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golchin-khiabani-azar--negar
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Development of a Covering Location Model in Congested Networks
, M.Sc. Thesis Sharif University of Technology ; Shavandi, Hassan (Supervisor)
Abstract
Plants, distribution centers, and other facilities generally function for years or decades, during which time the environment in which they operate may change substantially. Costs, demands, travel times, and other inputs to classical facility location models may be highly uncertain. So when making decisions of location considering the factors that may change is beneficial. In this thesis a version of covering location model under uncertainty in a congested system is proposed. The aim is to locate m facilities to maximize the captured customer utility, having in mind that there may be up to q facilities established in future; the only information at hand about the number of the new facilities...
Measuring limb darkening of stars in high-magnification microlensing events by the Finite Element Method
, Article Monthly Notices of the Royal Astronomical Society ; Volume 494, Issue 1 , 2020 , Pages 584-597 ; Rahvar, S ; Sharif University of Technology
Oxford University Press
2020
Abstract
The finite-size effect in gravitational microlensing provides a possibility to measure the limb darkening of distant stars. We use the Finite Element Method (FEM) as an inversion tool for discretization and inversion of the magnification-limb darkening integral equation. This method makes no explicit assumption about the shape of the brightness profile more than the flatness of the profile near the centre of the stellar disc. From the simulation, we investigate the accuracy and stability of this method and we use regularization techniques to stabilize it. Finally, we apply this method to the single lens, high-magnification transit events of OGLE-2004-BLG-254 (SAAO-I),...
Measuring Limb Darkening of Distant Stars Using Microlensing Events by Finite Element Method
, Ph.D. Dissertation Sharif University of Technology ; Rahvar, Sohrab (Supervisor)
Abstract
The finite-size effect in gravitational microlensing provides a possibility to measure the variation of surface brightness of stars from centre to limb which is called limb darkening profile. Measuring limb darkening profile provides information about star atmosphere. It is also useful in other fields of astrophysics. In this thesis we develop a numerical method to recover limb darkening of source stars from single lens microlensing light curves with finite source effect in which the lens transits the source disk. We use the Finite Element Method (FEM) as an inversion tool for discretization and inversion of the finite source effect integral equation. This method makes no explicit assumption...
Online Algorithms for Matching Points on the Plane
, M.Sc. Thesis Sharif University of Technology ; Zarrabizadeh, Hamid (Supervisor)
Abstract
Matching points is an important issue in the world of algorithms and has attracted the attention of many researchers with its wide applications. In recent years, researchers have proposed various issues in the field of matching points and looked at it from different perspectives. In recent years, this issue, like other issues, entered the online world and tried to be investigated online. In this thesis, we examine some examples of models of this problem that are projected on the plane and online and try to find a way to solve them or introduce a lower bound for them
Evaluating the Changes in the Mean Vector and Covariance Matrix of EDP Distribution for different IM and Ground Motion Selections
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofouei, Fayyaz (Supervisor)
Abstract
In this study, the changes in the mean vector and the covariance matrix of engineering demand parameter (EDP) distributions for different intensity measures and ground motion selections is evaluated. Although, the changes in the mean distribution of EDPs have been extensively studied in the literature, but the changes in the covariance matrix of EDPs distributions caused by ground motion selections has not been paid the due attention. In other words, no study has specifically looked into the effect of intensity measure changes on the covariance matrix; therefore, for the purpose of this study, several steel frame models were considered with perimeter special moment resisting frames (SMRF)....
Forced convective heat transfer in parallel flow multilayer microchannels
, Article Journal of Heat Transfer ; Volume 129, Issue 9 , 2007 , Pages 1230-1236 ; 00221481 (ISSN) ; Hajiaghaee Khiabani , R ; Sharif University of Technology
2007
Abstract
In this paper, the effect of increasing the number of layers on improving the thermal performance of microchannel heat sinks is studied. In this way, both numerical and analytical methods are utilized. The analytical method is based on the porous medium assumption. Here, the modified Darcy equation and the energy balance equations are used. The method has led to an analytical expression presenting the average dimensionless temperature field in the multilayer microchannel heat sink. The effects of different parameters such as aspect ratio, porosity, channel width, and the solid properties on the thermal resistance are described. The results for single layer and multilayer heat sinks are...
A goal programming approach for optimal PMU placement
, Article International Review on Modelling and Simulations ; Volume 6, Issue 2 , April , 2013 , Pages 490-497 ; 19749821 (ISSN) ; Hamidi, M ; Farahmand, K ; Aghatehrani, R ; Sharif University of Technology
2013
Abstract
This article proposes a multi-objective goal programming based approach with two objectives of maximizing the reliability and minimizing the placement cost of Phasor Measurement Units (PMUs) for full observability in power systems. The weighted sum goal programming formulation incorporates the reliability of individual PMUs and finds a placement to resolve the conflicting objectives of minimum number of PMUs cost-wise and maximum level of system-wide reliability. This multi-objective problem is formulated as a nonlinear goal programming model in which weights are associated with the objectives. The model is solved for several weight scenarios for the IEEE 14, 30, 57 and 118 bus test systems....
Analysis of micro channel heat sink performance
, Article 2005 SEM Annual Conference and Exposition on Experimental and Applied Mechanics, Portland, OR, 7 June 2005 through 9 June 2005 ; 2005 , Pages 1911-1918 ; 0912053909 (ISBN) ; Salehi, M ; Khiabani, R. H ; Sharif University of Technology
2005
Abstract
In the present research a numerical investigation has been made to evaluate the results of analytical approach in the analysis of micro channel heat sink (MCHS) which is increasingly used in the cooling of high heat dissipating electronic devices. In this regard the effects of geometrical and flow parameters affecting the absolute thermal resistance of MCHS have been analyzed. The effect of using different fluids in the value of the thermal resistance is considered as well. The accuracy of analytical method in predicting heat transfer and fluid flow regimes in micro channel is checked in comparison with numerical method. The effects of hydraulic and thermal entrance lengths of these systems...
Application of Data Mining in Prediction of Diabetes type 2
, M.Sc. Thesis Sharif University of Technology ; Akhavan Niaki, Taghi (Supervisor)
Abstract
Developments in the field of data storage which is due to computers have led to an extraordinary increase in medical data just like the increase in all other fields. As a result, physicians are faced with the problem of using the stored data. Therefore, the traditional manual data analysis is inadequate due to the large amounts of data. Furthermore, the ability to use this data to extract useful information is critical for the quality of medical care. Therefore, data mining techniques arose so that we will be able to extract knowledge through applying them to the raw data and subsequently help the doctors in making decisions.
In this study, we are pursuing four goals. First, in order to...
In this study, we are pursuing four goals. First, in order to...
Reviewing and Analyzing the Political Marketing Program of Candidates for Parliamentary Elections on Social Networks (Twitter and Instagram) in Parliamentary Elections
, M.Sc. Thesis Sharif University of Technology ; Karami, Naser (Supervisor) ; Honarvar, Ruhollah (Supervisor)
Abstract
With the emergence and expansion of social media in the societies, these media has become an integral part of modern society and the lives of citizens. These networks have improved communication facilities in the community and created an opportunity for politicians to use these media as a communication and marketing channel to communicate with citizens and use them to achieve their goals. Social media's ability to communicate has put politicians' relationship with citizens in a very strategic position. This has made it important to have a communication plan and, more generally, principled political marketing.Therefore, the main issue that this dissertation has investigated is the review of...
Salt-acid-surfactant synergistic effects on interfacial characteristics of water/oil systems: A molecular dynamics simulation study
, Article Journal of Molecular Liquids ; Volume 396 , 2024 ; 01677322 (ISSN) ; Kargozarfard, Z ; Khiabani, N. P ; Ayatollahi, S ; Sharif University of Technology
Elsevier
2024
Abstract
Low salinity water injection with surfactants is one of the standard approaches in enhanced oil recovery (EOR). This method relies on the interaction of surfactants and ions at oil/water interfaces to reduce the interfacial tensions. However, the details of the mechanisms governing the synergistic effects of these components are still debatable. In this study, molecular dynamic (MD) simulations have been employed to investigate the challenging interactions of chemicals and saline water at a molecular scale. The model oil phase used in this study was defined as a mixture of toluene and decane. In addition, the synergistic materials are NaCl, sodium dodecyl ethoxy sulfate (AES), and decanoic...
A latency-tolerant MAC protocol for underwater acoustic sensor networks
, Article ICCAS 2010 - International Conference on Control, Automation and Systems, 27 October 2010 through 30 October 2010, Gyeonggi-do ; 2010 , Pages 849-854 ; 9781424474530 (ISBN) ; Manzuri, M. T ; Sharif University of Technology
2010
Abstract
Wireless networks with the shared media require Medium Access Control (MAC) protocol that provides contention resolution mechanism. The design of MAC protocol in underwater sensor networks is a challenging issue because of limited energy source and high propagation delay. The most important goal of the MAC design for underwater sensor networks is to resolve data packet collision efficiently with respect to energy consumption. So, selection of MAC protocol is an important task because it has significant impact on the system efficiency. A suitable MAC protocol must consider some factors such as fairness, energy consumption, latency and throughput based on various applications. The bandwidth in...
Semi-empirical modelling of hydraulic conductivity of clayey soils exposed to deionized and saline environments
, Article Journal of Contaminant Hydrology ; Volume 249 , 2022 ; 01697722 (ISSN) ; Sadeghi, H ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Clay liners are widely used as porous membrane barriers to control solute transport and to prevent the leakage of leachate both in horizontal and vertical flow scenarios, such as the isolated base and ramps of sanitary landfills. Despite the primary importance of saturated hydraulic conductivity in a reliable simulation of fluid flow through clay barriers, there is no model to predict hydraulic conductivity of clayey soils permeated with saline aqueous solutions because most of the current models were developed for pure water. Therefore, the main motivation behind this study is to derive semi-empirical models for simulating the hydraulic conductivity of clayey soils in the presence of...
Theoretical and numerical study of contaminant transport in clayey barriers using a revised numerical model considering the dependency of membrane efficiency and hydraulic conductivity on solute concentration
, Article Heliyon ; Volume 9, Issue 5 , 2023 ; 24058440 (ISSN) ; Hedayati Azar, A ; Sharif University of Technology
Elsevier Ltd
2023
Abstract
Solid waste is often buried in landfills isolated with a bentonite-based clay barrier to guarantee the high quality of groundwater. As the efficiency of clay barriers is highly dependent on solute concentration, this study aims to modify membrane efficiency, effective diffusion, and hydraulic conductivity of bentonite-based clayey barriers exposed to saline environments for numerical investigation of solute transport in such barriers. Therefore, the theoretical equations were modified as a function of solute concentration instead of constant values. First, a model was extended for membrane efficiency as a function of void ratio and solute concentration. Second, an apparent tortuosity model...
Design, construction, and evaluation of “sensor lock”: an electromechanical stance control knee joint
, Article Disability and Rehabilitation: Assistive Technology ; Volume 13, Issue 3 , 2018 , Pages 226-233 ; 17483107 (ISSN) ; Ahmadi Bani, M ; Baniasad, M ; Samadian, M ; Golchin, N ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
Background and aim: Most currently-available stance control knee ankle foot orthoses (SCKAFOs) still need full knee extension to lock the knee joint, and they are still noisy, bulky, and heavy. Therefore, the aim of this study was to design, construct, and evaluate an original electromechanical SCKAFO knee joint that could feasibly solve these problems, and thus address the problems of current stance control knee joints with regards to their structure, function, cosmesis, and cost. Method: Ten able-bodied (AB) participants and two (knee ankle foot orthosis) KAFO users were recruited to participate in the study. A custom SCKAFO with the same set of components was constructed for each...
Design, construction, and evaluation of “sensor lock”: an electromechanical stance control knee joint
, Article Disability and Rehabilitation: Assistive Technology ; 2017 , Pages 1-8 ; 17483107 (ISSN) ; Ahmadi Bani, M ; Baniasad, M ; Samadian, M ; Golchin, N ; Sharif University of Technology
2017
Abstract
Background and aim: Most currently-available stance control knee ankle foot orthoses (SCKAFOs) still need full knee extension to lock the knee joint, and they are still noisy, bulky, and heavy. Therefore, the aim of this study was to design, construct, and evaluate an original electromechanical SCKAFO knee joint that could feasibly solve these problems, and thus address the problems of current stance control knee joints with regards to their structure, function, cosmesis, and cost. Method: Ten able-bodied (AB) participants and two (knee ankle foot orthosis) KAFO users were recruited to participate in the study. A custom SCKAFO with the same set of components was constructed for each...
Maneuverability improvement for an ultra eight airplane model using variable shape wing
, Article Collection of Technical Papers - AIAA Atmospheric Flight Mechanics Conference, Providence, RI, 16 August 2004 through 19 August 2004 ; Volume 1 , 2004 , Pages 467-476 ; 1563477009 (ISBN) ; Alemohammad, S. H ; Khiabani, R. H ; Khalighi, Y ; Sharif University of Technology
2004
Abstract
One of the significant methods to design airplanes with high capabilities is taking advantage of variable shape structures to improve flight efficiency. In present article the effect of a variable shape wing on an ultra light flyer has been considered. Very low weight of this kind of airplane limits the applicability of control surfaces to attain appropriate maneuvers. To overcome this problem, implementation of a variable shape structure using SMA actuators has been proposed. For simulation, deformed shape of wings has been calculated with finite element method; this data has been used to determine aerodynamic coefficients using computational fluid dynamic (CFD) and finally leads to flight...
Modeling and analysis of AN ultra light slow flyer with variable shape control surfaces using shape memory alloy actuators
, Article Proceedings of the 7th Biennial Conference on Engineering Systems Design and Analysis - 2004, Manchester, 19 July 2004 through 22 July 2004 ; Volume 2 , 2004 , Pages 153-162 ; 0791841731 (ISBN); 9780791841730 (ISBN) ; Alemohamad, S. H ; Khiabani, R. H ; Khalighi, Y ; Sharif University of Technology
American Society of Mechanical Engineers
2004
Abstract
Applying flexible variable shape control surfaces (wing and elevator) structures is a way to increase efficiency and maneuverability of the planes, which is recently under research. In this paper, modeling of the flight of an unmanned ultra light plane is discussed. The modeling is done based on a real ultra light plane presented recently. To increase maneuverability of the plane, flexible variable shape structures are designed for the wing and the elevator. In design procedure, having an ultra light plane is considered. The elevator and the wing are used as control surfaces for longitudinal and lateral maneuvers respectively. Shape memory alloys (SMA) are used for reshaping the flexible...
L-sorbose production by gluconobacter oxydans using submerged fermentation in a bench scale fermenter
, Article Applied Food Biotechnology ; Volume 7, Issue 1 , 2020 , Pages 41-48 ; Alemzadeh, I ; Sharif University of Technology
National Nutrition and Food Technology Research Institute
2020
Abstract
Background and objective: L-Sorbose, as a precursor of ascorbic acid, can be biologically produced using Gluconobacter oxydans. The aim of this study was to optimize production of L-Sorbose by controlling concentration of the substrates and starter cultures. Material and methods: In this study, effects of three various fermentation parameters on the concentration of L-sorbose were assessed using fermenter (28°C, 1.4 vvm) and response surface methodology. These parameters included quantities of D-sorbitol (120-180 g lDw-1) (Deionized water) and yeast extract (6-18 g lDw-1) and inoculum/substrate ratios (5-10%). Results and conclusion: Results showed that the fitted model with high values of...
Robust-fuzzy model for supplier selection under uncertainty: an application to the automobile industry
, Article Scientia Iranica ; Volume 25, Issue 4 , 2018 , Pages 2297-2311 ; 10263098 (ISSN) ; Modarres, M ; Azar, A ; Sharif University of Technology
Sharif University of Technology
2018
Abstract
This paper proposes an innovative robust-fuzzy method for multi-objective, multi-period supplier selection problem under multiple uncertainties. This approach integrates robust optimization and fuzzy programming. Uncertain parameters are modeled as random variables that take value within a symmetrical interval. However, due to the complexity or ambiguity of some real world problems and especially the nature of some of the available input data, the length of interval is also highly uncertain. This ambiguity motivated us to present a new approach, which could be applicable to multiple uncertainties conditions. Thus, in our approach, the half-length of these intervals is also represented by...