• Bulletin of the Korean Chemical Society
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• 제31권11호
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• pp.3163-3172
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• 2010

In this work, a novel method to synthesis of an acrylic superabsorbent hydrogel was reported. In the two stage hydrogel synthesis, first copolymerization reaction of acrylonitrile (AN) and acrylamide (AM) monomers using ammonium persulfate (APS) as a free radical initiator was performed. In the second stage, the resulted copolymer was hydrolyzed to produce carboxamide and carboxylate groups followed by in situ crosslinking of the polyacrylonitrile chains. The results from FTIR spectroscopy and the dark red-yellow color change show that the copolymerization, alkaline hydrolysis and crosslinking reactions have been do take place. Scanning electron microscopy (SEM) verifies that the synthesized hydrogels have a porous structure. The results of Brunauer-Emmett-Teller (BET) analysis showed that the average pore diameter of the synthesized hydrogel was 13.9 nm. The synthetic parameters affecting on swelling capacity of the hydrogel, such as AM/AN weight ratio and hydrolysis time and temperature, were systematically optimized to achieve maximum swelling capacity (330 g/g). The swollen gel strength of the synthesized hydrogels was evaluated via viscoelastic measurements. The results indicated that superabsorbent polymers with high water absorbency were accompanied by low gel strength. The swelling of superabsorbent hydrogels was also measured in various solutions with pH values ranging from 1 to 13. Also, the pH reversibility and on-off switching behavior makes the hydrogel as a good candidate for controlled delivery of bioactive agents. Finally, the swelling of synthesized hydrogels with various particle sizes obey second order kinetics.

• Macromolecular Research
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• 제15권2호
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• pp.185-190
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• 2007

Poly(norbornene dimethyl dicarboxylate)s, (PNDMD)s, were prepared by addition polymerization with palladium(II) catalyst from pure exo-monomers, and their structure and properties were compared with those of poly(norbornene dicarboxylic acid dialkyl ester)s, (PNDADA)s. Both polymer series exhibited good solubility in general organic solvents and excellent thermal stability up to $330^{\circ}C$. Wide-angle X-ray scattering (WAXS) study indicated the presence of nano-scale layer-like order in amorphous PNDADAs, while PNDMDs showed random amorphous structure. The glass transition temperatures and dielectric constants of solid polymers were found to decrease as the alkyl side-chain length increases for both polymer series. However, PNDMDs showed lower glass transition temperatures and higher dielectric constants, as compared with those of PNDADAs containing the same alkyl substituents. This difference, caused by the higher side-group mobility of PNDMDs, may be closely related to the nano-scale order in amorphous PNDADAs and its absence in PNDMDs.

• 대한기계학회논문집A
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• 제30권10호
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• pp.1173-1178
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• 2006

In a primary reactor cooling system(RCS), a dissimilar weld zone exists between cast stainless steel(CF8M) in a pipe and low-alloy steel(SA508 cl.3) in a nozzle. Thermal aging is observed in CF8M as the RCS is exposed for a long period of time to a reactor operating temperature between 290 and $330^{\circ}C$, while no effect is observed in SA508 cl.3. The specimens are prepared by an artificially accelerated aging technique maintained for 300, 1800 and 3600 hrs at $430^{\circ}C$, respectively. The specimens for elastic-plastic fracture toughness tests are according to the process in the thermal notch is created in the heat affected zone(HAZ) of CF8M and deposited zone. From the experiments, the $J_{IC}$ value notched in HAZ of CF8M presented a rapid decrease up to 300 hours at $430^{\circ}C$ and slowly decreased according to the process in the thermal aging time. Also, the $J_{IC}$ value presented a lower value than that of the CF8M base metal. And, the $J_{IC}$ of the deposited zone presented the lowest value of all other cases.

• 한국의류산업학회지
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• 제8권3호
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• pp.326-330
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• 2006

1-(2-cyclohexylmethoxy-6-hydroxyphenyl)-3-(4-hydroxymethylphenyl)-propenone의 미백 효능 및 작용기전의 연구 결과는 다음과 같다. 1.Propenone은 ${\alpha}$-MSH와 protoporphyrin IX 자극에 의하여 증가한 멜라닌 생성을 농도 의존적으로 억제하였으며, $IC_{50}$은 $6-8{\mu}M$이었다. 이것은 양성대조군으로 사용한 kojic acid와 비교하여 약 5-7배 정도로 억제 효과가 우수하였다. 2. Propenone은 생성된 멜라닌에는 탈색효과가 없었다. 3. Propenone은 mouse melanoma B16 세포에 대하여 $100{\mu}M$ 이상에 독성이 관찰되었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.72-77
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• 2004

In a primary reactor cooling system(RCS), a dissimilar weld zone exists between cast stainless steel(CF8M) in a pipe and low-alloy steel(SA508 cl.3) in a nozzle. Thermal aging is observed in CF8M as the RCS is exposed for a long period of time to a reactor operating temperature between 290 and $330^{\circ}C$, while no effect is observed in SA508 cl.3. The specimens are prepared by an artificially accelerated aging technique maintained for 300, 1800 and 3600 hrs at $430^{\circ}C$, respectively. The specimens for elastic-plastic fracture toughness tests are prepared one type, which notch is created in the heat affected zone(HAZ) of CF8M. And, the specimens for fatigue crack growth tests are prepared in three classes, which notches are created at the center of deposited zone, the HAZ of CF8M, and the HAZ of SA508 cl.3. From the experiments, the J-integral values with the increase of aging time decrease, and the differences of the fatigue crack growth behaviors are relatively small in the three classes specimens.

• 디지털산업정보학회논문지
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• 제20권1호
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• pp.99-107
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• 2024

This study conducted a survey of 330 students participating in the extracurricular curriculum program at K University in Chungcheongbuk-do to analyze the impact of extracurricular satisfaction and career decision self-efficacy on career preparation behavior. The main results and implications are as follows. First, the positive perception of participation in extracurricular curriculum programs had a significant impact on career preparation behavior. Second, high career decision self-efficacy was related to active career preparation behavior. It is necessary to provide continuous career program support, provide counseling tailored to the needs of each student, and establish a systematic career diagnosis system. This study is limited to extracurricular curriculum program participants and has limitations in generalization. Comparative and analytical research is needed by measuring the performance of various educational programs conducted in universities. It is necessary to support the development and operation of various extracurricular curriculum programs that reflect the needs of society and students and to prepare continuous quality management measures.

• 농촌의학ㆍ지역보건
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• 제7권1호
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• pp.43-49
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• 1982

Clonorchiasis sinensis is one of the most important endemic diseases in Korea, and this disease has been known to be one of public health concern in many areas of Korea. This survey was undertaken to evaluate the status of clonorchiasis in Yeoju Gun, Gyeong-gi Do from July to September 1980. A total of 1,194 male students were examined by intradermal test with Clonorchis antigen. In order to detect Clonorchis egg, the stool examinations were undertaken to 1,158 students, and the intensity of the Clonorchis infection was estimated by the Stoll's egg count. The prevalence rate was reanalyzed by the regional groups for an investigation of regional characteristics of infection. The following results were obtained in this survey. 1) Among 1,194 students in Yeoju Eup, positive rate of intradermal test with C. sinensis antigen was 17.2 percent. (middle school14.6% and high school 20.1%). 2) In the examination of 1,158 stool specimens, Clonorchis eggs were found in 97 (8.4%) cases. 3) Mean E.P.G. of Clonorchis infected case was $1,330{\pm}2,620$. 4) The degree of the intensity of Clonorchis infection by E.P.G. count was distributed as 73.6% in light infection (100-999), 22.6%, in moderate infection (1,000-9,999), and 3.8% in heavy infection (10,000-29,999). 5) High prevalence rate of Clonorchis sinensis was found in the Sang-Ri(9,3%) and Ha-Ri(8.4%) in Yeoju Eup. Neighbouring Bugnae Myun (11.5%), Gangcheon Myun(12.1%) and Neungseo Myun (11.1%) adjacent to the river had a similary high prevalence of C. sinensis.

• Journal of Preventive Medicine and Public Health
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• 제24권2호
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• pp.161-170
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• 1991

The purpose of this study is to find the tracking of blood pressure in primary school-age children. A follow-up study was conducted from 1986 to 1990 on 330 first grade children attending primary schools in Kangwha County, Kyungki-Do. Basically we employed a linear regression model with random coefficients to figure out the relation between blood pressure changes and initial blood pressure. We obtained the following results ; 1. The mean blood pressures were increased grade went up in both sexs and were generally higher in female than male except for the systolic blood pressure at first grade. The size of difference was about 0.8 mmHg in mean systolic blood pressure and 1.5 mmHg in mean diastolic blood pressure. 2. The average annual increasing rates of systolic blood pressure were 2.5 mmHg in male and 3.1 mmHg in female respectively. For the diastolic blood pressure IV the average annual increasing rates were observed to be 3.0 mmHg in male and 2.9 mmHg in female respectively. Increasing rate of systolic blood pressure was significantly higher in female than male. 3. The adjusted regression coefficient of systolic blood pressure change on initial value was -0.11 in male and -0.13 in female and that coefficient of diastolic blood pressure change on initial value was -0.01 in male and -0.11 in female. This result shows that children with higher initial blood pressure do not pick up their blood pressure faster than others with lower initial blood pressure. There is no evidence of tracking of blood pressure in children. It is essential to find the earliest age having the tracking of blood pressure and we leave it for the further study.

• 한국건축시공학회지
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• 제19권4호
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• pp.323-330
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• 2019

시멘트 산업은 온실가스 감축을 위한 주요 산업분야로 고려되고 있으며, 콘크리트에 시멘트를 대체할 수 있는 재료의 사용량을 증가시키는 것은 이산화탄소 감축을 위해 효과적인 방법으로 알려져 있다. 따라서 시멘트의 일부를 대체하여 사용할 수 있는 산업부산물을 다량으로 활용하기 위한 연구가 진행되고 있다. 그러나 산업부산물의 혼합량을 증가시키지 못하는 큰 이유로 초기강도 저하와 응결지연에 대한 문제점이 있다. 따라서 이 연구에서는 보통 시멘트를 사용한 경우와 고분말도 시멘트를 사용한 경우에 대해 플라이애시의 사용량에 차이를 두고 물리적 특성을 검토하여, 시멘트의 사용량을 줄이고 산업부산물을 다량으로 사용하기 위한 방안으로서, 고분말도 시멘트를 활용한 결과에 대한 기초 자료를 제시하였다.

• 한국식품저장유통학회지
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• 제11권3호
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• pp.325-330
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• 2004

대나무 추출액을 쌀에 코팅하는 조건, 코팅쌀의 취반 특성, 기능성 및 포장방법을 검토한 결과는 다음과 같다. 대나무 추출액 별 코팅 취반미의 관능은 알코을 추출액 코팅쌀이 향과 맛은 가장 양호하였으나 질감은 차이가 없었다. 대나무 알코을 추출액의 코팅량 별 쌀의 색도는 L, a, b값 모두 코팅 농도가 증가할수록 증가되었으나 밥은 L값만 감소되었으며 밥의 관능은 10$\%$ 코팅 처리에서 향과 맛이 양호하였다. 코팅쌀의 취반 후 물성은 경도, 검성, 씹힘성은 청결미 보다 높았고 응집성, 탄력성, 부착성은 낮은 경향이었다. 대나무 추출액 코팅쌀의 무기성분은 청결미보다 모든 성분 함량이 높았는데 특히 K 함량이 월등히 높았다. 코팅쌀의 취반특성은 청결미 보다 흡수율과 팽창율은 낮았으나 토요식미지수는 높았다. 코팅쌀의 포장방법 별 식미는 청결미보다 약간 우수하였으며 종이포장에서 토요식미지수와 알카리붕괴도가 가장 높았다. 코팅쌀 취반미의 24시간 저장후 총 균수는 청결미 보다 감소되었으며 물성 중 경도, 부착성, 검성, 씹힘성은 청결미 보다 컸다.