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961.
In the present paper we have found the range of values of μ ande for the linear stability of the triangular points for the doubly photogravitational elliptic restricted problem of three
bodies. It has been shown that some resonances of the third and the fourth order exist which will need special investigation
for the determination of complete stability of the libration points under our terms of reference. 相似文献
962.
It is well recognized that the time series of hydrologic variables, such as rainfall and streamflow are significantly influenced by various large‐scale atmospheric circulation patterns. The influence of El Niño‐southern oscillation (ENSO) on hydrologic variables, through hydroclimatic teleconnection, is recognized throughout the world. Indian summer monsoon rainfall (ISMR) has been proved to be significantly influenced by ENSO. Recently, it was established that the relationship between ISMR and ENSO is modulated by the influence of atmospheric circulation patterns over the Indian Ocean region. The influences of Indian Ocean dipole (IOD) mode and equatorial Indian Ocean oscillation (EQUINOO) on ISMR have been established in recent research. Thus, for the Indian subcontinent, hydrologic time series are significantly influenced by ENSO along with EQUINOO. Though the influence of these large‐scale atmospheric circulations on large‐scale rainfall patterns was investigated, their influence on basin‐scale stream‐flow is yet to be investigated. In this paper, information of ENSO from the tropical Pacific Ocean and EQUINOO from the tropical Indian Ocean is used in terms of their corresponding indices for stream‐flow forecasting of the Mahanadi River in the state of Orissa, India. To model the complex non‐linear relationship between basin‐scale stream‐flow and such large‐scale atmospheric circulation information, artificial neural network (ANN) methodology has been opted for the present study. Efficient optimization of ANN architecture is obtained by using an evolutionary optimizer based on a genetic algorithm. This study proves that use of such large‐scale atmospheric circulation information potentially improves the performance of monthly basin‐scale stream‐flow prediction which, in turn, helps in better management of water resources. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
963.
Cosmic-ray intensity data recorded with the ground-based neutron monitor at Deep River have been investigated taking into
account the associated interplanetary magnetic field and solar-wind plasma data during 1981 – 1994. A large number of days
having abnormally high or low amplitudes for five or more successive days as compared to the annual average amplitude of diurnal
anisotropy have been taken as high- or low-amplitude anisotropic wave-train events. The amplitude of the diurnal anisotropy
of these events is found to increase on days with a magnetic cloud as compared to the days prior to the event, and it is found
to decrease during the later period of the event as the cloud passes the Earth. The high-speed solar-wind streams do not play
any significant role in causing these types of events. However, corotating solar-wind streams produce significant deviations
in cosmic-ray intensity during high- and low-amplitude events. The interplanetary disturbances (magnetic clouds) are also
effective in producing cosmic-ray decreases. Hα solar flares have a good positive correlation with both the amplitude and
direction of the anisotropy for high-amplitude events, while the principal magnetic storms have a good positive correlation
with both amplitude and direction of the anisotropy for low-amplitude events. The source responsible for these unusual anisotropic
wave trains in cosmic rays has been proposed. 相似文献
964.
An analytical study is performed to examine the free-convection and mass transfer flow for the Sokes problem for an infinite vertical plate on taking into account the Soret effect (thermal diffusion effect). The Laplace transform technique is used to obtain the expressions for velocity and skin-friction. The effect of Soret numberS on velocity field and skin-friction is extensively discussed with the help of graphs and table. 相似文献
965.
B. Mishra C.S. Saravanan A. Bhattacharya S. Goon S. Mahato H.J. Bernhardt 《Gondwana Research》2007,11(4):504-515
A combined fluid inclusion and mineral thermobarometric study in groups of synchronous inclusions in quartz within weakly foliated granites from the Chottanagpur Gneissic Complex, India, reveals super dense carbonic (CO2 with minor CH4 and H2O) inclusions and hypersaline (H2O–NaCl ± NaHCO3) inclusions, with halite- and nahcolite daughter phases. This study documents the highest density (1.115 g cm− 3) CO2 fluids ever reported in granites. Fluid isochores, constructed from CO2 (± CH4) and halite-bearing inclusions, coupled with two-feldspar thermometry constrain the minimum P–T at 8 kbar/ 750 °C for fluid entrapment in granites. By contrast, the carbonic inclusions in quartz from granite-hosted metapelite enclaves contain substantial CH4 (up to 30 mol%), and the entrapment pressure ( 4.3 kbar/600 °C) is considerably lower compared to those in the granites. By implication, the sillimanite-free granites were not derived from the metapelitic enclaves, and instead were formed by partial melting of fluid-heterogeneous lower crustal protoliths, with fluid entrapment at magmatic conditions. 相似文献
966.
The ultimate bearing capacity of strip footings resting on subsoil consisting of a strong sand layer (reinforced/unreinforced)
overlying a low bearing capacity sand deposit has been investigated. Three principal problems were analysed based on results
obtained from the model tests as follows: (1) the effect of stratified subsoil on the foundations bearing capacity; (2) the
effect of reinforcing the top layer with horizontal layers of geogrid reinforcement on the bearing capacity; (3) effect of
reinforcing stratified subsoil (reinforced and unreinforced) on the settlement of the foundation. It has been observed that
reinforcing the subsoil after replacing the top layer of soil with a well-graded soil is beneficial as the mobilization of
soil-reinforcement frictional resistance will increase. 相似文献
967.
S. V. N. Rao Sudhir Kumar Shashank Shekhar S. K. Sinha S. Manju 《Hydrogeology Journal》2007,15(6):1157-1167
This report examines the problem involving the pumping of groundwater from a group of 90 existing wells along the banks of the Yamuna River, northwest of Delhi (India), underlain with geologically occurring saline water. It is known that unregulated pumping will lead to upconing of saline water and therefore it is necessary to determine optimal rates and associated well locations (from an existing group of candidate wells that supply drinking water to the city of Delhi) that will minimize the total salinity. The nonlinear, non-convex problem is solved by embedding the calibrated groundwater model within a simulation-optimisation (S/O) framework. Optimisation is accomplished by using simulated annealing (SA), a search algorithm. The computational burden is primarily managed by replacing the numerical model with a surrogate simulator-artificial neural network (ANN). The model is applied to the real system to determine the optimal pumping schedule. The results of the operational model suggest that the skimming wells must be operated from optimal locations such that they are staggered in space and time to obtain the least saline water. 相似文献
968.
A detailed water quality analysis was carried out in the quaternary aquifer system of the marginal alluvial plain (Ganga Plain)
in Bah Tahsil, Agra district, India. The electrical conductivity of 50 samples each from dug wells, hand pumps and tube wells
was analysed for the study of salinity levels in shallow, intermediate and deep aquifers. Out of 50, 20 samples of each were
also analysed for other chemical constituents such as Na+, K+, Cl−, F− and TDS. The analyses show drastic changes in the salinity levels of shallow, intermediate and deep aquifers. The deep aquifers
are more saline compared to the shallow and intermediate aquifers. On the contrary, the concentration of chemical constituents
such as Na+, K+, Cl− and F− was more in the shallow aquifers compared to the deep aquifers. Moreover, there is an indication that the salinity and concentration
of the above chemical constituents also escalate with time in each aquifer. The chemical constituents such as Na+, K+, Cl−, F− and TDS range from 51 to 165 mg/l, 1 to 14 mg/l, 224 to 1,459 mg/l, 0 to 1.5 mg/l and 750 to 2,650 mg/l, respectively. Over
a 3-year period, the salinity levels have sharply increased and the average F level has increased by 0.1–0.3 mg/l. An attempt
has been made here to discuss the factors causing the variation and escalation of chemical constituents and salinity in the
water of the three aquifers. 相似文献
969.
The Dharwar craton, Cuddapah basin and the Godavari graben characterise three diverse geological and tectonic settings in
the peninsular shield of India. Owing to their contiguous proximity, they offer a unique opportunity to document differences,
if any, in their seismic wave attenuation characteristics that might have a bearing on the seismogenic nature of the crust
in a craton, basin and a rift-like graben structure. An attempt is made here to bring out these differences using constraints
from coda-Q. We considered local earthquakes with epicentral distances ranging from␣14 to 150 km recorded at the digital broadband stations
at Dharwar (DHD), Cuddapah (CUD) and Kothagudem (KGD) regions to derive the frequency-dependent coda-Q relations. Using the single scattering method, we obtained the frequency-dependent Q
C relationship (Q
C = Q
0
f
n
)for each of the three geological units separately: DHD: Q
C = (730.62 ± 0.09)f
(0.54 ± 0.01); CUD: Q
C = (535.06 ± 0.13)f
(0.59 ± 0.01) and KGD: Q
C = (150.56 ± 0.08)f (0.91 ± 0.01). The Q
C values obtained for all the three sub-regions show moderate to strong frequency dependence and essentially reflect the level
of crustal heterogeneities to varying degrees. 相似文献
970.
First Order Seismic Microzonation of Delhi,India Using Geographic Information System (GIS) 总被引:2,自引:4,他引:2
William K. Mohanty M. Yanger Walling Sankar Kumar Nath Indrajit Pal 《Natural Hazards》2007,40(2):245-260
A first order seismic microzonation map of Delhi is prepared using five thematic layers viz., Peak Ground Acceleration (PGA)
contour, different soil types at 6 m depth, geology, groundwater fluctuation and bedrock depth, integrated on GIS platform.
The integration is performed following a pair-wise comparison of Analytical Hierarchy Process (AHP), wherein each thematic
map is assigned weight in the 5-1 scale: depending on its contribution towards the seismic hazard. Following the AHP, the
weightage assigned to each theme are: PGA (0.333), soil (0.266), geology (0.20), groundwater (0.133) and bedrock depth (0.066).
The thematic vector layers are overlaid and integrated using GIS. On the microzonation theme, the Delhi region has been classified
into four broad zones of vulnerability to the seismic hazard. They are very high (> 52%), high (38–52%), moderate (23–38%)
and less ( < 23%) zones of seismic hazard. The “very high” seismic hazard zone is observed where the maximum PGA varies from
140 to 210 gal for a finite source model of Mw 8.5 in the central seismic gap. A site amplification study from local and regional earthquakes for Delhi region using Delhi
Telemetry Network data shows a steeper site response gradient in the eastern side of the Yamuna fluvial deposits at 1.5 Hz.
The ‘high’ seismic hazard zone occupies most of the study area where the PGA value ranges from 90 to 140 gal. The ‘moderate’
seismic hazard zone occurs on either side of the Delhi ridge with PGA value varying from 60 to 90 gal. The ‘less’ seismic
hazard zone occurs in small patches distributed along the study area with the PGA value less than 60 gal. Site response studies,
PGA distribution and destruction pattern of the Chamoli earthquake greatly corroborate the seismic hazard zones estimated
through microzonation on GIS platform and also establishes the methodology incorporated in this study. 相似文献