• 대한기계학회논문집B
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• 제23권6호
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• pp.795-801
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• 1999

An experimental investigation has been conducted with the objective of studying the mixing mechanism near the nozzle exit in a tone-excited jet diffusion flame. The fuel jet was pulsed by means of a loudspeaker-driven cavity. The excitation frequencies were chosen for the two cases of the non-resonant and resonant frequency identified as a fuel tube resonance due to acoustic excitation. The effect of tone-excitations on mixing pattern near the nozzle exit and flame was visualized using various techniques, including schlieren photograph and laser light scattering photograph from $TiO_2$ seed particles. In order to clarify the details of the flame feature observed by visualization methods, hotwire measurements have been made. Excitation at the resonant frequency makes strong mixing near the nozzle. In this case, the fuel jet flow in the vicinity of nozzle exit breaks up into disturbed fuel parcels. This phenomena affects greatly the combustion characteristics of the tone excited jet and presumably occurs by flow separation from the wall inside the fuel nozzle. As a result, in the resonant frequency the flame length reduces greatly.

• 방재기술
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• 통권21호
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• pp.5-12
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• 1996

An experimental investigation has been made with the objcetive of studying the effects of air entrainment of fire strength. A rich jet flame is considered as an fire, and fire, and the air entrainment is controlled by introducing the tone excitation which is generated by means of a loudspeaker-driven cavity. The excitation frequency is chosen for the resonant frequency identified as a pipe resonance due to acoustic excitation. As the excitation intensity increases, the amplitude of oscillating velocity for inducing air entrainment is increased, the flame height decreased and the structure of diffusion flame gradually transformed to that of premixed flame.

• 대한후두음성언어의학회지
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• 제9권1호
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• pp.32-37
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• 1998

Tonsillectomy is the one of operation that is performed the most commonly in otolaryngology field. Many changes that include range of voice, tone, voice quality and resonance were made by tonsillectomy. Sometimes, any patients taken tonsillectomy has suffer from these voice problem after tonsillectomy. However there are less study for these problems until now. Then, we studied to find the anatomical findings that affected the voice quality when tonsillectomy was performed. We evaluated the voice in 2 groups, one is the group showed the normal pharyngeal space by using the transnasal fiberscopy, the other is group showed medially bulging tonsil at pharyngeal cavity by using same method, with perceptual evaluation, nasalance score, nasality, oral formant and nasal formant. We used the computerized speech analysis system, the nasometer and the spectrogram in the CSL program. We could not find any differences in perceptual evaluation between two groups. But objective measures were provided. Nasalance score and nasality on the nasometric analysis were increased significantly and oral formant on the spectrogram was changed singnificantly after tonsillectomy in Group 2. Authors thought medially bulging tonsil in the pharynx is able to affect the voice quality after tonsillectomy when we evaluted through the nasal cavity by the using of fiberscopy and this evaluation would be important especially in singers.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1823-1828
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• 2000

Power transformers, air-intakes, stacks in a combined thermal power plant are the main noise sources. Power transformer noise among them has being get a target of public complaint due to 480Hz component of its pure tone. The source is mainly magnetostrictive vibration of the transformer core. The first countermeasures was installing sound barrier on the front of transformer. However, 500Hz, center of the frequency is not reduced. This paper includes the measurements of noise level at the near resident apartment, the identification of noise transfer and the countermeasures for noise sources. Cavity resonance type of noise reduction devices was installed on enclosuring wall of transformers. As a result, the noise level from transformer is reduced about 3dB.

• 한국가시화정보학회지
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• 제2권2호
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• pp.3-7
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• 2004

In this paper, computational aeroacoustics (CAA) method is used for flow-noise analysis and flow-noise visualization. High order high resolution scheme of optimized high order compact is used to resolve the small acoustic quantities and large flow quantities at the same time. An adaptive nonlinear artificial dissipation model and generalized characteristic boundary condition are also used. Aeolion tone noise, cavity noise, and jet noise are investigated. The visualizations of flow-noise are successful and characteristics of noise are studied. It is observed that the propagation directivity of noise is different with that of flow. With the help of CAA method, the visualization of noise is possible.

• 동력기계공학회지
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• 제3권3호
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• pp.60-69
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• 1999

The noise and vibration sources of rotary compressor for room air-conditioner are pressure pulsation of compression process, cavity resonance of inner space, structural radiation noise of shell and impact noise of discharge valve. Among them, pressure pulsation is very important noise and vibration source. Because it transferred various kinds of noise and vibration like as mentioned above. In this reason, muffler and resonator are used in order to absorb and remove these noises. But an analytical prediction using acoustic analysis does not coincident with the experimental result. The difference between analysis and actual state is due to the assumption of analysis. This paper covered with new concept of muffler design based on the turbulence kinetic energy of flow by using CFD. From this analysis, it is possible to decide the best position of discharge port of muffler. Therefore $2{\sim}3dB$ noise reduction effect is acquired in rotary compressor of 5000 BTU grade. Also new approach of resonator design is suggested. From this study, the characteristics of resonator and surge hole (a kind of resonator without pipe length) are identified. The former is useful for pure tone noise (narrow frequency band), and the latter is effective for broad frequency band. This paper shows that it is very available to use 3 dimensional analysis of resonator in order to predict more exact tuning frequency. The result is proved by a lot of experiments. From combination of fluid analysis and acoustic analysis, up stream position is effective location of resonator concerning turbulence motion of fluid.

• 한국연소학회지
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• 제1권1호
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• pp.51-55
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• 1996

An experimental investigation has been made with the objective of studying the limits of equivalence ratio on mixing enhancement in a tone excited jet flame. The jet is pulsed by means of a loudspeaker-driven cavity and rich flames(${\phi}>1.5$) are used. The excitation frequency is chosen for the resonant frequency identified as a pipe resonance due to acoustic excitation. Methane, propane and butane are used to examine the effect of mixture property on the limit of equivalence ratio. Mixing is always enhanced in a methane/air flame as the excitation intensity increases. Constant lower limits of equivalence ratio for mixing enhancement are present in cases of propane/air and butane/air flames irrespective of mean mixture velocities. The equivalence ratio limits are also found to be related to the flame instability ; the lower Le, the higher the limit of equivalence ratio. Under the equivalence ratio limits, cellular flames are generated as the excitation intensity increases. The amplitude of oscillating velocity for generating a cellular flame in the equivalence ratio limit is proportional to a mean mixture velocity irrespective of fuels.

• 한국광학회지
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• 제10권2호
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• pp.146-151
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• 1999

고반복률의 안정된 솔리톤 펄스열 출력을 얻기 위해 재생형 위상 변조에 의한 고차 조화 모드록킹 방식을‘8’구조 광섬유 레이저에 적용하고 실험하였다. 레이저 펄스 출력의 종모드간 맥놀이 스펙트럼으로부터 모드록킹 기본 주파수의 96차 고조파인 400 MHz 성분을 추출하고. 이를 증폭하여 공진기 내의 위상 변조기를 구동함으로써 변조기의 변조 신호에 따라 등간격으로 정렬된 솔리톤 펄스열 출력을 얻을 수 있었다. 이때 솔리톤 펄스의 반치폭 930 fs, 반치 파장선폭은 3.1 nm 였으며, 펄스폭과 주파수 대역폭의 곱이 0.359로써 변환한계에 가까운 솔리톤 펄스임을 알 수 있었다. 변조 주파수가 레이저의 종모드간 주파수 차이와 언제나 정확히 일치하므로 능동형 모드록킹에서 흔히 요구되는 공진기 길이의 조절없이도 안정적인 고차 조화 모드록킹이 가능하였다.

• 대한기관식도과학회:학술대회논문집
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• 대한기관식도과학회 1977년도 제11차 학술대회연제 순서 및 초록
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• pp.4.4-5
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• 1977

중이의 impedance는 고막, 이소골연쇄 및 중이강.유양동.함기봉와의 공기강에 의해 결정되는 바, 저자는 우선 신선한 개의 중이를 재료로 하여 중이강의 강기체적을 변동시킴으로써 중이강의 공기체적인자가 중이의 impedance를 어떻게 변동시키는가를 조사하였고, 다음으로 과거력과 현재상태에서 외이도, 고막 및 중이에 병변이 없는 환자에서 중이의 impedance를 측정하고 아울러 측두골의 X-녹상을 언어 측두골의 함기도에 따라 중이의 static compliance의 변동을 조사하여 이과학의 임상적인 면에서의 중이의 static compliance의 또 하나의 이용가치를 구명하여 다음과 같은 결론을 얻었다. 1. 개의 중이는 control state에서 Type A의 tympanogram을 보였으며, 중이강의 공기체적의 변동에 의해 tympanogram curve의 채형은 변동하지 않았다. 2. 개의 중이에 있어서 중이의 static complance는 중이강의 공기체적의 변동에 의해 유의한 직선적인 증가를 보였으며, 중이강의 공기체적 1cc의 증가에 대해 $0.5{\pm}0.1$cc의 증가율을 보였다. 3. 측두골의 함기도가 양호해짐에 따른 중이의 static compliance의 증가경향과 개의 측두골표본에서의 실험적인 근거로부터 측두골의 함기도(x)와 중이의 static compliance (y)사이에 $y=0.19x+0.16{\pm}0.05$의 회귀방정식을 얻을 수 있었다. 따라서 중이강의 공기체적의 변동은 유의한 중이의 static compliance의 변동을 일으키며, electroacoustic impedance bridge (Madsen ZO 70, 220 Hz 의 probe tone을 사용)를 사용하였 중이의 static compliance를 측정함으로써 임상적으로 측두골의 X-선상을 촬영하지 아니하고도 간단히 측두골의 함기도를 알 수 있을 것으로 생각되어, impedance audiometry의 임상진단학적인 견지에서의 또 하나의 가치를 보고하는 바이다.

• 한국임상수의학회지
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• 제30권1호
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• pp.45-48
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• 2013

수컷, 12년령, 2 kg의 푸들견이 오른쪽 앞다리 파행 평가를 위해 내원하였다. 병력 검사에서 교통사고 후 1년 동안 재발성 양측 어깨 관절 탈구를 보이다가 최근 들어 왼쪽 어깨는 유지가 잘 되고 오른쪽 어깨는 탈구가 심해진 것을 확인 하였다. 신체 검사에서 오른쪽 앞다리 파행을 확인 하였고, 방사선 검사에서 상완골 내측 탈구와 상완골과 견갑골의 겹침 현상을 확인 하였다. 수술 중 근위축, 상완 두갈래 근육 톤 감소, 어깨 관절 내측 인대 파열, 어깨 아래근 정지부 파열을 확인 하였다. 상완 두갈래근 변위술을 사용하였으나 수술 7일 후 재탈구를 확인 하였다. 견갑골 어깨 관절 부위에 장착한 두 개의 $2mm{\times}6mm$ 피질용 본 앵커와 상완골 어깨 관절 부위에 장착한 한 개의 $4mm{\times}6mm$ 해면질용 본 앵커를 이용 어깨 관절 내측 인대 복원술을 실시 하였다. 수술 직후 및 6주 후 방사선 검사에서 어깨 관절 탈구를 확인 할 수 없었다. 수술 후 6개월 신체 검사에서 파행은 더 이상 관찰 되지 않았다.