• Journal of Ship and Ocean Technology
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• 제3권2호
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• pp.1-16
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• 1999

The incompressible Reynolds-Averaged Navier-Stokes(RANS) equations are solved using the standard $\textsc{k}-\varepsilon$ turbulence model and a finite volume method(FVM)with an O-type grid system. The computed results for its performance test are in good agreement with the published experimental data. The present method is applied to the study on the leading edge radius of a hydrofoil section Calculated results suggest that the leading edge radius has some effects on cavitation performances of a 2-D foil. A natural leading edge radius for the NACA66 section is determined from this study.

• Ocean and Polar Research
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• 제28권2호
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• pp.209-214
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• 2006

The East Sea Branch (ESB) of KORDI will be launched in 2008. She will take a role of monitoring the sea surface topography and temperature by satellites, short- and long-term sea levels by tide gauges, coastal currents and open-sea circulation by setting up coastal radars and mooring current-meters and acoustic equipments, as well as monitoring nearshore processes, coastal erosion and water pollution. A basic program of coastal zone management will help ocean-policy makers to set up right decisions based upon scientific background of the regional data in the East Sea. Networking among the neighboring countries around the sea will supply more useful information not only for experts but also for ordinary vacationers or fishermen. In order for this program to be successfully settled down during the next decade, it is necessary for a leader to have the right vision to attract more experts from global brain pools and to manage the ESB as a leading-edge observatory in the world. Details about this leading-edge operational program are introduced in the text.

• Journal of Ship and Ocean Technology
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• 제1권2호
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• pp.11-18
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• 1997

The leading edge of a low-drag super-cavitating foil has been made to be thick enough by using a point drag which is supposed to be a linear model of the Kirchhoff lamina. In the present paper, the relation between the point drag and the Kirchhoff lamina is made clear by analyzing the cavity drag of both models and the leading edge radius of the point drag model and the lamina thickness of Kirchhoff\`s profile K. The matched asymptotic expansion is effectively made use of in designing a practical super-cavitating fool which is not only of low drag but also structurally sound. Also it has a distinct leading edge cavity separation point. The cavity foil shapes of trans-cavitating propeller blade sections designed by present method are shown.

• Journal of Mechanical Science and Technology
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• 제18권12호
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• pp.2273-2283
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• 2004

The vortical flows over sharp-edged delta wings with and without a leading edge extension have been investigated using a computational method. Three-dimensional compressible Reynolds-averaged Navier-Stokes equations are solved to provide an understanding of the effects of the angle of attack and the angle of yaw on the development and interaction of vortices and the aerodynamic characteristics of the delta wing at a freestream velocity of 20 m/s. The present computations provide qualitatively reasonable predictions of vortical flow characteristics, compared with past wind tunnel measurements. In the presence of a leading edge extension, a significant change in the suction pressure peak in the chordwise direction is much reduced at a given angle of attack. The leading edge extension can also stabilize the wing vortex on the windward side at angles of yaw, which dominates the vortical flows over yawed delta wings.

• EDISON SW 활용 경진대회 논문집
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• 제6회(2016년)
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• pp.19-22
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• 2016

Leading edge thrust is generally caused by passing air flow from lower to upper surface and it is required to have sufficient angle of attack for notable leading edge thrust. To produce leading edge thrust at low angle of attack, utilizing expansion wave accompanying low pressure is able to be a solution. Fore structure changes the direction of flow, and this flow passes the projected edge. As a result, from a perspective of the edge, it is able to have high angle of attack, and artificial expansion wave is generated. This concept shows 9.48% increase of L/D in inviscid flow, at Mach number 1.3 and angle of attack $1^{\circ}$ in maximum, and this model shows the 3.98% of increasement at angle of attack $2^{\circ}$. Although advantage of the artificial expansion wave decreased as angle of attack increase, it shows the possibility of aerodynamical improvement with artificial expansion wave.

• 농촌지도와개발
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• 제15권4호
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• pp.659-681
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• 2008

The purpose of this study is to empirically analyze factors that influence farm managers' intentions to use an agricultural farm management information systems. It focused on "LFcenter System," a leading information system operated by the Rural Development Administration for farm management. Participants of this study are classified into two groups: a group of leading farm managers and a group fo regular farm managers. A total of 192 survey samples on users' intentions are collected; 85 samples from leading farm managers and 107 from regular farm managers. The theoretical background of this study is developed based on Theory of Reasoned Action(TRA), Technology Acceptance Model(TAM), Diffusion of Innovation(DOI), Social Cognitive Theory(SCT), and Theory of Planned Behavior(TPB). Partial Least Squares(PLS) method is used to test a proposed Structural Equation Model(SEM), including nine hypotheses. The differences between two groups are investigated using Smith-Satterthwait test. The findings from this study are: First of all, in terms of average comparison of most variables used in this study, a group of leading farm managers shows higher value that the other group in most cases. Second, hypothesis tests how that "subjective norms", "goal to study", "perceived usefulness", "perceived enjoyment", and "intention to use" significantly influence the intention to use an agricultural management information system in the group of leading farm managers. However, "subjective norms", "goal to study", "perceived ease of use", "perceived usefulness", "perceived enjoyment", and "intention to use" turned out to significantly influence the intention to use an agricultural management information system in the group of regular farms managers. Based on the results of Smith-Satterthwait test, compared with a group of leading farms managers, the impact of "goal to study" on "intention to use" is significantly stronger. On the other hand, in the group of leading farms managers, "perceived usefulness" and "perceived enjoyment" turned out to be main drivers of "intention to use."

• World Technopolis Review
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• 제4권2호
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• pp.62-78
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• 2015

The importance of university technology transfer has widely been brought to the center of attention over the last decades. Research and practice thereby often concentrate on issues related to patenting and licensing or entrepreneurship but abstract away from relationship- and network-focused initiatives. In this paper, we argue that efforts to systematically develop close, long-term collaboration partnerships - although complex and resource intensive - are likely to be more beneficial for both universities and industry in the long run. Drawing on data derived from interviews with technology transfer executives of 22 leading European and U.S. universities, we analyze and discuss well-established practices of network and relationship management and their possible impact on technology transfer success. Our findings indicate that dedicated relationship management approaches can yield a sustainable competitive advantage for universities. We thereby shift the focus away from transaction-orientation towards more forward-looking relationship-centric approaches and discuss their institutionalization in great detail.

• Journal of Power Electronics
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• 제18권6호
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• pp.1760-1770
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• 2018

This paper presents a control bandwidth extension method for inverters with a low carrier ratio. The bandwidth is extended at the price of decreasing the phase margin. Then the phase margin is compensated by introducing an extra leading angle into an inverse Park transformation. The model of the controller with the proposed method is established. The magnitude and phase characteristics are also analyzed. Then the influence on system stability when the leading angle is introduced is analyzed. The proposed method is applied to design an inverter controller with both a large bandwidth and a desired phase margin, and the experimental results verify that the controller performs well in the steady-state and in terms of transient response.

• World Technopolis Review
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• 제2권2호
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• pp.64-80
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• 2013

In "Creating the Technopolis: High Technology Development in Austin Texas," Smilor, Kozmetsky, and Gibson (1988) make the case that in the mid-1980s Austin was becoming a globally competitive high tech region. Indeed over the years and into 2013, Austin has established its reputation as a leading entrepreneurial and technology center and "talent magnet." Delegations from across the US and worldwide visit Austin to better understand how this central Texas city went from being a state government and university town to become a fast growing, globally competitive, technology hotspot leading the state and nation in job creation. Central to the concept of the Triple Helix and Technopolis Frameworks is the importance of university, business, and government cooperation. This paper gives examples of mechanisms, processes, and metrics on how The University of Texas at Austin; regional technology industry; federal, state, and local government policies; and support groups all contributed to growing and sustaining the Austin Technopolis.

• EDISON SW 활용 경진대회 논문집
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• 제5회(2016년)
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• pp.647-652
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• 2016

To reduce drag force at supersonic speeds, sharp leading edge is hugely efficient. It is, however, incompatible with leading edge shape to have fine aerodynamic characteristics at subsonic and transonic speeds. It is critical to reduce drag force for enhanced cruise performance and higher efficiency. An air superiority fighter, however, required to have high maneuverability for survivability, and sharp leading edge is not proper. Consequently, variable leading edge is demanded to reduce drag force significantly at supersonic speeds for cruise performance. Leading edge altering system is constructed with rigid material to improve possibility of realization, and minimized movement of its components in altering for reduce effects on flight. It is compared with bi-convex airfoil and NACA 65-006 airfoil, which have comparable maximum thickness. At Mach number 1.7 and zero angle of attack, supersonic mode of designed airfoil indicates approximately 17% higher drag coefficient than the bi-convex airfoil indicates, it is, however, 23% lower than the NACA 65-006 indicates. Also, subsonic mode of the designed airfoil shows fine aerodynamic characteristics in comparison with NACA 65-006 airfoil in subsonic and transonic speed range. In this regard, design of the airfoil achieved the object of this study satisfactorily.