2,525 research outputs found
Higher-order multi-scale deep Ritz method for multi-scale problems of authentic composite materials
The direct deep learning simulation for multi-scale problems remains a
challenging issue. In this work, a novel higher-order multi-scale deep Ritz
method (HOMS-DRM) is developed for thermal transfer equation of authentic
composite materials with highly oscillatory and discontinuous coefficients. In
this novel HOMS-DRM, higher-order multi-scale analysis and modeling are first
employed to overcome limitations of prohibitive computation and Frequency
Principle when direct deep learning simulation. Then, improved deep Ritz method
are designed to high-accuracy and mesh-free simulation for macroscopic
homogenized equation without multi-scale property and microscopic lower-order
and higher-order cell problems with highly discontinuous coefficients.
Moreover, the theoretical convergence of the proposed HOMS-DRM is rigorously
demonstrated under appropriate assumptions. Finally, extensive numerical
experiments are presented to show the computational accuracy of the proposed
HOMS-DRM. This study offers a robust and high-accuracy multi-scale deep
learning framework that enables the effective simulation and analysis of
multi-scale problems of authentic composite materials
On the validity of memristor modeling in the neural network literature
An analysis of the literature shows that there are two types of
non-memristive models that have been widely used in the modeling of so-called
"memristive" neural networks. Here, we demonstrate that such models have
nothing in common with the concept of memristive elements: they describe either
non-linear resistors or certain bi-state systems, which all are devices without
memory. Therefore, the results presented in a significant number of
publications are at least questionable, if not completely irrelevant to the
actual field of memristive neural networks
Nonlinear dynamics of full-range CNNs with time-varying delays and variable coefficients
In the article, the dynamical behaviours of the full-range cellular neural networks (FRCNNs) with variable coefficients and time-varying delays are considered. Firstly, the improved model of the FRCNNs is proposed, and the existence and uniqueness of the solution are studied by means of differential inclusions and set-valued analysis. Secondly, by using the Hardy inequality, the matrix analysis, and the Lyapunov functional method, we get some criteria for achieving the globally exponential stability (GES). Finally, some examples are provided to verify the correctness of the theoretical results
Bifurcations of piecewise smooth ļ¬ows:perspectives, methodologies and open problems
In this paper, the theory of bifurcations in piecewise smooth flows is critically surveyed. The focus is on results that hold in arbitrarily (but finitely) many dimensions, highlighting significant areas where a detailed understanding is presently lacking. The clearest results to date concern equilibria undergoing bifurcations at switching boundaries, and limit cycles undergoing grazing and sliding bifurcations. After discussing fundamental concepts, such as topological equivalence of two piecewise smooth systems, discontinuity-induced bifurcations are defined for equilibria and limit cycles. Conditions for equilibria to exist in n-dimensions are given, followed by the conditions under which they generically undergo codimension-one bifurcations. The extent of knowledge of their unfoldings is also summarized. Codimension-one bifurcations of limit cycles and boundary-intersection crossing are described together with techniques for their classification. Codimension-two bifurcations are discussed with suggestions for further study
Learning Homogenization for Elliptic Operators
Multiscale partial differential equations (PDEs) arise in various
applications, and several schemes have been developed to solve them
efficiently. Homogenization theory is a powerful methodology that eliminates
the small-scale dependence, resulting in simplified equations that are
computationally tractable. In the field of continuum mechanics, homogenization
is crucial for deriving constitutive laws that incorporate microscale physics
in order to formulate balance laws for the macroscopic quantities of interest.
However, obtaining homogenized constitutive laws is often challenging as they
do not in general have an analytic form and can exhibit phenomena not present
on the microscale. In response, data-driven learning of the constitutive law
has been proposed as appropriate for this task. However, a major challenge in
data-driven learning approaches for this problem has remained unexplored: the
impact of discontinuities and corner interfaces in the underlying material.
These discontinuities in the coefficients affect the smoothness of the
solutions of the underlying equations. Given the prevalence of discontinuous
materials in continuum mechanics applications, it is important to address the
challenge of learning in this context; in particular to develop underpinning
theory to establish the reliability of data-driven methods in this scientific
domain. The paper addresses this unexplored challenge by investigating the
learnability of homogenized constitutive laws for elliptic operators in the
presence of such complexities. Approximation theory is presented, and numerical
experiments are performed which validate the theory for the solution operator
defined by the cell-problem arising in homogenization for elliptic PDEs
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