• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.1
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• pp.19-25
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• 2015

In this paper, a design method for a CPW-fed slot antenna for harmonic suppression is studied. The structure of the proposed slot antenna is a rectangular slot antenna appended with stepped impedance resonators (SIRs) at both ends of the slot symmetrically. Optimal design parameters are obtained by analyzing the effects of the length and width of the SIRs on the input reflection coefficient. The optimized harmonic-suppressed slot antenna operating at 2.45 GHz WLAN band is fabricated on an FR4 substrate with a dimension of 42 mm by 30 mm. The slot length of the proposed harmonic-suppressed slot antenna is reduced to 33.3% compared to that of a conventional rectangular slot antenna owing to the appended SIRs. Experiment results show that the antenna has a desired impedance characteristic with a frequency band of 2.39-2.49 GHz for a VSWR < 2, and a measured gain of 2.5 dBi at 2.45 GHz.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.32 no.2
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• pp.64-74
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• 2021

Background and Objectives This study was to investigate the voice quality and articulation effects of laryngeal massage on muscle tension dysphonia (MTD). Materials and Method A systematic review of articles published between January 2000 and December 2020 in Cochrane, PubMed, ScienceDirect, SpingerLink, ERIC, and Naver Academic was conducted. From the total of 2094 articles identified, 10 peer-reviewed articles were included in a meta-analysis. Mean effect sizes of the variables related to voice quality (jitter, shimmer, harmonic to noise ratio or noise to harmonic ratio, high-F0, low-I, cepstral peak prominence) and articulation (F1, F2, F1 slope, F2 slope) were calculated by Hedges'g. Results Meta-analysis of the selected articles showed that laryngeal massage had medium to large effects on all variables of voice quality and articulation except F0-high and F1 slope in the MTD patients. Conclusion This study provided comprehensive clinical evidence that it is highly desirable to apply laryngeal massage to MTD patients.

• 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.

• Structural Engineering and Mechanics
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• v.65 no.5
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• pp.523-533
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• 2018

In this study, the dynamic response of a functionally graded material (FGM) circular plate in contact with incompressible fluid under the harmonic load is investigated. Analysis of the plate is based on First-order Shear Deformation Plate Theory (FSDT). The governing equation of the oscillatory behavior of the fluid is obtained by solving Laplace equation and satisfying its boundary conditions. A new set of admissible functions, which satisfy both geometrical and natural boundary conditions, are developed for the free vibration analysis of moderately thick circular plate. The Chebyshev-Ritz Method is employed together with this set of admissible functions to determine the vibrational behaviors. The modal superposition approach is used to determine the dynamic response of the plate exposed to harmonic loading. Numerical results of the force vibrations and the effects of the different geometrical parameters on the dynamic response of the plate are investigated. Finally, the results of this research in the limit case are compared and validated with the results of other researches and finite element model (FEM).

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1645-1655
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• 2016

A Dynamic Voltage Restorer (DVR) model is proposed to eliminate the short-term voltage disturbances that occur in the grid-connected mode, the switching between grid-connected mode and the stand-alone mode of a Microgrid. The proposed DVR structure is based on a conventional cascaded H-bridge multilevel inverter (MLI) topology; a novel composite control strategy is presented, which could ensure the compensation ability of voltage sag by the DVR. Moreover, the compensation to specified order of harmonic is added to implement effects that zero-steady error compensation to harmonic voltage in specified order of the presented control strategy; utilizing wind turbines-batteries units as DC energy storage components in the Microgrid, the operation cost of the DVR is reduced. When the Microgrid operates under stand-alone mode, the DVR can operate on microsource mode, which could ease the power supply from the main grid (distribution network) and consequently be favorable for energy saving and emission reduction. Simulation results validate the robustness and effective of the proposed DVR system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.10
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• pp.150-158
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• 2007

Large steel industries have time-varying nonlinear loads including electric arc furnaces. These nonlinear loads generate harmonic currents and create distortions on the sinusoidal voltage of the power system. Flicker can be defined as the effect produced on the human visual perception by a changing emission of light lamps subjected to magnitude fluctuations of their supply voltage. The main objective of the static var compensator(SVC) is to maintain the rms voltage at the point of common coupling within the limit. In this paper, harmonic and flicker mitigation studies with and without the SVC are investigated and are evaluated by the IEC 61000-3-6 and IEC 61000-3-7.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.1
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• pp.87-93
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• 2005

In this paper, we perform the harmonic filter design for Incheon international airport, especially passenger terminal based on the results of measurement and analysis. Also, we show the waveform of machines which produce harmonics as a harmonic source. For harmonic filter design, we propose the APF(Active Power Filter) and ZSF(Zero Sequence Filter) design. Also, we simulate the filter effects using EDSA package. The results show the effectiveness of the method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.5
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• pp.51-59
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• 2003

The utility and many customers employ capacitor banks(STATCON so called at the utility) to help control the power factor(customers) or voltage(the utility) by supplying reactive power to inductive loads. This paper presents analysis of transient overvoltages and harmonics due to utility STATCON switching. One simple and inexpensive means of limiting the voltage magnification transient and reducing harmonics is to switch the capacitor banks on a few minutes after the STATCON has been switched. Simulation results used the EDSA software package show the effects of decreased the transient voltage and harmonic reduction at the customer. And also harmonic limits based on the well-known international harmonic standards IEEE 519 and IEC 1000 are evaluated for the customer.

• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.106-111
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• 2000

EP(Electrostatic Precipitator) has been used to keep the natural environment from fly-ash in the industrial fields and operated in intermittent PEC(Pulse Energized Control) mode to improve dust-collecting efficiency. Intermittent PEC mode induces low-frequency harmonic currents into power system, therefore EP transformer vibrates. This continuous transformer vibration developes transformer abnormal audio-noise and if it is too much or operates in the region of natural frequency, transformer will be damaged in the end. EP interruption caused by transformer damage results in power generation stopped, power quality down and economic loss. Therefore, this paper explains harmonic currents and transformer vibration-core vibration, winding vibration, and proposes the measures of suppressing the vibration with EP operated in intermittent PEC mode. And this results is proposed to be used for future EP transformer design or EP control method to operate EP-concerned equipment safely keeping from system faults caused by transformer vibration.

• Structural Engineering and Mechanics
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• v.22 no.4
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• pp.483-510
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• 2006

The dynamic instability characteristics of laminated composite stiffened shell panels subjected to in-plane harmonic edge loading are investigated in this paper. The eight-noded isoparametric degenerated shell element and a compatible three-noded curved beam element are used to model the shell panels and the stiffeners respectively. As the usual formulation of degenerated beam element is found to overestimate the torsional rigidity, an attempt has been made to reformulate it in an efficient manner. Moreover the new formulation for the beam element requires five degrees of freedom per node as that of shell element. The method of Hill's infinite determinant is applied to analyze the dynamic instability regions. Numerical results are presented to demonstrate the effects of various parameters like shell geometry, lamination scheme, stiffening scheme, static and dynamic load factors and boundary conditions, on the dynamic instability behaviour of laminated composite stiffened panels subjected to in-plane harmonic loads along the boundaries. The results of free vibration and buckling of the laminated composite stiffened curved panels are also presented.