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371.
Takeshi Izumo 《Ocean Dynamics》2005,55(2):110-123
The equatorial undercurrent (EUC), the shallow meridional overturning cells feeding it, and their role in El Niño and decadal variability in the equatorial Pacific are studied using both in situ data and an ocean general circulation model. Using temperature and current data from the TAO/TRITON moorings at the equator, their data gaps are filled and it was shown that continuous time series of mass transport, temperature, depth, and kinetic energy of the EUC could be constructed for the period 1980–2002 with an excellent accuracy. This dataset was analysed and used to validate the output from an oceanic general circulation model (OGCM). The OGCM was then used to find that variations in the strength of the EUC, shallow meridional overturning (pycnocline convergence and surface divergence), and equatorial upwelling had the same variations in mass transport on interannual and longer time scales within the period 1951–1999. These variations are all caused by variations of the zonal wind stress zonally integrated, in agreement with simple linear and steady dynamics theories. Impact of these mass transport variations and of temperature variations on heat budgets in the entire equatorial band of the Pacific and in its eastern part are quantified. 相似文献
372.
1 INTRODUCTION The ocean is a very important source of heat and water vapor for the atmosphere. Its changes in state are mainly reflected by SST, which varies in high frequency (or called the ENSO variability) and low frequency (or known as interdecadal variability). Studies[1] have shown that the spatial structure for low frequency is much similar to that for high frequency, which is also known as ENSO-like mode. Called “teleconnection”, the anomalous link between the El Ni?o phen… 相似文献
373.
本文结合江西地勘局勘单位的实际,总结了在改革和发展中取得的经验教训,运用工商管理理论,就地勘单位如何实现现经营战略提出了基本对策,即确立目标,创新意识,调整战略,建立企业家群体。 相似文献
374.
本文结合盆地的区域地质背景,分析了三塘湖盆地的盖层沉积构造特征、找矿目的层的空间展布、地下水“补-径-排”系统和层间氧化带发育特征,认为该盆地相对稳定,埋藏浅的斜坡带地段具备了层间氧化带砂岩型铀矿成矿环境,应进一步开展工作。 相似文献
375.
R. R. Viana G. M. da Costa E. De Grave H. Jordt-Evangelista W. B. Stern 《Physics and Chemistry of Minerals》2002,29(1):78-86
The Mössbauer spectra of several blue beryls have been obtained in the temperature range of 4.2–500 K. A common feature observed in all room-temperature spectra is the presence of an asymmetric Fe2+ doublet (ΔE Q ?~?2.7?mm?s?1, δ?~?1.1?mm?s?1), with a very broad low-velocity peak. This asymmetry seems to be related to a relaxation process involving ferrous ions and water molecules in the structural channels, as suggested by Price et?al. (1976). Surprisingly, the spectrum at 500?K also shows a broad, but symmetrical, doublet, with a clear splitting of the lines indicating the presence of at least two Fe2+ components. The room-temperature spectrum obtained after the 500?K run shows the same features as prior to the heating. At 4.2?K the spectrum of a deep blue beryl was well fitted with four symmetrical doublets, one of which could be related to Fe2+ in the structural channels. Ferrous ion was also found to occupy the octahedral and tetrahedral sites, whereas ferric ion is most probably located in the octahedral site. A meaningful fit of the room-temperature spectrum, as well as an explanation for the temperature dependence of the Mössbauer spectra, are discussed. Finally, it is believed that the color in beryl will be dictated by the relative proportions of Fe3+ in the octahedral sites and of Fe2+ in the channels. 相似文献
376.
抚仙湖北岸景观生态建设 总被引:3,自引:0,他引:3
抚仙湖北岸是旅游业发展的黄金海岸,开发历史长,污染较为集中。通过对现存的主要环境问题的分析,根据流域生态学与管理学的原理,提出抚仙湖北岸景观生态建设的途径:(1)实施老环湖公路以下农田的退垦还湖,减少农田污染;(2)拆迁湖滨带居民点,消除农村污染。(3)拆除部分规模小、污染大的旅游度假设施,消除旅游污染和景观障碍。(4)建立主要人湖口经济性人工湿地,净化面源污水。(5)恢复万米沙滩,营造自然和谐的湖滨环境。(6)发展观光农业生态园,创建高原湖泊滨海旅游度假区新型模式。 相似文献
377.
Todor Ruskov Ivan Spirov Harry W. Green II Daniela Kovacheva Peter Tzvetkov Milena Georgieva Larissa Dobrzhinetskaya 《Physics and Chemistry of Minerals》2008,35(9):485-491
Analysis of 57Fe transmission Mössbauer spectra collected on a system where the proportional counter has been replaced with a silicon drift detector (SDD) to test milliprobing of mineral samples is described. In the region of the 14.4 keV Mössbauer line the detector has about 70% efficiency and is capable of delivering spectroscopic information with a high energy resolution and high counting rate. Satisfactory results are obtained from a phase analysis of mixtures of olivine and ilmenite in the proportion 97:3, 99:1 wt%, where in the latter case 2.4 μg of Fe3+ in the form of hematite was found in the ilmenite. New perovskite-type minerals (Pb1.33Ba0.67Fe2O5, Pb1.33Sr0.67Fe2O5 and Pb1.33Ba0.33Sr0.33Fe2O5), synthesised by a combustion method, were studied by X-ray diffraction and Mössbauer spectroscopy as well. The advantage of the system with SDD compared to a conventional Mössbauer spectrometer equipped with a proportional counter as a detector is demonstrated for the perovskite samples. The Mössbauer set-up with the silicon drift detector may be successfully used for a wide range of materials containing a negligible amount of iron. 相似文献
378.
A new ophiuroid species from the Hauptrogenstein Formation (Middle Jurassic, Bajocian) of the Rehhag ridge near Schöntal, northwestern Switzerland, is described based on 34 specimens. The impression of an indeterminate astropectinid sea star has also been found. The fully articulated specimens have been smothered by mobile oolitic dunes or sandwaves. The site can be genetically classified as an obrution deposit and belongs to the widely recognized “Hauptrogenstein type”. The remains are assigned to the genus Geocoma d’Orbigny 1850, best known from the type species, G. carinata (Münster), from the Tithonian Plattenkalk of Zandt. As suggested by Kutscher (1997) this species also includes Ophiocten kelheimense Boehm 1889, now documented by numerous well-preserved specimens from the Plattenkalk of Hienheim. Kutscher assigned the Hienheim specimens to the genus Sinosura Hess 1964 and used both names though G. carinata has priority. Despite rather small differences Sinosura is retained as a valid genus besides Geocoma, and both are placed in the family Aplocomidae Hess 1965. Geocoma and Sinosura share small adpressed arm spines with Aplocoma d’Orbigny 1852. Aplocoma is represented by a number of Triassic and Jurassic species, and the subfamily Aplocominae is proposed herein for the three genera. A second subfamily, Ophiopetrinae, is proposed for the genera Ophiopetra Enay &; Hess 1962 and Ophiohybris Hess 1964, and is characterized by larger, erect arm spines. 相似文献
379.
Kenneth R. Meyer 《Celestial Mechanics and Dynamical Astronomy》1998,70(3):159-165
We consider the evolution of the stable and unstable manifolds of an equilibrium point of a Hamiltonian system of two degrees of freedom which depends on a parameter,ν. The eigenvalues of the linearized system are complex for ν < 0 and purely imaginary for ν > 0. Thus for ν < 0 the equilibrium has a two‐dimensional stable manifold and a two‐dimensional unstable manifold, but for ν > 0 these stable and unstable manifolds are gone. We study the system defined by the truncated generic normal form in this situation. One of two things happens depending on the sign of a certain quantity in the normal form expansion. In one case the two families detach as a single invariant manifold and recedes from the equilibrium as ν tends away from 0 through positive values. In the other case the stable and unstable manifold are globally connected for ν < 0 and the whole structure of these manifolds shrinks to the equilibrium as ν → 0 and disappears. These considerations have interesting implications about Strömgren's conjecture in celestial mechanics and the blue sky catastrophe of Devaney. 相似文献
380.