• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.2
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• pp.87-96
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• 1999

To analyze the dynamic behavior of structure, direct integration and mode superposition may be utilized in time domain analysis. As finite number of frequencies can give relatively exact solutions, mode superposition is preferable in analyzing structural behavior. In non-linear analysis, however, mode superposition is seldom used since time-varying element stiffness changes stiffness matrix, and the change of stiffness matrix leads to the change of essential constants - natural frequencies and mode shapes. In spite of these difficulties, there are some attempts to adopt mode superposition because of low cost compared to direct integration, but the result is not satisfactory. In this paper, a method using mode superposition in non-linear analysis is presented by separating local element stiffness from global stiffness matrix with the difference between linear and non-linear restoring forces to the external force vectors included. Moreover, the hysteresis model changing with the relative deformation in each floor makes it possible to analyze non-linear behavior of structure. The proposed algorithm is applied to shear beam model and the maximum displacement is compared with the result using direct integration method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.5
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• pp.335-344
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• 2011

A curvilinear non-hydrostatic free surface model is developed to investigate nonlinear wave interactions in a circular channel. The proposed model solves the unsteady Navier-Stokes equations in a three-dimensional domain with a pressure correction method, which is one of fractional step methods. A hybrid staggered-grid layout in the vertical direction is implemented, which renders relatively simple resulting pressure equation as well as free surface closure. Numerical accuracy with respect to wave nonlinearity is tested against the fifth-order Stokes solution in a two-dimensional numerical wave tank. Numerical applications center on the evolution of nonlinear waves including diffraction and reflection affected by the curvature of side wall in a circular channel comparing with linear waves. Except for a highly nonlinear bichrmatic wave, the model's results are in good agreement with superimposed analytical solution that neglects nonlinear effects. Through the numerical simulation of the highly nonlinear bichramatic wave, the model shows its capability to investigate the evolution of nonlinear wave groups in a circular channel.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.1
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• pp.79-87
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• 2008

Seismic performance evaluation of structure requires an estimation of the structural performance in terms of displacement demand imposed by earthquakes on the structure. Incremental Dynamic Analysis(IDA) is a analysis method that has recently emerged to estimate structural performance under earthquakes. This method can obtained the entire range of structural performance from the linear elastic stage to yielding and finally collapse by subjecting the structure to increasing levels of ground acceleration. Most structures are expected to deform beyond the limit of linearly elastic behavior when subjected to strong ground motion. The nonlinear response history analysis(NRHA) among various nonlinear analysis methods is the most accurate to compute seismic performance of structures, but it is time-consuming and necessitate more efforts. The nonlinear approximate methods, which is more practical and reliable tools for predicting seismic behavior of structures, are extensively studied. The uncoupled modal response history analysis(UMRHA) is a method which can find the nonlinear reponse of the structures for ESDF from the pushover curve using NRHA or response spectrum. The direct spectrum analysis(DSA) is approximate nonlinear method to evaluate nonlinear response of structures, without iterative computations, given by the structural linear vibration period and yield strength from the pushover analysis. In this study, the practicality and the reliability of seismic performance of approximate nonlinear methods for incremental dynamic analysis of mixed building structures are to be compared.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.2
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• pp.1-7
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• 2003

Mode superposition method(MSM) is the most commonly used for solving linear response problems of structural dynamics. The major advantage of MSM is that usually a small number of lower mode is sufficient to analysis the response. However, the convergence is slow and many modes would be needed to give an accurate MSM in large structure with many degrees of freedom. The inaccuracies of MSM are caused by mode truncation in the solution. These demerits can be overcome by use of the mode acceleration method(MAM). Example analyses are carried out in simple beam subjected to harmonic loadings and compared the convergence of the joint displacements by the two methods. For relatively low frequency loadings, a good results was obtained by the lowest one mode in MAM, so the method is more economic in numerical analysis on an accurate solution.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.13-22
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• 1990

A general analysis method is proposed for analysis of the superposed structures with geometric and material nonlinearities. It is presumed that no friction occurs between structures. It utilizes a shell element for the geometric and material nonlinearities and imposes various deformation constraints for the contact and interaction between structures. To show the reliability and effectiveness of this method, superposed cantilevers for which exact solutions can be obtained and holddown spring assemblies which are now used in PWR reactors are chosen as analysis models. The results of analyses were compared with exact solution in the case of cantilevers and with test results in the case of holddown spring assemblies. The analysis results obtained by this method showed good agreement with the reference values.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.6
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• pp.478-485
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• 2005

This paper analysed the ionized fields around HVDC transmission line by the use of the charge simulation method. As this is very complex and expressed by a non-linear partial differential equations, it is hard to solve problems analytically. So, we developed a computer program which can apply in multi-polar HVDC transmission line with conductor bundles and calculated conductor surface gradient, corona current density and ion charge density to prove validity of a proposed algorithm in this paper.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.5
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• pp.1-11
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• 2001

The purpose of this study is to develop the main program and pre/post processor for the geometric and plastic non-linear analysis of steel jacket structures subjected to wave and earthquake loadings. In this paper, steel jackets are modelled using geometric non-linear space frames and wave loadings re evaluated based on Morrison equation using the linear Airy theory and the fifth Stokes theory. Random wave is generated using JONSWAP spectrum. For earthquake analysis, dynamic analysis is performed using artificial earthquake time history. Also the plastic hinge method is presented for limit analysis of steel jacket. In the companion paper, the pre/post processor is developed and the numerical examples are presented for linear and non-linear dynamic analysis of steel jackets.

• Journal of the Korea Computer Industry Society
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• v.2 no.4
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• pp.565-572
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• 2001

At the most recent years, laser medical instruments, laser applications and laser nuclear fusion need strong visible light and ultraviolet rays. Nonlinear optical devices, such as harmonic generators and parametric oscillators, provide a means of extending the frequency range of available laser sources. Frequency conversion is a useful technique for extending the utility of high-power lasers. It utilizes the nonlinear optical response of an optical medium in intense radiation fields to generate new frequencies. These progresses have been used to generate high-power radiation in all spectral regions, from the ultraviolet to the far infrared. Optical parametric oscillators and amplifiers generate two waves of lower frequency They are capable of generating a range of wavelengths from a single frequency source, in some cases spanning the entire visible and near infrared regions. Consequently, in order to obtain the green light, the pulsed Nd:YAG laser using multiple-mesh PFN(Pulsed Forming Network) method with Nonlinear optical device was adopted. We compared the current pulseshapes with the laser output energy, and conversion efficiency.

• Review of KIISC
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• v.14 no.3
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• pp.1-7
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• 2004

양자알고리듬들 중 쇼의 알고리듬은 공개키 암호체계의 근간을 이루는 소인수분해를 고전알고리듬보다 훨씬 빨리 처리할 수 있다. 고전컴퓨터로 N자리 수를 소인수분해 하는데 걸리는 시간은 exp$[(InN)^{1/3}(In In N)^{2/3})]$에 비례하지만 쇼의 양자풀이법을 사용하면 약$(InN)^3$ 보다 적은 시간이 걸린다. 이 알고리듬의 핵심은 양자계의 중첩이라는 성질을 이용해서 푸리에 변환을 모든 데이터에 대해 병렬적으로 동시에 처리함으로서 주기를 빠르게 찾는다는 것이다. 이러한 양자전산의 이점은 모든 연산이 중첩된 상태에 독립적으로 작용한다는 자연계의 선형성에서 비롯된다. 고전컴퓨터에서도 병렬처리를 하지만 양자적 병렬처리를 고전컴퓨터의 병렬처리로 대신할 수는 없다. N비트로 나타내지는$2^N$ 개의 숫자에 대해 동시에 병렬처리 하는데 양자컴퓨터는 한대면 되지만 고전컴퓨터는 $2^N$대가 필요하므로 비트수가 증가하면 필요한 고전컴퓨터의 수가 비현실적으로 증가하기 때문이다. 이 알고리듬의 수행으로 얻어지는 결과는 확정적인 것이 아니며 확률적으로 율은 당을 얻는다. 어떤 수가 약수가 되는지 아닌지는 금방 확인해 볼 수 있으므로 서너 번 이와 같은 시행착오 과정을 거쳐 옳은 답을 얻는다 해도 문제가 되지는 않는다.

• Publications of The Korean Astronomical Society
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• v.6 no.1
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• pp.16-26
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• 1991

스펙트럼선의 선폭증대 현상을 방출영역 내 기체입자들이 열운동에 의한 단순 도플러 효과로 가정하여 중심에서 어느 한쪽으로 심하게 치우친 스펙트럼 선윤곽를 해석한다. 본 연구에서는 태양활동영역에서 흔히 관측되는 좌우 비대칭의 선윤곽을 서로 다른 가우스속도분포의 기체성분들이 시선방향으로 중첩된 결과라 해석하고, 최소자승법을 이용한 비선형 선윤곽 맞춤질에 의해 스펙트럼 방출영역에서 떨어져 나가는 기채들의 온도 및 분출속도에 관련된 도플러선폭과 도플러이동량을 구하였다.