• Polymer(Korea)
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• v.25 no.5
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• pp.679-690
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• 2001

High resilience PU foams were prepared with polyether type cell opener. The influences of cell opener concentration on the kinetics, rheology, structural stability morphology and open cell content of the obtained foam were investigated and the role of cell opener during cell opening was determined. And mechanical properties as a function of cell opener concentration were studied. It was observed that urea formation reaction was delayed due to high hydrophilicity of cell opener The decrease of viscosity and the increase of tan $\delta$ were confirmed with increasing cell opener concentration so that the resulted foam had low structural stability and high open cell content. The deterioration of matrix and uniform dispersion of hydrogen-bonded urea in matrix with cell opener concentration was revealed by SEM analysis. As a result, elastic properties of the foam matrix were decreased due to high hydrophilicity of cell opener during the preparation of high resilience polyurethane foam and foam with high open cell content resulted. Hardness, tensile strength, tear strength, elongation of foam were decreased with increasing cell opener concentration.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.1
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• pp.64-78
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• 2019

The background concentrations of heavy metals in Korean coastal sediments were estimated using heavy metal data for 495 sediments obtained from 'National Marine Ecosystem Survey (Coastal ecosystem) in 2016-2017' and the extent of contamination was assessed. Al, Cs, and Li are chosen as appropriate indicators for sediment grain size. In the relationships between heavy metal and indicators concentrations, the lowest slope data were selected through the outlier removal and residual analysis, and the background concentrations were presented as a linear regression line between metal and indicator. Comparing the previous studies for the background concentrations of heavy metals in Korean coastal sediments, concentration levels were generally consistent but those for As and Cd were presented for the first time, and the background concentration using Li as the indicator was presented for the first time.

• Biomedical Science Letters
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• v.3 no.2
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• pp.83-88
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• 1997

In septic patients, disseminated intravascula. coagulation (DIC) occurs frequently and is a pathologic condition associated with a variety of critical illness. DIC may complicate the already complex clinical situations and contribute to the high mortality. Nevertheless, its pathogenic mechanisms are not completely elucidated. Present study was prospectively designed to understand the pathogenetic mechanisms involved in the development of DIC. 15 rats were subjected to study and according to the aim, they were divided into three groups： group I, control (not treated-endotoxin, n=5)； group II (12 hours after endotoxin injection, n=5)； group III (24 hours after endotoxin injection, n=5). Experimental DIC was induced in rats by a bolus injection of endotoxin (1mg/kg, E. coli serotype 055:B5). Blood was collected by direct puncture of the heart. Platelet count, fibrinogen and plasminogen concentration, antithrombin III, D-dimer and complement components (C3 and C4) were measured in all subjects. In group II and III, there were apparent signs of DIC, including thrombocytopenia, decreased fibrinogen (but increase in group III), reduced C3 and antithrombin III, and elevated D-dimer. These data indicated that endotoxin might induce the activation of several pathways such as coagulation, fibrinolytic and complement cascade, causing DIC and subsequent multiple organ failures. Ultimately, the increased knowledge of the various pathogenetic mechanisms of coagulation activation and fibrinolysis in endotoxin-induced DIC may have prophylactic or therapeutic implications.

• Journal of Korea Water Resources Association
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• v.54 no.spc1
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• pp.1037-1051
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• 2021

Biochemical oxygen demand (BOD) concentration, one of important water quality indicators, is treated as the measuring item for the ecological chapter in lakes and rivers. This investigation employed novel two-stage hybrid paradigm (i.e., wavelet-based gated recurrent unit, wavelet-based generalized regression neural networks, and wavelet-based random forests) to predict BOD concentration in the Dosan and Hwangji stations, South Korea. These models were assessed with the corresponding independent models (i.e., gated recurrent unit, generalized regression neural networks, and random forests). Diverse water quality and quantity indicators were implemented for developing independent and two-stage hybrid models based on several input combinations (i.e., Divisions 1-5). The addressed models were evaluated using three statistical indices including the root mean square error (RMSE), Nash-Sutcliffe efficiency (NSE), and correlation coefficient (CC). It can be found from results that the two-stage hybrid models cannot always enhance the predictive precision of independent models confidently. Results showed that the DWT-RF5 (RMSE = 0.108 mg/L) model provided more accurate prediction of BOD concentration compared to other optimal models in Dosan station, and the DWT-GRNN4 (RMSE = 0.132 mg/L) model was the best for predicting BOD concentration in Hwangji station, South Korea.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.249-250
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• 2001

최근 대도시 지역에서의 오존농도가 환경기준을 초과하는 빈도가 날로 증가하고 있는 실정이며, 이에 국내의 경우 오존농도 증가에 대비하여 대기 중 오존농도가 일정기준(시간당 0.12 ppm)보다 높게 나타났을 때 신속하게 경보를 발령, 시민들의 건강과 생활환경상의 피해를 최소화하기 위해 오존경보제를 시행해오고 있다. 한편 전세계적으로 대도시 지역에서의 지표면 오존농도가 환경기준을 초과함에 따라 오존생성과 관련된 전구물질(precursor)에 대한 제어과정이 지표면 오존농도의 저감을 실현하기 위한 가장 시급한 과제로 대두되고 있으며, 특히 미국의 경우 1993년부터 광화학평가측정망(Photochemical Assessment Monitoring Stations;PAMS)을 설치하여 이들 물질에 대한 보다 집중적인 모니터링을 실시하고 있는 것으로 알려져 있다. (중략)

• The Korean Journal of Rheology
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• v.3 no.1
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• pp.76-85
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• 1991

적은양의 분자량이 큰선형 고부자를 수용액에 첨가함으로서 얻어지는 마찰저항가소 연구가 rotating disk 장치를 이용해 수행되었다. 마찰저항 감소제로 poly(ethylene oxide)와 poly(acrylamide)를 사용하였으며 고분자 분자량 고분자 농도, disk 의 회전속도 및 온도 등 여러 가지 인자에 대한 마찰정항감소의 의존성을 연구하였다. 또한 마찰저항 감소 효과와 고분자 용액의 점도평균 분자량을 동시에 측정함으로서 고분자 퇴화에 대한 연구도 수행하 였다. 마찰저항감소는 고분자 농도가 증가함에 따라 임계농도에 도달할때까지 증가하였고 낮은 농도에서는 분자량이 큰 고분자일수록 더욱 큰 마찰저항 감소효과를 나타내었다. 마찰 감소 진행 중의 높은 전단력에 기인하는 고분자의 분해는 고분자 농도가 낮은데에서 더욱두 드러지게 나타났으며 온도 효과의 연구로부터 poly(acrylamide)가 poly(ethylene oxide)보다 열적으로 안정함을 알수 있었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1368-1372
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• 2007

바닥이 언덕과 저면으로 이루어진 연속적인 횡방향 바닥형상을 갖는 개수로 흐름의 부유사 농도분포를 수치모의 하였다. 비선형 ${\kappa}-{\varepsilon}$ 모형을 이용하여 흐름의 지배방정식인 곡선 직교좌표계에 대한 Navier-Stokes 방정식을 해석하였으며, 와점성계수 개념을 이용하여 부유사 수송 방정식을 해석하였다. 기존의 실험결과와 비교하여 모형이 격자형 이차흐름을 비교적 잘 예측하는 것을 확인하였으며, 동일한 흐름에 대하여 부유사 농도 분포를 계산하였다. 부유사량의 계산 결과 언덕 위의 부유사 농도분포가 저면 위의 농도분포보다 크게 나타났다.

• The Korean Journal of Rheology
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• v.10 no.1
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• pp.7-13
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• 1998

중량 평균 분자량이 1.22$\times$106이고 다분산도가 8.90이며 수분과 아밀로오스 함량이 각각 9.35%, 27%인 도토리 전분에 sucrose를 첨가하여 동적 유변학적 특성에 대한 온도와 농도의존성을 고찰하였다. AS(acorn starch)-sucrose 계의 점도는 전단속도가 증가하면 감 소하는 전단담화 현상을 나타내며 sucrose 농도가 증가할수록 점도가 증가하였고, Casson 식에 의해 얻어진 항복치는 sucrose 농도가 증가하면 증가하였다. 저장영률과 손실영률은 sucrose 농도가 증가하면 단일하게 증가하였고 손실 탄성률은 온도가 증가하면 감소하였다. DSC 측정자료를 zipper model에 적용시켜 본 결과 sucrose 농도가 증가할수록 zipper의 수 와 junc-tion zone의 수는 증가했으며 크기는 감소하였다. Sucrose는 전분과 수소결합을 형 성하여 용액내에서 가소제처럼 거동함을 알수있었다.

• The Korean Journal of Pesticide Science
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• v.8 no.1
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• pp.38-45
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• 2004

To elucidate the photolysis characteristics of the insecticide imidacloprid in the environment, $[^{14}C]$imidacloprid was treated into water and paddy soil-water system. In water system, the amount of $^{14}C$-radioactivity distributed in aqueous phase was rapidly increased up to 80% of total $^{14}C$ in water during 7 days of exposure to sunlight. Also, the amounts of imidacloprid in water at day 0 and 3 days after treatment were 1.2461 and 0.8594 mg/kg, respectively, not being detected 7 days after treatment, indicating rapid degradation of imidacloprid in water by sunlight. One photodegradation product, imidacloprid urea, in which the $N-NO_2$ moiety of imidacloprid was replaced by oxygen, was detected from water in water and water-paddy systems. The amount of the metabolite detected from water in water system was 0.0112 mg/kg 1 day after treatment and reached the top concentration of 0.0391 mg/kg 7 days after treatment. In case of water-paddy system, its amount was 0.0117 mg/kg 1 day after treatment and reached the highest concentration of 0.0259 mg/kg 3 days after treatment. Rapid transformation of imidacloprid into polar compounds continued until 7 days after treatment, considering that 80% of $^{14}C$ in water distributed in aqueous phase 7 days after treatment, amount of imidacloprid was 1.6538 mg/kg at day 0 and 0.8785 mg/kg 1 day after treatment, not being detected after 15 days, indicating rapid degradation of imidacloprid in water-paddy soil system by sunlight. The direct degradation of imidacloprid to imidacloprid urea would be a major photodegradation pathway in water and water-paddy soil systems.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.5
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• pp.543-551
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• 1993

This study was designed to observe the effects of the feeding mixed with the sardine oil containing n-3 EPA, DHA and the safflower oil in which rich n-6 linoleic acid on the improvement of the lipids and on the fatty acid matabolism of serum lipoprotein in the dietary hyperlipidemic rats. Experimental oils mixed with 16% butter(control group) and 8% butter+8% olive oil, 8% butter and various level of sardine and safflower oils were administered to the male rats of the Sprague Dawley for 4 weeks. Concentrations of total cholesterol in serum lipoproteins were highest in the LDL, followed by VLDL, HDL and chylomicron components. in the triglyceride concentrations, chylomicron were highest, and much VLDL, LDL, HDL components. There were highest in the HDL, followed by LDL, VLDL and chylomicron in phospholipid concentrations of serum lipoproteins. Concentrations of total cholesterol, triglyceride and phospholipid in serum lipoprotein were lower in the other groups than in the control groups, and particularly, lowest in the group 5(4% sardine oil+4% safflower oil). From this results, the feeding equal quantity mixed oil with n-3 PUFA rich sardine oil and n-6 PUFA rich safflower oil were effective on the improvement of the lipid composition in the serum lipoprotein. It might be due to the effects of appropriate rations of P/S, 0.85 and n-6/n-3P, 2.85 in the test lipids. In the fatty acid composition of serum lipoprotein, ratio of P/S and n-3/n-6P were influenced from the fatty acid compositions of the mixed test lipids. And EPA contents were higher in the chylomicron components.