• Journal of Ceramic Processing Research
• /
• 제13권spc2호
• /
• pp.403-406
• /
• 2012

Effect of thickness on ZnO properties including the compositional ratio and crystallinity has been systematically investigated using a variety of characterization tools of x-ray diffraction, field emission scanning electron microscopy, x-ray fluorescence and x-ray photoelectron spectroscopy. Interestingly, it was observed that ZnO films below 80 nm in thickness were in oxygen deficiency, while the oxygen ratio was increased in the films above the thickness, although the compositional ratio of ZnO film was not linearly varied with increasing film thickness. Also, ZnO crystallinity, which is characterized by (002) diffraction pattern, was clearly improved with increasing film thickness. The properties of ZnO film with different sputtering time and the nature of direct current reactive sputtering process were discussed in terms of compositional ratio, especially oxygen ratio in ZnO film.

• 천문학회보
• /
• 제46권1호
• /
• pp.30.2-30.2
• /
• 2021

The extended Lyα nebulae (also known as Lyα blobs or LABs) observed at z=2-6 can provide clues to galaxy formation in the early universe. The connection of LABs with the overdensities of compact Lyα emitters suggests that they are associated with matter density peaks in the universe and thus likely to evolve into the present-day groups and clusters of galaxies. However, the mechanism powering the extended Lyα emission in LABs is remained controversial. The detection of polarization signals that follow the theoretically predicted trend is interpreted as strong evidence supporting that the LABs are caused primarily by the resonance scattering of Lyα originating from star-forming galaxies and AGNs. However, Trebitsch et al. (2016) claimed that the radial profile of polarization could be better explained by the scenario in which Lyα photons are produced in the cooling gas surrounding galaxies and then self-scattered by the gas, rather than by the scattering scenario of photons originating from the central galaxies. In this presentation, using LaRT, a state-of-art Lyα radiative transfer code, it is demonstrated that the observed polarization pattern can be reproduced even with the scattering scenario.

• Asian-Australasian Journal of Animal Sciences
• /
• 제20권8호
• /
• pp.1196-1200
• /
• 2007

Eight feeds (mixture of wheat straw and oil seed cakes in 3:1 ratio) were evaluated for methane emission and fermentation pattern with buffalo rumen liquor as inoculum in an in vitro gas production test. The cakes tested were groundnut cake (GNC), soybean cake (SBC), mustard seed cake (MSC), cotton seed cake (CSC), karanj seed cake expeller extracted (KCEE), karanj seed cake solvent extracted (KCSE), caster bean cake expeller extracted (CBCEE) and caster bean cake solvent extracted (CBCSE). The gas production (ml/g dry matter) was significantly higher with SBC and MSC followed by CSC, GNC, KCSE, KCEE, CBCSE and was the lowest with CBCEE. Methane emission was significantly lower with KCEE, KCSE, CBCEE, CBCSE (20.32- 22.43 ml/g DM) than that with SBC, GNC, CSC (27.34-31.14 ml/g DM). Mustard seed cake was in-between the two groups of oil cakes in methane production. In vitro true digestibility was highest with SBC followed by GNC, CSC, MSC, KCSE, KCEE, CBCSE and CECEE. Ammonia nitrogen level was positively correlated with the amount of protein present in the cake. Total holotrich protozoa were significantly higher with SBC, whereas, large spirotrich protozoa tended to be lower than with other cakes. The counts of small spirotrich and total protozoa were similar with all the cakes. Total volatile fatty acid production and acetate to propionate ratio were significantly higher with SBC and significantly lower with KCEE as compared to the other cakes. Among the conventional oil cakes tested in the present experiment (GNC, SBC, MSC and CSC), mustard seed cake-based feed produced the minimum methane without affecting other fermentation characteristics adversely.

• 농약과학회지
• /
• 제2권3호
• /
• pp.79-84
• /
• 1998

콩나물중 carbendazim 잔류분을 정량하고 확인할 수 있는 새로운 분석법을 확립하고자 tandem HPLC(UV & FL) 및 APcI를 source로 사용한 LC/MS를 이용하였다. 이를 위해 FL(fluorescence) 검출기를 UV(ultraviolet) 검출기와 나란히 연결하여 UV 검출기의 경우 280 nm 파장을 그리고 FL 검출기의 경우는 excitation파장과 emission파장을 각각 280 mn와 310 nm로 설정하였다. 분석결과 carbendazim의 검출한계는 $0.04{\mu}g/kg$이었다. 콩나물에 carbendazim을 0.5, 1.0 및 2.0 ppm 수준으로 첨가하여 회수율을 측정한 결과 그 평균값은 89.1%이었다. APcI source를 사용한 LC/MS 질량스펙트럼 방법은 콩나물중 carbendazim 잔류분을 최종 확인할 수 있었다. APcI LC/MS 방법은 전자충격에 의한 질량스펙트럼에 비해 훨씬 간단한 fragment를 형성할 뿐 만 아니라 carbendazim의 경우 m/z 133, m/z 159, m/z 191($M^{+}$)의 전형적인 fragment 이온을 형성하므로, 이 방법을 병행한다면 콩나물중 carbendazim 잔류분을 효과적으로 확인할 수 있을 것으로 사료되었다.

• 공업화학
• /
• 제26권3호
• /
• pp.362-365
• /
• 2015

본 연구에서는 polyoxyethylenenonylphenylether (NP5) 계면활성제와 sodium bis(2-ethylhexyl) sulfosuccinate (AOT) 계면활성제가 형성하는 두 종류의 W/O 마이크로에멀젼을 이용해서 실리카에 담지된 ZnSe 양자점을 제조하였다. 본 방법으로 3 nm 크기의 cubic zinc blende 결정 구조를 갖는 ZnSe 입자를 합성하였으며 약 20 nm 크기의 실리카 입자에 효과적으로 담지 시킬 수 있었다. 합성된 입자의 photoluminescence (PL) 주변 온도 의존성을 $30^{\circ}C$에서 $60^{\circ}C$ 범위에서 확인한 결과, 온도가 증가함에 따라 PL intensity가 감소하였으며 PL intensity와 온도와는 높은 상관관계를 나타내었다. 아울러 PL intensity와 온도의 상관관계는 온도를 낮은 곳에서 올려가며 측정한 경우와 반대로 낮추며 측정한 경우 같은 상관도를 나타내어 온도 의존성이 가역적임을 알 수 있었다. 그 결과 실리카에 담지된 ZnSe 양자점이 온도 센서로 사용될 수 있는 잠재적인 매체임을 확인하였다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
• /
• pp.142.2-142.2
• /
• 2015

Plasma etch endpoint detection (EPD) of SiO2 and PR layer is demonstrated by plasma impedance monitoring in this work. Plasma etching process is the core process for making fine pattern devices in semiconductor fabrication, and the etching endpoint detection is one of the essential FDC (Fault Detection and Classification) for yield management and mass production. In general, Optical emission spectrocopy (OES) has been used to detect endpoint because OES can be a simple, non-invasive and real-time plasma monitoring tool. In OES, the trend of a few sensitive wavelengths is traced. However, in case of small-open area etch endpoint detection (ex. contact etch), it is at the boundary of the detection limit because of weak signal intensities of reaction reactants and products. Furthemore, the various materials covering the wafer such as photoresist (PR), dielectric materials, and metals make the analysis of OES signals complicated. In this study, full spectra of optical emission signals were collected and the data were analyzed by a data-mining approach, modified K-means cluster analysis. The K-means cluster analysis is modified suitably to analyze a thousand of wavelength variables from OES. This technique can improve the sensitivity of EPD for small area oxide layer etching processes: about 1.0 % oxide area. This technique is expected to be applied to various plasma monitoring applications including fault detections as well as EPD.

• Composites Research
• /
• 제16권4호
• /
• pp.74-79
• /
• 2003

Micromechanical 시험법과 음향방출을 이용하여 산소 플라즈마 처리된 PBO와 Kevlar 섬유강화 에폭시 복합재료의 계면물성과 미세파괴메카니즘을 고찰하여 상호 비교하였다. 산소 플라즈마 처리된 PBO와 Kevlar 섬유강화 에폭시 복합재료의 계면전단강도와 접착일은 극성 작용기의 도입으로 향상 시킬 수 있었다. 임계표면장력과 총 표면자유에너지 중 극성 표면자유에너지는 플라즈마 처리된 Kevlar 섬유에서 가장 컸으며. 미처리된 PBO의 섬유의 경우에서 가장 작았다. Microfibril 파단 형상은 산소 플라즈마 처리된 Keviar 섬유의 경우에서는 명확하게 관찰 되었으며. 미처리와 비교차여 microfibril 파단이 대각선 방향으로 연속적해서 일어나 가장 많은 섬유 파단 신호가 감지되었다 비파괴 음향방출법을 이용하여 얻은 섬유파단 감지 결과는 microdroplet과 두 섬유강화 복합재료 시험법에서 광학현미경을 이용하여 관찰한 미세파단 형상과 상호 일치하였다.

• 한국대기환경학회지
• /
• 제23권1호
• /
• pp.110-124
• /
• 2007

In this study, the control efficiency of odorous compounds was measured from diverse control process units of 14 individual companies located within the Ban-Wall industrial complex of Ansan city, Korea (January to July 2005), To quantify the control efficiency levels of major odorous compounds, we collected odor samples from both the front and rear side of 17 control process units ($N=17{\times}2=34$). If the control efficiency is compared for each of 32 compounds between different process units, wet scrubber (WS) was found to be the most effective unit in terms of the sum of pollutants showing the positive control signals. Although the WS system shows generally a good control pattern for VOC, it is not the case for most index odorous pollutants; only 3 out of 12 index compounds were found to show positive control efficiencies. The results of the study also indicated that the control efficiency differ greatly between different industrial sectors and/or control process types. In the case of leather industry, carbonyl compounds were found to exhibit the highest control efficiency with its values varying from 19 to 90%. On the other hand, in the case of metal production sector, VOC recorded the maximum control efficiency with values varying from 18 to 79%. According to this study, most air pollution control facilities operated in most companies show fairly poor control efficiencies for most malodor compounds. Hence, to obtain best control efficiency of odorous pollutant emission, acquisition of better information on source characteristics and establishment of effective control technologies are highly demanding.

• 터널과지하공간
• /
• 제15권4호
• /
• pp.250-263
• /
• 2005

암반 내 형성된 과도한 초기응력장은 굴착 공동 주변에 점진적이고 국부적인 취성파괴를 유발시킴으로서 시공의 안정성과 경제성을 확보하는데 장애 요인으로 작용할 수 있다. 이 논문에서는 응력 수준 증가에 따른 공동 주변의 취성파괴 거동 특성을 파악하기 위해 축소된 원형 터널 공시체를 이용한 이축압축시험과 입자 결합 모델을 이용하여 개별요소법의 일종인 $PFC^{2D}$ 해석에 의한 연구를 수행하였다. 실내 이축압축시험을 통해 취성파괴의 발생 영역과 형태 면에서 실제 암반 공동 주변에서 발생된 파괴 특성과 유사한 파괴 거동을 모사할 수 있었다. 응력 강도비 증가에 따라 진행된 균열 발전단계를 미소파괴음 특성 변수들에 대한 상세 분석을 통해 평가하였다. $PFC^{2D}$ 해석을 통해 공동 주변에서의 미세 균열 발생과 전파 과정을 성공적으로 가시화하였으며 이를 통해 이축 압축시험 결과의 신뢰성과 시험방법의 적정성을 확인할 수 있었다.

• 한국대기환경학회지
• /
• 제28권2호
• /
• pp.142-158
• /
• 2012

This paper investigates the physical and chemical characteristics of long-range transport (LRT) process of air pollutants by employing the MM5-CMAQ and its comparison with local emission dominant (LED) case over northeast Asia. We first classified high air pollution days into LRT and LED cases based on the synoptic meteorological variables of vorticity and geostrophic wind speed/direction at a geopotential level of over 850hPa. LRT cases are further categorized into three types of transport patterns (LRT-I-III) according to the air mass pathways from source regions. LRT-I-III are originated from northern, central, and southern China, respectively, identified by back trajectory analysis. Three LRT-I-III groups have different and unique locations of high pressure and transport pathways. The chemical characteristics showed that the simulated spatial distributions varied in terms of locations of maximum concentrations and the temporal variation of surface concentrations. The primary air pollutants such as $NO_x$, $PM_{10}$ and $SO_2$ of all of three LRT cases are well transported into Korea peninsula with different concentration levels. Of LRT cases, LRT-II has the greatest effect on air quality of Korea peninsula, followed by LRT-I and LRT-III. In comparison with LRT, the LED case shows relatively higher air pollution concentrations in general, but showed a variety of different air quality levels following the emission strength pattern. These widely varying patterns are impling the case dependent multi-directional approach for the development of indicators of long-range transport process over northeast Asia.