• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.6
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• pp.85-93
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• 1997

This paper analyzes the steady-state and dynamic characteristics of the watkings-johnson converter. the major contributions of this paper includ identification of the following characteristics unique to the watkins-johnson converter: (1) The output voltage of the converter is nearly constant at the continous conduction mode (CCM), and at discontinousou conduction mode (DCM) it decreses linerly as the output curretn increases. (2) The control-to-output transfer function is a second-order one with a left-half-plane (LHP) zero determined by the combination of the output capacitor and equivalent series resistor of the converter. This LHP zero signinificantly improves the stability of the converter. (3) The control-to-output transfer function reduces to a first-order one, as the converter moves from CCM to DCM. (4) The parastic resistance of the inductor does not cause any significant influence on poles and zeros of the transfer function.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.760-761
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• 2015

기어는 회전 기계 사이의 동력 전달을 위한 장치이며 현재 산업 전반의 통상적인 기어는 기계적 기어가 주류로서 형성되어 있다. 하지만 기계적 기어는 맞물린 톱니바퀴의 물리적 접촉에 의해 접촉 경계면의 마모 및 파손, 소음과 진동의 문제가 있으며 유지보수 비용 또한 크다. 따라서 최근 물리적 접촉이 없어 기계적 기어의 많은 문제를 해결할 수 있는 마그네틱 기어 (Magnetic Gear)에 대한 관심이 높아지고 있다. 마그네틱 기어는 영구자석에서 생성된 자계를 이용하여 비접촉 동력전달이 가능하며, 마찰손실 제거, 유지보수의 용이성, 매우 적은 소음 및 진동 등의 장점을 가지고 있다. 본 논문에서는 이러한 마그네틱 기어의 토크전달 방법과 형상변화에 따른 전달토크 특성을 2-D 유한요소해석법을 이용하여 해석하고 분석하고자 한다.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.138-141
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• 2002

BLDCM(Brushless D.C. Motor) is widely used for industrial application because of high efficiency and high power density Especially, in servo system and home appliance, BLBCM is very useful due to high control performance and low acoustic noise. In this paper, 2.5HP rated BLDCM controller and drive was developed for tread mill application. The prototype BLDCM has 4 poles rotor and 24 slots stator. Ferrite was used as a rotor magnet due to the cost and temperature characteristic. For the stable operation of tread mill, over current and high temperature can be detected by the DSP controller. For the commutation signal, switching patterns from the sensorless circuit and hall sensor signal are used in the DSP controller.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.2
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• pp.34-38
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• 2008

Commercially available magnetic barrel machines equipped with permanent magnets have certain limitations: work can only be finished effectively in limited areas of the container because permanent magnets are arranged two-dimensionally on the magnet disk. We overcame this problem by developing a new magnetic barrel machine equipped with a three-dimensional magnet arrangement. The effectiveness of the new machine has already been reported; this study improved the machine's polishing ability by changing the polarity of magnets on a magnet block. Polishing experiments confirmed the most effective arrangement of magnets on the magnet block. An alternating arrangement of north and south poles produced far superior polishing characteristics than a uniform arrangement of the same pole facing outward. Alternating polarity probably causes increased quantities of barrel media to work together. Finally, we introduced stronger permanent magnets to the magnet block, and found that the increased magnetic field also improved polishing ability.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.72-74
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• 2003

We fabricated textured Ag substrates for coated conductor and evaluated the effects of annealing temperature on microstructural evolution, texture formation, and surface morphology. A strong {110}〈110〉 textured Ag substrate was obtained by cold rolling and annealing at 80$0^{\circ}C$: the full-width at half-maximum(FWHM) value of {110}〈110〉 poles was as sharp as 10$^{\circ}$. Surface morphology was evaluated by using Atomic force microscopy(AFM). Root-mean-square(RMS) roughness of the substrate annealed at 80$0^{\circ}C$ was 39.2 nm. The substrate of strong texture and smooth surface, fabricated in our study, is considered to be suitable for use as a substrate for deposition of superconductor films.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.10
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• pp.1071-1077
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• 2002

In this paper, we have studied the dependence of insertion loss of the pressed microstrip PBG ring consisting of coupled two microstrip lines. When the distance decreases, two or three attenuation poles are created by the coupling between the lines. Thus the pressed PBG ring exhibits a wide stop band and sharp cutoff characteristics.

• Electrical & Electronic Materials
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• v.9 no.9
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• pp.891-899
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• 1996

A model for predicting the characteristics of elastic ferromagnetic materials having a moving gap was presented. Based on the model parameters concerning behavior of material, such as the instantaneous field intensity, attractive force between the poles, length of gap, and the induced current/ emf in the circuit can be determined from the numerical integrations of the governing equations derived. From the results of the model it is found that when dc emf is imposed on the circuit the current sharply rise and fall for very short duration then stabilize at extremely low level which depends mainly on elasticity, permeabilities and ratio of resistivity. Subsequently output emf is shown stabilized at constant value which depends on the previous parameters as well as the resistivity ratio of primary to secondary circuit after sufficient progress of time.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.7
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• pp.409-416
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• 2004

This paper presents the selection method o( the input current wave forms for the thrust force ripple of linear pulse motor (LPM). We have developed and tested a prototype 2-phase 4-poles LPM with the permanent magnet and its control driver. To obtain the thrust performance curve of LPM, the performance curve at the air gap and the thrust are calculated and estimated by the analytical method on the base of the magnetic equivalent circuit and the finite element method. And, the thrust characteristics at the static operation state are analyzed and experimented with the respect to the input wave forms such as the rectangular, the triangular micro-step and the sine micro-step wave forms to investigate the thrust ripple and the vibration effects of LPM.

• Lingua Humanitatis
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• v.1 no.2
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• pp.67-90
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• 2001

In the past few years, a trend has emerged emphasizing the interdisciplinary relationship between cultural and literary studies, and "memory" has been suggested as the central theme in this trend. According to Aleida and Jan Assmann, "memory" as collective memory (not individual recollection) has various functions and forms, of which communicative memory and cultural memory occupy opposite poles of a central axis. Whereas communicative memory relates to the living past shared among contemporaries, cultural memory relates to "recollected history" rather than factual history. Cultural memory finds transmission through symbolic media such as myths, festivities, and literary works. Literary works preserve critical and living memories as opposed to forgotten memories. In other words, literature should be better read as "criticism and memory" than "imitation and preservation." Works of literature are characterized by a turning away from repetition toward representation-the process of "making present" of what is past.

• Proceedings of the KIEE Conference
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• summer
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• pp.1019-1021
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• 2004

BLDCM(Brushless D.C. Motor) is widely used for industrial application because of high efficiency and high power density. Especially, in servo system and home appliance. BLDCM is very useful due to high control performance and low acoustic noise. In this paper, 2.5HP rated BLDCM controller and drive was developed for tread mill application. The prototype BLDCM has 4 poles rotor and 24 slots stator. Ferrite was used as a rotor magnet due to the cost and temperature characteristic. For the stable operation of tread mill. over current and high temperature can be detected by the DSP controller. For the commutation signal, switching patterns from the sensorless circuit and hall sensor signal are used in the DSP controller.