This paper presents a novel cost-effective automatic resonance tracking scheme with maximum power transfer (MPT) for piezoelectric transducers (PT). The conventional approaches compensate the PT with complex power factor correction schemes or drive it in resonance using intricate loops with limited operating range. The proposed tracking scheme is based on a band-pass filter (BPF) oscillator, exploiting the PT's intrinsic resonance point through a sensing bridge. It guarantees automatic resonance tracking and maximum electrical power converted into mechanical motion regardless of process variations and environmental interferences. Thus, the proposed BPF oscillator-based scheme was designed for an ultrasonic vessel sealing and dissecting (UVSD) system, where accurate PT displacement regulation over a wide range of loads is required. An amplitude control for a switching power stage was developed to regulate the output mechanical motion and provide different power levels for the specific surgical functions such as sealing and dissecting. A proportional-integral (PI) compensator was developed to ensure stable operation under various loading conditions. The sealing and dissecting functions were verified experimentally in chicken tissue and glycerin.

A new dual current-mode controller produces a fast, accurate constant-power high-frequency ac output, with maximum current and voltage limits for an electrosurgical generator. The regulation of ac output power is achieved with near-deadbeat control, without measurement or feedback of the output voltage or current. Compared to existing technology, the prototype generator reduces unintended tissue damage by significantly improving regulation of output power, while reducing complexity and parts count.

An enhancement in the power-conversion-efficiency (η) of a magneto-electric (ME) gyrator has been found by the use of Mn-substituted nickel zinc ferrite. A trilayer gyrator of Mn-doped Ni0.8Zn0.2Fe2O3 and Pb(Zr,Ti)O3 has η = 85% at low power conditions (∼20 mW/in3) and η ≥ 80% at high power conditions (∼5 W/in3). It works close to fundamental electromechanical resonance in both direct and converse modes. The value of η is by far the highest reported so far, which is due to the high mechanical quality factor (Qm) of the magnetostrictive ferrite. Such highly efficient ME gyrators with a significant power density could become important elements in power electronics, potentially replacing electromagnetic and piezoelectric transformers.

In a between-subject perception task, listeners either identified full words or vowels isolated from these words at F0s between 220 and 880 Hz. They received two written words as response options (minimal pair with the stimulus vowel in contrastive position). Listeners' sensitivity (A') was extremely high in both conditions at all F0s, showing that the phonological function of vowels can also be maintained at high F0s. This indicates that vowel sounds may carry strong acoustic cues departing from common formant frequencies at high F0s and that listeners do not rely on consonantal context phenomena for their identification performance.

The phonological function of vowels can be maintained at fundamental frequencies (f) up to 880 Hz [Friedrichs, Maurer, and Dellwo (2015). J. Acoust. Soc. Am. 138, EL36-EL42]. Here, the influence of talker variability and multiple response options on vowel recognition at high fs is assessed. The stimuli (n = 264) consisted of eight isolated vowels (/i y e ø ε a o u/) produced by three female native German talkers at 11 fs within a range of 220-1046 Hz. In a closed-set identification task, 21 listeners were presented excised 700-ms vowel nuclei with quasi-flat f contours and resonance trajectories. The results show that listeners can identify the point vowels /i a u/ at fs up to almost 1 kHz, with a significant decrease for the vowels /y ε/ and a drop to chance level for the vowels /e ø o/ toward the upper fs. Auditory excitation patterns reveal highly differentiable representations for /i a u/ that can be used as landmarks for vowel category perception at high fs. These results suggest that theories of vowel perception based on overall spectral shape will provide a fuller account of vowel perception than those based solely on formant frequency patterns.