A commentary on: Tropical deforestation: Albedo and the surface-energy balance   总被引：3，自引：0，他引：3  

Ann Henderson-Sellers 《Climatic change》1991,19(1-2):135-137

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Book reviews     

Robert S. Kandel  John Firor  A. Henderson-Sellers 《Climatic change》1991,19(4):421-429

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Applications of Universal Kriging to an Aquifer Study in New Jersey   总被引：1，自引：0，他引：1  

Amleto A. Pucci  Jr.  Jo Ann E. Murashige 《Ground water》1987,25(6):672-678

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Identification of regions enriched or depleted in radioelements through nondistributional analysis of aerial radiometric data     

Fredric L. Prikle  Thomas R. Bement  Jo Ann Howell  Charles D. Koch  Newton K. Stablein  Richard J. Beckman  Gary L. Tietjen 《Journal of Geochemical Exploration》1983,18(3):175-187

Throughout the aerial radiometric reconnaissance survey portion of the U.S. Department of Energy's National Uranium Resource Evaluation (NURE) program, the identification of outliers (anomalies) was an important approach to locating regions with radio-element concentrations that are either higher or lower than expected. The method introduced herein to locate such regions involves three steps: selection of a high (or low) threshold for the variate of interest; use of the sample percentile to identify all points of interest; and movement of a window over the selected data to locate significant clusters of observations. These steps, applied to aerial radiometric ²¹⁴Bi (equivalent uranium) data collected over the Copper Mountain area in Wyoming, resulted in the identification of areas enriched in that variate.  相似文献   

Global and continental water balance in a GCM     

G. Thomas  A. Henderson-Sellers 《Climatic change》1992,20(4):251-276

Surface hydrology is recognised as an important component of general circulation climate models. The global and regional climates simulated by such models are demonstrably sensitive to the parameterization of terrestrial hydrologic processes. There exists, therefore, a clear requirement to evaluate different parameterization approaches in terms of the representation of the terrestrial phase of the hydrologic cycle. One potential means of meeting this requirement is by using available continental water-balance summaries. In this study three versions of a GCM, the National Center for Atmospheric Research (NCAR) Community Climate Model Version l (CCM1), differing mainly in spatial resolution and the representation of the surface hydrology, are compared against existing water-balance studies. Additional streamflow data are incorporated as a means of further validating both the water-balance approach and the GCM surface hydrologic parameterization in capturing the gross features of continental-scale hydrology.  相似文献   

Continental cloudiness changes this century   总被引：6，自引：0，他引：6  

A. Henderson-Sellers Dr. 《GeoJournal》1992,27(3):255-262

Surface-based observations of total cloud amount have been collected from historical records for four continents: North America, Europe, India and Australia. The records extend from 1900 to around 1985. Of the 350 individual station records investigated worldwide, 86% show an increase in total cloud amount or no change. In all four continents there is evidence of an increase in total cloud amount. This upward trend appears to be statistically significant for at least two regions: North America Australia. For North America this finding is corroborated by other recent studies.  相似文献   

Numerical analyses of deformability tests in jointed rock — “Joint Perturbation” and “No Tension” Finite Element solutions     

Francois E. Heuzé  Richard E. Goodman  Ann Bornstein 《Rock Mechanics and Rock Engineering》1971,3(1):13-24

SummaryNumerical Analyses of Deformability Tests in Jointed Rock — Joint Perturbation and No Tension Finite Element Solutions Sound design of structures in or upon rock requires a thorough knowledge of the rock mass deformability. Field test data interpretation has generally relied upon analytical or Finite Element linear elastic solutions. However, when testing in jointed rock, these can no longer be readily used since the medium cannot resist the tension induced upon loading. Accordingly, other solutions are required. If the discontinuities of the rock mass can all be mapped and their surface properties determined, the Finite Element model will use a Joint Perturbation solution where the joint elements have variable stiffnesses to account for movements along the fractures. If the discontinuities cannot be satisfactorily mapped, a global approach is provided by a No Tension analysis of the stress transfer type. The two techniques are compared in the case of bore hole jack deformability tests and found to agree remarkably well, indicating an appreciable difference from results of linear elasticity.

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ZusammenfassungNumerische Analyse von Verformungsversuchen in geklüfteten Fels — Lösungen mittels Kluft-Perturbation und No Tension Analysis auf Grund der Methode der Finiten Elemente Der Entwurf von Bauwerken in oder auf Fels erfordert eine genaue Kenntnis des Formänderungsverhaltens der Felsmasse. Im allgemeinen basiert die Interpretation der Ergebnisse von Feldversuchen auf den Lösungen des zugehörigen Randwertproblems der linearen Elastostatik mittels klassischer analytischer Methoden oder der Methode der Finiten Elemente. Wenn die Versuche aber in geklüftetem Fels durchgeführt werden, müssen die theoretischen Methoden modifiziert werden, da das Medium keine Zugspannungen aufnehmen kann. Zwei Fälle können unterschieden werden. Erstens: die Kluftflächen der Felsmasse können geometrisch erfaßt und ihre Oberflächeneigenschaften können bestimmt werden; in diesem Falle kann die Finite-Elemente-Lösung eine Kluft-Perturbations-Methode verwenden, in welcher spezielle Kluft-Elemente verschiedener Steifigkeiten normal und tangential zu den Kluftflächen die Bewegungen entlang derselben bestimmen. Zweitens: die Diskontinuitäten der Felsmasse können nicht hinreichend beschrieben werden; für diesen Fall ist vorgekehrt durch die Finite-Element-Analyse vom Typ der Spannungsumlagerung unter Ausschaltung der Zugspannungen (No Tension Analysis), um das globale Verhalten der geklüfteten Felsmasse zu erfassen. Die Lösungen dieser beiden Methoden wurden für den Fall der Bohrloch-Verformungs-Tests verglichen; der Vergleich zeigt ausgezeichnete Übereinstimmung, im Gegensatz zu den Lösungen als lineares Elastizitätsproblem.

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RésuméLa méthode des Eléments Finis appliquée aux résultats d'essais de vérins cylindriques dans les roches fissurées — solutions dites Joint Pertubé et Sans Traction La construction de structures sur ou dans des roches nécessite une connaissance approfendie de la déformabilité du massif rocheux. L'analyse des résultats d'essais en place se fait généralement à l'aide de solutions analytiques ou par Eléments Finis, qui supposent une élasticité linéaire du milieu. De fait, dans les roches fissurées, ces solutions sont inadéquates puisque le milieu ne peut résister aux sollicitations de traction. Il s'agit donc d'utiliser d'autres méthodes d'analyse. Lors qu'il est possible de déterminer la géométrie et les propriétés de toutes les discontinuités, l'on pourra utiliser une solution par Eléments Finis, dite Joint Perturbé dans laquelle la rigidité de surface du joint (ou fissure) peut varier lorsque des movements prennent place au niveau du joint. Si cela est impossible, il faudra utiliser une approche globale dite Sans Traction qui redistribue les contraintes de traction et les dissipe. On compare ces deux types de solutions dans le cas des essais de vérins cylindriques unidirectionnels. Leurs résultats sont identiques et ont nettement différents de ceux obtenus avec une solution élastique linéaire.

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Research supported by the National Aeronautics and Space Administration — Contract NAS 8-21432.

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With 8 Figures  相似文献   

The helium-rich stars of early spectral type     

Ann S. Dinger 《Astrophysics and Space Science》1970,6(1):118-130

The properties of the known helium-rich stars of early type are reviewed and the elemental abundances are analyzed. Current evolutionary theories of mixing and mass loss may explain the origin of these stars.  相似文献   

Lunar Tidal Winds at Four American Stations     

B. Haurwitz  Ann D. Cowley 《Geophysical Journal International》1968,15(1-2):103-107

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The inhibition of marine nitrification by ocean disposal of carbon dioxide   总被引：1，自引：0，他引：1  

Huesemann MH  Skillman AD  Crecelius EA 《Marine pollution bulletin》2002,44(2):142-148

In an attempt to reduce the threat of global warming, it has been proposed that the rise of atmospheric carbon dioxide concentrations be reduced by the ocean disposal of CO2 from the flue gases of fossil fuel-fired power plants. The release of large amounts of CO2 into mid or deep ocean waters will result in large plumes of acidified seawater with pH values ranging from 6 to 8. In an effort to determine whether these CO2-induced pH changes have any effect on marine nitrification processes, surficial (euphotic zone) and deep (aphotic zone) seawater samples were sparged with CO2 for varying time durations to achieve a specified pH reduction, and the rate of microbial ammonia oxidation was measured spectrophotometrically as a function of pH using an inhibitor technique. For both seawater samples taken from either the euphotic or aphotic zone, the nitrification rates dropped drastically with decreasing pH. Relative to nitrification rates in the original seawater at pH 8, nitrification rates were reduced by ca. 50% at pH 7 and more than 90% at pH 6.5. Nitrification was essentially completely inhibited at pH 6. These findings suggest that the disposal of CO2 into mid or deep oceans will most likely result in a drastic reduction of ammonia oxidation rates within the pH plume and the concomitant accumulation of ammonia instead of nitrate. It is unlikely that ammonia will reach the high concentration levels at which marine aquatic organisms are known to be negatively affected. However, if the ammonia-rich seawater from inside the pH plume is upwelled into the euphotic zone, it is likely that changes in phytoplankton abundance and community structure will occur. Finally, the large-scale inhibition of nitrification and the subsequent reduction of nitrite and nitrate concentrations could also result in a decrease of denitrification rates which, in turn, could lead to the buildup of nitrogen and unpredictable eutrophication phenomena. Clearly, more research on the environmental effects of ocean disposal of CO2 is needed to determine whether the potential costs related to marine ecosystem disturbance and disruption can be justified in terms of the perceived benefits that may be achieved by temporarily delaying global warming.  相似文献