• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.12
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• pp.2199-2201
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• 2008

Sulfur hexafluoride($SF_6$) is a gaseous dielectric used in high voltage electrical equipment such as an insultor or arc quenching medium in the transmission and distribution of electricity. however, $SF_6$ is one of the greenhouse gases(GHG) with a global warming potential that is 23,900 times greater than that of carbon dioxide($CO_2$). for this reason, $SF_6$ emissions in electric equipment shall be controlled to reduce GHG and improve cost-effective use of $SF_6$ for economical benefits. Until recently there has not been any investigation on $SF_6$ emission characteristics and inventory in Korea. To understand emission characteristics during the use-phase, the scope of this study was limited to the following closed pressure system equipment from 10 substations in Korea. This study highlights (1) the investigation of sampling/analysis methodology for $SF_6$ emissions in high voltage equipment, (2) the estimation of $SF_6$ emissions in the use-phase, and (3) the comparison between the emission ratio and the mass-balance applied to inventory study. According to this study, the majority of emissions were related to electric equipment nameplates and the rest of the emissions were related to the handling of $SF_6$ during operations. from this result, emission ratios estimated from this study were similar; GIS was 14% and GCB was 13%, as maintenance process conditions were the same as manual process conditions for both equipment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2D
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• pp.255-266
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• 2011

In order to evaluate the environmental load occurring from the whole life cycle of a facility, LCA (Life Cycle Assessment) adopted by ISO is not only applied as an individual product but rather a complicated system involving buildings and/or infrastructure in a wide range of scope. The introducing of LCA to a wastewater reuse facility will assist to understand not only the treatment of water contaminants but also the overall system related to the interaction of involved, potential issues. This research implemented LCA for the establishment of the wastewater reuse facility. The results show that a fresh water aquatic Eco-toxicological Impact (88.3%) is the largest environment concern and the maintenance & operation phase has the most impact on the environment utilizing life cycle for the wastewater reuse facility. The civil works and chemical treatments in the maintenance & operation phase led to the biggest environmental impact. The results of this research can provide pertinent data of investigating opportunities for environmental improvement not limited to public officers regulating environmental policies, and could be used to make decisions for an environmentally sound and sustainable design in the initial phase of construction.

• Korean Journal of Materials Research
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• v.21 no.6
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• pp.327-333
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• 2011

Nanostructured cobalt materials have recently attracted considerable attention due to their potential applications in high-density data storage, magnetic separation and heterogeneous catalysts. The size as well as the morphology at the nano scale strongly influences the physical and chemical properties of cobalt nano materials. In this study, cobalt nano particles synthesized by a a polyol process, which is a liquid-phase reduction method, were investigated. Cobalt hydroxide ($Co(OH)_2$), as an intermediate reaction product, was synthesized by the reaction between cobalt sulphate heptahydrate ($CoSO_4{\cdot}7H_2O$) used as a precursor and sodium hydroxide (NaOH) dissolved in DI water. As-synthesized $Co(OH)_2$ was washed and filtered several times with DI water, because intermediate reaction products had not only $Co(OH)_2$ but also sodium sulphate ($Na_2SO_4$), as an impurity. Then the cobalt powder was synthesized by diethylene glycol (DEG), as a reduction agent, with various temperatures and times. Polyvinylpyrrolidone (PVP), as a capping agent, was also added to control agglomeration and dispersion of the cobalt nano particles. The optimized synthesis condition was achieved at $220^{\circ}C$ for 4 hours with 0.6 of the PVP/$Co(OH)_2$ molar ratio. Consequently, it was confirmed that the synthesized nano sized cobalt particles had a face centered cubic (fcc) structure and with a size range of 100-200 nm.

• Journal of the Korean Ceramic Society
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• v.51 no.6
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• pp.554-559
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• 2014

Gadolinium zirconate, $Gd_2Zr_2O_7$, is one of the most promising candidates for replacing yttira-stabilized zirconia (YSZ) in thermal barrier coating (TBC) applications due to its low thermal conductivity and chemical stability at high temperature. In this study, rare-earth zirconate ceramics in the $GdO_{1.5}-ZrO_2$ system with reduced gadolinia contents were fabricated via solid-state reaction as well as hot-pressing at $1800^{\circ}C$. The phase formation, microstructure, and thermo-physical properties of these oxides were examined. The potential application of $GdO_{1.5}-ZrO_2$ ceramics for TBC was also discussed.

• Korean Journal of Applied Biomechanics
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• v.28 no.2
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• pp.135-141
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• 2018

Objective: The purpose of this study was to investigate the effect of functional ankle instability (FAI) and surgical treatment (ST) on postural stability and leg stiffness during vertical-drop landing. Method: A total of 21 men participated in this study (normal [NOR]: 7, FAI: 7, ST: 7). We estimated dimensionless leg stiffness as the ratio of the peak vertical ground reaction force and the change in stance-phase leg length. Leg length was calculated as the distance from the center of the pelvis to the center of pressure under the foot. Furthermore, the analyzed variables included the loading rate and the dynamic postural stability index (DPSI; medial-lateral [ML], anterior-posterior [AP], and vertical [V]) in the initial contact phase. Results: The dimensionless leg stiffness in the FAI group was higher than that of the NOR group and the ST group (p = .018). This result may be due to a smaller change in stance-phase leg length (p = .001). DPSI (ML, AP, and V) and loading rate did not show differences according to the types of ankle instability during drop landing (p > .05). Conclusion: This study suggested that the dimensionless leg stiffness was within the normal range in the ST group, whereas it was increased by the stiffness of the legs rather than the peak vertical force during vertical-drop landing in the FAI group. Identifying these potential differences may enable clinicians to assess ankle instability and design rehabilitation protocols specific for the impairment.

• Journal of Magnetics
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• v.18 no.3
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• pp.245-249
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• 2013

A finite element model was built for MnBi/${\alpha}$-Fe nanocomposite permanent magnets, and the demagnetization curves of the magnets were simulated by micro-magnetic calculation. The microstructure of the cubic model is composed of 64 irregular grains with an average grain size of 20 nm. With the volume fraction of soft magnetic phase (t vol. %) ranged from 5 to 20 vol. %, both isotropic and anisotropic nanocomposite magnets show typical single-phase permanent magnets behavior in their demagnetization curves, illustrating good intergranular exchange coupling effect between soft and hard magnetic phases. With the increase of volume fraction of soft magnetic phase in both isotropic and anisotropic magnets, the coercive force of the magnets decreases monotonically, while the remanence rises at first to a peak value, then decreases. The optimal values of maximum energy products of isotropic and anisotropic magnets are 84 and $200kJ/m^3$, respectively. Our simulation shows that the MnBi/${\alpha}$-Fe nanocomposite permanent magnets own excellent magnetic properties and therefore good potential for practical applications.

• Nutrition Research and Practice
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• v.15 no.5
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• pp.555-567
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• 2021

BACKGROUND/OBJECTIVES: Abeliophyllum distichum is a plant endemic to Korea, containing several beneficial natural compounds. This study investigated the effect of A. distichum leaf extract (ALE) on adipocyte differentiation. MATERIALS/METHODS: The cytotoxic effect of ALE was analyzed using cell viability assay. 3T3-L1 preadipocytes were differentiated using induction media in the presence or absence of ALE. Lipid accumulation was confirmed using Oil Red O staining. The mRNA expression of adipogenic markers was measured using RT-PCR, and the protein expressions of mitogen-activated protein kinase (MAPK) and peroxisome proliferator-activated receptor gamma (PPAR𝛾) were measured using western blot. Cell proliferation was measured by calculating the incorporation of Bromodeoxyuridine (BrdU) into DNA. RESULTS: ALE reduced lipid accumulation in differentiated adipocytes, as indicated by Oil Red O staining and triglyceride assays. Treatment with ALE decreased the gene expression of adipogenic markers such as Ppar𝛾, CCAAT/enhancer binding protein alpha (C/ebp𝛼), lipoprotein lipase, adipocyte protein-2, acetyl-CoA carboxylase, and fatty acid synthase. Also, the protein expression of PPAR𝛄 was reduced by ALE. Treating the cells with ALE at different time points revealed that the inhibitory effect of ALE on adipogenesis is higher in the early period treatment than in the terminal period. Furthermore, ALE inhibited adipocyte differentiation by reducing the early phase of adipogenesis and mitotic clonal expansion. This was indicated by the lower number of cells in the Synthesis phase of the cell cycle (labeled using BrdU assay) and a decrease in the expression of early adipogenic transcription factors such as C/ebp𝛽 and C/ebp𝛿. ALE suppressed the phosphorylation of MAPK, confirming that the effect of ALE was through the suppression of early phase of adipogenesis. CONCLUSIONS: Altogether, the results of the present study revealed that ALE inhibits lipid accumulation and may be a potential agent for managing obesity.

• Journal of Powder Materials
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• v.29 no.1
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• pp.34-40
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• 2022

Recently, high-entropy carbides have attracted considerable attention owing to their excellent physical and chemical properties such as high hardness, fracture toughness, and conductivity. However, as an emerging class of novel materials, the synthesis methods, performance, and applications of high-entropy carbides have ample scope for further development. In this study, equiatomic (Hf-Ti-Ta-Zr-Nb)C high-entropy carbide powders have been prepared by an ultrahigh-energy ball-milling (UHEBM) process with different milling times (1, 5, 15, 30, and 60 min). Further, their refinement behavior and high-entropy synthesis potential have been investigated. With an increase in the milling time, the particle size rapidly reduces (under sub-micrometer size) and homogeneous mixing of the prepared powder is observed. The distortions in the crystal lattice, which occur as a result of the refinement process and the multicomponent effect, are found to improve the sintering, thereby notably enhancing the formation of a single-phase solid solution (high-entropy). Herein, we present a procedure for the bulk synthesis of highly pure, dense, and uniform FCC single-phase (Fm3m crystal structure) (Hf-Ti-Ta-Zr-Nb)C high-entropy carbide using a milling time of 60 min and a sintering temperature of 1,600℃.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.45.1-45.1
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• 2021

The polarization degree as a function of phase angle (the Sun-target-observer's angle), so-called the polarimetric phase curves (PPC), have provided priceless information on asteroids' albedos since B. Lyot (1929). Succeeding experimental works in 1970s have confirmed the Umow law: There is a universal and strong correlation between the albedo and the PPC slope (slope of the tangential line at the zero of the PPC at phase angle ~ 20 degrees). Experiments in 1990s (ref [1]), on the other hand, have demonstrated that the negative branch of PPC is dependent on the size parameter (X ~ π * particle-size / wavelength), especially when X <~5. The change in particle size changed the minimum polarization degree, location of the minimum, and the width of the negative branch (called the inversion angle). From polarimetry[2] and spectroscopy[3], large asteroids are expected to be covered with fine (<~ 10 ㎛ size) particles due to the gravity. The size parameters are X ~ 30 at the optical wavelength (λ ~ 0.5 ㎛) and X ~ 10 in near-infrared (J, H, Ks bands; λ ~ 1.2-2.2 ㎛), if the representative particle size of 5 ㎛ is considered. Accordingly, the near-infrared polarimetry has a great potential to validate the idea in ref[1]. We conducted near-infrared photopolarimetry of the large asteroid (4) Vesta using the Nishiharima Infrared Camera (NIC) at Nishi-Harima Astronomical Observatory (NHAO). NIC allows simultaneous polarimetric measurements in J, H, and Ks bands, and thus the change of PPC is obtained for three different size parameters. As a result, we found a signature of the change in the negative branch in the PPC of asteroid (4) Vesta. We will introduce our observation and the results and give an interpretation of the regolith on Vesta.

• Animal Bioscience
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• v.35 no.10
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• pp.1592-1605
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• 2022

Objective: The objective of this study was to select an effective in vitro digestion-fermentation model to estimate the effect of decreasing dietary crude protein (CP) on odor emission during pig production and to suggest potential prediction markers through in vitro and in vivo experiments. Methods: In the in vitro experiment, three diet formulations with different CP contents (170 g/kg, 150 g/kg, and 130 g/kg) but containing the same standardized ileal digestible essential amino acids (SID-EAA) were assessed. Each diet was evaluated by two different in vitro gastric-intestinal phase digestion methods (flask and dialysis), combined with fresh pig feces-ferment inoculation. Eighteen growing barrows (31.9±1.6 kg) were divided into three groups: control diet (180 g CP/kg, without SID-EAA adjustment), 170 g CP/kg diet, and 150 g CP/kg diet for 4 weeks. Results: The in vitro digestion results indicated that in vitro digestibility was affected by the gastric-intestinal phase digestion method and dietary CP level. According to the gas kinetic and digestibility results, the dialysis method showed greater distinguishability for dietary CP level adjustment. Nitrogen-related odor compounds (NH₃-N, indole, p-cresol, and skatole) were highly correlated with urease and protease activity. The feeding study indicated that both EAA-adjusted diets resulted in a lower odor emission especially in p-cresol and skatole. Both protease and urease activity in feces were also closely related to odor emissions from nitrogen metabolism compounds. Conclusion: Dialysis digestion in the gastric-intestinal phase followed by fresh fecal inoculation fermentation is suitable for in vitro diet evaluation. The enzyme activity in the fermentation and the fecal samples might provide a simple and effective estimation tool for nitrogen-related odor emission prediction in both in vitro and in vivo experiments.