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karami-mohammadi--reza
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Rapid Assesment of Peak Floor Acceleration of Structures Using Transfer Functions
, M.Sc. Thesis Sharif University of Technology ; Karami Mohammadi, Reza (Supervisor)
Abstract
Peak Floor Acceleration (PFA) is a necessary requirement in Industrial Buildings for the design of equipment, piping, cable tray and ventilation duct supports. The seismic analysis of equipments needs the determination of PFA at the points where the equipments are fixed on the supporting structure. The classical spectral methods (SRSS, CQC) do not allow this determination which can be done in using the time integration method. This last approach needs to perform numerous calculations with various realizations of the seismic excitation. This thesis aims to present a method allowing calculating the response properties of a linear elastic shear building structure loaded by a transient...
Effects of Stiffness Distribution on Demand Reduction in Elastic MDOF Structures
, M.Sc. Thesis Sharif University of Technology ; Karami Mohammadi, Reza (Supervisor)
Abstract
The present research illustrates the Effects of Stiffness Distribution on Demand Reduction in Elastic Multi Degree Freedom Structures. The structural configuration of a structure has an important effect on dynamic performance of it and its nonstructural contents. For equipment, the displacement or acceleration demand is defined in terms of the input motion applied at the appropriate attachment point(s) of the equipment. This demand or input motion is generally represented by an in-structure response spectrum (IRS). The IRS will differ significantly from the design base earthquake (DBE) spectrum because it is essentially filtered and/or amplified through the building. To assess the realistic...
Comparison between uniform deformation method and Genetic Algorithm for optimizing mechanical properties of dampers
, Article Earthquake and Structures ; Volume 14, Issue 1 , February , 2018 , Pages 1-10 ; 20927614 (ISSN) ; Mirjalaly, M ; Mirtaheri, M ; Nazeryan, M ; Sharif University of Technology
Techno Press
2018
Abstract
Seismic retrofitting of existing buildings and design of earth-quake resistant buildings are important issues associated with earthquake-prone zones. Use of metallic-yielding dampers as an energy dissipation system is an acceptable method for controlling damages in structures and improving their seismic performance. In this study, the optimal distribution of dampers for reducing the seismic response of steel frames with multi-degrees freedom is presented utilizing the uniform distribution of deformations. This has been done in a way that, the final configuration of dampers in the frames lead to minimum weight while satisfying the performance criteria. It is shown that such a structure has an...
Determination of Hydrazine and Phenylhydrazine Based on Formation of Gold Nanoparticles Stabilized with Non-ionic Surfactants
, M.Sc. Thesis Sharif University of Technology ; Hormozi Nezhad, Mohammad Reza (Supervisor)
Abstract
A simple and effective procedure is proposed for colorimetric detection of hydrazine and phenylhydrazine. It was found that the reduction of AuCl4- to gold nanoparticles (Au-NPs) by these compunds in the presence of Tween-20 as a stabilizing agent produced very intense surface plasmon resonance peak of Au-NPs. The plasmon absorbance of the Au-NPs allows the quantitative spectrophotometric detection of the hydrazine and phenylhydrazine. The calibration curves derived from the changes in absorbance at λ = 530 and λ = 550 nm for hydrazine and phenylhydrazine, respectively were linear with concentration of hydrazine and phenylhydrazine in the range of 1.0×10-6- 2.0×10-4 M, 5×10-6 - 4×10-4 M,...
Investigating the Effect of International Collaborations on the Network IndiCentralityces of the Selected Iranian Universities' Faculty Members
,
M.Sc. Thesis
Sharif University of Technology
;
Mirnezami, Reza
(Supervisor)
Abstract
Today, the importance of scientific collaborations is due to the fact that researchers who jointly publish an article, research connections are formed between them, and as a result, professional learning is obtained. Each of these researchers brings a feature and advantage to the research team, such as mastering a particular topic and its subdivisions, team thinking, and division of labor between them. The importance of these collaborations is doubled when researchers collaborate with each other at the international level, because the networking of researchers through collaboration with colleagues from different countries, especially central and developed countries in science, in addition to...
Enhanced Electronic Properties in Mesoporous TiO2 Via Passivation Treatment in Perovskite Solar Cells
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
Perovskite solar cells are the new generation of solar cells, and are mainly introduced in two types of structures.1) planer and 2) mesoscopic structure. The difference between these two structures derives from the absence of mesoporous layer in the planer structures. The mesoporous layer acts as an electron transporting layer, and is mainly a titanium dioxide semiconductor. To apply the mesoporous layer, the preparation of the TiO2 paste is needed.The synthesis of titanium dioxide nanopowder for the preparation of TiO2 paste requires high temperature heat treatment and is not desirable in terms of energy consumption.Another weakness of this layer is the presence of surface defects, which...
Coarse-gained Multi-scale Modeling for Numerical Simulation of Nonlinear Behavior of Materials in Nano-scale
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
In this thesis, a coarse-grained multi-scale method for 2D crystallyn solids based-on finite element consepts has presented. In this method, both scales are atomic scale and similar to what we see in non-local QC method, the entire atomic structure will be intact. Accordingly, calculations of potential functions and forces in the domain will have the atomic accuracy. In the presented method to reduce the domain’s degrees of freedom, the classical finite-element meshing concept to mesh the elastic linear areas in the domain is used and the MD calculations will done on the mesh nodes. Therefore, degrees of freedom in the system will reduce and consequently, the computational cost will reduce....
Optical Communication Impairments Mitigation Using Interpretable Machine Learning
, M.Sc. Thesis Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor) ; Hadi, Mohammad (Co-Supervisor)
Abstract
Optical impairments, as a challenging obstacle in optical communication systems, have been under deep attention of optical engineers in recent years. These impairments can be divided into two categories of linear and nonlinear impairments. Dispersion is a significant linear impairment leads to broadening of the optical signal and interference between transmitted symbols during detection. Nonlinear impairments such as cross-phase modulation (XPM) and self-phase modulation (SPM) also distort the transmitted signal through the fiber, causing interference at the receiver and degrading the system's performance. An appropriate solution for compensating optical fiber impairments is to utilize...
Morphological Manipulation of Photo-Anode Electrode of Nano-Structured TiO2 Dye-Sensitized Solar Cells
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
Dye-sensitized solar cells (DSSCs) are Photoelectrochemical cells using wide band gap nanoporous oxide semiconductors sensitized by dye molecules. For achieving high efficiency DSSCs preparation of photoanode electrode with high surface aea which leads to adequate dye absorption is necessary. In order to achieve proper morphology, thickness, particles size and porosity, producing a TiO2 nano-structured paste is required. TiO2 powder was prepared using sol-gel method. following a calcination process at 300 degrees, XRD patterns showed presence of anatase and brookite structures with average crystallite size of 9 nm. Additives such as diethylene glycol, acetylacetone and Triton X-100 were used...
The Impact of Nano-conjugation of Geinstein as Chemotherapeutic Agent against Cancer
,
M.Sc. Thesis
Sharif University of Technology
;
Mohammadi, Mohammad Reza
(Supervisor)
Abstract
With development of nanotechnology in medicine, nanoparticles are used for detection of tumor and cancer biomarkers. Magnetic nanoparticles are widely used for therapeutic and diagnostic objectives, because of their biocompatibility, ease of preparation and strong magnetic properties. Genistein (C15H10O5) is a soy isoflavone which is used for its anti-cancer activities. It is used for inhibition of cell proliferation, cell growth, and tumor invasion. The aim of this study is to assess the impact of nano-conjugation of geinstein as chemotherapeutic agent against cancer. For preparation of typical iron oxide Nanoparticles, Magnetite nanoparticles were synthesized by coprecipitating iron (II)...
Preparation of Mesoporous Titania Film Using Block Copolymer Template in Application of Dye-sensitized Solar Cell
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
The Mesoporous Titanium Dioxide film using Sol-Gel method and Evaporation-Induced Self-Assembly technique (EISA) was prepared. In this study, in order to employ the best coatings in anode electrode of dye-sensitized solar cell, different conditions of making this film, the effective parameters in final structure, and various methods of coating were analyzed. After optimizing the conditions of film creating, images of field emission scanning electron microscope (FESEM) proved the formation of a layer of mesoporous structure which thickness after three times of coating is about 1.5 micrometers. In order to increase the energy conversion efficiency of solar cells, a new formulation for...
Design of Doped TiO2 Dye-sensitized Solar Cells with Different Arrangement Modes of Photoanode Electrodes
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
In this thesis, pure –known as T- and chromium doped titanium dioxide nanoparticles –known as -CTx- with different dopant atomic ratio (0.1 to 5 %at.) were synthesized using a facile, fast and efficient method. FESEM and XRD studies showed no morphologic and structural change via Cr doping of nanoparticles (size in the range of 20-30 nm). However, according to DRS analysis, Cr intrusion in TiO2 crystal structure, drastically reduced band gap energy of pure TiO2 from 3.14 eV to 1.81 eV for CT3 powder and improved absorption range of UV-Vis spectrum. Mott-Schottky plots indicated that, Cr doping, caused reduction in donor density of TiO2 and an upward shift in the conduction band edge....
Improvement of Light Scattering Effect of Dye –sensitized Solar Cells Aided by Different Structures of Titanium Dioxide
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
Structure and morphology of titanium dioxide have an excessive effect on the photovoltaic properties of dye-sensitized solar cells (DSCs). Different approaches have been used to improve the efficiency of these cells. One is using a scattering layer. Studies have been shown that properties of scattering layer such as composition and morphology have great effect on photovoltaic properties of solar cell. In this project, the effect of cubic morphology of TiO2 as a scattering agent in photoanode of DSCs is studied. Titanium dioxide with various morphologies including nanoparticles, solid and hollow cubic structures have been synthesized by solvothermal and hydrothermal methods, respectively. The...
Sol-Gel Preparation and Study of Bio-Composite Scaffold Containing Chitosan-Gelatin/ Nano-Hydroxyapatite for Bone Tissue Engineering
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
In present work, hydroxyapatite nano-rods are synthesized using a simple sol-gel method with calcium nitrate and potassium dihydrogenphosphate as calcium and phosphorus precursors respectively and ammonia was used for adjusting the pH=9. To obtain rod shape hydroxyapaite powder, multi wall carbon nanotubes were added to the solution, nHA powder was calcinated at 60 and 450 ℃. In second step, chitosan-gelatin/nanoHA solution were prepared by blending chitosan and gelatin in different concentrations with nanoHA powder, then the solution was freeze dried to maintain a composite scaffold. The prepared HA powder and bio-composite scaffold were characterized by X-ray diffraction (XRD), field...
Preparation of Mg-doped TiO2 Nanoparticles for Dye-sensitized Solar Cell Applications
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
Dye-sensitized solar cell (DSSCS) is the third-generation of solar cells based on semiconductors formed between a photo sensitized anode and counter cathode which make a photo electrochemical system. They haven’t been commercially marketed due to their lower efficiency than the previous generations. In order to achieve the higher efficiency, the electron injection and light absorption must be increased. One way to increase electron injection is doping the semiconductor with an external ion to reduce lattice band gap. In this work, we made powder and Nano-structured film of titanium dioxide doped with various molar ratios of Mg by the sol-gel process. The effect of Mg:Ti molar ratio on...
Evaluation and Simulation of using Magnetite as Heat Transfer Medium in Direct Solar Absorption Collectors
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
In this study, application of a Magnetic Nanofluid consisting of Magnetite as Nanoparticle and Water as base fluid in DASC systems is investigated. The DASC system is modeled theoretically and behavior of such system is predicted.In this study a comparison between magnetite Nanofluid and some other common Nanofluids is conducted. The study shows that Magnetite Nanofluid has a better performance and efficiency than Water, Al2O3 Nanofluid and SiO2 Nanofluid. Also magnetite Nanofluid and TiO2 Nanofluid function are almost similar.Also effect of external magnetic field on the performance of magnetite Nanofluid is investigated. It is showed that when the magnetic Nanofluid is subjected to an...
A Sample Selection Method for Cost Reduction in Crowd Computing
, Ph.D. Dissertation Sharif University of Technology ; Rabiee, Hamid Reza (Supervisor)
Abstract
The goal of crowd labeling is to find labels of given samples using humans’ mind power.Since crowds are not necessarily experts, their provided labels are rather noisy and erroneous.This challenge is usually resolved by collecting multiple labels for each sample and aggregating them to estimate its true label. Although this mechanism leads to high-quality labels, it is not actually cost effective. Adaptive methods consider that only some samples are challenging and require more labels. They spend the budget more wisely, and iteratively collect the required labels. Using adaptive methods approach, we utilize statistical latent models to model and analyze the collected labels and low-rank...
Fabrication of Dye-Sensitized Solar Cells Based on TiO2-ZnO Double Layer Nanostructured Film
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
In the present work, one dimensional ZnO nanostructures were grown by seed-assisted hydrothermal method. Hydrothermal processing parameters were controlled to obtain ZnO nanorods with diameter lower than 120 nm. The products were characterized by FE-SEM, EDAX, XRD, PL, and ATR-FTIR analyses. ZnO nanoparticles were also synthesized via a simple solvothermal method and their photo peropeties were compared with onedimensional nanostructures. Thereafter dye-sensitized solar cells based on TiO2-ZnO double layer nanostructured film were fabricated. It was observed that DSSC efficiency increased with decreasing the thickness of the film. The highest efficiency of 2.41% was obtained
Modeling of Hydraulic Fracture Propagation in Fractured Non-isothermal Saturated Porous Media with XFEM
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
Investigation about Hydraulic Fracturing phenomenon in fractured porous medium which was occurred by in-situ fracture pressure upon the crack wings, owes the fact that creating enormous damages. However, it might include advantages such as increasing the rate of crude oil production from deep and high pressure/ high temperature reservoirs. On account of the fact that, existence of cracks and natural discontinuities and heat sources such as boundary of geo thermal reservoirs in porous mediums it is undeniable fact. Also, cross sectioning hydraulic fracturing cracks with natural cracks it is an obvious impact. Actually, investigation and analyzing the break throw of HF crack with natural...
Ni-doped TiO2 Photoanode Electrodes for Dye-sensitized Solar Cells Applications
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
A new strategy for enhancing the efficiency of TiO2 dye sensitized solar cells (DSSCs) doped with Ni ions with different molar percentages (i.e., 0, 0.5, 1, 5 and 10 mol%) was reported. The samples were prepared by sol-gel route and characterized by means of XRD, DRS, UV-visible, FESEM and photovoltaic measurment techniques. It was found that Ni-doped TiO2 nanoparticles had a mixture of anatase, rutile and brookite crystal structures. Moreover, the band gap energy was decreased with increasing Ni molar ratio, The highest cell efficiency of 5.4% was achieved for 1mol% Ni-doped TiO2, being 42% greater than that of pure TiO2 nanoparticles