The Experts below are selected from a list of 150 Experts worldwide ranked by ideXlab platform
Krisztina Kiss - One of the best experts on this subject based on the ideXlab platform.
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n-Dimensional Ratio-dependent predator-prey systems with memory
Differential Equations and Dynamical Systems, 2009Co-Authors: Krisztina Kiss, János TóthAbstract:This paper deals with Ratio-dependent predator-prey systems with delay. We will investigate under what conditions delay cannot cause instability in higher dimensions. We give an example when delay causes instability.
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On the dynamics of an n-Dimensional Ratio-dependent predator–prey system with diffusion
Applied Mathematics and Computation, 2009Co-Authors: Cosme Duque, Krisztina Kiss, Marcos LizanaAbstract:Abstract The main concern of this paper is to study the dynamic of an n -Dimensional Ratio-dependent predator–prey system with diffusion. More concretely, we study the dissipativeness, the persistence of the system and we obtain condition under which the nontrivial equilibrium is globally asymptotically stable.
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n-Dimensional Ratio-dependent predator–prey systems with diffusion
Applied Mathematics and Computation, 2008Co-Authors: Krisztina KissAbstract:Abstract This paper deals with a Ratio-dependent predator–prey system with diffusion. We will investigate under what conditions Turing stability or instability occurs in higher dimensions.
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Qualitative behavior of n-Dimensional Ratio-dependent predator–prey systems
Applied Mathematics and Computation, 2008Co-Authors: Krisztina Kiss, Sándor KovácsAbstract:Abstract This paper deals with the qualitative properties of an n -Dimensional autonomous system of differential equations, modeling the general Ratio-dependent predator–prey interaction.
Mohammad Mehdi Rashidi - One of the best experts on this subject based on the ideXlab platform.
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numerical investigation of water alumina nanofluid natural convection heat transfer and entropy geneRation in a baffled l shaped cavity
Journal of Molecular Liquids, 2016Co-Authors: T Armaghani, N Alavi, Abbas Kasaeipoor, Mohammad Mehdi RashidiAbstract:Abstract This article presents a numerical study of natural convection heat transfer and entropy geneRation of water-alumina nanofluid in baffled L-shaped cavity. The left vertical and bottom walls are placed in hot and constant Th temperature and the middle horizontal and right vertical walls are in cold and constant Tc temperature. The other walls are insulated. The baffle's temperature is Tc and their existence in cavity has a lot of impacts on flow behavior and it could disrupt flow order. The governing equations are solved numerically with Finite Volume Method using the SIMPLER algorithm simultaneously. The convection heat transfer results show: AR (aspect Ratio) increasing enhances heat transfer. With Dimensional Ratio increasing, nanofluid has a greater impact on Nusselt growing. By baffle length increasing nanofluid has less impact on cooling cavity, as a result heat transfer raises. The entropy geneRation of mentioned parameters are also investigated and discussed. Finally, with studding the e = Sm/Num (named thermal performance) the best AR and baffle length are introduced.
Boris Kaus - One of the best experts on this subject based on the ideXlab platform.
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factors that control the angle of shear bands in geodynamic numerical models of brittle deformation
Tectonophysics, 2010Co-Authors: Boris KausAbstract:Abstract Numerical models of brittle deformation on geological timescales typically use a pressure-dependent (Mohr–Coulomb or Drucker–Prager) plastic flow law to simulate plastic failure. Despite its widespread usage in geodynamic models of lithospheric deformation, however, certain aspects of such plasticity models remain poorly understood. One of the most prominent questions in this respect is: what are the factors that control the angle of the resulting shear bands? Recent theoretical work suggest that both Roscoe (45°), Coulomb angles (45 +/− ϕ/2, where ϕ is the angle of internal friction) and Arthur angles (45° +/− (ϕ + Ψ/4) where Ψ is the dilation angle), as well as all intermediate angles are possible. Published numerical models, however, show a large range of shear band angles with some codes favoring Arthur angles, whereas others yield Coulomb angles. In order to understand what causes the differences between the various numerical models, here I perform systematic numerical simulations of shear localization around an inclusion of given length scale. Both numerical (element type), geometrical and rheological (viscoplastic versus viscoelastoplastic) effects are studied. Results indicate that the main factor, controlling shear band angle, is the non-Dimensional Ratio between the length scale of the heterogeneity d and the size of the numerical mesh Δx. Coulomb angles are observed only in cases where the inclusion is resolved well (d/Δx > 5–10), and in which it is located sufficiently far from the boundary of the box. In most other cases, either Arthur or Roscoe orientations are observed. If heterogeneities are one element in size, Coulomb angles are thus unlikely to develop irrespective of the employed numerical resolution. Whereas differences in element types and rheology do have consequences for the maximum obtainable strain rates inside the shear bands, they only have a minor effect on shear band angles. Shear bands, initiated from random noise or from interactions of shear bands with model boundaries or other shear bands, result in stress heterogeneities with dimensionless length scales d/Δx ~ 1–2. Such shear bands are thus expected to form Roscoe or Arthur orientations, consistent with the findings in previous numerical models.
Sung Kun Chung - One of the best experts on this subject based on the ideXlab platform.
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Optical quality in central serous chorioretinopathy.
Investigative ophthalmology & visual science, 2014Co-Authors: Kyung-min Lee, Joonhong Sohn, Jong Gil Choi, Sung Kun ChungAbstract:PURPOSE To assess optical quality and intraocular scattering using the Optical Quality Analysis System (OQAS) in central serous chorioretinopathy (CSC) and to determine the effects of retinal changes on optical quality. METHODS This was a prospective, case-control study. Participants were 29 patients with diagnosis of CSC. The control group consisted of the patients' unaffected eyes. Initial logMAR visual acuity, central macular thickness (by spectral domain optical coherence tomography), and optical quality parameters including modulation transfer function (MTF) cutoff frequency, Strehl (2-Dimensional) Ratio, and OQAS values at 100%, 20%, and 9% contrast levels were investigated. Objective scattering index (OSI) at 4.0-mm pupil size was assessed in both eyes by using the OQAS. After 3 months of treatment, which included observation and focal laser or injections of antivascular endothelial growth factor, every CSC-affected eye was followed. Main outcome measures were differences between clinical parameters of the CSC-affected eye and those of the control eye and changes in those parameters according to the clinical course of CSC over 3 months. RESULTS In CSC-affected eyes, the MTF cutoff was significantly reduced (P = 0.01), and OSI was significantly increased (P = 0.03). As macular thickness decreased, OSI decreased but did not become normalized compared to the control eye, nor was it statistically significantly correlated with central macular thickness change. CONCLUSIONS Retinal change affected optical quality and intraocular scatter. Therefore, when the severity of a cataract is assessed using the OQAS, retinal status should be considered when interpreting OQAS values.
Abbas Kasaeipoor - One of the best experts on this subject based on the ideXlab platform.
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Physical investigation on silver-water nanofluid natural convection for an F-shaped cavity under the magnetic field effects
The European Physical Journal Plus, 2017Co-Authors: A. Yadollahi, Abbas Kasaeipoor, A. Khalesidoost, Mohammad Hatami, D. JingAbstract:The effects of a magnetic field on a free convection regime of silver-water nanofluid are investigated. The considered geometry is an F-shaped cavity under the influence of a constant magnetic field. The left vertical walls temperature is Th, while the middle and right walls are at a constant temperature Tc, and the other walls are insulated. A FORTRAN program is developed for the numerical simulation of the considered problem. The governing equations are solved using the FVM with the SIMPLE algorithm. The effect of important physical parameters such as the Rayleigh number, the Hartmann number, AR and $ \phi$ on the problem are discussed in detail. We have concluded that the increase in the Hartmann number causes a decrease in vertical velocity and heat transfer. By increasing the Rayleigh number, the influence of the Hartmann number will be increased. An increase in the Dimensional Ratio of the cavity causes a decrease in the Nusselt number except in AR = 0.4. The AR has the maximum impact on the local Nusselt number, at the bottom of the hot wall. The effect of the Dimensional Ratio of the cavity on the Nusselt number is reversed on top of the wall. The maximum value of the Nusselt number is observed at AR = 0.4.
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numerical investigation of water alumina nanofluid natural convection heat transfer and entropy geneRation in a baffled l shaped cavity
Journal of Molecular Liquids, 2016Co-Authors: T Armaghani, N Alavi, Abbas Kasaeipoor, Mohammad Mehdi RashidiAbstract:Abstract This article presents a numerical study of natural convection heat transfer and entropy geneRation of water-alumina nanofluid in baffled L-shaped cavity. The left vertical and bottom walls are placed in hot and constant Th temperature and the middle horizontal and right vertical walls are in cold and constant Tc temperature. The other walls are insulated. The baffle's temperature is Tc and their existence in cavity has a lot of impacts on flow behavior and it could disrupt flow order. The governing equations are solved numerically with Finite Volume Method using the SIMPLER algorithm simultaneously. The convection heat transfer results show: AR (aspect Ratio) increasing enhances heat transfer. With Dimensional Ratio increasing, nanofluid has a greater impact on Nusselt growing. By baffle length increasing nanofluid has less impact on cooling cavity, as a result heat transfer raises. The entropy geneRation of mentioned parameters are also investigated and discussed. Finally, with studding the e = Sm/Num (named thermal performance) the best AR and baffle length are introduced.