• 음성과학
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• 제12권4호
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• pp.95-112
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• 2005

We investigate Korean learners' speech-timing of English before and after instruction in comparison with native speech, in an attempt to resolve disagreements in the literature as to whether speech-timing is measurable (Lehiste, 1977; Roach, 1982; Dauer, 1983 vs. Low et al., 2000; Yun 2002; Jian, 2004). We measured the pair-wise variability between the adjacent stressed and unstressed syllables within a foot as well as that among adjacent feet in approximately 555 English sentences, which were read by 29 native speakers and 41 Korean learners in the intermediate proficiency level. The results show that in comparison with native American English, Korean learner speech is before instruction significantly (p<.001) smaller for the pair-wise variability between the adjacent stressed and unstressed syllables within a foot; and significantly (p=.01) bigger for the variability among adjacent feet within the utterance. The learner speech after instruction showed significant (p=.01) improvement in the pair-wise variability of syllable sequence toward native speech values. The variability among adjacent feet was progressively smaller for learner speech before and after instruction and for native speech (p=.03). We thus conclude that the speech timing difference between Korean English and American English is measurable in terms of the duration. of stressed and unstressed syllables and that the latter is stress-timed and the former is syllable-timing interfered.

• 음성과학
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• 제8권1호
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• pp.67-76
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• 2001

This study is targeted at introducing the three aspects of speech timing (articulatory, acoustic and auditory) and discussing their strong and weak points in describing speech timing. Traditional (extrinsic) articulatory timing theories exclude timing representation in the speaker's articulatory plan for his utterance, while the (intrinsic) articulatory timing theories headed by Fowler incorporate time into the plan for an utterance. As compared with articulatory timing studies with crucial constraints in data collection, acoustic timing studies can deal with even several hours of speech relatively easily. This enables us to perform suprasegmental timing studies as well as segmental timing studies. On the other hand, perception of speech timing is related to psychology rather than physiology and physics. Therefore, auditory timing studies contribute to enhancing our understanding of speech timing from the psychological point of view. Traditionally, some theories of speech timing (e.g. typology of speech rhythm: stress-timing; syllable-timing or mora-timing) have been based on our perception. However, it is problematic that auditory timing can be subjective despite some validity. Many questions as to speech timing are expected to be answered more objectively. Acoustic and articulatory description of timing will be the method of solving such problems of auditory timing.

• 음성과학
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• 제7권3호
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• pp.87-98
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• 2000

Timing in speech is determined by many factors. In this paper, we introduce and discuss some factors that have generally been regarded as important in speech timing. They include stress, syllable structure, consonant insertion or deletion, tempo, lengthening at clause, phrase and word boundaries, preconsonantal vowel shortening, and compensation between segments or within phonological units (e.g., word, foot), compression due to the increase of syllables in word or foot level, etc. and each of them may playa crucial role in the structuring of speech timing in a language. But some of these timing factors must interact with each other rather than be independent and the effects of each factor on speech timing will vary from language to language. On the other hand, there could well be many other factors unknown so far. Finding out and investigating new timing factors and reinterpreting the already-known timing factors should enhance our understanding of timing structures in a given language or languages.

• 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.

• 음성과학
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• 제9권4호
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• pp.165-173
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• 2002

Strong compression effects in a stressed vowel due to the addition of syllables have been adopted as evidence for stress-timing. In relation to this, Yun (2002) investigated the compression effects of number of syllables on Korean vowel. The results generally revealed that Korean had neither significant nor consistent anticipatory or backwards compression effects, especially when it came to the sentence level. This led us to claim that Korean would not be a stress-timed language. But the language investigated in the study was only Korean, and further cross-linguistic research was needed to confirm the claim. In this study, Yun's (2002) sentence level data are compared with Fowler's (1981) English data. The comparison reveals that Korean seems to be similar to English in the backwards compression effect, whereas the two languages are markedly different in the anticipatory compression effect. Thus, if English is a stress-timed language and the strong anticipatory compression effect is evidence in favour of stress-timing as is claimed, the present cross-linguistic study confirms Yun's (2002) suggestion-Korean is unlikely to be stress-timed. On the other hand, compression effects are revisited: the differences in vowel compression between English and Korean are discussed from the syntactic and phonological points of view.

• 음성과학
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• 제9권1호
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• pp.173-184
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• 2002

The question of Korean rhythmic type is still a controversial issue (syllable-timed; stress-timed; word-timed). As a step toward solving the question, an experiment was carried out to examine compression effects in Korean. There has been a general belief that the increase of the number of following or preceding syllables causes compression of a vowel (or syllable) in many languages, and a marked anticipatory compression effect can be especially indicative of stress timing. The purpose of this research, therefore, was to obtain some evidence to determine whether or not Korean is stress-timed. The durations of the target vowel/a/ of the monosyllabic word /pap/ were measured at both word and sentence level. In general, marked anticipatory and backward compression effects on the target vowel were observed across one-, two- and three-syllable words in citation form, whereas the effects were neither marked nor consistent at sentence level. These results led us to claim that Korean is not stress-timed.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1994년도 제11회 음성통신 및 신호처리 워크샵 논문집 (SCAS 11권 1호)
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• pp.323-327
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• 1994

There have been three contrastive claims over the classification of Korean. To answer the classification question, timing variables which would determine the durations of syllable, word and foot were investigated with various words either in isolation or in sentence contexts using Soundcoup/16 on Macintosh P.C., and a total of 284 utterances, obtained from six Korean speakers, were used. It was found 1) that the durational pattern for words tended to maintain in utterances, regardless of position , subjects and dialects 2) that the syllable duration was determined both by the types of phoneme and by the number of phonemes, the word duration both by the syllable complexity and by the number of syllables, and the foot duration by the word complexity, 3) that there was a constractive relationship between foot length in syllables and foot duration and 4) that the foot duration varied generally with word complexity if the same word did not occur both in the first foot and in the second foot. On the basis of these, it was concluded that Korean is a word timed language where, all else being equal, including tempo, emphasis, etc., the inherent durational pattern for words tends to maintain in utterances. The main difference between stress timing, syllable timing and word timing were also discussed.

• 한국자동차공학회논문집
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• 제10권4호
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• pp.23-32
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• 2002

Combustion and flame propagation characteristics of the liquid phase LPG injection (LPLI) engine were investigated in a single cylinder optical engine. Lean bum operation is needed to reduce thermal stress of exhaust manifold and engine knock in a heavy duty LPG engine. An LPLI system has advantages on lean operation. Optimized engine design parameters such as swirl, injection timing and piston geometry can improve lean bum performance with LPLI system. In this study, the effects of piston geometry along with injection timing and swirl ratio on flame propagation characteristics were investigated. A series of bottom-view flame images were taken from direct visualization using an W intensified high-speed CCD camera. Concepts of flame area speed, In addition to flame propagation patterns and thermodynamic heat release analysis, was introduced to analyze the flame propagation characteristics. The results show the correlation between the flame propagation characteristics, which is related to engine performance of lean region, and engine design parameters such as swirl ratio, piston geometry and injection timing. Stronger swirl resulted in foster flame propagation under open valve injection. The flame speed was significantly affected by injection timing under open valve injection conditions; supposedly due to the charge stratification. Piston geometry affected flame propagation through squish effects.

• Journal of Positioning, Navigation, and Timing
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• 제9권3호
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• pp.207-214
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• 2020

In this paper, we implement linear-quadratic-Gaussian based vector tracking loop (LQG-VTL) instead of conventional extended Kalman filter based vector tracking loop (EKF-VTL). The LQG-VTL can improve the performance compared to the EKF-VTL by generating optimal control input at a specific performance index. Performance analysis is conducted through two factors, frequency thermal noise and frequency dynamic stress error, which determine total frequency tracking error. We derive the thermal noise and the dynamic stress error formula in the LQG-VTL. From frequency tracking error analysis, we can determine control gain matrix in the LQG controller and show that the frequency tracking error of the LQG-VTL is lower than that of the EKF-VTL in all C/N0 ranges. The simulation results show that the LQG-VTL improves performance by 30% in Doppler tracking, so the LQG-VTL can extend pre-integration time longer and track weaker signals than the EKF-VTL. Therefore, the LQG-VTL algorithm is more robust than the EKF-VTL in weak signal environments.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.240-244
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• 2017

가스터빈 엔진의 구성품 개발단계에서 블레이드의 Aeromechanics 시험은 블레이드 진동설계와 구조 안정성 검증 프로세스 사이에서 중요한 연결 고리를 제공한다. 이 전제에 근거하여 본 연구에서는 NSMS(Non-Intrusive Stress Measuring Systems)를 축류 압축기 구성품 시험리그에 적용하여 Tip Timing 센서가 장착된 단에서 모든 블레이드의 정적/동적 변위를 시험적으로 측정하였다. 진동 특성 분석을 통해 블레이드 고주기 손상을 유발할 수 있는 피로임계위치(Fatigue Critical Location)에서의 진동 응력을 평가하였으며, 공력가진에 의한 비동기 진동응답 및 개별 블레이드 Mistuning 패턴을 제시하였다.