• Tunnel and Underground Space
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• v.22 no.2
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• pp.157-161
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• 2012

ZnO-98% and $Ga_2O_3$-2% powder were consolidated by shock compaction technique, which uses a high performance explosive. The microstructural and electrical characteristics of $ZnOGa_2O_3$ compact with density of 97% and hardness of 220~250 $H_v$ were investigated using SEM (Scanning Electron Microscope) and X-ray diffraction analysis, respectively. In the microstructures of the compact, there were no visible cracks at most of the surface areas, and interparticle bonding between powder particles was confirmed. The broadened peaks were detected due to deformation of crystallited size and high electric resistances were confirmed due to increased grains because of shock energy with a high pressure and high velocity.

• The Journal of Korean Society for Radiation Therapy
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• v.1 no.1
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• pp.47-51
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• 1985

Authors describe some useful data when constructing tissue-equivalent compensators which would compensate tissue deficit in the treatment field of high energy electromagnetic radiation Tissue equivalent compensator is made of lucite. The ratio of compensator thickness to the thickness of tissue deficit depends on radiation energy, field size and the distance from the compensator to patient skin. When the compensator is separated from skin surface, the thickness ratio is always smaller than 1.0. This means that the larger the separation, the contribution to the total dose by means of scattered radiation from a tissue equivalent compensator is smaller. Authors propose that the thickness of lucite as tissue equivalent compensator is 0.57 times tissue deficit and the separation between compensator and skin is at least 15m for Co-60 gamma ray and 25cm for 10MV X-ray.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.318.2-318.2
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• 2016

FeM2X4 spinel structures, where M is a transition metal and X is oxygen or sulfur, are candidate materials for spin filters, one of the key devices in spintronics. Both the Fe and M ions can occupy tetrahedral and octahedral sites; therefore, these types of compounds can display various physical and chemical properties [1]. On the other hand, the electronic and magnetic properties of these spinel structures could be modified via the control of cation distribution [2, 3]. Among the spinel oxides, iron manganese oxide is one of promising materials for applications. FeMn2O4 shows inverse spinel structure above 390 K and ferrimagnetic properties below the temperature [4]. In this work, we report on the structural and magnetic properties of epitaxial FeMn2O4 thin film on MgO(100) substrate. The reflection high energy electron diffraction (RHEED) and X-ray diffraction (XRD) results indicated that films were epitaxially grown on MgO(100) without the impurity phases. The valance states of Fe and Mn in the FeMn2O4 film were carried out using x-ray photoelectron spectrometer (XPS). The magnetic properties were measured by vibrating sample magnetometer (VSM), indicating that the samples are ferromagnetic at room temperature. The structural detail and origin of magnetic ordering in FeMn2O4 will be discussed.

• Nuclear Engineering and Technology
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• v.56 no.9
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• pp.3608-3615
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• 2024

This study introduces a lead-free alternative for enhanced radiation protection. While lead aprons effectively attenuate ionizing radiation, concerns regarding flexibility, weight, and environmental hazards persist. In response, the present research is focused on producing an innovative sheet shielding comprised of carefully selected dense metal oxide microparticles (DMOs-MPs) and liquid silicone rubber (LSR). To evaluate the efficacy of the LSR samples, the current study uses rigorous testing procedures, such as microstructure characterization using EDX and FESEM. Furthermore, the study investigated key attenuation parameters within the LSR samples. Radiation protection was greatly and effectively supplied using DMOs-MPs filler (Bi-1 to Bi-7) in LSR samples; this protection reached 99.9% in the X-ray energy range. Due to the unique characteristics of the Bi-7, the results demonstrated that the samples' shielding efficiency improved with the addition of high atomic number and high-density fillers. It had the greatest attenuation coefficient and density. At 60 keV, Bi-7's density was 2.980 gcm^-3, and its LAC and MAC were 19.2621 cm^-1 and 6.4638 cm²/g, respectively. It also had the lowest half-value layer values in the energy range of 60-120 keV. The LSR samples showed effective radiation absorption for different energy levels, indicating that LSR can enhance the flexibility and comfort of the apron while providing adequate radiation protection. The incorporation of the DMOs-MPs with LSR represents an effective contribution and a noteworthy stride to enhance the safety and well-being of medical professionals routinely exposed to ionizing radiation.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.156-168
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• 2023

This study investigates the high temperature oxidation behaviour of a Ni-20Cr-1.2Si (wt.%) alloy in steam from 1200 ℃ to 1350 ℃ by Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD). The results demonstrate that exposed Ni-based alloy developed a thin oxide scale, consisted mainly of Cr₂O₃. The oxidation kinetics obtained from the experimental results was applied to evaluate the hydrogen generation considering a simplified reactor core model with different cladding alloys following an unmitigated Loss-Of-Coolant Accident (LOCA) scenario in a hypothetical Small Modular Reactor (SMR). Overall, experimental data and simulations results show that both Fe-based and Ni-based alloys may enhance cladding survivability, delaying its melting, as well as reducing hydrogen generation under accident conditions compared to Zr-based alloys. However, a substantial neutron absorption occurs when Ni-based alloys are used as cladding for current uranium-dioxide fuel systems, even when compared to Fe-based alloys.

• Bulletin of the Korean Space Science Society
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• 1992.10a
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• pp.21-21
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• 1992

The X-ray binary pulsar Her X-1 was observed with Ginga on 1988 August 28 during the orbital phase of 0.76 to 0.85 at the main-on phase of the 35 day cycle. During the observations the X-ray intensity varied by a factor of five or more on a time scale as short as 30 sec, due mostly to the soft X-ray absorption in the pre-eclipse phase. From the studies of pulse profiles and energy spectra, we revealed that there exists in the dipphase an unpulsed component which is "3% of the intensity at the non-absorbed high-level. We suggest that scattering of the source continuum by the optically thin hot corona is responsible for the unpoised component. In the spectral analysis, we find that the high-state non-absorbed spectra can be fitted by a power-law without absorption, and the spectra observed in the different abgorption states by two components of a power-law with the same photon index. An iron-K emission line is required in to the cases of fitting. The estimated equivalent width of the iron line varies from 0.18 to 0.51 key according to the change in the absorption column density along the line of sight. We suggest that the fluorescent iron line arises in a cool and relatively small region, like the Alfvensur face, and may be partially intercepted by the optically thick gas cloud passing across the line of sight.1 Korea Astronomy Observatorya The Institute of Space and Astronautical Science in Japan3 Korea Advanced Institute of Science and Technology

• Journal of the Semiconductor & Display Technology
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• v.6 no.2 s.19
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• pp.65-68
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• 2007

High brightness and long persistent luminescence phosphor $CaAl_2O_4:Eu^{2+}$ was prepared with varying $Eu^{2+}$ concentration by solid state reaction technique. Synthesized materials were investigated by powder X-ray diffractometer (XRD), SEM, TEM, photoluminescence excitation and emission spectra. Broad band UV excited luminescence of the $CaAl_2O_4:Eu^{2+}$ was observed in the blue region (${\lambda}_{max}\;=\;440\;nm$) due to transitions from the $4f^65d^1$ to the $4f^7$ configuration of the $Eu^{2+}$ ion. The decay time of the persistence indicated that the persistent luminescence phosphor has bright phosphorescence and maintains a long duration. These materials have great potential for outdoor night time displays.

• Journal of the Korean Vacuum Society
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• v.9 no.1
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• pp.16-23
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• 2000

The epitaxial growth of $CeO_2$ films has been investigated on three different substrates-Si(111), $SrTiO_3$(001), and MgO(001)-over wide range of growth parameters using oxygen-plasma-assisted molecular beam epitaxy. Pure-phase, single-crystalline epitaxial films of $CeO_2$ (001) have been grown only on $SrTiO_3$(001). We discuss the growth conditions in conjunction with the choice of substrates required to synthe-size this oxide, as well as the associated characterization by menas of x-ray diffraction, reflection high-energy electron diffraction, low-energy electron diffraction, and x-ray photoelectron spectroscopy and diffraction. Successful growth of single crystalline $CeO_2$ depends critically on the choice of substrate and is rather insensitive to the growth conditions studied in this investigation. $CeO_2$(001) films on $SrTiO_3$exhibit the sturcture of bulk $CeO_2$ without surface reconstructions. Ti outdiffusion is observed on the films grown temperatures above $650^{\circ}C$.

• Journal of The Korean Astronomical Society
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• v.37 no.5
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• pp.307-313
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• 2004

Clusters of galaxies are believed to constitute a population of astrophysical objects potentially able to emit electromagnetic radiation up to gamma-ray energies. Evidence of the existence of non-thermal radiation processes in galaxy clusters is indicated from observations of diffuse radio halos, hard X-ray and EUV excess emission. The presence of cosmic ray acceleration processes and its confinement on cosmological timescales nearly inevitably yields in predicting energetic gamma-ray emission, either directly deduceably from a cluster's multifreqency emission characteristics or indirectly during large-scale cosmological structure formation processes. This theoretical reasoning suggests several scenarios to actually detect galaxy clusters at gamma-ray wavelengths: Either resolved as individual sources of point-like or extended gamma-ray emission, by investigating spatial-statistical correlations with unidentified gamma-ray sources or, if unresolved, through their contribution to the extragalactic diffuse gamma-ray background. In the following I review the situation concerning the proposed relation between galaxy clusters and high-energy gamma-ray observations from an observational point-of-view.

• Journal of Radiation Protection and Research
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• v.23 no.1
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• pp.33-47
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• 1998

Using a combination of an X-ray generator Installed in radiation calibration laboratory of Korea Atomic Energy Research Institute (KAERI) and a series of 8 radiators and filters described in ISO-4037, monoenergetic fluorescent X-rays from 8.6 keV to 75 keV were produced. This fluorescent X-rays generated by primary X-rays from radiator were discriminated $K_{\beta}$ lines with the aid of filter material and the only $K_{\alpha}$ X-rays were analyzed with the high purity Ge detector and portable MCA. The air kerma rates were measured with the 35 co ionization chamber and compared with the calculational results, and the beam uniformity and the scattered effects of radiation fields were also measured. The beam purities were more than 90 % for the energy range of 8.6 keV to 75 keV and the air kerma rates were from 1.91 mGy/h (radiator : Au, filter : W) to 54.2 mGy (radiator : Mo, filter : Zr) at 43 cm from center of the radiator. The effective area of beam at the measurement point of air kerma rates was 12 cm ${\times}$ 12 cm and the influence of scattered radiation was less than 3 %. The fluorescent X-rays established in this study could be used for the determination of energy response of the radiation measurement devices and the personal dosemeters in low photon energy regions.