排序方式： 共有58条查询结果，搜索用时 15 毫秒
21.
Corrado Massa 《Astrophysics and Space Science》2003,286(3-4):313-322
The photon-to-baryon ratio in the universe is much greater than unity (about109); this fact is unexplained in the standard model of the universe; it can be explained by a photon creation process related
to a time-dependent cosmological term.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
22.
S. Osterman J. Green C. Froning S. B��land E. Burgh K. France S. Penton T. Delker D. Ebbets D. Sahnow J. Bacinski R. Kimble J. Andrews E. Wilkinson J. McPhate O. Siegmund T. Ake A. Aloisi C. Biagetti R. Diaz W. Dixon S. Friedman P. Ghavamian P. Goudfrooij G. Hartig C. Keyes D. Lennon D. Massa S. Niemi C. Oliveira R. Osten C. Proffitt T. Smith D. Soderblom 《Astrophysics and Space Science》2011,335(1):257-265
The Cosmic Origins Spectrograph (COS) was installed in the Hubble Space Telescope in May, 2009 as part of Servicing Mission 4 to provide high sensitivity, medium and low resolution spectroscopy at far- and near-ultraviolet wavelengths (FUV, NUV). COS is the most sensitive FUV/NUV spectrograph flown to date, spanning the wavelength range from 900 Å to 3200 Å with peak effective area approaching 3000 cm2. This paper describes instrument design, the results of the Servicing Mission Orbital Verification (SMOV), and the ongoing performance monitoring program. 相似文献
23.
Marco Massa Francesca Pacor Lucia Luzi Dino Bindi Giuliano Milana Fabio Sabetta Antonella Gorini Sandro Marcucci 《Bulletin of Earthquake Engineering》2010,8(5):1175-1187
The Italian strong-motion database was created during a joint project between Istituto Nazionale di Geofisica e Vulcanologia
(INGV, Italian Institute for Geophysics and Vulcanology) and Dipartimento della Protezione Civile (DPC, Italian Civil Protection). The aim of the project was the collection, homogenization and distribution of strong motion data acquired in Italy in the
period 1972–2004 by different institutions, namely Ente Nazionale per l’Energia Elettrica (ENEL, Italian electricity company), Ente per le Nuove tecnologie, l’Energia e l’Ambiente (ENEA, Italian energy and environment organization) and DPC. Recently the strong-motion data relative to the 23th December 2009, Parma (Mw = 5.4 and Mw = 4.9) and to the April
2009 L’Aquila sequences (13 earthquakes with 4.1 ≤ Mw ≤ 6.3) were included in the Italian Accelerometric Archive (ITACA) database
(beta release). The database contains 7,038 waveforms from analog and digital instruments, generated by 1.019 earthquakes
with magnitude up to 6.9 and can be accessed on-line at the web site . The strong motion data are provided in the unprocessed and processed versions. This article describes the steps followed
to process the acceleration time series recorded by analogue and digital instruments. The procedures implemented involve:
baseline removal, instrumental correction, band pass filtering with acausal filters, integration of the corrected acceleration
in order to obtain velocity and displacement waveforms, computation of acceleration response spectra and strong motion parameters.
This procedure is applied to each accelerogram and it is realised to preserve the low frequency content of the records. 相似文献
24.
Corrado Massa 《Astrophysics and Space Science》2008,314(1-3):23-24
If gravity is a mixture of the ordinary attractive force carried by the massless graviton, and of a repulsive force carried
by a particle with nonzero mass, an evaporating black hole might leave a stable remnant. 相似文献
25.
Corrado Massa 《Astrophysics and Space Science》1993,209(2):307-308
The time variation of the gravitational constantG is discussed in the light of the gravity modified form of quantum electrodynamics. From the experimental upper limit |a/| < 5 × 10–15 yr–1 on the time variation of the electromagnetic fine structure constant one finds |/G| < 5 × 10–13 yr–1. 相似文献
26.
Derck P. Smits Cohen & Hutawarakorn 《Monthly notices of the Royal Astronomical Society》1998,296(1):L11-L14
We perform two-dimensional numerical calculations of the tidal interaction between the companion star and the disc around the primary in a cataclysmic variable system with parameters appropriate for the eclipsing dwarf nova binary IP Peg. We show that a spiral shock pattern is indeed obtained. We find, however, that it is impossible to reproduce the two-armed spiral that has been recently observed in IP Peg for realistic discs. 相似文献
27.
28.
Raman K. Prinja Derck Massa Ian D. Howarth & Alex W. Fullerton 《Monthly notices of the Royal Astronomical Society》1998,301(4):926-934
We present the results from a 28-day IUE time-series campaign monitoring the stellar wind of the O5-type giant HD 93843. The principal aim was to study variability in the wind of a star with a normal projected rotation velocity. Systematic changes are identified, amidst continuous line-profile variability, in the absorption troughs of the Si iv and N v resonance lines. The patterns observed have characteristic time-scales of several days and are mimicked by fluctuations (of several 100 km s−1 ) in the blue wings of the saturated C iv P Cygni profile. Fourier analysis provides support for the repeatability of wind structures in HD 93843 on a 7.1-d 'period'. Power at this frequency is evident only at intermediate and high velocities (i.e., above ∼0.3 of the terminal velocity). The long modulation time-scale suggests that changes in the star itself probably provide the physical source for triggering the onset of wind structure. Unfortunately the rotational, photometric, pulsational and magnetic properties of HD 93843 are too poorly constrained or known to permit a more detailed interpretation of the 7.1-d wind modulation in terms of potential inhomogeneities at the stellar surface. Nevertheless, our study demonstrates that the incidence of cyclic, possibly regular, stellar-wind variability is not restricted to rapid rotators. Comparisons with other OB stars which have exhibited repetitive wind changes on 'periods' of several days suggest that the time-dependent UV properties of HD 93843 are more akin to those of the O4-type supergiant ζ Puppis. 相似文献
29.
John Douglas Sinan Akkar Gabriele Ameri Pierre-Yves Bard Dino Bindi Julian J. Bommer Sanjay Singh Bora Fabrice Cotton Boumédiène Derras Marcel Hermkes Nicolas Martin Kuehn Lucia Luzi Marco Massa Francesca Pacor Carsten Riggelsen M. Abdullah Sandıkkaya Frank Scherbaum Peter J. Stafford Paola Traversa 《Bulletin of Earthquake Engineering》2014,12(1):341-358
This article presents comparisons among the five ground-motion models described in other articles within this special issue, in terms of data selection criteria, characteristics of the models and predicted peak ground and response spectral accelerations. Comparisons are also made with predictions from the Next Generation Attenuation (NGA) models to which the models presented here have similarities (e.g. a common master database has been used) but also differences (e.g. some models in this issue are nonparametric). As a result of the differing data selection criteria and derivation techniques the predicted median ground motions show considerable differences (up to a factor of two for certain scenarios), particularly for magnitudes and distances close to or beyond the range of the available observations. The predicted influence of style-of-faulting shows much variation among models whereas site amplification factors are more similar, with peak amplification at around 1s. These differences are greater than those among predictions from the NGA models. The models for aleatory variability (sigma), however, are similar and suggest that ground-motion variability from this region is slightly higher than that predicted by the NGA models, based primarily on data from California and Taiwan. 相似文献
30.
Laurent Millet Charly Massa Vincent Bichet Victor Frossard Simon Belle Emilie Gauthier 《Quaternary Research》2014
We performed a high-resolution study of chironomid assemblages in a sediment core retrieved from Lake Igaliku in southern Greenland. The well-dated core is located within the former Norse Eastern Settlement and covered the last 1500 yr. The comparison of chironomid stratigraphy (PCA axis scores) with instrumental temperature data, land use history and organic matter in the sediment over the last 140 yr suggested that the primary changes in chironomid fauna in 1988 ± 2 yr were driven by the shift to modern agriculture in the catchment. This unprecedented change in chironomid fauna was most likely triggered by a shift in in-lake processes. Within the instrumental period, subtle variations in the chironomid assemblages that occurred before 1988 ± 2 yr were significantly correlated with summer temperatures even in times of traditional extensive sheep farming in the catchment. The relevance of the chironomid-derived climate signal over the last 1500 yr was supported by its good concordance with previous studies in west Greenland and in the Arctic. The chironomid assemblage therefore appeared to be a valuable proxy for climate changes within the Norse colony area. Synchronous changes in Norse diet and chironomid-reconstructed climate give new insights into the interplay of Norse society with climate. 相似文献