• 대한기계학회논문집A
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• 제28권4호
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• pp.402-409
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• 2004

The purpose of this study is to investigate the effect of local wall thinning on the collapse of elbow subjected to internal pressure and bending moment. Thus, the nonlinear three-dimensional finite element analyses were performed to obtain the collapse moment of elbow containing various wall thinning defects located at intrados and extrados under two loading modes (closing and opening modes) with internal pressure. From the results of analysis, the effect of wall thinning defect on the global moment-rotation behavior of elbow was discussed, and the dependence of collapse moment of elbow on wall thinning depth, length, and circumferential angle was investigated under different loading mode and defect location.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.4060-4066
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• 2021

Flow-accelerated corrosion (FAC) of carbon steel piping is a significant problem in nuclear power plants. The basic process of FAC is currently understood relatively well; however, the accuracy of prediction models of the wall-thinning rate under an FAC environment is not reliable. Herein, we propose a methodology to construct pipe wall-thinning rate prediction models using artificial neural networks and a convolutional neural network, which is confined to a straight pipe without geometric changes. Furthermore, a methodology to generate training data is proposed to efficiently train the neural network for the development of a machine learning-based FAC prediction model. Consequently, it is concluded that machine learning can be used to construct pipe wall thinning rate prediction models and optimize the number of training datasets for training the machine learning algorithm. The proposed methodology can be applied to efficiently generate a large dataset from an FAC test to develop a wall thinning rate prediction model for a real situation.

• Journal of the Korean Wood Science and Technology
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• 제43권6호
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• pp.721-729
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• 2015

목재의 재질특성은 토양, 기후, 임분특성 등의 환경적 요인뿐만 아니라 인위적인 처리에 의해서도 바뀌게 되므로 남부지역의 전라남도 완도 수목원에서 무간벌, 약도간벌, 강도간벌의 간벌강도에 따른 목재의 조직 물리 역학적 특성을 평가 분석한 결과 간벌 강도에 따라 여러 조건에서 높은 상관관계를 나타내었다. 특히 간벌강도는 연륜폭과 역학적 특성에서 밀접한 상관관계를 나타내었다. 본 연구결과 붉가시나무의 간벌강도와 재질특성 사이에서 상관관계가 나타났고 이러한 결과는 목재를 시업체계와 육림방법 시스템에 적용할 수 있는 기초자료로서 활용가치가 높을 것으로 판단된다.

• The Korean Journal of Ecology
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• 제27권6호
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• pp.363-367
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• 2004

Photosynthetically active radiation (PAR) beneath the forest canopy, understory species richness and diversity, and biomass were measured in a Larix leptolepis plantation seven years after thinning in Yangpyeong. Four different thinning intensities (control, $10\%,\;20\%\;and\;40\%$ stocking reduction) were applied in 1997. The current PAR values were lower than those measured four years after thinning, and PAR at the heavy thinning plots was significantly higher than that of other thinning intensities. A total of 23 species including 9 tall-trees and 14 shrubs were found for the high layer while a total of 82 species including 10 tall-trees, 29 shrubs, and 43 herbs for the low layer. Species richness and diversity generally increased with thinning intensities, and the trends were more evident for the low layer. Aboveground biomass significantly differed among thinning intensities for both shrubs and herbs. Also there was a negative correlation between biomass and the current number of stems per hectare. The current study suggested that the effects of thinning on light conditions at the forest floor, species richness and diversity and production of understory vegetation continued seven years after the treatment.

• 한국가스학회지
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• 제12권2호
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• pp.57-62
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• 2008

배관 엘보우의 내호면(intrados)의 과 내부에 국부적으로 두께 감육이 발생한 경우, 내압과 엘보우를 닫는 방향으로의 굽힘하중을 부가하여 파손 모드를 연구하였다. 탄소성해석 시 반력-변위 곡선이 세 그룹으로 나뉘므로 각 그룹의 한 경우씩을 해석하여 소성붕괴에 의한 파손모드의 차이를 확인하였다. 이를 위해 주요 부위에서 하중-국부적응력 곡선이 어떻게 변화하는지 결정하여, 이로부터 관찰된 파손모드와 비교하여 설명하였다. 감육폭이 $90^{\circ}$인 경우 배관은 엘보우 측면부터 소성붕괴가 시작되었으며, $360^{\circ}$인 경우 내호면으로부터 소성변형이 시작되어 서로 다른 파손모드를 보여주었다. 배관의 감육측정에 의한 건전성 평가 시 이와 같은 파손 모드의 차이점을 고려하여 평가를 실시하여야 한다.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2019년도 추계학술대회
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• pp.63-63
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• 2019

The thinning Green ball apple was extracted using water and ethanol and a phenolic concentration of thinning Green ball apple was $50-200{\mu}g/mL$. The water and ethanol extracts of thinning Green ball apple showed 94.69% and 92.24% 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and 100.30% and 99.16% 2,2'-Azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity at phenolic concentration of $200{\mu}g/mL$, respectively. The water and ethanol extracts of thinning Green ball apple showed antioxidant protection factor of 1.76 antioxidant protection factor and 1.76 antioxidant protection factor, respectively. The water and ethanol extracts showed 101.46% and 99.64% anti-oxidative effect on thiobarbituric acid reactive substances at phenolic concentration of $200{\mu}g/mL$. Hence, the water and ethanol extracts of thinning Green ball apple can be considered a potential anti-oxidant. The water and ethanol extracts showed 33.28% and 32.14% hyaluronidase inhibition, respectively, at phenolic concentration of $150{\mu}g/mL$. The water and ethanol extracts showed 47.33% and 40.92% elastase inhibition and 46.19% and 65.58% collagenase inhibition at phenolic concentration of $200{\mu}g/mL$, respectively. About these experiments, thinning Green ball apple was found to exhibit anti-oxidation activity as well as hyaluronidase, elastase and collagenase inhibitory activities. Therefore, thinning Green ball apple can be considered a potential source for functional food.

• Journal of Ecology and Environment
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• 제46권1호
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• pp.85-98
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• 2022

Background: Korean white pine (Pinus koraiensis) is a major commercial species, and the importance of the oak trees (Quercus spp.) is increasing due to various factors such as environmental and ecological values. However, more information is required to clearly understand the growth characteristics of these species especially regarding thinning intensity. This study was performed to provide the basic information to develop the silvicultural guideline and field manual by analyzing tree and stand characteristics in line with thinning intensity in the Korean white pine plantation and oak-dominated natural deciduous forest. Results: Diameter at breast height (DBH) and volume changes by the thinning intensity in the Korean white pine plantation were significantly different from those in the oak-dominated deciduous natural forest. In particular, DBH distribution in the pine stand appeared that there were more large diameter trees as the thinning intensity was higher. DBH periodic annual increment (PAI) of the pine stand was higher as the thinning intensity was stronger and the growth period was shorter. This trend was similarly shown in the natural deciduous forest, but the amount of PAI was smaller than in pine stand. The volume PAI after thinning was not decreased over time. In each stand type, the PAI tended to be lower as stand density was higher. The volume PAI in the pine stand was significantly higher than that in the oak-dominated natural deciduous forest. Dead trees occurred the most in the unthinned plots of each stand type, and those were higher in the natural deciduous forest. Ingrowth trees were observed only in the natural deciduous forest, and its distribution was the lowest in unthinned plots; Korean white pine as ingrowth occurred the most frequently among many tree species. Conclusions: Different effects of thinning treatment on DBH and volume PAI, mortality, and ingrowth were observed for each stand. With respect to forest growth, Korean white pine plantation was superior to the oak-dominated natural deciduous forest. The results of this study offer fundamental information for the development of silvicultural guidelines for Korean white pine plantations and oak-dominated natural deciduous forests in Korea.

• 한국환경농학회지
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• 제42권2호
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• pp.104-111
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• 2023

As apple trees mature, it is important to maintain good light distribution within the canopy to produce marketable fruits. Tree thinning is the selective removal of a proportion of trees growing in the orchard to provide more growing space and a good light environment for the remaining trees. This study was conducted over 3 years (14-16 years after planting) to investigate the influence of tree thinning on vegetative growth, yield, fruit quality, and blooming in the 14 years old slender spindle 'Fuji'/M.9 apple trees planted with the tree space of 3.2×1.2 m. The trees were placed in a control group (no thinning; 260 trees per 10 a) or a tree thinning group (thinned 50% of the control; 130 trees per 10 a). The tree thinning successfully improved light penetration, yield per tree, fruit red color, and yield efficiency for 3 years, and the tree thinning controlled the occurrence of biennial bearing. However, tree thinning significantly decreased accumulated yield per 10 a compared with the control. The vegetative growth, yield per tree, soluble solid contents, and blooming were not clear by the occurrence of biennial bearing in the control. These results indicated that tree thinning was a good method for improving light penetration and preventing biennial bearing in the old 'Fuji'/M.9 high-density apple orchards.

• 대한전자공학회논문지SP
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• 제46권1호
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• pp.1-6
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• 2009

세선화 알고리즘은 문자인식, 도형 및 도면 인식 등에 매우 중요하게 사용되고 있다. 세선화 알고리즘은 여러 가지 방법으로 제안되어 왔다. 본 논문에서는 이전에 제안된 세선화 알고리즘 중 선처리가 후처리에 영향을 주지 않는 병렬 세선화 알고리즘 중에서 ZS, LW, 및 WHF 알고리즘의 문제점을 찾아내었다. ZS 알고리즘은 사선 방향에서 화소가 손실되는 문제점을 안고 있으며, LW 알고리즘은 사선 방향에서의 화소 두께가 1이 되지 못하는 문제점을 내포하고 있다. 따라서 본 알고리즘에서는 사선 방향에서 8근방을 이루며, 화소의 두께도 완전히 1이 되도록 개선시킨 병렬 세선화 알고리즘을 제안한다.

• 대한기계학회논문집A
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• 제27권1호
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• pp.8-17
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• 2003

Fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear Power Plant. In Pipes of energy Plants, sometimes, the local wall thinning may result from severe erosion-corrosion (E/C) damage. However, the effects of local wall thinning on strength and fracture behaviors of piping system were not well studied. In this paper, the monotonic bending tests were performed of full-scale carbon steel pipes with local wall thinning. A monotonic bending load was applied to straight pipe specimens by four-point loading at ambient temperature without internal pressure. From the tests, fracture behaviors and fracture strength of locally thinned pipe were manifested systematically. The observed failure modes were divided into four types; ovalization. crack initiation/growth after ovalization, local buckling and crack initiation/growth after local buckling. Also, the strength and the allowable limit of piping system with local wall thinning were evaluated.