Abstract: An ultrasonic wave generation device including: an ultrasonic wave generation source; an ultrasonic wave condensation part; and a waveguide. The ultrasonic wave condensation part has a first reflection surface opposed to the ultrasonic wave generation source and a second reflection surface opposed to the first reflection surface. The first reflection surface reflects the ultrasonic wave, generated from the ultrasonic wave generation source, toward the second reflection surface. The second reflection surface reflects the ultrasonic wave, which has been reflected by the first reflection surface, toward the waveguide so as to introduce the ultrasonic wave into the waveguide. The waveguide protrudes from the first reflection surface to a side opposite the second reflection surface. A recessed portion is formed from the first reflection surface to the second reflection surface side along an outer circumferential surface of the waveguide.

Abstract: In a control apparatus, a relative value calculation unit calculates a first relative value of a second communication quality parameter value acquired by an acquisition unit relative to a first communication quality parameter value acquired by the acquisition unit. The first communication quality parameter value is a communication quality parameter value for an in-use channel, and the second communication quality parameter value is a communication quality parameter value for a standby channel. Further, a channel switching control unit determines whether or not a radio channel set as the standby channel should be switched from the standby channel to the in-use channel based on a comparison result obtained by comparing the first relative value calculated by the relative value calculation unit and a first threshold.