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排序方式: 共有76条查询结果,搜索用时 15 毫秒
1.
Socio-economic and Environmental Implications of the Hydroelectric Projects in Uttarakhand Himalaya, India 总被引:1,自引:1,他引:0
This paper deals with detailed analysis of the fiasco created by the Tehri High Dam in Uttarakhand, India, particularly in terms of resettlement and rehabilitation of the local inhabitants. Aspects pertaining to the environmental issues are also discussed. Currently, the river valleys in Uttarakhand state of India are the targets of increasing hydroelectric projects. Virtually all rivers are being exploited for generating environmental friendly power. Having being learned the hard lesson from Tehri Dam, it has been decided to opt for such schemes in which comparatively little submergence and tempering with the fragile eco-systems is involved.However, our observations suggest that even in such schemes if due care is not taken they may turn out to be a failure. 相似文献
2.
Closed form analytical expressions of stresses and displacements at any field point due to a very long dip-slip fault of finite
width buried in a homogeneous, isotropic elastic half-space, are presented. Airy stress function is used to derive the expressions
of stresses and displacements which depend on the dip angle and depth of the upper edge of the fault. The effect of dip angle
and depth of the upper edge of the fault on stresses and displacements is studied numerically and the results obtained are
presented graphically. Contour maps for stresses and displacements are also presented. The results of Rani and Singh (1992b)
and Freund and Barnett (1976) have been reproduced. 相似文献
3.
Naresh Neupane 《大气科学进展》2016,33(6):767-782
The Gulf of Guinea in the equatorial Atlantic is characterized by the presence of strong subsidence at certain times of the year. This subsidence appears in June and becomes well established from July to September. Since much of theWest African monsoon flow originates over the Gulf, Guinean subsidence is important for determining moisture sources for the monsoon. Using reanalysis products, I contribute to a physical understanding of what causes this seasonal subsidence, and how it relates to precipitation distributions across West Africa.There is a seasonal zonal overturning circulation above the Congo basin and the Gulf of Guinea in the ERA-Interim, ERA-40, NCEP2, and MERRA reanalyses. The up-branch is located in the Congo basin around 20°E. Mid-tropospheric easterly flows constitute the returning-branch and sinking over the Gulf of Guinea forms the down-branch, which diverges at 2°W near the surface, with winds to the east flowing eastward to complete the circulation. This circulation is driven by surface temperature differences between the eastern Gulf and Congo basin. Land temperatures remain almost uniform, around 298 K, throughout a year, but the Guinean temperatures cool rapidly from 294 K in May to about 290 K in August. These temperature changes increase the ocean/land temperature contrast, up to 8 K, and drive the circulation.I hypothesize that when the overturning circulation is anomalously strong, the northward moisture transport and Sahelian precipitation are also strong. This hypothesis is supported by ERA-Interim and PERSIANN-CDR (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record) data. 相似文献
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6.
R. Pandiyan S. V. Subbarao T. Nagamani Chaitra Rao N. Hari Prasad Rao Harish Joglekar Naresh Kumar Surya Ratna Prakash Dumpa Anshu Chauhan B. P. Dakshayani 《Journal of Astrophysics and Astronomy》2017,38(2):35
On 28th September 2015, India launched its first astronomical space observatory AstroSat, successfully. AstroSat carried five astronomy payloads, namely, (i) Cadmium Zinc Telluride Imager (CZTI), (ii) Large Area X-ray Proportional Counter (LAXPC), (iii) Soft X-ray Telescope (SXT), (iv) Ultra Violet Imaging Telescope (UVIT) and (v) Scanning Sky Monitor (SSM) and therefore, has the capability to observe celestial objects in multi-wavelength. Four of the payloads are co-aligned along the positive roll axis of the spacecraft and the remaining one is placed along the positive yaw axis direction. All the payloads are sensitive to bright objects and specifically, require avoiding bright Sun within a safe zone of their bore axes in orbit. Further, there are other operational constraints both from spacecraft side and payloads side which are to be strictly enforced during operations. Even on-orbit spacecraft manoeuvres are constrained to about two of the axes in order to avoid bright Sun within this safe zone and a special constrained manoeuvre is exercised during manoeuvres. The planning and scheduling of the payloads during the Performance Verification (PV) phase was carried out in semi-autonomous/manual mode and a complete automation is exercised for normal phase/Guaranteed Time Observation (GuTO) operations. The process is found to be labour intensive and several operational software tools, encompassing spacecraft sub-systems, on-orbit, domain and environmental constraints, were built-in and interacted with the scheduling tool for appropriate decision-making and science scheduling. The procedural details of the complex scheduling of a multi-wavelength astronomy space observatory and their working in PV phase and in normal/GuTO phases are presented in this paper. 相似文献
7.
Navin juyal Yaspal Sundriyal Naresh rana Shipra chaudhary Ashok k. Singhvi 《第四纪科学杂志》2010,25(8):1293-1304
The present study aims to explain the spatial and temporal variability in phases of aggradation/incision in response to changes in climate and seismicity during the late Quaternary in the Alaknanda River valley (a major tributary of the river Ganges or Ganga). Geomorphology, stratigraphy and optical dating of the fluvial sediment reveal that the oldest fluvial landforms preserved in the south of the Main Central Thrust are debris flow terraces developed during the early part of pluvial Marine Isotopic Stage 3. Following this, a period of accelerated incision/erosion owing to an increase in uplift rate and more intense rainfall occurred. In the Lesser Himalaya, three phases of valley fill aggradation around 26 ± 3 ka, 18 ± 2 ka and 15 ± 1 ka and 8 ± 1 ka occurred in response to changes in monsoon intensity and sediment flux. The last phase was regionally extensive and corresponds to a strengthening of the early Holocene Indian Summer Monsoon. A gradual decline in the monsoon strength after 8 ± 1 ka resulted in reduced fluvial discharge and lower sediment transport capacity of the Alaknanda River, leading to valley fill incision and the development of terraces. The study suggests that fluvial dynamics in the Alaknanda valley were modulated by monsoon variability and the role of tectonics was subordinate, limited to providing accommodation space and post‐deposition modification of the fluvial landforms. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
8.
Karjan river is an important tributary of Narmada in Gujarat. Along with one of its own tributaries, called Terav it has carved a “meandering valley” across the block faulted rldge and valley Deccan Trap topography, south of Narmada. Karjan originates at Bardipada, which is much nearer to Tapti river than Narmada and in the initial stretches its channel is consequent to faults and fractures. However, before emerging on to the alluvial plain in north it has a sinuous valley. With confines of this valley the present stream channel wanders back and forth and has incised deep into various Deccan Trap flows. The geometry of such meanders shows that this is an symmetric meandering valley. The valley as such is an antecedent one in which the present stream channel is ur.derfit and ingrown. Natural fluvial processes, accelerated by dynamic rejuvenation of the area and wetter climatic phases during Pleistocene and Holocene seem to have carved this meandering valley and integrated the drainage. 相似文献
9.
This paper presents the computation of time series of the 22 July 2007 M 4.9 Kharsali earthquake. It occurred close to the Main Central Thrust (MCT) where seismic gap exists. The main shock and
17 aftershocks were located by closely spaced eleven seismograph stations in a network that involved VSAT based real-time
seismic monitoring. The largest aftershock of M 3.5 and other aftershocks occurred within a small volume of 4 × 4 km horizontal extent and between depths of 10 and 14 km.
The values of seismic moment (M
∘) determined using P-wave spectra and Brune’s model based on f
2 spectral shape ranges from 1018 to 1023 dyne-cm. The initial aftershocks occurred at greater depth compared to the later aftershocks. The time series of ground motion
have been computed for recording sites using geometric ray theory and Green’s function approach. The method for computing
time series consists in integrating the far-field contributions of Green’s function for a number of distributed point source.
The generated waveforms have been compared with the observed ones. It has been inferred that the Kharsali earthquake occurred
due to a northerly dipping low angle thrust fault at a depth of 14 km taking strike N279°E, dip 14° and rake 117°. There are
two regions on the fault surface which have larger slip amplitudes (asperities) and the rupture which has been considered
as circular in nature initiated from the asperity at a greater depth shifting gradually upwards. The two asperities cover
only 10% of the total area of the causative fault plane. However, detailed seismic imaging of these two asperities can be
corroborated with structural heterogeneities associated with causative fault to understand how seismogenesis is influenced
by strong or weak structural barriers in the region. 相似文献
10.
Samson Hagos L. Ruby Leung Yongkang Xue Aaron Boone Fernando de Sales Naresh Neupane Maoyi Huang Jin-Ho Yoon 《Climate Dynamics》2014,43(9-10):2765-2775
Land use and land cover (LULC) over Africa have changed substantially over the last 60 years and this change has been proposed to affect monsoon circulation and precipitation. This study examines the uncertainties of model simulated response in the African monsoon system and Sahel precipitation due to LULC change using a set of regional model simulations with different combinations of land surface and cumulus parameterization schemes. Although the magnitude of the response covers a broad range of values, most of the simulations show a decline in Sahel precipitation due to the expansion of pasture and croplands at the expense of trees and shrubs and an increase in surface air temperature. The relationship between the model responses to LULC change and the climatologists of the control simulations is also examined. Simulations that are climatologically too dry or too wet compared to observations and reanalyses have weak response to land use change because they are in moisture or energy limited regimes respectively. The ones that lie in between have stronger response to the LULC changes, showing a more significant role in land–atmosphere interactions. Much of the change in precipitation is related to changes in circulation, particularly to the response of the intensity and latitudinal position of the African Easterly Jet, which varies with the changes in meridional surface temperature gradients. The study highlights the need for measurements of the surface fluxes across the meridional cross-section of the Sahel to evaluate models and thereby allowing human impacts such as land use change on the monsoon to be projected more realistically. 相似文献