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21.
Sandra M. Meyers Cornelia Laule Irene M. Vavasour Shannon H. Kolind Burkhard Mädler Roger Tam Anthony L. Traboulsee Jimmy Lee David K.B. Li Alex L. MacKay 《Magnetic resonance imaging》2009
This study compared region of interest (ROI) and voxel-based analysis (VBA) methods to determine the optimal method of myelin water fraction (MWF) analysis. Twenty healthy controls were scanned twice using a multi-echo T2 relaxation sequence and ROIs were drawn in white and grey matter. MWF was defined as the fractional signal from 15 to 40 ms in the T2 distribution. For ROI analysis, the mean intensity of voxels within an ROI was fit using non-negative least squares. For VBA, MWF was obtained for each voxel and the mean and median values within an ROI were calculated. There was a slightly higher correlation between Scan 1 and 2 for the VBA method (R2=0.98) relative to the ROI method (R2=0.95), and the VBA mean square difference between scans was 300% lower, indicating VBA was the most consistent between scans. For the VBA method, mean MWF was found to be more reproducible than median MWF. As the VBA method is more reproducible and gives more options for visualization and analysis of MWF, it is recommended over the ROI method of MWF analysis. 相似文献
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Y. Hou P. D. Robinson C. Y. Meyers 《Acta Crystallographica. Section C, Structural Chemistry》1999,55(11):IUC9900144-IUC9900144
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G. AdomianR. E. Meyers 《Applied Mathematics Letters》1995,8(6):7-8
The generalized nonlinear Schrödinger equation with time-dependent dissipation [1] is considered using decomposition [2]. 相似文献
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O. T. Bruhns N. K. Gupta A. T. M. Meyers H. Xiao 《Archive of Applied Mechanics (Ingenieur Archiv)》2003,72(10):759-778
Summary We propose an exact analysis for finite bending of a compressible elastoplastic strip with combined hardening at a given
stretch normal to the bending plane. We apply the self-consistent eulerian rate-type elastoplastic model based on the logarithmic
rate, in conjunction with a Tresca-type loading function. Utilizing the maximum circumferential stretch at the outer surface
as an independent parameter, we derive exact analytic expressions for the bending angle, the bending moment, the outer and
inner radii, the radii of the two elastic-plastic interfaces and the circumferential stretches at these two interfaces, as
well as the stress distributions in every current cross section. In particular, we establish an explicit relation between
the two circumferential stretches at the two elastic-plastic interfaces, and we show that this relation is universal for all
cases of hardening. We show also that the maximum and minimum circumferential stretches at the outer and inner surfaces obey
a reciprocal relation in the course of both elastic and elastic-plastic deformations.
Received 4 June 2002; accepted for publication 14 November 2002
This research was carried out under financial support from the German Science Foundation (DFG) (Contract No.: Br. 580/26-2)
and from Alexander von Humboldt Foundation. We wish to express our sincere gratitude to these Foundations. 相似文献
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Norman G. Meyers 《Israel Journal of Mathematics》1972,11(3):271-283
It is shown that certain capacities associated with potentials of functions in Lebesgue classes are non-increasing under orthogonal
projection of sets. This inequality is then used to discuss continuity of traces of potentials on subspaces of possibly low
dimension. The case of principal interest is the Bessel potential.
This research was partially sponsored by the Air Force Office of Scientific Research, Office of Aerospace Research, United
States Air Force, under AFOSR Grant No. 883-67. 相似文献