Comments on the next generation of ground-based solar telescopes     

Jacques M. Beckers 《Solar physics》1996,169(2):431-442

The development of telescope capabilities tends to go in spurts. These are triggered by the availability of new techniques in optics, mechanics and/or instrumentation. So has nighttime telescope technology developed since the construction in the nineteen-forties of the 5-m Hale telescope, first by the introduction in the sixties of high efficiency electronic detectors, followed recently by the production of large 8- to 10-m mirrors and now by the implementation of adaptive optics. In solar astronomy, major steps were the introduction of the coronagraph by Lyot in the nineteen-thirties and the vacuum telescope concept by Dunn in the sixties. In the last thirty years, telescope developments in solar astronomy have relied primarily on improved instrumental capabilities. As in nighttime astronomy, these instruments and their detectors are reaching their limits set by the quantum nature of light and the telescope diffraction. Larger telescopes are needed to increase sensitivity and angular resolution of the observations. In this paper, I will review recent efforts to increase substantially the telescope capabilities themselves. I will emphasize the concept of a large all-wavelength, coronagraphic telescope (CLEAR) which is presently being developed.Dedicated to Cornelis de Jager  相似文献   

Vanadiferous minerals from the Nereus Deep, Red Sea     

Jacques Jedwab  Gérard Blanc  Jacques Boulegue 《地学学报》1989,1(2):188-194

The chemical analysis by EMPEDS of 140 samples in cores from six Red Sea troughs and basins has led to the discovery in the Nereus Deep of high vanadium concentrations (up to 1.3% V₂O₃) in several bulk samples, and to the isolation of a major magnetite phase. This vanado-magnetite, remarkable for its high content of vanadium (mean = 1.45% V₂O₃) and its lack of titanium, is frequently zoned, the V-content decreasing toward the outer zones. Oxides with up to 42% V₂O₃, have also been found. Since the origin of the magnetite is clearly authigenic, its high vanadium and low titanium concentrations are traced back to the differential hydrothermal leaching of Fe—Ti-oxides which occur profusely in basic eruptive rock clasts, actually present in some of the overlying seams.  相似文献   

Colombo's top     

Jacques Henrard  Charles Murigande 《Celestial Mechanics and Dynamical Astronomy》1987,40(3-4):345-366

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Periodic orbits emanating from a resonant equilibrium     

Jacques Henrard 《Celestial Mechanics and Dynamical Astronomy》1970,1(3-4):437-466

For a conservative Hamiltonian system with two degrees of freedom, in the case where the two frequencies at an equilibrium of the elliptic type are commensurable or close to being so, completely canonical transformations can be formally constructed in explicit terms under the form of Lie transforms to the effect that it renders one angle coordinate ignorable and gives to the transformed Hamiltonian the form of what Garfinkel calls an ideal problem of resonance. For the problem so reduced, the unnormalized residual being omitted, natural families of periodic orbits are analyzed, their emergence from the equilibrium is discussed as well as their characteristic exponents. Special attention is given to the evolution of the system of natural families under a continuous transition through the resonance band.  相似文献   

Seismic scattering and shallow structure of the moon in oceanus procellarum   总被引：1，自引：0，他引：1  

Anton M. Dainty  M. Nafi Toksöz  Kenneth R. Anderson  P. Jacques Pines  Y. Nakamura  G. Latham 《Earth, Moon, and Planets》1974,9(1-2):11-29

Long, reverberating trains of seismic waves produced by impacts and moonquakes may be interpreted in terms of scattering in a surface layer overlying a non-scattering elastic medium. Model seismic experiments are used to qualitatively demonstrate the correctness of the interpretation. Three types of seismograms are found, near impact, far impact and moonquake. Only near impact and moonquake seismograms contain independent information. Details are given in the paper of the modelling of the scattering processes by the theory of diffusion.Interpretation of moonquake and artificial impact seismograms in two frequency bands from the Apollo 12 site indicates that the scattering layer is 25 km thick, with a Q of 5000. The mean distance between scatterers is approximately 5 km at 25 km depth and approximately 2 km at 14 km depth; the density of scatterers appears to be high near the surface, decreasing with depth. This may indicate that the scatterers are associated with cratering, or are cracks that anneal with depth. Most of the scattered energy is in the form of scattered surface waves.Communication presented at the Lunar Science Institute Conference on Geophysical and Geochemical Exploration of the Moon and Planets, January 10–12, 1973.  相似文献   

Central forces depending on the distance only. Case where all the bounded orbits are periodic     

Jacques Roels  Christine Aerts 《Celestial Mechanics and Dynamical Astronomy》1988,44(1-2):77-85

It is shown in this paper that the only potentials corresponding to central force for which all the bounded orbits are periodic are the potential of the harmonic oscillator and of the two body problem. A discussion is given in the case where a circular orbit exists and when the orbits near the circular orbit are periodic.We calculate in these cases the angle between pericentre and apocentre.Celestial Mechanics  相似文献   

Elasto-Gravitational Deformation, Relative Gravity Changes and Earth dynamics     

Jacques Hinderer  Hilaire Legros 《Geophysical Journal International》1989,97(3):481-495

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Preface     

Jean Chapront  Jacques Henrard  Dieter Schmidt 《Celestial Mechanics and Dynamical Astronomy》1982,26(1):2-3

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The dynamics of the upper ocean: 2nd edn. O.M. Phillips. Cambridge University Press,Cambridge, 1980, viii + 336 pp., 67 illus., U.K. £ 7.95 (paperback).     

Jacques C.J. Nihoul 《Dynamics of Atmospheres and Oceans》1981,5(4):308

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A new solution to the Main Problem of Lunar Theory     

Jacques Henrard 《Celestial Mechanics and Dynamical Astronomy》1979,19(4):337-355

A new solution for the Main Problem on Lunar Theory is given. This solution maintains the advantages of an analytical solution and should be more accurate than previous analytical or numerical solutions. It contains the effects of the mass ratios which are often neglected in the definition of the Main Problem.  相似文献