• Nuclear Engineering and Technology
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• v.25 no.1
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• pp.136-147
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• 1993

The paper describes : ⅰ) Mathematical modeling of poloidal flux to define and calculate the tokamak plasma position based on a property of the plasma boundary which is always a flux surface. Controlling the plasma boundary position is therefore equivalent to equalizing the flux value on several points belonging to a curve tangent to the limiter. ⅱ) Experimental method for determining the outmost poloidal isoflux surface by a linear combination of measurements of magnetic fluxes, fields and field gradients, without requiring knowledge of internal plasma parameters for the feedback control, i.e., with neither corrections for variation in the poloidal beta and the plasma current distribution, nor compensations for the induced currents in the vacuum vessel. ⅲ) Feedback control algorithm for the regulation of plasma boundary position and its electronics hardware based on the PID control theory. ⅳ) Experimental results obtained from the RTP tokamak experiments using the present plasma control system.

• Transactions of the Society of Information Storage Systems
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• v.2 no.1
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• pp.13-20
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• 2006

In this paper, we propose novel optics design for media inside near-field recording(NFR) using hemispherical solid immersion lens(HMS). To obtain strong advantage of data protection and high data capacity simultaneously, HMS based near field optics using aplanatic position of super hemisphere is designed. In this design, to improve small optical tolerance of this aplanatic position, additional aspheric lens surface is added on top of the HMS and it is combined with zoom optics which composed of two single lenses having low numerical aperture(NA). Also, to compensate chromatic aberration which happens seriously in optics using blue laser diode, diffractive optical element is used. Using zoom optics, additional aspheric lens surface, and diffractive optical element together, wavefront aberration and chromatic aberration are effectively reduced in broad range of cover layer thickness and wavelength variation. In addition, in this paper, effect of gap induced aberration is investigated by analyzing different behavior of each TM and TE wave for designed media inside dual-layer NFR optics.

• Animal Systematics, Evolution and Diversity
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• v.36 no.3
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• pp.240-250
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• 2020

Member of the genus Tobrilus Andrássy, 1959, which belongs to Tobrilidae Filipjev, 1918, are known as free-living nematodes in freshwater habitat. This genus was previously unknown from Korea. Five Tobrilus species are here reported for the first time from Korea: Tobrilus aberrans (Schneider, 1925), Tobrilus diversipapillatus (Daday, 1905), Tobrilus gracilis (Bastian, 1865), Tobrilus longus (Leidy, 1851), and Tobrilus wesenbergi (Micoletzky, 1925). Specimens were collected from sediments of the Nakdong River in Korea. Morphological characters and measurements of the specimens generally agree with the original descriptions of Tobrilus species, except for some differences that can be attributed to intraspecific variation among populations(e.g., nerve ring position [% pharynx] and reproductive length). Each species can be distinguished from other members of the genus by specific characters (e.g., cephalic setae length and position, buccal cavity and pocket shape, vulva position, degree of development of reproductive system, and tail length and shape). Here, five species in the genus Tobrilus are fully redescribed and illustrated using optical microscopy images. DNA barcode sequence information (the D2-D3 region of 28S rDNA) is also provided for molecular species identification.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.269-272
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• 2008

Internal flow field of supersonic nozzle with pintle, which control thrust of solid rocket motor, is very complicated by pintle tip shape and contour of nozzle. For studying of pintle nozzle performance by effects of internal flow field variation with pintle position, cold flow test and numerical analysis about needle type pintle shape were performed and results were presented in this paper. As the results of this study, three types of internal shocks exists in the pintle nozzle and oblique shock is oscillated by pintle position

• Journal of the Korean Institute of Educational Facilities
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• v.14 no.4
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• pp.53-65
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• 2007

The present research has been conducted on the arranged form, the number and kinds, the area, the location of the rooms and the variation on exterior designs, based on a layout and a ground plan of each step, which are general plan, VE proposal and the final negotiation, for 11 elementary and middle and high schools that are designed in the way of BTL project. In consequence, it has been found out that there are some changes in the number and position of the rooms. However, the changes are not exceeding the overall arrangement form. This could not have led to the original aim, which is to induce creativity by PFI. It can be supposed that it is because the BTL system is stick to the old process, the method of financial investment and it is true to say that there needs to be solution for that.

• Journal of Astronomy and Space Sciences
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• v.13 no.1
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• pp.72-78
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• 1996

We evaluated the orbital elements of BV light curves of a short period RS CVn type eclipsing binary system UV Picsium that shows complication light variation, by analyzing with the Winson-Devinney's differential correction method. Because the analyzed light curves shows large light variation at outside eclipse region, we assumed spotted region of the primary component and calculated its position and size. The results show the UV Psc is a detached binary system of nearly the same radii and the primary component has high mass with high temperature. However this result is not consistant with customary stellar models, thus requires more observational data to confirm this problem.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.19-22
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• 1990

In this paper, in order to reduce the cogging torque in a permanent motor, a method to optimize the shape of permanent magnet and iron pole is presented. Because the cogging torque comes from the irregular system energy variation according to the rotor position, system energy variation is taken as object function and the object function is minimized to optimize the shape. The positions of permanent magnet surface and iron pole surface are chosen as design parameters and sensitivity of object function with respect to design parameter is calculated. The shape is changed according to sensitivity. Sensitivity can be generated by methods that exploit the FEM formulation. A numerical example shows that about 90% of the original cogging torque is reduced.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.87-90
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• 2006

The direct instantaneous torque control (DITC) method is presented in this paper, which enables torque to be generated during all region and instantaneous torque control to be possible. The hysteresis control mode with the compared value between given torque and instantaneous output torque as input is applied in respect region. The output torque function, that is instantaneous output torque with the variation of current and position of rotor, is achieved by experiment. In this control mode the torque subsection function and current control are not needed. The turn on angle with variation of load torque and speed is only selected and turn off angle can be neglected. The validity of method is tested by simulation and experiment.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.12
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• pp.1246-1252
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• 1990

In order to reduce the cogging torque in a permanent magnet motor, a method to optimize the shape of permanent magnet and iron pole is presented. Sine the cogging torque comes from the irregular system energy variation according to the rotor position, system energy variation is taken as object function and the object function is minimized to optimize the shape. The positions of permanent magnet surface and iron pole surface are chosen as design parameters and sensitivity of object function with respect to the design parameter is calculated. The shape is changed according to sensitivity can be generated by methods that exploit the FEM formulation. A numerical example shows that the cogging torque is reduced to about 10% of the original value.

• Transactions of Materials Processing
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• v.14 no.5 s.77
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• pp.439-443
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• 2005

Deep drawing and cold forging processes are combined to achieve near net shape forming of automotive part which has not only drum shape but also thickness variation. It is important to find out proper intermediate shape where two totally different forming methods should be joined seamlessly. In the course of development of the combined process, finite element analysis can be utilized effectively to decide optimal position for transferring from the sheet metal work to the bulk forming. Because machining process is eliminated, significant improvement in integrity, reliability, and durability of the part is expected. The developed process combination could be applied in real manufacturing process successfully.