• Analytical Science and Technology
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• v.25 no.2
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• pp.91-101
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• 2012

A list of volatile fatty acids (VFA) including propionic acid, butyric acid, isovaleric acid, valeric acid, etc. is well known for offensive odorants. The analysis of odorant VFA is a highly delicate task due to high reactivity and unstable recovery rate. At present, analytical methods of VFA are recommended to include alkali impregnation filter method and alkali absorption method by the malodor prevention law of the Korea Ministry of Environment (KMOE). In this review, a survey has been made to explore various approaches available for the analysis of VFA to include both official methods of the KMOE and others. In light of the unreliability of those established analytical methods, it is highly desirable to develop some substituting methods for VFA. Among such options, one may consider such option as sorbent tube (ST) sampling and cryogenic trapping-thermal desorption technique. Moreover, procedures used for standard preparation, sampling steps, and instrumental detection stage are also evaluated. Application of container sampling (like Tedlar bag) is however not recommendable due to significant (sorptive) loss in sampling and in storage stage. In the detection stage, the use of GC/MS is recommendable to replace GC/FID due to the presence of diverse interfering substances. Thus, it is essential to properly establish the basic quality assurance (QA) for VFA analysis in air.

• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.488-497
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• 2018

Quantitative classification of insect fauna in transgenic rice in 2 LMO(Living genetically Modified Organism) isolated paddy fields (Gyeongsang National University, Gyeongbuk National University) and rice in 4 paddy fields(Duryang 1, Duryang 2, Hwagye 1, Hwagye 2), were evaluated for consecutive 5 years (2013 to 2017) in Sacheon, Gyeongnam province, and for 2 consecutive years (2015 to 2016) in Gunwi Gyeongbuk province. Sampling insect fauna were evaluated by black light trapping, sticky trapping, visual surveying, and sweeping methods in each target paddy field, respectively. A total of 37,941 individuals, of 464 species from 15 orders, were collected in Sacheon for 5 years. A total of 10,030 individuals, of 366 species from 13 orders, were collected in Gunwi for 2 years. Based on results of comparison between transgenic and non-transgenic paddy fields for 5 consecutive years, the similarity index between LMO paddy field and common paddy field is not different. Thus, this difference is not due to the environment, not the LMO.

• Journal of the Korean GEO-environmental Society
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• v.12 no.10
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• pp.57-62
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• 2011

This study investigated the effects of various inorganic anions($Cl^-$, $NO_3{^-}$, $HCO_3{^-}$) on the Methyl tert Butyl Ether(MTBE) degradation by photocatalysis using statistical method. Generally, this process in general demands the generation of hydroxyl radicals(OH radical) in solution in the presence of UV light. The generation of radicals were affected by inorganic anions in solution that inhibited the photodegradation by their trapping hydroxyl radicals. The effects of inorganic anions were mathematically described as the independent variables such as $Cl^-$, $NO_3{^-}$, and $HCO_3{^-}$, and these were designed by mixture analysis that was one of the response surface methodology(RSM). Regression analysis on ANOVA showed significant p-value(p<0.0001) and high coefficients for determination value($R^2$=99.28%, ${R^2}_{adj}$=98.91%). Contour and response surface plots showed that the effects of inorganic anions for MTBE photodegradation based on $UV/H_2O_2$ process. In the result, $Cl^-$ and $HCO_3{^-}$ inhibited the photodegradation of the MTBE by their trapping hydroxyl radicals, and the interaction by these two factors was observed.

• Journal of Bio-Environment Control
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• v.31 no.1
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• pp.22-27
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• 2022

The attraction effects of light emitting diode (LED) trap to Spodoptera exigua and Spodoptera litura adults were evaluated in greenhouse and compared with those of no light trap, which is typical used in commercial trap. At this time, in order to attract these two species of moths, sex pheromone traps were installed at the top side according to the degree of tomato growth inside the tomato cultivation greenhouse around the LED trap. In addition, two types of light-emitting traps (420 nm, 470 nm) were installed in the greenhouse at 1/40 m², respectively. Also two sex pheromone were installed inside of the greenhouse according to the height of the tomato plants. 10 days later, Blue-light trap(BLB, 470 nm wavelength) was 3.1-3.5 times more attractive than Violet-light trap(VLB, 420 nm wavelength) in S. exigua (105.6 ± 7.3) and S. litura (42.0 ± 3.1) respectively, whereas the no-light trap was little attractive to S. exigua (33.7 ± 2.8) and S. litura (12.0 ± 1.5). On the other hand, after the installation of the sex pheromone trap and the LED trap, there was no damage to S. litura (Fabricius) and S. exigua in the pesticide-free area, indicating a high possibility of control. At this time, the operating cost of the two types of LED traps was 80 won/m² per unit area, and it was confirmed that both types of moths could be controlled. In addition, as a result of confirming the number of two types of moths caught in the sexual pheromone trap and two types of LED traps after 4 months, it was judged that eco-friendly control was possible as more than 373 moths/trap were attracted to the two types of moths.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.319.1-319.1
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• 2016

Recently, the Al-doped ZnO (ZnO:Al) films are intensively used in thin film a-Si solar cell applications due to their high transmittance and good conductivity. The textured ZnO:Al films are used to enhance the light trapping in thin film solar cells. The wet etch process is used to texture ZnO:Al films by dipping in diluted acidic solutions like HCl or HF. During that process the glass substrate could be damaged by the acidic solution and it may be difficult to apply it for the inline mass production process since it has to be done outside the chamber. In this paper we report a new technique to control the surface morphology of RF-sputtered ZnO:Al films. The ZnO:Al films are textured with vaporized HF formed by the mixture of HF and H2SiO3 solution. Even though the surface of textured ZnO:Al films by vapor etching process showed smaller and sharper surface structures compared to that of the films textured by wet etching, the haze value was dramatically improved. We achieved the high haze value of 78% at the wavelength of 540 nm by increasing etching time and HF concentration. The haze value of about 58% was achieved at the wavelength of 800 nm when vapor texturing was used. The ZnO:Al film texture by HCl had haze ratio of about 9.5 % at 800 nm and less than 40 % at 540 nm. In addition to low haze ratio, the texturing by HCl was very difficult to control etching and to keep reproducibility due to its very fast etching speed.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.76.1-76.1
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• 2015

Optical resonances of metallic or dielectric nanoantennas enable to effectively convert free-propagating electromagnetic waves to localized electromagnetic fields and vice versa. Plasmonic resonances of metal nanoantennas extremely modify the local density of optical states beyond the optical diffraction limit and thus facilitate highly-efficient light-emitting, nonlinear signal conversion, photovoltaics, and optical trapping. The leaky-mode resonances, or termed Mie resonances, allow dielectric nanoantennas to have a compact size even less than the wavelength scale. The dielectric nanoantennas exhibiting low optical losses and supporting both electric and magnetic resonances provide an alternative to their metallic counterparts. To extend the utility of metal and dielectric nanoantennas in further applications, e.g. metasurfaces and metamaterials, it is required to understand and engineer their scattering characteristics. At first, we characterize resonant plasmonic antenna radiations of a single-crystalline Ag nanowire over a wide spectral range from visible to near infrared regions. Dark-field optical microscope and direct far-field scanning measurements successfully identify the FP resonances and mode matching conditions of the antenna radiation, and reveal the mutual relation between the SPP dispersion and the far-field antenna radiation. Secondly, we perform a systematical study on resonant scattering properties of high-refractive-index dielectric nanoantennas. In this research, we examined Si nanoblock and electron-beam induced deposition (EBID) carbonaceous nanorod structures. Scattering spectra of the transverse-electric (TE) and transverse-magnetic (TM) leaky-mode resonances are measured by dark-field microscope spectroscopy. The leaky-mode resonances result a large scattering cross section approaching the theoretical single-channel scattering limit, and their wide tuning ranges enable vivid structural color generation over the full visible spectrum range from blue to green, yellow, and red. In particular, the lowest-order TM01 mode overcomes the diffraction limit. The finite-difference time-domain method and modal dispersion model successfully reproduce the experimental results.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.1
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• pp.35-40
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• 2015

In this study, an n-ZnO/p-Si heterojunction diode with embedded Ag nanoparticles was fabricated to investigate the possible improvement of light trapping via the surface plasmon resonance effect for solar cell applications. The Ag nanoparticles were fabricated by the physical sputtering method. The acquired current-voltage curves and optical absorption spectra demonstrated that the application of Ag nanoparticles in the n-ZnO/p-Si interface increased the photo current, particularly in specific wavelength regions. The results indicate that the enhancement of the photo current was caused by the surface plasmon resonance effect generated by the Ag nanoparticles. In addition, minority carrier lifetime measurements showed that the recombination losses caused by the Ag nanoparticles were negligible. These results suggest that the embedding of Ag nanoparticles is a powerful method to improve the performance of n-ZnO/p-Si heterojunction solar cells.

• Development and Reproduction
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• v.4 no.1
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• pp.1-6
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• 2000

Ultrastructure of the zona radiata the micropyle and fertilization process in the rainbow trout (Oncorhynchus mykiss) were examined by light, scanning and transmission microscopes . The egg micropyle of rainbow trout consists of a funnel-shaped vestibule and a tapered canal transversing the zona radiata. The micropyle showed the type with a flat pit leading into a long canal and the micropylar wall showed the clockwise spiral structure. There were a great number of microvilli secreting adhesive materials having trapping function attracting the spermatozoa in the vicinity of micropyle. It was apparent that ridges extended between the projections. In the initial stages of penetration, the spermatozoon still within the micropylar canal attached perpendicularly at its apical tip to the egg surface, then the sperm head was rapidly engulfed by the folded egg surface with its many microvilli. The spermatozoon disappeared from the outer surface of the egg before the fertilization cone completely retracted 250 seconds after insemination. No interconnecting ridges was present in the egg surface. In short, the block to polyspermy to permit entry of a single sperm is considered to be mechanical by the morphological design of the micropyle and fertilization cone.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.113-116
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• 2005

In this paper, silicon thin-film solar cells(Si- TFSC) and a-Si/c-Si heterojunction solar cells(HJ-cell) are investigated. The Si-TFSC was prepared on glass substrate by depositing $1-3{\mu}m$ thin-film silicons by glow discharge method. The $a-Si:H/{\mu}c-Si:H$ tandem solar cells on textured ZnO:A1 TCO (transparent conducting oxide) showed improved Jsc in top and bottom cells than that on $SnO_2:F$ TCO. This enhancement of jsc resulted from improved light trapping effect by front textured ZnO:A1. The a-Si/c-Si HJ-cells with simple structure without high efficiency features are suffering from low Voc and Jsc. The improvement of front nip and back interface properties by adopting high quality silicon-films at low temperature should be done both for increasing device performances and production cost.

• Journal of Information Display
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• v.9 no.4
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• pp.21-29
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• 2008

We studied both the wavelength and intensity dependent photo-responses (photofield-effect) in amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs). During the a-IGZO TFT illumination with the wavelength range from $460\sim660$ nm (visible range), the off-state drain current $(I_{DS_off})$ only slightly increased while a large increase was observed for the wavelength below 400 nm. The observed results are consistent with the optical gap of $\sim$3.05eV extracted from the absorption measurement. The a-IGZO TFT properties under monochromatic illumination ($\lambda$=420nm) with different intensity was also investigated and $I_{DS_off}$ was found to increase with the light intensity. Throughout the study, the field-effect mobility $(\mu_{eff})$ is almost unchanged. But due to photo-generated charge trapping, a negative threshold voltage $(V_{th})$ shift is observed. The mathematical analysis of the photofield-effect suggests that a highly efficient UV photocurrent conversion process in TFT off-region takes place. Finally, a-IGZO mid-gap density-of-states (DOS) was extracted and is more than an order of magnitude lower than reported value for hydrogenated amorphous silicon (a-Si:H), which can explain a good switching properties observed for a-IGZO TFTs.