Site response studies in Agartala Urban agglomeration   总被引：1，自引：0，他引：1  

S. N. Chowdhuri  O. P. Singh  R. K. Majumdar 《Natural Hazards》2011,59(1):329-345

A systematic investigation using digital microearthquake recorders with short period SS-1 seismometers, covering 76 sites in and around Agartala city, has been carried out for site response (SR) studies in the area. In the northern part of the area, SR varies from 1.15 to 1.85 corresponding to peak frequency 0.76 to 0.93 Hz where soil is mostly semi-consolidated and stiffer than recent Quaternary deposits (Haora River formation). In the southern part of the area, SR varies from 1.12 to 2.42 corresponding to peak frequency from 0.71 to 0.85 Hz within the Dupitila formation (early Quaternary). It is observed that estimated SR from H/V increases from edges to middle of the Haora River valley and impedance contrast fallows the similar trend. This reflects that site response by H/V is influenced by impedance contrast, whereas computed amplification from 1-D model shows opposite trend. The maximum amplification at fundamental frequency of resonance, 1.04 Hz estimated from H/V by near to BH-7, is 2.5 times greater than the impedance contrast/ratio derived from 1-D model for same location. Relationship between resonance frequency and depth was obtained by applying quarter wavelength and Bard (2000) methodologies, which shows linearity, whereas H/V shows its nonlinearity characteristic in soil across the valley part of Haora River. Shear wave velocities, and subsequently, SPT index and factor of safety (by cyclic stress approach) were estimated from geotechnical parameters. Vs30 and site response data were used in this study for getting a first hand information about soil stiffness condition in the area. The estimation of SPT index and factor of safety could be a useful tool for delineating liquefied and none liquefied zones at various depth levels, especially where water table exists at a very shallow level. The expected liquefiable zone was observed at depths varying from 6–25 m beneath the soil bearing zones where percentage of fines is estimated to be more than 35% for the area. This knowledge about subsurface soil characteristics will be useful for the civil engineers/city planners, which can be taken into account at the time of constructing earthquake-resistant structures in the area.  相似文献   

Emissions of greenhouse and non-greenhouse air pollutants from fuel combustion in restaurant industry     

D. Majumdar  A. Chintada  J. Sahu  C. V. Chalapati Rao 《International Journal of Environmental Science and Technology》2013,10(5):995-1006

Information on emissions from restaurant industry is limited in scientific literature. Emission inventory of greenhouse and non-greenhouse air pollutants from restaurant industry was prepared for two Class 1 Indian cities, viz. Nagpur and Raipur for 2010. Emissions were estimated from a primary database on type and amount of cooking fuel combusted in restaurant industry in the selected cities. Liquefied petroleum gas, charcoal, wood, coal, diesel and candy coal are used in this industry, first three being the major ones. Carbon dioxide emission was highest in both cities and liquefied petroleum gas, charcoal and wood were the major contributors to emissions. Total annual emissions of greenhouse gases, viz. carbon dioxide, methane and nitrous oxide were estimated to be 19,251, 27 and 1 Mg year^?1 in Nagpur and 21,207, 34 and 1 Mg year^?1 in Raipur, whereas total annual emissions of non-methane hydrocarbon (NMHC), carbon monoxide, total suspended particulate (TSP), sulphur dioxide, nitrogen oxides and black carbon (BC) were 96, 959, 31, 12, 19, 3 Mg year^?1 and 87, 1141, 78, 37, 28, 6 Mg year^?1 in Nagpur and Raipur, respectively, from all the fuels used in restaurant industry. Considering the huge growth of Indian restaurant industry in the last decade and the predicted growth in future, emissions from this industry is assumed to grow and will play a major role in governing regional and national emissions in India.  相似文献   

Effects of patch size,disturbances on diversity and structural traits of tropical semi-evergreen forest in the lowland Indo Burma hotspot: implication on conservation of the threatened tree species     

Koushik Majumdar  Badal Kumar Datta 《山地科学学报》2016,13(8):1397-1410

Information on geographic distribution, population and threat status of most globally red listed species in the Indo Burma zone are inadequate. Given the increase in the prevalence of isolated forest patches in the part of this hotspot, evaluation is necessary on how size of the remnant forest patches and on-going disturbances affects structure and diversity of remaining habitats including the population of some globally threatened tree species. Quantitative vegetation inventory by 500 m long and 10 m wide (0.5 ha) line transects were randomly set in nine fragmented tropical semi-evergreen forest patches in Tripura, Northeast India. The studied forests patches grouped into small, medium and large based on their respected sizes. Spatial variability was analysed in woody species diversity and structure along the patch size gradients and their response to both patch size and anthropogenic disturbances. Out of 167 species, 13 identified as red-listed species by IUCN under the present inventory. Most of the diversity and structural parameters showed statistically significant positive response with the forest patch size, except for stand dominance, disturbance, sapling density and number of aggregated distribution pattern decreased when patch size increased. In addition, most of the diversity and structural attributes showed negative response with disturbances. Present baseline data would serve as an effective tool for management and protection of this important forest type. Future habitat restoration programme and strategies for relocation of additional population and re-introduction of those globally threatened trees are recommended.  相似文献   

Geoid height versus topography of the Northern Ninetyeast Ridge: implications on crustal compensation     

S. Rajesh  T. J. Majumdar 《Marine Geophysical Researches》2009,30(4):251-264

In this paper we focused on understanding the isostatic compensation of the Ninetyeast Ridge in the overall context of the Bay of Bengal oceanic lithosphere and the interaction of the ridge system with the north Andaman subduction zone from north of 7–18°N. This region is characterized by the initial interaction of the Kerguelen hotspot with the Bay of Bengal oceanic lithosphere. We used satellite altimeter-derived marine geoid, as it should comprehensively reflect the compensations caused by large spatial wavelength dominated deeper anomaly sources in a hotspot affected lithospheric load like the Ninetyeast Ridge. Our analyses of the geoid-to-topography ratio (GTR), residual geoid, gravity-to-topographic kernel and upward continuation of anomalies show the existence of two different types of source compensation bodies beneath the northern (12–18°N) and southern (7–12°N) Ninetyeast Ridge. In the northern region, the geoid to topography ratio varies from 0.63 ± 0.05 to 0.44 ± 0.03, while in the southern region it ranges from 1.34 ± 0.09 to 1.31 ± 0.07 which resulted in a north to south increase in the apparent compensation depth from ~9 to 28 km. The presence of a shallow Moho, low GTR, broader gravity to topography kernel and the absence of a ridge anomaly from the mantle density dominated upward continued anomaly at z = 300 km indicates that at the northern segment the underplated low density crustal melt is the dominant isostatic compensating body. However, at the southern ridge segment the high GTR, strong gravity-to-topography kernel and the subsistence of the anomaly at long wavelengths, even at z = 300 km represents the existence of large volumes of hotspot related underplated dense material as the source of compensation. The proximity of the dense source compensating body of the southern Ninetyeast Ridge to the Andaman subduction zone affected the regional mantle driven density gradient flow, as observed from the z = 300 km continued gravity anomaly. The existence of a southern Ninetyeast Ridge in such a transpressional regime has caused the formation of a forearc sliver at its eastern flank, which is a major crustal deformational structure developed as a result of ridge-trench collision.  相似文献   

Cost analysis to determine optimum geometry of a retreating longwall face     

Santanu Majumdar  Subhas C. Ray 《Geotechnical and Geological Engineering》1983,1(3):261-266

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Residual geoid and free-air gravity over the indian offshore from ers-1 high resolution altimeter data     

R. Bhattacharyya  T. J. Majumdar 《Journal of the Indian Society of Remote Sensing》2006,34(3):289-298

In this study, ERS-1 altimeter data over the Indian offshore have been processed for deriving marine geoid and gravity. Processing of altimeter data involves corrections for various atmospheric and oceanographic effects, stacking and averaging of repeat passes, cross-over correction, removal of deeper earth and bathymetric effects, spectral analyses and conversion of geoid into free-air gravity anomaly. Methods for generation of residual geoid and free-air gravity anomaly using high resolution ERS-1 168 day repeat altimeter data were developed. High resolution detailed geoid maps, gravity anomaly and their spectral components have been generated over the Indian offshore using ERS-I altimeter data and ARCGIS system. A number of known megastructures over the study area have been successfully interpreted e.g. Bombay High, Saurastra platform, 90° east ridge etc. from these maps.  相似文献   

Sunyaev–Zel'dovich distortion from early galactic winds     

Subhabrata Majumdar  Biman B. Nath  Masashi Chiba 《Monthly notices of the Royal Astronomical Society》2001,324(3):537-546

We consider the distortion in the cosmic microwave background (CMB) resulting from galactic winds at high redshift. Winds outflowing from galaxies have been hypothesized to be possible sources of metals in the intergalactic medium, which is known to have been enriched to 10^−2.5 Z_⊙ at z ∼3. We model these winds as functions of mass of the parent galaxy and redshift, assuming that they activate at a common initial redshift, z _in, and calculate the mean y -distortion and the angular power spectrum of the distortion in the CMB. We find that the thermal Sunyaev–Zel'dovich (SZ) effect resulting from the winds is consistent with previous estimates. The distortion arising from the kinetic SZ (kSZ) effect is, however, found to be more important than the thermal SZ (tSZ) effect. We find that the distortion resulting from galactic winds is an important contribution to the power spectrum of distortion at very small angular scales ( l ∼10⁴). We also find that the power spectrum resulting from clustering dominates the Poisson power spectrum for l ≤(4–5)×10⁵. We show explicitly how the combined power spectrum from wind dominates over that of clusters at 217 GHz, relevant for PLANCK . We also show how these constraints change when the efficiency of the winds is varied.  相似文献   

Gamma Ray and Hadron generated Čerenkov Photon Spectra at Various Observation Altitudes     

M. A. Rahman  P. N. Bhat  B. S. Acharya  V. R. Chitnis  P. Majumdar  P. R. Vishwanath 《Experimental Astronomy》2001,11(2):113-131

We study the propagation of erenkov photons generated by Very HighEnergy -rays and hadrons in the atmosphere. The photon productionheight distributions are estimated from semi-empirical methods andcompared with those derived by standard simulation techniques. Incidentspectra at various observation altitudes are then derived after applyingwavelength dependent corrections due to photon attenuation in theatmosphere during the propagation of photons from the height of productionto the height of observation. These are generated both for -ray and hadron primaries of various energies. The derivedproduction height distributions agree very well with those generated bythe simulation package `CORSIKA' at all energies and for both -ray and proton primaries. The incident photon spectra are found to beboth altitude and primary energy dependent. The peak ofthe incident spectrum shifts towards the shorter wavelength withincreasing altitude of observation for a given primary. Also the peak ofthe photon spectrum shifts towards the shorter wavelength withincreasing energy of the primary at a given altitude. The fraction of the UVcomponent in the incident erenkov spectrum is estimated both for-ray and hadronic primaries at various observation altitudes andenergies. Hadron generated erenkov spectra are marginally richer in UVlight and the difference increases slightly at higher altitudes. The fraction of the UV to the visible light in the erenkov spectrum could be a usefulparameter to separate -rays from cosmic ray background only if onecan measure this fraction very accurately.  相似文献   

The hybrid SZ power spectrum: combining cluster counts and SZ fluctuations to probe gas physics     

J. M. Diego  Subhabrata Majumdar 《Monthly notices of the Royal Astronomical Society》2004,352(3):993-1004

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Low cost quantitative arsenic determination kit: A method by using silver nitrate     

S. Kar  R. K. Majumdar  M. K. Chaudhuri 《Journal of the Geological Society of India》2014,84(1):35-40

Arsenic sometimes found in ground water which has adverse effect on human health at levels as low as 10μg/L. Arsenic is known to be one of the most toxic element that cannot be destroyed once it has entered to the environment. It is a dangerous poison at high doses but can cure diseases such as syphilis and leukaemia at low doses. The present study comprises a low cost technique for determination of arsenic concentration in groundwater up to 1000μg/L. The method is based on the reaction of arsenic (V) with potassium iodide and stannous chloride in concentrated hydrochloric acid medium to convert to arsenic (III) and needs 15 to 20 minutes time for complete conversion. After reaction with the granulated zinc (arsenic free), the evolved arsine gas is passed through wet cotton wool of lead acetate for absorbing any sulphide impurities and is finally absorbed by wet filter paper of silver nitrate which gives brown colour. The intensity of the colour varies with respect to the arsenic concentration present in ground water. A master colour chart is prepared by the known arsenic standard solution from 0 to 1000 μg/L for measuring the concentration range of arsenic in contaminated ground water. The quantitative arsenic determination is done with the help of colorimetric study. The absorbed colour of filter paper is thoroughly scanned and Red, Green and Blue (R-G-B) values are obtained by colour picking technique with the help of the software ‘Microsoft Paint’ under the operating system ‘Microsoft Windows 7’. The known arsenic concentrations are plotted against the R-G-B values of the corresponding absorbed colour and three master curves are drawn by the software ‘Mat lab’ for measuring the exact concentration of arsenic in groundwater. For validation, arsenic contamination test is conducted for the ground water samples collected from different areas of 24 Parganas district using our very low cost kit and other costly instruments like Digital Arsenator and Atomic Absorption Spectrometer.  相似文献