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611.
Vinod Kumar Nagendra Kumar Krishna M. Srivastava R. C. Mittal 《Astrophysics and Space Science》1993,199(2):323-331
The problem of gravitational instability of an infinite homogeneous self-gravitating medium carrying a uniform magnetic field in the presence of Hall effect has been investigated to include the effect due to rotation. The dispersion relation has been obtained. It has been found that the Jeans's criterion for the instability remains unaffected even when the effect due to rotation is considered in the presence of Hall effect carrying a uniform magnetic. 相似文献
612.
Modeling fractionally integrated maximum temperature series in India in presence of structural break
Ranjit?Kumar?PaulEmail author Priyanka?Anjoy 《Theoretical and Applied Climatology》2018,134(1-2):241-249
In this study, the long memory behaviour of monthly maximum temperature of India for the period 1901 to 2007 is investigated. The correlogram of the series reveals a slow hyperbolic decay, a typical shape for time series having the long memory property. Wavelet transformation is applied to decompose the temperature series into time–frequency domain in order to study the local as well as global variation over different scale and time epochs. Significant increasing trend is found in the maximum temperature series in India. The rate of increase in maximum temperature accelerated after 1960s as compared to the earlier period. Here, an attempt is also made to detect the structural break for seasonally adjusted monthly maximum temperature series. It is found that there is a significant break in maximum temperature during July, 1963. Two-stage forecasting (TSF) approach to deal with the coexistence of long memory and structural change in temperature pattern is discussed thoroughly. The forecast performance of the fitted model is assessed on the basis of relative mean absolute prediction error (RMAPE), sum of squared errors (SSE) and mean squared errors (MSE) for different forecast horizons. 相似文献
613.
Kattel Dambaru Ballab Yao Tandong Panday Prajjwal Kumar 《Theoretical and Applied Climatology》2018,132(3-4):1129-1141
Theoretical and Applied Climatology - Based on climatic data from 18 stations on the southern slopes of the eastern Himalayas in Bhutan for the period from 1996 to 2009, this paper investigates... 相似文献
614.
M. N. S. Babu R. K. Somashekar S. A. Kumar K. Shivanna V. Krishnamurthy K. P. Eappen 《International Journal of Environmental Science and Technology》2008,5(2):263-266
The uranium isotopes during their course of their disintegration decay into other radioactive elements and eventually decay into stable lead isotopes. The cause of environmental concern is the emanation of beta and gamma radiation during disintegration. The present study tends to estimate uranium in groundwater trapped in granite and gneiss rocks. Besides, the study aims at estimating the radiation during natural disintegration process. The water samples were collected and analyzed following inductively coupled plasma mass spectrometric technique while water sample collection was given to the regions of Kolar District, South India, due to the representation. The significant finding was the observation of very high levels of uranium in groundwater compared to similar assays reported at other nearby districts. Also, the levels were considerable to those compared to groundwater levels of uranium reported by other scientists. On the basis of this study, it was inferred that the origin of uranium was from granite strata and there was a trend of diffusion observed in the course of flow-path of water in the region. 相似文献
615.
D. S. Suresh Babu Atul Kumar Sahai Mauricio Almeida Noernberg Eduardo Marone 《Hydrogeology Journal》2008,16(7):1427-1439
The unconfined aquifer supported by the extensive Holocene coastal plain of southern Brazil is found dissected at several places by tidally forced streams. One such unit of coastal plain, falling within the watershed limits of Perequê Stream in Paraná state, was analyzed using MODFLOW to assess the surface and subsurface water components under different stress conditions. The steady-state simulation suggests that ~23,000 m3/day of water forms the total budget of the designated aquifer zone and this zone discharges ~16,000 m3/day across the interface between the freshwater aquifer zone and the sea as direct submarine discharge. The maximum evaporation loss was assumed to be 2,700 m3/day. Any change in effective aquifer storage was insignificant, as there is no large-scale exploitation of local groundwater reserves. A calibration exercise, based on field measurements lasting 1 year, supports validity of the model considered. Simulations representing two different transient conditions point to the dynamic hydraulic response exhibited by the aquifer. A schematic map, showing directions and velocity of subsurface flows, and a three-dimensional model of the groundwater reserve helped to visualize the hydrogeologic changes and to formulate management plans. 相似文献
616.
617.
Continuous and campaign-based aerosol field measurements are essential in understanding fundamental atmospheric aerosol processes and for evaluating their effect on global climate, environment and human life. Synchronous measurements of Aerosol Optical Depth (AOD), Black Carbon (BC) aerosol mass concentration and aerosol particle size distribution were carried out during the campaign period at tropical urban regions of Hyderabad, India. Daily satellite datasets of DMSP-OLS were processed for night-time forest fires over the Indian region in order to understand the additional sources (forest fires) of aerosol. The higher values in black carbon aerosol mass concentration and aerosol optical depth correlated well with forest fires occurring over the region. Ozone Monitoring Instrument (OMI) aerosol index (AI) variations showed absorbing aerosols over the region and correlated with ground measurements. 相似文献
618.
GIS-based weights-of-evidence modelling of rainfall-induced landslides in small catchments for landslide susceptibility mapping 总被引:10,自引:0,他引:10
Ranjan Kumar Dahal Shuichi Hasegawa Atsuko Nonomura Minoru Yamanaka Takuro Masuda Katsuhiro Nishino 《Environmental Geology》2008,54(2):311-324
Landslide susceptibility mapping is a vital tool for disaster management and planning development activities in mountainous terrains of tropical and subtropical environments. In this paper, the weights-of-evidence modelling was applied, within a geographical information system (GIS), to derive landslide susceptibility map of two small catchments of Shikoku, Japan. The objective of this paper is to evaluate the importance of weights-of-evidence modelling in the generation of landslide susceptibility maps in relatively small catchments having an area less than 4 sq km. For the study area in Moriyuki and Monnyu catchments, northeast Shikoku Island in west Japan, a data set was generated at scale 1:5,000. Relevant thematic maps representing various factors (e.g. slope, aspect, relief, flow accumulation, soil depth, soil type, land use and distance to road) that are related to landslide activity were generated using field data and GIS techniques. Both catchments have homogeneous geology and only consist of Cretaceous granitic rock. Thus, bedrock geology was not considered in data layering during GIS analysis. Success rates were also estimated to evaluate the accuracy of landslide susceptibility maps and the weights-of-evidence modelling was found useful in landslide susceptibility mapping of small catchments. 相似文献
619.
Characterization and evaluation of the factors affecting the geochemistry of groundwater in Neyveli,Tamil Nadu,India 总被引:1,自引:0,他引:1
M. Jayaprakash L. Giridharan T. Venugopal S. P. Krishna Kumar P. Periakali 《Environmental Geology》2008,54(4):855-867
In order to achieve a better understanding of the nature of the factors influencing ground water composition as well as to
specify them quantitatively, multivariate statistical analysis (factor analysis) were performed on the hydrochemical data
of this area. R-mode factor analysis was carried out on the geochemical results of the 79-groundwater samples and the factor
scores were transferred to areal maps. Fundamental chemical parameters of the groundwater have been compounded together for
characterizing and interpreting a few empirical hydrogeochemical factors controlling the chemical nature of water. R-mode
factor analysis reveals that the groundwater chemistry of the study area reflects the influence of anthropogenic activities,
silicate weathering reactions, precipitation, dissolution and subsequent percolation into the groundwater. The data have been
put into few major factors and the seasonal variation in the chemistry of water has been clearly brought out by these factors.
Factor scores were transferred to contour diagrams and the factor score analysis has been used successfully to delineate the
stations under study with various factors and the seasonal effect on the sample stations. 相似文献
620.
Crop classification using biologically-inspired techniques with high resolution satellite image 总被引:5,自引:0,他引:5
S. N. Omkar J. Senthilnath Dheevatsa Mudigere M. Manoj Kumar 《Journal of the Indian Society of Remote Sensing》2008,36(2):175-182
Remote sensing provides a lucid and effective means for crop coverage identification. Crop coverage identification is a very
important technique, as it provides vital information on the type and extent of crop cultivated in a particular area. This
information has immense potential in the planning for further cultivation activities and for optimal usage of the available
fertile land. As the frontiers of space technology advance, the knowledge derived from the satellite data has also grown in
sophistication. Further, image classification forms the core of the solution to the crop coverage identification problem.
No single classifier can prove to satisfactorily classify all the basic crop cover mapping problems of a cultivated region.
We present in this paper the experimental results of multiple classification techniques for the problem of crop cover mapping
of a cultivated region. A detailed comparison of the algorithms inspired by social behaviour of insects and conventional statistical
method for crop classification is presented in this paper. These include the Maximum Likelihood Classifier (MLC), Particle
Swarm Optimisation (PSO) and Ant Colony Optimisation (ACO) techniques. The high resolution satellite image has been used for
the experiments. 相似文献