Masaharu Kondo

Evaluation of Thermal Tolerance in Initializing Thin Optical Discs

We simulated a temperature change in thin phase-change optical discs that have various substrate thicknesses in order to evaluate the thermal tolerance of a polycarbonate substrate during DC sheet beam initialization. We simulated the temperature change by applying a finite difference method to the partial differential equation for heat conduction. In discs with substrates on both sides, the difference between the sums of the given heat while the temperature of each substrate is more than or equal to glass transition temperature for a disc with a 100-µm-thick substrate on both sides and a disc with a 5-µm-thick substrate on one or both sides, was within 5%. The sum of the given heat to the substrate for a disc with a substrate on one side, was about 1.5 times larger than that for a disc with substrates on both sides. These results showed that the initialization margin needed to obtain a good-quality initialization state with no thermal damage to the substrate is smaller for a disc with a substrate on one side than for that with substrates on both sides.

Evaluation of Optimization Method for Inspection Scheduling of Power Distribution Facilities Using Maintenance Data Accumulated by Power Utility

Power distribution companies must establish an optimal maintenance schedule that balances the reliability and efficiency of a number of widely scattered facilities. Accordingly, we have developed an optimization method for inspection scheduling by which optimal inspection schedules are planned using 1) a method to predict the inspection priority for each facility and 2) a method to establish an inspection schedule that minimizes the inspection cost. In this study, for step 1, a practical method using both inspection history and facility attributes is proposed. The method consists of two approaches: a relation analysis and a defect prediction. In the relation analysis, relations between facility defect and other maintenance data are analyzed using a multiple correlation analysis method on the basis of chi-square testing. And then, facility defect is predicted using the data items that correlated with the facility defect obtained from the relation analysis. A modified quantification method type II introducing biased posterior probability is proposed for the prediction. Furthermore, proposed method is demonstrated by utilizing maintenance data accumulated by a certain Japanese power utility company. Evaluation results show that inspection cost can be reduced by 36–58% compared with the conventional twice-every-two-years inspection while retaining reliability.

Sub-Terabyte Optical Disc Realized by Three-Dimensional Pit Selection

Three-dimensional pit selection (3DPS) is proposed for optical discs with the capacity of hundreds of gigabytes, where the super-resolution and multi-layer techniques are combined. In this method, a high transmittance of each layer is obtained by discrete opaque data pits made of a super-resolution material. The dual-layer disc was fabricated using a phase-change material as a pit material. The experimental data show that the super-resolution effect is obtained for both layers. The additional advantages and the future expandability are discussed