• Electrical & Electronic Materials
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• v.8 no.2
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• pp.229-236
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• 1995

Multimedia has created a system environment that needs a combination of diverse peripherals, faster I/O, and easier configuration. The sheer volume of data one can expect with multimedia hardware and applications storage systems of higher capacity and faster data transfer rate. Unlike the magneto-optical(MO)disk technology which uses bias magnetic field in writing, both the reading and the writing in the phase change (PC) technology are performed only by laser light. In PC optical media, an active layer is reversibly converted between amorphous state and crystalline state by changing irradiation conditions of focused laser beam. Thus, as compared with MO disk, the PC disk has such great advantages that signals can be reproduced by change of reflectance of laser beams in the same manner as the compact disc. The reflectivity of a phase-change spot can be altered in a single pass under the head only through modulation of laser power. The principles and the current status of phase-change optical recording media combined with possible applications are discussed in the present article.

• Advances in materials Research
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• v.8 no.3
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• pp.237-257
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• 2019

The present article researches large-amplitude thermal free vibration characteristics of nonlocal two-phase piezo-magnetic nano-size beams having geometric imperfections by considering piezoelectric reinforcement scheme. The piezoelectric reinforcement can cause an enhanced vibration behavior of smart nanobeams under magnetic field. All previous studies on vibrations of piezoelectric-magnetic nano-size beams ignore the influences of geometric imperfections which are crucial since a nanobeam is not always ideal or perfect. Nonlinear governing equations of a smart nanobeam are derived based on classical beam theory and an analytical trend is provided to obtain nonlinear vibration frequency. This research shows that changing the volume fraction of piezoelectric phase in the material has a great influence on vibration behavior of smart nanobeam under electric and magnetic fields. Also, it can be seen that nonlinear vibration behaviors of smart nanobeam is dependent on the magnitude of exerted electric voltage, magnetic imperfection amplitude and substrate constants.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.271-272
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• 2009

We fabricated a hybrid aligned film using reactive rod-like mesogen to reduce light leakage of twisted nematic(TN) cell in off-axis of the dark state. We proved that the fabricated compensation film has hybrid alignment by changing phase retardation according to polar angle. In this paper, we confirmed characteristics of compensation film through simulation results and found the matching factor of simulation results and experimental result. In result, the maximum pretilt angle of hybrid compensated film is $19^{\circ}$ which has phase retardation 0.1445.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.1
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• pp.26-31
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• 2014

This study looks into changing building energy use by application of phase change material (PCM). PCM does not need extra energy for operation and is used for reducing building energy use and, CO2 output by displaying semi-permanent effects after installation. It also is able to avoid the maximum electric power time-zone by inducing a time lag phenomenon of cooling and heating loads with high thermal capacity using latent heat. To verify the efficiency of blinds and PCM, tests about the PCM operation mechanism using air conditioning machinery and nocturnal panel cooling were done. In the test results of the case using PCM installation, a $45^{\circ}$ blind angle with machinery air conditioning and nocturnal panel cooling at the same time shows a 22 percent energy saving effect against general space. The test results of each case were compared and analyzed based on the blind and window opening settings. Finally, the energy reduction of existing buildings using PCM application was reviewed based on the final measurement results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04a
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• pp.59-63
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• 2002

The purpose of this paper is to investigate the crystal texture of the 2223 phase and its relationship with PIT processing parameter. Ag-sheathed Bi-2223 multi-filament tapes were prepared by changing rolling reduction ratio. We analysed the degree of texture for 2223 phase after heat-treatment. According to X-ray pole-figure, the texture of the filaments located near surface and center were not so different each other for all rolling conditions. we found a little higher degree of texture for 60% rolling reduction. But its difference is not so high compared with those tapes with a lower rolling reduction ratio. Reaction induced texturing seemed to contribute with a large portion under present condition.

• Structural Engineering and Mechanics
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• v.66 no.2
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• pp.237-248
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• 2018

This study presents the investigation of wave dispersion characteristics of a magneto-electro-elastic functionally graded (MEE-FG) nanosize beam utilizing nonlocal strain gradient theory (NSGT). In this theory, a material length scale parameter is propounded to show the influence of strain gradient stress field, and likewise, a nonlocal parameter is nominated to emphasize on the importance of elastic stress field effects. The material properties of heterogeneous nanobeam are supposed to vary smoothly through the thickness direction based on power-law form. Applying Hamilton's principle, the nonlocal governing equations of MEE-FG nanobeam are derived. Furthermore, to derive the wave frequency, phase velocity and escape frequency of MEE-FG nanobeam, an analytical solution is employed. The validation procedure is performed by comparing the results of present model with results exhibited by previous papers. Results are rendered in the framework of an exact parametric study by changing various parameters such as wave number, nonlocal parameter, length scale parameter, gradient index, magnetic potential and electric voltage to show their influence on the wave frequency, phase velocity and escape frequency of MEE-FG nanobeams.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.355-362
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• 2009

Most material of engineering interest undergoes solidification process from liquid to solid state. Identifying the underlying mechanism during solidification process is essential to determine the microstructure of material which governs the physical properties of final product. In this paper, we expand our previous two-dimensional numerical technique to three-dimensional simulation for computing dendritic solidification process with fluid convection. We used Level Contour Reconstruction Method to track the moving liquid-solid interface and Sharp Interface Technique to correctly implement phase changing boundary condition. Three-dimensional results showed clear difference compared to two-dimensional simulation on tip growth rate and velocity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.149-150
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• 2009

In this paper we study on the semiconductor characteristic by calculating the variation of reflection function in microstrip lines, which has open-ended termination containing an optically induced plasma region. The variation of impedances resulting from the presence of plasma has evaluated with time and frequency domain. The responses have been also evaluated theoretically for changing the phase of the variation in the reflection.

• Journal of Powder Materials
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• v.11 no.6 s.47
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• pp.467-471
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• 2004

In order to fabricate a high density sintered body of ITO, nano-sized ITO powders were synthesized by coprecipitation methods. Aqueous solutions of indium and tin salts were mixed and coprecipitated by changing their pH. Coprecipitated ITO powders possessed 20-30 nm crystallite size and a relatively high BET value ($35m^2/g$), however, aggregation of particles were occurred. Therefore, a novel recrystallization technique was applied in order to eliminate the aggregates. The recrystallized ITO material consists of a little bit larger needlelike crystals, $20nm{\times}80nm$, and it possesses a higher BET value $(57m^{2}/g)$ compared to the plain coprecipitated material $(35m^{2}/g)$. Metastable phase formation and higher content of aggregated particles were observed in the coprecipitated materials. Densification was 95% to 98% complete after 5 hour sintering at $1500^{\circ}C$ for the recrystallized powders while densities of the coprecipitated powders were below 75%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.267-267
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• 2010

The structural and electrical properties of microcrystalline silicon films were investigated by hot wire chemical vapor deposition(HWCVD) often called catalytic chemical vapor deposition(Cat-CVD). The Si microcrystalline phase is easily controlled by changing the rate of the silane concentration of $SiH_4$ to $H_2$ during deposition. The Structural property was observed by Raman and SEM. Photo-conductivity and dark conductivity, and photo-sensitivity were observed by Sunsimulator (AM 1.5 illumination). The film color was changed by the variation of silane concentration. HWCVD is useful for the formation of Si thin films for solar cell and needs further commercialized development for mass production.