• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1757-1763
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• 2010

Flywheel energy storage system (FESS) is defined as a high speed rotating flywheel system that can save surplus electric power. The FESS is proposed as an efficient energy storage system because it can accumulate a large amount of energy when it is operated at a high rotating speed and no mechanical problems are encountered. The FESS consists of a shaft, flywheel, motor/generator, bearings, and case. It is difficult to simulate rotor dynamics using common structure simulation programs because these programs are based on the 3D model and complex input rotating conditions. Therefore, in this paper, a program for the FESS based on the 2D FEM was developed. The 2D FEM can model easier than 3D, and it can present the multi-layer rotor with different material each other. Stiffness changing of the shaft caused by shrink fitting of the hub can be inputted to get clear solving results. The results obtained using the program were compared with those obtained using the common programs to determine any errors.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.3
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• pp.138-148
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• 2005

Dynamic response of floating structures such as floating body and floating bridges subject to wave load is to be calculated in frequency domain. Added mass coefficient, damping coefficient and wave exciting force are obtained numerically from frequency domain formulation of linear potential theory and boundary element method for a floating body which is partially submerged into water and subjected to wave force. Next, the equation of motion for the dynamic behavior of a floating structure which is supported by the floating bodies and modeled with finite elements is written in frequency domain. hker a hemisphere is analyzed and compared with the published references as examples of floating bodies, the hydrodynamic coefficients for a pontoon type floating body which supports a floating bridge are determined. The dynamic response of the floating bridge subject to design wave load can be solved using the coefficients obtained for the pontoons and the results are plotted in the frequency domain. It can be seen from the example analysis that although the peak frequency of the incoming wave spectrum is near the natural frequency of the bridge, the response of the bridge is not amplified due to the effect that the peak frequency of wave exciting force is away from the natural frequency of the bridge.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.209-216
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• 2012

In this paper, we propose a novel tracking method which uses image features consisted of the area, average intensity, aspect ratio of a target image for the real-time IR surveillance system. The image features of the ground target can be modeled as a random process with exponential autocorrelation function mathematically. Finally, we derived a discrete target dynamic equation including kinematic states and geometric states of the target. Simulation results shows that the performance of the proposed method is better than that of the previous tracking method.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.10a
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• pp.40-41
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• 2009

In general, ships are towed to keep the safe operations in harbor or channel by tug boats. Due to increase in ocean traffic, many accidents are happened in harbor or channel in these days. Therefore it is necessary to predict manoeuvrability of tug-barge system, and to assure the safety of that system. Turg-barge system is composed of tug boat, barge, and towing cable, connecting both ships. Manoeuvring equations of tug-barge system are suggested, and the scopes of model tests are discussed to establish the mathematical models for tug boats in this paper.

• Membrane Journal
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• v.30 no.4
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• pp.242-251
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• 2020

Computer simulation tools mainly used for polymer materials and polymeric membranes are divided into various fields depending on the size of the object to be simulated and the time to be simulated. The computer simulations introduced in this review are classified into three categories: Quantum mechanics (QM), molecular dynamics (MD), and mesoscale modeling, which are mainly used in computational material chemistry. The computer simulation used in polymer research has different research target for each kind of computational simulation. Quantum mechanics deals with microscopic phenomena such as molecules, atoms, and electrons to study small-sized phenomena, molecular dynamics calculates the movement of atoms and molecules calculated by Newton's equation of motion when a potential or force of is given, and mesoscale simulation is a study to determine macroscopically by reducing the computation time with large molecules by forming beads by grouping atoms together. In this review, various computer simulation programs mainly used for polymers and polymeric membranes divided into the three types classified above will be introduced according to each feature and field of use.

• Journal of Ocean Engineering and Technology
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• v.28 no.5
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• pp.466-473
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• 2014

Underwater gliders do not have any external propulsion systems that can generate and control their motion. Generally, underwater gliders would obtain a propulsive force through the lift force generated on the body by a fluid. Underwater gliders should be equipped with mechanisms that can induce heave and pitch motions. In this study, an inner movable and rotatable mass mechanism was proposed to generate the pitch and roll motions of an underwater glider. In addition, a buoyancy control unit was presented to adjust the displacement of the underwater glider. The buoyancy control unit could generate the heave motion of the underwater glider. In order to analyze the underwater dynamic behavior of this system, nonlinear 6-DOF dynamic equations that included mathematical models of the inner movable mass and buoyancy control unit were derived. Only kinematic characteristics such as the location of the inner movable mass and the piston position of the buoyancy control unit were considered because the velocities of these systems are very slow. The effectiveness of the proposed dynamic modeling was verified through sawtooth and spiraling motion simulations.

• International Journal of Highway Engineering
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• v.7 no.4 s.26
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• pp.185-202
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• 2005

In this research, to get over restrictions of a field expreiment, we modeled a planning road through the 3D Virtual Reality and achieved data about dynamic response related to sector fluctuation and about driver's visual behavior on testers' driving the Driving Simulator Car with Eye Camera. We made constant efforts to reduce the non-reality and side effect of Driving Simulator on maximizing the accord between motion reproduction and virtual reality based on data Driving Simulator's graphic module achieved by dynamic analysis module. Moreover, we achieved data of driver's natural visual behavior using Eye Camera(FaceLAB) that is able to make an expriment without such attaching equipments such as a helmet and lense. In this paper, to evaluate the level of road's safety, we grasp the meaning of the fluctuation of safety that drivers feel according to change of road geometric structure with methods of Driving Simulator and Eye Camera and investigate the relationship between road geometric structure and safety level. Through this process, we suggest the method to evaluate the road making drivers comfortable and pleasant from planning schemes.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.11
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• pp.903-910
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• 2020

This paper introduces a simulator to assess the impacts of the wind and the airframe vibration on the performance of the Active Electronically Scanned Array (AESA) radar mounted in an aircraft. The AESA radar is mounted on the nose cone of an aircraft, and vibration occurs due to the drag force. This vibration affects the behavior of the AESA radar and can cause phase errors in signal. The simulator adopts the geometric model for nose cone, the mathematical models on the rigid-body dynamics of the aircraft, the average/turbulent winds, and the mode/ambient vibrations to compute the position and the attitude of the radar accurately. Numerical studies reflecting a set of test scenarios were conducted to demonstrate the effectiveness of the developed simulator.

• Journal of Korean Society of Transportation
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• v.21 no.4
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• pp.91-101
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• 2003

This study modeled 4-lane highway in three-dimensional virtual reality in order to overcome difficulties of field experiment. and the research subject was placed in a driving simulator. We survey the driver's cognitive characteristics to the alignment changes in the three-dimensional virtual reality highway. Especially, maximizing the identity of driving movements and virtual scenery on the basis of the data obtained by dynamic analysis module. we minimized simulator sickness for the graphic module of driving simulator. And we carried out cognitive evaluation on the basis of adjective words extracted by dictionary and the opinion of specialist. In this study LISREL model was used to detect the causal relation between geometry and safety in cognitive side, and found that geometric change affects the safety of drivers by static and dynamic road safety model in three-dimensional combined alignments. As the result, for constructing safety road. we consider drivers' cognitive characteristics as human factors in road design, and we think that they are very important factors to improve road safety.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.1035-1042
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• 2014

Reducing the friction of engine parts is an important issue in engine design. The loss of energy in the piston assembly due to mechanical friction ranges from 40 to 55%, and there is an increase in the total energy of about 5% if the friction of the piston can be removed. In order to reduce the friction loss at the level of each engine part, it is necessary to perform a comparative analysis with other engines to determine the important factors affecting the energy loss. Several studies have been performed to analyze the lubrication based on hydrodynamic modeling, since a piston lubrication system has dimensions in the nanoscale to microscale domain. Therefore, it is necessary to determine the correlations between the molecular and continuum systems. In this study, we investigated the friction changes due to the various interactions between molecules in the wall/fluid interface, where a microscopic movement of the oil film occurs along the cylinder liner of the engine.