• Human Ecology Research
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• v.59 no.2
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• pp.157-168
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• 2021

The purpose of this study was to examine the pathways between mothers' inappropriate smart device usage habits, preschoolers' immersion tendency and self-regulation, and children's cognitive ability. The subjects of the study were 308 preschoolers aged 4 and 5 years and their mothers in Seoul, Gyeonggi-do, Incheon, Gangwon-do, Daejeon, Busan, and Mokpo. Data were analyzed with descriptive statistics, t-test, one-way ANOVA, and Pearson correlation using the SPSS 25 program. A sequential mediation model was analyzed using the AMOS 22 program. Mothers' inappropriate smart device usage habits were found to have a negative effect on the preschoolers' self-regulation, and this association was mediated by the preschoolers' smart device immersion tendency. These findings show the mechanisms through which mothers' inappropriate smart device usage habits negatively affect preschoolers' smart device immersion and self-regulation which, in turn, has a negative impact on cognitive ability

• Korean Journal of Childcare and Education
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• v.16 no.6
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• pp.233-252
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• 2020

Objective: The purpose of this study is to verify the effect of childcare teachers' positive human relationships in childcare centers on care sensitivity to children through their work immersion. Methods: The subjects of this study were child care teachers who were conveniently sampled from Incheon City. A total of 380 surveys were distributed, and a total of 334 surveys were analyzed, Poor or incomplete questionnaires collected were excluded. The. Sobel Test and Baron & Kenny's multi-regression were used for the analysis with the SPSS 23.0 program. Results: Child care teachers' positive relationships with directors, with their fellow teachers, and with parents had an influence on teachers' care sensitivity to children. Teacher's positive relationships with their fellow teachers and with parents had an influence on teachers' work immersion, which mediated the relationships between teacher's human relationship and their care sensitivity to children. Conclusion/Implications: The positive relationships of child care teachers directly and indirectly affect their sensitivity to children through teachers' work immersion.

• Korean Journal of Applied Biomechanics
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• v.31 no.2
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• pp.79-86
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• 2021

Objective: The purpose of this study was to identify the effect of reduced plantar cutaneous sensation on gait kinematics during walking with and without CAI. Method: A total of 20 subjects involved in this study and ten healthy subjects and 10 CAI subjects participated underwent ice-immersion of the plantar aspect of the feet before walking test in this study. The gait kinematics were measured before and after ice-immersion. Results: We observed a before ice-immersion on plantar cutaneous sensation, CAI subject were found to reduced ankle dorsiflexion, knee external rotation, hip adduction, and internal rotation compared to control subject. After ice-immersion, CAI subjects were found to reduce knee external rotation, hip adduction. However, no significant ankle joint kinematics. Conclusion: While walking, gait pattern differences were perceived between groups with and without plantar cutaneous sensation. The results of the study may explain the abductions in the hip angle movements in CAI patients at initial contact compared to healthy subjects in the control group when plantar cutaneous sensation was reduced. A change in proximal joint kinematics may be a conservative strategy to promote normal gait patterns in CAI patients.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.3
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• pp.225-235
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• 2002

The color stability of current prosthetic composites is unknown, even though the quality of composite materials has been improving. This study examined the intrinsic color stability of various current prosthetic resins (ceramic-polymers) after an accelerated aging process and the extrinsic color stability after immersion in a coffee solution. By comparing the amount of discoloration after aging with that without aging, the effect of the accelerated aging process on external discoloration could be evaluated. Three current prosthetic composites (Artglass, Targis, Sculpture), one light polymerized direct composite (Z100) and one dental porcelain control (Ceramco) were assessed. The color changes (${\Delta}$E) of all the specimens were determined using the CIE $L^{*}a^{*}b^{*}$ color order system with a reflected spectrophotometer. The results were as follows: 1. The prosthetic composite materials subjected to the accelerated aging test showed no significant difference in color changes (p >.05). 2. In the coffee solution immersion test after the aging process, the color changes of the Targis and Artglass groups were not different from that of the Z100 group, which showed the highest color change. 3. In the immersion only test, a significantly high color change was observed in the sculpture glazing group. 4. The aging process influenced on the color changes more in the Targis, Artglass and Z100 groups than in the Sculpture and Ceramco groups.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.527-530
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• 2005

Shotcrete have become a deterioration which is used in the underground such as groundwater and soil in sulfate ion. Sulfate attack on concrete structures in service is not widespread, and the amount of laboratory-based research seems. to be disproportionately large. In this study, immersion test using $Na_2SO_4$ solution($1,2,5\%$) was performed to evalute the resistance of shotcrete. From the results of the immersion test for 112 days of exposure. In order to understand the deterioration mechanism due to seawater attack, test using scanning electron microscopy(SEM) analysis and X-ray diffraction showed that the deterioration mechanism due to sulfate attack in shotcrete.

• Journal of Ocean Engineering and Technology
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• v.17 no.3 s.52
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• pp.39-45
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• 2003

Shot peening is an effective method of improving the fatigue strength of components and structures. The compressive residual stress produced by surface plastic deformation with shot peening is usually regarded as the major factor in increasing fatigue strength. In this study, the influence of shot peening on corrosion was investigated. Spring steel immersed in $3.5\%$ NaCl prior was used to evaluate the effect of shot peening on fatigue properties. The immersion test was performed on the five kinds of specimens with shot peened and unpeened. The distributions of residual stresses of shot peened spring steels were measured in an X-ray diffraction apparatus, using the two-point method. Corrosion potential, polarization curve, residual stress, etc. were investigated, based on the experimental results. From test results, the effect of shot peening on the corrosion was evaluated.

• Corrosion Science and Technology
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• v.9 no.2
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• pp.92-97
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• 2010

Many kinds of alternative fuels such as biodiesel, ethanol, methanol, and natural gas have been developed in order to overcome the limited deposits in fossil fuels. In some cases, the alternative fuels have been reported to cause degrade materials. The corrosion rates of metals were measured by immersion test, a kind of time consuming test because low conductivity of these fuels was not allowed to employ electrochemical tests. With twin two-electrode cell newly designed for the study, however, electrochemical impedance spectroscopy (EIS) test was successfully applied to evaluation of the corrosion resistance ($R_p$) of zinc, iron, aluminum, and its alloys in an oxidized biodiesel and gasoline/ethanol solutions and the corrosion resistance from EIS was compared with the corrosion rate from immersion test. In biodiesel, $R_p$ increased in the order of zinc, iron, and aluminum, which agreed with the corrosion resistance measured from immersion test. In addition, on aluminum showing the best corrosion resistance ($R_p$), the effect of magnesium as an alloying element was evaluated in gasoline/ethanol solutions as well as the oxidized biodiesel. $R_p$ increased with addition of magnesium in gasoline/ethanol solutions containing chloride and the oxidized biodiesel. In the mean while, in gasoline/ethanol solutions containing formic acid, Al-Mg alloy added 1% magnesium had the highest $R_p$ and the further addition of magnesium decreased $R_p$. It can be explained with the fact that the addition of more than 1% magnesium increases the passive current density of Al-Mg alloys.

• Journal of the Korean Applied Science and Technology
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• v.40 no.4
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• pp.761-772
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• 2023

The purpose of this study is to help a recovery of fatigue through the effect of cold immersion treatment after rowing ergometer on blood fatigue substance, MDA and SOD in rowing athletes. For this, 10 subjects participated in this study and we divided them into cold water immersion group (CWI, n=10), non-cold immersion group (NCI, n=10). The exercise program was performed to 2000 m rowing ergometer for maintaining high intensity. The data was collected with regard to the interaction effect of the group and time among the CWI and NCI, ANOVA was used. As the post-hoc test, Bonferroni test was used. The significance was set at .05 and the following conclusions were deduced. For lactic acid, there were the main effect of time (p<.001) and significant difference in the both group (p<.001). Also, LDH were significant difference in the each group (p<.05). For MDA, there were the interaction between group and time (p<.05) and the main effect of group (p<.05) and time (p<.001). SOD were indicated main effect of group and time (p<.05), there was significant difference between each group in the after 30 min recovery (p<.05). Collectively, The results of this study suggest that positive effect on blood fatigue substances, reactive oxygen species and anti-oxidation enzyme through cold water immersion intervention. Therefore, we strongly recommend that performing the cold immersion intervention would be beneficial after high intervention exercise.

• International Journal of Concrete Structures and Materials
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• v.4 no.2
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• pp.109-112
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• 2010

Part I of this study was devoted to the electrical accelerated chloride diffusion in mortars. In this second part, natural chloride diffusion has been investigated for four types of mortars under exposure to a 0.5 mol/L NaCl solution for a period of up to 35 days. Two different types of sand were used for the production of test samples: siliceous sand (used as a reference) and limestone sand (used in this study). The effect of water to cement ratio and exposure time on the diffusion coefficients of mortars was also investigated. In this study, the total and free chloride content and penetration depth of mortar were measured after immersion, and Fick's second law of diffusion was fitted to the experimental data to determine the diffusion coefficient. Their results show that the use of crushed limestone sand in mortar had a positive effect on the chloride resistance. The apparent diffusion coefficient in all specimens was smaller than that in siliceous sand mortar. However, the chloride penetration of these mortars was increased as exposure time progressed.

• Journal of Applied Reliability
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• v.9 no.4
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• pp.275-290
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• 2009

This paper considers accelerated thermal degradation tests which are performed for rubber seal materials used for undersea tunnels constructed by immersion method. Three types of rubber seals are tested; rubber expansion seal, omega seal, and shock absorber hose. Main ingredient of rubber expansion seal is EPDM(Ethylene Propylene Diene Monomer) and that of both omega seal and shock absorber hose is SBR(Styrene Butadiene Rubber). The accelerated stress is temperature and an Arrhenius model is introduced to describe the relationship between the lifetime and the stress. From the accelerated degradation tests, dominant failure mode of the rubber seals is found to be the loss of elongation. The lifetime distribution and the service life of the rubber seals at use condition are estimated from the test results. The acceleration factor for three types of rubber seals are also investigated.