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후퇴각 날개끝이 있는 헬리콥터 로터깃의 회전주파수 해석
황호연,정건교 한국소음진동공학회 2000 소음 진동 Vol.10 No.2
To reduce the drag rise on the advancing helicopter rotor blade tips, the tip of the blade is modified to have sweep, anhedral and pretwist. The equations of motion of rotor blade with these tip angles were derived using Hamilton principle, programmed using FORTRAN and named as ARMDAS(Advanced Rotorcraft Multidisplinary Design and Analysis System). Rotating frequency analysis of rotor blades with swept tipe was performed that is necessary in conceptual and preliminary design phases of the helicopter design. Vibration analysis of non-rotating blades was also accomplished and compared with MSC/NASTRAN resutls for the basis of comparison with the vibration test data. The rotating frequency analysis of blades with an actual rotor blade data was also performed to verify coded program and to check the possibility of a resonance of an actual rotor blade at the specific rotating speed.
김한규,황호연 弘益大學校 科學技術硏究所 1999 科學技術硏究論文集 Vol.10 No.1
Computer supported cooperative work (CSCW) makes group task efficient by giving co-existence notion to geographically distributed group participants. The most important issue in CSCW is system architecture and concurrency control. Concurrency control influences the co-existence notion of group participants. In concurrency control for CSCW, it is very important to consider the group participants. A efficient Concurrency control method cannot be used if it hurts co-existence. In this paper we suggest the requirements of concurrency control for internet based fully distributed CSCW, analyze the reason why existing concurrency control method does not fulfill this requirements. And design concurrency control method that satisfy given requirements based on optimistic locking and commit candidate.
미세조류를 이용한 폐수처리 효율에 관한 연구: 영양염류 및 응집을 중심으로
황호연,송재준,김미숙,김도용 한국환경기술학회 2018 한국환경기술학회지 Vol.19 No.6
The efficiency of wastewater treatment using microalgae was investigated in this study, focusing on nutrients and flocculation. In the experiments for reducing nutrients by incubation of microalgae, the total phosphorus and total nitrogen were removed over 92 % and 99 %, respectively. The higher flocculation rates as the average values 94% of Poly Aluminum Chloride(PAC) and 92 % of FeCl3 were presented for the flocculation experiments under the conditions of Auto-flocculation and various additives. Also, the optimal(minimal) concentrations for over 90 % of flocculation were 30 mg/L and 40 mg/L for PAC and FeCl3, respectively. 본 연구에서는 영양염류 및 응집을 중심으로 미세조류를 이용한 폐수처리 효율에 관한 연구를 수행하였다. 미세조류 배양을 통한 폐수의 영양염류 저감의 가능성을 확인하기 위하여 미세조류의 배양에 따른 인 및 질소의 제거율을 관찰한 결과, 각각 약 92 % 및 99 % 이상의 제거율을 보였다. 효율적인 미세조류의 회수를 위하여 Auto-flocculation 조건 및 다양한 첨가물에 따른 응집실험을 진행한 결과, 응집제인 PAC(Poly Aluminum Chloride) 및 FeCl3를 첨가한 경우에 각각 평균 94 % 및 92 %의 높은 응집율을 보였다. 또한, 최소한의 농도로 90 % 이상의 응집율을 보이는 최적의 조건을 찾기 위하여 응집제별 최적농도 산출 실험을 진행하였으며, 그 결과 PAC는 30 mg/L, FeCl3는 40 mg/L가 최적의 농도임을 확인하였다.