At Pyropia farms, organic acid treatments have enhanced productivity and quality by removing pest algae (such as Ulva spp. and diatoms) and reducing the occurrence of diseases. Ulva spp. attaches to the Pyropia nets competing for inorganic nutrients & space and diminishing productivity. Additionally, the presence of attached contaminants (such as diatoms and middy particles) on the Pyropia nets negatively affects the quality of Pyropia. This study investigated the effects of removing Ulva linza and washing the Pyropia yezoensis nets using an activating treatment agent (organic acid and highly saline solution) with an air bubble device. The results of measuring the dead cell ratios after treatment under different conditions showed that the dead cell ratio of U. linza did not significantly increase when the air bubble device combined the activating treatment agent with the activating treatment agent alone. When washing the P. yezoensis nets, the air bubble device was about 19-37% more effective than the activating treatment agent alone. The findings of this study suggest that the air bubble device enhances the efficacy of the activating treatment agent, resulting in the effective cleaning of the Pyropia nets.

본 연구는 장미 ‘Bubble Gum’의 절화수명을 연장시키기 위하여 미산성 차아염소산수(Slightly acidic hypochlorous water, HOCl, pH 6.26)의 처리효과와 절화수명 연장제로써 의 가능성을 구명하고자 수행되었다. 침지처리는 30μL･L-1의 미산성 차아염소산수를 0분, 0.5분, 1분, 3분, 5분간 침지처 리 후 수돗물(Tap water, control)에 꽂아 두었다. 대조구의 절화수명은 8.7일인데 비해 5분 침치처리 시 10.8일로 대조 구보다 2.1일 수명을 연장시켰다. 상대생체중은 모든 처리구 에서 2일까지 증가하였고, 수분흡수율은 모든 처리구에서 6일 까지 증가하다가 감소하는 추세를 보였다. 화색 변화율인 ΔE 값은 3분(5.25), 5분(6.48), 30초(6.65), 1분(6.79) 침지처리 에서 대조구보다 낮았으며, 상대 화폭 증가율은 5분 침지 처 리구가 145%로 화폭의 증가율이 가장 컸고, 엽록소함량은 처 리 간 차이가 없었다. 결론적으로 절화장미 ‘Bubble Gum’의 절화수명은 미산성 차아염소산수의 5분 침지 처리가 효과적 으로 연장시켰다.

본 연구는 장미 ‘Bubble Gum’에 대한 수확 후 LED 광 환경 과 살균제 Azoxystrobin 보존용액 처리 시 절화품질에 미치는 영향을 구명하고자 수행되었다. 광은 백색 LED와 유색 LED (red:blue=5:1)로 처리하였고, 보존용액은 수돗물(tap water, TW)과 Azoxystrobin 0.05 mL･L-1를 처리하였다. 백색 LED처 리의 절화수명은 TW, Azoxystrobin처리구 각각 9.6일, 9.7일 로 LED 광과 보존용액 처리 간의 유의차가 없었다. 유색 LED 처리의 절화수명은 TW처리구가 13.6일, Azoxystrobin처리구 가 9.8일로, 유색 LED 처리구가 대조구(백색 LED + TW)에 비해 절화수명을 4일 연장시켰다. 절화수명 종료 증상은 LED 광 조건과 관계없이 Azoxystrobin처리구는 꽃잎 위조와 청변 화 증상을 감소시켰다. 모든 처리구에서 상대생체중과 수분흡 수율은 각각 처리 후 2일, 4일까지 증가하다 감소하는 경향을 보였다. 수확 직후 대비 처리 6일 후 화색 변화율과 잎의 엽록 소 함량은 수확 직후와 모든 처리구에서 차이가 없었으며, 화 폭증가율도 처리 간 차이가 없었다. 결론적으로 백색 LED + Azoxystrobin 보존용액처리는 절화장미의 꽃잎 위조와 청변화 증상을 감소시키지만, 절화수명 연장효과가 없었으며, 적색 +청색 LED 처리는 장미의 절화수명 연장효과에 효과적이었다.

This study aimed to develop an algae reduction device using bubbles to improve algal blooms occurring in lakes or reservoirs in summer, and to design a venturi, a major core device for bubble generation and supply. As a measure to improve the bubble generation effect of the venturi, the venturi was devised to change the air intake characteristics, and the flow characteristics were analyzed through CFD simulation to achieve the optimal design.

An important variable in the oil-water separation process is the size and dispersion diagram of the bubbles formed in the induced gas flotation(IGF). In this study, the influence of the behavior and characteristics of the fine bubbles generated in the IGF device on the oil-water separation performance was evaluated by a numerical analysis method. For this reason, it constitutes Grid system suitable for bubble characteristic analysis. By applying Reynolds-averaged Navier-Stokes equations, a continuous abnormal flow analysis model of water and air was established. For the numerical flow analysis model, we applied the Eulerian-Eulerian approach that can be used for the reaction model in which bubbles are formed at one point of the Euler method applied when the base is liquid. As a result, it was confirmed that the bubbles in the IGF device were evenly dispersed as the flow velocity of bubbles increased and the particle size decreased. Such a phenomenon was caused by changes in Reynolds number and drag related to the flow characteristics, and could be explained by Stokes' law of viscosity.

Mass mortality of mariculture fish due to high summer temperatures is a major issue in the mariculture industry in many coastal waters of Korea, yet measures to mitigate the impact are generally limited. We injected a micro-bubble of liquefied oxygen into the bottom of rockfish cages (about 6-8 m deep) in order to maximize the dispersal of micro-bubbled seawater and reduce fish mortality. The injection of low-temperature oxygen in micro-bubbles lowered the water temperature at the injection area by as much as 1℃ and increased dissolved oxygen concentration by 0.5 ppm. In early August, following a week with persistent high water temperature (above 28.5℃), there was an increase in fish mortality despite the micro-bubble system, which resulted in approximately 7% death of the total introduced fish population. However, this mortality appeared to be much lower than mortality reported in a neighboring mariculture facility (approximately 50% mortality). We also estimated the volume that can be recirculated with pumped seawater using a micro-bubble system. We suggest that this approach of injecting liquefied oxygen through a micro-bubble system may reduce fish mortality during high temperature periods.

This paper reports slug bubble dynamics on modified surface with two-dimensional graphene film in downward-facing nucleate boiling. Behaviors of slug bubbles were observed with high speed camera, and post-processing was followed to measure departing speed, frequency, and diameter of slug bubbles, which were important to analyze boiling performance change. The graphene-modified surface showed enhanced boiling heat transfer coefficient (BHTC) and critical heat flux (CHF). The effect of surface modification on slug bubble dynamics was quantitatively analyzed; bigger slugs departed from the modified surface with faster speed but same frequency, compared with the bare. It seems that the BHTC enhancement is caused by increase of bubble diameter, resulting in increase of its departing speed. The higher speed of departing bubble could extend the hydrodynamic limit of vapor removal from downward-facing surface, so that CHF performance could be enhanced.

본 연구는 도로시설물의 염화칼슘 제거를 위한 미세기포 세척장비의 최적 운용조건에 대하여 성능평가를 수행하였다. 실험에 사용된 미세기포의 직경은 196.6±100.6nm 에 1.36×108개/ml의 농도를 나타낸다. 세척장비의 분사장치에 대한 실험 성능결과, 100bar의 분사압력에서 100cm, 150cm 분사거리에 약 93%, 91%의 세척효율이 나타나는 것으로 확인되었다. 미세기포 생성(순환)횟수를 2-6회로 증가시킴에 따라 최소 1%에서 7%까지 염화물 제거율이 높아짐을 확인하였다. 미세기포 생성 공기유량을 4 ml/min에서 0.5 ml/min으로 낮춤에 따라 세척효율이 최대 30%까지 증가하는 것이 확인되었다. 일반 상수도와 미세기포의 세척효율은 미세기포가 일반상수도 보다 세척효율이 25% 높게 나타났다.

This paper reports an uncertainty analysis of quantitative visualization methodology for slug bubble dynamics in downward-facing nucleate boiling condition. Measurement of dynamics of slug bubble, i.e. departing speed, frequency, and diameter, is very important to predict safety margin of thermal systems in moving vehicle. By employing high speed visualization and post-processing, we quantitatively measured the volume and location of slug bubble, so that vapor generation rate and departing speed data were derived from their time differentiation. As a visualization methodology, its reliability was evaluated via uncertainty analysis. For 95% confidence interval, uncertainty of vapor generation rate and departing speed were 3% and 2%, respectively, and which were one order lower than standard deviation of those data.