• Journal of the Society of Naval Architects of Korea
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• v.32 no.4
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• pp.123-135
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• 1995

A numerical procedure is described for predicting steady drift forces an multiple three-dimensional bodies of arbitrary shape freely floating in waves. The developed numerical approach is based on combination of a three-dimensional source distribution method, wave interaction theory art the far-field method using momentum theory. Numerical results are compared with the experimental or numerical ones, which are obtained in the literature, of steady drift forces on 33(3 by 11) floating composite vertical cylinders in waves. The results of comparison confirmed the validity of the proposed approach. Finally, the interaction effects are examined in the case of an array of 40(4 by 10) freely floating rectangular bodies in shallow water.

• Journal of the Korean Data and Information Science Society
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• v.25 no.1
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• pp.119-130
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• 2014

This paper is based on water information system of NIE, National Institute of Environmental Research. We used monthly data of water quality from January, 2013 to August, 2013 starting from measuring point A (nbA) to measuring point N (nbN) located along the Nakdong river main stream. Statistical water quality analysis of BOD (biological oxygen demand) is specified by R programming depending on month, year, and points. Based on BOD measured from Nakdong river's measuring points, we used exploratory data analysis and locally weighted scatter plot smoother (Lowess) trend analysis, which is a method of non-parametic regression analysis, to analyze long-term water tendency and water quality distribution depending on points. Also, we analyzed the period and the measuring point of which the outliers are abundant. As a result, compared to BOD measured in nbM located in Busan along the downstream, BOD measured in nbG located in Daegu and nbI located in Changwon along the midstream showed higher rate of water pollution at a severe level.

• Journal of Periodontal and Implant Science
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• v.33 no.4
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• pp.739-745
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• 2003

Interleukine-1(IL-1)은 여러 가지 기능을 가진 싸이토카인으로써 미생물에 대한 면역반응을 일으킨다. IL-1의 유전자 다형성과 치주질환과의 관련성에 대한 많은 연구가 있어왔지만, 대부분이 백인을 대상으로 한 연구였다. 이후 중국인과 일본인을 대상으로 한 연구에서 IL-1의 유전자 다형성의 분포가 인종간에 차이를 보인다는 점이 발견되었다. 이번 연구에서는 치주적으로 건강한 한국인에서 IL-1${\beta}$-511, IL-1${\beta}$+3954, IL-1RN에 대한 유전자형의 분포를 조사하고자 하였다. 서울대학교 치과병원에 근무하는 치과의사, 치과위생사, 간호조무사 및 서울대학교 치과대학 4학년 학생 중 치주낭 깊이와 부착소실이 4mm 이하인 치주적으로 건강한 한국인 65명을 대상으로 하였다. IL-1${\beta}$-511, IL-1${\beta}$+3954, IL-1RN의 유전자 다형성은 분리한 DNA에 각 대립유전자에 특이성을 지닌 primer를 넣고 PCR(Polymerase Chain Reaction)법을 이용하여 증폭시킨후 전기영동법을 이용하여 각 대립유전자의 존재를 확인함으로써 결정하였다. IL-1${\beta}$-511 대립유전자 11, 대립유전자 12, 대립유전자 22의 유전자형에 대하여 각각 23.1%, 49.2%, 26.2%의 분포를 보였다. IL-1${\beta}$+3954의 유전자 다형성은 대립유전자 11, 대립유전자 12의 유전자형에 대하여 각각 89.2%, 10.8%의 분포를 보였으며, 대립유전자 22의 유전자형을 갖는 사람은 한명도 발견되지 않았다. IL-1RN의 유전자형은 5가지의 대립유전자 중에서 1, 대립유전자 2, 대립유전자 4만일 발견되었으며, 대립유전자 11, 대립유전자 12, 대립유전자 14의 유전자형이 86.2%, 12.3%, 1.5%로 분포하였다. 이를 바탕으로 각 대립유전자의 발생빈도 계산한 결과 IL-1${\beta}$-511에서는 대립유전자 1과 2의 비율이 거의 유사하였으나 (47.7%, 52.3%), IL-1${\beta}$+3954, IL-1RN에서는 대립유전자 1이 90%이상 발견되었으며, 또한 대립유전자 1외의 다른 대립유전자가 발견된 경우, 모두 이형접합체였다. 이 연구는 IL-1${\beta}$-511, IL-1${\beta}$+3954, IL-1RN에 대한 유전자형의 분포를 조사한 것으로 한국인에서 이들 유전자의 유전자형의 분포는 백인에서의 분포와 차이를 보이고 있었다. 이후 치주질환자의 유전자형 분포와의 비교로 치주질환과 IL-1${\beta}$-511, IL-1${\beta}$+3954, IL-1RN의 유전자다형성과의 관련성에 관한 추가적인 연구가 필요할 것으로 여겨진다.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.3
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• pp.31-40
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• 2001

Low-order panel methods are being used to design marine propellers. Since the potential value over each panel for these methods is assumed to be a constant, the accuracy of prediction is known to be limited. Therefore, a higher order boundary element method(HOBEM) has been studied to enhance the accuracy of prediction. In this paper, a HOBEM representing the body boundary surfaces and physical quantities by a 9-node Lagrangian shape function is employed to analyse the flow around marine propellers in steady potential flow. First, the numerical results for a circular wing with thickness variations are compared with Jordan's linear solution. Then, the computational results of two propellers(DTRC 4119 & DTRC 4842 propeller) are compared with the experimental and numerical results published. The pressure distribution on the surface of the propeller is also compared with experimental data.

• Journal of Ocean Engineering and Technology
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• v.21 no.4
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• pp.38-44
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• 2007

The structural response characteristics of Tension leg platforms(TLPs) in waves are examined for presenting the basic data for structural design of TLPs. The numerical approach is based on a combination of the three dimensional source distribution method and the structural response analysis method, in which the superstructure of TLP is assumed to be flexible instead of rigid. Hydrodynamic and hydrostatic forces on the submerged surface of a TLP have been accurately calculated by excluding the assumption of the slender body theory. The hydrodynamic interactions among TLP members, such as columns and pontoons, and the structural damping are included in structural analysis. The mooring forces are estimated as the sum of pretension of tendons and variational tension due to longitudinal displacements. Stiffness matrices of elastic beam elements connecting nodes are formulated by ordinary method of three dimensional frame analysis. The equation of motion about the whole structure is obtained by the sum of forces and moments acting on each nodes.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.3
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• pp.195-201
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• 2001

The time simulation of slow drift motions of moored FPSO in waves is presented. The equation of motion based on Cummin's theory of impulse responses are employed, and are consisted of horizontal plane motions such as surge, sway and yaw. The added mass, wave damping coefficients, first order wave exciting forces and the second order wave drift forces involved in the equations are obtained from three-dimensional panel method in the frequency domain. The mooring lines are modeled as quasi-static catenary cable. As a numerical example, time domain analyses are carried out for a box-type FPSO in long crest irregular wave condition.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.17-22
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• 2011

This study conducted wide-tank experiments and numerical calculations for a vessel in various positions such as upright and inclined by 2 and 4 degrees, with the goal of investigating the motion amplitude response of a small damaged fishing boat subject to a beam sea. Numerical calculations were conducted based on the three-dimensional source distribution method. The good agreement of the numerical calculation and experimental results confirmed that the present calculation method can be efficiently used for the initial design of a small fishing boat. In addition, while the chine-line type has been frequently adopted to improve a ship's resistance performance in the design of a small fishing boat, it is considered that the possibility of a deterioration in rolling performance should be thoroughly considered.

• Journal of the Korean Institute of Navigation
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• v.14 no.4
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• pp.41-52
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• 1990

Due to the constantly varying sea-state with which any wave energy conversion device must contend in order to extract energy efficiently , the ability to control the device's position relative to the incident waves is critical in achieving the creation of a truly functional and economical wave energy device. In this paper, the authors will propose methodology based on the theory of a variable structure system to utilize a three dimensional source distribution as a model to estimate anticipated surge, sway and yaw of a wave energy conversion device relative to varying angles and characteristics of incident waves and there from derive a feedback to a sliding mode controller which would reposition the device so as to maximize its ability to extract energy from waves in constantly varying ocean conditions.

• Journal of Navigation and Port Research
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• v.29 no.10 s.106
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• pp.839-845
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• 2005

A rudder roll control system is developed and analyzed to control the yawing and rolling motion of ship in irregular waves. The 4-DOF maneuvering equations of motion are derived to carry out the simulation of the motion of a ship and the wave forces are considered as the external forces of a ship in the simulation. The wave forces in the time domain analysis are generated from the frequency transfer function calculated by 3-D source distribution method. The rudder roll control system is developed by linear combination of PD rudder controllers of yawing and rolling motion. Rudder rate speed and Schilling rudder are considered to increase the roll reduction efficiency.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.55-61
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• 2005

A rudder roll control system is developed and analyzed to control yawing and rolling motion of ship in irregular waves. The 4-DOF maneuvering equations of motion are derived to carry out the simulation of the motion of a ship and the wave forces are considered as the external forces of a ship in the simulation. The wave forces in the time domain analysis are generated from the frequency transfer function calculated by 3-D source distribution method. The rudder roll control system is developed by linear combination of PD rudder controllers of yawing and rolling motion Rudder rate speed and Schilling rudder are considered to increase roll reduction efficiency.