• Applied Chemistry for Engineering
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• v.4 no.4
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• pp.709-714
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• 1993

The cetane number is a measure of ignition quality, specifically ignition delay, of diesel fuel. It is an engine measure of kinetic phenomena. The ignition quality such as kinetic behavior does correlate with the molecular structure, the carbon type structural composition. In fact, we use the group additivity rule to dissect the molecular structures and predict cetane number. In this study, the use of $^{13}C-Nuclear$ Magnetic Resonance spectroscopic measuring the molecular structure and group additivity rule at different diesel fuels, whose cetane numbers were determined on a number of standard cetane rating engines is proposed to predict cetane numbers that relate the carbon type structural composition. The effect of the molecular structures on the cetane numbers has been studied.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.287-290
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• 1997

각 스탠드 유한요소해석 결과인 기계적-열적 변수들을 이용하여 재결정계산을 한다. 이때 온도변화를 정확히 반영하기 위해 재결정부피율 계산과 결정성장 계산에 additivity rule을 도입하였다. 또한 여러단계의 압연공정 각각에서의 재결정거동을 계속 추적하기 위해 또한 이때의 재결정의 영향을 재료유동에 반영하기 위해 substructure의 개념을 도입하였다. 이러한 과정을 거쳐 7패스후의 최종 두께방향으로의 결정크기분포를 얻을 수 있다. 본 연구 에서는 이때의 최종결정크기 분포를 균일화 시킬 수 있는 공정을 유전 알고리즘을 이용하여 찾아보았다.

• Korean Journal of Pharmacognosy
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• v.11 no.3_4 s.43
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• pp.153-162
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• 1980

1) The hydroxy-substitution in the simple phenolic compounds follows an additivity rule in the chemical shifts of their aromatic carbon atoms. In para-and ortho-effects is a good agreement between calculated and measured values, but the meta-effect is not certain. 2) The additivity rule was applied to assign the chemical shifts of catechins. 3) The nuclear overhauser effect was applied to assign the chemical shifts of C-8 and C-6 atoms of catechins and their polymer. The signal of C-8 is lower in intensity and appear in lower field than C-6. 4) The results of the NOE were applied to determine the bonding positions of catechin units in the catechin dimer and trimer. The bonding positions are C-8a and C-8b atoms of the second and third catechin units. 5) It was tried to determine the conformation of the catechin dimer and trimer by analysing the signal shapes of C-3' and C-4' atoms in the catechol moieties. The catechol moieties lie in opposite side in the dimer and trimer structure. A combined analysis of $^{13}C-and\;^1H-NMR$ results lead to the suggestion that such a catechin polymer is a zigzag planar form.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.297-306
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• 2004

This study investigated Austenite Grain Size (AGS) distribution in Low-Speed Round-Oval Rolling. Rolling experiments were done along with the AGS numerical modeling to characterize the final AGS distribution and its kinetics behavior. For bar rolling experiment, we utilized the pilot rolling mill, operating at 34 fixed rpm, at POSCO Technical Research Laboratories. To investigate the microstructural observation, the rigid-viscoplastic finite element analysis was combined with Hodgson's AGS evolution model. To consider the transient thermal history in the integrative AGS modeling, additivity rule was introduced. The integrated analysis revealed that static or meta-dynamic recrystallization is responsible for the AGS difference in the inner or outer region of rolled bar. Comparative study showed that the current AGS modeling approach can be used to model the overall AGS distribution in bar rolling processes. For more accurate AGS prediction, the AGS modeling method should be verified under the various rolling conditions such as different rolling speeds and different deformations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.119-122
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• 2002

The calculated and measured dielectric constant of (1-x)(Al$\sub$1/2/Ta$\sub$1/2/)O$_2$-x(Mg$\sub$1/3/Ta$\sub$2/3/)O$_2$(O$\leq$x$\leq$1.0) solid solutions were investigated by variations of ionic polarizability and crystal structure. (Al$\sub$1/2/Ta$\sub$1/2/)O$_2$ and (Mg$\sub$1/3/Ta$\sub$2/3/)O$_2$were orthorhombic and tetragonal trirutile structure, respectively. When (Al$\sub$1/2/Ta$\sub$1/2/)O$_2$ was substituted by (Mg$\sub$1/3/Ta$\sub$2/3/)O$_2$, the phase transformed to tetragonal structure over 60 mole%. Because the ionic radius of (Mg$\sub$1/3/Ta$\sub$2/3/)O$_2$was slightly bigger than one of (A1$\sub$1/2/Ta$\sub$1/2)O$_2$, the cell parameters increased with an increase of (Mg$\sub$1/3/Ta$\sub$2/3/)O$_2$ substitution. The measured dielectric constant increased with an increase of (Mg$\sub$1/3/Ta$\sub$2/3/)O$_2$ substitution and coincided with dielectric mixing rule and the calculated dielectric constant with the molecular additivity rule. There were some differences between the measured and the calculated dielectric constant. The reason of the lowered dielectric constant comparing with the calculated one was compressed stress due to the electronic structure of tantalum.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.2
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• pp.108-112
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• 2003

The calculated and measured dielectric constants of (1-x)(A $l_{1}$2/ T $a_{1}$2/) $O_2$-x(M $g_{1}$3/ T $a_{2}$3/) $O_2$ (0$\leq$x$\leq$1.0) solid solutions were investigated by variations of ionic polarizability and crystal structure. (A $l_{1}$2/ T $a_{1}$2/) $O_2$ and (M $g_{1}$3/ T $a_{2}$3/) $O_2$ were orthorhombic and tetragonal trirutile structure, respectively. When (A $l_{1}$2/ T $a_{1}$2/) $O_2$ was substituted by (M $g_{1}$3/ T $a_{2}$3/) $O_2$, the phase transformed to tetragonal structure over 60 mole. Because the total ionic radius of [(Mg+2Ta)/3]$^{4+}$ was slightly bigger than one of [(Al+Ta)/2]$^{4+}$, the lattice parameters increased with an increase of (M $g_{1}$3/ T $a_{2}$3/) $O_2$ substitution. The measured dielectric constant increased with an increase of (M $g_{1}$3/ T $a_{2}$3/) $O_2$ substitution and coincided with dielectric mixing rule and the calculated dielectric constant with the molecular additivity rule. There were some differences between the measured and the calculated dielectric constant. The reason of the lowered dielectric constant comparing with the calculated one was compressed stress due to the electronic structure of tantalum.

• Korea-Australia Rheology Journal
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• v.11 no.3
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• pp.255-263
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• 1999

Blends of two thermotropic liquid crystalline polymers, HX2000 and Vectra A950, were prepared by melt blending. Effects of transesterification on these blends are investigated by comparing properties of the blends with and without the addition of an inhibitor, in terms of blend miscibility and rheology. Both the uninhibited and inhibited blends are found to be largely immiscible with very limited miscibility in HX2000-rich phase. No strong evidence indicates the occurrence of transesterification in the blends in the solid state. Dynamic rheological behaviour, such as shear storage modulus (G') and shear loss modulus (G") as a function of frequency, of the blends are interpreted by a three-zone model. HX2000 shows terminal-zone and plateau-zone behaviour, whilst Vectra A950 shows plateau-zone and transition-zone behaviour. The un- inhibited blends show plateau-zone behaviour up to 50% Vectra A950 content and the inhibited blends show plateau-zone behaviour up to 60% Vectra A950 content. Compositional dependence of the complex viscosities of the uninhibited and inhibited blends displayed positive deviations from additivity, which is a characteristic feature for the immiscible thermoplastic blends. When under steady shear, both the uninhibited and inhibited blends show shear thinning behaviour and their viscosities decrease monotonically with the addition of Vectra A950. Compositional dependence of the steady shear viscosities of the two sets of blends displayed negative deviations from additivity and the uninhibited blends were more viscous than the inhibited blends for the full composition range. Although limited agreement with the Cox-Merz rule is found for the inhibited blends, these two sets of blends, in general, do not follow the rule due to their liquid crystalline order and two-phase morphology. Despite being immiscible blends, transesterification, such as polymerization, in the blends might occur during the rheological characterization, supported by the facts that uninhibited blends show HX2000-dominant behaviour at lower Vectra A950 content and are more viscous than the inhibited blends. The addition of transesterification inhibitor in such blends is advised if only physical mixing is desired.ired.

• Polymer(Korea)
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• v.28 no.6
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• pp.460-467
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• 2004

The polymer blends of waste poly(vinyl chloride) (RPVC) and waste polyethylene (RPE) were prepared by melt mixing. Their morphologies and rheological properties were investigated and torque changes were also measured. Comparing the torques calculated by the log additivity rule with measured torque changes, the polymer blends showed the large negative deviation behavior (NDB) due to their incompatibility. The shear viscosities of the blends decreased with increasing shear rates, showing shear thinning behavior. The shear viscosity of the blends with compatibilizer was larger than that of the blends without compatibilizer. SEM micrographs of the strands after measurement showed that the domain size of the blends was slightly enlarged with increasing the shear rate. Also, RPVC domain size was larger in the core-sections of the strands from capillary viscometer than in the surface region.

• International Journal of Safety
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• v.2 no.1
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• pp.28-33
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• 2003

Thermal decomposition characteristics of ethyl methacrylate (EMA) and Styrene (St.) copolymer was investigated with synthesis at 8$0^{\circ}C$ in a continuous stirred tank reacto (CSTR) using toluene and benzoyl peroxide(BPO) as solvent and initiator, respectively. The thermal decomposition was considered to be side scission at below 30$0^{\circ}C$ and estimated 2nd-order reaction kinetics of EMA/St. copolymer. The activation energies of decomposition on this copolymers were in the ranges of 38-43 kcal/mol for EMA/St. and a good additivity rule was observed in each composition. The thermogravimetric trace curves agreed well with the theoretical calculation.

• Journal of the Korean Applied Science and Technology
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• v.19 no.4
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• pp.273-280
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• 2002

Thermal decomposition of the copolymer of butyl methacylate(BMA) with styrene(St) was investigated. The copolymer Was obtained at 80 $^{\circ}C$ in a continuous stirred tank reactor(CSTR) using toluene and benzoyl peroxide(BPO), as solvent and initiator, respectively. The reactor volume was 0.3 liters and residence time was 3 hours. The thermal decomposition followed the second order kinetics for BMA/St copolymer. The activation energies of thermal decompositon were in the ranges of 38 ${\sim}43$ kcal/mol for BMA with St copolymer and a good additivity rule was observed with the composition of copolymer. The thermogravimetric trace curve agreed well with the theoretical calculation.