Search for: homogenization
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    Homogenization of maximal monotone vector fields via selfdual variational calculus

    , Article Advanced Nonlinear Studies ; Volume 11, Issue 2 , Jan , 2011 , Pages 323-360 ; 15361365 (ISSN) Ghoussoub, N ; Moameni, A ; Sáiz, R. Z ; Sharif University of Technology
    We use the theory of selfdual Lagrangians to give a variational approach to the homogenization of equations in divergence form, that are driven by a periodic family of maximal monotone vector fields. The approach has the advantage of using Γ-convergence methods for corresponding functionals just as in the classical case of convex potentials, as opposed to the graph convergence methods used in the absence of potentials. A new variational formulation for the homogenized equation is also given  

    On some measures associated to the geodesic flow

    , Article Rocky Mountain Journal of Mathematics ; Volume 36, Issue 4 , 2006 , Pages 1229-1233 ; 00357596 (ISSN) Fanai, H. R ; Sharif University of Technology
    We generalize a previous result in [4] concerning some measures associated to the geodesic flows on compact negatively curved Riemannian manifolds and give also an application of the result in [5] to Anosov flows. Copyright © 2006 Rocky Mountain Mathematics Consortium  

    Monomeric and dimeric oxido-peroxido tungsten(VI) complexes in catalytic and stoichiometric epoxidation

    , Article Coordination Chemistry Reviews ; Vol. 268, issue , 2014 , Pages 83-100 ; ISSN: 00108545 Amini, M ; Haghdoost, M. M ; Bagherzadeh, M ; Sharif University of Technology
    Epoxides are important materials in the production of fine chemicals. Selective oxidation of alkenes to epoxides remains a challenge in synthetic chemistry. There has been considerable progress in tungsten-catalyzed epoxidation of alkenes in recent years. This review highlights the use of monomeric and dimeric oxido-peroxido tungsten(VI) complexes as catalysts or oxidants in homogeneous or heterogeneous catalytic systems for epoxidation of olefins  

    A water-oxidizing dinuclear iron complex as an efficient catalyst toward organic sulfide oxidation

    , Article Journal of Coordination Chemistry ; Vol. 67, issue. 18 , Jul , 2014 , p. 3026-3032 Amini, M ; Najafpour, M. M ; Zare, M ; Holynska, M ; Moghaddam, A. N ; Bagherzadeh, M ; Sharif University of Technology
    In this paper, we report that a known dinuclear Fe complex, [tpa(H2O)FeOFe(H2O)tpa](ClO4)4 (tpa: tris(2-pyridylmethyl)amine), is an efficient catalyst toward organic sulfide oxidation in the presence of urea-hydrogen peroxide  

    Einstein solvmanifolds and graphs

    , Article Comptes Rendus Mathematique ; Volume 344, Issue 1 , 2007 , Pages 37-39 ; 1631073X (ISSN) Fanaï, H. R ; Sharif University of Technology
    In this Note, we obtain Einstein solvmanifolds using Abelian extension of two-step nilpotent Lie algebras associated with graphs. To cite this article: H.-R. Fanaï, C. R. Acad. Sci. Paris, Ser. I 344 (2007). © 2006 Académie des sciences  

    Colloidal gold nanoparticles: an unexpected catalytic activity in aqueous phase with dioxygen

    , Article catalysis letters ; Volume 144, Issue 7 , July , 2014 , pp. 1219-1222 ; 1572-879X Salari, H. (Hadi) ; Robatjazi, H. (Hossein) ; Hormozi-Nezhad, M. (Mohammad Reza) ; Padervand, M. (Mohsen) ; Gholami, M. R. (Mohammad Reza) ; Sharif University of Technology
    Selective oxidations of alkenes were investigated using molecular oxygen in aqueous solution under mild conditions. Colloidal gold nanoparticles are particularly versatile catalysts for oxidation reaction with exceptionally high efficiency and significant selectivity. Gold nanorods (Au NRs) exhibited a slightly enhanced activity compare to gold nanospheres  

    An efficient glucose-based ligand for Heck and Suzuki coupling reactions in aqueous media

    , Article Journal of the Iranian Chemical Society ; Vol. 11, issue. 2 , April , 2014 , p. 441-446 Bagherzadeh, M ; Amini, M ; Derakhshandeh, P. G ; Haghdoost, M. M ; Sharif University of Technology
    The glucose-based ligand, N-salicylidene-d-glucosamine (Sal-d-glsmN), was readily obtained by reaction of salicylaldehyde (Hsal) with the d-glucosamine hydrochloride. Ligand Sal-d-glsmN was found to be an efficient ligand in the palladium-catalyzed Suzuki and Heck C-C coupling reactions in aqueous medium under aerobic condition. It was found that the use of Sal-d-glsmN/Pd(OAc) 2 system as a catalyst, aryl halides undergo Suzuki and Heck cross-couplings, respectively, with arylboronic acids and olefins to give the desired products in moderate to excellent yields  

    On the existence of Κ-homogeneous Latin bitrades

    , Article Utilitas Mathematica ; Volume 85 , 2011 , Pages 333-345 ; 03153681 (ISSN) Bagheri Gh., B ; Mahmoodian, E. S ; Sharif University of Technology
    Let T be a partial Latin square and L a Latin square such that T ⊆ L.Then T is called a Latin trade, if there exists a partial Latin square T * such that T* ∩ T = ∅ and (LT) ∪ T* is a Latin square.We call T* a disjoint mate of T and the pair (T,T*) is called a Latin itrade.A Latin bitrade where empty rows and columns are ignored, is called a Κ-homogeneous Latin bitrade, if in each row and each column it contains exactly κ elements, and each element appears exactly k times.The number of filled cells in a Latin trade is referred to as its volume.Following the earlier work on κ-homogeneous Latin bitrades by Cavenagh, Donovan, and Drápal (2003 and 2004) Bean, Bidkhori, Khosravi, and... 

    Microstructure and mechanical properties of dual phase steels, with different martensite morphology, produced during TLP bonding of a low C-Mn steel

    , Article Metals and Materials International ; Volume 22, Issue 5 , 2016 , Pages 856-862 ; 15989623 (ISSN) Fazaeli, A ; Ekrami, A ; Kokabi, A. H ; Sharif University of Technology
    Korean Institute of Metals and Materials 
    In this research, production of ferrite - martensite dual phase Steels with different martensite morphology was considered during transient liquid phase bonding of a low carbon steel. The steel was bonded using an iron base interlayer with melting point of 1443 K and 40 μm thickness. Bonding process carried out at 1473 K, under pressure of 0.5 MPa, at different holding time of 10, 20, 30 and 40 minutes. Microstructural studies of joint region showed that isothermal solidification completed at the bonding time of 40 minutes. Microstructure of joints made at the bonding time of 10, 20, and 30 minutes consists of two distinct region, athermal and isothermal solidified zones. Microstructure of... 

    Homogenization of a locally periodic time-dependent domain

    , Article Communications on Pure and Applied Analysis ; Volume 19, Issue 3 , 2020 , Pages 1669-1695 Fotouhi, M ; Yousefnezhad, M ; Sharif University of Technology
    American Institute of Mathematical Sciences  2020
    We consider the homogenization of a Robin boundary value problem in a locally periodic perforated domain which is also time-dependent. We aim at justifying the homogenization limit, that we derive through asymptotic expansion technique. More exactly, we obtain the so-called corrector homogenization estimate that specifies the convergence rate. The major challenge is that the media is not cylindrical and changes over time. We also show the existence and uniqueness of solutions of the microscopic problem. © 2020 American Institute of Mathematical Sciences. All rights reserved  

    Homogeneous Einstein varieties of negative scalar curvature: Construction with the aid of certain Clifford modules [Variétés homogènes d'Einstein de courbure scalaire négative: Construction à l'aide de certains modules de Clifford]

    , Article Geometriae Dedicata ; Volume 93, Issue 1 , 2002 , Pages 77-87 ; 00465755 (ISSN) Fanaï, H. R ; Sharif University of Technology
    Using certain Clifford modules, we give a method for constructing many examples of homogeneous Einstein spaces with negative scalar curvature  

    Stability under Γ-convergence of least energy solutions for semilinear problems in the whole ℝN

    , Article SIAM Journal on Mathematical Analysis ; Volume 43, Issue 4 , 2011 , Pages 1759-1786 ; 00361410 (ISSN) Moameni, A ; Sharif University of Technology
    We study the homogenization of semilinear elliptic equations in divergence form with discontinuous oscillating coefficients in the whole ℝN. As is well known, the homogenization process in a classical framework is concerned with the study of asymptotic behavior of solutions u Isin; of boundary value problems when the period ∈ > 0 of the coefficients is small. By extending some of the classical homogenization results for quasi-linear elliptic equations to unbounded domains and, making use of various variational techniques, we shall establish some stability results under Γ-convergence of least energy solutions for such boundary value problems  

    Computational homogenization of fully coupled multiphase flow in deformable porous media

    , Article Computer Methods in Applied Mechanics and Engineering ; Volume 376 , April , 2021 ; 00457825 (ISSN) Khoei, A. R ; Saeedmonir, S ; Sharif University of Technology
    Elsevier B. V  2021
    In this paper, a computational modeling tool is developed for fully coupled multiphase flow in deformable heterogeneous porous medium that consists of complex and non-uniform micro-structures using the dual continuum scales based on the computational homogenization approach. The first-order homogenization technique is employed to perform the multi-scale analysis. The governing equations of two-phase flow of immiscible fluids, including an equilibrium equation and two mass continuity equations, are considered based on the appropriate main variables. According to the well-known Hill–Mandel principle of macro-homogeneity, the proper energy types are defined instead of conventional stress power... 

    A nonlocal computational homogenization of softening quasi-brittle materials

    , Article International Journal for Numerical Methods in Engineering ; Volume 119, Issue 8 , 2019 , Pages 712-736 ; 00295981 (ISSN) Khoei, A. R ; Saadat, M. A ; Sharif University of Technology
    John Wiley and Sons Ltd  2019
    In this paper, a computational counterpart of the experimental investigation is presented based on a nonlocal computational homogenization technique for extracting damage model parameters in quasi-brittle materials with softening behavior. The technique is illustrated by introducing the macroscopic nonlocal strain to eliminate the mesh sensitivity in the macroscale level as well as the size dependence of the representative volume element (RVE) in the first-order continuous homogenization. The macroscopic nonlocal strains are computed at each direction, and both the local and nonlocal strains are transferred to the microscale level. Two RVEs with similar geometries and material properties are... 

    Performance Simulation of HCCI Engine Equipped with Direct Injection System

    , M.Sc. Thesis Sharif University of Technology Mozaffari, Behnam (Author) ; Mozafari, Ali Asghar (Supervisor)
    HCCI engines have lower NOX and PM emissions and higher thermal efficiency compared to spark ignition engines. But these engines have some deficiencies which up to now have prevented their widespread employment. These engines have not been very successful at high loads and speeds and in these conditions normally produce high pollution and noise. In order to solve this problem the present research proposes to equip the HCCI engines with fuel injection system so that at low loads and speeds operate at HCCI engine mode and at loads and speeds higher than pre-set limits, use the fuel injection system in order to operate at a combined HCCI and compression ignition engine mode and provide a... 

    Homogenization of Hamilton - Jacobi Equations

    , M.Sc. Thesis Sharif University of Technology Sadeghi Arjmand, Saeed (Author) ; Fotouhi, Morteza (Supervisor)
    The aim of homogenization theory is to establish the macroscopic behaviour of a system which is ‘microscopically’ heterogeneous, in order to describe some characteristics of the heterogeneous medium (for instance, its thermal or electrical conductivity). This means that the heterogeneous material is replaced by a homogeneous fictitious one (the ‘homogenized’ material), whose global (or overall) characteristics are a good approximation of the initial ones. From the mathematical point of view, this signifies mainly that the solutions of a boundary value problem, depending on a small parameter, converge to the solution of a limit boundary value problem which is explicitly described. In... 

    On the existence of 3 -way k-homogeneous Latin trades

    , Article Discrete Mathematics ; Volume 312, Issue 24 , December , 2012 , Pages 3473-3481 ; 0012365X (ISSN) Bagheri Gh., B ; Donovan, D ; Mahmoodian, E. S ; Sharif University of Technology
    A μ-way Latin trade of volume s is a collection of μ partial Latin squares T1, T2,⋯, Tμ, containing exactly the same s filled cells, such that, if cell (i,j) is filled, it contains a different entry in each of the μ partial Latin squares, and such that row i in each of the μ partial Latin squares contains, set-wise, the same symbols, and column j likewise. It is called a μ-wayk-homogeneous Latin trade if, in each row and each column, Tr, for 1≤r≤μ, contains exactly k elements, and each element appears in Tr exactly k times. It is also denoted as a (μ,k,m) Latin trade, where m is the size of the partial Latin squares. We introduce some general constructions for μ-way k-homogeneous Latin... 

    SHTV, as a technique for core calculation using spatial homogenization and temperature variation

    , Article Annals of Nuclear Energy ; Volume 37, Issue 9 , 2010 , Pages 1129-1138 ; 03064549 (ISSN) Maleki Moghaddam, N ; Zahedinejad, E ; Kashi, S ; Davilu, H ; Sharif University of Technology
    The accuracy of static neutronic parameters in the nuclear reactors depends upon the determination of group constants of the diffusion equation in the desired geometry. Although several methods have been proposed for calculating these parameters, there is still the need for more reliable methods. In this paper a powerful and innovative method based on Spatial Homogenization and Temperature Variation (SHTV) of physical properties of a WWER-1000 nuclear reactor core for calculating the relative power distribution of Fuel Assemblies (FA) and the hot fuel rod, is presented. The method is based on replacing the heterogeneous lattices of materials with different properties by an equivalent... 

    Quelques propriétés des métriques d'einstein sur les groupes de lie résolubles

    , Article Rocky Mountain Journal of Mathematics ; Volume 37, Issue 6 , 2007 , Pages 1893-1903 ; 00357596 (ISSN) Fanaï, H. R ; Sharif University of Technology
    Using the formula for the Ricci tensor of a standard solvmanifold, we prove some properties of the map which defines the semi-direct product between the abelian part and the nilpotent part when our manifold is Einstein. Copyright ©2007 Rocky Mountain Mathematics Consortium  

    Kinetics and mechanism of 2-pyridylacetic acid pyrolysis in the gas phase: A joint experimental and theoretical study

    , Article Chemical Physics ; Volume 330, Issue 3 , 2006 , Pages 394-400 ; 03010104 (ISSN) Izadyar, M ; Zamani, N ; Gholami, M. R ; Sharif University of Technology
    A combination of the experimental and theoretical study was carried out on the reaction mechanism associated with the pyrolysis of 2-pyridylacetic acid in the gas phase. Methylpyridine and carbon dioxide were analyzed as the products, using a static system over the pressure range of 18-55 torr and the temperature of 541.2-583.4 K. The experimental kinetic data show that the pyrolysis process is homogeneous, unimolecular and proceeds through a concerted mechanism. Theoretical studies at the B3LYP level using the 6-31G* basis set confirmed an asynchronous concerted mechanism for the reaction. Computed kinetic and activation parameters are in good agreement with the experimental one. © 2006...