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고유동 콘크리트용 분리저감형 유동화제의 개발에 관한 기초적 연구
전충근,손성운,김성수,한천구 청주대학교 산업과학연구소 2001 産業科學硏究 Vol.19 No.1
The purpose of this paper is to develope segregation reducing type superplasticizer for high fluidity concrete and to manufacture high fluidity concrete by applying developed segregation reducing type superplasticizer using flowing concrete method in the rane go of 45% of W/C. According to test results, as dosage of superplasticizer increases, it shows that fluidity and bleeding increase, while air content and segregation resistance decrease. It also shows that adding of viscosity agent reduce bleeding and improve segregation resistance. Dosage of AE agent recovers loss of air contents during flowing Procedure. Combination of proper contents of superplasticizer, viscosity agent and AE agent make possible to develope segregation reducing type soperplasticizer According to experimental results, optimal proportion of superplasticizer, viscosity agent and AE agent show to be 1'0.60'0.027 Compressive strength of high fluidity concrete is simihar to comprssive strength of base concrete
Flow Analysis for Evaluation of Thermal Comfort Inside Tractor Cabin
( Joo-seon Oh ),( Gwan-hee Son ),( Seung-je Cho ),( Seong-un Park ),( Young-jun Park ) 한국농업기계학회 2018 한국농업기계학회 학술발표논문집 Vol.23 No.1
In the agricultural tractor, the indoor thermal environment is an important variable of the worker's work efficiency, so research for improving the indoor thermal comfort of the tractor cabin is becoming an important issue. In the development of HVAC systems for tractors, the evaluation of the thermal environment is based on the target temperature and the arrival time, which is a simple evaluation method of air conditioning system that does not consider the influence of the passenger's heating value, radiation temperature. More specific and objective evaluation methods are required to control a more comfortable thermal environment. In this study, the basic governing equations and the turbulence model of the three - dimensional heat flow analysis are introduced for the comfort evaluation of the tractor cabin using numerical analysis. For the evaluation of thermal comfort, the predicted mean vote (PMV) evaluation method was considered and the required parameters were defined. Simulation of the flow analysis was carried out for the three cases in which the air conditioner vent of the tractor cabin was placed on the upper ceiling part, the front dashboard part and the side column part of the cabin, and the thermal comfort was evaluated through PMV evaluation for each case. As a result, it was found that the most uniform PMV distribution was obtained when the vent was placed on the front dashboard part, which provided the most comfortable thermal environment.