Publications

Displaying 1176 - 1200 of 1227

Publication	Date
A bilinear approach to the restriction and Kakeya conjectures Authors: Ana Vargas,Luis Vega,Terence Tao Bilinear restriction estimates have appeared in work of Bourgain, Klainerman, and Machedon. In this paper we develop the theory of these estimates (together with the analogues for Kakeya estimates). As a consequence we improve the ( L p… American Mathematical Society (AMS)	1998-01-01
Weighted Estimates for the Helmholtz Equation and Some Applications Authors: Barcelo, J.A,Ruiz, A,Vega, L We characterize the radial functionsVin Rnfor which the a priori inequality ‖∇u1/2‖2+k ‖uV1/2‖2⩽C ‖V−1/2(Δ+k2) u‖2holds with constant independent ofk. The condition is forVto have the X-rays transform everywhere bounded. We apply these estimates to the well posedness of evolution Schrodinger… Elsevier BV	1997-11-01
Global Solutions for the KdV Equation with Unbounded Data Authors: Kenig, Carlos E.,Ponce, Gustavo,Vega, Luis Elsevier BV	1997-09-01
New Observations and Studies of Saturn's Long-Lived North Polar Spot Authors: Pedro V. Sada,Agustín Sánchez-Lavega,Jose Félix Rojas,J. R. Acarreta,François Colas,Jean Lecacheux Abstract We report on a new series of ground-based CCD observations at visual wavelengths, covering a period of 1255 days between May 1992 and November 1995, of the longest-lived asymmetric feature known in Saturn's atmosphere: the north polar spot (NPS). This completes our previous analysis of… Elsevier BV	1997-08-01
Thermal diffusivity measurements in porous ceramics by photothermal methods Authors: Agustín Sánchez-Lavega,L.M. Villar,E. Gomez,L. Pottier,Agustín Salazar,A. Ocariz,E. Macho We present a study of the use of photothermal methods to measure the thermal diffusivity of porous ceramic materials as an alternative to other conventional methods. Specifically, we discuss the use of three modulated techniques - thermoreflectance, IR radiometry, and the mirage effect - as… Springer Science and Business Media LLC	1997-07-01
Photothermal study of subsurface cylindrical structures. I. Theory Authors: Agustín Sánchez-Lavega,A. Ocariz,Agustín Salazar A study of the photothermal signal generated by subsurface cylindrical structures is presented in two parts: theoretical modelization (Part I), and experimental measurements on calibrated samples (Part II). In this first part we develop a theoretical study of the scattering of planar and spherical… AIP Publishing	1997-06-01
Photothermal study of subsurface cylindrical structures. II. Experimental results Authors: Agustín Sánchez-Lavega,Agustín Salazar,A. Ocariz We present an extensive experimental study of the photothermal signal produced by subsurface cylinders immersed in opaque solids. The results provided by three different modulated photothermal techniques (thermoreflectance, infrared radiometry, and mirage) for a variety of sample and cylinder… AIP Publishing	1997-06-01
A Semilinear Dirac Equation inH^s(R³) fors> 1 Authors: M. Escobedo,Luis Vega Local and global well-posedness for the Cauchy problem associated with the nonlinear Dirac equation $$ i{\partial \psi \over \partial t}+i\alpha \cdot\nabla \psi -m\beta \psi +G(\psi)=0\quad \hbox{... Society for Industrial & Applied Mathematics (SIAM)	1997-03-01
Photothermal characterization of anisotropic materials with buried principal axes Authors: Agustín Salazar,Agustín Sánchez-Lavega,A. Ocariz We study theoretically and experimentally the ability of photothermal techniques to thermally characterize the anisotropic materials whose principal axes are not contained at the sample surfaces. We first determine the thermal diffusivity tensor when the directions of the principal axes are known.… SPIE-Intl Soc Optical Eng	1997-02-01
Temperature dependence of the thermal diffusivity of unidirectional composites by the mirage technique Authors: Agustín Salazar,Agustín Sánchez-Lavega,A. Ocariz Old City Publishing, Inc	1997-01-01
Convergence Properties of High-order Boltzmann Machines Authors: J. Antonio Lozano,F. Xabier Albizuri,Alicia D'Anjou,Manuel Graña The high-order Boltzmann machine (HOBM) approximates probability distributions defined on a set of binary variables, through a learning algorithm that uses Monte Carlo methods. The approximation distribution is a normalized exponential of a consensus function formed by high-degree terms and the… Elsevier BV	1996-12-01
Photothermal characterization of vertical and slanted thermal barriers: A quantitative comparison of mirage, thermoreflectance, and infrared radiometry Authors: Agustín Sánchez-Lavega,Albert-Claude Boccara,Didier Fournier,Agustín Salazar,A. Ocariz We present a quantitative and comparative study of three different photothermal techniques based on the signal produced on vertical/slanted thermal barriers under a variety of barrier/sample conditions. Models based on integral methods are developed to calculate the amplitude and phase of the… AIP Publishing	1996-09-01
Constructing an intelligent dictionary help system Authors: Eneko Agirre,Xabier Artola,Xabier Arregi,Aitor Soroa,Kepa Sarasola,A. Diaz de Ilarraza This paper discusses different issues in the construction and knowledge representation of an intelligent dictionary help system. The Intelligent Dictionary Help System (IDHS) is conceived as a monolingual (explanatory) dictionary system for human use (Artola and Evrard, 1992). The fact that it is… Cambridge University Press (CUP)	1996-09-01
The South Equatorial Belt of Jupiter, II: The Onset and Development of the 1993 Disturbance Authors: Agustín Sánchez-Lavega,J. Guarro,Jean Lecacheux,I. Miyazaki,J. M. Gomez,François Colas,D. Parker On April 6, 1993 an SEB disturbance commenced with a bright white spot at 15.5°S latitude. The spot was followed by a dark column lying only 24° from the eastern edge of the Great Red Spot. A continuous CCD and photographic survey at visual wavelengths of the event during the four months following… Elsevier BV	1996-05-01
The South Equatorial Belt of Jupiter, I: Its Life Cycle Authors: Agustín Sánchez-Lavega,J. M. Gomez Abstract The South Equatorial Belt (SEB) of Jupiter, located between latitudes ∼10°S and ∼20°S, represents the archetype of a cyclically changing band between the belt and zone stages. A new analysis of the historical records has been performed, using various published observations and additional… Elsevier BV	1996-05-01
Thermal diffusivity of anisotropic materials by photothermal methods Authors: Girish Pandey,Agustín Sánchez-Lavega,Dc. Fournier,Albert Claude Boccara,Agustín Salazar,A. Ocariz,J. Guitonny In this paper we analyze the possibility of extending the photothermal methods developed for thermal diffusivity measurements of isotropic materials [A. Salazar and A. Sánchez-Lavega, Rev. Sci. Instrum. 65, 2896 (1994)] to the case of anisotropic specimens. A full theoretical treatment of the… AIP Publishing	1996-04-15
Large-Scale Storms in Saturn's Atmosphere During 1994 Authors: Diane Gilmore,D. Parker,J. M. Gomez,Agustín Sánchez-Lavega,I. Miyazaki,Keith S. Noll,Jean Lecacheux,François Colas,P. Laques Large-scale storms are rarely observed in Saturn's atmosphere, but their appearance traces the wind velocity field, providing information on the vertical structure of the clouds and on the dynamics of the atmosphere. Two large-scale atmospheric disturbances formed by clouds highly reflective in the… American Association for the Advancement of Science (AAAS)	1996-02-02
Photothermal mirage characterization of vertical interfaces separating two different media Authors: A. Ocariz,Agustín Salazar,Ph. Forge,Agustín Sánchez-Lavega A theoretical and experimental study about the ability of the photothermal modulated mirage technique to characterize vertical interfaces (thermal resistances) separating two different opaque and thermally thick media with thermal conductivities larger than the medium surrounding the sample and… AIP Publishing	1996-01-15
Quadratic forms for the 1-D semilinear Schrödinger equation Authors: Gustavo Ponce,Carlos E. Kenig,Luis Vega This paper is concerned with 1-D quadratic semilinear Schrödinger equations. We study local well posedness in classical Sobolev space H s H^s of the associated initial value problem and periodic boundary value problem. Our main interest is to obtain the lowest… American Mathematical Society (AMS)	1996-01-01
A bilinear estimate with applications to the KdV equation Authors: Luis Vega,Gustavo Ponce,Carlos E. Kenig u(x, 0) = u0(x), where u0 ∈ H(R). Our principal aim here is to lower the best index s for which one has local well posedness in H(R), i.e. existence, uniqueness, persistence and continuous dependence on the data, for a finite time interval, whose size depends on ‖u0‖Hs . Equation in (1.1) was… American Mathematical Society (AMS)	1996-01-01
Novel results on thermal diffusivity measurements on anisotropic materials using photothermal methods Authors: Agustín Sánchez-Lavega,Agustín Salazar,J. C. Pandey,J. Guitonny,Albert-Claude Boccara,Didier Fournier,A. Ocariz We have applied two photothermal techniques (infrared radiometry and mirage) and conventional procedures to measure the thermal diffusivity of a highly anisotropic sample of pyrolytic graphite. Unexpected and strongly differing results are obtained with each technique. A theoretical analysis… AIP Publishing	1995-07-31
Motions of the SL9 impact clouds Authors: D. Parker,Jean Lecacheux,Agustín Sánchez-Lavega,J. M. Gomez,P. Laques,François Colas,I. Miyazaki A large number of CCD images of the SL9 impact clouds in the visible from July to October 1994 has allowed us to study the morphological changes and motions of the impact clouds. Our measurements show the existence of at least three different kind of motions: (1) Eastward expansion during the first… American Geophysical Union (AGU)	1995-07-01
Real time power supply quality measurement and monitoring multichannel system Authors: Elisabete Aramendi,J. Ortuondo,J. Izquierdo,Luis A. Leturiondo,N. Palacios,J. Amantegui,Jesus Ruiz This paper describes a multi-channel system for measuring and monitoring electric power supply quality in real-time. The hardware is simple but powerful, because it is based on a PC with an acquisition card, and a development card with a single dedicated DSP (digital signal processor). > Institute of Electrical and Electronics Engineers (IEEE)	1995-07-01
On the Zakharov and Zakharov-Schulman Systems Authors: Kenig, C.E.,Ponce, G.,Vega, L. Abstract We consider the initial value problem for the Zakharov system [formula] which models the long wave Langmuir turbulence in a plasma. Using the standard iteration scheme in the original system it is shown that the system is locally well-posed uniformly on λ (the ionic speed of sound) in… Elsevier BV	1995-01-01
Comments on ‘‘On the photothermal method applied to low thermal diffusivity measurements’’ [Rev. Sci. Instrum. 64, 1576 (1993)] Authors: Agustín Sánchez-Lavega,Agustín Salazar It is shown theoretically and experimentally that the method recently proposed by Bertolloti et al. to measure low thermal diffusivity samples presents errors of the same order as other ‘‘mirage’’ photothermal techniques previously proposed. AIP Publishing	1995-01-01