• Korean Journal of Optics and Photonics
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• v.15 no.6
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• pp.563-568
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• 2004

The high temperature proton exchange (HTPE) method was used to fabricate optical waveguides based on LiNbO$_3$, which gives rise to low propagation loss and high polarization extinction ratio. To characterize the refractive index distribution of the fabricated waveguides, the guided modes of each waveguide were observed using the prism coupling method and then the refractive index profile was calculated by the inverse WKB method with the least square fitting. Finally, we showed how the HTPE parameters such as the temperature of PE, the concentration of lithium additive, and the time of PE effect the refractive index profile.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2000.04a
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• pp.6-7
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• 2000

Recently, free radicals such as active oxygen species, nitric oxide, etc are believed to be one of the key substances in physiological and pathological, toxicological phenomena, and oxidative damages, and all organism have defencing system against such as free radicals. Formation and extinction of free radicals may be regulated through bio-redox system, in which various enzymes and compounds should be involved in very complicated manner. Thus, direct and non-invasive measurement of in vivo free radical reactions with living animals must be essential to understand the role of free radicals in pathophysiological phenomena. Electron spin resonance spectroscopy (ESR) is very selective and sensitive technique to detect free radicals, but a conventional ESR spectrometer has large detect in application to living animals, since high frequent microwave is absorbed with water, resulting in generation of high fever in living body. In order to estimate in vivo free radical reactions in living whole animals, we develop in vivo ESR-CT technique using nitroxide radicals as spin probes. Nitroxide radicals and their reduced forms, hydroxylamines, are known to interact with various redox systems. We found that! ! the signal decay due to reduction of nitroxyl radicals is influenced by aging, inspired oxygen concentration, ischemia-referfusion injury, radiation, etc. In the present paper, I will introduce in vivo ESR technique and my laboratory recent results concerning non-invasive evaluation of free radical reactions in living mice.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.87-92
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• 2005

Experiments at the Japan Microgravity Center(JAMIC) have investigated the interaction between diffusion flames and solid surfaces placed near flames. The fuel for the flames was $C_2H_4$. The surrounding oxygen concentration was 35% with temperatures of $T_a$=300. Especially, the effect of wall temperature on soot deposition from a diffusion flame placed near the wall has been studied by utilizing microgravity environment, which can attain very stable flame along the wall. Cylindrical burner with fuel injection was adopted to obtain two dimensional soot distributions by laser extinction method. In the experiment two different wall temperatures, $T_w$=300,800K, were selected as test conditions. The results showed that the soot distribution between flame and burner wall was strongly affected by the wall temperature and soot deposition increases with decrease in wall temperature. The comparison among the values for two different wall temperatures suggested that the change in thermophoretic effect is the most dominant factor to give the change in soot deposition characteristics.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.381.1-381.1
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• 2014

In this study, we investigated the deposition behavior and the etch resistivity of plasma polymerized carbon hardmask (ppCHM) film with the variation of process temperature. The etch resistivity of deposited ppCHM film was analyzed by thickness measurement before and after direct contact reactive ion etching process. The physical and chemical properties of films were characterized on the Fourier transform infrared (FT-IR) spectroscope, Raman spectroscope, stress gauge, and ellipsometry. The deposition behavior of ppCHM process with the variation of temperature was correlated refractive index (n), extinction coefficient (k), intrinsic stress (MPa), and deposition rate (A/s) with the hydrocarbon concentration, graphite (G) and disordered (D) peak by analyzing the Raman and FT-IR spectrum. From this experiment we knew an optimal deposition condition for structure of carbon hardmask with the higher etch selectivity to oxide. It was shown the density of ppCHM film had 1.6~1.9 g/cm3 and its refractive index was 1.8~1.9 at process temperature, $300{\sim}600^{\circ}C$. The etch selectivity of ppCHM film was shown about 1:4~1:8 to undoped siliconoxide (USG) film (etch rate, 1300 A/min).

• Journal of the Korean Chemical Society
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• v.9 no.2
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• pp.101-105
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• 1965

Spectrophotometric method for the determination of Co(Ⅱ) is developed based on the fact that Co(Ⅱ) forms a stable red complex with 7-nitroso-8-hydroxyquinoline-5-sulfonate at pH 4. 5. The absorbance is measured at 528$m{\mu}$, $25^{\circ}C$. Beer's law is followed in the concentration range of 0. 3 to 6. 0 p.p.m. of Co(Ⅱ) and molar extinction coefficient of the complex was $1.1{\times}10^4$. Of the diverse ions checked, Fe(Ⅱ), Fe(Ⅲ), Cu(Ⅱ), Mn(Ⅱ), Hg(Ⅰ), CN-, EDTA interfere. The composition of the complex is found to be 3:1 ligand to metal species by mole ratio and continuous variation methods.

• Journal of Technologic Dentistry
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• v.23 no.1
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• pp.75-83
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• 2001

This study was conducted to find antibacterial agent against growth of dental caries bacteria. St. mutans KDJ-50 from various medicinal plants of which safety was indetified. Medicinal plants used in this study was dried and grinded after purchased at Daegu yakryung sijang and Kyungsan jungang sijang. Medicinal plants extracted with 80% ethanol at boiling point for 3 hrs was used as antibacterial agent after freeze dried. This study was conducted to find antibacterial agent against growth of dental caries bacteria. St. mutans KDJ-50 from 32 medicinal plants of which safety was indetified. The result of using paper disc method. Caryophylli Flos. Coptidis Rhizoma. Phellodendri Cortex. Schizamdrae Fructs. Myristicae Semen, Crataegi Fructus and Acori Graminei Rhizoma was selected as antibacterial agent. The result of viable cell counting method. the antibacterial activity of Caryophylli Flos was highest among tested 7 medicinal plants followed by Phellodendri Cortex and Coptidis Rhizoma. The extinction effect of the St. mutans by Caryophylli Flos was shown with the addition of 0.5 (w/v) in the medium. The high antibacterial activity was acquired at high extraction temperature and long extraction temperature. The antibacterial activity of Caryophylli Flos was not effected by the concentration of ethanol.

• Journal of Radiation Industry
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• v.9 no.2
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• pp.57-62
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• 2015

In this study, we fabricated effect of storage conditions on graft of polypropylene (PP) non-woven fabric induced by electron beam. The electron beam irradiations on PP non-woven fabric were carried out over a range of irradiation doses from 25 to 100 kGy to make free radicals on fabric surface. The radical measurement was established by electron spin resonance (ESR) for confirming the changes of the alkyl radical and peroxy radical according to effect of storage time, storage temperature and atmosphere. It was observed that the free radicals were increased with irradiation dose and decreased with storage time due to the continuous oxidation. However, the radical extinction was significantly delayed due to reduced mobility of radicals at extremely low temperature. The degree of graft based on the analysis of ESR was investigated. The conditions of graft reaction were set at a temperature: $60^{\circ}C$, reaction time: 6 hours and styrene monomer concentration: 20 wt%.

• Bulletin of the Korean Chemical Society
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• v.16 no.12
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• pp.1218-1222
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• 1995

The pKa values of benzyltetrahydrothiophenium halides 1a-f in water have been estimated by measuring the absorbances of the solution in aqueous hydroxide ion solution. Assuming that the ratios of the activity coefficients remains close to unity, the absorbance of the solution can be expressed as A/[SH]o=(εSH+εS-K[OH-])/(1+K[OH-]), where A, [SH]o, K, εSH, and εS- are the absorbance of solution, the initial concentration of 1a-f, the equilibrium constant, and the extinction coefficients for SH and S-, respectively. The εS- and K values that best fit with this equation were calculated by a nonlinear regression analysis with a large number of absorbance data determined at different [OH-] and [SH]o. The pKa values of the SH were then calculated with the relationship Ka=-log K+14. The validity of this method has been demonstrated by the excellent agreements between the experimental and literature pKa values of three organic acids. The pKa values of 1a-f estimated by this method are in the range of 12.5-15.3 and correlate well with the Hammett equation. The large negative deviation for the pKa values of 1e and 1f from the Hammett plot has been attributed to the extra hydrogen bonding between the phenyl group and water molecules attracted by the hydrophilic substituents.

• Advances in nano research
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• v.14 no.6
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• pp.557-573
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• 2023

The rapid growth of zinc-oxide (ZnO) nanostructures (NSs) on woven carbon fiber (WCF) is reported in this study employing a microwave-aided chemical bath deposition process. The effects of different process parameters such as molar concentration, microwave duration and microwave power on morphologies and growth rate of the ZnO on WCF were studied. Furthermore, an attempt has been taken to study influence of different type of growth solutions on ZnO morphologies and growth rates. The surface functionalization of WCF fabrics is achieved by successful growth of crystalline ZnO on fiber surface in a very short duration through one-step microwave synthesis. The morphological, structural and compositional studies of ZnO-modified WCF are evaluated using field-emission scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy respectively. Good amount of zinc and oxygen has been seen in the surface of WCF. The presence of the wurtzite phase of ZnO having crystallite size 30-40 nm calculated using the Debye Scherrer method enhances the surface characteristics of WCF fabrics. The UV-VIS spectroscopy is used to investigate optical properties of ZnO-modified WCF samples by absorbance, transmittance and reflectance spectra. The variation of different parameters such as dielectric constants, optical conductivity, refractive index and extinction coefficient are examined that revealed the enhancement of optical characteristics of carbon fiber for wide applications in optoelectronic devices, carbon fiber composites and photonics.

• Journal of the Korean Chemical Society
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• v.29 no.5
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• pp.510-515
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• 1985

Color of $MoO_{(aq)}^{3+}$ in concentrated methanesulfonic acid (∼10M) changes dark green due to the formation of $Mo_2O_2(OH)_{2(aq)}^{4+}$ dimer. This color is similar to that shown by addition of water to that shown by addition of water to green $MoO_{(aq)}^{3+}$ solution in 15-16M methanesulfonic acid. The molar extinction coefficient of monomer in 15M methanesulfonic acid is about 20 at 415nm. Rate constants are independent on the aquomolybdenum (V) and hydrogen ion concentration under the condition of this experment. Bridging hydroxides of $Mo_2O_2(OH)_{2(aq)}^{4+}$ are dehydrogenated at the less concentration of ∼6 M for HPTS and ∼10M for $CH_3SO_3H$. The structure of both the yl-oxygens and the bridging oxygens of final product is identified to (*image)unit.