• Journal of Ceramic Processing Research
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• v.13 no.spc2
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• pp.403-406
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• 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.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.30.2-30.2
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• 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
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• v.20 no.8
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• pp.1196-1200
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• 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.

• The Korean Journal of Pesticide Science
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• v.2 no.3
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• pp.79-84
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• 1998

Tandem HPLC and atmospheric pressure chemical ionization(APcI) LC/MS method was used for the determination and confirmation of carbendazim residues in soybean sprout. Fluorescence(FL) detector was connected in tandem with the ultraviolet(UV) detector for dual detection of the carbendazim residue at the excitation and emission wavelength of 280 nm and 310 nm, respectively. The limit of detection for carbendazim was $0.1{\mu}g/kg$ sample. Recoveries of carbendazim from fortified soybean sprout at 0.5, 1.0 and 2.0 ppm were averaged 89.1%. Mass spectrometry using a APcI source confirmed the carbendazim residue in the soybean sprout sample. Fragmentation pattern on the APcI LC/MS spectrum of carbendazim was simpler than that from electron impact(EI) mass spectrum. Carbendazim produced 3 major ions including m/z 133, m/z 159 and m/z 191($M^{+}$). This method was sensitive enough to provide reliable and reproducible results for practical applications.

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.362-365
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• 2015

Silica encapsulated ZnSe quantum dots (QDs) were prepared by employing two microemulsion systems: AOT/water/cyclohexane microemulsions containing ZnSe quantum dots with NP5/water/cyclohexane microemulsions containing tetraethylorthosilicate (TEOS). Using this method, cubic zinc blende nanoparticles (3 nm in diameter) were synthesized and encapsulated by silica nanoparticles (20 nm in diameter). The temperature dependence of photoluminescence (PL) for silica-encapsulated ZnSe QDs was investigated to evaluate this material as a temperature sensor media. The fluorescence emission intensity of silica-encapsulated ZnSe nanoparticles (NPs) was decreased with an increase of ambient temperature over the range from $30^{\circ}C$ to $60^{\circ}C$ and a linear relationship between the temperature and the emission intensity was observed. In addition, the temperature dependence of PL intensity for silica-encapsulated ZnSe NPs showed a reversible pattern on ambient temperature. A reversible temperature dependence of the luminescence combined with its insensitivity toward quenching by oxygen due to silica coating established this material as an attractive media for temperature sensor applications.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.142.2-142.2
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• 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
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• v.16 no.4
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• pp.74-79
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• 2003

Comparison of interfacial properties and microfailure mechanisms of oxygen-plasma treated poly(p-phenylene-2,6-benzobisoxazole(PBO. Zylon) and poly(p-phenylene terephthalamide)(PPTA, Kevlar) fibers/ epoxy composites were investigated using micromechanical technique and nondestructive acoustic emission(AE). Interfacial shear strength(IFSS) and work of adhesion, Wa of PBO or Kevlar fibers/epoxy composites increased by oxygen-plasma treatment. Plasma-treated Kevlar fiber shooed the maximum critical surface tension and polar term, whereas the untreated PBO fiber showed the minimum value. Microfibril fracture pattern of plasma-treated Kevlar fiber appeared obviously. Based on the propagation of microfibril failure toward core region. the number of AE events for plasma-treated PBO and Kevlar fibers increased significantly. The results oi nondestructive AE were consistent well with microfailure modes by optical observation in microdroplet and two-fiber composites tests.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.1
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• pp.110-124
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• 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.

• Tunnel and Underground Space
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• v.15 no.4 s.57
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• pp.250-263
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• 2005

Progressive and localized brittle failures around an excavated opening by the overstressed condition can act as a serious obstacle to ensure the stability and the economical efficiency of construction work. In this paper, the characteristics of the brittle failure around an circular opening with stress level was studied by the biaxial compressive test using sealed specimen and by the numerical simulation with $PFC^{2D}$, one of the discrete element codes. The occurring pattern and shape of the brittle failure around a circular opening monitored during the biaxial loading were well coincided with those of the stress induced failures around the excavated openings observed in the brittle rock masses. The crack development stages with stress level were evaluated by the detailed analysis on the acoustic emission event properties. The microcrack development process around a circular opening was successfully visualized by the particle flow analysis. It indicated that the scaled test had a good feasibility in understanding the mechanism of the brittle failure around an opening with a high reliability.

• Journal of Korean Society for Atmospheric Environment
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• v.28 no.2
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• pp.142-158
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• 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.