• Journal of the Korean Society of Safety
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• v.15 no.4
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• pp.8-14
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• 2000

The remaining life estimation for the aged components in power plants as well as chemical plants are very important because mechanical properties of the components are degraded with time of service exposure in the high temperature. Since it is difficult to take specimens from the operating components to evaluate mechanical properties of components, accelerated aging technique are needed to estimate and analyse the material degradation. In the this study, test materials with 4 different degradation levels were prepared by isothermal aging heat treatment at $630^{\circ}C$. And tensile test, $k_{IC}$ test, hardness test and Scanning Electron Microscope analysis were performed in order to evaluate the degradation of 1Cr-1Mo-0.25V steels.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.115-118
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• 2009

Life time and number of use of liquid propellant rocket engine (LRE) should be carefully defined since those are crucial parameters affecting development costs and period. The present study surveyed the development and qualification records of LRE for space launch vehicles, especially concerning about test numbers and duration. It was shown that a single engine for expendable launch vehicle is tested with tens of ignition and several times duration of flight at least.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.886-892
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• 2013

Hydraulic hose assemblies are used as piping components for construction machinery, automobile, aircraft, industrial machinery, machine tools, and machinery for ships. Then the reliability of hose assemblies is important because total hydraulic system, which used to deliver the fluid power ($P^*Q$) needed to flexibility in the piping system, is not operated if the hose assembly failed in the system. The data of the accelerated life test estimated through the shape parameter(${\beta}$) resulting of the Weibull distribution analysis. This study has tried to reduce the test time resulting from varying impulse pressure range and the flexing diameter. Accelerated life test model for the test results was adopted the GLL(generalized log linear) and the accelerated indexes are identified as 6.64 for the pressure and 4.46 for flexing radius. Also, it found that shape parameter is 6.19, scale parameter(${\eta}$) is $1.035{\times}108$, which were adopted the pressure 35 MPa and the flexing diameter R100 mm in the used condition.

• Journal of Families and Better Life
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• v.22 no.6 s.72
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• pp.47-61
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• 2004

The purpose of this study is to develop a life planning program for retired elderly people. This program is not a preparation program for elderly people prior to their retirement but a readjustment and re-planning their life after retirement. This program help retired elderly people to solve the life problem and set up a affirmative ones future image. Also this program pay regard to social, home backgrounds of this generation. The program consists of four session curriculums session 1 is entitled to &Make my future by oneself&, session 2 is &Enjoy healthy life as much as one can&, session 3 is &Have a heart for family& and session 4 is &Set up a mature old age&. A fled study has been conducted with ten retired elderly people who want to participated in the program voluntarily. 4 sessions each of which consists of 2 hours were performed at Korean Association of Retired Persons. Field test for program evaluation is designed to three steps: pre-test, post-test and one month follow-up test to measure the effectiveness of the program. According to evaluation results, the program shows a significantly positive effect on the improvement of elderly people's understanding about elderly life. At the one month follow-up assessment, the effect of program is still remained strongly even though there is a Partial slight increase or reduction which is not statistically significant. Most of the program participants have expressed high level of satisfaction with the program. For further study, we need various contents which are suited to larger group with diverse socio0-demographic backgrounds. At the same time, the program has diverse instruction methods which are pertinent to levels of participants. Also, the program needs to continuous adjustment to the next generation with their social, home backgrounds.

• Journal of Korean Public Health Nursing
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• v.26 no.2
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• pp.328-340
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• 2012

Purpose: This study explored the degree of internet addiction and its influencing factors in lower grade elementary school children in rural areas. Methods: Subjects included 1,137 elementary school children. A structured questionnaire consisting of questions internet addiction, family function and school life satisfaction was used for data collection. Descriptive statistics, ${\chi}^2$-test, ANOVA and Correlation and Regression were performed using a SPSS program. Results: Among the subjects, 85.8% were regular users, 8.1% were potential risk users, and 6.1% were high-risk users. Career of internet use, daily internet access time, the number of conversations per week, the number of times spent eating out and traveling with parents within the last month and activities with friends, and satisfaction on school life differed significantly according to the degree of internet addiction. Finally, among the factors studied, daily internet access time, conversations within family, activities with friends and school life satisfaction in children in early elementary school was 20.7% of the explanatory power of the subjects' degree of internet addiction, collectively. Conclusion: Use of the internet by early elementary school children should be monitored and strategies to promote familial conversations, activities with peers and school life satisfaction should be developed.

• Food Science of Animal Resources
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• v.38 no.6
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• pp.1216-1225
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• 2018

Shelf-life is defined as the amount of time during which a food product retains its desired sensory, chemical, and physical characteristics while remaining safe for consumption. The food industry needs to rapidly obtain the necessary information for determining the shelf life of its products. Here we studied the approaches available for conducting accelerated shelf-life tests. Accelerated shelf-life testing is applied to a variety of products to rapidly estimate change in characteristics with time. The aim of this work was to use accelerated shelf-life testing to study the changes in pH, microbiology, and sensory characteristics of ice cream by the application of a kinetic approach and, based on the observations, to estimate its shelf life. As per the current law, there is no shelf life on ice cream. Our results suggest that the shelf life of an ice cream sample was 24.27 months at $-18^{\circ}C$, 2.29 months at $-6^{\circ}C$, 0.39 months at $-1^{\circ}C$, and 0.15 months at $4^{\circ}C$. Results of this study suggest that a set expiration date on ice cream might also contribute to effective management of ice cream characteristics in the retail chilled chain.

• 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.

• Korean Journal of Child Studies
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• v.26 no.5
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• pp.311-330
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• 2005

The purpose of this study was to examine the paternal involvement tendency and its effect on adolescent's self-esteem for boys and girls. Subjects were 607 1st and 2nd grade middle school students in Busan. The data were analyzed by t-test, one-way Anova, Pearson's correlation, and multiple regression analysis. The results were as follows. The scores on paternal involvement were influenced by the amount of time spent with parents, 5days work a week of father, flexibility of leaving work-time of mother, regularity of holiday work of mother as well as adolescents' and fathers' sociodemographic characteristic. For boys, self-esteem was influenced by all sub-scales of paternal involvement : the leisure-life, proffering information, academic support, eveηday life, material support, discipline, and tradition-inheritance. For girls, self-esteem was influenced by leisure-life, proffering information, academic support, everyday life, and material supports.

• Journal of the Korean Society of Safety
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• v.14 no.1
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• pp.41-48
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• 1999

The fatigue life tests were performed in strain control with triangular and hole-time wave-forms at $650^{\circ}C$. The fatigue lifes were investigated according to waveform examining damage mechanisms, which could be used to predict the fatigue life and estimate the remaining life. The results obtained are as follows; The fatigue lifes were in order of the fast-fast>the fast-slow>the slow-fast in the triangular waveforms, and the fatigue lifes in slow-fast waveforms got shorter in the hold-time waveforms. The damage mechanisms of the fracture surfaces were transgranular fracture in the fast-fast, the fast-slow waveforms and intergranular fracture in the slow-fast waveform.

• Proceedings of the Korean Reliability Society Conference
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• 2004.07a
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• pp.239-246
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• 2004

Accelerated degradation test (ADT) can be a useful tool for assessing the reliability when few or even no failure are expected in an accelerated life test. In this paper, MLCC (Multilayer Ceramic Capacitors), a sort of passive components which have large capacitance(X7R -55$^{\circ}C$~1$25^{\circ}C$) have been tested, and least-square analyses are used to illustrate our approach in which amount of degradation of a DUT following log-normal distribution. We assumed a simple and useful linear model to describe the amount of degradation over time subjected to different voltage levels applied. Tests for linearity of the performance-time relationship, and provide tests for how well the assumptions hold. Also, by using Eyring Model, MLCC's mean life time is assessed.