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Kim Suwhan,Park Won-Ju,Cho Seunghyeon,Lim Dae-Young,Yoo Yeongjae,Kim Hyeonjun,Kang Wonyang,Kang Kyung Wook,Moon Jai-Dong 대한직업환경의학회 2021 대한직업환경의학회지 Vol.33 No.3
Background: Previous studies have shown that morning types are less sensitive to pain. This study aimed to examine the relationship between chronotypes and musculoskeletal problems in workers with musculoskeletal burdens at work. Methods: This cross-sectional study included 119 male production workers from a large automobile manufacturing plant. All the participants worked 2 shifts and worked on the automobile assembly line. Data were obtained using structured questionnaires, including the reduced Morningness-Eveningness Questionnaire (rMEQ), and musculoskeletal symptom questionnaire. Participants with an rMEQ score of 18 points or more were defined as morning-type workers (MTWs). Participants whose scores were less than 18 points were defined as neither-type workers (NTWs). Results: The arithmetic mean age was 51.8 ± 5.3 years. MTWs and NTWs accounted for 35.3% and 64.7% of the total participants, respectively. Evening- and intermediate-type workers accounted form 6.7% and 58.0% of the participants, respectively. There was no significant difference in the health indicators when the MTW and NTW groups were compared. However, the musculoskeletal symptom questionnaire demonstrated a significant difference between the MTW and NTW groups. In the preceding year, the MTW group had significantly lower musculoskeletal pain and treatment ratios compared to the NTW group (35.7% vs. 62.3%, p = 0.005 and 14.3% vs. 32.5%, p = 0.031, respectively). After adjusting for variables, the odds ratio (OR) for musculoskeletal pain was significantly higher in the NTW group than in the MTW group (OR, 3.112; 95% confidence interval, 1.285–7.535; p = 0.012). Conclusions: In this study, the musculoskeletal pain ratio was significantly lower for MTWs when compared to NTWs. Chronotypes could play an important role in work-related musculoskeletal disorders. Further, larger-scale, follow-up studies on chronotypes are required to assist in the prevention of musculoskeletal disorders in future.
신뢰성을 고려한 효율적인 공력 형상 최적 설계에 대한 연구
김수환(Suwhan Kim),권장혁(Jang-hyuk Kwon) 한국항공우주학회 2006 韓國航空宇宙學會誌 Vol.34 No.7
일반적인 신뢰성 최적 설계는 결정론적 최적 설계에 비해 매우 많은 계산비용이 필요하므로 공력 형상 최적화와 같은 큰 문제에 직접 적용하기는 매우 어렵다. 본 연구에서는 이러한 한계를 극복하기 위하여 이접 근사화 기법과 adjoint 민감도 해석 기법을 결합한 효율적인 신뢰성 설계 과정을 제안한다. 이 방법은 계산비용은 결정론적 방법과 거의 동일하지만 계산 결과에 있어서는 기존의 신뢰성 설계 기법과 유사한 결과를 얻을 수 있다. 이를 이용하여 3차원 공력 형상 최적 설계를 매우 효율적으로 수행할 수 있었다. The conventional reliability based design optimization(RBDO) methods require high computational cost compared with the deterministic design optimization(DO) methods, therefore it is hard to apply directly to large-scaled problems such as an aerodynamic shape design optimization. In this study, to overcome this computational limitation the efficient RBDO procedure with the two-point approximation(TPA) and adjoint sensitivity analysis is proposed, that the computational requirement is nearly the same as DO and the reliability accuracy is good compared with that of RBDO. Using this, the 3-D aerodynamic shape design optimization is performed very efficiently.
Single channel EEG의 Attention을 통한 수면 단계 추정 의사결정지원시스템
백수환(Suwhan Baek),백재우(Jaewu Baek),유현수(Hyunsoo Yu),박철수(Cheolsoo Park) 대한전자공학회 2021 대한전자공학회 학술대회 Vol.2021 No.6
This paper propose classification model for AASM(American Academy of Sleep Medicine) based five level sleep staging(Wake, Rem, N1, N2, N3) by single channel EEG signal(F3). n particular, for explainable sleep phase estimation models unlike conventional models, we proceed with the analysis of signals via BEMD(Bidimensional Empirical Mode Decomposition), and prove that each sleep label was learned from which key signal components through back-analysis of the model through attention mechanisms. The cross-validation results of 425 subjects" data with signal analysis for Single Channel EEG showed an average of F1-Score 70.232 (±1.769) average accuracy of 83.15% (±1.35%) and we propose a explainable model for which electroencephalogram components were more effective in estimating each sleep stage.
근사신뢰도기법을 이용한 효율적인 공력 형상 설계에 관한 연구
김수환(Suwhan Kim),권장혁(Jang-Hyuk Kwon) 한국전산유체공학회 2004 한국전산유체공학회 학술대회논문집 Vol.2004 No.-
The conventional reliability based design optimization(RBDO) methods require high computational cost compared with the deterministic design optimization(DO) methods. To overcome the computational inefficiency of RBDO, single loop methods have been proposed. These need less function calls than that of RBDO but much more than that of DO. In this study, the approximate reliability method is proposed that the computational requirement is nearly the same as DO and the reliability accuracy is good compared with that of REDO. Using this method, the 3-D viscous aerodynamic shape design optimization with uncertainty is performed very efficiently.
Park Eunyoung,Kim Suwhan,Cho Seunghyeon,Kim Hyeonjun,Jung Inho,Moon Jai-Dong,Park Won-Ju 대한의학회 2023 Journal of Korean medical science Vol.38 No.26
Background: Lead exposure is a known risk factor for cardiovascular disease (CVD), and coronary artery calcification (CAC) is a biomarker for diagnosing atherosclerotic CVD. This study investigated the association between blood lead level (BLL) and CAC using coronary computed tomography (CT) angiography. Methods: This study enrolled 2,189 participants from the general population with no history or symptoms of CVD. All participants underwent coronary CT angiography, health examination, and BLL testing. The association between coronary artery calcium score (CACS) and BLL was analyzed. Results: The arithmetic mean of BLL was 2.71 ± 1.26 μg/dL, and the geometric mean was 2.42 (1.64) μg/dL, ranging from 0.12 to 10.14 μg/dL. There was a statistically significant positive correlation between CACS and BLL (r = 0.073, P < 0.001). Mean BLLs among predefined CACS categories were as follows: absent grade (CACS = 0), 2.67 ± 1.23 μg/dL; minimal grade (> 0, < 10), 2.81 ± 1.25 μg/dL; mild grade (≥ 10, < 100), 2.74 ± 1.29 μg/dL; moderate grade (≥ 100, < 400), 2.88 ± 1.38 μg/dL; severe grade (≥ 400): 3.22 ± 1.68 μg/dL. The odds ratio for severe CAC was 1.242 in association with an 1 μg/dL increase in BLL (P = 0.042). Conclusion: Using coronary CT angiography, we determined a positive correlation between BLL and CAC among participants without CVD from the general population. To reduce the burden of CVD, efforts and policies should be geared toward minimizing environmental lead exposure.
시계열 데이터 분석을 위한 컨볼루션 신경망 기반의 Empirical Mode Decomposition
유현수(Hyunsoo Yu),백수환(Suwhan Baek),박철수(Cheolsoo Park) 대한전자공학회 2021 대한전자공학회 학술대회 Vol.2021 No.6
EMD (Empirical Mode Decomposition) was proposed as a method for analyzing nonlinear and nonstationary data. In this study, an attempt was made to implement EMD with deep learning. The model used was a simple CNN (Convolutional Neural Network), and after prediction, it was shown that the prediction result and the true signal showed a similar tendency especially in the low-order IMF (Intrinsic Mode Function).