• Title/Summary/Keyword: harmonic-analysis

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Analysis of Novel Approach to Design of Ultra-wide Stopband Microstrip Low-Pass Filter Using Modified U-Shaped Resonator

  • Karimi, Gholamreza;Lalbakhsh, Ali;Dehghani, Khatereh;Siahkamari, Hesam
    • ETRI Journal
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    • v.37 no.5
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    • pp.945-950
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    • 2015
  • A novel microstrip low-pass filter is presented to achieve an ultra-wide stopband with 11 harmonic suppression and very sharp skirt characteristics. The filter is composed of a modified U-shaped resonator (which creates two fully adjustable transmission zeroes), a T-shaped resonator (which determines a cut-off frequency), and four radial stubs (which provide a wider stopband). The operating mechanism of the filter is investigated based on a proposed equivalent-circuit model, and the role of each section of the proposed filter in creating null points is theoretically discussed in detail. The presented filter with 3 dB cut-off frequency ($f_c=2.35GHz$) has been fabricated and measured. Results show that a relative stopband bandwidth of 164% (referred to as a 22 dB suppression) is obtained while achieving a high figure-of-merit of 15,221.

Aerodynamic loads and aeroelastic responses of large wind turbine tower-blade coupled structure in yaw condition

  • Ke, S.T.;Wang, T.G.;Ge, Y.J.;Tamura, Y.
    • Structural Engineering and Mechanics
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    • v.56 no.6
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    • pp.1021-1040
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    • 2015
  • An effective method to calculate aerodynamic loads and aeroelastic responses of large wind turbine tower-blade coupled structures in yaw condition is proposed. By a case study on a 5 MW large wind turbine, the finite element model of the wind turbine tower-blade coupled structure is established to obtain the modal information. The harmonic superposition method and modified blade-element momentum theory are used to calculate aerodynamic loads in yaw condition, in which the wind shear, tower shadow, tower-blade modal and aerodynamic interactions, and rotational effects are fully taken into account. The mode superposition method is used to calculate kinetic equation of wind turbine tower-blade coupled structure in time domain. The induced velocity and dynamic loads are updated through iterative loop, and the aeroelastic responses of large wind turbine tower-blade coupled system are then obtained. For completeness, the yaw effect and aeroelastic effect on aerodynamic loads and wind-induced responses are discussed in detail based on the calculating results.

Beating phenomena in spacecraft sine testing and an attempt to include the sine sweep rate effect in the test-prediction

  • Nali, Pietro;Bettacchioli, Alain
    • Advances in aircraft and spacecraft science
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    • v.3 no.2
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    • pp.197-209
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    • 2016
  • The Spacecraft (S/C) numerical sine test-predictions are usually performed through Finite Element Method (FEM) Frequency Response Analysis (FRA), that is the hypothesis of steady-state responses to harmonic excitation to the S/C base is made. In the test practice, the responses are transient and may be significantly different from those predicted through FRA. One of the most significant causes of discrepancy between prediction and test consists in the beating phenomena. After a brief overview of the topic, the typical causes of beating are described in the first part of the paper. Subsequently, focus is made on the sine sweep rate effect, which often leads to have beatings after the resonance of weakly damped modes. In this work, the approach illustrated in the literature for calculating the sine sweep rate effect in the case of Single-Degree-Of-Freedom (SDOF) oscillators is extended to Multi-Degrees-Of-Freedom (MDOF) systems, with the aim of increasing the accuracy of the numerical sine test-predictions. Assumptions and limitations of the proposed methodology are detailed along the paper. Several assessments with test results are discussed and commented.

Han-Thought and Nursing (한 사상과 간호)

  • 김문실;고효정;김애경;이옥자
    • Journal of Korean Academy of Nursing
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    • v.21 no.3
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    • pp.295-306
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    • 1991
  • Han-Thought is a philosophy unique to the native to Korean culture. From the point view of etymological analysis the word “Han” means “Large”, “High” means “Whole” Ancient Korean people planted their philosophical roots deep in what has come to be known an Han-Thought. The goal of this study was to explore “Han-Thought” for concepts and principles which may contribute to the building of a Korean nursing philosophy, ethic, paradigm, theory and eventully practice. Ontologlly, our ancient people attempted to learn what was most essential and meaningful in life Han-Thought embraces the thought of complete harmony with in wholeness. Han encompasses everything in the universe. A chracteristic of Han-Thought is that all things relate to each other in harmonic balance, not in conflict. The harmonious balance of all things excludes both disruption and confrontation, making all things into a large oneness. Thus Han-Thought applied to Holism traditionally embraced by nursing philosophy. The principles of Han-Thought emphasize the love of peace. Extreme individualism and egoism are not allowed in Han-Thought. Thus Han-Thought provide a humanistic and ethical foundation for nursing philosophy. Han-Thought is a valuable philosophy for Korean nurse to explore toward the development of the discipline in Korea.

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A Study on Nonlinear Motions of Submerged Circular Cylinder in Regular Wave (정현파중에서의 잠수된 원형실린더의 비선형 운동에 관한 연구)

  • Ho-Young Lee;Jong-Heul Hwang
    • Journal of the Society of Naval Architects of Korea
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    • v.35 no.1
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    • pp.32-39
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    • 1998
  • A numerical analysis for large amplitude motions of submerged circular cylinder is presented. The method is based on potential theory and two-dimensional motions in regular harmonic waves are tented as an initial value problem. The fully nonlinear free surface boundary condition is assumed in an inner domain and this solution is matched along an assumed an assumed common boundary to a linear solution in outer domain. Calculations of the large amplitude motion of a submerged circular cylinder are directly simulated in time domain. It is shown that relative motion between the body and fluid particle gives a significant effect on the lift and drift motions.

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A study on the Structural Stability about the Fan Blade by the Air Excited Forces. (공기 가진력에 의한 팬 블레이드 구조 안정성 평가에 관한 연구)

  • 정규강;김경희;조생현
    • Journal of the Korean Society of Propulsion Engineers
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    • v.4 no.1
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    • pp.93-101
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    • 2000
  • In a gas-turbine engine, fan blades in flow path are confronted with many kinds of loading. The study of the excited force by the wake of struts has proposed and the possibility of fatigue failure about rotating fan blades by the excited force at the steady state is evaluated. Equations of the excited force of wakes has been derived at the steady state and the maximum pressure distributions measured at the transient state are proposed. Dynamic characteristics and the fatigue strength of fan blades by experimental test were obtained. To evaluate HCF(High Cycle Fatigue) damage of fan blades, FEM analysis was performed with a steady state harmonic response, which was followed by high cycle fatigue damage factor from goodman diagram.

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Detection Performance and THD Analysis of Active Frequency Drift for Anti-Islanding (단독운전 방지를 위한 능동적 주파수 변환 기법의 검출 성능 및 THD 분석)

  • Jo, Yeong-Min;Choi, Ju-Yeop;Song, Seung-Ho;Choy, Ick;Lee, Young-Kwoun
    • Journal of the Korean Solar Energy Society
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    • v.35 no.2
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    • pp.11-19
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    • 2015
  • Islanding is a phenomenon that EPS(Electric Power System) is continuously energized by PV PCS(Photovoltaic Power Conditioning System) even when EPS is isolated from the grid. Unintentional islanding will result in safety hazard, power quality degradation and many other issues. So, islanding protection of grid-connected PV PCS is a key function for standards compliance. Nowadays, many anti-islanding schemes are researched. But existing anti-islanding schemes used in PV PCS have power quality degradation and non-detection zone issues. This paper analyses not only detection performance of existed anti-islanding schemes using active frequency drift but also THD of PCS output current according to each value disturbance for anti-islanding. In addition, the lowest value of disturbance in each scheme was tabulated under guarantee of anti-islanding condition.

Application of the Empirical Orthogonal Functions on the GRACE Spherical Harmonic Solutions

  • Eom, Jooyoung;Seo, Ki-Weon
    • Journal of the Korean earth science society
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    • v.39 no.5
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    • pp.473-482
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    • 2018
  • During the period of 2002 to 2017, the Gravity Recovery And Climate Experiment (GRACE) had observed time-varying gravity changes with unprecedented accuracy. The GRACE science data centers provide the monthly gravity solutions after removing the sub-monthly mass fluctuation using geophysical models. However, model misfit makes the solutions to be contaminated by aliasing errors, which exhibits peculiar north-south stripes. Two conventional filters are used to reduce the errors, but signals with similar spatial patterns to the errors are also removed during the filtering procedure. This would be particularly problematic for estimating the ice mass changes in Western Antarctic Ice Sheet (WAIS) and Antarctic Peninsula (AP) due to their similar spatial pattern to the elongated north-south direction. In this study, we introduce an alternative filter to remove aliasing errors using the Empirical Orthogonal Functions (EOF) analysis. EOF can decompose data into different modes, and thus is useful to separate signals from noise. Therefore, the aliasing errors are effectively suppressed through EOF method. In particular, the month-to-month mass changes in WAIS and AP, which have been significantly contaminated by aliasing errors, can be recovered using EOF method.

Comparative Analysis of Voltage Unbalance Factor on the use of Linear and Non-linear loads in Three-phase Four-wire Low Voltage Distribution Line (3상 4선식 저압 배전선로에서 선형 및 비선형 부하의 사용시 전압 불평형률 비교 분석)

  • Kim, Jong-Gyeum;Kim, Ji-Myeong
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.3
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    • pp.587-592
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    • 2017
  • In the three-phase four-wire low-voltage power distribution equipment, single-phase and three-phase load have been used mainly mixed. Also linear and nonlinear loads have been used together in the same conditions. In a three-phase four-wire distribution line, the current distribution of three-phase linear load is almost constant in each phase during driving or stopping, but the single-phase load is different from each other for each phase in accordance with the operation and stop. So that the voltage unbalance is caused by the current difference of each phase. In the three-phase four-wire distribution system, non-linear load is used with linear load. The presence of single-phase nonlinear loads can produce an increase in harmonic currents in three-phase and neutral line. It can also cause voltage unbalance. In the present study, we analyzed for the voltage unbalance fluctuations by the operation pattern of the single and three-phase linear and non-linear load in three-phase four-wire low voltage distribution system.

A Study on the Harmonic of the electrical Installations in Apartment Housing (아파트 전기설비에서의 고조파 실태 분석 연구)

  • 이기홍;성세진
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.15 no.2
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    • pp.105-110
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    • 2001
  • To analysis the effect by the Harmonics through Power facilities in Apartment housing, This paper measured the Harmonics at Lighting Transformer, Power Transformer and Services-entrance Conductors of electrical installation in apartment housing. The measured result is following as : 1) The Harmonics at Lighting Transformer is generated in the large of the 5th Harmonics. 2) The Harmonics at Power Transformer is generated in the large of the 5th and 7th Harmonics. And then 3) The THD at the Services-entrance Conductors is average 2.4[%], which is compared to the measuring Voltage, this meaning value is good condition until now against Harmonics effect. But, So the large capacitance of household electrical alliances with rectifiers in the future considered the effect of Harmonics at the Electric Power planning in apartment Housing.

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