排序方式： 共有39条查询结果，搜索用时 656 毫秒
21.
Elena Korobova Yadviga Anoshko Ausrele Kesminiene Aleksander Kouvyline Sergei Romanov Vanessa Tenet Eero Suonio Elisabeth Cardis 《Journal of Geochemical Exploration》2010
Variation of the stable iodine supply was evaluated in the soils of around more than 700 settlements in the regions (oblasts) of Belarus and the Russian Federation contaminated after the Chernobyl accident. It involved the use of regional information on iodine content in different types of soil cover, biogeochemical criteria of iodine deficiency in food chains, and the available soil maps. 相似文献
22.
Humood F. Al‐Mudhaf Mustafa I. Selim Aleksander M. Astel Abdel‐Sattar I. Abu‐Shady 《洁净——土壤、空气、水》2011,39(9):833-843
The present study reveals spatial variability of haloacetic acids and the basic physiochemical properties of drinking water samples through visualization based on the Kriging algorithm and hierarchical cluster analysis. Both projection and statistical method contributed to the logical classification of the indoor and outdoor water samples collected from various governorates covering more than 95% of the residential areas in Kuwait. Clustering of the variables led to the formation of several significant clusters corresponding to the effect of chlorine concentration and its residence time on the formation potential of chlorinated acetic acid derivatives in desalinated drinking water as well as to the total ionic composition of water samples and to the effect of the formation of brominated acetic acid derivatives. Clustering of samples, both indoor and outdoor, indicated that all of governorates located in the northern part of Kuwait are supplied with water containing high concentrations of chlorinated acetic acid derivatives, whereas significantly lower amounts of chlorinated or monobrominated acetic acids were found in water samples in the central and southern parts of the country. 相似文献
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24.
Aleksander Brzeziński 《Journal of Geodesy》2007,81(6-8):543-551
A simple digital filter is derived for application to studies concerning geophysical excitation of nutation. Attention is
focused on the inverse solution, i.e., inferring the excitation function from the time-series of the celestial pole offsets
observed by very long baseline interferometry (VLBI). Filter properties are discussed by comparing its transfer function with
that of the original differential equation of nutation. An excellent agreement in both the amplitude and phase response is
shown at frequencies between −5 and + 5 cycles per year, which is the frequency band with expected geophysical signals. The
difference appears at higher frequencies, leading to a spurious oscillation produced by the filter. This undesired effect
is considered and the algorithm enabling its removal is described. 相似文献
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26.
Piotr
roda Wojciech Czuba Marek Grad Aleksander Guterch Edward Gaczy
ski POLONAISE Working Group 《Tectonophysics》2002,360(1-4):169-185
This paper reports the results of 3-D tomographic modelling of crustal structure in the Trans European Suture Zone region (TESZ) of Poland, eastern Germany and Lithuania. The data are the product of a large-scale seismic experiment POLONAISE'97, which was carried out in 1997. This experiment was designed to provide some 3-D coverage. The TESZ forms the boundary between the Precambrian crustal terranes of the East European Craton (EEC) and the younger Phanerozoic terranes to the southwest. The 3-D results generally confirm the earth models derived by earlier 2-D analyses, but also add some important details as well as a 3-D perspective on the structure. The velocity model obtained shows substantial horizontal variations of crustal structure across the study area. Seismic modelling shows low (<6.1 km/s) velocities suggesting the presence of sedimentary rocks down to a depth of about 20 km in the Polish basin. The shape of the basin in the vicinity of the profile P4 shows significant asymmetry. Three-dimensional modelling also allowed tracing of horizontal irregularities of the basin shape as well as variations of the Moho depth not only along profiles, but also between them. The slice between P2 and P4 profiles shows about 10-km variations of the Moho over a 100-km interval. The crustal thickness varies from about 30 km in SW, beneath the Palaeozoic platform, to about 42 km beneath East European Craton in NE. High seismic velocities of about 6.6 km/s were found in the depth range 2–10 km, which coincides with K
trzyn anorthosite massif. The results of this 3-D seismic modelling of the POLONAISE'97 data will ultimately be supplemented by inversion of seismic data from previous experiments. 相似文献
27.
Seasonal variations in primary production, phytoplankton biomass, chlorophyll-a, dissolved inorganic phosphorus and nitrogen concentrations in the upper 10 m of the Kattegat were analysed by means of monitoring data from 1993–1997. Spatial optimal analysis, based on a stochastic model, was used to reconstruct weekly constituent fields onto a spatial grid. The reconstructed fields were spatially integrated, resulting in a relatively smooth seasonal variability of the average variables. A simple dynamical model, set up as a periodical boundary problem, is suggested for the average phytoplankton concentration, dissolved inorganic nitrogen and entrainment depth as state variables. The model is forced by the solar radiation, nitrogen load from the land sources and atmosphere as well as by nitrogen supply from the lower nutrient-rich layer. The latter process is modelled proportional to the water entrainment into the upper euphotic layer and is driven by atmospheric forcing, river runoff and the Baltic water inflow. Four model coefficient values were fitted by minimising the root mean square difference between the integrated monitoring data and the model output. The suggested diagnostic model reflects the main features in seasonal variability of phytoplankton and nitrogen concentrations by average values, including the magnitude and timing of such dynamic events as the spring and late summer phytoplankton blooms. The importance of different forcing factors is quantified and estimates of unobserved components such as new primary production can be computed. 相似文献
28.
Aleksander Grm Tomaž Šuštar Tomaž Rodič Franci Gabrovšek 《Mathematical Geosciences》2017,49(5):657-675
Scallops and flutes are common dissolution rock forms encountered in karst caves and surface streams. Their evolution is only partially understood and no numerical model that simulates their formation has been presented. This work at least partially fills the gap by introducing a numerical approach to simulate the evolution of different initial forms of soluble surfaces embedded in a turbulent fluid. The aim is to analyze wall dissolution phenomena from basic principles and to identify stable profiles. The analysis is based on a finite volume moving boundary method. The underlying mathematical model is a \(k-\epsilon \) turbulent model for fluid flow coupled with turbulent scalar transport. The rock wall is treated as a moving boundary, where the normal wall retreat velocity is proportional to the under-saturation of the boundary fluid cells with respect to the mineral comprising the wall. As the flow time scale is several orders of magnitude smaller than the dissolution time scale, stationary flow field, concentration field and wall propagation velocity are calculated for each iteration. The boundary at all points is then moved by distracting minimal velocity along the entire boundary from the actual velocity at a certain location, and then normalized to the maximum allowed shift, which is equal to half the height of the boundary cell. In this way only deformation of the initial wall is calculated. The method was applied to several different initial profiles. During the evolution, the profiles progressively converged towards stable forms. In this work, a framework is proposed for a computation of the moving boundary problem related to slow dissolution of a soluble surface. 相似文献
29.
Aerosol optical thickness (AOT) and seasonal variation of AOT over Belsk, Poland, in the UV wavelength range (310–380 nm)
have been analysed using results of measurements by Brewer spectrophotometer No. 064 and Cimel sunphotometer data for the
2002–2007 period. The comparison of AOT derived from direct Sun measurements by Brewer spectrophotometer in the 310–320 nm
range and retrieved from Cimel measurements at longer wavelengths shows good correlation (R = 0.96), with overestimation of retrieved values compared to the measured ones by about 6%. Basing on aerosol microphysical
properties taken from almucantar retrievals and Mie theory, optical properties of aerosol in the UV range has been calculated.
Analysis of seasonal variation of AOT at Belsk reveals two maxima: in April and July–August. Analysis of back-trajectories
in conjunction with analysis of fire maps from Fire Information For Resource Management System shows that these seasonal maxima
are connected with seasonal biomass burning in Eastern and Southern Europe. 相似文献
30.
Mateusz C. Strzelecki Witold Szczuciński Aleksander Dominiczak Piotr Zagórski Justyna Dudek Jasper Knight 《地球表面变化过程与地形》2020,45(5):1325-1334
Changes in the properties and dynamics of tidewater glacier systems are key indicators of the state of Arctic climate and environment. Calving of tidewater glacier fronts is currently the dominant form of ice mass loss and a major contributor to global sea-level rise. An important yet under-studied aspect of this process is transformation of Arctic landscapes, where new lands and coastal systems are revealed due to the recession of marine-terminating ice masses. The evolution of those freshly exposed paraglacial coastal environments is controlled by nearshore marine, coastal and terrestrial geomorphic processes, which rework glacial-derived sediments to create new coastal paraglacial landforms and landscapes. Here, we present the first study of the paraglacial coasts of Brepollen, one of the youngest bays of Svalbard revealed by ice retreat. We describe and classify coastal systems and the variety of landforms (deltas, cliffs, tidal flats, beaches) developed along the shores of Brepollen during the last 100 years. We further discuss the main modes of sediment supply to the coast in different parts of the new bay, highlighting the fast rate of coastal transformation as a paraglacial response to rapid deglaciation in the Arctic. This study provides an exemplar of likely coastal responses to be anticipated in similar tidewater settings under future climate change. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd 相似文献