• 한국유체기계학회 논문집
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• 제10권2호
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• pp.22-31
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• 2007

This paper describes the shape optimization of rotor blade in a transonic axial compressor rotor. Three surrogate models, Kriging, radial basis neural network and response surface methods, are introduced to find optimum blade shape and to compare the characteristics of object function at each optimal design condition. Blade sweep, lean and skew are considered as design variables and adiabatic efficiency is selected as an objective function. Throughout the shape optimization of the compressor rotor, the predicted adiabatic efficiency has almost same value for three surrogate models. Among the three design variables, a blade sweep is the most sensitive on the object function. It is noted that the blade swept to backward and skewed to the blade pressure side is more effective to increase the adiabatic efficiency in the axial compressor Flow characteristics of an optimum blade are also compared with the results of reference blade.

• 한국농공학회지
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• 제16권2호
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• pp.3395-3409
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• 1974

The purpose of this study is to test and compare the efficiency of heating-system for materials and construction of the wall, ceiling and window in soil brick house, cement house and boulder house respectively, in order to construct ideal farm houses in rural area. The results obtained were as follows: 1. In heat conservation due to construction of walls the thermal efficiency of cement brick house was equivalent to 66.3% of that of soil brick house, and boulder house 60.3% 2. In the case of ceiling, the thermal efficiency of paper ceiling was amounted to 84.2% of that of the composite ceiling (thickness 6mm veneer+thickness. l0m chaffs), and the common ceiling putting on soil above the ceiling, 76% of the composite while the efficiency of the ceiling putting on chaffs above them was 15.8% higher than that of the paper. 3. In the case of improving the window, the double type was 12% higher than. the efficiency of single type. 4. The warming velocity of conventional house was slower but the velocity of radiation was quicker than that of experimental one. It was thought to be due to unscietific constructions of the room bottom, fire inlet and chimney, 5. The temperature gradient line was not dependad upon the amount of throwing into fuel in the rural farm house. 6. It was concluded that the final thermal efficiency of the conventional farm house was 10.6% lower than that of experimental farm house.

• 한국도로학회논문집
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• 제18권6호
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• pp.145-152
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• 2016

OBJECTIVES : Visibility at night can be improved by using retroreflection for short distances and phosphorescent line markings for long distances. In this study, we analyzed the characteristics of the phosphorescent line marking through a laboratory luminance test. Field performance analysis was performed through tests conducted on the road. We also examined the luminance measurement methods using the digital image obtained during the phosphorescent visibility evaluation. METHODS : In this study, the laboratory luminance test of the phosphorescent line marking was conducted using seven specimens to characterize the luminance changes according to the type of the glass beads, the thickness of the phosphorescent line marking, and the brightness and irradiation time of the light source. Phosphorescent and general line markings were made at 150 m to investigate the field luminance performance. A preliminary review of the luminance measurement methods was made using a digital image from a digital single-lens reflex (DSLR) camera. The measured luminance ratio of the general and the phosphorescent line markings was compared with the calculated luminance ratio using luminance analysis. RESULTS : Through the laboratory luminance test, it was seen that the change in luminance, which corresponds to the brightness of the light source, appears large but the influence of the thickness and irradiation time is low. The field performance test of the phosphorescent line marking conducted on the road involved measuring the luminance on the day the marking was made and 7 days after the marking was made. The luminance was found to be $190mcd/m^2$ at 30 min after sunset and approximately $10-12mcd/m^2$ 4h after sunset. The results of the luminance test were captured using a digital image for each time group. The luminance ratio of the phosphorescent line marking, when compared to that of the general line marking, showed a similar trend within a 13% maximum error. Additionally, when this luminance ratio is compared to the direct field measurement, it could be confirmed that the luminance ratio, as captured in the digital image, showed a similar tendency. CONCLUSIONS : 1) The change in luminance corresponding to the brightness of the light source is significant in comparison with that corresponding to the thickness and the irradiation time. In addition, the results of the field test for the phosphorescent line marking satisfied the phosphorescent fire protection standard. 2) We examined the validity of the luminance measurement method using a digital image and we concluded that the change in the luminance ratio shows a similar tendency in both the cases. The results can form the basis for luminance measurement methodology for the construction and maintenance of phosphorescent line markings.

• 토지주택연구
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• 제8권3호
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• pp.189-200
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• 2017

The work breakdown structure and the precedence relations by work activity are very important because they are the basic data for estimating the construction duration in the construction work. However, there is no standard to accurately estimate the construction duration since the size of the school facilities construction is smaller than the general construction work. Therefore, some schools are unable to open in March or September and the delay of the construction duration can cause damage to the students. To solve this problem, this study developed a work breakdown structure of school facilities construction work and analyzed the precedence relations by work activities. The work breakdown structure of the school facilities construction is composed of three steps. The operations corresponding to level 1 and level 2 are as follows. (1) 2 preparatory work categories; preparation period and temporary construction. (2) 17 architectural work categories; temporary construction, foundation & pile work, reinforced concrete work, steel roof work, brick work, plaster work, tile work, stone work, waterproof construction, wood work, interior construction, floor work, metal work, roof work, windows construction, glazing work and paint construction. (3) 7 mechanic and fire work categories; outside trunk line work, plumbing work, air-conditioning equipment work, machine room work, city gas plumbing work, sanitation facilities and inspection & test working. (4) 4 civil work categories; wastewater work, drainage work, pavement work and other work. (5) 1 landscaping work categories; planting work. The work breakdown structure was derived from interviews with experts based on the milestones and detailed statements of existing school facilities. The analysis of precedence relations by school facilities work activity utilized PDM(Precedence Diagramming Method)which does not need a dummy and the relations were applied using FS(Finish to Start), FF(Finish to Finish), SS(Start to Start), SF(Start to Finish). The analysis of this study shows that if one work activity is delayed, the entire construction duration may be delayed because the majority of the works are FS relations. Therefore, it is necessary to use the Lag at the appropriate time to estimate the standard construction duration of the school facility construction. Lag is a term used only in the PDM method and it is used to define the relationship between the predecessor and the successor in creating the network milestone. And it means the delay time applied to the two work activities. The results of this study can reasonably estimate the standard construction duration of school facilities and it will contribute to the quality of the school facilities construction.

• 한국안전학회지
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• 제36권5호
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• pp.10-17
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• 2021

The controversy over the risk of the human body being affected by electromagnetic fields emitted from 60 Hz power lines continues without end. There are currently no new studies or research progress being made in this direction that is notable, and the number of civil complaints is gradually increasing. The problem is that each study produces different results, among which the effect of exposure to magnetic fields on childhood leukemia is a major one. In Korea, an electrician who was maintaining a 22.9 kV power line died of leukemia, which has recently been recognized as an occupational disease. Methods to reduce magnetic fields from power lines include shielding with wire loops, incorporating split phases and compaction techniques, installing underground power lines, converting to high-voltage direct current (HVDC), and increasing the ground clearance of transmission towers. Depending on whether a separate power supply is needed or not, there are two types of wire loops: passive loop and active loop. Magnetic field reduction is currently done through underground power lines; however, the disadvantage of this process is high construction costs. Installing passive loops, with relatively low construction costs, leads to lower magnetic field reduction rates than installing underground cables and a weakness to not solving the landscape problem. This methodological study aims at designing methods and reducing the effects of 2-wire set loops-the simplest and most practical. Since the method proposed in this study has been designed after analyzing the distribution of complex electromagnetic fields near the expected loop installation location, a practical design can be implemented without the need for any difficult optimization programming.

• 한국화재소방학회논문지
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• 제34권3호
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• pp.141-149
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• 2020

한국산업표준(KS)은 발포 플라스틱 제품에 대하여 소형화염에 의한 수평 연소성의 측정 방법 및 시험절차를 규정(KS M ISO 9772:2018)하고 측정 결과에 대한 압출법 단열판(이하 XPS)의 자기소화성과 관련한 성능 및 기준을 KS 규격(KS M 3808:2020)에서 규정하고 있다. KS 규격에 적합함을 인증 받은 제품은 연소성(이하 '자기소화성')을 가지고 있어야 함에도 공사현장에서 용접불티 등에 의해 착화 및 확산되어 대량의 인명과 재산 피해가 발생하고 있는 실정이다. 본 연구에서는 KS 인증을 받고 시중에 판매 중인 5개사의 XPS 단열재를 구입하여 공사현장에서 발생되는 용접불티에 의한 착화 및 확산 여부를 실험하였다. 실험결과, 5개사의 제품 중 3개사는 성능의 차이는 있으나 자기소화성이 있는 것으로 확인되었으나, 2개사는 쉽게 착화 및 확산되어 자기소화성이 있다고 보기 어려웠다. 동종의 제품에 대하여 KS 규정에 따른 실험결과, 용접불티에 의해 착화되었던 제품 2종을 포함한 총 3종의 제품이 KS M 3808에서 규정한 자기소화성이 없는 것으로 확인되었다.

• 한국정보통신학회논문지
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• 제21권8호
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• pp.1597-1603
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• 2017

지하공동구의 화재 발생 빈도는 다른 화재에 비하여 낮은 편이나 화재로 인한 피해는 경제적 손실 뿐만 아니라 사회운영 마비로 사회적 손실을 초래할 수 있다. 이에 본 논문은 지하공동구 내 설치된 누설 동축케이블을 이용하여 지하공동구의 상태감시시스템 구축에 대한 실증 시험 결과를 제시한다. 이를 위해 지하공동구에 설치된 누설 동축케이블에 삽입손실 특성이 $-6{\pm}2dB$인 유도성 커플러와 200 Mbps급 전력선 통신 모뎀을 연결하여 실증 시험한 결과, 500 m까지 IP 카메라의 송/수신을 확인하였다. 따라서 데이터 전송을 위한 통신선로의 추가 설치 없이도 지하공동구 내 설치된 누설 동축케이블을 이용하여 지하공동구에 상태감시시스템 구축이 가능할 것으로 판단된다.

• 한국터널지하공간학회 논문집
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• 제9권3호
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• pp.287-298
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• 2007

최근 새로운 철도를 건설하거나 기존선로를 개량하기 위하여 터널의 건설이 급속히 증가하고 있으며, 점점 장대화 되고 있는 실정이다. 그러나 터널이 장대화됨에 따라 터널내에서의 화재사고 발생시 치명적인 대형사고의 가능성이 증대되고 있어, 장대터널에서의 안전성에 대한 관심이 증가하고 있다. 이러한 이유로 터널내 위험도를 최소화하고 터널방재기준을 만족시킬 수 있는 터널내 방재시설에 대한 최적의 설계기준이 요구되고 있으며, 장대 철도터널의 합리적인 설계를 위하여 터널 방재 안전성에 대한 정량적인 평가방법이 필요하다 할 수 있다. 본 연구에서는 정량적 위험도 분석방법인 QRA 기법을 장대터널에서의 방재 안전성 평가에 적용하여 그 유효성을 검토하고자 하였다. 적용사례에서는 장대터널에서의 갱외탈출로 개념의 사갱 및 수직구 계획을 수립하기 위하여 각각의 경우에 대한 QRA분석을 실시하고, 장대터널의 방재 안정성을 평가하므로서 실행 가능한 합리적인 수준의 터널 방재설계를 수행하고자 하였다.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 춘계학술발표대회 논문집
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• pp.102-108
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• 2009

Fossil power plants firing lower grade coals or equipped with modified system for NOx controls are challenged with maintaining good combustion conditions while maximizing generation and minimizing emissions. In many cases significant derate, availability losses and increase in unburned carbon levels can be attributed to poor combustion conditions as a result of poorly controlled local fuel and air distribution within the boiler furnace. In order to develop a on-line combustion tuning system, field test was conducted at operating power boiler. During the field test the exhaust gases' $O_2$, NOx and CO was monitored by using a spatially distributed monitoring grid located in the boiler's high temperature vestibule and upper convective back-pass region. At these locations, the flue gas flow is still significantly stratified, and air in-leakage is minimal which enables tracing of poor combustion zones to specific burners and over-fire air ports. using these monitored information we can improving combustion at every point within the furnace, therefore the boiler can operate at reduced excess $O_2$ and gas temperature deviation, reduced furnace exit gas temperature levels while also reducing localized hot spots, corrosive gas conditions, slag or clinker formation and UBC. Benefits include improving efficiency, reducing NOx emissions, increasing output and maximizing availability. Discussion concerning the reduction of greenhouse gases is prevalent in the world. When taking a practical approach to addressing this problem, the best way and short-term solution to reduce greenhouse gases on coal-fired power plants is to improve efficiency. From this point of view the real time optimized combustion tuning approach is the most effective and implemented with minimal cost.

• 한국태양에너지학회 논문집
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• 제29권5호
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• pp.45-52
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• 2009

Fossil power plants firing lower grade coals or equipped with modified system for $NO_x$ controls are challenged with maintaining good combustion conditions while maximizing generation and minimizing emissions. In many cases significant derate, availability losses and increase in unburned carbon levels can be attributed to poor combustion conditions as a result of poorly controlled local fuel and air distribution within the boiler furnace. In order to develop a on-line combustion tuning system, field test was conducted at operating power boiler. During the field test the exhaust gases' $O_2,\;NO_x$ and CO was monitored by using a spatially distributed monitoring grid located in the boiler's high temperature vestibule and upper convective rear pass region. At these locations, the flue gas flow is still significantly stratified, and air in-leakage is minimal which enables tracing of poor combustion zones to specific burners and over-fire air ports. using these monitored information we can improving combustion at every point within the furnace, therefore the boiler can operate at reduced excess $O_2$ and gas temperature deviation, reduced furnace exit gas temperature levels while also reducing localized hot spots, corrosive gas conditions, slag or clinker formation and UBC. Benefits include improving efficiency, reducing $NO_x$ emissions, increasing output and maximizing availability. Discussion concerning the reduction of greenhouse gases is prevalent in the world. When taking a practical approach to addressing this problem, the best way and short-term solution to reduce greenhouse gases on coal-fired power plants is to improve efficiency. From this point of view the real time optimized combustion tuning approach is the most effective and implemented with minimal cost.