• International Journal of Highway Engineering
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• v.11 no.3
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• pp.41-49
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• 2009

Cement concrete pavement has become more common in Korean highway systems. However, as its service period increases, there are some technical problems occurs and no clear solution is available primarily due to the lack of active researches. This research, hence, aims to develop a new mix proportion that may provide better strength and durability with extended service life. Based on a variety of literature reviews, the experimental variables were determined as unit cement content, S/a ratio and W/C ratio. From the experimental works, it is recommended to increase the unit cement content up to 375kg/$m^3$, 400kg/$m^3$ and 425kg/$m^3$. The target slump and air content were set 40mm and 5%, respectively. The maximum size of coarse aggregate was decided to be 25mm because of the easiness of supply in the field. The reduction of W/C ratio was necessarily required and decreased to 0.4 which was proven not to cause any mixing problem with the increased unit cement contents along with polycarbon-based high range water reducing agent. In addition, it was known that the S/a ratio could be reduced to 0.34. The lowered S/a might be possible because of the increased cement paste and hence increased cohesiveness and workability.

• International Journal of Highway Engineering
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• v.19 no.2
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• pp.87-95
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• 2017

PURPOSES : The objectives of this study are to evaluate moisture sensitivity of various asphalt mixtures and to suggest an alternate method for the dynamic immersion test, which is used to determine the application of anti-stripping agent, by analyzing bond strength. METHODS : The bond strength of various asphalt mixtures such as hot mix asphalt, warm mix asphalt, and polymer-modified asphalt was evaluated by the ABS test. In order to characterize moisture sensitivity at different temperatures of the mixtures, the ABS test was conducted at $-10^{\circ}C$, $5^{\circ}C$, $20^{\circ}C$, $40^{\circ}C$, and $54^{\circ}C$ under both dry and wet conditions. The concept of the bond strength ratio was applied for objective moisture sensitivity analysis. Moreover, the bond strength characteristic was compared to the dynamic immersion test to suggest an alternate method to determine the application of anti-stripping agent. RESULTS AND CONCLUSIONS : Overall, the polymer-modified asphalt demonstrates the highest bond strength characteristic regardless of moisture condition and temperature. The bond strength characteristic displays a highly reliable linear relationship from $5^{\circ}C$ to $40^{\circ}C$, and the relationship could be used to predict bond strength at any intermediate temperature. Based on the analysis of bond strength and retained asphalt ratio, the bond strength value of 1254 kPa could be applied as a criterion for anti-stripping agent.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.6
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• pp.519-528
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• 1993

The biodegradation experiment, the TOD analysis and the element analysis for dispersant, Bunker-C and dispersant/Bunker-C oil mixtures were conducted for the purposes of evaluating the biodegradability of dispersnat/Bunker-C oil mixtures and studying the consumption of dissolved oxygen with relation to biodegradation in the seawater. The results of biodegradation experiment showed the mixtures with $1:10{\sim}5:10$ mix ratios of dispersant to 4mg/l of Bunker-C oil to be $0.34{\sim}2.06mg/l$ of $BOD_5$ and to be $1.05{\sim}5.47mg/l$ of $BOD_{20}$ in natural seawater. The results of TOD analysis showed 1mg of Bunker-C oil to be 3.16mg of TOD. The results of element analysis showed the contents of carbon and hydrogen to be $87.3\%\;and\;11.5\%$ for Bunker-C oil, respectively, but nitrogen element was not detected in Bunker-C oil. The biodegradability of dispersant/Bunker-C oil mixture shown as the ratio of $BOD_5$/TOD was increased from $3\%\;to\;11\%$ as a mix ratio of dispersant to 4mg/l of Bunker-C oil changed from 1:10 to 5:10, and the mixtures were found to belong in the organic matter group of low-biodegradability. The deoxygenation rates($K_1$) and ultimate oxygen demands($L_o$) obtained through the biodegration experiment and Thomas slope method were found to be $0.072{\sim}0.097/day$ and $1.113{\sim}6.746mg/l$ for the mixtures with $1:10{\sim}5:10$ mix ratios of dispersant to 4mg/l of Bunker-C oil, respectively. The ultimate oxygen demand of mixture was increased as a mix ratio of dispersant to Bunker-C oil changed from 1:10 to 10:5. This means that the more dispersants are applied to the sea for Bunker-C oil cleanup, the more decreases the dissolved oxygen level in the seawater.

• Korean Journal of Environmental Biology
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• v.26 no.1
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• pp.36-41
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• 2008

Induction of morphological deformities in Chironomus riparius larvae was assessed after exposure to 0.3, 1, 10 and 30 ${\mu}g\;L^{-1}$ potential endocrine disruption chemicals, Diethylhexyl phtalate (DEHP). We observed and subdivide types of mentum deformities and counted the incidence of mentum deformities. The mortality was not increased according to concentrations of DEHP, while was depend on the exposed days. The incidence of mentum deformities for MLT (median lateral teeth), LT (lateral teeth), and MIX (MLT+LT) of the mentum morphological structure showed MLT (2.8$\sim$11.4%)>LT (2.8$\sim$2.9%)>MIX (2.8$\sim$3.0%). The type of mentum deformities on C. riparius was classified six groups following exposure to DEHP. The incidence rate was occupied following to tooth addition (4.3%), tooth split (2.8%), tooth deletion (2.4%), tooth fusion (1.4%), $K"{o}hn$ gap (0.5%) and abnormal shape (0.5%). Especially tooth split and tooth fusion were observed in DEHP treated conditions.

• Journal of Nutrition and Health
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• v.17 no.3
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• pp.224-235
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• 1984

Vitamin E status affected by dietary high PUFA and Se was examined by biochemical and morphological means. Rats were fed four different diets(I : 15% p/s=1 control diet, II : 15% perilla oil diet, III : 15% perilla oil, vitamin mix -vitamin E, IV : 15% perilla oil, vitamin mix-vitamin E and salt mix -Se ) for $4\frac{1}{2}$ weeks. Various dietary treatments had no significant effects on body weight gains of rats. Activities of serum creatine phosphokinase known as an indicator of vitamin E deficiency were significantly higher( P < 0.001) in groups fed diets high in PUFA, regardless of the addition or omission of vitamin E from the vitamin mixture than those in control group. Vitamin E concentrations of serum and liver were affected by experimental diets and serum levels were more affected than those in liver. Electron microscopic observations of the liver revealed 1) the presence of swollen and degenerated mitochondria and lysosome-like body(II), and 2) markedly swollen and degenerated mitochondria, numerous lysosomes and decreased in size and number of microvilli along the bile canaliculus ( III, and 3) a remarkable accumulation of lipid droplets, nuclear pyknosis, degenerated mitochondria and increased number of lysosomes scattered along the cell junction in the hepatocytes (IV).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4199-4204
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• 2011

The dynamic modulus of hot mix asphalt is one of the important indicators to evaluate the durability and performance of asphalt pavement. In resent, the dynamic modulus is suggested by a key property of asphalt pavement design and analysis in AASHTO 2002 Design Guide and Korean Pavement Research Project(KPRP). Master curve from laboratory test results should be needed for pavement design and analysis. The process to get the master curve is standardized. But, there are some setup and testing error at low temperature(-$10^{\circ}C$) and high temperature ($55^{\circ}C$). In this paper, a simplified process which is used 3 testing temperatures (5, 21, 40) is adopted to get the master curve. Comparison was carried out for standard process and simplified process. The suggested process can be used to get the master curve of asphalt pavement, even though some difference was shown at high temperature.

• Journal of Physiology & Pathology in Korean Medicine
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• v.16 no.5
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• pp.899-904
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• 2002

For determination of the genotoxicity of VOCs(Volatile Organic Compounds) in water, in vitro Comet assay was performed using 3T3 cells. The selected 5 VOCs; Trichloroethylene(TCE), Tetrachloroethylene(PCE), Carbontetrachloride (CteC), Dichloromethane(DCM) and Chlorofrom(Chl) and mixed solvent(Mix), are the test items for drinking water quality. Author analyzed the genotoxicity of these solvents through their tail length (TL) values. Mix, PCE, Chl, TCE in order had cytotoxicity at the highest concentration, and CCl₄ and DCM had no cytotoxic effect. TCE, CCl₄, Chl, PCE, Mix, DCM had genotoxicity, Chl, PCE, Mix had both cytotoxicity and genotoxicity simultaneously, Cytotoxic effect of mixed organic solvents, compared with that of single component, at each concentration, was influenced by the synergistic effect of the interaction of each organic component.

• Korean Journal of Weed Science
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• v.31 no.4
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• pp.394-400
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• 2011

Ancient mix seeding that started in China and generated in Korea is one of the methods of securing foods against natural calamities. The history of this technology was excerpted and presented from Chinese agricultural books as "Jeminyosul"(closely one upon the other 5C), "Wangjungnongseo"(from 1313) and Korean agricultural books as "Nongsajikseol"(from 1429), "Hanjeongrok"(from 1610), "Saekyeong" (from 1676), "Jeungbosanrimkyeongje"(from 1766), "Kwanongsocho"(from 1799), "Rimwonkyeongje" (from 1843). In this study, we suggested new environment-friendly agricultural technique to save labors using ancient mix seeding principle, which is seeding different varieties rice without fertilizer and agricultural pesticides. It is essential prerequisite to have the process such as injecting Azolla, no-tillage direct and broadcast seeding with multiple varieties of rice. Based on the results of previous studies, we evaluated the practical validity.

• 한국도로학회:학술대회논문집
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• 2002.10a
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• pp.75-80
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• 2002

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.269-274
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• 1998

In this study, to increase fluidity and resistance of segregation of materials, the effect of each of the materials, which have effects on high performance concrete from investigating the properties of strength and drying shrinkage of high performance concrete made by the basic mix proportion used fly-ash and ground granulated blast-furnace slag after hardening, has been checked. According to the experimental results, fluidity on W/C = 34% was satisfied within slump-flow 65$\pm$ 5cm and U-type self-compactability difference 5cm. On the properties of strength, high performance concrete produced compressive strength over 400kg/$\textrm{cm}^2$ in 28days when powder was replaced by 40% of fly-ash and 60% of ground granulated blast-furnace slag. And compressive strength was taken over 600kg/$\textrm{cm}^2$ equal to non-replacement in 91days. Also, the length change of concrete with the addition of fly-ash was smaller than that without it. Therefore, it may be effective on the decrease of drying shrinkage volume.