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Modeling of semi-solid A356 alloy under upsetting process
, Article 9th International Conference on Semi-Solid Processing of Alloys and Composites, S2P 2006, Busan, 11 September 2006 through 13 September 2006 ; Volume 116-117 , 2006 , Pages 622-625 ; 10120394 (ISSN); 3908451264 (ISBN); 9783908451266 (ISBN) ; Aashuri, H ; Sharif University of Technology
Trans Tech Publications Ltd
2006
Abstract
The flow behavior of a semi-solid A356 alloy at high solid fraction was studied. The mushy zone was considered as an effective two-phase, so that the solid continuum can be compressible porous media, and the liquid phase interaction with the solid skeleton was of Darcy type. The semi-solid flow through the upsetting test was modeled in ABAQUS finite element method software. The Gurson yield criterion has been developed for the modeling process of the flow behavior of solid porous medium. Specimens were globulized by a thermomechanical process and then were tested for various percentages of upsetting. The distribution of solid fraction along the radius of the specimens at different height...
Modeling of semi-solid A356 alloy under upsetting process
, Article Solid State Phenomena ; Volume 116-117 , 2006 , Pages 622-625 ; 10120394 (ISSN) ; Aashuri, H ; Sharif University of Technology
Trans Tech Publications Ltd
2006
Abstract
The flow behavior of a semi-solid A356 alloy at high solid fraction was studied. The mushy zone was considered as an effective two-phase, so that the solid continuum can be compressible porous media, and the liquid phase interaction with the solid skeleton was of Darcy type. The semi-solid flow through the upsetting test was modeled in ABAQUS finite element method software. The Gurson yield criterion has been developed for the modeling process of the flow behavior of solid porous medium. Specimens were globulized by a thermomechanical process and then were tested for various percentages of upsetting. The distribution of solid fraction along the radius of the specimens at different height...
Investigation of oil recovery and CO2 storage during secondary and tertiary injection of carbonated water in an Iranian carbonate oil reservoir
, Article Journal of Petroleum Science and Engineering ; Volume 137 , 2016 , Pages 134-143 ; 09204105 (ISSN) ; Ayatollahi, S ; Riazi, M ; Sharif University of Technology
Elsevier
2016
Abstract
Gas injection process for more oil recovery and in particular CO2 injection is well-established method to increment oil recovery from underground oil reservoirs. CO2 sequestration which takes place during this enhanced oil recovery (EOR) method has positive impact on reducing the greenhouse gas emission which causes global warming. Direct gas injection into depleted oil reservoirs, encounters several shortcomings such as low volumetric sweep efficiency, early breakthrough (BT) and high risk of gas leakage in naturally fractured carbonate oil reservoirs. Carbonated water injection (CWI) has been recently proposed as an alternative method to alleviate the problems associated with gas...
Modeling and Analysis of the Powder Deposition Mechanisms of Selective Laser Sintering Process
, M.Sc. Thesis Sharif University of Technology ; Movahedi, Mohamad Reza (Supervisor)
Abstract
Selective laser sintering is a technique which uses a laser as the power source to sintering some selected points at a bed of powder in order to create a solid structure. In this research the SLS mechanisms of powder deposition is simulated and surface smoothness and layer density created by each mechanism is computed. For this purpose roller, blade and hopper mechanisms are simulated. For this simulation, polyamide 12 (PA2200) which is a common material is used. In this simulation at first powder specifications are extracted according to the references and for particle shape instead of using the spherical particle shape we use a certain shape that is more close to reality which created by...
Activating solution gas drive as an extra oil production mechanism after carbonated water injection
, Article Chinese Journal of Chemical Engineering ; Volume 28, Issue 11 , 2020 , Pages 2938-2945 ; Ayatollahi, S ; Riazi, M ; Sharif University of Technology
Materials China
2020
Abstract
Enhanced oil recovery (EOR) methods are mostly based on different phenomena taking place at the interfaces between fluid–fluid and rock–fluid phases. Over the last decade, carbonated water injection (CWI) has been considered as one of the multi-objective EOR techniques to store CO2 in the hydrocarbon bearing formations as well as improving oil recovery efficiency. During CWI process, as the reservoir pressure declines, the dissolved CO2 in the oil phase evolves and gas nucleation phenomenon would occur. As a result, it can lead to oil saturation restoration and subsequently, oil displacement due to the hysteresis effect. At this condition, CO2 would act as in-situ dissolved gas into the oil...
Proposed Method for Selecting the Most Suitable Contractor Using Risk Analysis
, M.Sc. Thesis Sharif University of Technology ; Mortaheb, Momamad Mehdi (Supervisor)
Abstract
At present, with some exceptions, the contracts are awarded based on the least proposed price. The records show that this method has not been successful especially for the infrastructure projects. In other words the projects awarded this way have been completed with time and cost overruns. Most of the times, such projects have not satisfied the stakeholders' expectations or have had problems during operation phase. The goal of this research is to suggest a method for selecting the most suitable contractor, considering the proposed price as well as incorporating the delay and other risks based on Contractors' actual past performance in the completed projects. Before selecting the Contractor,...
The impact of connate water saturation and salinity on oil recovery and CO2 storage capacity during carbonated water injection in carbonate rock
, Article Chinese Journal of Chemical Engineering ; 2018 ; 10049541 (ISSN) ; Riazi, M ; Ayatollahi, S ; Takband, M ; Sharif University of Technology
Chemical Industry Press
2018
Abstract
Carbonated water injection (CWI) is known as an efficient technique for both CO2 storage and enhanced oil recovery (EOR). During CWI process, CO2 moves from the water phase into the oil phase and results in oil swelling. This mechanism is considered as a reason for EOR. Viscous fingering leading to early breakthrough and leaving a large proportion of reservoir un-swept is known as an unfavorable phenomenon during flooding trials. Generally, instability at the interface due to disturbances in porous medium promotes viscous fingering phenomenon. Connate water makes viscous fingers longer and more irregular consisting of large number of tributaries leading to the ultimate oil recovery...
The impact of connate water saturation and salinity on oil recovery and CO2 storage capacity during carbonated water injection in carbonate rock
, Article Chinese Journal of Chemical Engineering ; Volume 27, Issue 7 , 2019 , Pages 1699-1707 ; 10049541 (ISSN) ; Riazi, M ; Ayatollahi, S ; Takband, M ; Sharif University of Technology
Chemical Industry Press
2019
Abstract
Carbonated water injection (CWI) is known as an efficient technique for both CO2 storage and enhanced oil recovery (EOR). During CWI process, CO2 moves from the water phase into the oil phase and results in oil swelling. This mechanism is considered as a reason for EOR. Viscous fingering leading to early breakthrough and leaving a large proportion of reservoir un-swept is known as an unfavorable phenomenon during flooding trials. Generally, instability at the interface due to disturbances in porous medium promotes viscous fingering phenomenon. Connate water makes viscous fingers longer and more irregular consisting of large number of tributaries leading to the ultimate oil recovery...
Investigation of the Effect of Particulate Emissions From Steel Complex on Adjacent Urban Areas Using Source and Receptor Modeling Approaches
, M.Sc. Thesis Sharif University of Technology ; Torkian, Ayoob (Supervisor)
Abstract
Expansion of city boundaries as a result of increased population has reduced the distance from industrial complexes and health effects of industrial air pollution have been intensified. As such, studies are needed to determine appropriate methodologies for quantifying the effect of these industries on the concentration of air pollutants in urban areas. In this study, particulate emissions from a steel mill complex was modeled using ADMS4 and the predicted results were compared with actual measurements made in the adjacent urban area. A receptor model (CMB8.2) was also used to quantify the share of the steel mill on the heavy metals' concentrations in the city by considering other sources...
Risk Assessment of Probable Domino Scenarios Between Two Petrochemical Units
, M.Sc. Thesis Sharif University of Technology ; Rashtchian, Davood (Supervisor)
Abstract
Hazard analysis and risk assessment are the two significant methods of controlling and reducing risk caused by industrial units. To achieve the required safety needed in either new or operating plants, risk assessments are being used for some specific hazards such as fire, explosion and toxic release. Increasing industrial developments and occurrence of several catastrophic accidents in chemical processing plants have contributed to striking disasters and have obliged experts to use analytical solutions to evaluate frequencies and consequences of such events. Congested plants in industrial areas like Mahshahr and Asalouyeh in Iran and other places in the world are the reason why it has...
Text-Independent Speaker Identification in Large Population Applications
, M.Sc. Thesis Sharif University of Technology ; Sameti, Hossein (Supervisor)
Abstract
The human speech conveys much information such as semantic contents, emotion and even speaker identity. Our goal in this thesis is the task of text-independent speaker identification (SI) in large population applications. Identification (test) time has become one of the most important issues in recent real time systems. Identification time depends on the cost of likelihood computation between test features and registered speaker models. For real time application of SI, system must identify an unknown speaker quickly. Hence the conventional SI methods cannot be used. The main goal in this thesis is to propose several methods that reduced identification time without any loss of identification...
Controller Design for A Nonlinear System in the Absence of Full State Measurements
, M.Sc. Thesis Sharif University of Technology ; Shahrokhi, Mohammad (Supervisor)
Abstract
In this study design of controller for a nonlinear system in the presence of state observer was investigated. First, nonlinear observers including non-adaptive and adaptive versions and their design procedures were studied. Then nonlinear adaptive controllers, based on sliding mode, feedback linearization and back-stepping techniques were implemented in the presence of observer dynamics. Two versions of adaptive law were proposed for unknown parameters identification in feedback linearization and sliding mode techniques. A new adaptive law was proposed to relax the restrictive condition that is used in adaptive observer design. The closed loop stability of back stepping technique was studied...
A Superhydrophobic Melamine Formaldehyde Sorbent for Micro Extraction of Pollutants from Aquatic Media
,
M.Sc. Thesis
Sharif University of Technology
;
Bagheri, Habib
(Supervisor)
Abstract
In this project, melamine formaldehyde was chosen as initial substrate for its high porosity. Then for having superhydrophobic surface, surface functional groups were silanized and deactivated as a result. It was assumed that high porosity of prepared sorbent and its nonpolar nature, can increase extraction efficiency. To study extraction efficiency of the prepared sorbent, it was filled inside a needle and used for needle-trap head-space extraction of BTEX (abbreviation for Benzene, Toluene, Ethylbenzene and Xylenes). Needle packed with sorbent was held on headspace of sample containing BTEX and head- space was pumped with a peristaltic pump. Pumping introduces fresh sample to sorbent...
Improving Robustness of Speaker Verification Systems Against Non-Identity Information
, Ph.D. Dissertation Sharif University of Technology ; Sameti, Hossein (Supervisor)
Abstract
Speaker verification as a kind of biometric methods aims to verify the identity of a person from characteristics of their voice. This method faces many challenges such as voice imitation (spoofing), use of recorded voice, high sensitivity to convolutive distortions resulted by channel, and a large performance degradation for short-duration utterances. The aim of this thesis is to propose different methods for reducing the effects of non-identity information,especially the channel, and also solving the problem of new methods for text-dependent speaker verification with very short utterances. i-vector has been the best speaker modeling method in recent years but it doesn’t result in good...
Hodge Structure on Fundamental Groups
, M.Sc. Thesis Sharif University of Technology ; Jafari, Amir (Supervisor)
Abstract
Deligne Proved that cohomology groups of algebraic varieties over C have mixed Hodge structures.It is also proved that homotopy groups of these varieties have mixed Hodge structures in a proper sense.In this thesis using iterated integrals that introduced by Chen,we explain Hain’s approach for defining Hodge structures on truncated first homotopy groups(fundamental groups). Note that there is another approach for defining Hodge structures on homotopy groups by Morgan,that uses minimal models of Sullivan.For explaining Hain’s approach,some basic results on Hodge structures are also explained
Modified Polystyrene Based Sorbents for Extraction of Trace Organic Pollutants with a Wide Range of Polarity
, Ph.D. Dissertation Sharif University of Technology ; Bagheri, Habib (Supervisor)
Abstract
The main focus of this thesis is based on surface modification of polystyrene in order to prepare extractive phases appropriate for extraction of analytes with a wide polarity range. This goal was achieved by increasing surface polarity. In fact, improved wettability and the possibility of interaction with polar analytes after addition of functional groups on polystyrene surface were the main reason for increased extraction capacity. In the first research, different functional groups including amine, nitro, carboxyl and acetyl were added on polystyrene particles by chemical bonding and to investigate their influence on extraction process, 22 analytes with a wide polarity range (LogP=-2 to...
Adaptive control strategy for treatment of hepatitis C infection
, Article Industrial and Engineering Chemistry Research ; Volume 58, Issue 33 , 2019 , Pages 15262-15270 ; 08885885 (ISSN) ; Shahrokhi, M ; Sharif University of Technology
American Chemical Society
2019
Abstract
In this work, an efficient treatment strategy for hepatitis C disease using interferon (IFN) has been proposed on the basis of the back-stepping control technique. The basic model of the hepatitis C virus (HCV) has been considered for controller design. To tackle the problem of model parameter variations, the adaptive version of the back-stepping method has been utilized. For applying the proposed treatment, all states should be available while only the viral load is measured. To solve this problem, a nonlinear Luenberger-like observer has been designed to estimate the unmeasured states. In the proposed treatment, limitation of the drug efficacy has been taken into account. Asymptotical...
Observer-based singularity free nonlinear controller for uncertain systems subject to input saturation
, Article European Journal of Control ; Volume 52 , 2020 , Pages 49-58 ; Shahrokhi, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this work, design of an observer-based nonlinear controller for a class of single input-single output (SISO) systems in the general strict feedback form subject to input saturation based on the back-stepping technique has been addressed. A full order adaptive observer is constructed to estimate the unknown states and system parameters simultaneously. The proposed control scheme is singularity free and can handle the input nonlinearity. Asymptotical stability of the closed-loop system in the presence of observer dynamics and input saturation has been established by the Lyapunov stability theorem. The effectiveness of the proposed controller is illustrated by applying the proposed scheme to...
Proposing a Stable Treatment Strategy for Hepatitis C
, Ph.D. Dissertation Sharif University of Technology ; Shahrokhi, Mohammad (Supervisor)
Abstract
The purpose of this study is to propose a stable treatment strategy for hepatitis C infection by considering several practical limitations of the treatment and using control theories. First, hepatitis C disease and its transmission, diagnosis, and treatment methods have been introduced. Then, the mathematical models of hepatitis C dynamics in the body have been presented, and their ability in predicting the observed clinical behaviors of the patients has been studied. Thereafter, the extended versions of these models by considering pharmacokinetics/dynamics equations of the drugs have been proposed to have a more realistic mathematical model. After that, the practical features of the disease...
Finite Element Modeling of Impact Problems with Friction and Large Deformations
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
One of the most important problems that challenge the researchers in modeling physical phenomena is the Impact Problem. The complexity of impact problems is due to the fact that this problem consists of various sub-problems, each of which of high complexity and in order to have a clear understanding and correct modeling of the problem, one needs to address each and every one of these problems with great effort, severity and punctuality.Impact problems often involve one or more dynamic systems that can also be subjected to dynamic loading. This loading could be a result of external agents or dynamic interaction of the two bodies with each other. In cases where the problem involves interaction...