• Journal of Korean Dental Science
• /
• v.8 no.1
• /
• pp.28-35
• /
• 2015

Purpose: To investigate the influence of crown margin design on the stress distribution and to localize critical sites in maxillary canine under functional loading by using three dimensional finite element analysis. Materials and Methods: The bite force of 100 N, 150 N, and 200 N was applied with an angulation of $45^{\circ}$ to the longitudinal axis of tooth. Six models were restored with IPS e.max (Ivoclar Vivadent, Schaan, Liechtenstein) with a different margin design. With lingual ledge and various thicknesses, three different core ceramics were designed in each model. Result: In the core ceramic, the maximum tensile stresses were found at the labiocervical region. In the veneering ceramic the maximum tensile stresses were found at the area where the force was applied in all models. Conclusion: Shoulder and chamfer margin types are acceptable for all-ceramic rehabilitations. A ledge on the core ceramic at cervical region may affect the strength of all-ceramic crowns.

• Korean Management Science Review
• /
• v.34 no.2
• /
• pp.85-101
• /
• 2017

Currently, the SW industry is the center of digital economy and it is very important industry in terms of market scale and ripple effect. Due to the suffering from poor working environment of the SW industry and the disproportion of manpower supply due to the lack of experienced SW manpower, it is hard to create jobs of high quality for the SW professionals who can be applied to various convergence industries. In this study, we try to analyze the benchmarking cases of successful foreign industrial innovative clusters in order to promote sustainable development direction of SW industry and to create high quality SW jobs. First, the comparison criteria are derived from the viewpoint of creation of high quality SW jobs through an analysis of SW environment by using expert FGI (Focus Group Interview) technique. The critical success factors (CSFs) are derived by comparing and analyzing each industrial cluster cases in terms of SW job creation. This article presents the desirable implications of the cluster of SW industry that can generate SW jobs continuously from the viewpoint of ecosystem environment infrastructure. Through this study, we propose a meaningful direction of SW clusters for job creation, and solve the business inconsistency and suggest ways to increase the sustainability of core competence manpower.

• Geomechanics and Engineering
• /
• v.30 no.2
• /
• pp.153-167
• /
• 2022

This study proposes a method to analyze the distribution of coal porosity disturbances after the excavation of ultra-large-diameter water jet boreholes using a coal wetting and softening model. The high-pressure jet is regarded as a short-term high-pressure water injection process. The water injection range is the coal softening range. The time when the reference point of the borehole wall is shocked by the high-pressure water column is equivalent to the time of high-pressure water injection of the coal wall. The influence of roadway excavation with support and borehole diameter on the ultra-large-diameter jet drilling excavation is also studied. The coal core around the borehole is used to measure the gas permeability for determining the porosity disturbance distribution of the coal in the sampling plane to verify the correctness of the simulation results. Results show that the excavation borehole is beneficial to the expansion of the roadway excavation disturbance, and the expansion distance of the roadway excavation disturbance has a quadratic relationship with the borehole diameter. Wetting and softening of the coal around the borehole wall will promote the uniform distribution of the overall porosity disturbance and reduce the amplitude of disturbance fluctuations.

• Nuclear Engineering and Technology
• /
• v.47 no.7
• /
• pp.875-883
• /
• 2015

The use of subcritical aqueous homogenous reactors driven by accelerators presents an attractive alternative for producing $^{99}Mo$. In this method, the medical isotope production system itself is used to extract $^{99}Mo$ or other radioisotopes so that there is no need to irradiate common targets. In addition, it can operate at much lower power compared to a traditional reactor to produce the same amount of $^{99}Mo$ by irradiating targets. In this study, the neutronic performance and $^{99}Mo$, $^{89}Sr$, and $^{131}I$ production capacity of a subcritical aqueous homogenous reactor fueled with low-enriched uranyl nitrate was evaluated using the MCNPX code. A proton accelerator with a maximum 30-MeV accelerating power was used to run the subcritical core. The computational results indicate a good potential for the modeled system to produce the radioisotopes under completely safe conditions because of the high negative reactivity coefficients of the modeled core. The results show that application of an optimized beam window material can increase the fission power of the aqueous nitrate fuel up to 80%. This accelerator-based procedure using low enriched uranium nitrate fuel to produce radioisotopes presents a potentially competitive alternative in comparison with the reactor-based or other accelerator-based methods. This system produces ~1,500 Ci/wk (~325 6-day Ci) of $^{99}Mo$ at the end of a cycle.

• Nuclear Engineering and Technology
• /
• v.55 no.9
• /
• pp.3301-3312
• /
• 2023

This study incorporates a high-fidelity transient analysis solver based on multigroup CMFD in the MOC code STREAM. Transport modeling with heterogeneous geometries of the reactor core increases computational cost in terms of memory and time, whereas the multigroup CMFD reduces the computational cost. The reactor condition does not change at every time step, which is a vital point for the utilization of CMFD. CMFD correction factors are updated from the transport solution whenever the reactor core condition changes, and the simulation continues until the end. The transport solution is adjusted once CMFD achieves the solution. The flux-weighted method is used for rod decusping to update the partially inserted control rod cell material, which maintains the solution's stability. A smaller time-step size is needed to obtain an accurate solution, which increases the computational cost. The adaptive step-size control algorithm is robust for controlling the time step size. This algorithm is based on local errors and has the potential capability to accept or reject the solution. Several numerical problems are selected to analyze the performance and numerical accuracy of parallel computing, rod decusping, and adaptive time step control. Lastly, a typical pressurized LWR was chosen to study the rod-ejection accident.

• Investigative Magnetic Resonance Imaging
• /
• v.19 no.3
• /
• pp.191-195
• /
• 2015

We present a 53-year-old woman with a large chest wall mass in the interpectoral space, which was eventually confirmed as a lipogranuloma resulting from hydrogel implant rupture. Ultrasonography (US) showed reduced implant volume with surrounding peri-implant fluid collection, suggesting the possibility of implant rupture. A heterogeneously hypoechoic mass was found between the pectoralis major and minor muscles adjacent to the ruptured implant. On magnetic resonance imaging (MRI), there was a large mass in the left interpectoral space of the upper inner chest wall. The mass showed slightly high signal intensity (SI) on pre-contrast T1-weighted image (WI) with mixed iso and high SI on T2-WI. The signal of the mass was suppressed using the water suppression technique but not with the fat suppression technique on T2-WI. The mass showed diffuse enhancement upon contrast enhancement. The enhancing kinetics showed persistent enhancement pattern. US-guided core needle biopsy revealed a lipogranuloma and removal confirmed a ruptured PIP hydrogel implant.

• Journal of The Korean Association For Science Education
• /
• v.33 no.2
• /
• pp.284-309
• /
• 2013

This study aims to explore how to characterize high school science inquiry. For this research, data were collected from fifteen science classes (18 hours), through observation and videotaping, interviews with a few students and their teacher, and documents such as lesson plan or activity sheet in 13 Science Core High Schools. All the data were transcribed and analyzed. Analyses of these transcripts were proceeded in three steps: first, classroom cases showing active interactions between teacher-students and among students were selected; second, according to cognitive process of inquiry (Chinn & Malhotra, 2002), each segment was analyzed and interpreted; lastly, distinctive cases were determined to show essential features of school science inquiry. Based on the analyses, we characterize high school science inquiry in terms of features of variables controlling-device improvement, design studies, evidence-explanation transformation, and reasoning to formulate explanations from evidence. Teachers' role and educational support were discussed as well as the practical characters or features of school science inquiry.

• Journal of The Korean Association For Science Education
• /
• v.41 no.6
• /
• pp.441-454
• /
• 2021

In this study, we propose the composition of contents on the area of astronomy for high school Earth Science elective courses for the 2022 revised curriculum based on high school students' perceptions of changes in Earth Science core concepts over the curriculum revisions, and analysis of learning elements in the area of astronomy for domestic and foreign Earth Science curriculum. Four Earth Science education experts compared and analyzed the astronomy contents presented in Korea, the US, British Columbia (BC) in Canada, Japan, and the International Baccalaureate Diploma Program (IBDP) curriculum. According to the survey results, high school students who answered that they were most interested in the core concepts of astronomy expressed a lot of regret that the contents related to astronomical observation were eliminated from the 2015 revised curriculum. As a result of comparing domestic and foreign curriculum, Korea and IBDP curriculum dealt with the largest amount of learning elements in astronomy. In the case of BC in Canada and IBDP, astronomy was offered as an independent subject, and the curriculums of Japan and Korea dealt with astronomy in the Earth Science subject. According to the results, it is necessary to develop general elective courses in Earth Science with astronomy-related contents with high discriminating power in order to strengthen astronomy education. Since astronomy requires background knowledge from various disciplines and inter-disciplinary learning was required, it is necessary to organize the career-related elective courses in Earth Science so that astronomy can be dealt with according to the knowledge structure of general Astronomy. Based on the research results, ways to organize astronomy contents for Earth Science elective courses were suggested.

• Korean Medical Education Review
• /
• v.18 no.3
• /
• pp.156-166
• /
• 2016

Medical school students learn a lot about medical knowledge and clinical experience in the classroom. Teaching is a main focus in medical schools; therefore, it is necessary to identify the characteristics of good teaching. The aim of this study is to analyze the characteristics of high-quality education in medical schools. In this study, in-depth interviews were conducted over two weeks on twelve fourth-year medical students. Participants were asked to define high-quality education, list the general ways in which high-quality classes are delivered, mention cases where they have experienced high-quality teaching, and describe the attitude required of students to make high-quality education possible. The results showed that students want to be taught in an interactive way on the core content needed in an actual clinical setting for the goal of cultivating primary care physicians. They want their education to include not only medical knowledge, but also liberal art subjects such as politics, economics, sociology, culture and ethics education to help instill a sound value system. In particular, students stressed the importance of instructors delivering appropriate post-evaluation feedback, and they also emphasized that learner mindset and attitude is important in supporting high-quality teaching in class. This paper also summarizes the elements of high-quality teaching in terms of educational goals, content, and method, and examines cases of instructors who have delivered high-quality classes.

• Journal of the Microelectronics and Packaging Society
• /
• v.27 no.3
• /
• pp.55-60
• /
• 2020

The recent semiconductor packaging technology is evolving into a high-performance system-in-packaging (SIP) structure, and copper-to-copper bonding process becomes an important core technology to realize SIP. Copper-to-copper bonding process faces challenges such as copper oxidation and high temperature and high pressure process conditions. In this study, the bonding interface quality of low-temperature copper-to-copper bonding using a two-step plasma treatment was investigated through quantitative bonding strength measurements. Our two-step plasma treatment formed copper nitride layer on copper surface which enables low-temperature copper bonding. The bonding strength was evaluated by the four-point bending test method and the shear test method, and the average bonding shear strength was 30.40 MPa, showing that the copper-to-copper bonding process using a two-step plasma process had excellent bonding strength.