• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.235-242
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• 2001

An optimization algoriam for the optimum design of prestressed concrete (PSC) box girder bridges is proposed in this paper. In order to optimize the tendon profile efficiently, a reduced basis technique is introduced. The optimization algorithm which includes the tendon profile, tendon size and concrete dimensions optimization problem of the PSC box girder bridges is verified on the Genetic algorikhm (GA) from the numerical examples. it may be positively stated that the optimum design of the PSC box girder bridges based on the new approach proposed in this study will lead to more rational and economical design compared with the currently available designs.

• Bulletin of the Korean Chemical Society
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• v.17 no.4
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• pp.373-376
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• 1996

The bulk thermal and photopolymerization of methyl methacrylate(MMA) with phenylsilane were performed to produce poly(MMA)s containing phenylsilyl moiety presumably as an end group. It was found for both thermal and photopolymerization that while the polymerization yields and polymer molecular weights decreased as the relative phenylsilane concentration increases, the TGA residue yields and the relative intensities of SiH IR stretching bands increased with increasing molar ratio of phenylsilane over MMA. The polymerization yield, molecular weight, and TGA residue yield for the thermal polymerization were higher than those for the photopolymerization. Thus, the phenylsilane seemed to significantly influence on the polymerization as both chain initiation and chain transfer agents. However, an appreciable silane effect was not observed on the thermal and photopolymerization of 4-vinylpyridine, acrylonitrile, styrene, and vinyltrimethoxysilane.

• Bulletin of the Korean Chemical Society
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• v.16 no.11
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• pp.1109-1112
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• 1995

Bis(silyl)alkylbenzenes such as bis(1-sila-sec-butyl)benzene (1) and 2-phenyl-1,3-disilapropane (2) were prepared in high yields by reduction of the corresponding chlorosilanes with LiAlH4. The dehydropolymerization of 1 and 2 was carried out with group 4 metallocene complexes generated in situ from Cp2MCl2/Red-Al and Cp2MCl2/n-BuLi (M=Ti, Hf), producing two phases of polymers. The TGA residue yields of the insoluble polymers were in the range of 64-74%. The molecular weights of the soluble polymers produced ranged from 700 to 5000 (Mw vs polystyrene) and from 500 to 900 (Mn vs polystyrene). The dehydropolymerization of 1 and 2 seemed to initially produce a low-molecular-weight polymer, which then underwent an extensive cross-linking reaction of backbone Si-H bonds, leading to an insoluble polymer.

• Bulletin of the Korean Chemical Society
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• v.18 no.12
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• pp.1264-1268
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• 1997

The poly(methylsilene) (1) was modified with the group 4 metallocene Cp2MCl2/Red-Al (M = Ti, Zr, Hf) combination catalyst and with the group 6 metal carbonyl M(CO)6 (M = Cr, Mo, W) catalyst, producing the highly cross-linked isoluble polymer and the lowly cross-linked soluble polymer, respectively. An interrelationship between molecular weight and percent ceramic residue yield with metal within the respective group was not found. The polymers modified with the group 4 metallocene combination catalysts have higher molecular weight and lower percent ceramic residue yield than the polymers modified with the group 6 metal carbonyl catalysts do. The catalytic activity of group 4 metallocene combinations appears to be higher at ∼100 ℃, but to be lower at very high temperature than those of group 6 metal carbonyls. The pyrolysis of the modified 1 yielded SiC ceramic.

• Bulletin of the Korean Chemical Society
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• v.18 no.12
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• pp.1291-1295
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• 1997

The catalytic dehydrocoupling of di-n-butylstannane n-Bu2SnH2 by the Cp2MCl2/Red-Al (M = Ti, Zr, Hf) and M(CO)6/Red-Al in situ combination catalysts yielded a mixture of two kinds of catenated products: one is a cross-linked insoluble solid, and the other is a non-cross-linked soluble solid (≒Sn5) or viscous oil (≒Sn2). The soluble oligostannanes could be produced by simple dehydrocoupling of n-Bu2SnH2, whereas the insoluble polystannanes could be obtained via disproportionation/dehydrocoupling combination process of n-Bu2SnH2. The disproportionation/dehydrocoupling combination process may initially produce a low-molecular-weight oligostannane with partial backbone Sn-H bonds which could then undergo an extensive cross-linking reaction of backbone Sn-H bonds, resulting in the formation of an insoluble polystannane.

• Polymer(Korea)
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• v.28 no.1
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• pp.67-76
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• 2004

The effects of drawing temperature and draw down ratio on thermal properties, crystallinity and orientation of poly(trimethylene terephthalate)/poly(ethylene terephthalate) (PTT/PET) 100/0 ,90/10, and 80/20 blends have been investigated. The crystallinity and glass transition temperature increased while cold crystallization temperature and cold enthalpy decreased due to the development of orientation and stress induced crystallization by the cord drawing. Introducing PET to PTT decreased the crystallinity of PTT. However, it enhanced the orientation of PTT/PET blends drawn at below the glass transition temperature of PET. This lead to the increase of tensile modulus and tensile strength of PTT/PET blends. The shrinkage increased with increasing orientation, which might be minimized by the development of crystalline morphology of PTT in the course of cold drawing.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.3
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• pp.73-77
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• 2015

This paper presents integrated polymeric spectrometer module which offers compact size, easily-fabricated structure and low cost. The proposed spectrometer module includes the nano diffraction grating with non-uniform pitch and planar optical waveguide with concave mirror to be fabricated by UV imprint lithography. To increase the reflection efficiency, we designed the nano diffraction grating with triangular profiles. The polymeric planar spectrometer includes a spectral bandwidth of 700 nm, resolution of 10 nm and precision below 5 nm. This polymeric planar spectrometer is well-suited for sensor system.

• Particle and aerosol research
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• v.7 no.4
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• pp.139-149
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• 2011

It is very important to measure atmospheric particles and evaluate the characteristics of them since aerosol can influence atmospheric environment, climate, and health. Satellite, aircraft, radio sonde are usually used to measure the vertical distribution of particle properties, temperature, humidity, and pressure. Although the method of using an aircraft is favorable to collect the horizontal distribution of the particles, but unadaptable to measure the vertical distribution of the particles. However, all-in-one balloon particle sampler system can collect particles depending on each altitude controling the balloon by winch. In this research, we performed the air sampling on the TEM grids using house made light weight impactor at the altitude of 300m and 900m. The collected particles were analyzed using TEM/EDS.

• Journal of Hydrogen and New Energy
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• v.21 no.4
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• pp.307-312
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• 2010

Poly (ether sulfone)s with Bisphenol-TP and Bisphenol-AF were prepared with Bisphenol-TP <4,4-dihydroxy tetraphenyl methane>, 4-Fluorophenyl sulfone, and Bisphenol-AF <4,4-(hexafluoroisopropylidene) diphenol> using Potassium carbonate in Sulfolane at $210^{\circ}C$. Sulfonated PBTP-AF were obtained by reaction of Chlorosulfuric acid with copolymers. A series of copolymers were studied by $^1H$-NMR spectroscopy, Differential Scanning Calorimeter (DSC), and Thermo Gravimetric Analysis (TGA). Sorption experiments were conducted to observe the interaction of polymers with water and methanol.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.1
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• pp.97-105
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• 2009

Analysis was done on the particle size distribution of sediments flown into Saemangeum from the Mankyung and Dongjin River. The organic pollutants and heavy metal existing in the sediments were analyzed, which was further used to study the properties of pollution in the sediments according to the particle size distribution. Conclusions shown below were made from these analyses. The particle size distribution showed a big difference between the upriver areas of Mankyung and Dongjin River. Particles under $75{\mu}m$ showed to be around 85% at Dongjin River, while it showed to be around 70% at Mankyung River. This kind of distribution in particle size concluded in greatly affecting the contamination density of the sediments. From the analysis done on the soil type of sediments, deposition in Mankyung River categorized into Silty loam and Sandy loam, where Silty loam covered most of area and deposition in Dongjin River categorized into Sand, Loamy sand, Silty loam, Sandy loam. Considering the weight ratio, the density of contamination of the sediments by particle size at Dongjin and Mankyung River has been analyzed to show that organic pollutants and heavy metals occupy more than 70% of the whole contamination in the range under the particle size of $75{\mu}m$.