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    Two-dimensional porous graphitic carbon nitride C6N7 monolayer: first-principles calculations

    , Article Applied Physics Letters ; Volume 119, Issue 14 , 2021 ; 00036951 (ISSN) Bafekry, A ; Faraji, M ; Fadlallah, M. M ; Abdolhosseini Sarsari, I ; Jappor, H. R ; Fazeli, S ; Ghergherehchi, M ; Sharif University of Technology
    American Institute of Physics Inc  2021
    The fabrication of the C6N7 monolayer [Zhao et al., Sci. Bull. 66, 1764 (2021)] motivated us to discover the optical, structural, mechanical, and electronic properties of the C6N7 monolayer by employing the density functional theory (DFT) method. We find that the shear modulus and Young's modulus of the C6N7 monolayer are smaller than the relevant values of graphene. However, Poisson's ratio is more significant than that of graphene. Applying the PBE (HSE06) functional bandgap of the C6N7 monolayer is 1.2 (1.97) eV, and the electronic dispersion is almost isotropic around the Γ point. C6N7 is more active in the ultraviolet region as compared to the visible light region. This study provides... 

    Extended gibbs free energy and laplace pressure of ordered hexagonal close-packed spherical particles: A wettability study

    , Article Langmuir ; Volume 37, Issue 28 , 2021 , Pages 8382-8392 ; 07437463 (ISSN) Bayat, A ; Ebrahimi, M ; Rahemi Ardekani, S ; Saievar Iranizad, E ; Zaker Moshfegh, A ; Sharif University of Technology
    American Chemical Society  2021
    The wetting property of spherical particles in a hexagonal close-packed (HCP) ordering from extended Gibbs free energy (GFE) and Laplace pressure view points is studied. A formalism is proposed to predict the contact angle (θ) of a droplet on the HCP films and penetration angle (α) of the liquid on the spherical particles. Then, the extended Laplace pressure for the layered HCP ordering is calculated and a correlation between the wetting angle, sign of pressure, and pressure gradient is achieved. Our results show that the sign and the slope of pressure are important criteria for determining the wettability state and it is found that the contact angle is independent of the particle radius, as... 

    Magnetoelastic coupling enabled tunability of magnon spin current generation in two-dimensional antiferromagnets

    , Article Physical Review B ; Volume 104, Issue 18 , 2021 ; 24699950 (ISSN) Bazazzadeh, N ; Hamdi, M ; Park, S ; Khavasi, A ; Mohseni, S. M ; Sadeghi, A ; Sharif University of Technology
    American Physical Society  2021
    We theoretically investigate the magnetoelastic coupling (MEC) and its effect on magnon transport in two-dimensional antiferromagnets with a honeycomb lattice. MEC coefficients along with magnetic exchange parameters and spring constants are computed for monolayers of transition-metal trichalcogenides with Néel magnetic order (MnPS3 and VPS3) and zigzag order (CrSiTe3, NiPS3, and NiPSe3) by ab initio calculations. Using these parameters, we predict that the spin-Nernst coefficient is significantly enhanced due to magnetoelastic coupling. Our study shows that although Dzyaloshinskii-Moriya interaction can produce spin-Nernst effect in these materials, other mechanisms such as magnon-phonon... 

    Symmetry enhanced spin-Nernst effect in honeycomb antiferromagnetic transition metal trichalcogenide monolayers

    , Article Physical Review B ; Volume 103, Issue 1 , 2021 ; 24699950 (ISSN) Bazazzadeh, N ; Hamdi, M ; Haddadi, F ; Khavasi, A ; Sadeghi, A ; Mohseni, S. M ; Sharif University of Technology
    American Physical Society  2021
    We investigate systematically the spin-Nernst effect in Néel and zigzag ordered honeycomb antiferromagnets. Monolayers of transition-metal trichalcogenides, MnPSe3, MnPS3, and VPS3 show an antiferromagnetic Néel order while CrSiTe3, NiPS3, and NiPSe3 show an antiferromagnetic zigzag order. We extract the exchange and Dzyaloshinskii-Moriya interaction parameters from ab initio calculations. Using these parameters, we predict that the spin-Nernst coefficient is at least two orders of magnitude larger in zigzag compared to the Néel ordered antiferromagnets. We find that this enhancement relies on the large band splitting due to the symmetry of magnetic configuration in the zigzag order. Our... 

    Reducing traffic congestion and increasing sustainability in special urban areas through one-way traffic reconfiguration

    , Article Transportation ; 2021 ; 00494488 (ISSN) Karimi, H ; Ghadirifaraz, B ; Shetab Boushehri, S. N ; Hosseininasab, S. M ; Rafiei, N ; Sharif University of Technology
    Springer  2021
    In the contemporary sustainable urban set up, one of the critical issues adversely affecting the quality of life in urban areas and inflicting immense costs on cities is traffic congestion. Traffic congestion is an outgrowth of increased traffic flow in certain locations of large cities. Recently, urban decision-makers and transportation planners resort to one-way traffic system as an effective traffic management strategy, which has a profound effect on reducing traffic congestion and improving traffic flow, leading to urban sustainability. In the present paper, the authors endeavored to develop a novel methodological framework based on optimization techniques in order to mitigate traffic... 

    Synthesis of CuCo2O4/BiVO4composites as promise and efficient catalysts for 4-nitrophenol reduction in water: Experimental and theoretical study

    , Article Journal of Environmental Chemical Engineering ; Volume 9, Issue 4 , 2021 ; 22133437 (ISSN) Mirzaee Valadi, F ; Gholami, M. R ; Sharif University of Technology
    Elsevier Ltd  2021
    This study investigates the synthesis of CuCo2O4, BiVO4, and CuCo2O4/BiVO4 nanocomposite by the solvothermal method. The Physico-chemical properties of the samples were verified through Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Transmission Electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDS), Brunauer-Emmett-Teller (BET). Evaluation of catalytic efficiency of the synthesized samples were done in promoting the 4-Nitrophenol reduction to 4-Aminophenol in the existence of high amount of sodium borohydride (NaBH4) as a reducing agent, and the progress of the catalytic reaction was monitored... 

    Inductance calculation of HTS transformers with multi-segment windings considering insulation constraints

    , Article Journal of Superconductivity and Novel Magnetism ; Volume 34, Issue 5 , 2021 , Pages 1329-1339 ; 15571939 (ISSN) Moradnouri, A ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
    Springer  2021
    High-temperature superconducting (HTS) transformers with multi-segment windings have been proposed in earlier literatures for the hysteresis loss reduction and short circuit electromagnetic force mitigation. The optimum distributive ratios for these multi-segment windings have been determined in earlier literatures. Asymmetrical seven segment winding with its optimum distributive ratio (k = 1/12) results in minimization of short circuit electromagnetic forces under normal tap and any adjusted tap. However, insulation design and leakage inductance calculation for the multi-segment winding of an HTS transformer have not been addressed in past literatures. Insulation design is one of the most... 

    Band alignment tuning of heptazine-g-C3N4/g-ZnO vdW heterostructure as a promising water-splitting photocatalyst

    , Article Physical Chemistry Chemical Physics ; Volume 23, Issue 36 , 2021 , Pages 20675-20685 ; 14639076 (ISSN) Rahimi, K ; Moshfegh, A. Z ; Sharif University of Technology
    Royal Society of Chemistry  2021
    Van der Waals (vdW) heterostructures of two-dimensional monolayers are a relatively new class of materials with highly tunable band alignment, bandgap energy, and bandgap transition type. In this study, we performed density functional theory calculations to investigate how a vdW heterostructure of heptazine-based graphitic carbon nitride (hg-C3N4) and graphitic zinc oxide (g-ZnO) monolayers is formed (hg-C3N4/g-ZnO). This heterostructure is a potential solar-driven photocatalyst for the water-splitting reaction. Upon the formation of the heterostructure, a type-I indirect bandgap (Eg = 2.08 eV) is created with appropriate conduction band minimum and valence band maximum levels relative to... 

    Operation and design analysis of an interleaved high step-up DC–DC converter with improved harnessing of magnetic energy

    , Article International Journal of Circuit Theory and Applications ; Volume 49, Issue 2 , 2021 , Pages 221-243 ; 00989886 (ISSN) Sabahi, M ; Tarzamni, H ; Kolahian, P ; Sharif University of Technology
    John Wiley and Sons Ltd  2021
    In this paper, a new interleaved DC–DC converter based on a coupled and a single input inductor is proposed. The suggested high step-up converter utilizes various inductive and capacitive methods to transfer magnetic energy more efficiently. The output voltage is regulated with the switches' duty cycle and the coupled inductor (CI) turns ratio, which provide a wide output voltage range. Interleaving improves the converter reliability, employs both the first and third areas of CI's B-H plane, cancels DC component of the CI, and reduces the input current ripple of the proposed converter with twice switching frequency. Utilization of two output ports for voltage stress and ripple reduction in... 

    Pressure induced structural, electronic, optical and thermal properties of CsYbBr3, a theoretical investigation

    , Article Journal of Materials Research and Technology ; Volume 10 , 2021 , Pages 687-696 ; 22387854 (ISSN) Saeed, M ; Ali, M. A ; Murad, S ; Ullah, R ; Alshahrani, T ; Laref, A ; Murtaza, G ; Sharif University of Technology
    Elsevier Editora Ltda  2021
    This article presents the variation of structural, electronic, thermal and optical properties of a halide perovskite CsYbBr3with increasing pressure, employing density functional theory. The pressure effect was determined in range of 0-15 GPa. In which stability of CsYbBr3remains valid, as, verified from negative values of enthalpy of formation and phonon dispersion curves. A significant change was observed in lattice constant, bond lengths, bulk modulus and its pressure derivative, volume and ground state energy, with increasing pressure. The calculated electronic properties presented CsYbBr3as a semiconductor with direct band gap of 3.61 eV. However, pressure rise shift the Yb-d states... 

    Impact of temporal correlations on high risk outbreaks of independent and cooperative SIR dynamics

    , Article PLoS ONE ; Volume 16, Issue 7 July , 2021 ; 19326203 (ISSN) Sajjadi, S ; Ejtehadi, M. R ; Ghanbarnejad, F ; Sharif University of Technology
    Public Library of Science  2021
    We first propose a quantitative approach to detect high risk outbreaks of independent and coinfective SIR dynamics on three empirical networks: A school, a conference and a hospital contact network. This measurement is based on the k-means clustering method and identifies proper samples for calculating the mean outbreak size and the outbreak probability. Then we systematically study the impact of different temporal correlations on high risk outbreaks over the original and differently shuffled counterparts of each network. We observe that, on the one hand, in the coinfection process, randomization of the sequence of the events increases the mean outbreak size of high-risk cases. On the other... 

    Nonlocal hcp kernel functions based on ab initio calculations: Pertinent dislocation problems revisited

    , Article Mechanics of Materials ; Volume 160 , 2021 ; 01676636 (ISSN) Shahvaghar Asl, S ; Shodja, H. M ; Sharif University of Technology
    Elsevier B.V  2021
    Eringen's nonlocal theory and an accurate determination of the nonlocal kernel functions for hexagonal close-packed (hcp) crystals are of interest. The kernel functions are closely related to the anisotropy as well as any crystalline symmetries. To this end, five new distinct nonlocal kernel functions which have the characteristics of discrete atomistic Green's functions in the stress space are obtained through consideration of the nonlocal dispersion relations associated with certain directions combined with ab initio Density Functional Perturbation Theory (DFPT) calculations of the pertinent phonon frequencies. This is the first work which provides the nonlocal hcp kernel functions... 

    Discrete kernel functions for fcc crystals within eringen’s nonlocal theory of elasticity

    , Article Journal of Elasticity ; Volume 143, Issue 1 , 2021 ; 03743535 (ISSN) Shodja, H. M ; Shahvaghar Asl, S ; Sharif University of Technology
    Springer Science and Business Media B.V  2021
    The dilemma with the deficiencies of the nonlocal kernel functions as the building blocks of the Eringen’s nonlocal theory has been of concern. The aim of the current work is to provide a remedy for the calculation of the components of the nonlocal moduli tensor pertinent to face center cubic (fcc) crystals accounting for their true symmetry group. To this end, three new distinct nonlocal kernel functions which are the discrete atomistic Green’s functions in the stress space are obtained through the nonlocal dispersion relations associated with the longitudinal and shear waves in fcc crystals combined with the corresponding ones calculated via ab initio based on density functional... 

    Degradation of BTEX in groundwater by nano-CaO2 particles activated with L-cysteine chelated Fe(III): enhancing or inhibiting hydroxyl radical generation

    , Article Water Supply ; Volume 21, Issue 8 , 2021 , Pages 4429-4441 ; 16069749 (ISSN) Sun, X ; Ali, M ; Cui, C ; Lyu, S ; Sharif University of Technology
    IWA Publishing  2021
    The simultaneous oxidation performance of benzene, toluene, ethylbenzene, and xylene (BTEX) by nanoscale calcium peroxide particles (nCaO2) activated with ferric ions (Fe(III)) and the mechanism of the enhancement of BTEX degradation by L-cysteine (L-cys) were investigated. The batch experimental results showed that the nCaO2/Fe(III)/L-cys process was effective in the destruction of BTEX in both ultrapure water and actual groundwater. A proper amount of L-cys could enhance BTEX degradation due to the promotion of Fe(II)/Fe(III) redox cycles by the participation of L-cys, but an excessive presence of L-cys would cause inhibition. Adding 1.0 mM L-cys to the nCaO2/Fe(III) system, the... 

    Sensitivity analysis of simple methods in determination of offshore jacket structures levels stiffness

    , Article Journal of Marine Science and Technology (Japan) ; 2021 ; 09484280 (ISSN) Tabeshpour, M. R ; Ahmadi, A ; Sharif University of Technology
    Springer Japan  2021
    Dynamic analyses are necessary problems in offshore jacket structures design and assessment. These analyses have various applications in recognition of dynamic behavior, fatigue analysis, damage detection, etc. Natural frequencies and mode shapes, as inherent vibrational features of a structure, are key parameters in referred analyses. These parameters are mainly affected by mass and stiffness matrices and slightly by damping. Therefore, it is more important to estimate the stiffness matrix of a structure accurately, especially in stiff structures such as offshore jacket platforms. In many cases, the stiffness of levels is required. For example, it can be useful in the construction of an... 

    Symptom prediction and mortality risk calculation for COVID-19 using machine learning

    , Article Frontiers in Artificial Intelligence ; Volume 4 , June , 2021 ; 26248212 (ISSN) Jamshidi, E ; Asgary, A ; Tavakoli, N ; Zali, A ; Dastan, F ; Daaee, A ; Badakhshan, M ; Esmaily, H ; Jamaldini, S. H ; Safari, S ; Bastanhagh, E ; Maher, A ; Babajani, A ; Mehrazi, M ; Sendani Kashi, M. A ; Jamshidi, M ; Sendani, M. H ; Rahi, J ; Mansouri, N ; Sharif University of Technology
    Frontiers Media S. A  2021
    Background: Early prediction of symptoms and mortality risks for COVID-19 patients would improve healthcare outcomes, allow for the appropriate distribution of healthcare resources, reduce healthcare costs, aid in vaccine prioritization and self-isolation strategies, and thus reduce the prevalence of the disease. Such publicly accessible prediction models are lacking, however. Methods: Based on a comprehensive evaluation of existing machine learning (ML) methods, we created two models based solely on the age, gender, and medical histories of 23,749 hospital-confirmed COVID-19 patients from February to September 2020: a symptom prediction model (SPM) and a mortality prediction model (MPM).... 

    Role of herzberg-teller vibronic coupling in surface-enhanced resonance raman spectra of 4,4′-diaminotolane with nearly close molecular and charge-transfer transitions

    , Article Journal of Physical Chemistry C ; Volume 125, Issue 31 , 2021 , Pages 17202-17211 ; 19327447 (ISSN) Jamshidi, Z ; Ashtari Jafari, S ; Smirnov, A ; Solovyeva, E. V ; Sharif University of Technology
    American Chemical Society  2021
    We have investigated the surface-enhanced resonance Raman spectroscopy (SERRS) for 4,4′-diaminotolane absorbed on silver experimentally and theoretically. Experimental observation shows greatly enhanced bg symmetric modes ν26 and ν27, which are silent in normal Raman spectroscopy and SERS on gold. The dependence of the surface-enhanced Raman spectroscopy (SERS) spectra on five excitation lines has also been registered and classified for single bands into three profiles referring to the different contributions of resonant transitions. Theoretical calculations based on the time-dependent path integral formalism by including the Herzberg-Teller correction reproduce the experimental spectra with... 

    New pathways of stability for NHCs derived from azole, di-azole, n-tetrazole, and ab-tetrazole, by DFT

    , Article Journal of Molecular Modeling ; Volume 26, Issue 11 , 2020 Ahmadi, A ; Kassaee, M. Z ; Ayoubi Chianeh, M ; Fattahi, A ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2020
    We have investigated the pathways of stability for NHCs derived from azole, di-azole, n-tetrazole, and ab-tetrazole (1a, 2a, 3a, and 4a, respectively), at the M06/6-311++G** level of theory. Optimization and vibrational frequency calculations of ground states (GS) and transition states (TS) are performed to identify Gibbs free energies and nature of stationary points, respectively. Two possible pathways of stability for 1a-4a are compared and contrasted which entail dimerization through hydrogen bonding (HB) and covalent bonding (CB). The CB pathway comprises head to head (HH) and head to tail (HT) dimerizations. Plausible reaction profiles are illustrated for 1a-4a along with the mechanism... 

    Frequency stability improvement in windthermal dominated power grids

    , Article IET Generation, Transmission and Distribution ; Volume 14, Issue 4 , 2020 , Pages 619-627 Ashouri Zadeh, A ; Toulabi, M ; Dobakhshari, A. S ; Ranjbar, A. M ; Sharif University of Technology
    Institution of Engineering and Technology  2020
    With the proliferation of intermittent renewable energy sources, power systems need to withstand an increasing number of disturbances that may affect system frequency. In this paper, we focus on the effects of high penetration level of wind turbine-generators (WTG) on the power system operational planning from the frequency point of view. Specifically, an exact formulation for the minimum frequency calculation is presented to increase accuracy and speed of analyses. Then, the effect of WTG's frequency response on the power system frequency stability is investigated to compute the maximum acceptable generation outage as a function of penetration level. Finally, as an application to power... 

    A methionine chemical shift based order parameter characterizing global protein dynamics

    , Article ChemBioChem ; 2020 Chashmniam, S ; Teixeira, J. M. C ; Paniagua, J. C ; Pons, M ; Sharif University of Technology
    Wiley-VCH Verlag  2020
    Coupling of side chain dynamics over long distances is an important component of allostery. Methionine side chains show the largest intrinsic flexibility among methyl-containing residues but the actual degree of conformational averaging depends on the proximity and mobility of neighboring residues. The 13C NMR chemical shifts of the methyl groups of methionine residues located at long distances in the same protein show a similar scaling with respect to the values predicted from the static X-ray structure by quantum methods. This results in a good linear correlation between calculated and observed chemical shifts. The slope is protein dependent and ranges from zero for the highly flexible...