Time filter

Source Type

Yazdi H.A.M.,Islamic Azad University at Maybod | Sulong N.H.R.,University of Malaya
Journal of Constructional Steel Research | Year: 2011

In this paper, a method based on genetic algorithm is proposed for determining the optimum connection point with the highest lateral buckling load in the Off-Centre bracing system. This type of bracing system is mostly used in seismic areas and it allows architects to have more openings in the panel area. In this system, the non-straight diagonal member introduces eccentricity to the system and is connected to the corner of the frame by a third member. In designing this system, designers often use "trial and error" to locate the connection point of the brace elements considering various parameters affecting the design such as opening and frame dimensions, cross sectional areas of brace elements and the location of the brace element connection. Hence, finding the best connection point with maximum lateral buckling load can be problematic by the conventional methods. To demonstrate the effectiveness of the proposed GA method, examples with different frame specifications were presented. © 2011 Elsevier Ltd. All rights reserved.

Mohseni Meybodi S.,Islamic Azad University at Maybod | Hosseini S.A.,Iranian Materials and Energy Research Center | Rezaee M.,Amirkabir University of Technology | Sadrnezhaad S.K.,Sharif University of Technology | Mohammadyani D.,Iranian Materials and Energy Research Center
Ultrasonics Sonochemistry | Year: 2012

A sonochemistry-based synthesis method was used to produce nanocrystalline nickel oxide powder with ∼20 nm average crystallite diameter from Ni(OH)2 precursor. Ultrasound waves were applied to the primary solution to intensify the Ni(OH)2 precipitation. Dried precipitates were calcined at 320 °C to form nanocrystalline NiO particles. The morphology of the produced powder was characterized by transmission electron microscopy. Using sonochemical waves resulted in lowering of the size of the nickel oxide crystallites. FT-IR spectroscopy and X-ray diffraction revealed high purity well-crystallized structure of the synthesized powder. Photoluminescence spectroscopy confirmed production of a wide band-gap structure. © 2011 Elsevier B.V. All rights reserved.

Ashrafzadeh A.,Islamic Azad University at Yazd | Sayadian S.,Islamic Azad University at Maybod
Computers in Human Behavior | Year: 2015

Abstract This study attempted to investigate the concerns and perceptions of Iranian EFL university instructors of technology integration in their classes. A sequential mixed method design was used in this study including Hall, George, & Rutherford's (1977) Stages of Concern Questionnaire (SoCQ) and Rogers' (1995) Diffusion of Innovation (DOI) questionnaire followed by a semi-structured interview. There were 91 university instructors asked to participate in the survey, out of whom nine were interviewed and finally, a focus group of five participants was conducted. The findings of the study revealed that the university instructors showed more Self concerns (Informational and Personal stages). "Relative advantage and compatibility" attributes of Diffusion of Innovation model were proved to be significantly different among instructors of different fields of study while the participants' gender revealed a significant difference in their "trialability" attribute. Moreover, based on the quantitative data of the study, lack of administrative facilities, instructors' technology literacy toward technology integration and accessibility of technology for all the students were reported to be the source of the instructors' concerns. © 2015 Elsevier Ltd. All rights reserved.

Mirjalili F.,Islamic Azad University at Maybod | Chuah L.,University Putra Malaysia | Mohamad H.,Universiti Sains Malaysia
Journal of Ceramic Processing Research | Year: 2011

The present paper tends to explore the effect of stirring time on the synthesis of nano α-Al 2O 3 particles. In this study, alumina nanoparticles were synthesized through an alkoxide route implementing sol-gel method in which aqueous solutions of aluminum isopropoxide and 0.5 M aluminum nitrate nanohydrate were used to prepare an alumina sol. Sodium dodecylbenzen sulfonate was used as the surfactant stabilizing agent. The prepared solution was stirred for different times (24, 36, 48 and 60 hours) at 60 °C. The samples were, then, characterized by Brunauer-Emmet-Teller method, X-ray diffraction, thermogravimetry analysis, differential scanning calorimetry, Fourier transform infrared spectrometry, scanning electron microscopy and transmission electron microscopy. The introduction of different stirring times affected the particle size and shape and the degree of aggregation. By increasing the stirring time (starting from 24 to 48 hours), the particle size decreased, but there was a harder agglomeration for the samples with 60 hours stirring time. The finest particle size (20-30 nm) was obtained at 48 hours stirring time.

Mirjalili F.,Islamic Azad University at Maybod
Journal of Composite Materials | Year: 2014

Polypropylene nanocomposites containing 1-5?wt% of nano α-alumina particles are prepared using a Hake internal mixer. Mixing of nano α-alumina particles is performed at 170°C and 50 rotational per minute is set for the rotor speed. To improve the dispersion of the nanoparticles, sodium dodecylbenzenesulfonate is used. X-ray analyses reveal that the basal spacing of polypropylene/nano α-Al2O3 composites compared to the pure polypropylene spreads out. The peak intensity for polypropylene / nano α-Al2O3 composites is stronger and narrower with larger amounts of the nano α-Al2O3 filler, in comparison with the virgin polypropylene. According to differential scanning calorimetry, the crystallinity of the nanocomposites is increased with increases in nano α-Al2O3 filler loading. The storage and loss modulus of the nanocomposites are found to be higher than that of pure polypropylene, because nanofiller increases the stiffness of the nanocomposites. The tensile strength and tensile modulus of the polypropylene nanocomposites are slightly improved up to 4% of nano α-Al2O3 particle filler adding. The addition of filler content higher than that amount leads to the reduction of these properties. The formation of filler agglomeration site within the matrix body affects the decreasing of properties. Transmission electron microscopy observations confirm these results. © 2013 The Author(s).

Discover hidden collaborations