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Synthesize of Graphene Nanoribbons with a Non-Zero Energy Band Gap for Inactivation of Alive Cells Using Infrared Irradiation
, M.Sc. Thesis Sharif University of Technology ; Akhavan, Omid (Supervisor)
Abstract
Graphene is a one layer atom thickness and zero energy gap so for using it in nano electronic and transistors baised on graphene it's energy gap should be opened.one of the methods for opening graphene band gap is creating nano scale boundaries or synthesize graphene nanoribbons. One of the new methods for graphene nanoribbon synthesize is longitudinal opening of carbon nanotube. In this thesis graphene nanoribbons synthesize with this method and analyze with AFM and Raman spectroscopy. Carbon nanotubes also have energy gap and IR absorption recently they used for living cell destruction. In this thesis we synthesize graphene nanoribbons and analyzing their optical absorption and use it for...
Fabrication of Graphene/TiO2 Nanowalls as Visible Lights Photocatalysts
, M.Sc. Thesis Sharif University of Technology ; Akhavan, Omid (Supervisor)
Abstract
TiO2 is known as a photocatalyst in near UV-Visible light region with better efficiency compared to other semiconductor photocatalysts. Many attempts have been done to increase the efficiency of this photocatalyst. also, application of 2D carbon nanostructures namely graphene for increasing the photocatalytic activity of TiO2 has shown positive results.
In this research, we first synthesized Graphene Oxide (GO) suspension by exfolation of graphite oxide suspension. then we fabricated TiO2 thin films on glass substrates by so-called sol-gel method. finally we fabricate Graphene Oxide/TiO2 nanowalls composite films as a photocatalyst in visible light. X-ray photoelectron spectroscopy...
In this research, we first synthesized Graphene Oxide (GO) suspension by exfolation of graphite oxide suspension. then we fabricated TiO2 thin films on glass substrates by so-called sol-gel method. finally we fabricate Graphene Oxide/TiO2 nanowalls composite films as a photocatalyst in visible light. X-ray photoelectron spectroscopy...
Fabrication of Graphene-WO3 Nanocomposites as Photocatalyst in the Visible Light Region
, M.Sc. Thesis Sharif University of Technology ; Akhavan, Omid (Supervisor)
Abstract
WO3 is known as a photocatalyst in the visible light region, but with lower efficiency compared to more interesting semiconductor photocatalysts such as TiO2 and ZnO. Many attempts have been done to increase the efficiency of this photocatalyst by incorporating metal and metal oxide nanoparticles or recently carbon nanotubes.On the other hand, application of graphene, as an unrolled carbon nanotube, for increasing the photocatalytic activity of TiO2 and ZnO has shown positive results. Furthermore, it was reported that such semiconductor photocatalysts (and very recently WO3) can photocatalytically reduce the chemically exfoliated graphene oxide sheets under UV-vis irradiation.
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Synthesis of Graphene Nanosheets for Stem Cells Applications
, M.Sc. Thesis Sharif University of Technology ; Akhavan, Omid (Supervisor)
Abstract
Graphene nanogrids fabricated by graphene nanoribbons obtained through oxidative unzipping of multi-walled carbon nanotubes, used as two-dimensional selective templates for accelerated differentiation of human mesenchymal stem cells (hMSCs), isolated from umbilical cord blood, into osteogenic lineage. The biocompatible and hydrophilic graphene nanogrids showed high actin cytoskeleton proliferations that coinciding with patterns of the nanogrids. The amounts of proliferations found are slightly better than proliferation on hydrophilic graphene oxide (GO) sheets, and significantly higher than non-uniform proliferations on hydrophobic reduced graphene oxide (rGO) sheets and polydimethylsiloxane...
Identifying the risks of Iranian Knowledge BasedFirms Using Fault Tree Analysis (FTA)
, M.Sc. Thesis Sharif University of Technology ; Fattahi, Omid (Supervisor)
Abstract
Knowledge Based Firms are considered to be important for the economic development of a country in regards to both employment growth and innovative activity. The latter is believed to contribute significantly to the increase in productivity and therefore the competitiveness of Iran’s economy. This study contributes to the above literature by investigating the factors that are believed to treat the growth of such firms in Iran. The purpose of this study is to identify functional risks of vital signs monitors via Fault Tree Analysis (FTA) method to use as a guide for manufacturers to identify and control hazards. Therefore, 30 knowledge based firms were selected as sample. Then, based on a...
Synthesis of Graphene from Waste by Chemical Exfoliation and Study of It’s Physical Characteristics
, M.Sc. Thesis Sharif University of Technology ; Akhavan, Omid (Supervisor)
Abstract
One atom thick layer of pure carbon in bonded and hexagonal lattice is named graphene. graphene has unique mechanical, optical, thermal and electrical properties and because of these properties has grabbed attention. graphene has been made from high pure graphite by different methods such as CVD(chemical vapor deposition) , chemical exfoliation , micromechanical cleavage and colloidal suspension. through these methods, green methods for synthesis of graphene, using eco-friendly reductants during synthesis of graphene instead of hydrazine and recently using waste(not graphite) are attractive for synthesis of graphene. Following this idea , a group has produced graphene from wastes such as...
The Use of Hydrogen Rich Water for Synthesis of Hydrogenized Graphene and Investigation of Its Properties
, M.Sc. Thesis Sharif University of Technology ; Akhavan, Omid (Supervisor)
Abstract
Graphene is a two dimensional lattice which is created from carbon atoms. Having special feature, it has such various medical usage, for example in diagnosing and treating cancer. Adding a particular factor to graphene could improve their efficiency. In comparis on with graphene itself, graphene oxide and reduced graphene oxide are much more successful in diagnosing and treating than others because of their higher hygroscopic. Recent studies state that hydrogenized combinations including hydrogenized graphene show desired results. Due to its higher hygroscopic and the possibility of adherence to the cells, hydrogenized graphene could be very effective in diagnosing and treating the sarcomas....
A Meta Heuristic Approach for Design of a Network System in Mass Customization
, M.Sc. Thesis Sharif University of Technology ; Fattahi, Omid (Supervisor)
Abstract
This study discusses about mass customization and optimization of supply network in which both goal considering to set the flow of raw material and final product to satisfy the customer demand. The mass customization is more important concept in this study, so that this goal is placed to the first objective. In this research, the model which contained both goal is presented. The model focus on mass customization and try to satisfy various products demand, which constitute 3 kind of speed demands. Each product can satisfy in 3 way: fast, normal, slow.In the first model the new approach present in which the speed affects all of supplying, manufacturing and distributing system. The system try...
Synthesis of Graphene Oxide and Study of its Fluorescence Properties
, M.Sc. Thesis Sharif University of Technology ; Akhavan, Omid (Supervisor)
Abstract
Graphene oxide is a single sheet of Carbon atoms which has been arranged on a two-dimensional honeycomb lattice. Functional groups such as epoxy, carboxyl and carbonyl are located on basal plane and at the edges of graphene oxide and they localize electrons on the surface of graphene oxide and open band gap in its band structure. Pure graphene has zero band gap, so existence of fluorescence properties is unlikely; but graphene oxide has fluorescence properties due to band gap in its band structure. Fluorescence properties of graphene have been used in live cell imaging and drug delivery, so study and increasing of fluorescence properties is significantly important. The purpose of this...
A Novel Reliability Model for Information Technology Web services
, M.Sc. Thesis Sharif University of Technology ; Fatahi Valilai, Omid (Supervisor)
Abstract
The Internet is often used for communication-based applications such as online banking, stock trading, and shopping where service interruption is unacceptable. Thus, analysis of the impact of the failures of hardware, software, and related services’ performance quality of the service provided to users is of importance to designers and managers in these functions. In this study, we developed a strategy to the design of a dynamic combination of file servers with the aim of providing reliability and SLA. At first, we examine the reasons for the violation of service level in file host services and datacenters, and then we introduce the criteria to measure the violation of service level on the...
Two-phase flow in microchannels with a bounding porous medium
, Article ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM 2011, 19 June 2011 through 22 June 2011 ; Volume 1 , June , 2011 , Pages 263-268 ; 9780791844632 (ISBN) ; Sharif University of Technology
2011
Abstract
This paper investigates numerical simulation of one-dimensional homogeneous adiabatic gas-liquid two-phase flow in a rectangular microchannel with one boundary porous wall under the assumption of hydrophobic condition. Gas enters the microchannel with a uniform velocity and liquid is injected through the porous side wall. The present approach is to simulate water injection effects and developing mechanism of two-phase flow. The modeling and solution of the conservation equations provide pressure drop, vapor quality, void fraction and tow-phase mixture velocity for different water injection rates. The results show that velocity and pressure drop significantly perturbed when the water...
A new approach to thermo-fluid behavior through porous layer of heat pipes
, Article Scientia Iranica ; Volume 25, Issue 3B , 2018 , Pages 1236-1242 ; 10263098 (ISSN) ; Sharif University of Technology
Sharif University of Technology
2018
Abstract
This paper developed a new mathematical model to investigate the heat transfer as well as wick's thickness of a heat pipe. The model was established by conservative equations of continuity, momentum, and energy in the thermal boundary layer. Using a similarity variable, the governing equations were changed to a set of ordinary differential equations and were solved numerically by the forth-order Runge-Kutta method. The flow variables, such as velocity components, wick's thickness, and Nusselt number, were obtained. The results show that the Nusselt number is proportional to the square root of the Darcy-modified Rayleigh number and to the distance from the edge of the condenser surface....
Analysis of vacuum venting in die casting
, Article Scientia Iranica ; Volume 11, Issue 4 , 2004 , Pages 398-404 ; 10263098 (ISSN) ; Sharif University of Technology
Sharif University of Technology
2004
Abstract
The present study is undertaken to calculate the rate of change of pressure and residual air mass in die casting for vacuum venting under choked flow conditions. In these calculations, the influence of friction factor, due to roughness and vent air velocity change through the Mach number, has been taken into account. The results show that there is a critical area ratio below which the pressure and vent inlet Mach number increase with time and above which decrease with time. In addition, for an area ratio less than the critical area, the rate of change of residual air mass seems to be more changed at the late stages than at the early stages of the filling time. The picture is reversed for a...
Analytical modeling of convective condensation in smooth vertical tubes
, Article Scientia Iranica ; Volume 8, Issue 2 , 2001 , Pages 123-129 ; 10263098 (ISSN) ; Sharif University of Technology
Sharif University of Technology
2001
Abstract
In this paper, an analytical model is presented for forced convective film condensation inside smooth vertical tubes, in which Prandtl mixing length theory, Van Driest hypothesis and Reynolds analogy are used. Comparison of this model with the available experimental data and three other correlations reported in the literature demonstrates that the results are in satisfactory and close agreement
Development of a novel solution to enable integration and interoperability for cloud manufacturing
, Article 6th International Conference on Changeable, September 2016 through 6 September 2016 ; Volume 52 , 2016 , Pages 6-11 ; 22128271 (ISSN) ; Fatahi Valilai, Omid ; Sharif University of Technology
Elsevier B. V
2016
Abstract
Nowadays, manufacturing enterprises have been faced with a globalized competitive environment. In this fierce condition, Cloud Manufacturing paradigm emerged as a promising concept for competition. It provides effective solutions and tools for manufacturing enterprises to collaborate in globalized market. The revolution that Cloud Manufacturing has created is based on the redefinition of the classic methods to those which are appropriate for todays' modern and globalized manufacturing environments. In parallel with cloud-based revolution, the expansion of internet-based technologies has been started. These technologies previously have been applied in many fields and resulted in...
Product Portfolio Management Using Life Cycle Considerations
, M.Sc. Thesis Sharif University of Technology ; Fattahi, Omid (Supervisor)
Abstract
Today’s organizations always encounter limitations on the way of achieving their goals. Budget constraint, inventory constraints, capital constraints are issues which complicates management decision making.
Global market has enabled manufacturers compete globally. Even position their factories in other countries and use of competitive advantages and other markets demand. This is why decision making in production and manufacturing domain has been complicated. Decision making in production and manufacturing should become faster and more precise in order to keep market competitiveness. Organization should make long term or strategic decisions and short term decisions about keeping the...
Global market has enabled manufacturers compete globally. Even position their factories in other countries and use of competitive advantages and other markets demand. This is why decision making in production and manufacturing domain has been complicated. Decision making in production and manufacturing should become faster and more precise in order to keep market competitiveness. Organization should make long term or strategic decisions and short term decisions about keeping the...
Fabricating Graphene Paper and Determining Its Electrical and Mechanical Properties and Using It for Proliferation and Differentiation of Neural Stem Cells
, M.Sc. Thesis Sharif University of Technology ; Akhavan, Omid (Supervisor)
Abstract
Nowadays, tissue engineering and stem cells-based therapies have outlined a promising prospect in neural networks regeneration. But it usually requires biocompatible and conductive scaffolds for culturing neural stem cells and directing their differentiation toward the neurons. Graphene due to its unique physical and chemical properties has attracted much interest in tissue engineering. For this purpose, in this study biocompatible graphene oxide foams have been used for neural stem cell culturing. For the first time, graphene oxide foam were fabricated by precipitation of chemically exfoliated graphene oxide sheets in an aqueous suspension onto the PET substrate at ~80 oC under UV...
Scheduling tasks with exponential duration on unrelated parallel machines
, Article Discrete Applied Mathematics ; Volume 160, Issue 16-17 , November , 2012 , Pages 2462-2473 ; 0166218X (ISSN) ; Ghodsi, M ; Sharif University of Technology
2012
Abstract
This paper introduces a stochastic scheduling problem. In this problem a directed acyclic graphs (DAG) represents the precedence relations among m tasks that n workers are scheduled to execute. The question is to find a schedule Σ such that if tasks are assigned to workers according to Σ, the expected time needed to execute all the tasks is minimized. The time needed to execute task t by worker w is a random variable expressed by a negative exponential distribution with parameter λ wt and each task can be executed by more than one worker at a time. In this paper, we will prove that the problem in its general form is NP-hard, but when the DAG width is constant, we will show that the optimum...
Space-query-time tradeoff for computing the visibility polygon
, Article 3rd International Frontiers of Algorithmics Workshop, FAW 2009, Hefei, 20 June 2009 through 23 June 2009 ; Volume 5598 LNCS , 2009 , Pages 120-131 ; 03029743 (ISSN); 3642022693 (ISBN); 9783642022692 (ISBN) ; Ghodsi, M ; Sharif University of Technology
2009
Abstract
Computing the visibility polygon, VP, of a point in a polygonal scene, is a classical problem that has been studied extensively. In this paper, we consider the problem of computing VP for any query point efficiently, with some additional preprocessing phase. The scene consists of a set of obstacles, of total complexity O(n). We show for a query point q, VP(q) can be computed in logarithmic time using O(n 4) space and O(n 4 logn) preprocessing time. Furthermore to decrease space usage and preprocessing time, we make a tradeoff between space usage and query time; so by spending O(m) space, we can achieve O(n 2 log √ m/n)/√ m)query time, where n 2≤m≤n 4. These results are also applied to...
A comparison between modal damping ratios identified by NExT-ERA and frequency domain impact test
, Article Journal of Computational and Applied Research in Mechanical Engineering ; Volume 8, Issue 1 , 2018 , Pages 15-24 ; 22287922 (ISSN) ; Hajirezayi, S ; Sharif University of Technology
Shahid Rajaee Teacher Tarining University (SRTTU)
2018
Abstract
In this research, the modal parameters of a beam in free-free condition are extracted by performing different experiments in the laboratory. For this purpose, two different techniques are employed. The first methodology is considered as a time domain method in Operational Modal Analysis. The other one is frequency domain impact hammer test which is categorized as an Experimental Modal Analysis method and can be regarded as the most common method in modal analysis. Checking the results obtained by the two methods, one can notice a distinct inconsistency in modal damping ratios extracted by each method. However, based on recent publications on the subject, it can be inferred that the time...