The future of space science in the 21st century     

R.M. Bonnet 《Astrophysics and Space Science》2001,277(1-2):371-378

Space Science helped the start of the open space race after the launch of Sputnik-1 in 1957. Conversely, the use of space vehicles during the cold war allowed the scientists to conduct many observations and make discoveries which have dramatically changed our views of our own Solar System and of the Universe. What will be the future of this activity in the next century, with the disappearance of the cold war justification and in the context of shrinking budgets? Is there a future for space exploration? For what benefit and how will space science programmes be conducted? Who will be the main players? Are there limits to our ability to explore? The pioneers of space research in the post-Sputnik-1 era, like J-L. Steinberg, had both an easier and a more difficult time than space scientists of today. Nevertheless, space science will only survive in the next century if it succeeds in reaching the deep interest and motivation of society at large.  相似文献   

Relative Sea‐Level Changes During Roman Times in the Northwest Mediterranean: The 1st Century A.D. Fish Tank of Forum Julii,Fréjus,France     

Christophe Morhange  Nick Marriner  Pierre Excoffon  Stphane Bonnet  Clment Flaux  Helmut Zibrowius  Jean‐Philippe Goiran  Mourad El Amouri 《Geoarchaeology》2013,28(4):363-372

Fish tanks become fashionable throughout the Mediterranean area between the 1st century B.C. and the 1st century A.D. Because of this narrow chronological window, and their link to former sea level, they constitute precious archives to investigate relative sea level (RSL) since the Roman period, especially when combined with fossilized marine benthos found attached to the fish tank walls. Here, we present new results from an integrated analysis of a fish tank located in the Roman colony of Fréjus, Southeastern France. The well‐preserved biological remains on the fish tank wall allow us to estimate an RSL rise of 40 ± 10 cm at Fréjus since Roman times, consistent with a recently published range of −32 to −58 ± 5 cm for the Northwestern Mediterranean for the same time. By contrast, the findings contradict the ∼150 cm of RSL change since Roman times reported for the Northwestern Mediterranean by some authors. © 2013 Wiley Periodicals, Inc.  相似文献   

Expériences thermomécaniques à la machine de cisaillement sur roches métamorphiques     

G. Bonnet  P. Hinzelin  P. Jouanna 《Rock Mechanics and Rock Engineering》1978,11(1):39-67

RésuméExpériences thermomécaniques à la machine de cisaillement sur roches métamorphiques. L'introduction du principe de la conservation de l'énergie en Mécanique des Roches conduit à s'intéresser aux phénomènes thermiques qui accompagnent les transformations mécaniques élémentaires à l'intérieur d'un massif rocheux ou de ses discontinuités.Le présent article expose une expérimentation en laboratoire sur de telles discontinuités, conduite en procédant à des mesures d'échauffement sur le joint, à la suite d'essais en cisaillement simple sur des matériaux avec joint prédécoupé.Un calcul numérique de l'échauffement permet d'obtenir la répartition des températures qui peut être attendue sur le joint moyennant certaines hypothèses de répartition des contraintes. Les résultats montrent que la surface probable de contact est nettement inférieure à la section de l'échantillon.Une telle concentration de contraintes conduirait à repenser la validité des hypothèses utilisées classiquement dans le calcul de la stabilité des massifs rocheux.

---

SummaryThermomechanic Experiments by Shear Machine on Metamorphic Rocks The introduction of the principle of energy conservation in the field of rock mechanics leads to examination of the thermic phenomena which accompany the elementary mechanics inside a rock mass, or its discontinuities.This article describes laboratory experiments on such discontinuities, carried out using heat measurements at joints, following a shear test on materials with precut joints.A numerical heat calculation gives the distribution of temperatures which may be expected at the joint, given certain assumptions on the distribution of stresses. The results show that the probable contact surface is considerably smaller than the section of the sample.Such a concentration of stresses could question the validity of the assumptions generally used in stability calculations for rock masses.

---

ZusammenfassungThermomechanische Versuche mit metamorphen Gesteinen mit einer Schermaschine. Das Einführen des Prinzips der Energieaufbewahrung im Bereich der Felsmechanik führt zur näheren Betrachtung der thermischen Erscheinungen, die die elementaren, mechanischen Umwandlungen innerhalb einer Gesteinsmasse oder ihrer Diskontinuitäten begleiten.Dieser Beitrag beschreibt Laborversuche, die über solche Diskontinuitäten durchgeführt wurden und bei welchen die Erhitzung in einer Kluft gemessen wurde, und zwar nach einfachen Scher-Versuchen mit einem Material mit vorgeschnittener Kluft.Die numerische Ermittlung der Erhitzung gibt die Temperatureinteilung an, die anhand bestimmter Voraussetzungen hinsichtlich der Belastungsverteilung zu erwarten ist. Die Ergebnisse beweisen, daß die wahrscheinliche Kontaktfläche wesentlich kleiner ist als die Schnittfläche der Probe.Eine solche Spannungsanhäufung sollte zur Überprüfung der Gültigkeit der Voraussetzungen führen, worauf die Stabilitätskalkulationen der Gesteinsmassen gewöhnlich beruhen.

---

Notations A énergie de surface - c chaleur massique de la roche - F effort de cisaillement - k coefficient caractérisant la chaleur échangée à température constante lors d'une augmentation de surface libre - N _i normale à la surface de contact - qi flux de chaleur produit à partir de la surface de contact - T température - T _i contrainte excercée sur la surface de contact - U énergie interne - u _i vitesse - v vitesse de cisaillement - W travail des forces extérieures - s surface libre formée au cours de l'essai - x déplacement relatif entre 2 surfaces en contact - ₁ conductivité thermique à l'intérieur de la roche - ₂ conductivité thermique à l'intérieur de l'enrobage - contrainte de cisaillement sur la surface en contact Avec 29 Figures  相似文献   

Neotectonic and seismic activity in the Armorican and Cornubian Massifs: Regional stress field with glacio-isostatic influence?     

B. Van Vliet-Lanoë  S. Bonnet  B. Hallegouët  M. Laurent 《Journal of Geodynamics》1997,24(1-4)

In Brittany and SW England, evidence for low magnitude Quaternary seismicity can be found in sand pit exposures and beach sections. Deformation is especially well seen in alluvial and estuarine complexes resting on Late Pliocene sands or thick saprolite. The deformations are shallow, dominantly hydroplastic (high water-table) and led to overconsolidated sands, silts or clays. They reveal normal loading at micro (millimetric) and macro (decametric) scales as controlled by the local rheological properties of the sediments, by strikeslip faults associated with positive flower structures, folding, and intraformational water expulsion or hill slope sliding with reverse microfaulting. All the sites where these features occur, are in the vicinity of presumed active faults or steep slopes in highly fractured Proterozoic basement rocks indicating a possible shear zone. In most cases, these features are not associated with synsedimentary deformation, as strong superficial red soils are generally reworked by them. All these features are reworked by microfaulting after overconsolidation. Additional periglacial phenomena are superimposed on them and are often confused with them. Deformation occurred after the development of Holstenian peats (isotopic stage 11,400 ka BP) at Crozon (Brittany), after 317 ka BP (beginning of isotopic stage 9) in the Vilaine estuary, and in most other sites before the last rubified pedogenesis in the Middle Pleistocene (presumed isotopic stage 9). These dates correspond to the same episode that gave rise to the last main reactivation of the fossil cliff around 300 ka BP and to local uplift. One or several seismic clusters have taken place, probably due to delayed crustal rebound after a major glacial event (stage 10) and to rapid loading resulting from younger ice sheet growth (stage 8). Similar events occurred in late stage 7 and late stage 5. These events might have locally amplified the crustal deformation of the old Brittany and Cornubian Hercynian massifs resulting from a regional stress field especially from 400 ka to 200 ka BP. Stratigraphical, geodynamical and paleoclimatological implications are discussed.  相似文献   

Real‐time hybrid experiments with Newmark integration,MCSmd outer‐loop control and multi‐tasking strategies     

P. A. Bonnet  C. N. Lim  M. S. Williams  A. Blakeborough  S. A. Neild  D. P. Stoten  C. A. Taylor 《地震工程与结构动力学》2007,36(1):119-141

Real‐time hybrid testing is a promising technique for experimental structural dynamics, in which the structure under consideration is split into a physical test of key components and a numerical model of the remainder. The physical test and numerical analysis proceed in parallel, in real time, enabling testing of critical elements at large scale and at the correct loading rate. To date most real‐time hybrid tests have been restricted to simple configurations and have used approximate delay compensation schemes. This paper describes a real‐time hybrid testing approach in which non‐linearity is permitted in both the physical and numerical models, and in which multiple interfaces between physical and numerical substructures can be accommodated, even when this results in very stiff coupling between actuators. This is achieved using a Newmark explicit numerical solver, an advanced adaptive controller known as MCSmd and a multi‐tasking strategy. The approach is evaluated through a series of experiments on discrete mass–spring systems. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Helioseismology in the future     

R. M. Bonnet 《Solar physics》1983,82(1-2):487-493

We review the observables of helioseismology that can contribute to our knowledge of the physical conditions in the solar interior. We discuss the limitations which presently prevent helioseismology from reaching its ultimate goal. We finally present a list of projects which either are already underway or that are planned for the near future, and we conclude by showing the crucial role that space observations may play in the future.  相似文献   

Sediment supply to the Orange sedimentary system over the last 150 My: An evaluation from sedimentation/denudation balance     

D. Rouby  S. Bonnet  F. Guillocheau  K. Gallagher  C. Robin  F. Biancotto  O. Dauteuil  J. Braun 《Marine and Petroleum Geology》2009

The South African plateau is bordered by passive margin basins preserving the terrigeneous sediment produced during onshore erosion. As such, these basins potentially provide a record of the variation in onshore elevation and relief over time. Here we bring new constraints on the uplift and erosion of the Southern African plateau over the last 150 Ma from the perspective of the stratigraphic architecture of these basins. We review published data to quantify the terrigeneous supply eroded in the drainage area and preserved in the basins. The novel aspect of our approach is the integration of the evolution of the whole domain in sedimentation (i.e. not only the platform) as well as the onshore eroding region.  相似文献   

Seasonal dynamics of trophic relationships among co-occurring suspension-feeders in two shellfish culture dominated ecosystems     

Sébastien Lefebvre  Julio César Marín Leal  Stanislas Dubois  Francis Orvain  Jean-Louis Blin  Marie-Paule Bataillé  Alain Ourry  Robert Galois 《Estuarine, Coastal and Shelf Science》2009

The temporal dynamics of carbon and nitrogen isotope values of co-occurring suspension-feeders in two shellfish culture areas (Normandy, France) were investigated over two years to evaluate the inter-specific trophic partitioning and relative contributions of organic matter sources to benthic suspension-feeders' diet. Oysters (Crassostrea gigas), mussels (Mytilus edulis), cockles (Cerastoderma edule), slipper limpets (Crepidula fornicata), and sand-mason worms (Lanice conchilega) were sampled in an estuarine environment (Baie des Veys, east Cotentin, Normandy), while oysters, mussels, slipper limpets, and honeycomb worms (Sabellaria alveolata) were sampled in an open-marine environment (Lingreville-sur-mer, west Cotentin, Normandy). Whatever the sampling period, the bivalves, C. gigas and M. edulis, exhibited the lowest values of δ¹³C and δ¹⁵N compared with the other species. Feeding relationships among suspension-feeders in both C. gigas culture areas exhibited temporal variations due to the marine/estuarine influence and seasonal changes in food supply. In the open-marine ecosystem, the contribution of phytoplankton remained the most important for all species except S. alveolata, while in the estuarine ecosystem, microphytobenthos and/or macroalgae detritus contributed a larger extent to the organisms' diets. During phytoplankton bloom periods (e.g. May and July) suspension-feeders, except for S. alveolata, relied strongly on phytoplankton; however, the majority of suspension-feeders exhibited different opportunistic behaviour in winter when phytoplankton biomass might be a limiting factor. We hypothesized that differences in particle capture and selection by the suspension-feeders influenced their isotopic values. Feeding ecology of suspension-feeders partly explained why competition was limited and why ecosystems can often support unexpectedly large numbers of suspension-feeders. We also showed that understanding ecosystem characteristics of the organic matter sources is of primary importance to determine the extent to which members of the suspension-feeding guild potentially compete for food.  相似文献   

L’analyse morphologique spatialisée : apports d’une méthode à la détection des accidents,une nécessité dans l’approche hydrodynamique et karstologique des aquifères fissurés. Exemples dans le Nord de la France crayeux     

Thierry Bonnet  Jean-Pierre Colbeaux 《Geodinamica Acta》2013,26(3-4):223-235

Résumé

L’analyse morphologique spatialisée est une nouvelle méthode de détection des accidents utilisant les données morphométriques du relief (pente, orientation, altitude), extraites d’un modèle numérique de terrain précis par un programme informatique. Ce programme, en tenant compte des commandes morphogénétiques (lithologie, climat, chronologie), permet l’identification de modes morphométriques pour chaque type de morphologie et l’extraction des anomalies à ces modes. Certaines anomalies, après un traitement de hiérarchisation spatiale, sont interprétées comme des signatures tectoniques, l’analyse étant possible à l’échelle du versant. L’existence effective des accidents est validée à l’aide de méthodes de géologie structurale classiques. Par une meilleure définition de la position et de la géométrie des accidents, cette méthode peut permettre l’optimisation des études hydrodynamiques en aquifère fissuré, et dans le cas de réservoirs carbonatés, une approche spatiale de la karstification. Elle est appliquée ici à l’aquifère crayeux du Nord de la France, où, couplée à des enregistrements fins de données hydrogéologiques, elle permet l’identification de zones à transfert hydrodynamique rapide au droit d’accidents. Ces constatations conduisent à de nouvelles pistes de réflexions dans une région où la karstification n’est pas reconnue. © Elsevier, Paris  相似文献   

Amazonian floodplain water balance based on modelling and analyses of hydrologic and electrical conductivity data          下载免费PDF全文

Marie‐Paule Bonnet  Sébastien Pinel  Jérémie Garnier  Julie Bois  Géraldo Resende Boaventura  Patrick Seyler  David Motta Marques 《水文研究》2017,31(9):1702-1718

In the Amazon basin, floodplains form a complex mosaic of freshwater systems with differing morphologies, resulting in varied inundation patterns and heterogeneous chemical and ecological characteristics. In this study, we focused on the Janauacá floodplain, a medium‐sized system (786 km², including the local watershed) located along the Solimões River. Based on in situ and satellite observations acquired from November 2006 to November 2011, we computed water fluxes between the mainstream and the floodplain and examined the temporal dynamics of floodplain storage from river flooding, rainfall, runoff, and exchanges with groundwater through bank seepage for the 5 years from 2006 to 2011. The mainstream was the main input of water to the flooded area, accounting on average for 93% of total water inputs by the end of the water year. Direct precipitation and runoff from uplands contributed less than or equal to 5% and 10%, respectively. The seepage contribution was less than 1%. Model uncertainties, evaluated using Monte Carlo analysis of the input data and model parameters, showed that all water fluxes were relatively well constrained except for outflow through seepage, which had a standard deviation across simulations greater than 60%. The water balance computation was verified using electrical conductivity as an assumed non‐reactive tracer. Except during periods of very low water, the simulated and measured conductivities agreed well. Moreover, conductivity data analysis confirmed that the Janauacá system can be considered homogeneous in terms of electrical conductivity for filling percentages equal to or greater than 40% (i.e., when the water level is above 19.5 m, generally from April to August) but presented large heterogeneities during the rest of the hydrological cycle.  相似文献