• 방사성폐기물학회지
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• 제18권1호
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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.

• 음성과학
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• 제2권
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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/.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권7호
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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.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 초전도 자성체
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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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• 제15권5호
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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.

• 디지털산업정보학회논문지
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• 제5권4호
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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.

• 한국분말재료학회지
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• 제23권6호
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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.

• 대한화학회지
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• 제17권6호
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• pp.406-410
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• 1973

Dimethylsulfamoyl chloride의 할라이드 교환반응을 무수 아세톤 용매속에서 방사성 할라이드 이온을 사용하여 두 온도에서 속도론적으로 연구하였다. 그 결과를 benzensulfonyl chloride의 경우와 비교해 보면 친핵성에 있어서는 거의 비슷한 경향성을 나타내나, 반응속도는 dimethylsulfamoyl chloride 쪽이 $10^{-2}$배 이상이나 느린 경향을 나타낸다. 또한 활성화 파라미터, ${\Delta}H^{\neq}$나 ${\Delta}S^{\neq}$는 benzensulfonyl chloride의 경우와는 반대로 dimethylsulfamoyl chloride의 경우는 $Cl^-\;>\;Br^-\;>\;I^-$의 순서로 감소함을 나타낸다. 이 결과를 bond-breaking, bond formation, electronic requirment 및 HSAB 원리로 설명하였다.

• 대한화학회지
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• 제37권1호
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• pp.148-153
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• 1993

진한 황상 용액에서 4'-halogenated azoxybenzene 유도체의 Wallach 자리옮김 반응을 UV-Vis 분광학적 방법으로 재조사하였다. 흥미롭게도 log(rate)와 pi 비편재화 파라미터라 불리우는 치환체 상수, ${\sigma}_R{^+}$와의 도시에서 아주 좋은 직선관계$(logk_{obs}=-0.61\;{\sigma}_R{^+} -3.29,\;{\gamma = 0.998)$를 얻었다. 그 겨로가로 공명효과에 의해 크게 안정화될 수 있는 즉 + 전하를 가진$(DC^{++})$중간체를 거치는 B-L 메카니즘이 Wallach 재배열 반응에 더욱 강력히 주장된다.

• 한국결정성장학회지
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• 제11권6호
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• pp.285-289
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• 2001

본 연구에서는 Langasite 보다 우수한 압전특성을 나타낼 것으로 기대되는 같은 구조를 갖는 새로운 화학조성을 각 자리의 치환을 조사하였다. 합성된 물질은 $Ca_3TaGa_5Si_{2}O_{14}$로서 고상합성법에 의한 합성이 되었으며 이를 바탕으로 $\mu$-PD(micro-pilling-down)와 Cz법에 의해 결정성장을 시도하였다. 성장된 결합은 XRD와 EPMA를 통해 격자상수 화학조성 분포가 분석되었다.