A global shallow-water model on an icosahedral-hexagonal grid by amulti-moment constrained finite-volume scheme

A third-order global shallow-water model was developed on an icosahedral-hexagonal grid with the application of the multi-moment constrained finite-volume (MCV) method. Using the hexagonal grid, the sphere is divided into quasi-uniform elements and free of polar problems. The MCV model defines seven degrees of freedom (DOFs) as the prognostic variables which are the point values at the six vertices and the centre for each hexagonal element to construct a third-order scheme. The time evolution equations to update the DOFs are derived through the constraint conditions on different moments, i.e. the point value and the volume-integrated average (VIA) moments. Rigorous conservation is guaranteed by the constraint on the VIA through a flux form. The MCV formulation is very simple and easy to implement. We evaluated the model with benchmark tests, and the competitive results reveal the proposed model to be an accurate and practical framework for developing general circulation models

High-quality-factor EH modes in microcylinder resonators predicted by 3D FDTD simulation

The mode characteristis of a microcylinders with center layer thickness 0.2 mu m and radius 1 mu m are investigated by the three-dimensional (31)) finite-difference time-domain (FDTD) technique and the Pade approximation. The mode quality factor (Q-factor) of the EH71 mode obtained by 3D FDTD increase with the increase of the refractive index of the cladding layer n(2) as n(2) smaller than 3.17, and can be as large as 2.4 x 10(4) as the vertical refractive index distribution is 3.17/3.4/3.17, which is much larger than that of the HE71 mode with the same vertical refractive index distribution