Diffraction engineering Anderson localization of light in nonlinear waveguide array with Kerr and two photon absorption effects

Role of two-photon absorption (TPA) effect on light propagation in one-dimensional nonlinear waveguide array (NWA) is studied numerically with solving nonlinear Schrodinger equation. Our investigation includes unperturbed, diagonally and off-diagonally disordered NWA with inclusion of Kerr and TPA and the results are compared with each other. The simulations show that the increase of incident wave amplitude to NWA intensifies TPA and Kerr effects and these nonlinear optical effects, dramatically affect the output intensity profile and loss. Variations of intensity distribution in periodic NWA is about two and three times higher than in off-diagonal and diagonal disordered NWA, respectively. It means that localization of light in periodic NWA is more tunable than disordered lattices. These variations of intensity distribution under nonlinear optical effects enable us to propose and design a reconfigurable localization and diffraction-engineered discrete soliton.     

Measuring and modelling the reflectance spectra of male Swinhoe's pheasant feather barbules

A range of iridescent colour appearances are presented by male Swinhoe''s pheasants'' (Lophura swinhoii) mantle feathers. Two distinct regions of the open pennaceous portion of its feathers display particularly conspicuous angle-dependent reflection. A bright blue band appears in one region at normal incidence that spatially shifts to another at higher illumination angles. The two-dimensional photonic crystal-like nanostructures inside the barbules of these two regions are similar. However, this study found that the spatial variation in their colour appearance results from a continuously changing orientation of barbules with respect to the alignment of their associated barb. A multi-layered rigorous coupled-wave analysis approach was used to model the reflections from the identified intra-barbule structures. Well-matched simulated and measured reflectance spectra, at both normal and oblique incidence, support our elucidation of the origin of the bird''s distinctive feather colour appearance.     

Estimates of the errors when determining the direction and localization of the magnetic-field source of a dipole model

Stationary methods for the direction finding and localization of a magnetic-field source of a dipole model in real time are considered. For each method, an analytical estimate is made of the root mean square deviation of the measurement errors. The estimates are made using computer modeling of the errors. The limiting ranges when the equipment contains flux-gate magnetometers and gradiometers are determined. The methods are compared with respect to stability, range, and accuracy and the best method is chosen. __________ Translated from Izmeritel’naya Tekhnika, No. 5, pp. 30–35, May, 2008.     

Modelling macroscopic imperfections for the prediction of flow localization and fracture

Ductile materials subjected to plastic deformation experience the different stages of void nucleation, growth and coalescence that eventually lead to ductile fracture. Several models have been proposed to assess the influence of this damage on flow localization and fracture. In general, the plastic behaviour is represented by a constitutive model for porous or damaged materials. It is typical to introduce a material imperfection, with porosity higher than average, which evolves up to localization and fracture. However, the void volume fraction in the imperfection is chosen more or less arbitrarily. In the present work, a model that evaluates this void volume fraction more rigorously is developed. The forming limit diagram (FLD) for a dual phase‐steel is calculated using the damage‐based imperfection calculation and validated with experimental results. The effect of void shape on the imperfection porosity level and limit strains in sheet forming is also assessed with the present method.     

Mixed nonlinear localization strategy for the buckling and post-buckling analyses of structures: parameter optimization and path following implementation

In previous work, the nonlinear localization was first presented and studied in the case of large displacements but only for globally stable structural responses. In this paper, the influence of the local error criterion on the performance of the strategy is investigated in structures exhibiting more complex behaviour, such as snap-through and snap-back. Second, a path following method is implemented in the domain decomposition framework of the strategy in order to track the solution around a critical point (snap-through and snap-back).