• Applied Chemistry for Engineering
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• v.32 no.1
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• pp.20-27
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• 2021

Effects of the etching treatment of SAPO-34 catalyst were investigated to improve the catalytic lifetime in DTO reaction. The aqueous NH3 solution was a more appropriate treatment agent which could control the degree of etching progress, compared to that of using a strong acid (HCl) or alkali (NaOH) solution. Therefore, the effect on characteristics and lifetime of SAPO-34 catalyst was observed using the treatment concentration and time of aqueous NH3 solution as variables. As the treatment concentration or time of aqueous NH3 solution increased, the growth of erosion was proceeded from the center of SAPO-34 crystal plane, and the acid site concentration and strength gradually decreased. Meanwhile, it was found that external surface area and mesopore volume of SAPO-34 catalyst increased at appropriate treatment conditions. When the treatment concentration and time were 0.05 M and 3 h, respectively, the lifetime of the treated SAPO-34 catalyst was the longest, and was significantly enhanced by ca. 36% (based on DME conversion of > 90%) compared to that of using the untreated catalyst. The model for the etching progress of SAPO-34 catalyst in a mild treatment process using aqueous NH3 solution was also proposed.

• Journal of Industrial Convergence
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• v.19 no.6
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• pp.21-35
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• 2021

The purpose of this paper is to examine how demand for labor affects the job seeker's decision on the level of investment in education. In the current paradigm of economic growth in which innovations and technological developments generally weaken the strength demand for labor and increases the uncertainty related to employment, this paper provides a theoretical framework that can be used as a basic framework in understanding the decision of investment in education in varying conditions of demand for labor. The following are the findings of this paper. First, the level of investment in education can generally be regarded to be higher as the demand for labor exacerbates but for the job seekers with a certain characteristic. Second, the Arrow-Pratt absolute risk-aversion measure is the characteristic of the job seeker that determines in what direction the job seeker changes in the level of investment in education, For an arbitrary level of demand for labor there exists a certain threshold which determines the minimum degree of risk-aversion required for the job seeker's Arrow-Pratt should go over to increase the level of education as demand for labor weakens. Third, the job seekers lower the level of education even though the demand condition in labor markets weakens if the compensation function does not depend on the level of education. This is surprising because it turns out that one of the reasons why job seekers invest in education is that they want to be recognized in their compensation for their level of education even when more education still raises the probability of employment.

• Korean Journal of Soil Science and Fertilizer
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• v.26 no.2
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• pp.132-137
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• 1993

This study was conducted to establish a safe cultivation technique of rice in the area irrigated with polluted water. The changes of water and grain quality were investigated in the two paddy soils which are located in the adjacent of Geumho river in 1991. The results obtained in this study are as follows : 1. The qualities of irrigation water were shown to be in the range of 6.7~7.4 in pH, 21.3~52.8ppm in COD. 3.2~5.3ppm in $NH_4-N$ and 1.6~6.0ppm in $PO_4$, respectively. Concentration of COD and $NH_4-N$ were over the standard levels. Therefore, the water pollution was mainly caused by organic waste matters. 2. Ranges of the Soil pH of Gyeongsan and Gyuam series were 5.6~6.0, 6.1~6.3 respectively. The contents of avaiable $P_2O_5$ and $SiO_2$ were high in the silicate treatment plots among other plots. 3. Degree of irrigation water pollution of Geumho river showed the highest peak in June. 4. Plant height, number of panicle and yield of rice grain were not decreased by the diminution of nitrogen fertilizer application. 5. The $Mg/(K{\times}N)$ ratio and Gel consistency of milled rice were increased in the nitrogen decreasing plot, but the alkali digestability value and protein content were decreased. Therefore, it was desirable to decrease the amount of nitrogen fertilizer application.

• Korean Journal of Soil Science and Fertilizer
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• v.27 no.2
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• pp.111-116
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• 1994

These studies were carried out to investigate the possibility on the agricultural utilization of lake sediment collected in the Daecheong Lake. Several parameters to estimate the degree of maturity of compost by windrow system were tested during a 50 day periods, and the results were as follows : During the composting of Daecheong Lake sediment, C/N ratio decreased gradually from 18.9 at the beginning to 13.1 at the final, while CEC increased from 33.5me/100g to 62.5me/100g. The temperature of lake sediment pile was the highest as $52^{\circ}C$ at 15th day and then decreased slowly until $30^{\circ}C{\sim}40^{\circ}C$ after 50 days. The results may be suggested that Daecheong Lake sediment compost reaches an acceptable level of stability after about 50 days. In order to know the effect of the Lake sediment and its compost on the growth of tomato(Lycopersicum esculentum M.), pot experiments were performed. The appiication of lake sediment(AS) itself, sediment organic fertilizer(SOF), and NPK mixed with sediment organic fertilizer(NSF) was more effective for tomato plant height, fresh and dry weight, and chlorphyll content than those of control treatment. Also, the lake sediment compost improved the physico-chemical properties of soil such as pH, total carbon, total nitrogen, available phosphorous and CEC.

• Journal of The Korean Society of Grassland and Forage Science
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• v.26 no.4
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• pp.277-284
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• 2006

Seed priming is a useful technique for early establishment of seedling. In this experiment, the conditions for priming of pasture seeds (tall fescue, orchardgrass, alfalfa and white clover) have been optimized to ensure an early germination and more uniform growth of seedlings. The experiment was conducted in a split plot design with three replications. The main plots consisted of five different materials such as $KNO_3,\;KH_2PO_4,\;K_3PO_4,\;Ca(NO_3){_2}$ and PEG. The subplots were consisted of three chemical concentration groups such as 500mM (or 10%), 100mM (or 20%) and 200mM (or 30%). Effect of priming materials and its concentrations were different in all four pasture seeds examined. Chemical concentration did not show any significant effects on the germination of tall fescue, however, germination of tall fescue primed with $Ca(NO_3){_2}\;and\;K_3PO_4$ materials were higher than the others. The concentration of prime materials did not affect on the germination of orchardgrass, but germination of orchardgrass primed with $KH_2PO_4$ was showed better result than the other materials examined. The seeds of alfalfa and white clover primed with PEG showed better germination capability than the other priming materials. In addition, chemical concentration of primed seeds also showed significant difference on the germination of alfalfa and white clover. These results suggest that seed priming induced earlier and higher germination for all four pastures tested. However, the, degree of priming effectiveness on pasture species depending on the priming materials and its concentrations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.499-508
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• 2018

The purpose of this study was to compare the degree of happiness between mothers of preschoolers (3-5yrs) and mothers of elementary school students (6-7yrs). The subjects of this study included 168 mothers of preschoolers and 170 mothers of elementary school students. They were randomly chosen. We measured and analyzed 338 mothers' happiness using Ryff's psychological well-being items. The results of this study reveal that although overall happiness level was similar, the two groups of mothers' happiness had statistically significant differences in 6 factors of mothers' happiness. Preschooler mothers had higher levels of happiness in autonomy and personal growth, while elementary school student mothers had higher levels of happiness in environment mastery, positive relationships, purpose of life, and self-acceptance. Also, the background of mothers, such as age, educational status, family income, and religion caused statistically significant differences in happiness level of both groups.

• Journal of Adhesion and Interface
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• v.3 no.2
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• pp.9-16
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• 2002

In the synthesis of water-based polyurethane using self-emulsification process, after being neutralized, polyurethane pre-polymers containing ionic pendant groups are dispersed by simple convective mixing. Preparation of dispersion is followed by chain extension reaction, which is considered as important step for growth of the molecular weight of polyurethane. In this work, pH variations in the aqueous phase were monitored during the chain extension process in the presence of water-soluble diamines. The optimum degree of chain extension and the average particle size in the polyurethane dispersions were examined with varying ionic pendent group contents, type of chain extenders, and feed rate of chain extenders, The initial pH value in the aqueous phase linearly increased and the optimum chain extension point could be obtained from the intersection of two linear lines having different slopes, All average particle sizes before chain extension reaction were almost same, however, the final average particle size increased as feed rates of chain extenders increased, In addition, as the ionic pendant group contents increased, the particle size decreased since the hydrophilicity and hydrodynamic volume increased. As carbon numbers of the chain extenders increased, the final particle size increased significantly. From the results, it was concluded that the chain extension reaction took place among the particles not only in a particle.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.4
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• pp.737-743
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• 2008

Regional odontodysplasia is a relatively rare developmental anomaly of dental hard tissue with characteristic clinical, radiographic and histologic features. It requires a continuous and multidisciplinary approaches, and the aim of treatment for these patients should include aiding mastication, improving aesthetics, maintaining normal vertical dimension and space, allowing normal jaw growth and eruptional management of affected teeth. This report describes three cases of regional odontodysplasia with 2-5 years of follow-up. Conservative treatment is chosen to preserve the affected teeth as long as possible, and periodic radiographic and clinical examination was done. During this time, all teeth except one showed progressive development. An interesting finding observed in our cases was that each tooth even in the same person showed different degree of tooth development and eruption rate. Thus, we colcluded that the treatment plan for regional odontodysplasia should be conservative and individualized and based on the assessment of each tooth.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.5
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• pp.391-407
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• 1987

To understand the effects of the cooling water system of the power plant on the succession of sessile zoobenthos, a series of experiments were carried out at the cooling water system of Samchonpo Power Plant from Hay 1985 to May 1986. The lowest species diversity of the zoobenthos was observed at the discharge canal. This is probably caused by both increased velocity and temperature of circulating water. It is also noticeable that species composition of the zoobenthos, to a certain degree, was affected due to the impingement of meroplankton during the entrainment process. While the number of species attached on the experimental substrata installed in the thermally altered area is smaller than that in the intake canal, the biomass is increased as the increased temperature eliminates some species and in turn stimulates reproduction and growth of the others. It is interesting that relatively high similarity exists between the summer communities in the intake canal and the spring communities in the thermally altered area, and the same relationship is also found between the fall communities in the intake canal and the winter communities in the thermally altered area. Ecological index curves of the zoobenthos of the intake canal follows the fluctuation pattern of the thermally altered area in one or two months of elapsed time, probably due to temperature increase by the inflow of heated water discharged from the power plant.

• Journal of the Korean Society of School Health
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• v.3 no.1
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• pp.48-58
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• 1990

This study was attempted to assess the effects of a long term regular sex education on the knowledge about anatomy and physiology of human reproductive organs and the attitude toward sex of second grade high school girls. The study population included 1,678 high school girls(542 educated second grade girls, 972 not educated second grade girls and 164 pre-educated first grade girls) attending in 3 high schools located in Kyungnam province. The data was collected by guestionnaire to assess knowledge of sexual anatomy and physiology and the attitude toward sex from 21 to 24 December 1988. The results were as follows: Most of students (educated group 99.3%, not educated group 98.1%) agreed to necessity of sex education. Among students 70.8% did not talk about their sexual problems with their parents and 30.1% of educated group obtained spxual knowledge from their teachers. There were significant differences between level of knowledge on anatomy and physiology of reproductive organs, secondary growth spurt, V D, pregnancy and contraceptives of educated group and not educated group (P < 0.01). There was significant difference between positive attitude about sexual intercourse before marriage, artificial abortion and family planning slogan of educated group and not educat.ed group (P < 0.05, P < 0.01). There were significant differences between degree of agreement about acquaintance with the other sex, knowledge of acquaintance with the other sex, talk freely with friend, parent and teacher of educated group and not educated group (P < 0.05, P < 0.01). Statistics revealed that high school girls of not educated group had less knowledge about acquaintance with the other sex than educated group (P < 0.01).