• 말소리와 음성과학
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• 제5권3호
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• pp.55-60
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• 2013

The purpose of this study was to investigate the acoustic characteristics of crying infants according to the communication intents such as hunger and pain in terms of acoustic differences in the fundamental frequency ($F_0$), jitter, shimmer, noise-to-harmonic ratio(NHR), habitual pitch, and intensity. The subjects were 20 healthy, normal infants, less than seven days old, from the city of Seoul and were born after 38 to 42 weeks(full term) of pregnancy. The sound of crying was recorded for three minutes. The crying due to pain was induced by means of the inborn metabolism error test, whereas the crying due to hunger was verified by means of the rooting reflex by waiting for the designated eating time. The results were as follows: (1) the fundamental frequency, noise-to-harmonic ratio(NHR), and intensity of the infants' crying due to pain was higher than that by hunger, showing a significant difference between the mean values. (2) the infants' crying due to hunger and that by pain did not have a significant difference in the mean jitter and shimmer values but both of them were largely outside of the normal threshold values(jitter by 1.04% and shimmer by 3.81%). This study was significant in the sense that it showed the acoustic characteristics of infants' crying from hunger and pain were very different from each other according to the communication intents in terms of the six acoustic parameters.

• 대한통합의학회지
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• 제6권4호
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• pp.191-206
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• 2018

Purpose : This study investigated the correlation between speech intelligibility and acoustic measurements of speech sounds produced by the children with speech sound disorders and children without any diagnosed speech sound disorder. Methods : A total of 60 children with and without speech sound disorders were the subjects of this study. Speech samples were obtained by having the subjects? speak meaningful words. Acoustic measurements were analyzed on a spectrogram using the Multi-speech 3700 program. Speech intelligibility was determined according to a listener's perceptual judgment. Results : Children with speech sound disorders had significantly lower speech intelligibility than those without speech sound disorders. The intensity of the vowel /u/, the duration of the vowel /${\omega}$/, and the second formant of the vowel /${\omega}$/ were significantly different between both groups. There was no difference in voice onset time between the groups. There was a correlation between acoustic measurements and speech intelligibility. Conclusion : The results of this study showed that the speech intelligibility of children with speech sound disorders was affected by intensity, word duration, and formant frequency. It is necessary to complement clinical setting results using acoustic measurements in addition to evaluation of speech intelligibility.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 13th KACG Technical Meeting `97 Industrial Crystallization Symposium(ICS)-Doosan Resort, Chunchon, October 30-31, 1997
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• pp.155-159
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• 1997

We investigated the effect of mechanical backside damage in Czochralski silicon wafer. The intensity of mechanical damage were evaluated by minority carrier recombination lifetime by a laser excitation/microwave reflection photoconductance decay method, photo-acoustic displacement method, X-ray section topography, and wet oxidation/preferential etch methods. The data indicate that the higher the mechanical damage intensity, the lower the minority carrier lifetime, and the photoacoustic displacement values are also increased proportionally.

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 동계학술발표회 논문집
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• pp.435-436
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• 2009

LNG 선박에 설치된 대용량 탱크의 누출을 검사하는 방법으로 $NH_3$를 사용하고 있다. 본 논문에서는 광음향효과를 이용하여 $NH_3$의 흡수선을 조사하였고, 이를 이용하여 $NH_3$의 농도를 측정하는 방법을 실험하였다.

• 대한음성학회지:말소리
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• 제67호
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• pp.1-16
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• 2008

Stress effects upon Korean vowels were investigated with reference to rhythm. We measured three acoustic correlates (Duration: VOT, Vowel Duration; F0; Intensity) of stress from the seven pairs of stressed vs. unstressed Korean vowels /i, ${\varepsilon}(e)$, a, o, u, i, e/. The results of the experiment revealed that stress gave only inconsistent and weak effects on duration, which supports that Korean is not a stress-timed language as far as strong stress effects on duration are still considered crucial in stress-timing. On the other hand, Korean stressed vowels were most characterized with higher F0 and next with stronger intensity. But speakers generally showed tactics to reversely use F0 and intensity in stressing an utterance rather than proportionately strengthening both of the two acoustic correlates of stress. There was found great inter-speaker variability especially in the variations of duration.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.170-173
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• 2002

The object of this study is to investigate the effect of compounded welding through the AE (Acoustic Emission) characteristics on static tensile test. This study was carried out a SM 490A, high tension steel using the low hydrogen type E4316 of electronic shield metal arc welding and compound wire of $CO_2$gas arc welding. $CO_2$welding, weak in the intensity of HAZ (Heat Affected Zone), can be improved by being combined with coated arc welding, Coated arc welding, weak in the intensity of the bead, can be improved by being combined with $CO_2$welding. Especially, electronic coated arc welding and $CO_2$welding complement the mechanical intensity of HAZ and the bead with each other. So, compounded welding increases the intensity in the special parts and enhances the quality of goods.

• 한국음향학회지
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• 제21권8호
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• pp.708-718
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• 2002

본 연구에서는 진동-음향계에서 방사되어 생성된 일반 근접장에서 음향 인텐시티 기법을 이용해 소음원을 파악하는 방법의 문제점에 관하여 논한다. 이를 위해 자동차나중장비의 엔진실을 모사하는 3차원 구조물 모델을 고려한다. 실제 상황과 유사하도록 모델에는 음원들이 복잡한 형상의 표면에 상호 연관성이 있는 또는 없는 형태로 분포한다. 즉, 음원들은 음향학적으로 단단한 상자들에 의해 형성된 좁은 공간으로 연결되어 있다. 따라서 반사가 심한 음장에 면한 표면에 배치되어 있으며, 전체 구조의 바닥 부분은 하부의 바닥과 작은 틈새만큼 떨어져 있다. 음향 경계요소법을 이용하여 근접 음장과 내부 음장의 인텐시티를 계산한다. 주어진 음원들간의 상대적 위상, 주파수, 위치에 따른 효과를 조사하였고, 그 결과를 등인텐시티선도, 벡터도 및 에너지 유선으로 표현하였다. 현장에서 종종 행해지는 바와 같이, 예를들어 엔진룸 상부에서 인텐시티를 측정하여 음원을 조사하는 것과 같은, 반사장이 강한 음장에서 음향 인텐시티 기법을 적용하여 음원탐색을 시도할 경우 가짜 음원이 검색될 수 있음을 보였다. 이와 같은 음장에서 정확한 결과를 얻기 위해서는, 음원탐색 수행 전에 음장의 리액티비티에 대한 조사가 먼저 필요하며, 측정을 시행하기 전에 음장의 리액티비티를 없애거나 대폭적으로 줄이는 작업이 선행되어야 할 것이다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.213-219
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• 2003

Acoustic emission behavior during fatigue crack growth test was investigated under various loading condition. To describe the acoustic emission activity, counts rate (d/dn) was related with SIFR (stress intensity factor range, K). Results indicated that SIFR could be divided into two parts according to its relationship with counts rate. For $K<25_{MPa\sqrt{m}}$, counts rate was increased as the SIFR increased. However, for values greater than $25_{MPa\sqrt{m}}$ , decreasing behavior was shown. This behavior of counts rate corresponding SIFR was keeping the same trend regardless of load range or crack length. Acoustic emission response to the single overload was sudden drop and slow recovery in counts rate like crack growth retardation. Under variable loading condition, counts rate of each loading block was same as that of constant amplitude loading. Overall experimental data was somewhat scattered since sensitive characteristics of acoustic emission method. However, these empirical relations indicated that counts rate was uniquely correlate with single parameter, SIFR.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.591-595
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• 2000

Sound absorbing characteristics of poroelastic materials is known to be greatly affected by high intensity acoustic waves. However, this effect has not been considered yet. In this study, the extended semilinear model based on Biot's theory for the porous materials and the characteristics of nonlinear waves in poroelastic sound absorbing materials were introduced. The expressions for the finite-amplitude acoustic plane waves were presented. By combining each nonlinear wave with appropriate matching conditions, we could investigate the effects of finite-amplitude acoustic waves on absorption characteristics of poroelastic materials. In the most ideal case considered in this paper, the absorption coefficient was found to become larger than that of linear incident waves. It was shown that the absorption coefficient became greater especially as frequency goes higher and as distance from the source goes larger. These phenomena may be inferred to result from 'dissipation effects due to nonlinearity'. This finding may have important implications for high intensity noise control.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권1호
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• pp.74-86
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• 2014

The optimization techniques are explored in the direction of arrival (DOA) estimation based on single acoustic pressure gradient vector sensor (APGVS). By analyzing the working principle and measurement errors of the APGVS, acoustic intensity approaches (AI) and the minimum variance distortionless response beamforming approach based on single APGVS (VMVDR) are deduced. The radius to wavelength ratio of the APGVS must be not bigger than 0.1 in the actual application, otherwise its DOA estimation performance will degrade significantly. To improve the robustness and estimation performance of the DOA estimation approaches based on single APGVS, two modified processing approaches based on single APGVS are presented. Simulation and lake trial results indicate that the performance of the modified approaches based on single APGVS are better than AI and VMVDR approaches based on single APGVS when the radius to wavelength ratio is not bigger than 0.1, and the two modified DOA estimation methods have excellent estimation performance when the radius to wavelength ratio is bigger than 0.1.