• Journal of Aerospace System Engineering
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• v.13 no.5
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• pp.32-38
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• 2019

The flying wing configuration with high sweep angles and rounded leading edge represent a complex flow of structures by the leading edge vortex. For control of the tailless flying wing configuration with unstable directional stability, flaperon is used. In this study, we conducted numerical simulations for a non-slender flying wing configuration with a rounded leading edge and analyzed the effect of the sideslip angle and flaperon. Through aerodynamic coefficient analysis, it was found that the effect of AoS on lift and drag coefficient was minimal and the side force and moment coefficient were markedly influenced by AoS. As the sideslip angle increased, the pitch break, which is related to the pitching moment coefficient, was delayed. Through stability analysis, the directional and lateral static stability of the flying wing configuration were increased by flaperon. Also, the structure and behavior of the leading edge vortex were analyzed by observing the contour of the pressure coefficient and the skin friction line.

• The KSFM Journal of Fluid Machinery
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• v.18 no.6
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• pp.63-70
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• 2015

This paper proposes a novel airfoil named "KA2" for the blade of the wind turbine systems. Dynamic loads characteristics are analyzed and compared using aerodynamic data of ten airfoils including the proposed airfoil. The blade is divided into the sixteen elements in the longitudinal direction of the blade for applying the Blade Element Method Theory (BEMT) method, and in each element, torque, thrust, and pitching moment are calculated using turbulent time varying wind speed and aerodynamic data of each wing. Additionally, each force and torque is accumulated in the whole region of the blade for the estimation of representative values. The magnitude of such forces is comparatively analyzed for different airfoils. The angle of attack is constant below the rated wind speed due to the fact that the tip speed ratio is kept at the constant value, and it increases in the region of over rated wind speed as the tip speed ratio decreasing with constant rated rpm and increasing wind speed. Such increase in the angle of attack causes the changes of the force acting on the airfoil with different characteristics of lift and drag in the stall region of each different airfoil. Even though the mean wind speed is in the rated speed in a given time, because of the turbulence, it has either the over rated or under rated speed most of the time. Furthermore, the dynamic properties of each force are analyzed in this rated wind speed in order to objectively understand the dynamic properties of the blades which are designed based on the different airfoils. These dynamic properties are also compared by the standard deviation of time varying characteristics. Moreover, the output characteristics of the wind turbine are investigated with different airfoils and wind speeds. Based on these investigations, it was revealed that the proposed airfoil (KA2) is well applicable to the blade with passive pitch control system.

• Korean Journal of Labor Studies
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• v.17 no.1
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• pp.139-176
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• 2011

Non-regular workers came to the fore while working class formation was in retreat along with the democratic labor movement of regular workers. The formation of principal agents, however, is yet to occur. Then, why non-regular workers' struggles could not yield a consequence in that regard? What kind of factors are to determine the outcome of the struggles and how do they do it? It is the aim of this study to answer those questions. In contrast with regular workers' struggles, non-regular workers' struggles tend to break out in response to capitalist offensives, rely on atypical and, often, extreme measures of struggle rather than strike in the form of work stoppage, drag out for too long, and appeal for social solidarity outside when the solidarity of regular workers is not available. Non-regular workers' struggles tend to end up with failure rather than success, and with weakening rather than strengthening of their organizational strength. So as to overcome the tendency to fail, non-regular workers' struggles need regular workers' solidarity in addition to their own strong mobilization power, while social solidarity or positional power could substitute for regular workers' solidarity in some cases. So as to build up their organizational strength, non-regular workers' struggles should win victories in the struggles, while a victory could turn into a trap in the case of conversion. Both regular workers' solidarity and the internal integration of the struggles are two foremost important factors in achieving the victory of struggles and the building-up of organizational strength. Those who have got involved in struggles are from the best organized sector among all the non-regular workers. As they have gone through weakening of organizational strength, it becomes more difficult for non-regular workers to form principal agents. Without non-regular workers' struggles, however, the capitalist offensives must have carried the day. In that sense, non-regular workers' struggles did a role in at least detaining capitalist offensives, if not stopping them. The practical implication of non-regular workers' struggles is that, if non-regular workers redefine the ultimate goal of their struggles as the formation of their principal agents for working class formation, it would be a strategically rational choice to identify the strategic objective of struggles with the maintaining and strengthening of their organizational strength rather than the achievement of their immediate demands.