• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.214-214
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• 2003

During a model test of Hutton TLP, a "ringing" response was first observed about 20 years ago. This phenomenon is a resonant build up over the time of wave period and this burst-like motion can cause the extreme load on the TLP tether. It is often detected in the large and steep irregular waves but the generation mechanism leading to the "ringing" is not yet well understood. According to the research since then, the higher order harmonic components may account for the "ringing" on the floating offshore structures. The main purpose of the present research is, thus, to measure the higher harmonic forces exerted on a vertical truncated circular column and to compare them with available data. A vertical truncated cylinder with a diameter of 3.5inch and a draft of 10.5inch is used as a test structure, which is a scaled model of ISSC TLP column. The cylinder is installed at a distance of 45ft from the wave maker in order to avoid parasitic waves created in the wave flap. Attached to the upper part of the cylinder are two force gages to measure the horizontal (surge) and vertical (heave) forces on the cylinder. The incoming waves are Stokes waves with a slope ranging from 0.06 to 0.24. The forces and waves are measured for 60 seconds with a sampling rate of 50 Hz. Among the recorded data, the first 10 waves are excluded because of transient behavior of the waves and the next The horizontal and vertical forces are analyzed up to 5th order harmonics. The horizontal forces are then compared to the values from the theoretical model called "FNV model". In addition, force transfer functions are also investigated. Major findings in this research are below. 1) The first order forces measured are slightly larger than the theoretical values of "FNV model" 2) The "FNV model" considerably overpredicts the second order forces. 3) The larger the amplitude and more extreme the wave slope, the smaller the predictions are compared to the experimental. 4) The higher harmonic forces are significantly smaller than the first harmonic force for all wave parameters. 5) The normalized forces vs. waves slopes are almost constant in the lower harmonics but vary a lot in the higher harmonics. 6) The trend of forces is more nonlinear in the horizontal forces than in the vertical forces as the wave slope increases. 7) The part of the results above is also observed by other researchers and confirmed again through the present work.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.5
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• pp.375-387
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• 2023

The subsea power cables are increasingly important for harvesting renewable energies as we develop offshore wind farms located at a long distance from shore. Particularly, the continuous flexural motion of inter-array dynamic power cable of floating offshore wind turbine causes tremendous fatigue damages on the cable. As the subsea power cable consists of the helical structures with various components unlike a mooring line and a steel pipe riser, the fatigue analysis of the cables should be performed using special procedures that consider stick/slip phenomenon. This phenomenon occurs between inner helically wound components when they are tensioned or compressed by environmental loads and the floater motions. In particular, Vortex-induced vibration (VIV) can be generated by currents and have significant impacts on the fatigue life of the cable. In this study, the procedure for VIV fatigue analysis of the dynamic power cable has been established. Additionally, the respective roles of programs employed and required inputs and outputs are explained in detail. Demonstrations of case studies are provided under severely sheared currents to investigate the influences on amplitude variations of dynamic power cables caused by the excitation of high mode numbers. Finally, sensitivity studies have been performed to compare dynamic cable design parameters, specifically, structural damping ratio, higher order harmonics, and lift coefficients tables. In the future, one of the fundamental assumptions to assess the VIV response will be examined in detail, namely a narrow-banded Gaussian process derived from the VIV amplitudes. Although this approach is consistent with current industry standards, the level of consistency and the potential errors between the Gaussian process and the fatigue damage generated from deterministic time-domain results are to be confirmed to verify VIV fatigue analysis procedure for slender marine structures.

• Journal of Sasang Constitutional Medicine
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• v.9 no.1
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• pp.127-153
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• 1997

Sasang-Medicine can classify all sympton with more simple classifying system than past Oriental-Medicine, because Sasang Byeon-Zeung(=classifying system of the sympton) separate by four clearly. The merit of this Sasang Byeon-Zeung can be seen more clearly on the part of the pathology of the expiratory-scattering and inspiratory-gathering of the Tae-Eum and Tae-Yang. On this view point, this thesis discussed the following subjects. 1. Investigate the theory of raising-falling and scattering-gathering developed in the Dongeui-Suse-Bowon. 2. Investigate the changes of the recognition of the Yang-Dog sympton and Jo-Yeol sympton argued as Interior-overheating-sympton of the Tae-Eum-In caused by liver's receiving heat. 3. Investigate the Yi-Je-Ma's view on the Eum-Yang in the argument of interior-overheating-sympton of the Tae-Eum-In caused by liver's receiving heat. As a result, the following conclusions were led to. 1. Dongeui-Suse-Bowon considers Spleen-Kidney has the couple motion of the raising Yang and falling Eum, and Liver-Lung has the couple motion of the expiratory-scattering and inspiratory-gathering. This theory of raising-falling and scattering-gathering is same as in the concept with the gathering. This theory of raising-falling and scattering-gathering is same as in the concept with the theory of raising-falling and floating-sinking of past Oriental-Medicine, but more consistently systematized in the pathology and prescription. 2. Dongeui-Suse-Bowon considers the Yang-Dog sympton and Jo-Yeol sympton as the interior-overheating-sympton of the Tae-Eum-In. As following the book, the fire of desire weeken the expiratory-scattering power of the lung, and deepen the shortage of the expiratory-scattering power comparison to the inspiratory-gathering power. Therfore the sympton can be treated by releasing ourselves from the desire and taking medicine strengthening the expiratory-scattering power. 3. In the early stage of the orintal medicine, they used prescriptions composed of So-Yang medicine and Tae-Eum medicine which can cool heat. Galgeun, Mawhang and Seungma were used in the age of Sanghanron, thereafter Jugoing's Jojung-Tang and Gongsin's Galgeunhaegi-Tang were developed as prescriptions of the interior-overheating-sympton of the Tae-Eum-In, and finally Tea-Uem-In Galgeunhaegi-Tang was settled by Yi-Je-Ma.