• 펄프종이기술
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• 제30권2호
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• pp.30-39
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• 1998

Effect of cationic starches and anionic colloidal silica on retention and drainage characteristics of Compozil system was investigated. Depending upon the degree of substitution and molecular weight of cationic starches and morphological characteristics of anionic colloidal silica, retention and drainage properties of Compozil system were significantly influenced. When cationic starch addition level increased above a certain limit retention and stock freeness were decreased. To elucidate this an electrostatic coagulation mechanism occurring between unadsorbed starch molecules and anionic colloidal silica was proposed. Unstructured colloidal silica showed greater improvement in retention than structured colloidal silica. Cationic corn starches with different degree of substitution and molecular weights were prepared and their effect as a constituent of Compozil system was also evaluated. By controlling the molecular weight and degree of substitution of cationic corn starch it was possible to achieve significant improvement in fines retention. Cationic corn starch with higher degree of substitution maintained its retention efficiency even when the stock conductivity was increased. Turbidity measurement technique was found to be a simple and useful method to measure the retention characteristics.

• Current Research on Agriculture and Life Sciences
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• 제31권3호
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• pp.177-181
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• 2013

본 연구에서는 셀룰로오스 에테르의 분자량, 치환도 및 치환체가 이들을 첨가한 쌀건면의 기계적 물성에 주는 영향에 대해 살펴보았다. HPMC의 분자량이 증가함에 따라, 쌀건면의 굽힘강도는 서서히 증가하였으나, 밀면의 강도보다는 낮은 수준을 나타냈다. 분자량이 증가함에 따라, 쌀건면의 굽힘신도는 서서히 감소하였으나, 밀면의 신도보다는 모두 높은 값을 나타내어 셀룰로오스 에테르 첨가가 쌀건면의 신도 향상에 기여했음을 확인하였다. 셀룰로오스의 치환도 및 치환체에 따라서는 굽힘강도 및 굽힘신도가 다소 차이가 있는 것으로 나타났다.

• 보존과학연구
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• 통권25호
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• pp.75-92
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• 2004

The conservation treatments of 10-storied pagoda in the temple of Kyoungchunsa is progressed favorably to come to the finish since 1995. Most of all, the important conservation treatments are stone crack, exfoliation and partial form modification. This pagoda has been made up a complicated structure constructed using 142 stones. Therefore, the stone crack and exfoliation have been occurred as very varied forms. Especially, the stylobate of the pagoda has 19 substitution stones of 48 stones, which is40% of modern stone substitution. It is supposed that there is serious weathering on the stones. The other stones, which are no substitution stones, have some kinds of weathering and so we carried out inside replenishment and partial outside reconstruction of crack stones using high molecular resin and substitution stone. The stone of each storey has also partial difference, but the condition of serious weathering on the whole. We can detect general degree through treatment of high molecule resin or distribution research of contaminated material on 10-storied pagoda in the temple of Kyoungchunsa. Especially, we are able to analyze general weathering degree and know details weathering of each storey or direction for the difference of replenishment quantity and different pattern of stone crack degree. Also, the distribution research will accomplish very important parts of examining environment effects and use as research data of cultural heritage conservation field.

• 펄프종이기술
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• 제35권1호
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• pp.41-47
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• 2003

Recently, interest in utilization plan of recycling paper have been enhanced. Therefore, this research aimed to develop the manufacture process of cellulose acetate using old newsprint by acetosolv pulping process. And the manufactured cellulose acetate was also analyzed, especially based on chemical properties. The summarized results in this research were as follows; Reaction time, kind and amount of catalyst, and ratio of liquor to material were varied during acetosolv pulping process of old newsprint. Ratio of liquor to material did not give the significant difference in reaction product. Delignification rate was increased with increasing reaction time during acetosolv pulping, but yield and degree of substitution decreased with increasing reaction time. Sulfuric acid are better catalyst than hydrochloric acid in acetosolv pulping process for old newsprint, and optimal addition amount of catalyst was 1% based on reaction material. Delignification, yield, and degree of substitution were influenced by the catalyst and reaction time. Under pulping condition of $120^{\circ}C$ in 1/12 liquor to material ratio and 60min, degree of substitution was about 0.7. The acetylation reaction was not completely caused by these reaction condition. The examination of the FT-IR spectra revealed that absorption band(1200$\textrm{cm}^{-2}$, 1,750$\textrm{cm}^{-1}$) caused by carbonyl group were confirmed.

• 콘크리트학회논문집
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• 제11권3호
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• pp.153-160
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• 1999

Water soluble hydroxyalkyl methycellulose ethers are used in a variety of applications incluing building industry as a supplementary agent used for incresing adhesives, water retention capacity, workability and viscosity modify. Water retention capacity(WRC) is the capability to contain water in the ploymer chain under condition of being mixed with cement. In general, the WRC is affected by the viscosity, the adding amount, the particle size, the rate of dissolving and the amount of substituted chemical in cellulose ethers. In the other words, WRC is increased as higher the viscosity, more adding amount, finer the particle size and longer the dissolving time of cellulose ethers. This thesis investigated each factor that effect the WRC, particularly the relation between degree of substitution(DS), molar of substitution(MS) and WRC. It is observed that WRC is not nearly affected by DS of cellulose ethers, but is changes proportionally as MS increases in the narrow range(0.10~2.25)

• East Asian Economic Review
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• 제21권1호
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• pp.81-100
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• 2017

This study measures the degree of dollarization in North Korea using results from a survey of 231 North Korean refugees. Specifically, we compare foreign currency use of households as both store-of-value substitutes (i.e., asset substitution) and transaction substitutes (i.e., currency substitution) before and after the confiscatory currency reform of 2009. The degree of dollarization has advanced since the currency reform in terms of both asset and currency substitutions. Survey results also indicate that the Chinese yuan is frequently used in the Sino-North Korean border area, whereas the US dollar is predominantly used in non-border areas. Furthermore, foreign currency increasingly serves as a medium of exchange not only for large transactions but also for smaller transactions, such as food purchases.

• International Journal of Contents
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• 제18권1호
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• pp.65-75
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• 2022

This study aims to reveal the various differences within the factors that influence use satisfaction, continuous use intention, and media substitution intention, specifically in regard to the use motives and use behaviors of Netflix viewers. This study's results demonstrate that the following various factors affected use satisfaction, continuous use intention, and media substitution intention in differential ways. Firstly, the diversity of content influenced use satisfaction to a greater degree than social relations; and the diversity of content, social relations, and active participation all positively influenced continuous use intention. In other words, the more positively users appreciated the diversity of content, and the more strongly they had social relations, and the more actively they participated within communities, the greater degree to which they increased their continuous use intention for Netflix. However, the diversity of content and the convenience of use also had a negative effect on the media substitution intention for Netflix, which means that the more diverse the content and the more convenient the use of Netflix, the fewer the number of users who intended to cancel Netflix and subscribe to another OTT service or resubscribe to traditional media sources.

• Journal of the Korean Wood Science and Technology
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• 제18권2호
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• pp.25-35
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• 1990

To investigate the effects of swelling treatment by ammonia on characteristics of carboxymethy1cellulose(CMC) and CMC solution, the domestic kraft pulp pretreated with 5%, 10%, 15% and 20% $NH_4OH$ solution, was carboxymethylated by the standard method, and then the CMC prepared was tested. The physical properties of CMC and CMC solution, such as degree of substitution, transparency. viscosity, weight increase and solubility, were measured, and the comparison with commercial domestic CMC used as a food additive was done. The results obtained were as follows; 1. In CMC manufactured by standard solvent method, hardwood bleached kraft pulp(LBKP) was more substituted than safwood bleached kraft pulp(NBKP), and viscosity of NBKP was higher than that of LBKP. 2. When ammonia swelling treatment was done, degree of substitution gradually decreased with increasing concentration of $NH_4OH$, and degree of substitution of LBKP decreased with a larger range than that of NBKP. 3. When ammonia swelling treatment was done. transparency of CMC solution from LBKP was hardly effected, but in case of NBKP gradually increased with increasing concentration of $NH_4OH$. 4. When ammonia swelling treatment was done, viscosity of CMC solution was higher than that of CMC solution without ammonia swelling treatment. Especially, CMC of high viscosity could be manufactured in 5%, 10% concentration levels of $NH_4OH$. 5. In CMC manufactured from domestic NBKP, CMC at the range of 0.40 to 0.50 in DS was dispersed easily and quickly dissolved, and CMC at more than 0.50 in DS was dispersed slowly in water solution. 6. In comparison with commercial domestic CMC used as a food additive, CMC manufactured from domestic NBKP was higher in DS, and was lower in viscosity and transparency.

• Journal of the Korean Wood Science and Technology
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• 제22권2호
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• pp.30-36
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• 1994

Steam explosion process is one of the most efficient, pretreatment method for the utilization of lignocellulosic biomass. The carbxymethyl-cellulose(CMC) was prepared with steam exploded wood(EXW), pine(Pinus densiflora) and oak(Quercus mongolica), by standard method using isopropyl alcohol and monochloroacetic acid. The range of water solubility of carboxymethylated pine exploded wood was 45.2~66.8 % and those of oak was 60.7~84.7 %. The degree of substitution(D.S) of carboxymethylated pine exploded wood was 0.11~0.33 and oak exploded wood was 0.48~0.76. The color of carboxymethylated pine and oak exploded wood was brown-black. When carboxymethylated EXW was purified by sulfuric acid, the yield of carboxymethylated wood was lower than non-treated one. However, the color was still brown-black although after delignification. In carboxymethylated EXM prepared after delignification, the water solubility and degree of substitution(D.S) of pine were 81.4~95.9 % and 0.71~0.79, and those of oak were 76.2~89.5 % and 0.79~1.05. The values were higher than non-treated. The degree of substitution of purified carboxymethylated wood prepared with delignified EXM, pine and oak were 0.50~0.71 and 0.70~0.88. The color of carboxymethylated wood was white. In carboxymethylated wood preparde after delignification of EXM, swelling ratio and water retention value of pine were 95.9~96.5 and 580.0~751.2, those of oak were 76.2~89.5 and 124.3~307.6.

• 공업화학
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• 제10권2호
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• pp.275-280
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• 1999

일반적으로 셀룰로오스는 그 골격구조 안에 서로 다른 반응성을 갖는 3개의 히드록시기를 가지고 있다. 이 기능기에 trimethylsiloxyl-, vinyldimethylsiloxyl-, allyldimethylsiloxyl-, phenyldimethylsiloxyl-, 3,3,3-trifluoropropyldimethylsiloxyl-과 tris(trimethylsiloxy)siloxyl-기를 치환반응을 이용하여 도입하였다. IR, NMR, 그리고 원소분석을 이용하여 그 구조분석 및 치환도, 그리고 siloxylation agent의 반응성을 검토하였다. 치환도는 각각 2.5, 2.2, 2.1, 2.2, 2.6, 0.7이었다.