• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1431-1433
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• 1996

Effective ionization coefficients for (100), (110) and (111) oriented gallium arsenide are extracted from the ionization coefficients far electrons and holes. Analytical formulas for the breakdown voltage of the GaAs Schottky rectifiers are derived by employing the ionization coefficients. The breakdown voltages obtained from our analytical model agree fairly well with the numerical results as well as the experimental ones reported in the range of $10^{14}\;cm^{-3}$ - $5{\times}10^{17}\;cm^{-3}$ doping concentrations.

• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.814-819
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• 1996

In search of simple host molecules for uranyl ion which form 1: 1-type complexes with high formation constants that can be used either in extraction of uranium from seawater or in catalysis of biologically important organic reactions, the uranophile activities of dihydroxyazobenzene derivative 1 were studied. Uranyl ion and 1 form a 1: 1-type complex with a very large formation constant. The formation constant was measured at pH 7-11.6 by competition experiments with carbonate ion. From the resulting pH dependence, ionization constants of the two aquo ligands coordinated to the uranium of the uranyl complex of 1 were calculated. The ionization constants were also measured by potentiometric titration of the uranyl complex of 1. Based on these results, the pKa values of the two aquo ligands were estimated as 7.1 and 11.0, respectively. At pH 7.5-9.5, therefore, the complex exists mostly as monohydroxo species. Under the conditions of seawater, 1 possesses greater affinity toward uranyl ion compared with other uranophiles such as carbonate ion, calixarene derivatives, or a macrocyclic octacarboxylate. In addition, complexation of 1 with uranyl ion is much faster than that of the calixarene or octacarboxylate uranophiles.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.6
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• pp.78-84
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• 2009

This paper presents measurement results of transient impedance for small-sized ground electrodes in a discharge region of soil. For a realistic analysis of ionization characteristics near the ground electrode, three types of ground rod installed outdoors and high voltage impulse generator were used for injecting test current. From the analysis of response voltage and current flowing ground electrode to earth, it is verified that the ionization near the ground electrode contributes to reduction of ground impedance and limits the ground potential rise effectively in high resistivity soil. As a threshold electric field density for ionization is small in low resistivity soil, the shape of ground electrode rarely contributes to the transient impedance. And, from the experiment result with shape of ground electrode, the rod with needles is more effective to reduce the transient impedance than the plate electrode in the voltage range including with ionization regions of soil.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.1
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• pp.27-31
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• 2011

In this paper, the electron transport characteristics in $CF_4$ has been analysed over the E/N range 1~300[Td] by a two-term approximation Boltzmann equation method and by a Monte Carlo simulation. The motion has been calculated to give swarm parameters for the electron drift velocity, longitudinal diffusion coefficient, the ratio of the diffusion coefficient to the mobility, electron ionization and attachment coefficients, effective ionization coefficient, mean energy, collision frequency and the electron energy distribution function. The electron energy distribution function has been analysed in $CF_4$ at E/N=5, 10, 100, 200 and 300[Td] for a case of the equilibrium region in the mean electron energy and respective set of electron collision cross sections. The results of Boltzmann equation and Monte Carlo simulation have been compared with experimental data by Y. Nakamura and M. Hayashi. The swarm parameter from the swarm study are expected to serve as a critical test of current theories of low energy electron scattering by atoms and molecules, in particular, as well as crucial information for quantitative simulations of weakly ionized plasmas.

• Mass Spectrometry Letters
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• v.4 no.1
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• pp.21-23
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• 2013

The effects of trifluoroacetic acid (TFA) were evaluated on the generation of multiply charged ions of cytochrome c in a 2-nitrophloroglucinol (2-NPG) matrix in high-vacuum, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The presence of 1% TFA in the 2-NPG matrix solution was more effective in generating multiply charged protein ions than matrix solutions containing 0.1% or 0% TFA. Regarding the matrix itself, with 1% TFA, 2-NPG was significantly more effective in generating multiply charged ions than 2,5-dihydroxybenzoic acid (2,5-DHB). The maximum charge state of cytochrome c was +8 when using a 2-NPG matrix containing 1% TFA.

• 전기의세계
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• v.28 no.4
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• pp.39-46
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• 1979

The effective ionization coefficient in $SF_{6}$/$N_{2}$ mixtures was attempted to derive from the pure gases. Measurements of static breakdown voltage were made under the uniform field at pressures up to 4 bar in order to compare with the results obtained from this assumption. The relative performance of $SF_{6}$/$N_{2}$ mixtures to pure $SF_{6}$ was also investigated. The effect of surface roughness on discharge thresholds in $SF_{6}$/$N_{2}$ mixtures was calculated employing the simplified model and mesurements of breakdown voltages for a gap with an artificial protrustion were also made. The experimental results show that the effective ionization coefficient in gas mixtures can not be reliably estimated from the values measured for the pure gases. Therefore, basic parameters for $SF_{6}$/$N_{2}$ mixtures must be measured by investigation of the mixtures themselves. The relative performance of mixtures to pure $SF_{6}$ could be considered with the values of pR.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.591-593
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• 2000

In this paper, we describe the results of a combined experimental theoretical study designed to understand and predict the dielectric properties of SF$_{6}$ and SF$_{6}$+Ar mixtures. The electron transport, ionization, and attachment coefficients for pure SF$_{6}$ and gas mixtures containing SF$_{6}$ has been analysed over the E/N range 30~300[Td] by a two term Boltzmann equation and by a Monte Carlo Simulation using a set of electron cross sections determined by other authors, experimentally the electron swarm parameters for 0.2[%] and 0.5[%] SF$_{6}$+Ar mixtures were measured by time- of- flight method, The results show that the deduced electron drift velocities, the electron ionization or attachment coefficients, longitudinal and transverse diffusion coefficients and mean energy agree reasonably well with the experimental and theoretical for a rang of E/N values. Electron energy distribution functions computed from numerical solutions of the electron transport and reaction coefficients as functions of E/N. We have calculated $\alpha$,η and $\alpha$-η the ionization, attachment coefficients, effective ionization coefficients, and (E/N), the limiting breakdown electric-field to gas density ratio, in SF$_{6}$ and SF$_{6}$+Ar mixtures by numerically solving the Boltzmann equation for the electron energy distribution. The results obtained from Boltzmann equation method and Monte Carlo simulation have been compared with present and previously obtained data and respective set of electron collision cross sections of theections of the

• BMB Reports
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• v.53 no.7
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• pp.349-356
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• 2020

Mass spectrometry (MS) is an ideal tool for analyzing multiple types of (bio)molecular information simultaneously in complex biological systems. In addition, MS provides structural information on targets, and can easily discriminate between true analytes and background. Therefore, imaging mass spectrometry (IMS) enables not only visualization of tissues to give positional information on targets but also allows for molecular analysis of targets by affording the molecular weights. Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) MS is particularly effective and is generally used for IMS. However, the requirement for an organic matrix raises several limitations that get in the way of accurate and reliable images and hampers imaging of small molecules such as drugs and their metabolites. To overcome these problems, various organic matrix-free LDI IMS systems have been developed, mostly utilizing nanostructured surfaces and inorganic nanoparticles as an alternative to the organic matrix. This minireview highlights and focuses on the progress in organic matrix-free LDI IMS and briefly discusses the use of other IMS techniques such as desorption electrospray ionization, laser ablation electrospray ionization, and secondary ion mass spectrometry.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.6
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• pp.22-27
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• 2008

Analytical models for breakdown voltage and specific on-resistance of 4H-silicon carbide Schottky diodes have been derived successfully by extracting an effective ionization coefficient $\gamma$ from ionization coefficients $\alpha$ and $\beta$ for electron and hole in 4H-SiC. The breakdown voltages extracted from our analytical model are compared with experimental results. The specific on-resistance as a function of doping concentration is also compared with the ones reported previously. Good fits with the experimental results are found for the breakdown voltage within 10% in error for the doping concentration in the range of about $10^{15}{\sim}10^{18}\;cm^{-3}$. The analytical results show good agreement with the experimental data for the specific on-resistance in the range of $3{\times}10^{15}{\sim}2{\times}10^{16}\;cm^{-3}$.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2143-2147
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• 2013

Matrix assisted laser desorption/ionization (MALDI) mass spectrometry (MS) is a very effective method for lipid mass fingerprinting. However, MALDI MS suffered from spectral complexities, differential ionization efficiencies, and poor reproducibility when analyzing complex lipid mixtures without prior separation steps. Here, we aimed to find optimal MALDI sample preparation methods which enable selective or class-wide mass fingerprinting of two totally different lipid classes. In order to achieve this, various matrices with additives were tested against the mixture of phosphatidylcholine (PC) and cerebrosides (Cers) which are abundant in animal brain tissues and also of great interests in disease biology. Our results showed that, from complex lipid mixtures, 2,4,6-trihydroxyacetophenone (THAP) with $NaNO_3$ was a useful MALDI matrix for the class-wide fingerprinting of PC and Cers. In contrast, THAP efficiently generated PC-focused profiles and graphene oxide (GO) with $NaNO_3$ provided Cer-only profiles with reduced spectral complexity.