Search for: aspect-ratio
Total 203 records
Investigating the Effects of Specimen Size and Dimensions Ratio on Compressive Strength of Concrete, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Tagi
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
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...
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 ; Lotfi, Marzieh
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
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...
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 ; Mahmoudi, Morteza
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...
Application of Experimental Design for Synthesis and Controlling Aspect Ratio of Metallic Nanorods, M.Sc. Thesis Sharif University of Technology ; Jalali-Heravi, Mehdi ; ormozi Nezhad, Mohammad Reza
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...
A novel field ionization gas sensor based on self-organized CuO nanowire arrays, Article Sensors and Actuators, A: Physical ; Vol. 216 , 2014 , pp. 202-206 ; ISSN: 09244247 ; Ahmadvand, H ; Iraji Zad, A ; Sharif University of Technology
In this study, we present fabrication and characterization of a gas ionization sensor based on high aspect ratio one-dimensional CuO nanowires as the field enhancing medium. Self-organized arrays of CuO nanowires have been synthesized based on a low-cost thermal oxidation method and integrated into a gas ionization sensor (GIS). The self-organized arrays of CuO nanowires have been employed to detect the identity of several gas species such as He, Ar and CO at ambient temperature and pressure. The sharp nanoscale size of CuO tips provide very high electric fields at moderate voltages (less than 100 V) and provoke the breakdown of different gases. The reduced breakdown current of the metal...
Numerical modeling of surface reaction kinetics in electrokinetically actuated microfluidic devices, Article Analytica Chimica Acta ; Vol. 838, issue , August , 2014 , pp. 64-75 ; ISSN: 00032670 ; Amini, Y ; Saidi, M. H ; Chakraborty, S ; Sharif University of Technology
We outline a comprehensive numerical procedure for modeling of species transport and surface reaction kinetics in electrokinetically actuated microfluidic devices of rectangular cross section. Our results confirm the findings of previous simplified approaches that a concentration wave is created for sufficiently long microreactors. An analytical solution, developed for the wave propagation speed, shows that, when normalizing with the fluid mean velocity, it becomes a function of three parameters comprising the channel aspect ratio, the relative adsorption capacity, and the kinetic equilibrium constant. Our studies also reveal that the reactor geometry idealized as a slit, instead of a...
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
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...
Buoyancy effects on gaseous slip flow in a vertical rectangular microchannel, Article Microfluidics and Nanofluidics ; Vol. 16, issue. 1-2 , 2014 , pp. 207-224 ; ISSN: 16134982 ; Sadeghi, A ; Saidi, M. H ; Sharif University of Technology
Consideration is given to the buoyancy effects on the fully developed gaseous slip flow in a vertical rectangular microduct. Two different cases of the thermal boundary conditions are considered, namely uniform temperature at two facing duct walls with different temperatures and adiabatic other walls (case A) and uniform heat flux at two walls and uniform temperature at other walls (case B). The rarefaction effects are treated using the firstorder slip boundary conditions. By means of finite Fourier transform method, analytical solutions are obtained for the velocity and temperature distributions as well as the Poiseuille number. Furthermore, the threshold value of the mixed convection...
Electrospun titania sol-gel-based ceramic composite nanofibers for online micro- solid-phase extraction with high-performance liquid chromatography, Article Journal of Separation Science ; Vol. 37, issue. 15 , August , 2014 , pp. 1982-1988 ; ISSN: 16159306 ; Piri-Moghadam, H ; Rastegar, S ; Taheri, N ; Sharif University of Technology
Titanium(IV) tetraisopropoxide was employed as a metal oxide sol-gel precursor to prepare ceramic composite nanofibers by the electrospinning system. To facilitate this process and obtain the desired nanofibers with higher aspect ratios and surface area, poly(vinylpyrrolidone) was added to the sol of titania. Four ceramic nanofibers sheets based on titania were prepared while each sheet contained different transition metals such as Fe-Mn, Fe-Ni, Fe-Co, and Fe-Mn-Co-Ni. The scanning electron microscope images showed good homogeneity for all the prepared ceramic composites with a diameter range of 100-250 nm. The sorption efficiency was investigated by a micro-solid-phase extraction setup in...
Simulation and control of multidimensional crystallization Processes, Article Chemical Engineering Communications ; Vol. 201, Issue. 7 , 2014 , pp. 870-895 ; ISSN: 0098-6445 ; Shahrokhi, M ; Sharif University of Technology
In this article, solving the population balance equation (PBE) and controlling the final particle size for crystallization problems have been addressed. For solving the general form of multidimensional PBE, a numerical method called conservation element and solution element (CE/SE) has been used. By applying this method to one- and two-dimensional crystallization problems, it has been shown that this technique can handle all types of source terms in the PBE. Model accuracy has been checked with experimental data reported in the literature and also with the analytical solution of PB-type equations. Control of final particle size was formulated in an optimization framework. To obtain a desired...
Dynamic instability of cantilevered composite pipe conveying flow with an end nozzle, Article 21st International Congress on Sound and Vibration 2014, ICSV 2014 ; Vol. 4, issue , 13- 17 July , 2014 , pp. 3564-3571 ; ISBN: 9781634392389 ; Abtahi, H ; Haddadpour, H ; Sharif University of Technology
In this paper, the instability of cantilevered horizontal composite pipes is investigated. To this aim, the lateral flow forces are modelled as a distributed lateral force and the nozzle effect is modelled as a compressive axial follower force and a concentrated end mass. The coupled bending-torsional equations of motion are derived using Hamilton's principal and Galerkin method. In order to obtain the stability margin of the pipe, the standard Eigen value problem is solved. Finally, effects of elastic coupling parameter and nozzle aspect ratio are considered on the stability margin of the pipe and some conclusions are drawn
CFD-aided simulation of frost growth inside a narrow duct with uniform wall temperature variation, Article ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM 2014, Collocated with the ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting ; 2014 ; ISBN: 9780791846278 ; Asgari, E ; Hajikaram, M ; Schneider, G. E ; Sharif University of Technology
In this paper, we study the frost formation and growth at the walls of a duct with uniform wall temperature variation. The simulation is performed for laminar flow regime considering suitable semi-empirical models incorporated with computational fluid dynamics (CFD) method. The frost growth is considered to be normal to the duct surface. Since the duct aspect ratio is high, we perform our simulations in two-dimensional zones. To simulate the frost layer properly, we solve both the energy and mass balance equations implementing some semi-empirical correlations on the frost side. At this stage, we suitably predict the required heat flux value at the solid boundary and the heat transfer...
An analysis of carbone monoxide distribution in large tunnel fires, Article Journal of Mechanical Science and Technology ; Vol. 28, Issue. 5 , 2014 , pp. 1917-1925 ; ISSN: 1738494X ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
Fire events and the related toxicants such as CO are responsible for many fatalities in the current century. These hazardous events are much more dangerous when they occur in enclosed spaces. In the present study, a theoretical relation is developed for horizontal distribution of CO in a large tunnel fire. Then, the developed criterion is used to study the effect of some rudimentary parameters such as the heat release rate (HRR) of fire and tunnel's aspect ratio (AR) on CO and temperature stratification. Theoretical results of various heat release rates and aspect ratios for horizontal distribution of CO are compared with numerical results using fire dynamics simulator (FDS5.5). It is found...
Bidirectional behavior of unreinforced masonry walls, Article Earthquake Engineering and Structural Dynamics ; Vol. 43, Issue 15 , 1 December , 2014 , pp. 2377-2397 ; ISSN: 00988847 ; Aref, A. J ; Yekrangnia, M ; Sharif University of Technology
Most of the studies related to the modeling of masonry structures have by far investigated either the in-plane (IP) or the out-of-plane (OP) behavior of walls. However, seismic loads mostly impose simultaneous IP and OP demands on load-bearing or shear masonry walls. Thus, there is a need to reconsider design equations of unreinforced masonry walls by taking into account bidirectional effects. The intent of this study is to investigate the bidirectional behavior of an unreinforced masonry wall with a typical aspect ratio under different displacement-controlled loading directions making use of finite element analysis. For this purpose, the numerical procedure is first validated against the...
Modeling of dislocation density and strength on rheoforged A356 alloy during multi-directional forging, Article Computational Materials Science ; Vol. 81 , 2014 , pp. 284-289 ; Saei, M ; Kazeminezhad, M ; Dodangeh, A ; Sharif University of Technology
In this study, a hybrid model is presented to predict the dislocation density and strength evolution of the rheoforged non-dendritic A356 alloy during multi-directional forging. Regarding the characteristics of non-dendritic A356 alloy, combination of Shear Lag and Nes models is used for the eutectic structure, and Nes model is used for the α-Al globular phase. The aspect ratio variations of Si particles in eutectic structure during 3 passes of multi-directional forging do not change the model predictions, significantly. Model predictions on shear stress are in good agreement with experimental results of shear punch test
Pressure effects on electroosmotic flow of power-law fluids in rectangular microchannels, Article Theoretical and Computational Fluid Dynamics ; Vol. 28, issue. 4 , 2014 , pp. 409-426 ; ISSN: 09354964 ; Sadeghi, A ; Saidi, M. H ; Sharif University of Technology
In this paper, the fully developed electroosmotic flow of power-law fluids in rectangular microchannels in the presence of pressure gradient is analyzed. The electrical potential and momentum equations are numerically solved through a finite difference procedure for a non-uniform grid. A complete parametric study reveals that the pressure effects are more pronounced at higher values of the channel aspect ratio and smaller values of the flow behavior index. The Poiseuille number is found to be an increasing function of the channel aspect ratio for pressure assisted flow and a decreasing function of this parameter for pressure opposed flow. It is also observed that the Poiseuille number is...
Thermal transport characteristics pertinent to electrokinetic flow of power-law fluids in rectangular microchannels, Article International Journal of Thermal Sciences ; Vol. 79, issue , 2014 , p. 76-89 ; Saidi, M. H ; Sadeghi, A ; Sharif University of Technology
In the present study, the thermal characteristics of electroosmotic flow of power-law fluids in rectangular microchannels in the presence of pressure gradient are investigated. The governing equations for fully developed flow under H1 thermal boundary conditions are first made dimensionless and subsequently solved through a finite difference procedure for a non-uniform grid. The influence of the major parameters on thermal features of the flow such as the temperature distribution and Nusselt number is discussed by a complete parametric study. The results reveal that the channel aspect ratio and the non-Newtonian characteristic of the fluid can affect the thermal behavior of the flow. It is...
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
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...