Effect of couple-stresses in a semi-infinite elastic medium due to impulsive twist over the surface     

Giriraj Tiwari 《Pure and Applied Geophysics》1971,91(1):71-75

Summary Displacement due to impulsive twist in a semi-infinite elastic medium is calculated in the light of Cosserats theory of couple stresses [1, 2]. Numerical results are obtained for a particular  相似文献   

Identification of groundwater prospective zones by using remote sensing and geoelectrical methods in Jharia and Raniganj coalfields, Dhanbad district, Jharkhand state   总被引：3，自引：0，他引：3  

Basudeo Rai  A. Tiwari  V. S. Dubey 《Journal of Earth System Science》2005,114(5):515-522

The Dhanbad district in Jharkhand faces acute water scarcity and is chronically drought-prone. The groundwater resources in the area have not been fully exploited. The present study was undertaken to evaluate the groundwater prospective zones. Landsat-5 Multi Spectral Scanner (MSS) data of band 2 and band 4 and false colour composite (FCC) of band 2, 3, 4 were interpreted visually to differentiate different hydromorphogeological units and to delineate the major trends of lineaments. The different geomorphic features identified are linear ridges, residual hills, and pediplain, buried pediment and dissected pediplain, besides lineaments. The study shows that the pediplain and buried pediments are promising zones for groundwater prospecting. The occurrence and movement of groundwater is restricted to the unconsolidated material, weathered and fractured rocks. For the selection of tube well sites, geoelectrical resistivity investigations have been carried out at the sites, which were found suitable based on hydrogeomorphological and hydrogeological studies. Twenty-six Vertical Electrical Soundings (VES) have been carried out by using Schlumberger electrode configuration, which have brought out 3 to 7 layered sub-surface layers. The resistivity of water-bearing weathered/fractured rocks varies from 120–150 ohm m. The integrated studies have revealed that the blue colour zones are most promising for groundwater exploration and dug wells may be dug up to depths of 30±5m.  相似文献   

Periodicities of palaeomagnetic intensity and palaeoclimatic variations: a Walsh spectral approach     

J.G. Negi  R.K. Tiwari 《Earth and Planetary Science Letters》1984,70(1):139-147

The Walsh power spectral technique has been applied to the non-sinusoidal palaeoclimatic (theGloborotalia menardii climatic curve) and palaeomagnetic intensity variation records of the last 1.2 Myr. The analysis reveals, in the case of palaeomagnetic variations, statistically significant peaks (at 90% confidence level) centered around 150, 60 and 24 kyr. The palaeoclimatic spectrum, however, indicates only two significant peaks of 60 and 24 kyr. The identical periodicities in both the phenomena may suggest a causal link between the geomagnetic intensity variations and climatic changes.  相似文献   

Analyzing hyper-spectral and multi-spectral data fusion in spectral domain     

H. Pande  Poonam S. Tiwari  Shashi Dobhal 《Journal of the Indian Society of Remote Sensing》2009,37(3):395-408

Image fusion is the combination of two or more different images to form a new image by using a certain algorithm. Despite the fact that the number and kind of satellite imagery are daily increasing, using fusion techniques, in a proper way, to eliminate the redundancy in data and increase the quality of data is an important challenge in Remote Sensing Image Processing. Fusion of multispectral images with a hyperspectral image generates a composite image which preserves the spatial quality from the high resolution (MS) data and the spectral characteristics from the hyperspectral data. For the present study three fusion algorithms (Principal Component Transformation, Colour Normalized and Gram-Scmidt Transformation) were analysed for Hyperion and IKONOS MSS data. Their ability to preserve the spectral quality of fused data, in comparison with original hyper-spectral image, has been investigated.  相似文献   

Neural network modelling and classification of lithofacies using well log data: a case study from KTB borehole site     

Saumen Maiti  Ram Krishna Tiwari  Hans-Joachim Kümpel 《Geophysical Journal International》2007,169(2):733-746

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Mechanism of aluminum release from variable charge soils induced by low-molecular-weight organic acids: Kinetic study   总被引：3，自引：0，他引：3  

Jiuyu Li  Renkou Xu  Diwakar Tiwari 《Geochimica et cosmochimica acta》2006,70(11):2755-2764

The kinetic curves of aluminum release from two variable charge soils and a kaolinite within 48 h can be divided into three stages: the first stage located within the initial 30 min, at which the release rate of Al was the fastest one and the released Al dominantly originated from exchangeable Al and amorphous Al pools. The Elovich equation fit the kinetics data at this stage fairly well. The moderate and the slow stages occurred within 0.5-2 and 2-48 h, respectively. During these two stages, the released Al was mainly attributed to Al oxides, poorly crystalline kaolinite and easily weathered hydrous mica. The different linear equations also fit the kinetics data at these two stages well. The rate of Al release decreased sharply with time during the fast stage, but the rate remained constant during the moderate and slow stages. In Ultisol, Al oxides were the more important pool for Al release than poorly crystalline kaolinite and easily weathered hydrous mica during the latter two stages. In Oxisol, poorly crystalline kaolinite was the more important Al pool. Compared to the control system, the presence of organic acids increased the rate and quantity of Al release from variable charge soils. The ability of organic acids to accelerate Al release followed the order: oxalic acid > citric acid > malic acid > lactic acid. This is generally in consistent with the magnitude of the stability constants of the Al-organic complexes. The release rate of Al also increased with the rise in concentration of organic acids.  相似文献   

Ion and electron beam effects on kinetic Alfvén waves in an inhomogeneous magnetosphere     

A.K. DwivediP. Varma  M.S. Tiwari 《Planetary and Space Science》2002,50(1):93-99

Kinetic Alfvén waves are examined in the presence of ion and electron beams with bi-Maxwellian distribution functions. The theory of particle aspect analysis is used to evaluate the trajectories of charged particles in the electromagnetic field of a kinetic Alfvén wave. The expressions for the field-aligned currents, perpendicular currents (with respect to B₀), dispersion relation and growth-rate with marginal instability criteria are derived. The significance of the investigation for the earth's magnetoplasma is discussed.  相似文献   

The M w 6.9 Sikkim–Nepal earthquake of September 2011: a perspective for wrench faulting in the Himalayan thrust zone     

N. Purnachandra Rao  V. M. Tiwari  M. Ravi Kumar  Pinki Hazarika  Dipankar Saikia  R. K. Chadha  Y. J. Bhaskar Rao 《Natural Hazards》2015,77(1):355-366

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Holocene climate variability from lake sediment core in Larsemann Hills,Antarctica     

Pawan Govil  Abhijit Mazumder  Anoop Tiwari  Sandeep Kumar 《Journal of the Geological Society of India》2011,78(1):30-35

A sediment core (L2) from Larsemann Hills, Antarctica was analyzed for Biogenic Silica (BSi), Sand (%) and Total Organic Carbon (TOC). The 78 cm core length represents the time span of ∼8.3 cal ka BP. The values of BSi from the core show prominent high productivity from ∼8.3 to ∼6 cal ka BP in comparison to less productivity in mid-late Holocene (∼6 cal ka BP to recent). Moreover, high sand (%) infers the glacio-fluvial deposition from ∼8.3 to ∼5 cal ka BP TOC shows little variation through out the core, except in the upper ∼10 cm (∼4 cal ka BP) part wherein it is comparatively high. The increased TOC in the upper part of the core possibly indicates presence of algal mat due to exposure of the lake to the ice free (glacier free) conditions.  相似文献   

Selachian fishes from Bhuban Formation,Surma Group,Aizawl, Mizoram     

Victor Zochhuana Ralte  R. P. Tiwari  Lalchawimawii  J. Malsawma 《Journal of the Geological Society of India》2011,77(4):328-348

An interesting selachian fish assemblage having stratigraphic and palaeoecological significance is being described from the two intraformational calcareous conglomeratic horizons within the Upper Bhuban unit of Bhuban Formation, Surma Group (Lower to Middle Miocene). The assemblage consists of eighteen species of selachian fishes including two new ones (Carcharhinus bhubanicus and Hemipristis unidenticulata) belonging to thirteen genera and another thirteen forms have been identified up to generic level. It is dominated by the families Carcharhinidae and Lamnidae, and is one of the most diversified Miocene assemblages from the Indian subcontinent. The fish fauna and the associated mega-invertebrates suggest Lower Miocene (Aquitanian - Burdigalian) age for the Upper Bhuban unit of Bhuban Formation. These further suggest that the fish yielding horizons were deposited under a warm shallow marine set-up near to the shoreline in a high-energy environment.  相似文献