• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.71-75
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• 2000

The effects of stitching thread on fatigue characteristics of polyurethane foam cored sandwich structures are investigated. Fatigue test and static test, being used in four point bending test, are performed with various diameters and distances of stitching thread. The Results show that the maximum load for bending tests is similar to each other, but after $1O^6$ fatigue cycles, the stiffness degradation of the stitching thread diameter $\emptyset$ 3mm specimen is a much larger than that of the $\emptyset$ 5mm specimen.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.5
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• pp.128-133
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• 1997

Due to their high strength and good wear resistance, nitro-carburizing materials have been used for many machine components. However, the nitro-carburizing materials are found to have one disadvantage ; that is, their strength and fatigue life show larger scatter than those of non-heated metals. In this paper, therfore, the statistical chracteristics of non-heated and nitro-carburized specimens for SCM415 are investi- gated under two different of stress levels 1.15 .sigma. /sub .omega. / .leq. / .sigma. / sub .alpha. / .leq. / 1.25 .sigma. /sub .omega. /. Seven specimens at each stress level are tested by using rotating bending fatigue tester. The relation between a crack length and fatigue cycles can be arranged for Weibull distribution, and S-N curve using 95% reliability function is obtalined for nitro-carburized specimen.

• Women's Health Nursing
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• v.7 no.3
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• pp.241-255
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• 2001

This is a cross-sectional descriptive study which compares the level of postpartum women's physical, phychological, neurosensory fatigue between rooming-in and non rooming-in groups. The data were collected by using self-report questionnaire from April 1 to May 31, 2001. Subjects were 68 mothers who opted the rooming-in choice and 98 mothers who did not choose the rooming-in at one hospital in Seoul, Korea. They all had NSVD. The research questionnaire consisted of 36 items on general chracteristics and 30 items on postpartum fatigue developed by Pugh (1993). The data were analyzed by using the SPSS 10.0 window program. The results of this study were as follow: 1. There was significant statistical difference in general characteristics between rooming-in and non rooming-in groups in prenatal class attendance ($x^2$=3.935, p=0.047), maternal fetal attachment score (t=2.130, p=0.035), husband attendance during the labor and delivery ($x^2$=9.147, p=0.002), breast feeding ($x^2$=12.503, p=0.000), and self feeding time including bottle feeding (t=4.588, p=0.000). 2. There was no significant statistical difference in the level of total fatigue score between two groups (t=0.282, p=0.780). 3. The physical and neurosensory fatigue scores were slightly higher in rooming-in group ($21.63{\pm}4.92$, $18.53{\pm}4.60$) than those ($20.71{\pm}5.78$, $18.23{\pm}5.39$) of non rooming-in group. And the phychological fatigue score was slightly higher in non rooming-in group ($17.67{\pm}4.95$) than that ($17.04{\pm}4.63$) of rooming-in group. However, there was no significant statistical difference in the level of three sub-dimension fatigue between two groups (t=1.068, p=0.287; t=-0.827, p=0.410; t=0.368, p=0.714). 4. Even after controlling characteristics showed significant differences between two groups, there was no significant statistical difference in the level of fatigue between two groups (F=0.135, p=0.714). According to this study, there was no significant statistical difference in the level of postpartum fatigue whether they were rooming-in or not. Based on this result, the common notion of rooming-in mothers will be more fatigue than non rooming-in mothers is proved to be false. However, it is necessary to develop appropriate nursing interventions to meet the need of mothers who decide to rooming-in.