npsm 새물리 New Physics : Sae Mulli

pISSN 0374-4914 eISSN 2289-0041
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  • Research Paper 2022-08-31

    Comparison of Au Nanocrystals Predicted Using the Linear Combination of Atomic Orbitals and Plane Waves

    Boseong Kim, Youbin Song, Ji-Sang Park*

    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.

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  • Research Paper 2022-08-31

    Feasibility Study of Convolutional Neural Networks for a Slow Control System and Fluor Discrimination in Emission Spectrum of Liquid Scintillator

    Ji Won Choi, Ji Young Choi, Han Il Jang et al.

    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.

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  • Research Paper 2022-07-31

    Atomic Structure and Electronic Structure of Si1-xGex and AlxGa1-xN: a Density Functional Theory Calculation

    Jeongjun Kim, Youbin Song, Ji-Sang Park*

    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.

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  • Research Paper 2022-07-31

    Optical Properties of CaTiO3: Eu3+ Perovskite Phosphorus Powders on Eu3+ Concentration and Annealing Temperature

    Da Young Kim, Gyeong Bok Jung*

    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 5D07F2 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.

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  • Research Paper 2022-06-30

    A Study on the Changes in the Physical Properties of MgxZn1-xO:In Thin Films Grown Using the Sol-gel Method according to the Precursor Concentration

    Hyo Jin Choi, Min Sang Lee, Hong Seung Kim et al.

    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.

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Current Issue

    August, 2022 | Volume 72, No. 8
  • Research Paper 2022-08-31

    Comparison of Au Nanocrystals Predicted Using the Linear Combination of Atomic Orbitals and Plane Waves

    Boseong Kim, Youbin Song, Ji-Sang Park*

    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.

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  • Research Paper 2022-08-31

    A Study on the Automatic Reconstruction of the Particles with Machine Learning at e+e- Collider Experiments

    Kyungho Kim, Kihyeon Cho

    Abstract : This paper shows the automatic reconstruction of particles, particularly B meson, at e+e- collider using a machine learning algorithm. During an e+e- collider process, a pair of B meson is created, one of which is regarded as a signal and reconstructed for analysis. The automatic reconstruction of the other B meson can enhance the quality of signal events by controlling information produced from another B meson. This technique is useful particularly when a complete reconstruction of signal B is impossible because of invisible particles are included in the decay mode such as neutrino. In utilizing automatic reconstruction, a ‘tagging’ method has been developed and used in B meson analyses. In this paper, we studied the tagging method of ‘other’ B meson using machine learning algorithms such as artificial neural networks and boosted decision trees. We also applied automatic reconstruction and checked its effect on the analysis of lepton-flavor-violating decay modes with simulation data. The result shows that automatic reconstruction effectively reduces background events and provides separation between signal and background.

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  • Research Paper 2022-08-31

    Reconsidering the Blind Spots of Neutralino Dark Matter: a Perturbative Approach

    Kyu Jung Bae*

    Abstract : We consider the blind spots of neutralino dark matter where the signals in direct detection experiments are extremely weak. The neutralino dark matter leaves its signal via the interaction mediated by Higgs bosons. However, the neutralino-Higgs coupling can be tiny due to some combinations of Bino-Higgsino or Wino-Higgsino mixing. Thus, blind spots may exist in direct detection experiments. In this paper, we review neutralino blind spots based on the Higgs low-energy theorem and revisit the same parameter space by using perturbation calculation. We also analyze the conditions for the blind spot when light and heavy Higgs contributions were substantial.

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  • Research Paper 2022-08-31

    Feasibility Study of Convolutional Neural Networks for a Slow Control System and Fluor Discrimination in Emission Spectrum of Liquid Scintillator

    Ji Won Choi, Ji Young Choi, Han Il Jang et al.

    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.

    Show More  
  • Research Paper 2022-08-31

    Google Trends as a Predictor of Presidential Elections and Analysis of the Korean Presidential Election in 2022

    Chae-Hyun Yoon, Jubin Park, Myung-Ki Cheoun

    Abstract : Big data in the form of Internet searches can provide simple and effective analysis and forecasting compared with previous traditional polls. In particular, Google, which has the largest number of users worldwide, provides a dynamic website called Google Trend, which investigates searched keywords and provides trends in the region. This study analyzed the results of the 17th-19th Korean presidential elections using Google Trend and showed that the winners of each presidential election can be predicted. In addition, we found a remarkable correlation between the difference in the average Google Trend value and the difference in the voting rate during a given election period. The recent 20th presidential election was also analyzed.

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  • Research Paper 2022-08-31

    Analysis of Structures of Empirical Research Papers in "New Physics: Sae Mulli" Journal: Focusing on Experimental Physics and Physics Education

    Kwanghee Jo*

    Abstract : The characteristics of empirical research papers on experimental physics and physics education were compared by analyzing their structure in the journal “New Physics: Sae Mulli”. A total of 20 experimental physics papers and 20 physics education papers published in 2020 and 2021 were collected for analysis. Consequently, their structural patterns were similar to, but not the same as, IMRD, a typical pattern of empirical research. Experimental physics papers were written in a relatively short length compared with physics education papers, and they primarily presented figures rather than tables with mostly IM[RD]C patterns. In physics education papers, the results were commonly presented in the third section based on tables and discussed with the conclusion in the last section. In addition, experimental physics papers tended to briefly present the conclusion section, but physics education papers had almost the same number of lines in the introduction, method, and last section, including the conclusion and discussion. This result indicates the difference in the structure of empirical research papers in the field of experimental physics and physics education.

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  • Research Paper 2022-08-31

    Design of a Dielectric Laser Accelerator with the On-chip Pulse-front-tilt Method

    Hyungyu Yu, Hyyong Suk

    Abstract : In this research, a photonic crystal for dielectric laser accelerator has been designed and analyzed by conducting finite-domain-time-differential (FDTD) simulations. The photonic crystal of dielectric materials, such as Si or SiO2, can confine electric field components of a laser pulse in space when it is designed as a cavity structure. The longitudinal electric field components can serve as a driving force for electrons. A maximum acceleration gradient is expected when the electron and acceleration field phases are matched. The phase matching can be achieved by tilting the front of the input laser pulse. In this study, a combined structure of a micro-scale prism and periodic cavities was considered to tilt the pulse front. The calculation of the acceleration field by FDTD simulations can give an energy gain of the incident electrons in dielectric laser acceleration (DLA).

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  • Research Paper 2022-08-31

    Study on the Emitting Properties of Layered Light-emitting Diodes Consisting of Remote Yellow Phosphors and Red Quantum Dot Films

    Min Woo Kim,  Yeong Ju Kim,  Hyuk Kyu Kwon et al.

    Abstract : Emitting properties of white light-emitting diodes (LEDs) consisting of a remote-type yellow phosphor plate and a red quantum-dot (QD) film were investigated. In particular, the difference in optical properties caused by different layered structures of the two color-converting materials was studied in detail. Luminous efficiency was improved when the yellow phosphor plate was placed on top of the blue LED chip, while the high color-rendering property was secured when the red QD film was placed over the blue LED chip. The present study showed that the color characteristics of white LEDs can be adjusted by changing the order of the layered structure of color-converting materials and that highly efficient high color-rendering white LEDs can be achieved without being affected by the high temperature of blue LED chips because of the remote design.

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Current Issue

August, 2022
Vol.72 No.8

pISSN 0374-4914
eISSN 2289-0041

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pISSN 0374-4914
eISSN 2289-0041