Particle precipitation in Brazilian geomagnetic anomaly during magnetic storms     

N.B. Trivedi  D.B. Rai  I.M. Martin  J.M. Da Costa 《Planetary and Space Science》1973,21(10):1699-1704

Particle precipitation in Brazilian geomagnetic anomaly during magnetic storms is investigated using riometer and VLF propagation data. It is found that during large storms the changes in the ionosphere caused by particle precipitation are detectable. There is a good correlation between the behavior of the absorption and the variations of the magnetic field intensity during different phases of a storm. In particular, there seems to be a close relationship between the precipitation of high energy particles and short-period fluctuations of the magnetic field intensity of the order of 5–6 min. During the main phase of the storm, when the field intensity reaches its minimum, the flux of soft electrons also plays a significant role in producing absorption. The nature of precipitation associated with a sudden commencement appears to be more complex; the predominance of low or high energy particle flux may depend on the magnitude of the field increase. The amplitude and phase records of VLF signals also show the effect of the disturbance, but it is difficult to correlate the changes in these records with the features observed on the magnetogram, because only a small part of the propagation path lies in the region of the anomaly. A more detailed analysis of riometer data from different stations and VLF phase and amplitude records for different paths will be helpful in understanding the mechanism of particle precipitation associated with magnetic disturbances. In future experiments it may also be fruitful to look for detectable radiation emitted by the precipitating electrons, for example, Cherenkov and synchrotron radiation.  相似文献   

Reservoir Geological Uncertainty Reduction: an Optimization-Based Method Using Multiple Static Measures     

Shahed Rahim  Zukui Li  Japan Trivedi 《Mathematical Geosciences》2015,47(4):373-396

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Characterization of Non-Gaussian Geologic Facies Distribution Using Ensemble Kalman Filter with Probability Weighted Re-Sampling     

Siavash Nejadi  Juliana Leung  Japan Trivedi 《Mathematical Geosciences》2015,47(2):193-225

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Hydrogeochemical attributes of the meltwater emerging from Gangotri glacier, uttaranchal     

Shashikant Trivedi  K. Gopal  Jaswant Singh 《Journal of the Geological Society of India》2010,76(2):105-110

The river at its origin known as “Bhagirathi” attains the title “Ganga” after its confluence with Alaknanda, originates from the snout of Gangotri glacier. Water samples were collected from the selected sites from Gaumukh to Haridwar (2000–2001) for two seasons (pre-monsoon and post-monsoon) and analyzed for various physico-chemical characteristics. The pH, nitrate (NO₃), conductance, chloride, alkalinity, total hardness, fluoride, sulphate and total dissolved solids were found to be in the ranges of 6.0–7.6, 0.225–10.6 mg/l, 73.0–978 μmhos, 5.0–70.0 mg/l, 15–90 mg/l, 10.0–250.0 mg/l, 0.23–1.60 mg/l, 12.0–150.0 mg/l and 37.0–190.6 mg/l respectively.  相似文献   

Kerr — Newman metric in cosmological background     

L. K. Patel  Hiren B. Trivedi 《Journal of Astrophysics and Astronomy》1982,3(1):63-67

A new solution of Einstein-Maxwell field equations is presented. The material content of the field described by this solution is a perfect fluid plus sourceless electromagnetic fields. The metric of the solution is explicitly written. This metric is examined as a possible representation of Kerr-Newman metric embedded in Einstein static universe. The Kerr-Newman metric in the background of Robertson-Walker universe is also briefly described.  相似文献   

Trace element and isotopic studies of Permo-Carboniferous carbonate nodules from Talchir sediments of peninsular India: Environmental and provenance implications     

Prosenjit Ghosh  S. K. Bhattacharya  A. M. Dayal  J. R. Trivedi  M. Ebihara  M. M. Sarin  A. Chakrabarti 《Journal of Earth System Science》2002,111(2):87-93

Syngenetic carbonate nodules constitute an interesting feature of the glaciogene sediments of various Talchir basins in peninsular India. Petrographic, cathodoluminescence and sedimentary results suggest that many of these nodules contain primary carbonate precipitates whose geochemical signatures can be used for determining environment of deposition and provenance of the sediments and drainage source. Several nodules were collected from Gondwana basins of east-central India and analyzed for stable carbon and oxygen isotope ratios, REE and trace element composition, and Sr isotope ratio. The mean δ¹⁸O and δ¹³C values of the calcites in the nodules are — 19.5% and-9.7% (w.r.t. PDB) respectively suggesting a freshwater environment (probably lacustrine) for formation of these objects. Trace element ratios (Eu/Eu * and La/Yb) of the nodule samples show that the source of the sediments in the Damodar valley basin was the granites, gneisses and intrusives in the Chotanagpur region. The sediments in the Mahanadi valley were derived from granulites, charnockites and granites of the eastern ghat region. The Sr concentration of the carbonate phase of the nodules is low, ranging from 10–60 ng/g. The⁸⁷Sr/⁸⁶Sr ratios of the samples from the west Bokaro basin and Ramgarh basin vary from 0.735 to 0.748 (mean: 0.739) and from 0.726 to 0.733 (mean: 0.730) respectively. These values are consistent with our proposition that water of these basins drained through the granitic rocks of the Chotanagpur region. In contrast, the⁸⁷Sr/⁸⁶Sr ratios of the samples from the Talchir basin (Type area) of Mahanadi valley vary from 0.718 to 0.723 (mean: 0.719). These⁸⁷Sr/⁸⁶Sr ratios are close to those of the granulites in the adjoining eastern ghat belt suggesting that area as the drainage source.  相似文献   

Settlement of compacted ash fills   总被引：1，自引：0，他引：1  

Ashutosh Trivedi  Vijay K. Sud 《Geotechnical and Geological Engineering》2007,25(2):163-176

The coal ash is a by-product of coal-fired thermal power station. It is extensively used as a geo-material for landfill. The compacted ash is used as a structural fill if it is properly characterized for load-bearing capacity and settlement. The main objective of the present work is to characterize ash material and to evaluate its settlement characteristics. The ash is normally compacted by vibration at or near optimum moisture for its performance as structural fill. The overt characteristics of ashes are viewed similar to cohesionless soils. However, the mass behavior may have differences due to the subtle influence of chemical and physical processes involved in its formation. The empirical and analytical methods predicting settlement of footing under static loading require direct or indirect measurement of density and stress state in the deposit. In the present work, experimental investigations for settlement prediction were carried out on compacted coal ash produced at Ropar thermal power station in India, which was conveniently classified as ASTM class F ash. The settlement was experimentally obtained for the rigid plates having least dimension more than 0.3 m on ashes compacted at varying degree of compaction. The predicted settlement based on the observed data of coal ash using conventional techniques for soils was found to be conservative. A relationship between settlement and foundation size is proposed at varying compaction to obtain the settlement of compacted ash. At a higher degree of compaction, the settlement of a foundation may not exceed the allowable settlements in the working stress range.  相似文献   

An equivalent-boundary method for the shell analysis of buried pipelines under fault movement   总被引：2，自引：0，他引：2  

刘爱文  胡聿贤  赵凤新  李小军  高田至郎  赵雷 《地震学报(英文版)》2004,17(Z1)

Introduction The history of research work on the response of buried pipeline under the fault movement hasbeen about 30 years. Several simplified design methods have been proposed to obtain the maxi-mum stress or strain in pipe. These methods include the theoretical method and the finite elementmethod (FEM). In the theoretical method, the pipe is usually modeled as a cable (Newmark, Hall1975; Kennedy, et al, 1977) or a beam (Wang, Wang, 1995; LIU, ZHANG, 2002). These theoreti-cal me…  相似文献   

植物生理学与地球物理学的结合点     

鸟山英雄  邹而联  苏丛柏 《山西地震》2002,(1):33-36

介绍了含羞草在台风前及榉树、枫树、山茶、月桂等树木生物电位在地震前的异常变化 ,指出了植物生理电位与地震前兆现象之间存在的相关关系 ,找到了植物生理学与地球物理学的结合点  相似文献   

含天然气水合物沉积物的岩石物性模型与似海底反射层的AVA特征   总被引：19，自引：5，他引：19       下载免费PDF全文

宋海斌  杨胜雄  吴能友  江为为  郝天珧 《地球物理学报》2002,45(4):546-556

研究含天然气水合物沉积物的岩石物性模型与似海底反射层的振幅随入射角变化(AVA)特征. 基于时间平均-Wood加权方程、三相介质波传播理论模型和弹性模量模型,计算并阐述含天然气水合物岩石弹性参数与水合物饱和度、含游离气岩石弹性参数与游离气饱和度的关系;给出不同模型AVA特征. 结果表明,不同天然气水合物饱和度、不同游离气饱和度的各种组合呈现形态相似但反射系数值不同的AVA特征.  相似文献