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71.
ABSTRACT This paper presents an analysis of trends in six drought variables at 566 stations across India over the period 1901–2002. Six drought variables were computed using standardized precipitation index (SPI). The Mann-Kendall (MK) trend test and Sen’s slope estimator were used for trend analysis of drought variables. Discrete wavelet transform (DWT) was used to identify the dominant periodic components in trends, whereas the significance of periodic components was examined using continuous wavelet transform (CWT) based global wavelet spectrum (GWS). Our results show an increasing trend in droughts in eastern, northeastern and extreme southern regions, and a decreasing trend in the northern and southern regions of the country. The periodic component influencing the trend was 2–4 years in south, 4–8 years in west, east and northeast, 8–64 years in central parts and 32–128 years in the north; however, most of the periodic components were not statistically significant. 相似文献
72.
73.
Alok K. Gupta Kosuke Onuma Kenzo Yagi Edward G. Lidiak 《Contributions to Mineralogy and Petrology》1973,41(4):333-344
The effect of silica concentration on the solubility of Al and Ti in diopsidic pyroxenes has been investigated at one atmosphere in the system diopside-CaTiAl2O6-SiO2 at temperatures between 1150–1420° C. The composition of pyroxene in the system diopside-CaTiAl2O6-SiO2 is influenced by the total SiO2 content. Near the join diopside-CaTiAl2O6, the pyroxene forms a solid solution with the CaTiAl2O6 molecule, and co-exists with perovskite for compositions greater than 11 weight percent CaTiAl2O6. Anorthite is an accompanying phase. With increasing total SiO2 content a series of mineralogical changes involving Ti-bearing phases occur. Sphene solid solution co-exists with diopside solid solution, anorthite, and perovskite in a small compositional range near the diopside-CaTiAl2O6 join. Additional total SiO2 results in the elimination of perovskite and a decrease of solid solution in the pyroxenes. With further increase in SiO2 content, tridymite appears and the pyroxene is approximately pure diopside. Rutile joins diopside, anorthite, sphene solid solution and tridymite over a broad compositional range in the Ti, Si-rich part of the system. These results demonstrate that increased silica concentration decreases the solubility of Al and Ti in diopsidic pyroxenes and controls the stability of co-existing Ti-bearing phases. 相似文献
74.
D. Singh C. V. V. Bhadram S. Goyal G. S. Mandal 《Theoretical and Applied Climatology》1996,54(3-4):117-123
Summary Analysis of mean sea level pressure (1925 to 1988) over the North Pacific Ocean (NPP) for the winter period (November to March) revealed a significant correlation with Indian Monsoon rainfall during the later period. Its correlation coefficients (CC) for different periods (during 1951–1988) are significant at the 1% to 5% levels. The temporal stability of these CCs is examined using 11, 21 and 31 year sliding windows. NPP is seen to play an important role in the regression models as revealed by the relative significance of its partial regression coefficients. The regression models developed are seen to perform well for the independent period.With 5 Figures 相似文献
75.
Goyal RS 《Population geography : a journal of the Association of Population Geographers of India》1988,10(1-2):61-72
Regional variations in the demography of India are explored using official data for the period 1971-1981. Socioeconomic and cultural determinants of such differentials, particularly female education and economic diversification, are addressed. 相似文献
76.
Siddharth Hariharan Siddhesh Tirodkar Alok Porwal Avik Bhattacharya Aurore Joly 《Natural Resources Research》2017,26(4):489-507
Data-driven prospectivity modelling of greenfields terrains is challenging because very few deposits are available and the training data are overwhelmingly dominated by non-deposit samples. This could lead to biased estimates of model parameters. In the present study involving Random Forest (RF)-based gold prospectivity modelling of the Tanami region, a greenfields terrain in Western Australia, we apply the Synthetic Minority Over-sampling Technique to modify the initial dataset and bring the deposit-to-non-deposit ratio closer to 50:50. An optimal threshold range is determined objectively using statistical measures such as the data sensitivity, specificity, kappa and per cent correctly classified. The RF regression modelling with the modified dataset of close to 50:50 sample ratio of deposit to non-deposit delineates 4.67% of the study area as high prospectivity areas as compared to only 1.06% by the original dataset, implying that the original “sparse” dataset underestimates prospectivity. 相似文献
77.
Kumar Gulshan Bhadwal Reetika Kumar Mukesh Kumari Punam Kumar Arvind Walia Vivek Mehra Rohit Goyal Ayush 《Natural Hazards》2022,111(3):2219-2240
Natural Hazards - This work reports radon-thoron monitoring at two depths (60 and 90 cm) and at 82 sites around Jawalamukhi thrust of NW Himalaya, India using Solid State Nuclear Track... 相似文献
78.
Abhinay Sharma Alok Kumar Praveer Pankaj Dinesh Pandit Ramananda Chakrabarti N.V. Chalapathi Rao 《地学前缘(英文版)》2019,10(3):1167-1186
Detailed mineralogical, bulk-rock geochemical and Sr-Nd isotopic data for the recently discovered Ahobil kimberlite(Pipe-16) from the Wajrakarur kimberlite field(WKF), Eastern Dharwar craton(EDC),southern India, are presented. Two generations of compositionally distinct olivine, Ti-poor phlogopite showing orangeitic evolutionary trends, spinel displaying magmatic trend-1, abundant perovskite, Tirich hydrogarnet, calcite and serpentine are the various mineral constituents. On the basis of(i) liquidus mineral composition,(ii) bulk-rock chemistry, and(iii) Sr-Nd isotopic composition, we show that Ahobil kimberlite shares several characteristic features of archetypal kimberlites than orangeites and lamproites. Geochemical modelling indicate Ahobil kimberlite magma derivation from small-degree melting of a carbonated peridotite source having higher Gd/Yb and lower La/Sm in contrast to those of orangeites from the Eastern Dharwar and Bastar cratons of Indian shield. The TDm Nd model age(~2.0 Ga) of the Ahobil kimberlite is(i) significantly older than those(1.5~1.3 Ga) reported for Wajrakarur and Narayanpet kimberlites of EDC,(ii) indistinguishable from those of the Mesoproterozoic EDC lamproites,and(iii) strikingly coincides with the timing of the amalgamation of the Columbia supercontinent. High bulk-rock Fe-Ti contents and wide variation in oxygen fugacity fO_2, as inferred from perovskite oxybarometry, suggest non-prospective nature of the Ahobil kimberlite for diamond. 相似文献
79.
Douglas M. Mackay Murray D. Einarson Phil M. Kaiser Mamie Nozawa‐Inoue Sham Goyal Irina Chakraborty Ehsan Rasa Kate M. Scow 《Ground water》2012,50(6):895-907
A tracer plume was created within a thin aquifer by injection for 299 d of two adjacent “sub‐plumes” to represent one type of plume heterogeneity encountered in practice. The plume was monitored by snapshot sampling of transects of fully screened wells. The mass injection rate and total mass injected were known. Using all wells in each transect (0.77 m well spacing, 1.4 points/m2 sampling density), the Theissen Polygon Method (TPM) yielded apparently accurate mass discharge (Md) estimates at three transects for 12 snapshots. When applied to hypothetical sparser transects using subsets of the wells with average spacing and sampling density from 1.55 to 5.39 m and 0.70 to 0.20 points/m2, respectively, the TPM accuracy depended on well spacing and location of the wells in the hypothesized transect with respect to the sub‐plumes. Potential error was relatively low when the well spacing was less than the widths of the sub‐plumes (>0.35 points/m2). Potential error increased for well spacing similar to or greater than the sub‐plume widths, or when less than 1% of the plume area was sampled. For low density sampling of laterally heterogeneous plumes, small changes in groundwater flow direction can lead to wide fluctuations in Md estimates by the TPM. However, sampling conducted when flow is known or likely to be in a preferred direction can potentially allow more useful comparisons of Md over multiyear time frames, such as required for performance evaluation of natural attenuation or engineered remediation systems. 相似文献
80.
Gopal-Krishna Alok C. Gupta Ram Sagar Paul J. Wiita U. S. Chaubey C. S. Stalin 《Monthly notices of the Royal Astronomical Society》2000,314(4):815-825
We report results of the observations at the Vainu Bappu Observatory and the Uttar Pradesh State Observatory of eight radio-quiet quasi-stellar objects (RQQSOs) during 1996–99. This is a part of our ongoing programme to search for intranight optical variability in RQQSOs. Additional evidence for very rapid variability in three of the five optically bright and very luminous RQQSOs we had observed earlier, 1049−006, 1444+408 and 1630+377, was found. Of the three newly observed RQQSOs, the data for 0043+039 are too noisy to allow conclusions about variability to be drawn, but 0748+294 and 0824+098 show strong hints of microvariability. We also present a summary of the results from our entire programme to date, which includes observations of 16 radio-quiet QSOs and one radio-weak QSO, and compare the general properties of rapid variability in radio-quiet versus radio-loud AGN as determined from our work and that of several other groups. Observations of this kind are likely to play a key role in understanding the relative contributions of accretion discs and relativistic plasma jets to rapid optical fluctuations of AGN. 相似文献