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pourabdollah--mahdi
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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) ; 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) ; 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 ; 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 ; 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) ; 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 ; 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) ; 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 ; 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...
MBBR and MBR Reactor Configuration for Better Performance
, M.Sc. Thesis Sharif University of Technology ; Borgheei, Mahdi (Supervisor)
Abstract
Membrane bioreactors (MBRs) which are commonly understood as the combination of membrane filtration and biological treatment using activated sludge have several advantages, but membrane fouling reduces the membrane efficiency, permeability and lifetime. An alternative is replacing a moving bed biofilm reactor (MBBR) with the activated sludge system which may reduce the effect of membrane fouling. The sludge produced in MBBRs has poor settling characteristics, therefore, their efficiency is limited by the sedimentation tank performance and they require a larger settling surface. The combination of moving bed biofilm reactors and membrane bioreactors can compensate for the drawbacks of both of...
Forecasting the effects of a Canada-US currency union on output and prices: A counterfactual analysis
, Article Journal of Forecasting ; Volume 32, Issue 7 , 2013 , Pages 639-653 ; 02776693 (ISSN) ; Sharif University of Technology
2013
Abstract
This paper is a counterfactual analysis investigating the consequences of the formation of a currency union for Canada and the USA: whether outputs increase and prices decrease if these countries form a currency union. We use a two-country cointegrated model to conduct the counterfactual analysis, where the conditional forecasts are generated based on the Gaussian assumption. To deal with structural breaks and model uncertainty, conditional forecasts are generated from different models/estimation windows and the model-averaging technique is used to combine the forecasts. We also examine the robustness of our results to parameter uncertainty using the wild bootstrap method. The results show...
Evaluation of Non-linear Combination Method (Neural Network) For Value-at-Risk Forecasting in Market
, M.Sc. Thesis Sharif University of Technology ; Barakchian, Mahdi (Supervisor)
Abstract
Value at risk of an asset, is the asset’s expected maximum loss for a certain period of time and at a specified confidence level. Value-at-Risk can be calculated in the bank with its inter-nal method or standardized method. when a method have more violation number then bank need to keep more daily capital requirements. under the Basel 2 agreement if the violation of method more than 10 times in year, the Bank uses the standardized method.
There are trade off Between daily capital charge and violations. Therefore, existing methods for calculating the value at risk, usually lead to much daily capital charge or many violations. Studies show with combination of different methods to calculate...
There are trade off Between daily capital charge and violations. Therefore, existing methods for calculating the value at risk, usually lead to much daily capital charge or many violations. Studies show with combination of different methods to calculate...
Using Complex Network Metrics for Evaluating the Influence of Conference and Journal Papers in Computer Science
,
M.Sc. Thesis
Sharif University of Technology
;
Jalili, Mahdi
(Supervisor)
Abstract
Journals and conferences in computer science are the major venue for publishing new achievement in the field. It is an expert opinion that a number of top conferences in computer science are even more important than journals. In this work we aim at studying this in terms of citation analysis. To this end, we took 100 top journals and 63 top conferences and extracted their citation graph through Scopus dataset. We then constructed the citation graph in which the nodes were the journals and conferences and the links corresponded to the citations of the papers. We used various measures to rank the nodes in the graph. The ranking methods included Prestige, PageRank, Eigenfactor, HITS and SALSA....
Design and Implementation of a VLSI Architecture for Time and Frequency Synchronization in the LTE
, M.Sc. Thesis Sharif University of Technology ; Shabany, Mahdi (Supervisor)
Abstract
The long term evolution (LTE) standard is introduced and developed by the 3rd generation partnership project (3GPP) based on orthogonal frequency division multiplexing (OFDM). OFDM systems, in spite of having many advantages such high performance in bandwidth usage, are very sensitive to inter carrier interference (ICI) as a drawback. In order to prevent ICI, the frequency offset, mainly caused by the miss-match between oscillators' frequency and also between the sampling frequency of the transmitter and the receiver, should be estimated and compensated. Frequency synchronization is a part of the tasks of a synchronizer. In this thesis, main tasks of a synchronizer are illustrated and...
A New Approach in Value-at-Risk (VaR) Estimation by Forecast Combination Methods
, M.Sc. Thesis Sharif University of Technology ; Barakchian, Mahdi (Supervisor)
Abstract
Value-at-Risk (VaR) is the most commontool for risk management. This tool is used to measure market risk and also used as a basis in determining financial standards for international financial institutions. VaR is the maximum loss of the asset portfolio at the specified confidence level and certain time horizon. Many parametric, nonparametric and semi parametric methods have been invented for VaR estimation. Each one of these methods has its advantages and disadvantages and different methods may perform better in differnet situations.When estimating VaR, we can choose one of these methods or we can combine the VaRs estimated by different methods. There are few researches conducted on VaR...
EEG Brain Functional Network Analysis in Cortex Level
, M.Sc. Thesis Sharif University of Technology ; Jalili, Mahdi (Supervisor)
Abstract
Complex networks science have received tremendous attention in recent years and the brain is one of the systems to which graph theoretical tools have been applied. Alzheimer’s disease (AD) is a neurodegenerative disease affecting many of elderly population. AD changes the anatomy of the brain, which subsequently results in changes in its functions. These changes have been frequently reported in signals recorded from the brain (such as MEG, fMRI and EEG). Among these neuroimaging techniques EEG is one of the most aproprate methods for extracting functional connectivites according to high temporal resolution. In this thesis, we aimed at analyzing the properties of EEG-based functional networks...
Learning Improvement in Phase Oscillator Models
, M.Sc. Thesis Sharif University of Technology ; Jalili, Mahdi (Supervisor)
Abstract
In the recent years, the problem of modeling a cognitive task using phase oscillators has been receiving a significant attention. In this view, single neurons are no longer elementary computational units. Rather, coherent oscillating groups of neurons are seen as nodes of networks performing cognitive tasks. From this assumption, we develop a model of stimulus-response learning and recognition. The most significant part of our work is defining learning methods for natural frequencies and coupling weights in a coupled phase oscillator network under Kuramoto conditions. In this thesis, we improved the previous models by not only emphasizing on the frequency of the oscillators but also taking...
Evaluation of Caviar Models Incorporated with Intraday Information ,the Case Study:Estimation Value at Risk of Gold
, M.Sc. Thesis Sharif University of Technology ; Barakchian, Mahdi (Supervisor)
Abstract
Value at risk (VaR) is the maximum loss of the asset portfolio at the specified confidence level and certain time horizon. This tool is used to measure market risk and also used as a basis in determining financial standards for international financial instituation. Conditional Autoregressive Value at Risk models or CAViaR models introduced by Engle and Manganelli (2004). This models calculate VaR base on quantile regession approach and show some promising performance properties.
In order to propose a more accurate model for calcutating VaR , we develop CAViaR models by incorporating them with intraday information then we calculate VaR with this kind of models and CAViaR...
In order to propose a more accurate model for calcutating VaR , we develop CAViaR models by incorporating them with intraday information then we calculate VaR with this kind of models and CAViaR...
Design and Implementation of a Spectrum Sensor for Cognitive Radio
, M.Sc. Thesis Sharif University of Technology ; Shabani, Mahdi (Supervisor)
Abstract
Frequency scarcity has emerged the necessity of opportunistic utilization of frequency bands, which can be realized through a cognitive radio system. During an agile communication between unlicensed users, a cognitive radio system must avoid collision with licensed users. Hence it should continuously observe the band of interest and report the presence of licensed user signals. This task is fulfilled by a vital part of a cognitive radio system, called the spectrum sensing core. Recently several techniques have been proposed for the spectrum sensing in literature. Some of them like matched filtering, cyclostationarity based detection are based on primary user signal features. However energy...
VLSI Architecture of Turbo Decoder for LTE
, M.Sc. Thesis Sharif University of Technology ; Shabany, Mahdi (Supervisor)
Abstract
Long Term Evolution (LTE) aims the peak data rates in excess of 300 Mb/s, which may appear to be challenging to achieve due to the existence of some blocks such as the turbo decoder. One efficient approach to achieve this throughput is by parallelizing the Log Maximum a Posteriori (MAP) algorithm in the turbo decoder. In fact, the interleaver is known to be a major challenging part of the turbo decoder due to its need to the parallel interleaved memory access. LTE uses Quadratic Permutation Polynomial (QPP) interleaver, which makes it suitable for the parallel decoding. In this thesis, first, we propose an efficient architecture for the QPP interleaver, called the Add-Compare-Select (ACS)...
Efficient Hardware Implementation of ECG Derived Respiration (EDR) System, Applied to Body Area Network (BAN)
, M.Sc. Thesis Sharif University of Technology ; Shabany, Mahdi (Supervisor)
Abstract
The rapid growth in the health care technology, has made the Body Area Network (BAN) as an attracting topic for research and design development. BAN devices have restrictions on their size and power consumption. Monitoring the respiratory signal is crucial in many medical applications and is normally part of a BAN system. Traditional methods for the respiration measurement are normally based on measuring the volume of air inhaled and exhaled by lungs (like a spirometer) or oxygen saturation in blood. However, these methods have numerous drawbacks including their high cost and limited accessibility. In this thesis, a novel scheme is proposed to derive the respiratory signal from the...