• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1068-1073
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• 2007

3D finite element analyses of a corrugated steel web girder and a steel truss web girder are conducted to investigate the static and dynamic behaviour of the hybrid girders. And the analyses results are compared with those by the equivalent beam theory. The equivalent theory is a theory that all section properties of a truss structure are replaced by section properties of a beam including the shear coefficient. When applying the equivalent beam theory, the shear coefficient of the corrugated steel web girder is estimated as the area ratio of total section to web section and that of the steel truss web girder is calculated by the equation proposed by Dewolf. Static deflections and natural frequencies by 3D finite element analyses and the those by the equivalent beam theory are relatively in good agreement.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.3
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• pp.80-88
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• 2010

A simple computational model for modeling of subsurface crack growth under cyclic contact loading is presented. In this model, it is assumed that the initial fatigue crack will initiate in the region of the maximum equivalent stress at certain depth under the contacting surface. The position and magnitude of the maximum equivalent stress are determined by using the equivalent contact model, which is based on the Hertzian contact conditions with frictional forces. The virtual crack extension method is used for simulation of the fatigue crack growth from the initial crack up to the formation of the surface pit due to contact fatigue. The relationships between the stress intensity factor and crack length are then determined for various combinations of equivalent contact radii and loadings.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1051-1060
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• 2005

Nonlinear Response Optimization using Equivalent Static Loads (NROESL) method/algorithm is proposed to perform optimization of non-linear response structures. The conventional method spends most of the total design time on nonlinear analysis. The NROESL algorithm makes the equivalent static load cases for each response and repeatedly performs linear response optimization and uses them as multiple loading conditions. The equivalent static loads are defined as the loads in the linear analysis, which generates the same response field as those in non-linear analysis. The algorithm is validated for the convergence and the optimality. The proposed algorithm is applied to a simple mathematical problem to verify the convergence and the optimality.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1316-1321
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• 2003

The systematic method to construct equivalent static load from the given dynamic load is proposed in the present study. Previously reported works to construct equivalent static load were based on ad hoc methods. They may results in unreliable structural design. The present study proposes a selection scheme of degrees of freedom(d.o.f) for imposing the equivalent static loads. The d.o.fs are selected by Two-level condensation scheme(TLCS). TLCS consists of two two-steps. The first step is the energy estimation in element-level and the second step consists of the traditional sequential elimination precudure. Through several numerical examples, the efficiency and reliability of proposed scheme is verified.

• Journal of Electrical Engineering and Technology
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• v.6 no.3
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• pp.408-413
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• 2011

In this paper, a real-coefficient approach to Adaptive Frequency Sampling (AFS) technique is developed for efficient equivalent circuit modeling of RF components. This proposed method is advantageous than the vector fitting technique and the conventional AFS method in terms of fewer samples leading to a lower order of a rational function on a given data and to a direct conversion to an equivalent circuit for PSPICE(Personal Simulation Program with Integrated Circuit Emphsis) simulation, respectively. To validate the proposed method, the distributed equivalent circuit of a presented multi-layered RF low-pass filter is obtained using the proposed real-coefficient AFS, and then comparisons with EM simulation and circuit simulation for the device under consideration are achieved.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.924-929
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• 1994

In using a performance model of a torque converter determined by its gemetric condition, it is possible that the analysis of two arbitrary converters produces the the same results because of the same value of equivalent parameters despite their different shapes. Therefore, it is necessary to understand the effect of shape factor on dynamic perfomance, and equivalent parameters reoresenting a performace model of a converter should into its defined by the behavior of flow field. In this study, torus flow of a torque converter is changed into its equivalent system defined by the behavior of flow, and govering equations for the system are presented and used for analysis. Equivalent parameters are obtained from the results of flow analysis and are compared with parameters of one dimensional performance model. The influence that shape change of a converter has on the behavior of flow and the equivalent parameters is studied qualitatively.

• Journal of KSNVE
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• v.9 no.5
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• pp.943-948
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• 1999

This paper proposes a feasible and effective method for measuring the mechanical-acoustic transfer function by the application of equivalent area and velocity transfer function, a manifestation of the vibro-acoustical reciprocity principle. On the contrary to the volume velocity used in traditional method, the equivalent area is a peculiar raidation characteristics of sound sources and not influenced by any input signal for driving sound source. This invariant property of equivalent area can get rid of boresome works to measure the volume velocity of a sound source every time the driving signal is changed. Moreover, this method has a remarkable advantage to use a general loudspeaker as an accoustic exciter without the assumption of point source and can be applied to all kinds of sound sources even if they are not omni-directional sources.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.304-308
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• 2006

The focus of this study is modeling technique for a bellows in vehicle exhaust system. Bellows was developed using tile finite element model by replacing with the equivalent beam. The equivalent beam model were studied in detail. Non-structural node in the cross section of original model is given to expressing their motion. Equivalent mass matrix and stiffness matrix calculated using Guyan reduction method. Material Properties of beam was obtained from the direct comparison between equivalent model and that of Timoshenko beam model. The calculated natural frequencies and mode shape are compared with the reference results and coincided well. The results were compared with the confirmed results, which were in good agreement.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.146-153
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• 2009

One dimensional site response analysis is widely used in prediction of the ground motion that is induced by earthquake. Equivalent linear analysis is the most widely used method due to its simplicity and ease of use. However, the equivalent linear method has been known to be unreliable since it approximates the nonlinear soil behavior within the linear framework. To consider the nonlinearity of the ground at frequency domain, frequency dependent algorithms that can simulate shear strain - frequency dependency have been proposed. In this study, the results of the modified equivalent linear analysis are compared to evaluate the degree of improvement and the applicability of the modified algorithms. Results show the novel smoothed curve that is proposed by this study indicates the most stable prediction and can enhance the accuracy of the prediction.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.11
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• pp.577-582
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• 2004

In this paper, lumped equivalent circuits for a conventional parallel directional coupler are proposed. This equivalent circuits only have self inductance and self capacitance, so we can design exact lumped equivalent circuit. The equivalent circuit and design formula for the presented lumped element coupler is derived based on the even- and odd-mode properties of parallel-coupled line. By using the derived design formula, we have designed the 3dB and 4.7dB MMIC couplers at the center frequency of 3.4GHz and 5.6GHz respectively. Measurements for the designed MMIC directional couplers show at 4dB and 5.2dB-coupling value at the center frequency of 3.4GHz and 5.6GHz. Excellent agreements between simulation results and measurement results on the designed directional couplers show the validity of this paper