Abstract: Proposed is a flextensional low-frequency sound projector including a piezoelectric actuator including a piezoelectric stack formed by stacking piezoelectric element and generating vibration in a lengthwise direction in response to an electrical signal that is input, and a stave mounted on the piezoelectric actuator in such a manner as to encompass an outer surface of the piezoelectric actuator and generating the vibration in the lengthwise direction, which is generated by the piezoelectric actuator, as vibration in a lateral direction perpendicular to the outer surface of the piezoelectric actuator, wherein the stave activates two vibration modes that use different resonance frequencies. The flextensional low-frequency sound projector that utilizes two vibration modes results from improving an existing flextensional low-frequency sound projector that is driven in a single vibration mode and thus has a narrow frequency bandwidth.

Abstract: A funnel-shaped underwater energy harvesting equipment includes a piezoelectric element configured to be installed at a seabed and to be moved by a fluid in order to convert vibration energy into electricity. The funnel-shaped underwater energy harvesting equipment further includes a fluid collector coupled to the piezoelectric element and configured to increase velocity of the fluid flowing toward the piezoelectric element. The harvesting equipment exhibits improved energy conversion efficiency, while simplifying the shape of the harvesting equipment.

Abstract: A funnel-shaped underwater energy harvesting equipment includes a piezoelectric element configured to be installed at a seabed and to be moved by a fluid in order to convert vibration energy into electricity. The funnel-shaped underwater energy harvesting equipment further includes a fluid collector coupled to the piezoelectric element and configured to increase velocity of the fluid flowing toward the piezoelectric element. The harvesting equipment exhibits improved energy conversion efficiency, while simplifying the shape of the harvesting equipment.