145 research outputs found
The Inviscid, Compressible and Rotational, 2D Isotropic Burgers and Pressureless Euler-Coriolis Fluids; Solvable models with illustrations
The coupling between dilatation and vorticity, two coexisting and fundamental
processes in fluid dynamics is investigated here, in the simplest cases of
inviscid 2D isotropic Burgers and pressureless Euler-Coriolis fluids
respectively modeled by single vortices confined in compressible, local,
inertial and global, rotating, environments. The field equations are
established, inductively, starting from the equations of the characteristics
solved with an initial Helmholtz decomposition of the velocity fields namely a
vorticity free and a divergence free part and, deductively, by means of a
canonical Hamiltonian Clebsch like formalism, implying two pairs of conjugate
variables. Two vector valued fields are constants of the motion: the velocity
field in the Burgers case and the momentum field per unit mass in the
Euler-Coriolis one. Taking advantage of this property, a class of solutions for
the mass densities of the fluids is given by the Jacobian of their sum with
respect to the actual coordinates. Implementation of the isotropy hypothesis
results in the cancellation of the dilatation-rotational cross terms in the
Jacobian. A simple expression is obtained for all the radially symmetric
Jacobians occurring in the theory. Representative examples of regular and
singular solutions are shown and the competition between dilatation and
vorticity is illustrated. Inspired by thermodynamical, mean field theoretical
analogies, a genuine variational formula is proposed which yields unique
measure solutions for the radially symmetric fluid densities investigated. We
stress that this variational formula, unlike the Hopf-Lax formula, enables us
to treat systems which are both compressible and rotational. Moreover in the
one-dimensional case, we show for an interesting application that both
variational formulas are equivalent
Psychomotor Development of 18-Months Children With Orofacial Clefts
Objective - To describe the global and language development of children with cleft palate or cleft lip and palate at the age of 18 months, and to evaluate whether the type of cleft has an impact on psychomotor development.
Study Design - Prospective cohort study.
Settings - Tertiary care hospital
Patients - All children born between December 2002 and November 2009 with an orofacial cleft, operated and seen at the developmental unit (UD) of the same hospital at the age of 18 months.
Outcome Measures - Developmental quotients of the Griffiths Mental Development Scale and the French Communicative Development Inventory (IFDC) were used to assess the overall and language development of the children.
Statistics- The population characteristics were described with means for continuous variables, and frequencies for binary or categorical variables. Chi-squared and regression analysis were used to analyse the results.
Results - 69 children with clefts were examined at the age of 18 months with the IFDC and the Griffith test. The results showed that there was no significant difference in the test results of language development and global psychomotor development between the children with different types of clefts, and all were within the normal range.
Conclusion - Psychomotor development is not affected by orofacial clefts, and there is no difference between children with cleft palate or cleft lip and palate
Coulomb system equivalent to the energy spectrum of the Calogero-Sutherland-Moser (CSM) model
The purpose of this paper is to prove an equivalence between the energy spectrum of the CSM model and the electrostatic energy of a one-dimensional lattice of quantized point charges interacting via Coulomb potential with Dirichlet boundary condition
The One-Dimensional Schrödinger-Newton Equations
We prove an existence and uniqueness result for ground states of one-dimensional Schrödinger-Newton equation
Surface correlations for two-dimensional Coulomb fluids in a disc
After a brief review of previous work, two exactly solvable two-dimensional
models of a finite Coulomb fluid in a disc are studied. The charge correlation
function near the boundary circle is computed. When the disc radius is large
compared to the bulk correlation length, a correlation function of the surface
charge density can be defined. It is checked, on the solvable models, that this
correlation function does have the generic long-range behaviour, decaying as
the inverse square distance, predicted by macroscopic electrostatics. In the
case of a two-component plasma (Coulomb fluid made of two species of particles
of opposite charges), the density correlation function on the boundary circle
itself is conjectured to have a temperature-independent behaviour, decaying as
the -4 power of the distance.Comment: 15 pages, Latex, submitted to J.Phys.:Condens.Matte
Lattice dynamics of anharmonic solids from first principles
An accurate and easily extendable method to deal with lattice dynamics of
solids is offered. It is based on first-principles molecular dynamics
simulations and provides a consistent way to extract the best possible harmonic
- or higher order - potential energy surface at finite temperatures. It is
designed to work even for strongly anharmonic systems where the traditional
quasiharmonic approximation fails. The accuracy and convergence of the method
are controlled in a straightforward way. Excellent agreement of the calculated
phonon dispersion relations at finite temperature with experimental results for
bcc Li and bcc Zr is demonstrated
Ăvaluation de six moteurs de recherche comme sources de veille dans le cadre dâune veille concernant trois sujets sur une pĂ©riode de deux semaines
La mise en place dâun dispositif de veille est devenue aujourdâhui dâune importance capitale pour les entreprises qui veulent gĂ©rer la surcharge informationnelle et rester compĂ©titives. Cependant, elles ne disposent pas toujours des ressources nĂ©cessaires et utilisent principalement les moteurs de recherche pour surveiller les marchĂ©s. Ce projet de recherche a lâambition dâĂ©valuer les qualitĂ©s de six moteurs de recherche en tant que sources de veille et dâutiliser exclusivement le flux RSS pour les surveiller, de maniĂšre Ă fournir des recommandations les concernant et poser quelques jalons pour une future Ă©tude. Quatre questions de recherche ont dâabord Ă©tĂ© Ă©tablies, touchant Ă la pertinence, la prĂ©cision, lâĂ©clectisme et lâexhaustivitĂ©, afin de pouvoir explorer notre sujet et satisfaire nos objectifs dâĂ©valuation des moteurs. Nous avons consultĂ© la littĂ©rature pour la mise en place dâune mĂ©thodologie, mais nâavons pas trouvĂ© dâĂ©tudes Ă©quivalentes. Afin de pallier ce manque, nous avons menĂ© une rĂ©flexion sur les outils et le processus Ă employer, consacrant ainsi une majoritĂ© du temps imparti Ă cette phase de la recherche. Notre travail se dĂ©ploie ainsi en six chapitres. Nous contextualisons dâabord notre recherche, puis nous fournissons les Ă©lĂ©ments mĂ©thodologiques, nous analysons ensuite les donnĂ©es collectĂ©es pour enfin en proposer une interprĂ©tation. Les rĂ©sultats dĂ©montrent que globalement Bing est la source plus prĂ©cise avec un taux de 40.27%, cependant notre recherche rĂ©vĂšle quâun moteur ne peut pas rĂ©pondre Ă tous les besoins informationnels. En effet, lorsquâil sâagit dâĂ©valuer les rĂ©sultats sous le prisme de diffĂ©rents sujets de veille, dâautres moteurs se montrent plus performants. Notre projet de recherche constitue une proposition tant pour lâapproche mĂ©thodologique que pour lâanalyse des donnĂ©es, nous espĂ©rons donc quâil fournisse des bases propices Ă des rĂ©flexions futures
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