• Journal of Korean Society of Environmental Engineers
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• v.30 no.4
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• pp.409-414
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• 2008

Porous carbon electrode for electrosorption was prepared by a wet phase inversion method. Carbon slurry that was a mixture of activated carbon powder(ACP) and PVdF solution was cast directly upon a graphite sheet by means of a casting knife. Porous carbon electrodes were fabricated by immersing the cast film in pure water as a non solvent. Physical and electrochemical properties of carbon electrodes prepared with various ACP contents(50.0, 75.0, 83.3, 87.5, 90.0 wt %). From the SEM images we can verify that the electrode was porous. The average pore sizes determined for the electrodes fabricated with various ACP contents ranged from 72.7 to 86.4 nm and the size decreased as the ACP content increased. The electrochemical properties were characterized by cyclic voltammetry(CV) method. All of the voltammograms showed typical behavior of an electric double layer charging/discharging on the carbon surface. The capacitance increased with the ACP content and the values ranged from 2.18 F/cm$^2$ for 50 wt% ACP to 4.77 F/cm$^2$ for 90 wt% ACP.

• Polymer(Korea)
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• v.35 no.3
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• pp.189-195
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• 2011

The design of new bioactive scaffolds offering physiologic environment for tissue formation is an important frontier in biomaterials research. In this study, we performed compressive strength, water-uptake ability, and SEM analysis for physical property assessment of 3-D silk/PLGA scaffold, and investigated the adhesion, proliferation, phenotype maintenance, and inflammatory responses of RAW 264.7 and NIH/3T3 for cell compatibility. Scaffolds were prepared by the solvent casting/salt leaching method and their compressive strength and water-uptake ability were excellent at 20 wt% silk content. Result of cell compatibility assay showed that inflammatory responses distinctly decreased, and initial adhesion and proliferation were maximized at 20 wt% silk content. In conclusion, we suggest that silk/PLGA scaffolds may be useful to tissue engineering applications.

• Membrane Journal
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• v.25 no.5
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• pp.406-414
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• 2015

In this study, partially fluorinated cation exchange membranes were prepared by direct sulfonation of Poly(VDF-co-hexafluoropropylene) copolymers (PVDF-co-HFP) followed by a casting method for application in the Membrane capacitive deionization (MCDI). The structure of sulfonated PVDF-co-HFP (SPVDF) was confirmed by Fourier-transform infrared (FT-IR) and $^1H$ Nuclear magnetic resonance ($^1H$ NMR) analysis. For quantitative analysis of the chemical composition, the X-ray Photoelectron Spectroscopy (XPS) was used. The membrane properties such as water uptake, ion exchange capacity and electrical resistance were measured. It was suggested that the optimum direct sulfonation condition of PVDF-co-HFP ion exchange membranes was $60^{\circ}C$ and 7 hours for temperature and duration of sulfonation, respectively. The water uptake of the SPVDF ion exchange membrane was 21.5%. The ion exchange capacity and electrical resistance were 0.89 meq/g and $3.70{\Omega}{\cdot}cm^2$, respectively. It was investigated that if it is feasible to apply these membranes in MCDI at various cell potentials (0.9~1.5 V) and initial flow rates (10~40 mL/min). In the MCDI process, the maximum salt removal rate was 62.5% in repeated absorption-desorption cycles.

• Polymer(Korea)
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• v.32 no.5
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• pp.403-408
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• 2008

Keratin is the major structural fibrous protein providing outer covering such as wool, hair, and nail. Keratin is useful as natural protein. We developed the keratin loaded poly(L-lactide-co-glycolide) (PLGA) scaffolds (keratin/PLGA) for the possibility of the application of the tissue engineering using bone marrow mesenchymal (BMSCs). Keratin/PLGA (contents 0%, 10%, 20% and 50% of PLGA weight) scaffolds were prepared by solvent casting/salt leaching method. We characterized porosity, wettability, and water uptake ability, DSC of keratin/PLGA scaffold. We seeded BMSCs isolated from the femurs of rat into the inner core of the hybrid scaffold. Celluar viability were assayed by 3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyl-tetrazolium bromide (MTT) test. We confirmed that keratin/PLGA scaffold is hydrophilic by wettability, and water uptake ability measurement results. In MTT assay results, cell viability in scaffolds impregnated 10 and 20 wt% of keratin were higher than other scaffolds. In conclusion, we suggest that keratin/PLGA scaffold may be useful to tissue engineering using BMSCs.

• Korean Journal of Ecology and Environment
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• v.38 no.4 s.114
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• pp.482-493
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• 2005

The objective of this research was to evaluate an sampling effect of fish species and individual number on sampling techniques of electrofishing and conventional capture methods of cast net and kick net in 38 stream sites sampled during June - September, 2005. For the study, sampling gears were categorized as three types of electrofishing method (EM), conventional sampling technique (CM), and the combined technique (CT) of the electrofishing and the conventional method to compare statistical differences. Major differences of species composition between the CM and EM method were found in some benthic species of Misgurnus mizolepis and Iksookimia koreensis along with lithophilic species of Pungtungia herzi. These species were predominated in the EM rather than the CM, indicating that conventional sampling can underestimate the abundance of benthic or lithophilic species. In contrast ,individual number of typical water column species such as Zacco platypus and Zacco temmincki were more sampled by the CM, so that these fish populations were community overestimated. Also, t-tests on the types of sampling gear from various watersheds of Chogang Stream, Yugu Stream, Daejeon Stream, and Gap Stream showed that total individual numbers and species number in each stream were significantly (t values = 2.806-6.896, p values<0.05, n = 5-14) greater in the CT than the CM. Similar statistical significance (p<1.001, n = (10-24) on sampling seasons were observed during the monsoon and postmonsoon. These results indicate that if the electrofishing is not added to the conventional gears, the abundance of fish population and community can be underestimated and some benthic or lithophilic species may be excluded from the analysis, resulting in overall errors including sampling, fish fauna, and final judgement of community abundance. Overall our results strongly suggest that new application of electrofishing method along with the conventional sampling gears reduce sampling bias on underestimation of the real fish populations and communities.

• Journal of the Korean Society of Costume
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• v.44
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• pp.181-199
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• 1999

The industry of modern clothing has deviated from the overflow of commercialism and the standardization and nowadays is going toward pursuing art, creativity, and high added value. This trend brings the return of the natural materials from the synthetic textiles and increases the value of old and handmade fabrics. Finally, the handmade-paper, which is a natural material, comes to be reconsidered as a new material for the clothing. Therefore, as the natural materials and the manufacture of handmade clothing are rising again, the qualitative improvement and globalization of clothing industry should be first realized through the developments of creative and various clothing materials and new expressing techniques. The above investigation and study have been synthesized and analyzed as follows: First, through the study on the origin of the paper clothing, its historical background and the process of its development, we've learned these two facts following : the paper clothing of the East in the past mostly had practiced meanings. On the other hand, in the West it had meanings which were raised the artist's emotions and beauty-consciousness to the artistic level by the various kinds of expressing methods. Second, handmade-paper was manufactured by the embedding method, which mixed mulberry pulp, gauze, corn, hair, sisal, silk and so on. It was found that handmade-paper had the affluent and proper texture as the clothing material and was be able to control the clarity through the variation of thickness. It was also confirmed that the creative and original texture with hand-worked molding beauty was obtained by the use of handmade-paper. Third, when the handmade-paper is used, the molding beauty of plane, relievo, and solid can be freely pursued, and various and effective molding conformation can be constructed by the effect of superposition and repetition. Also, because the maximum discretion from the various optional manufacturing methods is allowed, the molding beauty can be maximized when the clothes are manufactured with handmade-paper. Fourth, the gauze with strong drape was combined to overcome the stiffness and the tearing of the paper. As a result, the durability and the wearability of the paper were strengthened and thus the thus the applications as the clothing material were enlarged. In conclusion, in order to enhance the value, creativity, practicality, and artistic sense of the design for modern clothing, the clothes made of handmade-paper should be more studied. Moreover, for the generalization of paper clothes, the studies on the development of practical paper with paper with water resistance, post-treatment after dyeing, flexibility, and durability should be done. I really hope that this study will be the motive to provoke the possibility of handmade-paper as new clothing material in not only practical sense but also artistic sense.

• Journal of Powder Materials
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• v.17 no.4
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• pp.312-318
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• 2010

High speed steels (HSS) were used as cutting tools and wear parts, because of high strength, wear resistance, and hardness together with an appreciable toughness and fatigue resistance. Conventional manufacturing process for production of components with HSS was used by casting. The powder metallurgy techniques were currently developed due to second phase segregation of conventional process. The powder injection molding method (PIM) was received attention owing to shape without additional processes. The experimental specimens were manufactured with T42 HSS powders (59 vol%) and polymer (41 vol%). The metal powders were prealloyed water-atomised T42 HSS. The green parts were solvent debinded in normal n-Hexane at $60^{\circ}C$ for 24 hours and thermal debinded at $N_2-H_2$ mixed gas atmosphere for 14 hours. Specimens were sintered in $N_2$, $H_2$ gas atmosphere and vacuum condition between 1200 and $1320^{\circ}C$. In result, polymer degradation temperatures about optimum conditions were found at $250^{\circ}C$ and $480^{\circ}C$. After sintering at $N_2$ gas atmosphere, maximum hardness of 310Hv was observed at $1280^{\circ}C$. Fine and well dispersed carbide were observed at this condition. But relative density was under 90%. When sintering at $H_2$ gas atmosphere, relative density was observed to 94.5% at $1200^{\circ}C$. However, the low hardness was obtained due to decarbonization by hydrogen. In case of sintering at the vacuum of $10^{-5}$ torr at temperature of $1240^{\circ}C$, full density and 550Hv hardness were obtained without precipitation of MC and $M_6C$ in grain boundary.

• Journal of the Korean Applied Science and Technology
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• v.38 no.3
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• pp.903-913
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• 2021

Three-type PVC membranes denoted by AEM-1, AEM-2, and AEM-3 with a cross-linked anion-exchange group were prepared by substitution reaction of PVC with triethyldiamine (TEDA), 1,4-dimethylpiperazine (DMP), and 1,4-bis(imidazol-1-ylmethyl)benzene (BIB) in cyclohexanone, respectively. We confirmed the successful preparation of the AEM-1, AEM-2, and AEM-3 via ionic conductivity (S/cm), water uptake (%), contact angle, ion-exchange capacity (m_eq/g), thermal properties, SEM and XPS analysis, respectively. The electrochemical capacitor experiments using PVC membrane with cross-linked anion-exchange group in organic electrolytes were performed. The prepared AEM-1, AEM-2 AEM-3 have a good stability by charge and discharge performance in organic electrolyte. As a result, the AEM-2 and AEM-3 membrane based on PVC prepared by the solvent casting method after substituent reaction is suitable for the use as a separator in organic electrochemical capacitor (supercapacitor).

• Membrane Journal
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• v.21 no.2
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• pp.118-126
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• 2011

A method of light pre-irradiation, one of methods modifying hydrophobic surface to hydrophilic surface in a membrane, was proposed to overcome the drawback of previous methods such as blending, chemical treatment and post-irradiation, Process of membrane preparation in the study was comprised of 4 parts as follows: firstly process of precursor preparation to introduce hydrophilic nature under atmosphere and aqueous vapor by irradiating electron beam (EB), secondly process of dope solution preparation to cast on non-woven fabrics, thirdly process of casting to prepare membrane and finally process of coagulation in non-solvent to form porous structure. The merit of this method might show simple process as well as homogenous modification compared to previous methods. To carry it out, precursor was prepared by irradiating EB to powder PVDF at 75~125 K Gray dose. Precursor prepared was analyzed by FTIR, EDS and DSC to confirm the introduction of hydrophilic function and its mechanism. From their results, it was inferred I conformed that hydrophilic function was hydroxy1 and it was introduced by dehydrozenation. Hydrophilicity of membranes prepared was evaluated by contact angle (pristine PVDF : $62^{\circ}$, 125 K Gray-PVDF$13^{\circ}$). Porosity was evaluated by mercury intrusion method, simultaneously morpholoy and surface pore size were observed by SEM phothographs. The result showed the trend that more dose of EB led to smaller pore size and to lower porosity (pristine PVDF : 82%, 125 K Gray-PVDF : 63%). Trend of water permeability was similar to result above (pristine PVDF : 892 LMH, 125 K Gray-PVDF : 355 LMH).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.2
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• pp.151-156
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• 1984

The Chili fish, one of the most common species of the freshwater fishes, is distributed in the river basins of the western coast of Korea. However, any studies on this fish, especially its development or life history, have not been made so far. The authors, therefore, carried out an experiment to reveal some characteristics of egg develoment and fry in this fish. For accomplshing this study, we caught some adult Chili fish by means of a casting net at raceway in the vicinity of Kunsan in June and July, 1983; then, we injected 0. 1 cc Gonadotrophic hormone 1,000 unit solution (Puberogen) in order to induce the spawning on the abdominal cavity of male and female respectively, Approximately 12 hours after injection, the artificially fertilized eggs by using of the dry method and the naturally fertilized eggs were observed simultaneously in the aquarium ($30{\times}50{\times}70cm$). The fertilized eggs, in spherical shape, were sperative, demersel, adhesive nature and $1.38{\sim}1.59\;mm$ in diameter. The light yellow yolk was opaque and $1.17{\sim}l.27\;mm$ in diameter. The hatching of eggs took place at 29.5 hours after fertilization under the condition of $23.5{\sim}25.0^{\circ}C$ water temperature. Basically there were not found so many different aspects in comparison with the common species of Cyprinidae in the development process of eggs : however, there were a few noticable characteristics, that is, pigment cells, eye balls and blood circulation are invisible, or the velocity of egg development is rapid, seemed similar to the Loach's egg. Newly hatched larvae with the yolk sac (2.39 mm in size) were $3.87{\sim}3.99\;mm$ in total length and their myotome number was expressed as 28+15=43. About 20 hours after hatching, a caudal and a pectoral fin as well as an anus began to orgin. In addition, a few malanophore showed on the upper regin of the yolk sac of the larvae whose size was 4.73 mm in total length. The larvae developed about 5.02 mm in total length, and the median fin fold in the abdomen extended forward to two thirds or beyond of the yolk sac at 50 hours after hatching. Simultaneously, the eye balls and mouth also appeared. After 3 days, the yolk sac nearly disappeared, and the larvae (5.4 mm in total length) with perfect eye balls began to swim for themselves for the first time. Also, the specialization between the gill arches and the ailmentary canal, the development of each fins except dorsal fin as well as the blood circulation obviously distinguished in this stage. The larvae whose total length was 5.68 mm was very brisk: also, the development of the dorsal fin rudiment, nearly perfect formation of each organs and the function of the upper and lower jaws were noticeably observed 5 days after hatching.