175 research outputs found
Electric-field-induced displacement of a charged spherical colloid embedded in an elastic Brinkman medium
When an electric field is applied to an electrolyte-saturated polymer gel
embedded with charged colloidal particles, the force that must be exerted by
the hydrogel on each particle reflects a delicate balance of electrical,
hydrodynamic and elastic stresses. This paper examines the displacement of a
single charged spherical inclusion embedded in an uncharged hydrogel. We
present numerically exact solutions of coupled electrokinetic transport and
elastic-deformation equations, where the gel is treated as an incompressible,
elastic Brinkman medium. This model problem demonstrates how the displacement
depends on the particle size and charge, the electrolyte ionic strength, and
Young's modulus of the polymer skeleton. The numerics are verified, in part,
with an analytical (boundary-layer) theory valid when the Debye length is much
smaller than the particle radius. Further, we identify a close connection
between the displacement when a colloid is immobilized in a gel and its
velocity when dispersed in a Newtonian electrolyte. Finally, we describe an
experiment where nanometer-scale displacements might be accurately measured
using back-focal-plane interferometry. The purpose of such an experiment is to
probe physicochemical and rheological characteristics of hydrogel composites,
possibly during gelation
Mapping of the Influenza-A Hemagglutinin Serotypes Evolution by the ISSCOR Method
Analyses and visualizations by the ISSCOR method of influenza virus
hemagglutinin genes of different A-subtypes revealed some rather striking
temporal relationships between groups of individual gene subsets. Based on
these findings we consider application of the ISSCOR-PCA method for analyses of
large sets of homologous genes to be a worthwhile addition to a toolbox of
genomics - allowing for a rapid diagnostics of trends, and ultimately even
aiding an early warning of newly emerging epidemiological threats.Comment: 26 pages with figures (Figs. 1-4 in the main text, and Figs. S1-S5 in
supplementary materials
Infinite-Dimensional Adaptive Boundary Observer for Inner-Domain Temperature Estimation of 3D Electrosurgical Processes using Surface Thermography Sensing
We present a novel 3D adaptive observer framework for use in the
determination of subsurface organic tissue temperatures in electrosurgery. The
observer structure leverages pointwise 2D surface temperature readings obtained
from a real-time infrared thermographer for both parameter estimation and
temperature field observation. We introduce a novel approach to decoupled
parameter adaptation and estimation, wherein the parameter estimation can run
in real-time, while the observer loop runs on a slower time scale. To achieve
this, we introduce a novel parameter estimation method known as attention-based
noise-robust averaging, in which surface thermography time series are used to
directly estimate the tissue's diffusivity. Our observer contains a real-time
parameter adaptation component based on this diffusivity adaptation law, as
well as a Luenberger-type corrector based on the sensed surface temperature. In
this work, we also present a novel model structure adapted to the setting of
robotic surgery, wherein we model the electrosurgical heat distribution as a
compactly supported magnitude- and velocity-controlled heat source involving a
new nonlinear input mapping. We demonstrate satisfactory performance of the
adaptive observer in simulation, using real-life experimental ex vivo porcine
tissue data.Comment: Paper accepted to the 2022 IEEE Conference on Decision and Control
(CDC 2022
Dynamic interaction of plates in an inhomogeneous transversely isotropic space weakened by a crack
The problem of axisymmetric vibration of a flat thin rigid circular plate located inside a vertically exponentially graded, transversely isotropic material of infinite extent is addressed by means of a displacement potential method. The contact condition on one side of the foundation is assumed to be the perfect adhesion with the media but known to be faced by a penny-shaped crack at the other side as it occurs in anchors. The mixed boundary value problem is formulated with the aid of Hankel integral transforms and is written in the form of a set of singular integral equations. The analytical procedure for the special case of vertical movement of the rigid plate results in a closed form solution. The solution is pursued numerically for the general elastodynamic case. The physical quantities, such as contact stress on the plate and the stress and displacement fields in the non-homogeneous medium are obtained for different materials
A Stochastic Multi-scale Approach for Numerical Modeling of Complex Materials - Application to Uniaxial Cyclic Response of Concrete
In complex materials, numerous intertwined phenomena underlie the overall
response at macroscale. These phenomena can pertain to different engineering
fields (mechanical , chemical, electrical), occur at different scales, can
appear as uncertain, and are nonlinear. Interacting with complex materials thus
calls for developing nonlinear computational approaches where multi-scale
techniques that grasp key phenomena at the relevant scale need to be mingled
with stochastic methods accounting for uncertainties. In this chapter, we
develop such a computational approach for modeling the mechanical response of a
representative volume of concrete in uniaxial cyclic loading. A mesoscale is
defined such that it represents an equivalent heterogeneous medium: nonlinear
local response is modeled in the framework of Thermodynamics with Internal
Variables; spatial variability of the local response is represented by
correlated random vector fields generated with the Spectral Representation
Method. Macroscale response is recovered through standard ho-mogenization
procedure from Micromechanics and shows salient features of the uniaxial cyclic
response of concrete that are not explicitly modeled at mesoscale.Comment: Computational Methods for Solids and Fluids, 41, Springer
International Publishing, pp.123-160, 2016, Computational Methods in Applied
Sciences, 978-3-319-27994-
Computational Homogenization of Architectured Materials
Architectured materials involve geometrically engineered distributions of microstructural phases at a scale comparable to the scale of the component, thus calling for new models in order to determine the effective properties of materials. The present chapter aims at providing such models, in the case of mechanical properties. As a matter of fact, one engineering challenge is to predict the effective properties of such materials; computational homogenization using finite element analysis is a powerful tool to do so. Homogenized behavior of architectured materials can thus be used in large structural computations, hence enabling the dissemination of architectured materials in the industry. Furthermore, computational homogenization is the basis for computational topology optimization which will give rise to the next generation of architectured materials. This chapter covers the computational homogenization of periodic architectured materials in elasticity and plasticity, as well as the homogenization and representativity of random architectured materials
Minority carriers lifetime degradation during ion implanted silicon solar cell processing
In this work a silicon solar cell fabrication process based on ion implantation followed by low temperature thermal annealing is analysed. It is shown, by using the surface photovoltage technique, that the base lifetime degradation can be almost completely avoided, so that ion implanted solar cells with high conversion efficiency can be fabricated.Dans cet article on analyse un procédé de fabrication de photopiles solaires au Si basé sur l'implantation ionique suivie par un recuit thermique à basse température. On démontre que par l'utilisation de la technique du photovoltage de surface, la dégradation de la durée de vie de la base peut être presque complètement évitée; c'est pourquoi il est possible de construire des cellules solaires avec un rendement élevé de conversion
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