• 한국식품저장유통학회지
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• 제13권6호
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• pp.681-685
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• 2006

가루녹차를 알루미늄 포장에 보관하여 $-5^{\circ}C$에서 저장시 품질관련 화학성분인 총질소, 총아미노산, 탄닌, 카페인, 엽록소, 비타민 C 및 지방산은 저장기간이 길어질수록 함량이 감소되었다. 가루녹차의 표면색상은 $-5^{\circ}C$ 저장시 a값은 저장전 -17.40에서 저장 30일 -16.69, 저장 60일 -16.20, 저장 120일 -13.69로 저장기간이 길어질수록 녹색이 감소됨을 알 수 있었다. 외관과 내질에 따른 관능평가는 저장전 93점에서 저장 60일 88점, 저장 120일 73점으로 저장기간 경과에 비례해 품질이 열악해졌다. 품질을 고려하면 $-5^{\circ}C$에서 가루녹차를 저장하는 것이 우수한 저장방법이 되리라 생각된다.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2000년도 KIASC Conference 2000 / 2000년도 학술대회 논문집
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• pp.3-5
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• 2000

Among the various processing techniques used in HTS wire fabrication, the PIP(Powder In Tube) method is currently one of the most promising for applications on an industrial scale. In this study, we have fabricated Bi-2223/Ag superconducting tapes using the modified PIT process, where several process factors were changed and improved, ie., powder packing, drawing, rolling and heat treatment. We obtained Bi-2223 tape that have high critical current, 46 a at 77.3 K, have high critical current, 46A at 77.3 K, self field although the tape was not pressed but only rolled. The critical current of 100m class long length tape was measured 21.6A at the same criterion. Besides, the critical current of Bi-2223/Ag tape was measured applying magnetic fields with different directions at various temperatures.

• 대한치과보철학회지
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• 제43권4호
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• pp.478-486
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• 2005

Statement of problem : Fracture and dimensional change of an acrylic resin denture are a rather common occurrence. Purpose : The purpose of this study was to compare differences in dimensional changes and flexural strength of separate maxillary complete dentures after immediate deflasking by injection molding and conventional compression processing. Material and method: To evaluate dimensional stability, the maxillary dentures were fabricated by using different materials and methods. Lucitone 199(Dentsply Trubyte. york, pennsylvania, USA) and Vertex(Dentimex, zeist, Netherlands) were used as materials. Compression and injection packing methods were used as processing methods. The impression surface of the dentures was measured by 3D Scann-ing System(PERCEPTRON USA) and overlapped original impression surface of the master cast. To evaluate flexural strength, resin specimens were made according to the different materials, powder/liquid ratio and processing methods. Flexural strength of the complete resin specimens (64mm$\times$10mm$\times$3.3mm) were measured by INSTRON 4467. (INSTRON, England) The data was analyzed by ANOVA, t-test and Tukey test. (p<.05 level of significance) Result: The results were as follows 1. There was no significant differences between master model and denture base for each group in overall dimensional changes. 2. Palatal area was more stable than flange or alveolar area in dimensional stability. but. there was no significant differences among each area. 3. Materials and power/liquid ratio had an effect on flexural strength. (P<.05) Especially materials was most effective. (P<.05) 4. Lucitone 199(powder/liquid ratio followed by manufacturer's direction) showed higher flexural strength than Vertex. Conclusion : Dimensional stability or flexural strength are affected by materials rather than packing techniques.

• 한국분말재료학회지
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• 제23권5호
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• pp.358-363
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• 2016

Noncontact direct-printed conductive silver patterns with an enhanced electrical resistivity are fabricated using a silver ink with a mixture of silver nanoparticles and nanoplates. The microstructure and electrical resistivity of the silver pattern are systematically investigated as a function of the mixing ratio of the nanoparticles and nanoplates. The pattern, which is fabricated using a mixture with a mixing ratio of 3(nanoparticles):7(nanoplates) and sintered at $200^{\circ}C$ shows a highly dense and well-sintered microstructure and has a resistivity of $7.60{\mu}{\Omega}{\cdot}cm$. This originates a mutual synergistic effect through a combination of the sinterability of the nanoparticles and the packing ability of the nanoplates. This is a conductive material that can be used to fabricate noncontact direct-printed conductive patterns with excellent electrical conductivity for various flexible electronics applications, including solar cells, displays, RFIDs, and sensors.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.276-279
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• 2000

When high temperature superconducting tapes is fabricated using the PIT (Powder In Tube) method, the length of HTS tapes is increased more than 500 ${\sim}$ 1,000 times of initial powder packed billet. On mechanical processing, heterogeneous properties between the ceramic superconducting core and Ag/Ag alloy sheath occur the non-uniformity deformation as like sausaging that deteriorate the critical current properties of HTS tapes. In this study, we investigated the workability of Bi-2223/Ag/Ag alloy sheath tapes fabricated by the PIT method involving a number of different mechanical processes, multi drawing and rolling. In order to obtain the high critical current density and high uniformity of Bi-2223/Ag sheath tapes, the influences of powder packing density, drawing die angle and rolling parameters were studied. We found that the roll diameter is an important variable in the rolling process, as critical current of tapes rolled using 250 mm rolls was higher than that using 150 mm rolls.

• KIEE International Transactions on Electrophysics and Applications
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• 제12C권4호
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• pp.229-235
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• 2002

The apparent volume resistivity of powders measured by both the tapping and the compressing methods was compared in this study. Factors such as applied voltage, pressure, corona charging, and so on affecting the apparent volume resistivity of polymer powders were also examined experimentally. Powders of polyacrylonitrile and Nylon 11 were mainly used. The values of the apparent resistivity of polymer powders taken by the tapping method turned out to be larger than those taken by the compressing method, which indicates that the apparent volume resistivity of polymer powders depends strongly on the measurement method. The apparent resistivity of polymer powders increased with an increase in applied voltage while it decreased with an increase in pressure, tapping time, and particle size. The influence of the moisture content of powder and corona charging on the resistivity of polymer powders is also discussed.

• Carbon letters
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• 제8권4호
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• pp.326-334
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• 2007

In this study, graphite composites were fabricated by warm press molding method to realize commercialization of PEM fuel cells. Graphite composites have been considered as alternative economic materials for bipolar plate of PEM fuel cells. Graphite powder that enables to provide electrical conductivity was selected as the main substance. The graphite powder was mixed with phenolic resin and the mixture was pressed using a warm press method. First of all, the graphite powder was pulverized with a ball mill for the dense packing of composite. As the ball milling time increases, the average size of particles decreases and the size distribution becomes narrow. This allows for improvement of the uniformity of graphite composite. However, the surface electrical resistivity of graphite composite increases as the ball milling time increases. It is due to that graphite particles with amorphous phase are generated on the surface due to the friction and collision of particles during pulverizing. We found that the contact electrical resistivity of graphite particles increases as the particle size decreases. The contact electrical resistivity of graphite powders was reduced due to high molding pressure by warm press molding. This leads to improvement of the mechanical properties of graphite composite. Hydrogen gas impermeability was measured with the graphite composite, showing a possibility of the application for bipolar plate in fuel cell. And, I-V curves of the graphite composite bipolar plate exhibit a similar performance to the graphite bipolar plate.

• 한국자기학회지
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• 제6권5호
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• pp.310-316
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• 1996

본 연구에서 인가 자장의 세기, 압출 금형의 온도 및 압출 속도가 페라이트계 이방성 압출 본드 자석의 자기적 특성에 미치는 영향을 조사하였다. 압출 본드 자석 단면에 대한 X-선 회절실험 결과 압출 금형 내의 용융 흐름에 의해 자성 분말의 자장 방향으로의 배향이 억제됨을 알 수 있었다. 압출 금형의 온도가 $20^{\circ}C$ 일 때 4 kOe의 인가자장에서 82 %의 배향도를 얻을 수 있었으며, Sr-페라이트 분말의 충전율이 50 vol%일 때 잔류자속밀도 2.2 kG인 압출 본드 자석을 제조할 수 있었다.

• 한국세라믹학회지
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• 제46권5호
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• pp.488-492
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• 2009

Porous frit-bonded SiC ceramics were successfully prepared at a temperature as low as $800^{\circ}C$ from SiC, frit, and microbeads (glass or polymer). The effects of SiC starting particle size and microbead addition on microstructure, porosity, and flexural strength were investigated. The addition of hollow glass microbead improved the strength of frit-bonded SiC ceramics without the loss of porosity by acting additional binder phase between SiC grains. The 65 ${\mu}m$-sized SiC resulted in lower porosity and higher strength than 50 ${\mu}m$-sized SiC because of higher packing density. Typical flexural strengths of frit-bonded SiC were 23 MPa at 46% porosity and 19 MPa at 49% porosity.

• 한국세라믹학회지
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• 제22권5호
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• pp.35-42
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• 1985

$eta$-Sialon powders were prepared by reduction-nitridation from mixture of Wando pyrophyllite and graphite as a reducing agent at 135$0^{\circ}C$ in 80% $N_2$-20% $H_2$ atmosphere. As the reaction products $Si_2ON_2$, $\beta$-$Si_3N_4$ a--$Si_3N_4$ and $\beta$-SiC were observed. Additive agents of MgO, CaO, $Y_2O_3$ were used for promoting the reduction and nitridiation aeaction. The present study was conducted to investigate the effects of silica-carbon ratio ($SiO_2$/C=weight ratio), raction time gas flow rate pellet size and powder packing on synthesis of $\beta$-Sialon from Wando pyropyllite.