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41.
Subir Kumar Ghosh 《Tectonophysics》1974,21(3):249-272
Two series of experiments were carried out with soft model-materials in order to assess the relative importance of initial homogeneous strain, external rotation and late-stage strain in reorienting early lineations during superposed buckle-folding. In the first series cylindrical buckling folds were produced in embedded planar sheets containing a “lineation”. In the second series noncylindrical folds were produced by compression of a set of cylindrical folds. The experiments indicate that the ratio of buckle shortening to layer-parallel strain is much smaller when the principal extension is parallel to the fold-axis than in the case when the principal extension is perpendicular to the fold-axis. In very competent rocks, the reorientation of old lineations is mainly by external rotation and by the associated concentric longitudinal strain. In moderately competent rocks, the orientation of early lineations always changes by initial homogeneous strain before buckling becomes significant. Because of the unlike amounts of initial strain in layers of different competences, orientations of unrolled lineations may not be parallel in disharmonically folded layers of unlike competences. Under certain conditions the early lineation may become virtually parallel to the later fold-axis. The experiments indicate that the effects of late-stage strain in buckle-folding are largely restricted to the incompetent layers of a multilayer. Hence, if orientation data of early lineations in both competent and incompetent rocks are lumped together, the pattern of orientation may become quite complex. Even for a single competent layer, the pattern of early lineations can locally become complex because of the complex nature of concentric longitudinal strain (and strain resulting from stretching of middle surface of the layer), development of conical folds, development of shear strain along hinge zones of deformed early folds and also because of the development of different orders of folds in both the first and the second deformations. 相似文献
42.
The dispersion relation for magnetosonic waves within the upper atmospheric plasma has been derived. The result can be used to study the variation of the longitudinal and transverse component of velocities. 相似文献
43.
44.
Shamik Ghosh Pankaj Jain Gopal Kashyap Rahul Kothari Sharvari Nadkarni-Ghosh Prabhakar Tiwari 《Journal of Astrophysics and Astronomy》2016,37(4):25
There currently exist many observations which are not consistent with the cosmological principle. We review these observations with a particular emphasis on those relevant for the Square Kilometre Array (SKA). In particular, several different data sets indicate a preferred direction pointing approximately towards the Virgo cluster. We also observe a hemispherical anisotropy in the Cosmic Microwave Background radiation (CMB) temperature fluctuations. Although these inconsistencies may be attributed to systematic effects, there remains the possibility that they indicate new physics and various theories have been proposed to explain them. One possibility, which we discuss in this review, is the generation of perturbation modes during the early pre-inflationary epoch, when the Universe may not obey the cosmological principle. Better measurements will provide better constraints on these theories. In particular, we propose measurement of the dipole in number counts, sky brightness, polarized flux and polarization orientations of radio sources. We also suggest test of alignment of linear polarizations of sources as a function of their relative separation. Finally we propose measurement of hemispherical anisotropy or equivalently dipole modulation in radio sources. 相似文献
45.
We have analyzed the solar irradiance data from the Earth Radiation Budget Satellite(ERBS)during the time period from 1984 October 15 to 2003 October 15.By first filtering the data by Simple Exponential Smoothing,we have applied the periodogram method to the processed data in order to search for its time variation.The study exhibits multi-periodicities on these data around 110,118,574 and 740d with very high confidence levels(more than 99%).These periods are significantly similar to the periods of other solar activities which may suggest that solar irradiance may be associated with other solar activities. 相似文献
46.
Saibal Gupta Aditi Das Sudipta Goswami Ananda Modak Suman Mondal 《Journal of the Geological Society of India》2010,75(1):313-322
Inverted metamorphism in the Himalayas is closely associated with the Main Central Thrust (MCT). In the western Himalayas,
the Main Central Thrust conventionally separates high grade metamorphic rocks of the Higher Himalayan Crystalline Sequence
(HHCS) from unmetamorphosed rocks of the Inner sedimentary Belt. In the eastern Himalayas, the Inner sedimentary Belt is absent,
and the HHCS and meta-sedimentary Lesser Himalayan Sequence (LHS) apparently form a continuous Barrovian metamorphic sequence,
leading to confusion about the precise location of the MCT. In this study, it is demonstrated that migmatitic gneisses of
the sillimanite zone in the higher structural levels of the HHCS are multiply deformed, with two phases of penetrative fabric
formation (S1HHCS and S2HHCS) followed by third folding event associated with a spaced, NW-SE trending, north-east dipping foliation (S3HHCS). The underlying LHS schists (kyanite zone and lower) are also multiply deformed, with the bedding S0 being isoclinally folded (F1LHS), and subsequently refolded (F2LHS and F3LHS). The contact zone between the HHCS and LHS is characterized by ductile, top-to-the southwest shearing and stabilization
of a pervasive foliation that is consistently oriented NW-SE and dips northeast. This foliation is parallel to the S3HHCS foliation in the HHCS, and the S2LHS in the LHS. Early lineations in the HHCS and LHS also show different dispersions across the contact shear zone, implying
that pre-thrusting orientations of the two units were distinct. The contact shear zone is therefore interpreted to be a plane
of structural discordance, shows a shear sense consistent with thrust movement and is associated with mineral growth during
Barrovian metamorphism. It may well be considered to represent the MCT in this region. 相似文献
47.
Tapan Pal Biswajit Ghosh Anindya Bhattacharya S. K. Bhaduri 《Journal of Earth System Science》2010,119(1):19-25
The bedded felsic tuff exposed in Rutland Island, Andaman, consists of two facies:
– |
white massive tuff with ill-defined bedding contacts (facies-A) and 相似文献
48.
Haimanti Biswas Mitali Dey Dipnarayan Ganguly Tarun K. De Sandip Ghosh Tapan K. Jana 《Estuaries and Coasts》2010,33(2):395-398
Inter-annual variations of phytoplankton abundance and community organization were observed over a two-decade period along
with the ancillary parameters at the land–ocean boundary associated with the Sundarban mangrove forest (21°32′ and 22°40′
N and 88°05′ and 89° E), along the NE Coast of the Bay of Bengal. The number of definable Bacillariophyceae species exceeded Dinophyceae taxa, and the total number of bloom-forming species declined from a maximum of ten in 2000 and a minimum of two in 2007.
Blooms of the diatom Coscinodiscus radiatus were common in 2000 and 2007. Tide cycles and the onset of the monsoon season played important roles in diurnal and seasonal
variability of phytoplankton. Phytoplankton biovolume showed seasonality, with the highest levels during post-monsoon periods
and lowest levels during the monsoon period. Phytoplankton abundance was correlated to rainfall patterns, which may be altered
by long-term changes in climate. 相似文献
49.
Birendra Nath Ghosh Narinder Kumar Sharma Nurnabi Meherul Alam Raman Jeet Singh Gopal Prasad Juyal 《山地科学学报》2014,11(5):1208-1217
On farm bio-resource recycling has been given greater emphasis with the introduction of conservation agriculture specifically withclimate change scenarios in the mid-hills of the north-west Himalaya region(NWHR). Under this changing scenario, elevation, slope aspect and integrated nutrient management(INM) may affect significantly soil quality and crop productivity. A study was conducted during 2009-2010 to 2010-2011 at the Ashti watershed of NWHR in a rainfed condition to examine the influence of elevation, slope aspect and integrated nutrient management(INM) on soil resource and crop productivity. Two years of farm demonstration trials indicated that crop productivity and soil quality is significantly affected by elevation, slope aspect and INM. Results showed that wheat equivalent yield(WEY) of improved technology increased crop productivity by -20%-37% compared to the conventional system. Intercropping of maize with cowpea and soybean enhanced yield by another 8%-17%. North aspect and higher elevation increased crop productivity by 15%-25% compared to south aspect and low elevation(except paddy). Intercropping of maize with cowpea and soybean enhanced yield by another 8%-15%. Irrespective of slope, elevation and cropping system, the WEY increased by -30% in this region due to INMtechnology. The influence of elevation, slope aspect and INM significantly affected soil resources(SQI) and soil carbon change(SCC). SCC is significantly correlated with SQI for conventional(R2 = 0.65*), INM technology(R2 = 0.81*) and for both technologies(R2 = 0.73*). It is recommended that at higher elevation.(except for paddy soils) with a north facing slope, INM is recommended for higher crop productivity; conservation of soil resources is recommended for the mid hills of NWHR; and single values of SCC are appropriate as a SQI for this region. 相似文献
50.
Nonlinear kinetic analysis of phenol adsorption onto peat soil 总被引:1,自引:0,他引:1
Phenolic compounds are considered as a serious organic pollutant containing in many industrial effluents particularly vulnerable when the plant discharge is disposed on land. In the present study, the phenol removal potential of peat soil as adsorption media was investigated as the adsorption process are gaining popular for polishing treatment of toxic materials in industrial wastewater. Batch experiments were performed in the laboratory to determine the adsorption isotherms of initial concentrations for 5, 8, 10, 15, and 20 mg/L and predetermined quantity of peat soil with size ranges between 425 and 200 μm poured into different containers. The effects of various parameters like initial phenol concentration, adsorbent quantity, pH, and contact time were also investigated. From experimental results, it was found that 42 % of phenol removal took place with optimized initial phenol concentration of 10 mg/L, adsorbent dose of 200 g/L, solution pH 6.0 for the equilibrium contact time of 6 h. The result exhibits that pseudo-first-order (R 2 = 0.99) and Langmuir isotherm models are fitted reasonably (R 2 = 0.91). Adams–Bohart, Thomas, Yoon–Nelson, and Wolborska models were also investigated to the column experimental data of different bed heights to predict the breakthrough curves and to determine the kinetic coefficient of the models using nonlinear regression analysis. It was found that the Thomas model is the best fitted model to predict the experimental breakthrough curves with the highest coefficient of determination, R 2 = 0.99 and lowest root mean square error and mean absolute performance error values. 相似文献
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