• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.481-482
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• 2006

플라즈마 화상표시기 (PDP)의 보호막 물질로 사용 중인 다결정 MgO의 특성을 개선하기 위하여 본 연구에서는 MgO에 희토류계 원소를 치환하여 제조하였으며, 치환량에 따른 MgO 보호막의 광학적 특성과 전기적 특성을 고찰하였다. MgO + 100 ppm $Gd_2O_3$조성으로 제작한 MgO 박막의 이차전자 방출계수 값이 순수 MgO 보다 35% 높게 나타났다. $Gd_2O_3$ dopant가 100 ppm 첨가시까지 밀도가 증가하였으나, 그 이상 첨가시 감소하는 경향을 나타냈다. 가속전압 200 V에서 이차전자 방출계수는 0.138 이었고 표면거칠기는 5.77 nm 이었으며 투과율은 550 nm 에서 95.76% 이었다.

• Composites Research
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• v.32 no.2
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• pp.85-89
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• 2019

The size, morphology and composition of nanoparticles are regarded as the most important factors to the efficiency of catalytic reduction of various chemical compounds. In order to make a systematic comparison, gold, platinum and palladium nanoplates with 100 nm diameter with rough surface morphology were manufactured through the galvanic replacement reaction, and the reaction kinetics of the catalytic reduction of 4-nitrophenol and 4-nitroaniline was systematically analyzed by spectroscopic measurement. According to the observation, the catalytic reduction efficiency was significantly different against the constitutional elements in order of Pd > Au > Pt, and it was additionally influenced by the type of substrate.

• Journal of the Korean Chemical Society
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• v.35 no.5
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• pp.553-559
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• 1991

The elution characteristics of rare earth elements in $NH^{4+}$ form cation exchange resin had been investigated. Elution were performed varing the loading amount, column diameter, column length and eluent pH. Analysing the chemical species contained in each effluent, elution mechanisms of rare earth elements and the separation of rare earth elements in monazite could be understood. The resolution values of adjacent rare earth elements were improved increasing rare earths adsorption amount wfith the same column within it's exchange capacity. With $NH^{4+}$ resin form, column length does not affect on the resolution values and retention time of rare earth elements and the rare earth-EDTA complex were not adsorbed on $NH^{4+}$ resin form. pH of eluent affected on the reactivities between rare earth elements and EDTA. Decreasing eluent pH, resolution values of adjacent rare earth elements were increased while increasing elution time.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.11a
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• pp.205-208
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• 2001

본 연구에서는 소결온도와 치환원소에 따른 서클레이터/아이솔레이터용 YIG 페라이트의 미세구조와 전자기적 특성을 고찰하고자 하였다. Ca, V, In을 치환시킨 YIG 페라이트를 분무건조기를 사용하여 준구형 과립상태로 만들고, 일반적인 세라믹 제조 공정에 따라 12$50^{\circ}C$, 1275$^{\circ}C$, 130$0^{\circ}C$, 13$25^{\circ}C$에서 각각 소결하였다. 제조된 YIG 페라이트에 대한 기본 물성과 자기 특성을 밀도측정기, XRD, SEM, VSM, FMR(Ferromagnetic Resonance) 등을 이용하여 측정 분석하였다. $Y_{1.6}$C $a_{1.4}$F $e_4$ $V_{0.7}$I $n_{0.3}$ $O_{12}$ 조성의 YIG 페라이트에 대한 전자기적 특성 측정 결과 130$0^{\circ}C$에서 소결한 YIG 페라이트가 높은 포화자화(4$\pi$Ms) 값과 낮은 자기공명반치폭($\Delta$H)을 지닌 우수한 전자기적 특성을 나타내었다. 전자기적 특성을 나타내었다.나타내었다.다.

• Journal of the Korean Chemical Society
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• v.20 no.6
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• pp.453-459
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• 1976

Rate constants for the reaction of methyl chloroformate with substituted anilines, and for the halogen exchanges in phenyl chloroformate have been determined in acetone. Although the rate data can be interpreted equally well with the addition-elimination mechanism($S_AN$) involving an intermediate, results of MO and isotope effect studies strongly favor the synchronous ($S_N2$) mechanism for the reactions studied. It was concluded that for the fast reacting nucleophiles the transition state is of "late" type while for the slow reacting nucleophiles it is of "early" type.

• Nuclear Medicine and Molecular Imaging
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• v.40 no.4
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• pp.228-232
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• 2006

Purpose: electrophilic $^{18}F(T_{1/2}=110\;min)$ radionuclide in the form of $[^{18}F]F_2$ gas is of great significance for labeling radiopharmaceuticals for positron omission tomography (PET). However, its production In high yield and with high specific radioactivity is still a challenge to overcome several problems on targetry. The aim of the present study was to develop a method suitable for the routine production of $[^{18}F]F_2$ for the electrophilic substitution reaction. Materials and Methods: The target was designed water-cooled aluminum target chamber system with a conical bore shape. Production of the elemental fluorine was carried out via the $^{18}O(p,n)^{18}F$ reaction using a two-step irradiation protocol. In the first irradiation, the target filled with highly enriched $^{18}O_2$ was irradiated with protons for $^{18}F$ production, which were adsorbed on the inner surface of target body. In the second irradiation, the mixed gas ($1%[^{19}F]F_2/Ar$) was leaded into the target chamber, fellowing a short irradiation of proton for isotopic exchange between the carrier-fluorine and the radiofluorine absorbed in the target chamber. Optimization of production was performed as the function of irradiation time, the beam current and $^{18}O_2$ loading pressure. Results: Production runs was performed under the following optimum conditions: The 1st irradiation for the nuclear reaction (15.0 bar of 97% enriched $^{18}O_2$, 13.2 MeV protons, 30 ${\mu}A$, 60-90 min irradiation), the recovery of enriched oxygen via cryogenic pumping; The 2nd irradiation for the recovery of absorbed radiofluorine (12.0 bar of 1% $[^{19}F]fluorine/argon$ gas, 13.2 MeV protons, 30 ${\mu}A$, 20-30 min irradiation) the recovery of $[^{18}F]fluorine$ for synthesis. The yield of $[^{18}F]fluorine$ at EOB (end of bombardment) was achieved around $34{\pm}6.0$ GBq (n>10). Conclusion: The production of $^{18}F$ electrophilic agent via $^{18}O(p,n)^{18}F$ reaction was much under investigation. Especially, an aluminum gas target was very advantageous for routine production of $[^{18}F]fluorine$. These results suggest the possibility to use $[^{18}F]F_2$ gas as a electrophilic substitution agent.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.323-328
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• 1996

첨가원소에 따른 지르코늄합금의 재결정화 거동이 조사되었다. Zr-1.0 wt.% Nb-04 wt% Sn 합금에 V, Mo 및 Fe의 소량첨가원소를 각각 0.3 wt. % 첨가시켜 판재로 가공후 500-600 $^{\circ}C$에서 열처리 시간에 따른 경도변화 및 미세조직변화를 추적하였다. Fe가 첨가안된 Zr-1.0 wt.% Nb-0.4 wt.% Sn 합금과의 재결정현상을 비교할 때, 0.22 wt.%의 Fe의 첨가는 지르코늄합금의 재결정을 가속화시켰다. 그러나 소량의 V 또는 Mo의 첨가는 지르코늄합금의 재결정을 더디게 하였으며, 경도의 증가를 야기시켰다. 본연구결과는 지르코늄합금에 미소첨가되는 Fe가 지르코늄의 격자확산 및 치환확산을 가속한다는 것을 확증적으로 보여주는 것으로 중성자 조사조건에서 증폭해서 나타나는 조사성장, 부식, 크립등의 여러가지 현상들 (irradiation induced phenomena)도 미소첨가된 Fe의 재배열과 관계가 있는것으로 사료된다.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.4
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• pp.235-239
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• 2001

급속 표면가열과 기존의 전기로 열처리에서 얻어지는 경화의 가장 중요한 차이점은 전자가 불균질한 오스테나이트를 생성할 수도 있다는 것이다. 즉, 오스테나이트에 미용해 탄화물이 존재할 수도 있고 탄소와 합금원소의 농도 구배가 존재할 수도 있다. 합금강에서, 이러한 탄화물은 합금성분이 비교적 높기 때문에 철 탄화물에 비해서는 좀 더 천천히 기지에 용해된다. 또한 망간, 크롬, 니켈 및 몰리브덴과 같은 치환형 합금원소는 천천히 확산한다. 따라서, 균일한 오스테나이트를 생성하기 위해서는 더 많은 시간과 더 높은 온도가 요구된다. 그러나 표면 구역의 낮은 경화능에도 불구하고 냉각속도가 마르텐사이트의 체적분율이 큰 미세조직을 확보할 만큼 충분히 크기 때문에 경도는 높게 된다.

• Journal of Chest Surgery
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• v.40 no.6 s.275
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• pp.414-419
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• 2007

Background: Replacing the ascending aorta is a standard surgical option for treating acute type A aortic dissection. But replacing the aortic arch has recently been reported as an acceptable procedure for this disease. We compared the effects of aortic arch replacement for treating acute type A aortic dissection with the effects of ascending aortic replacement. Material and Method: From 2002 to 2006, 25 patients undewent surgical treatment for acute type A aortic dissection, 12 patients undewent ascending aortic replacement and 13 patients underwent aortic arch replacement. Among the aortic arch group, an additional distal stent-graft was inserted during the operation in 5 patients. 19 patients (11 arch replaced patients and 8 ascending aortic replaced patients) were followed up at the out patient clinic for an average of $756{\pm}373$ days. All the patients undewent CT scanning and we analyzed their distal aortic segments. Result: 4 patients who underwent ascending aortic replacement died, so the overall mortality rate was 16%. Among the 11 long term followed-up arch replacement patients, 2 patients (18.1 %) developed distal aortic dilatation and one of them underwent thoracoabdominal aortic replacement later on. However, among the 8 the ascending aortic replaced patients, 5 patients (62.5%) developed distal aortic dilatation. Conclusion: Aortic arch replacement is one of the safe options for treating acute type A aortic dissection. Aortic arch replacement for treating acute type A aortic dissection could contribute to a reduced distal aortic dilatation rate and fewer secondary aortic procedures.

• Journal of the Korean Chemical Society
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• v.59 no.3
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• pp.257-262
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• 2015