• The KSFM Journal of Fluid Machinery
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• v.2 no.1 s.2
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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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• v.7 no.1
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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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• v.11 no.1
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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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• v.4 no.1
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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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• v.26 no.6
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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.

• Journal of Internet Computing and Services
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• v.14 no.4
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• pp.73-84
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• 2013

This study, based on flow theory and unified theory of acceptance and use of technology (UTAUT), examines various factors that influence the continuous use of mobile applications, particularly those providing users with satisfaction and pleasure as well as useful information. This study extends the previous studies that have been based on technology acceptance model, in which usefulness and ease of use are key determinants of use of new technology, by introducing flow theory in explaining the use of various technologies in mobile environment. For this purpose, this study employes a survey based field study and collects data from individuals who use fashion mobile apps since these are considered to provide fun and pleasures. This study finds that flow theory is a proper framework to understand the use of mobile technology, indicating flow experience is an important variable to determine the usage of fashion apps. In addition, performance expectation, effort expectation, social influence, and facilitation condition are found to be significant in influencing use of mobile apps, suggesting UTAUT still plays an important role in understanding the use of mobile technology.

• Journal of Digital Convergence
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• v.17 no.4
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• pp.137-147
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• 2019

This paper studies the effect of content information quality of u-tourism information system on flow theory and satisfaction. The purpose of the research is to generate and propose flow-related information to satisfy tourists with content information quality. The meaning of this paper is to derive success factors for verifying satisfaction of content information quality to tourists, establish hypotheses as research models, and evaluate verification. The differentiation of this study is the design implementation of u-fusion tourism information system by combining flow relation information with flow theory. The contribution of this paper is the generation of flow related information and the elicitation of success factors of contents quality of u-tourism information system. The advantage is that tourists can be patterned by symbolization and the pattern can be illustrated. The limitations of this paper are limited to small areas, and the lack of objectivity is required and future tasks are needed to compensate for them.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.1
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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.

• The Journal of Information Systems
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• v.16 no.4
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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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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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.