• Journal of Korea Foundry Society
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• v.37 no.3
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• pp.63-70
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• 2017

In the present study, effects of an addition of Sn on the microstructure and corrosion behavior were investigated in Mg-4%Zn-(0-3)%Sn casting alloys. With an increase in the Sn content, the ${\alpha}-(Mg)$ dendritic cell size was reduced, whereas the total amount of precipitates increased due to the formation of the $Mg_2Sn$ phase. It was found in immersion and electrochemical corrosion tests that the addition of Sn has a detrimental effect on the corrosion resistance of the Mg-4%Zn alloy. Microstructural examinations of the corrosion product and the corroded surface indicated that an accelerated micro-galvanic effect by the $Mg_2Sn-phase$ particles and a less protective corrosion product on the surface were responsible for the increased corrosion rate at a higher Sn content.

• Proceedings of the Korean Society of Crop Science Conference
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• 1993.10a
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• pp.16-17
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• 1993

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.2
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• pp.338-344
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• 2001

According to the MARPOL 73/78 of Convention, all ships should have oil filtering equipment and 15 ppm bilge which satisfy Requirements of MARPOL 73/78. This study is concerned with designing and manufacturing a prototype Oil content Meter(OCM) used in machinery area of ship. The prototype OCM is composed of two parts which are oil content sensing module and data processing unit. The oil content sensing module consists of infra-red light source, photo-diode light receivers, and a glass tube for bilge water sample. The data processing unit has a micro-processor as hard core and peripheral devices. The experimental results of prototype OCM and analysis of collected data reveal linear property between transmitted light and scattered light as long as the bilge water has low level content of oil. And this linear property leads to a oil content detecting method which is programmed and loaded into the data processing unit. The performance of the prototype OCM is compared with that of the commercial OCM in the market.

• Advances in concrete construction
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• v.13 no.6
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• pp.423-431
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• 2022

Although the influence of moisture content on the mechanical properties of concrete has been studied for a long time, research related to its influence on the damping and energy dissipation property of concrete structure is still very limited. In this paper, the relationship between damping property and moisture content of concrete using cyclic uniaxial compression is firstly presented, and the mechanism of the influence of moisture content on concrete damping and energy dissipation capacity is analyzed. Based on the experimental research, moisture-related damping and energy dissipation model is proposed. Results show that the dissipated energy of concrete and loss factor increase as the moisture content increasing. The energy dissipation coefficient reflecting the influence of stress level of concrete under cyclic load, decreases first and then increases as the moisture content increasing. The mechanism of moisture-related energy dissipation behavior can be divided into the reactive force of water, the development of the internal micro cracks and the pore water pressure. Finally, the proposed moisture-related damping and energy dissipation model are verified.

• Korean Journal of Materials Research
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• v.20 no.7
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• pp.392-400
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• 2010

The electrospinning process was established as a promising method to fabricate nano and micro-textured scaffolds for tissue engineering applications. A BCP-loaded PCL micro-textured scaffold thus can be a viable option. The biocompatibility as well as the mechanical properties of such scaffold materials should be optimized for this purpose. In this study, a composite scaffold of poly ($\varepsilon$-caprolactone) (PCL)-biphase calcium phosphate (BCP) was successfully fabricated by electrospinning. EDS and XRD data show successful loading of BCP nano particles in the PCL fibers. Morphological characterization of fibers shows that with a higher loaded BCP content the fiber surface was rougher and the diameter was approximately 1 to 7 ${\mu}m$. Tensile modulus and ultimate tensile stress reached their highest values in the PCL- 10 wt% BCP composite. When content of nano ceramic particles was low, they were dispersed in the fibers as reinforcements for the polymer matrix. However, at a high content of ceramic particles, the particles tend to agglomerate and lead to decreasing tensile modulus and ultimate stress of the PCL-BCP composite mats. Therefore, the use of nano BCP content for distribution in fiber polymer using BCP for reinforcement is limited. Tensile strain decreased with increasing content of BCP loading. From in vitro study using MG-63 osteoblast cells and L-929 fibroblast like cells, it was confirmed that electrospun PCL-BCP composite mats were biocompatible and that spreading behavior was good. As BCP content increased, the area of cell spreading on the surface of the mats also increased. Cells showed the best adherence on the surface of composite mats at 50 wt% BCP for both L-929 fibroblast-like cells and MG-63 osteoblast cell. PCL- BCP composites are a promising material for application in bone scaffolds.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.9-9
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• 2008

Recently, the thickness of solar cell gets thinner to reduce the quantity of silicon. And the reduced thickness make it easy to be broken while PV module fabrication process. This phenomenon might make PV module's maximum power and durability down. So, when using thin solar cell for PV module fabrication, it is needed to optimize the material and fabrication condition which is quite different from normal thick solar cell process. Normally, gel-content of EVA sheet should be higher than 80% so PV module has long term durability. But high gel-content characteristic might cause micro-crack on solar cell. In this experiment, we fabricated several specimen by varying curing temperature and time condition. And from the gel-content measurement, we figure the best fabrication condition. Also we examine the crack generation phenomenon during experiment.

• Geomechanics and Engineering
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• v.29 no.6
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• pp.627-643
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• 2022

Water-rock interactions have a significant influence on the mechanical behavior of rocks. In this study, uniaxial compression and tension tests on different water-treated sandstone samples were conducted. Acoustic emission (AE) monitoring and micro-pore structure detection were carried out. Water-rock interactions and their effects on rock mechanical behavior were discussed. The results indicate that water content significantly weakens rock mechanical strength. The sensitivity of the mechanical parameters to water treatment, from high to low, are Poisson ratio (𝜇), uniaxial tensile strength (UTS), uniaxial compressive strength (UCS), elastic modulus (E), and peak strain (𝜀). After water treatment, AE activities and the shear crack percentage are reduced, the angles between macro fractures and loading direction are minimized, the dynamic phenomenon during loading is weakened, and the failure mode changes from a mixed tensile-shear type to a tensile one. Due to the softening, lubrication, and water wedge effects in water-rock interactions, water content increases pore size, promotes crack development, and weakens micro-pore structures. Further damage of rocks in fractured and caved zones due to the water-rock interactions leads to an extra load on the adjoining coal and rock masses, which will increase the risk of dynamic disasters.

• Journal of the Korean Society for Heat Treatment
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• v.30 no.3
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• pp.106-112
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• 2017

In this study dual-phase steels with different ferrite grain size and martensite fraction were fabricated by varying micro-alloying elements and intercritical anneling temperatures, and then the tensile properties were investigated in terms of yield and tensile strengths, elongation, and yield ratio. The addition of micro-alloying elements reduced ferrite grain size, and the increased intercritial transformation tempeature increased the martensite fracton. The tensile test results showed that yield and tensile strengths of all the steel specimens increased with increasing the martensite fraction. However, the elongation and yield ratio were differently changed according to variations in the morphology and carbon content of martensite, ferrite grain size, and precipitates resulting from the addition of micro-alloying elements and intercritical annealing.

• Journal of Plant Biotechnology
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• v.35 no.4
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• pp.257-263
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• 2008

Improvement of the macro- and micro-elements density of rice (Oryza sativa L.) is gradually becoming a new breeding objective. In this study, the genomic regions associated with potassium, calcium, magnesium and iron content in rice grain were identified and characterized by using a doubled haploid (DH) population. Fifty-six simple sequence repeat (SSR) and one hundred and twelve sequence tagged site (STS) markers were selected to construct the genetic linkage map of the DH population with a full length of 1808.3cM scanning 12 rice chromosomes. Quantitative trait loci (QTLs) were detected, and QTL effects and QTL interactions were calculated for five traits related to macro- and micro-elements in the DH population from a cross between 'Samgang' (Tongil) and 'Nagdong' (Japonica). Twelve QTLs were located on five chromosomes, consisting of two QTLs for potassium, three QTLs for calcium, two QTLs for magnesium, one QTL for iron content and four QTLs for the ratio of magnesium to potassium (Mg/K). Among them, qca1.1 was detected on chromosome 1 with an LOD value of 8.58 for calcium content. It explained 27% of phenotype variations with increasing effects from 'Samgang' allele. Furthermore, fifteen epistatic combinations with significant interactions were observed on ten chromosomes for five traits, which totally accounted for 4.19% to 12.72% of phenotype variations. The screening of relatively accurate QTLs will contribute to increase the efficiency of marker-assisted selection (MAS), and to accelerate the establishment of near-isogenic lines (NILs) and QTL pyramiding.

• Applied Chemistry for Engineering
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• v.28 no.3
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• pp.313-317
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• 2017

With the continuous increase of energy demand, low-grade coal is regarded as one of new energy sources. However, due to the high water content, the utilization efficiency of low-grade coal is not good to be used in recent conversion plants. Therefore, it requires a drying process to lower the water content in low-grade coals. Although a variety of drying experiments were conducted, drying characteristics in accordance with the pressure change has not been progressed. In this study, the flash drying characteristics of low grade coal with high moisture content (21.5 wt%) were determined in a pressurized micro-riser. The effect of operation conditions such as pressure (1-40 bar), dryer temperature ($200-600^{\circ}C$), and tube length (2-6 m) on drying ratios were investigated.