• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.854-858
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• 2002

In this study, Fatigue crack growth behavior of the laser welded sheet metal due to a single overload was investigated. From Fatigue crack propagation test, it was observed that the retardation of fatigue crack growth has been more effective in the welded specimen than in the base metal. And if the distance between the welded part and the position of overload is too close the retardation of fatigue crack growth at the welded part has been decreased. From FEM analysis, it was observed the retardation has been more effective compressive residual stress than plastic zone.

• Journal of the Korean Society of Safety
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• v.8 no.1
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• pp.54-58
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• 1993

The fatigue growth behavior of short cracks were studied various load ratios. Computer-aided unloading elastic compliance method was employed to measure the closure and the length of short cracks. In the dc/dN-$\Delta$K relationships. the decreasing behavior of the growth rate of short cracks is due to the decrease of crack opening ratio with increasing crack length. Irrespective of load ratio. the growth rate of short cracks can be well decribed in terms of the effective stress intensity factor range $\Delta$K$_{eff}$, which is calculated on the base of crack closure. dc/dN-$\Delta$K$_{eff}$ relationships of short cracks are found to coincide well with the corresponding long crack relationships. accordingly. the growth rate of short cracks can be predicted using that of long cracks.ort cracks can be predicted using that of long cracks.cks.

• Macromolecular Research
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• v.9 no.6
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• pp.319-326
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• 2001

Fatigue crack growth (FCG) behavior of natural rubber/ethylene-propylene-diene rubber (NR/EPDM) blend vulcanizates under dynamic tearing condition was investigated by using a fracture mechanics approach. It appeared that variation of crack growth rate with blend compositions was dependent on the level of imposed tearing energy G. At low tearing energy region, the FCG rates of the blend were lower as the EPDM content was increased, while at high tearing energy region, the trend was reversed. Over the measured range of tearing energy G, all blend compositions showed the lower crack growth rates compared to the average of properties of component elastomers. When the blends were thermally aged, the fatigue resistance of the blends was deteriorated in proportion to the concentration of EPDM phase. Fatigue crack growth behavior of the blends was supposed to be associated with the inhomogeneities of the crosslink structure of the blends arising from cure incompatibility of the EPDM and NR when they are sulphur cured.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.548-554
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• 1994

The high temperature fatigue crack growth behavior of SUS 304 stainless steel at $550^{\circ}C$ and $650^{\circ}C$ was investigated under various kinds of stress ratio and frequency in sinusoidal waveform on the basis of the non-linear fracture mechanics. The result arranging crack growth rate by modified J-integral J' showed influence of stress ratio and frequency. All the data obtained under the test at $550^{\circ}C$ were plotted within data band of da/dN-${\triangle}J_f$ relationship for cycle-dependent crack growth. On the basis of static creep and cycle-dependent data band; both time- and cycle-dependent crack growth behavior was observed under loading conditions at $650^{\circ}C$, but cycle-dependent crack growth behavior predominantly appeared and time-dependent crack growth behaviour was little observed under loading conditions at $550^{\circ}C$. Fractographic examinations for fracture surface indicated that the fracture mode was generally transgranular. The stripes were found on fracture surface and each stripe was accompanied by a crack tip blunting and an abrupt increase in the load-point displacement. The $J'_{an}$ had a validity in case of $650^{\circ}C, but scarcely had it in case of $550^{\circ}C$.

• Korean Journal of Community Nutrition
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• v.26 no.1
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• pp.1-11
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• 2021

Objectives: This study was conducted to assess the eating behavior, growth, and dietary practices of children aged 3~5 years living in the Seoul and Gyeonggi Provinces. Methods: Self-administered questionnaires were completed by 237 mothers of preschool children between April and June 2018. Z-scores for weight-for-age, height-for-age, and BMI-for-age were calculated to determine the children's growth status. Dietary practices were evaluated using the nutrition quotient for Korean preschoolers (NQ-P). Results: In our study, 29.5% of children were in the eating-small-amounts group, 46.8% of children were in the neophobic behavior group, and 61.2% of children were in the refusal-of-specific food group. Specific foods found to have a high frequency of rejection are listed in descending order as follows: shellfish, soy, mushroom, shrimp, vegetables, milk, eggs, yogurt, seaweed, meat, fruits, and fish. The eating-small-amounts group had lower Z-scores for weight-for-age, height-for-age, and BMI-for-age than the non-picky eaters' group. Compared to the non-picky eaters' group, the eating-small-amounts group of picky eaters had lower scores on the moderation and environment items of the NQ-P, the neophobic behavior group had lower scores on the balance and environment items of the NQ-P, and the refusal-of-specific food group had lower scores on the balance, moderation, and environment items of the NQ-P. Conclusions: Children classified with picky eating behavior had lower growth and development, lower diet diversity, less balanced food intake, and had greater difficulty in abstaining from eating unhealthy foods than non-picky eaters. Therefore, a lot of patience and intensive efforts are needed to encourage children to encounter, experience, and accept unfamiliar food. It is more effective to provide eating behavior guidance by gently encouraging children, than by being strict and forceful. Besides, since the eating behavior of children is influenced maximally by the dietary lifestyle at their homes, it is important to ensure that a healthy dietary lifestyle is maintained at home.

• Korean Journal of Childcare and Education
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• v.10 no.2
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• pp.153-174
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• 2014

This study started as an effort to solve the serious environmental program that the Korean government and internationally focused on. For the purpose of the study, a green based growth education program was composed that young children could participate in. With this program, the study participants could form attitudes, behavior, and knowledge of environmental preservation. To see the effectiveness of the green growth educational program, the study set up a control and an experimental group. The program was composed with four major content 'ecosystem', 'energy', 'resource', and 'green citizenship'. The study planned 20 sessions including fairy tales, storytelling, art, game, and science activities. The study's participants were a total of 42 five-year-old children. The result of the research showed that the experimental group's environmental preservation knowledge, attitude, and behavior score was significantly higher than the control group. The green growth educational program had a positive effect on young children's knowledge, attitude, and behavior of environmental preservation. This study included the realities of the difficulties applying green growth education in kindergarten, the result provided practical information regarding the green growth educational program to kindergarten teachers.

• Journal of Powder Materials
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• v.11 no.2
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• pp.165-170
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• 2004

Growth behavior of two different types of grains, faceted and rounded, in a liquid matrix has been studied in the (75WC-25TiCN)-30Co system. Powder samples were sintered above the eutectic temperature for various times under a carbon saturated condition. (Ti,W)(C,N) grains with a rounded shape and WC grains with a faceted shape coexisted in the same Co based liquid. With increasing sintering time, the average size of (Ti.W)(C,N) grains increased continuously and very large WC grains appeared. The growth of rounded (Ti,W)(C,N) grains followed a cubic law, r^3-r^3_0$=kt, where r is the average size of the grains, $r_0$ the initial average size, k the proportionality constant and t the sintering time. indicating a diffusion-controlled growth. On the other hand, the growth of the faceted WC grains resulted in a bimodal grain size distribution, showing an abnormal grain growth. These observations show that the growth behavior of different types of grains is governed by their shape, faceted or rounded, even in the same liquid matrix.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.2
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• pp.53-57
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• 2016

6H-SiC single crystals were grown by using a resistance heating system. It was recognized that the growth behavior was different according to the different growth temperatures. It was revealed that the temperatures at the source feeding and at the crystal growth position had to be controlled independently. In this report, the effect of growth temperature on the SiC crystal growth was discussed.

• Communications for Statistical Applications and Methods
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• v.17 no.6
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• pp.909-916
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• 2010

A trend in software reliability engineering is to take into account the coverage growth behavior during testing. A coverage growth function that represents the coverage growth behavior is an essential factor in software reliability models. When multiple competitive coverage growth functions are available, there is a need for a criterion to select the best coverage growth functions. This paper proposes a selection criterion based on the prediction error. The conditional coverage growth function is introduced for predicting future coverage growth. Then the sum of the squares of the prediction error is defined and used for selecting the best coverage growth function.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.1
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• pp.29-36
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• 1991

The effects of heat treatment on fatigue crack growth behavior were studied in continuously reinfored, magnesium-based composite (FP/ZE41A). Following an earlier TEM investigation, specimens were thermally aged to modify the interfacial zone between the alumina fibers and mg alloy matrix. The fatigue crack growth experiments were conducted with specimens having the fiber orientation normal to the crack growth direction(longitudinal) and also specimens with the fibers oriented parallel to the crack growth direction(transverse). A comparision of the fatigue crack growth behavior indicates that aged longitudinal specimens are more resistant to fatigue crack growth than as-fabricated longitudinal specimens. Conversely, as-fabricated transverse specimens are more resistant to fatigue crack growth than aged transverse specimens. SEM observations of fiber pullout and ductile tearing on the fatigue fracture surfaces indicate that the aging weakens the strength of the fiber/matrix interface, giving rise to the observed fatigue crack growth behavior.