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141.
This paper introduces a new method for simulating large-scale subsurface contaminant transport that combines an Analytic Element Method (AEM) groundwater flow solution with a split-operator Streamline Method for modeling reactive transport. The key feature of the method is the manner in which the vertically integrated AEM flow solution is used to construct three-dimensional particle tracks that define the geometry of the Streamline Method. The inherently parallel nature of the algorithm supports the development of reactive transport models for spatial domains much larger than current grid-based methods. The applicability of the new approach is verified for cases with negligible transverse dispersion through comparisons to analytic solutions and existing numerical solutions, and parallel performance is demonstrated through a realistic test problem based on the regional-scale transport of agricultural contaminants from spatially distributed sources. 相似文献
142.
Based on a large set of arrival times of the Pg phase reported by local and regional stations, we estimate azimuthal anisotropy of the Pg-wave velocity in focal volumes of the upper crust in NW Croatia. The method is based on analyses of the azimuthal dependence
of ratios of cumulative differences of arrival times and travel paths between foci of earthquake pairs, computed for rays
propagating within narrow azimuthal windows. The results clearly indicate the presence of anisotropy of 3.3% with the direction
of fast velocity (approximately NNE-SSW) coinciding with the direction of the maximum tectonic pressure as revealed by 23
available focal mechanisms and previous geological investigations. Although a large part of observed anisotropy can be explained
assuming that focal volumes are pervaded by a system of vertical extensive-dilatancy anisotropy (EDA) cracks aligned under
the influence of local tectonic stress field, there is indication that — to a smaller extent — some role was also played by
alignment of structural features in the region. 相似文献
143.
Summary ?This paper deals with variations and trends in some components of the water balance: the soil water content; evaporation
loss from the soil (from the surface and underlying layers); transpiration; ground water recharge and runoff. These components
are calculated by means of the Palmer procedure. This analysis is based on data from Osijek, Croatia from this century (1900–1995).
Besides the meteorological input parameters necessary for the water balance calculations, i.e. precipitation, temperature
and relative humidity, the pedological characteristics of this area have also been taken into account. Fluctuations have been
considered by means of the 11-year binomial filtered series and linear trends were tested by means of the Mann-Kendall rank
test. For a closer look on the trends of water balance components, a progressive analysis of the time series was performed,
too. The results show a significant increase in potential evapotranspiration and evapotranspiration and decrease in runoff
and soil water content has occurred during the century.
Received February 22, 1999/Revised August 3, 1999 相似文献
144.
Nikola Solarić 《Astrophysics and Space Science》1991,177(1-2):175-179
The paper deals with the automatic grid azimuth determination of an object on the earth using the electronic theodolite Kern E2 by observing the sun, a star, or a planet. The observation time and the readings of horizontal and vertical circles of the electronic theodolite enter automatically the electronic calculator Hewlett-Packard HP41CX. The calculator computes the grid azimuth of the terrestrial object and directs the observer what to do. Therefore, even a personnel without specific high education can make observations. For the solar observations it is not necessary to have an astronomical almanac, because the program computes the solar coordinates. The general input data, together with the measured ones, can be stored on a magnetic cassette and later on, if necessary, one can correct the general data and recalculate the azimuth. The method proved to be very practical in the field work. 相似文献
145.
Gojko Djurašević 《Astrophysics and Space Science》1993,208(1):85-92
The author considers current problems in the determination of the orbital and physical parameters for active close binaries (CB) of W Ser type based on the interpretation of photometric observations (Djuraevi, 1991). In this particular case, one analyses the light curves of CB SX Cas in the framework of the accretion-disc model explained in the second paper of this series (Djuraevi, 1992a). The light curve is analysed by applying the inverse-problem method described in the third paper of the series (Djuraevi, 1992b). On the basis of the observational material in theB andV filters (Shao, 1967), the light curves, the fundamental orbital and physical parameters of the system are estimated. In the paper a graphical illustration of the obtained solutions is also given. The obtained results confirm the general picture about the active processes in CB of W Ser type. 相似文献
146.
Snezana Maletic Jelena Beljin Dragana Tamindzija Marko Grgic Jelena Molnar Jazic Marijana Kragulj Isakovski Srdan Roncevic 《国际泥沙研究》2021,36(4):479-488
The purpose of the current study is to compare the influence of different aerobic conditions(biostimulation(BS),bioaugmentation(BA),and a combination of biostimulation and bioaugmentation(BB))on polycyclic aromatic hydrocarbons(PAH)degradation and compare the degraded amount with single step XAD-4 extraction as a new tool for bioavailability assessment for chronically contaminated sediment samples obtained from territory of Autonomous Province Vojvodina of Serbia(S1,S2,and S3).A great number of papers dealing with biodegradation of PAHs in spiked sediment or soil have been published,but to the authors’knowledge,a limited number of papers studied aged,historically polluted sediment and a sum of chosen U.S.Environmental Protection Agency(USEPA)PAHs.A significant reduction(up to67%)in PAH concentration was observed,while the percentage of reduction varied depending on the sediment sample and treatment used.BS treatment successfully stimulated growth of indigenous bacteria.Further,PAH-degrading strain Sphingomonas paucimobilis F8 inoculated in BA and BB treatment survived for up to 7 weeks after it was suppressed by unfavorable conditions or native microbes.Degraded amounts generally showed good correlation with results obtained from XAD-4 extraction.Results obtained in the current study represent a good start for standardizing a XAD-4 extraction technique as a simplified,easier,and lower cost method for bioavailability assessment. 相似文献
147.
Tonči Balić-Žunić 《Mineralogy and Petrology》2014,108(4):479-486
The crystal structure of bøgvadite, Na2SrBa2Al4F20, has been solved and refined to a R1 factor of 4.4 % from single-crystal data (MoKα X-ray diffraction, CCD area detector) on a sample from the cryolite deposit at Ivittuut, SW Greenland. Bøgvadite is monoclinic, P21/n space group, with unit cell parameters a?=?7.134(1), b?=?19.996(3) and c?=?5.3440(8) Å, β?=?90.02(1)o. A close proximity of the crystal structure to an orthorhombic symmetry and the presence of the two twin components in a nearly 1:1 ratio suggest that the investigated bøgvadite crystal has originally formed as a high-temperature orthorhombic polymorph which on cooling transformed to the stable low temperature monoclinic structure. The bøgvadite crystal structure has groupings of cation-fluoride coordination polyhedra similar to those found in the crystal structures of the genetically closely associated minerals jarlite and jørgensenite. However, its structure type is different from the latter two. The fluoridoaluminate framework of bøgvadite consists of infinite zig-zag chains of cis-connected AlF6 coordination octahedra. The 1 ∞[AlF5] chains are interconnected by infinite chains of Na-F coordination polyhedra which extend in the same direction. Na is coordinated by nine F atoms if its full surrounding is taken in consideration, but makes significant chemical bonds only to closest five. The chains of AlF6 and NaF9 coordination polyhedra form double layers. In the centre of layers, relatively large voids in the form of pentagonal antiprisms are occupied by Sr atoms which make chemical bonds with the closest six F atoms. Between the SrF10 coordinations in the centre of layers run empty channels. The double layers are interconnected by Ba atoms which are coordinated by eight F atoms and fill the spaces between the layers. Bøgvadite belongs to the group of fluoridoaluminates with infinite chains of cis-connected AlF6 coordination octahedra, alike those found in the crystal structures of Ba-fluoridoaluminates. 相似文献
148.
Summary A simple two-dimensional quasi-geostrophic linearized model of the atmosphere is used to investigate the behaviour of the quasi-geostrophic modes for five horizontal rectangular grids. Numerical expressions for frequencies of Rossby waves for all grids are evaluated. It was found that the B and C grids produce only negative frequencies as well as the continuous case. The D grid has negative and zero frequencies. Finally, it was found that the A and E grids produce positive frequencies and eastward moving Rossby waves.With 2 Figures 相似文献
149.
Xuechao Wu Qingzhen Hao B Marković Slobodan Yu Fu Namira Yang Song Zhengtang Guo 《地球科学进展》2020,35(4):363-377
Danube loess, located at the westernmost part of the widespread Eurasian loess belt, is one of the most well-preserved aeolian dust deposits in Europe with the basal age dating back over 1 Ma. Owing to its unique location and formation processes, Danube loess plays an important role in understanding the linkage of climate changes in different climate regimes over Eurasian continent and paleoclimatic changes in middle-high northern latitudes. Major research advances of the Danube loess, including compositions, provenance, chronology, stratigraphy and paleoenvironment changes were systematically reviewed and the focuses of future research were suggested. To better understand loess provenance, the compositions of sediments in all the potential source areas should be investigated, and methodological study of provenance indicators and application of multi-proxies approaches need to be carried out. Chronologically and stratigraphically, feldspar luminescence dating and tephrochronology methods should be widely used, and the establishment of a uniform stratigraphic framework and correlation scheme should be constrained by precise chronology. In terms of the paleoenvironment, it is necessary to conduct high-resolution multi-proxies reconstruction of paleoenviroment for the entire loess-paleosol sequence, extending from the last interglacial period (130 ka to present) to interval of last 1 Ma. The future progress in Danube loess is crucial to improving the study of continental paleoclimate comparison and paleoclimate dynamics over the Eurasian loess region. 相似文献
150.
Prof. Z. I. Janjić 《Meteorology and Atmospheric Physics》1995,55(1-2):1-16
Summary Two-time-level multiply-upstream semi-Lagrangian schemes were examined in the case of the self-advecting, one-dimensional nonlinear momentum conservation equation. The shock formation process was analyzed. It is pointed out that the shocks cannot be created in the truncated systems satisfying the Pudykiewicz, Benoit and Staniforth criterion.The numerical integrations were restricted to 12 h. It was shown that, at least in the sub-CFL range, increased complexity of the scheme can compensate reduced horizontal resolution. A considerable sensitivity of the schemes with respect to the time step was detected. In the super-CFL mode, several windows on various time scales were found within which the Pudykiewicz, Benoit and Staniforth criterion was satisfied. The time step of 1.44 times the maximum time step allowed by the CFL criterion was used in the semi-Lagrangian runs.The super-CFL, semi-Lagrangian solutions were diverging progressively from the sub-CFL ones as the forecasts advanced. This was also reflected in the energy spectra.Unacceptably large energy losses were encountered in the super-CFL, semi-Lagrangian runs. Most of these losses could be explained by the reduced mean wind speed, i.e., the amplitude of the zero wavenumber wave. At the same time, the energy content in the shorter waves increased. In a more complex model, such a situation would resemble a loss of zonal, and an increase of transient eddy kinetic energy.A trajectory error measure was defined as the maximum absolute value of the distance between the actual arriving point of the particle originating at the estimated departure point, and the grid point assumed to be the arrival point in the semi-Lagrangian procedure. In contrast to the sub-CFL regime, this measure could reach a considerable fraction of the grid distance in the computations with the super-CFL time steps.In the physical system considered, the trajectories are determined only by the velocities at the departure points. With the semi-Lagrangian schemes the distances traveled by the particles are estimated on the basis of the velocities at the points downstream with respect to the departure points. Thus, unless the solution is smooth (in space and time) on the scales of the extrapolation distances/times, the upstream extrapolation does not promise the convergence of the solution.With 16 Figures 相似文献