• Title, Summary, Keyword: harmonic loading

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Harmonics Measurement and Analysis for Korea High Speed Train Prototype (한국형 고속전철 시제차량 고조파 계측 및 분석)

  • Lee Tae-Hyung;Park Choon-Soo
    • Proceedings of the KSR Conference
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    • pp.1415-1419
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    • 2004
  • It is essential to evaluate harmonic characteristics of high speed train using power electronics equipment such as converter-driven motor drives, battery chargers and auxiliary power supplies. The purpose of this study is to measure and analyze harmonics characteristics of korea high speed train prototype. This paper presents result of harmonics measurement and analysis of harmonics characteristics in terms of loading, speed and operation mode.

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Effects of elastic foundation on the dynamic stability of cylindrical shells

  • Ng, T.Y.;Lam, K.Y.
    • Structural Engineering and Mechanics
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    • v.8 no.2
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    • pp.193-205
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    • 1999
  • A formulation for the dynamic stability analysis of cylindrical shells resting on elastic foundations is presented. In this previously not studied problem, a normal-mode expansion of the partial differential equations of motion, which includes the effects of the foundation as well as a harmonic axial loading, yields a system of Mathieu-Hill equations the stability of which is analyzed using Bolotin's method. The present study examines the effects of the elastic foundation on the instability regions of the cylindrical shell for the transverse, longitudinal and circumferential modes.

Dynamic Analysis of Francis Runners - Experiment and Numerical Simulation

  • Lais, Stefan;Liang, Quanwei;Henggeler, Urs;Weiss, Thomas;Escaler, Xavier;Egusquiza, Eduard
    • International Journal of Fluid Machinery and Systems
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    • v.2 no.4
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    • pp.303-314
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    • 2009
  • The present paper shows the results of numerical and experimental modal analyses of Francis runners, which were executed in air and in still water. In its first part this paper is focused on the numerical prediction of the model parameters by means of FEM and the validation of the FEM method. Influences of different geometries on modal parameters and frequency reduction ratio (FRR), which is the ratio of the natural frequencies in water and the corresponding natural frequencies in air, are investigated for two different runners, one prototype and one model runner. The results of the analyses indicate very good agreement between experiment and simulation. Particularly the frequency reduction ratios derived from simulation are found to agree very well with the values derived from experiment. In order to identify sensitivity of the structural properties several parameters such as material properties, different model scale and different hub geometries are numerically investigated. In its second part, a harmonic response analysis is shown for a Francis runner by applying the time dependent pressure distribution resulting from an unsteady CFD simulation to the mechanical structure. Thus, the data gained by modern CFD simulation are being fully utilized for the structural design based on life time analysis. With this new approach a more precise prediction of turbine loading and its effect on turbine life cycle is possible allowing better turbine designs to be developed.

PI Controlled Active Front End Super-Lift Converter with Ripple Free DC Link for Three Phase Induction Motor Drives

  • Elangovan, P.;Mohanty, Nalin Kant
    • Journal of Power Electronics
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    • v.16 no.1
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    • pp.190-204
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    • 2016
  • An active front end (AFE) is required for a three-phase induction motor (IM) fed by a voltage source inverter (VSI), because of the increasing need to derive quality current from the utility end without sacrificing the power factor (PF). This study investigates a proportional-plus-integral (PI) controller based AFE topology that uses a super-lift converter (SLC). The significance of the proposed SLC, which converts rectified AC supply to geometrically proceed ripple-free DC supply, is explained. Variations in several power quality parameters in the intended IM drive for 0% and 100% loading conditions are demonstrated. A simulation is conducted by using MATLAB/Simulink software, and a prototype is built with a field programmable gate array (FPGA) Spartan-6 processor. Simulation results are correlated with the experimental results obtained from a 0.5 HP IM drive prototype with speed feedback and a voltage/frequency (V/f) control strategy. The proposed AFE topology using SLC is suitable for three-phase IM drives, considering the supply end PF, the DC-link voltage and current, the total harmonic distortion (THD) in supply current, and the speed response of IM.

Detection of Ocean Tide Loading Constituents Based on Precise Point Positioning by GPS (GPS 정밀단독측위기법을 이용한 해양조석하중 분조성분 검출)

  • Won, Ji-Hye;Park, Kwan-Dong
    • Journal of Astronomy and Space Sciences
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    • v.26 no.4
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    • pp.511-520
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    • 2009
  • In this study, the Ocean Tide Loading (OTL) constituents were detected by the Precise Point Positioning (PPP) technique using GPS. Then, the GPS estimates of OTL constituents were compared with the predictions of the ocean tide models. We picked three permanent GPS stations as test sites and they are ICNW, SEOS, and CJUN. To detect the OTL constituents using GPS, we created vertical coordinate time series at 10-minute intervals using the PPP approach implemented in the GIPSY software. Through the tidal harmonic analysis of this height time series, the four major constituents ($M_2$, $S_2$, $K_1$, $O_1$) were determined. The amplitude obtained from the GPS height time series of the OTL constituents showed best match with the model predictions at CJUN, while the phase showed closest match at ICNW. The amplitude accuracy of the $M_2$, which is the dominant factor out of the 11 major constituents, was 24.8% on average.

Pressure loading, end- shortening and through- thickness shearing effects on geometrically nonlinear response of composite laminated plates using higher order finite strip method

  • Sherafat, Mohammad H.;Ghannadpour, Seyyed Amir M.;Ovesy, Hamid R.
    • Structural Engineering and Mechanics
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    • v.45 no.5
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    • pp.677-691
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    • 2013
  • A semi-analytical finite strip method is developed for analyzing the post-buckling behavior of rectangular composite laminated plates of arbitrary lay-up subjected to progressive end-shortening in their plane and to normal pressure loading. In this method, all the displacements are postulated by the appropriate harmonic shape functions in the longitudinal direction and polynomial interpolation functions in the transverse direction. Thin or thick plates are assumed and correspondingly the Classical Plate Theory (CPT) or Higher Order Plate Theory (HOPT) is applied. The in-plane transverse deflection is allowed at the loaded ends of the plate, whilst the same deflection at the unloaded edges is either allowed to occur or completely restrained. Geometric non-linearity is introduced in the strain-displacement equations in the manner of the von-Karman assumptions. The formulations of the finite strip methods are based on the concept of the principle of the minimum potential energy. The Newton-Raphson method is used to solve the non-linear equilibrium equations. A number of applications involving isotropic plates, symmetric and unsymmetric cross-ply laminates are described to investigate the through-thickness shearing effects as well as the effect of pressure loading, end-shortening and boundary conditions. The study of the results has revealed that the response of the composite laminated plates is particularly influenced by the application of the Higher Order Plate Theory (HOPT) and normal pressure loading. In the relatively thick plates, the HOPT results have more accuracy than CPT.

A Numerical Analysis on Acoustic Radiation Efficiency of One Side-Wetted Rectangular Mindlin Plate with Simply Supported Boundaries (Mindlin 판 이론을 적용한 단순지지 단면 접수평판의 음향방사효율 수치해석)

  • Lee, Jong-Ho;Cho, Dae-Seung
    • Journal of the Society of Naval Architects of Korea
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    • v.55 no.4
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    • pp.281-288
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    • 2018
  • Acoustic radiation efficiency is a crucial factor to estimate Underwater Radiated Noise (URN) of ships accurately. This paper describes a numerical method to analyse acoustic radiation efficiency of one side-wetted rectangular Mindlin plate with simply supported boundaries excited by a harmonic point force. Transverse displacements of plate and acoustic radiation pressures are evaluated by the mode superposition method. The acoustic radiation efficiencies analyzed by both Mindlin and thin plate theories show little differences at monopole and corner modes of low frequency regions but relatively large differences at edge and critical modes of high frequency regions. Especially, the critical frequency with the highest acoustic radiation efficiency evaluated by the Mindlin plate theory is higher than that of thin plate theory. In addition, the acoustic loading effect of fluid also increases bending wave-number of plate and its critical frequency. Finally, the acoustic radiation characteristics of plates with different aspect ratios and thicknesses through numerical analyses are investigated and discussed.

Determination of the Degree of Nonlinearity in the Response of Offshore Structures Using Higher Order Transfer Functions (고차 전이함수를 이용한 해양구조물 거동의 비선형도 결정)

  • 백인열
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.7 no.1
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    • pp.116-125
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    • 1995
  • Higher order nonlinear transfer functions are applied to model the nonlinear responses obtained Inn dynamic analysis of single degree of freedom systems (SDOF) subjected to wave and current loadings. The structural systems are subjected to single harmonic, two wave combination and irregular wave loading. Three different sources of nonlinearities are examined for each of the wave loading condition and it is shown that the nonlinear response appear at the resonance frequencies of the SDOF even when virtually no wave energy exists at those resonance frequencies. Higher order nonlinear transfer functions based on Volterra series representation are used to model the nonlinear responses mainly f3r the flexible systems and clearly shows the degrees of nonlinearity either as quadratic or cubic.

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Analysis of the Propagation Characteristics of Ultrasonic Guided Waves Excited by Single Frequency and Broadband Sources

  • Kang, To;Song, Sung-Jin;Kim, Hak-Joon;Cho, Young-Do;Lee, Dong-Hoon;Cho, Hyun-Joon
    • Journal of the Korean Society for Nondestructive Testing
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    • v.29 no.6
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    • pp.570-578
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    • 2009
  • Excitation and propagation of guided waves are very complex problems in pipes due to their dispersive nature. Pipes are commonly used in the oil, chemical or nuclear industry and hence must be inspected regularly to ensure continued safe operation. The normal mode expansion(NME) method is given for the amplitude with which any propagating waveguide mode is generated in the pipes by applied surface tractions. Numerical results are calculated based on the NME method using different sources, i.e., non-axisymmetric partial loading and quasi-axisymmetric loading sources. The sum of amplitude coefficients for 0~nineth order of the harmonic modes are calculated based on the NME method and the dispersion curves in pipes. The superimposed total field which is namely the angular profile, varies with propagating distance and circumferential angle. This angular profile of guided waves provides information for setting the transducer position to find defects in pipes.

Static and dynamic analysis of cable-suspended concrete beams

  • Kumar, Pankaj;Ganguli, Abhijit;Benipal, Gurmail
    • Structural Engineering and Mechanics
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    • v.64 no.5
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    • pp.611-620
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    • 2017
  • A new theory of weightless sagging planer elasto-flexible cables under point loads is developed earlier by the authors and used for predicting the nonlinear dynamic response of cable-suspended linear elastic beams. However, this theory is not valid for nonlinear elastic cracked concrete beams possessing different positive and negative flexural rigidity. In the present paper, the flexural response of simply supported cracked concrete beams suspended from cables by two hangers is presented. Following a procedure established earlier, rate-type constitutive equations and third order nonlinear differential equations of motion for the structures undergoing small elastic displacements are derived. Upon general quasi-static loading, negative nodal forces, moments and support reactions may be introduced in the cable-suspended concrete beams and linear modal frequencies may abruptly change. Subharmonic resonances are predicted under harmonic loading. Uncoupling of the nodal response is proposed as a more general criterion of crossover phenomenon. Significance of the bilinearity ratio of the concrete beam and elasto-configurational displacements of the cable for the structural response is brought out. The relevance of the proposed theory for the analysis and the design of the cable-suspended bridges is critically evaluated.