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moghimi--abolghasem
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Investigation of the Performance and Properties of a New Generation Additives with Dual Purpose, Cell Opening and Delay Action Catalyst; in MDI and Polyester Polyol Based PU System
, M.Sc. Thesis Sharif University of Technology ; Shojaei, Akbar (Supervisor) ; Moghimi, Abolghasem (Co-Supervisor)
Abstract
Polyurethanes are polymers prepared by the reaction of polyols with isocyanates. Due to the wide range of raw materials from which polyurethanes are synthesized, as well as their various applications, they are classified into several groups, of which polyurethane foams are one of the most important products that have significant consumption. One of the most important diisocyanates is methylene diphenyl diisocyanate and also one of the most commonly used polyols in the polyurethane industry are polyesters.In addition, chain extenders, catalysts and suitable additives such as foaming agents, surfactants, fillers, etc., are all raw materials that participate in the production of polyurethane...
Water electrolyte transport through corrugated carbon nanopores [electronic resource]
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 90, Issue 1, July 2014, Article number 012304 ; Moosavi. A
Abstract
We investigate the effect of wall roughness on water electrolyte transport characteristics at different temperatures through carbon nanotubes by using nonequilibrium molecular dynamics simulations. Our results reveal that shearing stress and the nominal viscosity increase with ion concentration in corrugated carbon nanotubes (CNTs), in contrast to cases in smooth CNTs. Also, the temperature increase leads to the reduction of shearing stress and the nominal viscosity at moderate degrees of wall roughness. At high degrees of wall roughness, the temperature increase will enhance radial movements and increases resistance against fluid motion. As the fluid velocity increases, the particles do not...
Investigation of Io's auroral hiss emissions due to its motion in Jupiter's magnetosphere
, Article Research in Astronomy and Astrophysics ; Volume 12, Issue 6 , 2012 , Pages 693-702 ; 16744527 (ISSN) ; Sharif University of Technology
2012
Abstract
The left-hand side of the auroral hiss emission observed by Galileo has a frequency time profile shaped very similar to the funnel shape observed in the Earth's auroral region. This close similarity indicates that we can use the theory of whistler-mode propagation near the resonance cone to locate the emission source. The general characteristics of the whistler mode are discussed. Then the position of the emission source is investigated using a geometrical method that takes into account the trajectory of Galileo. Initially a point source is assumed. Then the possibility of a sheet source aligned along the magnetic field lines which are tangent to the surface of Io is investigated. Both types...
Improvement of Software Quality Attributes based on the Properties of Relational and Non-relational data Models
, M.Sc. Thesis Sharif University of Technology ; Habibi, Jafar (Supervisor)
Abstract
With the growing use of computer systems, especially in form of web applications, software development and customer requirements has become more complex. Modern computer systems are supposed to achieve non-functional requirements in addition to functional requirements. Non-functional requirements are also called software quality attributes. One of the most important quality attributes for today's software systems is performance. Today’s softwares due to the growing number of their users, need more efficiency than ever to properly meet the performance request.Storage components and databases are the most important factors in causing performance bottlenecks in web applications. Most of...
Critical Behavior of Neuronal Systems: an Information Theory Viewpoint
, M.Sc. Thesis Sharif University of Technology ; Moghimi, Saman (Supervisor)
Abstract
Experiments conducted in recent two decades indicated critical behavior in neural activity at different scales. Theoretically occurrences of these critical and power-law behavior can significantly facilitate brain activities correspondent to computation and memory tasks, but attaining the critical point essentially demands externally fine-tuning which has not been established yet. This fine-tuning often lies with placing system at transition point. Recent studies of group showed that a transition from synchronous to asynchronous phase could be achievable by a change in external parameters. At the very transition point, neuronal avalanches statistically demonstrate a power-law behavior which...
Electrodeposition of Ni-Co/SiC Composite Coatings
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Ni-Co/SiC composite coatings with various contents of SiC nano particles were electrodeposited in a modified watt type of Ni-Co bath containing 20 nm SiC nano particles to be codeposited. The influences of the SiC concentration, current density, stirring rate of the deposition bath on the composition of the coatings were investigated and these parameters optimized for highest amount of SiC codeposition. The optimized deposition parameters were 40 g/l SiC and 480 rpm stirring rate and current density equal to 4 A/dm2. Ni-Co/SiC composite coating was deposited with the maximum particles content of 30.5 volume percent. Linear voltammetry demonstrates addition of the SiC to the Ni-Co deposition...
Cathodic Protection of Concrete by Zinc Sacrificial Anode in Persian Gulf Sea Water
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Many of the major structure over coastal waters in the Kish Island due to the aggressive condition are showing signs of reinforcement corrosion. Recent advances in the development of anodes make it practical to use zinc galvanic cathodic protection to protect this structure in this area. Five anode systems were tested on several samples as, (1) zinc metal spray applied by arc-spraying on the concrete, (2) a zinc foil with conductive adhesive backing, (3) a system of zinc mesh and grout jacket, (4) a system of zinc mesh and compression panels, and (5) a bulk zinc. These anodes are set up to comparison the effects of potential and current over the zinc galvanic cathodic protection during 4...
Electrodepositon of Platinum Nanotubes
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Platinum nanotubes were deposited inside the pores of polycarbonate template with the pore size of 200 nm by electrochemical methods. In this regard a solution containing of 0.05 M H2PtCl6 and 0. 1 M H2SO4 in doubly distilled water was utilized. The electrodeposition process was studied by electrochemical techniques such as voltammetry and chronoamperometry methods. It was observed that the process was conducted in several stages including; nucleation and growth in steady state regime. Furthermore, it was concluded that electrodeposition was affected by mass transport restriction and was controlled by a diffusion process. In this regard, all the voltammograms were shifted to more negative...
Electrodeposition of the Ni-P by Pulse Plating
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Ni-P alloy coatings were electrodeposited using pulse current in a watt type bath in various conditions. The influences of different parameters were investigated and optimized for the highest amount of coating hardness using the Design Of Experiment (DOE) method. The optimized deposition parameters were current density 23.7 A/dm2, duty cycle 75%, frequency equal to 188 Hz, temperature equal to 70ºC and 17.5 gr/l of H3PO3. The DOE prediction of hardness for the optimized coatings was between 700 and 750 the achieved micro-hardness was about 725.8 HV. It was obtained that an increase of the current density will improve micro-hardness, decreases P content and increase deposition rate. Also, the...
Protection of Steel Rebar in Concrete with Zinc Based Coatings in Persian Gulf
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Reinforced concrete is one of the most important structural materials used in the construction industry worldwide. Nevertheless, certain physical and chemical factors in the service environment can contribute to its deterioration and failure. One of the most significant factors is the reinforcing steel bar (rebar) corrosion. In order to minimize the rebars corrosion, different kinds of coatings were investigated and evaluated by scientists. In this investigation comparative studies were performed on two different kinds of coated rebars (zinc-rich epoxy and polyamide epoxy coated rebars) and uncoated rebar. In order to evaluate these reinforced concretes, the adhesion, durability, thickness...
Simulation of Nickel Electrodeposition
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
In this research project, Ni electrodeposition process has been modeled by a 3D coupled continuum-kinetic Monte Carlo simulation. Kinetic Monte Carlo module processes surface reactions along the substrate using electrochemical equations for the relating events. Continuum model also determines concentration of the whole system according to a 3D interpretation of diffusion law in solutions. After running each module, exchange of data between two codes is done and boundary conditions are updated. In fact, the whole simulation time is divided by small time steps relating to time fastest reactions need to proceed. Present model will generate three outputs: current-time curve, surface morphology...
CNT Modified Coatings for Glucose Sensing
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
This research describes a new and relatively general method to grow well-aligned carbon nanotubes (CNTs) on cobalt-deposited stainless steel by thermal chemical vapor deposition (CVD) of ethylenediamine precursor. The CNTs are vertically aligned at high density over large areas on the surface. Different effective parameters in growth of carbon nanotubes, as type of substrate, surface treatment, temperature of growth , feeding carbon supplies have been studied. Finally, aligned carbon nanotubes have been prepared by 100-150 nm diameter and 9µ length. CoOx•nH2O–MWCNTs nanocomposites were successfully synthesized, using a cathodic electrochemical reduction of H2O2 to deposit cobalt...
Modification of Vertically Aligned Carbon Nanotubes with RuO2 for a Solid-State pH Sensor
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
In this work, a novel type electrode based on RuO2 nanoparticles-modified vertically aligned carbon nanotubes (RuO2/MWCNTs) was investigated. ThisRuO2/MWCNTs electrode not only shows a high capacity nature,but also possesses a good response to the pH value. In order to develope this sensor, aligned carbon nanotubes were synthesized by the chemical vapor deposition at first and then modified with RuO2 nanopartcles by sol-gel method. Various parameters affecting the growth of nanotubes, such as substrate type, surface finishing, surface roughness, the growth temperature and carbon feed rate was studiedand and optimal conditions for growth were obtained. At last, aligned nanotubes with a...
Effects of Additives on Chromium Coating in Trivalent Chromium Bath
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
In this work, effects of different additives on trivalent Chromium bath and Chromium coating has been investigated. Malonic acid wich had been used as a complexing agent of the bath improved current efficiancy and coating quality obviously. Effects of Magnesum, zinc, Tin, Aluminium sulfates, Molybdic acid, TiO2 nano particles, Sodium hypophospite, formaldehead and mixtures of these compositions on hexavalent Chromium concentration of the bath were also studied. Concentration of Cr6+ ion decreased by 18 ppm due to adding these materials. Using Ti/ TiO2/ RuO2 Anode also could decrease Cr6+ concentration by 78 ppm. Remarkable results had been recorded in current efficiency and coating...
Wear-Resistant Nickel-Titanium Nitride Composite Coating by Electrochemical Method
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Metal matrix nanocomposites contains ceramic ultrafine particles in a metal matrix, are used to improve the mechanical properties such as hardness and wear of coatings. For developing metal matrix nanocomposites, there are many methods. Electrochemical deposition process is one of these methods that have some advantages like uniform depositions on substrates with complex shapes, low cost, good repeatability and reducing waste. In this project, for increasing the hardness and wear resistance of nickel, composite coatings of nickel - titanium nitride was created by using electrochemical deposition of Watts bath contained titanium nitride particles. In order to increase the amount of...
Synthesis of Colloidal Silver Nanoparticles by Microwave Method and Study of its Antibacterial Activity
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Silver nanoparticles are widely used in different industries because of their antibacterial effects. Many synthesis methods were used to obtain silver nanoparticles. In this study the microwave method is used to synthesize nanosilver. This method is easier and faster in comparison to other methods. The effect of precursors’ concentrations, using different solvents, different remaining time in microwave and microwave power were studied. By increasing the reaction time, microwave power and using different solvents, nanosilver particle size varies from 2 nm up to 300nm. The TEM images, size distribution, XRD patterns and UV-visible spectrum are shown. The obtained nanosilver was used to observe...
Deposition of Indium-tin-oxide on Glass By Sol-gel and Effect of Noble Dopants on the Optical and Electerical Properties of Indium-tin-oxide Thin Films
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Thin film of Indium oxide doped with tin is used as a transparent electrode for different applications like screening panels, solar cells, touch panels and elechtrochromic tools. Trading thin films of ITO are precipitated using sputtering. However sol gel method can be simple and economic to make transparent electrodes. In this thesis first ITO sols is prepared using Indium nitrate and tin chloride with two or four capacities due to the production of transparent oxides on soda lime glass. Then the effect of tin chloride with two and four capacities is investigated on resistance and optic properties. Results show that tin chloride with four capacities in comparison with tin of two capacities...
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
In recent years, different of nanoparticles as oil additives has been investigated in many studies . These research show that nanoparticles are deposited on the surface friction and improve tribology properties of base oil and also significant reduction of wear and friction caused by the nanoparticles. Compared with metal and metal oxide nanoparticles , carbon nanotubes (CNT) due to the high thermal conductivity and high aspect ratio , is an excellent candidate as the nanoparticle is dispersed . For preparing useful oil it is essential to stabilize nanoparticles in fluid that will not settle over long time . Oils containing nanoparticles by increasing the heat transfer coefficient...
Investigation and Fabrication of Cr2O3 Thin Film Coating on Soda Lime and Low Carbon Steel Substrate
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Chromium oxide coatings (Cr2O3) have been widely used due to their remarkable properties in corrosion, wear, optical and mechanical applications. So far, several methods have been used to prepare Cr2O3 thin films. In this study, the chromium oxide was produced by the sol-gel method and dip coated on the low carbon steel and glass substrates. In this context, we encountered with the problem of incoherency of the Cr2O3 ceramic coating to the steel substrates. It is highly likely that this problem be due to causes such as: a) thermal stresses due to the difference between the thermal expansion coefficients of the substrate and the coating, b) incoherent substrate/coating interface due to their...
Nickel Nano Particles Pulse Electrodeposition
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Syntheses of coats including nickel nano-particles by electrodeposition have been
investigated for over 10 years. A method of testing according to surface reply was chosen
to reveal the effect of each pulse parameters (including duty cycle, frequency, average
current density, off time (toff) and on time (ton)) and the effect of saccharin concentration
on electroplating cathode efficiency, nanostructure. Pulse electroplating test of nickel was
composed by 30 tests. Pulse electroplating with relatively high peak current density was
employed and saccharine was added to increase deposition and rate of nickel nucleation on
surface. According to the results of cathode...
investigated for over 10 years. A method of testing according to surface reply was chosen
to reveal the effect of each pulse parameters (including duty cycle, frequency, average
current density, off time (toff) and on time (ton)) and the effect of saccharin concentration
on electroplating cathode efficiency, nanostructure. Pulse electroplating test of nickel was
composed by 30 tests. Pulse electroplating with relatively high peak current density was
employed and saccharine was added to increase deposition and rate of nickel nucleation on
surface. According to the results of cathode...