Ex) Article Title, Author, Keywords
Abstract : We explored the configuration space of Au nanocrystals by using point group symmetry. For Au nanocrystals whose size is equal to or less than six atoms, linear combination of atomic orbitals (LCAO) was used to relax the structure and compare with plane-wave calculations. In general, the predicted shape and stability of nanocrystals were consistent, but the optimized bond lengths were longer in LCAO calculations. Similar to nanocrystals, the optimized lattice constant of the face-centered cubic Au was smaller in the plane-wave calculation. The structure and stability of Ag nanocrystals were also investigated using both methods.
Abstract : In this paper, we tried to estimate the fluor components of a liquid scintillator using a convolutional neural network (CNN) while applying and building the internet of things (IoT) and machine learning in a slow control system. Various factors affecting the fluorescent emission of liquid scintillators have been reported at the laboratory level. However, long-term performance studies are still ongoing under extreme environmental conditions in large-scale experiments beyond the laboratory level. Given the characteristics of neutrino experiments, the liquid scintillator is sealed inside the detector, making it difficult to observe non-invasive samples. In particular, the long-term physical and chemical stability of liquid scintillators in extreme environments with high radiation bombardment doses, such as nuclear power plants, has not been reported. Accessing a highly radioactive area requires considerable time and effort. In addition, the cost efficiency and reliability of embedded systems have improved with the development of microcontroller weight reduction, integration, and IoT technology. Therefore, researchers hypothesized that long-term liquid scintillators could ensure the operator’s safety and acquire environmental data under extreme conditions. Moreover, experimental know-how can be obtained by using low-gain semiconductor image sensors.
Abstract : To investigate the atomic and electronic structures of Si1-xGex and AlxGa1-xN, special quasi-random structures were generated. Before structure optimization, the positions of the constituting atoms were altered to reproduce the bond lengths in Si, Ge, AlN, and GaN as close as possible. The total energy of the optimized structure through the first-principles density functional theory calculation was only 0.03 eV per atom smaller than that of the structure optimization. The lattice constants generally increased as the proportion of Ge or Ga increased. The bond length tended to maintain its value before the mixing of materials, so the change in bond length was smaller than the change in the lattice constants. The band gap of AlxGa1-xN generally increased with the proportion of Al. In the hybrid density functional theory calculation, the band gap increased as the fraction of Hartree-Fock exchange in the functional increased.
Abstract : The Eu3+-doped CaTiO3 (CaTiO3:Eu3+) perovskite phosphorus powders were synthesized using high-energy ball-milling (HEBM). Their crystal structure, surface morphology, and photoluminescence properties were investigated as a function of the europium concentration and annealing temperature. The X-ray diffraction (XRD) peaks of the CaTiO3:Eu3+ powders were good matches with the standard XRD peaks of the orthorhombic CaTiO3 phase without impurities. The field emission scanning electron microscopy (FE-SEM) images of CaTiO3:Eu3+ powders show that the particles increased in size and agglomerated as the annealing temperature increased. The Fourier transform infrared (FT-IR) spectrum confirmed that the absorption bands of CaTiO3:Eu3+ and CaTiO3 were in good agreement, which confirmed that Eu3+ ions were effectively doped into CaTiO3. The highest photoluminescence (PL) emission intensity was observed at an annealing temperature of 1200 °C and a Eu3+ concentration of 6 mol%. The PL spectra showed the strong characteristic peak at 614 nm of the 5D0 → 7F2 electric dipole transition of Eu3+ at an excitation wavelength of 398 nm. These results suggest that the PL emission intensity of CaTiO3:Eu3+ perovskite phosphorus powder can be controlled by Eu3+ concentration and annealing temperature.
Abstract : In this paper, changes in physical properties of MgZnO:In thin films grown on a sapphire substrate using the sol-gel method were investigated as per the concentrations of In and Mg precursors. The properties of the grown thin films were analyzed using XRD, UV-Vis, Hall effect, and XPS. According to the XRD results, all samples showed the c-axis preferential orientation growth. UV-Vis analysis confirmed that the samples exhibited a transmittance of >80% in the visible region. Through the Hall effect measurement, the resistance was found to decrease with the increasing In amount. According to the XPS analysis, when >5 mol% of In was added, the Mg content decreased. The O 1s binding energy was also investigated using XPS, and the bonding state of the thin film was observed by comparing the OI/OII ratio. When >5 mol% of In was added, it interfered with the generation of oxygen vacancy during the synthesis of Mg, thus decreasing the OI/OII ratio.
Woo Tae Hong, Hyun Kyoung Yang
New Phys.: Sae Mulli 2021; 71(3): 236-241
Hyeong Seon PARK, Seong-Heum PARK, Hyunbok LEE, Heung-Sik KIM*
New Phys.: Sae Mulli 2020; 70(11): 920-927
YeonJung PARK, Joonghoe DHO*
New Phys.: Sae Mulli 2021; 71(5): 450-456