10,752 research outputs found
Differential variational inequalities
International audienceThis paper introduces and studies the class of differential variational inequalities (DVIs) in a finite-dimensional Euclidean space. The DVI provides a powerful modeling paradigm for many applied problems in which dynamics, inequalities, and discontinuities are present; examples of such problems include constrained time-dependent physical systems with unilateral constraints, differential Nash games, and hybrid engineering systems with variable structures. The DVI unifies several mathematical problem classes that include ordinary differential equations (ODEs) with smooth and discontinuous right-hand sides, differential algebraic equations (DAEs), dynamic complementarity systems , and evolutionary variational inequalities. Conditions are presented under which the DVI can be converted, either locally or globally, to an equivalent ODE with a Lipschitz continuous right-hand function. For DVIs that cannot be so converted, we consider their numerical resolution via an Euler time-stepping procedure, which involves the solution of a sequence of finite-dimensiona
Evolutionary-based sparse regression for the experimental identification of duffing oscillator
In this paper, an evolutionary-based sparse regression algorithm is proposed and applied onto experimental data collected from a Duffing oscillator setup and numerical simulation data. Our purpose is to identify the Coulomb friction terms as part of the ordinary differential equation of the system. Correct identification of this nonlinear system using sparse identification is hugely dependent on selecting the correct form of nonlinearity included in the function library. Consequently, in this work, the evolutionary-based sparse identification is replacing the need for user knowledge when constructing the library in sparse identification. Constructing the library based on the data-driven evolutionary approach is an effective way to extend the space of nonlinear functions, allowing for the sparse regression to be applied on an extensive space of functions. The results show that the method provides an effective algorithm for the purpose of unveiling the physical nature of the Duffing oscillator. In addition, the robustness of the identification algorithm is investigated for various levels of noise in simulation. The proposed method has possible applications to other nonlinear dynamic systems in mechatronics, robotics, and electronics
Prediction of Daily PM2.5 Concentration in China Using Data-Driven Ordinary Differential Equations
Accurate reporting and forecasting of PM2.5 concentration are important for
improving public health. In this paper, we propose a daily prediction method of
PM2.5 concentration by using data-driven ordinary differential equation (ODE)
models. Specifically, based on the historical PM2.5 concentration, this method
combines genetic programming and orthogonal least square method to evolve the
ODE models, which describe the transport of PM2.5 and then uses the data-driven
ODEs to predict the air quality in the future. Experiment results show that the
ODE models obtain similar prediction results as the typical statistical model,
and the prediction results from this method are relatively good. To our
knowledge, this is the first attempt to evolve data-driven ODE models to study
PM2.5 prediction
Two Species Evolutionary Game Model of User and Moderator Dynamics
We construct a two species evolutionary game model of an online society
consisting of ordinary users and behavior enforcers (moderators). Among
themselves, moderators play a coordination game choosing between being
"positive" or "negative" (or harsh) while ordinary users play prisoner's
dilemma. When interacting, moderators motivate good behavior (cooperation)
among the users through punitive actions while the moderators themselves are
encouraged or discouraged in their strategic choice by these interactions. We
show the following results: (i) We show that the -limit set of the
proposed system is sensitive both to the degree of punishment and the
proportion of moderators in closed form. (ii) We demonstrate that the basin of
attraction for the Pareto optimal strategy
can be computed exactly. (iii) We demonstrate that for certain initial
conditions the system is self-regulating. These results partially explain the
stability of many online users communities such as Reddit. We illustrate our
results with examples from this online system.Comment: 8 pages, 4 figures, submitted to 2012 ASE Conference on Social
Informatic
Fully Automated Myocardial Infarction Classification using Ordinary Differential Equations
Portable, Wearable and Wireless electrocardiogram (ECG) Systems have the
potential to be used as point-of-care for cardiovascular disease diagnostic
systems. Such wearable and wireless ECG systems require automatic detection of
cardiovascular disease. Even in the primary care, automation of ECG diagnostic
systems will improve efficiency of ECG diagnosis and reduce the minimal
training requirement of local healthcare workers. However, few fully automatic
myocardial infarction (MI) disease detection algorithms have well been
developed. This paper presents a novel automatic MI classification algorithm
using second order ordinary differential equation (ODE) with time varying
coefficients, which simultaneously captures morphological and dynamic feature
of highly correlated ECG signals. By effectively estimating the unobserved
state variables and the parameters of the second order ODE, the accuracy of the
classification was significantly improved. The estimated time varying
coefficients of the second order ODE were used as an input to the support
vector machine (SVM) for the MI classification. The proposed method was applied
to the PTB diagnostic ECG database within Physionet. The overall sensitivity,
specificity, and classification accuracy of 12 lead ECGs for MI binary
classifications were 98.7%, 96.4% and 98.3%, respectively. We also found that
even using one lead ECG signals, we can reach accuracy as high as 97%.
Multiclass MI classification is a challenging task but the developed ODE
approach for 12 lead ECGs coupled with multiclass SVM reached 96.4% accuracy
for classifying 5 subgroups of MI and healthy controls
Survey on Modelling Methods Applicable to Gene Regulatory Network
Gene Regulatory Network (GRN) plays an important role in knowing insight of
cellular life cycle. It gives information about at which different
environmental conditions genes of particular interest get over expressed or
under expressed. Modelling of GRN is nothing but finding interactive
relationships between genes. Interaction can be positive or negative. For
inference of GRN, time series data provided by Microarray technology is used.
Key factors to be considered while constructing GRN are scalability,
robustness, reliability and maximum detection of true positive interactions
between genes. This paper gives detailed technical review of existing methods
applied for building of GRN along with scope for future work
Learning Equilibria in Games by Stochastic Distributed Algorithms
We consider a class of fully stochastic and fully distributed algorithms,
that we prove to learn equilibria in games.
Indeed, we consider a family of stochastic distributed dynamics that we prove
to converge weakly (in the sense of weak convergence for probabilistic
processes) towards their mean-field limit, i.e an ordinary differential
equation (ODE) in the general case. We focus then on a class of stochastic
dynamics where this ODE turns out to be related to multipopulation replicator
dynamics.
Using facts known about convergence of this ODE, we discuss the convergence
of the initial stochastic dynamics: For general games, there might be
non-convergence, but when convergence of the ODE holds, considered stochastic
algorithms converge towards Nash equilibria. For games admitting Lyapunov
functions, that we call Lyapunov games, the stochastic dynamics converge. We
prove that any ordinal potential game, and hence any potential game is a
Lyapunov game, with a multiaffine Lyapunov function. For Lyapunov games with a
multiaffine Lyapunov function, we prove that this Lyapunov function is a
super-martingale over the stochastic dynamics. This leads a way to provide
bounds on their time of convergence by martingale arguments. This applies in
particular for many classes of games that have been considered in literature,
including several load balancing game scenarios and congestion games
Revealing hidden dynamics from time-series data by ODENet
To understand the hidden physical concepts from observed data is the most
basic but challenging problem in many fields. In this study, we propose a new
type of interpretable neural network called the ordinary differential equation
network (ODENet) to reveal the hidden dynamics buried in the massive
time-series data. Specifically, we construct explicit models presented by
ordinary differential equations (ODEs) to describe the observed data without
any prior knowledge. In contrast to other previous neural networks which are
black boxes for users, the ODENet in this work is an imitation of the
difference scheme for ODEs, with each step computed by an ODE solver, and thus
is completely understandable. Backpropagation algorithms are used to update the
coefficients of a group of orthogonal basis functions, which specify the
concrete form of ODEs, under the guidance of loss function with sparsity
requirement. From classical Lotka-Volterra equations to chaotic Lorenz
equations, the ODENet demonstrates its remarkable capability to deal with
time-series data. In the end, we apply the ODENet to real actin aggregation
data observed by experimentalists, and it shows an impressive performance as
well
Cycles in Nonlinear Macroeconomics
The monograph is concerned with some key problems of the theory of nonlinear
economic dynamics. The authors' concept consists in analyzing the problem of
structural instability of economic systems within the framework of the
synergetic paradigm. As examples, the classical models of macroeconomics are
considered. The authors present the results of the study of the phenomenon of
self-organization in open and nonequilibrium economic systems. The generation
of limit cycles, as well as of more complex periodic structures, is discussed;
the character of their stability is examined.Comment: 100 pages, 16 figures; the figures correcte
Splitting schemes for poroelasticity and thermoelasticity problems
In this work, we consider the coupled systems of linear unsteady partial
differential equations, which arise in the modeling of poroelasticity
processes. Stability estimates of weighted difference schemes for the coupled
system of equations are presented. Approximation in space is based on the
finite element method. We construct splitting schemes and give some numerical
comparisons for typical poroelasticity problems. The results of numerical
simulation of a 3D problem are presented. Special attention is given to using
hight performance computing systems.Comment: 19 pages, 8 figure
- …