Kind Of Mode Research Articles

Spectral characteristics of zonal flows in the edge plasmas of the HT-7 tokamak

The spectral characteristics of zonal flows, including both the geodesic acoustic mode (GAM) and the zero/low frequency zonal flow (LFZF), are investigated by applying the two-point correlation technique and bispectral analysis to the floating potential fluctuations measured by several Langmuir probe arrays on the HT-7 tokamak. The three-dimensional wavenumber and frequency spectra for the two modes have been estimated. The radial wavenumber spectra show that the LFZF packages propagate both outward and inward while the GAM packages propagate outward mostly. Nonlinear couplings betweeen zonal flows and ambient turbulence are observed in the biphase while the bicoherence at the GAM frequency is much larger than that at the LFZF frequency. A kind of mode with frequencies higher than that of GAM, which may also be generated from the ambient turbulence in a similar way as the zonal flows, is reported.

Optical Tamm States in Dielectric Photonic Crystal Heterostructure

We investigate one-dimensional dielectric photonic crystal and optical Tamm modes formed by superposition of two band gaps and find that this kind of mode can be explained by the single negative materials tunnelling effect. A finite-size dielectric photonic band gap can mimic one kind of effective single negative material and this property sensitively depends on the frequency location in stop-band regions and surface termination and so on. The effective impedance match and effective phase match give the precise position of the optical Tamm mode. Complete transparency via tunnelling is achieved by two opaque media and demonstrates the validity of our approach.

Kelvin waves and the singular modes of the Lamb–Oseen vortex

Columnar vortices are known to support a family of waves initially discovered by Lord Kelvin (1880) in the case of the Rankine vortex model. This paper presents an exhaustive cartography of the eigenmodes of a more realistic vortex model, the Lamb-Oseen vortex. Some modes are Kelvin waves related to those existing in the Rankine vortex, while some others are singular damped modes with a completely different nature. Several families are identified and are successively described. For each family, the underlying physical mechanism is explained, and the effect of viscosity is detailed. In the axisymmetric case (with azimuthal wavenumber m = 0), all modes are Kelvin waves and weakly affected by viscosity. For helical modes (m = 1), four families are identified. The first family, denoted D, corresponds to a particular wave called the displacement wave. The modes of the second family, denoted C, are cograde waves, except in the long-wave range where they become centre modes and are strongly affected by viscosity. The modes of the third family, denoted V, are retrograde, singular modes which are always strongly damped and do not exist in the inviscid limit. The modes of the last family, denoted L, are regular, counter-rotating waves for short wavelengths, but they become singular damped modes for long wavelengths. In an intermediate range of wavelengths between these two limits, they display a particular structure, with both a wave-like profile within the vortex core and a spiral structure at its periphery. This kind of mode is called a critical layer wave, and its significance is explained from both a physical and a mathematical point of view. Double-helix modes (m = 2) can similarly be classified into the C, V and L families. One additional mode, called F, plays a particular role. For short wavelenghs, this mode corresponds to a helical flattening wave, and has a clear physical significance. However, for long wavelenghts, this mode completely changes its structure, and becomes a critical layer wave. Modes with larger azimuthal wavenumbers m are all found to be substantially damped.

Partial electromagnetic wave guidance by a parabolic cylindrical chiroboundary with small flare angle

Summary Propagation of electromagnetic (EM) waves through an unbounded medium with two regions, having different values of chirality admittances separated by a parabolic cylindrical surface, is dealt with. The dispersion relations and cutoff conditions for such a chiroguide are described under the assumption of small flare angle of the parabolic cylindrical boundary. More emphasis is, however, given on the field cutoffs. A kind of mode bunching phenomenon is reported which is, however, partially localized in this case.

Elastic constants of the dioctanoyl peroxide/urea inclusion compound determined by Brillouin scattering.

Brillouin scattering is used to determine the elastic constants of the incommensurate inclusion compound of dioctanoyl peroxide and urea. The results are interpreted in terms of a simple microscopic model, based on the crystal structure of this compound. A detailed discussion is given concerning the absence of effects in Brillouin scattering due to the sliding (or Goldstone) mode. This kind of mode is expected to be present in incommensurate intergrowth compounds.

Low-frequency torsional oscillations in 1,3-dihalopropanes XH 2CCH 2CH 2Y

Torsional frequencies in conformers of the XH 2CCH 2CH 2Y molecules (X, YF, Cl, Br, I) have been calculated by normal-coordinate analysis using force constants derived from gas-phase data. Results for the symmetrically substituted 1,3-dihalopropanes have been included for comparison. The total range of torsional wavenumbers in these molecules is 34–173 cm −1. The lowest torsional mode had frequencies in the region 34–116 cm −1, while the highest torsional mode had values in the region 107–173 cm −1. Considering the lowest bending frequencies in these molecules, the wavenumbers are limited to the region 77–301 cm −1. In all cases the value of the lowest torsional mode in the GG conformer is below the value of the lowest bending mode, within the same molecule. Simple formulae have been derived for calculating approximately correct values of the lowest wavenumbers if the torsional force constants are known. Systematic trends among the wavenumbers have been pointed out. These trends can be used in estimating frequencies without doing the actual normal-coordinate analysis, and without knowing the torsional force constants. Generally it was found that for three molecules (XH 2C) 2CH 2, XH 2CCH 2CH 2Y and (YH 2C) 2CH 2 the relation ω 2 xy =ω xx ω yy is approximately valid, when the same conformer and the same kind of mode is considered. Thus, one of the wavenumbers may be obtained from the two remaining values.

Simulation of Automobile Side Member Collapse for Crash Energy Management

Vehicle collision characteristics are among the most im portant performance parameters to be examined at the design stage. These characteristics are greatly affected by the collapse mode of the box columns making up the side members of the vehicle body. An accordion-type collapse mode in which the columns do not bend but collapse in sequence is ideal. Beads or reinforcements are often used to produce this kind of mode; however, the work done on them to date has been mainly experi mental, owing to an absence of adequate analytical methods such as the finite element method. In this study, we have developed a new analytical method for providing beading on side members along the buckling mode using finite element analysis calculations.

Über biologische Wirkungen von Koordinationsverbindungen der Übergangsmetalle 2. Zur antiviralen Wirkung von 4-Methyl-2-amino-pyridin-palladiumchlorid (IV)

Abstract 4-methyl-2-amino-pyridine-palladiumchlorid (IV) showed an inactivation of cell-free enveloped DNA and RNA viruses in serum-free saline such as vaccinia, Pseudorabies, herpes type 1, Newcastle disease and influenza virus A/fowl plague, human influenza type A and B and vesicular stomatitis viruses, and adenovirus, a naked DNA virus, too. Picorna viruses were not inactivated, the inactivation of other viruses failed in medium with 10% serum. However the replication of enveloped viruses as checked with vaccinia and fowl plague viruses was inhibited, also when the compound was present only for 1 h after infection. Contrary to this the multiplication of adenovirus was depressed only with 90%. For the inactivation of viruses higher concentrations were necessary than for the inhibition of replication. Therefore more than one kind of mode of action have to be taken into consideration.