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521.
P. C. Ram 《Astrophysics and Space Science》1988,149(1):171-174
The two-dimensional unsteady free-convective flow through a porous medium bounded by an infinite vertical plate for an incompressible viscous and electrically conducting fluid is considered, when a strong magnetic field is imposed in a direction which is perpendicular to the free stream and makes an angle to the vertical direction. The effects of Hall currents on the flows are studied for various values of . 相似文献
522.
Wave-form modelling of body waves has been done to study the seismic source parameters of three earthquakes which occurred on October 21, 1964 (M
b
=5.9), September 26, 1966 (M
b
=5.8) and March 14, 1967 (M
b
=5.8). These events occurred in the Indochina border region where a low-angle thrust fault accommodates motion between the underthrusting Indian plate and overlying Himalaya. The focal depths of all these earthquakes are between 12–37 km. The total range in dip for the three events is 5°–20°. TheT axes are NE-SW directed whereas the strikes of the northward dipping nodal planes are generally parallel to the local structural trend. The total source durations have been found to vary between 5–6 seconds. The average values of seismic moment, fault radius and dislocation are 1.0–11.0×1025 dyne-cm, 7.7–8.4km and 9.4–47.4 cm, respectively whereas stress drop, apparent stress and strain energy are found to be 16–76 bars, 8.2–37.9 bars and 0.1–1.7×1021 ergs, respectively. These earthquakes possibly resulted due to the tension caused by the bending of the lithospheric plate into a region of former subduction which is now a zone of thrusting and crustal shortening. 相似文献
523.
A Gaussian correlation function characterizes smoothly heterogeneous media, while real heterogeneities in the Earth are often non-Gaussian in nature. Using the Born approximation, mean square amplitudes of the scattered waves have been derived for an elastic media characterized by the Von Karman correlation function. Heterogeneities with different power laws can be defined by the Von Karman correlation function. The sensitivity of fore- and backscattering to heterogeneities with different scales and properties (that is velocity and impedance) is discussed in this paper. The analytical expression for total scattered energy for the incident P waves is also derived for a random medium having the Von Karman correlation function. We find that at high frequencies, the scattered power of converted waves is a function of frequency. In the case of codawave excitation by local earthquakes, which must be handled by the full elastic-wave theory, we can define any type of inhomogeneity by the Von Karman correlation function. It also supports the idea that the lithosphere might have multiple-scale inhomogeneities. 相似文献
524.
M. T. Kayano N. J. Ferreira M. C. V. Ramírez 《Meteorology and Atmospheric Physics》1997,64(3-4):203-213
Summary Daily 200-hPa relative vorticity data have been used to study the dominant patterns related to the cyclonic vortices over the South Atlantic Ocean in the vicinities of northeast Brazil, during the 1980–1989 period. Reference modes were obtained through empirical orthogonal function (EOF) analysis of the 200-hPa filtered vorticity anomalies over northeast Brazil, considering all the southern hemisphere (SH) summers within the study period. The amplitude time series of the first reference mode, separately for each SH summer, was correlated with the corresponding filtered vorticity anomalies in a larger area extending from 20°N to 40°S and between 120°W and 20°W. The correlation patterns feature a wave-like structure along eastern South America, with three main centers: the first one, over the South Atlantic off the northeast Brazil coast, is associated with the cyclonic vortices; the second one, over eastern Brazil, represents the corresponding anomalously amplified ridges; and the third one, over southern Brazil/Uruguay, is related to the equatorward incursions of midlatitude upper level troughs. This wave-like pattern is consistent with the vortex formation mechanism suggested in previous works. Another wave-like pattern southwest-northeast oriented is evident over the tropical southeastern Pacific, for some years. The internannual variability of these patterns is discussed in this paper.With 9 Figures 相似文献
525.
Ram Krishan Sharma 《Astrophysics and Space Science》1987,135(2):271-281
This paper deals with the stationary solutions of the planar restricted three-body problem when the more massive primary is a source of radiation and the smaller primary is an oblate spheroid with its equatorial plane coincident with the plane of motion. The collinear equilibria have conditional retrograde elliptical periodic orbits around them in the linear sense, while the triangular points have long- or short-periodic retrograde elliptical orbits for the mass parameter 0 < crit, the critical mass parameter, which decreases with the increase in oblateness and radiation force. Through special choice of initial conditions, retrograde elliptical periodic orbits exist for the case = crit, whose eccentricity increases with oblateness and decreases with radiation force for non-zero oblateness. 相似文献
526.
A simple method for determining leaf area index (LAI), absorbed photosynthetically active radiation (APAR), dry biomass and yield in pearl millet (Pennisetum glaucum (L.) R. Br.) crop from remote sensing data is presented. The dry matter and yield can be simulated with maximum accuracy by normalised difference (ND) data during milking stage using the following models: $$\begin{array}{l} DM = - 435.45 + 786.86ND R^2 = 0.90 \\ Yield = - 95.43 + 180.00ND R^2 = 0.62 \\ \end{array}$$ 相似文献
527.
Non-linear stability of the libration point L 4 of the restricted three-body problem is studied when the more massive primary is an oblate spheroid with its equatorial plane coincident with the plane of motion, Moser's conditions are utilised in this study by employing the iterative scheme of Henrard for transforming the Hamiltonian to the Birkhoff's normal form with the help of double D'Alembert's series. It is found that L 4 is stable for all mass ratios in the range of linear stability except for the three mass ratios: $$\begin{gathered} \mu _{c1} = 0.0242{\text{ }}...{\text{ }}{}^{{\text{\_\_}}}0.1790{\text{ }}...{\text{ }}A_1 , \hfill \\ \mu _{c2} = 0.0135{\text{ }}...{\text{ }}{}^{{\text{\_\_}}}0.0993{\text{ }}...{\text{ }}A_1 , \hfill \\ \mu _{c3} = 0.0109{\text{ }}...{\text{ }}{}^{{\text{\_\_}}}0.0294{\text{ }}...{\text{ }}A_1 . \hfill \\ \end{gathered} $$ 相似文献
528.
P. C. Ram 《Astrophysics and Space Science》1991,176(2):263-270
An explicit finite-difference method is employed to study the MHD free convection heat generating fluid past an impulsively started vertical infinite plate when a strong magnetic field is applied perpendicular to the plate. The velocity and temperature profiles are shown on graphs and the results are discussed in terms of the non-dimensional parameters
e
(Hall parameter),
i
(ionslip parameter), (heat source parameter), and Gr (Grashof number). 相似文献
529.
In the southern part of the Indian Peninsula, there are a number of alkaline plutons of Proterozoic age. In the northern part of the South Indian granulite terrain, the Yelagiri (syenite, pyroxenite) and Sevattur (syenite, pyroxenite, carbonatite) plutons intrude Archaean epidote-hornblende gneisses. Geochemical and isotopic characteristics of the Yelagiri and Sevattur plutons indicate that the syenitic magmas formed from highly differentiated mantle-derived alkali basalts. The Yelagiri and Sevattur syenites are characterized by evolved Sr and Nd isotopic compositions, pronounced enrichment in LILE and large negative Nb anomalies. Trace element and Sr-Nd isotope characteristics of the Yelagiri and Sevattur syenites are similar to those of the subduction-related alkaline rocks. The scarcity of geological evidence for subduction activity at the time of syenite intrusion during Neoproterozoic does not support a link between the alkaline magmatism and subduction. However, our data are consistent with the model of derivation of the Yelagiri and Sevattur syenites from the subcontinental lithospheric mantle, which was previously enriched by slab derived component. The geochemical and isotopic signatures of other mantle-derived intrusive rocks in the northern part of the South Indian granulite terrain with ages ranging from ca. 2.5 Ga to 0.75 Ga also support the above idea. 相似文献
530.
LOCAL SCOUR AROUND BRIDGE ABUTMENTS 总被引:2,自引:0,他引:2
Er. Shri Ram CHAURASIA Pande B.B. LAL Assistant Professor Civil Engineering Department Madan Mohan Malaviya Engineering College Gorakhpur- 《国际泥沙研究》2002,17(1)
1 INTRODUCTION The protrusion of a bridge abutment or a spur dike into the main channel creates a disturbance and obstruction to the otherwise equilibrium state of sediment transportation in an alluvial river. The flow accelerates and separates at the upstream face of the abutment as it moves past the obstacle, creating a vortex trail that moves downstream in a direction approximately perpendicular to the structure. The result is that the bed around the structure is eroded locally. The l… 相似文献