• Journal of the Korean Society of Visualization
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• v.12 no.2
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• pp.18-22
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• 2014

Caenorhabditis elegans (C. elegans) is an undulatory nematode which exhibits two distinct locomotion types of swimming and crawling. Although in its natural habitat C. elegans lives in a non-Newtonian fluidic environment, our current understanding has been limited to the behavior of C. elegans in a simple Newtonian fluid. Here, we present some experimental results on the penetrating behavior of C. elegans at the interface from liquid to solid environment. Once C. elegans, which otherwise swims freely in a liquid, makes a contact to the solid gel boundary, it begins to penetrate vertically to the surface by changing its stroke motion characterized by a stiffer body shape and a slow stroke frequency. The particle image velocimetry (PIV) analysis reveals the flow streamlines produced by the stroke of worm. For the worm that crawls on a solid surface, we utilize a technique of traction force microscopy (TFM) to find that the crawling nematode forms localized force islands along the body where makes direct contacts to the gel surface.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.324-326
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• 2004

l2wt%Cr Steel has been applied on turbine bucket and nozzle partition material of power plant. Turbine bucket and nozzle get damaged by solid particle within steam, therefore they are protected by surface treatments such as ion nitriding, boriding and chrome carbide HVOF spray coating. In this study, solid particle erosion(SPE) characteristics after these surface treatments are examined at operating temperature 540$^{\circ}C$ and 590$^{\circ}C$ of fossil power plant and the mechanism of damage was studied. Erosion of 12wt%Cr steel is originated by micro cutting and that of boriding and chrome carbide HVOF spray is originated by these mechanism - repeating collision, crack initiation and propagation. As the results of SPE test at 540$^{\circ}C$ and 30$^{\circ}$ impact angle that is the most commonly occurred in power plant, Boriding had the best SPE -resistance property, Cr$_2$C$_3$-25(Ni20Cr) HVOF spayed and ion nitrided samples were also better than bare metals(l2wt%Cr Steels). At 590$^{\circ}C$ and 30$^{\circ}$ impact angle, Boriding had also the most superior characteristic and HVOF spay sample was better than bare metal.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.5
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• pp.747-753
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• 2006

Air flotation is a solid-liquid separation process that utilizes up-flow microbubbles to thicken activated sludge and enhance clarification efficiency. Continuous air flotation experiments were performed to investigate the effect of operation parameters such as initial MLSS (mixed liquor suspended solid) concentration, air pressure, surface loading rate, air to solid (A/S) ratio, and flotation time on thickening efficiency. An initial activated sludge concentration ranged from 3,000 to 12,000mgSS/L and thickened sludge concentration varied from 6,400 to 28,100mgSS/L. The result showed that the thickening efficiency was mainly dependent on surface loading rate, A/S ratio, and flotation time. The pressure did not affect the thickening efficiency when it kept in the range of 1.6 to 1.8 bar. Experimental results showed that the thickening efficiency of activated sludge was increased only when the feed sludge concentration exceeded 5,000mgSS/L and the thickened concentration was over 20,000mgSS/L. At this time, SS concentration in the clarified liquid was ranged from 5 to 10mg/L.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.912-914
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• 1999

Composite insulation system of liquid nitrogen and solid spacer is widely applied in high temperature superconducting power machine. This study has three step procedure. As follow, first step is composition of parallel deposited electrode and vertically deposited electrode along the direction of immersion in liquid nitrogen($LN_2$). Second step is investigation into surface flashover voltage of solid spacer under partially immersed in $LN_2$, and last step is comparison the result of this research with that of fully immersed in $LN_2$ and at cryogenic temperature gaseous nitrogen($GN_2$). This result presented that surface flashover voltage along solid spacer half immersed in $LN_2$ was almost the same as that of fully immersed spacer when the thickness of spacer(t) was t<10 mm. In the case of t>10 mm, however, spacer flashover voltage was equal to that obtained in $GN_2$ at cryogenic temperature.

• Journal of Educational Research in Mathematics
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• v.18 no.1
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• pp.81-101
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• 2008

This study points out that the way of teaching varies according to the kinds of figures in explaining the volume and the surface area of solid figures in the seventh grade curriculum. Especially, the study discusses the limitation of the explanation depending on the experimental method using physical objects. Considering the study of Archimedes' research about measuring sphere, we investigate its educational implications and, based on this result, suggest the complementary approach and the considerations for applying to current school mathematics curriculum.

• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.459-463
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• 2009

Furoxanaldehydes possessing phenyl or alkenyl groups at the 3- or 4-position of the furoxan ring were designed for alkyne formation on a solid surface. Furoxans 2 and 3 were prepared from the corresponding alkenes 2a and 3a by the reaction with NaN$O_2$ in acetic acid. Furoxan 4, in which the furoxan ring is conjugated with a double bond, was prepared from bis(bromomethyl)benzene 4a in 5 steps using the Wittig reaction of aldehyde 1 as the key step. The electron beam-mediated fragmentation of furoxanaldehydes 1-4 in a mass spectrometer was exploited by focusing on alkyne formation on the solid surface. The fragmentation of furoxan 3 possessing diaryl groups afforded diarylacetylene at high efficiency, suggesting that the aryl group conjugated with the furoxan ring could facilitate alkyne formation with the evolution of NO.

• Corrosion Science and Technology
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• v.20 no.6
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• pp.384-390
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• 2021

In this paper, durability evaluation and surface damage mechanism were investigated through solid particle erosion (SPE) test after applying hot-dip aluminizing (HDA) technology for the purpose of maintenance of marine economizer tube. Damaged surface shape was analyzed using SEM and 3D microscope. Compositional changes and microstructure of the HDA layer were analyzed through EDS and XRD. Durability was evaluated by analyzing weight loss and surface damage depth after SPE. HDA was confirmed to have a two-layer structure of Al and Al₅Fe₂. HDA+HT was made into a single alloy layer of Al₅Fe₂ by diffusion treatment. In the microstructure of HDA+HT, void and crack defect were induced during the crystal phase transformation process. The SPE damage mechanism depends on material properties. Plastic deformation occurred in the substrate and HDA due to ductility, whereas weight loss due to brittleness occurred significantly in HDA+HT. As a result, the substrate and HDA showed better SPE resistance than HDA+HT.

• Steel and Composite Structures
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• v.41 no.6
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• pp.805-820
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• 2021

In this research, the buckling and free vibration of three-phase carbon nanotubes/ fiber/ polymer piezoelectric nanocomposite face sheet sandwich microbeam with microsensor and micro-actuator surrounded in elastic foundation based on modified couple stress theory (MCST) is investigated. Three types of porous materials are considered for sandwich core. Higher order (Reddy) and sinusoidal shear deformation beam theories are employed for the displacement fields. Sinusoidal surface stress effects are extracted for sinusoidal shear deformation beam theory. The equations of motion are derived by Hamilton's principle and then the natural frequency and critical buckling load are obtained by Navier's type solution. The determined results are in good agreement with other literatures. The detailed numerical investigation for various parameters is performed for this microsensor-microactuator. The results reveal that the microsensor-microactuator enhanced by increasing of Skempton coefficient, carbon nanotubes diameter length to thickness ratio, small scale factor, elastic foundation, surface stress constants and reduction in porous coefficient, micro-actuator voltage and CNT weight fraction. The valuable results can be expedient for micro-electro-mechanical (MEMS) and nano-electro-mechanical (NEMS) systems.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.19-24
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• 2007

The deposition behavior of soot particles in a diffusion flame along a solid wall was examined experimentally by getting rid of the effect of natural convection utilizing microgravity environment. The microgravity environment was realized by using a drop tower facility. The fuel for the flame was an ethylene ($C_2H_4$) and the surrounding oxygen concentration 35% with the surrounding air velocity of $V_a$=2.5, 5, and 10 cm/s. Laser extinction method was adopted to measure the soot volume fraction distribution between the flame and burner wall. The results show that observation of soot deposition in normal flame was difficult from buoyancy and the relative position of flame and solid surface changes with time. The soot particle distribution region moves closer to the surface of the wall as the surrounding air velocity is increased. And the experiments determined the trace of the maximum soot concentration line. It was found that the distance between soot line and flame line is around 5 mm. That is, the soot particle near the flame zone tends to move away from flame zone because of thermophoretic force and to concentrate at a certain narrow area inside of the flame, finally, to adhere the solid wall.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.12
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• pp.1710-1719
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• 1997

An approximate analytical solution for the initial transient process of close-contact melting occurring between a phase change material kept at its melting temperature and an isothermally heated flat surface is derived. The model is so developed that it can cover both rectangular and circular cross-sectional solid blocks. Normalization of simplified model equations in reference to the steady solution enables the solution to be expressed in a generalized form depending on the liquid-to-solid density ratio only. A selected result shows an excellent agreement with the previously reported numerical data, which justifies the present approach. The solution appears to be capable of describing all the fundamental characteristics of the transient process. In particular, dependence of the solid descending velocity oft the density ratio at the early stage of melting is successfully resolved. The effects of other parameters except the density ratio on the transient behaviors are efficiently represented via the steady solution implied in the normalized result. A simple approximate method for estimating the effect of convection on heat transfer across the liquid film is also proposed.