• Korean Journal of Mathematics
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• v.30 no.3
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• pp.459-465
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• 2022

We exhibit various properties of the weighted Berezin operator T_α and its iteration T^k_α on L^p(𝜏), where α > -1 and 𝜏 is the invariant measure on the complex unit ball B_n. Iterations of T_α on L¹_R(𝜏) the space of radial integrable functions have performed important roles in proving 𝓜-harmonicity of bounded functions with invariant mean value property. We show differences between the case of 1 < p < ∞ and p = 1, ∞ under the infinite iteration of T_α or the infinite summation of iterations, most of which are extensions or related assertions to the propositions of the previous results.

• Communications of the Korean Mathematical Society
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• v.32 no.3
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• pp.779-787
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• 2017

Let m be the Lebesgue measure on ${\mathbb{C}}$ normalized to $m(D)=1,{\mu}$ be an invariant measure on D defined by $d_{\mu}(z)=(1-{\mid}z{\mid}^2)^{-2}dm(z)$. For $f{\in}L^1(D^n,m{\times}{\cdots}{\times}m)$, Bf the Berezin transform of f is defined by, $$(Bf)(z_1,{\ldots},z_n)={\displaystyle\smashmargin{2}{\int\nolimits_D}{\cdots}{\int\nolimits_D}}f({\varphi}_{z_1}(x_1),{\ldots},{\varphi}_{z_n}(x_n))dm(x_1){\cdots}dm(x_n)$$. We prove that if $f{\in}L^1(D^2,{\mu}{\times}{\mu})$ is radial and satisfies ${\int}{\int_{D^2}}fd{\mu}{\times}d{\mu}=0$, then for every bounded radial function ${\ell}$ on $D^2$ we have $$\lim_{n{\rightarrow}{\infty}}{\displaystyle\smashmargin{2}{\int\int\nolimits_{D^2}}}(B^nf)(z,w){\ell}(z,w)d{\mu}(z)d{\mu}(w)=0$$. Then, using the above property we prove n-harmonicity of bounded function which is invariant under the Berezin transform. And we show the same results for the weighted the Berezin transform in the polydisc.

• The Journal of the Acoustical Society of Korea
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• v.6 no.1
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• pp.39-47
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• 1987

It is well-known that analogizing a dynamic system to an equivalent circuit is a powerful tool on the analysis of the system. In this paper, an equivalent circuit of the piano has been constructed by the structural and acoustical analysis to visualize the sounding mechanism. Utilizing the mechanical reactance curve of the soundboard, a new method of reducing che inharmonicity in low frequency range has been built. With this method, by only choosing the proper excitation point on the soundboard, it will be possible to minimize the inharmonicity and thus to obtain mellow bass tone. It is shown that the missing fundamental in the lowest scale range results predominatly from the fact that the radiation impedance in such low frequencies is nearly pure reactive.

• Journal of Broadcast Engineering
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• v.18 no.6
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• pp.919-926
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• 2013

The acoustic signal from a distance sound source in an enclosed space often produces reverberant sound that varies depending on room impulse response. The estimation of the level of reverberation or the quality of the observed signal is important because it provides valuable information on the condition of system operating environment. It is also useful for designing a dereverberation system. This paper proposes a speech quality estimation method based on the harmonicity of received signal, a unique characteristic of voiced speech. At first, we show that the harmonic signal modeling to a reverberant signal is reasonable. Then, the ratio between the harmonically modeled signal and the estimated non-harmonic signal is used as a measure of standard room acoustical parameter, which is related to speech clarity. Experimental results show that the proposed method successfully estimates speech quality when the reverberation time varies from 0.2s to 1.0s. Finally, we confirm the superiority of the proposed method in both background noise and reverberant environments.

• Journal of Service Research and Studies
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• v.8 no.2
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• pp.67-76
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• 2018

Service quality research has been the subject of service studies for many years. This study is an exploratory study to improve the service quality measurement factor, and the research has been carried out reflecting the nature of the service; relationship quality, interactivity, horizontality, and harmony. Also, among the developed service quality measurement factors, the research model is reconstructed considering the major factors such as environmental quality, result quality, and convenience quality. Relationality and interactivity redesigned the quality factor, which is called interactive quality. The redesigned service quality factors consisted of interaction quality, result quality, environmental quality, convenience quality, harmonious quality, and horizontal quality. Experimental group evaluation was conducted on the quality factors and 18 measurement items were derived. A questionnaire was conducted to verify the validity of the 18 items. As a result of the questionnaire analysis, 6 factors and 15 items among the 18 items of service quality measurement factor were found valid. The six factors for the service quality measurement presented in this study are the results of the early stage research, but they can be used to improve the service quality factor in the future. However, this is significant because it reflects the characteristics of services that are consistent with the service economy. In particular, the horizontal quality and harmony quality factors are new factors not mentioned in the previous studies and need to be verified through further detailed studies. Further research is needed to improve the service quality measurement factors reflecting the nature of services and the characteristics of new services.