• Geomechanics and Engineering
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• v.28 no.6
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• pp.547-557
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• 2022

Dune sands are poorly graded collapsible soils lacking fines. This experimental study explored the technical feasibility of sustainable invigoration of fine waste materials to improve the geotechnical properties of dune sand. The fine waste considered in this study is fine marble waste. The fine waste powder was mixed with dune sand at different contents (5, 10,15, 20, 25, 50%), where the gradation, void ratio, compaction, and shear strength characteristics were assessed for each fine marble waste -dune sand blend. The geotechnical properties of the dune sand-fine marble waste mix delineated in this study reveal the enhancement in compaction and gradation characteristics of dune sand. According to the results, the binary mixture of dune sand with 20% of fine marble waste gives the highest maximum dry density and results in shear strength improvement. In addition, a numerical study is conducted for the practical application of the binary mix in the field and tested for an isolated shallow foundation. The elemental analysis of the fine marble waste confirms that the material is non-contaminated and can be employed for engineering applications. Furthermore, the numerical study elucidated that the shallow surface replacement of the site with the dune sand mixed with 20% fine marble waste gives optimal performance in terms of stress generation and settlement behavior of an isolated footing. For a sustainable mechanical performance of the fine marble waste mixed sand, an optimum dose of 20% fine marble waste is recommended, and some correlations are proposed. Thus, for improving dune sand's geotechnical characteristics, the addition of fine marble waste to the dune sand is an environment-friendly solution.

• Structural Engineering and Mechanics
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• v.82 no.3
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• pp.295-312
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• 2022

This study investigates the effects of nano silica (NS) and micro steel fiber on the properties of ultra-high-performance concrete (UHPC). The experimental consists of three groups, each one with five percentages of NS content (0%, 2%, 4%, 6% and 8%) in addition to the 20% silica fume and 20% quartz powder proportioned according to the weight of cement added to the mixtures. In addition, three percentages of micro steel fibers (0%, 1% and 2%) were considered. Different mixtures with varying percentages of NS and micro steel fibers were prepared to set the water-to-binder ratio, such as 0.16% and 1.8% superplasticizer proportioned according the weight of the binder materials. The fresh properties, mechanical properties and elevated temperatures of the mixtures were calculated. Then, the results from the microstructure analyses were compared with that of the reference mixtureand it was found that 6% replacement of cement with NS was optimum replacement level. When the NS content was increased from 0% to 6%, the air content and permeability of the mixture decreased by 35% and 39%, the compressive and tensile strength improved by 21% and 18% and the flexural strength and modulus of elasticity increased by 20% and 11.5%, respectively. However, the effect of micro steel fibres on the compressive strength was inconclusive. The overall results indicate that micro steel fibres have the potential to improve the tensile strength, flexure strength and modulus of elasticity of the UHPC. The use of 6% NS together with 1% micro-steel fiber increased the concrete strength and reduce the cost of concrete mix.

• Analytical Science and Technology
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• v.19 no.5
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• pp.389-393
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• 2006

The detector consisted of ZnS(Ag) scintillator and photomultiplier tube (PMT) is widely used as contamination monitor in the nuclear facilities. Such detectors are mainly manufactured by adhering the ZnS(Ag) powder onto the transparent plastic. In this study the preparation condition for ZnS(Ag) scintillator sheet using a simple method was established. The scintillator sheet was composed with a support polymer sheet and ZnS(Ag) scintillator layer. The base sheet was prepared by casting the polymer solution after solving the polymer with solvent and the scintillator layer was manufactured by printing the mixture solution with ZnS(Ag) and paste. It was found that the polysulfone(PSf) as a polymer for the base sheet and a cyano resin as a paste for adhering the ZnS(Ag) scintillator was suitable. Also, the prepared thin scintillator sheet had a sufficient mechanical strength, a optical transparency and an alpha-ray detection performance.

• Korean Journal of Materials Research
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• v.33 no.6
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• pp.257-264
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• 2023

To develop a high capacity lithium secondary battery, a new approach to anode material synthesis is required, capable of producing an anode that exceeds the energy density limit of a carbon-based anode. This research synthesized carbon nano silicon composites as an anode material for a secondary battery using the RF thermal plasma method, which is an ecofriendly dry synthesis method. Prior to material synthesis, a silicon raw material was mixed at 10, 20, 30, 40, and 50 wt% based on the carbon raw material in a powder form, and the temperature change inside the reaction field depending on the applied plasma power was calculated. Information about the materials in the synthesized carbon nano silicon composites were confirmed through XRD analysis, showing carbon (86.7~52.6 %), silicon (7.2~36.2 %), and silicon carbide (6.1~11.2 %). Through FE-SEM analysis, it was confirmed that the silicon bonded to carbon was distributed at sizes of 100 nm or less. The bonding shape of the silicon nano particles bonded to carbon was observed through TEM analysis. The initial electrochemical charging/discharging test for the 40 wt% silicon mixture showed excellent electrical characteristics of 1,517 mAh/g (91.9 %) and an irreversible capacity of 133 mAh/g (8.1 %).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.787-794
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• 2006

Generally, high performance concrete has characteristics such as low water-cementitious material ratio, lots of unit binder powder, thus the heat of hydration, autogenous shrinkage are tend to be increased. This study is to investigated the effect of the expansive additive and shrinkage reducing agent on the shrinkage properties of high performance concrete as a study to develop the reduction technology of the concrete shrinkage. Test results showed that the expansive additive and shrinkage reducing agent were effective the reduction of shrinkage of high performance concrete. Especially, the using method in combination with expansive additive and shrinkage reducing agent was more effective than the separately using method of that. Also, it analyzed that the combination of expansive additive of 5% and shrinkage reducing agent of 1% was the most suitable mixture, considering to the fluidity, strength and shrinkage properties.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.552-559
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• 2023

The purpose of this study is to evaluate the crack reduction performance of blast furnace slag concrete mixed with expansive and swelling admixtures. As a basic performance test, various ingredients such as blast furnace slag fine powder (BFS), calcium sulfoaluminate (CSA), bentonite, and hydroxypropyl methyl cellulose (HPMC) were used, and the results showed that bentonite showed superior performance compared to HPMC. Afterwards, a MOCK-UP test was conducted to evaluate cracking and drying shrinkage according to the mixing ratio. As a result, when bentonite and a small amount of calcium phosphate were added, drying shrinkage was reduced and cracking was reduced. In particular, a cement mixture consisting of 30 % BFS, 1 % bentonite, and 1 % calcium phosphate showed optimal crack-free performance. It is believed that BFS concrete will contribute to compensating for shrinkage through continuous expansion activity and can be used for field applications.

• Korean Journal of Food Science and Technology
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• v.37 no.6
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• pp.989-996
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• 2005

Ultraviolet (UV) induces photo aging, erythema, sunburn, photo-toxicity, photo-allergy, and skin tumor, To investigate photo-protective effects of AmorePacific Beauty-03 (APB-03; mixture of red ginseng extract powder and soybean extract powder) on UV-induced damaged skins, 40 SKH hairless female mice were orally administered APB-03 or saline five times a week and irradiated with UV three times per week far up to 12 weeks. Visible skin changes and skin damage in dermis and epidermis by replica image analysis and histological analysis. In APB-03-treated group, better skin, negative replica appearance and less wrinkle formation were observed compared to the UV control group. These results demonstrate oral administration of APB-03 have photo-protective effects on UV-damaged hairless mouse skin.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.4
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• pp.172-179
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• 2006

When $Al_2O_3-MoO_3$ mixture is reduced, $MoO_3$ is only reduced to Mo at $900^{\circ}C$. But a compound between $Al_2O_3$ and Mo is not formed up to $1300^{\circ}C$. In the case of $Al_2O_3-MoO_3-MnO_2$ mixture, an intermediate compound $Mn_2Mo_3O_8$ is firstly formed at $900^{\circ}C$ and changes to $MnAl_2O_4$ at $1100^{\circ}C{\sim}1300^{\circ}C$. $Al_2O_3/Mo/MnO_2$ composite are manufactured by a selective reduction process in which Mo is only reduced in the powder mixture of $Al_2O_3,\;MoO_3\;and\;MnO_2$ oxide. For $Al_2O_3/Mo$ composite, the average grain size was not changed with increasing Mo content because of inhibition of grain growth of $Al_2O_3$ matrix in the presence of Mo particles. Fracture strength increased with increasing Mo content due to phenomenon of grain growth inhibition of $Al_2O_3$ matrix. Hardness decreased because of a lower hardness value of Mo, whereas fracture toughness increased. For $Al_2O_3,\;Mo\;and\;MnO_2$ composite, grain growth was facilitated by MnOB and it showed a lower fracture strength because of grain growth effect with increasing Mo and $MnO_2$ content. Hardness decreased because of the grain growth of matrix and coalesced Mo particles to be located in grain boundary, whereas fracture toughness increased.

• Korean journal of applied entomology
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• v.55 no.4
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• pp.319-327
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• 2016

Chemical pesticides have been used to control persimmon pests, however the overuse of the pesticides caused insect resistance, followed by failure in pest management and residual problems. Herein we investigate the potential of eco-friendly organic pesticides (EFOP) on the control persimmon pests, Stathmopoda masinissa (persimmon fruit moth) and Riptortus pedestris (bean bug). Ten commercially available plant-derived organic pesticides and one microbial pesticide were sprayed on the target insects in laboratory conditions. The chemical pesticide, buprofezin+dinotefuran wettable powder served as a positive control. In the first bioassay against persimmon fruit moth, alternatively Plutella xylostella larvae were used due to the lack of persimmon fruit moth population from fields, and three organic pesticides showed high control efficacy, such as pyroligneous liquor (EFOP-1), the mixture of Chinese scholar tree extract, goosefoot and subtripinnata extracts (EFOP-2) and Bacillus thuringiensis subsp. aizawai NT0423 (EFOP-11). When the three selected organic pesticides were treated on the persimmon fruit moths, the EFOP-2 treatment showed the highest control efficacy: 27.7% (5 days), 13.3% (7 days) and 6.7% (10 days) of survival rates. In the bioassay against bean bugs, the mixture of Chinese scholar tree, goosefoot and subtripinnata extracts (EFOP-2 and EFOP-9) and the extracts of sophora and derris (EFOP-10) showed high control efficacy, particularly the highest in the treatment of EFOP-2: 20.0% (5 days) and 16.7% (10 days) of survival rates. These results suggest that the mixture of Chinese scholar tree, goosefoot and subtripinnata extracts (EFOP-2) has high and multiple potential in the management of the persimmon pests.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.4
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• pp.470-475
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• 1999

This study was conducted to evaluate the utilization of animal by-product mixture (ABPM) as a dietary animal protein source of fish meal replacer, and to determine the effect of dietary chromic oxide in growing rainbow trout, Oncorhynchus mykiss. ABPM is a mixture of five anmial by-products such as meat and bone meal (MBM) feather meal (FM), squid live, powder(SLP), poultry by-product (PBP) and blood- meal (BM) at a specific weight based ratio. Diet 1 and 2 were formulated on a isonitrogenous and a isocaloric basis of $46.5\%$ crude protein and 16.7 KJ/g diet; diet 1 (WFM 100), $100\%$ of the animal protein source came from white fish meal; diet 2 (ABPM 40), $60\%$ WFM+$40\%$ ABPM as the animal protein source; diet 3 (-Cr) commercial diet without chromic oxide; diet 4 (+Cr), commercial diet with chromic oxide. After eight weeks of feeding trials, fish fed diet 2 had a significantly lower body weight gain (WG) and feed efficiency (FE) than that of fish fed the other diets (P<0.05). When comparing diet 3 with diet 4, no significant differences were found in WG and FE (P>0.05). There were no significant differences on condition factor, hematocrit level, serum phosphorus, bone phosphorus, whole body phosphorus, and bone ash among fish from all four diet groups. Fish fed diet 4 had a significantly higher whole body lipid than that of fish fed the other diets (P<0.05), These results indicated that ABPM could be used less than $40\%$ in growing rainbow trout with a sufficient period of acclimation, In addition, the $0.5\%$ of chromic oxide can be used to determine the apparent digestibility of the nutrients in the feed without any adverse effects on growth and body composition.