• 대한산업공학회지
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• 제6권1호
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• pp.9-15
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• 1980

By the mid 1960's the rate of productivity growth in the manufacturing industries of the United States reached the lowest level ever recorded in the American economy. As a result the cost-offsetting operations that had been a century-long part of cost minimizing became less feasible. U.S. manufacturing firins apparently embarked on a pattern of a cost pass-along management. Accounting for price variation as a function of a shift from cost minimizing to cost pass-along is the main subject of this investigation. An econometric model of the inflation process is presented which indicates a clear shift in the modal behavior of manufacturing industries from cost minimizing (1948-1964) to cost pass-along (1965-1975). The latter behavior, initially triggered by the drag of resource diversion on the productivity growth process, undermines the pressure toward productive efficiency that is at the core of industrial engineering, and at the center of U.S. industry's ability to remain competitive.

• 국제지역연구
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• 제15권3호
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• pp.493-511
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• 2011

본 연구는 중국소비자들의 문화성향이 SNSs(Social Networking Sites)에서의 온라인 구전(eWOM) 행동에 어떠한 영향을 미치는 가를 분석하기 위해 실시되었다. 실증분석 결과 나타난 결과를 요약하면 다음과 같다. 첫째, 중국소비자의 집단주의 성향과 SNSs에서의 eWOM 행동 간의 관계에 관한 가설1, 2, 3을 실증 분석한 결과, 중국소비자의 집단주의성향은 SNS에서의 의견탐색행동과 통계적으로 유의한 정(+)의 관계를 가지는 것으로 나타나 가설1은 채택되었다. 그러나 중국소비자의 집단주의 성향과 의견선도 및 의견전달행동 간의 관계에 대한 가설2와 가설3은 통계적으로도 유의하지 않아 기각되었다. 다음으로 중국소비자의 불확실성 회피성향과 SNSs에서의 온라인 구전행동 간의 관계에 대한 가설4, 5, 6은 모두 가설에서 설정한 방향과 동일한 방향성을 가지는 것으로 나타났다. 마지막으로 의견탐색행동, 의견선도행동, 의견전달행동 간의 관계에 대한 가설7, 8, 9에 대한 검정결과, 의견선도행동이 의견전달행동에 정(+)의 영향을 미치는 것으로 나타났다. 본 연구의 결과는 중국시장에서 SNSs를 활용한 마케팅 전략의 성공 가능성을 높이기 위해, 중국소비자의 어떠한 문화적 성향에 초점을 맞춰야 할 것인가에 대한 실무적 함의점을 제공 할 수 있을 것으로 기대된다.

• 대한금속재료학회지
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• 제46권9호
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• pp.545-553
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• 2008

Dynamic deformation behavior of ultra-fine-grained pure coppers fabricated by equal channel angular pressing (ECAP) was investigated in this study. Dynamic torsional tests were conducted on four copper specimens using a torsional Kolsky bar, and then the test data were analyzed by their microstructures and tensile properties. The 1-pass ECAP'ed specimen consisted of fine dislocation cell structures elongated along the ECAP direction, which were changed to very fine, equiaxed subgrains of 300~400 nm in size as the pass number increased. The dynamic torsional test results indicated that maximum shear stress increased with increasing ECAP pass number. Adiabatic shear bands were not found at the gage center of the dynamically deformed torsional specimen of the 1- or 4-pass ECAP'ed specimen, while some weak bands were observed in the 8-pass ECAP'ed specimen. These findings suggested that the grain refinement according to the ECAP was very effective in strengthening of pure coppers, and that ECAP'ed coppers could be used without serious reduction in fracture resistance under dynamic torsional loading as adiabatic shear bands were hardly formed.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2771-2788
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• 2020

Experiments are conducted to study bubble flow behavior during the instability of subcooled boiling under uniform and non-uniform transverse heating. The non-uniform heat distribution introduces nonuniform bubble generation and condensation rates on the heated surface, which is different from the uniform heating. These bubble generation and condensation characteristics introduce a non-uniform local pressure distribution in the transverse direction, which creates an extra non-uniform pressure on the flowing bubbles. Therefore, different bubble flow behavior can be observed between uniform and non-uniform heating conditions. In the uniform heating, bubble velocity fluctuations are low, and the bubbles travel straight along the axial direction. In the non-uniform heating, more fluctuation in the bubble velocity occurs at low mass flow rate and high subcooled inlet temperatures, and reverse flow is observed. Additionally, the bubbles show a zigzag trajectory when they pass through the channel, which indicates the existence of cross flow in the transverse direction.

• Journal of Power Electronics
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• 제18권4호
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• pp.1165-1177
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• 2018

This paper investigates the active damping of grid-connected LCL filter resonance using high-pass filter (HPF) of the grid current. An expression for such HPF is derived in terms of the filter components. This expression facilitates a general study of the actively damped filter behavior in the discrete time domain. Limits for the HPF parameters are derived to avoid the excitation of unstable open loop poles since such excitation can reduce both the damping performance and the system robustness. Based on this study, straightforward co-design steps for the active damping loop along with the fundamental current regulator are proposed. A numerical example along with simulation and experimental results are presented to verify the theoretical analyses.

• 한국재료학회지
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• 제23권9호
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• pp.531-536
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• 2013

This paper investigates the effect of prolonged high temperature exposure on concentric laminated $Al_2O_3-ZrO_2$ composites. An ultrafine scale microstructure with a cellular 7 layer concentric lamination with unidirectional alignment was fabricated by a multi-pass extrusion method. Each laminate in the microstructure was $2-3{\mu}m$ thick. An alternate lamina was composed of 75%$Al_2O_3$-(25%m-$ZrO_2$) and t-$ZrO_2$ ceramics. The composite was sintered at $1500^{\circ}C$ and subjected to $1450^{\circ}C$ temperature for 24 hours to 72 hours. We investigated the effect of long time high temperature exposure on the generation of residual stress and grain growth and their effect on the overall stability of the composites. The residual stress development and its subsequent effect on the microstructure with the edge cracking behavior mechanism were investigated. The residual stress in the concentric laminated microstructure causes extensive micro cracks in the t-$ZrO_2$ layer, despite the very thin laminate thickness. The material properties like Vickers hardness and fracture toughness were measured and evaluated along with the microstructure of the composites with prolonged high temperature exposure.

• 대한의용생체공학회:의공학회지
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• 제13권4호
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• pp.339-352
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• 1992

A numerical simulation of the steady and pulsatile flow across the end-to-side anastomosis was performed In order to understand the role of flow dynamics in the preferential bevel opment of distal anastomotic intimal hyperplasla. The finite element technique was employed to solve two-dimensional unsteady pulsatile flow in that region. The results of the steady flow revealed that low shear stresses occur at the proximally occluded host artery and at the recirculation region in the Inner wall just distal to the toe region of the anastomosis. The nor- mal;zed wall shear rate was increased, as was the recirculation zone size in the host artery of the by-pass graft anastomosis, with increased anastomotic junction angle. In order to min imize the size of the low wall shear region which might result in the intimal hyperplasia in the by-pass graft anastomosis, a smaller anastomotic junction angle is recommended. The pulsatile flow simulation revealed flow that regions of low and ascillating mali shear do exist near the anastomosis as In the steady simulation. The shift of stagnation point depends on the pulsation of the flow. As the flow was accelerated at systole, the stagnation point moved downstream, disappered at early diastole and reappeared during late diastole. Low shear stress was also found along both walls of the occluded proximal artery. However, the diastolic flow behavior is quite different from the steady results. The vortex near the occluded artery moved downstream and inwardly during late systole, and disappeared during diastole. Recirculations proximal to the toe and heel regions were significant during diastole. Shear stress oscillation was found along the opposite wall. The results of the present study revealed that tow shear occurs at the proximally occluded host artery aud the recirculation region in the inner wall Just dlstal to the toe region of the anastomosis. The present study suggested that the regions of fluctuated wall shear stress wit flow separation is correlated with the preferential developing regions of anastomosis neointial fibrous hyperplasia.

• 전자공학회논문지B
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• 제30B권11호
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• pp.93-101
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• 1993

The transfer function of vector-controlled induction motor is represented along with both unstructured and structured uncertainty such as the error of rotor time constant and current ripple. The low-pass-filter behavior of a magnetizing inductance gets rid of unstructured uncertainty in the transfer function. The robust controller to compensate variation of the transfer function is designed using simple P-I linear controllers. The coefficients of speed PI controller are determined from an overshoot and a rising time of system and the coefficients of model-following PI controller are obtained using the solution of Riccati equation of LQR control in the state space equation of the error system. Experimental results with the DSP-based model-following robust controller are shown a good robustness against the structured uncertainty of the motor.

• 대한교통학회지
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• 제33권1호
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• pp.50-60
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• 2015

보행자는 일반적인 보행로를 따라 이동할 뿐만이 아니라 건물을 통과하거나 넓은 공간을 가로지르는 등 다양한 방식으로 이동한다. 본 연구는 이러한 일반적이지 않은 보행 경로를 social path로 정의하여 보행 네트워크 중 하나로 정의하였다. Social path는 일반적인 보행 네트워크상에서는 구현되지 않지만 현실에서는 많은 사람들이 이용해 통행하는 경로를 의미한다. 기존의 보행 접근성 연구에서는 이러한 현실적인 통행 패턴을 구현하지 못함으로 인해 보행로 및 시설의 보행 접근성을 올바르게 평가하지 못하였다. 이를 개선하기 위해 본 연구는 서울의 코엑스와 고속터미널 지역을 대상지로 선정하여 social path의 효과 분석을 수행하였다. 효과 분석을 위해서는 서비스 권역 분석과 UNA기법을 활용하였다. 특히, 네트워크의 구현 정도를 3step으로 구분하여 각 단계별 효과를 분석하였다. 그 결과, social path가 추가된 step3에서 보행 접근성 개선 효과가 가장 뛰어난 것으로 나타났다. 이를 통해 향후 관련 연구에서 보행 접근성을 평가하는데 있어 social path를 고려해야 한다는 필요성을 확인 할 수 있었다. 또한 social path로 인해 현재 보행 접근성 평가 측면에서 저평가를 받는 다양한 시설물들이 주목받을 것으로 기대한다.