• Journal of the Korean Geographical Society
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• v.43 no.6
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• pp.808-823
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• 2008

Sediment abrasion in rivers is caused by the interaction between bedrock channel bed and sediment particles transported through the river. Abrasion rate of sediment particles in rivers is controlled by two major factors; Sediment transport conditions including hydraulic conditions form the erosive forces and physical and chemical strengths of the particles form a resistance force against abrasion and other erosional processes. Physical experiments were performed to find the role of each variable on sediment abrasion process. Total 266 sediment particles were used in this experiment. All sediment particles were divided into 11 independent sediment groups with sediment particle size and sediment loads. Each sediment groups were abraded in tumbling mill for up to 8 hours. Changes in weight were recorded by run and total: 2,128 cases of abrasion rate were recoded. Physical strength of rock particles was measured with point load strength index. It is found that sediment abrasion rate has a negative functional relationship point load strength index ($I_{a(50)}$) ($R^2=0.22$). It was suggested that physical strength of sediment particles set the "maximum possible abrasion rate'. As sediment flux increases, abrasion rates of sediment particles with similar point load strength index were changed. It could be concluded that not only physical characteristics of sediment particles, but also sediment transport conditions control sediment abrasion rates.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.419-426
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• 1999

In this study, the reaction rate constant, activation energy, total crosslinking density, elastic constant, cure properties ($t_5,\;t_{90}$), modulus, and abrasion resistance of rubber compounds were investigated as a function of cure temperatures, cure systems and reinforcing filler loadings. Reaction rate constants showed strong dependence on thc carbon black loading, cure temperature and cure system, and increased sharply with increasing the reaction temperatures. The lowest activation energy was obtained in the efficient cure (EC) system which corresponds to the high level of sulfur to accelerator ratio, and the activation energy was decreased with decreasing the carbon black loadings. The change of carbon black loadings directly affects the modulus and abrasion resistance, but the change of cure system showed various effects on the rubber compounds. Increased carbon black loadings showed the high modulus, improved abrasion resistance and short scorch time but decrease in crosslinking density and elastic constant. Higher crosslinking density and elastic constant were shown in the EC cure system regardless of carbon black loadings, but scorch timc ($t_5$) was not affected by the change of the ratio of sulfur to accelerator. Rapid optimum cure time ($t_{90}$) were showen in the EC cure system. Also, the equivalent cure curve coefficient of rubber compound was 0.96 for conventional cure (CC) system, and 0.94 for semi-efficient cure (SEC) and EC system regardless carbon black loadings. As regarding the abrasion resistance, wear volume showed the logarithmic increase for the loaded weight.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.595-602
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• 2005

The purpose of this study is to utilize recycled concrete aggregates as permeable pavement materials. This study evaluates mechanical properties and durability of porous concrete depending on mixing rates of recycled aggregates and polyme. As a result, void ratio and permeability coefficient of porous concrete for pavement increased a little as mixing rate of recycled aggregates increased. Void ratio and permeability coefficient increased a lot as mixing rate of polymer increased. As polymer was mixed $20\%$, national regulation of permeable concrete for pavement($8\%$ and 0.01cm/sec) was met. Compressive strength and flexural strength decreased as mixing rate of recycled aggregates increased but they increased a lot as mixing rate of polymer increased. Even when recycled aggregates were mixed $75\%\;with\;10\%$ polymer mixed, national regulation of pavement concrete(18MPa and 4.5MPa) was met. In addition, regarding sliding resistance, BPN increased as mixing rate of recycled aggregates increased. But BPN decreased as polymer was mixed. Compared to crushed stone aggregates, abrasion resistance and freeze-thaw resistance decreased as mixing rate of recycled aggregates Increased. When polymer was mixed, abrasion resistance and freeze-thaw resistance improved remarkably. Compared to non-mixture, $10\%$ mixture of polymer improved abrasion resistance and freeze-thaw resistance about $8.6\%$ and 3.8times respectively.

• Journal of the Korean Applied Science and Technology
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• v.33 no.1
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• pp.92-99
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• 2016

Polyurethane resin used to leather coat was synthesized by the addition reaction of PPG and PTMG with different mole ratios. Physical characteristics of the synthesized polyurethane resin were measured by the SEM, FT-IR and the UTM. Increasing mole ratio of PTMG having four methylene groups caused the increase of abrasion resistance and tensile strength. The elongation was decreased. As we measured the solvent(toluene) resistance of poly urethane resin, it was found the there were no effect of PTMG mole ratios on the phyhsical properties of the resin. The viscosity was increased by ratio of PTMG mole ratio.

• Journal of the Korean Ceramic Society
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• v.19 no.1
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• pp.5-12
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• 1982

SiC-containing by-product from the surface abrasion process of porcelain cores is used as a starting material to develop the SiC-containing technical porcelain bodies. To prevent the bloating phenomenon of by-product specimen at firing temperature, it is acid treated. In order to enhance the workability and to lower the firing temperature of bodies, clay is added. Body containing 25% clay and 75% by-product fired at 135$0^{\circ}C$ showes extremely high thermal shock resistance and acid resistance.

• Elastomers and Composites
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• v.53 no.2
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• pp.48-51
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• 2018

10, 20, 30, and 40% of polyvinyl chloride (PVC) were added to nitrile butadiene rubber (NBR) to modify the latter. The NBR/PVC composites containing pure NBR were synthesized to investigate properties, such as crosslinking density, hardness, tensile strength, abrasion resistance, heat resistance, solvent resistance, and filler dispersion. The experimental result revealed a decrease in crosslinking density and heat resistance with increase in the PVC content. In contrast, addition of PVC to NBR resulted in enhancement of hardness, tensile strength, solvent resistance, and filler dispersion.

• Journal of the Korean Society of Clothing and Textiles
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• v.30 no.3 s.151
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• pp.481-486
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• 2006

There are attempts to utilize Hanji for apparel material, but, the reason that the strength and durability of Hanji decrease to a great extent in the wet condition, restricts the usability of Hanji. In order to improve the resistance against water, Hanji was treated with silicone type water repellent agents. The treatment was carried out by conventional pad-dry-cure method. The optimum treatment condition was obtained by varying the concentration of repellent agent, curing temperature and time. Water repellency was tested by spray rating method. Wet and dry tensile strength, tearing resistance and abrasion resistance were examined after the treatment. Flexural stiffness and wrinkle recovery angles of hanji were also measured. In result, the optimum condition of treatment was at resin concentration of 40g/l, catalyst concentration of 20g/l(half of resin concentration), curing temperature of 160$^{circ}C$, curing time of 120 sec. Flexural stiffness of Hanji was hardly increased and wrinkle recovery angle of Hanji was improved a little by resin treatment. After the treatment, in dry condition, tensile strength and tearing resistance were little changed but abrasion resistance was improved. In wet condition, tensile strength, tearing strength and abrasion resistance were improved.

• Journal of Korea Foundry Society
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• v.20 no.2
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• pp.104-109
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• 2000

Three different white cast irons alloyed with Cr, V, Mo and W were prepared in order to study their abrasion wear behavior in as-cast and heat-treated conditions. The specimens were produced using a 15㎏-capacity high frequency induction furnace. Melts were super-heated to $1600^{\circ}C$, and poured at $1550^{\circ}C$ into Y-block pepset molds. Three combinations of the alloying elements were selected so as to obtain the different types of carbides : 3%C-10%Cr-5%Mo-5%W(alloy No. 1: $M_7C_3$ and $M_6C$), 3%C -10%V-5%Mo-5%W(alloy No. 2: MC and $M_2C$) and 3%C-17%Cr-3%V(alloy No. 3: $M_7C_3$ only). A scratching type abrasion test was carried out in the states of as-cast(AS), homogenizing(AH), air-hardening(AHF) and tempering(AHFT). First of all, the as-cast specimens were homogenized at $950^{\circ}C$ for 5h under the vacuum atmosphere. Then, they were austenitized at $1050^{\circ}C$ for 2h and followed by air-hardening in air. The air-hardened specimens were tempered at $300^{\circ}C$ for 3h. 1 ㎏ load was applied in order to contact the specimen with abrading wheel which was wound by 120 mesh SiC paper. The wear loss of the test piece(dimension: $50{\times}50{\times}5$ mm) was measured after one cycle of wear test and this procedure was repeated up to 8 cycles. In all the specimens, the abrasion wear loss was found to decrease in the order of AH, AS, AHFT and AHF states. Abrasion wear loss was lowest in the alloy No.2 and highest in the alloy No.1 except for the as-cast and homogenized condition in which the alloy No.3 showed the highest abrasion wear loss. The lowest abrasion wear loss of the alloy No.2 could be attributed to the fact that it contained primary and eutectic MC carbides, and eutectic $M_2C$ carbide with extremely high hardness. The matrix of each specimen was fully pearlitic in the as-cast state but it was transformed to martensite, tempered martensite and austenite depending upon the type of heat-treatment. From these results, it becomes clear that MC carbide is a significant phase to improve the abrasion wear resistance.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.2071-2072
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• 2011

Withstand voltage characteristics of the nanocomposites, as a material with excellent abrasion resistance and water resistance, low shrinkage upon curing with moisture even in very good adhesion, workability is not lost. In this study, the fusion of nanoparticles and the high functionality epoxy nano-composite material produces the electricity. Degeneration of the unit based on this power structure and breakdown characteristics, efficiency and cross-measurement system as closely related organisms that can be applied to the power plant electrical efficiency of the nano-composite material is designed to develop skills.

• Proceedings of the Korean Nuclear Society Conference
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• 2003.10a
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• pp.418-418
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• 2003