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31.
Lei Chen Shengmiao Wu Feng Yuan 《Monthly notices of the Royal Astronomical Society》2009,398(4):1900-1904
We consider a thin accretion disc warped due to the Bardeen–Petterson effect, presenting both analytical and numerical solutions for the situation in which the two viscosity coefficients vary with radius as a power law, with the two power-law indices not necessarily equal. The analytical solutions are compared with numerical ones, showing that our new analytical solution is more accurate than the previous one, which overestimated the inclination change in the outer disc. Our new analytical solution is appropriate for moderately warped discs, while for extremely misaligned discs only a numerical solution is appropriate. 相似文献
32.
33.
Kuninao Tada Marut Suksomjit Kazuhiko Ichimi Yui Funaki Shigeru Montani Machiko Yamada Paul J. Harrison 《Journal of Oceanography》2009,65(6):885-891
The importance of the nitrogen source for phytoplankton growth in a highly eutrophic embayment, Dokai Bay, was investigated.
The DIN concentration often exceeded 100 μM of which 40–70% was NH4
+. During two incubation experiments, the natural assemblage of mainly diatoms took up NH4
+ instead of NO3
−. The growth of two Skeletonema species isolated in Dokai Bay were significantly faster on NH4
+ (1.86 and 1.27 div. d−1 respectively) than on NO3
− (1.55 and 1.04 div. d−1 respectively). Our results indicated that these diatoms could grow faster by using NH4
+ compared to NO3
− in this eutrophic bay. 相似文献
34.
A fully three-dimensional (3D), time-dependent, MHD interplanetary global model (3D IGM) has been used, for the first time, to study the relationship between different forms of solar activity and transient variations of the north-south component, Bz, of the interplanetary magnetic field (IMF) at 1 AU. One form of solar activity, the flare, is simulated by using a pressure pulse at different locations near the solar surface and observing the simulated IMF evolution of B (=-Bz) at 1 AU. Results show that, for a given pressure pulse, the orientation of the corresponding transient variation of Bz has a strong relationship to the location of the pressure pulse and the initial conditions of the IMF. Two initial IMF conditions are considered: a unipolar Archimedean spiral with outward polarity and a flat heliospheric current sheet (HCS) with outward polarity in the northern hemisphere and which gradually reverses polarity in the solar equatorial plane to inward polarity in the southern heliospheric hemisphere. The wave guide effect of the HCS is also demonstrated. 相似文献
35.
基于离散 Possion积分提出了一种灵活直接的向下延拓新方法 ,证明了方法的存在性 ,利用模拟数据进行的数值实验取得了很好的效果。 相似文献
36.
We present here a numerical modelling study of dislocations in perovskite CaTiO3. The dislocation core structures and properties are calculated through the Peierls–Nabarro model using the generalized stacking
fault (GSF) results as a starting model. The GSF are determined from first-principles calculations using the VASP code. The
dislocation properties such as collinear, planar core spreading and Peierls stresses are determined for the following slip
systems: [100](010), [100](001), [010](100), [010](001), [001](100), [001](010),
and All dislocations exhibit lattice friction, but glide appears to be easier for [100](010) and [010](100).
[001](010) and [001](100) exhibit collinear dissociation. Comparing Peierls stresses among tausonite (SrTiO3), perovskite (CaTiO3) and MgSiO3 perovskite demonstrates the strong influence of orthorhombic distortions on lattice friction. However, and despite some quantitative
differences, CaTiO3 appears to be a satisfactory analogue material for MgSiO3 perovskite as far as dislocation glide is concerned. 相似文献
37.
Anna Kwietniak 《Acta Geophysica》2015,63(1):201-213
Long Period Long Duration (LPLD) signals are unusual seismic events that can be observed during hydraulic fracturing. These events are very similar in appearance to tectonic tremors sequences, which were first observed in subduction zones. Their nature is not well known. LPLD might be related to the productivity of the reservoir. Different methods of the LPLD events’ detection recorded during hydraulic fracturing are presented. The author applied two methods for LPLD detection–Butterworth filtering and Continuous Wavelet Transform (CWT). Additionally, a new approach to LPLD events detection–instantaneous seismic attributes–was used, common in a classical seismic interpretation but not in microseismic monitoring. 相似文献
38.
Several horizons of a unique lithotype called “chertbreccia” are interbedded within the Proterozoic platform sediments of
the Peninsular India. These cherty rocks with brecciated texture appearing as blocky masses were earlier diversely interpreted
as being products of disparate processes such as fault-zone breccias, collapse breccias, and so on. Two of these horizons,
one from the Kaladgi Basin (Dharwar Craton) and the other from the Dhar Forest Inlier of the Vindhyanchal Basin (Bundelkhand
— Aravalli Craton) are compared in context of their geological setting, field relations and petrological constitution. A model
of the mode of development of these peculiar rocks is reconstructed, taking into account their characters and limitations
of previous interpretations. They are interpreted as transported debris deposits of syntectonogenic material released during
the episodic activity of the growth faults of the Kaladgi and Vindhyanchal Basins that was diagenetically silicified. 相似文献
39.
Tian Li Yan Liu Xiao Cheng LunXi Ouyang XinQing Li JiPing Liu Mohammed Shokr FengMing Hui Jing Zhang JiaHong Wen 《中国科学:地球科学(英文版)》2017,60(4):697-706
Antarctic tabular icebergs are important active components in the ice sheet-ice shelf-ocean system. Seafloor topography is the key factor that affects the drifting and grounding of icebergs, but it has not been fully investigated. This study analyzes the impact of seafloor topography on the drifting and grounding of Antarctic tabular icebergs using Bedmap-2 datasets and iceberg route tracking data from Brigham Young University. The results highlight the following points. (1) The quantitative distributions of iceberg grounding events and the tracking points of grounded icebergs are mainly affected by iceberg draft and reach their peak values in sea water with depths between 200 m and 300 m. The peak tracking point number and linear velocity of free-drifting icebergs are found in the Antarctic Slope Front (water depth of approximately 500 m). (2) The area of possible grounding regions of small-scale icebergs calved from ice shelf fronts accounts for 28% of the sea area at water depths less than 2000 m outside the Antarctic coastline periphery (3.62 million km2). Their spatial distribution is mainly around East Antarctica and the Antarctic Peninsula. The area of possible grounding regions of large tabular icebergs with long axes larger than 18.5 km (in water depths of less than 800 m) accounts for 74% of the sea area. (3) The iceberg drifting velocity is positively correlated with ocean depth in areas where the depth is less than 2000 m (R=0.85, P<0.01). This result confirms the effect of water depth variations induced by seafloor topography fluctuations on iceberg drifting velocity. 相似文献
40.
Precise photorealistic visualization for restoration of historic buildings based on tacheometry data
This paper puts forward a 3D reconstruction methodology applied to the restoration of historic buildings taking advantage of the speed, range and accuracy of a total geodetic station. The measurements representing geo-referenced points produced an interactive and photorealistic geometric mesh of a monument named ‘Neoria.’ ‘Neoria’ is a Venetian building located by the old harbor at Chania, Crete, Greece. The integration of tacheometry acquisition and computer graphics puts forward a novel integrated software framework for the accurate 3D reconstruction of a historical building. The main technical challenge of this work was the production of a precise 3D mesh based on a sufficient number of tacheometry measurements acquired fast and at low cost, employing a combination of surface reconstruction and processing methods. A fully interactive application based on game engine technologies was developed. The user can visualize and walk through the monument and the area around it as well as photorealistically view it at different times of day and night. Advanced interactive functionalities are offered to the user in relation to identifying restoration areas and visualizing the outcome of such works. The user could visualize the coordinates of the points measured, calculate distances and navigate through the complete 3D mesh of the monument. The geographical data are stored in a database connected with the application. Features referencing and associating the database with the monument are developed. The goal was to utilize a small number of acquired data points and present a fully interactive visualization of a geo-referenced 3D model. 相似文献