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We report the structural changes inside germania glass induced by femtosecond laser pulses. Inspection by polarization microscopy and secondary electron microscopy indicate that the periodic nanostructures consist of oxygen defects such as ODCs (oxygen deficient centers) and NBOHCs (nonbridging oxygen hole centers) for laser pulse energy less than 0.2 μJ. However, the glass network was dissociated and O2molecules were generated for laser pulse energy greater than 0.4 μJ. Two different structural changes, form-birefringence and dissociation, were induced in GeO[2] glass, depending on the laser pulse energy. The form-birefringence exhibited by the nanogratings in GeO[2] glass is larger than that in SiO2 glass for pulse energy less than 0.2 μJ, as the density of nanovoids enclosed by ODCs in GeO[2] glass is higher than that in SiO2glass. Arrhenius plots of the phase retardation caused by the nanogratings in GeO[2] and SiO2 indicate that the oxygen defects are relaxed at a temperature 100°C above the glass-transition temperature.

Electro-optic modulators using an antenna-coupled electrodes composed of patch antennas and a standing-wave resonant electrode have been analyzed for 5G mobile wireless communication systems. In this paper, the design of antenna-coupled-electrode electro-optic modulator for the 28 GHz band is reported.

Accidental falls may cause serious outcomes for the aged. Motor and sensory systems decay with aging, so reaction time as a placing reflex becomes delay to abrupt changes of the posture. Dynamic postural balance may provide more information than static postural balance. Dynamic postural balance was studied for proprioception of the neck and trunk, and for eyes control. Seven healthy volunteers participated in this study after informed consent. Repetitive alternative rotation of the head (M1) and of the head and thorax synchronized (M2); gazing at a projected point from a laser pointer set on the head, gazing at a fixation point on a screen and closed eyes; comfortable pace (P1) for repetitive alternative rotation, a faster pace than P1, and a slower pace than P1 were asked to do for 20 sec in every combination. A force plate was used for the center of foot pressure, and a wireless 3 axes accelero-meter were set on the top of the head for head motion. Powers were discussed at the same frequency as the head and/or thorax movements. Powers in M2 were significantly higher than those in M1. Neck proprioception should be important than that of thorax for dynamic postural balance.

Measuring center of foot pressure (COP) in motion might be more useful than only doing static COP to evaluate postural control. Active knees movements were applied to study COP with aging. Shifts and oscillation of COP were discussed in relation to age, body weight and height for 95 volunteers. Informed consent was obtained from them after fully explanation about this study. They had no past history of vestibular diseases. The subjects on a force plate were asked to stand upright for 5 sec, flex knees at an angle about 90 degrees as they could and keep knees flexed for 9.5 sec and extend knees to stand upright for 5 sec. Vertical, medial-lateral, anterior-posterior COP were tested. Medial-lateral shifts significantly correlated to age, and medial-lateral oscillation increased with aging. Anterior-posterior shifts in flexing knees correlated negatively to age, but anterior-posterior shifts at knees flexed correlated positively to age. Vertical shifts did not correlate to age, but they correlated to weight both in flexing and flexed knees, and anterior-posterior shifts correlated to weight in flexing knees. Both vertical and anterior-posterior shifts correlated to height in flexing knees. COP shifted anterior in knee-flexion. Oscillation about 2 Hz increased during flexed knees in the vertical direction.

制度:新 ; 報告番号:甲3579号 ; 学位の種類:博士(工学) ; 授与年月日:2012/3/15 ; 早大学位記番号:新5917