• 한국유체기계학회 논문집
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• 제2권1호
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• pp.22-28
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• 1999

In this study, a preliminary design method of the axial fan was systematically established based on the two-dimensional cascade theory. Flow deviation, lift coefficient, distribution of velocity and pressure coefficient on blade surfaces were predicted by an inviscid flow theory of Martensen method, which was also applied to select an airfoil for required performance in the present design process. The aerodynamic performance of designed blades can be predicted quickly and reasonably by using the through-flow calculation method in the preliminary design process. It would be recommendable to adopt three-dimensional viscous flow calculation at the final design refinement stage.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권1호
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• pp.174-194
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• 2015

In this paper, an Energy Flow Analysis (EFA) for coplanar coupled Mindlin plates was performed to estimate their dynamic responses at high frequencies. Mindlin plate theory can consider the effects of shear distortion and rotatory inertia, which are very important at high frequencies. For EFA for coplanar coupled Mindlin plates, the wave transmission and reflection relationship for progressing out-of-plane waves (out-of-plane shear wave, bending dominant flexural wave, and shear dominant flexural wave) in coplanar coupled Mindlin plates was newly derived. To verify the validity of the EFA results, numerical analyses were performed for various cases where coplanar coupled Mindlin plates are excited by a harmonic point force, and the energy flow solutions for coplanar coupled Mindlin plates were compared with the classical solutions in the various conditions.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.435-447
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• 2019

Energy Flow Finite Element Analysis (EFFEA) is a promising tool for predicting dynamic energetics of complicated structures at high frequencies. In this paper, the Energy Flow Finite Element (EFFE) formulation of complicated Mindlin plates was newly developed to improve the accuracy of prediction of the dynamic characteristics in the high frequency. Wave transmission analysis was performed for all waves in complicated Mindlin plates. Advanced Energy Flow Analysis System (AEFAS), an exclusive EFFEA software, was implemented using $MATLAB^{(R)}$. To verify the general power transfer relationship derived, wave transmission analysis of coupled semi-infinite Mindlin plates was performed. For numerical verification of EFFE formulation derived and EFFEA software developed, numerical analyses were performed for various cases where coupled Mindlin plates were excited by a harmonic point force. Energy flow finite element solutions for coupled Mindlin plates were compared with the energy flow solutions in the various conditions.

• International Journal of Fluid Machinery and Systems
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• 제4권1호
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• pp.114-132
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• 2011

We have proposed a new approach based on energy gradient concept for the study of flow instability and turbulent transition in parallel flows in our previous works. It was shown that the disturbance amplitude required for turbulent transition is inversely proportional to Re, which is in agreement with the experiments for imposed transverse disturbance. In present study, the energy gradient theory is extended to the generalized curved flows which have much application in turbomachinery and other fluid delivery devices. Within the frame of the new theory, basic theorems for flow instability in general cases are provided in details. Examples of applications of the theory are given from our previous studies which show comparison of the theory with available experimental data. It is shown that excellent agreement has been achieved for several configurations. Finally, various prediction methods for turbulent transition are reviewed and commented.

• Wind and Structures
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• 제26권6호
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• pp.355-367
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• 2018

This paper studies the aerodynamic stability of a tensioned, geometrically nonlinear orthotropic membrane structure with hyperbolic paraboloid in sag direction. Considering flow separation, the wind field around membrane structure is simulated as the superposition of a uniform flow and a continuous vortex layer. By the potential flow theory in fluid mechanics and the thin airfoil theory in aerodynamics, aerodynamic pressure acting on membrane surface can be determined. And based on the large amplitude theory of membrane and D'Alembert's principle, interaction governing equations of wind-structure are established. Then, under the circumstance of single-mode response, the Bubnov-Galerkin approximate method is applied to transform the complicated interaction governing equations into a system of second-order nonlinear differential equation with constant coefficients. Through judging the frequency characteristic of the system characteristic equation, the critical velocity of divergence instability is determined. Different parameter analysis shows that the orthotropy, geometrical nonlinearity and scantling of structure is significant for preventing destructive aerodynamic instability in membrane structures. Compared to the model without considering flow separation, it's basically consistent about the divergence instability regularities in the flow separation model.

• 인터넷정보학회논문지
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• 제14권4호
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• pp.73-84
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• 2013

본 연구는 모바일 앱, 특히 그 중에서도 개인에게 정보제공 뿐만 아니라 만족감과 즐거움을 동시에 제공하는 앱에 대해 플로우 이론과 통합기술수용모형에 근거하여 개인의 지속적인 이용행위에 영향을 미치는 요인을 살펴보고자 한다. 이는 기술의 유용성과 사용 용이성에 초점을 맞추어 일반적인 정보기술의 이용행위를 설명하고자 했던 기술수용모형 중심의 기존연구를 확장한 것으로 개인에게 재미라는 요소를 추가적으로 제공하는 많은 모바일 환경의 주요 기술들의 이용 과정을 설명하는데 있어서 플로우 이론의 유용성을 확인하기 위함이다. 이를 위하여 본 연구는 서베이 기반의 필드연구를 수행하였으며 즐거움을 추구하는 모바일 앱으로는 패션앱을 선택하였다. 연구결과, 패션앱의 이용을 설명하는데 있어서 플로우 경험이 매우 의미있는 변수라는 사실이 검정되어 기술의 이용행위에 몰입의 중요성이 확인되었다. 또한 통합기술수용모형의 주요 변수인 성과기대, 노력기대, 사회적 영향, 촉진조건 등의 변수가 모두 유의한 것으로 나타나 모바일 환경에서도 신기술의 이용이나 수용을 설명함에 있어서 통합기술수용모형의 유용성을 다시 한 번 확인하였다.

• 디지털융복합연구
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• 제17권4호
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• pp.137-147
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• 2019

논문은 u-관광정보시스템의 콘텐츠 정보품질이 플로우 이론과 만족에 미치는 영향을 연구한다. 연구 목적은 콘텐츠 정보품질이 관광객에게 만족감을 주기 위한 플로우 관계정보를 생성 및 제안이다. 본 논문 의미는 콘텐츠 정보품질이 관광객에게 만족감을 검증하기 위한 성공요인을 도출하여 연구 모형으로 가설 설정하고 검증 평가한다. 본 연구의 차별성은 플로우 관계정보를 제안 한 것과 플로우 이론을 접목시켜 플로우 관계정보 속성을 생성하고 u-융합 관광정보시스템을 설계 구현이다. 본 논문의 기여도는 플로우 관계정보를 생성으로 u-관광정보시스템의 콘텐츠 정보품질이 성공요인 도출이다. 장점은 관광객의 관광 성향을 기호화로 패턴이 가능하고 그 패턴을 도식화가 가능하다. 본 논문의 한계성은 소규모 지역으로 국한하여 진행한 것으로 객관성이 좀 떨어진다는 점과 그 점을 보완하기 위한 향후 과제가 필요하다.

• 대한기계학회논문집B
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• 제22권1호
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• pp.70-78
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• 1998

The present study has tested semi-empirical loss models for a reliable performance prediction of mixed-flow pumps with four different specific speeds. In order to improve the predictive capabilities, this paper recommends a new internal loss model and a modified parasitic loss model. The prediction method presented here is also compared with that based on two-dimensional cascade theory. Predicted performance curves by the proposed set of loss models agree fairly well with experimental data for a variety of mixed-flow pumps in the normal operating range, but further studies considering 'droop-like' head performance characteristic due to flow reversal in mixed-flow impellers at low flow range near shut-off head are needed.

• 한국정보시스템학회지:정보시스템연구
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• 제16권4호
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• pp.1-31
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• 2007

The current study investigates the relationship of antecedents of flow, organizational commitment, knowledge sharing, information technology usage for knowledge sharing, and job satisfaction of organizational employees. This study analyze the effects of psychological states of employees both on affective states of them and on knowledge sharing by applying the internet-based flow theory to knowledge sharing. The antecedents of flow are found to have positive effects on organizational commitment. In addition, it is found that organizational commitment has a positive effect on knowledge sharing, information technology usage for knowledge sharing, and job satisfaction. While it is found that knowledge sharing has a positive effect on job satisfaction, it is found that information technology usage for knowledge sharing does not have an effect on job satisfaction, but have a positive effect on knowledge sharing. The result of this study would not only provide significant insights to knowledge management researchers and practitioners but also contribute to applying the flow theory to knowledge sharing.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.916-919
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• 2004

The monopole theory has long been used to model air-pumped effect from the elastic cavities in car tire. This approach models the change of an air as a piston moving backward and forward on a spring and equates local air movements exactly with the volume changes of the system. Thus, the monopole theory has a restricted domain of applicability due to the usual assumption of a small amplitude acoustic wave equation and acoustic monopole theory. This paper describes an approach to predict the air-pumping noise of a car ave with CFD/Kirchhoff integral method. The type groove is simply modeled as piston-cavity-sliding door geometry and with the aid of CFD technique flow properties in the groove of rolling car tyre are acquired. And these unsteady flow data are used as a air-pumping source in the next Cm calculation of full tyre-road geometry. Acoustic far field is predicted from Kirchhoff integral method by using unsteady flow data in space and time, which is provided by the CFD calculation of full tyre-road domain. This approach can cover the non-linearity of acoustic monopole theory with the aid of using Non-linear governing equation in CFD calculation. The method proposed in this paper is applied to the prediction of air-pumping noise of modeled car tyre and the predicted results are qualitatively compared with the experimental data.