• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.241-250
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• 2007

In case of retrofitting a concrete structure subjected to blast load by using retrofit materials such as FRP (fiber-reinforced polymer), appropriate ductility as well as raising stiffness must be obtained. But the previous approximate and simplified models, which have been generally used in the design and analysis of structures subjected to blast load, cannot accurately consider effects on retrofit materials. Problems on the accuracy and reliability of analysis results have also been pointed out. In addition, as the response of concrete and reinforcement on dynamic load is different from that on static load, it is not appropriate to use material properties defined in the previous static or quasi-static conditions to in calculating the response on the blast load. In this study, therefore, an accurate HFPB (high fidelity physics based) finite element analysis technique, which includes material models considering strength increase, and strain rate effect on blast load with very fast loading velocity, has been suggested using LS-DYNA, an explicit analysis program. Through the suggested analysis technique, the behavior on the blast load of retrofitted concrete walls using CFRP (carbon fiber-reinforced polymer) and GFRP (glass fiber-reinforced polymer) have been analyzed, and the retrofit capacity analysis has also been carried out by comparing with the analysis results of a wall without retrofit. As a result of the analysis, the retrofit capacity showing an approximate $26{\sim}28%$ reduction of maximum deflection, according to the retrofit, was confirmed, and it is judged ate suggested analysis technique can be effectively applicable in evaluating effectiveness of retrofit materials and techniques.

• Journal of The Korean Association For Science Education
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• v.18 no.2
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• pp.245-256
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• 1998

In this study, we discussed about the implications of the idealization, which take an important role in physics, to the physics education. First, understanding of the idealization help the physics learning itself. This is because that various types of idealizations are included in the physics terms and concepts, derivation processes of physics laws and formulas, and explanation of natural phenomena and problem solving activities. Second, understanding of the idealization can help the application of the physics world to the real world. That is, by understanding the extent and the limit of idealization used in physics world, physics students can understand the discrepancies between the real world and the physics world. And also, by modifying or eliminating the idealization, students can extend the extent of understanding about how predictions based on the idealization used in the physics world will change. To do this, we suggested the application of computer simulation program in physics laboratories. Third, idealization take an important role in the inquiry learning for students' originality. The activities of identifying or controlling the variables, as one of the principal factors of scientific inquiry, need the appropriate establishment of the ideal conditions. And to analyze the limiting case or practice the thought experiments for understanding the impossible situation in the real world, ideal conditions also are needed. This study discussed above three aspects with various concrete examples and, with Park et al.'s study (Park et al., 1998), present the theoretical basis for the study of students' and teachers' understanding the idealization.

• Journal of Advanced Navigation Technology
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• v.28 no.2
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• pp.216-224
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• 2024

This paper presents a method for analyzing the reliability of hardware electronic equipment, taking into account failures caused by radiation. Traditional reliability analysis primarily focuses on the wear out failure rate and often neglects the impact of radiation failure rates. We calculate the wear out failure rate through physics of failure analysis, while the radiation failure rate is semi-empirically estimated using the Verilog Fault Injection tool. Our approach aims to ensure reliability early in the development process, potentially reducing development time and costs by identifying circuit vulnerabilities in advance. As an illustrative example, we conducted a reliability analysis on the ISCAS85 circuit. Our results demonstrate the effectiveness of our method compared to traditional reliability analysis tools. This thorough analysis is crucial for ensuring the reliability of FPGAs in environments with high radiation exposure, such as in aviation and space applications.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.32-34
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• 2002

Over the past two decades there has been a tremendous growth in the number of synchrotron radiation facilities in the world and also in Japan. The high flux and brightness radiation which derive from the third generation low emittance rings provide an ideal source for many applications in the medical sciences. The application of synchrotron radiation to medical imaging started in the early 80's in U.S.A, followed by European countries such as Germany and Russia. In Japan, researchs on intravenous coronary angiography started in 1884 at the Institute for High Energy Phisics(KEK) in Tsukuba. At present, it is the only application of syncrotron radiation which is at the stage of human study. In '90s, newer techniques such as phase and refraction contrast imaging appeared which are at the in vitro or animal study stage. Various types of x-ray CT have also been developed for three-dimensional imaging of the subjects. The present status of medical applications of synchrotron radiation in Japan is reviewed.

• Nuclear Engineering and Technology
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• v.49 no.3
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• pp.569-575
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• 2017

One of the important requirements for the application of reduced-activation ferritic/martensitic (RAFM) steel is to retain proper mechanical properties under irradiation and high-temperature conditions. To simulate the yield strength and stress-strain curve of steels during high-temperature and irradiation conditions, a multiscale simulation method consisting of both microstructure and strengthening simulations was established. The simulation results of microstructure parameters were added to a superposition strengthening model, which consisted of constitutive models of different strengthening methods. Based on the simulation results, the strength contribution for different strengthening methods at both room temperature and high-temperature conditions was analyzed. The simulation results of the yield strength in irradiation and high-temperature conditions were mainly consistent with the experimental results. The optimal application field of this multiscale model was 9Cr series (7-9 wt.%Cr) RAFM steels in a condition characterized by 0.1-5 dpa (or 0 dpa) and a temperature range of $25-500^{\circ}C$.

• Journal of The Korean Astronomical Society
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• v.56 no.1
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• pp.11-22
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• 2023

We report the result of a high-resolution spectroscopic study on seven magnesium (Mg) enhanced stars. The high Mg abundances in these stars imply that they were born in an environment heavily affected by the nucleosynthesis products of massive stars. We measure abundances of 16 elements including Mg and they show various abundance patterns implying their diverse origin. Three of our program stars show a very high Mg to Si ratio ([Mg/Si] ≈ 0.18-0.25), which might be well explained by fall-back supernovae or by supernovae with rapid rotating progenitors having an initial mass higher than about 20 M_⊙. Another three of our program stars have high light to heavy s-process element ratios ([Y/Ba] ≈ 0.30-0.44), which are consistent with the theoretical prediction of the nucleosynthesis in rapidly rotating massive stars with an initial mass of about M = 40 M_⊙. We also report a star having both high Y ([Y/Fe] = 0.2) and Ba ([Ba/Fe] = 0.28) abundance ratios, and it also shows the highest Zn abundance ratio ([Zn/Fe] = 0.27) among our sample, implying the nucleosynthesis by asymmetric supernova explosion induced by very rapid rotation of a massive progenitor having an initial mass between 20 M_⊙ ≲ M ≲ 40 M_⊙. A relative deficiency of odd-number elements, which would be a signature of the pair-instability nucleosynthesis, is not found in our sample.

• Nuclear Engineering and Technology
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• v.52 no.6
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• pp.1277-1281
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• 2020

A novel ceramic Gas Electron Multiplier (GEM) has been developed to meet the demand of high counting rate for the neutron detection which is an alternative to ³He-based detector at China Spallation Neutron Source (CSNS). An experiment was performed to measure the neutron transmittance of ceramic-GEM and FR4-GEM at the small angle neutron scattering (SANS) instrument. The result showed the ceramic-GEM has higher transmittance and less self-scattering especially for cold neutrons. One single ceramic GEM could give a gain of 10²-10⁴ in the mixture gas of Ar and CO₂ (90%:10%) and its energy resolution was about 27.7% by using ⁵⁵Fe X ray of 5.9 keV. A prototype has been developed in order to investigate the performances of the ceramic GEM-based neutron detector. Several neutron beam tests, including detection efficiency, spatial resolution, two-dimensional imaging, and wavelength spectrum, were carried out at CSNS and China Mianyang Research Reactor (CMRR). The results show that the ceramic GEM-based neutron detector is a good candidate to measure the high intensity neutrons.

• New Physics: Sae Mulli
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• v.68 no.12
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• pp.1356-1363
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• 2018

The purpose of this study was to investigate science high-school students' creativity and scientific attitude when an integrated science, technology, engineering and mathematics (STEM) project themed 'lighting of quantum dot solution' was applied to them. The subjects were a one team composed of 3 students in the 11th grade desiring to participate in the Korea Science Exhibition. They began with a scientific inquiry related to the physical properties of the QD solution and then gradually showed the process of expansion of their ideas into the integration of engineering, technology, and mathematics. Also, during the process, they showed problem solving ability and scientific attitudes, such as cooperation, endurance, and satisfaction of accomplishment.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.275-278
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• 2002

The recognition of the natural background radiation is important not only for radiological education but also for the promotion of people's scientific view about radiation. We made a "room" on the web showing natural background radiation as part of a VRM (Virtual Radiation Museum). The "room" shows the video images of the tracks of charged particles from natural background radiation, alpha and beta ray track from known sources using a Large Scale Diffusion Cloud Chamber. The purpose of this study is to make clear the origin of a kind of track (named A-track) which is thick and easy to recognize with the length less than several cm in the cloud chamber, and to make numerical explanation of its counting rate. The study was carried out using a Large Scale Diffusion Cloud Chamber (Phywe, Germany) installed in the Niigata Science Museum. The Model RNC (Pylon Electronics, Canada) was used as Rn-222 source. Ra-226 activity in RNC was 111.6 Bq calibrated with NIST protocol. Rn-222 gas was injected into the cloud chamber. Continuous video recording with use of Digital Handycam (SONY, Japan) was carried out for 360 min. after injection of Rn-222 gas. The number of alpha-ray track (alpha track) in the video images was analyzed. The growth and decay curve of the total activity of Rn-222 and its alpha emitting progeny were calculated and compared with the count of the alpha tracks. As a result the alpha tracks formed by Rn-222 injection resemble A-Tracks. The relationship between A-track in the cloud chamber and atmospheric Rn is discussed.

• Progress in Medical Physics
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• v.28 no.3
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• pp.92-99
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• 2017

In respiratory-induced proton therapy, the accuracy of tracking system and beam controlling is more important than photon therapy. Therefore, a high accuracy motion tracking system that can track internal marker and external surrogate is needed. In this research, our team has installed internal and external marker tracking system at our institution's proton therapy system, and tested the scanning with gating according to the position of marker. The results demonstrate that the developed in-house external/internal marker based gating system can be clinically used for proton therapy system for moving tumor treatment.