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排序方式: 共有140条查询结果,搜索用时 250 毫秒
31.
Tetsuya Tokano 《Planetary and Space Science》2010,58(5):814-829
The orientation of the atmospheric angular momentum vector of Titan and its temporal variation predicted by a general circulation model are analysed and interpreted. The atmospheric angular momentum vector is tilted by a few degrees from the polar axis and the vector rotates (precesses) westward with a constant period of 1 Titan day. The fast westward rotation is likely to be caused by migrating diurnal thermal tides. The tilt is almost cancelled out in the troposphere by the wavenumber 2 pattern of Saturn's gravitational tide, but is more pronounced in the stratosphere, where thermal tides are significant. The predicted tilt angle and the equatorial angular momentum vary with season and maximize when the hemispheric asymmetry of the axial angular momentum or superrotation attains its peak. 相似文献
32.
Roussos Dimitrakopoulos Richard B. McCammon Tetsuya Shoji 《Mathematical Geosciences》1994,26(8):877-878
33.
Michail A. Strunin Tetsuya Hiyama Jun Asanuma Tetsuo Ohata 《Boundary-Layer Meteorology》2004,111(3):491-522
This study investigates the convective boundary layer (CBL) that develops over anon-homogeneous surface under different thermal and dynamic conditions. Analysesare based on data obtained from a Russian research aircraft equipped with turbulentsensors during the GAME-Siberia experiment over Yakutsk in Siberia, from April to June 2000.Mesoscale thermal internal boundary layers (MTIBLs) that radically modified CBLdevelopment were observed under unstable atmospheric conditions. It was found thatMTIBLs strongly influenced the vertical and horizontal structures of virtual potentialtemperature, specific humidity and, most notably, the vertical sensible and latent heatfluxes. MTIBLs in the vicinity of the Lena River lowlands were confirmed by clouddistributions in satellite pictures.MTIBLs spread through the entire CBL and radically modify its structure if the CBL isunstable, and strong thermal features on the underlying surface have horizontal scalesexceeding 10 km. MTIBL detection is facilitated through the use of special parameterslinking shear stress and convective motion.The turbulent structure of the CBL with and without MTIBLs was scaled usingthe mosaic or flux aggregate approach. A non-dimensional parameterLRau/Lhetero (where LRau is Raupach's length and Lhetero is the horizontal scale of the surface heterogeneity)estimates the application limit of similarity and local similarity scaling models forthe mosaic parts over the surface. Normalized vertical profiles of wind speed, airtemperature, turbulent sensible and latent heat fluxes for the mosaic parts withLRauLhetero < 1 could be estimated by typical scalingcurves for the homogeneous CBL. Traditional similarity scaling models for the CBLcould not be applied for the mosaic parts with LRau/Lhetero > 1.For some horizontally non-homogeneous CBLs, horizontal sensible heat fluxes werecomparable with the vertical fluxes. The largest horizontal sensible heat fluxes occurred at the top of the surface layer and below the top of the CBL.Formerly affiliated to the Frontier Observational Research System for Global ChangeFormerly affiliated to the Frontier Observational Research System for Global Change 相似文献
34.
Norio Hori Norio Inoue Dangol Purushotam Tetsuya Nishida Jun Kobayashi 《地震工程与结构动力学》2006,35(13):1699-1719
To improve the seismic performance of masonry structures, confined masonry that improves the seismic resistance of masonry structures by the confining effect of surrounding bond beams and tie columns is constructed. This study investigated the earthquake resisting behaviour of confined masonry structures that are being studied and constructed in China. The structural system consists of unreinforced block masonry walls with surrounding reinforced concrete bond beams and tie columns. The characteristics of the structure include: (1) damage to blocks is reduced and brittle failure is avoided by the comparatively lower strength of the joint mortar than that of the blocks, (2) the masonry walls and surrounding reinforced concrete bond beams and tie columns are securely jointed by the shear keys of the tie columns. In this study, wall specimens made of concrete blocks were tested under a cyclic lateral load and simulated by a rigid body spring model that models non‐linear behaviour by rigid bodies and boundary springs. The results of studies outline the resisting mechanism, indicating that a rigid body spring model is considered appropriate for analysing this type of structure. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
35.
Ore value-tonnage diagrams for resource assessment 总被引:4,自引:0,他引:4
An ore value-tonnage diagram has been proposed for assessing mineral resources. Diagrams of W+Mo, and Pb+Zn deposits show
a good linearity between ore value and logarithms of cumulative ore tonnage. Diagrams of the massive sulfide, orthomagmatic,
placer, porphyry, replacement, and stratabound types are also linear. It is assumed, therefore, that deposits of each of these
commodities and these types belong to a single population. In contrast, the ore value-tonnage relations of all the deposits
analyzed here is approximated by the combination of two exponential functions. The same feature is seen for deposits of the
Cu+W+Mo, Cu+Pb+Zn, and Au+Ag commodities, and of the vein and unconformity-related types. This suggests that deposits belonging
to each of such categories are divided into the high and low value groups. We can expect, accordingly, to find high value
deposits of such categories. 相似文献
36.
Tetsuya Watanabe 《Solar physics》1990,126(2):351-366
This paper analyzes soft X-ray spectra obtained from the Hinotori spacecraft for the investigation of plasma motions during the initial phase of the great flare, 1982 June 6. The wavelength calibration of the scanning spectrometers is determined from information on the spacecraft attitude and from the position of the Fexxv resonance line during the decay phase. Hard X-ray bursts, nonthermal line broadenings and blueshifted components in X-ray lines are temporally correlated with time differences of 0–30 s. The possible contribution of the blueshifted component to the line width decreases more rapidly than the nonthermal broadening, which suggests dominant plasma motions are taking place at higher and higher altitude in the corona, because of the increase of electron density in flaring loops. The evolution of the input kinetic energy content to the thermal plasma inferred from line broadenings in the impulsive phase resembles that of the thermal energy content in the source of the Fexxvi emission, which is different from that deduced for Fexxv source. This suggests that the origins of the nonthermal line broadening and Fexxvi source are closely coupled. 相似文献
37.
Tetsuya Komabayashi Kei Hirose Nagayoshi Sata Yasuo Ohishi Leonid S. Dubrovinsky 《Earth and Planetary Science Letters》2007,260(3-4):564-569
A phase transition in pure CaSiO3 perovskite was investigated at 27 to 72 GPa and 300 to 819 K by in-situ X-ray diffraction experiments in an externally-heated diamond-anvil cell. The results show that CaSiO3 perovskite takes a tetragonal form at 300 K and undergoes phase transition to a cubic structure above 490–580 K in a pressure range studied here. The transition boundary is strongly temperature-dependent with a slightly positive dT / dP slope of 1.1 (± 1.3) K/GPa. It is known that the transition temperature depends on Al2O3 content dissolved in CaSiO3 perovskite [Kurashina et al., Phys. Earth Planet. Inter. 145 (2004) 67–74]. The phase transition in CaSiO3(+ 3 wt.% Al2O3) perovskite therefore could occur in a cold subducted mid-oceanic ridge basalt (MORB) crust at about 1200 K in the upper- to mid-lower mantle. This phase transition is possibly ferroelastic-type and may cause large seismic anomalies in a wide depth range. 相似文献
38.
Tetsuya TokanoFritz M. Neubauer 《Icarus》2002,158(2):499-515
The influence of Saturn's gravitational tide on the atmosphere of Titan is investigated by means of a three-dimensional general circulation model. Titan's orbital eccentricity of 0.0292 gives rise to time-dependent radial and librational tide whose potential circles eastward on Titan. Unlike atmospheric tides on terrestrial planets, Saturn's tide on Titan has a large impact on the dynamic meteorology down to the surface. The surface pressure oscillates by up to 1.5 hPa through the orbit. Near the surface the tidal wind dominates the atmospheric flow and exhibits strong temporal and spatial variation. The superposition of the annually present, thermally forced latitudinal pressure gradient and tidally caused pressure variation produces a unique wind pattern near the surface characterized by equatorward flow and high-latitude whirls. At higher levels the tidal wind manifests itself as eastward traveling planetary-scale wave of wavenumber 2 superposed on the background wind. In general tidal winds are more significant in the troposphere, where other forcing mechanisms are weak. Meridional tidal winds become as fast as 5 m s−1 in the troposphere and change direction periodically through the orbit and along the parallel of latitude. Except in the lower troposphere, zonal winds always remain prograde because the tidal wind amplitude is usually smaller than the mean zonal wind. The tide also has a large impact on the mean zonal circulation in the stratosphere. A meridional drift of the descending Huygens Probe in the troposphere would be the easiest way to verify the tidal wind on Titan, but more complete observations of tropospheric wind and surface pressure by a future mission would be required to unveil the complete details of the tidal wind. 相似文献
39.
40.
We investigated the geographical variations in abundance and biomass of the major taxonomic groups of micro- and net-zooplankton along a transect through Ise Bay, central Japan, and neighboring Pacific Ocean in February 1995. The results were used to estimate their secondary and tertiary production rates and assess their trophic roles in this eutrophic embayment in winter. Ise Bay nourished a much higher biomass of both micro- and net-zooplankton (mean: 3.79 and 13.9 mg C m–3, respectively) than the offshore area (mean: 0.76 and 4.47 mg C m–3, respectively). In the bay, tintinnid ciliates, naked ciliates and copepod nauplii accounted for, on average, 69, 18 and 13% of the microzooplankton biomass, respectively. Of net-zooplankton biomass, copepods (i.e. Acartia, Calanus, Centropages, Microsetella and Paracalanus) formed the majority (mean: 63%). Average secondary production rates of micro- and net-zooplankton in the bay were 1.19 and 1.87 mg C m–3d–1 (or 23.1 and 36.4 mg C m–2d–1), respectively, and average tertiary production rate of net-zooplankton was 0.75 mg C m–3d–1 (or 14.6 mg C m–2d–1). Available data approximated average phytoplankton primary production rate as 1000 mg C m–2d–1 during our study period. The transfer efficiency from primary production to zooplankton secondary production was 6.0%, and the efficiency from secondary production to tertiary production was 25%. The amount of food required to support the zooplankton secondary production corresponded to 18% of the phytoplankton primary production or only 1.7% of the phytoplankton biomass, demonstrating that the grazing impact of herbivorous zooplankton was minor in Ise Bay in winter. 相似文献