• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.3
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• pp.320-330
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• 2012

In this paper, we investigate the power integrity of grid structures for power and ground distribution on printed circuit board (PCB). We propose the 2D transmission line method (TLM)-based model for efficient frequency-dependent impedance characterization and PCB-package-integrated circuit (IC) co-simulation. The model includes an equivalent circuit model of fringing capacitance and probing ports. The accuracy of the proposed grid model is verified with test structure measurements and 3D electromagnetic (EM) simulations. If the grid structures replace the plane structures in PCBs, they should provide effective shielding of the electromagnetic interference in mobile systems. An analytical model to predict the shielding effectiveness (SE) of the grid structures is proposed and verified with EM simulations.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.450-454
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• 1999

In order to evaluate the integrity of nuclear power plants, J-integral calculation is crucial. For this purpose, finite element method is popularly used to obtain J-integral. However, high cost time consuming preprocess should be performed to design the finite element model of a cracked structure. Also, the J-integral should be verified by alternative method since it may differ depending on the calculation method. The objective of this paper is to develop a three-dimensional elastic-plastic J-integral analysis system which is named as EPAS. The EPAS program consists of an automatic mesh generator for a through-wall crack and a surface crack, a solver based on ABAQUS program, and a J-integral calculation program which provides DI(Domain Integral) and EDI(Equivalent Domain Integral) based J-integral calculation. Using the EPAS program, an optimized finite element model for a cracked structure can be generated and corresponding J-integral can be obtained subsequently.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.6
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• pp.691-697
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• 2007

Numerical eigen analysis of beam-like structure can be easily and effectively done by various conventional beam theory-based methods. However, in case of the structures composed of composite-sectioned beams, the application of conventional numerical methods requires one to derive both equivalent material and geometry properties. In the present paper, these equivalent properties are derived by the transformed section method and the test FEM program is coded. The numerical accuracy of the proposed method is verified through the comparison with the ANSYS 3-D model.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.9
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• pp.47-53
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• 2011

The signal transmission properties of the connector such as insertion loss and return loss are investigated using analysis procedure of S-parameter simulation, equivalent model extraction, and characteristic impedance calculation. S-parameter simulation is performed by connector's modeling and solving based on 3-dimensional finite element method. The connector's equivalent model of ${\pi}$ type is are proposed and extracted with an optimization process of circuit analysis simulator. The characteristic impedance of the connector is calculated with results of circuit analysis simulation and S-parameter data. According to the connector's characteristic impedance, it's revised design is carried out. In this work, the connector's effective contact area is increased and its body is applied as a high dielectric material in order to increase its capacitance and then obtain impedance matching. Therefore, return loss of the connector is improved by approximately 10 dB due to its design revision.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.939-942
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• 2016

One of the most important characteristic curves of a solar cell is its current density-voltage (J-V) curve under AM1.5G insolation. Solar cell can be considered as a semiconductor diode, so a diode equivalent model was used to estimate its parameters from the J-V curve by numerical simulation. Active layer plays an important role in operation of a solar cell. We investigated the effect thicknesses and defect densities (N_d) of the active layer on the J-V curve. When the active layer thickness was varied (for N_d = 8×10¹⁷ cm^-3) from 800 nm to 100 nm, the reverse saturation current density (J_o) changed from 3.56×10^-5 A/cm² to 9.62×10^-11 A/cm² and its ideality factor (n) changed from 5.28 to 2.02. For a reduced defect density (N_d = 4×10¹⁵ cm^-3), the n remained within 1.45≤n≤1.92 for the same thickness range. A small increase in shunt resistance and almost no change in series resistance were observed in these cells. The low reverse saturation current density (J_o = 9.62×10^-11 A/cm²) and diode ideality factor (n = 2.02 or 1.45) were observed for amorphous silicon based solar cell with 100 nm thick active layer.

• Journal of the Optical Society of Korea
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• v.8 no.2
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• pp.83-89
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• 2004

A variable optical attenuator with a bending-sensitive fiber (BSF) that can be used in optical networks is developed. The refractive index profile of the BSF is divided into four regions which are inner core, center dip of inner core, outer core and clad. The 3-dimensional finite difference beam propagation method (3D FD-BPM) is utilized to find the characteristics of the BSF, so the mode profile of the BSF and optical power attenuation according to the bending are investigated, and the equivalent model of the BSF is made. By using this equivalent model of the BSF, the BSF is fabricated, and the refractive index profile of the BSF is measured, which is similar to refractive index profile of the proposed BSF. The fabricated variable optical fiber attenuator (VOFA) consists of the BSF in a rectangular rubber ring with a fixed bend radius (BR) in a steady state. The VOFA using the proposed BSF was able to attenuate the optical power by more than about －38 ㏈ at certain wavelengths (1540∼1560 nm) based on adjusting the mechanical pressure applied to the upper surface of the rectangular rubber ring with the bent BSF. In addition, the proposed VOFA produced an insertion loss of 0.68 ㏈, polarization dependent loss (PDL) of about 0.5 ㏈, and return loss of less than －60 ㏈.

• Steel and Composite Structures
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• v.37 no.1
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• pp.37-49
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• 2020

In this paper, free vibration finite element analysis of axially moving laminated composite beams subjected to axial tension is studied. It is assumed that the beam has a constant axial velocity and is subject to uniform axial tension. The analysis is based on higher-order theories that have been presented by Carrera Unified Formulation (CUF). In the CUF technique, the three dimensional (3D) displacement fields are expressed as the approximation of the arbitrary order of the displacement unknowns over the cross-section. This higher-order expansion is considered in equivalent single layer (ESL) model. The governing equations of motion are obtained via Hamilton's principle. Finally, several numerical examples are presented and the effect of the ply-angle, travelling speed and axial tension on the natural frequencies and beam stability are demonstrated.

• International Journal of Ocean System Engineering
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• v.3 no.1
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• pp.22-32
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• 2013

A heuristic physical theory of diffraction (PTD) for an acoustic impedance wedge is proposed. This method is based on Ufimtsev's three-dimensional PTD, which is derived for an acoustic soft or hard wedge. We modify the original PTD according to the process of physical optics (or the Kirchhoff approximation) to obtain a 3D heuristic diffraction model for an impedance wedge. In principle, our result is equivalent to Luebbers' model presented in electromagnetism. Moreover, our approach provides a useful insight into the theoretical basis of the existing heuristic diffraction methods. The derived heuristic PTD is applied to an arbitrary impedance polygon, and a simple PTD formula is derived as a supplement to the physical optics formula.

• Advances in aircraft and spacecraft science
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• v.10 no.2
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• pp.127-140
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• 2023

The present article focuses on the thermoelastic deformation behavior of inhomogeneous functionally graded metal/ceramic cylindrical shell structure with multiple perforations using 2D finite element approximation. Here, cylindrical shell structure is considered with single (1×1) and multiple (2×2, 3×3 and 4×4) perforations. The temperature-dependent elastic and thermal properties of functionally graded material are evaluated using Voigt's micromechanical material scheme via power-law function. The kinematics of the proposed model is based on the equivalent single-layer first-order shear deformation mid-plane theory with five degrees-of-freedom. Here, 2D isoparametric finite element solutions are obtained using eight-node quadrilateral elements. The mesh refinement of present finite element model is performed to confirm the appropriate number of elements and nodes for the analysis purpose. Subsequently, a comparison test is conducted to demonstrate the accuracy of present results. In later section, numerous numerical illustrations are demonstrated at different set of conditions by varying structural, material and loading parameters and that confirms the significance of various parameters such as power-law index, aspect ratio, thickness ratio, curvature ratio, number of perforations and temperature on the deformation characteristics of functionally graded cylindrical shell structure.

• Transactions of Materials Processing
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• v.25 no.2
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• pp.91-95
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• 2016

This paper is concerned with modeling of a ductile fracture criterion for sheet metal considering anisotropy to predict the sudden fracture of advanced high strength steel (AHSS) sheets during complicated forming processes. The Lou−Huh ductile fracture criterion is modified using the Hill’s 48 anisotropic plastic potential instead of the von Mises isotropic plastic potential to take account of the influence of anisotropy on the equivalent plastic strain at the onset of fracture. To determine the coefficients of the model proposed, a two dimensional digital image correlation (2D-DIC) method is utilized to measure the strain histories on the surface of three different types of specimens during deformation. For the derivation of an anisotropic ductile fracture model, principal stresses (𝜎₁,𝜎₂, 𝜎₃) are expressed in terms of the stress triaxiality, the Lode parameter, and the equivalent stress (𝜂_𝐻, 𝐿,) based on the Hill’s 48 anisotropic plastic potential. The proposed anisotropic ductile fracture criterion was quantitatively evaluated according to various directions of the maximum principal stress. Fracture forming limit diagrams were also constructed to evaluate the forming limit in sheet metal forming of AHSS sheets over a wide range of loading conditions.