Selection criteria for linear regression models to estimate individual tree biomasses in the Atlantic Rain Forest,Brazil     

Carlos Roberto Sanquetta  Ana Paula Dalla Corte  Alexandre Behling  Luani Rosa de Oliveira Piva  Sylvio Péllico Netto  Aurélio Lourenço Rodrigues  Mateus Niroh Inoue Sanquetta 《Carbon balance and management》2018,13(1):25

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A Spherical Lens For The Ska     

John S. Kot  Richard Donelson  Nasiha Nikolic  Doug Hayman  Mike O’Shea  Gary Peeters 《Experimental Astronomy》2004,17(1-3):141-148

Spherical refracting lenses based upon the Luneburg lens offer unique capabilities for radioastronomy, but the large diameter of lens required for the Square Kilometre Array (SKA) means that traditional lens materials are either too dense or too lossy. We are investigating a composite dielectric that theoretically offers extremely low loss and low density, and is suitable for low-cost mass production. We describe our progress towards realising this material and demonstrating the manufacturing concept, via the manufacture and testing of a small (0.9 m) spherical lens.  相似文献   

Free rocking response of a regular stone masonry wall with equivalent block approach: experimental and analytical evaluation     

Alexandre A. Costa  António Arêde  Aníbal Costa 《地震工程与结构动力学》2013,42(15):2297-2319

The evaluation of the dynamic behaviour of rocking elements is directly correlated to the energy dissipated because of the impacts at the base interface, which can be represented by means of a coefficient of restitution. This schematization is commonly accepted as representative of the out‐of‐plane response of stone masonry walls. An experimental campaign (in a lab environment) aiming at assessing the value of this coefficient for a sacco granite masonry wall is presented in this work. The rocking motion at a predefined bed joint level was induced in the tested specimens in order to validate a novel test setup designed to assess the coefficient of restitution value by means of a realistic reproduction of the rocking behaviour of a single element, under the hypothesis of an infinitely stiff system above the bed joint level. As the main objective of the work was to assess the rocking behaviour of a masonry wall that looses energy at the impacts at a certain joint level, the flexural behaviour was not desirable and had to be avoided. For this purpose, a test setup based on the equivalent block approach was developed. In the final section of this work, comparisons between experimental and numerical results are presented together with some preliminary conclusions on the appropriate modelling strategy and the values of the coefficient of restitution to be used for the seismic assessment of the out‐of‐plane rocking behaviour of this type of sacco stone masonry walls. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Characterization of the glide planes of the [001] screw dislocations in olivine using electron tomography     

Alexandre Mussi  Patrick Cordier  Sylvie Demouchy  Claude Vanmansart 《Physics and Chemistry of Minerals》2014,41(7):537-545

A San Carlos olivine polycrystal has been deformed under uppermost mantle conditions, by compression at 900 °C, at a strain rate of 1.1 × 10^?5 s^?1, under a confining pressure of 300 MPa, using the Paterson press. Transmission electron tomography of dislocations has been performed by scanning transmission electron microscopy, by conventional transmission electron microscopy using the weak-beam dark-field technique, associated with precession or not, in order to determine the glide planes of [001] screw dislocations. This recent technique is the most suitable one since most [001] dislocations exhibit straight screw segments due to the high lattice friction on this character at low temperature. We find that [001] dislocations glide in (100), (010) and {110} as already reported, but also more unexpectedly in {120} and {130}. We show that at 900 °C, [001] {110} glide is dominant in polycrystals. We have, however, noted and characterized numerous cross-slip events in the specimen.  相似文献   

Investigation of the sampling performance of ensemble-based methods with a simple reservoir model   总被引：1，自引：0，他引：1  

Alexandre A. Emerick  Albert C. Reynolds 《Computational Geosciences》2013,17(2):325-350

The application of the ensemble Kalman filter (EnKF) for history matching petroleum reservoir models has been the subject of intense investigation during the past 10 years. Unfortunately, EnKF often fails to provide reasonable data matches for highly nonlinear problems. This fact motivated the development of several iterative ensemble-based methods in the last few years. However, there exists no study comparing the performance of these methods in the literature, especially in terms of their ability to quantify uncertainty correctly. In this paper, we compare the performance of nine ensemble-based methods in terms of the quality of the data matches, quantification of uncertainty, and computational cost. For this purpose, we use a small but highly nonlinear reservoir model so that we can generate the reference posterior distribution of reservoir properties using a very long chain generated by a Markov chain Monte Carlo sampling algorithm. We also consider one adjoint-based implementation of the randomized maximum likelihood method in the comparisons.  相似文献   

DFTopoSim: Modeling Topographically-Controlled Deposition of Subseismic Scale Sandstone Packages Within a Mass Transport Dominated Deep-Water Channel Belt     

Lisa Stright  Anne Bernhardt  Alexandre Boucher 《Mathematical Geosciences》2013,45(3):277-296

Facies bodies in geostatistical models of deep-water depositional environments generally represent channel-levee-overbank-lobe morphologies. Such models adequately capture one set of the erosional and depositional processes resulting from turbidity currents traveling downslope to the ocean basin floor. However, depositional morphologies diverge from the straight forward channel-levee-overbank-lobe paradigm when the topography of the slope or the shape of the basin impacts the timing and magnitude of turbidity current deposition. Subaqueous mass-transport-deposits (MTDs) present the need for an exception to the channel-levee-overbank-lobe archetype. Irregular surface topography of subaqueous MTDs can play a primary role in controlling sand deposition from turbidity currents. MTD topography creates mini-basins in which sand accumulates in irregularly-shaped deposits. These accumulations are difficult to laterally correlate using well-log data due to their variable and unpredictable shape and size. Prediction is further complicated because sandstone bodies typical of this setting are difficult to resolve in seismic-reflection data. An event-based model is presented, called DFTopoSim, which simulates debris flows and turbidity currents. The accommodation space on top of and between debris flow lobes is filled in by sand from turbidity currents. When applied to a subsurface case in the Molasse Basin of Upper Austria, DFTopoSim predicts sand packages consistent with observations from core, well, and seismic data and the interpretation of the sedimentologic processes. DFTopoSim expands the set of available geostatistical deep-water depositional models beyond the standard channel-levee-overbank-lobe model.  相似文献   

Discontinuous Galerkin method for two-component liquid–gas porous media flows     

Alexandre Ern  Igor Mozolevski 《Computational Geosciences》2012,16(3):677-690

We consider two-component (typically, water and hydrogen) compressible liquid–gas porous media flows including mass exchange between phases possibly leading to gas-phase (dis)appearance, as motivated by hydrogen production in underground repositories of radioactive waste. Following recent work by Bourgeat, Jurak, and Smaï, we formulate the governing equations in terms of liquid pressure and dissolved hydrogen density as main unknowns, leading mathematically to a nonlinear elliptic–parabolic system of partial differential equations, in which the equations degenerate when the gas phase disappears. We develop a discontinuous Galerkin method for space discretization, combined with a backward Euler scheme for time discretization and an incomplete Newton method for linearization. Numerical examples deal with gas-phase (dis)appearance, ill-prepared initial conditions, and heterogeneous problem with different rock types.  相似文献   

Iridium enrichment and poor fractionation from gold, platinum and palladium in clausthalite (PbSe), Tilkerode, eastern Harz, Germany     

Alexandre Raphael Cabral  Nikola Koglin  Helene Br?tz 《Mineralogy and Petrology》2012,105(3-4):113-119

Enrichments in platinum-group elements were found in clausthalite, PbSe, which occurs in carbonate–hematite veins hosted in black shale of Upper Wenlockian age in the eastern Harz, Germany. Spot measurements by laser ablation–quadrupole inductively coupled plasma mass spectrometry (LA–QICPMS) show that the clausthalite has Pt contents that average 0.459?ppm and range from 0.003 to 2.83?ppm. Other noble metals quantified in the present work include Au (0.226?ppm, 0.109–0.451?ppm), Ru (0.061?ppm, 0.006–0.264?ppm), Ir (0.071?ppm, 0.010–0.185?ppm), Pd (0.046?ppm, 0.017–0.107?ppm) and Os (0.010?ppm, <0.003–0.024?ppm). Elemental ratios of Au/Ir, Pd/Ir and Pt/Ir, the average values of which are respectively 4.6, 0.8, and 4.9, suggest that Au, Pd and Pt are poorly fractionated from Ir. The resulting Ir enrichment is unusual and should reflect a particularly soluble (and stable) aqueous complex of Ir in a highly oxidizing, low-temperature, Se-rich solution.  相似文献   

Dynamic phytoclimatology,an aid to spatial generalisation of external geodynamical studies     

Frédéric Alexandre  Alain Génin 《Geodinamica Acta》2013,26(6):367-376

Abstract

The statistics and mechanical studies of the spatial variability of rainfall do not seem to be entirely satisfactory for brief events, such as the showers generating gullying. Thus, indirect indications of vegetation may be useful. Botanical continuums do reflect some climatic changes that may be linked to the distribution of these events. As an example, the analyses of some floristic transects, located at the transition of Mediterranean and oceanic, and Mediterranean and arid climates are presented. Conducted in parallel with the dynamic interpretation of climatic fields, these analyses have, for instance, allowed to state more precisely the spatial extension of several features of rains such as their cumulated values and their regime. The floristic ‘signal’ mainly concerns the climatic variations of the cumulated value of rainfall, but, in a subtler way, vegetation may signal the variations of regime. These features are linked with the strength of showers, and, as a consequence with the erosive capacity of rainfall. Dynamic phytoclimatology is then liable to give an aid to the spatialization of external geodynamic studies. © 2000 Éditions scientifiques et médicales Elsevier SAS  相似文献   

The 3 December 1828 moderate earthquake at the border between Belgium and Germany     

Elisabeth Knuts  Thierry Camelbeeck  Pierre Alexandre 《Journal of Seismology》2016,20(2):419-437

On 3 December 1828 at half past six in the evening, the border region between Belgium and Germany was stricken by a moderate earthquake. Up to now, the available information on this event has been essentially provided by a few contemporaneous scientific studies. To better evaluate its impact, location and magnitude, we have searched for new original historical reports. We collected 57 additional witness testimonies, which complete those previously collected about the earthquake effects. Among the testimonies, we also retrieved a questionnaire sent by the Prussian government to local authorities with the purpose of quickly obtaining information on the earthquake effects in the western part of the kingdom of Prussia. This inquiry is the oldest of its kind that has been discovered to date in this part of Europe, suggesting a rare concern by a national authority about the seismic hazard, and prefiguring the seismic inquiries that scientific institutions use today. The analysis of these new data made it possible to evaluate the intensity in 50 cities out of the 75 where the earthquake was observed. From these intensity data, we determine that the epicentre was in the Hautes-Fagnes region [lat. 50.38°N/long. 6.19°E?±?30 km] where moderate damage, corresponding to EMS-98 intensity VI–VII, was observed. At large distances, the earthquake was felt as far as Düsseldorf to the north, Brussels to the west, Metz to the south and Wiesbaden to the east. These distances correspond to a perceptibility radius of about 150 km. The magnitude of this earthquake is evaluated to be M_L?=?4.7 (?0.2/+0.5) and M_W?=?4.2 (+0.4/?0.2).  相似文献