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Criticality and oscillatory behavior in non-Markovian contact process
, Article Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics ; Volume 65, Issue 3 , 2002 ; 1063651X (ISSN) ; Sharif University of Technology
2002
Abstract
A non-Markovian generalization of a one-dimensional contact process is being introduced in which every particle has an age and will be annihilated at its maximum age τ. There is an absorbing state phase transition which is controlled by this parameter. The model can demonstrate oscillatory behavior in its approach to the stationary state. These oscillations are also present in the mean-field approximation, which is a first-order differential equation with time delay. Studying dynamical critical exponents suggests that the model belongs to the direct percolation universality class. © 2002 The American Physical Society
Analysis and Study the Effect of Knowledge Management Implementation on Productivity Case Study: Tehran Regional Electric Company
, M.Sc. Thesis Sharif University of Technology ; Mostafavi, Mostafa (Supervisor)
Abstract
The successful development and implementation of a knowledge management system requires principles and instructions compatible with the organization. In the absence of essential and domestic components of a given organization, the process of knowledge management implementation will fail to be successfully completed. There are now various models for the implementation of knowledge management; however, these models only recommend general strategic guidelines, hardly offering any specific strategic plans as to how organizations can successfully and effectively implement knowledge management. Since the promotion of productivity is the ultimate goal of knowledge management, the present research...
Coordinated Scheduling of Power and Natural Gas Systems Considering Demand Uncertainty
, M.Sc. Thesis Sharif University of Technology ; Rafiee, Majid (Supervisor)
Abstract
The everyday increasing electricity consumption of household and industrial sectors across the world, and also the limited generation capacity and fuel supplies has led electricity companies, whether in private or government sectors, to focus deliberately on power generation planning, its costs, risks and constraints Because of many reasons including high efficiency, low cost of capital investment, expeditious permitting, and operation flexibility of gas-fired generating units, electricity companies prefer them to old ones like coal-fired or oil-fired generating units. Thus natural gas has gained a significant share in the portfolio of electricity generation fuel resources, and it is...
A framework for extending agile methodologies with aspect-oriented features
, Article Proceedings - International Conference on Research Challenges in Information Science, 19 May 2011 through 21 May 2011, Gosier ; 2011 ; 21511349 (ISSN) ; 9781424486694 (ISBN) ; Ramsin, R ; Sharif University of Technology
2011
Abstract
Aspect-Oriented Software Development (AOSD) concentrates on determination and modularization of orthogonal concerns that cut across system modules. An aspect-oriented extension framework helps transform existing methodologies into processes which support AOSD. The authors propose a framework for extending agile methodologies with AOSD features. The stages required for constructing the framework have been identified by scrutinizing existing aspect-oriented methodologies and practices in order to extract the AOSD-specific stages required in each phase of the agile development process. Analysis shows that a methodology extended through this framework can be superior in agility in comparison to...
Development of an Extension Framework for Agile Methodologies to Add Support for Aspect-Oriented Development
, M.Sc. Thesis Sharif University of Technology ; Ramsin, Raman (Supervisor)
Abstract
Aspect-Oriented Software Development (AOSD) concentrates on separation of global cross-cutting concerns, or aspects. The weaknesses of Object-Oriented Software Development (OOSD) in localizing orthogonal concerns simultaneously leads to distributing them across several modules, and thereby creating modules that have to deal with various concerns. This usually results in poor modularization and difficulties in tracing certain requirements (especially nonfunctional requirements) to their implementations. The AOSD approach determines the common aspects that exist across modules created through OOSD, and modularizes them. Thus, AOSD takes the next step in creating modular software. Applying this...
Design and Implementation of Power Switch with Smart Driver in High Voltage BCD 0.18μm Process
, M.Sc. Thesis Sharif University of Technology ; Medi , Ali (Supervisor)
Abstract
In this thesis, a power switch with a smart driver is designed. 4-ampere current can pass through the switch, and the driver is capable of switching the load with 50 kHz frequency. The smart driver consists of an internal oscillator, internal regulator, charge pump, current limit, a level shifter, overtemperature and over/under voltage circuit. All these circuits are designed and developed in high voltage BCD 0.18 um process and well discussed in the thesis. All four kinds of protections are designed and implemented; open load detection, short circuit detection, over temperature shut down, UV and OV detection. Charge pump idea is used instead of the bootstrap method, which makes it possible...
Optimization of Post-disaster Recovery: Integration of Bayesian Network and Agent-based Simulation
, M.Sc. Thesis Sharif University of Technology ; Mahsouli, Mojtaba (Supervisor)
Abstract
This thesis proposes a probabilistic framework for evaluating and enhancing the community recovery process following an earthquake occurrence. This framework serves as a recovery decision support tool, aiming to enhance community resilience through the optimal allocation of limited available resources following a disaster occurrence. To this end, Bayesian network and agent-based simulation are integrated, each of which forming one of the modules of the proposed framework. The first module, namely, the Bayesian network, leads to situational awareness of the status of the community after the earthquake by fusing data from various sources. The data, such as the earthquake event characteristics...
A history-dependent stochastic predator-prey model: Chaos and its elimination
, Article European Physical Journal B ; Volume 13, Issue 3 , 2000 , Pages 601-606 ; 14346028 (ISSN) ; Ejtehadi, M. R ; Sharif University of Technology
Springer New York
2000
Abstract
A non-Markovian stochastic predator-prey model is introduced in which the prey are immobile plants and predators are diffusing herbivors. The model is studied by both mean-field approximation (MFA) and computer simulations. The MFA results a series of bifurcations in the phase space of mean predator and prey densities, leading to a chaotic phase. Because of emerging correlations between the two species distributions, the interaction rate alters and if it is chosen to be the value which is obtained from the simulation, then the chaotic phase disappears
Robust DTC control of doubly-Fed induction machines based on input-output feedback linearization using recurrent neural networks
, Article Journal of Power Electronics ; Volume 11, Issue 5 , 2011 , Pages 719-725 ; 15982092 (ISSN) ; Hashemnia, M. N ; Faiz, J ; Sharif University of Technology
2011
Abstract
This paper describes a novel Direct Torque Control (DTC) method for adjustable speed Doubly-Fed Induction Machine (DFIM) drives which is supplied by a two-level Space Vector Modulation (SVM) voltage source inverter (DTC-SVM) in the rotor circuit. The inverter reference voltage vector is obtained by using input-output feedback linearization control and a DFIM model in the stator a-b axes reference frame with stator currents and rotor fluxes as state variables. Moreover, to make this nonlinear controller stable and robust to most varying electrical parameter uncertainties, a two layer recurrent Artificial Neural Network (ANN) is used to estimate a certain function which shows the machine...
New technique for calculation of well deliverability in gas condensate reservoir
, Article Deep Gas Conference and Exhibition 2010, DGAS 2010 ; January , 2010 , p. 51-59 ; SPE Deep Gas Conference and Exhibition, 24-26 January, Manama, Bahrain Publication Date 2010 ; Sadeghi, A ; Masihi, M ; Sharif University of Technology
2010
Abstract
Well deliverability is an important issue in forecasting the performance of many gas condensate reservoirs. Condensate accumulation near the wellbore can cause a significant reduction in productivity, even in reservoirs where the fluid is very lean. Generally, the well deliverability is affected by two pressure-drop sources due to depletion and condensate buildup. Recently Rapid spreadsheet tools have developed to evaluate the well performance using material balance equation for depletion and two-phase pseudo pressure integral for well inflow performance. Most of them account for the effects of negative inertia and positive coupling in the calculation of gas relative permeability. This paper...
New technique for calculation of well deliverability in gas condensate reservoir
, Article Deep Gas Conference and Exhibition 2010, DGAS 2010, 24 January 2010 through 26 2010 ; January , 2010 , Pages 51-59 ; 9781617381065 (ISBN) ; Sadeghi, A ; Masihi, M ; Sharif University of Technology
2010
Abstract
Well deliverability is an important issue in forecasting the performance of many gas condensate reservoirs. Condensate accumulation near the wellbore can cause a significant reduction in productivity, even in reservoirs where the fluid is very lean. Generally, the well deliverability is affected by two pressure-drop sources due to depletion and condensate buildup. Recently Rapid spreadsheet tools have developed to evaluate the well performance using material balance equation for depletion and two-phase pseudo pressure integral for well inflow performance. Most of them account for the effects of negative inertia and positive coupling in the calculation of gas relative permeability. This paper...
Numerical Study of Flow and Heat Transfer Around a Rotor
, M.Sc. Thesis Sharif University of Technology ; Nouri Borujerdi, Ali (Supervisor)
Abstract
The purpose of this study is to investigate the distribution of air flow and temperature in electric machines. The fluid flow equations are solved by using the characteristic Galerkin. The unsteady equations of the air flow and heat transfer between the rotor, stator and radial cooling channels of the generator are solved by finite element method. Tetrahedral elements are used, but hexahedral elements can also be used. The upwind method is used to discretize the convection terms, but the central difference for the diffusion parts, that is equal to Petrov-Galerkin method in steady state situation. Due to the large number of channels and specific geometry, to reduce the computation costs, the...
Alginate/PVP/Pomegranate Seed Hydrogels as Bio-sorbents of Water Pollutants
, M.Sc. Thesis Sharif University of Technology ; Frounchi, Masoud (Supervisor) ; Mollaabasi, Payam (Co-Supervisor)
Abstract
In the past decades, hydrogels have been used as an adsorbent with high potential to remove pollutants in water. Hydrogels are three-dimensional polymer networks that have the ability to absorb and store water and water-soluble compounds due to the presence of hydrophilic functional groups in their structure. Different particles with unique characteristics can be used to increase the efficiency of hydrogel absorption. Based on the type of pollutant, hydrogels are divided into three different forms, including particles, films and nanocomposites. In this research, the absorption effect of metal cations as well as the absorption kinetics of polyvinyl pyrrolidine-based hydrogels, sodium...
The Effect of Olive Leaf Green Inhibitor on the Corrosion Resistance of Steel Reinforcement in Geopolymer Concrete Pore Solution
, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdollah (Supervisor) ; Hosseini, Payam (Co-Supervisor)
Abstract
In this research project, the aim was to investigate the potential of olive leaf extract as an eco-friendly inhibitor for enhancing the corrosion resistance of reinforcing steel in simulated geopolymer concrete pore solution (GCP) containing chloride ions. The inhibitory effects of olive leaf extract were evaluated using various electrochemical techniques as well as scanning electron microscopy. The main phenolic compounds present in olive leaf extract were identified using high performance liquid chromatography (HPLC). Moreover, the elements and chemical bonds present in the surface passive film of the steel bar immersed in the olive leaf inhibiting system were characterized using...
Development of an equation to predict radial modulus of elasticity for single-walled carbon nanotubes
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 222, Issue 6 , 2008 , Pages 1109-1115 ; 09544062 (ISSN) ; Ahmadian, M. T ; Gerami, A ; Sharif University of Technology
2008
Abstract
Finite element (FE) method is used to model radial deformation of single-walled carbon nanotube (SWCNT) under hydrostatic pressure. Elastic deformation of the nanostructure is simulated via elastic beams. Properties of the beam element are calculated by considering the stiffness of the covalent bonds between the carbon atoms in the hexagonal lattice. By applying the beam elements in a three-dimensional space, elastic properties of the SWCNT in transverse direction are obtained. In this regard, influences of diameter and tube wall thickness on the radial and circumferential elastic moduli of zigzag and armchair SWCNTs are considered. It is observed that there is a good agreement between the...
Rehabilitation of Concrete Structures Using 3D Panels
, M.Sc. Thesis Sharif University of Technology ; Vafaii, Abolhasan (Supervisor) ; Gerami, Mohsen (Co-Advisor)
Abstract
A high percentage of reinforced concrete buildings are not earthquake resistant because they are often designed based on old regulations, which do not satisfy the requirements of new earthquake codes. Construction weaknesses make buildings more vulnerable, and thus, different approaches are needed to strengthen structures to resist lateral forces. 3D Panel system brings together the best qualities of in-situ and precast systems and improves their shortcoming. It includes the advantages of precast systems, such as having relatively low labor costs, less waste material and machinery, reducing implementation time and improving quality control. At the same time, serious problems related to...
Evaluation of Synchronization Mechanisms of Dual HW-RAID controllers in Data Storage Systems
, M.Sc. Thesis Sharif University of Technology ; Asadi, Hossein (Supervisor)
Abstract
Using single RAID HW-Controller in data storage systems can become a single point-of-failure. Hence, it will affect system availability. As a result, in enterprise-class storage systems, utilizing dual-HW-Controller architecture for managing redundant array of independent disks is prevalent to enhance performance and reliability. Employing such architecture, however, faces major challenges. One of these challenges is the synchronization of dual-HW-based controllers in case RAID arrays revealing erratic behaviours. No thorough study has been done for evaluating dual-controller architecture synchronization mechanisms and its performance. In this thesis, different configurations of enterprise...
Iran’s oil development scenarios by 2025 [electronic resource]
, Article Energy Policy ; Volume 56, May 2013, Pages 612-622 ; Sharif University of TechnologyDynamic Simulation and Control of Reactive Systems Involving Metabolic Pathways
, M.Sc. Thesis Sharif University of Technology ; Bozorgmehry Bozarjomehry, Ramin (Supervisor) ; Setoodeh, Payam (Co-Supervisor)
Abstract
In this project, modeling, simulation, and control of the Saccharomyces Cerevisiae were studied. In the first section, simulation and control of a structural model of saccharomyces Cerevisiae were performed. Fuzzy Logic Controller (FLC) as a model-independent controller and Global Linearization Controller (GLC) as a model-based controller were designed. Additionally, two types of Kalman filters were designed to predict all states of the structural model: 1-Extended Kalman Filter (EKF), 2- Unscented Kalman Filter (UKF). As a concise explanation, the control action of the GLC is a function of all states of the model, and since that measuring all metabolites is not practical, the EKF and UKF...
An improvement on modeling of forced gravity drainage in dual porosity simulations using a new matrix-fracture transfer function
, Article Transport in Porous Media ; Volume 94, Issue 1 , 2012 , Pages 207-223 ; 01693913 (ISSN) ; Masihi, M ; Gerami, S ; Ghazvini, M. G ; Sharif University of Technology
2012
Abstract
In fractured oil reservoirs, the gravity drainage mechanism has great potentials to higher oil recovery in comparison with other mechanisms. Recently, the forced gravity drainage assisted by gas injection has also been considered; however, there are few comprehensive studies in the literature. Dual porosity model, the most common approach for simulation of fractured reservoirs, uses transfer function concept to represent the fluid exchange between matrix and its neighborhood fractures. This study compares the results of different available transfer functions with those of fine grid simulations when forced gravity drainage contributes to oil production from a single matrix block. These...