The population of Croatia     

Sterc S  Crkvencic I 《GeoJournal》1996,38(4):417-424

Croatia is a Central European and Mediterranean state, located in contact with and under the influence of various spheres of civilization, which for centuries have penetrated and conflicted on and around the territory of Croatia. Such a position has resulted in various influences which did not always have a positive effect on the development of Croatia. The gradual narrowing and decrease of the Croatian ethnic territory, as well as the presence of national minorities in it, was also a result of the aforementioned position and outside influences (ulji 1993/1994).The demographic structure of Croatia indicates a series of specificities which were primarily conditioned by the historical development of Croatia and which is particularly expressed in constant emigration since the end of the nineteenth century, the relatively large direct and indirect losses to the population during and immediately after the First and Second World Wars, emigration as a type of population movement in all inter-census periods after 1945, the appearance of a natural decline and the aging of the population on almost one half of the state territory.  相似文献   

Hierarchical decomposition of variance with applications in environmental mapping based on satellite images     

Ferenc Csillag  Sándor Kabos 《Mathematical Geology》1996,28(4):385-405

A quadtree-based image segmentation procedure (HQ) is presented to map complex environmental conditions. It applies a hierarchical nested analysis of variance within the framework of multiresolution wavelet approximation. The procedure leads to an optimal solution for determining mapping units based on spatial variability with constraints on the arrangement and shape of the units. Linkages to geostatisiics are pointed out, but the HQ decomposition algorithm does not require any homogeneity criteria. The computer implementation can be parameterized by either the number of required mapping units or the maximum within-unit variance, or it can provide a spectrum of significances of nested ANOVA. The detailed mathematical background and methodology is illustrated by a salt-affected grassland mapping study (Hortobágy, Hungary), where heterogeneous environmental characteristics have been sampled and predicted based on remotely sensed images using these principles.  相似文献   

Automatic classification of volcanic earthquakes by using Multi-Layered neural networks     

S. Falsaperla  S. Graziani  G. Nunnari  S. Spampinato 《Natural Hazards》1996,13(3):205-228

The application of neural networks as classifiers of seismic events is described with the aim of developing an automatic system for the classification of explosion quakes at the Stromboli volcano. The architecture of the network that we trained to identify four different classes of shocks was a Multi-Layer Perceptron, using the Back Error Propagation algorithm. Five different approaches for representing the information embedded in the seismograms, both in the time and in the frequency domain, were considered, and the results compared. The direct use of the time series of the shocks was not satisfactory. The auto-correlation function worked well, but in some cases it was misleading. A better performance was obtained with a frequency domain representation. Finally, the use of the envelope function did not work well. Combining parameters such as the auto-correlation and envelope functions can improve one source of error, but it may introduce new ones. The performance obtained highlights the importance of the data attributes used for the training of the network. Topologies with eight neurons in a single hidden layer gave, on average, the best results among the considered neural network structures. The overall results provide a large number of events (89% with the best performance) correctly classified, indicating that this automatic technique is reliable, and encouraging further applications in the field of volcanic seismology.  相似文献   

Laboratory simulation of geogas microbubble flow   总被引：3，自引：0，他引：3  

G. Etiope  S. Lombardi 《Environmental Geology》1996,27(3):226-232

Preliminary laboratory tests provided first data on the behavior of gas microbubbles through porous media in the framework of the geogas theory. Under experimented conditions with laboratory equipment arranged for pressure controlled gas-tracer injection and sampling, gas microbubbles moved up to ten times faster than singlephase flow in dry media under the same injection pressure. Microbubbles were determined to be very sensitive to changes in injection pressure and their terminal velocity seems to be described with good approximation by the Stokes formula. The capability of microbubbles to pick up and transport upward for short distances solid ultra-small particles (metallic and radionuclide compounds) has been proved. Results are consistent with a time-dependent process linked to the transport properties of microbubbles (e.g., flotation), such as that reported by some authors.  相似文献   

Integrated chronostratigraphy of Proterozoic-Cambrian boundary beds in the western Anabar region, northern Siberia   总被引：2，自引：0，他引：2  

Kaufman AJ  Knoll AH  Semikhatov MA  Grotzinger JP  Jacobsen SB  Adams W 《Geological magazine》1996,133(5):509-533

Carbonate-rich sedimentary rocks of the western Anabar region, northern Siberia, preserve an exceptional record of evolutionary and biogeochemical events near the Proterozoic/Cambrian boundary. Sedimentologically, the boundary succession can be divided into three sequences representing successive episodes of late transgressive to early highstand deposition; four parasequences are recognized in the sequence corresponding lithostratigraphically to the Manykal Formation. Small shelly fossils are abundant and include many taxa that also occur in standard sections of southeastern Siberia. Despite this coincidence of faunal elements, biostratigraphic correlations between the two regions have been controversial because numerous species that first appear at or immediately above the basal Tommotian boundary in southeastern sections have first appearances scattered through more than thirty metres of section in the western Anabar. Carbon- and Sr-isotopic data on petrographically and geochemically screened samples collected at one- to two-metre intervals in a section along the Kotuikan River, favour correlation of the Staraya Reckha Formation and most of the overlying Manykai Formation with sub-Tommotian carbonates in southeastern Siberia. In contrast, isotopic data suggest that the uppermost Manykai Formation and the basal 26 m of the unconformably overlying Medvezhya Formation may have no equivalent in the southeast; they appear to provide a sedimentary and palaeontological record of an evolutionarily significant time interval represented in southeastern Siberia only by the sub-Tommotian unconformity. Correlations with radiometrically dated horizons in the Olenek and Kharaulakh regions of northern Siberia suggest that this interval lasted approximately three to six million years, during which essentially all 'basal Tommotian' small shelly fossils evolved.  相似文献   

Fluid--Rock Interaction during Low-Pressure Polymetamorphism of the Reynolds Range Group, Central Australia     

BUICK  IAN S.; CARTWRIGHT  IAN 《Journal of Petrology》1996,37(5):1097-1124

Marbles and metapelites from the Reynolds Range Group (centralAustralia) were regionally metamorphosed at low pressure duringM₂ at 1.6 Ga, M₂ ranged in grade from greenschist to granulitefacies along the length of the Reynolds Range, and overprinted1.78 Ga granites and their contact aureoles in the ReynoldsRange Group metasediments. At all M₂ grades the marbles andmetapelites have highly variable oxygen isotope ratios [marbles:¹⁸O(carb) 14–20%; metapelites: ¹⁸O 6–14%). Similarly, 1.78 Ga granites have highly variable oxygen isotope ratios(¹⁸O 5–13%), with the lowest values occurring at thegranite margins. In all rock types, the lowest oxygen isotopevalues are consistent with the infiltration of channelled magmaticand/or meteoric fluids. The variable lowering of oxygen isotopevalues resulted from pre-M₂ contact metamorphism and fluid—rockinteraction around the 1.78 Ga granites. In contrast, mineralassemblages in the marbles define a trend of increasing X_CO2with increasing grade from <0.05 (greenschist facies) to0.7–1.0 (granulite facies). This, together with the lackof regionally systematic resetting of oxygen isotope ratios,implies that there was little fluid—rock interaction duringprograde regional metamorphism. KEY WORDS: low pressure; polymetamorphism; fluids; stable isotopes; petrology ^*Corresponding author Fax: 61–3–94791272. e-mail: geoisb{at}lure.latrobe.edu.au  相似文献   

Non-ideal Mg-Fe binary mixing in cordierite: Constraints from experimental data on Mg-Fe partitioning in garnet and cordierite and a reformulation of garnet-cordierite geothermometer     

S. B. Dwivedi 《Journal of Earth System Science》1996,105(4):365-377

The non-ideal regular Mg-Fe binary in cordierite has been derived through multivariate linear regression of the expressionRT InK_D +(P- 1)ΔVK ₁ ⁰ , 298 along with updated subfegular mixing parameter of almandine-pyrope solution (Hackler and Wood 1989; Berman 1990). The data base used for multivariate analyses consists of published experimental data (n = 177) on Mg-Fe partitioning between garnet and cordierite in theP-T range 650–1050°C and 4–12 K bar. The non-ideality can be approximated by temperature-dependent Margules parameters. The retrieved values of ΔH_<T> ^o and ΔH_<T> ^o of exchange reaction between garnet and cordierite and enthalpy and entropy of mixing of Mg-Fe cordierite were combined with recent quaternary (Fe-Mg-Ca-Mn) mixing data in garnet to obtain the geothermometric expressions to determine temperature (T Kelvin): $$\begin{gathered} T(WH) = 6832 + 0.031(P - 1) - \{ 166(X_{Mg}^{Gt} )^2 - 506(X_{Fe}^{Gt} )^2 + 680X_{Fe}^{Gt} X_{Mg}^{Gt} + 336(X_{Ca} + X_{Mn} ) \hfill \\ (X_{Mg} - X_{Fe} )^{Gt} - 3300X_{Ca}^{Gt} - 358X_{Mn}^{Gt} \} + 954(X_{Fe} - X_{Mg} )^{Crd} /1.987\ln K_D + 3.41 + 1.5X_{Ca}^{Gt} \hfill \\ + 1.23(X_{Fe} - X_{Mg} )^{Crd} \hfill \\ \end{gathered} $$ $$\begin{gathered} T(Br) = 6920 + 0.031(p - 1) - \{ 18(X_{Mg}^{Gt} )^2 - 296(X_{Fe}^{Gt} )^2 + 556X_{Fe}^{Gt} X_{Mg}^{Gt} - 6339X_{Ca}^{Gt} X_{Mg}^{Gt} \hfill \\ - 99(X_{Ca}^{Gt} )^2 + 4687X_{Ca}^{Gt} (X_{Mg} - X_{Fe}^{Gt} ) - 4269X_{Ca}^{Gt} X_{Fe}^{Gt} - 358X_{Mn}^{Gt} \} + 640(X_{Fe} - X_{Mg} )^{Crd} \hfill \\ + 1.90X_{Ca}^{Gt} (X_{Mg} - X_{Ca} )^{Gt} . \hfill \\ \end{gathered} $$   相似文献   

Distances to planetary nebulae with [WR]-type central stars     

Sławomir K. Górny 《Astrophysics and Space Science》1996,238(1):79-82

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Photometric investigation of the evolved contact binary system DN Aur     

S. N. Goderya  K. C. Leung  E. G. Schmidt 《Astrophysics and Space Science》1996,246(2):291-298

We present here the photometric light curve analyses of the eclipsing binary star DN Aur. The CCD photometry, performed at the Behlen observatory using the 0.76 m automated telescope gave 646 individual data points inV andR bandpass filters. From this data we have determined a new epoch and an orbital period of 0.6168891 days. The published spectral classification is F3.The Wilson-Devinney model was used to derive the photometric solutions. DN Aur is a W UMa type contact binary system. The mass ratio, (q=m ₂/m ₁0.210, where star 2 is eclipsed at the primary minimum) suggests that the system has A-type configuration. The computed light curve has a third light of about 22 percent and a total eclipse in the secondary minimum. A solution with a cool spot on the secondary component is also found. We recommend spectroscopic study of DN Aur even though the light curve analysis show it to be a single line spectroscopic system. Generally contact systems of spectral type F3 have periods ranging from 0.25 to 0.5 days. The longer period of DN Aur suggests that it is an evolved contact system with case A mass transfer.  相似文献   

Motion of test particles in parabolic density distributions     

P. S. Negi  M. C. Durgapal 《Astrophysics and Space Science》1996,245(1):97-116

A detailed study of the motion of test-particles [either having a nonzero rest-mass or zero rest-mass] has been carried out for Tolman's type VII solution with vanishing surface density, which is one of the few physically relevant exact solutions of Einstein's field equations for static and spherically symmetric mass distributions.The trapping angles, 0, at which the test-particles escape these configurations are calculated and the trajectories of test-particles are studied in detail. The types of trajectories found for this spacetime geometry are: (1) arc-like trajectories, (2) spiral-like trajectories ending into a circle of constant radius, (3) trajectories with a cusp at the minimum distance, (4) double-bounded trajectories, and (5) double-bounded trajectories with a cusp at the minimum distance. The test-particles following the trajectories of type (1) and type (3) escape the configuration while others are trapped within the structure. Besides the advancement of periastron of the orbits the retrogradation of periastrons are also observed.The stability of the structures is considered by using the variational method (Chandrasekhar, 1964a,b), and its is seen that the structures remain stable at least for a central redshift,z0, as large as 5.09.These studies may distinguish relativistic cluster from a Newtonian one and may find application to the local models of quasi-stellar objects (QSOs).  相似文献