• Journal of Institute of Convergence Technology
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• v.6 no.2
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• pp.15-20
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• 2016

This paper presents the effects of a virtual mass on the stability boundary of a virtual spring in the haptic system. A haptic system consists of a haptic device, a sampler, a virtual rigid body and zero-order-hold. The virtual rigid body is modeled as a virtual spring and a virtual mass. According to the virtual mass and the sampling time, the stability boundary of the virtual spring is analyzed through the simulation. As the virtual mass increases, the value of the virtual spring to guarantee the stability gradually increases and then decreases after reaching the maximum value. These simulation results show that the addition of the virtual mass enables to expand the stability boundary of the virtual spring.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.2
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• pp.161-169
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• 2004

This paper deals with system identification of a three-story building model with active mass damper (MID) for the controller design. Observer Kalman filter identification (OKID) technique is applied to find the relationship between the experimental results of the input and output. The inputs to the building model with MID are ground accelerations and motor command signal, which are, respectively, simulated earthquake and equivalent control force. The outputs are each floor acceleration and MID acceleration. The MID controller is designed based on the experimentally identified building system. Finally it is shown that experimental results agree accurately with simulated results.

• Tunnel and Underground Space
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• v.21 no.4
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• pp.287-296
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• 2011

We performed a numerical modeling study of thermodynamic and multiphase fluid flow processes associated with underground compressed air energy storage (CAES) in a lined rock cavern (LRC). We investigated air tightness performance by calculating air leakage rate of the underground storage cavern with concrete linings at a comparatively shallow depth of 100 m. Our air-mass balance analysis showed that the key parameter to assure the long-term air tightness of such a system was the permeability of both concrete linings and surrounding rock mass. It was noted that concrete linings with a permeability of less than $1.0{\times}10^{-18}\;m^2$ would result in an acceptable air leakage rate of less than 1% with the operational pressure range between 5 and 8 MPa. We also found that air leakage could be effectively prevented and the air tightness performance of underground lined rock cavern is enhanced if the concrete lining is kept at a higher moisture content.

• Journal of Institute of Convergence Technology
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• v.7 no.2
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• pp.25-30
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• 2017

This paper presents the effects of a virtual mass with a low-pass filter on the stability boundary of a virtual spring in the haptic system. In general, a haptic system consists of a haptic device, a sampler, a virtual impedance model and zero-order-hold. The virtual impedance is modeled as a virtual spring and a virtual mass. However the high-frequency noise due to the sampling time and the quantization error of sampled data may be generated when an acceleration is measured to compute the inertia force of the virtual mass. So a low-pass filter is needed to prevent the unstable behavior due to the high-frequency noise. A finite impulse response (FIR) filter is added to the measurement process of the acceleration and the effects on the haptic stability are simulated. According to the virtual mass with the FIR filter and the sampling time, the stability boundary of the virtual spring is analyzed through the simulation. The maximum available stiffness to guarantee the stable behavior is reduced, but simulation results still show that the stability boundary of the haptic system with the virtual mass is larger than that of the haptic system without the virtual mass.

• Computational Structural Engineering
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• v.11 no.3
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• pp.173-185
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• 1998

본 연구에서는 자동차엔진 및 트랜스미션 성능시험을 위한 다이나모 베드구조물을 분석하고 설계하였다. 해석상에 고려된 베드구조물은 Ⅰ형강 구조물, 보강된 박스구조물 그리고 블록구조물로 제작되었으며, 시험을 위한 엔진 및 트랜스미션은 베드상판에 장착된다. 엔진구동시 회전에 의한 진동이 발생된다. 공진을 피하기 위해 베드구조는 충분한 구조적 일체성을 가져야 한다. 본 연구에서는 베드 구조물의 응력, 변위 그리고 자유진동해석이 ANSYS Code를 이용한 유한요소해석이 수행되었다. Ⅰ형강 구조형 베드 구조물에서 최대 응력은 23.2MPa에서 90.3MPa까지 나타났으며, 최대 처짐은 0.25㎜에서 0.92㎜까지 나타났다. 박스 구조형 베드 구조물에서 최대 응력은 0.028MPa에서 0.259MPa까지 나타났으며, 최대 처짐은 0.031㎜에서 0.413㎜까지 나타났다. 그리고 박스구조형 베드 구조물에서 최대 처짐은 0.92MPa에서 2.15MPa까지 나타났으며, 최대 처짐은 1.1㎜에서 2.7㎜까지 나타났다. 모든 구조물이 응력과 처짐 값에서 매우 안정적인 범위 내에서 발생됨을 볼 수 있었다. 구조진동해석에서 Ⅰ형강 베드구조물의 고유진동수는 112.03㎐에서 141.66㎐까지의 범위에 발생되었다. 박스 구조형 베드구조물에서의 고유진동수는 396.93㎐에서 755.11㎐까지의 범위에서 발생되었다. 마지막으로 블록구조형 베드구조물에서는 266.51㎐에서 244.67㎐까지의 고유진동수를 찾을 수 있었다. 모든 구조물에서 베드구조물의 무게증가에 따른 기본진동수는 증가된다. 베드시스템의 지지기초시스템은 2자유도계 시스템으로 설계되었으며, 다양한 질량변화 및 스프링상수 변화에 따른 진동해석을 수행하였다. 질량비가 증가될수록 고유진동수는 크게 감소되며, 스프링상수가 증가될수록 고유진동수는 감소된다.

• Proceedings of the ESK Conference
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• 1997.10a
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• pp.463-467
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• 1997

인간에게 운동감을 적절히 제시해주기 위하여는 Newton에 의한 운동의 세가지 법칙뿐만 아니라 EInstein의 상대성이론이 첨가되어야 한다. 즉, Newton운동의 제1법칙에 의하여 피실험자가 외력을 받지 않으면 등속운동 또는 정지상태를 계속 유지하게 되어 자신이 등속좌표계에 고정되어있기 때문에 시각적 인 정보가 없으면 어떠한 운동감도 못 느낀다. 이때 피실험자에게 정지해있는 기준좌표계에 대하여 등속 으로 움직이는 것을 인식시켜주기 위하여 피실험자에 대한 기준좌표계의 상대속도를 시각정보로 제공해 주어야 한다. 또한 Newton운동의 제2법칙에 의하여 똑같은 힘이 외력으로 작용하더라도 피실험자의 질량과 가속도는 서로 반비례하므로 화면이동속도변화를 피실험자의 질량에 반비례하도록 제시해 주어야 한다(김 정흠, 1982). 본 연구에서는 이러한 개념에 근거하여, 체중이 다른 여섯 피실험자들로 구성된 시스템에 대해서 각 피실험자에게 서로 다른 변위를 주고자할 때, 여섯가지 외력에 요구되는 작용시간을 Jacobi Iteration 방법과 Gauss-Seidel Iteration 방법으로 구하는 알고리즘을 제시하였다(D.V. Griffiths and I.M. Smith, 1991).

• Journal of the Korean Society for Precision Engineering
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• v.10 no.2
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• pp.86-94
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• 1993

In heavy industries forces which are exceeding the range of available force standard machines have to be measured. Force measuring system using build-up procedure can be applied to measure large forces efficiently. In this study strain gage type force sensors are designed and fabricated, and the build-up force measuring system with 4.5 MN capacity using the developed force sensors is 0.03% or less over the range of 600 kN .approx. 1.5 MN and the force measuring system is less than 0.06% or less over the range of 500 kN .approx. 4.5 MN.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.1
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• pp.23-28
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• 2022

Natural frequency variations in a vehicle-bridge interaction system is examined. The interaction system is designed for a simple beam subject to a moving vehicle. The equation of motion for the system is derived under the quarter-car condition, and numerical simulation is performed. Frequency amplification ratio (FAR) is defined as a ratio between the initial and the varying natural frequency of the system; a discontinuity in the FAR implies a resonance condition. Analysis is mainly focused on patterns, frequency variation characteristics, and discontinuity points of the FAR under the vehicle mass and tire stiffness variations. The result reveals that the interactions between the system affects the natural frequency of both the vehicle and the bridge in similar frequency regions that can be visually identified at the middle of the span using the FAR.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.4
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• pp.302-306
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• 2001

Because face Images have many variations(expression, illumination, orientation of face, etc), there has been no popular method which has high recognition rate. To solve this difficulty, data fusion that fuses various information has been studied. But previous research for data fusion fused additional biological informationUingerplint, voice, del with face image. In this paper, cooperative results from several face image recognition modules are fused without using additional biological information. To fuse results from individual face image recognition modules, we use re-defined mass function based on Dempster-Shafer s fusion theory.Experimental results from fusing several face recognition modules are presented, to show that proposed fusion model has better performance than single face recognition module without using additional biological information.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.90-98
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• 1998

A Dual Mass Flywheel(D.M.F.) system is an evolution to the reduction of torsional vibration and impact noise occurring in powertrain when a vehicle is either moving or idling. The D.M.F. system has two flywh-eels, which is different from the conventional clutch system. One section belongs to the mass moment of in-ertia of the engine-side. The other section increases the mass moment of inertia of the transmission-side. These two masses are connected via a spring/damping system. This reduces the speed at which the dreaded resonance occurs to below idle speed. Since 1984m D.M.F. system has been developed. However, the processes of development of D.M.F. system don't have any difference from the trial and error method of conventional clutch system. This paper present the method for systematical design of D.M.F. system with dimensionless design varia-bles of D.M.F. system, mass ratio between two flywheels, natural frequency rate of two flywheels, and visc-osity coefficient. And expermental results are used to prove these theoretical results.