• 펄프종이기술
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• 제44권1호
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• pp.1-9
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• 2012

In this study, 5 solvent soluble polymers were treated on Hanji. Mechanical properties, morphology and oxidation index with thermal aging were measured on the aged Hanji, dewaxed Hanji and polymer treated Hanji. Synthetic polymers(such as polylactic acid, polybutylene succinate, polystyrene) treated Hanji had higher strength and thermal stability than cellulose derivatives(such as cellulose nitrate and cellulose acetate) treated Hanji. Polymer treated Hanji showed a little bit of color change. The oxidation index of PS treated Hanji did not increase with thermal aging because it did not have a carboxyl group in chemical structure. Finally, polystyrene was found to be the most efficient method for strengthening the dewaxed Hanji. The best aging safety and thermal stability were obtained at the polystyrene 3% solution.

• 접착 및 계면
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• 제5권4호
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• pp.9-16
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• 2004

견섬유와 폴리라틱산(PLA) 사이의 계면접착 특성을 향상시키기 위하여 천연섬유 표면을 아르곤과 에틸렌 플라즈마로 각각 처리하였다. 플라즈마 표면처리 후, 견섬유의 표면 모폴로지와 접착이 크게 변화하였다. 다음의 여러 플라즈마 처리조건이 본 연구에 사용되었다: 10, 25, 50 그리고 150 W의 전력, 1, 3, 5, 7 그리고 10분의 처리시간 및 10과 50 sccm의 가스흐름속도, 플라즈마 처리된 Silk/PLA 바이오복합재료의 계면전단강도는 단섬유 micro-droplet debonding 시험방법으로 측정하였다. 결과는 Silk/PLA 바이오복합재료의 계면접착을 향상시키기 위한 최적의 플라즈마 처리 조건을 제공하여 주었다.

• Elastomers and Composites
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• 제55권1호
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• pp.46-50
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• 2020

Material extrusion (ME)-type 3D printing is the most popular among the 3D printing processes. In this study, the cross-section morphologies of ME-type 3D printing manufactured specimens were observed with respect to the thermal properties of the material. The cross-section morphology of a specimen is related to the deposition strength, and the outside profile of the cross-section is related to the surface roughness. The filaments used in this study, with different thermal conductivities, were the acrylonitrile-butadiene-styrene (ABS), the high impact polystyrene (HIPS), the glycol-modified polyethylene terephthalate (PETG), and the polylactic acid (PLA). The cross-sections and the surfaces of the 3D manufactured specimens were examined. In ME-type 3D printing, the filaments are extruded through a nozzle and they form a layer. These layers rapidly solidify and as a result, they become a product. The thermal conductivity of the material influences the cooling and solidification of the layers, and subsequently the cross-section morphology and the surface roughness.

• 대한방사선기술학회지:방사선기술과학
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• 제41권1호
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• pp.53-60
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• 2018

The purpose of this study was investigating the effect of 3D printing technology that changes the speed of sound (SOS) and the broadband ultrasound attenuation (BUA) by controlling the density of the media phantom. We used 3D printers which called additive manufacturing (AM) by using material with polylactic acid (PLA). The inside of the medium phantom was filled crossly with 100%, 90%, 80%, 70%, 60%, and 50% of the material. The ultrasonic instrument measured the SOS and the BUA using a 0.55 MHz ultrasound output in opposing mode with a pair of transducers. As a result, the density of the medium phantoms with the SOS showed very high correlation (r = 0.944), but the SOS showed very low correlation (r = 0.500). It is expecting that the manufacturing and measurement method of the medium phantom using 3D printing technology will be used as basic data for ultrasonic bone mineral density.

• Mycobiology
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• 제49권3호
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• pp.285-293
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• 2021

Polylactic acid (PLA) and polycaprolactone (PCL) are commercially available bioplastics that are exploited worldwide, and both are biodegradable. The PLA and PCL polymer-degrading activity of 30 fungal strains that were isolated from terrestrial environments were screened based on the formation of a clear zone around fungal colonies on agar plates containing emulsified PLA or PCL. Among them, five strains yielded positive results of biodegradation. Strains Korean Agricultural Culture Collection (KACC) 83034BP and KNUF-20-PPH03 exhibited PCL degradation; two other strains, KACC 83035BP and KNUF-20-PDG05, degraded PLA; and the fifth strain, KACC 83036BP, biodegraded both tested plastics. Based on phylogenetic analyses using various combinations of the sequences of internal transcribed spacer (ITS) regions, RPB2, LSU, CAL, and b-TUB genes, the above-mentioned strains were identified as Apiotrichum porosum, Penicillium samsonianum, Talaromyces pinophilus, Purpureocillium lilacinum, and Fusicolla acetilerea, respectively. Based on our knowledge, this is the first report on (i) plastic biodegraders among Apiotrichum and Fusicolla species, (ii) the capability of T. pinophilus to degrade biodegradable plastics, (iii) the biodegradative activity of P. samsonianum against PCL, and (iv) the accurate identification of P. lilacinum as a PLA biodegrader. Further studies should be conducted to determine how the fungal species can be utilized in Korea.

• Steel and Composite Structures
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• 제49권4호
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• pp.393-405
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• 2023

In this paper, the energy absorption capability of a novel cruciform composite lattice structure was evaluated through the simulation of compression tests. For this purpose, several test samples of Polylactic acid cellular reinforced with continuous glass fibers were prepared for compression testing using the additive manufacturing method of material extrusion. Using a conventional path design for material extrusion, multiple debonding is probable to be occurred at the joint regions of adjacent cells. Therefore, an innovative printing path design was proposed for the cruciform lattice structure. Afterwards, quasistatic compression tests were performed to evaluate the energy absorption behaviour of this structure. A finite element model based on local material property degradation was then developed to verify the experimental test and extend the virtual test method. Accordingly, different combinations of unit cells' dimensions using the design of the experiment were numerically proposed to obtain the optimal configuration in terms of the total absorbed energy. Having brilliant energy absorption properties, the studied cruciform lattice with its optimized unit cell dimensions can be used as an energy absorber in crashworthiness applications. Finally, a cellular structure will be suitable with optimal behavior in crush load efficiency and high energy absorption.

• Journal of Periodontal and Implant Science
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• 제29권1호
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• pp.193-207
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• 1999

The purpose of this study was to compare the clinical results of guided tissue regeneration(GTR) using a resorbable barrier manufactured from an copolymer of polylactic acid (PLA) and polylaetic-glycolic acid(PLGA) with those of nonresorbable ePTFE barrier. Thirty two patients(25 to 59 years old) with one radiographically evident intrabony lesion of probing depth ${\geq}$6mm participated in a 6-month controlled clinical trial. The subjects were randomly divided into three independent groups. The first group(n=8) received a ePTFE barrier. The second group (n=12) received a resorbable PLA/PLGA barrier. The third group (n=12) received a resorbable PLA/PLGA barrier combined with an alloplastic bone graft. Plaque index (PI), gingival index(GI), probing depth(PD), gingival recession, clinical attachment level(CAL), and tooth mobility were recorded prior to surgery and at 3, 6 months postsurgery, Statistical tests used to analyze these data included independent t-test, paired t-test, one-way ANOVA. The results were as follows : 1. Probing depth was significantly reduced in all groups at 3, 6 months postsurgery and there were not significant differences between groups. 2. Clinical attachment level was significantly increased in all groups at 3, 6 months postsurgery and there were not significant differences between groups. 3. There were not significant differences in probing depth, clinical attachment level, gingival recession, tooth mobility between second group (PLA/PLGA barrier) and third group (PLA/PLGA barrier combined with alloplastic bone graft) 4. Tooth mobility was not significantly increased in all groups at 3, 6 months postsurgery and there were not significant differences between groups. In conclusion, PLA/PLGA resorbable barrier has similar clinical potential to eP'IFE barrier in GTR procedure of intrabony pockets under the present protocol.

• Journal of Periodontal and Implant Science
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• 제35권4호
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• pp.877-889
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• 2005

This study was designed to compare the effects of treatment using chitosan membrane $(Nanogide-C^{(R)})$ resorbable barrier with control treated by polylactic acid/polylacticglycolic acid membrane(PLA/PLGA membrane, $Biomesh^{(R)}$). 44 furcation defecs from 44 patients with class 2 furcation degree were used for this study, 22 sites of them were treated by chitosan membrane as experimental group and 22 site were treated by PLA/PLGA membrane as control group. Clinical parameters including probing depth, gingival recession, attachment level and radiographic examination were evlauated at base line, 1 month, 2 month and 3 month. after surgery. Statistical test used to analyze these data included paired t-test, one way ANOVA. The results are as follows : 1. Probing depth was significanlly decreased in the two group and there were significant differences between groups(p<0.05). 2. Gingival recession was not significanlly increased in the two group and there were no significant differences between groups(p<0.05). 3. Loss of attachment was statistically decreased in the two group and there were no significant differences between groups(p<0.05). 4. Horizontal bone level was significanlly increased in the two group and there were significant differences between groups(p<0.05). On the basis of these results, chitoans resorbable membrane has similar potential to PLA/PLGA membrane in GTR for furcation defect.

• 생명과학회지
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• 제30권6호
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• pp.522-531
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• 2020

본 연구는 반응표면분석법을 이용하여 L(+)형 젖산 생산향상을 위한 배지조성을 확립하기 위해 수행되었다. L(+)형 젖산을 선택적으로 고생산하는 것으로 알려진 9종의 Lactobacillus paracasei 균주를 전국에서 수집한 김치 시료로부터 선별하였으며, 젖산 생산량과 glucose로부터의 전환률 분석을 통하여 젖산 생산 배지 최적화를 수행하기 위한 균주로 SRCM201474를 선발하였다. 선택된 11개의 배지 조성 중 젖산 생산에 가장 큰 영향을 미치는 요인을 분석하기 위한 방법으로 Plack-Burman design (PBD)을 설계하였으며, 통계분석을 통해 탄소원으로는 glucose, sucrose, molasses, 질소원으로는 peptone을 최종 선정하였다. 젖산 생산 배지 최적화를 위한 각 변수들의 농도 최적화를 수행하기 위한 방법으로 반응표면분석법 중 적은 실험수로도 최적값을 산출할 수 있는 hybrid design 설계 하였다. 실험 모델에 의한 L. paracasei SRCM201474 균주를 이용한 젖산 생산배지 조성과 최적 농도는 glucose 15.48 g/l, sucrose 16.73 g/l, molasses 39.09 g/l, peptone 34.91 g/l로 나타났으며, 이때의 젖산 생산량은 33.38 g/l로 예측되었다. ANOVA 분석을 통해 가정된 실험 모델의 적합성과 유의성을 확인하였으며, 최종적으로 분석된 최적배지에서의 반복실험을 통한 젖산 생산량을 측정하여 모델에 의해 예측된 젖산생산량과 동일함을 검증하였다. 본 연구를 통해 L(+)형 젖산을 선택적으로 고생산하는 균주를 선발하였으며, 배지 최적화를 수행하여 생분해성 플라스틱 생산을 위한 산업적 젖산 생산에 적용할 수 있는 연구자료로 활용될 수 있을 것으로 판단된다.

• 한국산학기술학회논문지
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• 제20권4호
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• pp.76-85
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• 2019

Vegetable oil은 자연 유래 물질로 낮은 가격 및 친환경적이라는 장점으로 최근 다양한 연구가 진행되고 있다. 하지만 vegetable oil 내의 이중결합의 낮은 반응성으로 인해 고분자 합성의 기반 물질로 사용하기 위해서는 반응성이 높은 관능기로 치환하여 사용하는 경우가 많다. Tung oil은 ${\alpha}$-eleostearic acid를 주성분으로 하는데, 이 구조는 3개의 이중결합이 공명구조 형태로 되어있기 때문에 다른 vegetable oil과는 달리 높은 반응성을 보인다. 본 연구에서는 이러한 tung oil을 styrene 및 divinylbenzene 등의 monomer와 양이온 중합을 통해 tung oil의 관능기 치환 과정이 없는 열경화성 수지를 합성하였으며, 각 monomer의 조성이 합성된 열경화성 수지에 미치는 영향을 확인하기 위해 열적 기계적 물성을 측정하였다. 그 결과, tung oil-styrene-divinybenzene copolymer는 단일 Tg를 갖는 homogeneous한 열경화성 고분자를 형성하는 것을 확인하였으며, 기계적 물성의 변화를 통해 tung oil 및 styrene은 soft segment로써 합성된 copolymer에 elastic한 성질을 부여하고, divinylbenzene은 hard segment로 작용하여 합성된 copolymer에 brittle한 성질을 부여하는 것을 확인하였다.