• Journal of Power Electronics
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• 제9권4호
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• pp.553-566
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• 2009

In-phase control and energy-optimized control are the two major control strategies proposed for series power quality controllers (SPQC). However quantitative analysis and comparison between these two control strategies is quite limited in previous publications. In this paper, an extensive quantitative analysis is carried out on these two control strategies through phasor diagram approach, and a detailed quantitative comparison is conducted accordingly. The load current is used as the reference phasor, and this leads to a simpler and clearer phasor diagram for the quantitative relationship. Subsequently detailed analysis of SPQC using in-phase control and energy-optimized control are provided respectively, under different modes both for under voltage/voltage sag and for over voltage/voltage swell. The closed form analytic expressions and the curves describing SPQC compensation characteristics are obtained. The detailed system power flow is figured out for each mode, and the detailed quantitative comparison between the two control strategies is then carried out. The comparison covers several aspects of SPQC, such as required compensating voltage magnitude, required capacity of energy storage component, and maximal ride-through time. In the end, computer simulation and prototype experimental results are shown to verify the validity of all the analysis and the result of the comparison.

• 한국초등과학교육학회지:초등과학교육
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• 제41권1호
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• pp.93-105
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• 2022

이 연구는 세 초등 예비교사의 과학 모의수업 시연에서 data-text의 변형 담화가 구현되는 양상을 탐색하여 교사의 인식론적 대화가 학습자의 과학지식 구성에 어떻게 작용할 수 있는지 조사하였다. 계절에 따른 별자리의 변화를 주제로 모의수업을 시연한 초등 예비교사 3명이 연구에 참여하였고, 그들의 모의수업 시연의 수업 담화 중 교수법적 발화에서 data-text의 변형 담화에 해당하는 발화를 선택하여 수업의 흐름에서 학습자의 과학지식 구성에 어떤 역할을 하는지 분석하였다. 연구 결과, 데이터에서 증거로 변형하는 담화와 증거에서 여러 모델에서 설명을 도출하는 변형 담화를 구현했던 예비교사의 수업은 학습자의 과학지식 구성에 기여할 수 있었다. 그러나 데이터를 인식하는 변형 담화 또는 증거를 찾는 변형 담화에 멈추거나 변형 담화가 발견되지 않은 예비교사의 교수법적 발화는 학습 목표로서 과학 지식을 전달할 수 있었지만, 학습자의 과학지식 구성을 효과적으로 유도하지 못했다. 세 예비교사의 모의수업 시연에서 구현된 교수법적 발화를 data-text의 변형 담화 측면에서 발전적인 부분과 제한적인 부분을 비교함으로써 과학적 의사소통 능력의 관점에서 예비교사의 과학 수업 역량을 증진시키기 위해 고려해야 할 지점을 논의하였다.

• 유공압시스템학회논문집
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• 제5권4호
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• pp.17-25
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• 2008

This study presents an analytical model of the pneumatic circuit of an air suspension system to analyze the characteristics of vehicle height control. The analytical model was developed through the co-simulation of Simulink(air spring) and HyPneu(pneumatic circuit). Variant effective area of air spring and flow coefficients of pneumatic valves were estimated experimentally prior to the system test, and utilized in simulation. One-comer test apparatus was established using the components of commercial air suspension products. The results of simulation and experiment were so close that the proposed analytical model in this study was validated. However the frictional loss of conduit and heat dissipation which were ignored in this study need to be considered in future study. As an application example of proposed analytical model, an alternative pneumatic circuit of air suspension to conventional WABCO circuit was evaluated. The comparison of simulation results of WABCO circuit and alternative circuit show that proposed analytical model of co-simulation in this study is useful for the study of pneumatic system of automotive air suspension.

• International Journal of Naval Architecture and Ocean Engineering
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• 제2권2호
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• pp.112-118
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• 2010

The numerical study about the vortex-induced vibration and vortex shedding in the wake has been presented. Prior to the numerical simulation of flexible riser systems concerning engineering conditions, efficiency validating of the proposed FSI solution method have been performed. The comparison between numerical simulation and published experimental data shows that the CFD method designed for FSI solution could give acceptable result for the VIV prediction of flexible riser/pipe system. As meaningful study on VIV and vortex shedding mode with the focus on flexible riser model systems, two kinds of typical simulation cases have been carried out. One was related to the simulation of vortex visualization in the wake for a riser model subject to forced oscillation, and another was related to the simulation of fluid-structure interaction between the pipes of coupled multi-assembled riser system. The result from forced oscillation simulation shows that the vortex-induced vibration with high response frequency but small instantaneous vibration amplitude contributes to vortex conformation as much as the forced oscillation with large normalized amplitude does, when the frequency of forced oscillation was relatively high. In the multi-assembled riser systems, it has been found that the external current velocity and the distance between two pipes are the critical factors to determine the vibration state and the steady vibration state emerging in quad-pipe system may be destroyed more easily than dual-pipe system.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권2호
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• pp.257-268
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• 2014

In this study, flow-driven rotor simulations with a given load are conducted to analyze the operational characteristics of a vertical-axis Darrieus turbine, specifically its self-starting capability and fluctuations in its torque as well as the RPM. These characteristics are typically observed in experiments, though they cannot be acquired in simulations with a given tip speed ratio (TSR). First, it is shown that a flow-driven rotor simulation with a two-dimensional (2D) turbine model obtains power coefficients with curves similar to those obtained in a simulation with a given TSR. 3D flow-driven rotor simulations with an optimal geometry then show that a helical-bladed turbine has the following prominent advantages over a straight-bladed turbine of the same size: an improvement of its self-starting capabilities and reduced fluctuations in its torque and RPM curves as well as an increase in its power coefficient from 33% to 42%. Therefore, it is clear that a flow-driven rotor simulation provides more information for the design of a Darrieus turbine than a simulation with a given TSR before experiments.

• 한국CDE학회논문집
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• 제17권4호
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• pp.274-281
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• 2012

This paper proposed a control simulation method for design and verification of the transport system in an automobile assembly line based on digital manufacturing system. The design of the transport system involves two major activities: mechanical design (device specification) and electrical design (device behavior and system control). Conventionally, the simulation and emulation system of the transport system focuses on the abstract level, which mainly deals with design verification, alternative comparison, and system diagnosis. Although it can provide overall system visibility in monitoring how well it works in the process and view, its simulation models are not sufficiently realistic to be used for a detailed design or for implementation purposes. In this paper, a digital simulation model for a transport system in an automotive assembly line is constructed by adapting a digital manufacturing methodology. We use the concept of the "Virtual Probe", which transport a carrier instead of the belt of the conveyor. In conclusion, the proposed method is valuable in the process of test run in the shop floor. This method would reduce the time and effort for validating the manufacturing system and improve the productivity and integrity of the control program.

• 한국자동차공학회논문집
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• 제18권4호
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• pp.107-114
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• 2010

Coupling systems for trains need more complicated buffer equipments than existing systems because the recent tendency of the regulations enforces trains to be safe for collisions even when the driving speed is higher than before. Using hydraulic buffer is an effective way to satisfy the requirement while it causes the increase of the cost for the coupling system. In this study, we introduce the methodology to build a simulation model for the hydraulic buffer, which could be installed into the coupling systems. In the simulation model of the hydraulic buffer, the reacting force is determined by both buffer stroke and speed whereas the elastic buffer model is designed by using only the buffer stroke in other studies. The simulation results with the advanced hydraulic buffer model shows that the simulating results can be close the real experimental results around 10%, and, if we considers friction forces, the simulation calculates the maximum force within 10% comparing to the experimental.

• 한국실천공학교육학회논문지
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• 제2권1호
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• pp.77-83
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• 2010

공학교육에서의 이러닝 실습의 효과성에 영향을 미칠 수 있는 요인은 온라인 시뮬레이션이 포함된 콘텐츠의 내용 구성방법과 완료된 콘텐츠의 활용방법이다. 공학분야에서 실습을 온라인으로 구현하려는 교수자는 실습 시뮬레이션을 만드는 것뿐만 아니라 온라인 실습을 효과적으로 실행하도록 다양한 학습활동을 구성해야 한다. 실습을 지도하는 교수자도 온라인 시뮬레이션의 효과를 담보하는 교수학습활동이 무엇인지를 알아야 한다. 즉, 공학교육의 모든 교수자는 이러닝 콘텐츠에서 온라인 실습의 효과를 높이기 위해서 어떠한 교수학습 활동 및 전략이 필요한지를 파악하여야 한다. 이를 위해 본 연구는 온라인 실습의 개발 유형을 구분하며 이 유형에 따른 교수학습활동을 분류하는 것을 목적으로 하였고 교수학습활동을 교육 이론과 비교, 검토하여 온라인 실습의 효과성을 높이기 위해 필요한 교수방법 및 전략의 방향을 제시하였다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2006년도 하계학술대회
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• pp.39-42
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• 2006

There are various analysis functions(including prediction of path loss, analyzing of capacity and coverage, etc.) of simulation tool to design and optimize the mobile communication network. Its reliability absolutely effects the performance of mobile communication network. Especially as the wireless network highly advancing focused on data service, it more needs to research and develop on the standard establishment of reliability of the simulation tool. Also it is important the systematic research how to improve the reliability of simulation tool. In this paper, to give the concrete process and skill about how to improve reliability, we define the kinds of reliability at first. And then we explain the comparison results between real field measurement data and theoretic simulation data.

• 한국산학기술학회논문지
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• 제10권10호
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• pp.2583-2588
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• 2009

본 논문에서는 반정현파 형태의 충격을 받는 HDD에 대한 충격해석을 수행하고, 그 타당성을 실험적으로 검증하였다. 일반적으로 센서를 이용한 제품의 충격실험을 통해서는 제한적인 정보만을 얻을 수 있지만, 컴퓨터를 이용한 해석기술은 제품의 파손현상을 규명하는데 필요한 보다 광범위하고 상세한 정보를 제공할 수 있는 장점을 가진다. 하지만, 이러한 해석결과는 여러 요인들에 따라 매우 민감하기 때문에 그 타당성을 검증하는 것이 중요하다. 따라서 본 연구에서는 200G/1ms의 전자기 충격실험과 300G/2ms의 낙하충격실험을 통하여 HDD의 조립단계별로 LS-DYNA를 이용한 유한요소해석의 신뢰성을 검증하였다.