• Proceedings of the KSRS Conference
• /
• 2009.03a
• /
• pp.227-236
• /
• 2009

This study investigates the characteristics of cloud top brightness temperature (CTBT) of WV and IR1 from MTSAT-1R when lightning strikes in South Korea. For temporal and spatial collocations, lightnings, occurred only within ${\pm}5$ minutes from the six minutes added official satellite observation time (e.g., not 0600 UTC but 0606 UTC, considering the real scan time over South Korea), were selected. And the CTBTs corresponding to lightning spots were determined using the nearest pixel within 5 km. The brightness temperature difference (BTD, defined as WV - IR1) between two channels is negatively large when no lightning occurrs, whereas it increases up to positive values (sometimes, +5 K) and the largest frequency distributes around 225 K and 205 K in lightning cases. The probablistic approach for lightning frequency forecast, presented by Machado et al. (2008) in Southern America, was applied over South Korea and new exponential equations, with high coefficients of determination around 0.95 to 0.99, were developed using two channels' BTDs when lightning strikes. Moreover, a case study on 10th June, 2006, the largest number of lightning occurred between 2002 and 2006, was made. The major finding is that lightning activity is closely related to the dramatic decreases in BT and the increases in BTD (esp., equal to or larger than 0 K). Lightning frequency increases exponentially when BTD increases up to 0 K. Therefore, lightning forecast skill will be improved when the integrated strategy (synoptic background and satellite-based CTBT and BTD) is applied. It is believed that this study contributes to the application of the Korean first geostationary satellite (COMS), scheduled to launch at the end of this year, to severe weather detections.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.30 no.2
• /
• pp.188-202
• /
• 1997

The seasonal variability of the sea surface winds over the last Sea of Korea (Japan Sea) is investigated by means of empirical orthogonal function (EOF) analysis. The combined representation of fields of three climatic variables by empirical orthogonal functions is discussed. The eigenvectors are derived from daily sea level pressure, wind speed and 10-day mean sea surface temperature (SST) during 15 years $(1978\~1992)$. The spatial patterns of the mean pressure are characterized by the high pressure in the western part and the low pressure in the eastern part. The spatial distribution of the standard deviation (SD) of pressure are characterized by max SD of 6.6 mb near the Vladivostok, and minima along the coast of the Japan. In Vladivostok, the maxima of SD of SST and south-north wind (WV) were also occurred. The representation of fields of individual meteorological variables by EOF shows that the first mode of the west-east wind (WU) explain over $47.3\%$ of the variance and the second mode of WU represents $30\%$. Especially, the first mode of the WV explain $70.9\%$ of the variance and their time series coefficients show 1-cpy, 0.5-cpy frequency spectrum. The spatial distribution of the first mode eigenvectors of SST are characterized by maximum near Vladivostok. The combined representation of fields of several variables (pressure, wind, SST) reveals that the first mode magnitudes of the variance of the combined eigenvectors (WU-PR) are increased. By means of this result, the 1-year peak and the 6-months peak are remarkable. In the three combined patterns (wind, pressure, SST), the second mode of the eigenvector (wind) is affected by the SST. Their time coefficients of the first mode show noticeable 1-year peak. The spectral analysis of the second mode shows broad seasonal signal with the period of 4-months and a significant peak of variability at 3-month period.

• Journal of Korean Society of Steel Construction
• /
• v.10 no.3 s.36
• /
• pp.537-551
• /
• 1998

The intention of this paper is to provide realistic values of design thermal loads applicable to composite box girder bridges on the basis of the statistical analysis of long-term measured temperature data. For this purpose, temperatures were recorded at a newly constructed composite box girder bridge during about 20 months. Before analyzing the extreme values, major thermal loading parameters that characterize the temperature profile are defined, and a seasonal behavior of those is examined in detail. The limit distributions of the thermal loading parameters are then determined by the tail-equivalence method, and the thermal loading parameters corresponding to selected return period are calculated. Finally, the results are compared to the specifications suggested in a current design code for thermal loads, and it is concluded that the current design code is unsuitable for representing the self-equilibrated thermal stresses in composite bridges, and the horizontal temperature difference which is not suggested in current design code should be taken Into account in particular cases.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.04a
• /
• pp.157-163
• /
• 2011

Combustion of magnesium dust particle were fabricated test devices and combustion experiments were carried out. The ignition delay time were measured in change of magnesium particle mass flow rate in premixed flame. According to increasing magnesium particle mass flow rate, ignition delay time were more shorter. In addition, magnesium dust combustion temperature were measured different particle sizes and o/f ratio by two wavelength pyrometry. Dust combustion flame temperature is almost similarly, through to equivalence ratio, confirm the combustion flame temperature range characteristics.

• Journal of the Korean earth science society
• /
• v.35 no.1
• /
• pp.54-68
• /
• 2014

In order to analyze the land surface properties in Seoul and its surrounding metropolitan area, several indices and land surface temperature were calculated by the Landsat satellites (e.g., Landsat 5, Landsat 7, and Landsat 8). The Landsat data came from only in the fall season with Landsat 5 on October 21, 1985, Landsat 7 on September 29, 2003, and Landsat 8 on September 16, 2013. The land surface properties used are the indices that represented Soil Adjusted Vegetation Index (SAVI), Modified Normalized Difference Wetness Index (MNDWI), Normalized Difference Wetness Index (NDWI), Tasseled cap Brightness, Tasseled cap Greenness, Tasseled cap Wetness Index, Normalized Difference Vegetation Index (NDVI) and Normalized Difference Built-up Index (NDBI) and the land surface temperature of the area in and around Seoul. Most indices distinguish very well between urban, rural, mountain, building, river and road. In particular, most of the urbanization is represented in the new city (e.g., Ilsan) around Seoul. According to NDVI, NDBI and land surface temperature, urban expansion is displayed in the surrounding area of Seoul. The land surface temperature and surface elevation have a strong relationship with the distribution and structure of the vegetation/built-up indices such as NDVI and NDBI. While the NDVI is positively correlated with the land surface temperature and is also negatively correlated with the surface elevation, the NDBI have just the opposite correlations, respectively. The NDVI and NDBI index is closely associated with the characteristics of the metropolitan area. Landsat 8 and Landsat 5 have very strong correlations (more than -0.6) but Landsat 7 has a weak one (lower than -0.5).

• Proceedings of the KSRS Conference
• /
• 2006.03a
• /
• pp.240-245
• /
• 2006

오늘날 도시인구집중화 현상에 따른 대규모 도시개발과 도시역의 확대로 지표면의 피복 변화가 극심하게 이루어지고 있는 한편 이러한 현상으로 인해 도시의 내 외적 경관변화 뿐만 아니라 지형 및 기온상승, 바람장의 변화 등 복합적인 국지기후 변화를 초래하게 되었다. 본 연구에서는 이러한 도시의 기후 변화에 따라 청계천 복원 전의 도시 지표 열 환경 특성을 분석을 수행하고자 한다 도시지역의 열환경 분석을 위하여 기존에는 주로 Landsat TM/ETM+ 위성영상 자료를 사용하였으나 2003년 5월 위성 센서의 고장으로 위성영상 자료의 사용이 불가피하게 되었다. 이에 대체 방안으로 ASTER 영상 열적외 센서에서 취득한 지표온도 값과 현장에서 취득한 AWS자료와의 상관성 분석을 실시하였으며, 이를 기반으로 청계천 주변의 근접성 분석 및 토지이용별 지표온도 분포 패턴 등 도시 열 환경 변화 탐지 및 분석을 위하여 GIS 및 RS 분석을 실시하였다.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.21 no.5
• /
• pp.29-36
• /
• 2017

In this study, a numerical analysis is made of the fluid flow and heat transfer characteristics in the solar arrays of HALE (High Altitude Lond Endurance) UAV. In the stratosphere where UAV operates, high level solar radiation is induced, heat transfer decreases due to natural convection and forced convection is dominated by ambient flow. In order to predict the solar array temperature range in this environment condition, the conjugate heat transfer analysis was carried out for the solar arrays on the main wing. The investigation focused on the temperature distribution of solar array and heat transfer characteristics according to influence of solar energy, flight condition as vehicle speed, air density, temperature.

• Polymer(Korea)
• /
• v.28 no.6
• /
• pp.487-493
• /
• 2004

The distribution of particles, in the mixture of poly(ethyl acrylate-co-t-butyl acrylate) (PEB) emulsion polymer and silica nanoparticles, was determined mainly depending on the pH of the mixture. The weak interfacial interaction was responsible for the severe coagulation of silica particles and the irregular dispersion for these nanocomposites. Methacryloxypropyltrimethoxysilane (MPS) was used to modify both the polymer and the silica. The nanocomposites which were prepared with these modified components had finer dispersion of silica nanoparticles and core-shell morphology due to the strong interfacial interaction. The strong hydrogen bonds were identified for these nanocomposites with FT-IR. The nanocomposites having strong interfacial interaction showed the increased glass transition temperature, the decreased ΔC$_{p}$ , and the increased decomposition temperature of the polymer chains. polymer chains.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.6
• /
• pp.1205-1215
• /
• 1992

The solidification rate is of special importance in determining the casting structures and properties. The heat transfer characteristics at the interface between the mold and the casting is one of the major factors that control the solidification rate. The thermal resistance exists due to the air-gap formation at the mold/casting interface during the freezing process. In this study two-dimensional Stefan problem with air-gap resistance in the rectangular mold is considered and the heat transfer characteristics is numerically examined by using the enthalpy method. The effects of the major parameters, such as mold geometry, thermal conductivity, heat transfer coefficient, and initial temperature of casting, on the thermal characteristics are investigated.

• Fire Science and Engineering
• /
• v.17 no.1
• /
• pp.62-67
• /
• 2003

The full-scale compartment fire tests were carried out to evaluate the characteristics of fire resistance of window material under actual fire conditions. The room size used for full-scale room fire tests was 4 by 3.8 m with 2.4 m high ceiling. The windows with PVC, Aluminum and AL+Wood frame materials were established, sofa and mattress were used as fire sources. The window contained pair glasses with the air between 6 mm glasses. Temperatures at total 32 points in the room were measured to find the temperature distribution in the room fire. It is examined that thermal effects on window frame materials such as charring, distortion, melting, structural collapse, and other effects.