• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.219.2-219.2
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• 2014

Characteristics of Argon metastable density with electron density have been studied by using Laser induced fluorescence (LIF) in ICP. Two different evolutions of measured metastable densities with electron density depending on a measurement position are addressed. The experimental result is explained by using a zero dimensional global model and is due to electron kinetic properties in the positions that can be seen from electron energy probability functions measured by Langmuir probe. The underlying physics on metastable density with electron density and an experimental method of LIF are presented in detail.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.6
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• pp.519-524
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• 2002

An experimental study has been conducted to investigate the effects of surface energy on frost formation. Test samples with two different surfaces are installed in a wind tunnel and exposed to a humid airflow. Dynamic contact angles (DCA) for these surfaces are $23^{\circ}\;and\;88^{\circ}$, respectively. The thickness and the mass of frost layer are measured and used to calculate the frost density while frost formation is visualized simultaneously with their measurements. Results show that frost density increases as time increases at specific test conditions. The air Reynolds number, the airflow humidity and the cold plate temperature are maintained at 12,000, 0.0042 kg/kg and $-21^{\circ}C$, respectively. The surface with a lower DCA shows a higher frost density during two-hour test, but no differences in the frost density have been found after two hours of frost generation. Empirical correlations for thickness, mass and density are assumed to be the functions of the test time and DCA.

• Journal of the Korean Institute of Gas
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• v.18 no.3
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• pp.31-37
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• 2014

The aim of this work is to provide new experimental data on the pyrolysis characteristics and the minimum ignition energy (MIE) by using the same high-density polyethylene (HDPE) powder in domestic HDPE dust explosion accident. To evaluate the explosion sensitivity of HDPE, thermo-gravimetric analysis (TGA), differential scanning calorimeter (DSC) and MIE apparatus (MIKE-3, K$\ddot{u}$hner) was conducted. The measurements showed the volume median diameter of $61.6{\mu}m$ but the particle number density of 98 % in the range $0.4{\sim}4{\mu}m$. The ignition temperature from the results of TGA and DSC in HDPE dust layers was observed in the range of $380{\sim}490^{\circ}C$. MIE was measured under 1 mJ in the HDPE dust concentration of $1200{\sim}1800g/m^3$, it was found that the ratio of particle number density in the range $0.4{\sim}4{\mu}m$ was very high (98%).

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.2
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• pp.79-83
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• 2008

In this paper, we introduced a LIF measurement method and summarized the theoretical side. When an altered wavelength of laser and electric power, lamp applied electric power, we measured the relative density of the metastable state in mercury after observing a laser induced fluorescence signal of 404.8nm and 546.2nm, and confirmed the horizontal distribution of plasma density in the discharge lamp. Due to this generation, the extinction of atoms in a metastable state occurred through collision, ionization, and excitation between plasma particles. The density and distribution of the metastable state depended on the energy and density of plasma particles, intensely. This highlights the importance of measuring density distribution in plasma electric discharge mechanism study. The results confirmed the resonance phenomenon regarding the energy level of atoms along a wavelength. change, and also confirmed that the largest fluorescent signal in 436nm, and that the density of atoms in 546.2nm ($6^3S_1{\to}6^3P_2$) were larger than 404.8nm ($6^3S_1{\to}6^3P_2$). According to the increase of lamp applied electric power, plasma density increased, too. When increased with laser electric power, the LIF signal reached a saturation state in more than 2.6mJ. When partial plasma density distribution along a horizontal axis was measured using the laser induced fluorescence method, the density decreased by recombination away from the center.

• Laser Solutions
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• v.13 no.4
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• pp.7-13
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• 2010

Today, the most common process for generating Through Silicon Vias (TSVs) for 3D ICs is Deep Reactive Ion Etching (DRIE), which allows for high aspect ratio blind holes with low surface roughness. However, the DRIE process requires a vacuum environment and the use of expensive masks. The advantage of using lasers for TSV drilling is the higher flexibility they allow during manufacturing, because neither vacuum nor lithography or masks arc required and because lasers can be applied even to metal and to dielectric layers other than silicon. However, conventional nanosecond lasers have the disadvantage of causing heat affection around the target area. By contrast, the use of a picosecond laser enables the precise generation of TSVs with less heat affected zone. In this study, we conducted a comparison of thermalization effects around laser-drilled holes when using a picosecond laser set for a high pulse energy range and a low pulse energy range. Notably, the low pulse energy picosecond laser process reduced the experimentally recast layer, surface debris and melts around the hole better than the high pulse energy process.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4341-4346
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• 2011

Impact sensitivity, one of the most important screening factors for novel high energy density materials (HEDMs), was predicted by use of quantitative structure-property relationship (QSPR) based on the electrostatic potential (ESP) values calculated on the van der Waals molecular surface (MSEP). Among various 3D descriptors derived from MSEP, we utilized total and positive variance of MSEP, and devised a new QSPR equation by combining three other parameters. We employed 37 HEDMs bearing a benzene scaffold and nitro substituents, which were also utilized by Rice and Hare. All the molecular structures were optimized at the B3LYP/6-31G(d) level of theory and confirmed as minima by the frequency calculations. Our new QSPR equation provided a good result to predict the impact sensitivities of the molecules in the training set including zwitterionic molecules.

• Laser Solutions
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• v.11 no.3
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• pp.5-9
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• 2008

The effect of a laser peening on the surface residual stress of SUS 304 was investigated using a second harmonic Nd:YAG laser beam. The energy density and the diameter of the laser beam were $400mJ/mm^2$ and about 1mm, respectively. According to the test results, the effect of a laser peening for improving the surface residual stress was not big enough to induce a high compressive stress on the SUS 304 surface. This is thought to be attributed to the small radius of the laser beam used in this study, even though its energy density is big enough. From this study, it can be concluded that to induce a recognizably high compressive stress on a metal surface, the energy density as well as the size (diameter) of the laser beam should be large enough to generate surface plasma with a high energy to have a big impact to a metal surface.

• Journal of the Korean Society of Radiology
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• v.17 no.7
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• pp.1017-1023
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• 2023

The purpose of this study was to improve the accuracy of effective atomic number (EAN) and relative electron density (RED) using a polynomial-based calibration method using dual-energy CT images. A phantom composed of 11 tissue-equivalent materials was acquired with dual-energy CT to obtain low- and high-energy images. Using the acquired dual-energy images, the ratio of attenuation of low- and high-energy images for EAN was calibrated based on Stoichiometric, Quadratic, Cubic, Quartic polynomials. EAN and RED were extracted using each calibration method. As a result of the experiment, the average error of EAN using Cubic polynomial-based calibration was minimum. Even in the RED image extracted using EAN, the error of the Cubic polynomial-based RED was minimum. Cubic polynomial-based calibration contributes to improving the accuracy of EAN and RED, and would like to contribute to accurate diagnosis of lesions in CT examinations or quantification of various materials in the human body.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.4
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• pp.321-327
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• 2010

Current rechargeable battery cannot provide high energy density and the operational durations required. But linear engine/generators provide high energy density for portable power applications because fuel is more high density. In this paper, we suggest that basic design of powerpack using linear engine for assisting power output. Efficiency is relatively high because linear engine don't have crank mechanism compared with rotary engine. We made prototype engine and had experiments to know moving characteristic about the Linear Engine. It was possible to operate velocity at 50 Hz at the firing and pressure in cylinder was 16bar.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.652-655
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• 2002

The embedded atom method based on the density functional theory is used for calculating ground state properties of realistic metal systems. In this paper, we had corrected constitutive formulae and parameters on the palladium for the purpose of doing Embedded Atom Method analysis. And then we have computed the properties of the palladium on the fundamental scale of the atomic structure. In result, simulated ground state properties, such as the lattice constant, elastics constants and the sublimation energy, show good agreement with Daw's simulation data and with experimental data.