• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.5
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• pp.1-8
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• 2008

The belief propagation method that has been studied recently yields good performance in disparity extraction. The method in which a target function is modeled as an energy function based on Markov random field(MRF), solves the stereo matching problem by finding the disparity to minimize the energy function. MRF models provide robust and unified framework for vision problem such as stereo and image restoration. the belief propagation method produces quite correct results, but it has difficulty in real time implementation because of higher computational complexity than other stereo methods. To relieve this problem, in this paper, we propose a fast algorithm of the belief propagation method. Energy function consists of a data term and a smoothness tern. The data term usually corresponds to the difference in brightness between correspondences, and smoothness term indicates the continuity of adjacent pixels. Smoothness information is created from messages, which are assigned using four different message arrays for the pixel positions adjacent in four directions. The processing time for four message arrays dominates 80 percent of the whole program execution time. In the proposed method, we propose an algorithm that dramatically reduces the processing time require in message calculation, since the message.; are not produced in four arrays but in a single array. Tn the last step of disparity extraction process, the messages are called in the single integrated array and this algorithm requires 1/4 computational complexity of the conventional method. Our method is evaluated by comparing the disparity error rates of our method and the conventional method. Experimental results show that the proposed method remarkably reduces the execution time while it rarely increases disparity error.

• Journal of Ocean Engineering and Technology
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• v.33 no.4
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• pp.350-357
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• 2019

The development of marine technology is expected to increase the demand for marine plants because of increasing oil prices. Therefore, there is also expected to be an increase in the demand for cylindrical structures such as URF (umbilical, riser, flowline) structures and spars, which are used operating in various seas. However, a cylindrical structure experiences vortex induced motion (VIM) in a current. In particular, for risers and umbilicals, it is important to identify the characteristics of the VIM because interference between structures can occur. In addition, various studies have been conducted to reduce VIM because it is the cause of fatigue damage to structures. The helical strake, which was developed for VIM reduction, has an excellent VIM reduction performance, but is difficult to install on structures and has a negative effect on heave motion. Therefore, the purpose of this study was to supplement the shortcomings of the helical strake and develop a high-performance reduction device. In the reduction device developed in this study, a string is placed around the structure inside the flow, causing vibration. The vibration of this string causes a small turbulence in the flow field, reducing the VIM effect on the structure. Finally, in this study, the 2-DOF motion characteristics of models without a suppression device, models with a helical strake, and models with a string were investigated, and their reduction performances were compared through model tests.