2063 research outputs found
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Three-dimensional soliton-like distortions in flexoelectric nematic liquid crystals: modelling and linear analysis
Get PDFThis article models experimentally observed three-dimensional particle-like waves that develop in nematic liquid crystals, with negative dielectric and conductive anisotropy, when subject to an applied alternating electric field. The liquid crystal is confined in a thin region between two plates, perpendicular to the applied field. The horizontal, uniformly aligned director field is at equilibrium due to the negative anisotropy of the media. However, such a state is unstable to perturbations that manifest themselves as confined, bullet-like, director distortions travelling up and down the sample at a speed of several hundred microns per second. It is experimentally predicted that flexoelectricity plays a key role in generating the soliton-like behaviour. We develop a variational model that accounts for ansiostropic dielectric, conductive, flexolectric, elastic and viscous forces. We perform a stability analysis of the uniformly aligned equilibrium state to determine the threshold wave numbers, size, phase-shift and speed of the soliton-like disturbance. We show that the model predictions are in very good agreement with the experimentally measured values. The work models and analyzes a three-dimensional soliton-like instability reported, for the first time in flexoelectric liquid crystals, pointing towards a potential application as a new type of nanotransport device
Conformal Parametric Microstructure Synthesis for Boundary Representations
Get PDFThe use of lattices and microstructures in geometric design have been recognized as potentially superior to solid
structures due to the potential benefits in improved strength-to-weight ratios, better control over heat exchange and
heat transfer, and so on.
In this work, we present a construction scheme to create parametric microstructures in a boundary representation
(B-rep) model, M, that are conformal to an arbitrary specification, including the boundary of M. Given a B-rep
model, M, either a polygonal or trimmed-spline based, a cage, T, is constructed around M to guide the synthesis of
the microstructures in M. Micro-elements are synthesized following T, and verified to be inside M while bridging
tiles are added as necessary. These parametric micro-elements can be heterogeneous in their material content, as well
as locally vary in their geometric properties.
We demonstrate these abilities with example microstructures synthesized from both polygonal B-rep models and
spline-based B-rep solids, including 3D printed parts
On the equivalence of the KMS condition and the variational principle for quantum lattice systems with mean-field interactions
Get PDFWe extend Araki’s well-known results on the equivalence of the KMS condition and the variational principle for equilibrium states of quantum lattice systems with short-range interactions, to a large class of models possibly containing mean-field interactions (representing an extreme form of long-range interactions). This result is reminiscent of van Hemmen’s work on equilibrium states for meanfield models. The extension was made possible by our recent outcomes on states minimizing the free energy density of mean-field models on the lattice, as well as on the infinite volume dynamics for such models.CNPq (309723/2020-5), CNPq (140782/2020-6) and FAPESP (2017/22340-9). Project of Basque Government through the grant IT1615-22. COST Action CA18232 financed by the European Cooperation in Science and Technology (COST). Project PID2020-112948GB-I00 funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe"
Motion of a rigid body in a compressible fluid with Navier-slip boundary condition
No full textIn this work, we study the motion of a rigid body in a bounded domain which is filled with a compressible isentropic fluid. We consider the Navier-slip boundary condition at the interface as well as at the boundary of the domain. This is the first mathematical analysis of a compressible fluid-rigid body system where Navier-slip boundary conditions are considered. We prove existence of a weak solution of the fluid-structure system up to collision
Variational Bayesian Framework for Advanced Image Generation with Domain-Related Variables
Get PDFDeep generative models (DGMs) and their conditional
counterparts provide a powerful ability for general-purpose
generative modeling of data distributions. However, it remains
challenging for existing methods to address advanced
conditional generative problems without annotations, which
can enable multiple applications like image-to-image translation
and image editing. We present a unified Bayesian
framework for such problems, which introduces an inference
stage on latent variables within the learning process. In particular,
we propose a variational Bayesian image translation
network (VBITN) that enables multiple image translation
and editing tasks. Comprehensive experiments show the effectiveness
of our method on unsupervised image-to-image
translation, and demonstrate the novel advanced capabilities
for semantic editing and mixed domain translation
Numerical Regge pole analysis of resonance structures in state-to-state reactive differential cross sections
Get PDFThis is the third (and the last) code in a collection of three programs [Sokolovski et al. (2011), Akhmatskaya et al. (2014)] dedicated to the analysis of numerical data, obtained in an accurate simulation of an atom-diatom chemical reaction. Our purpose is to provide a detailed description of a FORTRAN code for complex angular momentum (CAM) analysis of the resonance effects in reactive angular scattering [for CAM analysis of integral reactive cross sections see [Akhmatskaya et al. (2014)]. The code evaluates the contributions of a Regge trajectory (or trajectories) to a differential cross section in a specified range of energies. The contribution is computed with the help of the methods described in [Dobbyn et al. (1999), Sokolovski and Msezane (2004), Sokolovski et al. (2007)]. Regge pole positions and residues are obtained by analytically continuing S-matrix element, calculated numerically for the physical integer values of the total angular momentum, into the complex angular momentum plane using the PADE_II program [Sokolovski et al. (2011)]. The code represents a reactive scattering amplitude as a sum of the components corresponding to a rapid “direct” exchange of the atom, and the various scenarios in which the reactants form long-lived intermediate complexes, able to complete several rotations before breaking up into products. The package has been successfully tested on the representative models, as well as the F + H2→HF+H benchmark reaction. Several detailed examples are given in the text
A phenomenological model for interfacial water near hydrophilic polymers
Get PDFWe propose a minimalist phenomenological model for the ‘interfacial water’ phenomenon that
occurs near hydrophilic polymeric surfaces. We achieve this by combining a Ginzburg–Landau
approach with Maxwell’s equations which leads us to a well-posed model providing a
macroscopic interpretation of experimental observations. From the derived governing equations,
we estimate the unknown parameters using experimental measurements from the literature. The
resulting profiles of the polarization and electric potential show exponential decay near the
surface, in qualitative agreement with experiments. Furthermore, the model’s quantitative
prediction of the electric potential at the hydrophilic surface is in excellent agreement with
experiments. The proposed model is a first step towards a more complete parsimonious
macroscopic model that will, for example, help to elucidate the effects of interfacial water on
cells (e.g. neuronal excitability), the effects of infrared neural stimulation or the effects of drugs
mediated by interfacial water.Ikerbasque (The Basque Foundation for Science)
Inria Associated Team "NeuroTransSF
An active adaptation strategy for streaming time series classification based on elastic similarity measures
Get PDFIn streaming time series classification problems, the goal is to predict the label associated to the most recently received observations over the stream according to a set of categorized reference patterns. In on-line scenarios, data arise from non-stationary processes, which results in a succession of different patterns or events. This work presents an active adaptation strategy that allows time series classifiers to accommodate to the dynamics of streamed time series data. Specifically, our approach consists of a classifier that detects changes between events over streaming time series. For this purpose, the classifier uses features of the dynamic time warping measure computed between the streamed data and a set of reference patterns. When classifying a streaming series, the proposed pattern end detector analyzes such features to predict changes and adapt off-line time series classifiers to newly arriving events. To evaluate the performance of the proposed scheme, we employ the pattern end detection model along with dynamic time warping-based nearest neighbor classifiers over a benchmark of ten time series classification problems. The obtained results present exciting insights into the detection accuracy and latency performance of the proposed strategy.BERC-2022-20
A b-symplectic slice theorem
No full textIn this article, motivated by the study of symplectic structures on manifolds with boundary and the systematic study of b -symplectic manifolds started in Guillemin, Miranda, and Pires Adv. Math. 264 (2014), 864–896, we prove a slice theorem for Lie group actions on b-symplectic manifolds
Analysis of the initial phase of COVID-19 epidemics in Italy: a modeling study
Get PDFThis thesis describes the first years of COVID-19 pandemic in Italy. We started looking at the data given by the Italian Civil Protection and according to the trend we nally described the epidemiological curve through a SHAR model. In this model, the infection rate β changing according to different period that we identied during the rst year of pandemic. To model β, we have taken into account the effect of control measures (Lockdown, social distancing, protection devices) and seasonality