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Study and Practical Solutions to Reduce the Heat Load Air Cooler in unit 200 Bouali Sina Petrochemical Co. to Reduce the Flaring

, M.Sc. Thesis Sharif University of Technology Mohebbifar, Majid (Author) ; Farhadi, Fatollah (Supervisor)

Abstract

Inappropriate performance of the air-cooled condensers in the process industry will make the flow out of the air cooler not fully condensate and its pressure is greater than the design value. This will lead to product loss and safety issues. In this study, factors affecting the performance of air cooler and various solutions to solve these problems have been identified. As a case study, the first distillation tower of the Ali Siana Petrochemical Complex, which disrupts its function in some months of the year, has been investigated. Aspen Hysys process simulation software simulates the naphtha splitter unit and the Aspen Exchangers Design & Rating software simulates the air cooled condesor...

Experimental investigation of nano-biomaterial applications for heavy oil recovery in shaly porous models: A pore-level study

, Article Journal of Energy Resources Technology, Transactions of the ASME ; Volume 137, Issue 1 , August , 2014 ; 01950738 (ISSN) Mohebbifar, M ; Ghazanfari, M. H ; Vossoughi, M ; Sharif University of Technology

American Society of Mechanical Engineers (ASME) 2014

Abstract

Application of nano or biomaterials for enhanced oil recovery (EOR) has been recently much attended by petroleum engineering researchers. However, how would be the displacement mechanisms and how would change the recovery efficiency while nano and biomaterials are used simultaneously is still an open question. To this end, a series of injection tests performed on micromodel containing shale strikes. Three types of biomaterials including biosurfactant, bioemulsifier, and biopolymer beside two types of nanoparticles including SiO2 and TiO2 at different concentrations were used as injection fluids. The microscopic as well as macroscopic efficiency of displacements were observed from analysis of...

Experimental Study of Nano-bio Material Injection for Heavy Oil Recovery in Shaly Systems Using Micro-model Apparatus

, M.Sc. Thesis Sharif University of Technology Mohebbifar, Mahdi (Author) ; Vossoughi, Manouchehr (Supervisor) ; Ghazanfari, Mohammad Hossein (Co-Advisor)

Abstract

In this research we aim to find enhance oil recovery mechanisms involved in nano-bio material injection by micro model apparatus which has not been studied before. Especially for injection in heavy oil and shaly porous media that forms most of heavy oil reservoirs. To this end, microscopic images from injection of nano-bio materials to shaly patterns have been taken and analyzed to find the process mechanism. Also amount of enhance oil recovery in different conditions like type of microbe forming bio material, nano-bio material concentration and type of flow pattern (shale characteristics including length, direction and distance from injection and production wells) will be studied.Three...

MBBR and MBR Reactor Configuration for Better Performance

, M.Sc. Thesis Sharif University of Technology (Author) ; Borgheei, Mahdi (Supervisor)

Abstract

Membrane bioreactors (MBRs) which are commonly understood as the combination of membrane filtration and biological treatment using activated sludge have several advantages, but membrane fouling reduces the membrane efficiency, permeability and lifetime. An alternative is replacing a moving bed biofilm reactor (MBBR) with the activated sludge system which may reduce the effect of membrane fouling. The sludge produced in MBBRs has poor settling characteristics, therefore, their efficiency is limited by the sedimentation tank performance and they require a larger settling surface. The combination of moving bed biofilm reactors and membrane bioreactors can compensate for the drawbacks of both of...

Forecasting the effects of a Canada-US currency union on output and prices: A counterfactual analysis

, Article Journal of Forecasting ; Volume 32, Issue 7 , 2013 , Pages 639-653 ; 02776693 (ISSN) Mahdi Barakchian, S ; Sharif University of Technology

2013

Abstract

This paper is a counterfactual analysis investigating the consequences of the formation of a currency union for Canada and the USA: whether outputs increase and prices decrease if these countries form a currency union. We use a two-country cointegrated model to conduct the counterfactual analysis, where the conditional forecasts are generated based on the Gaussian assumption. To deal with structural breaks and model uncertainty, conditional forecasts are generated from different models/estimation windows and the model-averaging technique is used to combine the forecasts. We also examine the robustness of our results to parameter uncertainty using the wild bootstrap method. The results show...

What is it to be Physical?

, M.Sc. Thesis Sharif University of Technology Borgheai, Bahram (Author) ; Golshani, Mahdi (Supervisor)

Abstract

In this text to find the answer of the question “ what is it to be physical” in a definition form or a scheme of the term physical, firstly we sought for a possible consensus among recent physicists and philosophers. But from their answers not only we did not find any clear consensus but also most of them confess that the term is ambiguous and unclear. In a general aspect, we can categorize the answers to two theoretical and realistic perspective. The theoretical perspective, beside circularity and Hempel’s triviality, seems not to present any criteria for being physical. In realistic perspective, it seems that there is no ontologic constraint for being physical, that is from “being...

Biomass Separation in Moving Bed Biofilm Reactors (MBBR) by Natural And Innovative Filters

, M.Sc. Thesis Sharif University of Technology Ashrafi, Elham (Author) ; Borgheei, Mahdi (Supervisor)

Abstract

The application of membranes for separate of particles in mainly microbial flacs , are fast growing in biological treatment systems. Membrane bioreactors are now considered as one of the major new processes in wastewater treatment. However , membranes are expensive and costly. This study is carried out to test an innovative , locally made filters for separation of flocs in an MBBR reactor. This innovative filter is replacing a traditional settling tank. This type of filters is made very cheaply and has important advantages in installing and operation. Experiments were carried out in a laboratory scale MBBR unit. A filter unit consisting of 3 innovative filter tubes were placed and the...

Dynamic Security Assessment in Restructured Power Systems

, Ph.D. Dissertation Sharif University of Technology Kheradmandi, Morteza (Author) ; Ehsan, Mahdi (Supervisor)

Abstract

This thesis addresses the problem of dynamic security assessment in power sys-tems with an emphasis on its application in restructured power systems and issues arising in its applications. The new electric utility environment has an immedi-ate consequence of emphasis on reliability and secure operation of power systems. This requires faster and more precise methods to assess the dynamic aspect of se-curity. On the other hand, this issue is becoming challenging when the determined dispatch might not be accommodated due to violation of the limits.This thesis addresses the problem of dynamic security assessment in power sys-tems with an emphasis on its application in restructured power systems...

A Study on the Impact of the “Commodities’ Returns"on the Related “Firms’ Stock Returns” in Tehran Stock Exchange

, M.Sc. Thesis Sharif University of Technology Bigham, Mostafa (Author) ; Barakchian, Mahdi (Supervisor)

Abstract

Are the returns of the mineral companies in Tehran Stock Exchange affected by the changes in the commodity price at the Iran Mercantile Exchange? By implementing a Multi-Factor Model we will calculate the firms’ value elasticity to the commodity price changes. We try to explain the estimated elasticities on the basis of the firm’s fundamental variables using a discounted cash flow valuation model. An unbalanced panel data estimation is employed for this purpose. Afterwards, we will suggest a novel model on the ground of the assumption that the commodity prices and firm values follow the Geometric Brownian Motion. The result of the model is that the elasticity can be explained by commodity...

Analytical and Finite Element Modeling of Rubbing Phenomena in Rotors

, M.Sc. Thesis Sharif University of Technology Alvandi, Mahdi (Author) ; Behzad, Mahdi (Supervisor)

Abstract

Rotor contact with a stationary element of a rotating machine and the subsequent rubbing at the contact area is a serious malfunction that may lead to the machine’s catastrophic failure. In the past decades, many studies have been done on the rubbing phenomena, its different regimes and its various consequences on the machine performance and safety. However, most of them have used a simple model to investigate the rubbing interaction between the rotor and the stator. This simple model consists of the Jeffcott rotor, as a model for the real rotors, and a rigid annular block surrounding the rotor, as a model for the real stators. The objective of this thesis is to build an algorithm to...

Failure Tolerance of Epidemic Spreading in Complex Network

, M.Sc. Thesis Sharif University of Technology Mirzasoleiman, Baharan (Author) ; Jalili, Mahdi (Supervisor)

Abstract

Complex networks serve as generic models for many social, technological and biological systems that have been shown to share a number of common structural properties such as power-law degree distribution and small-worldness. These networks determine interactions and influence the spread of diseases, behaviours and ideas. Epidemics and failures like new behaviours ideas and innovations can spread throughout a network and prevent it from doing its functionalities. In this work, we investigate error and attack tolerance of epidemic spreading in complex networks. The main content of this thesis is arranged in three sections as follows: Firstly, the effect of random and systematic failures is...

Evaluation of Non-linear Combination Method (Neural Network) For Value-at-Risk Forecasting in Market

, M.Sc. Thesis Sharif University of Technology Rashnavadi, Leila (Author) ; Barakchian, Mahdi (Supervisor)

Abstract

Value at risk of an asset, is the asset’s expected maximum loss for a certain period of time and at a specified confidence level. Value-at-Risk can be calculated in the bank with its inter-nal method or standardized method. when a method have more violation number then bank need to keep more daily capital requirements. under the Basel 2 agreement if the violation of method more than 10 times in year, the Bank uses the standardized method.
There are trade off Between daily capital charge and violations. Therefore, existing methods for calculating the value at risk, usually lead to much daily capital charge or many violations. Studies show with combination of different methods to calculate...

Differences Between Standard Quantum Mechanics and Bohm's Quantum Mechanics

, M.Sc. Thesis Sharif University of Technology Asayesh, Omid (Author) ; Golshani, Mahdi (Supervisor)

Abstract

The purpose of introducing this thesis is to review the difference between Standard Quantum mechanics and Bohmian Quantum mechanics. The aim of this dissertation is not only to contrast these theories with respect to formulation, but also to briefly review their historical, philosophical and sociological aspects. This dissertation consists of two main sections. The first section is about reviewing the emergence profile of these theories and the formation of each theory along its historical path. In addition some beliefs about the founders of these theories and the impact of their beliefs on the evolution of their theories are put forward. As a complement to the above, the prevailing social...

Evaluation of Caviar Models Incorporated with Intraday Information ,the Case Study:Estimation Value at Risk of Gold

, M.Sc. Thesis Sharif University of Technology Karimi, Parvane (Author) ; Barakchian, Mahdi (Supervisor)

Abstract

Value at risk (VaR) is the maximum loss of the asset portfolio at the specified confidence level and certain time horizon. This tool is used to measure market risk and also used as a basis in determining financial standards for international financial instituation. Conditional Autoregressive Value at Risk models or CAViaR models introduced by Engle and Manganelli (2004). This models calculate VaR base on quantile regession approach and show some promising performance properties.
In order to propose a more accurate model for calcutating VaR , we develop CAViaR models by incorporating them with intraday information then we calculate VaR with this kind of models and CAViaR...

Design and Implementation of a Spectrum Sensor for Cognitive Radio

, M.Sc. Thesis Sharif University of Technology Safavi, Mahya (Author) ; Shabani, Mahdi (Supervisor)

Abstract

Frequency scarcity has emerged the necessity of opportunistic utilization of frequency bands, which can be realized through a cognitive radio system. During an agile communication between unlicensed users, a cognitive radio system must avoid collision with licensed users. Hence it should continuously observe the band of interest and report the presence of licensed user signals. This task is fulfilled by a vital part of a cognitive radio system, called the spectrum sensing core. Recently several techniques have been proposed for the spectrum sensing in literature. Some of them like matched filtering, cyclostationarity based detection are based on primary user signal features. However energy...

Learning Improvement in Phase Oscillator Models

, M.Sc. Thesis Sharif University of Technology Aghighi, Meysam (Author) ; Jalili, Mahdi (Supervisor)

Abstract

In the recent years, the problem of modeling a cognitive task using phase oscillators has been receiving a significant attention. In this view, single neurons are no longer elementary computational units. Rather, coherent oscillating groups of neurons are seen as nodes of networks performing cognitive tasks. From this assumption, we develop a model of stimulus-response learning and recognition. The most significant part of our work is defining learning methods for natural frequencies and coupling weights in a coupled phase oscillator network under Kuramoto conditions. In this thesis, we improved the previous models by not only emphasizing on the frequency of the oscillators but also taking...

EEG Brain Functional Network Analysis in Cortex Level

, M.Sc. Thesis Sharif University of Technology Pedrood, Bahman (Author) ; Jalili, Mahdi (Supervisor)

Abstract

Complex networks science have received tremendous attention in recent years and the brain is one of the systems to which graph theoretical tools have been applied. Alzheimer’s disease (AD) is a neurodegenerative disease affecting many of elderly population. AD changes the anatomy of the brain, which subsequently results in changes in its functions. These changes have been frequently reported in signals recorded from the brain (such as MEG, fMRI and EEG). Among these neuroimaging techniques EEG is one of the most aproprate methods for extracting functional connectivites according to high temporal resolution. In this thesis, we aimed at analyzing the properties of EEG-based functional networks...

Constructing EEG-Based Brain Functional Connectome Using Network-based Statistics

, M.Sc. Thesis Sharif University of Technology Barzegaran, Elham (Author) ; Jalili, Mahdi (Supervisor)

Abstract

In recent years, there have been increasing attempts to study brain connectivity. Among a number of brain mapping techniques, Electroencephalography is an easy to use and cheap method that can be used in the study of brain function. One way of understanding the intricate wiring pattern and functions of brain is to consider it as a complex network. In this approach, a graph of brain functions, based on the functional relation of recorded electric signals, is constructed and then the network is evaluated with a number of network metrics that measure its different aspect of structure. Different neurological and psychological diseases can affect the connectivity power within the brain; as a...

Incommensurability Problems: Feyerabend’s Linguistic Solution

, M.Sc. Thesis Sharif University of Technology Shafah, Alireza (Author) ; Nasrin, Mahdi (Supervisor)

Design and Implementation of a VLSI Architecture for Time and Frequency Synchronization in the LTE

, M.Sc. Thesis Sharif University of Technology Golnari, Amene (Author) ; Shabany, Mahdi (Supervisor)

Abstract

The long term evolution (LTE) standard is introduced and developed by the 3rd generation partnership project (3GPP) based on orthogonal frequency division multiplexing (OFDM). OFDM systems, in spite of having many advantages such high performance in bandwidth usage, are very sensitive to inter carrier interference (ICI) as a drawback. In order to prevent ICI, the frequency offset, mainly caused by the miss-match between oscillators' frequency and also between the sampling frequency of the transmitter and the receiver, should be estimated and compensated. Frequency synchronization is a part of the tasks of a synchronizer. In this thesis, main tasks of a synchronizer are illustrated and...