Phase Distribution In Space Research Articles

Shielding of Orbital Angular Momentum Waves by a Cavity With Apertures

In this article, for the first time, the shielding of orbital angular momentum (OAM) waves by a cavity with apertures is evaluated. This is particularly interesting because the distinguishing feature between the OAM modes is their phase distribution in space, and, hence, shielding effectiveness is a mode-dependent phenomenon. A perfectly electrically conducting cavity with multiple apertures and two OAM antennas, inside and outside the cavity, is investigated using a method of moments based tool. The behavior of OAM waves is analyzed by comparing the transmission between the OAM arrays for different cases, including their field patterns in front of and behind the apertures. The effects of the orientation and position of the transmitting antenna, the rotation, size, and form of the apertures and different cavities are explored. Additionally, the effect on the distance and the orientation angle of the outer antenna are studied. It is shown that the propagation of OAM waves through apertures is possible and that the resulting signal loss is similar to the loss of a plane wave or the field of a monopole. It is also shown that certain OAM waves penetrate the apertures better than others.

Phase transitions in filtration of Redlich–Kwong gases

In this paper we study a 3-dimensional filtration of real gases described by Redlich–Kwong equations of state. Thermodynamical states are considered as Legendrian (Lagrangian) submanifolds in contact (symplectic) space. Connection between singularities of their projection on the space of intensive variables and phase transitions is shown. Explicit formulae for the Dirichlet boundary problem are given and the distribution of phases in space is shown.

3D numerical modelling of the propagation of radiative intensity through a X-ray tomographied ligament

In order to explain the macroscopic radiative behaviour of an open-cell ceramic foam, knowledge of its solid phase distribution in space and the radiative contributions by this solid phase is required. The solid phase in an open-cell ceramic foam is arranged as a porous skeleton, which is itself composed of an interconnected network of ligament. Typically, ligaments being based on the assembly of grains more or less compacted, exhibit an anisotropic geometry with a concave cross section having a lateral size of one hundred microns. Therefore, ligaments are likely to emit, absorb and scatter thermal radiation. This framework explains why experimental investigations at this scale must be developed to extract accurate homogenized radiative properties regardless the shape and size of ligaments. To support this development, a 3D numerical investigation of the radiative intensity propagation through a real world ligament, beforehand scanned by X-Ray micro-tomography, is presented in this paper. The Radiative Transfer Equation (RTE), applied to the resulting meshed volume, is solved by combining Discrete Ordinate Method (DOM) and Streamline upwind Petrov-Garlekin (SUPG) numerical scheme. A particular attention is paid to propose an improved discretization procedure (spatial and angular) based on ordinate parallelization with the aim to reach fast convergence. Towards the end of this article, we present the effects played by the local radiative properties of three ceramic materials (silicon carbide, alumina and zirconia), which are often used for designing open-cell refractory ceramic foams.

Characterization of metachronal wave in beating cilia: distribution of phases in space.

We have examined phase differences between beating cilia measured in different directions on the surface. The measurements were performed on tissue cultures taken from frog palate epithelium. This experiment was based on a method developed earlier, which measures simultaneously scattered light from two different and relatively small areas. Moreover, the distance between the two small areas can be accurately defined and varied. Rotating the stage around the optical axis permits us to repat these measurements at different space angles. It was found that: a) the phase gradient is a periodic function of the angle of rotation; b) the periodicity can be described quantitatively by a cosine function; c) good agreement exists between Machemer's findings in protozoa and our results, despite the differences between the two systems and techniques used.