• Journal of the Korean Applied Science and Technology
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• v.13 no.2
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• pp.1-20
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• 1996

Surfactants are the surface-active molecules that display amphiphilicity, Because of this surface activity and amphiphilicity, surfactants have been used in wide industrial applications such as foods, detergents, cosmetics, medicine, polymers, paints, flotation, textiles. These days, their applications extend to high-technology industries such as microelectronics, magnetic recording material, advanced batteries, novel separations, etc. As new applications of surfactants are found and the demand of the surfactants increases, surfactant industry has been more pressed to face a formidable challenge, which is to develop surfactants that are envirionmentally friendly. In this regard biosurfactants may be alternatives to chemical surfactants, since biosurfactants are biologically compatible, more biodegradable, less toxic, and highly specific. Because of these excellent advantages over those of chemical surfactants, much efforts have been made in biosurfactant research. This article reviews biosurfactants in several aspects, that is, their definition, structures, properties, applications, and prospects.

• Progress in Superconductivity
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• v.6 no.1
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• pp.32-36
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• 2004

To investigate the influence of strip width and inter-strip separation on the ac loss, arrays of parallel strips with different widths and separations were prepared. Studies on the hysteresis-loss characteristics of multifilamentary YBCO films were performed. The local magnetic field due to magnetization currents is measured by a scanning Hall probe microscope. Based on these results a conceptual design for a low loss YBCO coated conductor is suggested.

• Membrane and Water Treatment
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• v.5 no.2
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• pp.147-170
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• 2014

This paper focuses on the study of the most recent ultra-filtration techniques, based on porous polymer membranes, used for the treatment of wastewater from oil, mine and hydrometallurgical industries. The performance of porous membranes used in separation and recovery of oil and heavy metals from wastewater, was evaluated by the polymer composition and by the membrane characteristics, as it follows: hydrophobicity or hydrophilicity, porosity, carrier (composition and concentration), selectivity, fouling, durability, separation efficiency and operating conditions. The oil/water efficient separation was observed on ultra-filtration (UF) techniques, with porous membranes, whereas heavy metals recovery from wastewater was observed using porous membranes with carrier. It can be concluded, that in the ultra-filtration wastewater treatments, a hybrid system, with porous polymer membranes with or without carrier, can be used for these two applications: oil/water separation and heavy metals recovery.

• The KSFM Journal of Fluid Machinery
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• v.3 no.4 s.9
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• pp.15-21
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• 2000

An anemometer employing the bulk PTC thermistor as the sensing element is investigated in this study. The numerical and experimental works are carried out to improve the sensitivity problem of the element by focusing fluid dynamics point of view. The typical shape of the sensing element has been used as a rectangular type, but this shape has a sensitivity problem because of flow separations on the sharp edge when the flow direction is different from that of the sensing element. In order to reduce the reading error, the installer has to be very careful about the flow direction. The reading error fluctuation by time as well as the sensitivity problem can be improved considerably through this study. It can be concluded that the small change of the sensor shape can improve the performance of the flow sensor.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.3
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• pp.179-186
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• 2006

End-Labeled Free-Solution Electrophoresis (ELFSE) is a new technique that is a promising bioconjugate method for DNA sequencing (or separation) and genotyping by both capillary and microfluidic device electrophoresis. Because ELFSE enables high-resolution electrophoretic separation in aqueous buffer alone (i.e., without a polymer matrix), it eliminates the need to load viscous polymer networks into electrophoresis microchannels. To achieve microchannel DNA separations with high performance, ELFSE requires monodisperse perturbing entities (i.e., drag-tags), which create a large amount of frictional drag when pulled behind DNA during free-solution electrophoresis, and which have other properties suitable for microchannel electrophoresis. In this article, the theoretical concepts of ELFSE and the required characteristics of the drag-tag molecules for the ultimate performance of ELFSE are reviewed. Additionally, the merits and limitations of current drag-tags are also discussed in the context of recent experimental data of ELFSE separation (or sequencing).

• Journal of Electrochemical Science and Technology
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• v.4 no.4
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• pp.153-156
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• 2013

Charge transfer between STM tip and Au(100) has been investigated by using a Scanning Tunneling Microscopy (STM) technique in dry, $H_2O$, and $D_2O$ atmospheres. Dry atmosphere was indicated by humidity as low as 5 % and high humidity as high as 98% was managed by injecting $H_2O$ and $D_2O$ to the chamber. The current decayed more slowly in high humidity than in dry atmosphere. The plateau currents were found to appear at separations larger than ca. $5{\AA}$ where the current decay stopped depending on applied bias voltages. The polarity dependence was observed at the STM junction between Pt-Ir tip and the gold. On the contrary, little dependence was seen at the one between Au tip and the substrate electrode.

• Publications of The Korean Astronomical Society
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• v.7 no.1
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• pp.25-30
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• 1992

Recent redshift surveys suggest that most galaxies may be distributed on the surfaces of bubbles surrounding large voids. To investigate the quantitative consistency of this qualitative picture of large-scale structure, we study analytically the clustering properties of galaxies in a universe filled with spherical shells. In this paper, we report the results of the calculations for the spatial and angular two-point correlation functions of galaxies. With ${\sim}20%$ of galaxies in clusters and a power law distribution of shell sizes, $n_{sh}(R){\sim}R^{-{\alpha}}$, ${\alpha}\;{\simeq}\;4$, the observed slope and amplitude of the spatial two-point correlation function ${\xi}_{gg}(r)$ can be reproduced. (It has been shown that the same model parameters reproduce the enhanced cluster two-point correlation function, ${\xi}_{cc}(r)$). The corresponding angular two-point correlation function $w({\theta})$ is calculated using the relativistic form of Limber's equation and the Schecter-type luminosity function. The calculated w(${\theta}$) agrees with the observed one quite well on small separations (${\theta}{\lesssim}2deg$).

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.409-410
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• 1996

Speckle Interferometer equipped with an ITT intensified CCD have been used on the NCUO ( National Central University Observatory, Taiwan) 24-inch telescope for studying the orbits of bright binary systems selected from the Yale's Bright Star Catalogue. The high resolution and high sensitivity ITT intensified solid state video camera ( F4577 ) has external gain and gate control functions which will simplify the design of the speckle camera and allow us to do precise speckle photometry. The goal of this project is trying to study the bright binary systems with separations between the average size of seeing disk and the diffraction limit of the 24-inch telescope. Recently some observing data have been reduced and compared with the other teams' results. We are now improving the data reduction technology and trying to use real time observing mode on the monthly routine observation.

• Journal of The Korean Astronomical Society
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• v.47 no.6
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• pp.279-291
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• 2014

I show that the WFIRST microlensing survey will enable detection and precision orbit determination of Kuiper Belt Objects (KBOs) down to $H_{vega}=28.2$ over an effective area of ${\sim}17deg^2$. Typical fractional period errors will be ${\sim}1.5%{\times}10^{0.4(H-28.2)}$ with similar errors in other parameters for roughly 5000 KBOs. Binary companions to detected KBOs can be detected to even fainter limits, $H_{vega}=29$, corresponding to R~30.5 and effective diameters D~7 km. For KBOs H~23, binary companions can be found with separations down to 10 mas. This will provide an unprecedented probe of orbital resonance and KBO mass measurements. More than a thousand stellar occultations by KBOs can be combined to determine the mean size as a function of KBO magnitude down to H~25. Current ground-based microlensing surveys can make a significant start on finding and characterizing KBOs using existing and soon-to-be-acquired data.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.426-437
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• 1993

The flowfield of Weis-Fogh type ship's Propulsion is visualized by numerical simulations using the discrete vortex method and by the hydrogen bubble technique. The simulations are performed by assuming that the separations occur at the trailing edge of the wing. The streak lines and time lines are calculated by introducing the tracers at adequate intervals. They agree well with experimental results. The flowfield is unsteady and complex, but the properties of the flow are clarified by numerical and experimental visualization.