npsm 새물리 New Physics : Sae Mulli

pISSN 0374-4914 eISSN 2289-0041
Qrcode
  • Research Paper 2024-05-31

    Influence of Anharmonic Effects on Phonon Dispersion in Cubic Perovskites

    Kwanhong Park, Jaejin Hwang, Jaekwang Lee

    Abstract : Perovskites are known to exhibit a variety of phases, including tetragonal, orthorhombic, and cubic, depending on the temperature. However, in the cubic phase, which indeed exists at room temperature, imaginary frequencies appear in the phonon dispersion based on the harmonic approximation. That’s why we need to consider the anharmonic effect to accurately capture the phonon dispersion. In this work, self-consistent phonon theory was utilized to calculate the phonon dispersion, including anharmonic effects, for the cubic phases of SrTiO3, BaTiO3, RbCaF3, and CsSrF3. This study demonstrates that the phonon dispersion of the cubic phase, present at room temperature, and their temperature dependency can be accurately predicted by considering the anharmonic effect.

    Show More  
  • Research Paper 2024-05-31

    Analysis of Elementary School Students’ Experimental Performance Characteristics and Difficulties in the Inquiry Activities on ‘Temperature and Heat’ Chapter

    Jung Yun Shin, Sangwoo Park

    Abstract : This study analyzed the characteristics and difficulties of elementary school students’ experiment processes in inquiry activities related to heat transfer in the ’Temperature and Heat’ unit of the 5th grade elementary school curriculum. After conducting inquiry activities with 12 students from 4th to 6th grade, we collected and analyzed students’ experiment process videos, researcher observation notes, student activity sheets, and post-interview data. The results showed that students encountered difficulties in conducting experiments precisely and interpreting the results to understand the concepts. Additionally, in the experiment on heat transfer in solids, students experienced experimental errors despite the experiment not being particularly difficult or time-constrained, and some students did not fully understand the concept of heat transfer in solids. Based on the research findings, we discussed solutions for addressing difficulties in setting up and operating experimental apparatus, the need for detailed description of experimental procedures for enhancing experimental skills.

    Show More  
  • 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

    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  
  • 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.

    Show More  

Current Issue

    May 2024 | Vol. 74 No. 5
  • Research Paper 2024-05-31

    Silicon Carbon Nanotube Composite for Supercapacitor Applications

    Mangesh Subedi, Hae Kyung Jeong

    Abstract : Supercapacitor finds appealing uses as an electrical energy storage device in consumer electronics and as an alternative power source due to its quick discharge/charge times and long-term operation stability. This study examines silicon and CNT (Si-CNT) composite, synthesized by a simple and easy method, for supercapacitor applications. The supercapacitor electrodes active material was a composite of Si and CNT. It was made by magnetic stirring, mixing, ultrasonication, vacuum filtration, and drying process of the powdered Si and CNT with a binder. The final composite shows the specific capacitance of 121.3 F/g, energy density of 10.86 Wh/kg, and power density of 403.2 W/kg at 1 A/g. It demonstrates that the composite material could boost the supercapacitor efficiency.

    Show More  
  • Research Paper 2024-05-31

    Influence of Anharmonic Effects on Phonon Dispersion in Cubic Perovskites

    Kwanhong Park, Jaejin Hwang, Jaekwang Lee

    Abstract : Perovskites are known to exhibit a variety of phases, including tetragonal, orthorhombic, and cubic, depending on the temperature. However, in the cubic phase, which indeed exists at room temperature, imaginary frequencies appear in the phonon dispersion based on the harmonic approximation. That’s why we need to consider the anharmonic effect to accurately capture the phonon dispersion. In this work, self-consistent phonon theory was utilized to calculate the phonon dispersion, including anharmonic effects, for the cubic phases of SrTiO3, BaTiO3, RbCaF3, and CsSrF3. This study demonstrates that the phonon dispersion of the cubic phase, present at room temperature, and their temperature dependency can be accurately predicted by considering the anharmonic effect.

    Show More  
  • Research Paper 2024-05-31

    Electronic Structure and Spontaneous Polarization of CsANb2O7 (A = Bi, Nd) from First Principles

    Junseok Kim, Bog G. Kim

    Abstract : The effect of octahedral tilting of CsANb2O7 (A = Bi, Nd) compounds has been investigated through symmetry mode analysis and density-functional theory. This compounds undergo a structural phase transition from tetragonal (P4/mmm) to orthorhombic (Pmc21). Through first-principle energy calculation, it has been demonstrated that the coupling of M3+ and M5 modes primarily contributes to this phase transition. Furthermore, the ferroelectricity observed in these compounds is induced by the Γ5 mode, which breaks mirror symmetry of the tetragonal phase. By examining the magnitude of the amplitude of the (Γ5) mode in each system, it becomes possible to estimate the magnitude of the spontaneous polarization. This comprehensive study offers a detailed analysis of the energetic behavior of the tilting modes concerning the structural phase transition in CsANb2O7 compounds, providing valuable insights for potential applications of these materials.

    Show More  
  • Research Paper 2024-05-31

    Study on Morphological and Magnetic Aspects of Lithium Addition in M-type Strontium Hexaferrites

    Sunghyun Yoon

    Abstract : Various aspects of lithium doping on M-type strontium hexaferrites have been examined by using crystallographic and magnetic measurements such as XRD, FE-SEM, VSM, and Mössbauer spectroscopy. Samples were prepared in three different ways either by simply adding Li2CO3 as a flux salt, by synthesizing thru flux-aided flash-annealing route, or by substituting Li1+ for Fe3+ into SrFe12O19 precursors. Subsequently, crystallographic, microstructural, and magnetic characteristics have been explored in terms of the role of Li1+ flux on morphology of the samples. The results strongly suggested that most of the flux salt Li1+ ions distributed throughout the grain boundary and acted like a surfactant that enhances the degree of grain separation and thereby reduced the coercivity HC and the magnetic anisotropy constant K of the sample. Contrarily, the HC and the K in the flux-aided flash-annealed sample were found to increase due to its fine-particle nature despite the enhanced degree of grain separation. 57Fe Mössbauer spectrum of the Li1+-substituted sample showed that Li1+ ions preferentially occupied the 2a site.

    Show More  
  • Research Paper 2024-05-31

    Analysis of Elementary School Students’ Experimental Performance Characteristics and Difficulties in the Inquiry Activities on ‘Temperature and Heat’ Chapter

    Jung Yun Shin, Sangwoo Park

    Abstract : This study analyzed the characteristics and difficulties of elementary school students’ experiment processes in inquiry activities related to heat transfer in the ’Temperature and Heat’ unit of the 5th grade elementary school curriculum. After conducting inquiry activities with 12 students from 4th to 6th grade, we collected and analyzed students’ experiment process videos, researcher observation notes, student activity sheets, and post-interview data. The results showed that students encountered difficulties in conducting experiments precisely and interpreting the results to understand the concepts. Additionally, in the experiment on heat transfer in solids, students experienced experimental errors despite the experiment not being particularly difficult or time-constrained, and some students did not fully understand the concept of heat transfer in solids. Based on the research findings, we discussed solutions for addressing difficulties in setting up and operating experimental apparatus, the need for detailed description of experimental procedures for enhancing experimental skills.

    Show More  
  • Research Paper 2024-05-31

    Investigation of Preservice Teachers' Physics Identity

    Junhee Kim, Sungmin Im

    Abstract : In this study, to investigate the physics identity of preservice physics teachers, we proposed a conceptual framework of physics identity consisting of four dimensions: interest, recognition, competency, and performance, and based on this, developed a 29-item Likert scale survey tool. The developed physics identity survey tool was applied to 36 preservice physics teachers to analyze the distribution of physics identity by dimension based on the response data, and to examine differences between groups according to gender, grade, and academic achievement. As a result, preservice physics teachers’ physics identity was highest in the performance dimension and lowest in the recognition dimension. Men show significantly higher scores in the interest and performance dimensions than women, and differences by grade do not show differences in physics identity. In addition, differences in physics identity according to academic achievement in the interest and competency dimensions are statistically significant.

    Show More  
  • Research Paper 2024-05-31

    Mathematical Analysis of Light Bending in Sugar Solution

    Dongseung Kang, Bongwoo Lee

    Abstract : The purpose of this study is to mathematically analyze the phenomenon of light bending in dense sugar solution and compare the results with experimental and simulation results. The mathematical analysis used Fermat’s principle to state that the path of light follows the shortest time path between two points. Since the speed of light is inversely proportional to the refractive index, and the refractive index in sugar solution is related only to depth, Euler’s equation can be converted into a simple integral equation. As a result of the analysis, the light path for Model 1, where the speed of light decreases in proportion to depth, is circular, and the light path for Model 2, where the refractive index increases in proportion to depth, is logarithmic. When the experimental conditions were applied, the difference between the two models was only 0.054%, which was very consistent with the light path obtained through the experiment. The difference between the mathematical results and the simulation results obtained by continuously applying Snell’s law by dividing the depth of the sugar water into equal intervals was very small at 0.052%. Additionally, the process and results presented in this study were discussed from a physics education perspective.

    Show More  
  • Research Paper 2024-05-31

    Content Analysis of Magnetic Materials Presented in the 2015 Revised Curriculum Physics I Textbooks

    Jihyeon Guk, Sangwoo Ha

    Abstract : This study aims to analyze whether the content on magnetic materials presented in the Physics I textbook of the revised 2015 curriculum is structured to achieve the learning objectives, whether the descriptions and illustrations are clearly organized to facilitate easy understanding for students, and whether inquiry activities are consistently structured to aid in the comprehension of conceptual understanding. The analysis focused on key topics, including atomic magnets, ferromagnets, paramagnets, diamagnets, applications of magnets, and inquiry content. The findings revealed a need for more clarity in textbook contents, consistency in explanations and illustrations related to magnetism, and improvements to meet the achievement standards. Variations were observed in the specific explanation contents across textbooks, with notable omissions of real-world application examples and discrepancies in the representation of experimental activities. Based on these results, the study discusses implications for refining textbook descriptions to better align with educational curriculum standards and enhance students meet these standards.

    Show More  
  • Research Paper 2024-05-31

    Comparison of Scoring Results for Physics Descriptive Items in GPT Language Models Based on Prompts

    Taeho Min, Bongwoo Lee

    Abstract : The purpose of this study is to automatically score descriptive evaluation using GPT language model and to analyze the scoring results according to prompts, comparison with experts’ scoring, and the characteristics of feedbacks. For this purpose, responses of one descriptive item related to the principles of seeing the colors of objects were collected from 7th grade students’ 117 data. Automated scoring was performed using 12 different prompts and the results were analyzed. The main results are as follows. First, the GPT language model scored more leniently than the expert scorers, and there was a difference in the distribution of scores. Second, the Cohen’s kappa coefficient between the GPT language model and the expert scorers was .12 to .34, and the Pearson correlation coefficient was .41 to .67, so the agreement rate was not high, but the correlation was relatively high. Third, Feedback was accurate regarding general knowledge, but sometimes inaccurate feedback was generated regarding the application of knowledge to specific situations, and the content of the feedback tended to depend on the scoring criteria. Based on the research results, the possibility of automated scoring using artificial intelligence was discussed from an educational perspective.

    Show More  
  • Research Paper 2024-05-31

    Investigation of Operational Performance of the Seoul Metropolitan Subway Network Using Smart Card Data

    Juhee Yoon, Heeju Kim, Gunn Kim

    Abstract : We studied the efficiency of the Seoul Metropolitan Subway system by analyzing travel time, distance, and speed for 333,506 station pairs using smart card data. We used a depth-first search algorithm to identify the most efficient travel paths, considering both distance and transfers. We found that the average travel time was 16 minutes. Further analysis revealed a well-planned network in which actual travel paths closely matched geodesic distances, confirming the strategic design of the network. The speed analysis showed that trains were mostly running in an optimal range of 10–30 km/h, indicating a balance between efficiency and passenger comfort. This study can contribute to the development of urban transportation by determining the operational efficiency of the network structure of the Seoul Metropolitan Subway system in terms of travel time, distance between stations, and travel speed.

    Show More  

All Newest Articles

Current Issue

May 2024
Vol.74 No.5

pISSN 0374-4914
eISSN 2289-0041

submit an article

Most Read

pISSN 0374-4914
eISSN 2289-0041