• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.1062-1073
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• 2007

Acoustic Target Strength (TS) is a major parameter of the active sonar equation, which indicates the ratio of the radiated intensity from the source to the re-radiated intensity by a target. In developing a TS equation, it is assumed that the radiated pressure is known and the re-radiated intensity is unknown. This research provides a TS equation for polygonal plates, which is applicable to near field acoustics. In this research, Helmholtz-Kirchhoff formula is used as the primary equation for solving the re-radiated pressure field; the primary equation contains a surface (double) integral representation. The double integral representation can be reduced to a closed form, which involves only a line (single) integral representation of the boundary of the surface area by applying Stoke's theorem. Use of such line integral representations can reduce the cost of numerical calculation. Also Kirchhoff approximation is used to solve the surface values such as pressure and particle velocity. Finally, a generalized definition of Sonar Cross Section (SCS) that is applicable to near field is suggested. The TS equation for polygonal plates in near field is developed using the three prescribed statements; the redection to line integral representation, Kirchhoff approximation and a generalized definition of SCS. The equation developed in this research is applicable to near field, and therefore, no approximations are allowed except the Kirchhoff approximation. However, examinations with various types of models for reliability show that the equation has good performance in its applications. To analyze a general shape of model, a submarine type model was selected and successfully analyzed.

• 한국소음진동공학회논문집
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• 제24권12호
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• pp.969-976
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• 2014

Nowadays, it is required for naval ships to estimate 3D underwater radiated noise pattern in all direction at peak frequencies of hull vibration for the reduction of being detected and doing the effective operation. For this purpose, the numerical method has to be developed to calculate 3D underwater radiated noise pattern with experimental data. It is very difficult to obtain the experimental data for the real ship. Alternative to get the experimental results is to use NAH(near-field acoustic holography) in acoustic tank with experimental model. Application of NAH in acoustic tank for the experimental model needs some investigation of reflection wave from the wall of the acoustic tank and unmeasured zone of the experimental model due to the supporting structure for it. In this study, the effect of reflection wave in the acoustic tank and unmeasured area of the experimental model when using the NAH was investigated with experiment and numerical model. From these, it is known for the error due to reflection wave can be reduced when the distance between the measurement plane and source is being shorten. Also, unmeasured area of the experimental model gives rise to some error in the estimation of the far-field acoustic pressure.

• 해양환경안전학회지
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• 제18권1호
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• pp.41-47
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• 2012

최근 국제 원유가의 폭등으로 선박의 연료비 부담이 상대적으로 가중되고 있으며, 또한 연료의 연소과정에서 발생하는 온실가스에 대한 국제적 규제 움직임도 가속되고 있다. 이와 같은 상황에서, 온실가스의 배출을 최소화하면서 연료소모량을 줄이기 위해 많은 선사들이 감속운항을 취하고 있으며, 선박용 엔진 개발 분야에서는 엔진의 연료 효율성 개선 문제와 대체에너지 사용 분야에 주력하고 있다. 따라서, 본 연구에서는 실제 해상에서의 선속대비 연료소모량을 계측하고, 건조과정에서 실시된 육상 엔진실험 자료와 2007~2009년까지의 AB-LOG를 분석하여, 특정 외력조건에서의 대상선박에 대한 연료소모량을 고려한 최적의 속력을 14~15노트, 주기관의 RPM을 140~150 RPM으로 제안하였다.

• 수산해양기술연구
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• 제27권1호
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• pp.83-90
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• 1991

현존하는 세장선 이론과는 아주 다르게 Kelvin 소오스와 그의 궤적 주위에 대한 점근전개를 행하여 전진 운동을 하는 세장체에 대한 공식을 유도하였다. 여기서 발전된 공식은 기본적으로 Neumann-Kelvin 문제의 Kernel함수에 대한 근사와 동등하게되었다. 경계치 문제는 현저하게 단순화되었으며 해는 선수 끝에서 시작하는 축차적분의 진행 절차에 따라 얻어졌다. 속도장과 압력분포는 2차원 속도 포텐시열의 미분에 의해 간단히 계산될 수 있었다. 이 방법은 비록 컴퓨터의 사용에는 Neumann-Kelvin문제처럼 많은 시간이 필요하게 되더라도 선체 주위의 유동장의 수치해석에 더욱 정확하리라는 가능성을 준다. 전진하는 진동 세장체의 문제에도 같은 방법이 유용하리라는 것을 또한 기대한다.

• 대한조선학회논문집
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• 제48권3호
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• pp.254-259
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• 2011

The first Korean-made icebreaking research vessel "ARAON" had her second sea ice trial in the Arctic Ocean in Aug. 2010 after her first voyage to Antarctic Ocean in Jan. 2010 to gather various material and strength characteristics of sea ice. This is a detail report of ARAON 2010 summer Arctic voyage and this paper describes a standard test procedure to obtain proper sea ice data which provide basic information to estimate ice loads and icebreaking performance of the ship. The data gathered from sea ice in the Chukchi Sea and Beaufort Sea during the Arctic voyage of the ARAON includes ice temperature/salinity and the compressive/flexural strength of sea ice. This paper analyses the gathered sea ice data in comparison with data from the first voyage of the ARAON during her Antarctic Sea ice trial.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2006년도 춘계학술발표회
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• pp.41-45
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• 2006

From the 1978 Seasat synthetic aperture radar(SAR) to present systems, spaceborne SAR has demonstrated the capability to image the Earth's ocean and land features over broad areas, day and night, and under most weather conditions. The application of SAR for surveillance of commercial fishing grounds can did in the detection of illegal fishing activities and provides more efficient use cf limited aircraft or patron craft resources. In the area of vessel traffic monitoring for commercial vessels, Vessel Traffic Service (VTS) which uses the ground-based radar system has some difficulties in detecting moving ships due to the limited detection range cf about 10 miles. This paper introduces the field testing results of ship detection by RADARSAT SAR imagery, and proposes a new approach for a Vessel Monitoring System(VMS), including VTS, and SAR combination service.

• Journal of Welding and Joining
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• 제28권2호
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• pp.27-31
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• 2010

Generally, angle pieces at the corners of cargo tank of membrane type LNG carrier ship are manually welded, due to their various shapes and positions. In this study, a GTA welding robot system was developed in order to improve productivity, which consists of a 7-axis manipulator, a system controller, a GTA welding power source, and peripheral devices. The welding system is characterized by capabilities of welding corrugated work pieces as well as 90/135 degree linear work pieces, and controlling the entire weld cycle automatically. The developed system was field tested on actual work pieces and its performance was proven to be successful.

• 제어로봇시스템학회논문지
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• 제14권2호
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• pp.118-124
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• 2008

Recently fishing industry is interested in efficiency and automation to acquire the international competitive power of national fishing industry. As an automation device of fishing boat, there are electric compasses using GPS and terrestrial magnetic sensor. Electric compass can be minimum size, high effectiveness with keeping the characteristic of a magnetic compass. This can be used a heading angle sensor to construct auto-navigation system in a small size ship. This paper develop electronic compass system that has serial output signal in NMEA 0183 and demonstrates the possibility of the electronics compass in navigation system for a small sized ship.

• 한국항해학회지
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• 제22권2호
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• pp.89-98
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• 1998

In the field of research of seakeeping quality, much development has been made incent years using the method of calculation based on the strip theory. It is indispensable to grasp quantitatively the seaworthiness of a ship in order to draw correct design at initial stage and to perform proper operations at sea services. In this paper, the responses of three fishing vessels are calculated using statistical and spectral analyzing method to get the characteristics of the motion response. From the theoretical result we know that the significant values of the pitching and rolling motion can be signiicantly affected by not only the ship's tonnage but also the mean wave period in spite of the similar sea environment. So we can apply these expected results to the safe maneuvering and fishing operations in rough weather conditions by combining environmental circumstance with the stability condition of vessels.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2007년도 춘계학술발표회
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• pp.127-132
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• 2007

From the 1978 Seasat synthetic aperture radar(SAR) to present systems, spaceborne SAR has demonstrated the capability to image the Earth's ocean and land features over broad areas, day and night, and under most weather conditions. The application of SAR for surveillance of commercial fishing grounds can aid in the detection of illegal fishing activities and provides more efficient use of limited aircraft or patrol craft resources. In the area of vessel traffic monitoring for commercial vessels, Vessel Traffic Service (VTS) which uses the ground-based radar system has some difficulties in detecting moving ships due to the limited detection range of about 10 miles. This paper introduces the field testing results of ship detection by RADARSAT SAR imagery, and proposes a new approach for a Vessel Monitoring System(VMS), including VTS, and SAR combination service.