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91.
A Model of Magmatic Crystallization 总被引:2,自引:0,他引:2
A computer model simulating fractional crystallization at oneatmosphere pressure incorporates nine broadly-defined mineralsmagnetite,olivine, hypersthene, augite, quartz, plagioclase, orthoclase,leucite, and nepheline. The crystallization temperature of eachmineral is considered to be a smooth function of the compositionof the magmatic liquid. These mineral temperature equationsare obtained by multiple linear regression analysis of informationfrom published silicate systems and rock melting experiments.The nine equations are solved for any primary liquid, withinthe broad range of common magma types, to select the crystallizingmineral or minerals. Partition ratios from published experimentsand analyses of lavas and phenocrysts permit calculation ofthe composition of the crystallizing mineral assemblage. Subtractionof a small amount of that composition from the primary liquidyields a new liquid, which may be recycled to yield a sequenceof liquids during fractional crystallization. The crystallizationmodel handles assemblages of co-precipitating minerals, andcan trace progressive saturation in new minerals, substitutionof a new mineral for an old mineral, and cessation of crystallizationof a mineral. The sequences of minerals and liquids derivedfrom a broad set of primary liquids are geologically realistic,so the model is useful in predicting phenocrysts in volcanicrocks and events during crystallization of shallow intrusions. 相似文献
92.
Timing and amount of solar radiation were examined as factors influencing the distribution of seven perennial plants on a small mountain located in the Chihuahuan Desert. Average direct beam solar radiation fluxes at differing times throughout the day and year were estimated with computer calculations. Principal components analysis was used to reduce the number of solar radiation parameters and include the maximum available information with a manageable number of variables. The remaining solar radiation parameters were compared to plant distributions using redundancy analysis and generalized additive models. Unimodal, bimodal, and monotonic responses were all found depending upon the species and solar radiation parameter. Niche separation at this location depends upon the timing as well as the amount of solar radiation. 相似文献
93.
H. Burtscher P. Cohn L. Scherrer H.C. Siegmann G. Faraci A.R. Pennisi V. Privitera R. Cristofolini V. Scribano 《Journal of Volcanology and Geothermal Research》1987,33(4)
Volcanic aerosol emissions have been studied for the first time by in situ photoelectric charging. Explorative studies on Mt Etna reveal large concentrations of particles below 1000 nm with the spectrum peaking in the size range of 100–1000 nm diameter. Although a large fraction of the particles is already charged upon emission, the net electrical charge carried by the aerosol turned out to be close to zero.Particles with high photoelectric yield vary greatly in their relative abundance and seem to occur mainly at active points of the volcano. 相似文献
94.
H. C. Aslyng 《Theoretical and Applied Climatology》1960,10(3):359-375
Summary Evaporation from an area covered with short clover-grass has been determined by means of evapotranspirometers (4 m2), open (12 m2) and screened (1/3 m2) evaporimeters, and it has been estimated on the basis ofPenman's andThornthwaite's theories, too. The results of the measurements with the various instruments are compared with each other and with the results derived from the cited theories.Further, radiation heat balances have been made, including evaporation and heating of soil and atmosphere.
With 8 Figures 相似文献
Zusammenfassung Die Verdunstung über einer mit kurzem Kleegras bedeckten Fläche wurde mittels Evapotranspirometern (4 m2), offenen (12 m2) und abgeschirmten (1/3 m2) Evaporimetern gemessen und auch auf Grund vonPenmans undThornthwaites Theorien berechnet. Die Meßergebnisse der verschiedenen Instrumente werden untereinander verglichen und auch den mittels der angeführten Theorien abgeleiteten Resultaten gegenübergestellt.Weiters wurde eine Strahlungs-Wärme-Bilanz aufgestellt, die auch die Verdunstung und die Erwärmung von Boden und Atmosphäre berücksichtigt.
Résumé On a mesuré l'évaporation sur une surface recouverte de trèfle court à l'aide d'évapotranspiromètres (4 m2) et d'évaporimètres ouverts (12 m2) et protégés (1/3 m2); les résultats de mesures, furent comparés entre eux et avec la théorie dePenman etThornthwaite.Puis on a dressé un bilan radiatif tenant compte, de l'évaporation et du réchauffement du sol et de l'atmosphère.
With 8 Figures 相似文献
95.
D. F. Dickinson G. Kojoyan C. R. Purton R. A. Sramek H. M. Tovmassian 《Astronomische Nachrichten》1976,297(6):283-286
Radio spectra of 16 Markarian galaxies are studied between 2.7 and 15.5 GHz. The Seyfert-type galaxies have power-law spectra with an average spectral index of -0.82, except for MRK 348, which is an active galaxy with a complex spectrum. The galaxies with featureless optical spectra have rather flat radio spectra, similar to BL Lac-type objects. 相似文献
96.
97.
B. C. Browne 《Journal of Geodesy》1949,23(2):146-148
98.
To implement a numerical model of atoll lagoon circulation, we characterized first the significant wave height (Hs) regime of the Western Tuamotu Archipelago and the local attenuation due to the protection offered by large atolls in the south Tuamotu. Altimetry satellite data and a WAVEWATCH III two-way nested wave model at 5km resolution from 2000 to 2010 were used. Correlation between altimetry and model was high (0.88) over the period. According to the wave model, the archipelago inner seas experienced attenuated Hs year-long with a yearly average Hs around 1.3m vs a minimum of 1.6m elsewhere. The island shadow effect is especially significant in the austral winter. In contrast with southern atolls, Western Tuamotu experienced only few days per year of Hs larger than 2.5m generated by very high Hs southern swell, transient western local storms, strong easterly winds, and during the passage of distant hurricanes. 相似文献
99.
The seismic ground motion of a test area in the eastern district of Naples is computed with a hybrid technique based on the mode summation and the finite difference methods. This technique allows us the realistic modelling of source and propagation effects, including local soil conditions. In the modelling, we consider the 1980 Irpinia earthquake, a good example of strong shaking for the area of Naples, which is located about 90 km from the epicenter.The detailed geological setting is reconstructed from a large number of drillings. The sub-soil is mainly formed by alluvial (ash, stratified sand and peat) and pyroclastic materials overlying a pyroclastic rock (yellow neapolitan tuff), representing the neapolitan bedrock. The detailed information available on mechanical properties of the sub-soil and its geometry warrants the application of the sophisticated hybrid technique.As expected, the sedimentary cover causes an increase of the signal's amplitudes and duration. If thin peat layers are present, the amplification effects are reduced, and the peak ground accelerations are similar to those observed for the bedrock model. This can be explained by the backscattering of wave energy at such layers, that tend to seismically decouple the upper from the lower part of the structure.For SH-waves, the influence of the variations of the S-wave velocities on the spectral amplification is studied, by considering locally measured velocities and values determined from near-by down-hole measurements. The comparison between the computed spectral amplifications confirms the key role of an accurate determination of the seismic velocities of the different layers.The comparison performed between a realistic 2-D seismic response and a standard 1-D response, based on the vertical propagation of waves in a plane layered structure, shows considerable difference, from which it is evident that serious caution must be taken in the modelling of expected ground motion at a specific site. 相似文献
100.
Numerical simulation of undersea cable dynamics 总被引:7,自引:0,他引:7
A fully three-dimensional code has been written to compute the motion of a towed cable. The code is based on a robust and stable finite difference approximation to the differential equations derived from basic dynamics. A 3500-ft (1.07 km) cable pulled at 18.5 knots (34.3 km hr−1) through a circular turn of 700 yd (0.64 km) radius has been computed in about half of the real time of the maneuver. The computed displacements are close to the measured ones; the changes in depth are within 2%. 相似文献