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Synthesis of TiO2 nano powder by the sol-gel method and its use as a photocatalyst
, Article Journal of the Iranian Chemical Society ; Volume 7, Issue SUPPL. 1 , 2010 , Pages S154-S160 ; 1735207X (ISSN) ; Sharif University of Technology
2010
Abstract
In this work the titanium dioxide powder was prepared by the optimized and simple Sol-Gel method and then characterized. The gelling pH was set to values of 3 (TiO2-A), 7 (TiO2-N) and 9 (TiO2-B) to observe the effect on the properties of the material. In these three cases nanoparticulated materials were obtained with particle sizes between 10nm and 20nm. The larger surface areas were obtained at pH 3, which is several times larger than the others. Furthermore, with the gelling condition pH 3, it was possible to synthesize pure anatase phase titania. Some preliminary results on the test of the photocatalytic activity of the synthesized materials in the reduction of nitric oxide are presented....
Study on modification of colloidal silica surface with magnesium ions
, Article Journal of Colloid and Interface Science ; 2009 , Pages 379-383 ; 00219797 (ISSN) ; Sharif University of Technology
2009
Abstract
The prepared colloidal silica via ion exchange was modified by adding Mg+2 ions in the surface growth process of colloidal silica. The particle size of the modified colloidal silica was decreased by increasing the seed concentration, whereas that of colloidal silica was slightly increased as the seeds concentration exceed 15 wt%. But the trend of changes in surface area was completely reversed. Magnesium ions on surface of the modified colloidal silica were identified by the measurement of energy-dispersive X-ray spectrometry (EDS). After modifying with Mg+2 ions, the iso-electric point (IEP) of colloidal silica in pH ∼ 2 without modification, disappears over the whole pH range. © 2008...
Comparing the Besancon Galaxy Model with Hipparcos data
, M.Sc. Thesis Sharif University of Technology ; Rahvar, Sohrab (Supervisor)
Abstract
e H-R diagram for stars within 100 parsecs from the sun were simulated using Padova isorones, Besanc¸on Galaxy disc model and various star formation rates. using Chi-square test the different star formation rates were compared. the results favours an increasing star formation rate
Robust Hover-flight Control Design for a Tail-sitter UAV with Ducted-fan Propulsion
, M.Sc. Thesis Sharif University of Technology ; Saghafi, Faribourz (Supervisor)
Abstract
In this thesis, the theory of robust control is applied to design a controller for hover flight of a tail-sitter unmanned aerial vehicle with 2 ducted-fan propulsion. The control surface deflection (in propeller slipstream) is considered as the input controller of the system. The aircraft dynamical model is developed based on the assumption of no aerodynamic loads on other parts of uav in low speed flight associated with the hovering condition. The controller is primarily designed using both classical and modern control techniques. Then H ∞ and µ synthesis approaches are applied to design the robust controller. The results obtained from different approaches are compared. It is shown that...
Periodic Solutions for a Weakly Dissipated Hybrid System
, M.Sc. Thesis Sharif University of Technology ; Hesaraki, Mahmoud (Supervisor)
Abstract
In this thesis, we consider the motion of a stretched string coupled with a rigid body at one end and we study the existence of periodic solution when a periodic force acts on the body. In this hybrid system, there is a weak dissipation that characterizes. The main difficulty of the study is related to the weak dissipation which does not ensure a uniform decay rate of the energy. In this thesis, firstly, under the condition of 0 1 0 , we prove there exists a periodic solution. Then, we change the conditions on , Indeed, we restrict ourselves to solve the problem. In this case, under the condition of 0 2 0 , we show there is a periodic solution for rational periods. In the last part, by...
Design of a Modern Compact Transmission Line for Electrical Energy Transmission in Long Distances at 400 kV
, M.Sc. Thesis Sharif University of Technology ; Vakilian, Mehdi (Supervisor)
Abstract
With new progresses in technology, a growing need to power energy has emerged. In Iran most of power plants are far from cities and therefore expansion of power network will cause long transmission lines with high capacities which connect power plants to cities. There are three solutions for these kinds of lines: 1) two-circuit transmission lines 2) higher voltages 3) new forms of transmission lines (HVDC and compact). In this thesis some of these suggestions have been analyzed to find the best solution for a 560 Km transmission line in Iran.
Designing transmission lines has a lot of steps which all are related to each other. In this project a comprehensive algorithm has been utilized to...
Designing transmission lines has a lot of steps which all are related to each other. In this project a comprehensive algorithm has been utilized to...
Positioning, Tracking and Shape Control in Micro-Beams Via Electrostatic Actuators and Incomplete State Feedback
, M.Sc. Thesis Sharif University of Technology ; Salarieh, Hassan (Supervisor)
Abstract
Systems that are electrostatically actuated have found a vast role in MEMS application. This technology is used in optical systems, sensors, micro switches, and deformable mirrors. Raising the use of these systems in fields that needs better performance highlighted the need to accurate study of dynamics and control of electrostatic actuated systems in micro scale. This work is dedicated to design of an estimation and control system for a micro-beam that is actuated by electrostatic. After a comprehensive survey on pervious works that are done on dynamic, applications, fabrication and control of these systems dynamic of the system is fully derived. The environmental factors like fringing...
3D Reconstruction of Football Player Using Multi-view Videos
, M.Sc. Thesis Sharif University of Technology ; Kasaei, Shohreh (Supervisor)
Abstract
One major problem in sport match analysis and interpretation is that there are restricted viewpoints of the game. 3D reconstruction allows us to have virtual replay from any viewpoint so that the events such as penalties can be detected easily. For achieving this purpose, we use many cameras with overlapped views that cover almost all parts of the field. After some preprocessing, 3D reconstruction and texture mapping, we can enhance the viewer experience by having arbitrary viewpoint of the match. In this research, we use two different visual hull methods for 3D reconstruction. In the first method, the visual hull of an object is computed efficiently and robustly from image contours. This...
Designing a Multi-Model Sliding Mode Controller for a Magnetic Levitation System
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohammad (Supervisor)
Abstract
In this project a complete simulator for a two-winding, 25cm air gap Maglev system by considering the pratical constaritns, position and velocity observer and the current sensor dynamics was derived. In order to control the ball in any desired position a twisting sliding mode controller was designed as the basic controller in the rest of project. The designed controller can not transfer the ball in far trajectory. In first step we modify that to reach a better performance by changing the value of current, passing through the coils in steady state. In the second step, the far trajectories are divided to a finite number of sub-trajectory such that the ball can pass these sub-trajectory by...
Investigation of Performance of Mutual Fund in Iran
, M.Sc. Thesis Sharif University of Technology ; Barakchian, Mehdi (Supervisor)
Abstract
Using a comprehensive data set on (surviving and non-surviving) Iranian equity mutual funds, we examine performance of mutual fund by using jensen’s model, fama & French three factor model and treynor & mussy’s model. we use as well as a cross-section bootstrapmethodology to distinguish between ‘skill’ and ‘luck’ for individual funds. This methodology allows for non-normality in the idiosyncratic risk of the funds — a major issue when considering those funds which appear to be either very good or very bad performers, since these are the funds which investors are primarily interested in identifying. Standard tests designed to identify mutual funds with non-zero alphas are problematic, in that...
Preparation and Characterization of Morphology and Mechanical Properties of PA6/Nanodiamond Composites
, M.Sc. Thesis Sharif University of Technology ; Shojaei, Akbar (Supervisor)
Abstract
Polyamide or Nylon, due to its remarkable mechanical and tribological properties, has many engineering applications. Hence, improving the properties can develop the polyamide applications. In this study, Polyamide 6 (PA6) has been used as matrix with nanodiamond (ND) reinforcement. Spherical shape, chemically active surface as well as remarkable mechanical properties make nanodiamond an ideal candidate for improving polymers properties. Poor dispersion and agglomeration are present however major problems in achieving improved properties in nanocomposites. To deal with this problem, nanodiamonds were surface modified using Ethylenediamine (EDA) and Hexamethylenediamine (HMD). Nanocomposite...
The influence of chromium substitution on an iron-titanium catalyst used in the selective catalytic reduction of NO
, Article Journal of Catalysis ; Volume 292 , August , 2012 , Pages 32-43 ; 00219517 (ISSN) ; Salehi, V ; Sharif University of Technology
Elsevier
2012
Abstract
A series of Cr-substituted Fe-Ti compounds were prepared by the co-precipitation method and were systematically investigated as catalysts for the selective catalytic reduction (SCR) of NO by NH 3. A variety of analytical techniques revealed that the Cr substitution amount affects the N 2 selectivity, SCR activity, redox behavior of NH 3/NO x, adsorption ability, and structure of catalysts in terms of surface properties, porosity, mobility of lattice oxygen, oxidative ability of Cr species, ratio of Bronsted acid sites and Lewis acid sites, NO x adsorption capacity, and structural disorder and distortion. In a series of Fe aCr 1-aTiO x (a = 1, 0.75, 0.5, 0.2, 0) catalysts, Fe 0.5Cr 0.5TiO x...
Numerical modeling of incline plate LiBr absorber
, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 47, Issue 3 , November , 2011 , Pages 259-267 ; 09477411 (ISSN) ; Farhanieh, B ; Sharif University of Technology
2011
Abstract
Among major components of LiBr-H 2O absorption chillers is the absorber, which has a direct effect on the chillier size and whose characteristics have significant effects on the overall efficiency of absorption machines. In this article, heat and mass transfer process in absorption of refrigerant vapor into a lithium bromide solution of water-cooled incline plate absorber in the Reynolds number range of 5
Design and Implementation of Complex Multi-Path Filters
, M.Sc. Thesis Sharif University of Technology ; Atarodi, Mojtaba (Supervisor)
Abstract
In most radio receivers like superheterodyne receivers, a weak desired incoming signal is accompanied with many interferer signals that are much more powerful than the desired signal itself. These interferers, also called blockers, can cause a great disturbance in the functionality of the receiver. Due to gain compression and an increase in the noise figure (NF) of the receiver, the blockers should be filtered before the arrival at the output of the LNA. Because of the low quality factors of the available on chip inductors and in order to eliminate the out of band interferer signals and image frequency (in superheterodyne receivers), usually an external surface acoustic wave (SAW) filter is...
Traffic Engineering In Cloud Infrastructure By Software Defined Networks
, M.Sc. Thesis Sharif University of Technology ; Akbari, Behzad (Supervisor)
Abstract
In the recent years, cloud data center issues have been the center of attention. Also for them topologies with multi paths between end hosts are offered. For use of multi path traffic engineering is essential. Researches show congestion occurred in the cloud data center networks, because the mean of link utilization is down. This means, some of links are congested while there are some other with much available bandwidth. Currently, the most common method is Equal Cost Multipath (ECMP) algorithm for routing flows in the data center network. ECMP decides on routing without any attention to network congestion condition. There, may be two big flows placed in the one path and it causes creation...
Grammaticality Judgment Tests and Magnitude Estimation
, M.Sc. Thesis Sharif University of Technology ; Salehi, Mohammad (Supervisor)
Abstract
The present study aims at examining interval scaling and magnitude estimation in grammaticality judgment tests in terms of reliability and validity. It also explores the probable impact of response formats on the participants’ performance. 30 Engineering students at Sharif university of Technology participated in this research. The instrument of the research is a grammaticality judgment test developed by Ellis (1990).Two computer-based programs were made in order to assess the two mentioned response formats in grammaticality judgment test. At the first phase of the study, the participants responded to the interval format and after an interval of one month, they attempted the second response...
A numerical study on the absorption of water vapor into a film of aqueous LiBr falling along a vertical plate
, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 46, Issue 2 , 2009 , Pages 197-207 ; 09477411 (ISSN) ; Farhanieh, B ; Sharif University of Technology
2009
Abstract
Absorber is an important component in absorption machines and its characteristics have significant effects on the overall efficiency of absorption machines. This article reports a model of simultaneous heat and mass transfer process in absorption of refrigerant vapor into a lithium bromide solution of water - cooled vertical plate absorber in the Reynolds number range of 5 < Re < 150. The boundary layer assumptions were used for the transport of mass, momentum and energy equations and the fully implicit finite difference method was employed to solve the governing equations in the film flow. Dependence of lithium bromide aqueous properties to the temperature and concentration and film...
Improvement of dry sliding tribological properties of polyamide 6 using diamond nanoparticles
, Article Tribology International ; Volume 115 , 2017 , Pages 370-377 ; 0301679X (ISSN) ; Shojaei, A ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
In the present study, it was revealed that incorporation of nanodiamond containing carboxylic group (ND-COOH) decreased considerably specific wear rate (∼30%) and COF (∼60%) of polyamide 6 (PA6) at 1 wt% loading. Compared with ND-COOH, amino functionalized ND enhanced further wear performance of PA6 which was associated with its finer dispersion as well as greater influence on the improvement of mechanical properties, toughness and crystallinity of PA6. Surface temperature increment caused by frictional heat was in close agreement with COF and wear characteristics of the samples. Optical microscopy images revealed that NDs promote the abrasive wear mechanism in PA6/ND composites. © 2017...
An Investigation on Elastic and Thermo-elastic Behavior of FGM Skew Plates under Mechanical and Thermo-mechanical Loading
, M.Sc. Thesis Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
In this research it is aimed to have an investigation on the thermo-mechanical analysis of functionally graded skew plates. In order to analyze the behavior of the skew FGM plates, a constant pressure load as a mechanical load is distributed through the plate. Also the thermo-mechanical load is a combination of this mechanical load and a temperature gradient in upper and lower surface applied as in-phase . Various boundary conditions considered in analysis are combination of simply support and clamped edges including CCCS, CCSS, CCCC. The analysis are based on CPT and the Von-Karman theory is used in the solution. The graded materials are distributed through the thickness according to P-FGM...
Morphological and mechanical properties of polyamide 6/nanodiamond composites prepared by melt mixing: effect of surface functionality of nanodiamond
, Article Polymer International ; Volume 66, Issue 4 , 2017 , Pages 557-565 ; 09598103 (ISSN) ; Shojaei, A ; Sharif University of Technology
John Wiley and Sons Ltd
2017
Abstract
Surface chemistry of as-received nanodiamond (ND) was first tailored by dry thermal oxidation to obtain carboxylated ND (ND-COOH) and by wet chemistry to obtain ethylenediamine-functionalized ND (ND-EDA). Then, the surface-functionalized ND particles were dispersed in polyamide 6 (PA6) using the melt-mixing method. Transmission optical and scanning electron microscopies indicated a fine dispersion at low nanodiamond concentrations, e.g. 0.25 wt%, particularly with ND-EDA. Differential scanning calorimetry revealed that ND-EDA favoured the α-phase crystal and enhanced the degree of crystallinity of PA6. Experimental data indicated that ND-EDA had considerably improved tensile properties at...