• Elastomers and Composites
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• v.50 no.3
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• pp.210-216
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• 2015

Polyurethane modified silicone (PUMS) was synthesized from various molecular weights of polydimethylsiloxane (PDMS 2000, PDMS 6000, PDMS 20000), polypropyleneglycol with molecular weight of 3000 g/mol (PPG 3000) and 2,4-toluenediisocyanate (TDI) under tin catalyst. Their structures were confirmed by the measurement of FT-IR and $^1H-NMR$, and the thermal properties were studied from DSC and TGA. Glass transition temperature of PUMS exhibited exothermic peak at $-63{\sim}-69^{\circ}C$, and residual weight was 19~35% at $800^{\circ}C$.

• Journal of the Korean Institute of Gas
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• v.13 no.4
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• pp.8-14
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• 2009

Dimethyl ether(DME) was synthesized from synthesis gas by a one-step process in which a hybrid catalyst was used. The hybrid catalyst consisted of Cu-ZnO-$Al_2O_3$ for the methanol synthesis reaction and aluminum phosphate or $H_3PO_4$-modified $\gamma$-alumina for the methanol dehydration reaction. The prepared catalysts were characterized by XRD, BET, SEM, FT-IR and $NH_3$-TPD. From the XRD analysis, it was verified that the aluminum phosphate was successfully synthesized. The specific surface areas of the synthesized aluminum phosphates were varied with the ratio of P/Al. The hybrid catalyst in which P/Al ratio of the aluminum phosphate was 1.2 showed the highest CO conversion of 55% and DME selectivity of 70%. There was no remarkable decrease in catalytic activity with the phosphoric acid treatment of $\gamma$-alumina. However, when treated with concentrated phosphoric acid(85%), the catalytic activity and DME selectivity decreased.

• Journal of the Korean Applied Science and Technology
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• v.22 no.3
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• pp.257-269
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• 2005

This study was focused on the maximization of flame-retardancy of polyesters by a synergism of simultaneously introduced chlorine and phosphorus into polymer chains of modified polyesters. To prepare modified polyesters, reaction intermediates, TD-adduct (prepared from trimethylolpropane /2,4-dichlorobenzoic acid (2,4-DCBA)) and TMBO (prepared from tetramethlene bis (orthophosphate)), were prepared first, then condensation polymerization of the prepared intermediates, adipic acid, and 1,4-butanediol were carried out. In the condensation polymerization, the content of phosphorus was fixed to be 2wt%, and the content of 2,4-DCBA that provides chlorine component was varied to be 10, 20, and 30wt%, and we designated the prepared modified polyesters containing chlorine and phosphorus as ABTTs. The prepared intermediates and modified polyesters were characterized with FT-IR, NMR, GPC, and TGA analysis. Average molecular weight and polydipersity index of the preparation of ABTTs were decreased with increasing 2,4-DCBA content because of the incease in hydroxyl group that retards reaction. We found that the thermal stability of the prepared ABTTs increased with chlorine content at high temperatures.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1361-1369
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• 1999

A hit-miss transform(HMT) using modified synthetic structuring elements(SEs) for distortion-invariant recognition of multiple objects is proposed. A fundamental problem in an HMT is the determination of the optimal SE needed to improve the false alarm rate, and detect distorted objects with various shapes. The proposed synthetic methods of SE provide good solutions against this problem. One is the multistage synthesis of each true class SE using only set theory, and the other is the multistage synthesis of each true class and false class SE using set theory and SDF(synthetic discriminant function) synthesis method. Simulation results show the proposed methods can be used for the recognition of distorted intraclass objects and the discrimination of similar interclass objects.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.817-821
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• 2016

Levodopa or L-3,4-dihydroxyphenylalanine (L-DOPA) is the direct precursor of the neurotransmitter dopamine. L-DOPA is a well-known neuroprotective agent for the treatment of Parkinson's disease symptoms. L-DOPA was synthesized using the enzyme, tyrosinase, as a biocatalyst for the conversion of L-tyrosine to L-DOPA and an electrochemical method for reducing L-DOPAquinone, the product resulting from enzymatic synthesis, to L-DOPA. In this study, three electrode systems were used: A glassy carbon electrode (GCE) as working electrode, a platinum, and a Ag/AgCl electrode as auxiliary and reference electrodes, respectively. GCE has been modified using electropolymerization of pyrrole to facilitate the electron transfer process and immobilize tyrosinase. Optimum conditions for the electropolymerization modified electrode were a temperature of $30^{\circ}C$ and a pH of 7 producing L-DOPA concentration 0.315 mM. After 40 days, the relative activity of an enzyme for electropolymerization remained 38.6%, respectively.

• Biotechnology and Bioprocess Engineering:BBE
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• v.4 no.1
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• pp.17-20
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• 1999

Facile synthetic methods of 2',5'-dideoxy-, 2',3'-dideoxy- and 3'-deoxy-1, N6-ethenoadenosine nucleosides by either an enzymatic dideoxyribosyl transfer reaction or a simple chemical reaction were proposed. The synthesis products were isolated and purified by preparative HPLC and their structures were confirmed by 1H NMR (500 MHz) and FAB-MS including high resolution mass measurement. These modified nucleoside analogs have not been reported yet. Therefore, these modified nucleoside analogs are of potential value to be studied further for biological activity such as anticancer or antiviral.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.3
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• pp.42-49
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• 1995

In this study, the optimum structural modification of the L-type structure by shape changes is suggested. The vibration characteristics of L-type structure are analyzed by the sub-structure synthesis method, and the coordinte sensitivities of each sub-structure are calculated and the change quantities of the positions to be modified are suggested by using the coordinate sensitivities. The results obtained are as follows : 1. The sensitivities of the natural frequency could be calculated by the sensitivity analysis. 2. The change quantities of the position to be modified could be suggested by the optimum structural modification method. 3. The developed program could reduce the process and time of computation, since the sensitivity was directly calculated by differential method, not finite difference method.

• The Korean Journal of Ceramics
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• v.6 no.3
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• pp.245-249
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• 2000

Consolidation of amorphous powders is emerging as a route for synthesis of high strength composite materials. Diffusion processes necessary for consolidation are expected to be more rapid in amorphous state(SRO) than in the crystalline state(LRO). A new synthesis technique of exploiting polymeric ceramic precursors(polysilazane and polyborosilazane) is derived for Si$_3$N$_4$/SiC and boron-modified nanocomposites for extremely high temperature applications up to 200$0^{\circ}C$. The characterization methods include thermal analysis of DTA, and XRD, NMR, TEM, after pyrolysis, as a function of time and temperature.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1290-1292
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• 2009

Modified-polyol protocol was utilized for synthesis of green-emitting ($^5D_4-^7F_j$ transitions of $Tb^{3+}$ ion) nanocrystalline $LaPO_4:Ce^{3+}$, $Tb^{3+}$ phosphors. Experimental parameters including chemical composition and annealing temperature were optimized to produce highly efficient, uniformly sized nanophosphors. Spin-deposited layer of $LaPO_4:Ce^{3+}$, $Tb^{3+}$ nanophosphors on glass substrate exhibited a transmittance of more than 80 %, indicating their efficacy for transparent display.

• Polymer(Korea)
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• v.29 no.6
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• pp.575-580
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• 2005

The hydroxy terminated aliphatic hyperbranched polyesters having different generations were synthesized by using melt polycondensation procedure. Then, the terminal groups of hyperbranched polyesters were modified by using acryloyl chloride and characterized by $\^{1}H$-NMR and GPC techniques. As a result of the modification of terminal groups for hyperbranched polyesters, the phase of the polymers were changed from sticky solid to high viscous liquid indicating that the glass transition temperatures of modified hyperbranched polyesters were lower than the original one. The thermal stabilities of hydroxy terminated hyperbranched polyesters were higher than those of terminal group-modified polymers.