Nobuyuki Ohya

First-principles study of type-I and type-VIII Ba8Ga16Sn30 clathrates

We calculated the electronic structures and the thermoelectric properties for type-I and type-VIII Ba8Ga16Sn30 (BGS) clathrates. The band structures show that type-I and type-VIII BGS are indirect semiconductors with band gaps of 0.51 eV and 0.32 eV, respectively. The calculated Seebeck coefficient of n-type type-I BGS is higher than that of n-type type-VIII BGS because of the larger density of states in type-I at the bottom of the conduction band. This is in good agreement with the experimental results. We also calculated the electrical conductivity and thermal conductivity due to charge carriers. Estimated thermoelectric figure of merit, ZT, exceeds 1.0 for both types.

A new, compact and quick-response dynamic focusing lens

A dynamic focusing lens having a completely new mechanism that can be miniaturized and allow for a quick response has been developed. This lens is structured to directly transform tie lens shape as crystalline lens of human eyes. The lens comprises two thin glass diaphragms as a refracting surface, transparent working fluid sealed between them, and a micro actuator. When the actuator is driven to push or pull the glass diaphragm at the actuator side, the other glass diaphragm is transformed into the lens shape (convex lens or concave lens) having various curvatures. The dynamic focusing lens shows quick response up to 150 Hz, because the lens does not have rotating nor sliding mechanism which are usually used in conventional focusing mechanism.

Bending and expanding motion actuators

Abstract Two types of bending and expanding motion actuators which are composed of multilayered PZT unimorph cells have been developed. Each PZT unimorph cells electrode is divided into three sectors and the facing sectors are connected to one another. The bending and expanding motion actuator (8 mm in diameter, 9.2 mm in length), which has three pillars on the PZT side of the unimorph cell and one pillar on the metal side, respectively, achieves a bending angle of 4.5°, and the expansion displacement is 610 μm with 100 V. The resonance frequency is 140 Hz with 25 V. Multidirectional bending is realized by controlling the driving voltage of each sector.

A compact and quick-response dynamic focusing lens

Abstract A dynamic focusing lens with a completely new mechanism that can be miniaturized and allows for a quick-response has been developed. This lens is structured to directly transform the lens shape as a crystalline lens of the human eye. The lens is comprised of two thin glass diaphragms as a refracting surface, with a transparent working fluid sealed between them, and a new type of piezoelectric bimorph actuator. The displacement of the actuator is enlarged by the bimorph structure. The generated force is determined by the layer number of the bimorph cells. When the actuator is driven to push or pull the glass diaphragm at the actuator side, the other glass diaphragm is transformed into a lens shape (convex lens or concave lens) having various curvatures. The focal length of the lens is controlled by the applied voltage to the actuator. The dynamic focusing lens shows quick response up to 150 Hz. When the lens is operated over 60 Hz, human visual perception cannot recognize the change of the focal length, and we can observe many images having different focal lengths simultaneously.

Bending and Expanding Motion Actuators

Two types of Bending and expanding motion actuators which are composed of multi-layered PZT unimorph cells have been developed. Each cells electrode is divided into three sectors and the facing sectors are connected to one another. Multi-directional bending is realized by controlling the driving voltage of each sector. The first (3&3) type /spl phi/ 12 mm actuator is 12 mm in diameter, 20 mm in length and 6.4g in weight. The bending angle was 2.2 degrees, and the expansion displacement was 700 /spl mu/m with 150 V. The second (3&1) type /spl phi/ 8 mm actuator is 8mm in diameter, 9.2 mm in length and 1.2g in weight. The bending angle was approximately 4.5 degrees, and the expansion displacement was 610 /spl mu/m with 100 V.