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31.
The essentially random motion of the towfish in a side scan sonar system limits the fidelity of the resultant image. Although corrective techniques have been developed to deal with the gross departures from a set of regular amplitude versus range samples along a straight locus as well as the gross rotational errors, sub-wavelength displacement errors are mostly ignored. This paper suggests a technique to estimate the appropriate displacement errors from the statistics of the measured data when there are few or no strong scatterers on an otherwise featureless sea floor. As it happens, the proposed technique is somewhat similar to an existing optical technique but is new to underwater sonar. We show in a series of simulated trials that it is possible to estimate the resultant sub-wavelength horizontal departure from a straight locus under some (hopefully) realistic operating conditions 相似文献
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M.P. Gough 《Planetary and Space Science》1975,23(8):1236
The photo-ionization produced in the night-time E region by the total stellar u.v. continuum is considered. It is shown to be approximately equal to that produced by the scattered Lyman β above about 115 km. 相似文献
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D. Gough 《Astrophysics and Space Science》2003,285(2):341-351
In 1970 Fred Hoyle encouraged a study of solar neutrino production which led to along-term investigation of the influence
of what have become known as `non-standard' processes (i.e. processes that are not accounted for in the relatively naively
constructed so-called `standard' theoretical solar models). The outcome is a very much sounder understanding of the structure
and dynamics of the Sun, which has yielded a knowledge of conditions in the energy-generating core so precise that one can
set quite tight reliable constraints on neutrino-producing nuclear reactions, and thereby provide an important contribution
to the study of neutrino transitions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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FIRST RESULTS FROM VIRGO,THE EXPERIMENT FOR HELIOSEISMOLOGY AND SOLAR IRRADIANCE MONITORING ON SOHO 总被引:1,自引:0,他引:1
Fröhlich Claus Andersen Bo N. Appourchaux Thierry Berthomieu Gabrielle Crommelynck Dominique A. Domingo Vicente Fichot Alain Finsterle Wolfgang Gómez Maria F. Gough Douglas Jiménez Antonio Leifsen Torben Lombaerts Marc Pap Judit M. Provost Janine Roca Cortés Teodoro Romero José Roth Hansjörg Sekii Takashi Telljohann Udo Toutain Thierry Wehrli Christoph 《Solar physics》1997,170(1):1-25
First results from the VIRGO experiment (Variability of solar IRradiance and Gravity Oscillations) on the ESA/NASA Mission SOHO (Solar and Heliospheric Observatory) are reported. The observations started mid-January 1996 for the radiometers and sunphotometers and near the end of March for the luminosity oscillation imager. The performance of all the instruments is very good, and the time series of the first 4–6 months are evaluated in terms of solar irradiance variability, solar background noise characteristics and p-mode oscillations. The solar irradiance is modulated by the passage of active regions across the disk, but not all of the modulation is straightforwardly explained in terms of sunspot flux blocking and facular enhancement. Helioseismic inversions of the observed p-mode frequencies are more-or-less in agreement with the latest standard solar models. The comparison of VIRGO results with earlier ones shows evidence that magnetic activity plays a significant role in the dynamics of the oscillations beyond its modulation of the resonant frequencies. Moreover, by comparing the amplitudes of different components ofp -mode multiplets, each of which are influenced differently by spatial inhomogeneity, we have found that activity enhances excitation. 相似文献