Voxel representation of solid object is a well known model that is widely used in CAD, robots, computer graphics, and medical image processing. Efficient algorithms for the tracing in voxel model are of great importance. A fast hardware oriented voxel tracing algorithm (called LCDDA) is proposed and implemented. All the voxels pierced by a given ray are generated incrementaly. To meve from a voxel to the next one only three fixed point additions and comparisons, which can be done using 3 parallel pipelines, and a ROM access are required. It takes 0.2 microseconds to do this under 5 MHz clock on a personal computer, which is 103 times faster than Fujimoto's and 1339 times than Glassner's algorithm on a workstation. As an application of this, time consuming ray tracing process is performed by this hardware implemented algorithm on a personal computer. Also, an active intersection table (AIT) is introduced to avoid multiple intersection of a ray and the same object. The high speed of these methods have been proved by experimental results.

Polyvinyl alcohol gel (PVA gel) has been applied in various fields as a biomedical material in Japan since the mechanical and the electrical characteristics are very similar to the human body. In this paper, the electrical characteristics of the electrode coated with PVA gel containing saline solution are described. The electrode has been applied to a stimulation electrode in an extracochlear prosthesis. It is expected that the coated electrode can stick to the round window membrane without scarring it. From the experimental results, is was found that the electrical impedance of a stimulation electrode coated with PVA gel exhibited good stability and the effective double-layer capacitance of the coated electrode was less dependent on the current than the capacitance of the Pt-Ir electrode. The electrical characteristics of the PVA electrode were proved to be very stable for long term use in-vivo. The coated electrode was ascertained to be able stimulate reliably the auditory nerves of a guinea pig.

In this note it is shown that it is possible to save time solving the firing squad synchronization problem in cellular automata with busses which work in a very restricted manner. Despite of the use of rather obvious procedures it will be proved--also by quite simple considerations--that the solutions are time optimal (in the order of magnitude). The main goal of this paper is to demonstrate how fairly small changes of the structure of cellular automata may influence their time behaviour.