• Korea-Australia Rheology Journal
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• v.18 no.4
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• pp.199-207
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• 2006

Measurements by Luap et al. (2005) of elongational viscosity and birefringence of two nearly monodisperse polystyrene melts with molar masses $M_{w}$ of $206,000g{\cdot}mol^{-1}$ (PS206k) and $465,000g{\cdot}mol^{-1}$ (PS465k) respectively are reconsidered. At higher elongational stresses, the samples showed clearly deviations from the stress optical rule (SOR). The elongational viscosity data of both melts can be modeled quantitatively by the MSF model of Wagner et al. (2005), which is based on the assumption of a strain-dependent tube diameter and the interchain pressure term of Marrucci and Ianniruberto (2004). The only nonlinear parameter of the model, the tube diameter relaxation time, scales with $M_{w}^{2}$. In order to get agreement with the birefringence data, finite chain extensibility effects are taken into account by use of the $Pad\'{e}$ approximation of the inverse Langevin function, and the interchain pressure term is modified accordingly. Due to a selfregulating limitation of chain stretch by the FENE interchain pressure term, the transient elongational viscosity shows a small dependence on finite extensibility only, while the predicted steady-state elongational viscosity is not affected by non-Gaussian effects in agreement with experimental evidence. However, deviations from the SOR are described quantitatively by the MSF model by taking into account finite chain extensibility, and within the experimental window investigated, deviations from the SOR are predicted to be strain rate, temperature, and molar mass independent for the two nearly monodisperse polystyrene melts in good agreement with experimental data.

• Korea-Australia Rheology Journal
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• v.21 no.4
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• pp.203-211
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• 2009

In flows with deformation rates larger than the inverse Rouse time of the polymer chain, chains are stretched and their confining tubes become increasingly anisotropic. The pressures exerted by a polymer chain on the walls of an anisotropic confinement are anisotropic and limit chain stretch. In the Molecular Stress Function (MSF) model, chain stretch is balanced by an interchain pressure term, which is inverse proportional to the $3^{rd}$ power of the tube diameter and is characterized by a tube diameter relaxation time. We show that the tube diameter relaxation time is equal to 3 times the Rouse time in the limit of small chain stretch. At larger deformations, we argue that chain stretch is balanced by two restoring tensions with weights of 1/3 in the longitudinal direction of the tube (due to a linear spring force) and 2/3 in the lateral direction (due to the nonlinear interchain pressure), both of which are characterized by the Rouse time. This approach is shown to be in quantitative agreement with transient and steady-state elongational viscosity data of two monodisperse polystyrene melts without using any nonlinear parameter, i.e. solely based on the linear-viscoelastic characterization of the melts. The same approach is extended to model experimental data of four styrene-butadiene random copolymer melts in shear flow. Thus for monodisperse linear polymer melts, for the first time a constitutive equation is presented which allows quantitative modeling of nonlinear extension and shear rheology on the basis of linear-viscoelastic data alone.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.306-308
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• 2013

• Membrane Journal
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• v.16 no.4
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• pp.241-251
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• 2006

In this study, crosslinked copolyimides with random (r-) and block (b-) structure were fabricated using N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid and pentanediol as crosslinkers. Linear r- and b-sulfonated copolyimides were also fabricated for comparison. Ion exchange capacities of r- and b-copolyimides were very similar to each other owing to their strong dependence of sulfonic acid content. The physical crosslinking via dimerization of carboxylic acid groups induced a reduced average interchain distance in b-copolyimide without crosslinkers. Consequently, its water uptake and methanol permeability were lower than those of r-sulfonated copolyimides. Simultaneously, the reduced interchain distance increased the content of fixed-charged ions per unit volume. The high fixed-charged ion density contributed to an enhancement of proton conductivity In the b-sulfonated copolyimide. Crosslinking caused the reduction of average interchain distance between polymer chains irrespective of types of crosslinker and polymer structure, leading to low methanol permeability. On the contrary, their proton conductivity was improved owing to formation of effective hydrophilic channels responsible for proton conduction. In particular, this trend was observed in r-copolyimide containing a fixed charged ion.

• Journal of Digital Convergence
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• v.19 no.5
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• pp.315-320
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• 2021

While blockchain platforms for various purposes have been developed and the blockchain ecosystem is being developed, interoperability problems are emerging in which each blockchain is isolated and operated. In this study, we introduce interchain and sidechain technologies, which are blockchain that connect blockchain, and explain examples of using heterogeneous blockchain transactions and functions by applying them. In addition, blockchain, artificial intelligence, and IoT technologies, which are drawing attention in the fourth industrial revolution, are going through a process of converging and developing beyond their own development. In this regard, we present processes for combining artificial intelligence or IoT in blockchain, and propose a model that can operate without intervention by applying the combination of blockchain and artificial intelligence IoT to processes for trading and exchange between heterogeneous blockchain.

• Bulletin of the Korean Chemical Society
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• v.24 no.6
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• pp.843-852
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• 2003

We present a brief account of the theory of diffusion-influenced kinetics of reactions involving polymers. The review will be based on the recent contributions from the authors. Both intrapolymer and interpolymer reactions are considered, and the effects of various physical factors, such as the chain length, chain stiffness, and hydrodynamic interactions, are described within a unified theoretical framework.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.143-146
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• 2000

We studied effects of alkyl($C_nH_{2n+1}$) chain length on characteristics of poly(3-alkylthiophene) electroluminescent diodes. Among the poly(3-alkylthiophene), poly(3-hexylthiophene)(n=6) and poly(3- octyIthiophene)(n=8) were mainly used for the emitting layer of the diode. The result of experiment, the emission intensity of poly(3-alkylthiophene) electroluminescent diodes depends on the alkyl chain length. Strong emission is obtained from a poly(3-alkylthiophene) diodes of long alkyl side chain length. Emission intensities are enhanced by a confinement of carriers on a main chain with a long interchain distance caused by a long alkyl side chain.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.1060-1061
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• 2003

We report photo- (PL), and electroluminescence (EL) realized via intrachain and interchain energy transfer in poly[9,9-(2'-octyl)fluorene-2,7-vinylene]-co-poly[2-methoxy,5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene] (PFV-co-MEH-PPV) copolymer systems. Energy transfer begins even at the device using 5 % MEH-PPV copolymer, and shows the best device performance for the 10 % MEH-PPV copolymer.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1993.04a
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• pp.58-58
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• 1993

면역 조절능이 우수하고 독성이 적은 신물질의 개발을 목표로 하여 초유에 들어있는 면역물질을 검색한 결과 초유로부터 자연 살해 세포의 기능을 활성화시키는 물질을 순수분리 하였다. 이 물질은 초유의 유청으로부터 ammonium sulfate에 의한 침전, DEAE-cellulose ion exchange, Sephadex G-200 gel filtration 등의 방법에 의하여 분리되었으며, 초유의 유청 100ml로부터 최종 수득량은 1.2 mg이었다. 이 물질은 SDS-polyacrylamide gel electrophoresis에서도 분자량의 변화가 없는 것으로부터 interchain disulfide bond가 없음을 확인할 수 있었다. 이 물질은 실온에 방치하거나 또는 37$^{\circ}C$로 가온하면 침전을 형성하고, 생성된 침전물을 4$^{\circ}C$로 냉각시키면 다시 용해되는 특이한 특성을 갖고 있으며, 침전이 형성되는 정도는 농도, 온도 및 이온 강도에 비례하여 증가하는 것으로 나타났다. 침전에 최적 pH는 중성인 것으로 나타났다. 이 물질을 사람의 말초혈액으로부터 분리한 림파구의 배양액에 가하고 18 시간동안 배양한 결과 림파구의 적 백혈병 암세포인 K-562 세포에 대한 자연 살해능이 증가됨을 확인할 수 있었다. 자연살해 세포의 활성화는 1.0 - 0.01$\mu\textrm{g}$/ml의 농도 범위에서 확인되었다.

• Bulletin of the Korean Chemical Society
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• v.19 no.7
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• pp.738-742
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• 1998

A new polyamide was prepared from 4,4'-(hexafluoroisopropylidene)di-aniline and 4-[NN-bis(2-carboxyethyl)] amino-4'-nitrostilbene. This polymer was cast into thin films by spin coating cyclohexanone solution. After being poled, the electro-optic coefficients of electrode poled polymer films were measured by the reflection measurement technique using an incident laser beam of 1.3 Jim. The film poled at the field strength of 1.2 V/μm exhibited the electro-optic coefficient (r33) of 5.9 pm/V. The relaxation behavior of the poled polymer film was compared with other reported polymers bearing the same NLO chromophores. Due to stiff and highly polar nature of the backbone and also due to formation of interchain hydrogen bonds, this polymer reveals a slower relaxation characteristics. The polymer is amorphous and soluble in various organic solvents.