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종속적 준비시간을 갖는 다단계 그룹가공 생산시스템에서의 그룹스케듈링에 관한 연구
황문영 한국산업경영시스템학회 1994 한국산업경영시스템학회지 Vol.17 No.31
Group scheduling, which is a kind of operations scheduling based on the GT concept is analyzed in a multi-stage manufacturing system. The purpose of this research is to develop and evaluate a heuristic algorithm for determining gro up sequence and job sequence within each group to minimize a complex cost function, i.e. the sum of the total pe-nalty cost for tardiness and the total holding cost for flow time, in a multi-stage manufacturing system with group setup time dependent upon group sequence. A heuristic algorithm for group sc heduling is developed, and a numerical example is illustrated. For the evaluation of the pro-posed heuristic algorithm, the heuristic solution of each of 63 problems is compared with that of random scheduling. The result shows that the proposed heuristic algorithm provides better solution in light of the proposed cost function.
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항공우주구조물의 충격 감지를 위한 PNN-PZT/CNT/Epoxy 페인트 센서의 압전 특성 변화에 관한 연구
황문영,강명철,강래형 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.11
본 연구에서는 항공우주구조물의 충격 감지를 위한 압전페인트 센서의 압전특성이 CNT 첨가에 따라 어떻게 변화하는지 기술하였다. 연구에 사용된 압전 페인트 센서는 유연 압전 재료인 PNN-PZT 와 에폭시 수지를 무게비 1:1 로 혼합하여 제작하였다. 그 후, Multi-walled CNT 가 압전 페인트 센서내에서 잘 분산될 수 있도록 아세톤 용매 내에서 초음파처리(Sonication)하였다. 60 x 10 x 1mm³ 크기의 몰드에서 제작된 시편의 위아래 면에 실버 페이스트를 사용하여 전극을 제작하였다. 분극전계는 4kV/mm 로 고정한 상태에서 분극 시간을 달리하여 상온에서 분극 작업을 시행했다. 시편에 가해지는 충격 망치의 힘에 대하여 센서에서 발생하는 출력 전압을 비교하여 살펴보았으며, 그 결과 CNT 가 첨가된 센서가 그렇지 않은 센서에 비해 감도향상이 있음을 확인할 수 있었다. In this study, the piezoelectric characteristic changes of a piezoelectric paint sensor with CNT for impact monitoring of aerospace structures was described. The piezoelectric paint sensor is composed of Pb(Ni₁/₃Nb⅔)03-Pb(Zr, Ti)O₂ (PNNPZT) powder and epoxy resin with 1:1 weight ratio, and multi-walled CNT used in the study is sonicated in acetone to increase a degree of dispersion. The dimensions of the paint specimen were 60 x 10 x 1 mm³, and the top and bottom plates were both coated with a silver paste. At room temperature, during the poling treatment, the electric field was set to 4kV/mm and the poling time was controlled to examine its effect on the piezoelectric properties. The sensitivity of paint sensor was compared by detecting output voltage from specimen when the impact hammer hits the specimen. In conclusion, it is founded the sensitivity of sensor with CNT is higher than that of sensor which didn’t use CNT.
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주거환경 및 개인 생활습관에 따른 화학물질 노출수준 차이 - 국민환경보건기초조사
황문영,홍수연,권영민,조혜정,박충희 한국환경보건학회 2019 한국환경보건학회지 Vol.45 No.2
Objectives: The aim of this study was to determine environmental chemical exposure related to residential and personal lifestyle characteristics in the adult Korean population. The observations of this study can provide information useful for developing reduction approaches for exposure to chemicals among the general adult population. Methods: The second stage of the Korean National Environmental Health Survey (KoNHES) was conducted from 2012 to 2014, with 6,478 persons participating. Using the results of the survey, the relationship between exposure levels of heavy metals and organic chemicals and exposure factors, e.g. residential and personal lifestyle characteristics, were analyzed. Results: The exposure levels of VOCs and PAHs were significantly lower in participants living at a distance of more than 100 m from roads versus living closer to roads. Home ventilation lowered VOC and PAH exposure but did not lower chemical exposure from household products. Use of public transportation showed lower exposure to heavy metals, VOCs, and PAHs. Current smoker was significantly higher for levels of heavy metals, VOCs, and PAHs, and the exposure trend was similar for current drinkers. Physical activity was related with higher exposure to phthalates and environmental phenols. Conclusion: Our observations based on a nationally representative population for Korea show that exposure to chemicals varies by residential and personal lifestyle, and this should be considered for developing appropriate mitigation measures and policies. Given the health concerns surrounding environmental chemicals, it is necessary to develop comprehensive measures to reduce chemical exposure.
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환경오염물질 노출수준의 계절적 변이와 그 함의 - 제2기 국민환경보건기초조사(2012-2014)
황문영,류정민,권영민,홍수연,박충희 한국환경보건학회 2018 한국환경보건학회지 Vol.44 No.6
Objectives: Human biomonitoring (HBM) is a measurement of the chemicals and their metabolites in human biological samples and has been successfully employed to determine the exposure levels of environmental chemicals. In this study, we analyzed seasonal variations of the blood or urinary levels of chemicals, and assessed that these differences could affect the results of association study. Methods: The Korea National Environmental Health Survey (KoNEHS) is a nationwide survey that analyzes exposure levels of environmental pollutants, 19 kinds of chemicals including heavy metals and organic chemicals, and the exposure factors in the general population. Based on KoNEHS data, we analyzed the levels of chemicals concentrations over the total survey period (2012-2014) and each season, and assessed the association of thyroid measures with phthalate metabolite and BPA. Results: Exposure levels of blood mercury and lead were lower in summer compare to winter. Bisphenol A and PAHs metabolites were higher in spring and summer, but lower in autumn. VOCs metabolites were generally lower in summer and autumn. Phthalate metabolites were higher in all other seasons than in winter. Pyrethroid metabolite, 3-PBA, was higher in summer and autumn. Regarding seasonal variation of chemical exposures, the statistical significance and size of effects between thyroid measures and phthalate and BPA were changed with season. Conclusion: Seasonal variations of chemical exposure and health outcome should be considered for interpreting biomonitoring results from a public health context.
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