Takao Miyashita

Method of Evaluating Tilt Domain in a Twisted Nematic Cell

The conditions for the formation of tilt domains in a twisted nematic cell have been studied in relation to the rubbing direction, the distribution of electric field at the electrode edges and the pretilt angle of liquid crystal molecules. The method of evaluating tilt domains in a twisted nematic cell using an electrode consisting of several segments with various angles to the rubbing directions was devised and some experiments were carried out. It is estimated that tilt domains are never induced when the pretilt angle is more than 1.2 degrees in a liquid crystal cell in the case where the angle between the upper surface rubbing direction and the lower surface rubbing direction, which is called the twisted angle, is 80 degrees.

Tree-deterioration mechanism of water immersed polyethylene coated wire and its improvement of the insulation life

In recent years, submersible pumping units have been winning greater recognition for their economy and their good performance properties. As a result, they have found wide use in the manufacturing industries. One insulating system of submersible motors is the type in which insulating wires are wound for the stator, and wires coated with polyethylene are often used as the insulating wires in this case.

New Evaluation Method of Dielectric Materials Using a Microwave Technique

A new nondestructive method of evaluating changes in characteristics or detecting internal defects in insulation materials with microwave techniques is discussed. The main feature of the method is that the amplitude and phase angle of a detected signal are displayed in a polar co-ordinate system, which allows changes in both the dielectric constant and loss tangent of a dielectric material to be obtained at the same time. The results of experiment on deterioration, the detection of foreign materials, and differences in the inner structure of complex insulation materials are shown.