• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.19 no.3
• /
• pp.222-227
• /
• 2007

Formation of freak waves is studied in deep water from transient wave packets propagating on current. Those waves are obtained by means of dispersive focusing. This process is investigated by solving both linear and nonlinear equations. The role of nonlinearity is emphasized in this interaction.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.1
• /
• pp.131-136
• /
• 1988

This study is a research on the dynamic characteristics of non-linear dynamic vibration absorber in which harmonic motion is applied to the foundation of the main system. The amplitude ratio of the system with non-linear dynamic vibration absorber was obtained by harmonic balance methods and the unstable region was determined by stability analysis. As a result of study, the amplitude ratio decreases as mass ratio increases.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.3 no.4
• /
• pp.244-254
• /
• 1991

The numerical analysis on tile behaviour of mooring system in the offshore guyed tower is presented. The governing equilibrium equations are derived by the principle of virtual work. The drag and inertia effects of fluid are included in a Morrison type equation. The finite element method is used in the computation. Geometric nonlinearities for the analysis of the mooring line are considered in which both modified Newton-Raphson method and Newmark-$\beta$ method are employed. Numerical experiments show the validity and the capability of the developed mathematical formulation.

• Journal of Ocean Engineering and Technology
• /
• v.13 no.4 s.35
• /
• pp.10-18
• /
• 1999

본 논문에서는 대형구조물의 해석에 있어서 부분구조합성법과 섭동법을 이용하여 복잡한 비선형시스템의 해석방법을 제안하였다. 해석방법은 전체시스템을 먼저 몇 개의 분계로 분할한다. 각 분계의 운동방정식에 비선형항이 존재하여도 전체시스템의 지배적 진동모드는 선형모드라는 가정하에 이 시스템의 각 분계를 모드좌표로 변환한다. 이때, 비선형항은 근사적으로 변환한다. 그리고 섭동법을 이용하여 각 분계의 모드좌표방정식은 섭동좌수별로 정식화되어 순차적으로 구해진다. 비선형의 감도는 비선형계수로 정의되고, 그에 상응하는 강성에 의해 구해진다. 제안된 해석방법으로 비선형회전체, 비선형 베어링-페데스탈로 구성된 대형시계구조물의 진동을 해석하였다. 해석방법의 유효성을 평가하기 위해 응답의 정도와 계산소요시간을 유한요소법의 결과와 비교 분석하였다.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.9 no.6
• /
• pp.711-717
• /
• 2014

Happiness has been studied in sociology and psychology as a matter of grave concern. In this paper the happiness model that a new second -order systems can be organized equivalently with a Spring-Damper-Mass are proposed. This model is organized a 2-dimensional model of identically type with Duffing equation. We added a nonlinear term to Duffing equation and also applied Gaussian white noise and period sine wave as external stimulus that is able to cause of happiness. Then we confirm that there are random motion, periodic motion and chaotic motion according to parameter variation in the new happiness model.

• Journal of Institute of Control, Robotics and Systems
• /
• v.5 no.2
• /
• pp.158-165
• /
• 1999

비행시험을 통해 획득한 데이터의 해석과정에서 대상 항공기의 크기가 소형인 경우에는 엔진진동이나 외부의 교란에 의한 잡음이나 바이어스 등의 강도가 높기 때문에 데이터의 처리과정에서 많은 문제점을 산출하게 된다. 이와 같은 문제점을 해결하기 위해 상태추정 알고리즘이 사용되며, 본 논문에서는 항공기의 비선형 세로운동 방정식의 경우에 확장형 칼만 필터를 적용하여 항공기 세로운동의 상태변수들을 추정하였으며, 또한 확률근사과정, 이노베이션에 대한 궤환 적응 등 적응형 칼만 필터를 사용하여 수렴속도와 정확도 둥을 향상시킨 알고리즘을 제안하고 그 결과를 나타내었다.

• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.1-1
• /
• 2000

본 논문에서는 3축이 연성되어 비선형 운동 방정식으로 표현되는 3축 안정화 인공위성 시스뎀에 입릭외란과 시스템의 불확실성이 존재할 경우에도 자제 정밀도를 유지하는 제어기를 설계한다. 비선헝 운동 방정식으로 표현되는 운동 방정식을 선형화하고 PID제어기를 구성하였다 선형화에 의한 시스템의 불확실성과 입력 외란을 신경회로망으로 추정하여 외란의 엉향을 제거하도록 구성된 PR제어기의 제어입력을 수정한다 수정된 제어입력은 외란을 상쇠시켜 시스템 출력에서 외란의 효과를 제거하게 된다. 신경회로망은 제어입력과 시스템 출력, 기준 운동 방정식간의 관계를 이용하여 외간과 시스템의 불확실성을 추정하며, 역전파 알고리즘을 사용한 학습 알고리즘으로 신경 회로망을 교육한다. 제안된 신경회로망을 이용한 외란 제거 제어기는 시뮬레이션을 통하여 자세 정밀도의 향상을 검증한다

• Journal of Korea Water Resources Association
• /
• v.31 no.6
• /
• pp.757-768
• /
• 1998

rate of outflow is equated to the total rate of flow, both the state equation and its linearized equation yield almost identical oscillations of water levels. This shows that effects of pipe resistance on the surges are small, and justifies a free oscillation analysis. Free oscillation equation has six eigen modes of different periods, including a rigid mode which is existed when the pumped rate of outflow differs from the total rate of inflow. The six modes constitute a variety of surges dependent on different inflow and outflow conditions. Presence of the rigid mode needs sophisticated pump operations adjusted to real flood inflows.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.5 no.6
• /
• pp.55-64
• /
• 2001

Industrial machines are sometimes exposed to the danger of earthquake. In the design of a mechanical system, this factor should be accounted for from the viewpoint of reliability to analyze a complex nonlinear structure system under random excitation is proposed. First, the actual random excitation, such as earthquake, is approximated to the corresponding Gaussian process for the statistical analysis. The modal equations of overall system are expanded sequentially. Then, the perturbed equations are synthesized into the overall system and solved in probabilistic way. Several statistical properties of a random process that are of interest in random vibration are evaluated in each substructure. Comparing with the results of the numerical simulation proved the efficiency of the proposed method.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.4
• /
• pp.367-371
• /
• 2009

Analysis on optimality of the proportional navigation guidance(PNG) law is presented in this paper. While most of previous studies on optimality of PNG were relied on the linear formulation, this paper is based on the nonlinear formulation. The analysis shows that PNG is an optimal solution minimizing a range-weighted control energy, where the weighting function is an inverse of $\alpha$ power of the distance-to-target. We show that the navigation constant N is related to $\alpha$ directly. And also the conditions required to ensure the analysis result are investigated.