• Journal of the Korean Society for Precision Engineering
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• v.9 no.1
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• pp.106-117
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• 1992

In this study, the propagation behaviour and the closure phenomena of physically small surface cracks were investigated by the techinque of the Kikukawa-unloading elastic compliance method using a back face strain gage. The surface cracks initiated and propagated from notched specimens under constant amplitude bending load. The crack shape (aspect ratio) with approximately semi-circular at the early stage was changed to semi-elliptical as the cracks grew larger. The crack depth (a) could be expressed uniquenly by the crack length (c). The dependence of the crack propagation rate on the stress ratio R was strongly related in the lower ${\Delta}K$ range. The deceleration of the surface crack propagation rate was prominent in lower R during the crack length was small. When the propagation rate was rearranged with the effective stress intensity factor range ${\Delta}$K_{eff} the dependence of the crack propagation rate on the stress ratio R was found to be diminshed. These were caused by the crack closure phenomena that was most prominent at the lower propagation rate. The mechanism of crack closure phenomena was dominated by the plasticity-induced mechanism.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.6
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• pp.488-495
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• 2008

In order to achieve long fatigue lifetimes for cyclically pressurized thick cylinders, multi-layered compound cylinder has been proposed. Such compound cylinder involves a shrink-fit procedure incorporating a monobloc tube which has previously undergone autofrettage. The basic autofrettage theory assumes elastic-perfectly plastic behaviour. Because of the Bauschinger effect and strain-hardening, most materials do not display elastic-perfectly plastic properties and consequently various autofrettage mo dels are based on different simplified material strain-hardening models, which is assumed that combination of linear strain-hardenig and power strain-hardening model. This approach gives a more accurate prediction than the elastic-perfectly plastic model and is suitable for different strain-hardening materials. In this paper, a general autofrettage model that incorporates the material strain-hardening relationship and the Bauschinger effect, based upon the actual tensile-compressive stress-strain curve of a material was proposed. The model was obtained using the von Mises yield criterion and plane strain condition. The tensile-compressive stress-strain curve was obtained by experiment. The parameters needed in the model were determined by fitting the actual tensile-compressive curve of the material. Finally, strain- hardening model was compared with elastic-perfectly plastic model.

• Journal of the Society of Disaster Information
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• v.19 no.2
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• pp.262-269
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• 2023

Purpose: In this study,fire-resistance test were executed to evaluate the effectiveness of the fireproof panel attached to the PSC slab in tunnel. Method: For the fire resistance test, the RWS curve was applied and the furnace of the KICT was used. Result: As a result of the experiment, the maximum temperature measured on the concrete surface of the PSC slab with the fireproof panel was 321.8℃, which was lower than the damage limit temperature of 380℃ for concrete. Also, at the t=25mm, the maximum temperature was 35.2℃, which was lower than the damage temperature of steel, 250℃. The use of precast fire resistance panel(t=30mm) improves fire resistance of PSC structures. Conclusion: As a result of the test, a reinforcement method for attached a fireproof panel in case of fire in a tunnel or an underground roadway is provided to protect a structure from fire. In the future, it is necessary to perform the static performance test of the slab to which the fireproof panel is attached, and to confirm the adhesion performance of the fireproof panel by performing the pull-off test and the fatigue test.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.2
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• pp.133-142
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• 1984

With the weld-joined compact tension specimens compared with each other, that is, transverse and lengthwise about the crack propagation direction, high and low in the input heat level, same as and lower than the base metal in the strength of weld material, the fatigue test were performed. With these data, the log-log curves between the fatigue crack propagation rate ${\frac{da}{dN}}$ and the transition range of the stress intensity factor ${\Delta}K$ ahead the crack tip were drawed. These curves were compared and estimated among each compared specimens, among each zones, that is, the base metal, the heat-affected metal and the weld-mixed metal, and between this study and the past studies. Basically, Little difference in the slope of the $da/dN-{\Delta}K$ relation was showed in all the welded directions, all the input heat levels and all the zones. But, First, to comparison with in the past studies about the base metals, it was showed that da/dN started in the much later rate, increased faster and stoped in the little faster rate. Second, it was showed that, near the time the crack's going from the heat-affected zone to the weld-mixed metal da/dN decreased a little for a while. Third, in the lengthwise weld compared with the transverse weld, in the high input heat weld compared with the low input heat weld in the case used the weld material of the same strength as the base metal, in the opposite case in the case used the one of the lower strength than the base metal, in the case used the weld material of the same strength as compared with the lower strength than the base metal beside the high input heat and the lengthwise weld, it was showed that the crack occured earlier in lower ${\Delta}K$ and later da/dN, the curves went with the same slope. Forth, in the lengthwise weld compared with the transverse weld in the low input heat weld, in the low input heat weld compared with the high input heat weld, it was showed that da/dN went with the lower level.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.11
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• pp.1-15
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• 2017

Understanding muslim consumers' needs and behaviour is an essential process for strategic product development in the Halal food market. For our study on Indonesian consumers of Halal food, we conduct a survey of 200 Muslims residing in Indonesia on awareness of ginseng (G) and red ginseng (RG) products, eating experience, like or dislike reasons, cognitive level on the efficacy of G and RG products, purchase behaviors, satisfaction and repurchase intention through a web-based questionnaire methodology. This study reveals that 58 % and 51% of the participants indicate an awareness of G and RG products. In particular, awareness amongst medium- and high-income male consumers in their 20s and 30s is relatively high. This group of participants is also more likely to consume eat G and RG products for health promotion, refreshment, and disease prevention, and positively evaluated product efficacy. They are also aware of the efficacy claims of these products with regard to enhancement of immunity, fatigue, and stamina. While Indonesian Muslim consumers express satisfaction with the health claims, packaging specifications, and design of the products, they are dissatisfied with product types, price, taste, and aroma. The results also found that participants would recommend G and RG products to acquaintances, and are willing to purchase them in the future. Therefore, the segmentation of Halal-certified G and RG products for Muslim consumers and analysis on their product needs could be advantageous for strategic product development.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.12
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• pp.37-50
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• 2017

This study was performed to understand Malaysian Muslims' awareness, attitudes and purchasing behaviour on ginseng (G) and red ginseng (RG) products. A survey of 200 Muslims residing in Malaysia was conducted on awareness, eating experience, preferences, cognitive efficiency of G and RG products, purchase behaviors and satisfaction through a online-survey methodology. Results shows that 50 % and 40% of the participants aware the G and RG products. In particular, awareness amongst female or married consumers is relatively high. Health promotion is the major reasons to consume eat G and RG products in this group of participants. However, the most frequently consumed type of G products was ginseng coffee, candies and chocolates, in their 40s and 50s or married consumers. Participants are also aware of the efficacy claims of these products with regard to improvement of fatigue, immunity and hypertension. While Malaysian Muslim consumers are satisfied with the health claims, convenience to purchase and tastes and aroma, they are dissatisfied with packaging specifications, price. Participants would intend to recommend G and RG products to relatives (82.6%), and are willing to buy them in the future (83.5%). Conclusively, there must be a clear interest and demands of Halal-certified G and RG products among Malaysian Muslims and it is deemed to need of strategic product development and marketing to enhance awareness of G and RG products in the future.