• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.565-568
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• 2006

This study evaluates the physical mchanical properties, durability of porous concrete for pavement according to content of polymer and steel fiber to elicit the presentation of data and the way to enhance its function for the practical field application of porous concrete as a material of pavement. The results of the test indicate that in every condition, the void ratio and the coefficient of water permeability of porous concrete for pavement satisfy both the domestic standards and proposition values. Among the properties of strength, the compressive strength satisfies the standards in the specification of Korea National Housing Corporation as for every factor of mixture but in the case of the flexural strength, more than 0.6Vol.% of steel fiber satisfied the Japan Concrete Institute proposition values. The case when 0.6Vol.% of steel fiber and 10Wt.% of polymer are used at the same time shows that the loss rate of mass by Cantabro test became 36.7% better and freeze-thaw resistance became 33% better.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.4
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• pp.185-195
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• 2001

Latex Modified Concrete(LMC) has been widely used for the pavement of highway bridges over the past 35years around the world since it is more resistant to the intrusion of chloride ions, has higher tensile, compressive, and flexural strength, and has greater freeze-thaw resistance. However, in Korea, it has not been introduced to fields due to higher initial construction cost for its overlay compared with that of conventional pavement materials. Due to durable characteristics, it should be noted that the LMC may be more cost-effective than conventional pavements such as asphalt pavement, when life-cycle cost(LCC) concept is considered. The objective of this study is intended to suggest a practical LCC analysis model for pavement projects and to demonstrate relative cost-effectiveness of the LMC overlays in comparison with conventional pavement techniques. It may be stated that the procedure proposed in this study may be utilized for making optimal decision on cost-effective pavement design.

• Tribology and Lubricants
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• v.16 no.5
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• pp.365-372
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• 2000

Tribological behavior of novolac resin-based friction materials with three different relative amounts of graphite and zirconium silicate was investigated by using a pad-on-disk type friction tester. The goal of this paper is to examine the effects of the relative amount of a lubricant and an abrasive in the automotive friction material on friction and wear characteristics at elevated temperature. Friction and wear of friction materials were affected by the existence of transfer film(3$\^$rd/ body layer) at friction interface and the composition of friction material, especially lubricant amount. The friction material with higher content of graphite indicated homogenized and durable transfer film, and resulted in stable friction coefficient regardless of the increase in friction heat. The experimental result also showed that the higher concentration of ZrSiO$_4$ in friction material aggravated friction stability and wear resistance due to the higher friction heat generated at fiction interface during high temperature friction test.

• Tribology and Lubricants
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• v.35 no.1
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• pp.24-29
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• 2019

In this work we investigated the friction and wear characteristics of a magnesium alloy, which has been receiving much attention as a light metal in industrial applications such as automobiles and aerospace. Magnesium is one of the lightest structural material that has high specific strength, lightweight, low density and good formability. However, current issue of using magnesium alloy is that magnesium has weakness against temperature. As the temperature increases, magnesium undergoes poor creep resistance and ease of softening, and therefore, its mechanical strength decreases sharply. To solve this issue, a new type of magnesium alloy that retains high strength at high temperature has been proposed. The tribological behavior of this alloy was investigated using a tribotester with reciprocating motion and heating plate. A stainless steel ball was used as a counter surface. Results showed that extrusion process has similar wear behavior to the commonly used casting process but retains good mechanical strength and durability. The presence of an alloying element enhanced the wear properties especially in high temperature. This study is expected to be utilized as fundamental data for the replacement of high density materials currently used in mechanical industries to a much lighter and durable heat-resistant materials.

• Corrosion Science and Technology
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• v.21 no.5
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• pp.390-411
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• 2022

Any design engineer or coating formulator's primary objective is to protect metals. Large investments in terms of money, time, labour, and other resources are necessary for constructing large-scale machinery and structures. In terms of economy, the structure's lifespan should be as long as feasible to create revenue. It is becoming essential to protect metal substrates from corrosion to prolong the lifespan of such huge structures. One of the most exciting, durable, useful, and effective methods to protect metals from corrosion is the application of corrosion-resistant coating. Graphene is a novel material with a wide range of applications because of its extraordinary features. The use of graphene in coating creates an obstacle and complicates the path for corrosive medium to reach the metal. As the path to the metal elongates, the corrosion medium takes longer to reach the metal. Thus, metal corrosion can be avoided. In this paper, the importance of graphene in coating formulation is discussed, including chemical modifications of graphene, the effect of graphene concentration on corrosion inhibition, and the contact angle of coating. This review also highlights the significance of water-based corrosion-resistant coating for preventing environmental damage.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.895-901
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• 2023

Oxide-dispersion- strengthened nickel alloys with Hf additions are expected to present high temperature mechanical properties and durable helium resistance based on first-principles density functional theory (DFT) calculations. Energetic and charge density evaluations of the helium behaviors were performed in Ni matrix, Y₂Hf₂O₇ oxide and the oxide/matrix interface. With the presence of coherent Y₂Hf₂O₇ in Ni matrix, chances of helium bubbles in Ni can be greatly diminished. The helium atoms shall occupy the interfacial site initially, then diffuse into in the octahedral sites of Y₂Hf₂O₇, and these oxide-captured He atoms prefer to separate individually. Much higher diffusion barrier of He in Y₂Hf₂O₇ than in nickel is related to the strong hybridization between interstitial He-1s and nearest-neighboring O-2p orbitals.

• Steel and Composite Structures
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• v.48 no.2
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• pp.131-143
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• 2023

The CFRP bar was used to achieve more ductile and durable headed-stud shear connectors in composite components. Three series of push-out tests were firstly conducted, including specimens reinforced with pure steel fibers, steel and CFRP bars. The distributed stress was measured by the commercial PPP-BOTDA (Pre-Pump-Pulse Brillouin optical time domain analysis) optical fiber sensor with high spatial resolution. A series of numerical analyses using non-linear FE models were also made to study the shear force transfer mechanism and crack response based on the test results. Test results show that the CFRP bar increases the shear strength and stiffness of the large diameter headed-stud shear connection, and it has equivalent reinforcing effects on the stud shear capacity as the commonly used steel bar. The embedded CFRP bar can also largely improve the shear force transfer mechanism and decrease the tensile stress in the transverse direction. The parametric study shows that low content steel fibers could delay the crack initiation of slab around the large diameter stud, and the CFRP bar with normal elastic modulus and the standard reinforcement ratio has good resistance to splitting crack growth in headed stud shear connectors.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.58 no.2
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• pp.91-106
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• 2013

Exserohilum turcicum is considered serious destructive disease of maize (Zea mays L.) in North Korea. This study aimed to understand genetic inheritance and combining ability of newly bred lines of maize tolerant to E. turcicum by diallel crosses. Three diallel sets for two different ecological regions and one agronomic trait; eastern (E), northern (N) and stay green (SG) involving 29 inbred lines were tested in eight locations of 2000 and 2001. E. turcicum infections were under natural conditions, respectively. Lines used were selected for high yield potential in test crosses with good agronomic traits and tolerance to biotic and abiotic stresses. Selection for race specific high resistance to biotic stresses was avoided to select quantitatively inherited genes. Host plant responses to E. turcicum were rated on a scale of 1 (highly tolerant) to 9 (highly susceptible). Highly significant variations were recorded in all trials. General combining ability (GCA) mean square was roughly twice that of specific combining ability (SCA). The genotype (G) by environment (E) interaction was highly significant. The overall results of genetic studies in three diallel sets show that genetic control for inbred tolerance to E. turcicum is polygenic and quantitatively inherited. New inbreds; E-3, N-1 and SG-4 confer better tolerance to E. turcicum than the widely used inbreds; Mo17, and B73. Proper use of genetic information from this study shall increase of corn production under high E. turcicum infection in the Far Eastern Regions of Korea and China.

• Journal of Conservation Science
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• v.17 s.17
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• pp.19-32
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• 2005

The exterior of Korean traditional wooden buildings have been painted with Danchung of painting method using glue and pigments. However because of losing traditional techniques and materials through the period of colonization and industrialization, many problems are occurring today. Especially after several years from painting, occurrence of scalings and flakings in painting layer is a serious problem. To improve weathering resistance of painting layer caused by stress from the difference of swelling and shrinkage between painting layer and wood plate, was examined by weathering tests. The stress is due to the hydrophilic property of wood, mechanical properties(tensile property and stress relaxation) of painting layer, and priming methods by various binders such as glue, acrylic emulsion(Primal AC-3444), acrylic resin(Paraloid B-72). Because stress relaxation of acrylic emulsion of which glasf transition temperature is below room temperature$(7^{\circ}C)$ is high, painting layers with acrylic emulsion generate no scalings and flakings and are in the most durable state in all weathering tests. Priming method which starts from low concentration to high concentration, is more effective to improve durability than other priming methods.

• Journal of the Korean Applied Science and Technology
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• v.35 no.3
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• pp.857-864
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• 2018

Demand for developing artificial green pearl that meets the needs of modern people has been increasing. In this paper, eco-friendly inorganic pearlescent pigment was used instead of organic pigment and urethane resin was substituted for nitrocellulose which has been used as main materials in previous preparation method, increasing gloss from 73.4% to 86.7%. Urethane was coated on substrate before finishing with CVD, resulting high gloss of 96%. Colorimeteric analysis shows that a* and b* of CIE value was changed from +37.7 and +24.5 to +31.9 and +14.2 respectively because of CVD finishing, obtaining colorful, high gloss and durable artificial pearl. Quality and toxicity of samples was established by chemical resistance, glossiness, colorimeter, surface roughness, wear resistance, content of heavy-metal, and salt water test.