• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3006-3013
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• 2015

Flat tube heat exchangers can improve the thermal performance significantly compared with round tube heat exchangers. For proper design of flat tube heat exchangers, one should know the tubeside heat transfer coefficients. In this study, convective boiling heat transfer coefficients of R-410A were obtained in a flat extruded aluminum tube with $D_h=1.41mm$. The test range covered mass flux from 200 to $600kg/m^2s$, heat flux from 5 to $15kW/m^2$ and saturation temperature from $5^{\circ}C$ to $15^{\circ}C$. The heat transfer coefficient curve shows a decreasing trend after a certain quality(critical quality). The critical quality decreases as the heat flux increases, and as the mass flux decreases. The early dryout at a high heat flux results in a unique 'cross-over' of the heat transfer coefficient curves. The heat transfer coefficient increases as the mass flux increases. At a low quality region, however, the effect of mass flux is not prominent. The heat transfer coefficient increases as the saturation temperature increases. The effect of saturation temperature, however, diminishes as the heat flux decreases. Both the Shah and the Kaew-On et al. correlations reasonably predicted the present data.

• Korean Journal of Ichthyology
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• v.33 no.2
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• pp.107-116
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• 2021

Two stone loaches (Nemacheilidae, Cypriniformes), Barbatula toni (Dybowski, 1869) and B. nuda (Bleeker, 1864), have been recognized in the Korean waters to date. Recently, due to indiscriminate artificial introduction as well as the change of their habitats induced by natural disasters, it seems to be concerned about the damage of species-specific geographic boundaries. We examined the genetic difference of two Korean Barbatula species by the haplotype network based on the Cytochrome b sequences of mitochondrial DNA and the phylogenetic relationships among them including Barbatula fishes occurring around the Korean peninsula. As a result, three and 29 haplotypes were obtained from B. toni and B. nuda, respectively, and totally three clades comprising "toni group", "nuda hangang group", and "nuda donghae group" were identified. The sequence variable sites among them was 10~24%, showing a difference of interspecific level. Phylogenetic relationships of the latter group, especially, forms an independent cluster discriminating with other two groups as well as the Chinese, Japanese, Russian, and European Barbatula species, suggesting the possibility of the specific level divergence.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.627-633
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• 2019

Rapid and accurate identification of marine microalgae causing harmful algal blooms (HABs) is a crucial tool for predicting and managing HABs. We previously developed a nuclease protection assay sandwich hybridization (NPA-SH) method for the in situ detection of blooming microalgae Cochlodinium polykrikoides. In this study, we improved the applicability of the NPA-SH method for the detection of C. polykrikoides by simplifying the reaction step. For this purpose, invertase (INV) was conjugated to the signal probe instead of using fluorescence, and sucrose was used as a reactant to induce a color reaction. The INV-signal probe conjugation was confirmed by SDS-PAGE and epifluoromicroscopy. The treatment time and appropriate amounts of the probe and sucrose that optimized the reaction were determined. As a result, the developed INV-SH reduced the treatment time in the field compared with NPA-SH, and also enabled the use of a relatively small volume and low-priced personal glucose meter, as well as an absorbance meter. INV-SH is the first C. polykrikoides species identification technology to which INV has been applied and could be an improved field technique.

• Korean Journal of Environment and Ecology
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• v.32 no.6
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• pp.582-590
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• 2018

Although there are many studies of the effect of climate change on the breeding phenology and community diversity of amphibians, the studies of variations in reproductive population size of individual species according to climate change are still lacking. We examined the effect of climate change on the reproductive population size of Rana huanrenensis and Hynobius leechii, which bred in mountain valleys, by surveying the reproductive population of the two species between 2005 and 2012 and analyzing the correlation between the variation of the outdoor population and the surrounding climate change factors, obtained from a meteorological observatory located at 5.6 km from the study site. The size of the reproductive population of the two species commonly fluctuated with aan pproximately 3.5-year cycle. That of H. leechii, in particular, decreased significantly over eight years. The air temperature tended to more closely relate with the reproductive population size of R. huanrenensis as was the case of the precipitation with that of H. leechii. The yearly mean highest temperature and spring mean temperature variation consistently decreased over the eight years, and the latter was related with the significantly decreased size of H. leechii reproductive population. These results showed that recent climate change directly could affect the reproductive population size of amphibians, particularly H. leechii, which breeds in mountain valleys.

• Korean Journal of Ecology and Environment
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• v.52 no.2
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• pp.136-142
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• 2019

Water spider(Argyroneta aquatica) inhabits only a small size wetland in Eundae-ri, Yeoncheon-gun. In this study to investigate environmental factors influencing on population of A. aquatica, we analyzed the relationship between density of A. aquatica and various physicochemical and biological factors. Density of A. aquatica increased with small habitat area and high $NH_4$ and electric conductivity. The relationship between density of A. aquatica and prey or predator was low but the water spider decreased with density of Pomacea canaliculata. And density of A. aquatica was not related to the coverage of emergent plant. However density of A. aquatica decreased as the increase of floating plant and increased as the increase of submerged plant. These results indicated that aquatic plants are important in the habitat environment of A. aquatica. Therefore we suggest necessity of management strategies for the invasive species, P. canaliculata which is a notorious predator of aquatic plants.

• Korean Journal of Plant Resources
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• v.32 no.2
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• pp.201-206
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• 2019

Alien invasive species are introduced with or without intent and spreading all over Korea. They are known to have negative effects on biodiversity such as economic and environmental damage and causing decrease or loss of native species. The habitats like wetland, reservoir and riverside are especially in danger of being invaded by alien species due to stress and disturbance. Therefore, Korea National Arboretum is steadily working on research and studies on managing alien invasive species. This research aims to collect basic information of Ludwigia peploides subsp. montevidensis (Spreng.) P.H. Raven which was found near riverside in Suwon-si and is concerned to become an invasive alien species. We expect the description, diagram and pictures of this taxon will be helpful for early detection and effective management.

• Korean Journal of Ecology and Environment
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• v.53 no.4
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• pp.427-435
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• 2020

The most important thing to successfully restore an oak forest is finding suitable climatic conditions and topographic factors for the oak species to be introduced. In this study, in order to find suitable environmental conditions for the five dominant oak trees on the Korean Peninsula, we carried out analysing the information on the location of forest vegetation on the Korean Peninsula. The range of annual mean temperature of the five oak trees was narrow in the order of Q. mongolica (7.7~14.3℃), Q. variabilis (9.2~13.8℃), Q. acutissima (10.5~14.3℃), Q. serrata (11.4~13.7℃), Q. aliena (11.0~12.9℃). The range of annual precipitation of oaks was narrow in order of Q. mongolica (1072.7~1780.9 mm), Q. variablis (1066.6~1554.9 mm), Q. acustissima (1036.5~1504.8 mm), Q. serrata (1062.6~1504.7 mm). The range of altitude was in order of Q. mongolica (147~1388m), Q. serrata (93~950m), Q. variabilis(90~913m), Q. acustissima (60~516m), Q. aliena (55~465 m). The range of slope was in the order of Q. mongolica (8~56°), Q. variabilis(5~52°), Q. serrata (11~45°), Q. aliena (15~38°), Q. acustissima (16~37°). These results are considered to be very useful in the case of ecological restoration using deciduous oak trees on the Korean Peninsula.

• Korean Journal of Poultry Science
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• v.49 no.2
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• pp.125-137
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• 2022

This study aimed to determine the effects of dietary microalgae (Tetradesmus sp. (TO)) on intestinal immunity and microbiota of pre-starter broilers. One hundred and twenty 1-day-old birds (Ross 308) were allocated to two dietary treatment groups with six blocks in a randomized complete block design. The two experimental diets consisted of a corn-soybean meal-based basal diet and a diet with 0.5% TO powder instead of cornstarch in the basal diet. After feeding the experimental diets for ten days, all birds' body weight and feed intake were measured, and representative eight birds were selected from each treatment group. Small intestinal lamina propria cells were isolated using flow cytometry to examine the frequency of immune cells. Cecal feces were harvested for 16s rRNA gut microbiota analysis and fecal IgA levels. Here, we found that 0.5% TO supplementation increased CD3⁺CD4⁺ T cells in the small intestine, but decreased CD3⁺CD8⁺ T cells in the small intestine. Gut microbial analysis showed that TO supplementation significantly increased the alpha diversity of the gut microbiome. Taxonomic analysis showed that TO treatment increased the abundance of Firmicutes and decreased that of Bacteroidetes at the phylum level. The distribution of Enterobacteriaceae containing many harmful bacteria at the family level, was lower in the TO group. In the LEfSe analysis, the TO group had a significantly enriched abundance of Agathobaculum at the genus level. Overall, results show that Tetradesmus sp. supplementation influences intestinal T-cell immunity and induces the expansion of beneficial gut microbes in pre-starter broiler chickens.

• Korean Journal of Ecology and Environment
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• v.56 no.1
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• pp.1-13
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• 2023

Targeting Microcystin (MC), which is most abundantly detected in the North-Han River water area, we analyzed the relationship between the MC biosynthesis gene (mcyA gene), cyanobacteria cell density, and MC concentration, derived an RNA-MC conversion formula, and derived the cyanobacteria. The concentration of MC present in cells was predicted. In the North-Han River waters, the mcyA gene was found mainly at downstream sites of the North-Han River after Muk-Hyeon Stream junction, and higher copy numbers were found on average than other sites. In the Uiam Lake waters upstream of the North-Han River, the mcyA gene copy number increased at the Kong-Ji Stream point, and after September, the mcyA gene copy number decreased throughout the North-Han River waters. The expression of the mcyA gene was concentrated in the short period of summer due to the spatio-temporal difference between upstream and downstream water bodies. The mcyA gene expression level was not only highly correlated with MC concentration, but also correlated with the cell density of Microcystis aeruginosa and Dolichospermum circinale, which are known to biosynthesize MC. Six conversion formulas derived based on the RNA-MC relationship showed statistical significance (p<0.05) and exhibited high correlation coefficients (r) of 0.9 or higher. The expression level of MC biosynthesis gene present in eRNA determines the synthesis of cyanotoxin substances in water, quickly quantifies gene activity, and can be fully utilized for early warning of MC development.

• Journal of Marine Bioscience and Biotechnology
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• v.15 no.2
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• pp.82-89
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• 2023

Microalgae, as photosynthetic organisms, possess the ability to produce a diverse array of bioactive compounds. This study focused on the transformant Chlamydomonas reinhardtii dZL and subjected it to cultivation under varying light intensities (60, 120, 180, and 240 µmol/m²/s). Our aim was to assess the impact of light intensity on both microalgal biomass and carotenoid production. The cultivation took place in 80 mL bubble column photobioreactors, specifically the Multi-cultivator. Notably, the culture exposed to 240 µmol/m²/s exhibited the most rapid cell growth, surpassing even the cell concentration achieved at 180 µmol/m²/s by day 8. A detailed analysis of the specific irradiance rate over time unequivocally revealed a sharp decline in growth rates when the rate fell below 2 × 10^-10 µmol/cell/s. Although the culture with 60 µmol/m²/s yielded the highest carotenoid content (1.2% of dry weight), the culture exposed to 240 µmol/m²/s recorded the highest carotenoid concentration at 8.9 mg/L owing to its higher biomass. Our findings reveal the critical importance of maintaining a specific irradiance rate above 2 × 10^-10 µmol/cell/s to enhance biomass and carotenoid productivity. This study lays the groundwork for defining optimal light intensity conditions applicable to mass culture systems, with the objective of augmenting C. reinhardtii biomass and optimizing carotenoid productivity.