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排序方式: 共有180条查询结果,搜索用时 15 毫秒
1.
The problem of perfect fluid distribution in spatially homogeneous and anisotropic Bianchi type VI0 space-time is considered in a scalar tensor theory of gravitation proposed by Saez and Ballester (1985). Exact solutions
of the field equations are derived when the metric potentials are functions of cosmic time only. Some physical and geometrical
properties of the solutions are also discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Biswajit Mukhopadhyay Michael J. Holdaway 《Contributions to Mineralogy and Petrology》1994,116(4):462-472
The equilibrium in which hydrous Fe-cordierite breaks down to almandine, sillimanite, quartz, and water was previously experimentally determined by Richardson (1968) and Holdaway and Lee (1977) using QMF buffer and by Weisbrod (1973) using QIF buffer. All these studies yielded similar results — a negative dP/dT slope for the equilibrium curve. However, based on theoretical arguments, Martignole and Sisi (1981), and based on Fe-Mg partitioning experiments on coexisting cordierite and garnet in equilibrium with sillimanite and quartz, Aranovich and Podlesskii (1983) suggested that this equilibrium curve has a positive dP/dT slope and its position depends on the water content of the equilibrium cordierite. We have redetermined this equilibrium using a much improved tecnique of detecting reaction direction, and cordierite starting material that contained virtually no hercynite. Hercynite was present as a contaminant in the cordierites of previous experimental studies and possibly reacted with quartz during the experimental runs to expand the apparent stability field of Fe-cordierite. We synthesized Fe-cordierite from reagent grade oxides at 710°C and 2 kbar (using QMF buffer) with two intermediate stages of grinding and mixing. The cordierite has a unit cell volume of 1574.60 Å3 (molar volume=23.706 J/bar) and no Fe3+ as indicated by X-ray diffraction and room temperature Mössbauer studies respectively. Reaction direction was concluded by noting20% change of the ratios of intensities of two key X-ray diffraction peaks of cordierite and almandine. Our results show that the four-phase equilibrium curve passes through the points 2.1 kbar, 650°C and 2.5 kbar, 750°C. This disagrees with all previous experimental studies. H2O in the Fe-cordierite, equilibrated at 2.2 kbar and 700°C and determined by H-extraction line in the stable isotope laboratory, is 1.13 wt% (n=0.41 moles). H2O content of pure Mg-cordierite equilibrated under identical conditions and determined by thermogravimentric conditions and determined by thermogravimetric analysis is 1.22 wt% (n=0.40). Similar determinations on Fe-cordierite and Mg-cordierite equilibrated at 2.0 kbar and 650°C show 1.27 wt% (n=0.46) and 1.47 wt% (n=0.48) of H2O respectively. Thus, H2O content appears to be independent of Fe/Mg ratio in cordierite, a conclusion which supports previous experimental determinations. The experimentally determined equilibrium curve represents conditions of PH2O=Ptotal. From this we calculated the anhydrous curve representing equilibrium under conditions of X
H2O
V
=0.0. A family of calculated equilibrium curves of constant n
H2O
Cord
cut the experimentally determined curve at a very small angle indicating a slight variation in n
H2O
Cord
in cordierite in equilibrium with almandine, sillimanite, and quartz under the conditions of constant X
H2O
V
. Ancther set of calculated equilibrium curves, each representing constant a
H2O
V
demonstrate that the slopes of the curves vary with X
H2O
V
, and are all positive in the full range of 0.0X
H2O
V
1.0. 相似文献
3.
4.
Satya Prakash Sahu Manish Yadav Dhruti Sundar Pradhan Neha Rani Arka Jyoti Das 《Arabian Journal of Geosciences》2018,11(10):241
The objective of the study is to investigate spatio-temporal variations of PM10, PM2.5, and PM1 concentrations at seven residential sites, located in the vicinity of opencast coal projects, Basundhara Garjanbahal Area (BGA), India. Meteorological parameters such as wind speed, wind direction, relative humidity, and temperature were collected simultaneously with PM concentrations. Mean concentrations of PM10 in the range 215 ± 169–526 ± 412 μg m?3, PM2.5 in the range of 91 ± 79–297 ± 107 μg m?3, PM1 in the range of 68 ± 60–247 ± 84 μg m?3 were obtained. Coarse fractions (PM2.5–10) varied from 27 to 58% whereas fine fractions (PM1–2.5 and PM1) varied in the range of 51–73%. PM2.5 concentration was 41–74% of PM10 concentration, PM1 concentration was 31–62% of PM10 concentration, and PM1 concentration was 73–83% of PM2.5 concentration. Role of meteorology on PM concentrations was assessed using correlation analysis. Linear relationships were established among PM concentrations using least square regression analysis. With the aid of principal component analysis, two components were drawn out of eight variables, which represent more than 75% of variance. The results indicated that major sources of air pollutants (PM10, PM2.5, PM1, CO, CO2) at the residential sites are road dust raised by vehicular movement, spillage of coal generated during transportation, spontaneous combustion of coal, and biomass burning in village area. 相似文献
5.
Barik Tapan K. Swain Surya N. Sahu Bijayalaxmi Tripathy Bibarani Acharya Usha R. 《海洋学报(英文版)》2020,39(6):26-35
Marine ecosystems provide a wide variety of diverse habitats that frequently promote migration and ecological adaptation. The extent to which the geographic distribution of marine organism has reshaped by human activities remains underappreciated. The limitations intrinsic to morphology-based identification systems have engendered an urgent need for reliable genetic methods that enable the unequivocal recognition of fish species,particularly those that are prone to overexploitation and/or market substitution. In the present study, however, an attempt has been taken to identify two locally adapted fish species, Siganus sutor(Valenciennes, 1835) and Seriolina nigrofasciata(Rüppell, 1829) of order Perciformes, which happens to be the first record in Odisha coast,Bay of Bengal. The diagnostic characteristics of Siganus sutor are: dorsal fin XIII-10, anal fin VII-9, pectoral fin 15,pelvic fin II-3, while that of Seriolina nigrofasciata dorsal fin VI-I-35, anal fin I-17, pectoral fin 16, pelvic fin 5. All COI barcodes generated in this study were matched with reference sequences of expected species, according to morphological identification. Bayesian and likelihood phylogenetic trees were drawn based on DNA barcodes and all the specimens clustered in agreement with their taxonomic classification at the species level. The phylogeographic studies based on haplotype network and migration rates suggest that both the species were not panmitic and the high-frequency population distribution indicates successful migration. The result of this study provides an important validation of the use of DNA barcode sequences for monitoring species diversity and changes within a complex marine ecosystem. 相似文献
6.
We study the evolution of the configuration entropy of HI distribution in the post-reionization era assuming different time evolution of HI bias.We describe time evolution of linear bias of HI distribution using a simple form b(a)=b0an with different index n.The derivative of the configuration entropy rate is known to exhibit a peak at the scale factor corresponding to theΛ-matter equality in the unbiasedΛCDM model.We show that in theΛCDM model with time-dependent linear bias,the peak shifts to smaller scale factors for negative values of n.This is related to the fact that the growth of structures in the HI density field can significantly slow down even before the onset ofΛdomination in the presence of a strong time evolution of the HI bias.We find that the shift is linearly related to the index n.We obtain the best fit relation between these two parameters and propose that identifying the location of this peak from observations would allow us to constrain the time evolution of HI bias within the framework of theΛCDM model. 相似文献
7.
Shanti Priya Devarapalli Rukmini Jagirdar M. Parthasarathy D. K. Sahu Vijay Mohan B. C. Bhatt Vineet S. Thomas 《Astrophysics and Space Science》2018,363(4):69
The analysis of spectroscopic data for 30 Algol-type binaries is presented. All these systems are short period Algols having primaries with spectral types B and A. Dominant spectral lines were identified for the spectra collected and their equivalent widths were calculated. All the spectra were examined to understand presence of mass transfer, a disk or circumstellar matter and chromospheric emission. We also present first spectroscopic and period study for few Algols and conclude that high resolution spectra within and outside the primary minimum are needed for better understanding of these Algol type close binaries. 相似文献
8.
Biswajit Mukhopadhyay 《Contributions to Mineralogy and Petrology》1991,106(2):253-264
Liquidus phase relationships in the CaAlAl–SiO6–Mg2SiO4–CaMgSi2O6–CaAlSi2O8 portion of the simplified basalt tetrahedron in the CaO–MgO–SiO2–Al2O3 system have been experimentally determined at 20 kbar pressure. The fo+di
ss+sp+li univariant curve, that pierces the fo-di-an join and meets the fo+di
ss+ enss+sp+li invariant point in the basalt tetrahedron, extends all the way to and pierces the di-fo-CaTs join, the limit of the simplified basalt tetrahedron toward the silica undersaturated portion.An algebraic method, relying on compositions of two successive liquids on a univariant curve and those of the crystalline phases in equilibrium with the respective liquids, is developed to identify the type of reaction that takes place along an isobarically univariant curve and to detect whether there is a temperature maximum on that curve. Use of this method for the di
ss+fo+sp+li univariant equilibria shows that a temperature maximum exists on this curve at the composition Fo11Di56An3CaTs30, very close to and slighthly to the SiO2-rich side of the fo-di-CaTs join. The temperature along the univariant curve continuously decreases from the temperature maximum (1500°C) to the invariant point (1475°C) where the univariant curve is terminated by the appearance of e
ss as a member of the equilibrium assemblage. Along this part of the curve, a reaction relationship occurs according to the equation fo+li=di
ss+ sp. Compositions of di
ss in equilibrium with the liquids from the temperature maximum to the fo+di
ss+enss+ sp+li invariant point range from Di66En9CaTs25 to Di36En40CaTs24. Because of the reaction relationship of forsterite with liquid, fractional crystallization of a model alkalic basaltic liquid would cause liquids to move off the fo-di
ss-sp-li univariant curve onto the sp-di
ss divariant surface. Crystallization of di
ss and sp would then lead to silica enrichment of residual liquids. Thus at pressures below 30 kbar, at which pressure the Al2O3–CaSiO3–MgSiO3 plane becomes a new thermal divide cutting through both the tholeiitic and alkalic volumes, alkalic liquids will fractionate toward tholeiitic compositions without crossing a thermal divide. This relationship would be expected to persist at pressures down to about 4 kbar where a maximum on the fo-di-an-li boundary line causes a thermal divide near the fo-di-an plane. Strongly SiO2-undersaturated liquids (e.g. nephelinites, basanites), on the other hand, cannot be derived from SiO2-undersaturated basalts (e.g. alkali olivine basalt) by fractional crystallization at 20 kbar. We also found that no gt primary phase volume cuts the wo-en-Al2O3 join at 20 kbar pressure. The wehrlite, the olivine clinopyroxenite, and the Al-augite group lherzolite xenoliths, containing highly aluminous clinopyroxenes (enriched in Ca-Tschermak), can be interpreted as crystal cumulates from alkalic basalts in the light of this experimental study. This is consistent with the mode of origin of these xenoliths proposed from petrographic, mineralogic, and geochemical studies.Abbreviations and notations
di
CaMgSi2O6
-
fo
Mg2SiO4
-
an
CaAl2Si2O8
-
CaTs
CaAlAlSiO6
-
sp
MgAl2O4
-
en
MgSiO3
-
wo
CaSiO3
-
gt
Ca3Al2Si3O12–Mg3Al2Si3O12
-
qz
SiO2
-
li
Liquid
-
gl
glass
-
ss
Solid Solution
- A
An mxn matrix
- X
A column vector
- kbar
kilobar 相似文献
9.
A wavelet‐based random vibration theory has been developed for the non‐stationary seismic response of liquid storage tanks including soil interaction. The ground motion process has been characterized via estimates of statistical functionals of wavelet coefficients obtained from a single time history of ground accelerations. The tank–liquid–soil system has been modelled as a two‐degree‐of‐freedom (2‐DOF) system. The wavelet domain equations have been formulated and the wavelet coefficients of the required response state are obtained by solving two linear simultaneous algebraic equations. The explicit expression for the instantaneous power spectral density function (PSDF) in terms of the functionals of the input wavelet coefficients has been obtained. The moments of this PSDF are used to estimate the expected pseudo‐spectral acceleration (PSA) response of the tank. Parametric variations are carried out to study the effects of tank height, foundation natural frequency, shear wave velocity of soil and ratio of the mass of tank (including liquid) to the mass of foundation on the PSA responses of tanks. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
10.
Sarira Sahu 《中国天文和天体物理学报》2010,10(10)
In the collapsar scenario of the long duration Gamma-Ray Bursts (GRBs),multi-TeV neutrino emission is predicted as the jet makes its way through the stellar envelope.Such a neutrino signal is also expected for more general failed GRBs in which a putative jet is choked by a heavy envelope.If the ν e →νμ neutrino oscillation parameters are in the atmospheric neutrino oscillation range,we show that the resonant oscillation of ν e νμ,τ can take place within the inner high density region of the choked jet prog... 相似文献