Results 1 - 10 of 18947
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[en] This is the continuation of the series reporting MORD studies to typical problem in Chemistry and Polymer Science. In our earlier papers the MORDsup1.2 studied only in visible region. In this present investigation we extended the application of the New Dispersion Relation in IR region to determine the MORD and tested to some simple systems
[en] It is shown formally that the real and imaginary parts of the effective potential operator for scattering problems obey a dispersion relation even when the hamiltonian is not hermitian. Model calculations are used to demonstrate that the equivalent local potential also satisfies the dispersion relation when absorption is present. It is also shown that the equivalent local potential is insensitive to the bare potential used in the entrance channel. (author)
[pt]E demonstrado formalmente que as partes real e imaginaria do operador potencial efetivo para problemas de espalhamento obedecem a relacao de dispersao mesmo quando a hamiltoniana nao e hermitiana. Sao usados calculos do modelo para demonstrar que o potencial local equivalente tambem satisfaz a relacao de dispersao quando a absorsao esta presente. Demonstra-se tambem que o potencial local equivalente e insensivel ao potencial nu usado no canal de entrada. (A.C.A.S.)
[en] This work is devoted to the study of hollow-core photonic crystal fibers (HCPCF) dispersion properties. An effective scheme of HCPCF eigenmodes analysis, lying in separate dispersion diagrams calculation for the cladding and for the HCPCF itself, was proposed. General recommendations concerning selection of proper fiber parameters were given.
[en] Two different methods are commonly used in the literature to derive parametric dispersion relations, the 'oscillating reference frame' technique (Silin) and the perturbative method. It has been argued, paradoxally, that they lead to different dispersion relations. We show that they are indeed quite equivalent provided that the coupling equations be developped up to second order in the pump field. The perturbative method as used by many authors, i.e. truncated at first order in the pump, is shown to be valid for resonant decay only. For studying the excitation of 'quasimodes' one must write coupling equations containing the square of the pump amplitude
[fr]Deux methodes differentes sont couramment utilisees dans la litterature pour obtenir les relations de dispersion parametriques, la methode du 'repere oscillant' et la methode perturbative. Paradoxalement, il a ete pretendu qu'elles conduisaient a des relations de dispersion differentes. On montre qu'elles sont en realite tout a fait equivalentes si l'on developpe les equations de couplage au deuxieme ordre dans l'amplitude de la 'pompe'. La methode perturbative telle qu'elle est utilisee par de nombreux auteurs, c'est-a-dire tronquee au premier ordre dans l'amplitude de la 'pompe', se trouve etre suffisante seulement pour la decomposition parametrique resonnante. Par contre pour l'etude des 'quasimodes' on doit ecrire les equations du couplage contenant les termes proportionnels au carre de l'amplitude de la 'pompe'
[en] An FFAG synchrotron differs from a synchrocyclotron by having a large radial field gradient; this large gradient greatly reduces the magnet volume while maintaining stable orbits for all energies, but it does induce substantial nonlinearities. A decade ago, the author proposed a dispersion-free insertion for an FFAG that provides regions of small volume for rf cavities, strippers, and injection and extraction elements, similar to a normal synchrotron. Here the author exploits this insertion to provide compensation of the lower order nonlinear driving fields, thereby greatly increasing the dynamic aperture as compared to an FFAG without insertions. The correction fields may be programmed to track the momentum or may be static, providing full compensation at the injection energy
[en] Space and astrophysical Alfven waves usually excist in a plasma containing thermal and nonthermal particles, and generally the thermal electron and ions have unequal number densities. Nevertheless, the linear properties of the waves are invariably assumed to be determined by a chargeneutral thermal plasma in the absence of the nonthermal particles, while the nonthermal particles cause growth or additional damping superposed onto the background model. Here, both analytic plasma theory and numerical solutions of the dispersion equation, unequal thermal electron and ion number densities (due to the presence of the nonthermal particles) may cause fundamental low wavenumber modifications to the Alfven modes, including the creation of a new resonance and severely modified dispersion. Thes results are found for both cold and warm plasmas. Previous work on Alfven waves should be re-evaluated in view of these results. (author). 6 refs.; 2 figs