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91.
Lines of equal optical thickness are calculated for cold plasma jets propagating in the simplest magnetic configuration. The paraxial approximation is used in the case of jets directed along the axis of a magnetic dipole. The results explain the apparently convergent as well as divergent shapes of the jets in a divergent magnetic configuration. 相似文献
92.
Zdeněk MikulÁšek Luboš Kohoutek Miloslav Zejda Ondřej Pejcha 《Astrophysics and Space Science》2005,296(1-4):465-468
We confirm the presence of regular UBV(RI)C light variations of the object in the center of the planetary nebula Sh 2-71, with an improved period of P = 68.132 ± 0.005 days. The shapes and amplitudes of light curves, in particular colours, are briefly discussed. 相似文献
93.
A. Dvořák 《Rock Mechanics and Rock Engineering》1970,2(4):245-248
Zusammenfassung
Aufgaben der Felsmechanik bei neuzeitlichen Tunnelrekonstruktionen. Für die neuzeitliche Tunnelbauweise müssen neue Erkundungsmethoden mit erweitertem Umfang felsmechanischer Prüfungen angewandt werden. Diese Forderung soll ebenso bei Rekonstruktionen erfüllt werden. Außer den mechanischen Eigenschaften werden auch die innere Spannung im Felsmassiv und in der Ausmauerung, die Mächtigkeit der gelockerten Zone sowie die Injektions- und Verankerungsmöglichkeit bestimmt.
Vortrag, gehalten beim XIX. Geomechanik-Kolloquium in Salzburg am 17. Oktober 1969.
Mit 2 Abbildungen 相似文献
Summary The Function of Rock Mechanics in Modern Tunnelling. For modern methods of tunnel driving it is necessary to apply new procedures of geological investigations including large-scale rock mechanics tests. This view holds equally for reconstruction projects. In addition to the mechanical properties of the rock masses it is necessary to determine the intrinsic stresses in the rock and in the tunnel lining, the thickness of the inelastic (relaxed) zone around the tunnel, as well as the possibility of grouting and anchoring.
Résumé Application de la mécanique des roches aux méthodes modernes de construction et de reconstruction des tunnels. Dans la technique moderne des tunnels il est nécessaire d'appliquer de nouvelles méthodes de reconnaissance comportant davantage d'essais de mécanique des roches. La même exigence est valable pour la reconstruction des tunnels. Outre les propriétés mécaniques du massif rocheux, on déterminera aussi les contraintes dans le rocher et dans le revêtement, l'épaisseur de la zone décomprimée et même les possibilités d'injection et de boulonnage.
Vortrag, gehalten beim XIX. Geomechanik-Kolloquium in Salzburg am 17. Oktober 1969.
Mit 2 Abbildungen 相似文献
94.
European floods during the winter 1783/1784: scenarios of an extreme event during the ‘Little Ice Age’ 总被引:1,自引:0,他引:1
Rudolf Brázdil Gaston R. Demarée Mathias Deutsch Emmanuel Garnier Andrea Kiss Jürg Luterbacher Neil Macdonald Christian Rohr Petr Dobrovolný Petr Kolář Kateřina Chromá 《Theoretical and Applied Climatology》2010,100(1-2):163-189
The Lakagígar eruption in Iceland during 1783 was followed by the severe winter of 1783/1784, which was characterised by low temperatures, frozen soils, ice-bound watercourses and high rates of snow accumulation across much of Europe. Sudden warming coupled with rainfall led to rapid snowmelt, resulting in a series of flooding phases across much of Europe. The first phase of flooding occurred in late December 1783–early January 1784 in England, France, the Low Countries and historical Hungary. The second phase at the turn of February–March 1784 was of greater extent, generated by the melting of an unusually large accumulation of snow and river ice, affecting catchments across France and Central Europe (where it is still considered as one of the most disastrous known floods), throughout the Danube catchment and in southeast Central Europe. The third and final phase of flooding occurred mainly in historical Hungary during late March and early April 1784. The different impacts and consequences of the above floods on both local and regional scales were reflected in the economic and societal responses, material damage and human losses. The winter of 1783/1784 can be considered as typical, if severe, for the Little Ice Age period across much of Europe. 相似文献
95.
Jiří Žák Scott R. Paterson Vojtěch Janoušek Petr Kabele 《Contributions to Mineralogy and Petrology》2009,158(4):447-470
The Mammoth Peak sheeted intrusive complex formed in the interior of a ~7–10 km deep magma chamber, specifically in the Half
Dome granodiorite of the Tuolumne batholith, central Sierra Nevada, CA (USA). The sheets consist of fractionated melts with
accumulated hornblende, biotite, magnetite, titanite, apatite, and zircon. The accumulation, especially of titanite, had a
profound effect on minor and trace elements (Nb, Ta, Ti, REE, U, Th, P, Zr, Hf, etc.), increasing their contents up to five
to six times. Our thermal–mechanical modeling using the finite element method shows that cooling-generated tensile stresses
resulted in the inward propagation of two perpendicular sets of dilational cracks in the host granodiorite. We interpret the
sheeted complex to have formed by a crack-seal mechanism in a high strength, crystal-rich mush, whereby outward younging pulses
of fractionated magma were injected into these syn-magmatic cracks at the margin of an active magma chamber. Thermal–mechanical
instabilities developed after the assembly of the sheeted complex, which was then overprinted by late ~NW–SE magmatic foliation.
This case example provides a cautionary note regarding the interpretation that sheeted zones in large granitoid plutons imply
a diking mechanism of growth because the sheeted/dike complexes in plutons (1) may display inverse growth directions from
the growth of the overall intrusive sequence; (2) need not record initial chamber construction and instead may reflect late
pulsing of magma within an already constructed magma chamber; (3) have an overprinting magmatic fabric indicating the continued
presence of melt after construction of sheeted complexes and thus a prolonged thermal history as compared to dikes; and (4)
because the scale of the observed sheeted complexes may be small (<1%) in comparison to large homogenous parts of plutons,
in which there is no evidence for sheeting or diking. Thus, where extensive dike complexes in plutons are absent, such as
in much of the Tuolumne batholith, the application of an incremental diking model to explain chamber construction is at best
speculative. 相似文献
96.
We introduce the freely available web-based Water in an Agricultural Landscape—NUčice Database (WALNUD) dataset that includes both hydrological and meteorological records at the Nučice experimental catchment (0.53 km2), which is representative of an intensively farmed landscape in the Czech Republic. The Nučice experimental catchment was established in 2011 for the observation of rainfall–runoff processes, soil erosion processes, and water balance of a cultivated landscape. The average altitude is 401 m a.s.l., the mean land slope is 3.9%, and the climate is humid continental (mean annual temperature 7.9°C, annual precipitation 630 mm). The catchment is drained by an artificially straightened stream and consists of three fields covering over 95% of the area which are managed by two different farmers. The typical crops are winter wheat, rapeseed, and alfalfa. The installed equipment includes a standard meteorological station, several rain gauges distributed across the basin, and a flume with an H-type facing that is used to monitor stream discharge, water turbidity, and basic water quality indicators. Additionally, the groundwater level and soil water content at various depths near the stream are recorded. Recently, large-scale soil moisture monitoring efforts have been introduced with the installation of two cosmic-ray neutron sensors for soil moisture monitoring. The datasets consist of observed variables (e.g. measured precipitation, air temperature, stream discharge, and soil moisture) and are available online for public use. The cross-seasonal, open access datasets at this small-scale agricultural catchment will benefit not only hydrologists but also local farmers. 相似文献
97.
Kryštof Materna Jiří Hasman David Hána 《Norsk geografisk tidsskrift. Norwegian journal of geography》2019,73(4):197-214
ABSTRACTThe development of globalisation has ushered in fundamental changes that have led to a break in the relationship between places of production and places of consumption, and sometimes a rejection of global products and corporations at the local level in accordance with neolocalism. The objective of the article is to examine the effect of regional identity on the local impacts of global processes by applying a multilevel analysis of the brewing industry, in which consumers are very sensitive to changes in the beer offered and can influence it, for example by putting pressure on representatives of restaurants. Beginning with extensive research on the international level, the authors point out the various impacts of brewery acquisitions in three Central European countries – Czechia, Poland and Slovakia – that differ regarding the role of beer in the identity of their inhabitants. Thereafter, they focus on two Czech beer brands, the production of which was relocated to other regions after acquisitions. Based on field studies in the regions of the brands’ original production, the authors find that both brands lost popularity among their original customers. They conclude that for Czech customers, the place of production may be an important factor when choosing a beer brand. 相似文献
98.
99.
Jana Spilková Jiří Vágner 《Norsk geografisk tidsskrift. Norwegian journal of geography》2018,72(1):1-12
The main research goals of the article are to explain the historical context of urban food gardens in Czechia, to describe the current spatial pattern of allotment gardens, and to introduce and analyse recent trends in urban gardening. The main method for achieving the first goal was a literature study. For the second goal, geographical mapping and analysis of data relating to the spatial distribution of allotment gardens were used. For the third goal, mapping together with analysis of semi-structured interviews carried out in community gardens in Prague were used. The analysis showed a strong tradition of urban agriculture and urban food gardening activities in Czechia. Both allotment gardens and newly emerged community gardens were concentrated mainly in the biggest cities and in areas with a rich industrial and mining tradition. This finding supports the significance of gardening as an important element of urban agriculture. However, uncertainty regarding land tenure and long-term sustainability were among the greatest obstacles for the future of allotment and community gardens. The authors’ main recommendations are that urban agriculture should be included as primary land use in sustainable planning and there should be broader community involvement in planning and decision-making processes. 相似文献
100.
Ivana Přidalová Jiří Hasman 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2018,118(1):72-87
The spatial distribution of immigrant groups is a more relevant topic now than ever before. While the study of this topic has a long tradition in the “traditional” immigration countries, it is rare in the very different context of Central and Eastern Europe, especially at the level of metropolitan areas. This study aims to address this gap by providing an analysis of the spatial distribution of various immigrant groups (defined by country of citizenship) in 17 Czech metropolitan areas, and its determinants. First, we characterize the specific situation of the Czech immigration system. Then we use cluster analysis to create a typology of neighbourhoods and compare the distribution of immigrant groups in each type of neighbourhood. Finally, we use regression analysis to examine which characteristics of the local environment are connected to concentrations of different immigrant groups. We show that the presence of foreigners remains associated with core urban areas. Some predominantly Western citizens act as gentrifiers, being associated with spacious pre-war apartments in prestigious inner-city areas, but there are also signs of suburbanization among more well-off immigrants to Czech metropolitan areas. We identify little evidence of ghettoization of immigrants into socially excluded areas. 相似文献