• 전기의세계
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• v.38 no.12
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• pp.26-28
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• 1989

전력은 모든 산업의 원동력이고 국민의 일상생활에 필수불가결한 요소로서 국가발전에 있어서 중요한 역할을 하고 있고 다양한 사회적 요구에 부응해 공합되므로서 실로 국민경제에 미치는 영향은 거대하다고 할수 있다. 그런 의미에서 볼대 전력산업은 양질의 전기일전압, 주파수 변동범위가 작고 무정전일를 값싸고 풍부하게 일반국민에게 공합해야 함을 지상목표로 삼고 합당한 수립, 시행해야 한다.

• Composites Research
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• v.35 no.3
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• pp.201-215
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• 2022

This paper presents the development of thin and lightweight ultra-high temperature radar-absorbing ceramic composites composed of an aluminosilicate ceramic matrix-based geopolymer reinforced ceramic fiber and sendust magnetic nanoparticles in X-band frequency range (8.2~12.4 GHz). The dielectric properties with regard to complex permittivity of ceramic/sendust-aluminosilicate composites were proportional to the size of sendust magnetic nanoparticle with high magnetic characteristic properties as flake shape and its concentrations in the target frequency range. The characteristic microstructures, element composition, phase identification, and thermal stability were examined by SEM, EDS, VSM and TGA, respectively. The fabricated total thicknesses of the proposed single slab ultra-high temperature radar absorber correspond to 1.585 mm, respectively, exhibiting their excellent EM absorption performance. The behavior of ultra-high temperature EM wave absorption properties was verified to the developed free-space measurement system linked with high temperature furnace for X-band from 25℃ to 1,000℃.

• The Journal of the Acoustical Society of Korea
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• v.27 no.7
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• pp.357-364
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• 2008

For the purpose of possibility study on development of an acoustic tweezer using standing waves and very high frequency ultrasound focused beams, a system which can manipulate the position of particles in water has been constructed. It can move the particles to near focal point of a focused beam by the radiation force of standing waves, and then the particles would be trapped by the radiating force of the focused beam. The results show that micro sphere particles were trapped well at nodes of the standing waves and their position can be easily manipulated by frequency control. And, even though the radiation force by single focused beam pushes a particle away from the transducer, two focused confronted beams can trap it at near center.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.1
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• pp.384-389
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• 2011

This article presents an ultra broadband resistive power divider circuit for smart grid applications. Since the future smart grid system is expected to deploy high speed power line communication, the frequency response of the resitive power divider circuit is naturally of significance. Employing a thin film technology, the resistive power divider was designed, measured, and fabricated. For the circuit design, the conductor-backed coplanar waveguide line was firstly designed and measured. The 3 dB cutoff frequency was 72 GHz and S11 remains <-20 dB upto 70 GHz. The fabricated resistive power divider shows the 3 dB cutoff frequency of 50 GHz. It was experimentally verified that the resistive power divider circuit shows the insertion loss of 6 dB for high-speed input signal (40 Gb/s).

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.2
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• pp.56-64
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• 1996

In the previous paper of this study, an incoherent intensity pattern of a conducting cylinder is obtained by averaging out the multi-frequency intensities of the time-harmonic fields scattered from this cylinder. in this paper, an incoherent imaging of a conducting cylinder is obtained via the back-projection of the incoherent intensity patterns calculated from the circular rotational measurement configuration. This imaging method is vlaidated by imaging a conducting circular and a conducting elliptic cylinder and the measurement conditions to get better image are investigated.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.4
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• pp.66-71
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• 1985

A MOSFET with multigates arrayed in periodic structure is studied as a transit time device for microwave amplification. The interactions between the periodic metal gates and the slow wave on the surface of the semiconductor can be observed in the vicinity of synchronism. The stability and the reciprocity of the active quadrupole are shown depending on the frequency and velocity of the carriers.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.9
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• pp.728-732
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• 2008

This paper presents ion-based micro vibration sensor for the ultra-high frequency vibration detection. Presented sensor uses the motion of anion and cation in an electrolyte. Electrolyte vibration sensors have the high shock survival characteristics and a simple read-out circuit because of the small mass and own charges of ions. Presented sensor measures the induced electric potential by the mechanical-electrical coupling. It consist of electrolyte chamber and detection electrode. Electrolyte chamber was fabricated by PDMS molding. Detection electrode was made of gold evaporation on pyrex glass. Size of electrolyte chamber was designed as $600{\times}600{\times}100um$. Detection electrode had 200nm-thick and 42um-gap. In the experimental study, 5.8M sodium Chloride (NaCl) solution was used as electrolyte in 36nl-chamber. Mechanical vibration was measured from 2kHz to 4MHz.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.1
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• pp.94-103
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• 2005

The low foamed high strengthen styrofoam samples made by dielectric heating are discussed. We used the oscillator which have the frequency of 13.6 MHz and the power of 7 kW. 3 times expanded beads by steaming method were used in our foam-molding test. Internal fusion properties and density of internal structure were improved by dielectric foaming process. At the temperature of $105-110^{\circ}C$, the internal fusion property was maximally improved.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.3
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• pp.371-377
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• 2007

In this paper, acceleration threshold of perception for the horizontal vibration of tall buildings was estimated. Excessive vibration of tall buildings by wind can give displeasure, such as giddiness and visual insecurity. To provide comfortable environment to residents of tall buildings, acceleration needs to be limited. For tall buildings the first mode of vibration is dominant. To reproduce the first mode of vibration, experiments were performed by generating sine waves by a shaking table. A nitration house was made and forty persons were employed for experiments. The forty persons were organized into five experimental groups, each of which was composed of eight persons, and the threshold of perception for horizontal vibration was measured by increasing acceleration in the range of 0.2Hz through 1.2Hz of frequency, Performance curves were obtained by dividing the distribution of perception for horizontal vibration into the range of $0{\sim}20%,\;21{\sim}40%,\;41{\sim}60%,\;61{\sim}80%\;and\;81{\sim}100%$ and by fitting curves.

• 전기의세계
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• v.34 no.8
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• pp.470-475
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• 1985

우주물질의 대부분이 플라즈마 상태에 있지마는 지구상에서는 천둥이 칠 때 생기는 방전이나 극지방에서 볼 수 있는 오로라와 같이 극히 일부분이 자연상태의 프라즈마로 존재한다. 지금까지 플라즈마의 이용은 그것이 내는 밝은 빛을 이용한 조명이나, 높은 열을 이용한 용접이나 절단이 고작이었으나, 최근에 들어 초고온, 고밀도 플라즈마를 이용한 핵융합 에너지 연구나 Free Electron Laser나 Gyrotron과 같이 새로운 Radiation Source로써 종래의 Source가 만들지 못하던 주파수 영역이나 Glow Discharge에서 생기는 저온 Plasma를 이용한 Plasma Etching PECVD(Plasma Enhanced CHemical Vapor Deposition), Plasma Ashing, Sputtering등은 VLSI의 제조에 필요불가결한 공정의 일부분이 되고 있다. 앞으로 수회에 걸쳐 본 기술해설란을 통하여 이들 Plasma의 이용 기술을 소개하고자 하며 본회에서는 그중에서 Plasma Etching에 대해서 그 원리와 기술상의 특징을 살펴보고자 한다.