• Nuclear Engineering and Technology
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• v.16 no.4
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• pp.202-216
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• 1984

The success of coarse-mesh nodal solution methods provides strong motivation for finding homogenized parameters which, when used in global nodal calculation, will reproduce exactly all average nodal reaction rates for large nodes. Two approximate theories for finding these ideal parameters, namely, simplified equivalence theory and approximate node equivalence theory, are described herein and then applied to the PWR benchmark problem. Nodal code, ANM, is used for the global calculation as well as for the homogenization calculation. From the comparative analysis, it is recommended that homogenization be carried out only for the unique type of fuel assemblies and for core boundary color-sets. The use of approximate homogenized cross-sections and approximate discontinuity factors predicts nodal powers with maximum error of 0.8% and criticality within 0.1% error relative to the fine-mesh KIDD calculations.

• Nuclear Engineering and Technology
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• v.52 no.7
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• pp.1386-1395
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• 2020

High fidelity nuclear reactor fuel assembly simulation using CFD method is an effective way for the structure design and optimization. The validated models and user practice guidelines play critical roles in achieving reliable results in CFD simulations. In this paper, the international benchmark MATiS-H is studied carefully and the best user practice guideline is achieved for the rod bundles simulation. Then a 5 × 5 rod bundles model in the advanced pressurized water reactor (PWR) is established and the detailed three-dimensional thermal-hydraulic characteristics are investigated. The influence of spacer grids and mixing vanes on the flow and hear transfer in rod bundles is revealed. As the coolant flows through the spacer grids and mixing vanes in the rod bundles, the drastic lateral flow would be induced and the pressure drop increases significantly. In addition, the heat transfer is enhanced remarkably due to the strong mixing effects. The calculation results could provide meaningful guidelines for the design of advanced PWR fuel assembly.

• Journal of Korean Elementary Science Education
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• v.32 no.4
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• pp.423-436
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• 2013

This research purports to analyze released items and G4 students' science achievement from TIMSS 2011 according to their academic achievement levels and gender. By doing so, it aims to draw educational implications for Korea from analyses results. Korea showed a lower rate of students at the advanced international benchmark - the highest achievement level - compared to Singapore. The difference was the smallest in Life Science among three content domains and knowing among three cognitive domains. The results of analysis according to gender showed that male students' achievement was significantly higher in Physical Science and Earth Science, and their achievement was also higher in the cognitive domains of Knowing and Applying. From the analysis of the released items, it was revealed that the students' achievement was low in items related to classification of organisms, functions of heart, matters that combust or emit light, and the concept of rotation. Moreover, students drew some illogical conclusions based on their personal experience. Male students were found to show high achievements in items that were not included in curriculum, constructed-response items in the form of short-answer questions, and multiple-choice items in the Knowing domain. Female students were found to show high achievement in items that were included in curriculum, constructed-response items that require reasons and methods, and items that represent experimental situations. Male students showed high achievement in forces concept and movements concept of bodies in the universe, while female students showed high achievement in solubility concept.

• The Journal of the Convergence on Culture Technology
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• v.9 no.6
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• pp.911-917
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• 2023

In today's world, we find ourselves facing energy crises due to factors such as war and climate crises. To prepare for these energy crises, many researchers continue to study systems related to energy monitoring and conservation, such as energy management systems, energy monitoring, and energy conservation. In line with these efforts, nations are making it mandatory for energy-consuming facilities to implement these systems. However, these facilities, limited by space and energy constraints, are exploring ways to improve. This research explores the operation of a data collection system using low-performance embedded devices. In this context, it proves that an optimized version of RocksDB, a Key-Value store, outperforms traditional databases when it comes to time-series data. Furthermore, a comprehensive database evaluation tool was employed to assess various databases, including optimized RocksDB and regular RocksDB. In addition, heterogeneous databases and evaluations are conducted using a UD Benchmark tool to evaluate them. As a result, we were able to see that on devices with low performance, the time required was up to 11 times shorter than that of other databases.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.5
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• pp.1091-1097
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• 2001

A numerical investigation was performed to determine the effect of airfoil on the optimum flap height using NACA 00XX and 44XX airfoils. The six flaps which have 0.5% chord height difference were selected . A Navier-Stokes code, FLUENT, was used to calculate the flow field of the airfoil. The code was first tested as a benchmark by modelling flow around a NACA 4412 airfoil. Predictions of local pressure coefficients are found to be in good agreement with the result of the experimental results. For every NACA 00XX and 44XX airfoil, flap heights ranging from 0.0% to 2.5% chord were changed by 0.5% chord interval and their effects were also studied. Representative results from each case are presented graphically and discussed. It is conclued that this initial approach gives an idea for the future development of the wind turbine optimum design.

• Structural Engineering and Mechanics
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• v.5 no.4
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• pp.471-490
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• 1997

In this paper, the classical Irons' patch tests which have been generally accepted for the convergence proof of a finite element are performed for Mindlin plate bending elements with a special emphasis on the nonconforming elements. The elements considered are 4-node and 8-node quadrilateral isoparametric elements which have been dominantly used for the analyses of plate bending problems. It was recognized from the patch tests that some nonconforming Mindlin plate elements pass all the cases of patch tests even though nonconforming elements do not preserve conformity. Then, the clues for the Mindlin plate element to pass the Irons' patch tests are investigated. Also, the convergent characteristics of some nonconforming Mindlin plate elements that do not pass the Irons' patch tests are examined by weak patch tests. The convergence tests are performed on the benchmark numerical problems for both nonconforming elements which pass the patch tests and which do not. Some conclusions on the relationship between the patch test and convergence of nonconforming Mindlin plate elements are drawn.

• Journal of Advanced Research in Ocean Engineering
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• v.2 no.2
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• pp.67-80
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• 2016

The resistance performance of an icebreaking cargo vessel with varied stem angles is investigated numerically and experimentally. Ship-ice interaction loads are numerically calculated based on the fluid structure interaction (FSI) method using the commercial FE package LS-DYNA. Test results obtained from model testing with synthetic ice at the Pusan National University towing tank and with refrigerated ice at the National Research Council's (NRC) ice tank are used to validate and benchmark the numerical simulations. The designed icebreaking cargo vessel with three stem angles ($20^{\circ}$, $25^{\circ}$, and $30^{\circ}$) is used as the target ship for three concentrations (90%, 80%, and 60%) of pack ice conditions. The comparisons between numerical and experimental results are shown and our main conclusions are given.

• International journal of advanced smart convergence
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• v.9 no.1
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• pp.193-201
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• 2020

The main objective of this study is to investigate the impact of additional modalities on the performance of emotion recognition using speech, facial expression and physiological measurements. In order to compare different approaches, we designed a feature-based recognition system as a benchmark which carries out linear supervised classification followed by the leave-one-out cross-validation. For the classification of four emotions, it turned out that bimodal fusion in our experiment improves recognition accuracy of unimodal approach, while the performance of trimodal fusion varies strongly depending on the individual. Furthermore, we experienced extremely high disparity between single class recognition rates, while we could not observe a best performing single modality in our experiment. Based on these observations, we developed a novel fusion method, called parametric decision fusion (PDF), which lies in building emotion-specific classifiers and exploits advantage of a parametrized decision process. By using the PDF scheme we achieved 16% improvement in accuracy of subject-dependent recognition and 10% for subject-independent recognition compared to the best unimodal results.

• Nuclear Engineering and Technology
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• v.44 no.2
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• pp.161-176
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• 2012

McCARD is a Monte Carlo (MC) neutron-photon transport simulation code. It has been developed exclusively for the neutronics design of nuclear reactors and fuel systems. It is capable of performing the whole-core neutronics calculations, the reactor fuel burnup analysis, the few group diffusion theory constant generation, sensitivity and uncertainty (S/U) analysis, and uncertainty propagation analysis. It has some special features such as the anterior convergence diagnostics, real variance estimation, neutronics analysis with temperature feedback, $B_1$ theory-augmented few group constants generation, kinetics parameter generation and MC S/U analysis based on the use of adjoint flux. This paper describes the theoretical basis of these features and validation calculations for both neutronics benchmark problems and commercial PWR reactors in operation.

• Journal of Ocean Engineering and Technology
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• v.34 no.2
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• pp.55-65
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• 2020

A review of the 2nd generation of intact stability by the International Maritime Organization is performed. The main issues with the new stability criteria are reviewed. In particular, the physical background and related mathematical formulations of the pure loss of stability and parametric roll are summarized. Based on a literature review, benchmark calculation results for 17 different types of ships are discussed, and the final results are in excellent agreement with our physical expectations. Some relatively serious design problems are found in the application of the new stability criteria to sample ships built in Korea, and possible technical solutions are proposed, which have to be improved in the coming years.