• Transactions on Electrical and Electronic Materials
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• v.17 no.1
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• pp.41-45
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• 2016

The Cs₃Sb photocathode was formed by non-vacuum process technology and successive in-situ photocathode vacuum device fabrication carried out in a process chamber. Performance testing of the device was followed. Light emission from the devices was induced by photoemitted electrons, which were accelerated by an anode electric field that was shielded from the photoemitter surface. The luminescent characteristics of the devices were investigated by measuring the optical parameters as functions of the applied anode voltages. The results showed that this approach could produce a more easily directed and controlled stream of light. These features make these devices suitable for a variety of planar lighting applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.155-156
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• 2007

Fabrication of dot-patterned carbon nanotube (CNT) emitters with excellent field emission properties using photo-sensitive CNT paste is described. The photosensitive CNT paste showed good photo-patternability, which led us to easily form $10-{\mu}m$-diameter dot arrays. We presented a parametric study on formulating the photo-sensitive paste and their resultant field emission characteristics.

• International Journal of Computer Science & Network Security
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• v.21 no.2
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• pp.40-43
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• 2021

In the article of instability on the peak power level, duration and repetition period of a multifrequency space-time signal, we calculated the maximum values of the errors of the parameters of the laws of spatial-phase-frequency control. Requirements for the accuracy of the location of the phase centers of the emitters in a cylindrical phased array antenna with pyramidal horns; it is advisable to calculate the radiation field using single-stage and multi-stage distribution laws. The phase centers of individual radiation sources of a cylindrical phased array antenna have been studied; they have almost no effect on the duration and period of recurrence.

• Journal of Korean Vacuum Science & Technology
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• v.3 no.1
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• pp.43-48
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• 1999

Using microwave plasma-enhanced chemical vapor deposition, diamond films were successfully grown on Ti-coated glass substrates at temperatures as low as around 500$^{\circ}C$ in behalf of practical applications to field emitters. Electron emission was observed at turn-on fields below 18V-$\mu\textrm{m}$. Field emission characteristics of diamond films were discussed in terms of their crystalline qualities. diamond films with poorer crystalline qualities showed better field emission properties.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.648-654
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• 2023

A dual-particle imager (DPI) is configured in a hand-held form factor, then one can efficiently and conveniently deploy the DPI to detect the presence of special nuclear materials (SNM) and identify any isotopic variations that differ from their natural abundances. Here we show that by maximizing the areal coupling between a pixelated scintillator array and the partitioned photosensor readout such as a silicon photomultiplier (SiPM), the information utilization of the gamma-ray and neutron information in the radiation field can be enhanced, thus enabling one to rapidly acquire spatial maps of the distributions on gamma-ray and neutron emitters.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.4
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• pp.326-331
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• 2023

The utilization of scanning transmission electron microscopy (STEM) in conjunction with cathodoluminescence (CL) has emerged as a valuable tool for the investigation of material optical properties. In recent years, this technique has facilitated significant advancements in the fields of plasmonics and quantum emitters by surpassing prior technical restrictions. The review commences by providing an outline of the diverse STEM-CL operating modes and technical aspects of the instrumentation. The review explains the fundamental physics of light production under electron beam irradiation and the physical basis for interpreting STEM-CL experiments for different types of excitations. Additionally, the review compares STEM-CL to other related techniques such as scanning electron microscope CL, photoluminescence, and electron energy-loss spectroscopy.

• 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.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.673-684
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• 2024

STREAM, developed by the Computational Reactor Physics and Experiment laboratory (CORE) of the Ulsan National Institute of Science and Technology (UNIST), is a deterministic neutron- and photon-transport code primarily designed for light water reactor (LWR) analysis. Initially, the photon module in STREAM did not account for fluorescence and bremsstrahlung photons. This article presents recent developments regarding the integration of atomic relaxation and bremsstrahlung models into the existing photon module, thus allowing for the transport of secondary photons. The photon flux and photon heating computed with the newly incorporated models is compared to results obtained with the Monte Carlo code MCS. The incorporation of secondary photons has substantially improved the accuracy of photon flux calculations, particularly in scenarios involving strong gamma emitters. However, it is essential to note that despite the consideration of secondary photon sources, there is no noticeable improvement in the photon heating for LWR problems when compared to the photon heating obtained with the previous version of STREAM.

• Progress in Medical Physics
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• v.25 no.1
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• pp.8-14
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• 2014

The amounts of radioactive wastes to be disposed in the medical institute have been increased due to development of radiation diagnosis and therapy rapidly. They are produced mostly by the very short lived radioisotopes such as $^{18}F$ used in PET/CT, $^{99m}Tc$, $^{123}I$, $^{125}I$ and $^{201}Tl$, etc. IAEA proposed a criteria for the clearance level of waste which depends on the individual ($10{\mu}Sv/y$) and collective dose (1 man-Sv/y), and concentration of each nuclide (IAEA Safety Series No 111-P-1.1, 1992 and IAEA RS-G-1.7, 2004). Radioactive wastes of $^{18}F$, $^{99m}Tc$, $^{123}I$, $^{125}I$ and $^{201}TI$ in the several types of container like Marinelli beaker, vial and plastic, were collected to measure the concentration of the waste of each nuclide in accordance with IAEA criteria. The measurement method and procedure of determining specific activity of the wastes using gamma emitters like MCA, gamma counter and beta emitters were developed. For the efficiency calibration of the detectors, CRM (certified reference material) which has the same dimension and shape was provided by Korea Research Institute of Standards and Science (KRISS). Correction factor of the radioactivity decay was calculated based on the measurement results, and the consideration of mutual relation with theoretical equation. The result of this study will be proposed as ISO standard.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.161-166
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• 2005

In KAERI, about 3,100 drums containing soil have been stored. The soils were generated from the decommissioning process of Seoul office in 1988. Those soils occupy about $27\%$ of the capacity of the radioactive waste storage facility and make it difficult to maintain the storage facility. The major radioactive nuclides contained in the soils were expected to be Co-60 and Cs-137. As 16 years have passed, the radioactivity of those nuclides have decayed a lot. In this study, as a basis of regulatory clearance, radionuclides and radioactivity concentration of soils were analyzed. As a result, there are only Co-60 and Cs-137 in soils as ${\gamma}-emitters$. The total concentration of ${\gamma}-emitters$ in soil is analyzed as about $0.01\;{\sim}\;0.12$ Bq/g. As the soils are expected to be regulatory cleared in 2009, those concentrations will decay to be less than 0.1 Bq/g. This concentration can be meet the regulatory criteria suggested by IAEA. The regulatory clearance will be proceeded based on not only the assessment results of environmental influence but also related regulations.