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Techno-Economic Comparison of Different Gas Turbine Inlet Cooling Techniques
, M.Sc. Thesis Sharif University of Technology ; Hakkaki Fard, Ali (Supervisor)
Abstract
Inlet air cooling is a simple and economical method to increase the power output of gas turbines. High-pressure fogging systems and mechanical chillers are two common methods. High water consumption, damage to compressor blades by water droplets, and inefficiency in humid climates are disadvantages of high-pressure fogging systems. Mechanical chillers have high electricity consumption and initial costs. In this research, an earth-to-air heat exchanger (EAHE) is introduced as a new method for inlet air cooling of gas turbines and is technically and economically compared with the two common methods in the long term in the climate of Tehran city. Temperature distribution in the ground is...
Aerodynamic Design of 100 kW Transonic Ducted Fan
, M.Sc. Thesis Sharif University of Technology ; Ghorbanian, Kaveh (Supervisor)
Abstract
The purpose of this research is the aerodynamic design of a 100 kW transonic ducted fan. Today, the aviation industry is moving towards the design of electric driven aircraft propulsion. Transonic ducted fans are one of the viable options that have been used in medium and heavy aircrafts due to their high specific power. In this research, the meanline model has been used for the initial design. By applying the design constraints, design limitations, design and functional parameters, the initial design point is found and then a sensitivity analysis is performed with respect to the effective design parameters to obtain the optimal design point. For the initial design of the transonic ducted...
Design and Optimization of Carbon Capture System from Exhaust Gases in the Process Industries
, M.Sc. Thesis Sharif University of Technology ; Rashtchian, Davood (Supervisor) ; Seif, Shayan (Co-Supervisor)
Abstract
Carbon dioxide is one of the main geenhouse gases emitted from factories as well as transportation vehicles that adversely affect the atmosphere and cause global warming. Among the proposed solutions to reduce carbon dioxide in the atmosphere, carbon dioxide separation would be the most viable medium-term approach. However, the high cost of carbon dioxide separation prevents the development of carbon dioxide absorption technologies. Therefore, it seems that integrating separation and production processes is the most efficient way to save energy and reduce carbon emissions. This method decrease a high proportion of the energy consumption in upstream operations (carbon dioxide removal,...
Generalizing of numerically solving methods of eigenvalue problems to asymmetrical, damping included case
, Article Proceedings of the 2001 ASME Design Engineering Technical Conference and Computers and Information in Engineering Conference, Pittsburgh, PA, 9 September 2001 through 12 September 2001 ; Volume 1 , 2001 , Pages 401-404 ; Sharif University of Technology
2001
Abstract
In this paper, "Subspace" method is generalized to asymmetrical case. In the new algorithm described here, "Lanczos" method is used to find the first subspace and to solve the eigenvalue problem resulted in generalized subspace method. To solve the standard eigenvalue problem developed by "Lanczos" method "Jacoby" method is used. If eigenvalue problem includes damping matrix, that will be imported in new defined mass and stiffness matrices
Optical Flow Based Flight of a Small Fixed-Wing Aircraft in Ideal Urban Environments
, Ph.D. Dissertation Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
This thesis represents the obstacle avoidance of a fixed-wing small aircraft using optical flow information of cameras mounted on the aircraft. The thesis consists of two main sections. In section one, the ideal optical flow has been simulated based on the camera model, complete six DOF of flight equations, and the geometry of the environment. An analytical formula has been derived to relate the obstacle detection distance to the maneuverability of the aircraft. Having the obstacle detection distance, the control and navigation algorithms have been developed to achieve a collision-free flight for the aircraft in urban canyons and junctions. The effect of some parameters such as approach...
Reconfiguration and Capcitor Placement in Distribution Systems for Loss Reduction and Reliability Enhancement
, M.Sc. Thesis Sharif University of Technology ; Vakilian, Mehdi (Supervisor)
Abstract
Capacitor setting and reconfiguration are of main means of loss reduction and voltage profile improvement in distribution system operation. Cooperation between these two strategies can effectively minimize power losses in distribution system automation. Also, from the medium and long term viewpoint, capacitor placement and reconfiguration can be used for loss reduction and reliability enhancement. In this section, the sum of losses cost, capacitor investment cost and reliability cost should be minimized. Regarding the need to solve two non-linear combinatorial optimization problems simultaneously, metaheuristic algorithms are used in this thesis. Specifically, Elitist Genetic Algorithm,...
Design of Robust Digital Circuits Against Soft Errors Considering Multiple Event Transients Fault (METs)
, M.Sc. Thesis Sharif University of Technology ; Miremadi, Ghasem (Supervisor)
Abstract
Nowadays, one of the most important challenges in the design of digital circuits is their susceptibility to the strike of high energy particles which leads to the Single Event Transient (SET) and Multiple Event Transients (MET). In fact, technology scaling which results in lower supply voltage, higher operating frequency, and lower nodal capacitance, makes today’s digital circuits more susceptible not only to high energy particles but also to low energy particles. Moreover emerging deep sub-micron technologies and the integration of more cells in today’s chips have caused higher probability of MET occurrences. A lot of research has tried to reduce the soft error rate due to high energy...
Using Time Series and Planning Uncertain Demand in Supply Chain with System Dynamics Approach
, M.Sc. Thesis Sharif University of Technology ; Kianfar, Farhad (Supervisor)
Abstract
In the field of supply chain, management constantly seeks to adopt strategies for realizing its targeted objectives. The supply chain, therefore, includes integrated production-distribution processes with all effective parts where proper management requires a comprehensive and dynamic approach. It is necessary to meet required items at required time. This becomes more important with the supply systems providing items. On the other hand, the difficulty of supply chain management, decisions, and policy-making can be increased by a wide range of conditions such as changes in demand. Thus, a comprehensive approach is needed to take the present dynamics into account. The current paper develops a...
Distributed Circuit Modeling of Plasmonic Nanostructures
, M.Sc. Thesis Sharif University of Technology ; Mehrany, Khashayar (Supervisor)
Abstract
The existing transmission line models of plasmonic nanostructures are modified in this thesis to study the electromagnetic characteristics of nano-plasmonic structures in a more efficeint yet accurate enough fashion. First, rectangular plasmonic cavities made by carving dielectric rectangles within a metallic region are modeled by trasnmission lines of finite length being appropriately terminated at their both ends. The resonance conditon in the proposed model yeilds the resonance frequencies, quality factors, and mode profiles of its correspondig plasmonic resonator. The accuracy of the proposed model is assessed by using the fully numerical finite-difference time-domain method (FDTD)...
Control of Unstable Non-minimum-phase Delayed Systems
, M.Sc. Thesis Sharif University of Technology ; Shahrokhi, Mohammad (Supervisor)
Abstract
The Smith Predictor does not work for unstable plants; therefore a lot of modifications have been proposed in order to solve this problem. In this project, advantages and disadvantages of most of these methods are studied in a general framework and based on Diophantine equation and using pole-placement technique. a discrete control scheme for unstable processes has been proposed. This structure can be used for non-minimum phase and stochastic processes. Robust stability of the suggested control structure has been shown. Performance of the proposed method is compared with previous works through computer simulations and its superiority for robust stability, load rejection; set-point tracking...
Numerical Analysis of an Afterburner Combustion Stability
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
Inlet flow of afterburners comes from the burnt products of the primary combustion chamber. The fuel is injected and the mixture is ignited to form a flame which is stabilized behind a flameholder in the afterburner. Flame stability stems from wake (recirculation zone) of flameholder. With the aid of high residence time of flow behind the flameholder reactants get the time to catch activation energy. Some parameters like oxygen content, mass flow rate, inlet temperature, and nozzle area ratio play an important role in afterburner combustion efficiency and flame stability. In this study we focused on afterburner combustion stability in GE J85-21 engine. This engine will be in service through...
The Role of Position Space in Measurement Process in Bohmian Mechanics
, M.Sc. Thesis Sharif University of Technology ; Golshani, Mehdi (Supervisor)
Abstract
In the early time of the discovery of the quantum mechanics and some decades after that, various interpretations of quantum mechanics were proposed. However, many years after that, the “indetermenistic” perspective well-known for Copenhagen perspective which was proposed mostly by Bohr and his colleagues became the dominant attitude among physicists. But nearly two decades after the fixation point of the Copenhagen perspective, a new interpretation of quantum mechanics was proposed by Bohm which was nonlocal but deterministic and it could reproduce all the predictions of quantum mechanics.Bohm’s theory responded to the many theoretical and philosophical objections assumed to the Copenhagen...
Robust controller design for discrete unstable non-minimum-phase delayed stochastic processes
, Article International Journal of Control, Automation and Systems ; Volume 11, Issue 5 , 2013 , Pages 893-902 ; 15986446 (ISSN) ; Shahrokhi, M ; Sharif University of Technology
2013
Abstract
Control of unstable non-minimum-phase delayed stochastic processes is a challenging problem. In this work based on the Diophantine equation and using pole-placement technique, a discrete control scheme for such processes has been proposed. Robust stability of the suggested control structure has been shown. Advantages of the proposed scheme over the existing algorithms have been shown through computer simulations. It has been shown that performance of the proposed scheme for handling model mismatch and colored noise is superior to the previous work proposed in the literature
The Effect of a Critical Reflective Course on the Construction of Iranian EFL Learners’ Identity: A Case of an Online EFL Class
, M.Sc. Thesis Sharif University of Technology ; Rezaei, Saeed (Supervisor)
Abstract
The present study examines the effects of participation in a critical reflective online course upon the participants’ identity. The study drew upon both qualitative and quantitative research methodologies. The 38 participants of the study who were first degree students at Sharif University of Technology participated in ten online sessions in which ten prompts concerning intercultural issues were introduced. The data collected in the online course underwent inductive qualitative content analysis which resulted in the extraction of five themes. Following this, 18 participants were interviewed to throw more light on these findings. Qualitative and Quantitative content analyses of the data...
Discussion of "optimal reconfiguration and capacitor allocation in radial distribution systems for energy losses minimization" by L.W. de Oliveira et al., International Journal of Electrical Power and Energy Systems 32 (2010) 840-848
, Article International Journal of Electrical Power and Energy Systems ; Volume 42, Issue 1 , November , 2012 , Pages 701- ; 01420615 (ISSN) ; Vakilian, M ; Sharif University of Technology
2012
Abstract
This article indicates the accurate method for load level calculation to solve the power flow problem when capacitor reactive power is involved. Using the correct method causes some changes in the results and conclusion stated in the discussed paper on optimal reconfiguration and capacitor placement in radial distribution systems
Optical flow-based obstacle avoidance of a fixed-wing MAV
, Article Aircraft Engineering and Aerospace Technology ; Volume 83, Issue 2 , 2011 , Pages 85-93 ; 00022667 (ISSN) ; Saghafi, F ; Sharif University of Technology
2011
Abstract
Purpose - The purpose of this paper is to describe optical flow-based navigation of a very light fixed-wing aircraft in flight between obstacles. Design/methodology/approach - The optical flow information of two cameras mounted on the aircraft is used to detect the obstacle. It is assumed that the image processing has been completed and the optical flow vectors have been obtained beforehand. The optical flow is used to detect the obstacles and make a rapid turn manoeuvre for the aircraft. Findings - It is shown that using the optical flow feedback by itself is unable to give a rapid turn to the aircraft and its rate should be employed into the control law. Six degree-of-freedom flight...
Distribution system efficiency improvement by reconfiguration and capacitor placement using a modified particle swarm optimization algorithm
, Article EPEC 2010 - IEEE Electrical Power and Energy Conference: "Sustainable Energy for an Intelligent Grid", 25 August 2010 through 27 August 2010 ; August , 2010 ; 9781424481880 (ISBN) ; Vakilian, M ; Sharif University of Technology
2010
Abstract
Capacitor placement/setting is one of the main means for loss reduction and voltage profile improvement in distribution systems. If capacitor placement is meant, the objective function will be the cost of energy losses besides the capacitors costs in a specified period of time. Here, reconfiguration can be used as a strategy to reform the base configuration of the distribution network in order to place the capacitors more efficiently with lower costs. On the other hand, if capacitors are already available in a network, optimum capacitors setting and network reconfiguration should be performed for power loss minimization. In this paper both power loss minimization and capacitor placement cost...
Modeling, Control and Simulation of a Swarm of Robots with Shell Structure
, M.Sc. Thesis Sharif University of Technology ; Alasty, Aria (Supervisor)
Abstract
Swarm robotics has attracted a lot of researches in recent decades due to its ability to overcome complexities despite of simple hardware used in each member of swarm. Developing control algorithms which can address connection, consensus and average consensus, position control, formation and swarm movement, is one of the main problems in the study of multi-agent systems and swarm robotics. Even though such methods have been developed and used by researchers for a few years, theoretical and operational issues still exist in the use of robotic swarms. For example, in leader-follower method, presence of repellent coordinator agent results in disruption in movement of other agents. Also...
Development of a Rubric for the Assessment of Prose Fictions Written by Creative Writing Students
, M.Sc. Thesis Sharif University of Technology ; Rezaei, Saeed (Supervisor)
Abstract
The present study is concerned with the development of a rubric which can help to have an objective, valid, and reliable assessment of short stories and novels written by creative writing students. The 30 participants of the study who were literature and creative writing experts took part in rubric development, validation, and reliability estimation. Review of the related literature, as well as the administration of a Likert scale questionnaire and a series of unstructured interviews led to the identification of ten elements which were used to construct the first version of the creative writing rubric. To ensure validity of the developed rubric, 18 literature and creative writing experts...
Cultural Identity Among Iranian English Language Teachers: A Multi-hase Mixed-Method Researc
, M.Sc. Thesis Sharif University of Technology ; Rezaei, Saeed (Supervisor)
Abstract
Teaching a foreign language and its culture implicitly might result in internalizing the foreign culture and identity (Brown, 2001). This might consequently cause cultural identity crisis and loss in a broader sense. As provided by Eslami Nodooshan (1998), considering the importance of cultural awareness raised through cultural studies and its influence on language policy and accordingly language classes provided the ground for this study to investigate the components of Iranian cultural identity, the degree of Iranian EFL teachers’ cultural identity, and the statistically significant difference between the Iranian EFL teachers’ cultural identity with different demographic characteristics....