• 한국진공학회지
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• 제18권4호
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• pp.254-258
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• 2009

순방향 전압에서 안정적인 전류 흐름을 가지고 낮은 turn-on 전압으로 구동하는 이리듐 합성물 기반의 인광 고분자 발광 다이오드를 제작하였다. Poly(N-vinylcabazole)와 tris(2-phenylpyridine)iridium 재료를 포함하는 유기 발광층은 $10{\mu}m$/s 와 $20{\mu}m$m/s의 저속도 dip-coating으로 만들었다. 제안한 방법으로 형성된 유기 발광 다이오드는 100 cd/$m^2$의 기준 휘도에서 각각 5.8 V와 6.7 V로 구동이 되었지만, 발광층을 스핀코팅으로 제작된 소자는 다소 높은 전압인 9.1 V를 기록하였다. 본 연구는 대면적, 용액 공정 기반의 고효율 특성을 요구하는 유기 발광 소자에서 발광층의 새로운 박막 형성기술로 이용될 수 있다.

• 한국전기전자재료학회논문지
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• 제34권1호
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• pp.16-20
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• 2021

In this study, we tried finding new materials to improve the stain resistance properties of polymer insulating materials. Using the filtered vacuum arc source (FVAS) with a graphite target source, DLC thin films were deposited on silicon and polymer insulator substrates depending on their thickness to confirm the surface properties, physical properties, and structural properties of the thin films. Subsequently, the possibility of using a DLC thin film as a protective coating material for polymer insulators was confirmed. DLC thin films manufactured in accordance with the thickness of various thin films exhibited a very smooth and uniform surface. As the thin film thickness increased, the surface roughness value decreased and the contact angle value increased. In addition, the elastic modulus and hardness of the DLC thin film slightly increased, and the maximum values of elastic modulus and hardness were 214.5 GPa and 19.8 GPa, respectively. In addition, the DLC thin film showed a very low leakage current value, thereby exhibiting electrical insulation properties.

• 한국진공학회지
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• 제7권s1호
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• pp.106-117
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• 1998

Fluorocarbonated-SiO2 films were deposited on p-type Si(100) substrate using FSi$(OC_2H_5)_3$ (FTES), and $O_2$ mixture gases by a helicon plasms source. High density $O_2$/FTES/Ar plasma of ~$10^{12} \textrm{cm}^{-3}$ is obtained at low pressure (<3mTorr) with RF power above 900 W in the helicon plasma source. Optical emission spectroscopy (OES) is used to study the relation between the relative densities of the radicals and the film properties. The FTES and $O_2$ gases are greatly dissociated at the helicon mode that is launched at the above threshold plasma density. FTIR and XPS spectra shows that the film has Si-F, and C-F bonds during the formation process of the film which may lower the dielectric constant greatly. The relative dielectric constant, leakage current density, and dielectric breakdown voltage are about 2.8, $8\times10^{-9}\textrm{A/cm}^2$, and > 12 MV/cm, respectively.

• 대한기계학회논문집B
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• 제34권9호
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• pp.867-873
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• 2010

수냉각 발전기 고정자 권선에서의 냉각수 누수 및 흡습에 의한 절연파괴 손상사례가 국내 및 국외에서 자주 발생되고 있다. 이러한 사고는 막대한 경제적 피해뿐만 아니라 전력의 안정적 공급 측면에서 매우 심각한 계통 사고로 연결될 수 있다. 특히 국내 발전기는 15년 이상 운전되어 열화가 진행된 발전기가 50% 이상이며, 계획예방정비 기간 중에 권선에서의 누설 및 흡습 권선이 종종 발견되고 있다. 기존에는 누수 시험 전 과정인 권선 건조 과정을 무시한 채 누수 시험 결과만으로 권선 누설 여부를 진단하였으나 본 논문에서는 누수 시험을 위한 준비 단계인 진공 건조 시의 권선 내부의 진공도 패턴 분석을 통해 권선 누설 및 흡습 여부를 예측진단할 수 있는 방법을 실험적으로 증명하였다.

• 한국재료학회지
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• 제12권5호
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• pp.382-386
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• 2002

We studied growth and characterization of $SrBi_2Ta_2O_9$ (SBT) thin films fabricated by low temperature process under vacuum and/or oxygen ambient. A metal organic decomposition (MOD) method based on a spin-on technique and annealing process using a rapid thermal annealing (RTA) method was used to prepare the SBT films. The crystallinity of a ferroelectric phase of SBT thin films is related to the oxygen partial pressure during RTA process. Under an oxygen partial pressure higher than 30 Torr, the crystallization temperature inducing the ferroelectric SBT phase can be lowered to $650^{\circ}C$. Those films annealed at $650^{\circ}C$ in vacuum and oxygen ambient showed good ferroelectric properties, that is, the memory window of 0.5~0.9 V at applied voltage of 3~7 V and the leakage current density of 1.80{\times}10^{-8}$ A/$\textrm{cm}^2$ at an applied voltage of 5V. In comparison with the SBT thin films prepared at 80$0^{\circ}C$ in $O_2$ ambient by furnace annealing process, the SBT thin films prepared at $650^{\circ}C$ in vacuum and oxygen ambient using the RTA process showed a good crystallization and electrical properties which would be able to apply to the virtul device fabrication precess.

• 식품과학과 산업
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• 제50권2호
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• pp.12-26
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• 2017

Processing steps such as washing and cutting, involved in preparing fresh-cut produce causes tissue damage, leading to rapid quality deterioration. Major defects of fresh-cut produce are discoloration, softening, off-odor development, and microbial growth. Packaging of fresh-cut produce has been changed to reduce these quality problems. Flexible packaging film is widely used to pack fresh-cut produce. Vacuum packaging was the popular packaging method in the beginning of fresh-cut industry in Korea. Vacuum packaging creates high $CO_2$ and low $O_2$ levels to control browning of fresh-cut produce. However, these conditions induce some visual defects and off-odor development. Discoloration problem was also found when fresh-cut produce was packaged with conventional packaging film or plastic tray. Modified atmosphere (MA) packaging is effective for prolonging shelf-life of fresh-cut produce by decreasing $O_2$ and increasing $CO_2$ concentration in the package. Retail MA packaging using different oxygen transmission rate (OTR) film and micro-perforated film has started to be applied to fresh-cut produce in Korea. Proper MA package design that provides optimum range of $O_2$ and $CO_2$ partial pressures is one of the major challenges in the industry. An initial package flushing with $N_2$ or an low $O_2$/high $CO_2$ atmosphere is also used to more rapidly establish steady-state MA condition. Film OTR and $O_2$ flushing affects the fermentative volatile production, off-odor development, electrolyte leakage, discoloration, $CO_2$ injury, microbial population of fresh-cut produce. There is also a demand for convenient packaging to attract consumers. Rigid fresh-cut produce container for retail market has increased since the packaging provides excellent protection from physical damage during transport. Rigid tray used as actual serving vessel for the consumer is increasing in Korea. The tray with flexible lid to wrap or seal fresh-cut produce is more and more gaining popularity. Further practical technology to control quality change and microbial growth for each fresh-cut product has been studied since various fresh-cut items were required. The fresh-cut industry also focuses on searching for more convenient and environmentally friendly packaging.

• Restorative Dentistry and Endodontics
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• 제20권2호
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• pp.780-788
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• 1995

The purpose of this study was to compare the apical seal following root canal shaping by different methods. From fourty extracted mandibular 1st and 2nd molars, fourty mesial roots whose canals have some degree of curvature were selected. The mesiobuccal root portion including mesiobuccal portion of a crown was sectioned in each molar. After access cavity preparation for the mesiobuccal canal, working length was determined with # 10 K-file. The sectioned roots were implanted in acrylic resin block and randomly divided into four groups. The canals of group I were shaped by step-down/balanced force, group II by stepdown/step-back, group III by step-back and group IV by conventional method. All of the shaped canals were obturated by Thermafil method and access cavities were filled with IRM. The roots were removed from acrylic resin block and placed in 100 % humidity for 7days. Except the root surfaces of apical 2mm, the root surfaces were nail-varnished 3 times. After the roots were placed in 700 torr vacuum pressure for 15 minutes, they were immersed in 2% methylene blue solution for 4 days. Nail varnishes were removed with acetone. After that, the roots were decalcified in 5 % nitric acid and dehydrated with alcohol series. Transparent specimens were made by methyl salicylate and the quality of apical seal was assessed by measuring the leakage linearly. The results were as follows. 1. The leakage in canals shaped by step-down/balanced force method was significantly less than that in canals shaped by step-back method(P<0.05) and was less but not statistically than that in canals shaped by step-down/step-back method (P>0.05). 2. The leakage in canals shaped by step-down/step-back method was less than that in canals shaped by step-back method, but there was no statistical significance(P>0.05). 3. The leakage in canals shaped by conventional method was significantly more than that in canals shaped by step-down/balanced force, step-down/step-back and step-back method (P<0.05).

• Tribology and Lubricants
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• 제19권1호
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• pp.9-14
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• 2003

The sealing performance of an elastomeric O-ring using the double layered material has been analyzed fer the contact stress behaviors that develop between the O-ring seal and the surfaces with which it comes into contact. The leakage of an O-ring will occur when the pressure differential across the seal Just exceeds the initial (or static) peak contact stress. The contact stress behaviors that develop in compressed O-rings, in common case of dovetail grooved geometry, are investigated using the finite element method. The FE analysis includes material hyperelasticity and axisymmetry. The computed FEM results show that the contact stress behaviors are related to the ratio of diameter between the inner ring and the outer ring, and the temperature of vacuum chamber.

• Tribology and Lubricants
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• 제16권2호
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• pp.138-143
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• 2000

The sealing performance of an elastomeric O-ring seal with a temperature gradient has been analyzed for the contact stress behaviors that develop between the O-ring seal and the housing surfaces with which it comes into contact in the dovetail groove. The leakage of an O-ring seal will occur when the pressure differential across the seal just exceeds the initial peak contact stress. The contact stress behaviors that develop in compressed O-rings, in common case of restrained geometry (grooved), are investigated using the finite element method. The FE analysis includes material hyperelasticity and axisymmetry The computed FEM results show that the contact stress behaviors are related to a compression rate and a temperature gradient between the vacuum chamber with a dovetail groove and the contacting plate with a cooling jacket.

• 산업기술연구
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• 제34권
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• pp.67-70
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• 2014

In this paper, we propose a diagnosis algorithm for 25.8kV $N_2$ insulated Pad-mounted Switchgear in oder to improve reliability by preventing of fault in advance. The proposed algorithm can diagnose the problems of Pad-mounted Switchgear such as gas leakage and VI(Vacuum Interrupter) trouble (contact abrasion, coil aging etc.) by using pressure sensor, stroke sensor and coil current sensor.