• 한국주거학회:학술대회논문집
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• 한국주거학회 2009년 춘계학술발표대회 논문집
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• pp.316-320
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• 2009

Recently, concerns about conserving proper size of urban green spaces and accessibility are increasing, regarding it as a solution to diverse urban environmental problems including pollution, ecosystem deterioration, urban climate change. Artificial ground greening such as green roofs is regarded as the only alternative that can conserve green spaces which are impossible to be secured on the ground. However, green roofs are not popularized yet and levels are very low in provincial cities despite of related technology development and support systems of related agencies. Based on the background, this study tries to present a theoretical basis of methods for green roofs, conducting green roof simulations and collecting ideas about problems and improving measures from green roof users. Finally, it aims to offer base data which help establish policy direction for activation of green roof technology. As a result of a simulation for verifying temperature reduction effect, it was possible to affirm effect of a plot that green roofs applied. Especially, it was revealed that a green roof method using ground covers such as mixed planting was the most effective way to reduce temperature. Activation methods for green roofs based on this study are as follows: First, it is a priority to readjust systems related to green roofs. Second, citizens' active and voluntary participation must be attained. Third, it is required to establish detailed promotion procedures which aim at actual conduct and to maintain an expert department which is able to manage and control the establishment. After conduct, continuous aftercare stages are also needed.

• 한국세라믹학회지
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• 제50권6호
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• pp.402-409
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• 2013

The objective of this study was to develop a synthesis process for ${\beta}$-SiC powders to reduce the synthesis temperature and to control the particle size and to prevent particle agglomeration of the synthesized ${\beta}$-SiC powders. A phenol resin and TEOS were used as the starting materials for the carbon and Si sources, respectively. $SiO_2$-C hybrid precursors with various C/Si mole ratios were fabricated using a conventional sol-gel process. ${\beta}$-SiC powders were synthesized by a carbothermal reduction process using $SiO_2$-C hybrid precursors with various C/Si mole ratios (1.6 ~ 2.5) fabricated using a sol-gel process. In this study, the effects of excess carbon and the addition of Si powders to the $SiO_2$-C hybrid precursor on the synthesis temperature and particle size of ${\beta}$-SiC were examined. It was found that the addition of metallic Si powders to the $SiO_2$/C hybrid precursor with excess carbon reduced the synthesis temperature of the ${\beta}$-SiC powders to as low as $1300^{\circ}C$. The synthesis temperature for ${\beta}$-SiC appeared to be reduced with an increase of the C/Si mole ratio in the $SiO_2$-C hybrid precursor by a direct carburization reaction between Si and excess carbon.

• 한국포장학회지
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• 제10권1호
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• pp.1-6
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• 2004

Amount of residual ink solvent on the packaging materials from Korea, Japan and Europe was measured and compared. The amount of packaging materials from Korea was much higher than that of Japan and Europe. To reduce the residual amounts of ink solvent, aging condition of printed packaging materials including aging time and temperature was modified and evaluated. Aging with high temperature and short time ($60^{\circ}C$ and 24 hours) was more effective for reduction of residual amount of ink solvent than that with low temperature and long time. To find out change of reduction pattern of residual amount of solvent according to plastic packaging material, several monolayer and multilayer packaging materials were selected. Among the monolayer packaging materials, the amount of EVOH and PET was lower than that of polyolefin plastic film including PE and PP. PP/EVOH/PET among the selected multilayer film showed the lowest amount of residual ink solvent on food packaging materials. Result of this research revealed that the residual amount of ink solvent can be reduced by proper selection of aging condition with and by appropriate application of mutilayer plastic film.

• 한국결정성장학회지
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• 제27권5호
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• pp.223-228
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• 2017

Aluminum nitride (AlN) powder was successfully synthesized at low temperature via carbothermal reduction and nitridation (CRN) assisted by microwave heating. The synthesis processes of AlN powder were investigated with X-ray diffraction, FE-SEM, FT-IR and TGA/DSC. Aluminum nitrate was used as an oxidizer and aluminum source, urea as fuel, and glucose as carbon source. These starting materials were mixed with D.I water and reacted in a flask at $100^{\circ}C$ for 20 minutes. After the reaction was finished, black foamy intermediate product was formed, which was considered to be an amorphous $Al_2O_3$ particles through intermediate product obtained by solution combustion synthesis (SCS) at the results of X-ray diffraction patterns and FT-IR. This intermediate product was nitridated at temperatures of $1300^{\circ}C$ and $1400^{\circ}C$ in $N_2$ atmosphere by a microwave heating furnace and then decarbonated at $600^{\circ}C$ for 2 hours in air. It should be noticed from FE-SEM images that as nitridated particles, identified as AlN from X-ray diffraction patterns, are covered with carbon residues. After decarbonating the nitridated powders, the spherical pure AlN powders were obtained without alumina and their particle sizes were dependent on the nitridating temperature with high temperature of $1400^{\circ}C$ giving large particles of around 70~100 nm.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.2094-2099
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• 2004

An experimental study on heat transfer characteristics near the critical pressure has been performed with an internally-heated vertical annular channel cooled by R-134a fluid. Two series of tests have been completed: (a) steady-state critical heat flux (CHF) and (b) heat transfer tests for pressure reduction transients through the critical pressure. In the present experimental range, the steady-state CHF decreases with the increase of the system pressure For a fixed inlet mass flux and subcooling, the CHF falls sharply at about 3.8 MPa and shows a trend toward converging to zero as the pressure approaches the critical point of 4.059 MPa. The CHF phenomenon near the critical pressure does not lead to an abrupt temperature rise of the heated wall because the CHF occurred at remarkably low power levels. In the pressure reduction transient experiments, as soon as the pressure passed through the critical pressure, the wall temperatures rise rapidly up to a very high value due to the occurrence of the departure from nucleate boiling. The wall temperature reaches a maximum at the saturation point of the outlet temperature, then tends to decrease gradually.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 춘계 학술논문 발표대회 1부
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• pp.83-85
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• 2011

This study investigated the results of insulation heat curing method using double layer bubble sheet in concrete in cold weather environment. First of all, when double bubble sheets are applied, it was shown that concrete was protected from early freezing by remaining between 7℃ and 3℃ even in case outside temperature drops -7℃ below zero until the 3d day from piling. The insulation heat preservation curing method using the double bubble sheet applied in this field prevented early freezing owing to stable curing temperature management, deterring concrete strength development delay at low temperature, and obtained the needed strength. Also, it was proven that the method is highly effective and economic for cold weather concrete quality maintenance through curing cost reduction like construction period shortening and labor cost reduction, etc by reducing the process of temporary equipment installation and disassembling.

• Nuclear Engineering and Technology
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• 제36권5호
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• pp.403-414
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• 2004

An experimental study of heat transfer characteristics near the critical pressure has been performed with an internally-heated vertical annular channel cooled by R-134a fluid. Two series of tests have been completed: (a) steady-state critical heat flux (CHF) tests, and (b) heat transfer tests for pressure reduction transients through the critical pressure. In the present experimental range, the steady-state CHF decreases with increase of the system pressure for fixed inlet mass flux and subcooling. The CHF falls sharply at about 3.8 MPa and shows a trend towards converging to zero as the pressure approaches the critical point of 4.059 MPa. The CHF phenomenon near the critical pressure does not lead to an abrupt temperature rise of the heated wall, because the CHF occurs at remarkably low power levels. In the pressure reduction transients, as soon as the pressure passes below the critical pressure from the supercritical pressure, the wall temperatures rise rapidly up to very high values due to the departure from nucleate boiling. The wall temperature reaches a maximum at the saturation point of the outlet temperature, and then tends to decrease gradually.

• 한국연소학회지
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• 제4권1호
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• pp.67-83
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• 1999

The objective of this study is development of low emission pulverized coal combustor for reducing pollutant emission generated from coal combustion. Low emission combustion technology for reducing NOx and fly ash was investigated by using 2 stage coaxial cyclone combustor. Staged combustion was employed for NOx reduction and high temperature slagging combustion was also studied for fly ash removal in the combustor. The result of this study shows that the low emission combustion system can reduce the amount of atmospheric pollutions with improved boiler efficiency and performance.

• Journal of Advanced Marine Engineering and Technology
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• 제29권6호
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• pp.628-636
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• 2005

In this paper. the effects of a WI(Water Injection) in the intake pipe for a 4-cylinder Dl(Direct Injection) diesel engine are investigated experimentally, The WI system was controlled by the duty cycle from the intake manifold's temperature and MAF(Manifold Air Flow) First. effect of EGR on NOx reduction was investigated. Then WI system was applied to reduce NOx As the results. we can make the NOx map and visualize the NOx results by variation of engine speed and engine load It was known that effect of WI system on NOx reduction without the EGR was better than the with EGR base engine except of low load and speed condition.

• Membrane and Water Treatment
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• 제10권1호
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• pp.39-44
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• 2019

LID facilities do not consider environmental factors, and due to inappropriate vegetation planting causing degradation in efficiency due to plant damage and difficulty in maintenance. Therefore, in this study, assessment of impact environmental factor by seasonal variation of chlorophyll and growth of vegetation planted in LID technologies and change of pollutant reduction were conducted. In the case of B-SJ and B-RI, growth rate decreased after summer (August), and B-MG showed steady growth until autumn (September). Chlorophyll was found to increase during spring season while it decreased during autumn season. The chlorophyll concentration was found to affect the plant growth pattern. TN reduction efficiency was highest with greater than 80% efficiency in summer, and it was analyzed that plants were identified as the main factor affecting the seasonal reduction efficiency of TN. Also, temperature and relative humidity were analyzed to affect plant growth, activity and pollutant removal efficiency. Plant type and growth pattern are considered as factors to be considered in selection of appropriate plant types in LID technologies.