• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.621-626
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• 1997

Combustion instability is a common phenomenon in a ducted flame burner and is known as accompanying low frequency oscillation. This is due to the interaction between unsteady heat release rate and sound pressure field, that is, thermoacoustic feedback. In Rayleigh criterion, combustion instability is triggered when the heat additions is in phase with acoustic oscillation. A Rijke type burner with a pre-mixed flame is built for investigating the effect of Reynolds number and equivalence ratio on thermoacoustic oscillation. In addition, the effect of wall temperature is presented. The results suggest that the frequency of max. oscillation is dependent on Reynolds number and equivalence ratio whereas its magnitude is not a strong function of these two parameters. On the other hand, the wall temperature distribution has much strong effects on the oscillation, even creates different mode of acoustic resonance.

• 전기학회논문지
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• 제62권10호
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• pp.1397-1402
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• 2013

This study researched cause of resonance noise for BLDC motor used in the refrigerator. it is difficult to measure dynamic characteristics for small sized fan & rotor system with conventional excitation method. Therefore this study performed electric exiting method and natural frequency method using microphone instead of conventional excitation and showed validity of these methods. Study result showed that tortional vibration frequency of fan & rotor system and natural bending frequency of the fan were matched with exciting frequency of BLDC motor caused by commutating ripple torque. And this frequency match caused resonance of the system. The study analyzed main parameters of this phenomenon and suggested alternative solution.

• 산업기술연구
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• 제24권A호
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• pp.75-81
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• 2004

The metal halide lamps are now widely used in the application and commercial lighting due to their attracting properties such as good color rendering and high efficiency. But, they have the serious problem of acoustic resonance for high frequency operation and they need the high voltage to ignite. So, they have not been applied to indoors. Over the past few years, a considerable number of studies have been conducted on the electronic ballast together with hot restarting and resonance phenomenon. But, very few attempts have been made with the adaptive ignition method according to the lamp state. In this paper, electronic ballast is proposed for metal halide lamps with an igniter for adaptive ignition. The proposed electronic ballast can generate different ignition voltages according to the arc tube state.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권7호
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• pp.370-376
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• 2004

The metal halide lamps are now widely used in the application and commercial lighting due to their attracting properties such as good color rendering and high efficiency. But, they have the serious problem of acoustic resonance for high frequency operation and they need the high voltage to ignite. So, they have not been applied to indoors. Over the past few years, a considerable number of studies have been conducted on the electronic ballast together with hot restarting and resonance phenomenon. But, Very few attempts have been made with the adaptive ignition method according to the lamp state. In this paper, electronic ballast is proposed for metal halide lamps with an igniter for adaptive ignition. The proposed electronic ballast can generate different ignition voltages according to the arc tube state.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2004년도 춘계학술대회 논문집
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• pp.205-209
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• 2004

The metal halide lamps are now widely used in the application and commercial lighting due to their attracting properties such as good color rendering and high efficiency. But they have the serious problem of acoustic resonance for high frequency operation and they need the high voltage to ignite. So, they have not been applied to indoors. Over the past few years, a considerable number of studies have been conducted on the electronic ballast together with hot restarting and resonance phenomenon. But very few attempts have been made with the adaptive ignition method according to the lamp state. In this paper, electronic ballast is proposed for metal halide lamps with an igniter for adaptive ignition. The proposed electronic ballast can generate different ignition voltages according to the arc tube state.

• 과학교육연구지
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• 제37권1호
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• pp.233-243
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• 2013

이 연구의 목적은 기주의 길이와 공명주파수의 관계를 정량 분석할 수 있는 교육용 실험기구를 개발하는 것이다. 일회용 플라스틱 주사기와 분자모형 조립용 플라스틱 구를 이용하여 '머리' 달린 기주 공명 장치를 제작하고 상용화된 소프트웨어를 이용하여 PC 실험시스템을 구성하였다. 연구 결과, PC 실험시스템은 전문가용 장비를 대신할 수 있는 것으로 나타났다. 주사기로 만든 이 실험기구는 '관'이 아닌 '헬름홀쯔 공명기'인 것으로 증명되었다. 실험으로 얻은 자료가 소리공명현상을 증명할 수 있는 것으로 나타났다. 결론적으로, 이 주사기 공명기는 중고등학생을 위한 영재교육이나 대학 음향실험용으로 사용가능한 실험장치이다.

• 음성과학
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• 제8권2호
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• pp.23-37
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• 2001

The primary sound produced by the vibration of vocal folds reaches the velopharyngeal isthmus and is directed both nasally and orally. The proportions of the each component is determined by the anatomical and functional status of the soft palate. The oral sounds composed of oral vowels and consonants according to the status of vocal tract, tongue, palate and lips. The nasal sounds composed of nasal consonants and nasal vowels, and further modified according to the status of the nasal airway, so anatomical abnormalities in the nasal cavity will influence nasal sound. The measurement of nasal sounds of speech has relied on the subjective scoring by listeners. The nasal sounds are described with nasality and nasalization. Generally, nasality has been assessed perceptually in the effect of maxillofacial procedures for cleft palate, sleep apnea, snoring and nasal disorders. The nasalization is considered as an acoustic phenomenon. Snoring and sleep apnea is a typical disorders due to abundant velopharynx. The sleep apnea has been known as a cessation of breathing for at least 10 seconds during sleep. Several medical and surgical methods for treating sleep apnea have been attempted. The uvulopalatopharyngoplasty(UPPP) involves removal of 1.0 to 3.0 cm of soft palate tissue with removal of redundant oropharyngeal mucosa and lateral tissue from the anterior and sometimes posterior faucial pillars. This procedure results in a shortened soft palate and a possible risk following this surgery may be velopharyngeal malfunctioning due to the shortened palate. Few researchers have systematically studied the effects of this surgery as it relates to speech production. Some changes in the voice quality such as resonance (nasality), articulation, and phonation have been reported. In view of the conflicting reports discussed, there remains some uncertainty about the speech status in patients following the snoring and sleep apnea surgery. The study was conducted in two phases: 1) acoustic analysis of oral and nasal sounds, and 2) evaluation of nasality.

• 조명전기설비학회논문지
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• 제18권3호
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• pp.7-14
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• 2004

현재까지 HID 램프는 광원이 가진 많은 장점에도 불구하고, 고온 순시 재 점등과 음향 공명 현상으로 인해서 실내 광원으로서의 사용이 제한되어왔다. 하지만 많은 연구를 통해서 램프가 뜨거운 상태에서도 순시 재 점등이 가능한 방법이 제시되어 왔고, 실제로 사용되어지고 있다. 하지만 이러한 방법은 램프 상태와 무관하게 200[kV] 정도의 전압을 램프에 인가하는 방법으로, 일반적으로 램프 수명이 감소하는 특징을 가지고 있다. 그러므로 순시 재 점등과 수명 문제는 중요한 연구대상으로 인식되어왔다. 본 논문에서는 램프가 차가운 상태에 필요한 점화 전압과 램프가 뜨거운 상태에서 점등에 필요한 점화 전압을 발생시키는 독립적인 2개의 점화기를 사용함으로써, 램프 상태에 따라 각기 다른 점화 전압을 램프에 인가하는 방법을 제안하고자 한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.633-638
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• 2002

The vacuum cleaner that has no dust bag generates very high level annoying noise. The dominant noise source is the 2$\^$nd/ BPF tone of the rotating impeller. In order to reduce the noise, we identify the acoustic characteristics and reduce the noise of the vacuum cleaner and centrifugal fan. The resonance phenomenon is observed in blade passages and we found out that the resonance frequency is very close to the 2$\^$nd/ BPF. In order to reduce this high-level peak noise, new impeller is designed in this paper. The trailing edge of new impeller is inclined and this makes the flow interactions between the rotating impeller and the stationary diffuser vane occurs with some phase shift. The performance of new impeller is similar to the old one but the overall SPL is reduced about 3.6dBA. The SPL of BPF is reduced about 6dBA and 2$\^$nd/ BPF is reduced about 20dBA. The vacuum cleaner, which uses newly developed centrifugal fan, generate more comfortable noise than the old model and the strong tonal sound was dramatically reduced.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 1992년도 추계학술발표회논문집
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• pp.16-21
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• 1992

Incandescent lamps and discharge lamps are generally used as light sources and special ballasts are needed thor stable operation of discharge lamps. In this paper, the author proposes the electronic ballast thor metal hallide lamps, experiments with high frequency square wave of frequency 22.52 KHz to avoid the acoustic resonance phenomenon and proves the usefulness of the proposed ballast. Furthermore, the author uses 220 AC voltage as a input voltage source of the proposed ballast. By examining the proposed ballast, lamp voltage of 139 V(max.) and lamp current of 1.4 A(max) can be measured. Furthermore, stable operation antral great luminouse fluxes are recognized.