Experiments and numerical simulations are carried out to verify the existence of the acoustic solitary wave in an air-filled tube with an array of Helmholtz resonators connected. Following up previous work (Sugimoto et al. 1999), the experiments are improved by using a newly designed piston driver to launch an initially plane pressure pulse and also by extending the tube length from 7.4 m to 10.6 m. To highlight the effect of the array of resonators, the case with no array is also examined in parallel. Direct and indirect checks are made to verify the existence of the solitary wave. The former compares the profiles and propagation speeds of pulses measured experimentally to the solitary-wave solution. The latter checks the validity of nonlinear wave equations in describing real wave evolution in the tube. Solving an initial-value problem numerically with weakly lossy effects of boundary layers and jet loss at the throat of the resonator, comparison is made between measured and simulated evolution. The validity of the equations in the lossy case is necessary to maintain the existence of the solitary wave in the lossless limit. It is revealed that nonlinear wave equations originally derived for unidirectional propagation in the tube can provide a good description of the real evolution, with some allowance for phase shifts on reflection at both ends of the tube. In particular, it turns out that the lossy effects are described quantitatively well. By establishing the validity of the equations, it is concluded that the acoustic solitary wave exists.
Two new components of botrytised wine were identified: 4,5-dimethyl-3-hydroxy-2(5//)furanone (Sotolon) and ethyl 9-hydroxynonanoate. Sotolon, the key substance of cane sugar aroma, was identified as the sugary flavor substance of botrytised wine by means of gas chromatography-mass spectrometry after column chromatographic separation on DEAE-Sephadex and silica gel. Ethyl 9-hydroxynonanoate was identified by chemical ionization and electron impact mass spectrometry. To evaluate the role of 17 volatile and 5 nonvolatile compounds characteristic of botrytised wine, these compounds were added to a normal wine. This produced a sweet, honey-like flavor similar to that of botrytised wine. The importance of Sotolon and the role of each group of flavor substances in producting this flavor was clarified by omission tests.
Experiments are performed to demonstrate the generation and propagation of acoustic solitary waves in an air-filled tube with a periodic array of Helmholtz resonators connected axially. The purpose is to verify the theoretical findings made so far that nonlinear acoustic waves do not evolve into a shock but into a solitary wave propagating steadily without any change of its smooth profile. To identify the solitary wave, the temporal pressure profile is compared directly with the theoretical profile of the solitary wave. Also checked are the relation between the peak sound pressure of the solitary wave and its halfvalue width in time, and the relation between the peak sound pressure and the deviation of propagation speed from sound speed. The experimental results show good quantitative agreement with the theory.
The aroma compound, damascenone, was found in many alcoholic beverages such as whiskey, brandy, rum, wine, and beer, and was considered to be significant to flavor. Damascenone in whiskey was formed from its precursor that came from barley during distillation. Beer contained none or very little, but it was formed by heating. In brandy production damascenone was present in grape and wine together with its precursor, and the precursor changed to it during distillation. It was also found in cane molasses.
Absolute configurations of Quercus lactones were investigated by studying paramagnetic shifts of PMR spectra and the chemical correlation with 2-hydroxyhexanoic acid of known configuration. Chiroptical properties of several mono-cyclic γ-lactones were also studied.
Effects of a periodic array of Helmholtz resonators on forced longitudinal oscillations of an air column in a closed tube are examined experimentally. The column is driven sinusoidally at a frequency near the lowest resonance frequency by oscillating bellows mounted on one end of the tube. Frequency responses are obtained for small and large amplitudes of the excitations. While the array lowers the resonance frequency and the peak value, its dispersive effect, i.e., the dependence of the sound speed on a frequency, can annihilate the shock effectively.
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