• 한국산학기술학회논문지
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• 제21권11호
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• pp.740-745
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• 2020

콘크리트 박스거더교의 합리적인 설계 온도하중을 산정하기 위하여, 1개의 교량시험체를 제작하였다. 교량시험체에 설치된 23개의 온도 게이지에서 1년간의 여름과 겨울기간에 30분 간격으로 하루에 48세트의 온도를 측정하였다. 상부 콘크리트와 측벽, 하부슬래브에 두께에 따른 온도변화를 검토하기 위하여 두께에 따라 여러 온도게이지를 부착하였다. 각 측점에서 측정된 온도를 통계 처리하여 추세선과 표준오차를 산정하고, 대표측점의 온도분포와 추세선을 제시하였다. 이를 바탕으로 Euro code에서 제시한 대기온도에서 여름철의 최고 유효온도와 겨울철의 최저 유효온도를 각각 산정하였다. 최고 유효온도는 35℃ 이상에서 Euro code와 비교하여 1.5~2℃ 높게 산정되었고, 최저 유효온도는 -13℃~-19℃에서 0.5~1.1℃로 더 낮게 분석되었다. 양산지방의 50년빈도 최고 및 최저 기온에 따른 본 연구의 유효온도와 비교해 보면, 최고 유효온도는 4.7℃ 높게, 최저 유효온도는 4.5℃ 더 낮게 산정되었다. 점점 높아지는 기후변동을 고려하고, 본 분석의 결과를 반영하면, 현 온도설계기준은 그 범위를 더 크게 하는 것이 필요한 것으로 판단된다.

• 한국수자원학회논문집
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• 제43권4호
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• pp.409-419
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• 2010

본 연구에서는 국내 기상관측소 중 관측년수가 30년 이상인 관측소 63개 지점을 대상으로 9개의 수문기상수문인자 즉, 연강수량, 연강수일수, 연평균기온, 연평균상대습도, 연일조시간, 연증발량, 연강수계속시간, 연적설일수, 연신적설일수 자료를 각 지점별로 수집하고, 수문기상인자에 대한 기본통계량, 선형회귀분석, 이동평균법을 통해 수문기상인자의 기본적인 특성을 알아보았다. 또한 통계학적기법인 Hotelling-Pabst 검정과 Mann-Kendall 검정을 통해 경향성을 분석하였다. 기본통계량 분석결과 우리나라의 기후특성상 여름철에 강우가 집중되며, 계절별 강수량의 편차가 큰 전형적인 특성을 확인할 수 있었다. 선형회귀 분석과 5년 이동평균법을 통해서는 시간이 경과함에 따라 연강수량과 연평균기온은 증가, 연평균상대습도와 연일조시간은 감소, 연강수일수는 지점별로 증가 또는 감소하는 추세를 보였다. Hotelling-Pabst 검정과 Mann-Kendall 검정을 통한 경향성분석에서는 연평균상대습도, 연평균기온에서 공통적으로 경향성이 나타났으며, 연강수량, 연강수일수, 연일조시간은 지역에 따라 상이한 결과를 보였다.

• 한국자동차공학회논문집
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• 제8권3호
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• pp.1-11
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• 2000

Instantaneous temperature probes were manufactured by pressing method. By using these probes, the instantaneous surface temperature and unsteady heat flux in the cylinder liner of DOHC engine were measured. The main results are as follows; ⅰ) the instantaneous surface temperature of cylinder liner are affected by the contact of piston ring as well as burning gas. ⅱ) the wall temperature of the siamese portion is much higher than other parts. ⅲ) it was shown that the rising trend of heat flux by burning gas are nearly limited to the 1/2-stroke distance from the top of cylinder liner.

• 대한설비공학회지:설비저널
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• 제16권2호
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• pp.176-184
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• 1987

The purpose of this research is to study the characteristics of the coefficient of perform-ance (COP) of the small absorption refrigeration system. This experimental study is performed with two selected variables, the temperature of the generator and the input temperature of the cooling water. In order to determine the input temperature of the generator which gives maximum COP, the experimental data are obtained with controlling the temperature of the generator in the range of $20-32^{\circ}C$ of the temperature of the cooling water. The range of the generator heat suppling temperature which gives maximum efficiency is about $90-95^{\circ}C.$ The temperature range depends on the characteristics of the equipment unit. The most important result in this experiment is the trends of the COP in accordance with the variation of these temperatures. This trend will furnish the informations and knowledges for designing and operating the absorption refrigerator.

• Fisheries and Aquatic Sciences
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• 제3권3_4호
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• pp.173-179
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• 2000

Recent changes in the coastal sea surface temperatures (SST) in Korea are studied by time series analysis of daily SST data during the last 60 years (1936-1995) at 18 coastal observation stations of the National Fisheries Research and Development Institute. The climate of coastal SST in Korea are rapidly changing in recent years. General trends of coast SST changes in Korea are as follows. The annual averages of SST are increasing. The annual ranges of SST variation are decreasing. The winter SST are increasing while the summer SST have a decreasing tendency. Climatic changes in coastal SST in recent 30 years (1965-1995) are more pronounced than those in the last 60 years (1936-1995). The observed trend of coast SST implies that the climate in Korea shows a tendency to shift from temperate zone to subtropical zone.

• Ocean and Polar Research
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• 제34권2호
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• pp.229-237
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• 2012

Using results from an Earth System model, we investigated change in primary production in the East China Sea, under a global warming scenario. As global warming progresses, the vertical stratification of water becomes stronger, and nutrient supply from the lower part to the upper part is reduced. Consequently, so is the primary production. In addition to the warming trend, there is strong decadal to interdecadal scale variability, and it takes a few decades before the warming trend surpasses natural variability. Thus, it would be very hard to investigate the global warming trend using data of several years' length.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2017년도 학술발표회
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• pp.183-183
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• 2017

Pan evaporation (Epan) is an important indicator of water and energy balance. Despite global warming, decreasing annual Epan has been reported across different continents over last decades, which is claimed as pan evaporation paradox. However, such trend is not necessarily found in seasonal data because the level of contributions on Epan vary among meteorological components. This study investigates long-term trend in seasonal pan evaporation from 1908 to 2016 across South Korea. Meteorological variables including air temperature (Tair), wind speed (U), vapor pressure deficit (VPD), and solar radiation (Rs) are selected to quantify the effects of individual contributing factor to Epan. We found overall decreasing trend in Epan, which agrees with earlier studies. However, mixed tendencies between seasons due to variation of dominant factor contributing Epan were found. We also evaluated the reference evapotranspiration based on Penman-Monteith method and compared this with Epan to better understand the physics behind the evaporation paradox.

• 한국환경과학회지
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• 제26권2호
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• pp.221-230
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• 2017

To determine the effect of air pollution reduction policies, the long-term trend of air pollutants should be analyzed. Kolmogorov-Zurbenko (KZ) filter is a low-pass filter, produced through repeated iterations of a moving average to separate each variable into its temporal components. The moving average for a KZ(m, p) filter is calculated by a filter with window length m and p iterations. The output of the first pass subsequently becomes the input for the next pass. Adjusting the window length and the number of iterations makes it possible to control the filtering of different scales of motion. To break down the daily mean $PM_{10}$ into individual time components, we assume that the original time series comprises of a long-term trend, seasonal variation, and a short-term component. The short-term component is attributable to weather and short-term fluctuations in precursor emissions, while the seasonal component is a result of changes in the solar angle. The long-term trend results from changes in overall emissions, pollutant transport, climate, policy and/or economics. The long-term trend of the daily mean $PM_{10}$ decreased sharply from $59.6ug/m^3$ in 2002 to $44.6ug/m^3$ in 2015. This suggests that there was a long-term downward trend since 2005. The difference between the unadjusted and meteorologically adjusted long-term $PM_{10}$ is small. Therefore, we can conclude that $PM_{10}$ is unaffected by the meteorological variables (total insolation, daily mean temperature, daily mean relative humidity, daily mean wind speed, and daily mean local atmospheric pressure) in Busan.

• 한국해양환경ㆍ에너지학회지
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• 제10권1호
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• pp.59-65
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• 2007

최근 지구온난화로 인하여 동해안 어족 자원의 감소와 변화, 해저 식생의 아열대화와 같이 동해 연안 생태계의 급격한 변화가 주목되고 있다. 따라서 본 연구에서는 1960년도부터 2005년 사이 지난 45년 동안 매년 월별로 정선해양관측한 수온, 염분, 용존산소 등의 자료를 분석하여 동해 연안에 존재하는 해수 수괴들의 특성과 지구온난화로 인한 수괴별 물리, 화학적 특성 변화를 고찰하였다. 전 수괴의 수온이 지난 45년 동안 상승하였으며, 대마난류계수(약 $1.6^{\circ}C$ 상승)보다 북한한류계수(약 $2.33^{\circ}C$)의 상승폭이 약 1.5배 크며, 기후변화의 직접적인 영향을 받는 대마난류계 표층 수온의 상승폭이 $2.57^{\circ}C$로 기온 변화폭 보다 크다. 이는 육상상태계보다 연안 생태계의 아열대화가 훨씬 빠른 속도로 진행될 수 있음을 암시한다. 반면, 표층수의 염분은 기온상승과 더불어 강수량의 증가 추세로 지난 45년 동안 약 $0.29\%_{\circ}$ 감소하였다. 용존산소농도는 전 수괴에서 감소하는 추세이며, 특히 수온 상승폭이 큰 북한한류계수의 용존산소농도 감소가 년 간 0.021 mg/l로 가장 크다. 동해고유수의 용존산소 감소는 수온 증가와 더불어 동해 내부해양순환 시스템의 변화를 암시하며, 차후, 수온 상승과 함께 연안 수산 생물의 서식환경에 부정적인 요인으로 작용할 것이다.

• 한국공작기계학회논문집
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• 제13권4호
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• pp.87-94
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• 2004

Recently, technical trend in machine tools is focused on enhancing of speed, accuracy and reliability. The high speed usually results in thermal displacement and structural deformation. To minimize the thermal effect, precision machine tools adopt a high precision cooling system. This study proposes a temperature control for an oil cooler system using Pill control with fuzzy logic. In the cooler system, refrigerant flow rate is controlled by rotational speed of a compressor, and outlet oil temperature is selected as the control variable. The fuzzy control rules iteratively correct PID parameters to minimize the error and difference between the outlet temperature and the reference temperature. Here, ambient temperature is used as the reference one. To show the effectiveness of the proposed method, a series of experiments are conducted for an oil cooler system of machine tools, and the results are compared with the ones of a conventional Pill control. The experimental results show that the proposed method has advantages of faster response and smaller overshoot.