• International Journal of Highway Engineering
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• v.18 no.6
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• pp.123-130
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• 2016

OBJECTIVES : The objective of this research is to determine the moisture resistance of the freeze-thaw process occurring in low-noise porous pavement using either hydrated-lime or anti-freezing agent. Various additives were applied to low-noise porous asphalt, which is actively paved in South Korea, to overcome its disadvantages. Moreover, the optimum contents of hydrated-lime and anti-freezing agent and behavior properties of low-noise porous asphalt layer are determined using dynamic moduli via the freeze-thaw test. METHODS : The low-noise porous asphalt mixtures were made using gyratory compacters to investigate its properties with either hydrated-lime or anti-freezing agent. To determine the dynamic moduli of each mixture, impact resonance test was conducted. The applied standard for the freeze-thaw test of asphalt mixture is ASTM D 6857. The freeze-thaw and impact resonance tests were performed twice at each stage. The behavior properties were defined using finite element method, which was performed using the dynamic modulus data obtained from the freeze-thaw test and resonance frequencies obtained from non-destructive impact test. RESULTS : The results show that the coherence and strength of the low-noise porous asphalt mixture decreased continuously with the increase in the temperature of the mixture. The dynamic modulus of the normal low-noise porous asphalt mixture dramatically decreased after one cycle of freezing and thawing stages, which is more than that of other mixtures containing additives. The damage rate was higher when the freeze-thaw test was repeated. CONCLUSIONS : From the root mean squared error (RMSE) and mean percentage error (MPE) analyses, the addition rates of 1.5% hydrated-lime and 0.5% anti-freezing agent resulted in the strongest mixture having the highest moisture resistance compared to other specimens with each additive in 1 cycle freeze-thaw test. Moreover, the freeze-thaw resistance significantly improved when a hydrated-lime content of 0.5% was applied for the two cycles of the freeze-thaw test. Hence, the optimum contents of both hydrated-lime and anti-freezing agent are 0.5%.

• Journal of Conservation Science
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• v.31 no.2
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• pp.125-130
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• 2015

Specific techniques and materials in conservation of traditional lacquer has not been transmitted. This study aims to compare the basic characteristics of the filler which used in the base layer of lacquer conservation. Tohoe(a mixture of lacquer and Clay) and the three kinds of additives which is mixed with Tohoe and Goksu(a mixture of lacquer, wood powder and rice starch) are estimated in drying rate, impact resistance, abrasion. Among those samples, the more amount of clay causes fast dryness speed and worse cracks on the surface. The impact resistance is weakened at high amount of clay. There is no significant differences of impact resistance between both additives that is mixed with the samples and additives. The samples that are mixed with Goksu and additives show high impact resistance. In the polishing test, the more amount of filling powders show higher grinding degree and the sample that are mixed with wood powder and charcoal show higher degree as well. The highest grinding degree is Maekchil and Goksu but the lowest one is the sample of the rooftile powder mixture.

• International Journal of Highway Engineering
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• v.13 no.2
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• pp.147-157
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• 2011

As a background study to apply the reliability-based resistance factors to the domestic concrete bridge design code, a comparative study is conducted for the design results and the reliability indexes obtained by adopting different resistance factor formats to yield the design strength of concrete structures. The design results which are calculated by applying the section resistance factors of the current domestic design code and the material resistance factors of Eurocode are compared for the concrete beam bridge. The reliability index is calculated by considering the uncertainties involved in material, dimension and strength equation during the design procedure to get the strength of concrete structure. Also, the sensitivity analysis is performed to figure out which design variables have great impact on the reliability index. The resistance factors of the current domestic bridge design code, AASHTO LRFD and Eurocode are applied to the bridge design for flexure and shear strength and the results show that the resistance factors of the domestic code give the largest reliability indexes. It is observed that the probabilistic distribution of the live load makes difference for the reliability index and the yield strength of reinforcing steel and the live load have great impact on the reliability of both flexural and shear strength of concrete beam through the sensitivity analysis.

• Journal of Korea Port Economic Association
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• v.35 no.4
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• pp.121-146
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• 2019

This study investigates the innovation resistance when blockchain technology is introduced for the shipping and port industry. For the development of a research model with suitable measures, we review and focus on innovation resistance factors with the blockchain technology derived from previous studies. In this research, we consider four factors (innovation characteristics, consumer characteristics, environmental characteristics, and cost characteristics) with innovation resistance as dependent variables. The innovation characteristics include relative benefits, complexity, and perceived risk. The consumer characteristics consider attitude toward existing products, innovation, and self-efficacy. Social impact variables are environmental characteristics and rationality of cost. In the statistical analysis, we set up eight hypotheses to test the significances between variables and find the following four empirical results. First, the relative advantage and the perceived risk have a significant effect on innovation characteristic, but the complexity of this characteristic has no significant effect on innovation resistance. Second, the rationality of cost has no significant effect on innovation resistance. Third, the attitude toward existing products has a positive effect and the innovation of the consumer characteristic has a negative effect on innovation resistance, while the self-efficacy has no significant effect. Finally, the social impact has a significant effect on innovation resistance to blockchain in the shipping and port industry.

• Composites Research
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• v.21 no.5
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• pp.23-30
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• 2008

Stab threats using sharp edged or pointed Instruments could be easily encountered by police officers or soldiers. In this study, the shear thickening fluids (STF) was impregnated into Kevlar fabrics to improve the stab protection and the resistance of STF impregnated Kevlar fabrics was experimentally investigated. The puncture and cut resistance were tested using a drop test machine withspike and knife indenters fabricated based on the National Institute of Justice (NIJ) standard. The STF was filled with spherical $SiO_2$ particles having an average diameter of 100nm, 300nm, and 500nm. The effect of particle size on puncture and cut resistance of STF impregnated Kevlar fabrics was also investigated. The measured impact load histories showed that STF impregnation into fabric leads to withstand higher peak loads than that of neat fabrics under spike test. The test results showed that Kevlar impregnated with STF exhibit remarkable improvements in puncture resistance while it is slightly influential on the cut resistance. Specifically, particle size is the one of the dominant factors controlling fabric resistance to puncture under spike impact test.

• Journal of the Korea Concrete Institute
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• v.28 no.5
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• pp.623-623
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• 2016

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.107-114
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• 2012

Fracture of brittle material due to dynamic load such a particle impact has been reported by many researchers as the fracture behavior by variation of stress for a short minute. Especially, the brittle material, such a ceramic, applied to the structural component of machine, is considered as the important project. In order to evaluate the improvement of impact resistance, the particle impact test for the $Al_2O_3-TiO_2$ coated glass is practiced. And then, the damage variation according to the impact energy of steel ball was evaluated. There was a large improvement by the ceramic coating on the surface of a glass substrate. The damage volume was especially imported to evaluate damage behavior in quantity. These data were plotted on logarithmic coordinate and experimental equations were induced by data analysis based on test results. And the variation of critical energy for crack initiation was analyzed with critical impact energy when each crack occurs.

• Korean Journal of Materials Research
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• v.12 no.1
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• pp.10-15
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• 2002

Melt blends of maleic anhydride grafted polypropylerle(PP-g-MA) and Nylon 6 were prepared to study the influence of chemical reaction between the two polymer components. By adding the MA grafted polystyrene pold (ethylene/butadiene) and polystyrene[SEBS-g-MA] as the compatible modifiers to reinforce the impact resistance, the Izod impact strength, high rate impact strength and morphology were studied. The notched Izod impact strength increased with the content of PP-g-MA and SEBS- g-MA. The energy of high rate impact strength increased as the thickness of specimen increased, while, it increased as the specimen displacement decreased. In the morphology observed by SEM, finally, we confirmed the improvement of the compatibilization and interfacial adhesion with the content of SEBS-g-MA. The continuous phase of PP-g-MA was the main cause of the modified properties.

• Structural Engineering and Mechanics
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• v.82 no.1
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• pp.81-92
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• 2022

Ultra-high performance fiber reinforced concrete (UHPFRC) is a composite building material with high ductility, fatigue resistance, fracture toughness, durability, and energy absorption capacity. The aim of this study is to develop a nonlinear finite element model that can simulate the response of the UHPFRC beam exposed to impact loads. A nonlinear finite element model was developed in ABAQUS to simulate the real response of UHPFRC beams. The numerical results showed that the model was highly successful to capture the experimental results of selected beams from the literature. A parametric study was carried out to investigate the effects of reinforcement ratio and impact velocity on the response of the UHPFRC beam in terms of midpoint displacement, impact load value, and residual load-carrying capacity. In the parametric study, the nonlinear analysis was performed in two steps for 12 different finite element models. In the first step, dynamic analysis was performed to monitor the response of the UHPFRC beam under impact loads. In the second step, static analysis was conducted to determine the residual load-carrying capacity of the beams. The parametric study has shown that the reinforcement ratio and the impact velocity affect maximum and residual displacement value substantially.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.171-174
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• 2004

In order to improve the damage tolerance of the conventional laminated composites, three­dimensional fiber structures incorporated with stitching yams have been utilized in this study. From the newly developed process termed as TAPIS(TApe Placement Incorporated with Stitching), carbon/epoxy composites have been fabricated. Two-dimensional composites with the same stacking sequence as 3D counterparts have also been fabricated for the property comparison. To examine the damage resistance performance the low speed drop weight impact test has been adopted. For the assessment of damage after the impact loading, specimens were subjected to C-scan nondestructive inspection compression after impact(CAI) were also conducted to evaluate residual compressive strength. Although the damage area of 3D composites was greatly reduced$(30-40\%)$ compared with that of 2D composites, the CAI strength did not show drastic improvement.