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101.
The propagation of plane magnetogasdynamic shock waves in an optically-thin grey atmosphere of non-uniform density has been discussed by the use of the similarity method, by use of Planck's diffusion approximation. The distribution of pressure, density, magnetic field, velocity, temperature, and radiation flux have been illustrated through graphs. The numerical integration has been done on a DEC-1090 computer under a RKGS programme. 相似文献
102.
An exact similarity solution for a spherical magneto-gas dynamic shock wave is obtained in the case when the loss of energy due to radiation escape is significant. The total energy of the shock wave is not constant but decreases with time. We have shown that due to the magnetic field, the radiation flux changes considerably. 相似文献
103.
R.R. Daniel S.K. Ghosh K.V.K. Iyengar T.N. Rengarajan S.N. Tandon R.P. Verma 《Icarus》1982,49(2):205-212
We present far-infrared observations of Saturn in the wavelength band 76–116 μm, using a balloon-borne 75-cm telescope launched on 10 December 1980 from Hyderabad, India, when B′, the Saturnicentric latitude of the Sun, was 4°.3. Normalizing with respect to Jupiter, we find the average brightness temperature of the disk-ring system to be 90 ± 3° K. Correcting for the contribution from rings using experimental information on the brightness temperature of rings at 20 μm, we find TD, the brightness temperature of the disk, to be 96.9 ± 3.5° K. The systematic errors and the correction for the ring contribution are small for our observations. We, therefore, make use of our estimate of TD and earlier observations of Saturn when contribution from the rings was large and find that for wavelengths greater than 50 μm, there is a small reduction in the ring brightness temperature as compared to that at 20 μm. 相似文献
104.
By taking into account the interaction with magnetic field, in an axially symmetric inhomogeneous medium and assuming Gaussian density profile in radial direction instead of the cusped exponential law, a point explosion has been investigated by generalising the method suggested by Laumbach and Probstein (1969). The shock envelope becomes increasingly elongated along the axis of rotation, until it finally breaks through into the intergalactic space before it can spread considerably in equatorial directions as in ordinary gasdynamics. A comparison has been made between our results and those obtained in ordinary gasdynamics.Explosion models of double radio sources and related objects are suggested. 相似文献
105.
Ignacio S. Torres-Alvarado Surendra P. Verma Gerardo Carrasco-Núñez 《Journal of Earth System Science》2000,109(1):67-78
Seven hundred and twenty-five Sr, two hundred and forty-three Nd and one hundred and fifty-one Pb isotopic ratios from seven
different Mexican magmatic provinces were compiled in an extensive geochemical database. Data were arranged according to the
Mexican geological provinces, indicating for each province total number of analyses, range and mean of values and two times
standard deviation (2σ). Data from seven provinces were included in the database: Mexican Volcanic Belt (MVB), Sierra Madre
Occidental (SMO), Baja California (BC), Pacific Ocean (PacOc), Altiplano (AP), Sierra Madre del Sur (SMS), and Sierra Madre
Oriental (SMOr). Isotopic values from upper mantle and lower crustal xenoliths, basement outcrops and sediments from the Cocos
Plate were also compiled. In the MVB the isotopic ratios range as follows:87Sr/86Sr 0.703003-0.70841;143Nd/144Nd 0.512496-0.513098;206Pb/204Pb 18.567-19.580;207Pb/204Pb 15.466-15.647;208Pb/204Pb 38.065-38.632. The SMO shows a large variation in87Sr/86Sr ranging from ∼0.7033 to 0.71387.143Nd/144Nd ratios are relatively less variable with values from 0.51191 to 0.51286. Pb isotope ratios in the SMO are as follows:206Pb/204Pb 18.060-18.860;207Pb/204Pb 15.558-15.636;208Pb/204Pb 37.945-38.625. PacOc rocks show the most depleted Sr and Nd isotopic ratios (0.70232-0.70567 for Sr and 0.512631-0.513261
for Nd). Pb isotopes for PacOc show the following range:206Pb/204Pb 18.049-19.910;207Pb/2047Pb 15.425-15.734;208Pb/204Pb 37.449-39.404. The isotopic ratios of the AP rocks seem to be within the range of those from the PacOc.
Most samples with reported Sr and Nd isotopic data are spread within and around the “mantle array”. The SMO seems to have
been formed by a mixing process between mantle derived magmas and continental crust. The MVB appears to have a larger mantle
component, with AFC as the dominant petrogenetic process for the evolved rocks. There is still a need for Pb isotopic data
in all Mexican magmatic provinces and of Nd isotopes in BC, AP, SMS, and SMOr. 相似文献
106.
V. K. Verma 《Journal of Astrophysics and Astronomy》2000,21(3-4):173-176
We report here a study of various solar activity phenomena occurring in both north and south hemispheres of the Sun during
solar cycles 8–23. In the study we have used sunspot data for the period 1832–1976, flare index data
for the period 1936-1993, Hα flare data 1993–1998 and solar active prominences data for the period 1957–1998.
Earlier Verma reported long-term cyclic period in N-S asymmetry and also that the N-S asymmetry of solar activity phenomena
during solar cycles 21, 22, 23 and 24 will be south dominated and the N-S asymmetry will shift to north hemisphere in solar
cycle 25. The present study shows that the N-S asymmetry during solar cycles 22 and 23 are southern dominated as suggested
by Verma. 相似文献
107.
Determination of the Concentration of Carbonic Species in Natural Waters: Results from a World‐Wide Proficiency Test
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Mahendra P. Verma Enrique Portugal Sophie Gangloff María Aurora Armienta Dornadula Chandrasekharam Mayela Sanchez Roberto E. Renderos Miguel Juanco Robert van Geldern 《Geostandards and Geoanalytical Research》2015,39(2):233-255
The results of an international interlaboratory proficiency test for the determination of carbonic species are presented. Eight laboratories analysed twelve water samples (four synthetic waters, one lake water, four geothermal waters, one seawater and two petroleum waters) by two methods: (a) individual laboratory analytical procedure and (b) acid–base titration curves in tabular form following a standardised protocol. In case (b), the concentrations of carbonic species were calculated by the organiser using the (1) Hydrologists' method, (2) Geochemists' method and/or (3) initial pH and total alkalinity method. For synthetic waters, the averaged % trueness and precision of measurement of the two methods were (trueness = 7.6, precision = 9.4) and (9.0, 3.4) for total alkalinity, and (6.6, 31.0) and (7.8, 6.1) for carbonic alkalinity, respectively. This indicates that the total alkalinity calculation procedure is in general correct in the individual laboratory method, but the carbonic alkalinity calculation procedure has serious problems. The measurements of total alkalinity for lake and seawaters were in agreement in both the methods; however, the individual laboratory measurement method for geothermal and petroleum waters was conceptually incorrect. Thus, the analytical procedures for the determination of carbonic species were reviewed. To apply the Hydrologists' and/or Geochemists' methods, the location of NaHCO3EP and H2CO3EP is necessary, even for samples with pH lower than that of NaHCO3EP, and a backward titration curve after complete removal of CO2 must be performed. The initial pH and total alkalinity method is appropriate where a complete analysis of species that contribute to the alkalinity is known. 相似文献
108.
The problem of equivalence in direct current (DC) resistivity and electromagnetic methods for a thin resistive and conducting layer is well‐known. Attempts have been made in the past to resolve this problem through joint inversion. However, equivalence still remains an unresolved problem. In the present study, an effort is made to reduce non‐uniqueness due to equivalence using global optimization and joint inversion by successive refinement of the model space. A number of solutions derived for DC resistivity data using very fast simulated annealing global inversion that fits the observations equally well, follow the equivalence principle and show a definite trend. For a thin conductive layer, the quotient between resistivity and thickness is constant, while for a resistive one, the product between these magnitudes is constant. Three approaches to obtain very fast simulated annealing solutions are tested. In the first one, layer resistivities and thicknesses are optimized in a linear domain. In the second, layer resistivities are optimized in the logarithmic domain and thicknesses in the linear domain. Lastly, both layer resistivities and thicknesses are optimized in the logarithmic domain. Only model data from the mean models, corresponding to very fast simulated annealing solutions obtained for approach three, always fit the observations. The mean model defined by multiple very fast simulated annealing solutions shows extremely large uncertainty (almost 100%) in the final solution after inversion of individual DC resistivity or electromagnetic (EM) data sets. Uncertainty associated with the intermediate resistive and conducting layers after global optimization and joint inversion is still large. In order to reduce the large uncertainty associated with the intermediate layer, global optimization is performed over several iterations by reducing and redefining the search limits of model parameters according to the uncertainty in the solution. The new minimum and maximum limits are obtained from the uncertainty in the previous iteration. Though the misfit error reduces in the solution after successive refinement of the model space in individual inversion, it is observed that the mean model drifts away from the actual model. However, successive refinement of the model space using global optimization and joint inversion reduces uncertainty to a very low level in 4–5 iterations. This approach works very well in resolving the problem of equivalence for resistive as well as for conducting layers. The efficacy of the approach has been demonstrated using DC resistivity and EM data, however, it can be applied to any geophysical data to solve the inherent ambiguities in the interpretations. 相似文献
109.
M. B. Verma P. S. Dandele G. Nagendra Babu K. Umamaheswar P. B. Maithani 《Journal of the Geological Society of India》2011,78(5):468-476
Relationship of hydro-uranium anomalies (2-649 ppb) vis-à-vis underlying uranium ore body has been attempted based on seventy nine water samples collected from the exploratory boreholes on the northern periphery of Srisailam sub basin, Nalgonda district, A.P. Water table is hosted in the granitoid aquifer which underlies the cover rocks of Srisailam Formation. TDS (total dissolved salt) range from 123 to 1088 ppm (x? = 329 ppm) and analyzed >500 ppm in eight samples. Water samples show a strong positive correlation of TDS with Cl? (r=0.90), Na+ (r=0.82), Mg (r=0.80) and a moderate positive correlation with Sr (r=0.48) and Ca (r=0.70). Low value (<0.4) of Normalised Magnesium (NMg) indicates that host rock aquifer has not undergone chloritisation. Accumulate contour plan of uranium ore body shows NW-SE trend and coincides with the hydro-uranium contour. Correlation sections of ore body display true as well as false hydro-uranium anomalies in N-S and E-W profiles. Hydro-uranium anomalies owe their origin to uranium cations, dissolved from the mineralized horizon in to groundwater. Hydro-geochemical orientation survey carried out at Chitrial plateau may be applied regionally in the Srisailam sub basin as an effective tool to explore the concealed unconformity type uranium mineralization below Srisailam Formation. 相似文献
110.
Surendra P. Verma Rosalinda González‐Ramírez Rodolfo Rodríguez‐Ríos 《Geostandards and Geoanalytical Research》2011,35(2):183-192
Pressed powder pellets and fused beads or glass disks are routinely used in X‐ray fluorescence spectrometry for the determination of major and trace elements, respectively, in geological materials. In order to evaluate the performance of these two sample preparation methods, we determined Ni and Cr concentrations of fourteen RMs from Japan, France and South Africa, and eighty‐five igneous and three sedimentary rock samples from Mexico in both powder pellets and glass beads. We also computed new values of statistical parameters for RMs from an outlier‐based multiple‐test method and compared them with the literature mean and confidence limit values. The results showed that the multiple‐test method provided more reliable central tendency and dispersion parameters for RMs than those obtained previously from the two or three standard deviation method, or from robust methods. The powder pellet and fused bead sample preparation methods provided consistent results for Ni and Cr at concentration levels > 50 μg g?1 in this application; for lower concentration levels, however, these methods showed somewhat greater differences. For quantitative comparisons, both ordinary and weighted least‐squares linear regression models were used to show that the two sample preparation methods provided generally unbiased results. 相似文献