• KSBB Journal
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• 제22권6호
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• pp.433-437
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• 2007

본 연구에서는 나노임프린트 리소그래피를 이용하여 500 nm line, 600 nm pore, $1{\mu}m$ pore, $2.5{\mu}m$ pore의 마이크로 수준에서 나노 수준에 이르는 다양한 크기와 모양의 nanopore 형태 패턴을 제작하였다. Thermal imprint 방식과 달리 상온, 저압에서 임프린팅이 가능하며 사용되는 스탬프의 수명을 늘리고 보다 미세하고 복잡한 형태의 패턴을 제작할 수 있는 UV-assisted imprint 방식을 사용하였다. E-beam lithography로 패턴을 각인한 quartz소재의 스탬프를 사용하였으며 스탬프의 재질이 투명하여 UV 조사시 UV curable resin이 경화될 수 있도록 하였다. 또한 스탬프의 표면을 (heptadecafluoro-1,1,2,2-tetrahydrodecyl) trichlorosilane의 monolayer 층으로 미리 코팅하여 임프린트 후 스탬프와 기판과의 releasing을 쉽게함과 동시에 패턴의 일부가 스탬프에 묻어 나와 전사된 패턴에 defect가 없도록 하였다. 또한, gold를 미리 증착하여 임프린팅함으로써 lift-off 시에 필요한 hi-layer 층이 필요 없게 되어 산소 플라즈마를 이용한 에칭이 더욱 쉽고 lift-off 공정이 생략될 수 있도록 하였다. 나노임프린트 공정에 있어 가장 큰 문제점은 잔여층의 생성이며 이러한 잔여층을 제거하고자 산소 플라즈마 에칭을 하였다. 에칭공정을 통해 gold의 표면이 완전히 드러났으며 산소 플라즈마를 통해 gold의 표면이 친수성으로 바뀌어 추후 단백질 고정화를 더욱 쉽게 하였다. 그리하여 나노임프린트 기술을 이용해 나노크기의 바이오소자 제작을 가능하게 하였다.

• 한국안전학회지
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• 제26권4호
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• pp.41-46
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• 2011

The purpose of this paper is to analyze the causes of accidents related to the 3 phase 170 kV gas insulated switchgear of a power system collected from accident sites to secure data for the prevention of similar accidents and provide important points of view regarding diagnosis for the prevention of accidents involving gas insulated switchgears. The analysis results of the causes of accidents involving gas insulated switchgears showed deformation of the manipulation lever installed at the S-phase, disconnection of the insulation rod connection, melting of the upper conductor, a damaged tulip, damage to the lower spacer and the spacer at the breaker, etc. It is believed from this result that the potential for accidents has expanded due to accumulated energy as a result of repeated deterioration. The carbonization depth of a GIS was formed near the screw (T2, T3) used to secure the lower pole of the S-phase tulip. It is not known what has caused the screws to be extruded and melted. However, it is thought that an unbalanced electromagnetic force, micro-discharge, surface discharge, etc., have occurred at that point. In addition, even though 16 years have passed since its installation, there was no installation defect, act of arson, accidental fire, etc. General periodical inspection and diagnosis failed to find the factors causing the accidents. As a system contained in a closed metal container, it has a high risk factor. Therefore, it is necessary to design, install and operate a GIS in accordance with the standard operational procedure (SOP). In addition, it is necessary to apply conversion technology for periodical SF6 gas analysis and precision safety diagnosis. It is expected that tracking and managing these changes in characteristics by recording the results on the history card will provide a significant accident prevention effect.

• 한국전기전자재료학회논문지
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• 제24권6호
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• pp.433-439
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• 2011

Poly Si TFTs (poly silicon thin film transistors) with p channel those are annealed HT (high temperature) with gate poly crystalline silicon and LT (low temperature) with metal gate electrode were fabricated on quartz substrate using the analyzed data and compared according to the activated grade silicon thin films and the size of device channel. The electrical characteristics of HT poly-Si TFTs increased those are the on current, electron mobility and decrease threshold voltage by the quality of particles of active thin films annealed at high temperature. But the on/off current ratio reduced by increase of the off current depend on the hot carrier applied to high gate voltage. Even though the size of the particles annealed at low temperature are bigger than HT poly-Si TFTs due to defect in the activated grade poly crystal silicon and the grain boundary, the characteristics of LT poly-Si TFTs were investigated deterioration phenomena those are decrease the electric off current, electron mobility and increase threshold voltage. The results of transconductance show that slope depend on the quality of particles and the amplitude depend on the size of the active silicon particles.

• 한국재료학회지
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• 제27권6호
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• pp.331-338
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• 2017

This study was carried out to investigate the optimum condition of a friction stir welding process for a joint of AA2219-T87 and AA2195-T8 dissimilar aluminum alloys. These alloys are known to have good cryogenic properties, and as such to be suitable for use in fuel tanks of space vehicles. The welding parameters include the travelling speed, rotation speed and rotation direction of the tool. The experiment was conducted under conditions in which the travelling speed of the tool was 120-300 mm/min and the rotation speed of the tool was 400-800 rpm. To investigate the effect of the rotation direction of the tool, the joining was performed by switching the positions of the two dissimilar alloys. After welding, the microstructure was observed and the micro-hardness were measured; non-destructive evaluation was carried out to perform tensile tests on defect-free specimens. The result was that the microstructure of the weld joint underwent dynamic recrystallization due to sufficient deformation and frictional heat. The travelling speed of the tool had little effect on the properties of the joint, but the properties of the joint varied with the rotation speed of the tool. The conditions for the best joining properties were 600 rpm and 180-240 mm/min when the AA2219-T8 alloy was on the retreating side(RS).

• Journal of Periodontal and Implant Science
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• 제52권4호
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• pp.312-324
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• 2022

Purpose: The role of hard-type crosslinked hyaluronic acid (HA) with particulate bone substitutes in bone regeneration for combined inlay-onlay grafts has not been fully investigated. We aimed to evaluate the effect of hard-type crosslinked HA used with bone substitute in terms of new bone formation and space maintenance. Methods: A 15-mm-diameter round defect was formed in the calvaria of 30 New Zealand White rabbits. All animals were randomly assigned to 1 of 3 groups: the control group (spontaneous healing without material, n=10), the biphasic calcium phosphate (BCP) graft group (BCP, n=10), and the BCP graft with HA group (BCP/HA, n=10). The animals were evaluated 4 and 12 weeks after surgery. Half of the animals from each group were sacrificed at 4 and 12 weeks after surgery. Samples were evaluated using micro-computed tomography, histology, and histomorphometry. Results: The BCP group showed higher bone volume/tissue volume (BV/TV) values than the control and BCP/HA groups at both 4 and 12 weeks. The BCP and BCP/HA groups showed higher bone surface/tissue volume (BS/TV) values than the control group at both 4 and 12 weeks. The BCP group showed higher BS/TV values than the control and BCP/HA groups at both 4 and 12 weeks. No statistically significant difference in newly formed bone was found among the 3 groups at 4 weeks. The BCP group showed significantly higher new bone formation than the BCP/HA group at 12 weeks. Conclusions: Hard-type crosslinked HA did not show a positive effect on new bone formation and space maintenance. The negative effect of hard-type crosslinked HA may be due to the physical properties of HA that impede osteogenic potential.

• Journal of Photoscience
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• 제9권2호
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• pp.186-189
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• 2002

Many of the adverse effects of solar UV exposure appear to be directly attributable to damage to epidermal DNA. In particular, cyclobutane pyrimidine dimers (CPD) may initiate mutagenic changes as well as induce signal transduction responses that lead to a loss of skin immune surveillance and micro-destruction of skin structure. Our approach is to reverse the DNA damage using prokaryotic DNA repair enzymes delivered into skin using specially engineered liposomes. T4 endonuclease V encapsulated in liposomes (T4N5 liposome lotion) enhanced DNA repair by shifting repair of CPD from the nucleotide excision to the base excision repair pathway. Following topical application to humans, increased repair limited UV-induction of cytokines, many of which are immunosuppressive. In a recent clinical study, topical treatment of UV-irradiated human skin with T4N5 liposome lotion reduced the suppression of the nickel sulfate contact hypersensitivity response. Similarly, the photoreactivating enzyme enhances repair by directly reversing CPDs after absorbing activating light. Here also treatment of UV-irradiated human skin with photoreactivating enzyme in liposomes and photoreactivating light restored the response to the contact allergen nickel sulfate. These findings confirm in humans the observation in mice that UV induced suppression of contact hypersensitivity is caused in part by CPDs. We have tested the ability of T4N5 liposome lotion to prevent UV-induced skin cancer in patients with xeroderma pigmentosum (XP), who have an elevated incidence of skin cancer resulting from a genetic defect in DNA repair. Daily use of the lotion for one year in a group of 20 XP patients reduced the average number of actinic keratoses by 68% and basal cell cancers by 30% compared to 9 patients in the placebo control group. Delivery of DNA repair enzymes to skin is a promising new approach to photoprotection.

• Structural Engineering and Mechanics
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• 제86권4호
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• pp.487-501
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• 2023

Nanoparticles have lower size and larger specific surface area, good stability and less toxic and side effects. In recent years, with the development of nanotechnology, its application range has become wider and wider, especially in the field of biomedicine, which has received more and more attention. Bone defect repair materials with high strength, high elasticity and high tissue affinity can be prepared by nanotechnology. The purpose of this paper was to study how to analyze and study the composite materials for sports bone injury based on multifunctional nanomaterials, and described the electrospinning method. In this paper, nano-sized zirconia (ZrO₂) filled micro-sized hydroxyapatite (HAP) composites were prepared according to the mechanical properties of bone substitute materials in the process of human rehabilitation. Through material tensile and compression experiments, the performance parameters of ZrO₂/HAP composites with different mass fraction ratios were analyzed, the influence of filling ZrO₂ particles on the mechanical properties of HAP matrix materials was clarified, and the effect of ZrO₂ mass fraction on the mechanical properties of matrix materials was analyzed. From the analysis of the compressive elastic modulus, when the mass fraction of ZrO₂ was 15%, the compressive elastic modulus of the material was 1222 MPa, and when 45% was 1672 MPa. From the analysis of compression ratio stiffness, when the mass fraction of ZrO₂ was 15%, the compression ratio stiffness was 658.07 MPa·cm³/g, and when it was 45%, the compression ratio stiffness is 943.51MPa·cm³/g. It can be seen that by increasing the mass fraction of ZrO₂, the stiffness of the composite material can be effectively increased, and the ability of the material to resist deformation would be increased. Typically, the more stressed the bone substitute material, the greater the stiffness of the compression ratio. Different mass fractions of ZrO₂/HAP filling materials can be selected to meet the mechanical performance requirements of sports bone injury, and it can also provide a reference for the selection of bone substitute materials for different patients.

• 반도체디스플레이기술학회지
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• 제22권3호
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• pp.130-135
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• 2023

Plasma-resistant ceramic (PRC) is a material used to prevent internal damage in plasma processing equipment for semiconductors and displays. The challenge is to suppress particles falling off from damaged surfaces and increase retention time in order to improve productivity and introduce the latest miniaturization process. Here, we confirmed the effect of suppressing plasma deterioration and reducing the etch rate through surface treatment of existing PRC with an initial illumination level of 200 nm. In particular, quartz glass showed a decrease in etch rate of up to 10%. Furthermore, it is believed that micro-scale secondary particles formed on the microstructure of each material grow as crystals during the fluoridation process. This is a factor that can act as a killer defect when dropped, and is an essential consideration when analyzing plasma resistance. The plasma etching suppression effect of the initial illumination is thought to be due to partial over etching at the dihedral angle of the material due to the sputtering of re-emission of Ar+-based cations. This means that plasma damage due to densification can also be interpreted in existing PRC studies. The research results are significant in that they present surface treatment conditions that can be directly applied to existing PRC for mass production and a new perspective to analyze plasma resistance in addition to simple etching rates.

• 비파괴검사학회지
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• 제32권2호
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• pp.162-169
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• 2012

본 논문은 초음파 적외선 열화상과 위상잠금 방법을 이용하여 이종금속용접(STS304 and SA106 Gr. b)된 파이프의 응력부식균열 결함을 검출하였다. 초음파 가진장치는 출력 250 Watt, 주파수 20 kHz이었다. 실험 결과 이종금속용접부의 파이프 내부에 위치한 균열을 적외선 열화상을 이용하여 검출할 수 있었다. 실제 PT검사를 통하여 배관 내부의 균열이 하나가 아닌 일정한 범위 안에 하나 이상의 크랙이 존재하여 열화상 이미지 상에 넓은 범위의 hot spot 이미지를 만들어 냈음을 파악할 수 있었다. 또한 기존 기술로 검출이 용이하지 못한 마이크로 폭의 미세균열을 검출할 수 있었다. 또한, 초음파탐상기술은 $10\;{\mu}m$ 미세크랙의 폭을 갖은 균열을 쉽게 검출하지 못하였다. 그러나 초음파 적외선 열화상 기술은 결함 검출하였다.

• 한국진공학회지
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• 제22권5호
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• pp.250-256
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• 2013

양전자 소멸 분광법으로 발광 박막 시료에 3.0 MeV 에너지를 가진 양성자 빔을 $0.0{\sim}20.0{\times}10^{13}$ protons/$cm^2$의 조사에 의해 생성된 결함을 측정하여 박막구조 특성에 대하여 실험하였다. 동시 계수 도플러 넓어짐 양전자 소멸법 스펙트럼의 수리적 해석 방법인 S-변수를 사용하고, 양전자 수명 측정 방법에 의한 양전자 수명 ${\tau}_1$과 ${\tau}_2$, 이에 따른 세기 $I_1$과 $I_2$를 사용하여, 박막구조에 대한 결함 특성 변화를 측정하였다. 측정된 S-변수는 박막에 조사된 양성자의 빔 조사량에 따라 양성자가 빈자리에 포획되어 감소하는 값을 보였다. 양전자 수명 ${\tau}_1$은 증가하고, ${\tau}_2$은 일정한 값을 나타내었으나, 반면에 세기 $I_1$과 $I_2$는 큰 변화가 없었다. 그 이유는 양성자 조사 빔의 변화에 따라서 단일 빈자리의 크기는 증가하고, 다 결정체 알갱이 빈자리 때문에 양성자에 의한 다수의 빈자리 결함의 양은 큰 차이가 없기 때문이다. 그리고 Bragg 피크로 인하여 박막 시료의 특정 깊이에 결함을 형성하여 박막 전체의 결함으로 잘 나타나지 않기 때문으로 판단된다.