| 1. |
- Argatov, Ivan, et al.
(författare)
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A note on artificial neural network modeling of vapor-liquid equilibrium in multicomponent mixtures
- 2019
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Ingår i: Fluid Phase Equilibria. - : Elsevier. - 0378-3812 .- 1879-0224. ; 502
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Tidskriftsartikel (refereegranskat)abstract
- Application of artificial neural networks (ANNs) for modeling of vapor-liquid equilibrium in multicomponent mixtures is considered. Two novel ANN-based models are introduced, which can be seen as generalizations of the Wilson model and the NRTL model. A unique feature of the proposed approach is that an ANN approximation for the molar excess Gibbs energy generates approximations for the activity coefficients. A special case of the ternary acetic acid-n-propyl alcohol-water system (at 313.15 K) is used to illustrate the efficiency of the different models, including Wilson's model, Focke's model, and the introduced generalized degree-1 homogeneous neural network model. Also, the latter one-level NN model is compared to the Wilson model on 10 binary systems. The efficiency of the two-level NN model is assessed by a comparison with the NRTL model. (C) 2019 Elsevier B.V. All rights reserved.
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| 2. |
- Argatov, Ivan, et al.
(författare)
-
A simple mathematical model for the resonance frequency analysis of dental implant stability : Implant clamping quotient.
- 2019
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Ingår i: Mechanics research communications. - : Elsevier. - 0093-6413 .- 1873-3972. ; 95, s. 67-70
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Tidskriftsartikel (refereegranskat)abstract
- A simple mathematical model for free vibrations of an elastically clamped beam is suggested to interpret the results of the resonance frequency analysis developed for implant stability measurements in terms of the Implant Stability Quotient (ISQ) units. It is shown that the resonance frequency substantially depends on the lateral compliance of the implant/bone system. Based on the notion of the lateral stiffness of the implant/bone system, a new measure of the implant stability is introduced in the form similar to the ISQ scale and is called the Implant Clamping Quotient (ICQ), because it characterizes the jawbone’s clamp of the implant. By definition, the ICQ unit is equal to a percentage of the original scale for the lateral stiffness of the implant/bone system.
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| 3. |
- Argatov, Ivan, et al.
(författare)
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An empirical model for sorption by glassy polymers : An assessment of thermodynamic parameters
- 2021
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Ingår i: Polymer testing. - : Elsevier. - 0142-9418 .- 1873-2348. ; 99
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Tidskriftsartikel (refereegranskat)abstract
- A new fitting model for sorption by glassy polymers is suggested based on the Flory–Huggins (FH) equation with a composite formula for the FH interaction parameter, χ, which is applicable if sorption experimental data shows a single-maximum variation of the FH parameter. Namely, a power-like and a linear approximation is assumed for χ(φ1), as a function of solvent volume fraction φ1, before and after the point of its maximum. After determining the maximum point from a direct inspection of the sorption data, the three fitting parameters are evaluated by solving two independent least-square minimization problems. Several sorption studies of biopolymers taken from the literature show that the endset of the glass transition region is correlated with the position of the maximum of the FH interaction parameter. Based on this hypothesis and the Vrentas–Vrentas model for sorption of glassy polymers, a theoretical framework for the glass transition analysis is developed. In particular, the solvent-induced glass transition temperature variation can be estimated from the sorption isotherm as a function of the solvent content corresponding to temperatures above the temperature of sorption.
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| 4. |
- Argatov, Ivan, et al.
(författare)
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Analysis of the minimal model for the enthalpy relaxation and recovery in glass transition : application to constant-rate differential scanning calorimetry
- 2021
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Ingår i: Continuum Mechanics and Thermodynamics. - : Springer. - 0935-1175 .- 1432-0959. ; 33, s. 107-123
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Tidskriftsartikel (refereegranskat)abstract
- The so-called minimal model is formulated for describing the enthalpy relaxation and recovery in glass transition. The model is based on the Arrhenius law for the enthalpy relaxation, which uses two-dimensional parameters, namely the activation energy and the so-called pre-factor (relaxation time at relatively high temperature). A numerically effective exact analytical solution is obtained for the case of constant-rate differential scanning calorimetry. The developed model is analyzed according to the logic of the model itself without introducing additional simplifying assumptions of thermodynamic nature. For typical range of the model parameters, the resulting differential equation contains a large parameter, which offers an opportunity for the application of asymptotic and approximate techniques. A number of simple approximations have been provided for some thermodynamic quantities of interest.
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| 5. |
- Argatov, Ivan, et al.
(författare)
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Axisymmetric JKR-type adhesive contact under equibiaxial stretching
- 2021
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Ingår i: The journal of adhesion. - : Taylor & Francis. - 0021-8464 .- 1563-518X .- 1545-5823. ; 97:2, s. 140-154
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Tidskriftsartikel (refereegranskat)abstract
- An axisymmetric frictionless adhesive contact problem for a spherical indenter pressed against an isotropic elastic incompressible half-space under equibiaxial stretching is studied in the framework of the generalized Johnson-Kendall-Roberts (JKR) theory, which accounts for the effect of weak coupling between fracture modes I and II by means of a phenomenological mode-mixity function. The model predicts that contact area can withstand a larger level of the substrate stretch under moderate pre-pulling force. We have provided simple formulas to evaluate the pull-off force and the critical contact radius at the detachment point.
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| 6. |
- Argatov, Ivan
(författare)
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Controlling the adhesive pull-off force via the change of contact geometry
- 2021
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Ingår i: Philosophical Transactions. Series A. - : The Royal Society. - 1364-503X .- 1471-2962. ; 379:2203
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Tidskriftsartikel (refereegranskat)abstract
- A first-order asymptotic analysis of the Griffith energy balance in the Johnson-Kendall-Roberts model of adhesive contact under non-symmetric perturbation of the contact geometry is presented. The pull-off force is evaluated in explicit form. A particular case of adhesive contact between a relatively stiff sphere and an elastic half-space is considered under the assumption that the sphere geometry is changed by the application of an arbitrary lateral normal surface loading. The effect of the sphere Poisson's ratio on controlling the adhesive pull-off force is considered.This article is part of a discussion meeting issue 'A cracking approach to inventing new tough materials: fracture stranger than friction'.
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| 7. |
- Argatov, Ivan, et al.
(författare)
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Dynamics of post-occlusion water diffusion in stratum corneum
- 2022
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Diffusion of water through membranes presents a considerable challenge, as the diffusivity often depends on the local concentration of water. One particular example with strong biological relevance is the stratum corneum (SC) as the primary permeability barrier for the skin. A simple alternative for the constant diffusivity model is provided by the Fujita's two-parameter rational approximation, which captures the experimentally observed fact that the SC diffusion constant for water increases with increasing the water concentration. Based on Fick's law of diffusion, a one-dimensional concentration-dependent diffusion model is developed and applied for the analysis of both the steady-state transepidermal water loss (TEWL) and the non-steady-state so-called skin surface water loss (SSWL) occurred after removal of an occlusion patch from the SC surface. It is shown that some of the age-related changes in the SSWL can be qualitatively explained by the variation of the dimensionless Fujita concentration-dependence parameter.
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| 8. |
- Argatov, Ivan, et al.
(författare)
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Elliptical adhesive contact under biaxial stretching
- 2020
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Ingår i: Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences. - : The Royal Society Publishing. - 1364-5021 .- 1471-2946. ; 476:2233
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Tidskriftsartikel (refereegranskat)abstract
- Adhesive contact of the Hertzian indenter with an incompressible elastic substrate bi-directionally stretched along the indenter principal planes of curvature is considered in the Johnson-Kendall-Roberts theoretical framework. An approximate model is constructed by examining energy release rate conditions only on the edges of the minor and major axes of the contact ellipse. The effect of weak coupling between fracture modes I and II is introduced using a phenomenological mode-mixity function. This study was motivated by the need to model a passive-adhesive mechanism in cell mechanics on stretchable substrates.
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| 9. |
- Argatov, Ivan
(författare)
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From Winkler's Foundation to Popov's Foundation
- 2019
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Ingår i: Facta Universitatis-Series Mechanical Engineering. - : University of Jyväskylä, Finnish Institute for Educational Research. - 0354-2025. ; 17:2, s. 181-190
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, the method of dimensionality reduction (DR) has started to figure as a very convenient tool for dealing with a wide class of elastic contact problems. The MDR modeling framework introduces an equivalent punch profile and a one-dimensional Winkler-type elastic foundation, called henceforth Popov's foundation. While the former mainly accounts for the geometry of contact configuration, the Popov foundation inherits the main characteristics of both the contact interface (like friction and adhesion) and the contacting elastic bodies (e.g., anisotropy, viscoelasticity or inhomogeneity). The discussion is illustrated with an example of the Kendall-type adhesive contact for an isotropic elastic half-space.
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| 10. |
- Argatov, Ivan, et al.
(författare)
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Gravitational settling of a cell on a high-aspect-ratio nanostructured substrate : An asymptotic modeling approach
- 2022
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Ingår i: Applied Mathematical Modelling. - : Elsevier. - 0307-904X .- 1872-8480. ; 108, s. 294-307
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Tidskriftsartikel (refereegranskat)abstract
- The problem of contact deformation of an elastic body loaded by gravitational forces and laying on several small rigid supports is considered in the framework of the linear theory of elasticity. Using the method of matched asymptotic expansions, the limit asymptotic model for determining the support reactions and the kinematic parameters of the body settling is derived. The effect of the body surface reinforcement is discussed. The case of a uniform (symmetric) settling is considered in detail.
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