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31.
Annick Blusson 《Earth, Moon, and Planets》1987,38(1):1-11
This study deals with the comparison between Landsat MSS usual data, extensively used in the past, and Spacelab new photographies for geological application. Both data have been processed but the best results were obtained by interpreting original data. Classical image processing techniques were applied but they did not help much apart from geometrical correction which is essential for Landsat MSS images. Geological and structural interpretations were conducted for both types of data and compared. The results show that, even if Landsat MSS images provide a good approach for geological mapping, Spacelab photos allow more accurate and detailed interpretations. This is mostly due to the 20 meters resolution of the photos (80 meters for Landsat), and also to the potentiality of stereoscopic view (not immediate with Landsat). Spacelab data seem to be today the best document a geologist can use to produce geologic and structural maps. 相似文献
32.
Annick Bec-Borsenberger 《Celestial Mechanics and Dynamical Astronomy》1982,26(3):271-276
We study a theory for the ninth satellite of Saturn, Phoebe, based on the literal solution we have obtained in the main problem of the lunar theory.These series were computed by solving, by successive approximations, the Lagrange's equations expressed in variables, functions of the elliptic elements.We may consider the case of Phoebe simpler than a lunar case because we seek less precision (1/10 geocentric) than in the Lunar case, although the eccentricity of Phoebe is stronger.Main problem: our series are computed to the complete seventh order and a great part of the perturbations of the eighth and ninth order, where we have attributed to the small lunar parameters the order 1 tom
0=n/n
0,e
0,e, sin (i
0/2), the order 2 to 0=(a
0/a)((M
1–)/(M
1+M)) and the order 4 toµ
0(a
0/a)M
1
M/M
1
2
–M
2.In the case of Phoebe,µ
0 equal zero and ±0 is the ratioa
0/a.We study the further development of these series by using, instead of parameterm
0, the quantity m
0=n/n
0–m
1 wherem
1 is an approached value ofm
0, in order to accelerate the convergence of the series with respect tom
0.Comparison with a numerical integration we are adjusting a numerical integration to the observations. We have already more than 100 observations, for the period 1900–1957.At first, we compare the series of the main problem to a numerical integration of the Keplerian problem.
Proceedings of the Conference on Analytical Methods and Ephemerides: Theory and Observations of the Moon and Planets. Facultés universitaires Notre Dame de la Paix. Namur, Belgium, 28–31 July, 1980. 相似文献
Proceedings of the Conference on Analytical Methods and Ephemerides: Theory and Observations of the Moon and Planets. Facultés universitaires Notre Dame de la Paix. Namur, Belgium, 28–31 July, 1980. 相似文献
33.
34.
General database for ground water site information 总被引:3,自引:0,他引:3
de Dreuzy JR Bodin J Le Grand H Davy P Boulanger D Battais A Bour O Gouze P Porel G 《Ground water》2006,44(5):743-748
In most cases, analysis and modeling of flow and transport dynamics in ground water systems require long-term, high-quality, and multisource data sets. This paper discusses the structure of a multisite database (the H+ database) developed within the scope of the ERO program (French Environmental Research Observatory, http://www.ore.fr). The database provides an interface between field experimentalists and modelers, which can be used on a daily basis. The database structure enables the storage of a large number of data and data types collected from a given site or multiple-site network. The database is well suited to the integration, backup, and retrieval of data for flow and transport modeling in heterogeneous aquifers. It relies on the definition of standards and uses a templated structure, such that any type of geolocalized data obtained from wells, hydrological stations, and meteorological stations can be handled. New types of platforms other than wells, hydrological stations, and meteorological stations, and new types of experiments and/or parameters could easily be added without modifying the database structure. Thus, we propose that the database structure could be used as a template for designing databases for complex sites. An example application is the H+ database, which gathers data collected from a network of hydrogeological sites associated with the French Environmental Research Observatory. 相似文献
35.
C. Pichon A. Siebert O. Bienaymé 《Monthly notices of the Royal Astronomical Society》2002,329(1):181-194
A method for inverting the statistical star counts equation, including proper motions, is presented; in order to break the degeneracy in that equation, it uses the supplementary constraints required by dynamical consistency. The inversion gives access to both the kinematics and the luminosity function of each population in three régimes: the singular ellipsoid, the constant ratio Schwarzschild ellipsoid plane-parallel models and the epicyclic model. This more realistic model is tailored to account for the local neighbourhood density and velocity distribution.
The first model is fully investigated, both analytically and by means of a non-parametric inversion technique, while the second model is shown to be formally its equivalent. The effect of noise and incompleteness in apparent magnitude is investigated. The third model is investigated by a non-parametric inversion technique where positivity of the underlying luminosity function is explicitly accounted for.
It is argued that its future application to data such as the Tycho catalogue (and in the upcoming satellite GAIA ) could lead – provided that the vertical potential and or the asymmetric drift or w⊙ are known – to a non-parametric determination of the local neighbourhood luminosity function without any reference to stellar evolution tracks. It should also yield the proportion of stars for each kinematic component and a kinematic diagnostic to split the thin disc from the thick disc or the halo. 相似文献
The first model is fully investigated, both analytically and by means of a non-parametric inversion technique, while the second model is shown to be formally its equivalent. The effect of noise and incompleteness in apparent magnitude is investigated. The third model is investigated by a non-parametric inversion technique where positivity of the underlying luminosity function is explicitly accounted for.
It is argued that its future application to data such as the Tycho catalogue (and in the upcoming satellite GAIA ) could lead – provided that the vertical potential and or the asymmetric drift or w
36.
Luca Sorriso-Valvo Vincenzo Carbone Valentina I. Abramenko Alain Noullez Annick Pouquet 《Planetary and Space Science》2004,52(10):937-943
The detection of magnetic field variations as a signature of flaring activity is one of the main goals in solar physics. Past efforts gave apparently no unambiguous observations of systematic changes. In the present study, we discuss recent results from observations that scaling laws of turbulent current helicity inside a given flaring active region change in response to large flares in that active region. Such changes can be related to the evolution of current structures by a simple geometrical argument, which has been tested using high Reynolds number direct numerical simulations of the MHD equations. Interpretation of the observed data within this picture indicates that the change in scaling behavior of the current helicity seems to be associated with a topological reorganization of the footpoint of the magnetic field loops, namely with the dissipation of small scales structures in turbulent media. 相似文献
37.
Rafael Fernandez-Carazo Elie Verleyen Dominic A. Hodgson Stephen J. Roberts Krzysztof Waleron Wim Vyverman Annick Wilmotte 《Journal of Paleolimnology》2013,50(1):15-31
Despite the dominance of cyanobacteria in polar freshwater aquatic ecosystems, little is known about their past biodiversity and response to climate and environmental changes. We explored the use of light microscopy of microfossils, high performance liquid chromatography of the fossil pigment composition and denaturing gradient gel electrophoresis of fossil 16S rRNA genes to study past and present-day differences in cyanobacterial community structure in response to climate changes in two adjacent maritime Antarctic lakes with contrasting depths (4 and 26 m) and light climates. Light microscopy was of limited use because of degradation of cell structures. Fossil cyanobacterial pigment concentrations were below the detection limits of our method in several sediment samples in the deep lake, but abundant and diverse in the sediment core from the shallow pond, probably as a consequence of increased light availability and/or a more diverse and abundant benthic cyanobacterial flora. Total carotenoid and chlorophyll concentrations were highest in both lakes between ca. 2,950 and 1,800 cal yr BP, which coincides with the late Holocene climate optimum recognised elsewhere in maritime Antarctica. Cyanobacterial molecular diversity was higher in the top few centimeters of the sediments in both lakes. In deeper sediments, the taxonomic turnover of cyanobacteria appeared to be relatively small in response to past climate anomalies in both lakes, underscoring the broad tolerance of cyanobacteria to environmental variability. This, however, may in part be explained by the low taxonomic resolution obtained with the relatively conserved 16S rRNA gene and/or the preferential preservation of particular taxa. Our results highlight the potential of fossil DNA in lake sediments to study colonization and succession dynamics of lacustrine cyanobacteria and warrant further investigation of the factors that affect preservation of cyanobacterial DNA. 相似文献
38.
J. Thiébaut C. Pichon T. Sousbie S. Prunet D. Pogosyan 《Monthly notices of the Royal Astronomical Society》2008,387(1):397-406
The onset of stochasticity is measured in Λ cold dark matter cosmological simulations using a set of classical observables. It is quantified as the local derivative of the logarithm of the dispersion of a given observable (within a set of different simulations differing weakly through their initial realization), with respect to the cosmic growth factor. In an Eulerian framework, it is shown here that chaos appears at small scales, where dynamic is non-linear, while it vanishes at larger scales, allowing the computation of a critical transition scale corresponding to ∼3.5 Mpc h −1 . This picture is confirmed by Lagrangian measurements which show that the distribution of substructures within clusters is partially sensitive to initial conditions, with a critical mass upper bound scaling roughly like the perturbation's amplitude to the power 0.15. The corresponding characteristic mass, M crit = 2 1013 M⊙ , is roughly of the order of the critical mass of non-linearities at z = 1 and accounts for the decoupling induced by the dark energy triggered acceleration.
The sensitivity to detailed initial conditions spills to some of the overall physical properties of the host halo (spin and velocity dispersion tensor orientation) while other 'global' properties are quite robust and show no chaos (mass, spin parameter, connexity and centre-of-mass position). This apparent discrepancy may reflect the fact that quantities which are integrals over particles rapidly average out details of difference in orbits, while the other observables are more sensitive to the detailed environment of forming haloes and reflect the non-linear scale coupling characterizing the environments of haloes. 相似文献
The sensitivity to detailed initial conditions spills to some of the overall physical properties of the host halo (spin and velocity dispersion tensor orientation) while other 'global' properties are quite robust and show no chaos (mass, spin parameter, connexity and centre-of-mass position). This apparent discrepancy may reflect the fact that quantities which are integrals over particles rapidly average out details of difference in orbits, while the other observables are more sensitive to the detailed environment of forming haloes and reflect the non-linear scale coupling characterizing the environments of haloes. 相似文献
39.
40.
L. Bourcier K. Sellegri P. Chausse J. M. Pichon P. Laj 《Journal of Atmospheric Chemistry》2012,69(1):47-66
The size-segregated chemical composition of aerosol particles was investigated during 1?year at the puy de D?me (1,465?m?a.s.l.), France. These measurements aimed to a better understanding of the influence of the air mass origin on the size-segregated chemical composition of the aerosol at an altitude site. Mountain site measurements are important because they are representative of long range transport and useful for model validation. PM1 mass concentration exhibits a seasonal variability with a summer maximum. The composition of PM1 did not change significantly in terms of relative contribution of water soluble inorganic ions but is rather variable in term of total mass concentrations. For the PM10-1, a different seasonal behaviour was found with maxima concentrations in autumn-winter. Aerosols were classified into four different categories according to their air mass origin: marine, marine modified, continental and Mediterranean. The PM10 aerosol mass at 50?% relative humidity was close to 2.5???g?m?3 in the marine, 4.3???g?m?3 in the marine modified, 10.3???g?m?3 in the continental and 7.7???g?m?3 in the Mediterranean sectors. We noted that the influence of the air mass origin (on the chemical properties) could be seen especially on the PM10-1. A significant PM10-1 mode was found in marine, modified marine, and Mediterranean air masses, and PM1 dominated in the continental air masses samples. As a result, the aerosol chemical composition variability at the puy de D?me is a function of both the season and air mass type and we provide a chemical composition of the aerosol as a function of each of these environmental factors. 相似文献