• Composites Research
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• v.26 no.6
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• pp.337-342
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• 2013

The good dispersion of nano-materials in epoxy matrix was important parameter for the reinforcement effect, and the evaluation of dispersion degree was to prove it. This work was studied to predict the dispersion condition of nano-SiC powders in SiC/epoxy composites using capacitance measurement. Capacitance was defined to be the electric capacity in proportional to electron charge of the measuring section. In case of nano-SiC powders, the electron charge of SiC/epoxy composites was higher than that of neat epoxy resin. Capacitance was evaluated for each section of SiC/epoxy composites. The prediction of dispersion condition was verified by using capacitance measurement. Dispersion condition of nano-SiC powders in epoxy matrix was evaluated with two different dispersion methods, i.e., sonication and stirring methods. The dispersion degree was also verified with the tensile strength correlating to capacitance.

• Journal of the Korean Chemical Society
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• v.28 no.2
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• pp.86-94
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• 1984

The single crystal ion-selective electrode,$ {\beta}-Ag_3SI/PVC-THF $membrane electrode has showed a linear potential response to the activities of iodide ion (10-1${\sim}$10-7M). The $ {\beta}-Ag_3SI$ membrane electrode was compared with AgI/PVC-THF membrane and copper metal plate membrane electrodes. In order to measure the selectivity coefficient of the electrodes toward $Cl^-$ and $Br^-$, the separation and mixed solution method were employed. The potential-time curve was obtained by the usual immersion technique and pH effect was also examined. The orders of selectivity for $Br^-$, $Cl^-$ and stability of response time are ${\beta}-Ag_3SI/PVC-THF $membrane > AgI/PVC-THF membrane > copper metal plate membrane. These electrodes could be used as indicating electrodes in the potentiometric titration of a single halide and mixed halides with the standard solution of silver nitrate.

• Journal of Korean Medical classics
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• v.27 no.1
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• pp.15-28
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• 2014

Objective : Jeol-sik, (festive seasons every 15 days based on sun cycle), refers to both Korean Traditional Festival food(jeol-sik), intertwined between months, and in-season meals(si-jeol-sik) in which the ingredients used are produced in each and one of the four season. I found that ingredients in Si-jeol-sik of Autumn are helpful for strengthening one's life force. Method : The study found that si-jeol sik for fall season has strong characteristic of casting out demons. When making songpyeon(half-moon-shaped rice cake) for Chuseok (Korean Thanksgiviing Day), they are steamed with pine needs spreaded underneath because pine needles are believed to have power in casting away evil spirits. For harvest ceremony, which were frequently held in October, people consumed steamed rice cakes garnished with red beans, which were considered to negate bad fortunes. Result : To prevent respiratory diseases caught esaily in fall due to wide daily temperature difference and dry weather, white good ingredients such as radish, pear, and taro are used. Conclusion : Main fall holidays are Chil-soek, Baek-Jung, Chu-seok. The best feature of Si-jeol-sik for fall season is that they cast out demons. Also, fall si-jeol-sik consist of many white ingredients for protecting lungs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.2
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• pp.188-193
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• 2010

In this paper, SI(Signal Integrity) characteristic of the 4-layer PCB(Printed Circuit Boards) with a through-hole via was analyzed by impedance mismatching between the through-hole via and the transmission line, and deterioration of clock pulse response characteristic due to the P/G plane resonances which are generated between the power and the ground plane. The minimized impedance mismatching between the through-hole via and the transmission line for the improving of SI characteristic is confirmed by the TDR(Time Domain Reflector) simulation and lumped element modeling of the through-hole via. And the cancellation method of P/G plane resonances for improvement of the SI characteristic is represented by simulation result.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.16-22
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• 2021

We search for an appropriate initial adsorption coordination of precursor on surface by using genetic algorithm (GA) and density functional theory. SiH₄ and Al(CH₃)₃ as precursor, and OH-terminated Si (001) as surface are used for this study. Selection, crossover, and mutation as hyperparameters of GA are applied to search for the adsorption coordination of the precursors on the surface as a function of generation. Bond distances between precursors and the surface are used to explain the adsorption behavior of the precursors.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.42-48
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• 2018

Silicon has attracted extensive attention due to its high theoretical capacity, low discharge potential and non-toxicity as anode material for lithium ion batteries. In this study, Si-CNT-C composites were fabricated for use as a high-efficiency anode material in a lithium ion battery. Aerosol self-assembly and post-heat treatment processes were employed to fabricate the composites. The morphology of the Si-CNT-C composites was spherical and an average particle size was $2.72{\mu}m$. The size of the composite increased as concentration of Si and CNT increased in the precursor solution. In the Si-CNT-C composites, CNT and C carbonized from glucose were attached to the surface of Si particles. Electrochemical measurement showed that the cycle performance of Si-CNT-C composites was better than that of silicon particles.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.35-41
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• 2021

Silicon is a promising next-generation anode material for lithium-ion battery, and it has been studied for commercialization due to the high theoretical capacity. However, it has problems of the volume change during charge-discharge and the poor electrical conductivity. To solve these problems, formation of SiO2 and carbon coating on the surface of silicon crystal were performed to protect the side reaction and enhance the electrical conductivity of silicon. CNT and CNF were also added to mitigate the volume change and increase the conductivity. Physical properties of asprepared samples were analyzed by XRD, SEM, and EDS. Electrochemical characteristics were investigated by electrical conductivity measurement, EIS, CV and cycle performance test. (Si/SiO2/C)+CNT&CNF showed high electrical conductivity and low charge-transfer resistance, and the capacity was 1528 mAh/g at 1st cycle and 1055 mAh/g at 50th cycle with 83% capacity retention.

• Journal of the Korean Chemical Society
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• v.47 no.4
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• pp.325-333
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• 2003

The geometrical parameters, vibrational frequencies, and relative energies for 1,2-, 1,3-dioxetanes, and 1,3-cyclodisiloxane have been investigated using high level ab initio quantum mechanical techniques with large basis sets. The geometries have been optimized at the self-consistent field(SCF), the single and double excitation configuration interaction(CISD), the coupled cluster with single and double excitation(CCSD), and the CCSD with connected triple excitations[CCSD(T)] levels of theory. The highest level of theory employed in this study is TZ2P CCSD(T). Harmonic vibrational frequencies and IR intensities are also determined at the SCF level of theory with various basis sets and confirm that all the optimized geometries are true minima. Also zero-point vibrational energies have been considered to predict the dimerization energies for 1,2- and 1,3-isomers.

• (The)Study of the Eastern Classic
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• no.36
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• pp.229-264
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• 2009

This paper aims for a study on the theory that mind is Li(principle). The method of research is laid emphasis on searching for the historical development of the perception Theory in late Cho-Sun. First of all, I investigated a meaning of the perception theories of Ho-Rak school, that were criticized in the Cho-Sun academic world. The next, I investigated the theory of Li-ju-Ki-ja that was raised by Yi Sang Jung. He thought that Li is supervisor and Ki is assistance. And he put a construction on the Perception Theories of Toegye school. Yi Jin sang's theory of perception is the result of criticism against Ho-Rak school, and a fresh and in-depth construction of Yi Sang Jung's perception theory. His viewpoint was contradiction to the theory of Sim si Ki(the theory that Mind is made of Ki). And he rediscovered the human conscience that was born endowed from Heaven.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.2
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• pp.112-120
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• 1998

A nondestructive evaluation technique was developed for the quantitative determination of the reinforcement volume fractions in particulate reinforced metal matrix composites. The proposed technique employed a composite micromechanics which accounts for the microstructure of the composite medium together with the measurement of anisotropic electrical conductivity. When the measured conductivity was coupled with the theoretically predicted conductivity, the unknown reinforcement volume fraction was calculated. An analytical model based on the Mori-Tanaka method was described which relates the NDE signatures to the composite microstructure. The volume fractions were calculated using eddy current measurements made on a wide range of silicon carbide particulate ($SiC_p$) reinforced aluminum (Al) matrix composites. The calculated $SiC_p$ volume fractions were in good agreement with the measured volume fractions in the range of 0-30%. The technique was also found to be effective in estimating the total volume percentage of reinforcement and intermetallic compound formed during the processing stage.