• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.12
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• pp.673-678
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• 2000

The dielectric barrier discharge(DBD) is a common method to create a nonthermal plasma in which electrical energy is used to create electrons with a high average kinetic energy. The unique aspect of dielectric barrier discharges is the large array of short lifetime(10ns) silent discharges created over the surface of the dielectric. A silent discharge is generated when the applied voltage exceeds the breakdown voltage of the carrier gas creating a conduction path between the applied electrode and grounded electrode. As charge accumulates on the dielectric, the electric field is reduced below the breakdown field of the carrier gas and the silent discharge self terminates preventing the DBD cell from producing a thermal arc. In fact, the most significant application of dielectric barrier discharges is to generate ozone for contaminated water treatment. Therefore, experiments were perfomed at 1∼2[bar] pressure using a coaxial geometry single dielectric barrier discharge for ozone concentrations and energy densities. The main result show that the concentration and efficiency of ozone are influenced by gas nature, gas quantity, gas pressure, supplied voltage and frequency.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.5
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• pp.331-337
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• 2017

Thermal batteries, reserve power source, is activated by melting of molten salt at the temperature range of $350{\sim}550^{\circ}C$. To immobile the molten state electrolyte when the thermal battery is activated, the binder must be added in electrolyte. Usually, molten salts include 30~40 wt% of MgO binder to ensure electrical insulation as well as safety. However, the conventional MgO binder tends to increase ionic conductive resistance and thus the inclusion of the binder increases the total impedance of the battery. This paper mainly focused on the study of yttria stabilized zirconia (YSZ) as an alternative binder for molten salt. The chemical stability between the molten salt and YSZ is measured by XRD and DSC. And the sufficient path for ionic conduction on molten salt could be confirmed by the enhanced wetting behavior and the enlarged pore size of YSZ. The electrochemical properties were analyzed using single cell tests so that it showed the outstanding performance than that using MgO binder.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.10
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• pp.820-826
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• 2009

The anisotropic phonon conductions with varying Joule heating rate of the silicon film in Silicon-on-Insulator devices are examined using the electron-phonon interaction model. It is found that the phonon heat transfer rate at each boundary of Si-layer has a strong dependence on the heating power rate. And the phonon flow decreases when the temperature gradient has a sharp change within extremely short length scales such as phonon mean free path. Thus the heat generated in the hot spot region is removed primarily by heat conduction through Si-layer at the higher Joule heating level and the phonon nonlocality is mainly attributed to lower group velocity phonons as remarkably dissimilar to the case of electrons in laser heated plasmas. To validate these observations the modified phonon nonlocal model considering complete phonon dispersion relations is introduced as a correct form of the conventional theory. We also reveal that the relation between the phonon heat deposition time from the hot spot region and the relaxation time in Si-layer can be used to estimate the intrinsic thermal resistance in the parallel heat flow direction as Joule heating level varies.

• Journal of Welding and Joining
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• v.33 no.6
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• pp.60-66
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• 2015

Molten zone shape of pulse laser welding is affected by welding conditions such as beam power, beam speed, irradiation time, pulse frequency, etc. and is divided into conduction type and keyhole type. It is necessary to design heat source model for irradiation of laser beam in the pulse laser welding. Shape variables and the maximum energy density value of the heat source model are different depending on the molten zone shape. In this paper, pulse laser welding simulation for joining of cylindrical part and circular cover was carried out. The heat source model for pulse laser beam with circular path was applied to the heat input boundary condition, radiative and conductive heat transfer were considered for the thermal boundary condition. For each phase, thermal and mechanical properties according to temperature were also applied to analysis. Analytical results were in good agreement with the molten zone size of specimen under the same welding conditions. So, the reliability of the welding simulation was verified. Finally, the improvements for reducing residual deformation after cover welding could be reviewed analytically.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.3
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• pp.63-66
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• 2014

In this study, we investigated the effects of Cu TSV on the thermal management of 3D stacked IC. Combination of backside point-heating and IR microscopic measurement of the front-side temperature showed evolution of hot spots in thin Si wafers, implying 3D stacked IC is vulnerable to thermal interference between stacked layers. Cu TSV was found to be an effective heat path, resulting in larger high temperature area in TSV wafer than bare Si wafer, and could be used as an efficient thermal via in the thermal management of 3D stacked IC.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.20 no.5
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• pp.67-81
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• 2017

Because of lack of accurate understanding of the mechanism of urban heat island (UHI) phenomenon and lack of scientific discussion, it is hard to come up with effective measures to mitigate UHI phenomenon. This study systematically described the UHI and suggested the solutions using green-infrastructure (green-infra). The factors that control UHI are very diverse: radiant heat flux, latent heat flux, storage heat flux, and artificial heat flux, and the air temperature is formed by the combination effect of radiation, conduction and convection. Green-infra strategies can improve thermal environment by reducing radiant heat flux (the albedo effect, the shade effect), increasing latent heat flux (the evapotranspiration effect), and creating a wind path (cooling air flow). As a result of measurement, green-infra could reduce radiant heat flux as $270W/m^2$ due to shadow effect and produce $170W/m^2$ latent heat flux due to evaporation. Finally, green-infra can be applied differently on the macro(urban) scale and micro scale, therefore, we should plan and design green-infra after the target objects of structures are set.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.3
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• pp.161-166
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• 1999

We investigate the device characteristics of the separated shorted-anode LIGBT (SSA-LIGBT), which suppresses effectively the negative differential resistance regime, by 2-dimensional numerical simulation. The SSA-LIGBT increases the pinch resistance by employing the highly resistive n-drift region as an electron conduction path instead of the lowly resistive n buffer region of the conventional SA-LIGBT. The negative differential resistance regime of the SSA-LIGBT is significantly suppressed as compared with that of the conventional SA-LIGBT. The SSA-LIGBT shows the lower forward voltage drop than that of the conventional SA-LIGBT.

• Journal of the Semiconductor & Display Technology
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• v.10 no.4
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• pp.37-42
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• 2011

In this paper, novel carbon nanotube (CNT)-filled Solderable electrically conductive adhesive (ECA) and joining process have been developed. To investigate the bonding characteristics of CNT-filled Solderable ECA, three types of Solderable ECAs with different CNT weight percent (0, 0.1, 1wt%) were formulated. For a joining process, the quad flat package (QFP) chip was used. The QFP chip had a size of $14{\times}14{\times}2.7$ mm and a 1 mm lead pitch. The test board had a Cu daisy-chained pattern with 18 ${\mu}m$ thick. After the bonding process, the bonding characteristics such as morphology of conduction path, electrical resistance and pull strength were measured for each formulated ECAs. As a result, the electrical and mechanical bonding characteristics for a QFP joints using CNT-filled ECA were improved about 10% compared to those of QFP joints using ECA without CNT.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.10
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• pp.1303-1313
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• 1997

A micro-macroscopic analysis on the conduction-controlled directional casting of Al-Cu alloys is performed, in which emphases are placed on the microstructural features. In order to facilitate the solution procedure, an iterative micro-macroscopic coupling algorithm is developed. The predicted results show that the effect of finite back diffusion on the transient solidification process in comparison with the lever rule depends essentially on the initial concentration of an alloy. In the final casting, the eutectic fraction is distributed in an increasing-decreasing-increasing pattern, each mode of which is named the chill, interior and end zones. This nonuniformity per se suffices to justify the necessity of this work because it originates from the combined effects of finite back diffusion and cooling path-dependent nature of the eutectic formation. As the cooling rate is enhanced, not only the influence depths of boundaries narrow, but also the eutectic fractions in the chill and interior zones increase. In addition, it is revealed for the first time that the micro segregation band is formed in response to a sudden change in cooling rate during the directional casting. An increasing change creates an overshooting band in the eutectic fraction distribution, and vice versa.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.142-147
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• 2002

폴리머/세라믹 복합체는 내장형 캐패시터(embedded capacitor)의 유전 재료로 많은 관심을 불러 일으키고 있다. 본 연구는 BaTiO$_3$분말의 크기와 함량이 에폭시/BaTiO$_3$복합체 캐패시터의 유전 상수와 누설전류에 미치는 영향에 대해 살펴보고 이에 대해 고찰하고자 하였다. BaTiO$_3$분말이 67vo1% 함유된 Epoxy/BaTiO$_3$composite 필름의 유전상수는 전반적으로 사용한 BaTiO$_3$분말의 크기가 커짐에 따라 증가하였다. 이것은 입자의 크기가 증가함에 따른 입자의 유전상수의 증가 때문이며 XRD 분석을 통해 입자의 크기가 증가함에 따라 tetragonality가 증가함을 확인하였다. 복합체 필름의 누설전류도 또한 사용한 입자의 크기가 커짐에 따라 증가하였으며 이는 분말의 크기가 증가함에 따라 단위길이 당 입자의 수가 감소하는 것으로, 단위 길이 당 입자의 수가 감소하여 전류의 흐름을 방해하는 입자/폴리머/입자 계면의 수가 감소하기 때문이다. 분말의 함량에 따른 유전상수는 unimodal과 bimodal의 경우 각각 73vo1%와 80vo1%에서 최대 값을 나타냈으며 그 이상에서는 감소하는 것이 관찰되었는데 이는 과량의 분말이 조밀 충전을 깨고 필름의 밀도를 낮추기 때문이었다. 누설전류의 경우 unimodal과 bimodal 각각에 대해 73vo1%와 80vo1%에서 급격한 증가를 관찰 할 수 있었으며 이는 percolation 현상의 발생에 의해 입자와 입자간에 접촉이 이루어져 BaTiO$_3$분말을 따라 전류가 잘 흐를 수 있는 conduction path가 형성 되기 때문이다.