• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.326-329
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• 1997

The surface of mica/epoxy paper(130${\mu}{\textrm}{m}$) is investigated with SEM(scanning electron microscope). SEM micrographs revealed that thermal aging has a strong influence on aged specimens. The mica/epoxy paper was exposed at 187$^{\circ}C$ in an ordinary electrical oven for 72hour. Stater windings from two generators were measured by tan delta(tan $\delta$)and maximum partial discharge(Qm). The values of tan $\delta$and Qm were fecund to be higher for new generator than old one. The insulation condition of mica/epoxy paper were measured by ac current and tan $\delta$. Test results are observed that the sound specimens are higher than those aged. Model bar coils subjected to various accelerated agings were evaluated by Qm.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.2
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• pp.10-15
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• 2005

For the development of compensation machining program, ultra precision grinding used in ultra precision machine and corrective machining was studied. We explored a new rough grinding technique on optical material such as zerodur. The facility used is a polishing machine with a custom grinding module and a range of diamond resin bond wheel. Surface roughness and form accuracy are measured by surface measurement equipment(Form Talysurf series2). Our compensation machining program has complied with a target of producing surface roughness better than $0.05{\mu}m$ Ra and form accuracy of around $0.05{\mu}m$ Rt and has been unveiled as a work-hour model.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04b
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• pp.132-135
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• 2002

In this paper, a new method to implement the photopolymer-based VHOE using the optimized exposure time schedule is proposed. The cumulative grating strength dependence on the exposure energy is mathematically modeled by using the fourth-order polynomial function and then using this model, the optimized exposure-time schedule of the photopolymer for recording the given multiple gratings is calculated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.161-161
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• 2010

In order to achieve low power consumption and the uniform power spectrum of LED BLU (Back Light Unit) system, new circuits with a 2 stage L-C (Inductor-Capacitor) coupler have been proposed. From the simulation results based on our proposed model, the ripple power of the L-C regulation-embedded BLU circuit shows a dramatic reduction by more than 89.3% as compared to the normal BLU (without L-C circuits). This indicates that the proposed circuit is very promising for the realization of high-efficiency BLU circuits.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.1
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• pp.43-47
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• 2009

Recently, an approach for nano-scale material deformation has been developed that couples the atomistic and continuum approaches using Finite Element Method (FEM) and Molecular Dynamics (MD). However, this approach still has problems to connect two approaches because of the difference of basic assumptions, continuum and atomistic modeling. To solve this problem, an alternative way is developed that connects the QuasiMolecular Dynamics (QMD) and molecular dynamics. In this paper, we suggest the way to make and validate the MD-QMD coupled model.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1553-1556
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• 2003

As the public use part of the railway and the road, the railway crossing is important to work properly by two transportation means. Also, It is important to provide the good face of friction on the railway crossing in aspect of protecting the railway crossing accident. Lately, the material of railway crossing panel is the wood. the asphalt, and the steel. As they have a various fault, it was studied to analyze the structural action of the new material. rubber panel. This paper analyzed eigenvalue, stress and displacement by truck passing weight and thermal stress using the FEM model.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.7 s.112
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• pp.762-768
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• 2006

To address the need for new intelligent sensing of systems, this study presents a novel strain sensor based on piezoresistivity of carbon nanotube (CNT) and its nanocomposites. Fabrication and characterization of the carbon nanocomposite material are discussed and an electrical model of the CNT strain sensor was derived based on electrochemical impedance spectroscopy analysis and strain testing. The dynamic response of the sensor on a vibrating beam was simulated using numerical analysis and it was compared with experimental test. The simulation showed good agreement with the strain response of the actual sensor.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.159-163
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• 2004

This study was conducted to calculate the permeability coefficient in a single fracture while taking the true fracture geometry into consideration. The fracture geometry was measured using the confocal laser scanning microscope (CLSM). The CLSM geometry data were used to reconstruct a fracture model for numerical analysis using a homogenization analysis (HA) method. The HA is a new type of perturbation theory developed to characterize the behavior of a micro-inhomogeneous material that involves periodic microstructures. The HA permeability was calculated based on the local geometry and local material properties (water viscosity in this case). The results show that the permeability coefficients do not follow the theoretical relationship of the cubic law.

• Structural Engineering and Mechanics
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• v.67 no.3
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• pp.291-300
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• 2018

In this work, a new trigonometry theory of shear deformation is developed for the static analysis of thick isotropic beams. The number of variables used in this theory is identical to that required in the theory of Euler-Bernoulli, sine function is used in the displacement field in terms of the coordinates of the thickness to represent the effects of shear deformation. The advantage of this theory is that shear stresses can be obtained directly from the relationships constitute, while respecting the boundary conditions at the free surface level of the beam. Therefore, this theory avoids the use of shear correction coefficients. The differential equilibrium equations are obtained using the principle of virtual works. A thick isotropic beam is considered, whose numerical study to show the effectiveness of this theory.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.247-253
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• 2014

In this paper, a new two dimensional (2D) analytical modeling and simulation for a Dual Material Double Gate tunnel field effect transistor (DMDG TFET) is proposed. The Parabolic approximation technique is used to solve the 2-D Poisson equation with suitable boundary conditions and analytical expressions for surface potential and electric field are derived. This electric field distribution is further used to calculate the tunnelling generation rate and thus we numerically extract the tunnelling current. The results show a significant improvement in on-current characteristics while short channel effects are greatly reduced. Effectiveness of the proposed model has been confirmed by comparing the analytical results with the TCAD simulation results.