• Electrical & Electronic Materials
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• v.10 no.5
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• pp.440-446
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• 1997

This research has been performed for the fabrication of high quality ferrite plastic magnet. The magnetic properties of S $r_{5.9}$F $e_2$ $O_3$ ferrite bonded magnets by injection moulding with a variety of applied magnetic field were investigated. 0.3wt% CaCO3, 0.2wt% $SiO_2$, 0.5wt% $Al_2$ $O_3$and 0.5wt% N $a_2$ $SiO_3$are added in order to improve the magnetic properties of Sr-ferrite plastic magnets during the powder fabrication. For carbon coating on chemical compound specimen, 5wt% polyvinyl alcohol is added, and then calcinated under $N_2$ environment of 12$25^{\circ}C$. The particle size is distributed from 0.9~1.2${\mu}{\textrm}{m}$ which approximates to the single domain. The obtained Sr ferrite powder is well mixed with silane coupling and calcium stearate of 1wt%. Nest, the specimen is pelleted after kneading each of them with polyamidel2 as a binder. When the temperature of injection and mould were 25$0^{\circ}C$ and 8$0^{\circ}C$ respectively at injection pressure of 200kgf/$\textrm{cm}^2$, the degree of orientation was 85.3% under the applied magnetic field of 12kOe. As the results, when the packing density of Sr ferrite powder was 90wt%, the magnetic properties of Sr ferrite bonded magnet were follows : $_{B}$ $H_{c}$=2.41kOe, Br=3.1kG, (BH)$_{max}$=2.21MgOe. Especially, the Sr-ferrite bonded magnet with 10wt% N $d_2$F $e_{14}$B additive were as follows : $_{B}$ $H_{c}$=2.57kOe, Br=3.14kG and (BH)$_{max}$=2.39MGOe.GOe.GOe.GOe.e.

• Korean Journal of Pharmacognosy
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• v.25 no.3
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• pp.209-213
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• 1994

For the investigation of medicinal resources from Taraxacum species, the studies were carried out to evaluate the pharmaco-constituents in the aerial part of Taroxacum hallaisanensis, an endemic plant of Korea. From BuOH fraction of the MeOH extract, compound 1 (protocatechuic acid, $C_7H_6O_4,\;3,4-dihydroxy\;benzoic\;acid)$, compound 2 $[C_{22}H_{31}O_6,\;luteolin-7-O-{\alpha}-_L-rhamnopyranosyl(1{\rightarrow}6)-{\beta}-_D-glucopyranoside]$, and compound 3 $[C_{15}H_{20}O_6,\;luteolin-7-O-{\beta}-_D-glucopyranoside]$ were isolated by column chromatographic separation using polyamide and ODS-gel. The structures were elucidated by means of physico-chemical evidences($^1H-NMR,\;{12}^C-NMR$, IR, EI-Mass, FAB-Mass and GC).

• Korean Journal of Human Ecology
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• v.11 no.4
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• pp.391-400
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• 2002

This study was intended to research the dyeing with natural walnut hull extracts over cotton, flax, rayon, wool, nylon and silk. We studied the dyeing conditions and mordant effect, and observed dyeability. The result are as follows: 1. In the dyeability with natural walnut hull extracts, protein and polyamide fiber has more dye uptake rather than cellulose fiber. 2. The optimum condition in the dyeing with natural walnut hull extracts was at $90^{\circ}C$, 12%(o.w.b) concentration in 90 mins. 3. In the case of the dyeability by repeated dyeing number, the dyeability of good dyeability fiber is improved in the first or second dyeing, but that of bad dyebality fiber is improved when it is dyed more repeatedly. 4. In the dyeablity treated with mordants, Al, Sn, and Mg don't have any differences, but Cu and Fe have some difference. The color of Fe mordant is green and the color of Cu mordant is blue. 5. In the case of the color fastness with mordant treatment, nylon is better than silk and wool in color fastness to washing but silk is better than nylon and wool in color fastness to light.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.7-12
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• 2004

Desalination system of revers osmosis(RO) membrane has been proven to be the most economical not only for the desalination of water containing salts, but also for the concentration of solute. RO membranes were traditionally made of inorganic polymers such. as cellulose acetate(CA), Polyamide(PA). To retain more minerals in deep ocean water, a new hybrid membrane composed of tourmaline film as organic material onto inorganic layer of CA polymer in asymmetric structure was developed for RO membrane process. The performance tests were carried out in the permeability of pure water and the rejection of NaCl solution to evaluate the adaptability for DOW desalination. The results of these basic tests show possibility to apply the new hybrid RO membrane for the desalination with function control.

• Food Engineering Progress
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• v.23 no.1
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• pp.55-61
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• 2019

For the vessel export of strawberries, modified atmosphere package (MAP) using polyamide (PA) film and linear low density polyethylene (LLDPE) film was investigated to extend the shelf life of strawberries. Because the temperature and relative humidity changes of the MAP were lower than the changes of the control, the weight loss of the MAP were lower than that of the control. The low oxygen level and high carbon dioxide level were effective to decrease the fungal decay rate and to increase the hardness of strawberries. The Hunter's color differences before and after storage showed no distinct difference between the MAP and the control. The lightness had a tendency to decrease while the redness increased. There were no significant changes of the soluble solids during the storage. The shelf life of strawberries could be extended to 16 days using the MAP considering the weight loss and the fungal decay rate. Thus, this MAP method using PA film and LLDPE film was effective to extend the shelf life of strawberries.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.527-533
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• 2017

As the clothing industry has advanced, dyeing technologies using various dyes have been developed. In recent years, interest in natural pigments has been increasing because of the negative impact of synthetic pigment on human health; therefore, development and application of microbial pigments is demanded. In this study, the dyeing effects on multifiber fabrics and biological activity were assessed using violet natural pigment from the marine bacterium, Microbulbifer sp. PPB12. The violet pigment produced by cultivation of Microbulbifer sp. PPB12 using Marine broth 2216 for 3 days was extracted using ethanol. Once dissolved in 20% ethanol, the violet pigment could be used to dye bleached cotton, diacetate, and especially polyamide. The optimal temperature, time, pH, and bath ratio under the dyeing conditions were $80^{\circ}C-90^{\circ}C$, more than 1 hour, pH 4-6, and 1:25, respectively. The mordant treatment was more suitable for color expression when $Na_2SO_4$ was used after 10 minutes of dyeing, but no significant difference was observed from untreated samples. The violet pigment also showed antibacterial activity against B. subtilis. The results of the present study indicate that the marine bacterial pigment could be an alternative for textile dyeing as a natural dye with antibacterial activity.

• Korean Journal of Construction Engineering and Management
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• v.21 no.6
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• pp.95-102
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• 2020

The number of use cases in machinery, aviation, and other industries that manufacture precise parts is increasing, and the construction industry is also increasingly using 3D printing technology. Although various materials for 3D printing are currently being developed and utilized, 3D printing manufacturing has a problem that the mechanical properties of the product may change when compared with conventional manufacturing methods such as injection and molding. This paper verifies the effect of the printing orientation on the mechanical properties of the product in the manufacture of PA12 material and providing basic data on the practical use of the materials as building subsidiary materials and structural materials. The results of the experiment showed that the product printed in the orientation of 0° showed the lowest overall strength and elongation rate, and the product printed in the orientation of 45° showed the highest figure. Overall, tensile strength and yield strength increased between 0° and 45°, and tended to decrease somewhat at 45° to 90°.

• The Journal of Advanced Prosthodontics
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• v.9 no.6
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• pp.453-462
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• 2017

PURPOSE. The purpose of this study was to investigate the in vitro cytotoxicity of thermoplastic denture base resins and to identify the possible adverse effects of these resins on oral keratinocytes in response to hot water/ food intake. MATERIALS AND METHODS. Six dental thermoplastic resin materials were evaluated: three polyamide materials (Smile tone, ST; Valplast, VP; and Luciton FRS, LF), two acrylic materials (Acrytone, AT; and Acryshot, AS), and one polypropylene resin material (Unigum, UG). One heat-polymerized acrylic resin (Vertex RS, RS) was chosen for comparison. After obtaining extracts from specimens of the denture resin materials (${\phi}=10$ mm and d=2 mm) under different extraction conditions ($37^{\circ}C$ for 24 hours, $70^{\circ}C$ for 24 hours, and $121^{\circ}C$ for 1 hour), the extracts (50%) or serial dilutions (25%, 12.5%, and 6.25%) in distilled water were co-cultured for 24 hours with immortalized human oral keratinocytes (IHOKs) or mouse fibroblasts (L929s) for the cytotoxicity assay described in ISO 10993. RESULTS. Greater than 70% viability was detected under all test conditions. Significantly lower IHOK and L929 viability was detected in the 50% extract from the VP ($70^{\circ}C$) and AT ($121^{\circ}C$) samples (P<.05), but only L929 showed reduced viability in the 50% and 25% extract from LF ($37^{\circ}C$) (P<.05). CONCLUSION. Extracts obtained from six materials under different extraction conditions ($37^{\circ}C$, $70^{\circ}C$, and $121^{\circ}C$) did not exhibit severe cytotoxicity (less than 70% viability), although their potential risk to oral mucosa at high temperatures should not be ignored.

• Composites Research
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• v.12 no.6
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• pp.53-64
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• 1999

Microstructural morphology and bending strengths of moulded composites of thermotropic liquid crystalline polymer(LCP) and polyamide 6 (PA6) have been studied as a function of epoxy fraction. Injection-moulding of a composite plaque at a temperature below the melting point of the LCP fibrils generated a multi-layered structure: the surface skin layer with thickness of $65\;-\;120{\mu\textrm{m}}$ exhibiting a transverse orientation; the sub-skin layer with an orientation in the flow direction; the core layer with arc-curved flow patterns. The plaques containing epoxy 4.8vol% exhibited superior bending strength and large fracture strain. With an increase of epoxy fraction equal to and beyond 4.8vol%, geometry of LCP domains was changed from fibrillar shape to lamella-like one, which caused a shear-mode fracture. An analysis of the bending strength of the composite plaques by using a symmetric layered model beam suggested that addition of epoxy component altered not only the microstructural geometry but also the elastic moduli and strengths of the respective layers.

• Membrane Journal
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• v.12 no.3
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• pp.182-191
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• 2002

Polyamide reverse osmosis (RO) membrane with thin film composite structure was commercialized for seawater desalination process. Recently, it has been reported that some RO processes for high pressure and recovery leads to reducing in energy cost and pretreatment scale compared with earlier process. The development of energy recovery, pumping device and RO elements with high pressure and rejection made high pressure and recovery process possible. In this study, permeation properties of commercialized seawater RO membrane were investigated under the condition of high pressure and recovery. In the RO sheet membrane test 3.5% NaCl of synthetic seawater was used. The synthetic seawater contained only sodium chloride. In the RO module test, natural seawater was used at Happo Bay, Masan city. As the results, RO membrane with high durability of pressure was better than that with high rejection of seawater for high pressure and recovery process. Seawater rejection of high concentrate tends to be improved by high pressure operation.