• 한국해양공학회지
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• 제8권1호
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• pp.123-130
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• 1994

일반적으로 규칙파 또는 불규칙파중에서의 반잠수식 해양구조물의 응답을 추정할때, 선형계에 적합한 주파수 영역해석법을 사용하고 있다. 대다수의 해양구조물은 Lower Hull과 단면적이 일정한 Column으로 구성되어 있지만, 만약 Column의 단면적이 홀수에 따라 변화한다면 복원력항에 비선형계를 적용해야만 한다. 따라서 본 논문에서는 비선형 복원력을 고려한 반잠수식 해양구조물의 응답을 추정할 수 있는 시간 영역 해석법을 개발하였다. 그리고, Column형상이 다른 5개의 모델을 선정하여, 이들의 시간 영역 해석결과와 주파수 영역 해석 결과를 서로 비교하였다. 또한 파랑외력으로서 불규칙파를 적용할 때, 비선형 복원력이 해양구조물에 응답에 미치는 영향을 조사 하였다.

• Journal of applied mathematics & informatics
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• 제29권1_2호
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• pp.75-85
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• 2011

In this paper, using the energy estimates and the bootstrap arguments, the global existence of classical solutions for a prey-predator model with non-monotonic functional response and cross-diffusion where the prey and predator both have linear density restriction is proved when the space dimension n < 10.

• Steel and Composite Structures
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• 제27권6호
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• pp.761-775
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• 2018

In the present work, the recently developed non-polynomial shear deformation theories are assessed for thermo-mechanical response characteristics of laminated composite plates. The applicability and accuracy of these theories for static, buckling and free vibration responses were ascertained in the recent past by several authors. However, the assessment of these theories for thermo-mechanical analysis of the laminated composite structures is still to be ascertained. The response characteristics are investigated in linear and non-linear thermal gradient and also in the presence and absence of mechanical transverse loads. The laminated composite plates are modelled using recently developed six shear deformation theories involving different shear strain functions. The principle of virtual work is used to develop the governing system of equations. The Navier type closed form solution is adopted to yield the exact solution of the developed equation for simply supported cross ply laminated plates. The thermo-mechanical response characteristics due to these six different theories are obtained and compared with the existing results.

• 응용통계연구
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• 제29권5호
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• pp.773-786
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• 2016

분위수 회귀는 반응변수의 조건부 분위수 함수를 추정함으로써 반응변수와 예측변수의 관계에 대한 포괄적인 정보를 제공한다. 그러나 여러 개의 분위수 함수를 개별적으로 추정하게 되면 이들이 서로 교차할 가능성이 있으며, 이러한 분위수 함수의 교차(quantile crossing) 현상 분위수의 이론적 기본 특성에 위배된다. 본 논문에서는 다중 비교차 분위수 함수의 추정의 대표적인 방법들의 특성을 적합식과 계산 알고리즘의 측면에서 살펴보고, 모의실험과 실제 자료 분석을 통해 그 성능을 비교하였다.

• Steel and Composite Structures
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• 제31권2호
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• pp.187-199
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• 2019

This paper presents the semi-analytical development of the dynamic instability behavior and the dynamic response of functionally graded (FG) cylindrical shallow shell panel subjected to different type of periodic axial compression. First, in prebuckling analysis, the stresses distribution within the panels are determined for respective loading type and these stresses are used to study the dynamic instability behavior and the dynamic response. The prebuckling stresses within the shell panel are the same as applied in-plane edge loading for the case of uniform and linearly varying loadings. However, this is not true for the case of parabolic loadings. The parabolic edge loading produces all the stresses (${\sigma}_{xx}$, ${\sigma}_{yy}$ and ${\tau}_{xy}$) within the FG cylindrical panel. These stresses are evaluated by minimizing the membrane energy via Ritz method. Using these stresses the partial differential equations of FG cylindrical panel are formulated by applying Hamilton's principal assuming higher order shear deformation theory (HSDT) and von-$K{\acute{a}}rm{\acute{a}}n$ non-linearity. The non-linear governing partial differential equations are converted into a set of Mathieu-Hill equations via Galerkin's method. Bolotin method is adopted to trace the boundaries of instability regions. The linear and non-linear dynamic responses in stable and unstable region are plotted to know the characteristics of instability regions of FG cylindrical panel. Moreover, the non-linear frequency-amplitude responses are obtained using Incremental Harmonic Balance (IHB) method.

• 한국자동차공학회논문집
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• 제16권1호
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• pp.71-77
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• 2008

This paper proposes an Electronic Throttle Body (ETB) model considering a non-linearity of DC motor driver which is integrated with a H-bridge and a gate driver. A propagation delay and reverse recovery time of switching components cause non-linear characteristic of DC motor driver. This non-linearity affects not only the amateur voltage of DC motor, but also entire behaviour and parameters of ETB. In order to analyze the behavior of ETB more accurately, this non-linear effect of DC motor driver is modeled. The developed ETB model is validated by use of the step response and ramp response experiments, and it shows relatively accurate results compared with linear DC motor driver model.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.477-484
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• 2000

Earthquake response analyses are conducted for the investigation of the ground shaking during the 1995 Hyogoken-nambu earthquake. Port Island a man made island with about 8{{{{ KAPPA m^2 }} area is chosen for this purpose Because earthquake measurement with vertical array was conducted there. Strain dependent characteristics of soil can be modeled well into Hardin-Drnevich Model. Four analyses are conducted : total stress analysis by equivalent linear method non-linear method. and two effective stress analyses. All analyses except equivalent linear analysis show fairy good agreement with observed record mainly because the non-linear behavior of Holocene clay layer has predominant effect on the behavior of fill, However detailed investigation show that effective stress analyses give much better prediction than total stress analyses.

• Selected Papers of The Society of Naval Architects of Korea
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• 제2권1호
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• pp.79-105
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• 1994

A ship in waves is suffered from the various wave loads that comes from its motion throughout its life. Because these loads are dynamic, the analysis of a ship structure must be considered as the dynamic problem precisely. In the rationally-based design, the dynamic structural analysis is carried out using dynamic wave loads provided from the results of the ship motion calculation as a rigid body. This method is based on the linear theory assumed low wave height and small amplitude of motion. But at the rough sea condition, high wave height, compared with ship's depth, induce the large ship motion, so the ship section configuration under waterline is rapidly changed at each time. This results in a non-linear problem. Considering above situation in this paper, a strength analysis method is introduced for the hull girder among waves considering non-linear hydrodynamic forces. This paper evaluates the overall or primary level of the ship structural dynamic loading and dynamic response provided from the non-linear wave forces, and bottom flare impact forces by momentum slamming theory. For numerical calculation a ship is idealized as a hollow thin-walled box beam using thin walled beam theory and the finite element method is used. This method applied to a 40,000 ton double hull tanker and attention is paid to the influence of the response of the ship's speed, wave length and wave height compared with the linear strip theory.

• Wind and Structures
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• 제35권1호
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• pp.35-54
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• 2022

A comparative study of aeroelastic vibrations of spring-mass cylinder and chimneys, with the help of a few wake oscillator models available in the literature, is presented. The models include those proposed by Facchinetti, Farshidian and Dolatabadi method-I, Farshidian and Dolatabadi method-II, de Langre, Skop and Griffin. Besides, the linear model proposed by Simiu and Scanlan is also incorporated in the study. For chimneys, the first mode oscillation is considered, and the top displacements of the chimneys are evaluated using the considered models. The results of the analytical model are compared with those obtained from the numerical solution of the wake-oscillator coupled equations. The response behavior of the cylinder and three chimneys of different heights are studied and compared with respect to critical parametric variations. The results of the study indicate that the numerical analysis is essential to capture the effect of non-linear aeroelastic phenomena in the solutions, especially for small damping. Further, except for the models proposed by Farshidian and Dolatabadi, other models predict nearly the same responses. The non-linear model predicts a much higher response as compared to the linear model.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.246-252
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• 1999

In this paper, the frequency response characteristics of the velocity controlled EHS system obtained by linear simulation method, nonlinear simulation method, and experimentation are compared one another, in order to verify propriety of the linearization method in case of analysis of hydraulic systems. The Bode diagrams are obtained by transforming time domain data of experimental results and nonlinear simulated ones with Fourier transform. The results of nonlinear simulation are more similar to the frequency response of the real systems than those of linear simulation. It is found that nonlinearity of hydraulic systems is mainly occurred from servo valve, and nonlinearity is increased as displacement of servo valve spool increases.