• 한국물환경학회지
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• 제36권5호
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• pp.392-404
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• 2020

The focus of this study was to quantify the thermal stratification and analyze the relationship between the stratification structure and the tributaries to understand flow variations in the Paldang Reservoir. The vertical distribution of the temperature and density gradients, and the depth and thickness of the thermocline were quantitatively calculated using a lake physics tool (rLakeAnalyzer) and high-frequency monitoring data. Based on a density gradient of 0.2 kg/㎥/m, the thermocline was formed from mid-May to early-September 2019 and the other periods were weakly stratified or mixed. The thickness of the thermocline was developed until 4.7 m and the depth of the thermocline was formed at a depth of 3 - 6 m at the front of the Paldang Reservoir. During the formation of the thermocline, the Namhangang and Gyeongancheon tributaries with relatively high water temperature (low-density) flowed into the upper layer of the reservoir, and the Bukhangang tributary with low water temperature (high-density) mainly affected the lower layer of the reservoir. This is because the density currents were formed due to the difference in the water temperature of the tributaries. The findings of this study may be used for constructing high-frequency monitoring and quantitative data analyses of reservoirs.

• 대기
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• 제26권2호
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• pp.227-241
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• 2016

This study investigated the cause of the heavy snowfall that occurred in the East Coast of Korea from 6 February to 14 February 2014. The synoptic conditions were analyzed using blocking index, equivalent potential temperature, potential vorticity, maritime temperature difference, temperature advection, and ground convergence. During the case period, a large blocking pattern developed over the Western Pacific causing the flow to be stagnant, and there was a North-South oriented High-to-Low pressure system over the Korean Peninsula because of this arrangement. The case period was divided into three parts based on the synoptic forcing that was responsible for the heavy snowfall; detailed analyses were conducted for the first and last period. In the first period, a heavy snowfall occurred over the entire Korean Peninsula due to strong updrafts from baroclinic instability and a low pressure caused by potential vorticity located at the mid-troposphere. In the lower atmosphere, a North-South oriented High-to-Low pressure system over the Eastern Korea intensified the easterly airflow and created a convergence zone near the ground which strengthened the upslope effect of the Taebaek Mountain range with a cumulative fresh snowfall amount of 41 cm in the East Coast region. In the last period, the cold air nestled in the Maritime Province of Siberia and Manchuria strengthened much more than that in the first half and extended to the East Sea. The temperature difference between the 850 hPa air and the SST was large and convective clouds developed over the sea. The highest cumulative fresh snow amount of 39.7 cm was recorded in the coastal area during this period. During the entire period, vertically oriented equivalent potential temperature showed neutral stability layer that helped the cloud formation and development in the East Coast. The 2014 heavy snowfall case over the East Coast provinces of Korea were due to: 1) stagnation of the system by blocking pattern, 2) the dynamic effect of mid-level potential vorticity of 1.6 PVU, 3) the easterly air flow from North-South oriented High-to-Low pressure system, 4) the existence of vertically oriented neutral stable layer, and 5) the expansion of strong cold air into the East Sea which created a large temperature difference between the air and the ocean.

• 한국산림과학회지
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• 제85권2호
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• pp.309-315
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• 1996

원목재배용(原木裁培用) 표고우량균주(優良菌株)를 육성(育成)하기 위해 균주수집(菌株蒐集)에 의한 선발육종(選拔育種)과 교배계(交配系)를 이용한 교잡육종(交雜育種)을 실시한 결과는 다음과 같다. 1. 국내외(國內外)에서 수집(蒐集)한 35종의 균주에 대한 원목재배를 실시하여 1세대(世代)(5년간(年間)) 버섯수확량(收穫量)이 신갈나무(Quercus mongolica) $1m^3$당(當) 139kg을 보이는 FRI 177 등 3개의 고온성균주(高溫性菌株)와 120kg을 나타낸 FRI 188 등 2개의 중온성균주(中溫性菌株) 및 96kg의 FRI 187 등 저온성(低溫性) 7개 균주를 우량품종(優良品種)으로 선발하였다. 2. Di-mon교배법(交配法)을 이용하여 제조한 교잡균주중(交雜菌株中) 실내검정(室內檢定)을 통하여 독립계통(獨立系統)으로 확인된 12균주(菌株)에 대하여 원목재배(原木栽培)를 실시하여 1세대(世代) 버섯수확량이 원목(原木) $1m^3$당(當) 108kg에 달하는 고온성균주(高溫性菌株) FRI 182와 103kg을 보이는 저온성균주(低溫性菌株) FRI 184 등 2개를 우량종균(優良種菌)으로 선발하였다. 3. 고온성, 중온성 및 저온성 등 온도형(溫度型)에 따른 생산성(生産性)의 유의차(有意差)는 없었으나, 계통간(系統間)의 생산성차이(生産性差異)는 인정(認定)되었다. 한편 원목재배(原木栽培)와 톱밥재배간(栽培間)의 생산성에는 어떤 상관관계(相關關係)도 보이지 않았다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권10호
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• pp.511-520
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• 2006

Recently, more attention has been paid to the development of high-speed permanent magnet (PM) synchronous motors, since they are conductive to high efficiency, high power density, small size, and low weight. In high-speed PM machines, core loss and windage loss form a larger proportion of the total losses than usual in conventional mid- or low speed machines. This article deals with the analysis on the core loss and windage loss in PM synchronous motor for high-speed application. Using the data information from a manufacturer and non-linear curve fitting, this paper investigates the magnetic behavior and its core losses in the stator core using the electrical steels. And, the windage loss is calculated according to the variation of the rotational speed, motor inner pressure and temperature.

• 대기
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• 제19권1호
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• pp.67-78
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• 2009

A strong negative correlation has been detected between the North Pacific Oscillation Index (NPI) and the Effective Drought Index (EDI) in May over Korea. In May of positive NPI year, anomalous patterns caused a drought in Korea as follows: the anomalous south-low, north-high low-level pressure patterns in the northeast and southeast of Korea have strengthened the anomalous northerlies to Korea. In addition, these anomalous northerlies have prevented western North Pacific (WNP) high from moving northward. As a result, anomalous descending flows have strengthened in the mid-latitude region in East Asia. In the WNP, the anomalous south-high, north-low sea surface temperature (SST) has been widely distributed, which has strengthened anomalous south-low, north-high low-level pressure patterns. These anomalous characteristics of pressure and SST patterns observed in May of positive NPI years have already been detected in previous winter (December-February) and early spring (March, April). In addition, the anomalous negative sea ice concentration in the North Pacific during two seasons has strengthened the anomalous anticyclonic circulation in the same region and in turn made a contribution to formation of anomalous south-low, north-high pressure patterns in May.

• KIEAE Journal
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• 제15권4호
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• pp.29-35
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• 2015

Purpose: Double skin facade is a representative advantageous passive technology of building skin in the aspect of energy saving and environment improvement, reduces heat loss with buffer space in winter season and enhances indoor air and comfort of residents by activating natural ventilation in mid-season. However, in summer season, temperature increase in the intermediate space due to solar energy from exterior transparent skin could be a potential problem; also, relatively weak buoyancy of air caused by low density difference between double-skin facade could increase cooling load as air of intermediate space in high temperature hangs. However, proof data is insufficient to objectify such phenomenon. Method: In this study, researchers surveyed air temperature of intermediate space and airflow and diagnosed its cause targeting on applied multistory facade in the building which gives thermal uncomfort to residents. Also, the researchers produced Solar-air heat transfer coefficient meter, measured thermal boundary condition of double-skin facade, and presented the result of measurement as an objectified verification material regarding overheating phenomenon in the intermediate space of double-skin facade in summer season. Result: Inefficient condition was verified that total heat increases and overheating due to insufficient natural ventilation in multistory facade. In addition, logic behind preceding research was objectified and verified regarding high temperature phenomenon in the intermediate space which could increase cooling load in summer season.

• Journal of Plant Biology
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• 제29권2호
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• pp.117-127
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• 1986

Phytoplankton community was investigated at the Paldang Dam Reservoir in the Mid-Han River by it's depth, in spring and summer known as the period of phytoplankton's blooming. It was only in summer that phytoplankton bloomed at the investigated area. 128 kinds of phytoplankton were identified and of them, diatoms were abundunt in spring but cyanophyta and chlorophyta were in summer. Because some species with high pollution index were observed in summer, it could be proved that the investigated area was polluted especially in summer. In spring shown the circulation period by vertical distribution pattern of chlorophyll-a and isothermal distribution pattern of water temperature, maximum value of phytoplankton standing crops appeared at the upper layer, except for surface layer. In summer shown the circulation period after the stagnation period by vertical distribution pattern of chlorophyll-a and immediate destruction after stratification of water temperature, maximum value of phytoplankton standing crops appeared at the lower layer. the layer at which the maximum value of chlorophyll-a appeared also accorded with that of phytoplankton standing crops. So, it could be approved that there existed a close relationship among phytoplankton standing crops, chlorophyll-a, and water temperature.

• 한국지역지리학회지
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• 제2권2호
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• pp.103-111
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• 1996

본 연구는 지표상의 기상 요소의 분포 특성이 이압계(氣壓系)뿐만 아니라 기압계를 지배하는 상충대기의 상층대기의 환류(還流)의 특성과도 밀접한 관계가 있음을 기준하여, 우리나라에 있어서 지난 30년간($1965{\sim}1994$) 28개 관측지점을 대상으로 동계 기온을 표준편차(標準偏差)에 의해 분류하였으며, 여기서 나타난 이상한(異常寒) 난월(暖月) 중 대표적인 1992년(이상난한동월(異常暖寒冬月), EH)과 1984년(이상한동월(異常寒冬月), EL)의 1월에 있어 500hPa면 고도 특성 및 몇 가지의 분석을 통하여 한 난동월의 특징을 살펴보았다. 난동월(暖冬月)에서는 강수량이 많았다. 우리나라의 경우 500hPa면은 난동월(暖冬月)에는 trough를 한동월(寒冬月)에는 남북유형(南北類型)유형을 나타내고 있다. 순환의 특징에서 우리나라 부근의 500hPa면 고도는 난동월년이 1984년에 비해 높았고, 동서지수에 있어서도 난동월이 높았다. 이외에도 환류형과 환류파수형에서는 난동월이 M형의 3파수, 1984년이 5형의 3파수(波數)로 나타나 단지 파수형(波數型)만으로는 한(寒) 난동월(暖冬月)을 구분하기가 어려운 것으로 밝혀지고 있다. 지상 기압에 있어서는 한동월이 난동월에 비해 서고동저(西高東底)의 기압배치가 강하게 나타나고 있다. 향후 동계 전월에 관해 850hPa면의 분석 등을 추가한 좀 더 포괄적인 연구를 하고자 한다.

• 생태와환경
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• 제35권1호통권97호
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• pp.21-27
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• 2002

낙동강 중${\cdot}$하류수역에서 1997년 1월부터 1999년 12월사이 3년간의 수온, Chl. a, 유량변동을 모니터링하였다. 유량별 Chl. a 지점별 분포는 강수량에 따른 하천유량의 증감으로 인해 Chl. a 최대농도지점이 상${\cdot}$하류로 이동하였고, 수온별 Chl. a 의 최대농도 분포 역시 수온변화에 따라 상${\cdot}$하류로 이동하여 하천유속과 수온이식물플랑크톤 최대현존량(Chl. a)지점 형성에 큰 영향을 미치는 것으로 나타났다. 하천유하시간을 이용하여 식물플랑크톤 최대성장시간을 수온별로 구분한 결과 저수온시에는 평균적으로 380시간, 상온시는 240시간, 고수온시는 120시간 정도에서 최고농도에 이르는 것으로 나타났다. 낙동강 중 ${\cdot}$하류수역에서 식물플랑크톤 농도 예측을 위한 수온별 성장 및 사멸계수는 $10{\circ}^C$ 이하에서는 0.201과 $-0.012\; day^{-1}$, $10{\sim}20{\circ}^C$에서는 0.254와 $-0.128\;day^{-1}$ 그리고 $20{\circ}^C$ 이상에서는 0.289와 $-0.193\;day^{-1}$로 각각 산정되었다. 이러한 결과로부터 영양염 공급이 풍부한 낙동강 중 ${\cdot}$ 하류수계에서는 식물플랑크톤의 최대농도 지점이 수온과 유속에 크게 영향을 받으며, 따라서 상수원과 같은 특정지점에서 식물플랑크톤의 최대현존량이 형성되는 것을 막기 위해서는 댐 방류량 조절을 통해 최대현존량지점을 상 ${\cdot}$ 하류지역으로 이동시킴으로서 식물플랑크톤 농도를 줄이는 효과를 얻을 수 있을 것으로 추정된다.

• 한국작물학회지
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• 제62권3호
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• pp.166-171
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• 2017

본 실험은 적미의 재배에 있어서 고품질 고수량을 위한 적정이앙시기를 구명하기 위해 네 품종의 적미를 재료로 2015~2016년에 밀양에서 실시하였다. 1. 수량구성요소 중 이앙시기 변화에 따라 가장 크게 달라지는 요인은 등숙률이었고 6월 20일 이후 이앙하면 등숙률이 낮아져 현미수량이 하락하였다. 2. 6월 20일에 이앙했을 때 폴리페놀 함량과 현미수량을 종합한 폴리페놀 생산량이 2,341~3,349 g/10a로 가장 높았다. 3. 출수 후 30일간 평균온도가 낮을 수록 폴리페놀 함량은 증가하였으나 일정 수준 이하로 온도가 떨어지면 현미수량이 감소하였기 때문에 $22{\sim}23^{\circ}C$ 정도가 고품질 고수량 적미를 생산하기에 가장 적정한 온도였다. 4. 출수 후 30일간 평균온도가 $22{\sim}23^{\circ}C$가 되는 시점을 최적 출수기로 하고 출수소요적산온도를 $1,660^{\circ}C$로 하여 계산한 최적 이앙시기는 밀양시가 6월 18일~6월 24일 이었다. 경상남도 지역은 6월 중순에서 7월 초순, 경상북도 지역은 6월 초순에서 6월 중하순이 최적 이앙기였다.