• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.311-320
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• 2011

Fly ash (FA), byproduct from power plant has been actively used as mineral admixture for concrete. However, since bottom ash (BA) is usually used for land reclaim or subbase material, more active reuse plan is needed. Pond ash (PA) obtained from reclaimed land is mixed with both FA and BA. In this study, 6 PA from different domestic power plant are prepared and 5 different replacement ratios (10%, 20%, 30%, 50%, and 70%) for fine aggregate substitutes are considered to evaluate engineering properties of PA as fine aggregate and durability performance of PA concrete. Tests for fine aggregate of PA for fineness modulus, density and absorption, soundness, chloride and toxicity content, and alkali aggregate reaction are performed. For PA concrete, durability tests for compressive strength, drying shrinkage, chloride penetration/diffusion, accelerated carbonation, and freezing/thawing are performed. Also, basic tests for fresh concrete like slump and air content are performed. Although PA has lower density and higher absorption, its potential as a replacement material for fine aggregate is promising. PA concrete shows a reasonable durability performance with higher strength with higher replacement ratio. Finally, best PA among 6 samples is selected through quantitative classification, and limitation of PA concrete application is understood based on the test results. Various tests for engineering properties of PA and PA concrete are discussed in this paper to evaluate its application to concrete structure.

• Clean Technology
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• v.18 no.4
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• pp.432-439
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• 2012

The electrocatalytic oxidation of CO was studied using carbon-supported 20 wt% PtRu (PtRu/C) catalysts, which were prepared with different Pt : Ru atomic ratios from 7 : 3 to 3 : 7 using a colloidal method combined with a freeze-drying procedure. The bimetallic PtRu/C catalysts were characterized by various physicochemical analyses, including X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). CO stripping voltammetry measurements indicated that the addition of Ru with a Pt catalyst significantly improved the electrocatalytic activity for CO electrooxidation. Among the tested catalysts, the $Pt_5Ru_5/C$ catalyst had the lowest onset potential (vs.Ag/AgCl) and the largest CO EAS. Structural modification via lattice parameter change and electronic modification in the unfilled d band states for Pt atoms may facilitate the electrooxidation of CO.

• Journal of the Korean Wood Science and Technology
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• v.37 no.6
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• pp.537-545
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• 2009

The objective of this study was to investigate potential usage of environmentally friendly building materials, liquid mortar and dry cement mortar mixed with charcoal, based on the test of their physical and chemical properties. From the test results of physical and chemical properties of the liquid mortar mixed with charcoal, liquid mortar containing over 20% of charcoal, the consistency viscosity and the non-volatile content met a standard requirement. Drying time was delayed with increase in charcoal contents in the liquid mortar, however they were fully cured within 60 minutes in all treated levels. Other properties were acceptable at standard requirement. From the results, it was found that the proper charcoal addition level to the liquid mortar was 25%. In the results on dry cement, it was found that samples containing 5% of charcoal showed the maximum compressive strength, whereas samples containing over 20% of charcoal did not reach the minimum requirement of KS standard. Water retention ability constantly increased as the charcoal ratio increased. The conventional dry cement mortar adsorbed 59.5% of it, in the test of adsorption rate on ammonia gas, whereas cement mortar containing 10% of charcoal showed 71.6% of ammonia gas adsorption.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.249-249
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• 2013

Surface-enhanced Raman spectroscopy (SERS) is a sensitive approach to detect and to identify a variety of molecules. To enhance the Raman signal, optimization of the gap between nanostructures is quite important. One-dimensional materials such as nanowires, nanotubes, and nanograsses have great potential to be used in SERS due to their unique sizes and shape dependent characteristics. In this study we investigate a simple way to fabricate SERS substrates based on randomly grown copper oxide (CuO) nanowires. CuO nanograss is fabricated on pre-cleaned Cu foils. Cu oxidized in an ammonium ambient solution of 2.5 M NaOH and 0.1 M $(NH_4)_2S_2O_8$ at $4^{\circ}C$ for 10, 30, and 60 minutes. Then, Cu(OH)2 nanostructures are formed and dried at $180^{\circ}C$ for 2 h. With the drying process, the Cu(OH)2 nanostructure is transformed to CuO nanograss by dehydration reaction. CuO nanograss are grown randomly on Cu foil with the average length of 10 ${\mu}m$ and the average diameter of a 100 nm. CuO nanograsses are covered by Ag with various thicknesses from 10 to 30 nm using a thermal evaporator. Then, we immerse uncoated and Ag coated CuO nanowire samples of various oxidation times in a 0.001M methanol-based 4-mercaptopyridine (4-Mpy) in order to evaluate SERS enhancement. Raman shift and SERS enhancement are measured using a Raman spectrometer (Horiba, LabRAM ARAMIS Spectrometer) with the laser wavelength of 532 nm. Raman scattering is believed to be enhanced by the interaction between CuO nanograss and Ag island film. The gaps between Ag covered CuO nanograsses are diverse from <10 nm at the bottom to ~200 nm at the top of nanograsses. SERS signal are improved where the gaps are minimized to near 10s of nanometers. There are many spots that provide sufficiently narrow gap between the structures on randomly grown CuO nanograss surface. Then we may find optimal enhancement of Raman signal using the mapping data of average results. Fabrication of CuO nanograss based on a solution method is relatively simple and fast so this result can potentially provide a path toward cost effective fabrication of SERS substrate for sensing applications.

• Journal of Radiation Industry
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• v.5 no.2
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• pp.159-164
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• 2011

A variety of natural polymers have been used as tissue engineering scaffolds, drug delivery system, and cosmetic materials due to their higher biocompatibility and water uptake. As a major component of extracellular matrix, hyaluronic acid consisting of D-glucuronic acid and N-acetylglucosamine has been popularly used as a hydrogel material. Even though it has good properties to be used in the tissue engineering and cosmetic industry, its higher viscosity has limited a potential use in a variety of applications; only low content should be applied in preparing above products. In the present study, we investigated the effect of electron beam irradiation on the properties of hyaluronic acid. Hyaluronic acid paste containing low contents of water changed to solution after electron beam irradiation ranging from 1 to 10 kGy, which didn't exhibit any alteration of surface properties and morphological change after freeze-drying. However, its viscosity was significantly decreased as absorbed dose increased, which was approximately one by hundred in comparison with the viscosity of original hyaluronic acid solution with same concentration. In addition, it can still interact with positive charged chitosan generating polyelectrolyte complex. Therefore, only viscosity was decreased after electron beam irradiation, whereas other properties of hyaluronic acid maintained. Consequently, these hyaluronic acids with lower viscosities can be used in a variety of applications in tissue engineering, drug delivery, and cosmetic industry.

• Journal of Chitin and Chitosan
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• v.23 no.4
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• pp.234-243
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• 2018

In this study, the physicochemical properties of freeze dried (FD) and spray dried powders (SD-MD10, SD-MD20, SD-CD10, SD-CD20) from green coffee bean extract were investigated. Yields were 91.46% for FD powder and 71.63~87.98% for SD powders, respectively. The moisture content of SD powders (1.39~1.86%) was lower than that of FD powder (3.19%). L, a and b value of SD powders were higher than of FD powder. The particle size of the FD powder ($147.67{\mu}m$) was higher than that of the SD powders ($54.23{\sim}66.07{\mu}m$). The water absorption index of the SD powders (0.51-0.59) were lower than that of the FD powder (0.72). The water solubility index of the SD powders, 77.26-90.07%, was higher than that of the FD powder (70.07%). The total phenolic and flavonoid contents of SD-CD10 were 20.67 g/100 g and 8.92 g/100 g, respectively. The chlorogenic acid content of SD-CD10 (12.04 g/100 g) was higher than other SD powders. The DPPH and superoxide radical scavenging activities of SD-CD10 at $1,000{\mu}g/mL$ were 88.02% and 86.89%, respectively. The SD-CD10 was better than other SD powders on protective effects against oxidative stress in L-132 cells (87.33%). In conclusion, we provided experimental evidence that spray-dried powder of green coffee bean extracts have potential as functional food materials.

• Journal of the Korean Applied Science and Technology
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• v.36 no.3
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• pp.821-829
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• 2019

This study was conducted to evaluate the applicability of the extracts from nipa palm, molokhia, and finger root in functional cosmetics as a natural active ingredient. The extracts were obtained through the processes of heating under reflux with ethanol, filtration, concentration, and freeze-drying. UV absorption and blocking effects of the extracts were examined by using the UV-vis spectrophotometer equipped with an integrating sphere. Antioxidant activity and its stability between the extracts were compared using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. Also, total polyphenol content in the extracts was determined quantitatively using the Folin-Ciocalteu reagent, with gallic acid as the standard. Antibacterial activity of the extracts was investigated by the disc diffusion test against Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative). Finally, collagenase inhibitor assay was performed to examine the anti-wrinkle effect of the extracts. From the results of this study, the extract of nipa palm showed the potential for use in cosmetics as an antioxidant and anti-wrinkle agent, and the extract of finger root as a sunscreen and antibacterial agent.

• The Journal of the Korea Contents Association
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• v.21 no.3
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• pp.609-615
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• 2021

The aim of the present study was to investigate the mechanical properties of melt-injected poly lactic acid (PLA) composites with β-tricalcium phosphate (β-TCP). The PLA mixed with calcined PLA/β-TCP powder to be contents of 0, 10, 30, 50 wt%, respectively, was dissolved in chloroform solvent under stirring for 24 h. Then the liquid mixtures were dropped into ethanol to extract solvent. After drying, the well-dispersed PLA/β-TCP composites were granulated and melt-injected to prepare specimens for various mechanical testing. PLA/β-TCP induced the precipitation of an apatite bone-mineral phase on the surface after immersion in a human simulated body fluid (SBF) for 90 days, showing in bioactivity. Mean various mechanical properties PLA/β-TCP composite were increased up to 10-30 wt% with significantly in part and composite were decreased 50 wt% of showing in mechanical properties. In conclusion, Over 30 wt% addition of β-TCP to PLA may be not advisable to improve the mechanical properties of melt-injected polymeric composites. Results indicated that β-TCP can be used considered as potential reinforcing agent for increasing mechanical properties for PLA. Therefore, it was suggest that the additional effects of β-TCP and research on a wide range of substances.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.48 no.1
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• pp.77-85
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• 2022

Retinaldehyde (RA), vitamin A derivative, is an intermediate between retinol and retinoic acid and has an excellent wrinkle improving effect. In this study, Drug-in-cyclodextrin-in-liposome (DCL) was used to enhance the stability and skin penetration of RA. The complex of RA and hydroxypropyl-beta-cyclodextrin (HP-β-CD) was prepared by the freeze-drying method, and the presence or absence of inclusion of retinal was confirmed by UV-Vis spectrometer, FT-IR and SEM images. RA was captured in HP-β-CD about 95.6% on 1 : 15 (w/w). The retinal-HP-β-CD complex was encapsulated in liposomes using a homomixer and microfluidizer, with an average particle size of 215 ± 4.2 nm and a zeta potential of -31.2 ± 0.5 mv. In the evaluation of the degradation stability of RA, degradation rate of RA-HP-β-CD-liposomes in water was 1.8% higher than RA-liposome (5.8%), RA-HP-β-CD complex (9.7%) and RA alone (37.6%). RA cream (0.05% RA) including RA-HP-β-CD-liposomes was prepared for clinical test with wrinkle-improving efficacy and skin dermis denseness evaluated for 2 or 4 weeks. RA cream showed a significant wrinkle improving effect without skin irritation. In conclusion, it was confirmed that the double stabilization technology using the DCL system contribu tes to the effect of improving skin wrinkles by increasing the stabilization of retinal.

• Journal of the Korean Geotechnical Society
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• v.24 no.1
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• pp.37-49
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• 2008

A geothermal heat pump system is a preferable alternative energy system in Korea because it uses the heat energy of the earth, which is environmentally friendly and inexhaustible. In order to characterize the thermal conductivity and viscosity of grout materials used for backfilling ground heat exchangers, nine bentonite grouts, one marine clay from Boryung, and cement grouts adapted in the United State have been considered in this study. The bentonite grouts indicate that the thermal conductivity and viscosity increase with the content of bentonite or filler (silica sand). In addition, material segregation can be observed when the viscosity of grout is relatively low. The marine clay turns out to be unsuitable for backfilling the ground heat exchanger due to its insufficient swelling potential. The saturated cement grouts appear to possess much higher thermal conductivity than the saturated bentonite grouts, and the reduction of thermal conductivity in the cement grouts after drying specimens is less than that in the case of the bentonite grouts. Maintaining the moisture content of grouts is a crucial factor in enhancing the efficiency of ground heat exchangers.