A VERTICAL DISTRIBUTION MODEL OF NUTRIENTS AND DISSOLVED OXYGEN IN THE SOUTHERN TAIWAN STRAIT   总被引：3，自引：0，他引：3  

商少凌  洪华生 《中国海洋湖沼学报》1995,13(1):51-61

Sinoe vertical transport of nutrients and dissolved oxygen are quite important in the water col-umn and have drawn serious attention these recent years, a one-dmension numerical model is tried to simulate the vertical distribution of nutrients and dissolved oxygen in June at two research sites in the southemTaiwan Strait. Physical transport parameters are calibrated by temperature simulation, and thenare used to simulate the profiles of NO_3, PO_4 and dissolved oxygen. The simulation was generally success-ful for both stations. The importance of various factors, such as upwelling tidal current andbiogeochemical activities, which influence the vertical distribution of nutrients and dissolved oxygen, is revealed by analysis of the modeling results. Some important rates, fluxes and ratios are also estimated anddiscussed on the basis of simulation.  相似文献   

Calculation of the structure and transition probabilities of low energy levels of Fe and Fe     

Xu Hai-guang  Zhang Shi-wei  Chen Jun-feng  You Jun-han 《Chinese Astronomy and Astrophysics》1995,19(4):495-506

We use analytical wave functions in intermediate coupling to make a complete relativistic calculation of the structure and transition probabilities for the n = 1, 2, 3 states of Fe⁺²⁴. Data for Fe⁺²⁵ are also given for comparison. The results have a high accuracy and those relating to the n = 3 state are given in detail for the first time here.  相似文献   

Numerical continuation of families of frozen orbits in the zonal problem of artificial satellite theory     

Martín Lara  André Deprit  Antonio Elipe 《Celestial Mechanics and Dynamical Astronomy》1995,62(2):167-181

In the zonal problem of a satellite around the Earth, we continue numerically natural families of periodic orbits with the polar component of the angular momentum as the parameter. We found three families; two of them are made of orbits with linear stability while the third one is made of unstable orbits. Except in a neighborhood of the critical inclination, the stable periodic (or frozen) orbits have very small eccentricities even for large inclinations.  相似文献   

《大气一号》气球卫星轨道倾角变化分析   总被引：1，自引：0，他引：1  

刘亚英 《天文学报》1995,36(2):200-207

引起《大气一号》两颗气球卫星（ＤＱ－１Ａ和ＤＱ－１Ｂ）轨道倾角变化的摄动因素主要是太阳光压摄动、大气旋转和日月引力摄动。太阳光压摄动引起气球卫星轨道倾角增大，平均每天变化约０．００１７，大气旋转引起轨道倾角减小，平均每天变化不到０．０００１，但随着高度下降，变化量亦增大，陨落前达０．００２。本文根据卫星轨道摄动理论，给出气球卫星轨道倾角变化的一种定量分析方法，得到的分析结果为：（１）由太阳光压摄动  相似文献   

Comment on the paper “Fast tidal cycling and the origin of life” by Richard Lathe     

P. Varga  K.R. Rybicki 《Icarus》2006,180(1):274-276

We show that the fast tidal cycling postulated by Lathe [Lathe, R., 2004. Icarus 168, 18-22] is not a plausible mechanism to explain the origin of life on Earth about 3.9 Ga ago. The value of LOD at this remote epoch was probably comprised between 15 to 17 h, and the Earth-Moon distance was only about 20% smaller than nowadays, implying that the tidal frequencies and amplitudes were not so dramatically different from the present ones as stated in Lathe's paper.  相似文献   

An explanation for the soft X-ray excess in active galactic nuclei   总被引：1，自引：0，他引：1  

J. Crummy  A. C. Fabian  L. Gallo  R. R. Ross 《Monthly notices of the Royal Astronomical Society》2006,365(4):1067-1081

We present a large sample of type 1 active galactic nuclei (AGN) spectra taken with XMM–Newton , and fit them with both the conventional model (a power law and blackbody) and the relativistically blurred photoionized disc reflection model of Ross & Fabian. We find that the disc reflection model is a better fit. The disc reflection model successfully reproduces the continuum shape, including the soft excess, of all the sources. The model also reproduces many features that would conventionally be interpreted as absorption edges. We are able to use the model to infer the properties of the sources, specifically that the majority of black holes in the sample are strongly rotating, and that there is a deficit in sources with an inclination >70°. We conclude that the disc reflection model is an important tool in the study of AGN X-ray spectra.  相似文献   

Interannual variability of water ice clouds over major martian volcanoes observed by MOC     

Jennifer L. Benson  Philip B. James  Ryan Remigio 《Icarus》2006,184(2):365-371

Using Mars Global Surveyor Mars Orbiter Camera daily global maps, cloud areas have been measured daily for water ice clouds associated with the topography of the major volcanoes Olympus Mons, Ascraeus Mons, Pavonis Mons, Arsia Mons, Elysium Mons, and Alba Patera. This study expands on that of Benson et al. [Benson, J.L., Bonev, B.P., James, P.B., Shan, K.J., Cantor, B.A., Caplinger, M.A., 2003. Icarus 165, 34-52] by continuing their cloud area measurements of the Tharsis volcanoes, Olympus Mons and Alba Patera for an additional martian year (August 2001-May 2003) and by also including Elysium Mons measurements from March 1999 through May 2003. The seasonal trends in cloud activity established by Benson et al. [Benson, J.L., Bonev, B.P., James, P.B., Shan, K.J., Cantor, B.A., Caplinger, M.A., 2003. Icarus 165, 34-52] for the five volcanoes studied earlier are corroborated here with an additional year of coverage. For volcanoes other than Arsia Mons, interannual variations that could be associated with the large 2001 planet encircling dust storm are minimal. At Arsia Mons, where cloud activity was continuous in the first two years, clouds disappeared totally for ∼85° of LS (LS=188°-275°) due to the dust storm. Elysium Mons cloud activity is similar to that of Olympus Mons, however the peak in cloud area is near LS=130° rather than near LS=100°.  相似文献   

Evidence for an Hesperian-aged South Circum-Polar Lake Margin Environment on Mars     

James Dickson 《Planetary and Space Science》2006,54(3):251-272

A broad pitted plain and an elongated low rise occur near the south pole of Mars between a region of major cavi (Cavi Angusti) and a regionally smooth and broad valley (Argentea Planum). Viking, Mars Global Surveyor (MGS), and Odyssey data reveal a densely pitted plain covering ∼6750 km², and containing >300 irregularly shaped, steep-walled and flat-floored depressions with a mean diameter of ∼3.5 km. At the southernmost (poleward) extent of this plain are 12 north/south trending linear valleys that are characterized by theater-shaped heads abutting a major cavi within Cavi Angusti. The pitted plain, which abuts Cavi Angusti to the southwest, is separated from the floor of Argentea Planum by a smooth, elongated low rise that extends parallel to the plain for ∼200 km. These unusual features are all found within the Hesperian-aged circumpolar Dorsa Argentea Formation, which has been interpreted by some workers to be an ice-rich glacier-related deposit. We interpret the pitted plain to represent the maximum northern extent of the Angusti lobe ice deposit. The pits are analogous in morphology and distribution to terrestrial kettle holes, which form from the melting of isolated ice-blocks surrounded and partly buried by sediment, to leave hollows. The linear valleys are consistent with sapping valleys formed from the release of an elevated groundwater table, fed by meltwater lakes. On the basis of these characteristics, relationships and analogs, we interpret the marginal facies to represent an ice-sheet/lake contact environment that existed during Hesperian time.  相似文献   

Viscous overstability and eccentricity evolution in three-dimensional gaseous discs     

Henrik N. Latter  Gordon I. Ogilvie 《Monthly notices of the Royal Astronomical Society》2006,372(4):1829-1839

We investigate the growth or decay rate of the fundamental mode of even symmetry in a viscous accretion disc. This mode occurs in eccentric discs and is known to be potentially overstable. We determine the vertical structure of the disc and its modes, treating radiative energy transport in the diffusion approximation. In the limit of very long radial wavelength, an analytical criterion for viscous overstability is obtained, which involves the effective shear and bulk viscosity, the adiabatic exponent, and the opacity law of the disc. This differs from the prediction of a two-dimensional model. On shorter wavelengths (a few times the disc thickness), the criterion for overstability is more difficult to satisfy because of the different vertical structure of the mode. In a low-viscosity disc a third regime of intermediate wavelengths appears, in which the overstability is suppressed as the horizontal velocity perturbations develop significant vertical shear. We suggest that this effect determines the damping rate of eccentricity in protoplanetary discs, for which the long-wavelength analysis is inapplicable and overstability is unlikely to occur on any scale. In thinner accretion discs and in decretion discs around Be stars overstability may occur only on the longest wavelengths, leading to the preferential excitation of global eccentric modes.  相似文献   

Periodic long-term X-ray and radio variability of Cygnus X-1     

Pawe&#; Lachowicz  rzej A. Zdziarski  Alex Schwarzenberg-Czerny  Guy G. Pooley  Shunji Kitamoto 《Monthly notices of the Royal Astronomical Society》2006,368(3):1025-1039

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