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najafkhani--farhang
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Fabrication of durable superhydrophobic surfaces using PDMS and beeswax for drag reduction of internal turbulent flow
, Article Applied Surface Science ; Volume 513 , 2020 ; Liravi, M ; Moosavi, A ; Nouri Borujerdi, A ; Najafkhani, H ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Nowadays, one of the biggest concerns in the world is increasing the CO2 emissions and global warming due to the over-consumption of fossil fuels. In addition, under the intense market competition, the demand for more efficient systems with higher performance and lower energy consumption has escalated. Since the drag force contributes to a considerable percentage of the energy loss and reducing the performance, a large number of studies have been conducted to improve the surface characteristics and, subsequently, declining the drag force. Making the surface superhydrophobic is one of the most effective ways for this purpose. In this work, two different superhydrophobic surfaces using SiO2...
Drag reduction in internal turbulent flow by fabricating superhydrophobic Al2O3/waterborne polyurethane coatings
, Article Surface and Coatings Technology ; Volume 421 , 2021 ; 02578972 (ISSN) ; Moosavi, A ; Nouri Boroujerdi, A ; Najafkhani, H ; Najafpour, S ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Nowadays, increasing the CO2 emissions are one of the inevitable challenges in the world. In addition, in many industries, fossil fuels are the main source of energy demands which worsen the problem. Since in most applications, the performance and energy loss are highly affected by the drag force, many investigations have been proposed to improve the surface properties to moving surface against the water, and consequently, increasing drag reduction. To this end, one effective way is utilizing superhydrophobic coatings. In this study, we prepare two different superhydrophobic coatings using Al2O3 nanoparticles (NPs) modified by HMDS (1,1,1,3,3,3-Hexamethyldisilazane) and PDMS...
Probing the local bubble with diffuse interstellar bands
, Article Proceedings of the International Astronomical Union ; Vol. 9, issue. S297 , February , 2014 , pp. 84-88 ; ISSN: 17439213 ; Khosroshahi, H. G ; Javadi, A ; Van Loon, J ; Sharif University of Technology
2014
Abstract
The Sun is located inside an enormous local cavity filled with a million degree, ionized hydrogen gas and surrounded by a wall of dense and cold gas, this cavity is known as the Local Bubble (LB). Since the tempreture of Local Bubble is high, the typical singly-ionized atoms or molecules can not survive at this high tempreture. To overcome this problem we should probe the Local Bubble using species which survive under this condition so we have done a whole sky survey in north hemisphere by observing absorptions in the Diffuse Interstellar Bands (DIBs) for sight-lines with distance >300 pc. We have done 30 nights observation and have observed 473 bright stars. We found that the correlations...
Experimental Evaluation of Light Frame Steel Shear Wall with K-Braced and Suitable Sheathing under Cyclic Loading
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayyaz (Supervisor) ; Farahbod, Farhang (Supervisor)
Abstract
Nowadays because of imbalance in supply and demand in the house industry, industrialization of building construction is one of the best ways to solve this problem. Currently, there is a strong tendency to develop guidelines for the design of Cold-Formed Steel (CFS) with different sheathing boards as seismic resistant shear walls. Also, the behavior of this systems is not very well known yet and more research is needed. In this work three K-braced frames with and without sheathing boards under lateral cyclic loading investigated experimentally. The first specimen as a control specimen is without sheathing board, second specimen was sheathed with Fibre-Cement board in one side and gypsum board...
Experimental and Numerical Evaluation of Light Steel Frame with Steel Shear Wall under Gravity Loadings and Subjected to Cyclic Loading
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayyaz (Supervisor) ; Farahbod, Farhang (Co-Supervisor)
Abstract
Because of imbalance in supply and demand in the housing industry, the industrialization of building construction is one of the best ways to explain this problem. Currently, there is a strong tendency to develop guidelines for the design of Cold-Formed Steel (CFS) with different sheathing boards as seismic resistant shear walls. Also, the behavior of these systems is not very well known yet and more research is needed. In this work, six K-braced frames with and without sheathing boards and gusset plate under gravity loading and lateral cyclic loading investigated experimentally. The first and second specimens (single stud) as a control specimens are without sheathing board under gravity...
Probing the Local Bubble with Diffuse Interstellar Bands (DIBs)
, Ph.D. Dissertation Sharif University of Technology ; Khosroshahi, Habib (Supervisor) ; Bahmanabadi, Mahmoud (Supervisor)
Abstract
We present a new high signal to noise ratio spectroscopic survey of the Northern hemisphere to probe the Local Bubble and its surroundings using the 5780Å and 5797Å Diffuse Interstellar Bands (DIBs). We have observed 432 sightlines to a distance of 200 pc over a duration of 3 years. In this study, for both inside and outside the Local Bubble, we establish the 5780and 5797correlations with Na i, Ca iiand E(B-V). The correlations show that among all neutral and ionized atoms, the Na ihas more similarity with 5780and Ca iihas strong correlation with 5797, which suggest that the ionization level of 5797is more than 5780. We study the 5780correlation with 5797, which shows a tight correlation...
Probing the local bubble with diffuse interstellar bands. III. The northern hemisphere data and catalog
, Article Astrophysical Journal, Supplement Series ; Volume 216, Issue 2 , February , 2015 ; 00670049 (ISSN) ; Khosroshahi, H. G ; Javadi, A ; Van Loon, J. T ; Sharif University of Technology
Institute of Physics Publishing
2015
Abstract
We present new high signal-to-noise ratio (S/N) observations of the diffuse interstellar bands (DIBs) in the Local Bubble and its surroundings. We observed 432 sightlines and obtain the equivalent widths of the λ5780 and λ5797 Å DIBs up to a distance of ∼200 pc. All of the observations were carried out using the Intermediate Dispersion Spectrograph on the 2.5 m Isaac Newton Telescope, during three years, to reach a minimum S/N of ∼2000. All of the λ5780 and λ5797 absorptions are presented in this paper and we tabulate the observed values of the interstellar parameters, λ5780, λ5797, Na ID1, and Na ID2, including the uncertainties
A sensitivity analysis of thermal lattices kinetic parameters with respect to the spectral weighting function using ultrafine BN method
, Article Progress in Nuclear Energy ; Volume 88 , 2016 , Pages 310-320 ; 01491970 (ISSN) ; Salehi, A. A ; Vosoughi, N ; Ayyoubzadeh, S. M ; Sharif University of Technology
2016
Abstract
Accurate calculation of kinetic parameters is of utmost importance in the safety analysis of a nuclear reactor. In the current paper, two approaches are investigated to evaluate these parameters in energy phase space. In the first approach, these parameters are derived from an energy-continuous form of the forward and adjoint transport equations and then integrals with respect to the energy variable are replaced by weighted summations over the energy groups, while in the second approach these parameters are extracted from the multi-group forward equation and its associate adjoint equation in which their multigroup constants are weighted by forward spectrum. The difference of weighting...
Design and implementation of spectrally-encoded spread-time CDMA transceiver
, Article IEEE Communications Letters ; Vol. 18, issue. 5 , 2014 , pp. 741-744 ; ISSN: 10897798 ; Hosseinianfar, H ; Akhoundi F ; Yazdian, E ; Farhang, M ; Salehi, J. A ; Sharif University of Technology
2014
Abstract
In this paper, we present and discuss the physical implementation and testing of a Spectrally-Encoded Spread-Time Code Devision Multiple Access (SE/ST-CDMA) transceiver. The proposed design is suitable for multiple-access and anti jamming wireless communication systems. The design and implementation takes into account the ability to automatically detect and mitigate tone jammers by altering the corresponding Gold sequence codes assigned uniquely to each user and setting the corresponding code's chip to zero. A simple real-time anti jamming mechanism capable of dealing with frequency hopping jammers is also proposed. The simulation results are provided in terms of Bit Error Rate (BER) versus...
Probing the local bubble with diffuse interstellar bands. II. The dib properties in the northern hemisphere
, Article Astrophysical Journal ; Volume 800, Issue 1 , February , 2015 ; 0004637X (ISSN) ; Khosroshahi, H. G ; Javadi, A ; Van Loon, J. Th ; Bailey, M ; Molaeinezhad, A ; Tavasoli, S ; Habibi, F ; Kourkchi, E ; Rezaei, S ; Saberi, M ; Hardy, L ; Sharif University of Technology
Institute of Physics Publishing
2015
Abstract
We present a new high signal-to-noise ratio spectroscopic survey of the Northern hemisphere to probe the Local Bubble and its surroundings using the λ5780Å and λ5797Å diffuse interstellar bands (DIBs). We observed 432 sightlines to a distance of 200 pc over a duration of three years. In this study, we establish the λ5780 and λ5797 correlations with Na I, Ca II and EB-V, for both inside and outside the Local Bubble. The correlations show that among all neutral and ionized atoms, the correlation between Ca ii and λ5780 is stronger than its correlation with λ5797, suggesting that λ5780 is more associated with regions where Ca+ is more abundant. We study the λ5780 correlation with λ5797, which...