• Proceedings of the KSR Conference
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• 2003.05a
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• pp.755-761
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• 2003

The dynamic analysis of the KTX can predict the dynamic motions which occurred in test drive. In this study an analytical model of the KTX is developed to find the critical speed. The numerical analysis for the nonlinear equation motions of 17 degrees of freedom show the running stability and the critical speed due to the hunting motion of the KTX. Also, the vibration modes of the KTX are calculated using the ADAMS/RAIL software, which show that the critical speed occurs for the yawing modes of the car body and the bogie. Finally, this paper shows that the critical speed of the KTX could be changed with the modifications of the design parameters of wheel conicity and wheel contact point.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.174-180
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• 2002

A virtual reality technology for multipurpose numerical simulation is developed to reproduce and investigate a variety of ocean environmental problems in a 3D-Numerical Wave Tank. The governing equations for solving incompressible fluid motion are Navier-Stokes equation and continuity equation, and the Marker-Density function technique is adopted to implement the fully-nonlinear free-surface kinematic condition. The marine environmental situations, i.e. waves, currents, wind, etc., are reproduced by use of multi-segmented wavemaker on the basis of the so-called "snake-principle". In this paper, some numerical reproduction techniques for regular and irregular waves, multi-directional waves, Bull's-eye wave, wave-current, and solitary wave are presented, and a model test in motion with large amplitude of roll angle is conducted in the developed 3D-NWT, using a overlaid grid system.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.3
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• pp.498-511
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• 2017

This work conducts a validation study for loads analysis of the UH-60A slowed rotor at high advance ratios. The nonlinear flexible multibody dynamics analysis code, DYMORE II, is used with a freewake model for the rotorcraft comprehensive analysis. Wind tunnel test data of airloads and structural loads of a full-scale UH-60A slowed rotor are used for this validation study. This analysis predicts well the thrust reversal phenomenon at the advance ratio of 1.0. The section airloads such as normal forces and pitching moments and the oscillatory blade structural moments in this analysis are compared well or moderately with the measured data, although the higher harmonics components of blade torsion moments are not captured well. This validation study assesses the prediction accuracy and investigates the unique aeromechanics characteristics of a slowed rotor at high advance ratio.

• IE interfaces
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• v.24 no.1
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• pp.40-50
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• 2011

We develop a nonlinear integer programming model which minimizes the total cost with the optimal number of operators to hire and their optimal allocation to the tasks under the diverse constraints such as the weekly, daily, and hourly maximum allowable abandonment rates for the time-varying inbound call volume. We present a case study based on actual data at a call center, in order to prove the validity of applying the optimization method proposed. By the one-sample two-tailed t-test, we confirm that the expected abandonment rates resulting from the optimization method are identical with the ones from the discrete-event simulation within specified confidence intervals.

• Journal of Information Processing Systems
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• v.4 no.4
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• pp.153-158
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• 2008

This paper deals with the geometric fitting algorithms for parametric curves and surfaces in 2-D/3-D space, which estimate the curve/surface parameters by minimizing the square sum of the shortest distances between the curve/surface and the given points. We identify three algorithmic approaches for solving the nonlinear problem of geometric fitting. As their general implementation we describe a new algorithm for geometric fitting of parametric curves and surfaces. The curve/surface parameters are estimated in terms of form, position, and rotation parameters. We test and evaluate the performances of the algorithms with fitting examples.

• Nuclear Engineering and Technology
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• v.39 no.3
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• pp.221-230
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• 2007

Wavelet theory was applied to detect a singularity in a reactor power signal. Compared to Fourier transform, wavelet transform has localization properties in space and frequency. Therefore, using wavelet transform after de-noising, singular points can easily be found. To test this theory, reactor power signals were generated using the HANARO(a Korean multi-purpose research reactor) dynamics model consisting of 39 nonlinear differential equations contaminated with Gaussian noise. Wavelet transform decomposition and de-noising procedures were applied to these signals. It was possible to detect singular events such as a sudden reactivity change and abrupt intrinsic property changes. Thus, this method could be profitably utilized in a real-time system for automatic event recognition(e.g., reactor condition monitoring).

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.325-328
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• 2008

In recent years, developments of light weight vehicle are one of the most important issues in automotive industry. It is important to know the variations of the mechanical properties in the hydro forming process for the safe and durable design purposes. Generally, tube hydroforming process consists of three main processes such as bending, preforming, and hydroforming. It means that the strain hardening histories of final products are nonlinear. In this study, strain hardening behavior during hydroforming has been investigated by hydroforming of engine cradle as a model process. The variation of mechanical properties such as local hardness and strength were used as an index of strain hardening during respective processes. The correlationship between strength and hardness obtained from tensile test has been equivalently converted into correlation between hardness and measured strain.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.11
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• pp.224-233
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• 1999

The quality of injection molded parts is affected by the variables such as materials, design variables of part and mold, molding machine, and processing conditions. It is difficult to consider all the variables at the same time to predict the quality. In this paper neural network was applied to analyze the relationship between processing conditions and volumetric shrinkage of part. Engineering plastic gear was used for the study, and the learning data was extracted by the simulation software like Moldflow. Results of neural network was good agreement with simulation results. Nonlinear regression model was formulated using the test data of 3,125 obtained from neural network, Optimal processing conditions were calculated to minimize the volumetric shrinkage of molded part by the application of RQP(Recursive Quadratic Programming) algorithm.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.6
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• pp.807-819
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• 2019

In this paper, it is proposed a new approach to motion control and kinematics analysis of articulated manipulator attachment with five degree of freedom for excavator. Unlike the well-established theory for the control of linear systems, there is little general control theory relatively for a robust control of nonlinear systems. The control technique is essential for providing a stable and robust performance for application of articulated manipulator control. The proposed control algorithm is one of robust control methods based on error informations of the position and velocity error informations using stability analysis of dynamic model. Through simulation test, the proposed control scheme is illustrated to be a efficient control technique for real-time control.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.180-190
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• 2006

Effects of panel zone (PZ) strength on cyclic seismic performance of the RBS connections was studied based on the validated finite element analysis. High-profile cyclic correlation of finite element model with the full-scale test results based on the material and geometric nonlinear post-buckling analysis was among the most significant consideration in this study. Numerical response results as affected by the panel zone strength reproduced the experimentally observed results quite reasonably. The finite element modeling capability of this study can be used to supplement or to replace in part the costly full-scale connection testing.