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991.
We characterize Poisson and Jacobi structures by means of complete lifts of the corresponding tensors: the lifts have to be
related to canonical structures by morphisms of corresponding vector bundles. Similar results hold for generalized Poisson
and Jacobi structures (canonical structures) associated with Lie algebroids and Jacobi algebroids. 相似文献
992.
993.
P L Melgarejo M Ternero I Gracia 《International journal of environmental analytical chemistry》1986,24(4):283-295
A study of the atmospheric pollution by suspended particulate lead in the city of Seville, Spain, was carried out during the period between March 1983 and February 1984. The results obtained from seven sampling stations allowed us to study the site to site variations; there are two locations with average annual concentrations higher than 2 micrograms X m-3. In one station, the meteorological and traffic effects and relationship with other traffic-related pollutants, were investigated. The regression analyses performed on the average monthly data have shown an inverse correlation with wind speed and temperature and a direct correlation with carbon monoxide and smoke concentrations, but no significant correlation was found with the lead deposition levels. 相似文献
994.
995.
996.
C. S. Munita L. P. Barroso P. M. S. Oliveira 《Journal of Radioanalytical and Nuclear Chemistry》2006,269(2):335-338
Summary In general, when characterizing samples, such as ceramic samples or other types of samples, for first time by means of chemical
elements, the analyst measures a large number of variables, many of which may not be very informative. In fact, some may even
be unrelated to the issue at hand and blur the picture instead of making it clearer. In subsequent studies the analyst may
wish to measure fewer variables for several reasons, such as being very time consuming; in cases where measurement time is
important, such as on-line monitoring; in order to reduce cost or effort; etc. Therefore, the hope is to determine those variables
that are most relevant without losing essential information and to remove the less productive information. The problem is
how to perform this in an objective way and to capture crucial information using a multivariate analysis. This paper aims
to describe and illustrate a stopping rule for the identification of redundant variables, and the selection of variable subsets,
preserving multivariate data structure using stepwise discriminant analysis, selecting those variables that are in some senses
adequate for discrimination purposes. One illustrative example using data sets obtained via INAA of ceramic samples from two
archaeological sites is provided. 相似文献
997.
998.
Andrea Grosso Marco Locatelli Fabio Schoen 《Computational Optimization and Applications》2007,38(3):351-370
In this paper we perform a computational analysis of a population based approach for global optimization, Population Basin
Hopping (PBH), which was proven to be very efficient on very challenging global optimization problems by the authors (see
). The experimental analysis aims at understanding more deeply how the approach works and why it is successful on challenging
problems. 相似文献
999.
Alan L. Andrew 《BIT Numerical Mathematics》2003,43(3):485-503
The asymptotic correction technique of Paine, de Hoog and Anderssen can dramatically improve the accuracy of finite difference or finite element eigenvalues at negligible extra cost if closed form expressions are available for the errors in a simpler related problem. This paper gives closed form expressions for the errors in the eigenvalues of certain Sturm–Liouville problems obtained by various methods, thereby increasing the range of problems for which asymptotic correction can achieve maximum efficiency. It also investigates implementation of the method for more general problems. 相似文献
1000.
G. Romero L. Alvarez E. Alanís L. Nallim R. Grossi 《Optics and Lasers in Engineering》2003,40(1-2):81-90
Real-time electronic speckle pattern interferometry (ESPI) was used for tuning and visualization of natural frequencies of a trapezoidal plate. The plate was excited to resonant vibration by a sinusoidal acoustical source, which provided a continuous range of audio frequencies. Fringe patterns produced during the time-average recording of the vibrating plate—corresponding to several resonant frequencies—were registered. From these interferograms, calculations of vibrational amplitudes by means of zero-order Bessel functions were performed in some particular cases. The system was also studied analytically. The analytical approach developed is based on the Rayleigh–Ritz method and on the use of non-orthogonal right triangular co-ordinates. The deflection of the plate is approximated by a set of beam characteristic orthogonal polynomials generated by using the Gram–Schmidt procedure. A high degree of correlation between computational analysis and experimental results was observed. 相似文献