• Title/Summary/Keyword: Draft depth

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A Feasibility Study on Introduction of Information Security Disclosure (정보보안 공시제도 도입을 위한 타당성 분석과 운영체계 제언)

  • Jun, Hyo-Jung;Kim, Tae-Sung
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.22 no.6
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    • pp.1393-1405
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    • 2012
  • This study intends to help establishing guidelines on providing easier access to security status-related information about business and public institutions by interested parties such as investors and civic societies, and to push ahead with the compulsory execution of the information security disclosure. We suggest a draft for the information disclosure system by reviewing the existing disclosure systems and validate the draft by surveying experts. It is expected that the result of this study will be the basis for the adoption of the information security disclosure system and be used as a referential material in the establishment of the relevant policy.

An Experimental Study on Ship-Bank Hydrodynamic Interaction Forces (선박에 작용하는 측벽영향에 관한 실험적 연구)

  • Lee, Chun-Ki
    • Journal of Navigation and Port Research
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    • v.37 no.3
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    • pp.251-256
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    • 2013
  • This paper is mainly concerned with the ship-bank interaction by model test. The experiments for the characteristics of hydrodynamic interaction forces and moments between vessel and bank with a mound were carried out in the seakeeping and maneuvering basin. A series of tests were carried out with ship model in parallel course along a vertical sidewall with a mound with varying lateral spacing between model ship and sidewall, length of sidewall and water depth. From the experimental results, it indicated that the hydrodynamic interaction effects increase as length of sidewall with a mound increases. Furthermore, for lateral spacing less than about 0.2L between vessel and bank, it can be concluded that the bank effects increase largely as the lateral spacing between vessel and bank decreases. However, for spacing between vessel and bank more than about 0.3L, the interaction effects increase slowly as lateral spacing decreases. Also, for the water depth to draft ratio(h/d) less than about 1.5, the hydrodynamic interaction effects increase dramatically as h/d decreases.

Numerical study of hydrodynamic interaction on a vessel in restricted waterways

  • Lee, Chun-Ki
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.4 no.1
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    • pp.1-8
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    • 2012
  • The hydrodynamic interaction between ship and bank can't be neglected when a vessel is app- roached toward the tip of a wedge-shaped bank in restricted waterways, such as in a harbor, near some fixed obstacles, or in a narrow channel. In this paper, the characteristic features of the hydrodynamic interaction acting on a slowly moving vessel in the proximity of a wedge-shaped bank are described and illustrated, and the effects of water depth and the spacing between ship and wedge-shaped bank are summarized and discussed based on the slender body theory. From the theoretical results, it indicated that the hydrodynamic interactions decrease as wedge-shaped bank of angle ${\beta}$ in-creases. For water depth to draft ratio less than about 2.0, the hydrodynamic interactions between ship and bank in-crease sharply as h/d decreases, regardless of the wedge-shaped bank of angle ${\beta}$. Also, for lateral separation more than about 0.2L between ship and wedge-shaped bank, it can be concluded that the bank effects decrease largely as the separation increases.

The Finite Depth Effect on the Ship Motion in Longitudinal Regular Head Waves (종규칙파중(縱規則波中)에서 수심(水深)이 선체운동(船體運動)에 미치는 영향(影響))

  • J.H.,Hwang;S.J.,Lee
    • Bulletin of the Society of Naval Architects of Korea
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    • v.12 no.2
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    • pp.59-66
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    • 1975
  • Recently, as the dimensions of energy carriers increase, especially in draft, a reliable prediction of the ship motions at finite depths of water becomes necessary. The purpose of this paper is to probe the effect of finite water depth on the hydrodynamic forces and ship motions, particularly heave and pitch, in longitudinal regular head waves, by comparing the experimental value of Freakes and Keay with the author's theoretical value obtained by applying the modified strip theory to the Mariner class ship. It is confirmed that generally the hydrodynamic coefficients in the equations of motion increase with decreasing water depth, and the wave exciting forces and moments decrease with decreasing water depth. Amplitudes of heave and pitch in longitudinal regular head waves decrease as the water depth in the range where the length of the incident wave is comparatively long. The effects of Froude Number on the hydrodynamic coefficients increase with decreasing water depth and is more noticeable in the case of heave than pitch. In heave, generally the discrepancy between the experimental value and the theoretical value is relatively small in the case of $F_n=O$, but it is very large in the case of $F_n=0.2$. It is considered that the trend stems from the ignorance of the three dimensional effect and the other effects due to shallowness of water on the hydrodynamic coefficients in the theoretical calculation. An extension of methods for calculating the two dimensional hydrodynamic forces to included the effect of forward speed should be recommended. It is required that more experimental works in finite water depths will be carried out for correlation studies between the theoretical calculation, according tp modified strip theory, and model experiments.

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Estimation of maneuvering characteristic of training ship Baek-Kyung according to water depth (수심에 따른 실습선 백경호의 조종성능 추정)

  • Chun-Ki LEE;Kyung-Jin RYU;Yoo-Won LEE;Su-Hyung KIM
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.59 no.3
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    • pp.261-263
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    • 2023
  • Recently, universities of fisheries and institutions related to fisheries are actively carrying out a project to build new fisheries training ships. These new fisheries training ships are significantly larger in size and longer in length than the previous ships. In addition, these new ships basically have space that can accommodate more than 100 crew and passenger. On the other hand, they are excluded from IMO maneuverability evaluation since the size of these ships are still less than 100 m in length (LBP). These results have had an impact on the study of maneuverability of fishing vessels including the fisheries training ships. Against these backgrounds, the authors conducted a study to estimate the maneuvering characteristics of fisheries training ship Baek-Kyung according to depth in order to prepare a maneuvering characteristic index that enables the large fisheries training ships to navigate more safely using a modified empirical formula. It was confirmed that the maneuvering characteristics of Baek-Kyung changed significantly as the values of the hydrodynamic force coefficients changed as the water depth gradually decreased from around 1.5 (approx. 8 m in depth) of the ratio of the water depth to the ship draft. The results of this study will not only help navigators understand the maneuvering characteristics of Baek-Kyung, but also serve as an indicator when navigating in shallow water. In addition, the accumulation of these results will serve as a basis for future study on maneuverability of fishing vessel types.

Reduction of UKC for Very Large Tanker and Container Ship in Shallow Water

  • Lee, Sang-Min
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.27 no.3
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    • pp.409-420
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    • 2021
  • The decrease in under keel clearance (UKC) due to the increase of draft that occurs during advancing and turning of very large vessels of different types was analyzed based on computational fluid dynamics (CFD). The trim change in the Duisburg test case (DTC) container ship was much smaller than that of the KRISO very large crude oil carrier 2 (KVLCC2). The sinkage of both ships increased gradually as the water depth became shallower. The amount of sinkage change in DTC was greater than that in KVLCC2. The maximum heel angle was much larger for DTC than for KVLCC2. Both ships showed outward heel angles up to medium-deep water. However, when the water depth became shallow, an inward heel was generated by the shallow water effect. The inward heel increased rapidly in very shallow water. For DTC, the reduction ratio was very large at very shallow water. DTC appeared to be larger than KVLCC2 in terms of the decreased UKC because of shallow water in advancing and turning. In this study, a new result was derived showing that a ship turning in a steady state due to the influence of shallow water can incline inward, which is the turning direction.

A Study on Design Guidelines of Learning Analytics to Facilitate Self-Regulated Learning in MOOCs

  • PARK, Taejung;CHA, Hyunjin;LEE, Gayoung
    • Educational Technology International
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    • v.17 no.1
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    • pp.117-150
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    • 2016
  • The purpose of this study was to develop design guidelines on the learning analytics which can help to promote students' self-regulated learning (SRL) strategies in MOOCs learning environments. First of all, to develop the first draft of design guidelines, relevant literature review and case analysis on current MOOCs platforms such as edX, K-MOOC, Coursera, Khan Academy and FutureLearn were conducted. Then, to validate the design guidelines, expert reviews (validation questionnaires and in-depth interviews) and learner evaluation (in-depth interviews) were conducted. Through the recursive validation, the design guidelines were finalized. Overall, the final version of design guidelines on learning analytics to facilitate SRL strategies was suggested. The final design guidelines consist of 15 items in 10 categories related to the information analyzed based on individual student's learning behaviors and activities on MOOCs environments. Moreover, the results of interview also revealed that the social comparisons, learning progress reports, and personalization might contribute to the improvements of their SRL competences. This study has an implication that MOOCs could offer a higher success or completion rate to students with low SRL skills by taking advantage of the information on learning analytics

A Simulation Study on the Improvement of the Entrance Channel of Masan Harbour (마산항 출입 항로의 개선 방안에 관한 시뮬레이션 연구)

  • 김환수
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.3 no.1
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    • pp.15-31
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    • 1997
  • This work aims at examining the navigational safety of the entrance channels of Masan harbour and suggesting the way to improve ships' navigational safety through the channels. It has been found, from the on-scene investigation of the navigational safety at Masan, that the depth of the Budo-Sudo channel is not deep enough to cater for the largest vessel visiting the harbour, and that the No.2 navigational channel is not wide enough for the vessel. An additional new waterway, therefore, has been recommended to be established in the south of the Budo-Sudo channel so that the deep draft vessel can detour. The No.2 navigational channel has been recommended to be widen. The width of the channel was suggested to be 280 meters. A waterway design simulation methodology has been applied to examine the safety of the newly suggested channels. New channels have been proved to be safe from the experiment.

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A Study on Upstream Waves for an Advancing Arbitrary Hull Shape in Restricted Water Channel

  • Kim, Sung-Young;Lee, Young-Gill
    • Journal of Ship and Ocean Technology
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    • v.4 no.2
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    • pp.24-37
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    • 2000
  • The purpose of this paper is to study the upstream waves in front of an advancing arbitrary hull shape in a restricted water channel. Conventionally, in a restricted water channel, shallow water effects are amplified because of the finite water depth and width. When the effects of shallow water and the restricted channel width are severe, upstream waves propagate forward from the fore-body of the advancing hull. In this study, numerical simulations are carried out for the relevant analysis of the flow phenomena by the draft variation of advancing hull in a restricted water channel. Numerical simulations are done with a finite-difference method based on the MAC scheme in a rectangular grid system.

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Quay Mooring Aanlysis for a Drillship in Typhoon Conditions (드릴쉽의 태풍 시 안벽 계류 해석)

  • Park, Moon-Kyu;Cho, Jin-Woog;Chung, Jin-Hyun
    • Special Issue of the Society of Naval Architects of Korea
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    • 2011.09a
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    • pp.70-74
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    • 2011
  • This paper describes the quay mooring analysis to verify the safety of a moored drillship in typhoon conditions. Mooring system consists of mooring equipments(deck bollards, shore bitts, mooring lines, fenders) to resist the extreme environmental condition. Wind force acting on the drillship is obtained from the wind tunnel test results. The strength of quay mooring system has been checked. The static mooring analysis shows that the designed mooring system satisfies the mooring design criteria. Vertical displacements of the drillship have been calculated considering the dynamic wave motions and static heelings due to the wind force acting on the ship. With the vertical displacements and the hull draft of drillship, the required water depth for quay mooring has been derived.

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