共查询到20条相似文献，搜索用时 828 毫秒
1.
Champa Mazumder 《Pure and Applied Geophysics》1973,105(1):810-815
Summary In this paper the displacement due to an impulsive twist produced by impulsive shearing stresses acting on a finite circular area on the plane surface of a semi-infinite solid of homogeneous anisotropic material has been found.Paper presented by Dr. A. K. Mitra of Jadavpur University. 相似文献
2.
Arabinda Mukhopadhyay 《Pure and Applied Geophysics》1966,65(1):29-36
Summary The disturbances produced by time-dependent torsional body forces in a layer of elastic material lying on a rigid foundation have been discussed in this paper. Solutions have been obtained first for a general type of body force, and the solutions for an impulsive cylindrical source and an impulsive torsional line source of finite length have been deduced. It has been found that for any point in the layer, there is no disturbance up to a certain instant, after which there is a sudden displacement, which gradually falls off and tends to zero as the timet increases. 相似文献
3.
Sakti Kanta Chakraborty 《Pure and Applied Geophysics》1961,48(1):23-26
Summary The disturbances produced in a visco-elastic medium by impulsive forces on the surface of a spherical cavity inside the medium have been studied. 相似文献
4.
Mr. Ghasi Ram Verma M. A. 《Pure and Applied Geophysics》1957,37(1):16-20
Summary In this note displacements and stresses produced in an infinite elastic solid by impulsive radial and twisting displacements applied to the inner surface of a spherical cavity have been determined. 相似文献
5.
《Journal of Atmospheric and Solar》2002,64(5-6):541-549
Recently, it has been shown that certain features of magnetotail dynamics in response to solar wind changes may resemble the behavior of a complex system near a dynamical critical state (Chang, Phys. Plasmas 6 (1999) 4137; Consolini and Chang, Space Sci. Rev. 95 (2001) 309), and of topological phase transitions (Chang, Phys. Scr. (2001), 80). Moreover, the impulsive part of the magnetotail response seems to be well described by cellular automata and other simulation models displaying criticality.Here, the relevance of the magnetic field topological disorder will be discussed in connection with observed complexity and near-criticality, showing how the impulsive character of the magnetotail response could be viewed as fluctuation-induced topological transitions among metastable configurations of magnetic field topology. 相似文献
6.
《Journal of Atmospheric and Solar》2007,69(14):1680-1689
The analysis of simultaneous observations of 128 cases of high-latitude magnetic impulse events (MIEs), as well as geomagnetic pulsations in the Pc1–2 band observed in the area of the dayside cusp, was carried out. We investigated magnetograms from the Mirny Observatory, Antarctica. As a result of the examination, three groups of impulses were identified: (1) impulses accompanied by impulsive bursts of intervals of pulsations with rising periods (IPRPs)-type geomagnetic pulsations—16% of all events, (2) impulses accompanied by impulsive bursts of the Pi1B type (bursts of irregular magnetic pulsations)—48% of all events, and (3) impulses which were not accompanied by geomagnetic pulsations within a high-frequency band—36% of all events.It was found that the maximum frequency of occurrence of the impulses accompanied by impulsive bursts of the IPRP and Pi1B types was observed between 1200 and 1300 MLT. The events of the first two groups were observed predominantly when Bz>0. It was shown that the filling frequency of impulsive bursts that accompany the occurrence of impulses depends on the amplitude of the bursts. The maximum frequency of the occurrence of impulses which were not accompanied by impulsive bursts is between 1000 and 1100 MLT. The events of the third group were observed predominantly when Bz<0. In most cases, the occurrence of impulsive bursts coincided with the leading edge of the MIE.It is supposed that the MIE generation is stimulated by intensification of the plasma turbulence level at the dayside magnetopause in consequence of modulation instability development or reconnection processes. 相似文献
7.
N. Bhanja 《Pure and Applied Geophysics》1971,85(1):182-188
Summary Stress and displacement components in a solid circular cylinder of transversely isotropic material under the torsional vibration set up by an impulsive twist applied at one and while the other end remains fixed, have been obtained by the application of Laplace transformation. 相似文献
8.
Bani Pramanik 《Pure and Applied Geophysics》1972,93(1):60-67
Summary In this note displacement of a thin perfectly conducting viscoelastic plate of Reiss type in contact with vacuum on both sides and in a uniform magnetic field has been discussed. The plate has been assumed to be acted on by an impulsive load. Solutions have been obtained for small and large values of time. Results have also been discussed for some particular cases. 相似文献
9.
Gopinath Sarkar 《Pure and Applied Geophysics》1966,65(1):43-47
Summary Wave motion due to two kinds of impulsive twist on the surface has been discussed. The discontinuous nature of solution has been obtained. A function-theoretic approach has been made for solving the problem. 相似文献
10.
Impulsive force of debris flow on a curved dam 总被引：8，自引：0，他引：8
Although Sabo dams are an efficient method for river and basin management, traditional Sabo dams have a great impact on ecology and landscape. Moreover, such dams are hit and often damaged by great impulsive force when they block the debris flow. Therefore, alternative shapes for Sabo dam deserve thorough investigation. In this investigation, a curved dam was designed by changing the upstream-dam-surface geometric shape to reduce the impulsive force of the debris flow, with enhanced stability and reduced concrete mass being the anticipated outcomes. In this study, the flume and laboratory facilities simulated the impulsive force of the debris flow to the Sabo dams. Three geometric forms, including vertical, slanted and curved Sabo dams, were used to determine the impulsive force. Impulsive force theories of the debris flow were derived from the momentum equation and the Bernoulli equation. In these, the impulsive force was balanced by the friction force of the Sabo dam and the opposite force of the load cell behind the dam as it was hit by the debris flow. Positive correlations were found when comparing the experimental data with the theoretical results. These findings suggest that our impulsive force theory has predictive validity with regard to the experimental data. The results from both theory and experimental data clearly show that curved darns were sustained less force than the other darns under the same debris flow. This comparison demonstrates the importance of curved geometry for a well-designed Sabo dam. 相似文献
11.
Midwater signatures of eight common types of marine seismic sources have been recorded and characteristics of importance for high-resolution reflection profiling have been analyzed. Analyzed characteristics include wavelet shape, peak frequency, bandwidth, repeatability and directivity. Digitization rates required to describe the signatures before any processing and after whitening deconvolution were determined.It was intended that most of the broad range of available source types be represented. Toward that end, both resonant and impulsive types were studied; the impulsive types being both electric-discharge and pneumatic. They included a conventional sonar transducer, a chirped sonar transducer, a boomer, a plasmagun, a multi tip sparker, a watergun, an airgun and three sizes of sleevegun.It was observed that the peak frequency of each conventional sonar is similar to its nominal value and that of the chirped sonar is about the midpoint of its nominal sweep bandwidth. The dominant frequencies of the electric-discharge impulsive sources are about an order of magnitude higher than those of the pneumatic impulsive sources. Among impulsive sources, the boomer has the highest peak frequency and the watergun has the broadest bandwidth. The sleevegun and airgun were found to be comparable, both having low frequencies, poor repeatability and weak directivity. The conventional sonar and the boomer are the most repeatable sources. The boomer shows the strongest directivity with the chip sonar and the watergun being the most nondirectional.Sample rates required to describe the unprocessed signatures vary from 2 to 88 times the peak frequency and from 1 to 4 times the bandwidth 40dB below peak power. The required rate depends largely on source type but can also be affected by energy level. Bandwidth seems to be a more stable indicator than peak frequency. Rates required to describe the results of applying whitening deconvolution to signatures were about 1.5–3 times higher than rates calculated for the unprocessed signatures. This leads to the conclusion that the digitization rate required in a specific situation can depend as much on the intended processing scheme as it does on source type. 相似文献
12.
Subhash Chandra Ghosh 《Pure and Applied Geophysics》1970,80(1):71-83
Summary The displacement produced in the half-space by uniform impulsive pressure acting over a circular portion of the surface has been obtained in terms of definite integrals. FollowingCagniard andGarvin, the displacement at an interior point on the axis of symmetry has been calculated. The approximate displacement at points far off from the axis of symmetry has been obtained by using saddle point method and Tauberian limit theorem. 相似文献
13.
S. Basu Mallik 《Pure and Applied Geophysics》1969,76(1):87-91
Summary The problem of disturbances in a visco-elastic medium due to Maxwell in contact with a liquid medium — both being perfectly conductive — has been investigated when an impulsive force acts along the plane of the contact. The electro-magnetic equations of Maxwell, equation of elasticity and the stress-strain relations of the material have been used in the investigation. 相似文献
14.
Shree Surendralal Ghosh 《Pure and Applied Geophysics》1969,75(1):88-92
Summary In this paper disturbances due to impulsive as well as transient load in a thin elastic finite circular plate resting on viscoelastic foundation of Pasternak type have been considered separately. 相似文献
15.
Gopinath Sarkar 《Pure and Applied Geophysics》1967,66(1):37-47
Summary The displacement due to vertical impulsive load has been obtained by function theoretic method. Graphs have been drawn for horizontal as well as for vertical displacement. It has been shown thatPekeris's [12]2) method is easier to apply than that ofCagniard [2] for the same purpose. 相似文献
16.
17.
Sukumar Basu Mallik 《Pure and Applied Geophysics》1972,96(1):52-60
Summary The propagation of disturbances in a composite viscoelastic layer when subjected to an impulsive force in the presence of a primary magnetic field, has been investigated in this note. The mechanical displacement has been derived from the electro-magnetic equations of Maxwell, the equation of motion and the stress-strain relations of the materials considered and has been computed for small values of time. 相似文献
18.
19.
G. Cristiani G. Martínez C.H. Mandrini C.G. Gimnez de Castro M.G. Rovira P. Kaufmann H. Levato 《Journal of Atmospheric and Solar》2005,67(17-18):1744
We present a detailed study of a 1B/M6.9 impulsive flare combining high time resolution (1 ms) and instantaneous emission source localization observations at submillimeter frequencies (212 GHz), obtained with the solar submillimeter telescope (SST), and Hα data from the Hα solar telescope for argentina (HASTA). The flare, starting at 16:34 UT, occurred in active region (AR) 9715 (NOAA number) on November 28, 2001, and was followed by an Hα surge. We complement our data with magnetograms from the Michelson Doppler Imager (SOHO/MDI). SST observed a short impulsive burst at 212 GHz, presenting a weak bulk emission (of about 90 sfu) composed of a few shorter duration structures. The integrated Hα and the 212 GHz light curves present a remarkable agreement during the impulsive phase of the event. The delay between both curves stays below 12 s (the time resolution of the Hα telescope). The flare as well as the surge are linked to new flux emergence very close to the main AR bipole. Taking into account the AR magnetic field evolution, we infer that magnetic field reconnection, occurring at low coronal levels, could have been at the origin of the flare; while in the case of surge this would happen at the chromospheric level. 相似文献
20.
D. Fischer 《地震工程与结构动力学》1979,7(6):587-601
The velocity potential of a compressible fluid is found by Galerkin's method. Free surface displacements and a flexible tank wall are assumed. Explicit expressions for the impulsive mass, the impulsive moment and the overturning moment are derived for wave number m = 1. In the case of m ≥ 1 the dynamic effect of the fluid is represented by a fictitious apparent mass in explicit form. 相似文献