• International Journal of Naval Architecture and Ocean Engineering
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• 제8권6호
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• pp.589-601
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• 2016

The hybrid grid was adopted and numerical prediction analysis of propeller unsteady bearing force considering free surface was performed for mode and full-scale KCS hull-propeller-rudder system by employing RANS method and VOF model. In order to obtain the propeller velocity under self-propulsion point, firstly, the numerical simulation for self-propulsion test of full-scale ship is carried out. The results show that the scale effect of velocity at self-propulsion point and wake fraction is obvious. Then, the transient two-phase flow calculations are performed for model and full-scale KCS hull-propeller-rudder systems. According to the monitoring data, it is found that the propeller unsteady bearing force is fluctuating periodically over time and full-scale propeller's time-average value is smaller than model-scale's. The frequency spectrum curves are also provided after fast Fourier transform. By analyzing the frequency spectrum data, it is easy to summarize that each component of the propeller bearing force have the same fluctuation frequency and the peak in BFP is maximum. What's more, each component of full-scale bearing force's fluctuation value is bigger than model-scale's except the bending moment coefficient about the Y-axis.

• 한국통계학회:학술대회논문집
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• 한국통계학회 2003년도 춘계 학술발표회 논문집
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• pp.151-156
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• 2003

Variable selection algorithm for principal component analysis using penalized likelihood method is proposed. We will adopt a probabilistic principal component idea to utilize likelihood function for the problem and use HARD penalty function to force coefficients of any irrelevant variables for each component to zero. Consistency and sparsity of coefficient estimates will be provided with results of small simulated and illustrative real examples.

• 한국지반공학회논문집
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• 제19권2호
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• pp.107-121
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• 2003

중력식 안벽의 내진 안정성을 분석할 때, 중력식 안벽에 발생하는 하중성분의 크기와 위상관계를 명확히 결정하는 것이 중요하다. 일반적으로 안벽에 발생하는 하중성분은 안벽 관성력, 토압 그리고 수압으로 구성되어 있으며, 각 하중성분들의 크기와 위상관계는 배면지반에 발생하는 과잉간극수압의 크기에 따라 변한다. 벽체배면과 뒤채움 토체 사이의 접촉면에서 발생하는 동적작용력은 이러한 힘들의 상호작용에 의하여 발생한다 본 연구에서는 벽체 작용하중 산정식들로부터 구한 각 하중성분들의 크기를 조합하여 배면 동적작용력의 크기와 위상변화를 배면 과잉간극수압의 함수로써 산정하는 간단한 하중산정 모델을 제안하였으며, 진동대 실험결과와 이 모델의 예측결과를 비교하여 모델의 적용성을 검증하였다.

• 한국강구조학회 논문집
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• 제13권2호
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• pp.201-210
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• 2001

본 연구에서는 편심 축력을 받는 가셋트-강관 접합부의 극한 내력을 파악하기 위하여 실험 및 유한요소해석을 수행하였다. 가셋트-강관 접합부의 내력에 영향을 주는 요소는 강관의 직경, 가셋트판 길이, 축력과 횡력의 비, 횡력에 의한 편심 등으로 이들이 주재의 좌굴내력에 미치는 영향을 정량적으로 파악하여 접합부 강도식을 제안하였다. 특히 횡력에 의한 편심이 주재에 작용할 때 이를 설계식에 반영하기 위하여 횡력을 등가의 모멘트 및 편심 축력으로 대치한 수치 모형을 제시하였다. 결과적으로 접합부의 작용하는 외력을 주주재 축력, 모멘트, 편심 축력으로 분해하고 각 외력에 대한 독립적인 극한내력을 구한후 이들의 상관 관계식을 구함으로써 접합부 극한강도식을 제시하였다.

• 한국생산제조학회지
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• 제18권6호
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• pp.629-635
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• 2009

In this research, KP-4, one of the plastic mold steels, was coated with the AlTiN from one layer to four layers by the PVD method in the $\Phi$ 8mm cemented carbide ball end mill. Coated KP-4 was processed with various conditions. For example, slope of $15^{\circ}$, $30^{\circ}$ and $45^{\circ}$ the spindle rotation speed was changed from 10,000rpm to 16,000rpm, the tool feeding speed was changed from 1,300mm/min to 1,700mm/min, the depth of cut was also changed from 0.3mm to 0.9mm, and etc. Cutting component force according to the coating layer number, and surface roughness were studied. The cutting component force showed a good agreement better the up ward direction than the down ward direction under all experimental conditions. In case of the condition per the material shape, it was lessen when the tool have larger angle because the average effective diameter of the tool is larger. The surface roughness showed good condition in case of the up ward than the down ward direction. And, in the 3rd layer of AlTiN coating, it showed the most suitable condition.

• 대한조선학회논문집
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• 제61권1호
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• pp.29-43
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• 2024

The present study concerns a feasibility study for applying principal component analysis to ship dynamics in maneuver. Using the four degrees of freedom standard modular model for ship dynamics maneuver simulations of large angle zigzag tests with rudder deflection angle variations are conducted. The datasets of ship motion, hydrodynamic force, and moment during the maneuver are acquired to identify the principal modes. The covariance matrix of obtained ship dynamics variables shows a strong linear correlation between the motion, hydrodynamic force, and moment, except the surge force. Four eigenvectors of the covariance matrix are selected as the principal modes of ship dynamics. Using the principal modes, ship motion in turning circle and zigzag tests is reconstructed, showing good agreement with the original data.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1448-1452
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• 2003

A scratch tester was developed to evaluate the adhesive strength at interface between thin-film and substrate(silicon wafer). Under force control, the scratch tester can measure the normal and the tangential forces simultaneously as the probe tip of the equipment approaches to the interface between thin-film and substrate of wafer. The capacity of each component of force sensor is 0.1 N ${\sim}$ 100 N. In addition, the tester can detect the signal of elastic wave from AE sensor(frequency range of 900 kHz) attached to the probe tip and evaluate the bonding strength of interface. Using the developed scratch tester, the feasibility test was performed to evaluate the adhesive strength of thin-film.

• Steel and Composite Structures
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• 제4권2호
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• pp.77-94
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• 2004

Steel beam-to-column joints are often subjected to a combination of bending and axial forces. The level of axial forces in the joint may be significant, typical of pitched-roof portal frames, sway frames or frames with incomplete floors. Current specifications for steel joints do not take into account the presence of axial forces (tension and/or compression) in the joints. A single empirical limitation of 10% of the beam's plastic axial capacity is the only enforced provision in Annex J of Eurocode 3. The objective of the present paper is to describe some experimental and numerical work carried out at the University of Coimbra to try to extend the philosophy of the component method to deal with the combined action bending moment and axial force.

• 한국의류학회지
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• 제15권4호
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• pp.431-435
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• 1991

The dispersion and Poiar force components of the surface free energy of PET fibers untreated and treated with hydrophilic chemicals, such as nonionic-soil release polymer (SRP), anionic, nonionic and hydrophilic silicone, were determined using harmonic-mean and geometric-mean methods. Contact angles of water and methylene iodide on the fibers were determined from the adhesion tensions using tensiometric method. Fibers treated with hydrophilic chemicals have the increased polar force component and the decreased dispersion force component. The adhesion tensions of triolein for the hydrophilic treated fibers were smaller than that for untreated fiber.

• 한국항만학회지
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• 제10권1호
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• pp.25-36
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• 1996

Generally, it is pointed out that a nonlinear analysis is needed to estimate accurately the water surface fluctuation and dynamic responses of a floating structure in case of large wave reflection. In this study, a frequency-domain method is applied and newly developed to analyze the nonlinear characteristics of the air-chamber floating breakwater. The air-chamber floating breakwater in this study can control well the wave transformation, motions of the structure and its natural frequency by adjusting the air depth in the chamber. Experiments are carried out to verify the numerical results. It is appeared that the mean water level is setup in the anti-node and setdown in the node, while the nonlinearity in wave profile is larger in the node than in the anti-node. Because of vertical mooring system, the sway, especially the time-independent nonlinear component, plays predominant role in the motion. On the other hand, the time-dependent component, as well as the time-independent one to the tensile force of mooring line contributes greatly, and the time averaged value presents tensional force oriented to the onshore side due drift force.