Publications

Displaying 1201 - 1225 of 1227

Publication	Date
Local regularity of solutions to wave equations with time-dependent potentials Authors: Luis Vega,Alberto Ruiz Duke University Press	1994-12-01
Thermal diffusivity measurements using linear relations from photothermal wave experiments Authors: Agustín Sánchez-Lavega,Agustín Salazar We present a methodology to retrieve the thermal diffusivity of bulk homogeneous samples based on a set of simple linear relations that exist between two measurable magnitudes in modulated photothermal experiments. The influence of the photothermal parameters involved (exciting beam radius and… AIP Publishing	1994-09-01
Thermal diffusivity measurements in opaque solids by the mirage technique in the temperature range from 300 to 1000 K Authors: Agustín Sánchez-Lavega,Agustín Salazar A method to measure the thermal diffusivity of solid samples as a function of temperature is presented. The measurement technique is based on the mirage effect and in its linear zero-crossing relation for the transverse deflection, whose slope directly gives the diffusivity of the material. A 3D… AIP Publishing	1994-08-01
Saturn’s Great White Spots Authors: Agustín Sánchez-Lavega The term, Great White Spot, is used for large and unusual atmospheric disturbances on the planet Saturn. The phenomenology has been recorded only in five occasions during the last century, and its evolution can be described in terms of four different phases: (i) Onset (first week), outburst and… AIP Publishing	1994-06-01
Photometry of Saturn's 1990 Equatorial Disturbance Authors: Agustín Sánchez-Lavega,F. Colas,Jean Lecacheux,P. Laques Abstract Multicolor CCD images at selected wavelengths from 370 to 900 nm obtained at Pic-du-Midi Observatory during four different phases of the development of Saturn's equatorial disturbance are used to analyze its photometric properties. Three epochs and four morphologically different regions… Elsevier BV	1994-03-01
On the Generalized Benjamin-Ono Equation Authors: Gustavo Ponce,Luis Vega,Carlos E. Kenig We study well-posedness of the initial value problem for the generalized Benjamin-Ono equation∂tu+uk∂xu−∂xDxu=0{\partial _t}u + {u^k}{\partial _x}u - {\partial _x}{D_x}u = 0,k∈Z+k \in {\mathbb {Z}^ + }, in Sobolev spacesHs(R){H^s}(\mathbb {R}). For small data and higher nonlinearities(k≥2)(k \… JSTOR	1994-01-01
Higher-order nonlinear dispersive equations Authors: Carlos E. Kenig,Luis Vega,Gustavo Ponce We study nonlinear dispersive equations of the form \[ ∂ t u + ∂ x 2 j + 1 u + P ( u… American Mathematical Society (AMS)	1994-01-01
Thermal diffusivity measurements on solids using collinear mirage detection Authors: Agustín Sánchez-Lavega,Agustín Salazar,J. Fernández A report on the adequacy of the collinear mirage technique for thermal diffusivity measurements on bulk homogeneous solids is presented. A 3D theoretical model for collinear deflection has been developed from which two simple linear relations between measurable parameters and the thermal… AIP Publishing	1993-08-01
The Cauchy problem for the Korteweg-de Vries equation in Sobolev spaces of negative indices Authors: Luis Vega,Carlos E. Kenig,Gustavo Ponce Duke University Press	1993-07-01
Ground-Based Observations of Saturn's North Polar Spot and Hexagon Authors: Agustín Sánchez-Lavega,P. Laques,François Colas,Jean Lecacheux Ground-based observations of two conspicuous features near the north pole of Saturn, the polar vortex and the hexagonal wave structure, were made from July 1990 to October 1991, 10 years after their discovery. During this period the polar spot drifted in longitude, relative to system III, by –0.… American Association for the Advancement of Science (AAAS)	1993-04-16
Well‐posedness and scattering results for the generalized korteweg‐de vries equation via the contraction principle Authors: Gustavo Ponce,Luis Vega,Carlos E. Kenig Wiley	1993-04-01
A new educational packet for passive and active filter design Authors: A. Ubierna,Jesus Ruiz,Elisabete Aramendi AbstractA new software package for the design, analysis, and simulation of passive and active filters in cascade is presented. This article is mainly directed to engineering education. The software can also be used to aid in the filter design needed in industry. The main characteristic of this new… Wiley	1993-01-01
A disturbance in Jupiter's high-speed North temperate jet during 1990 Authors: P. Laques,Jean Lecacheux,D. Parker,I. Miyazaki,Agustín Sánchez-Lavega Abstract During February 1990 a remarkable disturbance developed in the strongest Jovian atmospheric jet located at ≈24°N planetographic latitude. Our telescopic images at visible wavelenghts revealed the outbreak of two bright features with an initial length scale ≈6000km, the first discovered… Elsevier BV	1991-11-01
The Great White Spot and disturbances in Saturn's equatorial atmosphere during 1990 Authors: I. Miyazaki,P. Laques,Jean Lecacheux,Agustín Sánchez-Lavega,François Colas,D. Parker A giant storm, the Great White Spot, erupted at the end of September 1990 as a localized, bright cloud system close to Saturn's equator. Its evolution produced a complex planetary disturbance which affected the whole equatorial region a month later. Similar spots have appeared approximately once… Springer Science and Business Media LLC	1991-10-01
Photothermal detection and characterization of a horizontal buried slab by the mirage technique Authors: Agustín Sánchez-Lavega,Agustín Salazar,J. Fernández We present a theoretical and experimental analysis of the mirage detection and measurement of a semi-infinite horizontal buried slab of air within opaque solids. A detailed study on the effects introduced by the mirage parameters (pump and probe beam sizes, probe beam height) as well as by the… AIP Publishing	1991-09-15
Thermal diffusivity measurements in solids by the ‘‘mirage’’ technique: Experimental results Authors: Agustín Sánchez-Lavega,J. Fernández,Agustín Salazar This work provides the experimental confirmation of a generalized theory for thermal diffusivity measurements of solid samples using the ‘‘mirage’’ technique presented by the authors in a previous paper [A. Salazar, A. Sanchez-Lavega, and J. Fernandez, J. Appl. Phys. 65, 4150 (1989)]. Moreover the… AIP Publishing	1991-02-01
Unique continuation for Schrödinger operators with potential in Morrey spaces Authors: Ruiz, Alberto,Vega, Luis Let us consider in a domain O of Rn solutions of the differential inequality \|?u(x)\| = V(x)\|u(x)\|, x I O, where V is a non smooth, positive potential. We are interested in global unique continuation properties. That means that u must be identically zero on O if it vanishes on an open subset of O… Universitat Autonoma de Barcelona	1991-01-01
Well-posedness of the initial value problem for the Korteweg-de Vries equation Authors: Gustavo Ponce,Carlos E. Kenig,Luis Vega (1.1) &ItU + axu + U1xU = O, x, t E R { u(x, 0) = uo(x). The KdV equation, which was first derived as a model for unidirectional propagation of nonlinear dispersive long waves [21], has been considered in different contexts, namely in its relation with the inverse scattering method, in plasma… American Mathematical Society (AMS)	1991-01-01
Midscale dynamical features observed during 1987 in the North Equatorial Belt of Jupiter Authors: Agustín Sánchez-Lavega,D. Parker,G. Viscardy,P. Laques Abstract During the second half of 1987, we studied the motions and morphologic changes of features moving relative to a prominent dark oval and its associated “hollow” in Jupiter's North Equatorial Belt (NEB). Approximately 200 photographs and CCD images were analyzed and revealed numerous… Elsevier BV	1990-10-01
Motion of a ball on a rough horizontal surface after being stuck by a tapering rod Authors: Agustín Sánchez-Lavega,Agustín Salazar The horizontal motion of a sphere subject to slipping frictional forces and rolling and pivoting frictional torques is analysed. Seven cases occur depending on the initial value of the angular velocity. The conditions for each type of motion are discussed in terms of the impact and percussion angle… IOP Publishing	1990-07-01
Nonlinear small data scattering for the generalized Korteweg-de Vries equation Authors: Ponce, Gustavo,Vega, Luis Abstract We study the longtime stability of small solutions to the IVP for the generalized Korteweg-de Vries equation. We obtain a lower bound for the degrees of nonlinearity of the perturbation which guarantees that the small solutions of the nonlinear problem behave asymptotically like the… Elsevier BV	1990-05-01
Is the frictional force always opposed to the motion? Authors: Agustín Sánchez-Lavega,M A Arriandiaga,Agustín Salazar A common idea is that frictional force is always opposed to motion. With the aid of two examples the authors show how, in some cases, the frictional force acts in the same direction as the centre of mass velocity of the body accelerating it. IOP Publishing	1990-03-01
On the (generalized) Korteweg-de Vries equation Authors: Gustavo Ponce,Luis Vega,Carlos E. Kenig Duke University Press	1989-12-01
Theory of thermal diffusivity determination by the ‘‘mirage’’ technique in solids Authors: Agustín Salazar,J. Fernández,Agustín Sánchez-Lavega A complete theoretical treatment of the ‘‘mirage’’ (optical beam deflection) technique has been performed for thermal diffusivity measurements in solids. Numerical calculations of the transverse deflection show there is a linear relation between the first noncentral zeros of the real part of this… AIP Publishing	1989-06-01
Ground-based imaging of Jovian cloud morphologies and motions Authors: J.A. Quesada,Agustín Sánchez-Lavega Abstract Telescopic photographs of Jupiter obtained during one Jovian year (1975–1985) have been analyzed in order to study the morphology and motions of the great-scale cloud systems present in the northern hemisphere during the epoch pre- and post-Voyager flyby spacecraft mission (see Sanchez-… Elsevier BV	1988-12-01