Propagation of waves in high Brillouin zones: Chaotic branched flow and stable superwires

We report unexpected classical and quantum dynamics of a wave propagating in a periodic potential in high Brillouin zones. Branched flow appears at wavelengths shorter than the typical length scale of the ordered periodic structure and for energies above the potential barrier. The strongest branches remain stable indefinitely and may create linear dynamical channels, wherein waves are not confined directly by potential walls as electrons in ordinary wires but rather, indirectly and more subtly by dynamical stability. We term these superwires since they are associated with a superlattice.

On the propagation of waves in the atmosphere

The leading-order equations governing the unsteady dynamics of large-scale atmospheric motions are derived, via a systematic asymptotic approach based on the thin-shell approximation applied to the ellipsoidal model of the Earth’s geoid. We present some solutions of this single set of equations that capture properties of specific atmospheric flows, using field data to choose models for the heat sources that drive the motion. In particular, we describe standing-waves solutions, waves propagating towards the Equator, equatorially trapped waves and we discuss the African Easterly Jet/Waves. This work aims to show the benefits of a systematic analysis based on the governing equations of fluid dynamics.

Reflection-Refraction Coefficients and Energy Ratios in Couple Stress Micropolar Thermoviscous Elastic Solid

The reflection and refraction phenomenon of propagation of waves in couple stress micropolar thermoviscous elastic solid media with independent viscoelastic and micropolar properties have been studied. The structure of the model has been taken such that the plane interface is divides the given media into two half spaces in perfect contact. Here, we find that there are five waves, one of them is propagating independently while others are set of two coupled waves travelling with different speeds. Energy ratios, reflection and refraction coefficients relative to numerous reflected and refracted waves have been investigated when set of two coupled longitudinal waves and set of two coupled transverse waves strike at the interface through the solid medium. The inequality of energy ratios, refraction coefficients and reflection coefficients are evaluated numerically and presented graphically under three theories of thermoelasticity, namely, Green-Lindsay theory (GL), Lord-Shulman theory (LS), Coupled theory (CT) versus angular frequency and angle of incidence.

Electrohydraulic Forming of Low Volume and Prototype Parts: Process Design and Practical Examples

Electro-Hydraulic Forming (EHF) is a high rate sheet metal forming process based on the electrical discharge of high voltage capacitors in a water-filled chamber. During the discharge, the pulsed pressure wave propagates from the electrodes and forms a sheet metal blank into a die. The performed literature review shows that this technology is suitable for forming parts of a broad range of dimensions and complex shapes. One of the barriers for broader implementation of this technology is the complexity of a full-scale simulation of EHF which includes the simulation of an expanding plasma channel, the propagation of waves in a fluid filled chamber, and the high-rate forming of a blank in contact with a rigid die. The objective of the presented paper is to establish methods of designing the EHF processes using simplified methods. The paper describes a numerical approach on how to define the shape of preforming pockets. The concept includes imposing principal strains from the formed blank into the initial mesh of the flat blank. The principal strains are applied with the opposite sign creating compression in the flat blank. The corresponding principal stresses in the blank are calculated based upon Hooke’s law. The blank is then virtually placed between two rigid plates. One of the plates has windows into which the material is getting bulged driven by the in-plane compressive stresses. The prediction of the shape of the bulged sheet provides the information on the shape of the preforming pockets. It is experimentally demonstrated that using these approaches, EHF forming is feasible for forming of a fragment of a decklid panel and a deep panel with complex curvature.

Improving Predictions of the 3D Dynamic Model of the Plasmasphere

In this perspective paper, we review and discuss different ways that can be used to improve the predictions of the models of the plasmaspheric region. The density of the background cold plasma and the plasmapause position are very important to determine the formation and propagation of waves and interactions with the other regions of the magnetosphere. Improvement of predictions includes refinement of the forecast of the geomagnetic indices that influence the density and the temperature of the particles in some models. Progress is also necessary for the understanding of the physical processes that affect the position of the plasmapause and its thickness since this boundary is not always very sharp, especially during low geomagnetic activity. These processes include the refilling after geomagnetic storms and substorms, the links with the ionosphere, and the expanding plasmaspheric wind during prolonged quiet periods. Using observations from in situ satellites like Van Allen Probes (EMFISIS and HOPE instruments), empirical relations can be determined to improve the dependence of the density and the temperature as a function of the radial distance, the latitude, and the magnetic local time, inside and outside the plasmasphere. This will be the first step for the improvement of our 3D dynamic SWIFF plasmaspheric model (SPM).

New and more fractional soliton solutions related to generalized Davey–Stewartson equation using oblique wave transformation

The generalized fractional Davey–Stewartson (DSS) equation with fractional temporal derivative, which is used to explore the trends of wave propagation in water of finite depth under the effects of gravity force and surface tension, is considered in this paper. The paper addresses the full nonlinearity of the proposed model. To extract the oblique soliton solutions of the generalized fractional DSS (FDSS) equation is the dominant feature of this research. The conformable fractional derivative is used for fractional temporal derivative and oblique wave transformation is used for converting the proposed model into ordinary differential equation. Two state-of-the-art integration schemes, modified auxiliary equation (MAE) and generalized projective Riccati equations (GPREs) method have been employed for obtaining the desired oblique soliton solutions. The proposed methods successfully attain different structures of explicit solutions such as bright, dark, singular, and periodic solitary wave solutions. The occurrence of these results ensured by the limitations utilized is also exceptionally promising to additionally investigate the propagation of waves of finite depth. The latest found solutions with their existence criteria are considered. The 2D and 3D portraits are also shown for some of the reported solutions. From the graphical representations, it have been illustrated that the descriptions of waves are changed along with the change in fractional and obliqueness parameters.