Symmetric Three-layer Structure Research Articles

Nonlinear Surface Waves in a Symmetric Three-Layer Structure That Is Composed of Optical Media with Different Formation Mechanisms of Nonlinear Response

We consider the propagation of surface TM waves in a three-layer structure the inner layer of which is formed by a plate of a crystal with a Kerr type focusing nonlinearity, while its outer layers are uniaxial photorefractive crystals with the diffusion nonlinearity formation mechanisms. Nonlinear surface waves that differ in the character of their decay can propagate along the interfaces between the layers. The amplitudes of waves of one type decrease without oscillations with increasing distance from the interface as the waves propagate into the depth of the outer layers of the photorefractive crystals, while the amplitudes of waves of the other type decrease with oscillations. The wave profiles can be either symmetric or antisymmetric with respect to the center of the three-layer structure. The waves with the symmetric profile distribution, the amplitudes of which decrease into the depth of the photorefractive crystals either with or without oscillations, can be of two types, while those with the antisymmetric distribution can be only of one type. For the long-wavelength propagation regime of surface waves, explicit analytical dependences of the propagation constant on the characteristics of the layered structure are found and the conditions for their existence are determined.

Tunneling of Microwave Radiation through Three-Layer Structures Containing Ferrite Layer

Tunneling of microwave radiation through a symmetric three-layer structure in which the central ferrite layer is interfaced with two layers of a material with negative permittivity is considered. Conditions for perfect tunneling (i.e., transmission with zero reflection) are analyzed for normal incidence. It is shown that the transmittance of the structure can be controlled using external magnetic field that provides magnetization of the ferrite layer. A broad transmission band with a width of several gigahertzes in which almost perfect tunneling is implemented can exist in the frequency range corresponding to the negative effective permeability of the ferrite material.

Туннелирование СВЧ излучения через трехслойные структуры, содержащие ферритовый слой

AbstractTunneling of microwave radiation through a symmetric three-layer structure in which the central ferrite layer is interfaced with two layers of a material with negative permittivity is considered. Conditions for perfect tunneling (i.e., transmission with zero reflection) are analyzed for normal incidence. It is shown that the transmittance of the structure can be controlled using external magnetic field that provides magnetization of the ferrite layer. A broad transmission band with a width of several gigahertzes in which almost perfect tunneling is implemented can exist in the frequency range corresponding to the negative effective permeability of the ferrite material.

An anatomical hypothesis: a "concentric-structured model" for the theoretical understanding of the surgical anatomy in the upper mediastinum required for esophagectomy with radical mediastinal lymph node dissection.

Understanding the surgical anatomy is the key to reducing surgical invasiveness especially in the upper mediastinal dissection for esophageal cancer, which is supposed to have a significant impact on curability and morbidity. However, there is no theoretical recognition regarding the surgical anatomy required for esophagectomy, although the surgical anatomy in abdominal digestive surgery has been developed on the basis of embryological findings of intestinal rotation and fusion fascia. Therefore, we developed a hypothesis of a 'concentric-structured model' of the surgical anatomy in the upper mediastinum based on human embryonic development. This model was characterized by three factors: (1) a concentric and symmetric three-layer structure, (2) bilateral vascular distribution, and (3) an 'inter-layer potential space' composed of loose connective tissue. The concentric three-layer structure consists of the 'visceral layer', the 'vascular layer', and the 'parietal layer': the visceral layer containing the esophagus, trachea, and recurrent laryngeal nerves as the central core, the vascular layer of major blood vessels surrounding the visceral core to maintain the circulation, and the parietal layer as the outer frame of the body. The bilateral vascular distribution consists of the inferior thyroid arteries and bronchial arteries originating from the bilateral dorsal aortae in an embryo. This bilateral vascular distribution may be related to the formation of the proper mesentery of the esophagus and frequent lymph node metastasis observed in the visceral layer around recurrent laryngeal nerves. The three concentric layers are bordered by loose connective tissue called the 'inter-layer potential space'. This inter-layer potential space is the fundamental factor of our concentric-structured model as the appropriate surgical plane of dissection. The peripheral blood vessels, nerves, and lymphatics transition between each layer, thereby penetrating this loose connective tissue forming the inter-layer potential space. Recurrent laryngeal nerves also transition from the vascular layer after branching off from the vagal nerves and then ascend consistently in the visceral layer. We investigated the validity of this concentric-structured model, confirming the intraoperative images and the surgical outcomes of thoracoscopic esophagectomy in a prone position (TSEP) before and after the introduction of this hypothetical anatomy model. A total of 226 patients with esophageal cancer underwent TSEP from January 2015 to December 2016. After the introduction of this model, the surgical outcomes in 105 patients clearly improved for the operation time of the thoracoscopic procedure (160 min vs. 182 min, P=0.01) and the incidence of recurrent laryngeal nerve palsy (19.0% vs. 36.4%, P=0.004). Moreover, we were able to identify the concentric and symmetric layer structure through surgical dissection along the inter-layer potential space between the visceral and vascular layers ('viscero-vascular space') in all 105 cases after introduction of the hypothetical model. The concentric-structured model based on embryonic development is clinically beneficial for achieving less-invasive esophagectomy by ensuring a theoretical understanding of the surgical anatomy in the upper mediastinum.

Mechanical performance and in vivo bioactivity of functionally graded PEEK–HA biocomposite materials

A functionally graded material (FGM) of polyetheretherketone (PEEK)–hydroxyapatite (HA) with a symmetrical three-layer structure containing 8.7, 2.6 and 8.7 vol% HA, respectively, is successfully fabricated by hot pressing and evaluated by scanning electron microscopy and tensile testing. A good bonding between the HA particles and the PEEK matrix is achieved by virtue of an in situ method in fabricating each PEEK–HA composite layer. There are no apparent microcracks and microscopic interfaces within each layer of the FGM. The symmetrical PEEK–HA FGM does not fall apart or delaminate during loading with a tensile strength of 86.2 MPa, and its fracture energy is 56.5 kJ/m2. Furthermore, in vivo bioactivity of the FGM sample is also evaluated, showing that it has sound biocompability and bioactivity. Accordingly, the FGM in the future may be a promising biomaterial to be used as replacement implant of human bone through a proper design to balance mechanical properties and bioactivity.

Nonlinear asymmetric waves induced in a symmetrical three-layer structure by the generation of excitons and biexcitons in semiconductors

A theory of asymmetric TE-polarized quasi-surface waves propagating inside a symmetrical planar three-layer structure with a linear core and nonlinear plates is developed. The nonlinearity of the plates is associated with the inclusion of the optical exciton-biexciton conversion. The dispersion laws of the propagating waves are derived and investigated.

Nonlinear waveguide modes caused by generation of excitons and biexcitons in semiconductors in a symmetrical three-layer structure

A theory of nonlinear TE-polarized waveguide modes propagating inside a symmetrical planar three-layer structure with a linear core and nonlinear coatings is developed. The coatings are assumed to be nonlinear due to the optical exciton-biexciton conversion. The dispersion laws of the propagating waves are derived and investigated.

Nonlinear surface waves in a symmetrical three-layer structure caused by the generation of excitons and biexcitons in semiconductors

A theory of nonlinear TE-polarized surface waves propagating along the flat interfaces of a symmetric flat three-layer structure with a linear core and nonlinear coatings is developed. The coatings are nonlinear due to the optical exciton-biexciton conversion. The dispersion laws of the propagating waves are found and analyzed.

Influence of different factors on the stiffness and strength of multilayer composite elements

In the paper, the bending stiffness and strength of multilayer structural elements in relation to the mechanical properties of layers and their number layout and sizes are investigated and the corresponding correlations are established. It is found that the most rational structure of a multilayer element in bending is a symmetric three-layer structure formed from two materials with the thickness of the core less than the half-thickness of the element. The values of normal stresses in the layers of a multilayer beam in bending depends on its bending stiffness and the position of layers relative to the neutral axis. The influence of the number of layers on the stiffness of the structural element and on the magnitude of normal stresses is insignificant.

Simple computations involving two-component symmetric trilayers.

The equivalent properties of a symmetric three-layer structure are derived by a nontraditional method that provides useful insights and a simplified application to some thin-film design problems. The equations derived from this method may be used to design a three-layer replacement for a single layer in an interference coating. The equations are especially helpful for cases that involve complex numbers, such as metal layers or above-critical angle propagation in dielectric layers. Several multilayer design problems are solved to demonstrate the application of this approach.

Interaction Hamiltonian between an electron and polar surface vibrations in a symmetrical three-layer structure.

The Hamiltonian of the interaction between an electron and surface vibrations for a three-layer symmetrical structure is obtained. In the limiting case of infinite outer-layer thickness, the known results by Mori and Ando are reproduced.