• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.540-543
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• 2013

선박은 판과 보강재를 효율적으로 조립한 매우 복잡한 구조물이고, 이동하는 구조물로써는 최대규모의 구조물이다. 특히, 선체 구조의 설계란 "예상되는 모든 하중에 충분히 견딜 수 있는 강도(strength)와 강성(stiffness)을 가진 부재의 크기를 결정하고 적절히 배치하는 과정이다." 라고 말할 수 있다. 선체 구조의 설계는 부재의 배치가 얼마나 적절하게 잘되어 있는가에 달려 있다고 하여도 과언이 아닐 정도로 매우 중요하다. 주요 구조 부재의 부재 배치에 대한 기본적인 개념은 판 부재의 용접선(seam line), 종, 횡늑골의 간격, 종거어더 등을 예로 들 수 있으며, 부재의 배치는 최적 설계 및 공작상의 관점으로부터 선정되어야 하며, 또한 선체 전체의 구조적인 연결이 불연속이 되지 않도록 하여야 한다. 특히, 판 부재의 용접선은 여러 가지 표준치수로 생산되는 판 들 중, 판의 기준 폭이 얼마인 것을 사용하는 것이 공작상 또는 배치상 가장 편리한 가를 생각하여야 한다. 이것은 선박의 크기에 따라 다르겠지만, 조선소 크레인의 용량 및 가공상, 강도상의 문제를 고려하여 가능한 한용접선의 수를 줄이는 것이 바람직하다. 용접선을 줄이기 위해서는 판 부재의 폭을 넓게 하면 되나, 철강회사에서 표준으로 생산 판매하는 주판의 폭보다 넓은 판을 주문 구입 한다는 것은 곧 생산비용의 증가로 이어지는 것으로 이는 주판 구입 경비 측면에서는 바람직하지 않다. 따라 서, 주판 구입경비의 최소화를 유도하면서도 주판 폭의 적정 및 용접선 개수 최소화를 유지할 수 있도록 설계하는 것은 중요하지만, 용접선 배치의 문제는 다양한 입력 변수를 고려해야 하는 복잡한 문제이기 때문에 그간 최적화 관점에서 접근하지 못하고 시니어급 엔지니어가 가진 경험과 조선소의 지침서에 기재된 절차에 따라 대략적인 해를 결정하여 왔다. 본 연구는 이러한 복잡한 문제를 최적화 방법인 당금질(Simulated Annealing) 방법을 이용하여 해결한 결과를 소개하며, 그 결과와 효용성에 대해 논하도록 하겠다.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.102-114
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• 2021

Biofouling represents an important problem in the shipping industry since it causes the increase in surface roughness. The most of ships in the current world fleet do not have good coating condition which represents an important problem due to strict rules regarding ship energy efficiency. Therefore, the importance of the control and management of the hull and propeller fouling is highlighted by the International Maritime Organization and the maintenance schedule optimization became valuable energy saving measure. For adequate implementation of this measure, the accurate prediction of the effects of biofouling on the hydrodynamic characteristics is required. Although computational fluid dynamics approach, based on the modified wall function approach, has imposed itself as one of the most promising tools for this prediction, it requires significant computational time. However, during the maintenance schedule optimization, it is important to rapidly predict the effect of biofouling on the ship hydrodynamic performance. In this paper, the effect of biofilm on the ship hydrodynamic performance is studied using the proposed performance prediction method for three merchant ships. The applicability of this method in the assessment of the effect of biofilm on the ship hydrodynamic performance is demonstrated by comparison of the obtained results using the proposed performance prediction method and computational fluid dynamics approach. The comparison has shown that the highest relative deviation is lower than 4.2% for all propulsion characteristics, lower than 1.5% for propeller rotation rate and lower than 5.2% for delivered power. Thus, a practical tool for the estimation of the effect of biofouling with lower fouling severity on the ship hydrodynamic performance is developed.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.2
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• pp.94-103
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• 1998

Recently, many researches are carried for high-speed and light craft. In this study, the optimum structural design procedure and the computer program are developed to minimize the hull weight of SES(Surface Effect Ship) built of composite materials. Three types of composite materials-Sandwich, Single Skin and Hybrid type- are considered and the efficiency of each type is investigated. In design process, the optimum design of main members is performed at first considering longitudinal strength. And then, the transverse member design is performed considering torsional strength SSDP(Structural Synthesis Design program) of U.S. Navy is adopted for design algorithm and DnV classification nile for design loads and strength criteria. For optimum structural design, ES 1+1 optimization technique is used.

• Bulletin of the Korean Mathematical Society
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• v.48 no.3
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• pp.523-537
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• 2011

A receiver operating characteristic (ROC) curve plots the true positive rate of a classier against its false positive rate, both of which are accuracy measures of the classier. The ROC curve has several interesting geometrical properties, including concavity which is a necessary condition for a classier to be optimal. In this paper, we study the nonparametric maximum likelihood estimator (NPMLE) of a concave ROC curve and its modification to reduce bias. We characterize the NPMLE as a solution to a geometric programming, a special type of a mathematical optimization problem. We find that the NPMLE is close to the convex hull of the empirical ROC curve and, thus, has smaller variance but positive bias at a given false positive rate. To reduce the bias, we propose a modification of the NPMLE which minimizes the $L_1$ distance from the empirical ROC curve. We numerically compare the finite sample performance of three estimators, the empirical ROC curve, the NMPLE, and the modified NPMLE. Finally, we apply the estimators to estimating the optimal ROC curve of the variance-threshold classier to segment a low depth of field image and to finding a diagnostic tool with multiple tests for detection of hemophilia A carrier.

• International Journal of CAD/CAM
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• v.6 no.1
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• pp.3-8
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• 2006

The application of three-dimensional (3-D) CAD has been popularized for design and production and digital manufacturing has been spreading in many industrial fields. By simulation of the production process using 3-D digital models, which are the core of CIM (Computer Integrated Manufacturing) system, the efficiency and safety of production are improved at each stage of work, and optimization of manufacturing can be achieved. This paper firstly describes the concept of "simulation based production" in shipbuilding and also digital manufacturing; the 3-D CAD system is indispensable for effective simulation because ship structure is three dimensionally complex. By simulation, "computer optimized manufacturing" can be possible. The most effective fields of simulation in shipbuilding are in jobs where many parties have to cooperate, while existing two-dimensional drawings are hardly observed the whole structures due to interference between structures or equipment of complex shape. In this paper some examples of the successful application in IHIMU (IHI Marine United Inc.) are shown: assembly of a pipe unit, erection of a complex hull block, carriage of equipment, installation of a propeller, and access in an engine room.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.3
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• pp.184-192
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• 2014

The resistance of a high speed monohull can be dramatically increased at the high speed range due to the severe stern trim, spray formation and hull bottom pressure irregularity etc. In order to avoid these demerits associated with this resistance increase, various appendages such as the stern wedge, vertical wedge, stern flap, spray strip etc. have been studied. Each of appendage can control the trim angle and/or improve the resistance performance. If these appendages are combined for finding the maximal resistance reduction, there are enormous combination selections. This paper presents the DOE(Design of experiment) using an orthogonal array in order to decrease the model tests finding the optimum appendage combination. And we evaluate that the method introduced in this paper makes the optimal combination of appendages efficient and time-saving by applying to high speed semi-planing monohull. Here, the maximum speed and the least fuel expense are adopted as the decision criteria.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.1
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• pp.48-58
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• 2002

There is a purpose of this study for the proposal of the optimum technique utilized for the vibration design initial step. The stiffened plate structure for the ship hull is made for analysis model. To begin with, dynamic characteristics of stiffened plate structure is analysed using FEM. Main vibrational mode of the structure is decided in the analytical result of FEM. The simplified equation on the natural frequency of the main vibrational mode is induced. Next, sensitivity analysis is carried out using the simplified equation, and rate of change of dynamic characteristics is calculated. Then, amount of design variable is calculated using this sensitivity value and optimum structural modification method. The change of natural frequency is made to be an objective function. Thickness of panel, cross section moment of stiffener and girder become a design variable. The validity of the optimization method using simplified equation is examined. It is shown that the result effective in the optimum modification for natural frequency of the stiffened plate structure.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.3
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• pp.103-111
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• 1996

A generalized slope deflection method has already been developed by the authors from the existing one, and applied to the 3-dimensional structural analysis of tankers idealized as frame models to verify the effectiveness of the method from the analysis viewpoint. In this study, a minimum hull weight design program of tankers is developed to verify the effectiveness of the method from the design viewpoint by the combination of generalized slope deflection method and optimization method considering discrete design variables. By this program, it is possible to determine the scantling of each member of actual tankers that give minimum weight under given constraints. Also, a considerable weight saving has been found compared with existing ship.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.2
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• pp.138-147
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• 2014

This paper proposed an application of expert system to submarine arrangement design. Since all components of the submarine should be placed in a restricted place called pressure hull, expert knowledge has great effects on design of submarine arrangement. In this regard, a suitable knowledge-based expert system shell was applied to design of submarine arrangement process. To use expert system on the design of submarine arrangement effectively, a template model for submarine arrangement, which is proper to use in optimum design process, was developed. The proposed system was applied to simplified example of submarine arrangement problem to choose optimal design alternative. From this study, it was verified that expert system could be used in design of submarine arrangement with effect.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.2
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• pp.178-182
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• 2011

Generally in order to reduce the steel weight of stiffened plate, stiffener spaces tend to be narrow and the plate gets thin. However, it will involve more fabrication cost because it can lead to the increase of welding length and the number of structural members. In the yard, the design which is able to reduce the total fabrication cost is needed, although it requires more steel weight. The purpose of this study is to find optimum stiffener spaces to minimize the fabrication cost for the cargo tank of LPG Carriers. Global optimization methods such as ES(Evolution Strategy) and GA(Genetic Algorithm) are introduced to find a global optimum solution and the sum of steel material cost and labor cost is selected as main objective function. Convergence degree of both methods in according to the size of searching population is examined and an efficient size is investigated. In order to verify the necessity of the optimum design based on the cost, minimum weight design and minimum cost design are carried out.