• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.150-151
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• 2001

광컴퓨터에 있어서 비선형 물질의 역할은 매우 중요하다. 그러한 비선형 물질들은 빛과 상호작용하고 빛의 성질을 변조시킨다. 광컴퓨터의 몇몇 구성 성분들은 그들이 작용하는데 있어서 중요한 비선형물질을 필요로 한다. 하지만 모든 광학적 장치들의 사용이 사실상 제한되는 것은 현재 이용할 수 있는 비선형 광물질이 비효과적이고 응답과 스위칭에 대해서 많은 에너지를 필요로 하기 때문이다. (중략)

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.1
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• pp.20-33
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• 1999

The evolution of deep-sea waves is driven by energy input from wind, nonlinear energy transfer between wave components, and dissipation through whitecaps. A comparative study was implemented by the use of two wave models in which only the computation methods of nonlinear wave-wave interactions are different from each other. It was reaffirmed that the nonlinear interaction plays a central role in such phenomena that occurred during the spectral growth of wind-seas as down-shift of the spectral peak frequency, overshoot, undershoot, and formation of self-similar spectrum. Specifically, the directional distribution at high frequencies develops into bimodal form, which is attributed to the nonlinear interactions. As saturation stage is reached, spectral density at high frequencies becomes proportional to negative 4 power to the frequency. Perturbations introduced into the spectrum quickly vanished through the actions of the self-similar mechanism. Thus, the nonlinear transfer has important contribution to the stability of numerical ocean wave models.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.5
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• pp.1-12
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• 2010

This study presents a finite element analysis method that can accurately evaluate the nonlinear behaviour of structures affected by shallow soft subsoils and the soil-structure interaction. A two-dimensional finite element model that consists of a structure and shallow soft subsoil was used. The finite element model was used for a nonlinear time domain analysis of the OpenSees program. A parametric study was performed to investigate the effects of soil shear velocities, earthquake input motions, soft soil depth, and soil-structure interaction. The result of the proposed nonlinear finite element analysis method was compared with the result of an existing frequency domain analysis method, which is frequently used for addressing nonlinear soil behavior. The result showed that the frequency domain analysis, which uses equivalent secant soil stiffness and does not address the soil-structure interaction, significantly overestimated the response of the structures with short dynamic periods. The effect of the soil-structure interaction on the response spectrum did not significantly vary with the foundation dimensions and structure mass.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.2
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• pp.133-141
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• 2024

Considering fluid-structure-soil interactions, a finite-element model for a liquid-storage tank is presented and the nonlinear earthquake response analysis is formulated. The tank structure is modeled considering shell elements with geometric and material nonlinearities. The fluid is represented by acoustic elements and combined with the structure using interface elements. To consider the soil-structure interactions, the near- and far-field regions of soil are modeled with solid elements and perfectly matched discrete layers, respectively. This approach is applied to the seismic fragility analysis of a 200,000 kL liquid-storage tank. The fragility curve is observed to be influenced by the amplification and filtering of rock outcrop motions at the site when the soil-structure interactions are considered.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.2
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• pp.151-160
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• 1996

To construct the third generation model, nonlinear interaction was included in source terms. To calculate the nonlinear interaction, discrete interaction approximation to Boltzmann integral was used, as in WAM model. The general behavior and characteristics of nonlinear interaction were analyzed through the experiments for the durational growth and turning winds.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.86-86
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• 2020

수리구조물에 관한 기존 연구들은 대부분 기능성과 안정성 측면에서 본체에 작용하는 유체력에 대한 안정성에 주안점을 두고 있다. 수리구조물 상·하류의 수위차에 기인한 기초지반내의 흐름 및 간극수압 변화는 하천 구조물의 안정성을 연구하는데 매우 중요하다. 해양에서는 파랑하중에 의한 과잉간극수압이 액상화를 발생시켜 해안구조물의 안정에 큰 영향을 미치는 것으로 보고되며, 이에 관련 연구들이 활발하게 진행되고 있다. 반면, 하천구조물 주변 지반의 흐름 및 간극수압 뿐 아니라, 액상화에 관한 연구는 아직 미진한 실정이다. 본 연구에서는 수리구조물 주변의 유동 및 와동 현상 뿐 아니라, 수위차에 따른 지반 내부 유동장과 간극수압에 관한 특성을 분석하기 위해 유체-구조물-지반 비선형 상호작용을 고려할 수 있는 수치수조를 새롭게 제안하였다. 그리고 제안하는 수치수조의 타당성 및 유효성을 검증하기 위해 기존 실험값과 비교·검토를 수행하였고, 그 결과는 거의 유사한 경향을 나타내었다. 또한 이 수치수조에 다양한 입사조건(상·하류 수위차)에 적용하여 유체-구조물-지반의 비선형동적상호간섭 해석을 수행하였다. 최종적으로 수치수조에서 측정한 구조물 주변의 유동, 와동, 수위로부터 수리특성을 논의하였다. 게다가 지반내의 흐름과 간극수압을 측정하여 상·하류 수위차가 수리구조물의 안정성에 미치는 영향을 분석할 수 있었다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.95-102
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• 2014

In this paper, a coupling scheme for applying finite element analysis(FEA) programs, such as, LS-DYNA and MIDAS/Civil, to a nonlinear soil structure interaction analysis by the boundary reaction method(BRM) is presented. With the FEA programs, the structure and soil media are discretized by linear or nonlinear finite elements. To absorb the outgoing elastic waves to unbounded soil region as much as possible, the PML elements and viscous-spring elements are used at the outer FE boundary, in the LS-DYNA model and in MIDAS/Civil model, respectively. It is also assumed that all the nonlinear elements in the problem are limited to structural region. In this study, the boundary reaction forces for the use in the BRM are calculated using the KIESSI-3D program by solving soil-foundation interaction problem subjected to incident seismic waves. The effectiveness of the proposed approach is demonstrated with a linear SSI seismic analysis problem by comparing the BRM solution with the conventional SSI solution. Numerical comparison indicates that the BRM can effectively be applied to a nonlinear soil-structure analysis if motions at the foundation obtained by the BRM for a linear SSI problem excluding the nonlinear structure is conservative.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.11
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• pp.1663-1669
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• 2021

This paper considers the cooperative control problem for multiple leaders and a single follower with interactions. The leaders are controllable, and the follower has interactions with all leaders and is controlled by the interactions. Then, we study the cooperative control problem that achieves the consensus by controlling the leaders. The leaders and the follower are modeled by the single-integrator and the double-integrator, respectively, and it is assumed that the interactions have the nonlinearities. The leaders can estimate the interaction between the follower and exchange the estimated information with neighbors. Then, this paper proposes the consensus-based cooperative control algorithm using the information exchange of the estimated interactions and the virtual velocity variables to achieve the velocity consensus. We analyze the convergence of the agents to the common state based on the Lasalle's Invaraince Principle. Finally, we provide the numerical example to validate the theoretical results.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05d
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• pp.333-338
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• 1996

강진에 의한 원전구조물의 동적해석시 지반의 비선형특성은 반드시 고려해야 할 사항이다. 지반의 비선형특성은 지반-구조계의 동적응답을 구하는 과정에서 가장 중요한 요소중의 하나며 이를 고려한 비선형 지진해석은 일반적으로 매우 복잡하고 정해를 구하기가 매우 어려운 문제다. 본 연구에서는 비선형 해법으로 널리 사용되고 있는 등가선형화방법을 사용하여 계측결과가 있는 TEPSCO 비선형 지진문제를 해석하였으며 이 방법의 정확도와 적용성을 분석하였다. 아울러 축대칭기법을 사용하여 비선형지진해석을 수행할때의 문제점에 관해서도 검토하였다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.1
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• pp.95-102
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• 1996

The skewness of near-bottom velocity distribution caused by the nonlinear interaction of the second order waves proposed by Wells (1967) has been re-evaluated. The direction of cross-shore sediment transport was related to the sign of the third moment (skewness) of velocity distribution, and a new concept of neutral depth which can explain the recovery of beach equilibrium after a disturbance is suggested. The seasonal change of beach profile due to the change of wave condition (storm-swell profile) is interpreted in terms of nonlinear interaction of the waves rather than the conventional wave steepness. The beach is eroded (storm profile) when the nonlinear interaction of the waves is strong (storm wave), whereas the beach is accreted (swell profile) when the nonlinear interaction is weak (swell wave).