• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권7호
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• pp.379-386
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• 2002

This paper deals with dynamic analysis method of a slotless type permanent magnet linear synchronous motor(PMLSM) using 3-dimensional space harmonic method. The results are good agreement with FEA results because that slotless type PMLSM has simple structure and no saturation of core. And then, Under open-loop control, starting characteristic is analyzed by voltage equation combining with dynamic equation. In order to obtain more accuracy results, this paper use instantaneous back-EMF and thrust instead of back-EMF constant and thrust constant.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제2B권4호
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• pp.162-167
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• 2002

This paper presents the dynamic analysis method for a slotless permanent magnet linear synchronous motor (PMLSM) using the 3-D space harmonic method. Instantaneous emf and thrust are considered by movement of the PM and instantaneous armature current instead of $K_E$ (back-emf constant) and $K_F$(thrust force constant) for accurate results. The results of magnetic field distribution, back-emf, inductance, and thrust are in agreement with 2-D FEM and experimental results. To confirm the validity of this method, the calculated results are compared to measured ones.

• 한국항공우주학회지
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• 제38권12호
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• pp.1153-1161
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• 2010

본 연구에서는 주기적 비정상 유동 해석을 위해 푸리에 변환을 이용하는 조화 균형법의 효율적인 해법을 제안한다. 내재적으로 유속항을 처리하고 외재적으로 조화 원천항을 처리하였다. 외재적 조화 균형법 보다 더 빠르게 수렴 시킬 수 있으며 내재적 조화 균형법을 적용할 때 추가되는 자코비안 행렬을 처리할 필요가 없다. 또한 완전 내재적 기법에 상응하는 수준의 수렴안정성을 확인할 수 있었다. 2차원 비정상 유동 문제로 피칭하는 NACA0012 익형에 적용하였으며 이중 시간 적분법 및 외재적 Runge-Kutta기법의 해와 매우 일치하는 결과를 얻었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.732-739
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• 2005

The determination of sound pressure radiated from periodic plate structures is fundamental in the estimation of noise level in aircraft fuselages or ship hull structures. As a robust approach to this problem, here a very general and comprehensive analytical model is developed for predicting the sound radiated by a vibrating plate stiffened by periodically spaced orthogonal symmetrical beams subjected to a sinusoidally time varying point load. In this these, we experiment with the numerical analysis using the space harmonic series and the SYSNOISE for measuring the vibration mode and character of response caused by sound radiation with adding the harmonic point force in the thin isotropic plate supported by the rectangular lattice reinforcement. We used the reinforcements, beams of open type section like the style of 'ㄷ' letter; the space of the beams were chosen to be 0.2m, 0.3m, 0.4m. We studied the behavior of sound pressure levels, analysis of vibration mode between support points, connection between frequency function and sound pressure levels, and connection between position function and sound pressure levels.

• International Journal of Aeronautical and Space Sciences
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• 제14권1호
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• pp.19-29
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• 2013

This paper deals with the study of buckling, vibration, and parametric instability characteristics in a damaged cross-ply and angle-ply laminated plate like beam under in-plane harmonic loading, using the finite element approach. Damage is modelled using an anisotropic damage formulation, based on the concept of reduction in stiffness. The effect of damage on free vibration and buckling characteristics of a thin plate like beam has been studied. It has been observed that damage shows a strong orthogonality and in general deteriorates the static and dynamic characteristics. For the harmonic type of loading, analysis was carried out on a thin plate like beam by solving the governing differential equation which is of Mathieu-Hill type, using the method of multiple scales (MMS). The effects of damage and its location on dynamic stability characteristics have been presented. The results indicate that, compared to the undamaged plate like beam, heavily damaged beams show steeper deviations in simple and combination resonance characteristics.

• 대한수학회지
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• 제57권6호
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• pp.1435-1449
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• 2020

In this article we make a local classification of n-dimensional Riemannian manifolds (M, g) with harmonic curvature and less than four Ricci eigenvalues which admit a smooth non constant solution f to the following equation $$(1)\hspace{20}{\nabla}df=f(r-{\frac{R}{n-1}}g)+x{\cdot} r+y(R)g,$$ where ∇ is the Levi-Civita connection of g, r is the Ricci tensor of g, x is a constant and y(R) a function of the scalar curvature R. Indeed, we showed that, in a neighborhood V of each point in some open dense subset of M, either (i) or (ii) below holds; (i) (V, g, f + x) is a static space and isometric to a domain in the Riemannian product of an Einstein manifold N and a static space (W, gW, f + x), where gW is a warped product metric of an interval and an Einstein manifold. (ii) (V, g) is isometric to a domain in the warped product of an interval and an Einstein manifold. For the proof we use eigenvalue analysis based on the Codazzi tensor properties of the Ricci tensor.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.1022-1028
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• 2005

This paper is presented the analysis results and simulation results of cascaded H-bridge 7 level inverter with various modulation index. Stepped waveform having number of switching was used to eliminate harmonic components. Switching angles according to modulation index are calculated numerically. Therefore, 3 times of switching with 7 level topology and QWS(Quarter Wave Symmetry) could eliminate 5th and 7th harmonics. The harmonic characteristics are compared to those of space vector modulation method which known as common modulation method in industrial field. Stepped waveform method showed higher ability to reduce, especially lower order of harmonics.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 A
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• pp.192-194
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• 1997

This paper propose an efficient space harmonic analysis method for magnetic field. Permanent magnet and primary core considered slot are replaced by EMC(equivalent magnetizing current). And the resultant air gap flux density is calculated by superposition due to the permanent magnet and EMC. We analyze the harmonic distribution of air gap flux density taking into account slot for PMLSM.

• Journal of Astronomy and Space Sciences
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• 제35권4호
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• pp.219-225
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• 2018

Cosmic rays are ions that move at relativistic speeds. They generate secondary cosmic rays by successive collisions with atmospheric particles, and then, the secondary particles reach the ground. The secondary particles are mainly neutrons and muons, and the neutrons are observed by the ground neutron monitor. This study compared the diurnal variation in cosmic ray intensity obtained via harmonic analysis and that obtained through the pile-up method, which was examined in a previous study. In addition, we analyzed the maximum phase of the diurnal variation using four neutron monitors with a cutoff rigidity below approximately 6 GV, located at similar longitudes to the Oulu and Rome neutron monitors. Expanding the data of solar cycles 20-24, we examined the time of the maximum cosmic ray intensity, that is, the maximum phase regarding the solar cyclic modulation. During solar cycles 20-24, the maximum phase derived by harmonic analysis showed no significant difference with that derived by the pile-up method. Thus, the pile-up method, a relatively straightforward process to analyze diurnal variation, could replace the complex harmonic analysis. In addition, the maximum phase at six neutron monitors shows the 22-year cyclic variation very clearly. The maximum phase tends to appear earlier and increase the width of the variation in solar cycles as the cutoff rigidity increases.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1132-1134
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• 2005

This paper presents a design strategy of Slotless type BLDC motor using the space harmonic field method. The distribution of Back emf and torque are considered by movement of the Permanent Magnet and armature current. The result of magnetic field distribution, back-emf, and torque are in agreement with FEM.