• Korean Journal of Food Science and Technology
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• v.21 no.4
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• pp.468-479
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• 1989

The oxidative stability of the ramyon prepared with rapeseed oil fortified with antioxidants or blended with palm oil was studied to explore the possibility of substituting it for Imported frying fats and oils. Natural tocopherols, butylated hydroxyanisole(BHA), tertiarybutyl hydroquinone(TBHQ), and ascorbyl palmitate with citric acid were used at a level of 0.02 percent. Blended oils were prepared by adding a palm oil to the rapeseed oil at ratios of 7:3, 5:5, and 3:7(w/w), respectively. Ramyon samples were stored at $35.0{\pm}0.5^{\circ}C$. for 90 days. The values of parameters, such as peroxide value, unsaturation ratio, and dielectric constant, of the extracted oils were regularly determined. An organoleptic test for the flavor of the samples was also performed. The oxidative stability of the samples was estimated on the basis of the changes of the parameter values. The effectiveness of the antioxidants was in the order of TBHQ ${\gg}$ ascorbyl palmitate with citric acid>BHA>natural tocopherols. The oxidative stability of the ramyon prepared with the rapeseed oil containing 0.02 percent TBHQ was almost as good as that of the ramyon prepared with the palm oil. The stability of the ramyon prepared with the blended oil containing 70 percent palm oil was also as good as that of the ramyon prepared with the palm oil.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.67-75
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• 2005

For th aim of lightweight microwave absorbers, conductive and magnetic microspheres are fabricated by plating of Co films on hollow ceramic microspheres of low density. Metal plating was carried out in a two-step electroless plating process (pre-treatment of activation and plating). Uniform coating of the film with about $2{\~}3{\cal}um$ thickness was identified by SEM. High-frequency magnetic and microwave absorbing properties were determined in the rubber composites containing the Co-coated microspheres. Due to conductive and ferromagnetic behavior of the Co thin films, high dielectric constant and magnetic loss can be obtained in the microwave frequencies. Due to those electromagnetic properties, high absorption rate (25 dB) and thin matching thickness ($2.0{\~}2.5{\cal}mm$) are predicted in the composite layers containing the metal-coated microspheres of low density (about 0.84 g/cc) for the electromagnetic radiation in microwave frequencies.

• Journal of the Korean Magnetics Society
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• v.19 no.6
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• pp.203-208
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• 2009

Magnetic and Ka-band absorbing properties have been investigated in Ti-Co substituted M-type barium hexaferrites with $BaTi_{0.5}Co_{0.5}Fe_{11}O_{19}$ composition. The ferrite powders were prepared by conventional ceramic processing technique and used as absorbent fillers in ferrite-rubber composites. The magnetic properties were measured by vibrating sample magnetometer. The complex permeability and dielectric constant were measured by using the WR-28 rectangular waveguide and network analyzer in the frequency range 26.5~40 GHz. For the Ti-Co substituted M-hexaferrites, the ferromagnetic resonance is observed at Ka-band (29.4 GHz). The matching frequency and matching thickness are determined by using the solution map of impedance matching. A wide band microwave absorbance is predicted with controlled ferrite volume fraction and absorber thickness.

• Nuclear Engineering and Technology
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• v.5 no.1
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• pp.30-37
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• 1973

The Nishitani's equations for impedance of anodic oxide films have been derived based on a p-i-n model under the assumption of $\omega$$\varepsilon$$\rho$$_{ο}$<<4$\pi$<<$\omega$$\varepsilon$$\rho$$_{\omega}$, where $\omega$ is angular frequency, $\varepsilon$ is dielectric constant, and $\rho$$_{ο}$ and $\rho$$_{\omega}$ are the resistivity of the interface region and the intrisic region of the anodic oxide film, respectively. Since it is not possible to evaluate all parameters in the equations, however, any clear physical picture cannot be obtained from the equations. Therefore, the equations are modified under the assumption of $\omega$$\tau$$_{\omega}$>>1 and In(1+$\omega$$^2$$\tau$$_{ο}$$^2$)<<1, where $\tau$$_{\omega}$=$\varepsilon$$\rho$$_{\omega}$(4$\pi$) and $\tau$$_{ο}$=$\varepsilon$$\rho$$_{ο}$/(4$\pi$). The modified equations are then used to explain the change in the frequency characteristics of anodic oxide films when they are heated. The change in impedance of anodic oxide films when they are heated is attributed mainly to the increase in the diffusion layer and to the decrease in the resistivity of anodic oxide films.s.

• Journal of the Korean Chemical Society
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• v.36 no.2
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• pp.191-196
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• 1992

Reaction of N,N-dimethylaniline(N,N-DMA) and iodine in $CHCl_3,\;CH_2Cl_2 : CHCl_3$(1:1), $CH_2Cl_2$(1:1), and CH2Cl2 has been studied kinetically by using conductivity method. Pseudo first-order rate constants ($k_{obs}$) and second-order rate constants ($k_{obs}$/[N,N-DMA]) are dependent on the N,N-DMA concentration. Second-order rate constants obtained were decreased with increasing N,N-DMA concentration. We analysed these results on the basis of formation of charge transfer complex as a reaction intermediate. From the construction of reaction scheme and activation parameters for the formation and transformation of charge transfer complex. The equilibrium constants decreased when the dielectric constant of solvent was increased, and the value is 1.9${\sim}$4.2$M^{-1}$. The rate of transformation are markedly affected by the solvent polarity.${\Delta}H^{\neq}$ is 6.3-12.6kJ/mol, and ${\Delta}S^{\neq}$ is large negative value of -234J/mol K.

• Journal of the Korean Chemical Society
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• v.38 no.9
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• pp.640-652
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• 1994

This work is undertaken to determine alcohol homologues so-called fusel oil that may be present in the Korean folk sojues (distilled liquor) made from grains and to describe sample preparation and analytical method by GC-FID-MS. Solid phase extraction method for sample preparation by using porous styrene divinyl benzene polymer (Porapak Q) was compared with steam distillation and solvent extraction method. Retention behaviors of homologous series of alcohols were also studied. Log values of retention time, molecular weight, boiling point, and capacity factor of alcohols showed linear correlations to the carbon number of an alcohol, to the oven temperature, and to the dielectric constant. Components such as methyl alcohol, n-propyl alcohol, isobutyl alcohol, isopentyl alcohol, and phenethyl alcohol have been identified. The more amount of isopentyl alcohol than other alcohols are contained in the Korean folk sojues, while that of n-propyl alcohol are contained in Chinese kaoliangchiew. Degree of similarity or dissimilarity and classification of the individual samples were discussed using multivariate statistical analysis(principal components analysis) based on GC data.

• Fire Science and Engineering
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• v.25 no.6
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• pp.21-26
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• 2011

The purpose of this paper is to present the damage patterns of cellular phone (SCH_W830) batteries according to energy sources and have them utilized as data for the settlement of disputes between manufactures and consumers. The reliability was secured by maintaining the ambient temperature and humidity at $22{\pm}2^{\circ}C$ and 40~60 %, respectively. The voltage of the battery used for the tests was measured to be 4.18V between positive pole (+) and negative pole (-)(1), and 4.19 V between positive pole (+) and negative pole (-)(2). This study applied the Korean Industrial Standard (KS) to the flammability test of cellular phones due to a general flame applied to them and found that no damage occurred to the built-in battery even though the flame was applied to the cases of cellular phones for 30 seconds. From the results of immersing the cellular phones in the saline solution (NaCl, 0.9 %) for 180 seconds, it was found that there was a trace of carbonization and melting due to the heat caused by leaking current. It can be seen that when the cellular phones were heated for 70 seconds using a microwave oven (MWO), the areas containing the metal holder, recharging connector, antenna, etc., were melted and discolored and that other areas showed no particular problems. That is, while the external carbonization of cellular phones, built-in metals and dielectric materials, and damage and deformation of the battery terminal block, etc., occurred differently depending on the types of energy sources, the voltage showed comparatively constant characteristics. Therefore, it is thought to be possible to attribute the cause of damage to the battery by performing analysis taking into consideration comprehensively the characteristics of the flame spread pattern as well as the melting and deformation of metals.

• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1170-1175
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• 1998

PZT films without lower electrode were deposited on the highly doped Si(100) substrate with MgO buffer layer (Mgo/si) by RF magnetron sputtering method followed by the rapid thermal annealing at $650^{\circ}C$ . We investigated the dependences of the crystalline and electrical properties on the MgO thickness and the RTA post annealing. The PZT films on bare Si (without MgO) showed pyrochlore crystal structure while those on MgO(50 )/Si substrates showed the typical perovskite crystal structures. From SEM and AES analysis, the thickness of PZT films was about 7000 showing relatively smooth interface. The depth profiles indicated that atomic species were distributed homogeneously in the PZT/MgO/Si substrate. The dielectric constant($\varepsilon_{r}$ ) and remanent polarization(2Pr) were about 300 and $14\mu$C/$\textrm{cm}^2$;, respectively. The leakage current was about $3.2\mu$/A$\textrm{cm}^2$.

• Journal of Pharmaceutical Investigation
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• v.38 no.6
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• pp.373-380
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• 2008

In order to develop optimal formulation and iontophoresis condition for the transdermal delivery of levodopa, we have evaluated the effect of two permeation enhancers, ethanol and oleic acid in microemulsion, on transdermal delivery of levodopa. In vitro flux studies were performed at $33^{\circ}C$, using side-by-side diffusion cell and full thickness hairless mouse skin. Current density applied was $0.4\;mA/cm^2$ and current was off after 6 hours application. Levodopa was analysed by HPLC at 280 nm. The o/w microemulsions of oleic acid in buffer solution (pH 2.5 & 4.5) were prepared using oleic acid, Tween 80 and ethanol. The existence of microemulsion regions were investigated in pseudo-ternary phase diagrams. Contrary to our expectation, cumulative amount of levodopa transported from microemulsion (pH 2.5) for 10 hours was similar to that from aqueous solution in all delivery methods (passive, anodal and cathodal). When pH of the micro-emulsion was pH 4.5, cumulative amount of levodopa transported for 10 hours increased about 40% (anodal) to 50% (cathodal), when compared to that from aqueous solution. Flux from pH 4.5 microemulsion showed higher value than that from pH 2.5 in all delivery methods. These results seem to indicate that electroosmosis plays more dominant role than electrorepulsion in the flux of levodopa at pH 2.5. The effect of ethanol on iontophoretic flux was studied using pH 2.5 phosphate buffer solution containing 3% or 5% (v/v) ethanol. Flux enhancement was observed in passive and anodal delivery as the concentration of the ethanol increased. Without ethanol, cathodal delivery showed higher flux than anodal delivery. Anodal delivery increased the cumulative amount of levodopa transported 1.6 fold by 5% ethanol after 10 hours. However, in cathodal delivery, no flux enhancement of levodopa was observed during current application and only marginal increase in cumulative amount transported after 10 hours was observed by 5% ethanol. These results seem to be related to the decrease in dielectric constant of the medium and the lipid extraction of the ethanol, which decrease the electroosmotic flow, and thus decrease the flux. Overall, the results provide important insights into the role of electroosmosis and electrorepulsion in the transport of levodopa through skin, and provide some useful informations for optimal formulation for levodopa.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.477-477
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• 2008

For more than three decades, the gate dielectrics in CMOS devices are $SiO_2$ because of its blocking properties of current in insulated gate FET channels. As the dimensions of feature size have been scaled down (width and the thickness is reduced down to 50 urn and 2 urn or less), gate leakage current is increased and reliability of $SiO_2$ is reduced. Many metal oxides such as $TiO_2$, $Ta_2O_4$, $SrTiO_3$, $Al_2O_3$, $HfO_2$ and $ZrO_2$ have been challenged for memory devices. These materials posses relatively high dielectric constant, but $HfO_2$ and $Al_2O_3$ did not provide sufficient advantages over $SiO_2$ or $Si_3N_4$ because of reaction with Si substrate. Recently, $HfO_2$ have been attracted attention because Hf forms the most stable oxide with the highest heat of formation. In addition, Hf can reduce the native oxide layer by creating $HfO_2$. However, new gate oxide candidates must satisfy a standard CMOS process. In order to fabricate high density memories with small feature size, the plasma etch process should be developed by well understanding and optimizing plasma behaviors. Therefore, it is necessary that the etch behavior of $HfO_2$ and plasma parameters are systematically investigated as functions of process parameters including gas mixing ratio, rf power, pressure and temperature to determine the mechanism of plasma induced damage. However, there is few studies on the the etch mechanism and the surface reactions in $BCl_3$ based plasma to etch $HfO_2$ thin films. In this work, the samples of $HfO_2$ were prepared on Si wafer with using atomic layer deposition. In our previous work, the maximum etch rate of $BCl_3$/Ar were obtained 20% $BCl_3$/ 80% Ar. Over 20% $BCl_3$ addition, the etch rate of $HfO_2$ decreased. The etching rate of $HfO_2$ and selectivity of $HfO_2$ to Si were investigated with using in inductively coupled plasma etching system (ICP) and $BCl_3/Cl_2$/Ar plasma. The change of volume densities of radical and atoms were monitored with using optical emission spectroscopy analysis (OES). The variations of components of etched surfaces for $HfO_2$ was investigated with using x-ray photo electron spectroscopy (XPS). In order to investigate the accumulation of etch by products during etch process, the exposed surface of $HfO_2$ in $BCl_3/Cl_2$/Ar plasma was compared with surface of as-doped $HfO_2$ and all the surfaces of samples were examined with field emission scanning electron microscopy and atomic force microscope (AFM).