• Computers and Concrete
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• v.21 no.2
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• pp.167-179
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• 2018

Reactive powder concrete (RPC) is a type of ultra-high strength cement-based material with a dense microstructure, which is made of ultra-fine powders. RPC demonstrate a very brittle behavior, thus adding fibers improves its mechanical properties. In this study, it was attempted to investigate the effect of using steel and polyvinyl alcohol (PVA) fibers as well as their combination on the properties of RPC. In this regard, hooked-end crimped steel fibers together with short PVA fibers were utilized. Steel and PVA fibers were used with the maximum volume fraction of 3% and 0.75%, respectively, and also different combinations of these fibers were used with the maximum volume fraction of 1% in the concrete mixes. In total, 107 concrete specimens were prepared, and the effect of fiber type and volume fraction on the physico-mechanical properties of RPC including compressive strength, tensile strength, modulus of elasticity, density, and failure mode was explored. In addition, the effect of the curing type on the properties of compressive strength, modulus of elasticity, and density of RPC was evaluated. Finally, coefficients for conversion of cubic compressive strength to cylindrical one for the RPC specimens were obtained under the two curing regimes of heat treatment and standard water curing.

• The Korean Journal of Food And Nutrition
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• v.32 no.2
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• pp.133-137
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• 2019

Curcumin is a hydrophobic polyphenol extracted from turmeric that exhibits a variety of biological functions has albeit with limited efficacy as a functional food material owing to its low absorption when administered orally. The newly developed curcumin powder formulation exhibits improved absorption rate in vivo. This study evaluates the anti-oxidant effects of $Theracurmin^{(R)}$ (TC), which is highly bio-available in curcumin powder. The antioxidant activity of TC was investigated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, ferrous reducing antioxidant power (FRAP) assays, NO radical, superoxide radical, $H_2O_2$ scavenging activity, and total antioxidant capacity (TAC). Additionally, we evaluated the antioxidant activity of TC in high-fat diet (HFD)-fed streptozotocin (STZ)-induced Type 2 diabetic rats. As a result of oral administration of TC for 13 weeks in type 2 diabetic rats, the group administration of 2,000 mg/kg significantly increased FRAP, superoxide dismutase (SOD), and reduced the level of glutathione (GSH) in liver tissue 1.9, 1.2, and 1.2-times, respectively. Furthermore, serum TAC levels increased by 1.3-fold after the rats were administered with a dose of 500 mg/kg. These results were consistent with the in vitro assay results. In conclusion, TC exhibited its potential as a functional food material through its antioxidant properties.

• Journal of the Korean Society for Heat Treatment
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• v.15 no.1
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• pp.16-20
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• 2002

In conventional metallothermic reduction(MR) for obtaining tantalum powder in batch-type operation, it is difficult to control morphology and location of deposits because the reaction occurs by direct physical contact between reductants and feed materials. On the other hand, a electronically mediated reaction(EMR) is capable to overcome these difficulties through the reaction by electron transfer and have a merit of continuous process. In this study an MR and EMR method has been applied to the production of a tantalum powder by sodium reduction of $K_2TaF_7$. As the reduction temperature increases, the particle size and yield of tantalum powder obtained by MR and EMR method is increased.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.231-236
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• 1998

In general, the drying shrinkage of polymer-modified mortars using redispersible polymer powders is much higher than that of unmodified mortar. The purpose of this study is to reduce the drying shringkage of polymer-modified mortars using a redispersible poly(ethylene-vinyl acetate) (EVA) powder, which is widely used for the manufacture of prepackaged-type polymer-modified mortar products at present. Polymer-modified mortars using the redispersible EVA powder with powdered shrinkage-reducing agent were prepared with various polymer-cement ratios and shrinkage-reducing agent contents, and tested for drying shrinkage and strength. From the test results, the drying shrinkage of the redispersible EVA powder-modified mortars with a powdered shrinkage agent is remarkably reduced with increasing shrinkage-reducing agent content, and becomes approximately a half of that of the redispersible EVA powder-modified mortars with the same polymer-cement ratios and without the shrinkage-reducing agent at a shrinkage-reducing agent content of 6%.

• Journal of Powder Materials
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• v.20 no.3
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• pp.169-173
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• 2013

High-coercive (Nd,Dy)-Fe-B magnets were fabricated via dysprosium coating on Nd-Fe-B powder. The sputtering coating process of Nd-Fe-B powder yielded samples with densities greater than 98%. $(Nd,Dy)_2Fe_{14}B$ phases may have effectively penetrated into the boundaries between neighboring $Nd_2Fe_{14}B$ grains during the sputtering coating process, thereby forming a $(Nd,Dy)_2Fe_{14}B$ phase at the grain boundary. The maximum thickness of the Dy shell was approximately 70 nm. The maximum coercivity of the Dy sputter coated samples(sintered samples) increased from 1162.42 to 2020.70 kA/m. The microstructures of the $(Nd,Dy)_2Fe_{14}B$ phases were effectively controlled, resulting in improved magnetic properties. The increase in coercivity of the Nd-Fe-B sintered magnet is discussed from a microstructural point of view.

• Journal of the East Asian Society of Dietary Life
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• v.22 no.1
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• pp.52-61
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• 2012

This study sought to develop a healthier type of jeungpyeon, or Korean rice cake, by adding Korean black raspberry powder (Rubus coreanus). The moisture content, color, volume, symmetry, uniformity, texture, and sensory quality characteristics were evaluated in order to determine the optimal amount of raspberry powder to add to rice flour in order to get the best-tasting, healthiest food. We substituted 0.5%, 1.0%, 1.5% and 2.0% of rice flour with Rubus coreanus powder and mixed 3%, 6%, 9% and 12% Rubus coreanus concentrate with water to make dough. The result was stored for up to 48 hours at $20^{\circ}C$, and then evaluated. Jeungpyun with Rubus coreanus powder and Rubus coreanus concentrate had the right flavor, color, fermentation, and taste, compared to the other groups. Consequently, in overall acceptability, the highly rated Rubus coreanus powder-PW(1.5%) and Rubus coreanus concentrate - BA (6%) will be the most desirable.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.298-303
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• 2000

The 3 mol% yttria stabilized zirconia (3-Y PSZ) powder was heat treated at 50 0$^{\circ}C$ to evaporate the polymer binder and stabilize the tetragonal phase. The wear experiments were carried out on a ring-on-plate type reciprocating wear tester at selected temperatures with in the range room temperature to 600$^{\circ}C$ The results show that the heat treatment of powder decreases the wear rate due to the reduction of microcracks and pores in coatings and the stabilization of the tetragonal phase. Powder heat treatment enhanced the quality of the coating layer by removing remnant gases during coating process and the powder heat treatment at which tetragonal phase is stable diminished phase ratio of monoclinic. These two effects improved wear resistance characters.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.96-97
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• 2020

In this study, the compressive strength and porosity characteristics of cement mortar mixed with liquid and powder composite water repellent were evaluated. When the liquid water repellent was mixed, the compressive strength at 28 days of age was 42% compared to OPC, and the compressive strength was greatly reduced. However, the 28-day compressive strength of the powder water repellent mixture and P5L1, P6L1 liquid and powder composite water repellent was about 97% compared to OPC, and there was little decrease in compressive strength.

• Journal of Powder Materials
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• v.27 no.1
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• pp.58-62
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• 2020

Recently, electrochromic devices (ECDs) have gathered increasing attention owing to their high color contrast and memory effect, which make them highly applicable to smart windows, auto-dimming mirrors, sensors, etc. Traditional ECDs have a sandwich structure that contains an electrochromic layer between two ITO substrates. These sandwich-type devices are usually fabricated through the lamination of two electrodes and followed by the injection of a liquid electrolyte in the inner space. However, this process is sometimes complex and time consuming. In this study, we fabricated ECDs with a lateral electrode structure that uses only an ITO substrate and an all-in-one electrochromic gel, which is a mixture of electrolyte and electrochromic material. Furthermore, we investigated the EC properties of the lateral-type device by comparing it with a sandwich-type device. The lateral-type ECD shows strong blue absorption as the applied voltage increases and has a competitive coloration efficiency compared to the sandwich-type device.

• Korean Journal of Materials Research
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• v.19 no.8
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• pp.447-451
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• 2009

The long-period stacking order (LPSO) structures and stacking faults (SFs) in rapidly solidified powder metallurgy (RS P/M) $Mg_{97}Zn_1Y_2$ alloy were investigated by high resolution transmission electron microscopy (HRTEM) observations. The 18R-type LPSO structure with a stacking sequence of ACBCBCBACACACBABAB and a period of 4.86 nm was observed in the as-extruded RS P/M $Mg_{97}Zn_1Y_2$ alloy. After annealing at 773 K for 5 hr, the 18R-type LPSO structure was transformed to the 14H-type LPSO structure with a stacking sequence of ABABABACBCBCBC and a period of 3.64 nm. The 24R-type LPSO structure containing 24 atomic layers of ABABABABCACACACABCBCBCBC with period of 6.18 nm coexists with the 14H-type LPSO structure in the same grains. The LPSO structures contain intrinsic Type II SFs such as BCB/CABA and ABA/CBCB stacking sequences of a closely packed plane.