npsm 새물리 New Physics : Sae Mulli

pISSN 0374-4914 eISSN 2289-0041
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  • Research Paper 2023-04-30

    Fabrication of Lens Array Using a 3D Printer and Vacuum Forming

    Min-Ji Kim, Young-Gu Ju*

    Abstract : In this study, we used a 3D printer, vacuum forming, and soft molding methods to fabricate a lens array. We printed the first prototype of the lens array using a 3D printer. Then, we used vacuum forming to smooth the surface of the prototype with a melted plastic sheet. Subsequently, the smoothed prototype was used to create a soft mold using polydimethylsiloxane. We poured thermal epoxy into a soft mold and allowed it to harden, forming transparent epoxy lens arrays. The fabricated lens array produced good images of objects and exhibited excellent lens performance. Furthermore, the focal length of the lens arrays was varied by adjusting the radius of curvature of the prototype. The proposed fabrication approach offers the potential for students to create their lenses and practice optical theory.

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  • Research Paper 2023-04-30

    Improving Recommendation Systems through User Analysis using Triplet Loss

    Sunmo Koo, Sangjoon Park, Yongsung Kwon et al.

    Abstract : A service provider must understand the unique characteristics of the users to recommend appropriate products. Factors such as personality, social class, and hobbies can be used to identify the user and improve recommendations. This information can be obtained through direct questioning or analyzing user-generated content such as blog posts. This study uses a large language model and transfer learning to extract specific information, such as taste and knowledge, from text. The author’s characteristics are then embedded using a recurrent neural network and a triplet loss metric learning methodology to distinguish between users. Qualitative insights into their similarities were then obtained from analyzing the label distribution in the embedding space.

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  • Research Paper 2023-03-31

    Luminescence Enhancement of Y3Al5O12:Ce3+ Phosphor by Adding Potassium Silicate Solution for Low Temperature Synthesis

    Ji Hoon Yoo,  Woo Tae Hong,  Jong Won Chung et al.

    Abstract : Potassium silicate solution (PSS) added with Y3Al5O12:Ce3+(YAG:Ce3+) phosphors was synthesized by using a solid-state reaction method. The crystal structure, morphology, and luminescence properties of the phosphors were measured for various PSS concentrations. The X-ray diffraction pattern of the phosphors shows that the addition of PSS promotes the formation of a garnet structure at lower temperature than commercial YAG phosphors. FE-SEM images show that the addition of PSS promotes the growth of particle size and aggregation. With the addition of 10 wt.% of PSS, the PL spectra show that the emission intensity at 533 nm is 20% higher than the normal phosphor. In determining the performance of PSS-added YAG:Ce3+ phosphors, white LEDs were fabricated by combining blue LEDs and phosphors. The phosphor exhibited lower color temperature because of the enhancement of yellow emission. Result shows that PSS can be applied as a flux, which decreases the synthesis temperature of YAG phosphors.

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  • Research Paper 2023-03-31

    Unexpected Situations in Elementary School Electric Circuit Lessons: an Experienced Teacher's Responses and Science Teaching Beliefs

    Chaeyeon Shin, Jinwoong Song*

    Abstract : For this qualitative study, we conducted an in-depth analysis of unexpected situations that occur in sixth-grade electric circuit lessons in a South Korean elementary school, the causes of these situations, and factors affecting the teacher’s responses. We performed a detailed observation of electric circuit lessons taught by an experienced teacher and carried out pre-lesson and post-lesson interviews. The causes of unexpected situations were found to be students’ neglect of electrical components, poor quality electrical components, images in the textbook, and real-life examples and analogies used by the teacher. The situations considered unexpected by the teacher included an electric circuit that did not light up, incorrect experimental results, and student questions regarding the teacher’s real-life examples. The teacher handled these unexpected situations by explaining that electrical components are consumables, giving real-life examples, providing opportunities for inquiry, and limiting textbook use. These responses originated from the teacher’s belief that science teaching should be student-centered and inquiry-based, and needs to emphasize the relationship between science and real-life experience. The study offers implications for science education in general and the teaching of electric circuits, which presents significant difficulties for elementary school teachers.

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  • Research Paper 2023-02-28

    A Study on the Problems of an Electric Bulb in Physics Education (II): Calculation of Current

    Donggeul Hyun, Jeongwoo Park, Aekyung Shin

    Abstract : This paper proposes two methods for calculating current flow through an electric bulb, which is a nonlinear electric device: the graphical method and the optimal auxiliary function method. The currents flowing through an electric bulb of 2.5 V − 0.3 A with room temperature resistance R0 = 1.3 Ω according to the terminal voltages of it are calculated via the methods and are compared with the measured currents. Compared with the measured currents, the currents calculated via the graphical method have error rates below 5.95%, and the currents calculated via the optimal auxiliary function method have error rates below 2.44% in the operating region of the electric bulb. These low error rates demonstrate the validity and practicality of the two methods.

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Current Issue

    April, 2023 | Volume 73, No. 4
  • Research Paper 2023-04-30

    Energy Quantization in Rectangular Quantum Dots

    Hwanchul Jung, Seokyeong Lee

    Abstract : In this study, we investigated the eigenenergy and wave function structures of a mesoscopic rectangular quantum dot on a two-dimensional electron gas using the quantum transport simulation tool KWANT. From adjusting the ratio between the width and height of the quantum dot, we found that the eigenenergy was sensitively influenced by the ratio change and rearranged through the crossing. However, for certain energy states, the crossing was avoided, and anticrossing occurred instead. Further analysis revealed that the wave function became a rotating mode near the anticrossing point but could not evolve continuously through the rotating mode, leading to anticrossing. Our calculations demonstrated the possibility of rearranging the eigenenergy and wavefunctions and forming a rotating mode inside a quantum dot via deformation using nanodevices.

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  • Research Paper 2023-04-30

    Current-Voltage Characteristics of n-type Doped TiO2 Thin Films Deposited on p-Si Substrates

    Woo Il Jeong, Jin Young Maeng, Jong Hyun Song*

    Abstract : We fabricated p-n junction devices by depositing Nb-doped TiO2 thin films on p-Si (100) substrates using pulsed laser deposition method with Nb-doping rates of 0%, 3%, and 6% and carried out current–voltage (I-V) measurements to characterize their electrical transport properties. Results revealed that the undoped TiO2/p-Si device exhibited the ideal diode characteristics when the ideality factor, zero bias barrier height extracted by applying thermionic emission theory, T0 anomaly, and distribution of the zero bias barrier height versus the ideality factor were considered. Rectification characteristics were observed even in device without Nb doping. This phenomenon is interpreted as the natural n-type doping effect of TiO2 thin film due to oxygen deficiencies. For the Nb:TiO2/p-Si device with Nb doping, the inhomogeneities in barrier height increased compared with that of the undoped device. As a result, the characteristics of the diode device degraded. These observations provide insights into the optimal doping condition for the device applications of TiO2.

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  • Research Paper 2023-04-30

    Spin Clusters-Induced Electrical Transport Properties of Hexagonal and Orthorhombic Ni3Sn2

    Beopgil Cho, Jaemun Park, Keeseong Park*

    Abstract : Ni3Sn2 crystallizes into a hexagonal phase (HT-Ni3Sn2) at higher temperatures while it undergoes structural distortion and vacancy alignment to transform into an orthorhombic phase (LT-Ni3Sn2) at lower temperatures. LT-Ni3Sn2 has not been synthesized in a single-crystalline form, although spin heptamers of Ni atoms can constitute well-organized spin clusters and possibly influence various physical phenomena. This paper demonstrated a successful synthesis of both phases in single crystals using a flux method, and their electrical transport was measured. Both phases showed unusual metallic resistivity, which can be fitted via a power law. This power law behavior is frequently exhibited by compounds consisting of 3d transition metals because of their spin frustration. In magnetoresistance, LT-Ni3Sn2 showed an abrupt increase at a low temperature and weak magnetic field region, indicating an influence of the spin clusters or occurrence of a weak antilocalization due to a strong spin–orbit coupling.

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  • Research Paper 2023-04-30

    Study on the Deterioration of LiCoO2 Layers in NH3 Atmospheric Conditions

    Hong Tak Kim, Kiwon Yang, Jong-goo Bhak et al.

    Abstract : Lithium phosphorus oxynitride (LiPON) and lithium cobalt oxide (LCO) are representative solid-electrolyte and anode material in solid-state batteries. LiPON films were deposited on LCO-formed substrates through metal–organic vapor deposition. The deterioration of LCO films during LiPON deposition in ammonia (NH3) atmosphere was studied, and effects of the ultrathin aluminum oxide (Al2O3) layer on preventing damage to LCO were investigated. During the deposition, LCO underwent reduction reactions with active NH3-species. The LCO phase changed into a metallic cobalt phase while losing oxygen components. The increase in the cobalt layer thickness was almost linearly proportional to the rise in the temperature. The activation energy was ~25 kJ/mol, and the reduction of LCO occurred at a low temperature of 350 °C. These findings implied that the cobalt components in LCO acted as an effective catalyst for the activation of NH3 and accelerated the chemical reaction; furthermore, Al2O3 films effectively prevented the deterioration of LCO films. Therefore, this reduction-prevention layer is universally applicable in processes using NH3 precursors.

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  • Research Paper 2023-04-30

    Experimental Performance Characteristics of Elementary School Students in Measuring Extended Length of Spring with Weight

    Jung Yun Shin, Sang Woo Park

    Abstract : This study analyzed the characteristics and difficulties of elementary school students’ experimental performance in measuring the spring length extension with weight. The characteristics of experimental performance for 12 elementary school students from 3rd to 5th grade were analyzed on the basis of the recordings of the experimental process, researcher’s observation notes, student's activity sheets, and post-interview data. Results revealed that the students did not recognize the need to accurately decorate the experimental device, elaborate the procedure for precise measurement, and use a zero-point control weight. They also had difficulty recording the measured experimental data. Some students drew conclusions that did not reveal regularity, while some drew conclusions that revealed regularity but ignored or distorted the measured values.

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  • Research Paper 2023-04-30

    Exploring the Impact of Open Inquiry and Simulation Laboratory Teaching Experiences on the Perception of Preservice Physics Teachers

    Hyojoon Kim, Sangwoo Ha

    Abstract : Experiments are fundamental aspect of scientific inquiry and its role in science education is crucial. However, many experimental classes in schools tend to focus on confirmation experiments that limit students’ ability to explore and inquire. This study aims to help preservice teachers in understanding the value of inquiry-based experimental classes by inviting them to participate in an open-ended inquiry. Fifteen preservice teachers who had minimal prior experience in conducting an open inquiry and teaching formal classes participated in this study. Through this study, they were able to identify the benefits of an open-ended experiment, noting that it was enjoyable and beneficial in fostering a deeper understanding of concepts. Moreover, they observed that open-ended inquiry is similar to what scientists do and thus must be experienced by students. They thought that laboratory instruction was crucial for effective teaching in schools. Nevertheless, they acknowledged that teaching experimentation requires substantial preparation and an in-depth understanding of the experiment.

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  • Research Paper 2023-04-30

    Analysis of the Change of Preservice Teachers' Self-Efficacy on Science Teaching and Learning in Online Overseas Education Volunteer Activities and Phenomenological Description on Their Experience

    Ji-soo Yoon, Sungmin Im*

    Abstract : This study aims to explore the effect of online overseas education volunteer activities on preservice teachers’ self-efficacy on science teaching and learning and to qualitatively describe the experiences of preservice teachers. Changes in the self-efficacy of 17 preservice teachers who participated in online overseas education volunteer activities were analyzed, and the phenomenological meaning of their experiences was derived through qualitative research. Results showed that the self-efficacy of preservice teachers in science education major showed considerable improvement in learning efficacy dimension. Phenomenological description research revealed that preservice teachers’ communication ability and reflective practice were mediating factors that affect the practice of science teaching. Additionally, the restriction of the environment and tools in the context of online overseas education volunteer activities acted as obstacles that hinders the activities and as a means to grant agency so that preservice teachers can actively lead science classes as subjects.

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  • Research Paper 2023-04-30

    Fabrication of Lens Array Using a 3D Printer and Vacuum Forming

    Min-Ji Kim, Young-Gu Ju*

    Abstract : In this study, we used a 3D printer, vacuum forming, and soft molding methods to fabricate a lens array. We printed the first prototype of the lens array using a 3D printer. Then, we used vacuum forming to smooth the surface of the prototype with a melted plastic sheet. Subsequently, the smoothed prototype was used to create a soft mold using polydimethylsiloxane. We poured thermal epoxy into a soft mold and allowed it to harden, forming transparent epoxy lens arrays. The fabricated lens array produced good images of objects and exhibited excellent lens performance. Furthermore, the focal length of the lens arrays was varied by adjusting the radius of curvature of the prototype. The proposed fabrication approach offers the potential for students to create their lenses and practice optical theory.

    Show More  
  • Research Paper 2023-04-30

    Improving Recommendation Systems through User Analysis using Triplet Loss

    Sunmo Koo, Sangjoon Park, Yongsung Kwon et al.

    Abstract : A service provider must understand the unique characteristics of the users to recommend appropriate products. Factors such as personality, social class, and hobbies can be used to identify the user and improve recommendations. This information can be obtained through direct questioning or analyzing user-generated content such as blog posts. This study uses a large language model and transfer learning to extract specific information, such as taste and knowledge, from text. The author’s characteristics are then embedded using a recurrent neural network and a triplet loss metric learning methodology to distinguish between users. Qualitative insights into their similarities were then obtained from analyzing the label distribution in the embedding space.

    Show More  

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Current Issue

April 2023
Vol.73 No.4

pISSN 0374-4914
eISSN 2289-0041

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pISSN 0374-4914
eISSN 2289-0041