• Title/Summary/Keyword: Multi-layered materials

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Multi-Region Structural-Acoustic Coupling Analysis on Noise Reduction of Layered Structures using Finite Element and Boundary Element Technique (경계요소법과 유한요소법에 의한 흡음판의 소음저감에 관한 다영역 연성해석)

  • Ju, Hyun-Don;Seo, Won-Jin;Lee, Shi-Bok
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.309-313
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    • 2000
  • A structural-acoustic coupling problem involving fluid in a cavity divided with flexible walls and porous materials is investigated in this paper. In many practical problems, the use of finite elements to discretize the fluid region leads to large stiffness and mass matrices. But, since the acoustic boundary element discretization requires to put elements only on the surface of structure, the size of matrices is reduced considerably. Here, we developed a numerical analysis program for the structural-acoustic coupling problems of the multi-region cavity, using boundary elements for the fluid regions and finite elements for the structure. By considering sound transmission through layered systems placed in a cavity, the accuracy of the coupled acoustical-structural finite element model has been verified by comparing its transmission loss predictions with analytical sloutions. Example problems are included to investigate the characteristics of the multi-region structural-acoustic coupling system with porous material.

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Evaluation of the Dynamic Stiffness and Heavy-weight Floor Impact Sound Reduction by Composition of Resilient Materials (완충재 구성방법에 따른 동탄성계수 및 중량바닥충격음 저감특성 평가)

  • Kim, Kyoung-Woo;Jeong, Gab-Cheol;Sohn, Jang-Yeul
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.2
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    • pp.247-254
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    • 2008
  • Resilient materials are generally used for the floating floors to reduce the floor impact sound. Dynamic stiffness of resilient material, which has the most to do with the floor impact sound reduction. The resilient materials available in Korea include EPS(styrofoam), recycled urethane types, EVA(ethylene vinylacetate) foam rubber, foam PE(polyethylene). glass fiber & rock wool, recycled tire, foam polypropylene. compressed polyester, and other synthetic materials. In this study, we tested dynamic stiffness of resilient material and floor impact sound reduction characteristic to a lot of kinds of resilient materials. It was found that dynamic stiffness of multi-layered damping material could be estimated if know value of each layer that compose whole structure. And the test showed that the amount of the heavy-weight impact sound reduction appeared by being influenced from this dynamic stiffness of resilient material. The dynamic stiffness looked like between other resilient materials, a similar to the amount of the heavy-weight impact sound reduction was shown.

A Study on the Characteristics of Paper-based Packaging Materials with Bioplastics for Roasted Coffee Beans (바이오 플라스틱을 적용한 종이 합지 커피 포장재의 제품 특성에 관한 연구)

  • Yu, Ha Kyoung;Joo, Minjung;Woo, Jung Hee;Oh, Jae Young;Lim, Hyo Seung
    • KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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    • v.27 no.1
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    • pp.17-23
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    • 2021
  • Recent studies on recyclable materials in the packaging have an increased attention due to the eco-friendly policies of reducing carbon dioxide emissions in worldwide. Roasted coffee beans mostly packed in multi-layered films and papers according to their expiration date. To satisfy both recyclability and barrier properties, researches have been continued on paper-based packaging materials to enhance their properties. In this study, packaging materials for coffee beans are developed by laminating bioplastic films on papers. The tests of packaging materials were performed with mechanical properties, gas and water vaper permeability, recyclability and storage quality for coffee beans. Compared to other samples, the paper/bioplastics-based coffee package composed of starch coated papers and two bioplastics showed the lowest barrier properties, comparable mechanical strength and ability to maintain the quality of roasted coffee beans. Thus, it could be a good alternative for multi-layered packages for roasted coffee beans.

Reduction of Residual Stresses in Thick-Walled Composite Tubes (두꺼운 벽을 갖는 복합재료 튜브의 잔류응력 저감 연구)

  • 신의섭;정성남
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2003.04a
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    • pp.176-179
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    • 2003
  • This paper deals with the optimum design of thick-walled multi-layered composite tubes by minimizing the process-induced residual stresses under some constraints of structural stiffnesses. An analytic model based on quasi-static thermoelasticity is adopted for the calculation of the residual stresses in the multi-layered composite tubes. The numerical results of optimization show that, in the case of cross-ply CFRP tubes, the residual stresses can be reduced to a certain level by controlling ply thicknesses. However, the optimized tubes may be susceptible to cracking because the transverse residual stress is still large in a strength-based sense. To further suppress the residual stresses, the effects of stacking sequence, wall thickness and axial pretension on the optimum solutions are examined.

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FPCB Cutting Process using ns and ps Laser (나노초 및 피코초 레이저를 이용한 FPCB의 절단특성 분석)

  • Shin, Dong-Sig;Lee, Jae-Hoon;Sohn, Hyon-Kee;Paik, Byoung-Man
    • Laser Solutions
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    • v.11 no.4
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    • pp.29-34
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    • 2008
  • Ultraviolet laser micromachining has increasingly been applied to the electronics industry where precision machining of high-density, multi-layer, and multi material components is in a strong demand. Due to the ever-decreasing size of electronic products such as cellular phones, MP3 players, digital cameras, etc., flexible printed circuit board (FPCB), multi-layered with polymers and metals, tends to be thicker. In present, multi-layered FPCBs are being mechanically cut with a punching die. The mechanical cutting of FPCBs causes such defects as burr on layer edges, cracks in terminals, delamination and chipping of layers. In this study, the laser cutting mechanism of FPCB was examined to solve problems related to surface debris and short-circuiting that can be caused by the photo-thermal effect. The laser cutting of PI and FCCL, which are base materials of FPCB, was carried out using a pico-second laser(355nm, 532nm) and nano-second UV laser with adjusting variables such as the average/peak power, scanning speed, cycles, gas and materials. Points which special attention should be paid are that a fast scanning speed, low repetition rate and high peak power are required for precision machining.

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A study on the acoustic performance of an absorptive silencer applying the optimal arrangement of absorbing materials (흡음재 최적 배치를 적용한 흡음형 소음기의 음향성능 연구)

  • Dongheon Kang;Haesang Yang;Woojae Seong
    • The Journal of the Acoustical Society of Korea
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    • v.43 no.3
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    • pp.261-269
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    • 2024
  • In this paper, the acoustic performance of an absorptive silencer was enhanced by optimizing an arrangement of multi-layered absorbing materials. The acoustic performance of the silencer was evaluated through transmission loss, and finite element method-based numerical analysis program was employed to calculate the transmission loss. Polyurethane, a porous elastic material frequently used in absorptive silencers, was employed as the absorbing material. The Biot-Allard model was applied, assuming that air is filled inside the polyurethane. By setting the frequency range of interest up to the 2 kHz and the acoustic performance affecting properties of the absorbing materials were investigated when it was composed as a single layer. And the acoustic performance of the silencers with the single and multi-layered absorbing materials was compared with each other based on polyurethane material properties. Subsequently, the arrangement of the absorbing materials was optimized by applying the Nelder-Mead method. The results demonstrated that the average transmission loss improved compared to the single-layered absorptive silencer.

The effect of various parameters for few-layered graphene synthesis using methane and acetylene

  • Kim, Jungrok;Seo, Jihoon;Jung, Hyun Kyung;Kim, Soo H.;Lee, Hyung Woo
    • Journal of Ceramic Processing Research
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    • v.13 no.spc1
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    • pp.42-46
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    • 2012
  • The effect of the parameters for few-layered graphene growth by thermal CVD on nickel substrate was investigated. Graphene can be synthesized by using different strategies. Chemical vapor deposition (CVD) has known as one of the most attractive methods to produce graphene due to its good film uniformity, compatibility and large scale production. The control of parameters such as temperature, growth time and pressure in CVD process has been widely recognized as the most important process in graphene growth. Different carbon precursors, methane and acetylene, were introduced in the quartz tube with a variety of growth conditions. Raman spectroscopy was used to confirm the presence of a few- or multi-layered graphene.

Effect of Si3N4 Buffer Layer on Transmittance of TiO2/Si3N4/Ag/Si3N4/TiO2 Multi Layered Structure (TiO2/Si3N4/Ag/Si3N4/TiO2 다층구조에서 Si3N4 버퍼층이 투과율에 미치는 영향)

  • Lee, Seo-Hee;Jang, Gun-Eik
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.1
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    • pp.44-47
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    • 2012
  • The $TiO_2/Si_3N_4/Ag/Si_3N_4/TiO_2$ multi layered structure was designed for the possible application of transparent electrodes in PDP (Plasma Display Panel). Multi layered film was deposited on a glass substrate at room temperature by DC/RF magnetron sputtering system and EMP (Essential Macleod Program) was adopted to optimize the optical characteristics of film. During the deposition process, the Ag layer in $TiO_2/Ag/TiO_2$ became heavily oxidized and the filter characteristic was degraded easily. In thus study, Si3N4 layer was used as a diffusion buffer layer between $TiO_2$ and Ag. in order to prevent the oxidation of Ag layer in $TiO_2/Si_3N_4/Ag/Si_3N_4/TiO_2$ structure. It was confirmed that $Si_3N_4$ layer is one of candidate materials acting as diffusin barrier between $TiO_2/Ag/TiO_2$.