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Chinhae, South Korea

Lee S.E.,Pusan National University | Kim B.J.,Pusan National University | Seo J.K.,Pusan National University | Ha Y.C.,Pusan National University | And 4 more authors.
Ships and Offshore Structures | Year: 2015

This is a sequel to a previous paper by the same authors, which proposed a probabilistic approach to determine the nominal values of tank sloshing loads in the structural hull design of liquefied natural gas, floating production, storage and offloading units (LNG FPSO or FLNG). This study presents a procedure for the numerical computation of nonlinear impact responses in FLNG cargo tank structures under sloshing loads. The computations are performed using ANSYS/LS-DYNA nonlinear finite element software. Applied examples using a hypothetical FLNG are presented. The insights and conclusions obtained from the study are documented. © 2015 Taylor & Francis.

Jeong H.,STX Offshore and Shipbuilding Co. | Hwang J.,Korea Aerospace University | Kwon S.J.,Korea Aerospace University
Journal of Institute of Control, Robotics and Systems | Year: 2010

In the flat panel display and semiconductor industries, the visual alignment system is considered as a core technology which determines the productivity of a manufacturing line. It consists of the vision system to extract the centroids of alignment marks and the stage control system to compensate the alignment error. In this paper, we develop a Kalman filter algorithm to estimate the alignment mark postures and propose a coarse-fine alignment control method which utilizes both original fine images and reduced coarse ones in the visual feedback. The error compensation trajectory for the distributed joint servos of the alignment stage is generated in terms of the inverse kinematic solution for the misalignment in task space. In constructing the estimation algorithm, the equation of motion for the alignment marks is given by using the forward kinematics of alignment stage. Secondly, the measurements for the alignment mark centroids are obtained from the reduced images by applying the geometric template matching. As a result, the proposed Kalman filter based coarse-fine alignment control method enables a considerable reduction of alignment time. © ICROS 2010.

Park T.G.,Changwon National University | Kim J.M.,Changwon National University | Yoon H.Y.,Changwon National University | Lee J.H.,Changwon National University | And 2 more authors.
Journal of Korean Institute of Metals and Materials | Year: 2010

The charpy impact property was lower at the surface and middle regions than that at the root region in metal welded by Tandem EGW of 82 mm thick EH40-TM steel plates. Temperature distribution in the weld sample and the heating/cooling temperature throughout the various regions in the weld metal were estimated by the commercial weld simulation program SYSWELD. The microstructure of the weld metal consisted of acicular ferrite and grain boundary ferrite. Grain boundary ferrite in the acicular ferrite matrix was found more in the surface and middle regions than in the root region, and the acicular ferrite was also coarser in the surface and middle regions where the impact toughness was lower and the input temperature was higher. Our results indicated that the impact toughness property was related to the microstructure morphology, the distribution of grain boundary ferrite, and the acicular ferrite.

Kwon S.-H.,Catholic University of Korea | Kim T.-W.,Seoul National University | Choi H.I.,Seoul National University | Moon H.P.,Dongguk University | And 3 more authors.
CAD Computer Aided Design | Year: 2011

We present a blind watermarking scheme for rational Bézier and B-spline curves and surfaces which is shape-preserving and robust against the affine transformations and Mbius reparameterization that are commonly used in geometric modeling operations in CAD systems. We construct a watermark polynomial with real coefficients of degree four which has the watermark as the cross-ratio of its complex roots. We then multiply the numerator and denominator of the original curve or surface by this polynomial, increasing its degree by four but preserving its shape. Subsequent affine transformations and Mbius reparameterization leave the cross-ratio of these roots unchanged. The watermark can be extracted by finding all the roots of the numerator and denominator of the curve or surface: the cross-ratio of the four common roots will be the watermark. Experimental results confirm both the shape-preserving property and its robustness against attacks by affine transformations and Mbius reparameterization. © 2011 Elsevier Ltd. All rights reserved.

Nam J.-H.,Korea University | Kim D.-H.,STX Offshore and Shipbuilding Co.
Journal of Ship Production | Year: 2010

Ships use the ballast system to maintain stability. The ballast system greatly influences loading capacity and navigation of a ship as well as the ocean environment. Therefore, it is necessary to select an adequate ballast system not only to increase the efficiency of ship operation but also to protect the ocean from undesirable results of current ballasting process. The ship ballast system can be optimized by performance during the period of ship design and production. Until now most shipbuilders have implemented a ballast system based on similar data from previously built ships or experts' knowledge. If previous ballast data is unavailable, however, it is necessary to determine the most appropriate ballast system by trial-and-error. To have an efficient ship design and production process, this time-consuming and expensive bottleneck should be avoided. In this paper, a ballast simulation system that predicts the ballasting and deballasting processes using a computer model is introduced. The amount of fluid flowing through a ballast system is analyzed considering friction losses in the pipe's inner walls, junctions, and valves. The developed system uses the graphic user interface approach for convenient interaction between the user and the system. The results of real-time simulation will help the user to foretell the ballasting process with efficiency and accuracy.

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