• 한국정보통신학회논문지
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• 제11권6호
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• pp.1062-1068
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• 2007

유비쿼터스게임을 디자인하고 개발하기 위하여 현실세계과 가상세계와의 자연스럽고 다양한 상호작용이 필요하다. 이는 물리적인측면 뿐 아니라 상황변화에 알맞은 대응 감지기술을 필요로한다. 이를 위하여 가상세계와의 유저인터페이스 모델을 정의하고 이를 구현하기 위하여 텍타일감지 시스템을 제작하였다. 텍타일 데이터는 외부환경에 민감하므로 신호처리방법을 사용하여 잡음을 제거하고 유저인터페이스를 위한 데이터 형태로 외부입력을 분석 추론하였다. 이는 일반적인 게임에서 사용하는 마우스나 키보드에 따른 입력과 전혀 다른 형태의 입력으로 유비쿼터스 환경에서의 플레이어의 상황대응에 대한 중요한 정보를 제공하여준다. 구현한 시스템을 통하여 가상공간상에 존재하는 공에 작용한 힘을 3차원적으로 분석하여 힘의 위치, 크기, 분포, 방향 등을 분석하는 방법을 제시 해보았으며 이 같은 실세계 정보 분석을 통하여 가상공간상에서 3차원적인 자연스러운 반작용이 가능하도록 하는 가능성을 보였다. 이 같은 방법들은 유비쿼터스 게임의 상호작용 개발을 위한 기초자료로 사용될 수 있다.

• Smart Structures and Systems
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• 제32권5호
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• pp.281-295
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• 2023

The purpose of this study is to demonstrate and verify the application of phase-control absolute-acceleration-feedback active tuned mass dampers (PCA-ATMD) to multiple-degree-of-freedom (MDOF) building structures. In addition, servo speed control technique has been developed as a replacement for force control in order to mitigate the negative effects caused by friction and inertia. The essence of the proposed PCA-ATMD is to achieve a 90° phase lag for a structure by implementing the desired control force so that the PCA-ATMD can receive the maximum power flow with which to effectively mitigate the structural vibration. An MDOF building structure with a PCA-ATMD and a real-time filter forming a complete system is modeled using a state-space representation and is presented in detail. The feedback measurement for the phase control algorithm of the MDOF structure is compact, with only the absolute acceleration of one structural floor and ATMD's velocity relative to the structure required. A discrete-time direct output-feedback optimization method is introduced to the PCA-ATMD to ensure that the control system is optimized and stable. Numerical simulation and shaking table experiments are conducted on a three-story steel shear building structure to verify the performance of the PCA-ATMD. The results indicate that the absolute acceleration of the structure is well suppressed whether considering peak or root-mean-square responses. The experiment also demonstrates that the control of the PCA-ATMD can be decentralized, so that it is convenient to apply and maintain to real high-rise building structures.

• Journal of Mechanical Science and Technology
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• 제15권4호
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• pp.500-509
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• 2001

Offshore subsea pipelines must be stable against external loadings, which are mostly due to waves and currents. To determine the stability of a subsea pipeline on the seabed, the Morrison equation has been applied with prediction of inertia and drag forces. When the pipeline is placed in a trench, the force acting on it is reduced considerably. Therefore, to consider the stability of a pipeline in a trench, one must employ reduction factors. To investigate the stability of various trenches, we numerically simulated flows over various trenches and compared them with experimental data from PIV (Particle Image Velocimetry) measurements. The present results were produced ar Reynolds numbers ranging from 6$\times$10$^3$to 3$\times$10(sub)5 based on the diameter of the cylinder. Quasi-periodic flow patterns computed by large-eddy simulation were compared with experimental data in terms of mean flow characteristics fro typical trench configurations (W/H=1 and H/D=3, 4). The stability for various trench conditions was addressed in terms of mean amplitudes of oscillating lift and drag, and the reduction factor for each case was suggested for pipeline design.

• Structural Engineering and Mechanics
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• 제25권5호
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• pp.501-518
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• 2007

In this work, a new approach is developed for dynamic analysis of a composite beam with an interply crack, based on finite element solution of partial differential equations with the use of the COMSOL Multiphysics package, allowing for fast and simple change of geometric characteristics of the delaminated area. The use of COMSOL Multiphysics package facilitates automatic mesh generation, which is needed if the problem has to be solved many times with different crack lengths. In the model, a physically impossible interpenetration of the crack faces is prevented by imposing a special constraint, leading to taking account of a force of contact interaction of the crack faces and to nonlinearity of the formulated boundary value problem. The model is based on the first order shear deformation theory, i.e., the longitudinal displacement is assumed to vary linearly through the beam's thickness. The shear deformation and rotary inertia terms are included into the formulation, to achieve better accuracy. Nonlinear partial differential equations of motion with boundary conditions are developed and written in the format acceptable by the COMSOL Multiphysics package. An example problem of a clamped-free beam with a piezoelectric actuator is considered, and its finite element solution is obtained. A noticeable difference of forced vibrations of the delaminated and undelaminated beams due to the contact interaction of the crack's faces is predicted by the developed model.

• 대한기계학회논문집A
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• 제39권1호
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• pp.45-53
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• 2015

세탁기의 용량이 커지면서 세탁 및 탈수 시의 세탁물에 의한 질량 불균형 문제가 심해지고 있으며, 이러한 문제를 해결하기 위하여 세탁기에서도 다양한 형태의 서스펜션이 장착되고 있다. 본 연구에서는 마찰 서스펜션에서 발생하는 힘을 측정한 뒤, 물리적인 수식으로 마찰 서스펜션의 비선형 특성을 모델링 하였다. 최소 자승 해(least squares solution)를 구해 파라미터들을 추정하고, 시험과 동일한 조건의 시뮬레이션을 실시하여 개발된 마찰 서스펜션 모델링의 타당성을 검증하였다.

• 해양환경안전학회지
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• 제18권6호
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• pp.577-583
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• 2012

부유구조물은 해양에서 다양한 외력을 경험하게 되며 특히, 파랑하중은 구조물의 설계에 결정적인 지배인자로 간주되고 있다. 이런 구조물은 파장과 크기의 상대적 관계로 소형구조물, 대형구조물 등으로 구분될 수 있으며 전통적으로 소형구조물은 회절발생이 없는 것으로 가정하며 대형구조물은 회절 작용에 따른 관성력만을 고려하여 파랑하중을 산출한다. 따라서 이 연구에서는 해양과 강, 호수 등에서 주로 사용되고 있는 정사각형 부유구조물을 이용하여 동유체력과 구조응답의 상관관계를 파악하여 장방형 부유구조물의 안전성에 대한 영향을 검토하였다.

• 한국지진공학회논문집
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• 제7권5호
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• pp.1-9
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• 2003

국내 콘크리트댐의 경우 내진설계는 관성력을 고려한 진도법을 적용하여 설계를 하고 있으나, 보수적인 설계 방법으로 동적특성을 반영하지 못하는 단점이 있어, 동적특성을 고려한 댐 내진설계가 필요하다. 또한 콘크리트댐 내진성능평가는 동적해석으로 평가해야 하지만, 국내의 경우 대부분 진도법으로 평가를 하고 있어 현행 기준을 적용하기에는 어려운 점이 있다. 이에 본 연구에서는 진도법, 수정진도법, 동적해석 방법을 수행하여 내진설계 및 내진성능평가 결과에 대해서 비교 분석하였다.

• Structural Engineering and Mechanics
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• 제75권3호
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• pp.327-337
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• 2020

The stability and dynamic performance of a flapper-nozzle servo valve depend on several factors, such as the motion of the armature component and the deformation of the spring tube. As the only connection between the armature component and the fixed end, the spring tube plays a decisive role in the dynamic response of the entire system. Aiming at predicting the vibration characteristics of the servo valves to combine them with the control algorithm, an innovative dynamic stiffness based on a distributed parameter model (DPM) is proposed that can reflect the dynamic deformation of the spring tube and a suitable discrete method is applied according to the working condition of the spring tube. With the motion equation derived by DPM, which includes the impact of inertia, damping, and stiffness force, the mathematical model of the spring tube dynamic stiffness is established. Subsequently, a suitable program for this model is confirmed that guarantees the simulation accuracy while controlling the time consumption. Ultimately, the transient response of the spring tube is also evaluated by a finite element method (FEM). The agreement between the simulation results of the two methods shows that dynamic stiffness based on DPM is suitable for predicting the transient response of the spring tube.

• Smart Structures and Systems
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• 제18권6호
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• pp.1125-1143
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• 2016

Forced vibration analysis of a simple supported viscoelastic nanobeam is studied based on modified couple stress theory (MCST). The nanobeam is excited by a transverse triangular force impulse modulated by a harmonic motion. The elastic medium is considered as Winkler-Pasternak elastic foundation.The damping effect is considered by using the Kelvin-Voigt viscoelastic model. The inclusion of an additional material parameter enables the new beam model to capture the size effect. The new non-classical beam model reduces to the classical beam model when the length scale parameter is set to zero. The considered problem is investigated within the Timoshenko beam theory by using finite element method. The effects of the transverse shear deformation and rotary inertia are included according to the Timoshenko beam theory. The obtained system of differential equations is reduced to a linear algebraic equation system and solved in the time domain by using Newmark average acceleration method. Numerical results are presented to investigate the influences the material length scale parameter, the parameter of the elastic medium and aspect ratio on the dynamic response of the nanobeam. Also, the difference between the classical beam theory (CBT) and modified couple stress theory is investigated for forced vibration responses of nanobeams.

• 복합신소재구조학회 논문집
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• 제6권1호
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• pp.14-20
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• 2015

In this study, we propose an innovative lateral force distribution building system between tall buildings by utilizing the difference of moment of inertia, as the alternative design for highly integrated city area. Considering a tri-axial symmetric conditions and boundary conditions for the three-dimensional building structure system, a two-dimensional model is composed. In the proposed indeterminate structural model, important design variables are determined for obtaining minimum horizontal deflections, reactions and bending moments at the ground level of the buildings. Regarding a case of the provided two spatial structures connected to 4 buildings, the optimum location of middle located spatial structure is 45% from the top of the building, which minimize the end moments at the bottom of the buildings. In the considered verification examples, reduced drifts at the top location of the building systems are validated against static wind pressure loads and static earthquake loads. The suggested hybrid building system will improve the safety and reliability of the system due to the added internal truss-dome structures in terms of more than 30% reduced drift and vibration through the development of convergence of tall buildings and spatial structures.