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Aggregation Prodesses of Hydrophobically Modified Polythylene Oxide
백기욱,김범성,김응렬,손대원,Baek, Gi Uk,Kim, Beom Seong,Kim, Eung Ryeol,Son, Dae Won Korean Chemical Society 2000 Bulletin of the Korean Chemical Society Vol.21 No.6
Aggregation of hydrophobically end-capped poly(ethylene oxide)s: HEURs, denoted as $C_8$$EO_{380}$$C_8$, $C_12$$CO_{600}$$C_{12}$, and $C_{18}$$EO_{860}$$C_{18}$,are described using static fluorescence, dynamic light scattering, and atomic force microscope (AFM) techniques. The CAC (critical aggregation concentration) was determined by com-paring two fluorescent peaks which were influenced by the polarity of the probe dye molecules, pyrene. The aggregation occurs in concentrations higher than 10 g/L of $C_8$$EO_{380}$$C_8$ and the CAC decreases by increasing the side chain length. The dynamic light scattering experiment shows fast mode and slow mode decays, and both are diffusive. The fast mode does not depend on the concentration, but the slow mode shows concentration dependence influenced by the formation of an aggregated structure. The hydrophobic end groups effect more dominantly than the main chains for the formation of HEUR micelles. By increasing the concentration, the HEUR micelles change their structure from spheres to rodlike micelles, and finally make fused structures, which were visualized with atomic force microscopy.
일개 항공기 정비시설의 화학물질 노출의 정성 및 정량 노출평가
백기욱 ( Baek Kiook ),김민석 ( Kim Minseok ),박해동 ( Jang Konghwa ),장공화 ( Park Haedong ),정은교 ( Chung Eunkyo ) 국군의무사령부 2019 대한군진의학학술지 Vol.50 No.1
Objectives; To evaluate exposure of chemicals, especially organic solvent, of aircraft maintenance facility in Korean army. Methods; We sampled bulk sample of solvent and air sample from maintenece facility workplace; cleaning and painting process. Air sampling was done by area sampling and personal sampling method. Analysis of sampling was done by gas chromatography/ mass spectrometry. Results; Benzene, heptane, toluene, ethylbenzene, xylene were detected among cleaning process. Comparison of TLV limit value, benzene was detected at a level of 22% of time weighted average level. Toluene, ethylbenzene, xylene were detected among painting process. Conclusions; We detected several organic solvents which is not enlisted on material safety data sheet. Carcinogenic or reproductive toxic agents were detected. Although the level was lower than exposure limit, safetly and health issues of workers should be concerned.
제2기(2012-2014) 국민환경보건 기초조사 자료를 활용한 국내 남성 택시 기사의 심혈관계 위험도 관련 혈액학적 변화에 대한 연구: 성향점수 매칭을 활용하여
백기욱 ( Kiook Baek ) 한국산업보건학회 2021 한국산업보건학회지 Vol.31 No.4
Objectives: Taxi drivers are exposed to various hazards, such as long periods of sedentary work and traffic-related air pollutants. However, studies on the health effects among taxi drivers in South Korea are insufficient. Methods: To assess subclinical hematologic change related to cardiovascular disease among male taxi drivers, we analyzed data from the second Korean National Environmental Health Survey. Fifty-nine taxi drivers and 1,912 controls were included in the analysis. Propensity score matching was performed to adjust for age, body mass index, and urinary cotinine. A total of 295 subjects were matched with 59 taxi drivers. Leukocyte count, platelet count, hematocrit, triglyceride, total cholesterol, HDL cholesterol land total IgE of the taxi drivers were compared with the control groups. Results: Taxi drivers showed significantly elevated blood leukocytes and platelets. Serum total IgE was significantly reduced in taxi drivers. However, blood leukocytes, platelets, and serum total IgE were not significantly correlated with work period among taxi drivers. Conclusions: Regarding the change of the blood leukocyte count, platelet count, and serum total IgE, taxi driving has the possibility to be associated with peripheral inflammation, humoral immunity and cardiovascular risk.
Star Tracker Geometric Calibration Through Full-State Estimation Including Attitude
윤효상,백기욱,위준성 한국항공우주학회 2022 International Journal of Aeronautical and Space Sc Vol.23 No.1
A star tracker calibration method using star images is presented in this paper. Unlike previous works, the proposed method estimates all parameters and the attitudes at once in a single least-squares formulation for the optimal calibration, which can be easily converted to a recursive estimation form. In addition, this paper presents a method to estimate the overall star tracker performance for attitude determination from the calibration results. Since the proposed method uses star images only, it can be applied to both on-orbit and ground star tracker calibration. The simulations show improvements in calibration performance about four times compared to the previous calibration method. The calibration experiments with actual star images are conducted to test its application.