pISSN 0374-4914 eISSN 2289-0041
• ### Research Paper 2021-02-26

#### Dependence of the AC loss on Interval and Stacking Number in $z$ Stacked GdBCO Coated Conductor

Chan KIM, Young-kyoung KIM, Sung-min JEON et al.

Abstract : The 2G High-$T_{c}$ superconductor-coated conductors (2G HTS CC) with large aspect ratios have large AC losses for a perpendicular external magnetic field. A reduction of the AC loss is an important issue in 2G HTS CC applications. In a previous study, stacking of HTS CC was found to increase the full penetration field $H_{p}$ and to decrease the AC loss. The AC loss for the maximum applied magnetic field $H_{m}$ below $H_{p}$ was affected by the interval $D$ and the staking number $n$. In this study, to reduce the AC loss, we stacked GdBCO-coated conductors with the same geometries and with regular $D$, and we measured the magnetization curves of the stacked samples at a temperature of 83 K ($t = T/T_{c} = 0.88$). The AC losses were calculated using the experimental results, and the AC losses of the stacked samples were compared with phose for the single-layer sample. We investigated the dependences on $D$ and n of the AC losses of the stacked GdBCO CCs. As the interval decreases, the volume normalized AC loss decreased. In the case of $D$ = 0.10 mm, the AC loss was decreased by 16% and 37% in the 2-layer structure and the 3-layer structure, respectively, compared with the 1-layer structure.

• ### Research Paper 2021-02-26

#### The Comparison Study on Dose Distribution of $^{6}$He and $^{4}$He Ion Beams

Jong-Kwan WOO, Dong LIU*

Abstract : In this study, we evaluate the dose distributions of $^{4}$He and $^{6}$He ion beams under the same irradiation settings by using the Monte Carlo method. For the simulations, we defined a water phantom that which includes three normal regions and one target region for measuring the dose deposition in various regions. In addition, we define the $^{4}$He and the $^{6}$He ion beams with specified parameters. Then, we obtain the distributions of the doses and the tracks of $^{4}$He and $^{6}$He ion beams and calculate the dose deposited in each region. The calculated results show that in the proximal volume, lateral volume, distal volume, and target volume, the dose depositions of the $^{4}$He ion beam are 73.77%, 31.44%, 73.5%, and 98.50% of that of $^{6}$He ion beam. In conclusion, we can say from the aspect of physical dose distribution, that the $^{4}$He ion beam is more ideal than the $^{6}$He ion beam. To more objectively evaluate the therapatic effects of $^{4}$He and $^{6}$He ion beams, in our need experiment-based study, we will consider the biological effects of $^{4}$He and $^{6}$He ion beams.

• ### Research Paper 2021-01-29

#### Structural Evolution of Nitrogen-doped Titanium-dioxide Thin Films

Seaung-jae LEE, Ji-won JANG, Hye-won SEO*

Abstract : We have grown nitrogen-doped titanium dioxide thin films by using DC magnetron sputtering methods. During the growth, the nitrogen flow was altered to adjust the amount of nitrogen into the titanium-dioxide films. By a comparative study of X-ray diffraction and Raman spectroscopy results, we found that the insertion of nitrogen led to a reduction in crystal size/volume, distortion of Ti-O bending, and displacement of Ti atoms. As the nitrogen flow was increased, the degradation of crystal quality became more severe. A blue shift of the optical energy bandgap was observed for the titanium-dioxide films with nitrogen, which is possibly related to quantum-confinement effects.

• ### Research Paper 2021-01-29

#### Fabrication and Properties of Carbon Quantum dot and Carbon Quantum dot Film Using Fallen Leaves Through Hydrothermal Method

Sung Jun PARK, Hyun Kyoung YANG*, Byung Kee MOON et al.

Abstract : Carbon quantum dots were synthesized using the hydrothermal method with fallen leaves as carbon sources. The chemical structure, particle size and morphology, and luminescent characteristics of the prepared carbon quantum dots were investigated. The particle size and morphology of synthesized carbon dots were observed by using TEM (transmission electron microscopy). The ligand and chemical structures of the carbon quantum dots were confirmed by using FT-IR (Fourier transform infrared spectroscopy). The elemental components of the carbon quantum dots were investigated by using XPS (X-ray photoelectron spectroscopy). The photoluminescence spectrum of carbon quantum dots showed strong cyan fluorescence around 493 nm under 400-nm excitation. A UV blocking film for preventing eye and body damage was fabricated by using the prepared carbon quantum dots. Consequently we confirm the applicability of carbon dot films for shielding from UV light.

• ### Research Paper 2020-12-31

#### Pixel Design Study of a CMOS Monolithic Active Pixel Sensor for the Charge Collection time

Sanghyeon LEE, In-Kwon YOO*

Abstract : A new silicon chip (INVESTIGATOR) manufactured for R\&D purposes has 134 mini-matrices with various pixel designs. Each matrix consists of 8 $\times$ 8 pixels, which put out 64 analogue signals at 65 MHz. The silicon pixel design is based on the newest technology of the complementary metal-oxide-semiconductor (CMOS) monolithic active pixel sensor (MAPS), which integrates the silicon sensor and the read-out circuitry in a pixel. The MAPS has advantages of low power consumption, high granularity of a pixel, and fast read-out. In this paper, the charge collection time for different pixel designs and reverse bias voltages is studied by using the INVESTIGATOR. The charge collection time is estimated by fitting the waveform for changing pixel pitch, reverse bias voltage, diameter of collection n-well diode, and spacing. Based on these results, we discuss the dependence of the relative depletion volume and the charge collection time on the pixel geometry.

## Current Issue

February, 2021 | Volume 71, No. 2
• ### Research Paper 2021-02-26

#### The Ratio of NaBH$_{4}$ in the Synthesis of Water-soluble CdTe Nanocrystals

Il-gon KIM*, Dong-sun YOO

Abstract : The synthesis and the structural properties of CdTe quantum dots with high luminous efficiency were studied. Transmission electron microscopy (TEM), Fourier transform infrared (FTIR), and Raman spectra were measured to determine the structural characteristics of the synthesized samples. The Stokes shift for each sample was investigated using the absorption and the emission spectra from the three sample groups (S1, S2, S3) synthesized with NaBH$_{4}$/Te ratios of s 2, 5, and 10, the Stokes shift decreased with increasing heat-treatment time, but increased after a certain period of time. The CdS peak was seen at 300 cm$^{-1}$ in the Raman spectrum of the nanocrystals with a heat treatment time of 24 hours. From this observation, we were able to confirm that a CdS cell had been formed. The spectral ranges of the S1, S2, and S3 samples synthesized with different ratios were 500 ~ 540 nm, 620 ~ 690 nm, and 650 ~ 710 nm, respectively. The photoluminescence quantum yield of the sample group S2 with a NaBH$_{4}$ to Te ration of 5 was high, being 30 ~ 50%.

• ### Research Paper 2021-02-26

#### Dependence of the AC loss on Interval and Stacking Number in $z$ Stacked GdBCO Coated Conductor

Chan KIM, Young-kyoung KIM, Sung-min JEON et al.

Abstract : The 2G High-$T_{c}$ superconductor-coated conductors (2G HTS CC) with large aspect ratios have large AC losses for a perpendicular external magnetic field. A reduction of the AC loss is an important issue in 2G HTS CC applications. In a previous study, stacking of HTS CC was found to increase the full penetration field $H_{p}$ and to decrease the AC loss. The AC loss for the maximum applied magnetic field $H_{m}$ below $H_{p}$ was affected by the interval $D$ and the staking number $n$. In this study, to reduce the AC loss, we stacked GdBCO-coated conductors with the same geometries and with regular $D$, and we measured the magnetization curves of the stacked samples at a temperature of 83 K ($t = T/T_{c} = 0.88$). The AC losses were calculated using the experimental results, and the AC losses of the stacked samples were compared with phose for the single-layer sample. We investigated the dependences on $D$ and n of the AC losses of the stacked GdBCO CCs. As the interval decreases, the volume normalized AC loss decreased. In the case of $D$ = 0.10 mm, the AC loss was decreased by 16% and 37% in the 2-layer structure and the 3-layer structure, respectively, compared with the 1-layer structure.

• ### Research Paper 2021-02-26

#### Reduction of Water-soluble Nitrate ion in dust Using Alternative Compound Fuels in Fine-dust-reduction Cement Process

Sanghyeon KIM, Hyun Seok LEE*

Abstract : Fossil fuels in the cement manufacturing process generate dust including water-soluble salts during heating process. The nitrate and the sulfate components in the dust enter into the selective non-catalytic reduction facility and react with water containing urea, resulting in the formation of by-products such as sulfuric and nitric acids which may cause corrosion of the facility. Although wastes replace some parts of fossil fuels in the process, the risks from alternative fuels have yet to be systematically reported. Here, we investigate the correlation between alternative fuels in the heating process and the synthesized water-soluble components of dust. After three aromatic compounds are burned together with a cement mixture, the collected dust is made into aqueous solutions. Using ion chromatography, investigate the nitrate and sulfate ions in the aqueous solutions. As a result, the concentration of water-soluble nitrate ions in the dust is found to be lower for all aromatic compounds. We, thus, conclude that alternative fuels based on aromatic wastes can be effectively used in fine-dust-reduction cement processes.

• ### Research Paper 2021-02-26

#### The Comparison Study on Dose Distribution of $^{6}$He and $^{4}$He Ion Beams

Jong-Kwan WOO, Dong LIU*

Abstract : In this study, we evaluate the dose distributions of $^{4}$He and $^{6}$He ion beams under the same irradiation settings by using the Monte Carlo method. For the simulations, we defined a water phantom that which includes three normal regions and one target region for measuring the dose deposition in various regions. In addition, we define the $^{4}$He and the $^{6}$He ion beams with specified parameters. Then, we obtain the distributions of the doses and the tracks of $^{4}$He and $^{6}$He ion beams and calculate the dose deposited in each region. The calculated results show that in the proximal volume, lateral volume, distal volume, and target volume, the dose depositions of the $^{4}$He ion beam are 73.77%, 31.44%, 73.5%, and 98.50% of that of $^{6}$He ion beam. In conclusion, we can say from the aspect of physical dose distribution, that the $^{4}$He ion beam is more ideal than the $^{6}$He ion beam. To more objectively evaluate the therapatic effects of $^{4}$He and $^{6}$He ion beams, in our need experiment-based study, we will consider the biological effects of $^{4}$He and $^{6}$He ion beams.

• ### Research Paper 2021-02-26

#### Implementation of Interactive art Exhibits Based on Synthesis of Light Using Micro:bits

Yong Wook CHEONG*

Abstract : In this study, I explore the possibility of using a micro:bit as a physical computer for use in secondary physics education. First, I discuss the need to pay attention to micro:bits in physics education. Also, I illustrate that for subject of RGB-based light synthesis, the rich educational contents can be obtained using micro:bits. In this process, I first introduce a method of implementing any color included in the color triangle by utilizing micro:bits. Also, I implement interactive art exhibits based on RGB-based light synthesis through micro:bits. Through this, I exemplify that the learning threshold required to learn the functions of micro:bits is relatively low, but the output that can be implemented through micro:bits can be very high. The educational contents developed in this study can be used in the context of in-depth education related to RGB-based light STEAM convergence education.

• ### Research Paper 2021-02-26

#### A Survey of the Perceptions of Teachers and Experts about the Performance of Science Core Schools

Jeongwoo SON, Jaehyeok CHOI, Kew-Cheol SHIM et al.

Abstract : The purpose of this study is to investigate the perceptions of teachers and experts about the performance of Science Core Schools. For this purpose, 40 science teachers and 8 science educators completed in the questionnaires that included nine items consisting of features from Science Core Schools. Teachers and experts were asked to respond to each item, such as the degree of benefit to the students, the degree of difficulty in use, and the need for continuous maintenance. The most beneficial items for students were improved infrastructure such as laboratories and resource rooms, compulsory completion of specialized subjects (teachers’ opinion), and completion of eight science subjects (experts' opinion); the most difficult was specialized research and linkage to local resources. A necessary item was improved laboratories. The perceptions on the compulsory completion of eight science subjects were different between teachers and experts. Based on these results, the implications for the development of Science Core Schools were discussed.

• ### Research Paper 2021-02-26

#### Characteristic on the Sound Conceptions of Students

Jong Ho PARK*

Abstract : In this study, we investigated the concept of elementary school students about the process of propagating sound, and we targeted fourth-grade students who had learned about sound through a regular course and had drawn their own thoughts on three situations related to the propagation of sound. Three situations in which the other person asks the same concept as to how to hear a sound and how a dust or candle moves in front of a sound speaker were propsed. The students did not understand the transmission of sound due to vibrations in the medium, and they thought that matter moved with the transmission of sound. A correlation was found between the students' expression style and their misconceptions about sound. As a result of classifying the students' expression methods for sound transmission into a total of five, the students who expressed the arc type better understood the concepts of the medium and vibration. In addition, students who drew sound in a straight line or waves lacked understanding of vibration and medium and understood only the simple transmission of sound.

• ### Research Paper 2021-02-26

#### Theoretical Approach to Magnetic Force of Electromagnet

Youngseok JHUN, Donggeul HYUN*

Abstract : The quantitative representations for the magnetic forces of an electromagnet acting on ferromagnetic object were derived on the basis of three magnetization theories, the magnetic potential energy method, Gilbert model for magnetism, and Ampere model for magnetism. The magnetic forces of an electromagnet acting on a ferromagnetic object made of cast iron, cast steel, and sheet steel were calculated using the derived quantitative representations.

• ### Research Paper 2021-02-26

#### A Study of Nuclear Systems using A Classical Mechanics

Bo Seon KIM, Ghi Ryang SHIN*

Abstract : The study of the nuclear structure of nuclei has been an active research area ever since the birth of nuclear physics in 1932. The nuclear system is so complex that we only understand its properties for systems with 2 nucleons or infinitely many nucleons. In this research, we study a system of nucleons from a classical point of view, and are able to show in detail the internal motions of the constituent nucleons by assuming that the nucleons follow the lawn of classical mechanics. We find that a system of 2 nucleons with tensor factor 2 can be a stable cluster but most of multiple nucleon systems break into smaller cluster systems after internal adjustment times. We thus need to have a right isospin and spin state as well as right position and velocity to make stable heavy nuclei.

• ### Research Paper 2021-02-26

#### Development of Teaching Materials to Connect Light Path and Eye Vision

Seongsoo JEON*

Abstract : The purpose of this study is to develop teaching materials that connects the path of light to eye vision in optical learning. Despite much research and practice on optical learning, many students still cannot scientifically explain why objects appear larger in convex lenses and why fish in water appear to be floating. This is due to the lack of a process in which learners can think by connecting the path of light and eye vision in early optical learning to observe the image of an object. The teaching materials developed in this study enable operational exploration, which can be envisioned by connecting the image with the path of light by tracking the path of invisible light starting from the image. This feature allows observation of a phenomenon in which light is refracted at the interface of different media and, at the same time, can provide an experimental basis for the observed image being due to refracted light.

• ### Research Paper 2021-02-26

#### Visualization of Quantum Mechanics of College Students by Using Graph Representation Program

Jeongwoo PARK*

Abstract : In this study, we tried to make students visualize quantum mechanics by themselves by using graph representation program, and analyzed the student's activities that appeared in the process of visualization to understand its characteristics and to obtain educational implications. Twelve 4th graders of the college of education located in Seoul participated in the study. As a result of the study, by using a graph representation program, students performed representation transformation from equation to graph (2, 16.7%), performed verification experiment activity for verifying pre-knowledge (6, 50.0%) or performed inquiry experiment activity for exploring unknown situation (4, 33.3%). In this study, students performed their own experiments on quantum mechanics using the visualization materials developed by themselves as an experimental tool by self-directed. The various visualization topics and methods of quantum mechanics and process of application specifically introduced in this study provide different possibilities and application methods of educational programs and implications for further research.

• ### Research Paper 2021-02-26

#### Nonequilibrium critical dynamics of two dimensional Ising model under slow cooling and heating

Kangeun JEONG*, Bongsoo KIM, Sung Jong LEE

Abstract : We investigate the nonequilibrium dynamics of the two-dimensional kinetic Ising model for slow coolng (heating) to the critical temperature. In particular, we focus on the effects of nonlinear cooling (heating) protocols (with nonlinearity parameter $\alpha$) on the nonequilibrium dynamics. We find that the excess defect density (EDD) reveals characteristic time and length scales growing with $t_Q$, the time taken to reach the critical temperature. For all values of $\alpha$, the EDD exhibits a dynamic scaling when space and time are rescaled with these characteristic scales. Likewise, the spin correlation functions satisfy a critical dynamic scaling. While for $\alpha \ge 1$ ($\alpha = 1$ for linear cooling (heating)), these characteristic spatio-temporal scales exhibit power-law growth with $t_Q$ with the two exponents in accord with the predictions from the Kibble-Zurek mechanism. For $\alpha < 1$, these scales do not show a power-law growth with $t_Q$ within the present simulation time window. A power-law growth behavior may be seen when the simulation time is pushed further by at least one or two more decades.

• ### Research Paper 2021-02-26

#### Study on the Effect of ZrO$_{2}$ nano Particles on the Efficiency and Color Properties of White Light Emitting Diodes

Jun Yeong KIM, Hye-Rin KIM, Gi Jung LEE et al.

Abstract : The effect of the scattering from ZrO$_{2}$: Y$_{2}$O$_{3}$ nano particles on the emitting properties of white light emitting diodes (LEDs) consisting of red-green phosphors (CaAlSiN$_{3}$:Eu$^{2+}$ with Lu$_{3}$Al$_{5}$O$_{12}$:Ce$^{3+}$) and a blue LED chip was investigated in this study. The color coordinates of white LEDs increased with increasing concentration of nanoparticles, and their changes were more substantial at larger concentration. Especially, the relative intensity of the red component in the white spectrum became higher at larger concentrations, which was attributed to the multiple-scattering effect for blue photons and green photons. The luminous efficiency decreased with increasing concentration of nanoparticles due to multiple scattering, trapping and reabsorption of emitted light in the encapsulant of the white LED. This study showed that appropriate color properties can be achieved, even using a smaller amount of expensive red phosphors, by utilizing nanoparticles and suggests the possibility of realizing low-cost, high-CRI (color rendering index) lighting devices.

## Current Issue

• ### Crystallographic and Magnetic Structures of Fe7Se8

Eng Chan KIM*

New Phys.: Sae Mulli 2019; 69(3): 221-226
https://doi.org/10.3938/NPSM.69.221

• ### First-Principles Study on Temperature-Dependent Phase Transitions of Sn Polymorphs

Seong Min JANG, Chul Hong PARK*

New Phys.: Sae Mulli 2019; 69(3): 227-233
https://doi.org/10.3938/NPSM.69.227

• ### Magnetic Heat Effects of FeCoNi Nanoparticles Coated on Edge-Oxidized Graphene Sheets Under an Alternating Magnetic Field

Jinu KIM, Ki Hyeon KIM*, Taehoon KIM, Byungmun JUNG

New Phys.: Sae Mulli 2019; 69(3): 234-239
https://doi.org/10.3938/NPSM.69.234