• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.510-520
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• 2019

To investigate the morphology characteristics of air layer in the air cavity, a numerical method with the combination of RANS equations and VOF two-phase-flow model is proposed for a plate with air cavity. Based on the model above, the dynamic and developmental process of air layer in the air cavity is studied. Numerical results indicate that the air layer in the plate's air cavity exhibits the dynamic state of morphology and the wavelength of air layer becomes larger with the increasing speed. The morphology of air layer agrees with the Froude similarity law and the formation of the air layer is not affected by the parameters of the cavity, however, the wave pattern of the air layer is influenced by the parameters of the cavity. The stable air layer under the air cavity is important for the resistance reduction for the air layer drag reduction.

• 한국군사과학기술학회지
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• 제17권6호
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• pp.764-772
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• 2014

The stealth performance of supersonic aircraft in recent air battlefield is one of the most significant feature for latest fighters. Especially, as the technology is advancing, the IR stealth capability becomes more important because of its passive characteristic. To design an aircraft with stealth capability, we must know how much the IR signature is generated from the aircraft. Also, predicting the IR signature of enemy's aircraft is tactically crucial. In this study, we calculated MWIR and LWIR infrared signature of $5^{th}$ generation supersonic aircraft against air-to-air and surface-to-air threat using IR simulation code and CFD coupled procedure.

• Journal of the Korean Wood Science and Technology
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• 제14권3호
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• pp.16-22
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• 1986

Effective air-drying days for four seasons and districts were calculated from average monthly temperature, relative humidity and wind speed records for 24 districts in Korea and air-drying calendars were prepared. And these districts were divided into zones of effective air-drying days. These results were as follows. 1. Effective air-drying days for four seasons were 20 to 23 days in springtime, 30 days in summertime, 21 to 26 days in autumntime, and 8 to 17 days in wintertime. 2. Effective air-drying days variated from district to district and was 237 days, the shortest period, in Ch'unch$\breve{o}$n, and was 288 days, the longest period, in-S$\breve{o}$gwipo. 3. Effective air-drying days were primarilly related to the difference in temperature from month to month, and secondarily, especially in September, were related to the differences in relative humidity, and were not related to wind speed. 4. South Korea was divided into 4 zones of effective air-drying days and these zones had it little difference compared with meteorological zones.

• Transactions on Electrical and Electronic Materials
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• 제12권4호
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• pp.131-134
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• 2011

Back-end-of-line using ultra low-k (ULK; k < 2.5) has been required to reduce resistive capacitance beyond 45 nmtechnologies, because micro-processing units need higher speed and density. There are two strategies to manufacture ULK inter-layer dielectric (ILD) materials using an air-gap (k = 1). The former ULK and calcinations of ILD degrade the mechanical strength and induce a high cost due to the complication of following process, such as chemical mechanical polishing and deposition of the barrier metal. In contrast, the air-gap based low-k ILD with a relatively higher density has been researched on the trench-type with activity, but it has limited application to high density devices due to its high air-gap into the next metal layer. The height of air-gap into the next metal layer was reduced by changing to the via-typed air-gap, up to about 50% compared to that of the trench-typed air-gap. The controllable ULK was easily fabricated using the via-typed air-gap. It is thought that the via-type air-gap made the better design margin like via-patterning in the area with the dense and narrow lines.

• 설비공학논문집
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• 제21권1호
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• pp.1-8
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• 2009

The simulation of a heat pump dryer has been carried out to figure out the effect of air flow rate on the drying performance represented by MER, SMER, and so on. The simulation includes the analyses of one-stage heat pump cycle and simple drying process using the drying efficiency. The heat pump cycle with Refrigerant 134a has been considered. In the dryer, some of drying air from the drying chamber flows through the heat pump system, the rest of air bypasses the heat pump system. The two air flows joins before the drying chamber inlet. The performance parameters considered in the present study are MER, SMER, the temperature and humidity of drying air. Those parameters are compared for different total air flow rate or bypass air flow rate.

• 한국군사과학기술학회지
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• 제22권1호
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• pp.141-149
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• 2019

This study analyzed upper-air temperatures in order to make temperature conditions for weapon system operating in Korean Peninsula. One of important tasks of environmental analysis is to set-up suitable temperature conditions for successful development of weapon system. Many weapon system developers are setting air temperature conditions based on the MIL-STD-810G. However, for weapons systems that are used only in the upper-air of the Korean Peninsula, the air temperature conditions recommended by MIL-STD-810G are often not suitable. To establish the air temperature conditions for upper-air in the Korean Peninsula, the method of Percentage of Occurrence should has be built up as method of temperature analysis. Upper-air climate data of the Korea Peninsulas over the past decade is also analyzed based on this method. The study suggest upper-air temperature conditions for weapons systems that are operated only in the Korean peninsula.

• 한국산학기술학회논문지
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• 제13권11호
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• pp.4944-4949
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• 2012

이 논문의 목적은 작업장에서 사용하기 위한 에어건의 개발에 관련된 것이다. 에어건은 공작기계를 사용하는 산업현장에서 공작물 칩과 절삭유의 제거를 위한 도구이다. 그리고 그것은 일반적으로 압축공기를 분사하는 용도로 사용된다. 작업자는 에어의 흡입과 분사를 위해 각각의 에어건을 준비하여야 한다. 따라서 우리는 새로운 에어건을 개발하였다. 이 논문에서 우리는 에어건의 설계와 분석을 위한 연구를 한다. 에어건은 몸체, 파이프, 개폐 유닛, 전환 유닛, 에어 튜브 그리고 조립을 위한 요소들로 구성된다. 개발된 에어건은 그 효율을 확인하기 위해 실험된다.

• 설비공학논문집
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• 제17권4호
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• pp.347-354
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• 2005

This paper compared vertical temperature distribution between the existing balcony model without ventilator facilities and the improved balcony model with ventilator facilities using differential equation. As the air inside of balcony is heated by solar radiation this heated air is not exhausted in the existing balcony, remaining stagnant. The air temperature distribution was $26.7{\sim}29.3^{\circ}C$ in balcony without natural ventilator system. This heated air affected the rising air temperature of adjacent spaces such as living room and bedroom in the existing balcony. But, as the heated air inside of the improved balcony model is exhausted through natural ventilator facilities in summer, the air temperature in balcony has fallen. The air temperature distribution in improved balcony was $24.8{\sim}26.7^{\circ}C$ for the inlet air speed of 1 m/s and $24.6{\sim}26.7^{\circ}C$ for the inlet air speed of 3 m/s. The energy consumption of the improved balcony is 2.5 times less than of the existing balcony. The improved balcony with the closed damper makes a roll as the existing balcony in the aspect of the heating effect. When the heated air in the improved balcony is supplied, the air temperature is raised and the ventilation effect in adjacent spaces was improved.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2019년도 학술발표회
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• pp.43-47
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• 2019

본 연구에서는 수리모형실험을 통해 사이펀 여수로에 장착된 air slot의 방류량 조절 능력을 검토하였다. air slot의 단면 형상으로 원호 및 직사각형 형상을 채택하였으며, 개구부 면적을 조절할 수 있게 하였다. air slot이 장착된 경우 사이펀 관 내부에 공기와 물이 혼합된 복잡한 흐름이 발생하였다. air slot이 장착된 사이펀 여수로에서 저수지 내측 수위가 상승할 때와 하강할 때 동일한 수위에서 동일한 유량이 계측되었다. air slot의 무차원 개구부 면적이 증가할수록 무차원 방류량은 더 서서히 증가하였다. 수리모형실험 결과는 air slot의 면적 조절을 통해 사이펀을 통한 방류량 조절이 가능함을 보여주었다.

• 한국분무공학회지
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• 제28권4호
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• pp.198-206
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• 2023

In this study, visualization of in-cylinder spray behavior and spark channel stretching by air flow characteristics depending on engine operating conditions were investigated. For in-cylinder spray behavior, increase in engine rpm did not alter the counter-clockwise air flow direction and location of in-cylinder dominant air flow but increased average air flow velocity, which hindered spray propagation parallel to the piston surface. When injection timing was retarded, direction of in-cylinder dominant air flow was changed, and average air flow velocity was reduced resulting in an increase in spray penetration length and change in direction. For spark channel stretching, increase in air flow speed did not affect spark channel stretch direction but affected length due to increase in spark channel resistance and limitation of energy ignition coil can handle. Change in air flow direction affected spark channel stretch direction where the air flow was obstructed by ground electrode which caused spark channel direction to occur in the opposing direction of air flow. It also affected spark channel stretch length due to change in air flow speed around the spark plug electrode from the interaction between the air flow and ground electrode.