Finite-difference algorithm with local time-space grid refinement for simulation of waves     

Vadim Lisitsa  Galina Reshetova  Vladimir Tcheverda 《Computational Geosciences》2012,16(1):39-54

This paper presents a new approach to a local time-space grid refinement for a staggered-grid finite-difference simulation of waves. The approach is based on approximation of a wave equation at the interface where two grids are coupled. As no interpolation or projection techniques are used, the finite-difference scheme preserves second order of convergence. We have proved that this approach is low-reflecting, the artificial reflections are about 10^− 4 of an incident wave. We have also shown that if a successive refinement is applied, i.e. temporal and spatial steps are refined at different interfaces, this approach is stable.  相似文献   

On the interface error analysis for finite difference wave simulation   总被引：1，自引：0，他引：1  

Vadim Lisitsa  Olga Podgornova  Vladimir Tcheverda 《Computational Geosciences》2010,14(4):769-778

A common way to construct a finite difference scheme is to satisfy a desired order of approximation, typically as high as possible. For linear wave propagation problem approximation together with stability delivers convergence of the same order as approximation. If a wave propagation proses is considered convergence to a plane wave solution can be derived analytically by means of the dispersion analysis. However, mentioned techniques are applicable only to homogeneous media and provide no knowledge of reflection/transmission coefficients. In this paper we prove that the only way to get second order accuracy of the solution for media with discontinuous parameters is to use a conservative finite difference scheme of the second order, and the only way to do this is to use the arithmetic mean for the density and the harmonic mean for the bulk modulus in the vicinity of the interface.  相似文献   

Derivation of elemental abundance maps at intermediate resolution from optical interpolation of lunar prospector gamma-ray spectrometer data     

Yuriy G. Shkuratov  Vadim G. Kaydash  Larissa V. Starukhina  Serge D. Chevrel 《Planetary and Space Science》2005,53(12):1287-1301

We propose a technique that interpolates available lunar prospector gamma-ray spectrometer (GRS) data using Clementine UVVIS spectral reflectance images. The main idea is to use low resolution GRS data as a “ground truth” to establish relationships linking optical data and geochemical information maximizing the respective correlation coefficients. Then the relationships and Clementine UVVIS data are used to derive elemental abundance maps with significantly improved spatial resolution. The main limitation of the technique is its dependence on how well the abundance of the elements correlates with the Clementine UVVIS data. The technique can also be applied to analysis of coming D-CIXS/Smart-1 and AMIE/Smart-1 data to increase resolution of lunar compositional maps. As an illustration of the suggested technique, maps for the elements Fe, Ti, O, Al, Ca, and Mg with pixel size 15 km×15 km are presented. The Fe and Ti distributions resemble qualitatively to the maps obtained with the well-known technique by lucey et al. (2000a. Lunar iron and titanium abundance algorithms based on final processing of Clementine ultraviolet-visible images. J. Geophys. Res. 105, 20,297-20,306), though in our case the ranges of Fe and Ti variations are, respectively, wider and narrower than for lucey's maps. New maps for the elements Fe, Ti, O, Al, Ca, and Mg appear to be informative. For instance, the map of oxygen abundance demonstrates an anomaly in the crater Tycho. The maps of Fe and Al contents show for highland regions slight variations related to maturity degree. Reliability of this relation is confirmed with lunar sample data. The reason of the correlation between chemical composition and exposition age of the lunar surface can be the global transport of the lunar surface material due to meteorite impacts.  相似文献   

Khatyrka,a new CV3 find from the Koryak Mountains,Eastern Russia     

Glenn J. MacPherson  Christopher L. Andronicos  Luca Bindi  Vadim V. Distler  Michael P. Eddy  John M. Eiler  Yunbin Guan  Lincoln S. Hollister  Alexander Kostin  Valery Kryachko  William M. Steinhardt  Marina Yudovskaya  Paul J. Steinhardt 《Meteoritics & planetary science》2013,48(8):1499-1514

A new meteorite find, named Khatyrka, was recovered from eastern Siberia as a result of a search for naturally occurring quasicrystals. The meteorite occurs as clastic grains within postglacial clay‐rich layers along the banks of a small stream in the Koryak Mountains, Chukotka Autonomous Okrug of far eastern Russia. Some of the grains are clearly chondritic and contain Type IA porphyritic olivine chondrules enclosed in matrices that have the characteristic platy olivine texture, matrix olivine composition, and mineralogy (olivine, pentlandite, nickel‐rich iron‐nickel metal, nepheline, and calcic pyroxene [diopside‐hedenbergite solid solution]) of oxidized‐subgroup CV3 chondrites. A few grains are fine‐grained spinel‐rich calcium‐aluminum‐rich inclusions with mineral oxygen isotopic compositions again typical of such objects in CV3 chondrites. The chondritic and CAI grains contain small fragments of metallic copper‐aluminum‐iron alloys that include the quasicrystalline phase icosahedrite. One grain is an achondritic intergrowth of Cu‐Al metal alloys and forsteritic olivine ± diopsidic pyroxene, both of which have meteoritic (CV3‐like) oxygen isotopic compositions. Finally, some grains consist almost entirely of metallic alloys of aluminum + copper ± iron. The Cu‐Al‐Fe metal alloys and the alloy‐bearing achondrite clast are interpreted to be an accretionary component of what otherwise is a fairly normal CV3 (oxidized) chondrite. This association of CV3 chondritic grains with metallic copper‐aluminum alloys makes Khatyrka a unique meteorite, perhaps best described as a complex CV3 (ox) breccia.  相似文献   

Seasonal variations in methane concentrations and diffusive fluxes in the Curonian and Vistula lagoons,Baltic Sea     

Marina Ulyanova  Vadim Sivkov  Timur Kanapatskij  Nikolay Pimenov 《Geo-Marine Letters》2014,34(2-3):231-240

Expected seasonal variations in methane concentrations and diffusive fluxes from surficial sediments into near-bottom waters were investigated in autumn 2012 and winter 2013 in the Curonian and Vistula lagoons of the Baltic Sea, expanding on earlier findings for summer 2011. Methane concentrations in bottom sediments (upper ca. 2 cm) generally ranged from ca. 1 to 1,000 μmol/dm³, and in near-bottom waters from ca. 0 to 1 μmol/l. Highest concentrations were found in the Curonian Lagoon, plausibly explained by the influence of freshwater conditions and finer-grained, organic-rich sediments. Vistula Lagoon methane concentrations and fluxes are dampened by periodic saline water inflow from the open sea, intensifying sulphate reduction. Calculated diffusive methane fluxes from the upper sediment layer (usually 0–5 cm, i.e. excluding any fluffy layer) into near-bottom waters were highest—2.48 mmol/(m² day)—in clayey silts of the Curonian Lagoon in autumn (September) 2012, contrasting strongly with the minimum value of 0.002 mmol/(m² day) observed there in February 2013 under ice-covered conditions. Seasonal and even weekly variations in methane dynamics can be largely explained by two main drivers, i.e. wind and temperature, operating at various spatiotemporal scales via, for example, wind wave-induced resuspension of bottom sediments, and involving regional weather patterns including autumnal low-pressure zones over the Gulf of Gdansk.  相似文献   

Observations of internal undular bores on the Japan/East Sea shelf-coastal region     

Vadim Vasilevich Novotryasov  Dmitry Vadimovich Stepanov  Igor Olegovich Yaroshchuk 《Ocean Dynamics》2016,66(1):19-25

Observations are presented of internal undular bores (IUBs) on the Japan/East Sea coast. We found three types of IUB amplitude modulation functions. The first type (IUB₁) has a leading edge, which is formed by the soliton with maximal amplitude. The second type (IUB₂) has a soliton with maximal amplitude (SMA) located between the leading and trailing edges. The third type (IUB₃) consists of 2–3 solitons, which have identical amplitudes. The evolution of the IUB₂ from the moment of generation to the moment of maximal development was analyzed. The speed of the IUB₂ approached to the phase speed of linear internal waves with a period of 12.4 h. The amplitude modulation function of the IUB₂ is believed to be unique in ocean observations. Observations are discussed in the context of recently raised hypotheses concerning the evolution of IUBs in the coastal environment.  相似文献   

S 235 B explained: an accreting Herbig Be star surrounded by reflection nebulosity     

Paul A. Boley  rey M. Sobolev  Vadim V. Krushinsky  Roy van Boekel  Thomas Henning  Aleksei V. Moiseev  Maksim V. Yushkin 《Monthly notices of the Royal Astronomical Society》2009,399(2):778-782

The intent of this study is to determine the nature of the star and associated nebulosity S 235 B, which are located in a region of active star formation still heavily obscured by the parent molecular cloud. Low-resolution  ( R = 400)  long-slit spectra of the star and nebulosity, and medium-  ( R = 1800)  and high-resolution  ( R = 60 000)  spectra of the central star are presented along with the results of Fabry–Perot interferometric imaging of the entire region. Based on the long-slit and Fabry–Perot observations, the nebulosity appears to be entirely reflective in nature, with the stellar component S 235 B★ providing most of the illuminating flux. The stellar source itself is classified here as a B1V star, with emission-line profiles indicative of an accretion disc. S 235 B★ thus belongs to the relatively rare class of early-type Hebrig Be stars. Based on the intensity of the reflected component, it is concluded that the accretion disc must be viewed nearly edge-on. Estimates of the accretion rate of S 235 B★ from the width of the Hα profile at 10 per cent of maximum intensity, a method which has been used lately for T Tauri stars and Brown Dwarfs, appear to be inconsistent with the mass outflow rate and accretion rate implied from previous infrared observations by Felli et al., suggesting this empirical law does not extend to higher masses.  相似文献   

Volatile Phase Separation in Silicic Magmas at Bajo de la Alumbrera Porphyry Cu-Au Deposit, NW Argentina   总被引：7，自引：0，他引：7  

Anthony C. Harris    Vadim S. Kamenetsky    Noel C. White  David A. Steele 《Resource Geology》2004,54(3):341-356

Abstract. At the Bajo de la Alumbrera porphyry Cu-Au deposit, NW Argentina, several key textural elements preserve evidence for volatile separation. Interconnected miarolitic cavities, while being studied extensively in granites, have now been recognized in intrusions related to porphyry Cu mineralization. Pods of saccharoidal quartz are connected by narrow, anastomosing zones of graphic quartz-alkali feldspar intergrowths and ragged biotite (with lesser apatite and magnetite). Their connectivity can be as much as 15 cm; however, more commonly, the interconnected miarolitic cavities are approximately 1 to 2 mm across and 5 cm or less, long. Features such comb-quartz layered textures and magmatic-hydrothermal veins (P veins), combined with aqueous fluid phase equilibria from fluid inclusions, better constrain physical models of exsolution. We interpret these textures in the context of vapour phase formation, coalescence and accumulation in an evolving silicic magma. Recognition of textures, such as the interconnected miarolitic cavities reported here, may provide a simple exploration tool for porphyry Cu deposits, helping explorers to recognize evidence for a potentially fertile intrusions.  相似文献   

Late Jurassic–Early Cretaceous closure of the Mongol-Okhotsk Ocean demonstrated by new Mesozoic palaeomagnetic results from the Trans-Baïkal area (SE Siberia)     

Jean-Pascal Cogné  Vadim A. Kravchinsky  Nadir Halim  Fatim Hankard 《Geophysical Journal International》2005,163(2):813-832

  相似文献   

Potassic primary melts of Vulsini (Roman Province): evidence from mineralogy and melt inclusions     

Vadim Kamenetsky  Nicole Métrich  Raffaello Cioni 《Contributions to Mineralogy and Petrology》1995,121(3):336-336

The online version of the original article can be found at  相似文献