Crystallization in flow – II. Modelling crystal growth kinetics controlled by boundary layer thickness     

Stanislas Sizaret  Ivan Fedioun  Luc Barbanson  Yan Chen 《Geophysical Journal International》2006,167(2):1027-1034

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Significance of a combined approach for replacement stones in the heritage buildings’ conservation frame     

Olivier Rozenbaum  Luc Barbanson  Fabrice Muller  Ary Bruand   《Comptes Rendus Geoscience》2008,340(6):345-355

Stone substitution is a conventional operation during heritage buildings’ restoration, but becomes problematic for architects and restorers when the quarry is mined out. The compatibility of the substitution stones with the original ones has been for long mainly based on the aesthetical aspect, this resulting too often in a patchwork of original and substitution stones with different patina after several years because of differences of properties. In this study, the objective is to show how substitution stones can be selected by combining aesthetic criteria and stones properties that are relevant for analyzing their compatibility. A couple of French limestones with their potential substitution stones were selected for the study. Our results showed that potential substitution stones selected on their aesthetic criteria require to be rejected because of their differences of physical properties. On the other hand, our results showed also the possibility to select substitution stones with satisfactory aesthetic aspect and properties that enable to expect a satisfactory compatibility with the original stone.  相似文献   

Geochemical diversity in S processes mediated by culture-adapted and environmental-enrichments of Acidithiobacillus spp.     

Luc Bernier 《Geochimica et cosmochimica acta》2007,71(23):5684-5697

Coupled S speciation and acid generation resulting from S processing associated with five different microbial treatments, all primarily Acidithiobacillus spp. (i.e. autotrophic S-oxidizers) were evaluated in batch laboratory experiments. Microbial treatments included two culture-adapted strains, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans, their consortia and two environmental enrichments from a mine tailings lake that were determined to be >95% Acidithiobacillus spp., by whole-cell fluorescent hybridization. Using batch experiments simulating acidic mine waters with no carbon amendments, acid generation, and S speciation associated with the oxidation of three S substrates (thiosulfate, tetrathionate, and elemental S) were evaluated. Aseptic controls showed no observable pH decrease over the experimental time course (1 month) for all three S compounds examined. In contrast, pH decreased in all microbial treatments from starting pH values of 4 to 2 or less for all three S substrates. Results show a non-linear relationship between the pH dynamics of the batch cultures and their corresponding sulfate concentrations, and indicate how known microbial S processing pathways have opposite impacts, ultimately on pH dynamics. Associated geochemical modeling indicated negligible abiogenic processes contributing to the observed results, indicating strong microbial control of acid generation extending over pH ranges from 4 to less than 2. However, the observed acid generation rates and associated S speciation were both microbial treatment and substrate-specific. Results reveal a number of novel insights regarding microbial catalysis of S oxidation: (1) metabolic diversity in S processing, as evidenced by the observed geochemical signatures in S chemical speciation and rates of acid generation amongst phylogenetically similar organisms (to the genus level); (2) consortial impacts differ from those of individual strain members; (3) environmental enrichments of Acidithiobacillus spp. catalyze different S reaction arrays than pure strain Acidithiobacillus spp.; and (4) microbial catalysis of S reactions involves significant disproportionation tied to substantial H⁺ consumption, with the formation of as yet, poorly characterized intermediate S species, most likely polythionates and polysulfane monosulfonic acids that are thought to be involved in microbial S storage mechanisms.  相似文献   

Reconstruction of the surface-layer vertical structure from measurements of wind,temperature and humidity at two levels     

Luc Musson-Genon  Eric Dupont  Denis Wendum 《Boundary-Layer Meteorology》2007,124(2):235-250

We present a comparison between several methods used to reconstruct fluxes and vertical profiles of wind, temperature and humidity from measurements at two levels in the atmospheric surface layer for different practical applications. An analytical method and an iterative method are tested by evaluating the quality of estimations of surface fluxes from detailed field measurements obtained during a campaign on the site of Lannemezan in the south-west of France. The iterative method yields better results, but the analytical one can give results of the same level of accuracy provided that specific constants in its formulation are modified. Then these techniques are applied to wind and temperature reconstruction for an experiment dedicated to wind power estimates over flat terrain. If turbulent fluxes are not needed, a simple power law appears to be sufficient, as the method based on Monin–Obukhov theory does not improve the accuracy of the vertical profile reconstruction.  相似文献   

Seamless integration of spatial statistics and GIS: The S-PLUS for ArcView and the S+Grassland Links     

Shuming Bao  Luc Anselin  Doug Martin  Diana Stralberg 《Journal of Geographical Systems》2000,2(3):287-306

The extension of the functional capacity of geographic information systems (GIS) with tools for statistical analysis in general and exploratory spatial data analysis (ESDA) in particular has been an increasingly active area of research in recent years. In this paper, two operational implementations that combine the functionality of spatial data analysis software with a GIS are considered more closely. They consist of linkages between the S-PLUS software for data analysis and two different GIS implementations, the ArcView desktop system, which is mostly vector-oriented, and the primarily raster-based Grassland open GIS environment. We emphasize conceptual and technical issues related to the software implementation of these approaches and suggest future directions for linking spatial statistics and GIS. Received: 14 January 1999 / Accepted: 11 May 1999  相似文献   

Hydraulic Conductivities of Low Permeability Sediments Inferred from a Triple Pumping Test and Observed Vertical Gradients   总被引：2，自引：0，他引：2  

Luc Lebbe  Nathalie Van  Meir 《Ground water》2000,38(1):76-88

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New high resolution observations of the solar diameter from space and ground with the microsatellite program PICARD     

Luc Dam 《Journal of Astrophysics and Astronomy》2000,21(3-4):135-140

The PICARD microsatellite mission will provide 2 to 6 years simultaneous measurements of the solar diameter, differential rotation and solar constant to investigate the nature of their relations and variabilities. The 100 kg satellite has a 40 kg payload consisting of 3 instruments which will provide an absolute measure (better than 10 milliarcsec) of the diameter and the solar shape, a measure of total solar irradiance, and UV and visible flux in selected wavelength bands. Now in Phase B, PICARD is expected to be launched before mid-2003. The engineering model of the diameter telescope will be used on ground simultaneously with the satellite to investigate the atmospheric bias and state on the possible accuracy of the ground measurements carried up to now. We review the scientific goals linked to the diameter measurement, present the payload, and give a brief overview of the program aspects.  相似文献   

Effective strength of saturated double porous media with a Drucker–Prager solid phase     

Wanqing Shen  Zheng He  Luc Dormieux  Djimédo Kondo 《国际地质力学数值与分析法杂志》2014,38(3):281-296

This study aims at determining the macroscopic strength of porous materials having a Drucker–Prager solid phase at microscale and two populations of saturated pores with different pressures at both micro and meso scales. To this end, and taking account of the available results by Maghous et al. (2009), we first derive a closed‐form expression of approximate criterion for a dry porous medium whose matrix obeys to a general elliptic criterion. The methodology to formulate this criterion is based on limit analysis of a hollow sphere subjected to a uniform strain rate boundary conditions. The obtained results are then implemented in a two‐step homogenization procedure, which interestingly delivers analytical expression of the macroscopic criterion for dry double porous media whose solid phase at microscale obeys to a Drucker–Prager criterion. After a brief discussion of the results, we propose an extension to double porous saturated media, allowing therefore to quantify the simultaneous effects of the different pore pressures applied on each voids population. The results are discussed in terms of the existence or not of effective stresses. Finally, they are assessed by comparing them to recently available results. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Low‐frequency modulation and trend of the relationship between ENSO and precipitation along the northern to centre Peruvian Pacific coast          下载免费PDF全文

Luc Bourrel  Pedro Rau  Boris Dewitte  David Labat  Waldo Lavado  Aude Coutaud  Andrea Vera  Abigail Alvarado  Julio Ordoñez 《水文研究》2015,29(6):1252-1266

The relationship between El Niño Southern Oscillation (ENSO) and precipitation along the Peruvian Pacific coast is investigated over 1964–2011 on the basis of a variety of indices accounting for the different types of El Niño events and atmospheric and oceanographic manifestations of the interannual variability in the tropical Pacific. We show the existence of fluctuations in the ENSO/precipitation relationship at decadal timescales that are associated with the ENSO property changes over the recent decades. Several indices are considered in order to discriminate the influence of the two types of El Niño, namely, the eastern Pacific El Niño and the central Pacific El Niño, as well as the influence of large‐scale atmospheric variability associated to the Madden and Julian Oscillation, and of regional oceanic conditions. Three main periods are identified that correspond to the interleave periods between the main climatic transitions over 1964–2011, i.e. the shifts of the 1970s and the 2000s, over which ENSO experiences significant changes in its characteristics. We show that the relationship between ENSO and precipitation along the western coast of Peru has experienced significant decadal change. Whereas El Niño events before 2000 lead to increased precipitation, in the 2000s, ENSO is associated to drier conditions. This is due to the change in the main ENSO pattern after 2000 that is associated to cooler oceanic conditions off Peru during warm events (i.e. central Pacific El Niño). Our analysis also indicates that the two extreme El Niño events of 1982/1983 and 1997/1998 have overshadowed actual trends in the relationship between interannual variability in the tropical Pacific and precipitation along the coast of Peru. Overall, our study stresses on the complexity of the hydrological cycle on the western side of the Andes with regard to its relationship with the interannual to decadal variability in the tropical Pacific. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Early Devensian (MIS 5d–5b) occupation at Dartford,southeast England     

Francis F. Wenban‐Smith  Martin R. Bates  Jean‐Luc Schwenninger 《第四纪科学杂志》2010,25(8):1193-1199

A deeply buried horizon containing mint‐condition flint artefacts was discovered in 2006 during archaeological investigations in advance of major roadworks near Dartford, Kent, in southeast England. The context of the artefacts and the freshness of their condition suggest this horizon represents a buried occupation surface. Optically stimulated luminescence dating places this horizon in the period Marine Isotope Stage 5d–5b, early in the British Devensian glaciation. This paper describes details of the artefacts, their context and dates, and outlines how this apparent occupation fits in with the wider pattern of Neanderthal settlement in Britain and northwest Europe in the later Pleistocene. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献