The doubly oxonium-embedded picenes have been synthesized for the first time. They have a rigid planar electron-deficient core and are stabilized by the pyrylium aromaticity. The doping positions of oxygen atoms influenced their electrochemical and optoelectronic properties because of the different charge distributions in the skeletons. The donor–acceptor–donor-type molecules baring electron-donating triphenylamine moieties exhibited intramolecular charge-transfer absorption at the visible regions, indicating the large impact of the substituents on their electronic properties.

The vocal tract can be modeled as an acoustic tube in the low-frequency region because the plane wave propagation is dominant. Further, it can be considered static for a limited short period during running speech, such as vowels. Thus, its acoustic properties have been examined mainly using the transmission line model (TLM), that is, the one-dimensional static model in the frequency domain.In the present paper, we propose a one-dimensional static model in the time domain based on the finite-difference time-domain method. In this model, the vocal tract is represented by the cascaded acoustic tubes of different cross-sectional areas. The pressure and wall vibration effects are simulated at the center of each tube. On the other hand, the volume velocity is calculated at the labial end. According to the leapfrog algorithm, the pressure and volume velocity are sequentially computed. As a result, the impulse responses of the vocal tracts for the five Japanese vowels were calculated, and the corresponding transfer functions agreed well with those calculated by the TLM in the low-frequency region. The mean absolute percentage difference of the lower four peaks for the five vowels was 2.3%.

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