• Journal of the Korean Society of Safety
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• v.15 no.4
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• pp.20-27
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• 2000

The hat shaped section members, spot welded strength resisting structures are the most energy absorbing ones of automobile components during the front-end collision. Under the static axial collapse load in velocity of 10mm/min and quasi-static collapse load in velocity of 1000mm/min, the collapse characteristics of the hat shaped section and double hat shaped section member have been analyzed by axial collapse tests with respect to the variations of spot weld pitches on the flanges. In addition, the quasi-static collapse simulations have been implemented in the same condition to the experiment's using FEM package, LS-DYNA3D. The simulated results have been verified in comparison with these from the quasi-static axial collapse tests. With the computational approaches the optimal energy absorbing structures can be suggested. Simulations are so helpful that the optimized data be supplied in designing vehicles in advance.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.147-149
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• 1999

This paper deals with the determination of generator/exciter model parameters for a Cheju Hanlim steam turbine unit. Using the recorded data from the generator characteristic tests, the model parameters have been derived and verified by comparing the simulation results and recorded data. In addition to it, the closed-loop performance of voltage control on no-load condition has been assessed in the frequency domain by taking advantage of derived generator/exciter model parameters.

• Journal of Powder Materials
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• v.12 no.3
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• pp.208-213
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• 2005

Aluminum matrix composites strengthened by the quasi-crystalline (QC) phase were developed in the present study. The icosahedral $Al_{65}Cu_{20}Fe_{15}$ phase was produced by gravity casting and subsequent heat treatment. The mechanical milling process was utilized in order to produce the Al/QC composite powders. The microstructures of the composite powders were examined by optical microscopy (OM) and scanning electron microscopy (SEM). The composite powders were subsequently canned, degassed and extruded in order to produce the bulk composite extrusions with various volume fractions of QC. The microstructure and mechanical properties of the extrusions were examined by OM, SEM, Vickers hardness tests and compression tests. It was found that the microstructures of the Al/QC composites were uniform and the mechanical properties could be significantly improved by the addition of the QC phase.

• Journal of Engineering Education Research
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• v.15 no.6
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• pp.34-42
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• 2012

Problem solving by homework assignment is a process of practicing what were discussed in classrooms and thus is considered as an essential part of learning procedure in engineering education. We introduced the concept of cooperative learning, Student Teams-Achievement Division(STAD), to improve the students' learning efficiency by in-class problem solving. The instructor explained fundamental concepts, and lecture materials were handed out to compensate for the time of in-class team activity. Brief tests were given after every chapter, and team-based additional credits were given for the improvement comparing the average of previous tests of each student. This attempt of modified STAD was evaluated to have brought about a significant improvement in students' academic achievement, in addition to activating classroom atmosphere.

• Communications for Statistical Applications and Methods
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• v.19 no.6
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• pp.781-791
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• 2012

A $2{\times}2$ Cross-over design is widely used in clinical trials for comparison studies of two kinds of drugs or medical treatments. This design has many statistical methods such as Hills-Armitage's (1979) method or Koch's (1972) method. In this paper, we propose a nonparametric test for $2{\times}2$ Cross-over design based on a two-sample test suggested by Baumgartner et al. (1998). In addition, a Monte Carlo simulation study is adapted to compare the power of the proposed methods with those of previous methods.

• Transactions of Materials Processing
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• v.18 no.3
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• pp.256-261
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• 2009

Polyurethane has been one of the most important materials for automobile elastic parts such as bumper, head rest, instrument panel and so on since it covers very wide range of mechanical characteristics with low production costs. The processing variables such as formulation of ingredients and mold temperature, mixing speed, etc. can affect the quality of produced polyurethane foams so that process conditions should be determined appropriately. In this study, foaming behaviors of semi-rigid polyurethane were investigated by conducting cup foam tests with two major processing variables such as environmental temperature and blowing agent content. In addition, it was verified that processing conditions of real practice can be determined effectively by considering foaming characteristics obtained by the cup foam tests.

• Research in Mathematical Education
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• v.3 no.1
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• pp.57-68
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• 1999

In this paper, we investigate the comparative effectiveness of two kinds of instructional methods in transfer of mathematics learning: one based on the situated cognition, i.e. situated learning (SL) and the other based on traditional learning (TL). Both classes (of grade 2) studied addition and subtraction of 3-digit numbers. After that, they completed two written tests (Written Test 1 included computation problems, Written Test 2 included computation problems and story problems) and a real situation test. As a result, no significant differences were found between the two groups' performance on computation skill in Written Tests 1 and 2. But the SL group performed significantly better on the performance of story problem and real situation test than TL group. This result indicated that the SL made improvement in transfer of mathematics learning. As a result of interviews with 12 children of the SL group were able to use contextual resources in solving real situation as well as story problems.

• Korean Journal of Pharmacognosy
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• v.25 no.1
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• pp.35-40
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• 1994

Aqueous extreact of fresh ginseng (AFG) was examined for the antigenicity in Hartley guinea pigs in comparision with ovalbumin (OVA). When guinea pigs were sensitized with AFG emulsified with complete Freund's adjuvant (CFA), these animals showed negative reactions in active systemic anaphylaxis (ASA), active cutaneous anaphylaxis (ACA) and passive cutaneous anaphylaxis (PCA) tests and passive hemagglutination (PHA) reaction. On the contrary, when guinea pigs were sensitized with OVA emulsified with CFA as positive controls, these animals disclosed positive reactions in ASA, ACA and PCA tests and PHA reaction. From these results, AFG was considered not to possess antigenic properties in guinea pigs. In addition, the dose levels of AFG empolyed in the present experiment were confirmed not to suppress immune reactions.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.340-343
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• 2003

Soils contaminated by hazardous hydrophobic organic compounds, such as polycyclic aromatic hydrocarbons (PAHs), have become a major environmental issue due to toxic and carcinogenic properties of those compounds. In this work, we investigated effects of various metabolic inducers on phenanthrene biodegradation. Biodegradation tests were peformed with two different Pseudomonads: Pseudononrdia hydrocarboxydans (Gram positive) and Pseudomonas putida (Gram negative). Intermediates of phenanthrene metabolism (1-hydroxy-2-naphthoate, salicylate, catechol, phthalate and protocatechuate) were selected as inducers. The tests indicated that 1-hydroxy-2-naphthoate was the most effective inducer and enhanced the phenanthrene degradation rate up to 5.7 times, even though all the others also had induction ability to some extent. The effective induction could be achieved even at a low concentration of 1-hydroxy-2-naphthoate. Addition of metabolic inducers would be an attractive trick for the successful bioremediation of PAH-contaminated soil.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.216-217
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• 2018

The three kinds of tests are used to further study the effect of the amount of mineral powder in this mixture design. Firstly, comparing the relationship of the content of mineral powder and asphalt bitumen membrane thickness at different asphalt content, through film thickness to determine the range of gradation and asphalt content in laboratory tests, Grade A and Grade D, asphalt content 2.6%, 3.4% and 3.8% are set for the benchmark, then fatigue properties of the test are carried out in the established range, the result show that asphalt film thickness decreases with the addition of mineral powder. The result also show that fatigue properties of asphalt rubber mixture will reduced, when mineral powder added in, especially when the asphalt content is high.