Optical vortices in linear and nonlinear media may exhibit propagation dynamics similar to hydrodynamic vortex phenomena. Analytical and numerical methods are used to describe and investigate the interaction between vortices and the background field. We demonstrate that optical vortices that have quasi-point core functions, such as optical vortex solitons, may orbit one another at rates that ar...

Current stratospheric chemical model simulations underestimate substantially the large ozone loss rates that are derived for the Arctic from ozone sondes for January of some years. Until now, no explanation for this discrepancy has been found. Here, we examine the influence of intrusions of mid-latitude air into the polar vortex on these ozone loss estimates. This study focuses on the winter 19...

Iris image quality assessment is an important part of iris recognition system because the qualities of iris images would largely influence the recognition results. In this paper, we analyze and compare several representative quality assessment methods, and then propose an effective method based on Laplacian of Gaussian operator for iris image assessment. Through computer simulations of several ...

In this research we have implemented the Random Vortex Method to calculate velocity fields of fluids inside open cavities in both turbulent and laminar flows. the Random Vortex Method is a CFD method (in both turbulent and laminar fields) which needs the Schwarz-Christoffel transformation formula to map the physical geometry into the upper half plane. In some complex geometries like the flow in...

BACKGROUND Laminography is a tomographic technique that allows three-dimensional imaging of flat and elongated objects that stretch beyond the extent of a reconstruction volume. Laminography images can be reconstructed using iterative algorithms based on the Kaczmarz method. OBJECTIVE This study aims to develop and demonstrate a new reconstruction algorithm that may provide superior image rec...

This paper presents an integrated approach for tracking hands, faces and specific facial features (eyes, nose, and mouth) in image sequences. For hand and face tracking, we employ a state-of-the-art blob tracker which is specifically trained to track skin-colored regions. The skin-color tracker is extended by incorporating an incremental probabilistic classifier, which is used to maintain and c...

ii Abstract This report documents the modifications made to the frame processing module of the NUbot vision system for improvement in robot soccer competition and particularly in the variable lighting challenge. The frame processing module involves the classification of images with respect to a look up table (LUT), a new system of secondary colour classification for blue robots that uses edge d...

One of the solutions of the Helmholtz equation is the vortex beams. In the recent decades, production and applications of these types of beams have found serious attentions. Determination of the vortex beam topological charge and its sign are very important issues. Odd number of reflections of the vortex beam changes its vorticity. In this paper, we have used a q-plate to generate a vortex beam...

A new desingularization is introduced for the vortex method. The idea is to subtract off the most singular part in the discrete approximation to the velocity integral and replace it by the velocity of a vortex patch of constant vorticity, which can be evaluated explicitly. Stability and convergence of the method are obtained in the maximum norm. Preliminary numerical results are presented.

Superluminal motion has been interpreted as relativistically moving out flow. The increasing observations of such sources provide chance to investigate their mechanism in detail. This paper proposes that superluminal motion may be jet precession induced blob motion. This model can interpret a number of observational phenomena which are not well understood under the scenario of bulk motion, such...