• Bulletin of the Korean Chemical Society
• /
• v.31 no.11
• /
• pp.3163-3172
• /
• 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
• /
• v.15 no.2
• /
• pp.185-190
• /
• 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.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.10 s.253
• /
• pp.1173-1178
• /
• 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.

• Fashion & Textile Research Journal
• /
• v.8 no.3
• /
• pp.326-330
• /
• 2006

The results of the research for the whitening effect and functional machanism of 1-(2-cyclohexylmethoxy-6-hydroxyphenyl)-3-(4-hydroxymethylphenyl)-propenone are as follow : 1. Propenone inhibited concentration-dependently the generation of melanin increased by the stimulation of ${\alpha}$-MSH and protoporphyrin IX, and $IC_{50}$ value was six to eight ${\mu}M$. This was five to seven times superior in the inhibiting effect, compared with kojic acid used as positive control group. 2. Propenone did not have a decolorizing effect on melanin already generated. 3. Propenone was observed to have toxicity of over $100{\mu}M$ for the mouse melanoma B16 cells.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.72-77
• /
• 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.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.20 no.1
• /
• pp.99-107
• /
• 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.

• Journal of agricultural medicine and community health
• /
• v.7 no.1
• /
• pp.43-49
• /
• 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
• /
• v.24 no.2 s.34
• /
• pp.161-170
• /
• 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.

• Journal of the Korea Institute of Building Construction
• /
• v.19 no.4
• /
• pp.323-330
• /
• 2019

The cement industry is considered a major industry for reducing greenhouse gases, increasing the amount of binding materials that can replace cement in concrete is known as the most effective method for reducing carbon dioxide. Therefore, research is being carried out to utilize large quantities of by-products that can be used as alternatives to cement. However, there are problems with reduced strength at early age and retarded setting for major reasons that do not increase the amount of mixture of binders used to replace cement. Thus, in this study, normal cement and high-fineness cement were used and physical properties were reviewed by placing differences in fly ash usage depending on the type of cement. As a result, the characteristics of strength were similar, and the hydration temperature was the same level. Also, the durability test showed that the length change, carbonation resistance were better than those of normal cement. Therefore, it is confirmed that the use of high-fineness cement is effective to reduce the amount of cement used and using more by-products.

• Food Science and Preservation
• /
• v.11 no.3
• /
• pp.325-330
• /
• 2004

This study was conducted to investigate optimal processing conditions, cooking characteristics, antioxidant activity and packaging method of rice coated with bamboo extract. In sensory evaluation of cooked rice, rice coated with bamboo ethanol extract was higher smell and taste than the other extraction methods, but texture showed no difference. As coating concentration increasing, L, a and b values of coated rice were increased. But L value of coated rice after cooking was decreased. On sensory evaluation of cooked rice, smell and taste were best in 10$\%$ coated with bamboo ethanol extract. Mineral contents of coated rice with bamboo extract were higher than those of uncoated. Water absorption and volume expansion of coated rice were lower than uncoated rice but showed higher toyo value. Hardness, gumminess and chewiness values of cooked rice with coated rice were higher than uncoated rice. Antioxidant activity of coated rice was higher than uncoated rice about twice times. Toyo values and alkali digestive values of coated rice were highest in paper package than the other packaging conditions. The total bacterial counts of rice coated with bamboo extract after cooking was lower than uncoated rice during storage at 25 and 6O$^{\circ}C$.