Periodic rotations of a rigid body located at the libration point     

Andrzej J. Maciejewski  Zuzanna Niedzielska 《Celestial Mechanics and Dynamical Astronomy》1990,49(1):31-42

Periodic rotations of a rigid body close to the flat motions were found. Their orbital stability was investigated. Analysis was done up to second order of the small parameter. It was proved that solutions found are orbitally stable except of the third order resonance case. This resonance do not appear if terms up to the first order of small parameter are considered only.  相似文献   

Petrogenesis of Songshugou dunite body in the Qinling orogenic belt,Central China: Constraints from geochemistry and melt inclusions   总被引：3，自引：0，他引：3  

SU Li    SONG Shuguang & ZHOU Dingwu . Key Laboratory of Continental Dynamics of the Ministry of Education  Department of Geology  Northwestern University  Xi’an  China  . The Geological Lab Center  China University of Geosciences 《中国科学D辑(英文版)》2005,48(8):1146-1157

The chemical variation of the Earth’s mantle rocks has been interpreted to reflect multiple episodes of partial melting. With the increasing of melt generation and extraction, the readily molten minerals and incompatible elements decrease in the residual mantle peridotite. The present-day gladiate of the Earth, however, cannot cause mantle batch melting[1], nor 40% partial melting that allows pyroxenes to be completely dissolved into melt and forms dunite[2,3]. Recent studies show that mantl…  相似文献   

An application of the propagator matrix of dynamic ray tracing: The focusing and defocusing of body waves by three-dimensional velocity structure in the source region     

V. F. Cormier 《Geophysical Journal International》1986,87(3):1159-1180

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Geographical Variation of Body Size of Neocalanus cristatus, N. plumchrus and N. flemingeri in the Subarctic Pacific and Its Marginal Seas: Implications for the Origin of Large Form of N. flemingeri in the Oyashio Area     

Atsushi Tsuda  Hiroaki Saito  Hiromi Kasai 《Journal of Oceanography》2001,57(3):341-352

Size distributions of Neocalanus cristatus, N. flemingeri and N. plumchrus were investigated in the eastern and the western subarctic gyres and three marginal seas of the North Pacific during the diapause period to examine the geographical variation in body size of Neocalanus species and to clarify the origin of the large biennial N. flemingeri which has been observed in the Oyashio region. There were significant among region variations in body sizes for all three species of Neocalanus. Generally, the body sizes of the copepods were larger in the marginal seas and marginal areas of the open ocean. In the open ocean, the body sizes increased westward. These patterns of variation in the body sizes roughly correlated with local food availability. Distribution of biennial N. flemingeri was restricted to the Sea of Japan, the Okhotsk Sea and the Oyashio region. The large-sized biennial N. flemingeri were abundantly observed in the Okhotsk Sea, and the medium-sized biennial individuals were observed in the Sea of Japan. These facts strongly suggest that the large biennial N. flemingeri in the Oyashio region are advected from the Okhotsk Sea.  相似文献   

Idealised flow models to predict alluvial sandstone body distribution in the Middle Jurassic Yorkshire Basin     

Jan Alexander 《Marine and Petroleum Geology》1986,3(4)

Prediction of the subsurface position of alluvial channel sandstones is of great importance in the search for potential hydrocarbon reservoirs. For maximum production at minimum expense, wells need to be sited where there is abundant sandstone and, for enhanced oil recovery, detailed knowledge of sandstone-body geometry and connectivity is desirable. Attempts to predict the position of sandstone-bodies in the subsurface have included theoretical computer simulation and detailed empirical modelling of alluvial architecture (three-dimensional rock type distributions). Up to now, no reliable predictive method has been developed and any improvement is of significance.The method presented here combines the theoretical approach to tectonic control of alluvial architecture with the available geological data to predict subsurface concentrations and orientations of alluvial sandstone bodies.  相似文献   

A methodology for defining homogeneous water bodies in estuaries – Application to the transitional systems of the EU Water Framework Directive     

J.G. Ferreira  A.M. Nobre  T.C. Simas  M.C. Silva  A. Newton  S.B. Bricker  W.J. Wolff  P.E. Stacey  A. Sequeira 《Estuarine, Coastal and Shelf Science》2006,66(3-4):468-482

A methodology is developed and tested for division of estuarine and coastal systems into water bodies for monitoring and management purposes. This division is often implicit in the choice of sampling stations and in pollution abatement measures applied to different locations – it is now an explicit requirement of European Union Directive 2000/60/EC (Water Framework Directive) and recommended by United States Agencies such as EPA and NOAA. The approach considers both natural characteristics and the human dimension, by means of a stepwise methodology, which considers, on the one hand, morphology and salinity distribution, and, on the other, appropriate indicators of pressure and state. In the present application, nitrogen and phosphorus loading was used as the pressure component and chlorophyll a and dissolved oxygen as indicators of state. The criteria for system division were defined based on (1) an adimensional shape factor and salinity classes for the natural component; and (2) a normalised pressure index and (ASSETS) eutrophication symptom classes for the human dimension. Water quality databases and GIS were used to develop spatial distributions for the various components, and the results were aggregated into a final water body division, using tidal excursion as a “common sense” test. The methodology was applied to three well-studied systems in Portugal, a tubular estuary (Mondego), a wide lagunal estuary (Sado) and a coastal barrier island system (Ria Formosa). Although a final definition of water bodies will usually be a policy decision, this type of approach for the division of coastal systems into management units scientifically informs the decision-making process.  相似文献   

Numerical study on the reverse drift force of floating BBDB wave energy absorbers     

D. C. Hong  S. Y. Hong  S. W. Hong 《Ocean Engineering》2004,31(10):1257-1294

The motions and time-mean horizontal drift forces of floating backward-bent duct buoy wave energy absorbers in regular waves are calculated taking account of the oscillating surface-pressure due to the pressure drop in the air chamber above the oscillating water column within the scope of the linear wave theory. The present numerical results show that the time-mean drift forces of backward-bent duct buoys are in the reverse direction of propagation of the incident waves over specific frequency ranges as found by McCormick through his experimental work. The drift force has been calculated by the near-field method. A brief discussion on Maruo’s formula which shows that the time-mean drift force must be in the direction of propagation of the incident waves, has also been presented.  相似文献   

赤鼻棱鳀松果体显微结构研究     

邓红权  何大仁 《台湾海峡》1997,(2)

本文用组织学方法研究了赤鼻棱鳀（Thrissapurava）松果体的形态结构，结果表明赤鼻棱鳀有松果体窗，并有发达的松果体，感光细胞聚集成团，顶突伸入终囊腔中，终囊类型为折褶型。背囊由单层细胞构成，细胞大而圆，松果体司感光内分泌功能。  相似文献   

文昌鱼卵母细胞发育成熟过程中高尔基复合体数量的变化   总被引：1，自引：0，他引：1  

方永强  林秋明  齐襄 《台湾海峡》1992,(1)

本工作采用细胞学和电子显微镜技术,较详细观察了文昌鱼卵细胞在发育成熟过程中高尔基复合体数量的变化。研究结果表明,高尔基体的数量变化可作为卵母细胞发育成熟的标志,可为确定文昌鱼卵巢成熟度提供科学依据。  相似文献   

Reference points and reference directions for size-based indicators of community structure     

Jennings  Simon; Dulvy  Nicholas K. 《ICES Journal of Marine Science》2005,62(3):397-404

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