• Journal of the Korean Society of Child Welfare
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• no.36
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• pp.133-163
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• 2011

The aim of this study is to examine the relationships between social support and child behavior problems and cognitive development in low income female-headed families. Informed by the stress-coping theory, family process model, and theoretical perspectives related to social support, this study estimates both direct and indirect effects of social support on child behavior problems and cognitive development. In particular, we focus on how the relationship between child outcomes and social support is mediated by mothers' parenting stress. The first three waves of longitudinal data from a subsample of 1,315 single and non-cohabiting low-income mothers in the Fragile Families and Child Wellbeing Study were utilized in this study. Results suggest that social support is directly associated with child behavior problems and also indirectly associated with child behavior problems mediated by mothers' parenting stress. Social support did not have a direct effect on children's cognitive development but rather had an indirect effect, which was mediated by mothers' parenting stress. The policy and practice implications of these findings are discussed.

• Journal of Bio-Environment Control
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• v.13 no.4
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• pp.209-216
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• 2004

This study was aimed to assess the effects of microclimate factors on lettuce chlorophyll fluorescent responses and to develop an environment control system for plant growth by adopting a simple genetic algorithm. The photosynthetic responses measurements were repeated by changing one factor among six climatic factors at a time. The maximum Fv'/Fm' resulted when the ambient temperature was $21^{\circ}C,\;CO_2$ concentration range of 1,200 to 1,400 ppm, relative humidity of $68\%$, air current speed of $1.4m{\cdot}s^{-1}$, and the temperature of nutrient solution of $20^{\circ}C$. In PPF greater than $140{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, Fv'/Fm' values were decreased. To estimate the effects of combined microclimate factors on plant growth, a photosynthesis efficiency model was developed using principle component analysis for six microclimate factors. Predicted Fv'/Fm' values showed a good agreement to measured ones with an average error of $2.5\%$. In this study, a simple genetic algorithm was applied to the photosynthesis efficiency model for optimal environmental condition for lettuce growth. Air emperature of $22^{\circ}C$, root zone temperature of $19^{\circ}C,\;CO_2$ concentration of 1,400 ppm, air current speed of $1.0m{\cdot}s^{-1}$, PPF of $430{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, and relative humidity of $65\%$ were obtained. It is feasible to control plant environment optimally in response to microclimate changes by using photosynthesis efficiency model combined with genetic algorithm.

• Journal of Korea Society of Industrial Information Systems
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• v.25 no.6
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• pp.15-23
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• 2020

While research activities in the agricultural field for climate change are being actively carried out, smart agriculture using information and communication technology has become a new trend in line with the Fourth Industrial Revolution. Accordingly, research is being conducted to identify and respond to signs of abnormal growth in advance by monitoring the stress of crops in various outdoor environments and soil conditions. There are also attempts to analyze data collected in real time through various sensors using artificial intelligence techniques or big data technologies. In this paper, we propose a big data model that is effective in analyzing the growth environment informations and biometric information of crops by using the existing relational database for big data analysis. The performance of the model was measured by the response time to a query according to the amount of data. As a result, it was confirmed that there is a maximum time reduction effect of 23.8%.

• Korean Journal of Ecology and Environment
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• v.46 no.3
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• pp.395-408
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• 2013

Environmental condition can induce changes in early life-history traits in order to maximise the ecological fitness. Here I investigated how temperature change and variation in human aquatic activity/behaviour affect early life-history consequences in fish using a dynamic-state-dependent model. In this study, I developed a general fish's life-history model including three life-history states depend-ing on foraging activity, such as body mass, mass of reproductive tissue (i.e., gonadal development) and accumulated stress (i.e., cellular or physiological damage). I assumed the level of foraging activity maximises reproductive success-ultimately, fitness. The model predicts that growth rate, development of reproductive tissues and damage accumulation are greater in higher temperature whereas higher human aquatic activity rapidly reduced the growth rate and development of reproductive tissue and increased damage accumulation. While higher foraging activity in higher temperature is less affected by human aquatic activity, the foraging activity in lower temperature rapidly declined with human aquatic activity. Moreover, lower survival rate in higher temperature or human aquatic activity was independent on mortality rate due to human aquatic activity or mortality rate when foraging activity, respectively. However, the survival rate in lower temperature or human aquatic activity was dependent on these mortality rates. My findings suggest that including of early life-history traits in relation to climate-change and human aquatic activity on the analysis may improve conservation plan and health assessment in aquatic ecosystem.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.100.1-100.1
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• 2012

태양전지 모듈의 25년 이상 장기간 정상 발전을 위해 태양전지 모듈을 구성하는 부품 소재의 장기 열화메커니즘 연구가 중요시되고 있다. 결정질 및 박막 태양전지 모듈 내 셀을 보호하기 위한 봉지재(Encapsulation)로 다양한 폴리머 재료가 적용되고 있다. 봉지재 부품으로 적용되고 있는 에틸렌 비닐 아세테이트(Ethylene Vinyl Acetate, EVA)는 장기 열화특성 및 내구성 개선 연구가 중요하다. 따라서 EVA를 가속열화하여 열화메커니즘 분석과 25년 보증 내구성을 보유하고 있는지 연구가 필요하다. 본 연구에서는 EVA의 Ultraviolet(UV), 온도 복합 환경스트레스 조건을 적용한 가속시험을 수행하고 장기 열화메커니즘을 분석하였다. 수명 및 손상모델을 이용하여 실환경에서 변화하는 UV와 온도를 일정한 값으로 나타낼 수 있는 UV/온도 가속조건을 설계하였다. 이를 통해 UV/온도 가속조건을 설정하였고 1년 및 25년 동안 EVA에 인가되는 stress와 유사한 양을 인가할 수 있는 시험시간을 결정하였다. 시험 후 전자현미경, AFM, FT-IR, TGA, DSC 등의 분석을 통해 열화메커니즘을 도출하였다.

• The Journal of the Korea Contents Association
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• v.21 no.12
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• pp.662-675
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• 2021

In order to evaluate the effectiveness of the Jeollabuk-do social welfare errand center, this study focused on identifying the effects of users' personal characteristics and workers' job environment characteristics on user satisfaction. The data analyzed are survey data collected from users and workers at 11 social welfare errand centers in each city and county in Jeollabuk-do. In the detailed analysis, the first-level independent variable for the users' personal characteristics, the second-level independent variable for the worker's job environment characteristics, and the user satisfaction were set as the dependent variables, and then a hierarchical linear model analysis model was applied. As a result of the analysis, it was confirmed that households with disabilities, sense of job value, job stress, role overload, and salary satisfaction had a significant effect on the service satisfaction of users. The results of this analysis show that the characteristics of the job environment of the workers have a major effect on the satisfaction of service users. This suggests that there is a strong need for improvement in the fields.

• Korean Journal of Social Welfare
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• v.36
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• pp.199-228
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• 1998

This study is designed to find out the determinants of dual-earner wives' needs for family-supportive services. For this purpose, a hypothetical model which explains the relationships among 6 stressors, role overload, stress and needs for 4 family-supportive services is developed. Using the data collected by purposive sampling from 234 professional women and 208 blue-collar women living in Chinju and Sacheon, the hypothetical model developed in this study was tested. In order to examine occupational class differences, a model for professionals and another model for blue-collars were developed separately and compared. For data analysis, a covariance structure analysis was used. The best-fitting model for professional women (df=141, GFI=0.928, CFI=0.965) and the model for blue collar women (df=141, GFI=0.902, CFI=0.912) were found. As a result of comparing two models, 9 common relationships were found:l)Greater dissatisfaction with child care service increases role overload; 2)Longer work hours increases role overload; 3) Higher level of role overload increases stress; 4)Higher level of stress increase needs for leaves; 5)Older child increases needs for flexible work pattern; 6)Younger child increases needs for finalcial assistance for child care fee; 7)needs for financial assistance for child care increases needs for on-site child care services; 8)needs for on-site child care services increases needs for leaves; 9)needs for leaves increases needs for flexible work pattern. With the exception of these 9 common relationships, the analyses revealed substantial differences between professional and blue-collar dual-earner wives. Based on the common and differential needs between 2 groups of wives, the effective ways to provide family-supportive services according to the needs of individual dual-earner wives who are in different familial, financial, and work conditions were suggested.

• Knowledge Management Research
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• v.23 no.4
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• pp.251-273
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• 2022

Metaverse is one of the most frequently used words recently, with digitalization accelerated by the COVID-19 pandemic that started in 2019 and the development of information and communication technology. It is expected to bring a new revolution in our life as a whole in user experience. In particular, as telecommuting was adopted in the business area, interest in virtual office services such as digital video conferencing and remote offices, which are similar to the metaverse, has also increased. In this study, a study on the intention to use the metaverse service used in the work environment was applied to the Unified Theory of Acceptance and Use of Technology 2(UTAUT2). External variables for metaverse characteristics, such as self-presentation, telepresence, and technostress, were analyzed and discussed. In this study, PC-based Gather.town and VR-based Facebook Horizon, currently the most well-known and considered usable in work environments, were introduced to potential users and conducted a survey. This study has academic implications in that the research has examined the factors that affect the technology acceptance intention of users who want to apply the metaverse as a work environment based on the UTAUT2 model, unlike previous studies that have been mainly researched on the general metaverse. In practice, it may be helpful to suggest factors that should be considered when firms adopt the metaverse for business purposes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.138-142
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• 2018

This study used HILS to test an expansion joint, which is vulnerable to the water hammer effect. The operation data for the HIL simulator was the length rate of the expansion joint by the water hammer, which was used for life prediction based on the vibration durability. For the vibration durability test, the internal pressure of the expansion joint was assumed to be a factor of the durability life, and the lifetime prediction model equation was obtained by curve fitting the lifetime data at each pressure. During the test, the major failure modes of crack and water leakage occurred on the surface of the bellows part. The lifetime prediction model typically follows an inverse power law model. The pressure is a stress factor, and the model is effective in only a specific environment. Therefore, another stress factor such as temperature will be added and considered for a mixed lifetime prediction model in the future.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.6
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• pp.743-749
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• 2010

This paper proposes a derating design method for improving system reliability by using a probabilistic approach. In the proposed design, the focus is upon system levels in determining derated levels of stresses such as temperature and current, unlike recent design approaches that focus on component levels. System reliability is evaluated using component reliability metrics that are given as functions of time and unknown stresses; this evaluation is based on a series system-reliability model. The variation in stress, which was not considered in previous derating designs, is introduced in the present design to account for the uncertainty in both environmental and operating conditions at the customer' hands. Optimization problems for system reliability improvement are formulated and solved using FORM to determine the best derating design. An example of a derating design for an electrical system shows the details of the proposed method and its applicability to systems design for reliability improvement.