13,405 research outputs found
Two scenarios on a potential smoothness breakdown for the three-dimensional Navier-Stokes equations
In this paper we construct two families of initial data being arbitrarily
large under any scaling-invariant norm for which their corresponding weak
solution to the three-dimensional Navier-Stokes equations become smooth on
either or , respectively, where and are
two times prescribed previously. In particular, can be arbitrarily large
and can be arbitrarily small. Therefore, possible formation of
singularities would occur after a very long or short evolution time,
respectively.
We further prove that if a large part of the kinetic energy is consumed prior
to the first (possible) blow-up time, then the global-in-time smoothness of the
solutions follows for the two families of initial data.Comment: 16 pages, no figures. Some typos have been correcte
Non-radial pulsations in the Be/X binaries 4U0115+63 and SAXJ2103.5+4545
The discovery of non-radial pulsations (NRP) in the Be/X binaries of the
Magellanic Clouds (MC, eg. Fabrycky 2005, Coe et al. 2005, Schmidtke & Cowley
2005) provided a new approach to understand these complex systems, and, at the
same time, favoured the synergy between two different fields: stellar
pulsations and X-ray binaries. This breakthrough was possible thanks to the
MACHO and OGLE surveys. However, in our Galaxy, only two Be/X have been
reported to show NRP: GROJ2058+42 (Kiziloglu et al. 2007) and LSI+61 235 (Sarty
et al. 2009). Our objective is to study the short-term variability of Galactic
Be/X binaries, compare them to the Be/X of the MC and to the isolated Galactic
Be observed with CoRoT and Kepler. We present preliminary results of two Be/X
stars, namely 4U0115+63 and SAXJ2103.5+4545 showing multiperiodicity and
periodicity respectively, most probably produced by non-radial pulsations.Comment: 2 pages, 2 figures, IAUS 272 "Active OB stars: structure, evolution,
mass loss and critical limits" conference, Paris, July 2010, submitte
The Politics of Abstract Art. Forma 1 and the Italian Communist Party
Este artículo examina el papel del grupo de artistas abstractos Forma 1 en relación con la política cultural del Partido Comunista Italiano durante la posguerra, como ejemplo de los intentos de superar la dicotomía establecida en Italia entre arte abstracto y realismo socialista y producir una alternativa a la confrontación entre ambos discursos estéticos. Mientras los artistas realistas socialistas subrayaban la necesidad de expresar contenidos políticos explícitos con un estilo que asegurase su máxima legibilidad para una audiencia de masas, los artistas de Forma 1 argumentaban que la abstracción significaba una crítica de la representación pictórica que podía contribuir a la crítica de la ideología burguesa, armonizando de este modo el marxismo con los desarrollos artísticos más avanzados. El PCI, por su parte, basaba su política artística en amplias alianzas de artistas e intelectuales antifascistas, que cada vez eran más difíciles de mantener en el clima de creciente confrontación política y cultural que siguió a la II
Guerra Mundial
Convergence to suitable weak solutions for a finite element approximation of the Navier-Stokes equations with numerical subgrid scale modeling
In this work we prove that weak solutions constructed by a variational
multiscale method are suitable in the sense of Scheffer. In order to prove this
result, we consider a subgrid model that enforces orthogonality between subgrid
and finite element components. Further, the subgrid component must be tracked
in time. Since this type of schemes introduce pressure stabilization, we have
proved the result for equal-order velocity and pressure finite element spaces
that do not satisfy a discrete inf-sup condition.Comment: 23 pages, no figure
Using quality models in software package selection
The growing importance of commercial off-the-shelf software packages requires adapting some software engineering practices, such as requirements elicitation and testing, to this emergent framework. Also, some specific new activities arise, among which selection of software packages plays a prominent role. All the methodologies that have been proposed recently for choosing software packages compare user requirements with the packages' capabilities. There are different types of requirements, such as managerial, political, and, of course, quality requirements. Quality requirements are often difficult to check. This is partly due to their nature, but there is another reason that can be mitigated, namely the lack of structured and widespread descriptions of package domains (that is, categories of software packages such as ERP systems, graphical or data structure libraries, and so on). This absence hampers the accurate description of software packages and the precise statement of quality requirements, and consequently overall package selection and confidence in the result of the process. Our methodology for building structured quality models helps solve this drawback.Peer ReviewedPostprint (published version
Participation of Married Women in the Labour Market and the 'Added Worker Effect' in Europe
In this paper, we estimate labour participation equations for married women for eleven European countries, using data from the European Community Household Panel corresponding to the years 1994, 1995 and 1996. The main objective of our study is to test whether the 'added worker effect' holds. From our results it can be concluded that the labour market participation of the married woman basically depends on her personal and family characteristics, her non-wage income and her potential earnings. In only a few countries does the participation of married women seem to be related to the work status of the husband. However, the consistently significant and negative effect of the woman's non-wage income (basically the husband's wage) prevents the 'added worker effect' from being completely rejected as a hypothesis. It seems, therefore, that female labour market participation continues to have a 'secondary' role in the family sphere in some European countries.Female participation ; added worker effect
On the approximation of turbulent fluid flows by the Navier-Stokes- equations on bounded domains
The Navier-Stokes- equations belong to the family of LES (Large Eddy
Simulation) models whose fundamental idea is to capture the influence of the
small scales on the large ones without computing all the whole range present in
the flow. The constant is a regime flow parameter that has the
dimension of the smallest scale being resolvable by the model. Hence, when
, one recovers the classical Navier-Stokes equations for a flow of
viscous, incompressible, Newtonian fluids. Furthermore, the
Navier-Stokes- equations can also be interpreted as a regularization of
the Navier-Stokes equations, where stands for the regularization
parameter.
In this paper we first present the Navier-Stokes- equations on
bounded domains with no-slip boundary conditions by means of the Leray
regularization using the Helmholtz operator. Then we study the problem of
relating the behavior of the Galerkin approximations for the
Navier-Stokes- equations to that of the solutions of the Navier-Stokes
equations on bounded domains with no-slip boundary conditions. The Galerkin
method is undertaken by using the eigenfunctions associated with the Stokes
operator. We will derive local- and global-in-time error estimates measured in
terms of the regime parameter and the eigenvalues. In particular, in
order to obtain global-in-time error estimates, we will work with the concept
of stability for solutions of the Navier-Stokes equations in terms of the
norm
- …