1,422 research outputs found
A new model of binary opinion dynamics: coarsening and effect of disorder
We propose a model of binary opinion in which the opinion of the individuals
change according to the state of their neighbouring domains. If the
neighbouring domains have opposite opinions, then the opinion of the domain
with the larger size is followed. Starting from a random configuration, the
system evolves to a homogeneous state. The dynamical evolution show novel
scaling behaviour with the persistence exponent and
dynamic exponent . Introducing disorder through a
parameter called rigidity coefficient (probability that people are
completely rigid and never change their opinion), the transition to a
heterogeneous society at is obtained. Close to , the
equilibrium values of the dynamic variables show power law scaling behaviour
with . We also discuss the effect of having both quenched and annealed
disorder in the system.Comment: 4 pages, 6 figures, Final version of PR
Localized Computation of Newton Updates in Fully-implicit Two-phase Flow Simulation
AbstractFully-Implicit (FI) Methods are often employed in the numerical simulation of large-scale subsurface flows in porous media. At each implicit time step, a Newton-like method is used to solve the FI discrete nonlinear algebraic system. The linear solution process for the Newton updates is the computational workhorse of FI simulations. Empirical observations suggest that the computed Newton updates during FI simulations of multiphase flow are often sparse. Moreover, the level of sparsity observed can vary dramatically from iteration to the next, and across time steps. In several large scale applications, it was reported that the level of sparsity in the Newton update can be as large as 99%. This work develops a localization algorithm that conservatively predetermines the sparsity pattern of the Newton update. Subsequently, only the flagged nonzero components of the system need be solved. The localization algorithm is developed for general FI models of two phase flow. Large scale simulation results of benchmark reservoir models show a 10 to 100 fold reduction in computational cost for homogeneous problems, and a 4 to 10 fold reduction for strongly heterogeneous problems
CovNet: Covariance Networks for Functional Data on Multidimensional Domains
Covariance estimation is ubiquitous in functional data analysis. Yet, the
case of functional observations over multidimensional domains introduces
computational and statistical challenges, rendering the standard methods
effectively inapplicable. To address this problem, we introduce "Covariance
Networks" (CovNet) as a modeling and estimation tool. The CovNet model is
"universal" - it can be used to approximate any covariance up to desired
precision. Moreover, the model can be fitted efficiently to the data and its
neural network architecture allows us to employ modern computational tools in
the implementation. The CovNet model also admits a closed-form
eigendecomposition, which can be computed efficiently, without constructing the
covariance itself. This facilitates easy storage and subsequent manipulation of
a covariance in the context of the CovNet. We establish consistency of the
proposed estimator and derive its rate of convergence. The usefulness of the
proposed method is demonstrated by means of an extensive simulation study and
an application to resting state fMRI data.Comment: Substantial modification of the previous version. Application to fMRI
data added. Theoretical results extended to cover discrete observations with
measurement nois
A dermatologist guide to immunogenicity
AbstractDermatologists should be aware that autoantibody formation may occur after the initiation of biologic therapy. This phenomenon has been referred to as immunogenicity and biologic fatigue. Because of this, patients may experience loss of clinical efficacy to a particular drug. To combat this phenomenon, low-dose immunomodulators may be used in hopes of preventing autoantibodies. We review the current literature and provide a basic treatment algorithm for patients with moderate to severe psoriasis
Opinion dynamics model with domain size dependent dynamics: novel features and new universality class
A model for opinion dynamics (Model I) has been recently introduced in which
the binary opinions of the individuals are determined according to the size of
their neighboring domains (population having the same opinion). The coarsening
dynamics of the equivalent Ising model shows power law behavior and has been
found to belong to a new universality class with the dynamic exponent and persistence exponent in one dimension. The
critical behavior has been found to be robust for a large variety of annealed
disorder that has been studied. Further, by mapping Model I to a system of
random walkers in one dimension with a tendency to walk towards their nearest
neighbour with probability , we find that for any ,
the Model I dynamical behaviour is prevalent at long times.Comment: 12 pages, 10 figures. To be published in "Journal of Physics :
Conference Series" (2011
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