排序方式： 共有13条查询结果，搜索用时 62 毫秒
1.
Rabi Bastia M. Radhakrishna Suman Das Anand S. Kale Octavian Catuneanu 《Marine and Petroleum Geology》2010
The passive Eastern Continental Margin of India (ECMI) evolved during the break up of India and East Antarctica in the Early Cretaceous. The 85°E ridge is a prominent linear aseismic feature extending from the Afanasy Nikitin Seamounts northward to the Mahanadi basin along the ECMI. Earlier workers have interpreted the ridge to be a prominent hot spot trail. In the absence of conclusive data, the extension of the ridge towards its northern extremity below the thick Bengal Fan sediments was a matter of postulation. In the present study, interpretation of high resolution 2-D reflection data from the Mahanadi Offshore Basin, located in the northern part of the ridge, unequivocally indicates continuation of the ridge across the continent–ocean boundary into the slope and shelf tracts of the ECMI. Its morphology and internal architecture suggest a volcanic plume related origin that can be correlated with the activity of the Kerguelen hot spot in the nascent Indian Ocean. In the continental region, the plume related volcanic activity appears to have obliterated all seismic features typical of continental crust. The deeper oceanic crust, over which the hot spot plume erupted, shows the presence of linear NS aligned basement highs, corresponding with the ridge, underlain by a depressed Moho discontinuity. In the deep oceanic basin, the ridge influences the sediment dispersal pattern from the Early Cretaceous (?)/early part of Late Cretaceous times till the end of Oligocene, which is an important aspect for understanding the hydrocarbon potential of the basin. 相似文献
2.
Hydro‐climatic impacts in water resources systems are typically assessed by forcing a hydrologic model with outputs from general circulation models (GCMs) or regional climate models. The challenges of this approach include maintaining a consistent energy budget between climate and hydrologic models and also properly calibrating and verifying the hydrologic models. Subjective choices of loss, flow routing, snowmelt and evapotranspiration computation methods also increase watershed modelling uncertainty and thus complicate impact assessment. An alternative approach, particularly appealing for ungauged basins or locations where record lengths are short, is to predict selected streamflow quantiles directly from meteorological variable output from climate models using regional regression models that also include physical basin characteristics. In this study, regional regression models are developed for the western Great Lakes states using ordinary least squares and weighted least squares techniques applied to selected Great Lakes watersheds. Model inputs include readily available downscaled GCM outputs from the Coupled Model Intercomparison Project Phase 3. The model results provide insights to potential model weaknesses, including comparatively low runoff predictions from continuous simulation models that estimate potential evapotranspiration using temperature proxy information and comparatively high runoff projections from regression models that do not include temperature as an explanatory variable. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
3.
H. M. Abdel Magid R. E. A. Sabrah R. K. Rabi A. R. H. El Nadi S. I. Abdel Aal 《Journal of Arid Environments》1993,25(4)
Addition and incorporation of organic fertilizers is known to improve the properties of agricultural soils. Therefore, during 22 weeks of field incubation we studied the biodegradation (measured by static absorption of CO2) of two organic manures viz. municipal refuse and chicken manure incorporated into sandy soils, under sprinker irrigation, at the rates of 0, 16·5, 33·0, 49·5 and 66·0, and 0, 4·1, 8·25, 16·5, and 33·0 tonnes/ha, respectively.The results obtained indicated that the cumulative amount of CO2 respired was linearly correlated with the rate of organic material applied (p < 0.001). Statistical analysis of the data obtained showed that both the intercept (rate of decomposition) and the slope (rate of reaction with time) increased with increasing rate of application of organic manure. The magnitude of increment was highest at the application rates of 33·0 and 8·25 tonnes/ha for municipal refuse and chicken manure, respectively. The rate of increment, generally, declined thereafter thus indicating that these two rates are the optimum levels of incorporation of the appropriate organic manures under the conditions of this study.The maximum organic-carbon mineralized, accounting for 10·5 and approximately 50%, was obtained at the optimum rates for municipal refuse and chicken manure, respectively. Both simple and multiple regression equations describing the relationship between soil temperature and soil-moisture content each separately and in combination, as independent variables, and the cumulative rate of CO2 production were computed. A substantially strong relationship with soil temperature but inconsistent and contradicting results with soil moisture were obtained. Inclusion of soil temperature and moisture in a single model as an independent variable in relation to cumulative CO2 as a dependent variable improved the soil moisture-CO2 production relationship. 相似文献
4.
Saroja Kumar Barik Satyanarayan Bramha Tapan Kumar Bastia Dibakar Behera Pratap Kumar Mohanty Prasanta Rath 《国际泥沙研究》2019,34(3):251-261
The current study focuses on the vertical profile of different geochemical fractions of phosphorus - loosely bound (Lo–P), aluminium bound (Al–P), iron bound (Fe–P), calcium bound (Ca–P), and organic bound phosphorus (O–P) along with ecological risk assessment of sediment cores from Chilika Lake, east-coast of India. The percentage contribution of the different fractions to the sedimentary phosphorus in the sediment column of the whole lake are on the order: O–P (33.2%) > Ca–P (20.3%) > Fe–P (18%) > Al–P (6.7%) > Lo–P (0.35%). The Phosphorus Pollution Index (PPI) revealed the contamination of lake sediment with phosphorus. The principal component and cluster analyses highlighted the anthropogenic contribution of phosphorus. The negative loading of Ca–P with Ca points towards its origin from marine shells. The discriminate analysis showed that the variables like Ca–P, bio-available phosphorus (BAP), and pH were able to effectively discriminate the sectors in a significant manner. 相似文献
5.
Rahul Tripathi Rabi N. Sahoo Vinay K. Sehgal R. K. Tomar Debashish Chakraborty S. Nagarajan 《Journal of the Indian Society of Remote Sensing》2012,40(1):19-28
The current development of satellite technology particularly in the sensors like POLDER and MISR, has emphasized more on directional
reflectance measurements (i.e. spectral reflectance of the target measured from different view zenith and azimuth angles)
of the earth surface features mainly the vegetation for retrieval of biophysical parameters at regional scale using radiative
transfer models. This approach being physical process based and uses directional reflectance measurement has been found to
better and more reliable compared to the conventional statistical approach used till date and takes care of anisotropic nature
(i.e. reflectance from the target is different if measured from different view angles) of the target. Keeping this in view
a field experiment was conducted in mustard crop to evaluate the radiative transfer model for biophysical parameter retrieval
through its inversion with the objectives set as (i) to relate canopy biophysical parameters and geometry to its bidirectional
reflectance, (ii) to evaluate a canopy reflectance model to best represent the radiative transfer within the canopy for its
inversion and (iii) to retrieve crop biophysical parameters through inversion of the model. Two varieties of the mustard crop
(Brassica juncea L) were grown with two nitrogen treatments. The bidirectional reflectance data obtained at 5 nm interval
for a range of 400–1100 nm were integrated to IRS LISS–II sensor’s four band values using Newton Cotes Integration technique.
Biophysical parameters like leaf area index, leaf chlorophyll content, leaf length, plant height and average leaf inclination
angle, biomass etc were estimated synchronizing with the bi-directional reflectance measurements. Radiative transfer model PROSAIL model was
validated and its inversion was done to retrieve LAI and ALA. Look Up Table (LUT) of Bidirectional reflectance distribution
function (BRDF) was prepared simulating through PROSAIL model varying only LAI (0.2 interval from 1.2 to 5.4 ) and ALA (5°
interval from 40° to 55°) parameters and inversion was done using a merit function and numerical optimization technique given
by Press et al. (1986). The derived LAI and ALA values from inversion were well matched with observed one with RMSE 0.521
and 5.57, respectively. 相似文献
6.
AbstractMeasurements made in the past few decades undeniably indicate change in the climate. The most visible sign of global climate change is air temperature, while less visible indicators include changes in river water temperatures. Changes in river temperature can significantly affect the environment, primarily the biosphere. The physical, biological and chemical characteristics of the river are directly affected by water temperature, although estimation of this relationship presents a complex problem. Although river temperature is influenced by hydrological and meteorological factors, the purpose of this study is to model daily water temperature using only one known parameter, mean air temperature. The relationship between the daily mean air and daily water temperature of the River Drava in Croatia is analysed using linear regression, stochastic modelling or nonlinear regression and multilayer perceptron (MLP) feed-forward neural networks. The results indicate that the MLP models are much better models which can be used for the estimation and prediction of daily mean river temperature.
Editor D. Koutsoyiannis; Associate editor M. Acreman 相似文献
7.
Abhijit Bhattacharyya Sukumar Biswas Barun K. Chatterjee Mala Das Pradipta K. Das Tapan K. Das Tarun K. De M.H. Engineer Rabi N. Mukherjee Sibaji Raha S.C. Roy Swapan K. Saha A.K. Sen Bikash Sinha Debapriyo Syam 《Astrophysics and Space Science》1997,250(2):313-326
A Total Solar Eclipse (TSE) was observed from Diamond Harbour (lat. 22.2°N, long 88.2°E) on 24 October 1995. The variation of -ray intensity was measured in the energy range of 0.3–3.0 MeV for different time spans throughout the period of the eclipse. A CR-39 detector was used to look at the change in the fluxes of neutral and charged particles. The maximum drop ( 25%) in the intensity of -ray was observed in the range 2.5–3 MeV during TSE. The CR-39 results showed the appearance of a good number of tracks and a small variation of proton and neutron flux of 10% which was not significant statistically. Low energy -ray fluxes at sea level originate from the secondary electron-photon components of cosmic rays in the atmosphere; its modulation by TSE is interpreted as follows. The cooling of the atmosphere in the path of the umbra induces a reduction of the height of the main production layer of the nuclear component, as a result of which, fewer µ± mesons (from the decay of the± mesons) decay to e±. This leads to a small reduction in the flux of electron-photon component at sea level which originates from this branch; the main branch of e - component from 0 decay remains nearly unaffected. As the total mass of air remains the same, little or no change in the slow proton or the neutron flux at sea level is expected. These are consistent with the present observations. For a better understanding, further studies of this new phenomenon during future TSE are suggested. 相似文献
8.
The Bengal fan is the largest submarine fan in the world that has formed as a result of high sediment transport from the Himalaya by the Ganga–Brahmaputra river system. The Himalaya was formed as a result of the collision between the Eurasian and Indian plates. The initiation of this collision known as “soft” collision occurred around 59 Ma, whereas, the major collision, known as “hard” collision took place around 15 Ma ago. Prior to the collision, sediments into the Bay of Bengal were derived from the northwest by relatively smaller river system like Mahanadi–Godavari. The switching of river systems with time was not distinct but gradational. In the post- collision period, the sediment input from the NW was masked in most instances because of rapid sediment supply from the Himalaya to the north. Pre-collisional sediment dispersal pattern from the NW was largely affected by pre-existing basement high known as 85°E Ridge; this ridge was submerged during the post-collisional period. Post-collisional sediments are commonly referred to as the Bengal fan sediments and show huge accumulation along the shelf and beyond. High resolution 2D seismic data acquired along a corridor covering the upper, middle and distal parts of the present day active Bengal fan system indicates that the fan has prograded southward with time because of continuously increasing sediment supply and has, therefore, masked the effect of eustacy. The present day geometry of the fan shows a single active canyon and an associated single active fan. The active channel shows typical meandering pattern that shifts laterally with time. The seismic facies analysis indicates that both the pre- and post-collision basin has significant hydrocarbon potential. The thermogenic model is best suited for modeling source rock maturity in the pre-collision basin whereas both biogenic and thermogenic models best explain source rock maturity in the post-collision, younger Bengal fan. The wedge out against the 85°E Ridge is considered to be one of the important play types for hydrocarbon exploration in the deeper part of the basin. On the other hand, the channel levee complexes and frontal splay/basin floor fan are the possible target areas for petroleum exploration in relatively younger Bengal fan deposits. 相似文献
9.
Rabi Narayan Behera Chittaranjan Patra 《Geotechnical and Geological Engineering》2018,36(5):3029-3080
Extensive laboratory model tests have been carried out on a strip footing resting over dry sand bed subjected to eccentrically inclined load to determine the ultimate bearing capacity (Patra et al. in Int J Geotech Eng 6(3):343–352, 2012a. https://doi.org/10.3328/IJGE.2012.06.03.343-352, Int J Geotech Eng 6(4):507–514, b. https://doi.org/10.3328/IJGE.2012.06.04.507-514). Similarly, lower bound calculations based on finite element method were performed to compute the bearing capacity of a strip footing subjected to an eccentric and inclined load lying over a cohesionless soil with varying embedment depth and relative density (Krabbenhoft et al. in Int J Geomech ASCE, 2014. https://doi.org/10.1061/(ASCE)GM.1943-5622.0000332). The load may be applied in two ways namely, towards the center line and away from the center line of the footing. Based on the results (both experimental and numerical analyses), a neural network model is developed to predict the reduction factor that will be used in computing the ultimate bearing capacity of an eccentrically inclined loaded strip footing. This reduction factor (RF) is the ratio of the ultimate bearing capacity of the footing subjected to an eccentrically inclined load to the ultimate bearing capacity of the footing subjected to a centric vertical load. A thorough sensitivity analysis is carried out to evaluate the parameters affecting the reduction factor. Based on the weights of the developed neural network model, a neural interpretation diagram is developed to find out whether the input parameters have direct or inverse effect on the output. A prediction model equation is framed with the trained weights of the neural network as the model parameters. The predictions from ANN, and those from other approaches, are compared with the results computed from both experimentation and FEM analyses. The ANN model results are found to be more accurate and well matched with other results. 相似文献
10.
The eastern offshore of India covers a vast stretch of sedimentary tract fed by major rivers like Ganges, Brahmaputra and
Mahanadi in the north, Krishna and Godavari in the center, and Cauvery and Palar in the south, which led to variations in
shelf-slope characteristics, degree of slope and hence slope instability. The structure as well as seismic attribute maps
prepared from multibeam bathymetry and high-resolution 3D seismic data set has been analyzed to identify various geohazards
in the deep water offshore regions of the east coast of India. These can be categorized as slope instability, slope canyons,
shallow gas, mass transport complexes, sediment waves, gas hydrates, gas chimney, mud volcanoes and shallow faults. The slope
instability is primarily related to rapid sedimentation by the active river systems while the other geohazards are often developed
in association with shallow gas flows and leakages. The bottom simulating reflectors (BSRs) identified in the seismic sections
indicate the presence of gas hydrates. Rapid sedimentation, BSR formation, dissolution and expulsion of water as well as gas
and their subsequent vertical migration are responsible for the formation of shallow gas-related hazards. The results from
the above analysis are of immense help in minimizing the risk of shallow hazards during exploration, drilling and subsurface
installation activities along the eastern Indian offshore. 相似文献