C^k-Reconstruction of Surfaces from Partial Data     

Dominique Apprato  Christian Gout  Pascale Sénéchal 《Mathematical Geology》2000,32(8):969-983

In this paper, we study the problem of constructing a smooth approximant of a surface defined by the equation z = f(x ₁, x ₂), the data being a finite set of patches on this surface. This problem occurs, for example, after geophysical processing such as migration of time-maps or depth-maps. The usual algorithms to solve this problem are picking points on the patches to get Lagrange's data or trying to get local junctions on patches. But the first method does not use the continuous aspect of the data and the second one does not perform well to get a global regular approximant (C ¹ or more). As an approximant of f, a discrete smoothing spline belonging to a suitable piecewise polynomial space is proposed. The originality of the method consists in the fidelity criterion used to fit the data, which takes into account their particular aspect (surface's patches): the idea is to define a function that minimizes the volume located between the data patches and the function, and which is globally C ^k. We first demonstrate the new method on a theoretical aspect and numerical results on real data are given.  相似文献   

Analysis of Transient Data from Infiltrometer Tests in Fine-Grained Soils     

Dominique Guyonnet  Nadia Amraoui  Reda Kara 《Ground water》2000,38(3):396-402

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Dating fluvial erosion: fluvial response to climate change in the Moselle catchment (France,Germany) since the Late Saalian     

Stéphane Cordier  Manfred Frechen  Dominique Harmand 《Boreas: An International Journal of Quaternary Research》2014,43(2):450-468

This paper focuses upon the youngest terraces of the Moselle and its tributary the Meurthe (NE France and SW Germany). It includes research on several sections, in particular the key sections of Golbey‐Pré Droué and Thörnich‐Hochrech (located in the vicinity of the Vosges Massif and in the Rhenish Massif, respectively), and the use of the Optically Stimulated Luminescence (OSL) dating method. Our investigations made it possible to obtain a more robust chronostratigraphical framework and to update the previous model of fluvial response to climate change. The results demonstrate that the Moselle terrace M3 (first terrace formed after the capture of the Upper Moselle by the Palaeo‐Meurthe) has the same age from the Vosges to the Rhenish Massif. The formation of this terrace included two main periods of sedimentation attributed to the Late Saalian (MIS 6) and the Early Weichselian (MIS 5), respectively. They were separated by a major episode of fluvial erosion that may be allocated to the MIS 6–5 transition on the basis of chronological and sedimentological evidence. This erosion led to the removal of most of the MIS 6 deposits, whereas the MIS 5 deposits have been widely preserved following the subsequent (MIS 5–4) terrace incision. This evolution somewhat contrasts with that observed in the Sarre valley, the main tributary of the Moselle, and with many fluvial systems in western Europe, which show better preservation of deposits from cold periods. This atypical behaviour is explained by the relationship between the fluvial evolution and the glaciers covering the upper Moselle catchment (Vosges Massif) during the Pleistocene cold periods.  相似文献   

The ability of detainment bunds to decrease sediments transported from pastoral catchments in surface runoff     

Brian Levine  Lucy Burkitt  Dave Horne  Chris Tanner  James Sukias  Leo Condron  John Paterson 《水文研究》2021,35(8):e14309

Erosion leading to sedimentation in surface water may disrupt aquatic habitats and deliver sediment-bound nutrients that contribute to eutrophication. Land use changes causing loss of native vegetation have accelerated already naturally high erosion rates in New Zealand and increased sedimentation in streams and lakes. Sediment-bound phosphorus (P) makes up 71–79% of the 17–19 t P y⁻¹ delivered from anthropogenic sources to Lake Rotorua in New Zealand. Detainment bunds (DBs) were first implemented in the Lake Rotorua catchment in 2010 as a strategy to address P losses from pastoral agriculture. The bunds are 1.5–2 m high earthen stormwater retention structures constructed across the flow path of targeted low-order ephemeral streams with the purpose of temporarily ponding runoff on productive pastures. The current DB design protocol recommends a minimum pond volume of 120 m³ ha⁻¹ of contributing catchment with a maximum pond storage capacity of 10 000 m³. No previous study has investigated the ability of DBs to decrease annual suspended sediment (SS) loads leaving pastoral catchments. Annual SS yields delivered to two DBs with 20 ha and 55 ha catchments were 109 and 28 kg SS ha⁻¹, respectively, during this 12-month study. The DBs retained 1280 kg (59%) and 789 kg (51%) of annual SS loads delivered from the catchments as a result of the bunds' ability to impede stormflow and facilitate soil infiltration and sediment deposition. The results of this study highlight the ability of DBs to decrease SS loads transported from pastures in surface runoff, even during large storm events, and suggests DBs are able to reduce P loading in Lake Rotorua.  相似文献   

Seismic response characteristics of marine reflection profiling systems     

S. J. Tanner 《Geophysical Journal International》1984,78(1):51-64

Summary. Factors influencing the seismic response characteristics of marine profiling systems are reviewed. The single frequency case is used to illustrate the influence of different frequencies on the response, as well as the towing depths of the source and receiver, and the geometry of a linear receiving array. The more realistic case of band-limited source waveforms is considered, using frequency spectra calculated from theoretically derived airgun signals. The results show that the number and shape of sidelobes of the profiling system response, as well as the filtering characteristics for reflections arising from reflectors in the vertical plane perpendicular to the axis of the receiver array are determined by the depths of the source and receiver and the relative amplitudes of the frequencies in the source waveform. These factors, along with the configuration of the hydrophone elements in the receiver array, determine the frequency and amplitude attenuation of reflections in the vertical plane containing the receiver array.
The filtering characteristics of the system both in and out of the vertical plane containing the receiver array are discussed, with implications for discriminating between off-axis and in-plane reflections. A plan view of the response of the system is constructed in the time domain for various profiling configurations and sources of different frequency content at a given time. This example shows how useful the resulting pictures are for optimizing acquisition parameters in profiling experiments.  相似文献   

Gaseous drag and planetary formation by accretion     

Dominique Spaute  Bernard Lago  Anny Cazenave 《Icarus》1985,64(1):139-152

We have made numerical experiments of the collisional and gravitational interaction of a planetesimal swarm in the early Solar System. In particular we study the dynamical evolution of an initial population of kilometer-size planetesimals subject to collisions (accretion, rebound, cratering, and catastrophic fragmentation). This study is based on a Monte-Carlo statistical method and provides the mass and velocity distributions of the planetesimal swarm as a function of time as well as their distribution in heliocentric distance. Several experiments have been performed and three of them are presented here. They simulate the accretional growth of numerous planetesimals in the absence (or presence) of gaseous drag, with (or without) one larger embryo among them, and with (or without) a size gradient. The results show that (i) for a population of planetesimals submitted to a negative gradient in size as the heliocentric distance increases, the outer planetesimals spiral toward the Sun faster than inner ones, leading after some time to an accumulation of bodies inside the cloud which allows the formation of an embryo; (ii) the growth of one embryo among a population of planetesimals is accelerated by the presence of gas and is warranted as long as its feeding zone is fed by the inward flow of planetesimals due to gas drag. These results offer some complementary new insights in the understanding of the accretional formation of 4–5 terrestrial planets instead of the numerous Moon-size planets generally found in numerical experiments.  相似文献   

An Assessment of HOx Chemistry in the Tropical Pacific Boundary Layer: Comparison of Model Simulations with Observations Recorded during PEM Tropics A     

G. Chen  D. Davis  J. Crawford  B. Heikes  D. O'Sullivan  M. Lee  F. Eisele  L. Mauldin  D. Tanner  J. Collins  J. Barrick  B. Anderson  D. Blake  J. Bradshaw  S. Sandholm  M. Carroll  G. Albercook  A. Clarke 《Journal of Atmospheric Chemistry》2001,38(3):317-344

Reported are the results from a comparison of OH,H₂O₂CH₃OOH, and O₃ observationswithmodel predictions based on current HO_x–CH₄reaction mechanisms. The field observations are thoserecorded during the NASA GTE field program, PEM-Tropics A. The major focus ofthis paper is on thosedata generated on the NASA P-3B aircraft during a mission flown in the marineboundary layer (MBL) nearChristmas Island, a site located in the central equatorial Pacific (i.e.,2° N, 157° W). Taking advantage of thestability of the southeastern trade-winds, an air parcel was sampled in aLagrangian mode over a significantfraction of a solar day. Analyses of these data revealed excellent agreementbetween model simulated andobserved OH. In addition, the model simulations reproduced the major featuresin the observed diurnalprofiles of H₂O₂ and CH₃OOH. In the case ofO₃, the model captured the key observational feature whichinvolved an early morning maximum. An examination of the MBL HO_xbudget indicated that the O(¹D) + H₂Oreaction is the major source of HO_x while the major sinks involveboth physical and chemical processes involving the peroxide species,H₂O₂ and CH₃OOH. Overall, the generally goodagreement between modeland observations suggests that our current understanding ofHO_x–CH₄ chemistry in the tropical MBL isquite good; however, there remains a need to critically examine this chemistrywhen both CH₂O and HO₂are added to the species measured.  相似文献   

Delineation of Microscale Regimes of Fully-Developed Drainage and Implications for Continuum Models     

Yanis C. Yortsos  Baomin Xu  Dominique Salin 《Computational Geosciences》2001,5(3):257-278

Despite significant progress made in recent years, a fundamental understanding of immiscible displacements at the macroscale is lacking. In this paper we use a version of percolation theory, based on invasion percolation in a gradient, to connect drainage processes at the pore-network scale with the displacement at the macroscale. When the mobility ratio M is sufficiently small, the displacement is stabilized and can be described by invasion percolation in a stabilizing gradient. In the opposite case, it has common features with invasion percolation in a destabilizing gradient. A diagram delineating the regimes of fully developed drainage is developed. The transition between stabilized displacement and fingering is controlled by the change of the sign of the gradient of the percolation probability, and the transition boundary is described by a scaling law involving the capillary number and the viscosity ratio. We review recent work for random networks and extend the method to correlated pore networks. As the regimes of stabilized displacement are also those for which conventional theories (such as the Buckley–Leverett equation) are expected to apply, the phase diagram helps to delineate their validity.  相似文献   

Geodynamic evolution of Korea: A view   总被引：2，自引：0，他引：2  

Dominique  Cluzel Jean-Paul  Cadet† 《Island Arc》1992,1(1):64-70

Abstract Evidence for South Korean Palaeozoic geodynamic evolution is restricted to the Ogcheon Belt, which is a complex polycyclic domain forming the boundary between the Precambrian Gyeonggi Block to the northwest and the Ryeongnam Block to the southeast. Two independent sub-zones can be distinguished: the Taebaeksan Zone to the northeast and the Ogcheon Zone sensu stricto. The Taebaeksan Zone and Ryeongnam Block display characteristic features of the North China palaeocontinent. This domain remained relatively stable during the Palaeozoic. In contrast, the Ogcheon Belt s. s. is a highly mobile zone that belongs to the South China palaeocontinent and corresponds to a rift that opened during the Early Palaeozoic. In lowermost Devonian times, the rift basin was closed and the Ogcheon Belt was structured in a pile of nappes. From the lack of suture in the Ogcheon Belt it can be inferred that the Gyeonggi Block belongs to the South China palaeocontinent. Thus, the boundary between the North China and South China blocks should be located to the north of Gyeonggi Block, that is, in the Palaeozoic Imjingang Belt. From the Middle Carboniferous, sedimentation started again on a weakly subsiding paralic platform located in the hinterland of the Late Palaeozoic orogen of southwest Japan. In the Late Carboniferous, increasing subsidence recorded extensional tectonics related to the opening of the Yakuno Oceanic Basin (southwest Japan). In the Middle Permian, the end of marine influences in the platform and emplacement of terrestrial coal measures, may be correlated with the closure of the oceanic area and subsequent ophiolite obduction. In Late Permian to Early Triassic times, the Honshu Block (the eastern palaeomargin of the Yakuno Basin) collided with Sino-Korea. Post-collisional intracontinental tectonics reached the Ogcheon Belt in the Middle Triassic (Songnim tectonism). Ductile dextral shear zones associated with synkinematic granitoids were emplaced in the southwest of the belt. In the Upper Triassic, the late stages of the intracontinental transcurrent tectonics generated narrow intramontane troughs (Daedong Supergroup). The Daedong basins were deformed during two tectonic events, in the Middle (?) and Late Jurassic. The Upper Jurassic to Lower Cretaceous basins (Gyeongsang Supergroup), that are controlled by left-lateral faults, may have resulted from the same tectonic event.  相似文献   

Estimating airborne heavy metal concentrations in Dunkerque (northern France)     

Germán?SantosEmail author  Ignacio?Fernández-Olmo  ángel?Irabien  Frédéric?Ledoux  Dominique?Courcot 《Arabian Journal of Geosciences》2016,9(3):231

This work aims to estimate the levels of lead (Pb), nickel (Ni), manganese (Mn), vanadium (V) and chromium (Cr) corresponding to a 3-month PM₁₀ sampling campaign conducted in 2008 in the city of Dunkerque (northern France) by means of statistical models based on partial least squares regression (PLSR), artificial neural networks (ANNs) and principal component analysis (PCA) coupled with ANN. According to the European Air Quality Directives, because the levels of these pollutants are sufficiently below the European Union (EU) limit/target values and other air quality guidelines, they may be used for air quality assessment purposes as an alternative to experimental measurements. An external validation of the models has been conducted, and the results indicate that PLSR and ANNs, with comparable performance, provide adequate mean concentration estimations for Pb, Ni, Mn and V, fulfilling the EU uncertainty requirements for objective estimation techniques, although ANNs seem to present better generalization ability. However, in accordance with the European regulation, both techniques can be considered acceptable air quality assessment tools for heavy metals in the studied area. Furthermore, the application of factor analysis prior to ANNs did not yield any improvements in the performance of the ANNs.  相似文献