• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.53-53
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• 2002

Alkali-soluble random copolymer (ASR) was used as a functional resin in the emulsion polymerization of styrene to prepare structured nanoparticles. The calorimetric technique was applied to study the kinetics of emulsion polymerization of styrene using ASR and conventional ionic emulsifier, sodium dodecyl benzene sulfonate (SDBS). ASR could form aggregates like micelles and the solubilization ability of the aggregates was dependent on the neutralization degree of ASR. The rate of polymerization in ASR system was lower than that in SDBS system. This result can be explained by the creation of a hairy ASR layer around the particle surface, which decreases the diffusion rate of free radicals through this region. Although a decrease in particle size was observed, the rate of polymerization decreased with increasing ASR concentration. The higher the concentration of ASR is, the thicker and denser ASR layer may be, and the more difficult it would therefore be for radicals to reach the particle through this layer of ASR. The rate of polymerization decreased with increasing the neutralization degree of ASR. The aggregates with high neutralization of ASR are less efficient in solubilizing the monomer and capturing initiator radicals than that of the lower neutralization degree, which leads to decrease in rate of polymerization.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.615-618
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• 2002

Turbo-fan for ceiling cassette type air conditioner doesn't operate in general volute. It is operated by porous material, heat exchanger. Heat exchanger increases resistance of air conditioning system and disturbs exit-flow of impeller. Therefore it has some influences on impeller capacity. In this study, we want to how that influence of exchanger on impeller capacity for ceiling cassette type air conditioner. To research, we made circular case that didn't have asymmetric part unlike rectangular case. With and without heat exchanger we measured total pressure and static pressure of impeller and three-dimensional rear flow field From the result, a turbo fan , installed in the 35mm back of fan and operated in heat exchanger, experienced $2{\%}{\~}5{\%}$% total pressure loss over all flow rate. With heat exchanger impeller efficiency decrease as flow rate decrease when flow rate coefficient was below 0.18. Especially when flow rate coefficient was below 0.12, there was $20{\%}{\~}30{\%}$ decrease of impeller efficiency.

• Microbiology and Biotechnology Letters
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• v.17 no.3
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• pp.219-223
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• 1989

Effect of antifoam agents, silicone oil and neolin 302, was investigated on the production of prodnisolone by microbial $\Delta$$^1$-Dehydrogenation of hydrocortisone. The microbial process was conduct-ed by using a pseudo-crystallofermentation. By the hydrophobic-hydrophobic interaction, the steroid crystals aggregated with the antifoam agents. The aggregation resulted in a decrease of total mass transter area of substrate particles which is proportional to the dissolution rate of the solid substrate, and it consequently led to a significant decrease of the bioconversion rate. The bioconversion with neolin proceeded more slowly than with silicone oil. Increase of the concentration of the antifoam agents also yielded a significant decrease of the bioconversion rate.

• Journal of Pharmaceutical Investigation
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• v.13 no.3
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• pp.100-103
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• 1983

Coprecipitates of sulpiride and polyethylene glycol (PEG) decrease the dissolution rate of sulpiride and the degree of decrease is reversely proportional to molecular size of PEG and proportional to increase of PEG ratios in coprecipitates. The physical mixtures of sulpiride and PEG increase the dissolution rate of sulpiride.

• KDI Journal of Economic Policy
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• v.44 no.2
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• pp.45-71
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• 2022

This paper studies potentially relevant factors affecting changes in the number of self-employed in Korea during the period of 1986-2018. The number of self-employed had increased steadily until 2002 but started to decrease around that time and had continued to decline. The increasing trend in the number of self-employed during 1986-2001 is mostly explained by demographic changes, whereas the declining trend during 2002-2018 cannot be explained by demographic factors. In this study, I consider four institutional factors that potentially affect the decrease in the number of self-employed after 2002: i) a decrease in the job-separation rate of wage workers, ii) an increase in the income tax rate applied to the self-employed, iii) an increase in minimum wages, iv) an expansion of unemployment insurance benefits. Using a search and matching model with the self-employed, I quantify the effects of these four factors on the decrease in the number of self-employed during 2002-2018. Quantitative results show that the impact of the increase in the minimum wage is relatively large, whereas the effects of the other three factors are limited. The increase in the minimum wage accounts for approximately 17.5% (0.169 million) of the decrease in the number of self-employed during 2002-2018 (0.964 million).

• Clinical and Experimental Pediatrics
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• v.54 no.11
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• pp.429-435
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• 2011

Although Korean population has been growing steadily during the past four decades, the nation is rapidly becoming an aging society because of its declining birth rate combined with an increasing life expectancy. In addition, Korea has one of the lowest fertility rates in the world due to fewer married couples, advanced maternal age, and falling birth rate. The prevalence of low birth weight infants and multiple births has been increased compared with the decrease in the birth rate. Moreover, the number of congenital anomalies is expected to increase due to the advanced maternal age. In addition, the number of interracial children is expected to increase due to the rise in the number of international marriages. However, the maternal education level is high, single-mother birth rate is low, and the gender imbalance has lessened. The number of overweight babies has been decreased, as more pregnant women are receiving adequate prenatal care. Compared to the Asian average birth weight, the average birth weight is the highest in Asia. Moreover, the rate of low birth weight infants is low, and infant mortality is similarly low across Asia. Using birth data from Statistics Korea and studies of birth outcomes in Korea and abroad, this study aimed to assess the changes in maternal and infant characteristics associated with birth outcomes during the past four decades and identify necessary information infrastructures to study countermeasures the decrease in birth rate and increase in low birth weight infants in Korea.

• Development and Reproduction
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• v.20 no.2
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• pp.127-133
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• 2016

Purine metabolism is known factor for nuclear maturation of oocytes through both follicle cells and oocyte itself. However, it is largely unknown the roles of purine metabolism in the oocyte competence for fertilization and early development. In this study, the effects of adenosine in oocyte competence for development were examined using adenosine and its synthetic inhibitors. Adenosine treatment from GV intact stage for 18 hr (fGV) caused of decrease the fertilization rate but of increase the cleavage rate compared from the other stage treatment groups. Hadacidin did not effect on fertilization rate but increased cleavage rate without stage specificity. Adenosine did not block the effects of hadacidin with the exception of fGV group. Inhibition of purine synthetic pathways the fertilization rate was decreased in the fGV and fGVB groups but increased in the fMII group. Exogenous adenosine caused of decrease fertilization rate in the fGVB group but increase in the fMII group. Cleavage rate was dramatically increased in the adenosine treatment with synthetic inhibitors. It means that the metabolism of purine has stage specific effects on fertilization and cleavage. Exogenous adenosine had only can improve oocyte developmental competence when it treated at GV intact stage. On the other hand, endogenous synthesis in all maturation stage cause of increase the cleavage rate without effects on fertilization. These data suggest that adenosine at GV stage as a paracrine fashion and inhibitions of endogenous adenosine in all stage improve oocyte developmental competence.

• Korean Journal of Veterinary Research
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• v.15 no.2
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• pp.177-180
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• 1975

This study was undertaken to obtain more detailed knowledge of the oxygen consumption rate of chick embryos, of the relationship between the increasing rate of embryo weight and that of oxygen consumption, of the daily increase of oxygen consumption by that of embryo weight, and of the metabolic rate of the White Leghorn eggs. The results obtained are summarized as follows. 1. The average oxygen consumption rate of the chicken embryo at the 3rd day of incubation is 0.8ml/h, STPD. It is strongly suggested that this value can used as a physiological criterion to classify the fertilized and unfertilized eggs, on the other hand oxygen consumption rate of the fertilized eggs reaches a plateau between the 18th and 20th days. 2. There exists a parallel relationship between the increasing rate of embryo weight and that of oxygen consumption rate during the incubation period. 3. There are not exist a parallel relationship between the daily increase of embryo weight and that of oxygen consumption during the whole incubation period. 4. The metabolic rate of chicken embryo(ml/h/g) is highest in the early stage of incubation and it started to decrease sharply until the 8th day follow by slow decrease thereafter.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.40-45
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• 1999

This experimental study presents the strength properties of mortar using the blast-furnace slag sand. The mix disign of this study is based on the each three classes of unit water; (250, 275, 300)kg/㎥ and four classes of W/C; (45, 50, 55, 60)% and substitution rate(0, 25, 50, 75, 100)%. It gives following result. As W/C ratio increase, the strength is decrease. In case of mortar using air-cooled blast-furnace slag sand, the 3-days and 7-days compression strength is increase as substitution rate is higher. But in case of the mortar using the quenched blast-furnace slag sand, the compression strength is decrease as substitution rate is higher.

• YAKHAK HOEJI
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• v.26 no.2
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• pp.105-110
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• 1982

The antihypertensive effect of clonidine administered concurrently with labetalol or metoprolol were studied with spontaneously hypertensive rats (SHR). The changes of heart rate were also observed in the same rats. Every drug was orally administered single dose after prechecking the systolic blood pressure and heart rate of SHR. The blood pressure of SHR in concurrently administered group was more significantly decreased than in alone administered group. The effective and stable decrease of blood pressure was maintained at the group of clonidine with labetalol (0.05+50mg/kg) for 9 hours. The group of clonidine with metoprolol (0.05+100mg/kg) manifested more marked decrease of blood pressure than the group of metoprolol (100mg/kg) alone for 9 hours. The diminishing effect of heart rate was enhanced in group of administering clonidine with labetalol, decreasing the dose of labetalol from 50mg/kg via 25mg/kg to 12.5mg/kg. On the other hand, in the group that clonidine was administered concurrently with metoprolol, the diminishing effect of heart rate was decreased with decreasing doses of metoprolol from 100mg/kg via 50mg/kg to 25mg/kg.