• Title/Summary/Keyword: harmonic potential

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Low-Frequency Harmonic Eliminations on DC/AC Sides of a 3 Phase-Controlled Converter (3상 제어컨버터의 노치법에 의한 출력과 입출력의 저고조파 제거)

  • 홍성태;권순결;이현우;서기영;임근희
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.43 no.6
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    • pp.906-915
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    • 1994
  • Line-Current harmonics resulting from ac to dc power conversion interfere with power system operation and reduce power factor, hence resulting in increasing power source unnecessarily. This study describes a 3 phase phase-controlled converter eliminating low frequency harmonics in the output by inserting notches. Notch points are calculated by Newton-raphson method, The impacts of the choppings on ac and dc sides are analyzed in the steady state. Potential applications of the study are dc motor controls, high power dc power supplies for telecommunications, static var compensators and HVDC.

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Electromechanical analysis of 2-2 cement-based piezoelectric transducers in series electrically

  • Wang, Jianjun;Shi, Zhifei
    • Smart Structures and Systems
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    • v.14 no.3
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    • pp.267-284
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    • 2014
  • This paper aims to present the analytical solutions of 2-2 cement based piezoelectric transducers in series electrically based on the theory of piezo-elastic dynamics. The solutions of two different kinds of 2-2 cement based piezoelectric transducers under external harmonic load are obtained by using the displacement method. The effects of electrical connection of piezoelectric layers, loading frequency, thickness and distance of piezoelectric layers on the characteristics of the transducers are discussed. Comparisons with other related experimental investigations are also given, and good agreement is found. The proposed 2-2 cement based piezoelectric transducers have a great potential application in monitoring structural health in civil engineering and capturing mechanical energy or monitoring train-running safety in railway system and traffic safety in road system.

Conformational Analysis of Some Antibacterial Agent 4-Aminodiphenyl Sulfones

  • Lee, Sung-Hee;Chung, Uoo-Tae;Kang, Young-Kee
    • Archives of Pharmacal Research
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    • v.13 no.1
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    • pp.43-50
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    • 1990
  • Conformational free energy calculations using an empirical potential function (ECEPP/2) and hydration shell model were carried out on the four-4-aminodiphenyl sulfone analogues of 4, 4'-diamino-2' methyldiphenyl sulfone, 4, 2', 4-triaminodiphenyl sulfone, 4, 4'-diaminodiphenyl sulfone, and 4-aminodiphenyl sulfone as antibacterial agents on Mycobacterium lufu. The conformational energy was minimized from starting conformations which included possible combinations of torsion angles in the molecule. The conformational entropy change of each conformation was computed using a harmonic approximation. To understand the hydration effect on the conformation of the molecule in aqueous solution, the contributions of water-accessible volume and the hydration free energy of each group or atom in the lowest-free-energy conformation was calculated and compared each other. From comparison of the computed lowest-free-energy conformations of four analogues with their antibacterial activities, it is known that the conformation and the hydrophobicity of sulfonyl group and its adjacent carbon atom in each compound are the essential factors to show the strong antibacterial activity.

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Comparison and Analysis of Armature Reaction Magnetic Field of Linear Generator with Coreless/Cored Type Three Phases Concentrated Winding by using Space Harmonic Analytical Method (3상 집중권 권선을 갖는 코어리스/코어드 타입 리니어 발전기의 공간고조파 해석법을 이용한 전기자 반작용 자계특성 해석)

  • Seo, Sung-Won;Koo, Min-Mo;Kang, Han-Bit;Choi, Jang-Young
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.64 no.1
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    • pp.64-71
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    • 2015
  • This paper deals with analysis of armature reaction magnetic field of linear generator with three phases coreless/cored type concentrated winding. On the basis of a magnetic vector potential and Maxwell's equations, governing equations to predict armature reaction field are derived, and current density modeling is also performed analytically by using the Fourier series expansion. The analytical method used in this paper is confirmed by comparing with finite element analysis results.

Vibration of Liquid-filled Cylindrical Storage Tank with an Annular Plate Cover (환원판 덮개를 갖는 원통형 연료탱크의 진동해석)

  • 김영완
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.13 no.10
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    • pp.751-759
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    • 2003
  • The theoretical method is developed to investigate the vibration characteristics of the sloshing and bulging mode for the circular cylindrical storage tank with an annular plate on free surface. The cylindrical tank is filled with an inviscid and incompressible liquid. The liquid domain is limited by a rigid cylindrical surface and a rigid flat bottom. As the effect of free surface waves Is taken into account in the analysis, the bulging and sloshing modes are studied. The solution for the velocity potential of liquid movement is assumed as a suitable harmonic function that satisfies Laplace equation and the relevant boundary conditions. The Rayleigh-Ritz method is used to derive the frequency equation of the cylindrical tank. The effect of Inner-to-outer radius ratio and thickness of annular plate and liquid volume on vibration characteristics of storage tank is studied. The finite element analysis is performed to demonstrate the validity of present theoretical method.

Influence of time delay and saturation capacity to the response of controlled structures under earthquake excitations

  • Pnevmatikos, Nikos G.;Gantes, Charis J.
    • Smart Structures and Systems
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    • v.8 no.5
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    • pp.449-470
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    • 2011
  • During the last thirty years many structural control concepts have been proposed for the reduction of the structural response caused by earthquake excitations. Their research and implementation in practice have shown that seismic control of structures has a lot of potential but also many limitations. In this paper the importance of two practical issues, time delay and saturation effect, on the performance of controlled structures, is discussed. Their influence, both separately and in interaction, on the response of structures controlled by a modified pole placement algorithm is investigated. Characteristic buildings controlled by this algorithm and subjected to dynamic loads, such as harmonic signals and actual seismic events, are analyzed for a range of levels of time delay and saturation capacity of the control devices. The response reduction surfaces for the combined influence of time delay and force saturation of the controlled buildings are obtained. Conclusions regarding the choice of the control system and the desired properties of the control devices are drawn.

Structure, Spectroscopic Properties and Reactions of Interstellar Molecule HC2N and Isomers :Ab initio Study

  • Park, Sung-Woo;Lee, Seong-Yul
    • Bulletin of the Korean Chemical Society
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    • v.23 no.11
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    • pp.1553-1559
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    • 2002
  • Calculations are presented for the molecule HC2N and its geometrical isomers. The structures, harmonic frequencies and dipole moments are reported. The potential energy surface of the [H,C,C,N] system is investigated in detail, and the transition states, intermediate complexes, and the energies of barrier for the isomerization and dissociation reactions are computed in order to determine the reaction paths and to estimate the stability of the isomers. The barriers of isomerization among HCCN, HCNC and HNCC are computed to be rather large and dissociations of these molecules are highly endothermic, indicating that these molecules are kinetically stable. The association reactions HC + CN→HCCN, HC + NC→HCNC, and HN + CC →HNCC are barrierless and very exothermic, suggesting that they may be considered as efficient means of producing the HCCN and the isomers in the laboratory and in interstellar space.

THD Analysis of Output Current for Active Frequency Drift Method in Anti-islanding (능동적 주파수 변환기법의 출력전류 고조파 왜형율 분석)

  • Lee, Ki-Ok;Choi, Ju-Yeop;Choy, Ick;Yu, Gwon-Jong;An, Jin-Ung
    • Journal of the Korean Solar Energy Society
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    • v.30 no.1
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    • pp.7-12
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    • 2010
  • As many grid-connected photovoltaic power conditioning systems (PVPCS)are installed in many residential areas simultaneously, these have raised potential problems of network protection on electrical power system. One of the numerous problems is an Islanding phenomenon. In this paper, active frequency drift (AFD) method, one of the anti-islanding methods which is analyzed by current magnitude compensation and calculation of the fundamental component. Both harmonic component and RMS value of the output current for THD analysis are provided and verified by simulation.

A Study on Nano-Motor of Giga-hertz level Resonance Characteristics (나노모터의 기가급 공진 특성에 대한 연구)

  • Song, Young-Jin;Lee, Jun-Ha
    • Journal of the Semiconductor & Display Technology
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    • v.9 no.1
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    • pp.1-4
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    • 2010
  • We investigated a linear carbon nanotube motor serving as the key building block for nano-scale motion control by using molecular dynamics simulations. This linear nano-motor, is based on the electrostatically telescoping multi-walled carbon-nanotube with ultralow intershell sliding friction, is controlled by the gate potential with the capacitance feedback sensing. The resonant harmonic peaks are induced by the interference between the driving frequencies and its self-frequency. The temperature is very important factor to operate this nanomotor.

Nonlocal nonlinear dynamic behavior of composite piezo-magnetic beams using a refined higher-order beam theory

  • Fenjan, Raad M.;Ahmed, Ridha A.;Faleh, Nadhim M.
    • Steel and Composite Structures
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    • v.35 no.4
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    • pp.545-554
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    • 2020
  • The present paper explores nonlinear dynamical properties of piezo-magnetic beams based on a nonlocal refined higher-order beam formulation and piezoelectric phase effect. The piezoelectric phase increment may lead to improved vibrational behaviors for the smart beams subjected to magnetic fields and external harmonic excitation. Nonlinear governing equations of a nonlocal intelligent beam have been achieved based upon the refined beam model and a numerical provided has been introduced to calculate nonlinear vibrational curves. The present study indicates that variation in the volume fraction of piezoelectric ingredient has a substantial impact on vibrational behaviors of intelligent nanobeam under electrical and magnetic fields. Also, it can be seen that nonlinear free/forced vibrational behaviors of intelligent nanobeam have dependency on the magnitudes of induced electrical voltages, magnetic potential, stiffening elastic substrate and shear deformation.