• Nuclear Engineering and Technology
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• v.27 no.4
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• pp.544-554
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• 1995

Pool boiling of dilute aqueous solutions of polyethylene oxide polymer has been experimentally investigated for the purpose of understanding the physical mechanisms of the suppression of vapor explosions in this polymer solution. Tn solid spheres of 22.2mm and 9.5mm-diameter ore heat-ed and quenched in the polymer solutions of various concentrations at 3$0^{\circ}C$. The results showed that minimum film boiling temperature($\Delta$ $T_{MFB}$) in this highly-subcooled liquid rapidly decreased from over $700^{\circ}C$ for pure water to about 15$0^{\circ}C$ as the polymer concentration was increased up to 300ppm for 22.2mm sphere, and it decreased to 35$0^{\circ}C$ for 9.5mm sphere. This large decrease of minimum film boiling temperature in this aqueous polymer solution may explain its ability to suppress spontaneous vapor explosions. Also, tests with applying a pressure wave showed that the vapor film behaved more stable against an external disturbance at higher polymer concentrations. These observations together with the experimental evidences of vapor explosion suppression in dilute polymer solutions suggest that the application of polymeric additives such as polyethylene oxide as low as 300ppm to reactor emergency coolant be considered to prevent or mitigate energetic fuel-coolant interactions during severe reactor accidents.s.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.4
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• pp.437-443
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• 2015

Purpose: This study evaluated the optical and physical and characteristics of soft contact lens polymerized with addition of 3-chloropyridine-4-carboxylic acid and 3-fluoropyridine-4-carboxylic acid in the basic hydrogel contact lens material. In particular, the utility of 3-chloropyridine-4-carboxylic acid and 3-fluoropyridine- 4-carboxylic acid as a hydrogel contact lens material was investigated. Methods: In this study, 3-chloropyridine-4-carboxylic acid and 3-fluoropyridine-4-carboxylic acid were used as additives. Also, 2-hydroxyethyl methacrylate, acrylic acid, methyl methacrylate and a cross-linker EGDMA were co-polymerized in the presence of AIBN as an initiator. Results: The physical properties of the produced polymers were measured as followings. The water content of 34.54~37.15%, refractive index of 1.4320~1.4342, tensile strength of 0.2872~0.3608 kgf and contact angle of $57.82{\sim}79.57^{\circ}$, UV-B transmittance of 76.8~82.4% and UV-A transmittance of 84.6~86.6% were obtained respectively. Conclusions: Based on the results of this study, contact lens material containing 3-chloropyridine-4-carboxylic acid and 3-fluoropyridine-4-carboxylic acid is expected to be able to used as a material for high wettability and UV-block hydrogel contact lens.

• Resources Recycling
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• v.8 no.1
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• pp.11-17
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• 1999

This study was carried out to investigate the efficiency of stcclmaldng slag and sludge in removing metals existing in wastewater or leachate. Laboratory experiments were performed as a function of initial concentration of metals. pH a and temperature of the background solution and the presence of che1ating agent, EDTA. The test conditions were temperatures r ranging from $25^{\circ}C$ to $50^{\circ}C$; initial concentrations varying from 5mg/L to 50 mg/L; pH between 3 and 11; and Cu. Cd‘ and Pb a as adsorbates. The results of tests showed that overall rates of metals removal were 20~30% at pH 3 and greater than 90% at p pH 7 and 11. Metals were removed from the solution predominantly via adsorption in acidic conditions, and the combined e effects of adsorption and precipitation in neutral and alkaline conditions. In view of the test results and other engineering c characteristics of steelmaking slag and sludg$\xi$, these industrial by-products from steel industry have a high potential to be used l in wastewater treatment and are particularly beneficial when used as landfill liner additives due to thelJ ability to remove heavy m metals from leachate.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.3
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• pp.38-45
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• 1998

Soil and water contamination caused by the abundant use of agricultural chemicals including herbicides and fertilizers draws public concerns since these chemicals may pollute the agricultural lands as well as the food products grown on these lands. As a method to reduce the use of agricultural chemicals mulching with thin plastic film has been commonly practised for many years. Although use of the plastic film for mulching is very effective in preventing the growth of weed, it is almost impossible to remove all of the plastic film from the agricultural land and the remaining film eventually contaminates the soils. Therefore, it is very imperative to develop a mulching material that decomposes completely to prevent soil pollution problems and to enhance the competitive edge of domestic agriculture. Mulch papers are believed to have many positive characteristics in preventing problems caused by the plastic mulch film since it decomposes completely after use. However, the basis weight of mulch papers needs to be reduced to improve its handling properties and to reduce the raw material costs of pulps. In this paper the possibilities of using domestic old corrugated containers in producing mulch papers were examined. Also use of unbleached softwood kraft pulps and dry strength additives were exploited along with two-layered sheet forming technology in decreasing the basis weight of the mulch paper. Results showed that reduction of 20g/$m^2$ of basis weight of mulch paper was possible by the appropriate raw material selection and application of strength resin. To use the mulch papers in paddy fields, however, further research to improve its durability should be pursued.

• Membrane Journal
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• v.28 no.6
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• pp.379-387
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• 2018

This study was conducted to improve the membrane characteristics and performance by increasing hydrophilicity by adding additives to the ultrafiltration polysulfone (PSf) hollow fiber membrane. The mixed matrix membranes (MMMs) were prepared by dispersing 15 nm of fumed silica (FS) in the spinning solution at 0.1, 0.3 and 0.5 wt%. SEM analysis was carried out to confirm the cross-section and surface condition. It was confirmed that mean pore radius of the hollow fiber increased by 4 nm as FS was added. In addition, contact angle measurement was carried out for the hydrophilicity analysis of hollow fiber membranes, and it was confirmed that the hydrophilicity of MMMs were increased by adding of FS. In the case of water permeability, the membrane including FS showed 91~96 LMH and showed 5~11% more increase than PSf membrane. In the antifouling performance test, relative flux reduction ratios of FS mixed hollow fiber membranes were lower than that of PSf membranes, and it was confirmed that increase of hydrophilicity hinders adsorption of hydrophobic BSA on the membrane surface.

• Animal Bioscience
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• v.34 no.1
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• pp.48-55
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• 2021

Objective: This study was conducted to investigate the effects of wilting and microbial inoculant treatment on the fermentation pattern and quality of Italian ryegrass silage. Methods: Italian ryegrass was harvested at heading stage and ensiled into vinyl bags (20 cm×30 cm) for 60d. Italian ryegrass was ensiled with 4 treatments (NWNA, no-wilting noadditive; NWA, no-wilting with additive; WNA, wilting no-additive; WA, wilting with additive) in 3 replications, wilting time was 5 hours and additives were treated with 106 cfu/g of Lactobacillus plantarum. The silages samples were collected at 1, 2, 3, 5, 10, 20, 30, 45, and 60 days after ensiling and analyzed for the ensiling quality and characteristics of fermentation patterns. Results: Wilting treatment resulted in lower crude protein and in vitro dry matter digestibility and there were no significant differences in acid detergent fiber (ADF), total digestible nutrient (TDN), water-soluble carbohydrate (WSC), ammonia content, and pH (p>0.05). However, wilting treatment resulted in higher ADF and neutral detergent fiber content of Italian ryegrass silage (p<0.05), and the WNA treatment showed the lowest TDN and in vitro dry matter digestibility. The pH of the silage was higher in the wilting group (WNA and WA) and lower in the additive treatment group. Meanwhile, the decrease in pH occurred sharply between the 3-5th day of storage. The ammonia nitrogen content was significantly lower in the additive treatment (p<0.05), and wilting had no effect. As fermentation progressed, the lactic and acetic acid contents were increased and showed the highest content at 30 days of storage. Conclusion: The wilting treatment did not significantly improve the silage fermentation, but the inoculant treatment improved the fermentation patterns and quality of the silage. So, inoculation before ensiling is recommended when preparing high quality of Italian ryegrass silage, and when wilting, it is recommended to combine inoculation for making high quality silage.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.367-375
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• 2011

Succinic acid ester derivatives have been used as additives for the base oil of metal working fluids and pressure working oils. In this paper, a series of succinic acid alkyl half-esters were synthesized with over 97% yields by ring-opening reaction of succinic anhydride and fatty alcohol and were soluble in 100 N base oil within 1 wt% concentration. The structures and purities of ester derivatives were confirmed by $^1H-NMR$ and FT-IR spectrum and GC analysis. Anti-corrosion properties of the esters in sea water were evaluated through ASTM D665 method and weight loss method and compared to that of succinic alkyl esters without carboxylic acid group in the molecule. As the results, anti-corrosion properties of succinic acid alkyl half-esters with carboxylic acid group were better than those of succinic acid alkyl esters without carboxylic acid group. And, Anti-corrosion properties of the esters with a shorter alkyl chain of high concentration showed better performance than those with longer alkyl chain of low concentration. Inhibition efficiency % (IE%) of the esters was over 95% in the concentration of 80 ppm and corrosion rate (CR) was below 0.3 mm/year at the same concentration. Thus, the corrosion properties of succinic acid alkyl half-esters result from the carboxylic acid groups in molecules.

• Tunnel and Underground Space
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• v.32 no.1
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• pp.59-77
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• 2022

Currently, the design reference temperature of the buffer material for disposing of high-level radioactive waste is less than 100℃, so if the heat dissipation capacity of the buffer material is improved, the spacings of the disposal tunnel and the deposition hole in the repository can be reduced. First of all, this study tries to analyze the criteria for thermal-hydraulic-mechanical performance of the buffer materials and to investigate the researches regarding the enhanced buffer materials with improved thermal conductivity. First, the thermal conductivity should be as high as possible and is affected by dry density, water content, temperature, mineral composition, and bentonite type. the organic content of the buffer material can have a significant effect on the corrosion performance of a canister, so the organic content should be low. In addition, hydraulic conductivity of the buffer material should be less than that of near-field rock and swelling pressure should be appropriate for buffer materials to function properly. For the development of enhanced buffer materials, additives such as sand, graphite, and graphite oxide are typically used, and a thermal conductivity can be greatly improved with a very small amount of graphite addition compared to sand.

• Journal of Animal Science and Technology
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• v.64 no.1
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• pp.38-51
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• 2022

Whole-plant corn (Zea may L.) and sorghum-sudangrass hybrid [Sorghum bicolor (L.) Moench] are major summer crops that can be fed as direct-cut or silage. Proso millet is a short-season growing crop with distinct agronomic characteristics that can be productive in marginal lands. However, information is limited about the potential production, feed value, and ensilability of proso millet forage. We evaluated proso millet as a silage crop in comparison with conventional silage crops. Proso millet was sown on June 8 and harvested on September 5 at soft-dough stage. Corn and sorghum-sudangrass hybrid were planted on May 10 and harvested on September 10 at the half milk-line and soft-dough stages, respectively. The fermentation was evaluated at 1, 2, 3, 5, 10, 15, 20, 30, and 45 days after ensiling. Although forage yield of proso millet was lower than corn and sorghum-sudangrass hybrid, its relative feed value was greater than sorghum-sudangrass hybrid. Concentrations of dry matter (DM), crude protein, and water-soluble carbohydrate decreased commonly in the ensiling forage crops. The DM loss was greater in proso millet than those in corn and sorghum-sudangrass hybrid. The in vitro dry matter digestibility declined in the forage crops as fermentation progressed. In the early stages of fermentation, pH dropped rapidly, which was stabilized in the later stages. Compared to corn and sorghum-sudangrass hybrid, the concentration of ammonia-nitrogen was greater in proso millet. The count of lactic acid bacteria reached the maximum level on day 10, with the values of 6.96, 7.77, and 6.95 Log₁₀ CFU/g fresh weight for proso millet, corn, and sorghum-sudangrass hybrid, respectively. As ensiling progressed, the concentrations of lactic acid and acetic acid of the three crops increased and lactic acid proportion became higher in the order of sorghum-sudangrass hybrid, corn, and proso millet. Overall, the shorter, fast-growing proso millet comparing with corn and sorghum-sudangrass hybrid makes this forage crop an alternative option, particularly in areas where agricultural inputs are limited. However, additional research is needed to evaluate the efficacy of viable strategies such as chemical additives or microbial inoculants to minimize ammonia-nitrogen formation and DM loss during ensiling.

• Membrane Journal
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• v.32 no.5
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• pp.292-303
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• 2022

An eco-friendly energy conversion device without the emission of pollutants has gained much attention due to the rapid use of fossil fuels inducing carbon dioxide emissions ever since the first industrial revolution in the 18th century. Polymer electrolyte membrane fuel cells (PEMFCs) that can produce water during the reaction without the emission of carbon dioxide are promising devices for automotive and residential applications. As a key component of PEMFCs, polymer electrolyte membranes (PEMs) need to have high proton conductivity and physicochemical stability during the operation. Currently, perfluorinated sulfonic acid-based PEMs (PFSA-PEMs) have been commercialized and utilized in PEMFC systems. Although the PFSA-PEMs are found to meet these criteria, there is an ongoing need to improve these further, to be useful in practical PEMFC operation. In addition, the well-known drawbacks of PFSA-PEMs including low glass transition temperature and high gas crossover need to be improved. Therefore, this review focused on recent trends in the development of high-performance PFSA-PEMs in three different ways. First, control of the side chain of PFSA copolymers can effectively improve the proton conductivity and thermal stability by increasing the ion exchange capacity and polymer crystallinity. Second, the development of composite-type PFSA-PEMs is an effective way to improve proton conductivity and physical stability by incorporating organic/inorganic additives. Finally, the incorporation of porous substrates is also a promising way to develop a thin pore-filling membrane showing low membrane resistance and outstanding durability.