• East Asian mathematical journal
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• v.27 no.2
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• pp.141-161
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• 2011

This research is a laboratory study for the improvement of differential equation class, and the aim of this study is to propose the possibilities of applicable writing activities for differential equation courses in university. We analyzed how the writing activities can affect the improvement of abilities of the students' affective domain and cognitive domain. Although the results from the two areas did not show a big numerical improvements it proved that the writing activities have positive effects, especially for the group of lower level students. The students felt interested and became more confident with differential equation studies. Their understanding of the study has been increased further by acquiring new learning methods, including writing activities. Therefore, we conclude that teaching and learning method designed systematically to adopt writing activities improve the students' learning attitudes and achievements.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.180-181
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• 2006

In this paper, there have been brief review about the important consideration in laboratory planning and construction of the reliability assessment infrastructure including 400 kV, 120 kVA AC test system, which enable to evaluate the HV long-term overcharged withstand performance for spacers using in Gas Insulated Switchgears up to transmission class, Also it is described simply about its trial running of the whole test system and its assessment example. To inform the founded national code, RS C 0084, and the procedure for getting a reliability assessment certificate issued by the government, brief description of the code and summation of test results have been conducted.

• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.2899-2904
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• 2009

Esterification is an important class of reactions in the preparation of perfumery and flavor chemicals, wherein homogeneous, solid acidic, and superacidic catalysts are normally used. Now, an efficient and selective protocol for protection of various functionalized alcohols employing carboxylic acids as protecting agents is realized through the catalytic mediation of simple heteropolyoxometallates. In this methodology, water is the only by-product and notably the aspect of effluent treatments does not arise. The advantages include the operational simplicity, recycle ability of the catalyst and mild reaction conditions. The present catalytic system may be a potential candidate not only for laboratory practice but also for commercial applications and offers an environmentally safer alternative to the existing processes.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.278-281
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• 2004

To realize magnetic sails, momentum of the solar wind should be efficiently transferred to a spacecraft via magnetic field, which is produced around a spacecraft. In this paper, two important physical processes are addressed: 1) diffusive processes caused by plasma turbulence at the magnetospheric boundary around the spacecraft; and 2) field aligned current loops that will electrically connect the magnetospheric boundary and the spacecraft. The idea of the magnetic sails will be demonstrated by an experimental simulator, in which a fast plasma beam will penetrate into a dipole magnetic field. For that purpose, the two important physical processes should be scaled down to a small laboratory experiment in a space chamber. From the scaling considerations, the interaction can be scaled down if high-speed and high-density $(10^{19}m^{-3})$ plasma jet is used with 1-T-class magnetic field.

• Structural Engineering and Mechanics
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• v.58 no.4
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• pp.661-676
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• 2016

This paper presents an elastic/plastic model that neglects strain hardening during loading, but accounts for the Bauschinger effect. These mathematical features of the model represent reasonably well the actual behavior of several materials such as high strength steels. Previous attempts to describe the behavior of this kind of materials have been restricted to a class of boundary value problems in which the state of stress in the plastic region is completely controlled by the yield stress in tension or torsion. In particular, the yield stress is supposed to be constant during loading and the forward plastic strain reduces the yield stress to be used to describe reversed yielding. The new model generalizes this approach on plane stress problems assuming that the material obeys the von Mises yield criterion during loading. Then, the model is adopted to describe reversed yielding in thin hollow discs subject to external pressure.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2600-2602
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• 2001

The laboratory time for students in engineering has to be managed in that way that it provides students width maximal practice hours. However, it usually takes too much time to learn basic knowledge for the experiment and the directions of the equipment. In this paper, we introduce the web contents which students can study basic knowledge the directions of the equipment without regard to time or place. As the result that we let students study the contents before the class, they were easily adapted to handle the equipments for the experiment so that we can revise their execution abilities. And also there were effects such as reducing the total experiment's time and a rate of damage of equipment.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.221-224
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• 2003

This study was carried out to develope a basic form of planning hull type fishing boat. G/T 10ton class is selected as object hull form, and hull form is designed in Chosun University. A series of test results of LCG variations for 5 different LCG points are presented in this paper. The test was performed in Davidson Laboratory, and the scope of tests include resistance, trim and sinkage.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.81-85
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• 2004

This paper describes the testing facility to demonstrate the performance of the distribution class circuit breakers and switchgears and the testing methods. The field-test evaluation system consists of two parts. One is the distribution system for simulation of the condition on interruption mode of switches which are installed in the system and tested by the AFG(Artificial Fault Generator) and the thunderbolt generator just like in the real field. The other is a laboratory for confirmation or the important characteristics regarding to the insulation, gas, environment durability of equipment. For the fatal failure mode, a FMEA(Failure Modes and Effects Analysis) technique which is a kind of a structural analysis to consider a counter-plan was emploved.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2100-2102
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• 2005

In this Paper, there have been brief review about the important consideration in laboratory planning and designing the dielectric testing facilities for heavy electric apparatus up to 800kV-class in the high voltage testing fields. To improve and reinforce the existing dielectric test facilities in the way of econo-mical and optimal condition, wide investigation and an analysis for a solution, especially overshoot compensation method. have been suggested. With the brief description about those matters in constructing and improving the test facilities, the specification of each facility has been shown in the paper.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1750-1752
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• 2003

This paper, as a preliminary study, presents the important consideration in laboratory planning and designing 4.2MV impulse voltage generator(IVG), which enable to test and evaluate the UHV dielectric performance of power electric apparatus up to 765kv-class. To fix and confirm the kinds of loads and their capacities to be tested by KERI hereafter, wide investigation and an analysis of test objects, especially heavy electric apparatus of Korea, according to their ratings and test voltages have been conducted. With the special consideration concerning other matters in designing of 4.2MV IVG have been described with the practical examples and references.