• 한국진공학회지
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• 제13권4호
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• pp.182-188
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• 2004

이전의 연구에서의 소스 형태는 전기화학적 방법으로 에칭된 텅스텐 선에 코일형태의 히터를 부착한 것으로 액체금속을 직접 가열하는 방법이었다. 이전의 모델에서는 액체금속을 가열하는 과정에서 코일형태의 히터에 대한 과다한 전력소모가 발생함으로써 본 연구에서는 코일형태의 히터를 대체할 수 있는 새로운 방법을 제시하고 그의 특성을 연구하였다. Pre-etching된 250$\mu\textrm{m}$의 텅스텐 선을 7mm 단위로 절단, 이를 갈륨저장소로 만든 형태이다. 가열방식은 직접방식으로 갈륨을 저장소에 적재(loading)하는 과정과 빔의 안정도가 이전의 방법보다 더욱 향상되었음을 본 연구의 결과를 통해 볼 수 있다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.150-150
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• 2012

진공증착을 이용하여 제조된 알루미늄 박막은 증착 조건에 따라 그 특성이 현저히 달라지는 것으로 알려져 있다. 특히, 진공도와 증착율에 따라 비저항과 반사율, 표면 색상 등이 크게 달라지며 이에 따라 적절한 증발원 및 증착 방법의 선택이 박막의 특성을 좌우하게 된다. 알루미늄은 융점이 낮은 반면 증기화되는 온도가 높을 뿐만 아니라 고온에서는 대부분의 내화물 금속과 반응하기 때문에 저항가열 증발원을 이용하여 증발시키기가 매우 까다로운 물질중의 하나이다. 또한 전자빔으로 증발시킬 경우에는 열전도도가 커서 수냉 도가니를 통해 열이 빠져나가기 때문에 효과적인 증발을 위해서는 고전력을 투입해야 하는 어려움이 있다. 한편, 스퍼터링 증발원을 이용하여 알루미늄을 증착하면 낮은 증착율로 인해 반사율과 같은 제반 특성이 현저히 떨어지는 단점이 있다. 본 논문에서는 알루미늄 박막의 제조를 위한 최적의 증발원과 증착 방법을 소개하고 증착 조건과 박막 특성의 상관성 자료를 소개하였다. 이를 위해 각종 저항가열 및 전자빔 증발원 그리고 스퍼터링을 이용한 증발 실험 결과를 소개하고 증발원에 따른 알루미늄 박막의 특성 변화 그리고 제반 증착 조건이 박막의 특성에 미치는 영향을 소개하였다.

• 천문학회보
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• 제36권2호
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• pp.97.2-97.2
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• 2011

Rims of solar filaments often appear brighter than the background chromosphere, but their physical nature is still poorly known. Last year, we observed a filament with a bright rim. The rim was bright in H alpha but not in Ca II 8542 line. Using the cloud model, we inferred physical parameters of the region from the spectral profiles. As a result, we found that the Doppler width of the H alpha line is very large, which implies temperature as high as 50000K. In addition, the value of the source function of the H alpha line is 0.7 times the continuum intensity of background profile. These results suggest that the bright rims might be a region of intense heating, probably associated with a current sheet. To further investigate this possibility, we carried out more observations this summer. We will present new results obtained from the analysis of these observations and discuss the physical implication of these measurements on the nature of bright rims and the filaments.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.776-781
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• 2008

A ground heat exchanger in a GSHP system is an important unit that determines the thermal performance of a system and its initial cost. The Size and performance of this heat exchanger is highly dependent on the thermal properties. A proper design requires certain site-specific parameters, most importantly the ground effective thermal conductivity, the borehole thermal resistance and the undisturbed ground temperature. This paper is part of a research project aiming at constructing a database of these site-specific properties, especially ground effective thermal conductivity. The objective was to develop and evaluation method, and to provide this knowledge to design engineers. To achieve these goals, thermal response tests were conducted using a testing device at nearly 150 locations in Korea. The in-situ thermal response is the temperature development over time when a known heating load imposed, e.g. by circulating a heat carrier fluid through the test exchangers. The line-source model was then applied to the response test data because of its simplicity. From the data analysis, the range of ground effective thermal conductivity at various sites is $1.5{\sim}4.0\;W$/mK. The results also show that the ground effective thermal conductivity varies with grouting materials as well as regional geological conditions and groundwater flow.

• International Journal of Naval Architecture and Ocean Engineering
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• 제4권4호
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• pp.460-476
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• 2012

High-speed crafts suffer from losing a huge amount of their machinery energy in the form of heat loss with the exhaust gases. This will surely increase the annual operating cost of this type of ships and an adverse effect on the environment. This paper introduces a suggestion that may contribute to overcoming such problems. It presents the possibility of reusing the energy lost by the ships' exhaust gases as heating source for an absorption air condition unit onboard high-speed crafts. As a numerical example; the proposed method was investigated at a high-speed craft operating in Red Sea between Egypt and the Kingdom of Saudi Arabia. The results obtained are very satisfactory. It showed the possibility of providing the required ship's air condition cooling load during sailing and in port. Economically, this will reduce the annual ship's operating cost. Moreover, it will achieve a valuable reduction of ship's emissions.

• Journal of Astronomy and Space Sciences
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• 제34권4호
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• pp.251-256
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• 2017

The electric coupling between the lithosphere and the ionosphere is examined. The electric field is considered as a timevarying irregular vertical Coulomb field presumably produced on the Earth's surface before an earthquake within its epicentral zone by some micro-processes in the lithosphere. It is shown that the Fourier component of this electric field with a frequency of 500 Hz and a horizontal scale-size of 100 km produces in the nighttime ionosphere of high and middle latitudes a transverse electric field with a magnitude of ~20 mV/m if the peak value of the amplitude of this Fourier component is just 30 V/m. The time-varying vertical Coulomb field with a frequency of 500 Hz penetrates from the ground into the ionosphere by a factor of ${\sim}7{\times}10^5$ more efficient than a time independent vertical electrostatic field of the same scale size. The transverse electric field with amplitude of 20 mV/m will cause perturbations in the nighttime F region electron density through heating the F region plasma resulting in a reduction of the downward plasma flux from the protonosphere and an excitation of acoustic gravity waves.

• Environmental Engineering Research
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• 제24권4호
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• pp.529-542
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• 2019

Nowadays, drying methods for municipal solid waste quality improvement have been adopted in the developed and developing countries to valorize wastes for a renewable energy source, reduce dependency on fossil fuel and keep safer disposal at landfills. Among them, biodrying, biostabilization, thermal drying and solar drying are the most common. Drying of municipal solid waste could offer several environmental and economic benefits. Therefore, this review highlighted the drying methods for municipal solid waste quality improvement around the world and compared them based on the reduction of moisture, weight and volume of municipal solid wastes against drying temperature and time by using statistical analysis. It was observed that the drying temperature of different drying methods accounted for 115 ± 40℃ for thermal drying, 59 ± 37℃ for solar drying, 55 ± 15℃ for biodrying and 58 ± 11℃ for biostabilization. Among the drying methods, thermal drying provided the shortest drying time. The moisture reduction, weight reduction, volume reduction and heating value increase of municipal solid waste could vary with drying temperature and time. Finally, the benefits and drawbacks of different drying methods were specified, and recommendations were made for the future efficient drying.

• 한국수소및신에너지학회논문집
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• 제29권3호
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• pp.235-242
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• 2018

Hydrogen can be produced by reforming reaction of natural gas (NG) and biogas, or by water electrolysis. In this study, hydrogen production through water-electrolysis needs superheated steam above $700^{\circ}C$ for high efficiency. The production method of hydrogen like this was recommended for the 4-type processes for superheated steam ($700^{\circ}C$, 3 atm) by Bio-SRF combustion furnace. The 4-type processes to produce superheated steam at $700^{\circ}C$ from the heat source of SRF combustion furnace was simulated using PRO II. The optimum process was selected through exergy analysis. The difference of process 1 and 2 is to the order of depressure and heating process to change $180^{\circ}C$ and 7 atm to $700^{\circ}C$ and 3 atm. Process 3 and 4 is to utilize 25% of steam to generate superheated steam and remaining to use for the power generation by steam generator.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.465-465
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• 2008

Conjugated polymers have attracted much scientific and technological research interest during the past few decades because of their potential use such as polymer light-emitting diodes (PLEDs).1,2 Particularly, lots of phenylene-based polymers such as polyfluorene and its derivatives have been synthesized because of their high photoluminescence quantum efficiencies and thermal stabilities. However, troublesome long wavelength emission in polymer film of polyfluorenes on heating during device formation or operation has been the crucial problem for practical applications. The source of the long wavelength emission was initially believed to be solely due to excimer emission as a result of polymer aggregation. It has also recently been correlated with emissions from ketonic defects in the fluorene units. Many efforts have been made to reduce the tendency to red-shifted emission. Here, we report for the first time the design and synthesis of novel 9,9-spiro bifluornene-based polymers containing heteroatoms such as N, S in its molecular skeleton. Especially, the 9,9-spiro bifluornene-based polymers containing N atom showed stable blue electroluminescence, which did not show spectral change upon thermal annealing.

• 전기학회논문지
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• 제59권2호
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• pp.380-384
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• 2010

A micromirror for a laser display system actuated by the electromagnetic force induced by the surface coil and the permanent magnet was designed and analyzed through the coupled physics analyses incorporating the electromagnetics, mechanics, and electrothermal analysis because the mechanical rotation of the micromirror is driven by the electromagnetic driving force. The proposed micromirror has two torsion beams to sustain the mirror plate which has surface coils on the top and the two permanent magnets exists on both sides of the micromirror for an external magnetic field source. The designed micromirror has the resonant frequency of 3.82kHz. When the magnetic field of the permanent magnet is 0.4T, the coil has 4 turns, and the current density of coil is 3.6A/$mm^2$, the estimated z axis displacement of the mirror plate edge is 0.23mm which corresponds to the rotation angle of $14.2^{\circ}$. When considering the joule heating in the current-carrying coil, the maximum temperature of the mirror plate is obtained as 300.045K, which induces the negligible changes in the rotation angle and the resistance of the coil.