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21.
We present the results of the application of three-dimensional Hilbert transformation to the analysis of airborne total field magnetic anomalies over part of Southeastern Nigeria. This study not only substantiates the usefulness of 3-D Hilbert transforms in the interpretation of magnetic anomaly maps but also more clearly delineates the structural pattern of the area, of study. Results from the previous study are discussed in relation to the results of previous geological and geophysical studies of the area. 相似文献
22.
A comparison is made between the unsteady parallel fracture model using the double porosity approach and the anisotropic
aquifer-water table aquitard system. The presence of a moving water table in the weathered zone (unconfined block), influenced
by recharge from rainfall or other sources and leakage to the fracture zone, is discussed. The effect of fracture skin on
the block-fracture interface is studied for both double-porosity and aquifer-water table aquitard systems. Typical type curves
are presented. It is found that the effect of both fracture skin and water table is to lead to a flat drawdown behaviour for
a large time. The applicability of the present model for parameters estimation is illustrated on a field pumping test of 7
days duration.
Résumé: Une comparaison a étéétablie entre le modèle de fractures non constamment parallèles utilisant l'approche de la double porosité et une système composé d'un aquifère anisotrope et un bloc de faible perméabilité avec une surface libre. La présence d'une surface libre variable dans la zone d'altération (bloc non captif), inflluencée par la recharge (pluie ou autre) et par l'écoulement vers la zone fracturée, est discutée. L'effet d'une conche superficielle à l'interface bloc-fracture est étudié pour les deux systèmes, celui à double porosité et celui composé d'un aquifère et d'un bloc de faible perméabilité. Des combes typiques sont montrées. Les résultats montrent que les effets d'une conche superficielle et de la surface de la nappe conduisent à une evolution constante en rabattement pour un temps long. L'application du modèle pour l'estimation des paramètres est justifiée par les résultats d'un pompage d'essai de 7 jours.相似文献
23.
Journal of the Indian Society of Remote Sensing - In order to develop fully the application of Synthetic Aperture Radar (SAR) data, special image analysis techniques are required. In the present... 相似文献
24.
S.B. Rakesh Kumar Singh Mohan L. Gupta G.V. Rao 《Journal of Volcanology and Geothermal Research》1982,13(3-4)
Direct current resistivity surveys and shallow temperature measurements were carried out for geothermal exploration in a part of Parvati valley, goethermal field, Himachal Pradesh, India. At a few places, the Schlumberger soundings pointed to the presence of a relatively low-resistivity shallow layer, which probably represents fractured and jointed quartzite, saturated with hot/cold water. Wenner resistivity profiles indicate the presence of some possible shallow subsurface lateral hot water channels across the valley at Manikaran. Shallow temperature measurements show a good subsurface thermal anomaly near the confluence of the rivers Brahmaganga and Parvati. The results of the survey, together with other available geodata, suggest that an anomalous heat source does not lie beneath the study area.It is postulated that the meteoric water, originating at high elevations after heating as a result of circulation at depth, emerges at the surface in the Parvati valley as hot springs, after mixing in various proportions with near surface cold waters. 相似文献
25.
Impact of tsunami on texture and mineralogy of a major placer deposit in southwest coast of India 总被引:1,自引:0,他引:1
The great Indonesian earth quake (26 December 2004) triggered a tsunami wave across the Bay of Bengal and Indian Ocean basins
and has brought a major havoc in several countries including India. The coastal segment between Thotapalli and Valiazhikal
in Kerala state of southwest India, where considerably rich beach placer deposit with ilmenite percentage of more than 70%
is concentrated, has been investigated to understand the impact of tsunami on coastal sediments. The grain size analysis flashes
out the significant differences between the pre- and post-tsunami littoral environments. While the mineral grains collected
during pre-tsunami period show well-sorted nature, the post-tsunami samples represent moderately to poorly sorted nature.
Similarly, unimodal and bimodal distributions of the sediments have been recorded for pre- and post-tsunami sediments, respectively.
Further, mineral assemblages corresponding to before and after this major wave activity clearly indicate the large-scale redistribution
of sediments. The post-tsunami sediments register increasing trends of garnet, sillimanite and rutile. The total heavy mineral
percentage of the post-tsunami sediment also shows an improved concentration, perhaps due to the large-scale transport of
lighter fraction. Magnetite percentage of post-tsunami samples reflects higher concentration compared to the pre-tsunami samples,
indicating the intensity of reworking process. X-ray diffraction patterns of ilmenite grains have confirmed the increased
presence of pseduorutile, and pseudobrookite in post-tsunami samples, which could be due to the mixing of more altered grains.
SEM examination of grains also confirms the significant alteration patterns on the ubiquitous mineral of placer body, the
ilmenite. The reason for these textural, mineralogical and micromorphological changes in heavy minerals particularly in ilmenite,
could be due to the churning action on the deeper sediments of onshore region or on the sediments entrapped in the near shelf
region of the area, by the ∼ 6 m high tsunami waves. 相似文献
26.
Jaya K. Gurung Hiroaki Ishiga Mohan S. Khadka Nav R. Shrestha 《Environmental Geology》2007,52(3):503-517
The geochemical analyses of fluvial-lacustrine aquifer sediments of the Kathmandu Valley have been made as a step in assessing
the environment for the mobilization of arsenic in groundwater. Elements measured by X-ray fluorescence (XRF) include 4 major
oxides (Fe2O3, TiO2, CaO, P2O5) and 14 trace elements (As, Pb, Zn, Cu, Ni, Cr, V, Sr, Y, Nb, Zr, Th, Sc and TS). Elution tests of 15 selected core samples
were also carried out to determine the potential leaching of arsenic from the sediments. The XRF results show that average
bulk concentrations of the major oxides and trace elements are similar to modern unconsolidated sediments and average upper
continental crust. However, the abundance of elements varies with grain size, with higher concentrations in finer-size grades.
Variations in elemental abundances within the basin are strongly controlled by sediment facies. The elution tests show that
greater amounts of arsenic are generally eluted from the fine sediments, although the rates are variable. The results overall
suggest that As concentrations in the bulk sediments are not a controlling factor for elevated As in the Kathmandu Basin groundwater,
and the roles of other factors such as redox conditions and organic matter contents are likely to be more significant. 相似文献
27.
Vijay Mohan Bhatnagar 《Contributions to Mineralogy and Petrology》1969,22(4):375-378
High-precision, computer-refined values of the cell parameters of calcium hydroxyapatite, Ca10(PO4)6(OH)2, have been determined with an X-ray diffractometer, internally standardized by means of sodium chloride. The results obtained are as follows: a
0=9.4192 Å c
0/a
0=0.731 c
0=6.8867 Å volume=529.2 Å3
The apatite work was supported by a research grant DE-02105 from the United States Department of Health, Education, and Welfare. I am very grateful to Dr. W. R. Liebenberg, Dr. S. A. Hiemstra and Dr. H. V. R. von Rahden of National Institute for Metallurgy, South Africa for their valuable help and interest and Prof. Nelson Fuson and Prof. James R. Lawson for advice and discussion. 相似文献
28.
Kopal's method of Roche coordinates used by us in an earlier paper (Mohan and Singh, 1978) to study the problems of small oscillations of tidally-distorted stars has been extended further to take into account the effect of second-order terms in tidal distortion. Our results show that the effect of including terms of second order of smallness in tidal distortion in the metric coefficients of the Roche coordinates of tidally distorted stars is quite significant, especially in case of stars with extended envelopes and (or) larger values of the mass ratio of the companion star producing tidal distortion. Some of the models which were earlier found stable against small perturbations now become dynamically unstable with the inclusion of the terms of second order of smallness in tidal effects.At present on leave of absence with the department of Mathematics, College of Science, Baghdad, Iraq. 相似文献
29.
30.
R. Saravanathamizhan N. Mohan N. Balasubramanian V. Ramamurthi C. Ahmed Basha 《洁净——土壤、空气、水》2007,35(4):355-361
In the present investigation, treatment of textile effluent using an electrochemical technique was designed and analyzed using the Box-Behnken method. The influence of individual parameters on electro-oxidation of textile effluent has been critically examined using the response surface method (RSM), and a quadratic model for chemical oxygen demand (COD) reduction has been developed. It has been observed from the present analysis that the predicted values are in good agreement with experimental data with a correlation coefficient of 0.945. 相似文献