• Journal of the Korean Society for Precision Engineering
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• v.32 no.8
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• pp.693-698
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• 2015

Recently, the quality of products after the corresponding machining processes were scrutinized in the interest of maintaining a high product-quality standard. The structure and stability of machine tools are important for the prediction of product quality. A structural analysis needs to be carried out to achieve the stable design of machine tools before the initial design stage in the manufacturing process of a precision product. In this study, a structural analysis was carried out using a finite element analysis (FEA) simulation to obtain the design stability of the main parts of a grinding machine. The sizes and locations of both the maximum stress and deformation in consideration of the cutting force of the chuck, tail stock, and bearing of the grinding machine were analyzed. Finally the grinding machine was successfully developed.

• Journal of the Korean Society for Railway
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• v.13 no.6
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• pp.559-564
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• 2010

This paper proposes an advanced filter design to improve power quality of a head electric power (HEP) as a power conversion unit in centralized-power type electric railway vehicle. First of all, we have measured waveform of output power of transformer connected HEP to design the filter. Throughout experiment and simulation results, it is estimated that switching technique used HEP is advanced selected harmonic elimination PWM (SHEPWM) and the applied switching frequency is about 300Hz. In this paper, a filter to improve power quality considering estimated parameters is designed. As a result, the reduction of the magnitude of the overall harmonic is achieved and confirmed through simulations.

• IEIE Transactions on Smart Processing and Computing
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• v.1 no.1
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• pp.50-64
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• 2012

Quality of Service (QoS) and fairness considerations are undoubtedly essential parameters that need to be considered in the design of next generation scheduling algorithms. This work presents a novel game theoretic cross-layer design that offers optimal allocation of wireless resources to heterogeneous services in Orthogonal Frequency Division Multiple Access (OFDMA) networks. The method is based on the Axioms of the Symmetric Nash Bargaining Solution (S-NBS) concept used in cooperative game theory that provides Pareto optimality and symmetrically fair resource distribution. The proposed strategies are determined via convex optimization based on a new solution methodology and by the transformation of the subcarrier indexes by means of time-sharing. Simulation comparisons to relevant schemes in the literature show that the proposed design can be successfully employed to typify ideal resource allocation for next-generation broadband wireless systems by providing enhanced performance in terms of queuing delay, fairness provisions, QoS support, and power consumption, as well as a comparable total throughput.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.14-20
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• 1997

Due to several advantages of Pulse Width Modulated(PWM) Converter, such as unity power factor with low-harmonics and energy regeneration, PWM converter has been widely used in industrial application. In every application of energy conversion equipment, the design and implementation must be carried out considering performance and cost. High quality with low cost is the best choice for energy conversion equipment. High dc link voltage can reduce inverter and motor side losses and system dimension compare to low dc link voltage. Analog controller can make PWM converter cheaper without considerable degradation of the performance than digital controller. This paper shows the simplified analog controller-for 600V dc link voltage using stationary reference frame control and the simulation results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.107-110
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• 1999

The purpose of this research is for the development of a new type forging equipment H.C.G(Hyundai Continuous Grain-flow) by using two virtual build-up tools rigid viscoplastic FEM and downsized plasticine experiment. This forging equipment consists of consecutive horizontal and vertical pressure while the traditional forging method consists of only vertical pressure. Using this method high quality crankshafts can be forged as it can maintain a continuous grain flow. The factors considered in the development of equipment are die geometry for flawless deformed shape die reaction forces stress/strain distributions and continuous material flow. We carried out several numerical simulations and downsized plasticine experiments for the proper design of the forging equipment. The validity of those simulation results is confirmed by checking with the actual test results. Based on these simulation results the proper design of the H.C.G for ging equipment is enabled.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.2 s.179
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• pp.65-72
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• 2006

Downcoiler is one of the major facilities in hot strip mill operation. The key to good coiling is having good equipment, modem control systems, excellent maintenance and an understanding of coiling process. Therefore, this study aims to develop a program that is useful for calculating machine design parameters and simulating coiling process. In this study, the pinching and coiling mechanism of the downcoiler was thoroughly studied and some of operational factors and their effects on the coiling process were investigated. The software was developed to estimate engineering parameters for coiler component design and to determine optimal setting values for successful coiling operation. In order to check the accuracy and usefulness of the developed software, the simulation of the downcoiler in $\#2$ Hot Strip Mill in Pohang Works was performed. The simulation results suggested that the set-up value for unit tension could be lowered. Test coiling operation by using the lowered set-up value for unit tension resulted in much more successful coiling in the aspect of strip quality and power consumption.

• Transactions of Materials Processing
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• v.8 no.3
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• pp.237-244
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• 1999

The purpose of this research is for the development of a new type forging equipment. H.C.G.(Hyundai Continuous Grain-Flow), by using two virtual build-up tools, rigid viscoplastic FEM and downsized plasticine experiment. This forging method consists of only vertical pressuree. Therefore, high quality crankshafts can be forged with this method as it can maintain a continuous grain flow. The factors considered in the development of equipment are die geometry for flawless deformed shape, die reaction forces, stress/strain distributions and continuous material flow. We carried out several numerical simulations and downsized plasticine experiments for the proper design of the forging equipment. The validity of those simulation results is confirmed by checking with the actual test results. Based on these simulation results, the proper design of the H.C.G. forging equipment is enabled.

• International Journal of CAD/CAM
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• v.8 no.1
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• pp.41-44
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• 2009

This paper describes an implementation of virtual teeth modeling for a haptic dental simulation. The system allows dental students to practice dental procedures with realistic tactual feelings. The system requires fast and stable haptic rendering and volume modeling techniques working on the virtual tooth. In our implementation, a volumetric implicit surface is used for intuitive shape modification without topological constraints and haptic rendering. The volumetric implicit surface is generated from input geometric model by using a closest point transformation algorithm. And for visual rendering, we apply an adaptive polygonization method to convert volumetric teeth model to geometric model. We improve our previous system using new octree design to save memory requirement while increase the performance and visual quality.

• Journal of Industrial Technology
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• v.9
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• pp.87-99
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• 1989

It is desirable to predict the noise and vibration problems of a passenger car in its design stage for a better ride quality. Dominant frequencies of the noise inside a car range from about 50 Hz to 300 Hz and these are frequently caused by the coupling of the acoustic normal modes of the compartment cavity and structural modes of the body. In this paper, car interior noise problem is investigated in view of vibration-acoustic modes coupling and numerical simulation is performed on the interior noise. In the simulation, experimental modal data of the vehicle structure are utilized to improve the accuracy of the analysis. The results are in good agreement with those of experiment on a half scaled vehicle compartment model. Especially, strongly coupled modes can be predicted, which give useful informations to solve noise problems of real car at design stage.

• Earthquakes and Structures
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• v.23 no.5
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• pp.463-472
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• 2022

Reinforced concrete (RC) beam column joints (BCJ) have mostly exhibited poor seismic performance during several past earthquakes, typically due to the poor-quality concrete or lack of reinforcement detailing typical of pre-code design practice. The present study is motivated towards numerical simulation and seismic fragility assessment of one such RC-BCJ. The BCJ is loaded to failure and strengthened using Ultra High Performance-Hybrid Fiber Reinforced Concrete (UHP-HFRC) jacketing. The strengthening is performed for four different BCJ specimens, each representing an intermediate damage state before collapse. viz., slight, moderate, severe, and collapse. From the numerical simulation of all the BCJ specimens, an attempt is made to correlate different modelling and design parameters of the BC joint with respect to the damage states. In addition, seismic fragility analysis of the original as well as the retrofitted damaged BCJ specimens show the relative enhancement achieved in each case.