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51.
Jean-Pierre Macquart Kinwah Wu Diana C. Hannikainen Robert J. Sault David L. Jauncey 《Astrophysics and Space Science》2003,288(1-2):105-119
We compare the observational properties of the circular polarization in Galactic jet sources with that observed in AGN, and outline the constraints they place on the mechanism responsible for the circular polarization. We also discuss the implications of the time scale of polarization variations on the mechanism responsible for the circular polarization. 相似文献
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It is well known that the Babuska–Brezzi stability criterion or the Zienkiewicz–Taylor patch test precludes the use of the finite elements with the same low order of interpolation for displacement and pore pressure in the nearly incompressible and undrained cases, unless some stabilization techniques are introduced for dynamic analysis of saturated porous medium where coupling occurs between the displacement of solid skeleton and pore pressure. The numerical manifold method (NMM), where the interpolation of displacement and pressure can be determined independently in an element for the solution of u–p formulation, is derived based on triangular mesh for the requirement of high accurate calculations from practical applications in the dynamic analysis of saturated porous materials. The matrices of equilibrium equations for the second‐order displacement and the first‐order pressure manifold method are given in detail for program coding. By close comparison with widely used finite element method, the NMM presents good stability for the coupling problems, particularly in the nearly incompressible and undrained cases. Numerical examples are given to illustrate the validity and stability of the manifold element developed. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
54.
Hector Socas-Navarro David Elmore Anna Pietarila Anthony Darnell Bruce W. Lites Steven Tomczyk Steven Hegwer 《Solar physics》2006,235(1-2):55-73
The Spectro-Polarimeter for Infrared and Optical Regions (SPINOR) is a new spectro-polarimeter that will serve as a facility
instrument for the Dunn Solar Telescope at the National Solar Observatory. This instrument is capable of achromatic polarimetry
over a very broad range of wavelengths, from 430 to 1600 nm, allowing for the simultaneous observation of several visible
and infrared spectral regions with full Stokes polarimetry. Another key feature of the design is its flexibility to observe
virtually any combination of spectral lines, limited only by practical considerations (e.g., the number of detectors available, space on the optical bench, etc.).
Visiting Astronomers, National Solar Observatory, operated by the Association of Universities for Research in Astronomy, Inc.
(AURA), under cooperative agreement with the National Science Foundation. 相似文献
55.
The large-scale structure associated with the 2′N HNCO peak in Sgr B2 [Minh, Y.C., Haikala, L., Hjalmarson, Å., Irvine, W.M., 1998. ApJ 498, 261 (Paper I)] has been investigated. A ring-like morphology of the HNCO emission has been found; this structure may be colliding with the Principal Cloud of Sgr B2. This “HNCO Ring” appears to be centered at (l,b) = (0.7°,−0.07°), with a radius of 5 pc and a total mass of 1.0 × 105 to 1.6 × 106 M. The expansion velocity of the Ring is estimated to be 30–40 km s−1, which gives an expansion time scale of 1.5 × 105 year. The morphology suggests that collision between the Ring and the Principal Cloud may be triggering the massive star formation in the Sgr B2 cloud sequentially, with the latest star formation taking place at the 2′N position. The chemistry related to HNCO is not certain yet, but if it forms mainly via reaction with the evaporated OCN− from icy grain mantles, the observed enhancement of the HNCO abundance can be understood as resulting from shocks associated with the collision between the Principal Cloud and the expanding HNCO Ring. 相似文献
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We investigate the role of seasonal variations of Titan’s stratospheric composition on the temperature. We use a general circulation model coupled with idealized chemical tracers that reproduce variations of ethane (C2H6), acetylene (C2H2), and hydrogen cyanide (HCN). Enhancement of the mole fractions of these compounds, at high latitudes in the winter hemisphere relative to their equatorial values, induces a relative decrease in temperature above approximately 0.2 mbar, with a peak amplitude around −20 K, and a relative increase in temperature below, around 1 mbar, with a peak amplitude around +7 K. These thermal effects are mainly due to the variations of the cooling to space induced by the varying distributions. The ethane, acetylene, and hydrogen cyanide variations affect the cooling rates in a similar way, with the dominant effect being due to ethane, though its latitudinal variations are small. 相似文献
59.
The steady-state population of bodies resulting from a collisional cascade depends on how material strength varies with size. We find a simple expression for the power-law index of the population, given a power law that describes how material strength varies with size. This result is extended to the case relevant for the asteroid belt and Kuiper belt, in which the material strength is described by 2 separate power laws—one for small bodies and one for larger bodies. We find that the power-law index of the small body population is unaffected by the strength law for the large bodies, and vice versa. Simple analytical expressions describe a wave that is superimposed on the large body population because of the transition between the two power laws describing the strength. These analytical results yield excellent agreement with a numerical simulation of collisional evolution. These results will help to interpret observations of the asteroids and KBOs, and constrain the strength properties of those objects. 相似文献
60.