초음파 의료영상에서 컴파운딩 기법을 이용한 초음파의 평균 음속도의 측정과 음속도 영상의 구현

정목근,권성재,최민주,Jeong, Mok-Kun,Kwon, Sung-Jae,Choi, Min-Joo 대한의용생체공학회 2009 의공학회지 Vol.30 No.3

Using a spatial compound imaging technique in a medical ultrasound imaging system, the average speed of sound in a medium of interest is measured, and imaging of its distribution is implemented. When the brightness reaches the highest level in an ultrasonic image obtained as the speed of sound used in focusing is varied, it turns out that the focusing has been accomplished satisfactorily and that the speed of sound which has been adopted becomes the sought-after average speed of sound. Because spatial compound imaging provides many different views of the same object, the adverse effect of erroneous speed-of-sound estimation tends to be more severe in compound imaging than in plain B-mode imaging. Thus, in compound imaging, the average speed of sound even in the case of speckled images can be accurately estimated by observing the brightness change due to different speeds of sound employed. Using this new method that offers spatial diversity, we can construct an image of the speed of sound distribution in a phantom embedded with a 10-mm diameter plastic cylinder whose speed of sound is different from that of the background. The speed of sound in the cylinder is found to be different from that of the surrounding medium.

이어도 주변해역에서 수중음속의 시공간적 변동성

박경주 한국환경과학회 2020 한국환경과학회지 Vol.29 No.11

The impact of sound speed variability in the sea is the very important on acoustic propagation for the underwater acoustic systems. Understanding of the temporal and spatial variability of ocean sound speed in the sea around the Ieodo were obtained using oceanographic data (temperature, salinity). from the Korea Oceanographic Data Center, collected by season for 17 years. The vertical distributions of sound speed are mainly related to seasonal variations and various current such as Chinese coastal water, Yellow Sea Cold Water (YSCW), Kuroshio source water. The standard deviations show that great variations of sound speed exist in the upper layer and observation station between 16 and 18. In order to quantitatively explain the reason for sound speed variations, Empirical Orthogonal Function (EOF) analysis was performed on sound speed data at the Line 316 covering 68 cruises between 2002 and 2018. Three main modes of EOFs respectively revealed 55, 29, and 5% the total variance of sound speed. The first mode of the EOFs was associated with influence of surface heating. The second EOFs pattern shows that contributions of YSCW and surface heating. The first and second modes had seasonal and inter-annul variations.

파워 조절 방법에 따른 풍력 터빈의 방사 소음 특성

정철웅(Cheong, Cheol-Ung),정완섭(Cheung, Wan-Sup),신수현(Shin, Su-Hyun),전세종(Chun, Se-Jong),최용문(Choi, Yong-Moon),정성수(Jung, Sung-Soo) 한국소음진동공학회 2006 한국소음진동공학회 논문집 Vol.16 No.8

In the development of electricity generating wind turbines for wind farm application, only two types have survived as the methods of power regulation; stall regulation and full span pitch control. The main purpose of this paper is to experimentally identify the characteristics of noise emission of wind turbines according to the power regulation types. The sound measurement procedures of IEC 61400-11 are applied to field test and evaluation of noise emission from each of 1.5 MW and 660 kW wind turbines (WT) utilizing the stall regulation and the pitch control for the power regulation, respectively. Apparent sound power level, wind speed dependence, third-octave band levels and tonality are evaluated for both of WTs. It is observed that equivalent continuous sound pressure levels (ECSPL) of the stall control type of WT continue to increase with increasing wind speed whereas those of the pitch control type of WT show less correlation with wind speed. These observed characteristics are believed to be due to the different airflow patterns around the blade between the stall regulation and the pitch control types of WT; the airflow on the suction side of blade in the stall types of WT are separated at the high wind speed. It is also found that the 1.5 MW WT using the stall control emits lower sound power than 660 kW one using the pitch control at wind speeds below 8m/s, whereas sound power of the former becomes higher than that of the latter in the wind speed over 8m/s. This wind-speed dependence of sound power leads to the very different noise omission characteristics of WTs depending on the seasons because the average wind speed in summer is lower than 8m/s whereas that in summer is higher. Based on these experimental observations, it is proposed that, in view of environmental noise regulation, the developer of wind farm should give enough considerations to the choice of power regulation of their WTG based on the weather conditions of potential wind farm locations.

Speed-of-sound Estimation of Dual-acoustic Waves using Laser-activated Nanodroplets

윤희철,Stanislav Emelianov,Suhyun Park 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.5

A coherency of photoacoustic and ultrasound waves is dependent on the accuracy of the speed- of-sound. This study evaluates the feasibility of a speed-of-sound estimation method for dual pho- toacoustic and ultrasound waves using laser-activated phase-change per uorohexane nanodroplets (PFHnDs). The proposed method demonstrates that the estimated speed-of-sound (ESS) is close to the expected speed-of-sound for the medium (deviation = 0.3%), so it is useful for phase aberration correction in dual ultrasound and photoacoustic imaging.

Application of the Real Fabric Frictional Speeds to the Fabric Sound Analysis using Water Repellent Fabrics

Yang, Yoon-Jung,Kim, Chun-Jeong,Park, Jang-Woon,You, Hee-Cheon,Cho, Gil-Soo 한국섬유공학회 2009 Fibers and polymers Vol.10 No.4

This study aims to determine fabric frictional speeds between the arm and the trunk when people walk (1.3 m/s), jog (2.5 m/s) and run (4.5 m/s), and to apply the measured speeds to setting a sound generator for each motion to obtain fabric rustling sounds. By analyzing body motions captured by the Falcon motion analysis system and a camcorder, it was identified that the friction between the arm and trunk occurred within $10^{\circ}$ of shoulder angle along the center line of the trunk in the sagittal plane and the maximum frictional speed occurred at the elbow within the shoulder friction range. The averages (SDs) of maximum frictional speed at the elbow were found 0.63 m/s (0.17) at walking, 1.1 m/s (0.25) at jogging, and 1.98 m/s (0.35) at running. The frictional sounds of three coated nylon fabrics were obtained using these predetermined speeds. We calculated sound characteristics such as the sound pressure levels (SPL) and Zwicker's psychoacoustic parameter using 1/3 octave band analysis. The SPL values ranged from 74.2 dB at running to 79.0 dB at jogging, which was about the same noise level as in the busy street. The values of loudness (Z) at walking and jogging were higher than that at running, but the fluctuation strength (Z) increased in the order of walking, jogging, and running.

Precise measurement of sound speed in hydrogel tissue-mimicking material by a through-transmission method

Elmina Bernadette Carolina Fritzie,Baik Kyungmin,Kim Sung Mok,Kim Yong Tae 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.10

The water immersion through-transmission method is widely used owing to its simplicity and high precision in measuring sound speed. However, when measuring the sound speed of a compound material whose host medium is water, such as hydrogel tissue-mimicking material (TMM), the reproducibility and reliability of the measurements obtained under the state of water immersion method were found to be low. To solve this problem, the application of contact transmission method instead of the water immersion method was examined in this study. Unlike the water immersion method, the direct-contact method requires stability in target stiffness, which is difficult in TMM hydrogels due to their low-stiffness properties. Therefore, it is important to find a material that acts as a propagation medium, maintains thickness, and prevents percentage change of the material component in TMM. As a propagation medium, it is necessary for the material to have a low attenuation coefficient value to increase the signal-to-noise ratio. Among the investigated candidate materials, polymethyl methacrylate (PMMA) was selected, owing to its lowest signal attenuation value compared to other candidate materials. A measuring jig was designed and manufactured with this material. The sound speeds of agar and gelatin TMMs were measured by the conventional water immersion through-transmission method and the proposed indirect contact-type method for comparison. In the case of the conventional water immersion method, as the measurement was repeated, the measured sound speeds showed a decreasing trend. By contrast, the indirect contact-type measurements using the PMMA jig showed relatively high reproducibility and reliability.

Moving long baseline positioning algorithm with uncertain sound speed

Weisheng Yan,Wei Chen,Rongxin Cui 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.9

This paper presents a Moving long baseline (MLBL) positioning algorithm for the underwater target considering the uncertainunderwater sound speed. First, the positioning and the sound speed models are established. To tackle the uncertain sound speed, auncertain Least squares (ULS) positioning algorithm is applied to estimate the target position and the sound speed. Then it is essentiallyshown that four mobile buoys are necessarily (at least) required to locate the target. Further, it is found that under a singularityscenario in which the ranges between the target and each of the mobile buoys are equal, there is no solution to the positioning accordingto the classical geometrical equations. In order to solve this singularity problem, an ULS-based unscented Kalman filter(UKF) algorithm is proposed to obtain the estimated solution. Simulation results illustrate the effectiveness of proposed methods.

고속철도 차량의 공력 소음 저감 연구

김태민 ( Tae-min Kim ),김정수 ( Jung-soo Kim ) 한국환경기술학회 2017 한국환경기술학회지 Vol.18 No.1

본 연구는 고속철도 차량 주행 중 발생되는 소음 중 차간공간에서 발생되는 공력소음을 예측할 수 있는 수치 해석적 방법론을 연구하였으며, 더불어 차간공간의 공력소음저감을 위한 설계 방안을 제시하고자 하였다. 고속철도차량 차간공간의 주행속도에 따른 소음 영향을 분석하기 위해 고속철도 차간공간에 대한 풍동실험과 전산해석을 함께 수행하였다. 풍동실험 결과 차간공간의 공력소음의 경우 열차 속도의 약 7.7승에 비례하는 것으로 분석되었으며, 난류유동장 해석을 통해 와류 형성이 이러한 공력소음을 야기하는 것으로 분석되었다. 차간공간의 소음 저감 방안으로서 와류 생성을 최소화 할 수 있는 방안이 요구되며, 본 연구에서는 차간공간에 조류의 깃 형상을 모사한 장치를 부착하여 소음발생을 저감하고자 하였다. 와류 생성을 최대한 억제할 수 있는 장치를 설계하기 위해 깃 형상과 관련된 5개의 주요 인자를 선정하였으며, 실험계획법을 통해 각 인자의 기여도 분석을 수행하였다. 본 연구에서 최종 도출된 깃 형상의 소음저감 장치의 경우 유체의 박리를 최소화 하였으며 깃 형상을 따라 유동이 분산되어 와류 생성이 줄어드는 것으로 분석되었다. 수치해석결과 약 10 dB(A) 소음저감 효과가 있는 것으로 분석되어 고속철도 소음저감에 효과적인 것으로 판단된다. A numerical analysis method for predicting aerodynamic sound emission at inter-coach space of high-speed train, and a design for reducing the level of sound emission are proposed. The wind-tunnel testing measurements of the aerodynamic sound pressure level for the new generation Korean high-speed train have suggested that aerodynamic noise at inter-coach space varies approximately to the 7.7th power of the train speed. The turbulent flow field analysis at inter-coach space region demonstrates that vortex formation causes generation of this aerodynamic sound. A biologically motivated design based on bird feather morphology is proposed to be installed at inter-coach space for mitigating the sound emission. The five morphological parameters of the feather morphology are extracted and the optimal shape determined. The turbulent flow field analysis demonstrates that the optimal shape leads to diminished vortex formation by causing separation of the flow as well as allowing the fluid to climb up along the surface of the flight feather. When a device is installed at inter-coach space, the numerical simulation indicates that a sound reduction on the order of 10 dB(A) can be achieved.

한국연안에 있는 보름달물해파리의 체내 음속과 밀도 평가

윤은하 ( Eun A Yoon ),황두진 ( Doo Jin Hwang ) 한국어업기술학회 2013 수산해양기술연구 Vol.49 No.4

The sound-speed and density contrasts are important factors in estimating the target strength (TS) of moon jellyfish (Aurelia aurita). In this study, the sound-speed and density contrasts were measured using time-of-flight and neutral buoyancy methods, respectively. The sound-speed contrast of A. aurita was from 0.9966 to 1.0031 (mean±SD, 0.9999±0.0017) and no distinct differences in temperature or pulsation activity and weak were found. The density contrast was from 0.9994 to 1.0004 (mean±SD, 1.0000±0.0002). The density of A. aurita was substantially different but the density contrast of A. aurita was shown to be similar to that in the sampling location. The results can be used to estimate of TS of A. aurita by acoustic model.

해저 기반암을 통한 음파의 전파 특성

양우헌 ( Woo-hun Ryang ) 전북대학교 과학교육연구소 2017 과학과 과학교육 논문지 Vol.42 No.1

해양에서 음파의 속도를 계산하기 위한 음속 수식을 소개하였다. 또한 해저 기반암, 암석, 맨틀과 같은 고체 매질에서 전통적으로 이용하는 P파 속도와 S파 속도의 계산 수식을 유도하였다. 이 유도 과정은 직관적인 이해를 위한 설명 그림과 미분 수식으로 구성하였다. 이는 고등학교와 사범대학 학부과정의 지구과학 교과 내용 중, P파와 S파 속도의 정량적 특성과 음파 또는 지진파의 전파 특성을 이해하는데 기여할 것이다. An equation for sound speed was introduced for calculating the sound speed in sea water. It also derived classical equations of P-wave and S-wave velocity in solid medium such as marine basement, rock, and mantle. The derivation comprises explanation figures and differentiation equations for intuitive understanding. This will help to understand quantitative characteristics of P-wave and S-wave velocity and propagation property of sound or seismic waves among educational contents of the Earth science education in high-grade school and undergraduate course of education college.