VRI photometry of M67 for CCD standardization at 2.3m VBT     

P. N. Bhat  K. P. Singh  T. P. Prabhu  A. K. Kembhavi 《Journal of Astrophysics and Astronomy》1992,13(4):293-305

We present the results from CCD photometry in theV, R andI bands, of the ‘Dipper Asterism’ region of the open cluster M67 based on observations carried out at the prime focus of the 2.3 m Vainu Bappu Telescope of the Vainu Bappu Observatory, Kavalur. The CCD parameters like the system gain and the readout noise are measured using several flatfield frames taken through the standardI filter. The CCD chip is calibrated using the photometric standards in the field and linear colour transformation relations are derived. Also a few newVRI photometric measurements are reported for the members of the cluster.  相似文献   

Assessing the geoindicators of land degradation in the Kashmir Himalayan region, India     

Sumira Nazir Zaz  Shakil Ahmad Romshoo 《Natural Hazards》2012,64(2):1219-1245

The geoindicators of land degradation such as erosion, vegetation change and wetland loss were identified in the Kashmir Himalayan region using a geospatial model. Geomatics techniques were used to generate information on landuse/landcover, NDVI, slope and the lithological formations that form inputs to map the erosion risk. The results of erosion analysis revealed that 48.27?% of the area is under very high erosion risk. The Middle Himalayan watersheds were found to be under high erosion risk compared to the Greater Himalayan watersheds. Pohru and Doodhganga watersheds of the Middle Himalayas were found to be under very high erosion risk. These two watersheds were studied in detail from 1992 to 2001 for vegetation change and wetland loss. In Pohru watershed, significant change was found in the dense forest with 10?% decrease. Wular lake, an important wetland in the Pohru watershed, has shrunk by 2.7?km² during the last decade. The vegetation change analysis of the Doodhganga watershed revealed that there has been 9.13?% decrease in the forest, 7?% increase in built up and the largest wetland in the Doodhganga, Hokarsar, has reduced by 1.98?km² from 1992 to 2001. Field studies showed that anthropogenic activities and chemically deficit soil (Karewa) along Pir Panjal ranges are the main factors responsible for high land degradation in the area. The assessment of these geoindicators provided valuable information for identifying causes and consequences of the land degradation and thus outlining potential hazard areas and designing remedial measures.  相似文献   

Cosmic energy equation and clustering of non-point mass system of galaxies     

Abdul Wahid  Farooq Ahmad  Aasifa Nazir 《Astrophysics and Space Science》2011,333(1):241-246

Cosmic energy equation is an important equation for studying the gravitational galaxy clustering in the expanding universe. We derive the distribution function for fluctuations in particle number by using the cosmic energy equation for extended structures (galaxies with halos). From spatial distribution function, containing particle fluctuations, we derive the velocity distribution function to understand the influence of particle fluctuations on the velocities of galaxies.With the help of cosmic energy equation we try to find out the physical constraints for the application of quasi-equilibrium approximation.  相似文献   

Peaty Soil Improvement by Using Cationic Reagent Grout and Electrokintic Method   总被引：2，自引：1，他引：1  

Hossein Moayedi  Mansour Mosallanezhad  Ramli Nazir  Sina Kazemian  Bujang Kim Huat 《Geotechnical and Geological Engineering》2014,32(4):933-947

Peat is known as soft soil with low shear strength and high compressibility. Electrokinetic injection technique is being used by applying a direct electrical potential across the soil specimens to improve physicochemical characteristics of the peat. Such applications cause electrochemical effects on the soil, leading to changes in the soil’s chemical, physical, and mechanical properties. This paper presents the results of the undrained shear strength, pH, water content across the electrokinetic box after injecting the cationic grouts. Four cationic grouts namely; calcium chloride, calcium oxide, Aluminum hydroxide, and sodium silicates were selected as grout. The microstructures of the stabilized peats were investigated by scanning electron microscopy and energy dispersive X-ray spectrometer analysis. The result showed that the cationic stabilizer injected by the electrokinetic technique could significantly increase the peat soil’s shear strength. Furthermore, the result showed that the effect of calcium oxide was the highest on the shear strength of peat due to its physico-chemical properties. The shear strength, pH and moisture content of peats across the electrokinetic box also altered depending on the used electrolytes and time.  相似文献   

Characteristics of seismic wave attenuation in the Kishtwar and its adjoining region of NW Himalaya     

Sutar  Anup K.  Verma  Mithila  Bansal  Brijesh. K.  Bhat  G. M.  Pandey  Shiv J. 《Journal of Seismology》2021,25(6):1507-1523

Journal of Seismology - We investigate the attenuation characteristics of high frequency seismic waves in the Kishtwar and its adjoining region of NW Himalaya using 161 local earthquakes (M...  相似文献   

Grain size analysis and characterization of sedimentary environment along Thiruchendur coast, Tamilnadu, India   总被引：1，自引：0，他引：1  

V. C. Rajganapathi  N. Jitheshkumar  M. Sundararajan  K. H. Bhat  S. Velusamy 《Arabian Journal of Geosciences》2013,6(12):4717-4728

Thiruchendur coast of southern Tamilnadu, India has been studied for grain-size spectrum and textural parameters namely mean, sorting, skewness and kurtosis. The grain-size spectrum shows a marked variation in the berm, high tide line (HTL) and low tide line (LTL) stretches. Variation in energy condition is controlled by geomorphology of the sedimentary beach. Textural pattern shows complicated profile as a result of the fluctuation in the physicochemical conditions due to the sediments and the marine interactions. Abundance of the medium sand to fine sand shows the prevalence of comparatively moderate- to low-energy condition in the Thiruchendur area. Linear discriminate function of the samples indicates an aeolian, shallow marine deposition environment and less influence of fluvial (7 %) process. CM diagram (C = one percentile in microns M = medium in microns) of Thiruchendur coast sediments suggests that deposition takes place by (1) rolling, (2) bottom suspension, (3) graded suspension. This is also supported by the wave energy in different stretches in beach line and also tractive current figure implies the sediments disturbed by the tractive and turbidity currents. The heavy minerals are concentrated in the berm (average, 11.8 %) and high tide line (average, 11.2 %) because of high-energy condition and aeolian action. Quartz microtextures show the mechanical action due to high-energy condition in Manapad and Kuduthalai areas, the chemical action because of to low-energy condition along the Thiruchendur, Kallamozhi areas.  相似文献   

A spatial panel ordered-response model with application to the analysis of urban land-use development intensity patterns   总被引：1，自引：0，他引：1  

Nazneen Ferdous  Chandra R. Bhat 《Journal of Geographical Systems》2013,15(1):1-29

This paper proposes and estimates a spatial panel ordered-response probit model with temporal autoregressive error terms to analyze changes in urban land development intensity levels over time. Such a model structure maintains a close linkage between the land owner’s decision (unobserved to the analyst) and the land development intensity level (observed by the analyst) and accommodates spatial interactions between land owners that lead to spatial spillover effects. In addition, the model structure incorporates spatial heterogeneity as well as spatial heteroscedasticity. The resulting model is estimated using a composite marginal likelihood (CML) approach that does not require any simulation machinery and that can be applied to data sets of any size. A simulation exercise indicates that the CML approach recovers the model parameters very well, even in the presence of high spatial and temporal dependence. In addition, the simulation results demonstrate that ignoring spatial dependency and spatial heterogeneity when both are actually present will lead to bias in parameter estimation. A demonstration exercise applies the proposed model to examine urban land development intensity levels using parcel-level data from Austin, Texas.  相似文献   

Spatio-temporal Variability of Surface-layer Turbulent Fluxes Over the Bay of Bengal and Arabian sea During the ICARB Field Experiment     

Denny P. Alappattu  D. Bala Subrahamanyam  P. K. Kunhikrishnan  Radhika Ramachandran  K. M. Somayaji  R. Venkatesh  G. S. Bhat  A. Bhagavath Singh 《Boundary-Layer Meteorology》2008,126(2):297-309

We report the spatio-temporal variability of surface-layer turbulent fluxes of heat, moisture and momentum over the Bay of Bengal (BoB) and the Arabian Sea (AS) during the Integrated Campaign for Aerosols, gases Radiation Budget (ICARB) field experiment. The meteorological component of ICARB conducted during March – May 2006 onboard the oceanic research vessel Sagar Kanya forms the database for the present study. The bulk transfer coefficients and the surface-layer fluxes are estimated using a modified bulk aerodynamic method, and then the spatio-temporal variability of these air-sea interface fluxes is discussed in detail. It is observed that the sensible and latent heat fluxes over the AS are marginally higher than those over the BoB, which we attribute to differences in the prevailing meteorological conditions over the two oceanic regions. The values of the wind stress, sensible and latent heat fluxes are compared with those obtained for the Indian Ocean Experiment (INDOEX) period. The variation of drag coefficient (C _D ), exchange coefficients of sensible heat and moisture (C _H = C _E ) and neutral drag coefficient (C _DN ) with wind speed is also discussed.

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Equatorial modes observed in atmospheric variables     

L. Kiranmayi  G. S. Bhat 《Journal of Earth System Science》2009,118(3):181-192

Wavenumber-frequency spectral analysis of different atmospheric variables has been carried out using 25 years of data. The area considered is the tropical belt 25°S–25°N. A combined FFT-wavelet analysis method has been used for this purpose. Variables considered are outgoing long-wave radiation (OLR), 850 hPa divergence, zonal and meridional winds at 850, 500 and 200 hPa levels, sea level pressure and 850 hPa geopotential height. It is shown that the spectra of different variables have some common properties, but each variable also has few features different from the rest. While Kelvin mode is prominent in OLR and zonal winds, it is not clearly observed in pressure and geopotential height fields; the latter two have a dominant wavenumber zero mode not seen in other variables except in meridional wind at 200 hPa and 850 hPa divergences. Different dominant modes in the tropics show significant variations on sub-seasonal time scales.  相似文献   

Integration of geospatial technologies with RUSLE for analysis of land use/cover change impact on soil erosion: case study in Rib watershed,north-western highland Ethiopia     

Desalew Meseret Moges  H. Gangadhara Bhat 《Environmental Earth Sciences》2017,76(22):765

In recent times, soil erosion interlocked with land use and land cover (LULC) changes has become one of the most important environmental issues in developing countries. Evaluation of this complex interaction between LULC change and soil erosion is indispensable in land use planning and conservation works. This paper analysed the impact of LULC change on soil erosion in the north-western highland Ethiopia over the period 1986–2016. Rib watershed, the area with dynamic LULC change and severe soil erosion problem, was selected as a case study site. Integrated approach that combined geospatial technologies with revised universal soil loss equation model was utilized to evaluate the spatio-temporal dynamics of soil loss over the study period. Pixel-based overlay of soil erosion intensity maps with LULC maps was carried out to understand the change in soil loss due to LULC change. Results showed that the annual soil loss in the study area varied from 0 to 236.5 t ha^?1 year^?1 (tons per hectare per year) in 1986 and 0–807 t ha^?1 year^?1 in 2016. The average annual soil loss for the entire watershed was estimated about 40 t ha^?1 year^?1 in 1986 comparing with 68 t ha^?1 year^?1 in 2016, a formidable increase. Soil erosion potential that was estimated to exceed the average soil loss tolerance level increased from 34.5% in 1986 to 66.8% in 2016. Expansion of agricultural land at the expense of grassland and shrubland was the most detrimental factor for severe soil erosion in the watershed. The most noticeable change in soil erosion intensity was observed from cropland with mean annual soil loss amount increased to 41.38 t ha^?1 year^?1 in 2016 from 26.60 in 1986. Moreover, the most successive erosion problems were detected in eastern, south-eastern and northern parts of the watershed. Therefore, the results of this study can help identify the soil erosion hot spots and conservation priority areas at local and regional levels.  相似文献