Eclipse Observations of Compact Sources in the Outer Solar Corona     

R. Ramesh  K.R. Subramanian  Ch.V. Sastry 《Solar physics》1999,185(1):77-85

We report here on high angular resolution observations of solar noise storm sources at a frequency of 75 MHz. The data for the study were obtained at the Gauribidanur Radio Observatory (long.: 77°2612 E, lat.: 13°3612 N) about 100 km north of Bangalore, India, during the solar eclipse of 24 October 1995. Our main conclusion is that there are structures of angular size 2.5 arc min in the outer solar corona.  相似文献   

Geochemical fractionation of heavy metals in Chilka Lake (east coast of India)—a tropical coastal lagoon   总被引：1，自引：0，他引：1  

D. Panda  V. Subramanian  R. C. Panigrahy 《Environmental Geology》1995,26(4):199-210

Chilka lake, the largest coastal lagoon of Asia is one of the most dynamic ecosystems along the Indian coast. Historically the lagoon has undergone a considerable reduction in surface area due, in part, to input from natural processes but mostly due to human activities. The purpose of this investigation is to document the heavy metals' affinity for specific geochemical phases in the recently deposited sediments in the lagoon. Thirty-three samples were collected and analyzed for different geochemical phases of Fe, Mn, Cu, Cr, Ni, Pb, and Zn utilizing a sequential extraction scheme. In the nonlithogenous fraction, the exchangeable fraction was not geochemically significant, having <2% of the total metal concentration for all the elements. However, the carbonate fraction contained the following percentages of the total concentration: <1% Fe, 13% Mn, 6% Cu, 4% Cr, 8% Ni, 13% Pb, and 12% Zn, suggesting the detrital origin of the sediments. Reducible and organic matter-bound fractions were the significant phases in the nonlithogenous fraction, containing 9% Fe, 16% Mn, 15% Cu, 16% Cr, 16% Ni, 14% Pb, and 14% Zn in the former and 4% Fe, 3% Mn, 17% Cu, 3% Cr, 14% Ni, 15% Pb, and 14% Zn in the latter. The phenomenon has been attributed to the scavenging affinity of Fe-Mn oxides and affinity for sorption into organic matter of the lagoon sediments. The lithogenous, residual fraction generally considered as a guide for natural background values was determined to contain 87% Fe, 67% Mn, 61% Cu, 77% Cr, 61.3% Ni, 56% Pb, and 60% Zn of the total concentrations.  相似文献   

Reduction in the testosterone levels by PCBs and DDE in Dall''s porpoises of northwestern North Pacific     

An. Subramanian  S. Tanabe  R. Tatsukawa  S. Saito  N. Miyazaki 《Marine pollution bulletin》1987,18(12):643-646

The increasing residue levels of PCBs and DDE in the blubber of dalli-type Dall's porpoises were found to have a negative effect on the testosterone levels in blood. Decrease in the levels of testosterone was statistically significant with increase in DDE concentrations. The results obtained suggest that the present levels of environmental contamination by persistent organochlorines can cause an imbalance of sex hormones and subsequent reproductive abnormalities in wild. The other hormone measured, aldosterone, which has no sexual function, was independent of the effects of both PCBs and DDE.  相似文献   

Mass movement studies in Kosi catchment,mepal — A semi quantitative approach using aerial photographs     

S. K. Subramanian  D. P. Rao 《Journal of the Indian Society of Remote Sensing》1986,14(1):61-65

An area of about 5000 sq. km. in the upper parts of river basin of Sun Kosi falling in Nepal has been studied using medium and small scale aerial photographs of two different dates. The temporal variations in relation to mass movements that occur in the study area have been demarcated. The areas which have undergone increased erosion by slope failure and gully erosion over a period of 22 years are evaluated. An attempt has been made to quantify the increase in area of mass movement taking the advantage of three dimensional model of terrain as seen in the aerial photos.  相似文献   

Geochemistry and petrogenesis of lamproites,late cretaceous age,Woodson County,Kansas, U.S.A.     

Robert L. Cullers  Subramanian Ramakrishnan  Pieter Berendsen  Tom Griffin 《Geochimica et cosmochimica acta》1985,49(6):1383-1402

Lamproite sills and their associated sedimentary and contact metamorphic rocks from Woodson County, Kansas have been analyzed for major elements, selected trace elements, and strontium isotopic composition. These lamproites, like lamproites elsewhere, are alkalic (molecular $\text{K}{}_2\text{O + Na}{}_2\text{O}\text{Al}{}_2\text{O}{}_3\text{= 1.6–2.6}$), are ultrapotassic $\text{(}\text{K}{}_2\text{O}\text{Na}{}_2\text{O}\text{= 9.6–150)}$, are enriched in incompatible elements (LREE or light rare-earth elements, Ba, Th, Hf, Ta, Sr, Rb), and have moderate to high initial strontium isotopic compositions (0.7042 and 0.7102). The silica-saturated magma (olivine-hypersthene normative) of the Silver City lamproite could have formed by about 2 percent melting of a phlogopite-garnet lherzolite under high $\text{H}{}_2\text{O}\text{CO}{}_2$ ratios in which the Iherzolite was enriched before melting in the incompatible elements by metasomatism. The Rose Dome lamproite probably formed in a similar fashion although the extreme alteration due to addition of carbonate presumably from the underlying limestone makes its origin less certain. Significant fractional crystallization of phases that occur as phenocrysts (diopside, olivine, K-richterite, and phlogopite) in the Silver City magma and that concentrate Co, Cr, and Sc are precluded as the magma moved from the source toward the surface due to the high abundances of Co, Cr, and Sc in the magma similar to that predicted by direct melting of the metasomatized Iherzolite.Ba and, to a lesser extent, K and Rb and have been transported from the intrusions at shallow depth into the surrounding contact metamorphic zone. The Silver City lamproite has vertical fractionation of some elements due either to volatile transport or to variations in the abundance of phenocrysts relative to groundmass most probably due to flow differentiation although multiple injection or fractional crystallization cannot be conclusively rejected.  相似文献   

Intrinsic problems in the seasonal prediction of the Indian summer monsoon rainfall     

H. Annamalai 《Meteorology and Atmospheric Physics》1995,55(1-2):61-76

Summary The latest non-parametric statistical tool Singular Spectrum Analysis (SSA) has been shown to extract deterministic oscillations present in a nonlinear dynamical system. It has been hypothesized that the tropical ocean-atmosphere system consists of both deterministic and stochastic parts in the interannual time scales. In the present study SSA has been employed to extract the deterministic and random parts present in the Indian summer monsoon (ISM) and its predictors time series data sets.The dominant eigenmode pair of the ISM does not emerge as a pure and deterministic oscillation. However, about 34% variance is deterministically predictable in the inter-annual range. The second pair is significantly related to the first pair of Darwin pressure tendency and both emerge as deterministic parts. This relationship partially answers the questions raised by Webster and Yang (1992). The low frequency component of ENSO emerges as a deterministic oscillation in all the variables, except in Bombay pressure tendency. The presence of decadal-scale oscillations may possibly be responsible for the instability in the relationship between the ISM and its predictors. Some plausible explanations for the percent variance explained by the predictors in the existing empirical models have also been discussed. It has been proposed that empirical models can be constructed only with the deterministic parts which may help improve the predictive skill of existing models.With 12 Figures  相似文献   

The P3 kimberlite and P4 lamproite,Wajrakarur kimberlite field,India: mineralogy,and major and minor element compositions of olivines as records of their phenocrystic vs xenocrystic origin     

Shaikh  Azhar M.  Kumar  Satya P.  Patel  Suresh C.  Thakur  Satyajeet S.  Ravi  Subramanian  Behera  Duryadhan 《Mineralogy and Petrology》2018,112(2):609-624

Distinctly different groundmass mineralogy characterise the hypabyssal facies, Mesoproterozoic diamondiferous P3 and P4 intrusions from the Wajrakarur Kimberlite Field, southern India. P3 is an archetypal kimberlite with macrocrysts of olivine and phlogopite set in a groundmass dominated by phlogopite and monticellite with subordinate amounts of serpentine, spinel, perovskite, apatite, calcite and rare baddeleyite. P4 contains mega- and macrocrysts of olivine set in a groundmass dominated by clinopyroxene and phlogopite with subordinate amounts of serpentine, spinel, perovskite, apatite, and occasional gittinsite, and is mineralogically interpreted as an olivine lamproite. Three distinct populations of olivine, phlogopite and clinopyroxene are recognized based on their microtextural and compositional characteristics. The first population includes glimmerite and phlogopite–clinopyroxene nodules, and Mg-rich olivine macrocrysts (Fo 90–93) which are interpreted to be derived from disaggregated mantle xenoliths. The second population comprises macrocrysts of phlogopite and Fe-rich olivine (Fo 81–89) from P3, megacrysts and macrocrysts of Fe-rich olivine (Fo 85–87) from P4 and a rare olivine–clinopyroxene nodule from P4 which are suggested to have a genetic link with the precursor melt of the respective intrusions. The third population represents clearly magmatic minerals such as euhedral phenocrysts of Fe-rich olivine (Fo 85–90) crystallised at mantle depths, and olivine overgrowth rims formed contemporaneously with groundmass minerals at crustal levels. Close spatial association and contemporaneous emplacement of P3 kimberlite and P4 lamproite is explained by a unifying petrogenetic model which involves the interaction of a silica-poor carbonatite melt with differently metasomatised wall rocks in the lithospheric mantle. It is proposed that the metasomatised wall rock for lamproite contained abundant MARID-type and phlogopite-rich metasomatic veins, while that for kimberlite was relatively refractory in nature.

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Quasi-Periodicity in global solar radio flux at metric wavelengths during Noise Storms     

Sundaram  G.A. Shanmugha  Subramanian  K.R. 《Solar physics》2004,222(2):311-322

We present observational results from studying the quasi-periodicities in global solar radio flux during periods of enhanced noise storm activity, over durations of 4 hr a day (`intra-day' variations), observed at 77.5 MHz with the newly commissioned log-periodic array tracking system at the Gauribidanur Radio Observatory. Positional information on the storm centers was obtained with the radio imaging data from the Nan\c cay Radio Heliograph (NRH), while their active region counterparts on the photosphere (and the overlying chromosphere ) were located from the H images of the Big Bear Solar Observatory. The quasi-periodicity in flux was found to be 110 min, with the fluctuation in flux being 3(±1.5) solar flux units (s.f.u.). The results of such pulsations are interpreted qualitatively as evidence for coronal seismology.  相似文献   

Active fin control for yacht using virtual instrumentation     

V. Anantha Subramanian  G. Asokumar  V. Jagadeesh Kumar 《Ocean Engineering》2007,34(3-4):390-402

Virtual instrumentation represents a PC based control system which incorporates manipulation of data acquired from physical transducers in specific ways using a very high level graphical environment. The deployment of this non-traditional approach is demonstrated in this paper by application to design of a fin control system for a yacht. One of the disadvantages of the traditional stabilizer system is the enormous hardware involved in the controllers and instrumentation panels, which make maintenance and troubleshooting difficult. With the help of virtual instrumentation, design of the stabilization controller and instrumentation panels can be carried out much more effectively, in comparison with the traditional hardware approach. A multi-disciplinary approach is adopted here and it consists of the assessment of the hydrodynamic coefficients of the yacht using a numerical package, representation of the hydrodynamic coefficients by suitable polynomial functions, identification of the time dependent fundamental frequency in the roll disturbance signal sample, generation of control signal for an appropriate fin angle based on the fin lift characteristics of the chosen fin and employment of feedback control to maintain the fin at the appropriate angle for maximum control. Once the ship based hydrodynamic coefficients are generated, the entire control algorithm is developed in the virtual instrumentation mode using LabVIEW environment. The effectiveness of the system is verified through laboratory tests on a yacht hull form. The control algorithm permits choice of frequency dependent hydrodynamic coefficients by use of a harmonic distortion analyzer in the virtual instrumentation environment.  相似文献   

Twenty-first century projected summer mean climate in the Mediterranean interpreted through the monsoon-desert mechanism     

Annalisa Cherchi  H. Annamalai  Simona Masina  Antonio Navarra  Andrea Alessandri 《Climate Dynamics》2016,47(7-8):2361-2371

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