Questions concerning the existence of sympathetic flares     

V. Bumba  M. Klvaňa 《Astrophysics and Space Science》1993,199(1):45-52

Earlier results concerning sympathetic flares - physically related flares occurring in different active regions practically in the same time - and time-correlated radio bursts are compared with magnetic situation in active regions with related flaring and with the history and dynamics of its development. We found observational evidence abou the reality of sympathetic flares, demonstrating also that active regions in which they appear are physically related through common dynamical elements in which the evolution of their magnetic fields goes parallel. Such a process may sometimes occupy a very large volume of the photosphere and we believe that it might be related to the large-scale convective motions.  相似文献   

A Step Towards Evaluation of the Seismic Response Reduction Factor in Multistorey Reinforced Concrete Frames   总被引：1，自引：0，他引：1  

Barakat  Samar a.  Husein Malkawi  Abdallah I.  Al-Shatnawi  Anis S. 《Natural Hazards》1997,16(1):65-80

A seismic nonlinear time-history analysis was made for four-, six-, and eight-storey reinforced concrete buildings. These buildings were made as three-dimensional space frame structures with shear walls in both orthogonal directions. They have five bays with 4.8 m spacing each in the horizontal direction, and three bays with 4.2 m spacing each in the transversal direction. The frames were designed according to the Jordanian Seismic Code of practice for Seismic Zones 4, 3, 2, and 1 as proposed for Jordan by several authors. Time-history analysis was made using the El Centro (N-S) earthquake record of May 1940 as an actual earthquake excitation. The response reduction factor (R) that primarily consists of two factors that are the ductility reduction (Rµ) and the overstrength (), is obtained. It has been seen that the seismic zoning has a slight effect on the ductility reduction factor for different buildings, since it ranges from Zone 4 to Zone 1 as 2.37 to 2.52, 1.72 to 1.78, and 1.14 to 1.18 for four-, six-, and eight-storey buildings, respectively. Moreover, it is observed that, for different buildings and different seismic zones, the ductility reduction factor (Rµ) is slightly different from the system ductility factor (µ) especially for higher values of µ (i.e., Rµ µ). The response reduction factor, called overstrength (), was evaluated. The overstrength factor was found to vary with seismic zones (Z) , number of stories, and design gravity loads. However, the dependency on seismic zones was the strongest. The average overstrength of these buildings in Zones 4 and 1 was 2.61 and 6.94, respectively. The overstrength increased as the number of storeys decreased: overstrength of a four-storey building was higher than an eight-storey building by 36% in Zone 4, and 39% in Zone 1. Furthermore, buildings of the three heights had an average overstrength 165.9% higher in Zone 1 than in Zone 4. These observations have a significant implications for the seismic design codes which currently do not take into account the variation of the response reduction factor, R (i.e., ductility reduction factor times overstrength).  相似文献   

A calibration system for superconducting gravimeters     

Vladimiro Achilli  Paolo Baldi  Giuseppe Casula  Mario Errani  Sergio Focardi  Marco Guerzoni  Federico Palmonari  Giuseppe Raguní 《Journal of Geodesy》1995,69(2):73-80

A new method for the calibration of a superconducting gravity meter is described, in which a 273 Kg annular mass is placed around the meter and is moved up and down. The geometry of the apparatus is easy to model and the accuracy in the computation of the gravity variation induced by the mass, 6.7µgal, is limited only by the accuracy in the knowledge of value of the gravitational constant. Measurements done in 91 and 92 for the calibration of the instrument GWR-T015 are described. The calibration factor has been determined with a precision of about 0.3%.  相似文献   

The use of rogation ceremony records in climatic reconstruction: a case study from Catalonia (Spain)     

Javier Martín-Vide  Mariano Barriendos Vallvé 《Climatic change》1995,30(2):201-221

The use of rogation ceremonies due to environmental causes constitutes an important source of information in paleoclimatic reconstructions. Their specific characteristics and full documental records permit highly reliable series to be reconstructed with daily, monthly, seasonal or annual resolution over periods of several centuries (3–4 centuries in the case of Catalonia). The levels of intensity, reflected in the type of religious ceremony enacted, allows quantification. Comparative analysis is made possible by the similarity of the mechanisms developed in different localities. The use of these series in paleoclimatological studies is a promising line of research, particularly as regards the pro pluvia rogations celebrated in the Mediterranean countries and in South America.  相似文献   

Genetic and chemical relationships between berthierine,chlorite and cordierite in nodules associated to granitic pegmatites of Sierra Albarrana (Iberian Massif,Spain)     

María del Mar Abad-Ortega  Fernando Mieto 《Contributions to Mineralogy and Petrology》1995,120(3-4):327-336

Chlorite and berthierine occur through alteration of cordierite within enclaves of metamorphic rocks transformed by the Sierra Albarrana pegmatites. The coexistence of both phyllosilicates allows us to study their stability relationships and to compare their chemical compositions. Samples showing incipient replacement of cordierite by small cryptocrystalline aggregates can be identified by X-ray diffraction (XRD) as berthierine with small quantities of chlorite. Electron Microprobe (EMP) analyses give mixed compositions of berthierine and cordierite. Samples with extensive replacement of cordierite by aggregates show similar characteristics to those with incipient replacement, but some small crystals are present. The last type of sample shows complete replacement of cordierite by crystals showing optical properties of chlorite and EMPA compositions coherent with chlorite or berthierine. Their XRD pattern corresponds to chlorite and their high resolution transmission electron microscopy (HRTEM) images only show perfect sequences of 14 Å lattice fringes. The cryptocrystalline aggregates of the samples with incipient and extensive replacement present coexistent areas of 14 Å and 7 Å lattice fringes that are intergrown at different levels: (1) large areas (> 1 m) of 7 Å layers; (2) packets of 7 Å layers between 14 Å layer areas, with visible 7 Å to 14 Å lateral changes; (3) random mixed-layers 7 Å/14 Å. Chlorite is the final stable product of alteration of cordierite, with berthierine as an intermediate metastable phase. Energy dispersive X-ray spectrometry microanalyses of 14 Å, 7 Å and (14+7) Å areas show lack of systematic differences in chemical compositions between both phyllosilicates which may be considered as true polymorphs.  相似文献   

Geochronology and geochemistry of eclogites from the Mariánské Lázně Complex,Czech Republic: Implications for Variscan orogenesis     

Brian L. Beard  L. Gordon Medaris Jr  Clark M. Johnson  Emil Jelínek  J. Tonika  Lee R. Riciputi 《International Journal of Earth Sciences》1995,84(3):552-567

The Mariánské Lázn complex (MLC) is located in the Bohemian Massif along the north-western margin of the Teplá-Barrandian microplate and consists of metagabbro, amphibolite and eclogite, with subordinate amounts of serpentinite, felsic gneiss and calcsilicate rocks. The MLC is interpreted as a metaophiolite complex that marks the suture zone between the Saxothuringian rocks to the north-west and the Teplá-Barrandian microplate to the south-east. Sm-Nd geochronology of garnet-omphacite pairs from two eclogite samples yields ages of 377±7, and 367±4 Ma. Samples of eclogite and amphibolite do not define a whole rock Sm-Nd isochron, even though there is a large range in Sm/Nd ratio, implying that the suite of samples may not be cogenetic. Eclogites do not have correlated _Nd values and initial ⁸⁷Sr/⁸⁶Sr ratios. Five of the eight eclogite samples have high _Nd values (+10.2 to +7.1) consistent with derivation from a MORB-like source, but variable ⁸⁷Sr/⁸⁶Sr ratios (0.7033 to 0.7059) which probably reflect hydrothermal seawater alteration. Three other eclogite samples have lower _Nd values (+ 5.4 to –0.8) and widely variable ⁸⁷Sr/⁸⁶Sr ratios (0.7033 to 0.7096). Such low _Nd values are inconsistent with derivation from a MORB, source and may reflect a subduction or oceanic island basalt component in their source. The MLC is an important petrotectonic element in the Bohemian Massif, providing evidence for Cambro-Ordovician formation of oceanic crust and interaction with seawater, Late Devonian (Frasnian-Famennian) high- and medium-pressure metamorphism related to closure of a Saxothuringian ocean basin, Early Carboniferous (Viséan) thrusting of the Teplá terrane over Saxothuringian rocks and Late Viséan extension.  相似文献   

Current estimates of the Earth's principal moments of inertia     

Milan Burša 《Studia Geophysica et Geodaetica》1992,36(2):109-114

Summary The principal moments of the Earth's inertia and their differences have been computed and their actual accuracy estimated on the basis of the most recent values of the 2nd degree geopotential parameters (model GEM-T2) and of the parameter H in the precession constant. The contributions due to the zero frequency zonal term in the tidal potential have been determined.

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au m nmnmuaa 2- mnu (¶rt; GEM-T2) u naama nm nuu n¶rt; aua m uuu u u u amu u ¶rt;am u a mmu. u a¶rt; n¶rt; uu nm amu a a nuu nmuaa.

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Linear hydromagnetic stability of a differentially rotating non-uniformly stratified fluid layer     

Ján Boďa 《Studia Geophysica et Geodaetica》1992,36(2):139-150

Summary Our discussion is concerned with the common effect of the non-uniformity of layer rotation and stratification. We have assumed a model of differential rotation with the upper part of the layer rotating more slowly, the bottom part more quickly. The upper part of the layer is stratified stably, the bottom part unstably.The thermal instabilities are preferred in the strong differential rotation case and they are the most easily excited by a strong magnetic field (10²–10³). The direction of its propagation is westward in the uniformly stratified layer and eastward in the non-uniformly stratified layer.  相似文献   

Investigation of the instability of graveyard orbits due to the earth's gravitational perturbations     

Jan Kostelecký  Jaroslav Klokočník 《Studia Geophysica et Geodaetica》1992,36(4):297-301

Summary The Banach theorem is applied to the Lagrange planetary equation for the semimajor axis of a geostationary satellite orbit to estimate the stability of near-geostationary satellite orbits. To achieve a graveyard (disposal) orbit, which will not interfere (=cross) the initial geostationary orbit, the geostationary semi-major axis a_g have to be increased at least by 50 km. Numerical results for a variety of graveyard orbits show that the increase of a_g by about 100 km will yield sufficiently stable orbits (accounting for the Earth's gravitational perturbations only) during the next 150 years.Dedicated to the 75th Birthday of Professor Academician Tibor Kolbenheyer  相似文献   

On the determination of the European gravimetric geoid     

Drahomír Dušátko 《Studia Geophysica et Geodaetica》1992,36(4):392-393

Summary The method of the automated computation of the gravimetric deflections of the vertical and of the geoidal heights for the European region is described. The work was carried out during the period 1986–1988 by the Topographic Service of the Czechoslovak Army. The computation applies to 20 sheets of the international map 1:1 000 000 (total area of =16^c, =30^c - see Fig. 1). The mean values of the free-air anomalies for each surface element =5, =7.5, approximately 9 × 9 km, were used with radius of integration of 300 km.  相似文献