• (The)Korea Educational Review
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• v.24 no.1
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• pp.199-225
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• 2018

Using the 3rd to the 6th wave data from the Korean Children and Youth Panel Survey(KCYPS), we examined the effects of academic characteristics and social relations on the trajectories of the life satisfaction among adolescents. OLS results showed that male students were more satisfied with their lives than female students in the 3rd grade of middle school. As academic characteristics, academic achievement and the level of class adjustment improved life satisfaction but the amount of learning time spent had a negative effect on life satisfaction. However, the effect of academic achievement lost its statistical significance after including variables of social relations. Relationships with parents, teachers, and friends had positive effects on life satisfaction. The longitudinal analysis using the fixed effect estimation also showed a similar result of the associations among the variables to that in the OLS analysis. The life satisfaction gap between male and female students narrowed over time from the 3rd grade of middle school to the 2nd grade of high school. The effects of relationships with parents and friends showed significant effects on both female and male students, but the relationship with their teachers was significant only for female students. Based on the results, we discussed the issues of Korean education related to the life satisfaction among adolescents.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.346-353
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• 2020

The purpose of this study was to explore types of longitudinal changes in interactions between mothers and 4-year-old children in primary school as well as the effects on media device addiction. To explore interaction types between mothers and children, latent class growth modeling (LCGM) and BCH were used in a three-step approach. Data from the 6-10th wave of the Panel Study of Korea Children were used. First, the trajectory of the mother-child interactions was linear and decreased across time. This linear decrease was classified into the following three trajectories: high-decreasing, average-deceasing, and low-decreasing. Second, BCH was performed to examine media device addiction in each trajectory, and the findings show that children who had low initial mother-child interactions over time were more likely to experience daily disturbances in adaptive functions such as withdraw or tolerance than other groups of children. The results indicate that maximizing the quality of mother-child interactions in childhood through primary school can lower media device addiction in children.

• 한국노년학
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• v.40 no.3
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• pp.511-530
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• 2020

The present study aimed to examine the moderating effects of marital satisfaction (MS) on the association between the number of chronic disease (CD) and depressive symptoms (DS) among ol der men and women. The 6th wave of the Korean Longitudinal Study of Ageing was utilized and the sample was married men (N=585) and women (N=460) aged 65 and over. Multiple regression analysis using SPSS WIN 25.0 and Process Macro was used to test moderating effects of MS. Control variables were age, education, household income, parent-child relationship satisfaction, self-rated health, cognitive function, current smoking status and CD of spouse. Resul ts from elderly men showed the moderating effect of MS was significant. Specifically, those with more CD were more likely to report higher level of DS in the low MS group. However, the effect of CD on DS was not significant in the high MS group. Results from elderly women showed the moderating effect of MS was not significant. This study showed the moderating effect of MS on the association between CD and DS differed by gender in later life. It suggests practical intervention to utilize the resources of spouses is in need to promote mentally healthy aging even though having chronically ill in later life.

• Journal of the Korea Society of Computer and Information
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• v.27 no.9
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• pp.177-190
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• 2022

In this study, using data from the second wave of Panel Survey of Employment for The Disabled[PESD] (2016) to the sixth year (2021), the longitudinal changes between disability acceptance and job satisfaction of adult wage workers aged 20 or older with disabilities and the correlation An autoregressive cross-lagged model was applied to analyze the causal relationship. As a result of the analysis, first, the disability acceptance and job satisfaction at the previous time point of the disabled workers were stably significant to the disability acceptance(𝛽=.556~.610) and job satisfaction(𝛽=.554~.585) at the later time point. Second, disability acceptance at the previous point in time for wage workers with disabilities crosses the job satisfaction at the later time point(𝛽=.077~.090), and the job satisfaction at the previous point crosses the disability acceptance at the later time point(𝛽=.087~.092). Third, as a result of model fit analysis according to the gender group of wage workers with disabilities, the difference in the autoregressive effect between disability acceptance and job satisfaction and the cross-lagged effect between disability acceptance and job satisfaction according to the passage of time was not significant.

• Korean Journal of Social Welfare
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• v.58 no.4
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• pp.197-217
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• 2006

This study examined whether a relationship between retirement transitions and psychological well-being of the elderly may differ by gender and residential areas, and whether associative factors of psychological well-being may vary by gender and residential areas. The sample included 1,124 older adults aged 60 and over, which derived from the first wave and the third wave data of the "Aging and the Quality of Life of the Elderly in Korea: A Longitudinal Study" living in Seoul and Chuncheon. The total sample was divided into four sub-samples(urban male elders, rural male elders, urban female elders, and rural female elders) to answer research questions. Psychological well-being was measured by measured by the PGCMS developed by Lawton, and a retirement variable had four categories: being continuously non-retired, newly retired, newly non-retired, and being continuously retired with a reference group of being continuously non-retired. Multivariate OLS regression was run separately for the four groups. For urban male elders, retirement transition was associated with worse psychological well-being whereas no relationship between retirement transitions and psychological well-being was found for rural male elders, urban female elders, and rural female elders. Associative factors of psychological well-being varied by gender and residential areas. The findings implies that a relationship between retirement transitions and psychological well-being of the elderly may differ by gender and residential areas, and these differential effects of retirement transitions may be attributable to different life experiences and economic activities through a life course and different roles after retirement. Also, different associative factors of psychological well-being for the four sub-samples reflect variations in their different life course.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.503-515
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• 2017

Underground structures that have recently become larger are required to be stable not only during normal times but also during earthquakes. Especially, it is very important to maintain the stability of the subsea tunnels during the earthquake. The objective of this paper is to verify the effectiveness of the flexible segment, which is one of the breakthrough facilities to maintain the stability of the subsea tunnel during the earthquake using the shaking table test. Another goal of this paper is to propose the optimum position of the flexible segment through 3D dynamic numerical analysis based on the verified results from shaking table tests. The 1g shaking table test considering the similarity ratio (1:100) to the cross section of the selected artificial subsea tunnel was carried out considering the Geongju and Artificial seismic waves, longitudinal and lateral wave, and with/without flexible segments eight times or more. As a result of the shaking table test, it was confirmed that the flexible segment is effective in improving the seismic performance of the undersea tunnel in all the experimental results. In addition, 3D dynamic numerical analysis was performed to select the optimum position of the flexible segment which is effective for improving seismic performance. As a result, it was confirmed that the seismic acceleration is attenuated when the flexible segment is installed adjacent to the branch section in subsea tunnel.

• The Journal of the Acoustical Society of Korea
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• v.15 no.6
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• pp.81-89
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• 1996

It is very important for ultrasonic test method to evaluate the integrity of the class I components in nuclear power plants. However, as the rltrasonic test is affected by internal structures and configurations of test materials, backscattering, that is, time invariant noise is generated in large grain size materials. Due to the above reason, the received signal results in low signal to noise(S/N) ratio. Split spectrum processing(SSP) technique is effective to suppress the grain noise. The conventional SSP technique. however, has been applied to unique algorithm. This paper shows that MPO(minimization and polarity threshold) algorithm which two algorithms are applied simulatancously, was utilized, the signal processing time was shorten by using the new constant-Q SSP with the FIR filter which frequency to bandwidth ratio is constant and the optimum parameters were analysed for the signal processing to longitudinal wave and shear wave with the same requirements of inspection on nuclear power plant site. Moreover, the new ultrasonic test instrument, the reference block of the same product form and material specification, stainless stell test specimens and copper test specimens block of the same fabricated for the application of new SSP technique. As the result of experimental test with new ultrasonic test instrument and test specimens, the signal to noise ratio was improved by appying the new SSP technique.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.6
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• pp.528-535
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• 2004

Ultrasonic Vibrator is designed to achieve the maximum vibration amplitude at 30 kHz by in-cluding a horn (diameter, 40 mm), mechanical vibration amplifier at the top of the ultrasonic vibrator in the system and making the complete system resonate. In addition, it is experimentally visualized by particle imaging velocimetry (PIV) that the acoustic streaming velocity in the gap is at maximum when the gap between the ultrasonic vibrator and stationary plate agrees with the multiples of half-wavelength of the ultrasonic wave. This fact results from the resonance of the sound wave and the theoretical analysis of that is also accomplished and verified by experiment. It is observed that the magnitude of the acoustic streaming dependent upon the gap between the ultrasonic vibrator and stationary plate possibly changes due to the measurement of the average velocity fields of the acoustic streaming induced by the ultrasonic vibration at resonance and non-resonance. There exists extremely small average velocity at non-resonant gaps while the relatively large average velocity exists at resonant gaps compared with non-resonant gaps. It also reveals that there should be larger axial turbulent intensity at the hub region of the vibrator and at the edge of it in the resonant gap where the air streaming velocity is maximized and the flow phenomena is conspicuous than that at the other region. Because the variation of the acoustic streaming velocity at resonant gap is more distinctive than that at non-resonant gap, shear stress increases more in the resonant gap and is also maximized at the center region of the vibrator except the local position of center (r〓0). At the non-resonant gap there should be low values of vorticity distribution, but in contrast to the non-resonant gap, high and negative values of it exist at the center region of the vibrator with respect to the radial direction and in the vicinity of the middle region with respect to the axial direction. Acoustic streaming is noise-free due to the ultrasonic vibration and maintenance-free because of the absence of moving parts. Moreover, the proposed method by acoustic streaming can be utilized to the nano and micro-electro mechanical systems as a driving mechanism in addition to the augmentation of the streaming velocity.

• The Journal of the Korea Contents Association
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• v.19 no.12
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• pp.593-603
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• 2019

The purpose of this study is to analyze the effect of early health status on income status as young old adults grow older. Using Korean Retirement & Income Study(KReiS), this study finally included 923 older adults who were fully present from the first wave (2005) to the sixth wave (2015) for 10 years. The results of descriptive analysis show that the difference of income occurs due to the difference of health status at the early old age. In other words, older adults with good health status at the early old age(56 ~ 60 years old) have a relatively higher income level for 10 years compared with older adults with poor healthy status. In multiple regression analysis, the results represent that the better the health condition in early age, the higher the gross individual income, controlling for gender, spouse, and education level. In addition, older adults with good health at early old age stage have higher income level than those with poor health at early old age stage. The difference by health status continues as they are getting old. Therefore, this study suggests several policies and practical alternatives to improve the early health condition and to reduce the negative impact of early health condition on old age income.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.8-14
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• 2009

In a laser-plasma wakefield accelerator, the ponderomotive force of an ultrashort high intensity laser pulse excites a longitudinal wave or plasma bubble in a way similar to the excitation of a wake wave behind a boat as it propagates on the water surface. Electric fields inside the plasma bubble can be several orders of magnitude higher than those available in conventional RF-based particle accelerator facilities which are limited by material breakdown. Therefore, if an electron bunch is properly phase-locked with the bubble's acceleration field, it can gain relativistic energies within an extremely short distance. Here, in the bubble regime we show the generation of stable and reproducible sub GeV, and GeV-class electron beams. Supported by three-dimensional particle-in-cell simulations, our experimental results show the highest acceleration gradients produced so far. Simulations suggested that the plasma bubble elongation should be minimized in order to achieve higher electron beam energies.