• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.274-280
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• 2005

The objective of this study Is to investigate the heat transfer performance of plate discrete fin-and-tube heat exchangers with large fin pitch. In this study, twenty-two heat exchangers were tested with a variation of fin pitch, number of tube row, longitudinal tube pitch and fin alignment. Discrete fin type exchangers improved heat transfer performance more than 10% compared to tile continuous fin type heat exchangers. The air-side heat transfer coefficient decreased with a reduction of the fin pitch and an increase of the number of tube row, The staggered fin alignment improved heat transfer performance more than 6% compared to the inline fin alignment. The effect of longitudinal tube pitch was insignificant on the j-factor and experiments found opposite effects on the j-factor with respect to fin alignment. Heat transfer correlations were developed from the measured data for flat plate discrete fin-and-tube heat exchangers with large fin pitch. The correlations yielded good predictions of the measured data with mean deviations of 1,4% and 0.3% for tire inline and staggered tube alignment, respectively.

• 음성과학
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• 제10권2호
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• pp.111-128
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• 2003

Aerodynamic study is valuable information about the vocal efficiency in translating airflow to acoustic signal. The purpose of this study was to investigate the differences between trained singers and untrained controls under different two pitch by simultaneous using the airway interruption method and electroglottography (EGG). Under singing a Korean lied 'Gene', 20 (Male 10, Female 10) trained singers were studied on two one-octave different tone. Mean flow rate (MFR) , subglottic pressure (Psub) and intensity were measured with aerodynamic test using the Phonatory function analyzer (Nagashima Ltd. Model PS 77H, Tokyo, Japan). Closed quotients (Qx), jitter and shimmer were also investigated by electroglottography using Lx speech studio (Laryngograph Ltd, London, UK). These data were compared with those of normal controls. MFR and Psub were increased on high pitch tone in all subject groups. Statistically significant increasing of Qx and intensity were observed in male trained singers on high pitch tone (Qx;p = .025, intensity;p < .001). Beacasue of increasing of Qx and intensity, vocal efficiency was also significantly increased in male singers (p < .001). The trained singers' phonation was more efficient than untrained singers. The result means that the trained singers can increase the loudness with little changing of mean flow rate, subglottic pressure but more increasing of glottic closed quotients.

• 말소리와 음성과학
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• 제5권1호
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• pp.19-26
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• 2013

The aerodynamic characteristics (subglottal pressure (Ps) and mean airflow rate (MFR)), fundamental frequency (Fo), intensity (I), vocal efficiency (VE), and closed quotient (CQ) were compared during a sustained vowel /o/ sound under three conditions: in a comfortable loudness and pitch level (condition 1), in a maximum loudness level with a fixed pitch (condition 2), and in a maximum loudness level without a fixed pitch (condition 3). Also, multiple regression analyses were done to measure the aerodynamic characteristics affect on the VE and the CQ in each condition. The results showed the Fo, Ps, MFR, VE, and CQ increased as I increased with and without fixed pitch. Most notably, VE in condition 3 was the highest of all the conditions, but CQ was not very high. By the results of multiple regression analysis, VE was significantly affected by I and Ps in all conditions; Fo was the other main key for affecting VE in high pitch. However, none of the aerodynamic characteristics significantly affected CQ. As I increases, Fo should be increased by increasing Ps and VE. Therefore, researchers should consider and specify an a priori to Fo, Ps, and I when measuring VE to examine the complex and delicate vocal mechanism.

• 한국통신학회논문지
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• 제19권4호
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• pp.740-749
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• 1994

본 논문에서는 기존의 PSELP음성 부호화기의 성능을 개선하는 방법들을 제안하였다. 혼합 방법에 의한 주기추출법을 제안하여 기존의 PSELP음성 부호화기의 피치 주기 탐색시간을 줄였으며, 장기 필터(long term filter)의 출력 여기신호에서의 양자화 오차로 인해 발생할 수 있는 주기추출 오류를 개선시켰다. 또한 주기성을 향상기키고 잡음을 줄이기위해 본 논문에서 제안한 주기성 향상 필터를 복호기의 여기신호에 적용하여으며, 합성된 음성신호에서 음의 명료도를 높이기 위해 적응 일차 필터를 적용하였다. 작시한 방식과 필터를 적용한 결과 주기탐색시간이 기존에 대해 26%로 줄었으며, 최종합성음의 MOS(mean opinion score) 측정기에서 기존함성음은 3.19를 나타낸데 비해 개선된 합성읍의 4.04를 나타내었다.

• 설비공학논문집
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• 제17권10호
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• pp.930-937
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• 2005

The objective of this study is to investigate the heat transfer performance of flat plate finned-tube heat exchangers with large fin pitch. In this study, twenty-two heat exchangers were tested with a variation of fin pitch, number of tube row, and tube alignment. The heat transfer coefficient decreased with a reduction of the fin pitch and an increase of the number of tube row. The staggered tube alignment improved heat transfer performance more than $10\%$ compared to the inline tube alignment. A heat transfer correlation was developed from the measured data for flat plate finned-tubes with large fin pitch. The correlation yielded good predictions of the measured data with mean deviations of $3.6\%\;and\;6.4\%$ for the inline and staggered tube alignment, respectively.

• 음성과학
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• 제2권
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• pp.89-94
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• 1997

This study was attempted to analyze the acoustic characteristics of profoundly deaf students. The 59 profoundly hearing-impaired and 36 normal subjects were divided into 3 age groups: 6-10 yrs group, 11-15 yrs group, and 16-20 yrs group. The voice was sampled in /a/ prolongation, counting, reading, and conversation using the Computerized Speech ,Lab (CSL). The vocal pitch of the deaf subjects was significantly higher than the normal subjects. The younger in age was tended to be higher in pitch and jitter values of the deaf subjects. The three age groups of the deaf subjects did not show any difference in loudness and shimmer, excepted to minimum loudness. The pitch mean of males was significantly lower than that for females.

• Journal of Mechanical Science and Technology
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• 제19권8호
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• pp.1632-1648
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• 2005

The effects of Reynolds number on the non-nulling calibration of a typical cone-type five-hole probe have been investigated for the representative Reynolds numbers in turbomachinery. The pitch and yaw angles are changed from - 35 degrees to 35 degrees with an angle interval of 5 degrees at six probe Reynolds numbers in range between $6.60{\times}10^3\;and\;3.17{\times}10^4$. The result shows that not only each calibration coefficient itself but also its Reynolds number dependency is affected significantly by the pitch and yaw angles. The Reynolds-number effects on the pitch- and yaw-angle coefficients are noticeable when the absolute values of the pitch and yaw angles are smaller than 20 degrees. The static-pressure coefficient is sensitive to the Reynolds number nearly all over the pitch- and yaw-angle range. The Reynolds-number effect on the total-pressure coefficient is found remarkable when the absolute values of the pitch and yaw angles are larger than 20 degrees. Through a typical non-nulling reduction procedure, actual reduced values of the pitch and yaw angles, static and total pressures, and velocity magnitude at each Reynolds number are obtained by employing the calibration coefficients at the highest Reynolds number ($Re=3.17{\times}10^4$) as input reference calibration data. As a result, it is found that each reduced value has its own unique trend depending on the pitch and yaw angles. Its general tendency is related closely to the variation of the corresponding calibration coefficient with the Reynolds number. Among the reduced values, the reduced total pressure suffers the most considerable deviation from the measured one and its dependency upon the pitch and yaw angles is most noticeable. In this study, the root-mean-square data as well as the upper and lower bounds of the reduced values are reported as a function of the Reynolds number. These data would be very useful in the estimation of the Reynolds-number effects on the non-nulling calibration.

• 말소리와 음성과학
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• 제6권4호
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• pp.195-203
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• 2014

The aim of this study was to investigate the effects of phonation types ([+/- aspirated], [+/- fortis]) on aerodynamic measures with Korean bilabial stops. Sixty-three healthy young adults (30 males, 33 females) participated to evaluate the VOEF (Voicing Efficiency) tasks with bilabial stop consonants /$p^h$/, /p/, /p'/ using Phonatory Aerodynamic System (PAS) Model 6600 (Kay PENTAX Corp, Lincoln Park, NJ). All VOEF measures were significantly influenced by phonation types except RANP(pitch range)(p <.01). For sound pressure, maximum SPL, mean SPL, and Mean SPL during Voicing have been shown to be significantly greatest in fortis stop /p'/ than aspirated /$p^h$/ and lenis stop /p/ (p<.001). On the other hand, mean pitch after lenis stop was significantly lower than after aspirated and fortis stops (p<.001). Peak expiratory airflow, Target airflow, and FVC (Expiratory volume) were significantly lowest in fortis stop /p'/ which might be associated with higher aerodynamic resistance while peak air pressure and mean peak air pressure during closure were significantly lower in lenis stop /p/. Additionally, AEFF (Aerodynamic efficiency) was significantly higher in fortis stop /p'/ than lenis stop /p/ as well as aspirated stop /$p^h$/ (p<.001). Thus, sound pressure, airflow parameters, and aerodynamic resistance made crucial roles in distinguishing fortis /p'/ from lenis stop /p/ and aspirated. Additionally, pitch and subglottal air pressure parameters were important aerodynamic characteristics in distinguishing lenis /p/ from fortis /p'/ and aspirated /$p^h$/. Therefore, accurate aspirated /p/ stop consonant should be elicited when collecting the airflow, intraoral pressure related data with patients with voice disorders in order to enhance the reliability and relevance or validity of aerodynamic measures using PAS.

• 한국방사선학회논문지
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• 제14권7호
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• pp.981-989
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• 2020

본 연구는 Pitch의 변화에 따른 CT 감약계수(CT Number)와 잡음(Noise)의 변화를 정량적으로 측정하고자 자체 제작한 맞춤형 팬텀(Customized Phantom)을 사용하였다. 팬텀을 이용한 영상의 획득을 위해 팬텀 내부는 멸균증류수로 가득 채웠다. 유리관 내부에는 생리식염수와 조영제의 비율을 각각 생리식염수 100%, 400:1, 200:1, 100:1, 50:1로 희석한 용액을 담은 후 영상화하였고, 이때 용액의 희석비율별로 pitch를 0, 0.35, 0.7, 1.05, 1.4의 단계로 나누어 각각 영상화하였다. 희석비율별로 모든 ROI에서 측정한 CT number와 noise 값의 평균이 pitch의 변화에 따라 유의한 차이를 보이는지 검증하고자 일원 배치 분산분석(One-way ANOVA Analysis)과 사후검정을 시행하였다. 실험 결과 각 희석비율별 pitch의 변화에 대한 CT number의 변화는 통계적으로 유의한 차이가 없었지만, noise 값은 pitch의 증가에 따라 증가하는 경향을 보였으며, 통계적으로도 유의한 차이를 보이는 것으로 나타났다. 나선형 영상획득 방식은 pitch에 따라 noise가 유의한 수준으로 달라질 수 있다. 따라서 나선형 영상획득 방식을 적용한 CT 영상의 화질평가 항목과 기준을 설정할 필요가 있을 것이다.

• 대한방사선치료학회지
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• 제12권1호
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• pp.20-25
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• 2000

The accuracy of the target localization was evaluated by conventional and spiral CT in stereotactic radiosurgerv. Conventional and spiral CT images were obtained with geometrical phantom, which was designed to produce exact three-dimensional coordinates of several objects within 0.1mm error range. Geometrical phantom was attached by BRW headframe, intermediate head ring, and CT localizer. Twentv-seven slices of conventional CT image were scanned at 3 mm slice thickness. Spiral CT images were scanned at 3 mm slice thickness from the pitch value 1 to 3, and twenty-seven slices of image were obtained per each the pitch value. These CT images were transferred to a treatment planning system(X-knife, Radionics) by ethernet, Three-dimensional coordinates of these images measured from the treatment planning system were compared to known values of geometrical phantom. The mean localization error of the target localization of conventional CT was 1.4mm. In case of spiral CT, the error of the target localization was within 1.6mm from the pitch value 1 to 1.3, but was more than 30mm above the pitch value 1.5. In conclusion, as the localization error of spiral CT was increased in high pitch value compared to conventional CT, the application of spiral CT will be with caution in stereotactic radiosurgery.