State of geoscientific research within the lorandite experiment (LOREX)

The LORandite EXperiment (acronym LOREX) is the only geochemical solar neutrino experiment still actively persued. The Tl-mineral lorandite, TlAsS₂, occurs in the ore deposit Allchar, Macedonia, close to the border of Greece. The polychronous and polygenetic Sb-As-Tl-Au Allchar deposit was formed by complex physico-chemical processes occurring in a heterogeneous geological environment and by interaction of polyphase hydrothermal fluids with the surrounding magmatic, sedimentary and metamorphic rocks. The genesis of ore mineralization is related to the products of polyphase magmatic activity of Pliocene age (~6.5 to ~1.8?Ma) and its spatial location was controlled by magmatic, structural and lithological factors. The Allchar deposit comprises several orebodies of various shapes, textural-structural characteristics and element associations. Thallium mineralization, which is of significance for the LOREX project, has been proved in two locations: (i) ore body Crven Dol in the northern part and (ii) ore body Centralni Deo in the central part of the Allchar deposit. The age of Tl-mineralization is 4.22?Ma at the Crven Dol locality and 4.31?Ma at Rudina near to the Centralni Deo locality. The present depth of ore mineralization from the present soil surface is about 30?m to 140?m, whereas the paleodepth of its formation is considerably bigger. Using the method of quantitative geomorphological analysis, and AMS- and MS-measurements of cosmogenic radionuclides ²⁶Al, ²¹Ne, and ³He, the erosion rate has been established to be ~70?m/Ma in the broader area of the Crven Dol locality and ~130?m/Ma in the Centrani Deo of the Allchar deposit. On the basis of these erosion rates and ages of Tl-mineralization, we have calculated the paleo-depth of Lorandite to be ca 180?m?±?35?m to 420?m?±?80?m. Geochemical and mineralogical investigations on lorandite in particular its trace elements (Pb, U, and Th), the quantity of lorandite in the two ore bodies, the geological age and the paleo depth of Tl-mineralization have provided encouraging results and indicate the feasibility of the LOREX project.     

Seismic testing of large panel precast walls: Comparison of pseudostatic and shaking table tests

Urban housing has been provided economically in many parts of the world by large panel precast building systems; in seismic regions, however, special attention must be given to the connections between panels in order to achieve the necessary earthquake resistance. In this paper a comprehensive seismic test programme of concrete panel assemblages done as part of a U.S.-Yugoslavia cooperative research plan in earthquake engineering is described. The test structures were three-storey assemblages of 1/3 scale concrete panels supplied by a Yugoslavian construction company; the models were about 12 ft high and 6 ft long, with the panels interconnected by various types of joint systems along their tops, bottoms and sides. Cyclic pseudostatic testing of the models was done at the IZIIS Laboratories in Skopje, Yugoslavia. A second set of models was assembled at the University of California, Berkeley from identical panels that had been shipped from the Belgrade factory; these models were tested on the 20 ft square EERC shaking table. The purpose of this paper is to compare the earthquake response represented by the two different types of test procedures. A major conclusion was that the response mechanisms in both cases were similar, with the principal deformation being opening of the panel joint at the base of the model due to overturning moments. As the rocking response continued, tension and compression failure occurred alternately at the two ends of the joint. The principal difference between the results was that pseudostatic testing imposed an increasing sequence of symmetric deformation that was independent of the damage being developed in the model, while the shaking table response was greatly influenced by the damage as it occurred—leading to significant unsymmetry. Moreover, the damage occurred in a concentrated region with the shaking table test. This difference emphasizes the fact that pseudostatic test results must be interpreted with caution because they do not fully simulate an actual earthquake response.     

A real data simulation of the Adriatic bora and the impact of mountain height on bora trajectories

Summary This study addresses simulation of the local bora wind and its properties as reflected on typical trajectories. Trajectory calculations are implemented in the Eta Model. The Eta Model has a vertical coordinate which permits a step-like representation of mountains and quasi-horizontal coordinate surfaces, the so-called eta coordinate. A realistic real data simulation of a bora wind case in achieved using the model with a 28 km horizontal resolution and 16 layers in the vertical. Numerical experiments with different mountain heights and shapes in the bora wind region are performed. These are motivated by observational indications and theoretically based expectations that a certain intermediate mountain elevation is required for generation of downslope windstorms with bora wind properties. Three-dimensional trajectories over various mountains mimicing real mountains but differing primarily in elevation are calculated and analysed. The maximum bora wind speed is predicted as expected through three-dimensional channels in the step mountain representations. The results illustrate and are in agreement with the observational evidence that mountain barriers of the elevation of about 1000 m are a necessary requirement for the occurrence of the bora-type downslope windstorms.With 10 Figures     

Mapping average annual precipitation in Serbia (1961–1990) by using regression kriging

The appearence of geostatistics and geographical information systems has made it possible to analyze complex spatial patterns of meteorological elements over large areas in the applied climatology. The objective of this study is to use geostatistics to characterize the spatial structure and map the spatial variation of average values of precipitation for a 30-year period in Serbia. New, recently introduced, geostatistical algorithms facilitate utilization of auxiliary variables especially remote sensing data or freely available global datasets. The data from Advanced Spaceborn Thermal Emission and Reflection Radiometer global digital elevation model are incorporated as ancillary variables into spatial prediction of average annual precipitation using geostatistical method known as regression kriging. The R ² value of 0.842 proves high performance result of the prediction of the proposed method.     

Durability Characterization of Marls from the Region of Dalmatia,Croatia

Durability is one of the most important engineering properties of weak and clay-bearing rocks. Weathering can induce a rapid change in rock material from initial properties to soil-like properties. The sensitivity of a rock type against weatherability is usually described by a durability parameter, such as the slake durability index. However, marl resistance is not detected satisfactorily by the durability indices by using slake durability test as suggested by ISRM for two wetting–drying cycles. The results of this study are obtained from samples of compact or laminated eocene marls from region of Dalmatia, Croatia. The samples were subjected to 4 cycles of slake durability, point load tests, determination of dry density, determination of carbonate content and absorption of water. The scatter of data suggests that strength probably has no influence on the durability of marls. On the other hand a separate group of marl samples have a second-cycle slake durability index higher than approximately 85%, and the durability of these samples is classified as “medium-high” to “high”, although the visual inspection of samples after testing, suggests that they should have “medium” to “low” durability classification. According to obtained results these samples of marl fulfil the criterions for the durability classification: a carbonate content lower than approximately 65%, a dry density lower than 2.4 Mg/m³, and values of water absorption higher than 5%.     

Improved bora wind simulation using a nested Eta Model

Summary In connection with a number of recent publications on anomalous (excessive) absorption of shortwave radiation (SWR) by clouds, the data of aircraft observations of spectral and total SWR vertical profiles in the troposphere obtained within the CAENEX, GAAREX and FGGE programmes have been discussed. These data demonstrated persuasively the existence of substantial SWR absorption by clouds in the visible wavelength region. In this context, the results of simulation numerical medelling of the SWR transfer in clouds have been considered. These show a significant enhancement of the SWR absorption by clouds due to an increase of the mean free path of photons under an impact of multiple scattering in clouds. Another important consideration may be the impact of SWR-absorbing pollutants in clouds, especially soot aerosols.With 4 Figures     

Eta model forecasts of tropical cyclones from Australian Monsoon Experiment: The model sensitivity

Summary The Australian Monsoon Experiment (AMEX) (10 January through 15 February 1987) has resulted in the first ever quality mesoscale data set in the Australian tropics. This provides the first observational confirmation of previous hypotheses, modelling experiments and refinement of the parametrization of convective processes. During the AMEX a large area of convective activity off northwestern Australia accompanied four tropical cyclones onset:Connie, Irma, Damien andJason. As already reported by the author, the Eta Model of the University of Belgrade and the National Meteorological Centre, Washington (UB/NMC), successfully predicted the development, structure, associated precipitation and tracks of these cyclones.Using again the AMEX tropical cyclone cases, in the present study the sensitivity of the Eta Model is examined with respect to the initial and boundary conditions, the vertical coordinate and orography, the location of the initial vortex, the surface fluxes of heat and moisture, the sea surface temperature and the Betts-Miller convection parametrization scheme.Also, some available forecasts of the AMEX tropical cyclones were intercompared. These included the forecasts obtained by the Eta Model, the T106 global (then) operational European Centre for Medium-range Weather Forecasts (ECMWF) model, the ECMWF T106 limited area model and the Florida State University (FSU) limited area model. A review of the intercomparison results suggests that the Eta Model is highly competitive with the other sophisticated models, both in terms of quality and the computational effort required.With 9 Figures