A review of: “Finite-difference techniques for vectorized fluid dynamics calculations”     

N. O. Weiss 《地球物理与天体物理流体动力学》2013,107(4):344-345

Abstract

Edited by D. L. Book. Springer-Verlag, New York, 1981. 226 pp., DM 72,—, $33.60. (ISBN 0 387 104828)  相似文献   

Spectral models for solar-scaled and α-enhanced stellar populations     

P. Coelho  G. Bruzual  S. Charlot  A. Weiss  B. Barbuy  J. W. Ferguson 《Monthly notices of the Royal Astronomical Society》2007,382(2):498-514

  相似文献   

Pulsation period changes as a tool to identify pre-zero age horizontal branch stars     

V. Silva Aguirre  M. Catelan  A. Weiss  A. A. R. Valcarce 《Astrophysics and Space Science》2010,328(1-2):123-127

One of the most dramatic events in the life of a low-mass star is the He flash, which takes place at the tip of the red giant branch (RGB) and is followed by a series of secondary flashes before the star settles into the zero-age horizontal branch (ZAHB). Yet, no stars have been positively identified in this key evolutionary phase, mainly for two reasons: first, this pre-ZAHB phase is very short compared to other major evolutionary phases in the life of a star; and second, these pre-ZAHB stars are expected to overlap the loci occupied by asymptotic giant branch (AGB), HB, and RGB stars observed in the color-magnitude diagram (CMD). We investigate the possibility of detecting these stars through stellar pulsations, since some of them are expected to rapidly cross the Cepheid/RR Lyrae instability strip in their route from the RGB tip to the ZAHB, thus becoming pulsating stars along the way. As a consequence of their very high evolutionary speed, some of these stars may present anomalously large period change rates. We constructed an extensive grid of stellar models and produced pre-ZAHB Monte Carlo simulations appropriate for the case of the Galactic globular cluster M3 (NGC 5272), where a number of RR Lyrae stars with high period change rates are found. Our results suggest that some—but certainly not all—of the RR Lyrae stars in M3 with large period change rates are in fact pre-ZAHB pulsators.  相似文献   

Characteristics of oceanic impact‐induced large water waves—Re‐evaluation of the tsunami hazard     

Kai Wünnemann  Robert Weiss  Kay Hofmann 《Meteoritics & planetary science》2007,42(11):1893-1903

Abstract— The potential hazard of a meteorite impact in the ocean is controversial with respect to the destructive power of generated large ocean waves (tsunamis). We used numerical modeling of hypervelocity impact to investigate the generation mechanism and the characteristics of the resulting waves up to a distance of 100–150 projectile radii. The wave signal is primarily controlled by the ratio between projectile diameter and water depth, and can be roughly classified into deep‐water and shallow‐water impacts. In the latter, the collapse of the crater rim results in a wave signal similar to solitary waves, which propagate and decay in agreement with shallow‐water wave theory. The much more likely scenario for an asteroid impact on Earth is a relatively small body (much smaller than the water depth) striking the deep sea. In this case, the collapse of the transient crater results in a significantly different and much more complex wave signal that is characterized by strong nonlinear behavior. We found that such waves decay much more rapidly than previously assumed and cannot be treated as long waves. For this reason, the shallow‐water theory is not applicable for the computation of wave propagation, and more complex models (full solution of the Boussinesq equations) are required.  相似文献   

Radium and barium at GEOSECS stations in the Atlantic and Pacific     

L.H. Chan  J.M. Edmond  R.F. Stallard  W.S. Broecker  Y.C. Chung  R.F. Weiss  T.L. Ku 《Earth and Planetary Science Letters》1976,32(2):258-267

²²⁶Ra and Ba show a general linear correlation in the oceanic water column within the uncertainties of the data: the slope of the line is about 4.6 nanomoles (nmoles) Ra/mole Ba, the intercept being at about 4 nmoles Ba/kg. This demonstrates the usefulness of Ba as a “chemical analogue” of Ra. Box-model calculations indicate that the average deep-water excess of Ra over Ba should be about 10% relative to the surface. This is consistent with the observations outside the deep northeast Pacific. However, the uncertainties in the data are such that the regional variation in the primary input cannot be resolved. In the deep waters of the North Pacific there is in fact a large excess of Ra relative to Ba. The one detailed profile presently available (204) can be explained consistently by a simple vertical advection-diffusion model.  相似文献   

Large aspect ratio cells in two-dimensional thermal convection     

J.M. Hewitt  D.P. McKenzie  N.O. Weiss 《Earth and Planetary Science Letters》1980,51(2):370-380

Numerical experiments have been carried out on two-dimensional thermal convection, in a Boussinesq fluid with infinite Prandtl number, at high Rayleigh numbers. With stress free boundary conditions and fixed heat flux on upper and lower boundaries, convection cells develop with aspect ratios (width/depth) λ? 5, if heat is supplied either entirely from within or entirely from below the fluid layer. The preferred aspect ratio is affected by the lateral boundary conditions. If the temperature, rather than the heat flux, is fixed on the upper boundary the cells haveλ ≈ 1. At Rayleigh numbers of 2.4 × 10⁵ and greater, small sinking sheets are superimposed on the large aspect ratio cells, though they do not disrupt the circulation. Similar two-scale flows have been proposed for convection in the earth's mantle. The existence of two scales of flow in two-dimensional numerical experiments when the viscosity is constant will allow a variety of geophysically important effects to be investigated.  相似文献   

Al-rich calcic pyroxene in pseudotachylite: An indicator of high pressure and high temperature?     

H.R. Wenk  L.E. Weiss 《Tectonophysics》1982,84(2-4)

An aluminous pyroxene with an approximate formula (Ca_0.60Na_0.05□_0.20) (Mg_0.58Fe_0.11²⁺ Al_0.60^VI)[Si_1.68A1_0.32O₆] or {Jd_0.05Ts_0.32Es_0.20Wo_0.10En_0.27Fs_0.06} has been found in a pseudotachylite vein from gabbros in the Musgrave ranges, Central Australia. Textural evidence indicates that it formed by breakdown of calcic plagioclase, augite, and olivine which constitute the isochemical country rock. There is a large amount of M(2) vacancy compared to most pyroxenes. The vein mineral is most similar in composition to natural pyroxenes in kimberlites and eclogites and especially to synthetic pyroxenes which formed at pressures in excess of 3 GPa (= 30 kb). We suggest that these high pressures were not lithostatic but represent dynamic stresses released during catastrophic brittle rupture either at tips of propagating fractures or spallation of unsupported crackwalls. Such transient shear stresses may reach the shock range. We propose such a fracture mechanism as an alternative to frictional melting for the productoin of pseudotachylite veins.  相似文献   

Depth profiles of chlorofluoromethanes in the Norwegian sea     

A. Hahne  A. Volz  D. H. Ehhalt  H. Cosatto  W. Roether  W. Weiss  B. Kromer 《Pure and Applied Geophysics》1978,116(2-3):575-582

Depth profiles of the chlorofluoromethanes (CFM), CFCl₃ and CF₂Cl₂, have been obtained together with tritium profiles from water samples collected in the Norwegian Sea between surface and 2800 m depth. CFM analysis was performed by vacuum extraction of the dissolved gases from 500 ml samples of seawater and subsequent gaschromatographic measurement. The CFM concentration decreases with depth to about 10 percent of surface concentration at depths below 2000 m. The same behaviour is found for the tritium content. From a correlation of the CFM and tritium concentration the upper limit of the preindustrial atmospheric CFM levels can be estimated to 5 percent of the present day concentrations.  相似文献   

Characterization of sediments in an abandoned mining area; a case study of Mansfeld region,Germany   总被引：1，自引：0，他引：1  

Rainer?WennrichEmail author  Jürgen?Mattusch  Peter?Morgenstern  Klaus?Freyer  Hanns-Christian?Treutler  Hans-Joachim?St?rk  Lutz?Brüggemann  Albrecht?Paschke  Birgit?Daus  Holger?Weiss 《Environmental Geology》2004,45(6):818-833

The distribution of selected heavy metals, including some radionuclides, metalloids and non-metals was determined in stream sediments in a region influenced by abandoned copper mining and ore processing activities. A considerable amount of the ore processing waste with a very complex composition and highly elevated concentrations of zinc, sulfur, lead, copper, arsenic, and a lot of other elements in the range between 100 and 1,000 mg/kg (Sb, Mn, Ni, Cr, Cd, Hg, and Ag) was piled up on mine dumps. The dispersion of the pollutants originating from this source and their environmental impact were investigated. Both, sediments and original waste material were studied to indicate the pathways and the mobilization behavior of different pollutants. For this purpose, the process of the elution of pollutants by application of different fractionation schemes was studied. The capabilities of different analytical techniques are shown for the analysis of solid samples (X-ray fluorescence spectrometry, Gamma-spectrometry) and liquid ones (ICP-atomic emission spectrometry, ICP-mass spectrometry and different techniques of atomic absorption). Additionally, the coupling of ion chromatography and ICP-MS detection was used to study the distribution of arsenic species in the sediment cores of a lake which acts as a natural sink for the region.  相似文献   

Magnetohydrodynamics of stellar interiors     

David Hughes  Robert Rosner  Nigel Weiss 《Astronomy& Geophysics》2005,46(4):4.35-4.36

David Hughes, Robert Rosner and Nigel Weiss describe what was achieved during a programme on stellar magnetic fields at the Isaac Newton Institute in Cambridge. Over a four-month period more than 90 participants visited the Institute for a mixture of structured workshops and informal collaboration.  相似文献