• Journal of Forest and Environmental Science
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• 제13권1호
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• pp.114-133
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• 1997

우리나라산(産) 활엽수재 25과(科)45속(屬)78종(種)의 수종에 대하여 천공을 이루고 있는 구조를 주사전자현미경(SEM)을 사용하여 3차원적(次元的) 형태를 관찰하고, 이들의 미세한 천공구조의 본질을 조사하여 과(科), 속(屬), 종별(種別)로 고유의 특징을 구명하기 위하여 본 연구를 실시 하였으며 천공의 분류는 단천공(單穿孔), 계단천공(階段穿孔) 및 다공천공(多孔穿孔)(계단천공(階段穿孔) 이외의 다공천공(多孔穿孔))의 3가지로 구분하고 이것을 기초로하여 (1) 단천공(單穿孔)만을 갖는 수종(60종), (2) 계단천공(階段穿孔)만을 갖는 수종(5종), (3) 단천공(單穿孔)과 계단천공(階段穿孔)을 갖는 수종(4종), (4) 단천공(單穿孔)과 다공천공(多孔穿孔)을 갖는 수종(2종), (5) 계단천공(階段穿孔)과 다공천공(多孔穿孔)을 갖는 수종(5종), (6) 단천공(單穿孔), 계단천공(階段穿孔) 및 다공천공(多孔穿孔)을 갖는 수종(2종)의 6개의 그룹으로 분류 하였다. 그 결과 Betulaceae에 속하는 수종은 대부분이 계단천공(階段穿孔)을 나타내고 있으나 개서어나무에서는 단천공(單穿孔)이 출현하는 특징이 있으며, Fagaceae의 갈참나무에서는 단천공(單穿孔)의 천공연(穿孔緣)의 주연에 돌기물이 발생된 vesture천공이 관찰 되었다. 또한 계단천공(階段穿孔)의 상하의 bar가 서로 일치되고 있지않은 mismatching perforation plate가 물갬나무와 물오리나무에서 관찰되었으며 또한 계단천공의 bar사이에 벽물질이 남아 일부 또는 전부가 막혀 있거나 microfibrillar 모양의 substructure가 물박달나무와 계수나무에서 발견되었다.

• Journal of Forest and Environmental Science
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• 제8권1호
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• pp.51-66
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• 1992

This study was carried out to investigate the micromorphology of vessel wall sculpture such as shape of perforation plate, perforation rim, steepness of perforation plate, occurrence of vestured pit, warty layer and ray-vessel pitting on 13 species of Fagaceae in Korea. The results were summarized as follows ; 1. In the species examined, all sample species except Fagus crenata var. multinervis have simple perforation plate. But Fagus crenata var. multinervis has simple and scalariform perforation plate (it was called to combination perforation plate) in a tree stem. 2. The shapes of perforation rim could be classified into five types; Type A without tail, Type B with small tail on both sides, Type C with long tail on both sides, Type D with tail only one side and Type E with the very short interval between perforations. Among five types, Type Band C have higer frequency of distribution than the others. 3. The steepness of perforation plate measured was about 20 degree on pore zone and 43 degree on outside parts of pore zone. 4. Species with vestured pit were Q. aliena, Q, dentata, Q. variabilis, Fagus crenata var. multinervis, Castanopsis cuspidata var sieboldii, Q. acuta, Q. stenophylla, and Q. glauca. But the extent of vesturing was very slight and vestured pits were observed mainly in ray-vessel pit of some vessel elements. 5. Species with warty layer on the inner surface wall of all vessel elements were Q. acuta, Q. stenophylla, Q. glauca, Fagus crenata var. multinervis and species with warty layer of some vessel elements were Q. aliena, Q, dentata, Q. variabilis, Castanopsis cuspidata var. sieboldii. 6. Species with palisade ray-vessel pit were Q. acuta, Q. stenophylla, Q. glauca, Castanea crenata, Castanea bungeana, Q. aliena, Q. serrata, Q. mongolica, and species with scalariform ray-vessel pit was Fagus crenata var. multinervis and species with oval ray-vessel pit were Q, dentata, Castanopsis cuspidata var sieboldii.

• Wind and Structures
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• 제7권5호
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• pp.317-332
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• 2004

Wind tunnel experiments were conducted under highly turbulent and disturbed flow conditions over a solid/perforated plate with a long splitter plate in its plane of symmetry. The effect of varied level of perforation of the normal plate on fluctuating velocities and fluctuating pressures measured across and along the separation bubble was studied. The different perforation levels of the normal plate; that is 0%, 10%, 20%, 30%, 40% and 50% are studied. The Reynolds number based on step height was varied from $4{\times}10^3$ to $1.2{\times}10^4$. The shape and size of the bubble vary with different perforation level of the normal plate that is to say the bubble is reduced both in height and length up to 30% perforation level. For higher perforation of the normal plate, bubble is completely swept out. The peak turbulence value occurs around 0.7 to 0.8 times the reattachment length. The turbulence intensity values are highest for the case of solid normal plate (bleed air is absent) and are lowest for the case of 50% perforation of the normal plate (bleed air is maximum in the present study). From the analysis of data it is observed that $\sqrt{\overline{u^{{\prime}2}}}/(\sqrt{\overline{u^{{\prime}2}}})_{max}$, (the ratio of RMS velocity fluctuation to maximum RMS velocity fluctuation), is uniquely related with dimensionless distance y/Y', (the ratio of distance normal to splitter plate to the distance where RMS velocity fluctuation is half its maximum value) for all the perforated normal plates. It is interesting to note that for 50% perforation of the normal plate, the RMS pressure fluctuation in the flow field gets reduced to around 60% as compared to that for solid normal plate. Analysis of the results show that the ratio [$C^{\prime}_p$ max/$-C_{pb}(1-{\eta})$], where $C^{\prime}_p$ max is the maximum coefficient of fluctuating pressure, $C_{pb}$ is the coefficient of base pressure and ${\eta}$ is the perforation level (ratio of open to total area), for surface RMS pressure fluctuation levels seems to be constant and has value of about 0.22. Similar analysis show that the ratio $[C^{\prime}_p$ max/$-C_{pb}(1-{\eta})]$ for flow field RMS pressure fluctuation levels seems to be constant and has a value of about 0.32.

• Journal of Plant Biology
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• 제31권3호
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• pp.169-185
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• 1988

Vessel elements in lateral root, tap root, transition region, stem and mid vein of 1-year old, 3-year old and 5-year old ginseng (Panax ginseng C.A. Meyer) are studied with light microscope to clarify the distribution and differentiation of several kinds of vessel elements. Vessel elements are classified into five types such as ring vessel, spiral vessel, scalariform vessel, reticulate vessel and pitted vessel according to the secondary thickenings of cell wall. All of the five types are not observed in each organ, but diverse kinds of vessels are present in stem and mid vein compared with the underground organs such as tap root and lateral root. The length of vessel elements is longest (680$\mu$m) in stem and shortest (143$\mu$m) in tap root. The diameter of vessel elements is 19.0$\mu$m in tap root and the angle of perforation plate comes under 22$^{\circ}$-60$^{\circ}$. The degree of differentiation of vessel elements according to the length, diameter and angle of perforation plate of vessel elements is highest in tap root regardless of the age of ginseng. Three types of perforation plate such as scalariform, intermediate type of simple and scalariform, and simple perforation plate are observed. The vascular tracheids are characteristically observed in mid vein of 1-year old ginseng, and in transition region of 3 and 5-year old ginseng.

• 한국음향학회지
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• 제36권5호
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• pp.305-313
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• 2017

본 논문은 강체 덕트 내에 고정된 얇은 탄성 판의 흡음을 해석적으로 구하는 방법을 다루었다. 판의 개수는 1개 또는 2개이며 각각의 판은 미세천공(micro-perforation)을 포함할 수도 있다. 판의 진동과 덕트 내부 음장을 모드 함수의 무한 급수의 합으로 전개하였다. 평면파 가정하에서 저주파수 대역의 근사식을 판의 처음 몇 개의 모드만 고려하여 유도하였다. 미세천공이 없는 판의 흡음율은 공진주파수에서 피크를 보이는데 공진주파수는 판과 캐비티의 상호작용으로 인하여 캐비티 간격이 변하면 공진주파수도 변함을 알 수 있었다. 미세천공판의 경우 천공율이 흡음율에 가장 큰 영향을 미치는 요소임을 확인하였는데, 천공율이 몇 퍼센트에 이르면, 흡음율은 거의 판의 진동에 영향을 받지 않는다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.590-595
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• 2008

In the present paper, the impact damage behavior of steel plate reinforced concrete panels exposed to shock impulsive loading and fragment impact loading is investigated. To evaluate the retrofit performance of a steel-strengthened concrete panels, a numerical experiment using a numerical simulation with AUTODYN, an explicit analysis program is introduced because a real explosion experiment requires the vast investment and expense for facilities as well as the deformation mechanisms are too complicated to be reproduced with a conventional closed-form analyses. The model for the analysis is simplified and idealized as a two-dimensional and axisymmetric case controled with geometry, boundary condition and material properties in order to obtain a resonable computation time. As a result of the analysis, panels subject to either shock loading or fragment loading without the steel plate reinforcement experience the perforation with spalled fragments. In addition, the panels reinforced with steel plate can prevent the perforation and provide the good mechanical effect such as the increase of global stiffness and strength through the composite action between the concrete slab and the steel plate.

• Journal of Plant Biology
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• 제29권4호
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• pp.317-327
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• 1986

Anatomical characters of the trunk woods of Theaceae, including six genera and seven species collected in Korea, were studied to elucidate the relationship among the genera of the family. Among three genera in Ternstoemieae, Eurya is the least specialized, and Cleyera is less specialized than Ternstroemia in respect to the specialization of the perforation plate and the ray. In Theoieae consisting of three genera, the most primitive one is Thea, and Camellia is more primitive than Stewartia in the trive, from the view of the bar arrangement in scalariform perforation plate and the angle of end wall to the vessel axis. The specialization of the perforation plate of vessel element suggests that Theoieae is more advanced group than Ternstroemieae.

• Earthquakes and Structures
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• 제20권4호
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• pp.377-388
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• 2021

Thin perforated Steel Plate Shear Walls (SPSWs) are among the most common types of seismic energy dissipation systems to protect the main boundary components of SPSWs from fatal fractures in the high-risk zones. In this paper, the cyclic behavior of the different circular hole patterns under cyclic loading is reported. Based on the experimental results, it can be concluded that a change in the perforation pattern of the circular holes leads to a change in the locations of the fracture tendency over the web plate, especially at the plate-frame interactions. Accordingly, the cyclic responses of the tested specimens were simulated by finite element method using the ABAQUS package. Likewise, perforated shear panels with a new perforation pattern obtained by implementing Topology Optimization (TO) were proposed. It was found that the ultimate shear strength of the specimen with the proposed TO perforation pattern was higher than that of the other specimens. In addition, theoretical equations using the Plate-Frame Interaction (PFI) method were used to predict the shear strength and initial stiffness of the considered specimens. The theoretical results showed that the proposed reduced coefficients relationships cannot accurately predict the shear strength and initial stiffness of the considered perforated shear panels. Therefore, the reduced coefficients should be adopted in the theoretical equations based on the obtained experimental and numerical results. Finally, with the results of this study, the shear strength and initial stiffness of these types of perforated shear panels can be predicted by PFI method.

• Journal of Korean Neurosurgical Society
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• 제37권2호
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• pp.141-145
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• 2005

We report five patients of esophageal injuries confirmed by clinical signs and radiological evidences. They include a partial tear and a perforation which were not noticed during the operation, a perforation which was primarily repaired during the operation, and two perforations which occurred during the reoperations for the removal of mal-positioned screws or plate. The partial tear was not repaired. The perforation which occurred during the operation was primarily sutured and didn't receive further treatment. Two perforations which occurred during the reoperations were treated by irrigation, debridement with surgical drainage, and systemic antiobiotics. One who was diagnosed later after the operation showed the poorest outcome and required longest hospital days among our series. Early detection and appropriate treatment of esophageal injury following anterior spinal surgery can only improve the prognosis by preventing secondary complications.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.174-179
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• 2001

In order to investigate the fracture behaviors(perforation modes) and resistance to perforation during ballistic impact of aluminum alloy plate, ballistic tests were conducted. Depth of penetration experiments with 5.56mm-diameter ball projectile launched into 25mm-thickness Al 5052-H34 targets were conducted. A powder gun launched the 3.55g projectiles at striking velocities between 0.6 and 1.0 km/s. radiography of the damaged targets showed different penetration modes as striking velocities increased. Resistance to perforation is determined by the protection ballistic limit($V_{50}$), a statistical velocity with 50% probability for complete perforation. Fracture behaviors and ballistic tolerance, described by perforation modes, are respectfully observed at and above ballistic limit velocities, as a result of $V_{50}$ test and Projectile Through Plates (PTP) test methods. PTP tests were conducted with $0^{\circ}$ obliquity at room temperature using 5.56mm ball projectile. $V_{50}$ tests with $0^{\circ}$ obliquity at room temperature were conducted with projectiles that were able to achieve near or complete perforation during PTP tests. The effect of various impact velocity are studied with depth of penetration.