[en] The eikonal theory of wave propagation is developed by means of a Lorentz-covariant variational principle, involving functions defined on the natural eight-dimensional phase space of rays. The wave field is a four-vector representing the electromagnetic potential, while the medium is represented by an anisotropic, dispersive nonuniform dielectric tensor D/sup μν/(k,x). The eikonal expansion yields, to lowest order, the Hamiltonian ray equations, which define the Lagrangian manifold k(x), and the wave-action conservation law, which determines the wave-amplitude transport along the rays. The first-order contribution to the variational principle yields a concise expression for the transport of the polarization phase. The symmetry between k-space and x-space allows for a simple implementation of the Maslov transform, which avoids the difficulties of caustic singularities

[en] The eikonal theory of wave propagation is developed by means of a Lorentz-covariant variational principle, involving functions defined on the natural eight-dimensional phase space of rays. The wave field is a four-vector representing the electromagnetic potential, while the medium is represented by an anisotropic, dispersive nonuniform dielectric tensor D/sup μ sup ν/(k,x). The eikonal expansion yields, to lowest order, the Hamiltonian ray equations, which define the Lagrangian manifold k(x), and the wave action conservation law, which determines the wave amplitude transport along the rays. The first-order contribution to the variational principle yields a concise expression for the transport of the polarization phase. The symmetry between k-space and x-space allows for a simple implementation of the Maslov transform, which avoids the difficulties of caustic singularities

[en] A map model has been developed for studying the nonlinear interaction of alpha particles with the toroidal Alfven eigenmodes. The map is constructed by assuming a linear interaction during a single poloidal transit, which allows the study of the nonlinear interaction over many transits. By using this map, analytic expressions are obtained for the particle nonlinear bounce frequency, and the wave amplitude threshold for the onset of particle orbit stochasticity. The map model can also facilitate self-consistent simulations which incorporate the time variation of the waves

[en] Recently a new point of view has developed for describing saturation of discrete modes excited by weak sources. The method applies to the evolution of energetic particles in the beam plasma instability as well as to the description of how α particles evolve when they destabilize Alfven waves under reactor conditions. Over a wide range of parameters the system produces pulsations, where there are relativelybrief bursts of wave energy separated by longer intervals of quiescence. There are two types of pulsations; benign and explosive. In the benign phase, valid when particle motion is not stochastic, the distribution function is close to that predicted by classical transport theory, and the instability saturates when the wave trapping frequency equals the expected linear growth rate. If the field amplitude in a burst reaches the level where orbit stochasticity occurs, the quasilinear diffusion causes rapid transfer of particle energy to wave energy and rapid flattening of the particle distribution function. The bursting phaseis followed by a relatively long quiescent time interval where the source provides the necessary free energy to regenerate the cycle. The critical issue is whether the instability develops to a high enough level to produce stochastic diffusion. In general this question can be assessed by using mapping methods to obtain criteria of overlapping of orbit resonance

[en] The influence of secondary Y211 phase on the oxygen diffusion in the ceramic composite of Y123 with Y211 addition has been investigated by the isothermal electric resistance relaxation. The activation energy of oxygen diffusion in the Y123 matrix of the composite is obtained as 1.13, 1.04 and 0.97 eV for the composite of Y123 with x mol Y211, x=0, 0.2, 0.4 respectively, i.e., it is decreased with the Y211 addition in the investigated composition range

[en] We present a one-dimensional analytic theory of the ICRF gyroresonant absorption and mode-conversion, for the problem of minority fundamental resonance. Using the wave phase-space method, and the theory of linear mode conversion therein, we obtain explicit expressions for the coefficients of transmission (T), reflection (R), conversion (C), absorption (A). 7 refs., 2 figs

[en] Sr_0.75Ba_0.25Nb₂O₆ (SBN75) thin films were deposited on silicon substrate with MgO (100) or TiN (100) buffer layer by radio-frequency magnetron sputtering technique. X-ray diffraction confirmed that a 900 deg. C annealed SBN self-buffer layer introduced before SBN deposition can lead to the highly c-axis orientation of SBN75 thin film on MgO buffer layer. Energy-dispersive spectrometry analysis showed that the SBN75 films had target-film composition transfer and the TiN buffer layer was partially oxidized during SBN growth. The refractive index of SBN films on both MgO/Si and TiN/Si substrates was determined by fitting the measured reflectance curves with Sellmeier dispersion model in the visible region and the micro-structures were studied by scanning electron microscopy. In this paper, the conditions for SBN/MgO/Si treated as waveguide structure were also discussed.

[en] Plasma waves have traditionally been associated with electromagnetic fields. Accordingly, the standard approach to wave propagation has involved the derivation of a dielectric tensor, upon elimination of the linear plasma response to an electromagnetic perturbation. In the neighborhood of a local gyroresonance ω∼lΩ(x)(ω=fixed wave frequency, gyrofrequency Ω≡eB_o/mc, l=integer), the (non-Hermitian) dielectric tensor becomes rapidly varying in space, so that eikonal methods have failed. This difficulty is avoided by the introduction of gyroresonant ballistic waves (GBW), which represent the propagation of linear perturbations of the Vlasov distribution in the absence of electromagnetic perturbation. (author) 4 refs., 1 fig

[en] Tropical Cyclone (TC) formation regions are analysed in twelve CMIP5 models using a recently developed diagnostic that provides a model-performance summary in a single image for the mid-summer TC season. A subjective assessment provides an indication of how well the models perform in each TC basin throughout the globe, and which basins can be used to determine possible changes in TC formation regions in a warmer climate. The analysis is necessarily succinct so that seven basins in twelve models can be examined. Consequently, basin performance was reduced to an assessment of two common problems specific to each basin. Basins that were not too adversely affected were included in the projection exercise. The North Indian basin was excluded because the mid-summer analysis period covers a lull in TC activity. Surprisingly, the North Atlantic basin also had to be excluded, because all twelve models failed the performance assessment. A slight poleward expansion in the western North Pacific and an expansion towards the Hawaiian Islands in the eastern North Pacific is plausible in the future, while a contraction in the TC formation regions in the eastern South Indian and western South Pacific basins would reduce the Australian region TC formation area. More than half the models were too active in the eastern South Pacific and South Atlantic basins. However, projections based on the remaining models suggest these basins will remain hostile for TC formation in the future. These southern hemisphere changes are consistent with existing projections of fewer southern hemisphere TCs in a future warming world

[en] In this paper it will be demonstrated that conventional measures used to characterize contaminant concentration reduction are impractical and inadequate to describe the important case of a contaminant cloud. A new measure, the expected-mass-fraction function, is developed and shown to have desirable experimental and theoretical features. Some contaminant plume data is used to illustrate the application of this new measure