• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.1
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• pp.10-18
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• 2003

This paper presented a design and control of a biped walking RGO(robotic gait orthosis) and its simulation. The biped walking RGO was distinguished from the other one by which had a very light-weight and a new RGO system will be made of 12-servo motors and 12-controllers. The vibration evaluation of the dynamic PLS(posterior leaf splint) on the biped walking RGO was used to access by the 3-axis accelerometer with a low frequency vibration of less than 30 Hz. The galt of the biped walking RGO depends on the constrains of mechanical kinematics and the initial posture. The stability of dynamic walking was investigated by analyzing the ZMP (zero moment point) of the biped walking RGO. It was designed according to the human wear type and was able to accomodate itself to the environments of S.C.I. Patients. The Joints of each leg were adopted with a good kinematic characteristics. To analyse joint kinematic properties. we made the strain stress analysis of the dynamic PLS and the analysis study of FEM with a dynamic PLS.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.513-516
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• 2000

This paper presents the analytical studies on the stress and strain of driven valve system of internal combustion engines. The stress and strain is predict using FEM. The particular interest is the dynamic strain at a specific point of the valve and valve seat. Cam and follower Assuming that one rigid surface. This study forced the effects changing Young's modulus and density of valve and valve seat contact area. It supports that the indirect method using FEM is reliable for prediction the actual displacement, stress and strain in the valve system.

• Journal of Electrical Engineering and Technology
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• v.2 no.3
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• pp.346-352
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• 2007

In this paper, we present an analysis of dynamic characteristics of an electromagnetic actuator for circuit breakers. It is indispensable to simultaneously analyze magnetic, electric, and mechanical phenomena to obtain the dynamic characteristics of the electromagnetic actuator because these phenomena are closely related to each other in an electromagnetic actuator system. The magnetic equations are computed by using the finite element method (FEM). The electric equations and the mechanical equations, which include the time derivative terms, are calculated by using the time difference method (TDM). The calculated results, which have been obtained by means of the FEM and the TDM, are presented with experimental data.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.2
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• pp.103-112
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• 1990

This study examines the characteristics of soil behavior which includes many uncertainties in seismic design, evaluates the dynamic soil properties and studies the soil-structure interaction to generalize the applicability and economy of the available sites. An example analysis is performed for soil-structure system response assuming a containment structure built on site which includes soil layers using both elastic halfspace analysis and FEM analysis against the seismic loads from the actual design. This exercise is performed as a part of the safety analysis and economic assessment of the nuclear power plant built on soils. It includes the preparation of computer program capable of incorporating large nonlinearity in the analysis, resonable evaluation procedures to determine input soil data. Nonlinear FEM analysis of Seed and Idriss model is found suitable for the accurate analysis of dynamic response of soils. Linear FEM analysis using dynamic soil properties at strain level obtained by one-dimensional seismic response, and elastic half-space analysis using dynamic soil properties at strain level under static loads are recommended to evaluate the dynamic soil properties.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.3-5
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• 1995

For a linear induction motor(LIM), the constants of each phase are different due to the structure. In this paper, a vector control analysis method of a LIM taking into consideration its asymmetrical constants are proposed. And, in order to prove the propriety of proposed vector control method and to analyze the dynamic characteristics of LIM's vector control, FEM taking into account of movement and using stator tapped winding is used in the analysis region. So, It is confirmed that the proposed asymetrical constants vector control theory and simulation method of mixing with FEM is appropriate to dynamic characteristics analysis of LIM.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.10
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• pp.1043-1049
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• 2012

The FEM analysis of machine tools is the general analysis process to evaluate machine performance in the industry for a long time. Despite advances in FEM software, because of difficult simplicity of CAD drawing, little experience of joints stiffness modeling and troublesome manual contact area divide for bindings, the industry designers think the FEM analysis is still an area of FEM analysis expert. In this paper, the automation of modeling process with simplicity of drawing, modeling of joints and contact area divide is aimed at easy FEM analysis to enlarge utilization of a virtual machine tools. In order to verify the effects of modeling automation, a slant bed type model with tilting table is analyzed. The results show FEM modeling automation method only needed 45 minutes to complete the whole modeling process, while manual modeling method requires almost one month with 8200 calculations for coordinate transformations and stiffness data input.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.9
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• pp.68-74
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• 1998

The ESPI(Electronic Speckle Pattern Interferometry) is a real time, full-field, non-destructive optical measurement technique that allows static and dynamic deformation analysis and surface shape measurements of engineering structures. e .g. turbine blades. vehicle engine components, body panels, etc. This technique is very similar to holographic interferometry, but uses a solid static camera and an image processing board for recording and digital processing of speckle patterns. In this paper it is presented that FEM results for the free vibration of symmetrically laminated composite as [30/-30/90]s. The natural frequencies of laminated composite rectangular plates having the particular boundary condition are experimentally obtained. In order to demonstrate the validity of the experiment, FEM analysis using ANSYS was performed and natural frequencies experimentally obtained is compared with calculation by FEM analysis. The results obtained from both experiment and FEM analysis show a good agreement.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.10b
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• pp.51-58
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• 2000

The purpose of this study is the optimum modification of dynamic characteristics of stiffened plate structure. In the method of the optimization ,finite element method (FEM), sensitivity analysis and optimum structural modification method are used. To begin with, using FEM, the dynamic characteristics of stiffened plate structure is analyzed. Next, rate of change of dynamic characteristic by the change of design variable is calculated using the sensitivity analysis. Then, amount of change of design variable is calculated using this sensitivity value and optimum structural modification method. The change of natural frequency is made to be an objective function. Thickness of plate and cross section moment become a design variable. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate structure.

• International Journal of High-Rise Buildings
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• v.4 no.1
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• pp.9-25
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• 2015

Field measurements of various structures have been conducted for many purposes. Measurement data obtained by field measurement is very useful to determine vibration characteristics including dynamic characteristics such as the damping ratio, natural frequency, and mode shape of a structure. In addition, results of field measurements and modal identification can be used for modal updating of FEM analysis, for checking the efficiency of damping devices and so on. This paper shows some examples of field measurements and modal identification for structural health monitoring. As the first example, changes of dynamic characteristics of a 15-story office building in four construction stages from the foundation stage to completion are described. The dynamic characteristics of each construction stage were modeled as accurately as possible by FEM, and the stiffness of the main structural frame was evaluated and the FEM results were compared with measurements performed on non-load-bearing elements. Simple FEM modal updating was also applied. As the next example, full-scale measurements were also carried out on a high-rise chimney, and the efficiency of the tuned mass damper was investigated by using two kinds of modal identification techniques. Good correspondence was shown with vibration characteristics obtained by the 2DOF-RD technique and the Frequency Domain Decomposition method. As the last example, the wind-induced response using RTK-GPS and the feasibility of hybrid use of FEM analysis and RTK-GPS for confirming the integrity of structures during strong typhoons were shown. The member stresses obtained by hybrid use of FEM analysis and RTK-GPS were close to the member stresses measured by strain gauges.

• Journal of KSNVE
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• v.8 no.5
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• pp.949-956
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• 1998

Complex and large lattice type structures are frequently used in design of bridge, tower, crane and aerospace structures. In general, in order to analyze these structures we have used the finite element method(FEM). This method is the most widely used and powerful method for structural analysis lately. However, it is necessary to use a large amount of computer memory and computational time because the FEM requires many degrees of freedom for solving dynamic problems exactly for these complex and large structures. For analyzing these structures on a personal computer, the authors developed the transfer stiffness coefficient method(TSCM). This method is based on the concept of the transfer of the nodal dynamic stiffness coefficient matrix which is related to force and displacement vector at each node. And we suggested TSCM for free vibration analysis of complex and large lattice type structures in the previous report. In this paper, we formulate forced vibration analysis algorithm for complex and large lattice type structures using extened TSCM. And we confirmed the validity of TSCM through computational results by the FEM and TSCM, and experimental results for lattice type structures with harmonic excitation.