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991.
Gérard Clément Michael D. Scadron Jacqueline Stern 《Zeitschrift fur Physik C Particles and Fields》1993,60(2):307-310
A recent quenched lattice QCD estimate of the nucleon σ term leads to a value which is roughly half of the experimental value. We estimate the non-strange sea correction to be dominated by the σ-meson pole contribution, which accounts satisfactorily for the discrepancy. This large non-strange sea content in the nucleon does not necessarily imply a large strange sea content. 相似文献
992.
993.
L. Bongini M. Degli Esposti C. Giardinà A. Schianchi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(2):263-272
In this paper, we solve a general problem of optimizing a portfolio in a futures markets framework, extending the previous
work of Galluccio et al. [Physica A 259, 449 (1998)]. We allow for long buying/short selling of a relatively large number of assets, assuming a fixed level of margin
requirement. Because of non-linearity in the constraint, we derive a multiple equilibrium solution, in a size exponential
respect to the number of assets. That means that we can not obtain the unique efficiency frontier, but many of them and each
one is related to different levels of risk. Such a problem is analogous to that of finding the ground state in long-ranged
Ising spin glass with external field. In order to get the best portfolio (i.e. that is along the best efficiency frontier), we have to implement a two-step procedure, performing the exhaustive enumeration
of all local minima. We develop a concrete application, where the different part of the proposed solution are computed.
Received 31 December 2001 相似文献
994.
995.
In this paper, we study asymptotic properties (large deviations and functional central limit theorem) of generalized record
processes built on a triangular array of continuous and exchangeable random variables. As an application of these results,
the links with the Kendall's rank correlation statistic are studied and testing exchangeability is discussed.
AMS 2000 Subject Classification Primary—60F10
Secondary—60F17, 62G10 相似文献
996.
Antonio Laganà Ernesto Garcia Osvaldo Gervasi Ranieri Baraglia Domenico Laforenza Raffaele Perego 《Theoretical chemistry accounts》1991,79(3-4):323-333
Summary The calculation of rate constant values of theH+H
2 reaction for an extended range of excited vibrational states of the diatomic molecule and temperatures is relevant to the modeling ofH
– sources. To investigate the effect of isotopic substitutions on the efficiency of vibrational deexcitation processes, we extended the calculations to theD+D
2 system. These calculations were carried out using a program restructured to run on a shared memory vector and parallel computer. The dependence of the efficiency of vibrational deexcitation processes from both the initial vibrational state and temperature of reactants is reported. Restructuring strategies adopted for implementing the program on both shared and distributed memory computers as well as speedups achieved on both types of machines are also discussed. 相似文献
997.
Summary Some HPLC procedures with isocratic or gradient elution are reported for the identification and determination of most of the
characteristic components of cortical extracts.
The proposed solvent systems were: A) for normal phase chromatography, mixtures of chloroform-methanol-water on silica columns.
B) For reversed phase chromatography, mixtures of methanol-water or acetonitrile-water or tetrahydrofuran-water on octadecyl
silica columns of different brands. With these systems it was possible to identify and determine, in addition to the principal
corticosteroids, some minor components of the cortical extracts as the 20β-dihydroderivatives of compounds F, E, A, B, the
17-ketosteroids adrenosterone, 11β-hydroxyandrostendione and androstendione and finally, progesterone and 17-OH progesterone.
In reversed phase chromatography it was also possible, by monitoring the effluent at 205 nm, to reveal the 5α- and 5β-tetrahydroderivatives
of the main corticosteroids and to separate them from most of the steroidal components of the adrenal extracts; in these conditions
it was also possible to reveal some characteristic, unknown components of the cortical extracts. Some results of quantitative
analysis of cortical extracts are also reported, comparing different analytical procedures.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
998.
Sunto In questo lavoro si considerano due tests probabilistici di primalità per interi disparim di forma qualsiasi. Gli algoritmi sono tali che sem è dichiarato composto allora lo è certamente, mentre sem è dichiarato primo il risultato ha un certo margine di errore, che può essere reso arbitrariamente piccolo. Un programma
scritto e compilato in linguaggio FORTRAN, applicabile ad interi fino a 102000 ed adatto anche a personal computer, permette un confronto dei due tests sulla base del tipo dei risultati e del tempo di
elaborazione, fornendo diverse opzioni ed una stima del limite superiore per l’eventuale errore in una dichiarazione di probabile
primalità.
Summary In this paper we consider two probabilistic tests for determining the primality of any odd integerm. Both algorithms have the property that ifm is declared to be composite than it is guaranteed to be so. On the other hand, ifm is declared to be prime than it is sure to be prime only within a certain margin of error which can be made arbitrarily small. A program, written and compiled in the computer language FORTRAN enable this tests to be applied to integers up to 102000, allowing a comparison between the two tests with respect to their running time and with an esplicit bound for the maximum possible error whenm is declared prime. The program is sufficiently compact to be implemented on a personal computer such as an IBM PS/2 with an arithmetic co-processor相似文献
999.
High energy γγ-type reactions are investigated as a means for producing pairs of scalar superpartners of leptons and quarks. We report on the calculation of the cross sections and discuss on the competing background processes. 相似文献
1000.