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Ultra-broadband polarization-independent perfect absorber based on phase change material (Ge 2Sb 2Te 5 or GST) for the visible and infrared regions
, Article Optical and Quantum Electronics ; Volume 55, Issue 2 , 2023 ; 03068919 (ISSN) ; Arik, K ; Sharif University of Technology
Springer
2023
Abstract
Broadband optical absorbers are increasingly in demand in various applications, including solar cells and radiative cooling systems. Among various types of structures, absorbers based on metamaterial structures have attracted much attention. However, they generally suffer from the issues of narrow bandwidth, high-cost fabrication, and high sensitivity to polarization changes. This paper presents a broadband, polarization-independent metamaterial absorber working in both infrared and visible frequency regimes. This structure is composed of a continuous phase-change material film (Ge 2Sb 2Te 5) separated between two thin spacer layers of SiO 2, and an array of amorphous Silicon particles...
Deep learning-driven beamforming optimization for high-performance 5g planar antenna arrays
, Article 2023 13th International Conference on Computer and Knowledge Engineering, ICCKE 2023 ; 2023 , Pages 485-490 ; 979-835033015-1 (ISBN) ; Razavi Pour, S. R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2023
Abstract
The ability of 5G wireless communication networks to effectively and simultaneously interact with incoming signals is made possible by antenna arrays, which play a vital role in assisting the functioning of 5G wireless communication networks. The utilization of beamforming enables the enhancement of signal strength, expansion of coverage area, and reduction of interference, thereby optimizing the performance of the communication networks. This paper introduces a deep learning approach that utilizes a deep neural network (DNN). This approach establishes an appropriate framework to implement beamforming for planar antenna arrays. The DNN utilizes the desired radiation pattern as an input to...
Optimizing sidelobe levels in 5G antenna arrays: a grasshopper optimization algorithm approach for enhanced network performance
, Article 2023 14th International Conference on Computing Communication and Networking Technologies, ICCCNT 2023 ; 2023 ; 979-835033509-5 (ISBN) ; Razavi Pour, S. R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2023
Abstract
The deployment of 5G networks requires advanced antenna technologies to meet the increasing demands for high-capacity and low-latency communication. Antenna arrays, known for their beamforming capabilities, are vital in achieving these goals. However, sidelobes in the antenna radiation pattern can introduce errors and significantly impact the system's overall performance. This paper proposes a novel beamforming optimization technique for linear antenna arrays (LLA) in 5G networks. Our approach leverages the power of metaheuristic algorithms, precisely the Grasshopper Optimization Algorithm (GOA), to optimize the array configuration and reduce the Sidelobe Levels (SLL). The main objective is...
Nanocomposite of functionalized halloysite and Ag(0) decorated magnetic carbon dots as a reusable catalyst for reduction of dyes in water
, Article Journal of Physics and Chemistry of Solids ; Volume 152 , 2021 ; 00223697 (ISSN) ; Kazemeini, M ; Sadjadi, S ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
A new magnetic, catalytic nanocomposite of Hal-MT-Cys-Ag/MNCD was fabricated and utilized for catalyzing reductive de-colorization of methyl orange and rhodamin B in aqueous media at room temperature. To prepare this material, Cl-functionalized halloysite nanoclay was successively reacted with melamine and 2,4,6-trichloro-1,3,5-triazine to furnish multi-nitrogen containing ligand on halloysite surface. Then, magnetic carbon dots were crafted through a facile method and decorated with Ag nanoparticles and cysteine to furnish Cys-Ag/MNCD species. The final nanocomposite was obtained via incorporation of this latter species onto functionalized halloysite. This new composite was characterized...
An efficient spam mail detection by counter technique
, Article World Academy of Science, Engineering and Technology ; Volume 50 , May , 2011 , Pages 573-576 ; 2010376X (ISSN) ; Behnam Roudsari, S ; Nemaney Pour, A ; Sharif University of Technology
2011
Abstract
Spam mails are unwanted mails sent to large number of users. Spam mails not only consume the network resources, but cause security threats as well. This paper proposes an efficient technique to detect, and to prevent spam mail in the sender side rather than the receiver side. This technique is based on a counter set on the sender server. When a mail is transmitted to the server, the mail server checks the number of the recipients based on its counter policy. The counter policy performed by the mail server is based on some pre-defined criteria. When the number of recipients exceeds the counter policy, the mail server discontinues the rest of the process, and sends a failure mail to sender of...
An efficient spam mail detection by counter technique
, Article World Academy of Science, Engineering and Technology ; Volume 74 , May , 2011 , Pages 579-582 ; 2010376X (ISSN) ; Roudsari, S. B ; Pour, A. N ; Sharif University of Technology
2011
Abstract
Spam mails are unwanted mails sent to large number of users. Spam mails not only consume the network resources, but cause security threats as well. This paper proposes an efficient technique to detect, and to prevent spam mail in the sender side rather than the receiver side. This technique is based on a counter set on the sender server. When a mail is transmitted to the server, the mail server checks the number of the recipients based on its counter policy. The counter policy performed by the mail server is based on some pre-defined criteria. When the number of recipients exceeds the counter policy, the mail server discontinues the rest of the process, and sends a failure mail to sender of...
Calculation of the density and activity of water in ATPS systems for separation of biomolecules
, Article Journal of Solution Chemistry ; Volume 42, Issue 7 , 2013 , Pages 1423-1437 ; 00959782 (ISSN) ; Shirazian, S ; Pour, A. F ; Ziary, M ; Sharif University of Technology
2013
Abstract
In this study, the perturbed hard sphere chain equation of state is utilized to calculate the activity of water in binary and ternary solutions of polyethylene glycol (PEG), salt and water. The liquid density of the binary and ternary solutions is also predicted. To estimate the water activity in PEG-water binary systems, a linear correlation is obtained for the binary interaction parameter between water and PEG. Then, using this correlation and without introducing any additional binary parameters, the water activities are predicted in ternary solutions of water, salt and PEG with different molecular weights (MW). Our results show that the mean absolute average relative deviation (AARD %) of...
An efficient group key management protocol using code for key calculation: CKC
, Article Telecommunication Systems ; Volume 51, Issue 2-3 , 2012 , Pages 115-123 ; 10184864 (ISSN) ; Eidkhani, E ; Mortazavi, S. A ; Nemaney Pour, A ; Sharif University of Technology
2012
Abstract
This paper presents a new group key management protocol, CKC (Code for Key Calculation) for secure IP multicast. In this protocol which is based on logical key hierarchy, only the group key needs to be sent to new member at join. Then, using the group key current members and the new member calculate the necessary keys by node codes and one-way hash function. A node code is a random number assigned to each node to help users calculate necessary keys. Again, at leave server just sends the new group key to the remaining members. By this key, members calculate necessary keys using node codes and one-way hash function. The security of the keys is based on one-wayness of hash function. The results...
A new group key management protocol using code for key calculation: CKC
, Article 2010 International Conference on Information Science and Applications, ICISA 2010, 21 April 2010 through 23 April 2010 ; April , 2010 ; 9781424459438 (ISBN) ; Eidkhani, E ; Mortazavi, S. A ; Nemaney Pour, A ; Sharif University of Technology
2010
Abstract
This paper presents a new group key management protocol, CKC (Code for Key Calculation). This protocol is based on logical key hierarchy. When a new member joins the group, server sends only the group key for that member. Then, current members and the new member calculate the necessary keys using node codes and one-way hash function. Node code is a code which is assigned to each node of the key tree. Again at leave, server just sends the new group key to remaining members. By this key, members calculate necessary keys using node codes and one-way hash function. The security of the keys is based on one-wayness of hash function. The results show that CKC reduces computational and communication...
The effect of stiffness on stress intensity factor for a crack in annular disc under constant central torque
, Article International Journal of Damage Mechanics ; Volume 19, Issue 8 , 2010 , Pages 1001-1015 ; 10567895 (ISSN) ; Gowhari Anaraki, A. R ; Hardy, S. J ; Sharif University of Technology
2010
Abstract
The finite element method has been used to predict the stress intensity factors for cracked annular discs under constant central torque. Linear elastic fracture mechanics finite element analyses have been performed and the results are demonstrated in the form of crack configuration factors. To this end, the extensive ranges of crack configuration factors have been employed while considering the effect of disc stiffness. Then, the finite element results are applied to develop equivalent prediction equations using a statistical multiple nonlinear regression model. The accuracy of this model is measured using a multiple coefficient of determination, R2, where 0 ≤R2 ≤1. This coefficient is found...
Immobilized copper(II) on nitrogen-rich polymer-entrapped Fe3O4 nanoparticles: A highly loaded and magnetically recoverable catalyst for aqueous click chemistry
, Article Applied Organometallic Chemistry ; Volume 30, Issue 2 , 2016 , Pages 73-80 ; 02682605 (ISSN) ; Hosseini, S. H ; Pour Javadi, A ; Bennett, C ; Sharif University of Technology
John Wiley and Sons Ltd
2016
Abstract
A heterogeneous magnetic copper catalyst was prepared via anchoring of copper sulfate onto multi-layered poly(2-dimethylaminoethyl acrylamide)-coated magnetic nanoparticles and was characterized using various techniques. The catalyst was found to be active, effective and selective for one-pot three-component reaction of alkyl halide, sodium azide and alkyne, known as copper-catalyzed click synthesis of 1,2,3-triazoles. As little as 0.3 mol% of catalyst was found to be effective under the optimum conditions. The catalyst could also be recycled and reused up to seven times without significant loss of activity. Thermal stability, high loading level of copper on catalyst, broad diversity of...
Potential effects of alginate–pectin biocomposite on the release of folic acid and their physicochemical characteristics
, Article Journal of Food Science and Technology ; Volume 57, Issue 9 , March , 2020 , Pages 3363-3370 ; Alemzadeh, I ; Vaziri, A. S ; Beiroti, A ; Sharif University of Technology
Springer
2020
Abstract
Potential effects of folates on the treatment of several human diseases like cognitive function, neural tube defects, coronary heart disease and certain kinds of cancers have been discovered. However, the stability of folic acid against adverse conditions is a great concern. The present study investigates various alginate (A)–pectin (P) gastrointestinal-resistant hydrogel to immobilize folic acid. This involves evaluating different compositions of alginate–pectin to achieve higher encapsulation efficiency and stability during simulated gastric (SG) and simulated intestinal (SI) conditions. Coated alginate hydrogels with pectin resulted significant (p < 0.05) better protection of folic acid...
Nanosized NiFeSe2/NiCo2O4 hierarchical arrays on Ni foam as an advanced electrocatalyst for hydrogen generation
, Article Sustainable Energy and Fuels ; Volume 7, Issue 1 , 2022 , Pages 112-121 ; 23984902 (ISSN) ; Shekarabi, S ; Taherinia, D ; Zare Pour, M. A ; Sharif University of Technology
Royal Society of Chemistry
2022
Abstract
The rational design of composite catalysts is critically essential for electrochemical water splitting. Here, we report on a novel hierarchical composite that comprises NiFeSe2 nanoparticles and NiCo2O4 nanoflakes supported on nickel foam (NF) as an efficient electrocatalyst for the hydrogen evolution reaction (HER). The conjunction of the NiFeSe2 nanoparticles and NiCo2O4 nanoflakes introduces a new synergistic effect for the HER, resulting in an improved NiCo2O4 catalyst. The as-prepared NiFeSe2/NiCo2O4/NF electrode exhibited an enhanced HER activity, with a low overpotential of 83 mV at a current density of 10 mA cm−2, a low Tafel slope of 45 mV dec−1, and an excellent long-term...
Probabilistic failure analysis of hot gas path in a heavy-duty gas turbine using Bayesian networks
, Article International Journal of Systems Assurance Engineering and Management ; Volume 10, Issue 5 , 2019 , Pages 1173-1185 ; 09756809 (ISSN) ; Adib Nazari, S ; Maghsoud Pour, A ; Etemadi Haghighi, S ; Zareh, M ; Sharif University of Technology
Springer
2019
Abstract
Heavy-duty gas turbines are usually devised in power plants to generate electrical energy. Sudden failure in any of its parts or subdivisions will result in a decrement of the efficiency of the system or emergency shutdown of the system. The highest risk of failure in these turbines is subjected to the hot gas path (HGP) of the turbine. Due to the existence of uncertainty in diagnosing process or damage growth, in this research, a modified risk-based probabilistic failure analysis model using Bayesian networks (BN) was developed. First, a failure model was developed using the Fault Tree Analysis, and then it is transformed into a BN model. This model is capable of predicting and diagnosing...
Failure analysis of first stage nozzle in a heavy-duty gas turbine
, Article Engineering Failure Analysis ; Volume 109 , January , 2020 ; Adib Nazari, S ; Maghsoud Pour, A ; Etemadi Haghighi, S ; Zareh, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
First stage nozzles are considered as one of the most critical components in the heavy-duty gas turbines because of their operational in-service condition in the hot gas path. In the present research, the failure analysis of a first stage nozzle in a 159 MW gas turbine is investigated in order to specify the modes and mechanisms of the failure and their root causes. Various examinations including macroscopic and visual inspection of the nozzle outer surface, the micro examination of the fracture surface, chemical analysis and metallographic analysis were carried out to complete the investigation. The micro and macro examinations revealed cracks, erosion and oxidation damages in the nozzle...
Sifs for radial cracks in annular discs under internal and external shrinkage pressure and constant angular velocity
, Article ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007, 11 November 2007 through 15 November 2007 ; Volume 7 , 2007 , Pages 653-659 ; 0791843017 (ISBN) ; Gowhari Anaraki, A. R ; Hardy, S. J ; ASME ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2007
Abstract
Finite element method has been implemented to predict stress intensity factors (SIFs) for radial cracks in annular discs under constant angular velocity. Effects of internal and external uniform pressure on the SIFs have also been considered. Linear elastic fracture mechanics finite element analyses have been performed and results are presented in the form of crack configuration factors for a wide range of components and crack geometry parameters. These parameters are chosen to be representative of typical practical situations. The extensive range of crack configuration factors obtained from the analyses is then used to develop equivalent prediction equations via a statistical multiple...
Tailoring metallurgical and biological characteristics of Ti–6Al–4V alloy by synergetic application of Nd:YAG laser and drug-loaded electrospun PVA
, Article Journal of Materials Research and Technology ; Volume 24 , 2023 , Pages 3759-3771 ; 22387854 (ISSN) ; Naffakh Moosavy, H ; Bagheri, F ; Sadrnezhaad, S. K ; Pour, H. M ; Sharif University of Technology
Elsevier Editora Ltda
2023
Abstract
Titanium alloys have been used extensively as implants. However, they generally suffer from low biocompatibility as well as antibacterial activity. To date, several strategies have been proposed to address these issues. It is of practical interest to synergistically increase both cellular adhesion and antimicrobial activity in titanium-based implants. Here, Ti–6Al–4V alloys were surface-modified by Nd:YAG laser with different scanning speeds ranging from 1 to 5 mm s−1 and subsequently coated by drug-loaded polymer nanofibers for prolonged drug release. The laser-modified samples were both physically and metallurgically characterized through XRD, OM, AFM, FESEM, hardness, and wettability...
Natural frequencies of C60, C70, and C80 fullerenes
, Article Applied Physics Letters ; Volume 96, Issue 2 , 2010 ; 00036951 (ISSN) ; Vafai, A ; Sharif University of Technology
2010
Abstract
This letter adopts an atomistic modeling approach to study free vibrational characteristics of C60, C70, and C80 fullerenes. In this regard, we use the molecular structural mechanics consisting of equivalent structural beams to calculate the nonzero natural frequencies. The simulation results indicate that the first natural frequency of the fullerene is in the order terahertz and decreases nonlinearly with respect to the number of the carbon atoms
A macroscopic traffic flow model that includes driver sensitivity to the number of free spaces ahead
, Article Transportmetrica B ; 2017 , Pages 1-17 ; 21680566 (ISSN) ; Nassiri, H ; Sharif University of Technology
2017
Abstract
This paper addresses the first-order extension of the Lighthill–Whitham– Richards (LWR) macroscopic traffic flow model. Although previous studies have focused on the fluid aspect of traffic flow, none have addressed the sensitivity of drivers to the number of free spaces within a certain distance ahead of the subject driver. To incorporate driver behavior, we used the number of free spaces ahead of subject drivers and their sensitivity to the number of free spaces within a certain distance ahead. The resulting model is a convection-diffusion model. By computing Einstein's diffusion equation and comparing it with the diffusion coefficient in the extended model, a theoretical relation for the...
A macroscopic traffic flow model that includes driver sensitivity to the number of free spaces ahead
, Article Transportmetrica B ; Volume 8, Issue 1 , 2020 , Pages 290-306 ; Nassiri, H ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
This paper addresses the first-order extension of the Lighthill–Whitham– Richards (LWR) macroscopic traffic flow model. Although previous studies have focused on the fluid aspect of traffic flow, none have addressed the sensitivity of drivers to the number of free spaces within a certain distance ahead of the subject driver. To incorporate driver behavior, we used the number of free spaces ahead of subject drivers and their sensitivity to the number of free spaces within a certain distance ahead. The resulting model is a convection-diffusion model. By computing Einstein's diffusion equation and comparing it with the diffusion coefficient in the extended model, a theoretical relation for the...