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1.
- In order to employ cost effective frequency domain analysis for off-shore structures treatment of hydrodynamic loading is essential. Drag and inertia dominated, resonating and antiresonating cases under random sea states are analyzed to highlight the implications and relative merits of four salient linearization techniques. 相似文献
2.
Comparison of TOPEX/POSEIDON Altimeter Derived Wind Speed and Wave Parameters with Ocean Buoy Data in the North Indian Ocean 总被引:1,自引:0,他引:1
Results of comparison exercises carried out between the state-of-the-art TOPEX/POSEIDON altimeter-derived ocean surface wind speed and ocean wave parameters (significant wave height and wave period) and those measured by a set of ocean data buoys in the North Indian Ocean are presented in this article. Altimeter-derived significant wave height values exhibited rms deviation as small as ±0.3 m, and surface wind speed of ±1.6 m/s. These results are found consistent with those found for the Pacific Ocean. For estimation of ocean wave period, the spectral moments-based semiempirical approach, earlier applied on GEOSAT data, was extended to TOPEX/POSEIDON. For this purpose, distributions of first four years of TOPEX/POSEIDON altimeter data and climatology over the North Indian Ocean were analyzed and a new set of coefficients generated for estimation of wave period. It is shown that wave periods thus estimated from TOPEX/POSEIDON data (for the subsequent two years), when compared with independent data set of ocean data buoys deployed in the North Indian Ocean, exhibit improved accuracy (rms ~ ±1.4 nos) over those determined earlier with GEOSAT data. 相似文献
3.
R.P. Gupta D.P. Kanungo M.K. Arora S. Sarkar 《International Journal of Applied Earth Observation and Geoinformation》2008
Evaluation of maps generated from different conceptual models or data processing approaches at spatial level has importance in many geoenvironmental applications. This paper addresses the spatial comparison of different landslide susceptibility zonation (LSZ) raster maps of the same area derived from various procedures. 相似文献
4.
5.
In this paper, a theoretical investigation is undertaken of the group travel-time for the Sun's pulses to travel from the source of the pulse to the solar surface. For mathematical simplicity, we consider a simple ionized model of the Sun that includes the thermal effect and rotation with uniform angular velocity. The expression for the group travel time gives two terms: the term arising from the linear theory which varies inversely to (2-)1/2 and the term introduced by the thermal effect which is inversely proportional to (2-)7/2. The thermal effect variation has been shown and an estimation of the temperature of the medium has been made. Furthermore, the velocity distribution and the amplitude of the magnetic field of the wave, arising from the damping of ionized particles, have been calculated. 相似文献
6.
The present study is carried out to examine the performance of a regional atmospheric model in forecasting tropical cyclones
over the Bay of Bengal and its sensitivity to horizontal resolution. Two cyclones, which formed over the Bay of Bengal during
the years 1995 and 1997, are simulated using a regional weather prediction model with two horizontal resolutions of 165 km
and 55 km. The model is found to perform reasonably well towards simulation of the storms. The structure, intensity and track
of the cyclones are found to be better simulated by finer resolution of the model as compared to the coarse resolution. Rainfall
amount and its distribution are also found to be sensitive to the model horizontal resolution. Other important fields, viz.,
vertical velocity, horizontal divergence and horizontal moisture flux are also found to be sensitive to model horizontal resolution
and are better simulated by the model with finer horizontal grids. 相似文献
7.
At Malanjkhand, Central India, lode-type copper (-molybdenum) mineralization occurs within calcalkaline tonalite-granodiorite
plutonic rocks of early Proterozoic age. The bulk of the mineralization occurs in sheeted quartz-sulfide veins, and K-silicate
alteration assemblages, defined by alkali feldspar (K-feldspar ≫ albite) + dusty hematite in feldspar ± biotite ± muscovite,
are prominent within the ore zone and the adjacent host rock. Weak propylitic alteration, defined by albite + biotite + epidote/zoisite,
surrounds the K-silicate alteration zone. The mineralized zone is approximately 2 km in strike length, has a maximum thickness
of 200 m and dips 65°–75°, along which low-grade mineralization has been traced up to a depth of about 1 km. The ore reserve
has been conservatively estimated to be 92 million tonnes with an average Cu-content of 1.30%. Supergene oxidation, accompanied
by limited copper enrichment, is observed down to a depth of 100m or more from the surface. Primary ores consist essentially
of chalcopyrite and pyrite with minor magnetite and molybdenite. δ34S (‰) values in pyrite and chalcopyrite (−0.38 to +2.90) fall within the range characteristic of granitoid-hosted copper deposits.
δ18O (‰) values for vein quartz (+ 6.99 to +8.80) suggest exclusive involvement of juvenile water. Annealed fabrics are common
in the ore. The sequence of events that led to the present state of hypogene mineralization is suggested to be as follows:
fracturing of the host rock, emplacement of barren vein quartz, pronounced wall-rock alteration accompanied by disseminated
mineralization and the ultimate stage of intense silicification accompanied by copper mineralization. Fragments of vein quartz
and altered wall rocks and striae in the ore suggest post-mineralization deformation. The recrystallization fabric, particularly
in chalcopyrite and sphalerite, is a product of dynamic recrystallization associated with the post-mineralization shearing.
The petrology of the host rocks, hydrothermal alteration assemblages, ore mineral associations, fluid inclusions and the sulfur
and oxygen isotopes of ores are comparable to those in Phanerozoic (and reported Precambrian) porphyry-copper systems, and
the Malanjkhand deposit has important implications for both metallogenic models for, and mineral exploration in, Precambrian
terrains. 相似文献
8.
Irene Sarkar 《Journal of Asian Earth Sciences》2004,22(5):529
The moderate magnitude Chamoli earthquake that occurred in the Garhwal Higher Himalaya, in the early hours of March 29, 1999, caused intense damage to the ground and mountain slopes of the Alaknanda–Mandakini river valley and adjoining region. A systematic survey of this induced damage was conducted immediately after the earthquake occurred. Prominent shallow cracks of significant length, negligible width and indeterminate vertical extent, conspicuously tensile in nature, with little or no slip across the crack planes, were observed in the ground at several places along the surveyed route. These cracks had formed in the dynamic phase of the Chamoli earthquake process that is in the period of time during which the earthquake-generated seismic waves were passing through the geographic region of interest. However, we use the theory of earthquake-induced static (or long time) stress changes to visualize such cracks at some selected sites where ground damage was relatively more intense and varied to suggest lower bound estimates of the dynamic stress contributions of the main shock for their formation.Based on the results of our analysis we conclude that, just prior to the earthquake occurrence, under the influence of the local ambient stress field, the ground at these sites was already near failure in tension. To this, in its dynamic phase, the Chamoli earthquake induced stress perturbations, having, across the planes of the cracks, (i) shear components which were nearly equal and opposite to similar components of the ambient stress field and (ii) normal (tensile) components, necessary for triggering tensile failure of the ground. The σ3 (or minimum principal stress) component of the resultant perturbed failure stress field thus became sufficiently tensile while the transverse stresses became sufficiently insignificant. This facilitated formation of major tensile cracks in the ground there. Our static estimates of the tensile stress changes at the different sites are, in essence, estimates of the minimal triggering stress perturbations that was provided by the Chamoli earthquake in the dynamic state for the formation of the tensile cracks there. 相似文献
9.
The Chilka Lake igneous complex of Orissa, the largest known anortosite massif of the Indian Shield, occurs in a catazonal environment of high-grade metamorphics of the Eastern Ghats Precambrian Orogenic Province. The syntectonic massif consists of the anorthositic Balugaon dome, leuconoritic Rambha lobe and quartz-mangeritic Kallikota cover. A completely gradational suite comprising anorthosite-leuconorite-norite-minor jotunite (the anorthositic suite) constitutes most of the complex. The subordinate of suite of acid rocks spatially associated with this is of a broad quartz-mangeritic lithology with minor granitic rocks (the acidic suite). Geochemical evolution of the complex in the sequence anorthosite-leuconorite-norite-jotunite-acidic rocks shows moderate iron enrichment in the noritic-jotunitic stage and is marked by an overall decrease in Al2O3, CaO, MgO, Ni/Co, Sr/Ba, K/Rb and increase in SiO2, K2O, V/Ni, K/Ba and Rb/Sr. Such progressive variation in geochemical parameters appears (i) essentially gradual and frequently overlapping in rock members of the intergradational anorthositic suite and (ii) rather abrupt across transition zones between the anorthositic suite and the acidic suite due to near absence of intervening intermediate lithologies. RbSr whole rock isochron studies indicate that the complex was emplaced ca. 1400 Ma ago. The initial 87Sr/68Sr (0.70661) implies limited hybridisation of the parent magma prior to emplacement. A critical appraisal of all the available evidence suggests that (i) the anorthositic suite of rocks form a perfectly consanguinous and comagmatic assemblage and (ii) the spatially associated acidic suite emerged through a convergence of magmatic and metasomatic processes (the latter brought about by contact anatexis of the host rocks). The complex as well as the host metamorphics are intruded by an atectonic suite of noritic dykes emplaced ca 850 Ma ago. 相似文献
10.