Nutrient (P, N) dynamics in the southwestern Kattegat, Scandinavia: sedimentation and resuspension effects     

C. Christiansen  F. Gertz  M. J. C. Laima  L. C. Lund-Hansen  T. Vang  C. Jürgensen 《Environmental Geology》1997,29(1-2):66-77

 The yearly nutrient supply from land and atmosphere to the study area in SW Kattegat is 10 900 tons of N and 365 tons of P. This is only few percent of the supply from adjacent marine areas, as the yearly transport through the study area is 218 000 tons of N and 18 250 tons of P. Yearly net deposition makes up 1340 tons of N (on average 2.5 g m^–2 yr^–1) and 477 ton of P (on average 0.9 g m^–2 yr^–1). Shallow-water parts of the study area have no net deposition because of frequent (>35% of the year) resuspension. Resuspension frequency in deep water is <1% of the year. Resuspension rates, as averages for the study area, are 10–17 times higher than net deposition rates. Because of resuspension, shallow-water sediments are coarse lag deposits with small amounts of organic matter (1.1%) and nutrients (0.04% N and 0.02% P). Deep-water sediments, in contrast, are fine grained with high levels of organic matter (11.7%) and nutrients (0.43% N and 0.15% P). Laboratory studies showed that resuspension changes the diffusive sediment water fluxes of nutrients, oxygen consumption, and penetration into the sediment. Fluxes of dissolved reactive phosphate from sediment to water after resuspension were negative in organic-rich sediments (13.2% organic matter) with low porosity (56) and close to zero in coarse sediments with a low organic matter content (2.3%) and high porosity (73). Fluxes of inorganic N after resuspension were reduced to 70% and 0–20% in relation to the rates before resuspension, respectively. Received: 10 July 1995 · Accepted: 19 January 1996  相似文献   

FUZZY COMPREHENSIVE EVALUATION OF CONTAINER TRANSPORTATION MODES ALONG THE CHANGJIANG RIVER MAIN LINE AND ITS DELTA AREA   总被引：1，自引：0，他引：1  

ZHANGShi-yu XIAOHan-liang 《中国地理科学(英文版)》2003,13(3):259-261

The Changjiang River (Yangtze) is one of the fastest growth areas of container transportation in Chi-na. Rail, road and water transportation have competed against each other for container transportation in the Chang-jiang River main line and its delta area. It is of significance to assess these different transportation modes scientifi-cally in order to organize container transportation efficiently in this area and make decision for integral plan and construction of transportation system in this area. This paper outlines application of fuzzy comprehensive evaluation to appraise different modes of typical direction of containers. Twelve assessment indexes were decided. Membership functions were formulated. Evaluation results indicated that road transportation was optimal mode in the Changjiang River delta area, however water transportation was the primary way in the Changjiang River main line.  相似文献   

Transient chaos and resonant phase mixing in violent relaxation     

Henry E. Kandrup  Ileana M. Vass  Ioannis V. Sideris 《Monthly notices of the Royal Astronomical Society》2003,341(3):927-936

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On the universal outcome of star formation: is there a link between stars and brown dwarfs?     

Pavel Kroupa †  Jerome Bouvier  Gaspard Duchêne  Estelle Moraux 《Monthly notices of the Royal Astronomical Society》2003,346(2):354-368

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A high-resolution rotation curve of NGC 6822: a test-case for cold dark matter     

D. T. F. Weldrake  W. J. G. de Blok †  F. Walter 《Monthly notices of the Royal Astronomical Society》2003,340(1):12-28

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Latitudinal transport by barotropic waves in Titan's stratosphere.: II. Results from a coupled dynamics-microphysics-photochemistry GCM     

D. Luz  F. Hourdin  S. Lebonnois 《Icarus》2003,166(2):343-358

We present a 2D general circulation model of Titan's atmosphere, coupling axisymmetric dynamics with haze microphysics, a simplified photochemistry and eddy mixing. We develop a parameterization of latitudinal eddy mixing by barotropic waves based on a shallow-water, longitude-latitude model. The parameterization acts locally and in real time both on passive tracers and momentum. The mixing coefficient varies exponentially with a measure of the barotropic instability of the mean zonal flow. The coupled GCM approximately reproduces the Voyager temperature measurements and the latitudinal contrasts in the distributions of HCN and C₂H₂, as well as the main features of the zonal wind retrieved from the 1989 stellar occultation. Wind velocities are consistent with the observed reversal time of the North-South albedo asymmetry of 5 terrestrial years. Model results support the hypothesis of a non-uniform distribution of infrared opacity as the cause of the Voyager temperature asymmetry. Transport by the mean meridional circulation, combined with polar vortex isolation may be at the origin of the latitudinal contrasts of trace species, with eddy mixing remaining restricted to low latitudes most of the Titan year. We interpret the contrasts as a signature of non-axisymmetric motions.  相似文献   

Virial oscillations of celestial bodies: V. The structure of the potential and kinetic energies of a celestial body as a record of its creation history     

V. I. Ferronsky  S. A. Denisik  S. V. Ferronsky 《Celestial Mechanics and Dynamical Astronomy》1996,64(3):167-183

The physical meaning of the terms of the potential and kinetic energy expressions, expanded by means of the density variation function for a nonuniform self-gravitating sphere, is discussed. The terms of the expansions represent the energy and the moment of inertia of the uniform sphere, the energy and the moment of inertia of the nonuniformities interacting with the uniform sphere, and the energy of the nonuniformities interacting with each other. It follows from the physical meaning of the above components of the energy structure, and also from the observational fact of the expansion of the Universe that the phase transition, notably, fusion of particles and nuclei and condensation of liquid and solid phases of the expanded matter accompanied by release of energy, must be the physical cause of initial thermal and gravitational instability of the matter. The released kinetic energy being constrained by the general motion of the expansion, develops regional and local turbulent (cyclonic) motion of the matter, which should be the second physical effect responsible for the creation of celestial bodies and their rotation.  相似文献   

Dynamics of rotating triple systems: statistical escape theory versus numerical simulations     

M. Valtonen  A. Mylläri  V. Orlov  A. Rubinov 《Monthly notices of the Royal Astronomical Society》2005,364(1):91-98

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Hydrodynamical simulations of the decay of high-speed molecular turbulence – II. Divergence from isothermality     

Georgi Pavlovski  Michael D. Smith  Mordecai-Mark Mac Low 《Monthly notices of the Royal Astronomical Society》2006,368(2):943-958

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The radial distribution of blue straggler stars and the nature of their progenitors     

M. Mapelli  S. Sigurdsson  F. R. Ferraro  M. Colpi  A. Possenti  B. Lanzoni 《Monthly notices of the Royal Astronomical Society》2006,373(1):361-368

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