npsm 새물리 New Physics : Sae Mulli

pISSN 0374-4914 eISSN 2289-0041
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  • Research Paper 2024-04-30

    Gravitational Deflection of Light: A Heuristic Derivation at the Undergraduate Level

    Hongbin Kim, Dong-han Yeom, Jong Hyun Kim

    Abstract : In this paper, we present a new heuristic derivation of the gravitational deflection of light around the Sun at the undergraduate level. Instead of solving the geodesic equation directly, we compute the correct deflection angle by focusing on the acceleration term of null geodesics. Using this heuristic deviation, we expect that undergraduate students who have not learned general relativity will be able to experience this computation, which is one of the most remarkable evidences of general relativity.

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  • Research Paper 2024-04-30

    Analysis of South Korean Presidential Election Results Based on Regional Voter Turnout

    Euseo Gwon, Hyeong-Chai Jeong

    Abstract : This study investigates the link between regional voter turnout and presidential election outcomes in South Korea. Typically, the realistic prospects of winning are confined to one conservative and one liberal candidate. The country demonstrates a distinct regional pattern, with the southeast supporting the conservative party and the southwest favoring the liberal party. We analyzed regional patterns of voter turnout and political tendencies from the 15th to the 20th elections. Our findings show that election outcomes can be accurately predicted by analyzing voter turnout changes, based on both the data at the end of voting and the final data released before the end. The key insight is that shifts in voter turnout in politically biased regions align with party support changes in neutral areas, indicating their significance in accurately predicting election outcomes.

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  • Research Paper 2024-03-29

    Current-Voltage Characteristics of Ferroelectric SrBi2Ta2O9 Thin Films

    Sang Bo Bae, Hwan Min Kim, Ill Won Kim

    Abstract : We grow SrBi2Ta2O9 (SBT) thin films, one of the actively studied lead-free ferroelectric materials, with different Bi/Sr compositions using pulsed laser deposition (PLD) method and measured their leakage current characteristics according to electric field and temperature changes. Schottky barrier height, trap center level, and activation energy were studied. The current-voltage characteristics of the SBT thin film with a Bi/Sr composition ratio of 2.8 showed resistive leakage current characteristics in which the leakage current strongly depended on the delay time in the applied electric field of 80 kV/cm or less. Below 150 C, the SBT (Bi/Sr = 2.8) thin film showed linear current-voltage characteristics consistent with the Schottky emission conduction model at an applied electric field of 80 to 200 kV/cm, and the Schottky barrier height and trap center level were 1.02 eV and 0.83 eV, respectively. The activation energies of the SBT thin films of 2.8 Bi/Sr ratio showed 0.72 eV and 0.58 eV below 150 C, 3 V, and 10 and 100 sec delay time. This phenomenon is because Bi ions acted as charge carriers in the form of acceptors.

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  • Research Paper 2024-03-29

    A Comparison of the South Korean and German Secondary School Curricula in Quantum Physics

    Andreas Woitzik, Taegyoung Lee, Nam-Hwa Kang

    Abstract : With increasing attention drawn towards quantum physics and its applications in teaching and research, the question of which concepts of quantum theory can be taught at different educational levels becomes more and more important. To this end, we compare the curricula of Germany (Baden-Württemberg) and South Korea. In Germany, more students take physics courses that contain quantum physics than in South Korea. We find that many quantum physics learning objectives are commonly covered, but with recent increases in quantum physics content in both countries’ curricula their approaches increasingly differ. The South Korean curriculum focuses more on technology and classical quantum concepts, whereas the German curriculum is more concerned with epistemological questions. Through an investigation of the textbooks of both regions, we found differences in laboratory activities and approaches to deal with some concepts. The findings demonstrate some consensus on the content to be taught in high school physics while the differences in the curriculum and textbooks of the two regions provide insight into pedagogical approaches and future research.

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  • Research Paper 2024-02-29

    Magnetic and Structural Variations Depending on the Annealing Temperature of Co Films on Al2O3(0001)

    Kangjin Park, Yeongjun Son, Sehwan Song et al.

    Abstract : This study deposited a cobalt (Co) film on the Al2O3(0001) substrate by a flash evaporation method to examine the structural and magnetic property variations depending on the various post-annealing temperatures. Co-film formed islands during annealing due to the surface energy mismatch between the metallic film and the insulating substrate. As a result, the post-annealed Co particles formed an ellipsoid shape with improved crystallinity as temperature increased. Structural analysis confirmed that the Co particles grew in the Co(111)-oriented FCC structure. Interestingly, there are different annealing-temperature-dependent characteristics of magnetic properties depending on the magnetic field direction due to the competing nature between the crystalline and shape anisotropy of the aggregated Co particles.

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Current Issue

    April 2024 | Vol. 74 No. 4
  • Research Paper 2024-04-30

    Ferrimagnetic and Metallic Behaviors in Epitaxial NiCo2O4 Films Grown on (001)MgAl2O4 at Low Temperatures

    Jiseok Park, Joonghoe Dho

    Abstract : Using pulsed laser deposition, we deposited (001) NiCo2O4 films on (001) MgAl2O4 substrates while fixing other deposition parameters and reducing the deposition temperature from 320 C to 100 C. As the deposition temperature decreased to 150 C, X-ray diffraction patterns indicated a decrease in the out-of-plane lattice constant from 8.186 Å to 8.142 Å. Conversely, at a deposition temperature of 100 C, no film peak was observed, supporting the amorphous film. The polar magneto-optical Kerr effect revealed that the coercivity was approximately 1200 Oe in the film grown at 320 C and showed a significant decrease to around 200–300 Oe at the deposition temperatures below 250 C, with no observable perpendicular magnetic anisotropy at the deposition temperature of 100 C. The temperature at which the metal-insulator transition occurred was around 500 K in the film grown at 250 C, and exhibited weakened metallic behavior as the deposition temperature decreased to 150 C. This work demonstrated that even at a low deposition temperature of 150 C, the epitaxial NiCo2O4 film exhibited tetragonal lattice strain, perpendicular magnetic anisotropy, and metallic properties.

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  • Research Paper 2024-04-30

    Structural Defect Effect on All-dielectric Terahertz Metalens by 3D Printing

    Jeongmin Kim, Heonseong Ryu, Dahye Jang et al.

    Abstract : Terahertz (THz) metamaterials have been widely applied to biomedical sensing, security, and non-destructive imaging by taking advantage of their compact and flexible design and versatile light manipulation. Unlike conventional metamaterial fabrication including the lithography techniques, the recent 3D printing methods enable easy and rapid fabrication. However, because of its lower resolution than the nanofabrication technique, the difference in optical performances by structural defects should be considered. In this research, we investigate the optical performance of 3D printed metamaterial-based THz lenses by structural defect. By simple pillar array printed with various widths, structural defect including size errors was statistically analyzed using optical microscopy with a pattern-matching algorithm. The focal shift and the transmittance by the size error were compared using finite-difference time-domain (FDTD) calculation.

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  • Research Paper 2024-04-30

    Plasma Treated Highly Oriented Pyrolytic Graphite for Supercapacitor Applications

    Keshab Pandey, Hae Kyung Jeong

    Abstract : Highly Oriented Pyrolytic Graphite (HOPG) has captured the attention of researchers in the field of supercapacitors due to its layered structure, as well as its enhanced electrical and thermal conductivity, along with notable mechanical capabilities. In this study, HOPG is modified using ambient plasma to improve its applicability for supercapacitor applications. The influence of time-dependent plasma treatment for 0, 30, 60, 90, 120 min on HOPG is investigated in a coin-cell type symmetric supercapacitor, resulting that the optimum time (90 min) shows the best performance of high specific capacitance of 152.8 F/g, an energy density of 13.8 Wh/kg, and a power density of 802 W/kg at 1 A/g for the supercapacitor applications. To modify and functionalize a wide range of materials, including metals, carbon-based materials, and composites, plasma treatment is extremely useful, with the goal of advancing cost-effective energy storage devices by modifying and functionalizing surfaces.

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  • Research Paper 2024-04-30

    Study of the Dependence of Silicon Sensor Signal on Effective Thickness

    Faizan Anjum, Hongjoo Kim, Jik Lee

    Abstract : The silicon PIN diode sensor is widely utilized for radiation detection. Exposure of the silicon sensor to excessive radiation may lead to damage in the sensor, consequently causing an increase in the sensor’s leakage current. This elevated leakage current results in the sensor being operated at a lower bias voltage. The signal of the PIN diode sensor directly relies on the effective thickness, commonly known as the depletion depth, which is determined by the bias voltage. Therefore, it is crucial to investigate the signal’s dependence on the bias voltage and, consequently, on the effective thickness. We present the measurement of the capacitance of a PIN diode sensor as a function of the bias voltage to determine the dependence of the effective thickness on the bias voltage. We also present the measurement of the signal dependence of the sensor on the bias voltage and the effective thickness using a β-ray source. Finally, we compare the two measurements to validate the signal dependence of the sensor on the bias voltage and, consequently, the effective thickness.

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  • Research Paper 2024-04-30

    A Proposal for Improvement of Korean Science Inquiry Activities through an Analysis of Practicals of the IB DP Physics

    Munho Kwon

    Abstract : This study analyzed the operation of inquiry activities and internal assessment in the IB DP Physics course and examined the implications for science education in Korea. I found that IB DP(International Baccalaureate Diploma Programme) requires students to conduct quantitative experiments by giving specific guidelines on the number of class periods, types of inquiry activities, and evaluation in the Physics guide, and that it is operated as an open inquiry that only outlines the topic and approach to inquiry, and requires quantitative analysis and data processing of the results of the experiments. I also found that IB DP requires students to conduct self-directed inquiry activities through internal assessment to finally evaluate their inquiry competence. Through this study, it was suggested that self-directed inquiry activities and approaches for quantitative interpretation of data should be discussed in terms of the operation of inquiry activities, and that the development of inquiry activity evaluation criteria and the need for teacher-training program in inquiry activity evaluation are needed in terms of the evaluation of inquiry activities.

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  • Research Paper 2024-04-30

    Gravitational Deflection of Light: A Heuristic Derivation at the Undergraduate Level

    Hongbin Kim, Dong-han Yeom, Jong Hyun Kim

    Abstract : In this paper, we present a new heuristic derivation of the gravitational deflection of light around the Sun at the undergraduate level. Instead of solving the geodesic equation directly, we compute the correct deflection angle by focusing on the acceleration term of null geodesics. Using this heuristic deviation, we expect that undergraduate students who have not learned general relativity will be able to experience this computation, which is one of the most remarkable evidences of general relativity.

    Show More  
  • Research Paper 2024-04-30

    Effect of the Ion Flux Incident on the Wafer Depending on the Structure and Material of the Focus Ring in Capacitively Coupled Plasma Sources for the Semiconductor Etching Process

    Cheongbin Cheon, Hae June Lee

    Abstract : Computer simulations of capacitively coupled plasma sources for the semiconductor etching process were conducted using the particle-in-cell method with graphics processing unit devices, and analyses of the electron Ohmic heating and flux distributions were performed to improve the uniformity of the ion flux incident on the wafer. By moving the electron heating that occurs near the wafer edge toward the side wall of the chamber, the flux uniformity of electrons entering the wafer surface can be improved, and the ion flux uniformity toward the wafer to preserve the net flux is also improved. In addition, it was confirmed that the electric field distribution becomes uniform by changing the material and structure of the focus ring. Through this, etching uniformity can be improved by increasing the ion flux uniformity in the semiconductor etching process using a capacitively coupled plasma source, and we provided understanding of spatial uniformity control by changing the dielectric material and structure of the focus ring.

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  • Research Paper 2024-04-30

    A New Criterion for Retinal Image Resolution

    Bon-Yeop Koo, Myoung-Hee Lee, Yoo-Na Jang et al.

    Abstract : Visual information is perceived through images formed on the eye’s retina, which acts as an optical system consisting of the cornea and lens. These components act as detectors that focus light emitted from distant objects onto the retina and identify image characteristics. The performance of a device for displaying visual information is measured by its ability to produce high-resolution images by the human eye. In this study, we proposed a quantitative method to evaluate retinal images based on visibility and clarity. It was confirmed that clarity was appropriate when evaluating images located on the retina, while visibility was appropriate when evaluating images formed around the retina, that is, in front and behind the retina. The product of these two values was newly defined as retinal image resolution, and it was confirmed that the quantitative analysis results of not only the image formed at the exact retinal position but also the images formed in front and behind the retina matched very well with the qualitative results of the resolution evaluated with the naked eye.

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  • Research Paper 2024-04-30

    Effect of Spherical Aberration of Lens and Laser Intensity Distribution on Beam Quality

    Suchan Bae, Jin Seog Gwag, Jonghoon Yi

    Abstract : The effect of spherical aberration of the lens on M2, which represents the beam quality of the laser, was investigated. In order to change the beam diameter by blocking part of the beam, a continuous wave laser diode beam with M2 of 1.45 was passed through a beam expander to expand the beam diameter. Using an aperture, the diameter of the laser beam passing through a plano-convex lens with f = 5 cm was varied in the range of 2 to 10 mm, and M2 was measured according to the diameter. As the diameter of the laser beam increased, M2 also increased to 12.3 due to the effect of spherical aberration. To observe the effect of laser intensity distribution on M2, part of the laser beam was blocked using ND (neutral density) filters with various transmittances. The change in M2 was observed while allowing only half of the laser beam with a Gaussian beam distribution to pass through the ND filter, and as the transmittance decreased, M2 increased.

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  • Research Paper 2024-04-30

    Analysis of South Korean Presidential Election Results Based on Regional Voter Turnout

    Euseo Gwon, Hyeong-Chai Jeong

    Abstract : This study investigates the link between regional voter turnout and presidential election outcomes in South Korea. Typically, the realistic prospects of winning are confined to one conservative and one liberal candidate. The country demonstrates a distinct regional pattern, with the southeast supporting the conservative party and the southwest favoring the liberal party. We analyzed regional patterns of voter turnout and political tendencies from the 15th to the 20th elections. Our findings show that election outcomes can be accurately predicted by analyzing voter turnout changes, based on both the data at the end of voting and the final data released before the end. The key insight is that shifts in voter turnout in politically biased regions align with party support changes in neutral areas, indicating their significance in accurately predicting election outcomes.

    Show More  

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Current Issue

April 2024
Vol.74 No.4

pISSN 0374-4914
eISSN 2289-0041

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pISSN 0374-4914
eISSN 2289-0041