• Journal of Korean Society of Environmental Engineers
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• v.27 no.4
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• pp.394-401
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• 2005

A nonthermal plasma-assisted fuel reformer was developed and the effects of operating variables on the performance of this reformer were studied. The $H_2$-rich reformed gas from the reformer was injected into a diesel engine under an idle condition and the effects of the amount of injected gas on the NO and soot reduction were investigated. It was found that with increasing electric power consumption, the degree of facility of ignition of the reforming reaction in the reformer could be enhanced. The performance of the reformer including $H_2$ concentration, $H_2$ recovery, and energy conversion was affected only by the O/C mole ratio. This was because the equilibrium reaction temperature was governed by the O/C mole ratio. With increasing O/C mole ratio, the $H_2$ recovery and energy conversion passed through the maximum values of 33.4% and 66%, respectively, at an O/C mole ratio between 1.2 and 1.5. The reason why the $H_2$ recovery and energy conversion increased with increasing O/C mole ratio when the O/C mole ratio was lower than $1.2{\sim}1.5$ appeared to be that the complete oxidation reaction occurred more enough with increasing O/C mole ratio in this low O/C mole ratio range and accordingly the reaction temperature increased. Whereas the reason why the $H_2$ recovery and energy conversion decreased with increasing O/C mole ratio when the O/C mole ratio was higher than $1.2{\sim}1.5$ appeared to be that the complete oxidation reaction was further advanced and the $H_2$ recovery and energy conversion decreased. As the weight ratio of reformed diesel to total diesel which entered the diesel engine was increased to $18.2{\sim}23.5%$, NO and soot reduction efficiencies increased and reached as values high as 68.5% and 23.5%, respectively.

• Korean journal of applied entomology
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• v.21 no.1 s.50
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• pp.38-48
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• 1982

This study was conducted to investigate the changes in moth occurrence of striped rice barer, Chilo suppressalis (Walker), in relation to climatic factors, rice varieties, and cultural practices. The light trap data from 41 forecasting stations for 14 years from 1966 to 1979 were analyzed by means of the changes in the time and amount of borer occurrence in connection with the introduction of new rice varieties, the accumulated effective day-degree and its variation for completing one generation, and the climatic factors affecting the moth occurrence. The total number of moths caught by light traps in both spring and summer generations were considerably decreased with the wide cultivation of new rice varieties. In fact, the spring moths were remarkably decreased since the new varieties were introduced in 1972. The occurrence ratio of summer moths against the preceeding spring moths was higher in the middle region and middle southern mountainous area than the other regions. Its high ratio of regions was annually expanded from the middle region to the southern region. The $50\%$ emergence dates of both generations were later in the southeastern region than in the middle region. The ecological characteristics were clearly shown between the northern and southern region of Chupungryeong in terms of the occurrence of summer moths, the ratio of occurrence of summer moths to the preceeding spring moths, and $50\%$ emergence dates of the summer moths during the years of $1977\~1979$. The ratio of the summer moth occurrence to the preceeding generation was negatively correlated with the average temperature in lune and July, respectively, and the average precipitation in late June. The ratio of spring moth occurrence over the preceeding generation was positively correlated with the average temperature in September, October, November, and March, respectively, whereas it was negatively correlated with the average precipitation in early September and March, and the average humidity in early May. The effective day-degree for one generation was in the range from 600 to 900 DD at upper threshold $30^{\circ}C$ and lower threshold $10^{\circ}C$.

• Parasites, Hosts and Diseases
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• v.24 no.2
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• pp.121-136
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• 1986

Recently there have been some reports on human infections of Echinostoma hortense in Korea. It was found that a few species of freshwater fishes were playing the role of the second intermediate host of E. hortense. However, molluscan intermediate host has not been identified yet in Korea. The present study aimed to establish the life cycle of E. hortense in laboratory. Experimental studies such as egg production from the rat, development of the eggs in vitro, exposure of miracidia to freshwater snails, shedding pattern of cercariae from infected snails, morphology of cercariae, cercarial infection to the second intermediate host and infection of metacercariae to the definitive hosts were done. In addition, epidemiological surveys on the infection status in inhabitants and house rats, and on the natural infection of larval echinostomes in the snails and fishes were carried out along the South Hangang-river. The results obtained were as follows: 1. The eggs deposited from adults in physiological saline were cultivated at room temperature($20{\sim}24^{\circ}C$). The miracidia were firstly observed on 8 days after cultivation, and 85.5% of the eggs contained the mature miracidia on 11 days after cultivation. More than 90% formed the miracidia when cultivated at temperature $22{\sim}27^{\circ}C$. Hatching of the miracidia began on 12 days after cultivation and continued for a week. The size of the miracidia was $103.0{{\times}}51.4{\mu}m$ in average. The motility of the miracidia were active up to 8 hours after shedding, but they were all dead within 10 hours after shedding. 2. A freshwater snail, Radix auricularia coreana was cultivated in aquaria. A hatched $F_1$ snails from the egg masses were exposed to 20 miracidia respectively. Escape of cercariae started on 15 days after infecton. Radix auricularia coreana was experimentally identified as the first intermediate host of E. hortense in Korea. 3. Cercarial shedding started on $15{\sim}20$ days after infection by snail, continued for about 10 days (8.8 days in average). Infected snails were dead within 32 days after the miracidial infection. About 1,335 cercariae($328{\sim}1,994$) per snail were shed in its life, and 119 cercariae in average per snail per day were shed. The cercariae were motile for more than 24 hours, and then squirming at the bottom until death. The body and tail sizes of cercariae were $356{\times}186{\mu}m$ and $510{\times}68{\mu}m$ in average, respectively. The rediae parasitized in the snail hosts were found mainly around the pericardial regions, and their size was $1,575{\times}258{\mu}m$ in average. The numbers of developing cercariae in a mature redia were 14 in average ($7{\sim}20$ in range). The numbers of rediae in a snail were 102 in average on 15 days after miracidial infection and 221 in average on 28 days. 4. Three uninfected Misgurnus anguillicaudatus, less than 6.5cm long were used in for the cercarial infection. They were all exposed with 755 cercariae, and examined at 5-day intervals starting from 10 days after infection. All the fishes were infected with metacercariae of E. hortense and a total of 275 was found infected(36.4%). The metacercariae were fed to rats and the adult worms were obtained on 15 days after infection. 5. The infected rats began to deposit the eggs on 11 days after infection. The number of eggs deposited per day per worm (EPD/worm) was $400{\sim}500$ on 3 weeks after infection and was increased to $1,000{\sim}1,500$ on 4 to 17 weeks, then decreased to 800 on 21 weeks after infection. 6. A total of 745 stool specimens collected from 576 male and 169 female residents of 8 different villages along South Hangang basin was examined. Out of 745 specimens, the eggs of Echinostoma sp. were found in 2 cases (0.3%). Of 34 house rats one showed egg-positive (2.9%). 7. Total 971 Radix auricularia coreana collected from 7 sampling stations were examined for shedding of cercariae. Three snails (0.3%) shed the cercariae of E. hortense. A total of 119 out of 542 freshwater fishes (22.0%) had the metacercariae of E. hortense. The fishes parasitized with the metacercariae were 4 out of 14 examined species. The infection rates of 4 species were 34.1% (106 out of 311) in Misgurnus anguillicaudatus, 30.4% (7 out of 23) in Misgurnus mizolepis, 4.3% (2 out of 46) in Moroco oxycephalus and 22.2% (4 out of 18) in Odontobutis obscura interrupta. In summarizing the above results, the first intermediate host of E. hortense was found as Radix auricularia coreana in Korea. Also, it took about 46 days for the shortest completion of a life cycle of E. hortense in summer; that is, 10 days for miracidial development in eggs, 15 days for cercarial development in the snail, about 10 days for metacercarial development in the second intermediate hosts, and 11 days for the maturation as the adults in the definitive hosts. The natural infection rates of E. hortense in the intermediate hosts were relatively high but those in the definitive hosts were low in the middle areas of South Hangang basin.

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.908-913
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• 2001

Paper sludge Ash (PA) and Fly Ash (FA) wastes are usually land-filled for reclamation or substituted for cements as a resource. It could also offer some advantages when they are substituted for clay to preserve the environment. To recycle those wastes, the sintered specimen made of PA-FA-Clay system were examined to find the microstructure and physical properties. The ratio of clay to wastes was fixed as 30:70 by wt%, while PA to FA within waste portion were varied in the range of $1:6{\sim}7:0$. Those specimens were fired in $1150{\sim}1350^{\circ}C$. It was found that the relative density of sintered specimen was increased with amount of PA added at low sintering temperature (i.e, $1150{\sim}1200^{\circ}C$). This is due to increased amount of liquid during sintering. It is shown, however that at high sintering temperature ($1250{\sim}1350^{\circ}C$), the relative density of specimens was decreased with amount of PA added. This is because of overfiring phenomenon which may be able to induce an inhomogeneous microstructure and increased porosity. The mechanical properties of sintered specimen were depended upon the homogeneity of microstructure in accordance with SEM (Scanning Electron Microscopy) and pore size distribution analysis. For example, the compressive strength of 10PA-60FA-30Clay specimen sintered at $1225^{\circ}C$ was twice higher than that of 70PA-30Clay specimen even thought the relative density of those specimen was similar. This decreased strength of 70PA-30Clay specimen appears to be an inhomogeneity of microstructure due to overfiring.

• The Korean Journal of Malacology
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• v.29 no.1
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• pp.51-63
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• 2013

To assess the effect of environmental factors on the sustainability of cultured production shellfish, we investigated the habitat characteristics of tidal flat (Namhae-po in Taean). We measured the physiochemical parameters (temperature, salanity, pH, dissolved oxygen and nutrients) and the geochemical characteristics (chemical oxygen demand, ignition loss, C/N ratio and C/S ratio). Surface sediments were collected from several site of tidal flat to examine the geochemical characteristics of both the benthic environment and heavy metal pollution. The grain size for research area of tidal flat were similar at the ratio of silt and clay in comparison with the other site of it. The C/N ratio was more than 5.0, reflecting the range arising from the mix of marine organism and organic matter. The C/S ratio (about 2.8) showed that survey area had anoxic or sub-anoxic bottom conditions. The enrichment factor (Ef) and index of accumulation rate (Igeo) of the metals showed that those research areas can be classified as heavily polluted, heavily to moderately polluted, or more or less unpolluted, respectively. Adult surf clam (Mactra veneriformis) density was highest at St. 2 (middle part of the Namhae-po), on the other hand, surf clam spat density was highest at St. 3 (lower part of the Namhae-po). Heavy rain, terrigenous suspended clay with fresh water from neighboring agricultural land, and severe high air temperature during summer could be thought as detrimental causes of spat and adult mortality in Namhae-po tidal flat. We suggested that the growth of shellfish in the tidal flat was effected by the various environmental conditions, so an improvement in the cultured method was needed.

• Journal of the Korean Society of Food Science and Nutrition
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• v.15 no.1
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• pp.45-55
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• 1986

This paper aims to study the reactions of lipid or oxidized lipid with protein during drying and storing hair tail fish(Trichurus lepturus) and flounder(Kanakius kitaharai) being generally consumed as dried seafood products in Korea and their influence on the drop of in vitro protein digestibility of these fish meat. The results of the study are as follows: The digestibility of the raw materials of flounder and hair tail fish was 87.63% and 86.08% respectively, and that of sundried and hot air dried materials went down $1{\sim}2$ percent with drying process. But in case of defatted and sundried materials, the rate increased 85.15% and 87.15% respectivley. After 30 days of storage, the digestibility decreased in all materials, and hot air dried meat showed a significant decrease. Trypsin indigestible substrate (TIS) contents of flounder and hair tail fish, in case of raw materials were 0.88 and 0.96mg/g. solid repectiveiy and in case of defatted and sundried materials, TIS contents showed a low increase and digestibility showed a high increase. Brown pigment formation had a wide range of increase in case of the sundried and hot air dried materials and it was increased with duration of storage and temperature. The major fatty acids in the fats of hair tail fish and flounder were $C_{18:1},\;C_{16:0},\;C_{22:6}\;and\;C_{16:1}$ and rate of unsaturated to saturated fatty acids was 79.2:20.8 for flounder, 67.8:32.2 for hair tail fish. After 30 days of storage at room temperature. saturated fatty acids increased compared with the raw materials while unsaturated fatty acids showed a tendency to decrease. Avaialble lysine of hair tail fish was higher than that of flounder and both of them lost about 8.23% of that in raw materials after 30 days of storage.

• The Journal of the Petrological Society of Korea
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• v.18 no.3
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• pp.223-236
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• 2009

Ultramafic xenoliths from southeastern part of Jeju Island can be grouped into two types: Type I and Type II. Type I xenoliths are magnesian and olivine-rich peridotite (mg#=89-91), which are commonly found at the outcrop. Most previous works have been focused on Type I xenoliths. Type II xenoliths, consisting of olivine, orthopyroxene and clinopyroxene with higher Fe and Ti components (mg#=77-83) and lower Mg, Ni, Cr, are reported in this study. They are less common with a more extensive compositional range. The studied Type II xenoliths are wehrlite, olivine-clinopyroxenite, olivine websterite, and websterite. They sometimes show ophitic textures in outcrops indicating cumulate natures. The textural characteristics, such as kink banding and more straight grain boundaries with triple junctions, are interpreted as the result of recrystallization and annealing. Large pyroxene grains have exsolution textures and show almost the same major compositions as small exsolution-free pyroxenes. Although the exsolution texture indicates a previous high-temperature history, all mineral phases are completely reequilibrated to some lower temperature. Orthopyroxenes replacing clinopyroxene margin or olivine indicate an orthopyroxene enrichment event. Mineral phases of Type II are compared with Type I xenoliths, gabbroic xenoliths, and the host basalts. Those from Type II xenoliths show a distinct discontinuity with those from Type I mantle xenoliths, whereas they show a continuous or overlapping relation with those from gabbroic xenoliths and the host basalts. Our petrographic and geochemical results suggest that the studied type II xenoliths appear to be cumulates derived from the host magma-related system, being formed by early fractional crystallization, although these xenoliths may not be directly linked to the host basalt.

• Journal of the Korean Vacuum Society
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• v.19 no.4
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• pp.307-313
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• 2010

One-dimensional cubic phase silicon carbide nanowires (${\beta}$-SiC NWs) were efficiently synthesized by thermal chemical vapor deposition (TCVD) with mixtures containing Si powders and nickel chloride hexahydrate $(NiCl_2{\cdot}6H_2O)$ in an alumina boat with a carbon source of methane $(CH_4)$ gas. SEM images are shown that the growth temperature (T) of $1,300^{\circ}C$ is not enough to synthesize the SiC NWs owing to insufficient thermal energy for melting down a Si powder and decomposing the methane gas. However, the SiC NWs could be synthesized at T>$1,300^{\circ}C$ and the most efficient temperature for growth of SiC NWs is T=$1,400^{\circ}C$. The synthesized SiC NWs have the diameter with an average range between 50~150 nm. Raman spectra clearly revealed that the synthesized SiC NWs are forming of a cubic phase (${\beta}$-SiC). Two distinct peaks at 795 and $970 cm^{-1}$ in Raman spectra of the synthesized SiC NWs at T=$1,400^{\circ}C$ represent the TO and LO mode of the bulk ${\beta}$-SiC, respectively. XRD spectra are also supported to the Raman spectra resulting in the strongest (111) peaks at $2{\Theta}=35.7^{\circ}$, which is the (111) plane peak position of 3C-SiC. Moreover, the gas flow rate of 300 sccm for methane is the optimal condition for synthesis of a large amount of ${\beta}$-SiC NW without producing the amorphous carbon structure shown at a high methane flow rate of 800 sccm. TEM images are shown two kinds of the synthesized ${\beta}$-SiC NWs structures. One is shown the defect-free ${\beta}$-SiC NWs with a (111) interplane distance of 0.25 nm, and the other is the stacking-faulted ${\beta}$-SiC NWs. Also, TEM images exhibited that two distinct SiC NWs are uniformly covered with $SiO_2$ layer with a thickness of less 2 nm.

• Korean Journal of Environmental Biology
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• v.31 no.4
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• pp.429-439
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• 2013

This study was conducted to identify the relationship between environmental factors and algal bloom, and provide information for efficient management based on the results of monitoring the environmental parameters and algal diversity in the Jundai reservoir from March 2011 to October 2013. Little change in the weather conditions was observed during the study period except for a slight decrease in rainfall. Concentration of TN and TP in the reservoir exceeded water quality standards for agriculture and significant correlation between algal growth and environmental factors was observed. Phytoplankton in Jundai reservoir included 6 classes, 40 genus, 62 species, and the phytoplankton abundance was in the range of $1.3{\times}10^4{\sim}2.8{\times}10^6$ cells $mL^{-1}$. The annual average of phytoplankton abundance and Chl-a gradually decreased as TN and TP concentrations decreased. Overall Anabaena sp., Oscillatoria sp., and Microcystis sp. were the dominant species in Jundai reservoir. As the water temperature increased, the dominant species were Anabaena sp., Microcystis sp. and Oscillatoria sp., in that order. Anabaena sp. was dominant from spring to early summer with increase in water temperature and pollutant concentrations, and high correlation with environmental factors was observed. Microcystis sp. was dominant depending on changes in the nutrient levels. In the case of Oscillatoria sp., there was no significant correlation between phytoplankton biomess and Chl-a. However, efficient management of water environment and practical control of algal bloom in small scale reservoir polluted by livestock and farm irrigation should be achieved by identification of the relationship between algal growth and environmental factors.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.66 no.2
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• pp.120-129
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• 2021

Securing a range of wheat resources is of particular importance with respect to wheat breeding, as it provides a broad genetic foundation. Although wheat breeders have used different wheat germplasms as material resources in current breeding systems, the traits of most germplasms collected from foreign countries differ from the unique traits that have evolved in the Korean environment. In this study, conducted over a 2-year period (2018 and 2019), we therefore evaluated the agricultural traits 1,967 wheat germplasms collected not only in Korea but also worldwide. During the period from sowing to February, the average temperature in 2019 was greater than 1℃, whereas from March to June, the average temperature was approximately 0.9℃ higher in 2018. Compared with the growth recorded in 2018, the stem length in 2019 increased by approximately 20 cm in 2019, and there were notable differences heading date and maturation between 2018 and 2019. In 2019, the heading dates of 973 and 713 wheat resources were earlier and later than those in 2018, respectively. Moreover, stem length was found to be highly correlated with the heading date and maturation. In Korea, where the rainy season and tine of rice transplantation overlap with the time of wheat harvest, early flowering time with high grain yield has been the most important selection target with respect to wheat breeding. We anticipate that the findings of this study will provide would use a foundation for the selection of elite materials and the development of resource core-sets for Korean wheat breeding programs.