• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.427-431
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• 1986

3점 굽힘 시험편, 중앙균열 인장 시험편, 콤팩트 인장 시험편에 대한 J적분식을 하나의 일반화된 형태로 유도한다. 이 일반식은 Eftis와 Liebowitz에 의해 제안된 하중과 하중점 변위 사이의 관계와 Sumpter에 의한 탄성과 소성성분 J적분의 중첩개념을 이용함으로써 유도된다. 일반식에 포함된 .eta.계수를 위 3가지 시험편에 대해서 결정한다. 위 3가지 시험편에 대한 J적분의 최종식은 하중과 하중점 변위곡선 아래의 면적을 측정하지 않아도 되는 형태로 나타난다. 본 연구의 결과식은 Landes등에 의한 실험치와 비교하여 매우 잘 일치함을 보인다.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.617-621
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• 2001

This paper presents a maximum power point tracking algorithm for Photovoltaic array using only instantaneous output current information. The conventional Hill climbing method of peak power tracking has a disadvantage of oscillations about the maximum power point. To overcome this problem, we have developed a algorithm, that will estimate the duty ratio corresponding to maximum power operation of solar cell. The estimation of the optimal duty ratio involves, finding the duty ratio at which integral value of output current is maximum. For the estimation, we have used the well know Lagrange's interpolation method. This method can track maximum power point quickly even for changing solar insolations and avoids oscillations after reaching the maximum power point.

• Journal of Ocean Engineering and Technology
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• v.9 no.2
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• pp.98-111
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• 1995

High temperature low cycle fatigue shows that cycle-dependent crack growth owing to cyclic plastic deformation occurred simultaneosly with time-dependent crack growth owing to intergranular deformation. Consequently, to estimate crack growth rate uniquely, many to investigators have proposed various kinds of parameters and theories but these could not produce satisfactory results. Therefore the goal of this study is focused on prediction of crack growth rate using predominant damage rule, linear cumulative damage rule and transitional parameter ${\Delta}J_c/{\Delta}J_f$. On the basis of these sinusoidal loading waveform at 600$^{\circ}C$ and 700$^{\circ}C$.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.555-558
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• 1991

The IESF(Integral Error and State Feedback) controller, which incorporates state feedback as a modern control scheme and integral action as a classical control scheme, has better performance than that of the conventional PID controller in linear time-invariant systems. The IESF controller requires the measurement of all the state variables. But, unfortunately, it may be difficult or impossible to measure all state variables in many applications. And the IESF controller is applicable only to pole-assignable linear time-invariant system without time delay. In this paper, new IESF controller structure was proposed which performs feedback with only measurable state variables. In order to estimate the unmeasurable state variables. It was adopted the filter mode by full-order obserber. The good performance and effectiveness of the proposed controller was confirmed by computer simulation.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.1
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• pp.51-59
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• 1998

The purposes of the paper are to consider the failure phenomenon based on delamination and crack when the encapsulant of plastic IC package under hygrothermal loading in the IR soldering process is on elastic and viscoelastic behavior due to the temperature and to show the optimum design using fracture mechanics. The model for analysis is the plastic SOJ package with a dimpled diepad. The package model with the perfect delamination between chip and diepad is chosen to estimate the resistance to fracture by calculating J-integrals in low temperature and C(t)-integrals in high temperature with the change of the design under hygrothermal loading. The optimum design to depress the delamination and crack in the plastic IC package is presented.

• Journal of the Korean Society for Precision Engineering
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• v.6 no.3
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• pp.90-99
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• 1989

In this study, J-integral values obtained by various methods, i.e, R-Curve, Unloading Compliance, Strectched Zone Width [SZW], and Acoustic Emission [AE] methods are investigated. Elasto-plastic fracture toughness [$J_IC$] estimations by R-curve method are overestimated than those by SZW method, and those by unloading compliance method is around middle value of them. And the difference between them is little. The $J_IC$ value by AE method was almost agreed with that by SZW, and then proved to be useful. Crack propagation mechanism on fractography is a stable ductile fracture. For the identification of ductile fracture, both fractography analysis and AE method were applied to estimate the characteristics more precisely.

• Journal of Power Electronics
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• v.2 no.3
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• pp.155-161
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• 2002

This paper presents a maximum power point tracking algorithm for Photovoltaic array using only instantaneous output current information. The conventional Hill climbing method of peak power tracking has a disadvantage of oscillations about the maximum power point. To overcome this problem, we have developed an algorithm that will estimate the duty ratio corresponding to maximum power operation of solar cell. The estimation of the optimal duty ratio involves, finding the duty ratio at which integral value of output current is maximum. For the estimation, we have used the well know Lagrange's interpolation method. This method can track maximum power point quickly even for changing solar isolation and avoids oscillations after reaching the maximum power point.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.7
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• pp.740-748
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• 1990

In this paper, we consider the problem of parameter estimation, i.e., definding the internal structure of a linear distribution parameter system from its input/output data. First, a linear partial differential equation describing the system is double-integrated with respect to two variables and then transformed into an integral equation. Next the Walsh Operation Matrix for Walsh function and their integration are introduced to transform the integral equation into algebraic simultaneous equations. Finally, we develop an algorithm to estimate the parameters of the linear distributed parameter system from the simple linear algebraic simultaneous equations. It is also shown that our algorithm could be effective in real time data processing since it uses the Fast Walsh Transform.

• Journal of the Korean Society of Safety
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• v.24 no.1
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• pp.37-42
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• 2009

The present study is to estimate the effect of wave height affecting at the front face of breakwater systems, when a submarine trench is dredged in the distant offshore from outer breakwater. The wave diffraction field, which is important hydraulic factor in the ocean, is considered to be two dimensional(2D) plane and the configuration of the submarine trench on the sea bed designated by single horizontal long-rectangular system. The numerical simulation is performed by using Green function based on the boundary integral equation and meshed at moving boundary conditions. The results of present numerical simulations are illustrated by applying the normal incidence. It is shown that the ratios of wave height reduction at the front face of breakwater systems are approximately 20% by the effect of placing long trench on the sea bed. This study can effectively be utilized for safety assessment to various breakwater systems in the ocean field.

• Journal of the Korean Society of Safety
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• v.23 no.5
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• pp.91-96
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• 2008

A reflected breakwater can be affected by wave pressure and power because it is to be concentrated by wave energy. The present study is to estimate hydraulic behavior affecting around a reflected breakwater, which is discontinuity cases and various angle of coner at the breakwater. The numerical model to investigate wave diffraction, which is important hydraulic factor in the ocean, is performed by using direct boundary element method. The present numerical results are compared with the solutions of approximate and absolute based on an eigenfunction, and the solution of analytical by Fresnel integral. The results of the present numerical simulation agreed well with those of the published numerical and analytical data. As a result of this study, wave height is high at the comer of breakwater, and it is to be high if angle of conner at the reflected breakwater is small.