• Title, Summary, Keyword: 선저검사

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A Study on Underwater Camera Image Correction for Ship Bottom Inspection Using Underwater Drone (수중드론을 활용한 선박 선저검사용 수중 카메라 영상보정에 대한 연구)

  • Ha, Yeon-chul;Park, Junmo
    • Journal of the Institute of Convergence Signal Processing
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    • v.20 no.4
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    • pp.186-192
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    • 2019
  • In general, many marine organisms are attached to the bottom of a ship in operation or a ship in construction. Due to this phenomenon, the roughness of the ship surface increases, resulting in loss of ship speed, resulting in economic losses and environmental pollution. This study acquires / utilizes camera images attached to ship's bottom and underwater drones to check the condition of bottom. The acquired image will determine the roughness according to marine life by the administrator's visual confirmation. Therefore, by applying a filter algorithm to correct the image to the original image can help in the correct determination of whether or not attached to marine life. Various correction filters are required for the underwater image correction algorithm, and the lighting suitable for the dark underwater environment has a great influence on the judgment. The results of the research test according to the calibration algorithm and the roughness of each algorithm are considered to be applicable to many fields.

Modeling and Tracking Simulation of ROV for Bottom Inspection of a Ship using Component Drag Model (요소항력모델을 활용한 선저검사용 ROV 모델링 및 트래킹 시뮬레이션)

  • Jeon, MyungJun;Lee, DongHyun;Yoon, Hyeon Kyu;Koo, Bonguk
    • Journal of Ocean Engineering and Technology
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    • v.30 no.5
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    • pp.374-380
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    • 2016
  • The large drift and angle of attack motion of an ROV (Remotely operated vehicle) cannot be modeled using the typical hydrodynamic coefficients of conventional straight running AUVs and specific slender bodies. In this paper, the ROV hull is divided into several simple-shaped components to model the hydrodynamic force and moment. The hydrodynamic force and moment acting on each component are modeled as the components of added mass force and drag using the known values for simple shapes such as a cylinder and flat plate. Since an ROV is operated under the water, the only environmental force considered is the current effect. The target ROV dealt with in this paper has six thrusters, and it is assumed that its maneuvering motion is determined using a thrust allocation algorithm. Tracking simulations are carried out on the ship’s surface near the stern, bow, and midship sections based on the modeling of the hydrodynamic force and current effect.

A Study on the Ultimate Strength Behavior for Ship Perforated Stiffened Plate (선체 유공보강판의 최종강도 거동에 관한 연구)

  • Ko Jae-Yong;Lee Jun-Kyo;Park Joo-Shin;Bae Dong-Kyun
    • Proceedings of KOSOMES biannual meeting
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    • pp.141-146
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    • 2005
  • Ship have cutout inner bottom and girder and floor etc. Ship's structure is used much, and structure strength must be situated, but establish new concept when high stress interacts sometimes fatally the area. There is no big problem usually by aim of weight reduction, a person and change of freight, piping etc. Because cutout's existence grow up in this place, and, elastic buckling strength by load causes large effect in ultimate strength. Therefore, stiffened perforated plate considering buckling strength and ultimate strength is one of important design criteria which must examine when decide structural concept at initial design. Therefore, and, reasonable buckling strength about perforated stiffened plate need to ultimate strength limited design . Calculated ultimate strength varied several web height and cutout's dimension, and thickness in this investigated data. Used program(ANSYS) applied F.E.A code based on finite element method.

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Development of Designed Formulae for Predicting Ultimate Strength of the Perforated Stiffened Plate subjected to Axial Compressive Loading (압축하중을 받는 유공보강판 구조의 최종강도 설계식 개발)

  • Park, Joo-Shin;Ko, Jae-Yong;Lee, Kyung-Hwan
    • Journal of Navigation and Port Research
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    • v.31 no.5
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    • pp.435-445
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    • 2007
  • Ship structures are thin-walled structures and lots of cutouts, for example, of inner bottom structure, girder, upper deck hatch, floor and dia-frame etc. In the case where a plate has cutout it experiences reduced buckling and ultimate strength and at the same time the in-plane stress under compressive load produced by hull girder bending will be redistributed. In the present paper, we investigated several kinds of perforated stiffened model from actual ship structure and series of elasto-plastic large deflection analyses were performed to investigate into the influence of perforation on the buckling and ultimate strength of the perforated stiffened plate varying the cutout ratio, web height, thickness and type of cross-section by commercial FEA program(ANSYS). Closed-form formulas for predicting the ultimate strength of the perforated stiffened plate are empirically derived by curve fitting based on the Finite Element Analysis results. These formulas are used to evaluate the ultimate strength, which showed good correlation with FEM results. These results will be useful for evaluating the ultimate strength of the perforated stiffened plate in the preliminary design.

Characteristic of Buckling and Ultimate Strength of the Perforated Stiffened Plate (유공보강판의 좌굴 및 극한강도 특성에 관한 연구)

  • Park Joo-Shin;Ko Jae-Yong;Oh Kyoung-Gun
    • Journal of Navigation and Port Research
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    • v.30 no.6
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    • pp.439-446
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    • 2006
  • In ship structures many of the structural plates have cutouts, for example, at inner bottom structure, girder, upper deck hatch, floor and dia-frame etc. In the case where a plate has a cutout it experiences reduced buckling and ultimate strength and at the same time the in-plane stress under compressive load produced by hull girder bending will be redistributed In general, actual ship structure adopted reinforcement of stiffener around the cutout in order to preventing from buckling so it need to examine a buckling and ultimate strength behaviour considering a cutout because In many ship yards used class rule for calculating buckling strength but it is difficult to evaluate perforate stiffened plate with random size. In the present paper, we investigated several kinds of perforated stiffened model from actual ship and then was performed finite element series analysis varying the cutout ratio, web height, thickness and type of cross-section using commercial FEA program(ANSYS) under compressive load.