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윤진혁,유상봉,김인한 한국전자거래학회 2003 한국전자거래학회지 Vol.8 No.2
Along with the national and international movements to realize the electronic commerce, large amount of construction information has been converted into digital format and stored in database systems. However the access and utilization of the information is not effective enough. It is because different terminologies are often used for describing the same object in construction engineering. Furthermore the relationship among related objects is not captured effectively in the databases. In this paper, we utilize the relationship among construction terminologies in order to search construction drawings effectively. The relationship is saved in a ontology database and a prototype of search system that utilizes the relationship is presented in this paper.
평균 센싱 속도를 이용한 Re=300의 반구 주위 층류 유동의 비례 되먹임 제어
윤진혁,이정일 대한기계학회 2023 大韓機械學會論文集B Vol.47 No.3
In this study, proportional feedback control with a time-averaged sensing velocity is applied to laminar flow over a hemisphere. Blowing/suction actuation, as a control input, is distributed on a local slot on the surface of the hemisphere before flow separation, and its strength is linearly proportional to the time-averaged transverse velocity at a sensing location on the centerline of the wake. For this purpose, we perform numerical simulations of flow over a hemisphere at Re = 300. Through a parametric study, we determine the optimal proportional gain for reducing the lift fluctuations of the hemisphere. The present control attenuates the velocity fluctuations at the sensing location and weakens the strength of the vortex structures in the wake, resulting in a reduction in the lift fluctuations of the hemisphere. 본 연구에서는 시간 평균된 센싱 속도를 활용한 비례 제어 기법을 반구 주위 층류 유동에 적용하였다. 제어 입력으로서 분사/흡입 가진은 유동 박리 전 반구 표면의 국소적인 슬롯에서 일어나며, 가진의 강도는 후류 중심선에 위치한 횡방향 시간 평균 속도에 선형적으로 비례한다. 이를 위해 Re=300의 반구 주위 유동에 대한 수치해석을 수행하였다. 파라미터 연구를 통해 반구의 양력 섭동 감소를 위한 최적의 비례 게인 값을 찾아내었다. 본 연구의 비례 제어를 통해 센싱 위치의 속도 섭동을 감소시키고 후류의 와류 구조를 약화시켰으며, 이를 통해 반구가 받는 양력 섭동을 성공적으로 감소시킬 수 있음을 확인하였다.
저주파 통과 필터 처리된 센싱 속도 기반 원형 실린더 주위 난류 유동의 비례 되먹임 제어
윤진혁,이정일 대한기계학회 2023 大韓機械學會論文集B Vol.47 No.4
In this study, we perform a proportional control of turbulent flow over a circular cylinder using the low-pass filtered sensing velocity in the wake. Blowing/suction actuations, acting as control inputs, occur on the cylinder surface near the flow separation, with magnitudes proportional to the filtered transverse sensing velocity. The use of low-pass filters is to remove high-frequency components of the sensing velocity caused by turbulence. Both first and second-order low-pass filters are examined by conducting large eddy simulations of flow over a circular cylinder at Re = 3,900. The results show that the performance of the 1st order low-pass filter in reducing drag and lift fluctuations is better than that of the 2nd order low-pass filter, and is comparable to that of a time-averaged sensing velocity. The control using the 1st order low-pass filter achieves maximum reductions of drag and lift fluctuations by about 11% and 61%, respectively. 본 연구에서는 저주파 통과 필터 처리된 후류 센싱 속도를 활용한 원형 실린더 주위 난류 유동의 비례 되먹임 제어를 수행하였다. 제어 입력으로서 분사/흡입 가진은 유동 박리 근처의 실린더 표면에서 일어나며, 가진의 크기는 필터 처리된 수직 방향 센싱 속도에 비례한다. 저주파 통과 필터를 사용하는 것은 난류로 인해 발생하는 센싱 속도의 고주파수 섭동 성분을 제거하기 위함이다. 필터로서 1차 및 2차 저주파 통과 필터를 고려하였다. 제어 성능을 평가하기 위해 Re = 3,900의 원형 실린더 주위 유동의 큰 에디 모사를 수행하였다. 제어 결과, 1차 저주파 통과 필터를 사용한 경우, 2차 저주파 통과 필터를 사용한 경우보다 좋은 제어 성능을 보였으며, 시간 평균된 센싱 속도를 사용한 경우와 동일한 수준의 항력 및 양력 섭동 저감 성능을 보였다. 제어로 인한 최대 항력 및 양력 섭동 감소량은 각각 약 11%, 61%에 달한다.
가임기 전신성 홍반성 루푸스 환자의 혈청 DHEAS치에 관한 연구
윤진혁 ( Jin Hyuk Yun ),유승훈 ( Seung Hoon Ryu ),정원택 ( Won Tec Jung ),이성원 ( Sung Won Lee ),안원석 ( Won Suk An ),이혁 ( Hyuck Lee ),손춘희 ( Choon Hee Son ),김성은 ( Seong Eun Kim ),김덕규 ( Duk Gyu Kim ),정원태 ( Won Tae 대한류마티스학회 2002 대한류마티스학회지 Vol.9 No.2
Objective: Dehydroepiandrosterone sulphate (DHEAS), the major steroidal product of the human adrenal, is abnormally low in patients with SLE. Moreover, a recent study confirms a positive effect of the precursor DHEA on the disease course in SLE, which supports an etiologically important role of the hormone on SLE. The aim of this study is to search for an interrelation between clinical manifestations, laboratory findings, and disease activities and DHEAS in patients with SLE. Method: DHEAS were measured by radioimmunoassay kit using 125I-labeled DHEA-SO4 antibody-coated tube in the serum of 48 patients with SLE and in 46 control subjects. Laboratory findings, clinical symptoms, signs and SLE disease activity index (SLEDAI) in SLE patients were evaluated at blood sampling time. Results: DHEAS was lower in patients with SLE compared to controls (45.60±42.62 μg/dL vs 101.55±56.54 μg/dL, p<0.005). The serum DHEAS levels were significantly negative correlation with SLEDAI (r=-0.333, p<0.05). There were significantly negative correlations between daily steroid dose and DHEAS (r=-0.384, p=0.012), and the amount of steroid used during previous 2 months and DHEAS (r=-0.011, p=0.011). Conclusions: Patients with SLE have low levels of DHEAS and significant negative correlation between SLEDAI, steroid dose and DHEAS.
인공신경망 기반 벽 압력을 이용한 난류 채널 유동 내 벽 근처 속도 예측
윤진혁(Jinhyuk Yun),이정일(Jungil Lee) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
It is well known that the near wall velocity is closely related to the streaky structure in the wall bounded flow and it is a useful information for the control of the flow. In the present study, we construct an artificial neural network (ANN) to predict near wall velocity in turbulent channel flow. As an input for ANN, wall pressure distribution below the near wall velocity to be predicted is chosen. For the learning process to build this ANN, instantaneous flow data sets are obtained from direct numerical simulation of turbulent channel flow at Reτ = 178. The performance of ANN is examined according to the plane size of wall pressure as an input, number of hidden layer, number of hidden nodes, and etc. It is found that the present ANN based on wall pressure successfully predicts the near wall velocity. Also, we apply this ANN to the control of turbulent channel flow for the skin friction reduction, and its results will be given in the presentation.