• 한국표면공학회지
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• 제43권6호
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• pp.255-259
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• 2010

In this work, Ni-Co composites incorporated with nano-sized SiC particles in the range of 45-55 nm are prepared by electroplating. The effects of plating duration on the chemical composition, surface morphology, crystalline structures and hardness have been studied. The maximum hardness of Ni-Co-SiC composite coating is approximately 633 Hv at plating duration of 1 h. The hardness is gradually decreased with increasing plating duration, which can be attributed to the growth of crystalline size and the agglomerates of SiC nano-particles. It is therefore explained that the grain refinement of Ni-Co matrix and stable dispersion of SiC particles play an important role for strengthening, which indicate Hall-Petch relation and Orowan model were dominant for hardening of Ni-Co-SiC composite coatings.

• 수면정신생리
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• 제6권2호
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• pp.116-125
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• 1999

Objectives: The purpose of this study is to investigate the effect of exercise load on sleep structure and stress hormone secretion during sleep. Methods: Five male physical education students were included in this study after giving their written, informed consents in the Research Institute for Sports Science at the University of Hanyang. All subjects have performed for at least 3 years in a regular aerobic exercises such as football, basketball, and running. The subjects were divided into three groups ; NOE(non-exercise), MDE(middle duration exercise), LDE(long duration excercise). MDE group maintained a total of 120 min exercise, and LDE group maintained a total of 300 min exercise by football, basketball or badminton. All subjects were acclimatized to the experimental sleep condition by spending one night under expermental conditions, including the placement of an intravenous catheter. During the subsequent night(24:00-08:00), somnopolygraphic sleep recordings were obtained, and blood for measuring growth hormone, cortisol, testosterone, and $\beta$-endorphin was collected every 120 min throughout the night. Blood samples were obtained from prominent forearm veins of subjects. Then, the samples were immediately placed in ice and centrifuged within 10 min at 3000 rpm at $4^{\circ}C$. Statistical analyses were performed using the SPSS/$PC^+$. Data were analyzed by one-way ANOVA with repeated measures. Results: No significant differences among groups were observed in sleep latency, total sleep time, stage 2 sleep, and slow wave sleep. However, daytime exercise produced significant changes in stage 1 sleep, REM sleep, stage 2 sleep latency, REM sleep latency and sleep efficiency. Stage 1 sleep, stage 2 sleep latency, and REM sleep latency significantly increased in LDE compared to those of NOE and MDE groups. But the amount of REM sleep significantly decreased in LDE. Sleep efficiency of MDE was higher than those of NOE and LDE. The blood concentrations of growth hormone, testosterone, and cortisol during night sleep were significantly lower in LDE than in NOE. $\beta$-endorphin concentrations in blood during night sleep were not different among groups. Conclusion: The daytime exercise load was significantly related to sleep structure and stress hormone secretion during night sleep. Long duration exercise showed a harmful effect on sleep structure and hormone secretion. However, middle duration exercise had a beneficial effect on sleep structure and hormone secretion during sleep.

• Journal of Plant Biology
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• 제37권4호
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• pp.397-402
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• 1994

Possible roles of polyamines in the inhibition of cell elongation in Ranunculus petioles were investigated. Exogenously apoplied polyamines greatly inhibited the auxin-induced petiole growth, while treatment of the tissue with $\alpha$-difluoromethylarginine, the inhibitor of putrescine biosynthesis, further enhanced the growth in the presence of IAA. Inhibitory effect of spermine can also be apparent for fusicoccin-induced elongation, but not for growth induced by a low pH. Spermine also suppressed the ethylene-enhanced growth in the presence of auxin. Using computer-based video digitizer system, the inhibitory effects of spermine on petiole growth were kinetically analyzed. Auxin-induced growth was characterized by an initial and transient growth with a highly elevated rate followed by a steady growth with a slightly reduced rate. Spermine treatment was found to shorten the duration of the initial phase of growth, and to reduce the rates of both the initial and steady growth as well. The latent period for auxin induction was not affected by spermine.

• Current Research on Agriculture and Life Sciences
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• 제17권
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• pp.71-77
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• 1999

나리속(屬) 식물의 촉성재배에 있어 계통 및 품종별 차광정도와 기간에 따른 생육반응을 조사하였다. 초장은 초기차광에 의해 차광율이 높아짐에 따라 'Gelria'와 ' Casablanca'는 초장이 길어진 반면 'Jolanda'와 'Land'는 오히려 짧아지는 경향이었다. 또한 연속차광에 의해 'Gelria'를 제외한 3품종은 차광율이 높아짐에 따라 초장이 길어졌으나 'Gelria'의 초장은 대조구에 비해 차광구에서 초장이 짧았다. 개화는 생육초기에 차광함으로써 'Gelria'의 경우 차광율이 높아질수록 blasting의 발생이 많아지고 개화소요일수(開花所要日數)가 단축되었으나 암처리에 의해 다시 개화소요일수(開花所要日數)가 길어졌다. 다른 품종들은 큰 차이를 보이지 않았으나 암처리구에서 'Jolanda'의 경우 blasting이 15.7% 발생하였고 'Dream land'와 'Casablanca'는 착화수(着花數)가 감소되었다. 연속 차광함으로써 'Gelria'의 경우 차광정도에 관계없이 차광에 의해 화아(花芽)가 형성되지 않았고 'Jolanda'는 75%차광구, 'Dream Land'는 50%차광구부터 각각 화수(花數)가 줄어들었으며 꽃크기도 작아졌고 'Dream Land'는 75% 차광하에서 화아(花芽)가 형성되지 않았다. 그러나 'Casablanca'는 차광구에서 단지 개화소요일수(開花所要日數)만 길어졌다. 신구(新球)의 비대(肥大)는 생육초기 차광구에서 단지 'Casablanca' 품종만 차광에 의해 신구(新球)의 비대(肥大)가 저조하였고 다른 품종들은 차이가 없었다. 그러나 연속차광에 의해서는 공시품종 모두 차광에 의해 신구(新球)의 비대(肥大)가 저조했다.

• 한국패류학회지
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• 제28권1호
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• pp.29-35
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• 2012

Growth patterns of the Manila clam, Ruditapes philippinarum in each tidal level were studied in the intertidal zone in Tae-an on the west coast of South Korea from April to August 2009. Environmental factors and the specimens of R. philippinarum were monthly collected at three intertidal locations: low intertidal zone, low-middle intertidal zone and middle intertidal zone. Temperature of sediment in low intertidal zone were lower than those in other intertidal locations. Concentrations of Chl-${\alpha}$ were not significantly different between in each tidal level. Exposure hours in low intertidal zone were shorter than those in other intertidal locations. Density of each year class in low intertidal zone were higher than those in low-middle intertidal zone and middle intertidal zone. Growth factors of R. philippinarum in low intertidal zone were better than those in other intertidal locations. The growth rate of under one year class individuals of low intertidal zone were higher than those in low-middle intertidal zone and middle intertidal zone, before the main recruitment period of R. pilippinarum. Although the growth patterns of R. philippinarum may be affected by various environmental factors, we suggests that the exposure duration is the main affect in the growth patterns of R. philippinarum in intertidal zone.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2002년도 춘계학술발표회 초록집
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• pp.35-35
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• 2002

Atomic force microscopy was applied to study the formation and growth mechanism of thin chrome layers prepared under various pulse plating conditions. The chrome was electro-deposited from an electrolyte bath containing 250 gl-l of chromic acid, 25 gl-l of sulfuric acid using direct current density of $1.6{\;}mA.$\textrm{mm}^{-2} and pulse currents with on-off time from 5 to 900 ms. The higher current density enhanced nucleation rate which resulted in refining grain size. The chrome growth kinetics determining nodule size and shape significantly depends on the duration of on-time rather than duration of off-time and on/off time ratio.

• 한국관개배수논문집
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• 제19권1호
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• pp.87-96
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• 2012

Information of local solar radiation is essential for many field, including water resources management, crop yield estimation, crop growth model, solar energy systems and irrigation and drainage design. Unfortunately, solar radiation measurements are not easily available due to the cost and maintenance and calibration requirements of the measuring equipment and station. Therefore, it is important to elaborate methods to estimate the solar radiation based on readily available meteorological data. In this study, two empirical equations are employed to estimate daily solar radiation using Cheongju Regional Meteorological Office data. Two scenarios are considered: (a) sunshine duration data are available for a given location, or (b) only daily cloudiness index records exist. Simple linear regression with daily sunshine duration and cloudiness index as the dependent variable accounted for 91% and 80%, respectively of the variation of solar radiation(H) at 2011. Daily global solar radiation is highly correlated with sunshine duration. In order to indicate the performance of the models, the statistical test methods of the mean bias error(MBE), root mean square error(RMSE) and correlation coefficient(r) are used. Sunshine duration and cloudiness index can be easily and reliably measured and data are widely available.

• 대한건축학회논문집:구조계
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• 제35권4호
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• pp.175-184
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• 2019

To improve productivity in the architecture, construction and engineering industry, it is critical to understand both current and historic trends in construction productivity. This study analyzes and compares construction productivity trends of South Korea, the U.S., the U.K., and Japan 1995 to 2015 using the following three measures: construction labor productivity, construction duration per floor, and construction duration per 1,000 m2 floor area. As the results, the international competitiveness of each country varied according to which measures were used to analyze them. Among the four countries, the construction labor productivity of the U.S. was the highest, followed by that of South Korea. South Korea also had the second highest productivity growth rate, following that of Japan. On the other hand, when analyzed from the perspective of construction duration, the construction productivity in South Korea appeared relatively lower than those of other countries. There were differences in the location of construction competitiveness of each country analyzed by various measures. Therefore, to accurately diagnose and improve the construction competitiveness in South Korea, strategies based on various measures are need to established simultaneously.

• 한국작물학회지
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• 제65권4호
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• pp.426-435
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• 2020

본 연구는 남부지방에서 찰옥수수와 콩의 2모작 직파 표준재배법 확립을 위한 기초자료로 활용하고자 찰옥수수의 유묘기 저온에 따른 생육특성 변화 및 피해양상을 조사하였으며 그 결과는 다음과 같다. 일미찰옥수수 초장은 5℃ 이하 3일 처리구부터 저해가 나타나 모든 처리구에서 22% 이상의 저해율이 조사되었다. 경태도 저온기간이 길어지고, 온도가 낮아질수록 더 짧은 것으로 나타나, 제 2엽기 5℃ 이하 5일 처리구에서 저해율이 27% 이상으로 가장 높게 나타났다. 식생지수(NDVI)에서 저해율은 제 2엽기>제 1엽기>초엽기 순으로 높게 나타났으며, 회복기 저해율에서는 제 2엽기 5℃ 이하 7일 처리구에서 25~82%로 가장 높았다. 광합성능력지수(Fv/Fm)에서도 제 2엽기>제 1엽기>초엽기 순으로 저해율이 높게 조사되었다. 특히, -3℃ 처리구의 저온처리 및 회복기에서 생육특성의 변화가 없거나, 감소하는 것으로 조사되었다. 따라서 5℃ 이하 3일부터 저온기간이 길어지고, 온도가 낮아 질수록 생장이 저해되었고, 그 피해정도는 제 2엽기>제 1엽기>초엽기 순으로 높았다. 모든 유묘기에서 -3℃ 이하에 3일 이상 노출될 경우 생육이 정지되거나, 위조고사 하였다. 한편, 본 실험은 실내에서 수행된 결과이므로 차후 재배지역 적용여부에 대한 면밀한 추가 연구가 수행되어야 할 것으로 사료된다.

• 한국결정성장학회지
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• 제33권6호
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• pp.282-287
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• 2023

본 연구에서는 Laser Powder bed fusion(L-PBF) 공정을 사용하여 제작된 Ti-6Al-4V 합금 적층성형품의 응력제거 열처리 온도와 시간의 변화에 따른 미세조직, 잔류응력 그리고 경도의 변화를 연구하였다. 잔류응력 제거를 위한 열처리 시험 결과 823 K에서는 240분, 873K에서는 60분 이상 열처리시 치수변화 및 기계적 특성 저하를 야기하는 결정립 성장 및 상변화 발생 없이 대부분의 잔류응력이 3 0 MPa 이하로 감소되는 것을 확인하였다. 또한, 열처리 온도 및 시간의 증가와 함께 경도가 증가하는 경향을 보였다. 이러한 결과는 XRD 및 SEM-EBDS의 phase map 분석을 통해 확인되지 않지만, 773~873 K 온도범위에서 등온 열처리시 국부적인 침상 Martensitic α' 상의 미세화가 원인으로 추정된다.