• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.639-645
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• 2012

Waterborne polyurethane dispersion (PUD) was synthesized by capping the NCO groups of polyurethane prepolymers, prepared from isophorone diisocyanate, polycarbonate diol and dimethylol propionic acid, with aminopropyl triethoxysilane (APS). Subsequently, silylated acrylic polyurethane dispersion was synthesized by reacting the PUD with the mixture of acrylate monomers, 2-hydroxyethyl methacrylate and methyl methacrylate. The average particle size of silylated acrylic polyurethane dispersion, measured by the dynamic light scattering method, was increased from 39.0 nm to 399.8 nm by increasing the addition amounts of APS. Also, the pencil hardness of coating films of silylated acrylic polyurethane dispersion was enhanced from B grade to F grade with increasing APS content.

• Polymer(Korea)
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• v.39 no.3
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• pp.499-505
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• 2015

Polyorganosiloxane having controlled cross-linking density and phenyl group content were prepared by dimethyldimethoxysilane (DMDMS), methyltrimethoxysilane (MTMS) and phenyltrimethoxysilane (PTMS). The effect of cross-linking density and phenyl group content on the physical properties of siloxane resin and its coated film have been invetigated. Si-NMR results confirmed that synthesized siloxane resins have equivalent D $T^{Me}$ $T^{Ph}$ structures according to applied mole ratios of DMDMS, MTMS and PTMS. Polyorganosiloxane having higher cross-linking density with high phenyl content showed the high molecular weight and increasing phenyl content resulted in higher refractive index as well as better thermal stability. Cross-linking density is more important factor than phenyl content to obtain higher pencil hardness of coated film on the glass. Our results concluded that even polyorganosiloxanes having similar siloxane structures show different physical properties as function of cross-linking density and phenyl content in polyorganosiloxane.

• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.285-291
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• 2011

NCO terminated polyurethane prepolymers were synthesized from isophorone diisocyanate(IPDI), poly (tetramethylene glycol)(PTMG) and dimethylol propionic acid(DMPA). Subsequently, waterborne polyurethanes were prepared by capping the NCO groups of polyurethane prepolymers with different types of silane coupling agents, such as methyltrimethoxysilane(MTMS), glycidoxypropyl trimethoxysilane(GPTMS), methacryloxypropyl trimethoxysilane (MPTMS) and aminopropyl triethoxysilane(APS). The average particle size of the waterborne polyurethane solutions was increased by adding silane coupling agents. Also, the coating films prepared from GPTMS, MPTMS and APS, exhibited better pencil hardness than those from pure waterborne polyurethane. On the other hand, the coating films from MTMS did not show an improved pencil hardness than those from pure waterborne polyurethane.

• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.277-284
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• 2011

In this study, UV-curing type organic - inorganic hybrid hard coating solutions were prepared from alumina sols and acrylate monomers. The mixture of alumina sols, prepared from aluminum isopropoxide, and a silane coupling agent, methacryloxypropyl trimethoxysilane(MPTMS), was used as an inorganic component. Also, the mixture of acrylate monomers, pentaerythritol triacrylate(PETA), 1,6-hexanediol diacrylate(HDDA) and dipentaerythritol hexaacrylate (DPEHA), was used as an organic component. The organic-inorganic hybrid coating solutions were obtained by mixing the inorganic component and organic component, deposited on polycarbonate substrates by spin coating and densified by UV-curing. The effect of the amount of MPTMS in the inorganic component and the irradiation time during UV-curing was studied on the properties of coating films. As a result, when 0.20 mole of MPTMS was used, the pencil hardness of coated films showed an excellent pencil hardness of 3H and also exhibited a good abrasion resistance of 2% in haze.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.548-553
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• 2011

NCO terminated polyurethane prepolymers were synthesized from isophorone diisocyanate(IPDI), polycarbonate diol(PCD) and dimethylol propionic acid(DMPA). Subsequently, acrylic terminated polyurethanes were prepared by capping the NCO groups of polyurethane prepolymers with different types of acrylate monomers, such as 2-hydroxyethyl methacrylate(HEMA), 2-hydroxyethyl acrylate(HEA) and pentaerythritol triacrylate(PETA). The average particle sizes of the acrylic terminated polyurethane solutions were increased by capping acrylate monomers. Also, the prepared coating films showed better abrasion resistance and pencil hardness than those of pure waterborne polyurethanes. The coating film with PETA exhibited the best abrasion resistance and pencil hardness of coating films prepared with three acrylate monomers.

• KIISE Transactions on Computing Practices
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• v.24 no.1
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• pp.17-23
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• 2018

The assessment and rehabilitation of patients with cognitive dysfunction is a field that currently requires assistive technology. While the paper-and-pencil test, such as the line tracing test (LTT), is one of the most commonly used assessment methods for cognitive dysfunction, it has become time-consuming due to its manual characteristic. The aim of this study was therefore to establish a computer-based real-time assessment system for patients without compromising the usefulness of the conventional paper-and-pencil based user tools. A digital pen-based assessment and rehabilitation system, the ePen System, could eliminate the time required for manual assessment while maintaining the measurement accuracy. The proposed system may assist rehabilitation specialists to assess and diagnose patients with unilateral visual neglect. This system can be applied to a range of assessment and rehabilitation modalities based on pen and paper. It can also be used for various patients such as those with Parkinson's disease, stroke, or different forms of brain lesions.

• Journal of the Korea Computer Graphics Society
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• v.24 no.3
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• pp.101-109
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• 2018

Recently, the improvement of virtual reality and augmented reality technologies leverages many new technologies like the virtual study room, virtual architecture room. Such virtual worlds require free handed drawing technology such as writing descriptions of formula or drawing blue print of buildings. In nature, lots of view point modifications occur when we walk around inside the virtual world. Especially, we often look some objects from near to far distance in the virtual world. Traditional drawing methods like using fixed size image for drawing unit is not produce acceptable result because they generate blurred and jaggy result as view distance varying. We propose a novel method which robust to the environment that produce lots of magnifications and minimizations like the virtual reality world. We implemented our algorithm both two dimensional and three dimensional devices. Our algorithm does not produce any artifacts, jaggy or blurred result regardless of scaling factor.

• School Mathematics
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• v.9 no.2
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• pp.241-257
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• 2007

The study aims to figure out how to improve existing examination tools to distinguish mathematically gifted children and to clarify procedures and criteria for selecting candidates. Toward this end, it examined correlations between grades of gifted children selected through evaluation by pen-and-pencil tests and their creative problem-solving capability and performance assessment, and analyzed learning activities of the gifted children. According to the analysis, results of pen-and-pencil tests turned out to have low correlations with their creative problem-solving capability and performance assessment, but it was found that their creative problem-solving capability has high correlations with results of performance assessment. The analysis also found that there were some students who participated in a program for gifted children with high marks but had difficulties in adapting themselves to it. It found that there were children who joined the program with low marks but emerged as successive performers later on. In this regard, the existing examination tools to tell the gifted students apart need to be used to the fullest extent, and other diversified tools to evaluate mathematical capabilities that include mathematical creativity need to be further studied and developed. Qualitative studies on affective development of the gifted students and their creative problem-solving processes need to be conducted.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.1233-1238
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• 2009

This study's aim was to confirm that pseudoneglect affects visual attention through car laterality, using a driving simulator with either bisection or quadrisection strategies being applied to road usage. On the pencil and paper tests, the left quadrisection and bisection marks deviated significantly to the left. While driving, the car was significantly lateralized to the right of the lane regardless of conditions. However, in terms of relative laterality, the biggest left laterality occurred on roads 1(bisection), while the smallest left laterality occurred on roads 2 (right quadrisection). Thus, the effect of pseudoneglect was demonstrated in both the pencil and paper tests and the driving simulation task. Also, roads 2 and 4, which were driven on the right side of the lane, showed a tendency for drivers to avoid the centerline, as this was the expected cause of right laterality. This study demonstrated that the pseudoneglect phenomenon can occur in a routine driving task.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.2
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• pp.239-247
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• 2018

Adaptive Beamforming (ABF) algorithm, which is a typical jammer suppression algorithm, guarantees the performance on the assumption that the jamming characteristics of the TDS (Training Data Sample) are stationary, which are obtained immediately before and after transmitting the pulse signal. Therefore, effective jammer suppression can not be expected when the jamming characteristics are non-stationary. In this paper, we propose a new jammer suppression algorithm, of which power spectrum fluctuates fast. In this case, we assume that the location of the jammer station is fixed during the processing time. By applying the MPM (Matrix Pencil Method) to the jamming signal in TDS, we can estimate jammer parameters such as power and incident angle, of which the power will vary fast in time or range bins after TDS. Though we assume that the jammer station is fixed, the estimated jammer's incident angle has an error due to the noise, which degrades the performance of the jammer suppression as the jammer power increases fast. Therefore, the jammer's incident angle should be re-estimated at each range bin after TDS. By using the re-estimated jammer's incident angle, we can construct new covariance matrix under the non-stationary jamming environment. Then, the optimum weight for the jammer suppression is obtained by inversing matrix estimation method based on the matrix projection with the estimated jammer parameters as variables. To verify the performance of the proposed algorithm, the SINR (signal-to-interference plus noise ratio) loss of the proposed algorithm is compared with that of the conventional ABF algorithm.