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The modification of the spontaneous emission rate of an atom in a cavity can be seen as superradiance/subradiance induced by virtual image dipoles. This result is used to gain physical insight why the spontaneous emission is enhanced or suppressed in various cavity geometries. A general model for spontaneous emission engineering, which simultaneously handles dispersive and lossy cavities, is derived. 相似文献
286.
Patrick Susini Stephen McAdams Suzanne Winsberg Ivan Perry Sandrine Vieillard Xavier Rodet 《Applied Acoustics》2004,65(8):763-790
The aim of the psychoacoustic study presented here was to characterize listeners' preferences for a set of sounds produced by different brands and models of indoor air-conditioning units. In addition, some synthetic sounds, created by interpolation between recorded sound samples, were integrated into the set. The multidimensional perceptual space and the corresponding physical space representative of the sound set were determined with multidimensional scaling (MDS). Then the preferences for different classes of listeners were related to the physical space. The best spatial model yielded by the MDS had three common dimensions and specificities. The three dimensions are correlated with the ratio of the noisy part of the spectrum to the harmonic part (NHR), with the spectral center of gravity (SC) and with loudness (N). Two classes of listeners can be distinguished in terms of preference. For one, preference varied primarily with loudness, whereas for the other it varied more with SC and NHR. However, for one class the preference grew with the parameter NHR, while it decreased for the other class. The results replicate under different laboratory conditions and indicate the usefulness of this sound quality assessment approach for characterizing appliance noises. 相似文献
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We develop a Eulerian model for a particle suspension in fully developed turbulent liquid in a horizontal pipe. Virtual mass effects and hydrodynamic interactions are accounted for by an extension of the kinetic theory of Reeks and Swailes. 相似文献
288.
Akio Honda Hiroshi Shibata Jiro Gyoba Yukio Iwaya Yôiti Suzuki 《Applied Acoustics》2009,70(6):868-874
Transfer effects on two everyday auditory skills from playing an auditory game using a virtual auditory display (VAD) were investigated using two groups of 20 normally sighted participants. Representative auditory skills of blindfolded participants were pre-tested using communication and collision avoidance tasks. They performed the tasks two weeks later. Participants in a training group played the VAD-based game on seven days (30 min/day) during the two weeks: control group participants did not. Playing the VAD-based game significantly increased face-contacts in the communication task and significantly improved participants’ collision avoidance. No significant differences were found between the groups’ subjective ratings of the rated tension levels during the communication task or between rated levels for the collision threat. Performance revealed transfer effects of playing the VAD-based game on communication behaviors in social interaction and on avoidance of approaching objects: VAD-based games are effective training tools for auditory skills used in daily life. 相似文献
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R.S. Ming 《Applied Acoustics》2005,66(9):1074-1087
In this paper, a novel acoustical barrier based on the principle of the Helmholtz resonator is proposed for the mitigation of tonal noises and its in situ performance has been assessed in comparison with a reflecting barrier and an absorbent barrier. For a lightly damped thin-walled reflecting barrier, the energy transmitted through the barrier structure is comparable with that diffracted over the edges. The absorption treatment not only absorbs acoustical energy but also damps the barrier structure resulting in a negligible energy transmission. The results demonstrated that for tonal noises the proposed barrier is more effective than reflecting and absorbent barriers. 相似文献
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