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排序方式: 共有123条查询结果,搜索用时 219 毫秒
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Mazzucato E Smith DR Bell RE Kaye SM Hosea JC LeBlanc BP Wilson JR Ryan PM Domier CW Luhmann NC Yuh H Lee W Park H 《Physical review letters》2008,101(7):075001
Measurements with coherent scattering of electromagnetic waves in plasmas of the National Spherical Torus Experiment indicate the existence of turbulent fluctuations in the range of wave numbers k perpendicular rho(e)=0.1-0.4, corresponding to a turbulence scale length nearly equal to the collisionless skin depth. Experimental observations and agreement with numerical results from a linear gyrokinetic stability code support the conjecture that the observed turbulence is driven by the electron-temperature gradient. 相似文献
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Conservative methods for the Toda lattice equations 总被引:1,自引:0,他引:1
We are concerned with the numerical integration of the Todalattice equations by using different conservative methods. Numericalexperiments suggest that the global error for isospectral schemesdecreases exponentially with time but it is almost constantfor either symplectic or more general integrators. We providea theoretical explanation for these experimental findings. 相似文献
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Josiane Arnaud Robert L. Jones Alain LeBlanc Mi-Young Lee Olav Mazarrasa Patrick Parsons Marina Patriarca Andrew Taylor Jean-Philippe Weber Cas Weykamp 《Accreditation and quality assurance》2009,14(8-9):427-430
A critical issue in the organisation of Proficiency Testing/External Quality Assessment Schemes is the definition of the criteria against which the performance of individual laboratories should be evaluated. Organisers of EQAS in Occupational and Environmental Laboratory Medicine (http://www.occupational-environmental-laboratory.com) collaborate to define common acceptable levels of performance. The aim of this study was to compare the Horwitz function to the Fraser’s approach. Sets of results obtained from the distribution of test materials in the Network schemes (for the measurands: copper, selenium or zinc in serum) were used to calculate Z-scores according to both approaches. Quality specifications derived from both approaches were also compared to the standard deviations obtained. Except for selenium, Horwitz criteria suggests a more stringent evaluation than Fraser criteria, the latter being very stringent as regard the participant analytical variability. 相似文献
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Summary. Spiral waves are observed in numerous physical situations, ranging from Belousov-Zhabotinsky (BZ) chemical reactions, to
cardiac tissue, to slime-mold aggregates. Mathematical models with Euclidean symmetry have recently been developed to describe
the dynamic behavior (for example, meandering) of spiral waves in excitable media. However, no physical experiment is ever
infinite in spatial extent, so the Euclidean symmetry is only approximate.
Experiments on spiral waves show that inhomogeneities can anchor spirals and that boundary effects (for example, boundary
drifting) become very important when the size of the spiral core is comparable to the size of the reacting medium. Spiral
anchoring and boundary drifting cannot be explained by the Euclidean model alone.
In this paper, we investigate the effects on spiral wave dynamics of breaking the translation symmetry while keeping the rotation
symmetry. This is accomplished by introducing a small perturbation in the five-dimensional center bundle equations (describing
Hopf bifurcation from one-armed spiral waves) which is SO(2)-equivariant but not equivariant under translations. We then study the effects of this perturbation on rigid spiral rotation,
on quasi-periodic meandering and on drifting.
Received August 24, 1999; accepted August 8, 2000 Online publication October 11, 2000 相似文献
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The magnetic flux density in the cavity of a sintered tube of Yttrium Barium Copper Oxide (YBCO) is measured as a function of H, the axial magnetic field impressed and removed after zero field cooling (ZFC). We note that, in a short thick-walled hollow cylinder of a weak-linked polycrystalline high-Tc superconductor, the magnetic field in the cavity of the tube, Hz hole, rises above the applied field H when it is initially increasing. Consequently the standard approach to determine the critical current density from an ascending sweep of H alone, or a descending sweep alone cannot be exploited. However the field dependence of the intergranular critical current density Jcm can be reliably obtained from the horizontal traversals of Hz hole vs H. Comparison of the experimental data with model calculations for the horizontal traversals of the hysteresis curves show that the intergranular critical current density in the YBCO tube has a Kim-like field dependence. The magnetization of the grains has a significant influence on the flux density in the cavity of the tube. 相似文献
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