• Journal of the Korean Chemical Society
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• v.30 no.2
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• pp.188-194
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• 1986

The rate constants for the solvolysis reactions of p-chlorobenzyl chloride in ethanol-water mixtures were determinded at 30${\circ}\;and\;40{\circ}$C up to 1,600bar. Rates of reaction were increased with increasing temperature and pressure, and decreased with increasing solvent composition of ethanol mole fraction. The plots of ln k against pressure are fitted to a second-order function in P, and values of ${\Delta}V^{\neq}\;and\;${\Delta}{\beta}^{\neq}$ are obtained. The values of ${\Delta}V^{\neq}\;and\;${\Delta}{\beta}^{\neq}$ extremum behavior at about 0.20 mole fraction of ethanol. This behavior is discussed in terms of solvent structure variation. From the relation between the plots of ln k versus the solvent parameter, q ≡ (D-1)/(2D+1), or the logarithmic molar water concentration, In $C_w$, it could be estimated that the reaction proceeds through $S_N1(2)$ mechanism.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.95.1-95.1
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• 2013

The RBSPICE (Radiation Belt Storm Probes Ion Composition Experiment) is one of five instrument suites onboard the twin Van Allan Probes (or Radiation Belt Storm Probes; RBSP), launched August 30, 2012 by NASA. One of science targets of RBSPICE instrument is to determine "how changes in that ring current affect the creation, acceleration, and loss of radiation belt particles?". For that purpose, it measures ions and electrons simultaneously. Ion's energy range is from ~20 keV to ~1 MeV and electron's energy channel is from ~35 keV to 1 MeV in order to provide supplementary information about the radiation belts. In this paper, we investigate a reliability of the electron flux measured from the RBSPICE by comparing with ECT (The Energetic Particle, Composition and Thermal Plasma Suite) data. We found there is a critical proton contamination problem in the electron channels of ~ 1MeV of RBSPICE observations during one moderate storm event of Sym H ~ -76 nT on March 1, 2013.

• Journal of Astronomy and Space Sciences
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• v.37 no.3
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• pp.157-163
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• 2020

High resolution spectroscopic observation of V1719 Cyg were made at 1.8 meter telescope of Bohyunsan Optical Astronomy observatory in Korea. Spectral resolving power was R=45,000, signal to noise ratio S/N>100. The abundances of 28 chemical elements from carbon to dysprosium were found with the spectrum synthesis method. The abundances of oxygen, titanium, vanadium and elements with Z>30 are overabundant by 0.2-0.9 dex with respect to the solar values. Correlations of derived abundances with condensation temperatures and second ionization potentials of these elements are discussed. The possible influence of accretion from interstellar environment is not so strong as for ρ Pup and other stars with similar temperatures. The signs of accretion are absent. The comparison of chemical composition with solar system r- & s-process abundance patterns shows the enhancement of the photosphere by s-process elements.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.673-678
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• 2002

There are various methods for the electrochemical techniques to estimate diffusion coefficient of chloride ions in concrete, such as ASTM C 1202 test method, Andrade's method, Dhir's method, Tang's method, and etc. In the case of estimating diffusion coefficient of chloride ions in concrete by using these methods, applied voltage and resistivity nay exercise some influence on the characteristics of chloride ions diffusion. Thus. in this study, effect of applied voltage and resistivity on the characteristics of chloride ions diffusion in concrete were researched by applying voltage in 12V, 30V, and 60V, and by using resistivity in 0.2Ω and 1.0Ω, respectively. It can be concluded that diffusion coefficient of chloride ions are found to be increasing as the individual applied voltage and resistivity decrease, when water-cement ratio is constant.

• Journal of the Korean Vacuum Society
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• v.4 no.2
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• pp.124-134
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• 1995

포항가속기연구소에서는 PLS 2-GeV 선형가속기 클라이스트론의 교체 및 보수시에 사용하기 위하여, 80 MW급 S-band의 도파관 밸브를 개발중에 있다. PLS형 도파관 밸브는 결합수단 없이 대전력을 전송할 수 있는 구조로 설계되어, 전력전송에 대한 제한을 받지 않는 특징을 갖는다. 본 도파관 밸브의 주요구성부는 밀착구동체를 갖는 U자형 도파관부, 두 개의 H-코너가 부착된 진공함, 그리고 두 개의 Viton O-링이 장착된 진공기밀판으로 이루어져 있다. 시제품용 도파관 밸브의 특성조사 결과, 펄스폭 3.5 $\mu$sec, 반복율 30 Hz에서 65MW의 전력전송을 얻을 수 있었다. 본 논문에서는 PLS도파관 밸브의 설계 개념, 기계적 특성 및 가공의 순으로 자세히 논할 것이며, 또한 현재까지의 실험결과 및 앞으로의 계획에 대하여 보고하기로 한다.

• Reproductive and Developmental Biology
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• v.35 no.1
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• pp.17-22
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• 2011

This study was designed to determine the effect of electric field strength, duration and fusion buffer in fusion parameters on the rate of membrane fusion between the somatic cell and cytoplast for Korean cattle (HanWoo) somatic cell nuclear transfer (SCNT) procedure. Following electrofusion, effect of 5 or $10\;{\mu}M$ $Ca^{2+}$-ionophore of activation treatment on subsequent development was also evaluated. Cell fusion rates were significantly increased from 23.1% at 20 V/mm to 59.7% at 26 V/mm and 52.9% at 27 V/mm (p<0.05). Due to higher cytoplasmic membrane rupture or cellular lysis, overall efficiency was decreased when the strength was increased to 30 V/mm (18.5%) and 40 V/mm (6.3%) and the fusion rate was also decreased when the strength was at 25 V/mm or below. The optimal duration of electric stimulation was significantly higher in $25\;{\mu}s$ than 20 and $30\;{\mu}s$ (18.5% versus 9.3% and 6.3%, respectively, p<0.05). Two nonelectrolyte fusion buffers, Zimmermann's (0.28 M sucrose) and 0.28 M mannitol solution for cell fusion, were used for donor cell and ooplast fusion and the fusion rate was significantly higher in Zimmermann's cell fusion buffer than in 0.28 M mannitol (91.1% versus 48.4%, respectively, p<0.05). The cleavage and blastocyst formation rates of SCNT bovine embryos activated by $5\;{\mu}M$ $Ca^{2+}$-ionophore was significantly higher than the rates of the embryos activated with $10\;{\mu}M$ of $Ca^{2+}$-ionophore (70.0% versus 42.9% and 22.5% versus 14.3%, respectively; p<0.05). This result is the reverse to that of parthenotes which shows significantly higher cleavage and blastocyst rates in $10\;{\mu}M$ $Ca^{2+}$-ionophore than $5\;{\mu}M$ counterpart (65.6% versus 40.3% and 19.5% versus 9.7%, respectively; p<0.05). In conclusion, SCNT couplet fusion by single pulse of 26 V/mm for $25\;{\mu}s$ in Zimmermann's fusion buffer followed by artificial activation with $5\;{\mu}M$ $Ca^{2+}$-ionophore are suggested as optimal fusion and activation methods in Korean cattle SCNT protocol.

• Journal of Energy Engineering
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• v.5 no.1
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• pp.65-71
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• 1996

Decomposition reaction of methanol was conducted on Ni-Cu/SiO$_2$catalysts with several variables. Variables used in this study are S.V(Space Velocity), partial pressure of methanol, reaction temperature, and composition rate of Ni-Cu. The range of S.V is 10,000-30,000h$\^$-1/, the temperature range is 150-400$^{\circ}C$ and values of Cu/(Ni＋Cu) are 0, 0.25, 0.5, 0.75, and 1. Over Ni/SiO$_2$, and Ni-Cu/SiO$_2$, the conversion rate of decomposition reaction of methanol arrived at 100% with increasing of temperature. At this time the selectivity of CO on Ni/SiO$_2$, was suddenly decreased, but on Ni-Cu/SiO$_2$, it was still sustained highly. The main products of reaction were CO and H$_2$, and by-products were CO$_2$ and CH$_4$mainly.

• Journal of Korean Ophthalmic Optics Society
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• v.1 no.2
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• pp.37-42
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• 1996

The $Bi_{12}(Si,Ge)O_{20}$ single crystals were prepared by Czochralski method and the study of electrical and optical properties were carried out. The activation energy of the electrical conductivity was $E_g$=1.12 eV. The optical energy gap measured in the room temperature is found to be 2.3 eV. A.c. conductivity of crystal $Bi_{12}(Si,Ge)O_{20}$ was measured at temperatures from 290 K to 570 K in the frequency range from 50 kHz to 30 MHz. The a.c. conductivity is proportional to ${\omega}^s$. In view of this it should be hopping conduction mechanisms. At high frequencies, the power exponent was s=2. The low frequency dielectric constants were 54 for $Bi_{12}(Si,Ge)O_{20}$ and 41 for $Bi_{12}(Si,Ge)O_{20}$ single crystals.

• Resources Recycling
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• v.16 no.5
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• pp.57-64
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• 2007

Triboelectrostatic separation of mixed three kinds of plastics, PVC, PET and PMMA, in the range of similar gravity has been performed through a two-stage separation process. Polypropylene (PP) and high-impact polystyrene (HIPS) were found to be the most effective materials for a tribo-charger in the separation of PVC, PET and PMMA. In the 1st stage using the PP cyclone charger, PVC grade and recovery depended considerably on the air velocity (10 m/s), the relative humidity (<30%), the electric field (>200 kV/m) and the splitter position (+2 cm from the center) in the triboelelctrostatic separator unit. At an optimum condition a PVC grade of 99.6% and a recovery of 97.5% was achieved. In the 2nd stage using the HIPS cyclone charger, a PMMA grade of 98.3% and a recovery of 97.0% was obtained under the conditions of 10m/s air velocity, over 250 kV/m electric field, central splitter position and less than 40% relative humidity.

• Korean Journal of Food Science and Technology
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• v.32 no.1
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• pp.42-49
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• 2000

A new method for the quantitative determination of capsaicinoids in microcapsule has been developed. Among seventeen solvents tested for solubilizing wall material (gum arabic and modified starch) of microcapsule, dimethyl sulfoxide (DMSO) was selected as an optimal solvent. The most appropriate mixing ratio of microcapsule to DMSO for solubilizing wall material was 1 to 10(w/v). Appropriate carriersolubilizing temperature and time were $55^{\circ}C$ and 30 min, respectively. Also conditions for extracting oleoresin from the solubilized microcapsule were studied. The mixing ratio of ethanol to DMSO was optimal at 8 to 1(v/v). Optimized vortexing time was 5 min at 40㎐. Pecipitant was obtained by centrifugation at 21000 rpm for 15 min. The precipitant was reextracted with ethanol. The extracted supernatants were combined and adjusted to final volume of 25 ml. Extracted solutions were analyzed for quantitation of total capsaicinoids by employing HPLC and for quantitation of total carotenoids by spectrophotometric method. This method can be used to monitor changes of capsacinoid during manufacturing or storage of red pepper oleoresin microcapsule powder.