• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.224-227
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• 2002

In this paper, we have investigated the physical properties and electrical conduction properties of polyethylene terephthalate film due to temperature variation, and the measurement of volume resistivity used to highmegohm meter is measured from 1 to 10 minutes when the specimen applied the voltage accroding to the step voltage appling method. From FT-IR spectrum as an analysis of physical properties, the strong absorption in wavenumbers $1019[cm^{-1}]$, $1266[cm^{-1}]$ and $1752[cm^{-1}]$ observed by the C=O and benzene ring. From the analysis of DSC, the crystalline melting points of the specimen observed in the temperature $80[^{\circ}C]$ and $263[^{\circ}C]$, respectively.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1684-1687
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• 1997

In this paper, a three-dimensional algorithm for the insulation design of the high-voltage equipment is presented. In general, the insulation design consists of two steps. They are electric field calculation and correction of the shape to be designed. In the proposed algorithm, the combination method of charge simulation and surface charge simulation is used to calculate the three-dimensional electric fields. As for the correction of the shape, indirect control provided by rational B-spline is more useful than direct control. The use of rational B-spline reduces in the number of design variables and garrantees the smooth curvature of the designed shape. The proposed algorithm is applied to the design of the shape of the shield ring which has been designed by the method of trial and error.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1032-1038
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• 2008

KTX train system is composed of TORNAD* network for transmitting information of train's internal equipments and OBCS which proceed information within train. OBCS of one trainset consisted of 28 equipments takes intelligent and dynamic composition according to equipment handling, train command and control flow. Each OBCS which is installed within trainset handle and supervise mutually action information about equipments, transmit it to driver to transmit information about train operation and preventive management. This mutual supervision and information transmission use KTX TORNAD* network system. TORNAD* network system is the one which is uniquely developped by GEC ALSTHOM, the KTX trainset manafacturing provider and this field is excluded from technical know-how transfer item. Through the research on analysis method of KTX TORNAD* system data structure which is operating on Seoul-Pusan Line, I hope that this thesis can contribute to train network system's standardization after applying it to improvement of train network system maintenance, enhancing quality of train service and applying it to future Korean rolling stock network system development.

• Bulletin of the Korean Chemical Society
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• v.28 no.8
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• pp.1299-1304
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• 2007

New sulfur functionalized cyclopentadiene ligands, 1-[2-(thioanisole)]-2,5-dimethylcyclopentadiene (3), 1-[2- (thioanisole)]-2,3,5-trimethylcyclopentadiene (4), and 1-[2-(thioanisole)]-2,3,4,5-tetramethylcyclopentadiene (5), were prepared. In these ligands, the S-donor atom is connected to a cyclopentadiene ring by a rigid phenylene spacer. CpCo(III)-diiodo half-sandwich complexes (6-8) were obtained from reaction the ligands (3- 5) with Co2(CO)8, followed by treatment of I2. Substitution reaction of CpCo(III)-diiodo complexes with MeLi yielded the corresponding CpCo(III)-dimethyl complexes (9-11). Further transformation to the corresponding cationic cobalt complexes (12-14) were achieved by reaction of the CpCo(III)-dimethyl complexes with HB(ArF)4·2Et2O and trapping with CD3CN. The new sulfur functionalized cyclopentadiene ligands having a rigid phenylene spacer and the corresponding cobalt complexes were characterized by 1H, 13C and 19F NMR spectroscopy. The diiodo Complex 6 was also characterized by a single crystal X-ray diffraction method.

• Corrosion Science and Technology
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• v.17 no.1
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• pp.30-36
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• 2018

The high rate of corrosion of magnesium alloys makes it limited for industrial applications. Therefore, surface treatment is required to enhance their corrosion resistance. In our study, a chemical conversion coating for protecting the corrosion of the magnesium alloy, AZ31B, was prepared by using a phosphate-permanganate solution. The chemical conversion coating had a limited protection ability due to defects arising from cracks and pores in the coating layer. The sol-gel coating was prepared by using trimethoxymethylsilane (MTMS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) as precursors, and aluminum acetyl acetonate as a ring opening agent. The corrosion protection properties of sol-gel and conversion coatings in 0.35wt% NaCl solution were measured by the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization test. The EIS results indicated that the resistance of the chemical conversion coating with the sol-gel coating was significantly improved through the sol-gel sealed phosphate-permanganate conversion coating. The results of the potentiodynamic polarization test revealed that the sol-gel coating decreased the corrosion current density ($I_{corr}$). The SEM image showed that the sol-gel coating sealed conversion coating and improved corrosion protection.

• Macromolecular Research
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• v.17 no.2
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• pp.72-78
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• 2009

Size control of therapeutic carriers in drug delivery systems has become important due to its relevance to biodistribution in the human body and therapeutic efficacy. To understand the dependence of particle size on the formation condition during nanoprecipitation method, we prepared nanoparticles from biodegradable, amphiphilic block copolymers and investigated the particle size and structure of the resultant nanoparticles according to various process parameters. We synthesized monomethoxy poly(ethylene glycol)-poly($\varepsilon$-caprolactone) block copolymer, MPEG-PCL, with different MPEG/PCL ratios via ring opening polymerization initiated from the hydroxyl end group of MPEG. Using various formulations with systematic change of the block ratio of MPEG and PCL, solvent choice, and concentration of organic phase, MPEG-PCL nanoparticles were prepared through nanoprecipitation technique. The results indicated that (i) the nanoparticles have a dual structure with an MPEG shell and a PCL core, originating from self-assembly of MPEG-PCL copolymer in aqueous condition, and (ii) the size of nanoparticles is dependent upon two sequential processes: diffusion between the organic and aqueous phases and solidification of the polymer.

• Bulletin of the Korean Chemical Society
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• v.30 no.5
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• pp.1031-1034
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• 2009

Fluorescence of quinolones including norfloxacin, ciprofloxacin and S- and R-ofloxacin is quenched upon association with single and double-stranded DNA (ss- and ds-DNA). The ratios of fluorescence intensity in the presence of DNA to its absent were plotted with respect to the DNA concentration to construct the Stern-Volmer plot. The slope of the Stern-Volmer plot become larger as the temperature is lowered, ensuring that the fluorescence quenching is static process, i.e., the fluorescence is quenched by formation of the non-fluorescent complex between quinolone and DNA. In the static quenching mechanism, the quenching constant which is equivalent to the slope of the Stern-Volmer plot, is considered as the equilibrium constant for the association of quinolones and DNA. From the temperature-dependent equilibrium constant, ${\Delta}H^0\;and\;{\Delta}S^0$ was obtained using the van’t Hoff relation. In general, association of the quinolone with ds- as well as ss-DNA is energetically favorable (an exothermic) process while the entropy change was unfavorable. Due to the steric effect of the substituents, the effect of the quinolone ring is smaller on the ss-DNA compared to ds-DNA.

• Proceedings of the SCSK Conference
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• 2003.09b
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• pp.184-191
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• 2003

New pyranone derivative, 2-((3E)-4(2H, 3H, -benzo[3, 4-d] 1, 3-dioxolan-5-yl)-2-oxo-but-3-enyloxy)-5-hydroxy-4H-pyran-4-one (Seletinoid $G^{TM}$), was designed as a novel retinoid on the assumption that the pyranone ring may mimic the carboxylic acid moiety in retinoid structure. The enolic hydroxy of pyranone at five position was easily deprotonated to form an enolate. The role of enolate was similar to that of carboxylic acid. To evaluate the value of Seletinoid G as an anti-aging ingredient, various tests were performed for example inhibitory effect for MMP-l expression, anti-oxidative activity, procollagen synthesis in hairless mouse and primary skin irritation. The result of this study suggested that our new synthetic retinoid could be used as a safe material for anti-aging cosmetics.

• Archives of Pharmacal Research
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• v.19 no.1
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• pp.6-11
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• 1996

The trichothecenes are sesquiterpenoid mycotoxins characterized by the 12,13-epoxytrichothec-9-ene ring system. We have tested cytotoxicity of several naturally-occurring or synthesized trichothecenes against human solid tumor cell lines. Among them, trichothecin(I) and $4-\beta$-Acetoxy-12,13-epoxytrichothec-9-ene (trichodermin, II) exhibited highly cytotoxic activities. 4-.betha.-Hydroxy-12,13-epoxytrichothec-9-ene (trichodermol, III) and $4-\beta$-Methoxy-12,13-epoxytrichothec-9-ene (IV) had mild cytotoxicities. But 12,13-Epoxytrichothec-9-ene-4-one (V) and $4-\beta$-Hydroxy-12,13-epoxytrichothec-9-ene(VI) had no cytotoxicities up to 10 $\mug/ml$. And in the tested cell lines, HCT15 colon cancer cell line was the most sensitive to all tested trichothecenes.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05a
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• pp.207-210
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• 2004

The pore-filled anion-exchange membranes were prepared in this study with an asymmetric poly(vinylidene fluoride)(PVDF) membrane as a nascent membrane and poly(vinylbenzyl chloride)(PVBCl) as a polyelectrolyte. The solution of PVBCI having the chloromethylate aryl ring of 80 percents and 1,4-diaminobicyclo [2,2,2]octane(DABCO) was made with the solvent of tetrahydrofuran(THF) and N,N-Dimethylformamide(DMF), which is in the rotio of 8:2. A new preparation method in this study, i.e. in-situ crosslinking, enabled us to produce the pore-filled membranes without change of size, and to control the properties of final membrane with various degree of cross-linking. From the result of surface morphologies of SEM and AFM the polyelectrolyte exists in the pores of nascent membrane as a certain configuration. From the investigation of the solvent affecting much to the permeability and rejection, it was found. that the membranes using DMF and THF showed better performances than the membranes produced by THF only. The water permeability of the final membrane at low pressure(100㎪) showed a typical ultrafiltation membrane's permeability (8-10kg/㎡hr) and good values of rejection(55∼60 percent).