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H.V. Warren S.J. Horsky A. Kruckeberg G.H.N. Towers J.E. Armstrong 《Journal of Geochemical Exploration》1983,18(3):169-173
Summary of biogeochemical prospecting for mercury mineralization in the Pinchi Fault is given. One thousand two hundred and eight plant samples were collected and analyzed for mercury. In mineralized areas the typical mercury content of dried plants was not less than 0.2 and 0.4 μg/g and even concentrations between 0.6 and 1.6 μg/g were observed. In nonmineralized zones at least 90% of the plants contained no more than 0.15 μg/g of mercury. Analytical and sampling procedures are described. 相似文献
3.
Robustness of variograms and conditioning of kriging matrices 总被引:1,自引:0,他引:1
Current ideas of robustness in geostatistics concentrate upon estimation of the experimental variogram. However, predictive algorithms can be very sensitive to small perturbations in data or in the variogram model as well. To quantify this notion of robustness, nearness of variogram models is defined. Closeness of two variogram models is reflected in the sensitivity of their corresponding kriging estimators. The condition number of kriging matrices is shown to play a central role. Various examples are given. The ideas are used to analyze more complex universal kriging systems.Research performed while on leave at Centre de Geóstatistique et de Morphologie Mathématique, Fontainebleau. 相似文献
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William B. Armstrong 《Ground water》1978,16(6):446-447
Abstract. Hydrogeologic and geochemical investigations have recently been made at an existing municipal supply well in the Town of Pembroke, Massachusetts, to determine the feasibility of using the Vyredox Method (Hallberg and Martinell, 1976) to remove iron and manganese from the ground water. The unique Vyredox testing procedures confirmed the existence of an active iron and manganese precipitating bacteria colony in the productive zone of the aquifer, which was causing rapid plugging of the well. 相似文献
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Cindy Lee Robert A. Armstrong J. Kirk Cochran Anja Engel Scott W. Fowler Madeleine Goutx Pere Masqu Juan Carlos Miquel Michael Peterson Christian Tamburini Stuart Wakeham 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1363-1368
The MedFlux project was devised to determine and model relationships between organic matter and mineral ballasts of sinking particulate matter in the ocean. Specifically we investigated the ballast ratio hypothesis, tested various commonly used sampling and modeling techniques, and developed new technologies that would allow better characterization of particle biogeochemistry. Here we describe the rationale for the project, the biogeochemical provenance of the DYFAMED site, the international support structure, and highlights from the papers published here. Additional MedFlux papers can be accessed at the MedFlux web site (http://msrc.sunysb.edu/MedFlux/). 相似文献
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M. Marengo M. Karovska D.D. Sasselov C. Papaliolios J.T. Armstrong T.E. Nordgren 《Astrophysics and Space Science》2003,286(1-2):185-190
We present a new method to compute wavelength- and phase-dependent limb darkening corrections for classical Cepheids. These
corrections are derived from hydrodynamic simulations and radiative transfer modeling with a full set of atomic and molecular
opacities. Comparison with hydrostatic models having the same stellar parameters show a larger limb darkening for most phases
in our models, and temporal variations related to the hydrodynamics of the stellar pulsation. Weassess the implications of
our results with respect to the geometric Baade-Wesselink method, which uses interferometric measurements of Cepheid angular
diameters to determine their distances and radii. The relevance of the hydrodynamic effects predicted by our model on the
limb darkening of pulsating Cepheids is finally discussed in terms of the predicted capabilities of the VLTI.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
John C. Armstrong 《Earth, Moon, and Planets》2010,107(1):43-54
Following the analytical work of Armstrong et al. (Icarus 160:183–196, 2002), we detail an expanded N-body calculation of the direct transfer of terrestrial material to the Moon during a giant impact.
By simulating 1.4 million particles over a range of launch velocities and ejecta angles, we have derived a map of the impact
velocities, impact angles, and probable impact sites on the moon over the last 4 billion years. The maps indicate that the
impacts with the highest vertical impact speeds are concentrated on the leading edge, with lower velocity/higher-angle impacts
more numerous on the Moon’s trailing edge. While this enhanced simulation indicates the estimated globally averaged direct
transfer fraction reported in Armstrong et al. (Icarus 160:183–196, 2002) is overestimated by a factor of 3–6, local concentrations can reach or exceed the previously published estimate. The most
favorable location for large quantities of low velocity terrestrial material is 50 W, 85 S, with 8.4 times more impacts per
square kilometer than the lunar surface average. This translates to 300–500 kg km−2, compared to 200 kg km−2 from the previous estimate. The maps also indicate a significant amount of material impacting elsewhere in the polar regions,
especially near the South Pole-Aiken basin, a likely target for sample return in the near future. The magnitudes of the impact
speeds cluster near 3 km/s, but there is a bimodal distribution in impact angles, leading to 43% of impacts with very low
(<1 km/s) vertical impact speeds. This, combined with the enhanced surface density of meteorites in specific regions, increases
the likelihood of weakly shocked terrestrial material being identified and recovered on the Moon. 相似文献