• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.383-383
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• 2011

Generally, field emitters can be categorized into two types according to the emitter shape, one is a planar field emitter and the other is a point emitter. The planar field emitter is used for displays, flat lamps and signage boards. On the other hands, the point field emitter is expected to play a significant role in x-ray sources and electron beam sources. Such applications of the point field emitters, especially, need large emission current and high emission stability with a small electron beam size. A few reports announced point emitters made by carbon nanotubes (CNTs). However, they still have suffered from poor reproducibility and low emission current. Here, we demonstrated high performance CNT point emitters by attaching CNTs onto graphite rod. Graphite rod exhibited good electrical conductivity and chemical stability. In this method, the shape of the point emitter could be easily controlled by changing the length and diameter of the graphite rod. The CNT point emitter showed emission current over 1 mA at an applied electric field of 1.4 V/${\mu}m$. We consider that the stable emission performance is attributed to the stable contact between CNTs and graphite rod.

• Restorative Dentistry and Endodontics
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• v.17 no.1
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• pp.69-82
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• 1992

An experimental investigation of the physical properties of light curing composite resin P-50 was performed, in which an argon ion laser beam was irradiated. The physical and mechanical properties of laser polymerized composite resin were determined by measuring the compressive strength, diametral tensile strength, curing depth and microhardness depending upon the experimental conditions such as the laser irradiation time(10sec, 20sec, 30sec) and laser power(300mW, 500mW, 1000mW). These observations were compared with a conventional visible light curing technique. In addition, to evaluate the marginal adaptation, Class V cavity was prepared on the buccal or lingual surface of the extracted premolar and filled with P-50 light curing resin. The test samples were irradiated with both light sources so that the interface between the restoration and the tooth structure were observed under scanning electron microscope. The most of physical and mechanical properties of the laser cured resin showed a remarkable improvement than those treated with the conventional light source, while the observations with the scanning electron microscope provided no significant difference for two polymerized sources. From the results in the experiment it appears that the potential of an argon ion laser is of important value of the use in the polymerization of composite resin.

• Electronics and Telecommunications Trends
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• v.34 no.5
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• pp.1-13
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• 2019

In modern times, X-ray imaging has become a necessary tool for early diagnosis, quality control, nondestructive testing, and security screening. X-ray imaging equipment generally comprises an X-ray generator and an image sensor. Most commercially available X-ray generators employ filament-thermionic electron-based X-ray tubes, thus demonstrating typical analog behavior, such as slow response and large stray X-rays. Furthermore, digital X-ray sources, which have been studied extensively using field electron emitters manufactured from nanometer-scale materials, provide fast and accurately controlled ultra-shot X-rays. This could usher in a new era of X-ray imaging in medical diagnosis and nondestructive inspections. Specifically, digital X-ray sources, with reduced X-ray dose, can significantly improve the temporal and spatial resolution of fluoroscopy and computed tomography. Recently, digital X-ray tube technologies based on carbon nanotubes, developed by Electronics and Telecommunications Research Institute, have been transferred to several companies and commercialized for dental imaging for the first time.

• Food Science and Preservation
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• v.21 no.3
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• pp.315-320
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• 2014

This study evaluated the effects of a gamma ray (GR), electron beam (EB), and X-ray (XR) to improve the safety of black pepper powder. The black pepper powder was irradiated by GR, EB, and XR at 2, 4, 6, 8, and 10 kGy. The results of the total bacterial populations in the black pepper power sample showed a similar effect on microbial decontamination for radiation sources. Radiation sensitivity ($D_{10}$ value) on the initial bacteria loads in the sample was 2.24 kGy in GR, 2.37 kGy in EB, and 2.75 kGy in XR. In addition, there were no differences among the radiation sources. The color values, such as L (lightness), a (redness), and b (yellowness), were not changed significantly. The sensory characteristics of GR, EB, and XR irradiated black pepper powder were decreased when the radiation dose increased, but there was no significant changes among the radiation sources. The results can be applied to investigate the effects of radiation sources on the microbiological and sensory characteristics of black pepper powder.

• Korean Journal of Food Science and Technology
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• v.41 no.2
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• pp.131-135
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• 2009

The identification characteristics of irradiated commercial Ramen soup were investigated depending on radiation sources and doses by electron spin resonance (ESR) spectroscopy. Two commercial powder soups (RS-1, RS-2) were irradiated at 0 to 20 kGy under ambient conditions by both a Co-60 gamma irradiator and an electron beam (EB) accelerator, respectively. Crystalline sugar-induced multi-component signals with g-values of 2.010/2.011, 2.006, 2.002 and 1.999 were detected in the irradiated Ramen soup (RS-1, RS-2), whereas $Mn^{2+}$ signals were observed in non-irradiated samples, thereby distinguishing each other. Under the same analytical conditions, the intensity of ESR signals was higher in EB-irradiated samples than the gamma-irradiated ones. Determination coefficients ($R^2$) between irradiation doses and corresponding ESR responses were above 0.9665 in all the samples, and the magnetic field of specified g-value remained constant. The predominant ESR signals of $g_2$ (2.010-2.011) and $g_3$ (2.002) increased with corresponding doses of irradiation ($R^2$= 0.9750-0.9981).

• Journal of the Korean Vacuum Society
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• v.17 no.5
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• pp.426-434
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• 2008

A space averaged $SiH_4/O_2/Ar$ simulator for the high density inductively coupled plasma sources for $SiH_4/O_2/Ar$ discharge is developed. The developed simulator uses space averaged fluid equations for electrons, positive ions, negative ions, neutral species, and radicals in $SiH_4/O_2/Ar$ plasma discharge, and the electron heating model including the anomalous skin effect. Using the developed simulator, the dependency of the density of charged particles, neutral particles, and radicals, the electron temperature, the plasma resistance, and the power absorption coefficient for the RF power and pressure is calculated.

• Journal of Microbiology and Biotechnology
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• v.33 no.6
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• pp.707-714
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• 2023

Plant-derived insecticide-neonicotinoid insecticides (NIs) played a crucial role in the development of agriculture and food industry in recent years. Nevertheless, synthesis of these nitrogen-containing heterocyclic compounds with an effective and greener routing remains challenging especially to the notion raise of "green chemistry" and "atom economy". While bio-catalyzed methods mediated by nicotinate dehydrogenase (NDHase) then provide an alternative. The current review mainly focuses on the introduction of sources, components, structure, catalytic mechanism and applications of NDHase. Specifically, NDHase is known as nicotinic acid hydroxylase and the sources principally derived from phylum Proteobacteria. In addition, NDHase requires the participation of the electron respiratory chain system on the cell membrane. And the most important components of the electron respiratory chain are hydrogen carrier, which is mainly composed of iron-sulfur proteins (Fe-S), flavin dehydrogenase (FAD), molybdenum binding protein and cytochromes. Heterologous expression studies were hampered by the plasmid and host with high efficiency and currently only Pseudomonas entomophila L48 as well as Comamonas testosterone was successfully utilized for the expression of NDHase. Furthermore, it is speculated that the conjugate and inductive effects of the substituent group at position 3 of the substrate pyridine ring exerts a critical role in the hydroxylation reactions at position 6 concerning about the substrate molecular recognition mechanism. Finally, applications of NDHase are addressed in terms of pesticide industry and wastewater treatment. On conclusion, this critical review would not only deepen our understanding of the theory about NDHase, but also provides the guideline for future investigation of NDHase.

• Journal of Biosystems Engineering
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• v.38 no.2
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• pp.87-94
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• 2013

Purpose: Pineapple is now the third most important tropical fruit in world production after banana and citrus. Phytosanitary irradiation is recognized as a promising alternative treatment to chemical fumigation. However, most of the phytosanitary irradiation studies have dealt with physiochemical properties and its efficacy. Accurate dose calculation is crucial for ensuring proper process control in phytosanitary irradiation. The objective of this study was to optimize phytosanitary irradiation treatment of pineapple in various radiation sources using Monte Carlo simulation. Methods: 3-D geometry and component densities of the pineapple, extracted from CT scan data, were entered into a radiation transport Monte Carlo code (MCNP5) to obtain simulated dose distribution. Radiation energy used for simulation were 2 MeV (low-energy) and 10 MeV (high-energy) for electron beams, 1.25 MeV for gamma-rays, and 5 MeV for X-rays. Results: For low-energy electron beam simulation, electrons penetrated up to 0.75 cm from the pineapple skin, which is good for controlling insect eggs laid just below the fruit surface. For high-energy electron beam simulation, electrons penetrated up to 4.5 cm and the irradiation area occupied 60.2% of the whole area at single-side irradiation and 90.6% at double-side irradiation. For a single-side only gamma- and X-ray source simulation, the entire pineapple was irradiated and dose uniformity ratios (Dmax/Dmin) were 2.23 and 2.19, respectively. Even though both sources had all greater penetrating capability, the X-ray treatment is safer and the gamma-ray treatment is more widely used due to their availability. Conclusions: These results are invaluable for optimizing phytosanitary irradiation treatment planning of pineapple.

• Applied Microscopy
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• v.3 no.1
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• pp.45-54
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• 1973

The present study is to determine the toxicity of the fungi isolated from foodstuffs by observing the ultrastructural changes in the mouse liver cells. The results as follows: 1. The toxin-producing fungi were screened by the methods of toxin-screening test(cyto-toxicity test against to HeLa cells and thin layer chromatography). 2. All of the experimental animals treated with isolated fungi were observed the focal necrosis and inflammatory infiltration of liver parenchymal cells. 3. It showed the cytoplasmic changes, such as dilatation of rough endoplasmic reticulum (RER), swelling of mitochondria (mi). increased number of lipid droplet (li) and glycogen (gl), detachment of ribosomes (ri) by observing the electron microscopy. 4. Nuclear and nucleolar alteration were also noted the segregation of nucleolar element and irregularity of nuclear envelopes. 5. As a mass screening, the cytotoxicity test using HeLa cells and thin layer chromatography are feasible methods to detection of the mycotoxin producing fungi from various sources.

• Journal of the Korean Chemical Society
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• v.27 no.3
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• pp.213-217
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• 1983

Devices that mimic the natural photosynthetic pathway are of considerable interest as fuel sources. Quantum yield of viologen radical formation in several water-in-oil microemulsion system were measured. The yield of hexadecylviologen radical formation in microemulsion system using EDTA as an electron donor, ruthenium bipyridinium complex as photosensitizer, and hexadecylviologen as an electron acceptor was 12%. When benzylnicotinamide was inserted in the interface of the microemulsion and azo compound was dissolved in oil face, the quantum yield of hydroazo compound was 0.16. Organic dye (Rose bengal) was used as photosensitizer for the photoinduced electron transfer reaction. In anionic microemulsion no electrontransfer was observed.