We compare various preconditioners for the numerical solution of partial differential equations. We compare a coarse grid correction preconditioner used in domain decomposition methods with a so-called deflation preconditioner. We prove that the effective condition number of the deflated preconditioned system is always, i.e. for all deflation vectors and all restrictions and prolongations, belo...

When building process-intensive web applications, developers typically spend considerable effort on the exchange of specific data entities between specific web pages and operations under specific conditions, as called for by business requirements. Since the WWW infrastructure provides only very coarse data exchange mechanisms, we introduce a notation for the design of fine-grained conditional d...

We develop variational principles to study the structure and the stability of equilibrium states of axisymmetric flows. We show that the axisymmetric Euler equations for inviscid flows admit an infinite number of steady state solutions. We find their general form and provide analytical solutions in some special cases. The system can be trapped in one of these steady states as a result of an inv...

The present work is part of a research effort aimed at integrating a detailed model of airflow in large spaces with an algebraic multizone infiltration model to describe pollutant transport and coupled air flows within and between complex buildings and large spaces. In the past 15 years, zonal models were developed with the goal to obtain an approximate prediction of airflow characteristics in ...

Subgrid effects can have a strong influence on flow and transport in oil reservoirs. In this work, a new model for the representation of subgrid terms is introduced and applied to two-phase reservoir flows. The model entails a generalized convection-diffusion treatment of the saturation equation as well as an extended representation for total mobility in the pressure equation. Motivation for th...

The method of dissipative particle dynamics (DPD) is an effective, coarse grained model of the hydrodynamics of complex fluids. DPD simulations of wall-bounded flows are however often associated with spurious fluctuations of the fluid properties near the wall. We present a novel stochastic boundary forcing for DPD simulations of wall-bounded flows, based on the identification of fluctuations in...

â â â â â  abstract: â  as the number of independent countries increases and their economies become more integrated, we would expect to observe more multi-country currency ::::union::::s. this paper explores the pros and cons for different countries to adopt as an anchor the us dollar, the euro or the yen. in addition, it addresses the question of how co-movement of outputs and prices would res...

the main purpose of this paper is to establish a relation between universality of certain p-compactifications of a semitopological semigroup and their corresponding enveloping semigroups. in particular, we show that if we take p to be the property that the enveloping semigroup of a compactification of a semitopological semigroup s is left simple, a group, or the trivial singleton semigroup, the...

We provide the most comprehensive study to date on the correlation between network centrality measures and vehicular movement flows, using a model of the UK’s entire road network (2,031,971 nodes) and a very large dataset of vehicular movement counts (20,752 instances, evenly distributed over the UK’s territory). We describe the statistical associations between observed vehicular flows and the ...