• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.32-34
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• 2005

In this paper, an insertcore type PMLSM is proposed to improve the low thrust density of aslotless type PMLSM. Aneural network is applied to enhance thrust and to minimize the detent force caused by both the slot-teeth structure and end-effect. As the resultsof the optimal design, the thrust ripple rate is decreased conspicuously from 10.22[%] to 2.87[%] and the distortion factor of thrust form 5.82[%] to 1.65[%], respectively

• Journal of the Optical Society of Korea
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• v.6 no.2
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• pp.48-54
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• 2002

Experimental study is performed on flashlamp-pumped Ti: sapphire lasers with single, double, and four-partial-ellipse-pump cavities aiming at improving the performance of the lasers. The output energy of 604 mJ per pulse with a width of 25 $\mu$s at a total laser efficiency of 0.13% is achieved in the laser pumped by a light pulse of 45$\mu$s without a fluorescent converter The laser output energy versus its Ti: sappy ire rod length, pumping-light pulse duration, and electrical input energy are discussed with or without using a fluorescent converter. The result shows that much more output energy is obtained il a longer Ti: sapphire-rod laser pumped by a shorter light pulse when its output coupler has an optimized transmittance. In addition, an enhancement of output energy by a factor of 7 is achieved. in the laser using a fluorescent converter LD490.

• Korea-Australia Rheology Journal
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• v.17 no.4
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• pp.199-205
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• 2005

Carbon dioxide was absorbed into aqueous polyethylene oxide (PEO) solution containing AMP in a flat-stirred vessel to investigate the effect of non-Newtonian rheological behavior of PEO on the rate of chemical absorption of $CO_2$, where the reaction between $CO_2$ and AMP was assumed to be a first-order reaction with respect to the molar concentration of $CO_2$ and AMP respectively. The liquid-side mass transfer coefficient, which was obtained from the dimensionless empirical equation containing the properties of viscoelasticity of the non-Newtonian liquid, was used to estimate the enhancement factor due to chemical reaction. PEO with elastic property of non-Newtonian liquid made the rate of chemical absorption of $CO_2$ accelerate compared with Newtonian liquid based on the same viscosity of the solution.

• Proceedings of the Korean Society of Veterinary Clinics Conference
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• 2006.11a
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• pp.65-65
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• 2006

• International Journal of Air-Conditioning and Refrigeration
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• v.15 no.4
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• pp.163-168
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• 2007

The feature of six existing condensation heat transfer correlations for microfin tubes were evaluated with the consideration of vapor quality, mass flux, geometries, and various refrigerants. The Kosky and Staub [15] and the Jaster and Kosky [16] correlations for smooth tube were used for the evaluation of the heat transfer enhancement factor (EF). For the prediction of zeotropic mixtures, most correlations show discrepancy with previous measurements. The Yu and Koyama [4] and the Shikazono et al. [8] correlations do not consider spiral angle effect. The Han and Lee [10] correlation shows fin height growth deteriorates heat transfer. Experimental verification to develop reliable condensation heat transfer correlation for microfin tubes is still needed with the consideration of geometrical effects and working conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.8
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• pp.366-374
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• 2014

Experimental mass transfer data, which were obtained for the $CO_2$-water slug flows in vertical tubes with 2, 5, and 8mm diameters, were analyzed in comparison with the penetration theory. It was found that a penetration model with molecular diffusion coefficient cannot predict the experimental data accurately. An effective diffusion coefficient, which considers enhancement effect of interfacial waves, was suggested to improve prediction. Another empirical factor was also suggested to consider the effect of non-uniform interface velocity. A modified penetration model was found to be capable of predicting the experimental data reasonably well.

• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.78-81
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• 2011

We demonstrate a high-spatial-resolution imaging and spectroscopy tool using a solid immersion lens (SIL), a hemispherical lens made of high refractive index glass (n ~2). Photoluminescence (PL) images of single CdSe nanocrystals confirm a numerical aperture enhancement factor of ~2, close to the refractive index of the SIL. In particular, a bare-eye observation of PL signals emitted by single nanocrystals with ${\sim}10\;{\mu}m^{-2}$ densities was possible over an ${\sim}30\;{\mu}m$ diameter region. In addition, the PL spectra of single CdSe nanocrystals were successfully measured at room temperature. Thus, this SIL microscope ensures a simple but powerful method for nanostructure spectroscopy.

• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1311-1317
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• 2021

In this study, an airborne alpha detection system, which consists of a passivated implanted planar silicon (PIPS) detector and an air filter, was developed. A collimator applied to the alpha detection system showed an enhancement in resolution and a degradation in detection efficiency. The resolution and detection efficiency were compared and analyzed to evaluate the performance of the collimator. Thus, the resolution was found to be more important than the efficiency as a determining factor of the detection system performance, from the viewpoint of radionuclide identification. The performance was evaluated on three properties of the collimator: hole shape, hole length, and the ratio between the hole and frame pitches. From the hole shape performance evaluation, a hexagonal collimator showed the highest resolution. Further, the collimator with a hole pitch of 14 mm was found to have the highest resolution while that with a frame pitch of 4-6 mm (i.e., 1.2-1.4 times longer than the hole pitch) showed the highest resolution.

• Journal of the Korean Magnetic Resonance Society
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• v.23 no.3
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• pp.81-86
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• 2019

Overhauser dynamic nuclear polarization (O-DNP) has been an efficient method to boost the thermal nuclear polarization in liquids at room temperature. However, O-DNP for a benchtop NMR using a permanent magnet has remained unexplored yet. In this work, we report the development of an O-DNP system adopting a permanent magnet of 1.6 T. Q-band (~43 GHz) high-power amplifier produced 6 W microwave for saturation. Instead of resonator, we used an open-type antenna for the microwave irradiation. For several representative small molecules, we measured the concentration and frequency dependences of the enhancement factor. This work paves the way for the development of a benchtop DNP-NMR system overcoming its disadvantage of low quality signal when using a permanent magnet.

• Journal of Multimedia Information System
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• v.8 no.2
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• pp.111-120
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• 2021

As recent virtual reality technologies provide a more natural three-dimensional interactive environment, users naturally learn to explore space and interact with synthetic objects. The virtual reality researcher develops a technique that realizes realistic sensory feedback to get appropriate feedback to sense input behavior. Although much recent virtual reality research works extensively consider the human factor, it is not easy to adapt to all new virtual environment contents. Among many human factors, distance perception has been treated as very important in virtual environment interaction accuracy. We study the experiential virtual environment with the feature of the virtual object connected with the real object. We divide the three-dimensional interaction, in which distance perception and behavior have a significant influence, into two types (whole-body movement and direct manipulation) and analyze the real and virtual visual distance perception heterogeneity phenomenon. Also, we propose a statistical correction method that can reduce a near-body movement and manipulation error when changing the interaction location and report the experiment results proving its effectiveness.