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排序方式: 共有116条查询结果,搜索用时 15 毫秒
1.
Evaluation of geochemical impact of tsunami on Pichavaram mangrove ecosystem,southeast coast of India 总被引:1,自引:0,他引:1
The 26 December 2004-tsunami has deposited sediments in the Pichavaram mangrove ecosystem, east coast of India. Ten surface
and three core sediment samples were collected within 30 days of the event and analyzed for nutrients. Water samples were
also analyzed to see the impact of tsunami on the geochemical behavior of nutrients. An increase in the concentration of various
nutrients namely nitrate and phosphate was observed. The geochemistry of the mangrove forest was observed to be influenced
by a number of factors like rapid increase of aquaculture farms, agricultural practices and the anthropogenic discharge from
the nearby-inhabited areas. Further the sediment column was disturbed due to energetic tsunami waves, which has caused a sheer
increase in the dissolved oxygen in water. As a result, the change in the redox potential has resulted in change in the nutrients
absorbed/associated with the sediments. In addition, role of retreating water after tsunami on the nutrient geochemistry was
also evaluated. 相似文献
2.
Shubhra Goel Shalini Nihar Ranjan Patra 《Geotechnical and Geological Engineering》2006,24(6):1511-1525
Inclined anchors are widely used in a variety of civil engineering problems to resist oblique loads, most relevant being in
transmission towers and in rocks and dams for structural strengthening. In the present study, the breakout resistance of the
inclined anchors in sand has been worked out using limit equilibrium approach. The breakout resistance has been calculated
for different soil friction angles with varying relative depth ratio and anchor inclination. The break out factor increases
continuously with the inclination of the anchor. A comparison of predicted values of break out resistance of anchors by the
proposed analysis with the experimental values as reported by the other researchers showed reasonably good agreement. 相似文献
3.
Comparative analysis of contributing parameters for rainfall-triggered landslides in the Lesser Himalaya of Nepal 总被引:6,自引:0,他引:6
Ranjan Kumar Dahal Shuichi Hasegawa Minoru Yamanaka Santosh Dhakal Netra Prakash Bhandary Ryuichi Yatabe 《Environmental Geology》2009,58(3):567-586
In the Himalaya, people live in widely spread settlements and suffer more from landslides than from any other type of natural
disaster. The intense summer monsoons are the main factor in triggering landslides. However, the relations between landslides
and slope hydrology have not been a focal topic in Himalayan landslide research. This paper deals with the contributing parameters
for the rainfall-triggered landslides which occurred during an extreme monsoon rainfall event on 23 July 2002, in the south-western
hills of Kathmandu valley, in the Lesser Himalaya, Nepal. Parameters such as bedrock geology, geomorphology, geotechnical
properties of soil, and clay mineralogy are described in this paper. Landslide modeling was performed in SEEP/W and SLOPE/W
to understand the relationship of pore water pressure variations in soil layers and to determine the spatial variation of
landslide occurrence. Soil characteristics, low angle of internal friction of fines in soil, medium range of soil permeability,
presence of clay minerals in soil, bedrock hydrogeology, and human intervention were found to be the main contributing parameters
for slope failures in the region. 相似文献
4.
Martha Tapas Ranjan Roy Priyom Jain Nirmala Khanna Kirti Mrinalni K. Kumar K. Vinod Rao P. V. N. 《Landslides》2021,18(6):2125-2141
Landslides - India ranks first in the world in terms of fatal landslides. Large vulnerable area (0.42 million km2), high population density and monsoon rainfall make India’s landslide... 相似文献
5.
Alok Ranjan Tiwary Shibu K. Mathew A. Raja Bayanna P. Venkatakrishnan Rahul Yadav 《Solar physics》2017,292(4):49
The Multi-Application Solar Telescope (MAST) is a 50 cm off-axis Gregorian telescope that has recently become operational at the Udaipur Solar Observatory (USO). An imaging spectropolarimeter is being developed as one of the back-end instruments of MAST to gain a better understanding of the evolution and dynamics of solar magnetic and velocity fields. This system consists of a narrow-band filter and a polarimeter. The polarimeter includes a linear polarizer and two sets of liquid crystal variable retarders (LCVRs). The instrument is intended for simultaneous observations in the spectral lines 6173 Å and 8542 Å, which are formed in the photosphere and chromosphere, respectively. In this article, we present results from the characterization of the LCVRs for the spectral lines of interest and the response matrix of the polarimeter. We also present preliminary observations of an active region obtained using the spectropolarimeter. For verification purposes, we compare the Stokes observations of the active region obtained from the Helioseismic Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) with that of MAST observations in the spectral line 6173 Å. We find good agreement between the two observations, considering the fact that MAST observations are limited by seeing. 相似文献
6.
A riparian ecosystem downstream of a small dam in central Texas was instrumented for sap flow, soil moisture content, and stream level from 2001. Stable isotopes in water (D and 18O) were analysed from rainfall, stream, lake, and cored sapwood cellulose from cedar elm (Ulmus crassifolia). The isotope signature of water source to cedar elm was identified by back calculation starting with the water isotopes in cellulose, and accounting for leaf‐water evaporation and biological fractionation during cellulose synthesis. The estimated mean isotope of the source water to cedar elm was enriched above rainfall in similarity to stream water during 2002. Flow paths that may have contributed to estimated variability from regional base flow and recharge water were identified using the variably saturated HYDRUS‐2D model. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
7.
Effects of climate change on coastal fresh groundwater resources 总被引:1,自引:0,他引:1
This study evaluates the impacts of climate change on fresh groundwater resources specifically salinity intrusion in water resources stressed coastal aquifers. Our assessment used the Hadley Centre climate model, HadCM3 with high and low emission scenarios (SRES A2 and B2) for years 2000–2099. In both scenarios, the annual fresh groundwater resources losses indicate an increasing long-term trend in all stressed areas, except in the northern Africa/Sahara region. We also found that precipitation and temperature individually did not show good correlations with fresh groundwater loss. However, the relationship between the aridity index and fresh groundwater loss exhibited a strong negative correlation. We also discuss the impacts of loss of fresh groundwater resources on socio-economic activities, mainly population growth and per capita fresh groundwater resources. 相似文献
8.
Mesoscale surface circulation and variability of Southern Indian Ocean derived by combining satellite altimetry and drifter observations 总被引:1,自引:1,他引:0
BENNY N. Peter SHENBAKAVALLI Ranjan MAZLAN Hashim MOHD Nadzri Re MOHD Razali Mahmud 《海洋学报(英文版)》2015,34(9):12-22
High resoultion Eulerian mean velocity field has been derived by combining the satellite tracked surface drifter data with satellite altimetry and ocean surface winds. The drifter data used in this study includes Argos and surface drifter data from Global Drifter Program. Maps of Sea Level Anomaly(MSLA) weekly files with a resolution of(1/3)° in both Latitude and Longitude for the period 1993–2012 have been used. The Ekman current is computed using ocean surface mean wind fields from scatterometers onboard ERS 1/2,Quikscat and ASCAT. The derived mean velocity field exhibits the broad flow of Antarctic Circumpolar Current with speeds up to 0.6 m/s.Anomalous field is quite significant in the western part between 20° and 40°E and in the eastern part between 80°E and 100°E with velocity anomaly up to 0.3 m/s. The estimated mean flow pattern well agrees with the dynamic topography derived from in-situ observations. Also,the derived velocity field is consistent with the in-situ ADCP current measurements. Eddy kinetic energy illustrates an increasing trend during 1993–2008 and is in phase coherence with the Southern Annular Mode by three month lag. Periodic modulations are found in the eddy kinetic energy due the low frequency Antarctic Circumpolar Wave propagation. 相似文献
9.
Sunil Kumar Tripathy Dipanjali Behera Tushar Ranjan Routray 《Astrophysics and Space Science》2010,325(1):93-97
Spatially homogeneous and anisotropic LRS Bianchi type-I string cosmological models are studied in the frame work of general
relativity when the source for the energy momentum tensor is a bulk viscous fluid containing one dimensional strings. A barotropic
equation of state for the pressure and density is assumed to get determinate solutions of the field equations. The bulk viscous
pressure is assumed to be proportional to the energy density. The physical and kinematical properties of the models are discussed.
The role of bulk viscosity in getting an inflationary phase in the universe is studied. 相似文献
10.
The Nature and Distribution of Particulate Matter in the Mandovi Estuary,Central West Coast of India
Pratima Mohan Kessarkar Venigalla Purnachandra Rao Ranjan Shynu Prakash Mehra Blossom E. Viegas 《Estuaries and Coasts》2010,33(1):30-44
Systematic seasonal variations of suspended particulate matter (SPM) along a 44-km transect of the Mandovi estuary reveal
that the concentrations of SPM are low at river-end stations, increase generally seaward, and are highest at sea-end stations
of the estuary. An estuarine turbidity maximum (ETM) occurs at sea-end stations during June–September when river discharge
is high and also in February–May when river discharge is low. These are the two windiest times of year, the former associated
with the southwest monsoon and the latter characterized by a persistent sea breeze. The salinity vs. SPM plot shows that high
SPM is a seaward deposit and skewed landward. Suspended matter comprised of floccules, fecal pellets, and aggregates that
consist of clay and biogenic particles occur everywhere in the estuary. Diatoms are the most common and are of marine type
at the sea-end and freshwater-dominated at river-end stations of the estuary. SPM is characterized by kaolinite- and smectite-rich
clay mineral suites at the river- and sea-end stations, respectively. Smectite concentrations increase seawards with the increase
in SPM content and are not influenced by salinity. Wind-driven waves and currents and biogeochemical processes at the mouth
of estuary likely play an important role in the formation of ETM in resuspension and transformation of SPM into floccules
and aggregates and in their upkeep or removal. 相似文献