• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 추계기술심포지움논문집
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• pp.147-151
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• 2002

We fabricated and characterized a millimeter-wave ceramic package in a frequency range from 6 to 40㎓ using the LTCC(Low Temperature Cofired Ceramic) Technology and TRL(Thru-Reflect-Line) calibration method. From these measurement results, the fabricated feed-through structure achieved 0.5 dB, 14 dB of the insertion loss and the return loss at 30 GHz respectively. This ceramic package will be useful for MMIC(Monolithic Microwave Integrated Circuit) modules.

• Journal of Magnetics
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• 제4권3호
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• pp.98-101
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• 1999

In this work we htave constructed an under water sonar transducer using Terfenol-D rod employing open magnetic circuit. Normally Sonar transducer using Terfenol-D was designed under closed magnetic flux return path, and permanent magnet for dc bias marnetic field, but high magnetic field should be applied to the transducer coil for high sound power and it brings temperature increase inside of the transducer. To improve this heat dissipation problem, we have designed an open magnetic circuit type transducer and we can get 200 dB (re. 1 Pa @ 1m) sound power for the input power of 650 VA.

• Journal of Electrical Engineering and information Science
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• 제1권1호
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• pp.45-50
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• 1996

This paper mainly describes the wind load assumption of 765kV transmission towers. We analyzed wind velocity data a meteorological observatories to get the wind velocity of 50 years return period by using Gumbel I type extreme value distribution. By multi-correlative regression analysis method, wind velocity at no observation site was obtained. Reference dynamics wind pressure map was obtained from above analysis and the wind pressure was classified as three regio in high temperature season.

• 설비공학논문집
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• 제26권3호
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• pp.108-114
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• 2014

On a large scale of data center, heat generation rates from sever computers occupy almost the entire cooling load of the building, and it is gradually increasing. The efficiency of air distribution system in data centers can be affected by heat generation rates of server computers. In this study, the distributions of airflow and temperature in a data center have been investigated by CFD simulations under various conditions of heat generation rates for server computers. From the results, air around the cold aisle which has high temperature flows tremendously into the cold aisle according to the increase of heat generation rates for server computers and the air temperature in the cold aisle becomes higher. The SHI (supply heat index) and RHI (return temperature index) show almost similar values to the cases study because the air inflow rates to server computers increase with the heat generation rates of server computers.

• 한국태양에너지학회 논문집
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• 제27권4호
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• pp.43-49
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• 2007

This study is conducted to improve the efficiency of a thermal storage tank. The thermal storage tank was designed to store heat energy that obtained from the solar or the others heat sources. However, it has difficulties in storing heat with nonuniform temperature through the entire tank with respect to the vertical direction, This study is focused on the thermal stratification to improve thermal comfort for the resident in house. To enhance temperature stratification of the tank, a distributor was designed and installed in the middle of the storage tank vertically. The vertically designed distributor could supply the return water with stratified temperature in the storage tank with respect to the height. The water velocity from the distributor hole is the same with the other outlet in the distributor. However, gravity effect on the flow in the storage tank is much higher than that of the velocity effect due to that Froude Number is less than 1. During the heat charging process in the storage tank, temperature maintained with little difference with respect to the height. However the charging process takes long time to get a effective temperature for the heating or hot water supply because of all of water in the storage tank needs to be heated.

• Nuclear Engineering and Technology
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• 제56권5호
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• pp.1698-1711
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• 2024

Heat pipe cooled reactors have gained attention as a potential solution for nuclear power generation in space and deep sea applications because of their simple design, scalability, safety and reliability. However, under complex operating conditions, a control strategy for variable load operation is necessary. This paper presents a two-dimensional transient characteristics analysis program for a heat pipe cooled reactor and proposes a variable load control strategy using the recuperator bypass (CSURB). The program was verified against previous studies, and steady-state and step-load operating conditions were calculated. For normal operating condition, the predicted temperature distribution with constant heat pipe temperature boundary conditions agrees well with the literature, with a maximum temperature difference of 0.4 K. With the implementation of the control strategy using the recuperator bypass (CSURB) proposed in this paper, it becomes feasible to achieve variable load operation and return the system to a steady state solely through the self-regulation of the reactor, without the need to operate the control drum. The average temperature difference of the fuel does not exceed 1 % at the four power levels of 70 %,80 %, 90 % and 100 % Full power. The output power of the turbine can match the load change process, and the temperature difference between the inlet and outlet of the turbine increases as the power decreases.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.198-201
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• 2001

Porous structures of aluminum foam have been studied by using return aluminum scrap. The apparent foam shape, foam height, density, pore size and their distributions in various section areas of the experimental samples have been investigated. The sample have been cast into metallic mold, using aluminum foam prepared from a precursor based on pure Al ingot and return aluminum scrap mixed with various amounts of 1-2wt% increasing viscosity and foam agent materials. The process provides for flexibility in design of foam structures via relatively easy control over the amount of hydrogen evolution and the drainage processes which occur during foam formation. This is facilitated by manipulating parameters such as the foaming agent, thermal histories during solidification and mix melt viscosities. A metal for producing the foamed are decomposing a foaming agent in a molten metal such that there is an initial and a subsequent expansion due to foaming agent. It has been found that the Al porous foaming with variation amount of 1∼2wt% foam agent and at 2min holding time, which melting temperature has appeared homogeneous pore size at 650∼700$^{\circ}C$. The compression strength were 10-13 kg/min at 125ppi, and increased by higher pore density. The acoustical performance of the panel made with the foamed aluminum is considerably improved; its absorption coefficient shows NRC 0.6-0.8. It has been found that the Al foam is very preferable for the compactness of the thermal system.

• 대한한방소아과학회지
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• 제35권3호
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• pp.53-66
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• 2021

Objective The purpose of this study is to evaluate whether herbal bath shortens the duration of pediatric fever. Methods Databases, such as Medline, EMBASE, Cochrane library, OASIS, KISS, KMBASE, CNKI, Wanfang Med Online were used to search randomized controlled trials. Those trials that included children younger than 18-year-old were evaluated for the clinical efficacy of herbal bath in fever by analyzing 'body temperature (BT) drop start time' and 'time to return to normal BT'. Results 12 studies or 1306 participants were analyzed in the study. When applying herbal bath in combination with the controlled treatment, 'BT drop start time' was decreased by 0.11 hours, and 'time to return to normal BT' was decreased by 10.94 hours compared to the controlled group. When comparing herbal bath with tepid bath, 'time to return to normal BT' was reduced by 8.19 hours in herbal bath group. In regards to safety, 3 studies out of 12 studies mentioned about its adverse events: 2 studies did not have any adverse events, and a minor needle-shaped bleeding had occurred in one of the studies. Conclusion Use of herbal bath as a treatment of fever in children was associated with shortened duration of fever. However, cautious interpretation is necessary due to its limited safety data.

• Corrosion Science and Technology
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• 제23권4호
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• pp.315-323
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• 2024

This work examined pitting corrosion failure of a copper heat-return pipe used in a district heating system. The copper pipe was corroded with a 48% reduction in thickness due to localized corrosion on the inner surface exposed to heating water of 20 ~ 40 ℃. Fe and Si elements as corrosion products were found around pits. Cl element was also observed, which accelerated oxidation of copper inside pits. Cu₂O deposits on the pit's bottom surface decreased the pH inside the pit. X-ray diffraction analysis revealed hematite, cuprite, malachite and brochantite as corrosion products. Chemical analysis demonstrated that Fe and Si elements did not exist in the copper, supply water, or heating water, indicating that Fe and Si species might have entered into the pipe from the exterior. These results indicated that pits were initiated due to ion concentration gradient near Fe and Si species. Moreover, the interior of pits had lower pH due to Cl^- concentration and Cu₂O reactions, which accelerated the pit's growth and led to formation of pinholes. Additionally, we confirmed that the type of pitting corrosion was a complex combination of types I and II based on the HCO₃^-/SO₄^2- ratio, pH, temperature, and corrosion products.

• 자원ㆍ환경경제연구
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• 제15권2호
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• pp.319-353
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• 2006

본 논문은 날씨파생상품이 전기도매시장에서의 가격 및 수량 위험의 헤지수단으로서 활용될 수 있다는 것을 보여주고 있다. 또한 일별 수준의 가격과 물량이 아니라 여름기간 동안의 전기도매시장에서의 전기구입 비용 혹은 전기판매 수입을 대상으로 하여 날씨관련 계약형태의 위험헤지효과를 살펴보았다. 날씨관련 계약들이 전기도매시장의 시장신호를 더 잘 보전하고 있으며, 도매전기 구입관련 금융위험을 더 잘 헤지함을 발견하였다. 전기도매시장에서 선물계약과 날씨파생상품을 결합하였을 경우, 더운 날의 경우 높은 전기생산비용이 가격에 반영되며, 전기판매 수입 혹은 전기구입 비용의 변동성이 현저히 낮아진다는 것을 발견하였다.