Feature extraction and connectionist classification of SODAR echograms     

Choudhury  S. Mitra  S. 《Geoscience and Remote Sensing Letters, IEEE》2006,3(1):19-22

Sonic detection and ranging (SODAR) systems are efficient and economical tool to probe the lower planetary boundary layer on a continuous basis. The lower atmospheric patterns (each depicting a different atmospheric condition) recorded by this system can prove to be extremely useful if classified and interpreted correctly. The manual identification of these SODAR patterns is a laborious task and requires considerable expertise. A connectionist system has already been developed by the authors to automate the process to some extent. In this letter, we enhance its generalization of performance, by incorporating feature extraction using the fast Fourier transform. The results are compared with that in earlier work to demonstrate its effectiveness.  相似文献   

Characterization of agroecosystem based on land utilization indices using remote sensing and GIS     

Indrani Choudhury  M. Chakraborty  S. C. Santra  J. S. Parihar 《Journal of the Indian Society of Remote Sensing》2006,34(1):23-37

Information on various agricultural resource parameters at various levels is essential for proper management and efficient resource allocation for sustainable agricultural development. Limitations in ground-based method have encouraged the use of satellite data coupled with geographical information system (GIS) in providing spatial as well as temporal information over large and inaccessible areas. In the present study, an attempt has been made to generate raster maps using remote sensing and GIS techniques to characterize the agroecosystem of South 24 Paraganas district of West Bengal, based on land utilization indices. Information on multi-season landcover derived from the analysis of the multi-temporal RADARSAT-1 SAR and IRS-ID LISS III data as well as other ancillary information in GIS environment are the basic inputs used in the study. The present analysis shows that northern and northwestern parts are more diverse in terms of agricultural intensification as compared to the southern and northeastern parts whereas the central parts show moderate density. In terms of carrying capacity, the high carrying capacity has been observed in the southern to northeastern parts whereas the northwestern and central parts show moderate and northern parts show low carrying capacity. Overall, the characterization of agroecosystem using land utilization indices can be identified as major input to formulate a management plan for sustainable agriculture with concerns for the environment.  相似文献   

Coda power and modulation characteristics of a complex P signal from underground nuclear explosions     

Shiv Mohan G. Subhash  Mansur A. Choudhury 《Tectonophysics》1979,53(1-2)

Coda power characteristics of six underground nuclear explosions from two near by test sites of Novaya Zemlya are examined. It is shown that one of the events presenting a complex P waveform and distinctive coda power characteristics can be synthesised by superposition of two signals of simpler form from the same site. The relative P amplitudes of the two signals give a ratio of 0.7–1.0 and the relative delay of 0.8 sec. The modulation effect is clearly seen in band-pass filtered traces where a shift in the envelope maximum occurs for center frequencies between 0.6 and 0.8 Hz. The complex event is interpreted as a double explosion.  相似文献   

Equation of state and melting point studies of forsterite     

N. Choudhury  S. L. Chaplot  K. R. Rao 《Physics and Chemistry of Minerals》1989,16(6):599-605

We report in this paper results of lattice dynamical calculations of the thermodynamic properties, namely, the equation of state and the melting point of forsterite. The root mean square displacements of atoms and thermal parameters are also evaluated. It is observed from our results, that, a modified Lindemann criterion for melting may be proposed for an ionic ‘molecular’ solid like forsterite. Agreement among various theoretical and experimental results is satisfactory indicating that lattice dynamical studies based on microscopic quasiharmonic formulations help in understanding the macroscopic properties of forsterite, over a wide range of temperature and pressure.  相似文献   

SOILS: AGRICULTURAL AND ENGINEERING PROPERTIES     

Dulima Jali  Jahangir E. Elahi Choudhury 《Singapore journal of tropical geography》1993,13(1):1-13

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Computation of sliding displacements of seawalls under earthquake conditions     

Rajesh  B. Giridhar  Choudhury  Deepankar 《Natural Hazards》2019,96(1):97-119

To understand the serviceability aspects of seawalls, it is essential to study the permanent displacements of seawalls that occur during the earthquakes. Studies in the existing literature have concentrated on displacements of retaining walls with dry backfills; to the authors’ observation there is no specific analytical investigation devoted to the earthquake-induced displacements of retaining walls with submerged backfills. This paper focuses on sliding displacements of gravity type seawall retaining a submerged backfill under active earth pressure condition during the earthquakes. The threshold seismic acceleration coefficients required for initiation of sliding and the amount of sliding displacement due to seismic loading are calculated by adopting Newmark’s sliding block method. One of the prime features of the study is the estimation of seismic inertia forces in the submerged soil and wall applying the modified pseudo-dynamic method. The comparison of the results obtained using the proposed analytical formulation with the existing literature found to be in good agreement. A comprehensive parametric study has been conducted to understand the effects of different parameters such as seismic horizontal and vertical acceleration coefficients, soil and wall friction angles, width of the wall, wall inclination and excess pore water pressure ratio.

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Spatial variation of probabilistic seismic hazard for Mumbai and surrounding region   总被引：1，自引：1，他引：0  

Sarika S. Desai  Deepankar Choudhury 《Natural Hazards》2014,71(3):1873-1898

Mumbai city, the economical capital of India, is located on the west coast of stable intra-plate continental region of Peninsular India which has an experience of significant historical earthquakes in the past. The city stood as the fourth most populous city in the world. Recent seismo-tectonic studies of this city highlighted the presence of active West coast fault and Chiplun fault beneath the Deccan basalt. In the present study, spatial variability of probabilistic seismic hazard for Mumbai region (latitudes of 18.85–19.35°N and longitudes of 72.80–73.15°E at a grid spacing of 0.05°) which includes Mumbai city, Suburban, part of Thane district and Navi Mumbai, in terms of ground motion parameters; peak horizontal acceleration and spectral acceleration at 1.0-s period for 2 and 10 % probability of exceedance in 50 years are generated. The epistemic uncertainty in hazard estimation is accounted by employing seven different ground motion prediction equations developed for worldwide shallow crustal intra-plate environments. Further, the seismic hazard results are deaggregated for Mumbai (latitude 18.94°N, longitude 72.84°E) to understand the relative contributions of earthquake sources in terms of magnitude and distance. The generated hazard maps are compared with the zoning specified by Indian seismic code (IS1893: Part 1 in Indian standard criteria for earthquake-resistant design of structures, Part 1—General provisions and buildings. Bureau of Indian Standards, New Delhi, India, 2002) for rocky site. Present results show an underestimation of potential seismic hazard in the entire study region by non-probabilistic zoning prescribed by IS1893: Part 1 with significantly higher seismic hazard values in the southern part of Navi Mumbai.  相似文献   

Mineralogical and ash geochemical studies of coal-mine shale and its hydrocarbon potential: A case study of shale from Makum coalfield,Northeast India     

Rahul Choudhury  Jyotilima Saikia  Binoy K. Saikia 《Journal of the Geological Society of India》2017,90(3):329-334

The mineralogy and geochemical studies of the coal-mine shale collected from the Tirap opencast coal-mine (Makum coalfield, Northeast India) are reported in this paper. Thermo-chemical conversion (pyrolysis) of coal-mine shale has been studied to see its hydrocarbon potential. A combined approach using X-Ray diffraction (LTA-XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrophotometer (EDS), X-ray fluorescence spectrometry (XRF), thermogravimetry-derivative and differential thermogravimetric (TG-DTG and DTA) analysis is made to obtain new information on the mineralogical and geochemical studies of a coal-mine shale (CMS) sample. Gas chromatography-mass spectrometry (GC-MS) analysis is performed to evaluate the quality of the liquid fraction (tar) obtained after pyrolysis at 600°C. The shale sample is dominated by quartz, clay minerals (kaolinite and illite), sulphate bearing phase like gypsum with minor proportion of anatase, probably as artifacts of the plasma-ashing process. GC-MS analysis illustrates the presence of highly oxygenated organic components (M.W. around 94-108) and high molecular weight (M.W. 256) cyclic sulphur (e.g. octathiocane with molecular formula S₈) compounds along with the complex N-containing organic sulphur compounds (M.W. around 255-486) in the tar produced.  相似文献   

The sensitivity to the microphysical schemes on the skill of forecasting the track and intensity of tropical cyclones using WRF-ARW model     

Devanil Choudhury  Someshwar Das 《Journal of Earth System Science》2017,126(4):57

The Advanced Research WRF (ARW) model is used to simulate Very Severe Cyclonic Storms (VSCS) Hudhud (7–13 October, 2014), Phailin (8–14 October, 2013) and Lehar (24–29 November, 2013) to investigate the sensitivity to microphysical schemes on the skill of forecasting track and intensity of the tropical cyclones for high-resolution (9 and 3 km) 120-hr model integration. For cloud resolving grid scale (<5 km) cloud microphysics plays an important role. The performance of the Goddard, Thompson, LIN and NSSL schemes are evaluated and compared with observations and a CONTROL forecast. This study is aimed to investigate the sensitivity to microphysics on the track and intensity with explicitly resolved convection scheme. It shows that the Goddard one-moment bulk liquid-ice microphysical scheme provided the highest skill on the track whereas for intensity both Thompson and Goddard microphysical schemes perform better. The Thompson scheme indicates the highest skill in intensity at 48, 96 and 120 hr, whereas at 24 and 72 hr, the Goddard scheme provides the highest skill in intensity. It is known that higher resolution domain produces better intensity and structure of the cyclones and it is desirable to resolve the convection with sufficiently high resolution and with the use of explicit cloud physics. This study suggests that the Goddard cumulus ensemble microphysical scheme is suitable for high resolution ARW simulation for TC’s track and intensity over the BoB. Although the present study is based on only three cyclones, it could be useful for planning real-time predictions using ARW modelling system.  相似文献   

Arsenic distribution along different hydrogeomorphic zones in parts of the Brahmaputra River Valley,Assam (India)     

Runti Choudhury  Chandan Mahanta  Swati Verma  Abhijit Mukherjee 《Hydrogeology Journal》2017,25(4):1153-1163

The spatial distribution of arsenic (As) concentrations along three classified hydrogeomorphological zones in the Brahmaputra River Valley in Assam (India) have been investigated: zone I, comprising the piedmont and alluvial fans; zone II, comprising the runoff areas; and zone III, comprising the discharge zones. Groundwater (150 samples) from shallow hand-pumped and public water supply wells (2–60 m in depth) was analysed for chemical composition to examine the geochemical processes controlling As mobilization. As concentrations up to 0.134 mg/L were recorded, with concentrations below the World Health Organization and the Bureau of Indian Standards drinking-water limits of 0.01 mg/L being found mainly in the proximal recharge areas. Eh and other redox indicators (i.e., dissolved oxygen, Fe, Mn and As) indicate that, except for samples taken in the recharge zone, groundwater is reducing and exhibits a systematic decrease in redox conditions along the runoff and discharge zones. Hydrogeochemical evaluation indicated that zone I, located along the proximal recharge areas, is characterized by low As concentration, while zones II and III are areas with high and moderate concentrations, respectively. Systematic changes in As concentrations along the three zones support the view that areas of active recharge with high hydraulic gradient are potential areas hosting low-As aquifers.  相似文献