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    , M.Sc. Thesis Sharif University of Technology Farshid, Saman (Author) ; Adib Nazari, Saeed (Supervisor)
    Abstract
    First stage blades tempreture in the turbine rotor section for the advanced turbines has increased up to 1100oc. The blades should be under mentioned condition for the long times up to 70000 hours and accordingly creep happens. Fatigue–creep interaction is the main reason for the failures of many engineering components under high temperature and cyclic loading. In this thesis, a model for the life prediction of fatigue–creep interaction which was developed by other investigators has been modified to predict fatigue–creep interaction on the nickel-based superalloys. In this model, the law of energy conservation and the momentum conservation principle are used to describe the process of... 

    Molecular dynamics simulation of manipulation of metallic nanoclusters on double-layer substrates [electronic resource]

    , Article Physica E: Low-dimensional Systems and Nanostructures ; 2010, Vol. 42, No. 9, pp. 2364-2374 Mahboobi, H. (Hanif) ; Meghdari, Ali ; Jalili, Nader ; Amiri, Farshid ; Sharif University of Technology
    Abstract
    Molecular dynamics simulations are carried out to investigate the manipulation of metallic clusters on double-layer surfaces. The system parts are made of transition metals. The conditions which are subjected to change in the tests are material combinations for cluster, main substrate and lubricant layer (adlayer). In addition to qualitative observations, two criteria which represent the particle deformation and substrate abrasion are utilized as evaluation tools and are computed for each case. Obtaining this sort of knowledge is highly beneficial for further experiments in order to be able to plan the conditions and routines, which guarantee better success in the manipulation process  

    Planar molecular dynamics simulation of Au clusters in pushing process

    , Article International Journal of Nanomanufacturing ; Vol.5, No.3/4 , 2010 , pp.288-296 Mahboobi, S. H ; Meghdari, A. (Ali) ; Jalili, N. (Nader) ; Amiri, F. (Farshid) ; Sharif University of Technology
    2010
    Abstract
    Based on the fact that the manipulation of fine nanoclusters calls for more precise modelling, the aim of this paper is to conduct an atomistic investigation for interaction analysis of particle-substrate system for pushing and positioning purposes. In the present research, 2D molecular dynamics simulations have been used to investigate such behaviours. Performing the planar simulations can provide a fairly acceptable qualitative tool for our purpose while the computation time is reduced extremely in comparison to 3D simulations. To perform this study, Nose-Hoover dynamics and Sutton-Chen interatomic potential will be used to investigate the behaviour of the aforementioned system. Pushing of... 

    Molecular dynamics simulation of manipulation of metallic nanoclusters on stepped surfaces

    , Article Central European Journal of Physics ; Volume 9, Issue 2 , 2011 , pp 454-465 ; 1644-3608 Mahboobi, S. H ; Meghdari, A. (Ali) ; Jalili, N. (Nader) ; Amiri, F. (Farshid) ; Sharif University of Technology
    2011
    Abstract
    Molecular dynamics simulations are carried out to investigate the manipulation of metallic clusters on stepped surfaces. Five surface forms are considered in the simulations. The system parts are made of pure transition metals and Sutton-Chen many-body potential is used as interatomic potential. The conditions which are subjected to change in the tests include: materials used for particles and substrate, and surface step conditions. In addition to qualitative observations, two criteria which represent the particle deformation and substrate abrasion are utilized as evaluation tools and are computed for each case. Simulation results show the effect of the aforementioned working conditions on... 

    A uniquely 3-list colorable, planar and k4-free graph

    , Article Journal of Combinatorial Mathematics and Combinatorial Computing ; Volume 72 , 2010 , Pages 115-120 ; 08353026 (ISSN) Asadi, S. A ; Sharif University of Technology
    2010
    Abstract
    Let G be a graph with v vertices. If there exists a collection of list of colors S1, S1,..., Sv on its vertices, each of size k, such that there exists a unique proper coloring for G from this list of colors, then G is called a uniquely k-list colorable graph. In this note we present a uniquely 3-list colorable, planar and K4-free Graph. It is a counterexample for a conjecture by Ch. Eslahchi, M. Ghebleh and H. Hajiabolhassan [3]  

    Evaluating Reliability of SSDs Against Power Outage

    , M.Sc. Thesis Sharif University of Technology (Author) ; Asadi, Hossein (Supervisor)
    Abstract
    Solid-State Drives (SSDs) provide high performance, low power consumption, and hence are widely used in the I/O cache of enterprise storage systems and high performance servers. Although employing high performance SSDs in the I/O cache of storage systems significantly improves system performance, it comes with significant reliability threats for write operations upon power failures. In order to provide high level of reliability, storage architectures employ SSDs in I/O cache with RAID-1 configuration, however, such configuration only partially mitigates the reliability issues of the SSDs. In this thesis, we analyze the reliability of SSD-based I/O caches against power outage and high... 

    Multi directional forging of 2024 Al alloy after different heat treatments: Microstructural and mechanical behavior

    , Article Transactions of the Indian Institute of Metals ; 2016 , Pages 1-13 ; 09722815 (ISSN) Asadi, S ; Kazeminezhad, M ; Sharif University of Technology
    Springer India  2016
    Abstract
    Improvement of mechanical properties and microstructure of 2024 aluminum alloy by performing a severe plastic deformation method, called multidirectional forging (MDF), and heat treatment was the aim of this research. In this work, the effects of different heat treatments such as annealing, solid solution, peak ageing and over ageing before MDF on mechanical properties and microstructure of the alloy were studied. Microstructure evolution during severe plastic deformation was considerably affected by the precipitates and non-shearable particles. On the other hand, the severe plastic deformation had different effects on precipitates in the microstructure. Fragmentation, scattering and... 

    Utilizing mixed methods research in analyzing Iranian researchers' informarion search behaviour in the web and presenting the current pattern

    , Article Iranian Journal of Information Processing Management ; Volume 31, Issue 1 , 2015 , Pages 27-57 ; 22518223 (ISSN) Asadi, M ; Hariri, N ; Sharif University of Technology
    Iranian Research Institute for Scientific Information and Documentation  2015
    Abstract
    Using mixed method research the current study has analyzed Iranian researchers' information searching behavior on the Web. Based on extracted concepts, the model of their information searching behavior was revealed. Forty-four participants, including academic staff from universities and research centers were recruited for this study selected by purposive sampling. Data were gathered from questionnaires including ten questions and semi-structured interview. Each participant's memos were analyzed using grounded theory methods adapted from Strauss & Corbin (1998). Results showed that the main objectives of subjects were doing a research, writing a paper, studying, doing assignments, downloading... 

    The relationship between the research activity of Iranian medical universities and their web impact factor

    , Article Electronic Library ; Volume 27, Issue 6 , 2009 , Pages 1026-1043 ; 02640473 (ISSN) Asadi, M ; Shekofteh, M ; Sharif University of Technology
    2009
    Abstract
    Purpose - The aim of this paper is to look at the relationship between research in Iranian medical universities, together with their Web Impact Factor (WIF). Design/methodology/approach - The Altavista search engine was chosen because of its advanced search facilities for counting links and having a wider scope of academic web sites than other search engines. It was searched for determining the number of pages, in-links and self-links of 42 web sites of Iranian medical universities. The Web Impact Factor (WIF) was calculated by two formulas and the relationship between the two grades of universities (WIF and ISI) was calculated by using the Spearman's correlation coefficient. Findings -... 

    Multi directional forging of 2024 Al alloy after different heat treatments: microstructural and mechanical behavior

    , Article Transactions of the Indian Institute of Metals ; Volume 70, Issue 7 , 2017 , Pages 1707-1719 ; 09722815 (ISSN) Asadi, S ; Kazeminezhad, M ; Sharif University of Technology
    2017
    Abstract
    Improvement of mechanical properties and microstructure of 2024 aluminum alloy by performing a severe plastic deformation method, called multidirectional forging (MDF), and heat treatment was the aim of this research. In this work, the effects of different heat treatments such as annealing, solid solution, peak ageing and over ageing before MDF on mechanical properties and microstructure of the alloy were studied. Microstructure evolution during severe plastic deformation was considerably affected by the precipitates and non-shearable particles. On the other hand, the severe plastic deformation had different effects on precipitates in the microstructure. Fragmentation, scattering and... 

    Marker-less versus marker-based driven musculoskeletal models of the spine during static load-handling activities

    , Article Journal of Biomechanics ; Volume 112 , 2020 Asadi, F ; Arjmand, N ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    Evaluation of workers’ body posture in workstations is a prerequisite to estimate spinal loads and assess risk of injury for the subsequent design of preventive interventions. The Microsoft Kinect™ sensor is, in this regard, advantageous over the traditional skin-marker-based optical motion capture systems for being marker-less, portable, cost-effective, and easy-to-use in real workplaces. While several studies have demonstrated the validity/reliability of the Kinect for posture measurements especially during gait trials, its capability to adequately drive a detailed spine musculoskeletal model for injury risk assessments remains to be investigated. Lumbosacral (L5-S1) load predictions of a... 

    Alteration of initial and residual healing potential of asphalt binders due to aging, rejuvenation, and polymer modification

    , Article Road Materials and Pavement Design ; 2020 Asadi, B ; Tabatabaee, N ; Sharif University of Technology
    Taylor and Francis Ltd  2020
    Abstract
    Asphalt binders are known to exhibit an inherent ability to repair damage. Such self-healing potentially affects the fatigue damage performance of bituminous materials. There are contradicting findings about the effects of aging and polymer modification on healing. The effectiveness of rejuvenating agents also has not been sufficiently addressed. In the present study, three healing indices have been defined to provide a more complete representation with which to quantify the healing potential of binders. These indices have been defined using damage characteristic curves derived from interrupted linear amplitude sweep tests. Initial healing (IH) describes the immediate reduction in the damage... 

    Investigation of the gamma-ray shielding performance of the B2O3-Bi2O3-ZnO-Li2O glasses based on the monte carlo approach

    , Article Radiation Physics and Chemistry ; Volume 189 , 2021 ; 0969806X (ISSN) Asadi, A ; Hosseini, A ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    The purpose of this article is to investigate the shielding performance of the B2O3-Bi2O3-ZnO-Li2O glasses against the gamma-ray. To this end, the attenuation parameters of the gamma-ray inside the B2O3-Bi2O3-ZnO-Li2O glasses were evaluated in the energy range of 200–1500 keV. It was found that the mass attenuation coefficient of the composites increases with increasing the Li2O content. The relative percent deviation between the results of simulation using the MCNPX and XCOM database in most cases was less than 2%. Additionally, the Mean Free Path (MFP) and Half-Value Layer (HVL) parameters were evaluated, and the shielding efficiency of samples was compared with some conventional shielding... 

    MDA-based methodologies: An analytical survey

    , Article 4th European Conference on Model Driven Architecture - Foundations and Applications, ECMDA-FA 2008, Berlin, 9 June 2008 through 13 June 2008 ; Volume 5095 LNCS , 2008 , Pages 419-431 ; 03029743 (ISSN); 3540690956 (ISBN); 9783540690955 (ISBN) Asadi, M ; Ramsin, R ; Sharif University of Technology
    Springer Verlag  2008
    Abstract
    Model-Driven Development (MDD) has become a familiar software engineering term in recent years, thanks to the profound influence of the Model Driven Architecture (MDA). Yet MDD, like MDA itself, defines a general framework, and as such is a generic approach rather than a concrete development methodology. Methodology support for MDA has been rather slow in coming, yet even though several MDA-based methodologies have emerged, they have not been objectively analyzed yet. The need remains for a critical appraisal of these methodologies, mainly aimed at identifying their achievements, and the shortcomings that should be addressed. We provide a review of several prominent MDA-based methodologies,... 

    Alteration of initial and residual healing potential of asphalt binders due to aging, rejuvenation, and polymer modification

    , Article Road Materials and Pavement Design ; Volume 23, Issue 2 , 2022 , Pages 287-307 ; 14680629 (ISSN) Asadi, B ; Tabatabaee, N ; Sharif University of Technology
    Taylor and Francis Ltd  2022
    Abstract
    Asphalt binders are known to exhibit an inherent ability to repair damage. Such self-healing potentially affects the fatigue damage performance of bituminous materials. There are contradicting findings about the effects of aging and polymer modification on healing. The effectiveness of rejuvenating agents also has not been sufficiently addressed. In the present study, three healing indices have been defined to provide a more complete representation with which to quantify the healing potential of binders. These indices have been defined using damage characteristic curves derived from interrupted linear amplitude sweep tests. Initial healing (IH) describes the immediate reduction in the damage... 

    Performance Enhancement of Enterprise Storage Systems Using a Markov-Based Prefetching Method

    , M.Sc. Thesis Sharif University of Technology Sereshki, Sina (Author) ; Asadi, Hossein (Supervisor)
    Abstract
    With increasing rate of digital information in the world, design, configuration, and networking of enterprise storage systems has become an essential part in designing data centers. The performance of data storage systems in serving incoming requests is one of the major parameters of such systems. A major metric to measure performance is response time. This parameter is, in particular, crucial in enterprise applications such as financial, credit, multimedia, and real-time applications. A common approach to enhance the performance of enterprise storage systems is improving the hit ratio of the system global memory using prefetching technique. Using prefetching technique, a data block is... 

    Management of Storage Resources, Power, and Performance in Enterprise Storage Systems Using Prefetching Method

    , M.Sc. Thesis Sharif University of Technology Ramezani, Kaveh (Author) ; Asadi, Hossein (Supervisor)
    Abstract
    Nowadays, enterprise storage systems are widely used in data centers such as databases, servers, and bank institutes. Due to mechanical activity of disk drives, these systems are one of the most power consumptive components in data centers. Prefetching and RAID, which are employed to enhance performance, are widely used in data storage systems. These two methods, however, impose significant energy overhead to the system due to the increased disk activity. In this thesis, we first elaborate shortcomings of prefetching and RAID methods. Then, we propose a new energy efficient and RAID-compatible prefetching method (LPTAP), which aims at improving performance and energy consumption. To evaluate... 

    Evaluation of Seismic Criteria and Random Parameters on Fragility Curves of RC Frames

    , Ph.D. Dissertation Sharif University of Technology Asadi, Payam (Author) ; Bakhshi, Ali (Supervisor)
    Abstract
    There are many parameters which are utilized to obtain a more reasonable performance for structures under earthquake excitations in seismic provisions. It is well recognized that the main character to design of structures under seismic excitation is probabilistic rather than deterministic; therefore, it should be determined if the probability of structural damages is decreased when such parameters change in design of structures. In this thesis, fragility curves are developed in order to evaluate these parameters. Fragility curves are employed for various probability parameters. These diagrams are utilized to demonstrate when a coefficient or a number of parameters are used to improve... 

    Evaluating Availability of Backend Logic in Enterprise Storage Systems

    , M.Sc. Thesis Sharif University of Technology Eftekhari, Reza (Author) ; Asadi, Hossein (Supervisor)
    Abstract
    Data storage systems are an essential part of any Information Technology (IT) infrastructure. Unavailability of these systems can directly lead to service disruption to customers and can be very costly in enterprise applications such as ebanking, online reservation systems, and mobile services. Modeling availability of disk subsystem is a major step in design of data storage systems. Previous modeling techniques have mainly focused on data unavailability or data loss due to double or multiple disk failures. In this thesis, we present both simulation and analytical modeling techniques to investigate the effect of serviceability on the overall availability of disk subsystems. The proposed... 

    A Reconfigurable Architecture Using Non-voltatile Memories

    , M.Sc. Thesis Sharif University of Technology Ahari, Ali (Author) ; Asadi, Hossein (Supervisor)
    Abstract
    In recent years, emerging Non-Volatile Memories (NVMs) have become promising alternatives for existing memory technologies. Due to shortcomings of SRAM memory in nanometer era,NVMs such as Phase-Change Memory (PCM) can be used in configuration memories of Field-Programmable Gate Arrays (FPGAs). Despite prominent features of emerging NVMs, they suffer from high write-power, high write-latency, and limited number of reliable write opera-tions. In addition, a dedicated Peripheral Circuit (PC) which is required to convert the NVM state to the equivalent voltage level can impose significant area and power overheads to FPGAs.In this thesis, a reliable power-efficient hybrid architecture employing...