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891.
892.
Miloš Pick 《Studia Geophysica et Geodaetica》1990,34(4):289-312
The determination of the normal gravity according to the formula
相似文献
893.
Petar Milanović 《Environmental Geology》1990,15(1):5-11
The region of eastern Herzegovina and Dubrovnik coastal belt is one of the hydrogeologically and hydrologically most interesting regions of Yugoslavia karst. The main water course in the region is the Trebinjica river, the largest sinking river in Europe. All the poljes in the catchment area are temporary flooded, hydrologically separated, and closed karst entities. Enormous quantities of available water are not evenly disturbed neither in the time nor in the space. The Trebinjica Hydrosystem project uses the basic concept of total water regime organization and its multipurpose utilization. With the construction of seven dams, six artificial reservoirs, six tunnels (with total length, 57 km), and four canals (with total length 74 km) the natural regime of surface and underground waters has been completely changed.As a consequence of water regime disturbance, a lot of changes have been observed in the catchment area: changes in the karst aquifers; local changes of climate conditions; eolic erosion effect; influence on the karst underground and littoral belt; influence on the springs yield; influence on adjacent catchment area; pollution of karst aquifers and influence of storage reservoirs on seismicity—induced seismicity. This article presents influences observed after the first stage of hydrosystem construction. 相似文献
894.
Study of groundwaters using the environmental tritium and hydrochemical data in the Belgrade region 总被引:2,自引:1,他引:1
M. Hadžišehović M Župančić N. Miljević D. Paligorić M. Komatina 《Environmental Geology》1990,15(1):13-29
A study of tritium content and some physicochemical parameters has been performed in order to investigate interconnection between surface and atmospheric waters and underground waters in Belgrade area. Samples of the precipitation at Zeleno Brdo-Belgrade meteorological station, the Danube and the Sava river water, and underground water (Ranney wells and piezometers) have been analyzed. The3H content, the content of dissolved ions, total hardness, and electrical conductivity have been measured. The tritium data show existence of two water strata in the aquifer. The upper stratum (about 16 m thick) contains older water (mean monthly3H concentration of 17 TU) and has weak interaction with the river and the precipitation. Below this stratum lies the principal water bearing stratum, strongly connected with the river with the3H concentration similar to that of surface water (mean monthly3H concentration of 50 TU) and spreading out through the entire aquifer. The contribution of the Sava river water and the two water layers at the Ranney well are calculated starting with the hydrological aquifer model, which supposes that three water components are mixed in the pumped Ranney well water. According to calculation results using the3H concentration and physicochemical characteristics as parameters, more than 70 percent of the water pumped by the Ranney well (in 1983) comes from the Sava with a time delay of less that 15 days.Properties of tritium distribution in precipitation, river waters, and underground water in the Belgrade region are established from the results of measurements of3H concentrations in the period 1976–1983. 相似文献
895.
R. J. García López R. Rebolo L. Crivellari J. E. Beckman 《Astrophysics and Space Science》1990,169(1-2):109-111
Precise photometric observations of stars in the double cluster h and Persei reveal a large spread in the colours and magnitudes of the upper Main-Sequence; half of the stars are variables that are Be stars or related stars. The reported age difference between both clusters is found to be spurious. Rotation apparently affects both the intrinsic and the observed colours of the early-type stars in h and Persei. This result questions the validity of photometric calibrations that heavily rely on h and Persei or similar clusters.Paper presented at the 11th European Regional Astronomical Meeting of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
896.
A supplement to the theory of analytical continuation of circular orbits in the restricted three-body problem is presented. The first order stability is given analytically to the first power of mass parameter . The theory of the Kirkwood gaps is discussed from this point of view. The stability limit which should determine the size of accretion discs in binaries is found to be in good agreement with earlier numerical experiments for < 1/2. 相似文献
897.
Observations of internal structure and development of four helical prominences are presented. We assume that the helically twisted fine structure threads are outlining magnetic field lines and we found that it is possible to describe the magnetic fields by the uniform twist configuration, with the twists ranging between 2 and 7. The estimated lower limits for the magnetic fields were about 20 G which give lower limits for the currents flowing along the prominences in the range between 2 × 1010 A and 2 × 1011 A and current densities at the axis of the prominences about 10-4 A m-2. The upper limit of electron drift velocity could be estimated as 1 m s-1, which is far below the critical velocities for the onset of plasma microinstabilities.The stability of the studied prominences is discussed and the criteria for the onset of eruptive instability are established for a prominence modelled as a twisted and elliptically curved magnetic flux tube which is anchored in the photosphere and affected by its mirror-current. The eruption starts when the prominence attains a critical height which must be larger than half of the footpoint separation and depends on the values of twist, radius, and footpoint distance of the magnetic flux tube. The observed examples of eruptive prominences agree very well with the predictions. Possible applications to the two-ribbon flare process are outlined.Properties of stable cylindrical prominences in equilibrium are analyzed and a criterion for the distinction between the Kuperus-Raadu and Kippenhahn-Schlüter types of prominences is proposed. According to established criteria, two of the studied prominences were of the Kuperus-Raadu type, while the other two were of the Kippenhahn-Schlüter type. 相似文献
898.
Matyasovszky István Makra László Tusnády Gábor Csépe Zoltán Nyúl László G. Chapman Daniel S. Sümeghy Zoltán Szűcs Gábor Páldy Anna Magyar Donát Mányoki Gergely Erostyák János Bodnár Károly Bergmann Karl-Christian Deák Áron József Thibaudon Michel Albertini Roberto Bonini Maira Šikoparija Branko Radišić Predrag Gehrig Regula Rybníček Ondřej Severova Elena Rodinkova Victoria Prikhodko Alexander Maleeva Anna Stjepanović Barbara Ianovici Nicoleta Berger Uwe Seliger Andreja Kofol Weryszko-Chmielewska Elżbieta Šaulienė Ingrida Shalaboda Valentina Yankova Raina Peternel Renata Ščevková Jana Bullock James M. 《Theoretical and Applied Climatology》2018,133(1-2):277-295
Theoretical and Applied Climatology - The drivers of spatial variation in ragweed pollen concentrations, contributing to severe allergic rhinitis and asthma, are poorly quantified. We analysed the... 相似文献
899.
900.
Curdin Derungs Tanja Samardžić 《International journal of geographical information science》2018,32(5):856-873
Data-driven GIScience shows a growing interest in making spatial information from large text data. In this paper, we quantify and thus evaluate the relation between text frequency and properties of the outer-text, geographic setting by comparing text frequencies of mountain names to the respective geomorphometric characteristics. We focus on some 2000 unique mountain names that appear some 50,000 times in a large compilation of texts on Swiss alpine history. The results on the full data set suggest only a weak relation: only 5–10% of the variation in the text frequency being explained by the respective geomorphometric characteristics. However, an analysis of multiple scales allows us to identify a Simpson’s Paradox. What appears to be ‘noise’ in the analysis of all mountains in the whole of Switzerland shows significant local signals. Small spatial extents, found all over Switzerland, can show considerably strong correlations between text frequency and spatial prominence, with up to 90% of the total variation explained. We argue that our findings have practical implications for data-driven GIScience. Retrieving meaningful spatial information from text might only be possible if the spatial scale of analysis reflects the spatial scale described in the input text documents. 相似文献
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