• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.158-163
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• 2001

Performance of the water direct contact air conditioning system, in which heat and mass are transferred directly between air and water droplet, is simulated by semi-empirical method. This system improves transport efficiency compared to conventional indirect contact system and cooling, heating, dehumidification and humidification are attained with one unit. In this study, temperature and flowrate for air and water are measured in the various cooling and heating conditions, and correlations for $h_{c}A/c_{pm}$ are derived from these data. Cooling and heating characteristics of the water direct contact air conditioning system are investigated using correlations.

• 현장농수산연구지
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• 제3권1호
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• pp.30-47
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• 2001

This research was performed to develope a stable direct seeding method in rice cultivation using by a direct seeder with soil application. A principle of this methodology was introduced from seeding nursery system of machine transplanting enable to increase high seeding establishment direct seeding method with soil application was high of 89-95% while that of water seeding was 68%. During seeding growth plant height was ralatively small but seeding health was high. A total soil consumption of this methodology was 145kg/10a in dirll seeding and 26kg/10a in hill seeding respectively, there was 100% erected in direct seeding with soil application while water seeding was 45% in erected seeding stand. In direct seeding method with soil application total carbohydrate content was higher than that of water seeding. This machine was manufactured to attach and/or detach to a machine transplanter with riding type and machine cultivator with multipurpose. In the farmer's demonstrated rice field this method was well performed like machine transplanting in terms of rice growth and development. There was highly cost reduction for rice production like other direct seeding methods.

• 한국지열·수열에너지학회논문집
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• 제11권3호
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• pp.7-12
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• 2015

Currently water supply system with water storage is generally applied except for small building such as single-family houses, and water supply system on replacing water storage installed system by direct connecting system has been increasing because of sanitary and energy-saving aspects. The purpose of this study is to evaluate energy-saving and environmental efficiency of direct connecting booster pump system in comparison with the water storage installed system. The architectural condition of the evaluation subject is ten-story apartment house in which sixty households live. To calculate the power consumption of the pump, the volume of water supply was determined from existing data and other data, such as head, efficiency of the pump, was the value used for general application in design office. The power consumption of the water supply pump for one day was 8.5 kWh for direct connecting booster pump system, and 22.5 kWh for water storage installed system, and the former system showed energy savings of 62% compared to the latter system. Reduced power consumption also leads to reduction of $CO_2$ emission. According to the criteria presented in the Korea Energy Management Corporation, reducing the 2,410 kg $CO_2$ emission is possible per year.

• 대한환경공학회지
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• 제35권6호
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• pp.400-406
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• 2013

물 발자국(Water footprint)은 단위 제품 및 단위 서비스 생산 전과정(life cycle) 동안 직접 및 간접적으로 이용되는 물의 총량지표를 나타내는 것을 의미한다. 본 연구에서는 물 발자국 산정 방법을 이용하여 국내 산업에서의 직접 및 간접적인 용수량을 산정하여 효과적인 수자원 관리를 위한 하나의 방법을 제시하고자 하였다. 연구 결과로는 원단위 용수계수가 가장 큰 산업은 농림수산품으로 약 637 $m^3/won$으로 전체 산업의 93%를 차지했다. 농림수산품 다음으로 간접적인 원단위 용수계수가 큰 산업은 석유 및 석탄 제품으로 약 13 $m^3/won$을 나타냈다. 산업연관용수량의 경우 간접적인 용수량이 가장 많은 산업 역시 농림수산품으로 직접적인 용수량이 약 25억 $m^3$인데 비해 간접적인 용수량은 약 130억 $m^3$ 정도로 나타났으며, 조사한 전체 16개 산업 중 91%를 차지했다. 화학제품의 경우 직접적인 용수량이 약 2억 $m^3$, 간접적인 용수량은 약 4억5천만 $m^3$으로 나타났다. 연구결과 직접적인 용수량보다 간접적인 용수량이 전체적으로 큰 것으로 나타났으며, 이와 같이 국가적으로 전체 산업별 물 발자국 및 용수량의 흐름을 파악함으로써, 국가의 수자원 관리 정책 수립 시 기초자료로 활용 되어질 수 있을 것으로 사료된다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.986-990
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• 2009

Using artificial rainfall simulator, the soil loss, which is deemed as most cause of muddy water problem among Non-point source(NPS) pollutant, was studied by the analysis of direct runoff flow, groundwater runoff, and groundwater storage properties concerned with rainfall intensity, slope of area, and land cover. The direct runoff showed increasing tendency in both straw covered and bared boxes which are 5%, 10%, and 20% sloped respectively. Also the direct runoff volume from straw covered surface boxes were much lower than bared surface boxes. It's deemed as that the infiltration capacity of straw covered surface boxes were increased, because the surface sealing by fine material of soil surface didn't occurred due to the straw covering. Under the same rainfall intensity and slope condition, 2.4 ${\sim}$ 8.2 times of sediment yield were occurred from bared surface boxes more than straw covered surface boxes. The volume of infiltrated were increased due to straw cover, the direct runoff flow were decreased with decreasing of tractive force in surface. To understand of relationship the rate of direct runoff flow, groundwater runoff, and groundwater storage by the rainfall intensity, slope, and land cover, the statistical test was performed. It shows good relationship between most of factors, expect between the rate of groundwater storage and rainfall intensity.

• 한국분무공학회지
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• 제23권2호
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• pp.96-101
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• 2018

The purpose of this study is to investigate the effect of water injection on combustion characteristics of gasoline direct injection (GDI) engine with turbo-charger under low-load operating condition. The test engine used in this study has four-cylinder and 10.2 of compression ratio. In order to study the effect of water injection ratio on combustion characteristics, the water was injected into the intake port from 10% to 50%, based on fuel injection quantity. From the experiment, it revealed that the water injection induced the improvement of fuel economy because of the advance of spark-timing by the reduction of in-cylinder temperature. In addition, the water injection caused the prolong of extension of the ignition delay and slight increase of burn duration.

• 태양에너지
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• 제18권4호
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• pp.33-38
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• 1998

This paper reports the experimental results concerning the thermal performance of a freeze-protected direct solar water heating system. The direct system tested has been manufactured to prevent any breakage during harsh wintry conditions by specially designed riser and downcomer headers capable of relieving extra pressure due to freezing of water. The direct system tested has shown 10% improvement in its efficiency over that of a indirect type system using antifreeze as the heat transfer medium. It is felt that any direct system of its kind could galvanize the whole solar industry if further improvements are made to ensure its durability.

• 상하수도학회지
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• 제25권3호
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• pp.325-334
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• 2011

Market Environment around water work industry is rapidly changing. ISO, International Organization for Standardization, announced the international water work service standard for comparison and evaluation between nations and businesses. And developed countries in water work are introducing market principle for growth of nation's water industry and reinforcement of its competitiveness. Also, some local governments entrusted their water utilities for improvement of competitiveness of water work. However, as some failure cases from overseas came out with emphasis, there are many refuting perspective about entrusted operation achievements of domestic water market. Hence, this paper evaluated competitiveness of domestic local water utilities from the perspective of productivity. After evaluating productivity using Malmquist productivity index, the authors compared and analyzed whether there is a difference of productivity between two different operating types by using Mann-Whitney test. As a result of analysis, it has shown that local water utilities achieved higher productivity at entrusted operation type rather than direct operation type. The local water utilities which chose entrusted operation had increased the productivity 13.9% on total factor productivity(TFP) during experimenting period, while the local water utilities which chose direct operation had increased 0.2%. The background of achieving this high productivity in entrusted operation was analyzed as a result of the higher technological effectiveness of a special water company. The result of this study can be referred when local government needs to decide on what operating types they will use.

• 현장농수산연구지
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• 제20권1호
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• pp.5-18
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• 2018

벼 직파재배 유형(담수산파, 무논점파) 및 사용 종자별 생육특성 및 수량 비교 시험 결과를 요약하면 다음과 같다. ① 출아일수는 9~11일이 소요되었고, 싹튼 볍씨 사용이 철분코팅볍씨 사용 직파보다 1~2일이 빨랐으며, m²당 입모 수는 103~147개로 담수산파의 철분코팅볍씨 사용에서 가장 많았으나, 벼 직파방법 간에 통계적 유의성은 없었다. 결주율(무논점파)은 2.7~3.7%이었다. ② 초장생육에서 직파는 기계이앙 보다는 짧았고, 벼 직파방법 간에는 담수산파가 무논점파보다 파종 후 60일까지는 길었으나, 파종 후 75일 이후는 비슷하였다. 사용 종자 간에는 철분코팅볍씨 사용이 싹튼 볍씨 사용보다 길었고, 담수산파에서는 통계적 유의성도 있었다. ③ m²당 경수는 6월 17일(파종후 30일)에는 기계이앙이, 파종 후 45일과 60일에는 담수산파의 철분코팅볍씨 사용에서 가장 많았고, 파종 후 75일과 90일 m²당 경수는 352~405개로 벼 재배방법 간에 통계적으로 유의한 차이는 없었다. ④ 출수기는 직파에서 8월 21~23일로 기계이앙(8월 13일)보다는 8~10일이 늦었고, 직파방법 간에는 차이가 없었으나, 사용종자 간에는 철분코팅 볍씨 사용이 싹튼 볍씨 사용보다 2일이 빨랐다. ⑤ 성숙기 벼 생육특성에서 간장은 기계이앙(72.4cm)보다 철분코팅볍씨 사용 담수산파 및 무논점파는 통계적으로 각각 유의하게 길고 짧았으며, 수장은 무논점파의 싹튼 볍씨 사용(24.3cm)에서 가장 길었고, 담수산파 및 기계이앙과 통계적 유의성이 있었다. 벼 직파방법별 사용종자 간에는 수장은 별 차이가 없었다. m²당 수수는 357~407개로 담수산파의 철분코팅볍씨 사용에서 가장 많았으나 벼 재배방법별로 통계적 유의성은 없었다. 수당입수는 102~106개로 거의 같았다. ⑥ 수량구성요소는 m²당 입수는 37,105~42,450개, 현미천립중은 21.9~22.8g으로 담수산파의 철분코팅볍씨 사용에서 가장 많았고 무거웠다. 등숙비율은 77.6~86.3%으로 무논점파의 철분코팅볍씨 사용에서 가장 높았으나, 수량구성요소 모두 벼 재배방법 간에 통계적 유의성은 없었다. ⑦ 쌀 수량은 10a당 568~686kg으로 담수산파의 철분코팅 볍씨 사용(686kg/10a)에서 가장 높았으며 기계이앙 및 그 외 직파방법과 통계적 유의성도 있었다. 그 외 직파방법은 기계이앙(568kg/10a) 대비 3~7% 높았으나, 통계적 유의성은 없었다. ⑧ 잎도열병은 벼 생육초기 기계이앙과 담수산파에서 약간 발병하였고, 잎집무늬마름병과 이삭누룩병은 기계이앙>무논점파≥담수산파 순으로 심하였다. ⑨ 잡초는 담수산파의 싹튼 볍씨 사용에서 발생이 심했고, 8월 16일 이후는 벼 재배방법 다같이 후발피가 발생하였다. 잡초성벼는 기계이앙은 발생되지 않았으나, 싹튼 볍씨 사용 직파는 0.6~0.7%, 철분코팅볍씨 사용 직파는 0.1%정도 발생하였다.

• Membrane and Water Treatment
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• 제10권5호
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• pp.387-394
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• 2019

Membrane distillation (MD) is one of the water treatment processes which involves the momentum, heat and mass transfer through channels and membrane. In this study, CFD modeling has been used to simulate the heat and mass transfer in the direct contact membrane distillation (DCMD). Also, the effect of operating parameters on the water flux is investigated. The result shows a good agreement with the experimental result. Results indicated that, while feed temperature is increasing in the feed side, water flux improves in the permeate side. Since higher velocity leads to the higher mixing and turbulence in the feed channel, water flux rises due to this increase in the feed velocity. Moreover, results revealed that temperature polarization coefficient is rising as flow rate (velocity) increases and it is decreasing while the feed temperature increases. Lastly, the thermal efficiency of direct contact membrane distillation is defined, and results confirm that thermal efficiency improves while feed temperature increases. Also, flow rate increment results in enhancement of thermal efficiency.