Correlation Analysis for Compositional Data   总被引：1，自引：0，他引：1  

Peter Filzmoser  Karel Hron 《Mathematical Geosciences》2009,41(8):905-919

Compositional data need a special treatment prior to correlation analysis. In this paper we argue why standard transformations for compositional data are not suitable for computing correlations, and why the use of raw or log-transformed data is neither meaningful. As a solution, a procedure based on balances is outlined, leading to sensible correlation measures. The construction of the balances is demonstrated using a real data example from geochemistry. It is shown that the considered correlation measures are invariant with respect to the choice of the binary partitions forming the balances. Robust counterparts to the classical, non-robust correlation measures are introduced and applied. By using appropriate graphical representations, it is shown how the resulting correlation coefficients can be interpreted.  相似文献   

Seasonal evolution of runoff generation on agricultural land in the Belgian loess belt and implications for muddy flood triggering   总被引：1，自引：0，他引：1  

Olivier Evrard  Karel Vandaele  Charles Bielders  Bas van Wesemael 《地球表面变化过程与地形》2008,33(8):1285-1301

Muddy floods due to agricultural runoff are a widespread and frequent phenomenon in the European loess belt, and particularly in central Belgium. These floods are triggered when high quantities of runoff are generated on cropland and cause severe erosion. Three soil surface characteristics are relevant to determine the runoff potential of cultivated soils: soil cover by crops and residues, soil surface crusting and roughness. These characteristics have been observed on 65 cultivated fields throughout 2005. A heavy rainfall event representative for events triggering muddy floods in the region (60 mm h^?1 during 30 minutes) has been simulated using a 0·5 m² simulator on fields with the 17 most observed combinations of soil surface characteristics in central Belgium. Runoff is not observed in the case of (ploughed) bare uncrusted soils, nor in the case of soils covered by crops showing a transitional crust and a moderate roughness (1–2 cm). In the cases where runoff has been observed, mean runoff coefficients ranged from 13% (wheat in July) to 58% (sugar beet or maize in May and June). Grassed buffer strips (GBSs) and grassed waterways (GWWs) show a higher runoff coefficient (62% for GBSs and 73% for GWWs) than most cultivated soils (13–58%). Furthermore, it is demonstrated that small plot measurements can be used to estimate runoff generation at the field scale. A classification of runoff generation risk based on the surveys of soil surface characteristics has been applied to common crops of central Belgium. February as well as the period between May and September are the most critical for runoff at the field scale. However, it appears from monitoring of a 16 ha catchment that the highest runoff volumes and peak discharges are recorded between May and August after heavy rainfall, explaining why 85% of muddy floods are recorded during this period in central Belgium. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Rapid changes of the outer high-latitude ionosphere combined with a penetration of intensive ULF (Pcl) signals     

Karel Prikner  Dora S. Fligel 《Planetary and Space Science》1991,39(12):1657-1666

Variable values of the Pcl signal transmissivity through the ionosphere, experimentally obtained from the conjugated ULF experiment GEOS-1-Husafell during a roughly 1-h interval of the micropulsation disturbance on 13 July 1977, have been compared with the results of numerical simulation. Variations of the basic physical parameters of the high-latitude outer ionosphere have been considered. Quantitative estimates of the rapid changes of the ionized particle concentration in connection with the considered changes of the ionospheric plasma temperature have been made. It is assumed that the ioncyclotron waves themselves propagating along the plasmapause give rise to the non-stationary conditions in the outer high-latitude ionosphere (Φ≈ 70°).  相似文献   

Antwerp: A modern city with a significant historic heritage     

Karel Vroom 《GeoJournal》1991,24(3):277-284

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Filtration of Pc1 wave packets in the ionosphere. Conjugated experiment GEOS-1 — husafell and results of numerical modelling     

Karel Prikner  D. S. Fligel 《Studia Geophysica et Geodaetica》1991,35(1):13-32

Summary The spectral analysis of an hourly section of a synchronized conjugated record of an ULF signal made on the GEOS-1 satellite and the Husafell Observatory (Iceland) on July 13, 1977, has been carried out. The time variations of the spectral frequency-amplitude characteristics of the Pc1 wave packet in the neighbourhood of f 0.5 s^–1 at both measurement sites were examined. The transmissibility of the amplitude of the total magnetic component of the wave through the ionosphere towards the Earth's surface, found in the frequency range of the packets, varies from 0.03 to 0.07. Moreover, its time behaviour with the development of the micropulsation disturbance was studied. The frequency shift of the packet spectrum centre towards higher frequencies 0.04 s^–1) was determined at the Earth's surface as compared with the satellite conditions. Experimental results served to test the developed automated methods of numerical modelling of ionospheric filtration in the ULF range of Pc1 micropulsations. Good agreement between the experimental and numerical results of the two constructed limiting models of the daytime ionosphere at higher latitudes (low and high solar activity) was achieved. The values of the transmissibility calculated for the Pc1 packet frequencies vary from 0.075 to 0.3 and from 0.025 to 0.06.  相似文献   

Near-ultraviolet observation of four bright Mn stars     

Rosanna Faraggiana  Karel A. van der Hucht  Marijke Burger 《Astrophysics and Space Science》1975,38(1):243-249

Near-ultraviolet spectra, obtained with the ESRO TD-1A/S59 experiment, of the four Mn stars β Tau, γ Crv, α And, and μ Lep and six normal stars are compared. The normal stars show good agreement with synthetic spectra. The Mn stars have spectra which become hotter at shorter wavelengths. They also show strong Mnii lines and weak Mgii lines. A time-variation for Tiii λ 2828 was noted in γ Crv and α And.  相似文献   

Book reviews     

Daniel W. Gade  Manfred Domrös  Konrad Schliephake  G. Kunkel  M.O. Lawal  Andreas Grotewold  Bernd-M. Schulze  Alexander Zaporozec  Karel Bayer  Günter Borchert  Wolf Tietze 《GeoJournal》1987,14(3):390-323

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Gewichte in Nivellementnetzen     

Karel Kučera 《Studia Geophysica et Geodaetica》1961,5(1):21-29

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Theorie der im Elastischen Halbraum Durch eine Flächenförmige Quelle Erregten Weller (3. Teil)     

Karel Pěč 《Studia Geophysica et Geodaetica》1962,6(2):152-167

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Automatic Video System for Continues Monitoring of the Meteor Activity     

Pavel Koten  Karel Fliegel  Stanislav Vítek  Petr Páta 《Earth, Moon, and Planets》2011,108(1):69-76

In this paper we present current progress in development of new observational instruments for the double station video experiment. The Meteor Automatic Imager and Analyser (MAIA) system is based on digital monochrome camera JAI CM-040 and well proved image intensifier XX1332. Both the observations as well as the data processing will be fully automatic. We are expecting the recorded data of better quality and both spatial and time resolution in comparison with currently used analogue system. The main goal of the MAIA project is to monitor activity of the meteor showers and sporadic meteor each night for the period of at least 3 years. First version of the system was already assembled and has been intensively tested in the optical laboratory. Optical properties were measured and the result confirmed our expectations according to image quality and resolution. First night sky observation was already carried out.  相似文献