• Journal of the Korean Association of Geographic Information Studies
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• v.21 no.4
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• pp.26-49
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• 2018

The purpose of this study was to verify the reliability of the solar radiation model and discuss its applicability to the urban area of Seoul for summer heat stress mitigation. We extended the study area closer to the city scale and enhanced the spatial resolution sufficiently to determine pedestrian-level urban radiance. The domain was a $4km^2$ residential area with high-rise building sites. Radiance modelling (SOLWEIG) was performed with LiDAR (Light Detection and Ranging)-based detailed geomorphological land cover shape. The radiance model was evaluated using surface energy balance (SEB) observations. The model showed the highest accuracy on a clear day in summer. When the mean radiation temperature (MRT) was simulated, the highest value was for a low-rise building area and road surface with a low shadow effect. On the other hand, for high-rise buildings and vegetated areas, the effect of shadows was large and showed a relatively low value of mean radiation temperature. The method proposed in this study exhibits high reliability for the management of heat stress in urban areas at pedestrian height. It is applicable for many urban micro-climate management functions related to natural and artificial urban settings; for example, when a new urban infrastructure is planned.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.4
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• pp.41-51
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• 2014

천공복사를 구현할 수 있는 관류열전달계수 측정용 실내실험장치를 제작하고 국내에서 사용되고 있는 온실 피복재 및 보온재의 관류열전달계수를 측정하여 실외실험에서 측정된 결과와 비교하여 타당성을 평가하였다. 외부피복은 0.1 mm 두께의 폴리에틸렌 필름을 사용하여 일중 및 이중피복으로 처리하였다. 이중외부피복조건의 경우 4가지 종류의 보온재를 처리하여 총 6가지 피복처리에 대하여 실험을 실시하였다. 모든 피복처리조건에 대하여 야간복사 유무에 따른 관류열전달계수 측정실험이 수행되었다. 천공복사의 유무에 따라 온실피복재의 관류열전달계수의 변화 경향이 크게 차이가 있었기 때문에 실내실험을 통해 관류열전달계수를 측정하기 위해서는 반드시 실제의 천공복사를 구현할 수 있는 실험장치가 필요할 것으로 판단된다. 실내 실험결과와 실외 실험결과가 비교적 잘 일치하였으며 실내실험장치를 이용하여 관류열전달계수를 측정하는 것이 타당성이 있음을 확인할 수 있었다. 천공복사 유무에 따른 관류열전달계수의 차이는 핫박스 내외부의 온도차이가 증가함에 따라 감소하는 것으로 나타났다.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.32.2-32.2
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• 2016

We present the catalog of the KVN Calibrator Survey (KVNCS). This first part of the KVNCS is a single dish radio survey conducted at 22 (K band) and 43 GHz (Q band) simultaneously using the Korean VLBI Network (KVN) from 2009 to 2011. A total 2045 sources selected from the VLBA Calibrator Survey (VCS) with an extrapolated flux limit of 100 mJy at K band. The KVNCS contains 1533 sources in the K band with a flux limit of 70 mJy and 553 sources in the Q band with a flux limit of 120 mJy; it covers the whole sky down to -32. ${\circ}$ 5 in declination. Five hundred thirteen sources were detected in the K and Q bands, simultaneously; ~76% of them are flat-spectrum sources ($-0.5{\leq}{\alpha}{\leq}0.5$). From the flux-flux relationship, we anticipated that the most of the radiation of many of the sources comes from the compact components. Therefore, the sources listed in the KVNCS are strong candidates for high frequency VLBI calibrators.

• Journal of the Korean Solar Energy Society
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• v.27 no.1
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• pp.91-98
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• 2007

Perimeter zone is one of the weakest area in buildings and it makes an increase of heating and cooling loads, in addition to condensation or discomfort with cold-draft to residents in winter. Because of this, it needs to be reinforced by active systems. However, they use fossil fuel, and ultimately greenhouse effect is urged. Thus, we proposed BIPV system functioned as solar collector which can substitute active system. As an fundamental stage, heat balance equation in steady-state by Fortran was used not only, in winter for pre-heating effect and electric power capacity during the day, but also in summer, for the latter during the day and sky radiation effect during the night. Especially, we should have considered shading on PV by IES Suncast, since even a little bit of it makes the efficiency too low for the PV modules to work. As a result, in summer day, the PV panel should be tiled in 70 degrees to gain the most electric power. Moreover, we could verify that this model makes higher temperature and heat flux under 0.02 m/s. On the other hand, the PV had the high efficiency with high velocity because of cooling effect behind the PV. Therefore, we should regard the air current distribution later on.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.341-343
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• 2015

We present an analysis of the relation between star-formation (SF) and accretion luminosities of local type-2 active galactic nuclei (AGNs) at $0.01{\leq}z<0.22$. We match type-2 AGNs found in the Sloan Digital Sky Survey to current far-infrared (FIR) survey catalogues based on AKARI and Herschel. Estimating AGN luminosities from [$O{\small{III}}$]${\lambda}5007$ and [$O{\small{I}}$]${\lambda}6300$ emission lines, we find a positive linear trend between FIR and AGN luminosities over a wide dynamical range. This result appears to be inconsistent with recent reports that low-luminosity AGNs show no correlation between FIR and X-ray luminosities; this contradiction is likely due to Malmquist and sample selection biases. Moreover, we also find that pure-AGN candidates, for which the FIR radiation is thought to be AGN-dominated, show significant low-SF activities. These AGNs hosted by low-SF galaxies are rare in our sample. However, it is possible that the low fraction of low-SF AGN is caused by observational limitations, as recent FIR surveys are not sufficient to examine the population of high-luminosity AGNs hosted by low-SF galaxies.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.953-958
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• 2006

Perimeter zone has been reinforced by active systems, such as fan-coil units, because it causes an increase in heating and cooling loads, dew condensation in winter, or discomfort with cold-draft to residents in buildings, through poor insulation by light-weighed skin due to progressing multi-storied buildings and skyscrapers. However, because these active systems raise Its capacity so that fossil fuel is used as much as they are added, and ultimately, greenhouse effect is urged, we proposed BIPV system functioned as solar collector which can substitute active system. As an early stage, heat balance equation in steady-state by Fortran was used not only for pre-heating effect and electric power capacity during the day in winter, but also for electric power capacity during day in slimmer and sky radiation effect during night in summer. Especially, we should have considered shading on PV, since even a little bit of it makes the efficiency too low for the PV to work. Still, when the flux of pre-heated air was increased to make air-barrier, its temperature was not enough to make it because the speed of heat exchange was too fast to warm up the air, thus the capacity to meet the condition was evaluated, and electric power from PV was made used for it.

• Journal of the Korean Solar Energy Society
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• v.35 no.2
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• pp.73-83
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• 2015

When it comes to these buildings for business use, cooling load during summertime was reported to have great importance which, as a result, impressively increased interest in Solar Heat Gain Coefficient (SHGC). Such SHGC is considered to be lowered with the help of colors and functions of glass itself, internal shading devices, insulation films and others but basically, these external shading devices for initial blocking that would not allow solar heat to come in from outside the buildings are determined to be most effective. Of many different external shading devices, this thesis conducted an analysis on Exterior Venetian Blind. As for vertical shading devices, previous researches already calculated SHGC conveniently using concepts of sky-opening ratios. However in terms of the Venetian Blind, such correlation is not possibly applied. In light of that, in order to extract a valid correlation, this study first introduced a concept called shape factor, which would use the breadth and a space of a shade, before carrying out the analysis. As a consequence, the concept helped this study to find a very similar correlation. Results of the analysis are summarized as follows. (1) Regarding SHGC depending on the surface reflectance of a shade, an average of 2% error is observed and yet, the figure can always be ignored when it comes to a simple calculation. (2) As for SHGC of each bearing, this study noticed deviations of 4% or less and in the end, it is confirmed that extraction can be achieved with no more than one correlation formula. (3) When only the shape factor and nothing else is used for finding a correlation formula, the formula with a deviation of approximately 5% or less is what one would expect. (4) Since the study observed slight differences in bearings depending on ranges of the shape factors, it needed to extract a weighted value of each bearing, and learned that the smaller the shape factor, the wider the range of a weighted value. The study now suggests that a follow-up research to extract a simple calculation formula by dealing with all these various inclined angles of shade, solar radiation conditions of each region (the ratio of diffuse radiation to direct radiation and others) as well as seasonal features should be carried out.

• Journal of the Korean earth science society
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• v.36 no.4
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• pp.330-340
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• 2015

For this study, we developed an algorithm to estimate the total amount of clouds using sky image data from the Skyviewer equipped with CCD camera. Total cloud amount is estimated by removing mask areas of RGB (Red Green Blue) images, classifying images according to frequency distribution of GBR (Green Blue Ratio), and extracting cloud pixels from them by deciding RBR (Red Blue Ratio) threshold. Total cloud amount is also estimated by validity checks after removing sunlight area from those classified cloud pixels. In order to verify the accuracy of the algorithm that estimates total cloud amount, the research analyzed Bias, RMSE, and correlation coefficient compared to records of total cloud amount earned by human observation from the Gangwon Regional Meteorological Administration, which is in the closest vicinity of the observation site. The cases are selected four daily data from 0800 LST to 1700 LST for each season. The results of analysis showed that the Bias in total cloud amount estimated by the Skyviewer was an average of -0.8 tenth, and the RMSE was 1.6 tenths, indicating the difference in total cloud amount within 2 tenths. Also, correlation coefficient was very high, marking an average of over 0.91 in all cases, despite the distance between the two observation sites (about 4 km).

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.213-216
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• 2012

We have collected dozens of mid-infrared spectra showing UIR bands from diffuse Galactic emitting regions with the AKARI's Infrared Camera (IRC) onboard AKARI, as part of the ISMGN Mission Program. The datasets cover various directions in the inner Galactic Plane ($|l|$ < 70 deg), in the outer Galactic Plane ($|l|$ > 70 deg), and in the off-Plane ($|b|$ > 2 deg). The variations in the UIR band ratios are examined in terms of the radiation environments judged from the far-infrared ($50-170{\mu}m$) spectral energy distribution (SED) made with AKARI/FIS All Sky Survey data at each slit position where mid-IR spectra were obtained. We have found that the band ratios of $6.2{\mu}m/11.2{\mu}m$ and $7.7{\mu}m/11.2{\mu}m$ toward the inner Galaxy are systematically higher than those toward the outer Galaxy and off the Galactic plane. Likely causes of the variations in properties of UIR bands in diffuse emission on a Galactic scale are discussed in this paper.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.32.3-33
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• 2015

There exist scaling relations that link the mass of supermassive black holes with both the velocity dispersion and the mass of the central stellar cusp of their host galaxies. This implies that these two components grow in tandem. Feedback from actively accreting supermassive black holes (AGN), in the form of multi-phase gas outflows, has been argued to be the agent of this co-evolution. Here we employ the powerful GMOS integral field spectroscopy unit on the 8.2m Gemini-North telescope to investigate ionized gas outflows of luminous Type 2 AGN in the local Universe (z<0.1). Our sample of 6 galaxies is drawn from the Sloan Digital Sky Survey (SDSS) and was selected based on their [OIII] dust-corrected luminosity (>1042 erg/s) and signatures of outflows in the [OIII] line profile of their spatially integrated SDSS spectra. These are arguably the best candidates to explore AGN feedback in action since they are < 1% of a large local type 2 AGN SDSS sample selected based on their [OIII] kinematics. We combine a careful spectral decomposition of the [OIII] and $H{\alpha}$ line profiles with spatial information on ~0.5kpc scales to understand the outflow kinematics and energetics in these objects. We find clear evidence for strong outflows in [OIII] and occasionally $H{\alpha}$ that are clearly driven by the ionizing radiation of the AGN. We kinematically and spatially decompose outflowing and rotating ionized gas components. We find [OIII] to be a better tracer of AGN outflows, while $H{\alpha}$ appears to be strongly affected by both stellar rotation and outflows induced by ongoing star formation. The observed kinematics and spatial distribution of the ionized gas imply a large opening angle for the outflow. Finally, we find the projected outflow velocity to decrease as a function of distance, while its dispersion shows a more complex structure with a potentially initially increasing trend (out to 0.5-1kpc distances).