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791.
Emission fluxes of CN, C2 and C3 species observed in the coma of some comets are analysed in the framework of Haser model. CN, C2 and C3 production rates are determined using recently derived fluorescence efficiencies and dependence of CN, C2 and C3 production rates on the heliocentric distance is studied. Evidence for a burst type activity around January 15, 1974 in the post-perihelion period of comet Kohoutek (1973f) is observed. 相似文献
792.
P. D. Singh K. Sinha B. M. Tripathi Heloisa M. B. Roberty 《Earth, Moon, and Planets》1989,47(3):231-239
Post-perihelion observed emission fluxes at 388 nm (CN) and 516 nm (C2) of the coma of comets Austin (1982g) and Bradfield (1980t) are analysed in the framework of the Haser model. Ratios of Haser model CN and C2 parent production rates with expansion velocity show that each comet behaves normally. For comet Austin (1982g), the Q
CN/v and Q
c2/v values decrease with increase of heliocentric distance of comet. For an assumed %; activity of the total spherical surface area of the nucleus, the water vaporization theory coupled with derived water production rates from the International Ultraviolet Explorer H and OH flux data yields a nuclear diameter of about 6 km for comet Austin (1982g). For comet Bradfield (1980t), the derived nuclear diameter is expected to be of about 1 km. In each comet, the dust mass production rates as well as ratio of dust-to-gas mass production rates decrease with increase of heliocentric distance of comet. 相似文献
793.
Thermal-convective instability of a hydromagnetic, composite, rotating, inviscid, and infinitely conducting plasma in a stellar atmosphere has been studied in the presence of Hall currents. It is found that the criterion for monotonic instability holds good in the presence of the effects due to rotation and Hall currents. 相似文献
794.
In this note extending the technique developed for static fields by De (1964) to the static plane-symmetric solution of Taub (1951) and the conformastat gravitational universe of Das (1971) solutions for coupled gravitational and zero-rest-mass scalar fields have been obtained. Furthermore, it is found that the singularities of these empty spaces cannot be removed by the introduction of zero-rest-mass scalar fields. 相似文献
795.
Sediment transport in rill flows exhibits the characteristics of non‐equilibrium transport, and the sediment transport rate of rill flow gradually recovers along the flow direction by erosion. By employing the concept of partial equilibrium sediment transport from open channel hydraulics, a dynamic model of rill erosion on hillslopes was developed. In the model, a parameter, called the restoration coefficient of sediment transport capacity, was used to express the recovery process of sediment transport rate, which was analysed by dimensional analysis and determined from laboratory experimental data. The values of soil loss simulated by the model were in agreement with observed values. The model results showed that the length and gradient of the hillslope and rainfall intensity had different influences on rill erosion. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
796.
J.K. Singh 《Astrophysics and Space Science》2002,281(3):585-594
The Bianchi type-V cosmological solutions of massive strings in the presence and absence of the magnetic field are investigated.
The physical behavior of these models are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
797.
An analytical study is performed to examine the free-convection and mass transfer flow for the Sokes problem for an infinite vertical plate on taking into account the Soret effect (thermal diffusion effect). The Laplace transform technique is used to obtain the expressions for velocity and skin-friction. The effect of Soret numberS on velocity field and skin-friction is extensively discussed with the help of graphs and table. 相似文献
798.
During the analysis of archived VLF data from Indian low latitude ground stations, some discrete VLF emissions recorded at
the low latitude ground station Gulmarg (geomagnetic latitude 24°26′N; geomagnetic longitude 147°09′E, L = 1.28) during moderate
magnetic storm activity (Σ K
P
− = 32, K
P
index varies from 4 to 6 during the observation period) on 6/7 March, 1986 are presented in this paper. The dynamic spectra
of these discrete VLF emissions were observed along with tweeks and its harmonics, which is interesting and complex to explain.
In most of the events the harmonic frequency of tweeks correlates with the starting frequency of harmonics of discrete emissions.
In order to explain the observed features of discrete VLF emissions, we propose cyclotron resonance interaction between whistler
mode wave and energetic electrons of inner radiation belt as possible generation mechanism. An attempt is also made to determine
parallel energy, anisotropy and wave growth relevant to the generation process of VLF emissions. 相似文献
799.
The Biot linearized theory of fluid saturated porous materials is used to study the plane strain deformation of a two-phase
medium consisting of a homogeneous, isotropic, poroelastic half-space in welded contact with a homogeneous, isotropic, perfectly
elastic half-space caused by a two-dimensional source in the elastic half-space. The integral expressions for the displacements
and stresses in the two half-spaces in welded contact are obtained from the corresponding expressions for an unbounded elastic
medium by applying suitable boundary conditions at the interface. The case of a long dip-slip fault is discussed in detail.
The integrals for this source are solved analytically for two limiting cases: (i) undrained conditions in the high frequency
limit, and (ii) steady state drained conditions as the frequency approaches zero. It has been verified that the solution for
the drained case (ω → 0) coincides with the known elastic solution. The drained and undrained displacements and stresses are compared graphically.
Diffusion of the pore pressure with time is also studied. 相似文献
800.
Earthquakes cause a variety of hydrological phenomena, including changes in the ground water levels in bore wells. The Koyna
region in the peninsular shield of India, hitherto considered stable in terms of seismic activity, has been active since 1967.
More recently, the earthquakes have been localized to the newly impounded Warna reservoir, which is located south of Koyna,
where a burst of seismicity occurred in 1993. The region continues to remain seismically active even after four decades. Twenty-one
bore wells were drilled around the seismic source volume in the region to observe water level changes resulting from earthquake
phenomena. Our studies have shown coseismic anomalous water level changes to be associated with the moderate earthquakes of
April 25, 1997 and February 11, 1998. Our results show that changes in the ground water level in bore wells are correlated
with micro-earthquake activity, both preceding and following moderately sized earthquakes. The results have implications in
enhancing our understanding of earthquake mechanisms. 相似文献