Investigation Of Dispersion Characteristics Research Articles

An investigation of dispersion characteristics in shallow coastal waters

Hydrodynamic dispersion has a significant impact on the mass transport of sediments and contaminants within coastal waters. In this study apparent horizontal dispersion in a tidally-dominated shallow estuary was investigated using field observations and a numerical model. A cluster of four Lagrangian drifters was released in two shallow regions inside Moreton Bay, Australia: between two small islands and in an open water area. During a 16-h tracking period, the drifters generally showed similar behaviour, initially moving with the dominant current and remaining together before spreading apart at the change of tide. Two dispersion regimes were identified, a slow dispersion during the earlier stage and a rapid dispersion during the latter stage of deployment. Such change in regime typically occurred during the succeeding ebb or flow tides, which may be attributable to residual eddies breaking down during reversal of tidal direction. In addition, a power function of the squared separation distance over the apparent dispersion coefficient produced an R2 exceeding 0.7, indicating a significant relationship between them.By applying a three-dimensional hydrodynamic model, the trajectories of artificial particles spreading in the bay were simulated, which allowed the calculation of dispersion coefficients throughout the entire bay. The study results demonstrate that the tidal effects on dispersion were dependent on the effect of tidal excursion and residual current. The tide was found to be the most dominant driver of dispersion in the bay when unobstructed by land; however, bathymetric and shoreline characteristics were also significant localised drivers of dispersion between the two islands as a result of island wake.

Dispersion Compensating Photonic Crystal Fiber with Enhanced Properties Achieved by Modified Core Geometry

A novel dispersion compensating fiber based on photonic crystal fiber has been designed and studied in terms of optimal dispersion and operating bandwidth. The investigation of dispersion characteristics with respect to change in hole diameter and pitch has been provided. Further optimization of the designed fiber has been applied to the achieved fiber’s properties in order to achieve a potentially easy-to-fabricate dispersion compensating fiber.

Investigation of Dispersion Characteristics in Coaxial Disk-Loaded Slow-Wave Structures With Both Symmetric and Asymmetric Modes

Coaxial disk-loaded waveguide has been widely used in magnetically insulated transmission line oscillators. Although the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> mode is its main mode, the asymmetric mode might be excited by a slight asymmetry of the structure, asymmetric emission of the beam, or both. Therefore, research on the asymmetric mode in coaxial disk-loaded waveguide is necessary. The general dispersion equation of the coaxial disk-loaded slow-wave structures is obtained using the field match theory for the first time. Numerical calculation is carried out based on the dispersion function. The theoretical calculated results agreed well with the simulated results of the MAFIA code and experiment.