• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.21-21
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• 2011

A series of Quasi-Elastic Neutron Scattering (QENS) experiments helps us to understand the single-particle (hydrogen atom) dynamics of a globular protein and its hydration water and strong coupling between them. We also performed Molecular Dynamics (MD) simulations on a realistic model of the hydrated hen-egg Lysozyme powder having two proteins in the periodic box. We found the existence of a Fragile-to-Strong dynamic Crossover (FSC) phenomenon in hydration water around a protein occurring at TL=$225{\pm}5K$ by analyzing Intermediate Scattering Function (ISF). On lowering of the temperature toward FSC, the structure of hydration water makes a transition from predominantly the High Density Liquid (HDL) form, a more fluid state, to predominantly the Low Density Liquid (LDL) form, a less fluid state, derived from the existence of a liquid?liquid critical point at an elevated pressure. We showed experimentally and confirmed theoretically that this sudden switch in the mobility of the hydration water around a protein triggers the dynamic transition (so-called glass transition) of the protein, at a temperature TD=220 K. Mean Square Displacement (MSD) is the important factor to show that the FSC is the key to the strong coupling between a protein and its hydration water by suggesting TL${\fallingdotseq}$TD. MD simulations with TIP4P force field for water were performed to understand hydration level dependency of the FSC temperature. We added water molecules to increase hydration level of the protein hydration water, from 0.30, 0.45, 0.60 and 1.00 (1.00 is the bulk water). These confirm the existence of the FSC and the hydration level dependence of the FSC temperature: FSC temperature is decreased upon increasing hydration level. We compared the hydration water around Lysozyme, B-DNA and RNA. Similarity among those suggests that the FSC and this coupling be universal for globular proteins, biopolymers.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.333-333
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• 2011

We have investigated the breakdown properties in liquids by high voltage pulse system. High voltage pulse power system is consisted of the Marx-generator with two capacitors (0.5 ${\mu}F$, withstanding voltage is 40 kV), to which the charging voltage can be applied to maximum 30 kV DC, spark gap switch and charging resistor of 20 $M{\Omega}$. We have made use of tungsten pin electrodes of anode-cathode (A-K), which are immersed into the liquids. The breakdown voltage and current signals are measured by high voltage probe (Tektronix P6015A) and current monitor (IPC CM-1.S). Especially the high speed breakdown or plasma propagation characteristics in the pulsed A-K gap have been investigated by using the high speed ICCD camera. We have measured the electron temperature through the Boltzmann plot method from the breakdown spectrums. Here the A-K gap has been changed by 1 mm, 2 mm, and 3 mm. The used liquids are distilled water and solution of salt (0.9 %). The output voltage and current signals at breakdown in distilled water are shown to be bigger than those in saline solution. The breakdown voltage and current characteristics in liquids will be discussed in accordance with A-K gap distances. It is also found that the electron temperatures and plasma densities in liquids are decreased in conformity with A-K gap.

• 한국진공학회지
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• 제7권2호
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• pp.94-103
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• 1998

HFCVD(Hot Filament Chemical Vapor Deposition)방법을 이용한 다이아몬드의 핵 생성과 성장에 있어서, 인가한 직류 bias를 변수로 하여 핵생성 밀도와 증착율의 변화를 조 사하였다. 반응압력 20torr, 메탄농도 1.0%, Filament 온도 $2100^{\circ}C$ 그리고 Substrate 온도 $980^{\circ}C$에서 증착 단계를 핵생성기와 성장기로 구분하고 각 단계마다 bias의 방향과 크기를 다르게 인가하면서 다이아몬드 박막을 증착시켰다. Negative bias는 핵생성기에는 핵생성을 촉진시키지만 성장기에도 계속 인가하면 결정입자의 지속적인 성장을 방해하고 결정 구조를 비다이아몬드 성분으로 변화시키는 작용을 하여 박막의 morphology에 좋지 않은 영향을 주 었다. Positive bias는 핵생성기와 성장기에서 모두 $CH_4$의 분해를 촉진시킨 결과 증착율의 향상을 가져왔다. 따라서 다이아몬드 박막의 증착시 핵생성기에서는 negative bias를 인가하 고 성장기에는 positive bias를 인가하는 것이 핵생성 밀도와 증착율의 향상에 효과적인 것 으로 조사되었다.

• Applied Microscopy
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• 제47권1호
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• pp.55-62
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• 2017

This paper describes experiments aimed at characterizing the behavior of field electron emitters fabricated by coating carbon fibers with epoxylite resin. Polyacrylonitrile carbon fibers of type VPR-19, thermally treated at $2,800^{\circ}C$, were used. Each was initially prepared in a "uncoated" state, by standard electro polishing and cleaning techniques, and was then examined in a scanning electron microscope. The fiber was then baked overnight in a field electron microscope (FEM) vacuum chamber. Current-voltage characteristics and FEM images were recorded on the following day or later. The fiber was then removed from the FEM, coated with resin, "cured" by baking, and replaced in the FEM. After another overnight bake, the FEM characterization measurements were repeated. The coated fibers had significantly better performance than uncoated fibers. This confirms the results of earlier experiments, and is thought to be due in part to the formation of a conducting channel in the resin over layer. For the coated fiber, lower voltages were needed to obtain the same emission current. The coated fibers have current-voltage characteristics that show smoother trends, with greater stability and repeatability. No switch-on phenomena were observed. In addition, the emission images on the phosphor-coated FEM screen were more concentrated, and hence brighter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.223-225
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• 2008

In order to apply SFCLs into electric power systems, the urgent issues to be settled are as follows, such as initial installation price, operation and maintenance cost due to ac loss of superconductor and the life of cryostat, and high voltage and high current problems. We designed novel hybrid SFCLs which combine superconductor and conventional electric equipments including a vacuum interrupter, an electro-magnetic contactor and a current limiting reactor. The main purpose of the hybrid SFCL is to drastically reduce total usage of superconductor by adopting current commutation method by use of the superconductor and the fast switch. According to protective coordination and performance, we investigated two concepts of Hybrid SFCLs. First is a half cycle fault current limitation type and second is a non-half cycle fault current limitation type. We concluded that the non-half cycle fault current limitation type is batter than the other.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 추계기술심포지움논문집
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• pp.195-198
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• 2002

현재의 광통신, 이동통신 및 디지털 시대에서는 보다 소형화되고, 대용량의 데이터 저장 및 다기능 소자에 대한 요구가 많아지고 있다. 이러한 전자 산업 환경에서 MEMS 소자는 여러 요구조건을 만족시킬 수 있는 특징을 갖추고 있으며 실제 소자의 제작에 있어서 MEMS 소자를 이용하여 여러 물리 및 화학 센서 및 Actuator 제작에 응용이 되어지고 있고 Optical switch, Gyroscope, 적외선 어레이 센서, 가속도 센서, 위치 센서 등 여러 분야에서 실용화가 진행되어지고 있다. MEMS 구조물의 packaging 방법에 있어서는 내부 MEMS 소자의 동작을 위한 외부 환경으로부터의 보호를 위하여 Hermetic sealing에 대한 요구를 만족시켜야 한다. 본 발표에서는 이와 같은 MEMS device의 진공 패키지를 구현함에 있어서 기판 내부에 수동소자를 실장할 수 있는 LTCC 기술을 이용하여 진공 패키징하는 방법에 대하여 소개한다. 본 기술을 이용하는 경우 기존의 Hermetic sealing 이외에 향후 적층 기판 내부에 수동소자를 내장시켜 배선 길이 및 노이즈 성분을 감소시켜 더욱 전기적 성능을 향상시킬 수 있는 장점이 있게된다. 본 논문에서는 LTCC 기판을 이용하여 패키징 시킨 후, 내부 진공도에 영향을 줄 수 있는 계면들에서의 시간에 따른 진공도 변화의 특성치를 측정하여 LTCC 기판의 Hermetic sealing 특성에 관하여 조사하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.102-103
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• 2007

In order to apply resistive superconducting fault current limiters into electric power systems, the urgent issues to be settled are as follows, such as initial installation price of SFCL, operation and maintenance cost due to ac loss of superconductor and the life of cryostat, and high voltage and high current problems. The ac loss and high cost of superconductor and cryostat system are main bottlenecks for real application. Furthermore in order to increase voltage and current ratings of SFCL, a lot of superconductor components should be connected in series and parallel which resulted in extreme high cost. Thus, in order to make practical SFCL, we designed novel hybrid SFCL which combines superconductor and conventional electric equipment including vacuum interrupter, power fuse and current limiting reactor. The main purpose of hybrid SFCL is to drastically reduce total usage of superconductor by adopting current commutation method by use of superconductor and high fast switch. Consequently, it was possible to get the satisfactory test results using this method, and further works for practical applications are in the process.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.134-134
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• 2011

High-k dielectric materials such as $HfO_2$, $ZrO_2$ and $Al_2O_3$ increase gate capacitance and reduce gate leakage current in MOSFET structures. This behavior suggests that high-k materials will be promise candidates to substitute as a tunnel barrier. Furthermore, stack structure of low-k and high-k tunnel barrier named variable oxide thickness (VARIOT) is more efficient.[1] In this study, we fabricated the $WSi_2$ nanocrystals nonvolatile memory device with $SiO_2/HfO_2/Al_2O_3$ tunnel layer. The $WSi_2$ nano-floating gate capacitors were fabricated on p-type Si (100) wafers. After wafer cleaning, the phosphorus in-situ doped poly-Si layer with a thickness of 100 nm was deposited on isolated active region to confine source and drain. Then, on the gate region defined by using reactive ion etching, the barrier engineered multi-stack tunnel layers of $SiO_2/HfO_2/Al_2O_3$ (2 nm/1 nm/3 nm) were deposited the gate region on Si substrate by using atomic layer deposition. To fabricate $WSi_2$ nanocrystals, the ultrathin $WSi_2$ film with a thickness of 3-4 nm was deposited on the multi-stack tunnel layer by using direct current magnetron sputtering system [2]. Subsequently, the first post annealing process was carried out at $900^{\circ}C$ for 1 min by using rapid thermal annealing system in nitrogen gas ambient. The 15-nm-thick $SiO_2$ control layer was deposited by using ultra-high vacuum magnetron sputtering. For $SiO_2$ layer density, the second post annealing process was carried out at $900^{\circ}C$ for 30 seconds by using rapid thermal annealing system in nitrogen gas ambient. The aluminum gate electrodes of 200-nm thickness were formed by thermal evaporation. The electrical properties of devices were measured by using a HP 4156A precision semiconductor parameter analyzer with HP 41501A pulse generator, an Agillent 81104A 80MHz pulse/pattern generator and an Agillent E5250A low leakage switch mainframe. We will discuss the electrical properties for application next generation non-volatile memory device.

• 대한수의학회지
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• 제39권6호
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• pp.1210-1217
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• 1999

This study was carried out to develop a newly designed ovum pick-up(OPU) instrument for ultrasound-guided transvaginal follicular aspiration in cows. This new instrument consists of out- & inner-layer stainless pipes and a grip with a trigger(hand) switch. Some gauge types of disposable needles and tubes can be attached to this inner pipe. With this instrument, while grasping an ovary with one hand, the other hand can handle in apiration and vacuum on/off with the least assitant's help. With this instrument the mean recovery rate of bovine follicular oocytes was 45.2%. In recovered oocytes, usable oocytes(Grade I & II) were 30.4% and this rate meant 1.4 oocytes per ovary. For 30 days after initial aspiration with this instrument, some adverse effects such as adhesion, hemorrhage, hematoma and other mass formation in/with ovaries were also examined by rectal examination, ultrasonographic and endoscopic images. Adhesion was found in one ovary 1 week after aspiration, and hemorrhagic lesion was found 1-2 days and petechia were found 3-5 days after aspiration and there was no remarkable adverse effects. It was found that this instrument could be applicable and safe for ovum pick-up in cows.

• 한국초전도ㆍ저온공학회논문지
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• 제9권4호
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• pp.32-36
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• 2007

We fabricated and tested a novel hybrid superconducting fault current limiter (SFCL) of three-phase $24kV_{rms}/630A_{rms}$ rating. In order to apply conventional resistive SFCLs into electric power systems, the urgent issues to be settled are as follows, such as initial installation price of SFCL, operation and maintenance cost due to ac loss of superconductor and the life of cryostat, and high voltage and high current problems. The ac loss and high cost of superconductor and cryostat system are main bottlenecks for real application. Furthermore in order to increase voltage and current ratings of SFCL, a lot of superconductor components should be connected in series and parallel which resulted in extreme high cost. In addition, the method to quench all components at the same instant needs very sophisticated skill and careful operation. Due to these problems, the practical applications of SFCL were pending. Therefore, in order to make practical SFCL, the price of SFCL should be lowered and should meet the demand of utilities. We designed novel hybrid SFCL which combines superconductor and conventional electric equipment including vacuum interrupter, power fuse and current limiting reactor. The main purpose of hybrid SFCL is to drastically reduce total usage of superconductor by adopting current commutation method by use of superconductor and high fast switch. Consequently, it was possible to get the satisfactory test results using this method, and further works for field tests are in the process.