공기역학적 평가에서 음성 효율성 프로토콜의 반복 측정치 비교

이승진(Seung Jin Lee),임성은(Sung-Eun Lim),임재열(Jae-Yol Lim),최홍식(Hong-Shik Choi) 한국언어청각임상학회 2018 Communication Sciences and Disorders Vol.23 No.3

배경 및 목적: 음성 효율성 프로토콜(VOEF)의 반복 측정치 간의 차이나 반복 측정의 임상적 의의에 대해서는 충분히 규명되지 않았 다. 본 연구에서는 중증도를 통제하였을 때 집단과 회차에 따라 공기역학적 측정치의 차이가 있는지 알아보고자 하였다. 또한, 첫 번째 측정치와 세 측정치의 평균치가 갖는 진단적 유용성에 차이가 있는지 살펴보고자 하였다. 방법: 음성장애 환자군 80명과 정상 대조군 80명으로 하여금 Phonatory Aerodynamic System Model 6600 (PAS)의 VOEF를 3회씩 실시하도록 하였다. GRBAS 척도를 통해 측정한 중증도를 통제한 상태에서 집단과 회차에 따라 평균음압(PHODB), 평균음도(MEAP), 평균성문하압(MPAP), 평균호기류율(MFPHO)의 차이가 있는지 비교하였으며, 첫 번째 측정치(MPAP 1 , MFPHO 1 )와 세 회차의 평균 측정치(MPAP Avg , MFPHO Avg )의 곡선 아래 면적(AUC)을 비교하였다. 결과: MPAP (Wilk’s λ=.991)와 MADV (Wilk’s λ=.989)의 경우 회차와 집단에 따른 차이가 없었던 반면, PHODB 1 보다 PHODB 2 와 PHODB 3 이 더 높았으며, 환자군의 MFPHO가 대조군보다 낮았다. MPAP 1 와 MPAP Avg 의 AUC는 .683과 .687 로 차이가 없었고, MFPHO 1 과 MFPHO Avg 의 AUC 또한 각각 .644와 .625로 차이가 없었다. 논의 및 결론: MPAP와 MFPHO는 반복 측정에 따른 측정치와 진단적 유용성의 차이가 없어 VOEF의 1회 시행으로 충분할 것으로 보이며, 공기역학적 평가의 시간 대비 효율성을 제고할 수 있을 것으로 보인다. Objectives: The purpose of the present study was to determine whether voicing efficiency measures derived from the Phonatory Aerodynamic System differ according to repeated trials and the presence of voice disorders upon controlling for severity. In addition, the diagnostic ability of the first and averaged measures were compared. Methods: A total of 160 participants (80 patients and 80 controls; 23 males and 57 females for each group) participated in the study. Each participant was asked to perform the voicing efficiency protocol three times. Selected aerodynamic parameters including mean sound pressure level (PHODB), mean pitch (MEAP), mean peak air pressure (MPAP), mean airflow during voicing (MFPHO) were measured. A two-way repeated measures of ANCOVA upon controlling for severity and ROC curve analysis were performed. Results: Results indicated that there was no difference in MPAP and MFPHO among repeated trials upon controlling for severity, although a significant difference was found in PHODB (trial 1 < trial 2 = trial 3). The patient group showed lower MFPHO compared to the control group. ROC curve analysis revealed that the AUCs were .683 and .687 for the first and averaged MPAP; and .644 and .625 for the first and averaged MFPHO, respectively, suggesting no difference between measurement methods. Conclusion: In sum, the current data showed that MPAP and MFPHO measures did not differ according to repeated trials. Furthermore, the diagnostic ability of the first and averaged measures was similar, providing a rationale for the use of a time-efficient single trial protocol in clinics and research.

압축기 공력성능 측정 기법에 관한 연구

박태춘(Tae Choon Park),강영석(Young Seok Kang),양수석(Soo Seok Yang),강신형(Shin-Hyoung Kang) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11

The study on the measurement method of the aerodynamic performance of a turbo compressor was conducted. It is well known that the performance and the efficiency of the compressor can be calculated from the temperature and pressure distribution in each stage of the compressor. In the past Pitot tubes and thermocouples were used to measure pressure and temperature respectively, and recently pressure and temperature rake is used in order to decrease the measuring time and the number of measurement. The miniature total pressure rake which is available in the compressor with a small axial gap is designed and is under development.

A summertime near-ground velocity profile of the Bora wind

Petra Lepri,Hrvoje Kozmar,Željko Večenaj,Branko Grisogono 한국풍공학회 2014 Wind and Structures, An International Journal (WAS Vol.19 No.5

While effects of the atmospheric boundary layer flow on engineering infrastructure are more or less known, some local transient winds create difficulties for structures, traffic and human activities. Hence, further research is required to fully elucidate flow characteristics of some of those very unique local winds. In this study, important characteristics of observed vertical velocity profiles along the main wind direction for the gusty Bora wind blowing along the eastern Adriatic coast are presented. Commonly used empirical power-law and the logarithmic-law profiles are compared against unique 3-level high-frequency Bora measurements. The experimental data agree well with the power-law and logarithmic-law approximations. An interesting feature observed is a decrease in the power-law exponent and aerodynamic surface roughness length, and an increase in friction velocity with increasing Bora wind velocity. This indicates an urban-like velocity profile for smaller wind velocities and rural-like velocity profile for larger wind velocities, which is due to a stronger increase in absolute velocity at each of the heights observed as compared to the respective velocity gradient (difference in average velocity among two different heights). The trends observed are similar during both the day and night. The thermal stratification is near neutral due to a strong mechanical mixing. The differences in aerodynamic surface roughness length are negligible for different time averaging periods when using the median. For the friction velocity, the arithmetic mean proved to be independent of the time record length, while for the power-law exponent both the arithmetic mean and the median are not influenced by the time averaging period. Another issue is a large difference in aerodynamic surface roughness length when calculating using the arithmetic mean and the median. This indicates that the more robust median is a more suitable parameter to determine the aerodynamic surface roughness length than the arithmetic mean value. Variations in velocity profiles at the same site during different wind periods are interesting because, in the engineering community, it has been commonly accepted that the aerodynamic characteristics at a particular site remain the same during various wind regimes.

A summertime near-ground velocity profile of the Bora wind

Lepri, Petra,Kozmar, Hrvoje,Vecenaj, Zeljko,Grisogono, Branko Techno-Press 2014 Wind and Structures, An International Journal (WAS Vol.19 No.5

While effects of the atmospheric boundary layer flow on engineering infrastructure are more or less known, some local transient winds create difficulties for structures, traffic and human activities. Hence, further research is required to fully elucidate flow characteristics of some of those very unique local winds. In this study, important characteristics of observed vertical velocity profiles along the main wind direction for the gusty Bora wind blowing along the eastern Adriatic coast are presented. Commonly used empirical power-law and the logarithmic-law profiles are compared against unique 3-level high-frequency Bora measurements. The experimental data agree well with the power-law and logarithmic-law approximations. An interesting feature observed is a decrease in the power-law exponent and aerodynamic surface roughness length, and an increase in friction velocity with increasing Bora wind velocity. This indicates an urban-like velocity profile for smaller wind velocities and rural-like velocity profile for larger wind velocities, which is due to a stronger increase in absolute velocity at each of the heights observed as compared to the respective velocity gradient (difference in average velocity among two different heights). The trends observed are similar during both the day and night. The thermal stratification is near neutral due to a strong mechanical mixing. The differences in aerodynamic surface roughness length are negligible for different time averaging periods when using the median. For the friction velocity, the arithmetic mean proved to be independent of the time record length, while for the power-law exponent both the arithmetic mean and the median are not influenced by the time averaging period. Another issue is a large difference in aerodynamic surface roughness length when calculating using the arithmetic mean and the median. This indicates that the more robust median is a more suitable parameter to determine the aerodynamic surface roughness length than the arithmetic mean value. Variations in velocity profiles at the same site during different wind periods are interesting because, in the engineering community, it has been commonly accepted that the aerodynamic characteristics at a particular site remain the same during various wind regimes.

Wind-induced vibrations and suppression measures of the Hong Kong-Zhuhai-Macao Bridge

Cunming Ma,Zhiguo Li,Fanchao Meng,Haili Liao,Junxin Wang 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.32 No.3

A series of wind tunnel tests, including 1:50 sectional model tests, 1:50 free-standing bridge tower tests and 1:70 full-bridge aeroelastic model tests were carried out to systematically investigate the aerodynamic performance of the Hong Kong-Zhuhai-Macao Bridge (HZMB). The test result indicates that there are three wind-resistant safety issues the HZMB encounters, including unacceptable low flutter critical wind speed, vertical vortex-induced vibration (VIV) of the main girder and galloping of the bridge tower in across-wind direction. Wind-induced vibration of HZMB can be effectively suppressed by the application of aerodynamic and mechanical measures. Acceptable flutter critical wind speed is achieved by optimizing the main girder form (before: large cantilever steel box girder, after: streamlined steel box girder) and cable type (before: central cable, after: double cable); The installations of wind fairing, guide plates and increasing structural damping are proved to be useful in suppressing the VIV of the HZMB; The galloping can be effectively suppressed by optimizing the interior angle on the windward side of the bridge tower. The present works provide scientific basis and guidance for wind resistance design of the HZMB.

곤충형 날갯짓 비행체의 6자유도 비행 시뮬레이션을 위한 공력 예측 해석

김중관,한종섭,장조원,한재흥 한국항공우주학회 2011 한국항공우주학회 학술발표회 논문집 Vol.2011 No.11

This paper investigates a comparative study of unsteady aerodynamics measurement of Hawkmoth, Manduca Sexta wing and its quasi-steady aerodynamics estimation. Two flight regime: 1) Re=7500: real Hawkmoth's hovering regime, 2) Re=20000: normal micro air vehicles' (MAVs) operating regime, are tested in a water chamber with a scaled Hawkmoth wing model. For the quasi-steady estimation, a translational force component is modeled from lift and drag coefficient curves measured from a steady aerodynamics measurement of Re=8071. In addition, rotational force component is also modeled in the quasi-steady aerodynamic model for this comparative study. Results showed that the flapping cycle-averaged mean aerodynamic coefficients are well matched. In terms of time-varying sense, maximum aerodynamic peaks are well captured with quasi steady estimation, and peaks generated from rotational force components are also captured. However, peaks from wake-capture could not be properly estimated. This study provides a feasibility of applying reduced order aerodynamic model to a multibody dynamics based 6DOF flight simulation environment for insect-inspired flapping wing MAVs. 본 연구에서는 박각시나방(Hawkmoth, Manduca Sexta) 날개 상사모델의 비정상 공력 측정 실험과 준정상 공력 모델을 사용한 다물체 동역학 기반의 공력 예측 시뮬레이션의 비교 해석을 수행하였다. 실제 박각시나방의 제자리비행 조건과 유사한 Re=7500 및 일반적인 초소형비행체의 비행 조건인 Re=20000 두 가지 영역에 대하여 비정상 공력 발생 상사 수조 실험이 수행되었다. 공력 예측 시뮬레이션에 사용된 준정상 공력 모델은 Re=8071 의 정상 상태 공력 측정 실험으로부터 얻어진 양력계수 및 항력계수 커브를 통하여 병진공력성분(translational force)을 모델링 했으며, 추가적으로 회전공력성분(rotational force)에 대한 모델링도 이루어졌다. 비교 결과, 양력계수 및 항력계수의 날갯짓 1 주기 평균값을 잘 예측했으며, 날갯짓 한 주기 동안 변화하는 공력 특성 결과에서도 최대 공력 피크 및 회전공력성분에 의한 피크를 예측함을 확인했다. 하지만, 실험 결과에서 발생한 후류포획(wakecapture)에 의한 피크는 예측하지 못하였다. 본 연구를 통하여 곤충형 날갯짓 비행체의 비행동역학 및 비행안정성 연구에 적용 가능한 저차 공력 모델의 공력 예측 능력을 확인할 수 있었다. 이 결과는 추후 다물체 동역학 기반 6 자유도 비행 시뮬레이션 환경 개발에 활용될 것이다.

Study on the mechanism of the vortex-induced vibration of a bluff double-side box section

Yu Li,Chen Li,Feng Wang,Jia-Wu Li 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.2

At present, researchers mainly focused on the vortex-induced vibration (VIV) of the double-side I-shaped girder, while there are only a few literatures focused on the VIV of the bluff double-side box girder, especially the study on the synchronous pressure- and vibration- measured test for the bluff double-side box girder has not been reported. Therefore, in this study, the vibration-measured test, the Numerical Wind Tunnel Simulation, and the synchronous pressure- and vibration- measured test were conducted to study the VIV mechanism of the bluff double-side box girder. Firstly, a section model of the bluff double-side box girder was designed, and the vibration-measured test was conducted to study the influence of mass ratio, damping ratio, and aerodynamic countermeasures on the VIV of the bluff double-side box girder. Secondly, the Numerical Wind Tunnel Simulation was conducted to simulate the vorticity evolution of the bluff double-side box girder, which was used to help analyze the results of the synchronous pressure- and vibration- measured test. Finally, the synchronous pressure- and vibration- measured test was conducted to investigate the wind pressure distribution and aerodynamic forces on the surface of the double-side box girder, which was then used to study the VIV mechanism of the bluff double-side box girder by combining the simulated vorticity evolutions. So, when the VIV of the double-side box girder occurs, it is found that: there is a significant difference in the mean and fluctuating wind pressure between the upper and lower surfaces; moreover, at the leading and trailing edges, the aerodynamic forces contribute greatly to the VIV, the correlation between the aerodynamic forces and the vortex-induced aerodynamic forces is positive, and with the increase of this coefficient, it will lead to the more significant VIV.

Windproof ability of aerodynamic measures to improve the wind environment above a truss girder

Zewen Wang,Haojun Tang,Yongle Li,Junjie Guo,Zhanhui Liu 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.32 No.5

Aerodynamic measures have been widely used for improving the flutter stability of long-span bridges, and this paper focuses their windproof ability to improve the wind environment for vehicles. The whole wind environment around a long-span bridge located in high altitude mountainous areas is first studied. The local wind environment above the deck is then focused by two perspectives. One is the windproof effects of aerodynamic measures, and the other is whether the bridge with aerodynamic measures meets the requirement of flutter stability after installing extra wind barriers in the future. Furthermore, the effects of different wind barriers are analyzed. Results show that aerodynamic measures exert potential effects on the local wind environment, as the vertical stabilizer obviously reduces wind velocities behind it while the closed central slot has limited effects. The suggested aerodynamic measures have the ability to offset the adverse effect of the wind barrier on the flutter stability of the bridge. Behind the wind barrier, wind velocities decrease in general, but in some places incoming flow has to pass through the deck with higher velocities due to the increase in blockage ratio. Further comparison shows that the wind barrier with four bars is optimal.

On the mechanism of vertical stabilizer plates for improving aerodynamic stability of bridges

Chen, Airong,Zhou, Zhiyong,Xiang, Haifan Techno-Press 2006 Wind and Structures, An International Journal (WAS Vol.9 No.1

Vertical stabilizer plates have been found to be an effective aerodynamic measure to improve the aerodynamic stability of bridges either with an open cross section or with a streamlined box cross section in wind tunnel testings and have been adopted in some long span bridges. By taking an open deck II-shaped section and a closed box section as examples, the mechanism of vertical stabilizer plates for improving aerodynamic stability are investigated by using numerical simulation based on Random Vortex Method. It is found that vertical stabilizer plates can increase the amplitude of the heaving motion, and decrease that of the rotational motion of the bridge decks.

한국어 파열음의 발성 유형에 따른 공기역학 측정치 비교

최성희(Choi, Seong Hee),최철희(Choi, Chul-Hee) 한국음성학회 2014 말소리와 음성과학 Vol.6 No.4

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 /ph/, /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 /ph/ 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 /ph/ (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 /ph/. 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.