• Structural Engineering and Mechanics
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• v.84 no.6
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• pp.723-731
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• 2022

Functionally graded materials (FGMs) have been spotlighted as an advanced composite material, accordingly the intensive studies have focused on FGMs to examine their mechanical behaviors. Among them is thermal buckling which has been a challenging subject, because its behavior is connected directly to the safety of structural system. In this context, this paper presents the numerical analysis of thermal buckling of metal-ceramic functionally graded (FG) plates. For an accurate and effective buckling analysis, a new numerical method is developed by making use of (1,1,0) hierarchical model and 2-D natural element method (NEM). Based on 3-D elasticity theory, the displacement field is expressed by a product of 1-D assumed thickness monomials and 2-D in-plane functions which are approximated by NEM. The numerical method is compared with the reference solutions through the benchmark test, from which its numerical accuracy has been verified. Using the developed numerical method, the critical buckling temperatures of metal-ceramic FG plates are parametrically investigated with respect to the major design parameters.

• International journal of advanced smart convergence
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• v.12 no.1
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• pp.76-81
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• 2023

Journaling file systems are widely used to keep file systems in a consistent state against crash situations. As traditional journaling file systems are designed for block I/O devices like hard disks, they are not efficient for emerging byte-addressable NVM (non-volatile memory) media. In this article, we present a new in-memory journaling file system for NVM that is different from traditional journaling file systems in two respects. First, our file system journals only modified portions of metadata instead of whole blocks based on the byte-addressable I/O feature of NVM. Second, our file system bypasses the heavy software I/O stack while journaling by making use of an in-memory file system interface. Measurement studies using the IOzone benchmark show that the proposed file system performs 64.7% better than Ext4 on average.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2712-2722
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• 2023

For an accurate and efficient time-dependent Monte Carlo (TDMC) neutron transport analysis, several advanced methods are newly developed and implemented in the Seoul National University Monte Carlo code, McCARD. For an efficient control of the neutron population, a dynamic weight window method is devised to adjust the weight bounds of the implicit capture in the time bin-by-bin TDMC simulations. A moving geometry module is developed to model a continuous insertion or withdrawal of a control rod. Especially, the history-based batch method for the TDMC calculations is developed to predict the unbiased variance of a bin-wise mean estimate. The developed methods are verified for three-dimensional problems in the C5G7-TD benchmark, showing good agreements with results from a deterministic neutron transport analysis code, nTRACER, within the statistical uncertainty bounds. In addition, the TDMC analysis capability implemented in McCARD is demonstrated to search the optimum detector positions for the pulsed-neutron-source experiments in the Kyoto University Critical Assembly and AGN201K.

• ETRI Journal
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• v.46 no.1
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• pp.137-153
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• 2024

This study introduces a new approach in Korean morphological analysis combining dictionary-based techniques with Transformer-based deep learning models. The key innovation is the use of a BERT-based reranking system, significantly enhancing the accuracy of traditional morphological analysis. The method generates multiple suboptimal paths, then employs BERT models for reranking, leveraging their advanced language comprehension. Results show remarkable performance improvements, with the first-stage reranking achieving over 20% improvement in error reduction rate compared with existing models. The second stage, using another BERT variant, further increases this improvement to over 30%. This indicates a significant leap in accuracy, validating the effectiveness of merging dictionary-based analysis with contemporary deep learning. The study suggests future exploration in refined integrations of dictionary and deep learning methods as well as using probabilistic models for enhanced morphological analysis. This hybrid approach sets a new benchmark in the field and offers insights for similar challenges in language processing applications.

• Journal of The Korean Association For Science Education
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• v.26 no.4
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• pp.492-501
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• 2006

Gender differences in TIMSS 2003 science achievement by item type, benchmark, and content area were examined by producing a Gender Differences Index (GDI) in this study. International trends identified that male students performed better than female students in TIMSS 2003 science achievement in all types of items. The overall achievement of Korean male students was better than Korean female students, especially in multiple-choice type items. Male students outperformed females in three benchmarks, including advanced, high, and intermediate international benchmark, but they did not outperform females in the low international benchmark when gender differences of the international average as well as the Korean average were taken into account. The results of the analysis of the international average and the Korean average by content area showed that gender differences were the greatest in earth science and smallest in chemistry. In life science, female students excelled when considering the international average while male students excelled when considering the average of Korean students' performance. In addition, the number of items in which male students outperformed females was larger in both factual knowledge and the conceptual understanding domain. Implications for reducing gender differences in science achievement in Korea based on the results were provided.

• Journal of Radiation Protection and Research
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• v.9 no.2
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• pp.97-102
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• 1984

Criticality analyses of the KSC-1(Korean Shipping Cask-1) spent fuel shipping cask have been performed with the help of KENO-IV Monte Carlo computer code and 19-group CSLIB 19 cross section set which was generated from AMPX modular system. The analyses followed a benchmark calculation which has been made regard to the B & W CX-10 criticality facility in order to validate the Monte Carlo code cross section set described above. The KSC-1 shipping cask seems to be safe in the criticality point of view for the transport of one PWR spent fuel assembly under the normal conditions as well as the hypothetical accident conditions.

• Advances in aircraft and spacecraft science
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• v.10 no.1
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• pp.51-65
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• 2023

In this paper, the effect of deepness on in-plane free vibration behavior of a curved functionally graded (FG) nanobeam based on nonlocal elasticity theory has been investigated. Differential equations and boundary conditions have been developed based on Hamilton's principle. In order to figure out the size effect, nonlocal theory has been adopted. Properties of material vary in radial direction. By using Navier solution technique, the amount of natural frequencies has been obtained. Also, to take into account the deepness effect on vibrations, thickness to radius ratio has been considered. Differences percentage between results of cases in which deepness effect is included and excluded are obtained and influences of power-law exponent, nonlocal parameter and arc angle on these differences percentage are studied. Results show that arc angle and power law exponent parameters have the most influences on the amount of the differences percentage due to deepness effect. It has been observed that the inclusion of geometrical deep term and material distribution results in an increase in sensitivity of dimensionless natural frequency about variation of aforementioned parameters and a change in variation range of natural frequency. Finally, several numerical results of deep and shallow curved functionally graded nanobeams with different geometry dimensions are presented, which may serve as benchmark solutions for the future research in this field.

• Journal of Practical Engineering Education
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• v.11 no.2
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• pp.259-268
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• 2019

The purpose of the study was to examine the vocational educational system of Egypt, focusing on the effectiveness of the three consecutive cycle-based curriculum and integrated technical education clusters (ITECs) in order to suggest some implications for innovating the current vocational education system of Korea. The vocational education system of Egypt is similar to that of Korea, in terms of general education to go to university and vocational education to go to labor market. However, the Egyptian system is different from the system of Korea in light of the three consecutive cycle-based curriculum that links secondary vocational education, vocational education of college level, and advanced technical and vocational education. In addition, the Egyptian system has adopted the "cluster" approach which integrates technical secondary school, intermediate technical college, and advanced technical college around one physical area so as to promote vocational education in collaboration with regional industries and to guarantee education quality. In the last part, some potential implications were suggested for upgrading the quality of vocational education of Korea based upon the benchmark results of the Egyptian vocational education system and career development of students.

• Progress in Superconductivity
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• v.12 no.2
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• pp.75-81
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• 2011

We report on the progress that has been made in developing $MgB_2$ superconducting wires and tapes for commercialization and research efforts. A number of techniques have been developed to overcome the obstacle posed by the poor critical current density ($J_c$) of pristine $MgB_2$. Chemical doping has proved to be the effective way to modify and enhance the superconducting properties, such as the $J_c$ and the irreversibility field ($B_{irr}$). More than 100 different types of dopants have been investigated over the past 8 years. Among these, the most effective dopants have been identified to be SiC and malic acid ($C_4H_6O_5$). The best results, viz. a $B_{irr}$ of 22 T and $J_c$ of $30,000\;A{\cdot}cm^{-2}$ at 4.2 K and 10 T, were reported for malic acid doped $MgB_2$ wires, which matched the benchmark performance of commercial low temperature superconductor wires. In this work, we discuss the progress made in $MgB_2$ conductors over the past few years at the University of Wollongong, Hyper Tech Research, Inc., and Ohio State University.

• Smart Structures and Systems
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• v.10 no.3
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• pp.253-269
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• 2012

A split spectrum processing (SSP) method is proposed to accurately determine the time-of-flight (ToF) of damage-scattered waves by comparing the instantaneous amplitude variation degree (IAVD) of a wave signal captured from a damage case with that from the benchmark. The fundamental symmetrical ($S_0$) mode in aluminum plates without and with a notch is assessed. The efficiency of the proposed SSP method and Hilbert transform in determining the ToF of damage-scattered $S_0$ mode is evaluated for damage identification when the wave signals are severely contaminated by noise. Broadband noise can overwhelm damage-scattered wave signals in the time domain, and the Hilbert transform is only competent for determining the ToF of damage-scattered $S_0$ mode in a noise-free condition. However, the calibrated IAVD of the captured wave signal is minimally affected by noise, and the proposed SSP method is capable of determining the ToF of damage-scattered $S_0$ mode accurately even though the captured wave signal is severely contaminated by broadband noise, leading to the successful identification of damage (within an error on the order of the damage size) using a triangulation algorithm.