• Special Issue of the Society of Naval Architects of Korea
• /
• 2006.09a
• /
• pp.53-58
• /
• 2006

When the vibration troubles occur on the ship structure during the sea trial, the rectification work is very restricted because of in-situ limitation. Usually the finite element method is used to improve vibration characteristics of the structure, but it takes lots of time and effort in modeling the structure and adjusting the finite element model in order to consider appropriate boundary conditions of a complex ship structure. Therefore, experimental methods have been in general suggested to obtain proper countermeasures without time-consuming in modeling. In this paper, FRF(frequency response function) synthesis method is applied to estimate natural frequency of the modified ship structure, which is obtained from experimental and numerical methods.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.10
• /
• pp.486-492
• /
• 2019

The system-based approach is needed to select an optimal mix of weapon systems and ship platform among a variety of design alternatives with the uncertainties of the initial required operational capability. In the early-phase design, which included a feasibility study and concept design, it is possible to cause problems when a review of the operational concept, database development, and systematic design are not done, thereby producing uncertain and unstable requirements. To select the best solution without trial-and-error, the U.S. navy has applied the set-based method for the early-phase design of a new ship-to-shore connector. The ship synthesis model plays an important role in applying the set-based method, but only a few countries possess this model and have prohibited this model from being transferred to other countries. This paper suggests a set-based method using a genetic algorithm and decision-making theory through benchmarking existing ship data. The algorithm was verified using the DDG-51 class ship synthesis model to optimize the weapon system design, which has been released for research purposes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.176-180
• /
• 2006

When the vibration troubles occur on the ship structure during the sea trial, the rectification work is very restricted because of in-situ limitation. Usually, the finite element method is used to improve vibration characteristics of the structure, but it takes lots of time and effort in modeling the structure and adjusting the finite element model in order to consider appropriate boundary conditions of a complex ship structure. Therefore, experimental methods have been in general suggested to obtain proper countermeasures without time-consuming in modeling. In this paper, FRE(frequency response function) synthesis method is applied to estimate natural frequency of the modified ship structure, which is obtained from experimental and numerical methods.

• Journal of Internet Computing and Services
• /
• v.19 no.4
• /
• pp.35-44
• /
• 2018

Monitoring through Synthesis Aperture Radar (SAR) is responsible for marine safety from floating icebergs. However, there are limits to distinguishing between icebergs and ships in SAR images. Convolutional Neural Network (CNN) is used to distinguish the iceberg from the ship. The goal of this paper is to increase the accuracy of identifying icebergs from SAR images. The metrics for performance evaluation uses the log loss. The two-layer CNN model proposed in research of C.Bentes et al.[1] is used as a benchmark model and compared with the four-layer CNN model using data augmentation. Finally, the performance of the final CNN model using the VGG-16 pre-trained model is compared with the previous model. This paper shows how to improve the benchmark model and propose the final CNN model.

• Proceedings of KOSOMES biannual meeting
• /
• 2006.11a
• /
• pp.137-141
• /
• 2006

To consider the practical use of a ship's Digital Compass in earth's magnetic field high accurate Deviation and 얘 nation are required to obtain ship's true bearing. Variation can be obtain with World Magnetic Model (WMM) using the Earth's spherical harmonic model of the main field and of the secular variation at any location around the earth. Deviation can be obtain with deviation analysis and synthesis method based on the Poisson equations. As results of deviation and variation corrections to the Digital Compass, high accurate true bearing is obtained. This experiments are carried out during in the navigation of training ship 'SAE-NU-RI'.

• Journal of Ship and Ocean Technology
• /
• v.5 no.1
• /
• pp.14-29
• /
• 2001

Concept and preliminary structural design methods, including large scale FEM analysis and optimisation, for large passenger ships, car passenger and RoRo/ passenger ships are dis-cussed. Applications and experiences in practical design usage are presented.

• Journal of the Society of Naval Architects of Korea
• /
• v.30 no.3
• /
• pp.116-126
• /
• 1993

The finite element method(FEM) has been commonly used for structural dynamic analysis. However, the direct global application of FEM to large complex structures such as ships and offshore structures requires considerable computational efforts, and remarkably more in structural dynamic optimization problems. Adoption of the component-mode synthesis method is an efficient means to overcome the above difficulty. Among three classes of the component-mode synthesis method, the free-interface mode method is recognized to have the advantages of better computational efficiency and easier implementation of substructures' experimental results, but the disadvantage of lower accuracy in analytical results. In this paper, an advanced method to improve the accuracy in the application of the free-interface mode method for the vibration analysis of large complex structures is presented. In order to compensate the truncation effect of the higher modes of substructures in the synthesis process, both residual inertia and stiffness effects are taken into account and a frequency shifting technique is introduced in the formulation of the residual compliance of substructures. The introduction of the frequency shrift ins not only excludes cumbersome manipulation of singular matrices for semi-definite substructural systems but gives more accurate results around the specified shifting frequency. Numerical examples of typical structural models including a ship-like two dimensional finite element model show that the analysis results based on the presented method are well competitive in accuracy with those obtained by the direst global FEM analysis for the frequencies which are lower than the highest one employed in the synthesis with remarkably higher computational efficiency and that the presented method is more efficient and accurate than the fixed-interface mode method.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.5
• /
• pp.93-102
• /
• 2020

The design of large complex mechanical systems, such as automobile, aircraft, and ship, is a kind of Multidisciplinary Design Optimization (MDO) because it requires both experience and expertise in many areas. With the rapid development of technology and the demand to improve human convenience, the complexity of these systems is increasing further. The design of such a complex system requires an integrated system design, i.e., MDO, which can fuse not only domain-specific knowledge but also knowledge, experience, and perspectives in various fields. In the past, the MDO relied heavily on the designer's intuition and experience, making it less efficient in terms of accuracy and time efficiency. Process integration and the design optimization framework mainly support MDO owing to the evolution of IT technology. This paper examined the procedure and methods to implement an efficient MDO with reasonable effort and time using RCE, an open-source PIDO framework. As a benchmarking example, the authors applied the proposed MDO methodology to a bulk carrier's conceptual design synthesis model. The validity of this proposed MDO methodology was determined by visual analysis of the Pareto optimal solutions.