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19세기 남병철 『의기집설(儀器輯說)』 혼천의 용법 분석
최홍순,김상혁,민병희,남경욱,유경한,김용기,HONG SOON CHOI,SANG HYUK KIM,BYEONG-HEE MIHN,KYOUNG-UK NAM,GEOYOUNG-HAN YOO,YONGGI KIM 한국천문학회 2024 天文學論叢 Vol.39 No.1
The armillary sphere, an astronomical observation device embodying the Orbital Heaven Theory of the Later Han Dynasty in China, holds both historical and scientific significance. It has been produced in various forms by many individuals since its inception in the era of King Sejong in the Joseon Dynasty. A prominent figure in this field was Nam Byeong-cheol (南秉哲, 1817-1863), known for his work 'Uigijipseol' (儀器輯說), published in 1859, which detailed the history, production methods, and usage of the armillary sphere. This text particularly highlights 21 applications of the armillary sphere, divided into 33 measurements, covering aspects like installation, time, and positional measurements, supplemented with explanations of spherical trigonometry. Despite numerous records of the armillary sphere's design during the Joseon Dynasty, detailed usage information remains scarce. In this study, the 33 measurements described in 'Uigijipseol' (儀器輯說) were systematically classified into six for installation, nineteen for position measurement, seven for time measurement, and one for other purposes. Additionally, the measurement methods were analyzed and organized by dividing them into the ecliptic ring, moving equatorial ring, and fixed equatorial ring of the armillary sphere. In other words, from a modern astronomical perspective, the results of schematization for each step were presented by analyzing it from the viewpoint of longitude, right ascension, and solar time. Through the analysis of Nam's armillary sphere, this study not only aims to validate the restoration model of the armillary sphere but also suggests the potential for its use in basic astronomical education based on the understanding of the 19th-century Joseon armillary sphere.
자성유체에 잠긴 비자성체 부상현상의 다중물리수치해석 및 실험
최홍순(Hong-Soon Choi) 대한전기학회 2013 전기학회논문지 Vol.62 No.1
In this paper, magnetic buoyancy force on nonmagnetic solid object submerged in magnetic liquid was simulated and measured. For the evaluation of the force, a multi-physics approach of hydrostatic equilibrium considering magnetic body force as well as gravity is presented. The magnetic body force should be regarded as an additional forcing term in the momentum equation of hydrodynamics. It is also shown that the virtual air-gap based Kelvin’s force formula is a useful method for the calculation of force distribution in the magnetic liquid. The experimental result which was performed by a load-cell measurement system agreed quantitatively well with the numerical one.
비선형 효과를 고려한 IPM형 전동기의 DQ축 인덕턴스 및 역기전력상수 파라미터 추출
崔鴻洵(Hong-Soon Choi) 대한전기학회 2007 전기학회논문지 Vol.56 No.3
In this paper, we propose a precise parameter extraction of interior permanent magnet (IPM) motors based on finite element analysis. For the calculation of the two-axis inductances Ld and Lq, the slotting effect and cross magnetization due to torque angle are considered. It is examined that back electro-motive force (BEMF) constant is affected by the magnetic saturation in different ways dependent on motor types. Numerical analyses and some measurements are performed for a spoke type and a flux barrier type IPM motors
최홍순(Hong-Soon Choi) 한국자기학회 2018 韓國磁氣學會誌 Vol.28 No.1
In this paper, the implications of implementing a dielectric or magnetic body with a dipole model are discussed. The concept of bound charge canceled inside is basically a bound charge projected onto the surface, and the force on it can not be regarded as the density of the electromagnetic force. Projected bound charge is only effective when affecting the field outside the material and calculating the total electromagnetic force. It is shown that the introduction of virtual air-gap along with the projected bound charge can calculate the electromagnetic volumetric density.