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aspect-ratio
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Application of Experimental Design for Synthesis and Controlling Aspect Ratio of Metallic Nanorods
, M.Sc. Thesis Sharif University of Technology ; Jalali-Heravi, Mehdi (Supervisor) ; ormozi Nezhad, Mohammad Reza (Supervisor)
Abstract
Aspect ratio dependant optical properties of silver and gold nanorods is responsible for great attention toward controlling the aspect ratio of this class of the nanostructure for their application in variety of area, such as medical diagnosis, drug delivery, biosensing and treatment. In this research, gold and silver nanorods have been synthesized using chemical reducation and growth based on seed mediated method, which is the newest and one of the best methods with less difficulty for producing silver and gold nanorods. Absorption of the visible light by gold and silver nanorods results in appearing the longitudinal and transverse Plasmon bands in their absorption spectra which is related...
Determination of Protein Absorption Profile at the Surface of Biocompatible Superparamagnetic Iron Oxide Nanoparticles using Gel Electrophoresis
, M.Sc. Thesis Sharif University of Technology ; Hormozi Nezhad, Mohammad Reza (Supervisor) ; Mahmoudi, Morteza (Supervisor)
Abstract
Superparamagnetic Iron Oxide NPs (SPIONs) because of their multi-task capabilities (e.g. magnetic labeling, cell isolation, hyperthermiaand controlled drug release) have been recognized as one of the most promising NPs for theranosis applications.When NPs come in contact with a biological medium, the surfaces of them are covered by biomolecules (e.g., proteins, natural organic materials, and enzymes). Therefore, what a biological entity, such as cells, tissues, and organs, sees when interacting with NPs is different original pristine surface of the NPs and actually is hard protein corona. Shape of NPs has a great impact on proteins adsorb onto its surface and consequently on the way that...
Non-Equilibrium Interfacial Behavior of Dynamic Interfaces in Presence of Surfactants and Nanoparticles; Experimental and Computational Fluid Dynamic Investigations
, Ph.D. Dissertation Sharif University of Technology ; Bastani, Dariush (Supervisor) ; Lotfi, Marzieh (Supervisor)
Abstract
The present study has been performed for better understanding about the dynamic behavior of fluid interfaces in presence of surfactants, nanoparticles and their interactions in gas-liquid dispersion systems. One of the main purposes of this work is to investigate the influence of surface modified nanoparticles on the dynamic behavior of gas-liquid interfaces. For this purpose, the rising bubble experiment was used as one of the most conventional procedures. Local velocities of bubbles rising in nanoparticle solutions were determined experimentally. Influences of silica nanoparticles which were modified via three approaches were investigated in these experiments. Heat treatment was applied to...
Investigation of Effect of the Initial Bubble Shape on Rising Bubble Behaviour
, M.Sc. Thesis Sharif University of Technology ; Bastani, Daruoosh (Supervisor)
Abstract
In this experimental work terminal velocity, velocity profile and aspect ratio of bubble with 1.49 mm diameter which ascend in pure water and infected by surfactant nonionic C10DMPO and surfactant ionic SDS in regime that surface tension is dominant, have been considered. Observations showed that with respect to entering nozzle, bubbles with this diameter have two initial stable shape; spherical and extended form on surface for horizontal needle and vertical nozzle. Results are (1) Bubbles with initial spherical shape had lower terminal velocity and higher aspect ratio with respect to bubbles with initial extended form, (2) Spherical bubble had aspect ratio about 1 at whole bubble column...
Investigating the Effects of Specimen Size and Dimensions Ratio on Compressive Strength of Concrete
, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Tagi (Supervisor)
Abstract
Concrete is one of the most widely used building materials. Compressive strength of concrete is the most important property in designing reinforced concrete structures. Compressive strength test should be carried out on specimens with standard dimensions. In practice, dimensions of structural elements could be different from the dimensions of standard specimen. The dimensions’ ratio influences the strength of concrete specimen and the coefficient of strength variation. In the present study it is tried to obtain a meaningful relationship between size and strength based on the results of the tests on the specimens with different dimension ratios. Specimens examined in this study are C25 grade...
Evaluating of Geometric Factors Effects on Seakeeping Performance of HARTH Vessels
, M.Sc. Thesis Sharif University of Technology ; Seif, Mohammad Saeed (Supervisor)
Abstract
Performing research and development in the field of modern vessel types which serve several functions is considerably necessary because of their importance and rapid development. HARTH vessel is considered one of the important ships which has been recently attracted much attention from the world. In this respect, a full investigation of its performance could make a big contribution to its optimum design and appropriate exploitation.“HARTH” ship is the abbreviation for “High Aspect Ratio Twin Hull” is included in the catamaran vessel category with a high aspect ratio with respect to their underwater cross-section’s ratio of length to width.A host of crucial issues should be considered for...
Well-designed Ag/ZnO/3D graphene structure for dye removal: Adsorption, photocatalysis and physical separation capabilities
, Article Journal of Colloid and Interface Science ; Volume 537 , 2019 , Pages 66-78 ; 00219797 (ISSN) ; Samadi, M ; Asadian, E ; Zhou, Y ; Dong, C ; Zhang, J ; Moshfegh Zaker, A. R ; Sharif University of Technology
Academic Press Inc
2019
Abstract
In this research, adsorption and photocatalytic degradation process were utilized to remove organic dye from wastewater. To accomplish that, a newly-designed ternary nanostructure based on Ag nanoparticles/ZnO nanorods/three-dimensional graphene network (Ag NPs/ZnO NRs/3DG) was prepared using a combined hydrothermal-photodeposition method. The three-dimensional structure of graphene hydrogel as a support for growth of ZnO nanorods was characterized using field emission scanning electron microscopy (FESEM). In addition, diameter of silver nanoparticles grown on the ZnO nanorods with the average aspect ratio of 5 was determined in the range of 30–80 nm by using transmission electron microscopy...
Water drop impact on a semi-cylindrical convex hot surface for a diameter ratio of unity
, Article Experimental Thermal and Fluid Science ; Volume 106 , 2019 , Pages 68-77 ; 08941777 (ISSN) ; Morad, M. R ; Sharif University of Technology
Elsevier Inc
2019
Abstract
When a liquid drop impacts on a hot non-flat surface the curvature of the surface and its geometrical characteristics transmute the physical regimes and their boundary compared to a flat surface impact. The present experimental study is focused on water drop impingement on a mimetic solid semi-cylindrical convex hot surface, with a size equal to the drop. The thermal versus inertia map of generated regimes is obtained, while some well-known regimes associated with a flat surface are not observed for the present non-flat impacts. These include rebounding of the main drop and atomization which are common observed phenomena when the hot surface is flat. The maximum spreading of the droplet is...
Visual technique for detection of gas-liquid two-phase flow regime in the airlift pump
, Article Journal of Petroleum Science and Engineering ; Volume 75, Issue 3-4 , January , 2011 , Pages 327-335 ; 09204105 (ISSN) ; Ghanbarzadeh, S ; Saidi, M. H ; Sharif University of Technology
Abstract
Simplicity of manufacturing and high reliability of airlift pumps have promoted these pumps to be used in different industries, such as petrochemical and oil industries, especially in oil recovery from dead wells. One of the main parameters affecting the performance of these pumps is two-phase flow regime in the main pipe of the pump. In this research, experimental data are utilized to investigate the influence of the flow regimes on the performance of an airlift pump. The data are obtained for air-water two-phase flow in a vertical pipe with a diameter of d = 50. mm and an aspect ratio of L/d = 120. In this study, the gas liquid upward two-phase flow regime in the upriser pipe is...
Viscous damping effect on the aeroelastic stability of subsonic wings: Introduction of the U–K method
, Article Journal of Fluids and Structures ; Volume 73 , 2017 , Pages 1-15 ; 08899746 (ISSN) ; Dehghani Firouz Abadi, R ; Rahmanian, M ; Sharif University of Technology
Abstract
This study aims at introduction of a novel method for evaluating the effect of viscous damping on the aeroelastic stability boundaries. The K-method is well-known for being one of the fastest methods in determining the instability conditions (i.e. critical speed and its corresponding frequency). However, formulation of the K-method is developed for aeroelastic systems without viscous damping and solution is valid where the introduced artificial damping is zero. Taking into account the framework of the K-method in general, this study has tried to remove the major shortcoming of the K-method, i.e. investigation of the effect of viscous damping on the aeroelastic stability boundaries. The...
Variational formulation on Joule heating in combined electroosmotic and pressure driven microflows
, Article International Journal of Heat and Mass Transfer ; Volume 61, Issue 1 , June , 2013 , Pages 254-265 ; 00179310 (ISSN) ; Saidi, M. H ; Waezi, Z ; Chakraborty, S ; Sharif University of Technology
2013
Abstract
The present study attempts to analyze the extended Graetz problem in combined electroosmotic and pressure driven flows in rectangular microchannels, by employing a variational formulation. Both the Joule heating and axial conduction effects are taken into consideration. Since assuming a uniform inlet temperature profile is not consistent with the existence of these effects, a step change in wall temperature is considered to represent physically conceivable thermal entrance conditions. The method of analysis considered here is primarily analytical, in which series solutions are presented for the electrical potential, velocity, and temperature. For general treatment of the eigenvalue problem...
Unsteady solute dispersion by electrokinetic flow in a polyelectrolyte layer-grafted rectangular microchannel with wall absorption
, Article Journal of Fluid Mechanics ; Volume 887 , 2020 ; Saidi, M. H ; Moosavi, A ; Sadeghi, A ; Sharif University of Technology
Cambridge University Press
2020
Abstract
The dispersion of a neutral solute band by electrokinetic flow in polyelectrolyte layer (PEL)-grafted rectangular/slit microchannels is theoretically studied. The flow is assumed to be both steady and fully developed and a first-order irreversible reaction is considered at the wall to account for probable surface adsorption of solutes. Considering low electric potentials, analytical solutions are obtained for electric potential, fluid velocity and solute concentration. Special solutions are also obtained for the case without wall adsorption. To track the dispersion properties of the solute band, the generalized dispersion model is adopted by considering the exchange, the convection and the...
Universal rotation of nanowires in static uniform electric fields in viscous dielectric liquids
, Article Applied Physics Letters ; Volume 113, Issue 6 , 2018 ; 00036951 (ISSN) ; Esfandiar, A ; Moshfegh, A. Z ; Sharif University of Technology
American Institute of Physics Inc
2018
Abstract
The wide utilization of nanomanipulation as a promising approach in microorganisms, nanoelectromechanical systems, and assembly of nanostructures remarks the importance of nanostructures' motion in electric fields. Here, we study the rotational dynamics of metallic and non-metallic nanowires (NWs) in a static uniform electric field in viscous dielectric liquids. For metallic NWs, it has been theoretically shown that the electric field-induced rotation is practically independent of the geometrical dimensions and the electrical properties of NWs. Our experimental results for suspended silver (Ag) NWs in microscope oil are perfectly in agreement with this model. However, in the case of TiO2...
Towards defining new nano-descriptors: Extracting morphological features from transmission electron microscopy images
, Article RSC Advances ; Vol. 4, issue. 104 , Nov , 2014 , p. 60135-60143 ; Hormozi-Nezhad, M. R ; Jalali-Heravi, M ; Abedini, M. R ; Sharif-Bakhtiar, F ; Sharif University of Technology
Abstract
Due to the important role of surface-related properties of NPs in their biological behavior, simple and fast methods that could precisely demonstrate accurate information about NPs' surface, structure and morphology are highly desirable. In this study a set of surface morphological nano-descriptors (size, shape, surface area, agglomeration state, curvature, corner count and aspect ratio) have been defined and extracted from Transmission Electron Microscopy (TEM) images of nanoparticles (NPs) by Digital Image Processing methods. The extracted data represent a thorough description of the surface and morphologies of NPs lying beyond their TEM images and can supply the data required for a...
Time-average drag coefficient and void fraction in gas-liquid two phase flow
, Article Proceedings of the ASME Fluids Engineering Division Summer Conference 2009, FEDSM2009, 2 August 2009 through 6 August 2009, Vail, CO ; Volume 1, Issue PART B , 2009 , Pages 1083-1094 ; 9780791843727 (ISBN) ; Hanafizadeh, P ; Saidi, M. H ; Sharif University of Technology
Abstract
Two-phase flow simulations around a body were not studied before and considering these flows can play a significant role in long-term reliability and safety of industrial systems. In this paper, flow regimes, drag coefficient and void fraction around different cross-section prisms were considered. To achieve this aim, main equations of flow have been developed for investigation of drag coefficient in air-water two phase. Our numerical analyses were performed by a designed and written CFD package which is based on Eulerian-Eulerian approach. Geometries, which have been studied in this article, are: circle, rectangle and triangle, for different aspect ratio (length over width) and leading edge...
Three-dimensional numerical simulation of a novel electroosmotic micromixer
, Article Chemical Engineering and Processing: Process Intensification ; Volume 119 , 2017 , Pages 25-33 ; 02552701 (ISSN) ; Madadelahi, M ; Abdorahimzadeh, S ; Sharif University of Technology
Elsevier B.V
2017
Abstract
Lab-on-a-chip (LOC) systems have been widely used in chemical and medical analyses. In this study, a novel T-shaped electroosmotic micromixer was simulated and the effects of different parameters on the mixing process were examined. These parameters include; inlet angle, number of conducting hurdles, arrangements of the hurdles, geometry of hurdles and chambers, aspect ratios of the channel cross-sectional profile, hurdle radius, and depth. It was found that the inlet angle has a direct influence on mixing index (σ). The effect of various number of hurdles (one, two, three and four hurdles) and their orientations was investigated. Simulations revealed that using two conducting hurdles is the...
Thorough tuning of the aspect ratio of gold nanorods using response surface methodology
, Article Analytica Chimica Acta ; Volume 779 , 2013 , Pages 14-21 ; 00032670 (ISSN) ; Robatjazi, H ; Jalali Heravi, M ; Sharif University of Technology
2013
Abstract
In the present work a central composite design based on response surface methodology (RSM) is employed for fine tuning of the aspect ratios of seed-mediated synthesized gold nanorods (GNRs). The relations between the affecting parameters, including ratio of l-ascorbic acid to Au3+ ions, concentrations of silver nitrate, CTAB, and CTAB-capped gold seeds, were explored using a RSM model. It is observed that the effect of each parameter on the aspect ratio of developing nanorods highly depends on the value of the other parameters. The concentrations of silver ions, ascorbic acid and seeds are found to have a high contribution in controlling the aspect ratios of NRs. The optimized parameters led...
The UV photodetection enhancement of tailored ZnO nanorods by controlling the aspect ratio
, Article Surfaces and Interfaces ; Volume 28 , 2022 ; 24680230 (ISSN) ; Rajabi, M ; Moshfegh, A. Z ; Sharif University of Technology
Elsevier B.V
2022
Abstract
ZnO Nanorods (NRs) are deposited on glass substrate using the hydrothermal method by applying a strategic growth control to improve their aspect ratios. In this research, the aspect ratio was tuned by tailoring the synthesis parameters, including the seed layer annealing temperature, absence/presence of polyethylenimine (PEI) in the growth solution, and the solution preheating process. The effects of these parameters on the morphology, crystal structure, room temperature photoluminescence properties, and current-voltage characteristics were examined by FESEM, XRD, PL, and I-V measurements. It was demonstrated that by varying the seed layer annealing temperature and presence of PEI solution...
The study of magnetic field implementation on cylinder quenched in boiling ferro-fluid
, Article Applied Thermal Engineering ; Volume 64, Issue 1-2 , March , 2014 , Pages 331-338 ; ISSN: 13594311 ; Saboonchi, A ; Shafii, M. B ; Jahani, N ; Sharif University of Technology
Abstract
It has been shown that nanofluids in different investigations increase or decrease heat transfer rate in boiling phenomenon. The present study examined the effects of ferro-fluid concentrations and magnetic field implementation on the fluid throughout the boiling process. Obtained are the quenching curve and boiling curve on specified surface roughness in both water and ferro-fluid with two different concentrations. A silver cylinder with Aspect ratio of 10, and surface roughness of 689 nm was heated up to 350 C and then was overwhelmed in the fluid under study. Temperatures were measured by a thermocouple which installed in the center of the cylinder. The test was carried out 5 times. The...
The role of mixed reaction promoters in polyol synthesis of high aspect ratio ag nanowires for transparent conducting electrodes
, Article Journal of Electronic Materials ; Volume 49, Issue 8 , 2020 , Pages 4822-4829 ; Khosravi, A ; Dehghani, M ; Tajabadi, F ; Taghavinia, N ; Sharif University of Technology
Springer
2020
Abstract
In recent years, thin silver nanowires (Ag NWs) with diameters smaller than 150 nm have been synthesized by implementation of NaCl or FeCl3 as reaction promoters and high molecular weight polyvinylpyrrolidone (PVP) as the capping agent. However, the yield of Ag NWs still remains low, mostly due to the insufficient aspect ratio (AR) of the synthesized nanostructures and the production of Ag nanoparticles, which is an undesirable by product. This study proposes a modified technique to alleviate the problem by using a mixture of FeCl3/CuCl2 as the reaction promoter and two different types of PVP with molecular weight of 360 k and 40 k as the capping agents. The appropriate mixtures of...