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In recent years, there has been a growing increase in the use of electroencephalographic (EEG) signals for biometric systems. In investigating the use of EEG-based biometrics in a smart-device environment, this study focused on the development of a specific feature selection method, and on the feasibility of nonlinear dynamic characteristics of EEG signals for identifying individuals. We recorded sixteen EEG channel signals from seven subjects during two minutes in resting state with eyes closed, for a minimum of five times over several days. Power spectral density and the maximum Lyapunov exponents were calculated for the individual EEG characteristics. A specific criteria index (CI) that consisted of three types of variances was developed to quantify the level of EEG features, and to select adequate feature candidates with not only a low intra-subject variability but also high inter-subject discrimination. Statistical t-tests and a preliminary classification test using a linear support vector machine (SVM) classifier quantified the performance of feature selection, giving an accuracy rate of 94.9% for identifying each individual. In addition, they also revealed that the maximum Lyapunov exponents are one of the most feasible features for an EEG-biometric system, with an accuracy rate of 85.5% when using only maximum Lyapunov exponents from two EEG channels (T4, F4).

In this paper, it is investigated the effect of the cross linked polyethylene (XLPE) insulators was examined according to the temperature into XLPE which was used as the insulation of the electric power cable for the ultra-high voltage. In order to investigate the effect of changing tree phenomenon according to the temperature on the electrical conduction mechanism, a partial discharge experiment was conducted through the variation of temperature from 25[degC] to 80[degC], and voltage applied to the electrodes from 1[kV] to 40[kV]. The activity of partial discharge according to the temperature was examined using k-means distribution. As a result of experiments, we found that the specimen with 80[degC] has the lowest inception and breakdown voltage, center of clusters move 0, 180 degree at each positive and negative region in the k-means. We obtained that distribution of clusters concentrated on at inception condition, but the distribution spreads out widely at breakdown.

In this paper, we examine discharge characteristics of cross-linked polyethylene (since then; XLPE) according to void. Voltage was applied to power frequency by step method, and calibration of discharge was set to 50[pC] (slope=8.333). After the voltage was applied, for 10 [sec] (600 [cycle]), occurring discharge and number were detected. Determine of input pattern is difficult because discharge pattern is irregular. Therefore we investigated phi-q-n pattern using the clustering method, and investigated variation of center vector and cluster member

In the ITO/buffer layer/N,N'-biphenyl-N,N'-bis-(1-naphenyl)-[1,1'-biphenyl] 4,4'-diamine (NPB)/tris (8-hydroxy-quinoline) aluminum (AIq/sub 3/)/Al device, we investigated the effect of hole-injection buffer layer which is the one of the electrical characteristics of organic light-emitting diodes. A thermal evaporation was performed to make a thickness of NPB layer by the rate of 0.5 /spl sim/ 1 [/spl Aring//s] in a base pressure of 5x10/sup -6/ [Torr]. We measured V-I characteristic and efficiency with the thickness variation of hole-injection buffer layer. The PTFE and PVK materials used the buffer layer helped to improve the performance of the device in several aspect, such as good mechanical junction, reducing the operating voltage, energy band adjustment. Compared with the devices without hole-injection buffer layer, we have obtained optimal thickness 20 [nm] from the device structure of ITO/buffer layer/Alq/sub 3//Al. And using the PTFE of PVK buffer layer, the external quantum efficiency of devices has improved about 24.5 [%], and 51.3 [%], respectively.

A study has been carried out on volume resistivity of low density polyethylene (LDPE) which is irradiated with an electron beam by using an electron beam accelerator. From the analysis of DSC, the crystalline melting point of the specimen irradiated with electron beam is lower than that of original specimen. It is confirmed that the volume resistivity increased as temperatures increase from 60[/spl deg/C] to the crystalline melting point because of the defects of the solid structure and the formation of many trap centers by mean of electron beam irradiation, but decreased as temperatures go over the crystalline melting point because of the crystalline melting.

In this paper, the AC dielectric strength due to the mixture ratio of a film mixed with linear low density polyethylene (LLDPE) and ethylene vinyl acetate (EVA) was researched. Polyethylene, usually used as the insulating material of power cables, is a non-polar and low dielectric loss polymer. But it has defects of tree generation and accumulation of space charge by an applied voltage, resulting in the decreased life and performance. Therefore, to solve these problems, mixed films of LLDPE and EVA with similar physical properties in the case of low VA contents were made and tested for the mixture ratios of 80:20, 70:30, 60:40 and 50:50[wt%]. We analyzed physical properties and measured the dielectric strength to improve the performance of polyethylene. From the results, specimens of 70:30 and 50:50 were excellent at insulating performance.