• 대한조선학회논문집
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• 제57권1호
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• pp.52-59
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• 2020

This study aims to investigate the bow thruster performance of the research vessel "NARA" by full-scale maneuvering trials. The thruster test method refers to ITTC's recommended procedures and guidelines. Turning tests with the bow thruster are performed at speed conditions of 0, 2, and 4 knots. The test results indicate that the Rate of Turn (ROT) increased when the ship is in a higher speed condition. Due to the position of the propeller and the housing of the bow thruster, there is difference in the efficiency of the bow thruster according to the turning direction. Zigzag tests with the bow thruster were conducted at speed conditions of 2 and 4 knots. At speeds above 4 knots, it seems difficult to change the course only with the bow thruster.

• 대한조선학회논문집
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• 제42권4호
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• pp.350-356
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• 2005

Prediction of green water loads acting on the bow deck is au essential part for the design of bow structures against the green water impact. Proper technique of the green water simulation is highly required for the prediction of green water loads. in this paper, the green water flow on bow deck is simulated by FDM(finite difference method). Using the results of green water simulation, impact load on bow deck is calculated. Also, experiments are carried out to compare with the numerical calculation. Through the comparisons between experimental results and numerical results, it is verified that the present numerical tool is adequate as a practical calculation tool for the green water problem.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2018년도 춘계 종합학술대회 논문집
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• pp.7-8
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• 2018

본 연구에서는 Word2vec을 머신러닝 분류기를 이용해 효율적인 오피니언 마이닝 방법을 제안한다. 본 연구의 목적을 위해 BOW(Bag-of-Words) 방법과 Word2vec방법을 이용해 속성 셋을 구성했다. 구성된 속성 셋은 Decision tree, Logistic regression, Support vector machine, Random forest를 이용해 오피니언 마이닝을 수행했다. 연구 결과, Word2vec 방법과 RF분류기가 가장 높은 정확도를 나타냈다. 그리고 Word2vec 방법이 BOW방법 보다 각 분류기에서 높은 성능을 나타냈다.

• 대한조선학회논문집
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• 제49권1호
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• pp.79-86
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• 2012

It is very important to investigate and understand the motion of a FPSO on waves because green water phenomenon occurs owing to the relative motions between incident waves and a ship on them. In this research, both experimental and some numerical approaches have been performed in head sea conditions with regular waves. As an object model of this research, a FPSO model is set free to heave and pitch during the experiments. Also, the motions of the FPSO model which are the results of the experiments are used for the corresponding numerical computations. The purpose of this study is to clarify the effect of bow flare on green water load. In this research, it is found that the amount of green water entered from the side of bow is decreased by the increase of bow flare angle. Moreover, the relation between the green water on the bow upper deck and the impact load on the vertical wall located at turrethead is investigated. The results of this research could be used as one of the fundamental data to design bow flares. Also, an optimized bow flare angle is proposed in this study.

• 한국가스학회지
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• 제17권3호
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• pp.33-38
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• 2013

화학공장은 다량의 화학물질을 사용하기 때문에 사고가 발생하면, 많은 피해가 발생한다. 따라서 사고를 예방하기 위하여 위험성평가를 실시하고 있다. 화학공정은 HAZOP 기법을 이용하여 위험성평가를 실시하고 그 결과를 많이 활용하고 있다. 이 연구에서는 HAZOP 기법과 Bow-Tie 기법을 분석하고, Bow-Tie 위험성평가를 수행하였으며, 그 결과 다른 위험성평가에서 발견할 수 없었던 위험성이 도출되었고, 그 위험성을 제거하기 위한 14개의 개선사항이 도출되었다. Bow-Tie 위험성평가가 현장의 적용성과 위험요인을 도출하고 개선대책을 수립하는데 적합하다는 것을 확인하였다.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1485-1494
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• 2023

The bow of the nuclear fuel assembly is a well-known phenomenon. One of the vital criteria during the history of nuclear fuel development has been fuel assembly's mechanical stability. Once present, the fuel assembly bow can lead to safety issues like excessive water gap and power redistribution or even incomplete rod insertion (IRI). The extensive bow can result in assembly handling and loading problems. This is why the fuel assembly's bow is one of the most often controlled geometrical factors during periodic fuel inspections for VVER when compared e.g. to on-site fuel rod gap measurements or other instrumental measurements performed on-site. Our proposed screening method uses existing video records for fuel inspection. We establish video frames normalization and aggregation for the purposes of bow measurement. The whole process is done by digital image processing algorithms which analyze rotations of video frames, extract angles whose source is the fuel set torsion, and reconstruct torsion schema. This approach provides results comparable to the commonly utilized method. We tested this new approach in real operation on 19 fuel assemblies with different campaign numbers and designs, where the average deviation from other methods was less than 2 % on average. Due to the fact, that the method has not yet been validated during full scale measurements of the fuel inspection, the preliminary results stand for that we recommend this method as a complementary part of standard bow measurement procedures to increase measurement robustness, lower time consumption and preserve or increase accuracy. After completed validation it is expected that the proposed method allows standalone fuel assembly bow measurements.

• 한국안전학회지
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• 제39권2호
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• pp.75-86
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• 2024

Hydrogen has been selected as one of the key technologies for reducing CO₂ emissions to achieve carbon neutrality by 2050. However, hydrogen safety issues should be fully guaranteed before the commercial and widespread utilization of hydrogen. Here, a bow-tie risk assessment is conducted for the hydrogen fuel supply system in a gas turbine power plant, which can be a mass consumption application of hydrogen. The bow-tie program is utilized for a qualitative risk assessment, allowing the analysis of the causes and consequences according to the stages of accidents. This study proposed an advanced bow-tie method, which includes the barrier criticality matrix and visualized maps of quantitative risk reduction. It is based on evaluating the importance of numerous barriers for the extent of their impact. In addition, it emphasizes the prioritization and concentrated management of high-importance barriers. The radar chart of a bow tie allows the visual comparison of risk levels before/after the application of barriers (safety measures). The risk reduction methods are semi-quantitatively analyzed utilizing the criticality matrix and radar chart, and risk factors from multiple aspects are derived. For establishing a secure hydrogen fuel storage system, the improvements suggested by the bow-tie risk assessment results, such as 'Ergonomic equipment design to prevent human error' and 'Emergency shutdown system,' will enhance the safety level. It attempts to contribute to the development and enhancement of an efficient safety management system by suggesting a method of calculating the importance of barriers based on the bow-tie risk assessment.

• 대한두개안면성형외과학회지
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• 제11권1호
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• pp.19-22
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• 2010

The author presents a new method for the formation of Cupid's bow and the vermilion tubercle by using the inferior-based lip skin flap in a secondary bilateral cleft lip deformity. The length of the flap includes the entire length of the previous upper lip scar. Both skin flaps are elevated and turned down toward the central part of the vermilion. The distant portion of the turned-down skin flaps are deepithelialized and trimmed according to the new shape of Cupid's bow. The deepithelialized portions of both flaps are buried under the central vermilion mucosa in order to create the vermilion tubercle. The advantages of the proposed procedure are; provision of a more natural shape of Cupid's bow, the lip length is increased, and the vermilion tubercle can be reconstructed at the same time. Therefore, this technique is best suited for a case of a bilateral absence of Cupid's bow combined with a short lip in a sufficient upper lip of a bilateral cleft lip deformity. The proposed procedure, however, should be avoided in the tight upper lip because of a great deal of tension on the donor.

• 한국항해학회지
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• 제17권1호
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• pp.37-48
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• 1993

When the vessel is running at the very low Froude numbers, the free-surface is difficult to be disturbed, wave-making is negligible, and the double -model velocity potential gives a very good approximation for calculating the velocity distribution just outside the boundary layer. If the speed of incident flow is gradually increased, the most perceptible change is the rise of the flow surface at stem. With further increase in speed, the nature of the flow at the bow changes completely, The flow ahead of the bow becomes more distrubed, the rise at the stem to stagnation height disappear, and the first wave crest, of less than the stagnation height, appears a small distance downstream from the stem. The present study is concerned with a small region of this flow, mainly in the bow region. The present investigation is primarily an experimental study of the flow in the bow region of s ship model, and it is undertaken in order to investigated systematically, the effect of bow geometry on this flow. The long-range objective is to use these results to guide the development of a mathematical model for predicting the flow about a ship's bow.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 춘계학술대회 논문집
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• pp.195-204
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• 2000

In this paper a complicated structural behavior in collision and its effect of energy translation to the collision bulkhead was examined through a methodology of the numerical simulation to obtain a ideal bow construction and a location of collision bulkhead against head on collision. In the present the bow structure is normally designed in consideration of its specific structural arrangements and internal and external loads in these area such as hydrostatic and dynamic pressure, wave impact and bottom slamming in accordance with the Classification rules, and the specific location of collision bulkhead by SOLAS requirement. By these studies the behavior of the bow collapse due to collision was synthetically evaluated for the different size of tankers and its operational speed limits, and by the result of these simulation it provides the optimal design concept for the low construction to prevent the subsequent plastic deformation onto or near to the collision bulkhead boundary and to determine the rational location of collision bulkhead.