• Journal of Photoscience
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• v.6 no.3
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• pp.103-108
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• 1999

We present recent results on ablation mechanism, single-pulse laser micropatterning , pulsed-laser deposition(PLD) and particulates formation accompanying laser ablation, with special emplasis on polymers, in particular polymide, (PI), and polytetrafluoroethylene, (PTFE). Ablation of polymers is described on the basis of photothermal bond breaking within the bulk material. Here, we assume a first order chemical reaction, which can be described by an Arrhenius law. Ablation starts when the density of broken bonds at the surface reaches a certain critical value. Single-pulse laser ablation of polyimide shows a clear-length dependence of the threshold fluence. This experimental result strongly supports a thermal ablation model. We discuss the various possibilities and drawbacks of PLD and describe the morphology, physical properties and applications of PTFE films.

• Bulletin of the Korean Chemical Society
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• v.10 no.1
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• pp.19-22
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• 1989

The suitability of BMPI (2-bromo-N-methyl pyridinium iodide) for solid-phase peptide synthesis was investigated. The coupling rate of BMPI/HOBT procedure. BMPI/HOBT was superior to DCC/HOBT couplings using the solid-phase peptide bond formation proceeded to a greater degree of completion than DCC/HOBT method did. Double couplings with 2 equiv. of Bocamino acids and 1.5 equiv. of BMPI and $NEt_3$ and 2 equiv. of HOBT in DMF/MC (1:1 v/v) gave the best result for the preparation of a model compound. Stepwise solid phase peptide synthesis using BMPI/HOBT procedure was successfully utilized for the preparation of $(D-Ala)^2$-dynorphine A. BMPI/HOBT procedure for the synthesis of $(D-Ala)^2$-dynorphine gave better yield (20%) than DCC/HOBT procedure did.

• Bulletin of the Korean Chemical Society
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• v.3 no.2
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• pp.44-49
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• 1982

Dynamic and equilibrium structures of a polymer chain immersed in solvent molecules have been investigated by a molecular dynamic method. The calculation employs the Lennard-Jones potential function to represent the interactions between two solvent molecules (SS) and between a constituent particle (monomer unit) of the polymer chain and a solvent molecule (CS) as well as between two non-nearest neighbor constituent particles of the polymer chain (CC), while the chemical bond for nearest neighbor constituent particles was chosen to follow a harmonic oscillator potential law. The correlation function for the SS, CS and CC pairs, the end-to-end distance square and the radius of gyration square were calculated by varying the chain length (= 5, 10, 15, 20). The computed end-to-end distance square and the radius of gyration square were found to be in a fairly good agreement with the corresponding results from the random-flight model. Unlike earlier works, the present simulation rsesult shows that the autocorrelation function of radius of gyration square decays slower than that of the end-to-end distance square.

• Bulletin of the Korean Chemical Society
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• v.21 no.6
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• pp.557-561
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• 2000

Various enaryloxynitriles-terminated reactive polymer precursors containing rigid aromatic units were prepared from various diamines and 1-(p-formylphenyl)-1-phenyl-2,2-dicyanoethene (1). Arylate end-capped model compounds linked with azomethine bond were also prepared by reacting p-formylphenyl benzoate with diamines to compare the curing ability. The oligomers were highly soluble in polar aprotic solvents such as N,N-dimethylformamide, dimethylsulfoxide and N-methyl-2 -pyrrolidinone. They generally showed an exothermic curing process between $280-350^{\circ}C$, attributable to the thermal crosslinking of the dicyanovinyl group in DSC analysis, and no weight loss at curing temperature. Upon heating the polymer precursors, heat-resistant and insoluble network polymers were obtained. Thermogravimetric analyses of the precursors containing rigid aromatic units showed thermal stability with a 77-92% residual weight at $500^{\circ}C$ under nitrogen.

• Structural Monitoring and Maintenance
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• v.2 no.2
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• pp.133-143
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• 2015

Civil engineering infrastructure is aging and requires cost-effective maintenance strategies to enable infrastructure systems operate reliably and sustainably. This paper presents an approach for determining risk-cost balanced repair strategy of corrosion damaged reinforced concrete structures with consideration of uncertainty in structural resistance deterioration. On the basis of analytical models of cover concrete cracking evolution and bond strength degradation due to reinforcement corrosion, the effect of reinforcement corrosion on residual load carrying capacity of corroded reinforced concrete structures is investigated. A stochastic deterioration model based on gamma process is adopted to evaluate the probability of failure of structural bearing capacity over the lifetime. Optimal repair planning and maintenance strategies during the service life are determined by balancing the cost for maintenance and the risk of structural failure. The method proposed in this study is then demonstrated by numerical investigations for a concrete structure subjected to reinforcement corrosion. The obtained results show that the proposed method can provide a risk cost optimised repair schedule during the service life of corroded concrete structures.

• Journal of Industrial Convergence
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• v.3 no.1
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• pp.3-18
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• 2005

The purpose of this study is to examine the relationship between KOSPI200 Futures and KTB Futures in inter market and intra market. We are focusing on which market would be lead. The empirical results have indicated that there are no lead or lag effect between KOSPI200 Futures and KTB Futures market. But some positive correlation appeared, we used to know negative correlation between stock and bond market, which is a new finding. As a conclusion, the market still have an efficiency with co-movement.

• Computers and Concrete
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• v.24 no.1
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• pp.7-17
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• 2019

The complex phenomenon of the bond formation in geopolymer is not well understood and therefore, difficult to model. This paper present applied statistical models for evaluating the compressive strength of geopolymer. The applied statistical models studied are divided into three different categories - linear regression [least absolute shrinkage and selection operator (LASSO) and elastic net], tree regression [decision and bagging tree] and kernel methods (support vector regression (SVR), kernel ridge regression (KRR), Gaussian process regression (GPR), relevance vector machine (RVM)]. The performance of the methods is compared in terms of error indices, computational effort, convergence and residuals. Based on the present study, kernel based methods (GPR and KRR) are recommended for evaluating compressive strength of Geopolymer concrete.

• Bulletin of the Korean Chemical Society
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• v.7 no.4
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• pp.279-282
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• 1986

The MNDO calculations were performed in order to investigate the gas-phase reaction mechanism of 2-propene-1-al oxide, as a model compound of dypnone oxide(1,3-diphenyl-2-butene-1-one oxide) with the chloride ion. Optimized geometries and heats of formation for two probable concerted pathways, CHO and H migration, were determined and their activation energies were obtained. MO results show that although the formyl migration is thermodynamically more favorable than the hydride migration, the latter kinetically predominates over the formyl migration, which is contrary to the established migrating preferences. It is concluded that the hydride migratory propensity is catalyzed by the chloride ion by reducing the capability of the carbonyl ${\pi}$ bond to participate in the migration.

• Bulletin of the Korean Chemical Society
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• v.6 no.6
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• pp.354-358
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• 1985

Carbon-13 nuclear spin-lattice relaxation times have been measured over the range of temperature from 213K to 353K for carbons in n-heptane in neat liquid. The experimental data have been analyzed to obtain informations of segmental motions in the chain polymers by employing a model which describes jumps between several discrete states with different lifetimes. The overall reorientation of the molecule is assumed to be isotropic rotational diffusion. From the above analysis the activation energies of each C-C bond reorientation as well as the overall reorientation have been obtained through the Arrhenius-type temperature dependence.

• Korea Trade Review
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• v.47 no.1
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• pp.181-198
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• 2022

This paper investigates the arbitrage effect by the covered interest parity (CIP) deviation, as well as other push or pull factor effect on capital inflows and ouflows in the Korean bond market, by utilizing OLS, TSLS, IRF and VDC in EC model. The sample period covers February 2002 to December 2020. It is found that, the swap basis reflecting the CIP deviations have the significant effects on both debt investment inflows and debt investment outflows. Also, it is found that, the Korean risk factors have decreasing effects on foreigner's investment in the Korean bonds, while the global risk factors have decreasing effects on Korean resident's investment in the foreign bonds.