• Elastomers and Composites
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• v.33 no.5
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• pp.315-323
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• 1998

The purpose of this study was to investigate the crosslinking density and reinforcement of rubber compounds with various carbon black loadings, cure systems and cure temperatures. Bound rubber content increased with volume fraction of carbon black in rubber compounds, but total crosslinking density decreased with increasing the bound rubber content. Rate constant of cure reaction was changed significantly by cure system and cure temperature, especially it showed strong dependence on the cure temperature. High activation energys of cure reaction were shown in the rubber compound with high loading of carbon black under EC system and in the rubber compound with low loading of carbon black under CC system. High total crosslinking density of vulcanized compounds appeared in the rubber compound with low loading of carbon black and CC system among cure systems. Typical change of total crosslinking density by EC system was not shown. The highest elastic constant by Mooney-Rivlin equation was shown in the rubber compound with low loading of carbon black and SEC system. Modulus increased as increasing the loading of carbon black in the rubber compounds and showed the order of SEC, CC, and EC system for cure system.

• Journal of the East Asian Society of Dietary Life
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• v.25 no.2
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• pp.309-315
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• 2015

This study aimed to develop and validate an analytical method for ethyl carbamate (EC) in Maesilju. For accurate analysis of EC in Maesilju, an internal standard (d5-EC) and neutralization (pH=7) were performed. The limit of quantification (LOQ) was 3.65 ppb while the recovery rate ranged from 92.54% to 103.59%. Intra- and inter-day precision ranged from 0.87% to 1.99% and 2.67% to 5.64%, respectively. Maesilju samples comprised 10 homemade and five commercial ones. Samples contained EC at levels between 118.48 and 2,640.42 ppb. The average content of homemade Maesilju was higher than those of commercial ones. Based on manufacturers' labeling of commercial samples and information on homemade samples, various factors such as ingredients and soaking time of Maesil affected EC level in Maesilju. EC contents showed a positive correlation with age of Maesilju.

• Korean Chemical Engineering Research
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• v.48 no.2
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• pp.164-171
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• 2010

Recently, the waste of Polycarbonate(PC) is increase with the increase in demand of a polycarbonate. It is concerned with producing a new material and diol monomer, bishydroxyethyl ether of bisphenol A(BHE-BPA) through depolymerization of the polycarbonate waste at recycling. BHE-BPA can be used as a good raw material for the synthesis of polycarbonate type polyurethane. PC particles were depolymerized with base-catalyst NaOH, solvent EG, and ethylene carbonate(EC) was formed during the PC depolymerziation. EC was added to promote the conversion from bispenol-A to BHE-BPA. The characteristics of depolymeraion of polycarbonate as well as conversion of bispenol-A to BHE-BPA were investigated. BHE-BPA yield of 92% was obtained at temperature $220^{\circ}C$, 10% catalyst/PC mole ratio, 20 mmol of EC. BHE-BPA purity of better than 99% was achieved by crystallization of BHE-BPA.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.123-123
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• 2016

만곡부, 합류부 등의 복잡한 지형을 갖는 자연하천에서의 오염물의 혼합 거동에 대한 이해는 수자원의 관리에 있어서 매우 중요하다. 특히 하폐수처리장과 같은 처리시설의 방류수와 같이 연속적으로 유입되는 오염물의 경우 하천 생태계에 지속적인 영향을 끼치며, 이러한 방류수는 대부분 지류를 통해 본류로 유입되게 된다. 이러한 오염물질이 지류로부터 본류로 합류되는 초기구간(near-field)의 경우, 횡방향 및 연직방향의 혼합 거동에 대한 상세한 분석이 필요하다. 본 연구에서는 금호강과 진천천이 좌안으로부터 합류되는 낙동강 중류 구간에서의 초기 혼합 구간의 연구를 위하여 전기전도도(electrical conductivity: EC)를 이용한 농도 추적 실험을 수행하였다. 수온, 전기전도도, 이온화 물질 등과 같은 자연 추적자(natural tracers)를 이용하는 농도 추적 실험은 인공추적자 물질을 이용한 실험을 대체할 수 있는 방안으로서, 기존 추적자 실험과 비교하여 경제적, 환경적인 효과와 하폭이 넓은 중규모 이상의 하천에서도 수행할 수 있다는 장점을 가지고 있다. 실험 구간에서 합류되는 2개의 지류 모두 인근 하폐수처리장으로부터 방류수가 연속적으로 유입된다. 본류에서 정해진 측선을 따라 센서가 설치된 보트를 이용하여 실시간으로 농도, 수리량 데이터를 GPS 위치 데이터와 함께 취득하였다. 실험 수행 결과, 지류인 금호강과 진천천의 EC 농도가 합류 전 낙동강 본류의 EC 기저농도보다 더 높은 값을 나타내었다. 이후 지류가 합류된 직후의 측선에서 측정한 EC 농도분포를 분석한 결과, 연직방향의 편차가 크게 나타나는 것으로 나타났으며 특히 유량이 낮을수록 연직 방향 편차가 커지는 경향을 보였다. 전반적으로 수심이 깊은 구간의 저층부로 갈수록 전기전도도의 값이 증가하는 경향을 나타났으며 흐름방향으로 진행됨에 따라 연직 편차가 줄어드는 경향을 보였다. 횡방향 혼합의 경우 지류의 유입으로 인하여 본류 좌안 쪽에서 전기전도도의 값의 상승을 확인할 수 있었으며 하류로 이동할수록 불균등했던 전기전도도의 분포가 횡방향 혼합을 통하여 균등한 분포로 전환되는 것으로 나타났다.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.5
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• pp.830-835
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• 2011

Total soil microbial activities have great impact to soil management for organic farming. This study was evaluated in the soil microbial community by fatty acid methyl ester (FAME) in a controlled horticultural field for strawberry organic farm. Experimental plots were prepared with a high level of soil electrical conductivity (EC) and a optimum level of soil EC. Soil microbial biomasses and communities of total bacteria, Gram-negative bacteria, Gram-positive bacteria, actinomycetes, fungi, and arbuscular mycorrhizal fungi in the high level of soil EC were significantly larger than those in the optimum level of soil EC. Lower ratios of cy17:0 to 16:$1{\omega}7c$ and cy19:0 to 18:$1{\omega}7c$ were found in the optimum level of soil EC than those in the high level of soil EC, indicating that microbial stress decreased.

• The Korean Journal of Food And Nutrition
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• v.31 no.6
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• pp.828-835
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• 2018

The objective of this study was to examine the biochemical parameters of hepatic function such as serum level of ALT (alanine aminotransferase), AST (aspartate aminotransferase), ALP (alkaline phosphatase), LDH (lactate dehydrogenase), and content of TG (triglyceride) and cholesterol, and tissue immunological changes of the $CCl_4$-treated rats with administration of the mixed sample extract (MSE). The liver weight in $CCl_4$-administered experimental control group (EC) was slightly higher than that of normal control (NC) group. Hepatic damage parameters (ALT, AST, ALP, LDH & TG) in serum of the EC group were significantly higher than those in serum of the NC and silymarin-treated positive control (PC) group. On the other hand, these hepatic damage parameters of MSE-treated experimental (E1 & E2) groups were significantly lower than those of EC group. The number of WBC, neutrophils, lymphocytes and platelets, and the contents of hemoglobin, and hematocrit in EC group were significantly higher than those of NC group. However, the number of WBC and lymphocytes in E1 and E2 groups were significantly lower than those of EC group. Also, the collagen developmental areas in the liver of NC and PC groups by hepatic immuno-histological findings were found slightly positive. Whereas, hepatic fibrous developmental tissue of EC group was strongly positive brown color band, those of E1 & E2 groups were decreased. Therefore, it was concluded that the induction of hepatic fibrous tissue activation had a preventive effect of MSE against the $CCl_4$-induced hepatic damage in rats. However, further study is needed in this filed.

• Journal of Korean Society on Water Environment
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• v.35 no.3
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• pp.257-270
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• 2019

Followingthe Four Rivers Project, cyanobacterial blooms have been frequently observed in the upstream of the installed weirs. The aim of this study was to characterize the major environmental factors that are associated with the cyanobacteria dominance in Baekje Weir (Geum River) and Juksan Weir (Youngsan River) based on intensive experiments and systematic data mining methods. The factors related to the cyanobacteria dominance include7-days cumulative rainfall (APRCP7), 7-days averaged flow (Q7day), water temperature (Temp), stratification strength (${\Delta}T$), electronic conductivity (EC), DO, pH, $NO_3-N$, $NH_3-N$, TN, TP, $PO_4-P$, Chl-a, Fe, BOD, COD, TOC, and $SiO_2$. The most highly correlatedfactors to the dominant cyanobacteria were found to be EC, Temp, Q7day, $PO_4-P$ in theBaekje Weir. On the other hand, those dominant in the Juksan Weir were ${\Delta}T$, TOC, Temp, EC and TN. The EC showed a strong correlation with cyanobacteria dominance in both weirs because a high EC represents a persisted low flow condition. The cyanobacteria dominance was as high as 56 % when the EC was equal or greater than $418{\mu}S/cm$ in Baekje Weir. It was as high as 63% when the ${\Delta}T{\geq}2.1^{\circ}C$ in the Juksan Weir. However, nutrients showed a minor correlation with cyanobacteria dominance in both weirs. The results suggest that the cyanobacteria dominate in astate where the water flow rate is low, water temperature is high and thermal stratification is strengthened. Therefore, the improvement of flow regimes is the most important to prevent persistent thermal stratification and formation of cyanobacteria bloom in theBaekje and JuksanWeirs.

• Ocean and Polar Research
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• v.44 no.4
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• pp.311-317
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• 2022

Seed germination and seedling growth of a halophyte, Suaeda japonica were examined to measure the effects of seed preservation periods and various soil compositions in the mudflat of Saemangeum, Korea. Seed germination declined from 74.30% to 44.30% as the preservation period increased from 4 months to 12 months. After 14 days of seeding, seed germination was lowest in sandy soil (SS) at 8.67% and highest in earthworm cast+leaf mold (EC+LM) at 67.33%, showing 4~5 times higher than SS. The average lengths of seedlings were 12.20 mm in SS and 42.20 mm in EC+LM, respectively. These results suggest that seed germination and seedling growth enhanced in the soil that has more organic matter. In the experiment mixing Saemangeum soil (SMS), seed germination was from 4.00% in SMS to 88.00% in the soil of SMS+EC+LM after 14 days. Similar growth patterns were observed in the length of seedlings from 5.00 mm in SMS to 49.60 mm in SMS+EC+LM. The present results indicate that a population of Suaeda japonica could be established by stimulating seed germination and seedling growth by the addition of organic matters such as EC, LM, and EC+LM in the Saemangeum mud flat.

• Korean Journal of Agricultural Science
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• v.49 no.1
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• pp.1-10
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• 2022

One hundred and twenty imprinting control region (ICR) mouse with initial body weights of 26 ± 2 g (5 weeks old) were assigned to six treatments for a two-week feeding trial to determine the effect of Pediococcus pentosaceus strains (PpS) which were isolated from three different types of Kimchi in ICR mice infected with Escherichia coli (Ec) or Salmonella Typhimurium (ST). Six groups constituted a normal control group without Ec or ST orally administrated (NC-; n = 20), a normal control group (NC+; n = 20), a group for which Lactobacillus plantarum was orally administrated (LP; n = 20), a group for which PpS A was orally administrated (PSA; n = 20), a group for which PpS B was orally administrated (PSB; n = 20), and a group for which PpS C was orally administrated (PSC; n = 20), the latter five groups constituted the Ec infected groups and the ST infected groups of 10 mice each. LP and PSC showed significantly (p < 0.05) improved growth performance compared to the other groups, except for NC- in the Ec infected mice group. NC+ showed significantly lower (p < 0.05) growth performance compared to the other groups, except for NC- in the ST infected mice groups. Regarding the Ec and Salmonella counts in the intestine, the LP and PSC groups had significantly lower (p < 0.05) counts than the NC+ and PSB groups. In conclusion, LP and PSC strains isolated from Kimchi can act as probiotics by inhibiting Ec and ST.

• Journal of Internet of Things and Convergence
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• v.9 no.1
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• pp.125-129
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• 2023

Age of Information (AoI) has been introduced in wireless networked control systems (WNCSs) to guarantee timely status updates. In addition, as the edge computing (EC) architecture has been deployed in NCS, EC close to sensors can be exploited to collect status updates from sensors and provide control decisions to actuators. However, when lots of sensors simultaneously deliver status updates, EC can be overloaded, which cannot satisfy the AoI requirement. To mitigate this problem, this paper uses actuators with computing capability that can directly receive the status updates from sensors and determine the control decision without the help of EC. To analyze the AoI of the actuation update via EC or directly using actuators, this paper developed an analytic model based on timing diagrams. Extensive simulation results are included to verify the analytic model and to show the AoI with various settings.