• Human Ecology Research
• /
• v.60 no.4
• /
• pp.497-505
• /
• 2022

This study aims to examine the mediating role of peer attachment between affective school environments and the problematic behaviors of children using data from the Panel Study on Korean Children 10th wave (2017). Descriptive statistics, reliability analysis, correlation analysis, multiple regression analysis, Sobel test, and bootstrapping versification were performed using SPSS 28.0 and Process Macro 28.0. The results indicate that controlled and rigid school environments were negatively associated with peer attachment and positively associated with both internal and external behavior problems. Furthermore, peer attachment was negatively associated with both internal and external behavioral problems. Peer attachment completely mediated the link between affective school environments and internal behavioral problems, and partially mediated the link between affective school environments and external behavioral problems. These results show the important role of supportive and democratic school environments regarding peer attachment.

• Journal of the Korea Society of Computer and Information
• /
• v.26 no.4
• /
• pp.181-188
• /
• 2021

The purpose of the current study was to investigate the causal relationship between school life adjustment and life satisfaction among adolescents through longitudinal panel data. The current study analyzed the 1st through 7th wave data in the 4th grade panel of elementary school from the Korea Children and Youth Panel Survey (KCYPS). The research model was tested using auto-regressive cross-lagged model. The major results were as follows. First, adolescents' school life adjustment had a positive auto-regressive effect. Second, adolescents' life satisfaction had a positive auto-regressive effect. Third, adolescents' school life adjustment was a causal predictor of life satisfaction, but not vice versa. Finally, implications in terms of enhancing adolescents' school life adjustment and life satisfaction were also discussed.

• Journal of Periodontal and Implant Science
• /
• v.23 no.1
• /
• pp.16-26
• /
• 1993

In order to investigate the healing effect on inflammation and bone regeneration of low power density laser radiation in dogs, experimental periodontitis was made in dog mandibular 3rd, 4th premolars. All teeth were classified with four groups of two experimental group and control groups. The second group were irradiated on periodontitis site and the first group were control. The fourth group were irradiated on periodontitis site flap operation and the third group were flap control. Experimental groups were irradiated with GaAs low power density laser of pulse wave and continuous wave of 904nm every day by five days respectively and then control group and experimental groups were evaluated by histo-pathological study. The results were as follows : 1. Experimental periodontits site of dog were irradiated with GaAs low power laser results in reducing of pseudoepitheliomatous proliferation and inflammation at light microscope. 2. After irradiation with low power density laser, experimental groups were revealed that PDL forming activity were increased and newly formed collagen deposition were observed. 3. Low power density lsaer irradiation on experimental periodontits site after flap operation showed that decreasing of inflammation, reducing of osteoclast activity. Capillary proliferation, reduction of pseudoepitheliomatous proliferation. 4. After irradiation with low power density laser on flap experimental site, experimental groups were revealed that newly formed collagen in periodontal ligament and alveolar bone were detected on MT staining.

• Economic and Environmental Geology
• /
• v.18 no.2
• /
• pp.151-157
• /
• 1985

Events detected by the KIER microearthquake network operated in the Southern Part of Korea for 265 days in 1982~1984 were reviewed, and some of them were identified to be a dynamite explosion from several construction sites. The purpose of the present work is to determine the crustal structure of the Southern Korea using the time-destance data obtained from such explosion seismic records. The time·distance data can be well explained by a crustal model composed of four horizontal layers of which thickness, p and s-wave velocity ($V_p$ and $V_s$) are characterized as follows. 1st layer (surface) ; 0~2km, $V_p=5.5km/sec$, $V_s=3.3km/sec$ 2nd layer (upper crust) ; 2~15km, $V_p=6.0km/sec$, $V_s=3.5km/sec$ 3rd layer (lower crust) ; 15~29km, $V_p=6.6km/sec$, $V_s=3.7km/sec$ 4th layer (upper mantle) ; 29km~ , $V_p=7.7km/sec$, $V_s=4.3km/sec$ The relatively shallow crust·mantle boundary and low $P_n$ velocity compared with the mean values for stable intraplate region are noteworthy. Supposedely, it is responsible for the high heat flow in the South-eastern Korea or an anomalous subterranean mantle. The mean $V_p/V_s$ ratio calculated from the relation between p-wave arrival and s-p arrival times appears to be 1.735 which is nearly equivalent to the elastic medium of ${\lambda}={\mu}$. However, the ratio tends to be slightly larger with the depth. The ratio is rather high compared with that of the adjacent Japanese Island, and the fact suggests that the underlying crust and upper mantle in this region are more ductile and hence the earthquake occurrences are apt to be interrupted. As an alternative curstal model, a seismic velocity structure in which velocities are successively increased with the depth is also proposed by the inversion of the time·distance data. With the velocity profile, it is possible to calculate a travel time table which is appropriate to determine the earthquake parameters for the local events.

• Korean Journal of Optics and Photonics
• /
• v.9 no.1
• /
• pp.15-19
• /
• 1998

We have present an all-optical technique to significantly reduce the dispersion penalty of a spectrum-sliced channel in high-speed and long-distance transmissions. We have reduced the necessary optical bandwidth for the 2.5 Gb/s incoherent light transmission down to 0.1 nm by expanding the optical bandwidth of a received signal. The optical bandwidth expansion was realized using the intra-channel fiber four-wave mixing at the receiver resulting in an improvement of th signal-to-noise ratio of the received light channel. We have successfully demonstrated the transmission of a 2.5 Gb/s NRZ signal with the 0.1 nm bandwidth over a 300 km dispersion-shifted fiber. An error floor occurs at $1{\times}10^{-5}$ BER without the optical bandwidth expansion. With the optical bandwidth expansion, however, the error floor decreases to less than $1{\times}10^{-10}$. The transmission penalty was less than 0.5 dB at $1{\times}10^{-10}$ BER. To our knowledge, the optical bandwidth of 0.1 nm used in our experiment is the narrowest optical bandwidth reported so far.

• Journal of Preventive Medicine and Public Health
• /
• v.31 no.2 s.61
• /
• pp.183-198
• /
• 1998

In order to determine the prevalence rate and find out the sexual difference of abnormal electrocardiographic findings manifested by computerized EKG, which is equipped with auto-analyzing function, a total of 2,083 electrocardiograms that were taken from population over 20 years-old from October 1996 to February 1997 were studied according to their age, gender and blood pressure. 1. Using the electrocardiography with auto-analyzing function, 33 kinds of abnormal findings were manifested. The prevalence rate of abnormal findings was 52.8% in male and 43.7% in female. Among them, the most common finding was sinus brady-cardia found in 17.6% of male and 15.4% of female. Left ventricular hypertrophy by voltage criteria, minimal voltage of left ventricular hypertrophy, left axis deviation and atrial fibrillation were more common in male than in female statistically. Both of nospecific T wave and ST segment abnormality were more common in female than in male statistically. 2. Thirty-three kinds of abnormal findings were manifested. They revealed one abnormal finding alone or combined with some other ones making 128 kinds of abnormal finding. The most common abnormal finiding that manifested alone was right axis deviation (100%), then myocardial ischemia (95.7%) the next. The most common abnormal finding that complexed with other abnormal findings were left anterior fascicular block(percentage of single manifestation, 26.2%) and nonspecific T wave abnormality(percentage of single manifestation; 32.9%). Also, combination of sinus bradycardia and minimal voltage of left ventricular hypertrophy, and combination of sinus bradycardia and left ventricular hypertrophy were included in 25th sequences of abnormal findings. 3. The prevalence rate of abnormal electrocardiographic findings were higher in older group, hypertensive group, and the group of higher systolic or diastolic pressure in both sexes. 4. Abnormal findings that commonly manifested with sinus bradycardia were voltage criteria or minimal voltage of left ventricular hypertrophy(38.6%): sinus arrhythmia(10.5%): nonspecific T wave or ST segment abnormality(18.4%) and first degree AV block(7.2%) in descending order. 5. The most common site which manifested myocardial ischemia was posterior and inferior wall with equal percentage of 23.4%. And then anterior wall(19.1%), and antero-lateral wall and septum with equal percentage of 10.6% was noted in descending order.

• Sleep Medicine and Psychophysiology
• /
• v.3 no.2
• /
• pp.18-31
• /
• 1996

Jet-lag can be defined as the cumulative physiological and psychological effects of rapid air travel across multiple time zones. Many reports have suggested that age-related changes in sleep reflect fundamental changes in the circadian system and in significant declines in slow wave sleep. Jet lag is a dramatic situation in which the changes of the phase of circadian process and homeostatic process of sleep occur. Thus the authors evaluatead the changes of sleep-wake cycle from jet lag by age. Thirty-eight healthy travellers were studied for 3 days before and 7 days after jet-flights across seven to ten time zone. They were aged 19-70, They trareled eastbound, Seoul to North America (USA, Canada). Sleep onset time, wake-up time, sleep latency, awakening frequency on night sleep, awakening duration on night sleep, sleepiness at wake-up and nap length were evaluated. Our results suggest that by the 7 to 10 time zone shift, the old age group was significantly influenced in sleep-wake cycles. The date on which subjective physical condition was recovered was $6.23{\pm}83$ day after arrivals for old age group, while for young and middle age group, $4.46{\pm}1.50$ day and $4.83{\pm}1.52$ day, respectively. In old age group, sleep onset time was later than baselines and could not recover untill 7th day. But in other groups, the recovery was within 5th day. Nap dura fion was longer in old age group through jet lag than younger age group. In other parameters, there was no definite difference among three age groups. Our results suggested that the old age was significantly influenced by the disharmony between internal body clock and sleep-wake cycle needed at the travel site. Thus we proved that recovery ability from jet lag was age-dependent as well as travelling direction-dependent. To demonstrate more definite evidence, EEG monitoring and staging of sleep were funthun encouraged.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.4
• /
• pp.629-635
• /
• 2017

Free-Flooded Ring (FFR) transducer array for use in Sonar system can be driven with large amplitude in a wide frequency band due to its structural characteristics, in which two resonances of a ring mode (1st radial mode) and an inner cavity vibration mode occur in a low frequency band. Since its sound wave generation characteristics are not influenced by the water pressure, the FFR transducer array is widely used in the deep sea. So FFR has been recognized as a low-frequency active sound source and has received much attention ever since. In order to utilize the FFR transducer array for SONAR systems in military and industrial applications, its equivalent electric circuit model is necessary especially to design the matching circuit between the driving power amplifier and the FFR transducer array. Thus this paper proposes the equivalent electric circuit model of FFR transducer array by using measured values of parameter, and suggest the improved method of parameter identification. Finally it verifies the effectiveness of the proposed circuit model of FFR transducer array by experimental measurements.

• The Journal of the Korea Contents Association
• /
• v.19 no.12
• /
• pp.647-659
• /
• 2019

The purpose of this study was to investigate the influence of children's elementary school entrance to working conditions of employed mothers. The data from 4th to 8th wave of Panel Study on Korean Children (PSKC) were used for analysis. Specifically, we examined changes in wages, working hours and regular employment of employed mothers after their children entered elementary schools. We adopted Heck selection model for unbalanced panel data after controlling sample selection bias, and compare results of analysis for unbalanced and balanced panel data. The results showed that children's elementary school entrance reduces employed mothers' wage, working hours and regular employment. These results indicate that mother tend to leave regular job and could not entry into decent job when their children are in elementary school.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.20 no.2
• /
• pp.75-85
• /
• 2016

A pyrotechnic system consisting of donor/acceptor pair separated by a gap relies on shock attenuation characteristics of the gap material and shock sensitivity of the donor and acceptor charges. Despite of its common use, numerical study of such pyrotechnic train configuration is seldom reported because proper modeling of the full process requires precise capturing of the shock wave attenuation in the gap prior to triggering a full detonation of high explosive and accurate description of the high strain rate dynamics of the explosively loaded inert confinements. We apply a Eulerian level-set based multimaterial hydrocode with reactive flow models for pentolite donor and heavily aluminized RDX as acceptor charge. The complex shock interaction, critical gap thickness, acoustic impedance, and go/no-go characteristics of the gap test are quantitatively investigated.