• Journal of the Korean Wood Science and Technology
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• v.22 no.1
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• pp.40-43
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• 1994

본(本) 논문(論文)은 버즘나무과(科)의 버즘나무 (Platanus orientalis L.)에 있어서 목부(木部) 방사조직(放射組織)내에 천공(穿孔)을 지니는 방사조직(放射組織) 세포(細胞)가 존재(存在)함을 처음으로 보고(報告)하는 것으로 이들 방사조직(放射組織) 세포(細胞)의 천공판(穿孔板)은 도관요소(導管要素) 상호간(相互間)에 발달(發達)하는 천공판(穿孔板)과 동일(同一)하게 단일천공판(單一穿孔板)과 계단상천공판(階段狀穿孔板)을 지니는 것으로 밝혀졌다.

• The Journal of the Acoustical Society of Korea
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• v.36 no.5
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• pp.305-313
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• 2017

In this paper, sound absorption of thin elastic plates installed in a rigid duct is discussed using an analytic method. The number of plates can be one or two, and each plate might have micro-perforation. Vibration of the plates and sound pressure fields inside the duct and air cavity are expressed in terms of an infinite series of modal functions. Under the plane wave assumption, a low frequency approximation is derived by including the first few plate modes. It is found that the sound absorption coefficient of the plates without micro-perforation shows sharp peaks at resonance frequencies, and due to the interaction between the plates and air cavity, the resonance frequencies move as the cavity depth changes. For the case of micro-perforated plates, it is found that the sound absorption is mainly affected by the perforation ratio. When the perforation ratio is order of few percent, the sound absorption is almost independent of plate vibration.

• The Journal of the Acoustical Society of Korea
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• v.37 no.4
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• pp.181-187
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• 2018

In this paper, sound absorption of micro-perforated elastic plates installed in an impedance tube of a circular cross-section is discussed using an analytic method. Vibration of the plates and sound pressure fields inside the duct are expressed in terms of an infinite series of modal functions, where modal functions in the radial direction is given in terms of the Bessel functions. Under the plane wave assumption, a low frequency approximation is derived by including the first few plate modes, and the sound absorption coefficient is given in terms of an equivalent impedance of a single surface. The sound absorption coefficient using the proposed formula is in excellent agreement with the result by the FEM (Finite Element Method), and shows dips and peaks at the natural frequencies of the plate. When the perforation ratio is very small, the sound absorption coefficient is dominated by the vibration effect. However, when the perforation ratio reaches a certain value, the sound absorption is mainly governed by the rigid MPP (Micro-Perforated Plate), while the vibration effect becomes very small.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.5
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• pp.1015-1024
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• 2015

An experiment of composite beam was performed which utilized glass fiber reinforced polymer (GFRP) plank as the permanent formwork with cast-in-place high strength concrete. This research analyzed the flexural failure behavior of composite beam by setting the sand coated at GFRP bottom surface, the perforation and interval of the GFRP plank web, and the width of the top flange as the experimental variables. As a result of the experiments for effectiveness of sand attachment in case of not perforated web, approximately 43% higher ultimate load value was obtained when the sand was coated than not coated case. For effectiveness of perforation and interval of gap, approximately 23% higher maximum load value was seen when interval of the perforation gap was 3 times and the fine aggregate was not coated, and approximately 11% higher value was observed when the perforation gap was 5 times on the coated specimen. For effectiveness of top flange breadth, the ultimate load value was approximately 12% higher in case of 20mm than 40mm width.

• Journal of Forest and Environmental Science
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• v.13 no.1
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• pp.114-133
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• 1997

Perforation plate was observed in 78 species(45 genera, 25 families) of Korean native hardwoods using SEM and it was divided into three types, i.e., simple, scalariform and multiple perforation plates, Based on occurance of these types, the species examined were classfied into the following six groups : (1) 60species(35 genera, 21 families) having exclusively simple perforation, (2) 5 species(2 genera, 1 families) having exclusively scalariform perforation plates, (3) 4 species(4 genera, 3 families) having simple and scalariform perforation plates, (4) 2 species(2 genera, 1 families) having simple and multiple perforation plates, (5) 5 species(3 genera, 3 families) having scalariform and multiple perforation plates and (6) 2 species(2 genera, 2 families) having simple, scalariform and multiple perforation plates. Mismatching perforation plates were found in two species of Betulaceae, Alnus hirsuta var. sibirica and Alnus hirsuta and peculiar substructure between the bars of the scalariform perforation plate was observed in Betulaceae, Betula davurica and Cercidiphyllaceae, Cerdiphyllum japonicum and the vestured perforation plate was found in Quercus aliena.

• The Journal of the Acoustical Society of Korea
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• v.39 no.4
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• pp.270-278
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• 2020

In this paper, sound transmission of Micro-Perforated Plates (MPPs) installed in an impedance tube with a circular cross-section is described using an analytic method. Vibration of the plates is expressed in terms of an infinite series of modal functions, where modal function in the radial direction is given by the Bessel function. Under the plane wave assumption, a low frequency approximation is derived, and a formula for the sound transmission coefficient of multi-layered MPPs is presented using the transfer matrix method. The Sound Transmission Losses (STLs) of single and double MPPs are computed using the proposed method and compared with those done by the Finite Element Method (FEM), which shows an excellent agreement. As the perforation increases, the STL is degraded, since the STL becomes dominated by the perforation ratio rather than by vibration of the plate. The STL shows dips at natural frequencies as well as at the mass-spring-mass resonance frequency. The proposed model for the STL prediction in this study can be applied to an arbitrary number of MPPs, where each MPP may or may not have a perforation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.4
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• pp.372-378
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• 2013

An acoustical shape optimization problem is formulated for optimal design of a perforated reactive muffler with offset inlet/outlet. The mean transmission loss value in a target frequency range is maximized for an allowed pressure drop value between an inlet and an outlet. Partitions in the chamber are divided into several sub-partitions, whose lengths are selected as design variables. Each sub-partition has the same number of holes, whose sizes are equal. A finite element model is employed for acoustical and flow analyses. A gradient-based optimization algorithm is used to obtain an optimal muffler. The acoustical and fluidic characteristics of the optimal muffler are compared with those of a reference muffler. Validation experiment is carried out to support the effectiveness of our suggested method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.298-299
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• 2012

• 보건세계
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• v.58 no.1
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• pp.26-29
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• 2011

이번 호의 주제는 2011년 신묘년(辛卯年) 토끼의 해를 맞아 토끼 도안이 있는 1984년 씰로 선정하였다. 1984년도 씰(한국의 전래동화 시리즈)은 전래동화 5가지를 각 1행씩 구성하고 각 행은 전래동화별로 5칸으로 표현하여 5행${\times}$5칸의 총 25종(5${\times}$5)의 씰로 구성되어 있다. 여류화가이며 공예작가인 곽계정의 작품으로 1984년 씰은 다른 연도의 씰과 달리 변지의 천공(穿孔; Perforation)이 매우 다양하며 판형은 초판과 수정판이 존재하고 있다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.368-369
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• 2010