• Sleep Medicine and Psychophysiology
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• v.26 no.1
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• pp.16-22
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• 2019

Objectives: The objective of this study was to investigate the correlation between insufficient sleep and visuospatial memory in adolescents using a computerized neurocognitive function test. Methods: A total of 103 high school students (26 males and 77 females; mean age $17.11{\pm}8.50years$) without a serious psychiatric problem was recruited. All subjects were requested to complete a self-report questionnaire about weekday total sleep time and weekend total sleep time. The epworth sleepiness scale (ESS) and the beck depression inventory (BDI) were administered to measure daytime sleepiness and symptoms of depression. Seven subsets of the Cambridge Neuropsychological test automated battery were examined to assess visuospatial memory. Results: After controlling for age, sex, ESS, and BDI, longer weekend total sleep time was correlated with poor performance on delayed matching to sample (r = -0.312, p = 0.002) and immediate recall on pattern recognition memory (r = -0.225, p = 0.025). Increased weekend catch-up sleep time was correlated with poor performance of delayed matching to sample (r = -0.236, p = 0.018), immediate recall on pattern recognition memory (r = -0.220, p = 0.029), and delayed recall on pattern recognition memory (r = -0.211, p = 0.036) after controlling for age, sex, ESS, and BDI. Conclusion: This study showed that increased weekend catch-up sleep time reflecting insufficient weekday sleep were associated with poor performance in delayed recall tasks of visual memory. This finding suggests that insufficient sleep during adolescence might produce a decline of visuospatial memory.

• Korean Journal of Heritage: History & Science
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• v.46 no.1
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• pp.176-187
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• 2013

A study has been carried out on metal materials in order to identify the quantitative relation between the concentration and damage characteristics after evaluation of the damage characteristics according to the $SO_2$ concentration. The prepared metal samples, which were categorized according to the material (silver, copper, iron, lead, brass) were exposed to 0.01, 0.12, 1, 10, 100, 1,000, and 5,000ppm of $SO_2$ for 24 hours and the optical, physical, chemical deterioration rates both before and after testing were evaluated. The results showed optical deterioration, a loss of gloss on silver specimen with $SO_2$ 100ppm, an increase of color difference on brass, iron, copper and lead specimens with $SO_2$ 5,000ppm, as well as physical changes such as an increase of thickness and corrosion rate on iron sample with $SO_2$ 5,000ppm. In the case of chemical changes such as an increase sulfate ion ($SO{_4}^{2-}$) concentration and decrease of pH on iron and brass specimens were identified. These results suggest that $SO_2$ 100ppm caused clear optical deterioration on some metals such as silver and physicochemical and optical deterioration were identified at $SO_2$ 5,000ppm regardless of metal type. Also, It was concluded that iron and brass are the most susceptible of the metal specimens to $SO_2$.

• The Journal of the Korea Contents Association
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• v.19 no.6
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• pp.471-480
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• 2019

L-spine 3~4, L-spine 4~5, and L-spine 5~Sacrum 1 intervertebral disc(IVD) angle according to gender, age, body mass index(BMI), lumbar lordosis angle(LLA) were compared and analyzed. The anteriorposterior incidence angle of L-spine 3 ~ 4, L-spine 4 ~ 5 and L-spine 5~Sacrum 1 in body mass index were 5.66, 13.23 and 29.13 degrees in the head direction and L-spine 3 4, L-spine 4 ~ 5, L-spine 5~Sacrum 1 had 6.32 degrees, 16.09 degrees and 35.36 degrees in the head direction. The distortion area ratio comparison was performed with the phantom image using the proposed incidence angle. There was a significant difference in L-spine 4~5 and L-spine 5~Sacrum 1 IVD angle relative to body mass index and LLA(p<0.05), IVD angle and LLA were positively correlated(p<0.05).As a result of evaluating the usefulness of the image by applying the incidence angles of the disc angles according to the phantom angle of deviation to the head direction as 11 degrees for L4 and 26 degrees for L5, the distortion ratio area decreased from 14.90% to 12.11% in L4, And from 15.25% to 13.72% in L5. In anteriorposterior image of the Lumbar spine applying the incidence angle according to the measured disc angle, it is possible to reduce the distortion to purpose L4, L5. And improved the quality and diagnostic information of the target site.

• Korean Journal of Child Education & Care
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• v.19 no.3
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• pp.99-113
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• 2019

Objective: This study is a case study on mother's perceived the adaptation process and program of a one-year-old toddlers in daycare center. Methods: This study is a case study of four mothers who live in Seoul, South Korea and whose first child enters in daycare center at 18 or 20 months. The data collection method was applied to group interview and the individual in-depth interview method. Results: After the interview data was analyzed, first, they decided to enroll their child to a daycare center after two mothers were pregnant with the second child or the others received a phone call for admission. The first impression of the teachers had a great influence on the choice of admission when mother first visited the daycare center. mother, as well as toddlers who exhibited anxiety, experienced an adaptation process. Through communication between mother and teacher, mothers could feel the toddler's adaptation. Second, as for the difference of the adaptation program according to the daycare center type through the adaptation process of the one-year-old toddlers, there was a big difference in the program guide, the period, the content and the proceeding method. Conclusion/Implications: Based on the results of this study, it is expected that it will be a basic data for the development of the adaptation program for one-year-old toddlers in daycare center at the national level.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.4
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• pp.406-412
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• 2019

In this paper, we propose two algorithms for classifying services with similar delay characteristics into three classes and allocating radio resources according to priority in LTE-A system where H2H and M2M services coexist. The first is to allocate resources from the higher priority class to the lower priority class, and each class gives priority to H2H over M2M, and the other is to give priority to H2H regardless of delay characteristics except for the class with the highest priority. The RA success probability was analyzed according to the access rate(${\alpha}$) of M2M devices in each class. In comparison with the conventional systems, it was improved from 0.5 to 0.52 for ${\alpha}_{2M}=0.05$ in two classes. In the three classes, the success probability was slightly increased from 0.5 to 0.57 for ${\alpha}_{2M}={\alpha}_{3M}=1$ and from 0.5 to 0.58 for ${\alpha}_{2M}=0.5$ and ${\alpha}_{3M}=0.1$. Although 6 services are considered in the proposed scheme, the RA success probability is almost similar to the previous scheme because the average arrival rate of H2H of each class is set to the same.

• Korean Journal of Child Education & Care
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• v.19 no.3
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• pp.129-140
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• 2019

Objective: Teacher's professionalism means the ability to apply the knowledge, skills and attitudes related to child care effectively to carry out the child care process. Depending on the professionalism of the teacher, the teacher-infant interaction may be affected and the job satisfaction may be different. The purpose of this study was to investigate the level of perceived level of infant teachers' professionalism and to investigate the effect of professionalism of infant teachers on teacher-infant interaction and teacher's job satisfaction. In addition, through this study, it is aimed to help the infant teachers themselves to measure their own abilities and qualities and to develop individual growth by recognizing the importance of infant teacher's professionalism in the daycare center. Methods: For this study, a questionnaire survey was conducted on 329 infant teachers who were in charge of the ages between 0 and 2 years. The collected data were analyzed using SPSS / WIN 24.0 program. First, the mean and standard deviation of the subfactors of the infant teachers were determined in order to know the level of professionalism, teacher-infant interaction, In order to investigate the relationship between the variables, we conducted a Pearson correlation analysis. Finally, Multiple regression analysis was conducted to examine the effects of the teacher's professionalism on teacher-infant interaction and subfactors, and teacher job satisfaction and subfactors. Results: Teacher professionalism was found to have a positive effect on teacher-infant interaction, and caring interaction and teacher-parent-community relations were found to affect teacher-infant interaction. In addition, teacher professionalism had a positive effect on job satisfaction, and child development, curriculum, and teacher-parent-community relations were found to affect job satisfaction. Conclusion/Implications: Influence of teacher-infant interaction and teacher job satisfaction is different according to subfactors of teacher's professionalism. In particular, this suggests that it is necessary to consider ways to selectively raise the level of teacher professionalism according to the situation of infant teachers in each region.

• Phonetics and Speech Sciences
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• v.11 no.3
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• pp.49-55
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• 2019

This study sought to investigate whether mean speaking fundamental frequency (SFF) can be predicted by parameters of voice and speech range profile (VRP and SRP) in Korean normal adults. Moreover, it explored whether gender differences exist in the absolute differences between the SFF and estimated SFF (ESFF) predicted by the VRP and SRP. A total of 85 native Korean speakers with normal voice participated in the study. Each participant was asked to perform the VRP task using the vowel /a/ and the SRP task using the first sentence of a Korean standard passage "Ga-eul". In addition, the SFF was measured with electroglottography during a passage reading task. Predictive factors of the SFF were explored and the absolute difference between the SFF and the ESFF (DSFF) was compared between gender groups. Results indicated that predictive factors were age, gender, minimum pitch and pitch range for the VRP (adjusted $R^2=.931$), and pitch range (in semi-tones) and maximum pitch for the SRP (adjusted $R^2=.963$), respectively. The SFF and ESFF predicted by the VRP and SRP showed a strong positive correlation. The DSFF of the VRP and SRP, as well as their sum did not differ by gender. In conclusion, the SFF during a passage reading task could be successfully predicted by the parameters of the VRP and SRP tasks. In further studies, clinical implications need to be explored in patients who may exhibit deviations in SFF.

• Environmental and Resource Economics Review
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• v.28 no.3
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• pp.385-413
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• 2019

This study examines the determinants of net export of electricity among 30 European countries sharing electricity grid during the period of 1990~2014 by separating the sample period before and after 2005 in which ETS was introduced in Europe. The empirical method used in this study is generalize least squared one considering both heterogeneous and serial correlation in the balanced panel data. According to the empirical results, after 2005 introducing the ETS, holing energy resources, concentrating only on few electricity generation resources, and nuclear electricity generation had played more important role in net export of electricity, while renewable energy had negative effect on net export of electricity and coal and gas generation have no effect on net export after introduction of ETS in Europe probably because of high environmental cost. The policy implication of the results would be that reconsidering each country's optimal generation mix strategy and its role in case freely trading electricity.

• Korean Journal of Ecology and Environment
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• v.52 no.2
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• pp.81-93
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• 2019

Phytoplankton is one of the important primary producers providing organic matter through photosynthesis in aquatic environments. In order to determine a temporal and spatial variation in primary productivity after weir construction in the Nakdong River, we investigated carbon uptake rates using in-situ $^{13}C$ labeling experiments and identified algal communities contributing to primary productivity using HPLC-CHEMTAX analysis from October to December, 2017. The primary productivity gradually decreased from fall to early winter season ($249{\sim}933mgC\;m^{-2}d^{-1}$ in October, $64{\sim}536mgC\;m^{-2}d^{-1}$ in November and $60{\sim}274mgC\;m^{-2}d^{-1}$ in December, respectively). This is attributed to the temporally declining light intensity and the decreasing biomass and physiological activity of phytoplankton in winter. The contribution of diatoms to the phytoplankton community in the Nakdong River was approximately 63% at all the sampling sites and seasons, while the contribution of cryptophytes increased from 9% in October to 32% in November and December. The temporal changes in the primary productivity and the dominant phytoplankton species in the mid and downstream weirs of the Nakdong River was investigated for the first time, after construction of the weirs, and major environmental factors controlling the temporal variation in primary productivity and phytoplankton communities were identified in this study. We suggest that seasonal field investigations will provide further information on the major environmental factors which affect the annual variation of primary productivity and phytoplankton communities.

• Korean Journal of Heritage: History & Science
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• v.37
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• pp.267-284
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• 2004

As an initial step to understand the transitions in Korean bronze technology the present study has examined metallurgical microstructures of 8 artifacts excavated from the Silla Wang-Gyong site in Kyongju. Important trends have been found in alloy compositions and also in manufacturing processes. In the design of alloys, the Sn content was apparently changing toward the peritectic point, 22 mass %, of the Cu-Sn phase diagram while the Pb addition was intentionally avoided. This trend in composition was found accompanied by the introduction, subsequent to casting, of such special thermo-mechanical treatments as quenching and forging in artifact manufacture. In addition, the Sn content in alloys containing a significant amount of As was relatively low and no evidence of forging was observed in them. The use of quenching and forging and the rejection of Pb and As from alloys are all necessary requirements if the brittle nature of high Sn alloys is to be overcome in bronze working. This paper will show that the Wang-Gyong era corresponds to that of innovations leading to the technical climax in Korean bronze tradition, which has been maintained up to the present.