• 한국태양에너지학회 논문집
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• 제35권1호
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• pp.69-80
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• 2015

A series of numerical analyses was conducted to predict the thermal performance of a solar air heater depending on the hole configuration and geometry in the absorber plate. The planar dimensions of the prototype were 1 m (W) by 1.6 m (H), and the maximum air flow considered was $187m^3/h$. It was considered that protruding holes with a triangular opening in the absorber plate would invoke turbulence in the air flow to enhance the convection heat transfer. Six different hole configurations were investigated and compared with each other, while the hole opening height was considered as a design variable. Three-dimensional transient analyses were performed with a commercial software package on the airflow and heat transfer in the model. The numerical results were analyzed and compared from the view point of the outlet air temperature and its time response to derive the optimal hole pattern and hole opening height.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.801-806
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• 2000

This experimental study is to investigate the intermittent spray characteristics of a multi-hole nozzle in a heavy-duty DI diesel engine. Multi 8 hole$(d_n=0.25mm)$, Multi 3 hole$(d_n=0.42)$ and Sing hole nozzle$(d_n=0.25mm)$ were used in this experiment. By using the 2-D PDPA(phase Doppler particle analyzer), the droplet diameter and the velocity of a diesel spray injected intermittently from the multi and the single-hole nozzle into a still ambient were measured. In order to calculate the mean values such as mean velocity, SMD, AMD etc. and to analyze the intermittent characteristics, the time-window of 0.15ms were applied. In the spray, the small droplet$(D<10{\mu}m)$ was regarded as an air flow, and the correlation between the fuel droplet$(10{\mu}m and the air (low was examined. The normalized axial droplet-air relative velocity of the 8 hole, the 3 hole and the single hole nozzle was evaluated as 0.081, 0.067, 0.06 and in case of the radial droplet-air relative velocity, the normalized. value is 0.014, 0.013 and 0.008 respectively.

• 대한통합의학회지
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• 제7권2호
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• pp.133-139
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• 2019

Purpose : This study aims to investigate the rating of perceived exertion (RPE) and muscle activity of the inspiratory primary and accessory muscle during breathing exercise with different air hole diameters of the inspiratory muscle trainer (IMT). Methods : The Borg's scale and surface electromyography (EMG) was used to collect data of the RPE and muscle activity of the inspiratory primary the external intercostal (EI) and diaphragm (DIA) and accessory muscles anterior scalene (AS), sternocleidomastoid (SCM), pectoralis major (PM), and upper trapezius (UT) muscles during breathing exercise with different air hole diameters (6 mm, 4 mm, and 2 mm) of the IMT in healthy young male subjects. Results : The RPE and muscle activities of the AS, SCM, and UT are increased significantly in accordance to the decreasing diameter of air hole of air tip in IMT. However, there are no differences in the muscle activities of the PM, EI, and DIA based on differences of diameters of air hole of air tip in IMT. Conclusion : The smaller the diametr of IMT air-hole, RPE and muscle activities of AS, SCM and UT were increased. Therefore, further study would be necessary to investigate the proper intensity and relaxation posture for the exercise protocol to strengthen the inspiratory primary muscles.

• Current Optics and Photonics
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• 제2권6호
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• pp.525-531
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• 2018

The effect of eccentricity on dispersion and nonlinear properties of a photonic crystal fiber having elliptical air holes is investigated using a fully vectorial effective index method. It is found that the effective refractive index increases with increase of eccentricity. The dependence of dispersion and nonlinear properties of the PCF on the eccentricity of the air hole is investigated. It is revealed that eccentricity of the air hole affects the zero dispersion wavelength. Further, the nonlinear properties such as mode field area, nonlinear coefficient and self phase modulation of the Photonic crystal fibers are analyzed. The mode field area increases and the nonlinear coefficient decreases with increase in eccentricity. The variation of the self phase modulation with elliptical air hole is also discussed.

• 한국환경과학회지
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• 제27권3호
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• pp.155-165
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• 2018

Observations were conducted in Uiseong Binggye-ri Ice Valley of Korea, where a low temperature talus is located. The talus temperature at Ice Hole near the lower end of the talus remained at $0^{\circ}C$ until summer or autumn and averaged $-0.3^{\circ}C$ over 2 years. The talus temperature at Warm Hole was much higher than the external air temperature during autumn and winter. The outflow of warm air at Warm Hole begins in the late summer of fall. The direction of airflow through the talus surface was determined by the relationship between talus temperature and external air temperature. Annual variations in talus temperature and air exchange between the talus and the external environment can be divided into four periods. It was found that the airflow directions at Warm Hole and Ice Hole were not necessarily opposites. The outflows from the talus at Ice Hole and Warm Hole can occur simultaneously.

• Journal of electromagnetic engineering and science
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• 제18권3호
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• pp.160-168
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• 2018

A wide spectrum of potential applications using substrate integrated waveguide (SIW) technologies in conjunction with air hole regions is introduced, and an efficient optimization methodology to cope with the multiple air hole effect in SIW applications is proposed. The methodology adopts a genetic algorithm to obtain optimum air hole dimensions for the specific propagation constant that can be accurately calculated using the recursive and closed form equations presented. The optimization results are evaluated by designing an SIW bandpass filter, and they show excellent performance. The optimization methodology using the proposed equations is effective in performance enhancement for the purposes of low loss and broadband SIW applications.

• 한국축산시설환경학회지
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• 제8권2호
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• pp.73-78
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• 2002

The experiment was carried out to investigate the optimal air velocity for improving the ventilation efficiency of duct ventilation system used in Korean swine building. The results are followed ; In 2.2 m height of duct, the air velocity of hole was 5.0 m/s as the over level of recommendation. In different hole interval, the air velocity was various of 4.6${\sim}$11.6 m/s in narrow hole interval, 5.4${\sim}$10.9 m/s in broad hole interval. But the air velocity was 6.6${\sim}$7.7 m/s in duct system pierced hole with equal interval, and it was equal velocity in different parts of duct in this hole interval.

• Journal of the Optical Society of Korea
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• 제9권4호
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• pp.140-144
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• 2005

In this paper we have investigated the guiding properties of photonic crystal fibers (PCFs) with a square-lattice of air-holes in the cladding. We have shown numerical results of PCFs with various air hole sizes and hole-to-hole spacings over a wide wavelength range. The group velocity dispersion, effective area and effective refractive index of PCF have been calculated numerically. The waveguide dispersion has greatly affected the group velocity dispersion when hole-to-hole spacing is about $1{\mu}m$. The effective area is quite flat over the wide spectral range whether the hole-to-hole spacing is large or ratio of diameter to pitch is large. From the field distribution, we found that the field is tightly confined within the core region of PCF when the pitch is $3{\mu}m$ and the air-filling fraction is 0.9.

• 반도체디스플레이기술학회지
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• 제6권1호
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• pp.59-64
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• 2007

Non-contact transportation of a large-sized glass plate using air cushion for the vertical sputtering system of liquid crystal display (LCD) panel was considered. The objective of the study was to design an air pad unit which was composed of multiple injection and exhaust holes and mass flow supplying pipe. The gas was injected through multiple small holes to maintain the force for levitating glass plate. After hitting the plate, the air was vented through exhaust holes. Complex flow field and resulting pressure distribution on the glass surface were numerically studied to design the air injection pad. The exhaust hole size was varied to obtain evenly distributed pressure distribution at fixed diameter of the injection hole. Considering the force for levitating glass plate, the diameter of the exhaust hole of 30 to 40 times of the gas injection hole was recommended.

• 한국환경보건학회지
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• 제2권1호
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• pp.33-36
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• 1975

This study is aimed to increase the heat efficiency and to decrease the evolution of carbon monooxide during the combustion of holed coal-briquet by using of non-covered fire-box, and determined carbon monooxide versus combustion time and number of air-hole by the using of Orsat gas analyzer. The obtained results are as follows (1) Carbon monooxide are evolved the greatest quantity between 3rd and 6th hour from the hegining of combustion. (2) Combustion time of holed coal-briquet is not showed the difference to fire-boxes of A-type ($\phi$60mm) and B-type ($\phi$165mm). (3) Combustion temperature is decreased in turns of 4 air-hole>3 air-hole>2 air-hole to holed coal-briquet.