Search for: reflective-surfaces
Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 233, Issue 2 , 2019 , Pages 457-471 ; 09544100 (ISSN) ; Abedian, A ; Farsi, M. A ; Kalantarinezhad, R ; Sharif University of Technology
SAGE Publications Ltd 2019
High-temperature insulators protect structures against extreme thermal loads in various industries such as energy and space-related areas. For such insulations, radiation is the dominant mode of heat transfer. The intended multilayer high-temperature insulator utilizes reflection as the controlling mechanism for the radiative heat transfer. In the current study, the axiomatic design methodology is used to map the design process of a reflective multilayer high-temperature insulator. In addition, an analytical model is developed to simulate the combined radiation and conduction heat transfer in the reflective multilayer high-temperature insulator. The model was solved numerically and validated...
Physical Layer Security in Wireless Communication Networks in Presence of Intelligent Reflecting Surfaces, M.Sc. Thesis Sharif University of Technology ; Nasiri Kenari, Masoumeh ; Mirmohseni, Mahtab
The ever-increasing demand for wireless communication has raised the need for better utilization of bandwidth and energy. Intelligent Reflecting Surface (IRS) is an emerging technology that has been proposed for the sixth generation of wireless communication. In this thesis, we study the essential role these surfaces can play in improving the physical layer security.First, we consider a relatively realistic scenario for the location of the eavesdroppers. In this scenario, we will assume that the transmitters, users, and eavesdroppers all use a single antenna configuration, and the eavesdroppers are placed randomly across the studied region. Two notable parameters in physical layer security,...
Ph.D. Dissertation Sharif University of Technology ; Nasiri Kenari, Masoumeh ; Mirmohseni, Mahtab
In this thesis, we analyze the degree of freedom (DoF) of wireless multi-user networks in the presence of smart radio environment. The two most important wireless multi-user networks, K-user interference channel, and M*N wireless X network are considered and the effects of the presence of a smart radio environment on the DoF of these networks are evaluated. To this end, first, we consider Intelligent Reflecting Surfaces (IRSs), which are a practical model of smart radio environments and can control the propagation of waves toward the desired direction in the environment. Then, we consider the instantaneous relay as a general theoretical model, which is the most comprehensive model for smart...
Operation of an opto-mechanical scanning system for surface profiling using a plastic double-fiber probe, Article POF 2011: 20th International Conference on Plastic Optical Fibers - Conference Proceeding ; 2011 , Pages 459-464 ; Knowledge Development for POF; POF Application Center; Sojitz Corporation; Hamamatsu Photonics; Optogear ; Sharif University of Technology
Operation of an optical system for surface profiling is reported here. Reflection signals for the plane and cylindrical surfaces with different materials are reported. To investigate the precision and sensitivity of the reported system the reflection results of the curved and flat structured surface are compared with that of a structure-free surface. Reported system provides a simple and accurate means for the object shape study through the optical reflection measurements
An efficient approach for reflectivity and coupling computation in an abruptly ended planar layered waveguide using modified formulation of CGF-RFFM, Article German Microwave Conference, GeMiC 2016, 14 March 2016 through 16 March 2016 ; 2016 , Pages 128-131 ; 9783981266870 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2016
An efficient method for computation of surface wave (SW) reflectivity and coupling in an abruptly ended planar layered waveguide is presented. Using characteristic Green's function (CGF) technique, the original structure is approximated by a separable structure. Then by applying rational function fitting method (RFFM) a uniform and closed-form expression of spatial Green's function for separable structure is derived. Having a full wave solution of the original structure, an optimization problem is defined to find the reflection coefficients of SW modes. Unlike the previous presented CGF based method called CGF-complex images (CI), CGF-RFFM leads to easy incorporation of radiation modes...
Article IEEE Wireless Communications Letters ; Volume 10, Issue 6 , 2021 , Pages 1324-1328 ; 21622337 (ISSN) ; Zargari, S ; Wu, Q ; Ng, D. W. K ; Zhang, R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2021
In this letter, we study the resource allocation for a multiuser intelligent reflecting surface (IRS)-aided simultaneous wireless information and power transfer (SWIPT) system. Specifically, a multi-antenna base station (BS) transmits energy and information signals simultaneously to multiple energy harvesting receivers (EHRs) and information decoding receivers (IDRs) assisted by an IRS. Under this setup, we introduce a multi-objective optimization (MOOP) framework to investigate the fundamental trade-off between the data sum-rate maximization and the total harvested energy maximization, by jointly optimizing the energy/information beamforming vectors at the BS and the phase shifts at the...
Article Optics and Lasers in Engineering ; Volume 49, Issue 8 , 2011 , Pages 1032-1039 ; 01438166 (ISSN) ; Sharif University of Technology
Design and operation of an opto-mechanical system for surface profiling are reported in this study. 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 off the surface to a photodetector. By scanning the double-fiber assembly in one-direction, reflection properties of different curved surfaces are investigated. Reflection signals for the cylindrical surfaces made with different curvatures and materials are reported. In order to see the effect of the surface material, for a fixed radius cylinder, the surface is...
Article Optics and Laser Technology ; Volume 43, Issue 4 , 2011 , Pages 814-819 ; 00303992 (ISSN) ; Golnabi, H ; Sharif University of Technology
In this article, two optical-fibre probes used in displacement measurements are reported. In one arrangement, two optical fibres with protective buffer jackets are placed together, while in the second arrangement, the protective buffer jackets are removed and the two fibres are placed with the claddings in contact, with a concomitant smaller centrecentre distance. As the core and cladding diameters are the same in both probes, the effect of the centrecentre distance on double-fibre designs can be investigated. The reflected output powers are recorded for the probes as a function of the axial distance from a reflective surface. A theoretical model is also implemented, which considers the...
Input impedance and radiation pattern of a resonant dipole embedded in a two-dimensional periodic leaky-wave structure, Article IET Microwaves, Antennas and Propagation ; Volume 9, Issue 14 , 2015 , Pages 1567-1573 ; 17518725 (ISSN) ; Borji, A ; Sharif University of Technology
Institution of Engineering and Technology 2015
Array scanning method (ASM) is employed to study the input impedance and radiation pattern of a two-dimensional periodic leaky-wave antenna (LWA). The antenna consists of a narrow horizontal strip dipole of arbitrary length underneath a two-dimensional (2D) periodic screen of metallic patches, which acts as a partially reflective surface (PRS), and backed by a ground plane. First, the Green's function in the presence of the 2D array of metallic patches is calculated by means of the ASM and then the current distribution and input impedance of the source dipole are calculated through the electric field integral equation and method of moments. The far-field pattern is computed using the...
Assembly of CeO 2-TiO 2 nanoparticles prepared in room temperature ionic liquid on graphene nanosheets for photocatalytic degradation of pollutants, Article Journal of Hazardous Materials ; Volume 199-200 , 2012 , Pages 170-178 ; 03043894 (ISSN) ; Setayesh, S. R ; Habibi Yangjeh, A ; Hormozi Nezhad, M. R ; Gholami, M. R ; Sharif University of Technology
CeO 2-TiO 2 nanoparticles were prepared by the sol-gel process using 2-hydroxylethylammonium formate as room-temperature ionic liquid and calcined at different temperatures (500-700°C). CeO 2-TiO 2-graphene nanocomposites were prepared by hydrothermal reaction of graphene oxide with CeO 2-TiO 2 nanoparticles in aqueous solution of ethanol. The photocatalysts were characterized by X-ray diffraction, BET surface area, diffuse reflectance spectroscopy, scanning electron microscopy, and Fourier transformed infrared techniques. The results demonstrate that the room-temperature ionic liquid inhibits the anatase-rutile phase transformation. This effect was promoted by addition of CeO 2 to TiO 2....