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961.
962.
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
963.
964.
Dinesh Topwal U. Manju Sugata Ray S. Raj D. D. Sarma S. R. Krishnakumar M. Bertolo S. La Rosa G. Cautero 《Journal of Chemical Sciences》2006,118(1):87-92
Disordered Sr2FeMoO6 shows a drastic reduction in saturation magnetization compared to highly ordered samples, moreover magnetization as a function
of the temperature for different disordered samples shows qualitatively different behaviours. We investigate the origin of
such diversity by performing spatially resolved photoemission spectroscopy on various disordered samples. Our results establish
that extensive electronic inhomogeneity, arising most probably from an underlying chemical inhomogeneity in disordered samples, is
responsible for the observed magnetic inhomogeneity. It is further pointed out that these inhomogeneities are connected with
composition fluctuations of the type Sr2Fe1+x
Mo1-x
O6 with Fe-rich (x > 0) and Mo-rich (x < 0) regions.
Dedicated to Prof J Gopalakrishnan on his 62nd birthday. 相似文献
965.
966.
Golovchenko A. V. Pil'o S. G. Brovarets V. S. Drach B. S. 《Russian Journal of General Chemistry》2003,73(11):1832-1833
Russian Journal of General Chemistry - 相似文献
967.
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
968.
L. A. Falkovsky 《Journal of Experimental and Theoretical Physics》2003,96(2):335-339
The effect of free carriers on the dispersion and damping of coupled phonon-plasmon modes is considered in the long-wave approximation. The electron and phonon scattering rate, as well as Landau damping, is taken into account. 相似文献
969.
S Watanabe R R Anderson S Brorson G Dalickas J G Fujimoto T J Flotte 《Photochemistry and photobiology》1991,53(6):757-762
Threshold radiant exposures for grossly apparent immediate whitening and ultrastructural alterations of melanosomes in black guinea pig skin were determined for a series of red visible laser pulses ranging from 4 x 10(-4) to 6.5 x 10(-14) s. Threshold exposures for melanosomal injury were found to be independent of pulsewidth when the pulsewidths were below the estimated thermal relaxation time of melanosomes. Threshold radiant exposures for melanosomal injury were found to increase when the pulsewidths were approximately equal to or above the thermal relaxation time of melanosomes. At longer pulse durations, fracturing of melanosomes was not observed despite the longer exposures necessary for injury. Instead, perimelanosomal vacuoles were noted. These findings are consistent with the theory of selective photothermolysis and provide evidence for the thermal initiation of melanosomal disruption. 相似文献
970.