An upper-bound finite element solution for rolling of stainless steel 304L under warm and hot deformation conditions

, Article Multidiscipline Modeling in Materials and Structures ; Volume 12, Issue 3 , 2016 , Pages 514-533 ; 15736105 (ISSN) Pourabdollah, P ; Serajzadeh, S ; Sharif University of Technology

Emerald Group Publishing Ltd 2016

Abstract

Purpose: The purpose of this paper is to investigate the thermomechanical behavior of stainless steel AISI 304L during rolling at elevated temperatures. Design/methodology/approach: Two-dimensional finite element analysis together with the upperbound solution were used for predicting temperature field and required power in warm and hot rolling operations. The required power and heat of deformation were estimated employing an upper-bound solution based on cylindrical velocity field and at the same time, temperature distributions within the rolling steel and the work rolls were determined by means of a thermal finite element analysis. To consider the effect of flow stress and its dependence on...

A study on deformation behavior of 304L stainless steel during and after plate rolling at elevated temperatures

, Article Journal of Materials Engineering and Performance ; Volume 26, Issue 2 , 2017 , Pages 885-893 ; 10599495 (ISSN) Pourabdollah, P ; Serajzadeh, S ; Sharif University of Technology

Springer New York LLC 2017

Abstract

In this work, microstructural evolutions and mechanical properties of AISI 304L stainless steel were studied after rolling operations at elevated temperatures. Rolling experiments were conducted under warm and hot rolling conditions in the range of 600-1000 °C employing different reductions. Then, the developed microstructures and the mechanical properties of the steel were evaluated by means of uniaxial tensile testing, metallographic observations, and x-ray diffraction method. Besides, two-dimensional finite element analysis coupled with artificial neural network modeling was developed to assess thermo-mechanical behavior of the steel during and after rolling. The results show that...

Investigation and Modeling of Fouling and its Affecting Operational Parameters in Membrane Bioreactors (MBR) for Municipal Wastewater Treatment

, Ph.D. Dissertation Sharif University of Technology Pourabdollah, Mahdi (Author) ; Torkian, Ayoub (Supervisor)

Abstract

This study aims to investigate the influence of important operational parameters on membrane fouling with the approach of fouling layers and to model these influences in the membrane bioreactor (MBR) for municipal wastewater treatment. At the first phase, 11 operational scenarios were executed using a pilot setup for identifying the system behavior and the optimal scenario. Protein and carbohydrate as the fouling components (SMP) and the transmembrane pressure (TMP) as the fouling criteria were measured in the tests. By studying the influence of operational parameters (sludge retention time (SRT), aeration rate and filtration mode), some useful results obtained for the next phase, including...

Theoretical and Experimental Investigations of Deformation Behavior from Stainless Steel 304L During Rolling at Evelated Temperatures

, M.Sc. Thesis Sharif University of Technology Pourabdollah, Pegah (Author) ; Serajzadeh, Siamak (Supervisor)

The seismic performance of K-braced cold-formed steel shear panels with improved connections

, Article Journal of Constructional Steel Research ; Volume 135 , 2017 , Pages 56-68 ; 0143974X (ISSN) Pourabdollah, O ; Farahbod, F ; Rahimzadeh Rofooei, F ; Sharif University of Technology

Elsevier Ltd 2017

Abstract

In this paper the performance of light weight K-braced cold formed steel (CFS) shear panels under cyclic loading is experimentally evaluated. It is generally known that the brace-stud connection details has an important effect on the performance of the braced CFS shear panels in terms of lateral stiffness, energy dissipation, and ductility factor. In this study, four full-scale, 2.4 m × 2.4 m, braced CFS shear panels made of C-sections were tested. It was observed that proper modification of the currently utilized braced to stud connections in K-braced, CFS shear panels could enhance their performance considerably by increasing their ultimate shear resistance up to 7 folds. Furthermore,...

A triple fouling layers perspective on evaluation of membrane fouling under different scenarios of membrane bioreactor operation

, Article Journal of Environmental Health Science and Engineering ; Volume 12, Issue 1 , June 2014 Pourabdollah, M ; Torkian, A ; Hashemian, S. J ; Bakhshi, B ; Sharif University of Technology

June 2014

Abstract

One of the main factors affecting membrane fouling in MBRs is operational conditions. In this study the influence of aeration rate, filtration mode, and SRT on hollow fiber membrane fouling was investigated using a triple fouling layers perspective. The sludge microbial population distribution was also determined by PCR method. Through various applied operational scenarios the optimal conditions were: aeration rate of 15 LPM; relaxation mode with 40s duration and 8 min. interval; and SRT of 30 days. The similarity between SMP variations in triple fouling layers with its corresponding hydraulic resistance confirmed the effect of SMP on membrane fouling. Among three fouling fractions, the...

Experimental-numerical assessment of laterally-loaded CFS frames with steel sheathing and K-shaped braces

, Article Journal of Constructional Steel Research ; Volume 203 , 2023 ; 0143974X (ISSN) Rahimibala, M ; Rofooei, F. R ; Farahbod, F ; Pourabdollah, O ; Sharif University of Technology

Elsevier Ltd 2023

Abstract

In this study, the behavior of cold-form steel (CFS) frames equipped with various configurations of steel sheathing, and K-shaped braces are experimentally investigated. Low lateral resistance is a major problem with the CFS shear walls. Despite their advantages, such as being lightweight, ease of fabrication, and an environmentally friendly system, their lack of adequate lateral strength prevents engineers from widely using them, especially in areas with medium to high seismicity or mid-rise buildings. In this regard, a total of seven full-scale specimens with different configurations of steel sheathing and k-braced, with and without cladding, were tested to investigate their seismic...

Experimental Evaluation of Light Frame Steel Shear Wall with K-Braced and Suitable Sheathing under Cyclic Loading

, M.Sc. Thesis Sharif University of Technology Pourabdollah, Omid (Author) ; Rahimzadeh Rofooei, Fayyaz (Supervisor) ; Farahbod, Farhang (Supervisor)

Abstract

Nowadays because of imbalance in supply and demand in the house industry, industrialization of building construction is one of the best ways to solve this problem. Currently, there is a strong tendency to develop guidelines for the design of Cold-Formed Steel (CFS) with different sheathing boards as seismic resistant shear walls. Also, the behavior of this systems is not very well known yet and more research is needed. In this work three K-braced frames with and without sheathing boards under lateral cyclic loading investigated experimentally. The first specimen as a control specimen is without sheathing board, second specimen was sheathed with Fibre-Cement board in one side and gypsum board...

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 Emamy, Hamed (Author) ; 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 Rahimi, Kourosh (Author) ; 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...

Fabrication of Graphene-WO3 Nanocomposites as Photocatalyst in the Visible Light Region

, M.Sc. Thesis Sharif University of Technology Choobtashani, Mohammad (Author) ; 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.
In this...

Synthesis of Graphene Nanosheets for Stem Cells Applications

, M.Sc. Thesis Sharif University of Technology Shahsavar, Mahla (Author) ; 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 Sarhadi, Maryam (Author) ; 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 Mirsepah, Ali (Author) ; 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 Ghorbani, Fatemeh (Author) ; 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 Puresmaili, Ehsan (Author) ; 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 Akbari, Ebrahim (Author) ; 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 (Author) ; 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...

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) Delaram, J ; 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 Ebrahimian, Mahsa (Author) ; 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...