• Geophysics and Geophysical Exploration
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• v.14 no.2
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• pp.152-157
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• 2011

The small-loop electromagnetic (EM) method is one of the rapid and non-destructive geophysical methods and has been used widely for many geophysical investigations, particularly for shallow engineering and environmental surveys. Especially in the shallow marine environment, the small-loop EM technique is very effective because of rapid and convenient data acquisition, large signal and low noise level. However, the method has been rarely applied in the very conductive marine environment since it's penetration or investigation depth might be considered too low. In this study, we demonstrated that the small-loop EM method can be effectively applied in the extremely conductive marine environment through the analysis of 1D small-loop EM data. Furthermore, we confirmed that the resistivity distribution under the sea bottom can be quantitatively predicted from the 1D inversion results of synthetic and field data.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.1
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• pp.56-60
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• 2001

Tidal asymmetry which is generated at the mouth of an estuary tends to be more serious toward the upper stream due to the growth of shallow tides. Thus careful observations and applications for the shallow tides are needed if studies related to sediment or pollutant transport are carried on. An aim of the present study was to clarify the characteristics of generation and propagation of shallow tides by various numerical experiments including the effect of inter-tidal zone. The results of the present study will give a fundamental guide for the analysis of tidal envirorunental changes and for the design of a numerical model if coastal constructions are conducted.

• The Journal of the Acoustical Society of Korea
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• v.21 no.5
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• pp.485-493
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• 2002

Broadband interference patterns are studied using ship as an acoustic source in shallow waters with varying bathymetry. Waveguide invariant index (β) indicating the pattern of constructive (or destructive) interference in range-frequency domain is derived in a waveguide with constant bottom slope based on adiabatic mode theory. Using this invariant, changes of the interference patterns resulting from the variation of bottom bathymetry are analyzed. Results of the analytic interpretation is compared with those from sea experiments and numerical simulations.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.10a
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• pp.200-201
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• 2001

제주도 연안 천해역 환경은 대마난류수, 한국남해연안수, 중국대륙연안수, 황해 저층냉수 등의 외해에 분포하고 있는 여러 수괴에 의해 영향을 받고 있지만 이외에도 제주도의 강수량, 기온, 북서계절풍 등과 같은 기상상태나 육수유입, 파랑, 조석상태 등에 의해서도 크게 영향을 받아 시ㆍ공간적 차가 생길 것으로 판단된다. (중략)

• The Journal of the Acoustical Society of Korea
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• v.34 no.6
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• pp.411-422
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• 2015

This paper presents an overview of the geological environment investigation and underwater acoustic measurements for the purpose of "Study on the Relationship between the Geological Environment and Acoustic Propagation in Shallow Water", which are jointly carried out by KIOST (Korea Institute of Ocean Science & Technology) and Hanyang University in the western shallow water off the Taean peninsula in the Yellow Sea in April-May 2013. The experimental site was made up of various sediment types and bedforms due to the strong tidal currents and coastal geomorphological characteristics. The geological characteristics of the study area were intensively investigated using multi-beam echo sounder, sub-bottom profiler, sparker system and grab sampler. Acoustic measurements with a wide range of research topics in a frequency range of 20~16,000 Hz: 1) low frequency sound propagation, 2) mid-frequency bottom loss, 3) spatial coherence analysis of ambient noise, and 4) mid- frequency bottom backscattering were performed using low- and mid-frequency sound sources and vertical line array. This paper summarizes the topics that motivated the experiment, methodologies of the acoustic measurements, and acoustic data analysis based on the measured geological characteristics, and describes summary results of the geological, meteorological, and oceanographic conditions found during the experiments.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.429-432
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• 2000

수중에서 AUV신호나 화상데이터의 정확한 고속 전송 등을 위해 수중 데이터 통신에 대한 많은 연구가 진행되어 왔다. 수중 데이터 통신에서 잔향과 배경 잡음 등의 해양 환경 특성을 극복하는 것은 신뢰성 있는 통신 환경을 이룩하는데 중요하다. 특히 해면과 해저로 이루어진 천해 환경에서 해면과 해저 반사파에 의한 영향은 수중 데이터 통신의 성능을 좌우하는 중요한 요소 중의 하나로 알려져 있다. 이러한 환경적 영향을 최소화하여 높은 성능의 통신 환경을 제공하기 위해 다중경로의 영향을 적게 받는 변조방식을 선택하는 것이다. 수중 데이터 통신에서 일반적으로 사용되는 변조방식은 FSK, PSK, DPSK 등이 있다. 본 연구에서는 해면$\cdot$해저로 이루어진 해양 통신 채널에서 세 가지 변조방식의 성능을 수치모의실험을 통하여 비교$\cdot$분석하였다. 수치모의실험에서 해면 해저로 이루어진 천해의 해양 통신 채널은 음원 영상법을 적용하여 구성하였으며 각 변조방식의 성능은 BER(Bit Error Ratio)로 나타내었다.

• Korean Journal of Ichthyology
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• v.8 no.1
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• pp.9-13
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• 1996

To study on the growth of young stage Acanthopagrus schlegelii, samples were collected from the shallow waters off Kunsan, Korea from July to December, 1995. The planctonic larvae of Acanthopagrus schlegelii were collected in early June. The young fish of 12.7~26.6 mm in total length began to appear in the shallow water in late June. They grew up 19.9~51.4 mm in middle July, 24.8~75.0 mm in late July, 63.3~79.6mm in middle August. A. schlegelii disappear from the shallow water after middle August, and began to be collected in the outer bay off Kokunsan Isls. by long back net. This species that had spawned from Kunsan coast in late June to middle August grew up to 100mm in total length in December of that year.

• The Journal of the Acoustical Society of Korea
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• v.12 no.6
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• pp.5-12
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• 1993

고주파 음원을 사용하여 측정한 천해 해역에서의 잔향음 특성 변화와 해양 환경요소와의 연관성을 고찰하고자 하였다. 여름철에 실시한 현장실험에서 획득한 잔향음신호를 분석하여 다음과 같은 결과를 얻었다. 1) 수직 음속이 음의 기울기를 갖고 있어서 해저면 잔향음이 우세하다. 2) 음파발사 방위각에 따라 19dB 이상의 해저면 잔향음준위 차이를 보인다. 3) 계산된 해저면 후방산란 강도는 기존의 측정자료에 비해 약간 높게 나타난다.

• The Journal of the Acoustical Society of Korea
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• v.6 no.4
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• pp.64-73
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• 1987

Low frequency sound propagation in a range-dependent shallow water environment of the Korea Strait has been studied by using the adiabatic coupled mode, ADIAB. The range-dependent environment is unique in terms of horizontal variations of sound velocity profiles, sediment thickness and attenuation coefficients and water depths. For shallow source and receiver depths, the most important mechanism involved in the propagation loss is the depth changing character of mode functions that strongly depends on the local sound velocity profile. Application of the adiabatic coupled mode theory to shallow water environment is reasonable when higher modes are attenuated due to bottom interaction effects. Underwater sound propagation in a range-dependent shallow-water environment.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.10a
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• pp.81-83
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• 2009