• Journal of the Korean Ceramic Society
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• v.32 no.1
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• pp.63-70
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• 1995

A crack-free ceramic composite membrane with micropores has been synthesized by the pressurized sol-gel coating technique using the mixed Al2O3-SiO2 sols. The mixed sols were prepared by mixing nanoparticulate SiO2 and boehmite sols. These sols were more stable at lower pH, but very unstable when their copositions were in the range of 50~75mol% of SiO2 at the same pH. The mixed Al2O3-SiO2 membrane prepared from the mixed sol (0.2mol/$\ell$ of solid content and pH=2) containing 40mol% of SiO2 had the mean pore radius of 0.80nm and the specific surface area of 280$m^2$/g. The nitrogen permeability through the coated Al2O3-SiO2 layer was 42$\times$107mol/$m^2$.s.Pa. It was found that the thermal stability of aluminosilicate membranes, even through similar to that of SiO2 membranes, was much improved in comparison with ${\gamma}$-alumina membranes.

• Textile Coloration and Finishing
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• v.7 no.1
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• pp.10-22
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• 1995

Cellulosic fabrics, i.e. rayon, polynosic, and linen were treated with liquid ammonia at -33.4$^{\circ}C$. The fine structures, bending properties, tensile strength, wrinkle recoveries, and dyeing properties of the treated fabrics were studied. Dyeing was carried out with two direct dyes, C. I. Direct Red 2 and Blue 1. The liquid ammonia treatment for three fabrics brought about the transition of crystal lattices and the decrease of crystallinity; transforming cellulose I structure of original linen to cellulose I and III structure, and cellulose II structure of original rayon and polynosic to cellulose II and III structure. Moisture regain of liquid ammonia- treated polynosic and linen was higher than that for untreated, and water absorbency of liquid ammonia-traeated fabrics was all lower than that of untreated. Also, bending properties of treated fabrics were not improved compared with those of untreated ones. The rayon treated with liquid ammonia was increased not only the apparent diffusion coefficient and the rate of dyeing but also equilibrium dye adsortion, whereas polynosic and linen were increased only equilibrium dye adsortion. It is suggested that the pore sizes of liquid ammonia-treated rayon, polynosic, and linen are much smaller than that of liquid ammonia-treated cotton.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.201-204
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• 2007

A novel self-humidifying composite membrane for the proton exchange membrane fuel cell (PEMFC) at low humidity condition was developed. The $Pt/TiO_2 catalyst particles were synthesized via supercritical impregnation methods. Pt precursor was dissolved in supercritical carbon dioxide and impregnated onto $TiO_2$ particles. Pt precursors were platinum(II) acetylacetonate, Dimethyl(1,5-cyclooctadiene) platinum(II) and we controlled the ratio of Pt to $TiO_2$ The impregnated Pt precursor was converted to $TiO_2$ supported Pt nanoparticle under various reducing conditions. $TiO_2$ catalyst particles were dispersed uniformly into the Nafion solution, and then $Pt/TiO_2/Nafion$composite membrane was prepared using solution-cast method. The size, dispersion and content of the platinum had been characterized with Transmission Electron Micrograph (TEM), X-ray diffract ion (XRD) and Inductively Coupled Plasma - Atomic Emission Spectrometer (ICP-AES). The cell performance with the self-humidifying composite membrane was compared with a recast Nafion membrane under both humidified and dry conditions at 65 $^{\circ}C$.

• Journal of Korean Society on Water Environment
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• v.30 no.3
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• pp.304-310
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• 2014

The conventional methods for total residual chlorine such as iodometry and DPD colorimetric can cause secondary pollution due to additional agents, also have a wide error range. As for alternative, electrochemical method can measure TRC(Total residual chlorine), and is not required as additional agents, also very suitable for using the fields of ballast water because test time is relatively fast. Therefore, this study was investigated for changing charge by agitation, salt concentration, and temperature change. Charge showed differences based on changes of reduction peak with or without agitation. In contrast, TRC and charge were well correlated in constant agitation speed. As TRC and charge were analyzed with high correlations in constant salinity and temperature of ocean, thereby conductivity was firstly measured, and charge had high correlation for TRC in spite of changing salinity and temperature Pt electrode revealed high reliability ($r^2=0.960$) because it was rarely effected by TRC, On the other hand, Au electrode appeared inadequate ($r^2=0.767$) to use sensor in less than 1.0 ppm of TRC. For high accuracy and detection of TRC, Pt and Au electrodes for test time were, respectively, 14 and 22 seconds. As a result, Pt electrode was more valuable than Au electrode in terms of response time.

• The Korean Journal of Applied Statistics
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• v.29 no.6
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• pp.999-1005
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• 2016

The advent of big data brings the opportunity to answer many open scientic questions but also presents some interesting challenges. Main features of contemporary datasets are the high dimensionality and massive sample size. In this paper, we give an overview of major challenges caused by these two features: (1) noise accumulation and spurious correlations in high dimensional data; (ii) computational scalability for massive data. We also provide applications of big data in various fields including forecast of disasters, digital humanities and sabermetrics.

• Journal of the Korean Ceramic Society
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• v.47 no.4
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• pp.283-289
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• 2010

Physical properties of Plasma electrolytic oxidized 8 different kinds of Al alloys, A-1100, A-2024, A-5052, A-6061, A-6063, A-7075, ACD-7B and ACD-12 were investigated. The electrolyte for PEO was $Na_2SiO_3$ and NaOH and some alkali earthen metal salts system solution. $\eta$-alumina, as well as $\gamma$-alumina, was main crystal phase, which were ever reported. Also, $Al_{4.95}Si_{1.05}O_{9.52}$ was found only in this research. So we can conclude that the process conditions of PEO apparatus and composition and concentration of its electrolyte affects crystal structure and physical properties of PEO layers much more than the compositions of Al alloy.

• Journal of Korea Multimedia Society
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• v.8 no.9
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• pp.1177-1186
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• 2005

In vision-based interfaces for video games, gestures are used as commands of the games instead of pressing down a keyboard or a mouse. In these Interfaces, unintentional movements and continuous gestures have to be permitted to give a user more natural interface. For this problem, this paper proposes a novel gesture spotting method that combines spotting with recognition. It recognizes the meaningful movements concurrently while separating unintentional movements from a given image sequence. We applied our method to the recognition of the upper-body gestures for interfacing between a video game (Quake II) and its user. Experimental results show that the proposed method is on average $93.36\%$ in spotting gestures from continuous gestures, confirming its potential for a gesture-based interface for computer games.

• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.335-341
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• 1993

In the conversion of methanol, the effect of acide property of heteropoly compounds on the catalytic activity was investigated. The pretreatment of Cu-exchanged 12-tungstophosphoric acid with hydrogen enhanced both the selectivity for propane and the conversion of methanol, and the pretreatment of Al-exchanged 12-tungstophosphoric acid with water enhanced the acid strength of the catalyst. The water added into the reactant decreased the conversion of methanol, while the pretreatment temperature did not affect it but the propylene/propane ratio. Various partially-substituted Al salts of 12-tungstophosphoric acid showed different catalytic activities depending on the degree of Al-substitution.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.10
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• pp.135-140
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• 2006

In this paper, we present hybrid ARQ techniques to improve the throughput performance in high speed packet transmission such as Internet or multimedia services. In order to evaluate the performance of the three different types of hybrid ARQ schemes, systemized link level simulations based on WWW traffic model are considered. In this paper, we also consider the simulated performance for an average link throughput and a normalized packet delay to compare the hybrid ARQ with link adaptation scheme in GPRS.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.11
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• pp.1060-1066
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• 2010

This paper focuses on the application of the proposed aerodynamic optimization techniques to design the blade planform of helicopter rotors. The design problems are formulated to maximize the hover figure of merit and the equivalent lift-to-drag ratio for high forward speed by optimally distributing airfoils, twist, and chord along the blade span. The numerical characters are investigated by solving various design problems. The advantages and limitations with the present design approach and the present modeling features for performance prediction are discussed. The recommendations for the required model refinements to get more accurate optimal configurations are addressed as future research areas.