• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.4
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• pp.333-338
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• 2007

The object of this study is to find the optimal insulation design conditions of a HTS power cable cryostat. The optimum condition of a cable cryostat is obtained by varying types of MLIs, cable core weights, spacer diameters, winding pitches and MLI layer numbers. As the weight of cable core is increased, conduction heat transfer from surroundings to cable cryostat is increased. But as the spacer pitch is increased from 120 mm to 200 mm, the heat leak of cable cryostat remains almost constant. The optimal number of MLI layers is suggested. Double ply MLI is more effective than triple ply MLI and the insulation effect is best when the number of MLI layers is 36.

• Journal of Magnetics
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• v.20 no.3
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• pp.201-206
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• 2015

Using the Vienna ab initio simulation package (VASP) incorporating both semiempirical and nonlocal van der Waals interaction, the structural, adsorption, and magnetic properties of Ni/BN/Co systems were investigated. We proposed that the relative spin direction of Ni and Co magnets can be easily tuned, because the total energy difference between ferromagnetic (FM) and antiferromagnetic (AFM) states is small. Despite this feature, very interestingly, both Ni and Co layers manifest half-metallic state, whereas the spacer BN layer becomes weak metal for one monolayer (ML) thickness and an insulating barrier for two ML thicknesses. The half-metallic behavior of the magnetic layers seems very robust, because it is independent of the magnetic coupling between Ni and Co. This finding indicates that the Ni/BN/Co system can be used as a potential candidate for tunneling magnetoresistance system.

• Applied Science and Convergence Technology
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• v.24 no.6
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• pp.245-249
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• 2015

Vertically coupled low density InGaAs quantum dots (QDs) buried in GaAs matrix were grown with migration enhanced molecular beam epitaxy method as a candidate for quantum information processing devices. We performed excitation power-dependent photoluminescence measurements at cryogenic temperature to analyze the effects of vertical coupling according to the variation in thickness of spacer layer. The more intense coupling effects were observed with the thinner spacer layer, which modified emission properties of QDs significantly. The low surface density of QDs was observed by atomic force microscopy, and scanning transmission electron microscopy verified the successful vertical coupling between low density QDs.

• Proceedings of the Materials Research Society of Korea Conference
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• 1995.11a
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• pp.70-70
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• 1995

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.134-135
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• 2003

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1219-1221
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• 2008

The Authors have demonstrated highly efficient white organic light-emitting diodes using hybrid-spacer which was inserted between each emitting layer or/and codoped blue emitting layers with the different functional material. The characteristics of WOLEDs showed the maximum external quantum efficiency of 13.8%, power efficiency of 33.66 lm/W, and Commission Internationale de I'Eclairage coordinates of (x=0.36, y=0.37), respectively.

• Nuclear Engineering and Technology
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• v.45 no.7
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• pp.895-910
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• 2013

The reflood test data from the rod bundle heat transfer (RBHT) test facility showed that the grids in the upper portion of the rod bundle could become wet well before the arrival of the quench front and that the sizes of liquid droplets downstream of a wet grid could not be predicted by the droplet breakup models for a dry grid. To investigate the water droplet generation from a wet grid spacer, a viscous linear temporal instability model of the water sheet issuing from the trailing edge of the grid with the surrounding steam up-flow is developed in this study. The Orr-Sommerfeld equations along with appropriate boundary conditions for the flow are solved using Chebyshev series expansions and the Tau-Galerkin projection method. The effects of several physical parameters on the water sheet oscillation are studied by determining the variation of the temporal growth rate with the wavenumber. It is found that a larger relative steam velocity to water velocity has a tendency to destabilize the water sheet with increased dynamic pressure. On the other hand, a larger ratio of steam boundary layer to the half water sheet thickness has a stabilizing effect on the water sheet oscillation. Droplet diameters downstream of the spacer grid predicted by the present model are found to compare reasonably well with the data obtained at the RBHT test facility as well as with other data recently reported in the literature.

• Korean Journal of Optics and Photonics
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• v.8 no.6
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• pp.466-470
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• 1997

We fabricated the asymmetric Fabry-Perot etalon which contains amorphous $As_2S_3$ as a spacer layer by using the method of optical multilayer coating and observed the optical bistability with the polarization. Optical thickness of the spacer layer is 2$\lambda$ at $Ar^+$ ($\lambda $=514.5 nm) laser wavelength. Optical bistability was observed at the intensities between 80~100 mW and the experiment shows us that the trends of bistable loop of the reflected and the transmitted lights are quite different depending on the state of polarization. This phenomena can be explained as the phase differences of each polarizations are different in the nonlinear Fabry-Perot etalon.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.206.1-206.1
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• 2007

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.237.2-237.2
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• 2008