Future Trends in Geomathematics | R.G. Craig and M.L. Labovitz (Editors), 1981. Methuen,London, 318 pp., £stg. 12.00 (hardcover)     

R.W. Le Maitre 《Earth》1983,19(1):92-93

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Regions and Restructuring in New Zealand: Issues And Questions in the 1980s     

Stephen Britton  Richard Le  Heron 《New Zealand geographer》1987,43(3):129-139

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Verification of a Similar Cycle Prediction for the Ascending and Peak Phases of Solar Cycle 23   总被引：3，自引：0，他引：3  

Jia-Long  Wang  Jian-Cun  Gong 《中国天文和天体物理学报》2002,2(5):396-398

Reviews of long-term predictions of solar cycles have shown that a precise prediction with a lead time of 2 years or more of a solar cycle remains an unsolved problem. We used a simple method, the method of similar cycles, to make long-term predictions of not only the maximum amplitude but also the smoothed monthly mean sunspot number for every month of Solar Cycle 23. We verify and compare our prediction with the latest available observational results.  相似文献   

The GraF instrument for Imaging Spectroscopy with the Adaptive Optics     

A. Chalabaev  E. Le Coarer  P. Rabou  Y. Magnard  P. Petmezakis  D. Le Mignant 《Experimental Astronomy》2002,14(3):147-181

The GraF instrument using a Fabry-Perot interferometer cross-dispersed with a grating was one of the first integral-field and long-slit spectrographs built for and used with an adaptive optics system. We describe its concept, design, optimal observational procedures and the measured performances. The instrument was used in 1997–2001 at the ESO3.6 m telescope equipped with ADONIS adaptive optics and SHARPII+camera. The operating spectral range was 1.2–2.5 μm. We used the spectral resolution from 500 to 10 000 combined with the angular resolution of 0.1″–0.2″. The quality of GraF data is illustrated by the integral field spectroscopy of the complex0.9″ × 0.9″ central region of η Car in the1.7 μm spectral range at the limit of spectral and angular resolutions. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Cassini/VIMS hyperspectral observations of the HUYGENS landing site on Titan     

S. Rodriguez  S. Le Moulic  C. Sotin  H. Clnet  R.N. Clark  B. Buratti  R.H. Brown  T.B. McCord  P.D. Nicholson  K.H. Baines  the VIMS Science Team 《Planetary and Space Science》2006,54(15):1510-1523

Titan is one of the primary scientific objectives of the NASA–ESA–ASI Cassini–Huygens mission. Scattering by haze particles in Titan's atmosphere and numerous methane absorptions dramatically veil Titan's surface in the visible range, though it can be studied more easily in some narrow infrared windows. The Visual and Infrared Mapping Spectrometer (VIMS) instrument onboard the Cassini spacecraft successfully imaged its surface in the atmospheric windows, taking hyperspectral images in the range 0.4–5.2 μm. On 26 October (TA flyby) and 13 December 2004 (TB flyby), the Cassini–Huygens mission flew over Titan at an altitude lower than 1200 km at closest approach. We report here on the analysis of VIMS images of the Huygens landing site acquired at TA and TB, with a spatial resolution ranging from 16 to14.4 km/pixel. The pure atmospheric backscattering component is corrected by using both an empirical method and a first-order theoretical model. Both approaches provide consistent results. After the removal of scattering, ratio images reveal subtle surface heterogeneities. A particularly contrasted structure appears in ratio images involving the 1.59 and 2.03 μm images north of the Huygens landing site. Although pure water ice cannot be the only component exposed at Titan's surface, this area is consistent with a local enrichment in exposed water ice and seems to be consistent with DISR/Huygens images and spectra interpretations. The images show also a morphological structure that can be interpreted as a 150 km diameter impact crater with a central peak.  相似文献   

GALACSI – The ground layer adaptive optics system for MUSE     

Remko Stuik  Roland Bacon  Ralf Conzelmann  Bernard Delabre  Enrico Fedrigo  Norbert Hubin  Miska Le Louarn  Stefan Strbele 《New Astronomy Reviews》2006,49(10-12):618

MUSE, the Multi-Unit Spectroscopic Explorer, is an adaptive optics (AO)-assisted Integral Field Spectrograph, currently in the Preliminary Design Phase as a second generation instrument for the VLT. MUSE will feature two modes, each with an associated AO mode. The first mode is the wide field mode, mainly aiming at the study of high redshift galaxies. For this mode, the AO system has to deliver an improvement of at least a factor of two over the full 1′ × 1′ field of view. The second mode, the narrow field mode, aims at the high-resolution spectroscopy of nearby extended objects, for example, galaxies and globular clusters. For this mode, the AO system will have to deliver near-diffraction limited performance over a small field of view. In this paper, we discuss the trade-offs in the current design of GALACSI – the MUSE AO system – and illustrate with a number of simulations the expected performance in the wide- and narrow field modes.  相似文献   

50 Myr recovery from the largest negative δ13C excursion in the Ediacaran ocean     

Erwan Le Guerrou  Philip A. Allen  Andrea Cozzi  James L. Etienne  Mark Fanning 《地学学报》2006,18(2):147-153

Sedimentary rocks deposited during the Ediacaran period (～630–542 Ma) contain carbonates whose carbon isotopic ratios show a marked negative excursion consisting of a precipitous drop from +5‰ to ?12‰, followed by a sub‐linear recovery to positive δ¹³C values. Isotopic ages (U/Pb) and thermal subsidence modelling are combined to constrain the excursion in time and indicate an onset at ～600 Ma, and duration of recovery of approximately 50 Myr. The excursion is widely recognized in Oman and has potential correlatives in Ediacaran strata elsewhere, and may thus represent a characteristic feature of the Ediacaran period. The amplitude of this carbon isotope excursion far exceeds those of other Neoproterozoic anomalies. The isotopic trend of negative excursion and long‐term recovery spanned at least one short‐lived glacial episode (at 580 Ma), but appears unrelated to glaciation, which indicates that negative anomalies in the Neoproterozoic marine carbon isotope record are not directly or uniquely linked to ice ages.  相似文献   

Reply to the Comments by J. A. Battjes on ‘Relationships between narrow-band directional energy spectra and probability densities of deep and shallow water waves’     

B. Le Méhauté 《Applied Ocean Research》1983,5(2):110-111

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Atmospheric radiative equilibria in a simple column model     

Z.-X. Li  K. Ide  H. Le Treut  M. Ghil 《Climate Dynamics》1997,13(6):429-440

 An analytic radiative-equilibrium model is formulated where both short- and longwave radiation are treated as two-stream (down- and upward) fluxes. An equilibrium state is defined in the model by the vertical temperature profile. The sensitivity of any such state to the model atmosphere’s optical properties is formulated analytically. As an example, this general formulation is applied to a single-column 11-layer model, and the model’s optical parameters are obtained from a detailed radiative parametrization of a general circulation model. The resulting simple column model is then used to study changes in the Earth-atmosphere system’s radiative equilibrium and, in particular, to infer the role of greenhouse trace gases, water vapor and aerosols in modifying the vertical temperature profile. Multiple equilibria appear when a positive surface-albedo feedback is introduced, and their stability is studied. The vertical structure of the radiative fluxes (both short- and longwave) is substantially modified as the temperature profile changes from one equilibrium to another. These equilibria and their stability are compared to those that appear in energy-balance models, which heretofore have ignored the details of the vertical temperature and radiation profiles. Received: 22 December 1995/Accepted: 17 January 1997  相似文献   

Possible evidence for continued ejection of RR telescopii     

Michaël Friedjung 《Astrophysics and Space Science》1974,29(1):L5-L6

FeII and [FeII] intensity measures enable the size of the region containing singly ionized iron to be estimated, calculations for a phase near maximum light support a continued ejection model.  相似文献