Changes of parameters of magnetic anisotropy of foliated rocks under pressure     

Aleš Kapička  Miroslav Kobr  Richard Pichl 《Studia Geophysica et Geodaetica》1996,40(4):421-429

Summary The changes of magnetic anisotropy under pressure were studied on a set of rocks with marked macroscopic stratification, collected from the Rjvíz borehole. The anisotropy parameters are relatively very stable under directional pressure, acting parallel with the rocks' bedding, and, on the contrary, significantly unstable under pressure acting perpendicular to the bedding. Systematically different magnitudes of stress sensitivity coefficients, , for parallel directional susceptibility were observed in both cases in the same types of rocks. The main cause is probably the different capability of transferring external stress to ferrimagnetics via the stratified non-magnetic matrix. With regard to magnetomechanical phenomena, therefore, a singel value of the stress sensitivity coefficient is insufficient to characterize rocks with a markedly anisotropic matrix.  相似文献   

Radiation patterns of point sources situated close to structural interfaces and to the earth's surface     

Pert Jílek  Vlastislav Červený 《Pure and Applied Geophysics》1996,148(1-2):175-225

The seismic wave field is considerably influenced by local structures close to the source and to the receiver. This applies to sources and receivers situated close to localized inhomogeneities, to structural interfaces, to the earth's surface, etc. In this paper we concentrate our attention mainly to the ray-theoretical radiation patterns of point sources situated close to the structural interfaces and to the earth's surface. In numerical modeling of high-frequency seismic wave fields by the ray method, the interaction of the source with the earth's surface has not usually been taken into account.The proposed procedure of the computation of the radiation patterns of point sources situated directly on structural interfaces and on the earth's surface is based on the zero-order approximation of the ray method, assuming that the length of the ray between the source and the receiver is long. The derived equations are extended to point sources located close to structural interface, to the earth's surface and to thin transition layers using the hybrid ray-reflectivity method, seeervený (1989). The thin layer need not be homogeneous; it may include an arbitrary inner layering (transition layers, laminas, etc.) The only requirement is for the layer to be thin. Roughly speaking, we require its thickness to be less than one quarter of the prevailing wavelength. The hybrid ray-reflectivity method describes well even certain non-ray effects (tunneling.S ^* waves, etc.). Explicit analytical expressions for radiation patterns for all above listed point sources are found. These expression have a local character and may be easily implemented into computer codes designed for the routine computation of ray amplitudes and synthetic ray seismograms in 2-D and 3-D, laterally varying isotropic layered and block structures by the ray method.Numerical examples of radiation patterns ofP andS waves of point sources situated close to the earth's surface and to a thin low-velocity surface layer are presented and discussed. The explosive point source (center of dilatation) and the vertical and horizontal single force point sources are considered. It has been ascertained that the radiation patterns of point sources depend drastically on the depth of the source below the surface even if the depths vary within one quarter of the prevailing wavelength.  相似文献   

The analysis of four cosmic dust particles     

I. Kapišinský  V. Figusch  A. Hajduk  J. Ivan  K. Iždinský 《Earth, Moon, and Planets》1995,68(1-3):347-360

A set of four stratospheric particles was reanalysed. These particles registered in the NASA Cosmic Dust Catalogs (CDCs) were classified in the Houston Johnson Space Center (JSC) as the particles of cosmic origin (C). Present energy-dispersive X-ray (EDX) spectra confirmed previous classification and revealed additional features in the chemical composition of the cosmic dust particles.The particles are extremely fine-grained aggregates with bulk chondritic composition. Somewhat higher content of oxygen may indicate a presence of hydroxide containing minerals in their phase composition.  相似文献   

Regional VS30 model for the St. Lawrence Lowlands,Eastern Canada     

Miroslav Nastev  Michel Parent  Nicolas Benoit  Martin Ross  Danielle Howlett 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2016,10(3):200-212

Shear-wave velocity of the top 30?m, V_S30, is commonly used for prediction of the seismic site response. This paper presents development, validation and uncertainty assessment of a regional V_S30 model based on a combination of simplified 3D geology and statistically representative velocity values. Results identify soft marine sediments in deep sedimentary basins as zones most susceptible to seismic shaking. Compared to the available urban-scale seismic zonation studies, the regional model showed a success rate of roughly 64% in predicting local site category. The standard deviation was in average 30% of the expected V_S30 value.  相似文献   

Ten years of Czechoslovak research in numerical weather prediction     

Stanislav Brandejs  Miroslav Škoda  Vojtěch Vítek  Otakar Zikmunda 《Studia Geophysica et Geodaetica》1963,7(3):308-311

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Some minerals as new natural models of ferrites     

Václav Hanus  Miroslav Krs 《Pure and Applied Geophysics》1965,60(1):129-136

Summary The electron density distribution in the intermediateE-F layer is determined by developing theN(z) profile into a power series. The unknown coefficients are found by means of the boundary conditions for transition towards theE andF1 layers as well as by the value of the maximum electron density in the intermediate layer. In case that stratiform layers in theE-F layer which can be sounded are not available, the measured value for the nondeviative absorption at short waves reflected by theF layer is made use of. The comparisons show the reliable accuracy of the method when seven terms are used in the power series.  相似文献   

Le développement de la géodésie et cartographie tchécoslovaque de 1945 a 1940     

Josef Ryšavý 《Studia Geophysica et Geodaetica》1960,4(2):119-129

Sans résumé En collaboration avec les membres de la rédaction: prof. Ing. Ján Krajčí, Dr. Ing. Karel Kučera et Dr. Ing. Jan Kašpar. Adresse: Národní tř. 3, Praha 1.  相似文献   

Is radiomagnetization possible?     

Miroslav Krs 《Studia Geophysica et Geodaetica》1967,11(4):464-465

Резюме Дискутирована возможность, возникаетли под влиянием действия γ-облучения и постоянного магнитного поля на ферромагнитные вещества новыИ вид намагниченности, т. н. радионамагниченность. Приведеннее рассуждение частично обосновано экспериментами выполненнычi БродскоИ, которая лабораторным образом проверила некоторые изменения магнитных свойств минералов под влиянием γ-облучения. Остается пока необБясненным вопрос, если специфичные магнитные свойства верхнепалеозойских горных пород не были обусловлены интенсивным (или долговременным) воздействием γ-облучения при совместном воздействии геомагнитного поля.   相似文献   

A note on the problem of choosing a model of the Universe,III     

Vladimír Skalský 《Astrophysics and Space Science》1989,162(1):171-173

From the analysis of relativistic and quantum-mechanical processes at the creation of the expansive evolution phase of the Universe it follows that the Universe can expand only by the limit velocity of signal propagationc.  相似文献   

Formation of a regional image through geography textbooks: The case of north-west Bohemia     

Silvie R. Kučerová  Zdeněk Kučera  Kateřina Novotná 《Norsk geografisk tidsskrift. Norwegian journal of geography》2018,72(3):176-195

The purpose of the article is to examine the ways in which regional geography textbooks are used in elementary education, using north-west Bohemia as a case study. The authors analysed 18 textbooks published since the beginning of the 20th century, in two steps: (1) the construction of geographical names frequency maps indicating which parts of the case region are accentuated or suppressed in individual textbooks, and (2) a qualitative analysis of the textbooks’ content. The study revealed that a complex image of north-west Bohemia in interwar period in Czechoslovakia and in the period of accession to the European Union is presented in the textbooks. The textbooks published during communist era are imbued with the adoration of local industries, whereas those published later, in the period of political and socio-economic transformation, accentuate the risks of excessive environmental exploitation. At any time since the beginning of the 20th century, the places and regions that represent the values preferred by the governing ideology are emphasized within the studied textbooks. Thus, the geography textbooks, that reflect the society-wide discourse, disseminate not only knowledge but also dominant values. In this way, a desired image of reality is created that legitimates the aims and stances of those in power.  相似文献