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Sung‑Il Kim,Su‑Jin Lee,Jeong‑Jong Lee,Chang‑Eob Kim 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.3
Ferrite-bonded magnets have been extensively used in small brushless DC (BLDC) motors for low torque applications such as fans and pumps. In particular, some motors of them with ferrite-bonded magnets, frequently called as plastic magnets, do not have a rotor core in order to reduce manufacturing costs and inertia of the rotating part. Accordingly, the magnetization distribution of the bonded magnets has a polar anisotropic direction to secure more magnetic fux. As a result, the magnetization orientation of the magnets is highly signifcant to accurately predict the performances of the BLDC motors. This paper deals with the magnetization analysis of the polar anisotropic ferrite ring magnet applied to an outer rotor type BLDC motor. The motor is employed for an electric water pump, and its rotor including the impeller consists of only the ferrite-bonded magnet material and made by injection molding. Consequently, a magnetizing fxture and an impulse magnetizer are not used for the magnetization of the outer rotor type motor. Instead, samarium–cobalt (SmCo) magnets having a relatively high curie temperature are applied for generating magnetic feld. Finally, this paper presents a process to determine the anisotropic orientations of a ferrite ring magnet by fnite element method. In addition, the validity of the analysis method is verifed by test results
New Hidden Variable Theory of a Two-Dimensional Quantum System
Sang-GyuJo,Sang-DonChoi,Ho-IlKim,김명석 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.41 No.1
There exist some no-go theorems which say that it is impossible to construct realistic theory for quantum systems without contradictions. We, however, proposed in a recent paper a method to escape the so-called Bell-style paradox. Reasonable further research would be to embody our proposition in a concrete hidden-variable theory. As preliminary study, we try to extract lessons from a two-dimensional case. Although it is well known that a two-dimensional hidden-variable theory can be constructed without inconsistency with a quantum formalism, our model given here diers from the old ones in that ours has a possibility of being generalized to a higher dimensional system. Moreover, it is equipped with a non-uniform measure which is determined by the choice of a state.V
운동역학 : Backpropagation 알고리즘을 이용한 운동역학적 자료의 스무딩(smoothing)
김기영(Ky-HyoungKim),김진욱(Jim-UkKim),김성일(Sung-IlKim) 한국체육학회 2001 한국체육학회지 Vol.40 No.4
본 연구는 운동역학분야에서 자료의 처리부분에 해당되는 자료의 스무딩을 신경망(neural network)이론의 multi-layer모형에 의한 backpropagation학습방법과 digital filtering을 사용하여 비교하고 backpropagation의 타당도 검사를 통한 그 적용성을 제시하는데 있다. 분석에 사용된 자료는 Pezzack(1977)의 각속도에 대한 영상 자료이며 digital filtering을 통한 두 번의 수치미분값과 수치미분을 먼저 한 후 학습을 시켜나온 결과값을 비교했다. 결과는 backpropagation학습방법이 R<sup>2</sup> = 0.9421 로 R<sup>2</sup> = 0.8694의 값을 갖는 digital filtering보다 더 잘 적합시켰다. 그리고 네트워크의 안정성을 검증하는 신뢰도는 10회 모두 우수한 결과를 보여주었다. The purpose of this study is to compare backpropagation method in neural network to digital filtering, which is frequently used in the field of biomechanics and to present its application. The data used in this study is Pezzack's data(1977) and is often used by many researchers to find the new smoothing method. In backpropagation, finite differentiation was followed by neural network learning, In contrast, digital filtering was followed by finite differentiation in digital filtering method(The same cutoff frequency was used as Pezzack did) The comparison was made between two methods by RMSE(Root mean squared error) and R<sup>2</sup> of regression analysis. The values of R<sup>2</sup> for digital filtering and backpropagation were 0.8694 and 0.9421 respectively. The values R2 indicated that the backpropagation method is closer to the original accelerometer values than digital filtering. Therefore, backpropagation function approximation method is promising.