• Journal of Korean Society of Environmental Engineers
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• v.37 no.1
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• pp.69-72
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• 2015

This study investigated the effects of oil dose and soil texture on the analysis results for total petroleum hydrocarbon (TPH) in artificially oil-contaminated soils. The same amount of diesel was mixed with soils having different soil texture, and soil TPH concentrations were then analyzed for comparison. Presence of clay in the soil showed lower soil TPH analysis results than that of sand only. As the clay content was increased in the soil, the lower soil TPH concentration was obtained by incompleteness of solvent extraction. As the organic matter content in soil was increased from 5.2% to 10% (weight basis), a higher concentration of TPH was obtained by TPH analysis. However, at a higher organic content in the soil, 18%, resulted in a lower TPH concentration than those of 5.2% and 10%. Gasoline dose to the soil resulted in a significantly low TPH concentration due to the volatilization of gasoline while soil mixing and analysis. This study results would provide fundamental information either to the expectation of TPH concentration in artificially oil-contaminated soil or to estimation of oil release in the real oil-contaminated site.

• Korean Journal of Environment and Ecology
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• v.27 no.5
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• pp.550-560
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• 2013

This study was investigated the morphological characters, secondary sexual dimorphism, and habitat patterns of Korean Rattus animals collected on Jeju Island from April 2005 to October 2012. Two wild rat species, namely R. norvegicus and R. tanezumi were identified on Jeju Island based on morphological characteristics and molecular data; however, R. rattus, which had recorded formerly, was not found in this study. Individuals of R. norvegicus were captured from urban, rural, and natural habitats, while those of R. tanezumi were specially found in animal farms and the surrounding areas. Comparing of morphological characters of two species, R. norvegicus had a shorter tail and ears than R. tanezumi (p<0.05), and the ratios of tail length and ear length to those of head-body length showed significantly differences between two species (p<0.05). The body weights (BW) of urban populations of R. norvegicus were significantly heavier than those of rural populations (p<0.05). No secondary sexual dimorphism was found in R. norvegicus, but females of R. tanezumi showed heavier BW than those of males (p<0.05). These findings suggest that it is necessary to revise the records for the existence of R. tanezumi and to confirm the animal fauna and elucidate the distribution and ecological characteristics from further studies using extensive sampling and detailed investigations on Jeju Island and also on the Korean Peninsula.

• Economic Analysis
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• v.26 no.2
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• pp.1-42
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• 2020

This paper studies, from a quantity theory of money perspective, the reasons that North Korean inflation and exchange rates maintain stability while its economy is experiencing difficulties due to the international community's economic sanctions. In doing so, this paper uses both domestic and foreign currencies in an analytic model based on the quantity theory of money to cautiously reflect North Korea's dollarization as well as its management of its exchange rate. In particular, foreign currency holdings are divided into those for store-of-value purposes and those for transaction purposes. This paper shows that in the early stages, in which the amount of foreign currency holdings for store-of-value purposes is decreasing while the amount of foreign currency holdings for transaction purposes is intact, inflation and exchange rates both exhibit stable movements. In the middle stages, where the amount of foreign currency holdings for transaction purposes begins to fall, exchange rates show some increase and inflation decreases. In the final stages, when the amount of foreign currency holdings for transaction purposes significantly decreases, exchange rates and inflation both increase, and in some situations a crisis can happen. According to this paper's analysis, if the economic sanctions continue to the extent that the amount of North Korean foreign currency holdings for transaction purposes starts to fall, the exchange rate and inflation stability we see now are unlikely to be maintained.

• Membrane Journal
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• v.33 no.6
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• pp.439-446
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• 2023

Ceramic membranes are generally used for various industrial processes operating under extreme conditions because of its high thermal and chemical stability. However, due to the trade-off phenomenon of permeability and mechanical strength, preparation of high permeability-high strength membrane is necessary. In this study, the change in characteristics and performances of ceramic membranes was analyzed depending on the type of polymer binder and its mixing ratio. Because the solubility between solvent and polymer binder was higher in PSf (polysulfone) than in PES (polyethersulfone), the viscosity and discharge pressure of the PSf-based dope solution were higher than those of PES-based dope solution. When PSf was used as a polymer binder, ceramic membrane showed high mechanical strength and low water permeability due to the dense structure. On the other hand, in case of PES, the mechanical strength was slightly reduced and the water permeability was increased. It was confirmed that the optimum mixing ratio of the PSf and PES with high water permeability and mechanical strength was 9:1.