• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 1994년도 추계학술발표회
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• pp.79-90
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• 1994

The goal of this research is to get a measuring system for absorption characteristics of electromagnetic wave absorbers in ferrite type which are lat grid-type special type etc. It is however very difficult to measure the absorption characteristics as in low frequency as in 30 MHz, To solve the problem therefore we propose a standing wave method and a measurement method in time domain using parallel striplines construct the measuring system and measure the characteristics of ferrite microwave absorbers in grid type using the proposed measuring system.

• 한국전자파학회지:전자파기술
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• 제6권2호
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• pp.11-18
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• 1995

본 연구는 평판형, 그리드형, 특수형상 등의 페라이트 전파흡스체의 흡수능 측정시스템을 구축하는 데에 목적이 있다. 그러나 30MHz와 같이 낮은 주파수에서 흡수능을 측정하느 것은 대단히 곤란 . 이와같은 문제를 해결하기 위하여 평행평판 스 라인을 사용하여 정재파측정법 및 시간영역법을 제안하였으며, 실제 측정시스템을 구성하요 제안한 측정볍으로 그리드형 페라이트 전자파흡수체의 특성을 측정. 평가하였다.특성을 측정. 평가하였다.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.67-68
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• 2005

This thesis is concerned with basic research for development of EM wave absorbers in sheet type for mobile phones. By controlling the sendust ratio, the $Al(OH)_3$ coating, the thickness, the kind of binders, EM wave absorbers were prepared and examined. Centeral frequency shifts toward lower with increasing thickness of the absorber, and absorption ability controlled to adjust Sendust amount. The absorption band of the EM wave absorber coated with $Al(OH)_3$ becomes larger than that of non-coated one. Sendust composite microwave absorbers mixed with CPE were prepared at $70^{\circ}C$ in temperature. The fabricated EM wave absorbers show a reflection coefficient 5.56 dB at 1.8 GHz in thickness of 0.85 mm.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.185.2-185.2
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• 2016

The plasma density is an essential plasma parameter describing plasma physics. Furthermore, it affects the throughput and uniformity of plasma processing (etching, deposition, ashing, etc). Therefore, a novel technique for plasma density measurement has been attracting considerable attention. Microwave probe is a promising diagnostic technique. Various type of cutoff, hairpin, impedance, transmission, and absorption probes have been developed and investigated. Recently, based on the basic type of probes, modified flat probe (curling and multipole probes), have been developing for in situ processing plasma monitoring. There is a need for comparative study between the probes. It can give some hints on choosing the reliable probe and application of the probes. In this presentation, we make attempt of numerical study of different kinds of microwave probes. Characteristics of frequency spectrum from probes were analyzed by using three-dimensional electromagnetic simulation. The plasma density, obtained from the spectrum, was compared with simulation input plasma density. The different microwave probe behavior with changes of plasma density, sheath and pressure were found. To confirm the result experimentally, we performed the comparative experiment between cutoff and hairpin probes. The sheath and collision effects are corrected for each probe. The results were reasonably interpreted based on the above simulation.

• 한국환경과학회지
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• 제15권6호
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• pp.579-586
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• 2006

The purposes of this paper were to monitor the temperature rising courses and spark discharge of the modified granular activated carbon (GAC) by microwave (MW) irradiation and to evaluate absorption of benzene. The GAC coated on $SiO_2$, boron, talc, ferrite was named as the modified GAC. Thermal and spark discharge measurement of virgin GAC and modifed GAC has been carried out using a MW device operating at 2450 MHz under various energy conditions. The results of this paper as follows. First, the modified GAC is more efficient than the virgin GAC in temperature control. Temperature gradient of the modified GAC is more lower than that of virgin GAC. The temperature gradient of GAC was observed in the following order : virgin GAC, Mn-Zn ferrite/GAC, Ni-Zn ferrite,/GAC, $SiO_2/GAC$, Boron/GAC, Talc/GAC. Second, the spark discharge of the modified GAC was diminished, compared with that of virgin GAC. Because of its excellent electrical insulating properties, the coating material prevents the spark discharge. Finally, the benzene adsorption capacity of the modified GAC decreased due to diminishing of adsorption site by the coating material. Considering the temperature gradient and spark discharge of GAC, the GAC coated $SiO_2$ would be appropriate absorbent under irradiation of MW.

• Radiation Oncology Journal
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• 제8권2호
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• pp.155-162
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• 1990

마이크로파온열요법은 피부 및 국소종양에 대한 방사선과 병행요법으로서 치료성과를 얻고 있다. 저자들은 가정용 전기오븐을 이용하여 온도측정 및 조절장치를 할 수 있는 마이크로파온열기를 개발하여 적용가능한 환자를 치료하여 왔다. 그러나 선형단극 안테나로 제작된 applicator는 가열 깊이가 2\~4\;cm$로 낮고 온도분포가 불균일하여 많은 어려움이 있었다. 저자들은 안테나의 길이를 마이크로파의 파장과 같거나 배수로 하여 효율을 높게 하고 모양을 나선형으로 한 applicator를 여러개 제작하여 온열분포를 측정하였다. 안테나 길이가 파장과 같은 12.2cm이고 직경 4 cm 의 나선형모양을 가진 applicator의 온열분포가 대칭적이고 넓으며 (FWHM =3.5 cm) 보다 깊이 가열할 수 있어 ($D_{eff}=4\;cm$) 온열치료에 많은 도움을 줄 수 있다고 사료된다.

• 한국재료학회지
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• 제12권6호
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• pp.458-463
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• 2002

Carbon nanotubes were synthesized at various conditions using Ni-catalytic thermal chemical vapor deposition method and their characteristic properties were investigated by SEM, TEM and Raman spectroscopy. Carbon nanotubes were formed on very fine Ni-catalytic particles. The carbon nanotubes synthesized by thermal decomposition of acetylene at $700^{\circ}C$ had a coiled shape, while those synthesized at $850^{\circ}C$ showed a curved and Y-shape having a bamboo-like morphology. It was found that the carbon nanotube was also made on the fine Ni-catalytic particles formed on the surface of 100~400nm sized large ones after pretreatment with $NH_3$.ber composites show the high dielectric constant and large conduction loss which is increased with anisotropy of fiber arrangement. It is, therefore, proposed that the glass and carbon fiber composites can be used as the impedance transformer (surface layer) and microwave reflector, respectively. By inserting the foam core or honeycomb core (which can be treated as an air layer) between glass and carbon fiber composites, microwave absorption above 10 dB (90% absorbance) in 4-12 GHz can be obtained. The proposed fiber composites laminates with sandwitch structure have high potential as lightweight and high strength microwave absorbers.

• The Korean Journal of Ceramics
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• 제3권3호
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• pp.159-162
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• 1997

Diamond was uniformly nucleated on large area Si(001) substrate (3cm$\times$4cm) using the low pressure magnetoactive microwave plasma chemical vapor deposition. $CH_4/He$ gas mixture was used as source gas in order to obtain high radical density in the nucleation enhancement step. $CH_3$radical density was measured by means of infrared laser absorption spectroscopy. The effect of substrate bias voltage on diamond nucleation was examined. The results showed that a suitable positive bias voltage appled to the substrate with respect to the chamber could enhance diamond nucleation while a negative bias voltages leaded to deposition of only non-diamond phase carbon.

• 한국분말재료학회지
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• 제25권5호
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• pp.375-378
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• 2018

Conductive and dielectric SiC are fabricated using electroless plating of Ni-Fe films on SiC chopped fibers to obtain lightweight and high-strength microwave absorbers. The electroless plating of Ni-Fe films is achieved using a two-step process of surface sensitizing and metal plating. The complex permeability and permittivity are measured for the composite specimens with the metalized SiC chopped fibers dispersed in a silicone rubber matrix. The original non-coated SiC fibers exhibit considerable dielectric losses. The complex permeability spectrum does not change significantly with the Ni-Fe coating. Moreover, dielectric constant is sensitively increased with Ni-Fe coating, owing to the increase of the space charge polarization. The improvements in absorption capability (lower reflection loss and small matching thickness) are evident with Ni-Fe coating on SiC fibers. For the composite SiC fibers coated with Ni-Fe thin films, a -35 dB reflection loss is predicted at 7.6 GHz with a matching thickness of 4 mm.

• 한국결정성장학회지
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• 제27권3호
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• pp.135-142
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• 2017

본 연구에서는 국내 화력발전소에서 발생되는 바텀애쉬를 이용하여 질석 성형물을 제작하였으며, 이를 이용하여 흡음 건자재 제조를 위한 흡음성, 최고 휨파괴하중에 대하여 고찰하였다. 이러한 바텀애쉬와 질석의 성형물 제조를 위하여, 마이크로웨이브 건조방식의 공정를 사용하였다. 또한, 바텀애쉬의 볼밀링작업을 통하여 얻어진 $65{\mu}m$ 정도의 크기의 균일한 분말이 사용되었다. 5, 10 wt%의 바텀애쉬와 질석의 성형물을 제조하여, 최고 휨파괴하중 특성이 분석 되었다. 이러한 실험 결과들은 바텀애쉬의 재활용 기술에 필요한 기초적인 데이터를 제공한다.