• 펄프종이기술
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• 제45권1호
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• pp.35-41
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• 2013

In this study, we investigated the effect of the number of passes through agrinder on the pore characteristics of nanofibrillated cellulose (NFC) mat. The beaten pulp suspension was used to make NFC suspension using a grinder. To evaluate the pore characteristics of a NFC mat, the surface morphology of the dried NFC mat was observed with FE-SEM and the specific surface area was analyzed with BET nitrogen gas adsorption. The structure of NFC mat was changed with the different number of passes and drying methods. The specific surface area of NFC mat increased with the increase in the number of passes. The 20-passed NFC mat had 20 times larger specific surface area ($141m^2/g$) compared to the 0-passed NFC mat. The specific surface area was strongly correlated with the average pore size in NFC mat. The average pore diameter in NFC mat was calculated from the gas sorption isotherms using BJH model. The value was 13 - 15 nm, indicating that the NFC mat had mesoporous structure.

• 한국산학기술학회논문지
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• 제13권2호
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• pp.504-509
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• 2012

본 자동차 서스펜션 매트는 자동차 시트 백 프레임에 장착되며, 탑승자의 등 부위에 가해지는 압력을 시트서스펜션 매트로 받쳐줌으로써 압력이 집중되는 것을 방지하여 운전시 피로감을 최소화하고, 안락감을 증대할 수 있는 역할을 한다. 본 연구에서는 플라스틱 재질로 개발된 서스펜션 매트를 3D 모델링 하고, 진동 및 피로해석을 수행하였다. 해석 결과 플라스틱 서스펜션 매트의 고유 진동수는 30 Hz, 수명은 $10^6$ Cycle, 안전계수는 1.6055의 해석 결과를 얻었다. 이러한 해석적 기법을 활용하면 시트 설계 부분에서 그 개발 시간 및 평가 비용을 절감할 수 있을 것으로 사료된다.

• 식물조직배양학회지
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• 제25권6호
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• pp.477-485
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• 1998

감자 plastid 형질전찬을 위한 새로운 DNA 절편을 확보하고자, 감자의 trnK-matK 유전자를 PCR 방법으로 클로닝하고 특성을 조사하였다. 염기서열 분석을 통하여 trnK-matK 유전자에는 두 종류의 polymerase 인지부위[Prokaryotic site(plastid encoded polymerase)와 eukaryotic site (nuclear-encoded polymerase)]가 족재함을 알 수 있었다. 이 사실은 trnK-matK 유전자의 발현이 광합성조직과 비광합성조직에서 서로 다른 polymerase에 의하여 조절됨을 시사하였다. 한편 MatK의 아미노산서열을 분석한 결과 식물에 따라 아미노산 identity가 39-75%로 다양하였으나, 감자와 담배는 98%의 아주 높은 identity를 보였다. Northern분석을 통하여 포장과 기내에서 생육된 감자 식물체 모두에서, trnK-matK 의 전사 수준이 잎에서 높고 괴경에서는 낮음을 알 수 있었다. 한편 잎에서의 16s rDNA의 전사수준은 괴경에 비해 약 50배 높았다. 이것으로 미루어보아 괴경에서 수준이 낮을 것은, 괴경에서는 plastid genome copy 수가 적거나 plastid 수가 적기 때문으로 추정된다. 이상의 결과로서 엽록체와 amyloplst 모두에서 trunK-matK 유전자가 활발하게 발현되고 있음을 알 수 있었다. Plastid genomic DNA의 Southern 분석을 통하여 trnK는 1 copy로 존재하고, matK는 trnK intron을 포함하고 있음을 확인하였다. 따라서 감자 plastid형질전환의 새로운homologous recombination 부위로 trnK-matK유전자를 이용할 수 있을 것이다.

• 펄프종이기술
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• 제46권6호
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• pp.78-86
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• 2014

Since cellulose nanofibrils (CNF) has large specific surface area and high water holding capacity, it is very difficult task to remove water from the CNF suspension. However, dewatering of CNF suspension is a prerequisite of following processes such as mat forming and drying for the application of CNF. In this study, we evaluated the drainage of cellulose fibers suspension under vacuum and pressure conditions depending on the number of grinding passes. Also, the effect of the addition of cationic polyelectrolyte on dewatering ability of CNF suspension was investigated. Regardless of dewatering condition, the total drained water amount as well as the drainage rate were decreased with an increase in the number of grinding passes. Pressure dewatering equipment enables us to prepare wet CNF mat with relatively higher grammage. The cationic polyelectrolytes improved the dewatering ability of CNF suspension by controlling the zeta potential of CNF. The fast drainage was obtained when CNF suspension had around neutral zeta potential.

• Journal of Pharmaceutical Investigation
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• 제27권4호
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• pp.313-321
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• 1997

Ion exchange resin complexes of famotidine have been prepared by the reaction of famotidine solution with activated ion exchange resins. Complex formation efficiency between famotidine and ion exchange resin was about $80{\sim}90%$ in average, calculated by HPLC determination. Drug release characteristics from the resin complexes were evaluated by the modified percolation method. Famotidine release was dependent on the type of ion exchange resins. In the case of weakly acidic resin complexes, the cumulative released amount of famotidine was more than 90% for 1hr in pH 1.2 buffer solution. However, in the case of strongly acidic resin complexes, it was less than 5% for 3hr in the same medium. Strongly acidic resins revealed some advantages over weakly, acidic resins for overcoming instability of famotidine in gastric juice. In addition, strongly acidic resin complexes showed controlled release of famotidine in pH 6.8 buffer solution, showing the result of about 60 to 70% of drug release for 5hr. After oral administrations of famotidine-resin complexes to rats as dose of 40 mg equivalent/kg, the pharmacokinetic parameters of famotidine were obtained by model independent analysis and compared with those of famotidine solution or suspension. $C_{max}$ of famotidine-resin complex was lower than that of famotidine solution or suspension. MRT, MAT, and MDT of the complexes were greater than those of famotidine solution or suspension. From these results, it was expected that famotidine was released slowly from the complexes and absorbed continuously into systemic circulation. It was recognized that drug release from the complexes was the rate-limiting step in drug absorption, since there were close correlations between in vitro drug release and in vivo pharmacokinetic parameters.

• 농약과학회지
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• 제19권1호
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• pp.14-21
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• 2015

인삼의 재배환경에 따른 잔류특성을 조사하고 살포 농약의 행적을 알아보기 위하여 5년근 인삼포에 덮개 유무와 인삼 줄기의 움직임으로 생긴 구멍을 흙으로 메우는 방법 여부의 서로 다른 조건에서 azoxystrobin (20% SC)을 안전사용기준의 기준량과 배량농도로 수확 7일전까지 10일 간격으로 4회 살포하였으며, 행적 구명 시험을 위해서는 기준량을 1회 살포한 후 분석시료를 채취하였다. 재배기간 중 덮개를 설치하고 구멍을 막은 경우가 잔류량이 낮아 덮개 설치와 구멍 메우기가 잔류량 감소에 기여하는 것으로 판단되었다. 인삼에 살포한 azoxystrobin은 비표면적이 큰 잎에 가장 많이 분포하였으며, 살포시기가 인삼의 수확기에 근접할수록 잎 중 잔류량은 감소하였으나 토양표면의 검출량은 증가하였다. 뇌두를 포함한 인삼 뿌리 중 시험농약의 분포율은 약 0.1%이었으며, 인삼 섭취 시 뇌두를 제거할 경우 12.7-20.4%(평균 16.6%)의 잔류농약 섭취를 감소시키는 효과가 있었다.

• Mycobiology
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• 제46권2호
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• pp.92-100
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• 2018

The filamentous Ascomycota Colletotrichum gloeosporioides sensu lato is a fungus that has been reported worldwide as a causal agent of anthracnose disease in avocado and other crops. In Mexico, this species affects fruits from an early stage of development in the orchard until the post-harvest stage. Although fungicides are continuously applied to control Colletotrichum species, pericarp cankers and soft rot mesocarp in fruits are still frequently observed. Considering the lack of a precise description of the causative agent, the aim of the current study was to determine the pathogens involved in this symptomatology. Twenty-four isolates were consistently obtained from the pericarp of avocado fruits cv. "Hass" collected in the central avocado-producing area of Mexico. Morphological features such as colony growth, conidia size, and mycelial appressorium were assessed. Bayesian multilocus phylogenetic analyses were performed using amplified sequences of the internal transcribed spacer region of the nuclear ribosomal DNA; actin, chitin synthase, glyceraldehyde-3-phosphate dehydrogenase partial genes; and APn2-Mat1-2 intergenic spacer and mating type Mat1-2 partial gene from the nine selected isolates. In addition, fruits were inoculated with a conidial suspension and reproducible symptoms confirmed the presence of Colletotrichum fructicola in this area. This pathogenic species can now be added to those previously reported in the country, such as C. acutatum, C. boninense, C. godetiae, C. gloeosporioides, and C. karstii. Disease management programs to reduce the incidence of anthracnose should include C. fructicola to determine its response to fungicides that are routinely applied, considering that the appearance of new species is affecting the commercial quality of the fruits and shifting the original population structure.

• Membrane and Water Treatment
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• 제4권2호
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• pp.143-155
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• 2013

Four membranes were used to separate Chlorella sp. from their culture medium in cross-flow microfiltration (MF) experiments: cellulose acetate (CA), cellulose nitrate (CN), polypropylene (PP) and polyvinylidenefluoride (PVDF). It was found that the hydrophilic CA and CN membranes with a pore size of 1.2 ${\mu}m$ exhibited the best performances among all the membranes in terms of permeation flux. The hydrophobicity of each membrane material was determined by measuring the angle between the water (liquid) and membrane (solid). Contact angle measurements showed that deionized (DI) water had almost adsorbed onto the surfaces of the CA and CN membranes, which gave $0.00^{\circ}$ contact angle values. The PP and PVDF membranes were more hydrophobic, giving contact angle values of $95.97^{\circ}$ and $126.63^{\circ}$, respectively. Although the pure water flux increased with increasing pore diameter (0.8 < 1.2 < 3.0 ${\mu}m$) in hydrophilic CA and CN membranes, the best performance in term of filtration rate for filtering a microalgae suspension was attained by membranes with a pore size of 1.2 ${\mu}m$. The fouled membrane pore sizes and pore blocking were inspected using a scanning electron microscope (SEM). MF with large pore diameters was more sensitive to fouling that contributed to intermediate blocking, where the size of the membrane pores is almost equivalent to that of cells.

• Journal of the Korean Wood Science and Technology
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• 제43권4호
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• pp.518-527
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• 2015

본 연구에서는 바이오 매스기반의 셀룰로오스 나노크리스탈(cellulose nanocrystals, 이하 CNC)과 PLA (polylactic acid, 이하 PLA)를 tetrahydrofuran (THF)에 용해시킨 서스펜션으로부터 PLA 및 PLA/CNC 나노섬유 복합재 매트를 상온에서 전기방사법으로 제작하였다. PLA 및 PLA/CNC 나노복합재 매트의 형상은 섬유가 긴축을 따라 3차원 구조의 표면으로 정렬된 것으로 관찰되었다. PLA 및 PLA/CNC 나노섬유 복합재 매트의 인장강도는 CNC 함량이 증가할수록 감소하였는데, 이는 전기방사된 섬유 속에 형성된 비드와 PLA와 CNC의 낮은 계면접착력 때문으로 기인된다. PLA/CNC 복합재 매트를 구성하는 섬유의 평균 지름 크기는 CNC의 함량이 증가할수록 작아졌다. 한편 PLA/CNC 나노섬유 복합재 매트의 열안정성은 CNC의 함량이 증가할수록 증가하는 것을 보였다.