花岗岩—H₂O—HF体系相关系及氟对花岗质熔体结构的影响   总被引：4，自引：0，他引：4  

熊小林  朱金初 《地质科学》1997,32(1):1-10

通过在0.1GPa压力下钠长花岗岩-H₂O-HF体系相关系实验获得,随体系F含量的增加,石英的温度稳定域上限升高,长石的温度稳定域上限降低;石英、碱性长石的晶-液平衡热力学计算表明,F导致花岗质熔体中组分SiO₂的活度增加,组分NaAlSi₃O₈和KAlSi₃O₈的活度减小,且NaAlSi₃O₈活度较KAlSi₃O₈活度减小幅度大。这些结果显示了F在花岗质熔体中与Si以外的阳离子Al、Na、K等产生了结合,且F与Na结合的优先性大于K,破坏了具有电荷平衡离子Na、K的AlO₂^-四面体,使熔体架状网格中Si/(Si+Al)和K/Na比值增大。通过F与H₂O对花岗岩体系相平衡的影响比较,作者认为F不与Si结合是它与OH^-在干扰熔体结构方面的最大区别。  相似文献   

Potential of satellite data in delineation of wastelands and correlation with ground information     

R. Sugumaran  G. Sandhya  K. S. Rao  R. N. Jadhav  M. M. Kimothi 《Journal of the Indian Society of Remote Sensing》1994,22(2):113-118

In the present study an attempt has been made to delineate the wastelands at microlevel in Matar taluka of Kheda district. IRS OSS II digital data of 1991 has been used for the study which was analysed on VAX 11/780 image processing system. The digital data was classified following supervised classification algorithm. The three types of wastelands namely waterlogged, pasture/grazing and salt affected lands could be identified and mapped. The area statistics for the different wasteland categories present in the taluka were generated. Chemical analysis was also carried out for soils collected from different categories of wastelands to understand the exact nature of soils of each category.  相似文献   

Orbital elements and evolutionary nature of the long period RS CVn type eclipsing binary RZ eridani     

P. Vivekananda Rao  M. B. K. Sarma  B. V. N. S. Prakash Rao 《Journal of Astrophysics and Astronomy》1994,15(2):165-178

Light curves of the long period RS CVn type eclipsing binary RZ Eri, obtained during the period 1976–1979 with the 1.2 m telescope of the Japal-Rangapur Observatory are analysed, using Wilson-Devinney method, by fixing the two parametersT _h (7400°K) andq(0.963), resulting in the following absolute elements:A = 72.5 ± 1.4R _⊙,R _h = 2.84 ± 0.12R _⊙,R _c = 6.94 ± 0.20R _⊙,M _bol,_h = 1.35 ± 0.28,M _bol ,_c= 1.41 ± 0.28,m _h = 1.69 ± 0.6m _⊙ andmc= 1.63 ± 0.13m _⊙. The presence of humps and dips of varying amplitudes at a few phases in the normal UBV light curves is explained as due to residual distortion wave. The derived (B-V) and (U-B) colours of both the components appear to have been reddened to an extent of 0 ^m .20 in (B-V) and 0 ^m .16 in (U-B) colours. This reddening is attributed to the presence of an envelope around the system, the material of which might have come from the loss of mass experienced by the evolving cooler component. Taking into consideration the dereddened colours and temperatures of the components, spectral types ofF0 IV for the primary and G 5–8 III–IV for the secondary component were derived. The fractional radii of 0.039 and 0.096 of the two components, when compared with the radii of their critical Roche lobes of 0.378 and 0.372 suggest that these components are well within their critical sizes. From the position of the components on the. isochrones and the evolutionary tracks of stars of Pop I composition computed by Maeder & Meynet, it is concluded that the evolution of the components of RZ Eri is abnormal. This system is found to be situated at a distance of 185 pc, with an age of about 2.5 × 10⁹ yrs.  相似文献   

Structural interpretation of the Konkan basin,southwestern continental margin of India,based on magnetic and bathymetric data     

V. Subrahmanyam  K. S. Krishna  G. P. S. Murthy  D. Gopala Rao  M. V. Ramana  M. Gangadhara Rao 《Geo-Marine Letters》1994,14(1):10-18

Magnetic and bathymetric studies on the Konkan basin of the southwestern continental margin of India reveal prominent NNW-SSE, NW-SE, ENE-WSW, and WNW-ESE structural trends. The crystalline basement occurs at about 5–6 km below the mean sea level. A mid-shelf basement ridge, a shelf margin basin, and the northern extension of the Prathap Ridge complex are also inferred. The forces created by the sea-floor spreading at Carlsberg Ridge since late Cretaceous appears to shape the present-day southwestern continental margin of India and caused the offsets in the structural features along the preexisting faults.  相似文献   

The influence of wave-current sea states on the reliability estimates of offshore towers     

S. Gomathinayagam  M.V. Dharaneepathy  M.N. Keshava Rao 《Ocean Engineering》1990,17(1-2)

Since offshore towers are high-cost, high-risk structures, reliability analysis is of great importance in their design. This paper presents a possible practical approach to certify a design through selective critical member reliability estimates. After a brief review of current research in this field, the authors outline a procedure for reliability estimation of structural members in extreme stress and fatigue limit states. A spectral approach for the extreme response statistics with stochastic loading is described. The reliabilities are computed by the Level II first-order second moment (advanced) method. The fatigue reliability is estimated with a narrow-banded stress assumption with discrete, but significant sea states within the life of the structure. Two numerical examples, a three shallow water model and a two-dimensional deep water model are presented along with the influences of stochastic variables (sea state, current, tubular member diameter) on reliabilities (extreme stress and fatigue damage).  相似文献   

Sea Level Variations Associated with Upwelling/ Downwelling Along the West Coast of India     

A. D. Rao  S. V. Babu  Madhu Sharma 《Marine Geodesy》2001,24(3):153-170

A three-dimensional numerical model is developed and used to study the coastal upwelling processes and corresponding seasonal changes in the sea level along the west coast of India. The upwelling and associated sea level variations are seen as a response of coastal ocean to pure wind stress forcing. The model is designed to represent coastal ocean physics by resolving surface and bottom Ekman layers as realistically as possible. The prognostic variables are the three components of the velocity field, temperature, salinity and turbulent energy. The governing equations together with their boundary conditions are solved by finite-difference techniques. Experiments are performed to investigate sea level fluctuations associated with the thermal response and alongshore currents of the coastal waters. The model is forced with mean monthly wind stress forcing of January, May, July and September representing northeast monsoon and different phases of the southwest monsoon. It is known from the observational study that the upwelling process reaches to the surface waters by May along the coastal waters of the extreme southwest peninsular region. The process is more intense in July compared to May and September and its strength decreases from south to north. However, during the northeast monsoon season, which is represented by January wind stress forcing in the model, downwelling is simulated along the coast. The model simulations of the coastal response are compared with the observations and are found to be in good agreement. The maximum computed vertical velocity of about 2.0 ×10 -3 cm s -1 is predicted in July in the southern region off the coast.  相似文献   

Assessing the consistency between AVHRR and MODIS NDVI datasets for estimating terrestrial net primary productivity over India     

R K Nayak  N Mishra  V K Dadhwal  N R Patel  M Salim  K H Rao  C B S Dutt 《Journal of Earth System Science》2016,125(6):1189-1204

This study examines the consistency between the AVHRR and MODIS normalized difference vegetation index (NDVI) datasets in estimating net primary productivity (NPP) and net ecosystem productivity (NEP) over India during 2001–2006 in a terrestrial ecosystem model. Harmonic analysis is employed to estimate seasonal components of the time series. The stationary components (representing long-term mean) of the respective NDVI time series are highly coherent and exhibit inherent natural vegetation characteristics with high values over the forest, moderate over the cropland, and small over the grassland. Both data exhibit strong semi-annual oscillations over the cropland dominated Indo-Gangetic plains while annual oscillations are strong over most parts of the country. MODIS has larger annual amplitude than that of the AVHRR. The similar variability exists on the estimates of NPP and NEP across India. In an annual scale, MODIS-based NPP budget is 1.78 PgC, which is 27% higher than the AVHRR- based estimate. It revealed that the Indian terrestrial ecosystem remained the sink of atmospheric CO ₂ during the study period with 42 TgC y ^?1 NEP budget associated with MODIS-based estimate against 18 TgC y ^?1 for the AVHRR-based estimate.  相似文献   

Petrology, 40Ar/39Ar age,Sr-Nd isotope systematics,and geodynamic significance of an ultrapotassic (lamproitic) dyke with affinities to kamafugite from the easternmost margin of the Bastar Craton,India     

N. V. Chalapathi Rao  Atiullah  R. Burgess  Purnendu Nanda  A. K. Choudhary  Samarendra Sahoo  B. Lehmann  Ngazipmi Chahong 《Mineralogy and Petrology》2016,110(2-3):269-293

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Inter-seasonal variability of internal tides in the western Bay of Bengal     

Himansu K. Pradhan  A. D. Rao  Sachiko Mohanty 《Natural Hazards》2016,84(2):809-820

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The use and performance of mesoscale models over the Indian region for two high-impact events     

D. R. Sikka  P. Sanjeeva Rao 《Natural Hazards》2008,44(3):353-372

High-impact mesoscale weather events, occurring in different parts of India in all seasons, lead to major weather- and climate-related disasters. Several research groups and operational weather forecasting centres in India have adopted mesoscale models for research and operational usage. This paper reviews the work done by different groups with respect to two specific events, (1) unprecedented locally heavy rainfall near Mumbai (Santa Cruz) on 26 and 27 July 2005 and (2) the Orissa super-cyclone of 29 and 30 October 1999 from its incipient stage on 24 and 25 October 1999. Considerable variability in the prediction of the intensity and location of mesoscale heavy rainfall, as well as in the intensity and path of the super-cyclone, are found. In order to reduce uncertainty in dynamical prediction, it is necessary that the model dynamics, physics, resolution, boundary conditions and availability of data on land–ocean surface processes are tuned separately to the specific event types, such as heavy monsoon rainfall, tropical cyclone genesis and movement and severe local thunderstorms, as the processes controlling such types of events may require suitable treatments for their proper simulations through appropriate dynamics, physics and resolution.  相似文献