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The characteristics of boiling heat transfer were experimentally investigated for carbon dioxide with nitrogen impurities. The experimental setup was composed of a test section, a condensation section for the liquefaction of carbon dioxide before entering the pump, and a heating section for controlling the temperature of the entrance of the test unit. The test section was comprised of a double tube heat exchanger. A copper tube with a length of 4 m and a 1/2-inch diameter was located inside and the PVC pipe used for heating was outside. T-type thermocouples were installed in the annulus space of the test section to measure the brine temperature in the PVC and the surfaces of the copper tube. The experiment was performed under a mass flux of 200~700 kg·m<SUP>-2</SUP>s<SUP>-1</SUP> at a nitrogen concentration of 1.0~5.0 mol% and 0.1~0.9 of vapor quality. The boiling heat transfer coefficient of carbon dioxide with impurities decreased by an average of 14.7% compared to pure carbon dioxide.
The typical characteristics of seasonal winds were studied around the Pohang using two-stage (average linkage then k-means) clustering technique based on u- and v-component wind at 850 hpa from 2004 to 2006 (obtained the Pohang station) and a high-resolution (0.5 km grid for the finest domain) WRF-UCM model along with an up-to-date detailed land use data during the most predominant pattern in each season. The clustering analysis identified statistically distinct wind patterns (7, 4, 5, and 3 clusters) representing each spring, summer, fall, and winter. During the spring, the prevailed pattern (80 days) showed weak upper northwesterly flow and late sea-breeze. Especially at night, land-breeze developed along the shoreline was converged around Yeongil Bay. The representative pattern (92 days) in summer was weak upper southerly flow and intensified sea-breeze combined with sea surface wind. In addition, convergence zone between the large scale background flow and well-developed land-breeze was transported around inland (industrial and residential areas). The predominant wind distribution (94 days) in fall was similar to that of spring showing weak upper-level flow and distinct sea-land breeze circulation. On the other hand, the wind pattern (117 days) of high frequency in winter showed upper northwesterly and surface westerly flows, which was no change in daily wind direction.
The MM5, RAMS and WRF, meteorological models have provided the dynamical parameters as inputs to air quality model. A major content of this study is that significant characteristics of three models for high-ozone occurrence analyze for surface wind and air temperature fields and compare with observation data in Seoul metropolitan area. An analysis of air temperature field revealed that location of core in high temperature of MM5 and WRF differed from that of RAMS. MM5 and WRF indicated high temperature in Seoul but RAMS represented it on the outskirts of Seoul. MM5 and WRF were underestimated maximum temperature during daytime but RAMS simulated similar value with observation data. Surface wind field with three models, it was shown many differences at horizontal distribution of wind direction. RAMS indicated weak wind speed in land and strong sea breeze at coastal areas than MM5 and WRF. However wind speed simulated by three model were overestimated during both daytime and nighttime.
In this study, the effects of high-resolution land cover on the simulation of near-surface meteorological fields were evaluated in two different coastal regions using Weather Research and Forecasting (WRF) model. These analyses were performed using the middle classification land cover data upgraded by the Korean Ministry of Environment (KME). For the purpose of this study, two coastal areas were selected as follows: (1) the southwestern coastal (SWC) region characterized by complex shoreline and (2) the eastern coastal (EC) region described a high mountain and a simple coastline. The result showed that the application of high-resolution land cover were found to be notably distinguished between the SWC and EC regions. The land cover improvement has contributed to generate the realistic complex coastline and the distribution of small islands in the SWC region and the expansion of urban and built-up land along the sea front in the EC region, respectively. The model study indicated that the improvement of land cover caused a temperature change on wide areas of inland and nearby sea for the SWC region, and narrow areas along the coastal line for the EC region. These temperature variations in the two regions resulted in a decrease and an increase in land-breeze and sea-breeze intensity, respectively (especially the SWC region). Interestingly, the improvement of land cover can contribute large enough to change wind distributions over the sea in coastal areas.
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본 연구는 제조업의 혁신성과 창출을 위해 혁신활동에 있어 중소기업의 혁신성과에 정보원천의 영향요인을 살펴보고 혁신협력활동에 매개효과를 고찰하였다. 그 결과, 민간서비스업체와 대학 및 고등교육기관에 대해 협력여부가 매개효과를 나타낸 것으로 확인되었다. 특히 민간서비스업체와 대학 및 고등교육기관의 매개효과는 공정혁신과 제품혁신에 있어 상반되는 결과를 나타냈다. 이는 제조 중소기업의 경우에 제품혁신과 공정혁신활동에 있어 대학 및 고등교육기관과 민간서비스를 통한 정보에 대한 혁신협력활동이 유효하다는 것을 보여주는 것으로 중소기업의 혁신활동에서 민간서비스업체와 대학 등의 역할의 중요성을 확인할 수 있었다. This study examined the influence factors of information sources on the innovation performance of SMEs in innovation activities and examined the mediating effect on innovation collaboration activities. As a result, it was confirmed that collaboration between private service companies and higher education institutions had a mediating effect. In particular, the mediating effects of private service companies, universities and higher education institutions are opposite in process innovation and product innovation. This shows that in the case of manufacturing SMEs, innovation collaboration on information through higher education institutions and private service companies is effective in product innovation and fair innovation activities. Therefore, it was confirmed that the role of private service companies and higher education institutions in SMEs innovation activities is important.
정주희 ( Ju Hee Jeong ),오인보 ( In Bo Oh ),강윤희 ( Yoon Hee Kang ),방진희 ( Jin Hee Bang ),안혜연 ( Hye Yeon An ),석현배 ( Hyeon Bae Seok ),김유근 ( Yoo Keun Kim ),홍지형 ( Ji Hyung Hong ),김지영 ( Ji Young Kim ) 한국환경과학회 2016 한국환경과학회지 Vol.25 No.1
In order to improve the prediction of the regional air quality modeling in the Seoul metropolitan area, a sensitivity analysis using two PBL and microphysics (MP) options of the WRF model was performed during four seasons. The results from four sets of the simulation experiments (EXPs) showed that meteorological variables (especially wind field) were highly sensitive to the choice of PBL options (YSU or MYJ) and no significant differences were found depending on MP options (WDM6 or Morrison) regardless of specific time periods, i.e. day and night, during four seasons. Consequently, the EXPs being composed of YSU PBL option were identified to produce better results for meteorological elements (especially wind field) regardless of seasons. On the other hand, the accuracy of all simulations for summer and winter was somewhat lower than those for spring and autumn and the effect according to physics options was highly volatile by geographical characteristics of the observation site.
The evaporating heat transfer characteristics and the pressure drop of carbon dioxide, including impurities, were experimentally measured and compared with the predictions from existing models. The experimental setup consisted of a test section, a condenser, and a heating part. The test section used double-tube type, and the copper tube of 1/2 inch was located inside the PVC pipe. Total length of the test section was 4 meters. The temperature of carbon dioxide was measured by attaching the thermocouple to the test part using soldering. In addition, the temperature of the brine was measured by inserting the T-type thermocouple through the hole in the outer tube in order to measure the brine temperature in the PVC tube. The CO₂ mixture after the test section was condensed by using two plate-type heat exchangers. The impurity of nitrogen concentration was transformed by 1.0~5.0 wt.% under 400~500 kg․m<SUP>-2</SUP>s<SUP>-1</SUP> conditions. The heat transfer coefficients of pure CO₂ and CO₂+N₂ were compared by using the Shrock and Grossman model, the Gungor and Winterton model, and the Yoon et al.’s model. The pressure drops were compared using the Müller-Steinhagen model, the Heck and Chislom models, and the Yoon et al.’s model. The Yoon et al.’s model and the Chislom model showed the best performance when predicting the boiling heat transfer coefficient and pressure drop for the CO₂+N₂ mixture, respectively.