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71.
The motivation of this paper is to investigate two viscous fluid cosmological models in General Relativity in which the expansion
is only in two directions i.e. one of the Hubble parameters
is zero. In the first model, coefficient of shear viscosity is assumed to be constant while in the second model, the coefficient
of shear viscosity is proportional to the rate of expansion in the model. Here no additional condition is assumed except for
coefficient of shear viscosity. These models are new and different from those models obtained by Bali and Jain (1987, 1988)
in which free gravitational field was assumed to be Petrov Type D and non-degenerate for Marder (1958) metric and coefficient
of shear viscosity is proportional to the rate of expansion in the model. The various physical and geometrical aspects of
the models are also discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
72.
Enikő Bali Alberto Zanetti Csaba Szabó David W. Peate Tod E. Waight 《Contributions to Mineralogy and Petrology》2008,155(2):165-179
Mantle xenoliths in Neogene alkali basalts of the Bakony–Balaton Highland Volcanic Field (Western Hungary) frequently have
melt pockets that contain silicate minerals, glass, and often carbonate globules. Textural, geochemical and thermobarometric
data indicate that the melt pockets formed at relatively high pressure through breakdown of mainly amphibole as a result of
temperature increases accompanied, in most cases, by the influx of external metasomatic agents. New elemental and Sr–Nd–Pb
isotope data show that in several xenoliths the external agent was either a LIL-enriched aqueous fluid or a CO2-rich fluid, whereas in other xenoliths the melt pockets were additionally enriched in LREE and sometimes HFSE, suggesting
metasomatism by a silicate melt. The compositional character of the external agents might have been inherited by melting of
a hydrated and probably carbonated deeper lithospheric component, which itself was metasomatized by melts with significant
slab-derived components.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
73.
Delineation of potential sites for water harvesting structures using remote sensing and GIS 总被引:6,自引:0,他引:6
M. Girish Kumar A. K. Agarwal Rameshwar Bali 《Journal of the Indian Society of Remote Sensing》2008,36(4):323-334
Availability of groundwater varies spatially and temporally depending upon the terrain. The scarcity of water affects the
environmental and developmental activities of an area. Construction of small water harvesting structures across streams/watersheds
is gaining momentum in recent years. In the present study, potential sites for construction of rainwater harvesting structures
in the Bakhar watershed of Mirzapur District, Uttar Pradesh, India have been identified by using remote sensing and GIS techniques.
Various thematic maps such as Landuse/Landcover, geomorphology and lineaments, etc. were prepared using remote sensing. These
layers along with geology and drainage were integrated using GIS techniques to derive suitable water harvesting sites. Each
theme was assigned a weightage depending on its influence on ground water recharge (for example weightages 20,18,15,25,25
and 0 were assigned to geomorphology, landuse, geology, lineament, drainage and road and villages respectively). Each class
or unit in the map was assigned a knowledge based ranking of one to four depending on its significance in storage and transmittance
of groundwater, and these values were multiplied with layer weightage to form score. The average score for excellent region
is greater than 200, for good 121 to 200, for moderate 81 to 121 and the other polygon having value less than 80 (excluding
zero) were assigned to poor category. The final map showing different categories of suitability sites for water harvesting
structures such as Check dams, Contour bunding, Recharge pits, Wells and Contour trenching have been suggested. 相似文献
74.
Jacek?Majorowicz Jan??afanda Torun- Working Group 《International Journal of Earth Sciences》2008,97(2):307-315
High-precision temperature measurements were carried out up to a depth of 2,930 m in the 5.5-km-deep well Torun-1, 26 years
after completion of drilling. The temperature log provides equilibrium thermal state information for the Polish Lowland at
the western margin of the Precambrian craton. Geothermal gradient calculated from the equilibrium temperature log, together
with estimates of thermal conductivity from ‘net rock’ geophysical well logging analysis and available core measurements,
yields heat flow in the range 50–60 mW/m2 below 2-km depth. Heat flow of 50 mW/m2 plus ∼10 mW/m2 generated within thick sediments and highly metamorphosed sedimentary wedge is typical for the western margin of the Precambrian
East European craton. Heat-flow variations with depth can be explained by a model of surface-temperature changes >10°C (glaciation
to Holocene).
Torun-1 Working Group: Marta Wróblewska, Jacek Majorowicz, Jan Szewczyk, Jan Šafanda, Vladimír Cermák 相似文献
75.
Spatial and temporal variations of aridity indices in Iraq 总被引:1,自引:0,他引:1
Nermin??arlakEmail author Omar?M.?A.?Mahmood Agha 《Theoretical and Applied Climatology》2018,132(1-2):89-101
In this paper, a nonhydrostatic Weather Research and Forecasting (WRF) model has been used to simulate the extreme precipitation event of 25 November 2009, over Jeddah, Saudi Arabia. The model is integrated in three nested (27, 9, and 3 km) domains with the initial and boundary forcing derived from the NCEP reanalysis datasets. As a control experiment, the model integrated for 48 h initiated at 0000 UTC on 24 November 2009. The simulated rainfall in the control experiment depicts in well agreement with Tropical Rainfall Measurement Mission rainfall estimates in terms of intensity as well as spatio-temporal distribution. Results indicate that a strong low-level (850 hPa) wind over Jeddah and surrounding regions enhanced the moisture and temperature gradient and created a conditionally unstable atmosphere that favored the development of the mesoscale system. The influences of topography and heat exchange process in the atmosphere were investigated on the development of extreme precipitation event; two sensitivity experiments are carried out: one without topography and another without exchange of surface heating to the atmosphere. The results depict that both surface heating and topography played crucial role in determining the spatial distribution and intensity of the extreme rainfall over Jeddah. The topography favored enhanced uplift motion that further strengthened the low-level jet and hence the rainfall over Jeddah and adjacent areas. On the other hand, the absence of surface heating considerably reduced the simulated rainfall by 30% as compared to the observations. 相似文献
76.
In the standard method of electron density determination for soft X-ray (SXR) flare kernels, it is necessary to assume what
the extent is of a kernel along the line of sight. This is a source of significant uncertainty of the obtained densities. 相似文献
77.
S. Turck-Chi??ze G. Loisel D. Gilles L. Piau C. Blancard T. Blenski M. Busquet T. Caillaud P. Coss?? F. Delahaye G. Faussurier J. Fariaut F. Gilleron J. A. Guzik J. Harris D. P. Kilcrease N. H. Magee J. C. Pain Q. Porcherot M. Poirier G. Soullier C. J. Zeippen S. Bastiani-Ceccotti C. Reverdin V. Silvert F. Thais B. Villette 《Astrophysics and Space Science》2011,336(1):103-109
The lifetime of solar-like stars, the envelope structure of more massive stars, and stellar acoustic frequencies largely depend on the radiative properties of the stellar plasma. Up to now, these complex quantities have been estimated only theoretically. The development of the powerful tools of helio- and astero- seismology has made it possible to gain insights on the interiors of stars. Consequently, increased emphasis is now placed on knowledge of the monochromatic opacity coefficients. Here we review how these radiative properties play a role, and where they are most important. We then concentrate specifically on the envelopes of ?? Cephei variable stars. We discuss the dispersion of eight different theoretical estimates of the monochromatic opacity spectrum and the challenges we need to face to check these calculations experimentally. 相似文献
78.
Faruk?AydinEmail author Axel?K.?Schmitt Wolfgang?Siebel Mustafa?S?nmez Yal??n?Ersoy Abdurrahman?Lermi Kadir?Dirik Robert?Duncan 《Contributions to Mineralogy and Petrology》2014,168(5):1078
The late Neogene to Quaternary Cappadocian Volcanic Province (CVP) in central Anatolia is one of the most impressive volcanic fields of Turkey because of its extent and spectacular erosionally sculptured landscape. The late Neogene evolution of the CVP started with the eruption of extensive andesitic-dacitic lavas and ignimbrites with minor basaltic lavas. This stage was followed by Quaternary bimodal volcanism. Here, we present geochemical, isotopic (Sr–Nd–Pb and δ18O isotopes) and geochronological (U–Pb zircon and Ar–Ar amphibole and whole-rock ages) data for bimodal volcanic rocks of the Ni?de Volcanic Complex (NVC) in the western part of the CVP to determine mantle melting dynamics and magmatic processes within the overlying continental crust during the Quaternary. Geochronological data suggest that the bimodal volcanic activity in the study area occurred between ca. 1.1 and ca. 0.2 Ma (Pleistocene) and comprises (1) mafic lavas consisting of basalts, trachybasalts, basaltic andesites and scoria lapilli fallout deposits with mainly basaltic composition, (2) felsic lavas consisting of mostly rhyolites and pumice lapilli fall-out and surge deposits with dacitic to rhyolitic composition. The most mafic sample is basalt from a monogenetic cone, which is characterized by 87Sr/86Sr = 0.7038, 143Nd/144Nd = 0.5128, 206Pb/204Pb = 18.80, 207Pb/204Pb = 15.60 and 208Pb/204Pb = 38.68, suggesting a moderately depleted signature of the mantle source. Felsic volcanic rocks define a narrow range of 143Nd/144Nd isotope ratios (0.5126–0.5128) and are homogeneous in Pb isotope composition (206Pb/204Pb = 18.84–18.87, 207Pb/204Pb = 15.64–15.67 and 208Pb/204Pb = 38.93–38.99). 87Sr/86Sr isotopic compositions of mafic (0.7038–0.7053) and felsic (0.7040–0.7052) samples are similar, reflecting a common mantle source. The felsic rocks have relatively low zircon δ18O values (5.6 ± 0.6 ‰) overlapping mantle values (5.3 ± 0.3 %), consistent with an origin by fractional crystallization from a mafic melt with very minor continental crustal contamination. The geochronological and geochemical data suggest that mafic and felsic volcanic rocks of the NVC are genetically closely related to each other. Mafic rocks show a positive trend between 87Sr/86Sr and Th, suggesting simultaneous assimilation and fractional crystallization, whereas the felsic rocks are characterized by a flat or slightly negative variation. High 87Sr/86Sr gneisses are a potential crustal contaminant of the mafic magmas, but the comparatively low and invariant 87Sr/86Sr in the felsic volcanics suggests that these evolved dominantly by fractional crystallization. Mantle-derived basaltic melts, which experienced low degree of crustal assimilation, are proposed to be the parent melt of the felsic volcanics. Geochronological and geochemical results combined with regional geological and geophysical data suggest that bimodal volcanism of the NVC and the CVP, in general, developed in a post-collisional extensional tectonic regime that is caused by ascending asthenosphere, which played a key role during magma genesis. 相似文献
79.
Predrag Vuli? Ton?i Bali?-?uni? Louise Josefine Belmonte Volker Kahlenberg 《Mineralogy and Petrology》2011,101(3-4):185-194
Ten nepheline single crystals from five different localities representing rocks from nepheline-syenite pegmatites to urtite, ijolite and cancrinite-ijolite were investigated chemically and structurally. The chemical compositions were determined by electron microprobe, whereas the crystal structures were refined against X-ray diffraction data to R values of 0.022?C0.031. In all cases the crystal structures conformed to space group P63, but at the same time all crystals produced some satellite reflections testifying to the modulation effects in their structure. This work confirms the presence of satellite reflections as a universal property of nepheline and resolves some controversy about this issue present in older works. The samples show a range of compositions with variable excess of Si over Al combined with vacancies in the alkaline sites. Vacancies are present exclusively in the symmetric ditrigonal channels occupied preferentially by K atoms in natural nepheline. The influence of the variable amounts of K, Na and vacancies to the increase of volume at this site is shown to be in the order ??>K>Na. It has been confirmed that natural nepheline can partly depart from Loewenstein??s rule and show some degree of disorder in the Si/Al distribution. Most of the samples revealed a practically full Si-Al-ordering, but the crystals from one of the nepheline-syenite pegmatites in Langesundsfjord, Norway and from the type locality of ijolite, Iivaara, Finland, showed a disorder of 10?C20% suggesting a different cooling history for these rocks. 相似文献
80.
This paper examines hydrodynamic pressure diagrams due to earthquakes acting on distinct configurations of the upstream face of a dam, considering the reservoir length and different bathymetries of the reservoir bottom. Two suitable mathematical models are used to obtain the dynamic pressure on the dam, and the reservoir free surface oscillation. Conceptual mathematical models are proposed to study the impact of a landslide triggered by an earthquake, and its progress into the reservoir. The waves formed when a landslide advances into the reservoir are tested with the help of laboratory results. These waves and their propagation in the reservoir are studied using experimental data and numerical results, including wave-type analyses based on dimensionless parameters. Two distinct 1DH and 2DV numerical models based on different mathematical formulations are tested. A discussion of physical and numerical results is detailed in a general risk context and uncertainty associated with the input data in a deterministic model. Numerical simulations are performed for the upper and lower limits of the sliding mass velocity diagram which is obtained as a result of the intrinsic uncertainty of the stochastic nature of the friction angle. Finally, the findings are discussed and some conclusions drawn. 相似文献