• Title, Summary, Keyword: space harmonic analysis

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Determination of photorefrative constants in LiNbO$_3$ using second harmonic generation (제2고조파발생을 이용한 LiNbO$_3$의 중요 광굴절상수측정)

  • 김봉기;이범구
    • Korean Journal of Optics and Photonics
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    • v.12 no.3
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    • pp.230-234
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    • 2001
  • We report a simple method for determining photovoltaic constant and conductivities of any photorefractive crytals which have no inversion symmetry by utilizing the electric field dependence of non-phase-matched second harmonic generation. New theoretical expression for the electric field dependence of Maker fringes is derived and space charge field can be determined using this from the observed change of intensity of second harmonic wave. The photovoltaic constant, dark conductivity and photoconductivity are easily deduced from an analysis of the measured relaxation behavior of space-charge field at two different light intensities. We demonstrate this method for $LiNbO_3$ at 514.5 nm.4.5 nm.

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Some Theoretical Considerations in Body Tide Calculation (고체지구조석계산에 있어 몇 가지 이론적 고찰)

  • Na, Sung-Ho;Shin, Young-Hong;Baek, Jeong-Ho
    • Geophysics and Geophysical Exploration
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    • v.14 no.2
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    • pp.133-139
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    • 2011
  • The largest terms in the solid Earth body tide calculation are second degree spherical harmonic components due to the moon or the sun, and they compose about 98 percent of total contribution. Each degree harmonics of the tidal perturbation should be evaluated through multiplication with distinct Love numbers or their combinations. Correct evaluation of these terms in gravity tide is considered with re-calculated Love numbers. Frequency dependence of Love numbers for spherical harmonic tide upon the order number is discussed. Tidal displacement and tidally induced deviation of the vertical are also evaluated. Essential concepts underlying the body tide calculation are briefly summarized.

A State Space Analysis on the Stability of Periodic Orbit Predicted by Harmonic Balance

  • Sung, Sang-Kyung;Lee, Jang-Gyu;Kang, Tae-Sam
    • 제어로봇시스템학회:학술대회논문집
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    • pp.67.5-67
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    • 2001
  • A closed loop system with a linear plant and nonlinearity in the feedback connection is analyzed for its quasi-static orbital stability by a state-space approach. First a periodic orbit is assumed to exist in the loop which is determined by describing function method for the given nonlinearity. This is possible by selecting a proper nonlinearity and a rigorous justification of the describing function method.[1-3, 18, 20]. Then by introducing residual operator, a linear perturbed model can be formulated. Using various transformations like a modified eigenstructure decomposition, periodic-averaging, charge of variables and coordinate transformation, the stability of the periodic orbit, as a solution of harmonic balance, can be shown by investigating a simple scalar function and result of linear algebra. This is ...

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Eddy Current Loss Analysis in Radial Flux Type Synchronous Permanent Magnet Coupling using Space Harmonic Methods (공간고조파법을 이용한 반경방향 영구자석을 갖는 자기커플링의 와전류 손실 해석)

  • Min, Kyoung-Chul;Kang, Han-Bit;Park, Min-Gyu;Cho, Han-Wook;Choi, Jang-Young
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.63 no.10
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    • pp.1377-1383
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    • 2014
  • This paper deals with eddy current loss of magnetic coupling with radial permanent magnet (PM) using analytical method such as a space harmonic method. Superposition of two kinds analysis model is used to analyze eddy current loss induced in inner PM and outer PM of magnetic coupling. When the eddy current is induced, the environmental temperature increases, and the permanent magnet(PM) characteristics are degraded because the performance of PM is greatly influenced by temperature rise. Hence, the calculation of eddy current loss becomes an important factor in the magnetic coupling. In order to analyze eddy current loss, first, on the basis of the magnetic vector potential and two-dimensional(2-D) polar-coordinate system, the magnetic field solutions of the radial magnetized PM are obtained. And we obtain the analytical solutions for the eddy current density produced by permanent magnet. Lastly, analytical solutions for eddy current loss are derived by using equivalent, electrical resistance calculated from magnet volume and analytical solution for eddy current density. This analytical results are validated by comparing with the 2-D finite element analysis (FEA).

Vibratory Loads Behavior of a Rotor in High Advance Ratios (고속 전진비 조건에서의 로터 진동하중 특성 연구)

  • Na, Deok Hwan;You, Younghyun;Jung, Sung Nam
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.3
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    • pp.237-243
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    • 2018
  • In this study, the hub vibration load characteristic is evaluated for a rotor in high advance ratio conditions while investigating blade loads through the structural load prediction and harmonic analysis. Numerical studies are performed to validate the wind tunnel test data performed in NASA as the rotor advance ratios are varied from 0.40 to 0.71. A good correlation is obtained for rotor performance calculation at the range of advance ratios considered. It is observed that the hub vibration loads remain almost unchanged when the advance ratios are higher than 0.5, even though the amplitudes of blade structural loads become larger with increasing advance ratios. A harmonic analysis on blade moments is confirmed that the dominant structural mode is 3/rev component for flap bending moments and 4/rev for lag bending moments. The reason is due to the tendency of the second flap and lag mode frequencies which approach 3/rev and 4/rev, respectively, as the advance ratios are increased.

A Study on Time-space of Thesis in modern arcitecture space - Focus on concept of modem time - (근대 건축공간에서 시공간 개념에 관한 연구 - 근대적 시간의 개념을 중심으로 -)

  • 장세연;이성훈
    • Proceedings of the Korean Institute of Interior Design Conference
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    • pp.69-72
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    • 2001
  • We are defined a space as the activities of creating value in harmonic relations between human and environment. After Industrial Revolution, relations between human and space is changing because of speed and visualization's power in contemporary society. We we known information where is far by means of visualization. There is only difference of speed. Movement in space means the line of vision and circulation. But it is tried to think relations between human and space again in result to experience indirectly. This study aims at the analysis of expression of the modem Architecture space in Giedion' Space, Time, Architecture and aesthetic systems applied to it. On the basis of that , this study analyzed the difference of Bergson' consideration from Modern Architecture about movement.

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THE DETECTION OF INSTANTANEOUS DISTORTED CURRENT WITH THREE-DIMENSIONAL SPACE VECTOR

  • Mei, Tong;Jie, Tong;Jingpin, Jiangg
    • Proceedings of the KIPE Conference
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    • pp.615-619
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    • 1998
  • Active power filter is a kind of device used for compensating instantaneous reactive and harmonic current in three-phase circuits. An essential technology that determines the behavior of an active power filter is the method of detecting the distorted current. Using three-dimensional space vectors, this paper describes a simple method for detecting the distorted current without any coordinate transformation. The effectiveness of the novel method is verified by the theoretical analysis and simulation.

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A study on Optimization of the Design Variables of Linear Motor Using Genetic Algorithm (유전알고리즘을 이용한 리니어모터의 설계변수 최적화에 관한 연구)

  • Joo, Sang-Hyun;Jung, Jae-Han;Lee, Sang-Ryong
    • Journal of the Korean Society for Precision Engineering
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    • v.19 no.5
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    • pp.110-117
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    • 2002
  • This paper proposes a optimization of the design variables of linear motor for the improvement of thrust. Especially, this paper treats the shoe, which can be good to flow of a magnetic flux in linear motor. Firstly, this paper uses a space harmonic analysis method(SHAM) based on Fourier series, for analyzing the characteristics of core type linear motor, including slot structure and shoe. And compare the magnetic flux densities of linear motor at air gap with the results of the SHAM and the Finite Element Method(FEM). Secondly, this paper uses a genetic algorithm, which is good to find the global solutions. The design variables are the pole pitch of magnet, the pitch of slot, the height of slot, the width of shoe and the width of magnet. The maximum thrust with optimum design variables is about 247 N which is improved about 16%.

Comparison of the Characteristics in the Surface Mounted Permanent Magnet and Flux Concentrating Coaxial Magnetic Gears Having the Solid Cores

  • Shin, Ho-Min;Chang, Jung-Hwan
    • Journal of Electrical Engineering and Technology
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    • v.13 no.3
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    • pp.1275-1284
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    • 2018
  • The coaxial magnetic gear with the flux concentrating structure is known that it has the torque performance advantage over the coaxial magnetic gear having surface mounted permanent magnet, thanks to the flux focusing effect. But, if the solid cores are used in the modulating pieces and rotor cores to consider the mechanical reliability and cost reduction, the operating torque of the flux concentrating coaxial magnetic gear can be significantly diminished because the iron losses at the solid cores affect the actual transmitted torque. Furthermore, the modulating pieces and rotor cores have different characteristics of the iron losses from one another, because the space harmonic components of the magnetic flux density, which cause the iron losses, are different. Thus, in this paper, we focused on the analysis of the characteristics of the space harmonic components of the magnetic flux density and resultant eddy current losses in the surface mounted PM and flux concentrating coaxial magnetic gears, when these coaxial magnetic gears have the solid cores at the modulating pieces and rotor cores. The characteristics of pull-out torque (static torque), operating torque (dynamic torque), and efficiency are also researched, and compared by the 3D finite element analysis (FEA) and experiment.

Eddy-Current Loss Analysis in Rotor of Surface-Mounted Permanent Magnet Machines Using Analytical Method (해석적 방법을 이용한 표면부착형 영구자석 기기의 회전자 와전류 손실해석)

  • Choi, Jang-Young;Choi, Ji-Hwan;Jang, Seok-Myeong;Cho, Han-Wook;Lee, Sung-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.8
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    • pp.1115-1122
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    • 2012
  • This paper analyzes eddy-current loss induced in magnets of surface-mounted permanent magnet (SPM) machines by using an analytical method such as a space harmonic method. First, on the basis of a two-dimensional (2D) polar coordinate system and a magnetic vector potential, the analytical solutions for the flux density produced by armature winding current are obtained. By using derived field solutions, the analytical solutions for eddy current density distribution are also obtained. Finally, analytical solutions for eddy current loss induced in rotor magnets are derived by using equivalent electrical resistance calculated from magnet volume and analytical solutions for eddy-current density distribution. In particular, the influence of time harmonics in armature current on the eddy current loss is fully investigated and discussed. All analytical results are validated extensively by finite element analysis (FEA).