A geophysical survey of the Spitsbergen Margin and surrounding areas     

Dmitry Baturin  Tatiana Fedukhina  Leo Savostin  Artem Yunov 《Marine Geophysical Researches》1994,16(6):463-484

New geophysical information including multichannel seismic profiling data obtained by the PGO Sevmorgeologia Ministry of Geology of the former USSR, Murmansk during 1984–1988 is discussed and interpreted in this study. The deep structure, sedimentary cover and stratigraphy of the Spitsbergen Continental Margin, considered to be a passive margin, i.e. divergent in the northern part and strike-slip in the western part, is described.Two genetically different types of plateaus on the continental margin, Yermak in the north and Spitsbergen (Vestnesa) in the west, have been identified.The entire extent of the continental slope of the northern part of the Spitsbergen Continental Margin in the Eurasia Basin is underlain by attenuated continental crust, while at the base of the Southwest Continental Margin, the oceanic crust along almost the entire extent is observed. The sedimentary cover, up to 10 km thick within the West Spitsbergen Continental Margin, is likewise observed. Within the North Spitsbergen Margin, however, it does not exceed 3.5 km in thickness.The extension and deposition within the West Spitsbergen Margin began in early Oligocene, while the rifting with accompanying sedimentation within the North Spitsbergen Continental Margin started probably in Early Cretaceous.  相似文献   

The benefits of a high-resolution analysis of transit accessibility     

Itzhak Benenson  Eran Ben-Elia  Yodan Rofé  Dmitry Geyzersky 《International journal of geographical information science》2017,31(2):213-236

Accessibility is an important consideration in sustainable mobility policies, particularly for transit users. Measures suggested in the literature are based on coarse aggregate spatial resolution of traffic analysis zones that is sufficient for managing car travels only. To reflect a human door-to-door travel, transit accessibility demands an explicit view of the location of origin, transit stops and destination, as well as of the temporal fit between transit lines timetable and traveler’s needs. We thus estimate transit accessibility based on mode-specific travel times and corresponding paths, including walking and waiting, at the resolution of individual buildings and stops. Car accessibility is estimated at a high resolution too. A novel representation of transit network as a graph is proposed. This representation includes all modal components of a transit travel – walking, waiting at a stop, transit ride, transfers between lines, thus enabling unified view of a travel, regardless of mode. The use of modern high-performance graph database allows construction of high-resolution accessibility maps for an entire metropolitan area with its 100–200 K buildings. The application is tested and applied in a case study involving the evaluation of the 2011 bus line reform in the city of Tel Aviv. Specifically, we demonstrate that while the reform increased the average accessibility for the entire city the increase was not uniform with different areas of the city experiencing different absolute accessibility by transit and relative accessibility in comparison to car travel. The bus reform did in fact benefit travelers that experienced low relative accessibility, but the benefits are mainly accruing to longer trips. Our approach and computational methods can be employed for directly investigating the impacts of transportation infrastructure investments.  相似文献   

HALF-WIDTH OF A SOLAR DYNAMO WAVE IN PARKER'S MIGRATORY DYNAMO     

Kuzanyan  Kirill M.  Sokoloff  Dmitry 《Solar physics》1997,173(1):1-14

A kinematic -dynamo model of magnetic field generation in a thin convection shell with nonuniform helicity for large dynamo numbers is considered in the framework of Parker's migratory dynamo. The asymptotic solution obtained of equations governing the magnetic field has the form of an anharmonic travelling dynamo wave. This wave propagates over most latitudes of the solar hemisphere from high latitudes to the equator, and the amplitude of the magnetic field first increases and then decreases with propagation. Over the subpolar latitudes, the dynamo wave reverses; there the dynamo wave propagates polewards and decays with latitude. The half-width of the maximum of the magnetic field localisation and the phase velocity of the dynamo wave are calculated. Butterfly diagrams are plotted and analysed and these show that even a simple model may reveal some properties of the solar magnetic fields.  相似文献   

Energy spectra of gamma-ray bursts detected by the APEX experiment on phobos mission     

Dmitry A. Ushakov  Dmitry S. Anfimov  Igor G. Mitrofanov 《Astrophysics and Space Science》1995,233(1-2):195-198

Molecular clouds are clumpy on length scales down to the limits of observational resolution. At least some ultracompactHii regions (UCHiiR) may result from the interaction of a young early type star and this type of cloud. The clumps can act as reservoirs of ionized gas distributed within theHii region. These models reproduce the relatively long lifetimes implied by the population statistics of UCHiiR. We present line profile and emission measure plots based on the simplest case where the flow remains supersonic through to a recombination front. The morphology agrees with the shell-like UCHiiR as classified by Churchwell. The predicted line profiles are broad and double peaked with a separation of about 50 km s^–1 for the example given.  相似文献   

On the Singular Nature of the Second-Order Peaks in HF Radar Sea Echo   总被引：4，自引：0，他引：4  

Dmitry V. Ivonin Victor I. Shrira Pierre Broche 《Oceanic Engineering, IEEE Journal of》2006,31(4):751-767

  相似文献   

An Automated Iridium-Strip Heater for LA-ICP-MS Bulk Analysis of Geological Samples   总被引：1，自引：0，他引：1  

Brigitte Stoll  Klaus Peter Jochum  Kirstin Herwig  Marghaleray Amini  Michael Flanz  Berthold Kreuzburg  Dmitry Kuzmin  Matthias Willbold  Jacinta Enzweiler 《Geostandards and Geoanalytical Research》2008,32(1):5-26

In this paper we describe a flux‐free fusion technique for the highly precise LA‐ICP‐MS bulk analysis of geological samples. For this purpose we have developed an automated iridium‐strip heater with temperature and melt time control. To optimise the homogeneity of the fused glasses and to reduce possible depletion of volatile elements during melting, we undertook experiments with basaltic rock and glass powders using different melting temperatures (1300–1700 °C) and melting times (5‐80 s). Major and trace element microanalysis was performed using EPMA and LA‐ICP‐MS. Homogeneous glasses were obtained for temperatures ≥ 1500 °C and melting times ≥ 10 s. High loss (20‐90%) of highly volatile elements (e.g., Cs, Ge, Sn, Pb) was observed for high melting temperatures (≥ 1600 °C) and long melting times (80 s). Standard melting conditions (1600 °C, 10 s) represent a compromise, as the glasses were homogeneous with respect to major and trace elements and, at the same time, were not depleted in elements with condensation temperatures (at a pressure of 10^?4 bar) higher than about 900 K (e.g., Zr, Hf, Ba, Sr, REE, U, Mo, Ni, Rb, Ga). Several international geological reference materials with SiO₂ ranging between 47% m/m and 59% m/m were prepared using our standard melting conditions (1600 °C, 10 s) and subsequently analysed by LA‐ICP‐MS. These samples also include the new Brazilian basaltic reference material BRP‐1. Matrix‐matched calibration of the LA‐ICP‐MS data was performed using the basaltic reference glasses KL2‐G, ML3B‐G, BCR‐2G and BHVO‐2G. Most analytical data agreed within uncertainty at the 95% confidence level with the GeoReM preferred values published in the GeoReM database for reference materials of geological and environmental interest. To demonstrate routine bulk LA‐ICP‐MS analyses of geochemical and cosmochemical samples using the whole rock fusion technique, we also present trace element data for ocean island basalts from Lanai (Hawaii) and of Martian meteorites.  相似文献   

Galaxy formation and evolution,by Houjun Mo,Frank van den Bosch and Simon White     

Dmitry Sokoloff 《地球物理与天体物理流体动力学》2013,107(6):654-655

  相似文献   

Non-local effects in the mean-field disc dynamo I. An asymptotic expansion     

Vladimir Priklonsky  Anvar Shukurov  Dmitry Sokoloff  Andrew Soward 《地球物理与天体物理流体动力学》2013,107(1-2):97-114

Abstract

We reconsider thin-disc global asymptotics for kinematic, axisymmetric mean-field dynamos with vacuum boundary conditions. Non-local terms arising from a small but finite radial field component at the disc surface are consistently taken into account for quadrupole modes. As in earlier approaches, the solution splits into a local part describing the field distribution along the vertical direction and a radial part describing the radial (global) variation of the eigenfunction. However, the radial part of the eigenfunction is now governed by an integro-differential equation whose kernel has a weak (logarithmic) singularity. The integral term arises from non-local interactions of magnetic fields at different radii through vacuum outside the disc. The non-local interaction can have a stronger effect on the solution than the local radial diffusion in a thin disc, however the effect of the integral term is still qualitatively similar to magnetic diffusion.  相似文献   

The galactic dynamo: Axisymmetric and non-axisymmetric modes     

Yulia Krasheninnikova  Alexander Ruzmaikin  Dmitry Sokoloff  Anvar Shukurov 《地球物理与天体物理流体动力学》2013,107(1-3):131-146

Abstract

We discuss recent developments in the theory of large-scale magnetic structures in spiral galaxies. In addition to a review of galactic dynamo models developed for axisymmetric disks of variable thickness, we consider the possibility of dominance of non-axisymmetric magnetic modes in disks with weak deviations from axial symmetry. Difficulties of straightforward numerical simulation of galactic dynamos are discussed and asymptotic solutions of the dynamo equations relevant for galactic conditions are considered. Theoretical results are compared with observational data.  相似文献   

Mammal fauna during the Late Pleistocene and Holocene in the far northeast of Europe     

Dmitry Ponomarev  Andrey Puzachenko  Olga Bachura  Pavel Kosintsev  Johannes van der Plicht 《Boreas: An International Journal of Quaternary Research》2013,42(3):779-797

The paper summarises materials on the mammal remains in northeastern Europe, dated by radiocarbon. Altogether, 23 local faunas of small mammals and 47 local faunas of large mammals were analysed. Multidimensional statistical analysis shows a strong correlation between changes in small mammal fauna composition and climate changes throughout time. The correlations with the spatial gradients, however, are less pronounced. The faunas are classified into three groups: (1) faunas of Holocene age; (2) Late Pleistocene ‘stadial’ assemblages; and (3) Late Pleistocene ‘interstadial’ assemblages. In some cases, changes in species abundance are better understood in terms of biotic interrelations rather than of climatic effects. The most pronounced change in small mammal fauna composition and structure occurred at the Preboreal/Boreal boundary, and a less conspicuous alteration took place at the LGM/Lateglacial transition. The most noticeable transformation in the large mammal fauna composition is dated to the early Holocene. Less significant changes are observed at the Middle Weichselian/LGM transition and at the LGM/Lateglacial transition. It is safely concluded that variations in the faunas of small and large mammals recorded in NE Europe during the last 35 000 years occurred synchronously and unidirectionally.  相似文献