• 전기학회논문지
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• 제59권4호
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• pp.693-699
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• 2010

General transformer's life is known as paper insulation' life. If a transformer is degraded by these aging factors, it is known that electrical, mechanical and chemical characteristics for transformer's oil-paper are changed. When the kraft paper is aged, the cellulose polymer chains break down into shorter lengths. It causes decrease in both tensile strength and degree of polymerization of paper insulation. The paper breakdown is accompanied by an increase in the content of furanic compounds within the dielectric liquid. In this paper it is aimed at analysis on correlation between aging characteristics for insulating diagnosis of thermally aged paper. For investigating the accelerated aging process of oil-paper samples accelerating aging cell was manufactured for estimating variation of paper insulation during 500 hours at $140^{\circ}C$ temperature. To derive the results, it was performed analysis such as tensile strength(TS), depolymerization(DP), dielectric strength(DS), relative permittivity, water content(WC) and furan compound(FC) for aged paper. Also for analyzing correlation between insulating degradation characteristics, we used linear regression method. As as results of linear regression analysis, there was a close correlation between TS and DP. WC, FC. But dielectric strength was a weak correlation with aging time.

• Macromolecular Research
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• 제15권6호
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• pp.541-546
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• 2007

The combination of atom transfer radical polymerization (ATRP) and click chemistry was employed for the efficient preparation of well-defined block copolymers. Bromo terminated poly(methyl acrylate) (pMA-Br) was prepared by an ATRP initiator, ethyl-2-bromoisobutyrate (EBiB). Subsequently, the bromine chain end of pMA-Br was converted to an azide group by simple nucleophilic substitution reaction. ${\alpha}-Alkyn-{\omega}-bromo-functionalized$ polystyrene was also synthesized by ATRP using the alkyn-functionalized initiator, propargyl-2-bromoisobutyrate (PgBiB). In both cases, the conversion was limited to a low level to ensure a high degree of chain end functionality. Then the coupling reaction between the azide end group in $pMA-N_3$ and alkyn-functionalized PgBiB-pSt was performed by Cu(I)catalysis. This coupling reaction was monitored by gel permeation chromatography (GPC). The synthesized block copolymer was characterized by FT-IR, $^1H-NMR$ spectroscopy and $^1H-^1H$ COSY correlation spectroscopy.

• 한국식품영양학회지
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• 제9권4호
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• pp.413-418
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• 1996

식물 세포벽으로부터 펙틴을 추출하는데 있어 펙틴의 중합도를 높인 고 기능의 펙틴을 추출하기 위해 펙틴의 효소추출법을 사용하여 기존의 고온 산처리 펙틴 추출법과 비교하여 다음과 같은 결론을 얻었다. 1. 불용성의 WAIP로부터 일련의 산 추출 공정과 hemicellulase를 이용한 일련의 효소 추출 공정을 거친 결과, 추출물의 수율은 효소 추출법이 더 높았다. 2. 효소 추출법에 있어 추출 조건을 다양하게 변화시켜 가며 수율을 검토한 결과, 최적의 추출 조건은 hemicellulase 1.5g을 24hr동안 38$^{\circ}C$에서 반응시킨 것으로 나타났다. 3. 펙틴의 주요 성분인 galacturonic acid 함량으로 추출물의 펙틴 순도와 수율을 비교한 결과 산 추출물에 비해 효소 추출물은 수율은 높은 대신 순도가 낮았고 메톡실 함량은 비슷하였다. 4. 효소 추출법에서 추출한 펙틴물질은 중성당 분석, GC, HPLC 등을 통해 성분을 정밀하게 분석하고 다양한 방법으로 고기능 펙틴을 추출할 수 있는 조건도 찾고, 그를 통해 정확한 식물 세포벽 모델이 제시될 수 있을 것이다.

• 폴리머
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• 제27권1호
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• pp.75-83
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• 2003

다이시아네이트-점토 나노복합재료(dicyantate-clay nanocomposite)를 개질제의 종류와 cation exchange capacity (CEC)의 차이에 따라 용융 in-situ법에 의하여 제조하였고 이들의 물성과 분산을 측정하였다. 다양한 층간 삽입물을 함유하여 다양한 층간거리와 적층밀도를 갖는 montmorillonite (MMT)에 따라 다양한 구조의 나노복합재가 제조되었다. 사용된 다이시아네이트와 점토는 각각의 친화성에 따라 실리케이트 내부로의 삽입정도가 달라졌다. 다이시아네이트-점토 나노복합재료의 분산은 CEC와 개질제의 지방족 사슬길이에 의존하였으며 더 낮은 CEC를 가지고 지방족 사슬의 길이가 짧은 것이 좀 더 분산된 구조를 가지는 것으로 측정되었다. 또한 사용된 개질제에 고분자와의 반응성이 부여되면 층간 삽입이 더욱 용이한 것으로 나타났다. 다이시아네이트 나노복합재료의 전단탄성율은 반응성을 가지며 박리된 구조를 가지는 경우에 더 향상된 물성을 가지는 것으로 나타났다.

• 미생물학회지
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• 제54권4호
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• pp.445-447
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• 2018

한국의 전통시장에서 구입한 김치에서 분리된 Leuconostoc lactis CCK940은 sucrose와 maltose를 이용하여 중합도가 4이상인 올리고당을 생산하였다. L. lactis CCK940의 유전체는 1,741,511 bp의 2개 contig로 구성된 염색체로 조합되었으며 G + C의 비율은 43.33%로 나타났다. 염색체 DNA에서 1,698개의 코딩 유전자, 12개의 rRNA, 68개의 tRNA 유전자가 확인되었다. L. lactis CCK940은 올리고당을 생산할 수 있는 sucrose phosphorylase, maltose phosphorylase, ${\beta}$-galactosidase 등의 glucosyltransferase 생합성 유전자들을 지니고 있었다.

• Restorative Dentistry and Endodontics
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• 제23권1호
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• pp.1-19
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• 1998

After polymerizing composite resin with argon laser and visible light, four test, to be concretely, measurement of compressive strength using Instron testing machine, surface microhardness using Rockwell hardness tester, quantitative analysis of residual monomer using HPLC and analysis of degree of conversion using FTIR, were accomplished. Test groups were a sort of specimen with 3mm diameter, 4mm thickness for measuring compressive strength, two sort of specimen with 7mm diameter, 2mm and 3mm thickness for measuring surface microhardness, quantitative analysing of residual monomer after curing and measuring the degree of conversion, each were divided by six groups according to the condition of light exposure. In case of argon laser, in 1.0W and 0.5W output, the exposure time for specimen were 5 sec, 10 sec respectiyely. In case of visible light, the exposure time for specimen were 20 sec, 40 sec respectively. The test were accomplished and following results were obtained. 1. Compressive strength of composite resin was the highest in the group of 1 W output, exposing for 10 sec with argon laser, followed by the group of 0.5W, exposing for 10 sec with argon laser, the group of exposing for 40 sec with visible light. But there were statistically no significant difference between these three groups(p>0.05). 2. Surface microhardness of composite resin wasn't significantly affected by light curing conditions. 3. BIS-GMA within residual monomer was least detected in the group of exposing for 40 sec. TEGDMA was least detected in the group of 1 W output, exposing for 10 sec with argon laseboth 2mm and 3mm thickness specimen. 4. The degree of conversion of all groups in the 2mm thickness specimen were more than 50%, similar to each other but in the group of 1W, exposing 10 sec with argon laser the degree of conversion was highest in the 3mm thickness specimen. 5. Argon laser could make composite resin to has similar properties with 25% lesser exposure time than visible light.

• 대한치과보철학회지
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• 제45권1호
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• pp.21-33
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• 2007

Statement of problem: The esthetic component of dental care has become increasingly more important, while new tooth-colored materials are continually marketed. Various new indirect composite materials have been developed with required advantages. The most recent development in the indirect composites has been the introduction of the second-generation laboratory composite or poly-glass materials. They are processed by different laboratory techniques based on combinations of heat, pressure, vacuum and light polymerization. Although, second generation products became available in 1995, their characteristics and clinical performance have not been adequately investigated. Purpose: The aim of this study was to measure the mechanical properties of the second generation indirect resin system and compare these with an existing universal direct composite resin. Material and method: In this study four indirect composite material (Adoro LC, BelleGlass HP, Tescera, Synfony) were tested for flexural strength, wear resistance, hardness and their degree of conversion against Z250, a light cure direct composite. Results: Within the limitations of this study, the following conclusions were drawn: 1. From the abrasion wear result, Adoro showed the least volume loss while Synfony showed the greatest volume loss. Z250 and BelleGlass HP didn't show significant difference (p>0.05), but they showed significant difference with other groups (p<0.05). From the attrition wear, BelleGlass HP showed the least volume loss and it didn’t show significant difference with Tescera (p>0.05). While Synfony showed the greatest volume loss that it showed significant difference with other groups (p>0.05). 2. Mean values of flexural strength by means of three point bending test was in the order of Z250, Adoro, Belleglass HP, Tescera and Synfony. Mean elastic modulus was in the order of Z250, BelleGlass HP, Tescera, Adoro and Synfony. 3. The result of Vicker‘s microhardness value showed that significantly higher value in Z250 (p<0.05), and is in the order of BelleGlass HP, Tescera, Adoro and Synfony. 4. The degree of conversion measured by FT-IR showed significantly higher value in BelleGlass HP (p<0.05), and is in the order of Adoro, Synfony, Tescera and Z250. Conclusion: Significant differences were found in the flexural strength, wear resistance, hardness and their degree of conversion.

• 공업화학
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• 제9권5호
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• pp.680-688
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• 1998

친수성 단량체 glycidylmethacrylate (GMA)에 가교제인 divinylbenzene (DVB)과 세공형성제인 2,2,4-trimethylpentane (TMP)량을 각각 0~10 mol %과 0~100 vol %로 변화시켜 현탁중합법으로 macroreticular (MR)형 GMA-DVB 공중합체 (RG라 칭함)을 합성하였다. 이들 공중합체를 벤젠 존재하에서 인산으로 인산화시켜 인산기를 갖는 거대망상형 양이온 교환수지 (macroreticular type cation exchange resins containing phosphoric acid groups, RGP)을 제조하였으며, 이들 수지에 대한 물성과 우라늄의 흡착능을 고찰하였다. RGP수지들의 물성은 합성시 가교도와 희석제량에 따라 영향이 있었으며, 우라늄의 흡착능은 가교도 영향인 경우 $$RGP-10(50){\sim_=}RGP-1(50)>RGP-2(50)>RGP-5(50)>RGP-0(50)$$ 이며, 희석제량의 영향인 경우는 RGP-2(100)>RGP-2(75)>RGP-2(50)>RGP-2(30)>RGP-2(0)순이였다. RGP수지들의 물성과 우라늄의 흡착능에서 가교도의 영향인 경우 RGP 수지의 세공구조, 양이온 교환 용량 및 팽윤비에 의존하며, 희석제량의 영향인 경우는 양이온 교환 용량보다도 비표면적과 세공구조에 더 영향이 있었다.

• 한국미생물·생명공학회지
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• 제20권1호
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• pp.96-101
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• 1992

폐수중의 PVA를 생물학적 처리방법에 의한 제거를 위해 자연계로부터 PVA를 분해할 수 있는 세균을 분리하였으며, 그 중 균 성장육이 높고 PVA를 강력하게 분해, 자화할 수 있는 G5Y 균주와 PW 균주를 선별하여 동정 및 생육 특성을 조사하였다. 분리된 두 균주 G5Y와 PW는 혼합배양에 의해서만 PVa를 분해, 자화할 수 있으며, 두 균은 PVA 분해에 있어서 공생관계에 있음을 확인하였다. G5Y 균주와 PW 균주의 형태학적, 생화학적 등 제 특성에 따라 각각 Pseudomonas cepacia와 Pseudomonas pseudomallei로 동정되었다.

• 공업화학
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• 제5권3호
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• pp.451-456
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• 1994

천연계 비이온 계면활성제 APG(Alkyl Polyglucoslde)는 옥수수 성분의 글루코스와 팜, 야자유에서 얻어지는 지방 알코올을 이용하여 합성된다. 친수성인 글루코스의 중합도(D.P.=1.2~1.8)와 소수성인 alkyl chain 길이 (C8-C14)에 따른 계면특성(표면 계면장력, cmc, 기포력, effectiveness 등)을 조사한 바 중합도에는 영향이 적으나, alkyl chain 길이에는 큰 영향을 받았다. 지방산 오염에 대한 APG alkyl chain 길이별 세정력 평가를 한 결과 계면 장력이 낮을수록, 단위 면적당 흡착량이 많을수록 우수한 세정력을 나타내었으며, 그 순서는 APG 0814> APG 1214> APG 10> APG 0810> APG 08과 같다.