• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.732-737
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• 2016

Using the pyrolyzed carbon black (PCB) from waste tires, the performance of 13 mm dense-graded hot mix asphalt was evaluated. The Marshall mix design was carried out and the measured optimal asphalt content was 5.8%. The impact resonant test was conducted to obtain the elastic modulus and damping ratio of the hot mix asphalt. The elastic modulus of HMA increased with increasing amount of PCB. On the other hand, there was no significant change in the damping ratio. The Marshall mix design, indirect tensile test, permanent deformation test, and program analysis were carried out. The strength ratio of the PCB modified asphalt mixtures was within 10%. More 10% of PCB was not good for the permanent deformation of hot mix asphalt. From the pavement design program, the use of 5% PCB in hot mix asphalt showed a decrease in the top-down crack, bottom-up crack, and permanent deformation. Judging from the limited test and analysis, the use of 5% PCB is good for enhancing the pavement performance.

• Magazine of the Korea Concrete Institute
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• v.5 no.4
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• pp.156-166
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• 1993

The results of an experimental study on the manufacture and the mechanical properties of steel fiber reinforced polyester resin composites utilizing industrial waste products(fly ash) are presented in this paper. The composites using steel fiber, fly ash, unsaturated polyester resin, styrene monomer, catalyst (cobalt octate) and accelerator(methyl ethyl ketone peroxide), fine and coarse aggreates were prepared using various mixing conditions. As the test results show. the mechanical and physical properties, such as the compressive, tensile and flexural strengths, and the setting shrinkage of fly ash$\cdot$polyester resin composites were improved considerably by increasing the fly ash-binder ratio. And the workability of steel fiber reinforced fly ash$\cdot$polyester resin composites was reduced with increasing the fly ash-binder ratio and steel fiber content. Also, the compressive, flexural strength and toughness of the composites were remarkably increased by increasing steel fiber content.

• Polymer(Korea)
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• v.30 no.1
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• pp.14-21
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• 2006

Tissue engineering techniques require the use of a porous biodegradable/bioresorbable scaffold, which server as a three-dimensional template for initial cell attachment and subsequent tissue formation in both in vitro and in vivo. Small intestinal submucosa (SIS) has been investigated as a source of collagenous tissue with the potential to be used as biomaterials because of its inherent strength and biocompatibility. SIS-loaded poly(L-lactide-co-glicolide)(PLGA) scaffolds were prepared by solvent casting/particle leaching. Characterizations of SIS/PLGA scaffold were carried out by SEM, mercury porosimeter, and so on. Muscle-derived stem cells can be differentiated in culture into osteoblasts, chondrocytes, and even myoblasts by the controlling the culture environment. Cellular viability and proliferation were assayed by 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium-bromide(MTT) test. Osteogenic differential cells were analyzed by alkaline phosphatase(ALP) activity. SIS/PLGA scaffolds were implanted into the back of athymic nude mouse to observe the effect of SIS on the osteoinduction compared with controlled PLGA scaffolds. Thin sections were cut from paraffin embedded tissues and histological sections were conducted hematoxylin and eosin (H&E), Trichrome, and von Kossa. We observed that bone formatioin of SIS/PLGA hybrid scaffold as natural/synthetic scaffold was better thean that of only PLGA scaffold. It canb be explained that SIS contains various kinds of bioactive molecules for osteoinduction.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.14 no.2
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• pp.79-87
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• 1978

This is an experimental study on friction welding and heat treatment of engine exhaust valve materials whose welding combination is SCr4 as stem to 21-4N as head and SUH3 to 21-4N. In this study, not only the experiments of friction welding under the selected optimum welding condition and the examination of the mechanical properties were carried out, but also the heat treatment of friction welded specimens under the two selected conditions was taken to obtain the better welding character, eliminating the latent stress and the hardness peak which appeared at the welded zones of heat resisting steel(21-4N, SUH3) and low alloyed steel ($SCr_4$) friction weldments. The results obtained by the experiments and consideration in this study are as follows: I) It was experimentally proved quite reasonable that 'speed=3,OOO rpm, heating pressure Pl=8 kg/ mm2, upsetting pressure p, = 20 kg/mm', heating time $t_1$ = 3 see, upsetting time TEX>$t_2$ = 2.5 sec' was selected as the optimum welding condition for friction-welding the engine exhaust valve materials $SCr_4$ to 21-4 Nand SUH 3 to 21-4 N. 2) The results of the previous study and this one on friction welding of such dissimilar materials as SUH 3-SUH 31, SCr 4-SUH 31, SCr 4-SUH 3, SUH 3-CRK 22, SCr4-21-4 Nand SUH3-21-4 N agreed with each other substantially in the friction welding characteristics at welded interface zones. 3) It was also certified quite satisfactory that '600\ulcornerCX30 min. Xroom air cooling' as an optimum heat treatment condition of the friction welded materials SCr 4-21-4 Nand SUH 3-21-4 N was experimentally determined to eliminate the latent stress and the hardness peak at welded zones. 4) About 20% of the tensile strength before heat treatment of friction welded specimens was decreased after heat treatment 600\ulcornerCX30 min. Xair cooling, but the location of fracture was moved from heat affected zone to parent $SCr_4$ & SUH3. 5) Microscopic examination of the weld joints friction-welded and heat-treated under the above mentioned conditions revealed that the weld zone is very narrow and has a fine grained intermixed structure without any welding defects. 6) The above mentioned conditions can be also utilized as friction welding parameters of the other dissimiar materials for engine valve production.