• Solar Energy
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• v.19 no.4
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• pp.1-10
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• 1999

The phenomena of energy separation through the vortex tube was investigated experimentally, to see the effect of nozzle area ratio and partial admission rate on the energy separation and cooling capacity. The experiment was tarried out with various nozzle area ratios from 0.031 to 0.232 and partial admission rate from 0.176 to 0.956 by varying input pressure($0.2{\si\m}0.5$ MPa) and cold air mass fraction($y=0.1{\sim}1.0$). From the experimental result, we found the optimum nozzle area ratio and the effective partial admission rate for the available use and best cooling performance in given operation condition. While the maximum drop of cold air temperature was observed at around y=0.3 and $S_n=0.155$, the maximum cooling capacity was observed at around y=0.6 and $S_n=0.094$.

• Bulletin of the Korean Chemical Society
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• v.8 no.5
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• pp.366-372
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• 1987

Cryptand[2,2] was grafted to low crosslinked styrene-divinylbenzene copolymer by substitution reaction with chloromethylated styrene-divinylbenzene copolymer. This resin was stable in concentrated acid and base, and showed a good resistance to heat. The pH, time, and concentration dependence of the adsorption of metal ions by this resin were studied. Studies on the chromatographic separation of lanthanides, $Cu^{2+}$ and $UO_2^{2+_2}$ were also carried out with various eluents. These studies demonstrate that this resin has the applicability to the preconcentration and separation of metal ions.

• Journal of Sensor Science and Technology
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• v.9 no.3
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• pp.177-181
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• 2000

The tunneling current is exponentially dependent on the separation gap between a pair of conductors. The detection of displacement can be, therefore, carried out by measurment of a variation in the tunneling current. In this experiment, we fabricated pyramid-type silicon tunneling devices in which a tunneling current flow between a micro-tip and $Si_3N_4$ thin film membrane. A MEMS process was used for the fabrication of the tunneling devices. The micro-tips were formed on Si wafers by undercutting a differently oriented square of $SiO_2$ with KOH. The stiffness of the $Si_3N_4$ films were observed and the model for the stiffness calculation, which is useful in predicting the stiffness even when the stiffness ranges beyond the scope of the normal experimental condition, was suggested.

• Journal of the Korean Vacuum Society
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• v.7 no.1
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• pp.35-42
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• 1998

- The Si-$SiO_2$ interface of silicon on insulator (SOI) formed by 100 keV $O^+$ was ohserved using high resolution transmission electron microscopy (HRTEM), before and after annealing. The interface of as-implanted sample, ~$5\times 10^{17}\textrm{cm}^{-2}O^+$ implanted at $550^{\circ}C$ was very rough and it has many defectsoxide precipitate, stacking fault, coesite $SiO_2$ etc. However, the interface became flat by high temperature annealing at $1300^{\circ}C$ for 4 hour. It's roughness, observed by HRTEM, was comparable to the interface roughness of 3 keV $O_2^\;+$ ion beam oxide and -6 nm gate oxide formed by thermal oxidation.

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.1
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• pp.40-49
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• 2001

We have developed a repeatable process of forming uniform, small-size and high-density self-assembled Si nano-crystals. The Si nano-crystals were fabricated in a conventional LPCVD (low pressure chemical vapor deposition) reactor at $620^{\circ}c$ for 15 sec. The nano-crystals were spherical shaped with about 4.5 nm in diameter and density of $5{\times}l0^{11}/$\textrm{cm}^2$. More uniform dots were fabricated on nitride film than on oxide film. To take advantage of the above-mentioned characteristics of nitride film while keeping the high interface quality between the tunneling dielectrics and the Si substrate, nitride-oxide tunneling dielectrics is proposed in n-channel device. For the first time, the single electron effect at room temperature, which shows a saturation of threshold voltage in a range of gate voltages with a periodicity of ${\Delta}Ｖ_{GS}\;{\approx}\;1.7{\;}V$, corresponding to single and multiple electron storage is reported. The feasibility of p-channel nano-crystal memory with thin oxide in direct tunneling regime is demonstrated. The programming mechanisms of p-channel nano-crystal memory were investigated by charge separation technique. For small gate programming voltage, hole tunneling component from inversion layer is dominant. However, valence band electron tunneling component from the valence band in the nano-crystal becomes dominant for large gate voltage. Finally, the comparison of retention between programmed holes and electrons shows that holes have longer retention time.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.5
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• pp.583-595
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• 2018

Stiffened panels are widely used in naval architecture and ocean engineering, and knowledge about their dynamic behaviour represents important issue in the design procedure. Ordinary vibration analysis consists of natural frequencies and mode shapes determination and can be extended to forced response assessment, while the Structural Intensity (SI) analysis, assessing magnitude and direction of vibrational energy flow provides information on dominant transmission paths and energy distribution including sink positions. In this paper, vibrational energy flow in stiffened panels under harmonic loading is analyzed by the SI technique employing the finite element method. Structural intensity formulation for plate and beam element is outlined, and developed system combining in-house code and general finite element tool is described. As confirmed within numerical examples, the developed tool enables separation of SI components, enabling generation of novel SI patterns and providing deeper insight in the vibrational energy flow in stiffened panels, comparing to existing works.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.632-635
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• 2001

Microcrystalline Si films have been deposited by using five W-wire filaments of 0.5 mm diameter for hot-wire chemical vapor deposition (HWCVD). We compared the HWCVD grown films with the film exposed to transformer couple plasma system for the modification of seed layer. W-wire filament temperature was maintained below 1600$^{\circ}C$ to avoid metal contamination by thermal evaporation at the filament. Deposition conditions were varied with H$_2$dilution ratio, with and without plasma treatment. From the Raman spectra analysis, we observed that the film crystallization was strongly influenced by the H$_2$dilution ratio and weakly depended on the distance between the wire and a substrate. We were able to achieve the crystalline volume fraction of about 70% with an SiH$_4$/H$_2$ratio of 1.3%, a wire temperature of 1514$^{\circ}C$, a substrate separation distance of 4cm, and a chamber pressure of 38 mTorr. We investigated the influence of ${\mu}$c-Si film properties by using a plasma treatment. This article also deals with the influence of the H$_2$dilution ratio in crystallization modification.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.3
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• pp.179-186
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• 2019

This work investigated the effects of different conductive agents on the electrochemical properties of anodes. SiOx possesses high theoretical capacity and shows excellent cycle performance; however, the low initial coulombic efficiency and poor electrical conductivity limit its applications in real batteries. In this study, electrodes were fabricated using two different conductive agents, and the resulting physical and electrochemical properties were analyzed. SEM observations confirmed the formation of a CNT conductive network throughout the electrodes, while the electrical conductivity contributed to the electrode was confirmed by impedance measurements. Thus, the electrode fabricated with the CNT conductive agent showed greater capacity and superior cycle performance than did the electrode fabricated using the DB conductive agent.

• Journal of the Mineralogical Society of Korea
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• v.25 no.3
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• pp.143-153
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• 2012

Mica-type minerals (illites) in the shales of the Jigunsan formation at Seokgaejae in Samchuk-City, Gangwon-do are studied using electron probe micro analysis (EPMA). The average chemical formula of the mica-type mineral obtained from the quantitative analysis is $(K_{1.17}Na_{0.04}Ca_{0.01})(Al_{2.80}Mg_{1.17}Fe_{0.78})(Si_{6.34}Al_{1.66})O_{20}(OH)_4$, which shows a chemical formula within the range of illite. These illites so called can be considered as mixed-phases among muscovite, pyrophyllite and chlorite due to the low contents of interlayer cations and high Mg, Fe. The formula of illite is separated into those three minerals and the method for the separation is newly formulated and proposed in this study. From the formula of illite, the content of muscovite is estimated from K (Na and Ca included), the content of chlorite by Mg+Fe, and the rest remains as pyrophyllite. The chemical formula of muscovite can be calculated by subtracting the compositions of pyrophyllite and chlorite from the analyzed composition of illite using an ideal formula for pyrophyllite and analyzed average formula for chlorite. The calculated formula of muscovite is supposed to be stoichiometric in principle. The result of the separation of analyzed illite is 61% muscovite, 27.3% chlorite and 11.7% pyrophyllite and the calculated formula of muscovite after separation is $(K,Na,Ca)_{2.00}Al_{3.69}(Si_{6.75}Al_{1.25})O_{20}(OH)_4$. The calculated formula of muscovite slightly low in Al content can be considered to be reasonable in general when the low content of Al in the rock and the uncertainties of chlorite compositions used in the calculation are counted. This supports that the method of separation proposed in this study is also applicable.

• Journal of Hydrogen and New Energy
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• v.23 no.5
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• pp.421-428
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• 2012

The Sulfur-Iodine (SI) thermochemical hydrogen production process is one of the most promising thermochemical water splitting technologies. In the integrated operation of the SI process, the $O_2$ produced from a $H_2SO_4$ decomposition section could be supplied directly to the Bunsen reaction section without preliminary separation. A $HI_x$ ($I_2+HI+H_2O$) solution could be also provided as the reactants in a Bunsen reaction section, since the sole separation of $I_2$ in a $HI_x$ solution recycled from a HI decomposition section was very difficult. Therefore, the Bunsen reaction using $SO_2-O_2$ mixture gases in the presence of the $HI_x$ solution was carried out to identify the effect of $O_2$. The amount of $I_2$ unreacted under the feed of $SO_2-O_2$ mixture gases was little higher than that under the feed of $SO_2$ gas only, and the amount of HI produced was relatively decreased. The $O_2$ in $SO_2-O_2$ mixture gases also played a role to decrease the amount of a impurity in $HI_x$ phase by only striping effect, while that in $H_2SO_4$ phase was hardly affected.