• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.465-467
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• 1995

High impedance fault can not be easily detected by conventional method. But if it would not be detected and cleared quickly, it can result in fires, and electric shock. In this paper, ANN, which has learning capability, is used for high impedance fault detection. The potential of the neural network approach is demonstrated by simulation using KEPCO's measured data. Among ANN models used in this paper, CPN shows better result than BPN in respect of convergence and reliability.

• 한국재료학회지
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• 제28권12호
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• pp.719-724
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• 2018

Cordierite composed of an alumina-silica-magnesia compound has a low coefficient of thermal expansion(CTE) and excellent thermal shock resistance. It also has a low dielectric constant and high electrical insulation. However, due to low mechanical strength, it is limited for use in a ceramic heater. In this study, $ZrO_2$ is added to an 80 wt% cordierite-20 wt% mullite composition, and the effect of $ZrO_2$ addition on the mechanical strength and thermal shock resistance is investigated. With an increasing addition of $ZrO_2$, cordierite-mullite formed $ZrO_2$, $ZrSiO_4$ and spinel phases. With sintering conducted at $1400^{\circ}C$ with the addition of 5 wt% $ZrO_2$ to 80 wt% cordierite-20 wt% mullite, the most dense microstructure forms along with an excellent mechanical strength with a 3-point flexural strength of 238MPa. When this composition is quenched in water at ${\Delta}T=400^{\circ}C$, the 3-point flexural strength is maintained. Moreover, when this composition is cooled from $800^{\circ}C$ to air, the 3-point flexural strength is maintained even after 100 cycles. In addition, the CTE is measured as $3.00{\times}10^{-6}{\cdot}K^{-1}$ at $1000^{\circ}C$. Therefore, 80 wt% cordierite-20 wt% mullite with 5 wt% $ZrO_2$ is considered to be appropriate as material for a ceramic heater.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1581-1583
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• 1999

Epoxy Compound has been used as insulation material in cable accessories. During the applying voltage to cable, heat shock is induced to accessory by the temperature difference between atmosphere and conductor. In this study, crack resistance, thermal and mechanical properties were evaluated about conventional epoxy compound and rubber toughened epoxy compound. Because rubber absorbs the stress caused by heat shock, crack resistance of rubber toughened epoxy compound is high. In the case of low thermal expansion coefficient, the compound shows high crack resistance because of low volumetric change.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.653-654
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• 2006

This paper proposes a new linear magnetic damper for absorbing shock from a crash accident involving high speed vehicles. The magnetic damper is composed of a conductive plate, a yoke and permanent magnets which are constructed to a Halbach array to improve the damping force. In order to calculate the damping force, finite element analysis(FEA) using J-Mag, a commercial FEA tool, is performed and the results are validated by the experiment. Also, the design optimization of the plate generating the eddy current causing the damping force performed to obtain the most efficient damping force. Finally, the specifications and the performance of the proposed magnetic damper are represented.

• 대한의용생체공학회:의공학회지
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• 제26권4호
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• pp.251-255
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• 2005

When the extracorporeal shock wave lithotriptor is operated, sounds can be heard. Then that might be a question about the location where the sounds come from. For the purpose of investigating the fact, we identify the location of the sounds radiated using one hydrophone. In order to carry out the experiment, it is needed to obtain direct waves from objects. Therefore, we present an experimental method to reduce reflected waves for obtaining direct waves only. The experimental results show the amplitude of waves can be attenuated about 28dB due to a silicon rubber plate of 8.5mm attached at the bottom. This is a quantified result that can expect to obtain the direct waves using the proposed method. Then, we carried out the experiment for the sound source location. From the experimental results, we can undoubtedly present a fact that the sounds are radiated from the objects to be shot due to shock waves.

• 한국정밀공학회지
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• 제16권4호통권97호
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• pp.46-56
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• 1999

A semi-actively controlled impact system which adjusts an impulse exerted by the external impact is studies. The main control variables are internal pressure difference inside the cylinder and the shock absorber displacement while it travels. Compared to a conventional one so called a passive system with a variable orifice inside the cylinder, a semi-actively controlled system utilizes an external orifice controlled by a highly fast responding electrical proportional valve. This device overcomes the temperature and viscosity change due to continuous operating and keeps the desired pressure difference and displacement in every operation. In this article a new prototype impact system is designed and manufactured based on a semi-actively control system. Through computer simulations and experiments, we verify the possibility of controlling the shock absorber pressure and displacement. After investigating the control performance a modified semi-actively controlled system with better control performance is also proposed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2242-2244
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• 1999

Recently, An important research field of pulsed power is high voltage, high power generation with exploding wire opening switch. Another point of view exploding wire effects have been researched for generation of the pulsed high pressure shock wave. Theoretical considerations of the shock pressure generation along with experiment results are presented in this paper and. Some experimental results of hard rock fracturing show the possibilities of commercial using.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 F
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• pp.1981-1983
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• 1998

The principle of the MHD generation is based on Faraday's law of induction that a eletromotive force(u ${\times}$ B) is generated when the working gas of velocity u flows a channel in which magnetic field of strength(B) exists. In MHD power generation system, enthalpy of the working gas is converted to electric power directly through expansion in generator channel. It means that electric power can be generated without moving mechanical linkage such as turbine blades. There are two types in the MHD generator; linear type Faraday and disk type hall generator. Disk type hall generator is the main target of this paper. Isentropic efficiency and enthalpy extraction rate of disk type shock tube driven hall generator is discussed here.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전력기술부문
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• pp.246-248
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• 2004

The lower voltage distribution box of service wire has been usually employed to supply an electric power to the consumers through low voltage overhead line. Now-a-days, electric shock accident at the distribution box of service wire installed in the seashore areas has been often occurred. The reason is mainly due to the electric leakage in the distribution box of service wire. This paper described insulation breakdown mechanism of distribution box of service wire, analysis of electric shock path and safety countermeasure of distribution box of service wire.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.172-175
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• 2005

Since, similar to other commercial launch vehicles, various kinds of pyrotechnique devices are used in the KSLV-I(Korea Space Launch Vehicle), the electronic equipment on the vehicle equipment bay is exposed to the sever pyroshock environment during Pyrotechnique device detonation. In order to confirm the survivability of electrical instruments from these pyroshock conditions, shock tests are performed by using a pyroshock simulation during development and qualification phase. In this paper, the pyroshock simulator installed in KARI(Korea Aerospace Research Institute) are briefly introduced, and its performance of pyroshock generating is compared with the measured shock response spectrums from small scaled fairing jettisoning tests. The results show that the pyroshock simulator is still proper to generate severe pyroshocks similar to real pyrotechique detonating conditions, but the redesign on the test jigs is necessary to improve its test performance.