An example of karst catchment delineation for prioritizing the protection of an intact natural area     

Vesna Ristić Vakanjac  Zoran Stevanović  Aleksandra Maran Stevanović  Boris Vakanjac  Marina Čokorilo Ilić 《Environmental Earth Sciences》2015,74(12):7643-7653

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An iteratively reweighted least-squares approach to adaptive robust adjustment of parameters in linear regression models with autoregressive and <Emphasis Type="Italic">t</Emphasis>-distributed deviations     

Boris Kargoll  Mohammad Omidalizarandi  Ina Loth  Jens-André Paffenholz  Hamza Alkhatib 《Journal of Geodesy》2018,92(3):271-297

In this paper, we investigate a linear regression time series model of possibly outlier-afflicted observations and autocorrelated random deviations. This colored noise is represented by a covariance-stationary autoregressive (AR) process, in which the independent error components follow a scaled (Student’s) t-distribution. This error model allows for the stochastic modeling of multiple outliers and for an adaptive robust maximum likelihood (ML) estimation of the unknown regression and AR coefficients, the scale parameter, and the degree of freedom of the t-distribution. This approach is meant to be an extension of known estimators, which tend to focus only on the regression model, or on the AR error model, or on normally distributed errors. For the purpose of ML estimation, we derive an expectation conditional maximization either algorithm, which leads to an easy-to-implement version of iteratively reweighted least squares. The estimation performance of the algorithm is evaluated via Monte Carlo simulations for a Fourier as well as a spline model in connection with AR colored noise models of different orders and with three different sampling distributions generating the white noise components. We apply the algorithm to a vibration dataset recorded by a high-accuracy, single-axis accelerometer, focusing on the evaluation of the estimated AR colored noise model.  相似文献   

Influence of friction on the motion of quasigeostrophic vortices     

Boris Moro 《地球物理与天体物理流体动力学》2013,107(3-4):209-225

Abstract

Who show through numerical experiments that friction may enhance westward motion of vortices on the beta-plane and establish a relation betwen the dissipation coefficients and westward aceleration. This suggests an explanation fot the dunamics of westward intensification.  相似文献   

Response of littoral chironomid communities and organic matter to late glacial lake—level,vegetation and climate changes at Lago dell’Accesa (Tuscany,Italy)     

Laurent Millet  Boris Vannière  Valérie Verneaux  Michel Magny  Jean Robert Disnar  Fatima Laggoun-Défarge  Anne Véronique Walter-Simonnet  Gilles Bossuet  Elena Ortu  Jacques-Louis de Beaulieu 《Journal of Paleolimnology》2007,38(4):525-539

This study focuses on the response of lacustrine littoral chironomid communities to late glacial changes in limnological, environmental and climate conditions in the Mediterranean context. Late glacial chironomid (Diptera: Chironomidae) assemblages, organic petrography and geochemistry were analysed in a sediment core from the littoral zone of Lago dell’Accesa (Tuscany, Italy), where the lake-level fluctuations and the vegetation history have been previously reconstructed. Comparison of the chironomid stratigraphy to other proxies (pollen assemblages, organic petrography and geochemistry, lake-level) and regional climate reconstruction suggested the predominant influence of lake-level changes on the littoral chironomid fauna. The main lowering events that occurred during the Oldest and the Younger Dryas were followed by higher proportions of taxa typical of littoral habitats. A complementary study of organic matter suggested the indirect impact of lake-level on the chironomids through changes in humic status and habitat characteristics, such as the type of substrate and aquatic macrophyte development. Several chironomid taxa, such as Glyptotendipes, Microtendipes and Cricotopus type patens, were identified as possible indicators of low lake-level in the late glacial records. Nevertheless, this study suggested that parallel analyses of organic matter and chironomid assemblages may be needed to circumvent misinterpretation of littoral chironomid assemblage stratigraphy. There was a weak response of the chironomid assemblages to small lake-level lowerings that corresponded to the Older Dryas and Preboreal oscillations. A higher level of determination, e.g. to the species group level, may be necessary to increase the sensibility of the indicators to lake-level changes.  相似文献   

Garnet metagabbro-ultramafic complexes in the Pekulney Range, northeast Russia     

Akira  Ishiwatari  Galina V.  Ledneva  Boris A.  Bazylev  Yasutaka  Hayasaka  Suren A.  Palandzhyan  Odin L.  Morozov  Kazuto  Koizumi  Vasily D.  Stcherbakov  Sergey D.  Sokolov 《Island Arc》2007,16(1):1-3

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Response of alpine chironomid communities (Lake Chuna, Kola Peninsula, northwestern Russia) to atmospheric contamination   总被引：1，自引：0，他引：1  

Boris Ilyashuk  Elena Ilyashuk 《Journal of Paleolimnology》2001,25(4):467-475

A short sediment core from the deepest part of an alpine lake (Lake Chuna, Kola Peninsula, northwestern Russia), covering about the past 200 yrs of sediment accumulation, was analysed for chironomid head capsule remains. The lake has been receiving acidic precipitation and heavy metals loading from the atmosphere since the 1940's. A total of 22 chironomid taxa were recorded. The most important taxa were typical elements of oligotrophic lakes, i.e.Micropsectra insignilobus, Paratanytarsus penicillatus, Stictochironomus spp. and Heterotrissocladius marcidus. Based on the cluster analyses results for the reconstructed environmental variables and chironomid communities, three developmental stages were distinguished from the lake history: (1) Natural ontogeny stage (before ~1945); (2) Initial stage of anthropogenic ontogeny (~1945-~1982); and (3) Anthropogenic ontogeny stage (~1982-~1996). During the first period, the changes in the chironomid fauna were characterized as an anthropogenically undisturbed community, with M. insignilobus dominating (46-66%). The changes during the second period reflected the initial phase of anthropogenic succession associated with the beginning of acidification and heavy metal pollution. The main species showed opposite distributional patterns in this period; the abundance of the group M. insignilobus/Stictochironomus spp. decreased, whereas the abundance of P. penicillatus/H. marcidus increased. The third period was characterized by a major shift in the faunal assemblages, from M. insignilobus to other dominant species including P. penicillatus (19-30%). The increases of Orthocladiinae relative abundance and total organic content in the uppermost sediment layers may be explained by a decrease in lake productivity. The decreases of cold-stenothermal taxa Stictochironomus spp. and M. insignilobus in the uppermost sediment layers can be explained by the global warming during the 20th century. The lake ecosystem is likely to be affected by both inputs of airborne contaminants and climate changes.  相似文献   

Modelling of global ocean tides with allowance for island effects     

Prof. Dr. Boris A. Kagan  Dr. Gennady A. Kivman 《Ocean Dynamics》1993,45(1):1-13

Summary Parameterization schemes for single islands, island chains and archipelagos are described. It is shown that their utilization within the framework of a global tidal model leads not only to local peculiarities in the spatial structure of tidal characteristics, but also to cardinal restructuring of the tidal pattern far beyond the islands and an appreciable increase (about 0.5·10¹²W) of the global tidal energy dissipation. The latter is commensurable by the order of magnitude with the imbalance between estimates of tidal energy dissipation in the World Ocean as a whole and on the continental shelf.

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Modellierung der Gezeiten der weltmeere unter Berücksichtigung von Inseleffekten

Zusammenfassung Es werden parametrisierte Darstellungen von einzelnen Inseln, Inselketten und Inselgruppen beschrieben. Es wird gezeigt, daß ihre Anwendung bei einem globalen Gezeitenmodell nicht nur zu lokalen Besonderheiten in der geographischen Struktur der Gezeiten führt, sondern auch zur grundsätzlichen Restrukturierung des Gezeitenmusters weit über die Inseln hinaus und zu einer deutlichen Zunahme (etwa 0,5·10¹² W) des globalen Gezeiten-Energieverlusts für die M₂-Tide. Dieser hat etwa die Größenordnung des Unterschiedes zwischen dem Gezeiten-Energieverlust des gesamten Weltmeeres und dem auf dem Kontinentalschelf.

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Comparison of the classical and the global solutions of the Ideal Resonance Problem     

Boris Garfinkel 《Celestial Mechanics and Dynamical Astronomy》1972,5(4):451-469

The Ideal Resonance Problem is defined by the Hamiltonian $$F = B(y) + 2\varepsilon A(y) \sin ^2 x,\varepsilon \ll 1.$$ The classical solution of the Problem, expanded in powers of ε, carries the derivativeB′ as a divisor and is, therefore, singular at the zero ofB′, associated with resonance. With α denoting theresonance parameter, defined by $$\alpha \equiv - B'/|4AB''|^{1/2} \mu ,\mu = \varepsilon ^{1/2} ,$$ it is shown here that the classical solution is valid only for $$\alpha ^2 \geqslant 0(1/\mu ).$$ In contrast, the global solution (Garfinkelet al., 1971), expanded in powers ofμ=ε^1/2, removes the classical singularity atB′=0, and is valid for all α. It is also shown here that the classical solution is an asymptotic approximation, for largeα ², of the global solution expanded in powers ofα ^?2. This result leads to simplified expressions for resonancewidth and resonantamplification. The two solutions are compared with regard to their general behavior and their accuracy. It is noted that the global solution represents a perturbed simple pendulum, while the classical solution is the limiting case of a pendulum in a state offast circulation.  相似文献   

A potentiometric study of Eu complexation with acetate ligand from 25 to 170°C at P_sat     

Alexander V Zotov  Boris R Tagirov  Igor I Diakonov  K.Vala Ragnarsdottir 《Geochimica et cosmochimica acta》2002,66(20):3599-3613

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Rapid biotic molecular transformation of fulvic acids in a karst aquifer   总被引：2，自引：0，他引：2  

Florian Einsiedl  Norbert Hertkorn  Moritz Frommberger  Boris P. Koch 《Geochimica et cosmochimica acta》2007,71(22):5474-5482

The study of molecular transformation processes of dissolved organic carbon (DOC) in the environment significantly contributes to a better understanding of the global biogeochemical organic matter cycle. In an oxic karst groundwater system, in which the most powerful abiotic DOC degradative reactions, photodegradation and metal-mediated redox chemistry, are at best marginal contributors, a near complete turnover of fulvic acids (FAs) has been observed within decades (∼60 years). Depletion of oxygen for a very extensive range of aliphatic and aromatic carbon chemical environments has been confirmed as well as the formation of novel classes of compounds, suggesting a major contribution from biotic processes. From these results we infer that FAs must be perceived as a rather active participant in the global carbon cycle. Molecular-level alterations of such magnitude and rapidity on such short-time scales ought to be considered as widespread in the processing of “refractory” DOC in the environment.  相似文献