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When the viewers sitting around the table observe 3D images, the viewing direction is generally oblique and the viewpoints should be distributed as annular. In this paper, a tabletop integral imaging (II) three-dimensional (3D) display system based on annular point light sources is demonstrated, which can present 3D images to multiple viewers in a standard annular viewing area with oblique viewing direction. The proposed system consists of annular point light sources, a Fresnel lens, a lens array, a two-dimensional (2D) display panel, and a diffuser screen. Each point light source illuminates the Fresnel lens to form parallel light and then illuminates the lens array and the display panel. A viewing sub-area is generated at the position of the diffuser screen, in which the 3D images can be viewed. Multiple viewing sub-areas are created in a way of time-division multiplexing to form a 360° annular viewing area. Compared with the previous tabletop 3D display, the viewing area can be concentrated at an oblique angle near the tabletop. The experimental results demonstrate the feasibility of the tabletop II 3D display system.

We propose self-adaptive finite element methods with error control for solving elliptic and electromagnetic problems with discontinuous coefficients. The meshes in the methods do not need to fit the interfaces. New error indicators are introduced to control the error due to non-body-fitted meshes. Flexible h-adaptive strategies are developed, which can be systematically extended to a large class of interface problems. Extensive numerical experiments are performed to support the theoretical results and to show the competitive behavior of the adaptive algorithm even for interfaces involving corner or tip singularities.

A multigrid solver for the steady incompressible Navier-Stokes equations on a curvilinear grid is constructed. The Cartesian velocity components are used in the discretization of the momentum equations. A staggered, geometrically symmetric distribution of velocity components is adopted which eliminates spurious pressure oscillations and facilitates the transformation between Cartesian and co-or contravariant velocity components. The SCGS (symmetrical collective Gauss-Seidel) relaxation scheme proposed by Vanka on a Cartesian grid is extended to this case to serve as the smoothing procedure of the multigrid solver, in both "box" and "box-line" versions. Due to the symmetric distribution of velocity components of this scheme, the convergence rate and numerical accuracy are not affected by grid orientation, in contrast to a scheme proposed in the literature in which difficulties arise when the grid lines turn 90° from the Cartesian coordinates. Some preliminary numerical experiences with this scheme are presented.