• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.1-6
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• 2019

The objective of this study was to investigate performance characteristics of thermal management system(TMS) in a fuel cell electric vehicle with 100kW Fuel Cell(FC) system. In order to build up analytic modelling for TMS, each component was installed and tested under various operating conditions, such as water pump, radiator, 3-Way valve, COD heater, and FC stack etc. and as the results of them, correlations reflecting component's characteristics with flow rate, air velocity were developed. Developed analytic modelling was carried out under various operating conditions on the road. To verify modelling's accuracy, after prediction for optimum coolant flow rate was fulfilled under certain operating conditions, such as FC system, water pump speed, opening of 3-way valve, and pipe resistance, analytic and experimental values were compared and good agreement was shown. In order to predict cold-start operating performance for analytic modelling, coolant temperature variation was analyzed with $-20^{\circ}C$ ambient temperature and duration was predicted to rise in optimum temperature for FC. Because there is appropriate temperature difference between inlet and outlet of FC stack to operate FC system properly, related analysis was performed with respect to power consumption for TMS and heat rejection rate and performance map was depicted along with FC operating conditions.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.45-57
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• 2019

The resident characteristics of land-based pollutants were analyzed to manage the pollution sources affecting Suyeong Bay. These characteristics were analyzed using a hydrodynamic model and particle tracking model. Pollutants were represented by particles, and the amount of particles and pollutants was represented proportional. The resident characteristics were analyzed by comparing the amount of pollutant load, resident pollutants, and the ratio of resident pollutants remaining in the bay relative to the incoming load for each the of pollution sources. The order of the pollution sources was as follows, according to the amount of resident pollutants at Suyeong Bay. the Suyeong WasteWater Treatment Plant(WWTP), Nambu WWTP, Suyeong river and so on. The amount of resident pollutants was smaller for small load farther away from the interior of bay. Nambu WWTP had the greatest load among the pollution sources, but it showed the smallest ratio of pollutants remaining in the bay relative to incoming load among the pollution points. The result indicates that pollutants affect sea areas differently according to the characteristics each area and the topographic characteristics of pollution sources.

• Journal of Environmental Impact Assessment
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• v.28 no.1
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• pp.23-34
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• 2019

Global warming becomes a serious issue that poses subsidiary issues like a sea level rise or a capricious climate over the world. Because of severe heat-wave of the summer in Korea in 2016, a big attention has been focused on urban heat island since then. Not just about heat-wave itself, many researches have been concentrated on how to adapt in this trendy warming climate and weather in a small scope. A big part of existing studies is mitigating "Urban Heat Island effect" and that is because of huge impervious surface in urban area where highly populated areas do diverse activities. It is a serious problem that this thermal context has a high possibility causing mortality by heat vulnerability. However, there have been many articles of a green infrastructures' cooling impact in summer. This research pays attention to measure cooling effect of a street planting considering urban canyon and type of green infrastructures in neighborhood scale. This quantitative approach was proceeded by ENVI-met simulation with a spatial scope of a commercial block in Seoul, Korea. We found the dense double-row planting is more sensitive to change in temperature than that of the single-row. Among the double-row planting scenarios, shrubs which have narrow space between the plant and the land surface were found to store heat inside during the daytime and prevent emitting heat so as to have a higher temperature at night. The quantifying an amount of vegetated spaces' cooling effect research is expected to contribute to a study of the cost and benefit for the planting scenarios' assessment in the future.

• Clean Technology
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• v.27 no.3
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• pp.269-274
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• 2021

Bioenergy is generally considered to be one of the options for pursuing carbon neutrality. However, for a period of time, combustion of harvested plant biomass inevitably causes more carbon dioxide in the atmosphere than combustion of fossil fuels. This paper proposes a method that predicts and minimizes the total amount and payback period of this carbon debt. As a case study, a carbon cycle impact assessment was performed for immediate switching of the currently used fossil fuels to biomass. This work points out a fundamental vulnerability in the concept of carbon neutrality. As an action plan for the sustainability of bioenergy, formulas for afforestation proportional to the decrease in the forest area and surplus harvest proportional to the increase in the forest mass are proposed. The results of optimization indicate that the carbon debt payback period is about 70 years, and the carbon dioxide in the atmosphere increases by more than 50% at a maximum and 3% at a steady state. These are theoretically predicted best results, which are expected to be worse in reality. Therefore, biomass is not truly carbon neutral, and it is inappropriate as an energy source alternative to fossil fuels. The method proposed in this work is expected to be able to contribute to the approach to carbon neutrality by minimizing present and future carbon debt of the bioenergy that is already in use.

• Korean Journal of Veterinary Research
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• v.60 no.4
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• pp.215-223
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• 2020

Sasa (S.) quelpaertensis Nakai (Korean name, Jeju-Joritdae), which has anti-oxidative and anti-inflammatory activities, is a type of bamboo grass distributed widely in Jeju Island, Korea. S. quelpaertensis leaves are used for therapeutic purposes in traditional Korean medicine. This study examined the hepatoprotective effects of the S. quelpaertensis ethyl acetate fraction (SQEA) in a mouse model to mimic alcoholic liver damage. The mice were administered orally with 30% alcohol (5 g/kg) once per day with or without SQEA treatments (100 and 200 mg/kg) for 14 days consecutively. Alcohol consumption increased the serum alcohol content and histopathological changes but reduced the liver weight. Moreover, the livers of the alcohol group exhibited the accumulation of malondialdehyde and cytochrome P450 2E1 (CYP2E1), and lipid droplet coating protein perilipin-2. On the other hand, SQEA dose-dependently attenuated the alcohol-induced serum ethanol content and liver histopathological changes but increased the liver weight. Moreover, SQEA attenuated the level of CYP2E1 and inhibited alcohol-induced lipogenesis in the liver via decreased perilipin-2 expression. These results suggest that SQEA can provide a potent way to reduce the liver damage caused by alcohol consumption.

• Journal of the Korea Organic Resources Recycling Association
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• v.28 no.4
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• pp.5-13
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• 2020

This study was conducted to evaluate effects of compressed expansion rice hull (CERH) as bulking agent on physicochemical properties of composting poultry manure (PM) and of its fertilization on lettuce and pak choi growth. Treatments were designed as follows; sawdust treatment (90% PM + 10% sawdust; SP), peatmoss treatment (90% PM + 10% peatmoss; PP), and CERH treatments [PCR1 (90% PM + 10% CERH 1.3 mm) and PCR2 (90% PM + 10% CERH 3.0 mm)]. Physicochemical properties such as temperature, water content, pH, and total carbon of composted poultry piles for 31 days were unaffected by various bulking agents. However, total nitrogen content in compost pile was higher in PP and PCR1 than that of SP or PCR2. After composting for 31 days, content ranges of N, P2O5, and K2O in the composting PM piles were 19.1~19.7%, 47.6~51.6%, 2.76~3.65%, and 2.53~2.90%, respectively. As compared to SP treatment, dry weight of lettuce treated with PP and PCR1 increased by more than 10%, but only in PP for pak choi. These results indicated that CERH 1.3 could be used as bulking agents for composting PM on behalf of peatmoss or sawdust.

• Ecology and Resilient Infrastructure
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• v.7 no.4
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• pp.374-387
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• 2020

This study was conducted to provide basic data for monitoring the trend of ecosystem change and establishing management plans for wetland protection areas by understanding the status of naturalized plants. In 21 wetland protection areas, 129 taxa, including 10 invasive alien species, were recorded. The naturalized plants appeared mostly as 71 taxa in the Chimsil wetland and were not observed in the Moojechineup and Sumeunmulbaengdui wetlands. Among the naturalized plants, 42 taxa (32.6%) originated from North America. Annual and biennial plants accounted for 68.2% (88 taxa). The frequencies of occurrence of naturalized plants growing in dry secondary grasses such as Erigeron annuus and Trifolium repens were high, and clonal plants that propagated by making stolons and struck roots accounted for 19.4% (25 taxa). The naturalized and urbanization indices showed positive correlations with location factors such as wetland, agricultural land, and used area. However, a negative correlation was found between altitude and forest. Therefore, a management plan that synthetically considers the occurrence frequency and growth characteristics of naturalized plants as well as the locational characteristics of wetland protection areas is required.

• Journal of the Korean GEO-environmental Society
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• v.12 no.5
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• pp.43-50
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• 2011

As a result of population growth and economic growth, household and industrial wastes continue to rapidly increase every year. Especially, sewage sludge produced at final stage is increasing with the constant construction and putting in good order of the sewage plant. In addition to the government's prohibition for filling up the sludge, it became more and more difficult to discharge wastes to the sea as London Dumping Convention '96 came into effect. And sewage sludge and the livestock wastes are expected to be thoroughly prohibited from discharging to the sea from 2012. So we need desperately economical and useful alternatives to compact and reuse these wastes. The purpose of this study is to evaluate the utilization of solidified sludge-soil mixture as an enhancement and covering material. To determine the proper mixed ratio of solidified sludge, this study conducted basic physical properties tests, compaction tests, uniaxial compression tests, and permeability test. It was found that the higher the ratio of solidified sludge, the lower the coefficient of permeability. Upon the results of particle size distribution, the mixed ratio of solidified sludge that meet the enhancement material condition was 59% or lower for SP granite soil and 48% or lower for SM granite soil respectively.

• Journal of the Korean GEO-environmental Society
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• v.22 no.3
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• pp.5-13
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• 2021

Due to population growth and industrial development, the amount of industrial waste is increasing every year. In particular, in a thermal power plant using finely divided coal, a large amount of coal ash is generated after combustion of the coal. Among them, fly ash is recycled as a raw material for cement production and concrete admixture, but about 20% is not utilized and is landfilled. Due to the continuous reclamation of such a large amount of coal ash, it is required to find a correct treatment and recycling plan for the coal ash due to problems of saturation of the landfill site and environmental damage such as soil and water pollution. In recent years, the use of a fluid embankment material that can exhibit an appropriate strength without requiring a compaction operation is increasing. The fluid embankment material is a stable treated soil formed by mixing solidifying materials such as water and cement with soil, which is the main material, and has high fluidity before hardening, so compaction work is not required. In addition, after hardening, it is used for backfilling or filling in places where compaction is difficult because higher strength and earth pressure reduction effect can be obtained compared to general soil. In this study, the possibility of use of fluidized soil using high water content cohesive soil and coal ash is considered. And it is intended to examine the flow characteristics, strength, and bearing capacity characteristics of the material, and to investigate the effect of reducing the earth pressure when applied to an underground burial.

• Journal of Korean Society of Water and Wastewater
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• v.36 no.2
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• pp.81-95
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• 2022

The present study was performed to investigate the effects of NH₃-N and nitrifying microorganisms on the increased BOD of downstream of the Yeongsan river in Gwangju. Water samples were collected periodically from the 13 sampling sites of rivers from April to October 2021 to monitor water qualities. In addition, the trends of nitrogenous biochemical oxygen demand (NBOD) and microbial clusters were analyzed by adding different NH₃-N concentrations to the water samples. The monitoring results showed that NH₃-N concentration in the Yeongsan river was 22 times increased after the inflow of discharged water from the Gwangju 1st public sewage treatment plant (G-1-PSTP). Increased NH₃-N elevated NBOD levels through the nitrification process in the river, consequently, it would attribute to the increase of BOD in the Yeongsan river. Meanwhile, there was no proportional relation between NBOD and NH₃-N concentrations. However, there was a significant difference in NBOD occurrence by sampling sites. Specifically, when 5 mg/L NH₃-N was added, NBOD of the river sample showed 2-4 times higher values after the inflow of discharged water from G-1-PSTP. Therefore, it could be thought other factors such as microorganisms influence the elevated NBOD levels. Through next-generation sequencing analysis, nitrifying microorganisms such as Nitrosomonas, Nitroga, and Nitrospira (Genus) were detected in rivers samples, especially, the proportion of them was the highest in river samples after the inflow of discharged water from G-1-PSTP. These results indicated the effects of nitrifying microorganisms and NH₃-N concentrations as important limiting factors on the increased NBOD levels in the rivers. Taken together, comprehensive strategies are needed not only to reduce the NH₃-N concentration of discharged water but also to control discharged nitrifying microorganisms to effectively reduce the NBOD levels in the downstream of the Yeongsan river where discharged water from G-1-PSTP flows.