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91.
Vincent Mannings 《Astrophysics and Space Science》1995,224(1-2):185-188
Studies of circumstellar dust and gas in pre-main-sequence systems are in part motivated by a desire to probe possible sites of future or on-going planet formation and, should accretion onto young stars be taking place, to determine whether the observed remnants of embryonic envelopes might yet contribute significantly to the final masses of stars as they evolve towards the main sequence. New 0.35- to 1.3-mm flux measurements have been made for 13 intermediate-mass pre-MS systems in order to estimate total dust+gas masses and to investigate the spatial distribution of circumstellar material. At least two sources may be dominated by compact circumstellar disks; emission from extended envelopes appears to be important for the majority of sources. HD 163296 is an unusual object and warrants further examination. 相似文献
92.
Vincent M. Woolf C. Simon Jeffery Donald L. Pollacco 《Monthly notices of the Royal Astronomical Society》2002,329(3):497-501
We present an analysis of high-speed spectroscopy of the pulsating subdwarf B star PG 1605+072. Periodic radial motions are detected at frequencies similar to those reported for photometric variations in the star, with amplitudes of up to 6 km s−1 . Differences between relative strengths for given frequency peaks for our velocity data and previously measured photometry are probably a result of shifting of power between modes over time. Small differences in the detected frequencies may also indicate mode-shifting. We report the detection of line-shape variations using the moments of the cross-correlation function profiles. It may be possible to use the moments to identify the pulsation modes of the star. 相似文献
93.
Mark A. Vincent 《Celestial Mechanics and Dynamical Astronomy》1986,39(1):15-21
The relativistic equations of motion are derived for N self-gravitating, rotating finite bodies. These equations are then applied to the near-Earth satellite orbit determination problem. The apparent change of the shape of the Earth from the Earth centered frame to the Solar System barycentric frame changes the value of the Newtonian potential term in the metric. This in turn leads to a simplification of the equations of motion in the barycentric frame. 相似文献
94.
George Chatzigeorgiou Vincent Picandet Abdelhafid Khelidj Gilles Pijaudier‐Cabot 《国际地质力学数值与分析法杂志》2005,29(10):1005-1018
A significant increase of the permeability of concrete upon micro‐cracking and a good correlation between the evolution of damage (material stiffness) and permeability are observed experimentally. The present contribution investigates this correlation theoretically, with the help of lattice analyses. Scaling analysis of lattices which contain elastic brittle bonds has shown that the material degradation should be described by the evolution of the material stiffness, or compliance, in a continuum setting (damage models). This result is reviewed and further documented in the first part of the paper. In the second part, hydro‐mechanical problems are considered with the construction of a hydraulic lattice, dual to the mechanical one. We observe that the average permeability upon micro‐cracking is the lattice scale‐independent controlling variable in the hydraulic problem. Additionally, results show that in a continuum poro‐mechanical approach, the evolution of the material permeability ought to be related to the elastic unloading stiffness, described e.g. with the help of continuum damage variables. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
95.
96.
97.
A preliminary study of photomosaic maps of Mars suggests that large lateral relative motions of a relatively thick lithosphere may have occurred. Transform faults (at two different stages of their evolution) are described, together with a possible triple junction. Diffuse diverging plate boundaries can be found, whereas converging ones remain a problem. 相似文献
98.
ARSLOE was a multiorganization experiment held October 6-November 30, 1980, near Duck, North Carolina. It provided a large number of wind-wave and related measurements to intercompare and develop wave measurement systems, to evaluate and improve wave models, and to provide basic information on wave mechanics in shallow water. This paper provides an overview of the experiment. 相似文献
99.
Uhl VW 《Ground water》2006,44(5):626-627
100.
Charly Massa Bianca B. Perren émilie Gauthier Vincent Bichet Christophe Petit Hervé Richard 《Journal of Paleolimnology》2012,48(1):241-258
This is the first integrated multiproxy study to investigate climate, catchment evolution and lake ecology in South Greenland. A 4-m-long sedimentary sequence from Lake Igaliku (61o 00?? N, 45o 26?? W, 15?m asl) documents major environmental and climatic changes in south Greenland during the last 10?ka. The chronology is based on a 210Pb and 137Cs profile and 28 radiocarbon dates. The paleoenvironmental history is interpreted on the basis of magnetic susceptibility, grain size, total organic carbon, total nitrogen and sulphur, sedimentation rates, pollen, and diatom assemblages. The basal radiocarbon date at ca. 10?cal?ka BP provides a minimum age for the deglaciation of the basin, which is followed by ~500?years of high sedimentation rates in a glacio-marine environment. After the glacio-isostatic emergence of the basin ca. 9.5?cal?ka BP, limnological and terrestrial proxies suggests early warmth, which may have been interrupted by a cold, dry and windy period between 8.6 and 8.1?cal?ka BP. A dry and windy event ~5.3?C4.8?cal?ka BP preceded the Neoglacial transition at Lake Igaliku, which is characterized by a shift toward moister and perhaps cooler conditions ~4.8?cal?ka BP, causing major changes in terrestrial and aquatic ecological conditions. Significant cooling is documented after ~3?cal?ka BP. Since ~1?cal?ka BP the climatic-driven changes were overprinted by the human influence of Norse and recent agriculture. 相似文献