Performance Modeling Of Twin Shaft Gas Turbine as a Turbocomperessor

, M.Sc. Thesis Sharif University of Technology Mohajer Darabi, Abbas (Author) ; Ghorbanian, Kaveh (Supervisor)

Abstract

Gas turbines and centrifugal compressors are the preferred means of compressing the gas in pipeline systems. Both gas turbines and centrifugal compressors exhibit performance characteristics that depend on the operating point imposed on them by the pipeline operation. Simulation of gas turbine-driven centrifugal compressors is necessary for a variety of applications in the general area of pipeline simulation. This research focuses on modeling of twin shaft gas turbine dynamic and steady state performance. For this purpose, it was necessary to evaluate the thermodynamic working process of the gas turbine by using an in-house computer code. At design point, the calculations are solely based on...

Diffuse emissions of particles from iron ore piles by wind erosion

, Article Environmental Engineering Science ; Volume 28, Issue 5 , 2011 , Pages 333-339 ; 10928758 (ISSN) Afshar Mohajer, N ; Torkian, A ; Sharif University of Technology

2011

Abstract

Industrial air pollution from point and nonpoint sources of steel complexes has drawn increasingly more public attention in the past decades. Previous research efforts have been more concentrated on point sources of particulate emissions from these complexes. However, wind-induced particulate emissions from iron ore storage piles not only result in ambient air pollution but also increase economic adverse effects to the industry by loss of process raw materials. Experiments were conducted to assess the impact of wind speed and humidity on particulate emission rates from iron ore storage piles. A wind-generating system and specific iron ore, experimental piles (L:W:H of 30:11.5:5 cm) were...

Reactivity studies of biomimetic catalytic epoxidation of alkenes with tetrabutylammonium periodate in the presence of various manganese porphyrins and nitrogen donors: Significant axial ligand π-bonding effects

, Article New Journal of Chemistry ; Volume 28, Issue 6 , 2004 , Pages 740-747 ; 11440546 (ISSN) Mohajer, D ; Karimipour, G ; Bagherzadeh, M ; Sharif University of Technology

Royal Society of Chemistry 2004

Abstract

Highly selective epoxidation (> 95%) of unfunctionalized alkenes was performed by tetrabutylammonium periodate in the presence of six different phenyl substituted manganese(III) meso-tetraphenylporphyrins [Mn(Por)] and imidazole in CH2Cl2. Electron-withdrawing and bulky substituents on the phenyl groups lowered the catalytic activities of the corresponding Mn(Por). Less bulky alkenes with electron -rich double bonds showed greater reactivity in the epoxidation. Co-catalytic activities of four different classes of axial nitrogen donors are compared in the presence of various Mn(Por). In general no direct correlation was found between co-catalytic activities and the pKa values of the nitrogen...

Well Placement optimization using hybrid optimization technique combined with fuzzy inference system

, Article Petroleum Science and Technology ; Vol. 31, issue. 5 , Dec , 2009 , p. 481-491 ; ISSN: 10916466 Darabi, H ; Masihi, M ; Sharif University of Technology

2009

Abstract

Decision on the location of new wells through infill drilling projects is a complex problem that depends on the reservoir rock and fluid properties, well and surface facilities specifications, and economic measures. Conventional approach to address this is a direct optimization that uses the numerical flow simulation. However, this is computationally very extensive. In this study the authors use a hybrid genetic algorithm (HGA) optimization technique based on the genetic algorithm (GA) with helper functions based on the polytope algorithm and the neural network. This hybridization introduces hill-climbing into the stochastic search and makes use of proxies created and calibrated iteratively...

Well Placement optimization using hybrid optimization technique combined with fuzzy inference system

, Article Petroleum Science and Technology ; Volume 31, Issue 5 , 2013 , Pages 481-491 ; 10916466 (ISSN) Darabi, H ; Masihi, M ; Sharif University of Technology

2013

Abstract

Decision on the location of new wells through infill drilling projects is a complex problem that depends on the reservoir rock and fluid properties, well and surface facilities specifications, and economic measures. Conventional approach to address this is a direct optimization that uses the numerical flow simulation. However, this is computationally very extensive. In this study the authors use a hybrid genetic algorithm (HGA) optimization technique based on the genetic algorithm (GA) with helper functions based on the polytope algorithm and the neural network. This hybridization introduces hill-climbing into the stochastic search and makes use of proxies created and calibrated iteratively...

Illuminating the formal–informal dichotomy in land development on the basis of transaction cost theory

, Article Planning Theory ; 2018 ; 14730952 (ISSN) Darabi, H ; Jalali, D ; Sharif University of Technology

SAGE Publications Ltd 2018

Abstract

Transaction cost theory is largely used to investigate the formal domain of land and housing. In the informal domain, however, this perspective has been employed largely as a supplement in addressing the other fundamental notion in new institutional economics—property rights—despite the possibility that informality in land development can emerge regardless of the informality or formality of such rights. To cover this gap, this study developed a theoretical framework based on transaction cost theory to explain the formal–informal dichotomy in land development. The proposed framework maintains that land development depends on engaging in transactions that involve total or partial ownership of...

Coupled rotational and translational modeling of two satellites connected by a tether and their robust attitude control using optimal offset approach

, Article Advances in Space Research ; Volume 63, Issue 8 , 2019 , Pages 2455-2468 ; 02731177 (ISSN) Darabi, A ; Assadian, N ; Sharif University of Technology

Elsevier Ltd 2019

Abstract

In this study, the robust sliding mode attitude control of a tethered satellite system using optimal tether offset in the presence of perturbations and uncertainties is investigated. The three main goals of this study are: (1) comprehensive modeling of two satellites connected by a tether considering the coupling between their attitude and position, (2) finding a robust attitude control for both satellites, and (3) reducing the reaction wheels’ power consumption for attitude control utilizing the tether tension. In this regard, the 6 DOF governing equations of the coupled nonlinear rotational and translational dynamics of a two-satellite tethered system in the presence of perturbing forces...

Illuminating the formal–informal dichotomy in land development on the basis of transaction cost theory

, Article Planning Theory ; Volume 18, Issue 1 , 2019 , Pages 100-121 ; 14730952 (ISSN) Darabi, H ; Jalali, D ; Sharif University of Technology

SAGE Publications Ltd 2019

Abstract

Transaction cost theory is largely used to investigate the formal domain of land and housing. In the informal domain, however, this perspective has been employed largely as a supplement in addressing the other fundamental notion in new institutional economics—property rights—despite the possibility that informality in land development can emerge regardless of the informality or formality of such rights. To cover this gap, this study developed a theoretical framework based on transaction cost theory to explain the formal–informal dichotomy in land development. The proposed framework maintains that land development depends on engaging in transactions that involve total or partial ownership of...

A Cloud Based Architecture Design for Global Supply Chain

, M.Sc. Thesis Sharif University of Technology Darabi, Zahra (Author) ; Houshmand, Mahmoud (Supervisor)

Abstract

Supply chain as one of the most important and critical parts of the production process; could have significant effect on efficiency and productivity of the firms.Integration of supply chain (components from upstream to downstream of production system) has been recently noticed and considered remarkably since it could have a considerable impact on functional variables in supply chain systems such as: cost reduction, responsiveness, service level and decision making process. On the one hand, in the last decade, new trends in global economics and the ongoing pattern in multinationals to outsource their manufacturing process have made the integration process challenging and difficult. On the...

, M.Sc. Thesis Sharif University of Technology Darabi, Meisam (Author) ; Rashtchian, Davood (Supervisor)

Abstract

Emergency Shut Down systems are considered as one of the prominent protection layers in industries. In the situation that the process variables exist acceptable limits, the SIS brings the process in a safe state. According to standards, separate design and operation have been defined for BPCS and SIS. In this research, safety issues related to one of the gas refinery unit has been investigated. In fact, the unit does not have shut down system and all the safety loops are defined as DCS. In the first step, the Safety Integrated Levels of the loops which must be defined in shut down system have been specified by using Modified Calibrated Risk Graf. In next step, philosophy of shut down levels...

Parallel Multi-disciplinary Design Optimization of a Guided Flying Vehicle

, M.Sc. Thesis Sharif University of Technology Darabi, Davoud (Author) ; Nobahari, Hadi (Supervisor)

Abstract

Multi-disciplinary design optimization (MDO) of a surface to air flying vehicle has been done in this research, on the basis of flight simulation. The MDO problem have five disciplines consists of aerodynamic, propulsion, guidance, control, and fire control. Multiple campaign scenarios are defined. The MDO problem has 31 design variables and two objective functions. The objective functions are flying vehicle weight and miss distance. A new meta-heuristic algorithm has been designed to solve multi-objective optimization problems. The new algorithm has been called Multi-objective Adaptive Real-coded Memetic Algorithm (MARCOMA). The MARCOMA can solve large-scale and multi-objective problems and...

Coupled Rotational and Translational Modelling of Two Satellite Tethered Formation and their Robust Attitude Control

, M.Sc. Thesis Sharif University of Technology Darabi, Atefe (Author) ; Assadian, Nima (Supervisor)

Abstract

The 6DOF modelling and robust attitude control of two tethered satellites using tether tension moments is studied in this thesis. In this regard, the coupled rotational and translational dynamics of two satellites connected by a tether in the presence of Earth’s gravitational perturbation, aerodynamic drag, solar radiation pressure and third body effects (Sun and Moon) and also uncertainties in some of physical parameters of system and sensor’s outputs is modelled. Moreover, the tether attachment point to the satellites is different from their center of mass and its effect on dynamics of the system is taken into consideration. Then, the attitude of both satellites are controlled using robust...

Machine Learning for Optimizing Drug Dosing in Anti-Angiogenic Cancer Therapy

, M.Sc. Thesis Sharif University of Technology Darabi, Atyeh (Author) ; Moghadasi, Reza (Supervisor)

Abstract

Optimal drug dosing is one of the fundamental challenges in treating complex diseases such as cancer. Cancer, characterized by the rapid growth of tumors and the stimulation of angiogenesis to form new blood vessels for providing nutrients and oxygen, is one of the most significant public health threats. Angiogenesis is influenced by factors that guide the migration and aggregation of endothelial cells toward the tumor. In this study, the Anderson-Chaplain mathematical model was utilized to simulate the dynamics of angiogenesis and analyze the effects of relevant biological parameters.To better understand this process, topological data analysis and clustering methods were applied to the...

Randomized algorithms for comparison-based search

, Article Advances in Neural Information Processing Systems 24: 25th Annual Conference on Neural Information Processing Systems 2011, NIPS 2011, 12 December 2011 through 14 December 2011 ; December , 2011 ; 9781618395993 (ISBN) Tschopp, D ; Diggavi, S ; Delgosha, P ; Mohajer, S ; Sharif University of Technology

2011

Abstract

This paper addresses the problem of finding the nearest neighbor (or one of the R-nearest neighbors) of a query object q in a database of n objects, when we can only use a comparison oracle. The comparison oracle, given two reference objects and a query object, returns the reference object most similar to the query object. The main problem we study is how to search the database for the nearest neighbor (NN) of a query, while minimizing the questions. The difficulty of this problem depends on properties of the underlying database. We show the importance of a characterization: combinatorial disorder D which defines approximate triangle inequalities on ranks. We present a lower bound of Ω(Dlog...

A new online random particles optimization algorithm for mobile robot path planning in dynamic environments

, Article Mathematical Problems in Engineering ; Volume 2013 , 2013 ; 1024123X (ISSN) Mohajer, B ; Kiani, K ; Samiei, E ; Sharifi, M ; Sharif University of Technology

2013

Abstract

A new algorithm named random particle optimization algorithm (RPOA) for local path planning problem of mobile robots in dynamic and unknown environments is proposed. The new algorithm inspired from bacterial foraging technique is based on particles which are randomly distributed around a robot. These particles search the optimal path toward the target position while avoiding the moving obstacles by getting help from the robot's sensors. The criterion of optimal path selection relies on the particles distance to target and Gaussian cost function assign to detected obstacles. Then, a high level decision making strategy will decide to select best mobile robot path among the proceeded particles,...

Performance evaluation of custom power devices in process of motor bus transfer

, Article 2009 4th IEEE Conference on Industrial Electronics and Applications, ICIEA 2009, Xi'an, 25 May 2009 through 27 May 2009 ; 2009 , Pages 2279-2284 ; 9781424428007 (ISBN) Janaghaei, M ; Abedi, M ; Darabi, F ; Sharif University of Technology

2009

Abstract

Quality and continuity of electrical power to sensitive loads especially in power plants and industrial sectors is of great importance. For this reason, bus transfer is used. During the bus transfer interval, sensitive loads especially motors will be interrupted, and may encounter difficulties. So, it is used reactive power compensator and custom power devices to mitigate stress in motors and improve power quality indices. This paper presents the effect of reactive power compensator and custom power devices paralleling with motor in process of bus transfer which is done in two methods: EMTS and STS. Also, it is investigated dynamic performance of induction motor and spin-down curves in...

Optical modulation by surface states

, Article Semiconductor Science and Technology ; Volume 18, Issue 1 , 2003 , Pages 60-67 ; 02681242 (ISSN) Darabi, E ; Khorasani, S ; Rashidian, B ; Sharif University of Technology

2003

Abstract

In this paper, the effect of two-dimensional electron plasma formed on the surface of a semiconductor on the refraction phase of an optical beam is investigated. Both the density and effective mass of the surface state electrons can be controlled by a transverse electric field. While the surface density of electrons varies slowly with the applied field, their effective mass changes instantaneously. Therefore, a high bandwidth for the phase modulation can be obtained. It is expected that the device operates in the far-infrared region with a semiconductor as the base material. GaAs is one of the best candidates having both large dynamic range, and large ratio of free electron to the crystal...

Evaluation of the Impact of Exhaustible Energy Resources on Factor Productivity

, M.Sc. Thesis Sharif University of Technology Karami Darabi, Mohammad (Author) ; Saboohi, Yadollah (Supervisor)

Abstract

Economics is the science of using scarce resources, which helps to identify the optimal use of economic resources. Enhancement of productivity leads more efficient use of resources in economics sectors. Identification of ways and means of improving productivity is an important policy issue which requires an analysis of the effects of determinants of productivity. In the present research work, Total Factor Productivity (TFP) has been econometrically estimated; based on production function theory. Application of this concept indicates that the elasticities of total value-added (i.e. GDP minus oil rents) with respect to physical capital and labor are 0.8 and 0.2 respectively. It is further...

Gas absorption enhancement in hollow fiber membrane contactors using nanofluids: Modeling and simulation

, Article Chemical Engineering and Processing: Process Intensification ; Volume 119 , 2017 , Pages 7-15 ; 02552701 (ISSN) Darabi, M ; Rahimi, M ; Molaei Dehkordi, A ; Sharif University of Technology

Elsevier B.V 2017

Abstract

In this article, a comprehensive 2D mathematical model has been developed to simulate process intensification of carbon dioxide absorption in the presence of nanoparticles in hollow fiber membrane contactors (HFMCs). The influences of nanoparticle were taken into account considering Brownian motion and Grazing effect as dominant phenomena of mass-transfer enhancement in nanofluids. The obtained simulation results were validated against experimental data reported in the literature and excellent agreement was obtained. It was found that by adding 0.05 wt % silica nanoparticles, the absorption rate could be enhanced by 16%, while the corresponding value is 32% for CNT nanoparticles. High...

The Study of Megawatt Wind Turbine Rotor Performance in Presence of Contamination Using CFD

, M.Sc. Thesis Sharif University of Technology Mohajer, Abbas (Author) ; Darbandi, Masoud (Supervisor) ; Taiebi Rahni, Mohammad (Supervisor)

Abstract

Considering the negative effects of contamination on wind turbine blade performance, we investigate aerodynamics performance of a one- Megawatt wind turbine. To achieve this, we compare the performance and power of the wind turbine with and without contaminations. To calculate the wind turbine output power, we use a developed wind turbine calculator, which benefits from the Blade Element Momentum (BEM) theory. Furthermore, the aerodynamics calculations are performed using of a commercial software for clean and rough airfoils. Considering the change of Reynolds number along the blade axis, the airfoil characteristics are calculated for two Reynolds numbers of 0.5 and 3.5 millions to increase...