Nanocrystalline PbS as Ammonia Gas Sensor: Synthesis and Characterization          下载免费PDF全文

Subhankar Bandyopadhyay  Bappaditya Chatterjee  Pooja Nag  Amitava Bandyopadhyay 《洁净——土壤、空气、水》2015,43(8):1121-1127

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Effective medium theory and multiple linear regression-based velocity estimation in syn-rift clastic sequence of the Krishna–Godavari basin,India     

Prabal Shankar Das  Rima Chatterjee  Sumangal Dasgupta 《Geophysical Prospecting》2020,68(6):1793-1810

An inclusion model, based on the Kuster–Toksöz effective medium theory along with Gassmann theory, is tested to forward model velocities for fluid-saturated rocks. A simulated annealing algorithm, along with the inclusion model, effectively inverts measured compressional velocity (V_P) to achieve an effective pore aspect ratio at each depth in a depth variant manner, continuously along with depth. Early Cretaceous syn-rift clastic sediments at two different depth intervals from two wells [well A (2160–2274 m) and well B (5222–5303 m)], in the Krishna–Godavari basin, India, are used for this study. Shear velocity (V_S) estimated using modelled pore aspect ratio offers a high correlation coefficient (>0.95 for both the wells) with measured data. The modelled pore aspect ratio distribution suggests the decrease in pore aspect ratio for the deeper interval, mainly due to increased effective vertical stress. The pore aspect ratio analysis in relation to total porosity and volume of clay reveals that the clay volume has insignificant influence in shaping the pore geometry in the studied intervals. An approach based on multiple linear regression method effectively predicts velocity as a linear function of total porosity, the volume of clay and the modelled pore-space aspect ratio of the rock. We achieved a significant match between measured and predicted velocities. The correlation coefficients between measured and modelled velocities are considerably high (approximately 0.85 and 0.8, for V_P and V_S, respectively). This process indicates the possible influence of pore geometry along with total porosity and volume of clay on velocity.  相似文献   

Constraints from monazite and xenotime growth modelling in the MnCKFMASH‐PYCe system on the P–T path of a metapelite from Shillong‐Meghalaya Plateau: implications for the Indian shield assembly          下载免费PDF全文

N. Chatterjee 《Journal of Metamorphic Geology》2017,35(4):393-412

The Palaeo‐Mesoproterozoic metapelite granulites from northern Garo Hills, western Shillong‐Meghalaya Gneissic Complex (SMGC), northeast India, consist of resorbed garnet, cordierite and K‐feldspar porphyroblasts in a matrix comprising shape‐preferred aggregates of biotite±sillimanite+quartz that define the penetrative gneissic fabric. An earlier assemblage including biotite and sillimanite occurs as inclusions within the garnet and cordierite porphyroblasts. Staurolite within cordierite in samples without matrix sillimanite is interpreted to have formed by a reaction between the sillimanite inclusion and the host cordierite during retrogression. Accessory monazite occurs as inclusions within garnet as well as in the matrix, whereas accessory xenotime occurs only in the matrix. The monazite inclusions in garnet contain higher Ca, and lower Y and Th/U than the matrix monazite outside resorbed garnet rims. On the other hand, matrix monazite away from garnet contains low Ca and Y, and shows very high Th/U ratios. The low Th/U ratios (<10) of the Y‐poor garnet‐hosted monazite indicate subsolidus formation during an early stage of prograde metamorphism. A calculated P–T pseudosection in the MnCKFMASH‐PYCe system indicates that the garnet‐hosted monazite formed at <3 kbar/600 °C (Stage A). These P–T estimates extend backward the previously inferred prograde P–T path from peak anatectic conditions of 7–8 kbar/850 °C based on major mineral equilibria. Furthermore, the calculated P–T pseudosections indicate that cordierite–staurolite equilibrated at ~5.5 kbar/630 °C during retrograde metamorphism. Thus, the P–T path was counterclockwise. The Y‐rich matrix monazite outside garnet rims formed between ~3.2 kbar/650 °C and ~5 kbar/775 °C (Stage B) during prograde metamorphism. If the effect of bulk composition change due to open system behaviour during anatexis is considered, the P–T conditions may be lower for Stage A (<2 kbar/525 °C) and Stage B (~3 kbar/600 °C to ~3.5 kbar/660 °C). Prograde garnet growth occurred over the entire temperature range (550–850 °C), and Stage‐B monazite was perhaps initially entrapped in garnet. During post‐peak cooling, the Stage‐B monazite grains were released in the matrix by garnet dissolution. Furthermore, new matrix monazite (low Y and very high Th/U ≤80, ~8 kbar/850–800 °C, Stage C), some monazite outside garnet rims (high Y and intermediate Th/U ≤30, ~8 kbar/800–785 °C, Stage D), and matrix xenotime (<785 °C) formed through post‐peak crystallization of melt. Regardless of textural setting, all monazite populations show identical chemical ages (1630–1578 Ma, ±43 Ma). The lithological association (metapelite and mafic granulites), and metamorphic age and P–T path of the northern Garo Hills metapelites and those from the southern domain of the Central Indian Tectonic Zone (CITZ) are similar. The SMGC was initially aligned with the southern parts of CITZ and Chotanagpur Gneissic Complex of central/eastern India in an ENE direction, but was displaced ~350 km northward by sinistral movement along the north‐trending Eastern Indian Tectonic Zone in Neoproterozoic. The southern CITZ metapelites supposedly originated in a back‐arc associated with subducting oceanic lithosphere below the Southern Indian Block at c. 1.6 Ga during the initial stage of Indian shield assembly. It is inferred that the SMGC metapelites may also have originated contemporaneously with the southern CITZ metapelites in a similar back‐arc setting.  相似文献   

Galactic models in the light of collision dynamics     

Tapan K. Chatterjee 《Astrophysics and Space Science》1990,163(1):127-142

A simple and flexible model of a spiral galaxy is developed in the light of the study of the dynamics of colliding galaxies. As such interactions are strongly characterised by the binding energy distributions of the systems involved; hence, the main criterion used in constructing the model is its compatibility with the observed shapes and intensity distribution of light of spirals. The model basically consists of thick exponential disk component and a spherical polytropic bulge component. The relevant quantities pertaining to the model, significant for dynamical studies, are computed and analysed.The study of the dynamics of colliding galaxies require galactic models with and without halos, depending upon the problem under study and the effects to be accessed. Consequently, we have preferred to tackle the problem of galactic models with massive halos separately in the next paper.  相似文献   

A dynamical study of the frequency of merging galaxies     

Tapan K. Chatterjee 《Astrophysics and Space Science》1987,137(2):267-279

A study of the expected frequency of merging galaxies, involving spherical systems, is conducted, using the impulsive approximation. Results indicate that the expected frequency of such galaxies is several orders of magnitude smaller than the observational value, if mergers taking place only in a single crossing time are considered. This aspect will be further investigated in the continuing series of papers.  相似文献   

The formation of a ring galaxy during a head-on collision between a disk and a spherical galaxy     

Tapan K. Chatterjee 《Astrophysics and Space Science》1981,76(2):491-502

The tidal force effects of a spherical galaxy passing head-on through a disk galaxy have been studied at various regions of the disk galaxy and for various orientations of the disk galaxy with respect to the direction of relative motion of the two galaxies. The density distribution of the disk galaxy is taken to be, (r)=_ce^–4r/R , where _c is the central density andR is the radius of the disk. The density distribution of the spherical galaxy is taken to be that of a oolytrope of indexn=4. It is found that as a result of the collision, through the central parts and the outer parts of the disk galaxy remain intact, the region in between these two regions disrupts. Thus a ring galaxy with a nucleus embedded in the ring-i.e., a ring galaxy of the RN-type, is formed.  相似文献   

Long-period fading in atmospherics during severe meteorological activity and associated solar geophysical phenomena at low latitudes     

A. B. Bhattacharya  S. K. Kar  M. K. Chatterjee  R. Bhattacharya 《Annales Geophysicae》1998,16(2):183-188

The records of VLF atmospherics over Calcutta and then over Kalyani (West Bengal) during the torrential rainfall, caused by violent monsoon and post-monsoon depressions, exhibit distinct long-period fadings both at day and night. Interesting results obtained from an analysis of round-the-clock atmospherics data and associated meteorological parameters are reported in this paper. A possible correlation between the severe meteorological activity with the solar geophysical phenomena was studied. The results are indicative of an interesting sequence of solar-terrestrial events. A tentative conclusion is reached, suggesting an origin of the fading from atmospheric gravity waves generated in the centre of activity of the depressions concerned.Currently at: Department of Physics, Serampore College, Serampore, 712 201 West Bengal  相似文献   

Crustal thickness,rift‐drift and potential links to key global events     

Timothy Paulsen  Chad Deering  Jakub Sliwinski  Snehamoy Chatterjee  Olivier Bachmann  Marcel Guillong 《地学学报》2021,33(1):12-20

Orogenic crustal thickening leads to increased continental elevation and runoff into the oceans, but there are fundamental uncertainties in the temporal patterns of thickening through Earth history. U‐Pb age and trace element data in detrital zircons from Antarctica are consistent with recent global analyses suggesting two dominant peaks in average crustal thickness from ~2.6 to 2.0 Ga and ~0.8 to 0.5 Ga. Shifts in marine carbonate ⁸⁷Sr/⁸⁶Sr ratios show two primary peaks that post‐date these crustal thickness peaks, suggesting significant weathering and erosion of global continental relief. Both episodes correlate well with zircon trace element and isotope proxies indicating enhanced crustal and fluid input into subduction zone magmas. Increased crustal thickness correlates with increased passive margin abundance and overlaps with snowball Earth glaciations and atmospheric oxygenation, suggesting a causal link between continental rift‐drift phases and major transitions in Earth's atmospheric and oceanic evolution.  相似文献   

Step-wise Land-class Elimination Approach for extracting mixed-type built-up areas of Kolkata megacity     

Ansar Khan  Soumendu Chatterjee  Hashem Akbari  Saad Saleem Bhatti  Apurba Dinda  Chandana Mitra 《国际地球制图》2019,34(5):504-527

The extraction of urban built-up areas is an important aspect of urban planning and understanding the complex drivers and biophysical mechanism of urban climate processes. However, built-up area extraction using Landsat data is a challenging task due to spatio-temporal dynamics and spatially intermixed nature of Land Use and Land Cover (LULC) in the cities of the developing countries, particularly in tropics. In the light of advantages and drawbacks of the Normalized Difference Built-up Index (NDBI) and Built-up Area Extraction Method (BAEM), a new and simple method i.e. Step-wise Land-class Elimination Approach (SLEA) is proposed for rapid and accurate mapping of urban built-up areas without depending exclusively on the band specific normalized indices, in order to pursue a more generalized approach. It combines the use of a single band layer, Normalized Difference Vegetation Index (NDVI) image and another binary image obtained through Logit model. Based on the spectral designation of the satellite image in use, a particular band is chosen for identification of water pixels. The Double-window Flexible Pace Search (DFPS) approach is employed for finding the optimum threshold value that segments the selected band image into water and non-water categories. The water pixels are then eliminated from the original image. The vegetation pixels are similarly identified using the NDVI image and eliminated. The residual pixels left after elimination of water and vegetation categories belong either to the built-up areas or to bare land categories. Logit model is used for separation of the built-up areas from bare lands. The effectiveness of this method was tested through the mapping of built-up areas of the Kolkata Metropolitan Area (KMA), India from Thematic Mapper (TM) images of 2000, 2005 and 2010, and Operational Land Imager (OLI) image of 2015. Results of the proposed SLEA were 95.33% accurate on the whole, while those derived by the NDBI and BAEM approaches returned an overall accuracy of 83.67% and 89.33%, respectively. Comparisons of the results obtained using this method with those obtained from NDBI and BAEM approaches demonstrate that the proposed approach is quite reliable. The SLEA generates new patterns of evidence and hypotheses for built-up areas extraction research, providing an integral link with statistical science and encouraging trans-disciplinary collaborations to build robust knowledge and problem solving capacity in urban areas. It also brings landscape architecture, urban and regional planning, landscape and ecological engineering, and other practice-oriented fields to bear together in processes for identifying problems and analyzing, synthesizng, and evaluating desirable alternatives for urban change. This method produced very accurate results in a more efficient manner compared to the earlier built-up area extraction approaches for the landscape and urban planning.  相似文献   

An intercontinental correlation of the mid-Neoproterozoic Eastern Indian tectonic zone: evidence from the gneissic clasts in Elan Bank conglomerate, Kerguelen Plateau     

Nilanjan Chatterjee  Kirsten Nicolaysen 《Contributions to Mineralogy and Petrology》2012,163(5):789-806

The Kerguelen Plateau is a submarine, Cretaceous Large Igneous Province in the southern Indian Ocean. Drilling on Elan Bank, a western salient of the Kerguelen Plateau, yielded a ~26 m section of fluvial conglomerate intercalated with basalt. Chemical dating of monazite within garnet and matrix monazite in metapelitic clasts from the conglomerate indicates that high-grade metamorphism of the pelitic protolith occurred between 785 ± 12 and 694 ± 18 Ma. A calculated P–T pseudosection indicates that the observed core-to-inner rim compositional zoning in garnet is consistent with P/T decrease from 10.2 kb/760°C to 6.2 kb/560°C. In an Early Cretaceous paleogeographic reconstruction, the Elan Bank drill site is located on a SSW continuation of the Eastern Indian Tectonic Zone (EITZ), a 876–784 Ma, NNE–SSW metamorphic belt with sinistral shear zones in eastern India. The retrograde P–T path of the Elan Bank metapelitic clast overlaps with that of the EITZ metapelite, and the Elan Bank monazite chemical dates and previously determined 824–675 Ma U–Pb isotope monazite dates by the TIMS method are remarkably similar to the monazite chemical dates from the EITZ metapelites and high-grade metamorphic rocks from the eastern margin of the Eastern Ghats Belt. Based on the demonstrable affinity of metamorphic, geochronologic, and spatial data, this study concludes that the EITZ was likely a continuous, ~1,800–km-long tectono-metamorphic belt in the Rodinia supercontinent stretching from eastern India through the Eastern Ghats to the basement of Elan Bank and probably to the Rayner Complex of East Antarctica.  相似文献