• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.51-53
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• 2005

Considerable noise is sometimes associated with degeneration of the hee joint surface. Such noise may indicate roughness or softening of the cartilage surfaces, and may be a useful index for early disease. In this study, we have evaluated arthritic pathology using the acoustical analysis of knee joint sounds. During sitting and standing periods, subjects' active knee flexion and extension were monitored. Fundamental frequency, mean amplitude of pitch, jitter and shimmer were analyzed according to the position and the joint angle. The result showed that the fundamental frequency of the 2nd patient group and standing position was higher than the others, and that the pitch of sounds changed unstably. These results suggest that an analysis of knee joint sound might assist non-invasive diagnosis of an articular pathology.

• 대한기계학회논문집B
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• 제27권3호
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• pp.334-346
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• 2003

An experimental study was carried out to investigate near-wake characteristics of an elliptic airfoil oscillating in pitch. The airfoil was sinusoidally pitched about the half chord point between -5$^{\circ}$and +25$^{\circ}$angles of attack at the freestream velocities of 3.4 and 23.1 m/s. The corresponding Reynolds numbers based on the chord length were 3.3$\times$10$_{4}$ and 2.2$\times$10$^{5}$ , respectively. A hot-wire anemometer was used to measure the near-wake flow variables at the reduced frequency of 0.1. Ensemble-averaged velocity and turbulence intensity profiles were presented to examine the near-wake characteristics depending on the Reynolds number. The axial velocity deficit in the near-wake region tends to decrease with the increase in the Reynolds number as found in many stationary airfoil tests. Turbulence intensity in the near-wake region have a tendency to decrease with the -increase in the Reynolds number during the pitch-up motion, whereas it shows different feature during the pitch-down motion according to the separation characteristics.

• 한국음향학회지
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• 제28권7호
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• pp.646-652
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• 2009

본 논문에서는 점용접 너깃의 피로수명을 고려한 차량 서브프레임의 용접간격 최적화 설계기법이 제안된다. 주파수영역 피로해석기법에 의해 점용접 너깃의 피로수명이 평가된다. 피로해석에서 사용되는 입력 데이터는 벨지안로 프로파일을 통과하는 차량동역학 해석과 차량 서브프레임 유한요소모델의 모드 주파수 해석을 통해 얻는다. 주파수 영역 피로해석으로 부터 얻은 피로수명 결과로부터 용접간격 최적화를 수행 할 설계점들이 선정된다. 점용접 너깃의 피로수명을 최대화시키는 용접간격을 얻기 위하여 4-요인, 3-수준 직교배열 실험계획법이 사용된다. 본 연구를 통하여 최적화된 서브프레임은 초기모델에 비하여 최소 피로수명을 갖는 용접 너깃의 피로수명이 약 65.8 % 증대되는 것을 알 수 있다.

• 음성과학
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• 제9권3호
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• pp.35-45
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• 2002

A simple algorithm for discriminating voiced sounds in a speech is proposed. In addition to low-frequency energy and zero-crossing rate (ZCR), both of which have been widely used in the past for identifying voiced sounds, the proposed algorithm incorporates pitch variation to improve the discrimination rate. Based on TIMIT corpus, evaluation result shows an improvement of 13% in the discrimination of voiced phonemes over that of the traditional algorithm using only energy and ZCR.

• 음성과학
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• 제11권3호
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• pp.69-81
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• 2004

The purpose of this experimental study was to investigate characteristics of Korean vowels uttered by Japanese speakers. Eight Korean Vowels were uttered three times by ten male Korean and Japanese, female Korean and Japanese, respectively. Formant Frequencies were measured from sound spectrograms made by the Pitch Works. Results showed that female Japanese speakers uttered Korean vowels more similar to those uttered by Korean native speakers than did male Japanese speakers.. In particular, male Japanese speakers have articulatory problems pronouncing the back vowels(/ㅓ/, /ㅡ/, /ㅜ/). It appears that the width of male speakers' articulatory movements is comparatively narrower than those of female speakers.

• 대한음성학회:학술대회논문집
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• 대한음성학회 2004년도 춘계 학술대회 발표논문집
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• pp.199-204
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• 2004

The purpose of this paper is to find prosodic characteristics in voice imitation. Speakers change various phonetic features in voice imitation. Speakers change their pitch ranges in the most cases. Especially, the pitch range is important for word conditions. And, as imitators change the voice, the average value of f0 is close to high frequence than low frequence or middle level.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
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• pp.931-936
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• 1994

Although an ideal low-pass filter is not physically realizable, it can be approximated on the basis of time reversal techniques. In this paper, we describe a method to approximately implement the ideal low-pass filter and apply it to the pitch extraction system. Experimental results show that our method is effective to estimate the fundamental frequency of the speech signal.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2012년도 추계학술대회
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• pp.10-12
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• 2012

현재 표준등부표의 종류는 10가지이며, 가장 작은 등부표가 4.4m로 대형인 것이 현실이다. 본 연구에서는 제작, 설치비용이 적고, 교체와 수리가 용이한 소형 등부표를 검토하였다. 상대적으로 소형인만큼 외력으로 인한 유실, 위치 이동 등의 사고에 대비하기 위한 안정성 검토가 필요하다. 이 논문을 통해서 새로운 등부표의 운동성(Heave, pitch)을 Encounter Frequency별, Beaufort scale별로 구분하여 비교, 분석하였다.

• 비파괴검사학회지
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• 제27권3호
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• pp.268-279
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• 2007

The reliability of cold-bonding repair technique of carbon-fiber reinforced plastics (CFRP) laminates, often used as a temporary repair for the airplane maintenance, has been evaluated during cyclic loading and localized heating by nondestructive methods. Major concern was given to the evolution of damage after repair in the form of delaminations due to localized heating and cyclic loading combined. An area of interest both on the specimen repaired by cold-bonding and the specimen without repair where delaminations were induced by localized heating and cyclic loading was monitored by acoustic emission (AE) testing and further examined by pitch-catch low-frequency bond testing, and pulse-echo high-frequency ultrasonic testing. The results showed that the reliability of cold-bonding repair would be significantly reduced by the localized heating and cyclic loading combined rather than by the cyclic loading only. AE monitoring appeared to be an effective and reliable tool to monitor the integrity of temporarily repaired CFRP laminates in terms of the structural health monitoring (SHM) philosophy.

• Ocean Systems Engineering
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• 제4권2호
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• pp.99-115
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• 2014

When caissons are mounted on a floating transportation barge and towed by a tug boat in waves, motion of the floating dock creates inertia and gravity-induced slip forces on the caisson. If its magnitude exceeds the corresponding friction force between the two surfaces, a slip may occur, which can lead to an unwanted accident. In oblique waves, both pitch and roll motions occur simultaneously and their coupling effects for slip and friction forces become more complicated. With the presence of strong winds, the slip force can appreciably be increased to make the situation worse. In this regard, the safety of the transportation process of a caisson mounted on a floating dock for various wind-wave conditions is investigated. The analysis is done by both frequency-domain approach and time-domain approach, and their differences as well as pros and cons are discussed. It is seen that the time-domain approach is more direct and accurate and can include nonlinear contributions as well as viscous effects, which are typically neglected in the linear frequency-domain approach.