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951.
辽河外围西部发育了一系列晚中生代陆相沉积盆地。它们经历了前裂谷盆地期、同裂谷盆地期、后裂谷盆地期,以及盆地形成后的改造期四个阶段。在裂谷体制作用下,它们形成了相似的断陷构造样式。但基底结构的基异产生了盆地沉积建造与后裂谷阶段的重大差异。盆地盖层的发育主要决定于后者,因此在裂谷型盆地的油气成藏条件及其演化发带与成块特征。 相似文献
952.
本文在通过对大陆造山带研究历史回顾的基础上,对现令造山带的分类、研究内容、研究方法及前缘问题做了系统论述,认为以大陆动力学为指导思想的造山带主要研究内容应是:造山带的基本组成、结构构造以及造山带形成演化过程和动力学机制。造山后的伸展作用和隆升机制、高压超高压变质岩形成和折返机制、造山带与盆地耦合关系和动力学、以及造山带流体作用研究等是现今造山带研究的前线问题,它们不仅是解决造山带问题的关键,同时对发展完善大陆动力学理论体系有重要意义。 相似文献
953.
Cyrille Flamant Jacques Pelon Bart Brashers Robert A. Brown 《Boundary-Layer Meteorology》1999,93(1):47-73
The internal thermal boundary layer developing over the Mediterranean during a cold-air outbreak associated with a Tramontane event has been studied by means of airborne lidar, in situ sensors, and a modelling approach that consisted of nesting the University of Washington (UW) planetary boundary-layer (PBL) model in an advective zero-order jump model. This approach bypasses some of the deficiencies associated with each model: the absence of the dynamics in the mixed layer for the zero-order jump model and the lack of an inversion at the PBL top for the UW PBL model. Particular attention is given to the parameterization of the entrainment flux at the PBL top. Values of the entrainment closure parameter derived with the model when matching PBL structure observations are much lower than those derived with standard zero-order jump models. They also are in good agreement with values measured in different meteorological situations by other studies. This improvement is a result of the introduction of turbulent kinetic energy production in the mixed layer. 相似文献
954.
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956.
In this paper, a study on the transient response of an elastic structure embedded in a homogeneous, isotropic and linearly elastic half-plane is presented. Transient dynamic and seismic forces are considered in the analysis. The numerical method employed is the coupled Finite-Element–Boundary-Element technique (FE–BE). The finite element method (FEM) is used for discretization of the near field and the boundary element method (BEM) is employed to model the semi-infinite far field. These two methods are coupled through equilibrium and compatibility conditions at the soil–structure interface. Effects of non-zero initial conditions due to the pre-dynamic loads and/or self-weight of the structure are included in the transient boundary element formulation. Hence, it is possible to analyse practical cases (such as dam–foundation systems) involving initial conditions due to the pre-seismic loads such as water pressure and self-weight of the dam. As an application of the proposed formulation, a gravity dam has been analysed and the results for different foundation stiffness are presented. The results of the analysis indicate the importance of including the foundation stiffness and thus the dam–foundation interaction. 相似文献
957.
A.V.Ovcharenko 《中国地震研究》1999,(1)
Traditionally, when creating 4-D models of elastic offsets in the Earth's crust, the data from geodesic and GPS monitoring of offsets on the ground surface, earthquake catalogs, monitoring of the water level and radon content in wells, sea level fluctuations, as well as gravitational and magnetic fields, etc., can be taken as bases for information. In essence, the reason for creating a 4-D model of slow elastic deformations is to approximate the process by a set of plane deformation solitons (solitary waves). The parameters of a set of deformation solitons are obtained by a two-stage inversion. First, the parameters of the model are determined in a kinematic way by the use of a modified simplification of the method. Then, a calibration of the amplitude characteristics of the model is carried out in terms of elastic dynamic offsets. Taking Ural, Northern Tianshan, Greece, and China as examples, models for these regions are created on the basis of seismological, geodesic, deformation, hydrogeological, and 相似文献
958.
The continuous increase in concentration of greenhouse gases in the atmosphere is expected to cool higher levels of the atmosphere. There is some direct and indirect experimental evidence of long-term trends in temperature and other parameters in the mesosphere and lower thermosphere (MLT). Here we look for long-term trends in the annual and semiannual variations of the radio wave absorption in the lower ionosphere, which corresponds to the MLT region heights. Data from central and southeastern Europe are used. A consistent tendency to a positive trend in the amplitude of the semiannual wave appears to be observed. The reality of a similar tendency in the amplitude of the annual wave is questionable in the sense that the trend in the amplitude of the annual wave is probably induced by the trend in the yearly average values of absorption. The phases of both the annual and semiannual waves display a forward tendency, i.e. shift to an earlier time in the year. A tentative interpretation of these results in terms of changes of the seasonal variation of temperature and wind at MLT heights does not contradict the trends observed in those parameters. 相似文献
959.
Lake water levels change under the influences of natural and/or anthropogenic environmental conditions. Among these influences are the climate change, greenhouse effects and ozone layer depletions which are reflected in the hydrological cycle features over the lake drainage basins. Lake levels are among the most significant hydrological variables that are influenced by different atmospheric and environmental conditions. Consequently, lake level time series in many parts of the world include nonstationarity components such as shifts in the mean value, apparent or hidden periodicities. On the other hand, many lake level modeling techniques have a stationarity assumption. The main purpose of this work is to develop a cluster regression model for dealing with nonstationarity especially in the form of shifting means. The basis of this model is the combination of transition probability and classical regression technique. Both parts of the model are applied to monthly level fluctuations of Lake Van in eastern Turkey. It is observed that the cluster regression procedure does preserve the statistical properties and the transitional probabilities that are indistinguishable from the original data. 相似文献
960.
Both, observational and theoretical results support the close connection between bars and box/peanut‐shaped bulges in spiral galaxies. However, for the sub‐class of thick box/peanut‐shaped bulges, an environmental process instead of an internal mechanism is suggested to account for the prominence of the box/peanut component. In this paper a multiwavelength study of the morphology and the kinematics of a sample of thick box/peanut‐shaped bulges is presented. The results suggest a scenario in which interaction events play a significant role in the history of thick box/peanut‐shaped bulge galaxies. Most likely these sources have experienced a mass infall. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献