• Journal of the Korea Organic Resources Recycling Association
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• v.20 no.3
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• pp.21-24
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• 2012

In this study, Anaerobic Membrane Bioreactor(AnMBR) treating food waste leachate was operated to investigate treatment efficiency of anaerobic process, operational parameters and production of biogas. AnMBR was operated under the condition of filtration type of inside-out mode. AnMBR was operated under the condition that range of permeate flux was from 15 to 20 LMH and range of transmembrane pressure was from 1 to $3 kgf/cm^2$. It was not good that AnMBR was performed under direct connection between anaerobic reactor and external UF module. so, this connection method changed to indirect connection using buffer tank was placed between anaerobic reactor and UF external module. TCOD and SCOD values were that influent were about 113 g/L, 62 g/L and effluent were 25 g/L, 12 g/L, respectively. also TCOD and SCOD removal efficiency were 77% and 81%, respectively. but after added UF process, COD and SCOD removal efficiency was increased to 93% and 86%, respectively.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.915-921
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• 2008

In most PEM fuel cell research, effects of cell geometry, physical properties of component such as membrane, carbon cloth, catalyst, etc. and water transport phenomena are key issues. The scope of these research was limited to single cell and stack except BOP(Balance of plant) of fuel cell. The research fouced on the fuel cell system usually neglect to consider detailed transport phenomena in the cell. The research of the fuel cell system was interested in a system performance and system dynamics. In this paper, the effect of the anode recirculation is calculated using the 2D steady-state model. For this work, 2D steady-state modeling and experiments are performed. For convenience of modifying of model equation, not commercial pakage but the in-house algorithm was used in simulation. For an vehicle industry, the analysis of the anode recirculation system helps the optimization of operating condition of the fuel cell.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.336-341
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• 2018

The prestressing force introduced to the tendon in pretensioned concrete members is transferred by direct bond between tendon and concrete, which requires a proper estimation of stress transfer length. The use of pretensiond and/or precast members with UHPC (Ultra High Performance Concrete) may give many advantages in quality control. This paper presents an experiment to estimate the stress transfer length of UHPC for various compressive strength levels of UHPC, cover depths, diameters of tendons and tensioning forces. According to the result of this experiment, the stress transfer length of UHPC member is much reduced comparing that of normal strength concrete. The reduction in stress transfer length of UHPC may come from the high bond strength capacity of UHPC. The transfer lengths obtained from this experiment are compared to those in current design code and a new formula is proposed.

• Journal of Bio-Environment Control
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• v.24 no.2
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• pp.93-99
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• 2015

The purpose of this study was to determine the appropriate temperature for water curtain in greenhouses equipped with recirculated water curtain system. The study analyzed the changes in air temperature in non-heated greenhouses for strawberry cultivation based on outdoor temperature, water curtain temperature and night time. Three greenhouse units were used for this study: The first unit was assigned as a control (no water curtain system), two other greenhouses were equipped with recirculated water curtain system with water curtain temperatures of $10^{\circ}C$ and $15^{\circ}C$, respectively. Analysis showed that the indoor temperatures were directly correlated with the outdoor temperature in all experimental greenhouses. Heat insulating effect of $15^{\circ}C$ water curtain was increased by $1.3^{\circ}C$ compared to that in $10^{\circ}C$ water curtain system. The $15^{\circ}C$ water curtain treatment showed the highest average temperature and less temperature variation in comparison with control and $10^{\circ}C$ water curtain treatment. To maintain indoor temperature at $5^{\circ}C$, water curtain temperature of $10^{\circ}C$ was suitable when outdoor minimum and average temperatures were -1.3 and $1.5^{\circ}C$, and water curtain temperature of $15^{\circ}C$ was suitable when outdoor minimum and average temperatures were -4.7 and $-0.2^{\circ}C$, respectively. The highest temperature in greenhouses according to measurements in different periods of night time was observed after sunset (18:30-20:30), and the lowest temperature before sunrise (05:00-07:00). Water curtain maintained a target indoor temperature by acting as a layer of heat transfer insulator which decreased heat loss from greenhouses. Therefore, water temperature in recirculating water curtain systems should be determined by considering outdoor temperatures, changes in temperature at different periods of night time, and cultivated crop.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1B
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• pp.47-62
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• 2009

The climate change caused by global warming may affect on the hydro-meteorologic factor such as evaporation (IPCC, 2001). Furthermore, it is also necessary that the effect of climate change according to geographical condition on evaporation should be studied. In this study, considering geographical and topographical conditions, the 6 evaporation equations that have been applied to simulate annual and monthly pan evaporation were compared. 56 climatologic stations were selected and classified, basing on the geographical and topographical characteristics (urbanization, topographical slope, proximity to coast, and area of water body). The evaporation equations currently being used are applied. These evaporation equations are Penman, Kohler-Nordenson-Fox (KNF), DeBruin-Keijman, Priestley-Taylor, Hargreaves, and Rohwer. Furthermore, Penman equation was modified by calibrating the parameters of wind function and was verified using relative error. The study results indicate that the KNF equation compared best with the pan: relative error was 8.72%. Penman equation provided the next-best values for evaporation relative to the pan: relative error was 8.75%. The mass-transfer method (Rohwer) provided the worst comparison showing relative error of 33.47%. In case that there is a close correlation between wind function and wind speed, modified Penman equation provided a better estimate of pan evaporation.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.2
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• pp.20-25
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• 2011

The purpose of this work is an experimental investigation of combustion and emission characteristics in DI diesel engine applied high EGR rate as a method of low-temperature combustion. In order to analyze the effect of EGR rate variation, a single-cylinder DI diesel engine was operated under various EGR rate conditions. In addition, injection timing was variously controlled to investigate the effect of injection timing in DI diesel engine using the cooled-EGR system. The NOx emissions were decreased in accordance with the increase of EGR rate. On the contrary, soot emissions were generally increased under applied EGR conditions. However, soot emissions were decreased in a few injection timings under high EGR rate conditions. The EGR results show that the ignition delay were increased by decreased oxygen concentrations in combustion chamber under the high EGR rate.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.3
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• pp.143-148
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• 2010

In this study, the potential possibility of biodiesel fuel(BDF) and oxygenated fuel(ethylene glycolvmono-n-butyl ether; EGBE) was investigated as an effective method of decreasing the smoke emission. The smoke emission of blending fuel (BDF and EGBE 0~20 vol-%) was reduced in comparison with diesel fuel and it was reduced approximately 64% at 2000 rpm, full load in the 20% of blending rate. But torque and brake specific energy consumption( BSEC) didn't have no large differences. Also, the effects of exhaust gas recirculation(EGR) for the reduction of NOx emission has been investigated. Consequently, It was found that simultaneous reduction of smoke and NOx emission was achieved with BDF(90 vol-%) and EGBE(10 vol-%) blended fuel and cooled EGR method(5~10%).

• The KIPS Transactions:PartA
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• v.12A no.7 s.97
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• pp.563-570
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• 2005

Hardware and software codesign framework called PeaCE(Ptolemy extension as a Cod sign Environment) allows to express both data flow and control flow. To formally verify an fFSM specification which expresses control flow in PeaCE, the step semantics of the model was defined. In this paper, we introduce the automatic verification tool developed by formal semantics of previous work. This tool uses the SMV as inner model checker md, through our tool, users can formally verify some important bugs such as race condition, ambiguous transition, and circulartransition without directly writing logical formulae.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.65-71
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• 2005

Our environment is faced with serious problems related to the air pollution from automobiles in these days. In particular, the exhaust emissions of diesel engine are recognized main cause which influenced environment strong. In this study, the potential possibility of biodiesel fuel was investigated as an alternative fuel for a naturally aspirated D.I. diesel engine. The smoke emission of biodiesel fuel was reduced remarkably in com parison with diesel fuel, that is, it was reduced approximately 48.5% at 2500rpm, full load. But, power, torque and brake specific energy consumption didn't have no large differences. But, $NO_X$ emission of biodiesel fuel was increased com pared with commercial diesel fuel. Also, the effects of exhaust gas recirculation(EGR) on the characteristics of $NO_X$ emission has been investigated. It was found that simultaneous reduction of smoke and $NO_X$ was achieved with biodiesel fuel(20vol-%) and cooled EGR method($5{\sim}15%$).

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.5
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• pp.25-31
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• 2006

Controlled Auto Ignition(CAI) combustion has great potential in achieving significant increase in engine efficiency, while simultaneously reducing exhaust emissions. The process itself involves the auto ignition and subsequent simultaneous combustion of a premixed charge. In this study, NVO(Negative Valve Overlap) system was applied to a CAI engine in order to use residual gas. The fuel was injected directly to the cylinder under the high temperature condition resulting from heating the intake port to initiate CAI combustion. This paper introduced the valve timing strategy and experimental set-up. From this study, the effect of engine speed and valve timing on CAI combustion and exhaust emissions was clarified. In addition, stratified charge method was used to extend CAI operating region.