• Bulletin of the Korean Chemical Society
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• 제12권6호
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• pp.629-632
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• 1991

The rate constants for the formation and dissociation of nickel(II) and cobalt(II) complexes with mandelate have been determined by the pressure-jump relaxation study. The forward and reverse rate constants for the mandelate complex formation reactions were obtained to be $k_f=3.60{\times}10^4\;M^{-1}s^{-1}$ and $k_r=1.73{\times}10^2\;s^{-1}$ for the nickel(II), and $k_f=1.75{\times}10^5\;M^{-1}s{-1}$ and $2.33{\times}10^3\;s^{-1}$ for the cobalt(II) in aqueous solution of zero ionic strength ($(\mu{\to}0)\;at\;25^{\circ}C$. The results were interpreted by the use of the multistep complex formation mechanism. The rate constants evaluated for each individual steps in the multistep mechanism draw a conclusion that the rate of the reaction would be controlled by the chelate ring closure step in concert with the solvent exchange step in the nickel(II) complexation, while solely by the chelate ring closure step for the cobalt(II) complex.

• Nuclear Engineering and Technology
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• 제37권1호
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• pp.101-108
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• 2005

The neutron induced nuclear cross-section data for Pd-105, Ag-109, Xe-131, and Cs-133 were calculated and evaluated from an unresolved energy to 20 MeV. The energy dependent optical model potential parameters were extracted based on recent experimental data and applied up to 20 MeV. A spherical optical model and a statistical model for the equilibrium energy, and a multistep direct and a multistep compound model for the pre-equilibrium energy were used in the calculation. The direct capture model was recently introduced for fast neutron capture. The theoretically calculated cross-sections were compared with the experimental data and the evaluated files. The total and capture cross-sections calculated using the model were in good agreement with the reference experimental data. The evaluated cross-section results were compiled in ENDF-6 format and merged with the resonance component, already adopted in the ENDF/B-VI release 8. New data library files covering from thermal to 20 MeV were created. They are at the preliminary stage of an ENDF/B- VII release.

• Nuclear Engineering and Technology
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• 제34권4호
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• pp.370-381
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• 2002

The neutron induced nuclear data for Pr-141, Nd-143, Nd-145, Sm-147 and Sm-149 were calculated and evaluated from 10 keV to 20 MeV. The energy dependent optical model potential parameters were extracted based on the recent experimental data and applied up to 20 MeV. The s-wave strength function was calculated. Spherical optical model , statistical model in equilibrium energy, multistep direct and multistep compound model in pre-equilibrium energy and direct capture model were introduced in Empire calculation. The theoretically calculated cross sections were compared with the experimental data and the evaluated files. The model calculated total and capture cross sections were in good agreement with the reference experimental data. The capture cross sections in pre-equilibrium were enhanced in recent released Empire version. The evaluated cross section results were compiled to ENDF-6 format and will improve the ENDF/B-Vl.

• 공업화학
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• 제33권1호
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• pp.113-118
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• 2022

Multifunctional nanomaterials based on mesoporous silica nanoparticles (MSN) and metal oxide nanocrystals are among the most promising materials for theragnosis because of their ease of modification and high biocompatibility. However, the preparation of multifunctional nanoparticles requires time-consuming multistep processes. Herein, we report a simple one-pot synthesis of multifunctional Mn₃O₄/mesoporous silica core/shell nanoparticles (Mn₃O₄@mSiO₂) involving the temporal separation of core formation and shell growth. This simple procedure greatly reduces the time and effort required to prepare multifunctional nanoparticles. Despite the simplicity of the process, the properties of nanoparticles are not markedly different from those of core/shell nanoparticles synthesized by a previously reported multistep process. The Mn₃O₄@mSiO₂ nanoparticles are biocompatible and have potential for use in optical imaging and magnetic resonance imaging.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.128-129
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• 2003

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1999년도 춘계학술발표회요약집
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• pp.404-404
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• 1999

• 한국광학회:학술대회논문집
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• 한국광학회 2002년도 제13회 정기총회 및 2002년도 동계학술발표회
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• pp.50-51
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• 2002

• 전기학회논문지
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• 제63권2호
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• pp.250-256
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• 2014

In this study, we deposited and investigated ${\mu}c$-Si:H thin films prepared by Plasma Enhanced Chemical Vapor Deposition(PECVD) system. To deposition silicon thin films, we controlled $SiH_4$ gas concentration, RF input power, and heater temperature. According to the experiments, the more $SiH_4$ gas concentration increased, deposition rate also increased but crystalline property decreased at the same conditions. In the RF input power case, deposition rate and crystalline property increased together when the input power increased from 100[W] to 300[W]. If RF input power was 300[W], deposition rate has reached saturation point. In the heater temperature, deposition rate increased when heater temperature increased. Crystalline property maintained a certain level until heater temperature was $250[^{\circ}C]$. And then it was a suddenly increased. Multistep method has been proposed to improve the quality of ${\mu}c$-Si:H thin film. $SiH_4$ gas was injected with a time interval. According to the experiments, crystallite ratio improve about 20~60[%] and photo conductivity increased up to six times.

• 한국터널지하공간학회 논문집
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• 제5권1호
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• pp.3-11
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• 2003

터널 시공 시 막장의 안정은 주요 관심사이다. 그러나, 터널 지보재에 비해 상대적으로 터널 막장의 안정성 문제는 그리 많은 연구가 이루어지지 않은 실정이다. 또한 지하수위 하에서 터널 시공 시 터널 내로 지하수 흐름에 의해 발생된 침투수력은 막장의 안정성에 큰 영향을 미칠 수 있다. 본 논문에서는 두 가지 요소를 고려하여 터널 막장의 안정성을 평가하였다. 하나는 극한이론 중 상한치 이론으로 산출된 유효응력이며, 다른 하나는 정상류 흐름조건에서 수치해석으로부터 산출된 침투수력이다. 열악한 지반조건에서 터널 시공 시 터널의 안정과 인접 구조물의 손상을 방지하기 위해 보조공법이 적용된다. 강관 다단 그라우팅 공법은 근래 국내에서 적용되고 있는 보조공법 중의 하나이다. 본 논문에서는 강관 다단 그라우팅으로 보강된 터널의 막장 안정성도 함께 평가되었다.

• Restorative Dentistry and Endodontics
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• 제28권2호
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• pp.127-133
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• 2003

The object of this study was to compare the microleakage between various composite resin systems of multistep, one-bottle, and self-etching systems using electrical conductivity. After making class V cavities ($4{\times}3{\times}1.5{\;}mm$ around CEJ), they were bulk filled with three kinds of resins of A3. Teeth were storaged in a saline solution for one day, after then, they were finished and polished using Sof-Lex system. Another stress of thermocycling was made for 500 times from $5^{\circ}{\;}to{\;}55^{\circ}C$ with each dwelling time of 10 seconds. Electrical conductivity (microamphere, $\mu\textrm{A}$) was checked four times: before and after cavity preparation, after filing, after thermocycling. One-way ANOVA and 95% Scheffe Post Hoc test was used for checking any statistical difference among groups. Another 95% Paired Samples T-test was also used for estimating any significant difference within group after cavity filling or thermocycling. The results were as follows: 1 Every specimen showed various range of microleakage after filing. There was, however, no difference between composite resin systems. 2. All composite resin systems showed marked increase in microleakage with a thermocycling (p<0.05), there was, however, no difference between composite resin systems. 3. Although there was no significant difference between groups (p=0.078), one-bottle and self-etching systems seemed to be unstable than multistep system. Within the limits of this study, it was concluded that much more consideration should be needed when using thermally unstable one-bottle and self-etching systems that have multi-advantages from simplified step. More studies will be needed to solve these kinds of problems.