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Effect of Al_2O_3 and Y_2O_3 on the corrosion behavior of ZrO_2-benzotriazole nanostructured coatings applied on AA2024 via a sol–gel method

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International Journal of Minerals,Metallurgy and Materials 2018年第11期25卷 1344-1353页

作者： saeid Mersagh Dezfuli Ali Shanaghi saeid Baghshahi Department of Materials Science and Engineering Tehran Science and Research BranchIslamic Azad University Materials Engineering Department Faculty of EngineeringMalayer University

zirconia-based nanostructured coatings were deposited on AA2024 to improve the corrosion resistance properties. Three different nanostructured coatings, namely, zirconia–benzotriazole, zirconia–alumina–benzotriazole, and zirconia–yttria–benzotriazole, were applied on AA2024 via a sol–gel method using the dip-coating technique. Next, the coatings were annealed at 150°C after each dipping period. The phases and morphologies of the coatings were investigated using grazing incidence X-ray diffraction(GIXRD), Fourier transform infrared spectroscopy(FT-IR), field emission scanning electron microscopy(FESEM), and atomic force microscopy(AFM). The corrosion properties were evaluated using electrochemical methods, including polarization and electrochemical impedance techniques in 3.5 wt% NaCl solution. The obtained results confirm the formation of homogeneous and crack free zirconia-benzotriazole-based nanostructured coatings. The average roughness values for zirconia-benzotriazole, zirconia-alumina-benzotriazole, and zirconia-yttria-benzotriazole nanostructured coatings were 30, 8, and 6 nm, respectively. The presence of alumina as a stabilizer on zirconia coating was found to have a beneficial impact on the stability of the corrosion resistance for different immersion times. In fact, the addition of alumina resulted in the dominance of the healing behavior in competition with the corrosion process of zirconia-benzotriazole nanostructured coating.

关键词： zirconia hybrid coatings alumina yttria AA2024 sol-gel corrosion behavior

Object-based classification of hyperspectral data using Random Forest algorithm

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Geo-Spatial Information Science 2018年第2期21卷 127-138页

作者： saeid Amini saeid Homayouni Abdolreza Safari Ali A.Darvishsefat School of Surveying and Geospatial Engineering College of EngineeringUniversity of TehranTehranIran Department of Geography Environment and GeomaticsUniversity of OttawaOttawaCanada Faculty of Natural Resources Department of ForestryUniversity of TehranKarajIran

This paper presents a new framework for object-based classification of high-resolution hyperspectral *** multi-step framework is based on multi-resolution segmentation(MRS)and Random Forest classifier(RFC)*** first step is to determine of weights of the input features while using the object-based approach with MRS to processing such *** the high number of input features,an automatic method is needed for estimation of this ***,we used the Variable Importance(VI),one of the outputs of the RFC,to determine the importance of each image ***,based on this parameter and other required parameters,the image is segmented into some homogenous ***,the RFC is carried out based on the characteristics of segments for converting them into meaningful *** proposed method,as well as,the conventional pixel-based RFC and Support Vector Machine(SVM)method was applied to three different hyperspectral data-sets with various spectral and spatial *** data were acquired by the HyMap,the Airborne Prism Experiment(APEX),and the Compact Airborne Spectrographic Imager(CASI)hyperspectral *** experimental results show that the proposed method is more consistent for land cover mapping in various *** overall classification accuracy(OA),obtained by the proposed method was 95.48,86.57,and 84.29%for the HyMap,the APEX,and the CASI datasets,***,this method showed better efficiency in comparison to the spectralbased classifications because the OAs of the proposed method was 5.67 and 3.75%higher than the conventional RFC and SVM classifiers,respectively.

关键词： Object-based classification Random Forest algorithm multi-resolution segmentation(MRS) hyperspectral imagery

Effects of Welding and rotational speeds on the Microstructure and Hardness of Friction Stir Welded Single-Phase Brass

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Acta Metallurgica Sinica(English Letters) 2015年第6期28卷 766-771页

作者： Sajjad Emami Tohid saeid Materials Engineering Faculty Sahand University of Technology

This study focuses on the effects of rotational and welding speeds on the microstructure and hardness of joints in friction stir welded single-phase brass. Welds were achieved under low heat input conditions at rotational and welding speeds of 400-800 r/min and 100-300 mm/min, respectively. In order to characterize the obtained welds, optical microscopy and Vickers hardness measurements were taken on the weld cross sections. According to the obtained results, increasing the welding speed and/or decreasing the rotational speed caused the grain size of the stir zone to decrease and, hence, improved the average hardness of this region. These results are discussed with respect to the interplay between the welding parameters and the peak temperature in the weld thermal cycle.

关键词： Friction stir welding Single-phase brass Dynamic recrystailization Hardness

Correlation between process parameters,grain size and hardness of friction-stir-welded Cu-Zn alloys

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Rare Metals 2018年第5期37卷 388-398页

作者： Akbar Heidarzadeh Tohid saeid Faculty of Materials Engineering Sahand University of Technology

In this study, the effects of tool rotational speed, tool traverse speed, and Zn content on the grain size and hardness of the friction-stir-welded （FSWed） Cu-Zn alloy joints were investigated. The microstructures of the joints were examined using optical microscope （OM） and scanning transmission electron microscope （STEM）. Vickers hardness test was conducted to evaluate the hardness of the joints. In addition, the relationships between the process parameters, grain size, and hardness of the joints were established. The results show that the developed relationships predict the grain size and hardness of the joints accurately. The Zn content of the alloys is the most effective parameter on the grain size and hardness, where the tool traverse speed has the minimum effect. The relationship between the hardness and grain size of the joints has a deviation from the Hall-Petch equation due to formation of high dislocation density inside the grains. At higher Zn amounts, the dislocation tangles with high density form instead of dislocation cells, and hence, lower conformity with the Hall-Petch relationship is observed.

关键词： Friction stir welding Grain size Hardness Cu-Zn alloy

Conceptual study of X-braced frames with different steel grades using cyclic half-scale tests

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Earthquake Engineering and Engineering Vibration 2012年第3期11卷 313-329页

作者： Parviz Ebadi saeid Sabouri-Ghomi Structural Engineering Khaje Nasir Toosi University of Technology

In this paper, an experimental and analytical study of two half-scale steel X-braced flames with equal nominal shear strength under cyclic loading is described. In these tests, all members except the braces are similar. The braces are made of various steel grades to monitor the effects of seismic excitation. Internal stiffeners are employed to limit the local buckling and increase the fracture life of the steel bracing. A heavy central core is introduced at the intersection of the braces to decrease their effective length. Recent seismic specifications are considered in the design of the X-braced frame members to verify their efficiency. The failure modes of the X-braced frames are also illustrated. It is observed that the energy dissipation capacity, ultimate load capacity and ductility of the system increase considerably by using lower grade steel and proposed detailing. Analytical modeling of the specimens using nonlinear finite element software supports the experimental findings.

关键词： bracing low grade steel experimentation cyclic test seismic behavior analytical modeling ductility

Exploring the applications of 3D proximity analysis in a 3D digital cadastre

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Geo-Spatial Information Science 2021年第2期24卷 201-214,I0002页

作者： saeid Emamgholian Mohammad Taleai Davood Shojaei Faculty of Geodesy and Geomatics Engineering K.N.Toosi University of TechnologyTehranIran Geomatics Department Laval UniversityQuebecCanada Center for SDIs and Land Administration Department of Infrastructure EngineeringThe University of MelbourneMelbourneAustralia

Increasing population in urban areas and limitations of suitable lands for developing houses and urban infrastructure have led to the vertical development in ***,these developments are managed by a cadastral system which is mainly two-dimensional and cannot efficiently represent Rights,Restrictions,and Responsibilities(RRRs)in complex *** fact,a three-dimensional cadastre is required for efficiently registering and representing *** this paper,a 3D proximity analysis was proposed and implemented to determine RRRs and associated easement rights in non-topology-based data *** method can be used to investigate the surrounding spaces of a subject apartment unit or storage in a *** performance of the developed method was evaluated in a large complex high-rise in Tehran,*** results confirmed that the proposed method can correctly identify the neighbor spaces in complex scenarios.

关键词： 3D visualization 3D cadastre easements proximity analysis GIS

Steel rings as seismic fuses for enhancing ductility of cross braced frames

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Earthquake Engineering and Engineering Vibration 2022年第4期21卷 1103-1117页

作者： Farhad Behnamfar saeid Arman Hassan Zibasokhan Department of Civil Engineering Isfahan University of TechnologyIsfahan ***Iran Department of Civil Engineering Kermanshah University of TechnologyKermanshah ***Iran

A new remedy is proposed in this study to increase the ductility of cross-braced frames to a level comparable with ductile moment *** suggested system consists of one or two concentric steel rings installed in the cross-braced bay *** steel rings are designed such that they fail in bending sooner than failure of the braces in *** the rings act as seismic fuses with multiple bending plastic *** nonlinear static analysis,it is shown that the proposed system can be designed to behave like cross-braced frames with regard to stiffness and strength,and like special moment frames with regard to *** design factors for the proposed system are recommended based on nonlinear pushover and cyclic analysis studies.

关键词： cross brace special moment frame steel ring seismic fuse ductility

Influence of welding speed on microstructure formation in friction-stir-welded 304 austenitic stainless steels

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International Journal of Minerals,Metallurgy and Materials 2020年第11期27卷 1517-1524页

作者： Mohsen Hajizadeh Sajjad Emami Tohid saeid Faculty of Mechanical Engineering Sahand University of TechnologyTabrizIran Faculty of Materials Engineering Sahand University of TechnologyTabrizIran

The influence of welding speed on the joint microstructures of an austenitic stainless steel(ASS)produced by friction stir welding(FSW)was *** FSW process was conducted using a rotational speed of 400 r/min and welding speeds of 50 and 150 mm/*** study was carried out using electron backscattered diffraction(EBSD)technique in different regions of the resultant stir zones(SZs).The results show that the texture of the advancing side(AS)was mainly composed of C{001}〈110〉and cube{001}〈100〉texture components along with partial B/B{112}〈110〉*** from the AS toward the center and the retreating side(RS),the cube texture component disappeared and the A;/A*{111}(112)component developed and predominated the other *** welding speed greatly affected and decreased the intensity of the textures in the resultant ***,higher welding speed(lower heat input)resulted in lower frequency of cube texture in the AS.

关键词： friction stir welding stainless steels welding speed dynamic recovery shear texture continuous dynamic recrystallization

A Length Function for Weyl Groups of Extended Aitine Root Systems of Type A1

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Algebra Colloquium 2015年第4期22卷 621-638页

作者： saeid Azam Mohammad Nikouei School of Mathematics Institute for Research in Fundamental Sciences (IPM) P.O. Box 19395-5746 Tehran Irtm Department of Mathematics University of Isfahan P.O. Box 81745-163 Isfahan Iran

. In this work, we study the concept of the length function and some of its combinatorial properties for the class of extended affine root systems of type A1. We introduce a notion of root basis for these root systems, and using a unique expression of the elements of the Weyl group with respect to a set of generators for the Weyl group, we calculate the length function with respect to a very specific root basis.

关键词： afline reflection system extended affine root system length function Weylgroup extended afflne Weyl group