• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.1
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• pp.1-10
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• 2013

In this paper, a broadband planar monopole antenna for multi-band services is proposed. The physical size of the proposed antenna is miniaturized by folding a rectangular loop. And a resonance point in the 3.9 GHz band is reduced by a coupling phenomenon with the central part of the T-shaped patch and the folded rectangular loop. In addition, the T-shaped patch is inserted to the rectangular shaped monopole antenna due to deriving the broadband frequency characteristics. The frequency characteristic is optimized by adjusting the gap and length of the folded rectangular loops and a transverse diameter of the T-shaped patch. The antenna dimensions including the ground plane are $40{\times}60{\times}1.6mm^3$. It is fabricated on the FR-4 substrate(${\epsilon}_r$=4.4) using a microstrip line of $50{\Omega}$ for impedance matching. In the measured result, the bandwidth corresponding to the VSWR of 2:1 is 162 MHz(815~977 MHz) and 2,530 MHz(1.43~3.96 GHz). For analyzing the human effect by the proposed antenna, 1 g and 10 g averaged SARs are simulated and measured. As the simulated results, 1 g-averaged SAR is 1.044 W/kg, and 10 g-averaged SAR is 0.718 W/kg. This result are satisfied by the SAR guidelines which are 1.6 W/kg(1 g-averaged) and 2.0 W/kg(10 g-averaged).

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.8
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• pp.62-68
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• 1998

Optical broadband second harmonic genration (SHG) in thin film waveguide structure was investigated. The copolymer poly(MMA-co-DR1MA) which was consiste dof PMMA (polymethylmethacrylate) and DR 1 (disperse red 1) was spin coated on the pyrex substrate. The green and near UV SHG were observe dfrom the fundamental beam even though the poled polymer has the absorption in second harmonic wavelength range. It was able to genrate SHG by cerenkov type phase matching. Th epoled polymer film thickness was decided by theoretical analysis. The green (532nm) and near UV SHG (370nm) were observed from the Q-switched Nd-YAG laser (1064nm) and Ti-sapphire laser (740nm). It was in good agreement with the experimental results.

• Journal of the Optical Society of Korea
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• v.17 no.6
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• pp.481-485
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• 2013

A method for the measurement of the concentration of methane is experimentally demonstrated. The wavelength filter and gas cell are combined by using one Fabry-Perot etalon, which is filmed with the reflectivity of 96%. The optical broadband source is not only filtered to match the absorption wavelength of methane, but also absorbed by the methane in the same Fabry-Perot etalon. The concentration of the methane can be detected directly by measuring the transmission intensity. Compared with the conventional method, the proposed method possesses low costand high stability.

• Atmosphere
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• v.20 no.4
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• pp.519-530
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• 2010

In this paper we review current research on Atmospheric Brown Clouds (ABCs) with lightweight Unmanned Aerial Vehicles (UAVs) and miniaturized instruments. The UAV technology for in-situ measurements, including aerosol concentration, aerosol size distribution, aerosol absorption, cloud drop size distribution, solar radiation fluxes (visible and broadband), and spectral radiative fluxes, is a leading-edge technology for cost-effective atmospheric sounding, which can fill the gap between the ground measurement and satellite observation. The first experimental observation with UAVs in Korea, Cheju ABC Plume Monsoon Experiment (CAPMEX), conducted during summer 2008 revealed that the Beijing plumes exerted a strong positive influence on the net warming and fossil-fuel-dominated black-carbon plumes were approximately 100% more efficient warming agents than biomass-burning-dominated plumes. Long-term sustainable routine UAV measurements will eventually provide truly three-dimensional data of ABCs, which is necessary for the better understanding of their climate impacts and for the improvement of numerical models for air pollution, weather forecast and climate change.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.49.1-49.1
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• 2016

Asteroid taxonomy dates back to the mid-1970's and is based mostly on broadband photometric and spectroscopic observations in the visible wavelength. Different taxonomic classes have long been characterized by spectral slope shortward of 0.75 microns and the absorption band in 1 micron, the principal components. In this way, taxonomic classes are grouped and divided into four broad complexes; silicates (S), carbonaceous (C), featureless (X), Vestoids (V), and the end-members that do not fit well within the S, C, X and V complexes. The past decade witnessed an explosion of data due to the advent of large-scale asteroid surveys such as SDSS. The classification scheme has recently been expanded with the analysis of the SDSS 4th Moving Object Catalog (MOC 4) data. However, the boundaries of each complex and subclass are rather ambiguously defined by hand. Furthermore, there are only few studies on asteroid taxonomy using Johnson-Cousins filters, and those were conducted on a small number of objects, with significant uncertainties. In this paper, we present our preliminary results for a new taxonomic classification of asteroids using SMASS, Bus and DeMeo (2014) and the SDSS MOC 4 datasets. This classification scheme is simply represented by a triplet of photometric colors, either in SDSS or in Johnson-Cousins photometric systems.

• Journal of Magnetics
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• v.13 no.3
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• pp.92-96
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• 2008

There are few reports of high frequency loss behavior in the near-field for magnetic films with semiconducting properties, even though semiconducting magnetic materials, such as soft magnetic amorphous alloys and nanocrystalline thin films, have been demonstrated. The electromagnetic loss behavior of multilayer magnetic films with semiconducting properties on the microstrip line in quasi-microwave frequency band was analyzed numerically using a commercial finite-element based electromagnetic solver. The large increase in the absorption performance and broadband characteristics of the semiconducting/insulating layer magnetic films examined in this study were attributed to an increase in the loss factor of resistive loss. The electromagnetic reflection increased significantly with increasing conductivity, and the loss power deteriorated significantly. The numerical results of the magnetic field distribution showed that a strong radiated signal on the microstrip line was emitted with increasing conductivity and decreasing film thickness due to re-reflection of the radiated wave from the surface of the magnetic film, even though the emitted levels varied with film thickness.

• ETRI Journal
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• v.36 no.4
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• pp.654-661
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• 2014

We develop accurate finite-difference time-domain (FDTD) modeling of polymer bulk heterojunction solar cells containing Ag nanoparticles between the hole-transporting layer and the transparent conducting oxide-coated glass substrate in the wavelength range of 300 nm to 800 nm. The Drude dispersion modeling technique is used to model the frequency dispersion behavior of Ag nanoparticles, the hole-transporting layer, and indium tin oxide. The perfectly matched layer boundary condition is used for the top and bottom regions of the computational domain, and the periodic boundary condition is used for the lateral regions of the same domain. The developed FDTD modeling is employed to investigate the effect of geometrical parameters of Ag nanospheres on electromagnetic fields in devices. Although negative plasmonic effects are observed in the considered device, absorption enhancement can be achieved when favorable geometrical parameters are obtained.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.134.1-134.1
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• 2014

콜로이달 리소그래피는 나노미터 크기의 나노구를 자가조립에 의해 정렬시킴으로써, 파장이하 크기의 주기 구조를 저비용으로 쉽게 구현할 수 있는 패터닝 기법이다. 콜로이달 리소그래피나 소프트 리소그래피와 같이 대면적 패터닝이 가능한 공정을 태양전지를 위한 반사방지 및 광 포획 증대 구조에 적용함으로써, 기존 성능을 크게 향상시켰다. 본 연구에서는, 유한차분 시간영역 수치해석법을 이용하여 반사 방지 및 광 포획 증대 구조에 대한 이론적 검증 및 설계를 진행하였고, 콜로이달 리소그래피 및 반도체 공정을 통해 샘플을 제작하였으며, 제작된 샘플의 성능을 적분구를 겸비한 자외선 가시광 근적외선 영역 분광기를 통해 평가하였다. 반사방지 나노섬을 겸비한 나노 원뿔대 언덕형 굴절률 소자를 구현함으로써, 300나노미터 이하의 구조체를 사용하지 않고도 근자외선 영역을 포함하는 태양광 에너지의 손실을 최소화할 수 있는 광대역 방사방지 구조체를 제시하였다. 나노 원뿔대가 격자상수 이상의 파장에 대한 언덕형 굴절률을 제공하고, 4분의 1파장 나노섬 반사방지막이 격자 상수 이하의 근자외선 태양광을 추가적으로 흡수하여, 근자외선 영역에서의 평균 반사율을 3.8% 수준으로 달성 할 수 있었다. 또한, 낮은 양호계수를 갖는 속삭임 회랑 공진기 어레이를 이용하여, 박막 태양전지에 적합한 유전체 기반 광포획 증대 나노구조를 제시하였다. 나노반구, 나노고깔, 나노구, 함몰형 나노구 어레이 형태를 가지며, 500nm의 주기를 갖는 유전체 표면 텍스쳐드 구조를 초박형 비정질 실리콘 필름(100nm) 위에 제작하여 광대역 광 포획 증대 효과를 실험적으로 평가하였다. 구조들 중 함몰형 나노구 어레이가 결합된 비정질 실리콘 박막이 가장 높은 성능을 보였으며, 구조가 없는 경우 대비 약 67.6%의 가중 흡수율 증가를 나타내었다. 특히, 함몰형 나노구 어레이 구조 중 폴리메틸메타아크릴레이트로 제작된 평판형 함몰층은 나노구 비정질 박막 실리콘 사이의 접착력 및 기계적 강성을 향상시켰을 뿐 아니라, 함몰층 내부로 회절되고 산란된 빛들이 도파모드 효과에 의해 부가적인 광 포획 증대를 가져옴으로써, 가장 높은 광 포획 효과를 얻을 수 있었다. 유전체 기반 나노 구조들은 간단하고 저비용이며, 대면적으로 쉽게 제작할 수 있는 자가 조립 기반 콜로이달 리소그래피 및 소프트 리소그래피 기술을 이용하여 제작되었다.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.3 s.52
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• pp.237-244
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• 2005

Sunscreens have been in use for about 70years and 'tanning without burning' was propagated as their major advantage. The objective changed from 'getting a tanned skin' to 'getting skin protection' since UV have been proposed to a major risk of skin cancer and the risk of developing skin cancer related also to non-burning UVA. The new expectation from consumers has triggered the development of new UV absorbers and led to the approval of 7 new, organic UV absorbers in Europe over the last few years. The significant progress due to these new UV absorbers will be discussed in this report. These UV absorbers provide an efficient absorption of UV radiation (UVB and/or UVA) and easily incorporate in any kind of formulation. These are also safe, i.e. devoid of adverse effects. These new filters give the formulators new possibilities to cover the whole UV range iron 290 to 400 nm, and also to use less filter due to the boosting effect of the new UVA and broadband fitters.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.111.2-111.2
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• 2012

We observed an Ellerman bomb(EB) and its associated surge using the Fast Imaging Solar Spectrograph(FISS) and the broadband TiO filter of the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. As is well-known, the EB appears as a feature that is very bright at the far wings of the H alpha line. The lambdameter method applied to these wings indicates that the EB is blue-shifted up to 6km/s in velocity. In the photospheric level below the EB, we see rapidly growing "granule-like" feature. The transverse velocity of the dark lane at the edge of the "granule" increased with time as reached a peak of 6km/s, at the time of the EB's occurrence. The surge was seen in absorption and varied rapidly both in the H alpha and the Ca II 8542 line. It originated from the Ellerman bomb, and was impulsively accelerated to 20km/s toward us(blueshift). Then the velocity of the surge gradually changed from blueshift of 20km/s to redshift of 40km/s. By adopting the cloud model, we estimated the temperature of the surge material at about 27000K and the non-thermal velocity at about 10km/s. Our results shed light on the conventional idea that an EB results from the magnetic reconnection of an emerging flux tube and pre-existing field line.