Line emission from accretion discs around black holes: the analytic approach     

Andrej ?ade?  Claudio Fanton  Massimo Calvani 《New Astronomy》1998,3(8):528-654

The broad X-ray iron line observed in many active galactic nuclei spectra is thought to originate from the accretion disc surrounding the putative supermassive black hole. We show here how to perform the analytical integration of the geodesic equations that describe the photon trajectories in the general case of a rotating black hole (Kerr metric), in order to write a fast and efficient numerical code for modelling emission line profiles from accretion discs.  相似文献   

Seismic Zoning of Croatia     

Markušić  Snježana  Herak  Marijan 《Natural Hazards》1998,18(3):269-285

The territory of Croatia and neighboring regions is divided into 17 seismic source zones, considering available seismological and geological data. On this basis, seismic hazard elements (seismicity rate, maximum magnitude, b-value, probabilities of exceedance and return periods for a predefined set of magnitudes) are computed using the maximum likelihood method appropriate for treating data-sets with variable completeness thresholds. The values of long term expected peak horizontal acceleration obtained by using a combination of the deterministic and the probabilistic procedure are the highest in the Dubrovnik zone, while the Zagreb zone has the highest earthquake hazard in the continental part of the country. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

Electromagnetic induction of a three-dimensional conductivity inhomogeneity in the two-layered earth     

Milan Hvoždara  Reviewer V. Petr 《Studia Geophysica et Geodaetica》1981,25(2):167-180

Summary The calculation of the elements of Green's tensor function is presented for solving the problem of the electromagnetic induction by means of a vector integral equation. A two-layered Earth is considered as the medium, the surface layer including a three-dimensional conductivity inhomogeneity. Use is made of the boundary condition requiring the vertical component of the electric current to be zero at the Earth's surface which partly simplifies the theoretical computation. Long-period asymptotics of the individual complicated functions, occurring in Green's tensor function as well as in the tensor function required to calculate the components of the anomalous magnetic field at the surface of the halfspace, were effected. With the aid of these asymptotics one can obtain estimates of the functions occurring in the theoretical analysis of the problem.  相似文献   

Crustal thermal models for South Siberia     

L. S. Sokolova  A. D. Duchkov  Reviewer V. Čermák 《Studia Geophysica et Geodaetica》1978,22(2):200-207

Summary The results of geothermal research carried out in South Siberia (West-Siberian and Siberian Platforms, Altai-Sayan folded area and the Baikalian arched uplift zone) were employed to calculate the Earth's crustal temperatures. It is shown that temperature is a function of the heat flow value. The maps of the surface heat flow and the temperatures at the Moho discontinuity are presented and characteristic temperature-depth profiles were compiled for specific tectonic areas. The West-Siberian and Siberian Platforms, as well as the Altai-Sayan folded region are characterized by rather low heat flow, 42–50mW m ^–2 (1.0–1.2 µcal/cm ² s), and low temperatures at the Moho boundary.400–500 °C. The thermal conditions in the area of Lake Baikal are extreme, the heat flow reaches here100–142 mW m ^–2 (2.4–3.4 µcal/cm ² s), and the temperature at the crust's bottom may exceed1000 °C. The Moho-surface according to our calculations is nonisothermal.  相似文献   

Numerical modelling in laterally inhomogeneous geoelectrical structures   总被引：2，自引：0，他引：2  

Václav Červ  Oldřich Praus  Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1978,22(1):74-81

aam u m¶rt; ¶rt;uau m aum n - u -nuau ¶rt; ¶rt;¶rt; ¶rt;a. ¶rt;am umuu u, m m uam nuuu m¶rt;a am Va nuumuu n¶rt;am auauu muuu n¶rt;umu.

---

---

Dedicated to RNDr. Jan Pícha, CSc., on his 60th Birthday  相似文献   

Spectral analysis of oscillations with a time-variable frequency     

Jaroslav Střeštík  Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1979,23(4):333-348

Summary The paper presents a method of evaluating oscillations with a time-variable frequency using a computer. The given function is first interpolated at points which are not distributed equidistantly in time, but the digitizing step varies with time according to a known optional regularity. The spectrum of the obtained function is computed for various of these interpolations and tests are run to determine when the interpolation best compensates the time variation of the frequency. The initial and terminal frequency in the given sample is then determined. The usability of this method with respect to various types of oscillations with a variable frequency and its accuracy in comparison to sonagrams are discussed.  相似文献   

The use of laboratory measurements of electric resistivity of rocks for evaluating the magnetotelluric method     

Marcela Laštovičková  Josef Pek  Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1979,23(1):94-98

Summary A profile model of electric resistivity as a function of depth was compiled, the initial parameters being the values of the electric resistivity determined experimentally for basaltic and eclogitic rocks from the Bohemian Massif. The curves of the apparent resistivity were computed for this model and the measure of information evaluated for the various model layers. The dominant influence of the subsurface layer was proved.  相似文献   

Numerical properties of low-frequency expansions for the reflection and transmission coefficients from transition layers     

Oldřich Novotný  Vlastislav Červený  L. A. Molotkov  Reviewer I. Pšenčík 《Studia Geophysica et Geodaetica》1980,24(2):124-130

Summary The numerical properties of the low-frequency expansions for the reflection and transmission coefficients of SH-waves from transition layers, derived in [1], are studied. It is shown that the expansions are suitable for computations only when the thickness d of the transition layer is small in comparison with the wavelength of the incident wave (d0.5). For thicker transition layers, certain modifications of the method are suggested.  相似文献   

Masses d'air conditionnées par la fonte des neiges     

Par Marjan Čadež 《Pure and Applied Geophysics》1965,61(1):232-245

Summary In the paper it is shown in which manner the cooling of the air due to the melting of snowflakes causes the appearance of special air masses of greater or smaller dimensions. Here some examples are given of the formation of such air masses of melting in Yugoslavia on the north slopes of the Dinarian Alps.

---

Zusammenfassung In dieser Arbeit ist gezeigt, auf welche Weise die Abkühlung der Luft, die durch das Schmelzen der Schneeflocken bedingt ist, besondere Luftmassen von grösseren und kleineren Ausdehnungen zur Folge hat. Es sind einige Beispiele von solchen Luftmassen des Schmelzens in Jugoslawien gegeben, die auf der Nordseite der dynarischen Gebirge formiert sind.

  相似文献   

Approximate expression for the hilbert transform of a certain class of functions and their application to the ray theory of seismic waves     

Vlastislav Červený  Reviewer J. Vaněk 《Studia Geophysica et Geodaetica》1976,20(2):125-132

Summary Approximate expressions for the Hilbert transform of the functionf(t)=exp(- ₀ ² t ²/²) cos( ₀ t+v) are determined. This function, given a suitable choice of the three parameters ₀, and v, approximates a wide class of seismic signals very well. The approximate expressions for the Hilbert transform enable very simple formulae to be given for the elementary seismograms of the individual seismic body waves (in the zero approximation of the ray theory). This accelerates the computation of ray theoretical seismograms considerably.  相似文献