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전신경화증에서 Multi-Detector Computed Tomography로 측정한 관상동맥 석회화
조미라 ( Mi Ra Cho ),박영은 ( Young Eun Park ),백승훈 ( Seung Hoon Baek ),이정욱 ( Joung Wook Lee ),김근태 ( Geun Tae Kim ),이준희 ( Jun Hee Lee ),추기석 ( Ki Seok Choo ),정연주 ( Yeon Ju Jeong ),이선희 ( Sun Hee Lee ),김성일 ( Su 대한류마티스학회 2009 대한류마티스학회지 Vol.16 No.3
Objective: There is some controversy regarding the early onset or high incidence of coronary atherosclerosis in patients with systemic sclerosis (SSc). Measurements of the coronary calcification score (CCS) by multi-detector computed tomography (MDCT) is an accurate and non-invasive method for detecting coronary atherosclerosis, and a high level of CCS (≥160) can predict coronary events. This study examined the CCS using MDCT and evaluated the risk of coronary events in patients with SSc. Methods: The clinical and laboratory characteristics of 35 patients with SSc were examined. The CCS was measured by MDCT, and the risk of coronary events were evaluated by CCS and the Framingham risk score (FRS). Results: In 35 patients (2 males and 33 females, 20 with limited and 15 with diffuse type), the mean age was 52±12 years and the disease duration was 8±7 years. The mean CCS was 10.1±30.8, the CCS of 28 patients (80%) was 0, and all patients had a CCS<160. The CCS had no significant correlation with the clinical and laboratory characteristics. The FRS was evaluated in 29 patients. Twenty eight patients were categorized into the low-risk group (FRS<10%) and only one was classified into the moderate-risk group (FRS=13%). Conclusion: These results suggest that the risk of coronary events due to coronary atherosclerosis might not be high in patients with SSc.
이산공간에서 순차적 알고리듬(SOA)을 이용한 전역최적화
조범상(Bum-Sang Cho),이정욱(Jeong-Wook Yi),박경진(Gyung-Jin Park) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
In the optimized design of an actual structure, the design variable should be selected among any certain values or corresponds to a discrete design variable that needs to handle the size of a pre-formatted part. Various algorithms have been developed for discrete design. As recently reported, the sequential algorithm with orthogonal arrays(SOA), which is a local minimum search algorithm in discrete space, has excellent local minimum search ability. It reduces the number of function evaluation using orthogonal arrays. However it only finds a local minimum and the final solution depends on the initial value. In this research, the genetic algorithm, which defines an initial population with the potential solution in a global space, is adopted in SOA. The new algorithm, sequential algorithm with orthogonal arrays and genetic algorithm(SOAGA), can find a global solution with the properties of genetic algorithm and the solution is found rapidly with the characteristics of SOA.
이산공간에서 순차적 알고리듬(SOA)을 이용한 전역최적화
조범상,이정욱,박경진,Cho Bum-Sang,Yi Jeong-Wook,Park Gyung-Jin 대한기계학회 2005 大韓機械學會論文集A Vol.29 No.10
In structural design, the design variables are frequently selected from certain discrete values. Various optimization algorithms have been developed fDr discrete design. It is well known that many function evaluations are needed in such optimization. Recently, sequential algorithm with orthogonal arrays (SOA), which is a search algorithm for a local minimum in a discrete space, has been developed. It considerably reduces the number of function evaluations. However, it only finds a local minimum and the final solution depends on the initial values of the design variables. A new algorithm is proposed to adopt a genetic algorithm (GA) in SOA. The GA can find a solution in a global sense. The solution from the GA is used as the initial design of SOA. A sequential usage of the GA and SOA is carried out in an iterative manner until the convergence criteria are satisfied. The performance of the algorithm is evaluated by various examples.
최병재(Byungjae Choi),한인규(In-kyu Han),조정욱(Jeong-wook Cho) 한국소음진동공학회 2014 한국소음진동공학회 학술대회논문집 Vol.2014 No.10
Abnormal cab vibrations in the Y direction in commercial vehicles during driving(70~90kph) are not common vibrations that happen to vehicles during driving and can be an obstacle to normal driving. This study conducted Operation Deflection Shape(ODS) testing to identify the causes of those abnormal cab vibrations and find solutions for them and also a sine sweep test to find resonance and frequency in the cab suspension system and set directions for improvement. The study also altered the shape of the bush inner part for changes to the rigidity features of the cab bush in the Y direction and revised the design with optimal rigidity in the Y direction, thus improving abnormal cab vibrations in the Y direction during driving.
최병재(Byungjae Choi),한인규(In-kyu Han),조정욱(Jeong-wook Cho) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.10
This paper presents an investigation into the reduction of steering wheel vibration in large commercial vehicles. Since commercial vehicles have a complex steering system unlike passenger cars, there are limitations in approaching them with the old simple experimental methods or analytical modeling methods to simplify the system. In the present study, the investigators thus employed the Muller-BBM O.T.P.A. (Operational Transfer Path Analysis). The problems with the steering wheel vibration stem from excessive vibration in the loading- and driving-based engine blast and idle state. Those vibrations make the palms of the driver feel a tickle or stinging sensation. The investigators experimentally acquired the transfer function of complex steering wheel vibrations as a source or path according to the vibration size at each location of measurement with a source in case of large vibration size and a path in case of small vibration size. The transfer functions were then compared, and the contribution of each vehicle system was analyzed in the problematic sections. The physical properties of a system whose contribution was the biggest were changed to test the O.T.P.A. results and reduce the vibrations in the problematic sections of steering vibration.