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71.
72.
The structure of the Planetary Boundary Layer in the stationary case is investigated. The dynamic equations are written in an universal form deduced from Rossby Similarity. Then the system is closed using two semi-empirical formulations for the turbulent fluxes (Prandtl's formulation and the turbulent energy scheme) with a mixing-length chosen to be compatible with Rossby Similarity. For each formulation the system is solved using a new numerical procedure to compute universal profiles of wind and also the Similarity functions A and B in terms of stability. These profiles and functions are then compared to experimental data and good agreement is obtained. Investigating simpler formulations, it appears that good results are obtained with a simple two-layer model, patching a diabatic Ekman spiral with surface-layer profiles. Its formulation is analytical and it can incorporate constant baroclinicity. 相似文献
73.
Luc?AnselinEmail author Yong Wook?Kim Ibnu?Syabri 《Journal of Geographical Systems》2004,6(2):197-218
This paper deals with the extension of internet-based geographic information systems with functionality for exploratory spatial data analysis (esda). The specific focus is on methods to identify and visualize outliers in maps for rates or proportions. Three sets of methods are included: extreme value maps, smoothed rate maps and the Moran scatterplot. The implementation is carried out by means of a collection of Java classes to extend the Geotools open source mapping software toolkit. The web based spatial analysis tools are illustrated with applications to the study of homicide rates and cancer rates in U.S. counties.This research was supported in part by a number of grants from the US National Science Foundation: NSF Grant SBR-9410612, BCS-9978058, to the Center for Spatially Integrated Social Science (csiss), and a grant from the National Consortium on Violence Research (ncovr is supported under grant SBR-9513040 from the National Science Foundation). In addition, support was provided by grant RO1 CA 95949-01 from the National Cancer Institute. Special thanks to Dr. Eugene J. Lengerich of the Pennsylvania State Cancer Institute for providing the data on colon cancer diagnoses. 相似文献
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At Lucky Strike near the Azores Triple Junction, the seafloor setting of the hydrothermal field in a caldera system with abundant low-permeability layers of cemented breccia, provides a unique opportunity to study the influence of subsurface geological conditions on the hydrothermal fluid evolution. Coupled analyses of S isotopes performed in conjunction with Se and Fe isotopes have been applied for the first time to the study of seafloor hydrothermal systems. These data provide a tool for resolving the different abiotic and potential biotic near-surface hydrothermal reactions. The δ34S (between 1.5‰ and 4.6‰) and Se values (between 213 and 1640 ppm) of chalcopyrite suggest a high temperature end-member hydrothermal fluid with a dual source of sulfur: sulfur that was leached from basaltic rocks, and sulfur derived from the reduction of seawater sulfate. In contrast, pyrite and marcasite generally have lower δ34S within the range of magmatic values (0 ± 1‰) and are characterized by low concentrations of Se (<50 ppm). For 82Se/76Se ratios, the δ82Se values range from basaltic values of near −1.5‰ to −7‰. The large range and highly negative values of hydrothermal deposits observed cannot be explained by simple mixing between Se leached from igneous rock and Se derived from seawater. We interpret the Se isotope signature to be a result of leaching and mixing of a fractionated Se source located beneath hydrothermal chimneys in the hydrothermal fluid. At Lucky Strike we consider two sources for S and Se: (1) the “end-member” hydrothermal fluid with basaltic Se isotopic values (−1.5‰) and typical S isotope hydrothermal values of 1.5‰; (2) a fractionated source hosted in subsurface environment with negative δ34S values, probably from bacterial reduction of seawater sulfate and negative δ82Se values possibly derived from inorganic reduction of Se oxyanions. Fluid trapped in the subsurface environment is conductively cooled and has restricted mixing and provide favorable conditions for subsurface microbial activity which is potentially recorded by S isotopes. Fe isotope systematic reveals that Se-rich high temperature samples have δ57Fe values close to basaltic values (∼0‰) whereas Se-depleted samples precipitated at medium to low temperature are systematically lighter (δ57Fe values between −1 to −3‰). An important implication of our finding is that light Fe isotope composition down to −3.2‰ may be explained entirely by abiotic fractionation, in which a reservoir effect during sulfide precipitation was able to produce highly fractionated compositions. 相似文献
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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
79.
Patrick Weber Beda A. Hofmann Tamer Tolba Jean‐Luc Vuilleumier 《Meteoritics & planetary science》2017,52(6):1017-1029
The gamma‐ray activities of 33 meteorite samples (30 ordinary chondrites, 1 Mars meteorite, 1 iron, 1 howardite) collected during Omani‐Swiss meteorite search campaigns 2001–2008 were nondestructively measured using an ultralow background gamma‐ray detector. The results provide several types of information: Potassium and thorium concentrations were found to range within typical values for the meteorite types. Similar mean 26Al activities in groups of ordinary chondrites with (1) weathering degrees W0‐1 and low 14C terrestrial age and (2) weathering degree W3‐4 and high 14C terrestrial age are mostly consistent with activities observed in recent falls. The older group shows no significant depletion in 26Al. Among the least weathered samples, one meteorite (SaU 424) was found to contain detectable 22Na identifying it as a recent fall close to the year 2000. Based on an estimate of the surface area searched, the corresponding fall rate is ~120 events/106 km2*a, consistent with other estimations. Twelve samples from the large JaH 091 strewn field (total mass ~4.5 t) show significant variations of 26Al activities, including the highest values measured, consistent with a meteoroid radius of ~115 cm. Activities of 238U daughter elements demonstrate terrestrial contamination with 226Ra and possible loss of 222Rn. Recent contamination with small amounts of 137Cs is ubiquitous. We conclude that gamma‐ray spectroscopy of a selection of meteorites with low degrees of weathering is particularly useful to detect recent falls among meteorites collected in hot deserts. 相似文献
80.
Luc Lebbe 《Advances in water resources》1999,22(8):107
By means of a series of borehole resistivity measurements and a resistivity–salinity relation, a particular salt-freshwater inversion was found under the shore with semi-diurnal tides at the French–Belgian border. These resistivity data provide valuable information about the vertical variation of the saltwater percentage in different boreholes. At different places and depths fluctuations of freshwater heads are observed. A regression modelling procedure is proposed in which the hydraulic parameters for density dependent flow and solute transport can be simultaneously considered with the parameters of the resistivity–salinity relation. The object function comprises resistivity residuals and freshwater head residuals along with saltwater percentage residuals and parameter residuals. First, a synthetic problem is elaborated with this regression modelling procedure. It is followed by the application of the procedure on the observed fresh-saltwater flow problem under the shore. In the synthetic problem the identification of the hydraulic parameters was demonstrated without the inclusion of prior information about these parameters. The resistivity–salinity relation was slightly adjusted in this regression. During the regression modelling of the observations made in one of the shore-normal cross sections, the horizontal and vertical conductivity are identified along with the effective porosity and the longitudinal and transverse dispersivity. The optimal values of the dispersivities are very small. Finally, it is shown that the high waters on the back shore forms the main threat of saltwater enchroachment from the sea side of the dunes and that the isolated fresh-brackish lens under the lower part of the shore before the build up area of De Panne can be explained by overexploitation. 相似文献