• 한국전기전자재료학회논문지
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• 제19권10호
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• pp.966-970
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• 2006

We reported on characteristics of the piezoelectric ceramic-polymer composite for the application of the thick-film speaker. The PVDF-PZT composites were fabricated to incorporate the advantages of both ceramic and polymer with various mixing ratios by 3-roll mill mixer. The composite solutions were coated by the conventional screen-printing method on ITO electrode coated PET (Polyethylene terephthalate) polymer film. After depositing the top-electrode of silver-paste, 4 kV/mm of DC field was applied at $120^{\circ}C$ for 30 min to poling the composite films. The value of $d_{33}$ (piezoelectric charge constant) was increased when the PZT weight percent was increased. The maximum value of the $d_{33}$ was 24 pC/N at 70 wt% PZT. But the $g{33}$ (piezoelectric voltage constant) showed the maximum value of $32mV{\cdot}m/N$ at 65 wt% of PZT powder. The SPL (sound pressure level) of the speaker fabricated with the 65:35 composite film was about 68 dB at 1 kHz.

• 한국세라믹학회지
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• 제31권8호
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• pp.893-901
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• 1994

In this study, AlN powder of fine particle size and of high purity was synthesized by the carbothermal reduction-nitridation of monodisperse, spherical Al(OH)3 which had been prepared by sol-gel method using Al(O-sec-C4H9)3 as the starting material. Depending on the mixing order and kinds of reducing agents, the optimum condition for the preparation of AlN was determined as follows. AlN single-phase was produced by the carbothermal reduction-nitridation of (1) Benzene-washed Al(OH)3 and the reducing agent, carbon, which was mixed in a ball mill: for 5 hours at 140$0^{\circ}C$ under NH3 atmosphere; (2) The mixture prepared by hydrolysis of alkoxide solution into which carbon had been dispersed beforehand: for 5 hours at 135$0^{\circ}C$ ; (3) Al(OH)3 Poly(furfuryl alcohol) composite powder: for 2.5 hours at 135$0^{\circ}C$; (4) The mixture of Al(OH)3 and polyacrylonitrile: for 5 hours at 140$0^{\circ}C$. Addition of CaF2 increased the nitridation rate when carbon or polyacrylonitrile was used as the reducing agent; but it had no effect on the nitridation rate when furfuryl alcohol was used as the reducing agent.

• Journal of the Korean Wood Science and Technology
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• 제15권4호
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• pp.64-68
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• 1987

To develope the utilities of the chestnut bur, which is wasted after harvesting chestnut in farmhouses, the feasibilities of adhesion(urea resin) extenders of the powder for plywood were examined. These experiments were implemented on experimental scale at Forestry Research Institute(Seoul) and on a plywood mill scale at Eugon Industrial Co LTD(Inchon) for more reliable data. In this paper, it was proved that the chestnut bur powder caused to rise the glue viscosity but the chaff powder to down reversely. The most effective mixing ratio were wheat flour 5kg, chaff powder: 5kg and chestnut bur powder. 5kg per 100kg of urea resin. At this condition, the viscosity were most appropriate (1,320 2,230 cps) for glue spreading operations, and the dry shear strengthes were most adequate(10.7-13.2kg/$cm^2$), wood failure ratio 82-88%). The chestnut bur powder, can be utilized for plywood adhesion extenders without any change of present process lines in plywwod mills.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1712-1719
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• 2015

In recent days, there was a significant development on the electrical, thermal, mechanical, physical, chemical, magnetic and optical properties of the polyamide enamel, varnish and other insulating materials by the addition of nano fillers to it. Enamel was used in High Voltage Apparatuses used in Medical Electronics as insulation. Insulating materials determine the life time of the electrical apparatuses. The life time of the insulating materials was improved by the addition of nano fillers to it. Hence the life time of the electrical apparatuses was improved by the mixing of nano fillers to the enamel. In this research, the basic dielectric properties of the enamel and enamel mixed with nano composites of silica and alumina were analyzed and compared with each other. The addition of nano fillers has improved the quality factor and capacitance of the enamel. It was also observed that the addition of nano fillers has reduced the dissipation factor and dielectric losses of the enamel. Heat produced by the dielectric losses was also reduced by adding nano fillers to it.

• Carbon letters
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• 제12권4호
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• pp.243-248
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• 2011

Two different types of graphite, such as flake graphite (FG) and spherical graphite (SG), were used as anode materials for a lithium-ion secondary battery in order to investigate their electrochemical performance. The FG particles were prepared by pulverizing natural graphite with a planetary mill. The SG particles were treated by immersing them in acid solutions or mixing them with various carbon additives. With a longer milling time, the particle size of the FG decreased. Since smaller particles allow more exposure of the edge planes toward the electrolyte, it could be possible for the FG anodes with longer milling time to deliver high reversible capacity; however, their initial efficiency was found to have decreased. The initial efficiency of SG anodes with acid treatments was about 90%, showing an over 20% higher value than that of FG anodes. With acid treatment, the discharge rate capability and the initial efficiency improved slightly. The electrochemical properties of the SG anodes improved slightly with carbon additives such as acetylene black (AB), Super P, Ketjen black, and carbon nanotubes. Furthermore, the cyclability was much improved due to the effect of the conductive bridge made by carbon additives such as AB and Super P.

• 펄프종이기술
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• 제46권6호
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• pp.94-102
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• 2014

The physical and chemical properties of recycled fibers from mixed waste paper are more and more deteriorated because of unknown history of recycling times. In order to improve the mechanical properties of liner paper, the recycled fibers from wasted cotton clothes were used in papermaking process, and their applicabilities were evaluated in several points of fiber modification. Thus, two kinds of fiberizing methods from waste cotton clothes were considered by using rotary sandpaper and grinder mill. Finally, the rotary sandpaper method was relatively desirable in preserving longer fiber length and fibrillated fiber surface. The recycled cotton fibers by swelling treatment with NaOH and bleaching with reductive chemicals were mixed with OCC fibers, and the handsheets were prepared to basis weight of $80g/m^2$ and evaluated the mechanical properties of paper. The fibrous properties showed outstanding results in freeness and WRV improvements by alkali treatment and high brightness by reductive bleaching treatment. The physical and mechanical properties of sheet by mixing OCC fibers and recycled cotton fibers were also highly improved in tensile, burst strength and specially folding resistance.

• Elastomers and Composites
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• 제43권2호
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• pp.104-112
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• 2008

통상적인 고무블렌드 방법에 따라 개방식 2-롤밀을 사용하여 ethylene propylene diene terpolymer (EPDM)과 styrene butadiene rubber (SBR) 블렌드 배합물을 제조하여, 이들의 경화 특성, 기계적 성질 및 내오존성 등을 검토하였다. SBR함량이 증가할수록 가황곡선의 토크가 증가하였다. 최대 토크는 SBR 25wt% 일 때 가장 낮았으며 그 이상의 SBR 량에서는 직선적으로 증가하였다. 스코치시간 및 최적경화시간은 SBR고무 함량이 증가함에 따라 감소하였다. 경도는 SBR 함량이 50wt% 일 때 최고값을 보였으며 그 전후에서는 감소하는 경향을 보였다. 내오존시험에 있어서 소량의 EPDM 고무의 첨가에 의하여 내오존성이 크게 개선됨을 확인할 수 있었다.

• Environmental Engineering Research
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• 제25권3호
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• pp.400-408
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• 2020

Hydrodynamic study of Activated Sludge Process (ASP) is important to optimize the reactor performance and detect anomalies in the system. Residence time distribution (RTD) study has been performed using LiCl as tracer on a pilot scale aeration tank (AT) and ASP, treating the pulp and paper mill effluent. The hydraulic performance and treatment efficiency of the AT and ASP at different operating parameters like residence time, recycle rate was investigated. Flow anomalies were identified and based on the experimental data empirical models was suggested to interpret the hydrodynamics of the reactors using compartment modelling technique. The analysis of the RTD curves and the compartment models indicated increase in back-mixing ratio as the mean hydraulic retention time (MHRT) of the tank was increased. Bypassing stream was observed at lower MHRT. The fraction of dead zone in the tank increased by approximate 20-25% with increase in recycle rate. The fraction of the stagnant zone was found well below 5% for all performed experiments, which was under experimental error. The substrate removal of 91% for Chemical oxygen demand and 96% for Biochemical oxygen demand were observed for the ASP working at a hydraulic mean residence time 39 h MRT with a 20% recycling of activated sludge.

• Plant Resources
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• 제3권3호
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• pp.226-232
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• 2000

The availability of enokitake cultural waste for Lentinus edodes cultivation was investigated, although hardwood sawdust has traditionally been used as a substrate for this fungus. Firstly, physiochemical characteristics of cultural waste were analysed. Secondly, mycelial growth characteristics and fruiting yields of L. edodes on waste treated in some methods were determined. Physiochemical characteristics of enokitake cultural waste showed that the millwaste complex was a little degraded by enokitake fungus and suggested the probability that most component lost by enokitake could be rice bran. Mycelia of L. edodes grew and fruited well on waste supplemented by fresh rice bran and Quercus sawdust although didn't on waste only. Mycelial growths of these fungi on waste were accelerated when supplemented by rice bran to the percent of 40(w/w) but decreased or suppressed at above ratios(30, 40%, w/w). Supplementations of oak sawdust at above 40%(w/w) of the waste and rice bran at 20%(w/w) of the sawdust allowed such a good mycelial growth as to be selected as a pertinent mixing ratio for fruiting medium. A fruiting yield on enokitake cultural waste supplemented by oak sawdust (at 40% of the waste, w/w) and rice bran (at 20% of the sawdust, w/w) was not inferior to that on oak sawdust supplemented by rice bran only (at 20% of the sawdust, w/w). These results indicated strongly the potentiality of enokitake cultural waste as raw materials for shiitake cultivating substrates.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2004년도 수소연료전지공동심포지움 2004논문집
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• pp.281-286
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• 2004

[ $LiOH{\cdot}H^2O$ ]와 $Ni(OH)^2$를 기계적으로 혼합하여 고상법으로 $LiNiO^2$를 합성하고, $LiNiO^2$의 전기화학적 특성을 조사하였다. 기계적 혼합을 위해 SPEC mill을 사용하였으며, 1시간 동안 milling하여 공기 중 $450^{\circ}C$에서 5시간 동안 전처리한 후 $750^{\circ}C$에서 30시간 동안 산소를 흘려주면서 하소한 시료가 가장 좋은 전기화학적 특성을 나타내었다. $2.7\~4.15V$에서 0.1C로 충${\cdot}$방전시 초기방전용량은 그다지 높지 않았으나(145.8mAh/g) 좋은 싸이클 성능을 나타내었으며, $2.7\~4.2V$에서 0.1C로 충${\cdot}$방전시 높은 초기방전용량(164.7mAh/g)을 나타내었으나 싸비클 성능은 그리 좋지 않았는데, 이는 충${\cdot}$방전시 육방구조$(H^2)$에서 육방구조$(H^3)$로의 상전이가 영향을 주는 것으로 사료된다. 초기방전용량과 방전용량은 Cation mixing을 나타내는 $I^{003}/I^{104}$값보다 hexagonal ordering을 나타내는 R-factor에 더 의존하는 것으로 사료된다.