• Transactions of Materials Processing
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• v.20 no.6
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• pp.439-449
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• 2011

The temperature distribution and subsequent permanent deformation of SS400 carbon steel plate subjected to an induction-based line heating process were studied by a numerical method involving coupled 3-D electromagnetic-thermal-structural analysis. The numerical study revealed that the amount of permanent deformation is strongly related to the Joule loss caused by such process conditions as input power and moving speed of the heat source. To validate the numerical analysis results, line heating experiments were carried out with a high frequency(HF) induction heating(IH) equipment capable of bending thick plate with the moving accuracy of ${\pm}0.1mm$ in heating coil position. The amount of permanent deformation increased with decreasing moving speed and increasing input power.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.244-244
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• 2010

최근 활발히 연구되고 있는 AMOLED는 평판 디스플레이 분야를 이끌어 갈 차세대 선두 주자로 크게 주목 받고 있다. AMOLED는 전압 구동 방식인 AMLCD와 다르게 전류 구동 방식으로 a-Si TFT 보다 LTPS-TFT 사용이 요구되며, 대면적 기판으로 갈수록 결정립의 균일도가 매우 중요한 인자로 작용한다. 현재 양산이 가능한 AMOLED는 핸드폰이나 15인치 TV정도로 크기가 소형이며 대형 TV나 컴퓨터 모니터 등을 양산하기 위해 많은 방법이 시도되고 있다. 양산체제에서 사용되는 결정화 방법으로는 ELC가 가장 많은 부분을 차지하고 있다. 그러나 레이저를 사용하는 ELC 방법은 대면적으로 갈수록 레이저 빔 자체의 불균일성, shot to shot 불균일성, 레이저빔 중첩의 부정확도 등으로 인한 균일도의 부정확성이 커짐으로 인한 mura 현상이 나타나고 레이저 장비의 사용에 대한 비용 부담을 피할 수 없다. 따라서 non-laser 방식에 결정화 방법이 요구되나 SPC 경우는 상대적으로 고온에서 장시간이 걸리고, MIC 뿐만 아니라 MIC 응용 방법들은 금속 오염에 대한 문제가 발생하고 있는 실정이다. 이러한 문제로 인하여 결정립 크기의 균일도가 우수한 다결정 실리콘 박막을 제조하는 신기술에 대한 필요성이 매우 높은 실정이다. 본 연구에서는 비정질 실리콘 박막 상부 혹은 하부에 도전층을 개재하고, 상기 도전층에 전계를 인가하여 그것의 주울 가열에 의해 발생한 고열로 비정질 실리콘 박막을 급속 고온 고상 결정화하는 방법에 관한 기술인 JIC (Joule-heating Induced Crystallization) 결정화 공정을 개발하였다. 본 공정은 상온에서 수 micro-second 내에 결정화를 수행하는 것이 가능하며 도전층과 실리콘 박막 사이에 barrier층 삽입를 통하여 금속 오염을 막을 수 있으며 공정적인 측면에서도 별도의 chamber가 필요하지 않는 장점을 가지고 있다. 본 논문에서는 JIC 결정화 공정 조건에 따른 결정화 기구 및 JIC poly-Si의 미세구조 및 물리적 특성에 관한 논의가 이루어질 것이다.

• Journal of Astronomy and Space Sciences
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• v.24 no.2
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• pp.125-134
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• 2007

In this paper, we analyze the orbital variation of the Korea Multi-Purpose SATellite-1(KOMPSAT-1) in a strong space environment due to satellite drag by solar and geomagnetic activities. The satellite drag usually occurs slowly, but becomes serious satellite drag when the space environment suddenly changes via strong solar activity like a big flare eruption or coronal mass ejections(CMEs). Especially, KOMPSAT-1 as a low earth orbit satellite has a distinct increase of the drag acceleration by the variations of atmospheric friction. We consider factors of solar activity to have serious effects on the satellite drag from two points of view. One is an effect of high energy radiation when the flare occurs in the Sun. This radiation heats and expands the upper atmosphere of the Earth as the number of neutral particles is suddenly increased. The other is an effect of Joule and precipitating particle heating caused by current of plasma and precipitation of particles during geomagnetic storms by CMEs. It also affects the density of neutral particles by heating the upper atmo-sphere. We investigate the satellite drag acceleration associated with the two factors for five events selected based on solar and geomagnetic data from 2001 to 2002. The major results can be summarized as follows. First, the drag acceleration started to increase with solar EUV radiation with the best cross-correlation (r = 0.92) for 1 day delayed F10.7. Second, the drag acceleration and Dst index have similar patterns when the geomagnetic storm is dominant and the drag acceleration abruptly increases during the strong geomagnetic storm. Third, the background variation of the drag accelerations is governed by the solar radiation, while their short term (less than a day) variations is governed by geomagnetic storms.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.1
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• pp.29-34
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• 2024

The heating element utilizing the Joule heating generated when current flows through a conductor is widely researched and developed for various industrial applications such as moisture removal in automotive windshield, high-speed train windows, and solar panels. Recently, research utilizing heating elements with various nanostructures has been actively conducted to develop flexible heating elements capable of maintaining stable heating even under mechanical deformation conditions. In this study, flexible polyurethane possessing excellent flexibility was selected as the substrate, and silver (Ag) thin films with low electrical resistivity (1.6 μΩ-cm) were fabricated as the heating layer using magnetron sputtering. The 2D heating structure of the Ag thin films demonstrated excellent heating reproducibility, reaching 95% of the target temperature within 20 seconds. Furthermore, excellent heating characteristics were maintained even under mechanically deforming environments, exhibiting outstanding flexibility with less than a 3% increase in electrical resistance observed in repetitive bending tests (10,000 cycles, based on a curvature radius of 5 mm). This demonstrates that polyurethane/Ag planar heating structure bears promising potential as a flexible/wearable heating element for curved-shaped appliances and objects subjected to diverse stresses such as human body parts.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.5
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• pp.1-8
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• 2005

Flows in segmented arc-heaters have been calculated for prediction of experimental operating condition or for analysis and design of arc-heater itself. Some researchers succeeded in calculating accurately inner flows of a arc-heater, but could not made mathematical models which satisfy various operating conditions for many arc-heaters. this study is forced on turbulence for the generality of mathematical model. Instead of algebraic turbulence models which are frequently used for calculating inner flow of arc-heater, two equation turbulent models are used. Prediction results agree well with experiment data and it was confirmed that $k-\varepsilon$ two equation turbulence model is appropriate for a flow in an arc heater throughout extensive numerical testing.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.1
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• pp.43-47
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• 2022

In this study, we demonstrated an eco-friendly thin-metallic-film-based heater which can be operated in water. Based on the materials stability, Mo was selected as the heating element to secure long-term stability. Using a magnetron sputtering, 40 nm-thick Mo layers were deposited onto a glass substrate, followed by the deposition of 60-nm-thick ZnO layer to prevent oxidation during the heater fabrication process. Then, PVB (Polyvinyl Butyral) was applied on top of ZnO layer and an additional glass substrate was placed, which were heated at 150℃ for 2 hr. The PVB was cured with strong adhesion by the processing condition. We operated the Glass/Mo/ZnO/Glass heater in water, and it was shown that the water temperature reached 50℃ within 2 minutes, with a minimal resistance change of the heater. Finally, the heaters exhibit a semi-transparency, and this aesthetic advantage is expected to contribute to the added value of the heater.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.37-43
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• 2017

This review investigates the basic principle of physical interactions and failure mechanisms introduced in the materials and inner parts of semiconducting components under electromagnetic pulses (EMPs). The transfer process of EMPs at the semiconducting component level can be explained based on three layer structures (air, dielectric, and conductor layers). The theoretically absorbed energy can be predicted by the complex reflection coefficient. The main failure mechanisms of semiconductor components are also described based on the Joule heating energy generated by the coupling between materials and the applied EMPs. Breakdown of the P-N junction, burnout of the circuit pattern in the semiconductor chip, and damage to connecting wires between the lead frame and semiconducting chips can result from dielectric heating and eddy current loss due to electric and magnetic fields. To summarize, the EMPs transferred to the semiconductor components interact with the chip material in a semiconductor, and dipolar polarization and ionic conduction happen at the same time. Destruction of the P-N junction can result from excessive reverse voltage. Further EMP research at the semiconducting component level is needed to improve the reliability and susceptibility of electric and electronic systems.

• Korean Journal of Food Science and Technology
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• v.28 no.2
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• pp.324-329
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• 1996

In order to develop a novel dewatering process for soybean milk residue, hydraulic press with ohmic heating was built and its expression conditions were examined. The electric conductivity of raw soybean milk residue was 0.128 S/m and increased linearly with increasing temperature. Water content of the residue could be reduced to 74% with the conventional hydraulic press, but to less than 70% by applying ohmic heating to the hydraulic press. The most effective dewatering was achieved by applying alternative current with 5 kHz frequency at 60 V during expression. The solid content of the expressed liauid was markedly reduced from 10% to 3.3% by ohmic heating during expression. Temperature of the cake rose to above $95^{\circ}C$ during the dewatering due to ohmic heating.

• Journal of the Korea Convergence Society
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• v.9 no.3
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• pp.257-263
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• 2018

Hyperthermia supplies RF high-frequency energy above 1MHz to the tumor tissue through the electrodes. And the temperature of the tumor tissue is increased to $42^{\circ}C$ or more to cause thermal necrosis. A mathematical model can be derived a human body model for absorption and transmission of electromagnetic energy in the human model and It is possible to evaluate the distribution of temperature fields in biological tissues. In this paper, we build the human model based on the adult standard model of the geometric shape of the 3D model and use the FVM code. It is assumed that Joule heat is supplied to the anatomical model to simulate the magnetic field induced by the external electrode and the temperature distribution was analyzed for 0-1,200 seconds. As a result of the simulation, it was confirmed that the transferred energy progressively penetrates from the edge of the electrode to the pulmonary tumors and from the skin surface to the subcutaneous layer.

• Journal of Astronomy and Space Sciences
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• v.25 no.4
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• pp.405-414
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• 2008

To better understand the physical processes that control the high-latitude lower thermospheric dynamics, we analyze the divergence and vorticity of the high-latitude neutral wind field in the lower thermosphere during the southern summertime for different IMF conditions. For this study the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEG CM) is used. The analysis of the large-scale vorticity and divergence provides basic understanding flow configurations to help elucidate the momentum sources that ulti-mately determine the total wind field in the lower polar thermosphere and provides insight into the relative strengths of the different sources of momentum responsible for driving winds. The mean neutral wind pattern in the high-latitude lower thermosphere is dominated by rotational flow, imparted primarily through the ion drag force, rather than by divergent flow, imparted primarily through Joule and solar heating. The difference vorticity, obtained by subtracting values with zero IMF from those with non-zero IMF, in the high-latitude lower thermosphere is much larger than the difference divergence for all IMF conditions, indicating that a larger response of the thermospheric wind system to enhancement in the momentum input generating the rotational motion with elevated IMF than the corresponding energy input generating the divergent motion. the difference vorticity in the high-latitude lower thermosphere depends on the direction of the IMF. The difference vorticity for negative and positive $B_y$ shows positive and negative, respectively, at higher magnetic latitudes than $-70^{\circ}$. For negative $B_z$, the difference vorticities have positive in the dusk sector and negative in the dawn sector. The difference vorticities for positive $B_z$ have opposite sign. Negative IMF $B_z$ has a stronger effect on the vorticity than does positive $B_z$.