• 한국연소학회지
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• 제7권3호
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• pp.16-22
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• 2002

Combustion performance of an internally cycloned circulating fluidized bed for paper sludge was discussed through a series of batch type experiments. Operation parameters such as water content, feeding mass of sludge and secondary air injection rate were varied to find out the effect on the combustion performance, which was examined with carbon conversion rate and pollutant emission such as CO and NOx. A conventional solid fuel reaction was observed in the experiments of varying water content and feeding mass of the sludge, which is characterized with kinetic limited reaction zone, diffusion limited reaction zone and transition zone. Secondary air injection with swirl enhances the mixing of the gas phase as well as the solid phase, and improves combustion efficiency accompanied with higher carbon conversion rate and lower pollutant emission rate.

• 환경위생공학
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• 제14권2호
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• pp.90-95
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• 1999

The study on the fermented feeds production of garbages have been conducted to determine the optimum operation condition. The process variables considered for this study were initial air flow rate and temperature control. The results showed that optimum air requirement was $4{\ell}-air/min{\cdot}kg-$ garbages on dry weight basis which is equal to $0.8{\ell}-air/min{\cdot}kg-$ garbages on the basis of 80% moisture content. The optimum initial temperature control in the reactor was $40^{\circ}C$. Crude fiber content of fermented final byproducts were higher than feedstuffs standard for pig breeding and consequently final byproducts had to mix with single-component feed.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.383-393
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• 2006

This paper investigates strength characteristics and stress-strain behaviors of geogrid mixing reinforced lightweight soil. The lightweight soil was reinforced with geogrid in order to increase its compressive strength. Test specimens were fabricated by various mixing conditions including cement content, initial water content, air content and geogrid layer and then unconfined compression tests were carried out. From the experimental results, it was found that unconfined compressive strength as well as stress-strain behavior of lightweight soil were strongly influenced by mixing conditions. The more cement content that is added to the mixture, the greater its unconfined compressive strength. However, the more initial water content or the more air foam content, the less its unconfined compressive strength. It was observed that the strength of geogrid reinforced lightweight soil was increased due to reinforcing effect by the geogrid for most cases except cement content less than 20%. In reinforced lightweight soil, secant modulus $(E_{50})$ was increased as the strength increased due to the inclusion of geogrid.

• 유기물자원화
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• 제17권4호
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• pp.103-111
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• 2009

본 연구에서는 퇴비화에서 첨가제로 주로 사용하고 있는 톱밥을 대상으로 수분 혼합방식으로서의 습윤과정과 건조과정에서의 수분함량별 톱밥의 물리적 성상의 변화로 인한 공기투과성의 차이점을 파악하고자 하였다. 수분증가에 따라 겉보기밀도는 증가하며, 공기공극은 감소하였다. 그러나 습윤 및 건조과정에서 동일한 수분함량일지라도 습윤과정의 공기공극이 건조과정에 비하여 높게 나타나고 있어 습윤과정이 퇴비화 매체 내에서의 공기이동에 유리한 물리적 성상을 보이고 있다. 또한 수분이 증가함에 따라 톱밥 입자크기가 커지며, 수분함량 40%부터 60% 구간에서 습윤과정이 건조과정에 비하여 큰 입자를 형성하였다. 또한, 습윤과정에서는 수분이 증가함에 따라 공기공극이 작아짐에도 불구하고 수분함량 60% 정도에서 차감압력이 가장 낮아지고 이후 수분 포화상태에 도달하면 급격히 증가하고 있다. 건조과정에서는 습윤과정과는 다르게 포화상태에서부터 수분이 감소함에 따라 차감압력이 지속적으로 감소하는 경향을 보이고 있다. 퇴비화에서 주로 활용되는 건조기준 수분함량 0.67(습량기준 40%) 이상의 수분함량 구간에서 유입 공기유량이 동일할 경우 습윤과정이 건조과정에 비하여 차감압력이 낮아 공기투과성이 개선되어 있음을 알 수 있다. 또한 동일한 수분함량에서의 차감압력은 유입 공기유량에 비례하여 증가하고 있는 것으로 나타났다. 이러한 실험결과로서, 퇴비화공정에서 매체내의 공기이동성을 원활하게 하기 위하여는 습윤과정이 적절하며 수분함량 60% 정도가 최적의 운영조건이라 판단된다.

• 동력기계공학회지
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• 제15권3호
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• pp.46-51
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• 2011

Low temperature vacuum drying technique, whose drying time and quantity of exhausting energy is about 25~30% of hot air drying, is very excellent in the drying efficiency. This paper is made out in the aspects of heat engineering with the object of developing Korean drying machine which can dry once a large quantity of objects to be dried in the state of low temperature and vacuum. As the results, it took about 17 hours(3~4 days in case of hot air drying) for material to reach about 18% of the final moisture content in order to store products for a long time, from about 78~80% of the early moisture content at the beginning of drying, and maximum drying rate comes to about 0.35 kg/m2hr at about 400% of the moisture content.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.903-908
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• 2002

The production of waste glasses has been increased with the development of industry. The utilization of waste glass for concrete can cause the concrete to be cracked and to be weakened due to an expansion by alkali-silica reaction(ASR). When used the fibers with waste glass, there is an effect on reduction of expansion and strength loss due to ASR between the alkali in the cement paste and the silica in the waste glass. In this study, we conducted basic experimental research to analyze the possibilities of recycling of amber waste glass as fine aggregates for steel fiber reinforced concrete. Test results of fresh concrete. slump is decreased because grain shape is angular and air content is increased due to involving small size particles so much in waste glasses. Also. tensile and flexural strengths increased as the content of steel fibers increased. In conclusion, the content of waste glass below 40% is reasonable and usage of pertinent admixture is necessary to obtain workability or air content.

• Journal of the Korean Wood Science and Technology
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• 제27권1호
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• pp.50-55
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• 1999

Since ultrasonic stress wave velocity varies with wood temperature and moisture content, ultrasonic stress wave could be a tool to predict wood moisture content if temperature effect could be eliminated. This temperature effect was investigated by measuring the velocities of ultrasonic stress waves transmitting through air, a metal bar and a dimension lumber at various temperatures. For air the velocity and amplitude of the ultrasonic stress wave increase with temperature, while for a metal bar and a dimension lumber those decrease as temperature increases. However all three materials showed velocity hystereses with a temperature cycle. The effect of temperature and moisture content on stress wave velocity of a dimension lumber was depicted in the form of a three dimensional graph. The plot of stress wave velocity vs. wood moisture content was well fitted by two regression equations: a exponential equation below 46% and a linear equation above 46%.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.277-280
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• 2004

Recently, as structure is more higher and bigger, we need high strength and high performance concrete. Therefore it is necessary superplasticizer for high strength and high performance concrete. In this study, it is examined the properties of flow, air content and strength of concrete with polycarboxylate superplasticizer in comparison with existing superplasticizer. First, The slump loss of concrete used polycarboxylate superplasticizer showed 2cm until 120 minutes. Second, The air content loss of concrete used polycarboxylate superplasticizer showed $1\%$ until 120 minutes. Third, It is possible to manufacture $1000kgf/cm^2$ strength concrete using polycarboxylate superplasticizer with $806kg/m^3$ cement content, $18\%$ water-binder ratio, $15\%$ silica fume, $10\%$ fly-ash content.

• 설비공학논문집
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• 제16권12호
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• pp.1126-1133
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• 2004

This paper presents an experimental measurement of effective thermal conductivity in an adsorbent packed bed with silica gel A type. The effective thermal conductivity was measured under different conditions of the adsorbent bed temperature, pressure, particle size and water content by using the transient hot wire method. The measured effective thermal conductivity showed to become bigger with decreasing particle size or increasing water content, but it was a little affected with increasing bed temperature and pressure. The bed temperature was varied in the range of 1$0^{\circ}C$ (equation omitted) T (equation omitted) 5$0^{\circ}C$ and the pressure in the range of 10 kPa (equation omitted) P (equation omitted) 190 kPa. The results show that 0.10～0.18 W/mㆍK of effective thermal conductivity measured for the zero water content.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.647-650
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• 2001

The purpose of this study was the influence of cold weather ready mixed concrete quality according to needs of customer were investigated by measurements of slump, air content, temperature and compressive strength. As a results, cold weather ready mixed concrete using high standard admixtures, high early strength admixtures and cold weather concrete plant were similarly to slump, air content, temperature and compressive strength.