• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.8
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• pp.1771-1776
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• 2011

In this paper, as an attempt to improve the preparation conditions of $YBa_2Cu_3Ox$ superconducting bulk samples, the properties of $YBa_2Cu_3Ox$ superconductor depending on the particle size of YBCO powder and $BaPbO_3$ as an additive have been investigated, and a study on the effects of additive to the density, grain alignment, and porosity of samples that affect the critical current of superconductor has been performed. In order to prepare superconductor, $YBa_2Cu_3Ox$ powder synthesized by sol-gel method, showing a size distribution of 0.2~1 ${\mu}m$ was used. The $BaPbO_3$ added to promote grain growth and to decrease porosities and weak links between grain boundaries of $YBa_2Cu_3Ox$ superconductors. In the samples prepared by sol-gel synthesized powder with 10, 20, and 30 wt% conductive $BaPbO_3$ additives, the sample with 20 wt% $BaPbO_3$ obtained the highest critical current of 4.74 A, showing 20 wt% higher critical current than that with solid state synthesized powder.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.2
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• pp.84-95
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• 2014

Recently, as a variety of techniques of CMF (Compressed media filter) that has advantages of high porosity and compressibility have been developed in the U.S. and Japan. Therefore, the interest of intensive wastewater treatment using CMF has grown. This study examined the feasibility of CMF with varying sewage water quality to determine the optimum operating conditions. A preliminary tracer test that investigated the filtering process under various compression and flow rate conditions was performed. In a high compression condition, different porosities were applied to each depth of the column. Therefore, a distinct difference between a theoretical value and results of tracer test was observed. For the TSS (Total suspended solid) removal and particle size distribution of CMF for pre-treatment water under the various compression conditions, the compression ratio of 30 percent as the optimal condition showed greater than 70% removal efficiency. In addition, the compression ratio of >15% was required to remove small-sized particles. Also, an additional process such as coagulation is necessary to increase the removal efficiency for < $10{\mu}m$ particles, since these small particles significantly influence the effluent concentration. Modeling results showed that as the compression rate was increased, TSS removal efficiency in accordance with each particle size in the initial filtration was noticeably observed. The modeling results according to the depth of column targeting $10{\mu}m$ particles having the largest percentage in particle size distribution showed that 150-300 mm in filter media layer was the most active with respect to the filtering.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06b
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• pp.231-237
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• 2006

Grease barrier food containers are commonly used for packaging of fast food, cooked food, and food in general. Greaseproofing is also used for certificate paper and label paper etc. Different pulp raw materials, due to their different fiber morphology and chemical compositions, produce papers of varying characteristics. We used optical photomicroscopy and fiber analysis data to evaluate fiber morphology and traits under various beating conditions in order to understand which pulp raw materials produced superior greaseproofing property when a fluorinated greaseproofing agent was added internally. The experiment studied 9 species of pulps, including 2 softwood (northern pine and radiata pine) bleached kraft pulps which were beaten to 550 and 350 mL CSF, respectively; 3 hardwoods (eucalypts, acacia, mixed Indonesian hardwoods) bleached kraft pulps which were beaten to 450 and 250 mL CSF, respectively; and nonwood fibers of reed, bagasse, and abaca. A fluorinated greaseproofing chemical at 0.12% dosage with respect to dry pulp was added to each pulp preparation and formed handsheets. A total of 67 sets of handsheets were prepared, and their basis weights, thickness, bulks, opacities, wet opacities, air resistance, water absorption and degrees of greaseproofing were measured for an overall evaluation of pulp and freeness on greaseproofing papers. The experimental fiber length, coarseness and distribution characteristics and the greaseproofing results suggest that softwood pulps (radiate pine > northern pine) were superior to hardwood pulps (eucalypts > acacia > mixed Indonesian hardwoods). The unbeaten pulps gave papers with high porosities and nearly devoid of greaseproofing property. Greaseproofing is proportional to air resistance. Among the nonwood fibers, bagasse had the best greaseproofing property, followed by reed and abaca was the poorest. With regards to waterproofing property, hardwood pulps (mixed Indonesian hardwoods > acacia > eucalypts) were better than softwood pulps (northern pine > radiate pine). Among the Nonwood fibers, reed had the highest waterproofing property, and it was followed by abaca, while bagasse had the poorest waterproofing characteristic. In summary, bleached kraft northern pine, eucalypts and reed pulps were best suited for making greaseproofing papers, Freeness of the pulps should be kept at $200{\sim}280mL$ CSF for optimal performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.298-302
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• 2008

This study was carried out to evaluate brazing characteristics of the braze joint between superhard alloy particles and carbon steel. Two types of insert metals that made by mechanical alloying process were selected for this study. One is composed of Cu, Zn and Ag(MIM-1) and the other one is composed of Cu, Zn, Ag and Cd.(MIM-2) The chemical compositions of these insert metals were similar to AWS BAg-20 and BAg-2a system. And the commercial insert metals(CIM-1, CIM-2) were also evaluated for the comparative study. The characterization of the insert metals were conducted by wettability tests, shear tensile test and microstructural analyses. The results indicated that wettability tests displayed that MIM-1 and CIM-1 insert metals had the larger wetting angle than MIM-2 and CIM-2 and the wetting angle of the MIM-1 showed higher value than that of CIM-1. However these values are less than $25^{\circ}$ that is recommended for standard value for usual insert metals. The highest value of shear tensile tests was obtained from the brazed joint that made by MIN-1 and the value was $2.29{\times}10^2MPa$. This value is appeared to be higher or same as the commercial insert metals. The microstructures of the inserts metals were composed of Cu-rich proeutectic structure for matrix and Ag-rich eutectic structure. The braze joint between superhard alloy particles and carbon steel produced by the MIM-1(Ag-Cu-Zn) system showed sound joint showing stable microstructures. However there was also some porosities at the interface.

• Korean Journal of Soil Science and Fertilizer
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• v.11 no.2
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• pp.61-66
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• 1979

This experiment was conducted to find out the simple and economical method to improve physical properties of the soil that was very poor for the establishment of orchard. Jeonnam clay loam soils distributed mainly on rolling and hill side slope, were treated with the explosion of two kinds of dynamite at the depth of 1 m. The change of physical properties was investigated vertically and horizontally after soil profile had settled to some extent. The results were summarized as : 1. The original soil was very high in bulk density and soil hardness. Total porosity and aeration porosities were lower than critical level providing root elongation. It was more apparent in the subsoil than in the surface soil. 2. It was recognized that soil mass destruction and cracking by dynamite explosion decreased soil bulk density and soil hardness and increased porosity, especially non-capillary pores. 3. Effective radius of the improved physical properties by explosion with two dynamites was 100cm at 60cm depth and 30cm at 80cm depth. But with the use of three dynamites it was 100cm at 80cm depth. 4. It was thought that soil mass destruction and cracking caused by explosion was uneven in the two dynamites, and three dynamites was more effective to improve physical properties evenly. 5. With the use of two dynamites, Ammonium explosive was superior to gelatin dynamite.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.323-336
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• 2011

The hydro-mechanical behavior of the Earth's crust is strongly dependent on the fractional volume and geometrical structure of effective pore spaces. This study aims to understand the characteristics of pores using electrical impedance. We measured the electric impedance of core samples (diameter, 38-50 mm; length, 70-100 mm) of three types of granite (Hwangdeung, Pocheon, and Yangsan) and two types of sandstone (Boryung and Berea) with different porosities and pore structures, after saturation with saline water of varying salinities. The results show that resistance decreases but capacitance increases with increasing salinity of the pore fluid. For a given salinity, the resistivity and formation factor are reduced with increasing porosity of the rocks, and the capacitance increases. Berea sandstone shows anisotropy in resistance, tortuosity, and cementation factor, with these factors being highest normal to bedding planes. This result indicates that the connectivity of pores is weakest normal to bedding. In conclusion, the electrical characteristics of the tested samples are related not only to their porosity but also to the pore geometry.

• Journal of the Korean Geotechnical Society
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• v.31 no.6
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• pp.45-58
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• 2015

The aim of this study is to suggest a semi-empirical equation for estimating the hydraulic conductivity of sands using geoelectrical measurements technique. The suggested formula is based on the original Kozeny-Carman equation; therefore varying factors affecting the Kozeny-Carman equation were selected as the testing variables, and six different sands with varying particle sizes and particle shapes were used as the testing materials in this study. To measure both hydraulic and electrical conductivities, a series of constant head permeameter tests equipped with the four electrodes conductivity probe was conducted. Test results reveal that the effects of both pore water conductivity and flow rate in relation between hydraulic conductivity and formation factor (=pore water conductivity / measused conductivity of soil) of tested materials are negligible. However, because the variations of hydraulic conductivity of the tested sands according to particle sizes are significant, the estimated hydraulic conductivity using the formation factor varies with particle sizes. The overall comparison between the measured hydraulic conductivity and the estimated hydraulic conductivity using the suggested formula shows a good agreement, and the variation of hydraulic conductivity with varying Archie's m exponents is smaller compared with varying porosities.

• Horticultural Science & Technology
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• v.29 no.2
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• pp.95-101
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• 2011

The influence of physicochemical properties of root substrates on the growth of mother plants and occurrence of daughter plants in 'Seolhyang' strawberry propagation were investigated through plastic bag cultivation. Six different formulations of root substrates were coir dust + perlite (5:5, A), coir dust + perlite (6:4, B), coir dust + perlite (7:3, C), coir dust + coconut chip (7:3, D), coir dust + coconut chip (6:4, E), and peatmoss + vermiculite (5:5, v/v; F). The total porosities (TP) and container capacities (CC) of all root substrates were higher than 85% and 55%, respectively, indicating that all substrates were in the acceptable range. But the TP and CC of F substrate were 91.5% and 60%, respectively, which were the highest among the root substrates tested. In the soil chemical properties analyzed before planting and after harvesting of 'Seolhyang' strawberry mother plants, the root substrates of A, B, C, and F had higher electrical conductivity and $NO_3$-N concentrations than those of D and F. The root substrates of A, B, C, and F had heavier runner fresh and dry weights, longer runner lengths, and more daughter plant occurrence than those of D and F. The treatment F had higher tissue N content than any other treatments at 120 days after the transplanting of 'Seolhyang' strawberry and statistical differences were not observed among remained 5 substrates. The treatment of F also had the higher tissue contents of other nutrients except N analyzed at 120 days after transplanting. These results indicated that soil chemical properties rather than physical properties severely influenced the growth of runners and occurrence of daughter plants.

• International Journal of Advanced Culture Technology
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• v.3 no.1
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• pp.21-30
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• 2015

Ceramic foams are prepared as positive images corresponding to a plastic foam structure which exhibits high porosities (85-90%). This structure makes the ceramic foams attractive as a catalyst in a dry reforming process, because it could reduce a high pressure drop problem. This problem causes low mass and heat transfers in the process. Furthermore, the reactants would shortly contact to catalyst surface, thus low conversion could occur. Therefore, this research addressed the preparation of dry reforming catalysts using a sol-gel catalyst preparation via a polymeric sponge method. The specific objectives of this work are to investigate the effects of polymer foam structure (such as porosity, pore sizes, and cell characteristics) on a catalyst performance and to observe the influences of catalyst preparation parameters to yield a replica of the original structure of polymeric foam. To accomplish these objectives industrial waste foams, polyurethane (PU) and polyvinyl alcohol (PVA) foams, were used as a polymeric template. Results indicated that the porosity of the polyurethane and polyvinyl alcohol foams were about 99% and 97%. Their average cell sizes were approximate 200 and 50 micrometres, respectively. The cell characteristics of polymer foams exhibited the character of a high permeability material that can be able to dip with ceramic slurry, which was synthesized with various viscosities, during a catalyst preparation step. Next, morphology of ceramic foams was explored using scanning electron microscopy (SEM), and catalyst properties, such as; temperature profile of catalyst reduction, metal dispersion, and surface area, were also characterized by $H_2-TPR$ and $H_2-TPD$ techniques, and BET, respectively. From the results, it was found that metal-particle dispersion was relatively high about 5.89%, whereas the surface area of ceramic foam catalysts was $64.52m^2/g$. Finally, the catalytic behaviour toward hydrogen production through the dry reforming of methane using a fixed-bed reactor was evaluated under certain operating conditions. The approaches from this research provide a direction for further improvement of marketable environmental friendly catalyst production.

• Macromolecular Research
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• v.10 no.3
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• pp.158-167
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• 2002

In order to endow with new bioactive functionality from small intestine submucosa (SIS) powder as natural source to poly (L-lactide) (PLA) and poly (lactide-co-glycolide) (PLGA) synthetic biodegradable polymer, porous SIS/PLA and SIS/PLGA as natural/synthetic composite scaffolds were prepared by means of the solvent casting/salt leaching methods for the possibility of the application of tissue engineered bone and cartilage. A uniform distribution of good interconnected pores from the surface to core region was observed the pore size of 40~500 ${\mu}{\textrm}{m}$ independent with SIS amount using the solvent casting/salt leaching method. Porosities, specific pore areas as well as pore size distribution also were almost same. After the fabrication of SIS/PLA hybrid scaffolds, the wetting properties was greatly enhanced resulting in more uniform cell seeding and distribution. Five groups as PGA non-woven mesh without glutaraldehyde (GA) treatment, PLA scaffold without or with GA treatment, and SIS/PLA (Code No.3 ; 1 : 12 of salt content, (0.4 : 1 of SIS content, and 144 ${\mu}{\textrm}{m}$ of median pore size) without or with GA treatment were implanted into the back of nude mouse to observe the effect of SIS on the induction of cells proliferation by hematoxylin and eosin, and von Kossa staining for 8 weeks. It was observed that the effect of SIS/PLA scaffolds with GA treatment on bone induction are stronger than PLA scaffolds, that is to say, in the order of PLA/SIS scaffolds with GA treatment > PLA/SIS scaffolds without GA treatment > PGA nonwoven > PLA scaffolds only with GA treatment = PLA scaffolds only without GA treatment for the osteoinduction activity. The possible explanations are (1) many kinds of secreted, circulating, and extracellular matrix-bound growth factors from SIS to significantly affect critical processes of tissue development and differentiation, (2) the exposure of SIS to GA resulted in significantly calcification, and (3) peri-implant fibrosis due to covalent bonding between collagen molecule by crosslinking reaction. In conclusion, it seems that SIS plays an important role for bone induction in SIS/PLA scaffolds for the application of tissue engineering area.