• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.2
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• pp.232-244
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• 1997

In this paper weight function theory is extended to the determination of the stress intensity factors for the mode I in elliptic crack. For the calculation of the fundamental fields Poisson's theorem and Ferrers's method were employed. Fundamental fields are constructed by single layer potentials with surface density of crack harmonic fundamental polynimials. Crack harmonic fundamental polynimials up to order four were given explicitly. As an example of the application of the weight function theory the stress intensity factors along crack tips in nearly penny-shaped elliptic crack are calculated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.5
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• pp.967-973
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• 1997

In this paper, the designed and fabrication of a K-band push-push oscillator using miniaturized hairpin resonator have been presented. One experimenal oscillator has been designed and fabricated for K-band point-to-point operation. the miniaturized harpin resonator has been analyzed theoretically and simulated by MPIE(Mixed Potential Integral Equation) method. With this results, the analysis of hairpin resonator which coupled microstrip line has been carried out with transmission-mode using this results. an optimized output matching network for the suppression of the fundamental and the 3rd order harmonic was acquired by using a nonlinear analysis method. The fabricated oscillator shows the output power of -2.28dBm, the fundamental frequency suppression of -19dBc, the 3rd order harmonic suppressionof -24dBc and 0.33 percent effiiency at 22.8GHz. The experimental outputs are in good agreement with the theoretical and simulated results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.145-153
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• 1997

Dynamic characteristics are investigated when a nonlinear system showing periodic and chaotic responses under harmonic excitation is exposed to random perturbation. About two well potential problem, probability of homoclinic bifurcation is estimated using stochastic generalized Meinikov process and quantitive characteristics are investigated by calculation of Lyapunov exponent. Critical excitaion is calculated by various assumptions about Gaussian Melnikov process. To verify the phenomenon graphically Fokker-Planck equation is solved numerically and the original nonlinear equation is numerically simulated. Numerical solution of Fokker-Planck equation is calculated on Poincare section and noise induced chaos is studied by solving the eigenvalue problem of discretized probability density function.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.5
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• pp.484-491
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• 2007

Numerical experiments using a numerical wave tank have been performed to verier the nonlinear interaction between monochromatic waves and a submerged horizontal plate. As a model for numerical wave tank, we used a higher-order Boundary Element Method(BEM) based on fully nonlinear potential flow theory and CADMAS-SURF for solving Navier Stokes equations and exact free surface conditions. Both nonlinear models are able to predict the higher harmonic generation in the shallow water region over a submerged horizontal plate. CADMAS-SURF, which involves the viscous effect, can evaluate the higher harmonic generation by flow separation and vortices at the each ends of plate. The comparison of reflection and transmission coefficients with experimental results(Patarapanich and Cheong, 1989) at different lengths and submergence depths of a horizontal plate are presented with a good agreement. It is found that the transfer of energy from the incident fundamental waves to higher harmonics becomes larger as the submergence depth ratio decreases and the length ratio increases.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.15-27
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• 2014

양자화학 (quantum chemistry)을 처음 접했을 때, 이전까지의 고전역학 (classical mechanics)에 익숙한 대다수의 학생들은 양자화학을 받아들이는 데 어려움을 겪는다. 모형계에 양자역학 (quantum mechanics)을 직접 적용하여 봄으로써 생소한 양자 개념에 대한 이해를 도울 수 있다. 본 논문에서는 양자동역학 (quantum dynamics)을 수치적으로 구현하는 계산 프로그램을 모형계에 적용하여 양자 개념을 설명할 수 있는 몇 가지 예를 보이고자 한다. 1 차원 시간의존 슈뢰딩거 방정식 (1-D time-dependent $Schr{\ddot{o}}dinger$ equation)의 해를 얻어 양자동역학을 구현하였으며, 그에 해당하는 고전동역학은 뉴턴 방정식 (Newton's equation)의 해로 얻어졌다. 조화 진동자 퍼텐셜 (harmonic oscillator potential), 모스 진동자 퍼텐셜 (Morse oscillator potential), 이중 우물 퍼텐셜 (double-well potential), 네모 퍼텐셜 장벽 (rectangular potential barrier), 그리고 에카트 퍼텐셜 (Eckart potential)에 대한 계산을 수행하였다. 두 가지 동역학을 비교하기 위하여 계산 결과의 시각화 (visualization)를 이용하고 동역학 특성의 차이를 비교하는 차별화 (differentiation)를 강조한다. 영점에너지 (zero-point energy), 위상어긋남 (dephasing), 터널링 (tunneling), 그리고 반사 (reflection) 현상과 같은 양자동역학의 특징을 고전동역학과 비교함으로써 직관적인 이해를 도울 수 있었다. 이러한 결과는 양자화학에 입문하는 학생들을 대상으로 쓰일 수 있는 효율적인 강의 모델을 제시할 것으로 기대한다.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.8
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• pp.347-353
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• 2002

This paper presents an accurate method for measuring the ground resistance in powered grounding system. Most of substations and electric power equipments are interconnected to an extensive grounding network of overhead ground wires, neutral conductors of transmission lines, cable shields, and etc. The parasitic effects due to circulating ground currents and ground potential rise make a significant error in measuring the ground resistance. The test current transition method was proposed to reduce the effects of stray ground currents, ground potential rise and harmonic components in measurements of the ground resistance for powered grounding systems. The instrumental error of the test current transition method is decreased as the ratio of the test current signal to noise(S/N) increases. It was found from the test results that the proposed measuring method of the ground resistance is more accurate than the conventional fall-of-potential method or low-pass filter method, and the measuring error was less than 3[%]when S/N is 10.

• Korean Journal of Optics and Photonics
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• v.6 no.1
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• pp.39-44
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• 1995

3차원 .delta.-potential을 가진 원자 모델을 이용하여 Nd:YAG(1064nm), Ti:sapphire(806nm), 색소(616nm), XeCl(308nm) 레이저를 기본파로 하고, 1차 이온화된 K/sup +/, Na/sup +/, Li/sup +/ 등의 알칼리 금속 이온을 비선형 매질로 할 때 고차고조파 분포를 수치적으로 해석하였다. 계산 결과 고차고조파 발생에서 특징적으로 나타나는 plateau는 비선형 매질의 이온화 에너지가 클수록, 기본파의 파장이 길수록 높은 차수에서 폭넓게 나타나고, 그 강도는 감소한다.

• Communications of the Korean Mathematical Society
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• v.11 no.1
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• pp.175-190
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• 1996

In this paper we establish the existence of the conditional Feynman integral of certain functions which are not in the Banach algebra S of functions on Wiener space which are a kind of stochastic Fourier transform of complex Borel measures on $L^2[a, b]$. This result is used to provide the fundamental solution for the Schr$\ddot{o}$dinger equation for the forced harmonic potential.

• Bulletin of the Korean Mathematical Society
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• v.59 no.1
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• pp.101-110
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• 2022

In this article, the notion of *-conformal Ricci soliton is defined as a self similar solution of the *-conformal Ricci flow. A Sasakian 3-metric satisfying the *-conformal Ricci soliton is completely classified under certain conditions on the soliton vector field. We establish a relation with Fano manifolds and proves a homothety between the Sasakian 3-metric and the Berger Sphere. Also, the potential vector field V is a harmonic infinitesimal automorphism of the contact metric structure.

• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.592-596
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• 2004

Corrosion is never avoided in the use of materials with various environments. The underwater hull is normally protected against rusting by several coatings of anti-corrosive paint. The purpose of ICCP(Impressed Current Cathodic protection) system is to eliminate the rusting or corrosion, which occurs on metal immersed in seawater. The anode of ICCP system is controlled by an external DC source with converter. The function of anode is to conduct the protective current into seawater. The proposed algorithm includes the harmonic suppression control strategy and the optimum protection strategy and has tried to test the requirement current density for protection, the influence of voltage, the protection potential. This paper was studied the variation of potential and current density with environment factors, time and velocity, and the experimental results will be explained.