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shahsavar--morad
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Synthesis of Graphene Nanosheets for Stem Cells Applications
, M.Sc. Thesis Sharif University of Technology ; Akhavan, Omid (Supervisor)
Abstract
Graphene nanogrids fabricated by graphene nanoribbons obtained through oxidative unzipping of multi-walled carbon nanotubes, used as two-dimensional selective templates for accelerated differentiation of human mesenchymal stem cells (hMSCs), isolated from umbilical cord blood, into osteogenic lineage. The biocompatible and hydrophilic graphene nanogrids showed high actin cytoskeleton proliferations that coinciding with patterns of the nanogrids. The amounts of proliferations found are slightly better than proliferation on hydrophilic graphene oxide (GO) sheets, and significantly higher than non-uniform proliferations on hydrophobic reduced graphene oxide (rGO) sheets and polydimethylsiloxane...
, M.Sc. Thesis Sharif University of Technology ; Khonsari, Vahid (Supervisor)
Abstract
In this thesis, change of the behavior of frames due to adding damping devices to frames is taken into consideration and a non-linear static analysis computer program is developed . In numerical studies a few one and two story frames are used. The results of previous studies have shown that, adding energy damping devices to the structural systems, results in structure damping increase, story drift and base shear decrease. To reveal the behavior of the new bracing system, experimental and numerical studies are made. The main point in design of this bracing system, was the capability of easy replacement and maximum damping with minimum damage. It must be declared that design thought of this...
Graphene nanogrids for selective and fast osteogenic differentiation of human mesenchymal stem cells
, Article Carbon ; Volume 59 , 2013 , Pages 200-211 ; 00086223 (ISSN) ; Ghaderi, E ; Shahsavar, M ; Sharif University of Technology
2013
Abstract
Graphene nanogrids (fabricated by graphene nanoribbons obtained through oxidative unzipping of multi-walled carbon nanotubes) were used as two-dimensional selective templates for accelerated differentiation of human mesenchymal stem cells (hMSCs), isolated from umbilical cord blood, into osteogenic lineage. The biocompatible and hydrophilic graphene nanogrids showed high actin cytoskeleton proliferations coinciding with patterns of the nanogrids. The amounts of proliferations were found slightly better than proliferation on hydrophilic graphene oxide (GO) sheets, and significantly higher than non-uniform proliferations on hydrophobic reduced graphene oxide (rGO) sheets and...
A parameter-tuned genetic algorithm for the resource investment problem with discounted cash flows and generalized precedence relations
, Article Computers and Operations Research ; Volume 36, Issue 11 , 2009 , Pages 2994-3001 ; 03050548 (ISSN) ; Akhavan Niaki, T ; Shahsavar, M ; Sharif University of Technology
2009
Abstract
A resource investment problem with discounted cash flows (RIPDCF) is a project-scheduling problem in which (a) the availability levels of the resources are considered decision variables and (b) the goal is to find a schedule such that the net present value of the project cash flows optimizes. In this paper, the RIPDCF in which the activities are subject to generalized precedence relations is first modeled. Then, a genetic algorithm (GA) is proposed to solve this model. In addition, design of experiments and response surface methodology are employed to both tune the GA parameters and to evaluate the performance of the proposed method in 240 test problems. The results of the performance...
Statistical design of genetic algorithms for combinatorial optimization problems
, Article Mathematical Problems in Engineering ; Volume 2011 , 2011 ; 1024123X (ISSN) ; Najafi, A. A ; Niaki, S. T. A ; Sharif University of Technology
2011
Abstract
Many genetic algorithms (GA) have been applied to solve different NP-complete combinatorial optimization problems so far. The striking point of using GA refers to selecting a combination of appropriate patterns in crossover, mutation, and and so forth and fine tuning of some parameters such as crossover probability, mutation probability, and and so forth. One way to design a robust GA is to select an optimal pattern and then to search for its parameter values using a tuning procedure. This paper addresses a methodology to both optimal pattern selection and the tuning phases by taking advantage of design of experiments and response surface methodology. To show the performances of the proposed...
A two-part self-adaptive technique in genetic algorithms for project scheduling problems
, Article Journal of Modern Project Management ; Volume 4, Issue 2 , 2016 , Pages 64-73 ; 23173963 (ISSN) ; Akhavan Niaki, S. T ; Najafi, A. A ; Sharif University of Technology
Editora Mundos Sociais
2016
Abstract
The present paper introduces a novel two-part self-adaptive technique in designing the genetic algorithm for project scheduling problems. One part of the algorithm includes a self-adaptive mechanism for genetic operators like crossover and mutation. The second part contains another self-adaptive mechanism for genetic parameters such as crossover probability. The parts come in turn repeatedly within a loop feeding each other with the information regarding the performance of operators or parameters. The capability of the method is tested and confirmed in comparison to metaheuristic and exact algorithms based on well-known benchmarks
An efficient genetic algorithm to maximize net present value of project payments under inflation and bonus-penalty policy in resource investment problem
, Article Advances in Engineering Software ; Volume 41, Issue 7-8 , July–August , 2010 , Pages 1023-1030 ; 09659978 (ISSN) ; Akhavan Niaki, S. T ; Najafi, A. A ; Sharif University of Technology
2010
Abstract
In order to develop a more realistic resource-constrained project-scheduling model that is applicable to real-world projects, in this paper, the resource investment problem with discounted cash flows and generalized precedence relations is investigated under inflation factor such that a bonus-penalty structure at the deadline of the project is imposed to force the project not to be finished beyond the deadline. The goal is to find activity schedules and resource requirement levels that maximize the net present value of the project cash flows. The problem is first mathematically modeled. Then, a genetic algorithm (GA) is designed using a new three-stage process that utilizes design of...
Three self-adaptive multi-objective evolutionary algorithms for a triple-objective project scheduling problem
, Article Computers and Industrial Engineering ; Volume 87 , September , 2015 , Pages 4-15 ; 03608352 (ISSN) ; Najafi, A. A ; Niaki, S. T. A ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Finding a Pareto-optimal frontier is widely favorable among researchers to model existing conflict objectives in an optimization problem. Project scheduling is a well-known problem in which investigating a combination of goals eventuate in a more real situation. Although there are many different types of objectives based on the situation on hand, three basic objectives are the most common in the literature of the project scheduling problem. These objectives are: (i) the minimization of the makespan, (ii) the minimization of the total cost associated with the resources, and (iii) the minimization of the variability in resources usage. In this paper, three genetic-based algorithms are proposed...
On the proof of the first Carnot theorem in thermodynamics
, Article European Journal of Physics ; Volume 34, Number 6 , 2013 , Pages 1581-1588 ; 01430807 (ISSN) ; Momeni, F ; Sharif University of Technology
2013
Abstract
The proof of the first Carnot theorem in classical thermodynamics is revisited in this study. The underlying conditions of a general proof of this principle presented by Senft (1978 Phys. Educ. 13 35-37) are explored and discussed. These conditions are analysed in more detail using a physical description of heat and work to present a simpler proof of the first principle prior to using the violation of the second law of thermodynamics. Finally, a new simple proof is also presented based on Gibbs relation. This discussion will benefit the teaching of classical thermodynamics and promote better understanding of the proof of the first Carnot theorem in general form
Penetration of elliptical liquid jets in low-speed crossflow
, Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 141, Issue 1 , 2019 ; 00982202 (ISSN) ; Khosrobeygi, H ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2019
Abstract
Trajectory and penetration of elliptical liquid jets emerged into a low-speed crossflow of air are studied. The jets are introduced to the crossflow at different momentum ratios ranging from 1 to 300. The images are analyzed to obtain the trajectories of the outer boundary of the jets for two different aspect ratios. An empirical correlation is proposed for the present injector geometries and for the range of momentum ratio, Weber, and Reynolds numbers used in this study. Finally, a theoretical model for the trajectory of the liquid column for an initially elliptical liquid emerging into a crossflow is presented, and the associated drag coefficients are obtained for a precise trajectory...
Penetration of elliptical liquid jets in low-speed crossflow
, Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 141, Issue 1 , 2019 ; 00982202 (ISSN) ; Khosrobeygi, H ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2019
Abstract
Trajectory and penetration of elliptical liquid jets emerged into a low-speed crossflow of air are studied. The jets are introduced to the crossflow at different momentum ratios ranging from 1 to 300. The images are analyzed to obtain the trajectories of the outer boundary of the jets for two different aspect ratios. An empirical correlation is proposed for the present injector geometries and for the range of momentum ratio, Weber, and Reynolds numbers used in this study. Finally, a theoretical model for the trajectory of the liquid column for an initially elliptical liquid emerging into a crossflow is presented, and the associated drag coefficients are obtained for a precise trajectory...
Effect of temperature and concentration on thermal conductivity and viscosity of ferrofluid loaded with carbon nanotubes
, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; 2015 , Pages 1-9 ; 09477411 (ISSN) ; Saghafian, M ; Salimpour, M. R ; Shafii, M. B ; Sharif University of Technology
Springer Verlag
2015
Abstract
The aim of this paper is to investigate the thermal conductivity and viscosity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs), experimentally. The magnetic nanoparticles and CNTs are physically attached as the result of interaction between the TMAH and GA molecules. The morphology and structure of the samples are characterized with X-ray diffraction (XRD) and transmission electron microscopy (TEM). The experiments are carried out in the magnetic nanoparticles volume concentration range of 0.1–0.9 %, CNT volume concentration range of 0.05–1.35 % and the temperature range of 25–55 °C. The...
Experimental investigation on laminar forced convective heat transfer of ferrofluid loaded with carbon nanotubes under constant and alternating magnetic fields
, Article Experimental Thermal and Fluid Science ; Volume 76 , 2016 , Pages 1-11 ; 08941777 (ISSN) ; Saghafian, M ; Salimpour, M. R ; Shafii, M. B ; Sharif University of Technology
Elsevier Inc
2016
Abstract
In this paper, the effects of both constant and alternating magnetic fields on the laminar forced convective heat transfer of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs) flowing through a heated tube were investigated experimentally. The experiments were carried out over wide range of parameters such as Reynolds number (548-2190), volume concentrations of Fe3O4 (0.5-0.9%) and carbon nanotube (0.25-1.35%) nanoparticles, magnetic field strength (300-700 Gauss) and alternating magnetic field frequency (10-50 Hz). In present study, the experimental observations in the case without magnetic field...
Effect of temperature and concentration on thermal conductivity and viscosity of ferrofluid loaded with carbon nanotubes
, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 52, Issue 10 , 2016 , Pages 2293-2301 ; 09477411 (ISSN) ; Saghafian, M ; Salimpour, M. R ; Shafii, M. B ; Sharif University of Technology
Springer Verlag
2016
Abstract
The aim of this paper is to investigate the thermal conductivity and viscosity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs), experimentally. The magnetic nanoparticles and CNTs are physically attached as the result of interaction between the TMAH and GA molecules. The morphology and structure of the samples are characterized with X-ray diffraction (XRD) and transmission electron microscopy (TEM). The experiments are carried out in the magnetic nanoparticles volume concentration range of 0.1–0.9 %, CNT volume concentration range of 0.05–1.35 % and the temperature range of 25–55 °C. The...
An experimental study on the effect of ultrasonication on thermal conductivity of ferrofluid loaded with carbon nanotubes
, Article Thermochimica Acta ; Volume 617 , October , 2015 , Pages 102-110 ; 00406031 (ISSN) ; Salimpour, M. R ; Saghafian, M ; Shafii, M. B ; Sharif University of Technology
Elsevier
2015
Abstract
Nanofluids containing Fe3 O4 and carbon nanotubes nanoparticles emulsified and dispersed using gum arabic (GA) and tetramethylammonium hydroxide (TMAH) were made and characterized for potential use as heat transfer fluids. Due to the interaction between the TMAH and GA molecules, the magnetic nanoparticles and CNTs were physically adsorbed. This paper reports an experimental work on the effect of ultrasonication on thermal conductivity of this aqueous suspension. The characterization and surface morphology of the dried samples were studied by using XRD and TEM measurements. Experiments were conducted in the magnetic nanoparticles mass concentration range 0.494-2.428%,...
Effect of magnetic field on thermal conductivity and viscosity of a magnetic nanofluid loaded with carbon nanotubes
, Article Journal of Mechanical Science and Technology ; Volume 30, Issue 2 , 2016 , Pages 809-815 ; 1738494X (ISSN) ; Salim Pour, M. R ; Saghafian, M ; Shafii, M. B ; Sharif University of Technology
Korean Society of Mechanical Engineers
2016
Abstract
The present work examines experimentally the effect of magnetic field on the viscosity and thermal conductivity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and Gum arabic (GA) coated carbon nanotubes (CNTs). The hybrid nanofluid was prepared by using ultrasonic dispersion method. Magnetic field was created by a pair of spaced apart magnet plates. The effect of temperature on the time variation of thermal conductivity under applied magnetic field was also investigated. According to the results of this study, viscosity of the hybrid nanofluid increases with the strength of magnetic field, while it decreases with the increase of temperature....
Mechanical behaviour of A-III steel rebars under monotonic loadings at seismic strain rates
, Article Magazine of Concrete Research ; Volume 70, Issue 1 , 2018 , Pages 42-54 ; 00249831 (ISSN) ; Shabani, A ; England, G. L ; Shahsavar Gargari, M ; Sharif University of Technology
ICE Publishing
2018
Abstract
As the reinforcing bars used in concrete structures located in earthquake-prone areas experience strain rates higher than normal quasi-static ones, it is necessary to have a comprehensive understanding of the behaviour of such materials under these rates of loading. In this work, in order to study the behaviour of grade A-III reinforcing-bar steel (based on the GOST standard, a set of technical standards maintained by the Euro-Asian Council for Standardization, Metrology and Certification), a number of monotonic tests on its tensile and compressive strength on (short and long) specimens at various strain rates, 0·002, 0·01, 0·02 and 0·04 s-1, experienced during earthquakes, were carried out....
Experimental Study of Simple Orifice Geometry Variation on Liquid Jet Disintegration in a Gaseous Cross Flow
, M.Sc. Thesis Sharif University of Technology ; Morad, Mohammad Reza (Supervisor)
Abstract
In this thesis, elliptical liquid jet breakup in crossflow has been investigated. To do this, two elliptical nozzle with different aspect ratio were built. First, the effective and important dimensionless numbers were extracted. Then, the physical aspect of the question was analyzed. All the experiments have been done in atmospheric conditions with water fluid, air as the liquid jet, and gas crossflow respectively.To create crossflow, a square cross section channel and one blower which are set in the beginning of the channel were made use of. Water is injected into air crossflow by the injector installed under the channel. The system used in revealing the crossflow is shadowgraphy system....
Experimental Study of Flame Formation Using a Liquid Fuel Electrospray in Small Scales
, M.Sc. Thesis Sharif University of Technology ; Morad, Mohammad Reza (Supervisor)
Abstract
With increasing demand for more efficient combustion processes, alternative processes like application of magnetic and electric fields for modification of combustion have offered possible solutions. In the recent years, liquid electro-spraying has been a hot topic with growing interest due to its wide applications in such area as fuel atomization in combustion systems, which has been investigated in this project. Notice that in this method the liquid fuel in the high voltage electric field between electrodes will be broken into small droplets. In this thesis diffusion combustion of two alcoholic liquid fuels of ethanol and butanol at the exit of a small-scale combustor of vertical Pyrex...
Exprimental Study of Various Modes of Electrospray for Different Nozzles
, M.Sc. Thesis Sharif University of Technology ; Morad, Mohammad Reza (Supervisor)
Abstract
Electrospray is an interesting method to produce spray. This study has an insight on electrospraying phenomenon and its effective parameters. All modes, the forces and the situation to establish has been investigated for ethanol. Suitable configuration is introduced and for different flow rates and voltages the phenomenon is studied. Images are captured by two camera (high speed camera and high resolution camera) by using two method (shadowgraphy and light scattering). In the respect of producing fine and monodisperse droplets in cone-jet mode the stability of this mode is imported to enlarge. The special nozzle is design to increase stability of cone-jet mode even 70 times of using...