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    Semisolid joining of aluminum A356 alloy by partial remelting and mechanical stirring

    , Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 20, Issue 9 , September , 2010 , Pages 1792-1798 ; 10036326 (ISSN) Alvani, S. M. J ; Aashuri, H ; Kokabi, A ; Beygi, R ; Sharif University of Technology
    2010
    Abstract
    A method to reach the globular weld structure of A356 aluminum alloy using stirring the localized semisolid zone during butt-joining is developed. Since the heat conductivity of this alloy is very high, the accurate controlling of temperature during joining must be considered. A gas heating system was used to heat up the nitrogen gas up to the required temperature. A dried and free oxygen gas was prepared when a stream of nitrogen gas could pass closely around a hot element. Hot and pure nitrogen gas flow through a precise ceramic nozzle was used to create a localized semisolid pool. At this stage a fine stirrer was introduced into the weld seam in order to mix the two sides into a single... 

    Incremental Learning Approach in Spam Detection

    , M.Sc. Thesis Sharif University of Technology Ghanbari, Elham (Author) ; Beygi, Hamid (Supervisor)
    Abstract
    Studies show that a large proportion of sent emails are spam. Spam is one of the major problems of e-mail users that result in wasting time and cost. To overcome this problem different ways are used, one of the best ways is detecting spam based on their contents. Separating legitimate e-mails and spam within their contents can be categorized as text classification. So machine-learning approaches are extremely applied in text classification, that machine-learning algorithms can be used for spam classification. However, in the majority of these algorithms, training phase is in a batch. Whereas using incremental learning algorithms is preferred in many applications, especially spam detections.... 

    Tearing energy of an annealed bilayer sheet through multiple and single tensile tests

    , Article Materials Science and Engineering A ; Volume 528, Issue 29-30 , November , 2011 , Pages 8800-8803 ; 09215093 (ISSN) Beygi, R ; Kazeminezhad, M ; Sharif University of Technology
    2011
    Abstract
    Tearing energies of annealed Al-steel bilayer sheets are investigated through multiple and single tensile tests. Total tearing energy of two layers determined separately by single tensile test is equal to tearing energy of bilayer sheet. It means that the bond between two layers has no effect on tearing energy  

    Energy absorption mechanism of Alsteel bilayer sheets produced by cold roll welding during wedge tearing

    , Article International Journal of Mechanical Sciences ; Volume 52, Issue 12 , December , 2010 , Pages 1613-1619 ; 00207403 (ISSN) Beygi, R ; Kazeminezhad, M ; Sharif University of Technology
    2010
    Abstract
    The behavior of Alsteel bilayer sheets produced by cold roll welding is investigated through the wedge tearing process. It is observed that through tearing the energy absorbed by cold roll welded bilayer sheets is larger than that of non-welded ones, even though all parameters are identical. Also bilayer sheets with low bond strength have the same energy absorbed by non-welded bilayer sheets. By investigating all contributing mechanisms in tearing and mechanical properties of composite layers and developing theoretical equations, it is concluded that bending of sheets through wedge tearing plays a major role in difference of energy absorbed by welded and non-welded bilayer sheets. Moreover,... 

    The effects of annealing phenomena on the energy absorption of roll-bonded Al-steel sheets during wedge tearing

    , Article Materials Science and Engineering A ; Volume 527, Issue 27-28 , 2010 , Pages 7329-7333 ; 09215093 (ISSN) Beygi, R ; Kazeminezhad, M ; Sharif University of Technology
    2010
    Abstract
    The purpose of this paper is to investigate the effects of annealing phenomena on the energy absorption of Al-steel bilayer sheets, bonded by cold rolling, through wedge tearing. Tearing by wedge is a dissipating energy system that includes three components: cutting, friction and plastic deformation due to bending. In order to find the bonding and annealing effects on energy absorption, the non-bonded bilayer sheets are prepared in the same condition of bonded ones. The results show that energy absorption of bonded sheets is larger than that of non-bonded ones. This is due to different plastic bending moment of bonded and non-bonded bilayer sheets. Whenever the bond is improved by heat... 

    DM Water Plant Sedimentation as a Cheap and Waste Source of Catalyst for Biodiesel Production

    , Article International Journal of Chemical Reactor Engineering ; Volume 14, Issue 1 , 2016 , Pages 113-124 ; 15426580 (ISSN) Moradi, G ; Mohadesi, M ; Hosseini, S ; Davood Beygi, Y ; Moradi, R ; Sharif University of Technology
    Walter de Gruyter GmbH  2016
    Abstract
    Transesterification reaction was performed in the presence of soybean oil, methanol, and Demineralized water plant sedimentation catalyst at 60°C for 8 h in this study. Central composite design method was used to study the effect of catalyst concentration and methanol to oil molar ratio on purity and yield of produced biodiesel. The results showed catalyst concentration of 9.08 wt% and methanol to oil molar ratio of 22.49 as the optimum condition in which the values of purity and yield of the produced biodiesel in the second-order models were 99.89% and 81.83%, respectively. Experiments are in good agreement with the mentioned values as corresponded values are 99.95% and 86.68%,... 

    Microstructural evolution and fracture behavior of friction-stir-welded Al-Cu laminated composites

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Vol. 45, issue. 1 , 2014 , pp. 361-370 Beygi, R ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
    2014
    Abstract
    In this study, we attempt to characterize the microstructural evolution during friction stir butt welding of Al-Cu-laminated composites and its effect on the fracture behavior of the joint. Emphasis is on the material flow and particle distribution in the stir zone. For this purpose, optical microscopy and scanning electron microscopy (SEM) images, energy-dispersive spectroscopy EDS and XRD analyses, hardness measurements, and tensile tests are carried out on the joints. It is shown that intermetallic compounds exist in lamellas of banding structure formed in the advancing side of the welds. In samples welded from the Cu side, the banding structure in the advancing side and the hook... 

    Butt joining of Al-Cu bilayer sheet through friction stir welding

    , Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 22, Issue 12 , 2012 , Pages 2925-2929 ; 10036326 (ISSN) Beygi, R ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
    2012
    Abstract
    Butt joining of Al-Cu bilayer sheet produced by cold roll bonding was studied through friction stir welding (FSW). A defect free joint was obtained. Flow patterns and mixing of two layers during FSW were investigated. Microstructural investigations and hardness profile measurements were carried out. It is shown that material flow in stir zone leads to the formation of banding structure in Cu layer at advancing side. Traces of Al particles along with Al-Cu intermetallic compounds exist in the fined grain region of this banding structure which leads to higher hardness values  

    Impulsive noise removal from images using sparse representation and optimization methods

    , Article 10th International Conference on Information Sciences, Signal Processing and their Applications, ISSPA 2010, 10 May 2010 through 13 May 2010 ; May , 2010 , Pages 480-483 ; 9781424471676 (ISBN) Beygi Harchegani, S ; Kafashan, M ; Marvasti, F ; Sharif University of Technology
    2010
    Abstract
    In this paper, we propose a new method for impulsive noise removal from images. It uses the sparsity of natural images when they are expanded by mean of a good learned dictionary. The zeros in sparse domain give us an idea to reconstruct the pixels that are corrupted by random-value impulse noises. This idea comes from this reality that noisy image in sparse domain of original image will not have a sparse representation as much as original image sparsity. In this method we assume that the proper dictionary to achieve image in sparse domain is available  

    Driving Behavior Estimation with Smartphone Data

    , M.Sc. Thesis Sharif University of Technology Mohammad Beygi, Mohammad Sadegh (Author) ; Samimi, Amir (Supervisor)
    Abstract
    Identifying driving behaviors and building an efficient and accurate driving behavior recognition model is of paramount importance for improving driving safety. Nowadays, with the ubiquity of smartphone sensors, many researchers are using smartphone sensory data to create models which forecast driving behaviors. This research introduces a logit model that predicts nine types of driving events using accelerometer and gyroscope sensors with an accuracy of 76 percent  

    Effect of Friction Stir Welding on the Micro-Structure and Mechanical Properties of Al-Cu Bilayer Sheets Produced by Roll Welding

    , Ph.D. Dissertation Sharif University of Technology Beygi, Reza (Author) ; Kokabi, Amir Hossein (Supervisor) ; Kazeminezhad, Mohsen (Supervisor)
    Abstract
    Nowadays, bilayer sheets are increasingly used in various industries due to high mechanical properties, high corrosion resistance and low weight. Hence, it seems important to investigate welding of these materials. The main object of this study is to investigate mechanical properties and microstructure of friction stir butt welded Al-Cu bilayer sheets. For this purpose, tensile tests, microhardness measurements, metallographic images, SEM, EDS and XRD analyses have been carried out from the joints. The results show that contact condition between the shoulder and bilayer material (slipping or sticking), plays an important role in material flow during welding and weld quality. Also the... 

    Fracture properties of steel fiber reinforced high strength concrete using work of fracture and size effect methods

    , Article Construction and Building Materials ; Volume 142 , 2017 , Pages 482-489 ; 09500618 (ISSN) Kazemi, M. T ; Golsorkhtabar, H ; Beygi, M. H. A ; Gholamitabar, M ; Sharif University of Technology
    Elsevier Ltd  2017
    Abstract
    This paper deals with investigation of fracture behavior of steel fiber reinforced high strength concrete (SFRHSC) and compare it to plain high strength concrete (HSC). Based on an experimental program, a series of three point bending tests were carried out on 54 notched beams, as recommended by RILEM. The fracture parameters were measured by two methods: work of fracture method (WFM) and size effect method (SEM). Then the fracture parameters obtained from these two methods were compared. The results showed that with increase of steel fibers, fracture energy of GF in WFM and Gf in SEM increase but this increase in work of fracture method is more significant. The effective size of the process... 

    Experimental and analytical model analysis of Babolsar's steel arch bridge

    , Article 3rd International Conference on Bridge Maintenance, Safety and Management - Bridge Maintenance, Safety, Management, Life-Cycle Performance and Cost, Porto, 16 July 2006 through 19 July 2006 ; 2006 , Pages 235-237 ; 0415403154 (ISBN); 9780415403153 (ISBN) Beygi, M. H. A ; Kazemi, M. T ; Lark, B ; Tabrizian, Z ; Sharif University of Technology
    Taylor and Francis/ Balkema  2006
    Abstract
    The paper presents the experimental and analytical model analysis of a steel-girder arch bridge. The field test is carried out by ambient vibration testing under traffic excitations. Both the peak picking method in the frequency domain and the stochastic subspace identification method in the time domain are used for the output-only model identification. A good agreement in identified frequencies has been found between the two methods. It is further demonstrated that the stochastic subspace method provides better mode shapes. The three-dimensional finite element models are constructed and an analytical model analysis is then performed to generate natural frequencies and mode shapes in the... 

    Friction stir butt welding of Al-Cu bilayer laminated composites: analysis of force, torque, and temperature

    , Article International Journal of Advanced Manufacturing Technology ; Volume 88, Issue 1-4 , 2017 , Pages 393-400 ; 02683768 (ISSN) Beygi, R ; Kazeminezhad, M ; Zarezadeh Mehrizi, M ; Eisaabadi, B. G ; Loureiro, A ; Sharif University of Technology
    2017
    Abstract
    The effect of the layer in contact with tool (Al or Cu) and the depth of plunge on friction stir butt welding of Al-Cu bilayer laminated composites produced by cold roll welding were studied. The measurement of weld cross sections and variations of the axial load and torque during welding process showed that material flow is influenced by the material which is in contact with the shoulder. Being Al layer in contact with the shoulder led to higher force and torque during welding, and a defect-free weld could be obtained in this manner. By welding from Cu side, a higher plunge depth was needed to develop enough force and torque and thereby a defect-free weld. The amount of material swept by... 

    The effect of aging on the fracture characteristics and ductility of self-compacting concrete

    , Article Materials and Design ; Volume 55 , March 2014 , Pages 937-948 Beygi, M. H. A ; Kazemi, M. T ; Nikbin, I. M ; Vaseghi Amiri, J ; Sharif University of Technology
    March 2014
    Abstract
    Good knowledge of fracture parameters and cracking behavior of self-compacting concrete (SCC) from early ages until the SCC becomes mature plays an important role in design of SCC structure and also in evaluation of durability and consequently prevention of damage. In this paper, variation of fracture parameters and corresponding ductility behavior of SCC at different ages (e.g. 3days, 7days, 28days and 90days) for SCC mixes with w/c ratios of 0.45 and 0.65 have been experimentally studied. To do so, three-point bending tests were carried out on 120 notched beams. Then, size effect method (SEM) and work of fracture method (WFM) were applied to interpret the results. The results of analyses... 

    The effect of water to cement ratio on fracture parameters and brittleness of self-compacting concrete

    , Article Materials and Design ; Volume 50 , 2013 , Pages 267-276 ; 02613069 (ISSN) Beygi, M. H. A ; Kazemi, M. T ; Nikbin, I. M ; Amiri, J. V ; Sharif University of Technology
    Elsevier Ltd  2013
    Abstract
    The paper describes an experimental research on fracture characteristics of self-compacting concrete (SCC). Three point bending tests conducted on 154 notched beams with different water to cement (w/c) ratios. The specimens were made from mixes with various w/c ratios from 0.7 to 0.35. For all mixes, common fracture parameters were determined using two different methods, the work-of-fracture method (WFM) and the size effect method (SEM). Test results showed that with decrease of w/c ratio from 0.7 to 0.35 in SCC: (a) the fracture toughness increases linearly: (b) the brittleness number is approximately doubled: (c) the effective size of the process zone cf in SEM and the characteristic... 

    Influence of tool geometry and contact condition on friction stir welding of Al-Cu laminated composites

    , Article Advanced Materials Research ; Vol. 856 , 2014 , pp. 16-21 ; ISSN: 10226680 Beygi, R ; Kazeminezhad, M ; Kokabi, A. H ; Alvani, S. M. J ; Verdera, D ; Loureiro, A ; Sharif University of Technology
    2014
    Abstract
    In this study friction stir welding of Al-Cu laminated composites were carried out by two different tool geometries. Welding procedure was carried out from both sides of Al and Cu. Analyzing cross section of welds showed that different contact conditions between shoulder and material, offers different material flow behavior which is dependent on the tool geometry. SEM analyses showed that mixing of materials in nugget region is more pronounced in the advancing side. Also XRD results indicated that welding from Cu side, leads to intermetallic formation in mixed regions  

    Evaluation of the effect of maximum aggregate size on fracture behavior of self compacting concrete

    , Article Construction and Building Materials ; Vol. 55 , 2014 , pp. 202-211 ; ISSN: 09500618 Beygi, M. H. A ; Kazemi, M. T ; Vaseghi Amiri, J ; Nikbin, I. M ; Rabbanifar, S ; Rahmani, E ; Sharif University of Technology
    2014
    Abstract
    This paper presents and discusses the effect of maximum size of coarse aggregate on fracture characteristics and brittleness of self-compacting concrete (SCC). Based on an experimental program, a series of three point bending tests were carried out on 86 notched beams, as recommended by RILEM. For all mixes, the parameters were analyzed by the work-of-fracture method (WFM) and by the size effect method (SEM) and consequently a correlation between these methods was obtained which is used to calibrate cracking numerical models. Test results showed that with increase of size of coarse aggregate, (a): fracture energies of GF in WFM and Gf in SEM increase which may be explained by the change in... 

    Influence of Fe3O4 nanoparticles in hydroxyapatite scaffolds on proliferation of primary human fibroblast cells

    , Article Journal of Materials Engineering and Performance ; 2016 , Pages 1-9 ; 10599495 (ISSN) Maleki Ghaleh, H ; Aghaie, E ; Nadernezhad, A ; Zargarzadeh, M ; Khakzad, A ; Shakeri, M. S ; Beygi Khosrowshahi, Y ; Siadati, M. H ; Sharif University of Technology
    Springer New York LLC  2016
    Abstract
    Modern techniques for expanding stem cells play a substantial role in tissue engineering: the raw material that facilitates regeneration of damaged tissues and treats diseases. The environmental conditions and bioprocessing methods are the primary determinants of the rate of cultured stem cell proliferation. Bioceramic scaffolds made of calcium phosphate are effective substrates for optimal cell proliferation. The present study investigates the effects of two bioceramic scaffolds on proliferating cells in culture media. One scaffold was made of hydroxyapatite and the other was a mixture of hydroxyapatite and ferromagnetic material (Fe3O4 nanoparticles). Disk-shaped (10 mm × 2 mm) samples of... 

    Network vulnerability analysis through vulnerability take-grant model (VTG)

    , Article 7th International Conference on Information and Communications Security, ICICS 2005, Beijing, 10 December 2005 through 13 December 2005 ; Volume 3783 LNCS , 2005 , Pages 256-268 ; 03029743 (ISSN); 3540309349 (ISBN); 9783540309345 (ISBN) Shahriari, H. R ; Sadoddin, R ; Jalili, R ; Zakeri, R ; Omidian, A. R ; Sharif University of Technology
    2005
    Abstract
    Modeling and analysis of information system vulnerabilities helps us to predict possible attacks to networks using the network configuration and vulnerabilities information. As a fact, exploiting most of vulnerabilities result in access rights alteration. In this paper, we propose a new vulnerability analysis method based on the Take-Grant protection model. We extend the initial Take-Grant model to address the notion of vulnerabilities and introduce the vulnerabilities rewriting rules to specify how the protection state of the system can be changed by exploiting vulnerabilities. Our analysis is based on a bounded polynomial algorithm, which generates the closure of the Take-Grant graph...