• Proceedings of the KSRS Conference
• /
• 2005.10a
• /
• pp.415-417
• /
• 2005

In order to retrieve the latent and sensible heat fluxes, high-resolution airborne imageries with visible, near infrared, and thermal infrared bands and ground-base meteorology measurements are utilized in this paper. The retrieval scheme is based on the balance of surface energy budget and momentum equations. There are three basic surface parameters including surface albedo $(\alpha)$, normalized difference vegetation index (NOVI) and surface kinetic temperature (TO). Lowtran 7 code is used to correct the atmosphere effect. The imageries were taken on 28 April and 5 May 2003. From the scattering plot of data set, we observed the extreme dry and wet pixels to derive the fitting of dry and wet controlled lines, respectively. Then the sensible heat and latent heat fluxes are derived from through a partitioning factor A. The retrieved latent and sensible heat fluxes are compared with in situ measurements, including eddy correlation and porometer measurements. It is shown that the retrieved fluxes from our scheme match with the measurements better than those derived from the S-SEBI model.

• The Bulletin of The Korean Astronomical Society
• /
• v.39 no.2
• /
• pp.100.2-100.2
• /
• 2014

The DOTIFS is a new multi-object Integral Field Spectrograph (IFS) planned to be designed and built by the Inter-University Center for Astronomy and Astrophysics, Pune, India, (IUCAA) for cassegrain side port of the 3.6m Devasthal Optical Telescope (DOT) being constructed by the Aryabhatta Research Institute of Observational Sciences, Nainital. (ARIES) It is a multi-integral field unit (IFU) spectrograph which has 370-740nm wavelength coverage with spectral resolution R~1200-2400. Sixteen IFUs with microlens arrays and fibers can be deployed on 8 arcmin field. Each IFU has $8.7^{{\prime}{\prime}}{\times}7.4^{{\prime}{\prime}}$ field of view with 144 spaxel elements. 2304 fibers coming from IFUs are dispersed by eight identical spectrographs with all refractive and all spherical optics. In this work, we show optical design of the DOTIFS spectrograph. Expected performance and result of tolerance and thermal analysis are also shown. The optics is comprised of f=520mm collimator, broadband filter, dispersion element and f=195mm camera. Pupil size is determined as 130mm from spectral resolution and budget requirements. To maintain good transmission down to 370nm, calcium fluoride elements and high transmission optical glasses have been used. Volume Phase Holographic grating is selected as a dispersion element to maximize the grating efficiency and to minimize the size of the optics. Detailed optics design report had been documented. The design was finalized through optical design review and now ready for order optics.

• Proceedings of the KSRS Conference
• /
• 2008.10a
• /
• pp.68-71
• /
• 2008

Our goal is to obtain a better scientific understanding how to define the nature and role of remotely sensed land surface parameters and energy fluxes in the heat island phenomena, and local and regional weather and climate. By using the MODIS visible and thermal imagery data and analyzing the surface energy flux images associated with the change of the landcover and landuse in study area, we will estimate and present how significant is the magnitude of the heat island heat effect and its relation with the surface parameters and the energy fluxes in Taiwan. To achieve our objective, we used the energy budget components such as net radiation, soil heat flux, sensible heat flux, and latent heat flux in the study area of interest derived form remotely sensed data to understand the island heat effect. The result shows that the water is the most important component to decrease the temperature, and the more the consumed net radiation to latent heat, the lower urban surface temperature.

• KIEAE Journal
• /
• v.10 no.6
• /
• pp.139-144
• /
• 2010

The demands are increasing for the efficient heating and cooling system and thermal comfort environment because of changes in climate and environment, and deterioration of buildings and facilities can cause education budget to increase. So the study to apply heating and cooling system to university is urgently needed to improve an optimum energy saving system, educational environment and convenience of maintenance. For this reason, we selected a university campus in Seoul then came to understand the current situation and found some problems. We drew alternatives from comparative analysis of them. It selects representative building and carries out economic analysis to evaluate characteristics of energy consumption and economics on each type of heating and cooling system. As a result we drew the optimum system from those processes as previously stated. We studied 3 available systems, absorption chiller, EHP(Electric Heat Pump) and GHP(Gas Engine Heat Pump). According to LCC analysis suppose that the value of EHP is 1, it came out that the value of absorption chiller is 1.5 and the value of GHP is 2.2. This study, suggesting the optimum heating and cooling system, will support educational and research activities furthermore effect to maximize energy efficiency. Ultimately it is expected that it will contribute to make eco-friendly Green Campus.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.05a
• /
• pp.96-98
• /
• 1999

유기전계발광소자(OELD)의 성능 향상을 위한 많은 연구가 진행되고 있지만 아직까지 금속전극과 유기발 광층 사이의 접촉저항(Contact Resistance)에 관한 연구는 거의 보고되지 않고 있다. Ohmic 접합에서 접촉 저항은 효율적이고 신뢰성 있는 소자제작에 있어서 간과되어서는 안될 매우 중요한 부분이다. 본 연구에서는 금속전극과 유기발광충 사이의 접촉저항에 관해서 논의하고자 한다. 본 연구에서 제작된 샘플은 금속전극으로 Ag, 유기발광재료로서 Alq$_3$를 사용하였으며, Alq3의 두께를 100 $\AA$에서 500 $\AA$까지 각각 다르게 하여 서로 다른 두께의 유기발광층을 가지는 샘플을 제작하였다. 금속전극의 매트릭스 구조에 의해 형성된 적선의 크기는 3 mm x 2 mm이며, 제작된 샘플의 접촉비저항은 TLM(Transmission Line Measurement) 방법을 이용하여 구하였다. Planar한 TLM model로부터 새로운 vertical model을 유추하였으며, 이를 근거로 접촉저항 및 transfer length 등을 계산하였다. 상온에서 측정된 전체 저항값은 유기발광층의 두께가 증가함 에 따라 증가하는 경향을 나타냈으며, 이 때 계산된 접촉비저항은 1.49$\times$$10^1$ $\Omega$-$\textrm{cm}^2$ 이다. 접촉저항은 전극 사이의 거리의 증가에 따라 증가하지만, 측정시간의 thermal budget의 영향으로 상대적으로 전체저항이 감 소하였으나, 저항감소분의 포화에 따라서, 거리에 비례하여 다시 저항이 증가하였다.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.220-221
• /
• 2007

금속 촉매 성장 (Metal-induced growth) 를 이용하여, 마이크로 사이즈의 결정질 (Microcrystalline) 박막 실리콘 (Silicon, Si)을 성장하였다. 금속 촉매로서는 코발트, 니켈, 코발트/니켈 복합물질(Co, Ni, or Co/Ni) 이 사용되었으며, 실리콘과 반응하여 실리사이드 (Silicide) 층을 형성한다. 이러한 실리사이드 층은 실리콘과 격자 거리가 유사하여 (Little lattice mismatch), 그 위에 실리콘 박막을 성장하기 위한 모체 (Template) 가 된다. XRD (X-ray diffraction) 분석을 통하여, 실리사이드 ($CoSi_2$ or $NiSi_2$) 의 형성과 성장된 박막 실리콘의 결정성을 연구하였다. 이러한 박막을 이용하여, 쇼트키 태양전지 (Schottky Solar cell) 에 응용하였다. 코발트/니켈 복합물질을 이용하였을 경우에 10.6mA/$cm^2$ 단락전류를 얻었으며, 이는 코발트만을 이용한 경우보다 10 배만큼 증가하였다. 이러한 실리사이드를 매개로한 박막 실리콘의 성장은 공정상에서의 열부담 (Thermal budget) 을 줄일 수 있으며, 대면적 응용에 큰 가능성을 가지고 있다.

• Proceedings of the KSRS Conference
• /
• 2003.11a
• /
• pp.351-353
• /
• 2003

We present a retrieval scheme for the remote sensing of evapotranspiration (ET) over rice paddy. To perform the retrieval, high-resolution airborne imagery of multi-spectral visible and thermal infrared data, and ground-based meteorological measurements are utilized. Our ET retrieval scheme is based on the basic principal of surface energy budget, which is a result of balance in longwave and shortwave radiation, latent heat, sensible heat, and energy flux into the ground. To partition the latent and sensible heat fluxes of interest from the energy balance equation, three basic parameters are of most concern, including albedo, surface temperature, and normalized difference vegetation index (NDVI). The NDVI and albedo can be easily derived from the visible and near infrared spectral data, while the surface tem-perature can be determined through the analysis of the infrared data with the Stefan Boltzmann law. From the airborne imagery taken on 28 April 2003, we observe very good dry and wet pixels that can be easily corre-sponded to the radiation and evaporation controlled crite-ria, respectively, and, hence, for the further use in defin-ing the evaporative fraction needed to partition sensible and latent heat fluxes from the net energy flux. The de-rived ET is compared with the in situ measurements.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.5
• /
• pp.358-364
• /
• 1998

Retrograde well is a new process for ULSI fabrication. High energy ion implantation has been used for retrograde well formation. In this paper the forming condition for retrograde well using high energy ion implantation is compared with that for conventional well. TW signals for retrograde p-,n-well($900^{\circ}C$),after annealing are similar trends to those of conventional ones($1150^{\circ}C$), however the signals for RTA have the highest value because of small thermal budget. Junction depths of retrograde well are varied from about 1.2 to $3.0\{mu}m$ as for conventional well. The peak concentrations of retrograde well, however, are about 10 times higher in values than those of conventional ones so that they can be used as any types of potential barriers or gettering sites. The critical dose for phosphorus implantation in our experiments is between $3\times10^{13} and 1\times10^{14}/cm^2$. Under the above critical dose, there are many secondary defects near projected range such as dislocation lines and dislocation loops.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07a
• /
• pp.48-51
• /
• 2004

In this paper the importance of re-nitridation on a plasma-enhanced chemical-vapor deposited(PECVD) $SiO_2$ stacked on a thermally grown thin-nitrided $SiO_2$ on n-type 4H SiC have been investigated. Without the final re-nitridation process, the leakage current of metaloxidesemiconductor(MOS) was extremely large. It is believed that water and carbon, contamination from the low-thermal budget PECVD process, are the main factors that destroyed the high quality thin-buffer nitrided oxide. After re-nitridation annealing, the quality of the stacked gate oxide was improved. The reasons of this improvement are presented.

• The Bulletin of The Korean Astronomical Society
• /
• v.45 no.1
• /
• pp.46.2-46.2
• /
• 2020

Dust ejection activities have been discovered from a few tens of asteroids since the first confirmation in 2006. Those objects are known as active asteroids. They provide good observational chances to study ongoing phenomena in the solar system such as sublimation of icy volatiles, mutual collisions among asteroids, rotational disintegrations, thermal fatigue, etc. Although dust ejection mechanisms of individual cases have been investigated through observations, the frequencies of the events and their connection to the overall evolutionary budget of the solar system have not yet been studied thoroughly, mainly because previous studies were based on serendipitous discoveries without any systematic surveys of these objects. In this work, we made wide-field monitoring observations of asteroids using Korea Microlensing Telescope Network (KMTNet) during the 2018/2019 winter season. Among 3,644 asteroids in the field-of-view, we detected nine candidates of brightness enhancements which we suspect as possible activities. It is still possible that some of those brightness increases have caused by long-term rotations. However, our observed frequency and brightness enhancements size-frequency distribution agrees with the expectations from impacts with decimeter sized objects, when the main belt objects size-frequency distribution observed down to decameter sized bodies are extrapolated to decimeter size.