• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.6
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• pp.519-526
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• 2015

To measure the physical parameters of the simple microlayer model for the prediction of the heat flux and heat transfer rate due to the evaporation of the microlayer during nucleate boiling, the microlayer geometry was experimentally examined. The parameters, including initial thickness, moving velocity and microlayer radius, were measured by total reflection and interferometry techniques using a laser. Single-bubble nucleate boiling experiments were conducted using saturated water on a horizontal surface under atmospheric pressure. The geometric characteristics of the microlayer underneath the bubbles periodically nucleating at a nucleation site at an average heat flux of $200kW/m^2$ were analyzed. The experimental results in the present study show that the maximum initial thickness of the microlayer and the horizontal moving velocity are $5.4{\mu}m$ and 0.12 m/s, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.4
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• pp.355-359
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• 1987

Texture and mineralogy of different microlayers of deep-sea manganese nodules are investigted to reveal the environmental changes of nodules during a nodule formation. Basically a nodule can have three types (A, B and C) of microlayer. Some nodules show only one or two types of microlayer. The classification is based primarily on the texture. The surface torture of type A is coarsely porous globular microstructure whereas type B and C are intermediate to finely porous textures. The type A is characterized by its highest Mn content $(30.6\%)$ and relatively well-crystallized todorokite as veil as the rapid growth rate. Smectite and biogenic silica (radiolaria) are also easily observed in the type A layer. It appears that the hydrothermal activity is one of the favorable mechanism of formation for the type A layer. The hydrothermal solution is possibly supplied from nearby fracture zone and spreading center.

• Journal of Microbiology and Biotechnology
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• v.22 no.3
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• pp.283-291
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• 2012

Bioremediation efforts often rely on the application of surfactants to enhance hydrocarbon bioavailability. However, synthetic surfactants can sometimes be toxic to degrading microorganisms, thus reducing the clearance rate of the pollutant. Therefore, surfactant-resistant bacteria can be an important tool for bioremediation efforts of hydrophobic pollutants, circumventing the toxicity of synthetic surfactants that often delay microbial bioremediation of these contaminants. In this study, we screened a natural surfactant-rich compartment, the estuarine surface microlayer (SML), for cultivable surfactant-resistant bacteria using selective cultures of sodium dodecyl sulfate (SDS) and cetyl trimethylammonium bromide (CTAB). Resistance to surfactants was evaluated by colony counts in solid media amended with critical micelle concentrations (CMC) of either surfactants, in comparison with non-amended controls. Selective cultures for surfactant-resistant bacteria were prepared in mineral medium also containing CMC concentrations of either CTAB or SDS. The surfactantresistant isolates obtained were tested by PCR for the Pseudomonas genus marker gacA gene and for the naphthalene-dioxygenase-encoding gene ndo. Isolates were also screened for biosurfactant production by the atomized oil assay. A high proportion of culturable bacterioneuston was tolerant to CMC concentrations of SDS or CTAB. The gacA-targeted PCR revealed that 64% of the isolates were Pseudomonads. Biosurfactant production in solid medium was detected in 9.4% of tested isolates, all affiliated with genus Pseudomonas. This study shows that the SML is a potential source of surfactant-resistant and biosurfactant-producing bacteria in which Pseudomonads emerge as a relevant group.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.19 no.1
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• pp.88-98
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• 2014

Despite of emerging and increasing concerns to microplastics, no standard methodology has not been proposed for determination of microplastics. This study aims to develop the analysis method for microplastics in seawater by overviewing methodologies proposed by previous studies and by assessing some processes in those methodologies which possibly cause uncertainties in microplastic determination. Furthermore, we present preliminary results of distribution characteristics of microplastics in seawater of Incheon/Kyeonggi coastal region which is based on our new methodology. Microplastics in surface microlayer (SML) and subsurface water (SSW) were collected using mesh screen and planktonic nets (trawl net with $330{\mu}m$ mesh size and hand net with $20{\mu}m$ mesh size), respectively. Microplastics with < $300{\mu}m$ was predominant, indicating hand net as the better collection tool for SSW. As for SML, FT-IR based microplastic concentration was well matched with naked-eye based concentration which has been used in most of previous studies. However, a poor relationship was observed for SSW, indicating that concentration data of previous SSW studies should be corrected. Incheon/Kyeonggi bay seawater contained the similar concentration range with those in coastal region of the Nakdong River. Our methodology can be used as a basic tool for further microplatic studies.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.218-222
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• 2009

A level-set (LS) method is presented for computation of boiling phenomena which involve liquid-vapor interfaces that evolve, merge and break up in time, the flow and temperature fields influenced by the interfacial motion, and the microlayer that forms between the solid and the vapor phase near the wall. The LS formulation for tracking the phase interfaces is modified to include the effects of phase change on the liquid-vapor interface and contact angle on the liquid-vapor-solid interline. The LS method can calculate an interface curvature accurately by using a smooth distance function. Also, it is straightforward to implement for two-phase flows in complex geometries. The numerical method is applied for analysis of nucleate boiling on a horizontal surface and film boiling on a horizontal cylinder.

• Journal of Mechanical Science and Technology
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• v.15 no.7
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• pp.931-940
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• 2001

A numerical method for simulating bubble motion during nucleate boiling is presented. The vapor-liquid interface is captured by a level set method which can easily handle breaking and merging of the interface and can calculate an interfacial curvature more accurately than the VOF method using a step function. The level set method is modified to include the effects of phase change at the interface and contact angle at the wall as well as to achieve mass conservation during the whole calculation procedure. Also, a simplified model to predict the heat flux in a thin liquid microlayer is developed. The method is applied for simulation of a sliding bubble on a vertical surface to further understand the physics of partial boiling. Based on the computed results, the effects of contact angle, wall superheat and phase change on a sliding bubble are quantified.

• Korean Journal of Microbiology
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• v.22 no.4
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• pp.243-247
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• 1984

The effect of the heavy metals copper and cadmium on the natural populations of surface microlayer and subsurface water was investigated. Two microbiological parameters, number of colony-forming bacteria and $^{14}C-glucose$ uptake rate, were evalated. The two natural bacterial populations showed different tolerances of the heavy metals. The ingibition of bacterial growth and activity occurred more strongly in the 1m-depth samples than in neuston populations. The results support the existence of autochthonous bacterioneuston populations in marine environment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.1089-1095
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• 2011

Numerical simulation is performed for nucleate boiling on a micro-finned surface, which has been widely used to enhance heat transfer, by solving the equations governing the conservation of mass, momentum, and energy in the liquid and vapor phases. The bubble motion is determined by a sharp-interface level-set method, which is modified to include the effect of phase change and to treat the no-slip and contact-angle conditions, as well as the evaporative heat flux from the liquid microlayer on immersed solid surfaces such as micro fins and cavities. The numerical results for bubble formation, growth, and departure on a microstructured surface including fins and cavities show that the bubble behavior during nucleate boiling is significantly influenced by the fin-cavity arrangement and the fin-fin spacing.