• 태양에너지
• /
• 제20권3호
• /
• pp.31-38
• /
• 2000

In order to study on influence of fin pitch and shape of heat exchanger on the elevation of heat transfer efficiency, we make models of louvered fin type heat exchanger which was given a transformation of fin pitch in louvered fin type heat exchanger which are of en used now. And the influence of fin pitch on pressure drop and characteristics of heat transfer was experimented and analysed when air velocity and fin pitch was a variable. The results of experiment shows below. Pressure drop shows larger in louvered fin type heat exchanger than in plate fin type heat exchanger, size of pressure drop shows like this order that fin space is 4mm, 5mm, 6mm. Mean heat transfer coefficient shows higher in louvered fin type heat exchanger than in plate fin type heat exchanger, size of mean heat transfer coefficient by fin space shows same in both case in louvered fin type heat exchanger and plate fin type like this order that fin space is 4mm, 5mm, 6mm.

• 음성과학
• /
• 제14권2호
• /
• pp.23-33
• /
• 2007

This study examined the aerodynamic functions (mean airflow rate MFR, subglottal pressure Psub) and closed quotients (CQs) in the fixed pitch (C3, E3, G3, C4) with the variable loudness (70 and 80 dB) as well as in the fixed loudness at 70 dB and 80 dB with the variable pitch (C3, E3, G3, C4) in five classic male singers (Baritone). Results showed that MFR significantly increased at C3, E3, and G3 and Psub significantly increased at C4 when the loudness increased from 70 to 80 dB. At 70 dB, MFR and Psub significantly increased and CQ significantly decreased when the pitch increased from C3 to C4. At 80 dB, MFR significantly decreased when the pitch increased from C3 to G3. However, Psub showed the significant decrease with the pitch increased at 80 dB. In conclusion, as the loudness increases, the aerodynamic loss is getting higher and vocal efficiency becomes lower at low pitch than at higher pitch. At a low loudness level, the main mechanism to control loudness is the amount of medial compression of the vocal folds rather than the aerodynamic function. In addition, the aerodynamic function and medial compression of the vocal folds have a significant role in increasing the loudness level.

• 음성과학
• /
• 제15권1호
• /
• pp.87-98
• /
• 2008

This study compares the pitch production of children using cochlear implants (CI) with that of children with normal hearing. Twenty subjects from six to eight years old participated in the study. Three kinds of sentences were read and analyzed using Visi-Pitch $\blacktriangleright$(KAY Elemetrics, Model 3300). There were no considerable differences between the two groups regarding pitch, mean fundamental frequency (F0) and pitch range. In the cases of the slope value of F0 and duration, however, there were significant differences. Thus, it is concluded that duration and pitch control can be crucial factors in determining the intonation treatment of the children with cochlear implants.

• 대한기계학회논문집
• /
• 제14권6호
• /
• pp.1603-1612
• /
• 1990

본 연구에서는 5개의 원관으로 이루어진 일행관군에서의 원관 주위의 유동특 성의 해명과 유동장이 열전달에 미치는 영향등을 보다 상세히 밝히는데 목적이 있으며, 이를위해 원관의 표면압력, 관 주위의 유동장의 평균속도 및 난류강도, 관의 표면온도 등을 측정하였다.

• 말소리와 음성과학
• /
• 제3권1호
• /
• pp.97-102
• /
• 2011

Electroglottography (EGG) is a common method for providing non-invasive measurements of glottal activity. EGG has been used in vocal pathology as a clinical or research tool to measure vocal fold contact. This paper presents the results of pitch, jitter, and closed quotient (CQ) measurements in electroglottographic signals of young (mean = 22.7 years) and elderly (mean = 74.3 years) male and female subjects. The sustained corner vowels /i/, /a/, and /u/ were measured at around 70 dB SPL since the most notable among EGG variables is the phonation intensity, which showed positive correlation with closed phase. The aim of this paper was to measure EGG data according to age and gender. In CQ, there was a significant difference between young and elderly female subjects while there was no significant difference between young and elderly male subjects. The mean value for young males was higher than that for elderly males while the mean value for young females was lower than that for elderly females. Thus, it can be said that in mean values, increased CQ was related to decreased age for females, while CQ decreased for males as the speaker's age decreased. Although the laryngeal degeneration due to increased age seems to occur to a lesser extent in females, the significant increase of CQ in elderly female voices could not be explained in terms of age-related physiological changes. In standard deviation of pitch and jitter, the mean values for young and elderly males were higher than that for young and elderly females. That is, male subjects showed higher in mean values of voice variables than female subjects. This result could be considered as a sign of vocal instability in males. It was suggested that these results may provide powerful insights into the control and regulation of normal phonation and into the detection and characterization of pathology.

• 대한기계학회논문집
• /
• 제9권2호
• /
• pp.202-212
• /
• 1985

본 논문에서는 이러한 연구의 첫단계로 Gosman과 Ideriah가 다룬 TEACH-2E전 산프로그램을 모체로 하여 본 논문의 문제에 적합하도록 수정하여 사용하였다. 그러 나 기본적인 k-.epsilon.난류모델은 수정하지 않았다. 한편, 본 논문에서는 열선풍속계를 이용하여 평균 속도분포 및 난류특성을 계측하고 계산결과와 비교하였다. 이를 통하 여 표준형 k-.epsilon.모델을 이용한 TEACH-2E코드의 특성을 파악하고 이를 위한 실험 데이터 를 확보하는데 중점을 두었다.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• 제27권1호
• /
• pp.75-86
• /
• 2023

The angle of attack is highly sensitive to pitch point in the airfoil shape and the decline of pitch point value induces smaller angle of attack, which implies that airfoil profile possessing closer pitch point to the airfoil tip reacts more sensitively to upcoming wind. The method of conformal transformation functions is employed for airfoil profiles and airfoil surfaces are expressed with a trigonometric series form. Attack angle and ideal lift coefficient distributions are investigated for various airfoil profiles in wind turbine blade regarding conformal transformation and pitch point. The conformed angle function representing the surface angle of airfoil shape generates various attack angle distributions depending on the choice of surface angle function. Moreover, ideal attack angle and ideal lift coefficient are susceptible to the choice of airfoil profiles and uniform loading area. High ideal attack angle signifies high pliability to upcoming wind, and high ideal lift coefficient involves high possibility to generate larger electric energy. According to results obtained pitch point, airfoil shape, uniform loading area, and the conformed airfoil surface angle function are crucial factors in the determination of angle of attack.

• 한국정밀공학회지
• /
• 제23권8호
• /
• pp.72-79
• /
• 2006

We measured grating pitch standards using optical diffractometry and analyzed measurement uncertainty. Grating pitch standards have been used widely as a magnification standard for a scanning electron microscope (SEM) and a scanning probe microscope (SPM). Thus, to establish the meter-traceability in nano-metrology using SPM and SEM, it is important to certify grating pitch standards accurately. The optical diffractometer consists of two laser sources, argon ion laser (488 nm) and He-Cd laser (325 nm), optics to make an incident beam, a precision rotary table and a quadrant photo-diode to detect the position of diffraction beam. The precision rotary table incorporates a calibrated angle encoder, enabling the precise and accurate measurement of diffraction angle. Applying the measured diffraction angle to the grating equation, the mean pitch of grating specimen can be obtained very accurately. The pitch and orthogonality of two-dimensional grating pitch standards were measured, and the measurement uncertainty was analyzed according to the Guide to the Expression of Uncertainty in Measurement. The expanded uncertainties (k = 2) in pitch measurement were less than 0.015 nm and 0.03 nm for the specimen with the nominal pitch of 300 nm and 1000 nm. In the case of orthogonality measurement, the expanded uncertainties were less than $0.006^{\circ}$. In the pitch measurement, the main uncertainty source was the variation of measured pitch values according to the diffraction order. The measurement results show that the optical diffractometry can be used as an effective calibration tool for grating pitch standards.

• 음성과학
• /
• 제7권2호
• /
• pp.193-208
• /
• 2000

This paper describes a multi-step method of intonation modeling for corpus-based Korean speech synthesizer. We selected 1833 sentences considering various syntactic structures and built a corresponding speech corpus uttered by a female announcer. We detected the pitch using laryngograph signals and manually marked the prosodic boundaries on recorded speech, and carried out the tagging of part-of-speech and syntactic analysis on the text. The detected pitch was separated into 3 frequency bands of low, mid, high frequency components which correspond to the baseline, the word tone, and the syllable tone. We predicted them using the CART method and the Viterbi search algorithm with a word-tone-dictionary. In the collected spoken sentences, 1500 sentences were trained and 333 sentences were tested. In the layer of word tone modeling, we compared two methods. One is to predict the word tone corresponding to the mid-frequency components directly and the other is to predict it by multiplying the ratio of the word tone to the baseline by the baseline. The former method resulted in a mean error of 12.37 Hz and the latter in one of 12.41 Hz, similar to each other. In the layer of syllable tone modeling, it resulted in a mean error rate less than 8.3% comparing with the mean pitch, 193.56 Hz of the announcer, so its performance was relatively good.

• 한국정보전자통신기술학회논문지
• /
• 제14권4호
• /
• pp.247-256
• /
• 2021

본 논문에서는 피치 하모닉 움직임 예측과 적응적 신호 크기 예측을 이용한 패킷 손실 알고리즘을 제안한다. 스펙트럼 움직임 예측 방법은 사용 가능한 이전 패킷의 스펙트럼 상의 움직임을 일정한 부대역으로 나누어 손실된 신호의 움직임을 예측하여 복원한다. 제안하는 알고리즘에서는 음성신호를 유성음과 무성음으로 구분하여 유성음의 경우 피치 주파수를 활용하여 피치 하모닉으로 나누어 손실된 신호의 피치 하모닉 움직임을 예측하여 복원하고 무성음의 경우 스펙트럼 움직임 예측 방법을 사용하여 신호를 복원한다. 음성 프레임의 연속 손실이 발생한 경우 LMS(Least Mean Square) 예측기를 사용하여 이전 프레임의 이득 정보를 활용하여 신호 크기를 예측하여 출력 신호의 이득을 조절하는 방법을 제안한다. 객관적 평가방법인 PESQ (Perceptual Evaluation of Speech Quality) 시험을 통해 제안된 알고리즘의 성능을 평가하였고 기존의 방법보다 MOS 0.1의 성능 개선을 보였다.