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21.
Milan S. Dimitrijević Zoran Simić Andjelka Kovačević Aleksandar Valjarević Sylvie Sahal-Bréchot 《Journal of Astrophysics and Astronomy》2015,36(4)
We will consider Stark broadening of non hydrogenic spectral lines in the impact approximation in compact stars: pre-white dwarf and white dwarf atmospheres. In order to show an example, Stark broadening parameters have been calculated, using the impact semiclassical perturbation approach for four Xe VI spectral lines. Obtained results have been used to demonstrate the influence of Stark broadening in DA and DB white dwarf atmospheres. 相似文献
22.
Youssef Tawk Cyril Botteron Aleksandar Jovanovic Pierre-André Farine 《GPS Solutions》2012,16(2):243-258
The world of global navigation satellite systems has been enhanced with several new or improved signals in space aiming to
optimize accuracy, reliability, navigation solution, and interoperability between different constellations. However, such
developments bring various challenges to the receivers’ designers. For example, acquisition and tracking stages turn into
more complex processes while handling the increasing bandwidth requires additional processing power. In this context, we study
the code tracking of Galileo E5ab in a full band or of only one of its components, i.e., either E5a or E5b. More specifically,
an architecture for tracking the E5 pilot channel as an AltBOC(15,10) or BPSK(10) modulation is introduced, and the performance
of well-known discriminator types is analyzed using analytical derivations and simulations of linearity and stability regions,
thermal noise tracking errors, multipath error envelopes and tracking thresholds. Different parameters, such as the front-end
filter bandwidth, the early/late chip spacing, un-normalized and normalized discriminators, are taken into consideration.
The results obtained are used to illustrate the main advantages and drawbacks of tracking the E5 signal as well as to help
defining the main tracking loop parameters for an enhanced performance. 相似文献
23.
Dubravka Relić Aleksandar Popović Dragana Đorđević Josef Čáslavský 《Environmental Earth Sciences》2017,76(3):122
This study assessed the state of waters in Belgrade regarding pollution with musk compounds as the target contaminants. Eleven of these compounds were alicyclic, two were macrocyclic, and one was polycyclic. Solid-phase microextraction was used for the isolation of these compounds from waste, surface and underground waters and from processed water prepared for drinking, while comprehensive orthogonal two-dimensional gas chromatography with mass spectrometry was used as the final analytical method. In wastewater samples, galaxolide was detected in concentrations of 1.13 and 0.40 μg/L, while in the Sava River and underground water its concentrations were 0.09 and 0.038 μg/L. The lowest concentrations of the investigated musk compounds were detected in underground water samples, indicating that this is the cleanest water of all the analyzed sources with respect to musk compounds. Comparing the results of musk compound concentrations determined in surface river water samples and clean river water samples utilized for drinking, a lower concentration of these compounds was detected in the clean river water samples. The majority of musk compounds were found in waters utilized for drinking. Based on the concentration values, we conclude that the analyzed waters are moderately polluted with these compounds. 相似文献
24.
Deterministic and probabilistic floor response spectra 总被引：1，自引：0，他引：1
The paper presents a comparative study for computing floor response spectra (FRS) for complex structures. For the purpose of validation and evaluation of the methods for practical application, a systematic comparison of two concepts, classical deterministic and probabilistic, was carried out as an example of a nuclear power plants structure. The deterministic method utilizes time history analyses compatible with the prescribed design response spectrum. The probabilistic method uses an analysis of random vibrations for defining the probabilistic FRS influenced by random seismic soil movement. The seismic input is a power spectral density function (PSDF) compatible with the design response spectrum. The probabilistic approach based on PSDF provides satisfying FRS with far less effort and time consumption needed for calculation. 相似文献
25.
Edgar L Andreas Rachel E. Jordan Aleksandar P. Makshtas 《Boundary-Layer Meteorology》2005,114(2):439-460
A 4-month deployment on Ice Station Weddell (ISW) in the western Weddell Sea yielded over 2000 h of nearly continuous surface-level meteorological data, including eddy-covariance measurements of the turbulent surface fluxes of momentum, and sensible and latent heat. Those data lead to a new parameterization for the roughness length for wind speed, z0, for snow-covered sea ice that combines three regimes: an aerodynamically smooth regime, a high-wind saltation regime, and an intermediate regime between these two extremes where the macroscale or `permanent' roughness of the snow and ice determines z0. Roughness lengths for temperature, zT, computed from this data set corroborate the theoretical model that Andreas published in 1987. Roughness lengths for humidity,zQ, do not support this model as conclusively but are all, on average, within an order of magnitude of its predictions. Only rarely arezTand zQ equal to z0. These parameterizations have implications for models that treat the atmosphere-ice-ocean system. 相似文献
26.
The late Eocene to Neogene tectonic evolution of the Dinarides is characterised by shortening and orogen-parallel wrenching superposed on the late Cretaceous and Eocene double-vergent orogenic system. The Central Dinarides exposes NW-trending tectonic units, which were transported towards the Adria/Apulian microcontinent during late Cretaceous–Palaeogene times. These units were also affected by subsequent processes of late Palaeogene to Neogene shortening, Neogene extension and subsidence of intramontane sedimentary basins and Pliocene–Quaternary surface uplift and denudation. The intramontane basins likely relate to formation of the Pannonian basin. Major dextral SE-trending strike-slip faults are mostly parallel to boundaries of major tectonic units and suggest dextral orogen-parallel wrenching of the whole Central Dinarides during the Neogene indentation of the Apulian microplate into the Alps and back-arc type extension in the Pannonian basin. These fault systems have been evaluated with the standard palaeostress techniques. We report four palaeostress tensor groups, which are tentatively ordered in a succession from oldest to youngest: (1) Palaeostress tensor group 1 (D1) of likely late Eocene age indicates E–W shortening accommodated by reverse and strike-slip faults. (2) Palaeostress tensor group 2 (D2) comprises N/NW-trending dextral and W/WSW-trending sinistral strike-slip faults, as well as WNW-striking reverse faults. These indicate NE–SW contraction and subordinate NW–SE extension related to Oligocene to early Miocene shortening of the Dinaric orogenic wedge. (3) Palaeostress tensor group 3a (D3a) comprises mainly NW-trending normal faults, which indicate early/middle Miocene NE–SW extension related to syn-rift extension in the Pannonian basin. The subsequent palaeostress tensor group 3b (D3b) includes NE-trending, SE-dipping normal faults indicating NW–SE extension, which is likely related to further extension in the Pannonian basin. (4) Palaeostress tensor group 4 (D4) is characterised by mainly NW-trending dextral and NE-trending sinistral strike-slip faults. Together, with some E-trending reverse faults, they indicate roughly N–S shortening and dextral wrenching during late Miocene to Quaternary. This is partly consistent with the present-day kinematics, with motion of the Adriatic microplate constrained by GPS data and earthquake focal mechanisms. The north–north-westward motion and counterclockwise rotation of the Adriatic microplate significantly contribute the shortening and present-day wrenching in the Central Dinarides. 相似文献
27.
Aleksandar Ostoji&#x; Svetlana &#x;ur
i&#x; Ljiljana omi&#x; Marina Topuzovi&#x; 《洁净——土壤、空气、水》2005,33(6):605-613
The Gru?a Reservoir (located at 238…269 m a. s. l., volume 64.6 · 106 m3, surface 934 ha, drainage area 318 km2, max. depth 31 m, mean theoretical retention time 22 months) was investigated during the years 1996 to 2001. The obtained values of trophic state parameters (9…200 μg L?1 total phosphorus, 3…99 μg L?1 chlorophyll‐a, and 0.5…2 m transparency) indicate that water of the Gru?a Reservoir is eutrophic according to three types of classification: Carlson, OECD, and Jones and Lee. It was noticed that values of average biomass abundance are large in the Gru?a Reservoir, and they could indicate a richer trophic state. When these indices are cited in connection with parameters of the trophic state, it is apparent that the Gru?a Reservoir can be classified as a eutrophic water on the basis of total phosphorus content of chlorophyll‐a and hypertrophic water with respect to transparency. 相似文献
28.
Sanja Mrki?Ksenija Stojanovi? Aleksandar Kosti?Hans Peter Nytoft Aleksandra Šajnovi? 《Organic Geochemistry》2011,42(6):655-677
The origin, depositional environment and maturity of petroleum source rocks were determined via conventional whole rock and biomarker analysis of samples from wells in the Banat Depression, where the most important Serbian oil and gas fields are located. The organic matter (OM) in organic-rich upper Tertiary siltstones and marls consists predominantly of Type II kerogen. Numerous biomarker parameters indicated mixed algal-terrestrial OM, related to a brackish or freshwater environment, whose salinity decreased from Middle to Upper Miocene. The OM was deposited under variable redox conditions, reducing to sub-oxic.The wells in the Banat Depression experienced variable high rates of rapid heating, providing an opportunity for examining the applicability of different thermal indicators in a hyperthermal basin. Rock-Eval and numerous biomarker parameters indicate that the main stage of oil generation begins at ca.130 °C and vitrinite reflectance (Rc) ca. 0.63% and reaches a maximum at ca.145-150 °C and Rc ca. 0.72-0.75%, while the late stage of oil generation starts at ca.155 °C and ca. Rc 0.78%, which corresponds, depending on geothermal gradient, to relative depths of 2100-2300 m, 2600-2900 m and 3050-3100 m, respectively. The naphthalene and phenanthrene maturity parameters proved to be less applicable than the biomarker ratios, particularly in the early to moderate maturation range. The newly proposed parameter C(14a)-homo-26-nor-17α(H)-hopane/C30hopane (C30HH/C30H) proved applicable to a wide range of maturity. 相似文献
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30.
Dušan Jovanović Miro Govedarica Filip Sabo Dubravka Sladić Aleksandar Ristić 《国际地球制图》2015,30(5):483-505
Main objective of this study was to establish a relationship between land cover and land surface temperature (LST) in urban and rural areas. The research was conducted using Landsat, WorldView-2 (WV-2) and Digital Mapping Camera. Normalised difference vegetation index and normalised difference built-up index were used for establishing the relation between built-up area, vegetation cover and LST for spatial resolution of 30 m. Impervious surface and vegetation area generated from Digital Mapping Camera from Intergraph and WV-2 were used to establish the relation between built-up area, vegetation cover and LST for spatial resolutions of 0.1, 0.5 and 30 m. Linear regression models were used to determine the relationship between LST and indicators. Main contribution of this research is to establish the use of combining remote sensing sensors with different spectral and spatial resolution for two typical settlements in Vojvodina. Correlation coefficients between LST and LST indicators ranged from 0.602 to 0.768. 相似文献