• Journal of Korean Society on Water Environment
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• v.36 no.5
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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.

• Atmosphere
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• v.26 no.2
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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.

• Journal of Korean Society of Forest Science
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• v.85 no.2
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• pp.309-315
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• 1996

Selective breeding and hybridization were attempted to improve shiitake(Lentinus edodes) strains for bed-log cultivation, and the results obtained are as follows. 1. Thirty five strains collected in Korea and abroad were cultivated for one generation(five years) and fruit body yields were estimated by the amounts produced from $1m^3$ of oak tree(Quercus mongolica) logs. Thus, three high-temperature type strains including FRI 177 showing productivity of $139kg/m^3log$, two mid-temperature type strains including FRI 188 of $120kg/m^3log$, and seven low-temperature type strains including FRI 187 of $96kg/m^3log$ were selected as superior strains. 2. Twelve hybrid strains confirmed as independent strains through indoor-test with hybrid strains made by Di-mon mating method were cultivated for five years(one generation). Among them, FRI 182 and FRI 184 were turned out to be superior strains. FRI 182 of high-temperature type showed the yield of 108kg per $1m^3logs$ and FRI 184 of low-temperature type produced $103kg/m^3log$. 3. There were no significant differences in productivity among high-, mid- and low-temperature types, but some differences appeared among strain groups. The correlation was not shown in productivities between bed-log and sawdust cultivations.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.10
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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.

• Atmosphere
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• v.19 no.1
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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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• v.15 no.4
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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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• v.29 no.2
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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.

• Journal of the Korean association of regional geographers
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• v.2 no.2
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• pp.103-111
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• 1996

I followed the results of Lee and Min(1996) for classification of the months of cold and warm winter. The winter of 1992 and 1984 recorded extraordinary cold and warm. Study of the Synoptic Climatology on the January's cold and warm winter is below: (1) Climatology's characteristic. Temperature of extremely high temperature month is higher compared with extremely low temperature month. Also precipitation is more than over low temperature month compared with extremely high temperature month. (2) In circulation of 500hPa surface. (1) Extremely high temperature month At 500hPa, negative geopotential height anomalies in high latitude, three trough developed over eastern Canada. In midlatitude, a deep trough persisted in the central North Pacific and conspicuous positive height anomalies showed over northwestern Europe, Where a blocking anticyclone developed. It had been warmer than normal since last year in Korea due mainly to positive height anomalies stretched from central Siberia (2) Extremely low temperature month Appeared the strong meridional circulation and negative height anomalies showed from Far East to the Mid-Pacific and appeared ridge in the west of the North America and Atlantic. Alutien Low shows negative deviation during 1984. In northern hemisphere shows negative deviation. Therefore, we can show that the surface pressure distribution and height distribution of 500hPa level are closely connected with each other as parts of general circulation. (3) The characteristics of the general circulation pattern of the 500hPa (1) Extremely high temperature month is high than extremely low temperature month1984 in Zonal index (2) The majority type is S type in 500hPa level circulation of extremely high temperature month but extremely high temperature month is M type (3) The wave number in 500hPa all shows 3 wave. So can not distinguished by only predominant wave number pattern.

• Korean Journal of Ecology and Environment
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• v.35 no.1 s.97
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• pp.21-27
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• 2002

The frequent occurrence of excessive phytoplankton populations in the downstream Nakdong River has been an important water quality problem in recent years. The limnological survey of the Nakdong River was conducted from January 1997 to December 1999 on once or twice per month. A typical phenomenon of eutrophication appears with the persistent algal bloom due to high nutrients in the mid-lower part of the river. This study showed that the point at which Chl. a concentration reaches maximum was affected by the water temperature and the flow rate. For example, Chl. a concentration reached maximum after around 380, 240 and 120 hours which were estimated from the time of flow at low (${\le}10^{\circ}C$), mean ($10{\sim}20^{\circ}C$) and high (${\ge}20^{\circ}C$) water temperature conditions, respectively. It was estimated that increase coefficients of phytoplankton (Chl. a) on the water temperature are 0.201, 0.254 and $0.289\;day^{-1}$, on the contrary, decrease coefficients are -0.012, -0.128 and $-0.193\;day^{-1}$ in low, mean and high water temperature. Therefore, to prevent formation of Chl. a maximum concentration in the specific water resource, it is necessary to increase the discharge of dam as well as to decrease.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.62 no.3
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• pp.166-171
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• 2017

For high-quality colored rice production, the cultivation environment is a critical factor. The major environmental factor is temperature, which includes the accumulated and average temperature during vegetative and reproductive stages. Generally, during the cultivation period, the temperature can be controlled by shifting the transplanting date. This study was carried out to determine the optimum transplanting date for high-quality red-colored rice production. Four red-colored rice varieties (Jeokjinju, Jeokjinjuchal, Hongjinju, and Gunganghongmi) were used as test materials. The transplanting dates were May 20 and June 5, 20, and 30 in 2015~2016. The most variable factor controlled by the transplanting date was the grain filling rate. The varieties transplanted on June 30 showed low yields owing to the decrease in the grain filling rate. In contrast, the polyphenol content increased with increasing delay in the transplanting date. Collectively, these two results indicate that the optimum transplanting date was June 20. The average temperature for 30 days after the heading date (30DAH) highly affected the polyphenol content. A lower temperature during the 30DAH induced higher polyphenol contents but also caused low yield. The optimum 30DAH temperature for obtaining a higher yield and polyphenol content was $22{\sim}23^{\circ}C$. Using the average 30DAH and accumulated temperatures, the optimum transplanting date was calculated as June 18 to 24 in Miryang region. The optimum transplanting date of Kyeungsangnamdo region was approximately mid-June to early July, and that of Kyeungsangbukdo region was approximately early to mid-June.