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341.
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This paper deals with the earthquake response of wine barrel stacks using a physical model of rigid‐body components with discrete flexible and damped contact elements. An analytical 3D formulation of the complex dynamic behavior of different barrel stack configurations is presented. Such behavior includes the real geometry of the bodies, large displacements and rotations, the use of non‐linear contact elements to account for impact and sliding between bodies, and the resulting local energy dissipation at contact. The parameters defining the physical and mathematical model were calibrated experimentally, and the dynamic behavior of a benchmark barrel stack configuration was compared with the experimental results obtained from the literature. It was found that the model is able to predict the exact mode of collapse and the overall behavior of the system. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
343.
Long-period seismicity during magma movement at Volcán de Colima 总被引:1,自引:1,他引:0
Nick R. Varley Raúl Arámbula-Mendoza Gabriel Reyes-Dávila John Stevenson Rob Harwood 《Bulletin of Volcanology》2010,72(9):1093-1107
During the period from February to September 2005, Volcán de Colima produced 30 Vulcanian explosions of sufficient magnitude
to produce pyroclastic flows of variable size, with a total volume of at least 2.5 × 106 m3. Swarms of long-period events were associated with each event, their duration ranging from about 6 h to 3 days and each swarm
containing up to 886 events. The characteristics of the swarms have been studied to understand the source mechanism and their
relationship with the Vulcanian explosions. In total, 12,548 long-period events were analysed using various comparative and
statistical methods. Patterns were not apparent in the data with no correlation between different properties of the swarms
(duration, magnitude or frequency of occurrence of LP events) and the magnitude of the associated Vulcanian explosion, whether
recorded by seismicity, volume of pyroclastics or altitude of the eruption column. This, along with other characteristics
of the swarms, such as the continuation of the swarm after the explosion, with an increase in long-period event amplitude
in some cases, suggests that the mechanism is not merely associated with the pressurization under an impermeable cap and resulting
pressure differentials between adjacent volumes within the system. It is more likely that the production of long-period events
is dominated by brittle fracturing on the margins of an ascending magma body. A model is proposed whereby the unloading above
the ascending magma column produced by a Vulcanian explosion resulted in an increase in ascent rate, reflected in the increasing
amplitude of long-period events. The results reflect the complexity of non-linear processes involved during magma ascent,
degassing, crystallization and rupture of the impermeable plug during the Vulcanian process. At Volcán de Colima, as at many
volcanoes, long-period events represent a useful precursor for eruptive activity. For monitoring, this paper highlights some
useful analyses that can be carried out, which could illustrate certain characteristics of an eruptive episode. A preliminary
model is presented of the conduit processes at work during the cyclic extrusive and explosive activity during 2005. 相似文献
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Lemaire P. Wilhelm K. Curdt W. SchÜle U. Marsch E. Poland A. I. Jordan S. D. Thomas R. J. Hassler D. M. Vial J. C. KÜhne M. Huber M. C. E. Siegmund O. H. W. Gabriel A. Timothy J. G. Grewing M. 《Solar physics》1997,170(1):105-122
SUMER – Solar Ultraviolet Measurements of Emitted Radiation – is not only an extreme ultraviolet (EUV) spectrometer capable of obtaining detailed spectra in the range from 500 to 1610 Å, but, using the telescope mechanisms, it also provides monochromatic images over the full solar disk and beyond, into the corona, with high spatial resolution. We report on some aspects of the observation programmes that have already led us to a new view of many aspects of the Sun, including quiet Sun, chromospheric and transition region network, coronal hole, polar plume, prominence and active region studies. After an introduction, where we compare the SUMER imaging capabilities to previous experiments in our wavelength range, we describe the results of tests performed in order to characterize and optimize the telescope under operational conditions. We find the spatial resolution to be 1.2 arc sec across the slit and 2 arc sec (2 detector pixels) along the slit. Resolution and sensitivity are adequate to provide details on the structure, physical properties, and evolution of several solar features which we then present. Finally some information is given on the data availability and the data management system. 相似文献
346.
Yvon Halbwachs Gabriel Courrioux Xavier Renaud Philippe Repusseau 《Mathematical Geology》1996,28(5):625-656
The consistent geometric and topological representation of a fault network is possible through a method based on the implementation of 3-dimensional Generalized maps (3-G-map) enabling all subdivisions of space to be represented. The fault network is modeled as an assemblage of polygonal faces from a set of geometric data on the faults and a knowledge of the relationships between the faults. The resultant model is expressed in terms of a 3-G-map in which volume, surface, and topological information is constructed taking into account computed intersections between faults and known interception relations. The fault network can be edited through an interactive 3-D viewer which provides several tools for navigating within the 3-G-map. Information relevant to a fault network, such as block geometry, connectivity, adjacencies, and connectivity relationships, can be obtained by exploring the data structure of the 3-G-map. The fault network architecture is made comprehensive through interactive modeling and visualization. 相似文献
347.
Eit Observations of the Extreme Ultraviolet Sun 总被引:3,自引:0,他引:3
D. Moses F. Clette J.-P. Delaboudinière G. E. Artzner M. Bougnet J. Brunaud C. Carabetian A. H. Gabriel J. F. Hochedez F. Millier X. Y. Song B. Au K. P. Dere R. A. Howard R. Kreplin D. J. Michels J. M. Defise C. Jamar P. Rochus J. P. Chauvineau J. P. Marioge R. C. Catura J. R. Lemen L. Shing R. A. Stern J. B. Gurman W. M. Neupert J. Newmark B. Thompson A. Maucherat F. Portier-Fozzani D. Berghmans P. Cugnon E. L. Van Dessel J. R. Gabryl 《Solar physics》1997,175(2):571-599
The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft has been operational since 2 January 1996. EIT
observes the Sun over a 45 x 45 arc min field of view in four emission line groups: Feix, x, Fexii, Fexv, and Heii. A post-launch
determination of the instrument flatfield, the instrument scattering function, and the instrument aging were necessary for
the reduction and analysis of the data. The observed structures and their evolution in each of the four EUV bandpasses are
characteristic of the peak emission temperature of the line(s) chosen for that bandpass. Reports on the initial results of
a variety of analysis projects demonstrate the range of investigations now underway: EIT provides new observations of the
corona in the temperature range of 1 to 2 MK. Temperature studies of the large-scale coronal features extend previous coronagraph
work with low-noise temperature maps. Temperatures of radial, extended, plume-like structures in both the polar coronal hole
and in a low latitude decaying active region were found to be cooler than the surrounding material. Active region loops were
investigated in detail and found to be isothermal for the low loops but hottest at the loop tops for the large loops.
Variability of solar EUV structures, as observed in the EIT time sequences, is pervasive and leads to a re-evaluation of the
meaning of the term ‘quiet Sun’. Intensity fluctuations in a high cadence sequence of coronal and chromospheric images correspond
to a Kolmogorov turbulence spectrum. This can be interpreted in terms of a mixed stochastic or periodic driving of the transition
region and the base of the corona. No signature of the photospheric and chromospheric waves is found in spatially averaged
power spectra, indicating that these waves do not propagate to the upper atmosphere or are channeled through narrow local
magnetic structures covering a small fraction of the solar surface. Polar coronal hole observing campaigns have identified
an outflow process with the discovery of transient Fexii jets. Coronal mass ejection observing campaigns have identified the
beginning of a CME in an Fexii sequence with a near simultaneous filament eruption (seen in absorption), formation of a coronal
void and the initiation of a bright outward-moving shell as well as the coronal manifestation of a ‘Moreton wave’.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1004902913117 相似文献
348.
349.
350.
Oscillations in the emission in the ultraviolet lines of Cii, Oiv, and Mg x, detected by the Harvard College Observatory EUV spectroheliometer on Skylab are observed on August 7, 1973, during a loop brightening. The intensity of the EUV lines varies with a period of 141 s during the time of enhanced intensity of the coronal loop, lasting 10 min. The periodic oscillation is not only localized in the loop region but extends over a larger area of the active region, maintaining the same phase. We suggest that the intensity fluctuation of the EUV lines is caused by small-amplitude waves, propagating in the plasma confined in the magnetic loop and that size of the loop might be important in determining its perferential heating in the active region.On leave from the University of Torino, Italy. 相似文献