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Skin effect that all eigenmodes within a frequency range become edge states is dictated by the topological properties of complex eigenvalues unique in non-Hermitian systems. The prevailing attempts to realize such a fascinating effect are confined to either one-dimensional or nonreciprocal systems exhibiting asymmetric couplings. Here, inspired by a recent model Hamiltonian theory, we propose a realistic reciprocal two-dimensional (2D) photonic crystal (PhC) system that shows the desired skin effect. Specifically, we establish a routine for designing such non-Hermitian systems via revealing the inherent connections between the nontrivial eigenvalue topology of order-2 exceptional points (EPs) and the skin effects. Guided by the proposed strategy, we successfully design a 2D PhC that possesses the EPs with nonzero eigenvalue winding numbers. The spectral area along a specific wavevector direction is then formed by leveraging the symmetry of the macroscopic geometry and the unit cell. The projected-band-structure calculations are performed to demonstrate that the desired skin effect exists at the specific crystalline interfaces. We finally employ time-domain simulations to vividly illustrate this phenomenon by exciting a pulse at the center of a finite-sized PhC. Our results form a solid basis for further experimental confirmations and applications of the skin effect. [ABSTRACT FROM AUTHOR]

Rapid solidification occurs under large driving force of transformation from the metastable undercooled liquid phase to the stable crystalline state. Using a formalism of extended irreversible thermodynamics, a phase-field model of rapid solidification in binary systems is derived. An entropy approach together with a grand potential density of a binary system is used to obtain the main governing equations of the model. Special attention is paid to equations of a rapidly solidifying binary system which are accompanied by essential deviations from local equilibrium in the transport of the conservative variables (such as inner energy and mass) and in the dynamics of non-conservative variables (such as phase field). The obtained equations are analyzed and compared with recent models and outcomes based on the grand potential approach to solidification. [ABSTRACT FROM AUTHOR]

The structural reorganization of polyoxymethylene powders during sintering has been investigated through a detailed analysis of the SAXS data in order to determine the origin of the mechanical property improvement with regard to the compression-moulded counterpart. Two approaches afford a quantitative evaluation of the structural parameter evolutions. On one hand, the correlation and interface distribution functions were calculated for the samples submitted to various thermo-mechanical treatments. On the other hand, the Hosemann's paracrystalline model modified with Reinhold distributions of the crystal and amorphous phase thicknesses was used to evaluate the disorder in the lamella stacking. Both approaches suggest that a more perfect and regular crystalline structure with thicker and wider crystals develops in the sintered samples as compared with the parent powders and the material crystallized from the melt. Theses morphological modifications are discussed in relation to the very high stiffness and brittleness of the sintered materials. Two possible mechanisms of coalescence of the powder grains via the crystalline phase are proposed to account for these specific mechanical properties of the sintered materials. [ABSTRACT FROM AUTHOR]

The nature and the extent of reactive crystalline surfaces for colloidal particles is an essential factor for understanding of reactions at the solid-liquid interfaces. The measurement of this specific surface area for colloidal mineral particles is usually obtained from gas-adsorption isotherms. This measurement, based on adsorbate-adsorbent interactions, yields overall weight-averaged values that fail to display the distribution of geometrical specific surface areas of individual particles. The present work proposes to use three dimensional atomic force microscopy (AFM) images to characterize the distribution of geometrical features of hexagonal plate-like gibbsite [Al(OH)3] particles without microporosity. This sub-micrometer approach, which requires minute quantities of solids (picograms), demonstrates the broad distribution of specific surface areas (lateral, basal, and total) determined for each individual particle in our sample. The resulting weight-averaged specific surface area values of basal and lateral surfaces, calculated from this distribution, agree with values measured by Kr-adsorption isotherms. The lateral specific surface area values thus obtained confirm the estimates given by and are correlated with the infrared spectrum analysis proposed in our previous papers. Moreover, these results reveal the importance of the smallest particles in the overall distribution, whereas the weight-averaged value is monitored by high-mass particles that are few in number. This kind of specific surface area heterogeneity must be taken into account in describing the reactivity of anisotropic shaped mineral particles. [ABSTRACT FROM AUTHOR]

The article presents a study addressing the structural changes in a synthetic zircon from the irradiation with heavy ions. Study shows that the crystalline zircon has hosted underneath the surficial, amorphized, layer and is expected to deviate from the un-irradiated exemplar. It is noted that experimentation on irradiation have been an excellent means to scrutinize its effects in natural minerals.