Wave propagation through curved bends in integrated optical waveguides is governed by the evanescent field and the radiation loss of the eigenmodes. Since these parameters are influenced by the refractive index of the surrounding medium, circular bends in rib waveguides have been successfully employed as chemical sensors for liquids and gases. In this paper the electromagnetic field, the refractive index and the radiation loss of the eigenmodes are precisely determined by a fully vectorial approach based on the method of lines. An axial discretization and Bessel functions of complex order are employed for the rigorous computation of the evanescent field. The intensity distributions of the first modes in a rib waveguide are presented. The influence of the rib height on the sensitivity of the modal index to the refractive index of the surrounding medium is investigated. The results are useful for the optimization of the sensor design. 相似文献
A model is developed for the hadronic interaction in the two-nucleon system above pion threshold which is based on meson, nucleon and Δ degrees of freedom and which includes full meson retardation in the exchange operators. For technical reasons, the model allows maximal one meson to be present explicitly. Thus the Hilbert space contains besides NN and NΔ also configurations consisting of two nucleons and one meson. For this reason, only two- and three-body unitarity is obeyed, and the model is suited for reactions in the two-nucleon sector, where only one pion is produced or absorbed. Starting from a realistic pure nucleonic retarded potential, which had to be renormalized because of the additional π and Δ degrees of freedom, a reasonable fit to experimental NN-scattering data could be achieved. 相似文献
In this paper, the stellar pulsation theory is reformulated following an irreversible thermodynamic approach (Lavenda, Thermodynamics of Irreversible Processes, Denver, New York, 1993). A general stability criterion and a thermodynamic Langrangian for the pulsating star problem are obtained using a variational method (Sicardi and Ferro Fontán, Phys. Lett. 113A (1958) 263; Sicardi et al., J. Math. Phys. 32 (1991) 1350). This formulation, based on the calculation of a free energy excess function, is applied to the adiabatic, non-adiabatic, radial and non-radial cases and, as a result, the already known energy principles are obtained as particular cases of the general stability criterion mentioned above. Eigenvectors and eigenvalues can be calculated in a systematic way from the thermodynamic Lagrangian obtained for the general dissipative case (being independent of the adiabatic one). This allows a better determination of periods and oscillation frequencies. 相似文献
Polarization properties of strange baryons produced in pp reactions, p + p↦p + Λ0 + K+ and p + p↦p + Σ0 + K+, near thresholds of the final states pΛ0K+ and pΣ0K+ are analysed relative to polarizations of colliding protons. The cross-sections for pp reactions are calculated within the
effective Lagrangian approach accounting for strong pp rescattering in the initial state of colliding protons with a dominant
contribution of the one-pion exchange and strong final-state interaction of daughter hadrons (Eur. Phys. J. A 9, 425 (2000)).
Received: 22 October 2001 / Accepted: 14 November 2001 相似文献
Summary: The miscibility of a thermoplastic modifier with the precursors of an epoxy/diamine thermoset without chemical reaction was studied thermodynamically. The experimental cloud point curve showed a UCST behavior. A model based on the Flory‐Huggins lattice theory and on the Koningsveld approach was used for the thermodynamic analysis, in which the polydispersity of components was taken into account and the interaction parameter was considered depending on the temperature and composition. A phase diagram for the unreacted system was obtained. Calculations of species distributions in both separated phases were realized for different compositions of the modifier. Finally, the miscibility of our system was compared with that of the same system without diamine, obtaining a greater miscibility in the system with diamine.
Phase diagram for the system formed by the precursors of an epoxy thermoset without chemical reaction modified with different amounts of polystyrene. 相似文献
A variable separation approach is proposed and extended to the
(1+1)-dimensional physics system. The variable separation solution of
(1+1)-dimensional Ito system is obtained. Some special types of solutions
such as non-propagating solitary wave solution, propagating solitary wave
solution and looped soliton solution are found by selecting the arbitrary
function appropriately. 相似文献
In this paper,the variable separation approach is used to obtain localized coherent structures of the (2 1)-dimensional generalized Davey-Stewarson equations:iqt 1/2(qxx=qyy) (R S)q=0,Rx=-σ/2|q|y^2,Sy=-σ/2|q|2/x.Applying a special Baecklund transformation and introducing arbitrary functions of the seed solutions.and abundance of the localized structures of this model is derived,By selceting the arbitrary functions appropriately,some special types of localized excitations such as dromions,dromion lattice,breathers,and instantons are constructed. 相似文献
The Hamilton-Jacobi method of quantizing singular systems is discussed.The equations of motion are obtained as total differential equations in many variables.It is shown that if the system is integrable,one can obtain the canonical phase space coordinates and set of canonical Hamilton-Jacobi partial differential equations without any need to introduce unphysical auxiliary fields.As an example we quantize the O(2) nonlinear sigma model using two different approaches:the functional Schrodinger method to obtain the wave functionals for the ground and the exited state and then we quantize the same model using the canonical path integral quantization as an integration over the canonical phase-space coordinates. 相似文献