The geometry of the Archean, Paleo- and Neoproterozoic tectonics in the Southwest Cameroon     

Sbastien Owona  Joseph Mvondo Ondoa  Lothar Ratschbacher  Simon Pierre Mbola Ndzana  Flix M. Tchoua  Georges Emmanuel Ekodeck 《Comptes Rendus Geoscience》2011,343(4):312-322

  相似文献   

Simulating ocean acoustic tomography measurements with Hamiltonian ray tracing     

Georges  T. Jones  R. Riley  J. 《Oceanic Engineering, IEEE Journal of》1986,11(1):58-71

Tomographers map mesoscale ocean structure by inverting acoustic travel-time measurements through networks of underwater paths. To know where to deploy sensors and how to interpret their measurements, one must first understand the "forward problem," that is, how the sound channel and mesoscale features refract sound in three dimensions, and how such refraction alters the pulse-arrival sequence. We use a Hamiltonian ray-tracing program called HARPO to compute the refraction by continuous three-dimensional ocean models and to display the results in ways that add insight about refractive effects. We first simulate propagation in a simple range-independent sound channel, showing how pulse-arrival sequence depends on channel parameters and sensor placement. Next, we add linear range dependence and show that it is hard to extract range information from pulse measurements at one range. Finally, we add a simple model of a mesoscale eddy including its currents and show that deflection and splitting of the sound channel significantly alter the pulse-arrival sequence. Two diagrams that have not been widely used before are useful ways to display the arrival-time and ray-focusing perturbations caused by changes in ocean structure: they are plots of range versus launch angle and range versus travel time. Examples of azimuthal deflection, three-dimensional eigenrays, and reciprocal propagation through eddy currents are shown, and simplified methods for estimating the travel time of three-dimensional eigenrays are evaluated.  相似文献   

Primary nitrogen production at low Z     

Georges Meynet 《Astrophysics and Space Science》2002,279(1-2):183-186

Stellar models with axial rotation and very low metallicity Z, typical of the early star generations have been computed. These models account for the effects of rotation in the same way as previous grids which successfully reproduce the He- and N-enrichments observed at the surface of massive stars, and also the high numbers of red supergiants observed in low Z galaxies (Meynet and Maeder, 2000; Maeder and Meynet, 2001). At very low metallicity (Z = 0.00001, i.e. one two thousandth of the solar metallicity),these models naturally lead to the production of primary nitrogen. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

Gravitational potential harmonics from the shape of an homogeneous body   总被引：3，自引：0，他引：3  

Georges Balmino 《Celestial Mechanics and Dynamical Astronomy》1994,60(3):331-364

The spherical harmonic coefficients of the gravitational potential of an homogeneous body are analytically derived from the harmonics describing its shape. General formulas are given as well as detailed expressions up to the fifth order of the topography harmonics. The volume, surface and inertia tensor of the body are obtained as by-products. The case of a triaxial ellipsoid is given as example and used for numerical checking. Another numerical scheme for verification is provided. The application to Phobos is made and the convergence of the expressions for the harmonics is numerically established.

---

Résumé Les harmoniques du champ de gravitation d'un corps homogène de forme donnée sont calculés analytiquement à partir des harmoniques du développement en série du rayon vecteur exprimant la forme de la surface du corps. Outre la formule générale, des expressions détaillées, au cinquième ordre des harmoniques du rayon vecteur, sont données sous une forme bien adaptée à la programmation. Le volume, la surface et le tenseur d'inertie du corps sont calculés analytiquement `a partir des formules générales. Le cas de l'ellipsoide triaxial est pris comme test des formules établies. Un autre test numérique est fourni dans le cas le plus général. Ceci est appliqué à Phobos, et la convergence des expressions fournissant les harmoniques est numériquement démontrée.

  相似文献   

Matrix methods for generally stratified media     

Georges Jobert 《Geophysical Journal International》1976,47(2):351-362

  相似文献   

The 2010 European Venus Explorer (EVE) mission proposal     

Colin Frank Wilson  Eric Chassefière  Emmanuel Hinglais  Kevin H. Baines  Tibor S. Balint  Jean-Jacques Berthelier  Jacques Blamont  Georges Durry  Csaba S. Ferencz  Robert E. Grimm  Takeshi Imamura  Jean-Luc Josset  Fran?ois Leblanc  Sebastien Lebonnois  Johannes J. Leitner  Sanjay S. Limaye  Bernard Marty  Ernesto Palomba  Sergei V. Pogrebenko  Scot C. R. Rafkin  Dean L. Talboys  Rainer Wieler  Liudmila V. Zasova  Cyrill Szopa 《Experimental Astronomy》2012,33(2-3):305-335

The European Venus Explorer (EVE) mission described in this paper was proposed in December 2010 to ESA as an ‘M-class’ mission under the Cosmic Vision programme. It consists of a single balloon platform floating in the middle of the main convective cloud layer of Venus at an altitude of 55?km, where temperatures and pressures are benign (～25°C and ～0.5 bar). The balloon float lifetime would be at least 10 Earth days, long enough to guarantee at least one full circumnavigation of the planet. This offers an ideal platform for the two main science goals of the mission: study of the current climate through detailed characterization of cloud-level atmosphere, and investigation of the formation and evolution of Venus, through careful measurement of noble gas isotopic abundances. These investigations would provide key data for comparative planetology of terrestrial planets in our solar system and beyond.  相似文献   

A Review of “Turf Wars: Discourse,Diversity, and the Politics of Place”     

Georges G. Cravins 《The Professional geographer》2013,65(1):138-141

The spatial correlation, or colocation, of two or more variables is a fundamental issue in geographical analysis but has received much less attention than the spatial correlation of values within a single variable, or autocorrelation. A recent paper by Leslie and Kronenfeld (2011) contributes to spatial correlation analysis in its development of a colocation statistic for categorical data that is interpreted in the same way as a location quotient, a frequently used measure in human geography and other branches of regional analysis. Geographically weighted colocation measures for categorical data are further developed in this article by generalizing Leslie and Kronenfeld's global measure as well as specifying a local counterpart for each global statistic using two different types of spatial filters: fixed and adaptive. These geographically weighted colocation quotients are applied to the spatial distribution of housing types to demonstrate their utility and interpretation.  相似文献   

Experimental and theoretical study of the vibrational properties of diaspore (α-AlOOH)     

Simon?Delattre  Etienne?BalanEmail author  Michele?Lazzeri  Marc?Blanchard  Maxime?Guillaumet  Olivier?Beyssac  Eiken?Haussühl  Bj?rn?Winkler  Ekhard?K.?H.?Salje  Georges?Calas 《Physics and Chemistry of Minerals》2012,39(2):93-102

Vibrational properties of diaspore, α-AlOOH, have been re-investigated using room-temperature single-crystal Raman spectroscopy and low-temperature powder infrared (IR) transmission spectroscopy. First-principles harmonic calculations based on density functional theory provide a convincing assignment of the major Raman peaks and infrared absorption bands. The large width of the Raman band related to OH stretching modes is ascribed to mode–mode anharmonic coupling due to medium-strength H-bonding. Additional broadening in the powder IR spectrum arises from depolarization effects in powder particles. The temperature dependence of the IR spectrum provides a further insight into the anharmonic properties of diaspore. Based on their frequency and temperature behavior, narrow absorption features at ~2,000 cm⁻¹ and anti-resonance at ~2,966 cm⁻¹ in the IR spectrum are interpreted as overtones of fundamental bending bands.  相似文献   

Mineralium Deposita: change and continuity     

Georges Beaudoin  Bernd Lehmann 《Mineralium Deposita》2012,47(8):835-836

  相似文献   

Cosmogenic Be dating of a sackung and its faulted rock glaciers, in the Alps of Savoy (France)     

Jean-Claude Hippolyte  Didier Bourls  Rgis Braucher  Julien Carcaillet  Laëtitia Lanni  Maurice Arnold  Georges Aumaitre 《Geomorphology》2009,108(3-4):312-320

Sackungs are the largest gravitational deformation observed in mountains. They are characterized by the long-term slowness of the movements, but their mechanism is still not well understood. Nowadays cosmic ray exposure (CRE) dating methods allow dating the morphologic structures involved in sackung and can contribute at the understanding of their origin. In the Alps, the 5.3 km long Arcs sackung initiated during the activity of rock glaciers. Three samples from these faulted rock glaciers provide their first CRE ages and show that at 2000 m elevation these block accumulations moved during the Younger Dryas and stopped in early Holocene. Six ¹⁰Be ages of fault scarps show that the Arcs sackung lasted only a few thousand years and stopped at about 8462 ± 432 ¹⁰Be yr. They also reveal that deformation migrated upslope in agreement with a mechanism of flexural toppling of vertical layers. This unique and long gravitational event, characterized by migration of the deformation, does not support earthquake shaking as triggering mechanism for individual faults. It shows that, in the upper Isère valley, slope deformation was delayed of several thousand years after glacial debuttressing, and is not anymore active despite its fresh morphology.  相似文献