• Journal of Power Electronics
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• v.13 no.6
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• pp.939-954
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• 2013

The Direct Torque Control (DTC) technique for Permanent Magnet Synchronous Motors (PMSM) is receiving increased attention due to its simplicity and robust dynamic response when compared with other control techniques. The classical switching table based DTC results in large flux and torque ripples in the motors. Several studies have been reported in the literature on classical DTC. However, there are only limited studies that actually discuss or evaluate the classical DTC. This paper proposes, novel switching table / DTC methods for PMSMs to reduce torque ripples. In this paper, two DTC schemes are proposed. The six sector and twelve sector methodology is considered in DTC scheme I and DTC scheme II, respectively. In both DTC schemes a simple modification is made to the classical DTC structure. The two level inverter available in the classical DTC is eliminated by replacing it with a three level Neutral Point Clamped (NPC) inverter. To further improve the performance of the proposed DTC scheme I, the available 27 voltage vectors are allowed to form different groups of voltage vectors such as Large - Zero (LZ), Medium - Zero (MZ) and Small - Zero (SZ), where as in DTC scheme II, all of the voltage vectors are considered to form a switching table. Based on these groups, a novel switching table is proposed. The proposed DTC schemes are comparatively investigated with the classical DTC and existing literatures through theory analysis and computer simulations. The superiority of the proposed DTC method is also confirmed by experimental results. It can be observed that the proposed techniques can significantly reduces the torque ripples and improves the quality of current waveform when compared with traditional and existing methods.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.2
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• pp.63-77
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• 1990

The combined deckstructure-car system of a car carrier is especially sensitive to hull girder vibrations due to mechanical excitations and wave loads. For the free and forced vibration analysis of the system, the analytical methods based on the receptance method and two schemes for efficient applications of the methods are presented. The methods are especially relevant to dynamical reanalysis of the system subject to design modification or to dynamic optimization. The deck-car system is modelled as a combined system consisting of a stiffened plate representing deck, primary structure, and attached subsystems such as pillars, additional stiffeners and damped spring-mass systems representing cars/trucks. For response calculations of the system subjected to displacement excitations along the boundaries, the support displacement transfer ratio conceptually similar to the receptance is introduced. For the verification of accuracy and calculation efficiency of the proposed methods, numerical and experimental investigations are carried out.

• Journal of the HCI Society of Korea
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• v.5 no.2
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• pp.15-24
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• 2010

A Digilog Book is an augmented reality (AR) based next generation publication supporting both sentimental analog emotions and digitized multi-sensory feedbacks by combining a conventional printed book and digital contents. As a Digilog Book authoring software, ARtalet provides an intuitive authoring environment through 3D user interface in AR environment. In this paper, we suggest ARtalet authoring environment based trajectory editing method to generate and manipulate a movement path of an augmented 3D object on the Digilog Book. Specifically, the translation points of the 3D manipulation prop is examined to determine that the point is a proper control point of a trajectory. Then the interpolation using splines is conducted to reconstruct the trajectory with smoothed form. The dynamic score based selection method is also exploited to effectively select small and dense control points of the trajectory. In an experimental evaluation our method took the same time and generated a similar amount of errors as the usual approach, but reduced the number of control points needed by over 90%. The reduced number of control points can properly reconstruct a movement path and drastically decrease the number of control point selections required for movement path modification. For control manipulation, the task completion time was reduced and there was less hand movement needed than with conventional method. Our method can be applicable to drawing or curve editing method in immersive In-Situ AR based education, game, design, animation, simulation application domains.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.8
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• pp.807-812
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• 2005

This study is to investigate the correlation of pore structures of Zeolite 5As modified with acid and their adsorption capacity of toluene vapor using the dynamic adsorption method. The experimental results showed that the modification with acid allowed more micropores and enlarged the existing pores. Toluene vapor was mainly adsorbed on the surface of pores over $15\;{\AA}$ in diameter. The equilibrium adsorption capacity of toluene vapor of the modified Zeolite 5As was in the range of $15{\sim}70\;mg/g$ and the equilibrium adsorption capacity was increased to f times than that of the Zeolite 5A. The correlation between the total cumulative surface area and the equilibrium adsorption capacity was hard to say linear. The correlation in diameter between the cumulative surface area in the range of over $15\;{\AA}$ and the equilibrium adsorption capacity gate the highest correlation factor of 0.997.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.351-356
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• 1996

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