npsm 새물리 New Physics : Sae Mulli

pISSN 0374-4914 eISSN 2289-0041
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  • Research Paper 2022-11-30

    Grain Boundaries and Twin Boundaries in Cu(111) Thin Films

    Su Jae Kim, Young-Hoon Kim, Young-Min Kim et al.

    Abstract : Twin boundaries (TBs) are one of the defects that form in most single-crystal growth. Although they are usually considered as one of the grain boundaries (GBs) that satisfy a symmetry operation, the properties and formation mechanism of TBs are very different from those of GBs. In particular, in bulk crystals, TBs are usually analogous to ferroelastic domains. TBs are formed to relieve structurally occurring strain when a phase transitions from a high-temperature phase to a low-temperature phase. They are formed in thin films when two islands with different stacking orders at nucleation meet. At this point, TBs are formed when single-crystal islands meet coherently with a coplanar layer. By contrast, GBs are formed when arbitrarily oriented islands meet incoherently. The effects of TBs and GBs on physical properties are greatly different.

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  • Research Paper 2022-11-30

    Analysis of the Changes in Stabilization in Accordance with Division and Expansion Over Time of TiO2 Nanotube Arrays Fabricated by Using Anodization

    Bo Hyeon Kim, Sang Don Bu*

    Abstract : In this research, TiO2 nanotube arrays were fabricated by using anodization. The change in alignment due to the change in the diameter of the nanotube bottom in accordance with anodization time was analyzed by using field emission scanning electron microscopy. Individually separated TiO2 was confirmed to have formed in the initial stage of anodization. In this process, the expansion and division of the nanotube proceeded with the prolongation of anodization time. As large-diameter nanotubes divided, the distribution values of the diameters decreased, and the stability degree tended to improve. With the passage of time, when the division of the nanotube had been completed to some extent, the expansion of the nanotube proceeded more predominantly, and the average diameter tended to increase. These findings confirmed that the time of anodization affected the alignment and that the bottom diameter was randomly generated at the beginning. Moreover, during TiO2 nanotube growth, the bottom part not only expanded but also split.

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  • Research Paper 2022-10-31

    Optical Properties of Bi-doped In2O3 Films

    Youngjun Son,  Sehwan Song,  Jisung Lee et al.

    Abstract : P-type oxides using holes as carriers exhibit a relatively low hole mobility due to the deep O 2p level; thus, their potential applications are fewer than those of n-type oxides. Recently, a DFT study has reported that Bi-doped In2O3 forms a new in-gap state near the valence band, thereby lowering the formation energy of the acceptor and enabling the formation of a new p-type oxide through additional doping. In addition, a previous experiment on the Bi-doped In2O3 ceramics revealed the in-gap state. In this study, Bi-doped In2O3 films were grown under various conditions to examine the possibility of optical bandgap modulation. Consequently, from a structural viewpoint, the crystalline size grew as the deposition temperature increased; spectroscopically, two optical absorptions were confirmed. While the larger optical bandgap corresponded to bulk In2O3, the smaller one was associated with a newly formed in-gap state owing to Bi doping. Furthermore, the bandgap energy decreased as the deposition temperature increased. Therefore, the reduced optical bandgap with an increased deposition temperature was related to the reduced quantum size effect.

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  • Research Paper 2022-10-31

    Thickness-dependent the Optical and Electrical Properties of Amorphous Transparent Conductive SrRuO3 Thin Films Deposited by RF Magnetron Sputtering on Glass Substrate

    Hyo Jin Bang,  Hyun Min Kim,  Jong Hoon Lee et al.

    Abstract : The SrRuO3 electrode can improve the dielectric properties of the perovskite structure. Thus, it is the most suitable electrode material for Dynamic Random-Access Memory (DRAM). This study was conducted to investigate the possibility of the SrRuO3 thin film as a transparent conductive oxide (TCO). In this study, an SrRuO3 thin film was deposited on the glass substrates by the RF magnetron sputtering method at room temperature. To observe the difference in optical and electrical properties as per the thin film thickness, the deposition times were set to 5 and 50 min. As the deposition time increased, the film thickness increased from 5 to 68 nm, the optical transmittance decreased from 80% to 40%, and the resistivity (an electrical property) increased from 1.99 to 26.3 mΩ·cm. Consequently, when the SrRuO3 thin films were deposited on the glass substrates for 5 min, a transmittance of about 80% or more, a band gap of 4.57 eV, and a resistivity of 1.99 mΩ·cm were observed, thus verifying that an SrRuO3 electrode can improve the dielectric properties of perovskite.

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  • Research Paper 2022-09-30

    Neutrino Directionality According to Spatial Resolution of Liquid Scintillation Detector and Angle Calculation Method

    Oon Sang Lee, Myoung Youl Pac, June Ho Choi et al.

    Abstract : On the basis of Monte Carlo simulation, a liquid scintillation neutrino detector was used to study the conditions for determining the neutrino directionality. The emission angle of the neutron was calculated using the annihilation position of the positron generated through inverse beta decay, which was caused by the neutrino and the gamma-ray emitted by the neutron that was absorbed by gadolinium. When the neutron emission angle was considered as the neutrino directionality, the neutrino demission angle was linearly dependent on the neutrino incidence angle. Therefore, the calculation method for the emission angle of neutrons is a more critical factor in determining the incidence direction of neutrinos compared with the spatial resolution of the detector.

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Current Issue

    November, 2022 | Volume 72, No. 11
  • Research Paper 2022-11-30

    Grain Boundaries and Twin Boundaries in Cu(111) Thin Films

    Su Jae Kim, Young-Hoon Kim, Young-Min Kim et al.

    Abstract : Twin boundaries (TBs) are one of the defects that form in most single-crystal growth. Although they are usually considered as one of the grain boundaries (GBs) that satisfy a symmetry operation, the properties and formation mechanism of TBs are very different from those of GBs. In particular, in bulk crystals, TBs are usually analogous to ferroelastic domains. TBs are formed to relieve structurally occurring strain when a phase transitions from a high-temperature phase to a low-temperature phase. They are formed in thin films when two islands with different stacking orders at nucleation meet. At this point, TBs are formed when single-crystal islands meet coherently with a coplanar layer. By contrast, GBs are formed when arbitrarily oriented islands meet incoherently. The effects of TBs and GBs on physical properties are greatly different.

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  • Research Paper 2022-11-30

    Investigation of Atomic Interaction Energies in Semiconductors through Machine Learning Using Artificial Neural Networks

    Uy Yoon Park*, Chul Hong Park

    Abstract : We investigated the atomic interactions in Si, Ge, and C semiconductors through the machine learning (ML) method using artificial neural networks (ANN). The big data of atomic structures and the corresponding total energies were obtained through molecular dynamics simulation. The total energies were decomposed into i) the interatomic pair interaction depending on the distance between the nearest atoms and ii) the bond angle distortion energy. We optimized two types of ANNs, which simulated the total energies as the summation of two types of interaction energies, through ML. Interatomic potential and bond angle distortion energies were obtained from the optimized ANNs. We found that the optimal bond angle slightly deviated from the bond angle of the ideal tetrahedral structure depending on the difference between the atomic levels of the s- and p-orbitals.

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  • Research Paper 2022-11-30

    Analysis of the Changes in Stabilization in Accordance with Division and Expansion Over Time of TiO2 Nanotube Arrays Fabricated by Using Anodization

    Bo Hyeon Kim, Sang Don Bu*

    Abstract : In this research, TiO2 nanotube arrays were fabricated by using anodization. The change in alignment due to the change in the diameter of the nanotube bottom in accordance with anodization time was analyzed by using field emission scanning electron microscopy. Individually separated TiO2 was confirmed to have formed in the initial stage of anodization. In this process, the expansion and division of the nanotube proceeded with the prolongation of anodization time. As large-diameter nanotubes divided, the distribution values of the diameters decreased, and the stability degree tended to improve. With the passage of time, when the division of the nanotube had been completed to some extent, the expansion of the nanotube proceeded more predominantly, and the average diameter tended to increase. These findings confirmed that the time of anodization affected the alignment and that the bottom diameter was randomly generated at the beginning. Moreover, during TiO2 nanotube growth, the bottom part not only expanded but also split.

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  • Research Paper 2022-11-30

    Effects of Pulse Magnetic Field on T Cells

    Juyeon Jung, Hyunsook Lee*

    Abstract : T cells are lymphocytes that are responsible for antigen-specific adaptive immunity, cellular immunity, and homeostasis maintenance in the human body. However, immune T cells do not function properly in T lymphoma, a malignant tumor that occurs in lymphocytes, such that cancer cell proliferation and metastasis become active. Therefore, in this study, the effect of a pulsed magnetic field (PMF) on the regulation of pH homeostasis and proliferation rate of T lymphoma cells was investigated by using mouse EL4 cells. The restoration of extracellular pH homeostasis to the normal pH range of 7.35-7.45 was faster in EL4 cells stimulated with PMF for 24 h than in the control group. Moreover, homeostasis recovery increased rapidly as the magnetic field strength was increased. In addition, the number of T lymphoma cells decreased in the PMF stimulus group relative to that in the control group. PMF stimulus might induce the natural death of T lymphoma cells. Therefore, our study confirmed that PMF stimulation helps improve cancer treatment and balance immunosuppression and activity.

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  • Research Paper 2022-11-30

    Understanding of the Photoelectric Effect by Pre-service Physics Teachers

    Sangwoo Ha, Hunkoog Jho

    Abstract : This study aims to investigate the understanding of the photoelectric effect by pre-service physics teachers. Thus, we selected and translated the Photoelectric Effect Concept Inventory (PECI) and Quantum Physics Conceptual Survey (QPCS) and recruited 21 pre-service physics teachers as respondents. We asked the teachers to describe in detail the reasons for their responses to examine further their difficulties with the photoelectric effect. We found that the pre-service teachers had a relatively high understanding of the concept of the photoelectric effect. However, they encountered difficulties in understanding the work function, stopping voltage, and the role of the power supply. Moreover, we discovered that the teachers experienced challenges relating various variables and inverting the relationship between variables and lacked an understanding of specific experimental situations. Finally, we suggested several implications, including the need to distinguish several related variables of the photoelectric effect and to clarify the relationship between variables in accordance with the particle theory of light.

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  • Research Paper 2022-11-30

    Secondary Students' Process of the Conceptual Change of Motion of Objects in Dynamics Teaching Using Block Coding

    Ok Jeong, Wonkun Oh*

    Abstract : This study examines how students’ concepts of position, displacement, speed, and acceleration, which can be said to be the basis of dynamics, are formed and changed through the teaching of dynamics by using block coding and how metacognitive processes are enhanced in this process. A qualitative study was conducted on five students who engaged in a teaching class that introduced the block coding method to enable the students to check their own concepts. As a result, it was possible to discover misconceptions or conceptual difficulties related to dynamics that were formed in students, and to observe the cognitive conflicts experienced by the students themselves and the metacognitive process that appeared in the conflict resolution process.

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  • Research Paper 2022-11-30

    Transmission Deflectometry with Lissajous-Ellipse Fitting for 3D Measurement

    Sanghoon Shin, Younghun Yu

    Abstract : This work presents a method for obtaining phase data from fringe image data and investigated Hilbert-transformed data without data preprocessing. The fringe projection technique is an effective method for measuring the three-dimensional shape of an object, and phase extraction from the deformed fringe is an important process in three-dimensional measurement. Preprocessing for background noise removal and modulation normalization is required to obtain phase data by using a single fringe image data. In this study, a Lissajous figure was constructed from fringe and Hilbert-transformed data, and the method for obtaining the deformed phase of the stripe pattern without preprocessing using the elliptic equation fitting method was studied through computer simulation and transmission-type deflection experiments.

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  • Research Paper 2022-11-30

    COVID-19 Confirmed Cases and Subway Passengers

    Oh Min Kwon, Hyeong-Chai Jeong*

    Abstract : COVID-19 is mainly transmitted between people. Therefore, people's movement may cause the spread of COVID-19. Announcing an increase in the number of confirmed cases affects people's behavior and reduces people's movement. We analyzed the correlation between the number of COVID-19 confirmed cases and the change in the number of subway passengers in the metropolitan area to promote the understanding of the relationship between public transportation volume and COVID-19 confirmed cases. By using the reference number of subway passengers in 2016-2019, we calculated the decrease in passengers during the COVID-19 pandemic period from April 8, 2020 to July 29, 2021. Changes in subway passengers did not seem to affect the number of confirmed cases significantly. However, announcing an increase in confirmed cases greatly reduced the number of passengers. We also found that people avoided the subway on the basis of their normalized risk perception rather than absolute risk based on the number of daily confirmed cases.

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Current Issue

November, 2022
Vol.72 No.11

pISSN 0374-4914
eISSN 2289-0041

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pISSN 0374-4914
eISSN 2289-0041