• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.2 s.95
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• pp.123-128
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• 2005

Forced vibration of a thin circular ring with a concentrated harmonic force is analyzed when the ring is free and has only the in-plane motion. Using the unit doublet function for external force, the governing equation is obtained and is solved by the use of Laplace transform. The exact solutions of displacement components and bending moment are obtained. In order to verify the solutions of analysis, finite element analysis is performed and the results shows good agreement. Then, frequency response curves for displacement and bending moment are obtained. In deriving the governing equations and the solutions, nondimensional parameter of the exciting frequency and the magnitude of exciting force are extracted. As the displacement components are obtained, the remaining bending strain, slope, curvature, shear force, etc. can also be derived. With the results of this work, the responses of a free ring excited on multiple points with different frequencies can also be obtained easily by superposition.

• Journal of KSNVE
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• v.6 no.1
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• pp.27-34
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• 1996

In this paper, design sensitivity of vibration displacement and acceleration is computed and design sensitivity, the derivative information of responses with respect to design perameters, is used as a design guidance tool to reduce the vibration. First, the harmonic vibration analysis of deck and simplified ship structures is performed by finite element method and secondly continuum disign sensityivity for excessive dynamic response is computed by continuum method. Both the direct and modal frequency response methods for the finite element analysis are adopted. Sensitivities of structural components such as upper plate, side wall, bilge, bottom plate are compared and the reductionof vibration is obtained by the proper increase of thickness of each component.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.2183-2188
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• 2016

This paper deals with the design process for an outer-rotor-type surface-mounted permanent magnet synchronous motor (SPMSM) used in continuous variable valve timing (CVVT) systems in automobiles with internal combustion engines. When the same size, outer-rotor-type SPMSMs generate larger torque and more stable than inner-rotor-type SPMSMs. For the initial design, space harmonic analysis (SHA) is used. In order to minimize the cogging torque, an optimization was conducted using Response Surface Methodology (RSM). At the end of the paper, Finite Element Analysis (FEA) is performed to verify the performance of the optimum model.

• Journal of Mechanical Science and Technology
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• v.15 no.11
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• pp.1507-1516
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• 2001

An analytical method is presented for evaluation of the steady state periodic behavior of nonlinear structural systems. This method is based on the substructure synthesis formulation and a harmonic balance procedure, which is applied to the analysis of nonlinear responses. A complex nonlinear system is divided into substructures, of which equations are approximately transformed to modal coordinates including nonlinear term under the reasonable procedure. Then, the equations are synthesized into the overall system and the nonlinear solution for the system is obtained. Based on the harmonic balance method, the proposed procedure reduces the size of large degrees-of-freedom problem in the solving nonlinear equations. Feasibility and advantages of the proposed method are illustrated using the study of the nonlinear rotating machine system as a large mechanical structure system. Results obtained are reported to be an efficient approach with respect to nonlinear response prediction when compared with other conventional methods.

• Advances in materials Research
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• v.12 no.2
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• pp.83-100
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• 2023

In this paper, sandwich plate, constructed with orthotropic and isotropic composite materials, is analyzed to obtain the static and harmonic behavior. The analysis is done by using ANSYS APDL FEM tool. A solid-shell 190 and an 8-node solid 185 elements are employed for face and core material respectively to analyze the plate. Results was attained by using Reissner-Mindlin theory. Effect of increasing thickness ratio of face sheet to depth of the plate is presented on static, vibration and harmonic response on the sheet and the results are discussed briefly. Published work in open domain was used to validate the results and observed excellent agreement. It can be stated that proposed model presents results with remarkable accuracy. Results are obtained to reduce the weight of the plate and minimizing the vibration amplitudes.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.613-618
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• 2012

The Ultrasonic metal welding is used in the solid-phase welding method at room temperature or low temperature state. In welding process, the high frequency vibration energy is delivered to the welding part under the constant pressure for welding. In this study, we aimed to design and manufacture a 40,000 Hz band horn through finite element analysis. By performing modal analysis and harmonic response analysis, the modal analysis result is that the horn frequency was 39,599Hz and the harmonic response result that the horn frequency was 39,533Hz. These results were similar. In order to observe the designed horn's performance, about 4,000 voltage data was obtained from a light sensor and was analyzed by FFT analysis using Origin Tool. The result RMS amplitude was approximately $8.5{\mu}m$ at 40,000Hz, and maximum amplitude was $12.3{\mu}m$. Using this manufactured horn along with an ultrasonic metal welder and tension tester, the weldability of Cu sheets was evaluated. The maximum tensile force was 66.53 N in the welding condition of 2.0 bar pressure, 60% amplitude, and 0.32 s welding time. In excessive welding conditions, it was revealed that weldability is influenced negatively.

• Proceedings of the KIEE Conference
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• summer
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• pp.369-371
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• 2004

With the proliferation of nonlinear loads, high neutral harmonic currents in three-phase four-wire distribution system have been observed. It has been. known that the ground impedance has an effect on the neutral currents of a system which operates with harmonics present. On-site measurements of harmonic currents and voltages according to the fell-of-potential method under case study system were made and the ground impedance modeling using the pattern search method for the harmonic analysis was developed. The ground impedance model obtained by the proposed method was compared with the frequency characteristics by field tests and has shown appropriate results, and would be applicable to evaluate the harmonic and transient response characteristics of the ground system.

• Korean Journal of Remote Sensing
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• v.19 no.5
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• pp.381-392
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• 2003

Multi-temporal approaches using sequential data acquired over multiple years are essential for satisfactory discrimination between many land-cover classes whose signatures exhibit seasonal trends. At any particular time, the response of several classes may be indistinguishable. A harmonic model that can represent seasonal variability is characterized by four components: mean level, frequency, phase and amplitude. The trigonometric components of the harmonic function inherently contain temporal information about changes in land-cover characteristics. Using the estimates which are obtained from sequential images through spectral analysis, seasonal periodicity can be incorporates into multi-temporal classification. The Normalized Difference Vegetation Index (NDVI) was computed for one week composites of the Advanced Very High Resolution Radiometer (AVHRR) imagery over the Korean peninsula for 1996 ～ 2000 using a dynamic technique. Land-cover types were then classified both with the estimated harmonic components using an unsupervised classification approach based on a hierarchical clustering algorithm. The results of the classification using the harmonic components show that the new approach is potentially very effective for identifying land-cover types by the analysis of its multi-temporal behavior.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.8
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• pp.463-468
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• 2004

This paper was applied space harmonic method as a characteristic analysis technique for slotless PMLSM. There is advantages of active response to the change of design parameters as well as reduction of the calculation time. The method can be overcome disadvantages of finite element analysis that needs long times calculation, repetitions of pre and post-process. In this paper, 3D-space harmonic method was applied to consider the precise description of end turn coil shape and the changes of characteristic according to changes of length of z-axis direction. The thrust of optimal design was performed using genetic algorithm to enhance the thrust which is the disadvantage of slotless type PMLSM. For design parameters, width of permanent magnet, width of coil, width of coil inner and lengths of z-axis direction were selected. For objective functions. thrust per weight. thrust per volume. multi-objective function was selected.

• KEPCO Journal on Electric Power and Energy
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• v.7 no.2
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• pp.255-261
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• 2021

This paper proposes impedance-based stability analysis of DC-DC boost converters, where a harmonic state space (HSS) modeling technique is used. At first, the HSS model of the boost converter is developed. Then, the closed-loop output impedance of the converter is derived in frequency domain using small signal modeling including frequency couplings, where harmonic transfer function (HTF) matrices of the open-loop output impedance, the duty-to-output, and the voltage controller are involved. The frequency response of the output impedance reveals a resonance frequency at low frequency region and frequency couplings at sidebands of switching frequency which agree with the simulation and experimental result.