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René Michel 《Extremes》2007,10(3):83-107
The investigation of multivariate generalized Pareto distributions (GPDs) has begun only recently. For further progress with
these distributions simulation methods are an important part. We describe several methods of simulating GPDs, beginning with
an efficient method for the logistic GPD. The algorithm is based on the Shi transformation, which was already used for the
simulation of multivariate extreme value distributions (EVDs) of logistic type. In the sequel another algorithm is presented
simulating a broader class of GPDs. Due to its numerical complexity it is only practicably applicable in low dimensions. A
method is given to generate unconditional GPD random vectors from conditionally GPD distributed random vectors. A short application
of the simulation methods in the analysis of a real hydrological data set concludes the article. The simulation algorithms
are available on the author’s home page .
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The mean excess plot is a tool widely used in the study of risk, insurance and extreme values. One use is in validating a generalized Pareto model for the excess distribution. This paper investigates some theoretical and practical aspects of the use of the mean excess plot. 相似文献
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Let us call a lattice path in from to using , , and steps and never going below the -axis, a -path (of order ). A super -path is a -path which is permitted to go below the -axis. We relate the total number of humps in all of the -paths of order to the number of super -paths, where a hump is defined to be a sequence of steps of the form , . This generalizes recent results concerning the cases when and or . A similar relation may be given involving peaks (consecutive steps of the form ). 相似文献
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Wind storm and hurricane risks are attracting increased attention as a result of recent catastrophic events. The aim of this paper is to select, tailor, and develop extreme value methods for use in wind storm insurance. The methods are applied to the 1982-2005 losses for the largest Swedish insurance company, the Länsförsäkringar group. Both a univariate and a new bivariate Generalized Pareto Distribution (GPD) gave models which fitted the data well. The bivariate model led to lower estimates of risk, except for extreme cases, but taking statistical uncertainty into account the two models lead to qualitatively similar results. We believe that the bivariate model provided the most realistic picture of the real uncertainties. It additionally made it possible to explore the effects of changes in the insurance portfolio, and showed that loss distributions are rather insensitive to portfolio changes. We found a small trend in the sizes of small individual claims, but no other trends. Finally, we believe that companies should develop systematic ways of thinking about “not yet seen” disasters. 相似文献
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Davorka Moslavac Forjan Marijana Vinković Darko Kontrec Andreja Lesac Vladimir Vinković 《Structural chemistry》2007,18(5):585-591
Doubling of resonances in NMR spectra of chiral selectors with naphthyl group attached to the tertiary amide nitrogen atom
has been noticed what revealed the presence of two isomers. To test the enantiorecognition ability of these chiral selectors
they are covalently bonded to the HPLC silica gel. Those kind of chiral stationary phases were compared with analogous commercial
leucine chiral stationary phase. They exhibit the better enantioseparation results which indicate that the existence of cis/trans isomers does not have the negative influence on their enantioselective ability.
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Vladimir VinkovićEmail: |
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W. Schwarz 《Fresenius' Journal of Analytical Chemistry》1977,286(1-2):20-30
Zusammenfassung Durch energiedispersive Röntgenanalyse entstehen Spektren mit hohem Untergrundanteil. Es wurden von einzelnen Peaks die Koeffizienten A und B der Angenäherten Harmonischen Analyse (äquivalent der Diskreten- oder Fast-Fourier-Transform) ermittelt. Für die Analyse wurden N=48 Werte benutzt. Das Peak-Maximum wurde auf N/2 gelegt. Ein Vergleich der A-Koeffizienten von Peaks mit und ohne Untergrund zeigt, daß der Untergrund die Koeffizienten A
1 und A
2 nur unwesentlich beeinflußt. Spektral-Peaks werden allgemein als gaußförmig angesehen. Die Fourier-Transformierte einer Gauß-Funktion ist bekanntlich wieder eine Gauß-Funktion. Diese Tatsache erlaubt, aus A
1 und A
2 untergrundfreie Gauß-Peaks zu regenerieren. Die Genauigkeit der Resultate liegt innerhalb der infolge statistischer Schwankungen unvermeidlichen Fehler. Da nur 2 Fourier-Koeffizienten errechnet werden müssen und eine Rücktransformation nicht erforderlich ist, arbeitet die beschriebene Methode sehr schnell. Sie wird PARG (Peak-Analyse und Regeneration einer Gauß-Funktion) genannt. Wenn der Untergrund an der Stelle des Peak-Maximums einen Extrem-Wert aufweist, treten starke Fehler auf. Ebenso stören Absorptionskanten. Diese können zum großen Teil rechnerisch eliminiert werden.Herrn Dr. Hantsche, Bundesanstalt für Materialprüfung, Berlin, Laboratorium 5.32, dank ich für die Zuverfügungstellung von Zahlenmaterial. 相似文献
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Iwona Gęca 《Electroanalysis》2023,35(3):e202200256
An anodic stripping voltammetric procedure for the determination of bismuth in the presence of excess of Cu2+ ions at two ex situ plated gold film electrodes was described. The procedure is based on utilization of two deposition and two stripping steps system. The presented procedure ensures increasing the sensitivity of Bi3+ determination and minimization of interferences related to peaks’ overlapping. The calibration graph for bismuth determination was linear from 2.5×10−9 to 2×10−8 mol L−1 for deposition time of 300 s at both working electrodes while detection limit was 7.7×10−10 mol L−1. 相似文献
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