• Structural Engineering and Mechanics
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• v.68 no.2
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• pp.171-182
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• 2018

For the first time, nonlocal damped vibration and buckling analyses of arbitrary tapered bidirectional functionally graded solid circular nano-plate (BDFGSCNP) are presented by employing modified spectral Ritz method. The energy method based on Love-Kirchhoff plate theory assumptions is applied to derive neutral equilibrium equation. The Eringen's nonlocal continuum theory is taken into account to capture small-scale effects. The characteristic equations and corresponding first mode shapes are calculated by using a novel modified basis in spectral Ritz method. The modified basis is in terms of orthogonal shifted Chebyshev polynomials of the first kind to avoid employing adhesive functions in the spectral Ritz method. The fast convergence and compatibility with various conditions are advantages of the modified spectral Ritz method. A more accurate multivariable function is used to model two-directional variations of elasticity modulus and mass density. The effects of nanoscale, in-plane pre-load, distributed dashpot, arbitrary tapering, pinned and clamped boundary conditions on natural frequencies and buckling loads are investigated. Observing an excellent agreement between results of current work and outcomes of previously published works in literature, indicates the results' accuracy in current work.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.363-365
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• 2006

This paper proposes an estimation method for a circulating current of a Y-${\Delta}$ Transformer. The delta winding current can be decomposed into the two components i.e. a non-circulating component and a circulating component. The former can be estimated using the line currents. However, the latter can not be estimated directly using the line currents. A first order differential equation for the circulating current is derived by applying the Kirchhoff's voltage law on the loop of the delta side. The circulating current can be estimated by the solving the differential equation. The performance of the proposed algorithm is investigated under various conditions including magnetic inrush and over-excitation. The algorithm can estimate the circulating current very accurately even under magnetic inrush and over-excitation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.7
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• pp.787-794
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• 2016

In this study, the exact rigidity and the free vibration of trapezoidal corrugated plate are analyzed by being based on the Kirchhoff's plate theory and the Ritz method. The previous rigidity of corrugated plate analyzed by considering just a geometric characteristic, a basic assumption and an equivalent idea can cause large errors in practical behaviors. Accordingly, the exact rigidity supplemented by correction factors of the theoretical rigidity is needed. Therefore an analysis on the exact rigidity and the free vibration using the rigidity for the plate is performed in this paper.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.954-960
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• 2001

Axial fans are widely used in heavy machines due to their ability to produce high cooling of engines. At the same time. the noise generated by these fans causes or serious problems. This work is concerned with the low noise technique of discrete. The prediction model. which allowed the calculation of acoustic pressure at the frequency and it's harmonics, has been developed by Farrasat and the Helmholtz-Kir. The newly developed Helmholtz-Kirchhoff BEM for thin body is used to calculate the sound field of the fan that is located in a engine room. To calculate the unsteady resultant force over blade. Time-Marching Free-Wake Method are used. The fan noise of fan sys unsymmetric engine-room is predicted. In this paper. the discussion is confined to and discrete noise of axial fan and front Part of engine room in heavy equipments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.98-103
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• 2000

The cut-off is a unique feature associated with duct acoustics due to the presence of duct walls. Duct geometry effect on sound radiation is another issue of duct acoustics. The radiation of duct internal noise to ambient from duct open ends with various geometries is studied via numerical methods. The linearized Euler's equations in generalized curvilinear coordinates are solved by the DRP finite difference scheme. A number of accurate boundary conditions are used at boundaries for the computational domain to minimize the non-physical reflections. The far field sound pressure levels are computed by the Kirchhoff integration method. We investigate the cut off phenomana and duct geometry effects on sound radiation with numerical results.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.3
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• pp.168-174
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• 2004

This paper describes a new fault location algorithm based on the voltage equation at the relaying point using 6-phase current for untransposed 765㎸ parallel transmission lines. The proposed method uses the voltage and current collected at only the local end. By means of 3-phase circuit analysis theory to compensate the mutual coupling effects between parallel lines, the fault location is derived. The fault distance is determined by solving the 2nd distance equation based on KVL(Kirchhoff's Voltage Law). Extensive simulation results using EMTP(Electromagnatic Transients Program) have verified that the error of the fault location achieved is up to 4.56(%) in untransposed parallel transmission lines.

• Proceedings of the Korea Society for Simulation Conference
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• 2003.06a
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• pp.15-18
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• 2003

Most numerical techniques such as FEM, BEM, and MOM are able to analize electromagnetic scattering problems from arbitrary shapes. Although these methods could be applied to compute electromagnetic scattering problems in frequency domain, it was limited for electrodynamic problem in time domain. In this paper, electromagnetic scattering problem from Fresnel zone plate lens are considered. Some numerical results computed by TLM are compared with Kirchhoff's approximation and PO method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.49-50
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• 2011

Receiving sensitivity of the power gain by using Soret typed FZPL antenna should be worse when obliquely incident wave is illuminated on the FZPL. To solve this problem, elliptic Fresnel Zone Plate Lens antenna system should be introduced. Some numerical results computed by PO method are compared with Kirchhoff's approximation and measurement result.

• Advances in nano research
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• v.16 no.6
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• pp.601-613
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• 2024

A new analytical buckling solution of a thermo-electro-magneto-elastic (TEME) cylindrical nano-shell made of BiTiO₃-CoFe₂O₄ materials is obtained based on Hamiltonian approach. The Winkler and Pasternak elastic foundations as well as thermo-electro-magneto-mechanical loadings are applied, and two different types of edge conditions are taken into the investigation. According to nonlocal strain gradient theory (NSGT) and surface elasticity theory in conjunction with the Kirchhoff-Love theory, governing equations of the nano-shell are acquired, and the buckling bifurcation condition is obtained by adopting the Navier's method. The detailed parameter study is conducted to investigate the effects of axial and circumferential wave numbers, scale parameters, elastic foundations, edge conditions and thermo-electro-magnetic loadings on the buckling behavior of the nano-shell. The proposed model can be applied in design and analysis of TEME nano components with multi-field coupled behavior, multiple edge conditions and scale effect.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.6
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• pp.1221-1226
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• 2011

In order to analyze the receiver gain characteristic of the Soret-type FZPL lens antenna which is operated at 12GHz, TLM method can be applied. The application of the FZPL lens antenna is often use the receiver for satellite TV system, radio telescope, and Geodetic System. Some numerical results computed by TLM method are compared with Kirchhoff's approximation and PO method. The focal characteristic of receiver gain on main axis of the FZPL is mostly shown at the front side, which means that the position of the receiver should be properly calibrated.