Layer-by-layer self assembly deposition and characterization of TiO 2 nanoparticles by using a short chain polycation

, Article EPJ Applied Physics ; Volume 48, Issue 1 , 2009 , Pages 10602p1-10602p7 ; 12860042 (ISSN) Rahman, M ; Taghavinia, N ; Sharif University of Technology

2009

Abstract

Using low molecular weight polyethylenimine (PEI), transparent thin films of TiO2 nanoparticles were prepared by layer-by-layer self assembly method. UV-visible spectrophotometry was employed in a quantitative manner to monitor the adsorbed mass of TiO2 and PEI after each dip cycle. The adsorption of both TiO2 and PEI showed a saturation dip time of 10 min. The effect of dip time on the growth mode and surface morphology was investigated by scanning electron microscopy (SEM) and non-contact atomic force microscopy (AFM). It was found that growth proceeds in the form of laterally broad islands in case of short dip times, and taller but laterally smaller islands in case of longer dip times. A...

Undamped oscillations in fractional-order Duffing oscillator

, Article Signal Processing ; February , 2014 , Pages 361–367 ; ISSN: 01651684 Rostami, M ; Haeri, M ; Sharif University of Technology

2014

Abstract

This paper studies unamped oscillations of fractional-order Duffing system. Stability theorems for fractional order systems are used to determine the characteristic polynomial of the system in order to find the parametric ranges for undamped oscillations in this system. We also derive relations for estimating the frequency and the amplitude of the oscillations in this system using a describing function method. Finally numerical simulation results are provided to justify the analysis

Study of limit cycles and stability analysis of fractional arneodo oscillator

, Article Journal of Optimization Theory and Applications ; Volume 156, Issue 1 , 2013 , Pages 68-78 ; 00223239 (ISSN) Rostami, M ; Haeri, M ; Sharif University of Technology

2013

Abstract

This paper deals with the existence and the characteristics of the limit cycles in the fractional-order Arneodo system. The analysis is done using the describing function method. Our focus is on a special case where two limit cycles exist. The parametric range for the case of interest is derived, and the frequency and the amplitude of the oscillation are predicted. Numerical simulation results are presented to further demonstrate the reliability of the analysis

Undamped oscillations in fractional-order Duffing oscillator

, Article Signal Processing ; Volume 107 , February , 2015 , Pages 361-367 ; 01651684 (ISSN) Rostami, M ; Haeri, M ; Sharif University of Technology

Elsevier 2015

Abstract

This paper studies undamped oscillations of fractional-order Duffing system. Stability theorems for fractional order systems are used to determine the characteristic polynomial of the system in order to find the parametric ranges for undamped oscillations in this system. We also derive relations for estimating the frequency and the amplitude of the oscillations in this system using a describing function method. Finally numerical simulation results are provided to justify the analysis

Steel plate shear walls having door openings with different arrangements of stiffeners

, Article Advances in Structural Engineering ; Volume 22, Issue 10 , 2019 , Pages 2222-2235 ; 13694332 (ISSN) Rostami, P ; Mofid, M ; Sharif University of Technology

SAGE Publications Inc 2019

Abstract

As steel plate shear walls are typically used in the building central cores around the elevators and stairs, introduction of an opening as door seems to be inevitable in steel plate shear wall spans. Due to the weakening of the steel plate shear walls’ performance caused by this particular type of opening, the use of stiffeners around the opening is necessary. Nevertheless, introduction of stiffeners around all sides of the opening, which does continue to boundary elements, is very expensive and inefficient. Therefore, the study on the effect of different arrangements of stiffeners on the behavior of steel plate shear walls is significant. In this research, a number of steel plate shear...

A survey on exergy, energy and environmental analysis of sulfur recovery unit in case of five intensified configurations

, Article Chemical Papers ; Volume 73, Issue 6 , 2019 , Pages 1529-1539 ; 03666352 (ISSN) Rostami, A ; Tavan, Y ; Sharif University of Technology

Springer International Publishing 2019

Abstract

In this study, a combination of energy and exergy analysis is applied for the industrial sulfur recovery unit (SRU) in commercial simulation software. The data of energy and exergy are obtained from the simulator and Excel (for physical and chemical exergy), respectively. In doing so, five intensified SRU configurations namely: (1) hot gas bypass (2) acid gas bypass (3) inlet stream preheating (4) acid gas enrichment and (5) oxygen (air) enrichment are compared in terms of energy production, reaction furnace temperature, sulfur recovery and pollutant emission into environment. Then, irreversibility in these five arrangements is compared and all the proposed methods show higher useful exergy...

Topology awareness of overlay P2P networks

, Article Concurrency and Computation: Practice and Experience ; Volume 19, Issue 7 , 2007 , Pages 999-1021 ; 15320626 (ISSN) Rostami, H ; Habibi, J ; Sharif University of Technology

John Wiley and Sons Ltd 2007

Abstract

In overlay networks, the mechanism of a peer randomly joining and leaving a network, causes a topology mismatch between the overlay and the underlying physical topology. This causes a large volume of redundant traffic in the underlying physical network as well as an extra delay in message delivery in the overlay network. Topology mismatch occurs because overlay networks are not aware of their underlying physical networks. In this paper we present a mathematical model for topology awareness of overlay networks (degree of matching between an overlay and its underlying physical network) and the efficiency of message delivery on them. Then we experimentally show that the model is precise in the...

Minimum linear arrangement of Chord graphs

, Article Applied Mathematics and Computation ; Volume 203, Issue 1 , 1 September , 2008 , Pages 358-367 ; 00963003 (ISSN) Rostami, H ; Habibi, J ; Sharif University of Technology

2008

Abstract

The minimum linear arrangement (MINLA) is a NP-hard problem in general. But there are some classes of graphs optimally solvable in polynomial time. In this paper, we solve the minimum linear arrangement problem for a new class of graphs (Chord graphs) in polynomial time. Also, we present a closed formula for the cost of optimal arrangement. Our motivation to solve the problem for this class of graphs is its application in optimization of peer-to-peer overlay networks. © 2008 Elsevier Inc. All rights reserved

A mathematical foundation for topology awareness of P2P overlay networks

, Article 4th International Conference on Grid and Cooperative Computing - GCC 2005, Beijing, 30 November 2005 through 3 December 2005 ; Volume 3795 LNCS , 2005 , Pages 906-918 ; 03029743 (ISSN); 3540305106 (ISBN); 9783540305101 (ISBN) Rostami, H ; Habibi, J ; Sharif University of Technology

2005

Abstract

In peer-to-peer (P2P) overlay networks, the mechanism of a peer randomly joining and leaving a network, causes a topology mismatch between the overlay and the underlying physical topology. This causes a large volume of redundant traffic in the underlying physical network as well as an extra delay in message delivery in the overlay network. Topology mismatch occurs because overlay networks are not aware of their underlying physical networks. In this paper we present a mathematical model for topology awareness of overlay networks (degree of matching between an overlay and its underlying physical network) and the efficiency of message delivery on them. We also after determining the...

Optimal feature selection for SAR image classification using biogeography-based optimization (BBO), artificial bee colony (ABC) and support vector machine (SVM): a combined approach of optimization and machine learning

, Article Computational Geosciences ; Volume 25, Issue 3 , 2021 , Pages 911-930 ; 14200597 (ISSN) Rostami, O ; Kaveh, M ; Sharif University of Technology

Springer Science and Business Media Deutschland GmbH 2021

Abstract

Land cover classification is one of the most important applications of POLSAR images. In this paper, a hybrid biogeography-based optimization support vector machine (HBBOSVM) has been introduced to classify POLSAR images of RADARSAT 2 in band C acquired from San Francisco, USA. The main purpose of this classification is to minimize the number of features and maximize classification accuracy. The proposed method consists of three main steps: preprocessing, feature selection and classification. As preprocessing, radiometric calibration, speckle reduction and feature extraction have been performed. In the proposed HBBO, the combination of onlooker bee of artificial bee colony (ABC) and...

Investigation of Impurities and Structural Defects in Graphene

, M.Sc. Thesis Sharif University of Technology Rostami, Melika (Author) ; Faez, Rahim (Supervisor)

Abstract

In this thesis the effects of impurities and different defects on electrical and magnetic properties of monolayer and bilayer graphene is investigated. Calculations are performed using density function theory. Alloying monolayer graphene with boron and nitrogen the energy gaps of 0.7 and 0.6 eV are obtained, respectively. Moreover, we show that BN is a good candidate for opening the band gap in graphene. Alloying monolayer graphene with BN the energy gap of 1.2 eV is obtained. Another way of opening band gap is to somehow break the symmetry between layers of the bilayer graphene. By alloying one layers of bilayer graphene with B, N or B-N, although the symmetry of layers is broken, each...

On the Characteristics of The Behavior of Multi-story Steel Frames Accompanied by Steel Shear Walls with Openings

, M.Sc. Thesis Sharif University of Technology Rostami, Parisa (Author) ; Mofid, Massoud (Supervisor)

Abstract

As steel shear walls are usually applied in the central cores of buildings (around the elevators and stairs), the use of opening as door is inevitable in steel shear wall spans. On the other hand, because of weakening the performance of steel shear walls due to the presence of these openings, it is necessary to apply stiffeners around it. The use of stiffeners around all sides of opening continued to beams and columns, is very expensive. Therefore, the necessity of studying on the effect of different arrangements of stiffeners on the behavior of steel shear walls is felt. In this research, a number of steel shear walls with different characteristics in terms of plate aspect ratio, location...

Techno-Economical Analysis and Modeling of Carbon Capturing from Flue Gas by Adsorption

, M.Sc. Thesis Sharif University of Technology Rostami, Fatemeh (Author) ; Avami, Akram (Supervisor)

Abstract

Population growth require increasing demand of Energy. The fossil fuels are the main source of energy. However, they are main source of carbon dioxide emissions. Considerable amount of fossil fuels is used in the power plants. Increasing trend of electricity consumption as well as the lack of alternative fuels such as renewables in the short time will increase the consumption of fossil fuels and emissions. The most important greenhouse gas emitted from the power plants is carbon dioxide. That's why the separation of carbon dioxide from the gas stream of power plants is necessary.Separation of the carbon dioxide by adsorption is considered in this project both experimentally and...

Efficient Search in Peer-to-Peer Networks

, Ph.D. Dissertation Sharif University of Technology Rostami, Habib (Author) ; Habibi, Jafar (Supervisor)

Abstract

Peer-to-Peer networks are invented to enable participants (peers) to share their resources and find and use the shared resources of the others. So the main issue is the mechanism of finding granted resources of the other peers. In Peer-to-Peer networks, there is no central server to index shared resources of the peers. So peers should collaborate to provide a fully distributed mechanism for searching resources. Considering the huge size of peer-to-peer systems, it is apparent that efficiency of the search mechanism is very critical. In this thesis, to have efficient seach in Peer-to-Peer networks, we propose two approaches. Then based on these approaches, we propose the third approach to...

Prediction of Density, Surface Tension and Viscosity of Ionic Liquids using Artificial Intelligence

, M.Sc. Thesis Sharif University of Technology Torrik, Abdolhalim (Author) ; Rahman Setayesh, Shahrbanoo (Supervisor)

Abstract

Ionic liquids due to their unique physical and chemical properties are widely used in various fields of chemistry and chemical engineering. Determining properties of ionic liquids can be difficult, time consuming or even impossible. In first step of this study the IL thermo database was chosen as source of experimental data of ionic liquids. Viscosity, density, surface tension and melting temperature of ionic liquids based on bis(trifluoromethylsulfonyl)imide anion with cations imidazolium, pyridinium, pyrrolidinium, piperidinium and ammonium were modeled using QSPR approach. Linear and nonlinear models were built by means of multiple linear regression (MLR), multilayer perceptron neural...

Preparation, Characterization and Catalytic Application of Some Polyoxometalates for Esterification Reaction

, M.Sc. Thesis Sharif University of Technology Nazari, Pegah (Author) ; Rahman Setayesh, Shahrbanoo (Supervisor)

Abstract

Catalytic esterification of acetic acid with 1-hexanol was investigated over polyoxometalates. H3PW12O40 and H3PMo6W6O40 polyoxometalates with keggin structures were synthesized. Catalytic activity and recyclability of them were improved by loading on the γ-Al2O3 with impregnation method and Cs, K and NH4 salts preparing.Catalysts were characterized by XRD, SEM, FT-IR, BET, DRS and NMR techniques. According to XRD's results, catalysts have ace-centered cubic crystal systems. Loading on supports and preparing the salts do not destroy the structures of polyoxometalates. SEM images show the uniformity of catalysts' surface and catalysts' fixing on the support. It was seen that the keggin...

Electrochemical Degradation of Organic Pollutants in the Presence of Spinel Cobalt Ferrite Nanoparticles: Investigation of the Effective Parameters and Evaluation of Degradation Kinetics

, M.Sc. Thesis Sharif University of Technology Mousavi, Sadegh (Author) ; Rahman Setayesh, Shahrbanoo (Supervisor)

Abstract

In this study, CoFe2O4/CuO nanocomposite was synthesized by hydrothermal method and utilized for removal of metronidazole in electro-Fenton process. Nanocomposite was characterized by FT-IR, XRD, FE-SEM, VSM and BET methods. The Results of XRD patterns confirmed the monoclinic structure formation for copper(Ⅱ) oxide and the spinel structure for CoFe2O4. The FE-SEM images displayed the formation of CuO nanosheets for copper(Ⅱ) oxide and the decoration of cobalt ferrite nanoparticles on the surface of CuO nanosheets. Measurement of the surface area of nanocatalysts using BET isotherm represented the high surface area for CuO nanosheets and the increase of surface area of nanocomposite in...

Theoretical Study of Adsorption of Organic Pollutants on Polypyrrole with Density Functional Theory (DFT)

, M.Sc. Thesis Sharif University of Technology Rezaee, Mozafar (Author) ; Rahman Setayesh, Shahrbanoo (Supervisor)

Abstract

Phenolic compounds, which are one of the most dangerous compounds for the environment, are present in many effluents of various industries such as petrochemicals and pharmaceuticals, and the need to eliminate these compounds is increasingly felt. In this study, adsorption of three compounds of para-chlorophenol, para-nitrophenol and hydroquinone on polypyrrole adsorbent in the form of neutral, charged, copolymer with polyaniline and phosphorus-doped have been investigated using density functional theory (DFT). Calculations are performed at two levels of b3lyp/6-31+G(d,p) and wb97xd/631+G(d,p) for two different orientations of adsorbate molecules that the correlation-exchange function wb97xd...

Synthesis of Solar Light Responsive Nanocatalysts and Investigation of their Performance in Water Splitting Reaction

, M.Sc. Thesis Sharif University of Technology Mokhtari, Negin (Author) ; Rahman Setayesh, Shahrbanoo (Supervisor)

Abstract

Today, fossil fuels cause countless environmental pollutants, so replacing fossil fuels with clean energy sources is very important. Water splitting using light and a semiconductor is one of the new methods of producing oxygen and hydrogen, which due to its simplicity and cheapness, has attracted a lot of attention today. In this study, ZnMn2O4 photocatalyst nanoparticles were first loaded on a graphitic carbon nitride support in different ratios of ZnMn2O4 and carbon support by hydrothermal method. Then the photocatalysts were evaluated for evolution of oxygen and hydrogen photocatalysts through water splitting under visible light. In ZnMn2O4 / g-C3N4 (80:20) nanocomposite, the highest...

Theoretical Study of Organic Pollutants Adsorption on Graphene, Doped Graphene and Defective Graphene Nanosheets

, M.Sc. Thesis Sharif University of Technology Yeganeh, Raziyeh (Author) ; Rahman Setayesh, Shahrbanou (Supervisor)

Abstract

Among the xenobiotic compounds, chlorophenols are considered to be as the most dangerous compounds for the environment and living organisms. These compounds are abundantly found in the wastewater of many chemical industry factories. In this research, by using Gaussian software and density functional theory at the level of B3LYP / 6-31G (d, p),the adsorption of molecules such as phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol over graphene, nitrogen and boron doped graphene sheet are studied. The most stable configurations were determined and adsorption energies were calculated. In addition, to understand the adsorption mechanism, electron properties such as state density and...