• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.06a
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• pp.344-346
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• 2012

대산항 씨텍 제3번 돌핀부두에 최초 설계의 접안능력기준을 약간 상회하는 5만 DWT급 VLGC 선박이 접안작업을 할 경우, 돌핀의 용량에 따른 접안작업 동안의 안전성 여부를 대산항만의 입출항 제한 자연 환경조건을 적용하여 선박 계류측면에서의 안전성을 판단하고자 한다. 이를 위하여 대상선박의 부두에서의 최악의 외력조건과 계류장력과의 관계를 OCIMF에서 연구 발표한 결과를 바탕으로 계류안전성 계산공식을 적용하여 계류안전성을 평가하도록 한다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.466-471
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• 2011

본 연구에서는 장대 현수교 주케이블의 가설시 선형관리를 위한 기초적 연구를 수행하였다. 우선, 포물선 요소 및 탄성현수선 요소의 정식화 과정을 검토하고, 각 요소의 적용에 따른 현수교 주케이블 완성계 및 가설계의 형상, 장력, 무응력장 등을 비교검토 하였다. 또한, 탄성현수선의 적용시 주케이블 가설계의 setback량 산정 방법을 제시하였으며, 이에 따른 산정 결과를 유한요소해석 결과와 비교검토 하였다. 최종적으로, 주케이블 가설계의 중앙경간 새그량 변화에 따른 탑정 새들부에서의 미끌림 안정성에 대한 민감도 해석을 수행할 예정이다.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1092-1096
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• 2009

The spectral element modeling is known to provide very accurate structural dynamic characteristics, while reducing the number of degree-of-freedom to resolve the computational and cost problems. Thus, the spectral element model with variational method for an axially moving string subjected to axial tension is developed in the present paper. The high accuracy of the spectral element model is the verified by comparing its solutions with the conventional finite element solutions and exact analytical solutions. The effects of the moving speed and axial tension the vibration characteristics, wave characteristics, and the static and dynamic stabilities of a moving string are investigated.

• Journal of the Korean Chemical Society
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• v.8 no.3
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• pp.121-124
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• 1964

Considering the molecular orientation on the first surface layer and applying the significant structure theory of liquid water proposed by the authors in the previous paper, the surface tension of liquid water is calculated for various temperatures which agree well with the observed values.

• Journal of Adhesion and Interface
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• v.2 no.3
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• pp.9-15
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• 2001

To estimate the effect of the surface state of the EVA foam on an adhesion, the surface was treated with solvents having different values of a solubility parameter and a surface tension. The morphology and the contact angle were measured by SEM and contact angle tester, respectively. The value of the critical surface tension(${\gamma}_{c,0}$) of the EVA foam calculated by Zismann plot was 27.08 dyne/cm. The surface state and the ${\gamma}_c$ of the EVA foam were changed by solvent treatment. The swelling ratio of EVA foam was influenced by solubility parameter of a solvent, on the other hand the degree of change in the surface state was dependent on a surface tension of a solvent. When a surface tension of solvent. When a surface tension of solvent is lower than ${\gamma}_{c,0}$ of the EVA foam, the wettability of a solvent was good and the surface state was greatly changed. The adhesion strength of EVA foam was greatly improved to above 600% as compared to that of the untreated one. As the ${\gamma}_c$ of EVA was closed to the surface tension of the primer, the good adhesion strength was obtained.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.75-75
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• 2010

배변 후 toilet flushing 시 다량의 세균을 포함한 물방울들이 화장실 곳곳으로 퍼지는 현상이 있다. 이러한 현상을 방지하기 위해 변기 뚜껑에 자기 세정 효과를 갖는 초발수 표면을 위해 플라즈마를 이용한 표면 처리가 시도되고 있으며, 이 연구의 일환으로 flushing시의 변기내의 유동 분석을 초고속 카메라를 이용하여 수행하였다. Toilet flushing 시 물 튀김 현상은 육안으로는 잘 관찰하기 어렵지만 최고 1000 frame/sec의 속도를 갖는 CCD camera를 이용하여 정량적으로 물 튀김에 의한 오염 가능성을 촬영 분석하였다, 두 번째로 소변 시의 변기 표면에서의 튀김현상을 분석하기 위하여 소변의 발사각도 및 속도를 가장 실제와 유사한 조건으로 설정하고 이를 상용 전산 유체 역학 소프트웨어인 CFD- ACE+의 자유 표면 계산 기능과 두 가지 유체(액체 및 기체)의 혼합 계산 모델을 사용한 계산 결과와 비교 하였다. 그 결과 변기 표면의 표면장력을 아주 작게 설정한 경우(작은 접촉각, 친수성)에는 중력의 영향을 고려하였음에도 불구하고 소변이 변기에 충돌 후 상부로 상당부분 튀어 올라가는 결과를 얻었다. 여러 가지 각도와 발사 속도, 실제의 인체와 유사한 발사 부위의 형상 변화로 인한 유체 표면의 난류 발생과 이에 따른 변기 표면 충돌 현상 변화 등을 수치적으로 고찰하였다. 한 예로 5.6 mm 직경의 노즐에서 소변이 나오는 경우를 발사 속도 3 m/s, 각도 $10^{\circ}$로 주고 중력을 고려하여 10초 동안을 계산하면, 방뇨 시 toilet bowl 내부에서의 물의 유동과 toilet 표면을 맞고 튀기는 현상을 그림 1과 같이 볼 수 있었다.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.3
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• pp.173-184
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• 2005

A capillary action-induced tension develops in the tear layer between the contact lens and cornea, which leads to the restoring force due to difference in the layer thickness between either upper and lower or left and right side of the lens when it is displaced off the equilibrium position as a result of blinking. Suppose the lens was displaced a certain distance from the equilibrium position, lens starts to oscillate toward the equilibrium position with the decreasing amplitude due to the restoring force as well as the velocity dependent viscous damping force in the tear layer. A mathematical model which consists of the differential equations and their numerical solution was proposed to analyze the damped oscillations of lenses. The model predicts the time dependence of lenses after the blink varying the various parameters such as Be, diameters, masses and positions displaced from equilibrium. As the Be and mass of lens increases the rate of amplitude reduction decreases, which requires a more time for the lens to return to the equilibrium position. It seems that varying the lens' displacement and diameters affect the lens' motion very little.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.129-136
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• 2009

The paper presents an algorithm of selecting optimal locations for measuring displacements(OLD) to adjust cable tension forces during the construction of cable-stayed bridges. The rank for optimal locations can be determined from the effective independence distribution vectors(EIDV) that are computed from the Fisher Information Matrices(FIM) formulated with the displacement sensitivities. To examine the efficiency and reliability of the proposed algorithm for determining OLD, a simulation study on a cable-stayed bridge has been carried out. The results using FIM formulated with displacements are compared with those using FIM with displacement sensitivities through the simulation study. The effects of measurement noise and error in cable length on the adjustment of cable tension forces are evaluated statistically by applying the Monte Carlo scheme.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.1
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• pp.79-91
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• 2005

The behaviors and design procedures of wale in innovative prestressed support(IPS) system are presented in this paper. Using the theory of the beam on elastic foundation, the member forces of the wale under initial pretension are evaluated. Choosing cable tensions as redundant forces, member forces subjected to earth pressure are calculated by the statically indeterminate analysis. The computer analysis model under uniform and non-uniform earth pressure is constructed using beam element for the IPS wale, tension-only element for cable, and compression-only element for soil. Axial forces and bending moments of IPS wale under initial pretension and design earth pressure are calculated. The combined stresses due to these axial force and bending moment are estimated to satisfy the design formula.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.9 no.1
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• pp.1-7
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• 1976

1) The decrease in strength of netting twines at the knot may be regarded to be due mainly to the frictional force acting on the tip of the knot. The knot strength T may be given by $$T=\frac{T_0}{1+{\mu}\frac{s}{\rho}\varrho^{\mu\theta}$$ were $T_0$ is the tensile strength of unknotted netting twines, $\mu$ the coefficient of friction beween two netting twines forming a knot, s the contact length between the tip and the netting twine compressing it, $\rho$ the radius of curvature of the compressing, and $\theta$ the angle at which the compressing rubs with another one in the vicinity of the opposite tip. 2) Knots are arranged in order of strength as follows : the reef knot pulled lengthwise $\risingdotseq$ the trawler knot pulled breadtwise the reef knot pulled breadthwise.