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排序方式: 共有550条查询结果,搜索用时 15 毫秒
1.
The wave transmission and reflection characteristics of a rigidly fixed surface and submerged horizontal plate were investigated experimentally in detail for a wide range of incident wave steepnesses and for different depths of submerge of the plate in deep water conditions in regular water wave fields. The experiments were conducted at the Ocean Engineering Centre, Indian Institute of Technology, Madras, India, in a wave flume 10 m long, 0.3 m wide and in a constant water depth of 0.8 m. The horizontal plate is 0.22 m thick and 1.2 m in length, covering the enrire width of the flume. From the present investigation, it is found that for a rigid surface plate, the coefficient of transmission is a minimum and the coefficient of reflection is a maximum, but the maximum value of the coefficient of energy loss occurs for plates submerged closer to the still-water level (SWL) and not for the surface plate. It is also found that the value of the coefficient of reflection increases with the increase in the value of the Reddy-Neelamani (RN) number, the ratio of horizontal water particle excursion at the bottom of the plate in its absence to the length of the plate. The coefficient of transmission is found to decrease rapidly with increase in the value of RN number up to 0.1. The wave transmission is only 5% for RN from 0.1 to 0.2. It is also found that for RN number greater than 0.04, the minimum energy dissipation is consistently about 60% of the incident wave energy. 相似文献
2.
M. Arockiasamy H. El-Tahan A.S.J. Swamidas W.E. Russell D.V. Reddy 《Ocean Engineering》1984,11(5):463-490
The paper presents an analytical and experimental study on the transient response of semisubmersibles to bergybit impact and the strength of bergybit ice to high strain-rate loadings. Two approaches have been proposed for the solution of the semisubmersible-bergybit interaction problem, one using the energy approach and the other using the conventional structural dynamics approach with initial velocity conditions. In addition the local behaviour of the impacted regions have been analysed for deformation and failure. Numerical results have been given for local behaviour of an impacted column and global behaviour of semisubmersible-bergybit system. Experimental study has been reported on the impact strength of iceberg ice at strain rates of 10−3, 10−2 and 10−1; the indentation impact strength of ice is found to be 3–4 times the unaixial compressive strength, at the same strain rate. 相似文献
3.
In the present study, an attempt has been made to delineate and characterize the different geomorphic units of Tundiya river
catchment in a part of Lower Maharahstra Metamorphic Plateau, north-eastern part of Nagpur district, Maharashtra. The drainage,
contour and delineated geological units have been overlaid on IRS-ID LISS III satellite imagery (bands 2,3 and 4) in EASI/PACE
analysis system to delineate and characterize different geomorphological units and analysis of their processes based on the
field observations. The study area is basically of metamorphic in origin with different geological formations and is influenced
by the various fluvio-morphological processes. Based on the satellite data analysis, the distinct geomorphological units viz.,
table top summits, structural hills, subdued plateau, linear ridges, shallow, moderate and deeply buried foot slopes, shallow
valley fills and deep valley fills have been delineated and characterized. The information generated from satellite data in
the form of vector layers has been used in GIS to generate geological and geomorphological maps of the study area. The present
study demonstrates that IRS-ID LISS-III data in conjunction with geology, drainage and contour parameters to enable detailed
evaluation of different geomorphological units and analysis of their processes based on the field observations. The delineated
geomorphological units can be utilized for evaluation and management of natural resources and geo-environment on sustainable
basis at river catchment level. 相似文献
4.
R. Nagendra P. Sathiyamoorthy A. N. Reddy Harry Gilbert B. C. Jaiprakash 《Arabian Journal of Geosciences》2014,7(10):4133-4144
Grey shale Member of the Dalmiapuram Formation, Ariyalur Group, Cauvery Basin, India was studied for its stratigraphic position, age, and paleobathymetry with a re-look into the lithological relationship and foraminifer assemblages in the deepened limestone mine excavations at M/s Dalmia Cements, Dalmiapuram. Twenty grey shale samples from Kovandankurchchi (pit-4) and Kallakkudi mines yielded diversified calcareous, benthic, and rare index planktic foraminifera. The foraminiferal assemblages suggest a latest Albian age and middle neritic depositional conditions. The abundance of kaolinite and smectite clay minerals relate to warm/humid climate which corroborate with rising relative sea level during grey shale deposition. The grey shale occurs in patches within the marl bedded limestone member which exhibits cyclic deposition of limestone and marl. The limestone mine sections demonstrate that the grey shale forms part of basal marl bedded limestone, directly overlying the coral algal limestone. The present study demonstrates that the grey shale outcrops in Dalmiapuram Formation should be placed stratigraphically as part of marl bedded limestone. The member status for grey shale which is current usage stands discounted. 相似文献
5.
Jaya Naithani H. N. Dutta P. K. Pasricha B. M. Reddy K. M. Aggarwal 《Boundary-Layer Meteorology》1995,74(1-2):195-208
Turbulent fluxes have been evaluated for clear sunny days over the Indian Antarctic station, Maitri, using the basic meteorological data recorded at four levels of a 28 m tower. The data are supplemented with radiation data. The surface layer over Maitri remains thermally stratified during the hours of minimum solar insolation, the so-called nighttime period. The surface winds during this period are generally very strong resulting in high momentum fluxes. In particular, for high winds (>12 m s–1), the temperature gradient is found to be less positive than for moderate winds (4 to 7 m s–1). Solar insolation provided the daytime heating necessary for the diurnal variation of atmospheric stability, and hence, for the turbulent fluxes. Thus, on clear days daytime conditions are marked by upward transport of heat with reduced momentum flux, while stable nighttime conditions are marked by a downward heat flux with increased momentum fluxes. 相似文献
6.
7.
Groundwater targeting in a hard-rock terrain using fracture-pattern modeling, Niva River basin, Andhra Pradesh, India 总被引:1,自引:0,他引:1
In hard-rock terrain, due to the lack of primary porosity in the bedrock, joints, fault zones, and weathered zones are the
sources for groundwater occurrence and movement. To study the groundwater potential in the hard-rock terrain and drought-prone
area in the Niva River basin, southern Andhra Pradesh state, India, Landsat 5 photographic data were used to prepare an integrated
hydrogeomorphology map. Larsson's integrated deformation model was applied to identify the various fracture systems, to pinpoint
those younger tensile fracture sets that are the main groundwater reservoirs, and to understand the importance of fracture
density in groundwater prospecting. N35°–55°E fractures were identified as tensile and N35°–55°W fractures as both tensile
and shear in the study area. Apparently, these fractures are the youngest open fractures. Wherever N35°–55°E and N35°–55°W
fracture densities are high, weathered-zone thickness is greater, water-table fluctuations are small, and well yields are
high. Groundwater-potential zones were delineated and classified as very good, good to very good, moderate to good, and poor.
Electronic Publication 相似文献
8.
Electrokinetic remediation of metal contaminated glacial tills 总被引:2,自引:0,他引:2
This paper presents the results of an experimental investigation which studied the feasibility of using the electrokinetic process to remediate contaminated clays of glacial origin, otherwise known as glacial tills. An overview of the electrokinetic phenomena, as well as previously performed laboratory and field investigations, is first presented. The methodology of the electrokinetic experiments which were conducted to investigate the removal of metals from a glacial till is then described. A total of 16 experiments were conducted using glacial till samples obtained from a project site near Chicago. Sodium and calcium were used as the surrogate cationic metallic contaminants. These experiments demonstrated that ion transport during the electrokinetic process occurs due to both electro-osmosis and electromigration, but that due to electromigration is significantly higher than that due to electro-osmosis. Unlike other clays such as kaolinite, the glacial till used for this investigation possessed high buffering capacity because of its high carbonate content which prevented the acid front migration from the anode to the cathode during the electrokinetic process. The ion removal efficiency of the electrokinetic process was found to increase when: (1) the voltage gradient applied to the soil was increased, (2) the initial concentration of the contaminants was increased, and (3) the duration of the treatment process was increased. The ion removal efficiency was also greater for smaller ions which possess less ionic charge and when the ions existed independently in the soil as compared to when they coexisted. This investigation suggests that the electrokinetic process has significant potential for remediating glacial tills contaminated with metals. However, the properties of Na and Ca are not representative of contaminants, such as heavy metals, so further investigations are needed. 相似文献
9.
Nagapattinam, in the east coast of India, was severely affected during the deadliest Indian Ocean tsunami of December 26,
2004. The tsunami caused heavy damage to life and property, and the death toll was about 3,378 in Nagapattinam taluk. Certain
villages along the coast witnessed large inundation while adjacent villages were protected from the fury of the tsunami waves.
This study was carried out to examine the underlying causes for the vulnerability along Nagapattinam coast with the help of
field observations, remote sensing, and geographical information system as tools. Coastal areas with high sand dunes have
been protected from tsunami, and areas adjacent to backwaters were inundated. Realtime Kinematic Global Positioning System
and high-resolution satellite data were used to map the topographic information and maximum extent of inundation. Thematic
maps on land use, land cover, and coastal geomorphology were generated using remote sensing and field data. Using field data
as the primary source of information, tsunami hazard maps have been generated for Nagapattinam. 相似文献
10.
N. Subba Rao K. V. Srinivasa Rao P. Surya Rao Ch. Venkat Rao K. Arjunudu P. Madhusudhana Reddy A. Subrahmanyam 《Journal of the Geological Society of India》2009,73(5):651-656
Groundwater samples were collected from a coastal region of Andhra Pradesh to assess the possible conditions of the formation
of carbonates. The area experiences a semi-arid climate and is underlain by khondalites, over which the Quaternary sediments
occur. The study of the geochemistry of groundwater indicates that groundwater is mostly of fresh, with alkaline nature. The
study further suggest that the breakdown of feldspars as kaolinite during rock-water interaction, releases Ca2+. Soils/weathered products contribute high CO2 under the open system. The Ca2+ and CO2 are added to the groundwater through the infiltrating recharge water. They subsequently precipitate as fine-grained carbonates
in the weathering profile due to evapotranspiration under a freshwater environment. 相似文献