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거친 발수 표면에 충돌하는 유체 방울의 팽창 및 수축 역학: 미세 유체 방울의 형성
김의진(Uijin Kim),김정현(Jeong-Hyun Kim) 한국가시화정보학회 2021 한국가시화정보학회지 Vol.19 No.3
In this study, we investigated the dynamics of a droplet impacting rough hydrophobic surfaces through high-speed imaging. Micrometer-sized structures with grooves and pillars were fabricated on smooth Polydimethylsiloxane (PDMS) surfaces by laser ablation. We used Newtonian and non-Newtonian liquid droplets to study the drop impact dynamics. De-ionized water and aqueous glycerin solutions were used for the Newtonian liquid droplet. The solutions of xanthan gum in water were prepared to provide elastic property to the Newtonian droplet. We found that the orientation of the surface structures affected the maximal spreading diameter of the droplet due to the degree of slippage. During the droplet retraction, the dynamic receding contact angles were measured to be around 90° or less. It resulted in the formation of the micro-capillary bridges between the receding droplet and the surface structures. Then, the rupture of the capillary bridge led to the formation of micrometer-sized droplets on top of the surface structures. The size of the microdroplets was found to increase with increasing the impacting velocity and viscosity of the Newtonian liquid droplets. However, the size of the isolated microdroplets decreased with enhancing the elasticity of the droplets, and the size of the non-Newtonian microdroplets was not affected by the impacting velocity.
소방 실화재 훈련에서 사용하는 압축목재 가연물에서 발생하는 유해물질 특성
이용호(Yongho Lee),김진희(Jinhee Kim),김의진(Uijin Kim),최원준(Won-Jun Choi),이완형(Wanhyung Lee),강성규(Seong-Kyu Kang),이소연(So Yun Lee),함승헌(Seunghon Ham) 한국환경보건학회 2020 한국환경보건학회지 Vol.46 No.5
Objectives: To identify and investigate through qualitative and quantitative analysis the hazardous substances generated when compressed wood was burned at a live fire-training center. Methods: Four types of compressed wood that are actually used in live fire training were burned in a chamber according to KS F2271. The gaseous material was sampled with a gas detector tube and conventional personal samplers. Results: 1,3-butadiene, benzene, toluene, xylene, formaldehyde, hydrogen chloride, hydrogen cyanide, ammonia, carbon monoxide, and nitric acid were detected. In particular, 1,3-butadiene (497.04-680.44 ppm), benzene (97.79-125.02 ppm), formaldehyde (1.72-13.03 ppm), hydrogen chloride (4.71-15.66 ppm), hydrogen cyanide (3.64-8.57 ppm), and sulfuric acid (3.85-5.01 ppm) exceeded the Korean Occupational Exposure Limit as measured by sampling pump according to the type of compressed wood. Conclusions: We found through the chamber testing that firefighters could be exposed to toxic substances during live fire training. Therefore, firefighter protection is needed and more research is required in the field.