• Composites Research
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• v.35 no.3
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• pp.147-152
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• 2022

Low-temperature characteristics according to internal temperature conditions during rotational molding of Type 4 pressure vessel liners were studied in this paper. Since rotational molding has a sensitive effect on the formability of the liner depending on the temperature conditions, the temperature conditions for the polyamide used should be accurately set. The structural changes of polyamide as the liner material was analyzed the surface by atomic force microscope (AFM), and the crystallinity measured with a differential scanning calorimeter (DSC) is used to evaluate the change of the mechanical strength value at low temperature. In addition, the formability of the liner was confirmed by observation of the yellow index inside the liner. As a result, as the melting range of the internal temperature becomes wider, the yellow index shows a lower value, and the elongation and impact characteristics at low temperatures are improved. It was also confirmed that the structure of the polyamide was uniform and the crystallinity was high by AFM and DSC. These experimental results contribute to the improvement of characteristics at low temperatures due to changes in temperature conditions during rotational molding.

• Clinical and Experimental Pediatrics
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• v.48 no.4
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• pp.425-432
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• 2005

Purpose : Polyglutamine diseases are a group of diseases caused by the expansion of a polyglutamine tract in the protein. The present study was performed to verify if polyglutamine disease transgenic Drosophila models show similar dysfunctions as are seen in human patients. Methods : Polyglutamine disease transgenic Drosophila were tested for their climbing ability. And using genetic methods, the effects of anti-apoptotic gene bcl-2 and chemical chaperones on neurodegeneration were observed. Also, spinocerebellar ataxia 2 (SCA2) transgenic Drosophila lines were generated for future studies. Results : Expanded forms of spinocerebellar ataxia 3 (SCA3) transgenic protein causes characteristic locomotor dysfunction when expressed in the nervous system of Drosophila but the anti-apoptotic gene bcl-2 shows no evidence of ameliorating the deleterious effect of the expanded protein. However, Glycerol, a chemical chaperone, seemed to reduce the toxicity, at least in the eyes of the transgenic flies. The level SCA2 expression is too weak in the transgenic SCA2 Drosophila for evaluation. Conclusion : SCA3 transgenic Drosophila show ataxic behavior as observed in human patients. Chemical chaperones such as glycerol may prove beneficial in this class of genetic disease, which has no current method of cure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.12
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• pp.863-866
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• 2013

SiC crystal ingots were grown on 6H-SiC dual-seed crystals with different surface roughness and different seed orientation by a PVT (Physical Vapor Transport) method. 4H and 15R-SiC were grown on seed crystal with high root-mean-square (rms) value. The polytype of grown crystal on the seed crystal with lower rms value was confirmed to be 6H-SiC. On the other hand, all SiC crystals grown on seed crystals with different seed orientation were proven to be 6H-SiC. The surface roughness of seed crystals had no effect on the crystal structure of the grown crystals. However, the crystal quality of 6H-SiC single crystals grown on the on-axis seed were revealed to be slightly better than that of 6H-SiC crystal grown on the off-axis seed.

• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.397-402
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• 2006

We have investigated the effect of each ingredient in the light diffusing film (LDF) which was used as backlight unit (BLU) of TFT-LCD TV on physical, electrical, thermal and optical properties of LDF. In anti-blocking layer, the excellent anti-blocking ability was obtained when 0.5~1.5 wt% of acrylic bead was added, and good decay-time and water-stability were shown when 0.8 wt% of tertiary ammonium salt was added. Optimal results for adhesion strength, curing rates and flexibility on the surface of PET film have been obtained in the light diffusing layer by using acrylic polyol as a binder resin, and by addition of 30~35 wt% non-yellowing type HDI crosslinker. In addition, the highest normal luminance value was obtained by addition of 250 wt% poly-dispersive polystyrene ($20{\mu}m$ PS) and polymethylmethacrylate ($20{\mu}m$ PMMA) beads into the binder resin (100 wt%). The higher normal luminance could be got for PMMA beads than PS beads because of the transmittance difference.

• Economic and Environmental Geology
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• v.49 no.2
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• pp.97-104
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• 2016

Here we firstly present that a timing of reactivated event of Yangsan fault, the major fault in the southeastern Korean Peninsula, by using combined approaches of the optimized illite-polytype quantification, the K-Ar age-dating, and the recently developed illite-age-analysis (IAA) approach for the fault clays from Sangcheon-ri area of Yangsan main fault line. Two chronological record of brittle fault-activation event at about 41.5~43.5 and 50.7 Ma were determined from 3 fault gouges suggesting a crucial reactivation time-scheme. Furthermore, the regional processes that drive tectonics to form and reactivate the Yangsan fault may be explained from the chronological analysis for additional sites along the Yangsan fault.

• Elastomers and Composites
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• v.33 no.4
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• pp.267-273
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• 1998

Isocyante terminated urethane prepolymers were synthesized by the reaction of 4,4'-dimethyl phenyldiisocyanate(MDI) and ester type polyols such as ethylene glycol/ butanediol adipate(EBA), neopentylglycol/butanediol adipate (NBA) and hexanediol adipate (HA) . All of the NCO-terminated urethane prepolymers are solid at room temperature, but they become mobile enough to be disposed onto a substrate upon heating about $80^{\circ}C$. Subsequently, they are solidified and cured through the reaction with moisture. Tensile behavior of the ore-thane hotmelt exhibits characteristic features depending on the type of polyol. The adhesive strength determined by single lap shear joint is higher in order of HA, NBA and EBA based ore thane hotmelt, which can be correlated with the magnitude of breaking energy of the cured films. The failure mode are cohesive for all cases and the adhesive strength increases as the test is performed faster. This indicates that the strength of the adhesive joint is primarily dependent upon the bulk properties of the adhesives.

• Polymer(Korea)
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• v.31 no.3
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• pp.255-262
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• 2007

In this work, two types of copolymers are manufactured by a radical polymerization to develop a material for humid membrane. Each copolymer contains three monomers that have functions to improve humid-resistance, membrane stability, flexibility, impedance, and adhesion to the electrode. MDBAB (N,N'-dimethyl-2-methacryloxyethyl-3-bromopropyl ammonium bromide) having a salt form decreases the impedance of the humid membrane and reacts with amines to produce a cross-linking structure. HEMA (2-hydroxyethyl methacrylate) has an important role which reduces the impedance and increases the adhesion strength to the electrode. The other monomers are DAEMA (N,N'-dimethylamino ethyl methacrylate), 4-VP(4-vinyl pyridine), and 2-EHA(2-ethylhexyl acrylate) and all the monomers are formulated with several compositions to make a humid membrane. At specific composition, we could attain a satisfactory results having good performance and long term durability.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.464-464
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• 2013

그래핀 옥사이드(Graphene Oxide)는 그래핀과 마찬가지로 많은 분야로의 응용 가능성을 보이는 소자중 하나로 각광받고 있다. 그래핀 옥사이드가 가지는 유전체 특징은 전하 트랩층(charge trap layer)으로 사용을 가능하게 하고 또한 물에 녹는 수용성 특징은 스핀코터(spin coator)를 이용한 간단한 도포과정을 통하여 저비용으로 간단하게 소자를 제작 가능하게 한다. 이 연구에서 우리는 금속-절연체-반도체 구조를 가지는 메모리 소자를 제작하여 0.4 mg/ml의 농도로 DI에 용해된 그래핀 옥사이드가 플로팅게이트(floating gate)로써 사용되었을 때의 특성을 알아보기 위해 Boonton 720를 사용하여 C-V (hysteresis) 커브와 C-T(Capacitance-Time)를 측정하여 그래핀 옥사이드의 유무에 따른 메모리 윈도우 폭의 증가 및 저장된 정보가 손실되지 않고 얼마나 길게 유지 되는지를 살펴봄으로 플로팅게이트로써 그래핀 옥사이드의 특성을 살펴보았다. 먼저 터널링층으로 쓰이는 SiO2가 5 nm 증착된 P타입 Si기판위에 플로팅게이트로 쓰이는 그래핀 옥사이드층을 쉽게 쌓기 위하여 APTES 자기조립 단분자막 코팅을 한 후 그래핀 옥사이드를 3,000 rpm으로 40초간 스핀코팅을 하였다. 그 후 블로킹층으로 쓰이는 400 nm 두께의 폴리비닐페놀(PVP)를 3,000 rpm으로 40초간 스핀코팅을 하고 $130^{\circ}C$에서 열처리를 하였으며 $10^{-5}$ Torr의 압력에서 진공 열증착으로 알루미늄 게이트 전극을 증착했다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.219-219
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• 2010

기존의 플로팅 타입의 메모리는 소자의 소형화에 따른 인접 셀 간의 커플링 현상과 전계에 따른 누설전류의 증가 등과 같은 문제가 발생한다. 이에 대한 해결책으로서 전하 저장 층을 폴리실리콘에서 유전체를 사용하는 SONOS 형태의 메모리와 NFGM (Nano-Floating Gate Memory)연구가 되고 있다. 그러나 높은 구동 전압, 느린 쓰기/지우기 속도 그리고 10년의 전하보존에 대한 리텐션 특성을 만족을 시키지 못하는 문제가 있다. 이러한 문제를 해결 하고자 터널베리어를 엔지니어링 하는 TBM (Tunnel Barrier Engineering Memory) 기술에 대한 연구가 활발히 진행 중이다. TBM 기술은 터널 층을 매우 얇은 다층의 유전체를 사용하여 전계에 따른 터널베리어의 민감도를 증가시킴으로써 빠른 쓰기/지우기 동작이 가능하며, 10년의 전하 보존 특성을 만족 시킬 수 있는 차세대 비휘발성 메모리 기술이다. 또한 고유전율 물질을 터널층으로 이용하면 메모리 특성을 향상 시킬 수가 있다. 일반적으로 TBM 기술에는 VARIOT 구조와 CRESTED 구조로 나눠지는데 본 연구에서는 두 구조의 장점을 가지는 Staggered tunnel barrier 구조를 $Si_3N_4$와 HfAlO을 이용하여 디자인 하였다. 이때 HfO2와 Al2O3의 조성비는 3:1의 조성을 갖는다. $Si_3N_4$와 HfAlO을 각각 3 nm로 적층하여 리세스(Recess) 구조의 트랜지스터를 제작하여 차세대 비휘발성 메모리로써의 가능성을 알아보았다.

• Journal of the Korean Applied Science and Technology
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• v.34 no.1
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• pp.66-82
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• 2017

Organosilicone-based surfactants consist of hydrophobic organosilicone groups coupled to hydrophilic polar groups. Organosilicone surfactants have been widely used in many industrial fields starting from polyurethane foam to construction materials, cosmetics, paints & inks, agrochemicals, etc., because of their low surface tension, lubricity, spreading, water repellency and thermal and chemical stability, resulted from the unique properties of organosilicone. Especially, trisiloxane surfactants, having low molecular weight organosilicone as hydrophobe, exhibit low surface tension and excellent wettability and spreadability, leading to their applications as super wetter/super spreader, but have the disadvantage of vulnerability to hydrolysis. A variety of trisiloxane surfactant structures are required to provide the functional improvement and the defect resolution for reflecting the necessities in the various applications. This review covers the synthetic schemes of reactive trisiloxanes as hydrophobic siloxane backbones, the main reaction schemes, such as hydrosilylation reaction, for coupling reactive trisiloxanes to hydrophilic groups, and the synthetic schemes of the main trisiloxane surfactants including polyether-, carbohydrate-, gemini-, bolaform-, double trisiloxane-type surfactants.