• Ecology and Resilient Infrastructure
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• v.2 no.2
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• pp.167-176
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• 2015

The water quality of the Gulpo Stream flowing through Incheon, Bucheon, Seoul, and Kimpo is getting worse due to a slow flow rate and bank constructions by stream channelization as well as an inflow of pollutants from living-sewages and factory-sewages. Besides, a dry stream phenomenon caused by a lack of maintenance water upstream makes a self-purification system worse, and the water quality of the Gulpo Stream is currently at its lowest level. The accumulated sludge of the streambed is mostly formed by the deposition of particle pollutants due to the slow flow rate and an artificially straightened stream channel. This accumulated sludge adsorbs a great quantity of organic materials and heavy metals. Because of the internal contamination possibility by a re-gushing, even after the pollution source is removed, it can cause future water pollution. Without a total examination as previously recommended, it is considered difficult to accomplish practical efficiency. In conclusion, the management of periodic sediment management such as dredging would be necessary in the Gulpo Stream because sediment could be an internal pollution source of stream water under anaerobic conditions.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.10
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• pp.591-598
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• 2017

Power overshoot phenomenon was observed in microbial fuel cells (MFCs) used non-catalyzed graphite felt as cathode. Voltage loss in MFCs was mainly caused by cathode potential loss. Cheap stainless steel scrubber, which has high conductivity, and Pt/C coated graphite felt as cathode were used for overcoming power overshoot and reducing the cathode potential loss in MFCs. The MFCs used stainless steel scrubber showed no power overshoot even slow catholyte flow rate and produced 29% enhanced maximum current density ($23.9A/m^3$) than MFCs used non-catalyzed graphite felt while the power overshoot phenomenon was existed in Pt/C coated MFCs. Increasing catholyte flow rate resulted in disappearing power overshoot of MFCs used non-catalyzed graphite felt. In addition, maximum power density and current density of both MFCs used non-catalyzed graphite felt and stainless steel scrubber increased by 2-3.5 times. Cathode potential losses in all region of activation loss, ohmic loss, and mass transport loss were reduced according to increase of catholyte flow rate. Therefore, stainless steel scrubber has advantages that are economical materials as electrode and prevents power overshoot, leading to enhance electricity generation. In addition, increasing catholyte flux is one of great solution when power overshoot caused by cathodic overpotential is observed in MFCs.

• (The) Research of the performance art and culture
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• no.43
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• pp.325-356
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• 2021

This study is to analyze the current status of transmission and musical characteristics of Naeseo-deulilsori in Changwon, and the purpose of this study is to illuminate the value of deulilsori in Naeseo region, so that it can be continuously inherited. Naeseo-deulsori consists of the Mosimgi-sori, Nonmaegi-sori, and Chingchingi-sori. Mosimgi-sori, which is called when planting a seedling, is divided into 6 types according to the order and situation of work. ① rice planting sound, ② rice planting sound called in the morning, ③ rice planting sound called at lunch time, ④ rice planting sound called after lunch, ⑤ rice planting sound called when it is raining or cloudy, ⑥ rice planting sound called at sunset. Mosimgi-sori, which is called when planting a seedling, is based on Menali-tori, but partly influenced by Yugjabaegi-tori. However, it was typical Menali-tori in the slow The sound of rice planting in the nearby Haman region, but as the speed increased in the fast The sound of rice planting, the characteristics of Menali-tori faded and la↘mi perfect fourth descending frequently appeared. In the sound of rice planting in Goseong, both slow and fast sounds were strongly influenced by Yugjabaegi-tori. In the end, the sound of rice planting in the Naeseo region is less Yugjabaegi-tori than in the Goseong region and stronger than in Haman region. This combination of tori is a musical bargaining phenomenon that appears in the border region, and it can be said to be a geographical and regional characteristic of the Naeseo region. Nonmaegi-sori has the same sound as 'Sangsadeio' throughout the nearby Goseong and Haman regions. However, in Nonmaegi-sori in the Naeseo region, a strong Gyeong-tori tendency is found in the sound received. Looking at the flow of the melody of Nonmaegi-sori, it seems that the pitch has been changed by the intestines in recent years, and this modified melodic form has continued as it is. In order to guarantee locality, this part seems to need to be corrected in the future.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.863-870
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• 2016

We investigated the physical/chemical phenomena that a slow loss of $CO_2$ inventory into sodium after the sodium-$CO_2$ boundary failure in printed circuit heat exchangers (PCHEs), which is considered for the supercritical $CO_2$ Brayton cycle power conversion system of a sodium-cooled fast reactor (SFR). The first phenomenon is plugging inside narrow sodium channels by micro cracks and the other one is damage propagation referred to as wastage combined with the corrosion/erosion effect. Experimental results of plugging shows that sodium flow immediately stopped as $CO_2$ was injected through the nozzle at $300{\sim}400^{\circ}C$ in 3 mmID sodium channels, whereas sodium flow stopped about 60 min after $CO_2$ injection in 5 mmID sodium channels. These results imply that if pressure boundary of sodium-$CO_2$ fails a narrow sodium channel would be plugged by reaction products in a short time whereas a relatively wider sodium channel would be plugged with higher concentration of reaction products. Wastage by the erosion effect of $CO_2$ (200~250 bar) hardly occurred regardless of the kinds of materials (stainless steel 316, Inconel 600, and 9Cr-1Mo steel), temperature ($400{\sim}500^{\circ}C$), or the diameter of the $CO_2$ nozzle (0.2~0.8 mm). Velocities at the $CO_2$ nozzle were specified as Mach 0.4~0.7. Our experimental results are expected to be used for determining the design parameters of PCHEs for their safeties.