• The Journal of Korean Association of Computer Education
• /
• v.7 no.6
• /
• pp.95-105
• /
• 2004

It is important to understand how pre-service teachers perceive e-learning because their prior-experience with e-learning will have a great impact on their teaching after the graduation. Pre-service teachers (401 students) with cyber learning experience, which is a form of e-learning, were selected in 2004 in May and June. Survey was conducted regarding the instructional experience (working hours, tasks and evaluation, satisfaction about cyber learning and its academic achievement, difficulties and suggestions) and instructional methods (instructional activities, frequencies of interaction, strategies of interaction, collaborative activities, behaviors in the group instructional activities for knowledge development). The results are pre-service teachers tent to spend similar v slightly less working hours for cyber learning, similar or slightly less satisfaction level for the instruction and the academic achievement. It was interesting that female students were more negative than males students, considering female students have been more active in online discussion traditionally. Logical presentation of contents and instructional strategies for the cyber learning were the most wanting suggestions. E-mails and BBS for reference materials were the two most used functions in the online learning. The amount and types of tasks were satisfactory. Students did not interact freely during the group activities, they reported they did not learn much through the group activity. During the group work, they consider they do their roles with responsibility while they have slightly negative responses toward other members' contribution in the group activity. Off line meeting is strongly suggested.

• KDI Journal of Economic Policy
• /
• v.12 no.3
• /
• pp.47-69
• /
• 1990

The measures taken to reform the Dutch health insurance system hold valuable lessons for countries such as Korea, where there has been increased concern regarding the efficiency and effectiveness of the health services provided. The growing literature on comparative health insurance policies suggests that nations can learn from each other. In addition, Korean policymakers have shown great interest in the health insurance systems of foreign countries, particularly in Japan. The development of Korea's health insurance scheme during the past 12 years has made a significant contribution to the increased accessibility of health care services. Although the insurance coverage is universal, the health insurance system today in Korea is by no means a product of systematic and planned efforts. Moreover, it lacks due considerations of insured's needs as well as the long-term objectives of the social security health care system. There are growing gaps in premium burdens and benefits between the rural health insurance program and the employee's health insurance programs. Furthermore, the regional health insurance program is experiencing financial difficulties in spite of the fact that the amount of the government subsidy has been sharply increased in recent years. Under the present payment method solely based on the fee-for-service schedule, both consumers and providers are encouraged to utilize and prescribe more services. The combination of the utilization-inducing reimbursement system and continuous pushes for expanding health insurance has played a crucial role in raising the country's medical bills. Current trends in Korea's health care sector and those anticipated in the near future necessitate changes in the structure and funding of health care. As indicated in the above, there are various shortcomings in this context, the health policy authority in Korea can draw valuable lessons from the Dutch experiences in reforming their health insurance system. The main elements of the Dutch reform measures are a restructuring of the insurance system and a greater role for market forces in the health care system. On this basis a new system will be created which reflects the social nature of health care while at the same time containing sufficient mechanisms to allow the health care sector to operate in a cost-effective and efficient manner.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.12
• /
• pp.1946-1952
• /
• 2005

New group 15 organometallic compounds, M$(phenanthrenyl)_3$ (M = P (1), Sb (2), Bi (3)) have been prepared from the reactions of 9-phenanthrenyllithium with $MCl_3$. A reaction of 9-(diphenylphosphino)phenanthrene with 2,6-diisopropylphenyl azide led to the formation of (phenanthrenyl)${(Ph)}_2P$=N-(2,6-$^iPr_2C_6H_3$) (4). The crystal structures of 2 and 4 have been determined by single-crystal X-ray diffractions, both of which crystallize with two independent molecules in the asymmetric unit. Compound 2 shows a trigonal pyramidal geometry around the Sb atom with three phenanthrenyl groups being located in a screw-like fashion with an approximately $C_3$ symmetry. A significant amount of CH- -$\pi$ interaction exists between two independent molecules of 4. The phosphorus center possesses a distorted tetrahedral environment with P-N bond lengths of 1.557(3)$\AA$ (P(1) N) and 1.532(3)$\AA$ (P(2)-N), respectively, which are short enough to support a double bond character. One of the most intriguing structural features of 4 is an unusually diminished bond angle of C-N-P, attributable to the hydrogen bonding of N(1)-H(5A) [ca. 2.49$\AA$ between two adjacent molecules in crystal packing. The compounds 1-3 show purple emission both in solution and as films at room temperature with emission maxima ($\lambda_{max}$) at 349, 366, and 386 nm, respectively, attributable to the ligand centered $\pi$ $\rightarrow$ $\pi^\ast$ transition in phenanthrene contributed by the lone pair electrons of the Gp 15 elements. Yet the nature of luminescence observed with 4 differs in that it originates from $\pi$ (diisopropylbenzene)-$\pi^\ast$ (phenanthrene) transitions with the $\rho\pi$contribution from the nitrogen atom. The emission maximum of 4 is red-shifted ranging 350-450 nm due to the internal charge transfer from the phenanthrenyl ring to the N-arylamine group as deduced from the ab initio calculations.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.5 no.4
• /
• pp.114-121
• /
• 2010

Portland cement production is under critical review due to high amount of CO2 gas released to the atmosphere. Attempts to increase the utilization of a by-products such as fly ash and ground granulated blast-furnace slag to partially replace the cement in concrete are gathering momentum. But most of by-products is currently dumped in landfills, thus creating a threat to the environment. Many researches on alkali-activated concrete that does not need the presence of cement as a binder have been carried out recently. However, most study deal only with alkali-activated ground granulated blast furnace slag or fly ash, as for the combined use of the both, little information is reported. In this study, we investigated the influence of mixture ratio of fly ash/ blast furnace slag tand curing condition on the flowability and compressive strength of mortar in oder to develop cementless alkali-activated concrete. In view of the results, we found out that the mixture ratio of fly ash/blast furnace slag always results to be significant factors. But the influence of curing temperature in the strength development of mortar is lower than the contribution due to other factors. At the age of 28days, the mixture 50% fly ash and 50% ground granulated blast furnace slag activated with 1:1 the mass ratio of 9M NaOH and sodium silicate, develop compressive strength of about 65 MPa under $20^{\circ}C$ curing.

• Journal of Environmental Health Sciences
• /
• v.44 no.2
• /
• pp.143-152
• /
• 2018

Objectives: The purpose of this study was to provide basic data for air pollutant exposure modelling and understanding the contribution of respective microenvironments by assessing the time-activity patterns of Korean students according to variables such as grade, sex, weekday, and weekend. Methods: In this study, we compared the residential time of 521 (both weekday and weekend) lower elementary students, 1,735 (1,054 on weekdays, 681 on weekends) upper elementary students, 2,210 (1,294 on weekdays, 916 on weekends) middle school students, and 2,366 (1,387 on weekdays, 979 on weekends) high school students in different microenvironments according to grade, sex, weekday, and weekend. We used data from the 2014 Time-Use Survey by the Korean National Statistical Office for upper elementary students through high school students, and surveyed time-activity patterns of 521 lower elementary students aged 7-9 years. Each microenvironment was divided into indoor, outdoor, and transport. Indoor environments were divided into home, school, and other places. In addition, the results of previous studies were compared to this study. Results: Weekday time-activity patterns of Korean students indicated that lower elementary students spent $16.02{\pm}2.53hr$ in the home and $5.37{\pm}2.32hr$ in school. Upper elementary students spent $14.11{\pm}1.79hr$ in the home and $6.27{\pm}1.37hr$ in school. Middle school students spent $12.83{\pm}2.22hr$ in the home and $7.48{\pm}1.88hr$ in school. High school students spent $10.65{\pm}2.86hr$ in the home and $10.23{\pm}2.86hr$ in school on weekdays. High school students spent the least amount of time in the home and the most time in school compared to other grades Conclusions: Students spent most of their time indoors, including in the home, school, and other indoors. On weekdays, as the grade increases, home residential times were decreased and school residential times were increased. Differences in time-activity patterns according to sex were not found for either weekdays or weekends. It is estimated that Korean students could be affected by school indoor air quality. High school students could be most affected by school indoor air quality since they spent the most time at school.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.5 no.1
• /
• pp.49-58
• /
• 1987

The use of digital terrain model has been enlarged in calculating the earthwork due to the development of aerial photogrammetry. The calculation of earthwork plays a major role in plan or design of many civil engineering projects, and thus it has become very important to advance the accuracy of earthwork calculation. In this study, I have made an analysis of influences which DTM makes on the height accuracy of data ; on the basis of the analysis, we can develop the predictive model formula of profile shape coefficients by which the accuracy of earthwork can he preestimated in practical design according to data density of terrain, making thereby good contribution to the calculation of both earthwork amount and its expenses. This study shows that the accuracy of earthwork is more affected by the distances of cross-sections than by data density and that the effects by the standard errors of height decrease in proportion as the distances of cross-sections are great It also shows that when the prediction model formula of profile shape coefficients is applied to ordinary cases, the differences between the predicted earthwork errors and the errors by ordinary est imation are at 0.8374~3.1437$cm^3$/m, on flat terrain and 1.5628~6.967$cm^3$/m, on mountainous terrain-so little as to be ignored ; thus it can be safely ascertained that the accurate earthwork errors can be predicted applying the prediction model formula made in this study.

• Toxicological Research
• /
• v.29 no.2
• /
• pp.121-127
• /
• 2013

Nanotoxicological research has shown toxicity of nanomaterials to be inversely related to particle size. However, the contribution of agglomeration to the toxicity of nanomaterials has not been sufficiently studied, although it is known that agglomeration is associated with increased nanomaterial size. In this study, we prepared aerosols of nano-sized carbon black by 2 different ways to verify the effects of agglomeration on the toxicity and deposition of nano-sized carbon black. The 2 methods of preparation included the carbon black dispersion method that facilitated clustering without sonication and the carbon black dispersion method involving sonication to achieve scattering and deagglomeration. Male Sprague-Dawley rats were exposed to carbon black aerosols 6 hr a day for 3 days or for 2 weeks. The median mass aerodynamic diameter of carbon black aerosols averaged $2.08{\mu}m$ (for aerosol prepared without sonication; group N) and $1.79{\mu}m$ (for aerosol prepared without sonication; group S). The average concentration of carbon black during the exposure period for group N and group S was $13.08{\pm}3.18mg/m^3$ and $13.67{\pm}3.54mg/m^3$, respectively, in the 3-day experiment. The average concentration during the 2-week experiment was $9.83{\pm}3.42mg/m^3$ and $9.08{\pm}4.49mg/m^3$ for group N and group S, respectively. The amount of carbon black deposition in the lungs was significantly higher in group S than in group N in both 3-day and 2-week experiments. The number of total cells, macrophages and polymorphonuclear leukocytes in the bronchoalveolar lavage (BAL) fluid, and the number of total white blood cells and neutrophils in the blood in the 2-week experiment were significantly higher in group S than in normal control. However, differences were not found in the inflammatory cytokine levels (IL-$1{\beta}$, TNF-${\alpha}$, IL-6, etc.) and protein indicators of cell damage (albumin and lactate dehydrogenase) in the BAL fluid of both group N and group S as compared to the normal control. In conclusion, carbon black aerosol generated by sonication possesses smaller nanoparticles that are deposited to a greater extent in the lungs than is aerosol formulated without sonication. Additionally, rats were narrowly more affected when exposed to carbon black aerosol generated by sonication as compared to that produced without sonication.

• Korean Journal of Soil Science and Fertilizer
• /
• v.47 no.5
• /
• pp.374-380
• /
• 2014

To estimate greenhouse gas (GHG) emission, the inventory of rice cultivation at the farming without agricultural chemicals was established from farmers in Gunsan, Jeonbuk province in 2011~2012. The objectives of this study were to calculate carbon footprint and analyse the major factor of GHGs. To do this, we carried out a sensitivity analysis using the analyzed main factors of GHGs and estimated the mitigation potential of GHGs. Also we suggested agricultural methods to reduce GHGs that can be appled by farmers at this region. At the farming system without agricultural chemicals, carbon footprint of rice production unit of 1 kg was 2.15 kg $CO_2.-eq.kg^{-1}$. Although the amount of carbon dioxide ($CO_2$) emission was the largest among GHGs, methane ($CH_4$) emission had the highest contribution to carbon footprint on rice production system when it was converted to carbon dioxide equivalent ($CO_2-eq.$) multiplied by the global warming potential (GWP). Main source of $CO_2$ emission in the rice farming system without agricultural chemicals was combustion of fossil fuels used by agricultural machinery. Most of the $CH_4$ was emitted during rice cultivation practice and its major emission factor was flooded paddy field in anaerobic condition. Also, most of the $N_2O$ was emitted from rice cultivation process. Major sources of the $N_2O$ emission was application of fertilizer such as compound fertilizer. As a result of sensitivity analysis in energy consumption, diesel had the highest sensitivity among the energy inputs. With the reduction of diesel consumption by 10%, it was estimated that $CO_2$ potential reduction was about 2.0%. With reducing application rate of compound fertilizer by 10%, the potential reduction was calculated that $CO_2$ and $N_2O$ could be reduced by 0.5% and 0.9%, respectively. At the condition of 10% reduction of silicate and compost, $CO_2$ and $CH_4$ could be reduced by 1.5% and 1.6%, respectively. With 8 days more drainage than the ordinary practice, $CH_4$ emission could be reduced by about 4.5%. Drainage and diesel consumption were the main sources having the largest effect on the GHG reduction at the farming system without agricultural chemicals. Based on the above results, we suggest that no-tillage and midsummer drainage could be a method to decrease GHG emissions from rice production system.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2009.05a
• /
• pp.1112-1116
• /
• 2009

The importance of securing water resources and their efficient management has attracted more attention recently due to water deficit. In water budget analysis, however, evapotranspiration (${\lambda}E$) has been approximated as the residual in the water balance equation or estimated from empirical equations and assumptions. To minimize the uncertainties in these estimates, it is necessary to directly measure ${\lambda}E$. In this study, using the eddy covariance technique, we have measured ${\lambda}E$ in a mixed forest in the Seolmacheon catchment in Korea from September 2007 to December 2008. During the growing season (May - July), ${\lambda}E$ in this mixed forest averaged about 2.2 mm $d^{-1}$, whereas it was on average 0.5 mm $d^{-1}$ during the non-growing season in winter. The annual total ${\lambda}E$ in 2008 was 581 mm $y^{-1}$, which is about 1/3 of the annual precipitation of 1997 mm. Despite the differences in the amount and frequency of precipitation, the accumulated ${\lambda}E$ during the overlapping period (i.e., September to December) for 2007 and 2008 was both ${\sim}$ 110 mm, showing virtually no difference. The omega factor, which is a measure of decoupling between forest and the atmosphere, was on average 0.5, indicating that the contributions of equilibrium ${\lambda}E$ and imposed ${\lambda}E$ to the total ${\lambda}E$ were about the same. The results suggest that ${\lambda}E$in this mixed forest was controlled by various factors such as net radiation, vapor pressure deficit, and canopy conductance. In this study, based on the direct measurements of ${\lambda}E$, we have quantified the relative contribution of ${\lambda}E$in the water balance of a mixed forest in the Seolmacheon catchment. In combination with runoff data, the information on ${\lambda}E$ would greatly enhance the reliability of water budget analysis in this catchment.

• Journal of Nutrition and Health
• /
• v.34 no.1
• /
• pp.30-38
• /
• 2001

This research was conduced to 1) examine the influence of milk group intake on the dietary, considering dietary diversity and nutrient adequacy, 2) identify which foods truly contribute to the intake of specific nutrients 3) point out the dietary problems of this age group. The subjects were 664(male 357, female 307) healthy toddlers of the ages of 12-36 months, who had neither been taking any medicine-type supplements nor had any diseases that affect the dietary intakes, chosen among the outpatients of university and private hospitals in Seoul and Kyonggi province during Mach-August, 1999. The 24 hour recall method and CAN Pro(food analysis program) were used to analyze the amount of nutrient intake. The grouping of the subjects for the analysis by monthly age was based on the 98 Korean Child growth standard. The results that the milk group intake showed significant negative correlations with the grain group(r=-0.194, p<0.01), the vegetable group(r=-0.115, p<0.01) and the fruit group(r=-0.125, p<0.01). It also showed that the more the milk group intake, the lower the Dietary Diversity Score(r=-0.131, p<0.01), and the more the intake of raw milk, the more dificient the intake of iron(r=-0.211, p<0.01), vitamin A(r=-0.169,p<0.01), vitamin B$_1$(r=-0.078, p<0.05) and vitamin C(r=-0.187, p<0.01). Foods contributory to nutrient intake for of 12-14 months of were mostly infant formula, and the contribution ratio was high. In the age of 15-17 months, the subjects obtained most of the nutrients from raw milk., liquid-type yoghurt, soybean milk, cooked rice, etc. As for iron intake, the age of 21-23 month obtained the most from ionic drinks, and 24-29 months from raw milk, chocolate cakes, ionic drinks, etc. Though the NAR(Nutrient Adequacy Ratio) and MAR(Mean Adequacy Ratio) generally tended to increase accordingly with the DDs, as for nutrients Ca, vitamin A, vitamin B$_1$, and vitamin C the NAR marked the highest when the DDS marked the lowest(due to infant formula). And for iron, even when the DDS was 5 the NAR value was low. Im conclusion, the more the milk group intake, the lower was the dietary diversity. High dependency on infant formula and others from milk group over the age of 12 months proved to result in a decrease of nutritious solid food intake, iron deficiency and a low dietary diversity score, which can lead to an unbalanced diet. Therefore, nutrition education towards mothers/caretakers of toddler is of urgent need, in order to reduce the fluid milk group intake of low nutritional density and to provide various solid foods the children. (Korean J Nutrition 34(1):30-38, 2001)