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- 저자 : Nikzad, Akbar (검색결과 6 건)
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Lida Nikzad,Alireza Ehtesami-Sarabi 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.1
X-ray generation by interactions of quasi-monoenergetic electrons with solid lead targets is studied. Various electron energy spectra generated by a laser-plasma accelerator are employed to generateBremsstrahlung and characteristic X-rays. These X-ray photons are simulated by using theMonte Carlo N-Particle Transport Code (MCNP). The present work is mainly focused on exploringthe influence of two parameters of the electron profile, the peak energy (Ep) and the pulse width(E), on X-ray generation. If an electron source with higher Ep and smaller E is used, the efficiencyof X-ray creation is found to be increased in thick targets. However, in thin samples, theelectron profile with lower Ep and larger E dominates.
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High-energy ball milling of B-C-Ti mixtures for the fabrication of B4C and TiB2 nanocomposite powder
L. Nikzad 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.5
The present work reports the effect of high-energy ball milling on B-Ti-C mixtures. The milling process was carried out for up to 70 h and then the milled powders were heat treated between 800 ο and 1200 ο C for 1 h. The milled and heat treated powders were characterized by means of X-ray diffraction (XRD) and a scanning electron microscope (SEM). TiB2 was characterized as the only crystalline phase after milling for 6 h. B4C was formed after heat treatment of the milled powders above 1000 ο C. The crystallite sizes of TiB2 varied from 57.2 nm up to 7.5 nm after milling of powders from 6 to 70 h, respectively.
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Akbar Nikzad,Alireza Kiani,Seyed Alireza Kazerounian 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.88 No.5
The buckling-restrained braced frames with eccentric configurations (BRBF-Es) exhibit stable cyclic behavior and possess a high energy absorption capacity. Additionally, they offer architectural advantages for incorporating openings, much like Eccentrically Braced Frames (EBFs). However, studies have indicated that significant residual drifts occur in this system when subjected to earthquakes at the Maximum Considered Earthquake (MCE) hazard level. Consequently, in order to mitigate these residual drifts, it is recommended to employ self-centering systems alongside the BRBF-E system. In our current research, we propose the utilization of the Direct Displacement-Based Seismic Design method to determine the design base shear for a hybrid system that combines BRBF with an eccentric configuration and a self-centering frame. Furthermore, we present a methodology for designing the individual components of this composite system. To assess the effectiveness of this design approach, we designed 3-, 6-, and 9-story buildings equipped with the BRBF-E-SCF system and developed finite element models. These models were subjected to two sets of ground motions representing the Maximum Considered Earthquake (MCE) and Design Basis Earthquake (DBE) seismic hazard levels. The results of our study reveal that although the combined system requires a higher amount of steel material compared to the BRBF-E system, it substantially reduces residual drift. Furthermore, the combined system demonstrates satisfactory performance in terms of story drift and ductility demand.
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Mohammad Ali Atlasi,Alireza Moravveji,Hossein Nikzad,Vahid Mehrabadi,Homayoun Naderian 대한해부학회 2017 Anatomy & Cell Biology Vol.50 No.4
The learning approaches can help anatomy teachers design a suitable curriculum in harmony with their students’ learning styles. The research objective is to evaluate gross anatomy learning styles and strategies preferences of Iranian medical students at Kashan University of Medical Sciences (KAUMS). This cross-sectional questionnaire-based study was carried out on 237 Iranian medical students. The students answered questions on approaches to learning anatomy and expressed opinions about learning anatomy in medical curriculum. The data were analyzed to disclose statistically significant differences between male and female students. Iranian male and female students were interested in learning anatomy using notes, plastic models, pictures and diagrams, clinical context, dissection and prosection of cadavers; however, they rarely used cross-sectional images and web-based resources. Both groups of medical students used region and system in learning anatomy. However, there existed some striking differences, particularly in having difficulty in studying anatomy using cadaveric specimens, using books alone, and learning it in small groups. Male students were less interested in learning with cadavers than female counterparts. However, female students were more interested in learning anatomy in small groups. This study suggests that instructors should design gross anatomy curriculum based on limitations of using dissection of cadaver in Iranian universities, emphasis on the applied anatomy, and learning of gross anatomy in small groups.
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Eringen's nonlocal theory for non-linear bending analysis of BGF Timoshenko nanobeams
Azandariani, Mojtaba Gorji,Gholami, Mohammad,Nikzad, Akbar Techno-Press 2022 Advances in nano research Vol.12 No.1
In this paper, the non-linear static analysis of Timoshenko nanobeams consisting of bi-directional functionally graded material (BFGM) with immovable ends is investigated. The scratching in the FG nanobeam mid-plane, is the source of nonlinearity of the bending problems. The nonlocal theory is used to investigate the non-linear static deflection of nanobeam. In order to simplify the formulation, the problem formulas is derived according to the physical middle surface. The Hamilton principle is employed to determine governing partial differential equations as well as boundary conditions. Moreover, the differential quadrature method (DQM) and direct iterative method are applied to solve governing equations. Present results for non-linear static deflection were compared with previously published results in order to validate the present formulation. The impacts of the nonlocal factors, beam length and material property gradient on the non-linear static deflection of BFG nanobeams are investigated. It is observed that these parameters are vital in the value of the non-linear static deflection of the BFG nanobeam.
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Hamed Roghani,Seyed Ali Tayebifard,Asghar Kazemzadeh,Leila Nikzad 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.3
In this study, in situ synthesis of B4C-SiC nanocomposite powder (1 : 1 molar ratio) was performed by mechanically activatedvolume combustion synthesis (MAVCS) method. Raw materials were included Si, C, B2O3 and Mg. Milling process was usedto mechanically activate the raw materials. Synthesis of prepared samples was occurred in a tube furnace under argonatmosphere at 1000 oC. The milling parameters were examined to optimize the activating of the raw materials process. Synthesized samples after mechanical activation with milling parameters of 300 rpm rotation speed, 20 to 1 ball to powderratio and milling time of 9 and 12 h had best phase and morphology conditions. Average crystallite size of B4C and SiCcompounds were calculated less than 15 nm for these two samples. Transmission electron microscopy (TEM) analysis of thesetwo samples approved their formation from the grains in nanometers scale. The TEM analysis showed the sample with 12 hof milling the raw materials has formed from more uniform grains than the sample with 9 h of milling the raw materials. Particle size analysis showed more than 99% of the particles from both samples have a size less than 1000 nm.
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