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reflection
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Reflective journal writing: Exploring in-service EFL teachers' perceptions
, Article System ; Volume 41, Issue 3 , September , 2013 , Pages 503-514 ; 0346251X (ISSN) ; Hovassapian, A ; Teimournezhad, S ; Ghanbari, N ; Sharif University of Technology
2013
Abstract
Numerous studies have been conducted on the effectiveness of reflective journal writing in (second language) teacher education. However, only a few studies have explored pre-service and in-service teachers' own perceptions in this regard, especially in the context of ELT (English Language Teaching). To address this gap, a focus group discussion was conducted among six in-service teachers on the advantages and challenges of the journal writing task in a BA Second Language Teaching Methodology course they had attended. Thematic analysis of the discussion showed that the participants believed writing journals had contributed to their self-awareness, understanding of issues related to ELT,...
Products of rotations by a given angle in the orthogonal group
, Article Bulletin of the Australian Mathematical Society ; 2017 , Pages 1-5 ; 00049727 (ISSN) ; Sharif University of Technology
Abstract
For every rotation (Formula presented.) of the Euclidean space (Formula presented.) ((Formula presented.)), we find an upper bound for the number (Formula presented.) such that (Formula presented.) is a product of (Formula presented.) rotations by an angle (Formula presented.) ((Formula presented.)). We also find an upper bound for the number (Formula presented.) such that (Formula presented.) can be written as a product of (Formula presented.) full rotations by an angle (Formula presented.). © 2017 Australian Mathematical Publishing Association Inc
products of rotations by a given angle in the orthogonal group
, Article Bulletin of the Australian Mathematical Society ; Volume 97, Issue 2 , 2018 , Pages 308-312 ; 00049727 (ISSN) ; Sharif University of technology
Cambridge University Press
2018
Abstract
For every rotation of the Euclidean space ℝ(n≥3), we find an upper bound for the number such that is a product of rotations by an angle α( 0<≤π). We also find an upper bound for the number such that ρ can be written as a product of full rotations by an angle α. © 2017 Australian Mathematical Publishing Association Inc
Expanding Visibility Polygons by Mirrors
, M.Sc. Thesis Sharif University of Technology ; Ghodsi, Mohammad (Supervisor)
Abstract
We consider extending the visibility polygon of a given point q inside a simple polygon by converting one or some of the edges to mirrors. It is known that the visibility polygon of a point inside a polygon in the presence of a mirror can be computed in linear time. We propose a linear time algorithm that checks whether a given segment inside a simple polygon is visible by a given point q via a mirror-edge, and finds all such edges. And we prove that finding edges to add exactly k unit squares to the visibility polygon of a query point q in most cases is NP-complete and its minimization is NP-hard. These cases contain single and muliple, either with secular or difuse reflections. Moreover,...
Beam manipulation by hybrid plasmonic-dielectric metasurfaces
, Article Plasmonics ; 2019 ; 15571955 (ISSN) ; Hemmatyar, O ; Kavehvash, Z ; Sharif University of Technology
Springer
2019
Abstract
A hybrid plasmonic-dielectric metasurface is proposed in order to manipulate beam propagation in desired manners. The metasurface is composed of patterned hybrid graphene-silicon nano-disks deposited on a low-index substrate, namely silica. It is shown that the proposed hybrid metasurface simultaneously benefits from the advantages of graphene-based metasurfaces and dielectric ones. Specially, we show that the proposed hybrid metasurface not only provides reconfigurability, just like previously proposed graphene-based metasurfaces, but also similar to dielectric metasurfaces, is of low loss and CMOS-compatible. Such exceptional features give the metasurface exceptional potentials to realize...
Beam manipulation by hybrid plasmonic-dielectric metasurfaces
, Article Plasmonics ; Volume 15, Issue 3 , 2020 , Pages 639-645 ; Hemmatyar, O ; Kavehvash, Z ; Sharif University of Technology
Springer
2020
Abstract
A hybrid plasmonic-dielectric metasurface is proposed in order to manipulate beam propagation in desired manners. The metasurface is composed of patterned hybrid graphene-silicon nano-disks deposited on a low-index substrate, namely silica. It is shown that the proposed hybrid metasurface simultaneously benefits from the advantages of graphene-based metasurfaces and dielectric ones. Specially, we show that the proposed hybrid metasurface not only provides reconfigurability, just like previously proposed graphene-based metasurfaces, but also similar to dielectric metasurfaces, is of low loss and CMOS-compatible. Such exceptional features give the metasurface exceptional potentials to realize...
Propagation of light in photonic crystal fibre devices
, Article Journal of Optics A: Pure and Applied Optics ; Volume 7, Issue 11 , 2005 , Pages 663-668 ; 14644258 (ISSN) ; Akbari, M ; Mortensen, N. A ; Sharif University of Technology
2005
Abstract
We describe a semi-analytical approach for the three-dimensional analysis of photonic crystal fibre devices. The approach relies on modal transmission-line theory. We offer two examples illustrating the utilization of this approach in photonic crystal fibres: the verification of the coupling action in a photonic crystal fibre coupler and the modal reflectivity in a photonic crystal fibre distributed Bragg reflector. © 2005 IOP Publishing Ltd
Robust low-angle estimation by an array radar
, Article IET Radar, Sonar and Navigation ; Volume 4, Issue 6 , 2010 , Pages 780-790 ; 17518784 (ISSN) ; Sheikhi, A ; Nayebi, M. M ; Sharif University of Technology
2010
Abstract
One of the origins of error in the angle of arrival estimation of a signal is the response of the ground to the reflected waves from the target. In low-height target situations, this phenomenon can be so harrowing that it may result in much more error than thermal noise. In this article, two methods of fixed beam and double null are used as preliminary techniques to overcome the problem of low-altitude target angle estimation, and the optimum weights for beam-forming array radar are proposed. These beam-forming methods enable the radar to estimate the target angle precisely without the exact knowledge of the surface slope, whereas they are robust against diffuse and specular ground...
Visibility Via Reflection
, Ph.D. Dissertation Sharif University of Technology ; Ghodsi, Mohammad (Supervisor)
Abstract
This document deals with the following results in details:Given a simple polygon P with $n$ vertices, the visibility polygon (VP) of a point q, or a segment pq inside P can be computed in linear time. It is known that the visibility polygon of a point inside a polygon in the presence of a mirror can be computed in linear time. We propose a linear time algorithm to extend the VP of a viewer (point or segment) by converting some edges of P into mirrors (reflecting-edges with specular type of reflection), such that a given non-visible segment uw can also be seen from the viewer.Various definitions for the visibility of a segment, such as weak, strong, or complete visibility, are considered. Our...
Involutions of a clifford algebra induced by involutions of orthogonal group in characteristic 2
, Article Communications in Algebra ; Volume 43, Issue 9 , Jun , 2015 , Pages 3898-3919 ; 00927872 (ISSN) ; Nokhodkar, A. H ; Sharif University of Technology
Taylor and Francis Inc
2015
Abstract
Among the involutions of a Clifford algebra, those induced by the involutions of the orthogonal group are the most natural ones. In this work, several basic properties of these involutions, such as the relations between their invariants, their occurrences, and their decompositions, are investigated
Reflection optimization of nano-multilayer X-ray mirrors in three-edge energies: Cr-Kα, Co-Kα, and Ti-Kα
, Article Iranian Journal of Physics Research ; Volume 17, Issue 2 , 2017 , Pages 331-336 ; 16826957 (ISSN) ; Khosroabadi, H ; Otoukesh, M ; Sharif University of Technology
Isfahan University of Technology
2017
Abstract
In this paper, a practical simulation method for optimizing of x-ray reflection of nano-multilayer mirrors in three different edge energies: Cr-Kα, Co-Kα, and Ti-Kα is discussed in order to obtain the most reflection based on quarter-wave thickness method (QW). In this method, the reflected x-ray will have a constructive interference, and a peak, called Brag peak, will appear in reflection curve when the tickness of the layer is an odd multiple of the quarter-wave thickness. The quarter-wave thickness is dependent to on the angle and energy of the entrance photon beam. In the mentioned edge energies, for different nano-multilayer mirrors, and for incident angle ranges from 0.5 to 8 degrees,...
Nanostructured ternary composites of PPy/CNT/NiFe2O4 and PPy/CNT/CoFe2O4: Delineating and improving microwave absorption
, Article Comptes Rendus Chimie ; Volume 21, Issue 9 , 2018 , Pages 862-871 ; 16310748 (ISSN) ; Kheirjou, S ; Asgari, S ; Kazerooni, H ; Sharif University of Technology
Elsevier Masson SAS
2018
Abstract
Two different ternary nanocomposites, PPy/CNT/CoFe2O4 and PPy/CNT/NiFe2O4, were synthesized by in situ polymerization method. The resulting composites were characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. They were evaluated with the aim of investigating microwave absorption properties. The results showed that the value of microwave reflection decreases as that of prepared nanocomposites increases. This happens with increase in the PPy content and polymerization on the surface. © 2018 Académie des sciences
Iranian EFL learners’ identity construction in a critical reflective course: a case of an online course
, Article Open Learning ; Volume 35, Issue 1 , 2020 , Pages 63-81 ; Latifi, A ; Sharif University of Technology
Routledge
2020
Abstract
The present mixed-methods research examined the identity and attitude of Iranian English language learners as a result of their participation in an online critical reflective course. The participants were 38 English language students who attended ten online sessions within a five-month English language course. Their online posts underwent inductive qualitative content analysis and subsequently five themes were extracted. In addition, the content of the first and last two sessions were analysed quantitatively. A validated questionnaire was also administered and 18 participants were interviewed. Qualitative and quantitative content analyses of the data revealed eight finalised codes. The...
A simulation case study of THz reflection spectroscopy
, Article 29th Iranian Conference on Electrical Engineering, ICEE 2021, 18 May 2021 through 20 May 2021 ; 2021 , Pages 788-792 ; 9781665433655 (ISBN) ; Kavehvash, Z ; Fardmanesh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
We have modelled and simulated a simple THz spectroscopic system to identify materials. A Vivaldi antenna with suitable specifications was used as a transmitter in the simulation. In order to characterize the object, we applied two different methods based on the derivative of the reflectivity and the Kramers-Kronig relations. Also, to obtain the optimized incident angle, we calculated the reflection sensitivity of the sample to the angle of incidence using the Fresnel equations and verified our result by simulation. © 2021 IEEE
Bragg reflector for optical high voltage sensor applications
, Article Integrated Optical Devices: Fabrication and Testing, Brugge, 30 October 2002 through 1 November 2002 ; Volume 4944 , 2002 , Pages 287-292 ; 0277786X (ISSN) ; Mehrany, K ; Rashidian, B ; Tavakkoli, A ; SPIE ; Sharif University of Technology
2002
Abstract
Optical measurement of voltage because of its excellent advantages is studied by several research groups. In this paper, two optically voltage measurement method based on periodic structure have been introduced. First one is based on Bragg reflection effect. The coefficient of reflection from a periodic layered medium depends on properties of periodic structure. In this work a periodic structure on LiNbO3 substrate was considered and under a high voltage electric field perpendicular to surface of layers, refractive indices of substrate have been changed. Performance of reflection versus applied electric field was calculated. Second method was based on Guided-mode resonance effect. Guided...
Transmission enhancement of sharply bent nanoplasmonic slot waveguides
, Article Journal of the Optical Society of America B: Optical Physics ; Vol. 31, issue. 3 , 2014 , pp. 458-463 ; ISSN: 07403224 ; Hodaei, H ; Bahadori, M ; Rezaei, M ; Mehrany, K ; Sharif University of Technology
Abstract
The bending performance of standard nanoplasmonic slot waveguides is substantially improved by reducing the leakage loss and reflection in a systematic way. The out-of-plane power leakage is suppressed by using square metallic patches above and below the bend. The in-plane power leakage is reduced by elimination of the asymmetry between the electrical length of the inner and outer corners of the bend. The unwanted reflection is decreased by changing the shape of the outer corner of the bend. The partial reflections caused by the indentations of the modified shape destructively interfere with each other and thereby decrease the unwanted back reflection
Analytical approach for analyzing tapered transmission lines
, Article 2005 European Conference on Circuit Theory and Design, Cork, 28 August 2005 through 2 September 2005 ; Volume 3 , 2005 , Pages 181-184 ; 0780390660 (ISBN); 9780780390669 (ISBN) ; Eghlidi, M. H ; Mehrany, K ; Rashidian, B ; Sharif University of Technology
2005
Abstract
A new analytical method is introduced for the analysis of wave propagation in one-dimensional tapered transmission lines. Based on the analytical extension of ordinary transfer matrix into differential transfer matrix, this approach can be used for calculating reflection and transmission coefficients. Different numerical test cases are thoroughly studied and in each case an excellent agreement between the results of our differential transfer matrix method and exact solutions is observed. It is also shown that our approach is superior to the more common small reflection method
Liquid color recognition by using an optical reflection system
, Article Journal of Applied Sciences ; Volume 12, Issue 18 , 2012 , Pages 1917-1924 ; 18125654 (ISSN) ; Golnabi, H ; Sharif University of Technology
ANSInet
2012
Abstract
Operation of an optomechanical system for color reflection study is reported. The reported system consists of a double-fiber optical design and an electro-mechanical scanning system. In the double-fiber arrangement one fiber transmits the source light to the target surface and the second one sends the reflected light off the sample target to a photodetector. By scanning the double-fiber probe in one-direction reflection properties of different color liquid samples are investigated in this study. A cubic cell made of glass material is used as the liquid container and reflection signals are compared for different filled color liquids. The maximum reflection signals are: for the yellow color...
Role of fiber arrangements in operation of a double-fiber opto-mechanical system
, Article Journal of Applied Sciences ; Volume 11, Issue 16 , 2011 , Pages 3001-3007 ; 18125654 (ISSN) ; Golnabi, H ; Sharif University of Technology
2011
Abstract
Determination of the surface structure using the light reflection is an important issue. The aim is to study such surface reflections using an opto-mechanical system. The effects of the fiber arrangements in the operation of an opto-pair probe system for surface profiling are described. The opto-mechanical testing system consists of a double-fiber optical probe design and an electro-mechanical scanning system. Reflection signals for the plane and cylindrical surfaces made with different curvatures and materials are investigated with both probes and the results are compared. The reflection signal for the plane surface is independent of the double-fiber orientation in probe but for the curves...
Operation of an opto-mechanical system using a double-cell design for liquid color recognition
, Article Optics and Lasers in Engineering ; Volume 51, Issue 7 , July , 2013 , Pages 848-855 ; 01438166 (ISSN) ; Sharif University of Technology
2013
Abstract
Design and operation of an opto-mechanical system employing a double-cell is reported here for the color liquid reflection studies. The reported system consists of a double-fiber optical design and an electro-mechanical scanning system. In this arrangement one fiber transmits the source light to the object surface and the second one transmits the light reflected from the sample to a photodetector. By scanning the double-fiber assembly in one-direction reflection properties of different color liquids are investigated. Reflection signals depend on the cell surface structure and the cell filled material. Two sets of flat/cylindrical cells made of almost similar glass materials are used for this...