• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4507-4513
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• 2013

The developing unmanned underwater equipment can be used for underwater construction site such as underwater leveling works. If a optical camera is applied to the unmanned underwater equipment, recognition in underwater can be gone to low due to high turbidity in working field. To overcome this problem, a sonar will be installed to the unmanned underwater equipment. In this study, the resolution of the sonar and the quality test of the sonar image under high turbidity environment were conducted. And the method to indicate the boundary of the underwater construction site was proposed. By these results, the basic performance of the sonar was evaluated.

• Journal of the Institute of Convergence Signal Processing
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• v.21 no.3
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• pp.133-141
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• 2020

In this paper, the communication method of data information accepted by underwater drones and the implementation method to console display of data information were described, and the function of integrated monitoring system interface and the design and implementation of sonar interface were explained. The operation and posture of underwater drones can be controlled using a controller connected to the console, and the distance information between underwater drones and obstacles is obtained from sonar so that they can be visually displayed on the console screen along with camera images. The integrated monitoring navigation console is implemented to suit improvements, making it convenient and easy for workers to use. In addition, by upgrading integrated monitoring and control software functions, the company added user-specific project management functions and the output of reports for hull inspection to make them different and competitive from other underwater drones.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.22 no.2
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• pp.127-135
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• 2004

The calibration of lens to be used and the planning of photographing planning layout is very important to achieve the requested accuracy in the precision measurement by close-range photogrammetry. Establishment of absolute coordinate system is regarded as another important factor for the purpose of measuring absolute deformation of photogrammetric object. In this study, the following tasks were performed : (1) calibration of super-wide-angle lens or focal length 21mm fer close-range photographing used by 35mm metric camera, (2) development of the measuring system for monitoring of absolute deformation through periodic observation of small area, and, (3) application of this system to monitor the absolute deformation of surface of underwater structure in fixed cycle and to present the efficiency of the system.

• The Journal of the Acoustical Society of Korea
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• v.42 no.3
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• pp.233-242
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• 2023

In this paper, the effect of mass injection on the control of tip vortex cavitation was studied experimentally. A mass injection system for a 3D hydrofoil was designed to control the location of injection as well as the injection rate. A series of cavitation tests were carried out in a cavitation tunnel for different injection locations and rates. The cavitation behaviour was observed using a high-speed camera and the corresponding noise was measured using a hydrophone installed in the observation window. The results showed that the tip vortex cavitation was suppressed under certain conditions and the noise was reduced in some frequency bands. It was also found that there is a location where the effect of mass injection could be maximized and hence the noise reduction.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.1
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• pp.25-31
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• 1999

A real-time holography system using LCD with CCD camera is proposed. In this system, the rainbow hologram is used since it can be reconstructed by white light source. And to record on CCD camera, a kind of in-line holography method is used to widen the width of the fringe pattern. The interference fringe pattern by proposed system is detected with CCD camera and transferred to the LCD. A 3-dimensional image is reconstructed when the white light source illuminates the LCD. If the position of the input image is changed, that of the reconstructed image is also changed. So it can represent 3-dimensional moving images at real-time. In this paper, to confirm the usefulness of the proposed method, the reconstructed image by holographic film is compared to the same reconstructed image by LCD. In the recording process, the optimal ratio of the reference and object beam intensity is also investigated.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.2
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• pp.146-152
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• 2011

Underwater CCTV camera systems are increasingly replaced the traditional net approach of assessing the species, numbers and aggregation patterns of marine animals distributing around the artificial reefs installed in the inshore fishing grounds, in particular, in relation to the biological investigation of behavior and distribution patterns of target fishes. In relation to these needs, we developed a multi-directional underwater CCTV camera system to use in detecting and tracking marine animals in the artificial reef ground. The marine targets to be investigated were independently tracked by using a camera module toward the bottom and four camera modules installed in the interval of $90^{\circ}$ in horizontal plane and inclination of $45^{\circ}$ in vertical plane of the CCTV system without the overlap of video frames by each camera module. From the results of several field tests at sea, we believe that the developed multi-directional underwater CCTV camera system will contribute to a better understanding in evaluating the effect of artificial reefs installed in the inshore fishing grounds.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.3
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• pp.266-272
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• 2013

The objective of this study was to monitor and evaluate the schooling characteristics, including the distribution density (volume backscattering strength) and acoustic size (target strength), of commercially valuable species swimming in response to artificial reefs installed at Suyeong Man, Busan, Korea. Fish aggregations at two artificial reef areas and at a nearby natural rocky reef habitat were recorded and analyzed using a 70 kHz split-beam echo sounder and 330 kHz side-scan sonar from August to September, 2006. An underwater CCTV camera system was also used to observe marine organisms in physical contact with and swimming very close to artificial reefs. During the acoustic observations at three reef sites, useful information about schooling characteristics of fish aggregations responding to artificial reefs were obtained, but more trials are needed to confirm significant differences in schooling behavior and geographical distributions in areas containing natural reef structures and artificial reefs.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.4
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• pp.181-190
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• 2014

The underwater acoustic lens system is one of the systems getting high-resolution images on the seafloor by the beam forming method using acoustic lens. The beam forming using acoustic lenses reduces complexity and driving power. When receiving an incoming beam with the acoustic lens array, beam pattern analysis and arrangement problem of the array sensor must be addressed. Introducing SIR (Signal to Interference Ratio), the relationship among sensor interval, beam pattern and image quality would be analyzed. Generally if the sensor interval getting wider, the less effect of the side lobes makes SIR high. If the amplitude of a side lobe is high, SIR is generally getting low. The type of the apodization function changes the width, shape and amplitude of both main lobe and side lobes. Thus an appropriate apodization function can improve SIR. In this paper, SIR is stable at the sensor interval of 13mm with 0-10dB, which is not high relatively. By applying the Chebyshev function, the SIR becomes 80dB over the sensor interval of 37 mm or higher. The Hann and triangular functions demonstrate better SIR when the sensor interval becomes narrower.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1616-1621
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• 2006

하천 지형은 흐름과 유사거동에 의한 세굴 또는 퇴적에 의하여 끊임없이 변한다. 이 연구에서는 최근 하천지형의 변화가 크게 일어나고 있는 한강 신곡수중보 직하류 우안의 고수부지 형성 이력에 대한 조사 및 분석을 실시하였다. 조사결과, 1981년 이전까지 하중도(제주초도)가 안정된 형태로 존재하였으나, 1980년대 중반을 거치면서 하중도는 소멸되었고 1990년대 중반 이후부터 우안에 비슷한 규모의 고수부지가 생성되었음을 알 수 있었다. 이 고수부지의 형성과정을 평가하면 다음과 같다. 1) 초기단계(흐름 변화에 따른 이동사주의 정지): 1995년 이전까지는 하천 내 자연적/인위적 교란에도 불구하고 이열사주 형태의 이동상이 유지되다가 1995년 이후 1988년 준공된 신곡수중보의 직.간접적인 영향을 받는다. 이로 인한 하중도의 소멸이 가중되면서부터 신곡수중보 직하류 우안의 이동사주가 정지하기에 이른다. 2) 성장단계(조석에 따른 부유사 반복 퇴적): 이동상 사주가 정지된 뒤 매일 2회씩 반복되는 조석의 영향을 받은 고농도의 부유사가 정지된 사주 위에 반복되어 퇴적되는 양상이 일어난다. 3) 정착단계(정지사주의 고수부지화): 정지사주에서 부유사가 퇴적하고 갈대와 같은 초본류 식생이 활착하게 되면서 부유사 퇴적은 가중되어 간다. 이러한 과정에서 1999년과 같은 대홍수 때 부유사의 고수부지 내 퇴적이 결정적이었을 것이다. 4) 확장단계(고수부지 확장단계): 대홍수 때 고수부지의 퇴적과 아울러 산재하던 버드나무가 교란을 받아 고수부지에서 새로운 버드나무 군락의 터전을 이루어 밀생하게 된다. 향후 고수부지가 잠기는 규모의 홍수가 빈발할 경우 퇴적층의 유실보다는 부유사 퇴적이 많아져 고수부지는 확장단계에 접어들게 된다.70{\sim}90$ 시간 동안 실험을 수행하였다. 세굴의 측정은 투명한 아크릴로 제작된 수제 내부에 CC카메라를 수제 전 후면 및 측면에 설치하여 월류수제의 세굴 발생을 실시간으로 측정하며 동시에 수제의 각 면에 각각 3개의 압력센서를 설치하여 압력분포를 측정함으로써, 월류수제 주변의 압력변화에 따른 세굴심의 실시간 변화를 비교할 수 있도록 하였다. 수심이 연중 $25{\sim}35m$를 유지하는 H호의 경우 간헐식 폭기장치를 가동하는 기간은 물론 그 외 기간에도 취수구의 심도를 표층 10m 이하로 유지 할 경우 전체 조류 유입량을 60% 이상 저감할 수 있을 것으로 조사되었다.심볼 및 색채 디자인 등의 작업이 수반되어야 하며, 이들을 고려한 인터넷용 GIS기본도를 신규 제작한다. 상습침수지구와 관련된 각종 GIS데이타와 각 기관이 보유하고 있는 공공정보 가운데 공간정보와 연계되어야 하는 자료를 인터넷 GIS를 이용하여 효율적으로 관리하기 위해서는 단계별 구축전략이 필요하다. 따라서 본 논문에서는 인터넷 GIS를 이용하여 상습침수구역관련 정보를 검색, 처리 및 분석할 수 있는 상습침수 구역 종합정보화 시스템을 구축토록 하였다.N, 항목에서 보 상류가 높게 나타났으나, 철거되지 않은 검전보나 안양대교보에 비해 그 차이가 크지 않은 것으로 나타났다.의 기상변화가 자발성 기흉 발생에 영향을 미친다고 추론할 수 있었다. 향후 본 연구에서 추론된 기상변화와 기흉 발생과의 인과관계를 확인하고 좀 더 구체화하기 위한 연구가 필요할 것이다.게 이루어질 수 있을 것으로 기대된다.는 초과수익률이 상승하지만, 이후로는 감소하므로, 반전거래전략을 활용하는 경우 주식투자기간은 24개월이하의 중단기가 적합함을

• Ocean and Polar Research
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• v.27 no.3
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• pp.335-339
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• 2005

The underwater positioning system is important in interpreting data that are acquired from towing vehicles such as the deep-sea camera (DSC) system. Currently, several acoustic positioning systems such as long baseline (LBL), short baseline (SBL), and ultra short baseline (USBL), are used for underwater positioning. The accurate position of DSC, however, could not be determined in a R/V Onnuri unequipped with any of these underwater positioning systems. As an alternative, the DSC position was estimated based on the topography of towing track and cable length in the cruises before 1999. The great uncertainties, however, were found in the areas of flat bottom topography. In the 2003 and 2004 cruises these uncertainties were reduced by calculating the position of DSC with the cable length and seafloor depth below the vessel. The Japanese cruises for Mn-nodule used a similar estimation method for the DSC positioning system with a CTD sensor. Although the latter can provide better information for the position of DSC, the USBL underwater positioning system is strongly recommended for establishing better positioning of DSC and other towing devices.