• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.7
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• pp.319-325
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• 2005

In order to analyze ground potential rise of grounding system installed in buildings, the hemispherical grounding simulation system has been designed and fabricated as substantial and economical measures. Ground potential rise(GPR) has been measured and analyzed for shapes of grounding electrode using the system in real time. The system is apparatus to have a free reduced scale for conductor size and laying depth of a full scale grounding system and is constructed so that a shape of equipotential surface is nearly identified a free reduced scale with a real scale when a current flows through grounding electrode. The system was composed of a hemispherical water tank, AC Power supply, a movable potentiometer, and test grounding electrodes. The test grounding electrodes were fabricated through reducing grounding electrode installed in real buildings such as rod type, mesh grid type. When a mesh grid type was associated with a rod type, GPR was the lowest value. The proposed results would be applicable to evaluate GPR in the grounding systems. and the analytical data can be used 0 stabilize the electrical installations and prevent the electrical disasters.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.3
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• pp.60-65
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• 2005

The present work has developed non-electric and delay-type explosive bolt that does not need electric power supply device and has the delay function in the operation. Non-electric power supply system enables separation device system to be minimized. In order to prove the mechanism of the operation, the power of air resistance caused from aviation object used to ignite the initiator. we can be founded from the present work that the changes in the operation load influence directly the ignition of the initiator. The design of non-electric and delay type of explosive bolt is the most suitable for the separation system that is necessary to reduce the velocity of aviation object and safe landing of parachute system.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.56 no.1
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• pp.45-50
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• 2007

In this paper, this paper discusses how to improve the power control system of cold and hot water purifiers, in particular, system protecting device against abnormal voltage. The existing power supply control system came with a protecting device composed of varistor device only for impulse-type surges. Even though the existing system senses surge other than impulse-type, the system can not be protected. Accordingly, a new type of power control system was designed to protect the system from surge and ultimately prevent electricity accidents. The power control system suggested in this paper will be designed to protect the system by sensing input voltage and discontinuing power supply by means of SSR if voltage exceeding set value is sensed. To test the designed system, surge was imposed on the existing system and processes of system failure were experimented before safety of the designed power control system was simulated via P-spice program developed by Orcad in order to examine safety and reliability of the system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.13-19
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• 2003

A supersonic ground test facility to develop Ramjet and SCRamjet(Supersonic Combustion Ramjet) engine should be able to simulate high altitude and high Mach number conditions including air total pressure, oxygen level and specific heat ratio at the combustion chamber entrance. The test facility also should simulate the effect of oblique shock wave caused by the flight vehicle. The test facility developed in this study is supersonic free-jet blowdown type, which consists of high pressure air supply source(maximum pressure=32MPa), air heater(vitiation type), supersonic diffuser, ejector, and test chamber(nozzle exit dimension=200mm$\times$200mm).

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.4
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• pp.53-62
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• 2003

A supersonic ground test facility to develop Ramjet and SCRamjet(Supersonic Combustion Ramjet) engine should be able to simulate high altitude and high Mach number conditions including air total pressure, oxygen level and specific heat ratio at the combustion chamber entrance. The test facility also should simulate the effect of oblique shock wave caused by the flight vehicle. The test facility developed in this study is supersonic free-jet blow down type, which consists of high pressure air supply source(maximum pressure=32MPa), air heater(vitiation type), supersonic diffuser, ejector, and test chamber(nozzle exit dimension=200mm${\times}$200mm).

• Transactions of Materials Processing
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• v.29 no.2
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• pp.113-117
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• 2020

Various parameters are involved in the frictional behavior of steel sheet during stamping. We performed various tests in order to investigate the influence of tool surface texture directionality upon the resulting friction in sheet forming processes. Four different tools were manufactured which gave us a range of roughness for both parallel and transverse texture directions. Each of the tools was examined in flat type friction tests under identical test conditions. The tool with the transverse surface texture produces significantly lower levels of friction than the tool with parallel texture direction. Considering the lubrication mechanism associated with transverse texture, one can imagine the lubricant being constantly supplied from the reservoir of the micro valley to the point of contact and hence producing the lower levels of friction seen.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1159_1160
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• 2009

This paper presents the numerical simulation results on the supercodnucting electrodynamic suspension (EDS) simulator according to the variation of the ground conductor. The levitation force of the EDS system is formed by the reaction between the moving magnet and the fixed ground conductor. The possible way to simulate the EDS system were simulated in this paper by using finite element method (FEM). The static type simulator which consists of the fixed magnet, the fixed ground conductor and the ac current supply system. To verify the characteristics of high speed EDS system with the moving type simulator heavy, large and fast moving ground conductor is needed. The static type simulator can get the characteristics of the high speed EDS system by applying equivalent ac current to velocity, therefore it does not need large moving part. The static type EDS simulator, which can consist of an HTS magnet, the fixed ground conductor(s), an AC power supply and the measuring devices, also test the effect of the shape of the ground conductor easily. The plate type ground conductor made stronger levitation force than ring type ground conductor. Although the outer diameter 335 mm ring type ground conductor (Ring3) was larger than the outer diameter 235 mm ground conductor (Ring2), the levitation force by Ring2 was stronger than that by Ring3. From the calculation results on this paper, the consideration of the magnetic flux distribution according to the levitation height should be included in the process of the ground conductor design.

• Journal of Aerospace System Engineering
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• v.14 no.6
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• pp.85-90
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• 2020

The infrared signature that is associated with an aircraft is mainly caused by heat released from the engine and the exhaust plume. In this study, a test-system was designed to observe the overall infrared signature characteristics of a turbofan engine during operation under ground running conditions and the infrared reduction features that result from different exhaust nozzle configurations. A test stand was designed for the 1400 lbf class turbofan engine that included a bell-mouth type intake, fuel supply system, a measurement system, and a data acquisition/control system. The design and verification of the test system were conducted so that the basic nozzle and various 2D nozzles could be applied to study the infrared signature produced by a turbofan engine exhaust.

• Industry Promotion Research
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• v.5 no.1
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• pp.13-20
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• 2020

This study is about consumer preference of plastic toilets that can provide automatic supply of recycled water. First, the preference for plastic toilet seat design by gender and age group was preferred for gender type C and G for the sex. As the result of the chi-square test, the significance probability is .044 and the significance is P <.0 5. I could confirm that. Age, teens, 40 s, and 50 s or older prefer type C, 20 s and 30 s, but B type is not statistically significant. Second, the differences among the groups of preference for appearance design criteria according to general characteristics were all stable (stable appearance) in gender, age, region, education, and salary, but the chi-square test showed that they were not statistically significant. There was no difference between them. This study has implications for improving competitiveness and productivity by reducing the main production cost by commercializing toilets made of plastic materials.

• The Journal of the Korea Contents Association
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• v.21 no.1
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• pp.311-320
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• 2021

At present, the secondary school teacher employment examination(SSTEE) is the only gateway to become a national and public secondary teacher in Korea, and after the revision from the 2014 academic year, all the questions of the exam have been converted to supply-type test items, requiring more definitive, accurate, and solid answers. Compared to the selection-type test items that measure recognition memory, the supply-type questions, testing recall memory, require constant memorization and retrieval practices to furnish answers; however, there is not enough learning tools available to support the practices. At this juncture, this study invented a mobile app, called ONE PASS, for the SSTEE. By unpacking the functional mechanisms of the brain, the basis of cognitive processing, this ONE PASS app offers a set of tools that feature brain-based learning principles, such as a personalized study planner, motivation measurement scales, mind mapping, brainstorming, and sample questions from previous tests. This study is expected to contribute to the research on the development of learning contents for applications, and at the same time, it hopes to be of some help for candidates in their exam preparation process.