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Bending Waves Propagating in a Bar with Periodically Nonuniform Material Properties (재질이 주기적으로 불균일한 보에서 전파하는 굽힘 탄성파)

  • Kim, Jin-O;Mun, Byeong-Hwan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.8
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    • pp.1923-1930
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    • 2000
  • A bar with periodically nonuniform material properties is selected as a one-dimensional model of a flat-panel speaker. This paper describes a theoretical approach to the bending waves propagating i n the nonuniform bar. The phase speed of the wave is obtained using perturbation techniques for small amplitude, sinusoidal modulation of the flexural rigidity and mass density. It is shown that the wave speed is decreased due to the nonuniformity of the material properties by the amount proportional to the square of the modulation amplitude. The resonance occurring when the wavelength is half of the period of the material properties is analyzed by the method of multiple scales. It is also shown that the wave speed at the resonance mode is decreased by the amount proportional to the modulation amplitude but the wave of this mode does not propagate far enough due to attenuation.

Design of a Plasmonic Switch Using Ultrathin Chalcogenide Phase-change Material

  • Lee, Seung-Yeol
    • Current Optics and Photonics
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    • v.1 no.3
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    • pp.239-246
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    • 2017
  • A compact plasmonic switching scheme, based on the phase change of a thin-film chalcogenide material ($Ge_2Sb_2Te_5$), is proposed and numerically investigated at optical-communication wavelengths. Surface plasmon polariton modal analysis is conducted for various thicknesses of dielectric and phase-change material layers, and the optimized condition is induced by finding the region of interest that shows a high extinction ratio of surface plasmon polariton modes before and after the phase transition. Full electromagnetic simulations show that multiple reflections inside the active region may conditionally increase the overall efficiency of the on/off ratio at a specific length of the active region. However, it is shown that the optimized geometrical condition, which shows generally large on/off ratio for any length of active region, can be distinguished by observing the multiple-reflection characteristic inside the active region. The proposed scheme shows an on/off switching ratio greater than 30 dB for a length of a few micrometers, which can be potentially applied to integrated active plasmonic systems.

A Study on the Characteristics of Interior Finnishing Materials on Restaurant in Multi-use Facillity (다중이용시설로서의 레스토랑 실내건축의 내장재 특성에 관한 연구 - 창원시 상남일반상업지역을 대상으로 -)

  • Kim Dong-Han;Ko In-Seok;Seo You-Seok
    • Korean Institute of Interior Design Journal
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    • v.15 no.3
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    • pp.24-32
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    • 2006
  • Through the increasing of social economies and cultural activities, the Food service industry have been growing up steadily in spite of low economic activity. This is owing to increasing income, participation of women in public affairs and a dual-income family, automobile culture, desire for healthful food, shorten working hours, changing of cultural style. Moreover, the recent importance of Interior finishing materials by means of fire in the Restaurant, legal fractional multiple use business establishment are recognized of publicity. Therefore, This Study aim object at probing into the characteristic of Interior finishing material and then analysing the characteristics of space and material according to the typical distribution. In the Interior planning of Restaurant, firstly it is need to probe the Characteristics of interior finishing material at the basic element. This study is going to apprehend the constitution of space and difference of proportion or a point of sameness in the characteristics of material. Moreover, the recent importance of Interior finishing materials by means of fire in the Restaurant, legal fractional multiple use business establishment are recognized of publicity. Throughout probe and analysing, it can append more efficiency and elasticity in the usage of interior finishing material.

Development of a Material Mixing Method for Topology Optimization of PCB Substrate (PCB판의 위상 최적화를 위한 재료혼합법의 개발)

  • Han, Seog-Young;Kim, Min-Sue;Hwang, Joon-Sung;Choi, Sang-Hyuk;Park, Jae-Yong;Lee, Byung-Ju
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.16 no.1
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    • pp.47-52
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    • 2007
  • A material mixing method to obtain an optimal topology for a structure in a thermal environment was suggested. This method is based on Evolutionary Structural Optimization(ESO). The proposed material mixing method extends the ESO method to a mixing several materials for a structure in the multicriteria optimization of thermal flux and thermal stress. To do this, the multiobjective optimization technique was implemented. The overall efficiency of material usage was measured in terms of the combination of thermal stress levels and heat flux densities by using a combination strategy with weighting factors. Also, a smoothing scheme was implemented to suppress the checkerboard pattern in the procedure of topology optimization. It is concluded that ESO method with a smoothing scheme is effectively applied to topology optimization. Optimal topologies having multiple thermal criteria for a printed circuit board(PCB) substrate were presented to illustrate validity of the suggested material mixing method. It was found that the suggested method works very well for the multicriteria topology optimization.

Fabrication of Pair-Photonic Crystal Arrays using Multiple-Exposure Nanosphere Lithography (다중노광 나노구 리소그라피를 이용한 쌍-광자결정 어레이 제작)

  • Yeo, Jong-Bin;Han, Gwang-Min;Lee, Hyun-Yong
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.3
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    • pp.245-249
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    • 2010
  • Two dimensional(2D) pair-photonic crystals (pair-PCs) have been fabricated by a multiple-exposure nanosphere lithography (MENSL) method using the self-assembled nanospheres as lens-mask patterns and the collimated laser beam as a multiple-exposing source. The arrays of the 2D pair-PCs exhibited variable lattice structures and shape the control of rotating angle (${\Theta}$), tilting angle (${\gamma}$) and the exposure conditions. In addition, the base period or filling factor of pair-PCs as well as their shapes could be changed by experimental conditions and nanosphere size. A 1.18-${\mu}m$-thick resist was spincoated on Si substrate and the multiple exposure was carried out at change of ${\gamma}$ and ${\Theta}$. Images of prepared 2D pair-PCs were observed by SEM. We believe that the MENSL method is a suitable useful tool to realize the pair-periodic arrays of large area.

A topology optimization method of multiple load cases and constraints based on element independent nodal density

  • Yi, Jijun;Rong, Jianhua;Zeng, Tao;Huang, X.
    • Structural Engineering and Mechanics
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    • v.45 no.6
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    • pp.759-777
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    • 2013
  • In this paper, a topology optimization method based on the element independent nodal density (EIND) is developed for continuum solids with multiple load cases and multiple constraints. The optimization problem is formulated ad minimizing the volume subject to displacement constraints. Nodal densities of the finite element mesh are used a the design variable. The nodal densities are interpolated into any point in the design domain by the Shepard interpolation scheme and the Heaviside function. Without using additional constraints (such ad the filtering technique), mesh-independent, checkerboard-free, distinct optimal topology can be obtained. Adopting the rational approximation for material properties (RAMP), the topology optimization procedure is implemented using a solid isotropic material with penalization (SIMP) method and a dual programming optimization algorithm. The computational efficiency is greatly improved by multithread parallel computing with OpenMP to run parallel programs for the shared-memory model of parallel computation. Finally, several examples are presented to demonstrate the effectiveness of the developed techniques.

Multiple light diffraction theory in volume gratings using perturbative integral expansion method

  • Jin, Sang-Kyu
    • Journal of the Optical Society of Korea
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    • v.1 no.2
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    • pp.67-73
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    • 1997
  • Light wave diffraction from multiple superposed volume gratings is inestigated using a perturbative iteration method of the integral equation of Maxwell's wave equation. The host material and index gratings are anisotropic and non-coplanar multiple volume gratings are considered. In this method, the paraxial approximation and lack of backward scattering in conventional coupled mode theory are not assumed. Systematic analysis of anisotropic wave diffraction due to multiple noncoplanar volume index gratings is performed in increasing level of diffraction orders corresponding to successive iterations.

Running Performance Analysis for the High-speed Electric Multiple Unit 400km/h Experimental (차세대 고속열차 주행성능해석)

  • Lee, Tae-Hyung;Park, Choon-Soo;Han, In-Soo;Choi, Sung-Hoon;Kim, Sang-Soo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.478-479
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    • 2009
  • The HEMU-400X(High-speed Electric Multiple Unit 400km/h eXperimental) project starts in 2007. It is required to analysis and simulate the train performance throughout the project life cycle for a successful completion of the project. This paper is devoted to the development of a train performance analysis model for the high-speed electric multiple unit 400km/h experimental. The model consist of running resistance model, train model, traction model and braking model. So, this paper represents the results of the train performance analysis.

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Transmission Electron Microscopy Study of Stacking Fault Pyramids Formed in Multiple Oxygen Implanted Silicon-on-Insulator Material

  • Park, Ju-Cheol;Lee, June-Dong;Krause, Steve J.
    • Applied Microscopy
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    • v.42 no.3
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    • pp.151-157
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    • 2012
  • The microstructure of various shapes of stacking fault pyramids (SFPs) formed in multiple implant/anneal Separation by Implanted Oxygen (SIMOX) material were investigated by plan-view and cross-sectional transmission electron microscopy. In the multiple implant/anneal SIMOX, the defects in the top silicon layer are confined at the interface of the buried oxide layer at a density of ${\sim}10^6\;cm^{-2}$. The dominant defects are perfect and imperfect SFPs. The perfect SFPs were formed by the expansion and interaction of four dissociated dislocations on the {111} pyramidal planes. The imperfect SFPs show various shapes of SFPs, including I-, L-, and Y-shapes. The shape of imperfect SFPs may depend on the number of dissociated dislocations bounded to the top of the pyramid and the interaction of Shockley partial dislocations at each edge of {111} pyramidal planes.