• 한국구조물진단유지관리공학회 논문집
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• 제12권4호
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• pp.115-122
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• 2008

본 연구는 화재시 고강도 콘크리트의 폭렬발생에 대한 영향요인을 검토한 것으로써, 폭렬에 직접적인 상관관계에 있는 물-결합재비, 공기량 및 함수율 등을 PP섬유의 혼입률과 함께 변화시켜 실험을 실시하였다. 실험결과 유동특성은 섬유의 혼입률이 0.05 vol.% 증가함에 따라 약 11%정도 감소하는 것으로 나타났고, 공기량이 10%인 경우는 다량의 AE제 사용에 기인하여 섬유의 혼입률과 상관없이 거의 유사한 유동성을 나타냈다. 강도특성으로는 W/B 15, 25 및 35%일 경우 100, 80 및 60 MPa이상으로써 고강도 범위로 나타났으며, 공기량 변수의 경우는 H-air가 L-air에 비해 약 1/2배 정도로 낮게 나타났다. 폭렬특성으로는 KS F 2257-1에 규정되어 있는 표준가열곡선에 의해 1시간 내화시험을 실시한 결과, W/B는 고강도로 W/B가 낮을수록 심하게 발생하는데, 15%를 제외한 모든 경우에서 전반적으로 PP섬유의 혼입률 0.10 vol.%에서 폭렬이 방지되는 것으로 나타났고, 공기량을 10%로 많이 함유하는 시험체와 완전건조 시킨 시험체는 0.05 vol.% 혼입시에도 폭렬현상이 발생하지 않는 것으로 나타났다.

• Journal of Biosystems Engineering
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• 제5권1호
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• pp.15-23
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• 1980

Natural-air drying systems have been extensively used for cereal grains, and many researches on the systems have been conducted in foreign countries. However, little research on drying rough rice with natural air has been done. Especially . little research on natural air drying of rough rice based on weather data has been done in Korean. The objective of this study was to present fundamental data for estimating optimum requirements and basic information available for natural air drying of rough rice based on the weather data . The weather data analyzed in this study were the 10-year (1969 to 1978) record of air temperatures, wet-bulb temperatures and relative humidities, which were three-hourly observations in Taegu area. The results of this study are summarized as follows ; 1 From the results of weather data analysis the average air temperature was about $14.8^\circ$and the average relative humidty 67.5% . Average equilibrium moisture content appeared to be 13.8 percent on wet basis, which showed great potential for natural air drying in Taegue area in October. 2. Possible fan operation time based on the equilibrium moisture content of 15% on wet basis was about 14 hours a day during October in Taegu area. Probabilities of possible drying days based on minimum time available for drying in a day were analyzed. 3. Minimum air flow requirements based on the worst year were determined for different fan operation methods and initial moisture contents.

• 한국연소학회지
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• 제20권2호
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• pp.40-45
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• 2015

This study is aimed to study combustion characteristics of low $NO_X$ burner using petroleum cokes as fuel. The petroleum coke, which is produced through the oil refining process, is an attractive fuel in terms of its high heating value and relatively low price. But petroleum coke is a challenging fuel because of its low volatile content, high sulfur and nitrogen content, which give rise to undesirable emission characteristics and low ignitability. The petroleum cokes burner is operated at fuel rich condition, and overfire air are supplied to achieve fuel lean condition. The low $NO_X$ burner is designed to control fuel and air mixing to achieve air staged combustion, in addition secondary and tertiary air are supplied through swirler. Air distribution ratio of triple staged air are optimized experimentally. The result showed that $NO_X$ concentration is lowest when overfire air is used, and the burner function at a fuel rich condition.

• Preventive Nutrition and Food Science
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• 제16권2호
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• pp.189-193
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• 2011

Kohlrabi (Brassica oleracea var. gongylodes L.) slices were dehydrated with maltodextrin (MD) at concentrations of 20, 30, and 40% (w/w), and the dried samples were compared with the freeze-dried and hot-air dried samples regarding various physicochemical qualities. The MD-treated samples had better results than those of freeze-dried or hot-air dried samples in terms of rehydration ratio and color. The total phenolic content of the MD-treated sample was similar to that of the freeze-dried and higher than that of hot-air dried sample. The ascorbic acid content of the MD-treated samples was also higher than that of the hot-air dried one. These results suggest that kohlrabi can be dehydrated with MD instead of hot air.

• 한국환경보건학회지
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• 제10권2호
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• pp.69-77
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• 1984

Air pollution has been one of the severe problems in city area. Sulfur dioxide is the major pollutant among the air pollutants. And the lichen as a botanical indicator have been used to predict the air pollution level. This study was carried out to evaluate the air pollution level in Taejon area through the field survey which were checked lichen status and sulfur dioxide content in the atmosphere. The results were as follows 1. The average sulfur dioxide content in Taejon area was 0.031ppm. The comparison of measurement methods were regression equation, Y= 0.357$\times$+0.014 and correlation factor, r = 0.771. 2. The maximum point of the SO$_2$ level was site No. 2(Daehwa-Dong), 0.087 ppm and the minimum, site No. 8 (Doma 2-Dong), 0.009ppm. 3. Total amounts of sulfur dioxide yearly emitted from Taejon area by fuel consumption estimated 29829.6 tons. 4. The relationship between degree of lichen and sulfur dioxide contents were 0.000~0.020ppm : Zone No. 2 0.020~0.060ppm : Zone No. 1 over 0.060ppm : Zone No. 0

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.886-895
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• 1993

Experimental were conducted to obtain information on the effect of airflow rates and bed depths on the resistance of coffee cherries and coffee beans available locally (Coffea Liberica). The airflow used were in the range of 0.06 to 0.6 cu. m/s-sq.m. The moisture content of the coffee cherries ranged from 10 % to 50% (wet basis) and that of coffee beans ranged from 12% to 30% )wet basis). Two methods of filling were used i.e. loose fill and packed fill. Pressure drops across the material bed in a vertical column were measured at several depths using inclined manometer. The pressure drop increased directly with air flow rate as well as bed depths. The effects of air flowrates and moisture contents on the resistance in terms of pressure drip per unit bed depth were analysed. The pressure drop per unit depth across the material bed varied slightly due to different depth. The resistance to airflow decreased with the increase in moisture content for loose fill. However, the effect of moisture content is not apparent for packed fill.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2001년도 학술논문발표회
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• pp.76-81
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• 2001

Recently, the structure is higher and larger, so that the application of high-strength concrete is increased, And as the development of construction skills, it is possible to place during the winter. Concrete work during winter is indispensible to shorten time of completion and cut costs. When concrete work during winter is placed, it has anxiety that concrete freeze at low temperature. As repetition of concrete's freezing cause reduction of durability, it is necessary for mixing to pay attention to air content and W/C ratios. Accordingly, in this study, we estimate the frost resistance by air content and W/C ratios, and development of strength after early-frost damage in the high-strength concrete during the cold weather. In this study, it could be confirmed that factors which were air content, W/C ratios and early curing period, affected on the frost resistance.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.631-634
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• 2005

This paper discussed the influence of addition of aqueous additives such as various beverage and detergent on the properties of concrete during placement by workmen's mistake. Slump and air content were not highly affected by the addition of aqueous additives, while addition of detergent led to an remarkable increase in air content due to interfacial activated ingredient in detergent. For setting time, lactic-acid fermented milk exhibited a longest setting delay and in order of coffee and soda. Concrete containing setting retarding beverage had higher compressive strength than control concrete at 7 and 28days. Concrete containing detergent exhibited strength loss due to the presence of larger amount of air content.

• 산업기술연구
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• 제33권A호
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• pp.93-99
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• 2013

Shotcrete has been referred to as gunite, pneumatically applied mortar or concrete, sprayed concrete or mortar. There are sound reasons why sprayed mortar is one of the best portland cement based material for repairing old concrete structures. However, it is difficult to find the research results on the latex-modified mortar nevertheless on the impact of air onto the fresh and hardened properties of latex-modified mortar. So, the main experimental program included strength test, slump test, rapid chloride permeability test, image analysis for air void system, and chemical attacks with the main experimental variables of latex content, fine aggregate content, water-cement ratio, and air foamer content.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2005년도 추계 학술논문 발표대회
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• pp.85-88
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• 2005

This study investigates influence on concrete adding beverage or detergent, by work man's mistakes during concrete placement in field. Overall, concrete adding beverage or detergent does not affect slump and air content, compared with control concrete. However concrete adding detergent resulted in significantly higher air content, due to inter facial activation ingredient. For the properties of setting time, concrete adding lactic acid beverage indicated the longest retarding properties, next was coffee and soft drink in order. Compressive strength of concrete, which retarded setting time. exhibited slightly improved value at 7 and 28 days respectively, while that of concrete adding detergent significantly decreased, due to higher air content.