• Geomechanics and Engineering
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• 제27권6호
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• pp.615-626
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• 2021

The main objective of this study is to present a fast and reliable approach to predict the swelling potential of clay-bearing rocks. Investigations showed that there is a good correlation between the swelling potential of a rock and its desire to absorb water due to its clay content which could be measured using the "Contact Angle" test as one of the most common ways to determine the wettability. In this test, the angle between a water drop and the flat rock surface on which it rests is measured. The present method is very fast and returns repeatable results and requires minimal sample preparation. Only having a saw-cut surface of a sample with any shape is all one needs to perform this test. The logic behind this approach is that the swelling potential of a rock is a function of its mineral content and molecular structure, which are not only distributed in the bulk of the sample but also reflected on its surface. Therefore, to evaluate swelling behavior, it is not necessary to wait for a sample to get wet all the way to its "internal structure" (which, due to the low permeability of clay-bearing rocks, is very slow and time-consuming). Instead, one can have a good sense of swelling potential by studying its surface. Parametric studies on the effect of moisture content, porosity, and surface roughness on the contact angle measurements showed that using a saw-cut oven-dried sample is a convenient way to evaluate the swelling potential by this method.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.330-338
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• 2016

The U-Zr or U-TRU-Zr cylindrical metallic fuel slug used in fast reactors is known to swell significantly and to grow during irradiation. In neutronics simulations of metallic-fueled fast reactors, it is assumed that the slug has swollen and contacted cladding, and the bonding sodium has been removed from the fuel region. In this research, a realistic burnup-dependent fuel-swelling simulation was performed using Monte Carlo code McCARD for a single-batch compact sodium-cooled breed-and-burn reactor by considering the fuel-swelling behavior reported from the irradiation test results in EBR-II. The impacts of the realistic burnup-dependent fuel swelling are identified in terms of the reactor neutronics performance, such as core lifetime, conversion ratio, axial power distribution, and local burnup distributions. It was found that axial fuel growth significantly deteriorated the neutron economy of a breed-and-burn reactor and consequently impaired its neutronics performance. The bonding sodium also impaired neutron economy, because it stayed longer in the blanket region until the fuel slug reached 2% burnup.

• 폴리머
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• 제37권4호
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• pp.478-485
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• 2013

본 연구에서는 식품첨가물로 승인되어 있는 생물고분자 물질을 이용하여 신속팽윤성과 고흡수성을 갖는 하이드로젤을 제조하고 팽윤특성을 분석하였다. 하이드로젤을 제조하는 과정에서 기포발생제를 이용하여 기공을 형성시켜 기존 하이드로젤의 팽윤성 향상을 시도하였고 각 하이드로젤의 평형 팽윤도, 팽윤속도 및 세포독성을 비교하였다. Alginate hydrogel에서는 digital microscope 관찰을 통해 수백 ${\mu}m$ 크기의 열린 채널로 다공성 구조를 관찰하였으며 제조된 모든 하이드로젤들은 poly(acrylic acid)에 비해 높은 세포생존율을 보였다.

• 폴리머
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• 제35권6호
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• pp.520-525
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• 2011

초다공성 하이드로젤은 다공성 공극구조를 이용하여 기존 수화젤의 팽윤성을 획기적으로 향상시킨 것으로, 빠른 팽윤거동과 높은 흡수율로 다양한 의약용 응용분야에 유용한 재료이다. 본 연구에서는 장용 코팅제인 Eudragit 계열 고분자들을 사용하여 poly(acrylic acid-co-acrylamide)계 초다공성 하이드로젤을 코팅함으로써 pH 의존성 팽윤거동을 보이는 초다공성 하이드로젤을 제조하고자 하였다. 서로 다른 pH 영역에서 작용하는 Eudragit L100과 S100을 이용하여 딥 코팅에 의해 표면을 코팅한 후 SEM을 이용해 공극구조를 관찰하고 pH에 따른 초다공성 하이드로젤의 팽윤거동을 관찰하였다. Eudragit 계열 고분자들로 코팅된 하이드로젤은 낮은 pH 환경하에서는 팽윤이 억제되다가, 특정 pH 이상에서 팽윤성이 향상되는 pH 의존성 팽윤거동을 보였고, 이러한 pH 의존성은 사용한 장용 코팅제용 고분자들의 pH 특성에 의존하였다.

• 한국응용과학기술학회지
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• 제26권3호
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• pp.263-268
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• 2009

Superporous Hydrogels (SPHs) have been extensively investigated for various biomedical applications due to their fast swelling and superabsorbent properties. In this study, glycol chitosan that is one of most abundant natural polymers was used as a cross-linking agent instead of bisacrylamide (BIS), which is a broadly used crosslinking agent for preparation of SPHs. Glycol chitosan was modified to have reactive vinyl groups by chemical conjugation with glycidyl methacrylate (GMA). The vinyl group-containing glycol chitosan (GC-GMA) was characterized by FT-IR and $^1H$-NMR measurements. SPHs have been prepared in various synthetic conditions to establish the optimum synthetic process for making superporous structure, where the inner pores are interconnected to each other to form a open channel structure. Various SPHs with different GC-GMA contents have been successfully prepared and have been observed to show faster swelling properties than other conventional SPHs. From the study on the swelling behavior of SPHs, the GC-GMA content is considered to be an important factor for controlling their swelling properties.

• Journal of Forest and Environmental Science
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• 제29권2호
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• pp.109-115
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• 2013

Fast-grown wood generally contains a high proportion of juvenile wood that results in inferior dimensional stability and durability against biological deteriorations. In the present research, the Acacia mangium wood from plantation forests in Vietnam was treated with high temperature in air. The effects of heat treatment on physical properties of Acacia mangium wood, including mass loss (ML), water absorption (WA), water-repellent effectiveness (WRE) and anti-swelling efficiency (ASE) were examined. The results showed that the dimensional stability and the water-repellent effectiveness are increased by about 15-46% and 8-18%, respectively. However, the mass and dimension of wood are decreased. The results also indicated that both treatment temperature and treatment duration significantly affect the wood properties of Acacia mangium. It is thus concluded that heat treatment demonstrates an interesting potential to improve the wood quality of Acacia mangium for solid timber products. This technology provides an environmentally safe method of protecting sustainable common woods to give a new generation of value-added biomaterials with increased stability without the use of toxic chemicals.

• Journal of the Korean Wood Science and Technology
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• 제47권5호
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• pp.567-578
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• 2019

A common problem with fast-growing hardwoods is dimensional instability that limits use of their wood. In this study, we investigated the effects of pre-drying methods, temperatures, and heating duration on the specific gravity, water absorption, and dimensional stability of three tropical fast-growing hardwoods, jabon (Neolamarckia cadamba Roxb.), sengon (Falcataria moluccana Miq.), and mangium (Acacia mangium Willd.). Wood samples were pre-dried by two methods (fan and oven at $40^{\circ}C$), and heat treatments were performed at three temperatures (120, 150, and $180^{\circ}C$) for two different time periods (2 and 6 hours). The specific gravity, water absorption, dimensional stability, and structural changes of the samples were evaluated. The results revealed that heat treatments slightly reduced the specific gravity of all three wood species. In addition, the heat treatments reduced water absorption and significantly improved dimensional stability of the samples. Oven pre-drying followed by heat treatment at $180^{\circ}C$ for 6 hours resulted in good physical improvement of jabon and sengon wood. Fan pre-drying followed by heat treatment at $180^{\circ}C$ for 2 hours improved the physical properties of mangium wood. The heat treatment shows a promising technique for improving the physical characteristic of fast growing hardwoods.

• 대한화학회지
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• 제47권1호
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• pp.59-66
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• 2003

생물학적 의약품, 식품 등과 같이 저온 유통 체계(cold chain)를 관리하는데 있어서 제품 용기에 부착하여 보관 온도 이상에 노출될 경우 비가역적인 변화를 일으켜 고온 노출여부를 검지 할 수 있는 라벨의 소재로소 poly(N-isopropylacrylamide-co-t-butylacrylamide) [p(NIPAAm-co-t-BAM)]수화겔의 적용 가능성을 평가하였다. p(NIPAAm-co-t-BAM)수화겔은 cold chain 온도인 8$^{\circ}$C 이하에서 온도 민감성을 갖도록 t-BAM양을 조절하여 레독스 중합반응을 통하여 저온 (4$^{\circ}$C)합성하였고, 또한 oli해(NIPAAm-co-t-BAM) 공중합체를 그라프트하여 빗살 구조를 가지는 가교수화겔을 제조함으로써 수화겔의 수축 팽윤 속도를 향상시키고자 하였다. 합성 된 수화겔의 lower critical solution temperatures(LCSTs)는 흐림 점 측정법과 시차주사열량계(DSC)를 이용하여 측정하였으며, NIPAAm 단량체와 빗살형태의 t-BAM 공중합체의 조성비가 가교제의 양에 따라 수화겔의 수축과 팽윤 거동을 관찰하였다. 소수성기를 포함하는 t-BAM의 조성비율에 따라 8$^{\circ}$C 이하 저온에서 수화겔의 LCST조절이 가능하며, 빗살 형태로 그라프트된 공중합체의 조성비에 따라 수축-팽윤율 및 속도의 조절이 가능한 것으로 확인되었다.

• 폴리머
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• 제33권5호
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• pp.469-476
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• 2009

본 연구에서는 속팽윤성과 고흡수성을 갖는 초다공성 수화젤의 제조과정에서 생분해성 가교제를 이용하여 생분해성 초다공성 수화젤을 제조하고 특성분석을 수행하였다. 친수성 고분자인 poly(ethylene glycol)의 양말단에 D,L-lactide를 개환 중합시켜 PLA-PEG-PLA 삼중공중합체를 합성한 뒤, 양말단에 비닐기를 도입하여 생분해성 가교제를 합성하였다. 조성이 다양한 초다공성 수화젤을 제조하여 각각의 팽윤도, 팽윤속도 및 생분해성을 비교하였다. 중합된 고분자의 화학적 조성을 $^1H$-NMR, GPC, FT-IR 측정을 통해 확인하였고, 수화젤 표면 및 내부의 SEM 분석을 통해 수 백 ${\mu}m$ 크기의 공극들로 생성된 열린 채널구조의 초다공성 구조를 관찰하였다. 수은 다공도계로 수화절의 기공크기와 다공도를 측정하였고, 조성에 따라 물리회학적 성질이 조절될 수 있음을 알 수 있었으며, MTT분석에 의해 낮은 세포독성을 나타냄을 확인하였다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제31권2호
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• pp.161-163
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• 2005

In the reconstruction of the hard tissue defect of the oral cavity, the usefulness of the chin bone graft, one of the intraoral donor site, is gradually increased. The advantages include reduced resorption rate after graft due to its membranous bone nature, relatively ease to harvest under local anesthesia, reduced operative time because of the same operative field, decreased morbidity, and relatively large amount of bone can be harvested compared to other intraoral donor site. It has also postoperative complications including paresthesia of the lip or chin area, discomfort of lower anterior teeth, and facial swelling around chin area. Of these complications, facial swelling occurs more frequently, is more severe as a early postoperative discomfort, and prevents fast recover of patient's social activity since this procedure is generally accomplished in the outpatient base under local anesthesia. So we applied a modified " gull-wing" type incision to minimize this complication, and now we report this simple but effective surgical technique with clinically favorable result.