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991.
992.
We use the recently introduced concept of a ‘window’ of magnetic field strengths in which pulsars can be active to explain
the variation in morphology of supernova remnants. The striking difference between shell-type and filled-type remnants is
attributed to differences in he magnetic field strengths of the neutron stars left by the respective Supernovae. Field strengths
of a value permitting pulsar activity result in particle production and Crab-like centrally concentrated remnants. Other field
values lead to strong magnetic dipole radiation and consequent shell formation (e.g. Cas A). Several apparent inconsistencies concerning pulsar-supernova associations appear to find a logical explanation on
the basis of this hypothesis. 相似文献
993.
994.
Prikner K. Mursula K. Kangas J. Feygin F. Z. Kerttula R. 《Studia Geophysica et Geodaetica》2002,46(3):507-526
The ionospheric Alfvén resonator (IAR) was numerically simulated under non-stationary ionospheric and magnetospheric conditions of the IPDP event of December 4, 1986. The full numerical wave method was applied using height profiles of the ionospheric plasma parameters obtained from the Scandinavian EISCAT radar measurements close to the Ivalo latitude. An attempt to model the inverse problem of numerical simulation—prolongation of the electron density profiles at altitudes above the ionospheric F layer—was made on the basis of the IAR simulation in correlation with the IPDP frequency increase. The change of the IAR wave characteristics during the substorm was illustrated by height profiles of the total wave amplitude and various polarization characteristics, taking into consideration the ordinary L-mode and the extraordinary R-mode waves for parallel and non-parallel incidence with respect to the magnetic field line. 相似文献
995.
C. Camy-Peyret J. -M. Flaud A. Perrin C. P. Rinsland A. Goldman F. J. Murcray 《Journal of Atmospheric Chemistry》1993,16(1):31-40
Stratospheric volume mixing ratio profiles of N2O5, CH4, and N2O have been retrieved from a set of 0.052 cm–1 resolution (FWHM) solar occultation spectra recorded at sunrise during a balloon flight from Aire sur l'Adour, France (44° N latitude) on 12 October 1990. The N2O5 results have been derived from measurements of the integrated absorption by the 1246 cm–1 band. Assuming a total intensity of 4.32×10–17 cm–1/molecule cm–2 independent of temperature, the retrieved N2O5 volume mixing ratios in ppbv (parts per billion by volume, 10–9), interpolated to 2 km height spacings, are 1.64±0.49 at 37.5 km, 1.92±0.56 at 35.5 km, 2.06±0.47 at 33.5 km, 1.95±0.42 at 31.5 km, 1.60±0.33 at 29.5 km, 1.26±0.28 at 27.5 km, and 0.85±0.20 at 25.5 km. Error bars indicate the estimated 1- uncertainty including the error in the total band intensity (±20% has been assumed). The retrieved profiles are compared with previous measurements and photochemical model results.Laboratoire associé aux Universités Pierre et Marie Curie et Paris Sud. 相似文献
996.
Nestor A. Rivera S. Ray Jerry L. Jensen Andrew K. Chan Walter B. Ayers 《Mathematical Geology》2004,36(5):529-543
This study shows how wavelet analysis can be used on well log and drill core data to identify cyclicity in sedimentary sequences. Three possible methods for determining wavelength were investigated: the Morlet wavelet, the Fourier transform, and the semivariogram. When applied to several hypothetical signals similar to those observed in petrophysical measurements in hydrocarbon reservoirs, all three methods could identify the presence of cyclicity. Only the wavelet scalogram, however, gave a clear indication of when the cyclic element was present and where frequency changes occurred in the signal. To illustrate the wavelet analysis, we processed well log and core data from a well in the Ormskirk Sandstone and determined the wavelet coefficients for each zone and the wavelengths of the strongest cyclicities. The cyclicities observed corresponded well with sedimentary features of the formation (e.g., channels and channel sets). Also, ratios of the cyclicity wavelengths corresponded with ratios of the Milankovitch precession, obliquity, and eccentricity periods. This result is in agreement with other investigators, who have proposed that Milankovitch-driven climate changes exercised an important control on Ormskirk Sandstone deposition. 相似文献
997.
1BriefintroductionoftheanomaliesofshortperiodgeomagneticvariationsinShaanxiAtemporarymeasurementprofilecomposedofmeasurementsitesofShiquan,Foping,Banfangzi,Zhouzhi,Wugong,Qianling,BinxianandNingxian,whichisbasicalalongnorth-southdirectionfromShiquaninthesouthernpartofShaanxitoNingxianinGansu,wassetupandsimultaneousobservationofthree-componentgeomagneticshortperiodvariationswereperformedateightsitesduringSeptemberof1996.Observationalresultsshowthatthereisareversalaxisofgeomagneticverticalv… 相似文献
998.
王金平 《CT理论与应用研究》1999,8(4):14-19
本文具体给出了广义Radon变换在函数空间L^2(R^n,Wn)上的正交函数展开形式,由此得到了广义Radon变换的反演公式,从而推广了Louis和Davison的工作。 相似文献
999.
Osamu Kinoshita 《Island Arc》1999,8(2):181-189
A migration model of magmatism based on the granite ages in Southwest Japan is proposed to explain the ridge subduction beneath the Eurasia continent as the cause of the along-arc and across-arc youngings of the granite ages and the very high activity of the magmatism in the Cretaceous. For the construction of the magmatic model, the localities of the granite age samples are denoted by the cartesian coordinates X and Y, which are measured along and normal to the Median Tectonic Line (MTL), respectively, and their ages are set corresponding to the coordinate Z vertical to the X–Y plane. The age trend is then formulated by a regression plane of Z on X and Y, which inclines in both directions along and normal to the MTL, and approximates the ages with the very high multiple correlation coefficient 0.91. Evaluating the magmatic trend by such a method, various characteristics of the activities can be taken easily; for example, the isochronous line of the magmatism, which is an intersection of the regression plane and an arbitrary horizontal plane, is found to extend landward obliquely across the continental margin. The migrating rate of the isochronous line along the MTL is also taken to be 2.8 cm/year as a reciprocal of the inclination of the along-arc younging. The isochronous line is speculated to be the out-cropped manifestation of the subcrustal linear heat source. Such a migrating linear heat source is probably due to the subduction of an active ridge, the Kula (or Izanagi)–Pacific ridge in the Cretaceous. The migration model of magmatism harmonizes very well with the plates and the ridge motions in the East Asia area during the late Mesozoic. The ridge subduction is one of the important phenomena that explain the unusually active arc magmatism and the migrating slab window; it is important to grasp dynamically the geological messages issued from the system. 相似文献
1000.
The time series of the sea surface temperature(SST) anomaly,covering the eastern (western) equatorial Pacific,central Indian Ocean,Arabian Sea.Bay of Bengal and South China Sea(SCS),have been analyzed by using wavelet transform.Results show that there exists same interdeeadal variability of SST in the tropical Pacific and tropical Indian Ocean,and also show that the last decadal abrupt change occurred in the 1970s.On the interannual time scale,there is a similar interannual variability among the equatorial central Indian Ocean and the adjacent three sea basins(Arabian Sea.Bay of Bengal and South China Sea).but the SST interannual changes of the Indian Ocean lagged 4-5 months behind that of the equatorial central-east Pacific.Meanwhile,the interannual variability and long-range change between SST anomaly and Indian summer monsoon rainfall in recent decades have been explained and analyzed.It indicates that there existed a wet(dry) period in India when the tropical SST was lower(higher)than normal,but there was a lag of phase between them. 相似文献