which is also known as image inpainting. There are dozens of reasons why an image may get damaged, for instance, during data transmission, some blocks of an image (or frames of a video ) may get lost due to error in the telecommunication channel (this is known as block-loss). In this case image... 

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... 

In recent years, carbon dioxide is used for enhanced oil recovery of heavy oil. Steam Huff and Puff is one of the enhanced oil recovery methods used for heavy oil. In this study liquid CO2 was used as an injecting fluid instead of steam. In this paper a series of experiments were performed to demonstrate the effect of carbon dioxide injection pressure on huff and puff process. The experimental data are used in lab scale model simulated with commercial simulator Eclipse 300 to investigate the effect of soaking time, injection pore volume and rate of injection on the heavy oil recovery. Result of experiments showed that huff and puff process under miscible pressure condition gives the most... 

The gas injection is one of the most common methods of increasing recovery from oil reservoirs, especially when a suitable source for gas is available. For example, available sources of carbon dioxide or associated gas produced from the reservoir or adjacent reservoirs. In general, the gas injection may be miscible or immiscible, which is a function of the type and composition of the gas-oil and the reservoir conditions in terms of temperature and pressure. In miscible gas injection, different mechanisms such as molecular diffusion of gas in oil or evaporation of lighter components of oil in gas and condensation of heavier components of gas in the oil phase can be shown. To occur of such... 

Results showed that 9 factors of “Brand Equity”, “Product Quality”, “Service Quality”, “Service Recovery”, “Perceived Value”, “Relationship”, “Employee Satisfaction”, “Physical Environment” and “Distribution Channel” are most effective factors by researchers that have effect on customer satisfaction. Thus, the Macromodel of this research was designed based on these factors. Due to limitations and context of the research, “Service Quality”, “Service Recovery” and “Relationship” were chosen in the final model. Results of questionnaire showed that the 5 parameters of “Service Recovery Speed”, “Reliability”, “Responsiveness”, “Empathy” and “Seller-focused antecedents” was the most important... 

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... 

Nowadays, application of ultrasonic wave technology as a novel method of enhancing oil recovery and also gas an oil well stimulation is prevailing. Not only this method is environment friendly, but also it is economic. Although the application of this method is proved to be of outstanding positive influences in field operations, it suffers from lack of knowledge about the main governing mechanisms and also there are few mathematical models describing the process. In this study it is intended to investigate the role of ultrasonic waves on rate of recovery and the total recovery from porous media. A model is proposed which can predict the recovery at different times of operation. The results... 

Ground Source Heat Pumps (GSHP), as a renewable source heating, ventilating, and air conditioning (HVAC) technology, has the highest energy efficiency among different heat pump types. One of the major drawbacks of GSHPs is the long-term ground temperature variations as a result of heat accumulation or depletion in the ground. This contribution puts forward a novel ground thermal recovery system for horizontal ground heat exchangers in a hot climate. The proposed recovery system consists of open-loop horizontal Ground-Air Heat Exchangers (GAHEs) that are buried between the horizontal Ground-Water Heat Exchangers (GWHEs). A fan supplies ambient air to the GAHE pipes when the soil around GWHE...