Winter anomaly observations at the Panská Ves Observatory (Czechoslovakia), 1971–1973     

Jan Laštovička  Pavel Tříska  Reviewer J. Prokop 《Studia Geophysica et Geodaetica》1976,20(4):404-408

Summary The results of the winter anomaly observations at the Panská Ves Observatory on 2775 kHz and 2614 kHz (A3 method, f_eq1 and 0.8 MHz) are studied for the winters of 1971/72 and 1972/73. Ionospheric responses to minor (1972) and major stratospheric warmings are found to be different and relatively small. A regular winter-anomaly background absorption increase with a maximum in January was observed during both winters studied. Magnetic storms are found to play an insignificant, if any, role in the winter-anomaly phenomenon. The relation between magnetic activity and ionospheric absorption seems to be better in non-anomalous periods.  相似文献   

Oceanographic implications of features in NOAA satellite visible imagery     

P. E. La Violette  S. Peteherych  J. F. R. Gower 《Boundary-Layer Meteorology》1980,18(2):159-175

The sunglint areas of the ocean in NOAA satellite visible imagery appear as long swaths that extend from the northern extremes of the North Temperate Zone to the southern extreme of the South Temperate Zone. Examples are shown of complex features apparent in the sunglint area of visible imagery that closely match ocean-related thermal features in the companion infrared imagery. Various interpretations of these features are discussed. Data from the first phase of the Grand Banks Experiment (June 1978) are presented which demonstrate that such sunglint features are related to the strong ocean frontal processes present in this area. Although some of the features may be associated with fog or mist, side-looking airborne radar imagery collected during the experiment confirms the presence of surface roughness variations. The observations strongly suggest that these roughness variations are due to changes in the stability of the atmospheric boundary layer caused by the different surface water temperatures present in the area. The results demonstrate the usefulness of NOAA visible imagery as a tool to aid in the understanding of synoptic ocean processes, and suggest an important application for satellite and airborne synthetic aperture radars in mapping the roughness changes associated with ocean current systems.  相似文献   

A method of measuring the temperature dependence of the electrical conductivity of rocks     

Marcela Laštovičková  Jiří Popule  Reviewer J. Buben 《Studia Geophysica et Geodaetica》1974,18(4):370-380

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Impulsive phase heating by uni-directional current systems in solar flares     

T. N. La Rosa 《Solar physics》1990,126(1):153-175

The thermal interpretation of solar flare impulsive phase hard X-ray emission requires rapid heating of a substantial coronal volume to very high temperatures. In this study we investigate the possibility of producing such heating by current dissipation, driven by a tearing instability associated with a single uni-directional current system. Earlier research is synthesized by coupling the energy equation, including loss terms previously neglected, with an equation describing the evolution of the growing electric field. The resistivity due to the excitation of ion-cyclotron and ion-acoustic waves is computed by assuming marginal stability.It is found, for the fast tearing mode, that for initial growth rates _f 0.3 s^-1 (corresponding to a current channel width l 3 × 10⁵ cm), the electron heating is offset by convective losses, resulting in a very slow temperature rise. Furthermore, hard X-ray emitting temperatures (2 × 10⁸ K) are never realized. For the larger growth rates corresponding to smaller current channel widths, heating from 10⁷ to 10⁸ K can be achieved in a few seconds. However, in this regime the maximum volume that can be heated is only of order 10²⁰ cm³, some three to five orders of magnitude less than the volume of heated material that is inferred from hard X-ray emission measures. These results suggest that in the case of the fast tearing mode a more complicated geometry involving multiple small-scale, oppositely-directed, current channels may be necessary to achieve the required heating.  相似文献   

A practical method to estimate crack openings in concrete structures     

M. Matallah  C. La Borderie  O. Maurel 《国际地质力学数值与分析法杂志》2010,34(15):1615-1633

Numerical modelling of concrete cracking requires robust models able to describe opening and propagation of cracks. Structural concrete codes provide practical relations to describe crack openings. However, these empirical methods were developed for specific structures and cannot be used for general applications. Here, a continuous modelling approach based on damage mechanics is used to compute crack openings in a tie‐beam concrete structure. We propose a post‐processing method to extract crack openings from a continuum damage finite element computation. This method can be applied to all continuum damage/plasticity models. The tie‐beam concrete is characterized by a weak stress gradient; this aspect complicates predictions of crack positions and number. A stochastic method is used to take into account the spatial variability in concrete properties and create a spatially correlated random property field. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

An Inverse Analysis of the Comprehensive Medium Parameters and a Simulation of the Crustal Deformation of the Qinghai-Tibet Plateau   总被引：2，自引：0，他引：2  

杨志强  陈建兵  巨天乙  李天文 《《地质学报》英文版》2004,78(6):1250-1257

sedonthetheoryoffiniteelementanalysis,aninverseanalysismodelforthecomprehensivemediumparametersoftheQinghai-TibetPlateauissetup.WiththehelpofGPSvelocityfield,thecomprehensivecrustalmediumparametersoftheplateauareinverselyanalyzedandthecharacteristicsoftherelatedmovementmacroscopicallysimulated.ItisthenconcludedthatthetectonicdeformationoftheplateauismainlyintheformofaN-ScompressionaccompaniedbyanE-Wstretching,andthepresenttectonicsettingoftheplateaushouldbetheresultofthecollisionbetweentheIndianandtheEurasiancontinentsduringtheCenozoic.  相似文献   

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塔拉  陈阜超  郭良迁  陈聚忠  薄万举 《大地测量与地球动力学》2013,33(4):1-3

????1951??????????????????1999-2007???GPS???????????????????α???????о???????????????岻????ε????α???????????α?????8.0??????????????????????????????8.0?????????????α?????????????α???????????????????????????????????????骲???????????й????λ?????????????????????????????????????γ????????????????????????????????????  相似文献   

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塔拉  陈阜超  韩月萍 《大地测量与地球动力学》2013,33(5):11-15

????1998-2006??????????????????????????????????????о??????????????????????????????????????????39.3°N??磬?????????????????С???????????????????1998-2002???в????????????????????????2002-2004??????????????????????2004-2006??????????  相似文献   

云南地区地壳垂直运动与地震的关系     

郭良迁  塔拉  陈阜超  周海涛  陈聚忠  薄万举 《大地测量与地球动力学》2013,33(1):1-5

利用云南地区1951—2011年的水准复测资料,计算获得了1951—1980年、1980—1994年、1994—2011年、1951—2011年的垂直形变速率图和各个阶段的形变增量场,结合该区的地震活动,研究了垂直形变与地震的关系。结果表明：7级以上地震主要发生在上升区,与区域性上升有关;地震多数发生在垂直形变速率增量场的正值区。  相似文献   

中国大陆应变应力场研究     

郭良迁  周海涛  杜雪松  塔拉 《华南地震》2012,32(1):1-10

根据1999～2009年网络工程GPS观测资料计算得到的应变率参数,研究了中国大陆地壳的应变应力场及其地壳现今的水平活动特征。结果表明,中国大陆地壳西部青藏亚板块的压应力主方向围绕藏南和阿萨姆构造结向北、东、南依次辐射撒开。新疆亚板块自西向东由近SN向变为NE向。中国大陆东部地壳的压应力主方向自北向南由NEE变为近EW向,再变为SEE向。中国大陆主压应力作用强度西部显著大于东部。中国大陆地壳西部强于东部,南部强于北部,现今西部地壳以挤压、走滑为主,东部地壳既有挤压、走滑,也有拉张。  相似文献