• 한국소음진동공학회논문집
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• 제19권5호
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• pp.530-536
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• 2009

In this paper, the power flow analysis(PFA) has been used to analyze the vibration of a plate covered with a damping sheet. Experiments have been performed to measure the loss factor and frequency response functions of the plate covered with the damping sheet. The data for the loss factor has been used as the input data to predict the vibration of the coupled plates with PFA. The comparison between the experimental results and the predicted PFA results for the frequency response functions has been performed. It showed that PFA can be effectively used to predict structural vibration of a plate covered with a damping sheet in medium-to-high frequency range.

• 한국IT서비스학회지
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• 제14권2호
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• pp.111-128
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• 2015

In this paper, we examined the effects of emotional and individual variables on flow in the usage of mobile application. We selected four relevant emotional and individual factors such as positive affect, negative affect, addiction and habituation. We also attempted to figure out the moderating role of communication in the effect of positive affect, negative affect, and addiction on the flow. For empirical analysis, we surveyed real users of mobile application and applied PLS (Partial Least Square) methodology for SEM (Structural Equation Modeling). As a result, we found that positive affect, addiction, and habituation have significant and positive impact on the flow. Furthermore, we also found that the moderating effects of communication on the relationships between positive/negative affect and communication are significant. Our findings provide important theoretical grounds for the effects of human behavior and emotion on the flow of mobile applications. Lastly, we also suggest significant managerial implications for the development mobile applications industry.

• 한국소음진동공학회논문집
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• 제16권9호
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• pp.937-948
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• 2006

In this study, a fluid/structure coupled analysis system for simulating complex flow-induced vibration (FIV) phenomenon of cascades has been developed. The flow is modeled using Euler and Wavier-Stokes equations with different turbulent models. The fluid domains are modeled using the unstructured grid system with dynamic deformations due to the motion of structural boundary. The Spalart-Allmaras (S-A) and the SST ${\kappa}-{\omega}$ turbulent models are used to predict the transonic turbulent flows. A fully implicit time marching scheme based on the Newmark direct integration method is used in order to solve the coupled governing equations for viscous flow-induced vibration phenomena. For the purpose of validation for the developed FIV analysis system, comparison results for computational analyses of steady and unsteady aerodynamics and flutter analyses are presented in the transonic flow region. In addition, flow-induced vibration analyses for the isolated cascade and multi-blades cascade models have been conducted to show the physical fluid-structure interaction effects in the time domain.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.793-802
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• 2006

In this study, a fluid/structure coupled analysis system for simulating complex flow-induced vibration (FIV) phenomenon of cascades has been developed. The flow is modeled using Euler and Wavier-Stokes equations with different turbulent models. The fluid domains are modeled using the unstructured grid system with dynamic deformations due to the motion of structural boundary. The Spalart-Allmaras (S-A) and the SST ${\kappa}-{\omega}$ turbulent models are used to predict the transonic turbulent flows. A fully implicit time marching scheme based on the Newmark direct integration method is used in order to solve the coupled governing equations for viscous flow-induced vibration phenomena. For the purpose of validation for the developed FIV analysis system, comparison results for computational analyses of steady and unsteady aerodynamics and flutter analyses are presented in the transonic flow region. In addition, flow-induced vibration analyses for the isolated cascade and multi-blades cascade models have been conducted to show the physical fluid-structure interaction effects in the time domain.

• 한국가시화정보학회지
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• 제22권1호
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• pp.40-48
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• 2024

This study presents an in-vitro model designed to simulate mitral valve regurgitation, aiming to compare the quantification results between Proximal Isovelocity Surface Area(PISA) and 4D Flow MRI on both fixed and valve annulus tracking(VAT) views. The in-vitro model replicates the dynamic conditions of the mitral valve in a pulsatile environment, utilizing a piston pump set at 60 bpm. Through systematic experiments and analysis, the study evaluates the accuracy and effectiveness of PISA and 4D Flow MRI in assessing regurgitation severity, considering both fixed and valve annulus tracking. The displacement length measured in echo closely resembled that of optical measurements, making it advantageous for structural analysis. VAT-4D flow MRI exhibited the smallest deviation from actual flow rate values, establishing it as most accurate method for quantitative regurgitation assessment.

• 대한기계학회논문집B
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• 제26권1호
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• pp.133-140
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• 2002

This article presents an application of a large-scale structural mixing model(Broadwell et at. 1984) to the blowout of turbulent reacting cross flow jets. Experimental observations, therefore, aim to identify the existence of large-scale vortical structure exerting an important effect upon the flame stabilization. In the analysis of common stability curve, it is seen that the phenomenon of blowout are only related to the mixing time scale of the two flows. The most notable observation is that the blowout distance is traced at a fixed positions according to the velocity ratio at all times. Measurements of the lower blowout limits in the liftable flame are qualitatively in agreement with the blowout parameter $\xi$, proposed by Broadwell et al. Good agrement between the results calculated by a modified blowout parameter $\xi$'and the present experimental results confirms the important effect of large-scale structure in the stabilization feature of blowout.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.245-251
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• 1999

The structural analysis of a reactor coolant pump(RCP) of a nuclear power plant is very important for the safety assessment of the plant. Accurate boundary conditions for the heat transfer coefficient are required for reliable thermal stress analysis of the pump casing, especially in transient operations of the pump since the coolant properties are largely dependent on operational conditions. In the present study, a 3D mixed flow type coolant pump was modeled from the RCP drawings and analyzed in the steady state and number of transient flow conditions by using a commercial code STAR-CD. From the result of the computation, it is seem that the average heat transfer coefficients for the cases considered are found to be the suggested values of the manufacturer, Westinghouse Energy System. The unevenness in local heat transfer coefficients, however, is found to be considerable so that the use of average heat transfer coefficients in all boundaries might not give reliable thermal stresses.

• 한국콘텐츠학회논문지
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• 제22권5호
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• pp.527-541
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• 2022

본 연구는 COVID-19 확산으로 학습자가 급증하고 있는 유튜브를 통한 온라인 평생교육의 참여동기, 학업적 자기효능감, 학습몰입 간의 구조적 관계를 분석하였다. 연구를 위해 수도권에 거주하는 성인 학습자를 대상으로 2021년 7월 16일부터 30일까지 온라인 설문조사를 실시하였다. 조사 참여자는 총 428명이며, 불성실한 응답 19건을 제외하고 총 409부의 결과를 분석하였다. 주요 분석결과는 다음과 같다. 첫째, 연구모형의 적합도는 모두 분석에 적합한 것으로 검증되었다. 둘째, 연구모형의 각 경로 계수와 통계적 유의성을 확인한 결과, 유튜브 평생교육 참여동기는 학습몰입과 학업적 자기효능감에 정적 영향을 미치고, 학업적 자기효능감도 학습몰입에 정적 영향을 미치고 있다. 셋째, 유튜브 평생교육 참여동기가 학업적 자기효능감을 매개로 학습몰입에 미치는 영향은 통계적으로 유의미한 부분 매개로 확인되었다. 본 연구는 COVID-19에 의한 평생교육의 디지털 전환을 반영하여 유튜브를 활용한 온라인 평생교육의 참여동기, 학업적 자기효능감, 학습몰입 간의 구조적 관계분석을 검증하였다는 점에서 의미가 있다. 연구결과를 통해 COVID-19 이후에 형성된 평생교육 재규정 필요성 및 디지털 전환의 흐름을 반영하여 평생교육이 학습자의 참여동기를 제고하였다. 또한 학업적 자기효능감을 매개로 학습몰입을 강화할 수 있는 방법을 논의하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.901-904
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• 2007

The power flow analysis (PFA) can be effectively used to predict structural vibration in medium-to-high frequency ranges. In this paper, vibration experiments have been performed to observe the analytical characteristics of the power flow analysis of the vibration of various coupled plates. Those plates include two plates coupled with angles of $90^{\circ}$\;and\;30^{\circ}$, respectively. In the experiment, the loss factor and the input mobility at a source point on each coupled plate have been measured. The data for the loss factors have been used as the input data to predict the vibration of the coupled plates with PFA. The frequency response functions have been measured over the surface of the coupled plates. The comparison between the experimental results and the predicted PFA results for the frequency response functions has been performed.

• 한국분무공학회지
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• 제24권3호
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• pp.105-113
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• 2019

In this paper, a study of Urea-SCR System for Dosing Injector for responding to enhanced environmental regulations has been conducted. There is a limit to the experimental approach due to the structural characteristics of the injector. In order to overcome this problem, The analysis was performed assuming unsteady turbulent flow through computational fluid analysis and the internal flow characteristics of the injector were analyzed. By changing the nozzle shape of the injector, the performance factors of the swirl injector by shape were selected and compared. The design parameters were modified by changing the diameter of the nozzle at a constant ratio compared to the base model. Swirl coefficient, outlet mass flow, and sac volume were selected as performance parameters of the injector. The Conv. model to which the taper was applied showed the dominance in mass flow rate, discharge coefficient and swirl because of the smooth fluid flow by shape. Swirl coefficient, outlet mass flow, and sac volume were selected as performance parameters of the injector. As a result of the comparison coefficient derivation with those performance parameters for comparing the performance of the model-specific injector, the Conv-140 model with the nozzle diameter expanded by 140% showed the best value of the comparison coefficient.