• Aerospace Engineering and Technology
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• v.2 no.1
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• pp.164-170
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• 2003

KSR-III engine with film-cooled baffle was tested. The purpose of this test is to verify the effect of ablative baffle on avoiding combustion instability which occurred in the acoustic cavity case. The engine had expansion ratio of 5.04 and the test condition was design condition(oxidizer mass flow rate 42.04, and fuel 17.95 kg/s). In the test, combustion instability did not occur. So, the effect of film-cooled baffle on avoiding combustion instability was verified.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.10 no.1
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• pp.50-57
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• 1999

A study to get the data of normal stop consonants production as preliminary study for cleft palate patients was performed. Normal Korean native 21 speakers were pronounced $VCV(V=/a/,C=/P/,/{P^1}/,/P^h/,/t/,/{t^1}/,/{t^h}/,/k/,/{k^1}/,/{k^h}/)$ syllables with natural speech rate and intensity. With intrapharyngeal pressure waveforms by pressure sensor in oropharyngeal cavity, amplitude and time duration of intrapharyngeal pressure were analyzed, and with acoustic waveforms and spectrograms, closure duration and VOT were analyzed. As results, the highest amplitude of intrapharyngeal pressure showed in alveolars and heavily aspirated consonants. Velars and unaspirated consonants were higher than bilabials and slightly aspirated ones each, in intrapharyngeal pressure. Bilabilas, alveolars and velars showed similar rise time of intrapharyngeal pressure build-up, but in decay time and total duration time, bilabials were slightly shorter than alveolars and velars, with no statistic significance. In the aspects of tensity, unaspirated consonants showed the longest rise time, heavily aspirated, the second, and slightly aspirated consonants, the shortest, which were also seen in decay time and total duration time. In closure duration, slightly aspirated consonants had the shortest closure duration, and the heavily aspirated ones, the second, and unaspirated consonants showed the longest. In VOT, heavily aspirated consonants showed the longest, slightly aspirated ones, the second and unaspirated ones showed the shortest.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.861-866
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• 2012

Turbo-charger noise radiated from air intake part is one of the most important noise sources in diesel power plant. In this paper, intake noise control of the diesel power plant was studied using parallel baffle type silencer and concentric hole-cavity resonator simultaneously. Firstly, acoustical characteristics and attenuation performance for parallel baffle type silencer were investigated through theoretical approach and experimental method. Based on the results, optimal design of the parallel baffle silencer was suggested. Secondly, for reducing the low frequency noise contained in the intake noise, the concentric hole-type resonator was developed and the acoustic performance was verified from the test. By combining two types of silencers, it is expected that the overall insertion loss is about 50 dB. So, the combined silencer is very helpful in reducing the intake noise of diesel power plant.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.526-531
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• 2011

A dash panel component, close to passengers, plays a very important role to protect heat and noise from a power train. Meanwhile, it is also a main path that transfers vibration energy and eventually radiates acoustic noise into the cavity. Therefore, it seems important to provide an optimal design scheme incorporating sound packages such as dash isolation pad and carpet, as well as structures. The present study is the extension of the previous investigation how design variables affect sound radiation, which was carried out using the simple plate and framed system. The system taken into account in this paper is a dash panel component of a sedan, which includes A pillar, front side member, dash panel and the corresponding sound packages. Design variables such as panel thickness and sound package layers are investigated how they are related for the better radiation performance (i.e. structure-borne) and sound transmission loss (i.e. air borne).

• Journal of the Korean Society for Precision Engineering
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• v.28 no.10
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• pp.1196-1203
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• 2011

Statistical optimum methodology of table of orthogonal array, ANOM, ANOVA and RSM are applied to formulate optimum allocation design with design variables. It can be minimized average SPL of control volume, the objective function in closed system by optimal allocated positions of absorbing material. Structural natural frequency and acoustic natural frequency of cavity are analyzed by FEM and BEM in the closed system. Using BEM, average SPL of specific control volume is calculated according to the condition before using absorbing material and after using it. It is shown that noise is reduced by $5.02dB_{RMS}$ by absorbing material located at optimal position and minimum $1.83dB_{RMS}$ and maximum $3.47dB_{RMS}$ by the table of orthogonal array.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.4
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• pp.48-56
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• 2011

A Possibility of combustion instability on longitudinal mode has a high level at large scale of L/D. Solid propellant has a metal particle and a grain of control to pressure oscillation. Solid rocket motor in slotted-tube grain controls pressure oscillation of longitudinal mode. Slotted-tube grain restrains longitudinal 1st pressure oscillation. But cavity volume of aft. insulation ablation amplifies 2nd pressure o scillation by vortext shedding. A study has suppressed combustion instability and vortex shedding by modified 4 slotted tube solid rocket motor design.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.1
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• pp.1-7
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• 2011

Cavitation is the formation of vapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapor pressure. Various types of cavitations are generated on the propeller blades. As cavity bubbles passing the blade are forced to oscillate in size or shape and come to collapse, they cause very strong local acoustic waves in the fluid and radiate noise. Comparing the Sound Pressure Level(SPL) before and after cavitation, SPL increases 2dB per 1 knot increase in ship speed above the cavitation inception speed(CIS). Consequently, the CIS is an important criteria to design silent propellers. In this work, experimental measurements of radiated noise according to various types of cavitations from the model propeller are carried out in a large cavitation tunnel and their acoustical characteristics are extensively investigated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.35-38
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• 2011

Damping characteristic according to acoustic cavity's geometries was investigated to control the high frequency combustion instability occurring in the Liquid Rocket Combustion Chamber by experimental test and linear analysis. Its diameter was determined as a design parameter and its orifice length and diameter were appointed as fixed parameter in this study. Result shows that the damping capacity has been almost constant through all the experiments despite using the same orifice and helmholtz resonators which have different volume.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.1093-1096
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• 2011

현대 의료 분야는 질병의 진단과 치료뿐만 아니라 질병의 예방 및 건강증진을 위한 관리, 유지의 역할도 중요하게 대두되고 있다. 즉, 질병의 조기 발견과 진단으로 예방 및 관리를 생활화하고 건강수준을 높이는 방향을 제시하는 등 건강증진을 유도하는 계기를 증대시키고 있다. 따라서 본 논문에서는 간질환이 음성에 미치는 영향을 연구하기 위해 간 질환자를 대상으로 공명강과 발성의 변화를 측정하는 실험을 수행하였다. 이를 위해 간 질환자를 피실험자 집단으로 구성하여 간질환으로 인해 입원했을 때와 치료 후에 퇴원했을 때의 음성을 각각 수집하여 음성 분석 요소 중 제3포먼트 주파수 대역폭과 무성음 추출 패턴수를 측정하여 간 질환으로 인해 공명강과 발성에 미치는 영향을 분석하는 연구를 수행하였다.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.1
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• pp.95-111
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• 1997

The human speech organ consists of respiration system (lung, larynx), phonation system (vocal cord), articulation system (esophagus, pharynx, uvula, teeth, gingiva, palate, tongue, lip) and resonating system(oral cavity, nasal cavity, paranasal sinus). Because teeth are components of the articulation system, it has been reported that the persons with abnormally positioned teeth generally have abnormal occlusion and pronunciation. In this study, using /ㅅ(s)/, the most commonly mispronunced consonant in children with malocclusion, and the seven single vowels, /사(sa), 서($s\delta$), 소(so), 수(su), 스($s\omega$), 시(si), 세(se)/ and / ㅏ(a), ㅓ($\delta$), ㅗ(o), ㅜ(u), ㅡ($\omega$), 1(i), ㅔ(e)/ were recorded and analyzed using speech analysis program on computer by measuring formants and compared them for investigating the differences in pronunciation in children with Angle's class I occlusions and those with Angle's class II div.1 malocclusion. The result were as follows: 1. In the Angle's Class II div.1 group, there were no significant differences in F1 of all recorded sounds as compared with Angle's Class I group(p>0.05). 2. In the consonants, there were significant differences in F2 of /스($s\omega$)/ and F2/F1 ratio of /사(sa), 서($s\delta$), 시(si)/ between the two group(p<0.05). 3. In the vowels, there were significant differences F2/F1 ratio of /ㅓ($\delta$)/(p<0.05) and no significant differences in F2/F1 ratio between two group(p>0.05). 4. In the consonants, there were significant differences in F2 and F2/F1 ratio when succeeding vowels were high or low, and F2/F1 ratio when front in accordance with tongue position (p<0.05). 5. In the vowels, there were no significant differences in formant in accordance with tongue position(p>0.05)