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11.
A procedure for the dynamic initialization of wind and temperature fields within the atmospheric boundary layer (ABL) is presented. The procedure uses transilient turbulence theory to assess the turbulent fluxes from observed wind and temperature data, which are used to estimate the eddy transfer coefficients, so enabling a local closure ABL model to be integrated forward in time to a new steady state. The method has been applied to initialize kytoon data taken at Kharagpur (22.3° N, 87.2° E) during the MONTBLEX field programme. Results of a case study for 17 June 1990 are discussed. 相似文献
12.
Debarati Mukherjee 《Journal of the Geological Society of India》2018,91(3):295-300
An improvized version of the conventional core drilling technique, based on a new device is introduced in the current work for extracting cores from fossil bones to understand their microanatomy. A powerful, low-speed electric drill with an autolubrication facility is used as the new device, and the bone specimen is placed on a permanently fixed platform beneath the drill bit. It avoids the vibration-induced wobbling of the conventional handheld drill machine and helps in precision sampling. Long drill bits of the new device result in extraction of long cores, reduce premature breakages of cores, and recovery of the entire bone microstructure for high resolution deduction of palaeobiological information. As this version of drilling technique is less destructive, it has better sampling coverage, where fossil bones can be restored to their original shapes and preserved with almost no loss in gross morphology. This is first time such a device for extraction of fossil drill cores has been installed. After test run on dummy samples, the new device has been successfully implemented for extraction of eleven cores from various long bones of the early Jurassic sauropod dinosaur Barapasaurus tagorei. The fossil bones are restored to their pre-coring shapes, the detail protocols of which are discussed here for the first time. 相似文献
13.
Manasi Buzar Baruah Samiran Chatterjee Madhurjya P. Bora 《Astrophysics and Space Science》2010,325(2):217-225
In this work, we consider radiation (thermal) instability in a weakly ionized plasma with continuous ionization and recombination.
The situation can be visualized in the case of envelopes of planetary nebulae, which are envelopes of ionized plasmas surrounding
red giant stars. Various observations report continuous photoionization of these plasmas by the highly energetic streams of
photons emanating from the parent star. Recently, it has been shown that thermal instability can be a probable candidate in
such plasmas for the existence of small scale structures (viz., striations) whose kinematic age is much smaller than that
of the parent nebula. We therefore report a systematic study of these plasmas with photoionization and determine the instability
domain. We have shown that the continuous ionization and recombination may lead to modification of the underlying instability,
which may limit the size of the small structures that are believed to form from these instabilities, and may thus provide
an explanation of the physical processes responsible for the existence of these structures. We further show that in many cases
the system bifurcates to an ovserstable (growing wave) state from a condensation instability (monotonic) and vice versa. 相似文献
14.
The technique of linear parametric programming has been applied to derive sets of internally consistent thermodynamic data for 21 condensed phases of the quaternary system CaO-Al2O3-SiO2-H2O (CASH) (Table 4). This was achieved by simultaneously processing:
- calorimetric data for 16 of these phases (Table 1), and
- experimental phase equilibria reversal brackets for 27 reactions (Table 3) involving these phases.
15.
Tapan K. Chatterjee 《Astrophysics and Space Science》1993,199(1):35-44
A study of galaxy mergers, on the basis of the collisional theory, using galaxy models without halos and considering the evolution of the proginator galaxies only from a time when the gravitational interaction between them is physically significant, indicates that most of the mergers are affected in 2 to 3 orbital periods for progenitors of comparable mass: shorter and longer time-scales being underabundant. These results have a bearing on the evolution of binary galaxies; indicating that once the relative orbit of a binary is circularized, the components will merge during the subsequent orbit or the next one (in a time-scale ~ 108 years). These results are also indicative of the fact that binary evolution is very likely to cause a gradual evolution of the fundamental plane occupied by paired ellipticals from that of isolated ellipticals. After the merger, the remnant is very likely to define a fundamental plane with a slightly different slope. 相似文献
16.
M. Chatterjee J. Canário S. K. Sarkar V. Branco A. K. Bhattacharya K. K. Satpathy 《Environmental Geology》2009,57(5):1125-1134
Mercury concentrations (HgT) in fine-grained fraction (<63 μm) of core sediments of the Hugli–Matla–Bidyadhari estuarine complex, India were analyzed.
Results revealed a wide range of spatial variations (<4–93 ng g−1 dry weight) with a definite enhancement level at the lower stretch of the estuarine complex infested with mangrove plants,
which might act as a sink to HgT. An elevated concentration of Hg was encountered in surface/subsurface layer of the core in majority of the cases resulting
from physical, biogenic and postdepositional diagenetic processes that remobilized and resuspended the metal from deeper sediments.
A strong positive correlation was observed between the Hg and clay fraction content of the sediments, while the correlations
of Hg with Al, Fe and Mn were poor. Based on the index of geoaccumulation (I
geo) and effects range-low (ER-L) value, it is considered that the sediments are less polluted and thus there is less chance
of ecotoxicological risk to organisms living in sediments. 相似文献
17.
Niranjan D. Chatterjee Klaus Miller Walter Olbricht 《Physics and Chemistry of Minerals》1994,21(1-2):50-62
Internally consistent thermodynamic data, including their uncertainties and correlations, are reported for 22 phases of the quaternary system CaO-Al2O3-SiO2-H2O. These data have been derived by simultaneous evaluation of the appropriate phase properties (PP) and reaction properties (RP) by the novel technique of Bayes estimation (BE). The thermodynamic model used and the theory of BE was expounded in Part I of this paper. Part II is the follow-up study illustrating an application of BE. The input for BE comprised, among others, the a priori values for standard enthalpy of formation of the i-th phase, Δf H i 0 , and its standard entropy, S i 0 , in addition to the reaction reversal constraints for 33 equilibria involving the relevant phases. A total of 269 RP restrictions have been processed, of which 107 turned out to be non-redundant. The refined values for Δf H i 0 and S i 0 obtained by BE, including their 2σ-uncertainties, appear in Table 4; the Appendix reproduces the corresponding correlation matrix. These data permit generation of computed phase diagrams with 2σ-uncertainty envelopes based on conventional error propagation; Fig. 3 depicts such a phase diagram for the system CaO-Al2O3-SiO2. It shows that the refined dataset is capable of yielding phase diagrams with uncertainty envelopes narrow enough to be geologically useful. The results in Table 4 demonstrate that the uncertainties of the prior values for Δf H i Emphasis>0 , given in Table 1, have decreased by up to an order of magnitude, while those for S i 0 improved by a factor of up to two. For comparison, Table 4 also lists the refined Δf H i 0 and S i 0 data obtained by mathematical programming (MAP), minimizing a quadratic objective function used earlier by Berman (1988). Examples of calculated phase diagrams are given to demonstrate the advantages of BE for deriving internally consistent thermodynamic data. Although P-T curves generated from both MAP and BE databases will pass through the reversal restrictions, BE datasets appear to be better suited for extrapolations beyond the P-T range explored experimentally and for predicting equilibria not constrained by reversals. 相似文献
18.
Ephesite, Na(LiAl2) [Al2Si2O10] (OH)2, has been synthesized for the first time by hydrothermal treatment of a gel of requisite composition at 300≦T(° C)≦700 and \(P_{H_2 O}\) upto 35 kbar. At \(P_{H_2 O}\) between 7 and 35 kbar and above 500° C, only the 2M1 polytype is obtained. At lower temperatures and pressures, the 1M polytype crystallizes first, which then inverts to the 2M1 polytype with increasing run duration. The X-ray diffraction patterns of the 1M and 2M1 poly types can be indexed unambiguously on the basis of the space groups C2 and Cc, respectively. At its upper thermal stability limit, 2M1 ephesite decomposes according to the reaction (1) $$\begin{gathered} {\text{Na(LiAl}}_{\text{2}} {\text{) [Al}}_{\text{2}} {\text{Si}}_{\text{2}} {\text{O}}_{{\text{10}}} {\text{] (OH)}}_{\text{2}} \hfill \\ {\text{ephesite}} \hfill \\ {\text{ = Na[AlSiO}}_{\text{4}} {\text{] + LiAl[SiO}}_{\text{4}} {\text{] + }}\alpha {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}} {\text{ + H}}_{\text{2}} {\text{O}} \hfill \\ {\text{nepheline }}\alpha {\text{ - eucryptite corundum}} \hfill \\ \end{gathered}$$ Five reversal brackets for (1) have been established experimentally in the temperature range 590–750° C, at \(P_{H_2 O}\) between 400 and 2500 bars. The equilibrium constant, K, for this reaction may be expressed as (2) $$log K{\text{ = }}log f_{{\text{H}}_{\text{2}} O}^* = 7.5217 - 4388/T + 0.0234 (P - 1)T$$ where \(f_{H_2 O}^* = f_{H_2 O} (P,T)/f_{H_2 O}^0\) (1,T), with T given in degrees K, and P in bars. Combining these experimental data with known thermodynamic properties of the decomposition products in (1), the following standard state (1 bar, 298.15 K) thermodynamic data for ephesite were calculated: H f,298.15 0 =-6237372 J/mol, S 298.15 0 =300.455 J/K·mol, G 298.15 0 =-5851994 J/mol, and V 298.15 0 =13.1468 J/bar·mol. 相似文献
19.
P. C. Sinha Y. R. Rao S. K. Dube C. R. Murthy A. K. Chatterjee 《Estuarine, Coastal and Shelf Science》1999,48(6):649
This paper has two purposes. The first is to study the circulation and salinity in Hooghly Estuary, along the east coast of India and the second is to compare the performance of two turbulence closure schemes by modelling it. A breadth averaged numerical model using a sigma co-ordinate system in the vertical is briefly described. Vertical diffusion of momentum and salt are parameterized by a simple first-order turbulent closure or by a one equation model for turbulent kinetic energy (TKE) which uses a specified mixing length. The results are compared with the available neap and spring tide observations along the estuary for both low and high discharge periods.The computed elevations and currents are in reasonable agreement with the observations showing no major differences in vertical current profiles by both the turbulent schemes. However, there is a slight under-prediction of bottom currents. The salinity profiles predicted by TKE model show better matching with observations. Statistical tests are also conducted to study the comparative performance of the turbulent closure schemes. The maintenance of two layer structure in residual currents and salt variability are also studied by using the model. 相似文献
20.
The South Mountain Batholith (SMB) of southwestern Nova Scotia (Canada) is a Late Devonian (~375 Ma) composite intrusion,
which crops over an area of about 7,300 km2. This peraluminous granitoid body consists of rocks ranging from granodiorite through monzogranite and leucomonzogranite
to leucogranite that locally host greisen tin-base metal mineralization. K-feldspar displays large compositional variations
of trace elements and Pb isotopic ratios, particularly in the highly fractionated rocks. Many variations are consistent with
processes of fractional crystallization, but a distinct enrichment of Rb, Li and Cs accompanied by low K/Rb, Ba/Rb, Eu/Eu*
and K/Cs ratios point to the role of fluids during the late stages of magmatic evolution. The correlation of Pb isotopic ratios
with the enriched elements and their ratios implies that the isotopic variations are an integral part of the evolution of
the SMB. Together with well-defined isochronal relationships of Pb systems in the feldspars, the correlation suggests that
fractional crystallization accompanied in the late stages by fluid fractionation led to the formation of Li–F-rich leucogranites.
Internally derived U-rich fluids fractionated U/Pb ratios, which in turn produced distinct variations of 206Pb/204Pb and 238U/204Pb ratios in K-feldspars. This implies that the Pb isotopic values of K-feldspar, which have traditionally been used for tectonic
reconstructions, might have been modified in many granitic rocks. Thus, only early magmatic K-feldspars, which show no discernible
effects of fluid fractionation yield the initial Pb isotopic compositions of the parental granitic magmas and their sources.
The data also show that the geochemical characteristics of the leucogranites are the results of magmatic evolution rather
than a distinctive source. 相似文献