• Transactions of Materials Processing
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• v.17 no.4
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• pp.292-301
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• 2008

Type 2 compressed natural gas(CNG) storage vessels for automobiles are becoming widely used. They are not only supplied to automakers in Korea, such as Hyundai Motors, but increasingly, they are being exported overseas. Autofrettage is a process that produces beneficial residual stresses in a vessel by subjecting it to excessive internal pressure. This strengthens the vessel and improves its fatigue resistance. This paper presents research investigating the autoftettage process and residual stresses it produces in type 2 CNG storage vessels. A finite element analysis technique and a closed form equation are used. Then, fatigue resistance is analyzed through a fatigue evaluation performed according to ASME section VIII.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.420-422
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• 2003

Aging and failure of motor insulation depend on the stresses imposed on it. The insulation life time depends on the severity of the stresses. The electrical aging by transient surge is very important to traction motor in EMU(electric multiple unit). This paper Presents the insulation characteristics of stator coil by transient surge from inverter. There are several nondestructive tests available for checking the condition of motor insulation, the probable extent of aging,. and the rate of which aging is taking pace. So the insulation characteristics of stator coil were each analyzed by measurement of leakage current, dielectric loss($tan{\delta}$), capacitance, polarization index(PI) and partial discharge. The method of diagnosis is able to analyze the aging condition and Predict the life of the traction motor in EMU.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.623-627
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• 2003

Aging and failure of motor insulation depend on the stresses imposed on it. The insulation life time depends on the severity of the stresses. The electrical aging by transient surge is very important to traction motor in EMU(electric multiple unit). This paper presents the insulation characteristics of stator coil by transient surge from inverter. There are several nondestructive tests available for checking the condition of motor insulation, the probable extent of aging, and the rate of which aging is taking place. So the insulation characteristics of stator coil were each analyzed by measurement of leakage current, dielectric loss($tan{\delta}$), capacitance, polarization index(PI) and partial discharge. The method of diagnosis is able to analyze the aging condition and predict the life of the traction motor in EMU.

• International Journal of Reliability and Applications
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• v.18 no.2
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• pp.21-44
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• 2017

Accelerated life tests (ALTs) are frequently used in manufacturing industries to evaluate the reliability of products within a reasonable amount of time and cost. Test units are subjected to elevated stresses which yield quick failures. Most of the previous works on designing ALT plans are focused on tests that involve a single stress. Many times more than one stress factor influence the product's functioning. This paper deals with the design of optimum modified ramp-stress ALT plan for Burr type XII distribution with Type-I censoring under two stress factors, viz., voltage and switching rate each at two levels- low and high. It is assumed that usage time to failure is power law function of switching rate, and voltage increases linearly with time according to modified ramp-stress scheme. The cumulative exposure model is used to incorporate the effect of changing stresses. The optimum plan is devised using D-optimality criterion wherein the ${\log}_{10}$ of the determinant of Fisher information matrix is maximized. The method developed has been explained using a numerical example and sensitivity carried out.

• The Korean Journal of Community Living Science
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• v.13 no.2
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• pp.37-51
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• 2002

This study was performed to investigate the degree of different stresses and to search the influence of food habit and nutrient intakes at stress situation in university students and secondary school teachers. The data was collected by questionnaire method and searched nutrient intakes by 24 hours recall. The subjects were 282 students and 152 high school teacher in Kyunggi do. Physical status was no difference with two groups. Energy intake of teachers was lower than that of students, but the intakes of vitamin A and C were high in teachers' group. The university students had more stress situation than teachers in almost kind of stresses except overload stress. Self-diagnosed dietary habits were better in the group of teacher. Especially smoke and alcohol drink behavior were correlated with nutrient intakes in male teachers and students. The quantity of nutrient of nutrient intakes was correlated with different kind of stress. The stress of life event was correlated with the intakes of carbohydrate, minerals, thiamin and riboflavin, and the deprivation was with iron and vitamin A in teachers' group. The intake of almost nutrients was correlated with the stress of noise in students' group. By the analysis of stepwise multiple regression, although the $R^2$ values were very low, vitamin C intake was influenced in the factor at the stress of life events($R^2$=0.025), self-efface($R^2$=0.030) and noise($R^2$=0.020), thiamin was at food induced stress ($R^2$=0.021) and vitamin A was at the stress of type A behavior($R^2$=0.022) and anxiety response($R^2$=0.014). Therefore, we could concluded that different kind of stresses were influenced in dietary behavior and nutrient intakes. More research would be needed at the aspects of health promotion in the stressful situation of modern society.

• Korean Journal of Plant Resources
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• v.16 no.3
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• pp.238-244
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• 2003

During the life cycle, plants have to suffer from various environmental stresses. A common element in response to many environmental stresses is cellular dehydration. Dehydrins are a family of proteins commonly induced by environmental stresses associated with low temperature or dehydration and during seed maturation drying. For the study in the defense mechanism against various stresses, a cDNA clone encoding a dehydrin gene was isolated from a cDNA library prepared from tab root mRNAs of Codonopsis lanceolata. The cDNA, designated ClDhn1, is 893 nucleotides long and has an open reading frame of 480 bp with a deduced amino acid sequence of 159 residues. The ClDhn1 amino acid sequence is highly hydrophilic and possesses two conserved repeats of characterized lysine­rich K­segment (KIKEKLPG), and a 7­serine residue stretch prior to the first lysine­rich repeat that is common to many dehydrins. The DEYGNP conserved motif is, however, modified in the sequence of ClDhn1 gene. The deduced amino acid sequence of ClDhn1 was compared with other plant dehydrinls and showed high homology with Solanum commersonii

• Korean Journal of Human Ecology
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• v.18 no.1
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• pp.93-112
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• 2009

The purpose of this study is to identify stresses and adjustment elements of Chinese students in Korea. The data analysis was conducted by qualitative method based on interviews with sixteen Chinese students as a focus group by the help of two interpreters. The results were as follows: first, stresses of Chinese students were from 'cultural difference', 'language', and 'financial', 'educational' and 'psychological stress', and 'university culture in Korea'. Those categories were divided into several sub categories. Second, ten helpful elements Chinese students could adapt themselves to Korean university life were such as 'Help of Korean professor and friends', 'Chinese friends' help', 'English-oriented lecture', 'Cultural affinity to Korea', 'Fluency in Korean language', 'Integration to Korean culture', 'Pride in Chinese culture', 'Individual effort', 'Satisfaction with educational environment', 'Perception of self-growth'.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.10a
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• pp.29-33
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• 1989

An extended model for the assessment of fatigue reliability of steel structures In the presence of residual stresses Is developed. The model explicitly Includes the uncertainties of the lean stress and residual stress in terms of the zero-mean equivalent stress-range. It Is assumed that the fatigue life of welded Joints follows the Weibull distribution. Based on the numerical illustrations, It Is shown that the probability of fatigue fat lure and the allowable stress-range for fatigue design could be significantly affected by the presence of residual stresses. This effect may be represented through the mean stress at the welded joints.

• Journal of Families and Better Life
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• v.29 no.2
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• pp.39-50
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• 2011

The purpose of this study is to analyze the research trends in articles on parenting stress published in Korean academic journals. Between 1996 and 2010, 116 articles on parenting stress were published in 16 reliable journals in Korea. This study analyzed research frequency, contents and methodology. Results show that the number of studies has increased during the years. Most studies used methods categorized as quantitative data and cross-sectional surveys. The most frequently used measurement scale was Abidin's Parenting Stress Index. Many were analyze by using regression. The main content of these studies were the factor related to parenting stresses and the relationship between the factors and parenting stress.

• Journal of Applied Reliability
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• v.7 no.1
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• pp.1-11
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• 2007

This paper presents a derating design approach for reliability improvement of a regulator IC. The IC is usually used in SMPS. The main failure mechanism of interest is voltage drop due to the package delamination mainly caused by two stresses, i.e. temperature and current. The lifetime under stresses is modeled as a function of stresses and time using accelerating life testings. Quantitative and qualitative variation in lifetime according to stress variations are investigated using the modeled lifetime. Stress levels would be determined to achieve required reliability levels in the aspect of derating design for reliability.