• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1055-1060
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• 2002

The noise and vibration of rolling piston-type compressors used in the most of the airconditional system is a serious and important problem occurred during turning on and off as well as during operating. To analyze the vibration occurred during turning on and oft, the vibration analysis of motor-compressor coupling is required. In this paper, through modeling of the motor, solving the force from the equations of motion of the moving parts and considering the stiffness of the rubber mounts, the analysis of vibration was performed.

• Structural Engineering and Mechanics
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• 제3권3호
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• pp.215-228
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• 1995

For non-classically damped structures subjected to evolutionary random seismic excitations, the non-stationary random responses are computed by means of a high precision direct (HPD) integration scheme combined with the pseudo excitation method. Only real modes are used, so that the reduced equations of motion remain coupled for such non-classically damped structures. In the given examples, the efficiency of this method is compared with that of the Newmark method.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 춘계학술대회 논문집
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• pp.285-290
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• 2004

파도에 의한 힘과 모멘트는 운항하는 선박에 운동을 발생시킨다. 이러한 운동은 승무원의 작업 능률 저하, 화물의 안전 및 승선감 등에 영향을 주게 되어 안전 운항 저해 요소가 되므로 파도에 의한 운동이 큰 선박들은 자세제어장비(anti-rolling devices)의 장착이 요구된다. 본 연구에서는 수ㆍ능동의 이동질량 안정기(moving weight stabilizer), 감요탱크(anti-rolling tank), 핀 스태빌라이저(fin stabilizer)와 같은 자세제어장비의 동적 거동을 수학적으로 모델링 하였다. 기존에는 자세제어장비의 운동을 선박의 횡동요에만 고려한 반면, 본 연구에서는 선박의 6자유도 운동을 모두 고려하여 연성 운동방정식을 정립하였다. 마지막으로 자세제어장비를 장착한 선박의 파중 운동 계산 프로그램을 작성하여 시뮬레이션을 수행하였다.

• Structural Engineering and Mechanics
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• 제51권4호
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• pp.685-705
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• 2014

This paper presents a new formulation for forward scalar wave simulations in semi-infinite media. Perfectly-Matched-Layers (PMLs) are used as a wave absorbing boundary layer to surround a finite computational domain truncated from the semi-infinite domain. In this work, a hybrid formulation was developed for the simulation of scalar wave motion in two-dimensional PML-truncated domains. In this formulation, displacements and stresses are considered as unknowns in the PML domain, while only displacements are considered to be unknowns in the interior domain. This formulation reduces computational cost compared to fully-mixed formulations. To obtain governing wave equations in the PML region, complex coordinate stretching transformation was introduced to equilibrium, constitutive, and compatibility equations in the frequency domain. Then, equations were converted back to the time-domain using the inverse Fourier transform. The resulting equations are mixed (contain both displacements and stresses), and are coupled with the displacement-only equation in the regular domain. The Newmark method was used for the time integration of the semi-discrete equations.

• 한국정밀공학회지
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• 제22권11호
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• pp.111-117
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• 2005

The vibration problems associated with gear coupled rotors have been the focus of much engineering work. These systems are complex and difficult to analyze in that they have the problems associated with conventional rotors plus those additional problems associated with the gear couplings. This paper examines the problems peculiar to the gear mesh. Because of the meshing action of gears, the elasticity of the gear teeth introduces time-varying stiffness coefficients into the governing equations of motion. This means that system response must be thought of in terms of Mathieu-type equations, where multiple-frequency response occur due to the periodic coefficients. The meshing action of the gears also couples the lateral and torsional gear motions. Gear errors, such as tooth profile and spacing errors, produce forces and torque that excite the system at multiple frequencies, some of which are much higher than shaft rotational speed. To investigate how to the time-varying stiffness in the gear teeth and the gear errors act one the dynamic response of the gear coupled rotors, a three-dimensional dynamic model with lateral-tortional oscillation is developed. The harmonic balance technique is employed to solve this mathieu-type problem.

• 대한조선학회논문집
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• 제53권4호
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• pp.307-314
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• 2016

Energy flow analysis(EFA) is a representative method that can predict the statistical energetics of structures at high frequencies. Generally, as the frequency increases, the shear distortion and rotatory inertia effects in the out-of-plane motion of beams or plates become important. Therefore, to predict the out-of-plane energetics of coupled structures in the high frequency range, the energy flow analyses of Timoshenko beam and Mindlin plate are required. Unlike the energy flow model of Kirchhoff plate, the energy flow model of Mindlin plate is composed of three kinds of energy governing equations(out-of-plane shear wave, bending dominant flexural wave, and shear dominant flexural wave). This paper performed the energy flow finite element analysis(EFFEA) of coplanar coupled Mindlin plates. For EFFEA of coplanar coupled Mindlin plates, the energy flow finite element formulation of out-of-plane energetics in the Mindlin plate was performed. The general EFFEA program was implemented by MATLAB® language. For the verification of EFFEA of Mindlin plate, the various numerical applications were done successfully.

• Coupled systems mechanics
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• 제8권4호
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• pp.351-375
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• 2019

The present work investigates the use of a rigid rocking block as a tool to reduce vibrations in a frame structure. The study is based on a simplified model composed by a 2-DOF linear system, meant to represent a general M-DOF frame structure, coupled with a rocking rigid block through a linear visco-elastic device, which connects only the lower part of the 2-DOF system. The possibility to restrain the block directly to the ground, by means of a second visco-elastic device, is investigated as well. The dynamic response of the model under an harmonic base excitation is then analysed in order to evaluate the effectiveness of the coupling in reducing the displacements and the drift of the 2-DOF system. The nonlinear equations of motion of the coupled assemblage 2-DOF-block are obtained by a Lagrangian approach and then numerically integrated considering some reference mechanical and geometrical quantities as variable parameters. It follows an extensive parametric analysis, whose results are summarized through behaviour maps, which portray the ratio between the maximum displacements and drifts of the system, with and without the coupling with the rigid block, for several combinations of system's parameters. When the ratio of the displacements is less than unity, the coupling is considered effective. Results show that the presence of the rocking rigid block improves the dynamics of the system in large ranges of the characterizing parameters.

• Structural Engineering and Mechanics
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• 제68권1호
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• pp.1-15
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• 2018

In ocean industry, free surface type ART (Anti Roll tank) system has been widely used to suppress the roll motion of floating structures. In those, various obstacles have been devised to obtain the sufficient damping and to enhance the controllability of freely rushing water inside the tank. Most of previous researches have paid on the development of simple mathematical formula for coupled ship-ARTs analysis although other numerical and experimental approaches exist. Little attention has been focused on the use of 3D panel method for preliminary design of free surface type ART despite its advantages in computational time and general capacity for hydrodynamic damping estimation. This study aims at developing a potential theory based hydrodynamic code for the analysis of floating structure with baffled ARTs. The sloshing in baffled tanks is modeled through the linear potential theory with FE discretization and it coupled with hydrodynamic equations of floating structures discretized by BEM and FEM, resulting in direct coupled FE-BE formulation. The general capacity of proposed formulation is emphasized through the coupled hydrodynamic analysis of floating structure and sloshing inside baffled ARTs. In addition, the numerical methods for natural sloshing frequency tuning and estimation of hydrodynamic damping ratio of liquid sloshing in baffled tanks undergoing wave exiting loads are developed through the proposed formulation. In numerical examples, effects of natural frequency tuning and baffle ratios on the maximum and significant roll motions are investigated.

• 한국해양학회지:바다
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• 제13권3호
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• pp.237-245
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• 2008

우리는 해저 연약지반 주행차량과 주행차량의 상부에 결합되어 있는 유연관의 연성거동 동력학 해석 기법을 개발하였다. 연약지반 주행차량은 1개의 강체로 모델링되었으며, 질량집중매개변수 기법을 이용한 이산화기법을 적용하여 유연관을 모델링하였다. 강체 무한궤도 주행차량의 운동방정식과 유연관의 3차원 비선형 지배방정식을 결합시켰으며, 4개의 오일러 매개변수를 이용하여 주행차량과 유연관의 자세를 표현하였다. 주행차량과 유연관의 비선형 연성거동 동력학 방정식의 해를 구하기 위해, 증분-반복법을 이용하였다. 시간영역 수치적분을 위해 $Newmark-\beta$기법을 이용하였다. 증분-반복법을 적용하여 연성 운동방정식에 대한 자코비안 행렬을 유도하였다. 동적거동 동력학 해석 기법을 통해 유연관의 동적거동과 연약지반 위를 주행하는 무한궤도 차량의 동적거동 사이의 상호작용을 시간영역에서의 관찰하였다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.311-314
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• 2006

This paper concerns about total dynamic analysis of integrated mining system. This system consists of vertical steel pipe, intermediate buffer station, flexible pipe and self-propelled miner. The self-propelled miner and buffer are assumed as rigid-body of 6-dof. Discrete models of vertical steel pipe and flexible pipe are adopted, which are obtained by means of lumped-parameter method. The motion of mining vessel is not considered. Instead, the motion of mining vessel is taken into account in form of various boundary conditions (e.g. forced excitation in slow motion and/or fast oscillation and so on). A terramechanics model of extremely soft cohesive soil is applied to the self-propelled miner. The hydrodynamic forces and moments are included in the dynamic models of vehicle and lifting pipe system. Hinged and fixed constraints are used to define the connections between sub-systems (vertical steel pipe, buffer, flexible pipe, miner). Equations of motion of the coupled model are derived with respect to the each local coordinates system. Four Euler parameters are used to express the orientations of the sub-systems. To solve the equations of motion of the total dynamic model, an incremental-iterative formulation is employed. Newmark-b method is used for time-domain integration. The total dynamic responses of integrated mining system are investigated.