• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(2)
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• pp.76-79
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• 2000

The 3$\mu\textrm{m}$-thick PVDF (Polyvinyiidene fluoride) thin film have been prepared using physical vapor deposition with electric field, and its FT-IR specrum, dielectric property and electric conduction phenomenon have been investigated. Since the characteristic peaks ate detected at 509.45 and 1273.6〔cm〕 in the FT-IR spectrum, we are confirmed that the ${\beta}$ -phase is dominant in the PVDF thin film. In the results of dielectric properties, the PVDF thin film shows anomalous dispersion, i.e. gradual decrease of dielectric constant with increase of frequency, and also that the dielectric absorption point changes from 200Hz to 7000Hz with increasing temperature of thin film, which is consistent with the Debye's theory. The activation energy (ΔH) obtained from temperature dependence of dielectric loss is 21.64 ㎉/㏖. We confirm that the electric conduction mechanism of PVDF thin film is dominated by ionic conduction by investigating the dependence of the leakage current of the thin film on the temperature and the electric field.

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 동계학술발표회 논문집
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• pp.361-362
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• 2009

High-order harmonics from gaseous atoms driven by an intense femtosecond laser pulse can form an attosecond pulse train. By selecting suitable harmonic generation conditions, the harmonic spectrum can be broad enough to form sub-hundred attoseconds. One serious limitation, however, comes from the inherent attosecond chirp originating from the harmonic generation process. We have proposed to compensate for the positive attosecond chirp by making use of negative group delay dispersion of a metallic x-ray filter or a gaseous medium. We generated 240-as pulses from neon and compressed them to 60 as after propagating through argon, close to the transform-limited duration of 47 as.

• 한국염색가공학회지
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• 제9권1호
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• pp.1-14
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• 1997

Nylon 6 grafted with polyacrylamide(PAAm) was synthesized by a dispersion polymerization method at 6$0^{\circ}C$ for 2 hours, and a cresol-soluble graft polymer(CSGP) and water-dispersable graft polymer (WI)GP) were separated. Infra-red(IR) spectrum analysis, differential scanning calorimetery(DSC), thermogravimetery(TG), and X-ray diffraction analysis were carried out to research their structural characteristics.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2003년도 한국우주과학회보 제12권2호
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• pp.37-37
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• 2003

Electron whistlers frequently excite proton whistlers. The proton whistlers appear on the dynamic spectrum as rising tones, which start after the reception of a short electron whistler, asymptotically approaching the local proton gyro-frequency. The proton whistlers are dispersed forms of lightning impulses and their dispersion can be explained by the effects of heavy ions such as H+ and He+ on the propagation of an electromagnetic wave in the ionosphere. In the ionosphere, a right-handed circularly-polarized electron whistler becomes coupled to a left-handed circularly-polarized proton whistler when the frequency becomes close to a cross-over frequency. By adopting the multi-fluid numerical wave model, we examine how the mode coupling varies as the ion composition changes along altitude in the mid-latitude ionosphere. The time histories and dynamic spectra of electric fields are presented. In addition, we compare our results with the previous theoretical and observational studies.

• 한국환경과학회지
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• 제12권1호
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• pp.41-45
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• 2003

Magnetite powder for kerosene-based ferrofluid was synthesized by air oxidation of waste acid containing $Fe^{2+}$ and $Fe^{3+}$ ions in the pH=11 at $60^{\circ}C$. Stable kerosen-based ferrofluid was prepared by addition of polyoxyethylene nonylphenyl ether(POENPE) to the magnetite containing water. Dispersion mechanism of an addition POENPE to the magnetite was examined by means of the fraction of solid dispersed FT-IR spectrum. And magnetic properties of kerosen-based ferrofluid were examined by method of Vibrating Sample Magnetometer. In order to remove oil on the water surface by an addition of kerosen-based ferrofluid, the optimum conditions were examined.

• Journal of the Optical Society of Korea
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• 제13권4호
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• pp.423-427
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• 2009

The results of the experimental and theoretical studies conducted on terahertz filtering using two parallel-plate waveguides (PPWGs) are presented herein. The first PPWG with 355 ${\mu}m$ plate separation generates 4 THz bandwidth TM modes ($TM_0,\;TM_2,\;and\;TM_4$), whereas the second PPWG with 100 ${\mu}m$ plate separation operated the THz filter for the generated TM modes with 1.5 THz cutoff frequency. The outgoing THz wave of the two PPWGs was truncated until 1.5 THz, and the system was operated using a high-pass THz filter. The absorption and dispersion of the combined TM and TE modes for the filtering system were calculated. The theoretical calculation and measurement results for the cutoff and oscillation frequency in the spectrum domain agreed well.

• 한국광학회:학술대회논문집
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• 한국광학회 2008년도 하계학술발표회 논문집
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• pp.157-158
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• 2008

High-order harmonics from gaseous atoms driven by an intense femtosecond laser pulse can form an attosecond pulse train. By selecting suitable harmonic generation conditions, the harmonic spectrum can be broad enough to form sub-hundred attoseconds. One serious limitation, however, comes from the inherent attosecond chirp originating from the harmonic generation process. We have proposed to compensate for the positive attosecond chirp by making use of negative group delay dispersion of a metallic x-ray filter or a noble gas. We generated 241-as pulses from neon and compressed them to 106 as after propagating through argon, close to the transform-limited duration of 98 as.

• 한국광학회지
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• 제11권1호
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• pp.43-46
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• 2000

Kerr 렌즈 모드록킹된 티타늄 사파이어 레이저에서 상용화된 광학부품만을 이용하여 9 fs의 펄스를 생성하였다. 공진기 내부와 출령경을 지나면서 발생하는 군속도 분산을 각각 용융 프리즘 쌍을 이용하여 보상하였고, 넓은 스펙트럼을 얻기 위하여 광대역 거울을 사용하였다. 이전에 사용했던 광대역 거울과 반사율을 비교해 봄으로서 10fs 미만의 극초단 펄스를 생성하기 위해서는 180nm 이상의 넓은 반사대역을 갖는 거울을 선택하는 것이 필수적임을 확인하였다.

• Korean Chemical Engineering Research
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• 제46권1호
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• pp.106-111
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• 2008

폴리프로필렌(polypropylene, PP)/옥수수전분(corn starch) 마스터뱃취(MB)/실리케이트 복합체를 전분 함량을 10, 20, 30, 40, 50으로 변화시키면서 실험실 규모의 brabender mixer를 이용하여 $200^{\circ}C$에서 제조하였다. 실리케이트의 함량은 5 wt%로 고정하였다. 복합체에서 전분 MB 함량 변화는 적외선분광기(FT-IR)를 이용하여 수산기의 존재여부와 피크 강도 변화로 확인하였다. PP/전분 MB/실리케이트 복합체의 열적특성을 시차주사열용량분석기(DSC) 그리고 열중량분석기(TGA)를 이용하여 관찰하였다. PP/전분 MB/실리케이트의 용융온도에는 큰 변화가 나타나지 않음을 알 수 있었고, 분해온도는 전분 MB 함량에 따라 점차적으로 감소하는 경향을 보여주었다. 복합체의 실리케이트 분산정도는 X-선 회절(XRD)과 투과전자현미경(TEM)을 이용하여 측정하였다. 복합체의 실리케이트 분산은 전분 MB의 함량에 의존하였고, 전분 MB가 20 wt% 이상 첨가되었을 때 d-spacing과 피이크 강도에 큰 변화를 보였다. 복합체의 유변학적 특성은 전분 MB의 함량에 따라 shear thinning effect와 탄성특성에 있어 증가를 나타내었다. 또한 전분 함량이 20 wt% 이상 첨가되었을 때 이들 유변학적 특성에 있어서 큰 변화를 나타내었다. 이는 $200^{\circ}C$에서 동적유변학측정기를 이용하여 확인하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.76.1-76.1
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• 2015

Optical resonances of metallic or dielectric nanoantennas enable to effectively convert free-propagating electromagnetic waves to localized electromagnetic fields and vice versa. Plasmonic resonances of metal nanoantennas extremely modify the local density of optical states beyond the optical diffraction limit and thus facilitate highly-efficient light-emitting, nonlinear signal conversion, photovoltaics, and optical trapping. The leaky-mode resonances, or termed Mie resonances, allow dielectric nanoantennas to have a compact size even less than the wavelength scale. The dielectric nanoantennas exhibiting low optical losses and supporting both electric and magnetic resonances provide an alternative to their metallic counterparts. To extend the utility of metal and dielectric nanoantennas in further applications, e.g. metasurfaces and metamaterials, it is required to understand and engineer their scattering characteristics. At first, we characterize resonant plasmonic antenna radiations of a single-crystalline Ag nanowire over a wide spectral range from visible to near infrared regions. Dark-field optical microscope and direct far-field scanning measurements successfully identify the FP resonances and mode matching conditions of the antenna radiation, and reveal the mutual relation between the SPP dispersion and the far-field antenna radiation. Secondly, we perform a systematical study on resonant scattering properties of high-refractive-index dielectric nanoantennas. In this research, we examined Si nanoblock and electron-beam induced deposition (EBID) carbonaceous nanorod structures. Scattering spectra of the transverse-electric (TE) and transverse-magnetic (TM) leaky-mode resonances are measured by dark-field microscope spectroscopy. The leaky-mode resonances result a large scattering cross section approaching the theoretical single-channel scattering limit, and their wide tuning ranges enable vivid structural color generation over the full visible spectrum range from blue to green, yellow, and red. In particular, the lowest-order TM01 mode overcomes the diffraction limit. The finite-difference time-domain method and modal dispersion model successfully reproduce the experimental results.