• Korean Journal of Environmental Agriculture
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• v.39 no.4
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• pp.334-342
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• 2020

BACKGROUND: To quantify carbon exchange at agricultural ecosystems in South Korea, net ecosystem exchange (NEE) at three croplands including a rice paddy, a bean field and an apple orchard was measured on the basis of the eddy covariance technique. METHODS AND RESULTS: NEE of CO2 during the growing season (June to September) averaged over the recent two years (2018-2019) was the highest at rice (-4.49 g C m-2 day-1), followed by the bean (-3.12 g C m-2 day-1) and apple (-0.93 g C m-2 day-1). The diurnal variation of NEE was the highest at the rice, while the seasonal variation of it was the highest at the bean than others. In terms of yearly variation, the rice paddy and the bean field absorbed more CO2 in 2019 compared to 2018, while the apple orchard absorbed less. CONCLUSION: Our results confirmed that these croplands consistently acted as net sinks for CO2 during the growing season because an amount of CO2 uptake from photosynthesis was larger than one of its emissions from respiration. The quantification of net CO2 exchange at agricultural ecosystems may help to better understand the local carbon cycle over various time scales.

• Journal of Korean Society on Water Environment
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• v.27 no.3
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• pp.322-328
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• 2011

This study was performed to investigate the characteristics of nutrient removal of municipal wastewater in the membrane bioreactor system with the different types of membrane. Membrane bioreactor consists of three reactors such as two intermittent anaerobic and the submerged membrane aerobic reactor with flat sheet and hollow fiber membrane, respectively. The removal efficiencies of $COD_{cr}$, BOD, SS, TN and TP on the flat sheet membrane bioreactor were 94.3%, 99.0%, 99.9%, 70.3% and 63.1%, respectively. In addition, The removal efficiencies of $COD_{cr}$, BOD, SS, TN and TP on the hollow fiber membrane bioreactor were 94.0%, 99.3%, 99.9%, 69.9% and 66.9%, respectively. The estimated true biomass yield, specific denitrification rate (SDNR), specific nitrification rate (SNR) and phosphorus removal content on the flat sheet membrane bioreactor were $0.33kgVSS/kgBOD{\cdot}d$, $0.043mgNO_3-N/mgVSS{\cdot}d$, $0.031mgNH_4-N/mgVSS{\cdot}d$, and 0.144 kgP/d, respectively. In addition, the estimated true biomass yield, specific denitrification rate (SDNR), specific nitrification rate (SNR) and phosphorus removal content on the hollow fiber membrane bioreactor were $0.30kgVSS/kgBOD{\cdot}d$, $0.067mgNO_3-N/mgVSS{\cdot}d$, $0.028mgNH_4-N/mgVSS{\cdot}d$, and 0.121 kgP/d, respectively. There was little difference between the flat sheet and hollow fiber on the nutrient removal efficiencies except SNR and SDNR. These differences between them were caused by the air demand to prevent the membrane fouling. The flux and oxygen demand for air scouring were $19.0L/m^2/hr$ and $2.28m^3/min$ for the flat sheet membrane, and $20.7L/m^2/hr$ and $1.77m^3/min$ for the hollow fiber membrane on an average.

• Journal of Korean Society of Water Science and Technology
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• v.26 no.6
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• pp.99-107
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• 2018

This research has developed a high temperature steam cleaning technology using a ceramic membrane with durability against temperature and pressure conditions. In steam cleaning, steam of $120^{\circ}C$ is injected into the ceramic membrane to induce pyrolysis by the endothermic reaction to remove fouling from the membrane. The water quality of raw water was adjusted to turbidity 10, 25 NTU and DOC 2.5 mg/L, and the membrane was uniformly fouled by constant pressure operation at 100, 200, and 300 kPa. Physical backwashing was performed with water and air at a pressure of 500 kPa and steam at $120^{\circ}C$ was injected for 0 to 5 minutes. As the turbidity concentration and the operating pressure increased, the flux decreased by 0.7 to 14.4%. It is confirmed that 10.7 to 53.8% recovery is possible than physical cleaning at the injection of steam for 3 minutes, so it is considered that the steam cleaning of the ceramic membrane is effective. Compared with CEB after NaOCl (300 mg/L) filtration at 25 NTU and 300 kPa of turbidity, the steam cleaning result for 3 minutes was similar to 46.7% of CEB for 3 hours. It has been confirmed that steam cleaning is suitable for a ceramic membrane having excellent heat resistance against high temperature. It was considered to have better cleaning efficiency as compared with general physical backwashing.

• (The) Research of the performance art and culture
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• no.35
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• pp.287-338
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• 2017

Gojong' Birth Anniversary Memorial Banquet in the 1910s was forced to be performed differently from the performance style in Joseon Dynasty period that featured a harmonious majestic beauty of etiquette music. The banquet was separated into three different sessions of ceremony, luncheon and performance', which clearly revealed a distinctive pattern of etiquette music. The performance was accompanied by the dinner party or was lightly implemented as part of evening entertainment. With the use of the term entertainment, the performances belonging to this category fell into nothing but something to enjoy, amusement, fun and play. The contents of such performances were not closely woven into the fabric of the entire banquet but were individualized and scattered in a way of putting the performances in a state of flux in line with the circumstances. Therefore, it became increasingly hard to expect a high degree of completion and solid structure of performances. The items of performance included western music, popular vocal music, popular instrumental music, magic, and film, which were not played in traditional court banquet in the presence of Gojong rather than traditional music and dance performed in court. In other words, the court performance could not maintain its traditional heritage but was transformed into a mixture of popular performance and new forms of art. It was driven by the Japanese imperialism toward the atmosphere of entertainment in oblivion of tradition but not toward the external extension of court performances.

• (The)Study of the Eastern Classic
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• no.34
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• pp.339-362
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• 2009

If we try to define the concept of beauty in the large sense, as Kant and Chaung-tzu all agree, It can not be fixed in the one sense, but whose connotation and denotation should be extended infinitely. In this sense, I would like to say that the beauty is liberty. Aesthetics of Kant is oriented toward subjective and reflexive dimension, while that of Chuang-tzu is oriented toward natural and practical one. The difference between aesthetics of the two philosophers begins from their philosophical methodology. If the transcendental methode which is proper to Kant's philosophy prefers to discriminate and devide everything especially from dichotomic viewpoint by langage. But Chuang-tzu' methode called Za-Mang criticizes such a dichotomic division and langage itself. Even so, the two in the long run agree as to the foundation of beauty. But Kant's liberty is one of will or transcendental, meanwhile that of Chuang-tzu is based on recognize the fact that we are all production of nature. according to Chuang-tzu, in the great beginning, there was non-being. It had neither being nor name. The One originates from it. When things obtain it and come into existence. As the One, Tao is in the excrement and urine. Everything is under the constant flux. All species have originative or moving power. Although the universe is vast, its transformation is uniform. Because all things are one. Vacuity, tranquillity, mellowness, quietness, and taking no action characterize the things of universe at peace and represent the ultimate of Tao and virtue. The material was transformed to be form, form was transformed to become life, and now life has transformed to become death. A basic principle of Chuang-tzu's art is expressed in the phrase "taking off clothes and squatting down bare-backed". The key of Chuang-tzu's aesthetics is to dedicate to the expression of inner spirit instead of physical verisimilitude, and painting should be a spontaneous and instantaneous flow of the brush. Kant's concepts such as "disinterested" and "purposiveness of nature" seem to imply in the long run the unification of nature and human being which is fundament to Chuang-tzu's aesthetics.

• Journal of the Korean earth science society
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• v.41 no.6
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• pp.599-616
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• 2020

Sea-surface temperature (SST) is one of the most important oceanic variables for understanding air-sea interactions, heat flux variations, and oceanic circulation in the global ocean. Extremely low SSTs from 0℃ down to -2℃ should be more important than other normal temperatures because of their notable roles in inducing and regulating global climate and environmental changes. To understand the temporal and spatial variability of such extremely low SSTs in the global ocean, the long-term SST climatology was calculated using the daily SST database of satellites observed for the period from 1982 to 2018. In addition, the locations of regions with extremely low surface temperatures of less than 0℃ and monthly variations of isothermal lines of 0℃ were investigated using World Ocean Atlas (WOA) climatology based on in-situ oceanic measurements. As a result, extremely low temperatures occupied considerable areas in polar regions such as the Arctic Ocean and Antarctic Ocean, and marginal seas at high latitudes. Six earth science textbooks were analyzed to investigate how these extremely low temperatures were visualized. In most textbooks, illustrations of SSTs began not from extremely low temperatures below 0℃ but from a relatively high temperature of 0℃ or higher, which prevented students from understanding of concepts and roles of the low SSTs. As data visualization is one of the key elements of data literacy, illustrations of the textbooks should be improved to ensure that SST data are adequately visualized in the textbooks. This study emphasized that oceanic literacy and data literacy could be cultivated and strengthened simultaneously through visualizations of oceanic big data by using satellite SST data and oceanic in-situ measurements.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.87-96
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• 2020

To use a hydraulic structure effectively, the velocity of a river should be known in detail. In reality, velocity measurements are not conducted sufficiently because of their high cost. The formulae to yield the flux and velocity of the river are commonly called the Manning and Chezy formulae, which are empirical equations applied to uniform flow. This study is based on Chiu (1987)'s paper using entropy theory to solve the limits of the existing velocity formula and distribution and suggests the velocity and distance formula derived from information entropy. The data of a channel having records of a spot's velocity was used to verify the derived formula's utility and showed R2 values of distance and velocity of 0.9993 and 0.8051~0.9483, respectively. The travel distance and velocity of a moving spot following the streamflow were calculated using some flow information, which solves the difficulty in frequent flood measurements when it is needed. This can be used to make a longitudinal section of a river composed of a horizontal distance and elevation. Moreover, GIS makes it possible to obtain accurate information, such as the characteristics of a river. The connection with flow information and GIS model can be used as alarming and expecting flood systems.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.308-320
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• 2021

An integrated sediment management approach that includes the recovery of the amount of declined sediment supply is effective as a fundamental solution to coastal erosion. During planning, it is essential to analyze the transfer mechanism of the sediments generated from estuaries (the junction between a river and sea) to assess the amount and rate of sediment discharge (from the river to sea) supplied back to the coast. Although numerical models that interpret the tidal sand bar flushing process during flooding have been studied, thus far, there has been no study focusing on the formation and development processes of tidal sand bars. Therefore, this study aims to construct wave deformation, flow regime calculation, and topographic change analysis models to assess the amount of recovered sediment discharge and reproduce the tidal sand bar formation process through numerical analysis for integrated littoral drift management. The tidal sand bar formation process was simulated, and the wave energy and duration of action concepts were implemented to predict the long-term littoral movement. The river flux and wave conditions during winter when tidal sand bars dominantly develop were considered as the external force conditions required for calculation. The initial condition of the topographic data directly after the Maeupcheon tidal sand bar flushing during flooding was set as the initial topography. Consequently, the tidal sand bar formation and development due to nearshore currents dependent on the incident wave direction were reproduced. Approximately 66 h after the initial topography, a sand bar formation was observed at the Maengbang estuary.

• Nuclear Engineering and Technology
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• v.54 no.8
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• pp.3117-3129
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• 2022

Deeply understanding the phase change of thin liquid sodium film inside wick pore is very important for further studying high-temperature sodium heat pipe's heat transfer. For the first time, the evaporation and condensation of thin liquid sodium film are investigated by the Lennard-Jones potential of molecular dynamics. Based on the startup and normal operation of the sodium heat pipe, three different cases are simulated. First, the equilibrium is achieved and the Mass Accommodation Coefficients of the three cases are 0.3886, 0.2119, 0.2615 respectively. Secondly, the non-equilibrium is built. The change of liquid film thickness, the number of gas atoms, the net evaporation flux (J_net), the heat transfer coefficient (h) at the liquid-gas interface are acquired. Results indicate that the magnitude of the J_net and the h increase with the basic equilibrium temperature. In 520-600 K (the startup of the heat pipe), the h has approached 5-6 W m^-2 K^-1 while liquid film thickness is in 11-13 nm. The fact shows that during the initial startup of the sodium heat pipe, the thermal resistance at the liquid-gas interface can't be negligible. This work is the complement and extension for macroscopic investigation of heat transfer inside sodium heat pipe. It can provide a reference for further numerical simulation and optimal design of the sodium heat pipe in the future.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.91-97
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• 2022

The wettability and rheological properties of solder paste with the size of the solder powder were evaluated. To formulate the solder paste, three types of solder powder were used: T4 (20~28 ㎛), T5 (15~25 ㎛), and T6 (5~15 ㎛). The viscosities of the T4, T5, and T6 solder pastes at 10 RPM were 155, 263, and 418 Pa·s, respectively. After 7 days, the viscosity of the T4 solder paste slightly increased by 2.6% and that of T5 was increased by 20.6%. The viscosity of the T6 solder paste after 7 days could not be measured due to high viscosity. The viscosity variation with solder particle size also affected on the printability of the solder. In the case of the T4 solder paste, printability, slump, bridging, and soldering properties were excellent. On the other hand, T5 showed slight dewetting and solder ball defects. Especially, T6, which the smallest powder size, showed poor printability and dewetting at the edge of solder.