• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.1
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• pp.1-18
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• 2020

Molten salt solutions consisting of eutectic LiCl-KCl and concentrations of samarium chloride (0.5 to 3.0 wt%) at 500℃ were analyzed using both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The CV technique gave the average diffusion coefficient for Sm³⁺ over the concentration range. Equipped with Sm³⁺ diffusion coefficient, the Randles-Sevcik equation predicted Sm³⁺ concentration values that agree with the given experimental values. From CV measurements; the anodic, cathodic, and half-peak potentials were identified and subsequently used as a parameter to acquire EIS spectra. A six-element Voigt model was used to model the EIS data in terms of resistance-time constant pairs. The lowest resistances were observed at the half-peak potential with the associated resistance-time constant pairs characterizing the reversible reaction between Sm³⁺ and Sm²⁺. By extrapolation, the Voigt model estimated the polarization resistance and established a polarization resistance-concentration relationship.

• Speech Sciences
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• v.2
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• pp.67-88
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• 1997

The aim of this study is to develop an assessment program of speech rehabilitation for children having some language and speech disorders. Patients of dysarthria, tonsillectomy, tonsilhypertrophy, and nasal obstruction were selected for this experimental clinical phonetic study. Formant variations ($F_1\;&\;F_2$) show pre- and post-operation differences in tonsillectomy and cleft palate patients. Nasal formants ($NF_1\;&\;NF_2$) show pre- and post-operation differences in nasal obstruction. The articulation reaction time (ART) as a parameter was used to assess Voice Onset Time(VOT). It was shown longer duration for hypokinetic dysarthria and shorter for atoxic dysarthria.. The diadochokinetic rate was measured by Visi-pitch. Lower diadochokinetic rate appeared to spastic and dysarthria in comparison with the control group. It was shown that the nasalance of tonsilhypertrophy, nasal obstruction, and cleft palate patients was seen to increase after operation. In addition, the assessment of nasality can be measured only by simple vowels such as /a/ and /i/.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.7
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• pp.382-387
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• 2000

The $CdAl_2S_4 and CdAl_2S_4 : Co^{2+}$ single crystals were grown by the chemical transport reaction method using iodine as a transport agent. The $CdAl_2S_4 and CdAl_2S_4 : Co^{2+}$single crystals were crystallized into a defect chalcopyrite structure. The optical energy gap of the $CdAl_2S_4 and CdAl_2S_4 : Co^{2+}$ single crystals was found to be 3.377 eV and 2.924 eV, respectively, at 300 K. Blue emission with peaks in 456nm~466nm at 280K was observed in the $CdAl_2S_4$ single crystal. Optical absorption and emission peaks due to impurities in the $CdAl_2S_4 Co^{2+}$ single crystal were observed and described as originating from the electron transition between energy levels of the $Co^{2+} ion sited at the Td symmetry point.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04a
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• pp.59-63
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• 2002

The purpose of this paper is to investigate the crystal texture of the 2223 phase and its relationship with PIT processing parameter. Ag-sheathed Bi-2223 multi-filament tapes were prepared by changing rolling reduction ratio. We analysed the degree of texture for 2223 phase after heat-treatment. According to X-ray pole-figure, the texture of the filaments located near surface and center were not so different each other for all rolling conditions. we found a little higher degree of texture for 60% rolling reduction. But its difference is not so high compared with those tapes with a lower rolling reduction ratio. Reaction induced texturing seemed to contribute with a large portion under present condition.

• Journal of Welding and Joining
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• v.15 no.5
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• pp.104-114
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• 1997

The microstructure and bond strength were investigated on the SiC/SiC and SiC/mild steel joints brazed by Ag-5at%Ti alloy. Ag-5at%Ti-2at%Fe and -5at%Fe brazing alloys were also used to see the effects of Fe addition on the bond strength of SiC/SiC brazed joints. Brazing temperature and brazing gap were selected and examined as brazing variables. The microstructure of SiC/SiC brazed joints was affected by Fe addition to the Ag-5at%Ti alloy, but the bond strength was not. Increasing brazing temperature also changed the microstructure of $Ti_5Si_3$ reaction layer and brazing alloy matrix of the SiC/SiC and SiC/mild steel joints, but not the bond strength. Brazing gap had a great effects on the bond strength. Decreasing brazing gap from 0.2 mm to 0.1 mm in SiC/SiC brazing increased the bond strength from 187 MPa to 263 MPa and, in SiC/mild steel brazing, from 189 MPa to 212 MPa. It was concluded that the most important parameter on the bond strength in SiC/SiC and SiC/mild steel brazing was the relative ratio between brazing gap and specimen size.

• Journal of Korea Society of Digital Industry and Information Management
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• v.5 no.4
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• pp.11-17
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• 2009

Polarography is a subclass of voltammetry where the working electrode is a dropping mercury electrode. More, I developed the experiment for raising up mercury electrode. In Voltammetry, information about an analyte is obtained by measuring the current as the potential is varied at oxidation-reduction reaction. A plot of current vs. potential in a polarography experiment shows the current oscillations correspoding to the drops of Hg falling from the capillary. The drops growth causes capacitive and faradic current. These changing current effects combined with experiments where the potential is continuously changed can result in noisy traces. The raising up type improved upon the method of dropping in hardware. In reduction of the noise, moving average smoothing method have been used. But the other procedure is introduced based on Fourier transformation. So FFT and IFFT engine was implemented and installed in my experiment. However, after experimentation, peak height as the measuring parameter gave a good linear relationship to concentration. The resolution of potential peaks of various kinds, using Zn and Cu as the example, was improved using the smoothing method.

• Journal of Powder Materials
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• v.23 no.6
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• pp.453-457
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• 2016

In this work, we synthesize brilliant yellow color ${\alpha}$-FeOOH by controlling the rod length and core-shell structure. The characteristics of ${\alpha}$-FeOOH nanorods are controlled by the reaction conditions. In particular, the length of the ${\alpha}$-FeOOH rods depends on the concentration of the raw materials, such as the alkali solution. The length of the nanorods is adjusted from 68 nm to 1435 nm. Their yellowness gradually increases, with the highest $b^*$ value of 57 based on the International Commission on Illumination (CIE) Lab system, by controlling the nanorod length. A high quality yellow color is obtained after formation of a silica coating on the ${\alpha}$-FeOOH structure. The morphology and the coloration of the nal products are investigated in detail by X-ray diffraction, scanning electron microscopy, UV-vis spectroscopy, and the CIE Lab color parameter measurements.

• Journal of the Korean Chemical Society
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• v.17 no.6
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• pp.406-410
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• 1973

Kinetic study of halide exchange for dimethylsulfamoyl chloride in dry acetone by using radioisotopic halide ions has been carried out at two temperatures. The result of the order of nucleophilicity, as compared with benzenesulfonyl chloride, shows a similar tendency but reaction rate is slower, more than $10^{-2}$times, than benzenesulfonyl chloride. The activation parameter, ${\Delta}H^{\neq}\;and\;{\Delta}S^{\neq}$ decrease in sequence $Cl^-\;>\;Br^-\;>\;I^-$ in dimethylsulfamoyl chloride but it is the reverse order found for benzenesulfonyl chloride. The results are interpreted with bond-breaking, bond-formation, and electronic requirments, and in the light of HSAB Principle.

• Journal of the Korean Chemical Society
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• v.37 no.1
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• pp.148-153
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• 1993

The Wallach rearrangement of 4'-halogenated azoxybenzenes in strong sulfuric acid was reinvestigated by UV-Vis spectrophotometric method. Interestingly an excellent linearity $(logk_{obs}=-0.61\;{\sigma}_R{^+} -3.29,\;{\gamma = 0.998)$ was obtained on plotting log (rate) vs. substituent constant, ${\sigma}_R{^+}$, which is known as the Pi delocalization parameter. Thus B-H mechanism via a charged intermediate $(DC^{++})$, which can be largely stabilized by resonance, is far more favored for the Wallach rearrangement.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.6
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• pp.285-289
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• 2001

We investigated that each site was substituted by new chemical components in Langasite ($La_3Ga_5/SiO_{14}$)-type structure with superior piezoelectric characteristics than $La_3Ga_5/SiO_{14}$. In this study $Ca_3TaGa_5Si_{2}O_{14}$ was synthesized by soilid-state reaction and grown by the $\mu$-PD(micro-pilling-down)and Cz technique. Lattice parameter and chemical composition was investigated by XRD and EPMA respectively.