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Design and Additive Manufacturing of Octahedron Unit Cell-Based Lattice Structures and Investigation of Their Mechanical Behavior
, M.Sc. Thesis Sharif University of Technology ; Asghari, Mohsen (Supervisor) ; Mohammadi, Keyvan (Supervisor)
Abstract
Strut-based lattice structures have outstanding performance in load-bearing and energy absorption, and have attracted significant attention in various industries, including aerospace, medical, and automotive. With advancements in additive manufacturing methods, the use of these structures has become more attractive and practical. This study examines the deformation patterns and mechanical properties of hybrid-layered lattice structures based on the octahedron unit cell. One of the main objectives of this research is to create structures composed of different cells with suitable compatibility in a layered arrangement. Twelve different structures, including uniform and hybrid configurations of...
Energy and Economic Analysis of Vertical Farms Considering Solar Energy Utilization and CO2 Enrichment
, M.Sc. Thesis Sharif University of Technology ; Roshandel, Ramin (Supervisor)
Abstract
Given the growth of the world's population along with the increase in the percentage of urban population by 2050, the way of responding to food consumption will change in the future. Controlled Environment Agriculture will largely account for future food supply. Vertical Farming is one of these systems. But despite the efficiency of these systems in terms of land and water and also not being affected by weather conditions, the main challenge in these systems is the consumption of energy use per unit of crop production. The cost of energy is about 25 to 40 percent of the total costs. The purpose of this study is to develop an integrated dynamic model for the determination of vertical farm...
Monitoring of crack healing in geopolymer concrete using a nonlinear ultrasound approach in phase-space domain
, Article Ultrasonics ; Volume 134 , 2023 ; 0041624X (ISSN) ; Toufigh, V ; Keyvan, K ; Sharif University of Technology
Elsevier B.V
2023
Abstract
Ultrasonic testing is a robust non-destructive evaluation method frequently employed in the health monitoring of concrete structures. Cracking in concrete can be one of the most critical problems, and its healing is important for structural safety. The current study proposes the evaluation of crack healing in geopolymer concrete (GPC) using different linear and nonlinear ultrasonic techniques. In this regard, a notched GPC beam was constructed at the laboratory and geopolymer grout was applied as a repair material. Ultrasonic pulse velocity (UPV) and signal waveform tests were performed at several stages before and after grouting the notch. Nonlinear wave signals were processed in the...
Multi-Criteria Appraisal of Regular Bus, Bus Rapid Transit and Metro in Tehran
, M.Sc. Thesis Sharif University of Technology ; Vaziri, Manuchehr (Supervisor)
Abstract
Viewpoints of various interest groups should be addressed in any public service appraisal. Urban public transportation development and services have diverse impacts on users, operators and the community. The impacts can be characterized by a wide range of perspectives including: efficiency, effectiveness, efficacy, economic, social and environmental dimensions. Deployment of quantitative techniques, such as multicriteria decision making methods, would facilitate such a multidimensional analysis and appraisal. The objective of the study summarized herein was to shed some light on the perceived attributes pertinent to the Tehran regular transit service appraisal. The major services include...
Effect of predeformation and heat treatment conditions in the SIMA process on microstructural and mechanical properties of A319 aluminum alloy
, Article Journal of Alloys and Compounds ; Volume 468, Issue 1-2 , 2009 , Pages 130-135 ; 09258388 (ISSN) ; Khalifehzadeh, R ; Keyvan, H ; Khomamizadeh, F ; Sharif University of Technology
2009
Abstract
In this study the influences of predeformation and heat treatment conditions on stress-induced melt activating process (SIMA) of A319 aluminum alloy were investigated. At 30% of predeformation a dominant globular structure of grains was obtained. However, further increasing of the predeformation rate considerably reduced the shape factor. The holding time of 10-15 min at semi-solid temperature of 580 °C was suggested in order to prevent grain growth. Coarsening of the grains by excess time or temperature of heat treatment reduced the tensile strength of the alloy. © 2008 Elsevier B.V. All rights reserved
Durability Evaluation and Health Monitoring of Microcracked Slag-Based Geopolymer Concrete Due to Step by Step Pressure Loading
, M.Sc. Thesis Sharif University of Technology ; Ghaemian, Mohsen (Supervisor) ; Toufigh, Vahab (Co-Supervisor)
Abstract
The goal of this research is to study the effect of local microcracking due to step by step pressure loading on the durability properties of geopolymer concrete. To better understand the behavior of GGBS-based GPC under different pressure stress levels, some experiments such as water permeability and water absorption conducted on the samples at each state of damage. Also, non-destructive tests such as ultrasonic waveform and pulse velocity (UPV) was used to quantify the extent of damage at each step. GGBFS and a blend of sodium silicate solution and 10 molar sodium hydroxide solution with SSSH⁄ ratio of 2 were used for production of GPC samples. GPC, OGPC and OPC samples with water to binder...
3D distributed modeling of trolling-mode AFM during 2D manipulation of a spherical cell
, Article Journal of Nanoparticle Research ; Volume 23, Issue 4 , 2021 ; 13880764 (ISSN) ; Nejat Pishkenari, H ; Mohammadi Moghaddam, M ; Sharif University of Technology
Springer Science and Business Media B.V
2021
Abstract
In this study, a general 3D distributed modeling of Trolling-Mode AFM (TR-AFM) as a nanorobot is presented to analyze the 2D manipulation process of a spherical cell. To this aim, the analysis is categorized into 3 sections. In the first section, 6 deformations of TR-AFM are taken into account, and the standard model of the system is obtained. Moreover, the system is simulated in ANSYS Workbench. The results of modal and transient analyses of the system from both analytical and software methods reveal high agreement, which confirms the accuracy of the presented analytical model. In the second section, by utilizing the 3D derived model, displacement of a spherical yeast single cell (W303)...
Sol-gel nanostructured titanium dioxide: Controlling the crystal structure, crystallite size, phase transformation, packing and ordering
, Article Microporous and Mesoporous Materials ; Volume 112, Issue 1-3 , 2008 , Pages 392-402 ; 13871811 (ISSN) ; Fray, D. J ; Mohammadi, A ; Sharif University of Technology
2008
Abstract
The anatase phase of titania was stabilised with physically modifying particulate sol-gel process. Two major parameters, peptisation temperature and drying temperature, were identified which were responsible for retarding the anatase to rutile phase transformation, crystal growth and packing of primary particles. The critical nucleus size of transformation was controlled by natural (at 25 °C) and artificial (at 50 and 70 °C) peptisation techniques. Moreover, sintering of primary particles was controlled by cool (at 0 and 5 °C) and normal (at 25 °C) drying techniques. Fourier transform infrared spectroscopy (FT-IR) analysis confirmed that a full conversion of titanium isopropoxide is obtained...
Electrokinetic mixing and displacement of charged droplets in hydrogels
, Article Transport in Porous Media ; Vol. 104, Issue. 3 , Jun , 2014 , pp. 469-499 ; ISSN: 01693913 ; Sharif University of Technology
2014
Abstract
Mixing in droplets is an essential task in a variety of microfluidic systems. Inspired by electrokinetic mixing, electric field-induced hydrodynamic flow inside a charged droplet embedded in an unbounded polyelectrolyte hydrogel is investigated theoretically. In this study, the polyelectrolyte hydrogel is modeled as a soft, and electrically charged porous solid saturated with a salted Newtonian fluid, and the droplet is considered an incompressible Newtonian fluid. The droplet-hydrogel interface is modeled as a surface, which is located at the plane of shear, with the electrostatic potential ζ. The fluid inside the droplet attains a finite velocity owing to hydrodynamic coupling with the...
Electric-field-induced response of a droplet embedded in a polyelectrolyte gel
, Article Physics of Fluids ; Volume 25, Issue 8 , 2013 ; 10706631 (ISSN) ; Sharif University of Technology
2013
Abstract
The electric-field induced response of a droplet embedded in a quenched polyelectrolyte gel is calculated theoretically. The response comprises the droplet translation and the electric-field induced flow fields within the droplet. The gel is modeled as a soft, and electrically charged porous solid saturated with a salted Newtonian fluid. The droplet is considered an incompressible Newtonian fluid with no free charge. An analytical solution, using the perturbation methodology and linear superposition, is obtained for the leading-order steady response to a DC electric-field. The fluid within the droplet is driven due to hydrodynamic coupling with the electroosmotic flow. The fluid velocity...
Oscillatory response of charged droplets in hydrogels
, Article Journal of Non-Newtonian Fluid Mechanics ; Volume 234 , 2016 , Pages 215-235 ; 03770257 (ISSN) ; Sharif University of Technology
Elsevier
2016
Abstract
Characterization of droplet-hydrogel interfaces is of crucial importance to engineer droplet-hydrogel composites for a variety of applications. In order to develop electrokinetic diagnostic tools for probing droplet-hydrogel interfaces, the displacement of a charged droplet embedded in a polyelectrolyte hydrogel exposed to an oscillating electric field is determined theoretically. The polyelectrolyte hydrogel is modeled as an incompressible, charged, porous, and elastic solid saturated with a salted Newtonian fluid. The droplet is considered an incompressible Newtonian fluid with no charges within the droplet. The droplet-hydrogel interface is modeled as a surface with the thickness of zero...
Transport in droplet-hydrogel composites: response to external stimuli
, Article Colloid and Polymer Science ; Volume 293, Issue 3 , March , 2015 , Pages 941-962 ; 0303402X (ISSN) ; Sharif University of Technology
Springer Verlag
2015
Abstract
Determination of effective transport properties of droplet-hydrogel composites is essential for various applications. The transport of ions through a droplet-hydrogel composite subjected to an electric field is theoretically studied as an initial step toward quantifying the effective transport properties of droplet-hydrogel composites. A three-phase electrokinetic model is used to derive the microscale characteristics of the polyelectrolyte hydrogel, and the droplet is considered an incompressible Newtonian fluid. The droplet-hydrogel interface is modeled as a surface, which encloses the interior fluid. The surface has the thickness of zero and the electrostatic potential ζ. Standard...
A simple particulate sol-gel route to synthesize nanostructural TiO2-Ta2O5 binary oxides and their characteristics
, Article Materials Science and Engineering B: Solid-State Materials for Advanced Technology ; Volume 142, Issue 1 , 2007 , Pages 16-27 ; 09215107 (ISSN) ; Fray, D. J ; Sadrnezhaad, S. K ; Mohammadi, A ; Sharif University of Technology
2007
Abstract
Nanostructured and mesoporous TiO2-Ta2O5 films and powders with various TiO2:Ta2O5 molar ratios and high specific surface area (SSA) have been prepared by a straightforward particulate sol-gel route. Titanium isopropoxide and tantalum ethoxide were used as precursors and hydroxypropyl cellulose (HPC) was used as a polymeric fugitive agent (PFA) in order to increase the SSA. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that powders contained both hexagonal δ-Ta2O5 and monoclinic β-Ta2O5 phases, as well as anatase and rutile. It was observed that Ta2O5 retarded anatase-to-rutile transformation. Furthermore, δ → β phase transformation temperature increased...
Correction to: Controlled manipulation of a bio-particle using trolling mode atomic force microscope: a simulation study (Journal of Nanoparticle Research, (2021), 23, 10, (221), 10.1007/s11051-021-05301-6)
, Article Journal of Nanoparticle Research ; Volume 24, Issue 8 , 2022 ; 13880764 (ISSN) ; Nejat Pishkenari, H ; Mohammadi Moghaddam, M ; Sajjadi, M ; Sharif University of Technology
Springer Science and Business Media B.V
2022
Abstract
The original article contained a mistake in Equation 1. The corrected Equation 1 is shown below: MX+Cx+Kx=f.The original article has been updated © Springer Nature B.V. 2022
Experimental investigation of thermal resistance of a ferrofluidic closed-loop pulsating heat pipe
, Article Heat Transfer Engineering ; Vol. 35, issue. 1 , 2014 , pp. 25-33 ; ISSN: 01457632 ; Mohammadi, M ; Ghahremani, A. R ; Shafii, M. B ; Mohammadi, N ; Sharif University of Technology
2014
Abstract
For the present article, a pulsating heat pipe (PHP) is fabricated and tested experimentally by bending a copper tube. The effects of working fluid, heat input, charging ratio, inclination angle, magnets location, and ferrofluid (magnetic nanofluid) volumetric concentration have been investigated on the thermal performance of this PHP. Experimental results show that using ferrofluid as a working fluid improves the thermal performance of the PHP significantly. Moreover, applying a magnetic field on a ferrofluidic PHP reduces its thermal resistance. By changing the inclination angle of the PHP from vertical mode to angles close to the horizontal mode, the present PHP has a constant and...
Hybrid control of electrohydrodynamic 3D printer cone jet
, Article Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering ; Volume 237, Issue 4 , 2023 , Pages 1262-1272 ; 09544089 (ISSN) ; Abdullahi, M. A ; Salarieh, H ; Movahhedy, M. R ; Mohammadi, S ; Sharif University of Technology
SAGE Publications Ltd
2023
Abstract
In this article, the control of an electrohydrodynamic 3D printer is studied. The proposed controller has a hybrid piecewise linear feedback form which is designed based on a hybrid model of the printer. The hybrid model is obtained via a gray box identification process whose structure is proposed utilizing the results of the finite element simulation of the printer within the COMSOL Multiphysics software. The asymptotic stability of the hybrid control combined with a hybrid observer is proven using the Lyapunov theory. In addition, the obtained control is applied to the finite element model of the printer to check its performance which shows the success of the controlled system in tracking...
Bromo-lithium Exchange Reaction in Organic Synthesis and Continuous Separation of Organic and Aqueous phase Reactions by Microfloid Technique
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Ali Asghar (Supervisor) ; Bastani, Dariush (Supervisor)
Abstract
Today, with the development of micro-technology in chemical reactions, the use of appropriate systems for the separation and purification of synthesized chemicals seems to be necessary. In this study, the continuous synthesis of bromide-lithium exchange reaction and the separation of organic and aqueous phase products in micro systems was investigated.The method used to construct micro-separator and micro reactor, a laser engraving technique, and thermal bonding of glass to glass.In the first step, the factors affecting the separation of organic and aqueous phase in the capillary micro-separator, such as the width of the capillary, the length of the capillary, the number of capillaries and...
Semiconductor TiO2-Al2O3 thin film gas sensors derived from aqueous particulate sol-gel process
, Article Materials Science in Semiconductor Processing ; Vol. 27, issue , 2014 , p. 711-718 ; Sharif University of Technology
2014
Abstract
Nanostructured TiO2-Al2O3 films and powders were prepared by a straightforward aqueous particulate sol-gel route. Titanium (IV) isopropoxide and aluminum chloride were used as precursors, and hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the porosity. The effect of Al:Ti molar ratio was studied on the crystallization behavior of the products. X-ray diffraction (XRD) revealed that the powders crystallized at 800°C, containing anatase-TiO2, rutile-TiO2 and cubic-Al2O3 phases. Furthermore, it was found that Al2O3 retarded the anatase to rutile transformation. Transmission electron microscope (TEM) image showed that one of the smallest crystallite sizes was...
Concavity degree: A new feature for chromosome centromere localization
, Article AISP 2012 - 16th CSI International Symposium on Artificial Intelligence and Signal Processing ; 2012 , Pages 58-63 ; 9781467314794 (ISBN) ; Sharif University of Technology
2012
Abstract
Analyzing the features of the chromosomes can be very useful for diagnosis of many genetic disorders or prediction of the possible abnormalities that may occur in the future generations. For this purpose, karyotype is often used which to make it, there is necessary to identify each one of the 24 chromosomes from the microscopic images. Definition and extraction of the morphological and band pattern based features for each chromosome is the first step to identify them. An important class of the morphological features is the location of the chromosome's centromere. Thus, centromere localization is an initial step in designing an automatic karyotyping system. In this paper, a novel algorithm...
Optimal placement of PMUs for power system observability using topology based formulated algorithms
, Article Journal of Applied Sciences ; Volume 9, Issue 13 , 2009 , Pages 2463-2468 ; 18125654 (ISSN) ; Sharif University of Technology
2009
Abstract
This study presents optimal placement of Phasor Measurement Units (PMUs) for the purpose of power system observability using topology based formulated algorithms. The optimal PMU placement problem is formulated to minimize the number of PMUs installation subject to full network observability. The Branch and Bound (B and B) and genetic algorithm optimization methods are selected to solve the problem, which are suitable for problems with integer and Boolean variables. Topology-based algorithm used for observability analysis and a hybrid method of topology transformation and nonlinear constraint is used to form constraints. The IEEE 14, 30, 57 and 118-bus and the New England 39-bus test systems...