Ex) Article Title, Author, Keywords
Ex) Article Title, Author, Keywords
Abstract : In this study, binder-free carbon nanofibers (CNFs) were coated on a porous metallic nickel foam (NF) substrate using a solution-based spin-coating method to produce flexible supercapacitor electrodes. The morphology, elemental composition, and electrochemical performance of the flexible electrodes were analyzed. A specific capacitance of 89 ± 0.15 F/g and a specific energy of 8 Wh/kg with a high specific power of 400 W/kg at a current density of 1 A/g was measured from the flexible supercapacitor, using polyvinyl alcohol-potassium hydroxide as the gel electrolyte. The binder-free CNFs on the NF are an interesting flexible supercapacitor electrode because of its simple and easy electrode manufacturing process without the need for an external catalyst, expensive noble metals, and even complex thermal or chemical processes.
Abstract : Transition-metal dichalcogenides, including tungsten disulfide (WS2), are promising alternatives to noble-metal catalysts in an electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, the low density of active sites and low electrical conductivity in their natural forms severely limit their electrocatalytic performance. Here we synthesize WS2 by a simple hydrothermal method to improve the HER and OER activities. The WS2 synthesized at 200 °C for 24 h exhibits low overpotentials of -200 mV at -10 mA/cm2 and 190 mV at 10 mA/cm2 with low Tafel slopes of 92 mV/dec and 112 mV/dec for the HER and OER, respectively. The enhanced performance of the HER and OER is due to the higher electrochemically active surface area and lower impedance than those of commercial WS2. Hence, this work emphasizes the simple hydrothermal method for developing WS2, which has a high catalytic activity, a long lifetime, and low cost, for a variety of electrocatalytic applications.
Abstract : We conducted a study using 3D simulation with the The finite-difference time-domain (FDTD) method to investigate the transmitted light distribution for the sub-skin-depth metal array medium. We confirmed the negative refraction phenomenon in the metal plate structure reported in an earlier study. Furthermore, we analyzed the intensity distribution of light passing through the metal cylinder array structure with the results of the layered metal plate structure. Our findings showed that the cylindical metal array medium exhibited a beam splitting phenomenon, which was not observed in the metal plate medium. We determined that this phenomenon was due to multiple interactions of the light beam with the metal arrays arranged in open space.
Abstract : Considering the bulkiness of a storage tank, its inspection range is vast, and the inspection procedure is characterized by safety accidents, which include falling from a height owing to wall-thinning damage. Thus, an unmanned inspection system is required. An electromagnetic acoustic transducer (EMAT) is a noncontact transducer that can transmit and receive various ultrasonic wave modes to and from specimens, respectively, without a couplant. The endows the EMAT with high applicability to robot systems because high-speed scanning is possible and the system’s weight can be reduced. However, EMAT is characterized by an unfavorable signal-to-noise ratio owing to the wide dead area and low energy conversion efficiency. Thus, the existing pulse-eco thickness measurement method is characterized by a low measurement accuracy, which poses difficulties for reliable inspection. In this study, a frequency analysis method based on multiple reflected waves was applied for thickness measurement. An EMAT for generating vertical transverse waves was fabricated, and its accuracy was experimentally confirmed as 95%.
Abstract : W18O49 nanostructures assembled on carbon felt (WNACs) were fabricated using a simple solvothermal synthesis method. WNACs are composed of nanowire bundles with 3D structures that grow in the vertical direction of the CF. The CF was pretreated with HNO3, which increased the oxygen-containing functional groups on the surface. The pretreated and untreated CF samples showed XRD diffraction peaks in the same position, indicating that the pretreatment did not affect the crystal structure of the nanostructures grown on the CF surface. The increased oxygen-containing functional groups on the surface of CF improved the hydrophilicity of CF and the adsorption of metal ions, thus promoting the growth of uniformly distributed W18O49 nanostructures on the CF surface and providing additional active sites for electrochemical reactions. Analysis of electrochemical performance revealed that the HNO3-pretreated WNAC showed enhanced performances compared with nontreated WNAC. This work contributes to the synthesis of CF-based nanostructured electrodes and application research for performance improvement.
Abstract : The aim of this study was to analyze the operation of a computational physics course in preservice physics teacher education. The lecture plans of 14 universities were analyzed, and interviews and questionnaires were conducted with five professors. The main research results were as follows. First, the purposes of computational physics courses could be divided according to the area of emphasis: physics education or physics. Second, the content of lectures for each week consisted of digital literacy, physics, and physics education in a similar ratio. Third, a discrepancy existed between the goal and content of the lectures, and content related to the application of the actual education in the field was lacking. Fourth, the content and methods of computational physics education continued to change according to the changes in the educational environment. Fifth, physics software was not used, and the use of various programming languages or digital education for physics education was widely addressed. According to the research results, the implications for computational physics education were explored.
Abstract : In this study, we aimed to identify the types and characteristics of scaffolding performed by preservice physics teachers. For this purpose, questionnaires, observation diaries, and video recordings on the teaching demonstration process of seven preservice physics teachers were collected. Analysis of the data collected from seven preservice physics teachers showed that the teaching demonstrations of preservice physics teachers featured 26 types of scaffolding, and cognitive scaffolding appeared more than emotional scaffolding. Second, the cognitive scaffolding techniques were “relating learning topics,” “helping intuitive understanding,” “clarifying students' speech,” “narrowing concepts,” “reducing degrees of freedom,” “clarifying students' thoughts,” “maintaining the direction of student activities,” and “checking students' understanding.” Third, the emotional scaffolding approach involved a teacher helping students according to their emotional reactions. The middle categories included “respecting students” emotions” and “inducing interest/motivation,” and detailed types include “showing warmth and responsiveness,” “praising,” “listening,” “inducing interest,” “sharing curiosity,” “using humor,” and “giving meaning to learning.” According to the analysis results, physics education using scaffolding types was discussed.
Abstract : Various types of quantum dot components have been investigated to improve the color-rendering of conventional lighting. In this study, we investigated the light emission characteristics of direct white light-emitting diode (LED) lighting under different diffuser transmittances and numbers of red quantum dot caps. The number of quantum dot caps that enhance the spectrum in the red wavelength band had a much greater impact on the improvement of color-rendering properties than the diffuser transmittance. When the application conditions of the quantum dot caps were the same, the lower the diffuser transmittance, the greater the change in the color-rendering index, attributable to the enhancement effect of the vertical cavity formed by the high reflectivity of the diffuser. This study shows that through the application of a diffuser with appropriate transmittance and red quantum dot caps to a high-power direct white LED lighting fixture, an excellent high color-rendering lighting device with a color-rendering index of over 95 can be achieved.
Abstract : In this study, a continuous wave Alexandrite laser oscillator pumped in one side using a 638-nm laser diode was configured to measure the resonator characteristics and the laser output power and emission wavelength characteristics using a thermal lens. The CW Alexandrite laser output of 1.01 W was obtained at output coupler transmittance of 1%, laser crystal setting temperature of 50 °C, and laser diode pump power of 20 W. The slope efficiency of the laser output was 16.9% relative to the absorbed power, and the central wavelength was 760 nm. The central wavelength of emission laser was measured by gradually increasing the laser crystal setting temperature by 10 °C. The findings confirmed that the central wavelength shifted up higher by about 3 nm. The M2 values in the x- and y-axes for a CW Alexsandrite laser with a Gaussian intensity distribution were 1.11 and 1.10, respectively.
Abstract : Prior to patent application, relevant existing patents must first be searched. Patent attorneys investigate previous patents and technology trends, but this can be a time consuming process; thus, automating the process has become imperative. Previous research has used natural language processing models to recommend similar patents by vectorizing these patents in latent space. In the current study, we propose using PatentBERT, a pretrained language model for patents, to vectorize words and reduce the search scope of patents using the contrastive loss function. This model can reduce the time needed for preliminary patent investigation and can be applied to other areas, such as screening research papers or searching for similar references.
Geun Taek YU, Geun Hyeong PARK, Eun Been LEE, Min Hyuk PARK*
New Phys.: Sae Mulli 2021; 71(11): 890-900
Gang Seok Lee, Kyoung Hwa Kim, Jung Hyun Park, So Yoon Kim, Ha Young Lee, Hyung Soo Ahn*, Jae Hak Lee, Young Tea Chun, Min Yang, Sam Nyung Yi, InjunJeon, Chae Ryong Cho, Sang-Geul Lee, Hyojin No, Won Jae Lee, Suck-Whan Kim
New Phys.: Sae Mulli 2021; 71(8): 659-666
Sangwoon KWON, Hongbin KIM*
New Phys.: Sae Mulli 2021; 71(7): 616-629