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91.
J. K. Sharma 《Journal of the Indian Society of Remote Sensing》1980,8(2):11-18
North Maidan consist of seven districts of North Karnataka. It is named after its relatively low and subdued relief or landscape of monoto-nous plateau. Most of the area lies in the rain shadow of the Western Ghats. The land utilization map shows majority of the area during December and January months is under agriculture with fallow land as the second largest category Large areas of North Maidan are under grassland which look barren by the beginning of summer. A total of nine landuse categories were delineated wifh the help of Landsat data. 相似文献
92.
Rapid computation of magnetic anomalies and demagnetization effects caused by bodies of arbitrary shape 总被引:1,自引:0,他引:1
P. Vallabh Sharma 《Pure and Applied Geophysics》1966,64(1):89-109
Summary With the aid of formulae derived for the field caused by a finite rectangular prism, a machine method is developed for rapid computation of magnetic anomalies due to a body of any shape. Conversely, the method could be utilised for determination of the magnetization vector from the observed anomalies. An example is given to demonstrate the applicability, accuracy and speed of the method. The method is shown to be suitable also for the evaluation of magnetic terrain effects.In addition, a new method is presented which enables high speed calculation of demagnetization effect caused by a body of arbitrary shape where the magnetization in general may be inhomogeneous. Applicability and accuracy of the method are discussed. The method is applied to study the effect of susceptibility on inhomogeneity of the induced magnetization in a cube specimen.For a body of any shape with low susceptibility, a new concept of average demagnetization factor is introduced. Average demagnetization factors so calculated for a cylindrical specimen are tabulated.
Part I of the dissertation Theretical study of the magnetic attraction due to rock bodies and experimental investigation of the stability of rock magnetism submitted to the Swiss Federal Institute of Technology (ETH), Zurich, for the degree of Doctor of Natural Sciences. 相似文献
Zusammenfassung Unter Anwendung der Formeln für das Feld eines Quaders wird eine Methode entwickelt um die durch einen Körper beliebiger Form erzeugten magnetischen Anomalien mit Hilfe eines Rechenautomaten zu berechnen. Umgekehrt kann die Methode verwendet werden, um aus den beobachteten Anomalien den Magnetisierungsvektor zu bestimmen. An einem Beispiel wird die Anwendbarkeit, die Genauigkeit und die Schnelligkeit der Methode erläutert. Die Methode kann auch für die Berechnung von magnetischen Terraineffekten verwendet werden.Zudem wird eine neue Methode dargelegt, welche eine rasche Berechnung des Entmagnetisierungseffektes eines Körpers beliebiger Gestalt und inhomogener Magnetisierung ermöglicht. Anwendbarkeit und Genauigkeit der Methode werden besprochen. Die Methode wurde verwendet, um den Einfluss der Suszeptibilität auf die Inhomogenität der induzierten Magnetisierung in einem Würfel zu untersuchen.Für Körper beliebiger Form mit kleiner Suszeptibilität wls neuer Begriff der mittlere Entmagnetisierungsfaktor eingeführt. Mittlere Entmagnetisierungsfaktoren für eine zylindrische Probe werden tabelliert.
Part I of the dissertation Theretical study of the magnetic attraction due to rock bodies and experimental investigation of the stability of rock magnetism submitted to the Swiss Federal Institute of Technology (ETH), Zurich, for the degree of Doctor of Natural Sciences. 相似文献
93.
P. Vallabh Sharma 《Pure and Applied Geophysics》1976,114(2):195-206
Summary Measurements of bulk magnetic properties, including the natural remanent magnetization (NRM), susceptibility and the Königsberger ratio, on over 250 samples of Tertiary basalts from Disko and Nûgssuaq, West Greenland are reported.The NRM intensities in basalts (geometric mean value 3.3 A/m in SI units) were on average three to four times as large as the induced magnetization intensities. The susceptibilities (geometric mean value 2.1×10–2 SI units) were much more uniform than the NRM intensities. In the majority of samples, the NRM was predominantly of reverse (R) polarity, but samples from a few sites showed a remanence of normal (N) polarity.The NRM of both polarity classes (N, R) was very stable against alternating field (AF) demagnetization with median destructive fields of the order of 20,000–30,000 A/m (250–350 Oe), comparable to those for many stable continental and oceanic basalts. The viscous remanence intensity, as studied by storage tests on some specimens, was found to be an insignificant fraction of the original NRM, except in few cases.The low field hysteresis loops (Rayleigh loops) were studied for some specimens. A qualitative association was noted between wide hysteresis loop and relatively low AF stability, but no correlation was apparent between the loop type and the Königsberger ratio (Q
n) of a specimen.Contribution no. 6 Institute of Geophysics, University of Copenhagen. 相似文献
94.
Particulates amounting to 0.1–2.0 g efficiently collected from large volumes of Atlantic and Pacific surface waters have been analyzed for carbonate, opal, quartz and several natural and man-made radioisotopes.The concentrations of particles range between 10 and 600 μg/kg. In the equatorial regions particle concentrations are low and similar in both the oceans. At higher latitudes (>30°N or S), the Atlantic waters, however, have higher concentrations of particles compared to those in the Pacific. The latitudinal distribution exhibits a north-south symmetry with higher concentrations in the 30°–60° belt. Based on the particulate abundance for CaCO3 and opal and their sedimentation, we have estimated their production and in-situ integrated dissolution rates for a few regions.Radioisotopes having different source functions, namely14C and239Pu injected due to nuclear weapon tests,234Th,230Th and228Th produced in-situ in seawater,232Th which derives primarily from land,210Pb introduced via wet precipitations and226Ra introduced through diffusion from deep-sea sediments have been measured in the particulates. The relative enrichment factors for these nuclides in particles vary as Th ? Pu > Pb > Ra. The atmospheric bomb fallout pattern is discernible in the surface particulates; the239Pu concentration increases with latitude in both the hemispheres; however, the values are about a factor of two lower in the southern hemisphere.The distribution pattern of radioisotopes is found to be complex, even for234Th whose source function in the oceans is uniform. In view of the differences in the source functions it becomes possible to delineate the principal geochemical/geophysical processes which determine the concentrations of these nuclides in surface waters. 相似文献
95.
Ram S. Sharma 《Precambrian Research》1977,4(2):133-162
Large-scale structures, textures and mineral assemblages in the Precambrian rocks of the Banded Gneissic Complex and the overlying Delhi Group in north-central Aravalli Mountain reveal a complex deformational-crystallization history. In the basement Gneissic Complex at least three deformational events, D0, D1 and D2, and two separate episodes of metamorphism, M1 and M2, are recognized. The supracrustal Delhi Rocks display only two phases of deformation, D1 and D2, associated with a single protracted period of metamorphism, M2.The first phase of deformation (D1) of the Delhi orogeny (1650-900 m.y.) produced large isoclinal folds that are overturned towards the southeast and have gentle plunges in NE and SW directions. The second phase of deformation (D2) gave rise to tight open folds on the limbs and axial-plane surfaces of the D1 folds. These folds generally plunge towards the N and NNW at 30°–80°. In the Basement Complex one more deformation (D0) of the Pre-Delhi orogeny (> 2000 m.y.) is recorded by the presence of reclined and recumbent folds with W to WNW trending fold axes. The D0 folds were superimposed by D1 and D2 folds during the Delhi orogeny.The three deformational events have been correlated with the crystallization periods of minerals in the rocks and a setting in time is established for this part of the Aravalli range. 相似文献
96.
Water samples were collected from cold and warm karst springs for stable isotopes (δ18O and δD) and 3H from SE of Kashmir valley (western Himalayas) to distinguish the sources of recharge and infer their recharge areas. The spring water samples were most depleted in heavier isotopes in May (average δ18O: ?8.87‰ and δD: ?50.3‰) and enriched in September (average δ18O: ?7.58‰ and δD: ?48.1‰). The depleted 18O and 2H of spring waters bear the signatures of winter precipitation while as the enriched 18O and 2H of spring waters bear the signature of summer rainfall. D‐excess and 3H corroborate with the stable isotope results that the spring flow in spring season (May) and autumn (September) is dominantly controlled by the melting of winter snowmelt and summer rainfall, respectively. The results showed that unlike δD, the δ18O value in the karst spring waters decreases in January suggesting δ18O shift. The spring water samples also fall above the Local Meteoric Water Line and Global Meteoric Water Line indicating the δ18O shift due to interaction of groundwater with the host carbonate rocks during its traverse. The mean elevation of the recharge areas of the springs using δ18O and δD tracers was also estimated. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
97.
A. J. T. Jull D. Lal S. Taylor R. Wieler A. Grimberg L. Vacher L. R. McHargue S. P. H. T. Freeman C. Maden C. Schnabel S. Xu R. C. Finkel K. J. Kim K. Marti 《Meteoritics & planetary science》2007,42(10):1831-1840
Abstract— We report on studies of the concentrations of cosmogenic nuclides in the magnetic fraction of cosmic dust particles recovered from the South Pole Water Well (SPWW) and from Greenland. Our results confirm that cosmic dust material from these locations contains measurable amounts of cosmogenic nuclides. The Antarctic particles (and possibly those from Greenland as well) also contain minor amounts of solar Ne. Concentrations of cosmogenic nuclides are consistent with irradiation of this material as small objects in space, with exposure ages similar to the expected Poynting‐Robertson (P‐R) lifetimes of 50–200 kyr for particles 25–100 μm in size. 相似文献
98.
Sanjeev Sharma Jagdish C. Kuniyal J. C. Sharma 《山地科学学报》2007,4(3):221-236
Mountain ecosystem,on the earth,has plenty of natural resources. In Himachal Pradesh all the rivers are snowfed and therefore rich in water resources. These resources have been supporting enough for the generation of electricity through introducing hydropower projects since the last decade. However,every developmental activity has its own negative impacts on the surrounding environment. Due to the fragile nature of topography and delicacy of ecology of the Himalaya,it results in lot of disturbances because of high degree of human interferences like construction of major hydropower projects. The increased extent of geological hazards,such as landslides,rock fall and soil erosion,have mainly due to alike developmental interventions in the natural ecosystem. So understanding and analysing such impacts of the hydropower projects have mainly been on the environment in various forms but natural hazards have been frequent ones. The present study,therefore,focuses mainly on the Parbati Stage Ⅱ (800 MW) and the Parbati Stage Ⅲ (520 MW) hydropower projects; both of which fall within the Kullu district of Himachal Pradesh. Based on the perception survey of the local communities,the existing land use pattern,status of total acquired land of the residents by hydropower projects,frequent natural hazards and resultant loss to the local communities due to upcoming construction of hydropower projects surrounding to the Parbati Stage Ⅱ and Ⅲ have been analysed in the paper. Also,the preventive measures to mitigate these adverse impacts have been suggested to strengthen these projects in eco-friendly manner in the mountain context. 相似文献
99.
We present numerical simulations of kinetic Alfvén waves (KAWs) and inertial Alfvén waves (IAWs) applicable to the solar wind, the solar corona, and the auroral regions, respectively, leading to the formation of coherent magnetic structures when the nonlinearity arises from ponderomotive effects and Joule heating. The nonlinear dynamical equation satisfies the modified nonlinear Schrödinger equation. The effect of nonlinear coupling between the main KAW/IAW and the perturbation, producing filamentary structures of the magnetic field, has been studied. Scalings in the spectral index of the power spectrum at different times have been calculated. These filamentary structures can act as a source for particle acceleration by wave?–?particle interaction because the KAWs/IAWs are mixed modes and Landau damping is possible. 相似文献
100.