174 research outputs found
Le segment nord de la faille de la Tet (Pyrénées-Orientales) : fonctionnement néogÚne et implications géomorphologiques
International audienceDans les rĂ©gions Ă vitesses de dĂ©formations faibles Ă moyennes, l'Ă©valuation des tendances Ă©volutives des reliefs passe par l'identification des failles actives et leur expression gĂ©omorphologique. L'utilisation d'indicateurs mor-phologiques et sĂ©dimentaires permet de reconstituer les stades de croissance et de dĂ©gradation des reliefs. Le segment nord de la faille de la TĂȘt (F.T.N.) est un accident Ă forte signature morphologique s'exprimant par un escarpement orientĂ© N080 o Ă N050 o E et long de 30 kilomĂštres. Les outils morphomĂ©triques adaptĂ©s Ă la dĂ©tection des mouvements verticaux et le signal sĂ©dimentaire sont appliquĂ©s Ă la F.T.N. entre Prades et Ille-sur-TĂȘt (PyrĂ©nĂ©es-Orientales). Les mar-queurs caractĂ©ristiques de son Ă©volution sont la morphomĂ©trie des facettes triangulaires, des bassins versants et du rĂ©-seau hydrographique ainsi que la stratigraphie des dĂ©pĂŽts dĂ©tritiques pliocĂšnes. L'Ă©tude des lithofaciĂšs et des sĂ©quences Ă©lĂ©mentaires pliocĂšnes montre que la sĂ©dimentation est en Ă©troite relation avec l'activitĂ© de la faille. La gĂ©omĂ©trie ac-tuelle de la surface de remblaiement pliocĂšne supĂ©rieur du bassin du Conflent, la position altitudinale des palĂ©otalwegs et des ruptures sur le profil en long des cours d'eau montrent clairement que l'activitĂ© de faille s'estompe dĂšs le Plio-cĂšne supĂ©rieur. L'approche multicritĂšre (sĂ©dimentologie, structure et gĂ©omorphologie) montre que la F.T.N. n'est plus active au PlĂ©istocĂšne. L'escarpement de faille actuel est une ancienne structure exhumĂ©e rĂ©vĂ©lĂ©e par l'Ă©rosion diffĂ©ren-tielle. Au Quaternaire, l'exhumation de l'escarpement et du remplissage pliocĂšne est en relation avec le basculement de la marge du golfe du Lion
Rapport dâexpertise de la procĂ©dure de qualification des Ă©quipements ILS. Limites et ProbabilitĂ©s de confiance.
L'objet de cette Ă©tude est de clarifier certains passages du rapport "DERA/WSS/WX1/CR 980799/2.3 ILS Certification Requirements". Nous Ă©tudions en particulier le paragraphe 3.3 "Confidence Limits for Sequential Tests" p.28-34 et le paragraphe 2 de l'appendice D, p.69-72
Study of the ILS certification process. Confidence limits and probabilities.
The purpose of this study is to explain some parts of the DERA report DERA/WSS/WX1/CR 980799/2.3. "ILS Certification Requirements" (Ref. 2). We mainly study section 3.3 "Confidence Limits for Sequential Tests" p.28-34 and section 2 of the appendix D, p.69-72
Classical Symmetries of Some Two-Dimensional Models
It is well-known that principal chiral models and symmetric space models in
two-dimensional Minkowski space have an infinite-dimensional algebra of hidden
symmetries. Because of the relevance of symmetric space models to duality
symmetries in string theory, the hidden symmetries of these models are explored
in some detail. The string theory application requires including coupling to
gravity, supersymmetrization, and quantum effects. However, as a first step,
this paper only considers classical bosonic theories in flat space-time. Even
though the algebra of hidden symmetries of principal chiral models is confirmed
to include a Kac--Moody algebra (or a current algebra on a circle), it is
argued that a better interpretation is provided by a doubled current algebra on
a semi-circle (or line segment). Neither the circle nor the semi-circle bears
any apparent relationship to the physical space. For symmetric space models the
line segment viewpoint is shown to be essential, and special boundary
conditions need to be imposed at the ends. The algebra of hidden symmetries
also includes Virasoro-like generators. For both principal chiral models and
symmetric space models, the hidden symmetry stress tensor is singular at the
ends of the line segment.Comment: 51 pages, minor corrections and added reference
Higher-Order Gravitational Couplings and Modular Forms in Heterotic String Compactifications
The restrictions of target--space duality are imposed at the perturbative
level on the holomorphic Wilsonian couplings that encode certain higher-order
gravitational interactions in heterotic string compactifications. A
crucial role is played by non-holomorphic corrections. The requirement of
symplectic covariance and an associated symplectic anomaly equation play an
important role in determining their form. For models which also admit a type-II
description, this equation coincides with the holomorphic anomaly equation for
type-II compactifications in the limit that a specific K\"ahler-class modulus
grows large. We explicitly evaluate some of the higher-order couplings for a
toroidal compactification with two moduli and , and we express them in
terms of modular forms.Comment: 39 pages, Late
Classical and quantum N=2 supersymmetric black holes
We use heterotic/type-II prepotentials to study quantum/classical black holes
with half the supersymmetries unbroken. We show that, in the case of
heterotic string compactifications, the perturbatively corrected entropy
formula is given by the tree-level entropy formula with the tree-level coupling
constant replaced by the perturbative coupling constant. In the case of type-II
compactifications, we display a new entropy/area formula associated with
axion-free black-hole solutions, which depends on the electric and magnetic
charges as well as on certain topological data of Calabi--Yau three-folds,
namely the intersection numbers, the second Chern class and the Euler number of
the three-fold. We show that, for both heterotic and type-II theories, there is
the possibility to relax the usual requirement of the non-vanishing of some of
the charges and still have a finite entropy.Comment: 28 pages, LaTe
Perturbative Couplings of Vector Multiplets in Heterotic String Vacua
We study the low-energy effective Lagrangian of heterotic string vacua
at the classical and quantum level. The couplings of the vector multiplets are
uniquely determined at the tree level, while the loop corrections are severely
constrained by the exact discrete symmetries of the string vacuum. We evaluate
the general transformation law of the perturbative prepotential and determine
its form for the toroidal compactifications of six-dimensional
supersymmetric vacua.Comment: 44 pages, late
String Consistency for Unified Model Building
We explore the use of real fermionization as a test case for understanding
how specific features of phenomenological interest in the low-energy effective
superpotential are realized in exact solutions to heterotic superstring theory.
We present pedagogic examples of models which realize SO(10) as a level two
current algebra on the world-sheet, and discuss in general how higher level
current algebras can be realized in the tensor product of simple constituent
conformal field theories. We describe formal developments necessary to compute
couplings in models built using real fermionization. This allows us to isolate
cases of spin structures where the standard prescription for real
fermionization may break down.Comment: harvmac (available from xxx.lanl.gov), 30 pages (reduced format), if
you are using harvmac for the first time, make sure to adjust the "site
dependent options" at the beginning of the harvmac file. Shortened
introduction and added table 3, listing the complete massless spectrum with
U(1) charges of Model A. Version to appear in journa
Heat generation mechanisms of DBD plasma actuators
During the last twenty years DBD plasma actuators have been known by their ability for boundary layer flow control applications. However, their usefulness is not limited to this application field, they also present great utility for applications within the field of heat transfer, such as a way to improve the aerodynamic efficiency of film cooling of gas turbine blades, or de-icing and ice formation prevention. Nevertheless, there is a relative lack of information about DBDâs thermal characteristics and its heat generation mechanisms. This happens due to the extremely high electric fields in the plasma region and consequent impossibility of applying intrusive measurement techniques. Against this background, this work describes the physical mechanisms behind the generation of heat associated to the DBD plasma actuators operation. An experimental technique, based on calorimetric principles, was devised in order to quantify the heat energy generated during the plasma actuators operation. The influence of the dielectric thickness, as well as the dielectric material, were also evaluated during this work. The results were exposed and discussed with the purpose of a better understanding of the heat generation mechanisms behind the operation of DBD plasma actuators
Feedback and the Formation of Dwarf Galaxy Stellar Halos
Stellar population studies show that low mass galaxies in all environments
exhibit stellar halos that are older and more spherically distributed than the
main body of the galaxy. In some cases, there is a significant intermediate age
component that extends beyond the young disk. We examine a suite of Smoothed
Particle Hydrodynamic (SPH) simulations and find that elevated early star
formation activity combined with supernova feedback can produce an extended
stellar distribution that resembles these halos for model galaxies ranging from
= 15 km s to 35 km s, without the need for accretion of
subhalos.Comment: 15 pages, 15 figures, accepted MNRA
- âŠ