• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.7
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• pp.561-566
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• 2014

Our Korean traditional cultural inheritance Bangpae Kite has the stable rectangular shield shape decorated with artistic paint or poem and a good flight performance due to the central wind hole. In this paper, to analyse the wind hole effect to kite performance we performed the wind tunnel testing of the various design factor of kite model and air flow visualization passing through the wind hole. As the result of aerodynamic analysis, we knew that the wind hole of kite displays similar function of slot system for the wing high lift device. This fact demonstrates that our ancestor understood the function of slot system and applied effectively to the development of kite flight performance.

• Magazine of the Korean Society of Agricultural Engineers
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• v.15 no.3
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• pp.3053-3058
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• 1973

1. This study was conducted to examine the effects of change of the short range nozzle hole on the travelling distance. The results of this study are summarized as follows; a) Effect of change of the cap hole diameter on the travelling distance of sprayed particles was generally a linear, the increasing rate was about 0.27. b) When the difference between the sectional area of cap hole and that of grooves of swirl plate, was small the travelling distance was decreased by the decreasing of spraying speed at cap hole. 2. This study was conducted to examine the effects of change of the short range nozzle hole on the size of spraying particles. The results of this study are summarized as follows; a) The diameter of sprayed particles on travelling distances in the short range nozzle did not coincide with the kinetic energy principle derived from the momentum and the resistance. b) The average diameter of sprayed particle between 1m and 3m in which amount of sprayed particle was particularly a great deal, was big, because that some of sprayed particles were absorbed each other on the way to fall c) Effect of increase of cap hole diameter was generally enlarged the average diameter of sprayed particle with small rate.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2219-2226
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• 2003

Two perforated plates are placed in parallel and staggered arrangements with a gap distance of 2 times of the hole diameter, and initial crossflow passes between the plates. Both the injection and effusion hole diameters are 10 mm, and the Reynolds number based on the hole diameter and hole-to-hole pitch are fixed to 10,000 and 6 times of the hole diameter, respectively. To investigate the effect of crossflow, the flow rate of crossflow is changed from 0.2 to 2 times of that of the impinging jet. A naphthalene sublimation method is used to determine the local heat/mass transfer coefficients on the upward facing surface of the effusion plate. With the initial crossflow, the heat/mass transfer rates on the effusion (target) plate decrease as the velocity of crossflow increases, since the crossflow induces the locally low transfer regions formed at the mid-way between the effusion holes. However, the impingement/effusion cooling with crossflow presents higher heat/mass transfer rates than the array jet impingement cooling with the same initial crossflow.

• The Journal of the Acoustical Society of Korea
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• v.37 no.5
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• pp.317-322
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• 2018

It has been generally known that a hole presenting on the center of pole piece for the loudspeaker can be very helpful for the heat, which is radiated by Joule Effect at the voice coil, to emit to the outside of the magnetic gap. The existence of hole can also become a cause of the changes of the acoustical properties about the loudspeaker. The resonance frequency of loudspeaker increased with the increase of hole radius. However, increasing the hole length resulted in the decrease of the resonance frequency. These results are in an excellent agreement with the theoretical predictions for the equivalent mechanical circuit of Bass-Reflex cabinet system. The acoustical property of the loudspeaker with hole can be also predicted by the theoretical interpretation of Bass-Reflex cabinet system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1248-1255
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• 2003

Pressure coefficient in a rotating discharge hole was measured to gain insight into the influence of rotation on the discharge characteristics of rotating discharge holes. Pressures inside the hole were measured by a telemetry system that had been developed by the authors. The telemetry system is characterized by the diversity of applicable sensor type. In the present study, the telemetry system was modified to measure static pressure using piezoresistive pressure sensors. The pressure sensor is affected by centrifugal force and change of orientation relative to the gravity. The orientation of sensor installation for minimum rotating effect and zero gravity effect was found out from the test. Pressure coefficients in a rotating discharge hole were measured in longitudinal direction as well as circumferential direction at various rotating speeds and three different pressure ratios. From the results, the behaviors of pressure coefficient that cannot be observed by a non-rotating setup were presented. It was also shown that the discharge characteristics of rotating discharge hole is much more influenced by the Rotation number irrespective of pressure ratio.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.381-388
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• 2003

The material deficiencies in the form of pre-existing defects can initiated cracks and fractures. The stress distribution and fatigue crack initiation life of engineering materials may be associated with the size, the shape and the relative location of defects contained in the component. The objective of this study is to investigate the effect of arbitrarily located hole defect around the rivet hole of a wing section in monolithic aluminum and Al/GFRP laminates under cyclic bending moment during a service load. The stress distribution and the fatigue crack initiation behavior near a rivet hole of on the relationships between stress concentration factor ($K_t$) and relative position of defects were considered. The test results indicated the features of different stress field. Therefore, the stress concentration factor ($K_t$) and the fatigue crack initiation behavior was illustrated different behavior according to each position of hole defect around the rivet hole in monolithic aluminum and Al/GFRP laminates.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.101-106
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• 2001

This paper presents experimental results for the confining characteristics of cylinder with center-hole and spiral reinforcements. The experiments have been conducted for the specimens with primary variables i.e., spiral reinforcement ratio and diameter of center-hole which affect the compressive strength and stress-strain relationship. Through this research, it was found that the compressive strength and ductility were increased with the ratio of spiral reinforcement because the lateral expansion of the concrete inside the spiral was restrained by the spiral, but dependent on the size of center-hole.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1805-1808
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• 2006

In this paper, we describe a versatile use of fullerene(C60) as a charge transporting material for organic light-emitting diodes. The use of fullerene as a buffer layer for an anode, a doping material for hole transport layer, and an electron transport layer was investigated. Fullerene improved the hole injection from an anode to a hole transport layer by lowering the interfacial energy barrier and enhanced the lifetime of the device as a doping material for a hole transport layer. In addition, it was also effective as an electron transporting material to get low driving voltage in the device.

• Composites Research
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• v.25 no.1
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• pp.19-25
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• 2012

The study investigated the buckling behavior of sandwich composite columns with different hole sizes and hole positions when they were applied to a compressive load. The columns consisted of 1.7mm thick faces of glass fabric/epoxy and 23mm, 37mm, 48mm, and 61mm thick cores of urethane-foam. Different hole sizes with the diameter of 25mm and 38mm were considered in this experiment. To evaluate the effect of hole position on the buckling behavior, we considered three types of hole position: 25mm diameter hole located at the center, 25mm diameter hole at 1/4 position from the center to the end of the column, and 25mm diameter hole at 1/2 position from the center to the end of the column. According to the results, buckling and maximum loads of the column having 25mm diameter hole were lower by 10% compared to those of the column without hole, whereas the loads for the column having 38mm diameter hole were 30% less than those of the column without hole. Hole position appeared to have no effect on buckling and maximum loads. Major failure modes were observed as follows: the core shear failure for the thin columns having 23mm and 37mm thick cores, and the face-core debonding for the thick columns having 48mm and 61mm thick cores.

• Tunnel and Underground Space
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• v.20 no.2
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• pp.125-130
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• 2010

Model blast experiments of mortar blocks were performed to investigate the effect of the guide hole on crack growth. The mortar block specimens have a blast charge hole and 8 guide holes. Two of circular guide hole, notched guide hole, diamond shaped guide hole and diamond shaped guide holder are installed around 110 mm, 165 mm and 220 mm apart from the charge hole for each specimen. From the blast experiments, it was revealed that all the guide hole used in this study were effective for controlling the crack growth at the fracture control.