• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.81-85
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• 2006

The motion of a system composed of a plate, constant springs and varying dampers is considered when the system is subject to harmonic force. Letting the frequencies of harmonic force and damper variation ${\Large f}_1\;and\;{\Large f}_2$, respectively, the displacement at the center of the plate has the strongest component at frequency ${\Large f}_1$. The angular displacement of the plate has strong components at ${\Large f}_1-{\Large f}_2$, and the natural frequency of the rotational mode of the system. If these two frequencies coincide, the plate oscillates with almost single frequency and a large amplitude. These results can be applied to development of a moment shatter with low frequencies.

• 한국정보과학회논문지:시스템및이론
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• 제33권4호
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• pp.231-241
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• 2006

제어 가능하고 상황에 따라 반응하는 아바타의 제작은 컴퓨터 게임 및 가상현실 분야에서 중요한 연구 주제이다. 최근에는 아바타 애니메이션과 제어의 사실성을 높이기 위해 대규모 동작 캡처 데이타가 활용되고 있다. 방대한 양의 동작 데이타는 넓은 범위의 자연스러운 인간 동작을 수용할 수 있다는 장점을 갖는다. 하지만 동작 데이타가 많아지면 적절한 동작을 찾는데 필요한 계산량이 크게 증가하여 대화형 아바타 제어에 있어 병목으로 작용한다. 이 논문에서 우리는 레이블링(labeling)이 되어있지 않은 모션 데이타로부터 아바타의 행동을 학습시키는 새로운 방법을 제안한다. 이 방법을 사용하면 최소의 실시간 비용으로 아바타를 애니메이션하고 제어하는 것이 가능하다. 본 논문에서 제시하는 알고리즘은 Q-러닝이라는 기계 학습 기법에 기초하여 아바타가 동적인 환경과의 상호작용에 따른 시행착오를 통해 주어진 상황에 어떻게 반응할지 학습하도록 한다. 이 접근 방식의 유효성은 아바타가 서로 간에, 그리고 사용자에 대해 상호작용하는 예를 보임으로써 증명한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.651-652
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• 2011

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제13권4호
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• pp.247-256
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• 2009

In this paper, a motion detection algorithm which works well in low illumination environment is proposed. By using the level set based bimodal motion segmentation, the algorithm obtains an automatic segmentation of the motion region and the spurious regions due to the large CCD noise in low illumination environment are removed effectively.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.177.3-177
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• 2001

In this paper, the design of the in-motion alignment system of Strapdown Inertial Navigation System(SDINS) using Robust Extended Kalman Filter(REKF) is presented. The compensation of errors in the aided navigation system is accomplished by the indirect feedback filtering. The performance of the aided navigation algorithm is very sensitive to the accuracy of the initial estimate, which is the characteristic of the EKF. Unfortunately, the initial attitude error can be very large during the in-motion alignment. To overcome the in-motion alignment under large initial attitude error problem, the REKF using linear robust filtering technique is proposed. The linear robust H$_2$ filter can be adopted for nonlinear ...

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.227-235
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• 2007

The railway catenary is softer in the middle of a span than at the end. This stiffness variation induce the vertical motion of a moving pantograph, which results in the large variation of contact forces. To reduce the vertical motion of a pantograph, we can introduce a pre-sag of the contact wire. The pre-sag changes merely equilibrium position of the contact wire. Because the pantograph must follow the sag added to the motion of the contact wire, the sag gives downward forces to the pantograph. If the pre-sag is proper, the variation of the vertical motion of the pantograph is reduced. However, excessive sag worses the current collection performance because the pantograph receives too large downward forces by the contact wire. The objective of the paper is to establish the theoretical basis to understand how the pre-sag affect the contact force variation and to propose the proper sag for the railway catenary for the train speed up to 200 km/h.

• 대한조선학회논문집
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• 제37권4호
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• pp.75-81
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• 2000

대형 부유식 해양 구조물은 끝부분을 제외하고 작은 운동 특성을 보여주지만, 구조물 각 끝부분의 운동은 유탄성운동에 기인하여 더욱 크게 된다. 본 논문에서는 불규칙파 중에서 초대형 부유식 해양 구조물 운동 특성에 관한 수치적 추정을 제시한다. 불규칙파 중 구조물의 운동을 추정하기 위하여 소오스-다이폴 분포법과 유한요소법이 사용된다.

• Ocean Systems Engineering
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• 제4권3호
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• pp.215-241
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• 2014

Steel catenary riser (SCR) is a popular/economical solution for the oil/gas production in deep and ultra-deep water. The behavioral characteristics of SCR have a high correlation with the motion of floating production facility at its survival and operational environments. When large motions of surface floaters occur, such as FPSO in 100-yr storm case, they can cause unacceptable negative tension on SCR near TDZ (touch down zone) and the corresponding elastic deflection can be large due to local dynamic buckling. The generation, propagation, and decay of the elastic wave are also affected by SCR and seabed soil interaction effects. The temporary local dynamic buckling vanishes with the recovery of tension on SCR with the upheaval motion of surface floater. Unlike larger-scale, an-order-of-magnitude longer period global buckling driven by heat and pressure variations in subsea pipelines, the sub-critical local dynamic buckling of SCR is motion-driven and short cycled, which, however, can lead to permanent structural damage when the resulting stress is greatly amplified beyond the elastic limit. The phenomenon is extensively investigated in this paper by using the vessel-mooring-riser coupled dynamic analysis program. It is found that the moment of large downward heave motion at the farthest-horizontal-offset position is the most dangerous for the local dynamic buckling.

• 대한기계학회논문집
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• 제11권3호
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• pp.528-536
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• 1987

본 연구에서는 간헐적인 유동에 의거한 체적 대류 모델을 설정하고, 구배 확 산 모델에 유동장의 중심부와 외부에서 서로 다른 무게값을 부여하는 혼성 확산 모델 (hybrid diffusion model)을 제안하며, 이 모델을 검증하기 위한 첫 단계로서 평면 제 트 유동에 대하여 수치 계산을 수행하다. 여기에는 간헐도에 대한 난류 전달 방정식 이 필요한데 이 방정식의 생성항(production term)은 곧 외부의 비회전 유동이 난류성 유체로 유입되는 정도를 의미하게 된다.

• 한국해양공학회지
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• 제33권5호
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• pp.387-393
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• 2019

In this study, the free motion of a riser due to vortex shedding was numerically simulated with Large Eddy Simulation (LES) and Detached Eddy Simulation (DES) turbulence models. A numerical simulation program was developed by applying the Rhie-Chow interpolation method to the pressure correction of the OpenFOAM standard solver pimpleDyMFoam. To verify the developed program, the vortex shedding around the fixed riser at Re = 3900 was calculated, and the results were compared with the existing experimental and numerical data. Moreover, the vortex-induced vibration of a riser supported by a linear spring was numerically simulated while varying the spring constant. The results are compared with published direct numerical simulation (DNS) results. The present calculation results show that the numerical method is appropriate for simulating the vortex-induced motion of a riser, including lock-in phenomena.