• Journal of the Korean Data and Information Science Society
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• v.17 no.3
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• pp.945-952
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• 2006

Several accelerated life test plans use tests at only two levels of stress and thus, have practical limitations. They highly depend upon the assumption of a linear relationship between stress and time-to-failure and use only two extreme stresses that can cause irrelevant failure modes. Thus 3-level stress plans are preferable. When the lifetime distribution of test unit is exponential with mean lifetime $\theta_i$ at stress $x_i$, i=0, 1, 2, 3, we derive the optimum quadratic plan under the assumption that a quadratic relationship exists between stress and log(mean lifetime), and propose the compound linear plans, as an alternative to the optimum quadratic plan. The proposed compound linear plan is better than two other compromise plans for constant stress testing and nearly as good as the optimum quadratic plan, and has the advantage of simplicity.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.218-219
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• 2020

The risk of a fire in a building is closely related to the usage of the building. In particular, all fires that occur in a building are not risky to safety of human life, and it is associated with the combustion area and the increase of total floor area of the building. Therefore, this study focused on safety of human life in terms of the statistics of fire with considering the aspect of growing fires and analyzed the statistical data of fire for 10 years. As for the analysis on fire, the time of occurrence by usages of buildings, frequency of occurrence and the ratio of casualties etc. were analyzed. It is expected that results of this study could be used for evaluations on a variety of parts in terms of design, construction and maintenance of buildings.

• Journal of Welding and Joining
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• v.33 no.2
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• pp.47-55
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• 2015

With using adaptive control of the resistance spot welding machine, the advantage on electrode life time for galvanized steels has been addressed. This study was aimed to evaluate the electrode life time of galvanized steels with applying the constant current control and the adaptive control resistance spot welding process for a comparison purpose. The growth in diameter of electrode face was similar for both the constant current and the adaptive control up to 2000 welds. The button diameter was decreased with weld numbers, however, sudden increase in button diameter with use of the adaptive control after 1500 welds was observed. The peak load was continuously decreased with increasing number of welds for both the constant current and the adaptive control. The current compensation during a weld was observed with using the adaptive control after 1800 welds since the ${\beta}$-peak on dynamic resistance curve was detected at later weld time. The current compensation with adaptive control during resistance spot welding enhanced the nugget diameter at the faying interface of steel sheets and improved the penetration to thinner steel sheet.

• International conference on construction engineering and project management
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• 2005.10a
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• pp.796-801
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• 2005

Time management is one of the critical tasks in project management. Based on the theories of total quality management, this authors presented a project time management method, total time management (TTM), so as to facilitate highway project time management. This paper discussed the four fundamental characteristics of TTM: total factors management, staff management, project life cycle management, and Plan-Do-Check-Action (PDCA) cycle management. Now, most managers use computer software to manage the project. In order to make the theory of TTM more executable, the authors develop a project time management system suitable for TTM. This paper presents this time management system's analysis processes including system requirement, key functions etc..

• Journal of Family Resource Management and Policy Review
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• v.25 no.1
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• pp.91-112
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• 2021

This study aimed to explore the influence of family characteristics on the work-life balance of early adolescents. A series of data analyses was conducted on adolescents' use of time in daily life on the basis of 2018 Korean Children and Youth Panel Survey (KCYPS 2018). We found that the work-life balance of youth is related to their parents' health status, presence of older siblings, household income, parenting attitude, parent-child communication time, and mother's occupation. The work-life balance of the fifth graders is more likely to be influenced by family characteristics compared with that of the eighth graders. In particular, the fifth graders' sleep deprivation is affected by the mother's occupation, but there is no significant effect on the eighth graders' sleep deprivation. An important factor in skipping breakfast is household income, with adolescents from low-income families tending to skip breakfast more than five days a week. In addition, parents' health status and parenting attitude are significantly related to skipping of breakfast in early adolescents. Household income is related to the after-school private tutoring hours of both the fifth and eighth graders; however, parenting attitude and mother's occupation are also significant influencing factors of the fifth graders' after-school study. Mother's occupation is related to excessive cell phone use; specifically, the fifth graders whose mothers work white-collar jobs, sales and services or manufacturing are more likely to play with cell phones more than three hours a day than those whose mothers are full-time housewives. These results suggest that the work-life balance policies targeted at the family characteristics of adolescents can improve family environments in a manner that enhances adolescents' life balance, thus supporting the well-being of early adolescents and their families.

• Journal of Family Resource Management and Policy Review
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• v.27 no.4
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• pp.63-74
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• 2023

This study considered allocating and balancing time use as an important factor that determines the quality of life, and attempted to analyze the happiness of married women through the perspective of satisfaction with time use. We investigated the structure of time use, and analyzed the factors that affect happiness in the perspective of time use through the Time Use Survey data. Analyzing the happiness of married women, we found out that the level of happiness and the factors affecting happiness varied by generation. In the case of economically active women, the happiness of baby boomers and Generation X was mostly impacted by mandatory work hours, while the happiness of Generation Y was mostly impacted by the presence of care-dependent people. However, in the case of economically unactive women, the happiness of baby boomers and Generation X was mostly impacted by leisure and volunteering time that could be used freely, while the happiness of Generation Y was mostly impacted by the attitude toward gender roles. Therefore, through the perspective of time use, the happiness and the factors determining the happiness of married women differs by generation and economic activeness. This study has significant implications for the establishment of family policies for married women.

• Journal of Families and Better Life
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• v.15 no.1
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• pp.83-94
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• 1997

The purpose of this study was to review the technological deterministic debate that the development of household technology would decrease housework. For the purpose this study made use of all sorts of literature and the interview resources obtained from 86 housewives above 30 years old. It was expected the household capital goods would save housework time and labor. The total time spent in housework and fatigue however seemed not much lessened during the diffusion period. Household capital goods were also expected to enhace the housework satisfaction and increase much housework participation of husband and children; yet neither of them appeared much high during the diffusion period.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.638-644
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• 1999

Workability time of superplasticized concrete is maintained generally for 30-60 minutes only. Therefore it is of great advantage for the concrete producer to use a high range water reducer which provides an extended slump life. Recently slump retentive srperplasticizer has been developed. Concrete mixing tests were done to know slump, setting, air content, bleeding and hardening characteristics of concrete using slump retentive superplasticizer. With slump retentive superplasticizer, high quality concrete was produced and slump loss of concrete was reduced in big way, making long transportation time possible as a practical alternative to on-site addition.

• The Korean Journal of Applied Statistics
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• v.9 no.2
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• pp.119-134
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• 1996

Accelerated life testing (ALT) of a system is commonly used to reduce time and cost. ALT is achieved by subjecting the test systems to more severe conditions than the normal ones to obtain estimates of life distribution under normal condition. The major interest of this research is to use a model of incorporating the common environmental effect on the components serially linked into a system-so called frailty model for the system life time distribution under each stress and to discuss the related data analysis and comparison of the model with the generally used one. The profile likelihood is used to get an initial values required to compute maximum likelihood estimates and simulation is carried for comparison.

• Journal of Fashion Business
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• v.27 no.4
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• pp.1-20
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• 2023

This study proposes the practical design elements of sustainable fashion by understanding the values of the MZ generation and analyzing the design characteristics that can extend the life of clothing. The theoretical concept of sustainable fashion through previous studies was reviewed and in-depth interviews were conducted with the MZ generation on "design characteristics of clothes that they have actually used for a long time." The result was drawn by approaching the constant comparison method through the qualitative methodology. As a result of the study, the design characteristics of clothes that can be worn for a long time are as follows. First, simple design pursues simplicity that is not excessive to the essential characteristics of clothes. Second, sturdy material is durable and not easily damaged. The clothing storage method and laundry method were also factors that could extend the life of the garment. Third, emotional design is a design that fits well with your mood and body type and gives a special meaning to your emotions. This study is meaningful in suggesting elements necessary for extending the life cycle of clothing and providing basic data that can be applied to the practical design steps of the fashion industry.