• 대한치과보철학회지
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• 제36권3호
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• pp.453-467
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• 1998

This study helps to clarify conflicting reports by comparing the physical properties and accuracy of complete denture processed by the pack and press technique, continuous- pressure injection technique(SR-Ivocap system) and Mark press technique. The 6 different specimens have been evaluated using the SEM, Impact test, DSC (Differential Scanning Calorimetry) and DMTA (Dynamic Mechanical Thermal Analysis). Each sample was made of SR-Ivocap resin and QC-20 resin by different processing methods. The results were as follows ; 1. As the result of the observation on the fracture surface of resin by use of SEM, sample SR-Ivocap resin cured by continuous pressure injection method showed the most homogeneous structure. This is why molecules in SR-Ivocap resin have no orientation. 2. As the result of the Impact test in order to measure the deformity, fracture energy and impact resistance of resin, the samples with QC-20 acrylic resin and SR-Ivocap resin cured by continuous pressure injection method were exellent. 3. In consequence of measuring ${\alpha}$-glass transition temperature by use of DSC on the basis of temperature change, the glass transition temperatures of sample QC-20 resin cured by pack and press method and sample SR-Ivocap resin cured by continuous pressure injection method were very similar. Thus volumetric stability could not be evaluated only by glass transition temperature. 4. In comparing volumetric stability data by DMTA, the glass transition temperature(Tg) showed $137.88^{\circ}C$ at sample QC-20 resin cured by pack and press method and $139.78^{\circ}C$ at sample SR-Ivocap resin cured by continuous pressure injection method. Therefore sample SR-Ivocap resin cured by continuous pressure injection method seems to be superior to sample QC-20 resin cured by pack and press method in the dimensional stability at high temperature. 5. In comparing storage modulus data by DMTA, the storage modulus of sample SR-Ivocap resin cured by continuous pressure injection method was higher than that of sample QC-20 resin cured by pack and press method. So. sample SR-Ivocap resin cured by continuous pressure injection method seems to be superior to sample QC-20 resin cured by pack and press method in impact strength.

• 한국식품영양학회지
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• 제18권1호
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• pp.4-10
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• 2005

과요오드산-산화가용성전분은 Aspergillus awamori a-glucosidase의 pH 안정성을 증가시켰다. 40℃에서 두시간 항온시킨 결과, 과요오드산-산화가용성전분이 존재하지 않을 때의 효소는 pH 3∼7, 존재할 때의 효소는 pH 3∼9, 50℃에서 과요오드산-산화가용성전분이 존재하지 않을 때의 효소는 pH 3∼6, 존재할 때의 효소는 pH 3∼8 범위에서 안정하였다. 60℃에서는 과요오드산-산화가용성전분의 존재여부에 관계없이 효소는 pH 3∼6 범위에서 안정하였으나 pH 5와 6에서 과요오드산-산화가용성전분이 존재하면 효소의 잔존활성은 존재하지 않을 때보다 20% 더 높았다. 과요오드산으로 변형한 효소는 pH 9에서 활성이 70% 남았으나 변형하지 않은 효소는 남지 않아서 변형으로 안정성이 증가된 것으로 나타났다. 변형효소는 50℃에서 12%, 80℃에서 7%의 활성이 남았으나 변형시키지 않은 효소는 50℃에서 8%가 남고, 70℃이상에서는 남지 않았다. HPLC 분석 결과 pH 2 이하 및 9 이상에서는 효소의 서브유니트가 분리되고, 변성 중합되었다. 변형하지 않은 효소는 산성과 알칼리성 pH에서 변성되어 단백질의 구조가 무너졌지만 과요오드산-산화가용성전분이 존재하면 변성되지 않았다.

• 에너지공학
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• 제20권3호
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• pp.171-177
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• 2011

본 연구에서는 폴리비닐알코올(PVA)을 전해질 막으로 이용하기 위하여 가교제로서 글루타르알데히드(GLA)와 무기물 첨가제로 알루미늄실리케이트($Al_2O_3{\cdot}3SiO_2$)를 사용하여 PVA/GLA/$Al_2O_3{\cdot}3SiO_2$ 복합막을 제조하였다. PVA/GLA/$Al_2O_3{\cdot}3SiO_2$ 복합막은 GLA의 비율이 증가함에 따라 함수율이 감소되었고, 알루미늄실리케이트 함량이 증가함에 따라 함수율 향상이 예상되어 수소이온 전도도가 향상되는 경향을 보였다. 제조된 고분자의 가교결합은 IR과 함수율의 경향성으로 확인되었다. 제조된 고분자의 열분석은 TGA에 의해 수행되었다. TGA의 분석결과 PVA/GLA 복합막은 가교결합으로 인하여 PVA보다 열안정성이 우수하였으며, 복합막의 알루미늄실리케이트의 비율이 증가할수록 열안정성이 더욱 증대되는 것을 알 수 있었다. 본 연구에서 제조된 복합막은 열안전성을 갖으며 $60^{\circ}C$까지는 양이온전도도가 증가하는 경향을 갖지만 $90^{\circ}C$로 온도가 높아짐에 따라 성능이 낮아지는 경향을 보였다. 따라서 보다 적극적인 노력을 통하여 향후 이온전도성 복합 전해질막으로 적용 가능성을 타진해야 할 것으로 기대된다.

• 한국산학기술학회논문지
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• 제14권4호
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• pp.2037-2042
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• 2013

기존 DSSC의 상대전극을 TCO-less로 하여 도전성과 촉매기능을 동시에 가지고 있는 Pd의 안정성 확인을 위해 열증착기를 채용하여 유리기판 전면에 Pd를 90nm 두께로 증착하고 전해질과의 반응 안정성을 확인하였다. $0.45cm^2$급 면적을 가진 glass/FTO/blocking layer/$TiO_2$/dye/electrolyte(10 mM LiI + 1 mM $I_2$ + 0.1 M $LiClO_4$ in acetonitrile solution)/Pd/glass 구조의 DSSC 소자를 만들고, 시편제작 1시간, 12시간 후의 변화를 육안분석, 광학현미경과 FESEM을 이용하여 미세구조 분석을 진행하고, 전기적 분석은 각각 C-V(cyclic voltammetry measurements), I-V(current voltage) 분석을 통해 확인하였다. 미세구조 분석을 통하여 시간이 지남에 따라 확연히 Pd과 전해질이 반응하여 부식되는 것을 확인하였고, 전기적으로도 시간이 지남에 따라 촉매활동도와 효율이 감소하는 것을 확인하였다. 최종 효율은 1시간 후에는 0.34%의 광전효율을 보였으나 12시간 후에는 0.15%를 나타내어 약 44%로 감소하였다. 따라서 염료감응태양전지에 Pd촉매를 채용하기 위해 $I^-/I_3{^-}$ 전해질이 아닌 다른 전해질을 사용하거나 Pd 전극이 아닌 다른 촉매재를 사용해야 함을 확인하였다.

• 폴리머
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• 제36권5호
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• pp.656-661
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• 2012

케이지 구조의 POSS-$NH_3{^+}$를 이용하여 팔라듐 입자들의 자기 조직화로 인한 구조가 제어된 Pd-POSS 나노입자를 제조하였다. 또한 흑연을 강산과 산화제를 이용하여 산화된 그래핀 옥사이드(GO)를 합성한 후 얻어진 GO와 NaBH4와의 반응을 통하여 그래핀을 제조하였다. 합성된 그래핀과 acrylic acid와 라디칼 중합 반응을 통하여 그래핀 표면에 poly(acrylic acid)(PAA)가 결합된 PAA-grafted graphene을 얻었다. Pd-POSS와 PAA-grafted graphene을 이용한 나노복합체는 POSS-$NH_3{^+}$로 인하여 양전하를 띠는 Pd-POSS 나노입자와 PAA로 인하여 음전하를 띠는 PAA-grafted graphene와의 정전기적 인력을 이용하여 제조하였다. Pd-POSS 나노입자가 PAA로 치환된 그래핀 표면에 정전기적 인력으로 결합되어 있고, 나노복합체의 열적 안정성은 PAA와 PAA-grafted graphene 보다 우수한 것을 확인할 수 있었다. 제조된 Pd-POSS/PAA-grafted graphene 나노복합체의 구조 및 형태와 열적 안정성은 FE-SEM, AFM, TEM, EDX, FTIR과 TGA를 통하여 분석하였다.

• Journal of the Korean Wood Science and Technology
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• 제52권3호
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• pp.221-233
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• 2024

Lignin, a prominent constituent of woody biomass, is abundant in nature, cost-effective, and contains various functional groups, including hydroxyl groups. Owing to these characteristics, they have the potential to replace petroleum-based polyols in the polyurethane industry, offering a solution to environmental problems linked to resource depletion and CO₂ emissions. However, the structural complexity and low reactivity of lignin present challenges for its direct application in polyurethane materials. In this study, Kraft lignin (KL), a representative technical lignin, was fractionated with ethanol, an eco-friendly solvent, and mixed with conventional polyols in varying proportions to produce polyurethane films. The results of ethanol fractionation showed that the polydispersity of ethanol-soluble lignin (ESL) decreased from 3.71 to 2.72 and the hydroxyl content of ESL increased from 4.20 mmol/g to 5.49 mmol/g. Consequently, the polyurethane prepared by adding ESL was superior to the KL-based film, exhibiting improved miscibility with petrochemical-based polyols and reactivity with isocyanate groups. Consequently, the films using ESL as the polyol exhibited reduced shrinkage and a more uniform structure. Optical microscope and scanning electron microscope observations confirmed that lignin aggregation was lower in polyurethane with ESL than in that with KL. When the hydrophobicity of the samples was measured using the water contact angle, the addition of ESL resulted in higher hydrophobicity. In addition, as the amount of ESL added increased, an increase of 7.4% in the residual char was observed, and a 4.04% increase in Tmax the thermal stability of the produced polyurethane was effectively improved.

• 한국결정성장학회지
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• 제8권3호
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• pp.435-441
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• 1998

리튬 이온전지의 양극으로 사용되는 Li-SGICs를 혼합가압법에 의하여 Li의 함유량에 따라 합성하였다. 이들 합성된 화합물을 X-선 회절법 및 DSC 열 분석법을 이용하여 특성화하였다. X-선 회절 분석결과에 의하며 리튬의 함유량이 증가함에 따라 낮은 stage가 관찰되었으나, 각각의 화합물들은 혼재된 stage를 가지고 있음이 나타났다. Li30wt%-SGIC의 경우 지배적으로 1stage의 구조가 나타났지만 순수한 1stage의 화합물은 얻을 수가 없었고, 이는 인조 흑연의 구조적 특성 때문으로 예상할 수 있다. DSC에 의한 열역학적 결과로부터 화합물에 대한 엔탈피의 변화량($\Delta$H)과 엔트로피의 변화량($\Delta$S)을 구하였다. 이들로부터 Li-SGIC의 발열반응과 흡열반응의 결과들은 인조 흑연사이에 존재하던 리튬이 열에 의하여 deintercalation이 일어날 때의 열적 안정성과 관련이 있음을 알 수 있었다. 또한 열적 변이가 일어나는 동안 Li30wt%-SGIC의 구조변화에 대하여 토론하였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.33.1-33.1
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• 2011

Strontium doped lanthanum manganite (LSM) with perovskite structure for SOFC cathode material shows high electrical conductivity and good chemical stability, whereas the electrical conductivity at intermediate temperature below $800^{\circ}C$ is not sufficient due to low oxygen ion conductivity. The approach to improve electrical conductivity is to make more oxygen vacancies by substituting alkaline earths (such as Ca, Sr and Ba) for La and/or a transition metal (such as Fe, Co and Cu) for Mn. Among various cathode materials, $LaSrMnCuO_3$ has recently been suggested as the potential cathode materials for solid oxide fuel cells (SOFCs). As for the Cu doping at the B-site, it has been reported that the valence change of Mn ions is occurred by substituting Cu ions and it leads to formation of oxygen vacancies. The electrical conductivity is also affected by doping element at the A-site and the co-doping effect between A-site and B-site should be described. In this study, the $La_{1-x}Sr_xMn_{0.8}Cu_{0.2}O_{3{\pm}{\delta}}$ ($0{\leq}x{\leq}0.4$) systems were synthesized by a combined EDTA-citrate complexing process. The crystal structure, morphology, thermal expansion and electrical conductivity with different Sr contents were studied and their co-doping effects were also investigated.

• Transactions on Electrical and Electronic Materials
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• 제15권6호
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• pp.328-332
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• 2014

Thin film transistors (TFTs) with an amorphous silicon zinc tin oxide (a-2SZTO) channel layer have been fabricated using an RF magnetron sputtering system. The effect of the change of excitation electron on the variation of the total interfacial trap states of a-2SZTO systems was investigated depending on sputtering power, since the interfacial state could be changed by changing sputtering power. It is well known that Si can effectively reduce the generation of the oxygen vacancies. However, The a-2SZTO systems of ZTO doped with 2 wt% Si could be degraded because the Si peripheral electron belonging to a p-orbital affects the amorphous zinc tin oxide (a-ZTO) TFTs of the s-orbital overlap structure. We fabricated amorphous 2 wt% Si-doped ZnSnO (a-2SZTO) TFTs using an RF magnetron sputtering system. The a-2SZTO TFTs show an improvement of the electrical property with increasing power. The a-2SZTO TFTs fabricated at a power of 30 W showed many of the total interfacial trap states. The a-2SZTO TFTs at a power of 30 W showed poor electrical property. However, at 50 W power, the total interfacial trap states showed improvement. In addition, the improved total interfacial states affected the thermal stress of a-2SZTO TFTs. Therefore, a-2SZTO TFTs fabricated at 50 W power showed a relatively small shift of threshold voltage. Similarly, the activation energy of a-2SZTO TFTs fabricated at 50 W power exhibits a relatively large falling rate (0.0475 eV/V) with a relatively high activation energy, which means that the a-2SZTO TFTs fabricated at 50 W power has a relatively lower trap density than other power cases. As a result, the electrical characteristics of a-2SZTO TFTs fabricated at a sputtering power of 50 W are enhanced. The TFTs fabricated by rf sputter should be carefully optimized to provide better stability for a-2SZTO in terms of the sputtering power, which is closely related to the interfacial trap states.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.221-221
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• 2013

Striving to replace the well known silicon nanocrystals embedded in oxides with solution-processable charge-trapping materials has been debated because of large scale and cost effective demands. Herein, a silicon quantum dot-polystyrene nanocomposite (SiQD-PS NC) was synthesized by postfunctionalization of hydrogen-terminated silicon quantum dots (H-SiQDs) with styrene using a thermally induced surface-initiated polymerization approach. The NC contains two miscible components: PS and SiQD@PS, which respectively are polystyrene and polystyrene chains-capped SiQDs. Spin-coated films of the nanocomposite on various substrate were thermally annealed at different temperatures and subsequently used to construct metal-insulator-semiconductor (MIS) devices and thin film field effect transistors (TFTs) having a structure p-$S^{++}$/$SiO_2$/NC/pentacene/Au source-drain. C-V curves obtained from the MIS devices exhibit a well-defined counterclockwise hysteresis with negative fat band shifts, which was stable over a wide range of curing temperature ($50{\sim}250^{\circ}C$. The positive charge trapping capability of the NC originates from the spherical potential well structure of the SiQD@PS component while the strong chemical bonding between SiQDs and polystyrene chains accounts for the thermal stability of the charge trapping property. The transfer curve of the transistor was controllably shifted to the negative direction by chaining applied gate voltage. Thereby, this newly synthesized and solution processable SiQD-PS nanocomposite is applicable as charge trapping materials for TFT based memory devices.