• Journal of Mechanical Science and Technology
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• 제17권4호
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• pp.599-605
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• 2003

For practical calculations, the Reynolds equation is frequently used to analyze the lubricating flow. The full Navier-Stokes Equations are used to find validity limits of Reynolds equation in a lubricating flow regime by result comparison. As the amplitude of wavy upper wall increased at a given average channel height, the difference between Navier-Stokes and lubrication theory decreased slightly : however, as the minimum distance in channel throat increased, the differences in the maximum pressure between Navier-Stokes and lubrication theory became large.

• 한국해안해양공학회:학술대회논문집
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• 한국해안해양공학회 1991년도 정기학술강연회 발표논문 초록집
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• pp.6-10
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• 1991

The bottom friction model of combined wave-current flow developed by Bijker, Yoo and O'Conner (hereafter it is called BYO model) is fully based on the Prandtl's mixing length theory. Although the Prandtl's theory is dependant on some rationalism, it is widely recognized that the theory is generally acceptable for the description of any turbulent flow.(omitted)

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.84-91
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• 2008

Generalized hydrodynamic (GH) theory for multi-species gas and the computational models are developed for the numerical simulation of hypersonic rarefied gas flow on the basis of Eu's GH theory. The rotational non-equilibrium effect of diatomic molecules is taken into account by introducing excess normal stress associated with the bulk viscosity. The numerical model for the diatomic GH theory is developed and tested. Moreover, with the experience of developing the dia-tomic GH computational model, the GH theory is extended to a multi-species gas including 5 species; O$_2$, N$_2$, NO, O, N. The multi-species GH model includes diffusion relation due to the molecular collision and thermal phenomena. Two kinds of GH models are developed for an axisymmetric flow solver. By compar-ing the computed results of diatomic and multi-species GH theories with those of the Navier-Stokes equations and the DSMC results, the accuracy and physical consistency of the GH computational models are examined.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년 추계학술대회논문집
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• pp.84-91
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• 2008

Generalized hydrodynamic (GH) theory for multi-species gas and the computational models are developed for the numerical simulation of hypersonic rarefied gas flow on the basis of Eu's GH theory. The rotational non-equilibrium effect of diatomic molecules is taken into account by introducing excess normal stress associated with the bulk viscosity. The numerical model for the diatomic GH theory is developed and tested. Moreover, with the experience of developing the dia-tomic GH computational model, the GH theory is extended to a multi-species gas including 5 species; $O_2,\;N_2$, NO, O, N. The multi-species GH model includes diffusion relation due to the molecular collision and thermal phenomena. Two kinds of GH models are developed for an axisymmetric flow solver. By compar-ing the computed results of diatomic and multi-species GH theories with those of the Navier-Stokes equations and the DSMC results, the accuracy and physical consistency of the GH computational models are examined.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.180-183
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• 1999

It is well known that Fe3Al intermetallic compound shows an anomalous peak of the yield strength at about 50$0^{\circ}C$ and then decrease at higher temperatures The dislocation structure was examined by transmission electron microscopy and high temperatures. The dislocation structure was examined by transmission electron microscopy and high temperature mechanical properties were examined by tensile and load relaxation tests. The flow stress curves obtained from load relaxation tests were then analyzed in terms of internal variable deformation theory. it was found that the flow curves consisted of three micro-deformation mechanisms -i. e inelastic deformation mode plastic deformation mode and dislocation creep deformation mode depending on both dislocation structure and deformation temperature. The flow curves could be well described by the constitutive equations of these three micro-deformation mechanisms based on the internal variable deformation theory.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.341-344
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• 2008

The complicated helical flow formed in the regenerative turbomachines is usually decomposed into a peripheral component and a circulatory component. On the basis of the momentum exchange theory, the circulatory flow plays a critical role of imparting angular momentum to the peripheral flow. Therefore, the accuracy of performance prediction is dominated by the circulatory flow modeling. Until now the circulatory flow has been accounted of a standstill flow normal to the peripheral flow. However, the circulatory path from the impeller exit to the re-entrance inlet is exposed to the adverse pressure gradient, so it would be more realistic to describe that the circulatory flow is formed on the skewed plane not perpendicular to the peripheral flow. Present study suggests new circulatory flow loss model including the effect of adverse pressure gradient and modifies the effective circulatory flow rate and circulatory pivot which were previously published.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 춘계학술대회 논문집
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• pp.233-236
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• 2004

The major objective of this paper is to clarify the effect of constitutive laws on bulk forming design based on the ideal flow theory. The latter theory is in general applicable for perfectly/plastic materials. However, its kinematics equations constitute a closed-form system, which are valid for any incompressible materials, therefore enabling us to extend design solutions based on the perfectly/plastic constitutive law to more realistic laws with rate sensitive hardening behavior. In the present paper, several constitutive laws commonly accepted for the modeling of cold and hot metal forming processes are considered and the effect of these laws on one particular plane-strain design is demonstrated. The closed form solution obtained describes a non-trivial nonsteady ideal process. The design solutions based on the ideal flow theory are not unique. To achieve the uniqueness, the criterion that the plastic work required to deform the initial shape of a given class of shapes into a prescribed final shape attains its minimum is adopted. Comparison with a non-ideal process is also made.

• 대한조선학회논문집
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• 제44권2호
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• pp.74-82
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• 2007

Recently, the erosion due to cavitation frequently occurs on a horn-type rudder of a high-speed large container carrier. It is necessary to understand the flow characteristics around a rudder in fully wetted and cavitating flow condition, and the process of generation and collapse of cavitation for a rudder design to minimize the cavity-induced erosion. The flow characteristics around a two-dimensional hydrofoil(NACA66) are investigated through the computational method utilizing a viscous flow theory applied to a cavitation model. The computational results from the viscous flow theory are verified by the comparison with the experimental results, and are compared with those from the potential flow theory. The effects of angle of attack, Reynolds number, cavitation number, and thickness ratio on the cavitating flow are also investigated.

• Asia pacific journal of information systems
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• 제14권3호
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• pp.93-120
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• 2004

The current study investigates major factors which influence the acceptance of mobile internet services based on the theoretical backgrounds of the technology acceptance model(TAM) and the flow theory. This research extended the Davis' TAM model(1989) by including the flow concept as another major factor towards the intention to use the mobile device in order to explain the acceptance of divers mobile services. According to the marketing studies(Ghani & Desphande, 1994; Novak, Hoffman & Yung, 2000), flow is regarded a psychological state in which one is absorbed in something he or she is doing, and is known to be widely adopted in explaining one's acceptance in the area of game, sports, and even hobby. This study developed a research model to explain the use of mobile services employing usefulness, ease of use and flow as major research variables, and collected 221 survey responses from the high school students who had experiences with such mobile services as game and audio file download. The results of the current research indicates that usefulness and flow influence the intension to use mobile services, but the effect of ease of use did not appear significant to the intention to use. It was also found that flow affects both usefulness and ease of use, and then ease of use next influences usefulness.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 추계학술대회
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• pp.569-572
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• 2013

플로우 이론에 근거해서 본 연구는 개인의 성격이 UCC를 활용할 때 개인의 플로우 경험과 사용형태에 어떠한 영향을 미치는 가를 탐색하고자 한다. 연구결과는 외향성은 사용자가 오락의 목적으로 UGC를 활용할 때 긍정적인 영향관계를 보인다고 시사하고 있으며, 반면 커뮤니케이션이나 정보추구의 목적일 때는 부정적인 관계가 있음을 나타냈다. 한편, 신경성은 오락 및 커뮤니케이션 목적의 UGC 활용과 긍정적인 관계가 있었으며, 정신병리적 성향의 경우 정보추구적 목적의 UCC 활용과 부정적인 관계를 보였다. 본 연구는 플로우의 선행요인과 영향요인을 포함한 실증연구를 제시함으로써 플로우 이론을 확장함에 그 의의가 있다.