• 지질공학
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• 제5권3호
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• pp.277-288
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• 1995

최근, 암반내에 형성된 절리 및 단층에 대한 정확한 규명은 무엇보다 암반분류 내지 암반내 용질유동연구에어 대단히 중요한 과제로 되고 있다. 본 연구에서 소개된 텔레뷰어 검층장치는 주사되는 초음파를 초점화함으로서 절리상태를 고분해능으로 파악할 수 있는 기능을 갖고 있다. 즉, 초음파 발생원이 시추공 축상에서 선회하는 동안 시추공내벽으로 조밀하게 초음파빔을 주사하고 그로 인해 반사되는 초음파의 $\circled1$ 진폭변화는 바로 절리 및 단층의 크기, 경사, 및 방향은 물론 상대적인 암석강도변화도 정확하게 추출하게 하며, $\circled2$ 주시변화는 바로 고분해능 공경검층기능을 대변하게 되어 시추공 내벽상태 내지 암석의 응력장 분포도 쉽게 판단하게 하는 것이다. 본 논문은 국내 청양군 실험시추공에서 얻게 된 텔러뷰어 현장탐사결과를 예시함으로써 텔레뷰어의 다양한 응용성을 입증하고 있다.

• 한국수소및신에너지학회논문집
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• 제28권1호
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• pp.106-112
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• 2017

The present study describes flow induced noise generated from a ball valve used for a gas pipeline. Noise generation from a ball valve mainly induces by interference between unstable(or fluctuating) leakage flow and pipe wall when the ball valve is working closed or opened. To measure the positions of the noise source and the amplitude of noise with respect to measuring frequencies, a commercial acoustic camera is introduced. Noise characteristics generated by the ball valve have been performed by four valve opening rates: 30, 50, 70 and 100 percents. It is noted that 100 percent opening rate means that the valve is fully opened. Throughout the experimental measurements using the acoustic camera, the location of the noise source and the noise amplitude with respect to the frequencies for the test ball valve are clearly evaluated. It is found that the dominant frequencies come from the fluctuating flow at the downstream of the ball valve for four opening rates are observed between 3,000Hz and 3,200Hz. Maximum noise amplitude comes from the ball valve reaches 75dB at the valve opening rate of 50 percent.

• 수산해양기술연구
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• 제53권2호
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• pp.152-159
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• 2017

Rockfish was a commercially important fish specie in marine ranching areas in Korea. To estimate density and biomass of rockfish using acoustic method, target strength (TS) information is required on the species. This study measured TS dependence on tilt angle and size on 14 live rockfish individuals at 38, 70, and, 120 kHz by ex-situ measurement (tethered method) and acoustic scattering model (Krichhoff ray mode, KRM). The swimbladdered angle ranged from 18 to $30^{\circ}$ ($mean{\pm}s.d.=26{\pm}4^{\circ}$). The mean TS for all individuals was highest -35.9 dB of tilt angle $-17^{\circ}$ at 38 kHz, -35.4 dB of tilt angle $-25^{\circ}$ at 70 kHz, and -34.9 dB of tilt angle $-22^{\circ}$ at 120 kHz. The ex-situ TS-total length (TL, cm) relationships were $TS_{38kHz}=20log_{10}(TL)-67.1$, $TS_{70kHz}=20log_{10}(TL)-68.6$, and $TS_{120kHz}=20log_{10}(TL)-69.9$, respectively. The model TS-total length (TL, cm) relationships were $TS_{38kHz}=20log_{10}(TL)-66.4$, $TS_{70kHz}=20log_{10}(TL)-67.0$, $TS_{120kHz}=20log_{10}(TL)-67.0$. The two measurements between the ex-situ TS and KRM model for TS-tilt angle and fish size were found to be significantly correlated.

• 한국군사과학기술학회지
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• 제23권6호
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• pp.554-564
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• 2020

In environment of torpedo firing, underwater acoustic signal is generated by target and noise. Sound wave which is generated from acoustic signal is propagated by seawater and it is received through the sonar(sound navigation and ranging) system mounted on torpedo. In the ocean, acoustic signal or sound wave from target that is generated by the spread of broadband can be attenuated by ambient noise and can be lost by medium and environment. This research is designed to support teamwork training in Naval operations by constructing a simulation system that is more similar to the real-world conditions. This paper attempts to research the modeling of target detection and to develop the simulation of torpedo sonar(TOSO). In order to develop the realistic simulation, we researched the broadband sound modeling of target and noise source, the modeling of acoustic transmission loss by chemical component of seawater, and the modeling of signal attenuation by ambient noise environment which is approximated by experimental measurements in seawater surrounding the Korea Peninsular and by experience of Navy's actual torpedo firing. This research contributed to constructing more practical simulation of torpedo firing in real time and the results of this research were used to develop a teamwork training system for the Navy and their education.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 춘계학술대회 논문집
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• pp.466-471
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• 2014

The interior vehicle noise due to the exterior aerodynamic field is an important topic in the acoustic design of a car. The air flow detached from the A-pillar and impacting the side windows are of particular interest as they are located close to the driver / passenger and provides a lower insulation index than the trimmed car body parts. This paper presents a numerical analysis method for a simplified vehicle model. The internal air cavity including trim component are included in the simulation. The car body includes the windshield and two side windows. The body is made of aluminum and trimmed with porous layers. The methodology proposed in this paper relies on two steps: the first step involves the computation of the exterior flow and turbulence induced non-linear acoustic field using PowerFlow. The second step consists in the computation of the vibro-acoustic transmission through the window using the finite element vibro-acoustic solver Actran. Additionally in order to validate the numerical process, an experimental set-up has been created based on the simplified vehicle. The vibration of the windshield and windows, the total wind noise level results and the relative contributions of the different windows are then presented and compared to measurements. The influence of the flow yaw angle (different wind orientation) is also assessed.

• 한국소음진동공학회논문집
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• 제26권1호
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• pp.69-74
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• 2016

A technique for improving estimation accuracy is introduced in order to locate the impact position of artillery shell during the weapon scoring test. Study on localization of impacts using acoustic measurement has been conducted and the usability of sensor array is verified with experiments. When the blast occurs above the ground in the firing range, the acoustic sensor above the ground can measure the directly propagated sound with the ground-reflected one. In this study, a method for reducing estimation error by using the reflection signal measurements based on the time difference of arrival method. Considering the reflection sound works as same as placing a virtual sensor symmetrically through the ground. This idea enables a virtual three-dimensional array configuration with a two-dimensional plane array above the ground as such. The time difference between the direct and the reflected propagations can be estimated using cepstrum analysis. Performance test has been made in the simulation experiment in the football size area.

• 말소리와 음성과학
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• 제4권2호
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• pp.61-70
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• 2012

The current study observes the durational interaction of tautosyllabic consonants and vowels in the word-initial position of English and Korean child-directed speech (CDS). The effect of phonological laryngeal contrasts in stops on the following vowel duration, and the effect of the intrinsic vowel duration on the release duration of preceding stops in addition to the acoustic realization of the contrastive segments are explored in different prosodic contexts - phrase-initial/medial, focal accented/non-focused - in a marked speech style of CDS. A trade-off relationship between Voice Onset Time (VOT), as consonant release duration, and voicing phonation time, as vowel duration, reported from adult-to-adult speech, and patterns of durational variability are investigated in CDS of two languages with different linguistic rhythms, under systematically controlled prosodic contexts. Speech data were collected from four native English mothers and four native Korean mothers who were talking to their one-word staged infants. In addition to the acoustic measurements, the transformed delta measure is employed as a variability index of individual tokens. Results confirm the durational correlation between prevocalic consonants and following vowels. The interaction is revealed in a compensatory pattern such as longer VOTs followed by shorter vowel durations in both languages. An asymmetry is found in CV interaction in that the effect of consonant on vowel duration is greater than the VOT differences induced by the vowel. Prosodic effects are found such that the acoustic difference is enhanced between the contrastive segments under focal accent, supporting the paradigmatic strengthening effect. Positional variation, however, does not show any systematic effects on the variations of the measured acoustic quantities. Overall vowel duration and syllable duration are longer in English tokens but involve less variability across the prosodic variations. The constancy of syllable duration, therefore, is not found to be more strongly sustained in Korean CDS. The stylistic variation is discussed in relation to the listener under linguistic development in CDS.

• 한국음향학회지
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• 제38권4호
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• pp.387-395
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• 2019

수동소나에서의 표적기동분석은 방위 또는 방위-주파수와 같이 제한된 정보를 이용하여 수행된다. 표적기동분석을 빠르고 정확하게 수행하기 위해서는 정확한 표적기동 초기치의 추정이 필수적이다. 기존의 표적기동분석과 달리 신호 대 잡음비 정보와 음파전달모델을 추가로 이용하면 표적기동분석의 정확도를 향상시킬 수 있다. 이 방법은 표적의 방사소음수준은 알고 있다고 가정하지만 가정한 수준과 실제 수준간의 오차에 따라 표적기동분석의 정확도가 저하될 수 있다. 본 논문에서는 수동 소나로 탐지한 표적 방위정보, 탐지 신호 대 잡음비 정보 및 음파전달모델을 이용한 표적기동분석 알고리즘을 한국 해양환경(동해/서해/남해)에서 수행한다. 그리고 가정한 표적 방사소음수준과 실제 수준간의 차이에 따른 성능분석 결과를 제시한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.1026-1031
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• 2003

Numbers of people living in high rise apartments are growing due to the overcrowding in urban area. Acoustic environment in those residential buildings has been seriously deteriorated by the increase of wheeled transports. Commonly used sound barriers have a limitation in controlling noise influencing higher part of a residential building. The use of noise barrier tunnels can be an alternative to supplement the defects of conventional noise barriers. But intensive measurements on noise levels at apartments vicinity of current noise barrier tunnels show that the tunnel now has a limited advantage on reducing the noise levels from arterial roads. The present work aims at providing an useful design tool In designing noise barrier tunnels for residential areas adjacent to roads. Number of field measurements, scale model measurements, and computer simulations were performed to ensure whether the prediction from scale model and computer simulation are appropriate. Result shows that the predictions from scale models and computer simulations could be valid prediction tools for designing sound barrier tunnels.

• 한국방재학회 논문집
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• 제9권3호
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• pp.101-106
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• 2009

우리나라의 경우 1990년대 후반부터 ADCP(Acoustic Doppler Current Profiler)가 도입되기 시작하였으나 아직까지는 ADCP를 이용한 유량측정 기법과 현장 적용성 문제가 충분히 검토되지 못하고 있는 실정이다. 따라서, 본 연구의 목적은 회전식 유속계와 ADCP를 이용한 유속측정의 검증 및 적용에 관한 것이다. 검증방법은 실험실에서 측정된 유속 값을 이용하였다. ADCP와 회전식 유속계를 이용한 유속측정의 차이는 2.1% 이내로 이는 ADCP을 현장에 적용해도 무방한 것으로 나타났다. 검증을 실시 후 ADCP를 실제 하천에 적용하였다. 현장적용 대상하천으로는 매곡천을 선정하여 ADCP의 유속 및 회전식 유속계의 유속을 비교하였다. 결과에서 ADCP에 의한 유속측정 값은 기존에 전통적으로 사용되는 회전식 유속계의 측정과 비교해서 평균 10.5% 이내의 오차로 잘 일치하는 것으로 나타났다.