• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.12
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• pp.803-808
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• 2014

$Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3$ ceramics with an excess $Bi^{3+}$ and a deficiency of $Na^+$ and $K^+$ were synthesized by a conventional solid state reaction method. The structure and morphology of $Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3$ ceramics were characterized by X-ray diffraction and field emission scanning electron microscopy. The electric polarization and mechanical strain induced by external electric field, and the temperature dependence of dielectric constant were investigated. These results demonstrated that an ergodic relaxor phase can be induced by controls of the mole ratio of $Bi^{3+}$, $Na^+$ and $K^+$. A phase boundary between non-ergodic and ergodic relaxor phases can be observed at ambient temperature. The ergodic relaxor phase can be transferred to the ferroelectric phase by application of the electric field. The stability of the induced ferroelectric phases strongly depends on the mole ratio of $Bi^{3+}$, $Na^+$ and $K^+$. The maximum strain of 0.31% was observed in $Bi_{0.51}(Na_{0.78}K_{0.22})_{0.47}TiO_3$ ceramics sintered at $1,150^{\circ}C$ for 2 h.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.6
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• pp.1001-1009
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• 1994

The present paper deals with a new developed sensor for measuring the time-varying magnetic fields and describes the experimental results of trasient magnetic field that takes place during the operations of electric appliance. The operation principle of the self-integrating magnetic field sensor by using coaxial cable is analyzed and a calibration investigation is carried out. The frequency bandwidth of the magnetic field measurement system is from 40 Hz to about 300 kHz. The magnetic field induced by the starting and/or operation of electric appliance mainly includes the odd harmonics such as the third, the fifth and the seventh harmonics. The magnetic field intensity caused during the operation of ultrasonic washer is inversely proportional to distance, this correspodns to induction component. As a result, it was known that the odd harmonics of magnetic field in the desing of electromagnetic shield employed for protecting electronic circuit and control devices have to be considered.

• Journal of the Korean Society of Safety
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• v.29 no.6
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• pp.34-39
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• 2014

This paper is aimed to prevent danger of electrical fire at cattle barn to detect resistive and capacitive leakage current component for wiring type and length. In order to analysis for electric leakage component for cattle barn sizes and normal buildings, this paper was studied field state investigation which are at cattle barn companies(10 companies) in Cheong-won location and normal buildings at Nam-bu market in Jeon-ju location. Market to deduce the problems of electric leakage component is analyzed. The resistive and capacitive leakage current component for wiring type and length is analyzed at Beon-young cattle barn. Results show that electric leakage component suggested in this paper are valuable and usable to electrical fire in leakage current based on environment factor, which will prevent severe damage to human beings and properties and reduce the electrical fires in cattle barn. It is acceptable for electrical equipment use in an cattle barn.

• Journal of the Korea Society for Simulation
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• v.25 no.1
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• pp.11-20
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• 2016

Recently in the field of defense Modeling and Simulation (M&S), Component-Based Development technology is widely applying to save the cost and increase the reusability of weapon system development. Related with this, researches for rapid reconfiguration and simulation of the component-standardized weapon system is actively carrying out. To rapidly reconfigure the new weapon system, complex and various functions of component information has to be effectively searched. So, it requires differentiated search technique unlike existing Keyword-based Search method. Semantic Search System provides semantically related information among the extensive information. In this research, metadata of weapon system components and their representative functional words are built as an ontology. And it provides an ontology-based semantic search system.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.865-873
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• 2017

Converter transformer is the key equipment of high voltage direct current transmission system. The solid suspending particles originating from the process of installation and operation of converter transformer have significant influence on the insulation performance of transformer oil, especially in presence of DC component in applied voltage. Under high electric field, the particles easily lead to partial discharge and breakdown of insulating oil. This paper investigated copper particle effect on the breakdown voltage of transformer oil at combined AC and DC voltage. A simulation model with single copper particle was established to interpret the particle effect on the breakdown strength of insulating oil. The experimental and simulation results showed that the particles distort the electric field. The breakdown voltage of insulating oil contaminated with copper particle decreases with the increase of particle number, and the breakdown voltage and the logarithm of particle number approximately satisfy the linear relationship. With the increase of the DC component in applied voltage, the breakdown voltage of contaminated insulating oil decreases. The simulation results show that the particle collides with the electrode more frequently with more DC component contained in the applied voltage, which will trigger more discharge and decrease the breakdown voltage of insulating oil.

• Journal of Astronomy and Space Sciences
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• v.32 no.4
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• pp.305-310
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• 2015

In this study, we examined a morningside Pi2 pulsation, with a non-substorm signature, that occurred in very quiet geomagnetic conditions (Kp = 0) at 05:38 UT on December 8, 2012, using data obtained by Van Allen Probes A and B (VAP-A and VAP-B, respectively) and at a ground station. Using 1 sec resolution vector magnetic field data, we measured the X-component of the pulsation from the Abu Simbel ground station (L = 1.07, LT = UT +2 hr, where LT represents local time) in Egypt. At the time of the Pi2 event, Abu Simbel and VAP-A (L = 3.3) were in the morning sector (07:38 LT and 07:59 MLT, respectively, where MLT represents magnetic local time), and VAP-B was in the postmidnight sector (04:18 MLT and L = 5.7). VAP-A and VAP-B observed oscillations in the compressional magnetic field component (Bz), which were in close agreement with the X-component measurements of the Pi2 pulsation that were made at Abu Simbel. The oscillations observed by the satellites and on the ground were in phase. Thus, we concluded that the observed morningside Pi2 pulsation was caused by the cavity resonance mode rather than by ionospheric current systems.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.1
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• pp.53-60
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• 1998

In this paper, the principle of operation, the part characteristic, characteristic of component movement, analysis are carried out for camcoder iris assembly which is one of the important element component in Video camera large projection TV instrument. And some Know-how for development of element component is also included. The magnetic field circuit for the small and simple structure with low power consumption is introduced and new materials of yoke for small motor system is suggested. Especially, the relation with remained magnetic field and operation duration time is analyzed by experimental results. Some problems of nonlinear torque characteristics included in this system is considered to obtain the simple and low cost structure in domestic production. Furthermore, development procedure is suggested for iris assembly and some methods to reduce the burr with some check points for small precise accessories are explained.

• Bulletin of the Korean Chemical Society
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• v.19 no.8
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• pp.830-835
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• 1998

The characteristics of the ablation plume generated by 532 nm Nd: YAG laser irradiation of a Pb(Zr0.52Ti0.48)O3 (PZT) target have been investigated using a pulsed-field time-of-flight mass spectrometer (TOFMS). The relative abundance of O+, Ti+, Zr+, Pb+, TiO+, and ZrO+ ions has been measured and discussed. TiO+ and ZrO+ ions were also found to be particularly stable within the laser ablation plasma with respect to PbO+ species. The behavior of the temporal distributions of each ionic species was studied as a function of the delay time between the laser shot and the ion extraction pulse. The most probable velocity of each ablated ion is estimated to be Vmp=1.1-1.6x 105 cm/s at a laser fluence of 1.2 J/cm2, which is typically employed for the thin film deposition of PZT. The TOF distribution of Ti+ and Zr+ ions shows a trimodal distribution with one fast and two slow velocity components. The fast velocity component (6.8x 10' cm/s) appears to consist of directly ablated species via nonthermal process. The second component, originated from the thermal evaporation process, has a characteristic velocity of 1.4-1.6 x 105 cm/s. The slowest component (1.2 x 105 cm/s) is composed of a dissociation product formed from the corresponding oxide ion.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.1
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• pp.24-30
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• 1991

This paper deals with the analysis of the transient characteristics of a superconducting a.c. generator(SCG) using Finite Element Method. Since the magnetic field induced by the field current and the armature currents are not sinusoidally distributed in a generator, the conventional equivalent circuit method, in general, uses the fundamental component only and is done in frequency domain. But the finite element analysis makes it possible to analyze the transient magnetic field distribution and the electrical characteristics of the double shields of SCG in time domain.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.6
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• pp.635-644
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• 2003

To ensure the reliability of ultrasonic nondestructive testing techniques for modern structural materials, the effects of anisotropy and inhomogeneity and the influence of non-planar component geometries on ultrasonic wave propagation have to be taken into account. In this article, fundamentals and applications of two analytical approaches to three-dimensional elastic beam field calculation are presented. Results for both isotropic materials including curved interfaces and for anisotropic media like composites are presented, covering field profiles for various types of transducers and the modeling of time-dependent rf-signals.