• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권1호
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• pp.19-23
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• 2000

Partial discharges(PD)in air insulated electric power apparatus often lead to deterioration of solid insulation by electron bombardments and electrochemical reaction. The PD caused to reduce the life time of power apparatus and to increase power losses. Thus understanding and classification of PD patterns in air are very important to discern sources of PD. In this paper, PD in air by using statistical methods was investigated. We classified air discharges, corona, surface discharges and cavity discharges by Kohonen network. For classification of PD patterns, we used statistical operators and parameters such as skewness$(S^+,\; S^-),\; kurtosis(K^+, K^-),\; mean phase(AP^+, AP^-)$, cross-correlation factor(CC) and asymmetry derived from the mean pulse-height phase distribution$(H_{avg}(\phi))$, the max pulse-height phase distribution $(H_{qmax}(\phi))$, the pulse count phase distribution $(H_n(\phi))$ and the pulse height vs. Repetition rate $(H_q(n))$.

• 분석과학
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• 제15권4호
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• pp.381-387
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• 2002

미국산업위생학회 (American Industrial Hygiene Association, AIHA)와 미국환경보호청(US Environmental Protection Agency, EPA)에서 실시하는 납 분석 정도관리 프로그램에 가입하여 1999부터 2001년까지 매년 4회씩 공기, 페인트 칩, 토양 그리고 먼지 중 납을 분석하였다. 분석결과, 총 128개의 시료 중 126개의 결과가 적합 범위에 들어 전체적으로 'proficient' 인정을 받았다. 공기, 페인트 칩, 토양 그리고 먼지 중 납의 농도는 각각 $0.0089{\sim}0.3956mg/m^3$, 0.0500~8.9149%, 29.0~1697 mg/kg 그리고 $18.00{\sim}900.3{\mu}g/sample$ 이었다. 다양한 환경시료 중의 납은 각 매트릭스별로 적절한 전처리를 한 다음 불꽃 원자흡수분광광도법으로 불꽃 방법으로 분석하였다. 공기 중 납은 염산으로 추출하였고, 페인트 칩과 토양 시료는 마이크로웨이브와 핫플레이트에서 회화시키는 방법, 두 가지를 모두 이용하였다. 그리고 먼지 시료는 마이크로웨이브 회화법을 이용하였다. 각각의 전처리 방법에 따른 차이는 없었으며, 다양한 환경 시료 중의 납 분석방법으로 적당하였다.

• 대한임상검사과학회지
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• 제41권3호
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• pp.105-110
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• 2009

Yellow sand (or Asian dust) occurs mainly in spring in East Asia. Yellow sand from China and its surrounding regions transports air pollutants, such as aerosols, ozone, and heavy metals. The outdoor workers are frequently exposed to heavy metals during yellow sand phenomenon. This study was carried out to investigate the heavy metal levels in blood among 75 outdoor workers (exposed group) and 86 indoor workers (controled group) in Gyeonggi province from March 2008 to May 2009. Heavy metal levels in blood were analyzed by atomic absorption spectrophotometer. Mean blood lead levels in exposed group and controled group were $5.19{\pm}1.64{\mu}g/dL$, $4.24{\pm}1.34{\mu}g/dL$, respectively. Mean blood cadmium levels in exposed group and controled group were $1.28{\pm}0.89{\mu}g/dL$, $0.90{\pm}0.59{\mu}g/dL$, respectively. Lead and Cadmium levels in blood of exposed group were significantly higher than those of controled group. In the comparison of smoking status, lead and cadmium levels of smokers were significantly higher than those of non-smokers. In conclusion, the heavy metal levels of outdoor workers were significantly higher than those of indoor workers. And smoking was hazardous factor to elevate heavy metal levels in blood.

• 한국시뮬레이션학회논문지
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• 제29권1호
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• pp.39-46
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• 2020

인공지능(AI)를 교전상황에 활용하는 것은 최근 10년간 국방 분야의 주요 관심사였다. 이러한 응용을 위해서, AI 교전에이전트를 훈련해야 하며, 이를 위해 현실적인 시뮬레이션이 반드시 필요하다. 하드웨어 차원의 현실성을 가진 공중 무기체계 공중전 모델에서 AI 에이전트를 학습한 사례에 대해서 본 논문은 서술하고 있다. 특히, 본 논문은 기총만을 활용하는 공중전 상황에서 적을 어떻게 추적해야하는지 AI를 학습하였다. 본 논문은 현실적인 공중전 시뮬레이터를 작성하여, 에이전트의 행동을 강화학습으로 수행한 결과를 제시한다. 훈련 결과로는 Lead 추적을 활용하여 단축된 교전시간과 높은 보상을 갖는 에이전트의 학습에 성공하였다.

• 대기
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• 제21권1호
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• pp.109-121
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• 2011

This study revisits the definition of Changma, which is the major rainy season in Korea and corresponds to a regional component of the East Asian summer monsoon system. In spite of several decades of researches on Changma, questions still remain on many aspects of Changma that include its proper definition, determination of its onset and retreat, and relevant large-scale dynamical and thermodynamical features. Therefore, this study clarifies the definition of Changma (which is a starting point for the study of interannual and interdecadal variability) using a basic concept of air mass and front by calculating equivalent potential temperature (${\theta}_e$) that considers air temperature and humidity simultaneously. A negative peak in the meridional gradient of this quantity signifies the approximate location of Changma front. This front has previously been recognized as the boundary between the tropical North Pacific air mass and cold Okhotsk sea air mass. However, this study identifies three more important air masses affecting Changma: the tropical monsoon air mass related to the intertropical convergence zone over Southeast Asia and South China Sea, the tropical continental air mass over North China, and intermittently polar continental air mass. The variations of these five air masses lead to complicated evolution of Changma and modulate intensity, onset and withdrawal dates, and duration of Changma on the interannual time scale. Importantly, use of ${\theta}_e$, 500-hPa geopotential height and 200 hPa zonal wind fields for determining Changma onset and withdrawal dates results in a significant increase (up to~57%) in the hindcast skill compared to a previous study.

• Journal of Mechanical Science and Technology
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• 제15권4호
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• pp.459-464
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• 2001

The effects of internal air-pressing on deep drawability are investigated in this study to increase the deep drawability of aluminum sheet. The conventional deep drawing process is limited to a certain limit drawing ratio(LDR) beyond which failure will occur. The intention of this work is to examine the possibilities of relaxing the above limitation through the deep drawing with internal air-pressing, aiming towards a process with an increased drawing ratio. The idea which may lead to this goal is the use of special punch that can exert high pressure on the internal surface of deforming sheet during the deep drawing process. Over the ranges of conditions investigated for Al-1050, the local strain concentration at punch nose radius area was decreased by internal air-pressing of punch, and the deep drawing with internal air-pressing was proved to be very effective process for obtaining higher LDR.

• Journal of Forest and Environmental Science
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• 제40권3호
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• pp.227-240
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• 2024

Trees improve air quality through the accumulation of air pollutants in their leaves; however, the responses of different tree species to air pollution varies. Hence, this study evaluated the responses to air pollution of selected tree species in the Swamp Forest Research Station, Onne. Ten tree species (Cola pachycarpa, Khaya grandifoliolia, Irvingia gabonensis, Garcinia kola, Chrysophyllum albidum, Treculia africana, Dacryodes edulis, Tectonia grandis, Gmelina aborea, and Nauclea diderrichii) were selected based on their abundance in the area. Leaves were collected from all sides in 3 replicates for each tree species. Laboratory analysis was carried out using standard procedures. Portable Multi Gas Detector was used to determine the concentrations of air pollutants. One-way analysis of variance was employed to test for significant difference (p≤0.05) in biochemical parameters among the tree species while Pearson's correlation was utilized to determine the level of association between different biochemical parameters and APTI; heavy metals and APTI. Results showed high concentration of PM₁₀, CO, moderate concentration of NO₂, PM_2.5, and VOC, and low concentration of ground O₃. Heavy metals - Cadmium, Mercury, Lead, Nickel and Copper were all present in the tree species at varying rates. There were significant differences in the biochemical parameters and APTI values. C. pachycarpa exhibited the highest APTI value (89.88), while D. edulis had the lowest APTI value (8.24). C. pachycarpa, K. grandifoliolia, C. albidum, G. kola, T. africana, and N. diderrichii were identified as tolerant tree species to air pollution. G. aborea, T. grandis, and I. gabonensis were considered intermediate tolerant species, while D. edulis was the only tree species sensitive to air pollution. Ascorbic Acid, Chlorophyll, Hg and Ni had positive correlations with APTI; Cd and Cu had negative association with APTI at the 0.05 significance level. C. pachycarpa, T. africana, K. grandifoliolia, C. albidum, N. diderrichii and G. kola, are recommended for planting in pollution-prone areas.

• Nuclear Engineering and Technology
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• 제56권5호
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• pp.1887-1894
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• 2024

Fatigue strength of the structural materials of lead-cooled fast reactors (LFRs) and accelerator-driven systems (ADS) may be degraded in liquid metal (Lead or lead-bismuth eutectic (LBE)) environments. The fatigue crack growth (FCG) data of structural materials in liquid LBE are necessary for damage tolerance design, safety assessment and life management of key equipment. A novel monitoring system for fatigue crack length was designed on the compliance method and the monitor technology of crack opening displacement (COD) of CT specimens by the linear variable differential transformers (LVDT) system. It can be used to predict the crack length by monitoring the COD of CT specimens in harsh high-temperature liquid LBE using a LVDT system. The prediction accuracy of this system was verified by FCG experiments in room temperature air and liquid LBE at 150, 250 and 350 ℃. The first results obtained in the FCG test for T91 steel in liquid LBE at 350 ℃ are presented.

• 한국약용작물학회지
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• 제26권4호
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• pp.291-295
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• 2018

Background: The use of Rehmannia glutinosa of the family Scrophulariaceae, in traditional medicine is well known. This study was conducted to elucidate the effect of air curing of the seed rhizome of R. glutinosa on its storability and yield. Methods and Results: The root of the R. glutinosa cultivar (Dagang) was harvested in at the end of November. The seed rhizomes were air cured for one to seven days. They were subsequently wrapped with newspaper and further stored in a plastic container at $1^{\circ}C$. It was observed that the weight loss and decay rates were significantly lower in the air cured seeds than in the untreated ones. Moreover, the decay rate of the control was approximately 50%, 120 days after storage. However. the decay rate of all the air cured treatment groups was less than 1%. Additionally, air curing led to an increase in the germination rate of the seeds and the root yield when compared with the untreated groups. Taken together, the ideal treatment period for air curing was found to be 3 days. Under these conditions, the germination rate and yield were 88.7% and 2,185 ㎏/10a, respectively. Conclusions: This study successfully demonstrated that the air curing of seed rhizomes can lead to a considerable increase in the storability and yield of R. glutinosa.

• Current Research on Agriculture and Life Sciences
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• 제32권2호
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• pp.67-73
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• 2014

Mulberry fruits were semi-dried using hot air ($60-100^{\circ}C$) or cool air ($20-40^{\circ}C$), and the effects of the drying temperature and processing time on the quality of the final dried mulberry fruits were investigated. Response surface methodology was employed to establish a statistical model and predict the conditions resulting in minimal loss of the total phenolic content (TPC) and ascorbic acid. Thus, using overlapped contour plots, the optimal conditions for producing semi-dried mulberry fruits, which reduced the moisture residue to 45% and minimized the nutrient losses of TPC and ascorbic acid, were determined for the hot-air process ($60.7^{\circ}C$ for 5.4 h) and cool-air process ($34.8^{\circ}C$ for 23.3 h). Plus, a higher drying temperature was found to lead to a faster loss of moisture and ascorbic acid, while the TPC was significantly decreased in the cool-air dried mulberry fruits due to the higher activity of polyphenol oxidase between 30 and $40^{\circ}C$.