• Journal of the Korean Wood Science and Technology
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• 제36권2호
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• pp.20-28
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• 2008

This study was carried out to provide the so-called circumferential slicing method for investigating radial distributions of the tangential strains and of moisture contents within the log cross section (LC) of Kalopanax pictus during indoor drying it. While the heartwood showed an almost uniform moisture content distribution in the range of about 50~55% in case of the green wood, it has gradually decreased toward the outer side, showing about 19% of moisture content difference from the innermost slice. Although the moisture gradient along the radial direction has gradually become gentle as drying progresses, the sapwood of the outer side represented the moisture contents below the fiber saturation point after 24 hours of drying while the heartwood in the inner part showed the moisture contents higher than the fiber saturation point. The pith side was laid under the tensile stress after 24 hours of drying, and then gradually decreasing toward the bark side, and showed the distribution being switched again to the tensile stress on the bark side. As the drying has progressed, this trend got more intensified, and finally showed the U-shaped distribution model after 48 hours of drying. The circumferential slice test is considered to be suitable in quantitatively determining the tangential strains and moisture content within a LC.

• 한국산학기술학회논문지
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• 제15권1호
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• pp.506-514
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• 2014

최근 국내에서 도심지 홍수로 인한 피해 발생이 증가하면서 차집된 다량의 강우를 일시에 배출할 수 있는 와류 유입구에 대한 관심이 증가하고 있다. 이 중 접선식 유입구는 구조가 단순하고 크기가 작아 적용성이 높으나 설계 유량보다 작은 유량에 대해서 와류가 형성되지 못하는 단점이 있다. 본 연구에서는 이를 보완하여 새롭게 제안된 2가지 종류의 복단면형 접선식 와류 유입구의 수리 특성을 3차원 수치모의를 통해서 분석하였다. 기존에 제시된 한계수심 이론과 자유 배수 조건 이론을 이용하여 복단면 형상의 접선식 와류 유입구의 특성을 흐름 상태, 수면형, 수심-유량 관계, 공기 기둥 면적비 측면에서 분석하였다. 종합적인 수리 특성 분석 결과 완경사형 복단면 접선식 유입구가 최적안으로 판단되나 설계 유량이 작은 경우에는 급경사형 복단면도 가용한 것으로 나타났다.

• 대한수학회지
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• 제54권4호
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• pp.1163-1173
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• 2017

In this paper, we introduce the condition (I) (cf. Section 2) and prove that there is no nontrivial tangential holomorphic vector field of a certain hypersurface of infinite type in ${\mathbb{C}}^2$.

• Journal of the Korean Wood Science and Technology
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• 제40권6호
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• pp.418-423
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• 2012

원통형 단판적층재(LVL)의 구조재 이외의 공예재 등의 용도개발을 위하여 원통형 단판적층재의 내수접착성과 도장처리에 따른 내마모성 및 표면경도를 측정하였다. 레조시놀 수지와 경화제(paraformaldehyde)를 100 : 5의 혼합비로 하여 접착 경화한 원통형 단판적층재의 전체적인 접착층에 대한 삶음박리 접착력은 양호한 편이었다. 내마모성은 횡단면이 접선단면보다 상대적으로 우수하였으며, 접선단면에 자외선 차단 오일을 도장 처리한 경우 내마모성이 향상되었다. 표면경도는 횡단면의 경우, 낙엽송 중심재가 라디에타소나무 단판적층 부위보다 높았고, 접선단면의 경우에는 접착층 부위가 단판부위보다 높게 나타났다.

• Journal of the Korean Wood Science and Technology
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• 제48권4호
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• pp.569-576
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• 2020

This study investigated the characteristics of microfibril angle(MFA) in order to see if there was any difference in pine tree lumber quality among the three mountain areas surrounding the Taebaek Mountains in Korea - Yeongdong (Goseong-gun), Yeongseo (Hongcheon-gun) and Yeongnam (Bonghwa-gun). Pine trees of each mountain area were divided into earlywood and latewood in relation to heartwood part (1959 ~ 1961, 3 annual rings) and sapwood part (2002 ~ 2004, 3annual rings), and measured at tangential section. The microfibril angle showed significant differences between mountain areas. In general, Goseong Mountain was found to have 37.35°, followed by Hongcheon Mountain 32.42° and Bonghwa Mountain 25.75°, in order. The sapwood part had larger angle than heartwood part; and earlywood, than latewood. Variation within a single annual ring tended to be smaller from earlywood toward latewood.

• Journal of Plant Biology
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• 제38권3호
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• pp.281-288
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• 1995

The progressive differentiation of interfascicular cambium from residual meristem in the first internode of Ginkgo biloba seedlings was elucidated by light and electron microscopy. The cells of residual meristem were small and homogeneous and heterogeneous in their arrangement but those of the adjacent cortex and pith were large and homogeneous. Some interprocambial residual meristem progressively became elongated and vacuolated during the process of the differentiation. In tangential section, residual meristem composed of long and short cells. The eventual interfascicular cambium had long fusiform initials and short ray initials. Storage materials in the cells progressively disappeared from the interprocambial residual meristem and were absent in early interfascicular cambium. Both the radial and tangential walls of cells of the interprocambial residual meristem were almost the same, but the radial wall became progressively thicker than the tangential wall during differentiation of interfascicular cambium. From these results, it is clear that interfascicular cambium is gradually differentiated from residual meristem.

• 한국산림과학회지
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• 제7권1호
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• pp.3-7
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• 1968

본(本) 대학(大學) 연습림(演習林)에서 생육(生育)한 32년생(年生) 잎갈나무와 27년생(年生) 가래나무를 이용(利用)하여 시험(試驗)한 목재(木材)의 구조단면별(構造斷面別) 흡수성(吸收性) 및 수침시간(水浸時間)에 의(依)한 단면별(斷面別) 흡수성(吸收性)을 요약(要約)하면 다음과 같다. (1) 본시험(本試驗)에 사용(使用)한 시편(試片)($30{\times}30{\times}100cm$)을 각(各) 단면별(斷面別)로 흡수면(吸水面)만 남기고 paraffin과 vaseline과의 등량혼합물(等量混合物)로 방수(防水)하여 $25{\pm}1^{\circ}c$의 청수(淸水)에 8.5일간(日間) 침지(浸漬) 0.5일(일)(12시간)마다 중량(重量)을 측정(測定)하여 흡수성(吸水性) 조사(調査)하였다. (2) 목구면(木口面)에서의 흡수성(吸水性)은 구목면(柾目面)이나 구목면(柾目面)의 종단면(縱斷面)에서의 흡수성(吸水性)보다 대단(大端)히 크며 구목면(柾目面)과 판목면(板目面)에 있어서는 차이(差異)가 거의 없다. (3) 가래나무의 구목면(柾目面)을 제외(除外)하고는 비중(比重)이 비교적(比較的) 적은 가래나무가 비중(比重)이 보다 큰 잎갈나무보다 각(各) 단면(斷面)에서의 흡수성(吸水性)이 크다. (4) 침지시간(浸漬時間) 경과(經過)함에 따라 흡수성(吸水性)이 증가(增加)된다. 또한 침지초기(浸漬初期)에는 흡수성(吸水性)이 대단(大端)히 크나 시간(時間)이 경과(經過)함에 따라 그 정도(程度)는 점차(漸次) 감소(減少)된다. 흡수율(吸水率) 약(約) 반(半) 이상(以上)은 대게 침지(浸漬) 48시간(時間) 전후(前後)의 초기(初期)에 이루어진다. (5) 목구면(木口面)에서는 침지시간(浸漬時間)이 경과(經過)함에 따라 잎갈나무와 가래나무의 흡수성(吸水性) 점차(漸次) 큰 차이(差異)를 나타내며 구목면(柾目面)에서는 초기(初期)의 다소(多少)의 차이(差異)가 있으나 시간(時間)이 경과(經過)함에 따라 아주 일치(一致)한다. (6) 침지시간(浸漬時間)과 흡수량(吸水量)사이에는 다음과 같은 실험식(實驗式)이 성립(成立)한다.

• Journal of Advanced Marine Engineering and Technology
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• 제35권7호
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• pp.907-913
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• 2011

Swirling flows are related to the spiral motion in the tangential direction in addition to the axial and radial direction using several swirl generators. These type of flows are used in combustion chambers to improve flame stability, heat exchanger to enhance heat transfer coefficients, agricultural spraying machines and some vertical pipes to move slurries or transport of materials. However, only a few studies three dimensional velocity profiles in a vertical pipe have been reported. In this present paper, 3 dimension particle image velocimetry(PIV) technique was employed to measure the velocity profiles in water along a vertical circular pipe with Reynolds number from 6000 to 13,000. A tangential inlet condition was used as the swirl generator to produce the required flow. The velocities were measured with swirling flow in the water along the test section using the PIV technique.

• 한국가시화정보학회지
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• 제1권1호
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• pp.82-91
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• 2003

The study of swirl flow has been of technical and scientific interest because it has an internal recirculation field and its tangential velocity is related to the curvature of the streamline. The fluid flow for ducts or elbows of an internal engine has been much studied through numerical methods and experiments, but studies about swirl flow has been insufficient. Using the PIV (Particle Image Velocimetry) method, this study found the time-mean velocity distribution, time-mean turbulent intensity, with swirl and without swirl flow for Re=10,000, 15,000, 20,000, and 25,000 along longitudinal sections and the results appear to be physically reasonable. In addition, axial velocity distribution is compared with that of Jeong's, Kodadadi's and Murakami's. It was found that the highest velocity of swirl and non-swirl flow occurs in the opposite position at the center of a round tube, $\phi$=45$^{\circ}$

• Journal of Plant Biology
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• 제36권1호
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• pp.29-34
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• 1993

Observation was made on early ontogeny of vascular cambium in the cotyledonary node of Pinus koraiensis seedling in order to clarify the cambial ontogeny of the node which was hardly elongated. In transverse view, the derivatives by the early periclinal divisions at the outer region of the procambial strands differentiated to protophloem with establishing a certain degree of radial seriations. Later, some cells in the central region of the procambial strands begin divide periclinally, eventually the cells, differentiate gradually to the vascular cambium. In tangential view, early procambium is consisted of homogeneous short cells with transverse end walls which are tansformed into the long cells and short cells gradually. The long cells continue intrusive growth and the short cells repeat transverse division. Finally, the long and short cells differentiated to cambial fusiform initials and ray initials respectively. In tangential section, the differentiation pattern of cambial initials resembles that of the stem of Ginkgo biloba. But in transverse view, the characteristics in the origin of vascular cambium of the cotyledonary node resembles that of root. The vascular cambium in cotyledonary node is completed after eleven prophylls were formed.