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21.
Ilda Abe Rafael E. de Ges Jos L. Fabris Hypolito J. Kalinowski Mrcia Müller Meire C. Fugihara Rosane Falate Barbara W. Diesel Ricardo C. Kamikawachi Carmen L. Barbosa 《Optics and Lasers in Engineering》2003,39(5-6):537-548
In this work, we report production and modelling of both Bragg gratings and rocking filters in high birefringence fibre optics. Bragg gratings are produced by UV (257.0 nm) external interferometric exposition of a frequency-doubled Ar+ ion laser, whereas for rocking filters formation the visible Ar+ ion laser lines in 488.0 and 514.5 nm are used in an internal method. The spectral characteristics due to the birefringence properties are studied through numerical methods and experimental techniques. The spectral responsivity of the structures under temperature changes and stress application is presented. 相似文献
22.
A noncooperative game governed by a distributed-parameter predator-prey system is considered, assuming that two players control
initial conditions for predator and prey, respectively. Existence of a Nash equilibrium is shown under the condition that
the desired population profiles and the environmental carrying capacity for the prey are sufficiently small. A conceptual
approximation algorithm is proposed and analyzed. Finally, numerical simulations are performed, too. 相似文献
23.
José F. Cariñena Manuel F. Rañada 《Journal of Mathematical Analysis and Applications》2007,332(2):975-988
Given a smooth vector field Γ and assuming the knowledge of an infinitesimal symmetry X, Hojman [S. Hojman, The construction of a Poisson structure out of a symmetry and a conservation law of a dynamical system, J. Phys. A Math. Gen. 29 (1996) 667-674] proposed a method for finding both a Poisson tensor and a function H such that Γ is the corresponding Hamiltonian system. In this paper, we approach the problem from geometrical point of view. The geometrization leads to the clarification of several concepts and methods used in Hojman's paper. In particular, the relationship between the nonstandard Hamiltonian structure proposed by Hojman and the degenerate quasi-Hamiltonian structures introduced by Crampin and Sarlet [M. Crampin, W. Sarlet, Bi-quasi-Hamiltonian systems, J. Math. Phys. 43 (2002) 2505-2517] is unveiled in this paper. We also provide some applications of our construction. 相似文献
24.
Optimal explicit Runge–Kutta methods consider more stages in order to include a particular spectrum in their stability domain
and thus reduce time-step restrictions. This idea, so far used mostly for real-line spectra, is generalized to more general
spectra in the form of a thin region. In thin regions the eigenvalues may extend away from the real axis into the imaginary
plane. We give a direct characterization of optimal stability polynomials containing a maximal thin region and calculate these
polynomials for various cases. Semi-discretizations of hyperbolic–parabolic equations are a relevant application which exhibit
a thin region spectrum. As a model, linear, scalar advection–diffusion is investigated. The second-order-stabilized explicit
Runge–Kutta methods derived from the stability polynomials are applied to advection–diffusion and compressible, viscous fluid
dynamics in numerical experiments. Due to the stabilization the time step can be controlled solely from the hyperbolic CFL
condition even in the presence of viscous fluxes. 相似文献
25.
In this paper a cubic lattice L(S) is endowed with a symmetric implication structure and it is proved that L(S) \ {0} is a power of the three-element simple symmetric implication algebra. The Metropolis–Rota’s symmetries are obtained as partial terms in the language of symmetric implication algebras. 相似文献
26.
A fully coupled formulation combining reactive transport and an existing thermo-hydro-mechanical (THM) code is presented.
Special attention has been given to phenomena likely to be encountered in clay barriers used as part of containment systems
of nuclear waste. The types of processes considered include hydrolysis, complex formation, oxidation/reduction reactions,
acid/base reactions, precipitation/dissolution of minerals and cation exchange. Both kinetically-controlled and equilibrium-controlled
reactions have been incorporated. The total analytical concentrations (including precipitated minerals) are adopted as basic
transport variables and chemical equilibrium is achieved by minimizing Gibbs Free Energy. The formulation has been incorporated
in a general purpose computer code capable of performing numerical analysis of engineering problems. A validation exercise
concerning a laboratory experiment involving the heating and hydration of an expansive compacted clay is described. 相似文献
27.
Automatic detection and identification of shocks in Gaussian state‐space models: a Bayesian approach
An automatic monitoring and intervention algorithm that permits the supervision of very general aspects in an univariate linear Gaussian state–space model is proposed. The algorithm makes use of a model comparison and selection approach within a Bayesian framework. In addition, this algorithm incorporates the possibility of eliminating earlier interventions when subsequent evidence against them comes to light. Finally, the procedure is illustrated with two empirical examples taken from the literature. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
28.
L. G. Marcassa V. A. Nascimento L. L. Caliri A. Caires D. V. Magalhães V. S. Bagnato 《Laser Physics》2006,16(12):1722-1725
In this paper, we report observation of an enhancement of the ground state molecule Rb2 formation in a Rb magneto-optical trap due to a photoassociation laser. Such an enhancement effect is due to flux enhancement of atomic pairs at short internuclear distances. Our experimental observations consist in the measurement of the molecular formation rate constant due to a probe laser as a function of the trap laser intensity. The results are compared with a simple semi-classical model, showing good agreement. We conclude that the production of cold Rb2 may be enhanced using appropriate laser parameters; this may be useful for future experiments involving production and trapping of ultracold ground state molecules. 相似文献
29.
Magnetization measurements in the (Dy
x
Y1−x
)Fe2 intermetallic compounds show evidence of blocking of domain wall motion. This effect is a function of concentrationx. The direction of magnetization is also dependent on the Dy concentration. We have used the Mossbauer spectroscopy of57Fe to verify the direction of magnetization in the series as a function ofx and temperature. The results show that this change in easy direction occurs at higher temperatures than those where the blocking
is detected through DC magnetization measurements.
supported by RHAE/SCT. 相似文献
30.
J.C. Góes S.D. FigueiróJ.A.C. de Paiva I.F. de VasconcelosA.S.B. Sombra 《Journal of Physics and Chemistry of Solids》2002,63(3):465-470
In this paper, we report results of a study of the physicochemical, dielectric and piezoelectric properties of anionic and native collagen films, considering the development of new biomaterials which have potential applications in coating of cardiovascular prostheses, support for cellular growth and in systems for controlled drug delivery. The piezoelectric strain tensor element d14, the elastic constant s55, and the dielectric permittivity ?11 were measured for the anionic and native collagen films. It was observed that the collagen samples submitted to the alkaline treatment present lower thermal stability than those made from native collagen. However, the treated samples present a higher piezoelectricity compared with the native collagen. The frequency constant fL and the piezoelectric strain element d14, obtained for the alkaline-treated sample (72 h), present the highest values for the samples under study (444.1 kHz m and 0.079 pC/N, respectively). We believe that the alkaline treatment led to an increase of the organization of the microscopic fiber structure of the sample, which could result in an increase of the piezoelectricity. 相似文献