• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.619-619
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• 2009

Recently, silica nanostructures are widely used in various applicationary areas such as chemical sensors, biosensors, nano-fillers, markers, catalysts, and as a substrate for quantum dots etc, because of their excellent physical, chemical and optical properties. Additionally, these days, semiconductor silica and silicon with high purity is a key challenge because of their metallurgical grade silicon (MG-Si) exhibit purity of about 99% produced by an arc discharge method with high cast. Tremendous efforts are being paid towards this direction to reduce the cast of high purity silicon for generation of photovoltaic power as a solar cell. In this direction, which contains a small amount of impurities, which can be further purified by acid leaching process. In this regard, initially the low cast rice-husk was cultivated from local rice field and washed well with high purity distilled water and were treated with acid leaching process (1:10 HCl and $H_2O$) to remove the atmospheric dirt and impurity. The acid treated rice-husk was again washed with distilled water and dried in an oven at $60^{\circ}C$. The dried rice-husk was further annealed at different temperatures (620 and $900^{\circ}C$) for the formation of silica nanospheres. The confirmation of silica was observed by the X-ray diffraction pattern and X-ray photoelectron spectroscopy. The morphology of obtained nanostructures were analyzed via Field-emission scanning electron microscope(FE-SEM) and Transmission electron microscopy(TEM) and it reveals that the size of each nanosphares is about 50-60nm. Using the Inductively coupled plasma mass spectrometry(ICP-MS), Silica was analyzed for the amount of impurities.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권7호
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• pp.3066-3079
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• 2016

Recent years have witnessed a dramatic increase in topology research of wireless sensor networks (WSNs) where both energy consumption and survivability need careful consideration. To balance energy consumption and ensure survivability against both random failures and deliberate attacks, we resort to complex network theory and propose an energy-aware preferential attachment (EPA) model to generate a robust topology for WSNs. In the proposed model, by taking the transmission range and energy consumption of the sensor nodes into account, we combine the characters of Erdős -Rényi (ER) model and Barabasi-Albert (BA) model in this new model and introduce tunable coefficients for balancing connectivity, energy consumption, and survivability. The correctness of our theoretic analysis is verified by simulation results. We find that the topology of WSNs built by EPA model is asymptotically power-law and can have different characters in connectivity, energy consumption, and survivability by using different coefficients. This model can significantly improve energy efficiency as well as enhance network survivability by changing coefficients according to the requirement of the real environment where WSNs deployed and therefore lead to a crucial improvement of network performance.

• 생명과학회지
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• 제10권6호
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• pp.564-569
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• 2000

This study was designed to investigate the effect of silkworm (Bombyx mori L.) powder on lipofuscin, acetylcholine (ACh) and its related enzyme activities in brain of rats. Sprague-Dawley (SD) male rats ($160{\pm}10g$) were fed basic diet (control group), and experimental diets (SWP-200 and SWP-400 groups) added 200 and 400 mg/kg BW/day for 6 weeks. In case of liver membranes, lipofuscin (LF) levels resulted in a slight decreases (4.6% and 11.5%, respectively) in SWP-200 and SWP-400 groups compared with control group. But in case of barin as the most sensitive organ, LF levels were remarkably inhibited about 16.7% and 20.0% in SWP-200 and SWP-400 groups compared with control group. There were no significant differences in acetylcholine (ACh) syntheses as a very important neurotransmitter, and choline acetyltransferase (ChAT) activities as a synthesis enzyme of ACh, and acetylcholinesterase (AChE) activities as a hydrolysis enzyme, which were concerned in transmission of neuron through synapses in brain of SWP-200 and SWP-400 groups compared with control group. Monoamine oxidase-B (MAO-B) activities were significantly inhibited (about 10.2%) in brain of SWP-400 groups compared with control group. These results suggest that inhibiting effects of LF accumulation and MAO-B activity of silkworm powder (SWP) may play a pivotal role in attenuating a various age-related changes for improvement of brain function.

• Tribology and Lubricants
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• 제34권1호
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• pp.23-32
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• 2018

Coupling is a mechanical component that transmits rotational force by connecting two shafts. Curvic coupling is widely used in high-performance systems because of its excellent power transmission efficiency and easy machining. However, coupling applications change dynamic behavior by reducing the stiffness of an entire system. Contact surface stiffness is an important parameter that determines the dynamic behavior of a system. In addition, the roughness profile of a contact surface is the most important parameter for obtaining contact stiffness. In this study, we theoretically establish the process of contact and bending stiffness analysis by considering the rough surface contact at Curvic coupling. Surface roughness parameters are obtained from Nayak's random process, and the normal contact stiffness of a contact surface is calculated using the Greenwood and Williamson model in the elastic region and the Jackson and Green model in the elastic-plastic region. The shape of the Curvic coupling contact surface is obtained by modeling a machined shape through an actual machining tool. Based on this modeling, we find the maximum number of gear teeth that can be machined according to the contact angle. Curvic coupling stiffness is calculated by considering the contact angle, and the calculation process is divided into stick and slip conditions. Based on this process, we investigate the stiffness characteristics according to the contact angle.

• 소성∙가공
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• 제8권3호
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• pp.241-241
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• 1999

With the aim of assessing the degradation of Zr-2.5Nb pressure tubes operating in the Wolsong unit-1 nuclear power plant, characterization tests are being conducted on irradiated Zr-2.5Nb tubes removed after 10-year operation. The examined tube had been exposed to temperatures ranging from 264 to 306℃ and a neutron fluence of 8.9×$10^{21}$ n/cm²(E>1 MeV) at the maximum. Tensile tests were carried out at temperatures ranging from RT to 300℃. The density of a-type and c-type dislocations was examined on the irradiated Zr-2.5Nb tube using a transmission electron microscope. Neutron irradiation up to 8.9×$10^{21}$ n/cm²(E>1 MeV) yielded an increase in a-type dislocation density of the Zr-2.5Nb pressure tube to 7.5×$10^{14} m^{-2}$, which was highest at the inlet of the tube exposed to the low temperature of 275℃. In contrast, the c-component dislocation density did not change with irradiation, keeping an initial dislocation density of 0.8×$10^{14} m^{-2}$ over the whole length of the tube. As expected, the neutron irradiation increased mechanical strength by about 17-26% in the transverse direction and by 34-39% in the longitudinal direction compared to that of the unirradiated tube at 300℃. The change in the mechanical properties with irradiation is discussed in association with the microstructural change as a function of temperature and neutron fluence.

• 대한기계학회논문집A
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• 제36권5호
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• pp.555-561
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• 2012

자동차 변속기 내부에서 동력을 전달하는 헬리컬 기어의 소음 및 진동을 억제하기 위한 하나의 방법으로 정밀하게 가공된 기어를 검사하기 위한 방법에 관한 것이다. 본 연구에서는 측정 기준이 되는 표준 기어와 측정 대상 기어인 워크 기어를 정밀하게 측정하는 알고리즘에 관한 것이다. 기존의 방법은 표준 기어와 모니터 기어를 1회전하여 주파수 방법으로 측정 표준을 위한 마스터링 작업을 수행하였다. 본 연구에서는 제시된 알고리즘을 사용하여 표준 기어와 모니터 기어를 측정하고, 표준 기어와 모니터 기어의 오차를 계산하는 방법을 제시함으로써 기어 측정에 대한 정밀도를 높이도록 하였다. 또한 본 알고리즘을 사용하면 빠른 속도로 측정의 표준이 되는 마스터링 공정을 빠르고 정확하게 측정할 수 있을 것으로 예상된다.

• 비파괴검사학회지
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• 제37권1호
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• pp.1-6
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• 2017

본 논문에서는 테라헤르츠파 시간분광영상시스템을 이용하여 도핑된 실리콘 웨이퍼의 물리적 특성을 측정하는 것에 관한 연구를 진행하였다. 투과모드와 $30^{\circ}$의 입사각을 가진 반사모드를 이용하여 측정하였으며 실리콘 웨이퍼의 도핑 정도는 N-type과 P-type 모두에서 $10^{14}$에서 $10^{18}$까지 다양하게 준비하였다. 그 결과, 도핑 정도와 테라헤르츠파와의 상관관계를 찾았으며 이를 이용하면 모든 경우에 대한 도핑된 실리콘 웨이퍼의 도핑 정도를 확인할 수 있다. 또한, 각 도핑된 실리콘 웨이퍼의 도핑된 두께, 굴절률, 유전율을 테라헤르츠 시간영역 파형분석을 통하여 계산할 수 있었다. 따라서, 테라헤르츠 시간분광영상화 기술은 도핑된 실리콘 웨이퍼의 굴절률과 유전율과 같은 물리적 특성뿐만 아니라 도핑 정도를 측정할 수 있는 유용한 기술이 될 것으로 기대된다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.144-144
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• 2012

최근 폴리머를 기판으로 하는 고속 Flexible TFT (Thin film transistor)나 고효율의 박막 태양전지(Thin film solar cell)를 실현시키기 위해 낮은 비저항(resistivity)을 가지며, 높은 홀 속도(carrier hall mobility)와 긴 이동거리를 가지는 다결정 반도체 박막(poly-crystalline semiconductor thin film)을 만들고자 하고 있다. 지금까지 다결정 박막 반도체를 만들기 위해서는 비교적 높은 온도에서 장시간의 열처리가 필요했으며, 이는 폴리머 기판의 문제점을 야기시킬 뿐 아니라 공정시간이 길다는 단점이 있었다. 이에 반도체 박막의 재결정화 온도를 낮추어 주는 metal (Al, Ni, Co, Cu, Ag, Pd, etc.)을 이용하여 결정화시키는 방법(MIC)이 많이 연구되어지고 있지만, 이 또한 재결정화가 이루어진 반도체 박막 안에 잔류 금속(residual metal)이 존재하게 되어 비저항을 높이고, 홀 속도와 이동거리를 감소시키는 단점이 있다. 이에 본 실험은, 종래의 MIC 결정화 방법에서 이용되어진 금속 증착막을 이용하는 대신, HIPIMS (High power impulse magnetron sputtering)와 PIII&D (Plasma immersion ion implantation and deposition) 공정을 복합시킨 방법으로 적은 양의 알루미늄을 이온주입함으로써 재결정화 온도를 낮추었을 뿐 아니라, 잔류하는 금속의 양도 매우 적은 다결정 반도체 박막을 만들 수 있었다. 분석 장비로는 박막의 결정화도를 측정하기 위해 GIXRD (Glazing incident x-ray diffraction analysis)와 Raman 분광분석법을 사용하였고, 잔류하는 금속의 양과 화학적 결합 상태를 알아보기 위해 XPS (X-ray photoelectron spectroscopy)를 통한 분석을 하였다. 또한, 표면 상태와 막의 성장 상태를 확인하기 위하여 HRTEM(High resolution transmission electron microscopy)를 통하여 관찰하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.127-127
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• 2011

We investigate the transparent TFTs using a transparent ZnSnO3 (ZTO)/Ag/ZTO multilayer electrode as S/D electrodes with low resistivity of $3.24{\times}10^{-5}$ ohm-cm, and high transparency of 86.29% in ZTO based TFTs. The Transparent TFTs (TTFTs) are prepared on glass substrate coated 100 nm of ITO thin film. On atomic layer deposited $Al_2\;O_3$, 50 nm ZTO layer is deposited by RF magnetron sputtering through a shadow mask for channel layer using ZTO target with 1 : 1 molar ratio of ZnO : $SnO_2$. The power of 100W, the working pressure of 2mTorr, and the gas flow of Ar 20 sccm during the ZTO deposition. After channel layer deposition, a ZTO (35 nm)/Ag (12 nm)/ZTO(35 nm) multilayer is deposited by DC/RF magnetron sputtering to form transparent S/D electrodes which are patterned through the shadow mask. Devices are annealed in air at 300$^{\circ}C$ for 30 min following ZTO deposition. Using UV/Visible spectrometer, the optical transmittances of the TTFT using ZTO/Ag/ ZTO multilayer electrodes are compared with TFT using Mo electrode. The structural properties of ZTO based TTFT with ZTO/Ag/ZTO multilayer electrodes are analyzed by high resolution transmission electron microscopy (HREM) and X-ray photoelectron spectroscopy (XPS). The transfer and output characterization of ZTO TTFTs are examined by a customized probe station with HP4145B system in are.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.287-287
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• 2011

ITRS(international technology roadmap for semiconductors)에 따르면 MOS (metal-oxide-semiconductor)의 CD(critical dimension)가 45 nm node이하로 줄어들면서 poly-Si/SiO2를 대체할 수 있는 poly-Si/metal gate/high-k dielectric이 대두되고 있다. 일반적으로 metal gate를 식각시 정확한 CD를 형성시키기 위해서 plasma를 이용한 RIE(reactive ion etching)를 사용하고 있지만 PIDs(plasma induced damages)의 하나인 PICD(plasma induced charging damage)의 발생이 문제가 되고 있다. PICD의 원인으로 plasma의 non-uniform으로 locally imbalanced한 ion과 electron이 PICC(plasma induced charging current)를 gate oxide에 발생시켜 gate oxide의 interface에 trap을 형성시키므로 그 결과 소자 특성 저하가 보고되고 있다. 그러므로 본 연구에서는 이에 차세대 MOS의 metal gate의 식각공정에 HDP(high density plasma)의 ICP(inductively coupled plasma) source를 이용한 중성빔 시스템을 사용하여 PICD를 줄일 수 있는 새로운 식각 공정에 대한 연구를 하였다. 식각공정조건으로 gas는 HBr 12 sccm (80%)와 Cl2 3 sccm (20%)와 power는 300 w를 사용하였고 200 eV의 에너지로 식각공정시 TEM(transmission electron microscopy)으로 TiN의 anisotropic한 형상을 볼 수 있었고 100 eV 이하의 에너지로 식각공정시 하부층인 HfO2와 높은 etch selectivity로 etch stop을 시킬 수 있었다. 실제 공정을 MOS의 metal gate에 적용시켜 metal gate/high-k dielectric CMOSFETs의 NCSU(North Carolina State University) CVC model로 effective electric field electron mobility를 구한 결과 electorn mobility의 증가를 볼 수 있었고 또한 mos parameter인 transconductance (Gm)의 증가를 볼 수 있었다. 그 원인으로 CP(Charge pumping) 1MHz로 gate oxide의 inteface의 분석 결과 이러한 결과가 gate oxide의 interface trap양의 감소로 개선으로 기인함을 확인할 수 있었다.